The role of deformation-assisted by water influx on partial melting of a granite protolith, and its role in the evolution of southwestern Sao Francisco Craton margin, Brazil

Autor(es)

Juliao, Eduardo Lopes ^[1] ; Moraes, Renato ^[1] ; Faleiros, Frederico Meira ^[1] ; da Motta, Rafael Goncalves ^[2] ; Quiroz Valle, Francy Roxana ^[1] ; Leao Lopes, Leonardo Brenguere ^[3]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Geociencias, Dept Mineral & Geotecton, Rua Lago 562, BR-05508900 Sao Paulo, SP - Brazil

^[2] Univ Fed Rio Grande do Norte, Ctr Ciencias Exatas & Terra, Dept Geol, BR-59078970 Natal, RN - Brazil

^[3] CPRM Geol Survey Brazil, Rua 148, 485 Setor Marista, BR-74170110 Goiania, Go - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Journal of South American Earth Sciences; v. 112, n. 1 DEC 2021.
• Citações Web of Science: 0

Resumo

The Areado Granite-Migmatite Unit is part of the basement from the Southern Brasilia Orogen at southwestern Sao Francisco Craton margin, outcropping between Alfenas and Areado regions, Minas Gerais State, Brazil. This unit is composed of garnet meta-syenogranite, hornblende-garnet metatexite, and stromatic diatexite with different degrees of partial melting. This study characterizes the garnet meta-syenogranite, its migmatitic counterparts and investigates the different patterns of deformation and partial melting involved to produce the observed migmatites within the unit. The connection between the garnet meta-syenogranite, hornblende-garnet metatexite, and biotite diatexite is inferred from field observations and assemblage of accessory minerals. Petrography associated with modal analysis, structural data, quartz c-axis analysis, zircon U-Pb (LA-MC-ICP-MS and SHRIMP) dating, as well as trace elements chemical analysis in quartz and titanite to determine metamorphic, partial melting, and deformation evolution were used as tools in this investigation. The garnet meta-syenogranite has a crystallization age of 2069.8 +/- 5 Ma. Lower intercepts from zircon indicate a metamorphic and partial melting age between 671 +/- 58 and 657 +/- 40 Ma. Melt crystallization ages are inferred between 622 +/- 7 Ma and 604 +/- 6 Ma. Different rates of partial melt are structurally connected, being higher at the base of the unit, and are related with contrasting amounts of water influx and deformation. The deformation during metamorphism/partial melting was the main cause of the differential aspect of the produced rocks. Quartz c-axis thermometer yielded deformation temperatures of 765-935 degrees C and other pulses occurred between 590 and 715 degrees C, both between 11 and 15 kbar. Those values match the Zr-in-titanite thermobarometer data, which is 670-710 degrees C for low-temperature titanite and 785-815 degrees C for high-temperature crystals. These data indicate that the protolith was generated at a Rhyacian late magmatic stage of the Mineiro Belt and passed by a Neo-proterozoic deformational-metamorphic event of high temperature. (AU)

• Processo FAPESP: 18/10012-0 - Fluxo de fluidos, deformação e significado tectônico de zonas de cisalhamento regionais do Cinturão Ribeira Meridional
• Beneficiário: Frederico Meira Faleiros
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 16/22627-3 - Metamorfismo e fusão parcial em Orógenos antigos II
• Beneficiário: Renato de Moraes
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 13/04007-0 - Metamorfismo e fusão parcial em orógenos antigos
• Beneficiário: Renato de Moraes
• Modalidade de apoio: Auxílio à Pesquisa - Regular