Geochronology of unconformity-related uranium deposits in the Athabasca Basin,Saskatchewan, Canada and their integration in the evolution of the basin |
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Authors: | Paul Alexandre Kurt Kyser Dave Thomas Paul Polito Jim Marlat |
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Institution: | (1) Department of Geological Sciences and Geological Engineering, Queen’s University, Kingston, ON, Canada, K7L 3N6;(2) Cameco Corporation, 2121, 11th Street West, Saskatoon, SK, Canada, S7M 1J3 |
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Abstract: | The importance of geochronology in the study of mineral deposits in general, and of unconformity-type uranium deposits in
particular, resides in the possibility to situate the critical ore-related processes in the context of the evolution of the
physical and chemical conditions in the studied area. The present paper gives the results of laser step heating 40Ar/39Ar dating of metamorphic host-rock minerals, pre-ore and syn-ore alteration clay minerals, and laser ablation inductively
coupled plasma mass spectrometer (LA-ICP-MS) U/Pb dating of uraninite from a number of basement- and sediment-hosted unconformity-related
deposits in the Athabasca Basin, Canada. Post-peak metamorphic cooling during the Trans-Hudson Orogen of rocks from the basement
occurred at ca 1,750 Ma and gives a maximum age for the formation of the overlying Athabasca Basin. Pre-ore alteration occurred
simultaneously in both basement- and sandstone-hosted mineralizations at ca 1,675 Ma, as indicated by the 40Ar/39Ar dating of pre-ore alteration illite and chlorite. The uranium mineralization age is ca 1,590 Ma, given by LA-ICP-MS U/Pb
dating of uraninite and 40Ar/39Ar dating of syn-ore illite, and is the same throughout the basin and in both basement- and sandstone-hosted deposits. The
mineralization event, older than previously proposed, as well as several fluid circulation events that subsequently affected
all minerals studied probably correspond to far-field, continent-wide tectonic events such as the metamorphic events in Wyoming
and the Mazatzal Orogeny (ca 1.6 to 1.5 Ga), the Berthoud Orogeny (ca 1.4 Ga), the emplacement of the McKenzie mafic dyke
swarms (ca 1.27 Ga), the Grenville Orogeny (ca 1.15 to 1 Ga), and the assemblage and break-up of Rodinia (ca 1 to 0.85 Ga).
The results of the present work underline the importance of basin evolution between ca 1.75 Ga (basin formation) and ca 1.59 Ga
(ore deposition) for understanding the conditions necessary for the formation of unconformity-type uranium deposits.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Unconformity-type uranium deposits Geochronology Basin evolution Athabasca Basin Canada |
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