Faults Affecting the Northeast Thelon Basin: Improved Basement Constraints from Source Edge Processing of Aeromagnetic Data

Abstract 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 sub-basin. Combining these data revealed three age groups of faults. One group is seen only on the DEM; these faults are young brittle structures that have no effect on the sub-Thelon basement unconformity, and are not visible on the dip direction map. A second group is evident on the dip direction map but not the DEM; these faults are old basement structures that did not propagate upward through the Thelon Formation. The third group is expressed on both the DEM and dip direction map; these faults are also old structures that propagated upward during and/or after deposition of the Thelon Formation. The latter group of faults may be of greatest interest for uranium exploration, with reactivation increasing their potential to serve as conduits to transport uranium-rich fluids and focus deposition at or near the unconformity surface. This methodology has promise for comprehensive mapping of basin faults and tracking the tectonic development of the whole Thelon Basin through time.
Keywords: faults, uranium, Thelon Basin, source edge detection, lineament analysis
Résumé Une nouvelle méthode pour cartographier les failles dans les roches du socle qui sous la Formation de Thelon et les sédiments glaciaires été développée et testée dans le sous-bassin d’Aberdeen. Cette méthode utilise de nouvelles données aéromagnétiques, l'algorithme Blakely pour définir les bords de la source magnétique, une carte des directions de pendage calculées, un modèle numérique d'élévation (MNE) provenant de la Base canadienne de données altimétriques numériques et les positions des failles identifiés, déduites et nouvellement cartographiées situées à l'intérieur et à proximité de ce sous-bassin. La combinaison des données permis d’identifier trois groupes de failles d'âge différent. Un de ces groupes n’est perceptible que sur le MNE, ces failles sont de jeunes structures fragiles qui n'ont aucun effet sur la discordance séparant le socle du Thelon, et qui n’apparaissent pas sur la carte des directions de pendage. Un deuxième groupe apparait sur la carte des directions de pendage mais pas le MNE, ces failles sont des structures anciennes dans le socle qui ne se poursuivent pas verticalement dans la Formation de Thelon. Le troisième groupe est visible à la fois sur le MNE et la carte des directions de pendage, ces failles sont des structures anciennes qui sont demeurées actives pendant et / ou après le dépôt de la Formation de Thelon. Ce dernier groupe de failles est celui qui présente le plus d'intérêt pour l'exploration uranifère, parce que leur réactivation augmente la possibilité qu’elles aient servi au transport de fluides riches en uranium et qu’elles aient concentré la circulation de ces fluides vers la discordance. Cette méthode semble prometteuse pour la cartographie systématique des failles du bassin et pour le suivi de l'évolution tectonique globale du bassin de Thelon dans le temps.
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Summary: 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...
Publication: Exploration & Mining Geology
Author(s): LUKE OOTES, JEFF HARRIS, VALERIE A. JACKSON, BRONWYN AZAR, AND LOUISE CORRIVEAU
Keywords: Wopmay orogen, Great Bear magmatic zone, bedrock geochemistry, IOCG, unconformityrelated uranium
Issue: 1
Volume: 21
Year: 2013
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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: 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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