Geologia da porção norte do Cinturão Mineiro no contato com o Bloco Minas: uma abordagem litoestratigráfica, geoquímica, estrutural e metalogenética

Abstract

This work provides new geochronological, petrological, structural, and metallogenetic data for a volcano-sedimentary sequence, previously known as Lafaeite Formation, in the northern portion of the accretionary-to-collisional Mineiro Belt, southern of the São Francisco craton. The sequence begins with basalt to basaltic andesite formed in a forearc setting in 2170 Ma, showing a flat standard of REE, εHf ranging from -6.1 to -7.8. In 2150 Ma, a new pulse of magmatism associated with a picrite-to-boninite series was registered. Intruded in the volcanic sequence, we present new geochronological ages from a quartz-diorite member of the Alto Maranhão Suite in 2140 Ma with an aplite dyke cutting the quartz-diorite in 2130 Ma. Overlying the volcanic sequence is a clastic-chemical sequence with two different sources of sediments deposited between 2100 and 2065 Ma. Three main strike-slip shear zones set the boundaries of Archean-to-Paleoproterozoic terranes that comprise the Minas Block with the Mineiro Belt at the southeastern edge of the Archean São Francisco Protocontinent (SFC) accommodating the accretionary and collisional phases of the Minas-Bahia orogenic cycle, with Rhyacian age. The related structural and shear sense indicators indicate a dominant oblique dextral movement. However, the confined puzzle-like regional geometry of the terranes suggests a complex kinematic history with recurrent activity along the suture zones. In the northern margin of the Mineiro Belt, we propose a magmatic-hydrothermal type for the Fe-(Cu) Água Limpa deposit.