Serra do Barro Branco orthogneiss: An untimely record of West Gondwana amalgamation in the Sao Roque Domain

Autor(es)

Balis, Mikaella ^[1] ; Campos Neto, Mario da Costa ^[2] ; Alves, Adriana ^[2]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Geociencias, Programa Posgrad, Sao Paulo - Brazil

^[2] Univ Sao Paulo, Inst Geociencias, Dept Mineral & Geotecton, Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Precambrian Research; v. 350, NOV 2020.
• Citações Web of Science: 0

Resumo

The Paranapanema-Sao Francisco convergence is partially recorded in the arc-related high-K calc-alkaline intermediate magmatism of south-eastern Brazil (Southern Brasilia Orogen) during the West Gondwana assembly. Similar geochemical affinities are widespread in the crustal fault-bounded slice, Sao Roque Domain, as in tectonic domains of the eastern Sao Francisco margin. The Sao Roque Domain comprises metavolcano-sedimentary sequences of Statherian maximum depositional age. Detrital zircon provenance points to a Rhyacian (2.17 Ga) proximal source belonging to the Paranapanema block. Unprecedented Tonian zircon U-Pb ages suggest a protracted evolution. The domain initiated magmatic activity at 680 Ma (Barro Branco orthogneiss) with weak Hf-Nd radiogenic signatures that agree with the arc evolution of the Socorro-Guaxupe Nappe. Granitoids grading from intermediate metaluminous to evolved peraluminous compositions intruded at 625 Ma (inequigranular orthogneiss) and 620 Ma (Moinho granodiorite). The most voluminous magmatism occurred within 610-590 Ma. Hf-Nd radiogenic compositions of the Ediacaran granitoids imply crustal participation. All granitoids have arc-related affinity with high Sr/Y and LREE, low Nb and Ti, and absence of Eu anomalies that indicate a lower crustal source with residual garnet ( +/- amphibole +/- rutile). The petrogenetic and geochronological constraints favor a retro-arc setting for the Sao Roque Domain. Slab roll-back could have led to the northward migration of magmatism (Socorro-Guaxupe Nappe) producing a chronological gap in the retro-arc. The Ediacaran magmatism was probably triggered by the relaxation of the subducting angle. The last-longing subduction beneath the Paranapanema plate might have contributed to the high-K and radiogenic compositions through relamination. Monazite U-Pb ages from 630 to 600 Ma may be evidence of a thermal episode in the retro-arc, overlapping the syn-collisional metamorphism in the Southern Brasilia Orogen. (AU)

• Processo FAPESP: 15/03737-0 - O Cráton Rio de la Plata e o Gondwana Ocidental
• Beneficiário: Miguel Angelo Stipp Basei
• Modalidade de apoio: Auxílio à Pesquisa - Temático