Copper potential of KSK COW - Kalimantan Gold Corporation Limited
Copper potential of KSK COW - Kalimantan Gold Corporation Limited
Copper potential of KSK COW - Kalimantan Gold Corporation Limited
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<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> the <strong>Kalimantan</strong> Surya Kencana<br />
Contract <strong>of</strong> Work, Central <strong>Kalimantan</strong>, Indonesia<br />
Peter J. Pollard<br />
Pollard Geological Services Pty. Ltd.<br />
7 Jillinda Place, The Gap<br />
Queensland 4061, Australia<br />
peter@peterpollard.com<br />
January 2008
2<br />
___________________________________________________________________________________<br />
Executive Summary<br />
The <strong>Kalimantan</strong> Surya Kencana Contract <strong>of</strong> Work in Central <strong>Kalimantan</strong> contains several<br />
porphyry copper-gold systems where recent exploration by Oxiana <strong>Limited</strong> in joint venture<br />
with <strong>Kalimantan</strong> <strong>Gold</strong> <strong>Corporation</strong> <strong>Limited</strong> included geological mapping, reprocessing <strong>of</strong><br />
geophysical data and drilling 16 diamond drill holes. Many holes contained no significant<br />
copper mineralization and thereby downgraded parts <strong>of</strong> several prospects. Oxiana <strong>Limited</strong><br />
withdrew from the joint venture in late 2007.<br />
Of the sixteen new holes, five were drilled in the Main Zone at Beruang Kanan. All<br />
encountered low-grade copper mineralization, with the best intersections being in KBK0021<br />
with 44m @ 0.58% Cu from 16.6m and 41.7m @ 0.46% Cu from 147m. The drilling did not<br />
test the deeper part <strong>of</strong> the main target previously proposed by Leach (2001) in the vicinity <strong>of</strong><br />
BK09 and the mineralization is therefore open in this area. Similarly, two holes drilled in the<br />
South Zone at Beruang Kanan have not tested the main part <strong>of</strong> the coincident IP chargeability<br />
and copper in soil anomalies defined by previous work by Geiger et al. (2005).<br />
One hole drilled in Central Baroi targeted a conceptual geophysical and geochemical target<br />
but failed to intersect significant mineralization. Another hole was drilled in a base metal vein<br />
zone at Far East Baroi and confirmed earlier interpretations that there is no shallow porphyrystyle<br />
mineralization in this area. Two further targets in Central Baroi which were supported<br />
by the reprocessed IP data were not drilled. These remain targets for future exploration.<br />
Three holes were drilled at the Mansur prospect, two in the area <strong>of</strong> the main copper in soil<br />
anomaly and one targeting an IP anomaly further south. The holes returned no significant<br />
mineralization and indicate that it is highly unlikely an economic porphyry copper system is<br />
present at Mansur.<br />
Oxiana <strong>Limited</strong> drilled one hole at the Beruang Tengah prospect targeting high copper in rock<br />
chips as well as mapped phyllic alteration and milled breccia. The hole contained no<br />
significant copper mineralization and it was concluded that the prospect had no room to host a<br />
near-surface economic porphyry copper deposit. The prospect has been delineated by rock<br />
chip sampling <strong>of</strong> creek outcrops, but veining and surface limonite development extend<br />
beyond this area, particularly to the south and west. Although the recent drilling downgraded<br />
the current prospect area, there appears to be scope for further work at Beruang Tengah<br />
possibly involving an extended soil geochemical survey with IP and ground magnetics to help<br />
delineate further targets.<br />
No new drilling was carried out at Tumbang Huoi where the presence <strong>of</strong> copper in soil<br />
anomalies and widespread potassic alteration (biotite ± magnetite) in earlier drill holes<br />
suggest that this prospect may have some <strong>potential</strong>. Further work involving IP and ground<br />
magnetic surveys over the main copper in soil anomalies may help to delineate any sulphiderich<br />
zones for further work.<br />
Several other prospects and geochemical anomalies (e.g. Mamuring 1 and Rinjen) within the<br />
<strong>KSK</strong> <strong>COW</strong> have received limited exploration attention. These require collection <strong>of</strong> basic<br />
geological data, geochemical data and mineralized samples in order to allow their <strong>potential</strong> to<br />
be assessed. The <strong>potential</strong> for high-grade skarn-style copper-gold mineralization at Mamuring<br />
should be investigated.<br />
Although the recent work resulted in downgrading <strong>of</strong> some prospects, further work within the<br />
<strong>KSK</strong> <strong>COW</strong> is warranted to assess the <strong>potential</strong> <strong>of</strong> several untested porphyry copper targets.<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
3<br />
