Mining in Sumatera - Earth Fortune

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Mining in South Sumatera

South Sumatera is a mineralized area with a history of mining extractable base metals, including gold, silver, copper, nickel, zinc and lead. The area where the mining concessions are held is named “S Tuboh” and is an important historical mining area. Within the S Tuboh site, silver and gold were mined up to 60 and 100 years ago respectively by Old Dutch miners.

The S Tuboh site area is mainly a commercial forestry which has some rubber and coconut plantations. It is located about 250 km from the nearest sea port in Bengkulu Province and the other ports are about 400 km away which can be reached easily by road and train. The site is not too far from a Sumatra highway and can be reached by foot (about 3.5km) after crossing a river (Rawas) and from there, an inter-township road in good condition is connected to this river bank.

Mining and Exploration Concessions

Currently, a subsidiary company holds the mining right (Exploitation Right – KP) for 106 hectares in the Province of Musi Rawas, South Sumatera, known as S Tuboh. In the surrounding areas encompassing the current exploitation site, there is an area of 360 hectares, the company has obtained Approval in Principle issued by the Forestry Minister for full usage rights.

A chart showing the concession areas for mining (small areas outlined in red) and forestry usage 360 hectares (outlined in blue) are as follows:

History of the Discovery

The first mineral analysis on the S Tuboh site was carried out by M. Koperberg on behalf of the Indonesian Mining Bureau in 1906 and subsequently, the work continued until 1912. There is a reference to 8 core drillings being carried out on the site during the various studies done by the Mining Bureau in 1912 [source :The Geology of Indonesia – Volume II Economic Geology” produced by Martinus Nijhoff (1970)]. It was not until the 1980’s when further field works were conducted through a cooperative framework between the Government of Indonesia and Japan through the Japan International Cooperation Agency (JICA) from 1985 to 1987. The survey included geological, geophysical and drilling explorations.

The geology and mineralization at S Tuboh have been recorded by Dutch (in 1906 & 1912) and by JICA & the Department of Mineral Resources in Indonesia (JICA-DMR) through a jointed exploration done from 1985-1987. Thework conducted by JICA-DMR included a shallow drilling program of 23 drilling holes (at depths of between 100 and 220 meters per hole), with a discovery of mineral ores in 9 of the drilled holes. The thicknesses of ore belt varies from 0.1 up to 2.93 meters. The ore reserves are estimated about 1.76 million tonnes containing copper, silver, zinc, lead and lesser gold (source: Special Publication DMR, 1993).

Mineralization

The deposits are skarn type, vein, and massive sulphides. Of 23 holes drilled, 9 holes contain ores. The mineralized zones discovered are in depth of between 10-100 meters with a width thickness of 0.10-2.93 meters. The minerals consist of sphalerite (ZnS), galena (PbS), chalcopyrite (CuS), pyrite(S), pyrrhotite, and arsenopyrite. The ores are generally blanketed by skarn minerals such as hedenbergite, garnet, epidote and wollastonite.

Lithologies

There are veins and massive sulphide in Jurassic limestone-tuffs-sandstone formation intruded by Tertiary granite rocks.

Alteration

There are Skarnization and metamorphism effect covering marbleized limestone, silicified green tuff, quartz tic rocks.

(The contents of the above were all correct as of June 2010)