Petrologia e geoquímica dos litotipos neoarqueanos da região da Serra da Babilônia (Bom Sucesso – Minas Gerais): implicações geotectónicas

Abstract

In the southern portion of the São Francisco Craton (SFC), west of the Bom Successo-MG city, six distinct neoarchean metamorphosed lithotypes can be identified: (I) a biotite-muscovite gneiss, apparently related to the oldest rocks of the region; (II) a metagranitoid called Capela São Francisco related to 2750 Ma postcollisional to intraplate granites widely found in the southern portion of SFC, which are rich in K. It is peraluminous, with low Ca and negative anomalies of Ce and Eu. This unit derives from partial melting of continental crust; (III) post-collisional metacharnockites and metacharnoenderbites called Rio do Amparo-Bom Sucesso (2720-2690 Ma) derived from mantle and crustal sources, are metaluminous, calchoalkaline and with negative Eu and Nb anomalies; (IV) metaenderbites and metacharnoenderbites called Babilônia (2730 Ma), with origin from Kpoor mafic source, are metaluminous, Na-rich, ranging from calcic to calc-alkaline, with fractionated REE pattern without Eu anomalies, but with Nb negative anomalies typical of magmatic arc; (V) magmatic arc calcho-alkaline metanorites/metagabronorites (2660 Ma) and (VI) metaultramafic peridotites, with the first being the product of magmatic differentiation of the latter. They have each other similarities in the patterns of REE and spatial arrangement within the study area. Together, these Neoarchean lithotypes records the evolution of an important portion of the southern part of SFC on post-collisional extension stage related to the Mamona event and is similar to the same age and tectonic context described in cratons of other continents.