Universidad Nacional Autónoma de México
Centro de Geociencias
Programa de Posgrado en Ciencias de la Tierra
Estudio de la Geoquímica, la Estructura y elMetamorfismo en el Este del Complejo
Acatlán: Implicaciones Tectonicas yPaleogeograficas
——Continental arc development along the periphery of
Pangea: Late Paleozoic pluton emplacement and basinevolution in a transtensional setting, eastern Acatlán
Complex, Mexico
Moritz Kirsch
Tesis sometida en cumplimiento parcialde los requisitos para el grado de
Doctor en Ciencias de la Tierra
ASESORES:Dr. J. Duncan KeppieDr. J. Brendan Murphy
JURADO EXAMINADOR:Dra. Elena Centeno-García
Dr. Peter SchaafDr. J. Duncan Keppie
Dr. Luca FerrariDr. Michelangelo Martini
Juriquilla, Qro, México Agosto, 2012
Moritz Kirsch: Estudio de la Geoquímica, la Estructura y el Metamorfismo enel este del Complejo Acatlán: Implicaciones Tectonicas y Paleogeograficas, TesisDoctoral c© Agosto, 2012
En memoria cariñosa de mis abuelos Otto y Ruth Kirsch, y mi abueloSiegfried Schröder.
R E S U M E N
En el sector este del Complejo Acatlán, sur de México, se encuentra unconjunto de rocas de edad Paleozoico tardío, compuesto por un cuerpo in-trusivo de la asamblea gabro-diorita-tonalita-trondhjemita (plutón Totolte-pec) y una secuencia clástica-calcárea de bajo grado de metamorfismo (for-mación Tecomate). Estas rocas fueron emplazadas y depositadas despuésde la orogenia colisional asociada a la formación de Pangea. Por lo tanto, elárea de estudio ofrece la oportunidad de investigar procesos geológicos endiferentes niveles corticales de un arco magmático en la periferia de Pangeadurante el tiempo crucial entre amalgación y rotura del supercontinente.
El plutón Totoltepec con una superficie de afloramiento de 15 × 5 km estálimitado por dos fallas Pérmicas dextrales con orientación N–S, al sur poruna cabalgadura E–W con buzamiento norte, y al norte por una falla normalE–W. El plutón está compuesto por rocas máficas–ultramáficas subordina-das (306 ± 2 Ma; análisis concordante de U-Pb en circón) que afloran enel margen de la intrusión máfica–felsica principal (289 ± 2 Ma). La geoquí-mica de las rocas marginales muestra una afinidad toleítica a calco-alcalinacon alto LILE/HFSE (elementos litófilos de radio iónico grande/elementosde alto potencial iónico), tierras raras de espectro plano y valores inicialesde εNd entre +1.3 y +3.3. Los elementos traza de la fase plutónica másjoven describen una afinidad calco-alkalina con espectros de tierras rarasmoderadamente fraccionados y valores iniciales de εNd entre -0.8 a +2.6,lo cual también sugiere un ambiente de arco para su formación. Datos ter-mobarométricos indican que el cuerpo principal del plutón fue emplazadoa 620 km de profundidad y una temperatura de >700
◦C, y fue exhumadoa 11 km y 400
◦C en 4 ± 2 Ma. Se ha documentado la siguiente secuenciaintrusiva: (i) la fase máfica del margen norte de 306 Ma, (ii) la fase principaltrondhjemítica de 287 Ma, y (iii) diques subverticales de approx. 289–283
Ma que varian desde (a) N39◦E, no-deformados con crecimiento de cris-
tales perpendiculares a las márgenes, a (b) approx. N50–73◦E, foliados y
plegados con indicadores cinemáticos sinistrales, hasta (c) N73–140◦E con
estructuras tipo boudinage. La obliquidad del límite entre los diques ple-gados y estirados en relación a fallas dextrales de rumbo N-S sugiere unemplazamiento secuencial en un ambiente transtensional con 20 % de ex-tensión con dirección E-W, pasando por un campo de acortamiento bajodiferentes grados de rotación en sentido horario, acompañado por cizalla-miento lateral izquierdo, a un campo de extensión. La intrusión de approx.289–287 Ma contiene una foliación subvertical de rumbo ENE y un linea-miento que varia de subhorizontal a muy inclinada, probablemente debidoal emplazamiento en un ambiente de deformación triclínica. Se infiere queel magmatismo cesó cuando un componente de movimiento fue transferidode la falla del límite occidental a la falla del límite oriental, resultando en
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un cabalgamiento a lo largo del límite sur del plutón. Este mecanismo pue-de explicar el rápido levantamiento y exhumación del plutón entre approx.287 y 283 Ma.
La formación Tecomate se define actualmente como un compuesto deunidades de litología similar, depositadas desde el Carbonífero hasta el Pér-mico en múltiples cuencas limitadas por fallas. Al sur del plutón Totoltepec,la edad de depositación de la formación Tecomate está bien definida en ∼300
Ma en una sección, y entre ∼288 y ∼263 Ma en otra. Las rocas de la forma-ción Tecomate están interpretadas como derivados de un arco magmáticodel Paleozoico tardío, basandose en (i) su geoquímica de afinidad de arco,(ii) valores εNd(t) entre -5.6 a +0.3 (t = 288 Ma) que traslapan los del plu-tón Totoltepec, y (iii) una población dominante de circones con edades quevarian de Carbonífero a Pérmico. Las unidades de Totoltepec y Tecomateen el área de estudio forman parte de un arco continental que se extiendedesde Guatemala hasta California, lo cual implica subducción del paleo-Pacífico bajo el margen occidental en una configuración paleogeográfica dePangea-A.
A B S T R A C T
In the eastern Acatlán Complex of southern Mexico, a Late Paleozoicassemblage comprising a gabbro-diorite-tonalite-trondhjemite suite (Totol-tepec pluton) and clastic-calcareous metasedimentary rocks (Tecomate For-mation), post-dates collisional orogeny that resulted in the amalgamationof Pangea. This region offers a rare opportunity to examine assemblagesdeveloped at different crustal levels of a magmatic arc along the peripheryof Pangea at the critical stage between amalgamation and breakup.
The 15 x 5 km Totoltepec pluton is bounded by two N–S Permian dex-tral faults, an E–W thrust to the south, and an E–W normal fault to thenorth. The pluton consists of minor mafic–ultramafic rocks (306 ± 2 Ma;concordant U-Pb zircon analysis) that are marginal to the main mafic–felsicintrusion (289 ± 2 Ma). Geochemistry of the marginal rocks indicates anarc tholeiitic to calc-alkaline character with high LILE/HFS, flat REE pat-terns and initial εNd values of +1.3 to +3.3. The younger Totoltepec phaseexhibits a calc-alkaline trace element geochemistry with flat to moderatelyfractionated LREE enriched patterns, and initial εNd values of -0.8 to +2.6,which are also consistent with an arc environment. Thermobarometric dataindicate that the main, ca. 289–287 Ma part of the pluton was emplaced at620 km depth and >700
◦C, and was exhumed to 11 km and 400◦C in 4
± 2 Ma. The following intrusive sequence is documented: (i) the 306 Manorthern marginal mafic phase; (ii) the 287 Ma main trondhjemitic phase;and (iii) ca. 289–283 Ma subvertical dikes that vary from (a) N39
◦E, unde-formed with crystal growth perpendicular to the margins, through (b) ca.N50–73
◦E, foliated and folded with sinistral shear indicators, to (c) N73–140◦E and boudinaged. The obliquity of the boundary between the folded
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and stretched dikes relative to the N-S dextral faults suggests sequential em-placement in a transtensional regime (with 20 % E–W extension), followedby different degrees of clockwise rotation passing through a shortening fieldaccompanied by sinistral shear into an extensional field. The ca. 289–287 Maintrusion also contains a steep ENE-striking foliation, and hornblende linea-tions varying from subhorizontal to steeply plunging, probably the result ofemplacement in a triclinic strain regime. We infer that magmatism ceasedwhen some of the dextral motion was transferred from the western to theeastern bounding fault, causing thrusting to take place along the southernboundary of the pluton. This mechanism is also invoked for the rapid upliftand exhumation of the pluton between ca. 287 and 283 Ma.
The Tecomate Formation, as currently defined, is a composite of lithologi-cally similar strata deposited in several fault-bounded basins ranging fromCarboniferous to Early Permian in age. To the south of the Totoltepec plu-ton, the depositional age of the Tecomate Formation is tightly constrained inone section to ∼300 Ma but in another section it is between ∼288 and ∼263
Ma. The Tecomate Formation rocks are interpreted to have been derivedfrom a Late Paleozoic arc based on (i) its arc-related geochemistry, (ii) εNd(t)values ranging from -5.6 to +0.3 (t = 288 Ma) that overlap those of the Totol-tepec pluton, and (iii) detrital zircons with predominantly Carboniferous–Permian ages. The Totoltepec and Tecomate units in the study area formpart of a continental arc extending from Guatemala to California, whichnecessitates subduction of the paleo-Pacific oceanic lithosphere beneath thewestern margin of a Pangea-A configuration.
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Oh du schönes, o du wunderschönes,uraltes, sagen- und liederreiches Land Mexiko!
Desgleichen gibt es nicht wieder auf dieser Erde.
— B. Traven
A G R A D E C I M I E N T O S
Me gustaría reconocer a J. Duncan Keppie y J. Brendan Murphy por susupervisión, paciencia, motivación y financiación. Me siento tremendamen-te afortunado de haber tenido la oportunidad de venir a México y traba-jar con ustedes. Además de la geología espectacular que me tocó estudiar,realmente fue una experiencia cultural, tal como se había prometido. Heaprendido mucho de ustedes dos en estos cuatro años—Brendan, me ense-ñaste la importancia de principios y procesos en la redacción científica, noperder nunca vista del panorama completo, hacer mil cosas al mismo tiem-po, mantener impulso, estar pendiente de muestras y atar cabos sueltos, serarticulado y organizado. Duncan, tu experiencia geológica y sentido de laorientación en el campo, tu humor, tu parsimonia y eficiencia en todas lascuestiones científicas y burocráticas eran una verdadera inspiración. Estoyconvencido de que me han preparado bien para una carrera como geólogohard-rock.
Además de los asesores de mi tesis, quisiera dar las gracias a todas lasdemás personas que han contribuido de una manera u otra a este trabajo.Maria Helbig, Mario A. Ramos-Arias, Gonzalo Galaz, y Domingo Schieve-nini donaron su tiempo y esfuerzo para asistirme en el campo y ayudar-me con la preparación de muestras. Luigi Solari, Consuelo Macías Romo,Carlos Linares, Carlos Ortega-Obregón, Ofelia Pérez-Arvizu, Aldo Izagui-rre, Alex Iriondo, y Harald N. Böhnel brindaron asistencia invaluable enel laboratorio. He beneficiado mucho de la colaboración y las conversacio-nes inspiradoras con Maria Helbig, Luigi Solari, James K. W. Lee, FraserKeppie, Uwe Kroner, Fernando Ortega-Gutiérrez, R. Damien Nance, CecilioQuesada, Roberto S. Molina-Garza, Barbara M. Martiny, James Sears, ChrisSmith, y Axel Renno. También me gustaría agradecer a los miembros de micomité tutoral: Luigi Solari, Fernando Ortega-Gutiérrez, Duncan Keppie,y Brendan Murphy, así como el comité de mi examen predoctoral: ElenaCenteno-García, Peter Schaaf, Gustavo Tolson, y Dante J. Morán Zentenopor su tiempo y el asesoramiento profesional. Peter Schaaf, Bodo Weber,Luca Ferrari, W. Gary Ernst, y dos revisores anónimos son reconocidos porproporcionar revisiones constructivas de los manuscritos de los artículosque forman parte de esta tesis. Gracias a Roberto S. Molina-Garza y MaríaClara Zuluaga Velez por tomarse el tiempo para corregir la versión españolade la tesis.
Deseo extender un agradecimiento especial a la secretaria académica Mar-ta Pereda Miranda y la abogada Lic. Ana Paola González Cruz del Centro
vii
de Geociencias. Sin su ayuda competente me hubiera perdido en la junglade la burocracia académica.
Agradezco al Consejo Nacional de Ciencia y Tecnología y a la DirecciónGeneral de Estudios de Posgrado de la UNAM por las becas otorgadaspara la realización de mis estudios de doctorado. Además agradezco laCoordinación de Posgrado por el apoyo financiero brindado en la impresiónde la tesis.
Por último, deseo expresar mi profundo y sincero agradecimiento a mispadres, Bettina y Frank-Michael, y sus respectivas parejas Michael Freitagy Heike Kirsch, mi hermana Steffi, mis abuelos Ruth y Otto, y Brigitta ySiegfried, que me han aconsejado y apoyado a lo largo de mi educación.Gracias también a los padres de María, Martina y Johannes Helbig, por sugenerosidad y su perspectiva fresca. A mis amigos, tanto aquí en México– Domingo, María de la O, Oscar, Lina, Lariza, Gianluca, Daniele, Matteo,Ramón, Alma, Mario, Fabián, y el equipo de básquet INDEREQ – como losamigos de mi tierra: Martin, Matt, Bob, Mathias, Mel, Paul, Jo, y Nadja: lesdebo demasiado. Gracias por todos los buenos momentos! Estoy especial-mente agradecido a mi novia Maria, por su amor, aliento y su compañía enesta aventura mexicana. Tú eres la luz de mi vida.
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Í N D I C E G E N E R A L
1 introducción 1
1.1 Marco geológico . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Motivación, objetivos y metodología . . . . . . . . . . . . . . . 5
2 geoquímica y geocronología de las unidades del carbo-nífero–pérmico 10
3 historia estructural del plutón totoltepec 33
4 eventos del paleozoico tardío hasta el mesozoico tem-prano en la periferia de pangea 58
5 resumen y conclusión 76
a métodos analíticos 80
a.1 Geocronología U-Pb . . . . . . . . . . . . . . . . . . . . . . . . 80
a.2 Geoquímica . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
a.3 Geocronología 40Ar-39Ar . . . . . . . . . . . . . . . . . . . . . 81
b tablas geocronología u-pb 83
c tablas geoquímica 117
d tablas análisis de microsonda 138
e tablas geocronología40
ar/39ar 146
bibliografía 148
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1I N T R O D U C C I Ó N
Esta tesis se concentra en el estudio del plutón Totoltepec de edad Carbo-nífero–Pérmico y sus rocas encajonantes (parte del Complejo Acatlán), conénfasis en la geoquímica y el control estructural en el emplazamiento delplutón. A pesar de que la geoquímica publicada (basada en 6 muestras: Ma-lone et al., 2002) muestra una afinidad de arco, estos datos no fueron sufi-cientes para distinguir entre magmas formados en una zona de subduccióny magmas contaminados por la corteza continental (Pearce y Peate, 1995;Turner et al., 1996; Kuscu et al., 2010). Un muestreo más amplio y un conjun-to más exhaustivo de los elementos y los isótopos analizados constituyenla base para este estudio. Se obtuvieron datos geocronológicos adicionalesde U-Pb para determinar la edad y duración del evento de intrusión, com-plementándose con edades de 40Ar/39Ar para conocer también la historiatectono-térmica. El estudio además incluye análisis geocronológicos y geo-químicos de las rocas sedimentarias contemporáneas a la intrusión para loscuales no existían ningunos datos de este tipo. Aunque estudios anterioreshan sugerido que el emplazamiento del plutón Totoltepec fue sintectónico,los controles estructurales no eran conocidos. La base de datos mejoradaque aporta este estudio permite el desarrollo de un modelo estructural parael emplazamiento del plutón. Estas conclusiones se utilizan para documen-tar el desarrollo de un arco regional y para diferenciar entre los diferentesmodelos paleogeográficos para el Complejo Acatlán con respecto a Pangea(Keppie et al., 2010; Vega-Granillo et al., 2009; Böhnel, 1999).
1.1 marco geológico
Con una extensión superficial que supera los 10,000 km2, el ComplejoAcatlán de edad Ordovícico al Pérmico Medio constituye el basamento delterreno Mixteca y el mayor afloramiento de rocas paleozoicas en México(Ortega-Gutiérrez, 1978; Campa y Coney, 1983; Sedlock et al., 1993; Keppie,2004). Las rocas expuestas en la región de Acatlán registran una historiapaleozoica tectonotermal muy compleja que refleja la apertura y el cierrede una o más cuencas oceánicas y sus consiguientes interacciones continen-tales que culminaron en la amalgamación de Pangea (por ejemplo, Nanceet al., 2006). Estos eventos fueron acompañados por subducción durante elDevónico hasta el Pérmico a lo largo del sur de México (Keppie et al., 2008).
El Complejo Acatlán está limitado al este por la falla de Caltepec, una zo-na de cizalla con dirección N–S y mecanismo dextral, que lo separa de losgneises en facies de granulita de ∼1.0 Ga del Complejo Oaxaqueño (Elías-Herrera y Ortega-Gutiérrez, 2002). Al sur, está limitado por la falla Cenozoi-ca La Venta-Chacalapa (Tolson, 2007; Solari et al., 2007), que lo yuxtapone
1
1.1 marco geológico 2
contra las rocas plutónicas y metamórficas de alto grado del Complejo Xo-lapa (Pérez-Gutiérrez et al., 2009). Hacia el oeste, sobreyace en forma de ca-balgadura sobre carbonatos cretácicos de la plataforma Guerrero-Morelos,que están expuestos entre el Complejo Acatlán y el terreno compuesto deGuerrero (Centeno-García et al., 2008; Ramos-Arias y Keppie, 2011). Haciael norte, se encuentra cubierto discordantemente por rocas sedimentariasde origen continental y marino de edad Pérmico Superior–Jurásico Medio(Morán-Zenteno et al., 1993; Centeno-García et al., 2009), así como por rocasvolcánicas y volcaniclásticas del Mioceno Medio y Tardío de la Faja Volcá-nica Transmexicana (Ferrari et al., 1999).
El área de estudio se encuentra en la parte oriental del Complejo Acatlán,a unos 30 km al este de Acatlán de Osorio (estado de Puebla). Está limitadode forma aproximada por los pueblos Xayacatlán de Bravo al oeste, SantoDomingo Tianguistengo al este y San José Chichihualtepec al sur. Las ro-cas estudiadas ocurren en el bloque tectónico Tonahuixtla (Morales-Gámezet al., 2009), que está limitado en ambos lados por fallas normales-dextralesde rumbo N–S. En base a los mapas geológicos publicados (Ortega-Gutiérrez,1978; Malone et al., 2002; Keppie et al., 2004a), la estratigrafía del área de es-tudio está conformada por las siguientes unidades litotectónicas: el plutónTotoltepec, la Formación Tecomate y la Formación Cosoltepec. A continua-ción se resumen los datos publicados sobre cada una de estas unidades yse identifican las problemáticas científicas que se tratan de resolver en esteestudio.
El plutón Totoltepec, con una superficie de afloramiento de 15 × 5 km,constituye la parte central del área de estudio. El cuerpo intrusivo fue nom-brado por Fries et al. (1970) y primero cartografiado por Ortega-Gutiérrez(1975), como parte de su trabajo pionero en el Complejo Acatlán. De acuer-do con Ortega-Gutiérrez (1978), el plutón está en contacto intrusivo conrocas del Subgrupo Acateco y la Formación Cosoltepec (Grupo Petlalcingo,Fig. 1). Por otro lado, Malone et al. (2002) y Keppie et al. (2004a) ubican elplutón Totoltepec en el bloque cabalgante de una gran falla, estructuralmen-te sobreyaciendo las formaciones Tecomate y Cosoltepec. Hacia el norte, elplutón está sobreyacido discordantemente por capas rojas deformadas, perosin metamorfismo, de edad inferida jurásica (Malone et al., 2002).
El plutón Totoltepec está conformado principalmente por diorita de horn-blenda, trondhjemita y tonalita (Malone et al., 2002). Las fracciones de cir-cón de una fase félsica han dado una edad concordante U-Pb TIMS de 287
± 2 Ma (Yañez et al., 1991), mientras que una fase máfica de la parte surdel plutón dio una edad U-Pb TIMS de 289 ± 1 Ma (Keppie et al., 2004a).Ortega-Gutiérrez (1975) ha documentado cuerpos de gneises máficos de es-tructura migmática y bandeada en el margen norte del plutón Totoltepec,que Calderón-García (1956) sospecha pertenecen al basamento de la zona.La edad de estas rocas máficas marginales y su significado geodinámico esdesconocido.
Una cantidad limitada de datos estructurales del plutón (Malone et al.,2002; Morales-Gámez et al., 2009) sugieren la presencia de una foliación de
1.1 marco geológico 3
251260271
299
318
359
385
398
416428423444
461
472488501
510521
542
245235
Fm. CosoltepecFm. Xay-acatlán
FormaciónPatlanoaya(Dev. tardío –Pérmico medio)
GrupoPatlanoaya
& Fm.Tecomate
Fm. Chazumba
Gru
po P
iaxt
la
Mig. Magdalena
Orogenia Acateca(facies eclogita)
Fm. TecomategranitoidesEsperanza
PlutónLa Noria
(337±34 Ma)
PlutónTotoltepec (287±2 Ma)
PlutónTotoltepec
Orogenia Mixteca(facies esquisto verde)
Exumaciónde rocas de alta presión
(facies eclogita)
Evento Orogénico(facies esquisto verde)
Ortega-Gutiérrez et al. (1999)
Huerta, Amate, Las
Minas
magmatismobimodal
(480–440 Ma)
Nance et al. (2006)Keppie et al. (2008)
Unidad Salada ,
Cosoltepec
(440±14 Ma)
Grupo
Petlalcingo
P
C
D
S
O
_
^
Figura 1: Diagrama de relaciones espaciales y temporales que muestra la tectono-estratigrafía tradicional (izquierda) y revisada (derecha) del ComplejoAcatlán. Figura modificada de Ortega-Gutiérrez et al. (1999); Nance et al.(2006); Keppie et al. (2008).
rumbo norte y buzamiento de alto ángulo, así como pliegues de direcciónN–S, por cual la foliación se encuentra plegada a nivel local. Además, Malo-ne et al. (2002) sugieren que el emplazamiento del plutón puede haber sidosintectónico con respecto a la deformación regional.
Datos geoquímicos de un estudio de reconocimiento de rocas del putónTotoltepec reflejan una afinidad calco-alcalina (Malone et al., 2002). Isotópi-camente, el plutón Totoltepec ha dado valores de εNd(t) más positivos yedades modelo TDM más jóvenes (Yañez et al., 1991) en comparación a plu-tones contemporáneos en el sur de México, lo que indica que proviene deuna fuente de carácter más juvenil. La intrusión ha sido interpretada comoparte de un arco continental Pérmico–Triásico que se extiende a lo largo deMéxico centro-oriental (Torres et al., 1999; Malone et al., 2002; Keppie et al.,2004a). Alternativamente, de acuerdo con su modelo paleogeográfico, Vega-Granillo et al. (2009) consideran el plutón como un producto de la colisióncontinental y una expresión local de la orogenia Ouachita-Alleganiana.
La Formación Tecomate, originalmente definida por Rodríguez-Torres(1970), es una unidad clástica ligeramente metamorfoseada, pero intensa-mente deformada que consiste en alternancias de rocas psammiticas-pelíti-cas, mármoles y conglomerados de cantos rodados, así como rocas volcáni-cas que principalmente están formadas por flujos y tobas con escasas unida-des félsicas (Ortega-Gutiérrez, 1993; Sánchez-Zavala et al., 2000). En su áreatipo, la Formación Tecomate ocurre en una zona de cizalla subvertical deorientación N–S situado entre la ciudad de Acatlán de Osorio y el pueblode El Tecomate (Ortega-Gutiérrez, 1975), pero rocas correlacionables con la
1.1 marco geológico 4
Formación Tecomate también afloran localmente en los sectores norte y es-te (por ejemplo, Ortega-Gutiérrez et al., 1999), así como el sector oeste delComplejo Acatlán (Talavera-Mendoza et al., 2005; Vega-Granillo et al., 2009).Según mapas geológicos publicados de la zona de estudio, la FormaciónTecomate está en contacto con el plutón Totoltepec en su margen sur y este(Ortega-Gutiérrez et al., 1999), así como en sus bordes suroriente y oeste(Keppie et al., 2004a).
La edad de depositación de la Formación Tecomate es sujeto de controver-sia. Originalmente, se infirió como Devónica (Fig. 1) basada principalmenteen la presencia de equinodermos, crinoides, blastoideos y micromoluscosde edad pre-Carbonífero obtenidos en esta unidad (Ortega-Gutiérrez, 1993)y en la interpretación de que la formación está intruida por el granito LaNoria (Ortega-Gutiérrez et al., 1999), de los cuales datos U-Pb (circón) in-dicaban una edad Devónico Tardío. Sin embargo, más recientemente, lafauna recuperada de tres horizontes diferentes de mármol ha permitidoprecisar una edad pérmica temprana a media para la depositación de laFormación Tecomate en el área tipo (Keppie et al., 2004b). Estas restriccio-nes paleontológicos han sido corroboradas por edades U-Pb SHRIMP deaproximadamente 320–264 Ma de circones separados de cantos de granitoen los metaconglomerados de la Formación Tecomate en la parte orientaldel Complejo Acatlán. Sin embargo, datos geocronológicos publicados dela Formación Tecomate (Keppie et al., 2004b; Sánchez-Zavala et al., 2004;Talavera-Mendoza et al., 2005) sugieren que la unidad, como se define ac-tualmente, puede ser de diferentes edades en diferentes lugares.
La Formación Tecomate ha sido interpretada como un sedimento sino-rogénico depositado posterior al emplazamiento de una capa cabalgante(Ortega-Gutiérrez, 1993; Weber et al., 1997), una secuencia turbidítica rela-cionada a un arco volcánico depositado en la zona frontal de una colisiónde arco-continente (Sánchez-Zavala et al., 2000), un depósito de arco y deextensión intracontinental (Talavera-Mendoza et al., 2005) y un sedimentomarino somero de ante-arco (Keppie et al., 2004b).
Basado en el traslape de las edades de depósito y similitudes faunísticas,la Formación Tecomate se ha correlacionado con la Formación San SalvadorPatlanoaya de edad Devónico Superior a Pérmico Inferior en la parte nortedel Complejo Acatlán (Keppie et al., 2004b). Sin embargo, a diferencia de laFormación Tecomate que ha sido deformada en forma penetrativa y afecta-da por metamorfismo en facies del esquisto verde, la Formación Patlanoayano está metamorfoseada y casi no ha sido deformada.
Mediciones de la forma de clastos en metaconglomerados de la Forma-ción Tecomate en el área de estudio cerca de San José Chichihualtepec handado esferoides alargados, con dimensiones típicos de la deformación trans-tensional (Morales-Gámez et al., 2009). Una edad 40Ar/39Ar de 263 ± 3 Mapara una filita sericítica de la Formación Tecomate adyacente a la zona deestudio ((Morales-Gámez et al., 2009) define el límite de edad de esta de-formación. Adicionalmente, se ha documentado cizallamiento lateral N–Sentre aproximadamente 307 y 269 Ma a lo largo de la falla Caltepec (Elías-
1.2 motivación, objetivos y metodología 5
Herrera y Ortega-Gutiérrez, 2002; Elías-Herrera et al., 2005). El significadodel mecanismo y los límites temporales de la deformación con respecto a laconfiguración paleogeográfica regional y su papel en el emplazamiento delplutón Totoltepec permanecen inexplorados.
Se ha reportado que la Formación Cosoltepec aflora en la parte sur dela zona de estudio, donde está en contacto con el plutón Totoltepec en susmárgenes sur y oeste (Ortega-Gutiérrez, 1978; Ortega-Gutiérrez et al., 1999;Malone et al., 2002). En el mapa geológico de Keppie et al. (2004a), las rocasde la Formación Cosoltepec sólo afloran en una zona estrecha a lo largodel límite suroeste del plutón Totoltepec. La Formación Cosoltepec está de-finida como una secuencia monótona de metapelitas y metapsamitas conescasas intercalaciones de anfibolita. Originalmente la unidad fue incluidaen el Grupo Petlalcingo de edad Cámbrico–Ordovícico (Ortega-Gutiérrez,1978), pero trabajos geocronológicos recientes han identificado grupos decircones detríticos más jóvenes de edad Ordovícico (∼455 Ma: Keppie et al.,2004a, 2006), Devónico-Carbonífero (∼410 y/o ∼374 Ma: Talavera-Mendozaet al., 2005), o de edad Carbonífero (∼352 Ma: Morales-Gámez et al., 2008)en las unidades asignadas originalmente a la Formación Cosoltepec; estoindica que está compuesta por diferentes unidades. El ambiente tectónicopara la depositación de las rocas de la Formación Cosoltepec sigue siendoparte de la discusión en curso, ya que la unidad ha sido interpretada co-mo un prisma de acreción (Ortega-Gutiérrez et al., 1999), una secuencia delmargen pasivo (Talavera-Mendoza et al., 2005; Vega-Granillo et al., 2007) oun depósito de la eminencia continental (Keppie et al., 2006).
1.2 motivación, objetivos y metodología
Basado en una serie de estudios de reconocimiento del área (por ejem-plo, Yañez et al., 1991; Malone et al., 2002; Keppie et al., 2004a,b), el plutónTotoltepec y la Formación Tecomate son propuestos como pertenecientes aun arco magmático continental del Pérmico–Triásico que se extiende desdeel suroeste de los Estados Unidos y continua a lo largo de México centro-oriental (Centeno-García y Silva-Romo, 1997; Torres et al., 1999; Dickinsony Lawton, 2001). Sin embargo, la existencia de este arco se basa en (i) unacantidad limitada de datos geocronológicos, la mayoría de los cuales se hanobtenido utilizando métodos isotópicos K-Ar y Rb-Sr (por ejemplo, Torreset al., 1999; Schaaf et al., 2002; Yañez et al., 1991) que son conocidos por serindicadores menos confiables para establecer la edad de cristalización de unplutón en comparación a la geocronología U-Pb de circones (por ejemplo,Steiner y Walker, 1996), y (ii) escasos datos geoquímicos de rocas ígneas delPaleozoico tardío en México (Torres et al., 1999; Solari et al., 2001; Maloneet al., 2002; Rosales-Lagarde et al., 2005; Arvizu et al., 2009). Por otra parte,una firma geoquímica de arco en las rocas ígneas de composición félsicae intermedia suele interpretarse como una evidencia directa de magmatis-mo de arco contemporáneo. Sin embargo, modelos para la generación demagma intermedio y silícico incluyen tanto la diferenciación de magmas
1.2 motivación, objetivos y metodología 6
máficos derivados del manto por cristalización fraccionada dentro de lacorteza o el manto superior (por ejemplo, Gill, 1981), como la fusión parcialde rocas de la corteza pre-existente (por ejemplo, Thompson, 1982). Por lotanto, una firma geoquímica de arco en rocas ígneas de composición félsi-ca o intermedia puede ser adquirido como resultado de la subducción delitosfera oceánica (por ejemplo, Pearce y Peate, 1995), o por la fusión dela corteza continental que ha sido generada por procesos de subducción(por ejemplo, Turner et al., 1996; Kuscu et al., 2010). La composición isotópi-ca y/o la abundancia de xenolitos de granulita en las rocas ígneas que seutilizaron para definir el arco magmático continental del Pérmico–Triásicoindican que están significativamente contaminados por la corteza continen-tal. El terreno Oaxaquia, que incluye rocas de aproximadamente 1.0 Ga delnúcleo cristalino de México, registra un episodio de magmatismo de arcoentre aproximadamente 1300 y 1200 Ma (Keppie y Ortega-Gutiérrez, 2010).Por lo tanto, las abundancias de los elementos exhibidos por las rocas dearco principalmente félsicas, derivados de la corteza o contaminados queintruyen el basamiento de tipo Oaxaquia, puede reflejar una herencia enlugar de una firma de arco original. Antes de poder utilizar estas rocaspara reconstruir la evolución de un arco magmático, el origen de la firmageoquímica con respecto a la generación de magmas félsicos tiene que serevaluado críticamente. Se necesitan más datos y una evaluación rigurosade éstos para demostrar de manera incuestionable la existencia de un arcoregional del Paleozoico tardío. En este estudio, datos geocronológicos, geo-químicos y estructurales del plutón Totoltepec son combinados con datosgeoquímicos y geocronológicos de rocas volcaniclásticas contemporáneasde la Formación Tecomate, para proporcionar un modelo de los procesosrelacionados con la subducción en diferentes niveles de la corteza y ade-más refinar las características temporales y espaciales, así que la evolucióndel arco propuesto.
En cinturones orogénicos el plutonismo granitoide se presenta con fre-cuencia asociado espacial y temporalmente con sitios de deformación acti-va (Hutton, 1988), donde el ascenso y el emplazamiento de magma puedenser controlados por zonas de cizallamiento de niveles corticales profundos(Brown y Solar, 1998). En un estudio de reconocimiento, Malone et al. (2002)observaron que los diques que cortan la foliación de forma oblicua en el plu-tón Totoltepec contienen una foliación interna paralela a sus márgenes deldique, lo que sugiere un posible emplazamiento sintectónico con respec-to a la deformación regional. Sin embargo, no existen datos estructuralesdefinitivos que establezcan los plazos de la deformación en relación al es-tado de cristalización del plutón (siguiendo los criterios de, por ejemplo,Blumenfeld y Bouchez, 1988; Paterson et al., 1989, 1991; Miller y Paterson,1994) para sustanciar la naturaleza sin-cinemática de intrusión. Mostrar queel emplazamiento del plutón fue acompañado por deformación regional esde suma importancia, ya que los plutones sintectónicos bien datados sepueden utilizar para evaluar la temporalidad, el mecanismo y la historiatérmica de la deformación regional (por ejemplo, Ingram y Hutton, 1994;
1.2 motivación, objetivos y metodología 7
Tribe y D’Lemos, 1996). Teniendo en cuenta los trabajos anteriores, que hanrelacionado el plutón Totoltepec con un arco magmático regional, un plutónemplazado sintectónicamente marcaría un lugar excepcionalmente adecua-do para investigar la cinemática y el desarollo geodinámico de un sistemade falla en un arco continental antiguo y explorar la relación entre el mag-matismo granitoide y la deformación en un margen de placa convergente.Este estudio demuestra que el emplazamiento fue contemporáneo con la de-formación, proporciona límites en cuanto a profundidad de emplazamiento,tasa de exhumación e historia de enfriamiento del plutón, empleando unacombinación de geocronología U-Pb y 40Ar/39Ar, el análisis de meso y mi-crofábrica y de termobarometría de aluminio en hornblenda. Además, elestudio identifica el desarrollo de las fábricas, la secuencia temporal y losmecanismos de emplazamiento de las diversas fases intrusivas. Por otraparte, se desarrolla un modelo que pretende explicar el emplazamiento delplutón en el contexto de fallamiento regional de orientación N–S y meca-nismo transcurrente-dextral. Estos datos ayudan a entender la cinemáticadel sistema de fallas que permitió el emplazamiento y la exhumación delplutón como un medio para reconstruir la evolución geodinámica del arcomagmático del Paleozoico tardío.
Existen dos modelos en competencia concernientes a la posición paleo-geográfica del terreno Mixteco en relación a la configuración de Pangea enel Paleozoico. Keppie et al. (2010) y Weber et al. (2007) ubican el terreno Mix-teca en el margen activo occidental de Pangea, mientras que Vega-Granilloet al. (2009) consideran que el terreno se ubicó en la zona de colisión en-tre Gondwana y Laurentia. Un tercer modelo, que se basa en un modeloalternativo de Pangea (Pangea-B, Irving, 1977; Morel y Irving, 1981) invo-cando un mega-sistema de cizallamiento dextral, coloca el terreno Mixtecafrente al nordeste de Canadá en el Jurásico (Böhnel, 1999). Por lo tanto,la ubicación del terreno Mixteca en el sur de México en las reconstruccio-nes paleogeográficas del Paleozoico tardío tiene implicaciones profundaspara las hipótesis Pangea-A y -B. En este estudio, se evalúan los diferen-tes escenarios; la evaluación se basa en determinar la fuente de magmay el mecanismo de emplazamiento del plutón Totoltepec, así como el am-biente tectónico y la procedencia de la Formación Tecomate. A su vez, es-to permite evaluar el significado geodinámico de estas rocas en relacióncon la amalgamación y la desintegración de Pangea. Dependiendo de si laubicación paleogeográfica del terreno Mixteca en el Paleozoico tardío eraperiférica o interna con respecto a Pangea, el magmatismo y los procesosde formación de cuenca caracterizados por el plutón Totoltepec y la For-mación Tecomate representan eventos relacionados a la subducción en unorógeno periférico del tipo andino, o eventos colisionales parecidos a las dela orogenia Ouachita-Alleganiana en el sur de los Apalaches. Estos procesosdel Paleozoico tardío en cualquier de los dos ambientes tectónicos posiblesson pertinentes a un proceso importante de escala global que involucra latransferencia de las zonas de subducción desde el interior de Pangea a laperiferia (por ejemplo, Murphy y Nance, 2008; Murphy et al., 2009).
1.2 motivación, objetivos y metodología 8
En la primera sección de este trabajo se presentan los datos geológicos decampo, petrografía, geocronología U-Pb de circones y geoquímica de ele-mentos mayores y trazas, así como geoquímica isotópica de Sm-Nd parael plutón Totoltepec y la Formación Tecomate de la zona de estudio. Lasdescripciones detalladas de las metodologías están incluidas en el Apén-dice A.1. Las edades de cristalización de las fases plutónicas y las edadesdetríticas de las rocas metasedimentarias fueron obtenidas por medio de laablación láser (LA-ICP-MS) en el Laboratorio de Estudios Isotópicos (LEI),Centro de Geociencias, UNAM. Los granos de circón fueron separados utili-zando diferentes protocolos analíticos con el fin de maximizar la pureza delconcentrado obtenido, así como minimizar cualquier sesgo. Se realizaronobservaciones por catodoluminiscencia (CL) antes de los análisis LA-ICP-MS para ayudar a la selección de puntos y para aumentar la interpretabi-lidad geológica de los resultados. Los datos de edad son utilizados paraestablecer la secuencia de intrusión del plutón Totoltepec, la edad máximade sedimentación y la procedencia de la Formación Tecomate en el área deestudio. Los datos geoquímicos (véase el Apéndice A.2 para detalles me-todológicos), obtenidos del Regional Geochemical Centre de Saint Mary’sUniversity en Nueva Escocia, Canadá, se utilizan para evaluar el ambientetectónico del plutón Totoltepec y la Formación Tecomate. Datos isotópicosde Sm-Nd, adquiridos del Atlantic Universities Regional Isotopic Facility(AURIF), Memorial University en Terranova, Canadá, se emplean como tra-zador tectónico para investigar la fuente de magma del plutón Totoltepec ypara proporcionar información sobre la procedencia de las rocas de la For-mación Tecomate; éstos complementan los datos geocronológicos. Tambiénse incluye una revisión de los datos geocronológicos, geoquímicos e isotó-picos de los sistemas magmáticos aproximadamente coetáneos en México yGuatemala así como propios datos geoquímicos e isotópicos de los plutonesCozahuico y La Carbonera en el Complejo Oaxaqueño.
La segunda sección de la tesis contiene datos meso- y micro-estructurales,petrográficos, de microsonda, termobarométricos y geocronológicos del plu-tón Totoltepec; éstos se utilizan para investigar la historia de emplazamientodel plutón y su significado en el desarrollo geodinámico del arco continen-tal del Paleozoico tardío en el sur de México. Se llevó a cabo un extensotrabajo de campo para documentar las relaciones de contacto internos yexternos al plutón, recabar datos estructurales, así como muestrear parasecciones delgadas, análisis de microsonda y análisis geocronológicos. Lasobservaciones petrográficas de láminas delgadas y los análisis de microson-da se utilizan para examinar la asociación de fases y para determinar lacomposición de algunos minerales. La historia de la deformación del plu-tón está reconstruida sobre la base de microestructuras distintivas que sedesarrollan por diferentes mecanismos de recristalización dinámica. Con elfin de obtener una estimación de la profundidad del emplazamiento y latasa de exhumación, se emplea una combinación de termobarometría Al-en-hornblenda y dataciones por el método 40Ar/39Ar. Los datos químicosde plagioclasa y hornblenda coexistente fueron obtenidos mediante micro-
1.2 motivación, objetivos y metodología 9
sonda electrónica y espectrometría de dispersión por longitud de onda enel Laboratorio Universitario de Petrología (LUP) del Instituto de Geofísica(UNAM) en la Ciudad de México. Los fechamientos de moscovita median-te 40Ar/39Ar se llevaron a cabo por un procedimiento de calentamientoen pasos con láser en el Geochronology Research Laboratory de Queen’sUniversity en Kingston, Canadá (véase el Apéndice A.3 para las especifica-ciones técnicas y detalles del método analítico). En conjunto, estos datos seutilizan para explicar la intrusión, deformación y exhumación del plutónen el contexto del marco estructural regional.
La tercera sección está constituida por una guía de una excursión geo-lógica, publicada como parte del Programa Internacional de CorrelaciónGeológica Proyecto 597 (IGCP—amalgamación y ruptura de Pangea) y la108
a Reunión Anual de la Sección Cordillerana del GSA en Querétaro, Mé-xico (28 a 31 marzo 2012). La guía da una visión general de los eventos delPensilvánico–Jurásico en la periferia de Pangea. El capítulo correspondientea la zona de estudio describe las relaciones de campo en una serie de aflo-ramientos considerados principales y resume datos publicados. Además,contiene datos nuevos de geocronología U-Pb y 40Ar/39Ar, geoquímica ygeoquímica isotópica Sm-Nd.
2G E O Q U Í M I C A Y G E O C R O N O L O G Í A D E L A S U N I D A D E SD E L C A R B O N Í F E R O – P É R M I C O
Artículo: Kirsch, M., Keppie, J.D., Murphy, J.B., y Solari, L.A., 2012, Permi-an–Carboniferous arc magmatism and basin evolution along the westernmargin of Pangea: geochemical and geochronological evidence from theeastern Acatlán Complex, southern Mexico: Geological Society of AmericaBulletin, en prensa, doi: 10.1130/B30649.1.
Contribuciones individuales de los autores:
Moritz Kirsch: concepción y diseño del estudio; trabajo de campo elcual incluye mapeo, selección de puntos de muestreo y toma de mues-tras para análisis de geoquímica y geocronología U-Pb; adquisición delos datos LA-ICP-MS, incluyendo la separación de circones y catodo-luminiscencia; revisión de literatura; análisis e interpretación de datos;redacción del artículo.
J. Duncan Keppie: contribución a la concepción y el diseño; supervi-sión de las actividades de campo; participación en la interpretación delos datos y en la revisión del artículo remitido; adquisición de fondos.
J. Brendan Murphy: contribución a la concepción y el diseño; supervi-sión de las actividades de campo; participación en la interpretación delos datos y en la revisión del artículo remitido; adquisición de fondos.
Luigi A. Solari: participación en la interpretación de datos y en la revi-sión del artículo remitido; responsable de las instalaciones de análisisLA-ICP-MS.
10
Permian–Carboniferous arc magmatism and basin evolution along the western margin of Pangea: Geochemical and geochronological
evidence from the eastern Acatlán Complex, southern Mexico
Moritz Kirsch1,†, J. Duncan Keppie2, J. Brendan Murphy3, and Luigi A. Solari1
1Centro de Geociencias, Universidad Nacional Autónoma de México, Campus Juriquilla, 76230 Querétaro, QRO, Mexico2Departamento de Geología Regional, Instituto de Geología, Universidad Nacional Autónoma de México, 04510 México D.F., Mexico3Department of Earth Sciences, St. Francis Xavier University, Antigonish, Nova Scotia B2G 2W5, Canada
ABSTRACT
In the Acatlán Complex of southern Mex-ico, a late Paleozoic assemblage, consisting of a gabbro-diorite-tonalite-trondhjemite suite (Totoltepec pluton) and clastic-calcareous metasedimentary rocks (Tecomate Forma-tion), postdates collisional orogeny that re-sulted in the amalgamation of Pangea. This region offers a rare opportunity to examine assemblages developed at different crustal levels along the periphery of Pangea at the critical stage between amalgamation and breakup. The Totoltepec pluton consists of minor mafi c-ultramafi c rocks (306 ± 2 Ma; concordant U-Pb zircon analysis) that are marginal to the main mafi c-felsic intrusion (289 ± 2 Ma). Geochemistry of the marginal rocks indicates an arc tholeiitic to calc-alka-line character with high large ion litho-phile elements (LILEs)/high fi eld strength elements (HFSEs), fl at rare earth element (REE) patterns, and initial εNd values of +1.3 to +3.3. The younger Totoltepec phase exhibits a calc-alkaline trace-element geo-chemistry with fl at to moderately fraction-ated light (L) REE–enriched patterns and initial εNd values of –0.8 to +2.6, which are also consistent with an arc environment. The Sm-Nd isotopic signature is more primitive compared to contemporaneous arc-related igneous rocks in southern Mexico, suggest-ing the pluton was emplaced in a less ma-ture, outboard part of the arc, and/or along a fault conduit. The Tecomate Formation, as currently defi ned, is a composite of lithologi-cally similar strata deposited in several fault-bounded basins ranging from Carboniferous to Early Permian in age. To the south of the
Totoltepec pluton, the depositional age of the Tecomate Formation is tightly constrained in one section to ca. 300 Ma, but in another sec-tion, it is between ca. 288 and ca. 263 Ma. The Tecomate Formation rocks are interpreted to have been derived from a late Paleozoic arc based on (1) arc-related geochemistry, (2) εNd(t) values ranging from –5.6 to +0.3 (t = 288 Ma) that overlap those of the Totoltepec pluton, and (3) detrital zircons with predomi-nantly Carboniferous–Permian ages. The Totoltepec and Tecomate units in the study area form part of a continental arc extending from Guatemala to California, which neces-sitates subduction of the paleo-Pacifi c oce-anic lithosphere beneath the western margin of a Pangea-A confi guration.
INTRODUCTION
Although it is accepted that Pangea had largely been assembled by the Carboniferous–Permian, two competing models have been proposed for the late Paleozoic confi guration of the supercontinent: Pangea-A, essentially the “Wege nerian” fi t (Bullard et al., 1965; Smith and Hallam, 1970), and Pangea-B (Irving, 1977; Morel and Irving, 1981; Muttoni et al., 2003), which is based on the paleomagnetic data in which Gondwana is positioned ~3000 km farther east relative to Laurasia. In paleogeo-graphic reconstructions of Pangea-A, southern Mexico occupies a position similar to its present location relative to North America (Figs. 1A and 1B; e.g., Fang et al., 1989; Alva-Valdivia et al., 2002), whereas in reconstructions of Pangea-B, southern Mexico is placed off eastern Canada during the Jurassic (Fig. 1C; Böhnel, 1999). There are also variants of the Pangea-A recon-struction, in which southern Mexico is either peripheral (Keppie, 2004; Keppie et al., 2008a, 2010; Fig. 1A) or internal to Pangea, between
the Maya terrane and the southern United States (Talavera-Mendoza et al., 2005; Vega-Granillo et al., 2007, 2009; Fig. 1B).
Based on reconnaissance studies (e.g., Keppie et al., 2004a), the Totoltepec pluton and the Tecomate Formation in the eastern Acatlán Complex (Mixteca terrane) of southern Mexico are inferred to be part of a late Paleozoic con-tinental arc assemblage that extended from the south ern United States through Mexico to the northern Andes (Torres et al., 1999; Dickinson and Lawton, 2001). Alternatively, in accordance with their hypothesized within-Pangea location, Vega-Granillo et al. (2009) attributed late Paleo-zoic tectonothermal events in southern Mexico (including the eastern Acatlán Complex) to be related to continental collision (Alleghanian orogeny). In order to test the validity of these contrasting models, we investigated the tectonic setting of the Totoltepec pluton and Tecomate Formation using a combination of new geo-chemical, isotopic, and geochronological data. Examining magmatic systems in conjunction with sedimentary rocks enables the expression of tectonic events at different crustal levels to be documented.
Almost all of the crystallization ages of plu-tons used by Torres et al. (1999) to constrain the age of the hypothesized magmatic arc were obtained using K-Ar or Rb-Sr isotopic methods, which are known to be susceptible to postcrystallization processes and hence may be less precise than U-Pb zircon geochronology in obtaining ages of magmatic crystallization. The central phase in the Totoltepec pluton has been investigated by reconnaissance U-Pb geo-chronology (Yañez et al., 1991; Keppie et al., 2004a). However, mafi c igneous rocks at the margin of the Totoltepec pluton have not been dated, so the age range of the pluton is not con-strained, and its regional signifi cance is unclear. Although the existence of a Permian–Triassic
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GSA Bulletin; September/October 2012; v. 124; no. 9/10; p. 1607–1628; doi:10.1130/B30649.1; 15 fi gures; 1 table; Data Repository item 2012220.
†E-mails: [email protected]; [email protected]
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Kirsch et al.
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arc in Mexico has been proposed (e.g., Torres et al., 1999; Dickinson and Lawton, 2001; Centeno-García, 2005), geochemical data of late Paleozoic igneous rocks that would test this pro-posal are scarce (Torres et al., 1999; Solari et al., 2001; Malone et al., 2002; Rosales-Lagarde et al., 2005; Arvizu et al., 2009). Thus, neither the age nor the geochemistry of the magmatism, which are both crucial in assessing its potential geodynamic connection to the evolution of Pan-gea, is precisely constrained. We present U-Pb geochronology coupled with geochemical and Sm-Nd isotopic data to refi ne the age range of the hypothesized late Paleozoic arc in southern Mexico and to assess its geo dynamic signifi -cance relative to the amalgamation and breakup of Pangea.
Sedimentary sequences containing detritus from an orogenic source provide complemen-tary data that can be used to constrain the role of basin formation as well as uplift and exhuma-tion of the crust during orogenesis. Conglomer-ates in the Tecomate Formation in the study area contain granitic pebbles (Keppie et al., 2004b), suggesting a potential linkage between magma-tism and basin evolution. However, based on the available data, it is unclear whether the Teco-mate Formation, which has been mapped on the basis of lithologic comparison, is the same age in different locations. In this paper, we investi-gate this possibility by providing U-Pb laser-ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) age data of single detrital zircon grains to help constrain the depo-sitional age of the Tecomate Formation in the study area as well as enable a comparison with the equivalent data from the type area in the cen-tral Acatlán Complex. In addition, we combine these data with petrographic, geochemical, and Sm-Nd isotopic evidence to assess the prov-
enance and tectonic setting of these metasedi-mentary rocks.
Taken together, the data from the Totoltepec pluton and the Tecomate Formation constrain processes operating at different crustal levels at a critical time in the evolution of Pangea. These data also bear on the Pangea-A versus Pangea-B controversy and on the location of southern Mexico in reconstructions of Pangea. If indeed southern Mexico was in a periph-eral position with respect to Pangea in the late Paleo zoic (Pangea-A confi guration), then this region offers a rare opportunity to examine the subduction-related magmatic and basin-forming events after continental collision. If, on the other hand, the magmatism and basin for-mation refl ect collisional orogenesis (Pangea B confi guration), this region provides a record of these processes that can be compared with the Alleghanian orogeny in the Southern Appala-chians. Our results indicate that the Totoltepec pluton and Tecomate Formation were both situated on the outboard part of a regionally extensive Pennsylvanian–Permian continental arc, consistent with subduction of paleo-Pacifi c oceanic lithosphere beneath the western margin of North America in a Pangea-A confi guration.
GEOLOGICAL SETTING
The Acatlán Complex in southern Mexico is tectonically bounded to the east by the Permian Caltepec fault zone, which separates it from the ca. 1 Ga Oaxacan Complex (Elías-Herrera and Ortega-Gutiérrez, 2002), and to the south by the Cenozoic La Venta and Chacalapa faults (Tolson, 2007; Solari et al., 2007), juxtaposing it against the Xolapa Complex (Fig. 2). To the west, the Acatlán Complex is thrust over Cre-taceous platformal carbonates, located between the exposed Acatlán Complex and the emplaced
Guerrero terrane (Centeno-García et al., 2008; Ramos-Arias and Keppie, 2011). To the north, the complex is unconformably overlain by Meso zoic rocks and the Cenozoic Trans-Mexi-can volcanic belt (Ferrari et al., 1999).
The geological history of the Acatlán Com-plex was recently summarized by Keppie et al. (2008a) and Vega-Granillo et al. (2009) and is not repeated here. Despite differences in the interpretation of this history, all authors agree that the late Paleozoic events involved subduc-tion-related tectonothermal events; however, the polarity of subduction is debated, either eastward beneath Pangea (Keppie et al., 2008a) or northward beneath Laurentia (Vega-Granillo et al., 2009).
The Totoltepec pluton and the Tecomate For-mation both occur within the Tonahuixtla fault block (Morales-Gámez et al., 2009), which is bounded in the west by the N-S–trending dex-tral San Jerónimo fault (Fig. 3; Morales-Gámez et al., 2008), where the Tecomate Formation is tectonically juxtaposed against the Carbon-iferous Salada unit along N-striking, dextral-normal faults and above N-dipping shear zones (Morales-Gámez et al., 2008). In the east, the Totoltepec pluton and Tecomate Formation are delimited by the Tianguistengo normal fault (Fig. 3; Servicio Geológico Mexicano, 2001). Along its southern margin, the Totoltepec plu-ton is thrust over metasedimentary rocks of the Tecomate Formation (Malone et al., 2002). The southern limit of the Tecomate Formation is not exposed in the study area, but the unit is inferred to structurally overlie rocks of the Cosoltepec Formation further south (Malone et al., 2002). The Cosoltepec Formation was originally thought to have been deposited in the Cam-brian–Ordovician (Ortega-Gutiérrez, 1978), but recent geochronological data indicate that it is a composite of both Cambrian–Ordovician and
Early toMiddle Permian
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A B CFigure 1. Paleogeographic reconstructions showing the location of the Mixteca terrane (Mx) in different confi gurations: (A) at the western margin of Pangea-A (modifi ed after Weber et al., 2007), (B) within Pangea-A (modifi ed after Vega-Granillo et al., 2009), or (C) off eastern Canada in the Jurassic (Pangea-B; modifi ed after Böhnel, 1999). Oax—Oaxaquia terrane; Coa—Coahuila terrane; CM—Chiapas Massif; CA—Colombian Andes.
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Geological Society of America Bulletin, September/October 2012 1609
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Kirsch et al.
1610 Geological Society of America Bulletin, September/October 2012
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Permian–Carboniferous arc magmatism and basin evolution along the western margin of Pangea
Geological Society of America Bulletin, September/October 2012 1611
Devonian–Carboniferous units (Talavera-Men-doza et al., 2005; Keppie et al., 2006, 2008b; Morales-Gámez et al., 2008; Ortega-Obregón et al., 2009). To the northeast, an unnamed amphibolites-facies unit (consisting of garnet schist and quartzite with rare amphibolite dikes) is in tectonic contact with the Totoltepec pluton and the Tecomate Formation (Fig. 3). An uncon-formity, locally modifi ed by normal faulting, marks the northern contact between the pluton and overlying red beds of inferred Jurassic age (Malone et al., 2002).
The Totoltepec pluton is compositionally diverse, ranging from hornblendite and horn-blende gabbro through diorite to tonalite, trondhjemite, granodiorite, monzogranite, and quartz-rich granitoid. The petrography of these rocks is described in detail in Kirsch et al. (2012). Plagio clase-rich cumulates are found lo-cally in the central part of the pluton. The horn-blendite and hornblende gabbro occur only in three 0.2–0.6 km2 lens-shaped bodies along the northeastern margin of the pluton that coincide with relatively high-amplitude magnetic anom-alies (Servicio Geológico Mexicano, 2004a, 2004b). Although the exposed contacts between the main and marginal phases are faults, the mar-ginal bodies are cut by trondhjemitic dikes iden-tical to those in the main phase, implying that the faults have limited displacement. Only the trond-hjemite and diorite were dated, and they yielded ages of 287 ± 2 Ma and 289 ± 1 Ma, respectively (U-Pb thermal ionization mass spectrometry [TIMS] zircon ages; Yañez et al., 1991; Keppie et al., 2004a). Within the pluton, a locally devel-oped, subvertical fabric is defi ned by fl attened quartz and feldspar grains as well as by aligned hornblende. Al-in-hornblende thermobarometric data from the main phase (Kirsch et al., 2012) indicate that the pluton was emplaced into mid-crustal levels (~20 km).
The Tecomate Formation adjacent to the Totoltepec pluton consists of greenschist-facies metapelite, feldspar-bearing metapsammite with local intercalations of metaconglomer-ate, unfossiliferous marble horizons, and rare very fi ne-grained, green, tuffaceous layers. The metapsammites are made up of quartz, plagio-clase, and K-feldspar, phyllosilicates (white mica, biotite partially altered to chlorite), and opaque minerals, as well as secondary carbon-ate and epidote. Relict feldspar porphyroclasts in the metapsammites are angular to subrounded and display a wide range of grain sizes. Pebble- to cobble-sized clasts in the metaconglomerate are composed of trondhjemite, vein quartz, and metapsammite. Marble horizons, a distinctive feature of the Tecomate Formation, occur as intensely deformed, 1–2-m-thick tabular bodies that are occasionally boudinaged. Apart from
abundant quartz veins, thin granitoid dikes are localized to an area south of Santo Domingo Tonahuixtla. Though lithologically identical to the Tecomate Formation type area in the cen-tral Acatlán Complex (Ortega-Gutiérrez, 1978), reconnaissance geochronological analyses of Tecomate Formation metasedimentary rocks from the fi eld and the type area, respectively (Keppie et al., 2004b; Sánchez-Zavala et al., 2004), have yielded distinct detrital zircon age populations, suggesting contrasting sources for the two units.
U-Pb GEOCHRONOLOGY
Analytical Methods
Seven samples (see Table A1a1 and Fig. 3 for locations) were collected for U-Pb zircon dat-ing by LA-ICP-MS at the Laboratorio de Estu-dios Isotópicos (LEI), Centro de Geociencias, Universidad Nacional Autónoma de México, Mexico. Zircons were extracted using standard mineral separation techniques, as described by Solari et al. (2007). For details on the analytical procedure, see GSA Data Repository fi le 1 (see footnote 1).
In fi gures, tables, and results, 206Pb/238U ages are quoted for zircons younger than 1.0 Ga, whereas older grains are quoted using their 207Pb/206Pb ages (e.g., Gehrels et al., 2006). The latter ages become increasingly imprecise younger than 1.0 Ga due to small amounts of 207Pb. Zircon analyses with <10% normal and <5% reverse discordance are considered to be geologically meaningful (e.g., Harris et al., 2004; Dickinson and Gehrels, 2008; Gehrels, 2012) and are used to date the time of intrusion in igneous rocks or the maximum age of deposi-tion in metasedimentary rocks. The latter is con-sidered robust if it belongs to a cluster of three of more zircons with similar ages (e.g., Gehrels et al., 2006).
Results
Totoltepec PlutonA sample of hornblende gabbro from one
of the lens-shaped bodies at the northeastern margin of the Totoltepec pluton (TT-72) is com-posed of hornblende, plagioclase, epidote, and chlorite, as well as accessory zircon, apatite, and opaque minerals (Table A1a [see footnote 1]). Zircons from the marginal mafic phase are ≤370 µm in length and exhibit uniform igne-ous oscillatory- and sector-zoning patterns. The
analyses yielded 34 concordant 206Pb/238U ages (Table A1b [see footnote 1]; Figs. 4A and 4B) ranging from 299 ± 4 Ma to 311 ± 6 Ma. The TuffZirc (Ludwig and Mundil, 2002) 206Pb/238U age calculated from a coherent group of 25 zir-con analyses is 306 ± 2 Ma.
The quartz diorite sample from the central part of the Totoltepec pluton (TT-76B) consists of oligoclase, quartz, muscovite, and chlorite, with accessory apatite, zircon, and magnetite (Table A1a [see footnote 1]). Zircons separated from the dioritic phase are relatively small (≤200 µm in length) and possess a complex in-ternal texture with partially resorbed cores and zircon overgrowths, as revealed by cathodolu-minescence (CL) imaging. Zircon data (Table A1c [see footnote 1]; Figs. 4C and 4D) range from 278 ± 2 Ma to 310 ± 4 Ma, exhibiting a slightly right-skewed distribution. The TuffZirc algorithm yields a 206Pb/238U age of 289 ± 2 Ma for a coherent group of 22 analyses.
Interpretation. The TuffZirc age of 306 ± 2 Ma is interpreted as the time of intrusion of the Totoltepec hornblende gabbro. The other two marginal bodies (Fig. 3), which are spa-tially proximal to the one dated and have similar dimensions and petrologic characteristics, are inferred to be coeval. The TuffZirc age of 289 ± 2 Ma is interpreted as the crystallization age of the quartz diorite, corroborating earlier U-Pb dating by Yañez et al. (1991) and Keppie et al. (2004a), who reported concordant U-Pb zircon ages of 287 ± 2 Ma and 289 ± 1 Ma for the intru-sion of the Totoltepec pluton near Tonahuixtla, respectively.
Tecomate FormationThree metasedimentary samples from the
Tecomate Formation (TT-486A, TT-81, TT-82), one sample from metasedimentary rocks previ-ously mapped as the Cosoltepec Formation by Ortega-Gutiérrez (1978) (TT-612), and a sam-ple of a thin granitoid dike (TT-615) intruding these metasedimentary rocks were collected for geochronological analysis (Table A1a [see footnote 1]; Fig. 3). Zircons from the psammitic sample TT-486A (consisting of quartz, musco-vite, K-feldspar, and opaque minerals) from the Tecomate Formation in the northwestern part of the study area, in the hanging wall just above the fault contact with the Salada Unit (Fig. 3), yielded only Proterozoic ages (Figs. 5A–5B; Table A1d [see footnote 1]). Results show that 75% of the 99 concordant zircon analyses fall in the age range between ca. 1014 and 1368 Ma. The second-largest population consists of 17 zir-cons of early Mesoproterozoic age between ca. 1407 and 1629 Ma. The weighted mean age (in-corporating both internal analytical and external systematic error) of the youngest cluster over-
1GSA Data Repository item 2012220, analytical methods and tables of LA-ICP-MS geochronologi-cal and geochemical data, is available at http://www.geosociety.org/pubs/ft2012.htm or by request to [email protected].
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1612 Geological Society of America Bulletin, September/October 2012
lapping in age at 2σ, calculated using the DZ Age Pick program developed at the LaserChron Center of the University of Arizona (www.geo.arizona.edu/alc), is 1005 ± 17 Ma (three grains).
A metapsammite assigned to the Tecomate Formation in the eastern part of the fi eld area (TT-81) is composed mainly of quartz, plagio-clase, muscovite, and opaque minerals. Zircons separated from this sample yielded 79 concor-dant analyses ranging from 273 ± 10 Ma to 1796 ± 34 Ma (Figs. 5C–5D; Table A1e [see footnote 1]). The most prominent population is defi ned by 50 grains between the ages of ca. 277 and ca. 332 Ma. Three smaller populations are defi ned by ages of ca. 400–570 Ma, ca. 780–845 Ma, and ca. 925–1240 Ma, respectively. The youngest cluster overlapping in age at 2σ
error yields a weighted mean value of 288 ± 3 Ma (eight grains).
A metapelite sample (TT-82) from the same area as TT-81 contains quartz, chlorite, and muscovite, as well as accessory miner-als. Ninety-seven concordant zircons from this sample display an age span of 282 ± 2 Ma to 2621 ± 42 Ma (Figs. 5E–5F; Table A1f [see footnote 1]), where a group of 16 grains with ages between ca. 293 and ca. 313 Ma defi nes the largest probability peak at ca. 303 Ma. Ages be-tween ca. 905 Ma and 1230 Ma defi ne another signifi cant age cluster, whereas age populations of ca. 470–570 Ma and ca. 655–720 Ma are rep-resented by 10 and 4 zircons, respectively. Two zircon analyses with ages between ca. 362 and ca. 385 Ma indicate a subordinate Devonian
source. The youngest cluster overlapping in age at 2σ yields a weighted mean age of 299 ± 3 Ma (six grains).
The metapsammite (TT-612) collected south of Santo Domingo Tonahuixtla from a unit originally mapped as the Cosoltepec Forma-tion is primarily made up of quartz, plagioclase, K-feldspar, and muscovite. Zircon analyses from this sample (Figs. 5G–5H; Table A1g [see footnote 1]) yielded 90 concordant ages rang-ing from 289 ± 2 Ma to 2708 ± 22 Ma. The most dominant zircon population is made up of ages between ca. 299 and ca. 326 Ma, yield-ing a probability peak at ca. 309 Ma. Another major age population is defi ned by ages of ca. 950–1340 Ma. A smaller population has ages between ca. 420 and ca. 605 Ma, and includes
TT-72 Gabbron = 3490–105% conc.
A
Fre
quen
cy
0
5
10
15
Relative probability
TT-76B Quartz Diorite n = 40
90–105% conc.
C D
B
Relative probability
310 ± 2 Ma
285 ± 2 Ma
278 ± 1 Ma
289 ± 2 Ma286 ± 2 Ma286 ± 2 Ma286 ± 2 Ma
100 µm
294 ± 2 Ma
100 µm100 µmm
301 ± 2 Ma301 ± 2 Ma301 ± 2 Ma
309 ± 2 Ma309 ± 2 Ma309 ± 2 Ma
306 ± 2 Ma306 ± 2 Ma306 ± 2 Ma
309 ± 2 Ma309 ± 2 Ma309 ± 2 Ma
2σ error ellipses
2σ error ellipses
290290290300300300310310310320
19.2 19.6 20.0 20.4 20.8 21.2 21.6 22.0
280280280290290290300300300310310310320
19 20 21 22 23
0.062
0.058
0.054
0.050
0.046
0.064
0.060
0.056
0.052
0.048
207 P
b/20
6 Pb
207 P
b/20
6 Pb
238U/206Pb
Fre
quen
cy
0
5
10
15
Age (Ma)270 280 290 300 310 320
TuffZirc 206Pb/238U age
(94.8% conf, n = 22)280
290
300
310
TuffZirc 206Pb/238U age
(95.7% conf, n = 25)290
300
310
320
306 –1/+2 Ma
289 +1/–2 Ma
Figure 4. Histograms (A, C) as well as Tera-Wasserburg diagrams (B, D) for U-Pb laser ablation–inductively coupled plasma–mass spec-trometry (LA-ICP-MS) zircon analyses of Totoltepec pluton rocks; mean 206Pb/238U age calculated by TuffZirc age algorithm of Ludwig and Mundil (2002). Black error bars are for the arguably syngenetic zircons, gray error bars for zircons likely to be xenocrystic, and white error bars indicate analyses ignored due to anomalously high errors. Also displayed are cathodoluminescence images of representative zircon crystals from dated rock samples.
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Permian–Carboniferous arc magmatism and basin evolution along the western margin of Pangea
Geological Society of America Bulletin, September/October 2012 1613
TT-81 Metapsammiten = 79
90–105% conc.
C D309
288
400–570
780–845
925–1240
Fre
quen
cy
0
10
20
30
40
Relative probability
TT-82 Metapeliten = 97
90–105% conc.
E F303
282
342
470–570
655–720
905–1230Fre
quen
cy
0
10
20
30
40
Relative probability
TT-486A Metapsammiten = 99
90–105% conc.1150
1265
1430–1590Fre
quen
cy0
10
20
30
40
Relative probability
TT-612 Metapsammiten = 90
90–105% conc.
G
A
H
B
309
420–605 950–1340
Fre
quen
cy
0
10
20
30
Relative probability
400
600
800
1000
1200
1400
1600
1800
0 4 8 12 16 20 24 28
0.12
0.10
0.08
0.06
0.04
0.068
0.064
0.060
0.056
0.052
0.048
207 P
b/20
6 Pb
207 P
b/20
6 Pb
207 P
b/20
6 Pb
207 P
b/20
6 Pb
600
1000
1400
1800
0 4 8 12 16 20 24 28
0.20
0.16
0.12
0.08
0.04
0.13
0.11
0.10
0.09
0.08
0.07
0.06
0.20
0.16
0.12
0.08
0.04
600
1000
1400
1800
0 4 8 12 16 20 24 28
2σ error ellipses
2σ error ellipses
2σ error ellipses
2σ error ellipses
}}
}
} }}}
}
}
Age (Ma)0 500 1000 1500 2000 2500 238U/206Pb
0.062
0.060
0.058
0.056
0.054
0.052
0.050
0.064
0.060
0.056
0.052
0.084
0.080
0.076
0.072
800
1000 1000 1000
1200 1200 1200
1400 1400 1400
1600 1600 1600
1800 1800 1800
2 4 6 8 10
0
5
10
290 300 310 320 330 340
0
5
10
15
270 280 290 300 310 320 330 340
19.8 20.2 20.6 21.0 21.4 21.8 22.2
290 290 290 300 300 300 310 310 310 320 320 320
19.5 20.5 21.5 22.5
270 270 270 280 280 280 290 290 290 300 300 300 310 310 310 320 320 320 330 330 330
19 20 21
290 290 290 300 300 300 310 310 310 320 320 320 330 330 330 340 340 340
960 960 960
1000 1000 1000
1040 1040 1040
1080 1080 1080
5.4 5.6 5.8 6.4
I J
2σ error ellipses
207 P
b/20
6 Pb
0.20
0.16
0.12
0.08
0.04
TT-615 Granitoid diken = 57
90–105% conc.323
303
505–635 985–1310Fre
quen
cy
0
10
20
Relative probability
600
1000
1400
1800
0 4 8 12 16 20 24
} }
0.068
0.064
0.060
0.056
0.052
0
2
4
6
8
290 300 310 320 330 340
19 20 21
290 290 290 300 300 300 310 310 310 320 320 320 330 330 330 340 340 340
Weighted mean age = 288 ± 3 Ma
Weighted mean age = 299 ± 3 Ma
Weighted mean age = 303 ± 3 Ma
Weighted mean age = 1005 ± 17 Ma
Weighted mean age = 298 ± 3 Ma
0
5
10
280 300 320 340 360
635
Figure 5. Relative age probabil-ity and histogram plots (A, C, E, G, I) as well as Tera-Wasserburg concordia diagrams (B, D, F, H, J) for U-Pb laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) zir-con analyses of Chichihualtepec Tecomate Formation metasedi-mentary rocks and a granitoid dike. Black error ellipses in am-plifi ed concordia plot were used for weighted mean age calcula-tion of the youngest age group. Histograms indicate number of analyses within 100 m.y. inter-val; histograms of the youngest age group have a 10 m.y. bin width.
