Empang block is a porphyry Au-Cu prospect located at 70km east of Elang porphyry of Newmont Batu Hijau Project. Exploration work program conducted including stream sediment, rock and soil sampling, ground and airborne geophysical survey and shallow drilling program.
Initial regional stream sediment sampling done by Newmont 1987 has identified a several Au-Ag, ± Cu and ± As geochemistry anomalous in the vicinity of the concession. Newmont drilled 3 scout diamond holes and Rio Tinto drilled five shallow holes in 1996, totalling 1235m, and additional 4 holes in 1997 targeting porphyry.
The Empang area comprises andesitic and rhyodacitic volcanic rocks, intruded by Cu-Au mineralized porphyry stocks overprinted by hypogene acid-sulfate alteration with associated Cu- Au veining and brecciation. Surface rock chip and trenching samples returned elevated low gold copper values. Reconnaissance work identified widespread NW and NS trending HS sulphidation epithermal quartz vein up to 10 meter wide. Regional aeromagnetic confirmed conjugate NW to NE structural trends, consistent with mapped alteration and Au-Cu-As soil geochemistry at prospect scale.
Rio Tinto conducted 5 (five) drilled holes over the Empang block, with the best intercept was
179.70 m @ 0.30 g/t Au, 150 ppm Cu, included 6.0m@ 1.2 g/t Au, 440 ppm Cu and firstname.lastname@example.org g/t Au, 225 ppm Cu ( hole DD960PO4) and 43m @ 0.24 g/t Au , 1880 ppm Cu and 0.23 g/t Au, 1292 ppm Cu ( hole DD99OP06 ). Other holes returned with very low gold and copper content.
Based on the preliminary drilling exploration result, the Empang Project rough estimate contains of 194,428,000 ton ore with consisted of 1,673,325 ounce gold (Au), 5,897 kg silver (Ag) and 136,521 ton metal copper (Cu).
Rio Tinto relinquished the area in 1998 before acquired by PT JSM in 2006. A few drilling is located outside of the IUP boundary and the PT JSM has applied for the extension of the IUP boundary with government. Exploration program has identified a number of low gold-copper anomalous either from stream sediment, rock chip, trenching and drilling for hosting gold porphyry copper deposits and currently focus of exploration efforts.
Based on the exploration result of the Empang Project, especially from drilling result, the Empang project contains of gold-copper value. Exploration conducted by Vale Indonesia team recently also returned with gold-copper content either from soil and rock chip sampling. The Empang block is located in favourable geological setting for porphyry Cu-Au and in a giant porphyry deposit corridor and shown interesting alteration pattern of altered intrusion rock.
Access Location of Empang Project
Sumbawa Island Tectonic Setting
Sumbawa Porphyry Deposit Type Category
Ownership and Tenure
The concession area is located on the Indonesian Island of Sumbawa in province of West Nusa Tenggara, + 1600 km east of Jakarta.
PT SJR acquired this block in late 2006 by holding the mining rights (KP) of general survey. On November 13 2007, the mining right has been converted into exploration permit (KP Eksplorasi). Initially the concession area of general survey stage was 10.000 Ha but after examining the previous exploration program data of Empang Block, PT SJR reduced and shifted the block area into 8234 Ha. The new coordinate area of exploration stage is as follow :
Coordinate IUP Block Empang
Concession Area of Exploration Empang Block
IUP Empang Block
Mineralised outcrop at Gampit Prospect – Empang Block
The Empang area comprises andesitic and rhyodacitic volcanic rocks, intruded by Cu-Au mineralized porphyry stocks overprinted by hypogene acid-sulfate alteration with associated Cu-Au veining and brecciation. Surface rock chip and float samples returned elevated copper values up to 0.4% Cu, 12 ppm Mo) and gold grades commonly in excess of 0.4 g/t Au. Trenching reported values as high as 1.43 g/t Au and 0.78 % Cu.
Airborne Magnetic Survey
An Airborne Magnetic Survey was conducted by Rio Tinto in 1994. The result shows the Empang block to have a magnetic complex associated with the drill targets.
Aeromagnetic Anomaly- SO & RC Sample
Aeromagnetic Anomaly & Drill Hole location
Prospect Location – Airborne & Ground magnetic
A total of 5 (five) diamond holes were completed for a total depth 969 meter. Exploration program has identified a number of gold-copper anomalous as hosting gold porphyry copper deposits and currently focus on exploration efforts and target.
The estimate resource calculation is very preliminary stage, based on only from 5 holes. Estimate gold-copper resource was calculated based on assumed that the gold mineralisation zone occurred within 20 hectare area within Empang Block.
Based on the preliminary drilling exploration result, the Empang Project roughly estimate contains of 194,428,000 ton ore with consisted of 1,673,325 ounce gold (Au), 5,897 kg silver (Ag) and 136,521 ton metal copper.
Gold – Copper Resources Estimate