Targeted Geoscience Initiative 5: integrated multidisciplinary studies of unconformity-related uranium deposits from the Patterson Lake corridor, northern Saskatchewan

Abstract

Basement-hosted uranium deposits of the Patterson Lake corridor are located on the southwestern margin of the Athabasca Basin in atypical hosts: altered and metamorphosed granite, granodiorite, and ultramafic to mafic rocks. Fluid inclusions record incursion of two fluids, NaCl- and CaCl2-dominant, at temperatures up to 250°C and approximately 1 km into the basement during episodic brittle reactivation of high-strain-ductile to brittle-ductile structures, in particular late west- and north-northwest-striking brittle conjugate faults that crosscut the Athabasca sandstone. Isotopic data from pyrite and tourmaline record basinal fluid-rock interactions under fluctuating pressure and oxidizing to reducing conditions. New 3-D geophysical modelling illustrates linkages between the surface architecture and lower crust to mantle and influence of the Clearwater Domain granitic intrusions on the ore systems. High radiogenic heat production from these intrusions and other ca. 1.8 Ga felsic intrusions contributed to a prolonged, elevated geothermal gradient under the Proterozoic basins that permitted shallow (less than 3 km) depths of mineralization.

Deep learning based one-dimensional inversion of magnetotelluric data, and an application in the southwestern Athabasca Basin, Canada

“…The shallow layers shows the resistivity increasing to a depth of ~ 1 km corresponding to the thickness of the Athabasca Supergroup cover (Tschirhart et al, 2021). The predicted response using the CNN inversion matches the resistivity variant trend shown by a previous 2D inversions (Potter et al, 2020) at some points, particularly at depths less than 20 km, which is reasonable for the potential accuracy of a one dimensional study.…”

Deep Geological Controls on Formation of the Highest‐Grade Uranium Deposits in the World: Magnetotelluric Imaging of Unconformity‐Related Systems From the Athabasca Basin, Canada

“…Coincident gravity modeling (Figures 3a and 3b) further emphasizes the breadth of the intrusion, and its continuation from the surface to ∼22 km of depth below the Arrow deposit. A key to the high-grade nature of the deposits in the PLC may be the sustained elevated radiogenic heat from the voluminous Clearwater granites (Potter et al, 2020) driving fluid flow along semi-brittle structural corridors, as well as providing a source of uranium which would have been leached by the circulating basinal brines and hydrothermal fluids along faults that cut the body (Figure 3c). An analog to this model are the hot springs located along major fault systems in the 100 to 60 Ma Idaho batholith (Bennett, 1980;Bennett & Knowles, 1985;Fyfe, 1973;Hyndman, 1981) and surrounding Paleogene granites (Young, 1985).…”

Hydrodynamic Links between Shallow and Deep Mineralization Systems and Implications for Deep Mineral Exploration

“…These deposits are mostly located near the unconformity between the basin and the underlying Archean and Paleoproterozoic metamorphic rocks, and are named unconformity-related uranium (URU) deposits (Jefferson et al, 2007;Kyser and Cuney, 2015). However, some of the orebodies may extend to ~1 km below the unconformity (Potter et al, 2020;Rabiei et al, 2021). All the deposits are controlled by reactivated basement faults crosscutting and reversely offsetting the unconformity surface, and many of these faults are developed within graphitic lithologies (Jefferson et al, 2007;Kyser and Cuney, 2015;Potter et al, 2020).…”

“…However, some of the orebodies may extend to ~1 km below the unconformity (Potter et al, 2020;Rabiei et al, 2021). All the deposits are controlled by reactivated basement faults crosscutting and reversely offsetting the unconformity surface, and many of these faults are developed within graphitic lithologies (Jefferson et al, 2007;Kyser and Cuney, 2015;Potter et al, 2020). The URU deposits have been broadly classified into two types, one that is mainly developed above the unconformity, polymetallic (containing Ni-Co-Cu-As in addition to U) and has a broad alteration halo suggesting an egress fluid flow, and the other that is developed within the basement, monometallic (U) and has a narrow alteration halo indicating an ingress fluid flow (Jefferson et al, 2007).…”

“…Moreover, they have been preferably reactivated after the deposition of the Athabasca basin due to increased fluid pressure and geothermal gradients imposed by the deep processes. Thus, they are considered as having played a critical role in connecting the sites of mineralization near the unconformity with deep-seated heat source and reducing agents (Chi et al, 2018;Ledru, 2019;Potter et al, 2020). The coupling of these deep-seated processes with the development of uraniferous brines within the basin is the critical factor for the rich endowment of U deposits in the Athabasca Basin (Chi et al, 2019a, b).…”