Mt Morgan

Queensland, Qld, Australia

Main commodities: Cu Au
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The Mount Morgan copper-gold deposit is located on the Tropic of Capricorn in the coastal ranges of eastern Queensland, 36 km north-west of Rockhampton.   The deposit was discovered in 1882 and was mined by underground and glory hole methods to 1927, and as an open pit from 1932, up to 1981 when the ore was exhausted.

The host sequence belongs to the Calliope island arc which extends along the east coast from Rockhampton to Warwick on the New South Wales border.   In the Mount Morgan District this sequence, which has been folded into a 70 km long SE trending anticline and comprises the Early Devonian Mount Holly Beds, Middle Devonian Mine Corridor Volcanics and the Middle Devonian Capella Creek Beds.   An acid volcanic unit, the Mount Warner Volcanics which is found locally below the Capella Creek Beds is equated with the Mine Corridor Volcanics.

In the mine area the Mine Corridor Volcanics occur as a roof pendant within the Mount Morgan Tonalite and comprise from the base:
Lower Mine Pyroclastics, +850m thick - clean coarse grained quartz-feldspar crystal-lithic tuff and some coarse fragmentals,
Graben Sequence, 200m thick - interbedded fine ashy sediments and muddy coarse quartz-feldspar crystal-lithic tuff,
Banded Mine Sequence, 170-200m thick - thinly interbedded chert and quartz-feldspar crystal tuff with jasperoid at the top and a 15m thick limestone at the base,
Upper Mine Pyroclastics, 750m thick - clean coarse grained quartz-feldspar crystal-lithic tuff and some coarse fragmentals,
Arnold's Ridge Felsite, 60m thick - fine grained crystal ash tuff,
Baree Felsite, +400m thick - siliceous aphanitic rocks and quartz-feldspar crystal-ash tuff.

The mine exploited the Main Pipe body of pyritic massive sulphides and the adjacent siliceous stringer ore (10% sulphides) of the Sugarloaf orebody.   When the host sequence is re-oriented to a horizontal position, compensating for fault offsets, folds, etc., the orebody is shown to have a pipe like geometry at a high angle to stratigraphy with maximum dimensions of 750 x 250 x 300 m.   Minor conformable mineralisation adjacent to the stratigraphic top of the massive sulphides grades down dip away from the ore to a sequence of interbedded crystal tuff and cherty rocks which include some jasperoids of the Banded Mine Sequence.

The principal minerals in the ore zone are pyrite, quartz, pyrrhotite, chalcopyrite, magnetite and sphalerite.   Gold, gold tellurides and silver minerals, together with chalcopyrite and pyrite were commercially important.   Most of the recoverable gold occurred as disseminations of native gold of ultrafine to sub-microscopic dimensions.

The accompanying halo of alteration (an inner zone of silicification adjacent to ore, surrounded by quartz-sericite with an associated broad pyritic halo which is pronounced within 50 m of ore) has been cut by the late Devonian Mount Morgan Tonalite. This has in turn been overprinted by late stage mineralisation and alteration associated with the tonalite.

Total production by closure was 50 Mt @ 0.72% Cu, 4.75 g/t Au for 238.9 tonnes of gold and 360 616 tonnes of copper.

For more detail see 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:
Arnold G O, Sillitoe R H  1989 - Mount Morgan Gold-Copper deposit, Queensland, Australia: evidence for an intrusion-related replacement origin: in    Econ. Geol.   v84 pp 1805-1816
Frets D C, Balde R  1975 - Mount Morgan copper-gold deposit: in Knight C L, (Ed.), 1975 Economic Geology of Australia & Papua New Guinea The AusIMM, Melbourne   Mono 5 pp 779-785
Large R R  1992 - Australian volcanic-hosted massive sulfide deposits: features, styles, and genetic models: in    Econ. Geol.   v87 pp 471-510
Messenger P R, Taube A, Golding S D, Hartley J S  1998 - Mount Morgan gold-copper 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 715-722
Taube A  1990 - Mount Morgan Gold-Copper deposit: in Hughes F E (Ed.), 1990 Geology of the Mineral Deposits of Australia & Papua New Guinea The AusIMM, Melbourne   Mono 14, v2 pp 1499-1504
Taube A  1986 - The Mount Morgan Gold-Copper mine and environment, Queensland: a volcanogenic massive Sulfide deposit associated with penecontemporaneous faulting: in    Econ. Geol.   v81 pp 1322-1340
Taube A, Mawson R and Talent J A  2005 - Repetition of the Mount Morgan Stratigraphy and Mineralization in the Dee Range, Northeastern Australia: Implications for Exploration: in    Econ. Geol.   v100 pp 375-384
Ulrich T, Golding S D, Kamber B S, Zaw K, Taube A  2003 - Different mineralization styles in a volcanic-hosted ore deposit: the fluid and isotopic signatures of the Mt Morgan Au-Cu deposit, Australia: in    Ore Geology Reviews   v22 pp 61-90

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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