GEOLOGY AND STUDY OF ALTERATION – MINERALIZATION IN SETELUK DISTRICT, WEST SUMBAWA REGENCY, WEST NUSA TENGGARA PROVINCE

• Main Author: Pandapotan Napitupulu, Immanuel
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69737
• Institution: Institut Teknologi Bandung

Seteluk District, West Sumbawa Regency is one of the areas in Indonesia with geological conditions that may potentially contain metal minerals with economical amounts. Research is conducted within an area of 56 km2 with the aim of identifying geological conditions that include geomorphology, geological structures, and stratigraphy; and identify the zone of alteration, mineralization, and its relation to geological conditions. This research was conducted by field mapping, sampling in the form of fresh rocks, foxed rocks, veins and veins, and river sediments. Samples are analyzed with petrological, petrography, mineragraphy, elemental chemistry, and spectral analysis. The geomorphology of the research area is divided into the Rempe Alluvial Plain Unit, the Upper-Order Lava Flow Ridge Unit, and the Lamusung Fault Block Ridge Unit. Stratigraphy of the research area consists of The Sandstone Unit, Andesite Lava Unit, Andesite Breccia Unit, Granodiorite Unit, Limestone Unit, and Alluvial Unit. The geological structure that develops in the research area is relatively northeast – southwest and northwest – southeast. The alteration zones present in the research area were divided into epidote-chlorite zones with formation temperatures ranging from 200°C - 360°C and montmorilonite-illite±kaolinite zones with formation temperatures ranging from 140°C - 200°C. Mineralization is present in quartz veins and iron oxide veins with a relative orientation direction north northwest – south southeast. Mineralization formed in the form of ore minerals with formation sequences is initiated by pyrite minerals, chalcopyritesphalerite, galena, covellite, and limonite. Based on the alteration zone and mineral ores formed, the type of mineralization deposits in the research area is a type of low sulfide epithermal deposit. Presence of alteration – mineralization is controlled by geological conditions in the research area. The alteration zone is controlled by an andesite lithology and structures with a relatively northeast - southwest and northwest - southeast trend. The presence of mineralization in the veins is the result of openings from paired structures with northeast - southwest trend.