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1614 Geological Society of America Bulletin, September/October 2012
a single Ordovician zircon of 469 ± 4 Ma. The weighted mean of the youngest age cluster over-lapping at 2σ error is 303 ± 3 Ma (fi ve grains).
A sample of a thin granitoid dike (TT-615) intruding the TT-612 Tecomate metapsammites is principally composed of quartz, plagioclase, and muscovite. In total, 57 concordant zircon analyses exhibit an age range from 290 ± 2 Ma to 2614 ± 22 Ma (Figs. 5I–5J; Table A1h [see footnote 1]). The two most prominent probabil-ity peaks are defi ned by a group of 16 grains with ages of ca. 294–316 Ma and by a group of 11 zircons with ages of ca. 318–335 Ma, followed by smaller age populations between ca. 505 and 635 Ma and between ca. 985 and 1310 Ma. The youngest zircons that overlap within 2σ error give a weighted mean age of 298 ± 3 Ma (fi ve grains).
Interpretation. The ca. 1005 Ma age for the youngest detrital zircons in sample TT-486A, located near the stratigraphic base of the Teco-mate Formation, suggests that this part of the unit was deposited at a time when late Paleo-zoic igneous sources were not exposed. Simi-larly, the type Tecomate Formation yielded no zircons younger than ca. 1.0 Ga (Sánchez-Zavala et al., 2004).
U-Pb ages of detrital zircon grains in the other samples are used to constrain the maximum depo-sitional age of the Tecomate Formation in the study area (e.g., Dickinson and Gehrels, 2009). Of the three metasedimentary samples from the Tecomate Formation south of the Totoltepec pluton, TT-81 yields the youngest weighted mean age (288 ± 3 Ma, Lower Permian), which is taken to represent the maximum depositional age in that locality. A 40Ar/39Ar whole-rock age of 263 ± 3 Ma (Morales-Gámez et al., 2009) from a Tecomate sericitic phyllite northwest of the Totoltepec pluton provides a younger age limit for the deposition of the Tecomate Forma-tion as well as the age of metamorphism.
In another locality within the study area, the depositional age of the Tecomate Formation is more tightly constrained to ca. 300 Ma. Sample TT-612 contains detrital zircons of Permian age, so it is assigned to the Tecomate Forma-tion rather than the Devonian–Carboniferous Cosoltepec Formation, with which it was origi-nally associated (Ortega-Gutiérrez, 1978). This conclusion is consistent with fi eld observations. The weighted mean of the youngest age cluster in sample TT-612 is 303 ± 3 Ma, which is simi-lar within error to the weighted mean age of the youngest zircon cluster from the granitoid dike (298 ± 3 Ma) at the same locality, suggesting that the host metapsammite in this locality was deposited at ca. 300 Ma and intruded very soon afterward. This depositional age is older than the maximum depositional age obtained from
sample TT-81. The ca. 298 Ma age falls between the 306 ± 2 Ma age of the marginal gabbro and the 289 ± 2 Ma of the central Totoltepec pluton, suggesting that the dike is either a late phase of the marginal gabbro or an early phase of the main Totoltepec intrusion.
Whereas deposition of the Tecomate Forma-tion south of the Totoltepec pluton occurred at ca. 300 Ma in one location and between ca. 288 and ca. 263 Ma in another, fossiliferous lime-stone horizons in the type Tecomate Formation in the central Acatlán Complex range from latest Pennsylvanian to early Middle Permian (Keppie et al., 2004b) and middle Pennsylvanian (Kazi-movian = 306–304 Ma) to Early Permian. Thus, the Tecomate Formation may be a composite unit, collectively spanning the middle Penn-sylvanian–Early Permian, but of different ages in different locations. Nevertheless, these data suggest that some of the Tecomate Formation in the type area as well as in the study area was deposited before intrusion and exhumation of the Totoltepec pluton. To avoid confusion with rocks in the type area, in this paper, the Teco-mate Formation south of the Totoltepec pluton is informally designated Chichihualtepec Teco-mate Formation (CTF; Fig. 3).
Provenance of the Chichihualtepec Teco-mate Formation. Taken together, there are 144 zircon grains in the age range between ca. 344 and ca. 273 Ma in analyzed samples from the Chichihualtepec Tecomate Formation. A com-pilation of these ages (Fig. 6), including sensi-tive high-resolution ion microprobe (SHRIMP) data of a sample from granite cobbles in Chichi-hualtepec Tecomate Formation metaconglomer-ates (Keppie et al., 2004b), shows that (1) the distribution and range of ages are more or less continuous, and (2) there is a signifi cant overlap between the detrital zircon age spectra and ages obtained from samples of the Totoltepec pluton. The measured Th/U ratios (Table A1 [see foot-note 1]), which are >0.01, support a magmatic origin of these zircons (e.g., Rubatto, 2002). However, the Totoltepec pluton cannot be a source of these zircons, as thermobarometric data suggest that the pluton was at a depth of ~20 km at ca. 289 Ma, and 40Ar/39Ar data indi-cate it did not cool through the muscovite clo-sure temperature until 283 ± 1 Ma (Kirsch et al., 2012). Assuming this uplift rate of ~1.4 mm/yr was maintained, the Totoltepec pluton was not exposed until ca. 275 Ma. Zircons of Carbon-iferous–Permian age in parts of the Chichihual-tepec Tecomate Formation that were deposited before ca. 275 Ma therefore cannot have been derived from the Totoltepec pluton, and are in-terpreted to have been derived from the regional arc edifi ce and from epizonal plutons exposed during the Pennsylvanian and Early Permian.
All of the U-Pb samples from the Chichi-hualtepec Tecomate Formation contain major detrital zircon age peaks between ca. 920 and 1250 Ma, which are within the range of ages documented from the adjacent Oaxacan Com-plex (Keppie et al., 2001, 2003; Solari et al., 2003). Whereas ca. 600 Ma, 1500–1600 Ma, 1750–1900 Ma, and 2100–2500 Ma zircons could have been derived from Amazonia, Oaxa-quia, and/or Laurentia, those with 800–950 Ma ages can come only from Amazonia (Keppie et al., 2008a) or Oaxaquia (e.g., the ca. 917 Ma Etla pluton; Ortega-Obregón et al., 2003). The source for the fi ve zircons with ages between 454 and 476 Ma may be the rift-related gran-itoid plutons within the Acatlán Complex, which have yielded ages between 440 and 480 Ma (Keppie et al., 2008b). Five detrital zircons in the samples from the Chichihualtepec Tecomate Formation are Devonian–Mississippian, span-ning ages of 357–402 Ma. A postulated arc on the western margin of the Mixteca terrane, most of which was subsequently removed by subduc-tion erosion (Keppie et al., 2008a, 2010), may have been the source for these zircons.
GEOCHEMISTRY
Analytical Methods
In order to determine the tectonic setting for the igneous and metasedimentary rocks in the Totoltepec area, 34 samples from the Totolte-pec pluton and 41 metasedimentary rocks of the Tecomate Formation were analyzed for major and selected trace elements (Fig. 3) by X-ray fl uorescence at the Regional Geochemi-cal Centre , St. Mary’s University, Canada (for details of analytical methods, see Dostal et al., 1994). Of these, 15 representative samples from the Totoltepec pluton and 7 from the Teco-mate Formation were selected for analysis of addi tional trace elements (rare-earth elements [REEs], Y, Zr, Nb, Ba, Hf, Ta, and Th) by ICP-MS according to methods described in Jenner et al. (1990). Sm-Nd isotopic compositions of these 15 samples were determined in order to characterize the source regions and tectonic his-tory of the respective geological units according to the method described in Kerr et al. (1995). For details on the analytical procedures, see GSA Data Repository fi le 1 (see footnote 1).
Results
Results of the geochemical analyses are pre-sented in Table A2 (see footnote 1). The samples are affected to varying degrees by secondary processes, including low-grade metamorphism and deuteric alteration. These secondary proc-esses have modifi ed their primary chemical
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Geological Society of America Bulletin, September/October 2012 1615
composition, resulting in a scatter on diagrams featuring alkali and alkaline earth elements and elevated loss on ignition (LOI) values. Hence, inferences about the petrogenesis of the rocks are largely based on high fi eld strength elements (HFSEs) and rare earth elements (REEs), which are considered to be relatively “immobile” dur-ing alteration processes (e.g., Winchester and Floyd, 1977), and should refl ect original magma chemistry for the igneous rocks as well as prov-enance compositions of the sedimentary rocks (Taylor and McLennan, 1985).
Totoltepec PlutonGeochronological data indicate that the
Totoltepec pluton was formed in two distinct intrusive events. Hence, geochemical data for rocks from the ca. 306 Ma marginal bodies and for rocks from the ca. 289 Ma main body of the pluton are presented separately.
Older (ca. 306 Ma) Totoltepec rocks. Samples from the older marginal bodies of the Totoltepec pluton range from hornblende gabbro to horn-blendite with SiO
2 (LOI-free) between 41.9 and
51.1 wt%. These mafi c to ultramafi c rocks have relatively wide ranges in TiO
2 (0.19–0.99 wt%),
Fe2O
3 (2.89–12.6 wt%), MgO (2.45–11.3 wt%),
Cr (38–313 ppm), V (66–434 ppm), Co (11–
47 ppm), and Ni (21–163 ppm) (Fig. 7; Table A2a [see footnote 1]). The samples have low Nb/Y (0.03–0.15) and Zr/Ti (0.002–0.009), which is typical of subalkaline basaltic rocks (Fig. 8). The rocks are characterized by low Th/Yb and Ta/Yb and highly variable Th/Hf ratios. On discrimina-tion diagrams using these parameters, the data straddle the boundary between calc-alkaline and island-arc tholeiitic fi elds (Figs. 9A and 9B).
The hornblende gabbros exhibit relatively fl at chondrite-normalized REE patterns (Fig. 10A; average [La/Yb]n = 1.8) with ΣREE of 3–13 times chondrite, and positive Eu anomalies (up to Eu/Eu* = 2.6) that decrease with increasing SiO
2.
The presence of pronounced positive Eu anoma-lies in some gabbro samples suggests plagio-clase accumulation. The hornblendite sample is characterized by a concave-upward REE pattern ([La/Sm]n = 0.4; [Gd/Yb]n = 1.7), indicative of the dominance of cumulus amphibole.
The mid-ocean-ridge basalt (MORB)–nor-malized multi-element plot of the ca. 306 Ma marginal rocks (Fig. 10B) shows enrichment in large ion lithophile elements (LILEs; Cs, Rb, Ba, U, K, Pb, and Sr), moderate depletion in the less incompatible elements (Zr, Hf, Ti, middle to heavy REEs), and strong depletion in the HFSEs Nb and Ta. This signature refl ects
derivation from a mantle wedge affected by slab fl uxing processes, i.e., patterns that are typical of subduction-related magmas (e.g., Saunders et al., 1988; McCulloch and Gamble, 1991).
Sm-Nd isotope analyses on the older marginal Totoltepec rocks yield initial εNd ranging from +1.3 to +3.3 and 147Sm/144Nd ratios from 0.15 to 0.24 with a TDM model age (147Sm/144Nd < 0.165; Stern, 2002) of 0.84 Ga (Table 1; Fig. 11). The 306 Ma sample (TT-72) with the lowest εNd(i) plots well above the mantle depletion-enrich-ment array in Figure 9A and toward the Th apex in Figure 9B, indicating contamination by a crustal or a subduction component. Accord-ingly, on the εNd(t) versus 147Sm/144Nd diagram (Fig. 11B), this sample lies on a curve repre-senting assimilation and fractional crystalliza-tion (DePaolo, 1981) between one of the more juvenile 306 Ma samples and the average com-position of the Oaxacan Complex (Ruiz et al., 1988). By contrast, the Sm-Nd isotopic signa-ture of the other hornblende gabbro samples as well as the hornblendite is similar to Ordovician mafi c rocks within the Mixteca terrane (Murphy et al., 2006; Ortega-Obregón et al., 2010), which are interpreted to have been derived from a ca. 1.0 Ga subcontinental lithospheric mantle. The 306 Ma gabbro and hornblendite may hence
TT-81Metapsammite
TT-82Metapelite
TEC-10 Granite cobble
metaconglomerate(Keppie et al., 2004b)
270
280
290
300
310
320
Age
(M
a)
330
340
350
Ea
rly
Pe
rmia
nP
en
nsy
lva
nia
nM
issi
ssip
pia
n
CA
RB
ON
IFE
RO
US
PE
RM
IAN
Totoltepec plutonca. 289 Ma Qz diorite
Totoltepec plutonca. 306 Ma Hbl gabbro
TT-612 Metapsammite
TT-615 Granitoid dike
Frequency0 25 50
Rel. prob
n = 162
Figure 6. A 2σ error bar plot showing concordant 206Pb/238U ages of detrital zircons from the Chichihualtepec Tecomate Formation metased-imentary rocks. Data also include inherited zircons extracted from a granitoid dike intruding Chichihualtepec Tecomate Formation metapsammites as well as U-Pb sensitive high-resolution ion microprobe (SHRIMP) analyses of zircons separated from Chichihualtepec Tecomate Formation metaconglomerate granitoid cobbles (Keppie et al., 2004b). Diagonally hatched regions and histograms represent U-Pb age data from Totoltepec pluton rocks. Gray shaded histogram on the right-hand side shows the age distribution of all detrital zircon data featured in this diagram. Qz—quartz; Hbl—hornblende.
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Kirsch et al.
1616 Geological Society of America Bulletin, September/October 2012
be derived from the same subcontinental litho-spheric mantle as the Ordovician mafi c rocks. Mafi c rocks with similar isotopic compositions also occur along other parts of the Gondwanan margin (Avalonia: e.g., Murphy and Dostal , 2007; Iberia-western Europe: e.g., Murphy et al., 2008; Keppie et al., 2011), suggesting the
subcontinental lithospheric mantle that underlay the area in the late Paleozoic may have been re-gionally widespread.
Main-phase (ca. 289 Ma) Totoltepec rocks. Totoltepec pluton samples of ca. 289 Ma age consist of hornblende diorite, tonalite, quartz diorite, trondhjemite, quartz-rich granitoid, and
plagioclase-rich cumulates from the main body of the pluton. Trondhjemite dikes that intrude the ultramafi c and mafi c marginal bodies of the pluton are included in the ca. 289 Ma Totoltepec rocks based on matching petrographic and geo-chemical characteristics. The samples display a wide range in chemistry, with an SiO
2 content
15
20
25
30
0
0.2
0.4
0.6
0.8
1.0
0
5
10
15
Low K
Medium K
High K
0.1
1
10
100
SiO2 (wt%)
45 50 55 60 65 70 75
1
10
SiO2 (wt%)
45 50 55 60 65 70 75
TiO2 (wt%)
CaO (wt%)
Zr (ppm)
Al2O3 (wt%)
K2O (wt%)
(La/Yb)n
Quartz-rich granitoidTrondhjemitePlag-rich cumulateTonalite
289
Ma
306
Ma
Quartz dioriteHornblende diorite
Hornblende gabbroHornblendite
Cozahuico granite (270 Ma)
Chiapas Massif (272–251 Ma)
La Carbonera (275 Ma)
Tuzancoa (290–260 Ma)
Cuchumatanes (318–313 Ma)
A B
C D
E F
Figure 7. Variation diagrams for selected major elements, high fi eld strength trace elements, and ratios of Totoltepec pluton rocks and cor-relative Carboniferous–Permian igneous suites (labeled in part F). Division lines in K2O plot are from Le Maitre et al. (2002). Included in the comparison (from north to south) are geochemical data from (1) andesitic to basaltic lava fl ows from the 290–260 Ma Tuzancoa Forma-tion in the Sierra Madre terrane (Rosales-Lagarde et al., 2005); (2) the 270 ± 3 Ma Cozahuico granite (this paper), which intrudes the N-S dextral transpressive Caltepec fault zone (CFZ); (3) the 275 ± 4 Ma La Carbonera stock, which intrudes the northern Oaxacan Complex (Solari et al., 2001; this paper); (4) ca. 272–251 Ma orthogneisses of the Chiapas Massif (Maya block; Weber et al., 2005); and (5) ca. 318–313 Ma plutons in the Altos Cuchumatanes Range, Guatemala (Maya block; Solari et al., 2010; Solari, 2012, personal commun.).
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Permian–Carboniferous arc magmatism and basin evolution along the western margin of Pangea
Geological Society of America Bulletin, September/October 2012 1617
BA
Bas
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e w
ithin
-pla
te
basa
ltsD
= D
estr
uctiv
e pl
ate-
mar
gin
basa
lts:
isla
nd a
rc th
olei
ites
(Hf/T
h >
3)
and
calc
-alk
alin
e ba
salts
(H
f/Th
< 3
)
CA
B
IATC
AB
SH
O
TH
TR
ALK
NM
OR
B
OIB
EM
OR
B
Th/Yb 0.010.
1110
Ta/Y
b
0.01
0.1
110
Fig
ure
8. G
eoch
emic
al r
ock
clas
sifi c
atio
n of
sam
ples
from
the
Toto
ltep
ec p
luto
n an
d ot
her
igne
ous
suit
es o
f sim
ilar
age
(see
cap
tion
of F
ig. 7
fo
r re
fere
nces
). (
A)
Zr/
TiO
2-Si
O2 d
iagr
am a
nd (
B)
biva
riat
e N
b/Y
ver
sus
Zr/
Ti d
iagr
am (
afte
r W
inch
este
r an
d F
loyd
, 197
7; P
earc
e, 1
996)
.
Fig
ure
9. T
ecto
nic
disc
rim
inat
ion
diag
ram
s fo
r ro
cks
of th
e To
tolt
epec
plu
ton
and
com
para
tive
igne
ous
suit
es (s
ee c
apti
on o
f Fig
. 7 fo
r re
fere
nces
). (A
) Th/
Yb
vers
us T
a/Y
b di
agra
m
iden
tify
ing
man
tle
sour
ce a
nd s
ubdu
ctio
n co
mpo
nent
s (m
odifi
ed a
fter
Pea
rce,
198
2, 1
996)
. C
ompo
siti
onal
fi e
lds:
TH
—th
olei
itic
; T
R—
tran
siti
onal
; A
LK
—al
kalin
e; C
A—
calc
-al
kalin
e; S
HO
—sh
osho
niti
c. C
ompo
siti
ons o
f nor
mal
mid
-oce
an-r
idge
bas
alt (
N-M
OR
B),
enri
ched
(E) M
OR
B, a
nd o
cean
-isl
and
basa
lt (O
IB) a
re a
fter
Sun
and
McD
onou
gh (1
989)
; (B
) Th-
Hf/
3-Ta
dis
crim
inat
ion
diag
ram
aft
er W
ood
et a
l. (1
979)
. MM
—m
antl
e so
urce
; UC
—up
per
crus
t; L
C—
low
er c
rust
; SZ
—su
bduc
tion
com
pone
nt. (
C) Y
b ve
rsus
Ta
diag
ram
fo
r fe
lsic
roc
ks (a
fter
Pea
rce
et a
l., 1
984)
. VA
G—
volc
anic
arc
gra
nite
s; s
yn-C
OL
G—
sync
ollis
ion
gran
ites
; WP
G—
wit
hin-
plat
e gr
anit
es; O
RG
—oc
ean-
ridg
e gr
anit
es.
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1618 Geological Society of America Bulletin, September/October 2012
(LOI-free) spanning 51.6–77.7 wt% and Mg# (100 × Mg/[Mg + Fe] molar) of 21–63. With increasing silica, the samples show a decrease in TiO
2, Al
2O
3, CaO (Fig. 7), and Ni, suggest-
ing that these rocks may represent a comag-matic series with fractionating plagioclase and hornblende. When plotted against SiO
2, P
2O
5,
Zr, Nb, and Ce display convex-upward patterns,
indicating fractionation of apatite, zircon, and other accessory phases. The 289 Ma Totoltepec rocks are characterized by low abundances of Cr (≤27 ppm), V (≤288 ppm), Co (≤29 ppm), and Ni (≤19 ppm). On the Zr/TiO
2-SiO
2 diagram
(Fig. 8A; Winchester and Floyd, 1977; Pearce, 1996), the samples are classifi ed as mafi c to felsic in composition, and their low Zr/Ti ratios
are typical of subalkaline mafi c to intermediate rocks (Fig. 8B). Their subalkaline character is also indicated by their low Nb/Y (0.02–0.49) values as well as their position above the mantle array in the Ta/Yb versus Th/Yb plot (Fig. 9A). A volcanic arc origin is indicated on the Th-Hf-Ta and Yb versus Ta diagrams (Figs. 9B and 9C), and by Zr/Nb (~30), Ce/Yb (~12), and
Sample / chondrite1
10
100
Quartz-rich granitoidTrondhjemitePlag-rich cumulateTonaliteQuartz dioriteHornblende diorite
Hornblende gabbroHornblendite
289
Ma
306
Ma
Cozahuico granite 270 Ma
Chiapas Massif 272–251 Ma
La Carbonera 275 Ma
Tuzancoa 290–260 Ma
Cuchumatanes 318–313 MaSam
ple
/ cho
ndrit
e
1
10
100
Sample / chondrite1
10
100
La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Sam
ple
/ NM
OR
B
0.001
0.01
0.1
1
10
100
1000
Sam
ple
/ NM
OR
B
0.001
0.01
0.1
1
10
100
1000
Sam
ple
/ NM
OR
B
0.001
0.01
0.1
1
10
100
1000
Cs Rb Ba Th U Nb Ta K La Ce Pb Pr Sr P Nd Zr Hf Sm Eu Ti Dy Y Yb Lu
A B
D
F
C
E
Figure 10. Chondrite-normalized rare earth element (REE) patterns (A, C, E) and normal mid-ocean-ridge basalt (N-MORB)–normalized multi-element plots (B, D, F) for Totoltepec pluton rocks and comparative igneous suites (see caption of Fig. 7 for references). Normalizing values are from Sun and McDonough (1989).
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La/Nb (~3) ratios, which are typical of modern calc-alkaline suites (Gill, 1981; Pearce, 1982; Cabanis and Lecolle, 1989). However, some of the samples exhibit a more primitive tholeiitic character due to lower Th/Yb (Fig. 9A) and higher Hf/Th (Fig. 9B) ratios.
The chondrite-normalized REE patterns of the ca. 289 Ma diorite and tonalite samples (Fig. 10C) are characterized by fl at light (L) REEs (aver age [La/Sm]n = 1.5), fl at to moderately fractionated heavy (H) REEs ([Gd/Yb]n = 1.1–3.3), small neg-ative to small positive Eu anomalies (Eu/Eu* = 0.7–1.4), and ΣREE abundances of 12–21 times chondrite. Chondrite-normalized REE patterns of the trondhjemites, and samples of quartz-rich granitoid and plagioclase-rich cumu late (Fig. 10E) are typifi ed by an LREE enrichment (aver-age [La/Sm]n = 2.7; average [La/Yb]n = 4.6), fl at HREE patterns (average [Gd/Yb]n = 1.2), nega-tive to positive Eu anomalies (Eu/Eu* = 0.5–2.9), and low ΣREE. The general trend for these sam-ples is a decrease in ΣREE with increasing SiO
2,
which may be an effect of accessory phase frac-tionation (Miller and Mittlefehldt, 1982).
Multi-element patterns for diorite and tonalite normalized to N-MORB (Fig. 10D) show en-richment in LILEs (Cs, Ba, K, Pb, and Sr) and moderate depletion in the HFSEs Ta and Ti. Abundances of Nb, Zr, and Hf as well as the middle REEs are similar to N-MORB. The heavy REEs are depleted in all but one tonalite sample, which exhibits HREE values identical to N-MORB. Trace-element profi les (Fig. 10F) for the Totoltepec trondhjemites, and samples of quartz-rich granitoid and plagioclase-rich cumulate are enriched in strongly incom pati-ble elements (Cs, Rb, Ba, Th, U), moderately depleted in the less incompatible elements (middle to heavy REEs, Ti, Y), and show strong Nb and Ta negative anomalies. These patterns are a characteristic feature of arc magmas (e.g., Pearce and Peate, 1995).
The Sm-Nd isotopic data for the ca. 289 Ma Totoltepec rocks yield initial εNd values between
–0.8 and +2.6 and 147Sm/144Nd ratios from 0.12 to 0.20 (Table 1; Fig. 11). Rocks with 147Sm/144Nd < 0.165 yield TDM ages of 0.93–1.16 Ga. Although considerably less radiogenic than the contempo-rary depleted mantle, one of the ca. 289 Ma to-nalite samples (εNd[i] = 2.6) and the hornblende diorite (εNd[i] = 2.5) have similar isotopic com-positions to those of the ca. 306 Ma mafi c rocks, suggesting derivation from the same subconti-nental lithospheric mantle. The other ca. 289 Ma Totoltepec rocks exhibit lower εNd(i) and higher TDM values. These rocks could not have origi-nated by simple differentiation of a Totoltepec pluton mafi c parent, because simple fractional crystallization should not affect the 143Nd/144Nd ratio. Their position along assimilation and frac-tional crystallization (AFC) trajectories in the εNd(t) versus 147Sm/144Nd diagram (Fig. 11B) suggests that their isotopic signature may be an effect of mixing between a basaltic magma (P) and crustal melts (C) derived from Oaxacan Complex basement.
TABLE 1. Sm-Nd ISOTOPIC DATA FOR SAMPLES FROM THE TOTOLTEPEC AREA, ACATLÁN COMPLEX, MEXICO
Sample Rock typeNd
(ppm)Sm
(ppm) Sm/Nd 147Sm/144Nd 143Nd/144Nd 2σT(i)(Ma) εNd(0)* εNd(i)
TDM†
(Ga)Totoltepec plutonCa. 306 Ma marginal rocksTT-24 Hornblende gabbro 1.77 0.60 0.340 0.2054 0.512811 10 306 3.4 3.0 –TT-26A Hornblende gabbro 1.58 0.40 0.256 0.1548 0.512722 20 306 1.6 3.3 0.84TT-26B Hornblende gabbro 2.07 0.71 0.344 0.2077 0.512813 10 306 3.4 3.0 –TT-28 Hornblendite 4.44 1.74 0.391 0.2365 0.512858 6 306 4.3 2.7 –TT-72 Hornblende gabbro 6.45 1.86 0.288 0.1743 0.512659 7 306 0.4 1.3 (1.47)
Ca. 289 Ma rocksTT-12§ Quartz-rich granitoid 1.06 0.04 0.035 0.0213 0.512523 8 289 -2.2 4.2 (0.42)
90.15.11.09825246215.08751.0162.089.185.7etilanoTA31-TTTT-13B Tonalite 10.23 3.08 0.301 0.1821 0.512677 7 289 0.8 1.3 (1.74)TT-14 Hornblende diorite 10.05 2.60 0.259 0.1562 0.512690 7 289 1.0 2.5 0.94TT-16 Trondhjemite 2.03 0.47 0.233 0.1405 0.512561 7 289 –1.5 0.6 1.00TT-22 Trondhjemite 7.51 1.64 0.219 0.1322 0.512528 6 289 –2.1 0.2 0.97TT-27 Trondhjemite 1.23 0.40 0.327 0.1973 0.512747 8 289 2.1 2.1 (2.89)TT-52 Plagioclase-rich cumulate 1.90 0.44 0.234 0.1416 0.512492 7 289 –2.8 –0.8 1.16TT-74 Trondhjemite 3.07 0.61 0.199 0.1202 0.512458 4 289 –3.5 –0.7 0.96
39.06.20.19827196215.06551.0752.073.222.9etilanoT87-TT
Chichihualtepec Tecomate Formation (CTF)TT-5A Metapsammite 13.62 3.13 0.230 0.139 0.512520 7 288 –2.3 –0.2 1.07TT-6 Metapelite 22.03 5.14 0.233 0.1411 0.512396 8 288 –4.7 –2.7 1.35TT-7B Metapsammite 23.25 4.96 0.213 0.129 0.512299 6 288 –6.6 –4.1 1.33TT-36 Metapsammite 16.81 4.06 0.241 0.1459 0.512558 7 288 –1.6 0.3 1.09TT-39 Metapsammite 26.36 4.80 0.182 0.0988 0.512168 4 288 –9.2 –5.6 1.16TT-61A Metapsammite 39.88 7.74 0.194 0.1173 0.512308 5 288 –6.4 –3.5 1.16TT-67 Meta-arkose 16.91 3.51 0.208 0.1255 0.512319 8 288 –6.2 –3.6 1.25
Cozahuico granite91.17.3–3.6–0727313215.06021.0002.020.180.5etinarG065-TT73.10.3–0.5–0727483215.01141.0332.046.110.7etinarG365-TT
TT-564 Granite 10.82 1.79 0.166 0.1002 0.512287 7 270 –6.8 –3.5 1.02
La Carbonera Stock31.16.3–5.6–5727303215.09311.0881.043.317.71etiroiDA565-TT02.14.3–9.5–5727633215.03421.0602.088.427.32etiroiDB565-TT
TT-568 Gabbro 71.64 18.70 0.261 0.1578 0.512338 7 275 –5.9 –4.5 1.91TT-569 Granodiorite 22.29 3.782 0.170 0.1026 0.512311 6 275 –6.4 –3.1 1.00
Note: Analyses were performed at the Atlantic Universities Regional Isotopic Facility, Memorial University of Newfoundland. For details on analytical procedures, see GSA Data Repository File 1 (see text footnote 1).
*εNd values are relative to 143Nd/144Nd = 0.512638 and 147Sm/144Nd = 0.196593 for present-day chondrite uniform reservoir (CHUR; Jacobsen and Wasserburg, 1980) and λ147Sm = 6.54 × 10–12/yr (Steiger and Jäger, 1977).
†Depleted mantle model ages (TDM) were calculated using the depleted mantle model of DePaolo (1981). Values in parentheses denote model ages that may be unreliable due to high 147Sm/144Nd (>0.165; Stern, 2002).
§Sample has anomalously low Sm and Nd concentrations and is thus excluded from further consideration.
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Comparative GeochemistryIn order to evaluate their regional signifi-
cance, we compare the Totoltepec rocks to other Permian to Carboniferous igneous suites along the North American Cordillera for which ages have been determined by U-Pb geochronology
(Figs. 2 and 7). Some of these suites form part of the putative late Paleozoic continental magmatic arc extending along the length of Mexico (e.g., Torres et al., 1999; Centeno-García, 2005).
Harker diagrams display considerable over-lap between the Totoltepec pluton and the com-
parative suites for major elements TiO2, Al
2O
3,
Fe2O
3, and CaO (Fig. 7), but the Cozahuico gran-
ite, La Carbonera stock, and igneous rocks from the Chiapas Massif and the Altos Cuchumatanes exhibit consistently higher SiO
2 and K
2O. The
more felsic and more alkalic character of these
Figure 11. (A) εNd(t) versus time plot comparing Sm-Nd isotopic data of the Totoltepec pluton (vertically hatched) and the Chichihualtepec Tecomate Formation metasedimentary rocks (diagonally hatched) with metasedimentary rocks from the Tecomate Formation type area (Yañez et al., 1991), rocks from the Oaxacan Complex (Ruiz et al., 1988), and Ordo-vician amphibolites from the Asis area (Murphy et al., 2006). Modern depleted mantle com-position is from DePaolo (1988). (B) 147Sm/144Nd versus εNd(t) diagram for Totoltepec pluton rocks as a means to evaluate crustal contamination. Fields cor-respond to Sm-Nd data from the Cozahuico granite (this paper; Elías-Herrera et al., 2005; Torres et al., 1999), the La Car-bonera stock (this paper), the Altos Cuchumatanes granitoids (Solari, 2012, personal com-mun.), the Tuzancoa Formation volcanic rocks (Rosales-Lagarde et al., 2005), and Ordovician amphibolites from the Asis lithodeme (Murphy et al., 2006) and the Olinalá area (Ortega-Obregón et al., 2010). For comparison, εNd(t) data for all samples are shown at t = 289 Ma. The black curves show trends for assimilation and fractional crystallization (AFC; DePaolo, 1981) in which crust (C—aver-age composition of the Oaxacan Complex calculated from Ruiz et al., 1988) is assimilated by a basaltic parent magma (P—average composition of four most juvenile 306 Ma marginal ultra mafi c to mafi c rocks of the Totoltepec pluton). Values for r (rate of assimilation relative to fractional crystallization) are indicated adjacent to AFC lines. For r ≥ 1, curves extend to values of F (fraction of remaining liquid) = 5; for r < 1, curves end at F = 0.1. Partition coeffi cients are from Arth (1976). Composition of depleted mantle is from DePaolo (1988). Gray arrows indicate trends for pure fractional crystallization of olivine (Ol), pyroxene (Px), hornblende (Hbl), plagioclase (Plag), apatite (Ap), zircon (Zrc), and K-feldspar (K-fsp).
r = 0.25
r = 0.75
r = 2
r = 10
Ord. amphibolites Asis (Murphy et al., 2006)
Ord. amphibolites Olinalá (Ortega-Obregon et al., 2010)
Totoltepec pluton trondhjemite(Martiny-Kramer, 2008)
Depletedmantle
OaxacanComplex
εN
d(t =
289
Ma)
-8
-6
-4
-2
0
2
4
6
8
147Sm/144Nd
0.10 0.12 0.14 0.16 0.18 0.20 0.22 0.24
PlagOl, Px, Hbl
C
P
Ol, Px, Ap, Zrc K-fsp, Plag
Cozahuico granite 270 Ma
La Carbonera 275 Ma
Cuchumatanes 318–313 Ma
A
B
Depletedmantle
ε Nd(
t)
10
5
0
5
t (Ga)
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
Totoltepec pluton
Chichihualtepec Tec. Fm.
Asis amphibolites
Tecomate Fm. type area
Oaxacan Complex
MetapeliteMetapsammiteMeta-arkose
TrondhjemitePlag-rich cumulateTonalite
289
Ma
306
Ma
Quartz dioriteHornblende diorite
Hornblende gabbroHornblendite
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suites is also apparent in the rock classifi cation diagrams (Fig. 8), where they plot mainly in the fi elds of (trachy-)andesite, rhyolite, and trachyte. Lavas from the Tuzancoa Formation overlap the composition of Totoltepec pluton tonalite and quartz diorite. Tectonic discrimination diagrams (Fig. 9) classify the majority of the samples from the comparative igneous suites as calc-alkaline arc rocks, but they show higher Ta and Yb abun-dances as well as higher Ta/Yb and Th/Yb ratios than rocks of the Totoltepec pluton. Chondrite-normalized REE patterns of comparative igne-ous suites are more fractionated (higher[La/Yb]n ratios; Figs. 7F, 10A, 10C, and 10E), and they display higher total REE abundances than most samples of the Totoltepec pluton. The MORB-normalized spidergrams of comparative igneous suites (Figs. 10B, 10D, and 10F) are similar to those of rocks from the Totoltepec pluton, showing a jagged pattern with positive LILE enrichment and negative HFSE anomalies, typi-cal of arc-derived rocks. On average, however, the Totoltepec rocks have lower abundances of Nb, Ta, Zr, and LREE, and are less enriched in LILEs (Rb, Th, K) than comparative Carbon-iferous–Permian igneous rocks. The Sm-Nd isotopic signature of the Coza huico, La Carbo-nera, and the Altos Cuchumatanes rocks is less radiogenic than that of the Totoltepec pluton, displaying initial εNd values between –4.9 and –3.0, TDM model ages from 1.1 to 2.2 Ga, and 147Sm/144Nd ratios between 0.10 and 0.16 (Fig. 11; this paper : Table 1; Torres et al., 1999; Elías-Herrera et al., 2005; Solari, 2012, personal com-mun.). The Tuzancoa Formation volcanic rocks
exhibit an εNd(t) value of –1.3 (t = 275) and a TDM model age of 1.4 Ga (recalculated from Rosales-Lagarde et al., 2005). These values, which are less radiogenic than Totoltepec pluton rocks with similar SiO
2 content, suggest deriva-
tion by melting of older continental crust. This conclusion is consistent with an abundance of inherited zircons and/or crustal xenoliths docu-mented in these rocks (Elías-Herrera et al., 2005; Solari et al., 2001, 2010). Other plutonic rocks, for which their late Paleozoic ages are based on K-Ar or Rb-Sr dating (not shown), as well as sedimentary rocks of Permian–Carboniferous age exhibit εNd(i) values similar to the Coza-huico and La Carbonera stocks (Torres et al., 1999; Schaaf et al., 2002; Yañez et al., 1991) and therefore are in broad agreement with this interpretation.
Chichihualtepec Tecomate FormationSamples from the Chichihualtepec Tecomate
Formation collected for geochemistry include 16 metapsammites, 11 metapelites, 12 meta-arkoses , and 2 metaconglomerates. The major-element abundances of these metasedimentary rocks lie in the range of typical shales, sand-stones, and graywackes, with their SiO
2 content
ranging from 56.4 to 76.9 wt% and Al2O
3 values
from 11 to 21 wt% (LOI-free basis). SiO2 dis-
plays negative correlations with Al2O
3 (correla-
tion coeffi cient r = –0.84), Fe2O
3 (r = –0.92), Co
(r = –0.84), and V (r = –0.80), respectively, which refl ect the different proportions of clay/mud-rich and quartz-rich components, as documented in other sedimentary sequences (e.g., Bhatia, 1983).
The range of Al2O
3/TiO
2, Cr/Th, Th/Co,
Cr/V, and V/Ni ratios in the Chichihualtepec Tecomate Formation rocks suggests that the majority of samples are derived from felsic sources (Taylor and McLennan, 1985; Cullers, 1994; Girty et al., 1996), which is consistent with the low average MgO, Fe
2O
3, Cr, Ni, and
Co abundances. Incompatible elements such as Zr, Nb, Hf, Ta, Y, Th, and U have higher abun-dances in the Chichihualtepec Tecomate For-mation rocks than they display in sedimentary suites derived from mafi c sources (Feng and Kerrich, 1990). Similarly, Hf and La/Th charac-teristics of the Chichihualtepec Tecomate For-mation rocks (Floyd and Leveridge, 1987; Fig. 12A) indicate an acid arc to mixed felsic-basic source with a minor infl uence of older sedimen-tary components.
Chondrite-normalized REE patterns of the Chichihualtepec Tecomate Formation (Fig. 13A) are characterized by a moderate en-richment in LREE ([La/Yb]n = 3.0–7.1), fl at HREE ([Gd/Yb]n = 1.0–1.5), and negative Eu anomalies (Eu/Eu* = 0.62–0.82). These fea-tures suggest that the source of the clastic rocks was fractionated with respect to plagioclase (Slack and Stevens, 1994). One metapsammite sample exhibits a greater REE fractionation (LREE/HREE = 16.9, [La/Yb]n = 25.0) and a slightly steeper HREE slope ([Gd/Yb]n = 2.5). Total REE abundances for all samples range be-tween 20 and 150 times chondrite.
The Sm-Nd isotopic compositions for Chi-chihualtepec Tecomate Formation samples are highly variable (Fig. 11A), with εNd(t) values
BA MetapeliteMetapsammiteMeta-arkoseMetaconglomerateUpper continental crustNorth American Shale CompositePost Archean Australian Shale
Tholeiitic oceanicarc source
Andesiticarc source
Mixed felsic-basic sourceMixed felsic-basic sourceMixed felsic-basic source
Acid arc source
OIA – Oceanic island arcCA – Continental island arcACM – Active continental marginPM – Passive margin
Increasing old sediment component
Passivemarginsource
La/T
h
0
2
4
6
8
10
12
14
Hf (ppm)
0 2 4 6 8 10 12 14
PM
ACM
CA
OIA
Al 2O
3 / S
iO2 (
wt%
)
0
0.05
0.10
0.15
0.20
0.25
0.30
0.35
(Fe2O3+MgO) (wt%)
0 2 4 6 8 10 12 14 16
Figure 12. Discrimination diagrams for the metasedimentary rocks of the Chichihualtepec Tecomate Formation. (A) Hf versus La/Th diagram after Floyd and Leveridge (1987); (B) (Fe2O3 + MgO) versus (Al2O3/SiO2) diagram after Bhatia (1983). Post-Archean Australian Shale, upper continental crust (Taylor and McLennan, 1985), and North American Shale Composite (Gromet et al., 1984) are shown for comparison.
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1622 Geological Society of America Bulletin, September/October 2012
ranging from –5.6 to +0.3 (t = 288 Ma) and de-pleted mantle model ages (TDM) between 1.07 and 1.35 Ga. These data represent the weighted average of Sm-Nd isotopic compositions for all the detrital contributions from the source area (Arndt and Goldstein, 1987; Murphy and Nance, 2002). The εNd(t) evolution lines of the Chichihualtepec Tecomate Formation rocks lie between, and partially intersect, the Sm-Nd envelopes of both the Oaxacan Complex rocks and the Totoltepec pluton, suggesting compo-nents of both these sources in the clastic rocks. This interpretation is consistent with detrital zircon geochronological data, which indicate that the Oaxacan Complex and the regional
Carboniferous–Permian arc are the two main contributing source areas. In contrast to the data presented herein, the Tecomate Formation in the type area (Yañez et al., 1991) lacks a contribu-tion from the regional Carboniferous–Permian arc, as their εNd(t) values closely correspond with the Sm-Nd isotopic composition of the Oaxacan Complex (Fig. 11A). This inference is supported by U-Pb geochronological data of metasedimentary rocks from the Tecomate type area (Sánchez-Zavala et al., 2004), which yielded detrital zircon populations of Ordovi-cian and Mesoproterozoic age.
Upper continental crust–normalized trace-element patterns of the Chichihualtepec
Teco mate Formation (Fig. 13B) rocks are char-acterized by positive Cs, Ba, and U anomalies for some samples and a strong depletion in HFSEs, particularly Nb and Ta. This signature suggests that the Chichihualtepec Tecomate Formation was deposited in a sedimentary basin that formed in an arc environment. An arc-re-lated provenance is also indicated on the Hf ver-sus La/Th plot (Floyd and Leveridge, 1987; Fig. 12A) and the (Fe
2O
3 + MgO) versus Al
2O
3/SiO
2
ratio diagram (Bhatia, 1983; Fig. 12B). A lim-ited range in Ti/Zr ratios and the petrographic observations, such as the high modal abundance of feldspar, a wide range of grain sizes, and the angularity of relict porphyro clasts, point to a compositionally immature, poorly sorted sedi-ment that was only transported over a short dis-tance (Garcia et al., 1994).
SUMMARY AND DISCUSSION
Our results indicate that the late Paleozoic Totoltepec pluton and the metasedimentary Chichihualtepec Tecomate Formation postdate collisional orogenesis and developed at differ-ent crustal levels along the periphery of Pangea. The Totoltepec pluton consists of minor mafi c-ultramafi c rocks (306 ± 2 Ma) that are marginal to the main felsic-mafi c intrusion (289 ± 2 Ma). Both intrusive phases have an arc geochemistry but are more primitive than contemporaneous arc complexes in southern Mexico. The Chi-chihualtepec Tecomate Formation was derived from a late Paleozoic arc.
Along-Arc Variation
Whereas Torres et al. (1999) advocated the presence of a Permian–Triassic arc, the ca. 306 Ma age and the arc geochemistry of the gabbroic component of the Totoltepec pluton provide fi rm evidence of magmatic arc activity in the Pennsylvanian. Other igneous rocks of a similar age in the southern part of the North American Cordillera (Fig. 2) include the Cua-naná plutonic complex (Vega-Carrillo et al., 1998), which yielded a SHRIMP U-Pb age of 307 ± 2 Ma (Elías Herrera et al., 2005), and ca. 313–318 Ma granitic to dioritic intrusions in the Altos Cuchumatanes, Guatemala (Solari et al., 2010). Further north, the Aserradero rhyolite in the Sierra Madre terrane yielded a U-Pb TIMS age of 334 ± 39 Ma (Stewart et al., 1999), and in the Coahuila terrane, the La Pezuña rhyolite was dated at 331 ± 4 Ma (Lopez et al., 1996). However, due to the lack of geochemical data, an arc association of these Carboniferous rocks can only be substantiated for the Totoltepec plu-ton and the Altos Cuchumatanes granitoids.
The overall spatial, geochemical, and iso topic similarity of the ca. 289 Ma main body of the
Sample / chondrite
1
10
100
La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
B
A
Samples / upper continental crust
0.1
1
10
Cs Rb Ba Th U Nb Ta K La Ce Pr Sr Nd Zr Sm Eu Ti Dy Y Yb Lu Hf Tb Tm Gd Ho Er
UC (Taylor and McLennan,1985)
Metapsammite
Meta-arkose
Metapelite
Figure 13. (A) Chondrite-normalized rare earth element (REE) plot (normalizing values from Sun and McDonough, 1989); and (B) upper continental (UC) crust–normalized trace-element diagram (normalizing values from Taylor and McLennan, 1995) of Chichihualtepec Tecomate Formation metasedimentary rocks.
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Totoltepec pluton with the precursor 306 Ma gabbroic rocks suggests that regional arc ac-tivity continued into the Early Permian. Other evidence for Early Permian arc magmatism in southern Mexico (Figs. 2 and 14) includes the 270 ± 3 Ma Cozahuico granite (Elías-Herrera and Ortega-Gutiérrez, 2002; Elías-Herrera et al., 2005), the 275 ± 4 Ma La Carbonera stock (Solari et al., 2001), a 272 ± 10 Ma tonalitic gneiss in the Xolapa Complex (Ducea et al., 2004), and an arc-related orthogneiss in the Chiapas Mas-sif that yielded a U-Pb SHRIMP age of 272 ± 3 Ma (Weber et al., 2007). Arc-related ca. 270–280 Ma granitoid plutons intruding Caborca ter-rane basement in northwestern Mexico (Arvizu et al., 2009; Riggs et al., 2009, 2010) indicate that Early Permian arc magmatism extended into the North American craton.
Arc magmatism in southern Mexico is likely to have continued into the Middle to Early Permian , as suggested by an arc-related ortho gneiss of 258 ± 2 Ma age in the Chiapas Massif (Weber et al., 2005) and by a crystallization age of 254 ± 7 Ma for the Mixtequita stock in the Maya ter-rane (Murillo-Muñeton, 1994). The northern extension of the Early to Middle Permian con-
tinental arc into terranes of the North Ameri-can craton is represented by ca. 258 Ma to ca. 266 Ma arc-related granites and granodiorites in the Sierra Pinta (Arvizu et al., 2009).
This fragmentary record of late Paleozoic arc magmatism is in broad agreement with a num-ber of Permian K-Ar and Rb-Sr ages of igne-ous rocks in Mexico (Fig. 2; Ruiz-Castellanos, 1979; Damon et al., 1981; Torres et al., 1999; Grajales-Nishimura et al., 1999).
The Chichihualtepec Tecomate Formation strata, containing interstratifi ed arc-derived vol-canic and clastic rocks, provide complementary data on the nature of the late Paleozoic evolu-tion of the shallow crust. Much of the Chichi-hualtepec Tecomate Formation was deposited before the Totoltepec pluton was exposed. De-trital zircon, geochemical and Sm-Nd isotopic data, together with the presence of plutoniclastic conglomerate, indicate that the Chichihualtepec Tecomate Formation was largely derived from a regional arc. The local abundance of thin gran-itoid dikes and very fi ne-grained, green, tuffa-ceous strata in the Chichihualtepec Tecomate Formation suggests that arc activity was con-temporaneous with Chichihualtepec Tecomate
Formation deposition. Evidence of arc activity in southern Mexico (Figs. 2 and 14) may also be preserved in (1) the latest Pennsylvanian to Middle Permian Tecomate Formation type area, which contains mafi c fl ows, tuffs, and rare fel-sic units (Keppie et al., 2004b; Sánchez-Zavala, 2008), (2) the Middle Permian Los Hornos For-mation (Ramírez et al., 2000; Vachard et al., 2004), and (3) the uppermost Devonian to Lower Permian Patlanoaya Group, which con-tains intercalations of bentonite horizons repre-senting ash-fall deposits (Vachard et al., 2000; Vachard and de Dios, 2002). The un deformed Olinalá Formation of Middle to Upper Permian age (Buitrón et al., 2005) is potentially also partially correlative with the Chichihualtepec Tecomate Formation strata, although volcanic rocks have not been described in this unit. Fur-ther north, the magmatic arc is characterized by (1) the Early to Middle Permian Tuzancoa For-mation (Sierra Madre terrane), which contains andesitic to basaltic lava fl ows and felsic tuffs (Rosales-Lagarde et al., 2005), (2) the Early Permian bentonite-bearing Guacamaya Forma-tion in the Sierra Madre terrane (Gursky and Michalzik , 1989), (3) the late Mississippian to
PE
RM
IAN
CA
RB
ON
IFE
RO
US
MISSIS-
SIPPIAN
PENNSYL-
VANIAN
L
M
E
251
260
271
299
Age
(M
a)
318
359
Mixteca Oaxaquia Maya SierraMadre
Coahuila Xolapa Chihuahua Caborca
Toto
ltepe
c
Cuanana
Cozahuico
La Carbonera
Igneous arc-related rocksdated by U-Pb geochronology
Sedimentary arc-assemblagescontaining intercalated arc-related volcanic rocks
AltosCuchumatanes
La Pezuña
Teco
mat
e F
m./
CT
FP
atla
noay
a G
roup
Tuza
ncoa
Fm
.G
uaca
may
a F
m.
Las
Del
icia
s F
m.
Rar
a F
m.
Aserradero
TonaliticgneissChiapas
Massiforthogneiss
ChiapasMassif
orthogneiss
Mixtequita
Sierra Pinta
Los Tanques
Sonoyta
Toto
ltepe
c
Figure 14. Correlation chart of various arc-related igneous and sedimentary suites of Carboniferous to Permian age sorted according to their location in the various tectonostratigraphic terranes of Mexico. For references see text.
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Middle Permian Las Delicias Formation in the Coahuila terrane (McKee et al., 1999), which contains interstratifi ed rhyolites, and (4) the Early Permian, bentonite-bearing Rara Forma-tion of the Sierra del Cuervo in the southern ex-tension of the North American craton (Handschy and Dyer, 1987).
As one of the samples from near the strati-graphic base of the Chichihualtepec Tecomate Formation does not contain any Carboniferous–Permian zircons, this regional magmatic arc in southern Mexico is inferred to have started developing during Chichihualtepec Tecomate Formation deposition (Figs. 15A and 15B). The Totoltepec pluton did not become a source for the Chichihualtepec Tecomate Formation until ca. 275 Ma, by which time a signifi cant amount of the arc crust had been removed to expose the pluton (Fig. 15C). Although the population peak of the late Paleozoic detrital zircon record of the Chichihualtepec Tecomate Formation occurs at an age of ca. 307 Ma (Fig. 6), the detrital zir-con record extends back to ca. 344 Ma without any signifi cant gaps, suggesting that regional magmatic arc activity may have initiated in the Mississippian.
Taken together, the data suggest that arc mag-matism had commenced in some of the southern to central Mexican continental blocks by Mis-sissippian times, whereas it probably did not become established in the Laurentian (northern) part of Mexico until the Early Permian (Fig. 14).
Across-Arc Variation
There are subtle differences in the geochemi-cal and isotopic compositions between the various magmatic arc suites of southern Mexico and Guatemala. For rocks with the same SiO
2
content, the Totoltepec pluton exhibits lower HFSE (Nb, Ta, LREEs, Zr) and LILE (Rb, Th, K) abundances and more radiogenic Sm-Nd iso-topic compositions relative to the intermediate to felsic suites in both Oaxaquia and the Maya block, which also contain evidence of substan-tial crustal contamination. As certain southern Mexican arc suites of different age show simi-lar geochemical characteristics and certain arc suites of roughly the same age show different geochemical characteristics, the compositional differences cannot be ascribed to temporal variations in arc magmatism. Instead, observed contrasts in composition between the individual arc suites considered in this paper are attributed to spatial intra-arc variation.
In general, arc rock compositions vary both in time and with distance from the active trench, refl ecting increasing degrees of AFC as mag-mas pass through thicker crust, and a change from subduction-enriched to within-plate man-
Pre-arcca. 330 Ma (?)
Arcdevelopment
ca. 300 Ma
Late arc:Tt exhumation
ca. 270 Ma
Tt—TotoltepecCz—CozahuicoCu—CuananáCa—La CarboneraTz—TuzancoaCh—Chiapas MassifAc—Altos Cuchumatanes
ctf/tf—Chichihualtepec Tecomate/ Tecomatepa—Patlanoayagu/dm—Guacamaya/ Del Monte
Plutons
Lava flowMX—Mixteca terraneOAX—Oaxaquia terraneMAYA—Maya block
A
B
C
+++
v vv
Basement
Arc crust
Sedimenttransport
+ +++
+
Tt
Cu
pa
ctf/tf
Ac
++
++++
++
MX OAX MAYA
pa
ctf/tf
pagu/dm
ctf/tf
sea level
Fault
Fault, inferred
Tt CzCa
Tz
Ch
+++++
+ +++ ++
+ + ++
sea level
+ ++Ac
++ Cu
vv v
sea level
?
?
?
exposedbasement
50 km
Figure 15. Generalized sections across the active western margin of Pangea in the late Paleo-zoic, showing arc development and the relative locations of the various magmatic arc assem-blages in southern Mexico and Guatemala.
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tle sources (e.g., Brown et al., 1984). Typical transverse geochemical variations include a systematic increase in LILEs, HFSEs, and al-kalis and a decrease in LILE/HFSE ratios and εNd values from the front to the rear of the arc (Kimura et al., 2010, and references therein). Hence, in order to account for the more juvenile composition of the Totoltepec pluton in com-parison to other Carboniferous–Permian arc suites in Mexico and Guatemala, the Totoltepec pluton is inferred to have been emplaced into a more primitive, less mature location within the Carboniferous–Permian arc. In this model, the pluton would constitute a more trenchward part of the arc, lying to the west (modern coor-dinates) of the more mature arc suites inferred to represent a more inboard location (Figs. 15B and 15C). Assuming that the southern Mexican crustal blocks, in which the Mixteca terrane oc-cupies the western, most outboard position rela-tive to Oaxaquia and the Maya block (Fig. 1A), were only involved in lateral translation relative to each other along transcurrent faults trend-ing along strike of the arc (e.g., Dickinson and Lawton, 2001), the position of the Totoltepec pluton relative to the other southern Mexican arc suites should not have changed substantially since the late Paleozoic. Hence, the increased arc maturity is consistent with models that ad-vocate an eastward polarity of subduction (e.g., Centeno-García, 2005; Keppie et al., 2008a). An alternative (but not necessarily mutually exclusive) model to explain the geochemical differences between the Totoltepec pluton and contemporaneous arc-related plutonic rocks in southern Mexico involves the emplacement of the Totoltepec pluton along a fault in the arc that facilitated its ascent and made it less prone to contamination. This model is consistent with transtensional kinematics associated with strike-slip faulting documented in Chichihual-tepec Tecomate Formation metaconglomerates (Morales-Gámez et al., 2009) and evidence for the syntectonic emplacement of the Totoltepec pluton (Kirsch et al., 2012).
Pangea Implications
Late Carboniferous continental collision in Mexico was a key event in the amalgamation of Pangea and is expressed by a southerly source for fl ysch deposits in the Ouachitan orogeny in the Mississippian (Arbenz, 1989) and by the ap-pearance of early Mississippian fossils in Oaxa-quia with Midcontinent (U.S.) faunal affi ni ties (Navarro-Santillán et al., 2002). Because Car-boniferous to Permian continental arc mag-matism recorded by the Totoltepec pluton, the Chichihualtepec Tecomate Formation, and cor-relative rocks elsewhere in the belt postdates the
amalgamation of Pangea, a location of the Mix-teca terrane adjacent to a subducting part of the Panthalassa Ocean on the periphery of Pangea-A seems most likely (Fig. 1A). Such a location is preferable to models that assign the Mixteca terrane to a position within Pangea, either off northeastern Canada (Fig. 1C; Böhnel, 1999) or in the Gulf of Mexico, ~2000 km inland from the western margin of Pangea (Vega-Granillo et al., 2009; Fig. 1B), because these locations lie too far from any potential subducting ocean.
ACKNOWLEDGMENTS
We acknowledge the Consejo Nacional de Cien-cia y Tecnología (CONACyT; Project CB-2005-1: 24894), Programa de Apoyo a Proyectos de In-vestigación e Innovación Tecnológica (PAPIIT: IN100108-3), and a Natural Sciences and Engineer-ing Research Council of Canada Discovery grant to Murphy for funds to support the fi eld work and geochemical and isotopic analyses. Carlos Ortega-Obregón and Ofelia Pérez-Arvizu provided technical assistance in the Laboratorio de Estudios Isotópicos, Centro de Geociencias. Kirsch is grateful to Maria Helbig for help in the fi eld and with fi gure prepara-tion. We thank Associate Editor Luca Ferrari, and re-viewers Peter Schaaf and Bodo Weber, as well as two anonymous reviewers, for constructive comments on this and a previous version of the manuscript. This is a contribution to International Geological Correlation Project 597.
REFERENCES CITED
Alva-Valdivia, L.M., Goguitchaichvili, A., Grajales, M., de Dios, A.F., Urrutia-Fucugauchi, J., Rosales, C., and Morales, J., 2002, Further constraints for Permo-Carboniferous magnetostratigraphy: Case study of the sedimentary sequence from San Salvador–Patlanoaya (Mexico): Comptes Rendus Geoscience, v. 334, no. 11, p. 811–817, doi:10.1016/S1631-0713(02)01821-7.
Arbenz, J.K., 1989, The Ouachita system, in Bally, A.W., and Palmer, A.R., eds., The Geology of North America: An Overview: Boulder, Colorado, Geological Society of America, The Geology of North America, v. A, p. 371–398.
Arndt, N.T., and Goldstein, S.L., 1987, Use and abuse of crust-formation ages: Geology, v. 15, p. 893–895, doi:10.1130/0091-7613(1987)15<893:UAAOCA>2.0.CO;2.
Arth, J.G., 1976, Behaviour of trace elements during mag-matic processes—A summary of theoretical models and their application: Journal of Research of the U.S. Geological Survey, v. 4, no. 1, p. 41–47.
Arvizu, H.E., Iriondo, A., Izaguirre, A., Chávez-Cabello, G., Kamenov, G.D., Solís-Pichardo, G., Foster, D.A., and Cruz, R.L.-S., 2009, Rocas graníticas pérmicas en la Sierra Pinta, NW de Sonora, México: Magmatismo de subducción asociado al inicio del margen continental activo del SW de Norteamérica: Revista Mexicana de Ciencias Geológicas, v. 26, no. 3, p. 709–728.
Bhatia, M.R., 1983, Plate tectonics and geochemical com-position of sandstones: The Journal of Geology, v. 91, no. 6, p. 611–627, doi:10.1086/628815.
Böhnel, H., 1999, Paleomagnetic study of Jurassic and Cretaceous rocks from the Mixteca terrane (Mexico): Journal of South American Earth Sciences, v. 12, p. 545–556, doi:10.1016/S0895-9811(99)00038-3.
Brown, G.C., Thorpe, R.S., and Webb, P.C., 1984, The geo-chemical characteristics of granitoids in contrasting arcs and comments on magma sources: Journal of the Geological Society of London, v. 141, no. 3, p. 413–426, doi:10.1144/gsjgs.141.3.0413.
Buitrón, B.E., Pineda, S., de Dios, A., and Vachard, D., 2005, New Permian macrofauna and macrofl ora from the
Olinalá region, Guerrero State, Mexico: Annales de la Société Géologique du Nord, v. 11, no. 2, p. 169–176.
Bullard, E.C., Everett, J.E., and Smith, A.G., 1965, A sym-posium on continental drift—IV. The fi t of the conti-nents around the Atlantic: Philosophical Transactions of the Royal Society of London, ser. A, v. 258, p. 41–51, doi:10.1098/rsta.1965.0020.
Cabanis, B., and Lecolle, M., 1989, The La/10-Y/15-Nb/8 diagram—A tool for discriminating volcanic series and evidencing continental-crust magmatic mixtures and/or contamination: Comptes Rendus de l’Académie des Sciences, ser. 2, v. 309, no. 20, p. 2023–2029.
Centeno-García, E., 2005, Review of Upper Paleozoic and Lower Mesozoic stratigraphy and depositional envi-ronments of central and west Mexico: Constraints on terrane analysis and paleogeography, in Anderson, T.H., Nourse, J.A., McKee, J.W., and Steiner, M.B., eds., The Mojave-Sonora Megashear Hypothesis: De-velopment, Assessment, and Alternatives: Geological Society of America Special Paper 393, p. 233–258.
Centeno-García, E., Guerrero-Suastegui, M., and Talavera-Mendoza, O., 2008, The Guerrero composite terrane of western Mexico: Collision and subsequent rifting in a supra-subduction zone, in Draut, A., Clift, P.D., and Scholl, D.W., eds., Formation and Applications of the Sedimentary Record in Arc Collision Zones: Geologi-cal Society of America Special Paper 436, p. 1–30.
Cullers, R.L., 1994, The controls on the major and trace ele-ment variation of shales, siltstones, and sandstones of Pennsylvanian-Permian age from uplifted continental blocks in Colorado to platform sediment in Kansas, USA: Geochimica et Cosmochimica Acta, v. 58, no. 22, p. 4955–4972, doi:10.1016/0016-7037(94)90224-0.
Damon, P.E., Shafi qullah, M., and Clark, K.F., 1981, Evolu-ción de los arcos magmáticos en México y su relación con la metalogénesis: Revista Mexicana de Ciencias Geológicas, v. 5, no. 2, p. 223–238.
DePaolo, D.J., 1981, Trace element and isotopic effects of combined wallrock assimilation and fractional crystalli-zation: Earth and Planetary Science Letters, v. 53, no. 2, p. 189–202, doi:10.1016/0012-821X(81)90153-9.
DePaolo, D.J., 1988, Neodymium Isotope Geochemistry: An Introduction: Berlin, Springer Verlag, 187 p.
Dickinson, W.R., and Gehrels, G.E., 2008, Sediment deliv-ery to the Cordilleran foreland basin: Insights from U-Pb ages of detrital zircons in Upper Jurassic and Cretaceous strata of the Colorado Plateau: American Journal of Science, v. 308, p. 1041–1082.
Dickinson, W.R., and Gehrels, G.E., 2009, Use of U-Pb ages of detrital zircons to infer maximum depositional ages of strata: A test against a Colorado Plateau Mesozoic database: Earth and Planetary Science Letters, v. 288, p. 115–125, doi:10.1016/j.epsl.2009.09.013.
Dickinson, W.R., and Lawton, T.F., 2001, Carboniferous to Cretaceous assembly and fragmentation of Mex-ico: Geological Society of America Bulletin, v. 113, no. 9, p. 1142–1160, doi:10.1130/0016-7606(2001)113<1142:CTCAAF>2.0.CO;2.
Dostal, J., Dupuy, C., and Caby, R., 1994, Geochemistry of the Neoproterozoic Tilemsi belt of Iforas (Mali, Sahara): A crustal section of an oceanic island arc: Precambrian Research, v. 65, p. 55–69, doi:10.1016/0301-9268(94)90099-X.
Dowe, D.S., Nance, R.D., Keppie, J.D., Cameron, K.L., Ortega-Rivera, A, Ortega-Gutiérrez, F., and Lee, J.W.K., 2005, Deformational history of the Granjeno Schist, Ciudad Victoria, Mexico: Constraints on the closure of the Rheic Ocean?: International Geology Review, v. 47, no. 9, p. 920–937, doi:10.2747/0020-6814.47.9.920.
Ducea, M.N., Gehrels, G.E., Shoemaker, S., Ruiz, J., and Valencia, V.A., 2004, Geologic evolution of the Xolapa Complex, southern Mexico: Evidence from U-Pb zir-con geochronology: Geological Society of America Bulletin, v. 116, p. 1016–1025, doi:10.1130/B25467.1.
Elías-Herrera, M., and Ortega-Gutiérrez, F., 2002, Caltepec fault zone: An Early Permian dextral transpressional boundary between the Proterozoic Oaxacan and Paleo zoic Acatlán complexes, southern Mexico, and regional tectonic implications: Tectonics, v. 21, no. 3, p. 1–19, doi:10.1029/2000TC001278.
Elías-Herrera, M., Ortega-Gutiérrez, F., Sánchez-Zavala, J.L., Macías-Romo, C., Ortega-Rivera, A., and Iriondo,
on September 13, 2012gsabulletin.gsapubs.orgDownloaded from
Kirsch et al.
1626 Geological Society of America Bulletin, September/October 2012
A., 2005, La falla de Caltepec: Raíces expuestas de una frontera tectónica de larga vida entre dos terrenos con-tinentales del sur de México: Boletín de la Sociedad Geológica Mexicana, v. 57, no. 1, p. 83–109.
Fang, W., Van der Voo, R., Molina-Garza, R., Morán-Zenteno, D., and Urrutia-Fucugauchi, J., 1989, Paleo-magnetism of the Acatlán terrane, southern Mexico: Evidence for terrane rotation: Earth and Planetary Sci-ence Letters, v. 94, no. 1–2, p. 131–142, doi:10.1016/0012-821X(89)90089-7.
Feng, R., and Kerrich, R., 1990, Geochemistry of fine grained clastic sediments in the Archaean Abitibi greenstone belt, Canada: Implications for provenance and tectonic setting: Geochimica et Cosmochimica Acta, v. 54, p. 1061–1081, doi:10.1016/0016-7037(90)90439-R.
Ferrari, L., 2004, Slab detachment control on volcanic pulse and mantle heterogeneity in Central Mexico: Geology, v. 32, no. 1, p. 77–80, doi:10.1130/G19887.1.
Ferrari, L., López-Martinez, M., Aguirre-Díaz, G., and Carrasco-Núñez, G., 1999, Space-time patterns of Ceno zoic arc volcanism in central Mexico: From the Sierra Madre Occidental to the Mexican volcanic belt: Geology, v. 27, no. 4, p. 303–306, doi:10.1130/0091-7613(1999)027<0303:STPOCA>2.3.CO;2.
Floyd, P.A., and Leveridge, B.E., 1987, Tectonic environ-ment of the Devonian Gramscatho basin, south Corn-wall: Framework mode and geochemical evidence from turbiditic sandstones: Journal of the Geological Society of London, v. 144, no. 4, p. 531, doi:10.1144/gsjgs.144.4.0531.
Garcia, D., Fonteilles, M., and Moutte, J., 1994, Sedimen-tary fractionation between Al, Ti, and Zr and the gen-esis of strongly peraluminous granites: The Journal of Geology, v. 102, p. 411–422, doi:10.1086/629683.
Gehrels, G., 2011, Detrital zircon U-Pb geochronology: Current methods and new opportunities, in Busby, C., and Azor-Pérez, A., eds., Recent Advances in Tectonics of Sedimentary Basins: Chichester, UK, John Wiley & Sons, 664 p., doi:10.1002/9781444347166.ch2.
Gehrels, G., Valencia, V., and Pullen, A., 2006, Detrital zir-con geochronology by laser ablation multicollector ICPMS at the Arizona LaserChron Center, in Olszew-ski, T., ed., Geochronology: Emerging Opportunities: The Paleontological Society Papers 12, p. 67–76.
Gill, J.B., 1981, Orogenic Andesites and Plate Tectonics: Heidelberg, Germany, Springer, 390 p.
Girty, G.H., Ridge, D.L., Knaack, C., Johnson, D., and Al-Riyami, R.K., 1996, Provenance and depositional setting of Paleozoic chert and argillite, Sierra Nevada, California: Journal of Sedimentary Research, v. 66, no. 1, p. 107–118.
Grajales-Nishimura, J.M., Centeno-García, E., Keppie, J.D., and Dostal, J., 1999, Geochemistry of Paleozoic basalts from the Juchatengo Complex of southern Mexico: Tectonic implications: Journal of South American Earth Sciences, v. 12, no. 6, p. 537–544, doi:10.1016/S0895-9811(99)00037-1.
Gromet, L.P., Dymek, R.F., Haskin, L.A., and Korotev, R.L., 1984, The “North American shale composite”: Its compilation, major and trace element characteris-tics: Geochimica et Cosmochimica Acta, v. 48, no. 12, p. 2469–2482, doi:10.1016/0016-7037(84)90298-9.
Gursky, H.-J., and Michalzik, D., 1989, Lower Permian tur-bidites in the northern Sierra Madre Oriental, Mexico: Zentralblatt für Geologie und Paläontologie, v. 1, no. 5/6, p. 821–838.
Handschy, J.W., and Dyer, R., 1987, Polyphase deformation in Sierra del Cuervo, Chihuahua, Mexico: Evidence for Ancestral Rocky Mountain tectonics in the Ouachita foreland of northern Mexico: Geological Society of America Bulletin, v. 99, no. 5, p. 618–632, doi:10.1130/0016-7606(1987)99<618:PDISDC>2.0.CO;2.
