The Arrow Uranium Zone, a Rapidly Emerging Discovery - NexGen Energy Ltd.
*Note - this talk is on MONDAY September 14 at 4 pm
The Arrow uranium zone (“Arrow”) was discovered in February 2014 by NexGen Energy Limited (“NexGen”) at its Rook I property in the southwest Athabasca Basin, northern Saskatchewan. A total of 60 diamond drill holes totaling approximately 48,000 m have been drilled into Arrow to date, 58 of these having intersected uranium mineralization. The highest individual geochemical assay of 70.0% U3O8 over 1.0 m in drill hole AR-14-44b continues to confirm the high-grade nature of uranium mineralization at Arrow. Arrow is a basement-hosted, structurally-controlled, and hydrothermally-altered system located within the Patterson Lake Conductive Corridor (“PLCC”). The PLCC constitutes a series of 4 to 5 “discrete” parallel northeast-trending electromagnetic (EM) conductors hosting the: Arrow discovery, Bow discovery, Spitfire discovery (Purpoint/Cameco) and the Triple R Deposit (Fission). Uranium mineralization at Arrow is associated with numerous sub-vertical graphitic mylonitic zones contained within a 635 m strike length, 215 m width, with a depth extent from 100 m below surface to 900 m below surface, and remains open in all directions.
There are four sedimentary sequences uncomformably overlying the crystalline basement rocks: i) Quaternary glacial tills, ii) Cretaceous sandstone, mudstone and siltstone beds, iii) Devonian sediments of the La Loche Formation, and iv) Helikian-aged Athabasca sandstone of the Manitou Falls “A” member. The basement metamorphic assemblages are part of the Taltson Domain (e.g., East Lloyd Domain). The basement hosting Arrow mineralization is comprised of a major package of variable coarse-grained quartz-rich psammitic to semi-pelitic gneisses and granofels that are occasionally intercalated with relatively narrow graphitic mylonite zones. Uranium has been concentrated locally within the graphitic shears and on either side of the structures in splay offsets. Clay alteration is the most widespread alteration style observed at Arrow and proximal to high-grade mineralization. Hematite alteration is generally limited to a paleoweathering profile intersected immediately at the unconformity and down to approximately 50 m depth, or as local association with uranium mineralization as a part of redox fronts. Late hydraulic structures provide space for multiple dravite alteration events, with intermittent association of remobilized uranium mineralization.
A variety of mineralization styles occur at Arrow, which include disseminated nodules and flecks, fracture face linings, micro-stockworks, quartz-carbonate-uranium network vein complexes, “worm rock” or redox fronts, and massive to semi-massive veins and pods. The main uranium-bearing mineral present is uraninite, which is frequently partially altered to coffinite. A minor late stage of coffinite also exists.
Currently there is a 30,000 m drill program on-going on the Rook I property with focus on resource drilling on the Arrow Zone. The resource targeting has been aided by using the Devico Directional Drilling System operated by Tech Directional. The use of Devico has increased pierce point accuracy and the efficiency of drill meters all while minimizing the environmental footprint in achieving multiple pierce points from a single collar.
The Arrow discovery shines a light on the currently emerging southwest Athabasca Basin while adding to the potential for additional high-grade uranium discoveries to be made along the numerous prospective EM conductive corridors within the southwest Athabasca Basin.
Garrett Ainsworth, BSc, PGeo
Vice President, Exploration & Development - NexGen Energy Ltd