Petrografia e geoquímica das rochas metamáficas e metaultramáficas da região de jacuí-bom jesus da penha (MG)

Abstract

In the southern portion of the São Francisco Craton, between the municipalities of Jacuí and Bom Jesus da Penha, south/southeast of Minas Gerais State (Brazil), several bodies of metamafic and metaultramafic rocks occur, in lenticular to irregular shapes and decimetric to hectometric, sometimes kilometric, sizes, elongated and concentrated in an E-W or WNW/ESE belt. These bodies outcrop an area of approximately 70 m2, between the archean and paleoproterozoic infracrustal rocks and the neoproterozoic allochtonous supracrustal rocks, purportedly interpreted as part of an archean greenstone belt, while recent studies attribute them to an ophiolitic neoproterozoic subduction complex. The studied rocks include: amphibolites, amphibole schists, metaperidotites, among others. These rocks were affected by regional metamorphism at amphibolite facies (700-750°C and at least 7 kbar) followed by anatexis of granitic rocks, which are the same conditions observed for Araxá Group rocks that occur intercalated with. Geochemical data, in accordance with petrography, showed that protoliths are pyroxenites, peridotites and basic intrusions related to a subduction complex and revealed chemical modifications that indicate crustal contamination during tectono-metamorphic evolution.