Sylvestre Ganno
University of Yaoundé, Cameroon
Title: A mixed seawater and hydrothermal origin of superior-type banded iron formation (BIF)-hosted Kouambo iron deposit, Palaeoproterozoic Nyong Series, Southwestern Cameroon: Constraints from petrography and geochemistry
Biography
Biography: Sylvestre Ganno
Abstract
The Kouambo iron deposit with a typical banded iron formation is located in the northwestern margin of the Congo craton. The BIFs are hosted in Palaeoproterozoic Nyong series, a dominantly metasedimentary formation, and were metamorphosed into greenschist to amphibolite facies. The Kouambo BIFs belong to oxide facies iron formations and are characterized by fine- to medium-grained, very well banded and consist of alternating of Si-rich and Fe-rich mesobands. Geochemistry analyses reveal that these iron formations have a very simple chemical composition, with Fe2O3T and SiO2 representing more than 96 wt.% of the average composition; suggesting chemical precipitates of silica and iron. Moreover, these BIFs have low concentrations of Al2O3, TiO2 and HFSEs (high field strength elements, e.g., Zr, Hf, Ta, Pb and Th), suggesting that terrigenous detrital materials contributed insignificantly to the chemical precipitation. The PASS-normalized REE-Y patterns display minor LREE depletion and HREE enrichment, positive Y anomalies similar to seawater-like signature. However, they display weak positive Eu and negative Ce anomalies, a primitive chondrite-like “CHARAC†signature (23