GEOSCAN, résultats de la recherche

Menu GEOSCAN


TitreOre fluids recorded in the compositions of magnesiofoitite and alumino-phosphate-sulfate (APS) minerals in the basement along the P2 structure and the McArthur River deposit, Athabasca Basin
AuteurAdlakha, E E; Hattori, K; Zaluski, G; Kotzer, T; Potter, E
SourceL'Association géologique du Canada-L'Association minéralogique du Canada, Réunion annuelle conjointe, Recueil des résumés vol. 37, 2014 p. 4-5
Année2014
Séries alt.Secteur des sciences de la Terre, Contribution externe 20140044
ÉditeurGeological Assoc. Canada - Mineralogical Assoc. Canada
Réunion Gerological Association of Canada - Mineralogical Association of Canada annual meeting; Fredericton; CA; mai 21-23, 2014
Documentpublication en série
Lang.anglais
Mediapapier
Formatspdf
ProvinceSaskatchewan
SNRC74H/15; 64L
Lat/Long OENS-105.0000 -104.5000 58.0000 57.7500
Sujetsdéformation; failles; caractéristiques structurales; uranium; gisements d'uranium; altération; diagenèse; altération hydrothermale; Dépôt de Mcarthur River ; Bassin d'Athabasca ; géologie économique
ProgrammeÉtude des gîtes d'uranium, Initiative géoscientifique ciblée (IGC-4)
LiensOnline - En ligne
Résumé(disponible en anglais seulement)
The P2 reverse fault is a reactivated structure in the southeastern Athabasca Basin that hosts the McArthur River uranium deposit, the largest high-grade unconformity-type uranium deposit yet discovered. This study is to document alteration below the unconformity, specifically within and near the P2 deformation zone and the basement-hosted Zone 2 ore body, in order to evaluate the role of the P2 fault as the conduit for basinal and basement fluids and identify fertile alteration. The results of this study show that the P2 structure is the site of multiple stages of diagenetic-hydrothermal alteration, which produced illite, sudoite, Fe-Mg chlorite, clinochlore, kaolinite, aluminum phosphate-sulfate minerals (APS) and tourmaline. Below the unconformity, the assemblage of illite plus sudoite is common in pelite and pegmatite regardless of proximity to the P2 fault, and kaolinite is distributed along the unconformity; however, the assemblage of magnesiofoitite (alkali-deficient Mg-tourmaline) plus LREE-rich APS has only been found in close proximity to the P2 structure. Along the P2 fault, magnesiofoitite forms fine-grained (<0.2 mm) matrix, aggregates, overgrowths on metamorphic/magmatic dravite (< 2 mm), and veinlets (< 2 mm) that cross-cut sudoite and illite. APS form zoned pseudo-cubes (1 - 20 um), disseminated and clustered within fine-grained matrix in altered metapelite and pegmatite and vary compositionally from LREE-rich, to Ca- or Sr-rich. Magnesiofoitite contains low contents of LREE ([LREE]N/[HREE]N) ~ 0.2), yet significant amounts of U (0.2 - 3.7 ppm), Cr (2.9 - 110 ppm), V (65 - 260 ppm) and W (0.03 - 0.347 ppm). The low LREE in magnesiofoitite is consistent with its close proximity to LREE-rich APS, implying that the two minerals are contemporaneous. Some crystals of magnesiofoitite are essentially free of alkalis. Overall, low alkalis (<0.3 in apfu) and high U plus W in magnesiofoitite suggests that the fluids were acidic and oxidized in order to transport soluble complexes of U6+ and W6+. This fluid character is further supported by the coprecipitation of APS: significant Al solubility requires acidic fluids and the presence of SO4 2- confirms the oxidized nature of the fluids. The presence of these co-genetic minerals along the P2 structure suggests that the P2 fault was a conduit for uraniferous fluids; however, the fluids did not form uranium deposits all along the P2. The evidence further substantiates models in which the localization of large deposits required the focusing of an ascending reduced fluid to precipitate uraninite from the descending oxidized uraniferous fluid.
Résumé(Résumé en langage clair et simple, non publié)
L'Initiative géoscientifique ciblée (IGC-4) est un programme géoscientifique fédéral de collaboration qui fournit à l'industrie les connaissances géoscientifiques et les techniques novatrices de prochaine génération dont elle a besoin pour mieux détecter les gîtes minéraux enfouis, réduisant ainsi certains risques liés à l'exploration. Cette présentation résume les propriétés chimiques des minéraux d'altération précipités au cours des processus de minéralisation le long de la faille P2, qui renferme le gisement d'uranium dont la teneur est la plus élevée dans le monde (gisement de la rivière McArthur). Les résultats confirment les modèles existants de gisements, à savoir que des fluides uranifères oxydés ont pénétré dans la faille jusque dans les roches du socle, alors que la précipitation de l'uranium était contrôlée par la présence de milieux réducteurs dans le socle.
GEOSCAN ID293947