Tectonic implications of juxtaposed high- and low-pressure metamorphic field gradient rocks in the Turvo-Cajati Formation, Curitiba Terrane, Ribeira Belt, Brazil

Autor(es)

Ricardo, Bruna S. ^[1] ; Faleiros, Frederico M. ^[1] ; de Moraes, Renato ^[1] ; Siga Junior, Jr., Oswaldo ^[1] ; Campanha, Ginaldo A. C. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Geociencias, Rua Lago 562, BR-05508080 Sao Paulo, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Precambrian Research; v. 345, AUG 2020.
• Citações Web of Science: 0

Resumo

The Turvo-Cajati Formation (TCF) is an important unit forming the Curitiba Terrane, a major segment of the southern Ribeira Belt, SE Brazil. It is composed of rocks of greenschist (LTCF), amphibolite (MTCF) and granulite (HTCF) facies conditions. Previous studies in the HTCF indicate that the unit underwent extensive partial melting under high-pressure conditions (670-810 degrees C and 9.5-12 kbar), within the kyanite stability field. In this paper, a study of the metamorphic zoning within the LTCF and MTCF is undertaken using pseudosection modeling in the NCKFMASHTO and MnNCKFMASHTO model systems coupled with detrital zircon U-Pb geochronology. Four metamorphic zones are recognized for the LTCF and MTCF: biotite, garnet, staurolite and sillimanite zones, with predominance of sillimanite zone and pressures lower than 8 kbar, as staurolite breaks down straight to sillimanite, without formation of a kyanite zone. Pseudosections yielded metamorphic peak conditions of similar to 530-560 degrees C and similar to 6-7.5 kbar (garnet zone) and similar to 660-690 degrees C and similar to 6-7.5 kbar (sillimanite zone). The metamorphic field gradient is flat and of low to medium pressure, below the typical Barrovian-type baric regime, and different from the HTCF. Available petrological and geochronological data suggest that the TCF comprises a paired low-P and high-P metamorphic belt, associated with a major Ediacaran suture zone in the southern Ribeira Belt. Probability density plots from detrital zircon U-Pb ages indicate late-Cryogenian-Ediacaran arc-related and Rhyacian sources for all TCF sub-units. This scenario suggests that the TCF is made up of a collisional juxtaposition of an accretionary wedge (HTCF) and a back-arc basin (LTCF and MTCF) on the border of a microplate, which includes a Rhyacian basement microcontinent, the Atuba Complex. It is inferred the high metamorphic gradient recorded in the LTCF and MTCF was related with asthenospheric upwelling in the back-arc region, which also produced extensive partial melting in the Atuba Complex basement. (AU)

• Processo FAPESP: 18/01572-1 - Petrocronologia aplicada ao estudo do contexto tectono-metamórfico das rochas da Formação Turvo-Cajati, Domínio Curitiba, e sua influência na evolução da Faixa Ribeira, Cajati, SP
• Beneficiário: Bruna da Silva Ricardo
• Modalidade de apoio: Bolsas no Brasil - Mestrado
• Processo FAPESP: 15/04487-7 - Metamorfismo e evolução tectônica do Cinturão Ribeira meridional: relações entre os terrenos Embu, Apiaí e Curitiba
• Beneficiário: Frederico Meira Faleiros
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• 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: 16/12986-6 - Zonação metamórfica da formação Turvo-Cajati
• Beneficiário: Bruna da Silva Ricardo
• Modalidade de apoio: Bolsas no Brasil - Iniciação Científica