GRANITOS BORRACHUDOS: UM EXEMPLO DE GRANITOGÊNESE ANOROGÊNICA NA PORÇÃO CENTRAL DO ESTADO DE MINAS GERAIS

Abstract

The Borrachudos Suite, formed by granitoid rocks that crops out in the central part of the Minas Geraisstate, Brazil, presents very uniform chemical and mineralogical compositions.Microscopic and x-ray diffraction investigations show that these rocks are essencially constituted bymicrocline, albite, quartz, biotite, and hornblende. Allanite, zircon, magnetite, and ilmenite are the mainaccesory minerals, though xenotime, monazite, and epidote can be present. Biotite and hornblende are latercrystallized.They are alkaline rocks and plot as anorogenic granites on the geotectonic discrimination diagrams.The REE distribution pattern agrees with this classification. The geochemical data, to point a crustal origin.The age about 1.7 Ga obtained by Dossin et al. (1993) allows to link the Borrachudos granitoids to theopening of the Espinhaço Rift.