28 July 2018

Field Trip

Pongkor Gold Mine Business Unit. PT ANTAM Tbk

The History of Pongkor Gold Mine

PT Aneka Tambang, Tbk. is the only State-Owned Enterprise engaged in gold mining. One of the mining units owned by PT Antam, Tbk. is the Pongkor Gold Mining Business Unit. The discovery of gold reserves at Pongkor originated from the exploration of base metals at Mount Limbung at the end of 1979, was informed of pyritic sulphide mineralization in Pongkor Mountain Region. Following up on the findings, in 1980 the geological unit team of PT Antam, Tbk. doing reconnaissance to Pongkor Mountain Area and found quartz vein with Au metal content of 0.2 – 4 ppm and Ag metal at 100 – 400 ppm at Pasir Jawa location.

Exploration activities stopped in 1983 until 1988 because PT Antam, Tbk. concentrate more in the Cikotok area.
In 1988 exploration activities continued and found 3 new areas containing gold veins include Pongkor Mountain Area, Pasir Jawa, and Ciguha. Further exploration re-discovered new veins, namely Kubang Cicau and Ciurug. In 1989 up to 1992 detailed drilling activities were carried out and continued with the evaluation and calculation of resources. A feasibility study and a new mine plan can be implemented in 1992.

After obtaining the Exploitation Mining Authority, the construction begins. The first construction was made are access road from Parempeng to Pongkor along 12.5 km, construction of processing plant with a production capacity of 2.5 tons of gold bullion, and tailing dam. In 1994 the gold processing plant and the mine production section were merged into one unit of production under the name of the Gold Mining Unit (UPE) Pongkor. In 1997 the mine was developed in the Ciurug area, mining was done by mechanical system. The second plant is built so that the production capacity becomes 5 tons of gold bullion / year.

Location and Access

UBPE Pongkor is administratively located within the Sorongan area of Nanggung Sub-district, Bogor Regency, West Java Province. This location is about 55 km to the west from the City of Bogor and about 110 km to the southwest of Jakarta and about 229 km to West South from the city of Bandung.

Pongkor Gold Mine Location

Pongkor Gold Mine Location

Climate

The climate at UBPE Pongkor is tropical rain climate influenced by monsoons, with relatively high rainfall and humid air. The temperature range throughout the year occurs between 15 ° to 30 ° C, during the rainy season the temperature shifts towards 15 ° C, while the dry season shifts towards 30 ° C. The rainy season lasts from September to April and the dry season lasts from May to August.

Morphology

UBPE Pongkor is part of a regional unit that has a topographic area in the form of mountainous areas with altitudes ranging from 300 m to 900 m above sea level, with the hilltop still sharp and rounded, where the angle of the slope ranges between 20°-60° Cikaniki River is the main river with the direction of flow extends relatively south-north. The Cikaniki rivulet include the Cisarua River, Cikaret River, Cimanganten River, Ciguha River, Ciparay River, Cisaninten River and Ciparigi River.

The Cikaniki River valleys are generally narrow and steep. But in some places also found the river valley is rather wide and sloping and winding so as to form a fairly fertile sand deposits that can be utilized by local residents as rice fields. In general, the Cikaniki River and Ciguha River cliffs are very steep because it is a swift upstream area with active rock erosion and this cliff is very difficult to pass.

Geological Condition and Reserve

The Pongkor Gold Mine is located at the Bogor district, West Java, approximately 80 km southwest of Jakarta, Indonesia. It is situated at the northeastern flank of the Bayah dome, which is a product of volcanism in the Sunda-Banda Arc that was also responsible for other epithermal gold deposit. The age of the Pongkor deposit has been estimated to be 2.05 ± 0.05 Ma based on the 40Ar/39Ar dating.

Primary mineralization is structurally controlled (NNW-SSE directions) and occurs within veins system (named individually as the Pasir Jawa, Gudang Handak, Ciguha, Pamoyanan, Kubang Cicau, and Ciurug veins), and are located at the northern edge of a caldera-like structure. The Ciurug vein is the most important vein in this mine, and is located at the southernmost of the vein system currently mined. The thickness of the Ciurug vein varies from 2 meters near surface up to around 24 m at depth, with total length is approximately 2 kilometers along the strike.

Geology of Pongkor Gold Mine Site

Mining Method

Mining methode which applied in Pongkor is shrinkage stoping and cut-and-fill stoping Method. Pongkor is one of the underground gold mining companies which implements cutand-fill method. In this method, the ore body being mined is located in stopes, and the access to the stope is trough a crosscut from a ramp. Especially It was implemented In Ciurug Mine. Ciurug Mine has 3 Level opening stope, there are Level.500, 600 and 700.

Shrinkage stoping was conducted with conventional overhand stoping whereasminers work above broken ore and behind stope was mining. This Method was used on vein with relatively has 2-4 meters thickness and strongly in rock mass characteristics also it has steeply dipping with host rock in good conditions. Especially, it was implemented In Gudang Handak, Ciguha, Pamoyanan dan Kubang Cicau Mine

Ore Processing
Ore processing plant capacity in Pongkor is 500 dried metric ton (dmt) for plant I and 720 dmt for plant II. UBPE Pongkor use Cyanide which more popular as evolution AARL (Anglo American Research Laboratory) process.