A GEOTECTONIC VIEW OF THE RIBEIRA AND DOM FELICIANO BELTS

PAULO C. SOARES, ALBERTO P. FIORI, LUIGI CARMIGNANI, SIDNEY P. ROSTIROLLA

Resumo


The Ribeira and Dom Feliciano collision belts are constituted of many overthrust bounded entities, some of them with very different stratigraphic record. They were intensively modified by large transcurrent faults. Two supercycles, one Mesoproterozoic and the other Neoproterozoic, has been recognized in the evolution of the belts, mainly based on the study of the meta-sedimentary complexes. The Mesoproterozoic records a segmented sedimentary basin supercycle and metamorphism; in early Neoproterozoic the convergence zone was stretched and collapsed and the basins evolved through a complete sedimentary supercycle. Inversion is indicated by collisional granites from 750 Ma, culminating with strong deformation, closure of basins, metamorphism and allochthons formation in mainly frontal collision around 650 Ma. Flexural marine molasse basins were formed during Vendian. New inversion was produced by strong convergence and lateral movement of blocks, subcontinental mantle and crustal fusion, late tectonic migmatite and granite intrusions (600-560 Ma). Later on (540-490), alkaline granite intrusion affected many environments, felsic volcanism and continental sedimentary rocks accumulated in many extensional zones and graben-like basins. Syngenetic massive sulfide polymetallic exhalative mineralization is common in the Mesoproterozoic supercycle terranes, while in the Neoproterozoic the common mineralization are epigenetic Pb-Zn massive sulfides in limestones and Cu-Zn-Pb in terrigenous sediments.

Palavras-chave


Collision belts; Brazil Precambrian terranes; Ribeira belt.

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