AsiaPacific 2010 - Deposit Descriptions

Geological summaries of the deposits to be visited are as follows:

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Oyu Tolgoi, Mongolia .................................... Mon. 11, Tue. 12 Oct., 2010

The Oyu Tolgoi high sulphidation porphyry copper-gold-(molybdenum) deposit is located in the Gobi Desert of southern Mongolia, 550 km due south of the capital, Ulaanbaatar and 80 km north of the Chinese border. It was formed at 370 Ma (Late Devonian) in the Kazakh-Mongol magmatic arc, and is among the largest and richest known hypogene porphyry Cu-Au deposit in the world. The deposit contains at least 32 Mt of copper and 990 tonnes of gold in estimated resources and is owned by Ivanhoe Mines.

The Oyu Tolgoi deposit lies within the Middle Palaeozoic Kazakh-Mongol magmatic arc, represented by a 100 to 250 km wide arcuate swathe of arc-related terranes in southern Mongolia that follows the southern border between Mongolia and China, with a trend that curves from northeast in the east of Mongolia, to WNW where it passes into western China. The individual terranes are predominantly composed of island arc volcanic rocks and are extensively intruded by voluminous Permo-Carboniferous granites.

To both the north and south, the magmatic arc is bounded by tectonically complex suites of 'basement' terranes composed of Lower to Middle Palaeozoic back- and fore-arc sequences, volcanic rocks of the late Neoproterozoic to Lower Palaeozoic Tuva-Mongol magmatic arc and slivers of basement Meso- to Neoproterozoic metamorphics, separated by intra-arc suture related accretionary wedge sequences which include Late Neoproterozoic (Vendian) to Early Cambrian ophiolites.

Oyu Tolgoi is within the Gurvansayhan Terrane, which is located in the central-southern section of the magmatic arc where it trends roughly east-west. The geology of the 600 x 200 km triangular shaped terrane is predominantly composed of Silurian to Carboniferous terrigenous sediments, carbonates, volcani-sediments and intermediate to felsic volcanics, all cut by extensive Devonian granitoids and by Permo-Carboniferous diorite, monzodiorite, granite, granodiorite and syenite bodies, ranging in size from dykes to batholiths that are tens of kilometres across.

The original architecture of the sequence and the magmatic arc has been disrupted by intrusive masses, modified by both mid- to late-Palaeozoic accretion and Mesozoic thrust and sinistral strike-slip faulting, and masked by alluvium on a mature surface. This has resulted in a complex of imbricate thrust sheets, dismembered blocks, mélanges and high strain zones. The abundant Permo-Carboniferous intrusive complexes of the terrane appear to be closely related to a major northeast-trending fault zone known as the East Mongolian or Zuunbayan fault zone which cuts obliquely across the arc and forms the south-eastern boundary of the Gurvansayhan terrane.

The sequence within a 20 km radius surrounding Oyu Tolgoi is predominantly composed of Devonian basaltic to intermediate volcanic and volcaniclastic rocks, overlain by layered pyroclastics and sedimentary rocks with andesitic sills. Layered Carboniferous pyroclastic and sedimentary rocks, cut by andesitic sills overlie and are in fault contact with the Devonian hosts. Several large masses of granitic rocks surround the deposit, the largest being the 287±2 Ma (K-Ar) Hanbogd Mountain per-alkaline granite 5 km to the east, while the 308±2 Ma (U-Pb zircon) Javhalant Mountain Batholith is a similar distance to the south and the 348±2 Ma (U-Pb zircon) North Granite is closer to the north and west.

At the end of the Palaeozoic, the area was subjected to Basin and Range style rifting, with associated bimodal volcanism. This was followed during the early Mesozoic, by widespread uplift and associated thrusting which unroofed the magmatic arcs. Terrigenous sediments were deposited in fault controlled basins during both episodes. By the Late Cretaceous, the region had become increasingly arid.

The Oyu Tolgoi porphyry Cu-Au deposit comprises four discrete zones hosted at different stratigraphic levels within a sequence of pre-ore tholeiitic basaltic volcanic and dacitic pyroclastic rocks overlain disconformably by clastic sedimentary and volcaniclastic rocks, and by basalt to dacite lava flows that are locally peperitic. The Cu-Au mineralisation is associated with intermediate- to high-K granitoids emplaced as structurally controlled dykes and small plugs.

Outcrop is generally strongly weathered, and is sparse and subdued, and are largely masked by 40 m of a flat to gently south dipping, NNW trending terrace of Neogene(?) piedmont outwash red clay and gravel. The host succession within the deposit area, from the base to top, is as follows:

i). Laminated, andesitic volcaniclastic rocks.
ii). Augite Basalt lava flows and related breccias which are around 800 m thick and are altered to chlorite/biotite with augite phenocrysts.
iii). Dacitic to Andesitic Tuffs, 80 to 400 m thick, comprising an upper thin block-ash tuff and the underlying ash flow tuff, the bulk of the unit, disconformably overlying the Augite Basalt.
iv). Lower Sedimentary-Volcanic Sequence, approximately 350 m thick, disconformably overlying the dacitic tuffs. It is composed of red to green-brown siltstone and fine sandstone, with minor conglomerate and carbonaceous shale, and intercalated auto-brecciated basaltic lava and tuff. The lowest 50 m of this unit is a laminated siltstone with carbonaceous shale and coal.
v). A 250 m thick unit comprising a lower andesitic ignimbrite pile overlain by an slightly thinner upper sequence of coal, conglomerate, sandstone and a thin green tuff. This and the overlying three units are referred to as the Upper Sedimentary-Volcanic Sequence.
vi). Basaltic volcaniclastic unit, up to 400 m thick, comprising polymictic, subrounded, lapilli-sized clasts in a plagioclase-bearing to silty matrix intercalated with locally peperitic basalt, and has a thin andesitic lava flow at the base.
vii). Basaltic lava flows, up to 200 m thick, with minor intercalated breccia and tuff.
viii). Dacite flow, possibly a flow or dome facies, up to 200 m thick.

A wide variety of felsic to mafic dykes have been encountered throughout the deposit area, the orientations of which are largely controlled by the dominant structural fabric of the area, which trend at both 35 and 70°. The mineralisation appears to be genetically associated with a suite of variably altered and mineralised porphyritic quartz monzodiorite dykes that cut the Augite Basalt and Dacitic to Andesitic Tuff units in the lower part of the host sequence. Post mineral dykes include basalt, rhyolite, hornblende-biotite andesite, and biotite granodiorite intrusive rocks. The closest, large outcropping felsic intrusive mass, is approximately 3 km to the north-west of the deposit area, while gravity data suggests additional large granitoid intrusives to the west of the deposit area.

