Geology Seminar Series - Daniel Ferguson

Wed., Mar. 10, 2021 4:00 p.m. - Wed., Mar. 10, 2021 5:00 p.m.

Location: https://uregina-ca.zoom.us/j/6741541667

Title: Petrographic, paragenetic, and fluid inclusion study of uranium mineralization along the Midwest Trend, northeastern Athabasca Basin, Saskatchewan

Speaker: Daniel Ferguson, M.Sc. Student, University of Regina

Abstract:

The Athabasca Basin is host to a number of world-class unconformity-related uranium (URU) deposits, and is currently Canada’s sole U-producing district. The first discovery of high-grade ore was in 1968 at Rabbit Lake, but several significant discoveries have been made in the decades that followed. Exploration has been focussed on the eastern side of the basin, overlying the transition zone between the Wollaston and Mudjatik domains of the Churchill Province. More recent exploration has expanded to the south-central and western portions of the basin, with the most notable discoveries being the Phoenix/Gryphon, Triple R, Arrow, and Fox Lake deposits. As exploration shifts to progressively deeper targets, it is of utmost importance that our understanding of the formation of these deposits continue to be developed and improved.

The current genetic model for URU formation involves U transport by oxidized basinal fluids and the precipitation of ore at , or near, the intersection of reactivated basement structures and the unconformity. This genetic model has been successfully applied in U exploration, leading to the discovery of a number of high-grade deposits. However, there is a lack of understanding regarding what factors determine whether a basement fault will be mineralized or non-mineralized. The number of basement faults which are non-mineralized outnumber those which are host to ore, and areas displaying alteration similar to that associated with URU deposits are un-mineralized. The availability of reducing agents, such as graphitic lithologies, has been proposed as a determining factor but many such lithologies are barren. The availability of U-rich fluids to the site of mineralization has also been proposed to be critical, but evidence of U-enriched fluids has been found distal to mineralization.

The proposed research aims to address these issues through a geological and geochemical investigation of the Midwest Trend located on the eastern margin of the Athabasca Basin. The Midwest Trend comprises a reactivated basement fault zone that has offset the unconformity surface with reverse displacement and is host to two U deposits, the Midwest Main and Midwest A, separated by a barren zone containing only minor U occurrences. The Midwest Trend can be considered a “modèle réduit” for U mineralization in the Athabasca Basin, because it displays geological features characteristic to URU deposits, but in a more compact deposit size. The Midwest deposits are hosted below and at the unconformity, with a minor amount that is perched above the unconformity, and are separated by three kilometers of barren structure. The relationship between mineralization and non- mineralization along this structure presents a unique opportunity to study shared and unique features among the mineralized and barren portions of the structure.

The ultimate goal of this research is to determine which factors control mineralization and non-mineralization along the Midwest Trend. If the factors critical to formation of ore can beidentified, they can then be used to predict potential sites of mineralization elsewhere in the basin. This research will be of specific interest to the U exploration industry, as it can be used to more efficiently identify high-grade targets for future U exploration campaigns.