Pajingo, Vera-Nancy

Queensland, Qld, Australia

Main commodities: Au Ag
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The Pajingo mine currently exploits the Vera-Nancy group of adularia-sericite, low sulphidation, high grade gold-silver orebodies, located some 150 km SSW of the city of Townsville in north Queensland, Australia. Gold was originally discovered in the Pajingo Goldfield in 1983. Mining commenced on the Scott Lode in 1987 and has continued since then as new deposits were delineated within the mineralised system that occupies a circle of approximately 7 km radius defining an area of around 140 sq km. The larger Vera-Nancy line of deposits were discovered in 1994-95 and mining commenced in 1997, with high grade gold having subsequently been delineated over a strike length of about 3 km and to depths of more than 400 m.

The Pajingo mineralisation is in the northern portion of the Drummond Basin which was filled by Late Devonian to Carboniferous, largely continental, sediments and volcanics, comprising lower arenites, passing up into andesites, terrestrial sediments and felsic tuffs. It overlies the Ordovician to Devonian Lolworth-Ravenswood Batholith and lower Palaeozoic volcano-sedimentary packages to the north which host the Charters Towers, Ravenswood and Mount Leyshon gold deposits.

The immediate host sequence is composed of andesitic lava and tuff, with minor volcaniclastics of probable 350 Ma age. These volcanics are usually porphyritic andesitic lithic tuffs (fine ash to bomb size) that have been weathered to an average depth of 70 m. The surface expression of veins is often as low ridges of silicified, brecciated, moderately to strongly quartz-veined andesite which persists to depths of as much as 200 m before classic epithermal veins are intersected.

The vein field at Pajingo, which occupies an area of some 140 square kilometres, corresponds to a zone of thickening of the andesite, interpreted as representing a main volcanic centre. Numerous epithermal quartz-veins are hosted by NW, NE and E-W trending structures, which are mostly steeply dipping and from a few cms to occasionally 20 m in thickness. They are normally enclosed by an envelope of silicification that may be up to 50 m thick.

The Vera-Nancy series of lodes occur as shoots within a structure which is up to 7 km in length, strikes north-west, dips at 55 to 85 degrees SW, and hosts other high grade shoots beyond Vera and Nancy. This structure is interpreted to be a strike-slip fault with the individual shoots such as Vera and Vera North developed in dilational jogs. Propylitisation, characterised by dark green chlorite, extends for up to 80 m outwards from the veins, grading to strong phyllic alteration dominated by silica-pyrite adjacent to the veins. Moderate to strong hematite dusting occurs on the outer margin of the phyllic zone, overprinted by the silica-pyrite. The silica is a grey translucent chalcedony with fine grained pyrite accounting for up to 40% of the rock mass. Some minor argillic alteration (illite-smectite and kaolinite-dickite) is also included within the phyllic zone.

Gold is present as fine grains (5 to 150 microns) and electrum in quartz and chalcedony veins enveloped by a halo of silicification and brecciation that is often strongly pyritic.

Production from the original Scott Lode amounted to 1.35 Mt @ 8.86 g/t Au, 29.4 g/t Ag. The declarred resource at Vera-Nancy prior to mining in 1997 was 1.68 Mt @ 14.1 g/t Au, 10.8 g/t Ag at Vera plus 0.8 Mt @ 12.0 g/t Au, 15.6 g/t Ag at Nancy. The remaining reserve at Pajingo at the start of 2003 was 2.7 Mt @ 11.0 g/t Au, while the production in 2002 was 0.656 Mt @ 12.6 g/t Au.

The most recent source geological information used to prepare this summary 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.

  References & Additional Information
   Selected References:
Anonymous  1998 - Vera-Nancy (incl. Pajingo): in    Register of Australian Mining 1997/98    p 198
Anonymous  1998 - Normandy Mining Limited: in   Extracts from the Normandy Mining Limited 1997 Annual Report    pp 12-15, 26-28
Anonymous  1998 - Normandy Mining Limited: in   Extracts from the Normandy Mining Limited 1997 Annual Report    pp 12-14, 17, 26-28.
Bobis R E, Jaireth S, Morrison G W  1995 - The anatomy of a Carboniferous epithermal ore shoot at Pajingo, Queensland: setting, zoning, alteration, and fluid conditions: in    Econ. Geol.   v90 pp 1776-1798
Cornwell J and Tredinnick I,  1993 - Geology and geochemistry and mining of the Pajingo epithermal vein system: in    17th International Geochemical Exploration Symposium (IGES), May 1995, Townsville, Qld    pp 54-68
Evans R C, Jones B H  1997 - The discovery and evaluation of the Vera-Nancy deposit, North Queensland: in   World Gold 97 Conference, Singapore, 1-3 September 1997 AusIMM Pub., Melbourne   Ser. no. 2/97 pp 233-237
Parks, J. and Robertson, I.D.M.,  2003 - Pajingo epithermal gold deposit, NE Queensland: in   CRC LEME 2003 www.crcleme.org.au/RegExpOre/MtLeyshon.pdf    pp. 1-4
Porter R R G  1990 - Pajingo gold deposits: in Hughes F E (Ed.), 1990 Geology of the Mineral Deposits of Australia & Papua New Guinea The AusIMM, Melbourne   Mono 14, v2 pp 1483-1487
Richards D R, Elliott G J, Jones B H  1998 - Vera North and Nancy gold deposits, Pajingo: in Berkman D A, Mackenzie D H (Ed.s), 1998 Geology of Australian & Papua New Guinean Mineral Deposits The AusIMM, Melbourne   Mono 22 pp 685-690
White, N.C., Leake, M.J., McCaughey, S.N. andd Parris, B.W.,  1995 - Epithermal gold deposits of the southwest Pacific: in    J. of Geochemical Exploration   v.54, pp. 87-136.

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 takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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