Magmatic evolution of Serrinha suite, southernmost portion of São Francisco Craton, Minas Gerais State, Brazil

Abstract

The Serrinha suite outcrops at the southernmost portion of São Francisco Craton and comprises the Brito quartz-diorite, Brumado de Cima granodiorite, Brumado de Baixo granodiorite, two granophyres and two sub-volcanic – volcanic felsic bodies. The Serrinha suite intrudes metaultramafic, metamafic and metasedimentary rocks of the Nazareno greenstone belt and have amphibolite and quartzite xenoliths of the greenstone. The petrographic similarities of the bodies of the Serrinha suite suggest a same parental magma but the textural diversities point to different crystallization conditions due to the lost of volatiles and cooling of the magma in the various depth levels. In the bodies of the ‘granitic’ texture, volatile elements escape slowly from the magma, nucleation rate and velocity of growth of the crystals were high, while in the sub-volcanic – volcanic rocks volatile elements escape fast, the nucleation rate and the velocity of growth of the crystals were short. The interval age of the sub-volcanic – volcanic rocks (2220 ± 3 Ma – 1,8 Ga) correspond to a new felsic magmatic pulse of southernmost portion of the São Francisco craton.