Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original paper

Benjamin O. Omang, Stephanie Lohmeier, Akumbom Vishiti, Cheo Emmanuel Suh, Bernd Lehmann, Ateh K. Ijunghi, Jeremiah Shuster, Godwin Kave, Muyah V. Azah, Oko P. Ereh, Gordon Southam

Microchemical composition of alluvial gold from two Pan-African settings: Igarra schist belt, SW-Nigeria and Lom Series schist belt, E-Cameroon

Journal of Geosciences, volume 70 (2025), issue 4, 211 - 228

DOI: http://doi.org/10.3190/jgeosci.406

This study evaluates panned alluvial gold grains recovered from the Uneme-Dangbala drainage systems and the Lom river basin, both located within the Pan-African metasedimentary belts that define the mobile belt zone between the West African Craton and the Congo Craton, to infer their source rocks and the evolution of the gold grains during their transport into their depositional surficial environment. The Lom grains lack inclusions. They possess secondary gold precipitates, and evidence of amalgamation and bacterial growth in crevices. Gold grains from the Igarra schist belt contain Bi-Te bearing mineral inclusions such as hedleyite, sulphotsumoite, and aleskite with variable contents of Pb, S, and Au. Their drop-like shapes and multimineral composition suggest precipitation from a Bi-Te-Pb-Au melt. Compositionally, the inclusions vary from Bi-Te-Pb-S, Pb-S-Bi-Te, Bi-Te-Au-Pb-S, Pb-S-Bi, Pb-S, Bi-Te, Bi-Au to Au-Bi. The characteristic Bi-Pb-Te-S cluster indicates an oxidized calc-alkaline magmatic-hydrothermal origin. Thus, granitoids that intrude the metasedimentary rocks are the potential source of the hypogene gold mineralization. Gold from both schist belts, although derived from granitoids, has a different composition. The detrital gold particles from both areas correspond primarily to an Au-Ag alloy, although grains from the Lom basin reveal traces of Cu. Average gold finenesses of 884 in the Igarra schist belt and 925 in the Lom basin is lower than that of gold from most orogenic deposits.