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Table <strong>of</strong> Contents<br />
Executive Summary.......................................................................................................2<br />
Table <strong>of</strong> Contents...........................................................................................................3<br />
Statement <strong>of</strong> experience.................................................................................................4<br />
Introduction....................................................................................................................5<br />
Approach........................................................................................................................5<br />
Geological setting ..........................................................................................................5<br />
Porphyry copper prospects.............................................................................................8<br />
Beruang Kanan...............................................................................................................9<br />
Oxiana <strong>Limited</strong> drilling............................................................................................13<br />
Discussion................................................................................................................14<br />
Baroi.............................................................................................................................16<br />
Oxiana <strong>Limited</strong> Drilling...........................................................................................16<br />
Discussion................................................................................................................17<br />
Mansur .........................................................................................................................18<br />
Oxiana <strong>Limited</strong> drilling............................................................................................18<br />
Discussion................................................................................................................19<br />
Beruang Tengah...........................................................................................................20<br />
Oxiana <strong>Limited</strong> drilling............................................................................................20<br />
Discussion................................................................................................................21<br />
Tumbang Huoi .............................................................................................................22<br />
Conclusions..................................................................................................................23<br />
References (including uncited reports) ........................................................................24<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
4<br />
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Statement <strong>of</strong> experience<br />
Dr Peter Pollard is a consulting economic geologist with more than 20 years<br />
experience. He holds a PhD from James Cook University, Australia and is a Member<br />
<strong>of</strong> the Australasian Institute <strong>of</strong> Mining and Metallurgy and a Fellow <strong>of</strong> the Society <strong>of</strong><br />
Economic Geologists.<br />
Dr Pollard has consulted widely on porphyry copper-gold and iron oxide copper-gold<br />
deposits. He has worked on some <strong>of</strong> the world’s major porphyry copper-gold deposits<br />
including Grasberg (Indonesia), Escondida Norte (Chile) and Oyu Tolgoi (Mongolia).<br />
In addition, he has consulted on porphyry exploration programs in Australia, China,<br />
Indonesia, Iran, Kazakhstan, Mongolia, Peru, U.S.A. and Vietnam.<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
5<br />
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Introduction<br />
At the request <strong>of</strong> Mr Rahman Connelly <strong>of</strong> <strong>Kalimantan</strong> <strong>Gold</strong> <strong>Corporation</strong> <strong>Limited</strong>, the<br />
author spent 4 days in Palangkaraya, <strong>Kalimantan</strong> reviewing the results <strong>of</strong> recent<br />
exploration within the P.T. <strong>Kalimantan</strong> Surya Kencana Contract <strong>of</strong> Work (<strong>KSK</strong><br />
<strong>COW</strong>; Figs 1 and 2). The aim <strong>of</strong> this work was to evaluate the copper <strong>potential</strong> <strong>of</strong> the<br />
<strong>COW</strong> following the 2007 exploration program conducted by Oxiana <strong>Limited</strong> in joint<br />
venture with <strong>Kalimantan</strong> <strong>Gold</strong> <strong>Corporation</strong> <strong>Limited</strong>.<br />
Approach<br />
Oxiana <strong>Limited</strong> undertook an exploration program within the <strong>KSK</strong> <strong>COW</strong> in 2007<br />
