Uranium-Enriched Bedrock in the central Wopmay Orogen: Implications for Uranium Mineralization

Abstract We use the results of new bedrock mapping, combined with geochemical point data and airborne radiometric data (in particular equivalent uranium concentrations) to help determine which geological units in the Paleoproterozoic Great Bear magmatic zone (GBmz) contain elevated uranium. The data collectively indicate that the highest primary uranium concentrations are in equigranular granites and subvolcanic/volcanic porphyries. Notably, these rocks host the majority of known uranium-bearing deposits and/or prospects in the GBmz. We speculate that the uranium in these deposits/prospects was derived from nearby, uranium-enriched rocks and was mobilized by much younger, circulating hydrothermal fluids. Sedimentary rocks of the Thelon and Dismal Lakes groups unconformably overlie the GBmz and are known to host unconformity-type and sandstone-hosted uranium prospects. Most likely, the uraniumenriched rocks of the GBmz acted as a uranium donor to these overlying sedimentary basins. The method of investigation employed in this study may be applicable to other ‘granitic’ terrains in order to identify regions with favourable rocks for uranium exploration.
Keywords: Wopmay orogen, Great Bear magmatic zone, bedrock geochemistry, IOCG, unconformityrelated uranium
Résumé Nous avons combinéles résultats d'une nouvelle cartographie du substratum rocheux, des données géochimiques ponctuelles et un levé radiométrique aéroporté (en concentration d'équivalent uranium particulaire) pour aider à déterminer quelles unités géologiques de la zone magmatique Great Bear d’âge Paléoprotérozoïque (zmGB) contiennent des teneur élevées en uranium. Les données combinées indiquent que les concentrations d'uranium primaires les plus élevées se trouvent dans les granites et les porphyres équigranulaires subvolcaniques à volcanique. Ces roches contiennent la majorité des gîtes uranifères et des indices minéralisés connus dans la zmGB. Nous croyons que l'uranium dans ces gîtes et indices minéralisés est dérivé des roches environnantes enrichies en uranium et qu’il aurait été remobilisé par la circulation de fluides hydrothermaux considérablement plus jeunes. Les roches sédimentaires des groupes de Thelon et de Dismal Lakes recouvrent la zmGB en discordance le zmGB et elles contiennent des indices uranifères associés aux discordances et aux grès. Il est probable que les roches enrichies en uranium de la zmGB sont la source de l'uranium qui se trouve dans ces bassins sédimentaires. La méthode utilisée dans notre étude peut être appliquée à d'autres environnements granitiques afin d'identifier les régions dont les roches sont favorables à l'exploration uranifère.
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Summary: A 10-cm thick clay-rich layer near the top of the Manitou Falls Formation of the Athabasca Group is unusual in its breccia texture, alteration, and detrital mineral composition relative to the adjacent overlying and underlying sedimentary beds. This layer is composed of angular quartz grains set in an illite >> kaolinite + dickite matrix. Deformed clay-rich fragments within the layer have very similar mineral assemblages. The presence of euhedral accessory minerals including Ti-oxides and...
Publication: Exploration & Mining Geology
Author(s): JEANNE B. PERCIVAL, SEAN A. BOSMAN, ERIC G. POTTER, PAUL RAMAEKERS, KATHERINE E. VENANCE, PAT A. HUNT, WILLIAM DAVIS, AND CHARLES W. JEFFERSON
Keywords: microbreccia, hydrothermal alteration, hydraulic fracturing, uranium mineralization
Issue: 1
Volume: 21
Year: 2013
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Summary: The nature and distribution of radiation-induced defects (RIDs) in quartz from the Maw Zone, a yttrium- and rare-earth-element-enriched sandstone breccia complex exhibiting intense hydrothermal alteration, have been investigated by electron paramagnetic resonance (EPR) spectroscopy. EPR spectra show that detrital quartz in sandstone, from five diamond drill holes intersecting the Maw Zone and one above the crest of the so-called Quartzite Ridge, contain only background-level RIDs, indicating...
