Abstract: The Sato prospect is located between Aishihik Lake and Long Lake in southwestern Yukon Territory. Low grade porphyry-style copper mineralization was discovered on the property in 1969. The main country rock in the study area is a potassium feldspar megacrystic granite that is correlated with the Early Jurassic Aishihik and/or Long Lake plutonic suite. Mineralization on the property is hosted by a multiphase intrusive complex that is thought to represent a high level intrusive member of the Late Cretaceous Mount Creedon volcanic suite. The complex consists of three distinct phases, medium-grained diorite; coarse-grained diorite; and porphyritic quartz monzodiorite. U-Pb zircon dating of the medium-grained diorite and porphyritic quartz monzodiorite phases gives ages of 78.2 ± 0.1 Ma and 78.8 ± 0.2 Ma, respectively, which supports the correlation with the Mount Creedon Volcanic Suite.

Four alteration zones are recognized on the property. Alteration is mainly developed in the medium-grained diorite and quartz monzodiorite phases. In order of decreasing intensity, these zones include potassic, phyllic, albitic, and propylitic. Copper mineralization consists of chalcopyrite, which occurs as a replacement of earlier-formed magnetite in the potassic and phyllic zones, and malachite which occurs on weathered fracture surfaces.

Alteration and mineralization on the property are thought to be related either to fluids evolved during the latest stages of crystallization of the main phase diorite unit or from a buried, younger phase of the intrusive complex.

Authors: Lewis, J. and Mortensen, J.

NTS Mapsheet(s): 115I, 115J

Citation: Lewis, J. and Mortensen, J., 1998. Geology, alteration, and mineralization of the Sato porphyry copper prospect, southwestern Yukon. In: Yukon Exploration and Geology 1997, Roots, C.F. (ed.), Indian & Northern Affairs Canada/Department of Indian & Northern Development: Exploration & Geological Services Division, p. 153-160.