Petrology and geochemistry of the Neoproterozoic Guaxupégranulite facies terrain, southeastern Brazil

Iyer, Brijesh; Choudhuri, Asit; Pattison, David R.M.; Paoli, Glen R. De

doi:10.1016/0301-9268(95)00043-7

Cited by 23 publications

(7 citation statements)

References 54 publications

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“…1,078°C and 14.8 kbar) are interpreted as close to the metamorphic peak in the basal portion of the Guaxupé Complex and are in agreement with ultra-high temperature metamorphic conditions. The P-T peak and re-equilibration conditions are congruent with the maximum and minimal temperatures and pressures previously calculated for the basal granulite unit of Guaxupé Complex (850°C and 8.5 kbar - Iyer et al 1996;900°C and 12.5 kbar -Campos Neto and Caby 1999;1,040°C and 14.4 kbar -Del Lama et al 2000;890°C and 11 kbar -Garcia and Campos Neto 2003;900°C and 10 kbar -Nascimento and Oliveira 2012;900°C and 12 kbar -Rocha et al 2018;998 ± 23°C -Tedeschi et al 2018).…”

Section: Yardleysupporting

confidence: 86%

“…In the Southern Brasília Orogen, central-south Brazil, the Guaxupé Nappe comprises granulitic terranes that record high to ultra-high temperature metamorphism conditions (Iyer et al 1996, Campos Neto and Caby 1999, 2000, Del Lama et al 2000, Garcia and Campos Neto 2003, Nascimento 2010, Nascimento and Oliveira 2012, Rocha et al 2017, Tedeschi et al 2018, Leme 2019.…”

Section: Introductionmentioning

confidence: 99%

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Ultra-high temperature metamorphism in the Guaxupé Complex: a lower crust segment

2020

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The area is located at the northern boundary of the Guaxupé Complex, which corresponds to the northern domain of the Socorro-Guaxupé Nappe, in the Southern Brasília Orogen, close to the Varginha Shear Zone. This study integrates petrography, mineral chemistry, optimized geothermobarometry, and trace elements thermometry data, aiming to define and characterize the metamorphic conditions and the P-T path of the granulitic rocks from the northern portion of the Guaxupé Complex. In the area, the Guaxupé Complex consists predominantly of ortho-derived rocks represented by granulitic gneisses (orthopyroxene gneisses) of felsic to mafic composition with clinopyroxene, garnet, amphibole, biotite, and rare rutile. The calculated pressure and temperature conditions record metamorphic peak around 1,078°C and 14.8 kbar, compatible with ultra-high temperature metamorphism conditions, marked by grt + cpx + opx + pl ± qtz ± rt mineral assemblages, and granulite facies re-equilibration in the sillimanite stability field at P-T conditions of 930 to 800°C and 13.5 to 11.0 kbar. The results are compatible with deeper portions of the lower crust involved in a continental collision and suggest a clockwise P-T path, typical of crustal thickening zones, followed by near-isothermal decompression during tectonic exhumation.

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Section: Yardleysupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Ultra-high temperature metamorphism in the Guaxupé Complex: a lower crust segment

2020

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“…Vasconcellos et al (1991) estimated temperatures of 900AE 50 C, at pressures of 11 AE 1 kbar, and Del Lama (1993) presented data for peak-metamorphic conditions of 870±890 C and 11±12 kbar, with re-equilibration at 740±770 C and 9.2 kbar. Minimum conditions for peak metamorphism of 850 C and 8.5 kbar were estimated by Iyer et al (1996). Temperatures over 950 C are due to mangerite intrusions, which were emplaced in the southern part of the study area.…”

Section: Geological Settingmentioning

confidence: 98%

Exhumation of high‐pressure granulites of the Guaxupé Complex, southeastern Brazil