with a target <strong>of</strong> +300 million tonnes at 1% Cu. The exploration program involved<br />
geological mapping, re-logging <strong>of</strong> drill core and reprocessing <strong>of</strong> geophysical and<br />
geochemical data as well as drilling 16 new diamond drill holes in the Beruang<br />
Kanan, Beruang Tengah, Baroi and Mansur prospects. The drill holes mostly returned<br />
low grades <strong>of</strong> copper and gold and Oxiana subsequently withdrew from the joint<br />
venture. The current review considered the Oxiana <strong>Limited</strong> data as well as previous<br />
exploration data on these four prospects in order to assess their copper <strong>potential</strong>. In<br />
addition, the copper <strong>potential</strong> <strong>of</strong> the Tumbang Huoi prospect is also briefly<br />
considered.<br />
Geological setting<br />
The <strong>KSK</strong> <strong>COW</strong> is situated within the mid-Tertiary <strong>Kalimantan</strong> volcanic arc that hosts<br />
a number <strong>of</strong> porphyry copper-gold deposits and prospects including Mamut, Rina,<br />
Manto-Tebihi and those within the <strong>KSK</strong> <strong>COW</strong>. In addition, several low sulphidation<br />
epithermal deposits are present including Kelian, Indo Muro, Masuparia, Gunung Mas<br />
and Jelai-Mewet.<br />
Porphyry copper-gold mineralization in the <strong>KSK</strong> <strong>COW</strong> is associated with a number <strong>of</strong><br />
probable Oligocene age intrusions that were emplaced at the junction between<br />
Mesozoic metamorphic rocks to the south and accreted Lower Tertiary sediments to<br />
the north (Geiger and Prasetyo, 2004). Structures in the region are dominated by<br />
northeast-striking faults that are interpreted to be arc parallel or accretionary faults<br />
(Geiger and Prasetyo, 2004). Subsidiary northwest-trending arc normal or transfer<br />
faults cross-cut the northeast structures and the intrusions have commonly been<br />
emplaced within dilational settings at the intersections <strong>of</strong> these major structural<br />
features (Geiger and Prasetyo, 2004).<br />
Large circular features that are evident on satellite images commonly coincide with<br />
the mid-Tertiary intrusions and are interpreted to be volcanic collapse features (Geiger<br />
and Prasetyo, 2004). These host many <strong>of</strong> the porphyry prospects within the <strong>KSK</strong><br />
<strong>COW</strong>.<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
6<br />
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Figure 1. Location <strong>of</strong> the <strong>Kalimantan</strong> Surya Kencana Contract <strong>of</strong> Work within the<br />
<strong>Kalimantan</strong> magmatic arc.<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
7<br />
___________________________________________________________________________________<br />
Figure 2. Principal prospects and geochemical anomalies within the <strong>Kalimantan</strong><br />
Surya Kencana Contract <strong>of</strong> Work.<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
8<br />
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Porphyry copper prospects<br />
Previous exploration in the <strong>KSK</strong> <strong>COW</strong> has used a model <strong>of</strong> porphyry copper systems<br />
in the SW Pacific (Corbett and Leach, 1998; Geiger et al., 2002) as a general guide.<br />
The main porphyry prospects within the <strong>KSK</strong> <strong>COW</strong> have been placed within this<br />
general framework by Geiger et al. (2002) based on the observed alteration features<br />
and proximity <strong>of</strong> porphyry intrusions (Fig. 3). This model does not attempt to identify<br />
the size <strong>of</strong> porphyry systems in terms <strong>of</strong> surface or other dimensions and it is not clear<br />
whether an ‘economic porphyry system” in the <strong>KSK</strong> <strong>COW</strong> would be a broad<br />
intrusion-centered body <strong>of</strong> mineralization at kilometre scale or a narrow, structurally<br />
controlled zone <strong>of</strong> high-grade mineralization at 100-400m scale in plan. Concepts<br />
concerning room available to host a deposit need to be considered in this light as<br />
recent exploration successes at Ridgeway (Australia) and Oyu Tolgoi (Mongolia)<br />
have highlighted the occurrence <strong>of</strong> porphyry systems with limited surface expression<br />
linked to narrow dyke- or pencil-like intrusions.<br />
Figure 3. General model <strong>of</strong> Southwest Pacific porphyry copper systems (modified<br />
from Geiger et al., 2002).<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
9<br />
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Beruang Kanan<br />
The Beruang Kanan prospect is located within a 10-12 km wide circular feature near<br />
the intersection <strong>of</strong> regional NE and NNW-trending structures (Fig. 4). Alteration and<br />
mineralization at Beruang Kanan extends over an area <strong>of</strong> some 16 km 2 and is hosted<br />
