Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by KISTER, P. Articles by LAVERRET, E. Search for Related Content GeoRef GeoRef Citation

Thermodynamic constraints on the mineralogical and fluid composition evolution in a clastic sedimentary basin

¹ CREGU-UMR CNRS 7566 G2R, UHP, BP 239, F-54506 Vandoeuvre-lès-Nancy Cedex, France
² HYDRASA-UMR CNRS 6532, Université de Poitiers, 40 Avenue du Recteur Pineau, F-86022 Poitiers-Cedex, France
³ Saskatchewan Research Council, 125 - 15 Innovation Blvd., Saskatoon, SK, S7N 2X8, Canada

^* E-mail: philippe.kister{at}g2r.uhp-nancy.fr

To evaluate the critical parameters controlling the mineralogical evolution of a dominantly clastic sedimentary basin, the Athabasca Basin (Saskatchewan, Canada), activity diagrams have been constructed with respect to the mineralogy, thermo-barometry, and fluid composition documented from previous studies. Relative to standard diagrams, which exist for ideal clay minerals, the present diagrams are the first to include all of the significant minerals present in the sediments, accounting specifically for the occurrence of dravite, sudoite, and two types of illite having identical chemical compositions, but different crystal morphologies and structures.

The occurrence of the different mineralogical assemblages is mainly controlled by the K⁺/H⁺ and Mg²⁺/(H⁺)² activity ratios, and the silica and B(OH)₃ activities in addition to temperature and pressure. Variations in the activities of the major brine components (Cl^-, Na⁺, Ca²⁺) and the oxygen fugacity (above the hematite-magnetite buffer) have little effect on the mineral stabilities. The mineralogical evolution of the Athabasca Group sandstone results from mass transport processes involving a basement-derived fluid, richer in K, Mg, B, and/or pH, and possibly undersaturated in silica. The zoned distribution of the minerals in the uranium-mineralized Shea Creek area can be explained by a progressive interaction of the basement-derived fluid with the diagenetic brine and minerals of the Athabasca Group sandstone. During peak diagenesis, the brine in the basal Athabasca Group was buffered by the assemblage I Mc illite-kaolinite. During the syn-ore stage, the estimated values of log(K⁺/H⁺), log(Mg²⁺/(H⁺)²) and B(OH)₃ activity decrease from 3.9, 6.4, and 0.005 in breccia zones immediately above the orebody, down to 2.7-3.6, 4.7-6. 1, and 0.004 in the inner alteration halo, and down to 2.7, 4.9, and 0.003 in the outer alteration halo, respectively.

Key-words: thermodynamic modelling, sandstone basin, uranium, host-rock alteration, clay minerals.

This article has been cited by other articles:

				S. Gaboreau, M. Cuney, D. Quirt, D. Beaufort, P. Patrier, and R. Mathieu Significance of aluminum phosphate-sulfate minerals associated with U unconformity-type deposits: The Athabasca basin, Canada American Mineralogist, February 1, 2007; 92(2-3): 267 - 280. [Abstract] [Full Text] [PDF]

				P. E. Rosenberg and F. F. Foit Jr. MAGNESIOFOITITE FROM THE URANIUM DEPOSITS OF THE ATHABASCA BASIN, SASKATCHEWAN, CANADA Can Mineral, August 1, 2006; 44(4): 959 - 965. [Abstract] [Full Text] [PDF]