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Título

Diachronic onset of modern style plate tectonics: Episodic crustal growth and reworking: Minas Segment of the Minas Bahia Orogenic System

Texto do resumo

The petrogenesis, geochronology, and isotopic signatures of granitoid rocks are crucial for understanding the periodicity of tectonic processes associated with the supercontinent cycle throughout Earth’s history. The amalgamation of the Columbia supercontinent during the Orosirian (ca. 1.9 Ga) was preceded by a complex history of accretion of Archean nuclei and Proterozoic magmatic arcs. In Brazil, the Minas-Bahia Orogenic System juxtaposed Archean nuclei and Paleoproterozoic magmatic arcs to form the São Francisco-Congo Paleocontinent by the Rhyacian (ca. 2.05 Ga). The southern segment of the Minas-Bahia Orogenic System, known as the Minas segment, extends south to the currently exposed southern São Francisco craton and includes reworked thrust slices within the Ribeira belt. This segment comprises several key tectonic units: the Archean Campos-Gerais-Belo Horizonte block with the Minas Supergroup passive margin, the Mineiro Arc terrane with accreted magmatic arcs from c. 2.4 to 2.1 Ga, the Archean Piedade block-terrane with Paleoproterozoic magmatic arc records and significant late to post-collisional bimodal magmatism, and the Mantiqueira Juiz de Fora arc system. Phanerozoic accretionary and collisional orogenies involve preexisting stable continental lithosphere and oceanic crust consumption, representing end members of different plate tectonic settings. However, the mechanisms for continental crust formation during the Archean and Paleoproterozoic are still debated, with various geodynamic models proposed for magmatic rock addition. Our study indicates that the crust of the amalgamated Paleoproterozoic tectonostratigraphic terranes in the southern São Francisco craton was derived from varying proportions of mantle and crustal isotopic reservoirs. Plate tectonic processes are suggested by a sequence of events involving (1) generation of juvenile subduction-related magmatic arc rocks, (2) collisional orogenesis and remelting of older crust, and (3) post-collisional bimodal magmatism.

Palavras Chave

Paleoproterozoic; São Francisco Paleocontinent; Tectonic