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Uranium ore-forming systems of the - Geoscience Australia

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<strong>Uranium</strong> <strong>ore</strong>-<strong>forming</strong> <strong>systems</strong> <strong>of</strong> <strong>the</strong> Lake Frome regionLocality 11 (348350E ; 6651020N) Lady Buxton FaultImmediately alongside <strong>the</strong> track to East Painter/Paralana Hot Springs and near <strong>the</strong> Lady BuxtonCopper Mine is an exposure <strong>of</strong> field relationships demonstrating <strong>the</strong> neotectonic activity <strong>of</strong> <strong>the</strong>region. Here <strong>the</strong> Adelaidean Wywyana Formation has been thrust over Cenozoic sediments.The footwall <strong>of</strong> this thrust is composed <strong>of</strong> partially consolidated ferruginous lithic gravels withsub-angular to sub-rounded pebbles up to 10 cm in diameter. Pebble lithologies include anassortment <strong>of</strong> Mesoproterozoic and Neoproterozoic rock types. The matrix <strong>of</strong> this sedimentincludes granules and coarse sand to silt dominated by quartz and maghemite and minor lithicfragments, with ferruginous and carbonate cement. The hangingwall consists <strong>of</strong> wea<strong>the</strong>redNeoproterozoic marbles <strong>of</strong> <strong>the</strong> Wywyana Formation. The thrust is oriented 070 o and dips at 20 otoward <strong>the</strong> north-west. Linear grooves on <strong>the</strong> fault plane trend down dip, indicating mostrecently dominantly dip-slip movement. An estimate <strong>of</strong> displacement along <strong>the</strong> structure isproblematic as <strong>the</strong> thickness <strong>of</strong> <strong>the</strong> footwall sequence is unknown. The age <strong>of</strong> <strong>the</strong> thrust ispoorly constrained as <strong>the</strong> footwall lithology is unique within <strong>the</strong> field area.The abundance <strong>of</strong> maghemite granules in <strong>the</strong> footwall sediment suggest a Neogene age, asmaghemite becomes m<strong>ore</strong> prevalent in sediments in <strong>the</strong> region post-dating <strong>the</strong> Miocene. Themoderate degree <strong>of</strong> consolidation and development <strong>of</strong> carbonate and ferruginous indurationsuggest a degree <strong>of</strong> antiquity but is not inconsistent with a Neogene age. The interpretedenvironment <strong>of</strong> deposition for <strong>the</strong>se sediments is proximal colluvial-alluvial fans, which issimilar to <strong>the</strong> local sediments deposited in <strong>the</strong> contemporary landscape. These sediments mayrepresent a local lithological variation <strong>of</strong> <strong>the</strong> Willawortina Formation (Célérier, 2002).Page 136 <strong>of</strong> 151

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