Composition, weathering, and provenance of beach sands adjacent to volcanic rocks in the northern Gulf of Guinea, SW Cameroon


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Composition, weathering, and provenance of beach sands adjacent to volcanic rocks in the northern Gulf of Guinea, SW Cameroon
Journal of African Earth Sciences
Annick Kwewouo Janpou, Gabriel Ngueutchoua, Armel Zacharie Ekoa Bessa, Armstrong-Altrin John S., Ulrich Romaric Kankeu Kayou, Odilia-Alexandra Njike Njome Mbella Nguetnga, Théophile Njanko, Victorine Ambassa Bela, Myriam Solange Kanouo Tiotsop, Joseph Gael Tankou
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The southern coastal portion of the Tertiary Cameroon Volcanic Line (CVL), in the Gulf of Guinea, is bordered by
Pan-African granitoids, metamorphic rocks, and Cretaceous sedimentary successions, which are prone to
contribute sediments to the nearby Limbe beach. To better constrain the weathering intensity and provenance of
the beach sediments, the mineralogy and chemical composition of these sediments were analyzed. The low
values of SiO2/Al2O3 ratios and Zircon-Tourmaline-Rutile (ZTR) index, coupled with high Index of Compositional
Variability (ICV) indicate compositionally immature sediments. This is further supported by the presence of rock
forming minerals such as olivine, pyroxene, and amphibole. The Th/Sc versus Zr/Sc binary and Al2O3–TiO2–Zr
ternary diagrams suggest that the studied sediments have not experienced recycling. The Chemical Index of
Alteration (CIA), Plagioclase Index of Alteration (PIA), the A–CN–K and (A-K)-C-N triangular diagrams indicate
that the Limbe beach sediments were undergone moderate to intense weathering. Several provenance discrimination diagrams based on Al2O3, TiO2, Zr, TiO2, La/Sc, and Th/Co, and the ternary plot of V–Ni–Th*10, and the
comparison of chondrite normalized rare earth elements (REE) patterns of the studied sediments with potential
source rocks suggest that the source area is composed of mafc rocks of CVL. This indicates that the granitic,
metamorphic, and sedimentary rocks close to the volcanic structure do not signifcantly contribute to the
sedimentation of the studied beach. In addition, the results of this study indicate that longshore currents do not
influence the chemical composition of the sediments.
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25/11/2022 15:44
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18/07/2023 16:35
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