Copperhead, Bullfinch - Southern Cross Belt

Western Australia, WA, Australia

Main commodities: Au
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The Copperhead gold deposit is located 1 km east of Bullfinch and 35 km north of Southern Cross in the eastern part of the Bullfinch segment of the Southern Cross Greenstone Belt in the Southern Cross Domain, Youanmi Terrane of the Archaean Yilgarn Craton in Western Australia.

The 170 km strike length, NNW trending Bullfinch greenstone belt is approximately 7 km wide and comprises a layered sequence of ultramafic and mafic rocks overlain by lesser metasediments.   The greenstones are bounded by granitoids to the east and west and forms the northern section of the larger Southern Cross Greenstone Belt.

For background information on the Southern Cross Belt, its geological setting and deposits see also the Transvaal, Yilgarn Star, Marvel Loch, Bounty, Fraser and Nevoria records.

The mineralisation at Copperhead is found in the lower stratigraphic units of the mafic-ultramafic sequence, within 150 m of the eastern contact of the greenstone belt with coarse, banded granitoids.   Locally the hosts are high Mg basalt and tuff, BIF with minor sediments, all altered to a fine grained tremolite-actinolite, chlorite and talc-carbonate schist.   The BIF comprises alternating bands of pyrite, pyrrhotite, ferromagnesian minerals and quartzite.   Two zones of mineralisation are:  i). The Southern Series which is a banded iron lode associated with two isoclinally folded gold bearing BIFs, each generally <10 m thick, but enlarged to up to 35 m in drag fold noses,   and  ii). Dolomite lodes of the Northern Series in a tightly folded zone of tremolite-actinolite-chlorite schist with irregular quartz veins and stringers. The lode is strongly carbonate altered and has a strike length of 200 m, and a width of 10 to 25 m.

The mineralisation in both Series essentially trends east-west. The two series are divided by a poorly mineralised zone known as the Saddle.

Production has included:
    Underground mining 1910-1944 - 0.567 Mt @ 11.2 g/t Au.
    Underground and open pit 1952-1962 - 3.253 Mt @ 4.9 g/t Au.
    for a total of 21 t of recovered gold.

Production between 1988 and 1998, when the Copperhead mine closed was ~6.5 t of contained gold.

The drilled resource in 1989 was - 2 Mt @ 3.6 g/t Au to a depth of 125 m for a further 7.2 t of contained gold.

Indicated + Inferred Mineral Resources at Copperhead as of July 2016 were: 3.533 Mt @ 5.2 g/t Au for 18.35 t of contained gold (Cube Consulting, 2016)

For detail consult the reference(s) listed below.

The most recent source geological information used to prepare this summary was dated: 1990.    
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:
Bloem E J M, Dalstra H J, Groves D I and Ridley J R  1994 - Metamorphic and structural setting of Archaean amphibolite hosted gold deposits near Southern Cross, Southern Cross province, Yilgarn Block, Western Australia: in    Ore Geology Reviews   v9 pp 183-208
Carter D N, Grayson M I  1990 - Copperhead Gold deposit, Bullfinch: in Hughes F E (Ed.), 1990 Geology of the Mineral Deposits of Australia & Papua New Guinea The AusIMM, Melbourne   Mono 14, v1 pp 283-285
Doublier, M.P., Thebaud, N., Wingate, M.T.D., Romano, S.S., Kirkland, C.L., Gessnar, K., Mole, D.R. and Evans, N.,   2014 - Structure and timing of Neoarchean gold mineralization in the Southern Cross district (Yilgarn Craton, Western Australia) suggest leading role of late Low-Ca I-type granite intrusions: in    J. of Structural Geology   v.67, pp. 205-221.

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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