A Combined Ingress-Egress Model for the Kianna Unconformity-Related Uranium Deposit, Shea Creek Project, Athabasca Basin, Canada

Abstract

The Kianna deposit is an unconformity-related uranium deposit in the western Athabasca Basin of northern Saskatchewan, hosting uraninite in three distinct zones: 1) perched above the unconformity, hosted in sandstone; 2) at the unconformity, hosted in sandstone and basement rocks; and 3) below the unconformity in two separate pods, hosted by basement paragneiss. In situ secondary ion mass spectrometry (SIMS) was used to obtain radiogenic and stable isotope data to update the genetic model for the Kianna deposit. Primary basement-hosted ingress-style uraninite, associated with hematite and muscovite, has a minimum U-Pb age of ~1500 Ma. Recrystallization of basement uraninite occurred ~1100 Ma with the precipitation of coarsegrained illite. Late basement uraninite precipitated with fine-grained illite ~850 Ma. A separate, deeper basement pod formed ~1280 Ma. Egress-style uraninite at the unconformity, and perched uraninite in the sandstone, inter-grown with alumino-phosphate sulfate (APS) minerals and chalcopyrite, formed ~750 Ma. Later unconformity and perched uraninite precipitated with hematite, pyrite, and chalcopyrite ~500 Ma. Sulfides coeval with unconformity and perched uraninite have δ 34 S values from -1.9 to 8.1‰ and 15.1 to 25.4‰, indicating two sources of sulfur: 1) sulfides in the metamorphosed basement and 2) APS minerals in the sandstone. Average δ 18 O and δD mineral values for muscovite are 0.7 ± 4.3‰ and -33 ± 12‰, respectively, suggesting that muscovite formed from a marine brine. Average δ 18 O and δD mineral values for coarse-grained illite are 0.4 ± 4.1‰ and -79 ± 16‰, respectively, indicating formation from hydrothermal fluids, whereas fine-grained illite δ 18 O and δD mineral values are 6.5 ± 1.6‰ and -144 ± 21‰, respectively, suggesting formation from meteoric fluids.iii Acknowledgements

The Contact uranium prospect, Kiggavik project, Nunavut (Canada): Tectonic history, structural constraints and timing of mineralization

“…1500 Ma is the age of the emplacement of the Kuungmi lavas over the Thelon Basin (1540±30 Ma, Chamberlain et al, 2010). This age was obtained in several studies throughout the Western-Churchill province (Turner et al, 2003;Bridge et al, 2013;Gandhi et al, 2013;Dieng et al, 2013;Sheahan et al, 2015) and is possibly linked to a regional thermal event possibly reflecting a craton-scale process. If this thermal event has reset the U-Pb isotopic system (Davis et al, 2011;Peterson et al, 2015b), then the ages of the first stage of faulting and mineralization could be bracketed between ca.…”

Radioactivity recorded by clay minerals in the Shea Creek area, Athabasca Basin (Canada): Implications for uranium transfers and exploration

“…Besides, detailed mineralogical and isotopic data showed that several episodes of U ore formation occurred around 1500 Ma, 959 Ma, 300 Ma (Fayek and Kyser, 1997;Kotzer and Kyser, 1995;Kyser et al, 2000). In the Kianna deposit, one of the U deposits in the Shea Creek area, Sheahan et al (2016) proposed a genetic model with formation of basement mineralization at about 1500 Ma, remobilization of this mineralization at around 1280 Ma and 1100 Ma, and uraninite mineralization in the sandstone at~750 and~500 Ma.…”

“…1). In this area, the thickness of the Athabasca Group sandstone is 700 to 800 m. The Shea Creek area was selected for the present study because it is a good example of the Athabasca unconformity-related uranium deposits with pods hosted in the basement and the sandstone (Sheahan et al, 2016). In addition, this choice was motivated by access to samples by AREVA and the excellent knowledge of this deposit area from numerous studies (e.g.…”

“…In addition, this choice was motivated by access to samples by AREVA and the excellent knowledge of this deposit area from numerous studies (e.g. Kister et al, 2006;Laverret et al, 2006Laverret et al, , 2010Sheahan et al, 2016). The nearby Erica area was also selected because it is close to Shea Creek (about 10 km) and has a similar local geology.…”

“…Nevertheless, uranium is particularly important, owing to its relative abundance and mobility in oxidized environments and the relative immobility of Th, as previously shown for the Nopal U-deposit, Mexico (Allard and Muller, 1998) or the Coutras deposit, France (Allard et al, 2007). This study focuses on the Shea Creek area of the Athabasca Basin that represents a good example of the Athabasca unconformity-related U-deposits (Sheahan et al, 2016), and in which the clay minerals (i.e. kaolinite, dickite, illite, and sudoite) predated or were contemporaneous with the formation of the uranium deposits (Hoeve and Quirt, 1984;.…”