Abstract
The region near Santos Dumont town consists of a sequence of interlayered metabasic rocks and supracrustal gneisses. Two lithological units were individualized based on geological-structural mapping (1:50,000), petrography and lithogeochemistry: a metasedimentary sequence interlayered with metavolcanic rocks (Conceicao do Formoso Group), and a group of metabasic rocks (Oliveira Fortes Unit). The metavolcanic sequence is represented by gneisses of dacitic and riolitic compositions, with calc-alkaline affinity and weak peraluminous character, suggesting that the original magma was contaminated by crustal component. These gneisses have a geochemical signature of a destructive margin environment and their origin can be related to volcanic arc magmatism. The metabasic rocks present geochemical signature of intraplate tholeiitic basalts and are interpreted as sills interlayered within the metavolcanosedimentary sequence.
Highlights
Santos Dumont region, situated in the southeastern portion of Minas Gerais State, can be considered as a key area to unravel the tectonic evolution of Araçuaí and Ribeira belts
The area can be located within the Mantiqueira Province (Almeida et al, 1977, 1981), near the SSE boundary of the São Francisco Craton and raises different interpretations of its tectonic position
Trouw et al (2013) insert the region in the southernmost portion of the Araçuaí Belt limited to the south by the Brasília belt
Summary
Santos Dumont region, situated in the southeastern portion of Minas Gerais State, can be considered as a key area to unravel the tectonic evolution of Araçuaí and Ribeira belts. The area can be located within the Mantiqueira Province (Almeida et al, 1977, 1981), near the SSE boundary of the São Francisco Craton and raises different interpretations of its tectonic position. The existence of open to tight folding, associated with NE-SW low angle ductile shear zones characterize its position on the external portion of the Ribeira Belt. To the north of this thrust boundary, no basement associations were found and rocks consists of thick sequences of gneisses of different origins (Conceição do Formoso Group) interlayered with centimetric to hectometric (1cm to 100 m) metabasite bodies (Oliveira Fortes Unit), metamorphosed under amphibolite facies conditions. This work leads to regional correlations, adding data to broader discussions on tectonic models of the Araçuaí and Ribeira belts
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