Red Dome

Queensland, Qld, Australia

Main commodities: Au Ag
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The Red Dome gold deposit is one of the Mungana district mines located 15 km WNW of Chillagoe and 150 km west of Cairns in far north Queensland, Australia.

The mineralisation is hosted within the Hodgkinson Basin's Silurian-Devonian Chillagoe Formation which is separated from the Precambrian Dargalong Metamorphics of the Georgetown Block several kilometres to the west of the deposit by the regional scale north-south Palmerville Fault.   The Chillagoe Formation sediments were strongly deformed adjacent to the Georgtown Block which acted as buttress during Carboniferous deformation.

Red Dome is a skarn type gold deposit related to the intrusion of fault/shear controlled Permian-Carboniferous porphyritic rhyolite dykes.   The upper parts of the orebody are breccia hosted, believed to be due to solution collapse caused by dissolution of marble units and calcite in the skarns.   The breccia, within which the ore has been oxidised, is post ore and is bounded by post ore NE trending faults.   There have apparently been two generations of petrologically similar rhyolite dykes.

The sequence of intrusive activity and skarn development was as follows:
1). Early rhyolite and initial contact metamorphism to marble and hornfels,
2). Development of hedenbergite-quartz stockwork veining on the rhyolite margin grading out to massive hedenbergite endoskarn, with an outer, extensive halo of green-brown andradite exoskarn with minor diopside.   Massive magnetite lenses formed near the front between the garnet skarn and the marble, with variable, but minor accompanying sulphides.
3). A wollastonite skarn was subsequently formed at the contact between the hedenbergite endoskarn and the garnet exoskarn, replacing both, as well as the early rhyolite.
4). Patchy retrograde skarn followed, overprinting the earlier skarns with iron rich chlorite, quartz, calcite, opaques, etc., and late stage veining overprinting all of the lithologies described above.
5). Following the onset of retrograde alteration and during the veining the late rhyolite was emplaced, with a weak hedenbergite endoskarn and a pale green andradite exoskarn.

Gold was not deposited with the early skarns but during the wollastonite phase, the late veining and retrograde alteration.   Gold in the late garnet skarn appears to be reworked.   In general the gold is restricted to the skarns and in the primary state occurs as very fine free gold, either as inclusions in sulphides (bornite, chalcocite, chalcopyrite and arsenopyrite), associated with silicates and some tellurides (but not as a telluride) and as minor electrum in the retrograde zone, with free gold in the oxide zone.

Pre-mining geological resources in 1986 were - 15 Mt @ 2.6 g/t Au at a 1 g/t Au cutoff.
    Reserve - 9 Mt @ 2.35 g/t Au to an open cut depth of 200 m.

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:
Ewers G R, Torrey C E, Erceg M M  1990 - Red Dome Gold deposit: in Hughes F E (Ed.), 1990 Geology of the Mineral Deposits of Australia & Papua New Guinea The AusIMM, Melbourne   Mono 14, v2 pp 1455-1460

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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