Rio Aspen claim is underlain by Lower to Middle Jurassic Hazelton Group volcanics intruded by the Cretaceous Bulkley Intru- sion which is comprised of medium-grained, equigranular grano- diorite stock and quartz-monzonite. These rocks are unconformably overlain by Upper Jurassic to Lower Cretaceous Bowser Group sedi- ments. The Hazelton volcanics consist of a basal intermediate volcanic flow overlain by dacite and rhyodacite, followed by 10 metres of tuff which is overlain by massive andesite, andesitic flows and tuff. The sediments are in contact with the volcanics at elevation 1430 metres and strikes slightly south of east and dips 40 degrees north.

A narrow mineralized zone between 1970 to 2010 metres eleva- tion was prospected. The zone occurs in fine-grained granodiorite along a fault 5 centimetres in width. Jones (Geological Survey of Canada Summary Report, 1925) describes the showing as a sheared zone striking 040 degrees and dipping 43 degrees southeast in andesitic flows and breccia. The shear at the surface shows mineralization in the form of stringers containing galena, sphalerite, arsenopyrite and pyrite. In 1913, 1.8 tonnes of ore were shipped and assayed 44.11 grams per tonne gold, 2897 grams per tonne silver and 7 per cent copper (Minister of Mines Annual Report 1934, page C8).