The Tarn Creek occurrence is located approximately 4 kilometres north-northeast of the west end of Yohetta Lake. The valley at this location is referred to as Tarn Creek.
The valley is largely underlain by volcanic lithologies of Upper Cretaceous volcanics dominated by feldspar-hornblende porphyry flows and associated volcanic lithic fragmental rocks. A variety of dikes and irregularly shaped bodies of hornblende diorite porphyry intrude the volcanics on both sides of the valley. Quartz and/or carbonate alteration zones are common adjacent to the intrusives. Propylitic alteration in the volcanics has produced carbonate, epidote and chlorite as complete replacements of, or irregular haloes around, feldspar and hornblende phenocrysts. Argillic alteration or silicification are locally present.
Locally, a discontinuously exposed gossanous zone, covering an area of approximately 400 by 150 metres, surrounds a strongly developed quartz stockwork zone. Within this zone chalcopyrite, bornite, pyrrhotite and pyrite mineralization occurs in veinlets, as fracture coatings and as disseminations throughout all rock types. Magnetite and chlorite are common accessory minerals. The highest copper-gold values occur within fractured, chlorite-epidote– altered volcanic rocks peripheral to a chalcopyrite-bornite– mineralized quartz-hornblende-feldspar diorite with in a large zone of propylitic to argillic alteration.
Selected rock-chip samples from this zone assayed from 0.02 to 0.05 per cent copper, some with anomalous (3.0 grams per tonne) silver values (Bulletin 81). In 1992, float samples yielded up to 1.66 per cent copper and 0.48 gram per tonne gold, while values up to 0.55 per cent copper and 0.137 gram per tonne gold were obtained from bedrock samples taken from the valley floor (Assessment Report 22161).
In 1986, a program of prospecting and soil sampling was completed on the area as the Tarn 1-2 claims. In 1991 and 1992, programs of rock sampling, geological mapping and a ground magnetic and electromagnetic survey was completed by Bellex Mining.