The intrusive history of the deposit area can be summarised as follows, from oldest to youngest:

i). Early mineralised and altered quartz monzodiorite, mainly found at South Oyu;
ii). Late mineralised quartz monzodiorite, which only intrudes to the top of the Dacitic to Andesitic Tuff, and varies from moderately- to un-mineralised;
iii). Biotite Granodiorite which is largely unaltered, and intrudes the Lower Sedimentary-Volcanic Sequence and into the base of the overlying andesite ignimbrites. This phase is locally altered and mineralised in the Hugo Dummett deposit;
iv). Hornblende-biotite andesite dykes, persisting into the Basaltic volcaniclastic unit.
v). Rhyolite dykes, found to the top of the sequence
vi). Basalt dykes, found throughout the full sequence.
vii). Dolerite dykes, the youngest intrusive phase.

The four main mineralised centres at Oyu Tolgoi, namely: i). Hugo Dummett (divided into South and North Hugo, previously Far North Oyu); ii). Central Oyu; iii). South-West Oyu and iv). South Oyu are distributed over around 8 km of a more than 20 km long, NNE trending structural and mineralised corridor and appear to represent three porphyry centres at South and Central Oyu and near Hugo Dummett. For development purposes, these zones have been grouped into the Hugo North, Hugo South and Southern Oyu deposits.

The corridor appears to have been tilted to the north, such that erosion has removed much of the high sulphidation system at South and South-West Oyu, exposing the roots and mid levels of the porphyry system. In contrast, at Hugo Dummett North, the entire high sulphidation system and underlying and over printed porphyry mineralisation is preserved and plunges north at depth, below poorly mineralised hosts.

Mineralisation and alteration are associated with small plugs, dykes and hydrothermal breccias and occur as multiple porphyry Cu-Au centres with high sulphidation zones partially telescoped onto underlying porphyry systems. Alteration includes K silicate (quartz-K feldspar-biotite) and overprinting sericite-chlorite at South Oyu, while several advanced argillic and quartz-sericite-illite associations are dominant at Central and North Oyu, over printing and obliterating the earlier K silicate and quartz-sericite stages, particularly in association with hydrothermal breccias. Peripheral, magnetite stable propylitic alteration of calcite, chlorite and epidote is weak, low in pyrite and fringes the advanced argillic alteration at Central and Hugo Dummett.

The bulk of the Cu-Au-Mo mineralisation at South and SW Oyu is present as porphyry style heavily stockworked and sheeted veining and is pyrite poor and magnetite rich. The upper 30 to 60 m is characterised by a mixed sulphide-oxide zone. Only the roots of an original high sulphidation system remain.

SW Oyu is centred on a cluster of small 10 to 30 m wide syn- to late-mineral porphyritic quartz monzodiorite dykes, with mineralisation extending for more than 100 m into the adjacent basaltic volcanic hosts from each dyke. The higher-grade core of the centre, within a <1 g/t Au zone, has a 250 m diameter and extends down plunge to the southwest over a vertical interval of more than 800 m. The grade of mineralisation within the broader 0.3% Cu eq. shell at SW Oyu averages 0.41% Cu, 0.47 g/t Au, surrounding a core of 0.77% Cu, 1.44 g/t Au.

The main mineralisation is represented by early, relatively high temperature, milky white quartz veins, which cut both the quartz monzodiorite and in the basaltic wall rocks. Chalcopyrite and subordinate pyrite and bornite are found as disseminations and as late fracture fillings within both the quartz veins and the adjacent host rocks. Gold is very fine and is intergrown with chalcopyrite as veinlet infill, healing hydro-fracturing of pyrite crystals and as inclusions within, or on grain boundaries of chalcopyrite and bornite or gangue minerals. Grade increases with depth, from an Au g/t:Cu%) ratio of 2:1 near surface, to 3:1 at depth, while low grade propylitic basalts surrounding the main high grade core maintain a ratio of 1:1 over an area of 600 x 2000 m.

The dominant alteration in the quartz monzodiorite at SW Oyu comprises early pervasive albite, overprinted by quartz sericite and minor tourmaline and fluorite, while biotite-magnetite and late chlorite-sericite is the principal alteration facies in the surrounding basalts. Pervasive biotite alteration is found in the core of the deposit, but further outward is only present as selvages to the mineralised veinlets. A quartz monzodiorite dyke which forms the south-eastern margin of the deposit is altered to sericite in its upper levels with weak disseminated pyrite and chalcopyrite and is believed to represent the root zone of an eroded high sulphidation system.

South Oyu has similarities to SW Oyu and at a 0.3% Cu equivalent cut-off has an average grade of 0.46% Cu, 0.11 g/t Au

Central Oyu comprises a high sulphidation systems developed above, and partly telescoped onto, an underlying centre of porphyry mineralisation. Covellite and pyrite are developed within an upwardly flared zone of intense quartz-muscovite alteration with subordinate minamite, dickite and pyrophyllite, while primary apatite has been altered to secondary phosphates (crandellite, svanbergite and woodhousite). In addition, a supergene chalcocite blanket several tens of metres thick has been superimposed on the high sulphidation pyrite rich, hypogene chalcocite-covellite-tennantite (arsenosulvanite, sulvanite, chalcopyrite, bornite) suite that accompanied the advanced argillic alteration. This has produced sooty chalcocite coatings on pyrite and as fracture fillings below a 20 to 60 m thick hematite and goethite rich leached cap. The jarosite-goethite leached capping is 25 to 50 m thick, overlying a chalcocite blanket and a mixed supergene-hypogene zone to depths of 100 to 200 m. The upper 20 to 30 m of the enriched blanket (the main supergene enrichment) has steely chalcocite and minor covellite and digenite and carries from 0.6 to 1.9% Cu. Minor exotic copper mineralisation has been encountered in some drill adjacent to the main prospect. The grade of mineralisation at Central Oyu within the 0.3% Cu equivalent shell averages 0.62% Cu, 0.17 g/t Au. The distribution of gold is erratic and not well defined, with the high sulphidation systems partly telescoped onto the underlying porphyry system. Covellite-pyrite is related to an upwardly flared intense quartz-sericite zone, centred on a porphyry style quartz veined dyke swarm.

At Hugo Dummett also represents a high sulphidation system that has been telescoped onto porphyry-style mineralisation formed at an earlier stage in the evolution of the hydrothermal centre. High grade copper mineralisation extends over a distance of more than 4.5 km in two connected segments, Hugo Dummett South and North. Mineralisation is dominantly bornite, chalcocite and chalcopyrite, with subordinate pyrite, enargite and tetrahedrite-tennantite. The sulphides are directly related to the associated alteration assemblage, which in turn is partially dependent upon the lithology of the host rock, but also the position in the outward zonation from the core of the high-grade shell ellipse. The outward zonation from high to low grade Cu ore corresponds with the progression from bornite + chalcocite, to chalcopyrite (±tetrahedrite-tennantite) to pyrite (±enargite).

