Graduate Student Seminar

Please join us for a graduate student seminar this Friday October 19 at 3:30 pm in rm 155 Geology, presented by Eli Wiens, MSc candidate:

Analysis of Radiation-induced defects in quartz along the unconformity of the Athabasca Basin

Radiation induced defects occur in quartz from the Athabasca Basin, and have been suggested to form due to exposure to uranium-bearing fluids when found in the absence of radioactive minerals. In this study, defect types and concentrations in detrital quartz along the unconformity were measured from 48 drill cores from across the basin, with 2 samples measured per core.

Partial dissolution experiments of 6 samples indicate that defects are concentrated in the exterior of sand grains. This suggests the defects mainly formed from poorly penetrative α-irradiation in the Athabasca Basin, and were not originally present in the detrital quartz. Overgrowth generations Qa and Q1 are also commonly present in this exterior zone. Detrital quartz with and without overgrowths was found to contain somewhat consistent defect types, which differ from drusy quartz defects. This suggests different responses to irradiation between quartz generations, consistent with other more localized studies.

Powder and single crystal measurements indicate a variety of known silicon-vacancy defects and an oxygen-vacancy defect, which were confirmed using simulations. The concentrations of these defect types are correlated and form a continuous distribution from low to high concentration, indicating exposure to radiation all across the unconformity surface. The defect concentrations do not appear to be closely related to nearby concentrations of radiogenic elements (based on 11 paired samples).