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TitleFe isotopic composition of alteration minerals from McArthur River Zone 4 Deposit, Athabasca Basin
DownloadDownload (whole publication)
AuthorAcevedo, A; Kyser, T K
SourceTargeted Geoscience Initiative 4: unconformity-related uranium systems; by Potter, E G (ed.); Wright, D M (ed.); Geological Survey of Canada, Open File 7791, 2015 p. 61-73, (Open Access)
PublisherNatural Resources Canada
Documentopen file
Mediaon-line; digital
RelatedThis publication is contained in Potter, E G; Wright, D M; (2015). Targeted Geoscience Initiative 4: unconformity-related uranium systems, Geological Survey of Canada, Open File 7791
File formatpdf
ProvinceAlberta; Saskatchewan
NTS64E; 64L; 64M; 74E; 74F; 74G; 74H; 74I; 74J; 74K; 74L; 74M; 74N; 74O; 74P
Lat/Long WENS-112.0000 -102.0000 60.0000 57.0000
Subjectseconomic geology; radioactive minerals; unconformity-type deposit; unconformities; uranium deposits; uranium; mineral deposits; mineral occurrences; mineralization; isotope ratios; isotopes; iron; clays; Athabasca Basin; McArthur River zone 4 deposit
Illustrationslocation maps; photomicrographs; cross-sections; tables; histograms; plots
ProgramTargeted Geoscience Initiative (TGI-4), Uranium Ore Systems
Released2015 03 02 (08:30)
AbstractThis study examines the Fe isotopic composition of alteration minerals from the McArthur River deposit Zone 4 and investigates the premise that Fe isotopic values can be used to indicate how and where uranium ore deposition occurred. Iron isotopic signatures can be used to discriminate areas where significant redox reactions have occurred and thus, may indicate areas fertile for uranium mineralization. Iron plays an important role as a reducing agent during the formation of U deposits, particularly Fe2+ as it is involved in reducing U as follows:
U6+ (aq) + 2Fe2+ (aq) + 2H2O ? U4+O2(uraninite) + 2Fe3+ (chlorite or hematite) + 4H+ (aq)
Under equilibrium conditions, aqueous Fe3+ species or minerals that contain Fe3+ have higher 56Fe/54Fe ratios than those with Fe3+ and Fe2+ oxidation states.
The d56FeIRMM-014 values in clay mineral separates from both sandstone and basement rocks near the McArthur River deposit have a range of nearly 1.5perthousand. The d56Fe values of clay separates, however, do not correlate with distance from the mineralization nor do they correlate with Fe3+/Fetotal, other isotopic systems such as O or Pb, or any element other than Mg. Instead, d56Fe values are more complex than the single redox reaction above and can be divided into three distinct populations: (1) values ranging from 0 to 0.5perthousand which represent background values for the McArthur River deposit, as reflected by early chlorite in basement rocks that occurs distal to faults and furthest from the system; (2) d56Fe values < 0perthousand reflecting post-ore fluid events in samples that are located near lithologic boundaries or faults, which are susceptible to overprinting by the mineralizing system or later fluids; and (3) d56Fe values >0.5perthousand resulting from the oxidation of Fe during reduction of U6+ as recorded in samples near the ore zone or in the sandstone directly above the extension of the P2 fault system. The ?56Fe values indicate that samples above the silicified zone and up to 300m from the ore zone were affected by the primary dispersion of the mineralizing system and that Fe was a reductant of U in the mineralizing process. Based on these results, Fe isotopes reveal for the first time, processes associated with redox reactions in ore deposits. The redox population also provides an indication on the fertility of an alteration system, particularly along ore-hosting faults.