Structural evolution and related implications for uranium mineralization in the Patterson Lake corridor, southwestern Athabasca Basin, Saskatchewan, Canada

Abstract

The Patterson Lake corridor is situated along the SW margin of the Athabasca Basin and contains several basement-hosted uranium deposits and prospects. Drill core investigations during this study have determined that granite, granodiorite, mafic and alkali intrusive basement rocks are entrained in a deep-seated NE-striking subvertical heterogeneous high-strain zone defined by anastomosing ductile to semi-brittle shears and brittle faults. The earliest phases of ductile deformation (D 1 /D 2 ), linked with Taltson (1.94–1.92 Ga) orogenesis, involved interference between early fold sets (F 1 /F 2 ) and development of an associated ductile transposition foliation (S 1 /S 2 ). During subsequent Snowbird ( c. 1.91–1.90 Ga) tectonism, this composite foliation was re-folded (D 3 ) by NE-trending buckle-style folds (F 3 ), including a regional fold centred on the Clearwater aeromagnetic high. In continuum with D 3 , a network of dextral-reverse chloritic-graphitic shears, with C–S geometry, formed initially (D 4a ) and progressed to more discrete, spaced semi-brittle structures (D 4b ; c. 1.900–1.819 Ga). Basin development (D 5a ; < c. 1.819 Ga) was marked by a set of north-striking normal faults and related east- and NE-striking transfer faults that accommodated subsidence. Primary uranium mineralization (D 5b ; c . 1.45 Ga) was facilitated by brittle reactivation of NE-striking basement shears in response to WSW–ENE-directed compressional stress ( σ 1 ). Uraninite was emplaced along σ 1 -parallel extension fractures and dilational zones formed at linkages between NE- and ENE-striking dextral strike-slip faults. Uranium remobilization (D 5c ) occurred after σ 1 shifted to WNW–ESE, giving rise to regional east- and SE-striking conjugate faults, along which mafic dykes (1.27 and 1.16 Ga) intruded. Thematic collection: This article is part of the Uranium Fluid Pathways collection available at: https://www.lyellcollection.org/cc/uranium-fluid-pathways