Geochemical features of the Matomb alluvial rutile from the Neoproterozoic Pan-African belt,Southern Cameroon |
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Institution: | 1. Glycation, Oxidation and Disease Laboratory, Department of Research, Touro University California College of Osteopathic Medicine, Vallejo, CA, USA;2. Department of Internal Medicine, Showa University Northern Yokohama Hospital, Tsuzuki-ku, Yokohama City, Japan;3. Central Clinical Laboratory, Showa University Northern Yokohama Hospital, Tsuzuki-ku, Yokohama City, Japan |
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Abstract: | The Matomb region constitutes an important deposit of detrital rutile. The rutile grains are essentially coarse (> 3 mm), tabular and elongated, due to the short sorting of highly weathered detritus. This study reports the major, trace, and rare-earth element distribution in the bulk and rutile concentrated fractions. The bulk sediments contain minor TiO2 concentrations (1–2 wt%), high SiO2 contents (~77–95 wt%) and variable contents in Al2O3, Fe2O3, Zr, Y, Ba, Nb, Cr, V, and Zn. The total REE content is low to moderate (86–372 ppm) marked by high LREE-enrichment (LREE/HREE ~5–25.72) and negative Eu anomalies (Eu/Eu* ~0.51–0.69). The chemical index of alteration (CIA) shows that the source rocks are highly weathered, characteristic of humid tropical zone with the development of ferrallitic soils. In the concentrated fractions, TiO2 abundances exceed 94 wt%. Trace elements with high contents include V, Nb, Cr, Sn, and W. These data associated with several binary diagrams show that rutile is the main carrier of Ti, V, Nb, Cr, Sn, and W in the alluvia. The REE content is very low (1–9 ppm) in spite of the LREE-abundance (LREE/HREE ~4–40). The rutile concentrated fractions exhibit anomalies in Ce (Ce/Ce* ~0.58 to 0.83; ~1.41–2.50) and Eu (Eu/Eu* ~0.42; 1.20–1.64). The high (La/Sm)N, (La/Yb)N and (Gd/Yb)N ratios indicate high REE fractionation. |
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Keywords: | Cameroon Pan-African belt Weathering Alluvial rutile Geochemistry Trace elements |
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