STUDY OF GRANIOTIDS AND RARE EARTH ELEMENT IN BELITUNG ISLAND, BANGKA BELITUNG PROVINCE

• Main Author: Ferninand Gabe, Culbert
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/26325
• Institution: Institut Teknologi Bandung

Research area is administratively located in the Sijuk area, Belitung Regency and Tanjungklumpang, East Belitung Regency, Bangk Belitung Province. This research is based on the abundance of granitoid rocks in Belitung Island which has the potential as a source of rare earth elements so as to achieve goals which include knowing the granitoid type, distribution of rare earth elements, and factors that influence the distribution itsef. Granitoid distribution in Belitung Island is aged from Triassic to Cretaceous and formed by the process of magmatism due to the collision of the Sibumasu block and East Malaya block. The method used by observing thin slices of rock (petrography) and geochemical analysis. The results of the analysis of thin incisions of rocks in the Sijuk area (northern Belitung) show granite in the presence of muscovite in general and a small portion of hornblende minerals. This indicates that type I granite and type S granite are present in the area. Whereas in the Tanjungklumpang region (southern Belitung) is dominated by the presence of hornblenda but absence of muscovite minerals which indicate type I granite. The SiO2 variation diagram shows a decreasing trend in the proportion of TiO2, Fe2O3, MnO, MgO, CaO elements with increasing SiO2 influenced by fractionation with the alkaline high K calc magma affinity. Typology of peraluminous granitoid results on type S on Sijuk and type I granitoid on Tanjungklumpang granitoid. The deeper geochemical analysis of trace elements through the K / Rb-SiO2, Y-Rb, Y-SiO2, Th-Y diagrams produces granite I type and S granite type is found in Sijuk granitoid plutons and type I on Tanjungklumpang granitoid plutons. Granitoid in Belitung Island is related to collision events where type S which is aligned with Tanjungpandan Granite is formed on the discriminant tectonic of the continental collision which is Triassic while type I granitoid thought to form due to post orogenic collapse magmatism during Jura. The highest rare earth element content found in Sijuk type S granitoid with an average value of 360.75 ppm followed by type I Sijuk granitoid with an average value of 336.73 ppm and Tanjungklumpang S granitoid with an average value of 261.32 ppm . The value of increasing rare earths in the Sijuk area is found mainly from monazite and is related to the formation of type S granitoid as peralumine rock where the type S granite formation process involves metasedimen material from crustal which is a condition that supports rare earth element enrichment.