Geochemistry of Carboniferous peralkaline felsic volcanic rocks, central New Brunswick, Canada: examination of uranium potential
DOI:
https://doi.org/10.4138/atlgeol.2010.010Keywords:
rhyolite, mantle plume, uraniumAbstract
Felsic volcanic rocks from the ca. 335 Ma Cumberland Hill Formation of southern New Brunswick consist of peralkaline rhyolite and trachyte. These rocks are interpreted to have undergone extensive fractional crystallization from an alkali basaltic magma, although their different geochemical signatures indicate that the rhyolite was not derived from the trachyte via continuous fractional crystallization. The rhyolite is highly enriched in incompatible trace elements including uranium (up to ca. 20 ppm). Cumberland Hill peralkaline rhyolite suggests that a potentially economic source of uranium exists in the basin, based on the elevated uranium concentrations and high potential for remobilization into surrounding sedimentary units. RÉSUMÉ Les roches volcaniques felsiques de la Formation de Cumberland Hill, au sud du Nouveau-Brunswick, dont l’origine remonte à quelque 335 Ma se composent de rhyolite et de trachyte hyperalcalines. On estime que ces roches ont subi une cristallisation fractionnée intense à partir d’un magma de basalte alcalin, même si leurs diverses signatures géochimiques indiquent que la rhyolite n’est pas issue de la trachyte par un processus permanent de cristallisation fractionnée. La rhyolite est fortement enrichie d’éléments traces incompatibles, au nombre duquel se trouve de l’uranium (concentration qui peut atteindre environ 20 ppm). Si l’on se fie aux fortes concentrations d’uranium et à la grande possibilité de remobilisation dans les unités sédimentaires environnantes, la présence de la rhyolite hyperalcaline dans la Formation de Cumberland Hill porte à croire que le bassin pourrait contenir une source d’uranium vraisemblablement rentable.[Traduit par la redaction]Published
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