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TitleAn updated genetic model for the Kianna unconformity-related uranium deposit, Shea Creek, Athabasca Basin, Canada
AuthorSheahan, C A R; Fayek, M; Quirt, D; Jefferson, C W
SourceGeological Society of America, Abstracts With Programs vol. 45, no. 7, 2013 p. 725
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20130241
PublisherGeological Society of America
MeetingGeological Society of America, Annual Meeting; Denver, CO; US; October 27-30, 2013
File formathtml
NTS64E; 64L; 64M; 74E; 74F; 74G; 74H; 74I; 74J; 74K; 74L; 74M; 74N; 74O; 74P
Areanorthern Saskatchewan; Shea Creek
Lat/Long WENS-112.0000 -102.0000 60.0000 57.0000
Subjectseconomic geology; mineral deposits; mineral occurrences; mineralization; uranium; unconformity-type deposit; Athabasca Basin; Kianna Unconformity
ProgramGEM: Geo-mapping for Energy and Minerals, Uranium
AbstractThe Athabasca Basin, Saskatchewan is host to the world¿s highest-grade unconformity-related U deposits. These deposits are primarily located along the eastern part of the basin. The Kianna deposit at Shea Creek is one of the few unconformity-related deposits that occur in the western Athabasca Basin. It consists of disseminated to massive uraninite located in three distinct zones: 1) perched, above the unconformity, entirely in sandstone; 2) at the unconformity, hosted by sandstone and basement rocks; and 3) below the unconformity, hosted by basement paragneiss. In situ microanalysis by SIMS was used to obtain ages for uraninite and determine the source of sulfur. Basement-hosted uraninite occurs with hematite and muscovite and has a U-Pb age of 1448 ± 23 Ma. Uraninite at the unconformity is intermixed with hematite and is 390 ± 13 Ma whereas perched uraninite is inter-disseminated with alumino-phosphate sulfate (APS) minerals, sulfides, and hematite, and is 177 ± 20 Ma. Pyrite from the basement has d34S values from 2.1 to 4.7¿, suggesting that sulfur was derived from a metamorphic or igneous source. Sulfides associated with perched and unconformity-related mineralization have two ranges of d34S values, from 1.5 to 7¿ and 17.1 to 21.8¿, suggesting that there were two sources of sulfur, crystalline basement and sulfate associated with sandstone (e.g. APS minerals).
We have developed a genetic model for all three styles of uraninite. This model builds on previous studies for the formation of unconformity-type deposits. It also incorporates the fault-valve and suction pump models for the movement of large quantities of fluid along faults due to cyclic variations in stress. There were three stages:
1) An oxidizing, basinal brine moved downward along a fault and precipitated uraninite in basement rocks. Interaction with the basement rocks caused physiochemical changes to the fluid (e.g. lower fO2). Mineral precipitation and increase in frictional strength caused the fault to self-seal.
2) Increase in fluid pressure and a change in stress caused the fault to re-open; the reducing fluid moved upward along the same structure and uraninite precipitated at the unconformity due to fluid mixing.
3) Fluids continued upward along the fault, interacted with APS minerals and precipitated perched uraninite and sulfide minerals.
Summary(Plain Language Summary, not published)
A deeply buried primary uranium deposit at Shea Creek in the western part of the Athabasca Basin, Saskatchewan is located in crystalline rocks beneath hundreds of metres of sandstone. The primary deposit is herein dated at 1,448,000,000 years; it was remobilized to a higher location at 390,000,000 years and even higher at 177,000,000.