Geology and ore mineralization of Kertajaya area, Simpenan sub-district, Sukabumi, West Java, Indonesia

The research area is located on the Jampang Fm. and Quaternary Sedimentary Fm., Jampang Fm. is one of the prominent host Au-Ag deposits in West Java, Indonesia. The purposes of this research are to study the geological conditions, distribution of alteration, and ore mineralization based on field data of rock samples and vein samples. The analysis used in this study includes petrography, mineragraphy, and XRD. The research area composed of tuff breccia, andesite, dacite, and fluvial deposits. Alterations in the research area consisted of silicification (quartz-silica), silica-clay (quartz-silica-illite-kaolinite), argillic (illite-kaolinite), and propylitic (chlorite-epidote±calcite). The thickness of quartz veins found in the study area are 2cm-21cm with dominant directions of N2960E – N3400E and dip around 630 – 880. Quartz veins showing the texture of massive veins, comb, hydrothermal breccia, lattice bladed, and chalcedony. Sulfide minerals found are pyrite, galena, sphalerite, covellite, bornite, chalcopyrite, hematite, jarosite, showing textures of disseminated, intergrowth, replacement, and inclusion. Gangue minerals found are quartz, silica, jasper, illite, kaolinite, chlorite, epidote, and calcite. Precious metals found are gold, showing dissemination, inclusions, and space-filling textures.