within dacite tuff and volcaniclastic rocks. Soil geochemistry and geophysical data (IP<br />
and ground magnetics) have delineated three main prospects, the Main, South and<br />
West zones.<br />
Figure 4. Interpreted circular features, domes, faults and dilation zones in the<br />
southeastern part <strong>of</strong> the <strong>KSK</strong> <strong>COW</strong> (after Murphy, 2003).<br />
The Main Zone is an area <strong>of</strong> coincident copper, gold and molybdenum anomalism in<br />
soils and is associated with strong phyllic alteration (Figs. 5-7). Leach (2001) reported<br />
that alteration is zoned from deeper to shallower levels: chlorite-sericite-quartz-pyritechalcopyrite<br />
→ quartz-sericite-pyrite-chalcopyrite-bornite → quartz-dickite/kaolinitepyrite-chalcopyrite-bornite-tennantite<br />
→ quartz-alunite-pyrite-barite-enargite. Leach<br />
(2001) also reported an apparent zonation from chlorite-sericite-rich assemblages at<br />
deeper levels to the east to advanced argillic assemblages at shallow levels to the<br />
west, suggesting a fluid source deeper and to the east.<br />
Previous drilling in the Main Zone has intercepted <strong>potential</strong>ly economic grades <strong>of</strong><br />
copper mineralization over considerable down hole intervals (Table 4). Near surface<br />
mineralization is dominated by supergene chalcocite and minor chrysocholla and<br />
malachite, while at deeper levels the hypogene mineralization is dominated by<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
10<br />
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chalcopyrite ± bornite. Leach (2001) constructed cross sections highlighting the<br />
alteration, grade distribution and IP chargeability features along line 10050N (Figs. 6-<br />
8) and considered two sources for the mineralization:<br />
1. copper mineralization related to a breccia pipe inferred from milled breccia<br />
observed in BK8 (Fig. 5), or<br />
2. copper mineralization derived from another source, perhaps represented by a<br />
high chargeability anomaly.<br />
Table 1. <strong>Copper</strong> grades in earlier drill holes from the Beruang Kanan prospect (from<br />
Geiger et al., 2005).<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
11<br />
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Figure 5. Interpretive cross section with drill holes projected on to line 10050N<br />
showing the distribution <strong>of</strong> alteration and sulphide mineral types (from Leach, 2001).<br />
Figure 6. Interpretive cross section with drill holes projected on to line 10050N<br />
showing the distribution <strong>of</strong> copper grades (from Leach, 2001).<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
12<br />
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Figure 7. Interpretive cross section with drill holes projected on to line 10050N<br />
showing the distribution <strong>of</strong> chargeability anomalies (from Leach, 2001).<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
13<br />
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Oxiana <strong>Limited</strong> drilling<br />
Oxiana drilled 10 holes at Beruang Kanan (Fig. 8) where reprocessing <strong>of</strong> the IP data<br />
led them to believe that there was a strong correlation between near-surface<br />
conductive and chargeable zones and copper in drill holes and soils (Stewart et al.,<br />
2007).<br />
Drill hole Location Azimuth Inclination Length (m)<br />
KBK0019 South Zone 090 o -60 o 303.65<br />
KBK0200 Main Zone 090 o -70 o 304.90<br />
KBK0021 Main Zone 270 o -70 o 636.60<br />
KBK0022 Main Zone 270 o -65 o 451.70<br />
KBK0023 Main Zone 090 o -70 o 601.90<br />
KBK0024 South Polymetallic 090 o -70 o 305.00<br />
KBK0025 South Polymetallic 090 o -90 o 393.20<br />
KBK0026 Main Zone 270 o -50 o 454.70<br />
KBK0027 West Zone 070 o -60 o 278.70<br />
KBK0028 South Zone 090 o -70 o 151.30<br />
Table 2. Oxiana <strong>Limited</strong> drill holes at the Beruang Kanan Prospect (data from<br />
Stewart et al., 2007).<br />
Drill hole From (m) To (m) Cu (%) Au (g/t)<br />
KBK0020 9.6 52.0 0.12<br />
KBK0021 16.6 60.6 0.58<br />
KBK0021 147 188.7 0.46<br />
KBK0024 95.5 136.0 0.51<br />
KBK0028 0.0 61.0 0.21<br />
KBK0028 10.0 14.5 7.7<br />
Table 3. Significant intercepts in Oxiana drill holes at the Beruang Kanan Prospect<br />
(data from Stewart et al., 2007)..<br />
Five holes were drilled in the Main Zone and most targeted chargeability anomalies<br />
suspected to represent either shallow supergene mineralization or deeper, hypogene<br />
mineralization (e.g. KBK0021). In addition, one hole (KBK0020) tested the<br />
possibility that a buried porphyry could be represented by a low chargeability zone<br />
((Stewart et al., 2007).<br />
In the South Zone, two holes were sited in an area <strong>of</strong> high density quartz-sulphide<br />
stockwork veining with anomalous gold, molybdenum and copper soil geochemistry.<br />
Hole KBK0028 intersected 61m @ 0.21% Cu from surface, including 4.5m @ 7.7g/t<br />
Au from 10m. In the South Polymetallic Zone (Rawa Zone), two holes tested the base<br />
