· geoscience canada arc and slab-failure magmatism in cordilleran batholiths ii – the...

GEOSCIENCE CANADA

Arc and Slab-Failure Magmatism in CordilleranBatholiths II – The Cretaceous PeninsularRanges Batholith of Southern and Baja California

Robert S. Hildebrand1 and JosephB. Whalen2

1Department of Earth and Planetary Sciences, University of California, Davis,California 95616-8605, USAE-mail: [email protected]

2Geological Survey of Canada601 Booth St., Ottawa, OntarioK1A 0E8, Canada

SUMMARYEver since the late 1960s when WarrenHamilton proposed that the greatCordilleran batholiths of the westernAmericas are the roots of volcanic arcslike the Andes and were generated bylongstanding eastward subduction,most geologists have followed suit,despite the evergrowing recognitionthat many Cordilleran batholiths are

complex, composite bodies that devel-oped with intervals of intense shorten-ing and exhumation between and dur-ing periods of magmatism.

The Peninsular Rangesbatholith of Southern and Baja Cali-fornia provides a superb place tounravel the complexities because thereis a lot of data and because it is longi-tudinally composed of two parts: anolder western portion of weakly tomoderately deformed, low-grade vol-canic and epizonal plutonic rocks rang-ing in age from ~128–100 Ma; and amore easterly sector of deformedamphibolite grade rocks cut by compo-sitionally zoned, mesozonal plutoniccomplexes of the La Posta suite,emplaced from 99–86 Ma. While plu-tons of the La Posta suite are generallyconsidered to be the product of con-tinued eastward subduction, they areenigmatic, because they and their wallrocks were rapidly exhumed from asdeep as 23 km and eroded during, andjust after, their emplacement, unlikeplutons in magmatic arcs, which aregenerally emplaced in zones of subsi-dence.

Here we resolve the enigmawith a model where westward-dippingsubduction led to arc magmatism ofthe western sector, the Santiago Peak–Alisitos composite arc, during the peri-od ~128–100 Ma. Arc magmatism shutdown when the arc collided with awest-facing Early Cretaceous passivemargin at about 100 Ma. During thecollision the buoyancy contrastbetween the continental crust of theeastern block and its attached oceaniclithosphere led to failure of the sub-ducting slab. The break-off allowedsubjacent asthenosphere to upwell, adi-

abatically melt, and rise into the upperplate to create the large zoned tonalite–granodiorite–granite complexes of theLa Posta suite. While compositionallysimilar to arc plutons in many respects,the examples from the Southern Cali-fornia and Baja segments of thebatholith have geochemistry that indi-cates they were derived from partialmelting of asthenosphere at deeperlevels in the mantle than typical arcmagmas, and within the garnet stabilityfield. This is consistent with asthenos-phere upwelling through the tornlower-plate slab. We identify kindredrocks with similar geological relationsin other Cordilleran batholiths of theAmericas, such as the Sierra Nevada,which lead us to suggest that slab fail-ure magmatism is common, both spa-tially and temporally.

SOMMAIREDepuis la fin des années 1960, WarrenHamilton a proposé que les grandsbatholites de la Cordillère de l'ouestdes Amériques sont les racines d’arcsvolcaniques andéens issus de la sub-duction vers l'est de longue durée, etdepuis la plupart des géologues ontemboîté le pas, bien qu’un nombrecroissant d’indications montrent que denombreux batholites de la Cordillèresont des entités composites complexesqui se sont développés lors d’inter-valles intenses de contraction et d’ex-humation, durant et entre les périodesde magmatisme.

Le batholite Peninsular Rangesdu Sud de la Californie et de Baja Cali-fornia est un excellent endroit permet-tant de démêler les choses parce qu'il ya beaucoup de données et parce qu'ilest composé longitudinalement de

Volume 41 2014 399

PAUL F. HOFFMAN SERIES

Geoscience Canada, v. 41, http://dx.doi.org/10.12789/geocanj.2014.41.059 © 2014 GAC/AGC®

deux parties: une partie occidentaleplus ancienne, faiblement à modéré-ment déformée, de roches volcaniquesde faible métamorphisme et de rochesplutoniques épizonales âgées d’environ128 Ma à 100 Ma; et, d’un segmentplus à l'est de roches amphiboliquesdéformées recoupées par des roches decomposition zonée des complexesmésozonaux plutoniques de la suite dela Posta, mises en place entre 99 Ma et86 Ma. Bien que les plutons de la suiteLa Posta sont généralement considéréscomme le produit d’une subductionsoutenue vers l’est, ils posent prob-lème, parce qu'avec leurs roches encais-santes, ils ont été rapidement exhumésde profondeurs aussi grandes que 23km, et érodées durant et juste aprèsleur mise en place, contrairement auxplutons des arcs magmatiques, qui sontgénéralement mis en place dans leszones de subsidence.

Dans le présent article, nousproposons une solution à ce problème,avec un modèle de subduction versl'ouest qui conduit à un magmatismed'arc du secteur ouest, l'arc compositede Santiago Peak-Alisitos, durant lapériode d’environ 128 Ma à 100 Ma.Le magmatisme d’arc s’est arrêtélorsque l'arc est entré en collision avecune marge passive à pendage ouest dudébut du Crétacé, il y a environ 100Ma. Lors de la collision, le contraste deflottabilité entre la croûte continentaledu bloc de est et la lithosphèreocéanique qui y est rattachée a conduità l'avortement de la plaque plongeante.La cassure a entrainé la remontée del’asthénosphère sous-jacente, sa fusionadiabatique, et sa remontée dans laplaque supérieure pour former lesgrands complexes zonés de tonalite-granodiorite-granite de La Posta. Bienque de composition similaire aux plu-tons d'arc à bien des égards, les exem-ples des segments de batholites de Cal-ifornie du Sud et de Baja ont unegéochimie qui indique qu'ils provien-nent de la fusion partielle del’asthénosphère à des niveaux plus pro-fonds dans le manteau que les magmasd'arc typiques, à l’intérieur du domainede stabilité du grenat. Ce qui corre-spond à une remontée d’asthénosphèreà travers une dalle de plaque inférieurecassée. Nous connaissons des rochessemblables avec les relationsgéologiques similaires dans d'autres

batholites de la Cordillère desAmériques, tel celles de la SierraNevada, ce qui nous amène à penserque le magmatisme de cassure deplaque est commun, tant spatialementet temporellement.

INTRODUCTIONCordilleran batholiths are elongatemasses – many over 1000 km long – ofgregarious plutons emplaced within theAmerican Cordillera during the Creta-ceous (Larsen et al. 1958). They com-prise hundreds, if not thousands, ofindividual plutons, dykes and plugsranging in composition from gabbro togranite and are related to many impor-tant mineral deposits of the region.

In his now classic report onthe geology of the US–Canada bound-ary region, Reginald Daly recognizedthat the batholiths were emplaced inmountain belts (Daly 1912), but ulti-mately it was Hamilton (1969a, b) whoassociated the batholiths with subduc-tion: specifically, long-lived eastwardsubduction of Pacific lithospherebeneath the Americas. He argued,based on previous work elsewhere(Hamilton and Myers 1967), that thebatholiths were the roots of volcanoesbuilt along the western margins of theAmericas and were analogous to themodern Andean volcanic arc. Theseconcepts provided a basis for the morerecent interpretation of Cordilleranbatholiths as magmatic arc rocksemplaced during compressional defor-mation and great crustal thickening,which is considered to be related to (1)voluminous influx of magmas fromthe mantle; (2) underthrusting of thecrust in either a fore-arc or retro-arcsetting, commonly with shallow sub-duction; or (3) a combination of thetwo (Isacks 1988; Allmendinger et al.1997; Ducea 2001; Kay et al. 2005;Grove et al. 2008; DeCelles et al. 2009;Paterson et al. 2012; Chin et al. 2012).There are, however, complications.

Based on his work in Califor-nia’s Sierra Nevada, the tirelessSwedish-American economic geologist,Waldemar Lindgren, knew in a generalway that irrespective of age, plutoniccompositions there graded from moremafic in the west to more siliceous inthe east (Lindgren 1915), but it was upto the great American petrologist,Arthur Buddington, to clearly articulate

that the titanic Cordilleran-typebatholiths of western North Americacould be divided longitudinally intoparts: (1) a western zone of plutonswith dominantly dioritic and moremafic compositions; and (2) a moreeasterly tract of more siliceous andpotassic-rich plutons, such as granodi-orite and quartz monzonite (Budding-ton 1927). By 1948 Larsen had alsorealized that the more mafic bodies inthe Peninsular Ranges batholith ofSouthern and Baja California wereconfined to the western parts; butdespite these early forays intobatholithic division, it took until 1959for J.G. Moore to carry the observa-tions over the length of North Ameri-ca, and name the boundary betweenthe zones the quartz diorite line(Moore 1959; Moore et al. 1961).

The idea took root and iso-topic investigations by Kistler (Kistlerand Peterman 1973, 1978; Kistler1990) led to recognition that the east-ern and western sectors of the SierraNevada batholith have different base-ments. Similarly, detailed field studiesand geochronology within the Coastbatholith of Canada and southeasternAlaska led to the realization that it toocould be readily divided into two parts,there separated by the collapsed Nut-zotin-Dezadeash-Gravina basin andrelated fold–thrust belt (Rubin et al.1990; Journeay and Friedman 1993;Gehrels et al. 2009). And farther south,additional studies within the PeninsularRanges batholith demonstrated that itcould be readily divided into an older,more westerly, magnetite-bearing suiteand a younger, ilmenite bearing, highSr/Y suite to the east (Gastil et al.1975, 1990; Silver et al. 1979; Silverand Chappell 1988; Kimbrough et al.2001; Tulloch and Kimbrough 2003).

So despite widespread recog-nition among Cordilleran geologiststhat the major Cretaceous batholithsappeared to be constructed of twohalves (Fig. 1), our understanding ofCordilleran batholiths has barely pro-gressed since the late 1960s, largelybecause most workers still followHamilton’s original concept that theSierran and Peninsular Rangesbatholiths were built entirely by east-ward subduction of oceanic litho-sphere beneath the western margin ofthe Americas (Todd et al. 1988, 2003;

400

Walawender et al. 1990; Kimbrough etal. 2001, 2014a; Ducea 2001; Schmidtet al. 2002, 2009; Grove et al. 2003;Tulloch and Kimbrough 2003; Wet-more et al. 2003; Busby 2004; Lee et al.2007; Gehrels et al. 2009; DeCelles etal. 2009; Paterson et al. 2012; Kim-brough et al. 2014a; Shaw et al. 2014).In this paradigm, two subvariant mod-els, both with eastward-directed sub-duction, dominate the discussion: (1)the younger, more siliceous and potas-sic easterly plutons are related to, andthus document, progressive shallowingof eastward subducting oceanic litho-sphere with or without subduction ofthe older arc and forearc sediments; or(2) the western sector was separatedfrom the eastern sector by a narrowback-arc basin, and following closure,subduction-related magmatism simplycontinued to produce the eastern sec-tor of the batholiths.

In his regional synthesis ofthe North American Cordillera, Hilde-brand (2013) noted that within theSierran and Peninsular Ranges

batholiths there was a period ofintense deformation at ~100 Ma,which occurred between the magma-tism of the older western and theyounger eastern sectors. He outlined amodel in which the deformation wascaused by a collision between the twosectors, and that plutons emplaced dur-ing and after collision likely originatedby break-off and failure of thedescending oceanic lithosphere due tothe buoyancy contrast between conti-nental and oceanic lithosphere. As thedetached slab sank into the mantle, thewidening gap allowed the subjacentasthenosphere to upwell and melt adia-batically to create magmas that roseinto, and interacted with, the overlyingmantle lithosphere and lower crust. Itwas those magmas that led to theyounger, post-collisional halves ofCordilleran batholiths.

For this contribution then, weexamine the geology and geochemistryof the Peninsular Ranges batholith ofSouthern and Baja California in thecontext of arc, collision and slab fail-

ure to elucidate the geological develop-ment of the batholith, test the viabilityof the model, identify possible geo-chemical characteristics of slab failuremagmas, and end by integrating ourresults with other similar magmaticsuites. This is the second in a plannedseries on Cretaceous batholiths of theAmerican Cordillera (Hildebrand andWhalen 2014) and is an outgrowth ofboth authors’ long-standing interest inplutons and batholithic terranes (Hilde-brand 1981, 1984; Whalen 1985;Whalen and Chappell 1988).

GEOLOGICAL SETTINGThe Peninsular Ranges batholith,which comprises hundreds of distinctplutons, extends over 1000 km fromjust south of Los Angeles, California,at 34ºN to at least 28ºN near GuerreroNegro (Fig. 2), located just south ofthe frontier of Baja Norte de Califor-nia (Gastil et al. 1975). As the westernhalf forms a continuous linear belt ofmagnetic anomalies visible beneath theextensive Cenozoic volcano-sedimenta-

GEOSCIENCE CANADA Volume 41 2014 401

0 5

Bishop

Fresno >0.706

<0.706

P

Intra-batholithic break of Kistler,1990

Intra-batholithic break of Lackey et al., 2008

?

IBB-2

<5.505.50–6.006.00–6.50

6.50–7.007.00–7.50>7.50

18O (Zrc) ‰ VSMOW

High

Zon

e

Low

Zone

Tuolumne intrusive suite

Whitney intrusive suite

118ºW33ºN

USAMexico

Gu

l f of C

al i f o

r ni a

Pa

c i fic O

c e an

97

97

95 93

94

97

96

95

93

92

115ºW29ºN

Pa

c i fic O

c e an

StokesMountaincomplex

modified fromKimbrough et al., 2001

modified fromGehrels et al., 2009

Wr a

ng

el l i a

Al

ex

an

de

r

Chugach m

élang

e

PeninsularR anges

Coast plutoniccomplex

centralSierra Nevada

mod

ified

from

Lack

ey e

t al.,

200

8

Alisitosarc

La Posta plutons

GravinaB eltLate Cretaceous

sedimentar y ro cks

Valle Gro u p

John M

uir intrusive suite

Sono

ra in

trus

ive

suit

e

97

97

33ºN118ºW

guh

CCh

., 2009els et alehrG

ommodified fr

etteiituuisevisurtniin

arra

of Lackey et al., 2008

Intra-batholithic break

O (Zrc) ‰18

,1990of Kistler

Intra-batholithic break

VSMOW

94

97

95 93

33ºN

crasotisilA

flu

G

oxiceMUSA

ca

P eee

A

eee

n A

eg

naléél

mhcch

agga

re

dnnn

aaaxxx

elllll

AAA

S

rr

t it i ki ki

ki n

in

i a

re

55

r

el

?

ooluuo

TTu

onoS

he

Bt

uv

I

2-BB-BBBIIB

6.50–7.007.00–7.50>7.50

LZ

High

Zon

e

ttete iituui ui

sev

iissur

tni

enmm

nuum

lluool

oohJJo

<5.505.50–6.006.00–6.50

Low

Zone

naec

Oc

fiic

aP

29º

snotulpatsoPaL

996

95

93

92

ainr

ofil

aC

fo

9

6

naec

Oc

fiic

ºN115ºW

a

r

a

r

aill ill l

e

gn

arWWW

Fresno

70

<0.706 yy

070

0.70.

e

00

Bisho

>0.706>0.706 eeeyey

nnettniit

hhiWW

h

tteiituui

ssueviivssi

uusrruttr

nntiin

rr iiir

uui

MM

u

nhhnooh

n

op

iiny

., 20

08La

ckey

et a

lomm

odifi

edfr

segnaRralusnineP

snotulp

kcoryratnemidessuoecaterCetaL

l

., 200ough et alimbrKommodified frr

puu porro

GGr

elll l

aaalVV

sk

01

pmoclptsaoC

tleBanivarG

pmoctnuoM

kotS

xelpcinotu

xelniat

se

eNarreiSartnec

etteiituui

ssueviiv

ssiuus

rruttr

nnt

adavela

Figure 1. Sketch maps illustrating the composite nature of three Cordilleran batholiths of North America as recognized byothers. Peninsular Ranges modified from Kimbrough et al. (2001); Coast plutonic complex of British Columbia modified fromGehrels et al. (2009); central Sierra Nevada batholith adapted from Lackey et al. (2008).

ry cover (Langenheim et al. 2014), itprobably extends another 400 km tonear Cabo San Lucas at the tip of thepeninsula. As mentioned briefly in theintroduction, the batholith and its wallrocks are traditionally divided into twodistinct zones based on different tem-poral, lithological, geochemical, geo-physical, and isotopic characteristicsthat parallel the axis of the batholith(Gastil 1975; Silver et al. 1979;DePaulo 1981; Baird and Miesch 1984;

Todd et al. 1988; Silver and Chappell1988). Wall rocks in the west consist ofLower Cretaceous volcanic and relatedvolcaniclastic rocks, typically littlemetamorphosed, but generallydeformed. The volcanic and sedimen-tary rocks are collectively known as theSantiago Peak volcanics in the UnitedStates and the Alisitos Group on mostof the Baja Peninsula, Mexico. Theypresumably sit upon deformed andmetamorphosed Triassic–Jurassic rocks

whereas to the east Upper Cretaceousplutons intrude mainly Jurassic andPaleozoic upper amphibolite grademetasedimentary rocks that sit onunexposed crystalline basement.

Within the batholith itself,gabbroic plutons are mostly confinedto the western half (Larsen 1948; Kim-brough et al. 2014b) and so, accordingto some workers, their eastern bound-ary defines a gabbro line (Walawender1979; Smith et al. 1983). The gabbroline coincides closely with the westernextent of gneissic Jurassic plutons(Shaw et al. 2003). An I–S line, whichlargely reflects Jurassic plutonism, andan oxygen isotope gap, also closelyapproximate the other lines (Taylor andSilver 1978; Todd and Shaw 1985). Inthe west, Cretaceous plutons range inage from 128–100 Ma and have no sys-tematic age distribution; whereas to theeast large nested tonalite–granodior-ite–granite complexes, called the LaPosta suite, range in age from 99–92Ma and young progressively eastward(Silver and Chappell 1988; Walawenderet al. 1990; Johnson et al. 1999b; Kim-brough et al. 2001; Schmidt et al.2014). This distribution of ages led Sil-ver (Silver et al. 1979; Silver and Chap-pell 1988) to suggest that a magmaticarc remained fixed in the west until~105 Ma and then migrated eastward.Geophysical data also support the twosector division in that the westernmore mafic part is dense, magnetic, haslow heat flow, sparse seismicity, andseismic velocities > 6.25 km/s, where-as the more siliceous eastern sector isless dense, weakly and magneticallyquiet, has higher heat flow, abundantmicroseismicity, and seismic velocities< 6.25 km/sec (Langenheim et al.2014).

Due to the abundance of bothpre- and post-deformational plutons,and cover related to the opening of theGulf of California, the inferredboundary between the two zones isdifficult to locate, varies from workerto worker, and is possibly different atdepth than at the surface. In the Sierrade San Pedro Mártir of Baja (Fig. 2)there are two recognized boundaries,both marked by significant faults: (1) awestern fault known as the Main Már-tir fault, which dips steeply eastwardand places Jurassic and Lower Creta-ceous amphibolite grade gneiss,

402

AguaCaliente

Fault

MainMartirthrust

Cedros Is.

Vizcain

o P

enin

sula

SanDiego

Ensenada

SanQuintin

El Arco

Hermosillo

GuerreroNegro

Cabo SanLucas

Caborca

116

100 km

SAF

SGF

SJF SAF

ABF

EF C

eno

zoic vo

lcanics

La Paz

San Diego

Ensenada

San Quintin

Vizcaino peninsula

Punta Blanca

-420-360-300-240-180-120 -60 0 60 120 180 240 300 360 420 480 540 600 660 720

Magnetic Field(nT)

NIF

EPRMZ

LM

118°

30°

114°

26°

22°

100 km

Cataviñapluton

La Postapluton

Rosario Group

Cenozoic volcanic cover

Upper Cretaceous clastics

Undated plutons

<100 Ma La Posta suite

130-98 arc plutonsSantiago Peak-Alisitosvolcanic-volcaniclastic

Precambrian &Paleozoic rocks

Juro-Triassic rocks

Bisbee Basin &

Sonora platform

Mag

dalen

a

Agua Blancafault

Sierra San Pedro Mártir pluton

GSGG

11

SA

M

720

(nT)agnetic Field

scitsalcsuoecaterCreppU

revoccinaclovciozoneC

NIF

NIFIF

GF FA

116

S

EF SJFFJ

AF

AF

dE

ogeiDnaS

120 180 240 300 360 420 480 540 600 660 720

onplutostaLa P

so kcorcissairT-o

s

ruJc

kcorciozoelaP&nairbmacerP

citsalcinaclov-cs

inaclovo otisilA-kaeP

sgaitnaS

l notulppcra89-031

etiusatsoPaLaM001<

snotulpdetadnU

pp

BAA

P

S nt

a

30°118°

F

p

n

p

thrusttirarM

ainM

itniuQnaS

adanesnE

-420-360-300-240-180-120 -60 0

0 6 120

uor

Goi

raso

RRo

b o

aultFetalienC

guaA

aabCCa

lviñataaC ft

alp

aron

oS

nisa

Bee

bssbiB

faultgua BlancaA

ontir plutárMoedran Pa SSierr

BP

26

allauu

lssu

nns

iinnn

ieen

Po

niaai

czi

V

.sIsordeC

orgeNorerreuG

o

m

G

ocrl AE

llisomreH

acca

roorb

onplut ro &

114

a

elaal

dda

ggd

aMM

a

ci f

i cO

ce

an

Gu

l fo

fC

al i f o

rn

i a

22°

100 km

a

acuLSobaC

a

nn

a

een

Pa

c

sanaS 100 km

Figure 2. Aeromagnetic anomaly map of Southern and Baja California showingthe presumed continuation of the western part of the batholith southward beneathCenozoic volcanic cover (modified from Langenheim et al. 2014) and a geologicalsketch and location map based largely on Kimbrough et al. (2001) but updatedfrom various sources cited in the text. SAF–San Andreas fault, SJF–San Jacintofault, EF–Elsinore fault, ABF–Agua Blanca fault.

metavolcanic rocks of the SantiagoPeak volcanics, and plutons on the eastover much lower grade rocks of theAlisitos Group and plutons to the west(Johnson et al. 1999b; Schmidt et al.2009, 2014); and (2) a more easterlyfault, known as the Agua Caliente, thatdips moderately westward, and placeshigh-grade migmatitic and ultramy-lonitic gneiss on the west over anamphibolite grade carbonate–quartzitesuccession intruded by Jurassic gneissicplutons (Measures 1996; Schmidt et al.2009, 2014). Farther south, in the Sier-ra Calumague, the eastern boundary isthought to be represented by ductilefaults, which commonly, but not every-where, dip steeply eastward, and areprobably normal faults as they placelower grade rocks atop higher graderocks (Griffith and Hobbs 1993).

Within the US segment of thebatholith, the contact is generallyinferred to coincide with the geophysi-cal, isotopic, and geochemical breaks,yet similar plutonic rocks appear onboth sides of it, leading some workers,such as Todd et al. (2003) to argue thatCretaceous arc magmatism simplymigrated eastward over a pre-existingLate Jurassic–Early Cretaceous crustalboundary. They did not explain whyplutons and wall rocks older thanabout 100 Ma are deformed and meta-morphosed, whereas younger plutonsare not. Unfortunately, post-deforma-tional plutons paid little heed to theinferred crustal boundary and werealso emplaced on both sides of theboundary.

Whatever form it takes, andwhether observed or not, the contact isconsidered by most workers to repre-sent a suture zone related to either aclosed marginal basin or a collision in adoubly eastward-dipping subductionmodel (Todd et al. 1988; Johnson et al.1999b; Schmidt and Paterson 2002;Busby 2004; Lee et al. 2007; Schmidt etal. 2014; Wetmore et al. 2014; Shaw etal. 2014). Only Dickinson and Lawton(2001a) and a French group (Tardy etal. 1992, 1994) proposed westward-dip-ping subduction models. Here we willargue that the contact, inferred to bean important crustal boundary is anunconformity between Jurasso–Triassicrocks and overlying Lower Cretaceousvolcanic and sedimentary rocks andthat the critical suture lies well to the

east on the Mexican mainland.

PRE-BATHOLITHIC ROCKSThe rocks on each side of the tradi-tionally inferred crustal boundary (Fig.3) are quite different, both in terms oflithology and metamorphic grade. Atthe surface in the west, a Jurassic clas-tic succession (Silberling et al. 1961),the Bedford Canyon Formation, isunconformably overlain by the Creta-ceous volcanic and volcaniclastic rocksof the Santiago Peak volcanics andAlisitos Group, which are themselvesunconformably overlain by upper Cre-taceous sandstone and conglomeraticunits. Basement to the volcanic andvolcaniclastic rocks appears to be dom-inantly Jurassic and to comprise agroup of deformed and metamor-phosed Jurassic plutons, known as theHarper Creek and Cuyamaca Reservoirsuites, that intruded Jurasso–Triassichigh-grade migmatitic schist andgneiss, known as either the Julian orStephenson Peak schist (Shaw et al.2003; Todd 2004).

Supracrustal rocks in the eastare scarce, not only due to theemplacement of post-deformationalplutons, but also because they areburied by extensive volcanic and sedi-mentary cover related to the Tertiaryopening of the Gulf of California.Additionally, the structure is overprint-ed by structures formed both duringthe Laramide event (Hildebrand 2013)and extensional denudation duringopening of the Gulf. Where they dooutcrop, such as in the San JacintoMountains (Fig. 3), they are found tobe a sequence of interbedded quartziteand carbonate rocks of Paleozoic ageand finer grained siltstone, chert andargillite, commonly assumed to repre-sent deeper water equivalents of thequartzite–carbonate sequences (Gastiland Miller 1981; Gastil et al. 1991;Gastil 1993).

Western SectorThe Bedford Canyon Formation (Fig.3) comprises thousands of metres ofslightly metamorphosed argillite andslate, with lesser amounts of feldspath-ic sandstone, lenses of limestone, andpebbly conglomerate (Larsen 1948).The base of the formation is unex-posed and the rocks are probably iso-clinally folded making thickness esti-

mates unreliable (Schoellhamer et al.1981). Fossiliferous limestone unitscontain Callovian fossils, althoughsome geologists are concerned that thefossils are allochthonous and wereresedimented, but nevertheless therocks predate the Santiago Peak vol-canics (Silberling et al. 1961; Imlay1963; Moran 1976).

Just north of San Diego, a lat-est Jurassic group of marine volcani-clastic rocks, collectively named thePeñasquitos Formation, was folded, inplaces even overturned, prior to depo-sition of the Santiago Peak volcanics(Kimbrough et al. 2014a). Their detritalzircon data, plus similar fossils, suggestthat these rocks correlate with othervolcaniclastic rocks on the VizcainoPeninsula of Baja, as originally suggest-ed by Kimbrough and Moore (2003),and possibly with the lowermost strataof the Great Valley Group to thenorth. They are probably correlativewith rocks of similar age and deforma-tion in Sonora, where they are knownas the Cucurpe Formation (Mauel et al.2011).

Preserved volcanic rocks, col-lectively known as the SantiagoPeak–Estelle Mountain volcanics, are128–110 Ma in age and consist ofthousands of metres of basaltic to rhy-olitic lava and breccia, tuff, and vol-caniclastic rocks that sit uncon-formably upon rocks of the BedfordCanyon Formation and are overlainunconformably by Turonian fanglom-erates of the Trabuco Formation(Larsen 1948; Fife et al. 1967; Schoell-hamer et al. 1981; Tanaka et al. 1984;Buesch 1984; Gorzolla 1988; Anderson1991; Wetmore et al. 2003; Herzig andKimbrough 2014). Although there is avariety of more siliceous rocks, includ-ing hypabyssal intrusions, porphyriticbasaltic andesite, andesitic lava andrelated breccia are the most commonand widespread volcanic rocks in theformation (Schoellhamer et al. 1981;Herzig and Kimbrough 2014). Rocksin the west are less deformed and onlyweakly metamorphosed whereas to theeast amphibolite grade and isoclinallyfolded tuff, breccia, and basaltic,andesitic, and dacitic lava flows occuras concordant screens between andwithin Cretaceous plutonic sheets ofthe western section and are the sameage as the Santiago Peak volcanics


404

BorregoSpr ings

S anDiego

Paleozoic Desert Divide Groupand other mostly upper amphibolite grade rocks

Mid-Late Jurassic gneissicgranite, migmatitic schist

MSJ

B a nning Fault

Els inore Fault Zone

San Jacinto Fault Zone

Julian schist: Triassic-Jurassicmetasedimentary rocks, volcanic rocks & amphibolite

Lower Cretaceous SantiagoPeak and Estelle Mountain volcanic rocks

Cretaceous sedimentary rocks: Trabuco, Lusardi, and Baker conglomerate

Jurassic Bedford Canyon metaturbidites and allied rocks

U.S.A.Mexico

Cretaceous Peninsular Ranges batholith

Interstate 8

PalmSprings

PerrisBlock

S antaAna

Block

0 50

k m

Perris

Interstate 10

C o a c h e l l a V a l l e y

Sa

n J a

c

i nt o s

Sa

nt a

Ro

s a s

Eastern Peninsular Rangesmylonite zone

C

A

M

Mylonitic metasedimentaryrocks, anatexite, orthogneissof Palm Canyon Complex

San Andreas Fault Zone

Jurassic migmatitic schist and gneiss of Stephenson Peak

La Postaplutonic complex

Lo

s A

ng

el e

s B

as i

n

E l Centro

O r o c o p i a M t n s

Ch

oc

ol a

t e M

ou

n

t ai n

s

Lower Cretaceous gabbro

S anJacinto

Block

I mp

er i a

l Va

l l ey

SR

Figure 5

a

M-Iline

δ Ostep

18

nT

KMA

A'B'

-16-12

12 16

mGal

KM

Isostatic gravity Aeromagnetic

b c

PV

34º

01etatsretnInis

aB

sel

eg

nA

so

a

M

B

i

0

isrerP

caJ

na

S

t

J s

luaFFagninn

sSM

i

ggm

nirpSmlaP

0

mk

50

lehcaoC

ocksade rre gamphibolitand other mostly upper

oupt Divide Greseroic DzaleoP

tholithanges baReninsulareous PetacrC

onee zylonitmangeseninsular Rn PerEast

xompleon Cyanalm Cof Pneissthog, orexitet, anaocksr

ytarylonitic metasedimenM

p

L

PaPacacic ifiificficOcOceceaeanan

e

llV

n

noon

ZZo

tll tuul

aauF

erreoor

niinss ill sEEEEl

SRR

18

SaSanantntata

epstOδ

P

s

s

a

M

C

gnirpSogerroB

ottonnt

iincciaJJa

naanSSa

y

aso

R

s

tn

aS

A

otn

ee ylll l

aa l

Vall all l

e

B

M

aJ

SaSaltaltlaltotononSeSeaea

tll tuul

aauF

saaseea

rddrnnd

AAn

naanSSa

sni

at

nu

oM

etal

oc

oh

CCh

sntMaipocorO

kkccot

lBotnni

nca

naS

s

titic schistma, migeanitrgneissicassic ge Jurtid-LaM

ocksres and alliedbiditturmeta

on yand Coredfassic BJur

etaonglomerand Baker cdi, usar, LoabucrTocks:r

y tareous sedimenetacrC

ocksolcanic rvtaiounelle Meak and EstPtiaganeous Setacrer CwoL

ocks & amphiboolcanic rv, ocksy rtarmetasedimenaJur--iassicrTJulian schist:

oeous gabbretacrer CwoL

MM

tc

d

ingo

eolit

ssic

o

An

M

AnanaM

tM

tntnsns.

e 5igurF

a

Ztll t

uulaau

FFa

k

ann

AatnaaSS

colBsirreP

B

xelpmoccinotulpatsoPaL

linene-I-MM

S A

enneoon

ZZo

tsretnI

3

enneoon

ZZo

tll t

ortneClE

kkccolB

y

a

ell

aV

liir

ep

mI

8etat

3º

e

ocks & amphiboolcanic rv

eakPephensontneiss of Sand gtitic schistmaassic migJur

Isostatic gravity

o

egeiDnaSolit

n

1

o

17

º

t

mG

kacolBanA

B'B'BB1612

Gal

Aeromagnetic

oxiceM.S.A.U

11

6º

a

A

nT

a

KM

b

KM

-12-16

c

Figure 3. (a) Geological sketch map modified from Jennings (1977), Morton and Miller (2006), Todd (2004), and Todd et al.(1988) illustrating the general geology of the Peninsular Ranges of Southern California, the location of Figure 5, as well as theM–I (magnetite–ilmenite) line, the δ18O step, and the eastern limit of gabbroic rocks (Todd et al. 1988). PV–Paloma Valley ringcomplex; SR–Searl Ridge, MSJ–Mount San Jacinto, A–Asbestos Mountain, M–Martinez Mountain, C–Coyote Mountain. (b) Iso-static gravity anomaly map and (c) aeromagnetic anomaly map, both modified from Langenheim et al. (2004). Note the changein gravity and aeromagnetic anomalies coincident with other signatures between western Santiago Peak volcano-sedimentaryrocks and more easterly units.

(Todd 2004; Shaw et al. 2014).Based on the geochemistry of

the volcanic rocks, which are alteredand dominantly metamorphosed togreenschist grade, they represent boththoleiitic and subalkaline series, withoverall compositions similar to thecontemporaneous plutonic rocks(Tanaka et al. 1984; Herzig and Kim-brough 2014). Wetmore et al. (2003)used the Tanaka et al. (1984) data aswell as those of Gorzolla (1988) andHerzig (1991) and, based on the largenumber of rhyolitic analyses comparedto basalt analyses – but without anyvolume estimates – as well as the pres-ence of xenocrystic zircon grains, con-cluded that the arc was built on conti-nental crust, although the variety andsize of granitoid plutons demonstratethat as well. Premo and Morton (2014)dated a number of detrital zircongrains within metasedimentary rocksand found abundant Triassic and1740–1650 Ma grains, whereas high-grade gneiss units contained concor-dant Proterozoic zircon and where dis-cordant, Proterozoic upper interceptages, similar to those reported fromvolcanic rocks by Herzig and Kim-brough (2014).

Nd and Sr isotopic values forthe volcanic rocks are mostly similar toplutons of the western sector of thebatholith (Herzig and Kimbrough2014), and when coupled with theoverall intermediate to siliceous com-positions and xenocrystic zircon, clear-ly indicate that the arc was built oncontinental, not oceanic, crust.

Rocks included in the SantiagoPeak volcanics continue for at least 300km southward to just south of theAgua Blanca fault in Mexico (Fig. 2).There a NW-striking, steeply NE-dip-ping mylonitic shear zone, 50–100 mthick, separates the Santiago Peak vol-canics from rocks of the AlisitosGroup, which were deformed intosouthwest-vergent overturned foldsand thrusts prior to intrusion of 108Ma plutons (Wetmore et al. 2005;Alsleben et al. 2008). The zone is alsothe locus of a modern strike-slip faultwith ~22 km of dextral separation(Allen et al. 1960). South of the fault,in the type area, at least 7 km of LateAptian–Early Albian volcanic, volcani-clastic rocks, and shallow marine sedi-mentary rocks with abundant Tethyan

bivalves define most of the AlisitosGroup (Allison 1974). There, 2 km-thick piles of andesitic lava, breccia,volcaniclastic rocks, and intrusive por-phyry, likely representing ancient stra-tocones, are capped by reefal limestonebioherms.

Farther south on the BajaPeninsula, rocks of the formation aremostly greenschist grade, but generallylower grade in the west away from theplutons, compositionally diverse,deposited in both marine and subaerialsettings, and comprise andesitic strato-cones, silicic ignimbrite and associatedcalderas, a variety of volcanclasticrocks, hypabyssal porphyritic rocks andgranitoid plutons of dominantly Creta-ceous age (White and Busby-Spera1987; Schmidt et al. 2002; Busby et al.2006). Volcanic rocks and associatedplutons range from 116 to 100 Ma andare not known to contain inherited zir-con (Wetmore et al. 2003; Schmidt etal. 2014).

A 330º-trending swarm of~126 Ma basaltic to rhyolitic dykes,known as the San Marcos dyke swarmoccurs north of the Agua Blanca faultwhere it appears to be related to theSantiago Peak volcanics (Farquharson2004). A similar swarm south of thefault, with the same major and traceelement contents as those to the north,but at higher metamorphic grade, wascorrelated with the northern swarm bySchmidt et al. (2014), who used it tosuggest continuity between the Santia-go Peak and Alisitos segments,although only one dyke there is dated,at 120 Ma. If Schmidt et al. (2014)were correct then the Agua Blancafault is not a fault of great significance,at least after about 126–120 Ma.

Basement outcrops other thanthe deformed Bedford siliciclasticrocks were previously considered to bescarce, but we believe them to be morecommon. Near the state line at ElArco (Fig. 2) is a 6 km-thick section ofandesitic lava and breccia, and associat-ed pyroclastic and epiclastic rocks, allcut by a monzodioritic body dated at~165 Ma (Barthelmy 1975; Weber andLopéz Martínez 2006). These rocks areprobably basement to the AlisitosGroup, although the contact itself isnot exposed. Jurassic orthogneiss (Fig.4) occurs throughout the central por-tions of the Baja peninsula south of

the Agua Blanca fault, ranges in agefrom 170–149 Ma and is cut by gab-broic and tonalitic plutons ranging inage from 132–100 Ma, typical of thewestern sector (Schmidt et al. 2014).The gneiss is most likely rock exhumedfrom deep beneath the Alisitos arc andif so, would provide a reasonably clearpicture of the basement, which is con-tinental, but young, consistent withprimitive isotopic ratios obtained byWeber and Lopéz Martinez (2006) atEl Arco.

A steeply dipping panel ofamphibolite-grade, highly strainedmetavolcanic rocks of the SantiagoPeak volcanics lies along the westernflank of the gneiss, but east of theMain Mártir fault (Schmidt et al. 2014).We speculate that the contact betweenthe gneiss and volcanic rocks is mostlikely a highly tectonized unconformityand that the gneiss lies beneath thevolcano-sedimentary package. A care-ful search along this contact mightyield some evidence for this in theform of stretched pebbly conglomer-ate and/or arkosic sand lenses.

Within the US sector of thebatholith (Fig. 3) is another likely base-ment assemblage, comprising the JulianSchist and associated Jurassic ortho-and paragneiss. Rocks included in theLate Triassic–Mid Jurassic Julian Schistare diverse and include predominantlyschist and quartzite with subordinatequantities of amphibolite, mafic schist,gneiss, metaconglomerate, calc-silicaterock, quartzite, marble and talc schist(Todd et al. 1988; Germinario 1993;Shaw et al. 2003). Although the rocksare typically isoclinally folded, foliatedand metamorphosed, holding porphy-roblasts of sillimanite and/orandalusite, relict bedding is commonlyobserved (Germinario 1982). Todd etal. (2003) considered that the JulianSchist was restricted to the westernsector, but suggested that just to theeast were similar rocks containinggreater amounts of marble and quartz-rich metasandstone. The Jurassicmetasedimentary rocks contain abun-dant Paleozoic and Proterozoic detritalzircon (Gastil and Girty 1993; Groveet al. 2008).

A band of deformed Jurassicgranitoid rocks intruded the JulianSchist and extends through the westernpart of the eastern zone from southern


California well into Baja California.The plutons, dated to be 234–149 Ma,were subdivided into two suites, bothof which are dominantly ilmenite-bear-ing and strongly deformed: (1) the per-aluminous Harper Creek suite and (2)the Cuyamaca suite, which is transi-tional in bulk composition betweenmetaluminous and peraluminous (Toddand Shaw 1985; Shaw et al. 2003).They have δ18O ranging from 12 to 20per mil, initial 87Sr/86Sr ratios from~0.706 to ~0.713, zircon Hf data rep-resenting model ages between 1200and 800 Ma, and Proterozoic xenocrys-

tic zircon (Shaw et al. 2003, 2014).Large numbers of enclaves, as well asexterior mantling by intenselymigmatitic and gneissic sheaths ofStephenson Peak schist, are typical ofthe Harper Creek suite (Todd andShaw 1985). The plutons are elongatein the north-northwesterly directionand are strongly foliated, gneissic, ormylonitic (Todd 2004). They are gener-ally considered to be within the Cuya-maca–Laguna Mountain shear zone,which is a 5–20 km wide polygeneticfeature that extends for about 50 km,and dips steeply eastward (Thomson

and Girty 1994). The nature and originof the sheared rocks, which are cut bya 104 Ma pluton, are obscure, asdeformed, but coherent and mappable,Jurassic and Cretaceous plutons occurwithin the zone (Todd 2004). If themylonitic fabrics in the wall rocks rep-resent a shear zone of sizable displace-ment it must have been active prior toemplacement of the Jurassic plutons.

West of the San Jacinto faultzone (Fig. 3), the regional plungeappears to be gently to the northwest,as evidenced by the abundance ofstrongly deformed and amphibolite-

406

37

29

AguaCaliente

5.8

cover basement

164Ma

La Posta-type pluton

~132Ma

164 Ma

AguaCalientepluton

101 Ma

Rinconadacomplex

Sier

ra

San

Pe

dro

M

art i

r

F

ault

Ag

ua C

a l ient e

Fa

ult

La Suertecomplex

100Ma

Alisitos arc

Santiago Peakmetavolcanics

mainlysedimentary

mainlyvolcanic

2.0

118

5.4

5.7

5.3

6.4 5.0

5.0

4.8

This area not mapped in detail

biotitetonalite

Muscovite-bearing Jurassic pluton

meta-carbonate, quartzite, and chert

ultramylonite &shear zone rocks

orthogneiss

mainly gabbrohbd tonalite

sheeted tonalite

myloniticgranite

5 km

cover

N

Ma in M

ar t ir thru

st

Ro

sar i

to t

hrus t

unconformity?

~128 Ma

100.9 87.9 89.5 85.7 83.8 89.9 85.2 85.3 87.3 81.3 81.6 83.4 biotite

1600

0

A’A B B’

sihT

ma

l

m

iilaaittaeetddeniindeppppamtonaerreas mm

B

tluaF

notulpetneilaC

augA

t

r

t

oh

ss tuus

rhhr

ttthotiraass

ooR

a

x

L

elpmocadanocniR

aM101

5.4

eta Suer 5.3

6.4

5.0

ee

tAl ttnneeiiieiellaaaCCC

AguaAgua

Fett eneen

iiell iaa lCCa

aug

A

M

raM

or

461C

t

a

lltuulaFFa

riirtt ira

h

M

ico

B’

A

2.0

MM

c5.8

i

aL

MM

ttt irraa

MMn

Mnii

aaa iMM

7

x

a

aM

p

3

aM461

M22331

1

~

ompleceeta Suer

M100M

5.7

p

rr

yt-atsoPaLLa

A’5.0

4.8

eevvooov

ccco

n

d

otulpep

eP

naS

arrarrreiSSi

aS VaVa

lllleCh

NN

m5 k

888

ttssuurr

hhttthrrii

222111~~~

aa

889

1

a

82

a

11111

MMM

erc

voc

olcanicvmainly

ytarsedimenmainly

olcanicsvmetaeaktiago PanS

os arlisitA

tbasemen

onatbiot

sheaaultr

quarmeta

asJuruscM

eanitrgyloniticm

eonalited tsheet

eonalithbd tomainly gabbr

neissthogor

ealiteit

ocksone rr ze &ylonitm

t, and cheretzitr, etbonacara-

onssic pluting -bearevitoc

9.001

A

5

mit

.989.78

oronfunc

9

y?

.988.387.58

t

3.783.582.589

’A B

4.386.183.18

etitoib

0

0061

’B

Figure 4. Geological sketch map and section from Schmidt and Paterson (2002); Schmidt et al. (2014) showing the location andlocal geology in and around the Main Mártir thrust, the Agua Caliente fault, and the doubly vergent fan structure. Note thatplutons older than 100 Ma occur east of the Main Mártir thrust, indicating that it cannot be the main suture. Similarly, 164 MaJurassic plutons occur on either side of the Agua Caliente thrust suggesting that it also is not the bounding suture. We infer,based on relations elsewhere as discussed in the text, that the contact between the metavolcanic rocks and Jurassic rocks east ofthe Main Mártir thrust is a tectonized unconformity.

gradeJurassic plutons and gneiss andabsence of volcanic rocks in the south-east, and the abundance of green-schist-grade volcanic rocks andabsence of Jurassic plutons to thenorthwest. This fits with observationsin the western part of the block, whereShaw et al. (2003) found that plutoniccontacts of the Jurassic plutons aresharper, marginal facies more leuco-cratic, coarser grained, and with amphi-bole more common than biotite,whereas to the east, the plutons aremuch richer in metasedimentaryenclaves, clots of mica, their outercontacts tend to be more gradational,up to a km across, and are strongly ori-ented parallel to gneissic foliation.

All of the data presentedabove indicate that the Santiago Peakvolcanics, or as they are sometimescalled the Western metavolcanic rocks,sit unconformably upon the JulianSchist and the associated plutons andmigmatite. The contact is readily visibleon Figure 5, where 128–100 Ma plu-tons intrude both sides of the contact.It is implausible that it is a fault as thevolcano-sedimentary package is thesame age as, or only very slightly olderthan, the plutons that intruded thecontact: it must be an unconformity.This implies that the Jurassic rockswere exposed at the surface during theearly Cretaceous, and that there was asignificant basement complex beneaththe Santiago Peak rocks. In fact, thepresence of Proterozoic xenocrysticzircon within the Harper Creek rocksindicates that the basement containedProterozoic rocks or sedimentary rockscontaining Proterozoic detrital zircon.As all the Jurassic basement rocks werestrongly deformed and metamor-phosed prior to the deposition of theSantiago Peak rocks, it is reasonable toinfer that they were involved in a latestJurassic–earliest Cretaceous collision,likely the event responsible for thedeformation of the Peñasquitos andCucurpe formations, which is bracket-ed to be between about 145 and 136Ma (Peryam et al. 2012; Kimbrough etal. 2014a) more or less contemporane-ous with the widespread Nevadanevent (Schweickert et al. 1984). Anolder event, at ~160 Ma, postdated theemplacement of the Harper Creek andCuyamaca Reservoir suites and affect-ed Jurassic arc rocks from the Klamath

Mountains and western Nevada south-ward to the Sonoran Desert region(figure 42 in Hildebrand 2013).

A folded and now steeplyeastward-dipping unconformitybetween basement and cover can satis-fy the various elements, such as oxygenisotopic step, aeromagnetic anomaly,gravity, and I–M line that generallyhave been interpreted to represent asuture zone. Cretaceous plutonsintruded the basement, their owncover, and the unconformity betweenthem (Fig. 5).

