The Patterson Lake corridor of Saskatchewan, Canada: defining crystalline rocks in a deep-seated structure that hosts a giant, high-grade Proterozoic unconformity uranium system

Abstract

The Patterson Lake corridor in the Athabasca Basin region of Saskatchewan, Canada, hosts a large-scale uranium system with two major deposits already delineated. The corridor developed in crystalline rocks of the SW Rae Province, which host all of the known uranium endowment. Orthogneisses along with voluminous pegmatites are the hosts of the uranium mineralization. These rocks, however, underwent significant open-system metasomatic–hydrothermal modification. Principal amongst these alterations is early and pervasive quartz flooding that resulted in the development of widespread secondary quartzites and associated rock types. These secondary quartzites and their altered host rocks suffered ductile deformation, typically focused at silicification fronts. Late carbonatite dykes exploited the associated shear zones. Semi-brittle deformation zones nucleated near the previously developed ductile high-strain zones. Graphite and associated iron-sulfides precipitated in a semi-brittle structural regime. These graphitized zones provided the necessary structural architecture to focus the uranium system, which exploited the conduit hundreds of millions of years later at c. 1.425 Ga. Host rocks of the Patterson Lake corridor prove that metasedimentary rocks are not a requirement for the development of giant Proterozoic unconformity uranium deposits. Crustal-scale fault zones with access to the mantle (i.e. carbonatites) should be considered a key parameter in the exploration model for Proterozoic unconformity uranium deposits. Given the similarity of the mineral assemblages in the crystalline basement rocks of the main exploration corridor in the eastern Athabasca Basin region, it is likely that a similar, cryptic geological boundary focused the giant uranium system in that region. Thematic collection: This article is part of the Uranium Fluid Pathways collection available at: https://www.lyellcollection.org/cc/uranium-fluid-pathways