New South Wales, NSW, Australia

Main commodities: Au
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The Timbarra intrusion-related gold deposits are located in the southern New England Fold Belt of New South Wales, Australia.

The economically significant and distinctive mineralisation is related to granites that form a texturally complex, zoned pluton. The gold deposits occur within the 242 to 238 Ma Stanthorpe leuco-monzogranite, which intrudes and forms a core to the more mafic, barren, 248 to 243 Ma Bungulla monzogranite.

Gold is disseminated in the roof zone (upper 240 m) of a fractionated, magnetite- and ilmenite-bearing, I-type leuco-monzogranite phase of the Stanthorpe body. The entire gold resource occurs in the areally extensive main leucomonzogranite pluton and is hosted by a medium- to coarse-grained granite.

All five deposits at Timbarra, contain disseminated ore, which accounts for more than 95% of the overall resource. Each occurs predominantly as a gently dipping, tabular to lenticular body that is conformably constrained beneath a fine-grained aplite carapace and internal aplite layers.

The disseminated ore consists of gold-bearing muscovite-chlorite-carbonate alteration and infill of primary miarolitic cavities within massive leuco-monzogranite or microgranite, and contains no discernable vein, joint, or fracture control at the outcrop or hand specimen scale. Gold grains are generally <1 to 50 µm in size, but rarer grains as large as 1 mm in diameter have been observed.

Structurally controlled mineralization forms the remaining 5% of the Timbarra resource, and comprises minor, low-density (0.02 to 0.25 per metre), vein-dykes and quartz-molybdenite veins emplaced along steeply dipping ESE, ENE, and NNE striking cooling joints.

Both styles of mineralisation and alteration share a common paragenetic sequence of mineral precipitation, commencing with quartz, perthitic K-feldspar, minor biotite, and albite, the most abundant infill minerals which commonly line primary cavities and vein-dikes. Subsequent minerals include coeval arsenopyrite, pyrite, fluorite, and molybdenite. The final stage is characterised by an assemblage which includes muscovite, chlorite, gold, calcite, silver-bismuth telluride, lead-bismuth telluride, and rare galena and chalcopyrite.

The ore has a low total sulfide concentration (<1%), with elevated Bi, Ag, Te, As, Mo, and Sb. Gold is strongly correlated with Bi, Ag, and Te, but only weakly with Mo, As, and Sb.

The total identified mineral resource of the five known deposits amounts to:
    16.8 Mt @ 0.73 g/t gold, for a total of 12.3 tonnes (0.396 Moz) of gold.

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:
Cohen D R, Dunlop A C and Rose T,  2005 - Contrasting dispersion patterns for gold in stream sediments at Timbarra, NSW, Australia: in    J. of Geochemical Exploration   v85 pp 1-16
Mustard R  2001 - Granite-hosted gold mineralization at Timbarra, northern New South Wales, Australia: in    Mineralium Deposita   v36 pp 542-562
Mustard R, Nielsen R and Ruxton P A  1998 - Timbarra gold deposits: in Berkman D A, Mackenzie D H (Ed.s), 1998 Geology of Australian & Papua New Guinean Mineral Deposits The AusIMM, Melbourne   Mono 22 pp 551-560

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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