The PW occurrence is characterized by fracture-controlled molybdenite mineralization at the intersection of two fault systems in strongly altered intrusive rocks, 46 kilometres southwest of the community of Tatla Lake.
The area is underlain by a complex suite of gneisses and intrusions of the Klinaklini pluton of the Jurassic to Tertiary Coast Plutonic Complex (Geological Survey of Canada Open File 1163). The oldest rock is gneissic granite or granodiorite porphyry. This is intruded by biotite granite, the most abundant rock, and a 120 to 300- metre wide dyke-like body of coarse-grained biotite granite to granodiorite porphyry, which apparently emanates from a stock to the east. Several phases of dykes are also present, consisting of quartz-eye monzonite porphyry, andesite, aplite and monzonite.
Two main fault systems are present. A northwest-striking fault set, partly marked by dyke intrusion, generally separates the biotite granite from the granite-granodiorite porphyry to the northeast. A probably younger set of faults strikes north-northeast, and is also marked by dykes.
The main area of mineralization is at the intersection of these two fault systems, where there is much fracturing, dyke intrusion, and hydrothermal alteration. Alteration is primarily silicification, pyritization (usually about 3 per cent pyrite), oxidation, and leaching; there is also sporadic biotite, potassium feldspar and sericite. Oxidation has produced limonite and ferrimolybdite.
Mineralization is mainly hosted in the granite-granodiorite porphyry, which is locally capped by iron oxide and moderate to strong clay-silica alteration, and in narrow, randomly-oriented aplitic dykes. Significant molybdenite is present with minor pyrite in numerous quartz veins, 10 to 90 centimetres thick, hairline fractures, and vugs or fracture-fillings associated with quartz, biotite and potassium feldspar. Chalcopyrite-bearing fracture-fillings are also reported (Assessment Report 5494). A quartz vein about 300 metres east of the main mineralization contains scheelite; assay values of 0.09 per cent (oxide of) tungsten and 0.2 per cent molybdenum are reported (Assessment Report 9158).