Much of Hugo Dummett South is hosted by dacitic to andesitic ash flow tuff, in contrast to Hugo Dummett North which is predominantly within augite basalt and quartz monzodiorite. The difference in host lithology strongly influences both the alteration and sulphide species. Advanced argillic alteration within the ash flow tuffs comprises alunite, pyrophyllite, diaspore, dickite, topaz, zunyite, minor fluorite and rare dumortierite, with enargite, bornite+pyrite, and locally covellite. The mineralisation is related, both vertically and laterally to a series of porphyritic monzodiorite apophyses and to a deeper-seated porphyry-style intrusive core. Magnetite and chalcopyrite veining in biotite and chlorite altered porphyritic augite basalt, similar to SW Oyu occur at depth.

Hugo Dummett North is dominantly within basalt and quartz monzodiorite, and is characterised by assemblages of bornite+chalcocite and chalcopyrite with minor, enargite and tetrahedrite-tennantite. This section of the deposit has a continuous high-grade bornite dominant core which extends for at least 1.6 kilometres to the NNE from South Hugo. This core corresponds to a zone containing around 90% vein quartz. It has a vertical extent that varies from 100 m in the neck connecting Hugo Dummett South and North, but expands to more than 700 m to the north. The corresponding horizontal width of the high grade core ranges from 150 to 180 metres up to approximately 200 m in the south and north respectively and is entirely enveloped by the greater than 1% Cu grade shell which reaches a maximum horizontal thickness of 450 m at zero RL (1160 m below surface). Maximum gold grades are associated with bornite with Au g/t:Cu% ratios varying from 1:10 to as high as 1:1 in the northern part of the deposit.

The main Hugo Dummett North orebody is limited to the west by a thick dyke of late- to post-ore biotite granodiorite. It redevelops again on the western side of this dyke, hosted by quartz monzodiorite to form the gold and bornite rich Hugo Western Gold orebody which is up to 100 m thick, with a vertical extent of 300 m and a strike length in excess of 1 km, which in May 2004 was estimated to contain a minimum of 57.6 Mt @ 0.96% Cu, 0.85 g/t Au.

Molybdenite occurs locally in all rock types. A Re-Os determination from molybdenite in the orebody gave an age for the ore of 372 �1.2 Ma.

In February 2003, at a 0.3% Cu equivalent cut-off, the four deposits had:
- an indicated resource of 508.9 Mt @ 0.4% Cu, 0.59 g/t Au + an inferred resource of 1.602 Gt @ 0.63% Cu, 0.17 g/t Au.
In February 2003, at a 0.6% Cu equivalent cut-off, the same deposits yielded:
- an indicated resource of 266.9 Mt @ 0.53% Cu, 0.86 g/t Au + an inferred resource of 811.7 Mt @ 0.90% Cu, 0.21 g/t Au.
The indicated resource was all at SW Oyu.

In March 2007, at a 0.6% Cu equivalent cut-off, the same deposits yielded a:
- measured + indicated resource of 1.387 Gt @ 1.33% Cu, 0.47 g/t Au + an inferred resource of 1.397 Gt @ 0.98% Cu, 0.24 g/t Au.
- Total resource = 2.785 Gt @ 1.15% Cu, 0.35 g/t Au.

Total resource figures at March 2010, at a 0.6% Cu eq. cut-off for the full Oyu Tolgoi project (Ivanhoe Mines, 2008), including the Hugo North and South deposits, the Southern Oyu deposits (Central, Southern and SW), Heruga and Hugo North Extensions:
- Total measured + indicated resources of 1.387 Gt @ 1.33% Cu, 0.47 g/t Au; plus
- Total inferred resources of 2.367 Gt @ 0.78% Cu, 0.33 g/t Au
Total measured + indicated + inferred resources of 3.754 Gt @ 0.98% Cu, 0.38 g/t Au.

The March 2010 resource figures above include (at a 0.6% Cu cut-off - source Ivanhoe Mines, 2010):
* All Hugo North deposits:
- an indicated resource of 820.2 Mt @ 1.82% Cu, 0.42 g/t Au + an inferred resource of 818.3 Mt @ 1.00% Cu, 0.30 g/t Au.
* the Hugo South deposits:
- an inferred resource of 490.3 Mt @ 1.05% Cu, 0.09 g/t Au.
* the Southern Oyu deposits (Central, Southern and SW):
- a measured + indicated resource of 567.23 Mt @ 0.62% Cu, 0.55 g/t Au + an inferred resource of 88.5 Mt @ 0.47% Cu, 0.41 g/t Au. * the Heruga deposits (Ivanhoe and Javkhlant JV Heruga):
- an inferred resource of 970 Mt @ 0.48% Cu, 0.48 g/t Au.

Total reserve figures at May 2010, which are included within resource figures, (Ivanhoe Mines, 2008), including the Hugo North and Southern Oyu deposits were:
* the Hugo Dummett deposits: - a probable reserve of 437 Mt @ 1.90% Cu, 0.42 g/t Au.
* the Southern Oyu deposits: - a proven + probable reserves of 955 Mt @ 0.49% Cu, 0.35 g/t Au.
Total Oyu Tolgoi proven + probable reserves of 1.393 Gt @ 0.93% Cu, 0.37 g/t Au.

This summary is abbreviated from Seltmann & Porter (2005) which acknowledges the source of information quoted.

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Travelling from Mongolia to the Philippines .................................... Tue. 12, Wed. 13 Oct., 2010

Tampakan, southern Mindanao, Philippines .................................... Thu. 14, Fri. 15 Oct., 2010

Tampakan comprises a highly telescoped copper-gold deposit pair of high sulphidation-epithermal ores overprinting older, erosionally exhumed, deeper-level porphyry-Cu mineralisation within southern Mindanao, the Philippines. The deposit is hosted by sub-aerial andesites of Miocene to Pliocene age on the western flank of a deeply dissected andesitic stratovolcano belonging to the north-western Sangihe Arc. It lies within the centre of a 100 km wide sinistral strike-slip deformation zone represented by the NW-trending trans-Mindanao Cotabato Fault zone. NNE oriented dilational faults within the Pliocene stress field associated with the Cotabato Fault zone exert a stong control on the epithermal mineralisation at Tampakan.

The Tampakan district is centred on a deeply eroded polygenetic volcanic complex which was active episodically from the Late Miocene to late Quaternary. The volcanics and intrusives are dominated by mafic to silicic andesite flows and intrusives of Late Miocene to Middle Pliocene age, with lesser basaltic andesite flows of Late Miocene age and dacitic flow domes and plugs of Pleistocene age. The Tampakan porphyry mineralisation is hosted by Late Miocene and early Pliocene volcanics, whereas the Tampakan high-sulphidation deposit also lies within younger, middle Pliocene volcanic and intrusive rocks.

The principal host rocks to the high sulphidation mineralisation are the Tampakan Andesite Sequence of Late Miocene to Mid-Pliocene age. They comprise porphyritic hornblende-pyroxene andesite and silicic andesite flows that dip at 10 to 20° towards the WSW, sub-parallel to the mineralised lithocap in the deposit. Hornblende-diorite porphyry stocks intrude the Tampakan Andesite Sequence in the deposit area, varying from holocrystalline and equigranular to crowded-porphyry-textured intrusives with 70 to 80% phenocrysts. The intrusives form apophysis-like dykes and stocks, and tend to be altered but weakly mineralised.

