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Sci Rep. 2019 Apr 2;9(1):5530. doi: 10.1038/s41598-019-42032-0.

Uranium-rich diagenetic fluids provide the key to unconformity-related uranium mineralization in the Athabasca Basin.

Author information

1
Department of Geology, University of Regina, Regina, Saskatchewan, Canada. guoxiang.chi@uregina.ca.
2
Department of Geology, University of Regina, Regina, Saskatchewan, Canada. haixia.chu@cugb.edu.cn.
3
China University of Geosciences, Beijing, China. haixia.chu@cugb.edu.cn.
4
Geological Survey of Canada, Ottawa, Ontario, Canada.
5
Department of Earth and Planetary Sciences, McGill University, Montreal, Canada.

Abstract

The Proterozoic Athabasca Basin is well known for its unusually large-tonnage and high-grade 'unconformity-related' uranium (U) deposits, however, explanations for the basin-wide U endowment have not been clearly identified. Previous studies indicate that U-rich brines with up to ~600 ppm U and variable Na/Ca ratios (from Na-dominated to Ca-dominated) were present at the sites of U mineralization, but it is unknown whether such fluids were developed solely in the vicinity of the U deposits or at a basinal scale. Our microthermometric and LA-ICP-MS analyses of fluid inclusions in quartz overgrowths from the barren part of the basin indicate that U-rich brines (0.6 to 26.8 ppm U), including Na-dominated and Ca-dominated varieties, were widely developed in the basin. These U concentrations, although not as high as the highest found in the U deposits, are more than two orders of magnitude higher than most naturally occurring geologic fluids. The basin-scale development of U-rich diagenetic fluids is interpreted to be related to several geologic factors, including availability of basinal brines and U-rich lithologies, and a hydrogeologic framework that facilitated fluid circulation and U leaching. The combination of these favorable conditions is responsible for the U fertility of the Athabasca Basin.

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