MINERALIZATION SYSTEM OF THE IRON ORE DEPOSITS IN BONTOCANI DISTRICT AND ITS ADJACENT BONE REGENCY, SOUTH SULAWESI PROVINCE

PROCEEDINGS JOINT CONVENTION BALI 2007
The 32^nd HAGI, The 36^th IAGI, and The 29^th IATMI Annual Conference and Exhibition

MINERALIZATION SYSTEM OF THE IRON ORE DEPOSITS IN BONTOCANI DISTRICT AND ITS ADJACENT BONE REGENCY, SOUTH SULAWESI PROVINCE

Bambang Nugroho Widi, Bambang Pardiarto and Mulyana
Center for Geological Resources, Geological Agency
ABSTRACT

The genesis of primary iron ore mineralization in Bontocani district (Tanjung and Pakke area), Sub Regency of Bontocani –– Kahu is an interesting mineralization to be studied especially related to mineralization type of those areas. The interesting one of both areas is by discovering a number of mineral association that extremely different that where located near to each other. In Tanjung area, the specific of mineral association occurs from the carbonate –– silicate mineral group like garnet (brown and green color), pyroxene and epidote. While from the ore mineral group is magnetite (some parts is covered by malachite), associated with garnet, in the massive form or dissemination in diorite. Locally, magnetite to form a gradation layer structure with garnet mineral. Different with the minerals which was found in Tanjung, in Pakke area (5 km northeast of Tanjung), indicates an extremely different in mineralization pattern. In this area, iron ore mineralization occurs within carbonate rocks (limestone), forming ore zone with mineralization trend northeast-southwest. A side hematite, manganese mineral (associated with hematite) was also found in some locations . Alteration in the form sillisification only occurs around ore body. Quartz vein found locally, penetrates limestone with the same direction with hematite ore zone. Almost all in Pakke area were not found garnet and magnetite like which was found in Tanjung. Mineralization type occurs in this area is hematite, metallic grey to reddish brown, very hard, partly to form niddle and colloform structure at its hematite mineral. The obvious characteristic of this type is vuggy quartz structure in their ore and magnetite –– garnet type group were not found except in very small amount and limited area, near Pakke Village. According to the assay, Tanjung area’ ore shows the Fe total content is range from 59% - 67 %, SiO2: 0.7% - 4%, Mn: 0.08% - 1.4%, S :0% - 2% and P: 0 % - 0.09%, whereas the Pakke area’ ore have the Fe total content is range from 30% - 54%, SiO2: 2%-24%. Mn : 0.19%-12%, S: 0%-0.04% and P: 0%-0.08%. Based on field observation and chemical assay known those two areas have different in image and mineralization type. In Tanjung area is indicated by high iron content (the highest Fe total content attain 67%) and low silica ( SiO2 4%). This is suggested as skarn mineralization type where its indication was always characterized by the presence of garnet group as dominantly mineral at high temperature. While in Pakke, mineralization is characterized by low iron content ( max content of Fe total is 54% ) and high silica content ( SiO2 24%) with metallic minerals association is hematite and manganese. Garnet was not found while magnetite found in very limited location.

Based on those image, it is assumed that mineralization type was develop from high temperature and deep environment ( skarn type ?) in Tanjung area to low temperature and shallow environment (epithermal type ?) in Pakke area which is characterized by fissure filling iron ore in limestone with weakly to medium alteration intensity in country rocks (andesite). It seem mineralization style in this region have a unique phenomenon in geology where this case is rare found in other location in Indonesia.