Pustaka Ilmiah Universitas Padjadjaran

Abstrak

The Occurrences of Base Metal Mineralization in Cikadu-Cisungsang Area, Banten Province, Indonesia*)

The Cikadu-Cisungsang area is located in the Bayah gold district, Banten Province of Western Java. The base metal mineralization occurred in the limestone host rocks of Miocene age. The ore is occurring as banded and quartz vein within the limestone. The mineralized body is identified as hydrothermal breccias, banded sulfide-quartz and silicified limestone. The ore minerals consist of sphalerite, galena, arsenopyrite, pyrite, marcasite, silver minerals, chalcopyrite, and pyrrhotite. those are occur as hydrothermal breccias. Silver minerals of aguilarite, pyrargyrite, proustite, and canfildite occur as fine to very fine grained crystals in galena. Metal contents are mostly of Pb (~130,000 ppm), Zn (~2,9800 ppm), As (~7,300 ppm), Cu (~94 ppm), Sb (~151 ppm), Ag (~303 ppm), and Au (~1.88 ppm). The gangue minerals mostly are silica and small amount of calcite, and rarely clay minerals. The silica varies from fine to coarse-grained of quartz to chalcedony. Homogenization temperatures obtained from fluid inclusion in quartz are ranging from 240°C to 300°C, while the salinities are from 2.2 to 3.4 wt% NaCl eqv. Considering the mode of occurrence of ore and host rocks and the formation temperatures and depth the Cikadu-Cisungsang mineralized body might be formed in the mesothermal environment The present of canfildite mineral, which is uncommon in typical epithermal deposits, probably due to the reworking of older continent crust as the source of metal or magmatic activities, in which several dacitic lavas and intusions of similar ages are observed within the area. Further studies should be done with special attention from view point of island arc geologic and tectonic setting to clarify the time-spatial relationship of the base metal and gold mineralization in the Bayah district.