Hydrothermal Alteration, Ore Mineralization, and Fluid Inclusion Characteristics of Tarra Prospect, Awak Mas Deposit, Luwu Area, South Sulawesi,Indonesia.

Abstract

Tarra area is one of the Awak Mas gold prospect in Sulawesi, Indonesia. Geographically and geologically, this area is located in the central part of West Sulawesi, and occupies the southern part of the Latimojong Complex.  Host rock of gold mineralization in this area, known is the Meta-Sedimentary rock, which is a member of the Latimodjong Formation. The research carried out includes geological surveys by taking rock outcrop samples, as  well as taking samples from the drilling cores in the Company's Coreset. A total of 28 rock samples were petrographic analysis,19 samples were carried out by mineragraphic analysis, and 4 samples were analyzed for  fluid inclusion. The results of the study show that in the Tarra area there are two types of alteration, namely (1)  the phillic type alteration which is characterized by the presence of the quartz-sericite-opaque minerals assemblage, and (2) the propylitic type which is characterized by the presence of quartz-chlorite-epidote. Meanwhile, the results of the mineralization analysis show that there is sulfide mineralization, which consists of pyrite, chalcopyrite, and covellite, and the oxide minerals consist of hematite, and goethite. This study, has known that ore mineralization accompanies the formation of quartz veins. The results of the analysis of fluid  inclusions trapped in the quartz vein show that there are two fluid phases, namely double phase (liquid-rich), L +  V where L > 50% as a primary inclusion and mono-phase where L = 100% with a quartz vein temperature  around 260°C – 320°C, low salinity, minimum forming depth of 1050 meters under the paleo-surface. Based on the homogenization temperature (Th) of the fluid inclusion above, it should be interpreted that sulfide ore deposits in the Tarra Area are included in the type of Mesothermal deposits.