On the Vizcaino Peninsula ofBaja (Fig. 2), over 10 km of turbiditesof the Valles Group, interpreted torepresent a deep-sea fan complexdeposited on the edge of an oceanbasin (Minch et al. 1976), have adiverse fauna indicating an Albian toSantonian age (Berry and Miller 1984).They sit on older Jurasso–Triassicophiolitic, sedimentary, and volcanicrocks (Smith and Busby 1993). Accord-ing to Kimbrough et al. (2001), theValle Group is divided into three sub-basins containing sections of earlyCenomanian to middle Turoniancoarse clastic rocks enveloped in muchfiner grained shaly strata. The clasticsections contain coarse conglomeratebeds and abundant sand-rich turbidites,some of which are tightly dated by fos-sils as 92–91 Ma and contain abundant100–90 Ma detrital zircon grains,which are interpreted to have beenderived from the La Posta plutons(Kimbrough et al. 2001).

Another package of UpperCretaceous sedimentary rocks extendsfor over 500 km along the western sideof the Peninsular Ranges (Fig. 2),where they unconformably sit on rocksof the Santiago Peak volcanics, AlisitosGroup and the western batholith (Bot-tjer and Link 1984). Outcropping tothe north above the unconformity, areweakly consolidated sedimentary strataof Turonian age comprising coarseconglomerate with clasts up to 2 m,sandstone, and clayey siltsone (Pope-noe 1941; Schoellhamer et al. 1981).According to Popenoe (1941), whocounted clasts in several of the LateCretaceous conglomeratic units, theclasts are dominantly porphyriticandesite with lesser quantities of grani-toid, metamorphic and sedimentaryrocks. U–Pb dating of zircon from

four dacitic clasts within one of theconglomerate units yielded ages of108–106 Ma (Herzig and Kimbrough2014).

In the San Diego and north-ernmost Baja areas Turonian–Campan-ian non-marine bouldery fanglomerateand sandstone of the Trabuco, Baker,Lusardi, and Redonda formations (Fig.3) sit unconformably above plutonicand volcanic bedrock on a surface ofhigh relief and contain mostly clasts ofplutonic and pre-batholithic rocks to10 m (Flynn 1970; Nordstrom 1970).The conglomerate is unconformablyoverlain by Campanian–Maastrichtianmarine sandstone and shale (Kennedy1975). Farther south in Mexico, theTuronian–Campanian section is uncon-formably overlain by Campanian toMaastrichtian sedimentary rocks ofnon-marine to shallow marine clasticformations overlain by deep marinefan deposits of the Rosario Formation(Morris and Busby-Spera 1990).

Eastern SectorPre-batholithic rocks in the eastern halfof the batholith are highly varied, typi-cally strongly deformed, metamor-phosed to amphibolite grade, and with-out exposed crystalline basement in thePeninsular Ranges. Paleozoic clasticand carbonate rocks dominate and,based on age and lithology, most work-ers interpreted them as part of NorthAmerica. In the US sector Paleozoicmetasedimentary rocks of the DesertDivide Group (Fig. 3) are well exposedalong the spine of the San JacintoMountains, where it comprises over 4km of quartzose schist, paragneiss,metacarbonate rock and quartzite, all atamphibolite grade (Brown 1980, 1981).Gastil et al. (1991) described the rocksas compositionally similar to Neopro-terozoic and Lower Paleozoic sedimen-tary rocks of central Nevada.

Just to the east, sitting struc-turally above the Cretaceous plutons inthe Santa Rosa Mountains and rocks ofthe Desert Divide Group (Fig. 3), isthe Eastern Peninsular Rangesmylonite zone and its hanging wall ofintensely deformed metasedimentaryrocks of the Palm Canyon complex,which itself sits structurally beneathCretaceous plutons (Todd et al. 1988).Within the mylonite zone itself, whichhas Late Cretaceous deformation and


408

EC

CRQuaternary cover

Interstate 8

Descanso

Alpine

Pine Valley monzogranite: 129-109 Ma

Lusardi Formation: Late Cretaceousbouldery fanglomerate

Las Bancas tonalite: 109-100 Ma

Corte Madera monzogranite: 116-104 Ma

Japatul Valley Tonalite: 102-101 Ma

Alpine tonalite: 109-107 Ma

Granite Mtn tonalite: 126-100 Ma

Qtz diorite of East Mesa: 118 Ma Granodiorite of Cuyamaca Reservoir: 168-161 Ma

Gneiss of Harper Creek: 164 Ma

Migmatitic schist & gneissof Stephenson Peak

Early Cretaceous metavolcanic and metasedimentary rocks;Santiago Peak equivalents,128-110 Ma

Julian Schist: possibly Triassicin part

Cuyamaca gabbro: 107-99 Ma

5km

Cretaceous Jurassic

Chiquito Peak monzogranite:113-114 Ma

N

floor ofAlpine

tonalite

floor ofAlpine

tonalite

1

3

2

4

5

roof ofAlpine

tonalite

<100 Ma La Posta-type pluton

eonalittlpineA

floor of

CRQ

reervveoccoyrryaarnnarrneertteauuaQQu

EC

1

2

00001<

e

eeniplA

onalittlpineA

floor of

3

4

onalittlpineA

oof ofr

o

8etatsretnI

snacseD

P

y fanglomerbouldertion: Lmaordi FusarL

eonalite Mtn tanitGr

aLLaaMMa

0000

n

etaeousetacre CtLa

116-1e torC

ae: 126 100 M

eousetacrC

Chiqu

5oonttouutllupplee p

ppeyyptty--tattasstoosPPo

a04 Me: anitroga monzaderM

e:anitrogeak monzo Puit

: 1eekrper CGneiss of Har

tin parirTchist: possibly Julian S

assicJur

a164 M

assic

e: onalitLas Bancas t

onalitTToalley VtulJapa

e: 109-onalitlpine tA

eonalite Mtn tanitGr

o: 1amaca gabbruyC

129-1VineP

a109-100 M

ae: 102-101 Mt

a-107 M

ae: 126-100 M

tz dQ

128-1tiaanS

and mly CEar

a107-99 M

113-1

a09 Me:anitrogalley monzV

aesa: 118 Me of East Mitior

a10 M,tsaleneak equivago P

ocks;y rtarmetasedimenolcanicveous metaetacrC

a14 M

a: 168-161 MoirveserRamacuye of CitanodiorGr

: 1eekrper CGneiss of Har

eakephenson Ptof Sneistitic schist & gmaigM

m5k

ca

a164 M

ss

NN

Figure 5. Simplified geological map of part of the El Cajon map area (Todd 2004) showing the relationship of Early Creta-ceous metavolcanic and allied rocks (black) to the Jurassic rocks (blues). We interpret the relationship between the two as anunconformity because the contact is cut by plutons only slightly younger than the volcanic rocks. Note that metavolcanic rocksdon’t occur east of, nor Jurassic rocks west of, the interpreted unconformity. This figure also shows that the Early Cretaceousplutons, which are characterized by wall-rock contacts that are generally concordant with bedding, were sill-like in their originalform and are now complexly folded into a typical dome and basin interference pattern (see also Hildebrand 2013). The uncon-formity is overturned, dipping east (Langenheim et al. 2014), provides pre-deformational way-up to the west, and the map viewis an oblique crustal section. One can readily see how the sheets (numbered 1–5 to denote their relative structural position),although irregular in detail, are concordant on a large scale and form concentric layers around cores of folds. Note that thefloor of the Alpine tonalite is exposed again in the core of the WNW-trending synform between 4 and 5. Age data from Toddet al. (2003) and Shaw et al. (2014). CR –Cuyamaca, Reservoir, EC –El Capitan Reservoir.

exhumation, recognizable sedimentaryunits are as thin as a 1 m thick bed ofmarble to huge westerly vergent imbri-cate stacks and recumbent nappes ofamphibolite grade marble,feldspathized quartzite, gneiss andmetapelite more than 15 km thick – alloverprinted by Miocene detachmentfaulting and younger strike-slip defor-mation (Engel and Schultejann 1984).The westward thrusting was likelyrelated to the Laramide event at 80–75Ma, as suggested by cooling ages ofGrove et al. (2003) and Dokka (1984).Fossils are scarce, but conodonts fromthe carbonate units in the thrust stackat Coyote Mountain (Fig. 3) are EarlyOrdovician in age (Miller and Dockum1983). Similar rocks are recognizedsouthward through the eastern BajaPeninsula to the Sierra de San PedroMártir (Gastil et al. 1991).

Still farther south at 29ºN,several km of Devonian–Mississippianblack chert, argillite, pillowed and mas-sive alkali basalt were recumbently andisoclinally folded and are correlatedwith the Golconda–Roberts Mountainallochthons of Nevada (Gastil et al.1991; Campbell and Crocker 1993;Leier-Engelhardt 1993).

Rocks of the eastern block,which extend onto mainland Mexico,were correlated on the basis of litholo-gy and detrital zircon profiles withrocks of the North American passivemargin (Gastil et al. 1991; Gastil 1993;Alsleben et al. 2012). However, as theyoccur west of known exotic terranessuch as Caborca and Guerrero (Sed-lock 1993; Tardy et al. 1994; Centeno-García et al. 2008;), locally containsequences and rocks similar to those ofthe Roberts Mountain and Golcondaallochthons, during the Lower Creta-ceous they were more likely to havebeen part of Rubia, the CordilleranRibbon Continent of Hildebrand(2009, 2013), although their ultimateorigin was Laurentia. The presence ofabundant Baltic and North Atlanticfauna in Ordovician carbonate rocksjust south of the international border(Gastil and Miller 1981; Gastil et al.1991; Lothringer 1993) support thisconclusion.

THE CRETACEOUS BATHOLITHCretaceous plutonic rocks in the west-ern sector of the batholith are 128–100

Ma (Fig. 6), variably deformed, butmuch more so to the east, range incomposition from gabbro toleucogranite, and show no directionalvariation in composition with time (Sil-ver and Chappell 1988; Clausen et al.2014; Premo et al. 2014b; Morton et al.2014). We use the informal name SantaAna suite for these rocks after exten-sive outcrops within the Santa AnaMountains (Fig. 3). This suite includesthe more localized Escondido plutonsrecently studied by Clausen et al.(2014).

Overall, the Santa Ana suite isa calcic I-type suite with abundant pris-matic hornblende and lesser interstitialand anhedral biotite. In Mexico, anumber of small (< 10 km), dominant-ly epizonal gabbro–tonalite–trond-hjemite complexes are interpreted torepresent subvolcanic centres, rangingin age from 117–100 Ma (Johnson etal. 1999a, 2002; Tate and Johnson2000; Schmidt and Paterson 2002;Schmidt et al. 2009). Many plutons ofthe Santa Ana suite were originally a

series of sheets or sills (Fig. 5) as theyhave contacts that are concordant withbedding in their wall rocks and withfoliation adjacent to both shallow andsteep contacts (Todd 2004). Theyappear to be more prevalent above(west of) the contact of the Jurassicbasement, where they intruded what isassumed to be their own volcaniccover (Fig. 5). Recently acquired Hf inzircon data from the western plutons,including gabbro, indicate model agesof 900–250 Ma, which implies that theoriginal primitive mantle-derived meltslikely mixed or assimilated more than50% crustal material (Shaw et al. 2014).

Gabbroic plutons are scarce inthe east and common in the west (Figs.3, 4, 5), where they tend to be large,foliated and cumulate-layered plutonsof hornblende-bearing troctolite;anorthositic gabbro; andamphibole–olivine gabbronorite, sur-rounded by much smaller bodies offiner-grained hornblende gabbro, all ofwhich have ambiguous temporal andmingled relations with granitic plutons


Santa Ana suitePremo et al. (2014b)Shaw et al. (2014)Wetmore et al. (2005)

U-Pb zircon ages with 2σ errors

W E

Age of deformation

130

120

110

100

90

80

70

Age

(Ma)

Santa Rosa suite

La Posta suitePremo et al. (2014b)Shaw et al. (2014)Gastil et al. (2014)

San Pedro deMártir pluton

Figure 6. U–Pb zircon ages with 2σ errors for the Peninsular Ranges batholithplotted versus general longitude. Modified from Premo et al. (2014b) with addition-al ages from Shaw et al. (2014), Gastil et al. (2014), and Wetmore et al. (2005). Thepluton ages prior to 100 Ma are not aligned by geography, but by age. Most work-ers have recognized that the western Santa Ana suite didn’t migrate with time (Sil-ver and Chappell 1988; Shaw et al. 2014).

(Walawender 1979; Todd 2004). Fieldrelations indicating consanguinousemplacement were confirmed by Kim-brough et al. (2014b), who showed thatdated gabbroic plutons were emplacedover the same time interval as otherplutons of the Santa Ana suite in thatthey range between, or are within ana-lytic error of, 128–100 Ma.

Plutons of the Santa Ana suitewithin the southern California sectorare both normally and reversely zoned,isotropic to foliated or protomylonitic,sheeted plutonic complexes, highlyvariable in composition ranging fromtonalite through quartz diorite and gra-nodiorite to leucomonzogranite, locallywith abundant wall rock screens andmafic inclusions and containing varyingproportions of clinopyroxene ±orthopyroxene ± biotite ± hornblendeand mafic inclusions (Todd et al. 2003;Todd 2004). Morton et al. (2014) notedthat the westernmost plutons areisotropic whereas those farther east arefoliated so that there is a megascopical-ly visible deformation gradient fromwest to east. This gradient mightreflect the deeper levels of plutonicemplacement to the east with the morewesterly isotropic plutons emplacedinto their own cover at no more than2–3 kbar, whereas the foliated rockswere emplaced at pressures twice aslarge or greater (Morton et al. 2014).Alternatively, the foliated plutonsmight be closer to the deformationalfront.

Cumulate layering in gabbroicplutons is now mostly steeply dipping;contacts of plutons are folded, inmany places isoclinally, along with theirwall rocks; mineral foliation is steepand commonly transects plutonic con-tacts; and dykes of one pluton withinanother are isoclinally folded (Toddand Shaw 1979). Todd and Shaw(1979) also pointed out that in thinsection, Santa Ana plutons typicallyhave broken phenocrysts, a lack ofoscillatory zoning in plagioclase, andboth quartzo-feldspathic and maficminerals recrystallized under strain.These features, plus the map patterns(Fig. 5), clearly indicate that, prior todeformation at 100 Ma, many plutonsof the Santa Ana suite were flat sheets,sills, or laccoliths with dominantly con-cordant contacts and were subsequent-ly recumbently folded. Even seemingly

isotropic plutonic complexes of thewestern zone such as the Paloma ringcomplex (Fig. 3) appear to us to befolded sheets (Morton and Baird 1976)especially considering that the geologi-cal map (Morton and Miller 2006)shows the Santiago Peak wallrocks tobe folded.

In Baja California, large pre-100 Ma plutons are also stronglydeformed with concordant contacts,transecting cleavage, and obvious folds(Murray 1979; Johnson et al. 1999b,2003). Some plutons there, such as theRinconada pluton (Johnson et al.2002), were recumbently folded (Fig. 4;see also figure 5 in Johnson et al.2002). Overall, the data are compellingthat pre-100 Ma plutons of the Penin-sular Ranges batholith are complexlyfolded sills or sheets. This should beevident, for if the wall rocks wererecumbently folded at 100 Ma then thepre-100 Ma plutons must have been aswell.

Plutonic rocks of the easternsuite, named the La Posta plutons(Figs. 2 and 6), after a compositionallyzoned plutonic complex that spans theinternational border (Walawender et al.1990), range in age from 99–86 Ma(Premo et al. 2014b), possibly youngslightly eastward (Ortega-Rivera 2003),and are dominated by large, concentri-cally zoned, mostly weakly foliatedcomplexes comprising biotite andhornblende-bearing tonalitic marginalphases grading inward over several tensof metres to granodiorite and cored bygranite, in places containing bothbiotite and muscovite (Hill 1984; Silverand Chappell 1988; Walawender et al.1990). While xenocrystic zircon isscarce in both suites, local garnet-bear-ing monzogranite in the eastern suitedoes contain it. Euhedral titanite ischaracteristic of the La Posta plutons(Silver and Chappell 1988). Plutons ofthis suite were emplaced both aboveand below the basal unconformity(Johnson et al. 1999b; Schmidt andPaterson 2002; Shaw et al. 2014),although most were emplaced farthereast at greater depth within the base-ment complex.

The ilmenite-bearing 94 MaLa Posta intrusive complex comprises:(1) an outer titanite–hornblende–biotite tonalite, that is locally bandednear the outer contact, but character-

ized internally by inclusion-free horn-blende prisms up to 1 cm long, 0.5 cmtitanite crystals, and books of biotite;(2) a titanite–biotite granodiorite char-acterized by poikilitic potassiumfeldspar and hexagons of biotite up to1 cm across; and (3) an inner zonewith small euhedral biotite, potassiumfeldspar oikocrysts up to 5 cm across,and typically less than a couple percentmuscovite (Walawender et al. 1990).

Plutons of similar composi-tion, but slightly younger age (Fig. 6),sit structurally above the EasternPeninsular Ranges mylonite zone andare informally grouped as the SantaRosa suite, after their location withinthe Santa Rosa Mountains (Fig. 3). Allthree suites of plutons, Santa Ana, LaPosta, and Santa Rosa, were recognizedand dated from core recovered fromdrill holes in the Los Angeles basinarea farther north, demonstrating thatthe batholith presently extends to theTransverse Ranges (Premo et al.2014a), where similar rocks outcrop inthe Santa Monica Mountains just northof Los Angeles (R. Powell, D. Morton,personal communication 2014). Limit-ed Hf isotopic data from the La Postaplutons have model ages of about2300 Ma (Shaw et al. 2014).

Plutons of the La Posta–SantaRosa suites probably extend eastwardacross the Gulf of California intoSonora and Sinaloa, where a composi-tionally similar suite of 101 ± 2 to ~90Ma foliated to non-foliated tonaliteplutons occurs within 50 km of thecoast (Henry et al. 2003). They wereintruded into Jurassic and older green-schist-grade rocks common to the east-ern side of the Gulf (Gastil andKrummenacher 1977; Gastil 1979;Ramos-Velázquez et al. 2008). K–Arbiotite and hornblende ages are also inthe range 100–90 Ma (Henry et al.2003).

In the Sierra de San PedroMártir of Baja California (Figs. 2 and4), which might provide the bestexposed section across the boundarybetween eastern and western sectors,the Main Mártir thrust, commonlyconsidered by previous workers as thesuture between the two sectors, dipseastward as the westerly part of a dou-bly vergent fan structure (Goetz 1989;Johnson et al. 1999b; Schmidt andPaterson 2002; Schmidt et al. 2009,

410

2014); however, there are many LowerCretaceous gabbro bodies, characteris-tic of the western sector located eastof the fault. This suggests that anysuture may lie farther east.

Jurassic orthogneiss andparagneiss, located within the morecentral parts of the fan structure (Fig.4), appear to be part of the same pack-age as Jurassic rocks that we reason tolie unconformably beneath the Santia-go Peak rocks in the Santa Ana moun-tains of southern California (Fig. 5).Plutons in both places are dated at 164Ma (Schmidt and Paterson 2002; Shawet al. 2003). Thus, it is plausible, butperhaps difficult to document due tohigh strain, that the contact betweenhigher grade and very stronglydeformed rocks of Santiago Peak onthe west (Schmidt et al. 2014), and theJurassic gneissic rocks and pre-134 Marocks might be an unconformity (Fig.4). If correct, then the fan structurecontains a tectonically compressed sec-tion of crust within the Alisitos–Santi-ago Peak arc, much as the northwestplunge appears to do to the north inthe Southern California region.

One possible candidate for asuture appears to be the Agua Calientethrust (Fig. 4), which is a major faultthat dips moderately westward andalong which migmatitic flysch,deformed Cretaceous plutons, andsheeted gabbro plutons as young as100.1 ± 0.5 Ma, were transported east-ward over carbonate–quartzitemetasedimentary rocks, prior toemplacement of the La Posta plutons(Schmidt and Paterson 2002; Schmidtet al. 2009). The fault zone was recog-nized by Measures (1996) who mappeda section across it and described it as a200–500 m thick migmatitic zone con-taining imbricated slivers of amphibo-lite, Cretaceous orthogneiss, pre-batholithic schist, ultramylonite, andS–C mylonitic gneiss with northwestover southeast shear at amphibolite-facies conditions. The main problemwith selecting the Agua Caliente faultas the suture is that the footwall con-tains a muscovite-bearing pluton datedat 164 Ma that intruded the carbon-ate–quartzite succession. As this is thesame age and similar composition todated plutons beneath the arc complex,this fault is unlikely to be the suture. Ifthe Agua Caliente fault is not the

suture then it must be located farthereast, which barring structural complica-tions, implies that the arc basementcontained Paleozoic metasedimentaryrocks and very likely their basement,which we presume to be Precambrian.It also implies that the Baja Peninsulacontains the arc and significant quanti-ties of basement. We will return to thistopic and its implications later in thepaper.

AGE OF DEFORMATIONThe best constraints on the age ofdeformation within the CretaceousPeninsular Ranges batholith (Fig. 6)come from the detailed work ofPremo and Morton (2014) who dated awide variety of rocks on Searl Ridge(Fig. 3) in the Perris block where theyfound and dated zircon in a pre- tosyn-metamorphic diorite dyke to be103.3 ± 0.7 Ma and in a post meta-morphic pegmatite dyke to be 97.53 ±0.18 Ma, which they interpreted tohave been emplaced just after meta-morphism. Additionally, they datedmore than 30 hornblende separatesand determined that metamorphismtook place at or before 100.1 ± 0.6 Ma.This is consistent with older data col-lected farther south in the Sierra deSan Pedro Mártir, where the age of thedeformation is tightly constrained byplutons. There, 100 Ma gabbro and the101 Ma gabbro–tonalite–trondhjemiteRinconada complex, are composition-ally linked to the western zone, strong-ly deformed, and folded (Johnson et al.2002; Alsleben et al. 2008; Schmidt etal. 2009), yet the 97–90 Ma La Posta-type Sierra de San Pedro Mártir plu-tonic complex, which cuts the contactbetween the eastern and western sec-tors does not contain the same level ofdeformation (Ortega-Rivera et al. 1997;Gastil et al. 2014). Similarly, the ElPotrero pluton, located just 1–2 kmwest of the San Pedro Mártir body, is astrongly deformed tonalite with U–Pbzircon age of 102.5 ± 1.6 Ma and40Ar/39Ar ages of 101 ± 5 Ma forhornblende and 94 ± 1.4 Ma forbiotite (Johnson et al. 1999b; ChávezCabello et al. 2006).

We will use 100 Ma as the bestestimate for the age of deformation,but realize that some plutons of theSanta Ana suite may still have beencrystallizing as late as 98 Ma or that

early La Posta bodies might have char-acteristics of the Santa Ana suite. It isalso important to note that we arereferring here to deformation of theAlisitos–Santiago Peak arc, and notolder deformations, such as the ~160Ma Jurassic and 145–139 Ma post-Peñasquitos, both of which are con-fined to the basement, nor the younger~75 Ma Laramide deformation, as it isthe short-lived 100 Ma deformationthat appears to coincide with a majorchange in Cretaceous magmatism.

EXHUMATIONThe La Posta plutons (Fig. 6) representan intense magmatic pulse ranging inage from 99–85 Ma (Silver and Chap-pell 1988; Walawender et al. 1990;Kimbrough et al. 2001; Premo et al.2014b). The plutons were emplaced atdepths of 5–23 km into upper green-schist, but mainly amphibolite, gradewall rocks that are in many placesmigmatitic (Gastil et al. 1975; Agueand Brimhall 1988; Todd et al. 1988,2003; Grove 1993; Rothstein 1997;Rothstein and Manning 2003; Gastil etal. 2014). The plutons were intrudedduring a period of exhumation whenrocks at depths of 15–23 km werebrought rapidly to the surface bydetachment faulting and collapse(Krummenacher et al. 1975; Georgeand Dokka 1994; Ortega-Rivera et al.1997, Ortega-Rivera 2003; Grove et al.2003; Miggins et al. 2014). Large vol-umes of sediment were eroded fromthe uplifted terrane, as documented byabundant 100–90 Ma detrital zirconand feldspar deposited as part of avoluminous pulse of early Cenomanianto Turonian coarse clastic sedimenta-tion in basins located to the west(Lovera et al. 1999; Kimbrough et al.2001).

In the Southern Californiasegment of the batholith the depth ofemplacement of all plutons, based onAl-in-hornblende barometry, increasesfrom about 2 kbar or less in the west,to more than 5 kbar in the easternzone (Ague and Brimhall 1988; Toddet al. 2003). In the Sierra de San PedroMártir, farther south (Fig. 4), emplace-ment depths are similar, except there isa marked jump on the west from 2kbar to 5 kbar that coincides with aseries of closely spaced, easterly dip-ping, reverse faults (Schmidt et al.


2009). On the eastern side of the Gulfof California rocks are dominantlygreenschist and we are unaware of anygeobarometric studies on the plutonsthere.

At a regional scale, K–Ar agesdecrease eastward across the batholith(Silver et al. 1979), but there has beenlittle agreement on the origin of thepattern, with some relating it to region-al tilt, others to eastward-migratingmagmatism, and still others to two dis-crete events. Those who favour theidea of a regional tilt, based on shal-lower emplacement depths of plutonsin the east, generally relate the tilting toopening of the Gulf of California(Krummenacher et al. 1975), but basedon modern seismic analyses the effectsof the Neogene uplift extend onlyhalfway across the Baja Peninsula(Lewis et al. 2001), so it is unlikely tobe the cause. Models that relate theyounging to migrating magmatism(Ortega-Rivera 2003) don’t resolve theproblem, for the K–Ar ages in the eastare as much as 20 m.y. younger than LaPosta magmatism. Using 40Ar/39Ar inbiotite and potassium feldspar collect-ed in a more focused area across thecentral boundary, Grove et al. (2003)recognized two distinct periods ofexhumation and cooling in rocks ofthe Peninsular Ranges batholith: anearly ~95–86 Ma period, which theyascribed to emplacement of the LaPosta suite; and a < 78 Ma period,located farther east, which they relatedto the Laramide event. They clearlyrecognized two events and soexplained the regional timing, but theirtectonic model failed to explain theorigin of the La Posta plutons as wellas the 19–23 km of uplift and exhuma-tion during their emplacement.

GEOCHEMISTRYThe geochemistry of the PeninsularRanges batholith is historically impor-tant because it is close to the SouthernCalifornia megalopolis and its geologi-cally rich university community, so thatover the years many geochemical andpetrological studies were completed.The early field and petrological studiesby Larsen (1948) were highly regardedand strongly influenced several genera-tions of petrologists studyingbatholithic rocks. His geochemical dataset was employed for the ‘type’ calcic

suite used to define the boundarybetween alkali-calcic and calcic pluton-ic suites on the SiO2–MALI diagram ofFrost et al. (2001). His data set wasalso used to define the calcic trend onthe normative Q’–ANOR diagram(Whalen and Frost 2013).

During the late 1970s, A.K.Baird and coworkers collected 334granitic rock samples on a uniformgrid from the northern PeninsularRanges batholith in Southern Califor-nia (Baird et al. 1979). To obtain repre-sentative compositions, they collected 8samples within a 400 x 400 foot (122 x122 m) square from each site. Thesamples were then crushed and com-bined to yield one homogeneous pow-der from each sample site. To ourknowledge, this represents the mostsystematic and representative geochem-ical sampling of a batholith carried outto date. Major element results fromthis collection were discussed by Bairdet al. (1979) and published (withoutMnO and P2O5 determinations) byBaird and Miesch (1984). Subsequently,Kistler et al. (2003) published a compi-lation of isotopic data that contained

results for whole rock Sr, 83 for bulkrock oxygen and 103 for whole rockPb isotopes. This isotopic dataset, orportions thereof, was presented andinterpreted in several papers (Kistler1990, 1993). More recently, a subset of287 rocks from the Baird collectionwas re-analyzed by ICP–MS for majorand trace elements by Lee et al. (2007).

For this paper (Fig. 7), we uti-lized the Lee et al. (2007) data set,which included published sample loca-tion and initial Sr isotopic ratios(Kistler et al. 2003). To these data, weadded O and Pb isotopic data fromKistler et al. (2003) and more recent Srand Nd analyses from Premo et al.(2014b). We also added whole rockgeochemical data from a recent studyof the largest La Posta-type pluton inBaja California, the Sierra de San PedroMártir, by Gastil et al. (2014).

Instead of the purely geo-graphic division of plutonic rocks intoa western and eastern half favoured bymost previous workers, we used a basictwo-fold subdivision: pre- and post-100 Ma deformation, which does havesome geographic connotations in that

412

Eastern Peninsular

Ranges mylonite

zone

fault zone

San Andreas fault zone

San Jacinto

San Jacintoblock

Perrisblock

SantaAna

block

Santa Rosa suiteLa Posta suite Santa Ana suite

Elsinore

fault zone

gabbroline

δ Ostep

18

M-Iline

34º

erreoor

nnosiiinlsssin

Elllsi

EEls

affa

ottonntciiinccin

aacJJann J

aanSSa 11

7º

acac

tlltuulaffa

SS

enneoonzzotlltuulaffasaaseearreddrnnd

AAnnaanSSaS

anSa PLanS

116º

ena suitta Aneosta suitP

eta Rosa suitn

naA

taanS

e

tullltuultaauffa line

-IM

enneoon

zzotlltuul

ban S

ckblootacinJ

ck

Pacacicifiificfic

blo

enne

oonzzo

t

linegabbro

l

ckbloerrisPo

one zeylonit

angesm

gl i

ReninsularP

ern East

cOceceanan

18δ Oepst

18

33º

Figure 7. Map showing tectonic blocks (Santa Ana, Perris and San Jacinto),bounding faults, and locations of geochemical samples in the northern PeninsularRanges batholith of southern California based on figures 1 and 2 of Kistler et al.(2003) and figure 68 from Morton et al. (2014).

the pre-deformational plutons of theSanta Ana suite are concentrated, butnot limited to, the west, and post-100Ma plutons of the La Posta suite areconcentrated in the east. We use thisseparation because we believe that thedeformation represents a regional tec-tonic event and that magmatism beforeand after are compositionally quite dif-ferent, which suggests to us that theyhave distinct origins. Based on a newgeneralized geological map of thenorthern Peninsular Ranges batholithshowing Baird’s sample locations (fig-ure 68 in Morton et al. 2014), followedup by discussions with Doug Morton,who has detailed location maps, we fil-tered the Lee et al. (2007) data toexclude mylonitic, contact zone, sedi-mentary and Jurassic plutonic samples,so as to include only Santa Ana and LaPosta suite samples in this study.

As discussed earlier, webelieve that the major break defined byvarious attributes on the surfacereflects the Cretaceous–Jurassic uncon-formity (Fig. 5) rather than a steeplydipping and fundamental crustal breakor suture, and that the contact wasmore or less horizontal prior to defor-mation at 100 Ma. It now dips steeplyeastward (Langenheim et al. 2014) andmay represent the eroded remnant ofan overturned limb of a large nappeformed during the deformation.

Within the post-deformationalLa Posta suite we recognize two sub-groups: (1) the La Posta plutons prop-er; and (2) plutons, which we call theSanta Rosa suite, that are similar torocks of the La Posta, but slightlyyounger, and which are exposed in theSanta Rosa Mountains (Figs. 3, 6).Santa Rosa plutons have a limited geo-graphical distribution in that theyoccur above the East PeninsularRanges mylonite zone (Fig. 3), which isa Laramide-age, westerly vergent, shearzone (Todd et al. 1988; Morton et al.2014). We cannot rule out the unlikelypossibility that the plutonic rocks ofthe Santa Rosa suite are not geneticallyrelated to the La Posta plutons, so weuse different symbols to representthem on many of our geochemicalplots.

General Geochemical FeaturesAs outlined above, samples from thePeninsular Ranges batholith were sub-

divided into two main groups based onage. Rocks of the calcic Santa Anasuite (Fig. 8a) span a broad silica range,from 48 to 77% SiO2, whereas therange of the La Posta suite is muchmore limited, as all samples containgreater than 60% SiO2 (Fig. 8b). Ingeneral, mainly metaluminous compo-sitions (Fig. 8e) and amphibole-bearingmineralogy indicate that both suites arecomprised of I-type granite (Silver andChappell 1988; Chappell and Stephens1988). Santa Ana granitoid rocksdefine the calcic trend in Figure 8a,and lie in the calcic field on Figure 8c,whereas La Posta samples exhibit a cal-cic to calc-alkalic affinity. Similarly,samples from Santa Ana plutons plotalmost exclusively in the medium-Kfield (Fig. 8d), whereas members ofthe La Posta suite spread upward intothe high-K field at higher silica con-tents. Samples from both suites with< 70 wt.% SiO2 plot in the magnesian(oxidized) field in Figure 8b, but crossover into the ferroan (reduced) field athigher silica levels. On a SiO2 vs. Al2O3plot (Fig. 9a), the rocks of both suitesexhibit a high-Al trend (Barker andArth 1976), but with rocks of the LaPosta suite defining a slightly higher Altrend than analyses from rocks of theSanta Ana suite. For any given silicacontent, rocks of the Santa Ana suitehave higher concentrations of transi-tion metals, such as V+Cr, (Fig. 9b)than samples from the La Posta suite.For samples with silica contents lyingbetween 60 and 70 wt.% SiO2, rocks ofthe La Posta suite tend to exhibit sig-nificantly higher Ba and Sr and lower Ycontents than samples from the SantaAna suite (Fig. 9c to 9e). While bothsuites have similar Rb contents, thesuites are readily divisible on a Rb–Srplot (Fig. 9f) due to contrasting Sr con-tents (Wallawender et al. 1990; Tullochand Kimbrough 2003). Rocks of theSanta Ana and La Posta suites also dis-play marked differences in La/Yb,Gd/Yb, Nb/Y, and Sr/Y values andthese are readily apparent on his-tograms and Harker plots (Fig. 10).

Extended element-normalizedplots of average compositions (Table 1and Fig. 11) show that the La Postaaverage over the 60–70 wt.% silicarange is more enriched in all trace ele-ments to the left of Zr and moredepleted in heavy rare earth elements

(HREE) than the Santa Ana averageover similar silica contents. Both the LaPosta and Santa Ana suites have welldeveloped negative K, Nb, Zr, P, andTi anomalies. In rocks with > 70 wt.%silica, the Santa Ana average is moreenriched in all elements, except for Ba,P, and Ti than the felsic La Posta aver-age, but has a pronounced negative Sranomaly. The felsic La Posta average isgreatly depleted, and the Santa Ana isenriched, in HREE relative to their60–70 wt.% silica range suite averages.Extended element-normalized compo-sitional average patterns for the wellstudied Tuolumne intrusive suite ofthe Sierra Nevada (Fig. 11b) closelymatch the patterns and overall elemen-tal abundances of the La Posta rocks.We also plotted averages for the LaPosta suite, again over the 60–70% sili-ca range, and compared them withcompositional averages for other high-Al and La/Yb suites (Fig. 11c). Bothadakite suites differ from the La Postasuite in that they are more depleted inlarge ion lithophile elements (LILE)and HREE, but have strong positive Sranomalies. On Figure 11d we comparerocks of the Santa Ana suite with com-positional averages for primitive toevolved arc-type suites. There, the pat-tern for the Santa Ana rocks moreclosely resembles the continental arcaverage, but is more depleted in theLIL elements to the left of Zr, wherethey define a trend about halfwaybetween the continental and oceanicarc patterns.

PREVIOUS MODELSSilver et al. (1963; written in 1956) firstsuggested that the western part of thePeninsular Ranges batholith representsa primitive island arc constructed onoceanic lithosphere. In a subsequentcontribution, Silver and Chappell(1988) recognized the dual nature ofthe batholith; that the western batho-lith formed between 140–105 Ma as astatic arc above an eastward-dippingsubduction zone; that magmatismmigrated eastward between 105–80Ma; and that it was derived from adeeper, subcrustal eclogitic source toyield La Posta plutons. They consid-ered the batholith was a juvenile addi-tion to the crust and formed where nocontinental lithosphere existed. On theother hand, based on Nd and Sr iso-


topes, Allègre and Othman (1980) rec-ognized that plutons of the PeninsularRanges and Sierra Nevada batholithswere formed from mantle melts plussignificant quantities of continentalcrust.

In their landmark book on thereconnaissance geology of Baja, Gastilet al. (1975, submitted in 1971) wereunderstandably coy in their tectonicinterpretation, as plate tectonics hadonly recently “come on land” (Hoff-man 2013); yet in the time it took topublish the book, Gastil created andpublished a short paper waxing poeti-cally on a simple eastward-dipping sub-duction model in which “great welts oftonalitic magma accumulated near the base ofthe pre-existing crust . . . spawned plutonsthat rose as diapirs . . . then bled upward intoshallow plutons and extrusive masses”(Gastil 1975). By 1981, he had devel-oped a more complex model involvingtwo eastward-dipping subductionzones, one beneath a more westerlyfringing arc and the other to the eastbeneath the continental margin (Gastilet al. 1981). Following closure of theeastern basin, which led to crustalthickening and uplift, eastward subduc-tion continued and a shallowing slabled to arc magmatism farther east.

Based largely on differences indegree of deformation between theBedford Canyon and Santiago Peakrocks, Todd et al. (1988) also utilized atwo-arc model but argued that “Colli-sion of the Santiago Peak–Alisitos arc withwestern North America in the Early Creta-ceous resulted in folding of the continental-margin deposits and eventual underthrustingof the arc beneath the continental margin.”

Contemporaneously with sub-duction of the western island arc, mag-matism migrated slightly eastwardwhere it produced melts from the sub-ducted arc crust. Fifteen years later,Todd et al. (2003) concluded that “asingle Cretaceous arc migrated from west toeast across a preexisting Late Jurassic–earliestCretaceous lithospheric boundary.”

Meanwhile Busby et al. (1998)also developed a fringing arc modelbased on their extensive work in Baja.They posited that a Jurassic arc, whichdeveloped offshore, grew into a moremature fringing arc separated fromNorth America by a back-arc basin,and that, “an increase in plate convergencecollapsed the fringing arc against the continent

414

50

40

30

20

10

00 20 40 60 80 100

ANOR - 100*(An/(Or+An))

Q’ -

100

*Q/(

Q+O

r+A

b+A

n)

50 60 70 80

20

10

0

30

20

10

0

50 60 70 80

% O

ccur

renc

e

SiO2 (wt%)

La Posta

SantaRosaSSPM

Santa Ana

n=122

n=123

post 100 Ma

pre-100 Ma

Samples from the western Peninsular Ranges batholithdefine the type calcic trend

La Postasuite

Santa Rosasuite

Santa Anasuite

Sierra San Pedro Mártir

La Posta-typepluton in Baja

.4

.5

.6

.7

.8

.9

1

Fe*

= (F

eO/(

FeO

+ M

gO))

tota

lto

tal Fe*

alkali-calcic

calc-alkalic

-5

0

5

10

MA

LI =

(Na

O+K

O-C

aO)

22

-10

-15

80

SiO (wt %)2

45 50 55 60 65 70 75

calcic

Santa Anasuite

Santa Anasuite

La Postasuite


Santa Rosasuite

ferroan

magnesian

La Postasuite


Santa Rosasuite

123456

1.0

0.5

1.5

Al/(Na + K)

Al/(

Ca -

1.67

*P +

Na

+ K)

0

2

4

6

8

50 55 60 65 70 75 80

low-K

shoshonitic

high-K

medium-Klow-K

K2O

(wt%

)

peraluminous

metaluminous

La PostaSanta Rosa

SSPM

Santa Ana

Post 100 Ma

Pre 100 Ma

La PostaSanta Rosa

SSPM

Santa Ana

Post 100 Ma

Pre 100 Ma

La PostaSanta Rosa

SSPM

Santa Ana

Post 100 Ma

Pre 100 Ma

a.

b.

c.

d.

e.

SiO (wt %)2

50

a.esuit

nata AanS

eninsuPamplesS

tholithanges baular Rern estom the ws fr

30

40n)b+

Ar+

AQ

+O(

t

calcc-calc-a

20

30

taan

osta

S

a PL

cka

alkalicalic

define t

e

end

suitostaa PL

alcic tre cyphe tg

10

20

- 100

*Q/

’’Q

50

R

enc 2

wt%

0

60 70

e

ppre-100

crr

cur

%O

c

706050

0

10

20

0

10

20

n=123

1000 M0 MaMaaa122n=

nata AanS

MSSPRosa

ttaan

(wt%)

S

2SiO

e

posp stsp

80

80

00 MMa

plut

esuitta RosaanS

a PLedPSie

ca

aja

calalclcicicic

on in Bteyposta-tP

tiráro Mdran a Serr

0

r))M

gO

1

.9 reerf

.b

(wt%)

200AN

2SiO

n

e

aanosuitta RosaanS

6040On/(ANOR - 100*(

8

6

ostPaSaL

80n))r+AO

a100 Mta Rosaanostaa P

100

.d

lattaottolattaotto

+ M

eO/(

FeO

e* =

(FF

.8

.7

.6

.5

.4esuit

nata AanS

e*F

a

aL

tiráro MedrPana SSierr

iiassienggnam

n

esuitostaa P

aan

me

6

4

2

O (w

t%)

2KK2

e 1rPaS

SS

shoshonitic

edium-K

high-K

a100 Mnata Aan

MSP

l K

c

licaallkka-aallcc-aalccaa

22

)aOC-

OO

+KN

a

10

5

0

-5cca

.c

calciclcali-

alkka

iclcciaal

esuitostaa PL

áo MedrPaa SSierr

ta RosaanS

tirran

)7*

P +

Na

+ K

1.

1

50

i

5

0

6560550

mularep

ae 100 MrP

aost 100 MP

nata AanS

MSSP

ta RosaanSostaa PL

2SiO (wt %) 2

s

-K-K

807570

wwlowlow-K

uusoniin

45

-15

-10

ALI

= (N

M

550

esuitnata AanS

2SiO (wt %) 2

70656055

a

esuit

e 10rP

ost 1P

anS

SSP

anSaL

8075

a - 1

.67

Cl/(

A

0.

1.

a00 M

a100 M

nata An

MP

ta RosanostaP

s

345

)l/(Na + KA

5

0

6

uonimulatem

12

.e

Figure 8. (a) Representative samples from the two main suites of the PeninsularRanges batholith plotted on the normative Q’ (100*(Q/ (Q+Or+Ab+An)) versusANOR (100*(An/ (Or+An)) classification diagram (Streckeisen and LeMaitre1979). We use the Whalen and Frost (2013) compositional trends. SiO2 histogramsare for the Santa Ana and La Posta suites. Sample subdivision is shown in the sym-bol legend and discussed in the text. (b) Peninsular Ranges batholith samples plot-ted on the: FeOtotal/ (FeOtotal + MgO) (or Fe*) vs. SiO2; the boundary between fer-roan and magnesian plutons has been modified as suggested by Frost and Frost(2008); (c) Na2O+K2O–CaO (or MALI) vs. SiO2 granitic rock classification dia-grams of Frost et al. (2001). Ranges for alkali-calcic, calc-alkalic, and calcic rockseries, based on the alkali–lime classification of Peacock (1931). Together with alu-minum saturation index (ASI) (Shand 1943) (Fig. 8e), these plots comprise a three-tiered geochemical scheme for granitoid rock classification. The horizontal dashedline at ASI= 1.1 in the Shand plot, modified after Maniar and Piccoli (1989), is thedividing line between I- and S-type granites (Chappell and White 1992); and (d) aSiO2 vs. K2O plot with suite subdivisions: low-, medium-, and high-K fields fromLeMaitre (1989) and high-K, shoshonitic fields after Peccerillo and Taylor (1976).Analyses from Lee et al. (2007) and Gastil et al. (2014).

and caused the reverse faulting and uplift”.Based on geological mapping

and dating Johnson et al. (1999b)invoked a double eastward subductionmodel with two eastward-dipping sub-duction zones, largely because theybelieved that Nd and Sr isotopic val-ues, coupled with the absence ofinherited zircon in the Alisitos andrelated plutonic rocks, indicated anabsence of continental input. Collisionof the arc with a more easterly arcbuilt on western North America led to

crustal thickening whereas continuedeasterly subduction led to the youngermagmatism.

Several researchers developedsingle eastward subduction modelsbased largely on the composition andcharacteristics of the La Posta suite.Walawender et al. (1990) devised a sim-ple model where increased conver-gence caused the eastward-dippingsubducting slab to shallow, buckle andbreak, so that continued subductionwas able to melt the overlying oceanic

crust and mantle to produce the LaPosta magmas.

In an important paper, Kim-brough et al. (2001) tied together manycritical elements, such as the post-deformational nature of the La Postasuite, the rapid exhumation, and coevalsedimentation to the west, which theyviewed as the fore-arc region, but inthe end they attributed the La Postasuite to nothing more than a transientepisode of high-flux magmatism. Tul-loch and Kimbrough (2003) expanded


10

100

500

Cr+V

(ppm

)

15

20

25

45 50 55 60 65 70 75 80

Hi-Al

Lo-Al

Ba (p

pm)

400

800

1200

1600

2000

0

0

200

400

600

Sr (p

pm)

0

10

20

30

40

45 50 55 60 65 70 75 80Y

(ppm

)

0 40 80 120 160 200 2400

100

200

300

400

500

600

700Sr

Rb (ppm)

Santa Anasuite

La Postasuite


Santa Rosasuite

La PostaSanta Rosa

SSPM

Santa Ana

Post 100 Ma

Pre 100 Ma

La PostaSanta Rosa

SSPM

Santa Ana

Post 100 Ma

Pre 100 Ma

La PostaSanta Rosa

SSPM

Santa Ana

Post 100 Ma

Pre 100 Ma

La PostaSanta Rosa

SSPM

Santa Ana

Post 100 Ma

Pre 100 Ma

La PostaSanta Rosa

SSPM

Santa Ana

Post 100 Ma

Pre 100 Ma

La PostaSanta Rosa

SSPM

Santa Ana

Post 100 Ma

Pre 100 Ma

Santa Anasuite

La Postasuite


Santa Rosasuite

Santa Anasuite

La Postasuite


Santa Rosasuite

Santa Anasuite

La Postasuite


Santa Rosasuite

Santa Anasuite

La Postasuite


Santa Rosasuite

Santa Anasuite

La Postasuite


Santa Rosasuite

SiO2 (wt%)

SiO2 (wt%)

Al2O

3 (w

t%)

a.

b.

c.

d.

e.

f.

