Review of the geotectonic setting of the Graciosa Province SE-Brazil, and geological

characterization of the Mandira and Guara plutons.

Astrid Siachoque Velandia

Phd. Student Research

Docente Responsvel: Silvio RF Vlach

NOVEMBRO, 2016

SEMINRIOS GERAIS II

INTRODUCTION

The Mantiqueira Province

Orogenic Cycle

Brasiliano I: 880 Ma and 730-700 Ma

Brasiliano II: 640-620 Ma and 600 Ma

Brasiliano III: 595-560 Ma and 520-500 Ma

Dom Feliciano belt (south domain)

Ribeira belt (central domain)

Araua belt (north domain)

THE GRACIOSA PROVINCE

(from Heilbron et al., 2004; Prazeres Filho et al., 2003)

PETROGRAPHIC ASSOCIATIONS

ALKALINE

Metaluminous alkali-feldspar syenites to typically peralkaline hypersolvus granites. Biotite, Ca and Na-Ca pyroxenes, as well as, Na and Na-Ca amphiboles represent the major mafic phases. Zircon, apatite, allanite, sphene, magnetite and ilmenite

as accesory minerals.

Alkaline series I, II and II

ALUMINOUS

Has a subalkaline character and is composed of metaluminous to moderately peraluminoussubsolvus biotite syeno- and monzogranites.

Biotite and Ca-amphibole are the typical mafic minerals. Chevkinita, magnetite, ilmenite,

sphene and sphalerite as accesory minerals. Astrophyllite, narsarsukite, britholite and nacarenobsite occur in the most evolved

varieties.

Aluminous series I and II

(Gualda and Vlach, 2007b)

GEOCHEMISTRY

Data sources: Kaul and Cordani (2000), Gualda and Vlach (2007b) and Garinand Vlach (unpublished data)

Alkaline association

Aluminous association +

THE MANDIRA PLUTON

NEOPROTEROZOIC

CENOZOIC

MESOPROTEROZOIC

Cover sediments

Mandira 1 Acara

Foliated Granites

Mica schist

Migmatites

PALEOPROTEROZOIC

ARCHEAN

Mandira

Mandira Pluton

(From IPT, 1989; Oliveira, 1989).

MANDIRA

Peralkaline alkaline-feldspar granites, hypersolvus, leuco- to hololeucocratic withmassive structures or locally orientated by brittle deformation and equi- toinequigranular texture. i) Riebeckite alkaline feldspar granites, ii) Biotite mesoperthitegranites, iii) Alkali-feldspar granites.

(Oliveira, 1989).

MA

ND

IRA Riebeckite, brown biotite and green-white micas as mafic phases. Accessory minerals

include zircon, fluorite, allanite, astrophyllite, stilpnomelane and sphalerite.

MANDIRA ISieno- and alkaline-feldspar granites, subsolvus, leuco- to hololeucocratic with massive structures(sometimes orientated). Rocks from this unit present medium to fine-grained and inequigranular toporphyritic textures, commonly rapakivi. i) Biotite mesoperthite granites, ii) Porphyritic and/orRapakivi granites .

(Oliveira, 1989).

MA

ND

IRA

I Green biotite and subordinated hornblende are the main mafic phases. Allanite, opaques, fluorite, zircon, apatite and stilpnomelane as accessory minerals.

ACARAAlkaline feldspar, hypersolvus with coarse to medium-grained xenomorphic, localhipidiomorphic, inequigranular with occasionally granophyric textures. These granitespresented cataclastic textures associated with local fault zones. i) Alkali-(Fe)hastingsitegranites, ii) Biotite mesoperthite granites

(Oliveira, 1989).

Hornblende (Fe-hastingsite) as the characteristic mafic phase, accompanied by biotite,allanite, opaques, fluorite, titanite, zircon and stilpnomelane. Rarely riebeckite,carbonates and apatite.

AC

AR

A

AL

BIT

ISE

D G

RA

NIT

ES

Leucocratic granites with medium-grained inequigranular, hypidiomorphic granular texture and localgranophyre intergrowths. The replacement of perthitic alkali feldspar and plagioclase by late albiteforming typical chessboard pattern, albite swapped rims albite-mantled in plagioclase crystals arecommon features in these granites.

(Oliveira, 1989).

GR

EIS

EN

SAltered rocks with massive structure, medium to fine-grained heterogranoblastic texture. The mainconstituents of these rocks are quartz and sericite. Green biotite, sphalerite,albite. Zircon,fluorite, allanite, magnetite, ilmenita, galena, pyrite and chalcopyrite as accessory minerals.Rarely, garnet, cassiterite and carbonates. i) Quartz and sericite, ii) Quartz, iii) Sphalerite, sericiteand quartz, iv) Chlorite topaz and quartz.

(Oliveira, 1989).

THE GUARA PLUTON

Turvo Formation

Aungui Supergruop

Atuba Complex

Itapeuna Intrusive Suite

Guara Granite

Alluvian deposits

Banded gneiss Augen gneiss

Marble Phyllite Micaschist

Paragneiss Micaschist Phyllite

Granite

Desemborque Azeite NEOPROTEROZOIC

CENOZOIC

MESOPROTEROZOIC

PALEOPROTEROZOIC

(From CPRM, 2014).