SGS Seminar Series - Dan Ferguson, MSc Candidate, University of Regina - The Midwest Uranium Deposit

Thu., Oct. 27, 2022 12:00 p.m. - Thu., Oct. 27, 2022 1:00 p.m.

Location: Bushwakker Brewpub, 2206 Dewdney Ave, Regina

Speaker: Dan Ferguson, MSc Candidate, University of Regina

Location: Live in person at Bushwakker Brewpub, 2206 Dewdney Ave, Regina

Remote option via Zoom: https://uregina-ca.zoom.us/j/99749985253?pwd=dFZwNDI4OW12dzBWcmdtdUtqb0JZUT09

**Please RSVP if you would like lunch by noon on Tuesday. Contact Brendan Bishop at bab495@uregina.ca to RSVP. The cost for lunch is $20 and $10 for students.**

Title: The Midwest uranium deposit: a "modèle réduit" for polymetallic mineralization in the Athabasca Basin

Abstract: The Midwest deposit is a classic example of an unconformity-related uranium deposit in the Athabasca Basin but is more compact compared to world famous deposits like McArthur River or Cigar Lake. The deposit is polymetallic, containing elevated concentrations of Co, Ni, and As in addition to U. High-grade polymetallic ores are hosted predominantly along the unconformity between the underlying crystalline basement and overlying conglomeratic sandstones. Petrographic observations of ore textures and cross-cutting relationships indicate a complex, multi-stage paragenesis characterized by an initial phase of primary mineralization followed by at least two episodes of ore reworking. Three distinct generations of uraninite have been identified, with each generation separated by Ni-Co arsenide and sulfarsenide deposition. This sequence of mineral precipitation is consistent with geochemical path modelling involving mixing between an oxidizing, U-bearing fluid and a relatively reducing Ni-Co-As-bearing fluid. Bi-phase, liquid-dominated aqueous fluid inclusions from drusy quartz veins spatially related to mineralization are the target of microthermometric experiments, Raman spectroscopy, and LA-ICP-MS. Microthermometric experiments indicate that the fluid may be characterized by the H2O-NaCl-CaCl2 system, which was verified using cryogenic Raman spectroscopy. Microthermometric heating and freezing runs indicate the fluid salinities are between 22 and 29 wt.% NaCl equivalent, and that individual inclusions contain brines varying from NaCl-dominated to CaCl2-dominated. LA-ICP-MS analyses were used to determine the minor and trace element composition of the contained fluid. The relationship expressed between the main monovalent and divalent cations indicate that the CaCl2-rich brine was derived from the NaCl-rich brine through fluid-rock interactions. The results from Midwest are typical of an URU deposit hosted in the Athabasca Basin. Mineralogical, geochronological, and fluid inclusion study suggests the mineralization at Midwest is the product of a cyclic and long-lived hydrothermal system.

Speaker biography: Dan is currently a graduate student at the University of Regina, studying uranium mineralization in the Athabasca Basin. He completed his B.Sc. in Geology at the U of R in 2020 and will be completing his M.Sc. in early 2023. His interests lie in ore-forming processes and sediment-hosted ore deposits and he has spent the past two field seasons exploring for Rare Earth Elements in northern Saskatchewan.