Harris, A., Allen, C., Bryan, S., Campbell, I., Holcombe, R., and Palin, J., 2004, ELA-ICP-MS U-Pb zircon geochronology of regional volcanism hosting the Bajo de la Alumbrera Cu-Au deposit: Implications for por-phyry-related mineralization: Mineralium Deposita, v. 39, p. 46–67, doi:10.1007/s00126-003-0381-0.
Irving, E., 1977, Drift of the major continental blocks since the Devonian: Nature, v. 270, p. 304–309, doi:10.1038/270304a0.
Jacobsen, S.B., and Wasserburg, G.J., 1980, Sm-Nd isotopic evolution of chondrites: Earth and Planetary Science Letters, v. 50, no. 1, p. 139–155, doi:10.1016/0012-821X(80)90125-9.
Jenner, G.A., Longerich, H.P., Jackson, S.E., and Fryer, B.J., 1990, ICP-MS; a powerful tool for high-precision trace-element analysis in earth sciences; evidence from analysis of selected U.S.G.S. reference samples: Chemical Geology, v. 83, p. 133–148, doi:10.1016/0009-2541(90)90145-W.
Keppie, J.D., 2004, Terranes of Mexico revisited: A 1.3 bil-lion year odyssey: International Geology Review, v. 46, no. 9, p. 765–794, doi:10.2747/0020-6814.46.9.765.
Keppie, J.D., Dostal, J., Ortega-Gutiérrez, F., and Lopez, R., 2001, A Grenvillian arc on the margin of Ama-zonia: Evidence from the southern Oaxacan Complex, southern Mexico: Precambrian Research, v. 112, no. 3, p. 165–181, doi:10.1016/S0301-9268(00)00150-9.
Keppie, J.D., Dostal, J., Cameron, K.L., Solari, L.A., Ortega-Gutiérrez, F., and Lopez, R., 2003, Geochronology and geochemistry of Grenvillian igneous suites in the northern Oaxacan Complex, southern Mexico: Tectonic implications: Precambrian Research, v. 120, no. 3, p. 365–389, doi:10.1016/S0301-9268(02)00166-3.
Keppie, J.D., Nance, R.D., Dostal, J., Ortega-Rivera, A., Miller, B.V., Fox, D., Powell, J.T., Mumma, S.A., and Lee, J.K.W., 2004a, Mid-Jurassic tectonothermal event superposed on a Paleozoic geological record in the Acat-lán Complex of southern Mexico: Hotspot activity during the breakup of Pangea: Gondwana Research, v. 7, no. 1, p. 238–260, doi:10.1016/S1342-937X(05)70323-3.
Keppie, J.D., Sandberg, C.A., Miller, B.V., Sánchez-Zavala , J.L., Nance, R.D., and Poole, F.G., 2004b, Implications of latest Pennsylvanian to Middle Permian paleonto-logical and U-Pb SHRIMP data from the Tecomate Formation to re-dating tectonothermal events in the Acatlán Complex, southern Mexico: Inter national Geol ogy Review, v. 46, no. 8, p. 745–753, doi:10.2747/0020-6814.46.8.745.
Keppie, J.D., Nance, R.D., Fernandez-Suarez, J., Storey, C.D., Jeffries, T.E., and Murphy, J.B., 2006, Detrital zircon data from the eastern Mixteca terrane, southern Mexico: Evidence for an Ordovician-Mississippian continental rise and a Permo-Triassic clastic wedge adjacent to Oaxaquia: International Geology Review, v. 48, p. 97–111, doi:10.2747/0020-6814.48.2.97.
Keppie, J.D., Dostal, J., Murphy, J.B., and Nance, R.D., 2008a, Synthesis and tectonic interpretation of the west-ernmost Paleozoic Variscan orogen in southern Mexico: From rifted Rheic margin to active Pacifi c margin: Tec-tonophysics, v. 461, no. 1–4, p. 277–290, doi:10.1016/j.tecto.2008.01.012.
Keppie, J.D., Dostal, J., Miller, B.V., Ramos-Arias, M.A., Morales-Gamez, M., Nance, R.D., Murphy, J.B., Ortega-Rivera, A., Lee, J.K.W., Housh, T., and Cooper, P., 2008b, Ordovician–earliest Silurian rift tholeiites in the Acatlán Complex, southern Mexico: Evidence of rifting on the southern margin of the Rheic Ocean: Tec-tonophysics, v. 461, no. 1–4, p. 130–156, doi:10.1016/j.tecto.2008.01.010.
Keppie, J.D., Nance, R.D., Ramos-Arias, M.A., Lee, J.K.W., Dostal, J., Ortega-Rivera, A., and Murphy, J.B., 2010, Late Paleozoic subduction and exhumation of Cambro-Ordovician passive margin and arc rocks in the northern Acatlán Complex, southern Mexico: Geochronological constraints: Tectonophysics, v. 495, p. 213–229, doi:10.1016/j.tecto.2010.09.019.
Keppie, J.D., Murphy, J.B., Nance, R.D., and Dostal, J., 2012, Mesoproterozoic Oaxaquia-type basement in peri-Gondwanan terranes of Mexico, the Appala-chians, and Europe: TDM age constraints on extent and signifi cance: International Geology Review, v. 54, p. 313–324, doi:10.1080/00206814.2010.543783.
Kerr, A., Jenner, G.A., and Fryer, B.J., 1995, Sm-Nd iso-topic geochemistry of Precambrian to Paleozoic granitoid suites and the deep-crustal structure of the southeast margin of the Newfoundland Appalachians: Canadian Journal of Earth Sciences, v. 32, p. 224–245, doi:10.1139/e95-019.
Kimura, J.-I., Kent, A.J.R., Rowe, M.C., Katakuse, M., Nakano , F., Hacker, B.R., van Keken, P.E., Kawa-bata, H., and Stern, R.J., 2010, Origin of cross-chain
geochemical variation in Quaternary lavas from the northern Izu arc: Using a quantitative mass balance ap-proach to identify mantle sources and mantle wedge processes: Geochemistry, Geophysics, Geosystems, v. 11, no. 10, p. 1–24, doi:10.1029/2010GC003050.
Kirsch, M., Keppie, J.D., Murphy, J.B., and Lee, J.K.W., 2012, Arc plutonism in a transtensional regime: the late Palaeozoic Totoltepec pluton, Acatlán Complex, southern Mexico: International Geology Review (in press), doi:10.1080/00206814.2012.693247.
Le Maitre, R.W., and 14 others, 2002, A Classifi cation of Igneous Rocks and Glossary of Terms: Recommen-dations of the International Union of Geological Sci-ences Subcommission on the Systematics of Igneous Rocks (second edition): New York, Cambridge Uni-versity Press, 236 p.
Lopez, R., Jones, N.W., and Cameron, K.L., 1996, The pre-Jurassic evolution of the Coahuila terrane, Mexico: No evidence of a major change in magmatic source during the course of the Ouachita orogeny: Eos (Transactions, American Geophysical Union), v. 77, no. 46, p. F759.
Ludwig, K.R., and Mundil, R., 2002, Extracting reliable U-Pb ages and errors from complex populations of zircons from Phanerozoic tuffs: Geochimica et Cos-mochimica Acta, Goldschmidt Conference Abstracts, v. 66, no. 15A, p. 463A.
Malone, J.R., Nance, R.D., Keppie, J.D., and Dostal, J., 2002, Deformational history of part of the Acatlán Complex: Late Ordovician–Early Silurian and Early Permian orogenesis in southern Mexico: Journal of South American Earth Sciences, v. 15, no. 5, p. 511–524, doi:10.1016/S0895-9811(02)00080-9.
Martiny-Kramer, B.M., 2008, Estratigrafía y geoquímica de las rocas magmáticas del Paleógeno en el occidente de Oaxaca y su signifi cado petrogenético y tectónico [Ph.D. thesis]: México, D.F., Universidad Autónoma de México, 207 p.
McCulloch, M.T., and Gamble, J.A., 1991, Geochemical and geodynamical constraints on subduction zone magma-tism: Earth and Planetary Science Letters, v. 102, no. 3–4, p. 358–374, doi:10.1016/0012-821X(91)90029-H.
McKee, J.W., Jones, N.W., and Anderson, T.H., 1999, Late Paleozoic and early Mesozoic history of the Las Deli-cias terrane, Coahuila, Mexico, in Bartolini, C., Wilson, L.J., and Lawton, T.F., eds., Mesozoic Sedimentary and Tectonic History of North-Central Mexico: Geological Society of America Special Paper 340, p. 161–189.
Miller, C.F., and Mittlefehldt, D.W., 1982, Depletion of light rare-earth elements in felsic magmas: Geol-ogy, v. 10, no. 3, p. 129–133, doi:10.1130/0091-7613(1982)10<129:DOLREI>2.0.CO;2.
Morales-Gámez, M., Keppie, J.D., and Norman, M.D., 2008, Ordovician-Silurian rift-passive margin on the Mexican margin of the Rheic Ocean overlain by Carboniferous-Permian periarc rocks: Evidence from the eastern Acat-lán Complex, southern Mexico: Tectonophysics, v. 461, no. 1–4, p. 291–310, doi:10.1016/j.tecto.2008.01.014.
Morales-Gámez, M., Keppie, J.D., Lee, J.K.W., and Ortega-Rivera, A., 2009, Palaeozoic structures in the Xayacatlán area, Acatlán Complex, southern Mexico: Transtensional rift- and subduction-related deforma-tion along the margin of Oaxaquia: International Ge-ology Review, v. 51, no. 4, p. 279–303, doi:10.1080/00206810802688659.
Morel, P., and Irving, E., 1981, Paleomagnetism and the evolution of Pangea: Journal of Geophysical Research, v. 86, p. 1858–1872, doi:10.1029/JB086iB03p01858.
Murillo-Muñeton, G., 1994, Petrologic and Geochronologic Study of Grenville-Age Granulites and Post-Granulite Plutons from the La Mixtequita Area, State of Oaxaca in Southern Mexico, and their Tectonic Signifi cance [M.Sc. thesis]: Los Angeles, California, University of Southern California, 163 p.
Murphy, J.B., and Dostal, J., 2007, Continental mafi c mag-matism of different ages in the same terrane: Constraints on the evolution of an enriched mantle source: Geology, v. 35, no. 4, p. 335–338, doi:10.1130/G23072A.1.
Murphy, J.B., and Nance, R.D., 2002, Nd-Sm isotopic sys-tematics as tectonic tracers: An example from West Avalonia, Canadian Appalachians: Earth-Science Reviews, v. 59, p. 77–100, doi:10.1016/S0012-8252(02)00070-3.
on September 13, 2012gsabulletin.gsapubs.orgDownloaded from
Permian–Carboniferous arc magmatism and basin evolution along the western margin of Pangea
Geological Society of America Bulletin, September/October 2012 1627
Murphy, J.B., Keppie, J.D., Nance, R.D., Miller, B.V., Dostal, J., Middleton, M., Fernandez-Suarez, J., Jef-fries, T.E., and Storey, C.D., 2006, Geochemistry and U-Pb protolith ages of eclogitic rocks of the Asis Lithodeme, Piaxtla Suite, Acatlán Complex, southern Mexico: Tectonothermal activity along the southern margin of the Rheic Ocean: Journal of the Geological Society of London, v. 163, p. 683–695, doi:10.1144/0016-764905-108.
Murphy, J.B., Gutiérrez-Alonso, G., Fernández-Suárez, J., and Braid, J.A., 2008, Probing crustal and mantle lithosphere origin through Ordovician volcanic rocks along the Iberian passive margin of Gondwana: Tec-tonophysics, v. 461, no. 1–4, p. 166–180, doi:10.1016/j.tecto.2008.03.013.
Muttoni, G., Kent, D.V., Garzanti, E., Brack, P., Abrahamsen, N., and Gaetani, M., 2003, Early Permian Pangea ‘B’ to Late Permian Pangea ‘A’: Earth and Planetary Sci-ence Letters, v. 215, no. 3, p. 379–394, doi:10.1016/S0012-821X(03)00452-7.
Navarro-Santillán, D., Sour-Tovar, F., and Centeno-García, E., 2002, Lower Mississippian (Osagean) brachiopods from the Santiago Formation, Oaxaca, Mexico: Strati-graphic and tectonic implications: Journal of South American Earth Sciences, v. 15, no. 3, p. 327–336, doi:10.1016/S0895-9811(02)00047-0.
Ortega-Gutiérrez, F., 1978, Estratigrafía del Complejo Acat-lán en la Mixteca Baja, Estados de Puebla y Oaxaca: Universidad Nacional Autónoma de México, Instituto de Geología, Revista, v. 2, no. 2, p. 112–131.
Ortega-Obregón, C., Keppie, D.J., Solari, L.A., and Ortega-Gutiérrez, F., 2003, Geochronology and geochemistry of the ~917 Ma, calc-alkaline Etla granitoid pluton (Oaxaca, southern Mexico): Evidence of post-Grenvil-lian subduction along the northern margin of Amazo-nia: International Geology Review, v. 45, p. 596–610, doi:10.2747/0020-6814.45.7.596.
Ortega-Obregón, C., Keppie, J.D., Murphy, J.B., Lee, J.K.W., and Ortega-Rivera, A., 2009, Geology and geochronology of Paleozoic rocks in western Acatlán Complex, southern Mexico: Evidence for contiguity across an extruded high-pressure belt and constraints on Paleozoic reconstructions: Geological Society of America Bulletin, v. 121, no. 11–12, p. 1678–1694, doi:10.1130/B26597.1.
Ortega-Obregón, C., Murphy, J.B., and Keppie, J.D., 2010, Geochemistry and Sm-Nd isotopic systematics of Ediacaran–Ordovician, sedimentary and bimodal igne-ous rocks in the western Acatlán Complex, southern Mexico: Evidence for rifting on the southern margin of the Rheic Ocean: Lithos, v. 114, no. 1–2, p. 155–167, doi:10.1016/j.lithos.2009.08.005.
Pearce, J.A., 1982, Trace element characteristics of lavas from destructive plate boundaries, in Thorpe, R.S., ed., Orogenic Andesites and Related Rocks: Chichester, UK, John Wiley and Sons, p. 525–548.
Pearce, J.A., 1996, A user’s guide to basalt discrimination diagrams, in Wyman, D.A., ed., Trace Element Geo-chemistry of Volcanic Rocks: Applications for Mas-sive Sulphide Exploration: Geological Association of Canada Short Course Notes 12, p. 79–113.
Pearce, J.A., and Peate, D.W., 1995, Tectonic implications of the composition of volcanic arc magmas: Annual Review of Earth and Planetary Sciences, v. 23, p. 251–285, doi:10.1146/annurev.ea.23.050195.001343.
Pearce, J.A., Harris, N.B.W., and Tindle, A.G., 1984, Trace element discrimination diagrams for the tectonic inter-pretation of granitic rocks: Journal of Petrology, v. 25, p. 956–983.
Ramírez-Espinosa, J., Flores, A., Buitrón, B., Silva, A., and Vachard, D., 2000, Una nueva localidad del Paleo-zoico superior al norosete de Acatlán, Puebla: GEOS, Resúmenes y programas, v. 20, no. 3, p. 159.
Ramos-Arias, M.A., and Keppie, J.D., 2011, U-Pb Neo-proterozoic–Ordovician protolith age constraints for high- to medium-pressure rocks thrust over low-grade metamorphic rocks in the Ixcamilpa area, Acatlán Complex, southern Mexico: Canadian Journal of Earth Sciences, v. 48, no. 1, p. 45–61, doi:10.1139/E10-082.
Riggs, N.R., Barth, A.P., González-León, C., Walker, J.D., and Wooden, J.L., 2009, Provenance of Upper Triassic strata in southwestern North America as suggested by
isotopic analysis and chemistry of zircon crystals: Geo-logical Society of America Abstracts with Programs, v. 41, no. 7, p. 540.
Riggs, N.R., Barth, A.P., Wooden, J.L., and Walker, J.D., 2010, Use of zircon geochemistry to tie volcanic detritus to source plutonic rocks: An example from Permian northwestern Sonora, Mexico: Geological Society of America Abstracts with Programs, v. 42, no. 5, p. 267.
Rosales-Lagarde, L., Centeno-García, E., Dostal, J., Sour-Tovar, F., Ochoa-Camarillo, H., and Quiroz-Barroso, S., 2005, The Tuzancoa Formation: Evidence of an Early Permian submarine continental arc in east-central Mex-ico: International Geology Review, v. 47, p. 901–919, doi:10.2747/0020-6814.47.9.901.
Rubatto, D., 2002, Zircon trace element geochemistry: Parti-tioning with garnet and the link between U-Pb ages and metamorphism: Chemical Geology, v. 184, no. 1–2, p. 123–138, doi:10.1016/S0009-2541(01)00355-2.
Ruiz, J., Patchett, P.J., and Ortega-Gutiérrez, F., 1988, Protero zoic and Phanerozoic basement terranes of Mexico from Nd isotopic studies: Geological Society of America Bulletin, v. 100, no. 2, p. 274–281, doi:10.1130/0016-7606(1988)100<0274:PAPBTO>2.3.CO;2.
Ruiz-Castellanos, M., 1979, Rubidium-Strontium Geo-chronol ogy of the Oaxaca and Acatlán Metamorphic Areas of Southern Mexico [Ph.D. thesis]: Dallas, Texas, University of Texas, 192 p.
Sánchez-Zavala, J.L., 2008, Estratigrafía, Sedimentología y Análisis de Procedencia de la Formación Tecomate y su Papel en la Evolución del Complejo Acatlán, Sur de México [Ph.D. thesis]: México D.F., Universidad Autónoma de México (UNAM), 226 p.
Sánchez-Zavala, J.L., Jenner, G.A., Belousova, E.A., and Macías-Romo, C., 2004, Ordovician and Meso protero-zoic zircons from the Tecomate Formation and Esperanza granitoids, Acatlán Complex, southern Mexico: Local provenance in the Acatlán and Oaxacan Complexes: Inter-national Geology Review, v. 46, no. 11, p. 1005–1021, doi:10.2747/0020-6814.46.11.1005.
Saunders, A.D., Norry, M.J., and Tarney, J., 1988, Origin of MORB and chemically-depleted mantle reservoirs: Trace element constraints, in Menzies, M.A., and Cox, K.G., eds., Oceanic and Continental Lithosphere: Simi larities and Differences: Journal of Petrology, Spe-cial Issue, v. 1, p. 415–455.
Schaaf, P., Weber, B., Weis, P., Gross, A., Ortega-Gutiérrez , F., and Köhler, H., 2002, The Chiapas Massif (Mex-ico) revised: New geologic and isotopic data for basement characteristics, in Miller, H., ed., Contribu-tions to Latin American Geology: Neues Jahrbuch für Geologie und Paläontologie Abhandlungen, v. 225, no. 1, p. 1–23.
Servicio Geológico Mexicano, 2001, Carta Geológico-Minera, Orizaba E14–6: Pachuca, Mexico, Servicio Geológico Mexicano, scale 1:250,000, 1 sheet.
Servicio Geológico Mexicano, 2004a, Primera Derivada Vertical del Campo Magnético Total Reducido al Polo en Contornos a Color, Ixcaquixtla E14–B74: Pachuca, Mexico, Servicio Geológico Mexicano, scale 1:50,000, 1 sheet.
Servicio Geológico Mexicano, 2004b, Primera Derivada Vertical del Campo Magnético Total Reducido al Polo en Contornos a Color, Petlalcingo E14–B84: Pachuca, Mexico, Servicio Geológico Mexicano, scale 1:50,000, 1 sheet.
Slack, J.F., and Stevens, B.P.J., 1994, Clastic metasediments of the Early Proterozoic Broken Hill Group, New South Wales, Australia: Geochemistry, provenance, and metallogenic signifi cance: Geochimica et Cosmochi-mica Acta, v. 58, p. 3633–3652, doi:10.1016/0016-7037(94)90155-4.
Smith, A., and Hallam, A., 1970, The fi t of the southern conti-nents: Nature, v. 225, p. 139–144, doi:10.1038/225139a0.
Solari, L.A., Dostal, J., Ortega-Gutiérrez, F., and Keppie, J.D., 2001, The 275 Ma arc-related La Carbonera stock in the northern Oaxacan Complex of southern Mexico: U-Pb geochronology and geochemistry: Revista Mexi-cana de Ciencias Geológicas, v. 18, no. 2, p. 149–161.
Solari, L.A., Keppie, J.D., Ortega-Gutiérrez, F., Cameron, K.L., Lopez, R., and Hames, W.E., 2003, 990 and 1100 Ma Grenvillian tectonothermal events in the northern Oaxacan Complex, southern Mexico: Roots of
an orogen: Tectonophysics, v. 365, no. 1–4, p. 257–282, doi:10.1016/S0040-1951(03)00025-8.
Solari, L.A., de León, R.T., Hernández Pineda, G., Solé, J., Solis-Pichardo, G., and Hernandez-Trevino, T., 2007, Tectonic signifi cance of Cretaceous-Tertiary magmatic and structural evolution of the northern margin of the Xolapa Complex, Tierra Colorada area, southern Mex-ico: Geological Society of America Bulletin, v. 119, no. 9–10, p. 1265–1279, doi:10.1130/B26023.1.
Solari, L.A., Ortega-Gutiérrez, F., Elías-Herrera, M., Gómez-Tuena, A., and Schaaf, P., 2010, Refi ning the age of magmatism in the Altos Cuchumatanes, western Guatemala, by LA-ICPMS, and tectonic implications: International Geology Review, v. 52, no. 9, p. 977–998, doi:10.1080/00206810903216962.
Steiger, R.H., and Jäger, E., 1977, Subcommission on geochronology: Convention on the use of decay con-stants in geo- and cosmochronology: Earth and Plan-etary Science Letters, v. 36, p. 359–362, doi:10.1016/0012-821X(77)90060-7.
Stern, R.J., 2002, Crustal evolution in the East African oro-gen: A neodymium isotopic perspective: Journal of African Earth Sciences, v. 34, no. 3–4, p. 109–117, doi:10.1016/S0899-5362(02)00012-X.
Stewart, J.H., Blodgett, R.B., Boucot, A.J., Carter, J.L., and López, R., 1999, Exotic Paleozoic strata of Gond-wanan provenance near Ciudad Victoria, Tamaulipas, Mexico, in Ramos, V.A., and Keppie, D.J., eds., Lau-rentia-Gondwana Connections before Pangea: Geologi-cal Society of America Special Paper 336, p. 227–252.
Sun, S.S., and McDonough, W., 1989, Chemical and isotopic systematics of oceanic basalts: Implications for mantle composition and processes, in Saunders, A.D., and Norry, M.J., eds., Magmatism in the Ocean Basins: Geological Society of London Special Publication 42, p. 313–345.
Talavera-Mendoza, O., Ruiz, J., Gehrels, G.E., Meza-Figueroa, D.M., Vega-Granillo, R., and Campa-Uranga , M.F., 2005, U-Pb geochronology of the Acatlán Com-plex and implications for the Paleozoic paleogeog-raphy and tectonic evolution of southern Mexico: Earth and Planetary Science Letters, v. 235, p. 682–699, doi:10.1016/j.epsl.2005.04.013.
Taylor, S.R., and McLennan, S.M., 1985, The Continental Crust: Its Composition and Evolution: Oxford, UK, Blackwell Publishing, 312 p.
Taylor, S.R., and McLennan, S.M., 1995, The geochemical evo-lution of the continental crust: Reviews of Geophysics , v. 33, no. 2, p. 241–265, doi:10.1029/95RG00262.
Tolson, G., 2007, The Chacalapa fault, southern Oaxaca, México, in Alaniz-Álvarez, S.A., and Nieto-Samaniego, Á.F., eds., Geology of México: Celebrating the Cente-nary of the Geological Society of México: Geological Society of America Special Paper 422, p. 343–357.
Torres, R., Ruiz, J., Patchett, P.J., and Grajales-Nishimura, J.M., 1999, Permo-Triassic continental arc in eastern Mexico; tectonic implications for reconstructions of southern North America, in Bartolini, C., Wilson, J.L., and Lawton, T.F., eds., Mesozoic Sedimen-tary and Tectonic History of North-Central Mexico: Geological Society of America Special Paper 340, p. 191–196.
Vachard, D., and de Dios, A.F., 2002, Discovery of latest Devonian/earliest Mississippian microfossils in San Salvador Patlanoaya (Puebla, Mexico): Biogeographic and geodynamic consequences: Comptes Rendus Geo-science, v. 334, p. 1095–1101, doi:10.1016/S1631-0713(02)01851-5.
Vachard, D., de Dios, A.F., Buitrón, B.E., and Grajales, M., 2000, Biostratigraphie par fusulines des calcaires Carbonifères et Permiens de San Salvador Patlanoaya (Puebla, Mexique): Geobios, v. 33, no. 1, p. 5–33, doi:10.1016/S0016-6995(00)80145-X.
Vachard, D., de Dios, A.F., and Buitron, B., 2004, Guada-lupian and Lopingian (Middle and Late Permian) de-posits from Mexico and Guatemala, a review with new data: Geobios, v. 37, p. 99–115, doi:10.1016/j.geobios.2003.02.002.
Vega-Carrillo, J.J., Elías-Herrera, M., and Ortega-Gutiérrez, F., 1998, Complejo plutónico de Cuanana: Basamento prejurásico en el borde meridional del terreno Mixteco e interpretación litotectónica, in Alaniz-Álvarez, S.A., Ferrari, L., Nieto-Samaniego, Á.F., and Ortega-Rivera,
on September 13, 2012gsabulletin.gsapubs.orgDownloaded from
Kirsch et al.
1628 Geological Society of America Bulletin, September/October 2012
M.A., eds., Primera Reunión Nacional de Ciencias de la Tierra, 21 al 25 de septiembre de 1998 : México, D. F., Libro de Resúmenes, p. 145.
Vega-Granillo, R., Talavera-Mendoza, O., Meza-Figueroa, D.M., Ruiz, J., Gehrels, G.E., López-Martínez, M., and de la Cruz-Vargas, J.C., 2007, Pressure-temperature-time evolution of Paleozoic high-pressure rocks of the Acatlán Complex (southern Mexico): Implications for the evolution of the Iapetus and Rheic Oceans: Geo-logical Society of America Bulletin, v. 119, no. 9/10, p. 1249–1264, doi:10.1130/B226031.1.
Vega-Granillo, R., Calmus, T., Meza-Figueroa, D., Ruiz, J., Talavera-Mendoza, O., and López-Martínez, M., 2009, Structural and tectonic evolution of the Acatlán Complex, southern Mexico: Its role in the collisional history of Laurentia and Gondwana: Tectonics, v. 28, p. TC4008, doi:10.1029/2007TC002159.
Weber, B., Cameron, K.L., Osorio, M., and Schaaf, P., 2005, A Late Permian tectonothermal event in Grenville crust
of the southern Maya terrane: U-Pb zircon ages from the Chiapas Massif, southeastern Mexico: Inter national Geology Review, v. 47, p. 509–529, doi:10.2747/0020-6814.47.5.509.
Weber, B., Iriondo, A., Premo, W.R., Hecht, L., and Schaaf, P., 2007, New insights into the history and origin of the southern Maya block, SE México: U-Pb SHRIMP zircon geochronology from metamorphic rocks of the Chiapas massif: International Journal of Earth Sciences, v. 96, no. 2, p. 253–269, doi:10.1007/s00531-006-0093-7.
Winchester, J.A., and Floyd, P.A., 1977, Geochemical discrimination of different magma series and their differentiation products using immobile elements: Chemical Geology, v. 20, no. 4, p. 325–343, doi:10.1016/0009-2541(77)90057-2.
Wood, D.A., Joron, J.L., and Treuil, M., 1979, Re-appraisal of the use of trace-elements to classify and discriminate between magma series erupted in different tectonic set-
tings: Earth and Planetary Science Letters, v. 45, no. 2, p. 326–336, doi:10.1016/0012-821X(79)90133-X.
Yañez, P., Patchett, P.J., Ortega-Gutiérrez, F., and Gehrels, G.E., 1991, Isotopic studies of the Acatlán Complex, southern Mexico: Implications for Paleozoic North American tectonics: Geological Society of America Bul-letin, v. 103, no. 6, p. 817–828, doi:10.1130/0016-7606(1991)103<0817:ISOTAC>2.3.CO;2.
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Artículo: Kirsch, M., Keppie, J.D., Murphy, J.B., y Lee, J.K.W., Arc plu-tonism in a transtensional regime: the Late Palaeozoic Totoltepec pluton,Acatlán Complex, southern Mexico: International Geology Review, en pren-sa, doi: 10.1080/00206814.2012.693247.
Contribuciones individuales de los autores:
Moritz Kirsch: concepción y el diseño del estudio; trabajo de campoel cual incluye mapeo, obtención de datos estructurales, selección depuntos de muestreo y toma de muestras para el análisis de petrografíay de microsonda, así como la geocronología 40Ar/39Ar; adquisiciónde datos de microsonda; revisión de literatura; análisis y interpreta-ción de datos; redacción del artículo.
J. Duncan Keppie: contribución a la concepción y el diseño; supervi-sión de las actividades de campo; participación en la interpretación delos datos y en la revisión del artículo remitido; adquisición de fondos.
J. Brendan Murphy: contribución a la concepción y el diseño; supervi-sión de las actividades de campo; participación en la interpretación delos datos y en la revisión del artículo remitido; adquisición de fondos.
James K.W. Lee: participación en la interpretación de datos y en la re-visión del artículo sometido; encargado de las instalaciones de análisis40Ar/39Ar.
33
International Geology ReviewiFirst, 2012, 1–24
Arc plutonism in a transtensional regime: the late Palaeozoic Totoltepec pluton, AcatlánComplex, southern Mexico
Moritz Kirscha*, J. Duncan Keppieb , J. Brendan Murphyc and James K.W. Leed
aCentro de Geociencias, Universidad Nacional Autónoma de México, 76230 Querétaro, Mexico; bDepartamento de Geología Regional,Instituto de Geología, Universidad Nacional Autónoma de México, 04510 México D.F., Mexico; cDepartment of Earth Sciences,
St. Francis Xavier University, Antigonish, NS, Canada; dDepartment of Geological Sciences and Geological Engineering, Queen’sUniversity, Kingston, ON K7L 3N6, Canada
(Accepted 9 May 2012)
The ENE-trending, ca. 306–287 Ma, Totoltepec pluton is part of a Carboniferous–Permian continental magmatic arc onthe western Pangaean margin. The 15 km × 5 km pluton is bounded by two N–S Permian dextral faults, an E–W thrustto the south, and an E–W normal fault to the north. Thermobarometric data indicate that the main, ca. 289–287 Ma, partof the pluton was emplaced at ≤20 km depth and ≥700◦C and was exhumed to 11 km and 400◦C in 4 ± 2 million years.We have documented the following intrusive sequence: (1) the 306 Ma northern marginal mafic phase; (2) the 287 Mamain trondhjemitic phase; and (3) ca. 289–283 Ma sub-vertical dikes that vary from (a) N39E, undeformed with crystalgrowth perpendicular to the margins, through (b) ca. N50–73E, foliated and folded with sinistral shear indicators, to (c)N73–140E and boudinaged. The obliquity of the boundary between the folded and stretched dikes relative to the N–S dextralfaults suggests sequential emplacement in a transtensional regime (with 20% E–W extension), followed by different degreesof clockwise rotation passing through a shortening field accompanied by sinistral shear into an extensional field. The ca.289–287 Ma intrusion also contains a steep ENE-striking foliation and hornblende lineations varying from sub-horizontalto steeply plunging, probably the result of emplacement in a triclinic strain regime. We infer that magmatism ceased whensome of the dextral motion was transferred from the western to the eastern bounding fault, causing thrusting to take placealong the southern boundary of the pluton. This mechanism is also invoked for the rapid uplift and exhumation of the plutonbetween ca. 287 Ma and 283 Ma. The distinctive characteristics of the Totoltepec pluton should prove useful in identifyingsimilar tectonic settings within continental arcs.
Keywords: emplacement; syntectonic pluton emplacement; magmatic arc; transtension; Acatlán Complex; Mexico; Pangaea
Introduction
Calc-alkaline magmatism at convergent plate margins iscommonly associated with strike–slip faulting (e.g. Fitch1972; Jarrard 1986; Glazner 1991; Tobisch and Cruden1995; Gibbons and Moreno 2002), which provides conduitsfor magma ascent, accommodates pluton emplacement(Tikoff and Teyssier 1992; Grocott et al. 1994; Grocottand Taylor 2002), and facilitates the exhumation of deepercrustal sections (Crawford et al. 1999; Žák et al. 2005).Due to the complex interaction between thermal and struc-tural effects of plutonism and regional-scale deformation,the mechanisms responsible for pluton emplacement incontinental magmatic arcs have attracted much attention.
We present a case study of the mechanisms control-ling the emplacement of the ca. 306–287 Ma, supra-subduction zone Totoltepec pluton in the eastern AcatlánComplex, southern Mexico. This pluton is representativeof a Pennsylvanian to Early Permian arc assemblage
*Corresponding author. Email: [email protected]
along the western margin of Pangaea that developedsoon after Pangaea formed (e.g. Torres et al. 1999;Dickinson and Lawton 2001; Centeno-García 2005). A pre-vious contribution (Kirsch et al. 2012) documented thegeochemical/isotopic characteristics and age of the plu-ton, and indicates that the body is a composite intrusionwith mantle and crustal sources, emplaced along an imma-ture, trenchward part of the late Palaeozoic continentalarc. In this article, we use a combination of meso- andmicrofabric analyses, Al-in-hornblende thermobarometryand 40Ar/39Ar geochronology, which provide evidence for(1) the incremental assembly of the pluton (e.g. Colemanet al. 2004; Glazner et al. 2004; de Saint Blanquat et al.2006; Pignotta et al. 2010), (2) sequential injection ofsheets (Miller and Paterson 2001; Mahan et al. 2003),(3) progressive fabric development during crystallizationof the pluton in a strain field (e.g. Paterson et al. 1989,1998; Tribe and D’Lemos 1996; Barros et al. 2001), and
ISSN 0020-6814 print/ISSN 1938-2839 online© 2012 Taylor & Francishttp://dx.doi.org/10.1080/00206814.2012.693247http://www.tandfonline.com
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(4) intrusion in a transtensional environment (Petford andAtherton 1992; Paterson and Fowler 1993; Hanson andGlazner 1995; Kratinová et al. 2007). Given the plutonlocation, our data also provide insights into the geody-namic evolution of the late Palaeozoic magmatic arc thatdeveloped along the periphery of Pangaea.
Geological setting
The Totoltepec pluton is well-exposed in the eastern partof the Palaeozoic Acatlán Complex (Figure 1A; Mixtecaterrane) and is one of several Carboniferous to Permianintrusions associated with a continental magmatic arcthat formed as a consequence of subduction along thepalaeo-Pacific margin of Pangaea (Torres et al. 1999;Keppie et al. 2004a; Kirsch et al. 2012). The AcatlánComplex is tectonically bound to the south by theCenozoic La Venta/Chacalapa Fault (Solari et al. 2007;Tolson 2007), juxtaposing it against the Xolapa Complex(Figure 1A). To the west, the Acatlán Complex is thrustover Cretaceous platformal carbonates, located betweenthe exposed Acatlán Complex and the accreted Guerreroterrane (Centeno-García et al. 2008; Ramos-Arias andKeppie 2011). To the north, the complex is uncon-formably overlain by Mesozoic rocks and the CenozoicTrans-Mexican Volcanic Belt (Ferrari et al. 1999). To theeast, the Acatlán Complex is bounded by the >150 km-long, N–S-striking, dextral Caltepec Fault Zone (CFZ),which separates it from the ∼1 Ga Oaxacan Complex(Elías-Herrera and Ortega-Gutiérrez 2002). White micafrom a mylonitic mica schist in the CFZ yielded a40Ar/39Ar age of ca. 269 million years (Elías-Herreraet al. 2005). However, two syntectonic plutons – the ca.307 Ma Cuananá plutonic complex and the ca. 270 MaCozahuico granite – attest to tectonomagmatic activityalong this fault during late Pennsylvanian to Early Permiantimes.
The Totoltepec pluton is approximately elliptical inmap view; its long axis (15 km) trends roughly WNW–ENE (Figure 1B) and it crops out over an area of 68 km2
with a relief of 490 m. External contacts between theTotoltepec pluton and the surrounding strata are eithernon-conformable or tectonic (Malone et al. 2002), i.e.none of the original contact relationships are preserved.Along its southern margin, the Totoltepec pluton is thrustover intensely deformed, lower greenschist-facies metased-imentary rocks of the Pennsylvanian to Middle PermianTecomate Formation (Keppie et al. 2004b; Kirsch et al.2012). To the east, an unnamed, medium-grade metamor-phic unit consisting of garnet schist and quartzite with rareamphibolite dikes is faulted against the Totoltepec plu-ton (Kirsch et al. 2012). To the north, the granitoid bodyis unconformably overlain by and faulted against redbedsof inferred Jurassic age (Malone et al. 2002). The N–Strending, dextral San Jerónimo fault (Morales-Gámez et al.
2009) separates the pluton from the Tecomate Formationand Jurassic redbeds along its western margin.
Field relationships and geochronological data indicatethat the Totoltepec pluton was emplaced over a ca. 19 mil-lion year period involving at least two discrete intrusions,i.e. (1) 306 ± 2 Ma, mafic–ultramafic intrusive bodiesof hornblende-rich gabbros and hornblendites that occuras three minor (0.2–0.6 km2), elongate, fault-boundedbodies distributed along the northern and northeasternmargin of the pluton (Kirsch et al. 2012), and (2) themain body, making up approximately 98% of the exposedarea, dated at 287 ± 2 Ma (trondhjemite: Yañez et al.1991), 289 ± 1 Ma (diorite: Keppie et al. 2004a), and289 ± 2 Ma (quartz diorite: Kirsch et al. 2012), rang-ing in composition (in order of decreasing proportion)from trondhjemite (hornblende-rich) tonalite, and dioriteto quartz granitoid, granodiorite, monzogranite, and rareplagioclase-rich (cumulate?) layers.
Geochemistry of the older marginal Totoltepec mafic–ultramafic rocks indicates an arc tholeiitic to calc-alkalineaffinity characterized by high LILE/HFSE ratios, flat REEpatterns, and initial εNd values of +1.3 to +3.3 (t =306 Ma). The younger Totoltepec main body exhibits acalc-alkaline trace-element geochemistry with flat to mod-erately fractionated LREE-enriched patterns, and initialεNd values of –0.8 to +2.6 (t = 289 Ma; Kirsch et al.2012). Although minor degrees of crustal assimilation andfractionation processes are detected by simple isotopicmodelling, the isotopic data plot within the evolutionaryenvelope defined by Ordovician mafic rocks of the Mixtecaterrane interpreted to have been derived from a ca. 1.0 Gasubcontinental lithospheric mantle (Murphy et al. 2006;Ortega-Obregón et al. 2010).
Lithological units and internal contacts
The oldest, ca. 306 Ma gabbros and minor hornblenditesoccur in three fault-bounded, lenticular bodies along thenorthern and northeastern margin of the pluton. Thesemafic to ultramafic rocks are massive to weakly foliatedand, in places, possess a compositional banding. Locally,they are intruded by steep, <1 m-wide, intensely deformed,locally disrupted felsic dikes (Figure 2A) of inferred289–287 Ma age (Kirsch et al. 2012). The ca. 289–287 Marocks from the main body of the pluton have two modesof occurrence: (1) hornblende-bearing mafic to interme-diate rocks, which occur as sheets consisting of compo-sitionally banded, foliated, locally mylonitic, fine grainedto megacrystic hornblende diorite, quartz diorite, andtonalite and (2) felsic rocks, forming the interior andlargest proportion of the Totoltepec pluton, chiefly com-posed of equigranular, weakly to moderately foliatedtrondhjemite.
The mafic–intermediate sheeted domain occurs assmaller bodies along the southern margin of the pluton
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Figure 1. (A) Location of the study area (box) with respect to the principal geologic features of southern Mexico (modified from Keppieet al. 2008). (B) Simplified geological map and (C) interpretative cross section of the Totoltepec pluton and surrounding country rocks.Short, heavy dashes represent locations of measured foliations; crosses are interpreted foliation patterns.
and in a larger, margin-parallel, lenticular, sigmoidal zone(Figures 1B and 3). These zones are composed of steeplydipping to sub-vertical, aplitic to coarse-grained sheets,
or dikes of centimetre to several tens(?) of metres widthdisplaying variable degrees of pinch-and-swell undula-tions (Figure 2D). Locally, dikes occur as swarms of
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Figure 2. Diking in the Totoltepec pluton. (A) Disaggregated felsic dike in marginal hornblende gabbro. (B) Swarm of parallel, narrow,interconnected mafic dikes that locally display tapering terminations. (C) Boudinaged composite dike with a felsic interior and a maficmargin. (D) Sequence of pinching and swelling dikes composing the mafic–intermediate sheeted domain in the southern part of thepluton. (E) Gently folded pegmatite dike, and (F) fabric-discordant late felsic dike in the sheeted zone. (G) Close-up of Figure 2E,showing elongate, sigmoidal quartz grains growing perpendicular to the dike margin. (H) Sigmoidal internal fabric of a felsic dike inthe mafic–intermediate sheeted zone. (I) Deflection of amphibole into the plane of cross-cutting dikes. (J) Aplitic dike cross-cutting thefabric of megacrystic diorite. Note the dike-internal foliation parallel to the dike margin. (K) Trondhjemite dike in the felsic interior of thepluton.
many parallel, narrow (2–15 cm wide), steep, anasto-mosing sheets that locally show tapering terminations(Figure 2B), or as 10–15 cm-wide composite dikes with a
felsic, pegmatitic interior and a mafic margin (Figure 2C).Dikes of trondhjemitic or quartz-rich granitoid compo-sition, which are inferred to be co-magmatic with the
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felsic pluton interior based on matching petrographic andgeochemical characteristics (Kirsch et al. 2012), intrudethe mafic–intermediate sheeted domain and are commonlylaterally traceable for several metres along strike. Thesefelsic dikes are generally steep and either (1) fabric-discordant, around 10 cm wide, and undeformed to gen-tly folded (Figures 2E and 2F) or (2) fabric-concordant,5–40 cm wide, and exhibiting pinch-and-swell as well asboudinage structures (e.g. Figure 3D). The felsic dikes varyfrom fine grained to pegmatitic. The transition betweenthe mafic–intermediate sheeted zone and the more felsicpluton interior is characterized by the gradual decrease inthe occurrence of mafic dikes.
Compared with the mafic–intermediate sheeteddomain, the felsic interior part of the pluton is compo-sitionally and texturally more homogeneous. In certainlocations, however, the felsic interior exhibits elevatedmodal plagioclase or biotite, with subordinate granodioriteand monzogranite occurring near the northern boundaryof the pluton. Moreover, although less conspicuous dueto their compositional similarity, felsic dikes intrudetrondhjemite in the main body of the pluton (Figure 2K).
Enclaves in the Totoltepec pluton are very rareand heterogeneously distributed (Figure 4). In themafic–intermediate sheeted domain, these includecentimetre- to decimetre-sized, rounded to elongate,foliated microgranular enclaves (autoliths) of dioriticcomposition (Figure 4A), whose contacts with the igneoushost are defined by chilled margins or dark, hornblende-rich reaction rims (Figure 4B). Elongate enclaves arecommonly oriented parallel to the foliation in the hostrock (Figure 4C). Locally, within the mafic–intermediatesheeted domain, 5–15 cm-long, partly disaggregated clotsof hornblende can be observed (Figure 4D). The interiorfelsic domain locally contains (1) isolated, centimetre-sized, ovoid globules made up of coarse-grained biotite(Figure 4E) and (2) strongly sheared, fault-bounded micro-dioritic enclaves of 25 cm length (Figure 4F). No xenolithsderived from the surrounding country rocks have beenrecognized in the Totoltepec pluton, consistent with theabsence of xenocrystic zircons (Kirsch et al. 2012).
Locally within the mafic–intermediate sheeted domain,a steeply dipping textural and compositional banding isdeveloped, made up of alternating coarse-grained and fine-grained bands that coincide with subtle differences inthe relative proportions of hornblende and plagioclase.This banding is most conspicuous in an outcrop east ofSanto Domingo Tonahuixtla (Figures 1B and 3), whereindividual layers are continuous for several metres alongstrike. In diorite, the banding is irregularly spaced, consist-ing of a few millimetres to about 1.5 cm-wide leucocraticand relatively coarse-grained bands, and approximately0.5–3.5 cm, locally bifurcating, dark (fine-grained) bands(Figure 3H). In tonalite, dark and light bands have a sim-ilar average width of about 3 cm (Figure 3I). In bothlithologies, light bands exhibit a porphyritic grain-size
distribution, containing hornblende (diorite) or plagioclase(tonalite) phenocrysts of up to 0.5–1 cm length in a fine-grained matrix. Dark bands are composed of small grainswith roughly equal grain size. The transition between lightand dark layers is generally sharp and the rocks tend tosplit along this anisotropy plane. Locally, within bandedtonalite, however, plagioclase phenocrysts are observedto grow across the boundaries between fine-grained andcoarse-grained domains.
Petrography
The ca. 306 Ma marginal mafic–ultramafic bodies of theTotoltepec pluton are dominated by hornblende gabbro,with averages of 53% modal plagioclase (labradorite), 37%amphibole, and 10% other phases including magnetite,ilmenite, chalcopyrite, muscovite, titanite, and zircon, aswell as secondary minerals epidote, chlorite, sericite, andantigorite. Locally, the gabbro grades into hornblendite,which is characterized by approximately 90% modalamphibole.
The ca. 289–287 Ma main body of the pluton pre-dominantly consists of trondhjemite, whose average modalcomposition is 54% plagioclase (oligoclase), 35% quartz,and 11% other constituents, including primary muscovite,biotite, apatite, magnetite, titaniferous magnetite, ilmenite,and zircon, as well as rare K-feldspar and titanite.Secondary minerals include albite (after oligoclase),sericite, chlorite, epidote, antigorite, haematite, andcalcite. Mafic–intermediate rocks in the southern partof the pluton are composed of hornblende-rich tonalite(32% andesine, 38% amphibole, 23% quartz, and 7%of other phases), hornblende-rich diorite (40% andesine,53% amphibole, and 7% other), and quartz-diorite (80%andesine, 15% quartz, and 5% other). Rare leucocraticfelsic dikes (see above) intruding this mafic–intermediatedomain have a composition corresponding to eithertrondhjemite or quartz-rich granitoid (68% quartz, 30%albite, and 2% other). East of the town of Totoltepec deGuerrero (Figure 1B), plagioclase-rich rocks (93% albite,3% quartz, and 4% other) and biotite trondhjemite (55%oligoclase, 35% quartz, 7% biotite, and 3% other) arethe predominant lithologies. Towards the northern marginof the pluton, the felsic rocks locally contain abundantpotassium feldspar (up to 40%) and are classified as gran-odiorite and monzogranite according to the nomenclatureof Streckeisen (1976).
Plagioclase is the predominant mineral of theTotoltepec pluton, occurring as subhedral to euhedralgrains varying in size from 2 mm to 6 mm. Dependingon lithology, plagioclase varies in composition from albite,through oligoclase to labradorite. In tonalite, diorite, andgabbro, plagioclase exhibits normal compositional zoning(Table DR-1; see supplementary material at http://dx.doi.org/10.1080/00206814.2012.693247). Biotite occurs asisolated, tabular grains or as inclusions in plagioclase.
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Figure 3. Subset of Figure 1B showing detailed structural information as well as photographs and pictograms of the most intriguingstructures within the high-strain zone in the southern part of the Totoltepec pluton. Stereograms show foliations and dike orientationplotted as great circles (continuous and dashed lines, respectively), lineations as filled triangles (+ shear sense if kinematic indicatorsfound). (A) C’ type shear band fabric indicating sinistral shear. Angle between shear band cleavage and shear zone boundary (SBZ) is15–35◦ (Blenkinsop and Treloar 1995). (B) Sigma-type hornblende porphyroclasts indicating sinistral kinematics. (C) Randomly orientedhornblende on the foliation plane. (D) Foliation-parallel shearband boudins of a felsic dike indicating left-lateral shear. (E) Curvatureof foliation indicating sinistral shear. (F) Lens-shaped boudins of a mafic dike with sinistral kinematics. (G) Strong mineral lineation inmegacrystic hornblende diorite indicating top-to-SSE thrusting. (H–I) Compositional/textural banding in hornblende diorite and tonalitedefined by variation in grain size and modal proportions of feldspar and hornblende. Note the growth of plagioclase phenocrysts acrosslayer boundaries in Figure 3I.
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(D)
(B)
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(E) (F)
Figure 4. Magmatic enclaves in the Totoltepec pluton. (A) Foliated, rounded microgranular enclaves in hornblende diorite. (B)Hornblende-rich reaction rim marking the contact between a microgranular enclave and diorite host. (C) Elongate microgranular enclavealigned parallel to foliation of host diorite. (D) Disaggregated clot of hornblende in diorite. (E) Ovoid biotite globule in trondhjemite. (F)Strongly sheared, fault-bounded microdioritic enclave in trondhjemite.
Amphibole is by far the most abundant mafic min-eral in the Totoltepec pluton. It occurs as subhedralto euhedral, prismatic grains, 1–3 mm in length, andlocally as megacrysts up to 4 cm in length. It com-monly exhibits simple {100} twinning and commonly
contains inclusion of quartz, plagioclase, apatite, and titan-ite. In some thin sections, amphibole occurs as coarse,lath-shaped oikocrysts poikilitically enclosing euhedralplagioclase or subhedral to euhedral, oriented quartzgrains. In tonalite, quartz diorite, hornblende gabbro, and
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(B)
(C)
Magnesio-hornblende
Ferro-hornblende
Tschermakite
Ferro-tschermakitichornblende
Tschermakitichornblende
Ferro-tschermakite
Mg/
(Mg+
Fe
2+)
0.4
0.5
0.6
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Si (pfu)
5.86.06.26.46.66.87.0
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Hornblende
Tschermakitichornblende
Tschermakite
(Na+
K) A
0
0.2
0.4
Si (pfu)
6.06.16.26.36.46.56.66.76.86.97.0
EdTr, Rct
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PrgKtp
Al V
I p.f.
u.
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0 0.5 1.0 1.5 2.0
TT-13a,Tonalite (intermediate)TT-55, Tonalite (mafic)TT-54, Tonalite (mafic)TT-14, Qtz Diorite (mafic)TT-17, Hbl Gabbro (mafic)TT-28, Hornblendite (ultramafic)
Mainbody
Mar-ginal
Figure 5. Electron microprobe major-element data for amphiboles from the Totoltepec pluton (grey symbols – cores; black symbols –rims). (A) Mg/(Mg + Fe2+) vs. Si classification after Leake (1978) and Leake et al. (1997, 2004). (B) Plot of A-site occupancy against Si.Nomenclature after Leake (1978). (C) Six-fold Al plotted against 4-fold Al. Al determined according to the calculation scheme of Leake(1978) and Leake et al. (2004). Solid black line denotes slope of 1. Locations for different amphibole end-member compositions are fromLaird and Albee (1981). Mineral abbreviations after Whitney and Evans (2010).
hornblendite, amphiboles are calcic (i.e. have (Ca + Na)B
≥ 1.00 and NaB < 0.50 atoms per formula unit) (Leakeet al. 2003; Table DR-2; see supplementary material athttp://dx.doi.org/10.1080/00206814.2012.693247). On theMg/(Mg + Fe2+) vs. Si classification diagram (Figure 5A),
they range from (ferrian- to ferri-) tschermakite totschermakitic hornblende and magnesio-hornblende incomposition. A few amphiboles in the tonalite and horn-blendite have (Na + K)A ≥ 0.50, corresponding to hast-ingsite to magnesio-hastingsite. On the (Na + K)A vs.
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Si classification diagram (Figure 5B), the samples fall inthe field of hornblende, tschermakitic hornblende, parg-asitic hornblende, and tschermakite. Aluminium prefer-entially resides in the tetrahedral position (Figure 5C),which suggests the dominance of high-T edenite-type((Na, K)A AlIV = [ ]A Si) substitution. Si in all investi-gated amphiboles varies between 6.0 and 6.8. These overallcompositional characteristics are typical of igneous amphi-boles (Leake 1971; Leake et al. 2003). Although opticallycontinuous, most investigated amphiboles are zoned, andmost cores contain higher AlIV and (Na + K)A and lowerSi and Mg/(Mg + Fe2+) than rims.
Quartz generally occurs as interstitial, anhedral aggre-gates of variable grain size. The shapes of individual quartzclusters range from subspherical to lenticular. In places,quartz is present as hexagonal, equigranular, polygonizedgrains. It is also found as a vermicular intergrowth inplagioclase (myrmekite).
Biotite occurs as small euhedral inclusions in plagio-clase and more rarely as subhedral grains in the matrix.It is generally, partially, or entirely replaced by chlorite.In the area east of Totoltepec de Guerrero (Figure 1B),modal biotite is as high as 7%. Muscovite is ubiquitousin trondhjemite, occurring as large, discrete grains up to1.5 mm wide or as foliated aggregates wrapping aroundhornblende or plagioclase phenocrysts. Si contents ofinvestigated muscovite grains reach values of 3.17 performula unit (Table DR-3; see supplementary materialat http://dx.doi.org/10.1080/00206814.2012.693247), indi-cating the presence of a minor phengitic component (e.g.Massonne and Schreyer 1987).
Potassium feldspar occurs as rare interstitial, fine- tomedium-grained crystals of microcline. In granodiorite andmonzogranite near the northern margin, orthoclase formssubhedral phenocrysts up to 3 mm in diameter containingflame-shaped albite lamellae.
Opaque phases include (titaniferous) magnetite,ilmenite, and minor secondary pyrite and chalcopyrite(Table DR-4; see supplementary material at http://dx.doi.org/10.1080/00206814.2012.693247). Magnetite is spa-tially related to the main mafic minerals. It is dominantlysubhedral or euhedral with a diameter of up to 0.5 mm,containing lamellae of ilmenite, which are interpreted asoxidation–exsolution intergrowths. Two diorite samplesfrom the main body of the pluton contain ovoid interstitialintergrowths of ilmenite with euhedral apatite. Ilmeniteis also observed to form broad lamellae in sandwich-likeintergrowths with an impure Ti-Fe-Al bearing silicatephase.
Meso- and microstructures
Marginal, ultramafic–mafic plutonic phase (ca. 306 Ma)
Mesoscopic structures in the older, ultramafic–mafic rocksof the pluton are preserved in one of the gabbroic
bodies along the northern margin. Here, a weak magmaticfoliation, defined by the preferred orientation of prismaticto tabular amphibole, is steeply dipping to sub-vertical andappears to be folded about a steeply, westerly plungingfold axis (Figure 6F). An associated moderately plung-ing to sub-horizontal mineral lineation is locally definedby the alignment of sub- to euhedral, elongate amphibole.Dike orientations in this part of the marginal plutonic phaseare highly variable and can be explained by folding aboutan axis that coincides with the fold axis derived from thefoliation plane distribution. This suggests that the foliationand the dikes had similar pre-folding orientations.
Microstructures in the older, marginal phase of theTotoltepec pluton record magmatic through incipient solid-state deformation at high temperature. Magmatic texturesare typified by large, euhedral to subhedral, unstrained,and evenly distributed amphibole and plagioclase set ina feldspathic matrix that lacks evidence of plastic defor-mation. Plagioclase has a typically igneous composition(An54–57; Table DR-1) and is characterized by a nor-mal growth zoning. The amphibole also has an igneouscomposition (Figure 5) and occurs as independent, stubbyto lath-shaped crystals (Figure 7A) or as undeformedpoikilitic grains around plagioclase. Some thin sectionsfrom two of the ultramafic–mafic bodies at the north-eastern margin (Figure 8) contain textures indicative ofminor subsolidus deformation at high temperature, suchas (1) albite twins within plagioclase sub-grains that aremisoriented with respect to the host grain (Figure 7E), sug-gesting progressive sub-grain rotation recrystallization thatoccurred at temperatures above upper greenschist-faciesconditions (Fitz Gerald and Stünitz 1993; Rosenberg andStünitz 2003), and (2) evidence of myrmekite replacementat plagioclase grain peripheries, which has been interpretedto reflect deformation temperatures in excess of 500◦C(Menegon et al. 2006, and references therein).
Main, mafic–felsic plutonic phase (ca. 289–287 Ma)
The main body of the Totoltepec pluton contains amesoscopic foliation and lineation of variable intensity,which formed under a variety of temperature conditions.Foliations that are interpreted to reflect deformation inthe magmatic state or in a high-temperature solid stateare defined by the preferred orientation of elongate,undeformed, magmatic amphibole in mafic–intermediatelithologies. Commonly, amphibole is randomly distributedon the foliation plane (Figure 3C). Locally, however, asub-horizontal to sub-vertical lineation is defined by thealignment of sub- to euhedral amphibole laths within thefoliation plane. In the more leucocratic rocks, deforma-tion at magmatic to high-temperature, solid-state condi-tions is indicated by sub- to euhedral plagioclase andinterstitial quartz that define a weak planar grain-shapepreferred orientation as well as a poorly developed
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Mag
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ic d
omai
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h-te
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-sta
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n(S) = 13n(L) = 1
n(S) = 51n(L) = 13
n = 58
n(S) = 26n(L) = 8
n(S) = 174n(L) = 34
n(S) = 8n(L) = 3n(D) = 6
(E)
MA
IN B
OD
YM
AR
GIN
AL B
OD
IES
Poles to foliationMineral lineation
(F)
FoliationDikes
Calculatedfold axisS
imp
lesh
ear
73°
39°
Undeformed/folded
Extended/boudinaged
Unclassified
Trans tens io nTr anspressio
Figure 6. Mesoscopic structural data from the Totoltepec pluton. (A–D) Foliation and lineation data for the magmatic as well as high-temperature, moderate-temperature, and low-temperature solid-state domains in the main body of the pluton. (E) Lower hemisphere, equalangle projection of dike orientations in the main phase of the pluton. 39◦ corresponds to the minimum clockwise (interpreted as initial)dike angle; 78◦ marks the clockwise angle of transition between folded dikes, and dikes that show pinch-and-swell and/or boudinage.Grey lines and arrows indicate the theoretical transitions between the field of finite shortening, and the field of finite shortening followedby extension based on forward modelling along a vertical, dextral N–S-striking shear zone boundary (modified after Kuiper and Jiang(2010)). See text for details. (F) Orientation of structural elements in the marginal mafic–ultramafic bodies of the Totoltepec pluton. Allstereograms (except Figure 6E) are equal-area, lower-hemisphere projections. Contours were drawn according to the method of Kamb(1959) using a 3σ significance level and a 2σ contour interval.
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0.1 mm
(H) (I)
0.75 mm 0.75 mm
0.75 mm 0.25 mm 0.1 mm
0.25 mm 0.25 mm0.75 mm
(C)
(D) (E)
(G)
(F)
Figure 7. Photomicrographs of characteristic textures in the magmatic domain (m), as well as high-T (hss), medium-T (mss), and low-T(lss) solid-state domains of the Totoltepec pluton. (A) Euhedral, randomly distributed amphibole (m). (B) Quartz with chess-board sub-grain pattern (hss). (C) Rectangular, mosaic-like contours in quartz (hss). (D) Equigranular, polygonal quartz grains (hss). (E) Sub-grainrotation in plagioclase (hss). (F) Myrmekite formation in plagioclase at the boundary with K-feldspar (hss). (G) Glide twins in plagioclase(mss). (H) Quartz aggregate recrystallized by sub-grain rotation (mss). (I) Fractured plagioclase grain with development of new grains bymicrocracking and bulging-recrystallization (lss).
1 2 3 4 5 km
Magmatic
High-temperature solid state
Moderate-temperature solid state
Low-temperature solid state
Figure 8. Spatial distribution of microstructural types within the Totoltepec pluton based on thin section analyses using criteria outlinedby Blumenfeld and Bouchez (1988), Paterson et al. (1989), Miller and Paterson (1994), and Büttner (1999).
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lineation. Locally, in the mafic–intermediate sheeteddomain, the foliation is defined by primary igneouscompositional banding (Figures 3H and 3I).
Mesoscopic fabrics of tectonic origin occur withina high-strain zone in the southern part of the pluton(Figure 3) and show pervasive recrystallization under sub-solidus conditions. In this zone, the foliation is definedby the preferred orientation of amphibole and plagioclase,as well as mica. An associated linear fabric is definedby the alignment of stretched amphibole and plagioclase(Figure 3G), which show evidence of straining (both ductilerecrystallization and fracturing) in a section perpendicularto the foliation and parallel to the lineation. The com-positions of recrystallized amphibole and plagioclase aresimilar to those of igneous grains.
In agreement with the range of observed mesoscopicfabrics, the younger, main phase of the Totoltepec plutonshows a continuum from primary igneous (i.e. pre-fullcrystallization) microstructures to those corresponding todeformation in the solid state (i.e. subsolidus). Criteriaoutlined by Blumenfeld and Bouchez (1988), Patersonet al. (1989), Miller and Paterson (1994), and Büttner(1999) allow the distinction of four microstructural types:(1) magmatic, (2) high-temperature (>500◦C) solid state,(3) moderate-temperature (450–500◦C) solid state, and(4) low-temperature solid state.
Magmatic microstructures in the main body of thepluton are predominantly encountered in the northeast-ern part and locally within the mafic–intermediate sheeteddomain near the southern margin of the pluton (Figure 8).They are characterized by coarse-grained plagioclase andamphibole laths with angular outlines surrounded bya largely isotropic matrix composed of ovoid, intersti-tial, optically continuous quartz, smaller grains of ran-domly distributed plagioclase, and decussate, undeformedmuscovite, and/or biotite. The plagioclase has a typicallyigneous composition (An30–45; Table DR-1), shows normalcompositional zoning, and commonly displays grain aggre-gation (synneusis) textures. Igneous amphibole (Figure 5)occurs as single subhedral poikilitic grains or as euhedralinclusions in plagioclase.
The majority of samples in the main ca. 289–287 Mabody of the pluton exhibit microstructures consistentwith high-temperature subsolidus deformation (Figure 8).Quartz shows (1) basal and prismatic (chess-board)sub-grain patterns (Figure 7B), indicating deformationat temperatures of about 650–750◦C (Mainprice et al.1986; Kruhl 1996), (2) lobate grain boundaries typicalof recrystallization by grain boundary migration (Hirthand Tullis 1992), (3) rectangular, mosaic-like contours(Figure 7C), suggesting strong crystallographic controlon grain boundary orientations under high-temperaturedeformation (Gapais and Barbarin 1986), and (4) astrain-free, equigranular, polygonal texture, characteris-tic of recovery and recrystallization processes above
epidote-amphibolite facies conditions (Figure 7D; Simpson1985). Plagioclase grains locally show evidence of sub-grain rotation recrystallization and myrmekitic intergrowth(Figure 7F).
Microstructural features diagnostic of moderate-temperature solid-state deformation mostly occur in sam-ples of high-strain zones in the southern part of thepluton (Figure 8) and include plagioclase showing a sweep-ing undulatory extinction, bent or tapering twin lamellae(Figure 7G), as well as internal fracturing (Fitz Geraldand Stünitz 1993). Locally, plagioclase is recrystallizedalong its margins, forming core-and-mantle structures.Muscovite occurs as kinked or bent grains, and as alignedfine-grained anastomosing laths that enclose relict phe-nocrysts. K-feldspar exhibits abundant perthite flames(Pryer 1993). Quartz is characterized by large relict grainsexhibiting patchy, undulose extinction passing laterallyinto polycrystalline quartz aggregates with irregular grainboundaries developed predominantly by sub-grain rotationrecrystallization (Figure 7H).
Low-temperature, solid-state microstructures in main-phase rocks of the Totoltepec pluton are also locally presentin high-strain zones near the southern margin of the pluton(Figure 8) and are characterized by a pervasive cataclas-tic texture (Figure 7I). The presence of angular plagioclasegrains and a wide range of grain sizes suggest that grain-size reduction in feldspar is achieved by microcrackingand comminution (Tullis and Yund 1987). Quartz exhibitsdeformation lamellae transected by bands of small, newgrains formed by bulging recrystallization (Hirth and Tullis1992). Feldspar and amphibole are almost entirely replacedby chlorite, sericite, epidote, and antigorite, indicatingfluid-enhanced deformation under lower greenschist-faciesconditions.
Overall, the orientations of the foliation in the mainpart of the pluton vary from (1) moderately northerly dip-ping in the southern part of the pluton, (2) sub-vertical,E–W striking in the centre, to (3) steeply southerly dip-ping in the northern part, defining a fan-like pattern inN–S cross section (Figure 1C). There is a close agree-ment in the orientation of foliations over the entire rangeof deformation temperatures (Figures 6A–6D). Moderate-to low-temperature foliations tend to be less steeply dip-ping, because these occur mainly in the southern part ofthe pluton.
The foliation within the mafic–intermediate, sheetedzone is deformed into intrafolial, mesoscopic, recum-bent, tight to isoclinal, predominantly S-shaped folds(Figure 9). Regional variations in the trend of foliationplanes throughout the pluton are attributed to map-scale, open, upright, gently northerly plunging folds,about which the southern thrust contact is also folded(Figure 1B).
Lineations show a variation in orientation fromsub-horizontal to down-dip (Figures 3G and 6A–6D).
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(A)
(B)
N
NFigure 9. Photographs of tight to isoclinal intrafolial folds in the mafic–intermediate sheeted domain of the Totoltepec pluton.
Sigma-type hornblende porphyroclasts in mylonitictonalite and diorite indicate sinistral to top-to-SSE kine-matics (Figure 3B). Further evidence for sinistral shearis provided by C’-type shear bands (Figure 3A), asym-metrically boudinaged mafic and felsic dikes (Figures 3Dand 3F), and foliation deflection patterns (Figures 2G–2Iand 3E).
The predominant orientation of dikes in the main bodyof the pluton is concordant with respect to the foliation(Figure 6E). However, the overall range in the orientationsof individual dikes and the variations in the amount ofstrain they display indicate the occurrence of several gen-erations of dikes. Undeformed or gently folded dikes aresteeply dipping and have typical strikes of 36◦–67◦ (mea-sured clockwise from north), typically cutting the fabricdeveloped in the earlier intrusive phases (Figures 2E, 2Fand 2J), whereas dikes exhibiting pinch-and-swell struc-tures or boudinage commonly occur at a low angle toor in the foliation plane and have strikes of 71◦–136◦(Figures 2D, 2H, and 6E). Many dikes in the mafic–intermediate sheeted domain contain a foliation that iseither sigmoidal or parallel with respect to dike margins,irrespective of the orientation of the dikes relative to the
foliation of the surrounding rocks (Figures 2G, 2H, and 2J).In a section perpendicular to the foliation and parallelto the local sub-horizontal lineation, amphibole is locallyobserved to be deflected into the plane of cross-cuttingdikes (Figure 2I).
Some areas in the Totoltepec pluton, particularly nearthe contacts, exhibit brittle features (Figure 10), includ-ing tension gashes, faults, and associated brecciationzones, jointing, small-scale horst-and-graben structures,and quartz-carbonate veins that are attributed to hydraulicfracturing and fluid mobilization late in the coolinghistory of the pluton, and to episode(s) of regionalpost-emplacement deformation. N-dipping fault planesand associated N-plunging slickensides within the plutonare consistent with top-to-the-S thrusting of the plutonover metasedimentary rocks of the Tecomate Formationas implied by the regional map (Figure 1B; Maloneet al. 2002). Muscovite from the low-angle, brittle–ductilethrust contact between the Totoltepec pluton and theTecomate Formation yields a mid-Triassic age (Kirschet al. 2012). Locally, this shear zone is associated witha Fe-P-REE deposit containing the mineral associationmagnetite, apatite, barite, chlorite, quartz, chalcopyrite, and
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Trondhjemite
Gabbro
(A)
(D)
(B)
(C)
(E) (F)
Figure 10. Late- to post-emplacement brittle features in the Totoltepec pluton. (A) Fault contact between marginal gabbro and main bodytrondhjemite. (B) Small-scale, horst-and-graben structure in diorite. (C) Pegmatitic quartz-carbonate vein. (D) Jointing. (E) Myloniticthrust contact between the Totoltepec pluton and Tecomate Formation. (F) S-C fabrics in Tecomate Formation metasedimentary rocksindicating top-to-S thrusting.
a cerium mineral (Table DR-4; see supplementary mate-rial at http://dx.doi.org/10.1080/00206814.2012.693247).The mineralization is confined to two discrete, elongatedbodies of about 100 m length coinciding with strongaeromagnetic anomalies (Servicio Geológico Mexicano2004a,b).
Al-in-hornblende thermobarometry
Five samples of the Totoltepec pluton (one from the older,marginal bodies and four from the younger, main body)were selected for hornblende thermobarometry in orderto obtain an estimate of the emplacement temperaturesand pressures. For this purpose, coexisting hornblende and
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plagioclase were analysed by electron microprobe wave-length dispersive spectrometry (WDS) at the LaboratorioUniversitario de Petrología (LUP), Instituto de Geofísica,UNAM, Mexico City, Mexico. Representative analyticaldata are presented in Tables 1, DR-1, and DR-2.
As one of the only available means of calculatingemplacement temperatures in calc-alkaline igneous rocks,Blundy and Holland (1990) suggested that amphibole-plagioclase mineral pairs in equilibrium could be used asa geothermometer. Accounting for non-ideal amphibolesolid-solutions, the geothermometer was later extended byHolland and Blundy (1994), using two different exchangereactions: (A) edenite + 4 quartz = tremolite + albite,and (B) edenite + albite = richterite + anorthite. Whereasthermometer A is only applicable to quartz-bearing rocks,thermometer B can also be used for silica undersaturatedassemblages, but is restricted to temperatures in the rangeof 500–900◦C and plagioclase with XAn between 0.1 and0.9 as well as hornblende with XNa(M4) > 0.03, AlIV <
1.8 atoms per formula unit (pfu), and Si in the range of6.0–7.7 pfu. The precision of both thermometers is ±40◦Cat 1–15 kbar (Holland and Blundy 1994).
