The Cahill prospect occurs between Cahill and Sunset creeks, 4.5 to 5 kilometres east-northeast of Hedley.
The area between Cahill Creek and its south-flowing tributary, Sunset Creek, is underlain by massive andesitic crystal lithic ash tuff and siliceous ash tuff of the Upper Triassic Whistle Creek Formation (Nicola Group). These rocks are intruded by diorite and gabbro dikes and sills of the Early Jurassic Hedley Intrusions.
Up to a dozen shear zones striking 345 to 010 degrees and dipping 70 to 90 degrees are exposed in various old trenches and adits over an east-west distance of about 500 metres, between the two creeks, jut northeast of their confluence. The zones are up to 1 metre wide and cut fine grained, well-bedded, ash tuff and crystal lithic tuff, sometimes near or adjacent to diorite and gabbro dikes.
The zones contain massive to disseminated pyrrhotite, pyrite and chalcopyrite, sometimes in a quartz-carbonate gangue. Sphalerite is also evident in one of the shear zones. A sample from a shear zone containing massive to disseminated pyrite, pyrrhotite and chalcopyrite in green tuff contained 0.115 gram per tonne gold, 15.4 grams per tonne silver and 0.409 per cent copper (Assessment Report 14969, sample R83523).
Diamond drilling intersected hornfelsed and variably skarn-altered lithic tuffs and clastic sediments intruded by sills and dikes of porphyritic diorite. In a few instances, the original host units are totally replaced by a garnet-diopside-wollastonite skarn. These rocks are mineralized with pyrrhotite, pyrite, arsenopyrite and minor chalcopyrite. The zones of intense skarn alteration tend to be free of sulphides. One section of drill core assayed 3.57 grams per tonne gold over 2.7 metres (15.6-18.3 metres), and a second section assayed 8.50 grams per tonne gold over 0.91 metre (40.2-41.1 metres) (Property File - M.R. Sanford, 1987, page 22, hole BM86-1). The gold appears to be associated with arsenopyrite.
The property was extensively explored by Consolidated Sea Gold Corporation in 1986. The company completed geological, geophysical and soil surveys, trenching, sampling and 1259 metres of diamond drilling in 9 holes. In 1987, a follow-up exploration program was initiated to evaluate gold intersections from the 1986 program and additional geophysical surveys and drilling was completed. In 1995, Homestake Canada Inc. optioned the Cahill claims and completed 7 BQ diamond-drill holes totalling 947 metres. At the south end of the Cahill claims one hole (WW-95-6) was completed down to granodiorite basement. This hole returned 21.7 grams per tonne gold over 2.4 metres from a shear zone within a skarned package of volcaniclastic rocks. The favourable French/Hedley Formation was not intersected but could extend into the area. The possible intersection of this carbonate horizon and the gold feeder system represents an excellent exploration target.