Figure 9. Harker variation diagrams for (a) Al2O3; (b) Cr + V; (c) Ba; (d) Sr; (e) Y; and (f) Sr–Rb for Peninsular Rangesbatholith sample groups. In (a) the dividing line of Barker (1979) between high- (> 15 wt.%) and low-Al tonalite suites at SiO2= 70 wt.% is shown. Sample subdivision is shown in the symbol legend and discussed in the text. Note that on most of theseplots pre- and post-deformational plutons are compositionally distinct.

on the earlier model by recognizingthat the La Posta suite was a high Na,Sr and low Y suite and so created amodel in which the older, western andlow Sr, Y Santiago Peak–Alisitos arcwas underthrust beneath the arc duringslab-flattening, which shut off normalarc magmatism and generated the burstof La Posta magmatism. Grove et al.(2003) related the pre-90 Ma exhuma-tion to the emplacement of the LaPosta suite. Subsequently, Grove et al.(2008) developed a complex model –based largely on detrital zircon, theirTh/U ratios, and whole rock Pb iso-topes of the plutonic rocks – of east-ward-directed subduction, slab-flatten-

ing and subduction of forearc andaccretionary prism rocks, such as theCatalina schist. In their model, a hypo-thetical deep lithospheric mantle roothad formed beneath the La Posta beltbut was removed by Laramide shallowsubduction, so that it no longer existsbeneath the region.

Ortega-Rivera (2003), notingthe general eastward younging of plu-tonic ages, advanced a model of long-lived eastward subduction and varia-tions in dip and velocity of the sub-ducting plate to generate the magma-tism. Miggins et al. (2014) developed avague model, based on that of Groveet al. (2008), where eastward subduc-

tion built a near-margin or fringingextension arc built entirely on oceaniccrust, and that as arc magmatismmigrated eastward the tectonic regimewent from extensional to compression-al, which caused thrusting and exhu-mation of the western arc rocksbetween 105 and 98 Ma. They thenstated that between 98 and 91 Ma largeamounts of highly enriched magmawere formed and that it was theemplacement of the magma that led tothe exhumation of the eastern region.The reader was left to imagine whatcaused the events.

Schmidt et al. (2014) summa-rized over a decade of work by stu-

416

0.1

1.0

45 50 55 60 65 70 75 80

0 0.5 1.0 1.550

40

30

20

10

0

20

10

0

0 0.5 1.0 1.5

% O

ccur

renc

e

n =122

n=87

Nb/Y

Nb/

Y=0.

4

SiO2 (wt%)

Nb/

Y


Santa Ana suite

Santa Rosa suite

c.

La Posta suite

MORB

0 10 400

50

200

150

100

20 30

020406080

40

30

20

10

0

20

10

0

Sr/Y

Y (ppm)

% O

ccur

renc

e

Sr/Y

=10


Santa Ana suite

Santa Rosa suite

La Posta suite

Sr/Y

n =122

n=87

Adakites

020406080

Arcsd.

0 2 5 76431

50

40

30

20

10

0

30

20

10

00 5 76431 2

45 50 55 60 65 70 75 800.5

5.0

1.0

Gd/

Yb

SiO2 (wt%)


Santa Ana suite

Santa Rosa suite

La Posta suite

% O

ccur

renc

e

n =122

n=87

Gd/Yb

b.

Gd/

Yb=2

.00

40

30

20

10

0

20

10

0

50

60

0 1 2 3 4 5 6 70

10

20

30

40

50

60

70

MORB

La/Y

b=10

n =122

n=87

153045

015304560

60

La/Y

MORB

Yb (ppm)

La/Y

b

Adakites

Arcs

Santa Rosa suite

La Posta suite

Santa Ana suite

La/Yb=10

a.


Gd/Yb=2

Nb/Y=0.4

s

60

70etikadA

MártiSan P

60 4

n =1

ir plutonPedro de

0

10

20

05 30 15

122

0 0 5e

0

10

20

1 0 1 5

n =122 etiusasoRatnaS

San Pedro de

e La Posta suite

20

30

40

50

b

La Pos

La/Y

60 4

sta suite

Santa Ana suite

Santa Rosa suite

60

50

0

10

20

30

40

La/Y45 30 15 0

n=87

b=10

La/Y

1.00

b/Y

0.5een

ccu

rr%

Oc

0.500

10

20

30

40

50

b/Y=

0.4

N

N

N

1.0 1.5

1.51.0

n=87

b/YN

Nb/Y=0.4

Mártir pluton

0

40

50

0

Arcs

10

10

La Posta suite

432

b (ppm)

MORB

Y

Má ti l tSan Pedro de

7

a.65

La/Yb=10

0.1

c.5045

200

656055

(wt%)2SiO

807570

Santa Ana suite

20

5.0

0

10

20

30

40

1 3 420

b=2.

0

bd/

YG

d/Y

G

d/YG

een

ccu

rr%

Oc

4 6 75

b

etiusasoRatnaS

Y

n=87

Gd/Yb=2

Mártir pluton

a

150

100

Sr/Y

Mártir pluSan Pedro

La

dA

s

80 60

n =1

tono de

a Posta suite

etika

0

10

10

20

30

40

40 20 0

Sr/Y

=10

een

ccu

rr%

Oc

n=87

22

50

21 3 400

10

20

30

45

1.0

0.5

n

65

4 6 75

n =122

6055

(wt%)2SiO

Santa Ana

80

b.7570

suite

50

d.0

100

0

80

M

20

Y (ppm)

etiusasoRatnaS

60

40

s

0

MORB

30

40

Santa Ana suite

crA

20 0Sr/Y

Figure 10. Some trace element ratio plots for Peninsular Ranges plutonic suites. (a) La/Yb versus Yb plot and La/Yb his-tograms; (b) Gd/Yb versus SiO2 and Gd/Yb histograms; (c) SiO2 versus Nb/Y plot and Nb/Y; (d) Sr/Y versus Y plot andSr/Y histograms. In all insert histograms and 10a and 10d X-Y plots, only samples with > 60% silica are plotted, whereas in10b and 10c X-Y plots all samples are plotted, as in Figures 8 and 9. Fields are shown for adakite, arc andesite–dacite–rhyoliteand MORB from Richards and Kerrich (2007), as is the average medium-K arc andesite (blue cross in a). In the histograms, ver-tical lines approximately separate pre- and post-deformational granitoid rocks.

dents at USC and concluded that theSantiago Peak rocks were depositedupon Jurassic basement whereas theAlisitos rocks were established uponoceanic crust. In their model, the Alisi-tos and Santiago Peak arcs collidedalong the ancestral Agua Blanca andMain Mártir thrusts prior to 108 Maand the resulting contractional defor-mation and crustal thickening “culminat-ed in a major pulse of arc magmatism thatformed the 99–92 Ma La Posta suite.”Numerous difficulties with this model,which was based largely on work byWetmore et al. (2002), were summa-rized by Busby (2004), and include thesimilar basements and the presence ofinherited zircon for both groups ofrocks, as well the presence of abun-dant siliceous volcanic rocks within theAlisitos arc, including ignimbrite sheets(Busby et al. 2006), all cut by numerousintermediate–siliceous compositionplutons, which are atypical of arcs builton oceanic crust.

Another group of researcherslinked the Alisitos–Santiago Peak arcto the Guerrero composite terranelocated on the Mexican mainland (Cen-teno-García et al. 2008). A Frenchgroup (Tardy et al. 1992, 1994) alsoargued that the Alisitos arc was part ofthe Guerrero composite terrane butreasoned that it collided with the west-ern margin of North America over awestward-dipping subduction zone.Dickinson and Lawton (2001a) pre-sented a model in which the SantiagoPeak volcanics represented an arcaccreted to the western margin of theCaborca block, but that the contactwas obscured by younger plutons.

In an important contribution,Centeno-García et al. (2011) noted thestrong ties between the history of BajaCalifornia and the Guerrero compositeterrane, as well as the strong detritalzircon ties of both to North America,and so speculated that the arc fringedthe continent and was separated fromit by a marginal basin. They argued thatthe closure of the basin started in thewest during the Cenomanian, migratedeastward, and ended prior to deposi-tion of Santonian sediments betweenabout 93–84 Ma. They stated that “Arcextension ended by the Albian–Cenomanianboundary in Baja California, when the EarlyCretaceous Alisitos fringing arc underthrustthe Mexican continental margin and the crust


Table 1. Average compositions of Peninsular Ranges Batholith plutonic suites.

Group Santa Ana Suite La Posta SuiteSiO2 Range 60-70% 1 >70% 1 60-70% 1 >70% 1No. Samples 39 41 110 12Major Elements (wt.%)SiO2 66.48 8.46 76.47 0.77 65.93 2.14 71.54 0.84TiO2 0.61 0.25 0.16 0.06 0.71 0.16 0.29 0.07Al2O3 16.08 2.27 12.64 0.33 16.77 0.78 15.86 0.44Fe2O3

Total 3.09 2.05 1.87 0.35 4.27 2.00 2.01 0.94MnO 0.07 0.03 0.05 0.02 0.08 0.03 0.04 0.02MgO 1.25 0.62 0.22 0.11 1.47 0.48 0.46 0.17CaO 4.01 1.27 1.14 0.41 4.52 0.67 2.91 0.48Na2O 3.89 0.73 3.59 0.28 3.93 0.61 4.49 0.44K2O 2.36 0.77 3.79 0.77 2.21 0.55 2.45 0.78P2O5 0.18 0.06 0.07 0.02 0.20 0.04 0.09 0.03

Trace Elements (ppm)Cr 17 32 12 9 16 9 6 4Co 6 5 2 1 7 4 1 2Sc 7 4 6 4 7 3 5 2V 49 26 8 6 55 19 21 15Cu 12 11 8 8 14 11 3 3Zn 66 19 30 11 73 12 52 13W 0.3 0.2 0.4 0.2 0.3 0.2 0.0 0.1Mo 1.8 1.4 3.8 1.7 1.8 1.2 0.2 0.4Rb 80 30 123 47 77 24 70 22Cs 2.3 1.0 2.9 2.1 2.3 0.8 2.2 0.7Ba 899 317 809 316 920 302 962 328Sr 465 145 83 34 515 67 459 61Ta 0.8 0.5 0.8 0.4 0.8 0.6 0.4 0.2Nb 8.5 4.5 6.4 1.8 9.3 4.6 4.8 1.4Hf 4.4 1.2 4.3 1.3 4.6 1.1 3.2 0.5Zr 160 44 124 35 171 40 128 20Y 14 7 27 9 13 5 8 3Th 10.8 7.4 15.8 7.4 10.8 7.5 6.7 2.9U 1.9 1.2 3.2 1.6 1.9 1.1 0.8 0.2La 26.8 12.1 19.4 5.2 28.8 12.3 20.1 6.6Ce 55.8 25.1 43.7 11.1 60.0 25.6 37.8 12.0Nd 25.0 10.1 19.0 3.8 27.0 9.9 15.4 4.3Sm 5.1 2.0 4.7 1.4 5.4 1.9 2.9 0.8Eu 1.2 0.4 0.7 0.5 1.3 0.4 0.8 0.3Gd 3.7 1.4 4.2 1.3 3.8 1.3 2.1 0.6Tb 0.6 0.3 0.8 0.3 0.6 0.2 0.3 0.1Yb 1.4 0.9 3.5 1.2 1.3 0.6 0.7 0.2ParametersQ' 26.6 6.5 39.8 1.4 25.1 4.3 29.9 2.6ANOR 55.8 15.9 19.4 9.0 61.5 8.2 49.8 11.3MALI 2.2 1.8 6.2 1.0 1.6 1.1 4.0 1.1Fe* 0.74 0.10 0.89 0.04 0.73 0.03 0.80 0.03Zr Temp.(C) 748 89 766 23 760 31 726 16ASI1 0.99 0.12 1.05 0.02 1.00 0.03 1.04 0.02Alkali Index 1.79 0.32 1.27 0.09 1.90 0.17 1.59 0.12Isotopes

18O‰ 6.7 0.7 6.4 1.8 9.3 0.7 10.5 3.0i 87Sr/86Sr 0.7050 0.0054 0.7040 0.0006 0.7070 0.0001 0.7055 0.2720i206Pb/204Pb 18.772 0.092 18.867 0.110 19.211 0.181 18.931i207Pb/204Pb 15.603 0.020 15.612 0.017 15.682 0.024 15.626i208Pb/204Pb 38.446 0.138 38.496 0.118 38.787 0.125 38.657RatiosLa/Yb 5.86 2.96 6.62 3.18 26.80 19.22 31.90 14.07Gd/Yb 1.15 0.41 1.25 0.35 3.23 0.74 3.13 0.63Sr/Y 4.45 4.33 3.43 1.77 49.26 30.88 67.22 32.07Ba/Y 27.7 13.3 31.9 13.3 86.1 61.0 147.0 102.6Nb/Y 0.22 0.07 0.25 0.05 0.71 0.21 0.64 0.191. ASI = Al saturation index.

was greatly thickened” without explaininghow the arc ended up on the lowerplate and the continental margin theupper.

INTERPRETATIONIn what follows we show how the vari-ous components of the CretaceousPeninsular Ranges batholith can becombined into a new, dynamic, butentirely actualistic, model. We do thisfirst by succinctly examining some crit-ical attributes of modern arc terranes,then we move on to examine the sub-duction polarity for the Santiago Peak–Alisitos arc. This leads us directly intoa discussion of lithospheric slab failureduring collision and how it can parsi-moniously explain major features inthe development of the batholith.Next we look at the exhumation of thebatholith and touch on the formationof the doubly vergent fan structure.

We then interpret the geo-chemistry of the pre-collisional and

post-collisional plutonic rocks in orderto better understand the sources of themagmatism. To end – but prior to pre-senting our final conclusions – we con-cisely compare the development of thePeninsular Ranges batholith with someother Cordilleran batholiths of theAmericas.

ArcsAlthough Coats (1962) clearly arguedthat subduction of oceanic crust creat-ed the volcanoes of the Aleutian arc, itwas Hamilton (1969a, b) who hypothe-sized that the only modern volcanicfields of comparable size to greatMesozoic batholiths of the westernAmericas were Andean-type volcanicfields, where he suggested, “that a greatlate Cenozoic batholith, comparable in sizeand composition to the late Mesozoicbatholiths of western North America, hasformed beneath the young volcanic pile of thecentral Andes.” In many ways it is unfor-tunate that Hamilton chose the Andes

for it is atypical of continental arcs andso, many geologists, also strongly influ-enced by the supposedly deep Sierrancrustal root (Lawson 1936; Bateman etal. 1963; Bateman and Wahrhaftig1966; Christiansen 1966; Dodge andBateman 1988), assumed thatCordilleran batholiths were generatedin zones of great crustal thickening(Bateman 1992; Ducea 2001; Duceaand Barton 2007; Grove et al. 2008;DeCelles et al. 2009).

One only has to survey conti-nental arcs worldwide to recognize thatthere are problems in using a thickcrust Andean-type model, for, contraryto popular belief, thick sequences ofarc rocks erupted and deposited withina subsiding basin are the norm, notvolcanoes sitting on high-standingthick crust. Most continental arcs formwithin subsiding depressions or basinson crust of average or below averagethickness (Levi and Aguirre 1981;Hildebrand and Bowring 1984; Busby-

418

Santa Ana Suite (N=39)

Oceanic arc pluton (N=5)

Continental arc: andesite dacite-rhyolite (N=815)

Cenozoic Adakite (N=140)

post-Archean Adakite &

High-Al TTG (N=394)

10

100

1

10

100

1

La Posta 60-70% SiO2 averagewith Comparison Compositions

La Posta Suite avg (N=110)

Taiwan Unit KYS (N=6)

Santa Ana 60-70% SiO2 averagewith Comparison Compositions

c.

d.

1

10

100

Sa

mp

le/P

rim

itiv

e M

an

tle

1

10

100

Tuolumne Intrusive Suite averages

Peninsular Ranges batholith

a.

b.

La Posta Suite averages60-70% SiO2 (N=110)

>70 % SiO2 (N=12)

Santa Ana suite averages60-70% SiO2 (N=39)

>70 % SiO2 (N=41)

La Posta suite 60-70% SiO2 (N=110) average

TIS 70-75% SiO2 average (N=40)

TIS 60-70% SiO2 average (N=112)

TIS <60% SiO2 average (N=19)

Figure 11. Primordial mantle-normalized extended element plots for: (a) Peninsular Ranges batholith plutonic suite composi-tional averages from Table 1 for 60–70 and > 70 wt.% silica ranges; (b) Tuolumne Intrusive Suite compositional range averagescompared to La Posta 60–70% SiO2; (c) La Posta 60–70% SiO2 average compared to other similar units including KYS fromTaiwan (Wang et al. 2004), Cenozoic adakite bodies, post-Archean adakite bodies, and high-Al TTG suites; and (d) Santa Anasuite 60–70% average, oceanic arc pluton, and continental arc. Comparison compositions in (c) and (d) from Drummond et al.(1996) and Whalen (1985); data in (b) are based on a compilation of data from various sources including Memeti (2009). Pri-mordial mantle-normalizing values are from Sun and McDonough (1989).

Spera 1988b; Busby 2004, 2012). Mod-ern examples include the Cascades,where the volcanoes sit in a halfgraben (Williams and McBirney 1979;Mooney and Weaver 1989), the low-standing Alaskan Peninsula (Burk 1965;Fliedner and Klemperer 2000) wherevolcanoes such as Augustine are par-tially submerged in Cook Inlet (Poweret al. 2010), the Kamchatka Peninsulaof easternmost Russia where toweringstratovolcanoes sit in huge fault-bounded troughs (Erlich 1968, 1979;Levin et al. 2002a, b), to New Zealandwhere the Taupo zone sector of thearc is actively extending as calderas andstratocones erupt within it (Houghtonet al. 1991; Harrison and White 2006;Downs et al. 2014), and the CentralAmerican arc where volcanoes arealigned in a long linear depression(Williams et al. 1964; Williams andMcBirney 1969; Burkhart and Self1985; MacKenzie et al. 2008).

Furthermore, the stratigraphywithin pendants and wall rocks ofCordilleran batholiths provides no evi-dence of thick crust as they too sat ator below sea level during volcanism.The Sierra Nevada was clearly low-standing during magmatism, for it con-tains marine rocks deposited at about100 Ma (Nokleberg 1981; Saleeby et al.2008; Memeti et al. 2010). So was thewestern Peninsular Ranges arc, wherethe Santiago Peak and Alisitos vol-canics are interbedded with sedimenta-ry rocks containing marine fossils (Fifeet al. 1967; Allison 1974; Phillips 1993;Griffith and Hoobs 1993; Wetmore etal. 2005; Busby et al. 2006; Centeno-García et al. 2011). In South America,the 9 km thick Casma arc volcanicrocks, the wall rocks for the youngerCoastal batholith of Peru, are domi-nantly marine (Cobbing 1978, 1985;Atherton et al. 1985) as are many ofthe thick Jurasso–Cretaceous arc rockswithin the Ocoite arc of northernChile (Levi and Aguirre 1981; Åberg etal. 1984). Even ancient arcs, such asthe Paleoproterozoic Great Bear mag-matic zone of the Wopmay orogen,were low standing zones of subsidenceduring magmatism (Hoffman andMcGlynn 1977; Hildebrand andBowring 1984). Where arcs are con-cerned the Andes are the outlier – sim-ply atypical of modern and ancientarcs.

As stated earlier, the generalparadigm for generation of the Santia-go Peak–Alisitos arc and the PeninsularRanges batholith – and in fact all theCordilleran batholiths of the AmericanCordillera – has been east-directed sub-duction beneath the western margin ofNorth America. In what follows, weprovide evidence that indicates that atleast part of the Santiago Peak–Alisitosarc was constructed by magmatismarising from westerly, not easterly, sub-duction.

Polarity of SubductionAs indicated previously, nearly allresearchers who have presented mod-els for the origin of the PeninsularRanges batholith have assumed aneastward-dipping subduction regime.Yet as pointed out by Todd et al.(1988), it was only the presence ofscattered occurrences of blueschist-facies metamorphic rocks and ophiolitelocated to the west of the PeninsularRanges batholith in the California bor-derlands which suggested that subduc-tion was eastward. These rocks out-crop in the Sierra de San Andres onthe Vizcaino Peninsula and on CedrosIsland (Fig. 2). There, a sequence ofvolcanic and sedimentary rocks, gener-ally interpreted to represent a magmat-ic arc, active from at least 166 ± 3 Mauntil 160 Ma and again during the Cre-taceous, sits atop a Late Triassic andmid-Jurassic supra-subduction ophi-olitic basement, which in turn, sitsstructurally above a blueschist-bearingaccretionary complex and is separatedfrom it by a serpentinite mélange con-taining high-grade blocks (Rangin1978; Kimbrough 1985; Moore 1985,1986; Kimbrough and Moore 2003;Sedlock 2003). The blocks in themélange are typically eclogite andamphibolite, with ages in the 170–160Ma range, and blueschist-facies blocksranging in age from 115 to 95 Ma(Baldwin and Harrison 1989, 1992).The upper contacts of the blueschist-facies belts are interpreted as normalfaults and reflect their probable LateCretaceous–Paleogene exhumation(Sedlock 1996, 1999). Perhaps 10 kmof upper Albian–Cenomanian toConiacian–Maastrichtian siliciclasticturbidites, known as the Valle Groupand described earlier, sit uncon-formably on the older arc–ophiolite–

accretionary complex rocks (Minch etal. 1976; Boles 1986; Busby-Spera andBoles 1986; Sedlock 1993).

While most workers relate theophiolite–blueschist facies rocks–tur-bidite basin triad to an eastward-dip-ping subduction zone and forearcbasin related to the Alisitos arc–Penin-sular Ranges batholith, the Vizcainoophiolite is 221 ± 2 Ma, the CedrosIsland ophiolite 173 ± 2 Ma, and thearc plutons, 165–135 Ma (Kimbroughand Moore 2003) – all considerablyolder than the 128–100 Ma Alisitos arc.Given the age difference and the wideand flat Desierto de Vizcaino and theLlano de Magdalena (Fig. 2), bothextensive areas without bedrock out-crop, separating the Peninsular Rangesbatholith and its wall rocks from theSierra de San Andres, there is no com-pelling reason that the two areas haveany direct relationship to one another,nor that they were in close proximityduring the Early Cretaceous. Othersequences, such as those on CatalinaIsland and related rocks of the south-ern California borderlands (Grove etal. 2008), are of Early Cretaceous agein part, but are separated from thebatholith by deep water and/or anunknown number of major faults, suchas the Oceanside (Abbott and Smith1989; Crouch and Suppe 1993; Bohan-non and Geist 1998), so that there isno direct link to the batholith. Addi-tionally, as documented by Grove et al.(2008), most of the units within thethrust stack on Catalina Island areyounger than the age of deformationwithin the Peninsular Ranges batholithand are generally considered to be partof the Franciscan accretionary com-plex, which, along with rocks of theCoast Range ophiolite and Great Valleygroup, were unlikely to have beenlocated west of the Sierran–PeninsularRanges arc prior to 100 Ma (Wrightand Wyld 1997; Hildebrand 2013).

However, because the upper92–91 Ma Turonian sandstone of theValle Group is dominated by 100–90Ma detrital zircon, presumably derivedfrom the La Posta plutons (Kimbroughet al. 2001), one can reasonably arguethat rocks of the group were close tothe Peninsular Ranges batholith by theLate Cretaceous, but the nature of thebasin and its relationship to the Alisi-tos arc are obscure. Busby-Spera


(1988a) argued that the ophiolite andits overlying volcaniclastic apron onCedros Island represented a remnantof a back-arc basin of Mid-Jurassicage. Given that arc magmatism there isdated to be as young as 135 Ma (Kim-brough and Moore 2003), it is conceiv-able in a west-dipping scenario thatthis magmatism represents an oldersegment of the Alisitos arc and thatthe arc migrated eastward due to slabrollback. Alternatively, the 135 Ma plu-tonic package could be part of a pre-Alisitos arc.

If the subduction polaritywasn’t necessarily eastward, then wemust examine the region to the east onthe other side of the arc. Unfortunate-ly, due to the effects of the opening ofthe Gulf of California, the relations ofthe arc to the lower plate are not par-ticularly well exposed in Southern andBaja California; but as Baja is readilyrestored back to the Mexican mainland(Oskin and Stock 2003), the relation-ships might be clearer there. In fact,several workers (Tardy et al. 1994;Dickinson and Lawton 2001a; Cen-teno-García et al. 2008, 2011; Schmidtet al. 2014) suggested that the Alisitosarc formed part of the Guerrerosuperterrane of the western Mexicanmainland.

The Guerrero superterrane isa composite terrane made up of sever-al different terranes that were assem-bled during the Mesozoic (Centeno-García et al. 2003, 2008) and, alongwith other amalgamated terranes to theeast such as Oaxaquia, collided withNorth America during the Laramideevent at about 75 Ma. The Laramidedocking of the arc-bearing superter-rane (Tardy et al. 1994; Centeno-Garcíaet al. 2011) is documented by a well-developed thin-skinned fold and thrustbelt and associated foredeep, located inextreme eastern Mexico along the east-ern margin of Oaxaquia, just west ofthe Gulf of Mexico (Busch and Gavela1978; Tardy et al. 1992, 1994; Eguilizde Antuñano et al. 2000; Salinas-Prietoet al. 2000; Nieto-Samaniego et al.2006; Pérez-Gutiérrez et al. 2009;Hildebrand 2013). Where best exposedat the southern end of the Maya block,a southwest-facing carbonate-dominat-ed platform sitting on basement of theMaya block was drowned during theuppermost Campanian, buried by oro-

genic flysch during the Maastricht-ian–Danian (Fourcade et al. 1994), andoverthrust by ultramafic nappes. Rocksof the lower-plate crystalline basementwere metamorphosed to eclogite at 76Ma, which implies that part of theNorth America margin was subductedto greater than 60 km depth at aboutthat time and exhumed to amphibolitegrade levels a million years later(Martens et al. 2012), presumably byslab failure.

Some 25–30 m.y. earlier nearthe end of the Albian, much of east-central Mexico, such as Oaxaquia, Cen-tral and Mixteca terranes, formed acoherent block and was covered by awest-facing Lower Cretaceous carbon-ate platform (Fig. 12), known as theGuerrero–Morelos platform, or locallythe El Doctor platform, in the southand the Sonoran shelf in the north(LaPierre et al. 1992a; Monod et al.1994; Centeno-García et al. 2008;González-Léon et al. 2008; Martini etal. 2012). In the south, the platformwas built upon ~1000 m of LowerCretaceous red beds, alluvial sandstoneand conglomerate with thick evaporitedeposits and an older metamorphicbasement (Fries 1960). Locally, a suiteof Late Jurassic–earliest Cretaceousvolcanic and volcaniclastic rocks pre-dated the platform (Monod et al.1994).

The west-facing carbonateplatform was uplifted, eroded, pulleddown to deeper water, and buried byorogenic deposits (Fig. 13), knownlocally as the Mexcala flysch, duringthe latest Albian–early Cenomanian atabout 100 Ma (Monod et al. 2000).During drowning the platform shedcarbonate blocks up to 2 m across intothe lower parts of the flysch to thewest (Monod et al. 1994). This drown-ing was caused by the attempted sub-duction of the easterly block and itscover beneath a Lower Cretaceous arccomplex, now located in the Zihu-atanejo terrane, but which was builtupon Triassic–Jurassic basement com-prising a Triassic–Jurassic accretionarycomplex and associated 164–154 MaJurassic magmatic rocks (Salinas-Prietoet al. 2000; Bissig et al. 2008; Martini etal. 2010; Centeno-García et al. 2011;Martini and Ferrari 2011). The LowerCretaceous arc rocks, now folded andcut by plutons, one of which was dated

by U–Pb as 105 Ma, are strikingly simi-lar to those of the Alisitos Group inthat they are shallow marine sedimen-tary rocks, volcaniclastic rocks, and awide variety of subaerial–submarineintermediate composition volcanicrocks with reefal limestone ofmiddle–late Albian age towards the top(Tardy et al. 1992; Centeno-García etal. 2003, 2011). Martini and Ferrari(2011) showed that the carbonate rocksand their basement were folded duringthe Cenomanian prior to the 94 Mastart of deposition of clastic sedimen-tation. The results from more detaileddetrital zircon studies of sandstone inthe area show – in addition to clustersat 106–110 Ma, ~250 Ma, 480–650Ma, and 1.0–1.3 Ga – strong 160–162Ma peaks, presumably reflecting theJurassic basement, and in two youngerrocks, huge peaks at 99–97 Ma, whichmight represent La Posta type intru-sions (Centeno-García et al. 2011).

Given that when PeninsularBaja is restored to its pre-Gulf of Cali-fornia paleogeographical position (Fig.12), the Alistos arc is on strike with,and just north of, the Zihuatanejo ter-rane and its lower Cretaceous arc, cou-pled with the striking similarities inJurassic arc and Jurasso–Triassic accre-tionary complexes in the basement,their overall stratigraphic packages andsettings, as well as their similar ages,they almost certainly represent thesame arc complex (Centeno-García etal. 2011). In the Zihuatanejo terranethe relations are clear: the leading edgeof a west-facing Albian carbonate plat-form sitting atop older rocks waspulled beneath a Lower Cretaceous arcand its Jurasso–Triassic basement, atabout 100 Ma (Monod et al. 1994),consistent with relations inferred forthe Santiago Peak–Alistos arc in South-ern and Baja California. The collisionmarks the closure of an ocean alongthe western margin of the CordilleranRibbon Continent some 20–25 m.y.prior to the Laramide event, whichreflects terminal collision of the rib-bon continent with North America(Hildebrand 2013, 2014).

Far to the north in Sonora isthe Sonoran shelf (Fig. 12), anothersegment of the west-facing Albianplatform or ramp located in westernMexico, this one dominated by carbon-ate rocks of the Mural Formation

420

within the Bisbee Basin (Warzeski1987; Lawton et al. 2004; González-Léon et al. 2008). The shelf was partof a complex, west and southwest-fac-ing passive margin that developed fol-lowing rifting within the CordilleranRibbon Continent during the LateJurassic (Dickinson and Lawton 2001a,b).

Beneath the rocks of the Bis-bee Basin and sitting unconformablyatop Jurassic arc rocks, which extendfrom the Klamath Mountains to south-ern Arizona and were deformed duringa 160 Ma collision, are isoclinally fold-ed Oxfordian to Tithonian marine sed-imentary rocks of the SonoranCucurpe Formation (Fig. 14), whichwere largely derived from magmaticrocks of the bimodal Ko Vaya suite

(Mauel et al. 2011). Hildebrand (2013)interpreted rocks of the Ko Vaya suiteto represent slab failure magmasformed during and immediately follow-ing the 160 Ma collision, whereasDickinson and Lawton (2001b) consid-ered them to be magmatism associatedwith what they termed the Border Rift– an extensional system extendingfrom the Gulf of Mexico to Califor-nia.

Rocks of the Cucurpe Forma-tion might correlate with the TithonianPeñasquitos Formation of the westernPeninsular Ranges (Kimbrough et al.2014a), as both formations have similarbasements and contain similar rocks ofthe same age (Fig. 14). Furthermore,both sequences were deformedbetween about 145 and 139 Ma and are

both unconformably overlain by130–125 Ma rocks; in the east the Cur-curpe is overlain by rocks of the Bis-bee margin, and to the west, rocks ofthe Peñasquitos Formation are overlainby the Santiago Peak volcano-sedimen-tary sequence (Fig. 14). Kimbrough etal. (2014a) noted that anothersequence, the Mariposa Formation ofthe western Sierra Nevada (Fig. 14), isalso of the same age (Snow and Ernst2008), has a similar detrital zircon pro-file, and was intruded by 125–120 Maplutonic rocks of the Sierran batholith(Lackey et al. 2012a, b).

Coarse clastic sedimentationand eruption of bimodal volcanicrocks in the Bisbee basin are common-ly thought to have started around 150Ma, following the Early to Mid-Jurassic


EP

New MexicoTexas

Ari

zon

aN

ew M

exic

o

Ca l i forniaBaja Nor te

Zongolic a fold-thrust belt

SierraM

adreO

ccidental

Coahuila platform

Albian platformal carbonate

Bisbee basin clastics

Alisitos-Santiago Peak arc

Inferred Alisitos-Santiago Peak arc

Cenozoic volcanic cover

Sonoranshelf

Guerrero-Morelosplatform

Bajarestored

Pa

c ifi cO

ce a n

Gu lf o f Mexi co

Burro

Diablo

LlanoupliftMarathon

uplift

O uac hita su ture

Trans-Mexi can volcanic b el t

P

T

C

H

0 500

k m

USAMexico

Ch

Sabinas b a s i n

C hi h

ua

hu

an

t r o u g h

Bisb e e ba sin core

Zihuatanejosection of arc

Grenville basement of Oaxaquia

Laramidethrust belt

Caborca

Cortes

Tahue

Zihuatanejo

Tampico-M

isantla basin

Valles-San

Luis platform

ED

~100 MaGuerrero

suture

?

?

G

Figure 12. Geological sketch map illustrating the extent of the Guerrero–Alisitos–Santiago Peak arc, its terranes, and Albiancarbonate platforms to the east. The Laramide thrust belt and related foredeep are located even farther east as shown. ED–ElDoctor platform; G–Guanajuato; H–Hermosillo, C–Caborca, T–Tucson, P–Phoenix, EP–El Paso, Ch–Chihuahua. Map datafrom Dickinson and Lawton (2001a); Martini et al. (2012); Hildebrand (2013); restoration of Baja from Oskin and Stock (2003).

arc magmatism (Bilodeau et al. 1987;Krebs and Ruiz 1987; Lawton andMcMillan 1999; Dickinson and Lawton2001b), but the oldest sedimentaryrocks within the basin were recentlyshown by detrital zircon studies anddating of intercalated volcanic rocks tohave been deposited between 136 Maand 125 Ma (Peryam et al. 2012). With-in the Bisbee Basin, the lowermostclastic rocks have bimodal NE–SWpaleocurrents and reflect shelf, lagoon-al, tidal flat, and fluvial environments(Klute 1991), but pass upwards into aneastward-transgressive sequence of fin-ing-upwards fluvial to shallow marinedeposits (Peryam et al. 2012). Theoverlying carbonate platform had awell developed reefal rim along thesouthwest side (González-Léon et al.2008). Beginning in the Late Albian theplatform experienced rapid tectonicsubsidence and during the Cenomanianand Turonian was buried by at least1500 m of clastic sediment of the Cin-tura/Mojado formations shed in amore or less easterly direction anddeposited in a flexural basin (Mack1987; Gonzalez-Léon and Jacques-Ayala 1988). The most southwesternexposures of Cintura Formation are inexcess of 2000 m thick and are over-lain gradationally by latest Albian–Early Cenomanian fluvio-deltaic sand-stone holding pebbles of quartzite andlimestone and overthrust from thesouthwest by plutonic rocks (Jacques-Ayala 1992; T. Lawton, personal com-munication 2014).

The tectonic subsidence wascaused by west-to-east overthrustingduring the Cenomanian when Paleo-zoic platformal rocks unconformablyoverlain by Jurassic and Lower Creta-ceous volcanic rocks were placed atopthe western margin of the carbonateplatform (Pubellier et al. 1995). TheCintura Formation is overlain in Sono-ra by conglomerate of the CocósperaFormation interbedded with andesiticlava dated by the 40Ar/39Ar method tobe 93.3 ± 0.7 Ma (González-León etal. 2011). Anderson et al. (2005) alsodescribed the belt in some detail, andbased on the age of a little deformedpluton that cut mylonite of the zone,pointed out that the deformation wasolder than 84 Ma and attributed it todeformation along the Mojave–Sonoramegashear.

Taken in its entirety, the evi-dence in western Mexico suggests thatthe Alisitos–Santiago Peak arc collidedwith a west-facing passive margin atabout 100 Ma. The polarity of the sub-duction was clearly westward and thewestern edge of the passive marginwas partially subducted beneath thearc. The basin was apparently a mar-ginal basin open for about 30 m.y. andwas of unknown width, although itmust have been sufficiently wide to befloored by oceanic crust in order todrive the 100 Ma collision. If weassume that half of the 30 m.y. intervalwas spreading, then at average spread-ing and convergence rates of 5cm/year, the basin would have been

about 750 km wide. We call the basinthe Arperos–Bisbee Sea, and the colli-sion the Oregonian event, which wasthe name used by Rangin (1986) forthe Albian–Cenomanian deformationalevent in western Mexico.

Between the two areas aroundGuanajuato (Fig. 12) is another likelypiece of the arc. There, imbricated lat-est Jurassic and Lower Cretaceous vol-canic and plutonic rocks with anuppermost section of calc-alkalinebasalt and basaltic andesite, overlain byvolcaniclastic rocks and Albian reefalcarbonate rocks, sits on an ophioliticbasement (LaPierre et al. 1992b).Pieces of Lower Cretaceousseamounts, presumably off-scrapedinto the accretionary prism occur local-ly (Ortiz-Hernández et al. 2003).

Based on the location of thesuture, it appears that the basement tothe Santiago Peak–Alisitos arc wasmore extensive and varied than previ-ously thought with the Caborca,Cortes, Tahue and Zihuatanejo ter-ranes all forming part of the basementfor the arc (Fig. 12). Uppermost Trias-sic and Lower Jurassic arc magmatismappears to have occurred along thelength of the arc as it is preservedwithin the arc basement. Therefore, weentertain a model of arc rifting to sep-arate the arc terrane from the westernmargin of the Cordilleran RibbonContinent during the Jurassic. Othershave noted the presence of Jurassic arcrocks beneath the rifted margin on theribbon continent (Lawton and McMil-lan 1999), and Dickinson and Lawton(2001b) called upon slab rollback tocreate the extension leading to the Bis-bee basin.

The idea for two discretemid–late Cretaceous deformationalevents in western Mexico has becomemore popular (for example: Pubellier etal. 1995; Martini and Ferrari 2011;Hildebrand 2013) and here we notethat the two events, the ~100 Ma Ore-gonian and ~75 Ma Laramide, devel-oped on opposite sides of Oaxaquia(Fig. 12). The ~125–105 Ma Sevierdeformation of the western US and itshinterland, now located in the Canadi-an Cordillera (Hildebrand 2014), doesnot appear to have affected rocks inMexico.

Late Cretaceous volcanic rocksinterbedded with coarse conglomerate

422

coarse, massivebioclastic limestone

disconformity

well-beddedcalcarenites

coarse limestonebreccia in Mn-richcalcareous matrix

condensed horizonof Late Albian

Ammonites andrudist fragments

well-beddedcalcarenites

and carbonateturbidites

manganesecoatings

pelagicmudstone Mexcala

flysch

west-facingcarbonate

rimmed shelf

emergence & erosionas platform passed

over outer swellmargin subsiding as it

was pulled down into trenchtrench

sedimentation

W E

older youngero

ra

older

em

d shelfimmeeonatrbac

acingest-ffaw

ellas platform passe

er swer outvod

ll

genc osione & ergl f

merrgd d

gin suas pulled dwwa

gll

rrgmaench

ubsiding as ito trwn intdo

gid s dimentation

oungery

seenchtr

W

massioarsec

calca

y

e

cecbroarc

mitoronffodisc

iv

rudix mA

of ondc

treous maarichn-rcia in M

onerse limest

tso

menagist fres andmmonitlbiane AtLa

onizdensed hor

cma

on

tings

mudsticpelag

oanganese

E

schne

flycalaxeM

c

bioclastic limes, massioarsec

cal

oneelw

steiv

esenitcarll-bedded

biturand car

calcarell-bw

esiditetbonar

esenitredded

Figure 13. Detailed cross section of the uppermost few meters of the west-facingGuerrero–Morelos carbonate platform showing the rapid transition from carbonateshelf to orogenic deposits. Interpretation of stratigraphic units at top. Hoffman(2012) presents an excellent overview of the process of platform foundering at thebeginning of orogenesis. Figure modified from Monod et al. (2000).

units that post-date the Oregonianevent and predate the Laramide appearto be relatively common within west-ern and central Mexico (Fig. 14). Forexample, conglomerate of theCocóspera Formation of Sonora isintercalated with 93 Ma andesitic lava(González-León et al. 2011). Generallyconsidered correlative with theCocóspera Formation is the upper Cre-taceous El Chanate Group, which out-crops just east of Caborca (Fig. 12),and contains thick volcanogenic con-

glomeratic wedges that were interpret-ed to have been shed from the westand deposited in an elongate NW-SEthrust-front basin (Jacques-Ayala1999). Bouldery to cobbly polymicticconglomerate of the Altar Formation,located to the northeast of Caborca inthe Sierra El Batamote, is alsointerbedded with volcanic rocks(Nourse 2001) and contains Turonian-age detrital zircon (T. Lawton, personalcommunication 2014). To the south inthe Zihuatanejo terrane, and sitting

unconformably upon folded rocks ofthe older Albian limestone and vol-canic rocks are coarse volcanogenicconglomerate and sandstone layersintercalated with tuff beds andandesitic lava flows and breccia of theLa Unión and Zihuatanejo formations,dated to be Late Cenomanian to San-tonian in age (Martini et al. 2010; Mar-tini and Ferrari 2011). These Late Cre-taceous volcanic rocks, mostly andesiteto rhyolite, might represent a youngerperiod of arc magmatism erupted on


TriassicJurassic

Cretaceous

EastPaleogene

Oregonian event

60

80

100

120

140

160

180

200

220

240

Ma

Cucurpe

Cintura foredeep Mexcala flysch

Sonoran platform

clastics &volcanics

Guerrero-Morelosplatform

& basin fillBisb

eeba

sin

r i f t i n g

Tarahumara volcanics

Wes

tern

Sier

ran

arc

Alis

itos-

Sant

iago

Pe

ak a

rc

LaPosta

plutons

SierranCrest

plutons

Peñasquitos

Luning-Fencemaker event

PeninsularRanges & Sierra

Nevada

Nevadan event

Mariposa

Sierra Nevada extensional arc

Tutt

le C

reek

-Sa

ilor C

anyo

n

IDS-Ko Vaya

Kett

lero

ck

Kitt PeakTrigo Peak

NV-AZ-NMSonora

SouthernMexico

Foothills event

Humboldt assemblage: west-facing carbonate platform on Golconda

Nazas arc

Cocóspera-El ChanateAltar

60

80

100

120

140

160

180

200

220

240

Triassic

Jurassic

Cretaceou

s

Ma

WestPaleogene

Sevier eventof western US

Las

Olla

sco

mpl

ex

volcaniclastic andmarine sediments

foredeep fill

Acatlan complex

Taxco Viejo schists

Pale

ozoi

cba

sem

ent

RSH 2014

Laramide deformation

La UniónZihuatanejo

In Zihuatanejo areaunconformably

beneath arc volcanics

plutons RingboneSkunk Ranch

BCJu

lian

schi

st-S

teph

enso

n Pe

ak

volcanic arc

continental margin

basement complex

slab-failure rocks

Teloloapanmagmatism

aveN&segnaRsninePeneg

tsseW

adaarreiS&

ralusaronoS

MN-ZA-VV-N

ocixeMnrehtuoS

oela

PtssaE

a

a

canrn

ert

onsplutestrC

anrSier

veNoelaP

aM

suoecaterC

100

80

60

ZihL

a

olcanics

edeep

nee

ormtfan plaonorS

ora fturinC

vaahumararT

ck

ariago

g

k

os-

t

onsplutostaPLa

da

AltarCocóspera-El Chanatehuatanejo

La Unión

onsplut

ego

elos e

rOsch

orM-oeruerrG

cala flyxeM

S

deL

Skunk RanchRingbone

e

ent

nego

suoe

cate

rC

aM

100

80

60

entn evonia

evier ev

formationmide ara

e

c

arr

Sieres

tW

PiposaarM

on

ensiona

vesllihtthooF

k-

txeava NerrSieissaruJ180

160

140

120

g

e

t

ent

peucurC

basi

nnitfir

Bisb

eolcanicsv

clastics &eakti

Pk

anSlis

iA

oseñasquit

n evadaNevva

cneF-gninuL

-Ko Vaya

eak

ock

c

ne

igo PrTeakitt PK

SID

rl aada

platform on Golwest-facing carbHumboldt assem

BCea

kP

& basin fill

t

of wormtffoplaelosorM

neverekame

lcondabonate

mblage: Naza

tismeloloapan

mamagpi

TTe

c

S

issa

ruJ

180

160

140

120

as arc

ern UUSesttew

ca

anyo

Cai

lor

Sut

tle C

ree

T

issairT

240

220

200

orKe

ttle

xom

ple

cLas

Olla

s

tsine sedimenmarolcaniclastic andv

edeep fillorf

olcanc vth arbeneamablyoronfunc

tanejo arn ZihuaIephe

nson

p

t-S

Julia

n sc

hist

ocks

iejo schistsVo caxT

xompletlan ccaA

tnemesab

ciozoelaP

nicsyea

r-fslab

ompcbasem

ingmartaltinenonc

colcanic arv

ciss

airT

240

220

200

RSH 2014

e failur

xplet men

Figure 14. Regional correlation chart illustrating temporal relations between many of the rock units and their relationships toregional deformational events. BC–Bedford Canyon Formation.

the amalgamated Guerrero–Oaxaquiablock and generated by westerly sub-duction prior to the terminal Laramidecollision. The coarse conglomeratemight be debris shed from theexhumed Oregonian collision zone orbe alluvial fans on the flanks of volca-noes, or both.

Caborca terrane – located justto the west of the suture, the Sonoraplatform (Fig. 12) and the thrust belt –contains distinctive Neoproterozoicand Paleozoic strata that are a detailedmatch for strata found today in easternCalifornia–western Nevada (Stewart2005) and in the San BernardinoMountains near Los Angeles (Cameron1982; Stewart et al. 1984). Crystallinebasement is also exposed within theterrane west of the thrust belt in Sono-ra, where it comprises 1725–1696 Maorthogneiss, tabular granitoid bodies(Nourse et al. 2005), and anorthositiccomplexes dated at around 1100 Ma(Espinoza et al. 2003). In the SanBernardino Mountains the basement tothe metasedimentary section is 1750 ±15 Ma (Silver 1971). In fact, the base-ment west of the presumed suturecontrasts sharply with other Protero-zoic basement provinces of the south-western US, and is termed the Mojavebasement province (Bennett andDePaolo 1987; Wooden and Miller1990). These rocks form a band ofsimilar Proterozoic rocks from theCaborca terrane northwestwardthrough southwest Arizona and theTransverse Ranges of California (Fig.15). They probably represent the moreeasterly basement to the now dismem-bered arc.

