| Title | Fe and Mg signatures of the Bong Uranium Deposit, Thelon Basin, Nunavut |
| Download | Download (whole publication) |
| Author | Potter, E G; Sharpe, R; Girard, I; Fayek, M; Gammon, P; Quirt, D; Robbins, J |
| Source | Targeted 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. 52-60, https://doi.org/10.4095/295783 (Open Access) |
| Year | 2015 |
| Publisher | Natural Resources Canada |
| Document | open file |
| Lang. | English |
| Media | on-line; digital |
| Related | This 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 format | pdf |
| Province | Nunavut |
| NTS | 66A; 66B |
| Area | Sissons Lake |
| Lat/Long WENS | -99.0000 -97.0000 64.7500 64.2500 |
| Subjects | structural geology; radioactive minerals; geochemistry; unconformity-type deposit; unconformities; uranium deposits; uranium; mineral deposits; mineral occurrences; mineralization; iron geochemistry;
magnesium geochemistry; structural features; faults; alteration; hydrothermal alteration; illite; Athabasca Basin; Bong deposit; Kiggavik deposit; Thelon sub-basin; Woodburn Lake group |
| Illustrations | location maps; photographs; cross-sections; profiles |
| Program | Uranium Ore Systems, Targeted Geoscience Initiative (TGI-4) |
| Released | 2015 03 02 (08:30) |
| Abstract | The Bong deposit is one of several uranium occurrences located ca. 5 km southeast of the faulted margin of the Proterozoic Thelon sub-basin, within altered metasedimentary rocks of the Woodburn Lake
group. The deposit exhibits features in common with unconformity-related deposits of the Athabasca Basin, in particular a spatial association with the regional unconformity, alteration and ore mineralogy and structural context. Primary uranium
enrichment is associated with a broad hydrothermal alteration halo characterized by an inner illite-rich zone and an outer chlorite-rich zone. Whole rock and clay-sized fraction ?57FeIRMM-014 and ?26MgDSM-3 values of the least-altered host rocks
cluster near 0 ‰, within range of average values of crustal materials. Zones characterized by intense illite alteration have high ?57Fe and ?26Mg values, with average whole-rock values of ?57Fe = 0.87 }0.23‰ and ?26Mg = 0.61 }0.29‰, and clay-size
fraction values of ?57Fe = 0.77 }0.29‰ and ?26Mg = 0.82 }0.09‰. These isotopic values correlate with reductions in Fe2+ concentrations (average of 0.47 mol. % versus average of 2.30 mol. % Fe2+ in least-altered hosts). The high ?57Fe values support
leaching of Fe2+ (aq) with low ?57Fe compositions from the system, causing precipitation of iron-bearing minerals with ?57Fe values higher than the host rocks. The ?57Fe values may have been locally influenced by the formation of hematite and
Fe-oxyhydroxide minerals in secondary miniature roll-front mineralization due to redox reactions. The high ?26Mg values coincide with formation of illite, which preferentially incorporated heavier magnesium isotopes during the intense hydrothermal
alteration observed in both the ore zone and an upper hematitic horizon. Despite the significant shifts in isotopic compositions, the net iron depletion in the ore zone via selective leaching of Fe2+ without Fe3+ enrichment implies that redox
reactions were not the dominant mechanism of primary uranium mineralization at the Bong deposit. Mineralogical and geochemical data support primary uranium precipitation through reduction and neutralization of an oxidized, acidic fluid. As Fe2+ was
leached from the system in solution, enrichment of Fe-oxides and low whole-rock ?57Fe values may be a distal signature of these systems. |
| GEOSCAN ID | 295783 |
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