The selected samples satisfy all compositionalconstraints with respect to temperature and oxygenfugacity, so the geothermometers of Holland and Blundy(1994) are applicable. Because independent pressure dataare not available for the Totoltepec pluton, emplacementtemperatures were calculated at pressures ranging from0 kbar to 15 kbar using the HB-PLAG program devel-oped by Holland and Powell (http://www.esc.cam.ac.uk/research/research-groups/holland/hb-plag). Minimumand maximum pressures determined by the differentnon-temperature-corrected Al-in-hornblende barometers(Table 1) were used to define a narrow pressure interval,from which average temperature values were calculated.For sample TT-14 (gabbro from the older, marginal body),which does not contain quartz and thus does not fulfil theprerequisites of an Al-in-hornblende barometer, pressurelimits were adopted from the quartz-bearing tonalitesamples.
Geothermometric data yield essentially magmatic tem-peratures of mineral equilibration in all samples, rangingfrom 716◦C to 788◦C for thermometer A and 719◦Cto 843◦C for thermometer B. Using thermometer B,which according to Anderson (1996) yields more accu-rate results, the calculated median value of samples fromthe main body of the pluton is 762 ± 40◦C, whereas thehornblende gabbro from the northern marginal body yieldsa slightly higher median temperature of 807 ± 40◦C. Thesetemperatures are broadly consistent with temperatures cal-culated from the Ti-in-zircon geothermometer of Watsonet al. (2006), yielding 713 ± 76◦C (1σ error) for zir-cons of a quartz diorite from the main body of the plutonand 731 ± 49◦C for zircons from a marginal hornblende
gabbro sample (Table DR-6; see supplementary material athttp://dx.doi.org/10.1080/00206814.2012.693247).
Hammarstrom and Zen (1986) and Hollister et al.(1987) were the first to conduct empirical studies that sug-gested a relationship between the total Al-content of calcicamphiboles and the confining pressure. Subsequent exper-imental studies (Johnson and Rutherford 1989; Thomasand Ernst 1990; Schmidt 1992) confirmed this correla-tion. Based on these experiments, a number of calibrationsfor Al-in-hornblende barometry have been developed, withwhich an intrusion depth can be calculated from micro-probe measurements of amphiboles in granitoids. TheseAl-in-hornblende barometers only consider the pressure-dependent Tschermak substitution as an influence on theAl-content of hornblende. Their application, therefore,requires the presence of an appropriate buffer assemblage(Qz-Kfs-Pl-Hbl-Bt-Tit/Mag and fluid melt) to limit thethermodynamic degrees of freedom (Hammarstrom andZen 1986). Another important prerequisite is that anor-thite compositions of coexisting plagioclase should rangebetween 25% and 35% (Hollister et al. 1987).
Anderson and Smith (1995) recognized that tempera-ture also strongly influences the Al-content in hornblende(edenite substitution), developing a new formula that isbased on calibrations of Johnson and Rutherford (1989)and Schmidt (1992), but introducing a temperature-correction term to the pressure estimates. Apart from thelimitations mentioned above, the application of the Al-in-hornblende barometer of Anderson and Smith (1995) isfurthermore restricted to amphiboles that crystallized athigh f O2, i.e. have Fe# ≤ 0.65 and Fe3+/(Fe3++Fe2+) ≥0.25.
Hornblende crystallization pressures of the Totoltepecpluton were calculated with the calibration of Andersonand Smith (1995) and compared to the pressuresderived from Al-in-hornblende barometer calibrationsof Hammarstrom and Zen (1986), Hollister et al.(1987), Johnson and Rutherford (1989), and Schmidt(1992). The precision of these barometers is estimatedat ±0.5 to ±0.6 kbar (2σ ). All samples exhibit Fe#and Fe3+/(Fe3++Fe2+) ratios that indicate crystalliza-tion conditions under high oxygen fugacity, conformingto the requirements of the method. However, all of theselected samples from the Totoltepec pluton lack potassiumfeldspar, and most of them do not contain biotite or titanite(Table 1), so the calculated pressures should be consid-ered maximum values (Anderson and Smith 1995). Threesamples contain plagioclase with a higher An content thanrecommended, which may lead to lower Al content inhornblende and thus yield pressures that are lower thantheir true value (Anderson and Smith 1995). Temperaturecorrections were applied using median temperature valuescalculated by the amphibole-plagioclase thermometer ofHolland and Blundy (1994) (see above).
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Tabl
e1.
Res
ults
ofA
l-in
-hor
nble
nde
geot
herm
obar
omet
ry.
Lat
/L
onA
ge(d
ecim
alR
ock
type
Pair
PI
An
Am
pA
IP
Hzb
PH
olP
JRP
Sch
PA
Sc
Pav
gD
epth
dD
epth
T(e
dtr
)eT
(ed-
tr)f
Tav
gS
ampl
e(M
a)de
gree
s)as
sem
blag
eaA
mp-
PI
(%)
(tot
al)
(kba
r)(k
bar)
(kba
r)(k
bar)
(kba
r)(k
bar)
(km
)av
g(k
m)
(◦ C)
(◦ C)
(◦ C)
TT-
1428
9±
218
.208
433
Hbl
dior
ite
A1-
P1
44.1
1.72
14.
664.
873.
765.
183.
794.
1813
.715
.280
783
683
3−9
7.89
087
Hbl
PIM
sMag
lim
A2-
P3
45.2
1.90
05.
585.
894.
536.
034.
54±
16.5
±82
884
3±
A3-
P2
42.7
1.83
35.
245.
514.
245.
724.
260.
3915
.41.
480
382
211
TT-
13a
289
±2
18.2
1403
3To
nali
teA
1-P
131
.71.
992
6.06
6.43
4.93
6.47
4.93
5.29
18.0
19.3
788
780
755
−97.
8838
5H
blP
IQzB
tIIm
A2-
P3
32.5
2.12
96.
767.
215.
527.
125.
51±
20.1
±71
671
9±
A3-
P2
34.9
2.11
36.
667.
105.
447.
055.
440.
3119
.81.
176
576
632
TT-
5528
9±
218
.215
866
Tona
lite
A1-
P2
40.7
2.11
96.
667.
105.
447.
085.
475.
7919
.821
.174
375
575
5−9
7.88
085
Hbl
PIQ
zTiM
agA
2-P
341
.02.
379
7.97
8.57
6.54
8.31
6.56
±23
.8±
741
752
±A
3-P
140
.72.
104
6.60
7.04
5.39
7.01
5.40
0.65
19.6
2.4
750
757
3T
T-54
289
±2
18.2
2078
3To
nali
teA
1-P
129
.62.
327
7.74
8.31
6.34
8.07
6.35
6.03
23.1
22.0
757
752
762
−97.
8785
7H
blP
IMsQ
zIIm
A2-
P2
34.1
2.25
17.
347.
876.
017.
706.
02±
21.9
±78
878
8±
A3-
P3
29.3
2.18
37.
017.
505.
737.
385.
740.
3120
.91.
175
474
623
TT-
1730
6±
218
.258
100
Hbl
gabb
roA
1-P
156
.51.
398
3.07
3.08
2.42
3.64
1.41
2.49
8.8
9.1
774
802
808
−97.
8516
3H
blP
IQzM
agII
mA
2-P
156
.51.
394
3.05
3.05
2.40
3.63
1.39
±8.
7±
787
815
±A
3-P
253
.51.
453
3.35
3.40
2.66
3.90
1.62
0.14
9.7
0.5
786
807
7
Not
es:
Pre
ferr
edva
lues
indi
cate
din
bold
font
;a m
iner
alab
brev
iati
ons
afte
rW
hitn
eyan
dE
vans
(201
0);
bH
Z–
Ham
mer
stro
man
dZ
en(1
986)
;H
ol–
Hol
list
eret
al.(
1987
);JR
–Jo
hnso
nan
dR
uthe
rfor
d(1
989)
;S
ch–
Sch
mid
t(1
992)
;c t
empe
ratu
reco
rrec
tion
inP
(AS
)ba
sed
onav
erag
ete
mpe
ratu
res
calc
ulat
edfr
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-ri
tem
pera
ture
s(H
olla
ndan
dB
lund
y19
94)
lim
ited
byP
HZ
,P
Hol
,P
JR,
and
PS
ch;
dav
erag
ecr
usta
lden
sity
isas
sum
edas
2.8
gcm
–3;e t
empe
ratu
reca
lcul
ated
usin
gpl
agio
clas
e-ho
rnbl
ende
geot
herm
omet
erA
(ede
nite
-tre
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ite)
ofH
olla
ndan
dB
lund
y(1
994)
;f tem
pera
ture
calc
ulat
edus
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plag
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ase-
horn
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eter
B(e
deni
te-r
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land
and
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(199
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are
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llm
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ical
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mbl
age
requ
ired
for
the
ther
mob
arom
eter
.
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Hornblende diorite and marginal hornblende gabbroapparently yield much lower pressures than the other sam-ples of the Totoltepec pluton, because both of these sampleshave plagioclase compositions well outside the recom-mended range and, in addition, the diorite lacks quartz.They are thus omitted from further consideration. The aver-age hornblende Altot-content in tonalite from the mainbody of the pluton is 2.177 ± 0.122. Resulting pres-sures calculated with calibrations without a temperaturecorrection term range from 5.3 to 7.9 kbar (Table 1).The lowest values are obtained by the Al-in-hornblendebarometer of Johnson and Rutherford (1989), whereasthe formula of Hollister et al. (1987) yields the highestvalues. Because the amphibole-plagioclase thermometerof Holland and Blundy (1994) generates temperatureswell above the solidus of wet tonalite (Schmidt 1993), atemperature correction according to Anderson and Smith(1995) is reasonable. For samples within the recommendedcompositional range of plagioclase as well as tonalite sam-ple TT-55 with a slightly higher average XAn of 0.41,an average pressure of 5.7 ± 0.6 kbar is obtained. Thispressure value is equivalent to the average pressure calcu-lated with the Johnson and Rutherford (1989) barometer,which is attributable to the fact that the experiments con-ducted by Johnson and Rutherford (1989) were calibratedat temperatures between 720◦C and 780◦C, correspond-ing to the crystallization temperatures of hornblende fromthe Totoltepec pluton. The calculated emplacement pres-sure of 5.7 ± 0.6 kbar for tonalite from the main body ofthe pluton translates into a maximum emplacement depthof 20.7 ± 2.2 km, assuming an average crustal densityof 2.8 g/cm3. In summary, the main, ca. 289–287 Ma,body of the Totoltepec pluton was emplaced at mod-erate temperatures (762 ± 40◦C) and middle to highpressures (≤5.7 ± 0.6 kbar) into middle crustal levels(around 20 km).
40Ar/39Ar geochronology
Foliation-parallel muscovite between 180 and 250 μm insize was separated from a Totoltepec pluton trondhjemitesample E of Santo Domingo Tonahuixtla (TT-57: 18◦ 12′30′′ N, 97◦ 52′ 50′′ W). The mineral concentrate wasloaded into Al-foil packets and irradiated together withthe hb3gr hornblende standard (1072 ± 11 Ma) as a neu-tron flux monitor at the McMaster University researchreactor in Hamilton, Ontario, Canada. 40Ar/39Ar anal-yses were performed at the 40Ar/39Ar GeochronologyResearch Laboratory at Queen’s University in Kingstonby a laser step-heating procedure using a a 30W NewWave Research MIR 10–30 CO2 laser and a MAP216 mass spectrometer. The data, corrected for blanks,mass discrimination, and neutron-induced interferences,are presented in Table DR-5; see supplementary materialat http://dx.doi.org/10.1080/00206814.2012.693247 and in
AOR-1107 /TT-57Totoltepec pluton trondhjemiteMuscovite
2σ errors
Plateau age283 ± 1 Ma
App
aren
t age
(M
a)
220
240
260
280
300
Fraction 39Ar (%)
0 10 20 30 40 50 60 70 80 90 100
Figure 11. 40Ar/39Ar age spectrum for foliation-parallelmuscovite from Totoltepec pluton trondhjemite. For sample loca-tion see Figure 1B.
Figure 11. The plateau age and mean square of theweighted deviates (MSWD) are obtained based on the fol-lowing criteria, i.e. when the apparent ages of at least threeconsecutive steps, comprising a minimum of 50% of thetotal 39Ar released, agree within 2σ error with the inte-grated age of the plateau segment (e.g. McDougall andHarrison 1999; Baksi 2006). All age errors are quoted atthe 2σ level.
Muscovite from sample TT-57 yields an excellentplateau age of 283 ± 1 million years (MSWD = 0.248),defined by 11 fractions and representing 99.2% of the total39Ar released (Figure 11). The first step, comprising 31%of atmospheric argon, is associated with a small amountof contaminating phases as indicated by the correspondingCa/K ratio (Table DR-6). Assuming a relatively high cool-ing rate of 50◦C/million years, consistent with the plateauage spectrum, the closure temperature for muscovite fromthis sample is calculated to be 390–400◦C, using the equa-tion developed by Dodson (1973). These data suggest thatby 283 ± 1 Ma, the main body of the Totoltepec plutonhad cooled through 390–400◦C. Assuming a geothermalgradient of 35◦C/km, which is consistent with modelledvalues for active portions of continental magmatic arcs(e.g. Rothstein and Manning 2003), the calculated clo-sure temperature for muscovite corresponds to a depth of11.1–11.4 km. Given that barometric data indicate that themain phase of the pluton was emplaced at around 20 km,the 40Ar/39Ar data require a substantial and rapid upliftand exhumation of the pluton between ca. 287 and 283 Ma(around 2.25 km/million years).
Discussion
Structural context
The Totoltepec pluton is a component of a regionalCarboniferous–Permian continental arc extending from
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Guatemala to the southern USA (Kirsch et al. 2012). In thesouthern Mexican portion of this arc, ca. 307–269 Madextral shear along the >150 km-long, N–S-striking CFZthat separates the Acatlán Complex from the OaxacanComplex (Figure 1A) has been well-documented (Elías-Herrera and Ortega-Gutiérrez 2002; Elías-Herrera et al.2005). The significance of dextral shear along N–S-strikingfaults within the Mexican Carboniferous–Permian con-tinental arc is further supported by the presence of aS-directed, dextral, sub-vertical, ca. 330–300 Ma fault(Dowe et al. 2005) that separates the Palaeozoic GranjenoSchist (a correlative of the Acatlán Complex; e.g. Nanceet al. 2007) from the ca. 1 Ga Novillo Gneiss (a correlativeof the Oaxacan Complex; e.g. Ortega-Gutiérrez et al. 1995)in northeastern Mexico. In addition, the Totoltepec plu-ton is bounded to the W by the N–S dextral San Jerónimofault. Muscovite from the N–S Las Ollas fault lying to thewest yielded a 40Ar/39Ar age of 278 ± 2 million years(Morales-Gámez et al. 2009).
The emplacement history of the Totoltepec plutoncan be explained within this regional context. The plutonoccurs in a crustal block bounded by two N–S-strikingdextral faults – the San Jerónimo fault to the west andthe Caltepec fault to the east (Figure 12). Dextral shearalong these boundary faults is inferred to have led to
the development of an intervening, sub-vertical, SW–NEextensional fault (Figure 12A), which may have controlledthe emplacement of the Totoltepec pluton. Progressivedextral movement on the bounding faults would have ledto clockwise rotation of NE–SW lines and objects in theintervening block.
Interpretation of dike orientations
The systematic variation in dike orientation with progres-sive strain (Figure 6E) is consistent with the hypothesisthat the Totoltepec pluton was emplaced during defor-mation. The younger dikes, as identified by cross-cuttingrelationships, are steeply dipping to vertical, undeformedto gently folded, and are discordant with respect to thefoliation. These dikes exhibit a minimum clockwise angleof 39◦ with respect to the N–S boundary faults, which isinferred to represent the initial dike orientation. The per-pendicular orientation of plagioclase and quartz adjacentto the margins of late SW–NE pegmatitic dikes in the mainphase of the pluton (Figure 2G) attests to the orthogo-nal dilation accompanying initial intrusion. A permissivemechanism of pluton emplacement along extensional frac-tures is also supported by the relatively minor crustal con-tamination of the mantle-derived, ultramafic–intermediate
entrainedblocks
trond-hjemite
dioritetonalite
gabbro/hornblendite
thrust
thrust
A C C’ D D’A’ B B’
CFZSJF
ca. 306 Ma
CFZSJF
ca. 289 Ma
CFZSJF
ca. 287 Ma
CFZSJF
ca. 283 Ma
39°?
A’
A
B’
B
D’
D
(A) (B)
C’
C
(D)(C)
Figure 12. Plan-view structural models and hypothetical cross-sections illustrating the emplacement of the Totoltepec pluton. (A)Intrusion of early mafic to ultramafic magma along a lineament in the transfer zone between the dextral, N–S-striking San JerónimoFault (SJF) and the Caltepec Fault Zone (CFZ). (B) Ascent of several sheet-like mafic to intermediate magma batches during regionaltranstension along a vertical, initially extensional SW–NE fault that became a WSW–ENE, sinistral cross-fault, rotating clockwise dueto dextral displacement on N–S boundary faults. (C) Synkinematic emplacement of a larger, more felsic batch of melt during continuedclockwise rotation of a cross-fault in the regional transtension zone. (D) Transference of dextral motion on the SJF to the CFZ, resultingin south-southeastward thrusting of the pluton and rapid uplift/exhumation.
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rocks and the lack of xenoliths or xenocrystic zircon inmarginal and main phases of the pluton (Kirsch et al.2012).
In contrast, older, sub-vertical dikes are folded, vari-ably sheared, foliation-concordant bodies that appear tohave been reoriented during progressive dextral shear. Withprogressive dextral shear on the bounding faults, theseNE-striking dikes would have initially rotated clockwiseinto a sector involving sinistral shear (Figure 12B), whichis consistent with the orientation of the sigmoidal inter-nal fabric of some dikes (Figures 2G and 2H) and thelocally observed deflection of amphibole into dike planes(Figure 2I). Further clockwise rotation of the dikes led tothe development of extensional structures, such as boudi-nage and pinch-and-swell.
In order to assess the significance of the dike array interms of the strain regime that accompanied its emplace-ment, we compare the dike patterns in the Totoltepecpluton to theoretical finite strain geometries and pre-dicted material line sectors for simple shear, transpression,and transtension (Figure 6E). The present surface of theTotoltepec pluton limits the strain analysis to 2D ratherthan a comprehensive 3D analysis (Kuiper and Jiang 2010).The ca. 307–269 Ma dextral shear along bounding verti-cal N–S faults was synchronous with emplacement of theTotoltepec pluton. If the movement on the N–S faults waspurely strike–slip, the transition from the shortening to theextensional field of the finite strain ellipse, i.e. between theorientation of folded dikes, and dikes that have been foldedand subsequently boudinaged, should occur at angles of 90◦to the N–S Caltepec and San Jerónimo faults. However,in the Totoltepec pluton, this transition occurs at angles of73◦, i.e. before the clockwise rotation reaches 90◦ relativeto the N–S-striking shear zone boundaries. This geometri-cal distribution pattern of material line sectors is indicativeof transtensional deformation (Figure 6E; Kuiper and Jiang2010).
Transtensional strain within the crustal block thatcontains the Totoltepec pluton is consistent with theprolate spheroid shapes in pebbles of metaconglom-erates in the Pennsylvanian–Middle Permian TecomateFormation north and south of the Totoltepec pluton(Morales-Gámez et al. 2009). The long axes of theseclasts are oriented parallel to the shallow NNE-plungingstretching lineation in the metasedimentary rocks ofthe Tecomate Formation. A sericitic phyllite from theTecomate Formation northwest of the Totoltepec plutonyielded a 40Ar/39Ar whole-rock age of 263 ± 3 millionyears (Morales-Gámez et al. 2009) and may record syn-tectonic growth of sericite. However, earlier transtensionaldeformation is indicated by the ca. 306 million year ageof the mafic part of the Totoltepec pluton, suggestingthat dextral movement along N–S striking faults in theregional arc was long-lived. Three components of strainare documented in the Totoltepec pluton: (1) NW–SE
extension, as indicated by the orientation of late pegmatiticdikes; (2) sub-vertical emplacement, as indicated bydown-dip hornblende mineral elongation lineations; and(3) sub-horizontal, WSW–ENE-directed sinistral shear, asindicated by along-strike mineral lineations and a rangeof different kinematic indicators. As there is no evidencefor one set of lineations overprinting another, and as bothsets of lineations are defined by magmatic hornblende, i.e.formed during the early stages of pluton crystallization,these three components of shear are inferred to belong to asingle episode of deformation. Although only 2D data areavailable for the Totoltepec pluton, the vorticity axis wasprobably oblique to these axes, indicating triclinic defor-mation (e.g. Jiang and Williams 1998; Lin et al. 1999).In this context, the relative predominance of lineations withshallow and steep plunges in different parts of the mafic–intermediate sheeted domain may be attributed to eitherdeformation-path partitioning into simple shear-dominatedand pure shear-dominated movement components acrossthe shear zone (Lin and Jiang 2001), or superimpositionof the sinistral shear component on vertical emplacement.The latter is consistent with the clockwise rotation of thepluton, and the lack of significant lateral displacement inthe 2D outcrop shape of the pluton, suggesting that thesinistral component during emplacement was minor com-pared with the amount of vertical extension. The amount ofvertical emplacement is constrained by thermobarometricand geochronological data, which indicate a rapid (around2.25 km/million years) exhumation of the pluton betweenca. 287 Ma and ca. 283 Ma. Using the present horizon-tal width of the main plutonic phase (around 4 km) as ameasure for NW–SE extension yields around 20% of E–Wextension across the zone. More structural data are requiredto more rigorously quantify the strain in the pluton.
Ascent/emplacement mechanism
Geochronological data indicate that the Totoltepec plutonwas assembled by at least two magmatic episodes separatedby around 17 million years. According to thermal mod-elling results (e.g. Stimac et al. 2001), this time span ofpluton construction exceeds the thermal lifetime of a largemagma reservoir, indicating that the compositional vari-ability between the main and marginal phase of the plutonis not due to in situ differentiation of a steady-state magmachamber, but represents at least two compositionally dis-tinct magma pulses.
Field evidence indicates that the younger intrusionwas also generated by a series of different magma batchesranging from felsic to mafic in composition. Physicalinteraction between magmatic increments of this mainplutonic phase is indicated by the occurrence of autoliths,microgranular enclaves, and composite dikes. The crys-tallization ages obtained for various phases of the mainplutonic body are the same within error (Yañez et al. 1991;
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Keppie et al. 2004a; Kirsch et al. 2012). However, contactsbetween undated individual sheets, dikes, and enclavesare usually sharp and locally show chilled margins orreaction rims, suggesting that magmatic injections weresufficiently spaced in time for preceding increments to cooland solidify. On the other hand, within the compositionallybanded zone, which on the basis of its field relationships,steepness of banding, and lack of ‘sedimentary’ structures(e.g. Barbey 2009), is interpreted as having originated bymultiple dike injections, feldspar phenocrysts grow acrossdike margins, suggesting that some magmatic incrementswere intruded before the igneous host was completelycrystallized.
These relationships suggest that diking was an impor-tant emplacement mechanism, at least for the highlyheterogeneous mafic–intermediate sheeted zone in thesouthern part of the pluton, where individual narrow,sub-vertical sheets can be traced for tens of metres alongstrike and locally show tapering terminations (e.g. Patersonand Miller 1998; Petford et al. 2000). An emplacementmechanism involving magma migration through propagat-ing dike conduits is consistent with the regional structuralcontext indicating extension oblique to strike–slip faults,which favours the emplacement of plutons as multipleinjections with thin, dike-like geometry (e.g. Pitcher andBerger 1972). Trondhjemitic rocks in the interior of thepluton are more voluminous and more homogeneous incomposition with the marginal mafic–intermediate sheetedzone. This outcrop pattern agrees with thermal modelsthat predict a transitory sheeted-dike phase followed bythe formation of an ephemeral, central magma cham-ber (Hanson and Glazner 1995; Coleman et al. 2004).However, the identification of rare felsic dikes and thepresence of different microstructural types within thisdomain suggest that the trondhjemitic part of the plutonmay also have an episodic emplacement history. Moregenerally, Bartley et al. (2008) point out that intrusivecontacts between magmatic increments may be morenumerous than is apparent in the field because internalcontacts may have become cryptic due to recrystallizationprocesses related to the extended periods of high tem-peratures that accompany slow incremental growth of apluton.
Synthesis/intrusive sequence
Geochronological (Kirsch et al. 2012), combined withthermobarometric, structural, and kinematic data, lead usto propose the following sequence of intrusive events.Early mafic–ultramafic rocks were emplaced at ca. 306 Maalong a crustal lineament (Figure 12A). At ca. 289 Ma,renewed magmatic activity in a transtensional regimewithin the regional magmatic arc led to several successivesheet-like intrusions of dike-fed, mafic–intermediate mag-mas (Figure 12B). Heat provided by mafic–intermediate
magma and regional arc activity (Solari et al. 2001; Elías-Herrera et al. 2005; Rosales-Lagarde et al. 2005; Solariet al. 2010) may have led to crustal melting and theformation of felsic magma at ca. 287 Ma. The stabiliza-tion of partially molten pathways (e.g. Miller and Paterson2001) potentially allowed for these voluminous, more fel-sic batches of melt to become wedged between the oldermafic–intermediate rocks (Figure 12C). Parts of the oldermafic–ultramafic phase may have become entrained in therising felsic melts, physically disaggregated by diking,rotated and dispersed along the margin of the pluton.Entrainment of the mafic–ultramafic phase is consistentwith (1) the presence of inherited zircons of ca. 306 Ma agein ca. 289 Ma rocks from the pluton interior (Kirsch et al.2012), suggesting that these older mafic–ultramafic blockswere partly assimilated; (2) the scattered spatial distribu-tion of the marginal bodies; and (3) the visible evidencethat the marginal bodies are intruded by felsic dikes. Theoccurrence of undated boundinaged folded dikes, foldeddikes, and undeformed dikes suggests that dike intrusionstarted with, and continued after, intrusion of the mainphase. Immediately following intrusion, clockwise rota-tion of the main phase of the pluton into its currentWSW–ENE orientation produced a vertical foliation andhorizontal lineation as well as intrafolial folds in the pluton.Fabric development occurred synchronously with defor-mation over a large temperature range from magmatic tolow-temperature conditions and was spatially diachronous.This is consistent with the continuum from magmatic tosolid-state foliations and the parallelism between theserespective fabrics (e.g. Paterson et al. 1989; Vernon et al.1989; Miller and Paterson 1994; Tribe and D’Lemos 1996).With decreasing temperature, the plutonic body may havebecome increasingly coupled to the country rocks (e.g.Tribe and D’Lemos 1996; Barros et al. 2001), which ledto the overprinting of igneous structures by solid-statefabrics. Deformation was concentrated in zones of compe-tency contrast, i.e. the mafic–intermediate sheeted domainnear the pluton margin, where it produced discrete mylonitezones (Figure 3).
Structural evidence within these mylonite zones, suchas the local development of tectonic down-dip lineationswith kinematic indicators of top-to-SSE transport, sug-gests that in the last stages of the emplacement history,thrusting may have developed locally within the regionaltranstensional environment. Thrusting may be associatedwith a decrease of slip along the San Jerónimo fault andresulting transfer of dextral displacement onto the Caltepecfault (Figure 12C). This transfer may have led to (1) termi-nation of magma supply by truncating the magma conduit,although regional magmatism occurred elsewhere in thearc and (2) substantial (around 2.25 km/million years)uplift of the pluton between ca. 287 Ma and ca. 283 Ma asinferred by Al-in-hornblende thermobarometry combinedwith 40Ar/39Ar geochronology.
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Regional significance
Transtensional deformation is a common feature ofmagmatic arcs, resulting from oblique convergence andstrain partitioning at plate margins (e.g. Teyssier et al.1995; Dewey 2002). The southern Mexican portion of theextensive Carboniferous–Permian continental arc exhibitsa well-pronounced arc-parallel structure of N–S ori-ented, dextral strike–slip faulting and synkinematic plutonsemplaced along these faults. The Totoltepec pluton is inter-preted to have been emplaced along a SW–NE extensionalfault that was synchronous with the dextral shear alongN–S fault zones, and is thus an example of arc-transversestrike–slip tectonics in the southern Mexican arc. Thegeochemistry of the Totoltepec pluton, which is isotopi-cally more primitive than coeval igneous rocks elsewherein the regional magmatic arc (Kirsch et al. 2012), andthe intrusive history involving the incremental injectionof several sheet-like magma batches into mid-crustal lev-els during transtensional deformation, followed by localthrusting resulting in uplift and exhumation, may be char-acteristic of pluton emplacement in such a specializedtectonic environment and may be utilized in identifyingsimilar tectonic settings within continental arcs.
AcknowledgementsMK thanks Maria Helbig for invaluable assistance in the field andsupport throughout the writing process. MK also acknowledgesthe helpful discussions with Uwe Kroner, Luigi Solari, FernandoOrtega-Gutiérrez, Harald Böhnel, Axel Renno, and Ángel F. NietoSamaniego. Carlos Linares provided technical assistance duringmicroprobe work at the Laboratorio Universitario de Petrología,UNAM. This study was funded by CONACyT and PAPIITgrants to JDK, and by NSERC discovery grants to JBM andJKWL.
ReferencesAnderson, J.L., 1996, Status of thermobarometry in granitic
batholiths, in Brown, M., Candela, P.A., Peck, D.L.,Stephens, W.E., Walker, R.J., and Zen, E., eds., The ThirdHutton Symposium on the origin of granites and relatedRocks: Geological Society of America Special Paper 315,p. 125–138.
Anderson, J.L., and Smith, D.R., 1995, The effects of tempera-ture and oxygen fugacity on the Al-in-hornblende barometer:American Mineralogist, v. 80, p. 549–559.
Baksi, A.J., 2006, Guidelines for assessing the reliabilityof 40Ar/39Ar plateau ages: Application to ages relevantto hotspot tracks: http://www.mantleplumes.org/ArAr.html(accessed May 2012).
Barbey, P., 2009, Layering and schlieren in granitoids: Arecord of interactions between magma emplacement, crys-tallization and deformation in growing plutons (The AndréDumont medallist lecture): Geologica Belgica, v. 12, no. 3–4,p. 109–133.
Barros, C.E.M., Barbey, P., and Boullier, A.M., 2001, Role ofmagma pressure, tectonic stress and crystallization progressin the emplacement of syntectonic granites. The A-type
Estrela Granite Complex (Carajás Mineral Province, Brazil):Tectonophysics, v. 343, p. 93–109.
Bartley, J.M., Coleman, D.S., and Glazner, A.F., 2008,Incremental pluton emplacement by magmatic crack-seal:Transactions of the Royal Society of Edinburgh: EarthSciences, v. 97, p. 383–396.
Blenkinsop, T.G., and Treloar, P.J., 1995, Geometry, classifica-tion and kinematics of SC and SC’ fabrics in the Mushandikearea, Zimbabwe: Journal of Structural Geology, v. 17, no. 3,p. 397–408.
Blumenfeld, P., and Bouchez, J.-L., 1988, Shear criteria in gran-ite and migmatite deformed in the magmatic and solid states:Journal of Structural Geology, v. 10, no. 4, p. 361–372.
Blundy, J.D., and Holland, T.J.B., 1990, Calcic amphibole equi-libria and a new amphibole-plagioclase geothermometer:Contributions to Mineralogy and Petrology, v. 104, no. 2,p. 208–224.
Büttner, S.H., 1999, The geometric evolution of structuresin granite during continuous deformation from magmaticto solid-state conditions: An example from the centralEuropean Variscan Belt: American Mineralogist, v. 84,p. 1781–1792.
Centeno García, E., 2005, Review of Upper Paleozoic andLower Mesozoic stratigraphy and depositional environmentsof central and west Mexico: Constraints on terrane anal-ysis and paleogeography, in Anderson, T.H., Nourse, J.A.,McKee, J.W., and Steiner, M.B., eds., The Mojave-Sonoramegashear hypothesis: Development, assessment, and alter-natives: Geological Society of America Special Paper 393,p. 233–258.
Centeno-García, E., Guerrero-Suastegui, M., Talavera-Mendoza,O., and Universitaria, C., 2008, The Guerrero CompositeTerrane of western Mexico: Collision and subsequent rift-ing in a supra-subduction zone, in Draut, A., Clift, P.D., andScholl, D.W., eds., Formation and applications of the sedi-mentary record in arc collision zones: Geological Society ofAmerica Special Paper 436, p. 1–30.
Coleman, D.S., Gray, W., and Glazner, A.F., 2004, Rethinkingthe emplacement and evolution of zoned plutons:Geochronologic evidence for incremental assembly ofthe Tuolumne Intrusive Suite, California: Geology, v. 32,no. 5, p. 433–436.
Crawford, M.L., Klepeis, K.A., Gehrels, G., and Isachsen,C., 1999, Batholith emplacement at mid-crustal levels andits exhumation within an obliquely convergent margin:Tectonophysics, v. 312, p. 57–78.
de Saint Blanquat, M., Habert, G., Horsman, E., Morgan,S.S., Tikoff, B., Launeau, P., and Gleizes, G., 2006,Mechanisms and duration of non-tectonically assisted magmaemplacement in the upper crust: The Black Mesa pluton,Henry Mountains, Utah: Tectonophysics, v. 428, no. 1–4,p. 1–31.
Dewey, J.F., 2002, Transtension in arcs and orogens: InternationalGeology Review, v. 44, p. 402–439.
Dickinson, W.R., and Lawton, T.F., 2001, Carboniferousto Cretaceous assembly and fragmentation of Mexico:Geological Society of America Bulletin, v. 113, no. 9,p. 1142–1160.
Dodson, M.H., 1973, Closure temperature in coolinggeochronological and petrological systems: Contributions toMineralogy and Petrology, v. 40, no. 3, p. 259–274.
Dowe, D.S., Nance, R.D., Keppie, J.D., Cameron, K.L., Ortega-Rivera, A., Ortega-Gutiérrez, F., and Lee, J.K.W., 2005,Deformational history of the Granjeno Schist, CiudadVictoria, Mexico: Constraints on the closure of the RheicOcean? International Geology Review, v. 47, p. 920–937.
Dow
nloa
ded
by [
Mor
itz K
irsc
h] a
t 06:
52 1
8 Ju
ne 2
012
22 M. Kirsch et al.
Elías-Herrera, M., and Ortega-Gutiérrez, F., 2002, Caltepec faultzone: An Early Permian dextral transpressional boundarybetween the Proterozoic Oaxacan and Paleozoic AcatlánComplexes, southern Mexico, and regional tectonic implica-tions: Tectonics, v. 21, no. 3, p. 1–19.
Elías-Herrera, M., Ortega-Gutiérrez, F., Sánchez-Zavala, J.L.,Macías-Romo, C., Ortega-Rivera, A., and Iriondo, A., 2005,La falla de Caltepec: raíces expuestas de una fronteratectónica de larga vida entre dos terrenos continentales delsur de México: Boletín de la Sociedad Geológica Mexicana,v. 57, no. 1, p. 83–109.
Ferrari, L., López-Martínez, M., Aguirre-Díaz, G., and Carrasco-Núñez, G., 1999, Space-time patterns of Cenozoic arc vol-canism in central Mexico: from the Sierra Madre Occidentalto the Mexican Volcanic Belt: Geology, v. 27, no. 4,p. 303–306.
Fitch, T.J., 1972, Plate convergence, transcurrent faults, and inter-nal deformation adjacent to Southeast Asia and the WesternPacific: Journal of Geophysical Research, v. 77, no. 23,p. 4432–4460.
Fitz Gerald, J.D., and Stünitz, H., 1993, Deformation of grani-toids at low metamorphic grade. I: Reactions and grain sizereduction: Tectonophysics, v. 221, p. 269–297.
Gapais, D., and Barbarin, B., 1986, Quartz fabric transition ina cooling syntectonic granite (Hermitage Massif, France):Tectonophysics, v. 125, no. 4, p. 357–370.
Gibbons, W., and Moreno, T., 2002, Tectonomagmatism incontinental arcs: Evidence from the Sark arc Complex:Tectonophysics, v. 352, no. 1, p. 185–201.
Glazner, A.F., 1991, Plutonism, oblique subduction, and conti-nental growth: An example from the Mesozoic of California:Geology, v. 19, p. 784–786.
Glazner, A.F., Bartley, J.M., Coleman, D.S., Gray, W., and Taylor,R.Z., 2004, Are plutons assembled over millions of years byamalgamation from small magma chambers?: GSA Today,v. 5173, no. 4/5, p. 4–11.
Grocott, J., Brown, M., Dallmeyer, R.D., Taylor, G.K., andTreloar, P.J., 1994, Mechanisms of continental growth inextensional arcs: An example from the Andean plate-boundary zone: Geology, v. 22, p. 391–394.
Grocott, J., and Taylor, G.K., 2002, Magmatic arc fault systems,deformation partitioning and emplacement of granitic com-plexes in the Coastal Cordillera, north Chilean Andes (2530’S to 27 00’S): Journal of the Geological Society, London,v. 159, no. 4, p. 425–443.
Hammarstrom, J.M., and Zen, E.-An, 1986, Aluminum inhornblende: an empirical igneous geobarometer: AmericanMineralogist, v. 71, p. 1297–1313.
Hanson, R.B., and Glazner, A.F., 1995, Thermal requirements forextensional emplacement of granitoids: Geology, v. 23, no. 3,p. 213–216.
Hirth, G., and Tullis, J., 1992, Dislocation creep regimes inquartz aggregates: Journal of Structural Geology, v. 14, no. 2,p. 145–159.
Holland, T.J.B., and Blundy, J.D., 1994, Non-ideal interac-tions in calcic amphiboles and their bearing on amphibole-plagioclase thermometry: Contributions to Mineralogy andPetrology, v. 116, no. 4, p. 433–447.
Hollister, L.S., Grissom, G.C., Peters, E.K., Stowell, H.H., andSisson, V.B., 1987, Confirmation of the empirical corre-lation of Al in hornblende with pressure of solidifica-tion of calc-alkaline plutons: American Mineralogist, v. 72,p. 231–239.
Jarrard, R.D., 1986, Terrane motion by strike-slip faulting offorearc slivers: Geology, v. 14, no. 9, p. 780–783.
Jiang, D., and Williams, P.F., 1998, High-strain zones: a uni-fied model: Journal of Structural Geology, v. 20, no. 8,p. 1105–1120.
Johnson, M.C., and Rutherford, M.J., 1989, Experimental cal-ibration of the aluminum-in-hornblende geobarometer withapplication to Long Valley caldera (California) volcanicrocks: Geology, v. 17, no. 9, p. 837–841.
Kamb, W.B., 1959, Ice petrofabric observations from BlueGlacier, Washington, in relation to theory and experiment:Journal of Geophysical Research, v. 64, no. 11, p. 1891–1909.
Keppie, J.D., Dostal, J., Murphy, J.B., and Nance, R.D., 2008,Synthesis and tectonic interpretation of the westernmostPaleozoic Variscan orogen in southern Mexico: From riftedRheic margin to active Pacific margin: Tectonophysics,v. 461, no. 1–4, p. 277–290.
Keppie, J.D., Nance, R.D., Dostal, J., Ortega-Rivera, A., Miller,B.V., Fox, D., Powell, J.T., Mumma, S.A., and Lee, J.K.W.,2004a, Mid-Jurassic tectonothermal event superposed on aPaleozoic geological record in the Acatlán Complex of south-ern Mexico: Hotspot activity during the breakup of Pangea:Gondwana Research, v. 7, no. 1, p. 239–260.
Keppie, J.D., Sandberg, C.A., Miller, B.V., Sánchez-Zavala,J.L., Nance, R.D., and Poole, F.G., 2004b, Implicationsof Latest Pennsylvanian to Middle Permian paleontologi-cal and U-Pb SHRIMP data from the Tecomate Formationto re-dating tectonothermal events in the Acatlán Complex,Southern Mexico: International Geology Review, v. 46, no. 8,p. 745–753.
Kirsch, M., Keppie, J.D., Murphy, J.B., and Solari, L.A., 2012,Permian–Carboniferous arc magmatism and basin evolu-tion along the western margin of Pangea: Geochemicaland geochronological evidence from the eastern AcatlánComplex, southern Mexico: Geological Society of AmericaBulletin (in prep.).
Kratinová, Z., Schulmann, K., Edel, J.B., Jezek, J., andSchaltegger, U., 2007, Model of successive granitesheet emplacement in transtensional setting: Integratedmicrostructural and anisotropy of magnetic suscepti-bility study: Tectonics, v. 26, no. 6, p. TC6003. doi:10.1029/2006TC002035.
Kruhl, J.H., 1996, Prism- and basal-plane parallel subgrainboundaries in quartz: A microstructural geothermobarom-eter: Journal of Metamorphic Geology, v. 14, no. 5, p.581–589.
Kuiper, Y.D., and Jiang, D., 2010, Kinematics of deformationconstructed from deformed planar and linear elements: Themethod and its application: Tectonophysics, v. 492, no. 1–4,p. 175–191.
Laird, J., and Albee, A.L., 1981, High-pressure metamorphismin mafic schist from northern Vermont: American Journal ofScience, v. 281, no. 2, p. 97–126.
Leake, B.E., 1971, On aluminous and edenitic hornblendes:Mineralogical Magazine, v. 38, p. 389–405.
Leake, B.E., 1978, Nomenclature of amphiboles: AmericanMineralogist, v. 63, p. 1023–1052.
Leake, B.E., Woolley, A.R., Arps, C.E.S., Birch, W.D., Gilbert,M.C., Grice, J.D., Hawthorne, F.C., Kato, A., Kisch, H.J.,Krivovichev, V.G., Linthout, K., Laird, J., Mandarino,J.A., Maresch, W.V. et al., 1997, Nomenclature of amphi-boles: Report of the subcommittee on amphiboles ofthe International Mineralogical Association, Commissionon New Minerals and Mineral Names: The CanadianMineralogist, v. 35, p. 219–246.
Leake, B.E., Woolley, A.R., Birch, W.D., Burke, E.A.J., Ferraris,G., Grice, J.D., Hawthorne, F.C., Kisch, H.J., Krivovichev,
Dow
nloa
ded
by [
Mor
itz K
irsc
h] a
t 06:
52 1
8 Ju
ne 2
012
International Geology Review 23
V.G., Schumacher, J.C., Stephenson, N.C.N., and Whittaker,E.J.W., 2003, Nomenclature of amphiboles: Additions andrevisions to the International Mineralogical Association’s1997 recommendations: Canadian Mineralogist, v. 41,p. 1355–1362.
Leake, B.E., Woolley, A.R., Birch, W.D., Burke, E.A.J., Ferraris,G., Grice, J.D., Hawthorne, F.C., Kisch, H.J., Krivovichev,V.G., Schumacher, J.C., Stephenson, N.C.N., and Whittaker,E.J.W., 2004, Nomenclature of amphiboles: Additions andrevisions to the International Mineralogical Associationsamphibole nomenclature: American Mineralogist, v. 89, p.883–887.
Lin, S., and Jiang, D., 2001, Using along-strike variation in strainand kinematics to define the movement direction of curvedtranspressional shear zones: An example from northwesternSuperior Province, Manitoba: Geology, v. 29, p. 767–770.
Lin, S., Jiang, D., and Williams, P.F., 1999, Discussion on trans-pression and transtension zones: Journal of the GeologicalSociety, London, v. 156, no. 5, p. 1045–1050.
Mahan, K.H., Bartley, J.M., Coleman, D.S., Glazner, A.F., andCarl, B.S., 2003, Sheeted intrusion of the synkinematicMcDoogle pluton, Sierra Nevada, California: Bulletin of theGeological Society of America, v. 115, no. 12, p. 1570–1582.
Mainprice, D., Bouchez, J.-L., Blumenfeld, P., and Tubià,J.M., 1986, Dominant c slip in naturally deformed quartz:Implications for dramatic plastic softening at high tempera-ture: Geology, v. 14, no. 10, p. 819–822.
Malone, J.R., Nance, R.D., Keppie, J.D., and Dostal, J., 2002,Deformational history of part of the Acatlán Complex: LateOrdovician–Early Silurian and Early Permian orogenesis insouthern Mexico: Journal of South American Earth Sciences,v. 15, no. 5, p. 511–524.
Massonne, H.-J., and Schreyer, W., 1987, Phengite geobarometrybased on the limiting assemblage with K-feldspar, phlogopite,and quartz: Contributions to Mineralogy and Petrology, v. 96,p. 212–224.
McDougall, I., and Harrison, T.M., 1999, Geochronology andthermochronology by the 40Ar/39 Ar method (second edi-tion): Oxford, Oxford University Press, 269 p.
Menegon, L., Pennacchioni, G., and Stünitz, H., 2006, Nucleationand growth of myrmekite during ductile shear deformationin metagranites: Journal of Metamorphic Geology, v. 24,p. 553–568.
Miller, R.B., and Paterson, S.R., 1994, The transition frommagmatic to high-temperature solid-state deformation:Implications from the Mount Stuart batholith, Washington:Journal of Structural Geology, v. 16, no. 6, p. 853–865.
Miller, R.B., and Paterson, S.R., 2001, Construction of mid-crustal sheeted plutons: Examples from the north Cascades,Washington: Geological Society of America Bulletin, v. 113,no. 11, p. 1423–1442.
Morales-Gámez, M., Keppie, J.D., Lee, J.K.W., and Ortega-Rivera, A., 2009, Palaeozoic structures in the Xayacatlánarea, Acatlán Complex, southern Mexico: transtensionalrift- and subduction-related deformation along the marginof Oaxaquia: International Geology Review, v. 51, no. 4,p. 279–303.
Murphy, J.B., Keppie, J.D., Nance, R.D., Miller, B.V., Dostal,J., Middleton, M., Fernandez-Suarez, J., Jeffries, T.E.,and Storey, C.D., 2006, Geochemistry and U-Pb protolithages of eclogitic rocks of the Asis Lithodeme, PiaxtlaSuite, Acatlán Complex, southern Mexico: Tectonothermalactivity along the southern margin of the Rheic Ocean:Journal of the Geological Society, London, v. 163,p. 683–695.
Nance, R.D., Fernández-Suárez, J., Keppie, J.D., Storey, C.,and Jeffries, T.E., 2007, Provenance of the GranjenoSchist, Ciudad Victoria, México: Detrital zircon U-Pb ageconstraints and implications for the Paleozoic paleogeog-raphy of the Rheic Ocean, in Linnemann, U., Nance,R.D., Kraft, P., and Zulauf, G., eds., The evolution ofthe Rheic Ocean: From Avalonian-Cadomian active mar-gin to Alleghenian-Variscan collision: Geological Society ofAmerica Special Paper 423, p. 453–464.
Ortega-Gutiérrez, F., Ruiz, J., and Centeno-García, E., 1995,Oaxaquia, a Proterozoic microcontinent accreted to NorthAmerica during the late Paleozoic: Geology, v. 23, no. 12,p. 1127–1130.
Ortega-Obregón, C., Murphy, J.B., and Keppie, J.D., 2010,Geochemistry and Sm–Nd isotopic systematics of Ediacaran–Ordovician, sedimentary and bimodal igneous rocks in thewestern Acatlán Complex, southern Mexico: Evidence forrifting on the southern margin of the Rheic Ocean: Lithos,v. 114, no. 1–2, p. 155–167.
Paterson, S.R., and Fowler., T.K., Jr. 1993, Extensional pluton-emplacement models: Do they work for large plutonic com-plexes? Geology, v. 21, no. 9, p. 781–784.
Paterson, S.R., Fowler, T.K., Schmidt, K.L., Yoshinobu, A.S.,Yuan, E.S., and Miller, R.B., 1998, Interpreting magmaticfabric patterns in plutons: Lithos, v. 44, no. 1–2,p. 53–82.
Paterson, S.R., and Miller, R.B., 1998, Mid-crustal magmaticsheets in the Cascades Mountains, Washington: Implicationsfor magma ascent: Journal of Structural Geology, v. 20,no. 9–10, p. 1345–1363.
Paterson, S.R., Vernon, R.H., and Tobisch, O.T., 1989, A reviewof criteria for the identification of magmatic and tectonicfoliations in granitoids: Journal of Structural Geology, v. 11,no. 3, p. 349–363.
Petford, N., and Atherton, M.P., 1992, Granitoid emplacement anddeformation along a major crustal lineament: The CordilleraBlanca, Peru: Tectonophysics, v. 205, no. 1–3, p. 171–185.
Petford, N., Cruden, A.R., McCaffrey, W.D., and Vigneresse, J.L.,2000, Granite magma formation, transport and emplacementin the Earth’s crust: Nature, v. 408, p. 669–673.
Pignotta, G.S., Paterson, S.R., Coyne, C.C., Anderson, J.L., andOnezime, J., 2010, Processes involved during incrementalgrowth of the Jackass Lakes pluton, central Sierra Nevadabatholith: Geosphere, v. 6, no. 2, p. 130–159.
Pitcher, W.S., and Berger, A.R., 1972, The geology of Donegal: Astudy of granite emplacement and unroofing: New York, JohnWiley and Sons, 435 p.
Pryer, L.L., 1993, Microstructures in feldspars from a majorcrustal thrust zone: The Grenville Front, Ontario, Canada:Journal of Structural Geology, v. 15, no. 1, p. 21–36.
Ramos-Arias, M.A., and Keppie, J.D., 2011, U-PbNeoproterozoic–Ordovician protolith age constraints forhigh- to medium-pressure rocks thrust over low-grademetamorphic rocks in the Ixcamilpa area, Acatlán Complex,southern Mexico: Canadian Journal of Earth Sciences, v. 48,no. 1, p. 45–61.
Rosales-Lagarde, L., Centeno-García, E., Dostal, J., Sour-Tovar,F., Ochoa-Camarillo, H., and Quiroz-Barroso, S., 2005, TheTuzancoa formation: Evidence of an early Permian subma-rine continental arc in East-Central Mexico: InternationalGeology Review, v. 47, p. 901–919.
Rosenberg, C.L., and Stünitz, H., 2003, Deformation and recrys-tallization of plagioclase along a temperature gradient: Anexample from the Bergell tonalite: Journal of StructuralGeology, v. 25, p. 389–408.
Dow
nloa
ded
by [
Mor
itz K
irsc
h] a
t 06:
52 1
8 Ju
ne 2
012
24 M. Kirsch et al.
Rothstein, D.A., and Manning, C.E., 2003, Geothermal gradientsin continental magmatic arcs: Constraints from the east-ern Peninsular Ranges batholith, Baja California, México,in Johnson, S.E., Paterson, S.R., Fletcher, J.M., Girty, G.H.,Kimbrough, D.L., and Martín-Barajas, A. eds., Tectonicevolution of northwestern Mexico and the southwesternUSA: Geological Society of America Special Paper 374,p. 337–354.
Schmidt, M.W., 1992, Amphibole composition in tonalite as afunction of pressure: An experimental calibration of the Al-in-hornblende barometer: Contributions to Mineralogy andPetrology, v. 110, no. 2–3, p. 304–310.
Schmidt, M.W., 1993, Phase relations and compositions intonalite as a function of pressure: An experimental studyat 650◦C: American Journal of Science, v. 293, no. 10, p.1011–1060.
Servicio Geológico Mexicano, 2004a, Primera Derivada Verticaldel Campo Magnético Total Reducido al Polo en Contornos aColor, Ixcaquixtla E14-B74, Scale 1:50 000, 1 sheet.
Servicio Geológico Mexicano, 2004b, Primera Derivada Verticaldel Campo Magnético Total Reducido al Polo en Contornos aColor, Petlalcingo E14-B84, Scale 1:50 000, 1 sheet.
Simpson, C., 1985, Deformation of granitic rocks across thebrittle-ductile transition: Journal of Structural Geology, v. 7,no. 5, p. 503–511.
Solari, L.A., Dostal, J., Ortega-Gutiérrez, F., and Keppie, J.D.,2001, The 275 Ma arc-related La Carbonera stock inthe northern Oaxacan Complex of southern Mexico: U-Pb geochronology and geochemistry: Revista Mexicana deCiencias Geológicas, v. 18, no. 2, p. 149–161.
Solari, L.A., Ortega-Gutiérrez, F., Elías-Herrera, M., Gómez-Tuena, A., and Schaaf, P., 2010, Refining the age of magma-tism in the Altos Cuchumatanes, western Guatemala, by LA–ICPMS, and tectonic implications: International GeologyReview, v. 52, no. 9, p. 977–998.
Solari, L.A., Torres de León, R., Hernández Pineda, G., Solé,J., Solís-Pichardo, G., and Hernández-Treviño, T., 2007,Tectonic significance of Cretaceous–Tertiary magmatic andstructural evolution of the northern margin of the XolapaComplex, Tierra Colorada area, southern Mexico: GeologicalSociety of America Bulletin, v. 119, no. 9, p. 1265–1279.
Stimac, J.A., Goff, F., and Wohletz, K., 2001, Thermal modelingof the Clear Lake magmatic-hydrothermal system, California,USA: Geothermics, v. 30, p. 349–390.
Streckeisen, A.L., 1976, To each plutonic rock its proper name:Earth-Science Reviews, v. 12, no. 1, p. 1–33.
Teyssier, C., Tikoff, B., and Markley, M., 1995, Oblique platemotion and continental tectonics: Geology, v. 23, no. 5,p. 447–450.
Thomas, W.M., and Ernst, W.G., 1990, The aluminium contentof hornblende in calc-alkaline granitic rocks: A mineralogic
barometer calibrated experimentally to 12kbar, in Spencer,R.J., and Chou, I.M., eds., Fluid-mineral interactions: Atribute to H.P. Eugster: The Geochemical Society SpecialPublication 2, p. 59–63.
Tikoff, B., and Teyssier, C., 1992, Crustal-scale, en echelon ‘P-shear’ tensional bridges: A possible solution to the batholithicroom problem: Geology, v. 20, no. 10, p. 927–930.
Tobisch, O.T., and Cruden, A.R., 1995, Fracture-controlledmagma conduits in an obliquely convergent continentalmagmatic arc: Geology, v. 23, no. 10, p. 941–944.
Tolson, G., 2007, The Chacalapa fault, southern Oaxaca,México, in Alaniz-Álvarez, S.A., and Nieto-Samaniego, Á.F.,eds., Geology of México: Celebrating the Centenary ofthe Geological Society of México: Geological Society ofAmerica Special Paper 422, p. 343–357.
Torres, R., Ruiz, J., Patchett, P.J., and Grajales-Nishimura, J.M.,1999, Permo-Triassic continental arc in eastern Mexico:Tectonic implications for reconstructions of southern NorthAmerica, in Bartolini, C., Wilson, J.L., and Lawton, T.F., eds.,Mesozoic sedimentary and tectonic history of north-centralMexico: Geological Society of America Special Paper 340,p. 191–196.
Tribe, I.R., and D’Lemos, R.D., 1996, Significance of a hia-tus in down-temperature fabric development within syn-tectonic quartz diorite complexes, Channel Islands, UK:Journal of the Geological Society, London, v. 153, no. 1,p. 127–138.
Tullis, J., and Yund, R.A., 1987, Transition from cataclas-tic flow to dislocation creep of feldspar: Mechanisms andmicrostructures: Geology, v. 15, no. 7, p. 606–609.
Vernon, R.H., Paterson, S.R., and Geary, E.E., 1989, Evidence forsyntectonic intrusion of plutons in the Bear Mountains faultzone, California: Geology, v. 17, no. 8, p. 723–726.
Watson, E.B., Wark, D.A., and Thomas, J.B., 2006, Crystallizationthermometers for zircon and rutile: Contributions toMineralogy and Petrology, v. 151, no. 4, p. 413–433.
Whitney, D.L., and Evans, B.W., 2010, Abbreviations for namesof rock-forming minerals: American Mineralogist, v. 95,no. 1, p. 185–187.
Yañez, P., Patchett, P.J., Ortega-Gutiérrez, F., and Gehrels,G.E., 1991, Isotopic studies of the Acatlán Complex,southern Mexico: Implications for Paleozoic North AmericanTectonics: Geological Society of America Bulletin, v. 103,no. 6, p. 817–828.
Žák, J., Holub, F.V., and Verner, K., 2005, Tectonic evo-lution of a continental magmatic arc from transpressionin the upper crust to exhumation of mid-crustal oro-genic root recorded by episodically emplaced plutons: TheCentral Bohemian Plutonic Complex (Bohemian Massif):International Journal of Earth Sciences, v. 94, no. 3,p. 385–400.
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4E V E N T O S D E L PA L E O Z O I C O TA R D Í O H A S TA E LM E S O Z O I C O T E M P R A N O E N L A P E R I F E R I A D EPA N G E A
Guía de la excursión geológica: Keppie, J.D., Galaz-Escanilla, G., Helbig,M., y Kirsch, M. (2012). Late Paleozoic–Early Mesozoic of the Acatlán andAyú complexes, southern Mexico: events on the periphery of Pangæa syn-chronous with amalgamation and breakup. GSA Cordilleran Section, 108thAnnual Meeting, Field Trip 1, 31 March – 4 April, Geological Society ofAmerica, IGCP Project 597, 17 p.
Contribuciones individuales de los autores:
J. Duncan Keppie: líder y organizador de la excursión; concepción ydiseño de la guía de excursión.
Gonzalo Galaz-Escanilla: co-líder de la excursión; descripción de lasparadas 3-1 a 3-7; redacción de las figuras 7 y 8.
Maria Helbig: co-líder de la excursión; descripción de las paradas 1-1a 1-6; redacción de las figuras 3, 4 y 5.
Moritz Kirsch: co-líder de la excursión; descripción de las paradas 2-1 a 2-8; elaboración de la figura 6; con respecto a los nuevos datosde una unidad metamórfica del Misisipiense en la parte oriental delárea de estudio: trabajo de campo incluyendo mapeo y muestreo parala geocronología 40Ar/39Ar; análisis geoquímico e isotópico; adquisi-ción de datos de los análisis 40Ar/39Ar incluyendo la separación deminerales, el análisis y la interpretación de datos.
58
GSA Cordilleran Section, 108th Annual MeetingField Trip 1
31 March–4 April 2012
Amalgamation and Breakup of Pangæa: the type example of the supercontinent Cycle
International Geological Correlation Program Project #597: Late Paleozoic–Early Mesozoic of the Acatlán and Ayu complexes, southern Mexico: events on the periphery of Pangæa synchronous with amalgamation and breakup
J. Duncan KeppieGonzalo Galaz-Escanilla
Departamento de Geología Regional, Insituto de Geología, Universidad Nacional Autónoma de México, 04510 Mexico, D.F.Maria HelbigMortiz Kirsch
Centro de Geociencias, Universidad Nacional Autónoma de México, Campus Juriquilla, 76230 Querétaro, QRO, Mexico
INTRODUCTION
There is widespread acceptance that between 300 and 200 million years ago, all of the Earth’s continental land masses were assembled into a giant supercontinent, Pan-gæa, surrounded by a superocean, Panthalassa. However, different confi gurations have been proposed, e.g., Pangæa A1, A2, B, and C (Fig. 1A). Reconstructions based on Mexican paleomagnetic data have been used to support both A and B models:
(a) PANGEA-A. A Permo-Triassic Pangea-A reconstruction where southern Mexico lies approximately in its present location relative to North America (Fang et al., 1989, Alva-Valdivia et al., 2002);
(b) PANGEA-B. A Pangea-B reconstruction placing southern Mexico off eastern Canada during the Jurassic (Fig. 1B: Böhnel, 1999).
There are also Middle American variants of the Pangea-A reconstruction:(i) southwestern Mexico is placed either along the western margin of Pan-
gea (Fig. 1C and 1D: Keppie, 2004, Keppie et al., 2008, 2010), or within Pangea between the Maya terrane and southern USA (Fig. 1E: Talavera-Mendoza et al.,2005, Vega-Granillo et al., 2007, 2009);
(ii) the Yucatan block is placed either within Pangea along the southern mar-gin of USA (Fig. 1F: Pindell and Dewey, 1982), or on the western margin of Pangea during the mid-late Permian migrating into the Gulf of Mexico by the Middle Jurassic (Steiner, 2005);
(iii) the Chortis block has generally been placed off southwestern Mexico on the western marin of Pangea (Fig. 1E)(e.g., Pindell and Dewey, 1982), or within the within Pangea along the eastern margin of Mexico (Fig. 1G: Keppie and Keppie, in review).
On this fi eld trip we will examine the evidence for subduction-related tectonics during the Pennsylvanian-Jurassic in the Ayu and Acatlán complexes, which suggests proximity to an ocean that is more consistent with the Pangea-A model (Fig. 2).
1
AB
C350–330 Ma 300–270 Ma
D
E
FG
Figure 1. Reconstructions of Pangea by various authors.
2 Keppie et al.
Figure 2. (A) Terranes of Middle America (after Keppie, 2004); (B) Ages od units in the Acatlán Complex; (C) Map of the Acatlán Complex (modifi ed after Keppie et al., 2010) showing the fi eld trip route.
Amalgamation and Breakup of Pangæa: the type example of the supercontinent Cycle 3
DAY 1Maria Helbig and J. Duncan Keppie
The Triassic-Jurassic Ayú Complex Southern Mexico: Evidence for Deposition on the Proximal Margin of a Backarc Basin, Underthrusting and Extrusion into the Acatlán Complex during the Breakup of Pangea-A
Helbig, M, Keppie, J.D., Murphy, J.B., and Solari, L.A., in press. U-Pb geochonological constraints on the Triassic–Jurassic Ayú Complex southern Mexico: derivation from the western margin of Pangea: Gondwana Research.
ABSTRACT
Rocks of the newly designated Ayú Complex are located in the eastern Mixteca terrane (southern Mexico), and comprise polyphase-deformed turbiditic rocks (Chazumba Lithodeme) that are intercalated with boudinaged ortho-amphibolites. In the south, the metasedimentary sequence is affected by partial melting and grades into the ~171 Ma Magdalena Migmatite. Migmatitzation was accompanied by 171–168 Ma granitoid minor intrusions and pegmatites with inherited zircon popula-tions of ca. 260–290, 320–360, 420–480, 880–990, and 1080–1250 Ma that are also found in the Chazumba Lithodeme. Detrital U/Pb zircon ages from the migmatized and unmigma-tized Chazumba Lithodeme yielded clusters of ca. 297, 266, 250, 214, 198, and 192 Ma, suggesting Upper Triassic—Lower Jurassic deposition. The MORB tholeiitic geochemistry of the amphibolites within the Chazumba Lithodeme indicates a back-arc environment with sedimentation occurring along the inboard rifted passive margin, the Upper Triassic–Lower Jurassic detrital zircons being derived from a contemporane-ous, outboard magmatic arc. These characteristics suggest cor-relation with the lens-shaped Central terrane typifi ed by the Potosi turbiditic fan in the rift-passive margin of Pangea that is absent west of the Mixteca terrane. The presence of this arc requires deposition adjacent to a subducting ocean and thus supports a Pangea-A reconstruction. Early Jurassic fl attening of the subduction zone is inferred to have led telescoping of the Triassic–Early Jurassic back arc basin, during which the Chazumba Lithodeme was thrust beneath the Pangean margin where it was metamorphosed under amphibolite facies meta-morphic conditions. It is further inferred that Middle-Upper Jurassic steepening of the subducting zone led to tectonic exhumation of the Chazumba Lithodeme by normal faulting along the reactivated Providencia Shear Zone. Deposition, underthrusting and exhumation of the Chazumba Lithodeme are synchronous with the breakup of Pangea and the opening of the Gulf of Mexico.
STOP 1-1 (W97.78834, N17.9387426: Fig. 3)Location: Road between Sta. María Ayú and Ahuehuetitlán, riverbed of Río La Peña.
Micaceous schists and garnet-biotite gneisses are inter-calated with boudinaged amphibolites, that underwent migmati-zation at ~171 Ma (leucosome dated by Keppie et al., 2004) and formed a mappable unit, called the Magdalena Migmatite. This tectonothermal event was accompanied by syntectonic intrusion of granitic, granodioritic and dioritic dikes and sheets (Yañez et al., 1991). A granite dike that cuts the paleosome yielded only one igneous zircon of 171 ± 4 (Middle Jurassic), whereas the rest of the dated grains are inherited zircons. Two paleosome samples of the Magdalena Migmatite yielded youngest detrital zircons of ~198 Ma (Early Jurassic) and 214 Ma (Late Triassic ), respectively. Amphibolites were previously dated by Keppie et al. (2004) and showed 40Ar/39Ar cooling ages of 150 ± 2 Ma for biotite and 136 ± 2 for hornblende, suggesting rapid exhuma-tion. Geochemically, amphibolites sampled across the Ayú Com-plex are MORB-like, rift-related tholeiites (Helbig et al., 2010). The majority of the ortho-amphibolites have jagged NMORB-normalized REE patterns that imply contamination either by a crustal and/or subduction component and suggest a formation in a back-arc basin.
STOP 1-2 (W97.807052°°, N17.9987634°°: Fig. 3)Location: short road stop east of Tetaltepec.
Structural relationships in the Magdalena Migmatite: Large scale, close to open, upright to gently inclined parasitic fold (F
4)
that folds the leucosome and boudinaged S3-parallel granite
sheets.
STOP 1-3 (W97.830789°°, N18.036058°°: Fig. 3)Location: Riverbed, south of San Miguel Ixtápan.
Partially molten, and strongly deformed metasedimentary rocks that are intruded by granodiorites and pegmatites. Xeno-liths are probably the metasedimentary host rock and show in-ternal foliation as well as partial melting of the fertile domains. 40Ar/39Ar dating of a pegmatite and a granitic sheet yielded 167 ± 2 Ma for muscovite, and 155 ± 5 Ma for biotite (Keppie et al., 2004).
STOP 1-4 (W97.832239°°,N18.0421378°°: Fig. 3)Location: Road section, south of San Miguel Ixtapan.
Outcrop exhibits a dike that cuts across the micaceous schists and feeds a granite sheet. The emplacement of the granite sheet is parallel to the main foliation, infl ating the surrounding metapelitic host rock. The dike continues its way into the hang-ing metasedimentary host rock. Where in the contact with the host rock, the dike is overprinted by the same fabric as in the metasedimentary rocks. The rock is affected by later brittle nor-mal block faulting. The fabric-parallel granite sheets show sharp contacts with the metapelites and exhibit minor pinch-and-swell structures and a distinct tectono-magmatic foliation at their mar-gins suggesting stress-related emplacement.
4 Keppie et al.
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°06′
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Figure 3. Geological map and section of the Totoltepec-Ayu area, southern Mexico showing fi eld trip stops (modifi ed after Helbig et al., in press).
Amalgamation and Breakup of Pangæa: the type example of the supercontinent Cycle 5
STOP 1-5 (W97.828639°°, N18.0526397°°: Fig. 4)Location: Foothills of the Cerro de La Peña (Cenozoic volcanic plug), north of Tejepillo; San Miguel Ixtapan road exit to Tultitlán.
Micaceous schists intercalated with minor quartzites are in-truded by granites, leucogranitic and aplitic dikes. A granite dike cuts a tight, recumbent E-trending F
3 fold in the metasedimentary
host rock. Small leucogranite veins that probably originate from the dike are parallel to the folded S
2 fabric. These relationships
suggest that the intrusion was syn- to late-tectonic with respect to F
3. The granite is characterized by zircon inheritance and the
crystallization age is inferred from the youngest grain with an age of 168 Ma. U-Pb detrital zircon analyses of a psammitic and a pelitic mica schist yielded maximum depositional ages of ~269 Ma and ~263 Ma (Middle Permian), respectively.
In the hanging wall, the mafi c-ultramafi c Tepejillo lens lies structurally as a nappe above the Chazumba Lithodeme (Keppie et al., 2004) and consists of four bodies that crop out along the foothills of Cenozoic volcanic plug (C. La Peña). The Tepejillo lens comprises coarse crystalline ultramafi c (mainly dunite) to gabbroic rocks that are cut by diabase dikes. Geochemically, they are interpreted as part of a cumulatic body intruded into the lower continental crust (Keppie et al., 2004). The contact be-tween the metasedimentary rocks of the Chazumba Lithodeme and the Tepejillo lens has been mapped as a folded thrust (Kep-pie et al., 2004). The Tultitán lens, 4 km to the northeast of the Tepejillo lens, consists of massive amphibolite and a core of metamorphosed norite. One concordant U-Pb LA-ICP-MS analysis of a prismatic tip of a euhedral zircon from a metanorite yielded an age of 174 ± 1 Ma, which is interpreted as age of intrusion for both lens (Keppie et al., 2004). Biotite from a gab-broic dike of the Tepejillo lens yielded a 40Ar/39Ar cooling age of 166 ± 2 Ma, whereas muscovite from a granite dike yielded a 40Ar/39Ar age of 161 ± 2 Ma (Keppie et al., 2004), suggesting excess argon in the biotite. Lower power increments of Late Cre-taceous to Tertiary age can be observed in almost all 40Ar/39Ar analyses, implying that the Ayú Complex was affected by a later deformational event.
STOP 1-6 (W97.899842°°, N18.113004°°: Fig. 5)Location: road section near the town La Providencia, on the road between Petlalcingo and Tonhuixtla.
Reactivation of a Triassic S-vergent thrust fault as a lis-tric normal fault in the Middle-Late Jurassic. The Providencia shear zone forms a major structural feature between rocks of the Acatlán Complex (Tecomate Formation and Cosoltepec Forma-tion) and the Ayú Complex and comprises weathered mylonites.