The high sulphidation mineralisation and associated acid alteration form a manto-like zone extending along an erosion surface that exhumed the low grade porphyry Cu system which predated the epithermal phase by ~1 M.y. There is a strong structural and stratigraphic control to the high sulphidation mineralisation, which occurs as a flat lying to gently dipping 200 to 500 m thick body that covers a surface area of some1.6 x 2 km, and lies within a district wide advanced-argillic and argillic lithocap exceeding 90 sq. km. in area. The Pula Bato Fault Zone, which comprises a NNE-trending series of faults that transect the Pliocene volcanic edifice, lies along the long-dimension of the Tampakan orebody. High-sulphidation mineralisation pinches downward along this fault zone, and mushrooms upward into a broad, manto-like, stratabound zone of advanced-argillic alteration that encapsulates the central zones of high-sulphidation ore. The ore is in turn encompassed by a gently dipping, tabular zone of partial to massive silicification accompanied by multiphase brecciation and acid leaching (producing vuggy porosity). The high sulphidation mineralisation is dominated by vein and vug-filling enargite-bornite-digenite-chalcocite-covellite±molybdenite, and is associated with an assemblage of silica-pyrophyllite-dickite-alunite-diaspore±sericite. This alteration grades downwards to sericite-chlorite and relict potassic biotite-chlorite-magnetite-anhydrite alteration and associated weakly mineralised, but pervasively developed quartz stockwork veining that is interpreted to represent the outer shell of a porphyry system.

Porphyry Cu-Au mineralisation is widespread below the high sulphidation ores. It is encountered at depths of 400 to 500 m where drilling has passed into low grade chalcopyrite-bornite-pyrite in pervasive quartz stockwork veining, hosted by andesitic flows and the roof zone of high level hornblende-diorite stocks. The principal sulphide and oxide minerals in equilibrium with porphyry-stage anhydrite-biotite alteration are chalcopyrite, bornite, pyrite, magnetite (up to 8%), subordinate specular hematite and molybdenite. This mineralisation is dominated by pink-grey coloured, multi-directional, crudely laminated veins with medial crack-seal textures that contain traces of bornite and/or chalcopyrite and/or pyrite. Anhydrite-bearing veins are less prevalent. Chalcopyrite is the dominant sulphide occurring as disseminated grains, as anhedral inclusions within and along the margins of hydrothermal magnetite grains, and as elongate laths that extend along cleavage planes of hydrothermal biotite grains. Bornite is subordinate to chalcopyrite, and both are always in textural equilibrium, often forming composite sulphide grains. Molybdenite and hematite are minor phases in the potassic alteration zone. Porphyry-stage sulphides also occur as fracture-controlled disseminations within the wallrock to quartz-dominated and lesser anhydrite-bearing veins.

The deposit in 2005 (Indophil Resources website) was estimated to contain 12 Mt of copper and 500 tonnes (16 Moz) of gold, but is open both to the west and at depth.
At a cut-off of 0.2% Cu the mineral resource has been calaculated at 2.5 Gt @ 0.48% Cu
At a cut-off of 0.5% Cu the mineral resource is estimated to be 900 Mt @ 0.75% Cu

In 2010, the measured + indicated + inferred resource estimate, using a 0.3% copper cut-off (Sagittarius Mines, Inc. website) totalled:
2.4 Gt @ 0.6% Cu, 0.2 g/t Au, 70 ppm Mo, comprising 13.5 Mt of Cu and 490 t of contained Au.

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Travelling from Mindanao to Sumbawa Island, Indonesia .................................... Sat. 16, Sun. 17 Oct., 2010

Batu Hijau, Sumbawa, Indonesia .................................... Mon. 18, Tue. 19 Oct., 2010

The Batu Hijau porphyry copper-gold deposit is located on the south-western corner of the island of Sumbawa in central Indonesia. It is a joint venture between the Sumitomo controlled Nusa Tengarra Mining Corporation of Japan and PT Pukuafu Indah. Newmont is the operator and holds a 45% equity in the mine.

The deposit lies within the east-west trending Sunda-Banda magmatic arc at the convergent intersection of the Australian-Indian and the Eurasian plates. The northern half of Sumbawa is occupied by recent volcanoes, while the southern segment, where Batu Hijau is located, comprises oceanic crust overlain by low K calc-alkaline to weakly alkaline andesitic volcanics and volcaniclastics, associated intermediate intrusives and minor shallow marine sediments and limestones. In the mine area the sequence is represented by andesitic volcanic lithic breccias, volcaniclastic sandstones and mudstones and hypabyssal porphyritic andesites, with a younger thick sequence of quartz diorite in the east. Multiple tonalite porphyry intrusions were emplaced along the contact between the andesitic volcaniclastics and the quartz diorite. These tonalites, around which the mineralisation is zoned, are divided into the Old, Intermediate and Young Tonalites. Each has associated quartz veining and Cu-Au mineralisation, with the Old Tonalite having the highest grades and most intense associated alteration. The two following phases have progressively lower grades, vein densities and alteration.

Alteration and mineralisation has been divided into five temporally and spatially overlapping stages, namely: 1). Early pervasive biotite, secondary magnetite and plagioclase with fine 'A' type stockwork veining and bornite-digenite-chalcocite mineralisation, 2). Transitional oligoclase/albite-sericite-quartz±vermiculite with planar 'B' veins containing chalcopyrite±bornite (representing 50 to 70% of the Cu in the deposit) and rare 'C' veining, 3). Late feldspar destructive sericitic + other minerals (propylitic) alteration with associated 'D' veins of pyrite and quartz±chalcopyrite, 4). Very Late feldspar destructive alteration producing smectite and chlorite with associated sphalerite, galena, tennantite, pyrite and chalcopyrite, 5). Zeolite alteration, a low temperature phase of open space filling, The final influence was oxidation to depths of 210 m with weak supergene sooty chalcocite enrichment in a thin 15 to 60 m thick layer.

Based on the feasibility study prior to the commencement of production in 2000, the Batu Hijau deposit had a resource of 1.1 Gt @ 0.525% Cu, 0.37 g/t Au. (Newmont website)
Proven+probable reserves at the end of 2003 were stated as 570 Mt @ 0.55% Cu, 0.37 g/t Au, representing 2.9 Mt of Cu and 215 tonnes of Au.

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Travelling from Sumbawa to Timika in West Papua, Indonesia .................................... Tue. 19, Wed. 20 Oct., 2010

Grasberg and Ertsberg, West Papua, Indonesia .................................... Thu. 21, Fri. 22 Oct., 2010

For personal security reasons the actual site visit to the Grasberg/Ertsberg operation will be restricted to detailed briefings and comprehensive drill core inspections at the company's secure core facility in Timika.