Fragments of the northeast-vergent fold and thrust belt separatingthe arc rocks and their basement fromthe Albian platformal rocks may con-tinue to the north in the Big MariaMountains (Hamilton 1982) and theClark, Ivanpah, and Mescal mountains(Walker et al. 1995) of eastern Califor-nia, where strongly tectonized strati-graphic sections, similar to those ofthe southwestern US continental mar-gin, occur with Mesozoic volcanic andplutonic rocks. Cross-cutting thrusts,younger than those of the 125–105 MaSevier fold-thrust belt in southernNevada and eastern California (Pavliset al. 2014), are of approximately theright age and orientation to have been

formed during the 100 Ma collision.The collisional belt also likely contin-ues up along the eastern side of, oreven into, the Sierra Nevada, whichprobably led to its present juxtaposi-tion nearly orthogonal to structuresand facies in central Nevada; but thattakes us far afield, so additional discus-sion of this interesting topic is with-held for a subsequent contribution.

Nevertheless, pieces of thepresumed North American passivemargin are included within the arc and,along with other Neoproterozoic–Lower Paleozoic sequences in the base-ment, likely accumulated on the south-western continental edge of NorthAmerica as that margin has long beenknown to be truncated and missing itspassive margin (Hamilton and Myers1966; Burchfiel and Davis 1972).When, and precisely where, the pieceswere torn off North America is opento speculation, but apparently frag-

ments were incorporated within theCordilleran Ribbon Continent, only tobe rifted off during the Late Jurassicand return some 30–40 m.y. later.When considered together, all the evi-dence indicates that subduction waswestward beneath the Alisitos arc,occurred within a broad marginal sea,and that the lower plate during the col-lision was located well to the east andcontained a west-facing passive margincapped by an Albian carbonate plat-form.

As arc magmatism in the San-tiago Peak–Alisitos shut down at 100Ma during the collision, and the rockswere rapidly deformed, it was theactive pre-collisional arc. The centralarea of the arc underwent extremeexhumation, uplift, and erosion duringand immediately following La Postamagmatism, which is atypical for mag-matic arcs, so something unique hap-pened during the collision that led to

424

Proterozoic basementwithin Peninsular Rangesbatholithic block

Undivided Proterozoic basement of North America and CordilleranRibbon Continent

119º 115º 111º

36º

34º

32º

30º

?

San GabrielMountains

San BernardinoMountains

GilaMtns

Sierra LosAlacranes

CerroLos Ojos

MohawkMountains

Quitovac

Peninsular Ranges batholith100 km

Yuma

?

Phoenix

Tucson

Nogales

Ajo

Caborca

Magdalena

119º

115º

111º

Mo

ee

ooMojojajavaveveTrTraranansnsveverersrsese

dddd

vevededeseseserert

?

CoCo

Co

3

ColololororaradadodoPlPlalateteaeau

36º

P

tains

tains

ac

ounMdinoernaran BS

ounMabrielan GS

Ra

s

MtnilaG

Ranangngegeses

luulsn

iinnni

eenP

umaY

S

tains

s

a

ounMwkohaM

a

S

hoenix

3

xP

34º

cificO

cean

sanlacrAa LSierr

egnaan

RRara

l

Se

S

Q

jos

nes

Seaeao

o

ab

os OLoerrC

osL

C

joAA

n

S

n

ac

onoranandeser t

ca

vouit

3

or

Nogales

ucsonT

32º

onibbon CRica anmerA

t obasemenUndivided P

tholithic baeniwithin PoiczoerotrP

l

ttinennandillerord C

thof Noroic zoerotrP

blockangesnsular R

tc basemen

oolhho

tthaat

b

h

ofof CoCorortrtetezez

ittthiith

lliool

m

3

100 k

CaCababororcrcaca

agdalenaM

?

30º

Figure 15. Sketch map modified from Kistler et al. (2014) showing distribution ofProterozoic rocks, locations of rocks in Figure 17, and likely basement rocks in thePeninsular Ranges batholithic block.

the emplacement of the voluminousLa Posta suite and simultaneous exhu-mation characteristic of the region.

If arcs are not zones ofcrustal thickening why did the easternPeninsular Ranges batholith have suchintense exhumation and uplift? We sug-gest that the attempted subduction ofthe eastern block beneath the westernarc effectively doubled the thickness ofthe crust and that due to the buoyancycontrast between subducting oceaniclithosphere and the difficulty tosubduct continental lithosphere of thelower eastern plate, the lower oceanicportion of the slab broke off and sankinto the mantle allowing the collisionzone to rise. Next we look at theprocess of slab failure and show how itcan generate not only the exhumation,but also the post-collisional La Postamagmatism and other features.

Slab FailureBecause the continents are very oldand oceanic lithosphere young by com-parison, it is obvious that every colli-sion that entails the closure of anocean basin wide enough to drive colli-sion, must involve break-off of thesubducting slab, for the alternatives arefor continents to be subducted or forslabs to dangle off continental marginsinto the mantle. Neither is observed.Therefore, slab failure, or break-off asit is sometimes called, is an integralcomponent of plate tectonics and anatural consequence of subduction(Roeder 1973; Price and Audley-Charles 1987; Sacks and Secor 1990;Davies and von Blanckenburg 1995;Davies 2002; Atherton and Ghani2002; Cloos et al. 2005).

Over 40 years ago, seismolo-gists suspected that when the edges oflarge continental masses are partiallysubducted, their buoyancy leads to fail-ure of the subducting slab (McKenzie1969; Isacks and Molnar 1969). This isbecause the buoyancy forces resistingthe subduction of continental litho-sphere are as large as those pullingoceanic lithosphere downward (Clooset al. 2005). Eventually, the greaterdensity of the oceanic lithospherecauses the lower plate to break, pre-dominantly by viscous necking (Duretzet al. 2012) at its weakest point, andsink into the mantle.

Once the subducting slab fails

and the lower plate is freed of itsoceanic anchor, rocks of the partiallysubducted continental margin rise dueto buoyancy forces (Duretz et al.2011). The failure also allows asthenos-phere to upwell through the tear, meltadiabatically, and rise into the collisionzone, where it interacts especially withsubcontinental lithosphere and crust ofthe upper plate. The resulting magmas,which form linear arrays above tears inthe descending slab, are upwellingsflowing through the breach in the slab(Macera et al. 2008). They commonlyoverlap the terminal stages of defor-mation. If the magmas intrude theupper plate, they may form a linearbelt atop or alongside the old arc andappear temporally continuous with theolder magmatism, and so be readilyconfused with it. Magmas might alsointrude rocks of the foredeep and/orthe shortened passive margin of thelower plate, or both (Hoffman 1987;Hildebrand and Bowring 1999; Hilde-brand et al. 2010).

There is now a burgeoning lit-erature on the effects of slab failure,ranging from currently active to Pre-cambrian (Hildebrand and Bowring1999; Teng et al. 2000). The effects ofslab failure are important, diverse, andmay be responsible for features such asrapid uplift (Chatelain et al. 1992), syn-collisional magmatism (Davies and vonBlanckenburg 1995; Keskin 2003; Mac-era et al. 2008), tomographic gaps inthe descending slab (Wortel and Spak-man 1992), thick-skinned forelanddeformation (Cloos et al. 2005), seis-mic discontinuities (Wortel and Spak-man 1992), crustal recycling (Hilde-brand and Bowring 1999), transitorypulses of mafic magmatism (Ferrari2004) doubly vergent orogens (Regardet al. 2008), plateau uplift (Rodgers etal. 2002), ultra-high pressure exhuma-tion (Anderson et al. 1991; Babist et al.2006; Xu et al. 2010), changes in platemotion (Austerman et al. 2011); sub-horizontal swarms of deep earth-quakes (Chen and Brudzinski 2011),lateral shifts in foredeep sedimentation(van der Meulen et al. 1998), openingof small ocean basins (Carminati et al.1998), switchover from foredeep flyschto orogenic molasse (Sinclair 1997;Wilmsen et al. 2009), and porphyrycopper and other mineralization(Solomon 1990; de Boorder et al. 1998;

Cloos et al. 2005; Hildebrand 2009).Several factors are important

in slab failure and govern where andwhen during the collision the slab willrupture. First, the age of the subduct-ing lithosphere is perhaps most impor-tant because young lithosphere isweaker and therefore break-off will befast, commonly less than 1 m.y. afterinitial collision (Duretz et al. 2012), andwill occur at shallow levels, whereaswith older, thicker and stronger litho-sphere, break-off is slower and thecontinental edge is subducted deeperinto the mantle. The depth of break-off largely controls the width of theorogen, for it is the rebound of thepartially subducted continent that willlead to the region of intense uplift andexhumation (Duretz et al. 2011, 2012;Duretz and Gerya 2013). Thus, shallowbreak-off creates narrow orogens,lower-grade metamorphism, andintense, rapid and higher rates of exhu-mation, whereas deep break-off createsbroad orogens with higher grades ofmetamorphism and slow, more sub-dued rebound (Duretz et al. 2011). Inthe case of deep failure the subductedmargin might be sufficiently buoyantthat it initially rises to the Moho, whereit might stall until the over-thickenedcrust collapses by extension and/ordenuded by erosion (Walsh and Hacker2004).

The depth of break-off likelyalso controls the volume of slab failuremagmatism because in shallow failurethe asthenosphere upwells to shallowerdepths, which generates greater vol-umes of melt due to adiabatic melting(McKenzie and Bickle 1988). Addition-ally, during shallow failure theupwelling asthenosphere, say at 35–50km depth, creates an advective heatsource capable of generating melts inthe lithospheric mantle, the asthenos-pheric mantle and the crust (van deZedde and Wortel 2001). Thus, shallowbreak-off will create larger quantitiesof magma and they are likely to becompositionally varied. Furthermore,because the asthenospheric mantlesource region is highly variable (Men-zies et al. 1987; Foley 1992), andbecause the rising magmas can assimi-late between 10% and 75% crust-derived materials during their risethrough the crust (McDowell et al.1996; Housh and McMahon 2000;


McMahon 2000, 2001; Chung et al.2003), the resultant magmas can beheterogeneous, ranging from pureasthenospheric melts, mixtures involv-ing lithospheric mantle melts, to com-plex crustal melts and, of course, mix-tures of the three (e.g. Hart et al.2004).

When the break-off is locatedbeneath the arc, or nearly so, upwellingasthenosphere rises into the region oflittle or no lithospheric mantle, and theresulting magmas might look verymuch like those of an arc, but wherethe break-off occurs adjacent to thearc the magmas might be quite differ-ent in composition because theasthenosphere would impinge first onthe subcontinental lithospheric mantle.And given that those mantle regionshave different properties, such as com-position, depending on their age (Jor-dan 1978; Pearson and Nowell 2002;Poupinet and Shapiro 2009), magmascreated in those areas might have dif-ferent compositions from place toplace and orogen to orogen. Magma-tism might start out reflecting meltingwithin enriched lithospheric mantleand quickly revert to asthenosphericmelts as the lithosphere is thermallythinned and transected by deeper levelmelts (Perry et al. 1987). Additionally,given that the margin breaks off atdepth beneath and more or less parallelto the arc, it might be common for theasthenosphere to rise, at least in part,beneath the transition from arc to con-tinental lithosphere, which would gen-erate additional compositional varia-tions, and might even appear as asmooth transition between two entirelydifferent magma types.

In Southern and Baja Califor-nia, the shutdown of arc magmatism at~100 Ma marked the collision and,within 1–2 m.y. of collision, the earliestplutonic complexes of the 99–86 MaLa Posta suite were emplaced (Kim-brough et al. 2001; Premo et al.2014b). The magmatism was especiallyvoluminous and magmas appear tohave been emplaced during a period ofimmediate exhumation close to andoverlapping with the upper plate arc(Fig. 16). They are contemporaneouswith deposition of thick Cenoman-ian–Turonian clastic successions to thewest, which involved a rapid changefrom flysch-type sedimentation to

coarse cobbly andbouldery molasseduring the earlyCenomanian (Kim-brough et al. 2001).These are all charac-teristics of shallowbreak-off and sosuggest that theoceanic lithospherewas not particularlyold, but based onthermomechanicalmodels, older thanabout 30 millionyears at the time(Duretz et al. 2011).

Exhumation andOrigin of the Doubly Vergent FanStructureOnce the subductingoceanic slab fails, theleading edge of thelower plate is nolonger being pulleddown beneath theupper plate, and dueto buoyancy forces,will rise, typically at arapid rate, limitedonly by the erosionrate (Burbank 2002)and strength of thelithosphere (Avouacand Burov 1996). Atthe same time,asthenospheric man-tle is streamingupward through thetear and creatingbuoyant melts thatwill also rise into thecollision zone, the exact locationdepending on how and where thedescending plate failed. For example ifthe tear is at or near the oceanic–conti-nent interface, then diachronous tear-ing (Wortel and Spakman 2000; Schild-gen et al. 2014), or perhaps basal trac-tion (Alvarez 2010), would cause con-tinued convergence, either or both ofwhich would pull the subducting slabover the rising asthenospheric welt andcause slab failure magmas to rise justinboard of the tear. Similarly, re-entrants and promontories in the lowerplate might fail at different placesalong strike so that the slab failure

magmas might span tectonic bound-aries in the resultant orogen. Also,changes in the subduction regime canhappen abruptly along strike and havehuge impacts on the form of deforma-tion and magmatism (Ely and Sandi-ford 2009).

In a somewhat similar fashion,the leading edge of the lower plate ispulled beneath the overriding plate andhow far depends on the buoyancy con-trast and strength of the plate. As stat-ed earlier, younger lithosphere willbreak more quickly, in less than 1 m.y.,and in those cases the continental edgeisn’t subducted deeply but instead is

426

100 86 Ma

PC & Paleozoic basementMesozoic basement

arcvolcanics

deformedplutons post-collisional

plutons

Ribbon continentAlisitos-SParc

Alisitos-SantiagoPeak arc

La Posta slab-failure plutons

128

pre-collision

85 Ma

Albian carbonate platform

forelandbasinCenomanian

molasse

Juro-Trias Precambrian & PaleozoicPaleoz

W E

Figure 16. Tectonic model showing the development ofthe Alisitos–Santiago Peak arc above a westward-dippingsubduction zone and its collision with the western marginof the Cordilleran Ribbon Continent and its west-facingAlbian carbonate platform as discussed in the text. Thecollision was followed by slab failure of the lower plate andemplacement of the La Posta plutons during a period ofmajor exhumation.

barely tucked beneath the arc. In thecase of shallow break off, as soon asthe slab fails it rises and immediatelybegins to exhume the overriding plate.Thus, the time between initial collisionand initiation of exhumation and mag-matism due to slab failure is very short.

The rapid response to slabfailure is important but given that thelower plate typically represents a for-merly thinned section of continentallithosphere, it is unlikely to rebound tosea level but instead will have a cara-pace or veneer of upper plate rocksatop it. Depending on the crustalthickness, strength profile, and perhapsrate of exhumation of the upper plateas governed by rainfall (Hoffman andGrotzinger 1993), it might get liftedgently to form a broad dome, or alter-natively it might fail and there will be amajor fault in the upper plate separat-ing the hinterland from the relict arc.In some instances a bivergent orogen,such as the Alps, might form (Regardet al. 2008).

Following exhumation, upliftand erosion, one should find a zone ofhigher grade upper plate rocks betweenthe upper plate arc rocks and the lowerplate. The grade should rise graduallytowards the hinterland in the lowerplate, then increase rapidly at thesuture as the base of the upper plate isencountered. In the case of a faultedupper plate, the grade should remainhigh, perhaps decreasing gently due tothe thinner lower plate, until the faultis crossed, where the grade will dropprecipitously in the upper plate, whichwas never buried.

If one assumes that subduc-tion prior to collision was westward,then the Sierra de San Pedro Mártircross-section (Fig. 4) of the PeninsularRanges batholith displays the featuresdescribed above that are characteristicof slab failure with a faulted upperplate. In this case the leading edge ofthe eastern block was partially subduct-ed beneath the Alisitos arc and slabfailure occurred at 100 Ma. Once theslab failed, magmas rising from theupwelling asthenosphere rose into thecrust to produce the La Posta suite.Although the plutons intruded botheastern and western sectors, they weremostly emplaced into the deeper east-ern sector. The fan structure might bea root zone (Roeder 1973).

Due to the release of thedownward pull of the oceanic litho-sphere, and perhaps fueled byupwelling asthenosphere and risingmagma, the orogenic root began itsbuoyant upheaval, lifting the upperplate on its back. However, the upperplate was simply not strong enough towithstand the forces so it failed moreor less above the distal edge of thelower plate. As the dynamically risinghot hinterland was elevated it spreadlaterally over the Alisitos arc and per-haps eastward as well. In this interpre-tation, the western part of the doublyvergent fan structure marks theapproximate western limit of the lowerplate at depth. Good seismic profilesshould show the upper plate within thehinterland as a fairly thin sheet sittingabove a gently inclined to broadlywarped, reflector representing the colli-sional suture.

The uplift, exhumation, andconsequent erosion also created hugevolumes of coarse debris, much ofwhich was shed to the windward, wetside of the rising orogenic welt, whichin this case would have been westward.And that is what is observed as flyschsedimentation to the west was abruptlyswamped during the early Campanianby voluminous coarse debris (Kim-brough et al. 2001). This is similar tothe transition from flysch to molasse inthe Alpine belt, which is thought tohave been caused by slab failure (Sin-clair 1997).

In many ways, parts of thePeninsular Ranges orogen are similarto the Alps of Europe, in that bothorogens are doubly vergent with ametamorphosed crystalline core andmuch lower grade thrust sheets on theexternal flanks. The main differencesare the amount of magmatism and thewidth of the orogen, which could bedirectly related to the depth of break-off. The Main Mártir thrust, whichplaced amphibolite-grade rocks of thearc and its basement westward overlower grade arc rocks, is more or lessan equivalent structure to the InsubricLine, an antithetic thrust fault, whichplaced amphibolite-grade rocks of theupper plate over the Southern Alpinenappes to the south.

In the preceding sections wedeveloped a coherent, actualistic, andtestable model that explains all of the

critical observations, which the currentlong-lived eastward-dipping subductionmodels fail to do. In our model, thewestward-dipping subduction led topartial subduction of the eastern blockand its west-facing passive marginbeneath the arc, which caused itsyoung oceanic lithosphere to break offand generate slab failure magmatism ofthe La Posta suite within 1 m.y. of thecollision. Rebound of the eastern, par-tially subducted plate caused rapiduplift and exhumation during theemplacement of the plutons.

Detrital ZirconOur recognition that basement to theSantiago Peak–Alisitos arc rifted fromrocks to the east at about 139–136 Ma,and that it was composed of a widevariety of Jurasso–Triassic rocks, aswell as a nearly complete section ofPaleozoic and Neoproterozoic sedi-mentary rocks built on Precambriancrystalline basement, provides a readyoutboard, or offshore, source for awide detrital zircon spectrum in sedi-mentary rocks of the arc complex andprecludes that they must have beenderived directly from North Americaas argued by some researchers (Gehrelset al. 2002; Kimbrough et al. 2006,2014a). This conclusion, coupled withthe likelihood that fragments of Lau-rentia such as the Antler platform ofthe Great Basin region and Caborcaterrane in Sonora (Ketner 1986; Gastilet al. 1991; Stewart 2005; Hildebrand2009, 2013; Premo et al. 2010) wereprobably derived from the southwestcorner of Laurentia in what is thepresent day Mexico region and incor-porated within the Cordilleran RibbonContinent, possibly during the transi-tion from Pangea B to A (Irving 1977,2004; Kent and Muttoni 2003), servesto complicate correlations and detritalzircon studies. Terranes derived fromthe southwest corner of North Ameri-ca should contain North Americanflora and fauna, but also large quanti-ties of Grenville age zircon reflectingtheir proximity to that belt, which wasrich in Grenvillian basement (Hoffman1989).

Also, it appears as though thewestern Sierra Nevada batholith has aremarkably similar history to the Santi-ago Peak–Alisitos arc, including anolder arc complex in the west, and


compositionally zoned, post-deforma-tional, plutonic complexes, such as theTuolumne, Whitney, John Muir, andSonora, of the Sierran Crest magmaticevent (Coleman and Glazner 1998) tothe east. The Snow Lake pendant (Fig.17), located along the north edge ofthe Tuolumne intrusive complex inYosemite National Park is yet anotherfragment of the distinctive Neopro-terozoic–Early Paleozoic sequencefound in the Death Valley and Caborcaareas (Stewart 1970, 2005; Lahren et al.1990; Memeti et al. 2010) and, like thePeninsular Ranges, it represents part ofthe basement to the arc. The originallocation of the sections remains uncer-tain. We now look a bit more closely atthe Sierra Nevada to ascertain if thereare features there that might informour understanding of the PeninsularRanges batholith and related rocks.

Comparison with Other CordilleranBatholithsJust over a decade ago Ducea (2001)proposed an eastward-directed subduc-tion model for the origin of Californ-ian Cordilleran batholiths to explainwhat he thought was a period ofunusually high magmatic flux, from100–85 Ma, within the Sierra Nevada.In his model, eastward directed retro-arc, thin-skinned thrusting in the GreatBasin area was balanced by westwardunderthrusting of middle to lowercrust, which as a result was shovedbeneath the Sierran arc, melted to pro-duce the 100–85 Ma magmatism, andall the excess material, or restite, sink-ing into the mantle. Others soonexpanded on the model (Ducea andBarton 2007; DeCelles et al. 2009),whereas some workers, mindful of alikely sedimentary component to themagmatism, proposed that large vol-umes of crustal material were subduct-ed from the west beneath the Peninsu-lar Ranges in order to thicken the crust(Todd et al. 1988; Grove et al. 2008;Miggins et al. 2014; Premo and Mor-ton 2014).

Hildebrand (2013) pointedout: (1) that it is difficult, if not impos-sible, to get the requisite 400 km ofNorth American cratonic lithospherebeneath the Sierra Nevada–PeninsularRanges batholiths because it is simplytoo buoyant unless attached to nega-tively buoyant oceanic lithosphere; (2)

that even if it was possible to get thecrust beneath them, by Ducea’s (2001)own admission there is no obviousmechanism to melt such a large vol-ume of continental crust; (3) thatbecause the bulk composition of thebatholiths is so close to that of bulkmiddle and lower crust (Ducea 2002;Rudnick and Gao 2003), there wouldbe very little restite to drip into themantle, which means that the crustshould be very much thicker thanobserved; (4) because the thrustingtook place at the scale of the litho-sphere, the Ducea model provided noactualistic mechanism to dispose ofthe sub-continental lithospheric man-tle; and (5) that the so-called flare-upmay not be beyond the bounds ofmagmatic flux in young arcs.

Ducea (2001) also noted thatsince it took time for the isotherms torebound after crustal thickening, themelting event, however it was caused,postdated the thickening by ~15–25m.y. However, such an early thickeningis countermanded by the deposition ofshallow marine sedimentary rocks atabout 100 Ma within both the Sierranand Alisitos–Santiago Peak arc ter-ranes. As these rocks were depositedimmediately prior to the regionaldeformation and within a couple ofmillion years of the emplacement ofthe post-deformational plutons, thereis no evidence of crustal thickeningwithin the arc prior to the ~100 Madeformational event.

As touched upon in the earlypart of this contribution, the majorCordilleran batholiths of North Amer-ica are clearly composite bodies thatshare significant similarities. The SierraNevada has long been known to becomposed of two halves: an olderwestern sector and a younger easternsector separated by an apparent breakin the lithosphere, as defined by geo-chemistry, magnetic susceptibility, age,radiometric and stable isotopes, wallrock provenance, and basement types(Nokleberg 1983; Kistler 1990, 1993;Chen and Tilton 1991; Bateman et al.1991; Coleman and Glazner 1998;Saleeby et al. 2008; Lackey et al. 2008,2012a, 2012b; Chapman et al. 2012).Just as with the Peninsular Rangesbatholith, the western sector of theSierra Nevada represents an ~125–100Ma arc (Bateman 1992) constructed

upon crust assembled mainly duringthe Jurassic, whereas the eastern halfcontains large compositionally zonedtonalite–granodiorite–granite complex-es, such as the Tuolumne, Whitney,John Muir, Domelands, and Sonora(Fig. 17), emplaced during the 98–86Ma Sierran Crest magmatic event(Coleman and Glazner 1998; Saleeby etal. 2008). And just like the PeninsularRanges batholith, rocks of the SierraNevada contain evidence of an~103–100 Ma deformational event thatpostdated all known sedimentary andvolcanic wall rocks within the westernarc (Peck 1980; Nokleberg and Kistler1980; Bateman et al. 1983; Saleeby etal. 1990; Bateman 1992; Wood 1997;Memeti et al. 2010; Hildebrand 2013)yet predated, or was partly coeval with,the compositionally zoned plutoniccomplexes of the Sierran Crest mag-matic event (Greene and Schweickert1995; Coleman and Glazner 1998;Davis et al. 2012). The plutons wereemplaced more or less simultaneouslywith development of mylonitic shearzones, a rapid increase in cooling ratesbetween about 90–87 Ma, andincreased sedimentation in the basin tothe west during the Turonian (Mans-field 1979; Renne et al. 1993; Tobischet al. 1995). Thus, by analogy with thePeninsular Ranges batholith, we sug-gest that the western half of the Sier-ran batholith was an arc generated bywestward subduction, and that the arccollided at ~103 Ma with the westernmargin of the Cordilleran RibbonContinent. Slab failure of the partiallysubducted eastern block led to volumi-nous magmatism of the Sierran Crestmagmatic event.

There is support for the gen-eral slab failure model in Sierran xeno-liths, which also provide feedback thatcan be applied to the PeninsularRanges batholith. First, ultramaficxenoliths collected from much youngervolcanic rocks (Fig. 18) suggest thatthe xenoliths are dominantly residualcumulates remaining after extraction ofpartial melts from both upper mantleand subcontinental lithosphere atdepths of at least 32–18 kb(Mukhopadhyay and Manton 1994;Chin et al. 2012), consistent withupwelling mantle and adiabatic meltingresulting from slab failure. Ducea andSaleeby (1998) showed that the cumu-

428


dgo

??

??

???

?Other Rocks & Terranes

Bass Lake tonalite

?

Argus Range

El Paso Mtns

Wh

i te

s

In

yo

s

Ow

en

sV

al l e

y

Bishop

San Andreas fault

Bakersfield

Fresno

Merced

Chico

Marysville

Truckee

LakeTahoe

LakeAlmanor

Susanville

Bridgeport

Visalia

Mojave

Garlock

fault

C

LakeMono

SC

KINGS

SEQUENCE

PENDANTS

John Muir

Lone Pine

Possible paleotrace

Snow Lake-M

ojavefault

Sonora

Tuolumne

Mt. Whitney

Domelands

and Tuttle Lake and Sailor Canyon Fms.

Kc

LT

LT

LTLT

Sierra Nevada batholith;mainly 125 Ma to 82 Mapurples are <100 Maeastern zoned complexes

~140 Ma

~150 Ma

~160 Ma

~170 Ma

~200 Ma

> ~370 Ma

Unclassified

Tethyan fossil fauna (Permian)

McCloud fossil fauna (Permian)

Soda Ravine terrane; slaty argillite with tectonic blocks of Permian and Late Triassic limestone

Taylorsville sequence: Late Devonian to Pennsylvanian; depositional on Shoo Fly complex

Jurassic volcanic arc units: Kettlerock and Mt. Jurasequences, and Tuttle Creek and Sailor Canyon Fms.

Calaveras terrane; late Paleozoic and/orTriassic chert-argillite melange

Central belt: Includes Fiddle Creek, Slate Creek, Lake Combie, & American River terranes, Tuolumne ophiolitic melange, Jasper Point Fm., Peñon Blanco Fm., and serpentinite melange

Smartville complex

Jurassic volcanic and sedimentary rocks

Red Ant Schist; Triassic(?) metamorphic age

Roof pendants in Sierra Nevada batholith; Paleozoic to mid-Cretaceous

Kings-Kaweah ophiolitic melange

Don Pedro terrane; pre-Jurassic melange overlain by Jurassic volcanic and sedimentary rocks

Feather River terrane: mostly serpentinized peridotiteand related ultramafic and mafic rocks; includes DevilsGate ophiolite

Permian volcanic arc sequence

~130 Ma

Shoo Fly Complex; includes four thrust slices of Ordovician(?) to pre-Late Devonian rocks

124° 122° 120°

S a n A n d r e a s F a u l t

42°

40°

38°

36°

OREGON

CALIFORNIA

NEVADA

Medford

EurekaRedding

Chico

SanFrancisco

Sacramento

Plutonic Rocks

Si e

r r a Ne v a d

a

Coast Ranges

Gr e

a t V a l l e y

Sal in ian block

Klam

ath

Mtn s

M o d o cP l a t e a u

B a s i n&

R a n g e

Pa

ci

fic

Oc

ea

n

Great Valley Group; upper Cretaceous

Proterozoic to Mesozoic sedimentary rocksof the White-Inyos and other ranges east ofthe Sierra Nevada

120

39

119

38

118

117

37

36

11735

118

119

40

0 20 40 60 800 20 40 60 80 100 km

HC

Kern Canyonfault &

proto-fault

KERN PLATEAU PENDAN

TS

Snow Lakependant

Figure 17. Generalized geological map of the Sierra Nevada batholith and environs, showing the basement terranes, location ofthe Snow Lake pendant, and the distribution of major plutonic complexes of the post 100 Ma Sierran Crest magmatic suite(modified from Irwin and Wooden (2001) with additional data from Dunne et al. (1978), Saleeby et al. (1978), Bateman (1992),and Saleeby and Busby-Spera (1993). Distribution of post 100 Ma suite modified from Van Buer and Miller (2010).

late rocks are the same age as Sierrangranitoid magmatism. The idea ofupwelling mantle and adiabatic meltingis supported by the detailed work ofLee et al. (2001), who also studied Sier-ran mantle xenoliths and found evi-dence for a cool subcontinental litho-sphere of Proterozoic age underplatedby hot asthenosphere during the Meso-zoic.

Second, our model for west-ward-dipping subduction of the west-

ern margin of the Cordilleran RibbonContinent beneath the arc readilyresolves the difficulties of Chin et al.(2013) when trying to interpret gran-ulitic quartzite xenoliths from aMiocene diatreme in the central SierraNevada. They were baffled becausetheir extensive data from the quartzitexenoliths – T = 700–800ºC, P = 7–10kb, ~103 Ma mean metamorphic agefrom U–Pb analyses in zircon, Protero-zoic and Archean U–Pb crystallization

ages for the cores of detrital zircon,and Hf isotopic ratios like those fromProterozoic basement of the easternSierra Nevada – appeared to indicatethat rocks of the North American pas-sive margin were transported deepbeneath the arc and metamorphosedclose to 100 Ma; yet they had no viablemechanism for getting them there inan eastward-directed subductionmodel. The presence of the quartzitexenoliths, their ages and isotopic char-acteristics thus provide an unexpectedtest and confirmation of our west-ward-dipping subduction model.

Because of the paradigm thatthe Sierran batholith was built on thewestern margin of North America,other researchers used the eclogite-facies quartzite xenoliths, with theirNorth American isotopic signatures, asevidence that the sub-batholithic crustwas at least 70 km thick and was sim-ply thickened North American crust(Ducea and Saleeby 1998; Ducea2001). They also used the presence ofgarnet peridotite xenoliths to suggestthat the mantle lithosphere was at~120 km depth.

In our model, the westernmargin – whether you believe it wasNorth America or the ribbon conti-nent – was subducted beneath the arc(Fig. 14), which readily accounts forthe quartzite xenoliths, the eclogite-facies metamorphism and their iso-topic signatures. It also provides amore actualistic method of gettingmantle lithosphere to the inferreddepths and, given that the xenoliths arerestite or cumulate from removal ofmelt along an adiabatic geotherm from~3.5–1.7 GPa (Mukhopadhyay andManton 1994), they confirm the con-cept of mantle rising through the tornslab and melting adiabatically to pro-duce the slab failure magmas. This wascorroborated by two other detailedstudies of peridotite xenoliths (Fig. 18),the first by Lee et al. (2001), who, asmentioned, found two types of xeno-liths with contrasting thermal historiesand concluded that hot asthenosphereand cold Proterozoic lithospheric man-tle “were suddenly juxtaposed, a feature con-sistent with the aftermath of rapid lithospher-ic removal or sudden intrusion of asthenos-pheric mantle into the lithosphere” duringthe Mesozoic. The second by Chin etal. (2012), showed that peridotite

430

Present day Sierran geotherm

Spinel websterite

Spinel peridotite

Garnet websterite

gabbro

LiquidGarnet peridotite

0 600º 1200º5

10

15

20

25

30

35

P (k

b)

T (ºC)1800º

SierraNevada

Lee et al.2001

Chin et al.2012

Mukhopadhyay& Manton 1994

Figure 18. P–T grid illustrating the final equilibrium conditions calculated for vari-ous groups of mantle xenoliths from the Sierra Nevada. Although the arrays areartifacts of the different reaction kinetics of the geothermometers and geobarome-ters, the points represent minimum P values (Chin et al. 2012). These high pres-sures (~3 GPa) support the model presented here in that the La Posta and SierranCrest magmatic suites resulted from melting at great depth caused by slab failure,upwelling of asthenosphere, and melting within the garnet stability field.

underwent shallow melt depletion at1–2 GPa and was re-fertilized atdepths of about 3 GPa, which couldreadily be accomplished by taking par-tially subducting depleted lithospherethen re-fertilizing it by upwellingasthenosphere. Thus, the quartzite andperidotite xenoliths, as well as their fea-tures and histories – so difficult toexplain in static eastward subductionmodels – are readily accounted for inan actualistic westward subduction–collision–slab failure model.

Similar types of xenoliths areknown from the Pamirs and TibetanPlateau where they are generally inter-preted to represent fragments of sub-ducted continental crust (Hacker et al.2000, 2005; Ducea et al. 2003).Detailed study of samples from thePamir found much older detrital zirconthat appears to have had a Gond-wanan, as opposed to Indian, sourceand so suggests a subduction polarity(Hacker et al. 2005), just as do the Sier-ran examples.

As is well known, the westernSierran arc has a basement comprisingnumerous Jurassic and Paleozoic ter-ranes (Saleeby 1981; Irwin and Wood-en 2001; Hildebrand 2013). Late Juras-sic sedimentary rocks of the MariposaFormation (Fig. 14), commonly inter-preted to represent forearc deposits toa more easterly arc are part of thisbasement (Snow and Ernst 2008) andare consistent with similar age rockscontaining comparable detrital zirconsuites along the west side of the Penin-sular Ranges batholith (Kimbrough etal. 2014a) and in Sonora (Mauel et al.2011).

The Coast plutonic complexof British Columbia is another com-posite batholith built of two blocks:190–110 Ma to the east and 160–100Ma to the west (Gehrels et al. 2009). Awest-vergent fold-thrust belt, thatdeveloped around 100 Ma (Rubin et al.1990; Haeussler 1992), places high-grade rocks of the eastern belt overlower grade rocks of theGravina–Dezadeash–Nutzotin belt toform a thrust stack that is of highermetamorphic grade upwards (Lynch1992, 1995; Journeay and Friedman1993; Crawford et al. 2000; McClellandand Mattinson 2000). Although thedeformation is about the same age, thepolarity is the reverse of the more

southerly batholiths. A group of post-deformational plutons (Gehrels et al.2009) are likely slab failure bodies.

In this contribution we haveshown how the Peninsular Rangesbatholith comprises two distinct peri-ods of magmatism – separated by adeformational event – that are simplyand logically explained by a period ofarc magmatism followed by anarc–continent collision, which causedrapid shutdown of the arc, thickeningof the subjacent crust as the continen-tal edge was partially subducted, andconsequent failure of the westward-dipping slab to produce slab failuremagmas (Fig. 16). The consilience ofso many independent lines of evi-dence, from isotopic to structural data,stratigraphy to plate kinematics, mantlexenoliths and xenocrystic zircon torapid exhumation gives us great confi-dence in our overall model for west-ward-dipping subduction beneath the130–100 Ma Alisitos–Santiago Peakand Sierra Nevadan arc terranes. Notonly does the model tie together manydisparate bits of geology, it also placesthem within a modern and actualisticplate tectonic framework.

PetrogenesisGiven that the Cordilleran batholithsdescribed here are composed of twocompositionally distinct magmaticsuites separated by a period of defor-mation, it might be enlightening tolook briefly at their petrogenesis. Bothsuites would seem to involve partialmelts of asthenosphere and variableamounts of mantle lithosphere andcrust, yet they are quite different incomposition. Here we present a fewideas and constraints on their petroge-nesis.

The presence of basaltic lavasand gabbroic intrusions, coupled withtheir overall calcic nature (Fig. 8a, b),within the Santiago Peak–Santa Anaarc indicate that mafic melts were ulti-mately responsible for the magmatismin the arc, although there appear to beno primary mantle melts present theretoday. Recently, the most detailed stud-ies to date on the Santiago Peak–SantaAna arc concluded that the arc wasbuilt upon oceanic crust (Clausen et al.2014), or a heterogeneous Jurassicbasement deposited at or near a conti-nental margin (Herzig and Kimbrough

2014). The Santa Ana plutons have acontinuous compositional range fromgabbro to granite, with 47%–77% SiO2(Fig. 8) typical of arcs, yet Clausen etal. (2014) suggested that the maficmagmas rising from the mantle into alower crust dominated bygabbro/amphibolite created the spec-trum of melts by partial melting,magma mixing and fractional crystal-lization. The main problem with alower crustal scenario, which they rec-ognized, is that the overall processwould create huge volumes of high-density ultramafic restite in the lower-most crust for which there is no geo-physical, or other, evidence.

Based on comparison with theLa Posta plutons, they suggested thatthere is something peculiar about thecomposition of plutons within theSanta Ana suite in that they have initialSr ratios lower than 0.704 and SiO2contents > 55%, but they comparedapples to oranges because they con-trasted them with the slab failure-typeplutons (Clausen et al. 2014). If theyhad compared them to other arc suitesof the western US they would havefound them to be rather typical. Forexample, the western, or arc portion,of the Sierra Nevada contains plutons,such as the multiply folded sheets ofthe Stokes Mountain complex (Fig. 1),with the same characteristics (ClemensKnott 1992). Furthermore, nearly allthe Quaternary volcanic rocks of theCascades from 51ºN to 41ºN have87Sr/86Sr lower than 0.704 independentof SiO2 content and amount of con-tamination by varied continental crustand mantle lithosphere (Hildreth2007). It is the slab failure plutons thatare markedly different from the arcbodies as seen on our various geo-chemical and isotopic figures.

Overall, there can be littledoubt that batholiths and associatedsiliceous volcanic rocks are generatedin continental crust, for in volcanicarcs built on oceanic crust there are nobatholiths or plutonic complexes likethose observed in western NorthAmerica, (Waters 1948; Bateman 1981;Whalen 1985). One has only to studythe differences in magmatism in theKurile–Kamchatka and Aleutian–Alas-ka Peninsula arcs where the transitionbetween the two crustal types is readilyobserved. On continental crust, mag-


mas are richer in silica and incompati-ble elements, intermediate–siliceousignimbrites are common, and largecomposite batholiths are emplaced intothe volcanic suprastructure (Hilde-brand and Bowring 1984).

Crustal melts were generated

early on within the Santiago Peak arcas indicated by early eruption of volu-minous quartz porphyritic siliceous tuffthat predated the andesitic eruptions(Herzig and Kimbrough 2014). Giventhat the immediate crust beneath thearc was Jurassic, it is not surprising that

plutons assimilating such young crusthave low initial Sr (Fig. 19). However,Santa Ana–Santiago Peak arc magma-tism exhibits an initial εNd range of+8.2 to –0.6 and depleted mantlemodel ages (TDM) ranging from 0.31 to1.03 Ga and are clearly not directly

432

MORB

CHUR

Mohawk

Alacranes

Gila

Quitovac

Quitovac

Quitovac

Mohawk

SG

Los Ojos

10

5

0

-5

10

-15

-20

0.706 0.710 0.714 0.718

Sri

Northtt weww st

Sonorarr

Nd i

εPre-100 Ma

westernarc rocks

Post 100 Maeastern slabfailure rocks

86 Ma SantaRosa suite

SierraNevada

E & W

Post 103 Maeastern Sierran

slab failure rocks

Jurassic and Late Cretaceousplutonic rocks of Transverse Ranges and northern Sonora

Peninsular RannggesSahwavecomplexNevada

GG

GP

GP

G

SP

GL

Santa Rosa plutonic suiteLa Posta plutonic suiteSanta Ana plutonic suiteDrill holes-greater LA areaZarza intrusive complexSantiago Peak volcanics

Sierra Nevada (DePaolo)Tuolumne intrusive complexLamarck granodioriteMt. Whitney intrusive suiteYC, Taft, Sentinal, El CapitanSierran xenolith120 Ma Stokes Mtn complex

Pe n i n s u l a r Ra n g e s

S i e r ra N e va d a

120 Ma SierranStokes Mt. arc

rocks

OnionValley

Figure 19. εNd versus Srinitial of various suites within the Peninsular Ranges batholith showing the evolved nature of the plutonsand their similarities to Mesozoic rocks of the Transverse Ranges; eastern, post 103 Ma plutons of the Sierra Nevada (invertedtriangles), and likely basement rocks of the northwest Caborca terrane (purple triangles). Modified from Premo et al. (2014b).Peninsular Ranges samples from drill holes in greater Los Angeles area from Premo et al. (2014a); Zarza intrusive complex, aSanta Ana arc pluton in Baja, from Tate et al. (1999); Santiago Peak volcanics from Herzig and Kimbrough (2014); Sierranxenoliths: SP–spinel peridotite; GP–garnet peridotite; GG–garnet granulite; G–granulite. 120 Ma Stokes Mountain plutons ofwestern Sierran arc from Clemens Knott (1992); Sierran xenolith data from Domenick et al. (1983); post 103 Ma plutons ofeastern Sierra Nevada: Sierra Nevada from DePaolo (1981); Tuolumne intrusive suite from Memeti (2009); 94 Ma Lamarck gra-nodiorite from Coleman et al. (1992); 88–83 Ma Mt. Whitney intrusive suite from Hirt (2007); 103–95 Ma Yosemite Creek (YC),Taft, El Capitan, and Sentinal from Ratajeski et al. (2001); Onion Valley, a 92 Ma hornblende gabbroic sill complex, from Sissonet al. (1996); 93–89 Ma Sahwave intrusive suite–a post 100 Ma zoned complex, located in western Nevada, and similar in com-position, zoning and petrography to Sierran Crest plutons, from Van Buer and Miller (2010).

DMM-derived magmas. Thus, we seethe Santiago Peak–Santa Ana arc to bea rather typical arc suite (Fig. 11d).

The La Posta plutons havemore evolved Nd, Sr, Pb and O iso-topic signatures than the Santa Anasuite (Figs. 19, 20, 21) and clearlyinvolved crustal contamination. Over-all, the Pb isotopic dataset appears tobe a mixing trend between a moreprimitive, less radiogenic end-member,represented by the lowest 207Pb/204Pband 208Pb/204Pb samples forming theSanta Ana suite, and the consistentlymost radiogenic or evolved samples ofthe Santa Rosa suite (Fig. 20). Elevated207Pb/204Pb signatures, relative to DMMand especially the most radiogenic end-member Santa Rosa suite, resultedfrom decay of the almost extinct 235Uparent of 207Pb, a mostly Archeanprocess. Thus, these 207Pb/204Pb signa-tures indicate very long-lived sourcedifferences and substantiate input froman ancient upper crustal component, inboth the La Posta and Santa Anasuites. Although input from ancientcrust within the Santa Ana suite mayhave been volumetrically minor, theobserved 207Pb/204Pb signatures areincompatible with derivation solelyfrom juvenile DMM-like sources with-in an isolated intra-oceanic arc setting.

Initial Pb–Sr and Nd ratiosfrom the Proterozoic basement west ofthe suture zone within the Caborca ter-rane (Iriondo et al. 2004; Farmer et al.2005; Nourse et al. 2005) are a good fitfor the continental crustal componentof the La Posta plutonic rocks (Kistleret al. 2014). SHRIMP analyses docu-mented xenocrystic cores of Protero-zoic zircon within La Posta plutonsthat also support the probability thatthe Proterozoic terranes or sedimenta-ry rocks derived from them could havebeen the crustal component in the plu-tons (Kistler et al. 2014). This fits wellwith recently acquired data from plu-tons on Searl Ridge (Fig. 3) that show,based on detrital zircon grains andPb–Sr–Nd isotopic data, a stronginvolvement of older crust, likely Pro-terozoic (Premo and Morton 2014).

Hafnium data from bothJurassic and Cretaceous plutons thatcut the Jurassic basement suggest that,in addition to the primitive mantlecomponent, at least three additionalcomponents are required: (1) a com-

bined Proterozoic–Paleozoic–Mesozoicmetasedimentary component; (2) aNeoproterozoic constituent; and (3) anelement with a model age of about2300 Ma (Shaw et al. 2014). When theHf model ages are combined with theoverall low δ18O isotope data (Fig. 21)from the Santa Ana suite and their lowinitial Sr ratios the best fit for a crustalsource is a large ion lithophile element-depleted lower crust of Neoprotero-zoic age because the low δ18O valuesrule out a metasedimentary source(Shaw et al. 2014).

An important point to remem-ber is that, based both on models(Reiners et al. 1995) and experiments(Watson 1982), large changes in traceelement content and isotopic composi-tions can take place with very littlechange in major element chemistry

when mantle basalt is interacting withcontinental crust, especially whenhybridization is incomplete. We com-pared the 0.2 Ma Kuanyinshan basalt(8.4–5.8% MgO) from Taiwan with theLa Posta plutons on Figure 11c. As canbe seen, the trace elements are similaryet major elements differ widely. Thissuggests to us that the rocks from Tai-wan spent little time in contact withcrust prior to eruption, whereas thepresumably much larger volumes of LaPosta magma were able to assimilatemuch greater volumes of crustal mate-rial, but that nearly all of the transferof trace elements took place very earlyon with very small amounts of partialmelting. This early hybridizationfavours increasing asymmetry of Srand Nd isotopic ratios because the dif-fusion rates for Sr are faster than those


15.4

15.5

15.6

15.7

37

38

39

0.0 Ga

0.2 Ga

=8.5

dmm

Geo

chro

n

100

Ma

207P

b/20

4Pb

208P

b/20

4Pb

206Pb/204Pb

MojaveProvince

CentralArizona

~1.75 Ma Bamori paragneiss

1.7 Ga CerroRajon granite

CentralArizona

MojaveProvince

dmm

~1.75 Ma Bamori paragneiss

1.7 Ga CerroRajon granite

La PostaSanta Rosa

Santa Ana

Post 100 Ma

Pre 100 Ma

a.

b.

a.

ia Bamor~1 75 M

15 5

15.6

15.70.4 Ga

0

0.6 Ga

100

=9

on

1

00M

bP20

4b/ eo

chrro

a.

eanitrajon gRorera C1.7 G

0.0Ga

a

0.2 Ga

00MM

a

neissagparia Bamor~1.75 M

evincorPevojaM

t 100 MP

.

