The area is underlain by quartz diorite to granodiorite of the Jurassic Cloudburst pluton of the Coast Plutonic Complex. The area to the west is overlain by basalt to rhyodacite flows and pyroclastics of the Tertiary Garibaldi Group. Also mapped in the area are pendants consisting of volcanics, sediments and greenstone of the Lower Cretaceous Gambier Group.

The main rock types in the Cheakamus Bridge occurrence area are porphyritic quartz diorite and hornblende diorite or amphibolite, or a migmatite complex. Andesitic to rhyodacitic intrusions are present, as are several near vertical lamprophyre and felsic dykes. The marginal phase zones have been strongly sheared and in places the rocks have schistose to gneissic textures.

Several sulphide mineral zones are have been exposed which generally occur near the contact between the more siliceous and the mafic rock formations. The main sulphide zone occurs as a light grey to buff sericitic schistose phase containing pyrite, chalcopyrite and other metallic minerals. One sample assayed 1.02 per cent copper, 10.29 grams per tonne silver and a trace of gold (Prospectus - Challenger Exploration Ltd., 1973).