metals zone with limited success. One hole was drilled in the West Zone where an<br />
extensive area <strong>of</strong> anomalous copper in soil geochemistry is present. The drill hole did<br />
not intersect any significant mineralization and the last 100 metres was in postmineral<br />
porphyry.<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
14<br />
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Figure 8. Geology <strong>of</strong> the Beruang Kanan prospect showing the distribution <strong>of</strong> drill<br />
holes (modified from Stewart et al., 2007).<br />
Discussion<br />
Of the two holes in the Main Zone which returned significant intersections (Table 3),<br />
one was drilled in a high chargeability zone (KBK0021) and the other in a low<br />
chargeability zone (KBK0020). This must raise a question over the inferred<br />
relationship between chargeability and copper mineralization in this area and suggests<br />
that interpretations based solely on the IP data must be treated with caution.<br />
The principal porphyry target in the Main Zone delineated by Leach (2001) was not<br />
tested by the recent drilling and the mineralization still remains open at depth in the<br />
area near BK09. In order to test this target, holes would need to be sited east and<br />
northeast <strong>of</strong> BK09 and drilled to the west at -50-60 o .<br />
In the South Zone, KBK0028 appears to have been drilled some 200 metres south <strong>of</strong><br />
the main soil geochemistry and IP target described by Geiger et al. (2005)(see fig. 9).<br />
The main target zone therefore remains untested.<br />
Strong clay-pyrite alteration is present in the west zone but the source <strong>of</strong> copper and<br />
the style <strong>of</strong> any copper mineralization are not known. Further work could be<br />
undertaken to identify the style(s) <strong>of</strong> mineralization. This could involve mapping<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
15<br />
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within the copper anomalous areas as well as outcrop and boulder sampling. If<br />
positive indications for the presence <strong>of</strong> porphyry style mineralization are found, then<br />
it may be considered worthwhile drilling the western part <strong>of</strong> the deep chargeability<br />
anomaly beneath the resistive siliceous porphyry dome(?) as interpreted on line<br />
9965N at around 13000E (see Geiger et al., 2005).<br />
Figure 9. Soil geochemistry, IP anomaly and stockwork vein distribution at Beruang<br />
Kanan South Zone (Geiger et al., 2005) showing the location <strong>of</strong> two holes drilled by<br />
Oxiana <strong>Limited</strong>.<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
16<br />
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Baroi<br />
The Baroi prospect is located within the southwestern part <strong>of</strong> the <strong>KSK</strong> <strong>COW</strong> (Fig. 1)<br />
and is hosted within an 8 km wide circular feature which is interpreted as a caldera<br />
structure. The main lithologies at Baroi include andesitic volcanics which have been<br />
intruded by monzonite and dacite porphyry intrusions at the margin <strong>of</strong> a large<br />
granodiorite pluton. The alteration and mineralization explored to date occurs in the<br />
southern part <strong>of</strong> the circular structure where it is intersected by regional NE and NNW<br />
oriented structures. The Central Zone and the Far East Zone have been the focus <strong>of</strong><br />
exploration to date.<br />
Mineralization in both the Central and Far East Zones is hosted by northwest and<br />
north northwest-trending veins up to 10 metres wide. The veins typically contain<br />
chalcopyrite, galena and sphalerite together with quartz and chlorite. Hole BF05<br />
drilled 83 metres down the dip <strong>of</strong> one such vein and returned 2.64% Cu, 0.62% Pb,<br />
1.85% Zn and 61 g/t Ag and 0.22 g/t Au. SRK considered that the vein density is not<br />
high enough to form a significant resource (Munroe and Clayton, 2006) however, they<br />
may ultimately <strong>of</strong>fer small volumes <strong>of</strong> high grade material to supplement other ore<br />
sources. Deep drilling at the Far East Zone (to 600 metres) has not indicated the<br />
presence <strong>of</strong> shallow porphyry style mineralization beneath the vein system.<br />
Veins similar to those at Far East also occur in the Central Zone where a number <strong>of</strong><br />
short holes have intersected a series <strong>of</strong> subparallel veins with Zn ≥ Pb ≥ Cu. The<br />
predominance <strong>of</strong> sericitic and argillic alteration coupled with the presence <strong>of</strong> these<br />
base metal veins in the Central Zone is consistent with the exposed material<br />
representing the outer/upper parts <strong>of</strong> a porphyry system.<br />
Oxiana <strong>Limited</strong> Drilling<br />
Oxiana drilled two new holes at Baroi, one in a conceptual target in Central Baroi<br />
