Detrital rutile morphology and bulk geochemistry from the Lokoundjé area of southern Cameroon as a guide to titanium exploration

Abstract Detrital rutile is both a titanium resource and an indicator of nearby titanium-bearing source rocks, but rutile in the coastal hinterland of southern Cameroon has not been documented. This study characterises detrital rutile from ten sampling sites in the Lokoundjé area (Ocean Division), on the north-western margin of the Congo Craton, and evaluates its relevance for titanium exploration. A total of 160 rutile grains were hand-picked from panned heavy-mineral concentrates. Forty grains from six sites (ST-01 to ST-06) were characterised for size, morphology, diagnostic physical properties including specific gravity, and optical microtextures in thin section. Six composite powders, each prepared from the rutile grains of one of these sites, were analysed by energy-dispersive X-ray fluorescence (ED-XRF); these data represent averaged bulk compositions of multiple grains, not single-crystal chemistry. The characterised grains are coarse (length 20–33 mm, width 12–25 mm), mainly prismatic (50%) or equant (30%), and angular to sub-angular, with specific gravity of 4.1–5.9 (mean 4.68). Thin sections show cleavage traces, polysynthetic twinning and quartz inclusions. The composite powders contain 68.4–86.7 wt% TiO₂, 2.7–8.5 wt% Fe₂O₃, 4.9–9.3 wt% Al₂O₃ and 4.3–11.0 wt% SiO₂, and 1,550–14,000 ppm Nb. The high Al₂O₃ and SiO₂ contents most likely reflect silicate inclusions or adhering silicate material rather than rutile lattice substitution. Grain morphology suggests limited transport, and the combined dataset identifies the area as a prospective target for titanium exploration.