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Deposit Synonyms
Mineral District
Radium Hill Uranium
Deposit Summary
uraniferous lodes occur as shear replacements along reverse faults developed in domed anticline in granitised metasediments. 974 732 tons mined at average 2.62lbs U3O8/ton.
Deposit Description
RADIUM HILL was discovered in 1906 by Sir Douglas Mawson who identified the presence of uranium and named the mineral davidite, after the late Sir Edgeworth David. Epigenetic-style mineralisation occupied narrow, steep, pegmatitic quartz-biotite-ilmenite-feldspar veins in sericitic shears with intense alteration haloes within high metamorphic grade quartzo-feldspathic paragneiss and amphibolite.
Mapping identified host metasediment folded into slightly overturned, doubly plunging F3 antiform, axial plane trend 055-060, dip steep SE. Doming of the F3 hinge line was considered a significant factor in entrapment of mineralised fluid. Mineralisation was confined to 3 main NE-trending lodes, Main, South Hill, and Valley Lodes, total strike length >7,000m, of which 1400m was mined. Also 5 smaller lodes, Playford, Smith, Dickinson, and South. Main lode was a zone of shears developed along the axial planes of F3 folds. Lodes varied greatly in width, averaging ~1m, locally extending to 7.5m. Higher grades appeared to be associated with the flattest dips. Some mineralisation was associated with offsetting cross fracturing. At surface the main lodes were reasonably continuous, becoming en echelon at depth.
Amphibolite interpreted as intrusive mafic bodies of the Lady Louise Suite were suggested as an important factor in the focusing of mineralisation, with uranium minerals forming at the intersection of lode shear zones and amphibolite. In places pegmatite appeared to pre-date mineralisation, intruding into shear planes to effectively seal former potential ore channels.
Paragenetic sequence was biotite-chlorite-sericite infilled shears followed Fe and Ti mineralisation, with davidite appearing to be a late stage replacement of Fe-Ti minerals. Best ore concentrated in lodes adjacent to both amphibolite and soda pegmatite. Unfoliated sodic aplitic granite and microgranite intrusive clearly crosscut and obliterated the mineralised lodes, suggesting a minimum age for mineralisation of ~1580Ma. Minor sulphide mineralisation in quartz-calcite veins was the final stage.
The government of South Australia operated the mine intermittently from 1906-1931 for production of 589mg of radium bromide from 229 tonne of concentrate extracted out of carnotite from the secondary alteration zone within 30m of the surface. From 1954-61 the focus moved to the production of uranium from davidite, mining 954,000 tonne of ore @ 1.2 kg/t U3O8 to produce 850t of U3O8 and some rare earth minerals including lanthanum, cerium, yttrium and scandium. The deposit was eventually worked to a depth of 290m on nine levels over a strike length of 1400m. Mineralisation was intersected in drillholes to a depth of 420m, with the remaining resource below the mine workings estimated at 904,240 tonne @ 0.009% U3O8 (see appendix 4, ann rpt, 1980, Env 03447). McCleary in 2004 determined a total resource for Main and South Hill lodes of 291,236 tonne at 858ppm U3O8 for 270,727 Kg U3O8. The tailings dump in 1980 contained ~100,000 tonne fine-grained, mica-rich material assaying 0.9 Ib U3O8 per ton. Testwork (MR 109 pp47-48) indicated a mica content of 31% from which a mica concentrate was produced by flotation. In the early 1950s samples of black sands from drainage to the north of Radium Hill identified quantities of xenotime, but not in sufficient quantity to be considered an economic proposition.
Of interest is a line of outropping lamprophyre (minettes) that runs in a NNE-trend in a line ~500m to SE and weakly sub-parallel to the more NE-trending Radium Hill lodes. Host to the lamprophyres is Willyama Complex metamorphics. OFE 1689 has dates for the minette ranging from 464-424ma (late Delamerian). No geochemical analyses undertaken.
Discovery Year
? 1906
Commodities
Uranium, Radium, Rare Earths, Uranium Oxide, Mica
Ore Minerals
Carnotite, Chalcopyrite, Davidite, Hematite, Ilmenite, Magnetite, Metatorbernite, Rutile, Uranospinite
Gangue Minerals
Arsenopyrite, Biotite, Calcite, Feldspar, Pyrite, Quartz, Sericite, Titanite, Xenotime, Zircon
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