Mineralogical and Geochemical Characteristics of Lateritic Bauxite in Tayan, West Kalimantan

Abstract

This research presents the mineralogical and geochemical characteristics of lateritic soil profiles developed over gabbroic and granitic bedrocks in the bauxite mining area of PT. Antam, Tbk, Tayan, West Kalimantan, which lies within the Southeast Asian Tin Belt. We analyzed two bedrock samples of different compositions along with six of their lateritic products for mineralogy (using petrography and X-ray diffraction) and whole-rock major elements using inductively coupled plasma atomic emission spectometry (ICP-AES). The gabbro bedrock is composed of plagioclase, hornblende, chlorite, and opaque mineral. While the graonodiorite is composed of plagioclase, quartz, orthoclase, biotite, hornblende, and opaque mineral. The lateritic bauxite profile associated with gabbro bedrock are composed of gibbsite, kaolinite, goethite, hematite, and magnetite. The granodiorite-associated laterites consist of the same mineral suites with addition of quartz, but magnetite are absent. Laterite deposit developed from granodiorite bedrock is characteristically kaolinitic bauxite, which shows high SiO2 content (ranges from 23.7 to 61.6 wt%). Meanwhile, lateritic bauxites associated with gabbro bedrock is ferritic in character, indicated by high Al2O3 and Fe2O3 (29.7% to 50.2 wt% and 13.15% to 15.1 wt%, respectively). The lateritic products of gabbroic bedrock tend to show higher range of Al and Fe but lower range of Si. Our findings suggest that identification of bedrock distribution may streamline lateritic bauxite exploration.