The application of shortwave infrared (SWIR) reflectance spectroscopy to the characterization of clay minerals in the Athabasca Basin, in Saskatchewan, has been evaluated by detailed examination of 70 mineral separates (20 of kaolinite, 10 of dickite, 19 of illite, 16 of chlorites and 5 of magnesiofoitite). Clay minerals in the Athabasca Basin are widespread in the sandstones and are particularly abundant in alteration haloes associated with unconformity-type U deposits. SEM, TEM, XRD, EMPA, EPR and SWIR analyses confirm that dickite is a major clay mineral in the sandstones. Kaolinite from different geological settings has distinct values of crystallinity (i.e., Hinckley index in the range 0.84 to 1.61 in alteration haloes, 0.45 to 0.7 in the bleached zones of the paleoregolith, and 0.12 to 0.31 in late fractures and cavities). The SWIR reflectance spectroscopy is capable of quantitatively estimating the crystallinity of kaolinite by using a "14SP Index". Attempts to use SWIR reflectance spectroscopy for structural and compositional analysis of Athabasca illite and sudoite were complicated by the common occurrence of impurities in these minerals. Binary and ternary mixtures using well-characterized mineral standards reveal that SWIR reflectance spectroscopy is capable of identifying clay minerals at abundances as low as 1 wt%. Also, numerical relationships between spectral features and the abundances of clay minerals have been established from the muscovite -kaolinite, muscovite -dickite and muscovite -sudoite mixtures, and have been used to improve an empirical SWIR method for quantitative analysis of clay minerals in the Athabasca Basin. The estimated precision and accuracy of the improved empirical method are between 5 to 10%, comparable to those of conventional XRD methods. The detection limits of the SWIR method for samples containing multiple species of clay minerals are approximately 5 wt.% in relative abundance.Keywords: shortwave infrared reflectance spectroscopy, clay minerals, alteration assemblages, uranium deposits, Athabasca Basin, Saskatchewan. SOMMAIRENous avons évalué l'applicabilité de la spectroscopie par réflectance dans l'infra-rouge à ondes courtes (SWIR) pour caractériser les argiles du bassin d'Athabasca, au Saskatchewan, en utilisant soixante-dix concentrés (20 de kaolinite, 10 de dickite, 19 d'illite, 16 de chlorites et 5 de magnésiofoïtite). Les argiles sont répandues dans les grès du bassin d'Athabasca Basin, et surtout dans les auréoles d'altération associées aux gisements d'uranium localisés près d'une non-conformité. Les analyses par microscopie électronique à balayage et à transmission, par diffraction X, par microsonde électronique et par SWIR confirment que la dickite est une phase majeure dans les grès. La kaolinite provenant de divers contextes géologiques possède des valeurs distinctes de cristallinité (i.e., indice de Hinckley dans l'intervalle de 0.84 à 1.61 dans les auréoles d'altération, de 0.45 à 0.7 dans les zones lessivées du paléorégolithe, et de 0.12 à 0.31 ...
Magnetic and gravity inversions are used to create 2D or 3D models of the magnetic susceptibility and density, respectively, using potential field data. Unconstrained inversions generate an output based on mathematical constraints imposed by the inversion algorithm. Constrained inversions integrate lithological, structural, and petrophysical information in the inversion process to produce more geologically meaningful results. This study analyses the validity of this assertion in the context of the NSERC-CMIC Mineral Exploration Footprints project. Unconstrained and constrained geophysical inversions were computed for three mining sites: a gold site (Canadian Malartic, Québec), a copper site (Highland Valley, British Columbia), and a uranium site (Millennium – McArthur River, Saskatchewan). After initially computing unconstrained inversions, constrained inversions were developed using physical property measurements, which directly link geophysics to geology, and lithological boundaries extracted from an interpreted geological model. While each derived geological model is consistent with the geophysical data, each site exhibited some magnetic complexity that confounded the inversion. The gold site includes regions with a strong magnetic signature that masks the more weakly magnetic zone, thereby hiding the magnetic signature associated with the ore body. Initial unconstrained inversions for the copper site yielded solutions with invalid depth extent. A consistency between the constrained model and the geological model is reached with iterative changes to the depth extent of the model. At the uranium site, the observed magnetic signal is weak, but the inversion provided some insights that could be interpreted in terms of an already known complexly folded geological model.
Multiparameter downhole geophysical measurements in two representative boreholes in the eastern Athabasca Basin are compared to visual, petrographic, mineralogical, and lithogeochemical analyses of their drill cores. Natural gamma-ray spectrometry data exhibit increased levels of radioactivity in the Read and Manitou Falls formations that relate mainly to natural thorium and, to a lesser extent, uranium abundances, whereas potassium responses are generally low. Thorium responses in these quartz-dominated fluvial deposits are closely correlated with detrital grain-size parameters such as the per cent of grains greater than 2 mm and are therefore interpreted to relate to primary heavy mineral accumulations and their diagenetic products (crandallite-group minerals) within coarser grained beds. Diagenetic attributes such as porosity and silicification are positively correlated with density, resistivity, and acoustic velocity. Natural gamma-ray logs are thus guides to stratigraphy, and other geophysical parameters calibrate ore-related alteration features, thereby facilitating integration of geological and geophysical transects.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.