Compositional provenance study of alluvial cassiterite at Bambol and Mayo Seni localities of the Mayo Darlé massif, northern Cameroon

Cassiterite mineralization occurs in both the rock and the alluvial sediments in the Mayo-Darlé massif of northern Cameroon. Active alluvial mining by artisans constitutes the most important rural economic activity. This study focuses on the morphology, mineral inclusions, and composition of alluvial cassiterite derived from Bambol and Mayo Seni localities. Backscattered electron (BSE) images primarily analyzed the cassiterite grains to investigate their morphological characteristics and mineral inclusions. The composition was examined through electron microprobe analysis (EMPA). The cassiterite grains have an irregular to sub-rounded morphology, indicating proximity to the source, although cassiterite grains display evidence of mechanical transport and abrasion. EMPA results show mainly high SnO 2 content (up to 100 wt.%), highlighting the weathering resistance of the cassiterite grains and providing a database for comparative cassiterite compositional studies around the world. Among the Sn substituting elements, only Fe, Ta, and Mn were detected at very low concentrations (Fe = 0.02–0.3 FeO, Mn = 0–0.04 MnO, and Ta = 0–0.2 Ta 2 O 5 , all in wt.% respectively), suggesting little variation in the alluvial cassiterite compositions. This high SnO 2 content indicates the purity of cassiterite in the area. These chemical signatures are useful tools to explore the unknown primary source and help in mineral exploration in northern Cameroon. Binary plots of compositional variation have similar clusters, suggesting cassiterite was derived from a single bedrock source, despite having a mixed signature of pegmatite- and hydrothermal-derived cassiterite. Mineral inclusions include quartz, hematite, and columbite group minerals (CGMs), which were similar in all the samples, suggesting a homogeneous source. The quartz inclusions highlight quartz veins associated with the mineralization and potential felsic plutonic bedrocks. Granites of the Mayo-Darlé massif have been reported as having NE–SW-trending hydrothermal quartz veins, and both the veins and the hydrothermally altered zones of the granite contain disseminated cassiterite.