Composition and Distribution Patterns of Major and Trace Elements in Gradually Weathered Andesite Rock from FELDA Jengka 4, Pahang, Malaysia

The composition of selected trace elements and major elements in gradually weathered andesite rock collected from FELDA Jengka 4, Pahang were determined using XRF technique. Eleven samples consisting of concentric layers from the weathered rock (outermost layer) to the fresh rock (inner layer) were obtained. The exfoliated layer, soil and fresh rock samples were pulverized for the determination of trace and major elements, For major elements the SiO2 was the most abundant followed by Fe2O3, Al2O3, MgO and CaO, Other elements such as TiO2, MnO, Na2O, K2O and P2Os were present in amounts less than 1% content by weight. The percentage of SiO2, MgO and CaO decreased as the andesite layer gradually weathered, whereas the percentage of Fe2O3 and Al2O5 increased. In general, the concentration of trace elements in the most weathered layer was higher than their content in most fresh layer and soils. Correlation analysis showed that Co, Cr, Cu, and Pb negatively correlated at more than the 5% level of significance with MgO, Co, Cr, Cu, and Pb positively correlated at more than the 5% level of significance with Fe2O3 and Al2O3. Some of the trace elements were positively correlated with each other indicating a similar favorable condition for their enrichment. Fe and Al became enriched as weathering progressed leading to the formation of more Fe and Al oxides and hydroxides in the weathered layer.