0

15.4

15.5

0.00.2 Ga

=8.5

e

39

bP20

7 GGe

ojMb

dmm

eva

onaizrAaltrenC

ae 100 MrP

aost 100 MP

nata AanS

ta RosaanSostaa PL

ThTh

=8.5

38

Ga0.2 Ga

0.0 GabP

204

b/P20

8

vorPojM

ThTh/h/U/U=

4

evinceva

neissagpari a Bamor~1.75 M

37

eanitrajon gRorera C1.7 G

ThThdmm

bP204b/P206

h/h/U/U

= 2

onaizrAaltrenC

Figure 20. Plots of whole rock (a)207Pb/204Pb; and (b) 208Pb/204Pb vs.206Pb/204Pb for Peninsular Rangesbatholith plutonic groups compared toProterozoic basement of the Mojaveprovince and central Arizona and twobasement samples from the Caborcaregion from Farmer et al. (2005) andmodel Th/U of 4 and 2 for 1.7 Gareservoirs from Iriondo et al. (2004).Single stage reference growth curvesfor 238U/204Pb ratios (μ) of 8.5 and 9, a232Th/204Pb ratio of 40.5 and thegeochron were calculated using 4.5 Gafor the age of the Earth and CanyonDiablo troilite (Tatsumoto et al. 1973)for initial values.

.704

La Postasuite

older

youngerMantle-like sources

Mantle-like sources

Supracrustal s

ources

Supracrustal sources

207P

b/20

4Pb

Init

ial 8

7Sr/

86Sr

Init

ial 8

7Sr/

86Sr

Whole Rock δ18O vsmow

207Pb/204Pb

.702

.706

.708

.710

.702

.704

.706

.708

5 7 9 11 13

15.55

15.60

15.65

15.70

15.75

Santa Anasuite

La Postasuite

Santa Rosasuite

La PostaSanta Rosa

Santa Ana

Post 100 Ma

Pre 100 Ma

Santa Anasuite

La Postasuite

Santa Rosasuite

Santa Anasuite

Santa Rosasuite

La PostaSanta Rosa

Santa Ana

Post 100 Ma

Pre 100 Ma

a.

b.

c.

Pb04

15.75

15.70

esuitta RosaanS

20Pb

/20

7

15.65

15.60

15.55

esuitnata AanS

esuitostaa PL

e 100 MP

aost 100 MPta RosaanSostaa PL

l 87S

r/86

Sra

.708

.706

sua PL

esuitta RosaanS

ae 100 MrPnata AanS

euitostaP

W

ani

tiI

75

.704

.702

wsmovck δ18Ooe RolhW119

esuitnata AanS

w13

87Sr

/86S

r

.710

.708

.706esuit

ta RoanS

esuitostaa PL

osa

esuitnata AanS

.

l ani

tiI .704

.702c

207Pb/204Pb

P

P

ae 100 MrP

aost 100 MP

nata AanS

ta RosaanSostaa PL

Figure 21. Plots of (a) 207Pb/204Pb; and(b) initial 87Sr/86Sr vs. δ18O(VSMOW)(‰); and (c) initial 87Sr/86Srvs. 207Pb/204Pb for Peninsular Rangesbatholith plutonic groups. Isotopicdata from Kistler et al. (2003, 2014).

for Nd (Lesher 1994). Thus, there islittle doubt that rocks of the Santa Anasuite had significant crustal input. Andgiven the even more evolved isotopesin the La Posta rocks, there can be lit-tle doubt that they too involved a sig-nificant crustal component.

The main question concernsthe origin of the mafic component ris-ing into the crust from the mantle. Therare earth element (REE) concentra-tions of the two suites are different asoriginally noted by Gromet and Silver(1987), who suggested that rocks ofthe Santa Ana arc were derived frompartial melting of plagioclase-richsources whereas La Posta rocks werederived from garnet-bearing assem-blages. They also pointed out that gen-eration of La Posta rocks involved ahigher δ18O source. Silver et al. (1979)noted that the extremely heavy natureof the oxygen in the La Posta plutons(Fig. 21a, b) required that they had aprior history of access to surfacewaters. As the La Posta plutons wereemplaced into the mid and lower crust,an unlikely source region for surfacefluids, the source of fluids was morelikely to have been within the mantlesource region. As the Santa Ana andLa Posta plutons do not have the sameoxygen signature they must have haddifferent mantle sources.

In the Sierra Nevada, deep-seated plutons contain abundant evi-dence for young supracrustal contami-nation, even in gabbroic plutons, basedon high δ18O in zircon values (Lackeyet al. 2005). These, along with similarvalues in La Posta rocks (Fig. 21),might indicate that parts of the leadingedge of the subducted plate melted orat least dehydrated to produce suffi-cient water to contaminate the mantlemelts before they ever reached theupper plate crust. Later melts of theSanta Rosa suite have lower δ18O values(Fig. 21), which suggest that the sourceregion was depleted in the fluid phaseby about 86 Ma.

Mafic and ultramafic xenolithsin the Sierra Nevada shed some lighton the mantle melts involved in slabfailure, for the xenoliths, dated to bethe same age as the plutons of theeastern slab failure plutons, have simi-lar Nd and Sr isotopic values alongwith elevated δ18O, and are arguablycumulates left behind after extraction

of melts (Ducea and Saleeby 1998;Lackey et al. 2005). As the xenolithsprovide minimum pressure bounds(Chin et al. 2012), they clearly wereformed within the garnet peridotitefield (Fig. 18), and as La Posta plutonshave REE patterns of residual garnet(Gromet and Silver 1987), it is reason-able to assume that the slab failurebasalt magma originated from risingasthenosphere at deeper levels, say inthe garnet stability field (Grove et al.2013), than the precursors to typicalarc magmas, which appear to beformed at shallower levels by meltingin the plagioclase and spinel stabilityfields (Till et al. 2012).

We cannot evaluate whetheror not subcontinental mantle wasinvolved in slab failure magmatism, butit is possible that it was. Given thatboth Nd and Sr isotopes and trace ele-ment patterns within the plutons aresimilar to early lithospheric mantlemelts of the Rio Grande rift (Perry etal. 1987) or even oceanic islands (Sis-son et al. 2002) we cannot separatethem on the basis of isotopic composi-tion. It might be that only the earliestLa Posta magmas involved a lithos-pheric mantle component, but dating isnot yet sufficient to evaluate this possi-bility.

Geochemical Identification of SlabFailure-Related Granitoid MagmasOn the Rb–Y + Nb diagram of Pearce(1996), all samples from the PeninsularRanges batholith plot in the volcanicarc granite (VAG) field within which

almost all the Santa Ana and about halfof the La Posta samples fall in theoverlapping fields of VAG and post-collisional granites (Fig. 22a). On theNb–Y diagram of Pearce et al. (1984),all samples plot in the VAG plus syn-collisional granite field; however, dueto differences in Nb/Y between theSanta Ana and La Posta suites (Fig.10c), there is quite good separationbetween these two groups on this plot,though not into the fields defined byPearce et al. (1984). In our opinionthese tectonomagmatic diagrams can-not be reliably employed for the geo-chemical identification of slab failureversus normal arc-type granitoid mag-mas. However, there is the possibilitybased on our few examples, that vol-canic arc granite and slab-failure gran-ite can be distinguished as on Figure22b.

Although we firmly believethat the best indicator of slab-failuremagmatism is its post-collisional tim-ing, we tried to discriminate betweenarc and slab-failure magmas by utilizingthe differences in trace element con-centrations shown on histograms (Fig.10). We did this empirically by observ-ing the separation of trace elementconcentrations to arrive at values ofLa/Yb, Gd/Yb, Nb/Y, and Sr/Y thatseparate the largest numbers of pre-and post-deformational samples.

As can be seen from Figure23, the pre- and post-deformationalrocks of the Peninsular Rangesbatholith fall predominantly into twodiscrete groups on all three plots. We

434

arc plutons

slab failureplutons

10 100

10

100

ORG

WPG

Nb

(ppm

)

Y (ppm)

ORG

VAG

syn-COLG

post-COLG

WPG

Nb + Y (ppm)Rb

(ppm

)

10

1000

100

10 100

a. b.a b

b (p

pm)

GOLCsyn-

a.

R

1000

100

GOLC-post

WPG

10

plutslab fa

100

b (p

pm)

N

onsteailur

WPG.b

b

GAVVA

N

10

10Y (ppm)

ORG

b +100

N

10

onsc plutar

Y (ppm)100

ORG

Figure 22. (a) Rb vs. Y + Nb; and (b) Nb vs. Y plots for Peninsular Rangesbatholith plutonic groups with fields from Pearce (1996). In (b), we divided the for-mer volcanic arc plus collisional granite field of Pearce et al. (1984) into arc andslab failure fields, based on data presented here.


1 110

100

Sr/Y=10

Sla

b F

ail

ure

gra

nit

oid

s

Tu

olu

mn

e s

uit

e>

70

% S

iO2

60

-70

% S

iO2

<6

0%

SiO

2Nb/

Y=0.

4

La/Y

b=10

Gd/

Yb=2

Apl

ites

Sa

hw

av

e s

uit

e>

70

% S

iO2

60

-70

% S

iO2

120

Ma

Sier

ran

Stok

esM

tn c

ompl

ex-a

rc ro

cks

La/Yb

Sr/Y

Gd/Yb

Nb/

Y= 0

.4

Sr/Y=10

La/Y

b=10

Gd/

Yb=2

.0

10 50

1010

0

1.0

5.0

0.5

sla

b f

ail

ure

gra

nit

oid

s

San

Pedr

o de

Már

tirLa

Pos

ta-t

ype

plut

on

Sa

nta

Ro

sa s

uit

e

La

Po

sta

plu

ton

s

Sa

nta

An

a s

uit

e

arc

plu

ton

ic s

uit

e

Sr/Y

110

100

Sr/Y

Sr/Y= 10

1

1

0.1

Flui

d m

etas

omat

ized

Ba/R

b ty

pica

lly <

1

youn

ger

olde

r

SW

NE

Sr/Y=10

Sla

b F

ail

ure

gra

nit

oid

s

110

100

Tls

Kys

Ttvg

Klvg

Pcy

Mhy

Kbs

Sbs

Ta

iwa

n

0.2

Ma

0.2-

0.5

Ma

0.2

Ma

2.6

Ma Sr

/Y

Back

arc

exte

nsio

nal

rock

s

2.6

Ma

1 M

a

a.

Pe

nin

sula

r R

an

ge

sb

. S

ierr

as

& N

ev

ad

ac.

Oth

er

ex

am

ple

sd

. Ta

iwa

n

7.5

-2.5

Ma

Iri

an

Ja

ya

vo

lca

nic

s

24

-19

Ma

An

ato

lia

n p

luto

ns

56

-40

Ma

Ba

lka

n p

luto

ns

sla

b f

ail

ure

gra

nit

oid

s

Nb/

Y=0.

4

La/Y

b=10

Gd/

Yb=2

Nb/

Y=0.

4

La/Y

b=10

Gd/

Yb=2

Nb/Y

1.010

en

ins

Sr/Y=10b/

Y=0

4N

oid

sa

nit

gr

esl

ab

fail

ur

a.

P10 1.

0

b/Y N

an

ge

s

S

sula

r R

ad

a

% S

iO2

60

-70

2>

70

%S

iO

ee

suit

va

wa

hS

ve

as

& N

. S

ierr

b

the

r e

. O

ca

xa

mp

les

aiw

TTa

McPKTtyKKylT

e

an

oung

Sr/Y=10

y

a

an

w

yM

hycg

lvgvtsyls

M0.

2-0.

5

a0.

2M

a

aiw

TTa

. d

1 M

ger

b

50

b/Y=

0.4

N

0.1

a

Lab=

10La

/Y

onyp

e pl

utos

ta-t

La P

tirár

o de

Med

ran

PS

eo

nic

suit

c p

lut

ar

b/

b=10

a/Y

N

oc

r-a

rx

ompl

eM

tn c

oktan

Sa

Sier

r12

0M

/Y=0

.4

ocksesk

b=10

La/Y

b/Y=

0.4

SbKN

olde

r

SW

a

bsbs

2.6

M

a0.

2 M

a2.

6M

b/Y=

N

=0.4

b a/Y L

5.010 1

1

grla

S

b10

La/Y

en

a s

uit

ta A

an

S

on

so

sta

plu

ta

PL

eta

Ro

sasu

ita

nS

Sr/Y=10

a/Y

oid

sa

nit

re

ail

ur

ab

F

% S

iO2

60

<

% S

iO2

60

-70

2>

70

%S

iO

uo

lum

ne

suT

2

eu

it

r/Y= 10

b10

56

-40

M

24

-19

M

7.5

-2.5

oid

s

La/Y a

nit

gr

esl

ab

fa

ilu

r

on

s

an

grla

bS

o

an

plu

ta

lka

BM

on

so

lia

n p

lut

tn

aa

AM

an

ics

olc

a v

ya

ria

n J

a I

MrentxeacB

NE

000

oid

sn

ite

ail

ur

F

ocks

km

~1000km

b

nsio

nal

cck

arLa

/Y

b=10

b d/Y G

S0.

5

1.0

101

1

G

Sr/Y

100

b=2.

0d/

YG

100

es

10

Sr/Y

plit

A

b=2

d/Y

G

ypi

b ty

a/R

Bluid

met

asF

S

ical

ly <

1

Sr

b=2

101

edtiz

som

a

d/Y

G

Sr/Y

100

1

d/Y

G

100

b=2

10Sr

/Y

Y

Fig

ure

23.

(a) F

elsic

(>60

% S

iO2)

Peni

nsul

ar R

ange

s Bat

holit

h pl

uton

ic sa

mpl

es p

lotte

d on

Nb/

Y, L

a/Y

b, a

nd G

d/Y

b vs

. Sr/

Y d

iagra

ms.

Das

hed

lines

are

ratio

valu

es o

btain

ed fr

om h

istog

ram

s (Fi

gure

10b

, c, a

nd d

) tha

t sep

arat

e m

ost S

anta

Ana

arc

-type

plu

toni

c sa

mpl

es fr

om L

a Po

sta–

Sant

a Ro

sa sl

ab fa

ilure

plu

toni

cro

cks.

Ana

lyses

from

the

Sier

ra S

an P

edro

Már

tir p

luto

n, a

La

Post

a-ty

pe p

luto

n in

Baja

Cali

forn

ia, a

re a

lso p

lotte

d us

ing

data

from

Gas

til e

t al.

(201

4). (

b) S

ampl

esfr

om th

e 94

–84

Ma

Tuol

umne

intr

usiv

e co

mpl

ex o

f th

e Si

erra

Nev

ada

from

Mem

eti (

2009

) and

93–

89 M

a Sa

hwav

e in

trus

ive

suite

–a p

ost 1

00 M

a zo

ned

com

plex

,lo

cate

d in

wes

tern

Nev

ada,

and

simila

r in

com

posit

ion,

zon

ing

and

petro

grap

hy to

Sier

ran

Cres

t plu

tons

, fro

m V

an B

uer a

nd M

iller

(201

0). (

c) A

nalys

es fr

om7.

5–2.

5 M

a po

st-c

ollis

iona

l mag

mat

ism in

Irian

Jaya

from

McM

ahon

(200

0, 2

001)

; 24–

19 M

a po

st-c

ollis

iona

l plu

toni

c ro

cks f

rom

wes

tern

Ana

tolia

, Tur

key

(Altu

nkay

nak

et a

l. 20

12);

and

analy

ses f

rom

the

56–4

0 M

a po

st-c

ollis

iona

l Rho

dope

Mas

sif o

f so

uthe

rn B

ulga

ria–n

orth

ern

Gre

ece

(Mar

chev

et a

l. 20

13).

(d) S

am-

ples

from

a 1

000

km-lo

ng sw

ath

of 2

.5–0

.2 M

a vo

lcano

es e

xten

ding

nor

thea

stw

ard

from

nor

ther

n Ta

iwan

alo

ng th

e A

sian

cont

inen

tal m

argi

n (W

ang

et a

l. 20

04).

were encouraged by the differences intrace element ratios and so plotted afew more suites in order to see if thediscrimination based on the PeninsularRanges worked for other post-colli-sional magmatic suites inferred to haveformed by slab failure magmatism.

We plotted post-Sierran arcplutons of the well-studied Tuolumneintrusive complex on the same figure(Fig. 23), along with 120 Ma rocks ofthe Stokes Mountain complex, repre-sentative of arc magmatism in thewesternmost Sierran batholith(Clemens Knott 1992). Modern andcomplete analyses of the older Sierranrocks are scarce, and even the data setfrom the Stokes Mountain complexdoes not include complete REE analy-ses. Nevertheless, samples from thepost 103 Ma Tuolumne intrusive com-plex, inferred here to be a result ofslab failure, fall mostly within our pro-posed slab failure field, whereas thebulk of the arc rocks do not. Both Ndand Sr isotopic compositions from theTuolumne and other post-deforma-tional plutons of the eastern SierraNevada are nearly identical to those ofthe La Posta–Santa Rosa suite (Fig. 19),whereas Stokes Mountain samples haveisotopic compositions that plot withthe Santiago Peak–Santa Ana arc rocks(Fig. 19). Rocks of the Sahwave com-plex (Van Buer and Miller 2010), aTuolumne-like intrusive complex ofsimilar age located in northwesternNevada, also plot within our proposedslab failure fields. We note that rockswith greater than 70% SiO2 may havesignificant interaction with a volatilecomponent and do not plot within theslab failure field.

We also plotted (Fig. 23) sam-ples from Irian Jaya, where 7.5–2.5 Mamagmatic rocks are interpreted to haveformed as the result of collision of thenorthern margin of Australia with thesouth-facing 20–9 Ma Marimumi arc(Cloos et al. 2005). The rocks are dom-inantly intermediate calc-alkaline, high-K shoshonitic and syenitic with rela-tively unradiogenic Nd and moderatelyradiogenic Sr isotopic compositions(Housh and McMahon 2000) broadlysimilar to those of the La Posta suite,but with lower εNd reflecting theArchean basement. The rocks shownin the plot are dominantly andesitewhereas most of the other suites are

dominated by samples with > 60%SiO2, which might explain why theIrian Jaya samples cluster near the bot-tom of the slab-failure field on two ofthe plots.

Samples from western Anato-lia, where 24–19 Ma magmatismformed following the collision of theSakarya and Anatolide–Tauride blocks(Altunkaynak et al. 2012), also fallwithin the slab failure field on our dis-crimination diagrams (Fig. 23) andhave similar Nd and Sr isotopic com-positions to the La Posta suite. Alsowithin the Alpine belt, and plotted onFigure 23, likely slab-failure magma-tism occurred in the Macedonian–Rhodope–North Aegean zone of thesouthern European Balkans, whereEarly–Middle Eocene magmatism wasbookended by Late Cretaceous arcmagmatism and Oligocene extensionalmagmatism (Marchev et al. 2013).They list Nd and Sr isotopic composi-tions similar to the other examplescited here.

Our last example (Fig. 23) ofpost-collisional magmatism is also theyoungest and while one would think ittherefore the simplest, they would bemistaken. Volcanic rocks ranging in agefrom 2.5 Ma to 0.2 Ma occur sporadi-cally in a linear band extending fromnorthern Taiwan for about 1000 kmalong the Asian margin. According toWang et al. (2004), from whom thisdescription was extracted, the oldestmagmas, from Mienhuayu and Sek-ibisho (MHY and SBS) have: (1) Mgcontents of ~6–8%; (2) the highest143Nd/144Nd and relatively elevated87Sr/86Sr; and (3) were derived fromasthenospheric sources that werefluxed by slab fluids during opening ofthe Okinawa back-arc basin. In con-trast, the youngest rocks, Tsaolingshan(TLS) and Kuanyinshan (KYS), whichwere both erupted on the northwest-ern part of the island of Taiwan atabout 0.2 Ma have: (1) Mg0 contentsof about 15%; (2) the lowest Nd andhighest Sr isotopic compositions; (3)model Nd ages falling between 2.5 and2.0 Ga, which suggest derivation inpart from Proterozoic domains in thesubcontinental lithospheric mantle(SCLM) or the crust; and (4) Kuanyin-shan rocks typically have Ba/Rb <1,indicating significant fluid metasoma-tism. Remarkably, these young highly

magnesian basaltic magmas, whichappear to have resulted from verysmall degrees of partial melting ofmetasomatized SCLM, have trace ele-ment concentrations nearly identical tothose of the seemingly much morevoluminous La Posta suite (Fig. 11),perhaps providing a real world case ofearly assimilation of trace elementsduring partial assimilation.

It is important to understandthat these are not universal discrimina-tion plots, for some arc suites, such asthe Bodie Hills of eastern California(John et al. 2012; du Bray et al. 2013),which sit atop the eastern Sierran slab-failure rocks, likely scavenged sufficientsubjacent crustal material so that theytoo would plot in the upper right on allthese plots. Even the bimodalPlio–Pleistocene volcanic rocks of theAurora Volcanic field, located in theextensional Basin and Range provincejust north of Mono Lake, have similargeochemical signatures that also sug-gest involvement of plutonic rocks ofthe Sierra Nevada (Kingdon et al.2014).

Criteria for Identification of SlabFailure-Related Plutonic RocksWe showed earlier in the paper that thebatholith was likely the upper plate in acollision with an Albian carbonate plat-form located to the east and that thewestern edge of the eastern continen-tal margin was pulled beneath the arc.The timing of the collision was ~100Ma and following collision, or perhapsin part overlapping it, major magma-tism of the La Posta suite took placeover the length of the batholith. It isthe timing of magmatism during anddirectly after collision, coupled withthe strong exhumation, that providesthe most compelling evidence that theLa Posta plutons are slab-failure bod-ies, not the geochemistry. That is notto say that our discrimination diagramsdo not work, for they do seem to sepa-rate slab-failure magmas from arcrocks in the cases that we investigated.However, it must be noted that earlyslab-failure magmas might be morearc-like as the asthenospheric meltsinteract with the subcontinental lithos-pheric mantle. Following slab failure inmany collisional orogens, a new sub-duction zone commonly starts up, butwith opposite polarity. The new arc

436

may form atop the pre-collisional arcand the post-collisional slab-failuremagmas to form a complex amalgama-tion of deformed and little deformedmagmatic rocks. This, coupled withcoincidental opening of a marginalbasin, such as the Okinawa trough,behind the Ryukyu arc during collision,can make a mockery of simplisticmodels and serves as a cautionary tale.

Some Implications of Our Model1. Lee et al. (2007) employed geo-

chemical data from the PeninsularRanges batholith to examine link-ages between arc magmatism andPhanerozoic continental crust for-mation. They concluded thatrefinement into a felsic crustoccurred after oceanic arc accre-tion during ‘the continental arcstage’ when an accretion-thickenedcrustal and lithospheric columnwas thermally reworked byemplacement of subduction-gen-erated basaltic magmas. There areseveral problems with their model.First, the Santiago Peak–Alisitosarc was not a primitive arc built onoceanic crust, for it contains fartoo large a volume of felsic rocks,and its basement, where exposed,comprises abundant Jurassicorthogneiss and Paleozoicmetasedimentary rock. Second,there is no evidence that the LaPosta suite was derived from sub-duction of oceanic lithosphere,and third, the crustal materialsinvolved were likely the older Pro-terozoic–Paleozoic basement ofthe batholith as demonstrated byxenocrystic cores in zircon grainsand Pb–Sr–Nd isotopes (Premoand Morton 2014; Kistler et al.2014), augmented by fluids andpossibly melts from the subductedcontinental margin.

In our model, the thermalevent that refined mantle materialsinto more evolved continentalcrust was directly related to shal-low slab failure and consequentupwelling of asthenosphere, whichwas the advective heat sourceresponsible for the major, short-lived, and focused thermal pulserequired to drive the crustal melt-ing and reworking process.Because every collision should

have a slab-failure component, thismechanism adds significantly toour understanding of how conti-nental crust formed, grew, and wasrecycled over Earth history (Hilde-brand and Bowring 1999). A possi-ble check on our hypothesis wouldbe to investigate whether majorpulses or peaks in crust formationduring Earth history postdatemajor ocean-closure events, suchas supercontinent amalgamation. Arecent study of δ18O in zircon on aworldwide basis suggests that sub-duction of sediment and surficiallyweathered rocks during collisionshas led to a long-term record ofsupercontinent amalgamation asdocumented by the heavy natureof the δ18O of zircon (Spencer etal. 2014).

2. Geologists studying the geochemi-cal characteristics of plutonic andvolcanic associations with highSr/Y and La/Yb values have gen-erated an abundant literature overthe last 20 years as they attemptedto classify and understand the pet-rogenesis and tectonomagmaticimplications of rocks such asadakite (Defant and Drummond1990; Sajona et al. 2000; Macpher-son et al. 2006; Moyen 2009),Archean tonalite–trondhjemite–granodiorite (TTG) suites (Martin1986, 1987, 1994; Smithies 2000;Kamber et al. 2002; Whalen et al.2004), Archean sanukitoid suites(Whalen et al. 2004; Martin et al.2005, 2009) and adakitic granite(Wang et al. 2007; Whalen et al.2010). To our knowledge, only oneof the published petrogeneticmodels for these various igneoussuites link them to possible slabfailure (Whalen et al. 2010), yetthey are similar chemically to theLa Posta suite, as well as Cenozoicexamples, such as northernmostTaiwan, where comparable mag-mas were erupted as the exhumedmountain belt collapsed within afew m.y. of collision (Chung et al.2001; Wang et al. 2002, 2004) andTibet, where enigmatic magmatismaccompanied uplift and exhuma-tion (Turner et al. 1993, 1996;Mahéo et al. 2002; Kohn andParkinson 2002). These two exam-ples of probable slab failure mag-

matism might typify the shallowand deep break-off end membersrespectively, as reflected in theirorogenic width, proximity to thesuture, and differences in timingrelative to the collision. That said,the mantle and crust are sufficient-ly heterogeneous that it is likelythat no discrimination plot can beunfailingly diagnostic.

3. We believe that our model for thePeninsular Ranges batholith is gen-erally applicable to other orogenicbelts, and so ‘paired’ plutonic belts(Tulloch and Kimbrough 2003)consisting of arc-related magma-tism, followed by post-tectonicslab failure type plutonism, couldrepresent substantive evidence forthe presence of major tectonicsutures in much more deeply erod-ed terranes, much as do remnantsof suprasubduction ophiolites pre-served in less denuded terranes. Itis worth emphasizing that in casesof deep break-off that slab-failuremagmatism may occur a significantdistance from the suture and longafter the initial collision.

4. In an attempt to reconcile juxta-posed basement blocks and theircover, such as the abrupt north-eastern edge of the Caborca ter-rane in Sonora, Silver and Ander-son (1974) hypothesized that LateJurassic sinistral motion along amajor strike-slip fault, which theytermed the Mojave–Sonora megas-hear, separated rocks of Caborcafrom similar rocks in the DeathValley region. Our rifting and colli-sional model presents a viablealternative to the Mojave–Sonoramegashear hypothesis (Andersonand Silver 2005) because in ourmodel lithological units, consid-ered to be offset along the megas-hear, may have originally formedmore coherent blocks that wereseparated by rifting and break-upleading to widening of the Bis-bee–Arperos sea. When the seaclosed, some 30 m.y. later, thosefragmented blocks, such as Cabor-ca, simply did not return to theiroriginal locations; but instead wereaccreted farther south.

5. Previously, paleogeographic recon-structions of the pre-160 MaJurassic arc of the Klamath Moun-


tains and northern Sierra requiredit to bifurcate southeast to headinto southern Arizona and south-west to Baja California. Our modelsimplifies the paleogeography inthat the Jurassic arc of Baja wasrifted from the eastern strand atabout 139–130 Ma as the Bisbeemargin formed.

6. Another peculiarity that might beresolved by our model, or at leastpartially so, is the Klamath Moun-tains block, which contains manysimilar rock packages as the SierraNevada, including a Jurassic arcthat is generally correlated with thenorthern Sierran rocks (Irwin andWooden 2001), but lacks the Sier-ran Cretaceous arc and slab failuremagmatism. Because the westernKlamaths were deformed duringthe ~145 Ma Nevadan event, itthus seems likely that it was sepa-rated from both rocks to the eastand the Sierran block during the139–130 Ma rifting event.

7. We now recognize that the Bis-bee–Arperos sea had an easternboundary that trended more orless southeast from southwest Ari-zona to southern Mexico (Fig. 12)yet Dickinson and Lawton (2001b)suggested that the Bisbee basinformed part of what they termedthe Border rift system, which wasan intracontinental rift extendingfrom the Gulf of Mexico north-west through the Sabinas basinand Chihuahua trough to at leastthe Bisbee basin (Fig. 12). If activeat the same time they likelyformed oceanic margins on boththe eastern and western sides ofthe Oaxaquian terrane. Closure ofthe Arperos–Bisbee sea on thewest occurred during the Oregon-ian event at about 100 Ma and anunnamed sea – but possibly thelast vestiges of the Panthalassicocean – formerly located along theeastern margin of Oaxaquia, van-ished during the Laramide event atabout 75 Ma.

8. An unresolved question is whatcaused the Bisbee–Arperos sea toopen? Presumably, it was subduc-tion reversal following the defor-mation of the Nevadan collisionalevent responsible for the strongdeformation of the Cucurpe–

Peñasquitos–Mariposa rocks. Thissituation would have been analo-gous to Taiwan where the Oki-nawa trough opened as the resultof collision, slab failure and sub-duction reversal (Viallon et al.1986; Teng et al. 2000) or varia-tions on this theme as seen innumerous other examples(McCabe 1984; Wallace et al.2009). If it was a marginal sea thenthere should have been an arcbehind which the sea could open.However, there was little timebetween the deformation of theCucurpe–Peñasquitos–Mariposarocks, bracketed to be 145–139Ma, and the deposition of theunconformably overlying rocks ofthe Bisbee basin dated to be136–125 Ma (Mauel et al. 2011;Peryam et al. 2012; Kimbrough etal. 2014a). Perhaps the 141–135Ma volcanic and plutonic rocks ofthe Vizcaino Peninsula (Kim-brough and Moore 2003) representa remnant of the arc, as might theswarm of 143–140 Ma plutons inthe western Sierra Nevada (Irwinand Wooden 2001; Day and Bick-ford 2004). In any case, possiblearc rocks of this age are not par-ticularly common. If the basinopened as a marginal sea thenthere was also an unidentifiedevent that caused the subductionto step into the basin and reversepolarity to dip westward. Whetherthis was the attempted subductionof an oceanic plateau or a collisionof terranes is unknown but a rea-sonable candidate might be theproposed arc–arc collisionbetween the Alisitos and SantiagoPeak blocks (Alsleben et al. 2008;Schmidt et al. 2014). Theydescribed a narrow SW-vergent110–108 Ma fold-thrust belt,which extends southward from theAgua Blanca fault through at leastthe northern Baja Peninsula (Fig.2). The proposed suture placed theSantiago Peak block atop the Alisi-tos block (Alsleben et al. 2008).However, given the likely large-scale meridional migration of out-board Cordilleran terranes, it isalso possible that the arc rocks arenow located far to the north.

9. The model proposed here, that

many Cordilleran batholiths arecomposed of two magmatic phas-es, arc and slab failure, might beused to reconstruct widely separat-ed terranes. For example, withinthe American Cordillera there aretwo batholithic terranes recognizedas out-of-place orphans: the Salin-ian block (Ross 1978), located justwest of the San Andreas fault incentral California; and the Coastalbatholith of Peru with its Are-quipa–Antofalla basement (Loewyet al. 2004). In our accompanyingcontribution (Hildebrand andWhalen 2014: this volume) webriefly describe the geology ofthose terranes, hypothesize thatthe two were formerly joined, andthat the high-grade Salinian blockwith its 100–82 Ma plutonsformed the opposing block to thedominantly lower grade, mainlyAlbian, arc complex of the Coastalbatholith.

10. A major unanswered question iswhere is the arc that is inferred tolie to the east of the Franciscanmélange, Coast Ranges ophiolite,and Great Valley Group? Based ondeformation (Hildebrand 2013)and detrital zircon (Wright andWyld 2007), it seems clear thatthose rocks were not adjacent tothe Sierra Nevada prior to the 100Ma collision. A possible candidateis the Xolapa terrane of southernMexico, which contains Late Juras-sic and Early Cretaceous plutons(Herrmann et al. 1994; Ducea etal. 2004), yet has long been knownto lack a forearc and accretionarycomplex (Karig et al. 1978).

11. Arcs appear on their face to bevery simple elements, and duringsubduction probably are relativelyso, at least at a regional scale.However, appearances are oftendeceiving, and as arcs commonlycollide with other tectonic ele-ments, the subducting slab tearsoff to allow different magmas torise into or adjacent to the arc, andnew oppositely dipping subductioncan start up very quickly, typicallywithin a million years, to create acomplex and commonly confusingmagmatic tableau (Dewey 2005;Huang et al. 2006; van Staal et al.2007; Hildebrand et al. 2010). Fur-

438

thermore, as these events takeplace at continental margins andwithin ribbon continents, the pos-sibility that these complex arc-bearing terranes might be tornapart by rifts and/or strike-slipfaults and strewn laterally alongthe margin, only to have new arcsbuilt atop them, must be consid-ered. On a world covered by mov-ing plates, simplicity is not neces-sarily correct.

CONCLUSIONS1. The Peninsular Ranges batholith is

a composite batholith comprisinga western arc complex, the Santia-go Peak–Alistos–Guerrero arc,that formed between 128–100 Maon Jurassic, Paleozoic and Precam-brian crust dominantly above awestward-dipping subductionzone, and a 99–86 Ma suite ofpost-deformational plutons thatwere emplaced after the arc collid-ed with a composite terrane locat-ed to the east.

2. The basement within the arc com-plex appears to have rifted fromthe Cordilleran Ribbon Continentbetween about 139 and 130 Ma.

3. The Santiago Peak–Alistos–Guer-rero arc collided at about 100 Mawith a Lower Cretaceous passivemargin, located to the east andtopped by a west-facing Albiancarbonate platform terrace, whichwas pulled into the trench, buriedby orogenic flysch, and overthrustby exotic allochthons containingslices of the arc and its basement.This platform is intermittentlyexposed from Caborca, where it isknown as the Sonoran shelf, toZihuatanejo, where it is known asthe Guerrero–Morelos platform.

4. During the short-lived collision,the oceanic lithosphere of thelower plate was relatively young sobroke off at shallow depths andsank into the mantle, whichallowed asthenosphere to risethrough the tear to shallow depths,adiabatically melt, and enter theoverlying lithospheric mantle andlower crust where it formed com-posite plutonic complexes of the99–86 Ma La Posta suite. The shal-low break-off created a narroworogen because little of the lower

plate was subducted.5. Plutons of the La Posta suite were

emplaced during a period of majorexhumation, which reflects therebound of the lower plate follow-ing slab break-off.

6. The switchover from flysch tomolasse in basins to the west ofthe batholith occurred during theearly Cenomanian and it reflectedthe rapid uplift and erosion of therising orogenic welt following slabfailure.

7. Shallow slab break-off during the100 Ma collision provides a simpleand actualistic model that tiestogether the voluminous magma-tism of the La Posta suite, the nar-row orogen, and its rapid exhuma-tion.

8. Although they have similar com-positions and are ultimatelyderived from asthenosphericsource material, slab-failure mag-matism appears to form at greaterdepths than does arc magmatismand is governed by melting in thepresence of garnet as opposed tomantle-derived magmas of arcs,which appear to form in thespinel–plagioclase regime.

9. We note similar relations in otherCordilleran batholiths such as theSierra Nevada and suggest thatpaired batholiths might generallyrepresent both pre-collisional arcand syn- to post-collisional slabfailure magmatism.

10. Arcs are dominantly extensionaland are not regions of thickenedcrust unless they are built on oldercollisional terranes.

11. Arcs are not generally deformedunless they collide with anotherblock. It is collision and attemptedsubduction of the lower plate thatthickens the crust.

ACKNOWLEDGEMENTSWe are pleased to present this paper onbatholiths in the Paul F. Hoffman vol-ume, for while many think of Paul forSnowball Earth or United Plates ofAmerica, most are unaware that hemapped a 2º sheet in the northernGreat Bear batholith of Wopmay oro-gen in the mid-1970s, and it was thatwork which provided the stimulus forthe senior author to study the magmat-ic rocks there for his dissertation. Con-

nections often run deep in geology andPaul held the prestigious Sturgis Hoop-er chair at Harvard University for 15years whereas another Canadian, Regi-nald A. Daly, author of Igneous Rocksand their Origin and who recognized thatbatholiths were emplaced in mountainbelts, was Sturgis Hooper Professorfrom 1912–1942.

Dave Kimbrough, KeeganSchmidt, Helge Alsleben, Paul Wet-more, Wayne Premo, and Vicki Lan-genheim generously shared importantpreprints with us as we wrote the initialdraft of this paper before publicationof GSA Memoir 211 on the PeninsularRanges batholith. We are especiallygrateful to Schmidt and Langenheim,as well as Jade Star Lackey, who pro-vided vector versions of their figuresso that we could readily modify themto suit our needs and include themhere. Ongoing discussions with TimLawton clarified many questions onthe geology of Sonora and the south-western US. Doug Morton helpedlocate geochemical samples so that wewere able to remove samples collectedfrom contact or highly altered zones.We thank C-T. Lee for helping us bet-ter understand the ins and outs of theSierran mantle xenoliths. KeeganSchmidt, Doug Morton, and Tim Law-ton reviewed earlier versions of themanuscript. Reviews by A. Zagorevskiand J.B Murphy were helpful. The sen-ior author especially thanks SamBowring for 30+ years of stimulatingdiscussions about arcs and batholithicterranes. This is more self-fundedresearch. NRCan contribution20140247.

REFERENCESAbbot, P.L., and Smith, T.E., 1989, Sonora,

Mexico, source for the Eocene PowayConglomerate of southern California:Geology, v. 17, p. 329–332,http://dx.doi.org/10.1130/0091-7613(1989)017<0329:SMSFTE>2.3.CO;2.

Åberg, G., Aguirre, L., Levi, B., Nyström,J.O., and Aguirre, L., 1984, Spreading-subsidence and generation of ensialicmarginal basins: an example from theearly Cretaceous of central Chile, inKokelaar, B.P., and Howells, M.F., eds.,Marginal Basin Geology: Volcanic andAssociated Sedimentary and TectonicProcesses in Modern and AncientMarginal Basins: Geological Society,


London, Special Publications, v. 16, p.185–193, http://dx.doi.org/10.1144/GSL.SP.1984.016.01.14.

Ague, J.J., and Brimhall, G.H., 1988, Mag-matic arc asymmetry and distributionof anomalous plutonic belts in thebatholiths of California: Effects ofassimilation, crustal thickness, anddepth of crystallization: GeologicalSociety of America Bulletin, v. 100, p.912–927, http://dx.doi.org/10.1130/0016-7606(1988)100<0912:MAAADO>2.3.CO;2.

Allègre, C.J., and Othman, D.B., 1980,Nd–Sr isotopic relationship in grani-toid rocks and continental crust devel-opment: a chemical approach to oro-genesis: Nature, v. 286, p. 335–342,http://dx.doi.org/10.1038/286335a0.

Allen, C.R., Silver, L.T., and Stehil, F.G.,1960, Agua Blanca fault—a majortransverse structure of northern BajaCalifornia, Mexico: Geological Societyof America Bulletin, v. 71, p. 467–482,http://dx.doi.org/10.1130/0016-7606(1960)71[467:ABFMTS]2.0.CO;2.

Allison, F.C., 1974, The type Alisitos for-mation (Cretaceous, Aptian–Albian) ofBaja California and its bivalve fauna, inGastil, G., and Lillegraven, J., eds.,Geology of Peninsular California:AAPG-SEPM-SEG Pacific Section49th Annual Meeting Field TripGuidebook, p. 20–59.

Allmendinger, R.W., Jordan, T.E., Kay,S.M., and Isacks, B.L., 1997, The evo-lution of the Altiplano-Puna plateauof the central Andes: Annual Reviewof Earth and Planetary Science, v. 25,p. 139–174, http://dx.doi.org/10.1146/annurev.earth.25.1.139.

Alsleben, H., Wetmore, P.H., Schmidt,K.L., Paterson, S.R., and Melis, E.A.,2008, Complex deformation duringarc–continent collision: Quantifyingfinite strain in the accreted Alisitosarc, Peninsular Ranges batholith, BajaCalifornia: Journal of Structural Geol-ogy, v. 30, p. 220–236,http://dx.doi.org/10.1016/j.jsg.2007.11.001.

Alsleben, H., Wetmore, P.H., Gehrels,G.E., and Paterson, S.R., 2012, Detri-tal zircon ages in Palaeozoic andMesozoic basement assemblages ofthe Peninsular Ranges batholith, BajaCalifornia, Mexico: constraints fordepositional ages and provenance:International Geology Review, v. 54, p.93–110, http://dx.doi.org/10.1080/00206814.2010.509158.

Altunkaynak, Ş., Dilek, Y., Genç, C.Ş.,Sunal, G., Gertisser, R., Furnes, H.,Foland, K.A., and Yang, J., 2012, Spa-tial, temporal and geochemical evolu-

tion of Oligo–Miocene granitoid mag-matism in western Anatolia, Turkey:Gondwana Research, v. 21, p.961–986, http://dx.doi.org/10.1016/j.gr.2011.10.010.

Alvarez, W., 2010, Protracted continentalcollisions argue for continental platesdriven by basal traction: Earth andPlanetary Science Letters, v. 296, p.434–442, http://dx.doi.org/10.1016/j.epsl.2010.05.030.

Anderson, C.I., 1991, Zircon uranium–leadisotopic ages of the Santiago PeakVolcanics and spatially related plutonsof the Peninsular Ranges batholith:Unpublished MSc thesis, San DiegoState University, San Diego, CA, 111p.

Andersen, T.B., Jamtveit, B., Dewey, J.F.,and Swensson, E., 1991, Subductionand eduction of continental crust:major mechanisms during continent-continent collision and orogenicextensional collapse, a model based onthe south Norwegian Caledonides:Terra Nova, v. 3, p. 303–310,http://dx.doi.org/10.1111/j.1365-3121.1991.tb00148.x.

Anderson, T.H., and Silver, L.T., 2005, TheMojave-Sonora megashear—Field andanalytical studies leading to the con-ception and evolution of the hypothe-sis, in Anderson, T.H., Nourse, J.A.,McKee, J.W., and Steiner, M.B., eds.,The Mojave-Sonora MegashearHypothesis: Development, Assess-ment and Alternatives: GeologicalSociety of America Special Papers, v.393, p. 1–50, http://dx.doi.org/10.1130/0-8137-2393-0.1.

Anderson, T.H., Rodríguez-Castañeda, J.L.,and Silver, L.T., 2005, Jurassic rocks inSonora, Mexico: Relations to theMojave-Sonora megashear and itsinferred northwestward extension, inAnderson, T.H., Nourse, J.A., McKee,J.W., and Steiner, M.B., eds., TheMojave-Sonora Megashear Hypothe-sis: Development, Assessment, andAlternatives: Geological Society ofAmerica Special Papers, v. 393, p.51–95, http://dx.doi.org/10.1130/0-8137-2393-0.51.

Atherton, M.P., and Ghani, A.A., 2002,Slab breakoff: A model for Caledon-ian, Late Granite syn-collisional mag-matism in the orthotectonic (meta-morphic) zone of Scotland and Done-gal, Ireland: Lithos, v. 62, p. 65–85,http://dx.doi.org/10.1016/S0024-4937(02)00111-1.

Atherton, M.P., Warden, V., and Sanderson,L.M., 1985, The Mesozoic marginalbasin of central Peru: A geochemicalstudy of within-plate-edge volcanism,

in Pitcher, W.S., Atherton, M.P., Cob-bing, E.J., and Beckinsale, R.B., eds.,Magmatism at a Plate Edge, the Peru-vian Andes: Blackie Halstead Press,Glasgow, p. 47–58, http://dx.doi.org/10.1007/978-1-4899-5820-4_6.

Austermann, J., Ben-Avraham, Z., Bird, P.,Heidbach, O., Schubert, G., and Stock,J.M., 2011, Quantifying the forcesneeded for the rapid change of Pacificplate motion at 6 Ma: Earth and Plan-etary Science Letters, v. 307, p.289–297, http://dx.doi.org/10.1016/j.epsl.2011.04.043.

Avouac, J.P., and Burov, E.B., 1996, Ero-sion as a driving mechanism of intra-continental mountain growth: Journalof Geophysical Research, v. 101, p.17747–17769, http://dx.doi.org/10.1029/96JB01344.

Babist, J., Handy, M.R., Konrad-Schmolke,M., and Hammerschmidt, K., 2006,Precollisional, multistage exhumationof subducted continental crust: TheSesia Zone, western Alps: Tectonics, v.25, TC6008, http://dx.doi.org/10.1029/2005TC001927.

Baird, A.K., and Miesch, A.T., 1984,Batholithic rocks of southern Califor-nia – a model for the petrochemicalnature of their source materials: U.S.Geological Survey Professional Paper1284, 42 p.

Baird, A.K., Baird, K.W., and Welday, E.E.,1979, Batholithic rocks of the north-ern Peninsular and Transverse Ranges,southern California: chemical compo-sition and variation, in Abbott, P.L.,and Todd, V.R., eds., Mesozoic Crys-talline Rocks: California State Univer-sity, Department of Geological Sci-ences, San Diego, CA, p. 111–132.

Baldwin, S.L., and Harrison, T.M., 1989,Geochronology of blueschists fromwest-central Baja California and thetiming of uplift in subduction com-plexes: The Journal of Geology, v. 97,p. 149C163,http://dx.doi.org/10.1086/629291.

Baldwin, S.L., and Harrison, T.M., 1992,The P-T-t history of blocks in serpen-tinite- matrix mélange, west-centralBaja California: Geological Society ofAmerica Bulletin, v. 104, p. 18–31,http://dx.doi.org/10.1130/0016-7606(1992)104<0018:TPTTHO>2.3.CO;2.

