KARAKTERISTIK UBAHAN DAN GENESA MINERALISASI HIDROTERMAL DI DAERAH ALOR BARAT DAYA, PROVINSI NUSA TENGGARA TIMUR

• Main Author: Stefen Asa Imanuel Teln, Albert
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/37198
• Institution: Institut Teknologi Bandung

The study area is in Alor island, Southwest Alor District, Alor Regency, East Nusa Tenggara, and has coordinates 124o35’21,9997”- 124o33’44,2143”-124o33'45" east longitude and 8o24’4,3593”-8o24’3,6677” south latitude. This island is a part of Banda Volcanic Arc, where there are several earth resources potential along this arc, such as Flores geothermal in the western part and Wetar’s VMS mineralization, in the eastern part of the study area, which is indicates that hydrothermal activity works well along this arc. This study aims to conduct geological studies, alteration characteristics and also to see the genesis of hydrothermal mineralization in the study area. The methode of this study was conducted with megascopic and microscopic analysis methods including petrographic, mineragraphic, x-ray diffraction and atomic absorption spectroscopy to determine rock units, alteration zones and mineralization textures, alteration mineral paragenesis, element association, and the determination of mineralization system in the study area. The lithology of the research area is entirely composed of volcanic rocks, namely Dacite Lava, Tuff which is consist of crystal tuff and vitric tuff, and Pyroclastic Breccia unit intercalated with tuff and accretionary lapilli. The hydrothermal alteration zone is quartz-illite-smectite-kaolinite (argillic), quartz-sericitechlorite± muskovite (phyllic), and albit-epidot-calcite±chlorite-zeolite (propylitic). The present of sulfide minerals are pyrite, chalcopyrite, sphalerite, galena, bornite and covelite, and malachite and limonite as a result of oxidation. The vein filling texture was quartz-pyrite veinlet and also the quartz-sulfide vein controled by the northeast-southwest dextral fault and the northwest-southeast tensional fracture. Mineral paragenesa consists of four mineral formation stages, consisting of; stage I: quartz-ilite-smectite-kaolinite±paligorskit-zeolite, stage IIa: quartz-chlorite-sericite±muscovite, stage IIb: quartz, sphalerite, markasite, galena, pyrite, chalcopyrite, bornite, covellite, stage III: albit-epidote-calcitechlorite± zeolite-pyrophilite, and stage IV: malachite-goetite-limonite. Geochemical element analysis showed the following threshold elements: 209,69 ppm Cu, 4436,26 ppm Pb, 1311,12 ppm Zn, 0,02 ppm Au and 4,18 ppm Ag, with the element association is Pb-Cu-Zn-Au-Ag-Sb-As. Based on the presence of alteration minerals, sulfide minerals, mineralization texture and element association, the alteration and mineralization in the study area is best to develops as a low sulfidation epithermal system.