STUDY OF URANIUM PRESENCE BASED ON GROSS-COUNT GAMMA RAY LOG IN LEMAJUNG SECTOR, KALAN, WEST KALIMANTAN

• Main Author: GUNAWAN MUHAMMAD, ADI
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/14636
• Institution: Institut Teknologi Bandung

Lemajung sector, Kalan, West Kalimantan is one area where uranium was found. U mineralization is found associated with metasiltstone and schistose metapelite tilted ± 70 ? to the north relatively parallel with schistocity planes. In order to improve the status of U resources in this sector, the information about the quality, in this case the concentration or grades of uranium mineralization and the geometry of the mineralized body is absolutely necessary. In the radioactive mineral exploration, particularly uranium, gross count gamma-ray logging is a quantitative method which is simple and relatively quick, in identifying and evaluating the uranium mineralization. Gross count gamma-ray logging system utilizing specific character of U, so it can be used to identify the presence of U mineralization in a rock. However, studies about the presence of uranium mineralization based on gross count gamma-ray log is still rarely done and this is what encourages this study, with the aim of determining the quality (grade) uranium mineralization in rocks quantitatively and knowing the geometry of the mineralized body by integrating the analysis of gross count gamma-ray log with the surface geological information and core data. From the analysis result of gross count gamma-ray log, supported with correlation between drilling wells, making of the iso total thickness maps, 3-dimensional and iso grade cross sections, it is known that uranium mineralization in Lemajung sector is developing as a group of veins or breccia mineralization as tectonic breccia matrix filling associated with pyrite and pyrrhotite minerals, individually have lens-shaped with dimensions ranging from a few meters to several tens of meters. U mineralization mostly stand alone and partly interconnected or intersecting each other, with maximum thickness 4.9 meters in LEML-33 filling fractures opening or schistocity in metasiltstone and schistose metapelite bounded by andalusite metapelite in the south and bitotite metapelite in the northern part which is massive with the highest % eU3O8 0,0658 ? 557,97 ppm eU. There are 3 main factors that control the presence of U mineralization in Lemajung sector, these factor are: Sukadana Granite intrusion that occurred in the Late Cretaceous, the availability of way for magmatic fluid carrying U to flow and the development of secondary porosity and permeability (fracturation/ brecciation) in metasiltstone and schistose metapelite that allowing these rocks act as trap rock of mineralization. With the highest % U3O8 0,0658 ? 557,97 ppm eU less than 1% U then, the existing mineralization type of U in the Lemajung sector can be categorized as low-grade U mineralization