originally defined by Burke (1996) on the basis <strong>of</strong> coincident magnetic and resistivity<br />
anomalies flanked by conductivity highs, and the other in the Far East Zone in an area<br />
<strong>of</strong> weakly anomalous copper and gold geochemistry.<br />
KBC009 in Central Baroi was drilled to a depth <strong>of</strong> 542.6m without intersecting<br />
significant mineralization. The presence <strong>of</strong> unaltered carbonaceous shale underlying<br />
andesitic volcanics was believed to explain the resistivity contrast.<br />
KBF0050 in Far East Baroi intersected several quartz-chalcopyrite-pyrite-chlorite<br />
veins which were thought to be up to 0.5m wide. Significant intercepts comprise<br />
(Stewart et al., 2007):<br />
• 14 metres @ 1.61 ppm Ag and 1710.57 ppm Cu (from 30 metres);<br />
• 30 metres @ 0.12 ppm Au, 7.11 ppm Ag and 6586 ppm Cu (from 56 metres);<br />
• 6 metres @ 0.11 ppm Au, 6.73 ppm Ag and 5223.33 ppm Cu (from 112.00<br />
metres).<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
17<br />
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Discussion<br />
The conceptual target in Central Baroi proposed by Bob Burke on the basis <strong>of</strong><br />
geophysical data was tested by KBC009. Reprocessed IP data led Rowston (2007) to<br />
downgrade the significance <strong>of</strong> this target because <strong>of</strong> the low chargeability in the<br />
central part. Even though the hole appears to have stopped short <strong>of</strong> the central part <strong>of</strong><br />
the target, it does appear to have intersected the marginal chargeability anomaly<br />
flanking the central zone which was envisaged as a <strong>potential</strong> pyrite-rich shell. No<br />
significant mineralization was present in the hole and the amount <strong>of</strong> pyrite was<br />
generally low. The drill hole did intersect several zones <strong>of</strong> milled breccia containing<br />
pyrite and silica-pyrite fragments, but the lower part <strong>of</strong> the hole was composed <strong>of</strong><br />
carbonaceous shale. The lack <strong>of</strong> strong pyrite development and the presence <strong>of</strong><br />
carbonaceous shale suggest that the target should be downgraded.<br />
Two further targets in central Baroi proposed by Pollard (2006) were not drilled<br />
despite receiving support from the reprocessed IP data (Rowston, 2007). The large<br />
high chargeability feature observed on the old level 7 chargeability data on the<br />
western side <strong>of</strong> Baroi Central could represent a zone <strong>of</strong> sulphide mineralization above<br />
a buried porphyry intrusion (Geiger and Prasetyo, 2004). Although this was partially<br />
tested in BC-08, a further hole was suggested via drilling the proposed hole BC-09 on<br />
line 30600N (Geiger and Prasetyo, 2004; Pollard, 1996). Based on the reprocessed IP<br />
data, Rowston (1977) supported drilling a 400m vertical hole in this conductive,<br />
chargeable feature at 30600N and 45800E.<br />
The resistivity low and chargeability high located near 30800N and 48200E, was also<br />
proposed as a target worth drilling by Pollard (2006). This area is a gap in the mapped<br />
NW-trending base metal vein system and is associated with a topographic low. It is<br />
<strong>potential</strong>ly the centre and source region <strong>of</strong> the vein system and it was recommended<br />
(Pollard, 2006) that all drill hole data from the eastern sector (Baroi Far East) be<br />
examined for temperature vectors (trends in ratios <strong>of</strong> Zn/Pb, Cu/Zn, etc.) toward this<br />
area. If present, they would support drilling a deep hole to test for mineralization<br />
linked to a deeper porphyry, possibly associated with sericitic alteration similar to that<br />
reported from holes BB-01 and BB-02. Rowston (2007) also advanced this area as a<br />
target based on the reprocessed IP data.<br />
KBF0050 confirmed previous interpretations that shallow porphyry style<br />
mineralization is not present beneath the vein system at Far East Baroi.<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
18<br />
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Mansur<br />
The Mansur prospect is located in the northwestern portion <strong>of</strong> the <strong>KSK</strong> <strong>COW</strong> within a<br />
circular topographic feature and associated strong magnetic anomaly. Surface<br />
mapping indicates the presence <strong>of</strong> a diorite intrusion within a sequence <strong>of</strong> sediments<br />
that includes siltstone, sandstone and chert. Potassic alteration in the form <strong>of</strong> biotite ±<br />
magnetite alteration and/or K-feldspar veins and alteration forms a broad zone<br />
extending more than 500 metres east and west <strong>of</strong> the diorite within the sedimentary<br />
sequence. A semicircular zone <strong>of</strong> >500 ppm Cu in soils extends around the western<br />
side <strong>of</strong> the diorite (Fig. 10) within the zone <strong>of</strong> potassic alteration.<br />
