Geology and Lithogeochemistry of the Supracrustal Sequence and Interlayered Metabasites of NE Santos Dumont Region (MG)

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 (Conceição 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.