Radiation induced defects in quartz and applications to the Arrow uranium deposit in the Athabasca basin, Saskatchewan
Cerin, Daniele 1992-
This thesis presents the results of a combined electron paramagnetic resonance (EPR) and cathodoluminescence (CL) study of quartz from the Arrow uranium deposit and its surrounding areas in the southwest margin of the Athabasca basin, Saskatchewan. Detailed EPR analyses of quartz samples from both the basement and the overlying sandstones revealed the presence of a host of different paramagnetic defects (i.e., oxygen vacancy electron centers and silicon vacancy hole centers) previously observed in quartz from the eastern part of the Athabasca basin. The silicon vacancy hole centers were previously shown to have formed from bombardment of alpha particles emitted from the decay series of ^238U, ^235U and ^232Th. Characteristic spectral differences have been observed between quartz from different lithologies, such as the lack of the H'_3 centers in basement quartz. Thermal annealing and neutron irradiation experiments suggest that these spectral differences are linked with different diamagnetic precursors, which might be related to growth defects formed during crystallization. Of the four different types of drusy quartz (translucent, milky, pink and smoky) identified in the basement at the Arrow deposit, only the pink and smoky types contain significant concentrations of paramagnetic defects. Blue quartz in metasedimentary rocks from the basement is characterized by low concentrations of radiation induced defects, suggesting no pervasive uranium-bearing fluids in the basement. Quartz of high EPR intensities is restricted to ~7 m from mineralized areas, confirming the structurally controlled nature of uranium-bearing fluids. CL imaging and spectral analyses also confirmed the EPR results that the translucent and milky types of quartz contain only low levels of radiation induced defects. Smoky quartz with elevated radiation induced defects as revealed by EPR, on the other hand, is characterized by characteristic CL halos and patches associated with uranium-rich minerals and often features well-developed continuous rims, which cross-cut the growth zoning of quartz crystals and apparently suggests remobilization of uranium after quartz crystallization. Pink quartz with elevated radiation induced defects as revealed by EPR does not have the characteristic CL halos, patches or continuous rims, suggesting a homogeneous distribution of radiation induced defects in this type of quartz and pointing to their formation during crystallization from a uranium-bearing fluid. This result, combined with the common occurrence of pink quartz in veins and breccias associated with dravite alteration, suggests that this uranium-bearing fluid might represent the main mineralization event at the Arrow deposit. The intensities and distribution of alpha-particles-induced defects in detrital quartz close to the sandstone-basement unconformity suggest that uranium-bearing fluids at the Arrow deposit are restricted to the areas immediately above the basement-hosted mineralization. This distribution, together with the low radiation induced defects in detrital quartz, suggests that the basinal fluid along the sandstone-basement unconformity at the Arrow deposit, if present, was low in uranium, which was mainly transported in basement fluids. The present results further support the suggestion that combined EPR and CL analyses of radiation induced defects in quartz is a powerful tool for the exploration of uranium deposits in the Athabasca basin.
DegreeMaster of Science (M.Sc.)
CommitteeMerriam, Jim; Ansdell, Kevin; Yao, Yansun
Copyright DateDecember 2016
Uranium, Quartz, EPR