Previous drilling at Mansur had focused on the gold in soil anomaly which occurs<br />
mainly within the diorite and this returned mostly low grade values for copper and<br />
gold (e.g. CSM1 – 250m @ 873ppm Cu and CSM3 – 250m @ 1180ppm Cu and 0.06<br />
g/t Au; <strong>KSK</strong> Staff, 2006). Trenching over the Cu in soil anomaly produced low<br />
copper and gold values (70-1210 ppm Cu and
19<br />
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Figure 10. Soil geochemistry and drill hole location at the Mansur Prospect (from<br />
Johansen, 2997).<br />
Discussion<br />
The new drilling at Mansur appears to have downgraded the prospect and the chance<br />
<strong>of</strong> discovering an economic porphyry system in the area defined by the soil copper<br />
anomaly is now considered to be low. The new holes together with the earlier Cyprus<br />
Amax holes (CSM1 – 250m @ 873 ppm Cu and CSM3 – 250m @ 1180 ppm Cu and<br />
0.06 g/t Au) have effectively tested this area without intersecting significant widths or<br />
grades <strong>of</strong> mineralization.<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
20<br />
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Beruang Tengah<br />
The Beruang Tengah prospect is hosted within the same circular structure and<br />
southeast <strong>of</strong> Beruang Kanan (Fig. 4). <strong>Copper</strong>-gold mineralization is hosted within<br />
dioritic to dacitic intrusions that were emplaced between sediments and tuffs to the<br />
west and older granodiorite to the east. A zone <strong>of</strong> intense quartz-sericite alteration and<br />
sheeted sulphide-quartz veins surrounds a central zone <strong>of</strong> biotite-magnetite alteration,<br />
and quartz stockwork veins crop out at lower levels (Geiger and Prasetyo, 2004). A<br />
400 metre wide zone <strong>of</strong> >0.1% copper in rock chips (Fig. 11) coincides with the zone<br />
<strong>of</strong> quartz-sericite alteration. Some 500 metres to the west, a 1 km long zone <strong>of</strong> phyllic<br />
alteration coincides with a zone <strong>of</strong> >0.1 g/t Au in soils (Geiger and Prasetyo, 2004).<br />
Three previous diamond drill holes intersected low-grade copper-gold mineralization<br />
at Beruang Tengah (e.g. BT2 – 240 metres @ 0.19% Cu and 0.12 g/t Au) and together<br />
with the mapped alteration at surface, have indicated the presence <strong>of</strong> a porphyry<br />
copper-gold system with significant molybdenum.<br />
Oxiana <strong>Limited</strong> drilling<br />
Oxiana <strong>Limited</strong> drilled one additional hole at Beruang Tengah which targeted high<br />
copper in rock chips (Fig. 11), known phyllic alteration, as well as an outcropping<br />
milled breccia. The hole returned low values <strong>of</strong> copper and gold (Table 4), especially<br />
in the milled breccia which from observations <strong>of</strong> the skeleton core is a post-mineral<br />
feature.<br />
Drill hole From (m) To (m) Cu (%) Au (g/t) Mo (ppm)<br />
KBT 004 19.7 121.0 0.12 0.2 42<br />
KBT 004 232.2 507.5 0.08 185<br />
Table 4. Mineralized intercepts in KBT004 at Beruang Tengah.<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
21<br />
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Figure 11. Rock chip copper geochemistry and location <strong>of</strong> drill holes at Beruang<br />
Tengah (from Johansen, 2007).<br />
Discussion<br />
The new drilling at Beruang Tengah has significantly downgraded this part <strong>of</strong> the<br />
system and Oxiana considered that there was insufficient room remaining within the<br />
prospect for an economic porphyry deposit.<br />
The Beruang Tengah prospect area has been defined from rock chip sampling <strong>of</strong> creek<br />
outcrops rather than by a broader soil sampling program. It is considered that followup<br />
work is warranted aimed at more fully delineating the extent <strong>of</strong> veining and<br />
mineralization and identifying sulphide-rich parts <strong>of</strong> the system. Stockwork and<br />
sheeted veins with limonites after sulphides extend to the south and west beyond the<br />
copper anomaly that has been the focus <strong>of</strong> recent work (Geiger, pers. comm., 2008).<br />
Extension <strong>of</strong> the geochemical coverage into these areas via a soil survey together with<br />
an IP survey over the main copper anomalies may serve to highlight sulphide-rich<br />
parts <strong>of</strong> the system for follow-up drilling. Given the observed association <strong>of</strong><br />
secondary biotite and magnetite in several <strong>of</strong> the <strong>KSK</strong> prospects, reprocessing <strong>of</strong> the<br />
existing ground magnetic data and extension to the new soil grid may also serve to<br />
better highlight structure and alteration distribution.<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
22<br />
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Tumbang Huoi<br />
The Tumbang Huoi prospect is located within a large circular structure in the<br />
