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Deposit Synonyms
ANKATA; KALAYA; MALU OPEN PIT; MALU UNDERGROUND; ML 6228; MUNDA; PAPA; URANUS
Mineral District
Deposit Summary
IOCG deposit host hematite breccia complex. Production from 2009-11, 248,530 tonne copper concentrate at 53%Cu, 13.2g/tAu, 122.3g/tAg. Resources as of June 2011 272.7Mt at 0.98%Cu, 0.7g/tAu, 2.4g/tAg. Weak U mineralisation at 106ppmU.
Deposit Description
PROMINENT HILL, Cu-Au-Ag-(Co-U-La-Ce) deposit discovered under ~100m of cover sediment. Initial target was a near coincident magnetic and gravity feature. The gravity anomaly had an overall east pointing "V" form, with a 1km long N arm trending WNW-ESE, with associated magnetic anomaly, and 2km long main mineralised S arm trending WSW-ENE, and with no magnetic expression.
N arm is ~500m N of the orebody, and across a Hangingwall Fault. It represents a package of magnetite-chlorite-tremolite-phlogopite altered metasomatic 'skarn-like' altered calc-silicate/carbonate-rich metamorphics intercalated with highly altered, intermediate, porphyritic intrusives and chlorite matrix tectonic breccias.
The ore deposit comprises several phases of hematite alteration with associated sericite, clay minerals and chlorite, hosted by a N-dipping series of interbedded lithic sandstone and greywacke, siltstone, coarse grained sedimentary and volcanic breccias, and dolostone. Mineralisation is relatively late stage and overprints at least one phase of massive hematite replacement of the breccias. In the open pit, individual bodies of breccia occur as a series of strata-bound, steeply dipping, tabular EW-trending sheets and W-plunging shoots, collectively bound to the N by dolostone/Hangingwall Fault Zone and to the S by volcanics. Host rocks are intensely altered by hematite-sericite-chlorite-carbonate (±quartz ±barite ±fluorite ± REE phosphate). Cu mineralisation occurs as fine grained disseminations of chalcocite, bornite and chalcopyrite in breccia matrices, and to a lesser extent within clasts of hematite-rich breccia. Cu sulphides display a variety of intergowth, replacement and infill textures including chalcocite-bornite and replacement of early formed pyrite.
Current weight of evidence indicates mineralisation originated through relatively passive infiltration of hydrothermal fluids and metasomatism localised by porosity within a sequence of coarse grained sedimentary breccia. Cu and Au mineralisation was paragenetically very late in the sequence. Geochemical trends suggest a strong relationship between gold mineralisation (in the copper-rich zones of the deposit) and REE phosphate. Mineralisation age 1585 +/- 8Ma (zircon, U-Pb).
Mineralisation appears to be zoned from an upper Au-rich zone, down to a Cu-Au +/- U with chalcopyrite and bornite. Uraninite is with late stage fluorite, La and Ce are enriched throughout, reaching grades of 0.2-0.6%.
Production from late February 2009 to June 2017 is estimated from company reports at 110 Mtonne ore mined for 87 Mtonne ore treated for production of 1.75 Mtonne copper concentrate, for recovery of 939,611 tonne copper metal, 1,138,557 oz gold, and 6.87 Moz silver. Remaining resource as of July 2016 as reported by OZ Minerals was, for copper resource estimate, 148 Mtonne at 1.2%Cu, 0.6g/tAu, 2.9g/tAg, and for gold resource estimate, 25 Mtonne at 0.1%Cu, 1.3g/tAu, and 1.6g/tAg. The figures are inclusive of 20Mt combined copper + gold ore surface stockpiles. Cut off copper grade for open pit is 0.25% Cu.
Discovery Year
? 2001
Commodities
Copper, Gold, Silver, Uranium
Ore Minerals
Argentite, Bornite, Chalcocite, Chalcopyrite, Covellite, Digenite, Gold, Rare Earths, Uraninite
Gangue Minerals
Barite, Carbonate, Chlorite, Feldspar, Fluorite, Hematite, Pyrite, Quartz, Sericite
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