Geochemistry and source area weathering of soils around Mount Bamboutos (Cameroon Volcanic Line)

Abstract

<p class="MsoNormal" style="text-align: justify; text-justify: inter-ideograph; line-height: 120%; layout-grid-mode: char; mso-layout-grid-align: none; punctuation-wrap: simple; margin: 12.0pt 0cm 6.0pt 0cm;"><span lang="EN-US" style="font-size: 10.0pt; mso-bidi-font-size: 11.0pt; line-height: 120%; font-family: 'Times New Roman',serif; mso-fareast-language: ZH-CN;">This study aimed at investigating the weathering of the source area and the geochemistry of the soils around Mount Bamboutos, West Region, Cameroon. In this study, soil samples were collected from a depth of 0–40 cm. The soil samples were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). Significant SiO<sub>2</sub> (63.37–73.05 wt.%) content recalculated to an anhydrous basis and adjusted to 100% (SiO<sub>2</sub> (adj)) indicates the abundance of quartz and kaolinite in soil samples. The enrichment of Al<sub>2</sub>O<sub>3</sub> (9.98–15.12 wt.%) suggests the presence of aluminosilicate minerals such as clay minerals, muscovite, and feldspars. The considerable Fe<sub>2</sub>O<sub>3</sub> (0.01–11.04 wt.%) content relates to the mechanical erosion of ferrallitic soil or to Fe-source rock weathering. The elevated LaN/YbN levels indicate that the soils were derived from heterogeneous source rocks during weathering. The inverse correlation between SiO<sub>2</sub> and Fe<sub>2</sub>O<sub>3</sub>, MgO, TiO<sub>2</sub>, and P<sub>2</sub>O<sub>5</sub> indicates the prevalence of heavy minerals, which are likewise influenced by the relative amount of quartz. The positive Ce anomalies may result from the redox conditions. Weathering indices such as the plagioclase index of alteration (PIA: 77.03%–97.75%), Chemical Index of Weathering (CIX: 58.25%–66.83%), chemical weathering index (CIW: 91.31%–99.13%), and chemical index of alternation (CIA: 50%–70%) all signify moderate to intense weathering in the source area, which occurred in hot, humid climatic conditions. This is evidenced by the removal of labile cations (Ca, Na, and K) in relation to stable residual components (Al and Ti). The relatively high Ce anomalies in the soil samples (Ce/Ce* = 0.01 to 7.44; average 2.39) suggest intense chemical weathering.</span></p>

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