[en] Thorium and uranium in Bangka Island are mainly found in monazite mineral. In the geological point of view the monazite formed in S type granite, sandstones and alluvial deposits. In Bangka Barat where several S types granite and also alluvial deposits and this area considered as a potential area for monazite placer. S type granites are predicted as a source of monazite while alluvial deposits are considered as a dispersion place for deposition of monazite. The purpose of this study is to determine the geological information and to know the hypothetical potency of thorium and uranium resources in alluvial deposits. The methods used in this study are geological mapping, measurement of thorium and uranium contents in the rock, sampling of granite for petrographic analysis, sampling of heavy mineral in alluvial deposits for grain size analysis. Results of the research show that the lithology of West Bangka region composed of schist unit, meta-sandstone unit, granite intrusion, diabase intrusion, sandstone unit and alluvial deposits. Monazite is found in granite intrusion, sandstone unit and alluvial deposits. Evolving fault strand to northwest-southeast, northeast-southwest and west-east. The results of the grain size analysis of heavy mineral shows the average percentage of monazite in the heavy mineral is 6.34%. Other potential minerals contained in placer deposits are zircon 36.65%, ilmenite 19.67% and cassiterite 14.75%. (author)

[en] West Manggarai Regency is a new regency as a result of regional development of Manggarai-Raya Regency. Based on information from the local mining service authorities dealing with groundwater, Mbuit village undergo clean water shortages in the dry season. One alternative to overcome the water shortages is the use of groundwater. The investigation of groundwater is intended to determine the characteristics of the geology, hydrogeology and characteristics of the electrical properties of the subsurface rocks which required to determine the potential rock layers that containing groundwater (aquifers). To achieve these objectives carried out the topography measurement, collecting data of geological/hydrogeology, and electrical resistivity measurement. Based on result of observations, analysis of the surface geological survey and supported by subsurface resistivity data in the investigation area, the potential aquifer is found. The aquifers potential has been found in a fractured aquifer system, in the northern of investigation region and distributed relatively west-east. The best aquifer is found in the line C at the point C15–C17, line G at the point G17–G18 (Humpung village), line D at the point D14–D17, line E at the point E14–E19 (Tureng village) with a resistivity value of 5–43 Ωm and the depth of 50–120 meters. (author)