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Operations
Gosowong
| Ownership |
82.5% Newcrest / 17.5% PT Aneka Tambang |
| Location |
Gosowong, Halmahera Island, North Maluku, Indonesia |
| Year commenced operations |
February 2005 |
| General Manager Operations |
Iwan Irawan |
| Style of mineralization |
Epithermal vein |
| Contained metals |
Gold/silver |
| Resources* |
4.6Mt @ 19g/t Au for 2.8 Moz (100% basis) |
| Reserves* |
4.9Mt @ 15g/t Au for 2.3 Moz (100% basis) |
| Mining method |
Underground |
| Processing method |
Cyanide leach |
| Nominal treatment rate |
0.42 Mtpa |
| Product |
Bullion |
| Forecast mine life |
2015 |
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* Per 30 June 2010 Mineral Resource and Ore Reserve statement.
Overview
Kencana is one of the highest grade, underground gold mines in the world today. The mine is located within the Gosowong gold province, which covers an area of approximately 30,000 hectares. Gosowong is situated on Halmahera Island, in the North Maluku province, Indonesia and is 2,400 kilometres northeast of the national capital, Jakarta.
Kencana is the third mine to be developed by Newcrest at the Gosowong site and the first underground mine. Kencana is located 1 kilometre south of the original Gosowong pit.
Underground development of the Kencana mine commenced in February 2005 with the first underground ore mined in March 2006.
Geology
Economic mineralization is hosted within the Gosowong Formation, which is dominated by basalts, dacites, volcaniclastic rocks and intermediate intrusions. Volcanic rocks overlie the Gosowong Formation. In the late Pliocene, the Gosowong and volcanic sequences were locally intruded by andesite porphyry and quartz diorite.
Two styles of mineralization have been recognized to date within the Gosowong district, low-grade, uneconomic copper-gold porphyry mineralization and high-grade gold-silver epithermal veining. A number of epithermal deposits have been recognized to date, including Gosowong, Toguraci, Gosowong North, Dongak, Tobobo, Langsat and Kencana.
Mining
Kencana K1 is the first underground mine at the Gosowong site. Due to the ground conditions at Kencana and variability of the orebody, an underhand cut-and-fill mining method using paste fill was chosen. Mining is carried out using twin boom jumbos, loaders and articulated dump trucks. Mined out areas are backfilled with cemented paste fill.
Processing
The existing Gosowong processing plant is used to process Kencana ore. The processing plant comprises a primary jaw crusher followed by a SAG and ball mill ahead of a cyanide leach circuit. Gold and silver is recovered from the pregnant solution using the Merrill-Crowe (zinc precipitation) process before smelting to produce doré bars.
Improvement programs are underway to increase throughput of the Gosowong process plant in the short term, through removal of key bottlenecks.
Future Developments
The Gosowong Extension Project is based on the development of K2 and K Link gold deposits located adjacent to the existing Kencana mine. Refer to projects section.
Recent exploration results highlight the potential to extend the life of the Kenanca mine, in addition to identifying additional ore bodies within the Gosowong province.
Key production and cost data for Gosowong is illustrated in the graphs below (graphs refer to the Gosowong province - Gosowong, Toguraci and Kencana).
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