MINERALIZATION IN JAMPANG DISTRICT FOR SMALL SCALE MINING, INDONESIA

Jampang district is a part of calc-alkaline arc in Southern Java Mountains, where volcanic activities developed in Middle Eocene. These resulted in formation of epithermal deposits throughout Jampang district. “Old Andesite” in Jampang Formation is one of the earliest volcanic deposits close to eruption center, and hosted the hydrothermal deposits. The Cigaru epithermal deposit is located in relatively steep Cimanggu Hills and being operated as small-scale mine now. The first stage mineralization is strongly structurally controlled to NS orientation, while the second stage is correlated with major fault of EW orientation. Au-Ag-Cu-Zn-Pb bearing minerals, such as native gold, chalcopyrite, galena and sphalerite occur in veins and stockwork veins. Those were formed in relatively shallow environment system. Hydrothermal alteration is characterized by illite ± quartz formed in near neutral pH environment. Smectite/muscovite zone mixed layer extends over of the area. Fluid inclusion analysis indicated ore-forming condition temperature from 280 to 302 ⁰C and salinity from 5.4 to 7.5 wt% NaCl equivalent. On the basis of the mineral assemblages and fluid inclusion data, the Cigaru deposit is identified as a low-sulfidation type of base-metal deposit.