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.
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 main granodiorite pluton (Klinaklini pluton) has been assigned to the Late Cretaceous to Paleocene Bendor suite. Small granodiorite stocks underlying the VB, A & E and PW prospects are assigned to the Eocene Mission Ridge suite.
Ground observations recorded the oldest rock as gneissic granite or granodiorite porphyry intruded by biotite granite, the most abundant rock, and a 120- to 300-metre wide dike-like body of coarse-grained biotite granite to granodiorite porphyry, apparently emanating from a stock (Mission Ridge Suite?) to the east. Several phases of dikes are also reported, 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 dikes. The main area of mineralization is at the intersection of these two fault systems, where there is much fracturing, dike 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 dikes. 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).
In 1974, Cities Service Minerals Corporation collected 89 rock and 49 soils samples from their PW group of claims (Assessment Report 5494). Detailed mapping was also completed. Results showed a zone of coincident copper and molybdenum. This anomaly was reported to occur at the junction of two faults systems and is marked by a very strongly leached out area of shattering, silicification and pyritization. Molybdenite has been observed as fracture filling sheets and hairline fractures. In 1980, John Mirko and Mel de Quadros spent 5 days investigating the PW prospect which they held the Keno 1 to 4 claims (Assessment Report 9158).
See VB (092N 013) and A & E (092N 032) for related geological and work history details.