A micaceous metapsammite just south of the shear zone yielded only seventeen concordant analyses. Relatively narrow age spectra ranging from 194 to 339 Ma were obtained with the two youngest grains (190 ± 4, 193 ± 4 Ma) forming a mean of 192 ± 19 Ma (Early Jurassic). To the north of the shear zone, a
mylonitic phyllite yielded a youngest detrital zircon age of 314 ± 4 Ma, which lies within the error of the mean of the three young-est grains with an age of 321 ± 30 Ma (Late Mississippian/Early Pennsylvanian). A graphite- and feldspar-bearing mylonitic metasedimentary rock, yielded two youngest detrital zircon ages of 281 ± 4 Ma and 295 ± 8 Ma with a mean age of 284 ± 71 Ma (Early Permian).
The presence of a major shear zone (Providencia Shear Zone) that separates the Acatlán Complex from the Ayú Complex was previously mapped as a thrust based on s-c fabrics in the hang-ing block (Malone et al., 2002; Keppie et al., 2004). However, 40Ar/39Ar cooling ages for amphibole of an amphibolite lens and muscovite from micaceous schists, north of the shearzone yielded cooling ages of ~214 Ma and ~224 Ma, respectively (Keppie et al., 2004). These fabrics are Late Triassic, and thus developed before or during the deposition of the Chazumba Lithodeme. It is envisaged that this Triassic shear zone was reactivated during or after the Middle Jurassic as a listric normal fault and formed the upper boundary of the exhuming Chazumba Lithodeme.
DAY 2Moritz Kirsch and J. Duncan Keppie
Lower Permo-Carboniferous Arc Magmatism and Sedimentation on the Margin of Pangea-A
Kirsch, M., Keppie, J.D., Murphy, J.B., and Solari, L.A. in press. Permian-Carboniferous arc magmatism and basin evolution along the western margin of Pangea: geochemical and geochronological evidence from the eastern Acatlán Complex, southern Mexico: GSA Bulletin.
ABSTRACT
The Late Paleozoic evolution of Mexico records part of a continental arc that extends along the western margin of Pan-gea from western USA to the northern Andes. In the Acatlán Complex of southern Mexico, an arc assemblage consisting of a Permo-Carboniferous intrusion (Totoltepec pluton) and Permian sedimentary rocks (Tecomate Formation) offers a rare opportunity to examine events along the periphery of Pangea at the critical stage of fi nal amalgamation.
The Totoltepec pluton ranges in composition from horn-blendite and hornblende gabbro through diorite to tonalite, trondhjemite, granodiorite and monzo-granite. U-Pb LA-ICP-MS zircon analyses yield concordant ages of 306 ± 2 Ma in minor marginal mafi c to ultramafi c rocks and 289 ± 2 Ma for the main, more voluminous mafi c to felsic intrusion. Major and trace element geochemistry of the Totoltepec rocks exhibit a tholeiitic to calc-alkaline character, high LILE/HFSE and fl at REE patterns, which is typical of arc-related magmas. The pre-cursor gabbroic rocks display εNd(t) values ranging from +1.3 to +3.3 (t = 306 Ma), whereas rocks from the main body of the pluton have εNd(t) values between −0.8 and +2.6 (t = 289 Ma).
6 Keppie et al.
B
A
B′
A′
B′B
A′
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Figure 4. Stop 1-5: geological map, age data, and section of the Tepejillo ultramafi c lens (after Keppie et al., 2004).
Amalgamation and Breakup of Pangæa: the type example of the supercontinent Cycle 7
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8 Keppie et al.
All of the samples are variably affected by wall rock assimi-lation, mixing and fractionation processes, but are more juve-nile compared to contemporaneous arc-related igneous rocks in southern Mexico, suggesting the pluton was emplaced into thinner crust in a less mature part of the arc or along a fault that acted as a conduit for mantle-derived melts.
The Tecomate Formation consists of low-grade, poorly sorted, compositionally immature and largely unweathered metapsammites and metapelites. Several factors indicate deri-vation from the Permo-Carboniferous arc: (i) an arc-related geochemistry, (ii) εNd(t) values ranging from −5.7 to +0.3 (t = 280 Ma) that overlap those of the Totoltepec pluton, and (iii) detrital zircons with predominantly Permo-Carboniferous ages. The depositional age of the Tecomate Formation is con-strained between the youngest detrital zircon population (ca. 280 Ma) and a published Ar/Ar age of 263 ± 3 Ma from the Teco-mate Formation in the adjacent area. However, a metapsammite sample from the base of the Tecomate Formation yielded only Proterozoic zircons, indicating that deposition may have initi-ated earlier. Possible correlative sequences that may have been deposited in a similar peri-arc setting include the latest Pennsyl-vanian to Middle Permian Tecomate Formation type area, the latest Devonian to Lower Permian Patlanoaya Group, the Early to Middle Permian Tuzancoa Formation, the Middle Permian Los Hornos Formation, and the Olinalá Formation of Middle to Upper Permian age.
Kirsch, M., Keppie, J.D., Murphy, J.B. and Lee, J.K.W., in preparation. Structural history of the arc-related Totoltepec pluton, Acatlán Complex, southern Mexico: Syntectonic emplacement along a mid-crustal transpressional shear zone.
ABSTRACT
The 306–289 Ma tholeiitic to calc-alkaline Totoltepec plu-ton in the eastern Acatlán Complex, southern Mexico, is part of a Permo-Carboniferous continental magmatic arc along the western margin of Pangea. The pluton is a well-exposed, com-posite, felsic to ultramafi c intrusive suite containing a conspicu-ous mesoscopic fabric, making it an ideal place to study the relationship between tectonic processes in magmatic arcs and pluton emplacement.
We use an integrated approach combining fi eld observa-tions, structural measurements, analysis of micro-fabrics, as well as Al-in-hornblende thermobarometry and 40Ar/39Ar thermo-chronology to decipher the structural evolution of the Totolte-pec pluton. The data suggest that the pluton was emplaced in ~20 km depth and rapidly uplifted to allow it to cool to ~400 °C within 6 ± 2 Ma. The elongate pluton shape, parallel, decreas-ing temperature fabrics, similar crystallization and deformation ages and the rapid exhumation of the pluton speak for a syn-tectonic emplacement. A subvertical, fanning foliation and sub-horizontal to subvertical lineations as well as the presence of internal, margin-parallel sinistral shear zones suggest emplace-
ment along a transpressional fault. Hornblende-bearing diorites and tonalites within the low to medium-temperature solid-state domain in the southern part of the pluton exhibit a composi-tional and textural banding that is interpreted to have formed by a combination of steep igneous layering, layer-parallel dike injection and melt-enhanced deformation.
Although we were unable to document any regional-scale structures that may have controlled its intrusion, the timing and emplacement mechanism of the Totoltepec pluton is similar to that reported for syn-tectonic Late Carboniferous to Early Permian plutons along the Caltepec Fault zone that separates the Mixteca terrane from the Oaxacan Complex. Strike-slip tec-tonism along this fault may be associated with oblique subduc-tion of the paleo-Pacifi c beneath the western margin of Pangea.
STOP 2-1. (W97.88385°°, N18.214033°°: Fig. 6)
Transpressional shear zone within the Totoltepec pluton near Santo Domingo Tonahuixtla. Here, strongly banded and foliated hornblende-bearing diorite and tonalite is intruded by felsic and mafi c dikes at low angles to the WSW-striking planar fabric. Hornblende fi sh and asymmetrically boudinaged dikes consis-tently display sinistral kinematics. The crystallization age of the mafi c rocks give an age of 289 ± 2 Ma (Keppie et al., 2004), whereas foliation-parallel muscovite in trondhjemite (1 km due SE) yield a 40Ar/39Ar age of 283 ± 1 Ma.
STOP 2-2 (W97.890711°°, N18.208455°°: Fig. 6)
Aplitic dikes intruding megacrystic hornblende diorite/tonalite north of Santo Domingo Tonahuixtla. Dikes are mostly foliation-parallel, but are locally observed to cut the foliation at low angles. Some dikes contain an internal tectono-magmatic fabric parallel to the dike wall and dike-host contacts are sharp to irregular suggesting dike emplacement was syntectonic and occurred prior to complete crystallization of the host. The mega-crystic hornblende-bearing rocks are laterally traceable. Whereas at this location, lineations are weakly developed or subhori zontal with sinistral kinematics, further east, between the villages of Tonahuixtla and Totoltepec, the rocks possess a strong down-dip mineral lineation and sigma-shaped tails on hornblende porphyro-blasts suggest thrusting toward the south.
STOP 2-3 (W97.874964°°, N18.207481°°: Fig. 6)
Compositional/ textural banding in hornblende-bearing tonal-ites east of Tonahuixtla. Rocks at this stop have a mylonitic fab-ric and contain a conspicuous banding defi ned by a more or less rhythmic variation in grain size and modal proportions of feldspar and hornblende. Locally, these rocks exhibit gentle, ca. 2 m wave-length, fold-like structures resembling trough-banding characteris-tic of layered intrusions. These features indicate that the banding may have a complex, multi-stage history of development, involv-ing magma chamber, injection as well as tectonic processes.
Amalgamation and Breakup of Pangæa: the type example of the supercontinent Cycle 9
SubalkalineBasalt
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RhyodaciteDacite
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SiO
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]
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quartz-rich granitoidtrondhjemiteplag-rich cumulatetonalite
289
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quartz dioritehornblende diorite
hornblende gabbrohornblendite
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Chichihualtepec
Totoltepec de Guerrero
Santo Domingo Tonahuíxtla
San Jerónimo de Xayacatlán
Santo Domingo Tianguistengo
97°48′0″W97°50′0″W97°52′0″W97°54′0″W
18°16′0″N
18°14′0″N
18°12′0″N
0 1 20.5km
Scale 1:65,000
CretaceousJurassicTecomate FormationAmarillo UnitSalada Unit
Totoltepec Pluton
granodiorite, monzo-granitetrondhjemitediorite, tonalite, felsic and mafic dikeshornblende gabbro, hornblendite
ContactContact, inferredStrike-slip FaultNormalfaultThrustfault
Hbl Gabbro306 ± 2 Ma
2σ error ellipses
290300310320
19.2 19.6 20.0 20.4 20.8 21.2 21.6 22.0
0.064
0.060
0.056
0.052
0.048
207 P
b/20
6 Pb
238U/206Pb
TuffZirc 206Pb/238U age306 –1 +2 Ma
(95.7% conf, n=25)290
300
310
320
Qtz Diorite289 ± 2 Ma
2σ error ellipses
280290300310320
19 20 21 22 23
0.062
0.058
0.054
0.050
0.046
207 P
b/20
6 Pb
238U/206Pb
TuffZirc 206Pb/238U age289 +1 –2 Ma
(94.8% conf, n=22)280
290
300
310
TT-81Metapsammite
TT-82Metapelite
TEC-10 Granite cobble
Metacongl.(Keppie et al., 2004)
270
280
290
300
310
320
330
340
350
Ea
rly
Pe
rmia
nP
en
nsy
lva
nia
nM
issi
ssip
pia
n
CA
RB
ON
IFE
RO
US
PE
RM
IAN
Totoltepec Pluton~289 Ma Qz Diorite
Totoltepec Pluton~306 Hbl Gabbro
TT-612 Metapsammite
TT-615Granite veinlet
(detrital zircons)
Frequency
0 25 50
Rel. Prob
n = 162
B
t [Ga]
D DepletedMantle
Nd(t
)
10
5
0
5
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Totoltepec pluton
Tonahuixtla Member
Asis amphibolites
Tecomate Fm. type area
Oaxacan Complex
metapelitemetapsammitemetaarkose
A
Figure 6. Stops 2-1 to 2-8: geological map of the Totoltepec pluton (after Kirsch et al., in press) showing fi eld trip stops.
10 Keppie et al.
STOP 2-4 (W97.86816°°, N18.218361°°: Fig. 6)
Hornblende gabbro at the northern margin of the Totoltepec pluton in contact with Jurassic redbeds. This outcrop is located in one of three ca. 0.2–0.6 km2, fault-bounded, precursor (306 ± 2 Ma) gabbroic phase, which is distributed along the northern and north-eastern margin of the pluton. Locally, these rocks are intruded by intensely deformed felsic dikes. To the north, the pluton is unconformably overlain by redbeds of inferred Jurassic age, which sit steeply against the pluton buttress due to a subse-quent period of normal faulting.
STOP 2-5 (W97.851633°°, N18.2581°°: Fig. 6)
Amarillo Unit (new name), SE of Santo Domingo Tian-guistengo. This unit is characterized by medium- to high-grade metasedimentary rocks locally intruded by amphibolite dikes. Youngest detrital zircons from a garnet schist sample indicate a maximum depositional age of 337 ± 4 Ma (Mississippian). The amphibolite dikes exhibit a MORB-like geochemistry with εNd(i) values of +5.2 to +7.6 and TDM model ages between 333 and 433 Ma. These features are very similar to those documented in the Salada Unit (Morales-Gámez et al., 2008), on the western side of the Totoltepec pluton.
STOP 2-6 (W97.776016°°, N18.257016°°: Fig. 6)
Thrust contact between the Totoltepec pluton and the Teco-mate Formation metasedimentary rocks. The exposed contact is a low-angle brittle-ductile thrust. At another location, this thrust is mylonitic and yielded a Middle Triassic 40Ar/39Ar age on mus-covite. The contact is furthermore associated with a Fe-P-REE deposit containing the mineral association magnetite, apatite, barite, chlorite, quartz, chalcopyrite, and a cerium mineral. The mineralization is confi ned to two discrete, elongated bodies of ~100 m length coinciding with strong aeromagnetic anomalies.
STOP 2-7 (W97.794857°°, N18.262697°°: Fig. 6)
S-C fabrics in the Tecomate Formation ~1 km south of the margin of the Totoltepec pluton, indicating top-to-the-south thrusting. Thermochronological data from this area as well as other samples from the Tecomate Formation and Amarillo Unit reveal a regionally significant tectonothermal event of mid-Triassic age.
STOP 2-8 (W97.892266°°, N18.190066°°: Fig. 6)
Pebble metaconglomerates of the Tecomate Formation near Chichihualtepec. The pebbles from this outcrop, which are petro-graphically similar to the Totoltepec pluton trondhjemite, yielded zircons with ages between 320 and 264 Ma (Keppie et al., 2004). Morales-Gámez et al. (2009) conducted strain measurements in these rocks, documenting prolate spheroids typical of transten-
sional deformation. Rotated pebbles with asymmetric tails show top-to-the-south shear, which is consistent with other kinematic indicators in this area.
DAY 3Gonzalo Galaz-Escanilla and J. Duncan Keppie
A High Pressure Zone within the Acatlán Complex: Uppermost Devonian: Lower Carboniferous Subduction and Extrusion under Extension during the Initial Stages of Pangea Amalgamation
Center of High Pressure Zone
Keppie, J.D., Nance, R.D., Dostal, J., Lee, J.K.W., and Ortega-Rivera, A. 2011 Constraints on the subduction erosion/extrusion cycle in the Paleozoic Acatlán Complex of southern Mexico: geochemistry and geochronology of the type Piaxtla Suite. Gondwana Research, doi:10.1016/j.gr.2011.07.020
ABSTRACT
The type high-pressure (HP) Piaxtla Suite in the Acatlán Complex of southern Mexico consists of retrogressed eclogite (amphibolite), megacrystic granitoids and high-grade meta-sedimentary rocks. Exhumation of these HP rocks has recently been interpreted as the result of extrusion into the upper plate, rather than by return fl ow up the subduction zone. Geochemical analyses of the retrograde eclogites indicate that they have a rift tholeiitic-transitional alkalic composition. These are closely associated with a megacrystic meta-granitoid that has yielded an intrusive age of 452 ± 6 Ma (concordant U-Pb zircon analy-ses) with inherited zircon populations at ca. 800–950 Ma and 1000–1200 Ma derived from the underlying basement, prob-ably the Oaxacan Complex which borders the Acatlán Complex to the east. The bimodal nature of these igneous rocks and their close association with continentally-derived sedimentary rocks is similar to most HP rocks in the Acatlán Complex derived from a rifted passive margin. The youngest detrital zircon population in a metapsammite sample yielded an U-Pb age of 365 ± 15 Ma with older analyses distributed along a chord with an upper intercept of 1287 ± 29 Ma. The ca. 365 Ma age pro-vides a maximum age for the time of deposition of this sample. 40Ar/39Ar ages from the retrogressed eclogites provided horn-blende plateau ages of 342 ± 2 Ma and 344 ± 2 Ma, whereas muscovite from the granitoid and metapsammite yielded 334 ± 2 Ma plateau ages. These data constrain the subduction erosion-extrusion cycle to ≤35 my during which the rocks were taken to a depth of ca. 40 km at a rate of 2.7 km/my and back to the surface at 2.4 km/my. Such exhumation rates are slower than those in continent-continent collision zones, but similar to those in the Iberia-Czech Variscan belt where tectonic interpretation also suggests extrusion into the upper plate.
Amalgamation and Breakup of Pangæa: the type example of the supercontinent Cycle 11
Western Boundary of High Pressure Zone: A High-Pressure Folded Klippe Explaced during the Lower Carboniferous at TehuitzingoGalaz E., Gonzalo, et al., in press. A high-pressure folded klippe at Tehuizingo on the western margin of an extrusion zone, Acatlán Complex, southern Mexico
ABSTRACT
The Acatlán Complex is divided into two blocks of low-grade metamorphic rocks by a central belt of high-pressure (HP) rocks, which at Tehuitzingo is composed of metabasites, serpen-tinite, granite and mica schist. 580–430 Ma detrital zircon ages indicate that these rocks were deposited adjacent or very close to the Gondwana supercontinent during the Early Paleozoic and are more consistent with a development on the southern margin of the Rheic Ocean rather than the Iapetus Ocean. These rocks were then removed by a subduction-erosion to depths of ~50km, reaching a metamorphic peak of ~16 kbar and 750 °C (eclogite facies). The HP rocks underwent rapid extrusion during a major Late Devonian-Pennsylvanian tectonothermal event indicated by 40Ar/39Ar analyses, which yielded ages of ~373 Ma (hornblende in metabasite) and of 328–317 Ma (muscovite in granite, mica schist and metabasite) that indicate cooling through ~570 °C and ~350 °C respectively, indicating a very high cooling rate of ~4.9–3.9 °C/m.y. During the extrusion process these rocks were affected by retrogression to amphibolite-epidote and green schist facies, and fi nally emplaced as a klippe on a greenschist facies psammite-pelite unit that constitutes the western block of the Acatlán Complex. Petrologic, deformational and geothermo-barometric data suggest that west and east blocks belong to the same terrane, indicating that a subduction-erosion process and subsequent extrusion is more consistent with the genesis of the HP central belt than a collisional event as has been proposed. The P-T-t pattern of these HP rocks is consistent with subduc-tion environments reported elsewhere in the world and suggests a serpentinite extrusion channel on the western margin of Pangea.
Eastern Boundary of High Pressure Zone: A Listric Normal Shear Zone Synchronous with Deposition of the Uppermost Devonian–Lower Permian Patlanoaya Group
Keppie, J.D., Nance, R.D., Ramos-Arias, M.A., Lee, J.K.W., Dostal, J., Ortega-Rivera, AQ., and Murphy, J.B. 2010. Late Paleozoic subduction and exhumation of Cambro-Ordovician passive margin and arc rocks in the northern Acatlán Complex, southern Mexico: geochronological constraints. Tectonophysics, v. 495, p. 213–229.
ABSTRACT
The origin and age of high pressure (HP) rocks is crucial for paleogeographic reconstruction because they either mark an oceanic suture or an extrusion zone within the upper plate. HP
rocks in the San Miguel Las Minas area in the northern part of the complex has been inferred to be of early Paleozoic age and to mark oceanic sutures. However, blueschists in the northern part of the Acatlán Complex in southern Mexico have yielded Mis-sissippian 40Ar/39Ar plateau ages of 344 ± 5 Ma for glaucophane and 338 ± 3 Ma and 337 ± 2 Ma for muscovite. These ages are slightly younger than recently published ages: a U-Pb zircon age of 353 ± 1 Ma from associated eclogite, and a 347 ± 3 Ma muscovite age from the tectonically overlying, greenschist facies Las Minas Unit. Taken together, these data indicate rapid cooling between 700° and 340°C in ca. 17 Myr. On the other hand, asso-ciated Ordovician Anacahuite Amphibolite cooled through ca. 500°C at 299 ± 6 Ma (40Ar/39Ar on hornblende) suggesting a sec-ond, Permian period of exhumation. Protoliths of the high grade rocks include Cambrian-Ordovician, rift-passive margin, psam-mites, pelites, and tholeiitic dykes, an Ordovician mafi c intrusion (Anacahuite Amphibolite dated at 470 ± 10 Ma: U-Pb zircon) and megacrystic granite (dated at 492 ± 12 Ma: U-Pb zircon), and arc-related mafi c rocks of unknown age. These upper plate rocks are inferred to have been removed by subduction erosion and taken to depths between 35 and 55 km where they underwent blueschist-eclogite facies metamorphism. This was followed by rapid extrusion along a channel bounded by an easterly dipping, Mississippian, listric normal shear zone, and a thrust modifi ed by a Permian dextral fault. Rocks above and below the extrusion zone are mainly Cambro-Ordovician rift-passive margin units, but a small vestige of the arc preserved as dikes cutting rocks lying unconformably beneath the fossiliferous latest Devonian-Lower Permian Patlanoaya Group. Since faunal data indicate that Pangea had amalgamated by the Mississippian, at which time the Acatlán Complex lay 1500–2000 km south of the Ouachita col-lisional orogen between Gondwana and Laurentia, it is inferred that subduction and extrusion of the high pressure rocks occurred on the active western margin of Pangea.
Ramos-Arias, M., Keppie, J.D., Ortega-Rivera, A., and Lee, J.W.K. 2008. Extensional late Paleozoic deformation on the western margin of Pangea, Patlanoaya area, Acatlán Complex, southern Mexico. Tectonophysics, v. 448, p. 60–76.
ABSTRACT
New mapping in the northern part of the Paleozoic Acatlán Complex (Patlanoaya area) records several ductile shear zones and brittle faults with normal kinematics (previously thought to be thrusts). These movement zones separate a variety of units that pass structurally upwards from: (i) blueschist-eclogitic meta-morphic rocks (Piaxtla Suite) and mylonitic megacrystic granites (Columpio del Diablo granite ≡ Ordovician granites elsewhere in the complex); (ii) a gently E-dipping, listric, normal shear zone with top to the east kinematic indicators that formed under upper greenschist to lower amphibolite conditions; (iii) the Middle-Upper Ordovician Las Minas quartzite (upper greenschist facies psammites with minor interbedded pelites intruded by mafi c dikes
12 Keppie et al.
and a leucogranite dike from the Columpio del Diablo granite) unconformably overlain by the Otate meta-arenite (lower green-schist facies psammites and pelites): roughly temporal equiva-lents are the Middle-Upper Ordovician Mal Paso unit and pre-latest Devonian Ojo de Agua unit (interbedded metasandstone and slate, and metapelite and mafi c minor intrusions, respectively)—the Otate and Mal Paso units are intruded by the massive, 461 ± 2 Ma, Palo Liso megacrystic granite: decussate, contact metamor-phic muscovite yielded a 40Ar/39Ar plateau age of 440 ± 4 Ma; (iv) a steeply-moderately, E-dipping normal fault; (v) uppermost Devonian-Lower Permian sedimentary rocks (Patlanoaya Group: here elevated from formation status). The upward decrease in metamorphic grade is paralleled by a decrease in the number of penetrative fabrics, which varies from (i) three in the Piaxtla Suite, through (ii) two in the Las Minas unit (E-trending sheath folds deformed by NE-trending, subhorizontal folds with top to the southeast asymmetry, both associated with a solution cleav-age), (iii) one in the Otate, Mal Paso, and Ojo de Agua units (steeply SE-dipping, NE-SW plunging, open-close folds), to (iv) none in the Patlanoaya Group. 40Ar/39Ar analyses of muscovite from the earliest cleavage in the Las Minas unit yielded a plateau age of 347 ± 3 Ma and show low temperature ages of ~260 Ma. Post-dating all of these structures and the Pat lanoaya Group are NE-plunging, subvertical folds and kink bands. An E-W, vertical normal fault juxtaposes the low-grade rocks against the Anaca-huite amphibolite that is cut by megacrystic granite sheets, both of which were deformed by two penetrative fabrics. Amphibole from this unit has yielded a 40Ar/39Ar plateau age of 299 ± 6 Ma, which records cooling through ~490 °C and is probably related to a Permo-Carboniferous reheating event during exhumation. The extensional deformation is inferred to have started in the latest Devonian (~360 Ma) during deposition of the basal Patlanoaya Group, lasting through the rapid exhumation of the Piaxtla Suite at ~350–340 Ma synchronous with cleavage development in the Las Minas unit, deposition of the Patlanoaya Group with active fault-related exhumation suggested by Mississippian and Early Permian conglomerates (~340 and 300 Ma, respectively), and continuing at least into the Middle Permian (≡ 260 Ma muscovite ages). The continuity of Mid-Continent Mississippian fauna from the USA to southern Mexico suggests that this extensional defor-mation occurred on the western margin of Pangea after closure of the Rheic Ocean.
STOP 3-1 (N18°° 11.728′, W98°° 14.690′ to N18°° 11.652′, W98°° 15.065′: Fig. 2)
Contact between a deformed, Ordovician megacrystic grani-toid, a Tertiary dike, and the HP Piaxtla Suite at Piaxtla.
STOP 3-2 (UTM: 1405110/2023872: Fig. 7)
Thrust contact between Tehuitzingo serpentinite and polydeformed psammitic-pelitic rocks at Solozuchitl near Atopoltitlan.
The Piaxtla serpentinites are composed almost entirely of secondary minerals. Decussate, acicular and fi brous crystals serpentine aggregates make up 95% of the rock, magnetite, cal-cite, white mica and talc, and accessory chromite, clinochlore, undulose quartz, amphibole and epidote. This serpentinite are thrust over the low grade psammite-pelite unit along a gently NW-dipping thrust (320/15°), on which there are striae that plunge westwards (290/12°): associated recumbent folds, S-C fabrics and thrust horses indicate thrusting toward the west. Cut-ting across this thrust zone are several N-S vertical faults with subhorizontal striae.
The low grade psammite-pelite unit (498 ± 2 Ma, U-Pb de-trital zircon; Galaz-Escanilla et al., in press) is composed mainly of primary minerals such as quartz, feldspar and zircon (acces-sory), which suggests a medium-grained quartz-arenitic (0.25–0.5 mm) and shaly (<0.06 mm grain size) protoliths respectively. The equilibrium secondary mineralogy is composed of quartz, albite (Ab
99–100), Mg-Fe-chlorite (ripidolite type), phengite, epidote,
calcite and leucoxene, whose geothermobarometry indicated P-T conditions of ~2.7 kbar and ~350 °C (greenschist facies; Galaz-Escanilla and Keppie, in press).
STOP 3-3 (UTM: 140571085/2023811: Fig. 7)
Serpentinite, amphibolite, metabasite, Ordovician granitic and psammitic-pelitic rocks along the eastern margin of the Tehuit zingo serpentinite at Tecolutla.
In Tecolutla area outcrop a HP unit (eclogitic facies) that mainly consists of serpentinized harzburgite with small marginal fault blocks of metabasite, metagranitoid (485 ± 3 Ma, U-Pb zircon age: Galaz-Escanilla et al., in press) and mica schist (433 ± 3 Ma, U-Pb detrital zircon: Galaz-Escanilla et al., in press) juxta-posed by N-S structures. The serpentinized harzburgites contain elliptical meta basite lenses up to several meters in size, which have fi ne grained margins that may refl ect an original intrusive relationship. The long axes of the elliptical lenses are parallel to the foliation indi cat ing ductile deformation. On the other hand, the high-grade metasediments have a composite foliation where S
1 is parallel to a second S-C foliation with the S
2 planes sub-
parallel to the border of the block and oriented ~128/27° (dip direction/dip angle), and C
2 planes oriented ~147/58°.
The HP unit is tectonically juxtaposed against a low grade psammite-pelitic unit along N-S structures. This unit has a planar fabric composed mainly of white mica and chlorite evidencing a low-temperature (greenschist) ductile deformation.
The geothermobarometry suggests a common prograde meta morphic history for the Tehuitzingo HP rocks: (a) a metamor-phic peak eclogite facies of zoisite-amphibole, with a tempera-ture of ~750 °C and a pressure of ~16 kbar; (b) retrogression to amphibolite-epidote facies, with a temperature of ~472 °C and variable pressures between ~7.1–3.4 kbar; (c) retrogression to green-schist facies with a temperature of ~360 °C and whose pressures were not obtained (Galaz-Escanilla et al., in press). The Piaxtla serpentinite contains three types of serpentine group minerals :
Amalgamation and Breakup of Pangæa: the type example of the supercontinent Cycle 13
Figure 7. Stops 3-2 and 3-3: geological map, structural data, and section (after Galaz-Escanilla et al., in press).
14 Keppie et al.
Figu
re 8
. Sto
ps 3
-4, 3
-5, 3
-6 a
nd 3
-7: g
eolo
gica
l map
and
sec
tion
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er K
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201
0).
Amalgamation and Breakup of Pangæa: the type example of the supercontinent Cycle 15
chrysotile, lizardite and antigorite. Based on the stability fi eld of the latter was estimated a P-T peak of ~550 °C and ~9 kbar (González-Mancera, 2001), however, has been reported in sub-duction zones antigorite reaching ~720 °C and high pressures of ~20 kbar (Ulmer and Trommsdorff, 1995).
The geochemistry data of the eclogitic mafi c rocks indicate that these rocks have an arc affi nity (author´s unpublished data). The P-T-t pattern of these rocks is consistent with subduction environments and serpentinite subduction channel exhumation (e.g., Guillot et al. 2009), where the driving forces for exhuma-tion are a combination of buoyancy and channel fl ow coupled with underplating of slabs.
STOP 3-4 (N18°° 31.051′, W98°° 19.733′: Fig. 8)
Listric normal shear zone between megacrystic, Columpio del Diablo granitoid and Ordovician Las Minas unit.
The Columpio del Diablo megacrystic granite (492 ± 12 Ma, U-Pb zircon age: Keppie et al., 2010) consists of blastomylonitic granite containing quartz, K-feldspar (perthitic orthoclase), white mica, chlorite, epidote, and accessory opaque minerals. The megacrystic granite is cut by thin leucogranite sheets that consist mainly of quartz and potassium feldspar and are inferred to be a late differentiates of the granite. Structurally, the gran-ite varies from an L-tectonite to an L-S tectonite with kinematic indicators, such as σ fabrics associated with the feldspars and generally vertical, extensional, quartz-fi lled fractures within the feldspars that indicate top-to-east movement along the contact with the Las Minas Unit: a minor, brittle fault has been super-imposed on the contact. The Las Minas unit consists predomi-nantly of polydeformed, low-grade psammites interbedded with thin pelitic phyllites, and intruded by many tholeiitic mafi c dikes and sills (Keppie et al., 2008). The psammites consist mainly of quartz with minor muscovite, chlorite, and K-feldspar, and ac-cessory zircon, whereas the phyllites are composed of muscovite, chlorite, quartz, and opaque minerals. The youngest concordant detrital zircon is dated at 496 ± 25 Ma (Keppie et al., 2008) The mafi c intrusions contain amphibole (tremolite-actinolite), chlo-rite, epidote, quartz, plagioclase, muscovite, and accessory cal-cite, and opaque minerals. 40Ar/39Ar analyses of muscovite from the earliest cleavage in the Las Minas unit yielded a plateau age of 347 ± 3 Ma (Mississippian) and show low temperature ages of ~260 Ma.
STOP 3-5 (N18°° 30.351′, W98°° 17.57′: Fig. 8)
The Cerro Puntiagudo Formation of Strunian age (latest Devo nian) is 63 m thick and consists of shale, sandstone, and limestone. It is overlain by conglomerates of the Potrerillo Formation (124 m thick) that consists of red sandstone with Oseagean fossils and conglomerate with large K-feldspar clasts: these clasts are inferred to have been derived from the nearby megacrystic granitoids. The Cerro Puntiagudo Formation rests unconformably upon the Ojo de Agua unit, which consists of
fi nely bedded, black pelitic rocks intruded by green, fi ne grained, mafi c dikes with an arc-related chemistry. These latter rocks are deformed by isoclinal, upright-steeply inclined, NE- and SE- trending, subhorizontal folds. The youngest detrital zircons in this unit are 466 ± 25 Ma (Keppie et al., 2008), abd 471 ± 9 Ma (Keppie et al., 2010).
STOP 3-6 (N18°° 30.66′ W98°° 17.78′: Fig. 8)
The La Junta Formation is a 126 m thick shale unit contain-ing Missourian fossils; the Tepazulco Formation (193 m thick) is made up of interbedded limestone, shale, and sandstone and con-tains Virgilian-Missourian fossils. An Ordovician plug is faulted against the Patlanoaya Group at this locality.
STOP 3-7 (N18°°31′, W°°16.79′: Fig. 8)
The Lower Permian La Mesa, La Cuesta and La Cueva For-mations consist of a conglomerate (45 m thick) and calcareous sandstone unit containing Wolfcampian fossils; interbedded shale and limestone with mid-Wolfcampian to middle Leonardian fos-sils; and sandstone (>280 m thick) containing late Leonardian fossils at its base.
REFERENCES CITED
Alva-Valdivia, L.M., Goguitchaichvli, A., Grajales, M., Flores de Dios, A., Urrutia-Fucugauchi, J., Rosales, C., and Morales, J., 2002, Further con-straints for Permo-Carboniferous magnetostratigraphy: case study of the sedimentary sequence from San Salvador-Patlanoaya (Mexico): Comptes Rendus Geoscience, v. 334, p. 811–817, doi:10.1016/S1631-0713(02)01821-7.
Böhnel, H., 1999, Paleomagnetic study of Jurassic and Cretaceous rocks from the Mixteca terrane (Mexico): Journal of South American Earth Sciences, v. 12, no. 6, p. 545–556, doi:10.1016/S0895-9811(99)00038-3.
Bullard, E.C., et al., 1965, A symposium on continental drift-IV. The fi t of the continents around the Atlantic: Philosophical Transactions of the Royal Society, v. 258, p. 41–51, doi:10.1098/rsta.1965.0020.
Fang, W., Van der Voo, R., Molina-Garza, R., Moran-Zenteno, D.J., and Urrutia-Fucugauchi, J., 1989, Paleomagnetism of the Acatlan terrane, southern Mexico: evidence for terrane rotation: Earth and Planetary Science Let-ters, v. 94, no. 1-2, p. 131–142, doi:10.1016/0012-821X(89)90089-7.
Galaz-Escanilla, G., Keppie, J.D., Lee, J.K.W., and Ortega-Rivera, A., in press, A high-pressure folded klippe at Tehuitzingo on the western margin of an extrusion zone, Acatlán Complex, southern Mexico: Gondwana Research.
González-Mancera, G., 2001, Mineralogía y petrología de las serpentinitas del cuerpo ultramáfi co de Tehuitzingo, Estado de Puebla: Tesis de Maestría, Universidad Nacional Autónoma de México, 103p.
Guillot, S., Hattori, K., Agard, P., Schwartz, S., and Vidal, O., 2009, Exhuma-tion Processes in Oceanic and Continental Subduction Contexts: A Re-view, in Lallemand, S., Funiciello, F., eds., Subduction Zone Geodynamics. Springer-Verlag Berlin Heidelberg, p. 175–205.
Helbig, M., Keppie, J.D., Murphy, B., and Solari, L., 2010, Jurassic Amphibo-lites of the Eastern Acatlan Complex (Southern Mexico) Related to Both Back-Arc Rifting and the Opening of the Gulf of Mexico?: Geological Society of America Abstracts with Programs, v. 42, no. 5, p. 679.
Irving, E., 1977, Drift of the major continents since the Devonian: Nature, v. 270, p. 304–309, doi:10.1038/270304a0.
Keppie, J.D., 2004, Terranes of Mexico revisited: A 1.3 billion year odyssey: International Geology Review, v. 46, no. 9, p. 765–794, doi:10.2747/0020-6814.46.9.765.
Keppie, D.F., and Keppie, J.D., in review, An alternative Pangean reconstruc-tion for Middle America with the Chortis and Yucatan blocks in the Gulf of Mexico: implications for Mesozoic and Cenozoic tectonics: Interna-tional Geology Review.
16 Keppie et al.
Keppie, J.D., Nance, R.D., Dostal, J., Ortega-Rivera, A., Miller, B.V., Fox, D., Powell, J., Mumma, S., and Lee, J.W.K., 2004, Mid-Jurassic Tectonother-mal Event Superposed on a Paleozoic Geological Record in the Acatlán Complex of Southern Mexico: Hotspot Activity During the Breakup of Pangea: Gondwana Research, v. 7, p. 238–260, doi:10.1016/S1342-937X(05)70323-3.
Keppie, J.D., Dostal, J., Murphy, J.B., and Nance, R.D., 2008, Synthesis and tectonic interpretation of the westernmost Paleozoic Variscan orogen in southern Mexico: From rifted Rheic margin to active Pacifi c margin: Tec-tonophysics, v. 461, no. 1-4, p. 277–290, doi:10.1016/j.tecto.2008.01.012.
Keppie, J.D., Nance, R.D., Ramos-Arias, M.A., Lee, J.K.W., Dostal, J., Ortega-Rivera, A., and Murphy, J.B., 2010, Late Paleozoic subduction and ex-humation of Cambro-Ordovician passive margin and arc rocks in the northern Acatlán Complex, southern Mexico: Geochronological con-straints: Tectonophysics, v. 495, no. 3-4, p. 213–229, doi:10.1016/j.tecto.2010.09.019.
Kirsch, M., Keppie, J.D., Murphy, J.B., and Solari, L.A., in press, Permian–Carboniferous arc magmatism and basin evolution along the western margin of Pangea: geochemical and geochronological evidence from the eastern Acatlán Complex, southern Mexico: GSA Bulletin.
Malone, J., Nance, R.D., Keppie, J.D., and Dostal, J., 2002, Deformational his-tory of part of the Acatlan Complex: Late Ordovician-early Silurian and early Permian orogenesis in southern Mexico: Journal of South Ameri-can Earth Sciences, v. 15, no. 5, p. 511–524, doi:10.1016/S0895-9811(02)00080-9.
Morales-Gámez, M., Keppie, J.D., and Norman, M.D., 2008, Ordovician-Silurian rift-passive margin on the Mexican margin of the Rheic Ocean overlain by Carboniferous-Permian periarc rocks: Evidence from the eastern Acatlán Complex, southern Mexico: Tectonophysics, v. 461, p. 291–310, doi:10.1016/j.tecto.2008.01.014.
Morales-Gámez, M., Keppie, J.D., and Dostal, J., 2009, Carboniferous tholeiitic dikes in the Salada unit, Acatlán Complex, southern Mexico: a rec ord of extension on the western margin of Pangea: Revista Mexicana De Ciencias Geológicas, v. 26, p. 133–142.
Pindell, J.L., and Dewey, J.F., 1982, Permo-Triassic reconstruction of western Pangaea and the evolution of the Gulf of Mexico/Caribbean region: Tec-tonics, v. 1, p. 179–211, doi:10.1029/TC001i002p00179.
Pindell, J.L., and Dewey, J.F., 1982, Permo-Triassic reconstruction of western Pangaea and the evolution of the Gulf of Mexico/Caribbean region: Tec-tonics, v. 1, p. 179–211, doi:10.1029/TC001i002p00179.
Smith, A.G., et al., 1981, Phanerozoic paleocontinental world maps. Cambridge University Press, Cambridge, 102 p.
Steiner, M.B., 2005, Pangean reconstruction of the Yucatan Block: Its Permian, Tri-assic, and Jurassic geologic and tectonic history, in Anderson, T.H., Nourse, J.A., McKee, J.W., and Steiner, M.B., eds. The Mojave-Sonora megashear hypothesis: Development, assessment, and alternatives. Geological Society of America Special Paper 393, p. 457–480. doi: 10.1130/2005.2393(17).
Talavera-Mendoza, O., Ruiz, J., Gehrels, G.E., Meza-Figueroa, D., Vega-Granillo, R., and Campa-Uranga, M., 2005, U-Pb geochronology of the Acatlán Complex and implications for the Paleozoic paleogeography and tectonic evolution of southern Mexico: Earth and Planetary Science Let-ters, v. 235, p. 682–699, doi:10.1016/j.epsl.2005.04.013.
Ulmer, P., and Trommsdorff, V., 1995, Serpentine Stability to Mantle Depths and Subduction-Related Magmatism: Science, v. 268, no. 5212, p. 858–861, doi:10.1126/science.268.5212.858.
Van der Voo, R., and French, R.B., 1974, Apparent polar wandering for the Atlantic-bordering continents: Late Carboniferous to Eocene: Earth-Science Reviews, v. 10, p. 99–119, doi:10.1016/0012-8252(74)90082-8.
Vega-Granillo, R., Meza-Figueroa, D., Ruiz, J., Talavera-Mendoza, O., and López-Martínez, M., 2009, Structural and tectonic evolution of the Acatlán Complex, southern Mexico: Its role in the collisional his-tory of Laurentia and Gondwana: Tectonics, v. 28, no. 4, p. TC4008, doi:10.1029/2007TC002159.
Vega-Granillo, R., Talavera-Mendoza, O., Meza-Figueroa, D., Ruiz, J., Gehrels, G.E., and López-Martínez, M., 2007, Pressure-temperature-time evolu-tion of Paleozoic high-pressure rocks of the Acatlán Complex (southern Mexico): Implications for the evolution of the Iapetus and Rheic Oceans: Geological Society of America Bulletin, v. 119, no. 9/10, p. 1249–1264, doi:10.1130/B226031.1.
Yañez, P., Patchett, P.J., Ortega-Gutierrez, F., and Gehrels, G.E., 1991, Iso topic studies of the Acatlán Complex, southern Mexico: Implications for Paleo-zoic North American Tectonics: Geological Society of America Bulle-tin, v. 103, no. 6, p. 817–828, doi:10.1130/0016-7606(1991)103<0817:ISOTAC>2.3.CO;2.
Printed in the U.S.A.
Amalgamation and Breakup of Pangæa: the type example of the supercontinent Cycle 17
5R E S U M E N Y C O N C L U S I Ó N
Este trabajo documenta el desarrollo de un sistema de arco Carbonífero-Pérmico a lo largo del margen occidental de Pangea junto a una zona desubducción del océano Paleo-Pacífico. Se proporciona información detalla-da sobre la relación entre el plutonismo, la formación de cuencas y la defor-mación a escala regional en un orógeno periférico. Las principales conclu-siones son las siguientes:
a. La cartografía geológica detallada de la zona en combinación con losdatos de la geocronología U-Pb de circones da como resultado la mo-dificación de la distribución espacial y las relaciones de contacto de lasunidades litotectónicas previamente mapeadas en el área de estudio.Los contactos externos entre el plutón Totoltepec y las rocas circun-dantes son o no conformables, o son tectónicos (es decir, ninguna delas relaciones de contacto originales son preservadas). Sin embargo, laedad de diques graníticos delgados que ocurren dentro de la Forma-ción Tecomate sugieren que pueden ser comagmáticos con el plutónTotoltepec, lo que implica una relación originalmente intrusiva entreel plutón y la Formación Tecomate.
b. Rocas clásticas al suroeste del plutón Totoltepec que fueron asignadosoriginalmente a la Formación Cosoltepec contienen circones detríti-cos de edad Pérmico y por lo tanto se consideran equivalentes a laFormación Tecomate. Esta interpretación es coherente con la presen-cia de metaconglomerados y mármoles en esta parte de la zona decampo. Además, en la parte oriental del área de estudio se identificauna unidad metamórfica de grado medio y edad Misisipiense (artícu-lo en preparación), que consiste en cuarcitas y esquistos de granatecon escasos diques de anfibolita; esto limita la distribución espacialde la unidad previamente mapeada como la Formación Tecomate. Launidad Misisipiense está en contacto de falla con el plutón Totolte-pec, cabalgando en dirección sur sobre la Formación Tecomate y estásobreyacida por capas rojas del Jurásico hacia el norte. Con base endatos isotópicos y geoquímicos, las rocas de esta unidad Misisipiensese pueden correlacionar con las de la Unidad Salada del Carbonífe-ro (Morales-Gámez et al., 2008) que afloran en el lado occidental delplutón Totoltepec.
c. Circones detríticos extraídos de rocas de la Formación Tecomate en elárea de estudio en combinación con datos publicados de 40Ar/39Arproporcionan límites temporales de depositación a alrededor de 300
Ma en un nivel estratigrafico, y a entre 288 ± 3 Ma y 263 ± 3 Ma en
76
resumen y conclusión 77
otro. Estos datos coinciden con la edad bioestratigráficamente deter-minada en el área tipo de la Formación Tecomate (Keppie et al., 2004b)e indican que la formación, como se define actualmente de maneracolectiva se extiende desde el Pensilvánico medio hasta el PérmicoInferior, pero puede haber sido depositada en distintas sub-cuencasde diferentes edades. Una de las muestras analizadas, que provienede cerca de la base estratigráfica de la Formación Tecomate, produjosolamente circones de edad Proterozoica, lo cual sugiere que esta par-te de la unidad fue depositada cuando fuentes ígneas paleozoicas noestaban expuestas o no fueron muestreadas por el sistema de drena-je local. La última explicación también podría aclarar la discrepanciaentre las edades de las poblaciones más jóvenes de circones detríti-cos de la zona de estudio y el área tipo de la Formación Tecomate(Sánchez-Zavala et al., 2004), respectivamente.
d. La secuencia intrusiva del plutón Totoltepec se establece mediante ladocumentación del rango composicional, los contactos internos y laedad de las fases magmáticas; esto se basa en el análisis petrográficoy trabajo de campo detallado, complementado por la geocronología deU-Pb y 40Ar/39Ar. Estos datos sugieren que el plutón es una intrusióncompuesta, formado por (i) tres cuerpos discretos, alargados e inten-samente fallados de 306 ± 2 Ma, que consisten en gabro hornblendicoy hornblendita, aflorando a lo largo del margen norte del plutón; (ii)trondhjemita de 287 ± 2 Ma, la litología predominante del plutón, lo-calmente mostrando una mayor abundancia de biotita o plagioclasa ytransformándose a una composición granodiorítica y monzograníticacerca del margen norte; y, (iii) cuerpos intrusivos de tonalita y dioritahornblendica junto con diques félsicos que se presentan en el partesur del plutón, los cuales fueron emplazados secuencialmente entre289 ± 2 y 283 ± 1 Ma.
e. Tanto la fase marginal (gabróica) como la fase principal (trondhjemita-tonalita-diorítica) del plutón Totoltepec muestran una afinidad geo-química toleítica a calco-alcalina, típico de magmas asociados consubducción. Estos datos proporcionan evidencia de un manto litos-férico subcontinental hidratado por fluidos de subducción ya en 306
Ma aproximadamente, mucho antes de lo que varios estudios pro-ponen. Datos isotópicos de Sm-Nd indican una relación genética deasimilación-cristalización fraccionada (AFM) por cantidades menoresentre la fase marginal y principal del plutón. Plutones coetáneos delarco Carbonífero–Pérmico en el sur de México y Guatemala son másfélsicas y más alcalinas en composición, muestran patrones de tierrasraras más diferenciados y tienen una firma isotópica de Sm-Nd menosradiogénico; esto indica una mayor contaminación cortical en compa-ración con el plutón Totoltepec y sugiere que el plutón fue emplazadoen una parte más primitiva, más cercana a la trinchera del arco y/o alo largo de una falla que facilitó su ascenso.
resumen y conclusión 78
f. Las rocas de la Formación Tecomate en el área de estudio son deriva-das del edificio del arco regional y de plutones epizonales expuestosdurante el Carbonífero y el Pérmico Inferior, lo cual es indicado por:(i) la ocurrencia de estratos intercalados de rocas volcánicas y clásti-cas que son derivados de un arco; (ii) la inmadurez composicional ytextural de los sedimentos; (iii) la firma geoquímica de arco de lasrocas clásticas; (iv) composiciones isotópicas de Sm-Nd relativamenteradiogénicos que sugieren un componente de procedencia juvenil; y,(v) el predominio de circones detríticos del Carbonífero–Pérmico pro-cedentes de una fuente ígnea. Por lo tanto, circones detríticos de laFormación Tecomate complementan el registro detrítico fragmentadode la actividad del arco magmático regional en el sur de México. Enconjunto con otras rocas ígneas y sedimentarias relacionadas con elarco en México y Guatemala, cuya edad también está bien definidapor bioestratigrafía o por geocronología U-Pb, los datos sugieren quela actividad de arco ya había iniciado en el Misisípico en los bloquesmás al sur y probablemente no fue establecido en los terrenos delnorte de México hasta el Pérmico Inferior.
g. La historia estructural para la fase principal del plutón Totoltepec deaproximadamente 289–287 Ma, como se infiere a partir de la termoba-rometría Al-en-hornblenda y la geocronología 40Ar/39Ar involucróel emplazamiento de magma en niveles medianos de la corteza (unos20 km de profundidad) y un levantamiento rápido hasta aproximada-mente 11 km en 4 ± 2 Ma. La forma superficial elíptica del plutón,una progresión de una fábrica de flujo magmático a una fábrica deestado sólido de baja temperatura, así como el paralelismo entre lasfoliaciones de temperaturas distintas indican que el emplazamientode la fase principal del plutón fue controlada tectónicamente. La in-trusión principal contiene una foliación subvertical paralela al eje lar-go del plutón, y una lineación mineral que varia desde subhorizontalcon cinemática sinistral hasta muy inclinada con indicadores de cabal-gamiento de vergencia sur. La variación en la orientación y el gradode deformación manifestado por las diferentes poblaciones de diquessugieren que los diques fueron emplazados secuencialmente y fueronsometidos a diferentes grados de rotación en sentido horario.
h. En el marco del arco regional que está dominado por cizallamientodextral a lo largo de fallas N–S, el emplazamiento del plutón Totol-tepec se infiere haber tenido lugar a lo largo de un sistema de fallastransversales al arco de extensión oblicua y dirección NE en un ré-gimen general de transtensión. El magmatismo puede haber cesadoen la zona cuando una parte del cizallamiento dextral de la falla de-limitante del oeste fue trasladado a la falla delimitante del este, queculminó en cabalgamiento cerca del margen sur del plutón. Por úl-timo, como parte de un evento importante de deformación regionalen el Triásico Medio a Tardío, que se registra en las rocas tanto de
resumen y conclusión 79
la Formación Tecomate como de la unidad Misisipiense sin nombre(artículo en preparación), el plutón fue cabalgado sobre las rocas me-tasedimentarias de la Formación Tecomate.
i. Este estudio documenta la evolución geodinámica de un arco conti-nental del Paleozoico tardío en el Complejo Acatlán. Los datos sugie-ren subducción oblicua de litosfera oceánica hacia el este, por debajodel terreno Mixteco, que produjo el desarrollo de fallas laterales N–Sparalelas a la trinchera y fallas antitéticas de orientación NE que pro-movió el plutonismo y dio lugar a la formación de múltiples cuencaspull-apart. Esta situación tectónica es más compatible con una ubica-ción paleogeográfica del terreno Mixteco en el margen de Pangea queuna posición en el Golfo de México, varios miles de kilómetros haciael interior, o incluso una ubicación frente al noreste de Canadá.
AM É T O D O S A N A L Í T I C O S
A.1 y A.2: Material suplementario publicado en línea como parte del ar-tículo: Kirsch, M., Keppie, J.D., Murphy, J.B., y Solari, L.A., 2012, Permian–Carboniferous arc magmatism and basin evolution along the western mar-gin of Pangea: geochemical and geochronological evidence from the easternAcatlán Complex, southern Mexico: Geological Society of America Bulletin,en prensa, doi: 10.1130/B30649.1.
a.1 geocronología u-pb
About 70 grains for igneous analyses and 150 grains in case of detritalzircon analyses were handpicked and mounted on double-sided adhesivetape. To avoid introducing bias into sample preparation, no selection wasmade on the basis of optical and physical characteristics. The mount wasthen cast in epoxy resin, ground with sandpaper to expose the crystals andpolished. Cathodoluminescence imaging was performed using an ELM-3Rluminoscope, to reveal internal zoning of the zircons, helping with the spotselection and aiding the geological age interpretation. The isotopic analy-ses were performed with a Resolution LPX220 ArF Excimer laser ablationsystem coupled to a Thermo Xii series quadrupole ICP-MS (Solari et al.,2010) installed in the Laboratorio de Estudios Isotópicos (LEI), Centro deGeociencias, UNAM. A 34 µm spot was used for all the analyses performedduring the current work. Repeated standard measurements of the Plešovicestandard zircon, (Sláma et al., 2008) enabled mass-bias correction, as well asdownhole and drift fractionation corrections. The analytical routine inclu-des a standard glass (normally NIST 610 is analyzed), 5 standard zircons,5 unknown zircons, and then 1 standard zircon every 5 unknowns, endingwith 2 standard zircons. The same analytical protocol is employed (timing,energy density, laser frequency, spot size) for all the analyses, both stan-dard and unknowns. NIST standard glass analyses are used to recalculatethe zircons trace element concentrations. Time-resolved analyses are thenreduced off-line using an in-house developed sofware written in R (Solariy Tanner, 2011), and the output is then imported into Excel, where the con-cordia as well as age-error calculations are obtained using Isoplot v. 3.70
(Ludwig, 2008), while the probability density distribution and histogramplots are produced using AgeDisplay (Sircombe, 2004). During the analyti-cal sessions in which the data presented in this paper were measured at LEI,UNAM, the observed uncertainties (1σ relative standard deviation) on the206Pb/238U, 207Pb/206Pb and 208Pb/232Th ratios measured on the Plešo-vice standard zircon were 0.6, 0.9 and 1.1 % respectively. Those errors arequadratically added to the quoted uncertainties observed on the measured
80
A.2 geoquímica 81
isotopic ratios of the unknown zircons. This last factor takes into accountthe heterogeneities of the natural standard zircons. 204Pb, which would beused to correct for initial common Pb, is not measured because its tiny sig-nal is swamped by 204Hg, normally present in the He carrier gas. CommonPb is thus evaluated using the 207Pb/206Pb ratio, carefully graphing all theanalyses on Tera y Wasserburg (1972) diagrams. Correction, if needed, isthen performed with the algebraic method of Andersen (2002).
a.2 geoquímica
Major and certain trace elements (V, Cr, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr,Nb, Ba, La, Pb, Th, U, Ce, Nd, Cs) were determined by X-ray fluorescen-ce spectrometry (XRF) at the Regional Geochemical Centre at Saint Mary’sUniversity, Nova Scotia. Precision and accuracy are generally within 5 % formost major elements, and within 5–10 % for minor and trace elements. De-tails of the analytical procedures are given in Dostal et al. (1986, 1994). REEsand selected trace elements were analyzed by inductively coupled plasmamass spectrometry (ICP-MS) at Memorial University, Newfoundland. Theaccuracy and precision of these data are better than 10 %; the analytical pro-cedure is detailed in Longerich et al. (1990). Sm-Nd isotopic analyses wereperformed at the Atlantic Universities Regional Isotopic Facility (AURIF),Memorial University, Newfoundland. Sm and Nd concentrations as well asisotopic compositions and ratios were measured by isotope dilution thermalionization mass spectrometry (ID-TIMS) after chemical separation of Ndand Sm by ion exchange chromatography (see Kerr et al., 1995). Instrumen-tal mass fractionation of Nd isotopes is corrected relative to 146Nd/144Nd= 0.7219 (O’Nions et al., 1977) using a Raleigh fractionation law. Externalprecision is assessed by replicate analyses of the JNdi-1 standard (Tana-ka et al., 2000). The difference between the certified value (143Nd/144Nd =0.512115) and the mean (0.512101 ± 0.000008 [n = 45]) is added to the measu-red value for 143Nd/144Nd after it has been spike-corrected. Errors quotedin Table 1 represent standard errors of individual 143Nd/144Nd measure-ments at the 95 % confidence level. εNd parameters were calculated relativeto 143Nd/144Nd = 0.512638 for CHUR (Goldstein et al., 1984). For initial va-lues, 147Sm/144Nd = 0.1967 (Jacobsen y Wasserburg, 1980) and λ147Sm =6.54 x 10
−12 yr−1 (Steiger y Jäger, 1977) were used. Depleted mantle modelages (TDM) are calculated in two ways: TDM(1) using the depleted mantlemodel of DePaolo (1981, 1988), and TDM(2) which assumes a linear evolu-tion of the depleted mantle between a value of +10 (present day) and 0 at4.5 Ga (Goldstein et al., 1984). TDM(1) values are quoted in the text.
a.3 geocronología40
ar-39ar
Los separados de minerales y los monitores de flujo (estándares) fueronenvueltos en papel de aluminio y apilados verticalmente en una cápsula deirradiación 8.5 cm de largo y 2.0 cm de diámetro. Esta se irradió con neutro-
A.3 geocronología40
ar-39ar 82
nes rápidos en la posición 5C del Reactor Nuclear de McMaster (Hamilton,Ontario) para una duración de 24 h (a 2.5 MWh). Los paquetes de monitoresde flujo se encuentran a intervalos de aprox. 1 cm a lo largo del contenedorde irradiación y valores de J para las muestras individuales se determinaronpor interpolación polinómica de segundo orden entre los análisis repetidospara cada posición del monitor en la cápsula. Típicamente, valores de J va-rían menos que 10 % a lo largo de la cápsula. No se controlan gradienteshorizontales de flujo ya que se consideran ser de menor importancia en elnúcleo del reactor.
Para la fusión total de los monitores y el calentamiento por pasos utili-zando un láser, las muestras se colocan en un portamuestras de cobre, pordebajo del viewport ZnS de una celda de acero inoxidable conectado a unsistema de la purificación del vacío ultra-alto. Para el calentamiento por pa-sos se utilizó un láser New Wave Research MIR 10-30 de CO2 con potenciasde hasta 30W y una lente de facetas. Los periodos de calefacción son aprox.3 minutos por cada incremento de energía (2 % a 20 %; diámetro del haz 3.8mm). El gas liberado, después de la purificación mediante un getter SAESC50 (unos 5 minutos), es conducido a un espectrómetro de masas MAP 216
con una fuente Bäur Signer y un multiplicador de electrones (ajustado auna ganancia de 100 por el detector de copa de Faraday). Posteriormente,los análisis rutinarios del blanco se restan de las fracciones de gas de lasmuestras. Los blancos de extracción son típicamente <10 × 10
−13, <0.5 ×10
−13, <0.5 × 10−13, y <0.5 × 10
−13 cm−3 STP para las masas 40, 39, 37, y36, respectivamente.
Mediciones de los picos de los isótopos de argón son extrapolados altiempo cero, normalizados a la relación 40Ar/36Ar atmosférica (295.5) utili-zando los valores obtenidos para el argón atmosférico, y corregidos a 40Arproducido por potasio, 39Ar y 36Ar por calcio, y a 36Ar producido por cloroRoddick (1983). Las fechas y los errores se calcularon utilizando el procedi-miento de Dalrymple et al. (1981) y las constantes de Steiger y Jäger (1977).La meseta e la inversa correlación de las fechas isotópicas se calcularon uti-lizando ISOPLOT v. 3.60 (Ludwig, 2008). Una meseta se define aquí como3 o más etapas contiguas que contienen >50 % del 39Ar liberado, con unaprobabilidad de ajuste >0.01 y un promedio ponderado de las desviacionescuadráticas <2. Si los pasos contiguos contienen <50 % del 39Ar liberado,se conoce como un segmento de meseta.
Los errores citados en la tabla y en los espectros de edad representan laprecisión analítica a 2σ, suponiendo que los errores en las edades de losmonitores de flujo son cero. Esto es adecuado para comparar la variacióndentro del espectro y determinar cuáles pasos forman una meseta (por ejem-plo, McDougall y Harrison (1988), p. 89). Una estimación conservadora deeste error en el valor de J es de 0.5 %; este se puede agregar para la compa-ración entre muestras. Las fechas están referenciadas a hornblenda Hb3Grde 1072 Ma (Turner et al., 1971; Roddick, 1983).
BTA B L A S G E O C R O N O L O G Í A U - P B
Material suplementario publicado en línea como parte del artículo: Kirsch,M., Keppie, J.D., Murphy, J.B., y Solari, L.A., 2012, Permian–Carboniferousarc magmatism and basin evolution along the western margin of Pangea:geochemical and geochronological evidence from the eastern Acatlán Com-plex, southern Mexico: Geological Society of America Bulletin, en prensa,doi: 10.1130/B30649.1.
Tabla 1: Description of samples for LA-ICP-MS U-Pb geochronology from the Totol-tepec area, Acatlán Complex.
Sample Latitude Longitude Rocktype Mineralogy Age
(◦N) (◦W) Primary Secondary Accessory (Ma)*
Permian granitoids (Totoltepec pluton)
TT-72 18.2581000 97.85163333 Hbl gabbro Hbl+Pl Ep+Chl Ap+Zrn+Op 306±2
TT-76b 18.2286500 97.86343333 Qz diorite Pl+Qz+Ms Chl Ap+Zrn+Op 289±2
Permian low-grade metasedimentary rocks
TT-81 18.25146667 97.78271667 Metaps. Qz+Kfs+Ms Chl Zrn+Op 288±3
TT-82 18.25058333 97.78281667 Metapel. Qz+Ms Chl+Ser Zrn+Op 299±3
TT-612 18.1912838 97.898541 Metaps. Qz+Kfs+Ms Chl Zrn+Op 303±3
TT-486A 18.2840884 97.9111441 Metaps. Qz+Kfs+Ms Chl Zrn+Op 1005±17
Thin dikes intruding Carboniferous–Permian low-grade metasedimentary rocks
TT-615 18.1908117 -97.8990905 Granitoid Qz+Pl+Ms Zrn+Op 298±3
Abbreviations: Qz–quartz, Kfs–K-feldspar, Pl–plagioclase, Hbl–hornblende, Bt–biotite, Ms–muscovite, Ser–sericite, Ep–epidote, Chl–chlorite, Ap–apatite, Grt-garnet, Tnt–titanite, Zrn–zircon, Op–opaque minerals* LA-ICP-MS U-Pb zircon ages representing the age of crystallization in igneous rocks andan average of the youngest detrital zircon cluster in metasedimentary rocks, respectively(see text for details).
