GEOLOGICAL EVOLUTION OF MIGMATITES FROM THE INFRASTRUCTURE OF SOUTHERN BRASÍLIA BELT NAPPE SYSTEM

Abstract

The Southern Brasília Belt is configured as a nappe system with tectonic transport, of at least 300km, towards ENE. This system of nappes represents three major tectonic settings (WSW-ENE): (1) magmatic arc domain developed in the active continental margin of the Paranapanema plate (Socorro-Guaxupé), (2) subducted continental domain (Andrelândia Nappe System) and (3) passive continental margin and rift domain related to the São Franscisco plate (Carrancas and Lima Duarte nappe systems). The infrastructure of the nappe system consisting predominantly of Archean to Paleoproterozoic orthogneisses crops out on a range of more than 300km long with ENE-WSW trend. In the western portion of this range the polycyclic Archean migmatites of Amparo Complex occur as an antiformal core. Towards the east occur the Rhyacian migmatites associated with the Andrelândia nappe system. In the northeast occur migmatites of the infrastructure of Carrancas nappe system. These migmatites that form the infrastructure of southern Brasília Belt nappe system will be investigated in this research. In-situ mineral analysis associated with petrography, elemental and isotope (Rb-Sr and Sm-Nd) geochemistry will be used as tools in the search for a petrogenetic model for these migmatites. The different zircon crystals domains will be defined through imaging techniques such as cathodoluminescence. Geochemical and isotope (U-Pb and Lu-Hf) analysis will be conducted in the different crystal domains. This combined study enables to define the true meaning of multiple ages. It is intended to establish the tectonic evolution of these migmatites and their relation to events of continental growth and the supercontinents history, from Columbia to Gondwana, through an integrated study of elemental and isotope geochemistry, petrology and structural geology.