southwest part <strong>of</strong> the <strong>KSK</strong> <strong>COW</strong> (Fig. 2). Mapping and sampling were undertaken in<br />
the latter part <strong>of</strong> 1987 and 15 short holes were drilled in 1992 primarily focused on<br />
gold. Potassic alteration characterized by veins and wispy trails <strong>of</strong> biotite ± magnetite<br />
and veins with K-feldspar ± quartz is present in several drill holes and copper in soil<br />
anomalies are present in several parts <strong>of</strong> the prospect (Fig. . Further work perhaps<br />
involving extension <strong>of</strong> the soil grid, together with IP and ground magnetic surveys is<br />
needed in order to highlight possible sulphide-rich parts <strong>of</strong> the prospect.<br />
Figure 12. <strong>Copper</strong> in soil map <strong>of</strong> the Tumbang Huoi prospect.<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
23<br />
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Conclusions<br />
This brief review <strong>of</strong> recent exploration <strong>of</strong> the major porphyry copper prospects within<br />
the <strong>KSK</strong> <strong>COW</strong> in Central <strong>Kalimantan</strong> indicates that several <strong>of</strong> these systems still have<br />
untested <strong>potential</strong>. In particular, the Beruang Kanan Main and South Zones and the<br />
Baroi Central prospect have untested drill targets that were proposed in earlier work<br />
by <strong>KSK</strong> staff and external consultants. The Baroi targets were also supported<br />
following reprocessing <strong>of</strong> the IP data during the Oxiana joint venture.<br />
Several other prospects within the <strong>KSK</strong> <strong>COW</strong> including Beruang Tengah, Tumbang<br />
Huoi, and Beruang West require further field inspection, geochemical sampling and<br />
geophysical work in order to define targets for further exploration. Other prospects<br />
not considered here including Rinjen and Mamuring also require further work,<br />
especially to assess the <strong>potential</strong> for high-grade skarn-style mineralization at<br />
Mamuring.<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
24<br />
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Acknowledgements<br />
The author would like to acknowledge the help provided by <strong>KSK</strong> staff in<br />
Palangkaraya, especially Mansur Geiger, Didik Prasetyo and Rachmat Setiawan<br />
References (including uncited reports)<br />
Corbett, G.J. and Leach, T.M., 1998. Southwest Pacific rim gold-copper systems:<br />
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Geiger, M. and Prasetyo, D., 2004. Appraisal and exploration summary: Baroi and<br />
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<strong>Kalimantan</strong>, Indonesia. Unpublished report to P.T. <strong>Kalimantan</strong> Surya Kencana.<br />
Omer-Cooper, W., 1990. P.T. Pancaran Paringa <strong>Kalimantan</strong> Riah Janda Contract <strong>of</strong><br />
Work: Tumbang Huoi gossan, Unpublished report 4p and appendices.<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>
25<br />
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Pollard, P.J., 2006. <strong>Copper</strong>(-gold) prospects within the <strong>Kalimantan</strong> Surya Kencana<br />
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exploration. Unpublished report to <strong>Kalimantan</strong> <strong>Gold</strong> <strong>Corporation</strong> <strong>Limited</strong>.<br />
Prasetyo, D., 1999a. Drilling data: Beruang Tengah porphyry copper-gold.<br />
Unpublished report to P.T. <strong>Kalimantan</strong> Surya Kencana.<br />
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<strong>Kalimantan</strong>, Exploration Summary March 15 – September 15, 1996, vol. 1.<br />
Unpublished report.<br />
Rowston, P., 2007. <strong>Copper</strong>-gold porphyry prospect geophysics Baroi Central/East,<br />
Central <strong>Kalimantan</strong>: Modeling and interpretation report. Unpublished report by<br />
Geophysical Resources and Services Pty. Ltd.<br />
SRK Consulting, 2006. Competent person’s report on the mineral exploration assets<br />
<strong>of</strong> <strong>Kalimantan</strong> <strong>Gold</strong> <strong>Corporation</strong> <strong>Limited</strong>. Unpublished report to <strong>Kalimantan</strong> <strong>Gold</strong><br />
<strong>Corporation</strong>.<br />
Stewart, A., Smith, S., Hamid, D. and Muryanto, A., 2007. 2007 exploration report<br />
KGC <strong>COW</strong> project, Central <strong>Kalimantan</strong>, Republic <strong>of</strong> Indonesia. Oxiana <strong>Limited</strong><br />
report No. 1141.<br />
Wake, B. and Setiawan, R., 2006. Baroi Prospect, Baroi Far East Zone deep diamond<br />
drilling report (interim). Unpublished report to P.T. <strong>Kalimantan</strong> Surya Kencana.<br />
___________________________________________________________________________________<br />
Peter J. Pollard<br />
<strong>Copper</strong> <strong>potential</strong> <strong>of</strong> <strong>KSK</strong> <strong>COW</strong>, Central <strong>Kalimantan</strong>