The Gunung Bijih (or Ertsberg) mining district of West Papua (formerly Irian Jaya) contains a diverse group of large porphyry and skarn ore deposits. The district incorporates the super-giant Grasberg porphyry deposits associated with the 3.2 to 2.7 Ma Grasberg Igneous Complex, porphyry ores of the 4.4 to 3.0 Ma Ertsberg Diorite 2.5 km to the south, and a series of skarns deposits surrounding the latter and between the two intrusive complexes. Together these deposits account for near 80 Mt of copper and around 3900 tonnes of gold (including inferred resources). All are mined as part of a large integrated operation owned by PT Freeport Indonesia. The operation is one of the world's largest gold mines with an annual production (2007) of around 68 tonnes of gold and 560 000 tonnes of copper.

The mine is situated immediately adjacent to the 5030 m high Puncak Jaya, the highest mountain in Australasia, in the core of the Papuan Fold Belt that forms the spine of the island of New Guinea. The fold belt marks the northern margin of the stable platform of the northward migrating Australian continental plate, several hundred kilometres south of its convergent intersection with the current south subducting Caroline oceanic plate. The fold belt was initiated when the Australian plate entered the earlier north dipping subduction zone of the Melanesian Arc during the Miocene (at ~12 Ma) and deposited while that same northward subduction continued.

The mobile belt comprises thrust wedges of Proterozoic and Palaeozoic rocks overlain by Mesozoic marine clastics and Tertiary carbonates and platform sediments. In the mine area the Mesozoic is represented by >700 m of quartz sandstones, shales and the uppermost shale, sandstone and limestones of the Cretaceous Kembelangan Formation; overlain by the 1700 m thick Tertiary New Guinea Group. The New Guinea Group has been subdivided into the Paleocene Waripi Formation composed of ~300 m of grey to dark grey, thin bedded dolomite, dolomitic limestone, calcarenite, siltstone and white to light grey, usually calcareous sandstone with significant evaporite nodules and lenses; overlain by the Eocene to Lower Oligocene Faumi Formation which comprises a lower 70 m of grey-brown, locally sandy dolosparite and an upper 130 m of greyish-brown biosparite to biomicrite; followed by 50 m of Oligocene quartzose and calcareous sandstones and conglomerates and shales of the Sirga Formation; ~800 m of Late Oligocene to Miocene Kais Formation (or New Guinea Limestone), comprising a thick limestone succession. The Waripi Formation and to a lesser degree, the Faumi Formation are the principal hosts to skarn mineralisation in the district.

Within the Gunung Bijih mining district, the structure is dominated by an arc-parallel, WNW-ESE (110°) trending set of north dipping thrusts (with lesser strike-slip movement and strike-slip normal faults) and folds (limbs dipping at 50 to 80°), parallel to the major Mapenduma Thrust and anticline separating the Papuan Fold Belt and Fly Platform, 30 km to the south. A a second, NE to ENE trending set of steep faults also cuts the district.

Around 16 Pliocene hypabyssal intrusions have been delineated in the Gunung Bijih mining district, mainly dykes, sills or plugs with areas of outcrop ranging from a few to several hundred square metres. The Ertsberg Diorite and the Grasberg Igneous Complex (GIC) are the largest, with areas of a few square kilometres. These intrusions have similar chemistries, but the Grasberg Diorite is largely porphyritic whereas the bulk of the Ertsberg is dominantly equigranular. McDowell et al., (1996) reported 13 K-Ar ages from these intrusions that indicate magmatic activity in the district ranged from 4.4 to 2.6 Ma (mean 3.22 Ma). The Grasberg complex has returned dates of 3.2 to 2.8 Ma (K-Ar - McDowell et al., 1996) and 3.33 to 3.02 (Ar-Ar - Pollard et al., 2001).

The 2.5 x 1 km Ertsberg Diorite is mainly an even grained equi-granular quartz monzodiorite with lesser biotite-pyroxene diorite and porphyritic quartz monzonite dykes which cut the other two phases. This intrusive complex has been dated at 2.7 to 2.58 Ma (Pollard et al., 2005), and hosts, or is rimmed by, the Ertsberg skarn and the Ertsberg disseminated ores, the latter apparently related to a set of the quartz-monzonite dykes which are 5 to 15 m wide.

The Grasberg Igneous Complex (GIC), around 2.5 km to the NNW, is an upwardly flaring funnel shaped 1.7 x 2.4 km volcanic vent or diatreme (800 m diameter 1000 m below) with an intrusive core, composed of:
i). An early Dalam Igneous Complex (3.33 Ma; Pollard et al., 2005) comprising a lower Dalam Diorite phase and an upper andesitic phase which comprises matrix supported breccias, pyroclastics, volcaniclastic sediments and trachy-andesite lavas. On the margins, the upper andesitic phase is differentiated into a bedded volcanic unit, which is a thin band of bedded, water-lain volcaniclastic sediments that occur along the northeast and southwest edges of the complex, a unit of coarse andesite porphyry flows cut by dykes and sills, the Dalam Andesite and the core of breccias and pyroclastics, the Dalam Fragmentals. The Dalam Volcanic and Dalam Fragmentals are, respectively, polymict and monomict matrix supported breccias, typically containing 5% to 10%, but locally up to 30% clasts. The Dalam Igneous Complex represents an explosive, gas driven, space-generating eruption, which has produced a maar complex that has vented to the surface. It is now the un-eroded roots of a 2 to 3 km tall composite stratovolcano which has been removed by the strong uplift that produced the 5000 m Puncak Jaya and the surrounding mountain range.
ii). The Main Grasberg Intrusion (MGI) which is interpreted to have been passively emplaced as a non-venting plug in the centre of the Dalam phase rocks. It is characterised by coarse, relatively equigranular textures and a near lack of fragments. This is in turn divided into a). Early Main Grasberg - a 600 x 430 m stock of porphyritic quartz monzodiorite with a vertical extent of more than 2800 to 4250 m, dated at 2.83 Ma (?); b). Late Main Grasberg - a 900 m diameter stock of porphyritic quartz monzodiorite with associated dykes and a vertical extent of 2800 to 3800 m.
iii). Kali Intrusion - which occurs as a nest of quartz monzodiorite porphyritic dykes with crowded plagioclase-hornblende-biotite phenocrysts, and disseminated magnetite set in a finer groundmass of quartz, feldspar and biotite. The intrusion has been divided into a). Early Kali (3.16 Ma; Pollard et al., 2005) - an irregular 600 x 250 m stock-like dyke with a vertical extent of >4000 m, and b). Late Kali (3.13 Ma; Pollard et al., 2005) - mainly dykes and a 500 x 250 m stock with a vertical extent of more than 4000 m.

No volcanic deposits extend beyond the mapped limits of the GIC into the surrounding district.

