Geology Talk

Wed., Feb. 6, 2019 4:00 p.m. - Wed., Feb. 6, 2019 5:00 p.m.

Location: Classroom Building 130

Presenter: Mr. Moteza Rabiei，Ph.D Student in the Department of Geology at University of Regina

Topic: Comparison of fluid characteristics between uranium mineralization in the Patterson Lake Corridor and eastern Athabasca Basin

Abstract: It is generally agreed that the Unconformity-Related Uranium (URU) deposits in the Athabasca Basin formed from basinal brines derived from evaporated seawater under diagenetic-hydrothermal conditions. URU deposits formed where these brines interacted with the reduced fluids or lithologies in the basement along the intersections between the basal unconformity and basement-rooted reverse faults. Fluid inclusion analyses for the URU deposits in the eastern part of the Athabasca Basin indicate that two types of brines (NaCl-dominated and CaCl_2-dominated brines ) were involved during mineralization with salinities ranging from 25 to 35 wt% NaCl equivalent and the total homogenization temperatures from 120 to 200 ̊C. Preliminary fluid inclusion analyses of samples from the Patterson Lake area in the western part of the Athabasca Basin shows comparable characteristics for the ore fluids with those from the eastern part of the basin, suggesting a similar fluid history for both systems. However, in contrast to uranium deposits in the eastern part of the basin, the deposits in the Patterson Lake area are exclusively hosted in basement rocks and extend to significant depths (up to ~1 km) below the unconformity surface. Further study of the pressure, temperature and composition of the ore fluids in the Patterson Lake area is required in order to better understand the relationships between the mineralization systems in the western and eastern parts of the Athabasca Basin.

Petrographic studies indicate multiple phases of silicification in the Patterson Lake area. Drusy quartz veining is the main phase of silicification coexists with white mica, chlorite, and tourmaline, the dominant alteration minerals accompanying uranium mineralization. Petrographic studies on these quartz veins demonstrate the coexistence of liquid-dominated, vapor-dominated and vapor-only fluid inclusions in growth zones and individual fluid inclusion assemblages, suggesting fluid boiling, a feature that has also been documented from uranium deposits in the eastern part of the Athabasca Basin. Fluid inclusion analyses for the Patterson Lake area indicates salinities ranging from 24 to 26 wt% NaCl + CaCl₂ and the total homogenization temperatures from 80 ̊C to more than 250 ̊C. Our fluid inclusion data suggests that the uranium deposits along the Patterson Lake Corridor formed under conditions comparable to the deposits in the eastern part of the Athabasca Basin.

Co-Authors: Guoxiang Chi, Department of Geology, Univesrity of Regina; Eric Potter, Geology Survey of Canada, Ottawa, Ontario; Cameron Mackay, Scott Frosted, Purepoint Uranium Group Inc, Saskatoon; Ross McElroy, Raymond Ashley, Fission Uranium Crop, Kelowna, British Colombia