Geochemical controls of parent rocks on bauxite quality in Melugai, West Kalimantan, Indonesia

The lateritic bauxite deposits discovered in Melugai Village, West Kalimantan, occur within a lateritic belt zone characterized by extensive and high-quality bauxite occurrences. This study aims to examine the geochemical control of parent rocks influencing the ALCC content in lateritic bauxite deposits. The methods employed include geological mapping, petrographic and petrological analyses, X-Ray Diffraction (XRD) and X-ray fluorescence (XRF) testing. Geomorphologically, the study area is divided into two morphological units gently undulating hills and moderately undulating hills. The drainage pattern in the study area is classified as dendritic. Bauxite deposits are classified into two types based on their parent rocks, namely metatuff and meta-andesite. Bauxite derived from metatuff has an average AL-Ch content of 47.53% (range 44.86-50.06%), categorized as medium-grade bauxite with intense lateritization. In contrast, bauxite derived from meta-andesite has an average ALCh content of 32.25% (range 26.27-38.24%), classified as low-grade bauxite with weak to moderate lateritization. These results indicate that bauxite derived from meta-tuff exhibits a superior AL-Ch content compared to bauxite originating from meta-andesite. This finding suggests that meta-tuff-sourced bauxite contains a more abundant presence of gibbsite minerals, which subsequently controls the high AL-Ch concentration within the bauxite ore.