The 1 km wide core of the Grasberg deposit has a strong associated potassic alteration suite of K feldspar-biotite-quartz-magnetite, grading out to a propylitic halo of epidote ±chlorite-magnetite-calcite represented by pockets and remnants. Strong magnetite (>8%) occupies a 600 x 300 m core to the potassic zone. The potassic alteration has been overprinted by intense phyllic alteration to form an exterior annular zone, ~500 m across, which is dominated by sericite+anhydrite+pyrite with small amounts of kaolinite, in places to within 400 m of the centre of the system. A 100 m wide zone of brecciated marble surrounds the GIC.

There are a number of pulses of mineralisation associated with the GIC. A major episode of pervasive alteration and disseminated Cu-Au mineralisation occurred in association with the Dalam Diorite that predated the intrusion of the MGI. A second major episode of Cu-Au mineralisation was post-MGI and pre-Kali emplacement. This event caused moderately intense alteration and ore mineralisation that was largely veinlet-hosted (Paterson and Cloos, 2005 and sources quoted therein).

The bulk of the copper ore is present as stockwork veins and veinlets and disseminations that postdate the potassic alteration, but predates the phyllic phase. Mineralisation occurs as a horseshoe shaped mass surrounding the Kali intrusive contact and extends from the surface at an elevation of 4200 m, to below 2700 m asl. In general, it comprises an inner annulus around 100 to 150 m outward from the barren core of >3% (much in excess of 4%) Cu equivalent, surrounded by a 150 to 250 m wide interval of 1 to 3% Cu equivalent ore with an outer diameter of 500 to 800 m. Copper minerals are dominated by chalcopyrite and bornite. Gold is closely associated with chalcopyrite and bornite and some is with digenite. High Au grade zones always coincide with the high Cu grade zone. A rind of strong pyrite forms at the contact between the GIC and the enclosing limestone, with no sulphides extending further into the limestone except as skarns in faults that the GIC intersects.

In the Ertsberg Diorite, mineralisation and alteration comprises: i). early feldspar stable potassic alteration with hairline bornite veining, ii). transitional green sericite veins with chalcopyrite and chalcopyrite-pyrite veins and endoskarn development and iii). late quartz-sericite-pyrite±chalcopyrite. The bulk of the ore at Ertsberg has been produced from high grade magnetite-rich, calcium/magnesian skarns which are characterised by magnetite and high temperature assemblages including forsterite, monticellite and minor melilite, as well as diopsidic clinopyroxene, anhydrite and phlogopite. At least 3 garnets have been recognised which decrease with depth. Talc, serpentine, tremolite-actinolite and chlorite are common retrograde minerals. Copper is texturally associated with early retrograde alteration. Chalcopyrite dominated in some bodies (eg. GB and Dom), while bornite is the principal copper sulphide at GBT. The endoskarn of this complex has been dated at 2.71 Ma, while the exoskarns have returned ages of 2.58 Ma (Pollard et al., 2005).

Mineralisation associated with the Ertsberg intrusive includes: The Ertsberg stockwork which contained a resource of 122 Mt @ 0.54% Cu, 0.90 g/t Au in 2005.
The skarn mineralisation, which includes the: i). GB (Gunung Bijah) - 33 Mt @ 2.5% Cu, 0.8 g/t Au (the original reserve on which mining in the district was commenced), which is surrounded by Ertsberg Diorite near its NW margin; ii). GBT Complex (the vertically stacked GBT, IOZ & DOZ), 1.5 km east of GB on the northern contact, with reserves of >230 Mt @ 1% Cu, 0.8 g/t Au, iii). Dom Skarn, 0.5 km south of GBT, partially enclosed by the intrusive near its SE margin, with >70 Mt @ 1.4% Cu, 0.4 g/t Au, iv). Big Gossan within a fault zone cutting sediments to the west of the Ertsberg Diorite with 33 Mt @ 2.81% Cu, 1 g/t Au, v). Kucing Liar (dated at 3.42 Ma, the oldest mineralisation in the district, predating the Dalam Diorite) is associated with a fault zone between the two intrusive complexes, but close to the Grasberg complex, contains >225 Mt @ 1.42% Cu, 1.57 g/t Au.

The total proven+probable reserve at the Grasberg/Ertsberg operation at the end of 2007 were:
2.712 Gt @ 1.04% Cu, 0.90 g/t Au (Rio Tinto, 2008).
The total measured + indicated + inferred resource (which are in addition to the reserves) at the same date were:
3.049 Gt @ 0.55% Cu, 0.49 g/t Au (Rio Tinto, 2008).

Production in 2006 from the Grasberg open pit totalled 57.5 Mt of ore, while an additional 19.5 Mt was from underground in the Ertsberg operation.

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Travelling from West Papua, Indonesia to Papua New Guinea .................................... Fri. 22, Sat. 23 Oct., 2010

Golpu / Wafi Papua New Guinea .................................... Sun 24 Oct., 2010

Recent drilling at this deposit is continuing to expand the known resources of high grade porphyry Cu-Au mineralisation, overain by a leached cap, supergene blanket and well developed lithocap as well as extensive epithermal mineralisation.

The Wafi gold deposits and the related Golpu porphyry copper-gold deposit around 1 km to the north-east, are both parts of a complex hydrothermal system comprising porphyry, as well as high and low sulphidation Cu-Au mineralisation, often with overprinting alteration relationships. These deposits fall within the Morobe Goldfield in Morobe Province, Papua New Guinea, approximately 60 km south-west of the port of Lae and 70 km NNW of the Hidden Valley project. Location: 6° 53'S, 146° 27'E.

Gold was originally reported from the Wafi River from the 1930s. A 1977 geochemical sampling program conducted in the area by CRAE (no gold assays), part of a program that led to the discovery of the nearby Wamum porphyry copper, returned low level base metal anomalies which were followed up in 1977. During this follow-up program, a pyritic float boulder was identified that assayed 22 g/t Au, 0.57% Pb, 89 g/t Ag. Upstream follow up led to the recognition of altered pyritic volcanics of the Wafi high sulphidation system. The Wafi gold zones were subsequently delineated, but due to the low grade and refractory nature of the gold, the area was joint ventured the property to Elders in 1988. The JV however required Elders to drill 4 conceptual holes based on a consultants structural and fluid flow model to test the source of the high sulphidation fluid. The third of these holes in 1989, intersected 263 m @ 1.86% Cu, 0.27 g/t Au. Elders were subsequently acquired by another party who sold their mineral holdings, which were bought back by CRA. In 2002 the property was taken over by Aurora Gold, then Abelle Ltd who have subsequently been bought by Harmony, the current holder whose principal interest is gold.

The Wafi project lies within the Wau Basin, the north-south structural corridor that divides the western and eastern segments of the New guinea Orogen. One of the most intense structures that constitute this corridor, the Wafi Structure, localises the hydrothermal system at Wafi and also produces a dextral offset of the Ramu Fault to the north.

