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The Peak |
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New South Wales, NSW, Australia |
| Main commodities:
Au
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Peak gold mine is in the Cobar Mineral Field, 8 km SSE of Cobar, within the Lachlan Fold Belt and is located in central New South Wales, ~550 km WNW of Sydney in Australia (#Location: 31° 33' 51"S, 145° 52' 37"E).
Gold was first reported in the Peak area in 1887, although major discoveries were not made until 1895 when the Blue Lode was discovered. Other lodes along the Peak ridge were made in 1896 and between 1899 and 1900. The main activity was between 1896 and 1911. The various mines were exploited by small companies and syndicates between 1911 and the 1950's, but none were deeper than 97 m.
Various companies had explored at The Peak without success until Cobar Mines Pty Ltd intersected steeply dipping high grade gold and base metals over a horizontal width of 19 m in 1981 at a depth of 300 m. Drilling between 100 and 250 m only encountered narrow mineralised stringers. The eighth hole intersected the high grad lode and 270 m. Subsequent drilling from 1982 to 1985 delineated the main resource.
For details of the regional geological and tectonic setting, see the Geological Setting section of the Cobar Mineral Field record.
The Peak is one of a north-south cluster of structurally controlled gold, copper and lead-zinc deposits distributed along a linear, largely shear controlled contact between two early Devonian Units, the sandstones and siltstones of the Chesney Formation and the overlying siltstones and mudstones of the Great Cobar Slate. This cluster of occurrences is distributed over an interval of some 11 km, with the Peak being near the southern end. This shear zone is close to the eastern margin of the Devonian rift into which these sediments were deposited.
Mineralisation at The Peak is contained within the NNW trending Peak Shear, an anastomosing, thrust-type fault zone which is sub-parallel to the contact described above, and is some 3 km long and up to 300 m wide. It parallels the prominent regional cleavage and transects a series of parasitic folds on the regional anticline whose axis is to the west.
While the surface expression of mineralisation is near the major contact described above, the orebody is entirely within the Chesney Formation, and is developed in the apical portions of a series of blind, flow banded rhyolites (K-feldspar, chlorite, quartz, sericite-altered) and rhyolitic sub-volcanic breccia bodies (pervasive quartz, K-feldspar, sericite and chlorite altered variably clast and matrix supported, poorly sorted, monomict lithic sub-volcanic breccia with a fine quartz, K-feldspar and sericite matrix). These volcanics are only known from drilling and underground openings.
The Peak orebody is confined between 300 and 700 m below the surface, and extends over a strike length of 300 m, but has a maximum horizontal length of 150 m. Broadly it is a vertically elongate envelope parallel to the regional cleavage and the Peak Shear and lies on the contact of, or within, the rhyolites, although two lenses are peripheral to the volcanics within pervasively silicified sediments.
There are at least 17 separate ore lenses known within the deposit, each with an arcuate to planar in form paralleling the shear. Individual lenses vary from 3 to 25 m in thickness, and may be 50 to 250 m long. Within these lenses, sulphide minerals (pyrrhotite, chalcopyrite, sphalerite, galena and pyrite) occur as splashes, fracture fillings, sheeted veins, veins and disseminations.
Historic production from the shallow deposit between 1896 and 1951 - 0.299 Mt @ 21.7 g/t Au, 498 g/t Ag, for 6.5 t Au,
Production from 1992 to 1995 + reserves in 1995, amounted to:
4.6 Mt @ 7.6 g/t Au, 0.9% Cu, 1% Pb, 0.9% Zn, 8 g/t Ag.
Resource and reserve figures published by Peak Gold Ltd (2008), as at 31 December, 2006, were:
Measured + indicated resources - 3.52 Mt @ 4.05 g/t Au, 1.12% Cu
Inferred resources - 1.99 Mt @ 6.5 g/t Au, 0.53% Cu
Proved + probable reserves - 1.68 Mt @ 6.75 g/t Au, 0.74% Cu.
The resources are exclusive of the reserves.
The most recent source geological information used to prepare this decription was dated: 2001.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
The Peak
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Cook W G, Pocock J A, Stegman C L 1998 - Peak gold-copper-lead-zinc-silver deposit, Cobar: in Berkman D A, Mackenzie D H (Ed.s), 1998 Geology of Australian & Papua New Guinean Mineral Deposits The AusIMM, Melbourne Mono 22 pp 609-614
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Hinman M C, Scott A K 1990 - The Peak Gold deposit, Cobar: in Hughes F E (Ed.), 1990 Geology of the Mineral Deposits of Australia & Papua New Guinea The AusIMM, Melbourne Mono 14, v2 pp 1345-1351
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Munro S and Berthelsen R 2004 - The Perseverance gold deposit - the next step at Peak: in Hi Tech and World Competitive Mineral Success Stories Around the Pacific Rim, Proc. Pacrim 2004 Conference, Adelaide, 19-22 September, 2004, AusIMM, Melbourne, pp 339-344
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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