Composition of heavy minerals in the Gulf of Guinea beach sediments

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Abstract A mineralogical survey was conducted in the Gulf of Guinea sands to assess the transport history, depositional environment, weathering conditions and, provenance. Heavy mineral assemblages are abundant in augite, followed by opaque minerals, diopside, zoisite, enstatite, tourmaline, zircon, rutile, sillimanite, garnet, apatite, hornblende, epidote, kyanite, chloritoid and staurolite. The variety of this minerals show that the sands studied come from the igneous source rocks, mainly from a metamorphic source, in particular the gneisses and basalts, which is consistent with the geology of the study area. The bulk mineralogy detected using XRD and the chemical properties obtained by SEM-EDS reveals that the sands were dominated by quartz. Nineteen microtextures were observed on heavy minerals like hornblende, chloritoid, sillimanite, garnet, augite and staurolite, which were subsequently classified as mechanical (13 features), chemical (4 features), and combined mechanical and chemical (2 features) origins. The dominance of mechanical features suggest that the grains underwent high-energy transport. The abundance of angular and subangular heavy minerals indicate distance or nearby source. The mineral composition suggests that the source rocks underwent moderate weathering. The sub-rounded and rounded heavy minerals indicate a long transport. The predominance of heavy minerals in sediments suggest that the nearby source rocks are rich in heavy minerals.

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