Selenium and Molybdenum Enrichment in Uranium Roll-Front Deposits of Wyoming and Colorado, USA - 2017

Uranium (Nuclear Minerals) / Exploration, Mining, Marketing, & Acquisitions

Bullock and Parnell reported 2017 that sandstone uranium (U) roll-front deposits of Wyoming and Colorado (USA) are important U resources, and may
provide a terrestrial source for critical accessory elements, such as selenium (Se), molybdenum (Mo), and tellurium (Te). Due to their associated toxicity, Mo-Se-Te occurrences in roll-fronts should also be carefully monitored during U leaching and ore processing. While elevated Mo-Se concentrations in roll-fronts are well established, very little is known about Te occurrence in such deposits. This study aims to establish Mo-Se-Te concentrations in Wyoming and Colorado roll-fronts, and assess the significance of these deposits in an environmental and mineral exploration context.

Sampled roll-front deposits, produced by oxidized groundwater transportation through a sandstone, show high Mo-Se content in specific redox zones, and low Te, relative to crustal means. High Se concentrations (up to 168 ppm) are restricted to a narrow band of alteration at the redox front. High Mo content (up to 115 ppm) is typically associated with the reduced mineralized nose and seepage zones of the roll-front, ahead of the U orebody. Elevated trace element concentrations are likely sourced from proximal granitic intrusions, tuffaceous deposits, and local pyritic mudstones. Elevated Mo-Se content in the sampled roll fronts may be regarded as a contaminant in U in-situ recovery and leaching processing, and may pose an environmental threat in groundwaters and soils, so extraction should be carefully monitored. The identification of peak concentrations of Mo-Se can also act as a pathfinder for the redox front of a roll-front, and help to isolate the U orebody, particularly in the absence of gamma signatures.