Poison Mountain porphyry copper-goldmolybdenum deposit, south-central British Columbia

Special Volume, Vol. SV 46, No. 1995, 1995

The Poison Mountain Cu-Au-Mo deposit, 90 km north of Lillooet, British Columbia, on the eastern edge of the Coast Plutonic Belt, is jointly hosted by hornfelsed Lower Cretaceous continental arenaceous sedimentary rocks and Late Paleocene stocks and dikes of biotite quartz diorite composition. Concentric zones of sulphide and minor oxide mineralization surround a barren, similar aged, central intrusion of granodiorite. The inner zone, characterized by fracture-controlled and disseminated sulphides and potassic alteration, is surrounded by an outer pyrite halo with magnetite, hematite, and minor phyllic and propylitic alteration. Six new K-Ar age determinations are presented, together with major and trace element analyses. The latter are compared to results from unaltered rocks outside the deposit, and with potassic alteration zones elsewhere. Environmental ore reserve, metallurgical mining and milling methodologic, and economic studies are summarized indicating that at present metal prices, the Poison Mountain deposit is sub-economic.

Keywords: Cu-Au-Mo deposit, Poison Mountain, Biotite quartz diorite, K-Ar age determination.