The Chemical and Mineralogical Characteristics of Quaternary Volcanic Rock Weathering Profile in the Southern Part of Bandung Area, West Java, Indonesia

Abstract: Upstream Citarum river basin is located in the southern part of Bandung Regency. This region is composed by Quaternary volcanic products. In general, the exposed rocks have been weathered with varying levels. Several studies have linked the chemical and mineralogical characteristic of the weathering process has been carried out, among them are Sukiyah et al (2000), Sukiyah et al (2005), Sukiyah (2009), Sukiyah et al (2010). The results showed that at certain weathering level will result soil with specific chemical and mineralogical characteristics as well. Nevertheless, the correlations among these variables have not been analyzed in detail. This study aimed to determine changes in the chemical and mineralogical of volcanic rocks at different levels of weathering and the correlation between them. Volcanic rocks in the study area can be grouped in alterated and unalterated rocks. Major oxides obtained from 33 rock samples with varying degree of weathering. The chemical characteristics data (major oxides) obtained by XRF methods performed in the laboratory. Meanwhile, the minerals data obtained through petrographic analysis using the polarizing microscope, XRD, and SEM. The probabilistic approach is used to analyze the data to determine the chemical and mineralogical characteristics at different levels of weathering. The analysis showed that major oxides proportion of altered volcanic rocks not influenced by the degree of weathering of rocks is significantly. Otherwise, the degree of weathering strongly correlate with the proportion of the major oxides in unaltere