83
tablas geocronología u-pb 84
Tabl
a2
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Toto
ltep
ecpl
uton
horn
blen
dega
bbro
.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_31
_04
30
.49
0.0
58
91
2.2
10
.34
26
52
.34
0.0
42
24
0.8
00.3
32
67
22
99
65
64
47
26
72
Zrc
_19
_02
90
.54
0.0
53
32
2.1
00
.34
85
32
.18
0.0
47
48
0.5
90.2
72
99
23
04
63
42
46
299
2Z
rc_2
1_0
32
0.3
90
.05
30
63
.20
0.3
45
50
3.4
50
.04
74
41
.31
0.3
72
99
43
01
93
31
71
299
4Z
rc_2
4_0
35
0.4
80
.05
30
42
.39
0.3
47
32
2.4
80
.04
75
70
.61
0.2
63
00
23
03
63
31
53
300
2Z
rc_0
2_0
09
0.6
10
.05
22
02
.30
0.3
44
37
2.4
10
.04
78
80
.73
0.3
03
01
23
00
62
94
50
301
2Z
rc_0
9_0
17
0.6
00
.05
49
32
.60
0.3
61
84
2.6
90
.04
78
30
.71
0.2
63
01
23
14
74
09
56
301
2Z
rc_0
5_0
12
0.4
20
.05
76
92
.89
0.3
81
16
3.0
10
.04
80
40
.81
0.2
83
02
23
28
85
18
62
302
2Z
rc_1
0_0
18
0.4
20
.05
58
82
.70
0.3
69
09
2.7
90
.04
79
50
.71
0.2
53
02
23
19
84
48
58
302
2Z
rc_1
7_0
27
0.5
40
.05
32
62
.29
0.3
51
47
2.3
90
.04
79
60
.65
0.2
93
02
23
06
63
40
50
302
2Z
rc_0
1_0
08
0.5
20
.05
34
52
.51
0.3
54
38
2.6
00
.04
80
60
.71
0.2
63
03
23
08
73
48
54
303
2Z
rc_0
3_0
10
0.5
50
.05
49
42
.29
0.3
62
74
2.4
10
.04
80
60
.73
0.3
13
03
23
14
74
10
50
303
2Z
rc_3
8_0
50
0.5
10
.05
17
32
.20
0.3
42
35
2.2
60
.04
81
00
.52
0.2
23
03
22
99
62
73
49
303
2Z
rc_0
4_0
11
0.5
50
.05
38
62
.10
0.3
58
98
2.2
20
.04
83
10
.72
0.3
33
04
23
11
63
65
46
304
2Z
rc_3
5_0
46
0.5
30
.05
21
32
.09
0.3
47
37
2.1
90
.04
83
60
.62
0.3
03
04
23
03
62
91
47
304
2Z
rc_3
2_0
44
0.5
50
.05
42
52
.19
0.3
61
86
2.3
00
.04
84
60
.68
0.3
13
05
23
14
63
81
48
305
2Z
rc_3
4_0
45
0.4
50
.05
20
92
.30
0.3
46
87
2.4
10
.04
84
10
.70
0.2
93
05
23
02
62
89
51
305
2Z
rc_0
7_0
15
0.5
30
.05
36
52
.11
0.3
58
74
2.2
30
.04
86
30
.74
0.3
33
06
23
11
63
56
46
306
2Z
rc_0
8_0
16
0.4
30
.05
33
32
.91
0.3
55
95
2.9
80
.04
85
60
.68
0.2
23
06
23
09
83
43
64
306
2
Con
tinue
don
next
page
...
tablas geocronología u-pb 85
Tabl
a2
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Toto
ltep
ecpl
uton
horn
blen
dega
bbro
.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_12
_02
10
.50
0.0
54
11
2.2
00
.36
17
22
.29
0.0
48
61
0.6
20.2
73
06
23
13
63
76
48
306
2Z
rc_1
6_0
26
0.4
60
.05
49
12
.60
0.3
68
24
2.7
00
.04
86
40
.74
0.2
63
06
23
18
74
09
56
306
2Z
rc_2
2_0
33
0.4
00
.05
21
12
.71
0.3
48
04
2.7
80
.04
85
60
.66
0.2
33
06
23
03
72
90
60
306
2Z
rc_2
7_0
38
0.6
10
.05
43
02
.39
0.3
62
95
2.4
80
.04
85
40
.64
0.2
63
06
23
14
73
84
53
306
2Z
rc_1
3_0
22
0.5
50
.05
41
82
.49
0.3
64
20
2.5
90
.04
87
20
.70
0.2
83
07
23
15
73
79
54
307
2Z
rc_2
8_0
39
0.4
70
.05
19
63
.00
0.3
50
12
3.1
10
.04
88
90
.82
0.2
63
08
23
05
82
84
67
308
2Z
rc_2
9_0
40
0.4
00
.05
12
12
.89
0.3
45
82
2.9
80
.04
89
40
.65
0.2
43
08
23
02
82
50
65
308
2Z
rc_3
7_0
49
0.4
90
.05
33
42
.10
0.3
59
55
2.2
10
.04
89
20
.67
0.3
13
08
23
12
63
43
46
308
2Z
rc_3
9_0
51
0.3
70
.05
34
13
.30
0.3
56
17
3.8
60
.04
89
12
.00
0.5
23
08
63
09
10
34
67
330
86
Zrc
_20_0
30
0.4
10
.05
44
13
.11
0.3
66
35
3.1
90
.04
91
00
.75
0.2
33
09
23
17
93
88
68
309
2Z
rc_3
0_0
41
0.4
20
.05
28
32
.31
0.3
57
07
2.3
80
.04
91
40
.61
0.2
43
09
23
10
63
22
51
309
2Z
rc_3
6_0
48
0.4
90
.05
28
72
.10
0.3
57
70
2.2
20
.04
91
70
.71
0.3
23
09
23
10
63
23
47
309
2Z
rc_0
6_0
14
0.3
00
.05
84
13
.41
0.3
94
74
3.5
20
.04
92
00
.91
0.2
53
10
33
38
10
54
57
231
03
Zrc
_26_0
37
0.3
00
.05
69
53
.11
0.3
85
95
3.1
90
.04
93
10
.73
0.2
23
10
23
31
94
90
67
310
2Z
rc_4
1_0
53
0.4
80
.05
32
72
.59
0.3
59
62
2.7
20
.04
92
50
.79
0.3
03
10
23
12
73
40
57
310
2Z
rc_1
1_0
20
0.5
90
.05
45
62
.20
0.3
71
71
2.3
00
.04
95
00
.69
0.3
03
11
23
21
63
94
48
311
2Z
rc_1
5_0
24
0.3
40
.05
52
93
.60
0.3
75
43
3.7
00
.04
94
40
.87
0.2
33
11
33
24
10
42
47
831
13
tablas geocronología u-pb 86
Tabl
a3
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Toto
ltep
ecpl
uton
quar
tzdi
orit
e.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_56
_07
40
.01
0.0
51
90
1.4
30
.31
57
81
.59
0.0
44
13
0.4
80
.40
27
81
27
94
28
13
327
81
Zrc
_81
_10
40
.65
0.0
52
71
1.9
00
.32
36
82
.15
0.0
44
61
1.0
10
.47
28
13
28
55
31
64
328
13
Zrc
_52
_06
91
.19
0.0
52
39
1.2
00
.32
62
11
.33
0.0
45
15
0.5
80
.42
28
52
28
73
30
22
628
52
Zrc
_57
_07
50
.27
0.0
52
94
1.9
10
.32
93
91
.99
0.0
45
17
0.6
00
.28
28
52
28
95
32
64
028
52
Zrc
_47
_06
30
.63
0.0
52
01
1.5
00
.32
58
81
.57
0.0
45
43
0.4
60
.30
28
61
28
64
28
63
228
61
Zrc
_76
_09
80
.27
0.0
53
01
2.2
10
.33
20
02
.28
0.0
45
42
0.6
20
.26
28
62
29
16
32
95
028
62
Zrc
_79
_10
10
.29
0.0
54
52
2.4
90
.34
05
22
.57
0.0
45
32
0.6
00
.24
28
62
29
87
39
35
628
62
Zrc
_59
_07
70
.42
0.0
53
76
1.9
00
.33
77
82
.00
0.0
45
56
0.6
10
.31
28
72
29
55
36
14
028
72
Zrc
_66
_08
60
.52
0.0
53
34
1.5
90
.33
56
11
.70
0.0
45
60
0.5
70
.35
28
72
29
44
34
33
428
72
Zrc
_70
_09
00
.35
0.0
52
70
1.7
10
.33
23
81
.78
0.0
45
70
0.5
00
.27
28
81
29
14
31
63
928
81
Zrc
_74
_09
50
.62
0.0
51
59
1.6
10
.32
50
91
.69
0.0
45
72
0.5
20
.30
28
81
28
64
26
73
728
81
Zrc
_42
_05
70
.72
0.0
54
44
1.6
00
.34
36
51
.69
0.0
45
84
0.5
50
.33
28
92
30
04
38
93
328
92
Zrc
_46
_06
20
.28
0.0
52
58
2.2
10
.33
11
42
.30
0.0
45
81
0.6
80
.29
28
92
29
06
31
14
728
92
Zrc
_49
_06
50
.29
0.0
49
66
2.5
00
.31
35
12
.60
0.0
45
82
0.7
00
.27
28
92
27
76
17
95
428
92
Zrc
_64
_08
30
.32
0.0
54
26
1.8
10
.34
36
51
.91
0.0
45
91
0.6
30
.32
28
92
30
05
38
23
828
92
Zrc
_69
_08
90
.53
0.0
53
37
1.5
00
.33
76
11
.61
0.0
45
87
0.5
90
.36
28
92
29
54
34
53
428
92
Zrc
_78
_10
00
.39
0.0
54
12
1.9
00
.34
12
12
.00
0.0
45
83
0.6
30
.31
28
92
29
85
37
64
328
92
Zrc
_72
_09
30
.35
0.0
51
70
1.8
00
.32
82
51
.86
0.0
45
99
0.5
00
.26
29
01
28
85
27
24
129
01
Con
tinue
don
next
page
...
tablas geocronología u-pb 87
Tabl
a3
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Toto
ltep
ecpl
uton
quar
tzdi
orit
e.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_82
_10
50
.59
0.0
52
44
1.3
90
.33
35
91
.48
0.0
46
06
0.5
00
.35
29
01
29
24
30
53
129
01
Zrc
_48
_06
40
.32
0.0
52
29
1.8
00
.33
26
91
.93
0.0
46
16
0.6
90
.37
29
12
29
25
29
83
829
12
Zrc
_55
_07
20
.34
0.0
53
02
1.7
90
.33
71
11
.90
0.0
46
10
0.6
10
.34
29
12
29
55
33
03
829
12
Zrc
_65
_08
40
.56
0.0
52
52
1.8
10
.33
40
41
.93
0.0
46
20
0.6
90
.35
29
12
29
35
30
83
829
12
Zrc
_58
_07
60
.62
0.0
52
38
1.3
90
.33
41
11
.51
0.0
46
27
0.5
60
.39
29
22
29
34
30
23
029
22
Zrc
_67
_08
70
.33
0.0
52
96
1.7
00
.33
88
11
.79
0.0
46
36
0.5
60
.31
29
22
29
65
32
73
829
22
Zrc
_44
_05
90
.61
0.0
52
45
1.5
10
.33
59
71
.60
0.0
46
44
0.5
60
.34
29
32
29
44
30
53
229
32
Zrc
_68
_08
80
.40
0.0
52
66
1.9
00
.33
86
12
.00
0.0
46
58
0.6
20
.32
29
32
29
65
31
44
329
32
Zrc
_75
_09
60
.38
0.0
53
14
1.9
00
.34
07
01
.97
0.0
46
51
0.5
20
.26
29
31
29
85
33
54
329
31
Zrc
_77
_09
90
.52
0.0
52
05
1.5
00
.33
41
51
.57
0.0
46
53
0.4
70
.31
29
31
29
34
28
83
429
31
Zrc
_80
_10
20
.26
0.0
52
78
2.1
00
.33
93
82
.20
0.0
46
65
0.6
40
.29
29
42
29
76
31
94
729
42
Zrc
_50
_06
60
.35
0.0
53
05
2.5
10
.34
10
32
.61
0.0
46
81
0.7
50
.28
29
52
29
87
33
15
329
52
Zrc
_53
_07
00
.40
0.0
51
74
2.2
00
.33
47
02
.28
0.0
46
85
0.6
00
.26
29
52
29
36
27
44
729
52
Zrc
_54
_07
10
.27
0.0
50
76
2.0
10
.32
71
42
.12
0.0
46
80
0.6
80
.31
29
52
28
75
23
04
329
52
Zrc
_43
_05
80
.40
0.0
51
67
1.9
90
.33
45
82
.10
0.0
47
02
0.6
40
.32
29
62
29
35
27
14
329
62
Zrc
_71
_09
20
.33
0.0
52
91
2.1
00
.34
41
12
.24
0.0
47
20
0.7
60
.35
29
72
30
06
32
54
729
72
Zrc
_51
_06
80
.27
0.0
52
25
2.7
90
.34
30
22
.90
0.0
47
64
0.7
60
.27
30
02
29
98
29
66
030
02
Zrc
_62
_08
10
.25
0.0
51
76
6.3
90
.34
10
96
.70
0.0
47
80
0.9
00
.24
30
13
29
81
72
75
13
630
13
Con
tinue
don
next
page
...
tablas geocronología u-pb 88
Tabl
a3
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Toto
ltep
ecpl
uton
quar
tzdi
orit
e.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_63
_08
20
.38
0.0
56
26
2.2
00
.37
22
12
.37
0.0
47
94
0.9
00
.37
30
23
32
17
46
34
630
23
Zrc
_60
_07
80
.44
0.0
52
40
1.7
00
.34
82
21
.79
0.0
48
22
0.5
60
.31
30
42
30
35
30
33
630
42
Zrc
_73
_09
40
.36
0.0
51
90
1.9
10
.34
84
61
.98
0.0
48
70
0.5
50
.27
30
72
30
45
28
14
330
72
Zrc
_45
_06
00
.58
0.0
53
61
2.8
00
.36
25
62
.87
0.0
49
23
0.6
50
.23
31
02
31
48
35
55
931
02
Tabl
a4
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apsa
mm
ite
TT-4
86
A.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_06
_01
40
.55
0.0
68
02
1.7
11
.06
95
01
.94
0.1
13
98
0.9
30
.47
69
66
73
81
08
69
35
696
6Z
rc_5
7_0
75
0.3
80
.07
09
80
.85
1.5
24
90
0.9
20
.15
60
00
.34
0.3
89
35
39
40
69
57
17
935
3Z
rc_1
3_0
22
0.0
20
.07
16
50
.75
1.6
18
10
0.8
40
.16
39
80
.36
0.4
49
79
39
77
59
76
14
979
3Z
rc_8
1_1
04
0.3
80
.07
20
81
.53
1.6
69
74
1.7
30
.16
80
20
.45
0.3
71
00
14
99
71
19
88
31
1001
4Z
rc_8
4_1
07
0.3
60
.07
28
70
.84
1.6
78
10
0.9
10
.16
72
40
.36
0.4
09
97
31
00
06
10
10
17
1010
17Z
rc_3
9_0
53
0.1
80
.07
40
80
.86
1.7
43
20
0.9
40
.17
08
40
.37
0.3
91
01
73
10
25
61
04
41
610
4416
Zrc
_21
_03
20
.43
0.0
74
74
0.8
31
.87
92
00
.91
0.1
82
65
0.3
70
.41
10
81
41
07
46
10
62
15
1062
15Z
rc_0
8_0
16
0.4
80
.07
49
11
.29
1.7
65
60
1.3
80
.17
13
80
.46
0.3
41
02
04
10
33
91
06
62
610
6626
Con
tinue
don
next
page
...
tablas geocronología u-pb 89
Tabl
a4
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apsa
mm
ite
TT-4
86
A.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_93
_11
80
.38
0.0
74
92
1.0
91
.79
30
01
.15
0.1
73
88
0.3
50
.32
10
33
31
04
38
10
66
22
1066
22Z
rc_6
7_0
87
0.1
20
.07
60
61
.00
2.2
56
70
1.0
80
.21
54
50
.41
0.3
81
25
85
11
99
81
09
72
010
9720
Zrc
_97
_12
30
.26
0.0
76
51
1.0
11
.70
04
01
.89
0.1
60
53
1.6
00
.85
96
01
41
00
91
21
10
82
011
0820
Zrc
_54
_07
10
.32
0.0
76
86
1.7
01
.92
07
01
.76
0.1
81
36
0.4
50
.25
10
74
41
08
81
21
11
83
111
1831
Zrc
_25
_03
60
.39
0.0
77
08
1.6
01
.74
46
01
.70
0.1
64
36
0.5
70
.34
98
15
10
25
11
11
23
29
1123
29Z
rc_1
5_0
24
0.2
20
.07
73
01
.20
1.9
37
10
1.2
80
.18
20
90
.45
0.3
51
07
84
10
94
91
12
92
211
2922
Zrc
_16
_02
60
.81
0.0
77
30
1.2
01
.93
71
01
.28
0.1
82
09
0.4
50
.35
10
78
41
09
49
11
29
22
1129
22Z
rc_7
2_0
93
0.2
20
.07
74
50
.98
1.9
79
50
1.1
00
.18
57
70
.49
0.4
41
09
85
11
09
71
13
31
911
3319
Zrc
_05
_01
20
.48
0.0
77
48
0.8
32
.04
26
00
.90
0.1
91
38
0.3
40
.39
11
29
41
13
06
11
34
15
1134
15Z
rc_1
9_0
29
0.5
30
.07
76
61
.70
2.0
72
40
1.8
40
.19
40
90
.71
0.3
91
14
37
11
40
13
11
38
31
1138
31Z
rc_7
8_1
00
0.4
70
.07
77
30
.81
2.0
24
00
0.8
90
.18
90
40
.36
0.4
01
11
64
11
24
61
14
01
611
4016
Zrc
_83
_10
60
.06
0.0
77
81
0.8
72
.09
84
00
.93
0.1
95
76
0.3
40
.35
11
53
41
14
86
11
42
17
1142
17Z
rc_4
7_0
63
0.2
80
.07
78
40
.87
2.0
86
20
0.9
50
.19
45
10
.35
0.3
91
14
64
11
44
71
14
31
611
4316
Zrc
_55
_07
20
.51
0.0
77
83
1.9
01
.88
79
01
.97
0.1
76
50
0.5
20
.26
10
48
51
07
71
31
14
33
511
4335
Zrc
_70
_09
00
.44
0.0
77
90
1.0
02
.14
20
01
.07
0.1
99
67
0.3
80
.35
11
74
41
16
27
11
44
20
1144
20Z
rc_9
9_1
25
0.3
10
.07
79
00
.95
2.1
38
90
1.0
30
.19
92
70
.41
0.4
01
17
14
11
61
71
14
41
911
4419
Zrc
_07
_01
50
.34
0.0
77
93
0.8
92
.13
66
01
.01
0.1
98
94
0.4
70
.48
11
70
51
16
17
11
45
17
1145
17Z
rc_6
3_0
82
0.7
80
.07
80
10
.79
2.1
65
40
0.8
70
.20
14
40
.35
0.4
11
18
34
11
70
61
14
71
611
4716
Con
tinue
don
next
page
...
tablas geocronología u-pb 90
Tabl
a4
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apsa
mm
ite
TT-4
86
A.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_94
_11
90
.26
0.0
78
06
0.9
92
.09
03
01
.08
0.1
94
44
0.4
20
.40
11
45
41
14
67
11
48
19
1148
19Z
rc_5
3_0
70
0.6
40
.07
81
31
.42
2.0
88
83
1.7
40
.19
39
00
.51
0.4
91
14
25
11
45
12
11
50
26
1150
26Z
rc_5
8_0
76
0.4
80
.07
82
81
.00
2.1
20
90
1.0
80
.19
66
90
.40
0.3
81
15
84
11
56
71
15
41
911
5419
Zrc
_98
_12
40
.44
0.0
78
29
0.8
82
.23
18
01
.08
0.2
07
11
0.6
30
.58
12
13
71
19
18
11
54
17
1154
17Z
rc_7
6_0
98
0.4
80
.07
83
71
.30
1.9
89
10
1.4
10
.18
43
60
.55
0.3
91
09
15
11
12
10
11
56
25
1156
25Z
rc_9
6_1
22
0.5
10
.07
84
30
.92
2.1
35
40
1.0
00
.19
76
00
.39
0.4
01
16
24
11
60
71
15
81
811
5818
Zrc
_45
_06
00
.36
0.0
78
54
0.7
82
.17
93
00
.85
0.2
01
34
0.3
30
.40
11
83
41
17
46
11
61
14
1161
14Z
rc_3
1_0
44
0.7
10
.07
86
11
.00
2.1
56
20
1.2
10
.19
92
10
.68
0.5
61
17
17
11
67
81
16
21
811
6218
Zrc
_65
_08
40
.23
0.0
78
59
0.8
92
.13
31
00
.96
0.1
97
02
0.3
50
.36
11
59
41
16
07
11
62
17
1162
17Z
rc_0
4_0
11
0.1
40
.07
86
20
.83
2.2
23
90
0.9
00
.20
54
10
.35
0.4
01
20
44
11
89
61
16
31
511
6315
Zrc
_46
_06
20
.33
0.0
78
64
1.0
02
.11
06
01
.07
0.1
94
93
0.3
90
.35
11
48
41
15
27
11
63
18
1163
18Z
rc_6
4_0
83
0.3
80
.07
86
30
.86
2.1
58
70
0.9
20
.19
93
10
.34
0.3
51
17
24
11
68
61
16
31
711
6317
Zrc
_82
_10
50
.27
0.0
78
65
1.2
82
.17
27
91
.47
0.2
00
37
0.4
60
.40
11
77
51
17
21
01
16
32
511
6325
Zrc
_80
_10
20
.31
0.0
78
77
1.2
12
.14
52
01
.29
0.1
97
85
0.4
80
.36
11
64
51
16
49
11
66
23
1166
23Z
rc_7
4_0
95
0.7
10
.07
88
90
.93
2.1
19
20
1.0
00
.19
50
00
.38
0.3
91
14
84
11
55
71
16
91
811
6918
Zrc
_51
_06
80
.32
0.0
78
93
0.9
52
.14
82
01
.04
0.1
97
59
0.4
30
.41
11
62
51
16
47
11
70
17
1170
17Z
rc_6
6_0
86
0.1
80
.07
89
31
.20
2.3
63
60
1.3
40
.21
73
20
.60
0.4
41
26
87
12
32
10
11
70
23
1170
23Z
rc_2
7_0
39
0.2
20
.07
90
50
.83
2.1
81
30
0.9
30
.20
05
10
.39
0.4
31
17
84
11
75
61
17
31
511
7315
Con
tinue
don
next
page
...
tablas geocronología u-pb 91
Tabl
a4
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apsa
mm
ite
TT-4
86
A.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_14
_02
30
.39
0.0
79
08
1.4
02
.22
39
01
.49
0.2
04
51
0.5
00
.33
12
00
51
18
91
01
17
42
511
7425
Zrc
_24
_03
50
.40
0.0
79
57
1.2
82
.17
30
01
.49
0.1
98
06
0.4
20
.35
11
65
51
17
21
01
18
62
311
8623
Zrc
_29
_04
10
.69
0.0
79
55
1.1
12
.12
06
01
.15
0.1
93
66
0.3
40
.28
11
41
41
15
68
11
86
20
1186
20Z
rc_3
6_0
50
0.5
10
.07
95
51
.29
2.2
07
40
1.3
80
.20
15
40
.45
0.3
41
18
45
11
83
10
11
86
23
1186
23Z
rc_5
2_0
69
0.7
20
.07
96
61
.00
2.2
21
20
1.0
70
.20
22
70
.37
0.3
41
18
84
11
88
71
18
91
811
8918
Zrc
_86
_11
00
.58
0.0
79
90
1.2
02
.15
90
01
.28
0.1
96
17
0.4
40
.34
11
55
51
16
89
11
95
23
1195
23Z
rc_1
2_0
21
0.3
20
.08
00
91
.10
2.2
61
30
1.2
00
.20
50
50
.48
0.4
01
20
25
12
00
81
19
92
011
9920
Zrc
_09
_01
70
.48
0.0
80
24
1.5
02
.17
78
01
.56
0.1
97
09
0.4
10
.27
11
60
41
17
41
11
20
32
912
0329
Zrc
_22
_03
30
.40
0.0
80
44
0.9
22
.25
65
01
.00
0.2
03
88
0.4
00
.40
11
96
41
19
97
12
08
17
1208
17Z
rc_5
0_0
66
0.3
30
.08
04
90
.99
2.1
93
40
1.0
80
.19
80
00
.42
0.4
01
16
54
11
79
81
20
91
812
0918
Zrc
_35
_04
80
.51
0.0
80
59
1.9
12
.31
16
02
.19
0.2
08
03
0.5
00
.34
12
18
61
21
61
61
21
23
512
1235
Zrc
_75
_09
60
.37
0.0
80
71
1.4
02
.16
76
01
.50
0.1
95
19
0.5
30
.35
11
49
61
17
11
01
21
42
712
1427
Zrc
_43
_05
80
.28
0.0
80
76
0.9
92
.33
12
01
.06
0.2
09
62
0.3
90
.37
12
27
41
22
28
12
16
18
1216
18Z
rc_5
9_0
77
0.3
50
.08
10
81
.10
2.3
32
10
1.1
80
.20
88
50
.43
0.3
71
22
35
12
22
81
22
32
112
2321
Zrc
_88
_11
20
.59
0.0
81
19
1.3
12
.34
13
01
.42
0.2
09
14
0.5
70
.39
12
24
61
22
51
01
22
62
512
2625
Zrc
_23
_03
40
.36
0.0
81
98
1.0
02
.28
86
01
.11
0.2
02
79
0.4
90
.44
11
90
51
20
98
12
45
18
1245
18Z
rc_6
0_0
78
0.2
90
.08
23
41
.51
2.2
84
00
1.5
70
.20
16
70
.48
0.2
91
18
45
12
07
11
12
54
29
1254
29Z
rc_4
4_0
59
0.0
80
.08
25
91
.30
2.4
54
10
1.4
60
.21
58
30
.67
0.4
61
26
08
12
59
11
12
60
23
1260
23
Con
tinue
don
next
page
...
tablas geocronología u-pb 92
Tabl
a4
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apsa
mm
ite
TT-4
86
A.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_85
_10
80
.28
0.0
82
62
0.9
22
.34
64
00
.99
0.2
06
02
0.3
60
.36
12
08
41
22
67
12
60
18
1260
18Z
rc_3
3_0
46
0.3
60
.08
29
61
.10
2.3
08
10
1.1
70
.20
21
10
.41
0.3
61
18
74
12
15
81
26
82
012
6820
Zrc
_28
_04
00
.33
0.0
83
00
0.8
92
.38
37
01
.00
0.2
08
66
0.4
50
.45
12
22
51
23
87
12
69
16
1269
16Z
rc_6
1_0
80
0.5
30
.08
29
71
.21
2.2
91
40
1.2
90
.20
03
80
.48
0.3
61
17
75
12
10
91
26
92
312
6923
Zrc
_18
_02
80
.54
0.0
83
18
1.0
02
.34
66
01
.09
0.2
04
93
0.4
30
.40
12
02
51
22
78
12
73
18
1273
18Z
rc_3
8_0
52
0.0
20
.08
32
30
.83
2.4
92
60
1.0
20
.21
73
70
.59
0.5
81
26
87
12
70
71
27
51
512
7515
Zrc
_56
_07
40
.03
0.0
83
30
1.2
02
.25
62
01
.27
0.1
96
93
0.4
30
.34
11
59
51
19
99
12
76
21
1276
21Z
rc_0
3_0
10
0.4
40
.08
34
91
.40
2.3
11
80
1.5
40
.20
13
90
.63
0.4
11
18
37
12
16
11
12
81
25
1281
25Z
rc_1
0_0
18
0.2
50
.08
36
10
.80
1.9
64
30
1.0
70
.17
03
10
.71
0.6
61
01
47
11
03
71
28
31
412
8314
Zrc
_77
_09
90
.53
0.0
84
32
1.0
02
.60
86
01
.08
0.2
24
64
0.4
20
.40
13
06
51
30
38
13
00
19
1300
19Z
rc_2
6_0
38
0.4
30
.08
46
01
.50
2.5
02
80
1.5
60
.21
50
70
.44
0.2
81
25
65
12
73
11
13
06
27
1306
27Z
rc_4
8_0
64
1.5
30
.08
45
90
.93
2.5
74
70
1.0
10
.22
10
00
.39
0.3
81
28
75
12
93
71
30
61
713
0617
Zrc
_69
_08
90
.35
0.0
84
94
0.7
72
.59
93
00
.83
0.2
22
09
0.3
40
.39
12
93
41
30
06
13
14
15
1314
15Z
rc_1
1_0
20
0.6
40
.08
51
11
.10
2.6
97
40
1.2
00
.23
00
50
.48
0.3
91
33
56
13
28
91
31
81
913
1819
Zrc
_37
_05
10
.20
0.0
85
11
0.8
02
.71
16
00
.87
0.2
31
17
0.3
50
.40
13
41
41
33
26
13
18
14
1318
14Z
rc_7
1_0
92
0.2
50
.08
51
70
.79
2.6
86
20
0.8
50
.22
88
00
.32
0.3
91
32
84
13
25
61
31
91
513
1915
Zrc
_01
_00
80
.27
0.0
85
43
1.5
32
.66
92
41
.66
0.2
26
60
0.4
50
.34
13
17
51
32
01
21
32
52
713
2527
Zrc
_87
_11
10
.50
0.0
85
65
1.0
02
.87
22
01
.09
0.2
43
41
0.4
30
.39
14
04
51
37
58
13
30
19
1330
19
Con
tinue
don
next
page
...
tablas geocronología u-pb 93
Tabl
a4
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apsa
mm
ite
TT-4
86
A.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_02
_00
90
.26
0.0
87
51
1.1
02
.83
16
01
.20
0.2
35
09
0.4
80
.41
13
61
61
36
49
13
72
19
1372
19Z
rc_9
5_1
20
0.2
70
.08
98
30
.83
2.9
28
00
0.9
50
.23
65
50
.46
0.4
81
36
96
13
89
71
42
21
614
2216
Zrc
_42
_05
70
.40
0.0
90
45
0.7
82
.65
16
00
.89
0.2
12
79
0.4
00
.46
12
44
51
31
57
14
35
14
1435
14Z
rc_3
0_0
42
0.4
00
.09
06
70
.92
3.1
29
70
0.9
90
.25
05
30
.37
0.3
81
44
15
14
40
81
44
01
614
4016
Zrc
_41
_05
60
.27
0.0
90
89
0.8
33
.20
96
00
.93
0.2
56
43
0.4
20
.46
14
72
61
45
97
14
44
14
1444
14Z
rc_4
0_0
54
0.2
00
.09
18
50
.87
2.9
41
67
1.0
70
.23
22
70
.45
0.4
81
34
65
13
93
81
46
41
514
6415
Zrc
_62
_08
10
.29
0.0
92
49
0.9
93
.37
91
01
.05
0.2
65
25
0.3
60
.33
15
17
51
50
08
14
77
19
1477
19Z
rc_2
0_0
30
0.1
90
.09
26
90
.83
3.3
63
60
0.9
20
.26
34
80
.39
0.4
21
50
85
14
96
71
48
21
414
8214
Zrc
_91
_11
60
.17
0.0
93
03
0.8
93
.43
71
00
.98
0.2
68
25
0.4
20
.42
15
32
61
51
38
14
88
17
1488
17Z
rc_7
3_0
94
0.3
70
.09
36
30
.85
3.2
23
80
0.9
60
.24
98
20
.45
0.4
61
43
86
14
63
71
50
11
615
0116
Zrc
_34
_04
70
.34
0.0
95
27
0.8
93
.36
21
01
.07
0.2
56
26
0.5
90
.55
14
71
81
49
68
15
33
15
1533
15Z
rc_1
00
_12
60
.22
0.0
95
44
1.0
53
.57
21
81
.17
0.2
71
46
0.4
10
.45
15
48
61
54
39
15
37
18
1537
18Z
rc_9
2_1
17
0.5
30
.09
67
20
.78
3.5
54
00
0.8
50
.26
67
50
.33
0.4
01
52
44
15
39
71
56
21
415
6214
Zrc
_49
_06
50
.21
0.0
98
35
0.9
93
.75
92
01
.06
0.2
77
68
0.3
90
.38
15
80
51
58
49
15
93
17
1593
17Z
rc_7
9_1
01
0.4
60
.09
84
00
.80
3.6
77
80
0.8
80
.27
13
30
.37
0.4
11
54
85
15
67
71
59
41
515
9415
Zrc
_89
_11
30
.38
0.0
98
64
0.8
13
.81
13
00
.88
0.2
80
37
0.3
50
.39
15
93
51
59
57
15
99
15
1599
15Z
rc_1
7_0
27
0.6
20
.09
89
20
.97
3.9
33
80
1.1
60
.28
86
00
.63
0.5
41
63
59
16
21
91
60
41
716
0417
Zrc
_90
_11
40
.32
0.0
99
48
1.0
03
.91
22
01
.09
0.2
85
72
0.4
40
.41
16
20
61
61
69
16
14
18
1614
18
Con
tinue
don
next
page
...
tablas geocronología u-pb 94
Tabl
a4
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apsa
mm
ite
TT-4
86
A.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_32
_04
50
.55
0.1
10
98
0.7
54
.99
47
00
.93
0.3
26
76
0.5
50
.59
18
23
91
81
88
18
16
12
1816
12
Tabl
a5
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apsa
mm
ite
TT-8
1.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_44
_05
91
.73
0.0
85
70
2.2
10
.40
64
72
.37
0.0
35
12
0.8
80
.37
22
32
34
67
13
31
41
22
32
Zrc
_90
_11
40
.44
0.0
57
25
5.4
00
.34
15
76
.14
0.0
43
27
1.7
30
.32
27
35
29
81
65
01
11
827
35
Zrc
_06
_01
40
.52
0.0
53
63
2.2
90
.32
90
22
.37
0.0
44
51
0.5
80
.25
28
12
28
96
35
65
128
12
Zrc
_67
_08
70
.34
0.0
54
10
13
.11
0.3
34
03
14
.03
0.0
44
78
1.4
30
.25
28
24
29
33
63
75
28
528
24
Zrc
_23
_03
40
.72
0.0
52
80
1.5
90
.32
86
21
.70
0.0
45
03
0.5
80
.35
28
42
28
94
32
03
628
42
Zrc
_65
_08
40
.44
0.0
52
80
2.2
90
.32
90
42
.39
0.0
45
18
0.6
40
.28
28
52
28
96
32
05
128
52
Zrc
_05
_01
20
.49
0.0
53
60
2.2
90
.33
55
22
.39
0.0
45
30
0.6
60
.28
28
62
29
46
35
45
128
62
Zrc
_34
_04
70
.63
0.0
48
62
10
.02
0.3
04
53
10
.44
0.0
45
43
0.9
00
.10
28
63
27
02
51
29
21
02
86
3
Zrc
_03
_01
00
.56
0.0
57
14
1.5
10
.36
11
21
.58
0.0
45
73
0.5
00
.31
28
81
31
34
49
73
328
81
Zrc
_51
_06
80
.46
0.0
54
92
6.9
90
.34
67
17
.35
0.0
45
78
0.8
10
.21
28
92
30
21
94
09
15
428
92
Zrc
_36
_05
00
.79
0.0
56
94
2.7
90
.36
39
02
.95
0.0
46
40
0.9
30
.32
29
23
31
58
48
96
129
23
Con
tinue
don
next
page
...
tablas geocronología u-pb 95
Tabl
a5
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apsa
mm
ite
TT-8
1.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_52
_06
90
.51
0.0
56
31
1.9
00
.36
37
12
.13
0.0
46
38
0.9
70
.45
29
23
31
56
46
54
129
23
Zrc
_54
_07
10
.44
0.0
55
80
2.0
10
.35
72
12
.09
0.0
46
35
0.6
00
.28
29
22
31
06
44
44
329
22
Zrc
_83
_10
60
.34
0.0
56
39
2.5
00
.36
38
12
.58
0.0
46
81
0.6
20
.24
29
52
31
57
46
85
529
52
Zrc
_09
_01
70
.50
0.0
51
39
2.8
00
.33
19
72
.91
0.0
46
98
0.7
90
.27
29
62
29
17
25
86
429
62
Zrc
_38
_05
20
.33
0.0
53
32
2.0
10
.34
74
22
.20
0.0
47
10
0.9
10
.41
29
73
30
36
34
24
529
73
Zrc
_88
_11
20
.11
0.0
54
14
2.2
00
.35
30
82
.29
0.0
47
25
0.6
60
.29
29
82
30
76
37
74
929
82
Zrc
_58
_07
60
.13
0.0
53
30
1.8
00
.34
92
11
.87
0.0
47
40
0.5
10
.27
29
91
30
45
34
23
929
91
Zrc
_72
_09
30
.34
0.0
52
47
1.9
40
.34
32
62
.33
0.0
47
44
0.7
20
.50
29
92
30
06
30
64
329
92
Zrc
_11
_02
00
.60
0.0
52
30
1.4
00
.34
65
31
.48
0.0
48
02
0.4
80
.33
30
21
30
24
29
93
130
21
Zrc
_04
_01
10
.60
0.0
53
07
1.5
10
.35
46
51
.56
0.0
48
36
0.4
30
.26
30
41
30
84
33
23
430
41
Zrc
_12
_02
10
.35
0.0
52
70
2.5
00
.35
14
62
.57
0.0
48
31
0.6
20
.23
30
42
30
67
31
65
630
42
Zrc
_02
_00
90
.59
0.0
52
86
1.6
10
.35
51
31
.69
0.0
48
60
0.5
30
.30
30
62
30
94
32
33
830
62
Zrc
_85
_10
80
.28
0.0
59
94
1.8
00
.40
24
01
.88
0.0
48
56
0.5
40
.28
30
62
34
35
60
13
83
06
2
Zrc
_95
_12
00
.30
0.0
52
84
1.6
10
.35
53
31
.70
0.0
48
66
0.5
80
.32
30
62
30
95
32
23
630
62
Zrc
_40
_05
40
.52
0.0
52
45
1.9
10
.35
33
92
.01
0.0
48
74
0.6
60
.32
30
72
30
75
30
54
230
72
Zrc
_63
_08
20
.75
0.0
53
95
2.3
00
.36
38
42
.40
0.0
48
71
0.6
80
.28
30
72
31
56
36
95
030
72
Zrc
_92
_11
70
.47
0.0
57
74
1.7
00
.38
77
91
.79
0.0
48
70
0.5
50
.31
30
72
33
35
52
03
730
72
Zrc
_14
_02
30
.56
0.0
53
49
1.7
90
.36
14
31
.90
0.0
48
91
0.5
90
.32
30
82
31
35
35
04
030
82
Con
tinue
don
next
page
...
tablas geocronología u-pb 96
Tabl
a5
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apsa
mm
ite
TT-8
1.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_27
_03
90
.37
0.0
51
48
2.1
00
.34
80
32
.21
0.0
48
97
0.6
90
.32
30
82
30
36
26
24
830
82
Zrc
_75
_09
60
.58
0.0
54
56
3.7
40
.36
86
64
.20
0.0
49
01
0.9
00
.29
30
83
31
91
23
94
83
308
3Z
rc_8
7_1
11
0.5
30
.05
60
81
.60
0.3
79
35
1.7
20
.04
89
40
.63
0.3
73
08
23
27
54
56
35
308
2Z
rc_2
0_0
30
0.3
60
.05
19
91
.50
0.3
52
53
1.5
70
.04
90
90
.47
0.2
93
09
13
07
42
85
34
309
1Z
rc_2
9_0
41
0.4
80
.05
34
62
.10
0.3
62
49
2.1
80
.04
90
80
.57
0.2
83
09
23
14
63
48
47
309
2Z
rc_5
0_0
66
0.5
50
.05
44
12
.79
0.3
67
85
2.8
90
.04
90
50
.69
0.2
53
09
23
18
83
88
61
309
2Z
rc_1
5_0
24
0.3
90
.05
27
32
.60
0.3
57
94
2.6
90
.04
92
10
.67
0.2
63
10
23
11
73
17
59
310
2Z
rc_3
5_0
48
0.5
10
.05
19
11
.60
0.3
53
81
1.7
00
.04
94
10
.59
0.3
43
11
23
08
52
81
36
311
2Z
rc_1
8_0
28
0.5
00
.05
12
01
.60
0.3
50
85
1.7
00
.04
96
00
.58
0.3
43
12
23
05
42
50
36
312
2Z
rc_2
6_0
38
0.6
10
.05
40
12
.50
0.3
68
69
2.6
00
.04
95
70
.73
0.2
83
12
23
19
73
71
56
312
2Z
rc_5
3_0
70
0.5
20
.05
21
31
.59
0.3
58
58
1.7
00
.04
98
30
.58
0.3
53
13
23
11
52
91
35
313
2Z
rc_8
1_1
04
0.3
90
.05
28
61
.89
0.3
65
16
1.9
90
.04
99
00
.60
0.3
23
14
23
16
53
23
42
314
2Z
rc_7
1_0
92
0.7
80
.05
19
71
.50
0.3
59
29
1.5
90
.05
00
30
.54
0.3
43
15
23
12
42
84
34
315
2Z
rc_0
1_0
08
0.4
40
.05
23
21
.80
0.3
62
58
1.9
30
.05
02
10
.70
0.3
63
16
23
14
52
99
43
316
2Z
rc_8
2_1
05
0.2
70
.05
34
72
.00
0.3
71
95
2.0
90
.05
03
60
.62
0.3
03
17
23
21
63
49
45
317
2Z
rc_2
1_0
32
0.5
20
.05
23
31
.80
0.3
61
50
3.0
00
.05
05
42
.39
0.8
03
18
73
13
83
00
40
318
7Z
rc_5
6_0
74
0.4
30
.05
56
81
.90
0.3
88
48
1.9
70
.05
05
40
.51
0.2
63
18
23
33
64
40
41
318
2Z
rc_5
9_0
77
0.3
50
.05
38
72
.41
0.3
75
36
2.7
80
.05
05
40
.77
0.3
53
18
23
24
83
66
53
318
2
Con
tinue
don
next
page
...
tablas geocronología u-pb 97
Tabl
a5
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apsa
mm
ite
TT-8
1.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_70
_09
00
.28
0.0
53
84
2.1
50
.37
51
92
.39
0.0
50
54
0.6
50
.31
31
82
32
37
36
44
831
82
Zrc
_93
_11
80
.45
0.0
52
89
1.8
00
.36
98
31
.90
0.0
50
64
0.5
90
.32
31
82
32
05
32
44
031
82
Zrc
_07
_01
50
.55
0.0
55
20
2.5
70
.39
13
22
.92
0.0
51
41
0.7
60
.38
32
32
33
58
42
05
732
32
Zrc
_91
_11
60
.33
0.0
54
03
1.7
00
.38
34
71
.78
0.0
51
42
0.5
30
.29
32
32
33
05
37
23
832
32
Zrc
_33
_04
60
.69
0.0
55
94
2.0
90
.39
99
12
.31
0.0
51
76
0.9
50
.42
32
53
34
27
45
04
632
53
Zrc
_41
_05
60
.72
0.0
53
70
1.8
10
.38
55
92
.00
0.0
51
98
0.8
80
.43
32
73
33
16
35
83
932
73
Zrc
_42
_05
70
.39
0.0
60
44
6.6
30
.43
57
16
.92
0.0
52
28
0.7
10
.13
32
92
36
72
16
20
14
13
29
2
Zrc
_61
_08
00
.33
0.0
57
08
2.5
90
.41
12
82
.73
0.0
52
28
0.8
40
.32
32
93
35
08
49
55
532
93
Zrc
_94
_11
90
.44
0.0
60
11
5.1
90
.47
21
17
.14
0.0
56
97
2.7
60
.68
35
71
03
93
23
60
71
12
357
10Z
rc_7
4_0
95
0.1
90
.05
78
81
.83
0.5
13
17
2.0
00
.06
43
00
.58
0.3
14
02
24
21
75
25
39
402
2Z
rc_3
2_0
45
1.2
10
.05
56
41
.20
0.5
61
24
1.3
10
.07
30
20
.52
0.3
94
54
24
52
54
38
26
454
2Z
rc_1
9_0
29
0.3
30
.06
29
11
.61
0.6
38
35
2.4
10
.07
33
01
.80
0.7
54
56
85
01
10
70
53
445
68
Zrc
_89
_11
30
.43
0.0
70
07
1.8
00
.77
36
23
.24
0.0
77
38
2.7
00
.83
48
01
35
82
14
93
03
64
80
13
Zrc
_45
_06
00
.26
0.0
56
89
1.3
00
.60
98
11
.41
0.0
77
57
0.5
40
.38
48
23
48
35
48
72
848
23
Zrc
_66
_08
60
.31
0.0
68
34
2.4
00
.80
17
74
.00
0.0
80
10
3.2
00
.80
49
71
55
98
18
87
94
84
97
15
Zrc
_69
_08
90
.24
0.0
63
60
1.7
90
.73
05
82
.11
0.0
81
11
1.1
00
.53
50
35
55
79
72
83
750
35
Zrc
_68
_08
80
.27
0.0
67
36
2.8
10
.78
27
83
.18
0.0
83
62
1.4
90
.47
51
87
58
71
48
49
57
51
87
Zrc
_43
_05
80
.19
0.0
58
97
1.4
90
.68
33
81
.57
0.0
83
91
0.4
60
.31
51
92
52
96
56
63
151
92
Con
tinue
don
next
page
...
tablas geocronología u-pb 98
Tabl
a5
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apsa
mm
ite
TT-8
1.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_16
_02
60
.88
0.0
59
09
1.6
90
.75
45
21
.79
0.0
92
49
0.5
50
.32
57
03
57
18
57
03
657
03
Zrc
_76
_09
80
.25
0.0
62
04
2.0
00
.84
77
72
.90
0.0
93
77
2.1
00
.72
57
81
26
23
14
67
64
257
812
Zrc
_60
_07
80
.18
0.0
67
70
1.3
01
.06
17
01
.59
0.1
13
01
0.9
20
.58
69
06
73
58
85
92
669
06
Zrc
_47
_06
30
.57
0.0
66
74
2.0
81
.18
94
42
.46
0.1
29
25
0.6
70
.41
78
45
79
61
48
30
42
784
5Z
rc_8
0_1
02
0.2
80
.07
04
51
.41
1.2
81
80
1.7
00
.13
08
50
.96
0.5
67
93
78
38
10
94
22
879
37
Zrc
_73
_09
40
.22
0.0
67
87
1.1
11
.25
74
01
.70
0.1
33
23
1.3
00
.76
80
61
08
27
10
86
52
280
610
Zrc
_10
_01
80
.05
0.0
72
58
0.9
91
.35
90
91
.11
0.1
35
82
0.5
20
.43
82
14
87
16
10
02
20
821
4Z
rc_3
1_0
44
0.3
90
.06
89
01
.20
1.3
38
10
1.3
10
.14
05
50
.52
0.3
98
48
48
62
88
96
24
848
4Z
rc_8
6_1
10
0.3
50
.06
94
91
.42
1.4
90
16
1.6
90
.15
55
40
.55
0.4
39
32
59
26
10
91
32
993
25
Zrc
_55
_07
20
.42
0.0
71
51
1.9
61
.60
30
42
.26
0.1
62
59
0.6
20
.37
97
16
97
11
49
72
39
971
6Z
rc_1
7_0
27
0.3
90
.07
31
41
.09
1.7
88
50
1.1
90
.17
70
70
.45
0.3
91
05
14
10
41
81
01
82
210
1822
Zrc
_13
_02
20
.35
0.0
73
65
1.4
01
.76
04
01
.52
0.1
73
11
0.5
90
.39
10
29
61
03
11
01
03
22
810
3228
Zrc
_39
_05
30
.26
0.0
74
16
1.2
91
.75
82
11
.60
0.1
71
96
0.6
20
.51
10
23
61
03
01
01
04
62
510
4625
Zrc
_49
_06
50
.32
0.0
75
08
1.2
01
.84
75
01
.35
0.1
77
78
0.6
10
.46
10
55
61
06
39
10
71
23
1071
23Z
rc_3
0_0
42
0.2
30
.07
65
11
.01
1.9
10
90
1.0
80
.18
06
90
.41
0.3
61
07
14
10
85
71
10
82
011
0820
Zrc
_96
_12
20
.37
0.0
78
10
1.2
01
.94
18
01
.48
0.1
79
28
0.8
70
.58
10
63
91
09
61
01
14
92
311
4923
Zrc
_10
0_1
26
0.1
00
.08
14
80
.99
1.8
95
50
1.1
10
.16
78
70
.48
0.4
41
00
04
10
80
71
23
31
912
3319
Zrc
_57
_07
50
.60
0.0
82
36
2.0
02
.33
51
02
.15
0.2
05
46
0.8
00
.37
12
05
91
22
31
51
25
43
812
5438
Con
tinue
don
next
page
...
tablas geocronología u-pb 99
Tabl
a5
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apsa
mm
ite
TT-8
1.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_25
_03
60
.30
0.0
82
99
1.1
02
.41
16
01
.18
0.2
10
17
0.4
40
.38
12
30
51
24
69
12
69
21
1269
21Z
rc_3
7_0
51
0.3
70
.08
93
31
.00
2.9
17
70
1.1
00
.23
62
50
.45
0.4
21
36
76
13
87
81
41
11
914
1119
Zrc
_46
_06
20
.92
0.1
09
79
0.9
64
.84
97
01
.09
0.3
19
58
0.5
10
.48
17
88
81
79
49
17
96
17
1796
17
Tabl
a6
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apel
ite
TT-8
2.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_19
_02
90
.07
0.0
51
17
1.5
00
.31
54
41
.56
0.0
44
70
0.4
30
.26
28
21
27
84
24
83
428
21
Zrc
_53
_07
20
.83
0.0
53
51
2.6
90
.33
30
12
.80
0.0
45
17
0.7
50
.28
28
52
29
27
35
06
028
52
Zrc
_14
_02
30
.89
0.0
53
08
1.8
10
.33
86
21
.88
0.0
46
28
0.5
60
.28
29
22
29
65
33
24
029
22
Zrc
_09
_01
70
.45
0.0
51
75
1.7
00
.33
43
11
.94
0.0
46
92
0.9
40
.48
29
63
29
35
27
43
829
63
Zrc
_99
_12
70
.64
0.0
55
70
3.5
90
.36
20
03
.85
0.0
47
13
0.6
20
.29
29
72
31
41
04
41
77
297
2Z
rc_3
3_0
48
1.0
90
.05
31
41
.39
0.3
47
30
1.4
50
.04
73
90
.38
0.2
92
98
13
03
43
35
31
298
1Z
rc_9
7_1
25
0.7
10
.05
28
81
.70
0.3
46
72
1.7
80
.04
75
20
.53
0.2
92
99
23
02
53
24
37
299
2Z
rc_3
7_0
53
0.7
90
.05
28
52
.50
0.3
46
77
2.5
90
.04
77
00
.67
0.2
63
00
23
02
73
22
56
300
2Z
rc_9
3_1
20
0.3
70
.05
42
02
.90
0.3
57
77
3.0
00
.04
78
60
.75
0.2
63
01
23
11
83
79
63
301
2
Con
tinue
don
next
page
...
tablas geocronología u-pb 100
Tabl
a6
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apel
ite
TT-8
2.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_77
_10
10
.77
0.0
54
44
1.5
10
.36
05
01
.56
0.0
47
98
0.4
20
.25
30
21
31
34
38
93
430
21
Zrc
_40
_05
60
.47
0.0
51
43
2.5
10
.34
07
22
.58
0.0
48
05
0.6
20
.23
30
32
29
87
26
05
730
32
Zrc
_13
_02
20
.44
0.0
52
81
2.4
00
.35
09
32
.47
0.0
48
26
0.5
80
.23
30
42
30
57
32
15
330
42
Zrc
_69
_09
10
.58
0.0
52
23
1.9
00
.34
73
11
.98
0.0
48
21
0.5
60
.29
30
42
30
35
29
54
230
42
Zrc
_68
_09
00
.39
0.0
52
79
2.6
00
.35
25
62
.71
0.0
48
53
0.7
60
.29
30
52
30
77
32
05
730
52
Zrc
_79
_10
30
.68
0.0
52
98
1.7
00
.35
57
51
.76
0.0
48
68
0.4
50
.26
30
61
30
95
32
83
930
61
Zrc
_25
_03
80
.62
0.0
55
21
3.1
00
.36
98
13
.19
0.0
48
76
0.7
60
.24
30
72
32
09
42
16
730
72
Zrc
_73
_09
60
.60
0.0
53
06
2.6
00
.35
83
62
.70
0.0
49
12
0.7
10
.26
30
92
31
17
33
15
930
92
Zrc
_87
_11
30
.83
0.0
52
83
1.5
00
.35
78
21
.56
0.0
49
07
0.4
30
.28
30
91
31
14
32
23
430
91
Zrc
_65
_08
60
.91
0.0
54
56
1.7
00
.37
16
01
.78
0.0
49
34
0.5
10
.28
31
02
32
15
39
43
731
02
Zrc
_23
_03
60
.62
0.0
57
01
4.1
40
.39
52
44
.41
0.0
50
28
0.5
60
.26
31
62
33
81
34
92
89
316
2Z
rc_5
2_0
71
0.5
70
.05
61
41
.91
0.3
89
37
1.9
60
.05
03
60
.48
0.2
33
17
13
34
64
58
42
317
1Z
rc_9
2_1
19
0.4
90
.05
44
71
.60
0.3
78
27
1.6
50
.05
03
70
.42
0.2
63
17
13
26
53
91
35
317
1Z
rc_1
6_0
26
0.7
10
.05
57
74
.27
0.4
04
19
4.6
70
.05
25
60
.80
0.2
43
30
33
45
14
44
39
233
03
Zrc
_78
_10
20
.42
0.0
53
71
1.9
90
.38
89
52
.07
0.0
52
49
0.5
30
.28
33
02
33
46
35
94
533
02
Zrc
_70
_09
20
.87
0.0
58
08
2.7
00
.42
25
13
.03
0.0
52
76
0.5
90
.24
33
12
35
89
53
35
833
12
Zrc
_80
_10
40
.44
0.0
73
03
2.6
20
.53
70
42
.96
0.0
53
33
0.8
30
.41
33
53
43
61
01
01
55
33
35
3
Zrc
_98
_12
60
.93
0.0
51
58
2.0
00
.38
06
12
.07
0.0
53
54
0.5
20
.26
33
62
32
76
26
74
433
62
Con
tinue
don
next
page
...
tablas geocronología u-pb 101
Tabl
a6
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apel
ite
TT-8
2.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_67
_08
90
.60
0.0
55
89
1.8
10
.41
57
71
.87
0.0
53
69
0.5
00
.26
33
72
35
36
44
83
933
72
Zrc
_75
_09
80
.75
0.0
54
34
2.1
00
.40
56
12
.16
0.0
54
08
0.5
20
.24
34
02
34
66
38
54
734
02
Zrc
_47
_06
50
.08
0.0
52
53
1.4
10
.39
52
61
.45
0.0
54
55
0.3
80
.24
34
21
33
84
30
93
234
21
Zrc
_64
_08
50
.49
0.0
55
12
2.0
00
.41
85
82
.23
0.0
54
85
0.9
80
.44
34
43
35
57
41
74
334
43
Zrc
_27
_04
10
.76
0.0
54
56
2.1
10
.42
41
12
.37
0.0
56
05
1.1
10
.46
35
24
35
97
39
44
635
24
Zrc
_63
_08
40
.62
0.0
56
49
2.8
00
.45
35
32
.88
0.0
57
78
0.6
70
.24
36
22
38
09
47
26
036
22
Zrc
_88
_11
40
.24
0.0
54
87
1.2
90
.46
72
41
.40
0.0
61
60
0.5
00
.37
38
52
38
95
40
72
938
52
Zrc
_57
_07
70
.35
0.0
58
98
2.1
00
.58
51
33
.04
0.0
69
04
2.2
00
.72
43
09
46
81
15
66
45
430
9Z
rc_4
5_0
62
0.8
30
.05
60
31
.61
0.5
85
22
1.6
70
.07
57
20
.48
0.2
74
71
24
68
64
54
35
471
2Z
rc_4
2_0
59
0.2
40
.05
63
61
.40
0.5
96
44
1.4
60
.07
67
00
.40
0.2
74
76
24
75
64
67
31
476
2Z
rc_0
6_0
14
0.3
10
.05
87
31
.80
0.6
43
66
1.8
70
.07
95
30
.49
0.2
54
93
25
05
75
57
38
493
2Z
rc_2
2_0
35
0.6
80
.05
80
11
.40
0.6
84
03
1.4
70
.08
54
70
.44
0.3
15
29
25
29
65
30
30
529
2Z
rc_2
1_0
34
0.4
10
.05
87
81
.80
0.6
96
53
1.8
50
.08
59
70
.43
0.2
25
32
25
37
85
59
38
532
2Z
rc_1
0_0
18
0.3
70
.05
84
11
.51
0.6
97
67
1.6
80
.08
63
90
.75
0.4
45
34
45
37
75
45
32
534
4Z
rc_0
8_0
16
0.3
60
.07
08
52
.10
0.8
46
27
2.3
90
.08
66
30
.70
0.3
45
36
46
23
11
95
34
25
36
4
Zrc
_36
_05
20
.41
0.0
64
99
1.4
90
.80
32
01
.86
0.0
88
11
1.1
00
.60
54
46
59
98
77
43
154
46
Zrc
_18
_02
81
.01
0.0
59
62
1.3
90
.74
14
51
.53
0.0
89
94
0.6
30
.42
55
53
56
37
59
02
955
53
Zrc
_34
_04
90
.38
0.0
59
90
1.9
00
.76
13
71
.95
0.0
92
33
0.4
30
.21
56
92
57
59
60
04
156
92
Con
tinue
don
next
page
...
tablas geocronología u-pb 102
Tabl
a6
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apel
ite
TT-8
2.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_05
_01
20
.35
0.0
60
38
1.7
10
.89
49
01
.77
0.1
07
54
0.5
10
.28
65
83
64
99
61
73
665
83
Zrc
_11
_02
00
.03
0.0
61
23
1.3
10
.94
42
71
.35
0.1
11
80
0.3
60
.25
68
32
67
57
64
72
768
32
Zrc
_91
_11
80
.97
0.0
61
69
1.3
00
.95
91
41
.38
0.1
12
67
0.4
50
.33
68
83
68
37
66
32
768
83
Zrc
_43
_06
00
.67
0.0
62
29
1.6
11
.01
45
01
.68
0.1
18
17
0.5
10
.29
72
03
71
19
68
43
472
03
Zrc
_03
_01
00
.40
0.0
66
63
2.0
01
.28
23
02
.09
0.1
39
42
0.6
00
.29
84
15
83
81
28
26
40
841
5Z
rc_3
1_0
46
0.3
30
.06
99
02
.40
1.4
50
90
2.5
50
.15
05
00
.85
0.3
39
04
79
10
15
92
54
990
47
Zrc
_83
_10
80
.06
0.0
72
80
1.3
01
.51
86
01
.36
0.1
51
15
0.4
00
.28
90
73
93
88
10
08
26
907
3Z
rc_6
0_0
80
0.3
10
.06
94
51
.50
1.4
95
30
1.5
60
.15
60
50
.44
0.2
99
35
49
28
10
91
23
093
54
Zrc
_02
_00
90
.27
0.0
69
11
1.7
91
.50
93
01
.92
0.1
58
40
0.6
60
.35
94
86
93
41
29
02
36
948
6Z
rc_9
4_1
21
0.4
50
.06
99
01
.40
1.5
90
10
1.4
50
.16
48
00
.38
0.2
69
83
39
66
99
25
28
983
3Z
rc_7
1_0
94
0.2
30
.07
23
81
.20
1.7
77
00
1.2
90
.17
77
20
.46
0.3
51
05
54
10
37
89
97
24
997
24Z
rc_5
5_0
74
0.4
10
.07
26
01
.50
1.8
06
90
1.5
80
.18
02
90
.51
0.3
21
06
95
10
48
10
10
03
30
1003
30Z
rc_7
2_0
95
0.2
40
.07
30
51
.40
1.8
32
10
1.4
70
.18
18
80
.45
0.3
11
07
74
10
57
10
10
15
27
1015
27Z
rc_3
0_0
44
0.5
70
.07
31
01
.50
1.9
50
00
1.5
70
.19
33
60
.46
0.2
81
14
05
10
98
11
10
17
30
1017
30Z
rc_3
9_0
55
0.3
40
.07
33
71
.89
1.7
76
80
2.0
00
.17
58
80
.62
0.3
21
04
46
10
37
13
10
24
38
1024
38Z
rc_4
4_0
61
0.3
00
.07
33
81
.70
1.8
69
50
1.7
70
.18
47
70
.48
0.2
61
09
35
10
70
12
10
24
34
1024
34Z
rc_3
5_0
50
0.2
40
.07
33
91
.40
1.8
03
10
1.4
80
.17
83
70
.48
0.3
21
05
85
10
47
10
10
25
28
1025
28Z
rc_5
9_0
79
0.3
50
.07
35
31
.50
1.8
08
20
1.5
60
.17
81
10
.43
0.2
91
05
74
10
48
10
10
29
30
1029
30
Con
tinue
don
next
page
...
tablas geocronología u-pb 103
Tabl
a6
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apel
ite
TT-8
2.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_54
_07
30
.37
0.0
73
74
1.5
11
.85
49
01
.56
0.1
82
38
0.4
40
.27
10
80
41
06
51
01
03
43
010
3430
Zrc
_04
_01
10
.34
0.0
73
97
1.7
01
.86
69
01
.81
0.1
82
75
0.6
10
.33
10
82
61
06
91
21
04
13
310
4133
Zrc
_29
_04
30
.28
0.0
74
00
1.5
01
.82
73
01
.56
0.1
79
06
0.4
30
.28
10
62
41
05
51
01
04
12
910
4129
Zrc
_85
_11
00
.37
0.0
74
02
1.5
01
.66
50
01
.58
0.1
63
03
0.5
00
.32
97
45
99
51
01
04
23
010
4230
Zrc
_46
_06
40
.37
0.0
74
28
1.6
01
.87
25
01
.68
0.1
82
53
0.5
20
.31
10
81
51
07
11
11
04
93
210
4932
Zrc
_10
0_1
28
0.1
80
.07
42
91
.31
1.8
22
90
1.3
50
.17
77
20
.37
0.2
61
05
54
10
54
91
04
92
510
4925
Zrc
_76
_10
00
.26
0.0
74
46
1.4
01
.81
37
01
.51
0.1
76
51
0.5
70
.38
10
48
61
05
01
01
05
42
810
5428
Zrc
_07
_01
50
.26
0.0
74
59
1.6
01
.83
18
01
.71
0.1
78
14
0.6
00
.36
10
57
61
05
71
11
05
73
110
5731
Zrc
_96
_12
40
.48
0.0
74
87
1.5
01
.95
14
01
.57
0.1
88
67
0.4
80
.31
11
14
51
09
91
11
06
52
910
6529
Zrc
_15
_02
40
.14
0.0
75
03
1.3
12
.06
56
01
.37
0.1
99
65
0.4
40
.31
11
73
51
13
79
10
69
26
1069
26Z
rc_0
1_0
08
0.2
80
.07
62
11
.40
2.0
55
60
1.4
60
.19
56
50
.42
0.2
81
15
24
11
34
10
11
01
27
1101
27Z
rc_4
8_0
66
0.6
40
.07
71
41
.59
2.0
20
90
1.6
80
.18
98
90
.51
0.3
11
12
15
11
23
11
11
25
32
1125
32Z
rc_2
4_0
37
0.3
80
.07
74
01
.78
1.9
73
96
1.9
80
.18
49
60
.49
0.3
41
09
45
11
07
13
11
32
34
1132
34Z
rc_3
2_0
47
0.3
80
.07
75
01
.30
2.1
12
10
1.3
90
.19
75
90
.49
0.3
51
16
25
11
53
10
11
34
26
1134
26Z
rc_1
7_0
27
0.3
90
.07
75
41
.70
2.1
15
60
1.7
70
.19
78
20
.50
0.2
81
16
45
11
54
12
11
35
33
1135
33Z
rc_4
9_0
67
0.3
30
.07
78
21
.40
2.1
40
40
1.4
50
.19
92
30
.39
0.2
71
17
14
11
62
10
11
42
28
1142
28Z
rc_4
1_0
58
0.4
30
.07
80
51
.40
2.1
89
60
1.4
60
.20
34
30
.43
0.3
01
19
45
11
78
10
11
48
27
1148
27Z
rc_5
6_0
76
0.5
10
.07
82
41
.30
2.1
63
20
1.3
50
.20
03
10
.38
0.2
71
17
74
11
69
91
15
32
611
5326
Con
tinue
don
next
page
...
tablas geocronología u-pb 104
Tabl
a6
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apel
ite
TT-8
2.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_62
_08
30
.47
0.0
78
33
1.4
02
.20
26
01
.47
0.2
03
82
0.4
40
.29
11
96
51
18
21
01
15
52
711
5527
Zrc
_12
_02
10
.26
0.0
78
68
1.3
02
.19
53
01
.37
0.2
02
32
0.4
30
.32
11
88
51
18
01
01
16
42
511
6425
Zrc
_38
_05
40
.39
0.0
78
69
1.5
02
.17
29
01
.56
0.2
00
03
0.4
10
.26
11
75
41
17
21
11
16
42
911
6429
Zrc
_66
_08
80
.31
0.0
78
70
1.3
02
.27
64
01
.35
0.2
09
49
0.3
60
.28
12
26
41
20
51
01
16
52
511
6525
Zrc
_86
_11
20
.29
0.0
79
59
1.2
92
.22
04
01
.36
0.2
01
87
0.4
10
.31
11
85
41
18
71
01
18
72
611
8726
Zrc
_28
_04
20
.33
0.0
80
41
1.8
02
.29
12
01
.88
0.2
05
96
0.5
50
.29
12
07
61
21
01
31
20
73
512
0735
Zrc
_50
_06
80
.30
0.0
80
71
1.3
02
.44
49
01
.39
0.2
19
48
0.4
90
.35
12
79
61
25
61
01
21
42
512
1425
Zrc
_51
_07
00
.27
0.0
81
67
1.8
02
.41
27
01
.89
0.2
14
20
0.5
70
.30
12
51
61
24
61
41
23
83
512
3835
Zrc
_61
_08
20
.26
0.0
81
68
1.3
02
.53
49
01
.36
0.2
25
02
0.4
00
.30
13
08
51
28
21
01
23
82
512
3825
Zrc
_74
_09
70
.26
0.0
82
29
1.4
02
.50
11
01
.46
0.2
20
14
0.4
10
.29
12
83
51
27
21
11
25
22
712
5227
Zrc
_82
_10
70
.18
0.0
82
43
1.3
02
.48
27
01
.63
0.2
17
78
0.9
80
.60
12
70
11
12
67
12
12
56
25
1256
25Z
rc_9
0_1
16
0.5
20
.08
38
21
.40
2.3
88
40
1.4
70
.20
64
30
.45
0.3
11
21
05
12
39
11
12
88
26
1288
26Z
rc_9
5_1
22
0.4
20
.08
50
41
.51
2.7
68
00
1.5
70
.23
59
80
.48
0.2
91
36
66
13
47
12
13
16
28
1316
28Z
rc_8
1_1
06
0.3
50
.08
60
81
.41
2.7
71
00
1.4
90
.23
33
40
.52
0.3
41
35
26
13
48
11
13
40
27
1340
27Z
rc_2
6_0
40
0.4
30
.09
43
61
.20
3.5
92
80
1.2
80
.27
65
20
.44
0.3
51
57
46
15
48
10
15
15
22
1515
22Z
rc_5
8_0
78
0.8
90
.09
61
51
.30
3.8
26
70
1.3
60
.28
84
20
.41
0.3
01
63
46
15
98
11
15
51
24
1551
24Z
rc_8
9_1
15
0.1
70
.13
69
11
.20
7.9
07
40
1.2
50
.41
83
50
.36
0.2
92
25
37
22
21
11
21
88
20
2188
20Z
rc_2
0_0
30
0.4
70
.17
66
31
.30
12
.36
60
01
.36
0.5
07
43
0.3
90
.28
26
46
82
63
31
32
62
12
126
2121
tablas geocronología u-pb 105
Tabl
a7
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apsa
mm
ite
TT-6
12
.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_72
_09
30
.21
0.0
53
89
1.2
10
.33
88
51
.27
0.0
45
84
0.4
80
.32
28
91
29
63
36
62
528
91
Zrc
_16
_02
60
.20
0.0
55
18
2.5
90
.35
04
22
.63
0.0
46
27
1.6
20
.18
29
21
30
57
42
05
729
21
Zrc
_04
_01
10
.36
0.0
57
27
4.3
00
.36
89
74
.33
0.0
46
85
1.6
60
.12
29
51
31
91
25
02
95
295
1Z
rc_4
6_0
62
0.2
80
.05
42
91
.81
0.3
56
68
1.8
70
.04
78
80
.52
0.2
63
01
13
10
53
83
41
301
1Z
rc_7
5_0
96
0.5
80
.05
63
32
.70
0.3
70
81
2.7
80
.04
79
50
.60
0.2
43
02
23
20
84
65
56
302
2Z
rc_3
8_0
52
0.5
00
.05
77
84
.29
0.3
81
98
4.3
40
.04
80
90
.77
0.1
53
03
23
28
12
52
19
530
32
Zrc
_54
_07
10
.44
0.0
58
99
3.3
10
.38
84
53
.36
0.0
48
08
0.6
20
.18
30
32
33
31
05
67
72
303
2Z
rc_3
0_0
42
0.4
60
.05
98
35
.20
0.3
97
36
5.2
50
.04
82
31
.22
0.1
43
04
23
40
15
59
71
12
30
42
Zrc
_53
_07
00
.64
0.0
53
65
1.3
00
.35
67
81
.36
0.0
48
45
0.4
30
.29
30
51
31
04
35
62
930
51
Zrc
_71
_09
20
.49
0.0
57
18
3.3
90
.37
90
93
.45
0.0
48
56
0.6
80
.18
30
62
32
61
04
99
70
306
2Z
rc_9
0_1
14
0.8
90
.05
73
42
.30
0.3
82
20
2.3
40
.04
86
50
.49
0.1
93
06
13
29
75
05
47
306
1Z
rc_6
5_0
84
0.8
40
.05
54
51
.70
0.3
71
43
1.7
80
.04
88
50
.41
0.3
03
07
23
21
54
30
35
307
2Z
rc_1
8_0
28
0.8
00
.05
61
72
.71
0.3
77
13
2.7
30
.04
89
60
.47
0.1
43
08
13
25
84
59
59
308
1Z
rc_5
5_0
72
0.5
80
.05
63
42
.59
0.3
77
82
2.6
60
.04
88
60
.51
0.2
33
08
23
25
74
66
58
308
2Z
rc_7
0_0
90
0.9
40
.05
37
21
.51
0.3
61
64
1.5
80
.04
91
00
.45
0.3
03
09
23
13
43
59
32
309
2Z
rc_8
5_1
08
0.9
50
.05
60
61
.80
0.3
76
98
1.8
50
.04
90
90
.45
0.2
23
09
13
25
54
55
37
309
1Z
rc_8
2_1
05
0.3
00
.05
50
41
.71
0.3
71
61
1.7
70
.04
92
00
.53
0.2
53
10
13
21
54
14
36
310
1Z
rc_9
_01
70
.69
0.0
56
49
2.0
00
.38
19
72
.05
0.0
49
32
0.4
90
.22
31
01
32
86
47
24
131
01
Con
tinue
don
next
page
...
tablas geocronología u-pb 106
Tabl
a7
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apsa
mm
ite
TT-6
12
.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_96
_12
20
.87
0.0
54
27
1.3
10
.36
64
81
.38
0.0
49
21
0.3
90
.31
31
01
31
74
38
22
731
01
Zrc
_3_0
10
0.8
40
.05
93
72
.80
0.4
04
03
2.8
50
.04
94
81
.52
0.2
03
11
23
45
85
81
60
311
2Z
rc_3
5_0
48
0.7
20
.06
16
69
.78
0.4
19
89
10
.40
0.0
49
39
0.3
40
.14
31
13
35
63
16
62
21
63
11
3
Zrc
_17
_02
70
.41
0.0
58
18
2.7
00
.39
69
62
.76
0.0
49
73
0.6
40
.21
31
32
33
98
53
75
831
32
Zrc
_27
_03
90
.73
0.0
55
89
1.5
00
.38
22
31
.56
0.0
49
83
0.4
20
.26
31
31
32
94
44
83
331
31
Zrc
_05
_01
20
.41
0.0
58
60
3.6
00
.40
37
93
.67
0.0
50
14
1.1
80
.19
31
52
34
41
15
52
79
315
2Z
rc_0
8_0
16
0.8
20
.06
04
62
.50
0.4
17
20
2.5
60
.05
01
00
.96
0.2
13
15
23
54
86
20
50
31
52
Zrc
_29
_04
10
.64
0.0
58
62
3.5
10
.40
48
13
.84
0.0
50
09
0.2
00
.22
31
52
34
51
15
53
71
315
2Z
rc_1
0_0
18
0.4
70
.05
42
91
.60
0.3
74
29
1.6
90
.05
01
60
.50
0.3
23
16
23
23
53
83
35
316
2Z
rc_4
8_0
64
0.5
70
.05
87
23
.00
0.4
05
09
3.0
70
.05
02
10
.68
0.2
23
16
23
45
95
57
66
316
2Z
rc_5
6_0
74
0.4
80
.06
27
14
.10
0.4
32
88
4.1
50
.05
02
51
.23
0.1
63
16
23
65
13
69
88
13
16
2
Zrc
_14
_02
30
.54
0.0
57
46
3.1
00
.39
80
63
.14
0.0
50
55
0.7
70
.17
31
82
34
09
50
96
731
82
Zrc
_66
_08
60
.58
0.0
60
54
3.0
40
.42
15
43
.38
0.0
50
50
0.2
00
.28
31
82
35
71
06
23
61
31
82
Zrc
_57
_07
50
.48
0.0
56
53
2.0
00
.39
30
22
.09
0.0
50
65
0.6
70
.29
31
92
33
76
47
34
131
92
Zrc
_76
_09
80
.66
0.0
54
42
1.4
00
.37
88
71
.46
0.0
50
81
0.4
10
.30
31
91
32
64
38
82
931
91
Zrc
_31
_04
40
.83
0.0
55
24
1.5
00
.39
01
91
.56
0.0
51
53
0.4
10
.26
32
41
33
54
42
23
432
41
Zrc
_58
_07
61
.08
0.0
58
31
1.7
00
.41
37
71
.85
0.0
51
76
0.6
60
.40
32
52
35
26
54
13
532
52
Zrc
_59
_07
70
.79
0.0
53
39
1.5
90
.37
96
11
.67
0.0
51
88
0.4
40
.30
32
61
32
75
34
53
432
61
Con
tinue
don
next
page
...
tablas geocronología u-pb 107
Tabl
a7
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apsa
mm
ite
TT-6
12
.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_50
_06
60
.17
0.0
54
92
2.0
20
.40
18
32
.27
0.0
53
07
0.2
30
.37
33
32
34
37
40
94
633
32
Zrc
_81
_10
40
.59
0.0
60
33
2.7
00
.44
03
62
.79
0.0
53
21
0.6
00
.24
33
42
37
19
61
55
433
42
Zrc
_78
_10
00
.37
0.0
57
69
1.9
90
.43
18
22
.07
0.0
54
58
0.6
80
.27
34
32
36
46
51
84
134
32
Zrc
_02
_00
90
.07
0.0
57
68
3.6
90
.43
40
93
.76
0.0
54
86
3.7
40
.19
34
42
36
61
25
18
80
344
2Z
rc_2
8_0
40
0.1
80
.05
83
12
.09
0.5
43
41
2.1
60
.06
79
00
.87
0.2
54
23
24
41
85
41
45
423
2Z
rc_6
3_0
82
0.8
00
.05
85
11
.01
0.6
06
60
1.0
80
.07
55
30
.38
0.3
74
69
24
81
45
49
20
469
2Z
rc_2
1_0
32
0.6
80
.05
95
71
.49
0.6
68
55
1.5
80
.08
16
60
.47
0.3
35
06
25
20
65
88
32
506
2Z
rc_8
6_1
10
0.1
70
.05
80
11
.29
0.6
49
89
1.3
80
.08
16
80
.59
0.3
45
06
25
08
65
30
26
506
2Z
rc_9
1_1
16
0.8
60
.06
14
21
.81
0.7
33
27
1.8
90
.08
70
30
.47
0.3
05
38
35
58
86
54
36
538
3Z
rc_4
0_0
54
0.1
70
.06
38
42
.30
0.8
39
05
2.3
60
.09
58
21
.34
0.2
15
90
36
19
11
73
64
959
03
Zrc
_97
_12
30
.95
0.0
63
20
2.1
00
.83
16
52
.19
0.0
96
25
0.4
70
.28
59
24
61
51
07
15
41
592
4Z
rc_4
5_0
60
0.8
60
.06
12
10
.78
0.8
19
20
0.9
70
.09
74
10
.40
0.5
95
99
36
08
46
47
17
599
3Z
rc_1
9_0
29
0.9
30
.06
05
81
.40
0.8
18
73
1.4
60
.09
84
60
.58
0.2
86
05
26
07
76
24
30
605
2Z
rc_3
9_0
53
0.1
40
.06
07
71
.00
0.8
26
30
1.0
70
.09
89
40
.59
0.3
46
08
26
12
56
31
22
608
2Z
rc_7
4_0
95
1.1
00
.06
20
81
.30
0.8
58
90
1.3
80
.10
09
20
.41
0.3
26
20
36
30
66
77
26
620
3Z
rc_0
1_0
08
0.8
10
.06
15
51
.80
0.8
65
68
1.8
60
.10
23
40
.43
0.2
36
28
36
33
96
59
38
628
3Z
rc_4
4_0
59
0.1
60
.07
16
81
.31
1.1
61
40
1.8
80
.11
75
20
.32
0.6
77
16
77
83
10
97
72
771
67
Zrc
_84
_10
70
.47
0.0
65
05
0.8
11
.05
84
00
.92
0.1
18
45
0.4
10
.46
72
23
73
35
77
61
672
23
Con
tinue
don
next
page
...
