Geology and Uranium Resources of the Central Mineral Belt, Labrador

摘要

Exploration for uranium in the Central Mineral Belt (CMB) of Labradorstarted soon after the end of World War 2. British Newfoundland Explorationachieved substantial success, discovering many deposits including Kitts andMichelin. Airborne radiometry with ground follow up proved to be themost successful exploration techniques. Declining uranium price lead to theabandonment of the deposits, which were neglected until about ten yearsago when interest in the region was rekindled by perception of prospectivityfor IOCG deposits. An increasing uranium price lead companies such asFronteer to focus on uranium rather than copper, and this resulted in rapidresource growth at Michelin and rediscovery of the Jacque’s Lake deposit.Paladin acquired the CMB project from Fronteer in February 2011. Totalresources now attributed to Paladin are 135 Mlb U_3O_8 in six albitite-typeuranium deposits. Michelin is the flagship deposit with 103 Mlb U_3O_8 at0.1 per cent.Michelin, Jacques Lake and Rainbow are associated with a belt of Proterozoic(1.8 Ga) felsic volcanic rocks of the Aillik Group. Deposits of the Inda Laketrend (Inda, Gear, Nash and Kitts) are hosted by underlying volcaniclasticmetasediments and mafic metavolcanics of the Post Hill Group (2.0 Ga). Thestructural history of the region remains poorly defined. The most prominentfeature is a number of ENE-WSW trending thrust faults that dismember theAillik Group, and probably relate to collision between the Archaean Nainprovince rocks to the north and Grenville province rocks to the south.Most uranium deposits of the CMB can be classified as ‘albitite-type’(‘metasomatite-type’ of the IAEA classification). Albitite-type uraniumdeposits occur worldwide, and are typically large and of low-grade(<1 per cent U_3O_8). Collectively, this deposit group contains over 1 Mt of U_3O_8.Ore minerals include a combination of coffinite, brannerite, nenadkevite,wolsendorfite, uraninite and unidentified U-Zr phases. These phases areusually disseminated (Michelin, Rainbow) but also occur in megascopicveins (Jacque’s Lake), within and adjacent to albitised mylonites. Grain sizeis uniformly fine (<50 microns). Gangue minerals include albite, calcite,dolomite, sodic pyroxene, sodic amphibole, zircon and fluorapatite.The Moran Lake deposit contains a subeconomic U resource of 6 MlbsU_3O_8 and 17 Mlbs of V2O5 with significant low-grade copper in brecciatedand highly altered pillowed metabasalt. Large volumes of hydrothermalhematite invites comparison with the IOCGU deposit style as exemplifiedby Olympic Dam or Mount Gee.