Barker, F., 1979, Trondhjemite: definition,environment and hypothesis of origin,in Barker, F., ed. Trondhjemite, dacites,and related rocks: New York, Elsevier,p. 1–12.

Barker, F., and Arth, J.G., 1976, Generationof trondhjemite-tonalitic liquids andArchean bimodal trondhjemite-basalt

440

suites: Geology, v. 4, p. 596–600,http://dx.doi.org/10.1130/0091-7613(1976)4<596:GOTLAA>2.0.CO;2.

Barthelmy, D.A., 1975, Geology of ElArco-Calmallí area, Baja California,México: Unpublished MSc thesis, SanDiego State University, San Diego,CA, 130 p.

Bateman, P.C., 1981, Geologic and geo-physical constraints on models for theorigin of the Sierra Nevada batholith,California, in Ernst, W.G., ed., TheGeotectonic Development of Califor-nia, Rubey Volume 1: Prentice-Hall,Englewood Cliffs, NJ, p. 71–86.

Bateman, P.C., 1992, Plutonism in the Cen-tral Part of the Sierra NevadaBatholith: U.S. Geological Survey Pro-fessional Paper 1483, 186 p.

Bateman, P.C., and Wahrhaftig, C., 1966,Geology of the Sierra Nevada, inBaily, E.H., ed., Geology of NorthernCalifornia: California Division ofMines and Geology Bulletin 190, p.107–172.

Bateman, P.C., Clark, L.D., Huber, N.K.,Moore, J.G., and Rinehart, C.D., 1963,The Sierra Nevada Batholith—A Syn-thesis of Recent Work across the Cen-tral Part: U.S. Geological Survey Pro-fessional Paper 414-D, 46 p.

Bateman, P.C., Busaca, A.J., and Sawka,W.N., 1983, Cretaceous deformationin the western foothills of the SierraNevada, California: Geological Societyof America Bulletin, v. 94, p. 30–42,http://dx.doi.org/10.1130/0016-7606(1983)94<30:CDITWF>2.0.CO;2.

Bateman, P.C., Dodge, F.C.W., and Kistler,R.W., 1991, Magnetic susceptibilityand relation to initial 87Sr/86Sr forgranitoids of the central SierraNevada, California: Journal of Geo-physical Research, v. 96, p.19555–19568, http://dx.doi.org/10.1029/91JB02171.

Bennett, V.C., and DePaolo, D.J., 1987,Proterozoic crustal history of thewestern United States as determinedby neodymium isotopic mapping:Geological Society of America Bul-letin, v. 99, p. 674–685,http://dx.doi.org/10.1130/0016-7606(1987)99<674:PCHOTW>2.0.CO;2.

Berry, K.D., and Miller, P.L., 1984, Meso-zoic biostratigraphy, Vizcaino Peninsu-la and Cedros Island, Baja CaliforniaSur, Mexico, in Frizzell V.A., Jr., ed.,Geology of the Baja California Penin-sula: Society of Economic Mineralo-gists and Paleontologists, Pacific Sec-tion, v. 39, p. 67–87.

Bilodeau, W.L., Kluth, C.F., and Vedder,L.K., 1987, Regional stratigraphic, sed-imentologic, and tectonic relationshipsof the Glance Conglomerate in south-eastern Arizona, in Dickinson, W.R.,and Klute, M.F., eds., Mesozoic rocksof southern Arizona adjacent areas:Arizona Geological Society, Digest 18,p. 229–256.

Bissig, T., Mortensen, J.K., Tosdal, R.M.,and Hall, B.V., 2008, The rhyolite-hosted volcanogenic massive sulfidedistrict of Cuale, Guerrero Terrane,west-central Mexico: Silver-rich, basemetal mineralization emplaced in ashallow marine continental margin set-ting: Economic Geology, v. 103, p.141–159, http://dx.doi.org/10.2113/gsecongeo.103.1.141.

Bohannon, R.G., and Geist, E., 1998,Upper crustal structure and Neogenetectonic development of the Califor-nia continental borderland: GeologicalSociety of America Bulletin, v. 110, p.779–800, http://dx.doi.org/10.1130/0016-7606(1998)110<0779:UCSANT>2.3.CO;2.

Boles, J.R., 1986, Mesozoic sedimentaryrocks in the Vizcaino Peninsula - Islade Cedros area, Baja California, Mexi-co, in Abbott, P.L., ed., CretaceousStratigraphy, Western North America:Pacific Section, Society of EconomicPaleontologists and Mineralogists, p.63–79.

Bottjer, D.J., and Link, M.H., 1984, A syn-thesis of Late Cretaceous southernCalifornia and northern Baja Califor-nia paleogeography, in Crouch, J.K.,and Bachman, S.B., eds., Tectonics andsedimentation along the Californiamargin: Society of Economic Paleon-tologists and Mineralogists, PacificSection, v. 38, p. 171–188.

Brown, A.R., 1980, Limestone deposits ofthe Desert Divide, San Jacinto Moun-tains, California, in Fife, D.L., andBrown, A.R., eds., Geology and miner-al wealth of the California desert:Santa Ana, California: South CoastGeological Society, p. 284–293.

Brown, A.R., 1981, Structural history ofthe metamorphic, granitic, and cata-clastic rocks in the southeastern SanJacinto Mountains, in Brown, A.R.,and Ruff, R.W., eds., Geology of theSan Jacinto Mountains: South CoastGeological Society, California AnnualField Trip Guidebook, v. 9, p.100–138.

Buddington, A.F., 1927, Coast Range intru-sives of southeastern Alaska: Journalof Geology, v. 35, p. 224–246,http://dx.doi.org/10.1086/623404.

Buesch, D.C., 1984, The depositional envi-

ronment and subsequent metamor-phism of the Santiago Peak volcanicrocks, Camp Pendleton, California:Unpublished MSc thesis, CaliforniaState University, Los Angeles, CA, 113p.

Burbank, D.W., 2002, Rates of erosion andtheir implications for exhumation:Mineralogical Magazine, v. 66, p.25–52, http://dx.doi.org/10.1180/0026461026610014.

Burchfiel, B.C., and Davis, G.A., 1972,Structural framework and evolution ofthe southern part of the Cordilleranorogen, western United States: Ameri-can Journal of Science, v. 272, p.97–118, http://dx.doi.org/10.2475/ajs.272.2.97.

Burk, C.A., 1965, Geology of the AlaskanPeninsula–island arc and continentalmargin (Part 1): Geological Society ofAmerica Memoirs, v. 99, 265 p.,http://dx.doi.org/10.1130/MEM99-p1.

Burkart, B., and Self, S., 1985, Extensionand rotation of crustal blocks innorthern Central America and effecton the volcanic arc: Geology, v. 13, p.22–26, http://dx.doi.org/10.1130/0091-7613(1985)13<22:EAROCB>2.0.CO;2.

Busby, C., 2004, Continental growth atconvergent margins facing large oceanbasins: a case study from Mesozoicconvergent-margin basins of Baja Cal-ifornia, Mexico: Tectonophysics, v.392, p. 241–277, http://dx.doi.org/10.1016/j.tecto.2004.04.017.

Busby, C., 2012, Extensional and transten-sional continental arc basins: Casestudies from the southwestern U.S.and Mexico, in Busby, C., and Azor,A., eds., Recent Advances in Tectonicsof Sedimentary Basins: London,Wiley-Blackwell, p. 382–404.

Busby, C., Smith, D., Morris, W., and Fack-ler-Adams, B., 1998, Evolutionarymodel for convergent margins facinglarge ocean basins: Mesozoic Baja Cal-ifornia, Mexico: Geology, v. 26, p.227–230, http://dx.doi.org/10.1130/0091-7613(1998)026<0227:EMFCMF>2.3.CO;2.

Busby, C.J., Adams, B.F., Mattinson, J., andDeoreo, S., 2006, View of an intactoceanic arc, from surficial to meso-zonal levels: Cretaceous Alisitos arc,Baja California: Journal of Volcanolo-gy and Geothermal Research, v. 149,p. 1–46, http://dx.doi.org/10.1016/j.jvolgeores.2005.06.009.

Busby-Spera, C.J., 1988a, Evolution of aMiddle Jurassic back-arc basin, CedrosIsland, Baja California: Evidence froma marine volcaniclastic apron: Geolog-


ical Society of America Bulletin, v.100, p. 218–233, http://dx.doi.org/10.1130/0016-7606(1988)100<0218:EOAMJB>2.3.CO;2.

Busby-Spera, C.J., 1988b, Speculative tec-tonic model for the early Mesozoic arcof the southwest Cordilleran UnitedStates: Geology, v. 16, p. 1121–1125,http://dx.doi.org/10.1130/0091-7613(1988)016<1121:STMFTE>2.3.CO;2.

Busby-Spera, C.J., and Boles, J.R., 1986,Sedimentation and subsidence styles ina Cretaceous forearc basin, southernVizcaino Peninsula, Baja California,Mexico, in Abbott, P.L., ed., Creta-ceous Stratigraphy, Western NorthAmerica: Pacific Section, Society ofEconomic Paleontologists and Miner-alogists, p. 79–90.

Busch, D.A., and Gavela, A., 1978, Stratig-raphy and structure of Chicontepecturbidites, southeastern Tampico-Mis-antla basin, Mexico: American Associ-ation of Petroleum Geologists, v. 62,p. 235–246.

Cameron, C.S., 1982, Stratigraphy and sig-nificance of the Upper PrecambrianBig Bear Group, in Cooper, J.D., Trox-el, B., and Wright, L., eds., Geology ofSelected Areas of the San BernardinoMountains and Western MojaveDesert, and Southern Great Basin ofCalifornia: Geological Society ofAmerica, Cordilleran Section, FieldTrip, no. 9, p. 5–20.

Campbell, M., and Crocker, J., 1993, Geol-ogy west of the Canal de Las Ballenas,Baja California, Mexico, in Gastil,R.G., and Miller, R.H., eds., The Pre-batholithic Stratigraphy of PeninsularCalifornia: Geological Society ofAmerica Special Papers, v. 279, p.61–76, http://dx.doi.org/10.1130/SPE279-p61.

Carminati, E., Wortel, M.J.R., Spakman, W.,and Sabadini, R., 1998, The role ofslab detachment processes in theopening of the western-centralMediterranean basins: some geologicaland geophysical evidence: Earth andPlanetary Science Letters, v. 160, p.651–665, http://dx.doi.org/10.1016/S0012-821X(98)00118-6.

Centeno-García, E., Corona-Chávez, P.,Talavera-Mendoza, O., and Iriondo,A., 2003, Geologic and tectonic evolu-tion of the western Guerrero ter-rane—A transect from Puerto Vallartato Zihuatanejo, Mexico, in Alcayde,M., and Gómez-Caballero, A., eds.,Geologic Transects across CordilleranMexico: Puerto Vallarta, Jalisco, Mexi-co: Guidebook for the field trips ofthe 99th Geological Society of Ameri-

ca Cordilleran Section Annual Meet-ing, April 4–7, 2003, UniversidadNacional Autónoma de México, Insti-tuto de Geología, Special Paper 1, p.201–228.

Centeno-García, E., Guerrero-Suastegui,M., and Talavera-Mendoza, O., 2008,The Guerrero Composite Terrane ofwestern Mexico: Collision and subse-quent rifting in a supra-subductionzone, in Draut, A.E., Clift, P.D., andScholl, D.W., eds., Formation andApplications of the SedimentaryRecord in Arc Collision Zones: Geo-logical Society of America SpecialPapers, v. 436, p. 279–308,http://dx.doi.org/10.1130/2008.2436(13).

Centeno-García, E., Busby, C., Busby, M.,and Gehrels, G., 2011, Evolution ofthe Guerrero composite terrane alongthe Mexican margin, from extensionalfringing arc to contractional continen-tal arc: Geological Society of AmericaBulletin, v. 123, p. 1776–1797,http://dx.doi.org/10.1130/B30057.1.

Chapman, A.D., Saleeby, J.B., Wood, D.J.,Piasecki, A., Kidder, S., Ducea, M.N.,and Farley, K.A., 2012, Late Creta-ceous gravitational collapse of thesouthern Sierra Nevada batholith, Cal-ifornia: Geosphere, v. 8, p. 314–341,http://dx.doi.org/10.1130/GES00740.1.

Chappell, B.W., and Stephens, W.E., 1988,Origin of infracrustal (I-type) granitemagmas: Transactions of the RoyalSociety of Edinburgh: Earth Sciences,v. 79, p. 71–86, http://dx.doi.org/10.1017/S0263593300014139.

Chappell, B.W., and White, A.J.R., 1992, I-and S-type granites in the LachlanFold Belt: Transactions of the RoyalSociety of Edinburgh: Earth Sciences,v. 83, p. 1–26, http://dx.doi.org/10.1017/S0263593300007720.

Chatelain, J.-L., Molnar, P., Prévot, R., andIsacks, B., 1992, Detachment of partof the downgoing slab and uplift ofthe New Hebrides (Vanuatu) Islands:Geophysical Research Letters, v. 19, p.1507–1510, http://dx.doi.org/10.1029/92GL01389.

Chávez Cabello, G., Molina Garza, R., Del-gado Argote, L., Contreras Flores, R.,Ramírez, E., Ortega Rivera, A., Böh-nel, H., and Lee, J., 2006, Geology andpaleomagnetism of El Potrero pluton,Baja California: Understanding criteriafor timing of deformation and evi-dence of pluton tilt during batholithgrowth: Tectonophysics, v. 424, p.1–17, http://dx.doi.org/10.1016/j.tecto.2006.03.018.

Chen, J.H., and Tilton, G.R., 1991, Appli-

cations of lead and strontium isotopicrelationships to the petrogenesis ofgranitoid rocks, central Sierra Nevadabatholith, California: Geological Socie-ty of America Bulletin, v. 103, p.439–447, http://dx.doi.org/10.1130/0016-7606(1991)103<0439:AOLASI >2.3.CO;2.

Chen, W.-P., and Brudzinski, M.R., 2001,Evidence for a large-scale remnant ofsubducted lithosphere beneath Fiji:Science, v. 292, p. 2475–2479,http://dx.doi.org/10.1126/sci-ence.292.5526.2475.

Chin, E.J., Lee, C.-T.A., Luffi, P., and Tice,M., 2012, Deep lithospheric thicken-ing and refertilization beneath conti-nental arcs: Case study of the P, T andcompositional evolution of peridotitexenoliths from the Sierra Nevada, Cal-ifornia: Journal of Petrology, v. 53, p.477–511, http://dx.doi.org/10.1093/petrology/egr069.

Chin, E.J., Lee, C.-T.A., Tollstrup, D.L.,Xie, L., Wimpenny, J.B., and Yin, Q.-Z., 2013, On the origin of hotmetasedimentary quartzites in thelower crust of continental arcs: Earthand Planetary Science Letters, v. 361,p. 120–133, http://dx.doi.org/10.1016/j.epsl.2012.11.031.

Christiansen, M.N., 1966, Late Cenozoiccrustal movements in the SierraNevada of California: GeologicalSociety of America Bulletin, v. 77, p.163–182, http://dx.doi.org/10.1130/0016-7606(1966)77[163:LCCMIT]2.0.CO;2.

Chung, S.-L., Wang, K.-L., Crawford, A.J.,Kamenetsky, V.S., Chen, C.-H., Lan,C.-Y., and Chen, C.-H., 2001, High-Mg potassic rocks from Taiwan: impli-cations for the genesis of orogenicpotassic lavas: Lithos, v. 59, p.153–170, http://dx.doi.org/10.1016/S0024-4937(01)00067-6.

Chung, S.-L., Liu, D., Ji, J., Chu, M.-F., Lee,H.-Y., Wen, D.-J., Lo, C.-H., Lee, T.-Y.,Qian, Q., and Zhang, Q., 2003,Adakites from continental collisionzones: Melting of thickened lowercrust beneath southern Tibet: Geolo-gy, v. 31, p. 1021–1024,http://dx.doi.org/10.1130/G19796.1.

Clausen, B.L., Morton, D.M., Kistler, R.W.,and Lee, C.-T.A., 2014, Low-initial-Srfelsic plutons of the northwesternPeninsular Ranges batholith, southernCalifornia, and the role of mafic-felsicmagma mixing in continental crustformation, in Morton, D.M., andMiller, F.K., eds., Peninsular RangesBatholith, Baja California and South-ern California: Geological Society ofAmerica Memoirs, v. 211, p. 317–344,

442

http://dx.doi.org/10.1130/2014.1211(08).

Clemens Knott, D., 1992, Geologic andisotopic investigations of the EarlyCretaceous Sierra Nevada batholith,Tulare Co., CA, and the Ivrea Zone,NW Italian Alps: Examples of inter-action between mantle-derived magmaand continental crust: UnpublishedPhD thesis, California Institute ofTechnology, Pasadena, CA, 349 p.

Cloos, M., Sapiie, B., van Ufford, A.Q.,Weiland, R.J., Warren, P.Q., andMcMahon, T.P., 2005, CollisionalDelamination in New Guinea: TheGeotectonics of Subducting SlabBreakoff: Geological Society of Amer-ica Special Papers, v. 400, 51 p.,http://dx.doi.org/10.1130/2005.2400.

Coats, R.R., 1962, Magma type and crustalstructure in the Aleutian Arc, in Mac-donald, G.A., and Kuno, H., eds., TheCrust of the Pacific Basin: AmericanGeophysical Union, GeophysicalMonograph Series, v. 6, p. 92–109,http://dx.doi.org/10.1029/GM006p0092.

Cobbing, E.J., 1978, The Andean geosyn-cline in Peru, and its distinction fromAlpine geosynclines: Journal of theGeological Society, v. 135, p. 207–218,http://dx.doi.org/10.1144/gsjgs.135.2.0207.

Cobbing, E.J., 1985, The tectonic setting ofthe Peruvian Andes, in Pitcher, W.S.,Atherton, M.P., Cobbing, E.J., andBeckinsale, R.B., eds., Magmatism at aPlate Edge, the Peruvian Andes:Blackie Halstead Press, Glasgow, p.3–12, http://dx.doi.org/10.1007/978-1-4899-5820-4_1.

Coleman, D.S., and Glazner, A.F., 1998,The Sierra Crest magmatic event:Rapid formation of juvenile crust dur-ing the Late Cretaceous in California,in Ernst, W.G., and Nelson, C.A., eds.,Integrated Earth and EnvironmentalEvolution of the Southwestern UnitedStates: The Clarence A. Hall, Jr. Vol-ume: Geological Society of America,International book series, v. 1, p.253–272.

Coleman, D.S., Glazner, A.F., and Frost,T.P., 1992, Evidence from the Lamar-ck Granodiorite for rapid Late Creta-ceous crust formation in California:Science, v. 258, p. 1924–1926,http://dx.doi.org/10.1126/sci-ence.258.5090.1924.

Crawford, M.L., Crawford, W.A., andGehrels, G.E., 2000, Terrane assemblyand structural relationships in the east-ern Prince Rupert Quadrangle, BritishColumbia, in Stowell, H.H., andMcClelland, W.C., eds., Tectonics of

the Coast Mountains, SoutheasternAlaska and British Columbia: Geologi-cal Society of America Special Papers,v. 343, p. 1–21, http://dx.doi.org/10.1130/0-8137-2343-4.1.

Crouch, J.K., and Suppe, J., 1993, LateCenozoic tectonic evolution of theLos Angeles Basin and inner Califor-nia borderland: A model for corecomplex-like crustal extension: Geo-logical Society of America Bulletin, v.105, p. 1415–1434, http://dx.doi.org/10.1130/0016-7606(1993)105<1415:LCTEOT>2.3.CO;2.

Daly, R.A., 1912, Geology of the NorthAmerican Cordillera at the forty-ninthparallel: Geological Survey of CanadaMemoir 38, 856 p.,http://dx.doi.org/10.4095/100513.

Davies, J.H., 2002, Earth Science: Breakingplates: Nature, v. 418, p. 736– 737,http://dx.doi.org/10.1038/418736a.

Davies, J.H., and von Blanckenburg, F.,1995, Slab breakoff: A model of litho-sphere detachment and its test in themagmatism and deformation of colli-sional orogens: Earth and PlanetaryScience Letters, v. 129, p. 85–102,http://dx.doi.org/10.1016/0012-821X(94)00237-S.

Davis, J.W., Coleman, D.S., Gracely, J.T.,Gaschnig, R., and Stearns, M., 2012,Magma accumulation rates and ther-mal histories of plutons of the SierraNevada batholith, CA: Contributionsto Mineralogy and Petrology, v. 163, p.449–465, http://dx.doi.org/10.1007/s00410-011-0683-7.

Day, H.W., and Bickford, M.E., 2004, Tec-tonic setting of the Jurassic Smartvilleand Slate Creek complexes, northernSierra Nevada, California: GeologicalSociety of America Bulletin, v. 116, p.1515–1528,http://dx.doi.org/10.1130/B25416.1.

de Boorder, H., Spakman, W., White, S.H.,and Wortel, M.J.R., 1998, Late Ceno-zoic mineralization, orogenic collapseand slab detachment in the EuropeanAlpine Belt: Earth and Planetary Sci-ence Letters, v. 164, p. 569–575,http://dx.doi.org/10.1016/S0012-821X(98)00247-7.

DeCelles, P.G., Ducea, M.N., Kapp, P., andZandt, G., 2009, Cyclicity in Cordiller-an orogenic systems: Nature Geo-science, v. 2, p. 251–257,http://dx.doi.org/10.1038/ngeo469.

Defant, M.J., and Drummond, M.S., 1990,Derivation of some modern arc mag-mas by melting of young subductedlithosphere: Nature, v. 347, p.662–665,http://dx.doi.org/10.1038/347662a0.

DePaolo, D.J., 1981, A neodymium and

strontium isotopic study of the Meso-zoic calc-alkaline granitic batholiths ofthe Sierra Nevada and PeninsularRanges, California: Journal of Geo-physical Research, v. 86, p.10470–10488, http://dx.doi.org/10.1029/JB086iB11p10470.

Dewey, J.F., 2005, Orogeny can be veryshort: Proceedings of the NationalAcademy of Sciences of the UnitedStates of America, v. 102, p.15286–15293, http://dx.doi.org/10.1073/pnas.0505516102.

Dickinson, W.R., and Lawton, T.F., 2001a,Carboniferous to Cretaceous assemblyand fragmentation of Mexico: Geo-logical Society of America Bulletin, v.113, p. 1142–1160, http://dx.doi.org/10.1130/0016-7606(2001)113<1142:CTCAAF >2.0.CO;2.

Dickinson, W.R., and Lawton, T.F., 2001b,Tectonic setting and sandstone petro-facies of the Bisbee basin (USA–Mex-ico): Journal of South American EarthSciences, v. 14, p. 475–504,http://dx.doi.org/10.1016/S0895-9811(01)00046-3.

Dodge, F.C.W., and Bateman, P.C., 1988,Nature and origin of the root of theSierra Nevada: American Journal ofScience, v. 288-A, p. 341–357.

Dokka, R.K., 1984, Fission-trackgeochronologic evidence for Late Cre-taceous mylonitization and Early Pale-ocene uplift in the northeastern Penin-sular Ranges, California: GeophysicalResearch Letters, v. 11, p. 46–49,http://dx.doi.org/10.1029/GL011i001p00046.

Domenick, M.A., Kistler, R.W., Dodge,F.C.W., and Tatsumoto, M., 1983, Ndand Sr isotopic study of crustal andmantle inclusions from the SierraNevada and implications for batholithpetrogenesis: Geological Society ofAmerica Bulletin, v. 94, p. 713–719,http://dx.doi.org/10.1130/0016-7606(1983)94<713:NASISO>2.0.CO;2.

Downs, D.T., Rowland, J.V., Wilson, C.J.N.,Rosenberg, M.D., Leonard, G.S., andCalvert, A.T., 2014, Evolution of theintra-arc Taupo-Reporoa Basin withinthe Taupo Volcanic Zone of NewZealand: Geosphere, v. 10, p. 185–206,http://dx.doi.org/10.1130/GES00965.1.

Drummond, M.S., Defant, M.J., andKepezhinskas, P.K., 1996, Petrogene-sis of slab-derived trondhjemite-tonalite-dacite/adakite magmas: Trans-actions of the Royal Society of Edin-burgh: Earth Sciences, v. 87, p.205–215, http://dx.doi.org/10.1017/S0263593300006611.


du Bray, E.A., John, D.A., Box, S.E.,Vikre,P.G., Fleck, R.J., and Cousens, B.L.,2013, Petrographic and geochemicaldata for Cenozoic volcanic rocks ofthe Bodie Hills, California andNevada: U.S. Geological Survey DataSeries 764, 10 p.

Ducea, M., 2001, The California arc: Thickgranitic batholiths, eclogitic residues,lithospheric-scale thrusting, and mag-matic flare-ups: GSA Today, v. 11, no.11, p. 4–10.

Ducea, M.N., 2002, Constraints on thebulk composition and root founderingrates of continental arcs: A Californiaarc perspective: Journal of Geophysi-cal Research, v. 107, 2304,http://dx.doi.org/10.1029/2001JB000643.

Ducea, M.N., and Barton, M.D., 2007,Igniting flare-up events in Cordilleranarcs: Geology, v. 35, p. 1047–1050,http://dx.doi.org/10.1130/G23898A.1.

Ducea, M.N., and Saleeby J.B., 1998, Theage and origin of a thick mafic-ultra-mafic keel from beneath the SierraNevada batholith: Contributions toMineralogy and Petrology, v. 133, p.169–185, http://dx.doi.org/10.1007/s004100050445.

Ducea, M.N., Lutkov, V., Minaev, V.T.,Hacker, B., Ratschbacher, L., Luffi, P.,Schwab, M., Gehrels, G.E.,McWilliams, M., Vervoort, J., and Met-calf, J., 2003, Building the Pamirs: Theview from the underside: Geology v.31, p. 849–852,http://dx.doi.org/10.1130/G19707.1.

Ducea, M.N., Gehrels, G., Shoemaker, S.,Ruiz, J., and Valencia, V.A., 2004,Geologic evolution of the Xolapacomplex, southern Mexico: Evidencefrom U–Pb zircon geochronology:Geological Society of America Bul-letin, v. 116, p. 1016–1025,http://dx.doi.org/10.1130/B25467.1.

Dunne, G.C., Gulliver, R.M., and Sylvester,A.G., 1978, Mesozoic evolution ofrocks of the White, Inyo, Argus andSlate ranges, eastern California, inHowell, D.G., and McDougall, K.A.,eds., Mesozoic Paleogeography of theWestern United States: Society ofEconomic Paleontologists and Miner-alogists, Pacific Section, Pacific CoastPaleogeography Symposium 2, p.189–207.

Duretz, T., and Gerya, T.V., 2013, Slabdetachment during continental colli-sion: Influence of crustal rheologyand interaction with lithosphericdelamination: Tectonophysics, v. 602,p. 124–140, http://dx.doi.org/10.1016/j.tecto.2012.12.024.

Duretz, T., Gerya, T.V., and May, D.A.,2011, Numerical modelling of sponta-neous slab breakoff and subsequenttopographic response: Tectonophysics,v. 502, p. 244–256, http://dx.doi.org/10.1016/j.tecto.2010.05.024.

Duretz, T., Schmalholz, S.M., and Gerya,T.V., 2012, Dynamics of slab detach-ment: Geochemistry, Geophysics,Geosystems, v. 13, Q03020,http://dx.doi.org/10.1029/2011GC004024.

Eguiliz de Antuñano, S., Aranda Garcia,M., and Marrett, R., 2000, Tectónicade la Sierra Madre Oriental, Mexico:Boletín del Instituto de Geología, Uni-versidad Nacional Autónoma de Méxi-co, v. 53, p. 1–26.

Ely, K.S., and Sandiford, M., 2010, Seismicresponse to slab rupture and variationin lithospheric structure beneath theSavu Sea, Indonesia: Tectonophysics,v. 483, p. 112–124, http://dx.doi.org/10.1016/j.tecto.2009.08.027.

Engel, A.E.J., and Schultejann, P.A., 1984,Late Mesozoic and Cenozoic tectonichistory of south-central California:Tectonics, v. 3, p. 659–675,http://dx.doi.org/10.1029/TC003i006p00659.

Erlich, E.N., 1968, Recent movements andQuaternary volcanic activity within theKamchatka Territory: Pacific Geology,v. 1, p. 23–39.

Erlich, E.N., 1979, Recent structure ofKamchatka and position of Quater-nary volcanoes: Bulletin Vol-canologique, v. 42, p. 13–42.

Espinoza, I., Iriondo, A., Primo, W., Paz,F., and Valencia, M., 2003, Geochem-istry and SHRIMP U–Pb zircongeochronology of anorthositic rocksat Sierra El Tecolote in the Caborcablock, northwestern Sonora, Mexico(abstract): Geological Society ofAmerica Abstracts with Programs, v.35, no. 4, p. 84.

Farmer, G.L., Bowring, S.A., Matzel, J.,Maldonado, G.E., Fedo, C., andWooden, J.L., 2005, PaleoproterozoicMojave Province in northwesternMexico? Isotopic and U–Pb zircongeochronologic studies of Precambri-an and Cambrian crystalline and sedi-mentary rocks, Caborca, Sonora, inAnderson, T.H., Nourse, J.A., McKee,J.W., and Steiner, M.B., eds., TheMojave-Sonora Megashear Hypothe-sis: Development, Assessment andAlternatives: Geological Society ofAmerica Special Papers, v. 393, p.183–198, http://dx.doi.org/10.1130/0-8137-2393-0.183.

Farquharson, P.T., 2004, Geology of theRancho San Marcos Dike Swarm, Baja

California, Mexico: Unpublished MScthesis, San Diego State University, SanDiego, CA, 79 p.

Ferrari, L., 2004, Slab detachment controlon mafic volcanic pulse and mantleheterogeneity in central Mexico: Geol-ogy, v. 32, p. 77–80,http://dx.doi.org/10.1130/G19887.1.

Fife, D.L., Minch, J.A., and Crampton, P.J.,1967, Late Jurassic age of the SantiagoPeak volcanics, California: GeologicalSociety of America Bulletin, v. 78, p.299–304, http://dx.doi.org/10.1130/0016-7606(1967)78[299:LJAOTS]2.0.CO;2.

Fliedner, M.M., and Klemperer, S.L., 2000,Crustal structure transition fromoceanic arc to continental arc, easternAleutian Islands and Alaska Peninsula:Earth and Planetary Science Letters, v.179, p. 567–579, http://dx.doi.org/10.1016/S0012-821X(00)00142-4.

Flynn, C.J., 1970, Post-batholithic geologyof the La Gloria-Presa Rodríguezarea, Baja California, Mexico: Geologi-cal Society of America Bulletin, v. 81,p. 1789–1806, http://dx.doi.org/10.1130/0016-7606(1970)81[1789:PGOTLG]2.0.CO;2.

Foley, S., 1992, Vein-plus-wall-rock meltingmechanisms in the lithosphere and theorigin of potassic alkaline magmas:Lithos, v. 28, p. 435–453,http://dx.doi.org/10.1016/0024-4937(92)90018-T.

Fourcade, E., Mendez, J., Azema, J., Bellier,J., Cros, P., Michaud, F., Carballo, M.,and Villagran, J.C., 1994, Dating ofthe settling and drowning of the car-bonate platform, and of the over-thrusting of the ophiolites on theMaya Block during the Mesozoic(Guatemala): Newsletters on Stratigra-phy, v. 30, p. 33–43.

Fries, C., Jr., 1960, Geología del Estado deMorelos y de Partes Adyacentes deMéxico y Guerrero, Región CentralMeridional de México: Boletín delInstituto de Geología, UniversidadNacional Autónoma de México, v. 60,236 p.

Frost, B.R., and Frost, C.D., 2008, A geo-chemical classification for feldspathicigneous rocks: Journal of Petrology, v.49, p. 1955–1969, http://dx.doi.org/10.1093/petrology/egn054.

Frost, B.R., Barnes, C.G., Collins, W.J.,Arculus, R.J., Ellis, D.J., and Frost,C.D., 2001, A geochemical classifica-tion for granitic rocks: Journal ofPetrology, v. 42, p. 2033–2048,http://dx.doi.org/10.1093/petrolo-gy/42.11.2033.

Gastil, R.G., 1975, Plutonic zones in thePeninsular Ranges of southern Cali-

444

fornia and northern Baja California:Geology, v. 3, p. 361–363,http://dx.doi.org/10.1130/0091-7613(1975)3<361:PZITPR>2.0.CO;2.

Gastil, R.G., 1979, A conceptual hypothesisfor the relation of differing tectonicterranes to plutonic emplacement:Geology, v. 7, p. 542–544,http://dx.doi.org/10.1130/0091-7613(1979)7<542:ACHFTR>2.0.CO;2.

Gastil, R.G., 1993, Prebatholithic history ofpeninsular California, in Gastil, R.G.,and Miller, R.H., eds., The Pre-batholithic Stratigraphy of PeninsularCalifornia: Geological Society ofAmerica Special Papers, v. 279,p.145–156, http://dx.doi.org/10.1130/SPE279-p145.

Gastil, R.G., and Girty, M.S., 1993, Areconnaissance U–Pb study of detritalzircon in sandstones of peninsularCalifornia and adjacent areas, in Gastil,R.G., and Miller, R.H., eds., The Pre-batholithic Stratigraphy of PeninsularCalifornia: Geological Society ofAmerica Special Papers, v. 279, p.135–144, http://dx.doi.org/10.1130/SPE279-p135.

Gastil, R.G., and Krummenacher, D., 1977,Reconnaissance geology of coastalSonora between Puerto Lobos andBahia Kino: Geological Society ofAmerica Bulletin, v. 88, p. 189–198,http://dx.doi.org/10.1130/0016-7606(1977)88<189:RGOCSB>2.0.CO;2.

Gastil, R.G., and Miller, R.H., 1981, LowerPaleozoic strata on the Pacific Plate ofNorth America: Nature, v. 292, p.828–830,http://dx.doi.org/10.1038/292828a0.

Gastil, R.G., Phillips, R.P., and Allison,E.C., 1975, Reconnaissance Geologyof the State of Baja California: Geo-logical Society of America Memoirs, v.140, 201 p., http://dx.doi.org/10.1130/MEM140-p1.

Gastil, R.G., Morgan, G., and Krummen-acher, D., 1981, The tectonic historyof Peninsular California and adjacentMexico, in Ernst, W.G., ed., The Geot-ectonic Development of California,Rubey Volume 1: Prentice-Hall,Englewood Cliffs, NJ, p. 284–306.

Gastil, R.G., Diamond, J., Knaack, C.,Walawender, M., Marshall, M., Boyles,C., Chadwick, B., and Erskine, B.,1990, The problem of the magnetite/ilmenite boundary in southern andBaja California, in Anderson, J.L., ed.,The Nature and Origin of CordilleranMagmatism: Geological Society ofAmerica Memoirs, v. 174, p. 19–32,http://dx.doi.org/10.1130/MEM174-

p19.Gastil, R.G., Miller, R., Anderson, P.,

Crocker, J., Campbell, M., Buch, P.,Lothringer, C., Leier-Engelhardt, P.,DeLattre, M., Hoobs, J., and Roldán-Quintana, J., 1991, The relationbetween the Paleozoic strata on oppo-site sides of the Gulf of California, inPérez-Segura, E., and Jacques-Ayala,C., eds., Studies of Sonoran geology:Geological Society of America SpecialPapers, v. 254, p. 7–18,http://dx.doi.org/10.1130/SPE254-p7.

Gastil, R.G., Kimbrough, D.L., Kim-brough, J.M., Grove, M., and Shimizu,M., 2014, The Sierra San Pedro Mártirzoned pluton, Baja California, Mexico,in Morton, D.M., and Miller, F.K., eds.,Peninsular Ranges Batholith, Baja Cal-ifornia and Southern California: Geo-logical Society of America Memoirs, v.211, p. 739–758, http://dx.doi.org/10.1130/2014.1211(24).

Gehrels, G.E., Stewart, J.H., and Ketner,K.B., 2002, Cordilleran-marginquartzites in Baja California – implica-tions for tectonic transport: Earth andPlanetary Science Letters, v. 199, p.201–210, http://dx.doi.org/10.1016/S0012-821X(02)00542-3.

Gehrels, G., Rusmore, M., Woodsworth,G., Crawford, M., Andronicos, C.,Hollister, L., Patchett, J., Ducea, M.,Butler, R., Klepeis, K., Davidson, C.,Friedman, R., Haggart, J., Mahoney,B., Crawford, W., Pearson, D., andGirardi, J., 2009, U–Th–Pbgeochronology of the Coast Moun-tains batholith in north-coastal BritishColumbia: Constraints on age and tec-tonic evolution: Geological Society ofAmerica Bulletin, v. 121, p.1341–1361,http://dx.doi.org/10.1130/B26404.1.

George, P.G., and Dokka, R.K., 1994,Major Late Cretaceous cooling eventsin the eastern Peninsular Ranges, Cali-fornia, and their implications forCordilleran tectonics: Geological Soci-ety of America Bulletin, v. 106, p.903–914, http://dx.doi.org/10.1130/0016-7606(1994)106<0903:MLCCEI>2.3.CO;2.

Germinario, M., 1982, The depositionaland tectonic environments of theJulian schist, Julian, California:Unpublished MSc thesis, San DiegoState University, San Diego, CA, 95 p.

Germinario, M., 1993, The early MesozoicJulian Schist, Julian, California, inGastil, R.G., and Miller, R.H., eds., ThePrebatholithic Stratigraphy of Penin-sular California: Geological Society ofAmerica Special Papers, v. 279, p.

107–118, http://dx.doi.org/10.1130/SPE279-p107.

Goetz, C.W., 1989, Geology of the RanchoEl Rosarito area: Evidence for latestAlbian, east over west, ductile thrust-ing in the Peninsular Ranges: Unpub-lished MSc thesis, San Diego StateUniversity, San Diego, CA, 134 p.

González-Léon, C., and Jacques-Ayala, C.,1988, Estratigrafía de las rocas cretáci-cas del área de Cerro de Oro, SonoraCentral: Boletín de Departmento deUniversidad Sonora, v. 5, p. 1–23.

González-Léon, C.M., Scott, R.W., Löser,H., Lawton, T.F., Robert, E., andValencia, V.A., 2008, Upper Aptian-Lower Albian Mural Formation:stratigraphy, biostratigraphy and depo-sitional cycles on the Sonoran shelf,northern México: CretaceousResearch, v. 29, p. 249–266,http://dx.doi.org/10.1016/j.cre-tres.2007.06.001.

González-León, C.M., Solari, L., Solé, J.,Ducea, M.N., Lawton, T.F., Bernal,J.P., González Becuar, E., Gray, F.,López Martínez, M., and Lozano San-tacruz, R., 2011, Stratigraphy,geochronology, and geochemistry ofthe Laramide magmatic arc in north-central Sonora, Mexico: Geosphere, v.7, p. 1392–1418, http://dx.doi.org/10.1130/GES00679.1.

Gorzolla, Y.R., 1988, Geochemistry andpetrography of the Santiago Peak vol-canics, Santa Margarita and Santa Anamountains, southern California:Unpublished MSc thesis, San DiegoState University, San Diego, CA, 145p.

Greene, D.C., and Schweickert, R.A., 1995,The Gem Lake shear zone: Cretaceousdextral transpression in the NorthernRitter Range pendant, eastern SierraNevada, California: Tectonics, v. 14, p.945–961, http://dx.doi.org/10.1029/95TC01509.

Griffith, R., and Hobbs, J., 1993, Geologyof the southern Sierra Calamajue, BajaCalifornia Norte, Mexico, in Gastil,R.G., and Miller, R.H., eds., The Pre-batholithic Stratigraphy of PeninsularCalifornia: Geological Society ofAmerica Special Papers, v. 279, p.43–60, http://dx.doi.org/10.1130/SPE279-p43.

Gromet, L.P., and Silver, L.T., 1987, REEvariations across the PeninsularRanges Batholith: Implications forbatholithic petrogenesis and crustalgrowth in magmatic arcs: Journal ofPetrology, v. 28, p. 75–125,http://dx.doi.org/10.1093/petrolo-gy/28.1.75.

Grove, M., 1993, Thermal histories of


southern California basement terranes:Unpublished PhD thesis, University ofCalifornia, Los Angeles, CA, 419 p.

Grove, M., Lovera, O., and Harrison, M.,2003, Late Cretaceous cooling of theeast-central Peninsular RangesBatholith (33 degrees N): Relationshipto La Posta pluton emplacement,Laramide shallow subduction, andforearc sedimentation, in Johnson,S.E., Patterson, S.R., Fletcher, J.M.,Girty, G.H., Kimbrough, D.L., andMartín-Barajas, A., eds., Tectonic evo-lution of northwestern Mexico andthe Southwestern USA: GeologicalSociety of America Special Papers, v.374, p. 355–379, http://dx.doi.org/10.1130/0-8137-2374-4.355.

Grove, M., Bebout, G.E., Jacobson, C.E.,Barth, A.P., Kimbrough, D.L., King,R.L., Zou, H., Lovera, O.M., Mahoney,B.J., and Gehrels, G.E., 2008, TheCatalina Schist: Evidence for middleCretaceous subduction erosion ofsouthwestern North America, inDraut, A.E., Clift, P.D., and Scholl,D.W., eds., Formation and Applicationsof the Sedimentary Record in ArcCollision Zones: Geological Society ofAmerica Special Papers, v. 436, p.335–361, http://dx.doi.org/10.1130/2008.2436(15).

Grove, T., Holbig, E.S., Barr, J.A., Till,C.B., and Krawczynski, M.J., 2013,Melts of garnet lherzolite: experi-ments, models and comparison tomelts of pyroxenite and carbonatedlherzolite: Contributions to Mineralo-gy and Petrology, v. 166, p. 887–910,http://dx.doi.org/10.1007/s00410-013-0899-9.

Hacker, B.R., Gnos, E., Ratschbacher, L.,Grove, M., McWilliams, M., Sobolev,S.V., Jiang, W., and Wu, Z., 2000, Hotand dry deep crustal xenoliths fromTibet: Science, v. 287, p. 2463–2466,http://dx.doi.org/10.1126/sci-ence.287.5462.2463.

Hacker, B.R., Luffi, P., Lutkov, V., Minaev,V.T., Ratschbacher, L.R., Plank, T.,Ducea, M.N., Patiño-Douce, A.E.,Ducea, M.N., McWilliams, M.O., andMetcalf, J., 2005, Near-ultrahigh pres-sure processing of continental crust:Miocene crustal xenoliths from thePamir: Journal of Petrology, v. 46, p.1661–1687, http://dx.doi.org/10.1093/petrology/egi030.

Haeussler, P.J., 1992, Structural evolutionof an arc-basin: The Gravina Belt incentral southeastern Alaska: Tectonics,v. 11, p. 1245–1265,http://dx.doi.org/10.1029/92TC01107.

Hamilton, W.B., 1969a, Mesozoic Califor-

nia and the underflow of Pacific man-tle: Geological Society of AmericaBulletin, v. 80, p. 2409–2430,http://dx.doi.org/10.1130/0016-7606(1969)80[2409:MCATUO]2.0.CO;2.

Hamilton, W.B., 1969b, The volcanic cen-tral Andes, a modern model for theCretaceous batholiths and tectonics ofwestern North America: OregonDepartment of Geology and MineralIndustries Bulletin, v. 65, p. 175–184.

Hamilton, W.B., 1982, Structural evolutionof the Big Maria Mountains, north-eastern Riverside County, southeasternCalifornia, in Frost, E.G., and Martin,D.L., eds., Mesozoic–Cenozoic Tecton-ic Evolution of the Colorado RiverRegion, California, Arizona, andNevada: San Diego, Cordilleran Pub-lishers, p. 1–27.

Hamilton, W.B., and Myers, W.B., 1966,Cenozoic tectonics of the westernUnited States: Reviews of Geophysics,v. 4, p. 509–549, http://dx.doi.org/10.1029/RG004i004p00509.

Hamilton, W.B., and Myers, W.B., 1967,The Nature of Batholiths: U.S. Geo-logical Survey Professional Paper 554-C, 30 p.

Harrison, A., and White, R.S., 2006,Lithospheric structure of an activebackarc basin: the Taupo VolcanicZone, New Zealand: GeophysicalJournal International, v. 167, p.968–990, http://dx.doi.org/10.1111/j.1365-246X.2006.03166.x.

Hart, C.J.R., Mair, J.L., Goldfarb, R.J., andGroves, D.I., 2004, Source and redoxcontrols on metallogenic variations inintrusion-related ore systems, Tomb-stone-Tungsten Belt, Yukon Territory,Canada, in Ishihara, S., Stephens, W.E.,Harley, S.L., Arima, M., and Nakajima,T., eds., Fifth Hutton Symposium onthe Origin of Granites and RelatedRocks: Geological Society of AmericaSpecial Papers, v. 389, p. 339–356,http://dx.doi.org/10.1130/0-8137-2389-2.339.

Henry, C.D., McDowell, F.W., and Silver,L.T., 2003, Geology and geochronolo-gy of granitic batholith complex,Sinaloa, México: Implications forCordilleran magmatism and tectonics,in Johnson, S.E., Paterson, S.R.,Fletcher, J.M., Girty, G.H., Kim-brough, D.L., and Martín-Barajas, A.,eds., Tectonic Evolution of North-western Mexico and the SouthwesternUSA: Geological Society of AmericaSpecial Papers, v. 374, p. 237–273,http://dx.doi.org/10.1130/0-8137-2374-4.237.

Herrmann, U.R., Nelson, B.K., and

Ratschbacher, L., 1994, The origin ofa terrane: U/Pb zircon geochronologyand tectonic evolution of the XolapaComplex (southern Mexico): Tecton-ics, v. 13, p. 455–474,http://dx.doi.org/10.1029/93TC02465.

Herzig, C.F., 1991, Petrogenetic and tec-tonic deveopment of the SantiagoPeak Volcanics, northern Santa AnaMountains, California: UnpublishedPhD thesis, University of California,Riverside, CA, 376 p.

Herzig, C.T., and Kimbrough, D.L., 2014,Santiago Peak volcanics: Early Creta-ceous arc volcanism of the westernPeninsular Ranges batholith, southernCalifornia, in Morton, D.M., andMiller, F.K., eds., Peninsular RangesBatholith, Baja California and South-ern California: Geological Society ofAmerica Memoirs, v. 211, p. 345–363,http://dx.doi.org/10.1130/2014.1211(09).

Hildebrand, R.S., 1981, Early ProterozoicLaBine Group of Wopmay orogen:remnant of a continental volcanic arcdeveloped during oblique conver-gence, in Campbell, F.H.A., ed., Pro-terozoic basins in Canada: GeologicalSurvey of Canada Paper 81–10, p.133–156.

