Texturas e inclusões em cromita da Mina Ipueira: contribuição para o entendimento da formação de cromititos no Complexo Jacurici, BA

Chromite textures and inclusions in the Ipueira Mine: contribution to the understanding of the chromitite formation of the Jacurici Complex, BA

Abstract

Chromite is a mineral belonging to the spinel group and constitutes the sole source of metallic chromium, essential in stainless steel production. The formation of chromitites has been a subject of debate. In Brazil, the mafic-ultramafic Jacurici Complex, exploited by the Companhia de Ferro Ligas da Bahia - FERBASA, hosts the country's largest chromium deposit and has been interpreted as a large magmatic system with ore formed in a conduit, subsequently tectonically ruptured. Previous studies suggest the influence of crustal contamination and volatiles in the exclusive crystallization of chromite with possible mechanical concentration in the formation of the thicker layer. In this study, petrographic analyses supported by Scanning Electron Microscopy and X-ray microtomography were conducted on samples from the Ipueira segment, area hosting a major underground mine. The results support previous studies and suggest that chromium supersaturation is reflected in the denser stage of the layer, which exhibits higher volumes of chromite with multiple hydrated inclusions. The abrupt contact between the semimassive and massive portions, and compaction in the main layer, suggest a change in the formation process, possibly starting with in-situ crystallization and evolving into a more complex process involving the transport and accumulation of crystals.