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Beruang Kanan Main Zone -- Porphyry Copper
Beruang Kanan Main Zone is part of the greater Beruang prospect area where 8 mineralized zones are located at the margins of a 12 kilometer in diameter caldera. Exploration work at the Beruang Kanan Main Zone included 19 medium depth diamond drill holes which returned results up to 167 meters @ 0.59% copper. Five major mining companies conducted technical due diligence in 2001, but withdrew from discussions because of the unstable political and economic climate in Indonesia at the time.
Prospect Location:
Beruang Kanan is located in the SE corner of the CoW and can be reached from Palangka Raya, the capital of Central Kalimantan in 1 day by speedboat and logging road. A well established base camp has been built at Beruang Kanan. Some road and bridge repair is necessary to ensure this access is maintained.
General Geological Setting and Exploration Background:
The Beruang porphyry copper systems are hosted in a 10-12 km wide circular topographic feature, which occurs at the intersection of the regional NE and NNW trending structures.
At Beruang Kanan alteration (propylitic, local phyllic, rare advanced argillic) and anomalous copper in soils (>200ppm in soils) extend over an area of more than 16 km2 and is open in most directions. This alteration and mineralization are hosted in a sequence of dacite tuffs of probable Oligocene age which overlays lower Tertiary volcanoclastic siltstone and sandstones in the eastern prospect area. Pre-mineral Sintang dacite porphyry intrusions of probable Oligocene age, and post-mineral [(? Miocene)] andesite, dacite to basalt-gabbros dykes are intruded into the tuffs and sediments.
Structures in the Beruang Kanan area are dominated by the regional NE and NW lineaments, as well as local E-W features.
Geological, geochemical (soil, ridge and spur auger and rock chip) and geophysical (induced polarisation and ground magnetic) surveys have delineated three centres of porphyry-style alteration and mineralization:
- Beruang Kanan Main Zone
- Beruang Kanan Silver and Associated Minerals Prospect
- Beruang Kanan Main South Zone
Figure 6: Beruang Soil Copper Analysis Map
Figure 7: Porphyry Copper Gold Model in Kalimantan
Beruang Kanan Main Zone: Geological Setting and Exploration Background
Exploration activity to date at Beruang Kanan has been focused on the Main Zone, that is defined by a north-south elongate, 1 x 1.5 km area of anomalous copper (>0.1% in rock chips) ± gold-molybdenum geochemistry, high chargeability, and by intense phyllic alteration.
The phyllic alteration is capped at high elevations on the western margin of the Main Zone by advanced argillic alteration. The alteration and mineralization are hosted almost entirely in dacite tuff. These are cut by post-mineral dacite dykes that are defined by ground magnetics and geological mapping to be up to 100-200 metres wide and radiate north-west and west through the prospect area. Copper-gold-molybdenum in soils are aligned NE within the Main Zone, possibly indicating that possible ore shoots are aligned in this direction.
Zinc, and to a lesser extent lead, form broad halos around the Main Zone, and occur as massive NE-trending, polymetallic mineralization that outcrops to the north and south of the Main Zone. Limited drilling into these zones to the north intersected up to 16m @ 2.8% lead, 5.8% zinc, 58 gpt silver, 0.65 gpt gold and 0.17% Cu ( DDH BKZ-1) associated with quartz-chlorite-illite-base metal sulphide (sphalerite, galena, tennantite, chalcopyrite-bornite) as wallrock disseminated grains, in shear zones and as sheeted veins. Such mineral assemblages are often associated with transitional phases between a high sulphidation system and porphyry.
Between 1998 and 2001, 25 diamond drill holes drilled by KGC to 280 metres depth have intersected a NNW-trending zone of intensely sheared and silicified, highly pyritic, zoned phyllic to advanced argillic alteration, with copper grades up to 167m @ 0.59% Cu.
Higher grade copper (> 0.5% Cu) occurs in two zones: a shallow flat lying zone (down to 375m RL) that is composed predominantly of supergene covellite and chalcocite forming a sort of supergene blanket; and a deeper zone below 300 m RL that is composed mostly of hypogene chalcopyrite.
The IP surveys displays well the highly pyritic NNE-trending shear zone, which hosts most of the copper mineralization in the Main Zone. A high chargeability anomaly at depth in the central-east part of the Main Zone is interpreted to be the source zone for mineralizing hydrothermal fluids. This is indicated by zonations in alteration and mineralization.
Chargeability anomalies at progressively shallow levels reflect the inferred outflow to the NNE and also to the south-west. It is postulated that the deep chargeability anomaly is the downward plunge of the pyritic milled matrix breccia encountered at shallow levels in DDH BK-8, and is a potential target for a breccia pipe.
Figure 8: Beruang Kanan Main Zone EW IP Section
There are two copper mineralization models that can be conceptualized:
- The copper mineralization may be genetically related to the breccia pipe, with copper mineralization coming in late and migrating upwards along the side to the quartz-pyrite shear zone, or the copper.
- Copper mineralization may be derived from a source other than the inferred breccia pipe, e.g. a high chargeability anomaly at depth immediately north of the Main Zone.
Both these models will be tested during a drilling program to be conducted when finances permit.
Exploration Work to Date
- Airborne geophysics and satellite image interpretation.
- Geological mapping and rock chip sampling 1190 samples.
- Ridge and spurs, and grid based soil geochemistry 1476 samples.
- Grid base ground magnetics and Induced Polarisation (IP) surveys totaling 72 kilometres.
- Diamond drilling 25 holes totaling 4760 metres, including the North Polymetallic.
- Two independent technical data reviews by Mr. Terry Leach of New Zealand and Mr. David Howard of Canada.
Estimated Expenditure to Date
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