review of the geotectonic setting of the graciosa province se-brazil, and geological...
TRANSCRIPT
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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
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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)
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THE GRACIOSA PROVINCE
(from Heilbron et al., 2004; Prazeres Filho et al., 2003)
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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)
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GEOCHEMISTRY
Data sources: Kaul and Cordani (2000), Gualda and Vlach (2007b) and Garinand Vlach (unpublished data)
Alkaline association
Aluminous association +
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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).
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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).
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MA
ND
IRA Riebeckite, brown biotite and green-white micas as mafic phases. Accessory minerals
include zircon, fluorite, allanite, astrophyllite, stilpnomelane and sphalerite.
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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).
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MA
ND
IRA
I Green biotite and subordinated hornblende are the main mafic phases. Allanite, opaques, fluorite, zircon, apatite and stilpnomelane as accessory minerals.
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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).
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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
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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).
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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).
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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).