Mineralizações ferríferas (especularíticas) e depósitos do tipo Jacutinga (Au-Pd-Pt), Quadrilátero Ferrífero e sul da Serra do Espinhaço (MG)

Abstract

Geochemical characteristics of rocks, minerals and fluids associated with the Fe-enrichment and Au-PGE processes that occurred in Quadrilátero Ferrífero (QF) and Southern Espinhaço Range (SER) were studied using the methodologies: petrography, geochemistry, whole rock geochemistry, fluid inclusions and LA-ICP-MS. The whole rock geochemistry results show that the obtained patterns are mostly similar to those found in the literature. Chemical signatures of iron oxides from dolomitic itabirite and high-grade iron ore from the Esperança deposit, located in the QF, indicate that polycyclic processes involving changing of chemical and redox conditions are responsible for the iron enrichment on Cauê Formation from Minas Supergroup. The results indicate that dolomitic itabirite is the main precursor of the iron ore in that deposit. Long-lasting percolation of hydrothermal fluids and shifts in the redox conditions have contributed to changes in the Y/Ho ratio, light/heavy rare earth elements ratio and Ce anomaly with successive iron oxide generations (martite-granular hematite), as well as lower abundance of trace elements including rare earth elements in the younger specularite generations. Studies of fluid inclusions in quartz and specularite crystals suggest the presence of different fluids in terms of salinity, temperature and chemical composition. Data obtained indicate that the fluids found in the different areas, QF and SER, are distinct from each other, suggesting the absence of genetic correlations or at least not contemporary processes for Fe and Au-PGE enrichment.