Occurrence of granulite-facies rocks in the Mineiro Belt, Minas Gerais, Brazil

Abstract

Paleoproterozoic granitoids intruding the Archean greenstone belt of Rio das Velhas are found in the region of Lagoa Dourada, which belongs to the Mineiro Belt. The granitoids are cut by amphibolitized mafic rocks which contain xenoliths of granulite facies rocks. The rocks are mafic granulites, characterized by their granoblastic texture and by parageneses orthopyroxene-clinopyroxene-amphibole-plagioclase. As secondary minerals, actinolite, carbonate, epidote, cummingtonite, garnet and quartz can be found. Geothermometric determinations based on the mineral pairs orthopyroxene-clinopyroxene and amphibole-plagioclase yielded temperature values between 700°C and 853°C. The secondary mineral phases are interpreted as a result of a younger metamorphic event.