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Petrology and structure of the Tuzo Creek Molybdenite Prospect near Penticton, British Columbia. Leary, George Merlin


The Tuzo Creek Molybdenite Prospect is in southern British Columbia approximately twenty air-miles east-southeast of Penticton within the Nelson-Valhalla batholithic complex. A stock of porphyritic quartz monzonite, approximately 1½ miles in diameter, and younger sub-volcanic sills, dykes and masses of quartz-albite-sanidine porphyry were eraplaced into a basement of Nelson granodiorite of probable Jurassic Age. Mid (?) Tertiary alkaline basic dykes are the youngest intrusions present. Porphyries were emplaced successively at three different times along structures developed either by subsidence of the stock or by regional deformation. Differentiation, level of crystallization of phenocrysts, level of emplacement and regional correlation of acid intrusions are discussed. Two phases of hydrothermal activity are recognized, separated in time by intrusions of porphyry. In both cases, alteration was controlled by fractures and local shear and breccia zones. The first phase resulted in widespread wallrock alteration, quartz veining and mineralization throughout most of the stock and bodies of pre-mineral porphyry. Zoning of argillization, potash feldspathization and silicification and of oxide or sulphide fields of mineralization occurs on a large scale throughout the alteration halo. A large zone of low grade molybdenite mineralization occurs in a zone of more intense wallrock alteration containing stockworks of quartz veins and pyrite. The chemical and physical aspects of wallrock alteration and mineralization are considered in light of experimental studies done by others. The second phase of hydrothermal activity only occurred locally and involved development of secondary sericite and quartz with associated Zn, Pb, Cu, Pe and Mo sulphides and calcite and fluorite. All structures can be explained either by periods of subsidence of the stock or by genetic relationship to forces developed by periodic movements along a nearby regional fault zone following the West Kettle River valley. Source rocks of hydrothermal fluids, paragenesis, zoning and exploration potential for molybdenite are discussed.

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