ORE MINERALOGY AND HOST ROCK GEOCHEMISTRY OF THE POLYMETALLIC EPITHERMAL DEPOSIT AT SORIPESA PROSPECT AREA, EAST SUMBAWA, INDONESIA

The Sorepisa prospect area is located at the eastern part of the Sumbawa Island, Indonesia. The mineralization of the research area is mainly structural control and the trend direction of the all quartz veins is mainly NW-SE and NE-SW direction. The mineralization of the research area is investigated by petrographic study, ore mineralogy microscopic study, X-ray fluorescence method for geochemistry and X-ray diffraction oriented clay mineral analysis for alteration mineralogy associated with mineralization. According to the Na2O+K2O vs SiO2 diagram and Ti/Zr vs Nb/Y diagram, the geochemical characteristics of the host rock in the research area show basalt, basaltic andesite, andesite to dacite series and basaltic/andesite and andesite field. On the other hand, according to the Cr-Y diagram, the vein host rock in the research area is included in the volcanic arc basalt field and within the plate basalt field. The ore mineral composition of the research area is gold, silver, galena, pyrite, chalcopyrite, sphalerite, chalcocite, goethite, malachite and azurite. But according to the microscopic study, gold is rarely occurred and abundant in chalcopyrite and sphalerite. According to the study of petrographic and X-rary diffraction oriented clay mineral analysis, the alteration associated with mineralization in the research area is prophylitic alteration and low temperature argillic alteration