Lama¹,

Zanardo

Oliveira

et al. 2000

Geological Journal

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This paper describes tectonic and metamorphic features of Precambrian rocks from the Guaxupe Â Complex and Varginha Shear Zone (VSZ) near the city of Guaxupe Â in the southern part of the Sa Äo Francisco Craton, southeastern Brazil. The VSZ separates the metasediments of Araxa Â Group to the north from the granulites of Guaxupe Â Complex to the south. The sinistral transcurrent VSZ crosses the entire area striking approximately E±W, bending towards SE in the eastern part. Because of this bend, transpressional movement occurred, facilitating the exhumation of the garnet-rich rocks of the deepest exposed part of the granulitefacies terrane.In the garnet granulites the highest pressure±temperature conditions recorded are approximately 1040 C and 14.4 kbar. The rocks underwent decompression from 14.0 kbar to 8.0 kbar, cooling from 980 C to 710 C, the retrograde path following the boundary between the kyanite and sillimanite stability ®elds. This interval is interpreted to record the uplift of the lower crustal granulite-facies terrane and re-equilibration during magmatic intrusions. For the felsic granulites an interval of 700±810 C and 8.0±11.5 kbar was attained, also pointing to regional decompression.The granulites of the Guaxupe Â Complex comprise a medium-to high-pressure lower-crustal terrane, with local occurrences of higher-pressure garnet-rich gneisses, which were uplifted along a transpressional segment of the VSZ. Figure 1. Schematic geological map and location of the research area (adapted from Fonseca et al. 1979).232e. a. del lama et al.

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“…A crustal duplex structure along the lower crust nappes and upper nappes has been proposed previously by Haralyi and Hasui (1982) and following works by Valeriano et al (2008), Hasui (2010) and Campos Neto et al (2011) with geochemistry constraints for deep crust involvement (Campos Neto & Caby 1999, Iyer et al 1996, Lama et al 1998. Complex geometries for both thrust-folding and shear systems observed in forward models, structural and metamorphism features are expected in a continuum crustal model for orogen evolution (Boyer & Elliott 1982, Sanderson 1984, Sylvester 1988.…”

Section: Gravity Domains (From a To H) Tectonic Frameworkmentioning

confidence: 61%

Geophysical perspective on the structural interference zone along the Neoproterozoic Brasília and Ribeira fold belts in West Gondwana

Motta

Morales²,

Filho³

2017

Braz. J. Geol.

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ABSTRACT:The Brasília and Ribeira fold belts have been established in south-southwestern São Francisco Craton during the Brasiliano-Pan African orogeny (0.9-0.5 Ga -Tonian to Cambrian), and played an important role in West Gondwana continent assembly. The region is given by a complex regional fold and thrust belt superposed by shearing during the orogeny late times, with superposing stress fields forming a structural interference zone. These thrust sheets encompasses assemblies from lower-to upper--crust from different major tectonic blocks (Paranapanema, São Francisco), and newly created metamorphic rocks. Re-evaluation of ground gravity datasets in a geologically constrained approach including seismology (CRUST1 model) and magnetic data (EMAG2 model) unveiled details on the deep-crust settings, and the overall geometry of the structural interference zone. The Simple Bouguer Anomaly map shows heterogeneous density distribution in the area, highlighting the presence of high-density, high metamorphic grade rocks along the Alterosa suture zone in the Socorro-Guaxupé Nappe, lying amid a series of metasedimentary thrust scales in a regional nappe system with important verticalization along regional shear zones. Forward gravity modeling favors interpretations of structural interference up North into Guaxupé Nappe. Comparison to geotectonic models shows similarities with modern accretionary belts, renewing the discussion. KEYWORDS: modeling; gravity; magnetics; thrust tectonics; shear zones. RESUMO: Os cinturões de dobramento Brasília e Ribeira foram estabelecidos na porção sul-sudoeste do Cráton São Francisco durante a orogenia

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Petrology and geochemistry of the Neoproterozoic Guaxupégranulite facies terrain, southeastern Brazil

Cited by 23 publications

References 54 publications

Ultra-high temperature metamorphism in the Guaxupé Complex: a lower crust segment

Ultra-high temperature metamorphism in the Guaxupé Complex: a lower crust segment

Exhumation of high‐pressure granulites of the Guaxupé Complex, southeastern Brazil

Geophysical perspective on the structural interference zone along the Neoproterozoic Brasília and Ribeira fold belts in West Gondwana

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