The country rock to the mineralised system comprises metasediments of the lower Jurassic to Cretaceous Owen Stanley Metamorphics derived from a sequence of argillite, phyllite, metagreywacke, conglomerate and schist, subsequently metamorphosed to lower greenschist facies and strongly deformed into a series of tight NE trending folds. In the project area, the dominant lithologies are clast supported gabbro-rich conglomerate, sandstone, siltstone and shale, with fine to medium grained sandstones. These have been intruded by the middle Miocene (12.9 ±2Ma) Morobe Granodiorite and the 14 Ma Golpu diorite porphyry, and are unconformably overlain by the Pliocene Babwaf Conglomerate.

The mineralised system is reflected at surface by a zone of disseminated pyrite surrounding areas of higher gold content within an advanced argillic, quartz-alunite lithocap. Mineralisation and alteration are associated with a Miocene to Pliocene intrusive complex whose influence is spread over an area of 9 sq. km, centred on the Miocene Golpu diorite to dacite porphyry plug and a late stage overprinting diatreme breccia.

The 800 x 400 m maar-diatreme breccia pipe has steep-dipping margins and comprises a polymictic milled matrix breccia. Several phases of xenolith bearing Wafi dacite porphyry intrusions cut the milled matrix breccia about the pipe margins, as possible endogenous domes. The late-mineral Heking Andesite cuts the dacite porphyry. Potassic alteration within the concealed Golpu diorite porphyry has been dated at 14 Ma and is cut by the diatreme breccia, which is inferred to be associated with the later intrusion event leading to the epithermal gold mineralisation, dated of 13 Ma from alunite within the high sulphidation alteration

The Golpu porphyry copper-gold deposit is associated with a near vertical diorite stock with a diameter of 300 m in its upper sections, contracting to 150 m some 650 m lower. It has a vertical extent in excess of 1200 m and is bounded in part by two NE striking post mineralisation faults. The porphyry system is vertically zoned, with the upper part, below the pyritic advanced argillic quartz-alunite lithocap, being overprinted by a high sulphidation epithermal event that has produced an enargite-covellite-tennantite assemblage. The high sulphidation zone has a well marked base, below which covellite development is associated with a zone of phyllic (silica-sericite-pyrite) alteration, overprinting a lower mass of chalcopyrite-bornite mineralisation at depth accompanied by a core of potassic alteration (biotite-quartz-magnetite±Kfeldspar). Immediately outside of the porphyry contact a 5 to 30 m wide shell of porphyry related stockwork A and D style veining is developed within the meta-sediments (with grades of up to 1% Cu, 2 g/t Au), grading out into propylitic alteration (inner actinolite-epidote and outer epidote-chlorite) and a molybdenum anomalous outer halo. The upper part of the system, above the advanced argillic layer, has a leached cap overlying a thin, rich (eg., 4 m @ 7% Cu) supergene chalcocite-digenite blanket.

The characteristics of the deposit (from Williamson and Hancock, 2005) are:
i). the lack of any surface geochemical manifestations of the porphyry within the barren quartz-alunite cap;
ii). supergene copper enrichment grades of 2.5 to 3.5% Cu which extend from below the base of oxidation at 100 m below surface to 250 m depth, as a several metre thick high-grade zone of chalcocite-diginite, underlain by transition zone silica-alunite-altered porphyry containing covellite-enargite-pyrite (chalcocite-tennantite). In this zone the porphyry Cu-Au mineralisation is overprinted by high sulphidation alteration and remobilised mineralisation;
iii). the upper portion of hypogene phyllic-argillic altered porphyry extending to a depth of 350 m yields grades of 1 to 2% Cu and 0.3 to 0.8 g/t Au in association with pyrite-covellite;
iv). at the deepest levels, where the potassic alteration is preserved and pyrite-chalcopyrite±gold±bornite±molybdenite ores have grades of 1 to 3% Cu and 1 to 2.5 g/t Au, although much of the pyrite is interpreted to have been introduced during the later high sulphidation event. Native gold occurs as minute inclusions within chalcopyrite and bornite.

In mid 2008 the identified mineral resource at Golpu was quoted at 163.1 Mt @ 1.08% Cu, 0.13% Mo, 0.57 g/t Au for 92.2 tonnes (2.96 Moz) of gold (Harmony Gold, website).

Recent drilling (2009-10) has indicated extensions of the main Golpu deposit to the northwest and at depth with intersections of 379 m @ 0.88g/t Au and 1.05% Cu from 1062 m (including: 156 m @ 1.09g/t Au and 1.48% Cu from 1149 m), and 528 m @ 0.70g/t Au and 1.41% Cu from 551 m (including: 187 m @ 1.57g/t Au and 3.16% Cu from 892 m). These and other intersections suggest an exploration target in the range of 500 to 800 Mt at grades of between 0.7% and 1.1% Cu and 0.5 to 0.7g/t Au, including the current resource (Harmony Gold press release, April 2010).

The Wafi Gold deposit comprises four key zones, (Zone A, Zone B, the Link Zone and the Western Zone) distributed around a core dacitic vent. Two breccias are the centre of interest for the gold mineralisation. The first is limited in extent and is found in the east and south-east of the complex and is fragment rich. The second in the west is a diatreme complex with surface dimensions of around 500 x 1000 m, narrowing drastically with depth to a wine glass shape. It is matrix supported and has milled shale, siltstone and feldspar porphyritic diorite clasts, and a matrix of rock flour, lithic fragments, feldspar and rare quartz crystals. Intense alteration makes the recognition of primary textures difficult, although accretionary lapilli have been recognised. The unmineralised Pliocene Babwaf Conglomerate overlies both the altered and mineralised Owen Stanley Metamorphics, intrusive feldspar porphyritic diorite of the Golpu porphyry and the diatreme. The diatreme breccias which host the Wafi gold orebodies are younger than the main feldspar porphyritic diorite and the potassic and phyllic alteration and associated Golpu porphyry copper, gold and molybdenum mineralisation. The main gold ore occurs with disseminated sulphides within the breccias or as veins in the porphyry and metamorphics. A 2.3 sq km surface zone of pyrite alteration centred on the main diatreme, and extending out into the surrounding Owen Stanley Metamorphics, is overlain by a soil gold anomaly of >0.2 g/t Au and encloses the gold rich bodies that comprise the gold resource. Alteration is concentric from a central advanced argillic core surrounded by an acid-argillic zone of quartz-kaolinite (with up to >75% silica) and then to irregular zones with phyllic and argillic assemblages and finally to propylitic alteration of the surrounding country rock. Gold, with rare exceptions, is submicroscopic and occurs in advanced argillic and phyllic alteration zones.

The high sulphidation gold event alteration overprints the Golpu porphyry style alteration and mineralisation, with the diatreme carrying fragments of the earlier porphyry alteration. The high sulphidation event has been interpreted to have remobilised pre-existing porphyry-related copper from the phyllic-argillic altered upper porphyry and deposited this as zoned enargite-tennantite-covellite-chalcopyrite mineralisation, while most gold was introduced in association with pyrite of the high sulphidation event.

