Heavy Mineral Characteristics and Sediment Maturity of Alluvial Tin Deposits in Kemingking, Central Bangka, Indonesia

Abstract

Bangka-Belitung is part of the Southeast Asian tin belt, which has significant potential for alluvial tin deposits formed by weathering, transportation, and redeposition from its primary sources. This study aims to identify the characteristics of alluvial tin deposits in the Kemingking area, Sungaiselan District, Central Bangka Regency, using grain counting (GCA), petrography, and zircon-tourmaline-rutile (ZTR) index analyses from four drill wells. GCA results identified eleven types of heavy minerals, namely cassiterite, zircon, monazite, ilmenite, rutile, tourmaline, garnet, topaz, anatase, epidote, and quartz, with subangular to subrounded-rounded grain shapes indicating medium to long-distance transport. Mineral distribution patterns indicate hydrodynamic sorting by density, with cassiterite concentrated in the high-energy downstream zone. The ZTR index values ​​in the four wells ranged from 34.71 to 58.27% (average 52.16%), indicating a generally mature sedimentary maturity. These findings suggest that alluvial tin deposits in the study area were formed through long-distance transport from source rocks, with a depositional environment that can be interpreted as an ancient placer system.