Publication: Exploration & Mining Geology
Author(s): YUANMING PAN, GARY YEO, BRETT ROGERS, CHRISTINE AUSTMAN, AND BAOQUAN HU
Keywords: quartz EPR, radiation-induced defects, hydrothermal alteration, uranium exploration, Athabasca Basin
Issue: 1
Volume: 21
Year: 2013
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Summary: The use of CR-39 plastic polymer as a solid state nuclear track detector in the textural analysis of radioactive minerals in geological samples was first described by I.R Basham in 1981. CR-39 autoradiographs provide a detailed, high-resolution image of the in situ distribution of the radioactive minerals within geological samples on both the macroscopic and microscopic scales. This technique is an inexpensive and effective means of obtaining detailed textural information that provides...
Publication: Exploration & Mining Geology
Author(s): G.W. SPARKES
Keywords: uranium, CR-39, autoradiograph, Labrador, uraninite
Issue: 1
Volume: 21
Year: 2013
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Summary: The U-Th-REE mineralization at Fraser Lakes Zone B is hosted by granitic pegmatites and leucogranites, which lie along the deformed contact between Paleoproterozoic metasedimentary gneiss of the Wollaston Group and Archean orthogneiss, approximately 25 km from the southeastern edge of the Athabasca Basin. The pegmatites/leucogranites are subcordant to concordant with the regional foliation and are concentrated within a northeast-plunging antiformal fold nose, the study area, which lies west...
Publication: Exploration & Mining Geology
Author(s): CHRISTINE L. MCKECHNIE, IRVINE R. ANNESLEY , AND KEVIN M. ANSDELL
Keywords: U-rich pegmatites, Th-REE-rich pegmatites, Fraser Lakes Zone B, Wollaston Domain, Athabasca Basin, U metallogeny
Issue: 1
Volume: 21
Year: 2013
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Summary: A new method for mapping faults within basement rocks underlying the Thelon Formation and glacial overburden was developed and tested in the Aberdeen Sub-basin. This method utilizes newly acquired aeromagnetic data, the Blakely algorithm for defining magnetic source edges, a calculated dip-direction map, a digital elevation model (DEM) derived from the Canadian Digital Elevation Database, and the positions of identified, inferred and newly mapped faults that are within and adjacent to this...
Publication: Exploration & Mining Geology
Author(s): VICKI TSCHIRHART, BILL MORRIS, AND CHARLES JEFFERSON
Keywords: faults, uranium, Thelon Basin, source edge detection, lineament analysis
Issue: 1
Volume: 21
Year: 2013
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Summary: The Dragon Lake Zone (uranium prospect) comprises a N160º trending vein that is approximately 110 m long, up to 5 m wide and from 1 to 40 m high. The zone is mostly within altered sandstone of the Fair Point Formation, the basal unit of the Paleoproterozoic Athabasca Group, but it also extends downward (up to 3.5 m) into basement rocks that occupy the northerly trending Maybelle River Shear Zone (MRSZ). This subvertical shear zone separates graphitic paragneiss and weakly deformed granitoid...
Publication: Exploration & Mining Geology
Author(s): K. WHEATLEY AND C. CUTTS
Keywords: uranium, unconformity, Alberta, Maybelle River, Dragon Lake, Athabasca
Issue: 1
Volume: 21
Year: 2013
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Summary: Lac Cinquante is a mineralogically simple, vein-hosted uranium deposit in Archean basement rocks (Angikuni greenstone belt) that originally were unconformably overlain by Proterozoic sedimentary and volcanic rocks of the Baker Lake Group (BLG). Basement rocks are mainly pillowed and massive tholeiitic lavas (N-MORB) with interbedded tuff; overlying sedimentary rocks comprise a basal talus/fault breccia that grades upward into fluvial sedimentary rocks and subaerial, trachytic volcanic rocks;...
Publication: Exploration & Mining Geology
Author(s): N.J. BRIDGE, N.R. BANERJEE, S. PEHRSSON, M. FAYEK, C.S. FINNIGAN, J. WARD, AND A. BERRY
Keywords: NW Hearne, Archean basement, Baker Lake Group, Angikuni subbasin, vein-hosted uranium, graphite
Issue: 1
Volume: 21
Year: 2013
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