Minas Supergroup in Serra de Bom Sucesso, extreme southwest of the Quadrilátero Ferrífero – MG: petrography, geochemistry and U-Pb isotope

Abstract

The banded iron formation (BIF) hosted Bom Sucesso Metassedimentary Sequence (BSMS) is exposed in the southwestpart of the Quadrilátero Ferrífero, Minas Gerais. This sequence has normal stratigraphic stacking and comprises three units:the lower Lagoa da Prata carbonate schist, the intermediate Bom Sucesso BIF and the upper Tabuãozinho schist. U-Pbdetrital zircon data from samples of the Lagoa da Prata unit indicate a maximum age of deposition of 2603 ± 7.3 Ma, correlatedwith the basal Caraça Group of the Minas Supergroup. The Bom Sucesso BIF has predominant mineralogy formedby bands of iron oxide (maghemite) and amphibole; it is interlayered with discontinuous ferruginous dolomite lenses andit grades upwards to a ferruginous metapelitic layer at the top of the unit. The geochemical signature of the BIF is characterizedby positive anomalies of Eu, Y and La, relative enrichment of heavy Rare Earth Elements (REE) and absence ofa negative Ce anomaly, analogous to the itabirites of the Itabira Group. The mineral assemblage of the BSMS indicatescontact metamorphism associated with alkaline metasomatism, generated by the intrusion of the Tabuões Granite duringthe Transamazonian orogeny.

Keywords

• Quadrilátero Ferrífero
• Banded iron formation
• Zircon
• Minas Supergrup
• Bom Sucesso
• REE.