Abstract

ABSTRACT: The Dom Feliciano Belt is an important Neoproterozoic to Cambrian orogenic complex, extending from eastern Uruguay to southern Brazil. It comprises a collage of oceanic domains and continental fragments developed between 900 and 540 Ma between the Rio de La Plata, Congo and Kalahari cratons. The integration of field and structural data with recent isotopic results has introduced new insights on the sources of the magmatism and sedimentary processes. This paper presents a review of the geochronological results combined with stratigraphic, structural and geochemical data. The evolution of the Dom Feliciano Belt involved three orogenic events known as the Passinho (0.89 - 0.86 Ga), São Gabriel (0.77 - 0.68 Ga) and Dom Feliciano (0.65 - 0.54 Ga). The first two events involved the closure of the Charrua Ocean generating an intra-oceanic arc (Passinho) and, subsequently, an active continental margin arc (São Gabriel). This ocean separated the continental areas represented by the Rio de la Plata Craton and the Nico Perez continental microplate. Closure of the Adamastor ocean resulted in an important collisional event between the Nico Perez Microplate/Rio de La Plata Craton and Kalahari and Congo cratons between 650 and 620 Ma, involving high T/intermediate P metamorphism. At this time of crustal thickening, the partition of the deformation controled the final evolution of the belt with important escape tectonics, responsible for nucleating crustal-scale transcurrent shear zones. These structures were deep and promoted the rise of mafic magmas, which, associated with high regional thermal gradient, lead to an important event of crustal reworking, responsible for the formation of the Pelotas Batholith. The orogenic collapse is represented by late magmatism of Pelotas Batholith and deposition of upper section of the Camaquã Basin.

Highlights

  • The Mantiqueira orogenic system is of one of the main Neoproterozoic orogens formed during the assembly of West Gondwana

  • We present a review of the data on the Dom Feliciano Belt (DFB) geological evolution, in particular the new U-Pelotas Batholith (Pb) geochronological data on igneous and metamorphic rocks and sedimentary

  • The evolution of the São Gabriel Terrane is preserved in igneous zircon grains, indicating ages of 0.93 Ga to 0.9 for the opening of the Charrua Ocean and 0.9 to 0.7 Ga for the closure and generation of the intraoceanic Passinho Arc (0.9 – 0.86 Ga) and the São Gabriel Arc (0.77 – 0.68 Ga)

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Summary

INTRODUCTION

The Mantiqueira orogenic system is of one of the main Neoproterozoic orogens formed during the assembly of West Gondwana. It comprises the Dom Feliciano (Uruguay and southern Brazil), Ribeira (Paraná, São Paulo, Minas Gerais and Rio de Janeiro states) and Araçuaí belts (Espírito Santo, eastern Minas Gerais and southern Bahia states) (e.g.: Heilbron & Machado 2003). The Dom Feliciano Belt (DFB) formed during a longlived evolution of ca. 450 My, starting with the opening of the Charrua Ocean in the southwestern portion of Gondwana, at 950 – 900 Ma. The Dom Feliciano Belt (DFB) formed during a longlived evolution of ca. We present a review of the data on the DFB geological evolution, in particular the new U-Pb geochronological data on igneous and metamorphic rocks and sedimentary

G Gariep
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CONCLUSIONS

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