Pustaka Ilmiah Universitas Padjadjaran

Abstrak

Te-bearing gold-silver-basemetal mineral deposit of Arinem, Western Java, Indonesia

The Arinem area is located in a part of the Sunda-Banda magmatic arc (well known as gold copper belt) within the Indonesia archipelago at the southern margin of the Sundaland and the Eurasian plate (Fig. 1). The mineralized body is in form of quartz vein trending N140-160°E for about 5,900m long and 3-5m width, exposed at elevation 365-530m above sea level. The ore body is hosted in andesitic lava, breccias and tuff of the Oligocene-Middle Miocene Jampang Formation. The pyroclastic host rocks mainly suffered of propylitic and argillic alterations and are characterized by the occurrence of chlorite, sericite, kaolinite, and in place by carbonate. Outcrop and drill core samples containing gold-silver are intimately associated with basemetal minerals of copper, lead and zinc. K-Ar dating of sericite associated with the quartz vein indicates a Late Miocene age (8.8±03 Ma) for the ore mineralization. The ore mineral deposition could be categorized into three stages, where stages I and II are Au-Ag bearing, and stage III is barren. The ore mineral assemblages of the deposit consist of sphalerite, galena, chalcopyrite, pyrite, marcasite, arsenopyrite with a little amount of pyrrhotite, bornite, calcocite, covellite, hematite, argentite, electrum and sulfosalt minerals of enargite and tennantite. Some of Te-bearing minerals such as hessite, tetradymite, stutzite, petzite and altaite are observed in the mineralization stage II. The deposit is characterized by low iron content in sphalerite, ranging from 025-4.71 wt%. Gold is detected in petzite with the ranges of 1432-1832 wt%, while in some hessite and altaite grains up to 137 and 0.55 wt%, respectively. Otherwise, up to 1.31 wt% selenium element is detected in tetradymite.