The Glória quartz-monzodiorite: isotopic and chemical evidence of arc-related magmatism in the central part of the Paleoproterozoic Mineiro belt, Minas Gerais State, Brazil

Ciro A Ávila,Ronaldo M Pereira,Liu Dunyi,Umberto G Cordani,Wilson Teixeira,Héctor R Barrueto,Veridiana T.S Martins

doi:10.1590/s0001-37652006000300013

Abstract

The Glória quartz-monzodiorite, one of the mafic plutons of the Paleoproterozoic Mineiro belt, is intrusive into banded gneisses, amphibolites, schists and phyllites of the Rio das Mortes greenstone belt, in the southern portion of the São Francisco Craton, State of Minas Gerais, Brazil. The Glória quartz-monzodiorite yields a SHRIMP U-Pb zircon age of 2188 +/- 29 Ma, suggesting a tectonic relationship with the pre-collisional phase of the Mineiro belt. According to the Nd isotopic evidence (epsilonNd(T) = -3.4; T DM = 2.68 Ga) the original magmas was formed by a mixture among Archean crustal material and Paleoproterozoic juvenile magma. The Glória quartz-monzodiorite shows metaluminous and calc-alkaline tendency with intermediate K content, comparable to that of volcanic-arc rocks. The primary mineralogical assemblage was partly modified by metamorphism, dated between 2131-2121 Ma in nearby coeval plutons. Such metamorphism is significantly older than the reported metamorphic episodes of the Mineiro belt in the Quadrilátero Ferrífero region (2059-2041 Ma) in the eastern portion of the study area. This evidence, together with chemical and isotopic data from other mafic and felsic plutons coeval with the Glória quartz-monzodiorite, indicate a tectonic and magmatic migration within the Mineiro belt from west to east.

Highlights

AND REGIONAL GEOLOGYThe geological framework of the southern border of the São Francisco Craton comprises Archean and Proterozoic lithotectonic units of varied age and nature, which are exposed side by side in response to multiple magmatic, tectonic and erosional processes (Figure 1)
Gneisses (Campo Belo, Bonfim, Passa Tempo and Belo Horizonte complexes) and greenstone belt remnants (e.g., Rio das Velhas Supergroup in the Quadrilátero Ferrífero region) further intruded by Archean felsic plutons; ii) a Paleoproterozoic terrane occurring along the southern edge of the craton, containing the Rio das Mortes and Nazareno greenstone belts, as well as voluminous mafic and felsic plutonic intrusions; and iii) Proterozoic supracrustal sequences of different ages (Minas Supergroup, and São João del Rei, Carandaí and Andrelândia megasequences)
The Paleoproterozoic plutons constitute most of the Proterozoic terrane and are genetically associated with the pre, syn- and late-tectonic stages of the Mineiro belt (Noce et al 2000, Teixeira et al 2000)

Summary

Introduction

AND REGIONAL GEOLOGYThe geological framework of the southern border of the São Francisco Craton comprises Archean and Proterozoic lithotectonic units of varied age and nature, which are exposed side by side in response to multiple magmatic, tectonic and erosional processes (Figure 1). The new isotopic (Sm-Nd) and geochronological (SHRIMP U-Pb zircon) data of the Glória pluton are compared with those of contemporary plutonic bodies to better understand the Paleoproterozoic evolution of the central part of the Mineiro belt, in the southern edge of the São Francisco Craton.

Results

Conclusion