USING CL MICROSCOPY, CL SPECTROSCOPY, AND RAMAN SPECTROSCOPY TO DETERMINE THE EFFECTS OF RADIATION DAMAGE ON QUARTZ GRAINS IN A ROLL-FRONT URANIUM DEPOSIT

Radiation damage halos form in minerals such as quartz when exposed to natural sources of alpha particles. To test whether the presence of radiation halos in quartz can be used to vector towards roll-front uranium deposits hosted in clastic sediments, sandstone samples from the Three Crow deposit in Nebraska were investigated. CL microscopy was performed to detect radiation damage in quartz and to classify its textural context. The CL investigations revealed that radiation halos in quartz are common in the investigated sandstone samples. Orange CL halos commonly envelop mineral inclusions in quartz such as zircon or monazite. In addition, CL rims occur along the edges of individual quartz grains, in particular in samples collected closest to the roll-front. This suggests that radiation damage in quartz can be caused by the ore minerals, implying that the roll-front at Three Crow moves slowly enough to allow dosage accumulation. In addition to the CL microscopy, spectral CL measurements were carried out on both the radiation halos and the surrounding pristine portions of the quartz grains. The spectral CL investigations revealed an increase in the 650 nm band within the radiation halos, which is related to non-bridging oxygen hole centers in the quartz structure. Raman spectroscopy further indicated that the radiation halos in the quartz grains are typified by structural damage. The Raman peak at 465 cm^-1 shows a significant peak broadening within the radiation halos when compared to the pristine areas of the quartz grains. Both the CL and Raman characteristics of the radiation halos are in agreement with those observed on artificially irradiated natural and synthetic quartz.