Within plate, arc, and collisional Neoproterozoic granitic magmatism in the Araxá Group, Southern Brasília belt, Minas Gerais, Brazil

Abstract

Three Neoproterozoic granitic episodes associated with the Arax Group, in Southern Braslia Belt between the cities of Arax and Cascalho Rico, Minas Gerais State, Brazil, are characterized from the geologic, geochemical, and geochronological points of view. The earliest episode, of 833 Ma, generated in a within-plate environment, is represented by the Quebra Anzol Granite, which has: low 87 Sr/ 86 Sr = 0.706 ratios and Nd(833) = -3.98; high levels of SiO 2 , Na 2 O, MnO, Nb, Y and Co; and low concentrations of Sr and Ba, with the absence of anorthite and presence of diopside, acmite, and positive Eu anomaly, therefore it may have been originated from mantle sources with small crustal contamination. The second episode, of 790 Ma, is represented by the pre-collisional Monte Carmelo Granitic Complex, which was partially remobilized in a collisional event around 630 Ma. It is metaluminous to peraluminous with low 87 Sr/ 86 Sr ratios of 0.706, high light rare earth elements fractionation relative to heavy rare earth elements, and negative Nb, Ta, Sr, P, and Ti anomalies. Their Nd(790) = -2.218, with T DM = 1.29 Ga, indicate an origin from juvenile sources and reveal the existence of a late Mesoproterozoic magmatic arc in this region. The last granitic episode has taken place in a collisional tectonic environment between 642 and 630 Ma, generating peraluminous granites with muscovite, garnet, and tourmaline denominated Serra Velha, Tamandu, Pirapetinga, Galheirinho, Perdizes, Estrela do Sul, and Cascalho Rico. They have negative Ndt , Nd model ages from Neo to Mesoproterozoic, and variable rare Earth elements enrichment patterns, with strong negative Eu anomalies.