Hildebrand, R.S., 1984, Geology of theCamsell, River-Conjuror Bay area,Northwest Territories: early Protero-zoic cauldrons, stratovolcanoes andsubvolcanic plutons: Geological Sur-vey of Canada Paper 83–20, 42 p.

Hildebrand, R.S., 2009, Did Westward Sub-duction Cause Cretaceous–TertiaryOrogeny in the North AmericanCordillera?: Geological Society ofAmerica Special Papers, v. 457, 71 p.,http://dx.doi.org/10.1130/2009.2457.

Hildebrand, R.S., 2013, Mesozoic Assem-bly of the North American Cordillera:Geological Society of America SpecialPapers, v. 495, 169 p.,http://dx.doi.org/10.1130/2013.2495.

Hildebrand, R.S., 2014, Geology, mantletomography, and inclination correctedpaleogeographic trajectories supportwestward subduction during Creta-ceous orogenesis in the North Ameri-can Cordillera: Geoscience Canada, v.41, p. 207–224, http://dx.doi.org/10.12789/geocanj.2014.41.032.

Hildebrand, R.S., and Bowring, S.A., 1984,Continental intra-arc depressions: Anonextensional model for their origin,with a Proterozoic example fromWopmay orogen: Geology, v. 12, p.73–77, http://dx.doi.org/10.1130/0091-7613(1984)12<73:CIDANM>2.0.CO;2.

446

Hildebrand, R.S., and Bowring, S.A., 1999,Crustal recycling by slab failure: Geol-ogy, v. 27, p. 11–14,http://dx.doi.org/10.1130/0091-7613(1999)027<0011:CRBSF>2.3.CO;2.

Hildebrand, R.S., and Whalen, J.B., 2014,Arc and slab-failure magmatism inCordilleran Batholiths I – The Creta-ceous Coastal Batholith of Peru andits role in South American orogenesisand hemispheric subduction flip: Geo-science Canada, v. 41, p. 255–282,http://dx.doi.org/10.12789/geo-canj.2014.41.047.

Hildebrand, R.S., Hoffman, P.F., andBowring, S.A., 2010, The Calderianorogeny in Wopmay orogen (1.9 Ga)northwestern Canadian shield: Geo-logical Society of America Bulletin, v.122, p. 794–814,http://dx.doi.org/10.1130/B26521.1.

Hildreth, W., 2007, Quaternary magmatismin the Cascades–Geologic perspec-tives: U.S. Geological Survey, Profes-sional Paper 1744, 125 p.

Hill, R.I., 1984, Petrology and Petrogenesisof Batholithic Rocks, San JacintoMountains, Southern California:Unpublished PhD thesis, CaliforniaInstitute of Technology, Pasadena,CA, 660 p.

Hirt, W.H., 2007, Petrology of the MountWhitney Intrusive Suite, eastern SierraNevada, California: Implications forthe emplacement and differentiationof composite felsic intrusions: Geo-logical Society of America Bulletin, v.119, p. 1185–1200,http://dx.doi.org/10.1130/B26054.1.

Hoffman, P.F., 1987, Early Proterozoicforedeeps, foredeep magmatism andSuperior-type iron-formations of theCanadian Shield, in Kröner, A., ed.,Proterozoic Lithospheric Evolution:American Geophysical Union Geody-namics Series, v. 17, p. 85–98,http://dx.doi.org/10.1029/GD017p0085.

Hoffman, P.F., 1989, Precambrian geologyand tectonic history of North Ameri-ca, in Bally, A.W., and Palmer, A.R.,eds., The Geology of North Ameri-ca—An Overview: Geological Societyof America, Geology of North Amer-ica, v. A, p. 447–511.

Hoffman, P.F., 2012, The Tooth of Time:How do passive margins becomeactive?: Geoscience Canada, v. 39, p.67–73.

Hoffman, P.F., 2013, The Tooth of Time:The North American Cordillera fromTanya Atwater to Karin Sigloch: Geo-science Canada, v. 40, p. 71–93,http://dx.doi.org/10.12789/geo-

canj.2013.40.009.Hoffman, P.F., and Grotzinger, J.P., 1993,

Orographic precipitation, erosionalunloading, and tectonic style: Geology,v. 21, p. 195–198, http://dx.doi.org/10.1130/0091-7613(1993)021<0195:OPEUAT>2.3.CO;2.

Hoffman, P.F., and McGlynn, J.C., 1977,Great Bear Batholith: a volcano-plu-tonic depression, in Baragar, W.R.A.,Coleman, L.C., and Hall, J.M., eds.,Volcanic Regimes in Canada: Geologi-cal Association of Canada, SpecialPaper 16, p. 170–192.

Houghton, B.F., Hayward, B.W., Cole, J.W.,Hobden, B., and Johnston, D.M.,1991, Inventory of Quaternary vol-canic centres and features of theTaupo Volcanic Zone (with additionalentries for Mayor Island and the Ker-madec Islands): Geological Society ofNew Zealand Miscellaneous Publica-tion 55, 156 p.

Housh, T.B., and McMahon, T.P., 2000,Ancient isotopic characteristics ofNeogene potassic magmatism in west-ern New Guinea (Irian Jaya, Indone-sia): Lithos, v. 50, p. 217–239,http://dx.doi.org/10.1016/S0024-4937(99)00043-2.

Huang, C.-Y., Yuan, P.B., and Tsao, S.-J.,2006, Temporal and spatial records ofactive arc-continent collision in Tai-wan: A synthesis: Geological Societyof America Bulletin, v. 118, p.274–288,http://dx.doi.org/10.1130/B25527.1.

Imlay, R.W., 1963, Jurassic fossils fromsouthern California: Journal of Pale-ontology, v. 37, p. 97–107.

Iriondo, A., Premo, W.R., Martínez-Torres,L.M., Budahn, J.R., Atkinson, W.W.,Jr., Siems, D.F., and Guarás-González,B., 2004, Isotopic, geochemical, andtemporal characterization of Protero-zoic basement rocks in the Quitovacregion, northwestern Sonora, Mexico:Implications for the reconstruction ofthe southwestern margin of Laurentia:Geological Society of America Bul-letin, v. 116, p. 154–170,http://dx.doi.org/10.1130/B25138.1.

Irving, E., 1977, Drift of the major conti-nental blocks since the Devonian:Nature, v. 270, p. 304–309,http://dx.doi.org/10.1038/270304a0.

Irving, E., 2004, The case for Pangea B,and the Intra-Pangean megashear, inChannell, J.E.T., Kent, D.V., Lowrie,W., and Meert, J.G., eds., Timescales ofthe Paleomagnetic Field: AmericanGeophysical Union, GeophysicalMonograph 145, p. 13–27,http://dx.doi.org/10.1029/145GM02.

Irwin, W.P., and Wooden, J.L., 2001, Maps

showing plutons and accreted terranesof the Sierra Nevada, California, witha tabulation of U/Pb isotopic ages:U.S. Geological Survey Open-FileReport 01-299, 1 sheet.

Isacks, B.L., 1988, Uplift of the centralAndean Plateau and bending of theBolivian orocline: Journal of Geo-physical Research, v. 93, p. 3211–3231,http://dx.doi.org/10.1029/JB093iB04p03211.

Isacks, B., and Molnar P., 1969, Mantleearthquake mechanisms and the sink-ing of the lithosphere: Nature, v. 223,p. 1121–1124, http://dx.doi.org/10.1038/2231121a0.

Jacques-Ayala, C., 1992, Stratigraphy of theLower Cretaceous Cintura Formation,Sierra El Chanate, northwestern Sono-ra, Mexico: Universidad NacionalAutónoma de México, Instituto deGeologia Revista, v. 10, p. 129–136.

Jacques-Ayala, C., 1999, Stratigraphy of ElChanate Group (Late Cretaceous) andits implications for the tectonic evolu-tion of northwestern Sonora, Mexico:Revista Mexicana de Ciencias Geológi-cas, v. 16, p. 97–120.

Jennings, C.W., compiler, 1977, Geologicmap of California: Sacramento, Cali-fornia Division of Mines and Geolo-gy, scale 1:750,000.

John, D.A., du Bray, E.A., Blakely, R.J.,Fleck, R.J., Vikre, P.G., Box, S.E., andMoring, B.C., 2012, Miocene magma-tism in the Bodie Hills volcanic field,California and Nevada: A long-livederuptive center in the southern seg-ment of the ancestral Cascades arc:Geosphere, v. 8, p. 44–97,http://dx.doi.org/10.1130/GES00674.1.

Johnson, S.E., Paterson, S.R., and Tate,M.C., 1999a, Structure and emplace-ment history of a multiple-center,cone-sheet−bearing ring complex: TheZarza Intrusive Complex, Baja Cali-fornia, Mexico: Geological Society ofAmerica Bulletin, v. 111, p. 607–619,http://dx.doi.org/10.1130/0016-7606(1999)111<0607:SAE-HOA>2.3.CO;2.

Johnson, S.E., Tate, M.C., and Fanning,C.M., 1999b, New geologic mappingand SHRIMP U–Pb zircon data in thePeninsular Ranges batholith, Baja Cali-fornia, Mexico: Evidence for asuture?: Geology, v. 27, p. 743–746,http://dx.doi.org/10.1130/0091-7613(1999)027<0743:NGMA-SU>2.3.CO;2.

Johnson, S.E., Schmidt, K.L., and Tate,M.C., 2002, Ring complexes in thePeninsular Ranges Batholith, Mexicoand the USA: magma plumbing sys-


tems in the middle and upper crust:Lithos, v. 61, p. 187–208,http://dx.doi.org/10.1016/S0024-4937(02)00079-8.

Johnson, S.E., Fletcher, J.M., Fanning,C.M., Vernon, R.H., Paterson, S.R.,and Tate, M.C., 2003, Structure,emplacement and lateral expansion ofthe San José tonalite pluton, Peninsu-lar Ranges batholith, Baja California,México: Journal of Structural Geolo-gy, v. 25, p. 1933–1957,http://dx.doi.org/10.1016/S0191-8141(03)00015-4.

Jordan, T.H., 1978, Composition anddevelopment of the continental tec-tosphere: Nature, v. 274, p. 544–548,http://dx.doi.org/10.1038/274544a0.

Journeay, J.M., and Friedman, R.M., 1993,The Coast Belt thrust system: Evi-dence of Late Cretaceous shorteningin southwest British Columbia: Tec-tonics, v. 12, p. 756–775,http://dx.doi.org/10.1029/92TC02773.

Kamber, B.S., Ewart, A., Collerson, K.D.,Bruce, M.C., and McDonald, G.D.,2002, Fluid-mobile trace element con-straints on the role of slab meltingand implications for Archaean crustalgrowth models: Contributions to Min-eralogy and Petrology, v. 144, p.38–56, http://dx.doi.org/10.1007/s00410-002-0374-5.

Karig, D.E., Cardwell, R.K., Moore, G.F.,and Moore, D.G., 1978, Late Cenozoicsubduction and continental margintruncation along the northern MiddleAmerica trench: Geological Society ofAmerica Bulletin, v. 89, p. 265–276,http://dx.doi.org/10.1130/0016-7606(1978)89<265:LCSACM>2.0.CO;2.

Kay, S.M., Godoy, E., and Kurtz, A., 2005,Episodic arc migration, crustal thick-ening, subduction erosion, and mag-matism in the south-central Andes:Geological Society of America Bul-letin, v. 117, p. 67–88,http://dx.doi.org/10.1130/B25431.1.

Kennedy, M.P., 1975, Geology of westernSan Diego metropolitan area, Califor-nia: California Division of Mines andGeology Bulletin 200, p. 9–39.

Kent, D.V., and Muttoni, G., 2003, Mobilityof Pangea: Implications for Late Pale-ozoic and Early Mesozoic paleocli-mate, in LeTourneau, P.M., and Olsen,P.E., eds., The Great Rift Valleys ofPangea in Eastern North America,Volume 1. Tectonics, Structure, andVolcanism: Columbia University Press,NY, p. 11–20.

Keskin, M., 2003, Magma generation byslab steepening and breakoff beneath

a subduction-accretion complex: Analternative model for collision-relatedvolcanism in Eastern Anatolia, Turkey:Geophysical Research Letters, v. 30,8046, http://dx.doi.org/10.1029/2003GL018019.

Ketner, K.B., 1986, Eureka quartzite inMexico? – Tectonic implications:Geology, v. 14, p. 1027–1030,http://dx.doi.org/10.1130/0091-7613(1986)14<1027:EQIMI>2.0.CO;2.

Kimbrough, D.L., 1985, Tectonostrati-graphic terranes of the VizcainoPeninsula and Cedros and San BenitoIslands, Baja California, Mexico, inHowell, D.G., ed., TectonostratigraphicTerranes of the Circum-PacificRegion: AAPG, Circum Pacific Coun-cil for Energy and Mineral Resources,Earth Science Series no. 1, p. 285–298.

Kimbrough, D.L., and Moore, T.E., 2003,Ophiolite and volcanic arc assem-blages on the Vizcaino Peninsula andCedros Island, Baja California Sur,México: Mesozoic forearc lithosphereof the Cordilleran magmatic arc, inJohnson, S.E., Paterson, S.R., Fletcher,J.M., Girty, G.H., Kimbrough, D.L.,and Martín-Barajas, A., eds., TectonicEvolution of Northwestern Mexicoand the Southwestern USA: Geologi-cal Society of America Special Papers,v. 374, p. 43–71, http://dx.doi.org/10.1130/0-8137-2374-4.43.

Kimbrough, D.L., Smith, D.P., Mahoney,J.B., Moore, T.E., Grove, M., Gastil,R.G., Ortega-Rivera, A., and Fanning,C.M., 2001, Forearc-basin sedimentaryresponse to rapid Late Cretaceousbatholith emplacement in the Peninsu-lar Ranges of southern and Baja Cali-fornia: Geology, v. 29, p. 491–494,http://dx.doi.org/10.1130/0091-7613(2001)029<0491:FBSRTR>2.0.CO;2.

Kimbrough, D.L., Abbott, P.L., Grove, M.,Smith, D.P., Mahoney, J.B., Moore,T.E., and Gehrels, G.E., 2006, Con-trasting cratonal provenances forupper Cretaceous Valle Groupquartzite clasts, Baja California, inGirty, G.H., and Cooper, J.D., eds.,Using stratigraphy, sedimentology, andgeochemistry to unravel the geologichistory of the southwesternCordillera: Pacific Section SEPMBook #101, p. 97–110.

Kimbrough, D.L., Abbott, P.L., Balch,D.C., Bartling, S.H., Grove, M.,Mahoney, J.B., and Donohue, R.F.,2014a, Upper Jurassic PeñasquitosFormation—Forearc basin westernwall rock of the Peninsular Rangesbatholith, in Morton, D.M., and Miller,

F.K., eds., Peninsular Ranges Batholith,Baja California and Southern Califor-nia: Geological Society of AmericaMemoirs, v. 211, p. 625–643,http://dx.doi.org/10.1130/2014.1211(19).

Kimbrough, D.L., Grove, M., and Morton,D.M., 2014b, Timing and significanceof gabbro emplacement within twodistinct plutonic domains of thePeninsular Ranges batholith, southernand Baja California: Geological Socie-ty of America Bulletin, B30914-1,http://dx.doi.org/10.1130/B30914.1.

Kingdon, S.A., John, D.A., and du Bray,E.A., 2014, Pliocene to late Pleis-tocene magmatism in the Aurora Vol-canic Field, Basin and Range province,Nevada and California, USA(abstract): Geological Association ofCanada Abstracts, Annual Meeting, p.139–140.

Kistler, R.W., 1990, Two different litho-sphere types in the Sierra Nevada, Cal-ifornia, in Anderson, J.L., ed.,TheNature and Origin of CordilleranMagmatism: Geological Society ofAmerica Memoirs, v. 174, p. 271–281,http://dx.doi.org/10.1130/MEM174-p271.

Kistler, R.W., 1993, Mesozoic intra-batholithic faulting, Sierra Nevada,California, in Dunne, G., andMcdougall, K., eds., Mesozoic Paleo-geography of the Western UnitedStates — II: Pacific Section SEPM, v.71, p. 247–262.

Kistler, R.W., and Peterman, Z.E., 1973,Variations in Sr, Rb, K, Na, and initialSr87/Sr86 in Mesozoic granitic rocksand intruded wall rocks in central Cali-fornia: Geological Society of AmericaBulletin, v. 84, p. 3489–3512,http://dx.doi.org/10.1130/0016-7606(1973)84<3489:VISRKN>2.0.CO;2.

Kistler, R.W., and Peterman, Z.E., 1978,Reconstruction of crustal rocks ofCalifornia on the basis of initial stron-tium isotopic compositions of Meso-zoic granitic rocks: U.S. GeologicalSurvey Professional Paper 1071, 17 p.

Kistler, R.W., Wooden, J.L., and Morton,D.M., 2003, Isotopes and ages in thenorthern Peninsular Ranges batholith,Southern California: U.S. GeologicalSurvey Open-File Report 03-489, 45p.

Kistler, R.W., Wooden, J.L., Premo, W.R.,and Morton, D.M., 2014, Pb–Sr–Nd–O isotopic characterization of Meso-zoic rocks throughout the northernend of the Peninsular Rangesbatholith: Isotopic evidence for themagmatic evolution of oceanic

448

arc–continental margin accretion dur-ing the Late Cretaceous of southernCalifornia, in Morton, D.M., andMiller, F.K., eds., Peninsular RangesBatholith, Baja California and South-ern California: Geological Society ofAmerica Memoirs, v. 211, p. 263–316,http:/dx.doi.org/10.1130/2014.1211(07).

Klute, M.A., 1991, Sedimentology, sand-stone petrofacies, and tectonic settingof the late Mesozoic Bisbee Basin,southeastern Arizona: UnpublishedPhD thesis, University of Arizona,Tucson, TX, 268 p.

Kohn, M.J., and Parkinson, C.D., 2002,Petrologic case for Eocene slabbreakoff during the Indo-Asian colli-sion: Geology, v. 30, p. 591–594,http://dx.doi.org/10.1130/0091-7613(2002)030<0591:PCFESB>2.0.CO;2.

Krebs, C.K., and Ruiz, J., 1987, Geochem-istry of the Canelo Hills volcanics andimplications for the Jurassic tectonicsetting of southeastern Arizona, inDickinson, W.R., and Klute, M.A., eds.,Mesozoic Rocks of Southern Arizonaand Adjacent Areas: Arizona Geologi-cal Society Digest 18, p. 139–151.

Krummenacher, D., Gastil, R.G., Bushee,J., and Doupont, J., 1975, K–Ar appar-ent ages, Peninsular Ranges batholith,southern California and Baja Califor-nia: Geological Society of AmericaBulletin, v. 86, p. 760–768,http://dx.doi.org/10.1130/0016-7606(1975)86<760:KAAPRB>2.0.CO;2.

Lackey, J.S., Valley, J.W., and Saleeby, J.B.,2005, Supracrustal input to magmas inthe deep crust of Sierra Nevadabatholith: Evidence from high- δ18Ozircon: Earth and Planetary ScienceLetters, v. 235, p. 315–330,http://dx.doi.org/10.1016/j.epsl.2005.04.003.

Lackey, J.S., Valley, J.W., Chen, J.H., andStockli, D.F., 2008, Dynamic magmasystems, crustal recycling, and alter-ation in the Central Sierra NevadaBatholith: The oxygen isotope record:Journal of Petrology, v. 49, p.1397–1426, http://dx.doi.org/10.1093/petrology/egn030.

Lackey, J.S., Cecil, M.R., Windham, C.J.,Frazer, R.E., Bindeman, I.N., andGehrels, G.E., 2012a, The Fine GoldIntrusive Suite: The roles of basementterranes and magma source develop-ment in the Early Cretaceous SierraNevada batholith: Geosphere, v. 8, p.292–313, http://dx.doi.org/10.1130/GES00745.1.

Lackey, J.S., Eisenberg, J.I., and Sendek,

C.L., 2012b, Day 2: The Fine Goldintrusive suite—Records of the nas-cent Cretaceous arc, in Formation ofthe Sierra Nevada Batholith: Magmaticand Tectonic Processes and TheirTempos: Geological Society of Ameri-ca Field Forum Field Trip Guide, p. 2-1–2-23.

Lahren, M.M., Schweickert, R.A., Mattin-son, J.M., and Walker, J.D., 1990, Evi-dence of uppermost Proterozoic toLower Cambrian miogeoclinal rocksand the Mojave–Snow Lake fault:Snow Lake pendant, central SierraNevada, California: Tectonics, v. 9, p.1585–1608, http://dx.doi.org/10.1029/TC009i006p01585.

Langenheim, V.E., Jachens, R.C., Morton,D.M., Kistler, R.W., and Matti, J.C.,2004, Geophysical and isotopic map-ping of preexisting crustal structuresthat influenced the location and devel-opment of the San Jacinto fault zone,southern California: Geological Socie-ty of America Bulletin, v. 116, p.1143–1157,http://dx.doi.org/10.1130/B25277.1.

Langenheim, V.E., Jachens, R.C., andAiken, C., 2014, Geophysical frame-work of the Peninsular Rangesbatholith— Implications for tectonicevolution and neotectonics, in Morton,D.M., and Miller, F.K., eds., PeninsularRanges Batholith, Baja California andSouthern California: Geological Socie-ty of America Memoirs, v. 211, p.1–20, http://dx.doi.org/10.1130/2014.1211(01).

LaPierre, H., Tardy, M., Coulon, C., OrtizHernandez, E., Bourdier, J.-L.Martínez Reyes, J., and Freydier, C.,1992a, Caractérisation, genèse et évo-lution géodynamique du terrain deGuerrero (Mexique occidental): Cana-dian Journal of Earth Sciences, v. 29,p. 2478–2489,http://dx.doi.org/10.1139/e92-194.

LaPierre, H., Ortiz, L.E., Abouchami, W.,Monod, O., Coulon, C., and Zimmer-man, J.-L., 1992b, A crustal section ofan intra-oceanic island arc: The LateJurassic–Early Cretaceous Guanajuatomagmatic sequence, central Mexico:Earth and Planetary Science Letters, v.108, p. 61–77, http://dx.doi.org/10.1016/0012-821X(92)90060-9.

Larsen, E.S., Jr., 1948, Batholith and asso-ciated rocks of Corona, Elsinore, andSan Luis Rey quadrangles, southernCalifornia: Geological Society ofAmerica Memoirs, v. 29, 185 p.,http://dx.doi.org/10.1130/MEM29-p1.

Larsen, E.S., Jr., Gottfried, D., Jaffe, H.W.,and Waring, C.L., 1958, Lead-alpha

ages of the Mesozoic batholiths ofwestern North America: U.S. Geologi-cal Survey Bulletin 1070-B, 62 p.

Lawson, A.C., 1936, The Sierra Nevada inthe light of isostasy: Geological Socie-ty of America Bulletin, v. 47, p.1691–1712, http://dx.doi.org/10.1130/GSAB-47-1691.

Lawton, T.F., and McMillan, N.J., 1999, Arcabandonment as a cause for passivecontinental rifting: Comparison of theJurassic Mexican Borderland rift andthe Cenozoic Rio Grande rift: Geolo-gy, v. 27, p. 779–782,http://dx.doi.org/10.1130/0091-7613(1999)027<0779:AAAACF>2.3.CO;2.

Lawton, T.F., González-León, C.M., Lucas,S.G., and Scott, R.W., 2004, Stratigra-phy and sedimentology of the upperAptian–upper Albian Mural Lime-stone (Bisbee Group) in northernSonora, Mexico: Cretaceous Research,v. 25, p. 43–60, http://dx.doi.org/10.1016/j.cretres.2003.09.003.

Lee, C.-T., Rudnick, R.L., and Brimhall,G.H., Jr., 2001, Deep lithosphericdynamics beneath the Sierra Nevadaduring the Mesozoic and Cenozoic asinferred from xenolith petrology:Geochemistry, Geophysics, Geosys-tems, v. 2, 1053, http://dx.doi.org/10.1029/2001GC000152.

Lee, C.-T.A., Morton, D.M., Kistler, R.W.,and Baird, A.K., 2007, Petrology andtectonics of Phanerozoic continentformation: From island arcs to accre-tion and continental arc magmatism:Earth and Planetary Science Letters, v.263, p. 370–387, http://dx.doi.org/10.1016/j.epsl.2007.09.025.

Leier-Engelhardt, P., 1993, Middle Paleo-zoic strata of the Sierra Las Pintas,northeastern Baja California Norte,Mexico, in Gastil, R.G., and Miller,R.H., eds., The Prebatholithic Stratigra-phy of Peninsular California: Geologi-cal Society of America Special Papers,v. 279, p. 23–42, http://dx.doi.org/10.1130/SPE279-p23.

Le Maitre, R.W., 1989, A Classification ofIgneous Rocks and Glossary ofTerms: Oxford, Blackwell, 193 p.

Lesher, C.E., 1994, Kinetics of Sr and Ndexchange in silicate liquids: Theory,experiments, and applications to uphilldiffusion, isotopic equilibration, andirreversible mixing of magmas: Jour-nal of Geophysical Research, v. 99, p.9585–9604, http://dx.doi.org/10.1029/94JB00469.

Levi, B., and Aguirre, L., 1981, Ensialicspreading-subsidence in the Mesozoicand Palaeogene Andes of centralChile: Journal of the Geological Socie-


ty, v. 138, p. 75–81, http://dx.doi.org/10.1144/gsjgs.138.1.0075.

Levin, V., Shapiro, N., Park, J., and Ritz-woller, M., 2002a, Seismic evidencefor catastrophic slab loss beneathKamchatka: Nature, v. 418, p.763–766, http://dx.doi.org/10.1038/nature00973.

Levin, V., Park, J., Brandon, M., Lees, J.,Peyton, V., Gordeev, E., and Ozerov,A., 2002b, Crust and upper mantle ofKamchatka from teleseismic receiverfunctions: Tectonophysics, v. 358, p.233–265, http://dx.doi.org/10.1016/S0040-1951(02)00426-2.

Lewis, J.L., Day, S.M., Magistrale, H., Cas-tro, R.R., Astiz, L., Rebollar, C.,Eakins, J., Vernon, F.L., and Brune,J.N., 2001, Crustal thickness of thePeninsular Ranges and Gulf Exten-sional Province in the Californias:Journal of Geophysical Research:Solid Earth, v. 106, p. 13599–13611,http://dx.doi.org/10.1029/2001JB000178.

Lindgren, W., 1915, The igneous geologyof the Cordilleras and its problems, inRice, W.N., Adams, F.D., Coleman,A.P., Walcott, C.D., and others, eds.,Problems of American Geology: YaleUniversity Press, New Haven, CT, p.234–286.

Loewy, S.L., Connelly, J.N., and Dalziel,I.W.D., 2004, An orphaned basementblock: The Arequipa–Antofalla base-ment of the central Andean margin ofSouth America: Geological Society ofAmerica Bulletin, v. 116, p. 171–187,http://dx.doi.org/10.1130/B25226.1.

Lothringer, C.J., 1993, AllochthonousOrdovician strata of Ranchos SanMarcos, Baja California Norte, Mexi-co, in Gastil, R.G., and Miller, R.H.,eds., The Prebatholithic Stratigraphy ofPeninsular California: Geological Soci-ety of America Special Papers, v. 279,p. 11–22, http://dx.doi.org/10.1130/SPE279-p11.

Lovera, O.M., Grove, M., Kimbrough,D.L., and Abbott, P.L., 1999, Amethod for evaluating basement exhu-mation histories from closure age dis-tributions of detrital minerals: Journalof Geophysical Research, v. 104, p.29419–29438, http://dx.doi.org/10.1029/1999JB900082.

Lynch, G., 1992, Deformation of EarlyCretaceous volcanic-arc assemblages,southern Coast Belt, British Columbia:Canadian Journal of Earth Sciences, v.29, p. 2706–2721,http://dx.doi.org/10.1139/e92-214.

Lynch, G., 1995, Geochemical polarity ofthe Early Cretaceous Gambier Group,southern Coast Belt, British Columbia:

Canadian Journal of Earth Sciences, v.32, p. 675–685,http://dx.doi.org/10.1139/e95-058.

Macera, P., Gasperini, D., Ranalli, G., andMahatsente, R., 2008, Slab detachmentand mantle plume upwelling in sub-duction zones: An example from theItalian South-Eastern Alps: Journal ofGeodynamics, v. 45, p. 32–48,http://dx.doi.org/10.1016/j.jog.2007.03.004.

Mack, G.H., 1987, Mid-Cretaceous (lateAlbian) change from rift to retroarcforeland basin in southwestern NewMexico: Geological Society of Ameri-ca Bulletin, v. 98, p. 507–514,http://dx.doi.org/10.1130/0016-7606(1987)98<507:MLACFR>2.0.CO;2.

MacKenzie, L., Abers, G.A., Fischer, K.M.,Syracuse, E.M., Protti, J.M., Gonzalez,V., and Strauch, W., 2008, Crustalstructure along the southern CentralAmerican volcanic front: Geochem-istry Geophysics Geosystems, v. 9,Q08S09, http://dx.doi.org/10.1029/2008GC001991.

Macpherson, C.G., Dreher, S.T., and Thirl-wall, M.F., 2006, Adakites without slabmelting: High pressure differentiationof island arc magma, Mindanao, thePhilippines: Earth and Planetary Sci-ence Letters, v. 243, p. 581–593,http://dx.doi.org/10.1016/j.epsl.2005.12.034.

Mahéo, G., Guillot, S., Blichert-Toft, J.,Rolland, Y., and Pêcher, A., 2002, Aslab breakoff model for the Neogenethermal evolution of South Karako-rum and South Tibet: Earth and Plan-etary Science Letters, v. 195, p. 45–58,http://dx.doi.org/10.1016/S0012-821X(01)00578-7.

Maniar, P.D., and Piccoli, P.M., 1989, Tec-tonic discrimination of granitoids:Geological Society of America Bul-letin, v. 101, p. 635–643,http://dx.doi.org/10.1130/0016-7606(1989)101<0635:TDOG>2.3.CO;2.

Mansfield, C.F., 1979, Upper Mesozoicsubsea fan deposits in the southernDiablo Range, California: Record ofthe Sierra Nevada magmatic arc: Geo-logical Society of America Bulletin, v.90, p. 1025–1046, http://dx.doi.org/10.1130/0016-7606(1979)90<1025:UMSFDI>2.0.CO;2.

Marchev, P., Georgiev, S., Raicheva, R.,Peytcheva, I., von Quadt, A.,Ovtcharova, M., and Bonev, N., 2013,Adakitic magmatism in post-collisionalsetting: An example from theEarly–Middle Eocene magmatic beltin southern Bulgaria and northern

Greece: Lithos, v. 180–181, p.159–180, http://dx.doi.org/10.1016/j.lithos.2013.08.024.

Martens, U.C., Bruekner, H.K., Mattinson,C.G., Liou, J.G., and Wooden, J.L.,2012, Timing of eclogite-facies meta-morphism of the Chuacús complex,Central Guatemala: Record of LateCretaceous continental subduction ofNorth America’s sialic basement:Lithos, v. 146–147, p. 1–10,http://dx.doi.org/10.1016/j.lithos.2012.04.021.

Martin, H., 1986, Effects of steeperArchean geothermal gradient on geo-chemistry of subduction-zone mag-mas: Geology, v. 14, p. 753–756,http://dx.doi.org/10.1130/0091-7613(1986)14<753:EOSAGG>2.0.CO;2.

Martin, H., 1987, Genesis of Archeantrondhjemites, tonalites, and granodi-orites from eastern Finland: Major andtrace element geochemistry: Journal ofPetrology, v. 28, p. 921–953,http://dx.doi.org/10.1093/petrolo-gy/28.5.921.

Martin, H., 1994, The Archean grey gneiss-es and the genesis of continentalcrust, in Condie, K.C., ed., Archeancrustal evolution: Developments inPrecambrian Geology, v. 11, Elsevier,New York, NY, p. 205–259,http://dx.doi.org/10.1016/S0166-2635(08)70224-X.

Martin, H., Smithies, R.H., Rapp, R.,Moyen, J.-F., and Champion, D., 2005,An overview of adakite, tonalite-trondhjemite-granodiorite (TTG), andsanukitoid: Relationships and someimplications for crustal evolution:Lithos, v. 79, p. 1–24,http://dx.doi.org/10.1016/j.lithos.2004.04.048.

Martin, H., Moyen, J.-F., and Rapp, R.,2009, The sanukitoid series: magma-tism at the Archean–Proterozoic tran-sition: Earth and Environmental Sci-ence Transactions of the Royal Societyof Edinburgh, v. 100, p. 15–33,http://dx.doi.org/10.1017/S1755691009016120.

Martini, M., and Ferrari, L., 2011, Style andchronology of the Late Cretaceousshortening in the Zihuatanejo area(southwestern Mexico): Implicationsfor the timing of the MexicanLaramide deformation: Geosphere, v.7, p. 1469–1479, http://dx.doi.org/10.1130/GES00743.1.

Martini, M., Ferrari, L., López-Martínez,M., and Valencia, V., 2010, Strati-graphic redefinition of the Zihuatane-jo area, southwestern Mexico: RevistaMexicana de Ciencias Geológicas, v.

450

27, p. 412–430.Martini, M., Fitz, E., Solari, L., Camprubi,

A., Hudleston, P.J., Lawton, T.F., Tol-son, G., and Centeno-García, E., 2012,The Late Cretaceous fold-thrust beltin the Peña de Bernal–Tamazunchalearea and its possible relationship tothe accretion of the Guerrero Ter-rane, in Aranda-Gómez, J.J., Tolson,G., and Molina-Garza, R.S., eds., TheSouthern Cordillera and Beyond: Geo-logical Society of America FieldGuides, v. 25, p. 19–38,http://dx.doi.org/10.1130/2012.0025(02).

Mauel, D.J., Lawton, T.F., González-Léon,C., Iriondo, A., and Amato, J.M., 2011,Stratigraphy and age of Upper Jurassicstrata in north-central Sonora, Mexico:Southwestern Laurentian record ofcrustal extension and tectonic transi-tion: Geosphere, v. 7, p. 390–414,http://dx.doi.org/10.1130/GES00600.1.

McCabe, R., 1984, Implications of paleo-magnetic data on the collision relatedbending of island arcs: Tectonics, v. 3,p. 409–428, http://dx.doi.org/10.1029/TC003i004p00409.

McClelland, W.C., and Mattinson, J.M.,2000, Cretaceous–Tertiary evolutionof the western Coast Mountains, cen-tral southeastern Alaska, in Stowell,H.H., and McClelland, W.C., eds., Tec-tonics of the Coast Mountains, South-eastern Alaska and British Columbia:Geological Society of America SpecialPapers, v. 343, p. 159–182,http://dx.doi.org/10.1130/0-8137-2343-4.159.

McDowell, F.W., McMahon, T.P., Warren,P.Q., and Cloos, M., 1996, PlioceneCu–Au–bearing igneous intrusions ofthe Gunung Bijih (Ertsberg) district,Irian Jaya, Indonesia: K–Argeochronology: The Journal of Geol-ogy, v. 104, p. 327–340,http://dx.doi.org/10.1086/629828.

McKenzie, D.P., 1969, Speculations on theconsequences and causes of platemotions: Geophysical Journal Interna-tional, v. 18, p. 1–32,http://dx.doi.org/10.1111/j.1365-246X.1969.tb00259.x.

McKenzie, D., and Bickle, M.J., 1988, Thevolume and composition of melt gen-erated by extension of the lithosphere:Journal of Petrology, v. 29, p.625–679, http://dx.doi.org/10.1093/petrology/29.3.625.

McMahon, T.P., 2000, Magmatism in anarc-continent collision zone: An exam-ple from Irian Jaya (western NewGuinea), Indonesia: Buletin Geologi,v. 32, p. 1–22.

McMahon, T.P., 2001, Origin of a colli-sion-related ultrapotassic to calc-alka-line magmatic suite: The latestMiocene Minjuah volcanic field, IrianJaya, Indonesia: Buletin Geologi, v. 33,p. 47–77.

Measures, M.A., 1996, Geology of theAgua Caliente region, southeast SierraSan Pedro Mártir, Baja CaliforniaMexico: Unpublished MSc thesis, Cali-fornia State University, San Diego,CA, 105 p.

Memeti, V., 2009, Growth of the Creta-ceous Tuolumne batholith and syn-chronous regional tectonics, SierraNevada, CA: A coupled system in acontinental margin arc setting: Unpub-lished PhD thesis, University ofSouthern California, Los Angeles, CA,282 p.

Memeti, V., Gehrels, G.E., Paterson, S.R.,Thompson, J.M., Mueller, R.M., andPignotta, G.S., 2010, Evaluating theMojave–Snow Lake fault hypothesisand origins of central Sierranmetasedimentary pendant strata usingdetrital zircon provenance analyses:Lithosphere, v. 2, p. 341–360,http://dx.doi.org/10.1130/L58.1.

Menzies, M., Rogers, N., Tindle, A., andHawkesworth, C.J., 1987, Metasoma-tism and enrichment processes inlithospheric peridotites, an effect ofasthenosphere-lithosphere interaction,in Menzies, M.A., and Hawkesworth,C.J., eds., Mantle Metasomatism: Aca-demic Press, London, UK, p.313–361.

Miggins, D.P., Premo, W.R., Snee, L.W.,Yeoman, R., Naeser, N.D., Naeser,C.W., and Morton, D.M., 2014, Ther-mochronology of Cretaceousbatholithic rocks in the northernPeninsular Ranges batholith, southernCalifornia: Implications for the LateCretaceous tectonic evolution ofsouthern California, in Morton, D.M.,and Miller, F.K., eds., PeninsularRanges Batholith, Baja California andSouthern California: Geological Socie-ty of America Memoirs, v. 211, p.199–261, http://dx.doi.org/10.1130/2014.1211(06).

Miller, R.H., and Dockum, M.S., 1983,Ordovician conodonts from metamor-phosed carbonates of the SaltonTrough, California: Geology, v. 11, p.410–412, http://dx.doi.org/10.1130/0091-7613(1983)11<410:OCFMCO>2.0.CO;2.

Minch, J.A., Gastil, G., Fink, W., Robinson,J., and James, A.H., 1976, Geology ofthe Vizcaino Peninsula, in Howell,D.G., ed., Aspects of the geologic his-tory of the California Continental

Borderland: American Association ofPetroleum Geologists, Pacific Section,Miscellaneous Publication, v. 24, p.136–195.

Monod, O., Faure, M., and Salinas, J.-C.,1994, Intra-arc opening and closure ofa marginal sea: The case of the Guer-rero Terrane (SW Mexico): Island Arc,v. 3, p. 25–34, http://dx.doi.org/10.1111/j.1440-1738.1994.tb00002.x.

Monod, O., Busnardo, R., and Guerrero-Suastegui, M., 2000, Late Albianammonites from the carbonate coverof the Teloloapan arc volcanic rocks(Guerrero State, Mexico): Journal ofSouth American Earth Sciences, v. 13,p. 377–388, http://dx.doi.org/10.1016/S0895-9811(00)00030-4.

Mooney, W.D., and Weaver, C.S., 1989,Regional crustal structure and tecton-ics of the Pacific coastal states; Cali-fornia, Oregon, and Washington, inPakiser, L.C., and Mooney, W.D., eds.,Geophysical framework of the conti-nental United States: Geological Socie-ty of America Memoirs, v. 172, p.129–161, http://dx.doi.org/10.1130/MEM172-p129.

Moore, J.G., 1959, The quartz dioriteboundary line in the western UnitedStates: The Journal of Geology, v. 67,p. 198–210,http://dx.doi.org/10.1086/626573.

Moore, J.G., Grantz, A., and Blake, M.C.,Jr., 1961, The quartz diorite boundaryline in northwestern North America:U.S. Geological Survey ProfessionalPaper 424-C, p. 87–90.

Moore, T.E., 1985, Stratigraphy and tecton-ic significance of the Mesozoictectonostratigraphic terranes of theVizcaino Peninsula, Baja CaliforniaSur, Mexico, in Howell, D.G., ed.,Tectonostratigraphic Terranes of theCircum-Pacific Region: AAPG Cir-cum-Pacific Council for Energy andMineral Resources, Earth ScienceSeries, no. 1, p. 315–329.

Moore, T.E., 1986, Petrology and tectonicimplications of the blueschist-bearingPuerto Nuevo mélange complex, Viz-caino Peninsula, Baja California Sur,Mexico, in Evans, B.W., and Brown,E.H., eds., Blueschists and Eclogites:Geological Society of America Mem-oirs, v. 164, p. 43–58,http://dx.doi.org/10.1130/MEM164-p43.

Moran, A.I., 1976, Allochthonous carbon-ate debris in Mesozoic flysch depositsin the Santa Ana Mountains, Califor-nia: American Association of Petrole-um Geologists Bulletin, v. 60, p.2038–2043.

Morris, W.R., and Busby-Spera, C., 1990, A


submarine-fan valley-levee complex inthe Upper Cretaceous Rosario Forma-tion: Implications for turbidite faciesmodels: Geological Society of Ameri-ca Bulletin, v. 102, p. 900–914,http://dx.doi.org/10.1130/0016-7606(1990)102<0900:ASFVLC>2.3.CO;2.

Morton, D.M., and Baird, A.K., 1976,Petrology of the Paloma Valley ringcomplex, southern Californiabatholith: U.S. Geological Survey Jour-nal of Research, v. 4, no. 1, p. 83–89.

Morton, D.M., and Miller, F.K., 2006, Geo-logical map of the San Bernardinoand Santa Ana 30’ x 60’ quadrangles,California: U.S. Geological SurveyOpen File Report 2006-1217.

Morton, D.M., Miller, F.K., Kistler, R.W.,Premo, W.R., Lee, C.-T.A., Langen-heim, V.E., Wooden, J.L., Snee, L.W.,Clausen, B.L., and Cossette, P., 2014,Framework and petrogenesis of thenorthern Peninsular Ranges batholith,southern California, in Morton, D.M.,and Miller, F.K., eds., PeninsularRanges Batholith, Baja California andSouthern California: Geological Socie-ty of America Memoirs, v. 211, p.61–143,http://dx.doi.org/10.1130/2014.1211(03).

Moyen, J.-F., 2009, High Sr/Y and La/Ybratios: The meaning of the “adakiticsignature”: Lithos, v. 12, p. 556–574,http://dx.doi.org/10.1016/j.lithos.2009.04.001.

Mukhopadhyay, B., and Manton, W.I.,1994, Upper-mantle fragments frombeneath the Sierra Nevada Batholith:partial fusion, fractional crystallization,and metasomatism in a subductionrelated ancient lithosphere: Journal ofPetrology, v. 35, p. 1417–1450,http://dx.doi.org/10.1093/petrolo-gy/35.5.1417.

Murray, J.D., 1979, Outlines of the struc-ture and emplacement history of atonalite pluton in the PeninsularRanges batholith, northern Baja Cali-fornia, Mexico, in Abbott, P.L., andTodd, V.R., eds., Mesozoic CrystallineRocks: California State University,Department of Geological Sciences,San Diego, CA, p. 163–176.

Nieto-Samaniego, A.F., Alaniz-Alvarez,S.A., Silva-Romo, G., Eguiza-Castro,M.H., and Mendoza-Rosales, C.C.,2006, Latest Cretaceous to Miocenedeformation events in the easternSierra Madre del Sur, Mexico, inferredfrom the geometry and age of majorstructures: Geological Society ofAmerica Bulletin, v. 118, p. 238–252,http://dx.doi.org/10.1130/B25730.1.

Nokleberg, W.J., 1981, Stratigraphy andStructure of the Strawberry MineRoof Pendant, Central Sierra Nevada,California: U.S. Geological SurveyProfessional Paper 1154, 18 p.

Nokleberg, W.J., 1983, Wallrocks of theCentral Sierra Nevada Batholith, Cali-fornia: A Collage of AccretedTectono-Stratigraphic Terranes: U.S.Geological Survey Professional Paper1255, 28 p.

Nokleberg, W.J., and Kistler, R.W., 1980,Paleozoic and Mesozoic Deforma-tions, Central Sierra Nevada, Califor-nia: U.S. Geological Survey Profes-sional Paper 1145, 24 p.

Nordstrom, C.E., 1970, Lusardi Formation:A post-batholithic Cretaceous con-glomerate north of San Diego, Cali-fornia: Geological Society of AmericaBulletin, v. 81, p. 601–606,http://dx.doi.org/10.1130/0016-7606(1970)81[607:ROCSIT]2.0.CO;2.

Nourse, J.A., 2001, Tectonic insights froman Upper Jurassic–Lower Cretaceousstretched-clast conglomerate, Cabor-ca–Altar region, Sonora, Mexico: Jour-nal of South American Earth Sci-ences, v. 14, p. 453–474,http://dx.doi.org/10.1016/S0895-9811(01)00051-7.

Nourse, J.A., Premo, W.R., Iriondo, A., andStahl, E.R., 2005, Contrasting Protero-zoic basement complexes near thetruncated margin of Laurentia, north-western Sonora–Arizona internationalborder region, in Anderson, T.H.,Nourse, J.A., McKee, J.W., and Steiner,M.B., eds., The Mojave-Sonora Megas-hear Hypothesis: Development,Assessment, and Alternatives: Geolog-ical Society of America Special Papers,v. 393, p. 123–182, http://dx.doi.org/10.1130/0-8137-2393-0.123.

Ortega-Rivera, A., 2003, Geochronologicalconstraints on the tectonic history ofthe Peninsular Ranges Batholith ofAlta and Baja California: Tectonicimplications for western México, inJohnson, S.E., Paterson, S.R., Fletcher,J.M., Girty, G.H., Kimbrough, D.L.,and Martín-Barajas, A., eds., TectonicEvolution of Northwestern Mexicoand the Southwestern USA: Geologi-cal Society of America Special Papers,v. 374, p. 297–335, http://dx.doi.org/10.1130/0-8137-2374-4.297.

Ortega-Rivera, A., Farrar, E., Hanes, J.A.,Archibald, D.A., Gastil, R.G., Kim-brough, D.L., Zentilli, M., López-Mar-tinez, M., Féraud, G., and Ruffet, G.,1997, Chronological constraints onthe thermal and tilting history of theSierra San Pedro Mártir pluton, BajaCalifornia, México, from U/Pb,

40Ar/39Ar, and fission-trackgeochronology: Geological Society ofAmerica Bulletin, v. 109, p. 728–745,http://dx.doi.org/10.1130/0016-7606(1997)109<0728:CCOTTA>2.3.CO;2.