The low sulphidation Link Zone, which occurs on the diatreme margin, between and below the Zones A and B high sulphidation gold mineralisation, is characterised by veins of mainly of pyrite with lesser quartz (quartz-sulphide-gold style), which are overprinted by more than one generation of pyrite-sphalerite-galena-carbonate veins (carbonate-base metal-gold style). Selective sampling sows the gold in this zone is related to the arsenian pyrite of the quartz-sulphide style veins, while the multi-stage low-arsenic carbonate-base metal veins contribution to the gold grade is insignificant.

In mid 2004 the identified mineral resource at Wafi Gold was quoted at 109.6 Mt @ 1.85 g/t Au for 202.5 tonnes (6.51 Moz) of gold (Harmony Gold, website).

The project is controlled by the Morobe Mining Joint Venture (Harmony 50%, Newcrest 50%).

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Travelling from Papua New Guinea to New South Wales, Australia .................................... Mon. 25 Oct., 2010

Cadia Valley Operation, NSW, Australia .................................... Tue. 26 Oct., 2010

The Cadia and Ridgeway porphyry gold-copper deposits are located 20 km south of Orange in the central tablelands of New South Wales, Australia, some 200 km WNW of Sydney. Cadia Hill and related adjacent resources are low grade, bulk mining, porphyry style Au-Cu deposits while Ridgeway, 3 km to the north-west of the Cadia Hill open pit and 500 m below surface, comprises quartz veins, sheeted and stockwork quartz and quartz-sulphide veins and disseminated mineralisation with higher grade gold and associated copper mineralisation.

The Cadia district falls within the Molong Volcanic Belt in the eastern part of the lower Palaeozoic Lachlan Fold Belt of south-eastern Australia where a number of relatively undeformed, shoshonitic, Ordovician volcano-intrusive complexes host porphyry and high sulphidation epithermal gold mineralisation. The largest such deposits are in the Cadia district. The Cadia-Ridgeway cluster of deposits are principally associated with a 3 x 1.5 km late Ordovician composite quartz-monzonite to dioritic porphyry stock and its probable co-magmatic volcanic wall rocks and intercalated volcaniclastics that together form part of an Ordovician volcano-intrusive complex. Overall the stock has an alkaline composition, with mineralisation and alteration being associated with porphyritic quartz-monzonite phases that are altered over an area of 5.5 x 3 km and to a depth of up to 1.6 km, defining a NW trending corridor that encloses the known deposits.

There are five components to the Cadia porphyry system within the mineralised corridor, namely:
  (i) Intrusion- and volcanic wall rock hosted sheeted veins at Cadia Hill. Alteration is principally propylitic with little recognised potassic developments, while a late stage phyllic phase was restricted to zones of faulting and is followed by late carbonates. Mineralisation is mainly chalcopyrite and pyrite with lesser bornite within and disseminated around sheeted 1 to 20 mm thick quartz veins in a 100 to 350 m wide, 65° dipping zone that is 1 km long and has not been closed at depth;
  (ii) Volcanic wall rock hosted disseminated and sheeted vein mineralisation at Cadia East within moderately to strongly altered lavas and volcaniclastic breccias. Alteration and mineralisation is centred on a steeply dipping, 300 m wide, east plunging core of steeply dipping sheeted quartz-calcite ±chalcopyrite ±bornite ±molybdenite ±covellite ±pyrite ±magnetite veins within a disseminated envelope of chalcopyrite, bornite and pyrite. This core persists down plunge for at least 1.6 km. Alteration types include weak propylitic, weak sericite-silica-albite, moderate to strong silica-albite flooding with hematite and K feldspar, and strong sericite-albite with silica-albite flooding ±tourmaline;
  (iii) Intrusion hosted sheeted veins at Cadia Quarry, developed as a 1 km long by 200 m wide package controlled by faulting and fracturing;
  (iv) The up to 70 m thick distal, stratabound hematite-magnetite skarns at Big and Little Cadia. Chalcopyrite is the dominant sulphide, with pyrite and calcite interstitial to the magnetite and hematite blades;
  (v) Probable late stage distal veins.

The Ridgeway deposit is an upright, bulbous body of stockwork quartz veining zoned about a 50 to 100 m diameter plug of porphyritic Cadia Hill Monzonite where it intrudes Ordovician andesitic volcanics to the west of the main Cadia multiple intrusion. The highest grade gold accompanies the most intense alteration and stockwork development immediately adjacent to the monzonite porphyry, with the best being localised directly above the plug compared to grades on its lateral margins. Grades decrease laterally outwards and inwards from the intrusive contact. The ore minerals are predominantly veined, but are also disseminated and comprise native gold, chalcopyrite and bornite, with accessory magnetite. The more intense mineralisation is accompanied by a potassic alteration suite of orthoclase, albite, actinolite, magnetite and biotite, overprinted by a propylitic assemblage of epidote, chlorite, iron carbonates, calcite and hematite dusting. NW-SE trending pre-mineral faults appear to have exerted a strong control on mineralisation.

The total pre-mining resources were:
Cadia Hill in 1977 - 352 Mt @ 0.63 g/t Au, 0.16% Cu for 221.3 t of contained Au;
Cadia Quarry in 2003 - 50 Mt @ 0.40 g/t Au, 0.21% Cu for 21.7 t of contained Au;
Ridgeway in 2002 - 54 Mt @ 2.5 g/t Au, 0.77% Cu for 132.6 t of contained Au.
Cadia East was un-mined in 2010.

The remaining proved+probable reserves in August 2010 (Newcrest website) were:
Cadia Hill - 116 Mt @ 0.60 g/t Au, 0.14% Cu;
Ridgeway underground - 101 Mt @ 0.81 g/t Au, 0.38% Cu;
Cadia East underground - 1073 Mt @ 0.60 g/t Au, 0.32% Cu.
The total measured+indicated+inferred resources at the same date were:
Cadia Hill - 408 Mt @ 0.42 g/t Au, 0.12% Cu;
Cadia Extended - 83 Mt @ 0.35 g/t Au, 0.20% Cu;
Ridgeway underground - 155 Mt @ 0.73 g/t Au, 0.38% Cu;
Big Cadia - 42 Mt @ 0.38 g/t Au, 0.40% Cu;
Cadia East underground - 2347 Mt @ 0.44 g/t Au, 0.28% Cu.

The total declared measured+indicated+inferred resource in the Cadia district was estimated in 2010 to contain 1360 tonnes (43.7 Moz) of gold and 7.99 Mt of copper. The Cadia-Ridgeway mines are operated by Newcrest Mining Ltd.

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The summaries above were prepared by T M (Mike) Porter from a wide range of sources, both published and un-published. Most of these sources are listed on the "Tour Literature Collection" available from the AsiaPacific 2010 Tour options page.

		Another PGC International Study Tour Developed & Managed by Porter GeoConsultancy AsiaPacific 2010 Asia Pacific Porphyry Cu-Au Deposits 11 to 26 October 2010
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	Image: In the Batu Hijau pit, Sumbawa, Indonesia.