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Geology of the Ox Lake Cu - Mo porphyry deposit Richards, Gordon Gwyn

Abstract

The Ox Lake copper-molybdenum deposit is locallized in the margin and contact zone of a Late Cretaceous granodiorite porphyry. Hazelton Group rocks, including a lower Felsic Tuff, a middle Andesitic Tuff and an upper Sandstone-SiItstone, are country rocks in the area. The granodiorite porphyry is nearly circular in cross-section with a radius of 1500 feet and plunges fifty degrees west. Intrusive breccia occurs mainly along the southwestern contact of the porphyry. Nine vein types are grouped into four stages of vein development based on relative ages determined from vein intersections. They are: Stage I Potassic and Biotite Veins Stage II Propylitic and Pyrite-Chalcopyrite Veins Stage III Quartz-Molybdenite and Quartz Veins Stage IV Calcite, Gypsum and Sphalerite Veins Potassic, albitic, propylitic, sericitic and intermediate argillic alteration zones are related to host rock and position around the intrusion. In the east, an outer potassic alteration zone is separated from the intrusion by a zone of albitic-propylitic alteration. Three propylitic assemblages are distributed zonally about the intrusion. Sericitic and intermediate argillic alteration occur only in rocks of acidic composition. The intrusion is unaltered except within 100 feet of its western contact. Brecciated and unbrecciated hornfels west of the intrusion contains the highest and most persistent grades of copper and molybdenum--about 0.5 per cent copper and 0.02 per cent molybdenum. Within this zone, feldspar porphyry contains two to five times the molybdenum content and about one-half the copper content of adjacent andesitic rocks. The Ox Lake porphyry deposit is one of a group having similar geological features, that includes Len, Fab, Laura and Bergette deposits. All contain copper and molybdenum mineralization and have apparent K-Ar ages of 83 ± 3 my, except for the Bergette with an age of 76.7 ± 2.5 my [Carter and Harakal personal communication].

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