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Study of the Brasilia Belt in the Northwestern Passos Nappe Region


The Passos Nappe is located at the Southern portion of the Brasilia Belt and records an inverted metamorphic gradient that increases from greenschist facies, at the bottom of the sequence, to high-pressure granulite at the top. Although several studies have been carried out in the area, detailed mapping and metamorphic studies have never been carried out on its NW portion. In recent geological mapping campaigns, geological boundaries between the Internal Domain (Passos Nappe) and the External Domain of the Brasilia Belt have been better constrained. New geological units have been identified and the relationship of these units with the geologic evolution of the areas has to be better investigates. Taking into account the new findings, as well as previously available data, three questions need to be answered and are the main aim of this project: 1) the lack of geochronological data on the External Domain sequences that puts in check the stratigraphic correlations proposed by the literature; 2) the intriguing occurrence of garnet mega-porphyroblasts (3 to 7 cm in size) that occur in the middle portion of the sequence; 3) Is the metamorphic gradient continuous? Are the discontinuities within the sequence? This project proposal aims to answer these questions by means of U-Pb provenance studies in detrital Zircons, detailed in situ chemical studies of the garnet mega-porphyroblasts with electron microprobe, and termobarometric studies using the Zr in Rutile and Ti and Quartz geothermo(baro)meter. The results will support a better understanding of the tectonic and metamorphic evolution of the southern portion of Brasilia Belt. It will also support a better understanding of the deformational and metamorphic processes that are involved in the formation of orogenic belts. (AU)

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Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
HARTUNG, RAFAEL F.; SIMOES, LUIZ S. A.; TROUW, RUDOLPH A. J.; SILVA, ALEX J. C. A.. Growth mechanism of garnet megaporphyroblasts of the Passos Nappe, Southern Brasilia Orogen, Brazil. Journal of South American Earth Sciences, v. 102, . (17/03663-1)
SILVA, ALEX J. CHOUPINA A.; SIMOES, LUIZ SERGIO A.; DUFRANE, SCOTT ANDREW; SA ALKMIN, LEONARDO AZEVEDO; CERRI, RODRIGO IRINEU. U-Pb ages of detrital zircon grains for the Canastra Group and Passos Nappe units and U-Pb and Lu-Hf isotope analyses from orthogneisses: Provenance and tectonic implications, southern Brasilia Belt, Brazil. Precambrian Research, v. 346, . (17/03663-1)
SILVA, ALEX J. CHOUPINA A.; SIMOES, LUIZ SERGIO A.; DUFRANE, SCOTT ANDREW. Tectonic implications of U-Pb ages of detrital zircon grains in metasedimentary rocks of the northwestern sector of the Passos Nappe, southern Brasilia Belt, Brazil. Journal of South American Earth Sciences, v. 95, . (17/03663-1)

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