tablas geocronología u-pb 108
Tabl
a7
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apsa
mm
ite
TT-6
12
.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_61
_08
00
.42
0.0
65
32
2.0
11
.09
07
02
.07
0.1
21
69
0.4
40
.25
74
04
74
91
17
85
39
740
4Z
rc_9
5_1
20
0.0
90
.07
17
20
.73
1.5
63
30
0.8
40
.15
88
30
.51
0.5
09
50
49
56
59
78
14
950
4Z
rc_3
4_0
47
0.1
80
.07
14
70
.80
1.5
97
00
1.1
00
.16
25
30
.70
0.6
99
71
79
69
79
71
16
971
7Z
rc_2
2_0
33
0.2
70
.07
30
20
.97
1.8
31
30
1.0
70
.18
24
60
.42
0.4
21
08
04
10
57
71
01
51
910
1519
Zrc
_77
_09
90
.34
0.0
73
04
1.0
01
.67
33
01
.10
0.1
66
88
0.4
10
.42
99
54
99
87
10
15
19
1015
19Z
rc_1
00
_12
60
.29
0.0
73
65
1.1
01
.74
53
01
.18
0.1
72
76
0.4
00
.37
10
27
41
02
58
10
32
22
1032
22Z
rc_8
0_1
02
0.6
00
.07
36
90
.83
1.7
39
70
0.9
00
.17
20
40
.37
0.4
01
02
33
10
23
61
03
31
610
3316
Zrc
_87
_11
10
.17
0.0
74
70
3.7
61
.65
14
83
.97
0.1
60
35
0.2
30
.21
95
96
99
02
51
06
07
010
6070
Zrc
_49
_06
50
.29
0.0
74
86
1.4
01
.84
82
01
.46
0.1
79
87
0.5
30
.28
10
66
41
06
31
01
06
52
810
6528
Zrc
_89
_11
30
.08
0.0
75
11
0.6
71
.74
22
30
.80
0.1
68
23
0.1
20
.52
10
02
41
02
45
10
71
12
1071
12Z
rc_3
6_0
50
0.2
50
.07
54
21
.50
1.8
51
00
1.7
00
.17
85
90
.60
0.4
81
05
98
10
64
11
10
80
30
1080
30Z
rc_1
1_0
20
0.4
00
.07
56
21
.90
1.6
77
20
1.9
40
.16
15
80
.58
0.1
99
66
31
00
01
21
08
53
810
8538
Zrc
_07
_01
50
.25
0.0
76
34
0.8
12
.05
10
00
.92
0.1
95
39
0.4
40
.46
11
51
51
13
36
11
04
15
1104
15Z
rc_9
3_1
18
0.1
90
.07
64
51
.50
1.8
84
60
1.5
80
.18
00
00
.67
0.3
11
06
75
10
76
11
11
07
28
1107
28Z
rc_9
9_1
25
0.0
80
.07
66
14
.33
1.6
92
31
4.6
50
.16
02
20
.37
0.2
59
58
81
00
63
01
11
18
011
1180
Zrc
_62
_08
10
.30
0.0
76
67
1.7
01
.91
84
01
.77
0.1
82
39
0.5
80
.29
10
80
51
08
81
21
11
33
211
1332
Zrc
_69
_08
90
.27
0.0
76
79
0.7
61
.85
84
00
.92
0.1
76
28
0.3
90
.57
10
47
51
06
66
11
16
14
1116
14Z
rc_3
7_0
51
0.5
60
.07
69
11
.00
2.0
36
80
1.0
90
.19
27
50
.40
0.3
91
13
64
11
28
71
11
92
011
1920
Con
tinue
don
next
page
...
tablas geocronología u-pb 109
Tabl
a7
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apsa
mm
ite
TT-6
12
.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_06
_01
40
.44
0.0
77
45
1.3
91
.93
08
01
.51
0.1
81
42
0.6
00
.39
10
75
61
09
21
01
13
32
611
3326
Zrc
_92
_11
70
.26
0.0
77
64
1.8
01
.91
53
01
.90
0.1
79
86
0.7
20
.32
10
66
61
08
61
31
13
83
311
3833
Zrc
_25
_03
60
.14
0.0
77
95
1.1
02
.06
24
01
.16
0.1
92
70
1.3
60
.32
11
36
41
13
68
11
46
22
1146
22Z
rc_8
3_1
06
0.3
90
.07
80
91
.10
1.8
55
20
1.1
70
.17
29
80
.40
0.3
41
02
94
10
65
81
14
92
011
4920
Zrc
_68
_08
80
.31
0.0
78
36
1.6
01
.98
34
01
.67
0.1
84
31
0.7
40
.30
10
90
51
11
01
11
15
62
911
5629
Zrc
_15
_02
40
.14
0.0
78
68
1.1
92
.22
34
01
.28
0.2
05
89
0.8
60
.36
12
07
51
18
89
11
64
23
1164
23Z
rc_2
6_0
38
0.7
70
.07
88
90
.99
2.1
62
10
1.0
60
.19
93
60
.37
0.3
71
17
24
11
69
71
16
91
911
6919
Zrc
_41
_05
60
.69
0.0
80
34
1.1
02
.24
59
01
.18
0.2
03
70
0.4
80
.37
11
95
51
19
68
12
05
22
1205
22Z
rc_5
2_0
69
0.2
10
.08
03
60
.71
2.3
20
90
0.8
10
.21
01
30
.38
0.4
81
23
04
12
19
61
20
61
412
0614
Zrc
_13
_02
20
.32
0.0
80
93
0.8
02
.33
51
00
.88
0.2
09
85
0.3
70
.41
12
28
41
22
36
12
20
16
1220
16Z
rc_2
4_0
35
1.2
50
.08
11
81
.40
2.3
07
70
1.4
90
.20
68
10
.36
0.3
31
21
26
12
15
11
12
26
27
1226
27Z
rc_5
1_0
68
0.3
00
.08
14
90
.99
2.1
99
90
1.0
90
.19
66
00
.43
0.4
11
15
75
11
81
81
23
32
012
3320
Zrc
_79
_10
10
.27
0.0
81
64
0.7
52
.46
65
00
.84
0.2
20
16
0.3
70
.46
12
83
41
26
26
12
37
14
1237
14Z
rc_4
2_0
57
0.4
60
.08
32
01
.90
2.3
57
50
1.9
60
.20
63
20
.66
0.2
61
20
96
12
30
14
12
74
37
1274
37Z
rc_9
4_1
19
0.3
20
.08
33
11
.30
2.4
85
07
1.6
00
.21
63
40
.17
0.5
21
26
27
12
68
12
12
77
23
1277
23Z
rc_6
7_0
87
0.3
90
.08
67
11
.20
2.7
58
30
1.2
90
.23
16
40
.42
0.3
71
34
36
13
44
10
13
54
22
1354
22Z
rc_2
3_0
34
0.1
60
.08
70
70
.88
2.9
60
60
0.9
80
.24
75
40
.52
0.4
31
42
65
13
98
71
36
21
713
6217
Zrc
_60
_07
80
.29
0.0
88
38
1.1
02
.94
34
01
.20
0.2
42
81
0.6
00
.40
14
01
61
39
39
13
91
20
1391
20
Con
tinue
don
next
page
...
tablas geocronología u-pb 110
Tabl
a7
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
met
apsa
mm
ite
TT-6
12
.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_43
_05
80
.58
0.0
97
20
0.6
93
.75
43
00
.78
0.2
81
04
0.3
50
.46
15
97
51
58
36
15
71
13
1571
13Z
rc_6
4_0
83
0.4
00
.09
76
40
.76
3.5
53
00
0.9
40
.26
50
80
.43
0.5
91
51
67
15
39
71
58
01
315
8013
Zrc
_47
_06
30
.36
0.1
12
27
0.8
05
.04
42
00
.94
0.3
26
37
0.3
70
.53
18
21
81
82
78
18
36
15
1836
15Z
rc_3
2_0
45
0.1
80
.13
57
30
.71
5.9
67
11
0.9
60
.31
88
40
.16
0.6
41
78
49
19
71
82
17
31
221
7312
Zrc
_98
_12
40
.48
0.1
86
09
0.7
21
2.1
05
00
0.9
10
.47
39
80
.36
0.6
12
50
11
22
61
39
27
08
11
2708
11
Tabl
a8
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
gran
ite
dike
TT-6
15
.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_24
_03
50
.46
0.0
61
40
2.3
10
.38
56
02
.57
0.0
45
55
0.5
30
.40
28
71
33
17
65
34
82
87
1
Zrc
_6_0
14
0.7
40
.05
49
71
.80
0.3
49
50
1.8
70
.04
60
70
.50
0.2
72
90
13
04
54
11
36
290
1Z
rc_3
1_0
44
0.5
20
.06
01
71
.65
0.3
83
66
2.0
10
.04
62
50
.65
0.4
32
91
23
30
66
10
35
29
12
Zrc
_36
_05
00
.26
0.0
55
40
2.4
70
.35
68
02
.69
0.0
46
71
0.6
40
.30
29
42
31
07
42
85
529
42
Zrc
_11
_02
00
.33
0.0
54
86
2.2
10
.35
65
62
.27
0.0
47
07
0.5
50
.23
29
72
31
06
40
74
829
72
Zrc
_02
_00
90
.25
0.0
52
87
1.1
00
.34
62
11
.20
0.0
47
39
0.4
60
.40
29
81
30
23
32
32
429
81
Zrc
_29
_04
10
.49
0.0
58
33
4.9
20
.38
24
95
.26
0.0
47
56
0.8
60
.24
30
03
32
91
55
42
10
730
03
Con
tinue
don
next
page
...
tablas geocronología u-pb 111
Tabl
a8
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
gran
ite
dike
TT-6
15
.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_71
_09
10
.33
0.0
59
19
2.5
00
.38
82
53
.07
0.0
47
57
1.0
50
.59
30
03
33
39
57
45
330
03
Zrc
_35
_04
81
.37
0.0
55
02
1.1
10
.36
30
61
.56
0.0
47
85
1.1
10
.70
30
13
31
44
41
32
430
13
Zrc
_66
_08
60
.53
0.0
51
40
1.1
10
.34
08
01
.18
0.0
47
95
0.4
20
.33
30
21
29
83
25
92
330
21
Zrc
_45
_06
00
.52
0.0
52
04
1.1
90
.34
56
91
.28
0.0
48
12
0.4
40
.36
30
31
30
13
28
72
730
31
Zrc
_51
_06
80
.51
0.0
53
38
0.9
40
.35
61
71
.01
0.0
48
29
0.3
90
.38
30
41
30
93
34
51
930
41
Zrc
_46
_06
20
.44
0.0
54
72
2.2
50
.36
61
12
.45
0.0
48
53
0.5
40
.24
30
52
31
77
40
15
030
52
Zrc
_15
_02
40
.69
0.0
56
25
1.3
00
.38
05
21
.37
0.0
49
02
0.4
50
.32
30
91
32
74
46
22
830
91
Zrc
_25
_03
60
.49
0.0
59
70
1.8
90
.40
50
82
.19
0.0
49
12
1.1
00
.51
30
93
34
56
59
34
03
09
3
Zrc
_16
_02
60
.53
0.0
57
38
4.9
80
.39
12
05
.20
0.0
49
45
0.5
50
.12
31
12
33
51
55
06
10
731
12
Zrc
_17
_02
70
.52
0.0
58
39
3.1
00
.39
83
33
.30
0.0
49
48
0.5
70
.20
31
12
34
01
05
44
65
311
2Z
rc_5
7_0
75
0.6
60
.06
15
42
.39
0.4
20
05
2.6
60
.04
95
00
.65
0.3
03
11
23
56
86
58
46
31
12
Zrc
_60
_07
80
.95
0.0
61
24
1.5
00
.41
79
31
.56
0.0
49
40
0.4
50
.28
31
11
35
55
64
82
93
11
1
Zrc
_05
_01
20
.46
0.0
60
45
9.7
80
.41
31
21
0.0
80
.04
95
70
.99
0.1
23
12
33
51
30
62
01
92
31
23
Zrc
_65
_08
40
.59
0.0
56
90
3.0
10
.38
82
33
.05
0.0
49
56
0.5
20
.17
31
22
33
39
48
86
031
22
Zrc
_18
_02
80
.69
0.0
62
30
2.3
00
.42
64
82
.50
0.0
49
69
0.9
70
.39
31
33
36
18
68
44
73
13
3
Zrc
_38
_05
20
.71
0.0
52
99
1.4
00
.36
57
61
.45
0.0
49
95
0.3
60
.27
31
41
31
74
32
83
131
41
Zrc
_50
_06
60
.56
0.0
56
92
1.7
00
.39
46
31
.77
0.0
50
32
0.5
00
.27
31
62
33
85
48
83
431
62
Zrc
_64
_08
30
.53
0.0
61
88
4.0
20
.43
07
14
.23
0.0
50
48
0.7
30
.21
31
72
36
41
36
70
78
31
72
Con
tinue
don
next
page
...
tablas geocronología u-pb 112
Tabl
a8
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
gran
ite
dike
TT-6
15
.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_37
_05
10
.58
0.0
53
77
1.3
00
.37
55
51
.35
0.0
50
57
0.3
60
.26
31
81
32
44
36
12
931
81
Zrc
_56
_07
40
.63
0.0
61
85
2.3
90
.43
47
12
.48
0.0
51
00
0.6
10
.26
32
12
36
78
66
94
63
21
2
Zrc
_44
_05
90
.51
0.0
59
50
1.3
90
.42
04
71
.49
0.0
51
21
0.5
10
.35
32
22
35
64
58
53
032
22
Zrc
_63
_08
20
.51
0.0
57
59
1.6
00
.40
73
91
.67
0.0
51
19
0.4
70
.29
32
21
34
75
51
43
232
21
Zrc
_62
_08
10
.74
0.0
55
46
1.1
00
.39
39
51
.18
0.0
51
43
0.4
30
.36
32
31
33
73
43
12
232
31
Zrc
_01
_00
80
.45
0.0
52
39
1.3
00
.37
29
21
.36
0.0
51
57
0.4
10
.30
32
41
32
24
30
22
932
41
Zrc
_28
_04
00
.98
0.0
59
60
4.6
50
.42
40
65
.11
0.0
51
61
0.8
30
.26
32
43
35
91
55
89
10
032
43
Zrc
_39
_05
30
.93
0.0
54
45
1.8
90
.38
78
01
.95
0.0
51
56
0.4
50
.25
32
41
33
36
39
04
232
41
Zrc
_59
_07
70
.42
0.0
56
63
3.0
00
.40
52
03
.14
0.0
51
89
0.6
00
.21
32
62
34
59
47
76
032
62
Zrc
_33
_04
60
.57
0.0
59
57
4.1
80
.43
25
74
.45
0.0
52
66
0.7
40
.19
33
12
36
51
45
88
90
331
2Z
rc_3
4_0
47
0.6
40
.05
34
61
.50
0.3
89
54
1.5
90
.05
27
70
.53
0.3
43
32
23
34
53
48
33
332
2Z
rc_2
1_0
32
1.0
60
.05
51
31
.40
0.4
05
22
1.6
20
.05
33
30
.81
0.5
03
35
33
45
54
17
30
335
3Z
rc_5
4_0
71
0.7
10
.07
70
01
1.8
70
.56
71
71
2.4
40
.05
34
21
.55
0.1
83
35
54
56
46
11
21
21
63
35
5
Zrc
_43
_05
80
.70
0.0
59
97
1.8
00
.47
70
91
.93
0.0
57
50
0.7
10
.37
36
02
39
66
60
33
936
02
Zrc
_30
_04
20
.65
0.0
61
72
1.3
00
.69
83
61
.42
0.0
81
96
0.5
60
.40
50
83
53
86
66
42
750
83
Zrc
_32
_04
50
.37
0.0
63
81
1.3
00
.76
54
81
.35
0.0
86
90
0.3
80
.28
53
72
57
76
73
52
753
72
Zrc
_08
_01
60
.60
0.0
61
04
1.0
00
.75
04
71
.06
0.0
89
05
0.3
60
.34
55
02
56
85
64
12
155
02
Zrc
_03
_01
00
.19
0.0
60
81
1.9
10
.76
64
91
.98
0.0
91
49
0.5
50
.26
56
43
57
89
63
34
156
43
Con
tinue
don
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page
...
tablas geocronología u-pb 113
Tabl
a8
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
gran
ite
dike
TT-6
15
.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_26
_03
80
.28
0.0
63
85
1.1
00
.80
77
91
.18
0.0
91
58
0.4
40
.38
56
52
60
15
73
72
356
52
Zrc
_58
_07
60
.56
0.0
61
91
1.1
00
.82
18
81
.17
0.0
96
14
0.4
10
.35
59
22
60
95
67
12
159
22
Zrc
_20
_03
00
.21
0.0
61
62
0.8
60
.88
17
40
.94
0.1
03
65
0.3
80
.40
63
62
64
24
66
11
863
62
Zrc
_52
_06
90
.44
0.0
79
66
1.4
11
.42
97
01
.59
0.1
29
52
0.7
50
.47
78
56
90
19
11
89
25
78
56
Zrc
_69
_08
90
.18
0.0
71
76
0.7
21
.44
98
30
.83
0.1
46
52
0.3
20
.42
88
13
91
05
97
91
488
13
Zrc
_41
_05
60
.15
0.0
72
33
1.3
01
.64
72
01
.37
0.1
64
83
0.4
40
.32
98
44
98
89
99
52
698
44
Zrc
_10
_01
80
.07
0.0
70
42
0.7
01
.60
68
00
.75
0.1
65
12
0.3
00
.38
98
53
97
35
94
11
498
53
Zrc
_04
_01
10
.42
0.0
74
60
1.3
01
.82
97
01
.35
0.1
77
37
0.3
70
.27
10
53
41
05
69
10
58
26
1058
26Z
rc_2
2_0
33
0.5
50
.07
46
81
.10
1.8
99
70
1.1
90
.18
42
70
.46
0.3
91
09
05
10
81
81
06
02
110
6021
Zrc
_48
_06
40
.12
0.0
75
09
1.3
11
.85
50
01
.38
0.1
79
00
0.4
50
.32
10
62
41
06
59
10
71
24
1071
24Z
rc_4
7_0
63
0.2
70
.07
93
60
.84
2.2
60
80
0.9
10
.20
61
80
.32
0.3
71
20
84
12
00
61
18
11
511
8115
Zrc
_09
_01
70
.25
0.0
79
48
0.8
12
.25
32
00
.91
0.2
05
12
0.4
20
.47
12
03
51
19
86
11
84
16
1184
16Z
rc_5
5_0
72
0.2
70
.07
97
90
.95
2.2
50
60
1.0
10
.20
41
60
.33
0.3
21
19
84
11
97
71
19
21
711
9217
Zrc
_72
_09
20
.33
0.0
79
80
1.0
02
.18
68
01
.09
0.1
98
36
0.4
40
.40
11
67
51
17
78
11
92
19
1192
19Z
rc_1
3_0
22
0.4
80
.08
00
80
.87
2.2
10
90
0.9
50
.19
98
70
.39
0.4
01
17
54
11
84
71
19
91
711
9917
Zrc
_42
_05
70
.35
0.0
80
19
1.4
02
.19
08
01
.58
0.1
98
15
0.4
90
.34
11
65
51
17
81
11
20
22
712
0227
Zrc
_70
_09
00
.24
0.0
80
88
1.2
21
.99
66
51
.37
0.1
79
04
0.4
70
.35
10
62
51
11
49
12
19
24
1219
24Z
rc_2
3_0
34
0.3
00
.08
12
00
.76
2.4
88
90
0.8
20
.22
19
80
.30
0.3
61
29
24
12
69
61
22
61
412
2614
Con
tinue
don
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page
...
tablas geocronología u-pb 114
Tabl
a8
:LA
-IC
P-M
SU
-Pb
isot
opic
data
for
Teco
mat
eFo
rmat
ion
gran
ite
dike
TT-6
15
.
Spot
nam
eT
h/U
Isot
opic
rati
os(e
rror
sin
%)
Age
s(M
a)
207
Pb/206
Pb1σ
207
Pb/235
U1σ
206
Pb/238
U1σ
Rho
206
Pb/238
U1σ
207
Pb/235
U1σ
207
Pb/206
U1σ
Best
age1σ
Zrc
_53
_07
00
.29
0.0
81
42
1.4
12
.22
24
31
.58
0.1
97
96
0.5
60
.40
11
64
61
18
81
11
23
22
512
3225
Zrc
_40
_05
40
.36
0.0
81
71
0.7
32
.45
49
00
.81
0.2
17
45
0.3
50
.42
12
68
41
25
96
12
39
14
1239
14Z
rc_4
9_0
65
0.1
00
.08
52
50
.75
2.5
68
50
1.2
60
.21
85
10
.96
0.7
91
27
41
11
29
29
13
21
13
1321
13Z
rc_6
1_0
80
0.7
80
.08
61
41
.20
2.1
86
40
1.3
10
.18
37
60
.53
0.4
11
08
75
11
77
91
34
12
113
4121
Zrc
_12
_02
10
.65
0.0
94
30
0.8
03
.48
90
00
.87
0.2
67
89
0.3
50
.41
15
30
51
52
57
15
14
14
1514
14Z
rc_1
4_0
23
0.5
40
.15
20
30
.63
8.4
84
73
0.8
80
.40
47
60
.45
0.6
02
19
18
22
84
82
36
91
023
6910
Zrc
_27
_03
90
.21
0.1
75
80
0.7
01
0.5
93
97
0.8
60
.43
70
70
.43
0.5
22
33
88
24
88
82
61
41
126
1411
Tabl
a9
:Ti-
in-z
irco
nth
erm
omet
ryfo
rro
cks
ofth
eTo
tolt
epec
plut
on.
Sam
ple
Age
Con
cord
ance
Ti(p
pm)
log(
Ti)
T(◦
C)
Sam
ple
Age
Con
cord
ance
Ti(p
pm)
log(
Ti)
T(◦
C)
TT-7
6B(Q
uart
zD
iori
te)
TT-7
2(H
ornb
lend
eG
abbr
o)
Zrc
_56_0
74
278
0.3
621
.18
1.3
3811
.54
Zrc
_19_0
29
299
1.6
43
.25
0.5
1651
.04
Zrc
_52_0
69
285
0.7
013
.42
1.1
3767
.48
Zrc
_21_0
32
299
0.6
65
.97
0.7
8697
.61
Zrc
_57_0
75
285
1.3
81
.20
0.0
8583
.65
Zrc
_02_0
09
301
-0.3
318.9
71
.28
800
.54
Zrc
_47_0
63
286
0.0
06
.01
0.7
8698
.13
Zrc
_05_0
12
302
7.9
39
.13
0.9
6733
.02
Con
tinue
don
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page
...
tablas geocronología u-pb 115
Tabl
a9
:Ti-
in-z
irco
nth
erm
omet
ryfo
rro
cks
ofth
eTo
tolt
epec
plut
on.
Sam
ple
Age
Con
cord
ance
Ti(p
pm)
log(
Ti)
T(◦
C)
Sam
ple
Age
Con
cord
ance
Ti(p
pm)
log(
Ti)
T(◦
C)
TT-7
6B(Q
uart
zD
iori
te)
TT-7
2(H
ornb
lend
eG
abbr
o)
Zrc
_76_0
98
286
1.7
21
.52
0.1
8598
.65
Zrc
_10_0
18
302
5.3
34
.22
0.6
3670
.43
Zrc
_79_1
01
286
4.0
33
.00
0.4
8645
.14
Zrc
_17_0
27
302
1.3
15
.65
0.7
5693
.14
Zrc
_59_0
77
287
2.7
12
.01
0.3
0617
.09
Zrc
_01_0
08
303
1.6
214
.03
1.1
5771
.62
Zrc
_70_0
90
288
1.0
33
.66
0.5
6659
.74
Zrc
_03_0
10
303
3.5
06
.08
0.7
8699
.05
Zrc
_74_0
95
288
-0.7
09.1
30
.96
733
.04
Zrc
_38_0
50
303
-1.3
413.4
71
.13
767
.85
Zrc
_46_0
62
289
0.3
46
.88
0.8
4709
.09
Zrc
_04_0
11
304
2.2
57
.18
0.8
6712
.65
Zrc
_64_0
83
289
3.6
712
.41
1.0
9760
.32
Zrc
_35_0
46
304
-0.3
35.6
60
.75
693
.29
Zrc
_69_0
89
289
2.0
320
.83
1.3
2809
.86
Zrc
_32_0
44
305
2.8
74
.94
0.6
9682
.53
Zrc
_78_1
00
289
3.0
21
.01
0.0
1573
.16
Zrc
_07_0
15
306
1.6
14
.33
0.6
4672
.41
Zrc
_72_0
93
290
-0.6
97.6
20
.88
717
.59
Zrc
_08_0
16
306
0.9
715
.85
1.2
0783.1
2
Zrc
_48_0
64
291
0.3
414
.48
1.1
6774
.61
Zrc
_12
_021
306
2.2
45
.51
0.7
4691.1
2
Zrc
_55_0
72
291
1.3
622
.78
1.3
6818
.88
Zrc
_16_0
26
306
3.7
77
.75
0.8
9719.0
1
Zrc
_58_0
76
292
0.3
42
.04
0.3
1618
.06
Zrc
_22_0
33
306
-0.9
99.6
10
.98
737.4
7
Zrc
_68_0
88
293
1.0
19
.14
0.9
6733
.16
Zrc
_27_0
38
306
2.5
510
.19
1.0
1742.6
5
Zrc
_75_0
96
293
1.6
86
.04
0.7
8698
.49
Zrc
_13_0
22
307
2.5
416
.04
1.2
1784.2
9
Zrc
_77_0
99
293
0.0
012
.04
1.0
8757
.58
Zrc
_29_0
40
308
-1.9
98.9
00
.95
730.8
2
Con
tinue
don
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page
...
tablas geocronología u-pb 116
Tabl
a9
:Ti-
in-z
irco
nth
erm
omet
ryfo
rro
cks
ofth
eTo
tolt
epec
plut
on.
Sam
ple
Age
Con
cord
ance
Ti(p
pm)
log(
Ti)
T(◦
C)
Sam
ple
Age
Con
cord
ance
Ti(p
pm)
log(
Ti)
T(◦
C)
TT-7
6B(Q
uart
zD
iori
te)
TT-7
2(H
ornb
lend
eG
abbr
o)
Zrc
_80_1
02
294
1.0
14
.03
0.6
1666
.95
Zrc
_37_0
49
308
1.2
814
.40
1.1
6774
.04
Zrc
_50_0
66
295
1.0
18
.88
0.9
5730
.61
Zrc
_20_0
30
309
2.5
27
.94
0.9
0721
.05
Zrc
_53_0
70
295
-0.6
82.3
80
.38
628
.83
Zrc
_30_0
41
309
0.3
214
.84
1.1
7776
.91
Zrc
_71_0
92
297
1.0
010
.61
1.0
3746
.19
Zrc
_36_0
48
309
0.3
214
.88
1.1
7777
.18
Zrc
_51_0
68
300
-0.3
36.1
30
.79
699
.74
Zrc
_06_0
14
310
8.2
87
.37
0.8
7714
.83
Zrc
_62_0
81
301
-1.0
120.0
91
.30
806
.24
Zrc
_26_0
37
310
6.3
411
.12
1.0
5750
.38
Zrc
_73_0
94
307
-0.9
91.0
30
.01
574
.06
Zrc
_41_0
53
310
0.6
416
.02
1.2
0784
.18
Zrc
_45_0
60
310
1.2
712
.45
1.1
0760
.62
Zrc
_11_0
20
311
3.1
21
.25
0.1
0586
.28
Zrc
_15_0
24
311
4.0
110
.26
1.0
1743
.27
MED
IAN
713.
34M
EDIA
N73
0.82
STD
EV76
.04
STD
EV48
.77
CTA B L A S G E O Q U Í M I C A
Material suplementario publicado en línea como parte del artículo: Kirsch,M., Keppie, J.D., Murphy, J.B., y Solari, L.A., 2012, Permian–Carboniferousarc magmatism and basin evolution along the western margin of Pangea:geochemical and geochronological evidence from the eastern AcatlánComplex, southern Mexico: Geological Society of America Bulletin, enprensa, doi: 10.1130/B30649.1.
117
tablas geoquímica 118
Tabl
a1
0:C
hem
ical
resu
lts
for
rock
sof
the
Toto
ltep
ecPl
uton
.Aca
tlán
Com
plex
,Pue
bla,
Mex
ico
(par
t1
/3).
Nam
eT
T-11
TT-
12T
T-13
AT
T-13
BT
T-14
TT-
15T
T-16
TT-
18T
T-20
TT-
22T
T-24
Lat
18.2
28
36
61
8.2
14
11
61
8.2
14
03
31
8.2
14
03
31
8.2
08
43
31
8.2
23
06
61
8.2
22
76
61
8.2
57
38
31
8.2
60
23
31
8.2
63
01
61
8.2
78
83
3
Lon
-97.8
59
43
-97.8
83
7-9
7.8
83
85
-97.8
83
85
-97.8
90
86
6-9
7.8
99
78
3-9
7.9
00
5-9
7.8
505
33
-97
.83
86
33
-97.8
32
43
3-9
7.7
99
4
Lith
olog
ytr
ondh
j.Q
zgr
anit
oid
tona
l.to
nal.
hbld
iori
teto
nal.
tron
dhj.
tron
dhj.
tron
dhj.
tron
dhj.
hblg
abbr
o
Age
(Ma)
28
92
89
28
92
89
28
92
89
28
93
06
28
930
63
06
SiO2
(wt%
)7
0.6
77
.56
0.2
55
.45
1.1
52.3
73
.17
0.1
71
.767
.64
6.0
TiO2
0.2
30
.10
0.6
10
.76
0.7
80.7
20
.19
0.2
40
.17
0.3
10
.31
Al 2
O3
16.8
13
.91
6.3
15
.82
3.6
16.2
15
.01
6.7
15
.316
.12
1.3
Fe2
O3
1.6
60
.17
8.2
21
1.6
5.7
01
1.4
0.9
21.6
01.1
02.9
58
.13
MnO
0.0
30
.02
20.1
47
0.2
25
0.0
71
0.1
90
.04
10
.036
0.0
41
0.0
76
0.1
49
MgO
0.7
00.1
12
.79
3.9
82
.43
6.1
30
.54
0.6
70
.33
1.8
48
.36
CaO
2.6
92.1
96
.69
7.0
39
.65
4.6
21.0
62.3
02
.40
2.2
38
.63
Na 2
O5.4
95.4
43
.72
3.6
25
.22
4.1
26.2
05
.97
5.5
55
.48
1.9
9
K2
O0.7
00.2
50
.48
0.4
20
.22
1.1
41.2
81
.00
0.7
61
.16
1.3
5
P 2O5
0.0
70.0
10
.10
0.0
90
.25
0.1
00.0
60
.07
0.0
50
.11
0.0
1
LOI
1.0
70.3
20.7
51
.02
1.0
21
.28
1.2
21
.71
2.6
02
.16
3.7
7
Tota
l1
00.0
10
0.0
10
0.0
10
0.0
10
0.0
98.2
99.5
10
0.4
100
.01
00
.01
00
.0
Mg#
42.9
53.5
37.7
37
.94
3.2
48
.95
1.1
42
.734
.852
.66
4.7
V(p
pm)
29
10
16
62
88
11
12
72
82
42
26
51
50
Cr
10
15
20
71
21
01
61
32
72
63
Co
41
17
27
13
45
34
84
3
Ni
55
78
95
56
51
07
6
Cu
21
10
45
81
11
21
16
23
Zn
41
76
81
04
55
43
39
19
21
51
66
Ga
18
15
14
16
26
18
18
15
15
16
14
Con
tinue
don
next
page
...
tablas geoquímica 119
Tabl
a1
0:C
hem
ical
resu
lts
for
rock
sof
the
Toto
ltep
ecPl
uton
.Aca
tlán
Com
plex
,Pue
bla,
Mex
ico
(par
t1
/3).
Nam
eT
T-11
TT-
12T
T-13
AT
T-13
BT
T-14
TT-
15T
T-16
TT-
18T
T-20
TT-
22T
T-24
Lat
18.2
28
36
61
8.2
14
11
61
8.2
14
03
31
8.2
14
03
31
8.2
08
43
31
8.2
23
06
61
8.2
22
76
61
8.2
57
38
31
8.2
60
23
31
8.2
63
01
61
8.2
78
83
3
Lon
-97.8
59
43
-97.8
83
7-9
7.8
83
85
-97.8
83
85
-97.8
90
86
6-9
7.8
99
78
3-9
7.9
00
5-9
7.8
505
33
-97
.83
86
33
-97.8
32
43
3-9
7.7
99
4
Lith
olog
ytr
ondh
j.Q
zgr
anit
oid
tona
l.to
nal.
hbld
iori
teto
nal.
tron
dhj.
tron
dhj.
tron
dhj.
tron
dhj.
hblg
abbr
o
Age
(Ma)
28
92
89
28
92
89
28
92
89
28
93
06
28
930
63
06
Rb
14
39
80
27
27
30
17
25
28
Sr7
08
33
12
87
26
51
12
96
91
62
93
28
32
356
94
01
Y4
39
266
42
88
75
Zr
73
4259
4869
73
754
54
657
3
Nb
0.0
0.1
2.0
3.6
1.3
0.0
1.1
0.0
0.0
2.4
0.1
Ba
52
712
426
118
211
55
59
400
78
047
714
0483
6
Cs
0.0
1.8
4.3
0.3
0.0
1.8
0.0
0.0
0.0
0.0
8.7
La1.
54.
46.
43.
51.
86.
30.
9
Ce
11.8
2.7
9.7
15.4
8.9
9.0
3.7
12.4
6.6
12.8
1.9
Pr0.
31.
22.
21.
50.
41.
60.
3
Nd
0.9
6.1
9.5
8.7
1.6
7.1
1.2
Sm0.
21.
42.
82.
10.
51.
80.
6
Eu0.
20.
60.
80.
90.
20.
40.
4
Gd
0.3
2.0
4.0
1.9
0.5
1.4
0.6
Tb
0.07
0.26
0.69
0.26
0.09
0.22
0.13
Dy
0.4
1.9
4.7
1.3
0.5
1.3
1.0
Ho
0.09
0.39
1.03
0.23
0.11
0.28
0.19
Er0.
41.
23.
10.
60.
20.
90.
6
Tm
0.06
0.18
0.49
0.08
0.07
0.09
0.08
Yb
0.4
1.2
3.1
0.5
0.3
0.8
0.8
Con
tinue
don
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page
...
tablas geoquímica 120
Tabl
a1
0:C
hem
ical
resu
lts
for
rock
sof
the
Toto
ltep
ecPl
uton
.Aca
tlán
Com
plex
,Pue
bla,
Mex
ico
(par
t1
/3).
Nam
eT
T-11
TT-
12T
T-13
AT
T-13
BT
T-14
TT-
15T
T-16
TT-
18T
T-20
TT-
22T
T-24
Lat
18.2
28
36
61
8.2
14
11
61
8.2
14
03
31
8.2
14
03
31
8.2
08
43
31
8.2
23
06
61
8.2
22
76
61
8.2
57
38
31
8.2
60
23
31
8.2
63
01
61
8.2
78
83
3
Lon
-97.8
59
43
-97.8
83
7-9
7.8
83
85
-97.8
83
85
-97.8
90
86
6-9
7.8
99
78
3-9
7.9
00
5-9
7.8
505
33
-97
.83
86
33
-97.8
32
43
3-9
7.7
99
4
Lith
olog
ytr
ondh
j.Q
zgr
anit
oid
tona
l.to
nal.
hbld
iori
teto
nal.
tron
dhj.
tron
dhj.
tron
dhj.
tron
dhj.
hblg
abbr
o
Age
(Ma)
28
92
89
28
92
89
28
92
89
28
93
06
28
930
63
06
Lu0.
040.
140.
480.
070.
040.
080.
10
Hf
3.9
1.2
1.3
1.5
1.7
1.3
0.1
Ta0.
000.
050.
100.
030.
030.
040.
00
Pb0.2
10.5
12.1
9.3
0.0
0.0
0.0
2.0
5.0
4.4
11.2
Th
0.3
0.5
1.4
0.1
0.2
1.0
0.0
U0.0
0.8
1.5
1.7
0.0
0.3
0.0
0.2
1.9
0.0
0.0
Tabl
a1
1:C
hem
ical
resu
lts
for
rock
sof
the
Toto
ltep
ecPl
uton
.Aca
tlán
Com
plex
,Pue
bla,
Mex
ico
(par
t2
/3).
Nam
eT
T-25
TT-
26A
TT-
26B
TT-
27T
T-28
TT-
49T
T-50
TT-
51T
T-52
TT-
53T
T-54
Lat
18.2
66
66
61
8.2
59
71
8.2
59
71
8.2
60
51
8.2
60
11
61
8.2
29
31
61
8.2
32
68
31
8.2
35
43
31
8.2
29
218.2
20
31
8.2
20
78
3
Lon
-97.7
88
78
3-9
7.7
81
15
-97.7
81
15
-97
.78
27
33
-97.7
83
45
-97.8
05
51
6-9
7.8
12
46
6-9
7.8
265
5-9
7.8
38
38
3-9
7.8
78
51
6-9
7.8
78
56
6
Lith
olog
ytr
ondh
j.hb
lleu
coga
bbro
hblg
abbr
otr
ondh
j.H
bl-i
tetr
ondh
j.tr
ondh
j.Pl
cum
ul.
Plcu
mul
.tr
ondh
j.to
nal.
Age
(Ma)
28
93
06
30
63
06
30
62
89
28
92
89
28
92
89
28
9
SiO2
(wt%
)7
1.6
44.7
47.3
75.7
40
.76
8.3
69
.166
.46
2.7
69.1
52.2
TiO2
0.1
80.1
80.2
40
.11
0.9
60.2
40
.21
0.2
50
.26
0.2
60.6
7
Al 2
O3
15.7
29.5
19.1
14.6
18
.71
6.2
16
.419.6
18
.617.1
17.5
Fe2
O3
1.1
92.7
97
.55
0.2
81
2.3
1.6
01
.26
1.0
51
.22
1.8
01
1.1
Con
tinue
don
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page
...
tablas geoquímica 121
Tabl
a1
1:C
hem
ical
resu
lts
for
rock
sof
the
Toto
ltep
ecPl
uton
.Aca
tlán
Com
plex
,Pue
bla,
Mex
ico
(par
t2
/3).
Nam
eT
T-25
TT-
26A
TT-
26B
TT-
27T
T-28
TT-
49T
T-50
TT-
51T
T-52
TT-
53T
T-54
Lat
18.2
66
66
61
8.2
59
71
8.2
59
71
8.2
60
51
8.2
60
11
61
8.2
29
31
61
8.2
32
68
31
8.2
35
43
31
8.2
29
218.2
20
31
8.2
20
78
3
Lon
-97.7
88
78
3-9
7.7
81
15
-97.7
81
15
-97
.78
27
33
-97.7
83
45
-97.8
05
51
6-9
7.8
12
46
6-9
7.8
265
5-9
7.8
38
38
3-9
7.8
78
51
6-9
7.8
78
56
6
Lith
olog
ytr
ondh
j.hb
lleu
coga
bbro
hblg
abbr
otr
ondh
j.H
bl-i
tetr
ondh
j.tr
ondh
j.Pl
cum
ul.
Plcu
mul
.tr
ondh
j.to
nal.
Age
(Ma)
28
93
06
30
63
06
30
62
89
28
92
89
28
92
89
28
9
MnO
0.0
29
0.0
57
0.1
65
0.0
18
0.1
80
0.0
32
0.0
29
0.0
22
0.0
44
0.0
39
0.2
16
MgO
0.5
92.3
79
.79
0.2
41
0.9
50
.33
0.2
10.2
11
.06
0.7
44.7
9
CaO
1.6
11
4.4
89.0
50
.88
11
.34.6
43
.54
0.4
82
.14
3.2
97.9
3
Na 2
O5
.41
1.3
41
.96
5.8
31
.35
5.0
15
.83
11.2
81
0.3
35.6
03.7
7
K2
O0.9
71
.27
1.3
01
.93
0.6
80.4
00
.47
0.2
50
.22
0.7
70.5
3
P 2O5
0.0
50
.03
0.0
10
.05
0.0
20.0
70
.06
0.0
70
.08
0.0
80.0
8
LOI
2.6
43
.32
3.5
50
.38
2.8
73
.27
2.9
80.4
93
.29
1.2
41.2
7
Tota
l1
00.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
100
.01
00.0
10
0.0
10
0.0
Mg#
46.9
60
.26
9.8
60
.46
1.4
26
.92
2.9
26.3
60
.84
2.3
43.6
V(p
pm)
21
66
11
41
04
34
29
28
27
32
30
27
0
Cr
12
10
33
13
16
64
81
36
13
10
5
Co
11
13
60
47
42
11
32
4
Ni
64
31
63
36
24
64
76
13
Cu
22
23
82
97
32
12
45
0
Zn
73
17
78
63
33
19
422
49
98
Ga
13
18
14
15
15
19
16
15
13
19
18
Rb
18
44
35
32
22
81
07
61
51
1
Sr3
48
56
95
15
16
82
70
59
15
39
198
21
38
74
22
9
Y3
25
410
52
52
53
8
Zr
52
24
1111
72
58
70
857
84
4
Con
tinue
don
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page
...
tablas geoquímica 122
Tabl
a1
1:C
hem
ical
resu
lts
for
rock
sof
the
Toto
ltep
ecPl
uton
.Aca
tlán
Com
plex
,Pue
bla,
Mex
ico
(par
t2
/3).
Nam
eT
T-25
TT-
26A
TT-
26B
TT-
27T
T-28
TT-
49T
T-50
TT-
51T
T-52
TT-
53T
T-54
Lat
18.2
66
66
61
8.2
59
71
8.2
59
71
8.2
60
51
8.2
60
11
61
8.2
29
31
61
8.2
32
68
31
8.2
35
43
31
8.2
29
218.2
20
31
8.2
20
78
3
Lon
-97.7
88
78
3-9
7.7
81
15
-97.7
81
15
-97
.78
27
33
-97.7
83
45
-97.8
05
51
6-9
7.8
12
46
6-9
7.8
265
5-9
7.8
38
38
3-9
7.8
78
51
6-9
7.8
78
56
6
Lith
olog
ytr
ondh
j.hb
lleu
coga
bbro
hblg
abbr
otr
ondh
j.H
bl-i
tetr
ondh
j.tr
ondh
j.Pl
cum
ul.
Plcu
mul
.tr
ondh
j.to
nal.
Age
(Ma)
28
93
06
30
63
06
30
62
89
28
92
89
28
92
89
28
9
Nb
0.0
0.2
0.2
0.4
0.4
0.0
0.0
0.0
0.4
0.0
3.9
Ba
66
281
293
679
256
23
95
34
886
705
61
65
7
Cs
3.8
7.2
10
.31
.50.0
1.5
3.1
3.5
3.6
4.6
6.9
La1.
30.
81.
00.
91.
9
Ce
15
.52.
72.
02.
53.
21
0.1
2.6
12
.34.
11
1.1
9.5
Pr0.
30.
30.
30.
60.
5
Nd
1.2
1.5
1.1
3.8
2.0
Sm0.
40.
40.
41.
60.
4
Eu0.
30.
30.
10.
70.
3
Gd
0.4
0.8
0.5
2.1
0.6
Tb
0.05
0.13
0.07
0.33
0.05
Dy
0.4
0.9
0.7
2.2
0.4
Ho
0.11
0.19
0.15
0.42
0.12
Er0.
40.
60.
51.
10.
3
Tm
0.06
0.08
0.06
0.18
0.04
Yb
0.3
0.5
0.5
1.0
0.4
Lu0.
040.
080.
080.
130.
05
Hf
0.1
0.2
0.5
0.6
2.4
Ta0.
000.
000.
010.
000.
01
Pb3.3
4.9
0.0
13.1
6.6
0.0
10
.96.7
1.5
0.0
6.0
Con
tinue
don
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page
...
tablas geoquímica 123
Tabl
a1
1:C
hem
ical
resu
lts
for
rock
sof
the
Toto
ltep
ecPl
uton
.Aca
tlán
Com
plex
,Pue
bla,
Mex
ico
(par
t2
/3).
Nam
eT
T-25
TT-
26A
TT-
26B
TT-
27T
T-28
TT-
49T
T-50
TT-
51T
T-52
TT-
53T
T-54
Lat
18.2
66
66
61
8.2
59
71
8.2
59
71
8.2
60
51
8.2
60
11
61
8.2
29
31
61
8.2
32
68
31
8.2
35
43
31
8.2
29
218.2
20
31
8.2
20
78
3
Lon
-97.7
88
78
3-9
7.7
81
15
-97.7
81
15
-97
.78
27
33
-97.7
83
45
-97.8
05
51
6-9
7.8
12
46
6-9
7.8
265
5-9
7.8
38
38
3-9
7.8
78
51
6-9
7.8
78
56
6
Lith
olog
ytr
ondh
j.hb
lleu
coga
bbro
hblg
abbr
otr
ondh
j.H
bl-i
tetr
ondh
j.tr
ondh
j.Pl
cum
ul.
Plcu
mul
.tr
ondh
j.to
nal.
Age
(Ma)
28
93
06
30
63
06
30
62
89
28
92
89
28
92
89
28
9
Th
0.0
0.1
0.4
0.1
0.3
U0.0
4.2
0.0
2.3
2.0
0.0
0.7
1.3
3.0
0.0
0.1
Tabl
a1
2:C
hem
ical
resu
lts
for
rock
sof
the
Toto
ltep
ecPl
uton
.Aca
tlán
Com
plex
,Pue
bla,
Mex
ico
(par
t3
/3).
Nam
eT
T-55
TT-
56T
T-57
TT-
59T
T-60
TT-
72T
T-73
TT-
74T
T-76
BT
T-77
TT-
78T
T-79
Lat
18.2
15
86
61
8.2
16
31
61
8.2
08
31
61
8.2
07
43
31
8.2
00
56
61
8.2
58
11
8.2
50
21
8.2
39
418.2
286
518
.22
31
66
18.2
18
65
18.2
20
95
Lon
-97.8
80
85
-97.8
80
55
-97.8
80
45
-97.8
74
9-9
7.8
86
95
-97.8
51
63
3-9
7.8
49
71
6-9
7.8
50
45
-97.8
63
43
3-9
7.8
68
-97.8
68
06
6-9
7.8
88
3
Lith
olog
yto
nal.
tron
dhj.
tron
dhj.
tona
l.to
nal.
hblg
abbr
otr
ondh
j.tr
ondh
j.qu
artz
dior
ite
tron
dhj.
tona
l.qu
artz
dior
ite
Age
(Ma)
28
92
89
28
92
89
28
93
06
28
92
89
28
92
89
28
92
89
SiO2
(wt%
)5
1.9
66
.86
9.1
54
.34
9.8
48
.07
2.9
69
.96
8.6
68.6
52
.56
9.8
TiO2
0.7
70
.35
0.2
60
.71
0.8
60
.79
0.2
00.2
30
.26
0.2
70
.67
0.2
4
Al 2
O3
22.7
17
.51
7.5
17
.22
0.6
17
.51
6.3
16.5
16
.51
7.4
23
.41
7.0
Fe2
O3
5.8
82
.43
1.8
49
.68
6.6
91
0.5
0.5
61.5
31
.86
1.8
65
.37
1.5
6
MnO
0.0
81
0.0
43
0.0
37
0.1
85
0.0
74
0.1
31
0.0
17
0.0
29
0.0
33
0.0
41
0.0
75
0.0
34
MgO
3.1
01
.36
0.7
24
.20
3.8
05.2
20.2
20.2
10
.95
0.9
72
.17
0.7
4
CaO
7.3
83
.33
3.7
76
.23
7.2
57.8
50.2
43.0
22
.53
2.9
68
.29
1.8
5
Na 2
O5
.53
5.6
95
.39
2.7
66
.47
3.4
47
.83
5.4
76
.46
5.4
75
.45
6.5
0
Con
tinue
don
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page
...
tablas geoquímica 124
Tabl
a1
2:C
hem
ical
resu
lts
for
rock
sof
the
Toto
ltep
ecPl
uton
.Aca
tlán
Com
plex
,Pue
bla,
Mex
ico
(par
t3
/3).
Nam
eT
T-55
TT-
56T
T-57
TT-
59T
T-60
TT-
72T
T-73
TT-
74T
T-76
BT
T-77
TT-
78T
T-79
Lat
18.2
15
86
61
8.2
16
31
61
8.2
08
31
61
8.2
07
43
31
8.2
00
56
61
8.2
58
11
8.2
50
21
8.2
39
418.2
286
518
.22
31
66
18.2
18
65
18.2
20
95
Lon
-97.8
80
85
-97.8
80
55
-97.8
80
45
-97.8
74
9-9
7.8
86
95
-97.8
51
63
3-9
7.8
49
71
6-9
7.8
50
45
-97.8
63
43
3-9
7.8
68
-97.8
68
06
6-9
7.8
88
3
Lith
olog
yto
nal.
tron
dhj.
tron
dhj.
tona
l.to
nal.
hblg
abbr
otr
ondh
j.tr
ondh
j.qu
artz
dior
ite
tron
dhj.
tona
l.qu
artz
dior
ite
Age
(Ma)
28
92
89
28
92
89
28
93
06
28
92
89
28
92
89
28
92
89
K2
O0.5
70
.50
0.5
00
.58
0.1
20
.42
0.4
80
.58
0.5
30.8
40
.28
0.9
3
P 2O5
0.3
00
.11
0.0
80
.14
0.3
30
.10
0.0
50.0
60
.08
0.0
90
.26
0.0
7
LOI
1.8
11
.86
0.7
93
.99
4.0
23
.07
1.2
02.4
82
.20
1.5
11
.55
1.3
6
Tota
l1
00.0
10
0.0
10
0.0
10
0.0
10
0.0
97.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
Mg#
48.4
49
.94
1.1
43
.65
0.3
47
.04
1.2
19.6
47
.64
8.2
41
.94
5.8
V(p
pm)
11
65
03
02
44
11
62
57
22
30
30
33
96
28
Cr
41
11
00
14
38
15
91
211
51
0
Co
16
64
28
29
30
24
46
95
Ni
11
74
11
19
21
56
55
10
5
Cu
16
12
51
35
90
13
43
3
Zn
66
42
37
97
83
11
15
23
42
46
61
38
Ga
25
21
19
16
17
13
16
17
18
21
27
19
Rb
81
07
19
23
41
31
21
318
52
4
Sr1
12
27
01
73
23
68
62
83
35
19
55
58
604
66
29
93
64
2
Y8
54
21
914
62
24
63
Zr
71
67
73
37
27
444
964
72
71
846
8
Nb
0.0
0.0
0.0
3.9
1.2
2.1
0.0
0.4
0.0
0.0
1.4
0.0
Ba
20
53
22
42
25
21
42
1042
20
546
740
85
07
119
46
3
Cs
1.3
3.1
1.2
4.0
0.0
1.5
3.7
1.9
2.2
5.0
4.9
0.0
La4.
53.
03.
7
Con
tinue
don
next
page
...
tablas geoquímica 125
Tabl
a1
2:C
hem
ical
resu
lts
for
rock
sof
the
Toto
ltep
ecPl
uton
.Aca
tlán
Com
plex
,Pue
bla,
Mex
ico
(par
t3
/3).
Nam
eT
T-55
TT-
56T
T-57
TT-
59T
T-60
TT-
72T
T-73
TT-
74T
T-76
BT
T-77
TT-
78T
T-79
Lat
18.2
15
86
61
8.2
16
31
61
8.2
08
31
61
8.2
07
43
31
8.2
00
56
61
8.2
58
11
8.2
50
21
8.2
39
418.2
286
518
.22
31
66
18.2
18
65
18.2
20
95
Lon
-97.8
80
85
-97.8
80
55
-97.8
80
45
-97.8
74
9-9
7.8
86
95
-97.8
51
63
3-9
7.8
49
71
6-9
7.8
50
45
-97.8
63
43
3-9
7.8
68
-97.8
68
06
6-9
7.8
88
3
Lith
olog
yto
nal.
tron
dhj.
tron
dhj.
tona
l.to
nal.
hblg
abbr
otr
ondh
j.tr
ondh
j.qu
artz
dior
ite
tron
dhj.
tona
l.qu
artz
dior
ite
Age
(Ma)
28
92
89
28
92
89
28
93
06
28
92
89
28
92
89
28
92
89
Ce
11.0
18
.83
.51
3.0
6.9
9.9
7.3
6.5
4.9
5.0
9.0
4.2
Pr1.
30.
81.
4
Nd
6.0
3.4
8.3
Sm1.
50.
71.
8
Eu0.
60.
20.
9
Gd
2.1
0.5
1.9
Tb
0.38
0.07
0.20
Dy
2.3
0.4
1.2
Ho
0.54
0.08
0.24
Er1.
60.
20.
6
Tm
0.26
0.04
0.09
Yb
1.5
0.2
0.5
Lu0.
260.
050.
08
Hf
1.0
1.8
1.9
Ta0.
070.
010.
02
Pb0.0
0.0
3.2
0.0
1.7
7.4
6.1
0.4
13.5
0.0
0.0
0.6
Th
1.5
0.5
0.1
U0.5
0.0
0.0
0.0
0.0
0.0
1.9
0.0
0.2
0.0
0.0
0.0
tablas geoquímica 126
Tabl
a1
3:C
hem
ical
resu
lts
for
the
Teco
mat
eFo
rmat
ion.
Aca
tlán
Com
plex
,Pue
bla/
Oax
aca,
Mex
ico
(par
t1
/4.)
Nam
eT
T-5A
TT-
5BT
T-6
TT-
7AT
T-7B
TT-
8AT
T-8B
TT-
32T
T-33
TT-
34A
TT-
34B
TT-
35
Lat
18.2
00
11
61
8.2
00
11
61
8.1
99
55
18.2
07
51
61
8.2
07
51
61
8.2
12
18
.21
21
8.2
56
03
31
8.2
55
81
8.2
422
16
18
.24
22
16
18.2
44
31
6
Lon
-97.8
16
66
6-9
7.8
16
66
6-9
7.8
16
86
6-9
7.8
21
61
6-9
7.8
21
61
6-9
7.8
33
85
-97.8
33
85
-97
.77
74
66
-97.7
77
9-9
7.7
889
66
-97.7
88
96
6-9
7.7
87
58
3
Lith
olog
ym
etap
s.m
etap
s.m
etap
el.
met
apel
.m
etap
s.m
etap
s.m
etap
s.m
etap
s.m
etap
s.m
etap
el.
met
apel
.m
etap
el.
SiO2
(wt%
)7
1.5
68
.86
4.1
64
.36
5.2
66
.86
4.5
67.1
61
.95
7.0
53.5
58.8
TiO2
0.3
90
.40
0.6
00
.68
0.6
60
.50
0.5
40.5
10
.64
0.8
30
.52
0.8
1
Al 2
O3
11.7
11
.31
6.6
16
.41
5.1
14
.71
3.3
13.1
15.7
18
.31
6.9
20.3
Fe2
O3
3.7
34
.16
6.5
87
.05
5.4
34.3
04
.61
3.6
15.7
47
.69
9.0
67.7
5
MnO
0.0
64
0.0
94
0.0
66
0.0
70
0.0
60
0.0
56
0.0
59
0.0
80
0.0
72
0.0
97
0.1
34
0.1
06
MgO
1.6
11
.59
2.5
62
.41
2.0
62.0
01
.85
1.3
42
.46
5.7
4.8
72.0
7
CaO
3.4
34
.68
1.1
90
.84
3.1
92.7
34
.83
4.2
33
.60
0.7
65
.67
0.3
4
Na 2
O3.2
03
.57
2.7
93
.83
3.7
44.4
82
.62
4.8
52
.73
1.3
03
.79
0.5
1
K2
O0.6
90
.55
1.4
11
.00
1.0
30.7
71
.43
0.6
71
.71
3.0
40
.42
4.7
0
P 2O5
0.0
50
.06
0.1
40
.18
0.1
30.1
40
.13
0.1
00.1
60
.17
0.0
30.2
0
LOI
3.7
34
.82
3.8
93
.33
3.5
03.5
86
.12
4.4
85
.29
5.0
75
.17
4.4
5
Tota
l1
00.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
100
.010
0.0
10
0.0
10
0.0
Mg#
43
.54
0.5
40
.93
7.9
40
.34
5.3
41
.73
9.8
43.3
56
.94
8.9
32.2
V(p
pm)
10
61
15
16
11
58
13
59
41
08
11
11
58
18
51
80
18
1
Cr
21
19
75
80
53
13
65
34
68
36
81
09
10
1
Co
88
17
17
15
91
67
16
32
33
22
Ni
12
11
26
38
27
10
28
17
27
20
74
04
8
Cu
91
03
13
62
22
41
333
21
52
67
Zn
54
48
10
21
21
85
69
10
26
213
01
26
78
13
4
Ga
14
11
19
20
16
15
17
12
18
27
19
29
Rb
30
24
65
47
52
33
66
32
81
11
71
22
06
Con
tinue
don
next
page
...
tablas geoquímica 127
Tabl
a1
3:C
hem
ical
resu
lts
for
the
Teco
mat
eFo
rmat
ion.
Aca
tlán
Com
plex
,Pue
bla/
Oax
aca,
Mex
ico
(par
t1
/4.)
Nam
eT
T-5A
TT-
5BT
T-6
TT-
7AT
T-7B
TT-
8AT
T-8B
TT-
32T
T-33
TT-
34A
TT-
34B
TT-
35
Lat
18.2
00
11
61
8.2
00
11
61
8.1
99
55
18.2
07
51
61
8.2
07
51
61
8.2
12
18
.21
21
8.2
56
03
31
8.2
55
81
8.2
422
16
18
.24
22
16
18.2
44
31
6
Lon
-97.8
16
66
6-9
7.8
16
66
6-9
7.8
16
86
6-9
7.8
21
61
6-9
7.8
21
61
6-9
7.8
33
85
-97.8
33
85
-97
.77
74
66
-97.7
77
9-9
7.7
889
66
-97.7
88
96
6-9
7.7
87
58
3
Lith
olog
ym
etap
s.m
etap
s.m
etap
el.
met
apel
.m
etap
s.m
etap
s.m
etap
s.m
etap
s.m
etap
s.m
etap
el.
met
apel
.m
etap
el.
Sr1
59
17
12
20
17
17
21
29
42
39
33
723
39
13
07
12
2
Y20
25
303
324
19
28
18
29
38
29
36
Zr
125
98
179
16
030
01
37
21
61
56
157
22
44
42
25
Nb
5.3
1.7
9.7
9.1
9.4
2.4
7.3
0.4
5.9
15.6
0.0
16
.7
Ba
234
18
646
74
13
582
33
56
01
32
84
17
76
64
99
86
7
Cs
5.4
2.2
1.1
5.0
3.6
1.9
7.5
0.0
6.0
6.3
4.9
8.0
La13
.320
.322
.9
Ce
26.7
26.3
41.1
42.8
45.8
31
.15
0.3
31.3
52
.49
6.7
4.8
63.9
Pr3.
45.
46.
2
Nd
13.3
22.8
24.0
Sm3.
25.
44.
7
Eu0.
71.
21.
1
Gd
3.3
5.4
4.9
Tb
0.51
0.86
0.79
Dy
3.5
5.8
4.9
Ho
0.77
1.24
1.01
Er2.
23.
42.
9
Tm
0.38
0.50
0.44
Yb
2.4
3.2
2.7
Lu0.
380.
510.
43
Hf
3.3
3.9
6.8
Con
tinue
don
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page
...
tablas geoquímica 128
Tabl
a1
3:C
hem
ical
resu
lts
for
the
Teco
mat
eFo
rmat
ion.
Aca
tlán
Com
plex
,Pue
bla/
Oax
aca,
Mex
ico
(par
t1
/4.)
Nam
eT
T-5A
TT-
5BT
T-6
TT-
7AT
T-7B
TT-
8AT
T-8B
TT-
32T
T-33
TT-
34A
TT-
34B
TT-
35
Lat
18.2
00
11
61
8.2
00
11
61
8.1
99
55
18.2
07
51
61
8.2
07
51
61
8.2
12
18
.21
21
8.2
56
03
31
8.2
55
81
8.2
422
16
18
.24
22
16
18.2
44
31
6
Lon
-97.8
16
66
6-9
7.8
16
66
6-9
7.8
16
86
6-9
7.8
21
61
6-9
7.8
21
61
6-9
7.8
33
85
-97.8
33
85
-97
.77
74
66
-97.7
77
9-9
7.7
889
66
-97.7
88
96
6-9
7.7
87
58
3
Lith
olog
ym
etap
s.m
etap
s.m
etap
el.
met
apel
.m
etap
s.m
etap
s.m
etap
s.m
etap
s.m
etap
s.m
etap
el.
met
apel
.m
etap
el.
Ta0.
190.
370.
36
Pb1
5.5
07
.01
6.9
22
.98.1
8.5
10.7
11.1
18.6
17
.85.4
13
.2
Th
3.3
6.8
6.6
U2.2
2.2
2.4
4.1
0.6
0.0
0.0
2.4
4.5
1.4
2.5
2.5
Tabl
a1
4:C
hem
ical
resu
lts
for
the
Teco
mat
eFo
rmat
ion.
Aca
tlán
Com
plex
,Pue
bla/
Oax
aca,
Mex
ico
(par
t2
/4.)
Nam
eT
T-36
TT-
37A
TT-
37B
TT-
38A
TT-
38B
TT-
39T
T-40
BT
T-43
TT-
61A
TT-
61B
TT-
62T
T-63
A
Lat
18.2
44
03
31
8.2
45
58
31
8.2
45
58
31
8.2
47
01
61
8.2
47
01
61
8.2
47
96
61
8.2
48
51
61
8.2
53
81
8.1
962
18.1
962
18
.19
67
83
18.1
93
65
Lon
-97.7
87
43
3-9
7.7
86
1-9
7.7
86
1-9
7.7
85
83
3-9
7.7
85
83
3-9
7.7
85
48
3-9
7.7
84
1-9
7.7
80
46
6-9
7.8
946
16
-97.8
94
61
6-9
7.8
93
68
3-9
7.8
94
2
Lith
olog
ym
etap
s.m
etap
s.m
etap
el.
met
aps.
met
apel
.m
etap
s.m
etap
el.
met
apel
.m
etap
s.m
etap
s.m
etap
s.m
eta-
ark.
SiO2
(wt%
)6
6.4
66.9
58
.76
7.9
59
.36
8.0
67.3
61
.87
2.1
70.6
71.2
56.1
TiO2
0.5
10.4
70
.76
0.4
50
.73
0.3
80.6
60
.61
0.3
50.3
70
.54
1.7
0
Al 2
O3
14.5
13.4
17
.61
5.0
14
.31
5.1
15.8
14
.51
4.2
14.0
13.4
16.4
Fe2
O3
5.2
04.5
27
.24
4.5
97
.03
3.0
25.1
15
.77
1.3
01.9
73
.31
11.3
MnO
0.0
82
0.0
74
0.0
62
0.0
72
0.1
20
0.0
66
0.0
56
0.0
79
0.0
18
0.0
23
0.0
16
0.1
82
MgO
2.4
92.1
43
.36
1.7
33
.77
1.1
91
.81
2.7
14.7
65.7
42
.79
3.4
4
CaO
2.5
63
.25
1.8
32.0
85
.51
2.2
90
.65
4.1
70.0
80.1
50
.54
2.4
8
Na 2
O3.8
14
.57
1.6
76.1
03
.88
4.4
72
.89
1.9
40.1
40.1
14
.35
2.0
6
Con
tinue
don
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page
...
tablas geoquímica 129
Tabl
a1
4:C
hem
ical
resu
lts
for
the
Teco
mat
eFo
rmat
ion.
Aca
tlán
Com
plex
,Pue
bla/
Oax
aca,
Mex
ico
(par
t2
/4.)
Nam
eT
T-36
TT-
37A
TT-
37B
TT-
38A
TT-
38B
TT-
39T
T-40
BT
T-43
TT-
61A
TT-
61B
TT-
62T
T-63
A
Lat
18.2
44
03
31
8.2
45
58
31
8.2
45
58
31
8.2
47
01
61
8.2
47
01
61
8.2
47
96
61
8.2
48
51
61
8.2
53
81
8.1
962
18.1
962
18
.19
67
83
18.1
93
65
Lon
-97.7
87
43
3-9
7.7
86
1-9
7.7
86
1-9
7.7
85
83
3-9
7.7
85
83
3-9
7.7
85
48
3-9
7.7
84
1-9
7.7
80
46
6-9
7.8
946
16
-97.8
94
61
6-9
7.8
93
68
3-9
7.8
94
2
Lith
olog
ym
etap
s.m
etap
s.m
etap
el.
met
aps.
met
apel
.m
etap
s.m
etap
el.
met
apel
.m
etap
s.m
etap
s.m
etap
s.m
eta-
ark.
K2
O0.9
50.6
93
.45
0.4
60
.62
.85
2.9
22
.32
3.6
03.3
61
.25
1.2
7
P 2O5
0.1
10.1
00
.21
0.1
90
.27
0.1
60.1
70
.17
0.0
50.0
90
.12
0.3
0
LOI
3.4
43.8
95
.07
1.4
64
.52
2.5
02.7
15
.93
3.4
03.6
32
.54
4.8
3
Tota
l1
00.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
Mg#
46
.04
5.8
45
.34
0.2
48
.94
1.2
38.7
45
.68
6.7
83.8
60.0
35
.2
V(p
pm)
12
91
15
18
03
87
45
81
02
15
015
40
51
19
8
Cr
46
49
97
21
17
11
47
08
75
10
33
7
Co
13
13
17
92
44
14
12
41
21
41
6
Ni
19
17
39
89
11
03
33
47
91
32
6
Cu
20
19
38
10
20
11
15
33
113
82
8
Zn
79
67
14
35
26
25
99
81
34
35
71
09
Ga
15
14
23
16
15
18
22
18
15
14
14
21
Rb
37
29
11
38
14
78
10
28
469
78
27
77
Sr2
91
25
91
45
30
94
11
25
31
73
20
011
11
96
13
5
Y25
25
27
22
29
123
63
133
38
35
34
Zr
143
11
91
78
12
61
71
175
20
51
66
291
324
20
51
21
Nb
5.9
0.9
11
.72.8
6.7
13.5
15.5
7.2
11.9
11.7
6.9
10.2
Ba
364
24
89
15
24
33
21
951
75
27
52
600
18
00
48
65
28
Cs
5.7
3.8
5.4
0.0
0.5
4.6
6.3
2.0
8.7
0.0
0.5
2.8
La13
.940
.739
.6
Ce
28.8
22.7
66
.62
9.1
37
.779
.38
1.2
43.0
74.6
66.7
52.6
47
.7
Con
tinue
don
next
page
...
tablas geoquímica 130
Tabl
a1
4:C
hem
ical
resu
lts
for
the
Teco
mat
eFo
rmat
ion.
Aca
tlán
Com
plex
,Pue
bla/
Oax
aca,
Mex
ico
(par
t2
/4.)
Nam
eT
T-36
TT-
37A
TT-
37B
TT-
38A
TT-
38B
TT-
39T
T-40
BT
T-43
TT-
61A
TT-
61B
TT-
62T
T-63
A
Lat
18.2
44
03
31
8.2
45
58
31
8.2
45
58
31
8.2
47
01
61
8.2
47
01
61
8.2
47
96
61
8.2
48
51
61
8.2
53
81
8.1
962
18.1
962
18
.19
67
83
18.1
93
65
Lon
-97.7
87
43
3-9
7.7
86
1-9
7.7
86
1-9
7.7
85
83
3-9
7.7
85
83
3-9
7.7
85
48
3-9
7.7
84
1-9
7.7
80
46
6-9
7.8
946
16
-97.8
94
61
6-9
7.8
93
68
3-9
7.8
94
2
Lith
olog
ym
etap
s.m
etap
s.m
etap
el.
met
aps.
met
apel
.m
etap
s.m
etap
el.
met
apel
.m
etap
s.m
etap
s.m
etap
s.m
eta-
ark.
