Mineralogical characterization of banded iron formations in Vipongos, Namibe province, Angola

Abstract

One of the main mineral resources of the Republic of Angola is iron formation; however, just some studies refer to formation containing banded iron known as BIF (Banded Iron Formation). This article focuses on the mineralogical characterization, by means of diffractometry and X-ray fluorescence techniques, of the existing BIF formation in Vipongos, Namibe province. In the central sector of Vipongos, the largest and best-developed bodies appear, composed mainly of quartz and hematite, with carbonates (calcite and dolomite); they are associated with stratified and folded chloritic-micaceous schists (clinochlor, muscovite and biotite). To the northeast, there are gabbro-dioritic rock dikes that intrude sequences of green schists. The lithological and geochemical features of BIF formation in Vipongos allow them to be assigned to an Algoma-type formation environment, as they are closely associated with green schists and sometimes with volcanic rocks. On the other hand, the existence of minor elements (V, Co and Sr) and traces (Ag, In and Ta) testify the occurrence of hydrothermal activity. These results support the idea that Vipongos BIFs are an extension of Damara Mobile Belt Supergroup from South Africa.

Keywords

• formación bandeada
• hierro
• bif
• chert
• magnetita
• hematita
• esquistos verdes
• vipongos.