PETROGRAPHIC AND GEOCHEMICAL STUDY ON RARE EARTH ELEMENTS DISTRIBUTION IN WEATHERED GRANITE OF BANGKA ISLAND

• Main Author: IRSINA HANINI , FILDZIA
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/22166
• Institution: Institut Teknologi Bandung

Petrographic and geochemical studies on rocks and weathered granite of Bangka Island are carried out to predict the primary factors which influence the weathering process and distribution of rare earth elements. Research focused on S-type granitoids of Klabat Granite, which is located in Bangka Induk Regency, North Bangka. The research is conducted on 9 samples of rock and 18 samples of weathered Klabat Granite. The analysis consists of petrography, XRF, XRD, and ICP-MS, supported by secondary data and references. The granite in the research area consists of alkali felspar, quartz, biotite, plagioclase, muscovite, opaque, and REE-bearing minerals such as apatite, monazite, and zircon. Weathering processe result in dominant secondary minerals such as kaoline, gibbsite, quartz residuals. Weathered granite consists of O, A, B, C horizon, and parent rocks. Rare earth elements can mobilized and commonly distributed or accumulated in B horizons by adsorption of clay minerals. The accumulation of rare earths in B horizons is influenced by the fractionation of LREE/HREE by their affinities with kaoline and gibbsite. In B horizons, LREE are highly accumulated than HREE, because HREE are preferred to leaching. Rare earth elements in weathered profile of Kangurung, Sambunggiri 1, Sambunggiri 2, and Pemali, are accumulated in B horizons. However, rare earth elements in weathered profile of Belinyu 1 and Air Nyatoh are not accumulated. Factors such as topography, drainage, weathering index and mineralogy are important factors that affecting the distribution of rare earth elements in weathered profile.