The OYA showing is situated in an upper cirque basin approximately 3 kilometres north of Shazah Creek, and 4 kilometres upslope from Tulsequah River. Is is approximately 85 kilometres south of Atlin, B.C.
The area is underlain by a Paleozoic to Lower Triassic volcano- sedimentary belt which extends north-northwest and consists mainly of andesitic to felsic flows, tuffs, breccia, and minor sedimentary lime- stone, chert, and siltstone. These are intruded by a Tertiary- Cretaceous quartz monzonite pluton which is thought to be correlative with the Sloko Group volcanics. The volcano-sedimentary rocks have undergone regional greenschist facies metamorphism.
On the property the rocks are divided into two packages, one dominated by andesitic sediments and tuffs with prominent limestone intervals and the other dominated by felsic volcanic rocks mixed with volcanic-cherty-carbonate sediments. Massive and disseminated volcanogenic sulphides occur in both packages.
The property hosts one known zone of mineralization. Immediately below the glacier is a thick limestone unit which contains sphalerite- galena-pyrite-arsenopyrite-chert lenses up to 20 centimetres wide and 10 to 15 metres long which parallel the bedding. In 1981, two samples from this sulphide lens returned 20.9 grams per tonne gold, 2200 grams per tonne silver, 0.16 per cent copper, 16.6 per cent lead, 11.65 per cent zinc, 7.1 per cent arsenic, and 24 grams per tonne gold, 1887 grams per tonne silver, 0.13 per cent copper, 13.6 per cent lead, 9.85 per cent zinc, and 4.75 per cent arsenic, respectively (Assessment Report 9007).
Near the massive sulphides, several breccia lenses, up to 30 metres in length, occur. They consist of angular limestone clasts surrounded and partly replaced by pyrite-sphalerite-galena matrix. The breccias are thought to be the result of sulphide remobilization during deformation. Due west of the sulphide showing, the limestone is seamed with a stockwork of native sulphur veins and larger, malachite stained cherty veins.
Exploration work conducted by Ecstall Mining Corp. in 1990 rock sampled and soil geochemed the OYA showing area, referring to it as the North Zone. Best results came from a showing approximately 300 m southeast of the Oya showing. Here, a massive sulphide lens containing 40 - 50 per cent sulphides (TQCR-084, 085) consists of, in order of relative decreasing amounts, pyrite-sphalerite-galena-stibnite. The lens is bedding parallel to the host limestone and 20 metres long varying in width from 30 cm to 1 m wide. The contact with the adjacent limestone is abrupt although some wall rock mineralization consisting of minor pyrite-galena-sphalerite ( 1-3 per cent) occurs in the limestone. The mineralization in the limestone unit is probably the result of remobilization of sulphides from the adjacent dacite and andesite volcanics. At least three rock samples showed very encouraging results. A chip sample (TQCR-085) over 1.3 metres assayed 3.9 grams per tonne Au, 391 grams per tonne Ag, 0.04 per cent Cu, 2.18 per cent Pb, 2.85 per cent Zn and 0.83 per cent Sb (Assessment Report 20657).
