Mapeamento Geológico das Rochas Gnáissicas-Migmatíticas e Metassedimentares do Grupo Araxá na Região de Araguari (MG) - Cumari (GO)

Abstract

The following project resulted in a geological map with a scale of 1: 50,000, in an area of 6000 ha on the border between the States of Minas Gerais and Goiás. The area is located in the Triângulo Mineiro and in the Southeast of Goiás, at the height of the km- 0 from the federal highway BR-050 and extends over 12 km over the Paranaíba River downstream of the Emborcação Dam. The geological context is inserted in the Brasília Meridional Belt and is composed by meta-sedimentary rocks of the Araxá Group, gneiss and migmatitic rocks of the Ortognaisse Goiandira and metavolcan-sedimentary sequences of the Maratá Complex. The purpose of this mapping is to detail and integrate the continuity of these units between the states of Minas Gerais and Goiás, so that there is a unified and more detailed cartography, contributing to the advancement of Brazilian geological cartography. The main justification is the lack of work on the transition of units between these two States, especially when it comes to the Precambrian units of the Brasília Belt. The local geology is represented by two units, metasedimentary and Gnáissica Migmatítica, subdivided into garnet-biotite-muscovite schist, quartzite / muscovite shale, garnet-biotite-muscovite gneiss and migmatite respectively. The metasedimentary rocks were associated with the Araxá B Group and the quartz-feldspathic rocks with the Ortognaisses Goiandira. Two tectonic foliations were identified, Sn, marked by compositional banding and schistosity, and Sn + 1, characterized by being a more spaced foliation marked by crenulation cleavage and axial plane folds, in addition to these structures, there is the occurrence of shear with dextral kinematics (Dn + 2). The area was divided into West and East domains, separated by the push failure. The first is made up of metasedimentary rocks and has typical paragenesis of the amphibolite facies. The second consists of quartz-feldspar rocks and has paragenesis compatible with upper amphibolite facies, with minimum temperatures of 700ºC. All units were retrometamorphized to green schist facies, evidenced mainly by the chloritisation of biotite and garnet, and the saussuritization of plagioclases. With regard to geological cartography, this work represents how important are the detailed studies along the boundary of these states, in order to obtain detailed information about the Southern Brasília Belt.