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Uranium

Uranium deposits in South Australia

About uranium

Uranium (U) is a radioactive metal of high specific gravity. Its main primary minerals are:

  • uraninite (UO2)
  • pitchblende (a mixed oxide, usually U3O8)
  • brannerite (oxide of uranium, rare earths, iron and titanium)
  • coffinite (uranium silicate).

Uranium occurs in nature as a mixture of three isotopes — U238 (99.28%), U235 (0.71%) and U234 (0.01%).

U235 is the only naturally occurring fissionable element, and the vast majority of nuclear power reactors are fuelled by ‘enriched’ uranium, in which the U235 content has been raised from 0.71% to ~3.5%.

Australia’s uranium is exported as unenriched U3O8 concentrate.

South Australia’s uranium deposits occur in a range of Proterozoic rocks and in Tertiary palaeochannels draining the Gawler and Curnamona Cratons.

More information about uranium in South Australia

Proterozoic deposits

Olympic Dam

The Olympic Dam copper–uranium–gold–silver deposit is one of the world’s largest known accumulation of metals. Western Mining Corporation discovered the deposit in 1975 and underground mining commenced in 1988 with a major expansion program from 1997 to 1999.

The deposit is within the Mesoproterozoic Hiltaba Suite Roxby Downs Granite (1588 Ma) beneath ~300 m of undeformed Adelaidean and Cambrian platform sediments of the Stuart Shelf. Mineralisation is hosted by a large, broadly zoned hydrothermal haematite–granite breccia complex comprising a barren core of haematite–quartz breccia flanked by 1–2 km wide mineralised zones of haematite-rich breccias intermingled with altered granitic breccias.

Ore mineralisation mainly comprises disseminated and fragmental chalcocite, bornite, chalcopyrite, pitchblende and finely disseminated free gold, with sulphide veinlets developed locally.

Stuart Shelf prospects

A number of large hydrothermal iron oxide bodies with associated copper–uranium(–gold) mineralisation have been revealed in deep drillholes intersecting Mesoproterozoic basement rocks. Significant deposits include Acropolis, Emmie Bluff, Oak Dam and Wirrda Well.

Radium Hill

Uranium mineralisation was discovered at Radium Hill in 1906. Deposits were worked intermittently by various small companies until 1931, principally as a source of radium for medical purposes. Between 1954 and 1961, the underground mine was operated by the South Australian Government to supply the UK–USA Combined Development Agency with uranium oxide. The ore was concentrated on site and railed to a treatment plant which operated at Port Pirie from 1955 to 1962.

The main ore mineral was davidite, a complex titanate of iron, uranium and rare earths. Mineralisation occurred as pegmatitic veins (pink K-feldspar, blue quartz, fluorophlogopite, ilmenite, haematite, davidite, chalcopyrite) within a steep northeast-trending sericitic shear zone in formerly high-grade quartzofeldspathic gneiss and amphibolite of the Willyama Supergroup. A total of 954 000 t of davidite ore averaging 1.2 kg/t U3O8 were mined.

Crocker Well

At Crocker Well, thorian brannerite occurs as disseminations and in fractures, breccias, and quartz veins in a sodic granitoid. Mineralisation is extensive but low grade.

Mount Painter

In the Mount Painter – Mount Gee area, bodies of granitic and haematitic breccia extend in a crude northeasterly alignment over a distance of 11 km. These breccia bodies are host to significant uranium mineralisation, with resources at the Armchair, Streitberg, Mount Gee, Radium Ridge and Hodgkinson prospects totalling 3.8 Mt and averaging 0.1% U3O8. In addition, several million tonnes of low-grade uranium mineralisation are present at nearby East Painter.

Myponga

Uranium mineralisation occurs within Barossa Complex gneiss of the Myponga Inlier at the Wild Dog Mine, 5 km southwest of Myponga township. Production from underground exploration during 1954–55 totalled 346 t at 0.36% U308, which was treated at the Port Pirie plant.

Eyre Peninsula

Unconformity style uranium mineralisation associated with Palaeoproterozoic Katunga Dolomite and adjacent, locally graphitic Mangalo Schist has been a target for mineral exploration on central Eyre Peninsula.

Tertiary sedimentary deposits

Beverley

Sedimentary uranium mineralisation was discovered at Beverley in the western part of the Frome Embayment in 1969. The deposit consists of three principal mineralised zones within a buried, confined palaeochannel containing unconsolidated sand and interbedded clay of the Tertiary Namba Formation. Mineralisation, which occurs at depths of 100–130 m, is separated from Cretaceous sediments of the Great Artesian Basin by at least 100 m of dense plastic clay (Alpha Mudstone). The principal ore mineral is coffinite, a uraniferous hydrosilicate thought to have been derived by leaching of primary mineralisation in the Mount Painter Inlier, 12 km to the west. The total resource is 16 300 t of U3O8.

Heathgate Resources Pty Ltd acquired the deposit in 1990, and received Commonwealth and State environmental clearances in April 1999. Australia’s first uranium mine using in situ recovery (ISR) techniques was opened at Beverley on 21 February 2001. Anticipated production is 1000 t/year of U3O8.

Honeymoon

Sedimentary uranium deposits were discovered in Tertiary sediments within the Frome Embayment to the north of the Willyama Inlier during 1969–73.

Location diagram and tenements for the Honeymoon project (.gif)
The Honeymoon and nearby East Kalkaroo deposits occur at depths of 100–120 m, predominantly in ‘basal sand’ of the Eyre Formation within the Tertiary Yarramba Palaeochannel (.gif). The deposits are overlain by Namba Formation clay. 

At Goulds Dam deposit, 80 km northwest of Honeymoon, a resource of 17 600t of U3O8 has been outlined in the Billeroo Palaeochannel.

Southern Cross Resources Australia Pty Ltd proposes to establish an ISL mining operation based on the Honeymoon and East Kalkaroo deposits, with anticipated production of 1000 t/year of U3O8.
Schematic ISL wellfield, Honeymoon deposit .gif)

Eucla Basin

Significant sedimentary uranium mineralisation has been delineated in Tertiary palaeochannels on northwestern Eyre Peninsula. The Yarranna 1 deposit within the Narlaby Palaeochannel comprises low-grade mineralisation over a 3 km2 area, while the Warrior deposit comprises a low-grade resource distributed in seven discrete zones along 12 km of the Warrior Palaeochannel.  

Additional Reading

Curtis, J.L., Brunt, D.A. and Binks, P.J., 1990. Tertiary palaeochannel uranium deposits in South Australia. In: Hughes, F.E.( Ed.), Geology of the mineral deposits of Australia and Papua New Guinea. Australasian Institute of Mining and Metallurgy. Monograph Series, 14:1631-1636.

Howles, S.R., Beverley uranium project: groundwater resources, management and monitoring. MESA Journal, 17:4-6.

Reeve, J.S., Cross, K.C., Smith, R.N. and Oreskes, N., 1990. Olympic Dam copper–uranium–gold–silver deposit. In: Hughes, F.E. (Ed.), Geology of the mineral deposits of Australia and Papua New Guinea. Australasian Institute of Mining and Metallurgy. Monograph Series, 14:1009-1035.