Pr3.
88.
98.
9
Nd
14.8
32.7
39.3
Sm4.
05.
17.
1
Eu0.
91.
11.
4
Gd
4.1
3.5
6.5
Tb
0.70
0.49
0.95
Dy
4.6
2.6
6.1
Ho
0.96
0.47
1.28
Er3.
11.
34.
0
Tm
0.46
0.17
0.57
Yb
3.3
1.2
4.0
Lu0.
460.
190.
64
Hf
3.4
4.1
7.6
Ta0.
210.
470.
51
Pb1
5.1
10.6
89
.41
7.3
3.1
24.4
15
.01
9.7
6.4
2.2
7.7
14.5
Th
4.8
15.2
6.6
U3.4
4.5
3.6
0.0
3.0
7.7
0.6
4.8
4.2
3.1
0.7
2.3
tablas geoquímica 131
Tabl
a1
5:C
hem
ical
resu
lts
for
the
Teco
mat
eFo
rmat
ion.
Aca
tlán
Com
plex
,Pue
bla/
Oax
aca,
Mex
ico
(par
t3
/4.)
Nam
eT
T-63
BT
T-65
TT-
66T
T-67
TT-
68T
T-69
TT-
70T
T-83
AT
T-84
TT-
85T
T-86
TT-
87
Lat
18.1
93
65
18
.18
98
51
8.1
90
11
8.1
90
21
8.1
90
68
31
8.1
91
46
61
8.1
91
85
18.2
00
11
618
.19
38
16
18.1
894
18.1
77
61
61
8.1
77
9
Lon
-97.8
94
2-9
7.8
99
56
6-9
7.8
99
33
3-9
7.8
99
16
6-9
7.8
98
88
3-9
7.8
98
3-9
7.8
97
85
-97.8
16
66
6-9
7.8
93
26
6-9
7.8
92
25
-97.8
87
9-9
7.8
87
Lith
olog
ym
etap
el.
met
a-ar
k.m
eta-
ark.
met
a-ar
k.m
eta-
ark.
met
a-ar
k.m
etap
el.
met
a-co
ngl.
met
a-ar
k.m
eta-
ark.
met
aps.
met
a-co
ngl.
SiO2
(wt%
)6
0.3
72
.97
2.2
70
.07
2.1
68
.96
0.5
72
.863
.170.3
64
.17
4.0
TiO2
0.8
80.4
20
.39
0.6
20
.44
0.5
00.6
40.2
20.7
20
.47
0.5
90.3
4
Al 2
O3
19.3
12.8
12
.91
3.1
13
.51
4.2
14.4
10.7
17.9
12
.61
5.2
11.7
Fe2
O3
7.3
03.5
83
.40
4.5
53
.89
5.0
96.1
61.5
96.6
64
.48
6.0
62.4
3
MnO
0.1
09
0.0
85
0.1
02
0.0
81
0.0
90
0.1
03
0.0
77
0.0
65
0.0
78
0.0
91
0.0
83
0.0
65
MgO
2.1
51.3
11
.74
1.5
21
.58
1.8
82.7
20.7
22.3
51
.94
2.8
90.7
2
CaO
0.3
61.8
91
.43
2.2
11
.13
1.9
04.7
34.5
20.5
22
.18
2.2
92.5
6
Na 2
O0.8
43.4
74
.06
3.7
84
.23
3.5
01.5
75.1
20.8
63
.27
3.2
95.7
6
K2
O4.1
11.1
21
.01
1.0
41
.01
1.1
92.6
10.2
54.3
11
.03
1.3
00.2
6
P 2O5
0.1
80.0
90
.08
0.0
70
.10
0.1
00.1
60.0
30.1
80
.06
0.1
30.0
7
LOI
4.5
32.3
32
.75
3.0
62
.00
2.5
76.3
83.9
93.2
83
.55
4.0
22.1
2
Tota
l1
00
.01
00
.01
00
.01
00
.01
00
.01
00.0
10
0.0
10
0.0
100
.01
00.0
10
0.0
10
0.0
Mg#
34.4
39.5
47
.73
7.3
42
.03
9.7
44.0
44.7
38.6
43
.64
5.9
34.6
V(p
pm)
13
86
55
71
08
74
10
61
42
38
130
113
15
33
4
Cr
10
02
01
83
02
62
39
21
386
41
74
13
Co
18
75
94
81
73
16
11
15
5
Ni
41
13
10
14
15
13
43
737
17
27
6
Cu
24
10
10
11
91
12
61
132
93
33
3
Zn
11
44
44
16
74
85
31
36
19
75
64
10
72
1
Ga
27
13
12
13
14
16
19
12
26
13
18
8
Rb
18
84
23
54
74
14
89
65
12
94
35
45
Con
tinue
don
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page
...
tablas geoquímica 132
Tabl
a1
5:C
hem
ical
resu
lts
for
the
Teco
mat
eFo
rmat
ion.
Aca
tlán
Com
plex
,Pue
bla/
Oax
aca,
Mex
ico
(par
t3
/4.)
Nam
eT
T-63
BT
T-65
TT-
66T
T-67
TT-
68T
T-69
TT-
70T
T-83
AT
T-84
TT-
85T
T-86
TT-
87
Lat
18.1
93
65
18
.18
98
51
8.1
90
11
8.1
90
21
8.1
90
68
31
8.1
91
46
61
8.1
91
85
18.2
00
11
618
.19
38
16
18.1
894
18.1
77
61
61
8.1
77
9
Lon
-97.8
94
2-9
7.8
99
56
6-9
7.8
99
33
3-9
7.8
99
16
6-9
7.8
98
88
3-9
7.8
98
3-9
7.8
97
85
-97.8
16
66
6-9
7.8
93
26
6-9
7.8
92
25
-97.8
87
9-9
7.8
87
Lith
olog
ym
etap
el.
met
a-ar
k.m
eta-
ark.
met
a-ar
k.m
eta-
ark.
met
a-ar
k.m
etap
el.
met
a-co
ngl.
met
a-ar
k.m
eta-
ark.
met
aps.
met
a-co
ngl.
Sr4
79
59
81
34
90
12
02
16
15
96
41
39
20
71
21
Y4
73
22
917
32
33
34
67
38
23
30
40
Zr
20
61
32
11
429
01
43
12
71
59
15
91
87
17
01
63
19
5
Nb
20.3
5.5
3.3
8.7
3.5
3.0
9.1
3.4
16
.42.7
5.4
2.9
Ba
92
44
26
35
136
63
08
41
67
39
74
689
420
46
92
13
Cs
7.7
2.3
0.3
0.0
1.6
5.5
6.6
5.9
2.6
3.6
2.9
0.6
La17
.2
Ce
10
1.0
29.6
35
.535
.32
9.8
31
.26
4.1
46.3
82.2
28
.23
6.6
22.5
Pr4.
3
Nd
16.8
Sm3.
6
Eu0.
9
Gd
3.4
Tb
0.50
Dy
3.5
Ho
0.74
Er2.
1
Tm
0.32
Yb
2.6
Lu0.
40
Hf
6.6
Con
tinue
don
next
page
...
tablas geoquímica 133
Tabl
a1
5:C
hem
ical
resu
lts
for
the
Teco
mat
eFo
rmat
ion.
Aca
tlán
Com
plex
,Pue
bla/
Oax
aca,
Mex
ico
(par
t3
/4.)
Nam
eT
T-63
BT
T-65
TT-
66T
T-67
TT-
68T
T-69
TT-
70T
T-83
AT
T-84
TT-
85T
T-86
TT-
87
Lat
18.1
93
65
18
.18
98
51
8.1
90
11
8.1
90
21
8.1
90
68
31
8.1
91
46
61
8.1
91
85
18.2
00
11
618
.19
38
16
18.1
894
18.1
77
61
61
8.1
77
9
Lon
-97.8
94
2-9
7.8
99
56
6-9
7.8
99
33
3-9
7.8
99
16
6-9
7.8
98
88
3-9
7.8
98
3-9
7.8
97
85
-97.8
16
66
6-9
7.8
93
26
6-9
7.8
92
25
-97.8
87
9-9
7.8
87
Lith
olog
ym
etap
el.
met
a-ar
k.m
eta-
ark.
met
a-ar
k.m
eta-
ark.
met
a-ar
k.m
etap
el.
met
a-co
ngl.
met
a-ar
k.m
eta-
ark.
met
aps.
met
a-co
ngl.
Ta0.
33
Pb2
3.9
12
.91
2.2
13
.16
.51
2.9
14
.34
2.0
10
.810.5
15
.11
8.6
Th
4.8
U8.6
2.3
3.3
0.0
4.0
3.7
0.0
6.1
3.7
3.2
4.4
3.1
tablas geoquímica 134
Tabla 16: Chemical results for the Tecomate Formation. AcatlánComplex, Puebla/Oaxaca, Mexico. (part 4/4)
Name TT-88 TT-89 TT-90 TT-91 TT-486B
Lat 18.178133 18.1788 18.179283 18.176533 18.28409
Lon -97.886583 -97.887366 -97.8867 -97.88415 -97.91114
Lithology meta-ark. meta-ark. meta-ark. meta-ark. metaps.
SiO2 (wt %) 65.7 64.2 71.2 71.1 75.16
TiO2 0.57 0.61 0.43 0.46 0.853
Al2O3 13.3 16.1 13.4 13.3 11.31
Fe2O3 4.30 6.12 3.72 3.99 3.92
MnO 0.100 0.083 0.067 0.068 0.053
MgO 1.82 2.99 1.53 1.64 0.97
CaO 4.02 1.80 2.08 1.96 1.07
Na2O 4.30 3.14 4.71 4.13 2.18
K2O 1.08 1.69 0.70 0.88 2.16
P2O5 0.14 0.15 0.08 0.10 0.124
LOI 4.70 3.16 2.04 2.44 2.26
Total 100.0 100.0 100.0 100.0 100.06
Mg# 43.0 46.5 42.3 42.3
V (ppm) 113 144 84 83 77.4
Cr 42 86 25 43 49.3
Co 13 14 10 13 10.5
Ni 24 27 12 21 19.4
Cu 22 29 20 11 35.9
Zn 74 112 52 60 47.1
Ga 15 19 14 15 16.6
Rb 51 70 23 39 77.9
Sr 277 216 237 217 127.2
Y 19 28 24 19 40.8
Zr 146 162 105 130 459.3
Nb 4.0 7.7 2.9 4.2 18.3
Ba 614 633 363 309 786
Cs 5.6 1.6 3.0 3.1 4.3
La
Ce 36.8 42.3 24.7 39.1 66.1
Pr
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Hf
Ta
Pb 16.5 14.3 99.6 67.7 8
Th 14.8
U 3.0 2.5 2.4 3.3 1.8
tablas geoquímica 135
Tabl
a1
7:C
hem
ical
resu
lts
for
the
Coz
ahui
cogr
anit
eas
wel
las
LaC
arbo
nera
stoc
k,Pu
ebla
/Oax
aca,
Mex
ico.
Coz
ahui
cogr
anit
eLa
Car
bone
rast
ock
Nam
eT
T-55
8T
T-55
9T
T-56
0T
T-56
1T
T-56
2T
T-56
3T
T-56
4T
T-56
5AT
T-56
5BT
T-56
6T
T-56
8T
T-56
9
Lat
18.1
26
19
32
18
.12
68
12
71
8.1
27
82
42
18
.19
57
65
18
.19
57
82
21
8.1
95
40
56
18
.20
19
81
31
7.2
99
66
217
.299
66
21
7.2
997
66
91
7.2
99
98
66
17.2
99
93
34
Lon
-97.4
50
30
84
-97.4
49
79
7-9
7.4
50
55
66
-97.5
00
51
7-9
7.5
01
70
58
-97.5
00
97
34
-97.5
13
28
29
-97.0
10
95
35
-97.0
10
95
35
-97.0
116
32
6-9
7.0
12
57
95
-97.0
11
31
75
Lith
olog
ygr
anit
egr
anit
egr
anit
egr
anit
egr
anit
egr
anit
egr
anit
edi
orit
edi
orit
edi
orit
ega
bbro
gran
odio
rite
SiO2
(wt%
)7
0.5
71
.37
0.6
77
.47
5.5
76
.47
3.1
58.9
57
.45
7.0
48.6
67.1
TiO2
0.1
60
.15
0.1
60
.17
0.3
30.4
20.2
30.5
50.7
90.8
41.5
40.2
9
Al 2
O3
16.9
16
.61
6.8
13
.71
2.6
12.6
15.2
21.2
18.2
18.4
11.6
17.8
Fe2
O3
1.0
00
.80
0.9
10
.97
2.2
30.7
31.0
63.6
58.0
27.7
61
9.1
3.3
7
MnO
0.0
16
0.0
15
0.0
20
.00
10.0
40
0.0
26
0.0
34
0.0
50.1
50.1
40.2
10.0
4
MgO
0.3
0.3
30.2
90
.15
0.1
80.0
60.1
60.8
31.8
32.2
05.6
20.4
1
CaO
1.6
91
.28
1.9
30
.28
0.7
0.6
70.7
17.0
36.4
67.0
68.2
94.1
8
Na 2
O5.9
05
.74
5.7
24
.58
2.9
52.8
64.1
54.4
43.5
33.6
11.9
64.6
3
K2
O2.7
52
.76
2.6
72
.11
5.0
15.4
94.3
11.5
31.7
71.5
61.5
41.7
7
P 2O5
0.0
50
.04
0.0
50
.04
0.0
40.0
40.0
70.1
90.4
60.5
60.5
50.1
0
LOI
1.2
91
.16
1.1
51
.16
1.0
50.9
81.4
40.7
71.0
01.0
11.0
50.5
6
Tota
l1
00.5
10
0.2
10
0.3
10
0.6
10
0.6
10
0.3
10
0.4
99
.19
9.6
100
.21
00.0
10
0.3
Mg#
37.3
45
.03
8.7
23
.51
3.8
14.0
23.0
31.1
31.1
36.0
36.9
19.4
V(p
pm)
11
11
13
13
14
11
16
14
39
55
20
36
Cr
00
00
00
00
04
10
90
Co
10
12
30
13
810
34
2
Ni
42
45
44
35
56
42
1
Cu
63
16
16
23
13
68
39
43
5
Zn
37
37
32
82
08
12
74
12
51
21
21
86
5
Con
tinue
don
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page
...
tablas geoquímica 136
Tabl
a1
7:C
hem
ical
resu
lts
for
the
Coz
ahui
cogr
anit
eas
wel
las
LaC
arbo
nera
stoc
k,Pu
ebla
/Oax
aca,
Mex
ico.
Coz
ahui
cogr
anit
eLa
Car
bone
rast
ock
Nam
eT
T-55
8T
T-55
9T
T-56
0T
T-56
1T
T-56
2T
T-56
3T
T-56
4T
T-56
5AT
T-56
5BT
T-56
6T
T-56
8T
T-56
9
Lat
18.1
26
19
32
18
.12
68
12
71
8.1
27
82
42
18
.19
57
65
18
.19
57
82
21
8.1
95
40
56
18
.20
19
81
31
7.2
99
66
217
.299
66
21
7.2
997
66
91
7.2
99
98
66
17.2
99
93
34
Lon
-97.4
50
30
84
-97.4
49
79
7-9
7.4
50
55
66
-97.5
00
51
7-9
7.5
01
70
58
-97.5
00
97
34
-97.5
13
28
29
-97.0
10
95
35
-97.0
10
95
35
-97.0
116
32
6-9
7.0
12
57
95
-97.0
11
31
75
Lith
olog
ygr
anit
egr
anit
egr
anit
egr
anit
egr
anit
egr
anit
egr
anit
edi
orit
edi
orit
edi
orit
ega
bbro
gran
odio
rite
Ga
19
19
19
17
17
12
21
22
21
21
17
20
Rb
32
31
31
46
77
79
13
32
535
27
25
22
Sr8
98
76
79
72
11
68
61
15
18
41
03
770
37
24
25
07
03
Y5
54
23
57
47
162
857
4
Zr
16
01
45
105
11
63
54
459
140
367
130
123
273
175
Nb
1.7
1.8
1.5
7.0
2.5
4.3
5.9
5.9
6.9
9.2
155.
9
Ba
14
67
11
88
1603
40
21
00
411
9740
911
4612
368
71
1057
1546
Cs
1.2
0.7
La5.
46.
714
.418
.719
.329
.321
.2
Ce
22.2
20
.910
.73
9.2
53
.811
.225
.737
.440
.54
9.6
85.1
42.5
Pr1.
41.
53.
04.
795.
3314
.55.
32
Nd
4.4
5.9
5.4
14
.61
8.0
6.4
10.8
19.2
22.8
37.0
073
.021
.0
Sm1.
11.
61.
83.
614.
6218
.13.
54
Eu0.
41.
40.
51.
791.
662.
851.
31
Gd
0.7
1.3
0.9
2.06
3.50
14.8
1.65
Tb
0.10
0.24
0.14
0.30
0.56
2.27
0.23
Dy
0.6
1.6
0.8
1.70
3.23
13.1
1.04
Ho
0.12
0.32
0.16
0.27
0.58
2.30
0.14
Er0.
40.
90.
50.
691.
565.
840.
35
Tm
0.06
0.12
0.07
0.08
0.22
0.75
0.05
Con
tinue
don
next
page
...
tablas geoquímica 137
Tabl
a1
7:C
hem
ical
resu
lts
for
the
Coz
ahui
cogr
anit
eas
wel
las
LaC
arbo
nera
stoc
k,Pu
ebla
/Oax
aca,
Mex
ico.
Coz
ahui
cogr
anit
eLa
Car
bone
rast
ock
Nam
eT
T-55
8T
T-55
9T
T-56
0T
T-56
1T
T-56
2T
T-56
3T
T-56
4T
T-56
5AT
T-56
5BT
T-56
6T
T-56
8T
T-56
9
Lat
18.1
26
19
32
18
.12
68
12
71
8.1
27
82
42
18
.19
57
65
18
.19
57
82
21
8.1
95
40
56
18
.20
19
81
31
7.2
99
66
217
.299
66
21
7.2
997
66
91
7.2
99
98
66
17.2
99
93
34
Lon
-97.4
50
30
84
-97.4
49
79
7-9
7.4
50
55
66
-97.5
00
51
7-9
7.5
01
70
58
-97.5
00
97
34
-97.5
13
28
29
-97.0
10
95
35
-97.0
10
95
35
-97.0
116
32
6-9
7.0
12
57
95
-97.0
11
31
75
Lith
olog
ygr
anit
egr
anit
egr
anit
egr
anit
egr
anit
egr
anit
egr
anit
edi
orit
edi
orit
edi
orit
ega
bbro
gran
odio
rite
Yb
0.4
0.9
0.5
0.70
1.51
4.64
0.20
Lu0.
070.
140.
090.
100.
240.
680.
03
Hf
2.8
10.0
3.7
6.48
2.96
6.85
3.94
Ta0.
080.
210.
330.
220.
290.
390.
19
Pb0.0
03
.40
.01
0.0
12
.51
0.3
9.4
0.0
05.5
00.2
09.7
00.0
0
Th
0.5
0.2
5.3
2.59
2.09
3.09
2.16
U0.7
0.7
0.0
5.0
0.2
2.7
1.4
0.0
01.7
00.8
03.6
02.1
0
DTA B L A S A N Á L I S I S D E M I C R O S O N D A
Material suplementario publicado en línea como parte del artículo: Kirsch,M., Keppie, J.D., Murphy, J.B., y Lee, J.K.W., Arc plutonism in atranstensional regime: the Late Palaeozoic Totoltepec pluton, AcatlánComplex, southern Mexico: International Geology Review, en prensa, doi:10.1080/00206814.2012.693247.
138
tablas análisis de microsonda 139
Tabl
a1
8:A
vera
gepl
agio
clas
eco
mpo
siti
ons
ofro
cks
from
the
Toto
ltep
ecpl
uton
.
Sam
ple
TT-
14T
T-14
TT-
14T
T-13
aT
T-13
aT
T-13
aT
T-55
TT-
55T
T-55
TT-
54T
T-54
TT-
54T
T-17
TT-
17Sp
ecim
enP1
P3P2
P1P3
P2P2
P3P1
P1P2
P3P1
P2
wt.
%Si
O2
57
.66
58
.12
59
.06
61.2
56
0.0
45
9.7
75
8.3
55
8.6
45
8.6
56
0.6
16
0.2
36
2.7
75
5.6
55
6.0
3
TiO2
0.0
00
.00
0.0
00.0
00
.00
0.0
00
.00
0.0
00
.00
0.0
00.0
00
.00
0.0
00
.00
Al 2
O3
27
.38
27
.41
26
.31
24.3
32
5.2
22
5.0
82
6.6
72
6.4
22
6.2
82
4.6
62
5.1
12
4.2
82
8.4
72
8.3
2
FeO
0.0
60
.06
0.0
30.0
50
.04
0.0
50
.04
0.0
40
.04
0.0
40.0
20
.07
0.0
70
.10
MgO
0.0
00
.00
0.0
00.0
10
.00
0.0
00
.00
0.0
00
.00
0.0
00.0
00
.00
0.0
00
.00
CaO
9.0
19
.30
8.7
16.5
56
.70
7.2
78
.45
8.4
28
.32
6.1
27.1
46
.17
11
.63
11
.03
Na 2
O6
.29
6.2
06
.43
7.7
57
.66
7.4
46
.78
6.6
66
.68
7.9
57.5
88
.18
4.9
35
.25
K2
O0
.04
0.0
50
.05
0.1
00
.05
0.1
00
.05
0.0
40
.03
0.1
40.0
70
.08
0.0
40
.06
SrO
0.0
50
.03
0.0
70
.00
0.0
00
.02
0.0
40
.02
0.0
40.0
00.0
00
.02
0.0
00
.01
NiO
0.0
10
.00
0.0
00
.00
0.0
00
.00
0.0
20
.00
0.0
10.0
00.0
10
.00
0.0
10
.01
BaO
0.0
00
.02
0.0
00
.00
0.0
10
.01
0.0
10
.01
0.0
10.0
20.0
00
.00
0.0
30
.01
Tota
l1
00
.50
10
1.2
01
00
.66
10
0.0
49
9.7
49
9.7
51
00.4
11
00
.25
10
0.0
79
9.5
41
00.1
71
01
.56
10
0.8
21
00
.83
Num
ber
ofio
nson
the
basi
sof
8ox
ygen
atom
sSi
2.5
72
.57
2.6
22
.72
2.6
82
.67
2.6
02
.61
2.6
22.7
12.6
82
.74
2.4
92
.50
Ti0
.00
0.0
00
.00
0.0
00
.00
0.0
00
.00
0.0
00
.00
0.0
00.0
00
.00
0.0
00
.00
Al
1.4
41
.43
1.3
81
.27
1.3
31
.32
1.4
01
.39
1.3
81.3
01.3
21
.25
1.5
01
.49
Fe2+
0.0
00
.00
0.0
00
.00
0.0
00
.00
0.0
00
.00
0.0
00.0
00.0
00
.00
0.0
00
.00
Con
tinue
don
next
page
...
tablas análisis de microsonda 140
Tabl
a1
8:A
vera
gepl
agio
clas
eco
mpo
siti
ons
ofro
cks
from
the
Toto
ltep
ecpl
uton
.
Sam
ple
TT-
14T
T-14
TT-
14T
T-13
aT
T-13
aT
T-13
aT
T-55
TT-
55T
T-55
TT-
54T
T-54
TT-
54T
T-17
TT-
17Sp
ecim
enP1
P3P2
P1P3
P2P2
P3P1
P1P2
P3P1
P2
Mg
0.0
00
.00
0.0
00.0
00
.00
0.0
00
.00
0.0
00
.00
0.0
00.0
00
.00
0.0
00
.00
Ca
0.4
30
.44
0.4
10.3
10
.32
0.3
50
.40
0.4
00
.40
0.2
90.3
40
.29
0.5
60
.53
Na
0.5
40
.53
0.5
50.6
70
.66
0.6
40
.59
0.5
80
.58
0.6
90.6
50
.69
0.4
30
.45
K0
.00
0.0
00
.00
0.0
10
.00
0.0
10
.00
0.0
00
.00
0.0
10.0
00
.00
0.0
00
.00
Sr0
.00
0.0
00
.00
0.0
00
.00
0.0
00
.00
0.0
00
.00
0.0
00.0
00
.00
0.0
00
.00
Ni
0.0
00
.00
0.0
00.0
00
.00
0.0
00
.00
0.0
00
.00
0.0
00.0
00
.00
0.0
00
.00
Ba0
.00
0.0
00
.00
0.0
00
.00
0.0
00
.00
0.0
00
.00
0.0
00.0
00
.00
0.0
00
.00
Tota
l4
.99
4.9
84
.97
4.9
84
.99
4.9
94
.99
4.9
84
.98
4.9
94.9
94
.98
4.9
84
.98
mol
%A
n4
4.1
45
.24
2.7
31
.73
2.5
34
.94
0.7
41
.04
0.7
29.6
34.1
29
.35
6.5
53
.5A
b5
5.7
54
.55
7.0
67
.86
7.2
64
.55
9.0
58
.75
9.1
69.6
65.5
70
.24
3.3
46
.1O
r0
.30
.30
.30.5
0.3
0.6
0.3
0.2
0.2
0.8
0.4
0.5
0.2
0.3
Tota
l1
00
.01
00
.01
00
.01
00.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
10
0.0
tablas análisis de microsonda 141
Tabl
a1
9:A
vera
geam
phib
ole
com
posi
tion
sof
rock
sfr
omth
eTo
tolt
epec
plut
on.
Sam
ple
TT-
14T
T-14
TT-
14T
T-13
aT
T-13
aT
T-13
aT
T-55
TT-
55T
T-55
TT-
54T
T-54
TT-
54T
T-28
TT-
28T
T-28
TT-
17T
T-17
TT-
17
Spec
imen
A1
A2
A3
A1
A2
A3
A1
A2
A3
A1
A2
A3
A1
A2
A3
A1
A2
A3
wt.
%
SiO2
45.0
14
3.5
14
3.9
34
2.7
24
2.1
34
2.8
54
3.9
94
2.5
14
4.1
54
1.5
24
1.4
84
2.3
34
3.4
144.6
343.6
14
6.7
84
6.3
14
6.0
7
TiO2
0.9
20
.97
1.0
40.7
20.7
10.6
60
.62
0.5
00.6
10.5
60.6
00.6
41.4
91.2
31.5
21.2
81.3
31.1
8
Al 2
O3
10.0
91
1.0
11
0.6
01
1.4
41
1.9
01
2.1
81
2.3
01
3.6
31
2.2
81
3.2
81
2.8
41
2.5
211
.92
12.0
91
2.3
08
.17
8.1
08.4
4
FeO
15.2
41
6.1
71
5.5
21
9.2
71
9.0
11
9.6
11
6.5
31
7.1
21
6.4
61
8.9
21
8.6
81
8.6
112.5
213.3
412.8
31
7.5
31
7.6
61
6.9
4
MgO
13.1
21
2.0
51
2.3
49.5
58.2
29.0
01
0.8
69
.78
11
.08
8.9
99
.47
9.5
313.3
012.5
213.0
01
1.5
31
1.4
81
1.7
8
MnO
0.8
30.7
90.7
31.5
01.2
01
.41
0.7
40
.59
0.6
81.1
81
.27
1.1
30.5
20
.46
0.5
10.9
61
.05
0.9
0
CaO
10.9
81
0.9
61
0.8
91
1.1
81
1.1
51
1.2
51
0.8
01
0.8
81
1.1
21
1.1
61
1.0
01
1.1
811.5
111.8
211
.51
11.4
41
1.2
51
1.4
3
Na 2
O1
.69
1.7
91.7
11
.90
1.9
41
.81
1.9
31.9
91.9
51.9
21.9
41.8
42.1
72.0
42.1
31.1
31.1
11.1
3
K2
O0.1
70.2
10.1
80
.74
0.7
30.7
50
.20
0.2
20.2
10
.73
0.6
70.6
60
.25
0.2
10.2
60
.73
0.7
20.5
5
Tota
l9
8.0
59
6.1
09
6.9
49
9.0
29
6.9
89
9.5
59
7.9
69
7.2
29
8.6
79
8.2
29
7.9
59
8.4
39
7.0
89
6.1
09
7.6
89
9.5
69
9.0
19
8.4
2
Form
ula
c.f.
Hol
land
and
Blun
dy(1
994)
T-si
tes
Si6.5
16.3
76.4
46
.31
6.4
06.3
06
.43
6.2
96.4
26
.17
6.1
76.2
66
.34
6.4
66.3
36
.79
6.7
66.7
3
AlIV
1.4
91.6
31
.56
1.6
91
.60
1.7
01.5
71.7
11.5
81.8
31.8
31.7
41.6
61.5
41.6
71.2
11.2
41.2
7
Sum
T8.0
08.0
08
.00
8.0
08.0
08.0
08.0
08.0
08.0
08.0
08.0
08.0
08.0
08.0
08.0
08.0
08.0
08.0
0
M1–
3si
tes
AlVI
0.2
30.2
70.2
80
.30
0.5
20.4
20.5
50.6
70
.52
0.5
00.4
20
.44
0.3
90.5
20
.44
0.1
90.1
60
.18
Ti0.1
00.1
10.1
10
.08
0.0
80.0
70.0
70.0
60
.07
0.0
60.0
70
.07
0.1
60.1
30
.17
0.1
40.1
50
.13
Fe3+
0.9
31.0
10.9
40
.89
0.5
10.8
20.7
40.7
10
.73
0.8
60.9
70
.86
0.6
00.4
30
.57
0.6
10.6
50
.73
Mg
2.8
32.6
32.7
02
.10
1.8
61.9
72
.36
2.1
62.4
01.9
92.1
02.1
02.8
92.7
02.8
12.4
92.5
02.5
6
Mn
0.1
00
.10
0.0
90.1
90.1
50.1
80
.09
0.0
70.0
80.1
50.1
60.1
40.0
60.0
60.0
60.1
20.1
30.1
1
Con
tinue
don
next
page
...
tablas análisis de microsonda 142
Tabl
a1
9:A
vera
geam
phib
ole
com
posi
tion
sof
rock
sfr
omth
eTo
tolt
epec
plut
on.
Sam
ple
TT-
14T
T-14
TT-
14T
T-13
aT
T-13
aT
T-13
aT
T-55
TT-
55T
T-55
TT-
54T
T-54
TT-
54T
T-28
TT-
28T
T-28
TT-
17T
T-17
TT-
17
Spec
imen
A1
A2
A3
A1
A2
A3
A1
A2
A3
A1
A2
A3
A1
A2
A3
A1
A2
A3
Fe2+
0.8
10
.89
0.8
81.4
31.8
71.5
41
.19
1.3
31.2
01.4
41.2
91.3
90.8
91.1
60.9
41.4
51.4
21.2
9
Sum
M1–3
5.0
05
.00
5.0
05.0
05.0
05.0
05
.00
5.0
05.0
05.0
05.0
05.0
05.0
05.0
05.0
05.0
05.0
05.0
0
M4
site
Fe0.1
10.0
80.0
80.0
50.0
30.0
50
.09
0.0
80.0
70.0
50
.06
0.0
50.0
40
.02
0.0
40.0
60
.08
0.0
5
Ca
1.7
01.7
21.7
11.7
71.8
11.7
71
.69
1.7
21.7
31.7
81
.75
1.7
71.8
01
.83
1.7
91.7
81
.76
1.7
9
Na
0.1
90.2
00.2
10.1
80.1
50
.17
0.2
20
.20
0.2
00.1
70
.18
0.1
70.1
60
.14
0.1
60.1
60
.16
0.1
6
Sum
M4
2.0
02.0
02.0
02.0
02.0
02
.00
2.0
02.0
02.0
02.0
02.0
02.0
02.0
02.0
02.0
02.0
02.0
02.0
0
A-s
ite
Na
0.2
80.3
10.2
80
.37
0.4
20
.34
0.3
30.3
70.3
50.3
80.3
70.3
50.4
50.4
30.4
40.1
60.1
60.1
6
K0
.03
0.0
40.0
30
.14
0.1
40.1
40
.04
0.0
40.0
40.1
40.1
30.1
20.0
50.0
40.0
50.1
40.1
30.1
0
Sum
A0.3
20.3
40.3
20
.51
0.5
60.4
80
.37
0.4
10.3
90
.52
0.5
00.4
80
.50
0.4
70.4
80
.30
0.2
90.2
6
Sum
cati
on1
5.3
21
5.3
41
5.3
21
5.5
11
5.5
61
5.4
81
5.3
71
5.4
11
5.3
91
5.5
21
5.5
01
5.4
81
5.5
01
5.4
71
5.4
81
5.3
01
5.2
91
5.2
6
Al(
tota
l)1.7
21.9
01.8
31
.99
2.1
32.1
12.1
22.3
82.1
02.3
32.2
52.1
82.0
52.0
62.1
11.4
01.3
91.4
5
tablas análisis de microsonda 143
Tabla 20: Mica compositions of rocks from the Totoltepec pluton, Puebla, Mexico.
Sample TT-13a TT-13a TT-14 TT-14 TT-54 TT-54 TT-54 TT-54 TT-28 TT-28
Specimen Mc-1 Mc-2 Mc-1 Mc-2 Mc-1 Mc-2 Mc-3 Mc-4 Mc-1 Mc-2
wt. %SiO2 46.58 46.32 42.53 43.10 35.42 33.83 35.44 35.44 42.90 42.38
TiO2 0.07 0.08 0.03 0.28 0.05 0.01 0.11 0.12 0.00 0.02
Al2O3 31.44 32.13 32.37 32.34 28.24 28.51 27.94 27.91 34.32 35.18
FeO 3.92 3.83 3.15 2.72 1.80 1.72 1.87 1.89 0.93 0.76
MgO 1.46 1.25 0.81 0.90 1.06 1.05 0.94 0.97 0.12 0.00
MnO 0.01 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00
CaO 0.00 0.02 0.02 0.05 0.00 0.01 0.01 0.03 0.00 0.00
Na2O 0.86 0.92 1.19 1.45 0.90 0.89 0.96 0.94 0.26 0.23
K2O 10.41 10.43 10.53 10.12 6.64 7.59 6.57 6.68 12.60 12.66
Cr2O3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
NiO 0.00 0.00 0.02 0.01 0.03 0.01 0.01 0.00 0.00 0.01
Total 94.75 94.98 90.66 90.99 74.14 73.60 73.85 73.97 91.13 91.24
Formula calculated on the basis of 11 oxygen atoms
T-siteSi 3.17 3.14 3.04 3.05 3.02 2.93 3.03 3.03 3.03 2.99
AlIV 0.83 0.86 0.96 0.95 0.98 1.07 0.97 0.97 0.97 1.01
Sum T 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00
M-siteAlVI 1.69 1.71 1.76 1.75 1.86 1.85 1.85 1.84 1.89 1.91
Mg 0.15 0.13 0.09 0.10 0.14 0.14 0.12 0.12 0.01 0.00
Fe 0.22 0.22 0.19 0.16 0.13 0.12 0.13 0.13 0.05 0.04
Ti 0.00 0.00 0.00 0.01 0.00 0.00 0.01 0.01 0.00 0.00
Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Ca 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Cr 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Ni 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Sum M 2.06 2.06 2.04 2.03 2.12 2.11 2.11 2.11 1.96 1.96
A-siteNa 0.11 0.12 0.17 0.20 0.15 0.15 0.16 0.16 0.04 0.03
K 0.90 0.90 0.96 0.91 0.72 0.84 0.72 0.73 1.14 1.14
Sum A 7.08 7.08 7.16 7.14 7.00 7.10 6.99 7.00 7.13 7.13
tablas análisis de microsonda 144
Tabl
a2
1:E
nerg
y-di
sper
sive
x-ra
ysp
ectr
osco
py(E
DX
)re
sult
sof
sele
cted
min
eral
sfr
omTo
tolt
epec
plut
onro
cks.
Sam
ple
TT-
514
TT-
514
TT-
514
TT-
514
TT-
514
TT-
14T
T-14
TT-
14T
T-14
TT-
13a
TT-
13a
TT-
13a
TT-
54
Spec
imen
#1#2
#3#4
#5O
p1#1
Op1
#2O
p2#1
Op2
#2Pl
1#1
Pl1#
2Pl
1#3
Am
p3#1
wt.
%Si
O2
1.5
73
0.0
00
30
.61
70
.00
00
.00
00
.00
00
.18
82
5.5
61
0.0
00
0.2
51
0.1
77
0.5
81
0.0
00
TiO2
0.0
00
0.1
08
0.0
45
n.d.
n.d.
46
.78
44
3.3
29
16.8
61
52.6
60
13
.91
14
9.7
79
0.2
14
49
.92
5
Al 2
O3
1.1
94
0.0
00
19
.55
80
.00
00
.00
00
.28
70
.00
09.2
27
0.0
00
0.0
00
0.0
35
0.2
34
0.2
48
FeO
93.9
73
0.1
92
29
.78
70
.00
00
.18
85
1.7
72
55
.05
72
7.1
68
46.5
28
84
.64
84
6.5
62
97
.42
04
3.6
23
MgO
0.7
96
0.1
00
16
.54
40
.00
00
.89
10
.00
00
.46
76.9
15
0.0
00
0.0
00
0.0
00
0.0
00
0.3
10
MnO
0.0
14
0.0
00
1.4
35
0.5
26
0.0
00
0.0
00
0.0
00
0.0
00
0.0
00
0.7
64
1.9
78
0.4
76
4.3
04
CaO
0.1
39
46.9
11
0.1
29
0.0
65
15
.65
60
.13
60
.18
41
3.9
44
0.5
91
0.0
00
0.0
57
0.5
88
0.3
91
Na 2
O2
.16
40.0
00
0.0
00
0.0
00
0.0
00
0.0
00
0.0
00
0.0
00
0.0
00
0.0
13
0.6
69
0.0
06
0.9
95
K2
O0
.11
50.0
48
0.0
00
0.0
00
0.0
00
0.0
00
0.0
00
0.3
24
0.0
00
0.1
66
0.0
85
0.0
00
0.0
00
Cr 2
O3
0.0
00
0.0
00
0.4
50
0.0
00
0.0
00
0.1
05
0.5
37
0.0
00
0.0
13
0.0
96
0.2
34
0.4
81
0.0
00
NiO
0.0
00
0.4
88
0.0
00
0.1
14
0.7
83
0.6
13
0.2
36
0.0
00
0.0
31
0.1
51
0.4
25
0.0
00
0.2
04
CuO
0.0
00
0.0
00
0.1
03
0.5
15
0.0
00
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
SO3
0.0
30
0.2
80
0.5
93
32
.64
80
.65
10
.30
30
.00
00.0
00
0.1
77
n.d.
n.d.
n.d.
n.d.
P 2O5
n.d.
51.8
74
0.7
40
0.0
00
1.3
79
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
BaO
n.d.
n.d.
n.d.
66.1
32
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
Ce 2
O3
n.d.
n.d.
n.d.
n.d.
80
.45
2n.
d.n.
d.n.
d.n.
d.n.
d.n.
d.n.
d.n.
d.
Tota
l9
9.9
98
10
0.0
01
10
0.0
01
10
0.0
00
10
0.0
00
10
0.0
00
99
.99
81
00.0
00
10
0.0
00
10
0.0
00
10
0.0
01
10
0.0
00
10
0.0
00
Min
eral
Mag
Ap
Chl
Brt
Ce-
carb
onat
eIl
mIl
mTi
-Fe-
Silic
ate
Mag
Ti-M
agIl
mM
agIl
m
n.d.
–no
tde
term
ined
Min
eral
abbr
evia
tion
saf
ter
Whi
tney
yEv
ans
(20
10).
tablas análisis de microsonda 145
Tabla 21: Energy-dispersive x-ray spectroscopy (EDX) results of selectedminerals from Totoltepec pluton rocks. (cont.)
Sample TT-17 TT-17 TT-17 TT-28 TT-28Specimen Amp2#1 Amp2#2 Amp3#1 Amp1#1 Amp3#1
wt. %SiO2 0.000 3.223 31.016 24.43 0.000
TiO2 0.966 76.356 0.000 43.656 0.000
Al2O3 0.734 0.136 17.259 1.135 0.171
FeO 96.814 16.289 34.596 0.35 25.213
MgO 0.046 0.000 16.141 0 0.000
MnO 0.149 0.465 0.416 0 0.000
CaO 0.000 2.801 0.078 29.921 0.000
Na2O 0.335 0.482 0.139 0 0.000
K2O 0.120 0.000 0.000 0 0.031
Cr2O3 0.836 0.250 0.356 0.466 0.096
NiO 0.000 0.000 0.000 0 0.000
CuO n.d. n.d. n.d. 0 29.630
SO3 n.d. n.d. n.d. 0.042 44.858
P2O5 n.d. n.d. n.d. n.d. n.d.BaO n.d. n.d. n.d. n.d. n.d.Ce2O3 n.d. n.d. n.d. n.d. n.d.Total 100.000 100.002 100.001 100.000 99.999
Mineral Mag Ilm Chl Ttn Ccp
n.d. – not determinedMineral abbreviations after Whitney y Evans (2010).
ETA B L A S G E O C R O N O L O G Í A 40A R / 39A R
Material suplementario publicado en línea como parte del artículo: Kirsch,M., Keppie, J.D., Murphy, J.B., y Lee, J.K.W., Arc plutonism in atranstensional regime: the Late Palaeozoic Totoltepec pluton, AcatlánComplex, southern Mexico: International Geology Review, en prensa, doi:10.1080/00206814.2012.693247.
Tabla 22: 40Ar/39Ar analysis of muscovite sample TT-57 from the Totoltepec pluton.
Step Laser Isotope Volumes∗
Power 40Ar 2σ 39Ar 2σ 38Ar 2σ 37Ar 2σ 36Ar 2σ Ca/K
1 0.5 115.453 0. 411 8.798 0.145 0.260 0.045 0.572 0.769 0.121 0.019 0.119
2 <0.75> 724.844 1.276 61.362 0.364 0.827 0.071 0.849 0.883 0.155 0.020 0.025
3 <1.00> 1717.235 3.381 148.840 0.853 1.923 0.143 0.835 1.480 0.212 0.036 0.010
4 <1.25> 1538.433 2.489 135.730 0.714 1.720 0.133 0.953 1.115 0.104 0.030 0.013
5 <1.50> 1568.868 2.644 137.229 0.853 1.755 0.108 0.941 1.226 0.162 0.033 0.013
6 <1.75> 1326.309 1.736 116.912 0.650 1.494 0.117 0.446 0.767 0.088 0.024 0.007
7 <2.00> 1551.918 3.273 137.506 0.810 1.759 0.104 0.994 1.431 0.087 0.029 0.013
8 <2.25> 614.138 1.157 54.235 0.286 0.680 0.061 0.568 0.585 0.028 0.022 0.019
9 <2.50> 512.826 1.202 45.257 0.348 0.589 0.065 0.276 0.879 0.031 0.017 0.011
10 <2.69> 773.110 1.389 68.506 0.478 0.869 0.060 0.565 0.578 0.051 0.019 0.015
11 <2.86> 824.468 1.242 73.204 0.368 0.941 0.059 0.373 0.885 0.035 0.017 0.009
12 <3.02> 647.662 1.231 57.382 0.355 0.723 0.058 0.584 0.885 0.030 0.019 0.019
13 <7.00> 1349.433 2.196 120.344 0.687 1.573 0.104 1.475 1.034 0.038 0.029 0.022
Note: J-Value = 0,015342± 0,000046∗ Measured volumes are 1× 1012cm3 NTP
146
tablas geocronología40
ar/39ar 147
Tabl
a2
2:40
Ar/39
Ar
anal
ysis
ofm
usco
vite
sam
ple
TT-5
7fr
omth
eTo
tolt
epec
plut
on.(
cont
.)
Step
Lase
rIs
otop
eC
orre
lati
onD
ata
Pow
er%
40
Ar a
tm
%39
Ar
40
Ar/
39
ArK
2σ
Age
(Ma)†
2σ
36
Ar/
40
Ar
2σ
39
Ar/
40
Ar
2σ
r
10
.53
1.0
20
.75
9.0
20.6
72
33
.91
6.3
0.0
01
05
30.0
00
16
90.0
76
37
20.0
01
29
60.0
04
2<
0.7
5>
6.3
16
.02
11.0
40.1
22
82
.22
.90
.00
02
14
0.0
00
02
80.0
84
87
10.0
00
52
70.0
03
3<
1.0
0>
3.6
41
8.7
91
1.0
90.1
02
83
.42
.30
.00
01
23
0.0
00
02
10.0
86
90
10.0
00
52
80.0
04
4<
1.2
5>
1.9
93
0.4
41
1.0
80.0
92
83
.22
.20
.00
00
68
0.0
00
02
00.0
88
46
20.0
00
48
80.0
01
5<
1.5
0>
3.0
54
2.2
21
1.0
50.1
02
82
.62
.40
.00
01
03
0.0
00
02
10.0
87
70
10.0
00
56
60.0
02
6<
1.7
5>
1.9
65
2.2
51
1.0
90.0
92
83
.52
.10
.00
00
66
0.0
00
01
80.0
88
38
30.0
00
50
60.0
01
7<
2.0
0>
1.6
56
4.0
51
1.0
70.0
92
83
.02
.20
.00
00
56
0.0
00
01
90.0
88
84
10.0
00
55
80.0
02
8<
2.2
5>
1.3
46
8.7
01
1.1
40.1
32
84
.73
.20
.00
00
45
0.0
00
03
50.0
88
54
60.0
00
49
70.0
00
9<
2.5
0>
1.7
97
2.5
81
1.1
00.1
42
83
.73
.40
.00
00
61
0.0
00
03
30.0
88
48
50.0
00
71
40.0
00
10
<2
.69>
1.9
67
8.4
61
1.0
30.1
22
82
.12
.70
.00
00
66
0.0
00
02
50.0
88
84
80.0
00
64
20.0
01
11
<2
.86>
1.2
38
4.7
41
1.0
90.0
92
83
.62
.20
.00
00
42
0.0
00
02
10.0
89
02
80.0
00
46
90.0
00
12
<3
.02>
1.3
88
9.6
61
1.1
00.1
22
83
.72
.90
.00
00
47
0.0
00
03
00.0
88
83
60.0
00
57
70.0
00
13
<7
.00>
0.8
39
9.9
91
1.0
90.1
02
83
.52
.30
.00
00
28
0.0
00
02
20.0
89
42
10.0
00
53
20.0
00
†In
tegr
ated
Age
=282
,85±1
,10Ma
;Is
otop
eC
orre
lati
onA
ge=283
,41±3
,68Ma
(99.2
%of39
Ar,
step
sm
arke
dby<
);Pl
atea
uA
ge=283
,22±
1,10Ma
(99.2
%of39
Ar,
step
sm
arke
dby>
);M
SWD
=0.2
48
B I B L I O G R A F Í A
Andersen, T. Correction of common lead in U–Pb analyses that do notreport 204Pb. Chemical Geology 192(1-2):59–79 (2002)
Arvizu, H.E., Iriondo, A., Izaguirre, A., Chávez-Cabello, G., Kamenov,G.D., Solís-Pichardo, G., Foster, D.A., y Cruz, R.L.S. Rocas graníti-cas pérmicas en la Sierra Pinta, NW de Sonora, México: Magmatismo desubducción asociado al inicio del margen continental activo del SW deNorteamérica. Revista Mexicana de Ciencias Geológicas 26(3):709–728 (2009)
Blumenfeld, P. y Bouchez, J.L. Shear criteria in granite and migmatitedeformed in the magmatic and solid states. Journal of Structural Geology10(4):361–372 (1988)
Böhnel, H. Paleomagnetic study of Jurassic and Cretaceous rocks from theMixteca terrane (Mexico). Journal of South American Earth Sciences 12:545–556 (1999)
Brown, M. y Solar, G. Shear-zone systems and melts: feedback rela-tions and self-organization in orogenic belts. Journal of Structural Geology20(2/3):211–227 (1998)
Calderón-García, A. Estratigrafía del Mesozoico y tectónica del sur delEstado de Puebla; Presa de Valsequillo, Sifón de Huexotitlanapa y proble-mas hidrológicos de Puebla. En Congreso Geológico Internacional, Libro-guíade la excursión A-11, tomo 20, págs. 9–33. México D.F. (1956)
Campa, M.F. y Coney, P.J. Tectono-stratigraphic terranes and mineral resour-ce distributions in Mexico. Canadian Journal of Earth Sciences 20(6):1040–1051 (1983)
Centeno-García, E. y Silva-Romo, G. Petrogenesis and tectonic evolutionof central Mexico during Triassic-Jurassic time. Revista Mexicana de Cien-cias Geológicas 14(2):244–260 (1997)
Centeno-García, E., Guerrero-Suastegui, M., y Talavera-Mendoza, O.The Guerrero Composite Terrane of western Mexico: Collision and subse-quent rifting in a supra-subduction zone. En A. Draut, P. Clift, y D. Scholl(editores), Formation and Applications of the Sedimentary Record in Arc Co-llision Zones, Special Paper, tomo 436, págs. 1–30. Geological Society ofAmerica (2008)
Centeno-García, E., Mendoza-Rosales, C.C., y Silva-Romo, G. Sedi-mentología de la Formación Matzitzi (Paleozoico superior) y significa-do de sus componentes volcánicos, región de Los Reyes Metzontla-SanLuis Atolotitlán, Estado de Puebla. Revista Mexicana de Ciencias Geológicas26(1):18–36 (2009)
148
bibliografía 149
Dalrymple, G., Alexander, Jr., E., Lanphere, M., y Kraker, G. Irradiationof samples for 40Ar/39Ar dating using the Geological Survey TRIGAReactor. Professional Paper 1176, U.S. Geological Survey (1981)
DePaolo, D.J. Neodymium isotopes in the Colorado Front Range and crust-mantle evolution in the Proterozoic. Nature 291:193–197 (1981)
DePaolo, D.J. Neodymium isotope geochemistry: An introduction. Berlin, Sprin-ger Verlag (1988)
Dickinson, W.R. y Lawton, T.F. Carboniferous to Cretaceous assembly andfragmentation of Mexico. Geological Society America Bulletin 113(9):1142–1160 (2001)
Dostal, J., Dupuy, C., y Caby, R. Geochemistry of the Neoproterozoic Ti-lemsi belt of Iforas (Mali, Sahara): a crustal section of an oceanic islandarc. Precambrian Research 65(1-4):55–69 (1994)
Dostal, J., Baragar, W., y Dupuy, C. Petrogenesis of the Natkusiak conti-nental basalts, Victoria Island, Northwest Territories, Canada. CanadianJournal of Earth Sciences 23(5):622–632 (1986)
Elías-Herrera, M. y Ortega-Gutiérrez, F. Caltepec fault zone: An EarlyPermian dextral transpressional boundary between the Proterozoic Oa-xacan and Paleozoic Acatlán complexes, southern Mexico, and regionaltectonic implications. Tectonics 21(3):1–19 (2002)
Elías-Herrera, M., Ortega-Gutiérrez, F., Sánchez-Zavala, J.L., Macías-Romo, C., Ortega-Rivera, A., y Iriondo, A. La falla de Caltepec: raícesexpuestas de una frontera tectónica de larga vida entre dos terrenos con-tinentales del sur de México. Boletín de la Sociedad Geológica Mexicana57(1):83–109 (2005)
Ferrari, L., López-Martinez, M., Aguirre-Díaz, G., y Carrasco-Núñez,G. Space-time patterns of Cenozoic arc volcanism in central Mexico:from the Sierra Madre Occidental to the Mexican Volcanic Belt. Geology27(4):303–306 (1999)
Fries, Carl, J., Rincón-Orta, C., Solorio-Munguía, J., Schmitter-Vilada, E., y Cserna, Z.d. Una edad radiométrica ordovícica de Totolte-pec, Estado de Puebla. En Libro-guía de la excursión México-Oaxaca, págs.164–166. Sociedad Geológica Mexicana, México D.F. (1970)
Gill, J. Orogenic Andesites and Plate Tectonics. Heidelberg, Springer (1981)
Goldstein, S., O’Nions, R., y Hamilton, P. A Sm-Nd isotopic study ofatmospheric dusts and particulates from major river systems. Earth andPlanetary Science Letters 70(2):221–236 (1984)
Hutton, D. Granite emplacement mechanisms and tectonic controls: infe-rences from deformation studies. Transactions of the Royal Society of Edin-burgh 79:245–255 (1988)
bibliografía 150
Ingram, G.M. y Hutton, D.H.W. The Great Tonalite Sill: Emplacement intoa contractional shear zone and implications for Late Cretaceous to earlyEocene tectonics in southeastern Alaska and British Columbia. GeologicalSociety Of America Bulletin 106(5):715–728 (1994)
Irving, E. Drift of the major continental blocks since the Devonian. Nature270:304–309 (1977)
Jacobsen, S.B. y Wasserburg, G.J. Sm-Nd isotopic evolution of chondrites.Earth and Planetary Science Letters 50(1):139–155 (1980)
Keppie, D.J. y Ortega-Gutiérrez, F. 1.3-0.9 Ga Oaxaquia (Mexico): Rem-nant of an arc/backarc on the northern margin of Amazonia. Journal ofSouth American Earth Sciences 29(1):21–27 (2010)
Keppie, J.D., Nance, R.D., Dostal, J., Ortega-Rivera, A., Miller, B.V.,Fox, D., Muise, J., Powell, J.T., Mumma, S.A., y Lee, J.K.W. Mid-Jurassictectonothermal event superposed on a Paleozoic geological record in theAcatlán Complex of southern Mexico: hotspot activity during the brea-kup of Pangea. Gondwana Research 7(1):239–260 (2004a)
Keppie, J., Nance, R., Ramos-Arias, M., Lee, J., Dostal, J., Ortega-Rivera, A., y Murphy, J. Late Paleozoic subduction and exhumation ofCambro-Ordovician passive margin and arc rocks in the northern AcatlánComplex, southern Mexico: geochronological constraints. Tectonophysics495:213–229 (2010)
Keppie, J.D. Terranes of Mexico revisited: A 1.3 Billion year odyssey. Inter-national Geology Review 46(9):765–794 (2004)
Keppie, J.D., Sandberg, C.A., Miller, B.V., Sánchez-Zavala, J.L., Nance,R.D., y Poole, F.G. Implications of Latest Pennsylvanian to Middle Permi-an paleontological and U-Pb SHRIMP data from the Tecomate Formationto re-dating tectonothermal events in the Acatlán Complex, southern Me-xico. International Geology Review 46(8):745–753 (2004b)
Keppie, J.D., Nance, R.D., Fernández-Suárez, J., Storey, C.D., Jeffries,T.E., y Murphy, J.B. Detrital zircon data from the eastern Mixteca terrane,southern Mexico: evidence for an Ordovician-Mississippian continentalrise and a Permo-Triassic clastic wedge adjacent to Oaxaquia. InternationalGeology Review 48:97–111 (2006)
Keppie, J.D., Dostal, J., Murphy, J.B., y Nance, R.D. Synthesis and tectonicinterpretation of the westernmost Paleozoic Variscan orogen in southernMexico: From rifted Rheic margin to active Pacific margin. Tectonophysics461(1-4):277–290 (2008)
Kerr, A.C., Jenner, G.A., y Fryer, B.J. Sm-Nd isotopic geochemistry ofPrecambrian to Paleozoic granitoid suites and the deep-crustal structureof the southeast margin of the Newfoundland Appalachians. CanadianJournal of Earth Sciences 32:224–245 (1995)
bibliografía 151
Kuscu, I., Kuscu, G.G., Tosdal, R.M., Ulrich, T., y Friedman, R. Mag-matism in the southeastern Anatolian orogenic belt: transition from arcto post-collisional setting in an evolving orogen. En M. Sosson, N. Kay-makci, R. Stephenson, F. Bergerat, y V. Starostenko (editores), SedimentaryBasin Tectonics from the Black Sea and Caucasus to the Arabian Platform, Spe-cial Publications, tomo 340, págs. 437–460. Geological Society of London(2010)
Longerich, H., Jenner, G., Fryer, B., y Jackson, S. Inductively coupledplasma-mass spectrometric analysis of geological samples: A critical eva-luation based on case studies. Chemical Geology 83(1-2):105–118 (1990)
Ludwig, K. Isoplot 3.7. A geochronological toolkit for Microsoft Excel. Ber-keley Geochronology Center Special Publication 4:77 pp. (2008)
Malone, J.R., Nance, R.D., Keppie, J.D., y Dostal, J. Deformational historyof part of the Acatlán Complex: Late Ordovician-Early Silurian and EarlyPermian orogenesis in southern Mexico. Journal of South American EarthSciences 15(5):511–524 (2002)
McDougall, I. y Harrison, T. Geochronology and thermochronology by the40Ar/39Ar method. Oxford University Press, New York (1988)
Miller, R.B. y Paterson, S.R. The transition from magmatic to high-temperature solid-state deformation: implications from the Mount Stuartbatholith, Washington. Journal of Structural Geology 16(6):853–865 (1994)
Morales-Gámez, M., Keppie, J.D., y Norman, M.D. Ordovician-Silurianrift-passive margin on the Mexican margin of the Rheic Ocean overlain byCarboniferous-Permian periarc rocks: Evidence from the eastern AcatlánComplex, southern Mexico. Tectonophysics 461(1-4):291–310 (2008)
Morales-Gámez, M., Keppie, J.D., Lee, J.K.W., y Ortega-Rivera, A. Palaeo-zoic structures in the Xayacatlán area, Acatlán Complex, southern Mexico:transtensional rift- and subduction-related deformation along the marginof Oaxaquia. International Geology Review 51(4):279–303 (2009)
Morán-Zenteno, D.J., Caballero-Miranda, C., Silva-Romo, G., Ortega-Guerrero, B., y González-Torres, E. Jurassic-Cretaceous paleogeo-graphic evolution of the northern Mixteca terrane, southern Mexico. Geo-física Internacional 32(3):453–473 (1993)
Morel, P. y Irving, E. Paleomagnetism and the evolution of Pangea. Journalof Geophysical Research 86:1858–1872 (1981)
Murphy, J.B. y Nance, R.D. The Pangea conundrum. Geology 36(9):703–706
(2008)
Murphy, J.B., Nance, R.D., y Cawood, P.A. Contrasting modes of super-continent formation and the conundrum of Pangea. Gondwana Research15(3-4):408–420 (2009)
bibliografía 152
Nance, R.D., Miller, B.V., Keppie, J.D., Murphy, J.B., y Dostal, J. AcatlánComplex, southern Mexico: Record spanning the assembly and breakupof Pangea. Geology 34:857–860 (2006)
O’Nions, R.K., Hamilton, P.J., y Evensen, N.M. Variations in143Nd/144Nd and 87Sr/86Sr ratios in oceanic basalts. Earth and Plane-tary Science Letters 34:13–22 (1977)
Ortega-Gutiérrez, F. The pre-Mesozoic geology of the Acatlán area, south Me-xico. Tesis Doctoral, University of Leeds, England (1975)
Ortega-Gutiérrez, F. Estratigrafía del Complejo Acatlán en la Mixteca Ba-ja, Estados de Puebla y Oaxaca. Universidad Nacional Autónoma de México,Instituto de Geología, Revista 2(2):112–131 (1978)
Ortega-Gutiérrez, F. Tectonostratigraphic analysis and significance ofthe Paleozoic Acatlán Complex of Southern Mexico, Guidebook of Field-trip B. En F. Ortega-Gutiérrez, E. Centeno-García, D. Morán-Zereno, yA. Gómez-Caballero (editores), Terrane Geology of Southern Mexico, FirstCircum-Atlantic Terrane Conference, Guanajuato, Mexico, págs. 54–60. Uni-versidad Nacional Autónoma de México, Instituto de Geología (1993)
Ortega-Gutiérrez, F., Elías-Herrera, M., Reyes-Salas, M., Macías-Romo, C., y López, R. Late Ordovician-Early Silurian continental collisio-nal orogeny in southern Mexico and its bearing on Gondwana-Laurentiaconnections. Geology 27(8):719–722 (1999)
Paterson, S.R., Tobisch, O.T., y Vernon, R.H. Emplacement and deforma-tion of granitoids during volcanic arc construction in the Foothills terrane,central Sierra Nevada, California. Tectonophysics 191:89–110 (1991)
Paterson, S., Vernon, R., y Tobisch, O. A review of criteria for the identi-fication of magmatic and tectonic foliations in granitoids. Journal of Struc-tural Geology 11(3):349–363 (1989)
Pearce, J.A. y Peate, D.W. Tectonic implications of the composition ofvolcanic arc magmas. Annual Review of Earth and Planetary Sciences 23:251–285 (1995)
Pérez-Gutiérrez, R., Solari, L.A., Gómez-Tuena, A., y Martens, U. Me-sozoic geologic evolution of the Xolapa migmatitic complex north of Aca-pulco , southern Mexico : implications for paleogeographic reconstruc-tions. Revista Mexicana de Ciencias Geológicas 26(1):201–221 (2009)
Ramos-Arias, M.A. y Keppie, J.D. U–Pb Neoproterozoic–Ordovician proto-lith age constraints for high- to medium-pressure rocks thrust over low-grade metamorphic rocks in the Ixcamilpa area, Acatlán Complex, sout-hern Mexico. Canadian Journal of Earth Sciences 48(1):45–61 (2011)
Roddick, J. High precision intercalibration of 40Ar/39Ar standards. Geo-chimica et Cosmochimica Acta 47:887–898 (1983)
bibliografía 153
Rodríguez-Torres, R. Geología metmórfica del área de Acatlán, Estado dePuebla. En Libro-Guía de la excursión México-Oaxaca, págs. 55–66. SociedadGeológica Mexicana (1970)
Rosales-Lagarde, L., Centeno-García, E., Dostal, J., Sour-Tovar, F.,Ochoa-Camarillo, H., y Quiroz-Barroso, S. The Tuzancoa Formation:Evidence of an Early Permian submarine continental arc in east-centralMexico. International Geology Review 47:901–919 (2005)
Sánchez-Zavala, J.L., Ortega-Gutiérrez, F., y Elías-Herrera, M. La oro-genia Mixteca del Devónico del complejo Acatlán, sur de México. GEOSUnión Geofísica Mexicana 20(3):321–322 (2000)
Sánchez-Zavala, J.L., Jenner, G.A., Belousova, E.A., y Macías-Romo, C.Ordovician and Mesoproterozoic zircons from the Tecomate Formationand Esperanza Granitoids, Acatlán Complex, southern Mexico: local pro-venance in the Acatlán and Oaxacan Complexes. International GeologyReview 46(11):1005–1021 (2004)
Schaaf, P., Weber, B., Weis, P., Gross, A., Ortega-Gutiérrez, F., y Köhler,H. The Chiapas Massif (Mexico) revised: New geologic and isotopic datafor basement characteristics. En H. Miller (editor), Contributions to LatinAmerican Geology, Neues Jahrbuch für Geologie und Paläontologie Abhandlung,tomo 225, págs. 1–23. E. Schweizerbart Science Publishers (2002)
Sedlock, R.L., Ortega-Gutiérrez, F., y Speed, R.C. Tectonostratigraphic te-rranes and tectonic evolution of Mexico, Special Paper, tomo 278. GeologicalSociety of America (1993)
Sircombe, K.N. AgeDisplay: an EXCEL workbook to evaluate and dis-play univariate geochronological data using binned frequency histogramsand probability density distributions. Computers and Geosciences 30:21–31
(2004)
Sláma, J., Košler, J., Condon, D., y Crowley, J.L. Plešovice zircon—Anew natural reference material for U-Pb and Hf isotopic microanalysis.Chemical Geology 249(1-2):1–35 (2008)
Solari, L.A., de León, R.T., Hernández-Pineda, G.A., Solé, J.,Hernández-Treviño, T., y Solís-Pichardo, G. Tectonic significance ofCretaceous–Tertiary magmatic and structural evolution of the northernmargin of the Xolapa Complex, Tierra Colorada area, southern Mexico.Geological Society of America Bulletin 119(9/10):1265–1279 (2007)
Solari, L. y Tanner, M. UPb.age, a fast data reduction script for LA-ICP-MS U-Pb geochronology. Revista Mexicana de Ciencias Geológicas 28(1):83–91 (2011)
Solari, L.A., Dostal, J., Ortega-Gutiérrez, F., y Keppie, J.D. The 275 Maarc-related La Carbonera stock in the northern Oaxacan Complex of sout-
bibliografía 154
hern Mexico: U-Pb geochronology and geochemistry. Revista Mexicana deCiencias Geológicas 18(2):149–161 (2001)
Solari, L.A., Gómez-Tuena, A., Pablo Bernal, J., Pérez-Arvizu, O., y Tan-ner, M. U-Pb zircon geochronology with an integrated LA-ICP-MS mi-croanalytical workstation: achievements in precision and accuracy. Geos-tandards and Geoanalytical Research 34(1):5–18 (2010)
Steiger, R.H. y Jäger, E. Subcommission on geochronology: Conventionon the use of decay constants in geo- and cosmochronology. Earth andPlanetary Science Letters 36:359–362 (1977)
Steiner, M.B. y Walker, J.D. Late Silurian plutons in Yucatan. Journal ofGeophysical Research 101(B8):17727–17735 (1996)
Talavera-Mendoza, O., Ruiz, J., Gehrels, G.E., Meza-Figueroa, D.M.,Vega-Granillo, R., y Campa-Uranga, M.F. U-Pb geochronology of theAcatlán Complex and implications for the Paleozoic paleogeography andtectonic evolution of southern Mexico. Earth and Planetary Science Letters235:682–699 (2005)
Tanaka, T., Togashi, S., Kamioka, H., Amakawa, H., Kagami, H., Hama-moto, T., Yuhara, M., Orihashi, Y., Yoneda, S., Shimizu, H., Kunima-ru, T., Takahashi, K., Yanagi, T., Nakano, T., Fujimaki, H., Shinjo, R.,Asahara, Y., Tanimizu, M., y Dragusanu, C. JNdi-1: a neodymium iso-topic reference in consistency with LaJolla neodymium. Chemical Geology168(3–4):279–281 (2000)
Tera, F. y Wasserburg, G.J. U-Th-Pb systematics in three Apollo 14 basaltsand the problem of initial Pb in lunar rocks. Earth and Planetary ScienceLetters 14:281–304 (1972)
Thompson, A. Dehydration melting of pelitic rocks and the generation ofH2O-undersaturated granitic liquids. American Journal of Science 282:1567–1595 (1982)
Tolson, G. The Chacalapa fault, southern Oaxaca, México. En S.A. Alaniz-Álvarez y Á.F. Nieto-Samaniego (editores), Geology of México: Celebratingthe Centenary of the Geological Society of México, Special Paper, tomo 422,págs. 343–357. Geological Society of America (2007)
Torres, R., Ruiz, J., Patchett, P.J., y Grajales-Nishimura, J.M. Permo-Triassic continental arc in eastern Mexico; tectonic implications for re-constructions of southern North America. En C. Bartolini, J.L. Wilson,y T.F. Lawton (editores), Mesozoic sedimentary and tectonic history of north-central Mexico, Special Paper, tomo 340, págs. 191–196. Geological Societyof America (1999)
Tribe, I. y D’Lemos, R. Significance of a hiatus in down-temperature fa-bric development within syn-tectonic quartz diorite complexes, ChannelIslands, UK. Journal of the Geological Society, London 153(1):127–138 (1996)
bibliografía 155
Turner, G., Huneke, J., Podosek, F., y Wasserburg, G. 40Ar–39Ar agesand cosmic ray exposure ages of Apollo 14 samples. Earth and PlanetaryScience Letters 12:19–35 (1971)
Turner, S., Arnaud, N., Liu, J., Rogers, N., Hawkesworth, C.J., Harris,N., Kelley, S.P., Calsteren, P.V., y Deng, W. Post-collision, shoshoniticvolcanism on the Tibetan plateau: Implications for convective thinning ofthe lithosphere and the source of ocean island basalts. Journal of Petrology37(1):45–71 (1996)
Vega-Granillo, R., Talavera-Mendoza, O., Meza-Figueroa, D.M., Ruiz,J., Gehrels, G.E., López-Martínez, M., y de la Cruz-Vargas, J.C.Pressure-temperature-time evolution of Paleozoic high-pressure rocksof the Acatlán Complex (southern Mexico): Implications for the evolu-tion of the Iapetus and Rheic Oceans. Geological Society America Bulletin119(9/10):1249–1264 (2007)
Vega-Granillo, R., Calmus, T., Meza-Figueroa, D., Ruiz, J., Talavera-Mendoza, O., y López-Martínez, M. Structural and tectonic evolution ofthe Acatlán Complex, southern Mexico: Its role in the collisional historyof Laurentia and Gondwana. Tectonics 28:TC4008 (2009)
Weber, B., Meschede, M., Ratschbacher, L., y Frisch, W. Structure andkinematic history of the Acatlán Complex in the Nuevos Horizontes-SanBernardo region, Puebla. Geofísica International 36:63–76 (1997)
Weber, B., Iriondo, A., Premo, W., Hecht, L., y Schaaf, P. New insightsinto the history and origin of the southern Maya block, SE México: U–Pb–SHRIMP zircon geochronology from metamorphic rocks of the Chia-pas massif. International Journal of Earth Sciences (Geologische Rundschau)96(2):253–269 (2007)
Whitney, D.L. y Evans, B.W. Abbreviations for names of rock-formingminerals. American Mineralogist 95(1):185–187 (2010)
Yañez, P., Patchett, P.J., Ortega-Gutiérrez, F., y Gehrels, G.E. Isotopicstudies of the Acatlán Complex, southern Mexico: Implications for Pa-leozoic North American Tectonics. Geological Society of America Bulletin103(6):817–828 (1991)