Ortiz-Hernández, L.E., Acevedo-Sandoval,O.A., and Flores-Castro, K., 2003,Early Cretaceous intraplate seamountsfrom Guanajuato, central Mexico: geo-chemical and mineralogical data:Revista Mexicana de Ciencias Geológi-cas, v. 20, p. 27–40.

Oskin, M., and Stock, J., 2003,Pacific–North America plate motionand opening of the Upper Delfínbasin, northern Gulf of California,Mexico: Geological Society of Ameri-ca Bulletin, v. 115, p. 1173–1190,http://dx.doi.org/10.1130/B25154.1.

Paterson, S.R., Memeti, V., Cao, W., Lackey,J.S., Putirka, K.D., Miller, R.B., Miller,J.S., and Mundil, R., 2012, Day 6:Overview of arc processes and tem-pos, in Formation of the SierraNevada Batholith: Magmatic and Tec-tonic Processes and Their Tempos:Geological Society of America FieldForum Field Trip Guide, p. 2-1–2-23.

Pavlis, T.L., Rutkofske, J., Guerrero, F., andSerpa, L.F., 2014, Structural overprint-ing of Mesozoic thrust systems ineastern California and its importanceto reconstruction of Neogene exten-sion in the southern Basin and Range:Geosphere, v. 10, p. 732–756,http://dx.doi.org/10.1130/GES00993.1.

Peacock, M.A., 1931, Classification ofigneous rock series: The Journal ofGeology, v. 39, p. 54–67,http://dx.doi.org/10.1086/623788.

Pearce, J.A., 1996, Sources and settings ofgranitic rocks: Episodes, v. 19, p.120–125.

Pearce, J.A., Harris, N.B.W., and Tindle,A.G., 1984, Trace element discrimina-tion diagrams for the tectonic inter-pretation of granitic rocks: Journal ofPetrology, v. 25, p. 956–983,http://dx.doi.org/10.1093/petrolo-gy/25.4.956.

Pearson, D.G., and Nowell, G.M., 2002,The continental lithospheric mantle:characteristics and significance as amantle reservoir: Philosophical Trans-actions of the Royal Society of Lon-don, Series A, v. 360, p. 2383–2410,http://dx.doi.org/10.1098/rsta.2002.1074.

Peccerillo, A., and Taylor, S.R., 1976, Geo-chemistry of the Eocene calc-alkalinevolcanic rocks from the Kastamonuarea, northern Turkey: Contributionsto Mineralogy and Petrology, v. 58, p.

452

63–81, http://dx.doi.org/10.1007/BF00384745.

Peck, D.L., 1980, Geologic map of theMerced Peak quadrangle, central SierraNevada, California: U.S. GeologicalSurvey Geologic Quadrangle MapGQ-1531, scale 1:62,500.

Pérez-Gutiérrez, R., Solari, L.A., Gómez-Tuena, A., and Valencia, V.A., 2009, Elterreno Cuicateco: ¿Cuenca oceánicacon influencia de subducción delCretácico Superior en el sur de Méxi-co? Nuevos datos estructurales, geo-químicos y geocronológicos: Revistade la Mexicana de Ciencias Geológi-cas, v. 26, p. 222–242.

Perry, F.V., Baldridge, W.S., and DePaolo,D.J., 1987, Role of asthenosphere andlithosphere in the genesis of LateCenozoic basaltic rocks from the RioGrande Rift and adjacent regions ofthe southwestern United States: Jour-nal of Geophysical Research, v. 92, p.9193–9213, http://dx.doi.org/10.1029/JB092iB09p09193.

Peryam, T.C., Lawton, T.F., Amato, J.M.,González-León, C.M., and Mauel, D.J.,2012, Lower Cretaceous strata of theSonora Bisbee Basin: A record of thetectonomagmatic evolution of north-western Mexico: Geological Society ofAmerica Bulletin, v. 124, p. 532–548,http://dx.doi.org/10.1130/B30456.1.

Phillips, J.R., 1993, Stratigraphy and struc-tural setting of the mid-CretaceousOlvidada Formation, Baja CaliforniaNorte, Mexico, in Gastil, R.G., andMiller, R.H., eds., The PrebatholithicStratigraphy of Peninsular California:Geological Society of America SpecialPapers, v. 279, p. 97–106,http://dx.doi.org/10.1130/SPE279-p97.

Popenoe, W.P., 1941, The Trabuco andBaker conglomerates of the Santa AnaMountains: The Journal of Geology, v.49, p. 738–752,http://dx.doi.org/10.1086/625004.

Poupinet, G., and Shapiro, N.M., 2009,Worldwide distribution of ages of thecontinental lithosphere derived from aglobal seismic tomographic model:Lithos, v. 109, p. 125–130,http://dx.doi.org/10.1016/j.lithos.2008.10.023.

Power, J.A., Coombs, M.L., and Frey-mueller, J.T., 2010, The 2006 eruptionof Augustine volcano, Alaska: USGSProfessional Paper 1769, 667 p.

Premo, W.R., and Morton, D.M., 2014,SHRIMP-RG U–Pb ages of prove-nance and metamorphism from detri-tal zircon populations and Pb–Sr–Ndsignatures of prebatholithic metasedi-mentary rocks at Searl Ridge, northern

Peninsular Ranges batholith, southernCalifornia: Implications for their age,origin, and tectonic setting, in Morton,D.M., and Miller, F.K., eds., PeninsularRanges Batholith, Baja California andSouthern California: Geological Socie-ty of America Memoirs, v. 211, p.449–498, http://dx.doi.org/10.1130/2014.1211(14).

Premo, W.R., Poole, F.G., and Amaya-Martínez, R., 2010, Provenance ofdetrital zircons in Ordovician Iapetusocean-basin quartzites in Sonora,Mexico (abstract): Geological Societyof America Abstracts with Programs,v. 42, No. 5, p. 427.

Premo, W.R., Morton, D.M., and Kistler,R.W., 2014a, Age and isotopic system-atics of Cretaceous borehole and sur-face samples from the greater LosAngeles Basin region: Implications forthe types of crust that might underlieLos Angeles and their distributionalong late Cenozoic fault systems, inMorton, D.M., and Miller, F.K., eds.,Peninsular Ranges Batholith, Baja Cal-ifornia and Southern California: Geo-logical Society of America Memoirs, v.211, p. 21–59, http://dx.doi.org/10.1130/2014.1211(02).

Premo, W.R., Morton, D.M., Wooden, J.L.,and Fanning, C.M., 2014b, U–Pb zir-con geochronology of plutonism inthe northern Peninsular Rangesbatholith, southern California: Impli-cations for the Late Cretaceous tec-tonic evolution of southern Califor-nia, in Morton, D.M., and Miller, F.K.,eds., Peninsular Ranges Batholith, BajaCalifornia and Southern California:Geological Society of America Mem-oirs, v. 211, p. 145–180,http://dx.doi.org/10.1130/2014.1211(04).

Price, N.J., and Audley-Charles, M.G., 1987,Tectonic collision processes after platerupture: Tectonophysics, v. 140, p.121–129, http://dx.doi.org/10.1016/0040-1951(87)90224-1.

Pubellier, M., Rangin, C., Rascon, B.,Chorowicz, J., and Bellon, H., 1995,Cenomanian thrust tectonics in theSahuaria region, Sonora: Implicationsabout northwestern Mexico megas-hears, in Jacques-Ayala, C., González-León, C.M., and Roldán-Quintana, J.,eds., Studies on the Mesozoic of Sono-ra and Adjacent Areas: Boulder: Geo-logical Society of America SpecialPapers, v. 301, p. 111–120,http://dx.doi.org/10.1130/0-8137-2301-9.111.

Ramos-Velázquez, E., Calmus, T., Valencia,V., Iriondo, A., Valencia-Moreno, M.,and Bellon, H., 2008, U–Pb and

40Ar/39Ar geochronology of thecoastal Sonora batholith: New insightson Laramide continental arc magma-tism: Revista Mexicana de CienciasGeológicas, v. 25, p. 314–333.

Rangin, C., 1978, Speculative model ofMesozoic geodymanics, central BajaPeninsula to northeastern Sonora, inHowell, D.G., and McDougall, K.A.,eds., Mesozoic Paleogeography of theWestern United States: Society ofEconomic Paleontologists and Miner-alogists, Pacific Section, Pacific CoastPaleogeography Symposium 2, p.85–106.

Rangin, C., 1986, Contribution à l’étudegéologique form du systèmeCordillerain mesozoique du nord-ouest du Mexique: Societé Géologiquede France, Memoire 148, 136 p.

Ratajeski, K., Glazner, A.F., and Miller,B.V., 2001, Geology and geochemistryof mafic to felsic plutonic rocks in theCretaceous intrusive suite of YosemiteValley, California: Geological Societyof America Bulletin, v. 113, p.1486–1502, http://dx.doi.org/10.1130/0016-7606(2001)113<1486:GAGOMT>2.0.CO;2.

Regard, V., Faccenna, C., Bellier, O., andMartinod, J., 2008, Laboratory experi-ments of slab break-off and slab dipreversal: insight into the AlpineOligocene reorganization: Terra Nova,v. 20, p. 267–273, http://dx.doi.org/10.1111/j.1365-3121.2008.00815.x.

Reiners, P.W., Nelson, B.K., and Ghiorso,M.S., 1995, Assimilation of felsic crustby basaltic magma: Thermal limits andextents of crustal contamination ofmantle-derived magmas: Geology, v.23, p. 563–566, http://dx.doi.org/10.1130/0091-7613(1995)023<0563:AOFCBB>2.3.CO;2.

Renne, P.R., Tobisch, O.T., and Saleeby,J.B., 1993, Thermochronologic recordof pluton emplacement, deformation,and exhumation at Courtright shearzone, central Sierra Nevada, Califor-nia: Geology, v. 21, p. 331–334,http://dx.doi.org/10.1130/0091-7613(1993)021<0331:TROPED>2.3.CO;2.

Richards, J.P., and Kerrich, R., 2007,Adakite-like rocks: Their diverse ori-gins and questionable role in metallo-genesis: Economic Geology, v. 102, p.537–576, http://dx.doi.org/10.2113/gsecongeo.102.4.537.

Rodgers, R.D., Kárason, H., and van derHilst, R.D., 2002, Epeirogenic upliftabove a detached slab in northernCentral America: Geology, v. 30, p.1031–1034, http://dx.doi.org/10.1130/0091-7613(2002)030


<1031:EUAADS>2.0.CO;2.Roeder, D.H., 1973, Subduction and oroge-

ny: Journal of Geophysical Research,v. 78, p. 5005–5024,http://dx.doi.org/10.1029/JB078i023p05005.

Ross, D.C., 1978, The Salinian block–AMesozoic granitic orphan in the Cali-fornia Coast Ranges, in Howell, D.G.,and McDougall, K.A., eds., MesozoicPaleogeography of the Western Unit-ed States: Society of Economic Pale-ontologists and Mineralogists, PacificSection, Pacific Coast PaleogeographySymposium 2, p. 509–522.

Rothstein, D.A., 1997, Metamorphism anddenudation of the eastern PeninsularRanges batholith, Baja CaliforniaNorte, Mexico: Unpublished PhD the-sis, University of California, LosAngeles, CA, 445 p.

Rothstein, D.A., and Manning, C.E., 2003,Geothermal gradients in continentalmagmatic arcs: Constraints from theeastern Peninsular Ranges batholith,Baja California, México, in Johnson,S.E., Patterson, S.R., Fletcher, J.M.,Girty, G.H., Kimbrough, D.L., andMartin-Barajas, A., eds., Tectonic Evo-lution of Northwestern Mexico andthe Southwestern USA: GeologicalSociety of America Special Papers, v.374, p. 337–354, http://dx.doi.org/10.1130/0-8137-2374-4.337.

Rubin, C.M., Saleeby, J.B., Cowan, D.S.,Brandon, M.T., and McGroder, M.F.,1990, Regionally extensive mid-Creta-ceous west-vergent thrust system inthe northwestern Cordillera: Implica-tions for continent- margin tectonism:Geology, v. 18, p. 276–280,http://dx.doi.org/10.1130/0091-7613(1990)018<0276:REM-CWV>2.3.CO;2.

Rudnick, R.L., and Gao, S., 2003, Compo-sition of the continental crust, in Hol-land, H.D., and Turekian, K.K., eds.,Treatise on Geochemistry, v. 3: Elsevi-er-Pergamon, Oxford, UK, p. 1–64.

Sacks, P.E., and Secor, D.T., Jr., 1990,Delamination in collisional orogens:Geology, v. 18, p. 999–1002,http://dx.doi.org/10.1130/0091-7613(1990)018<0999:DICO>2.3.CO;2.

Sajona, F.G., Maury, R.C., Pubellier, M.,Leterrier, J., Bellon, H., and Cotton, J.,2000, Magmatic source enrichment byslab-derived melts in a young post-col-lision setting, central Mindanao(Philippines): Lithos, v. 54, p. 173–206,http://dx.doi.org/10.1016/S0024-4937(00)00019-0.

Saleeby, J.B., 1981, Ocean floor accretionand volcano-plutonic arc evolution in

the Mesozoic Sierra Nevada, Califor-nia, in Ernst, W.G., ed., The Geotec-tonic Development of California,Rubey Volume 1: Prentice-Hall,Englewood Cliffs, NJ, p. 132–181.

Saleeby, J.B., and Busby-Spera, C., 1993,Paleogeographic and tectonic settingof axial and western metamorphicframework rocks of the southern Sier-ra Nevada, California, in Dunne, G.,and McDougall, K., eds., MesozoicPaleogeography of the Western Unit-ed States—II: Pacific Section, Societyof Economic Paleontologists andMineralogists, Book 71, p. 197–226.

Saleeby, J.B., Goodin, S.E., Sharp, W.D.,and Busby, C.J., 1978, Early Mesozoicpaleotectonic-paleogeographic recon-struction of the southern SierraNevada region, in Howell, D.G., andMcDougall, K.A., eds., Mesozoic Pale-ogeography of the Western UnitedStates: Society of Economic Paleon-tologists and Mineralogists, PacificSection, Pacific Coast PaleogeographySymposium 2, p. 311–336.

Saleeby, J.B., Kistler, R.W., Longiaru, S.,Moore, J.G., and Nokleberg, W.J.,1990, Middle Cretaceous silicicmetavolcanic rocks in the KingsCanyon area, central Sierra Nevada,California, in Anderson, J.L., ed., TheNature and Origin of CordilleranMagmatism: Geological Society ofAmerica Memoirs, v. 174, p. 251–271,http://dx.doi.org/10.1130/MEM174-p251.

Saleeby, J.B., Ducea, M.N., Busby, C.J.,Nadin, E.S., and Wetmore, P.H., 2008,Chronology of pluton emplacementand regional deformation in thesouthern Sierra Nevada batholith, Cal-ifornia, in Wright, J.E., and Shervais,J.W., eds., Ophiolites, Arcs, andBatholiths: A Tribute to Cliff Hopson:Geological Society of America SpecialPapers, v. 438, p. 397–427,http://dx.doi.org/10.1130/2008.2438(14).

Salinas-Prieto, J.C., Monod, O., and Faure,M., 2000, Ductile deformations ofopposite vergence in the eastern partof the Guerrero Terrane (SW Mexi-co): Journal of South American EarthSciences, v. 13, p. 389–402,http://dx.doi.org/10.1016/S0895-9811(00)00031-6.

Schildgen, T.F., Yildirim, C., Cosentino, D.,and Strecker, M.R., 2014, Linking slabbreak-off, Hellenic trench retreat, anduplift of the Central and Eastern Ana-tolian plateaus: Earth-Science Reviews,v. 128, p. 147–168, http://dx.doi.org/10.1016/j.earscirev.2013.11.006.

Schmidt, K.L., and Paterson, S.R., 2002, A

doubly vergent fan structure in thePeninsular Ranges batholith: Trans-pression or local complex flow arounda continental margin buttress?: Tec-tonics, v. 21, 1050, http://dx.doi.org/10.1029/2001TC001353.

Schmidt, K.L., Wetmore, P.H., Johnson,S.E., and Paterson, S.R., 2002, Con-trols on orogenesis along an ocean-continent margin transition in theJura– Cretaceous Peninsular Rangesbatholith, in Barth, A., ed., Contribu-tions to Crustal Evolution of theSouthwestern United States: Geologi-cal Society of America Special Papers,v. 365, p. 49–71, http://dx.doi.org/10.1130/0-8137-2365-5.49.

Schmidt, K.L., Paterson, S.R., Blythe, A.E.,and Kopf, C., 2009, Mountain buildingacross a lithospheric boundary duringarc construction: The CretaceousPeninsular Ranges batholith in theSierra San Pedro Mártir of Baja Cali-fornia, Mexico: Tectonophysics, v. 477,p. 292–310, http://dx.doi.org/10.1016/j.tecto.2009.04.020.

Schmidt, K.L., Wetmore, P.H., Alsleben,H., and Paterson, S.R., 2014, Mesozoictectonic evolution of the southernPeninsular Ranges batholith, Baja Cali-fornia, Mexico: Long-lived history ofa collisional segment in the MesozoicCordilleran arc, in Morton, D.M., andMiller, F.K., eds., Peninsular RangesBatholith, Baja California and South-ern California: Geological Society ofAmerica Memoirs, v. 211, p. 645–668,http://dx.doi.org/10.1130/2014.1211(20).

Schoellhamer, J.E., Vedder, J.G., Yerkes,R.F., and Kinney, D.M., 1981, Geologyof the northern Santa Ana Mountains,California: U.S. Geological SurveyProfessional Paper: 420-D, 109 p.

Schweickert, R.A., Bogen, N.L., Girty,G.H., Hanson, R.E., and Merguerian,C., 1984, Timing and structuralexpression of the Nevadan orogeny,Sierra Nevada, California: GeologicalSociety of America Bulletin, v. 95, p.967–979, http://dx.doi.org/10.1130/0016-7606(1984)95<967:TASEOT>2.0.CO;2.

Sedlock, R.L., 1993, Mesozoic geology andtectonics of blueschist and associatedoceanic terranes in the Cedros–Viz-caino–San Benito and Magdalena–Santa Margarita regions, Baja Califor-nia, Mexico, in Dunne, G., andMcDougall, K., eds., Mesozoic Paleo-geography of the Western UnitedStates—Volume II: Pacific Section,Society of Economic Paleontologistsand Mineralogists, Book 71, p.113–126.

454

Sedlock, R.L., 1996, Syn-subduction fore-arc extension and blueschist exhuma-tion in Baja California, Mexico, inBebout, G.E., Scholl, D.W., Kirby,S.H., and Platt, J.P., eds., SubductionTop to Bottom: American Geophysi-cal Union Geophysical Monograph, v.96, p. 155–162, http://dx.doi.org/10.1029/GM096p0155.

Sedlock, R.L., 1999, Evaluation of exhu-mation mechanisms for coherentblueschists in western Baja California,Mexico, in Ring, U., Brandon, M.T.,Lister, G.S., and Willett, S.D., eds.,Exhumation Processes: Normal Fault-ing, Ductile Flow, and Erosion: Geo-logical Society, London, Special Publi-cations, v. 154, p. 29–54,http://dx.doi.org/10.1144/GSL.SP.1999.154.01.02.

Sedlock, R.L., 2003, Geology and tectonicsof the Baja California Peninsula andadjacent areas, in Johnson, S.E., Pater-son, S.R., Fletcher, J.M., Girty, G.H.,Kimbrough, D.L., and Martin-Barajas,A., eds., Tectonic Evolution of North-western Mexico and the SouthwesternUSA: Geological Society of AmericaSpecial Papers, v. 374, p. 1–42,http://dx.doi.org/10.1130/0-8137-2374-4.1.

Shand, S.J., 1943, Eruptive rocks, their gen-esis, composition, classification, andtheir relation to ore deposits: Revised,2nd ed., John Wiley & Sons, NewYork, 444 p.

Shaw, S.E., Todd, V.R., and Grove, M.,2003, Jurassic peraluminous gneissicgranites in the axial zone of thePeninsular Ranges, southern Califor-nia, in Johnson, S.E., Paterson, S.R.,Fletcher, J.M., Girty, G.H., Kim-brough, D.L., and Martín-Barajas, A.,eds., Tectonic Evolution of North-western Mexico and the SouthwesternUSA: Geological Society of AmericaSpecial Papers, v. 374, p. 157–183,http://dx.doi.org/10.1130/0-8137-2374-4.157.

Shaw, S.E., Todd, V.R., Kimbrough, D.L.,and Pearson, N.J., 2014, A west-to-eastgeologic transect across the PeninsularRanges batholith, San Diego County,California: Zircon 176Hf/177Hf evidencefor the mixing of crustal- and mantle-derived magmas, and comparisonswith the Sierra Nevada batholith, inMorton, D.M., and Miller, F.K., eds.,Peninsular Ranges Batholith, Baja Cal-ifornia and Southern California: Geo-logical Society of America Memoirs, v.211, p. 499–536, http://dx.doi.org/10.1130/2014.1211(15).

Silberling, N.J., Schoellhamer, J.E., Gray,C.H., Jr., and Imlay, R.W., 1961, Upper

Jurassic fossils from Bedford Canyonformation, southern California: Amer-ican Association of Petroleum Geolo-gists Bulletin, v. 45, p. 1746–1765.

Silver, L.T., 1971, Problems of crystallinerocks of the Transverse Ranges(abstract): Geological Society ofAmerica Abstracts with Programs, v.3, p. 193–194.

Silver, L.T., and Anderson, T.H., 1974, Pos-sible left-lateral early to middle Meso-zoic disruption of the southwesternNorth American craton margin(abstract): Geological Society ofAmerica Abstracts with Programs, v.6, no. 7, p. 955–956.

Silver, L.T., and Chappell, B., 1988, ThePeninsular Ranges batholith: Aninsight into the Cordilleran batholithsof southwestern North America:Royal Society of Edinburgh Transac-tions: Earth Science, v. 79, p. 105–121.

Silver, L.T., Stehli, F.G., and Allen, C.R.,1963, Lower Cretaceous pre-batholith-ic rocks of northern Baja California,Mexico: American Association ofPetroleum Geologists Bulletin, v. 47,p. 2054–2059.

Silver, L.T., Taylor, H.P., Jr., and Chappell,B., 1979, Some petrological, geochem-ical and geochronological observationsof the Peninsular Ranges batholithnear the international border of theU.S.A. and Mexico, in Abbott, P.L.,and Todd, V.R., eds., Mesozoic Crys-talline Rocks: California State Univer-sity, Department of Geological Sci-ences, San Diego, CA, p. 83–110.

Sinclair, H.D., 1997, Flysch to molassetransition in peripheral forelandbasins: The role of the passive marginversus slab breakoff: Geology, v. 25, p.1123–1126, http://dx.doi.org/10.1130/0091-7613(1997)025<1123:FTMTIP>2.3.CO;2.

Sisson, T.W., Grove, T.L., and Coleman,D.S., 1996, Hornblende gabbro sillcomplex at Onion Valley, California,and a mixing origin for the SierraNevada batholith: Contributions toMineralogy and Petrology, v. 126, p.81–108, http://dx.doi.org/10.1007/s004100050237.

Sisson T.W., Lipman P.W., and Naka J.,2002, Submarine alkalic throughtholeiitic shield-stage development ofKilauea volcano, Hawai‘i, in TakahashiE., Lipman P.W., Garcia M.O., Naka J.,and Aramaki S., eds., Hawaiian volca-noes: deep underwater perspectives:American Geophysical Union Geo-physical Monograph 128, p. 193–219,http://dx.doi.org/10.1029/GM128p0193.

Smith, D.P., and Busby, C.J., 1993, Mid-

Cretaceous crust extension recordedin deep-marine half-graben fill, CedrosIsland, Mexico: Geological Society ofAmerica Bulletin, v. 105, p. 547–562,http://dx.doi.org/10.1130/0016-7606(1993)105<0547:MCCERI>2.3.CO;2.

Smith, T.E., Huang, C.H., Walawender,M.J., Cheung, P., and Wheeler, C.,1983, The gabbroic rocks of thePeninsular Ranges batholith, SouthernCalifornia: Cumulate rocks associatedwith calc-alkaline basalts andandesites: Journal of Volcanology andGeothermal Research, v. 18, p.249–278, http://dx.doi.org/10.1016/0377-0273(83)90011-2.

Smithies, R.H., 2000, The Archaeantonalite-trondhjemite-granodiorite(TTG) series is not an analogue ofCenozoic adakite: Earth and PlanetaryScience Letters, v. 182, p. 115–125,http://dx.doi.org/10.1016/S0012-821X(00)00236-3.

Snow, C.A., and Ernst, W.G., 2008, Detritalzircon constraints on sediment distri-bution and provenance of the Mari-posa Formation, central Sierra NevadaFoothills, California, in Wright, J.E.,and Shervais, J.W., eds., Ophiolites,Arcs, and Batholiths: A Tribute toCliff Hopson: Geological Society ofAmerica Special Papers, v. 438, p.311–330, http://dx.doi.org/10.1130/2008.2438(11).

Solomon, M., 1990, Subduction, arc rever-sal, and the origin of porphyry cop-per-gold deposits in island arcs: Geol-ogy, v. 18, p. 630–633,http://dx.doi.org/10.1130/0091-7613(1990)018<0630:SARATO>2.3.CO;2.

Spencer, C.J., Cawood, P.A., Hawkesworth,C.J., Raub, T.D., Prave, A.R., andRoberts, N.M.W., 2014, Proterozoiconset of crustal reworking and colli-sional tectonics: Reappraisal of thezircon oxygen isotope record: Geolo-gy, v. 42, p. 451–454,http://dx.doi.org/10.1130/G35363.1.

Stewart, J.H., 1970, Upper Precambrianand Lower Cambrian Strata in theSouthern Great Basin, California andNevada: U.S. Geological Survey Pro-fessional Paper 620, 206 p.

Stewart, J.H., 2005, Evidence for Mojave-Sonora megashear—Systematic left-lateral offset of Neoproterozoic toLower Jurassic strata and facies, west-ern United States and northwesternMexico, in Anderson, T.H., Nourse,J.A., McKee, J.W., and Steiner, M.B.,eds., The Mojave-Sonora MegashearHypothesis: Development, Assess-ment and Alternatives: Geological


Society of America Special Papers, v.393, p. 209–231, http://dx.doi.org/10.1130/0-8137-2393-0.209.

Stewart, J.H., McMenamin, M.A.S., andMorales-Ramirez, J.M., 1984, UpperProterozoic and Cambrian Rocks inthe Caborca Region, Sonora, Mexi-co—Physical stratigraphy, Biostratigra-phy, Paleocurrent Studies, and Region-al Relations: Isotopic U–Pb Ages ofZircon from the Granitoids of theCentral Sierra Nevada, California: U.S.Geological Survey Professional Paper1309, 36 p.

Streckeisen, A.L., and LeMaitre, R.W.,1979, Chemical approximation tomodal QAPF classification of theigneous rocks: Neus Jahrbuch furMineralogie, v. 136, p. 169–206.

Sun, S.-s., and McDonough, W.F., 1989,Chemical and isotopic systematics ofoceanic basalts: implications for man-tle composition and processes, inSaunders, A.D., and Norry, M.J., eds.,Magmatism in the Ocean Basins: Geo-logical Society, London, Special Publi-cations, v. 42, p. 313–345,http://dx.doi.org/10.1144/GSL.SP.1989.042.01.19.

Tanaka, H., Smith, T.E., and Huang, C.H.,1984, The Santiago Peak volcanicrocks of the Peninsular Rangersbatholith, southern California: Vol-canic rocks associated with coevalgabbros: Bulletin Volcanologique, v.47, p. 153–171, http://dx.doi.org/10.1007/BF01960546.

Tardy, M., Lapierre, H., Bourdier, J.L.,Coulon, C., Ortiz-Hernández, L.E.,and Yta, M., 1992, Intraoceanic settingof the western Mexico Guerrero ter-rane – Implications for the Pacific-Tethys geodynamic relationships dur-ing the Cretaceous: UniversidadNacional Autóma de México, Institutode Geología, Revista, v. 10, p.118–128.

Tardy, M., Lapierre, H., Freydier, C.,Coulon, C., Gill, J.-B., Mercier de Lep-inay, B., Beck, C., Martinez R., J.,Talavera M., O., Ortiz H., E., Stein,G., Bourdier, J.-L., and Yta, M., 1994,The Guerrero suspect terrane (west-ern Mexico) and coeval arc terranes(the Greater Antilles and the WesternCordillera of Colombia): A late Meso-zoic intra-oceanic arc accreted to cra-tonal America during the Cretaceous:Tectonophysics, v. 230, p. 49–73,http://dx.doi.org/10.1016/0040-1951(94)90146-5.

Tate, M.C., and Johnson, S.E., 2000, Sub-volcanic and deep-crustal tonalite gen-esis beneath the Mexican PeninsularRanges: The Journal of Geology, v.

108, p. 721–728,http://dx.doi.org/10.1086/317948.

Tate, M.C., Norman, M.D., Johnson, S.E.,Fanning, C.M., and Anderson, J.L.,1999, Generation of tonalite andtrondhjemite by subvolcanic fractiona-tion and partial melting in the Zarzaintrusive complex, Western PeninsularRanges Batholith, northwestern Mexi-co: Journal of Petrology, v. 40, p.983–1010, http://dx.doi.org/10.1093/petroj/40.6.983.

Tatsumoto, M., Knight, R.J., and Allègre,C.J., 1973, Time differences in the for-mation of meteorites as determinedfrom the ratio of lead-207 to lead-206:Science, v. 180, p. 1279–1283,http://dx.doi.org/10.1126/sci-ence.180.4092.1279.

Taylor, H.P., and Silver, L.T., 1978, Oxygenisotope relationships in plutonicigneous rocks of the PeninsularRanges batholith, Southern and BajaCalifornia, in Zartman, R.E., ed., Shortpapers of the Fourth InternationalConference, Geochronology, Cos-mochronology, Isotope Geology,1978: U.S. Geological Survey Open-File Report 78-701, p. 423–426.

Teng, L.S., Lee, C.T., Tsai, Y.B., and Hsiao,L.-Y., 2000, Slab breakoff as a mecha-nism for flipping of subduction polar-ity in Taiwan: Geology, v. 28, p.155–158, http://dx.doi.org/10.1130/0091-7613(2000)28<155:SBAAMF>2.0.CO;2.

Thomson, C.N., and Girty, G.H., 1994,Early Cretaceous intra-arc ductilestrain in Triassic–Jurassic and Creta-ceous continental margin arc rocks,Peninsular Ranges, California: Tecton-ics, v. 13, p. 1108–1119,http://dx.doi.org/10.1029/94TC01649.

Till, C.B., Grove, T.L., and Krawczynski,M.J., 2012, A melting model for vari-ably depleted and enriched lherzolitein the plagioclase and spinel stabilityfields: Journal of GeophysicalResearch Solid Earth, v. 117, B06206,http://dx.doi.org/10.1029/2011jb009044.

Tobisch, O.T., Saleeby, J.B., Renne, P.R.,McNulty, B., and Tong, W., 1995, Vari-ations in deformation fields duringdevelopment of a large-volume mag-matic arc, central Sierra Nevada, Cali-fornia: Geological Society of AmericaBulletin, v. 107, p. 148–166,http://dx.doi.org/10.1130/0016-7606(1995)107<0148:VIDFDD>2.3.CO;2.

Todd, V.R., 2004, Preliminary GeologicMap of the El Cajon 30’ x 60’ Quad-rangle, Southern California: U.S. Geo-

logical Survey Open-File Report 2004-1361.

Todd, V.R., and Shaw, S.E., 1979, Structur-al, metamorphic, and intrusive frame-work of the Peninsular Rangesbatholith in southern San DiegoCounty, California, in Abbott, P.L.,and Todd, V.R., eds., Mesozoic Crys-talline Rocks: California State Univer-sity, Department of Geological Sci-ences, San Diego, CA, p. 177–231.

Todd, V.R., and Shaw, S.E., 1985, S-typegranitoids and an I-S line in the Penin-sular Ranges batholith, southern Cali-fornia: Geology, v. 13, p. 231–233,http://dx.doi.org/10.1130/0091-7613(1985)13<231:SGAAIL>2.0.CO;2.

Todd, V.R., Erskine, B.G., and Morton,D.M., 1988, Metamorphic and tectonicevolution of the northern PeninsularRanges batholith, southern California,in Ernst, W.G., ed., Metamorphism andCrustal Evolution of the WesternUnited States, Rubey Volume VII:Prentice Hall, Englewood Cliffs, NJ, p.894–937.

Todd, V.R., Shaw, S.E., and Hammarstrom,J.M., 2003, Cretaceous plutons of thePeninsular Ranges batholith, SanDiego and westernmost ImperialCounties, California: Intrusion acrossa Late Jurassic continental margin, inJohnson, S.E., Patterson, S.R., Fletch-er, J.M., Girty, G.H., Kimbrough, D.L.,and Martín-Barajas, A., eds., TectonicEvolution of Northwestern Mexicoand the Southwestern USA: Geologi-cal Society of America Special Papers,v. 374, p. 185–235, http://dx.doi.org/10.1130/0-8137-2374-4.185.

Tulloch, A.J., and Kimbrough, D.L., 2003,Paired plutonic belts in convergentmargins and the development of highSr/Y magmatism: Peninsular Rangesbatholith of Baja-California and Medi-an batholith of New Zealand, in John-son, S.E., Patterson, S.R., Fletcher,J.M., Girty, G.H., Kimbrough, D.L.,and Martín-Barajas, A., eds., TectonicEvolution of Northwestern Mexicoand the Southwestern USA: Geologi-cal Society of America Special Papers,v. 374, p. 275–295, http://dx.doi.org/10.1130/0-8137-2374-4.275.

Turner, S., Hawkesworth, C., Liu, J.,Rogers, N., Kelley, S., and van Cal-steren, P., 1993, Timing of Tibetanuplift constrained by analysis of vol-canic rocks: Nature, v. 364, p. 50–54,http://dx.doi.org/10.1038/364050a0.

Turner, S., Arnaud, N., Liu, J., Rogers, N.,Hawkesworth, C., Harris, N., Kelley,S., van Clasteren, P., and Deng, W.,1996, Post-collision, Shoshonitic vol-

456

canism on the Tibetan Plateau: Impli-cations for convective thinning of thelithosphere and the source of oceanisland basalts: Journal of Petrology, v.37, p. 45–71, http://dx.doi.org/10.1093/petrology/37.1.45.

Van Buer, N.J., and Miller, E.L., 2010, Sah-wave batholith, NW Nevada: Creta-ceous arc flare-up in a basinal terrane:Lithosphere, v. 2, p. 423–446,http://dx.doi.org/10.1130/L105.1.

van de Zedde, D.M.A., and Wortel, M.J.R.,2001, Shallow slab detachment as atransient source of heat at midlithos-pheric depths: Tectonics, v. 20, p.868–882, http://dx.doi.org/10.1029/2001TC900018.

van der Meulen, M.J., Meulenkamp, J.E.,and Wortel, M.J.R., 1998, Lateral shiftsof Apenninic foredeep depocentresreflecting detachment of subductedlithosphere: Earth and Planetary Sci-ence Letters, v. 154, p. 203–219,http://dx.doi.org/10.1016/S0012-821X(97)00166-0.

van Staal, C.R., Whalen, J.B., McNicoll, V.J.,Pehrsson, S., Lissenberg, C.J.,Zagorevski, A., van Breemen, O., andJenner, G.A., 2007, The Notre Damearc and the Taconic orogeny in New-foundland, in Hatcher, R.D., Jr., Carl-son, M.P., McBride, J.H., and MartínezCatalán, J.R., eds., 4-D Framework ofContinental Crust: Geological Societyof America Memoirs, v. 200, p.511–552, http://dx.doi.org/10.1130/2007.1200(26).

Viallon, C., Huchon, P., and Barrier, E.,1986, Opening of the Okinawa basinand collision in Taiwan: a retreatingtrench model with lateral anchoring:Earth and Planetary Science Letters, v.80, p. 145–155, http://dx.doi.org/10.1016/0012-821X(86)90028-2.

Walawender, M.J., 1979, Basic plutons ofthe Peninsular Ranges batholith,Southern California, in Abbott, P.L.,and Todd, V.R., eds., Mesozoic Crys-talline Rocks: California State Univer-sity, Department of Geological Sci-ences, San Diego, CA, p. 151–162.

Walawender, M.J., Gastil, R.G., Clinken-beard, J.P., McCormick, W.V., East-man, B.G., Wernicke, R.S., Wardlaw,M.S., Gunn, S.H., and Smith, B.M.,1990, Origin and evolution of thezoned La Posta–type plutons, easternPeninsular Ranges batholith, southernand Baja California, in Anderson, J.L.,ed., The Nature and Origin ofCordilleran Magmatism: GeologicalSociety of America Memoirs, v. 174,p. 1–18, http://dx.doi.org/10.1130/MEM174-p1.

Walker, J.D., Burchfiel, B.C., and Davis,

G.A., 1995, New age controls on initi-ation and timing of foreland beltthrusting in the Clark Mountains,southern California: Geological Socie-ty of America Bulletin, v. 107, p.742–750, http://dx.doi.org/10.1130/0016-7606(1995)107<0742:NACOIA> 2.3.CO;2.

Wallace, L.M., Ellis, S., and Mann, P., 2009,Collisional model for rapid fore-arcblock rotations, arc curvature, andepisodic back-arc rifting in subductionsettings: Geochemistry, Geophysics,Geosystems, v. 10, Q05001,http://dx.doi.org/10.1029/2008GC002220.

Walsh, E.O., and Hacker, B.R., 2004, Thefate of subducted continental margins:two-stage exhumation of the high-pressure to ultrahigh-pressure WesternGneiss Region, Norway: Journal ofMetamorphic Geology, v. 22, p.671–689, http://dx.doi.org/10.1111/j.1525-1314.2004.00541.x.

Wang, K.-L., Chung, S.-L., Chen, C.-H.,and Chen, C.-H., 2002, Geochemicalconstraints on the petrogenesis ofhigh-Mg basaltic andesites from thenorthern Taiwan volcanic zone:Chemical Geology, v. 182, p. 513–528,http://dx.doi.org/10.1016/S0009-2541(01)00338-2.

Wang, K.-L., Chung, S.-L., O’Reilly, S.Y.,Sun, S.-S., Shinjo, R., and Chen, C.-H.,2004, Geochemical constraints for thegenesis of post-collisional magmatismand the geodynamic evolution of thenorthern Taiwan region: Journal ofPetrology, v. 45, p. 975–1011,http://dx.doi.org/10.1093/petrolo-gy/egh001.

Wang, Q., Wyman, D.A., Xu, J., Jian, P.,Zhao, Z., Li, C., Xu, W., Ma, J., andHe, B., 2007, Early Cretaceous adakiticgranites in the Northern Dabie Com-plex, central China: Implications forpartial melting and delamination ofthickened lower crust: Geochimica etCosmochimica Acta, v. 71, p.2609–2636, http://dx.doi.org/10.1016/j.gca.2007.03.008.

Warzeski, E.R., 1987, Revised stratigraphyof the Mural Limestone: a Lower Cre-taceous carbonate shelf in Arizonaand Sonora, in Dickinson, W.R., andKlute, M.F., eds., Mesozoic Rocks ofSouthern Arizona Adjacent Areas:Arizona Geological Society, Digest 18,p. 335–363.

Waters, A.C., 1948, Discussion, in Gilluly,J., ed., Origin of Granite: GeologicalSociety of America Memoirs, v. 28, p.104–108, http://dx.doi.org/10.1130/MEM28-p106.

Watson, E.B., 1982, Basalt contamination

by continental crust: Some experi-ments and models: Contributions toMineralogy and Petrology, v. 80, p.73–87, http://dx.doi.org/10.1007/BF00376736.

Weber, B., and Lopéz Martínez, M., 2006,Pb, Sr, and Nd isotopic and chemicalevidence for a primitive island arcemplacement of the El Arco porphyrycopper deposit (Baja California, Mexi-co): Mineralium Deposita, v. 40, p.707–725, http://dx.doi.org/10.1007/s00126-005-0028-4.

Wetmore, P.H., Schmidt, K.L., Paterson,S.R., and Herzig, C., 2002, Tectonicimplications for the along-strike varia-tion of the Peninsular Rangesbatholith, southern and Baja Califor-nia: Geology, v. 30, p. 247–250,http://dx.doi.org/10.1130/0091-7613(2002)030<0247:TIFTAS>2.0.CO;2.

Wetmore, P.H., Herzig, C., Alsleben, H.,Sutherland, M., Schmidt, K.L.,Schultz, P.W., and Paterson, S.R., 2003,Mesozoic tectonic evolution of thePeninsular Ranges of southern andBaja California, in Johnson, S.E.,Paterson, S.R., Fletcher, J.M., Girty,G.H., Kimbrough, D.L., and Martín-Barajas, A., eds., Tectonic Evolution ofNorthwestern Mexico and the South-western USA: Geological Society ofAmerica Special Papers, v. 374, p.93–116, http://dx.doi.org/10.1130/0-8137-2374-4.93.

Wetmore, P.H., Alsleben, H., Paterson,S.R., Ducea, M., Gehrels, G., andValencia, V., 2005, Field trip to thenorthern Alisitos arc sergment: Ances-tral Agua Blanca fault region: Fieldtrip guide for the VII InternationalMeeting of the Peninsular GeologicalSociety, 40 p.

Wetmore, P.H., Hughes, S.S., Stremtan, C.,Ducea, M.N., and Alsleben, H., 2014,Tectonic implications of postcontrac-tional magmatism of the Alisitos arcsegment of the Peninsular Ranges,Baja California, Mexico, in Morton,D.M., and Miller, F.K., eds., PeninsularRanges Batholith, Baja California andSouthern California: Geological Socie-ty of America Memoirs, v. 211, p.669–690, http://dx.doi.org/10.1130/2014.1211(21).

Whalen, J.B., 1985, Geochemistry of anisland-arc plutonic suite: the Uasilau-Yau Yau intrusive complex, NewBritain, P.N.G.: Journal of Petrology,v. 26, p. 603–632, http://dx.doi.org/10.1093/petrology/26.3.603.

Whalen, J.B., and Chappell, B.W., 1988,Opaque mineralogy and mafic mineralchemistry of I- and S-type granites of


the Lachlan Fold Belt, southeast Aus-tralia: American Mineralogist, v. 73, p.281–296.

Whalen, J.B., and Frost, C.D., 2013, The Q-ANOR diagram: A tool for the petro-genetic and tectonomagmatic charac-terization of granitic suites (abstract):South-Central Section, GeologicalSociety of America Abstracts withPrograms, v. 45, no. 3, p. 24.

Whalen, J.B., Percival, J.A., McNicoll, V.J.,and Longstaffe, F.J., 2004, Geochemi-cal and isotopic (Nd–O) evidencebearing on the origin of late- to post-orogenic high-K granitoid rocks in theWestern Superior Province: Implica-tions for late Archean tectonomagmat-ic processes: Precambrian Research, v.132, p. 303–326, http://dx.doi.org/10.1016/j.precamres.2003.11.007.

Whalen, J.B., Wodicka, N., Taylor, B.E., andJackson, G.D., 2010, Cumberlandbatholith, Trans-Hudson Orogen,Canada: Petrogenesis and implicationsfor Paleoproterozoic crustal and oro-genic processes: Lithos, v. 117, p.99–118, http://dx.doi.org/10.1016/j.lithos.2010.02.008.

White, J.D.L., and Busby-Spera, C.J., 1987,Deep marine arc apron deposits andsyndepositional magmatism in theAlisitos Group at Punto Cono, BajaCalifornia, Mexico: Sedimentology, v.34, p. 911–927, http://dx.doi.org/10.1111/j.1365-3091.1987.tb00812.x.

Williams, H., and McBirney, A.R., 1969,Volcanic history of Honduras: Univer-sity of California Publications in theEarth Sciences, v. 85, 101 p.

Williams, H., and McBirney, A.R., 1979,Volcanology: Freeman, Cooper andCo., San Francisco, CA, 397 p.

Williams, H., McBirney, A.R., and Dengo,G., 1964, Geological reconnaissanceof southeastern Guatemala: Universityof California Publications in the EarthSciences, v. 50, 62 p.

Wilmsen, M., Fürsich, F.T., Seyed-Emami,K., Majidifard, M.R., and Taheri, J.,2009, The Cimmerian Orogeny innorthern Iran: tectono-stratigraphicevidence from the foreland: TerraNova, v. 21, p. 211–218,http://dx.doi.org/10.1111/j.1365-3121.2009.00876.x.

Wood, D.J., 1997, Geology of the easternTehachapi Mountains and Late Creta-ceous–Early Cenozoic tectonics of thesouthern Sierra Nevada region, KernCounty, California: Unpublished PhDthesis, California Institute of Technol-ogy, Pasadena, CA, 287 p.

Wooden, J.L., and Miller, D.M., 1990,Chronologic and isotopic frameworkfor Early Proterozoic crustal evolution

in the eastern Mojave Desert region,SE California: Journal of GeophysicalResearch, v. 95, p. 20133–20146,http://dx.doi.org/10.1029/JB095iB12p20133.

Wortel, M.J.R., and Spakman, W., 1992,Structure and dynamics of subductedlithosphere in the Mediterraneanregion: Verhandelingen van hetKoninklijke Nederlandse Akademievan Wetenschappen, v. 95, p. 325–347.

Wortel, M.J.R., and Spakman, W., 2000,Subduction and slab detachment inthe Mediterranean-Carpathian region:Science, v. 290, p. 1910–1917,http://dx.doi.org/10.1126/sci-ence.290.5498.1910.

Wright, J.E., and Wyld, S.J., 2007, Alterna-tive tectonic model for Late Jurassicthrough Early Cretaceous evolution ofthe Great Valley Group, California, inCloos, M., Carlson, W.D., Gilbert,M.C., Liou, J.G., and Sorensen, S.S.,eds., Convergent Margin Terranes andAssociated Regions: A Tribute to W.G.Ernst: Geological Society of AmericaSpecial Papers, v. 419, p. 81–95,http://dx.doi.org/10.1130/2007.2419(04).

Xu, W.-C., Zhang, H.-F., Parrish, R., Harris,N., Guo, L., and Yuan, H.-L., 2010,Timing of granulite-facies metamor-phism in the eastern Himalayan syn-taxis and its tectonic implications:Tectonophysics, v. 485, p. 231–244,http://dx.doi.org/10.1016/j.tecto.2009.12.023.

Received September 2014Accepted as revised September 2014First published on the web October 2014

458

· geoscience canada arc and slab-failure magmatism in cordilleran batholiths ii – the...

Documents