The GAR (Sylvan 1) occurrence is located on a north-facing slope, east of Angus Creek and approximately 3.6 kilometres southeast of its junction with Hellroaring Creek.
Regionally, the area is underlain by Mesoproterozoic rocks of the Purcell Supergroup, including the lower members up-sequence of the Aldridge, Creston and Kitchener formations. Included within the sedimentary package are primarily sills but also dikes of the gabbroic Moyie Intrusions. The quartzite-dominated turbidites of the Aldridge Formation give way to quartzites and siltstones of the Creston Formation. Granitic intrusives in the region are of two distinct ages and are very dissimilar. Proterozoic pegmatites of the Hellroaring Creek assemblage form sills, dikes, and small stocks that only intrude the Aldridge Formation. Much younger, likely Cretaceous, stocks such as the Angus Creek stock are composed of granodiorite to quartz monzonite.
Locally, silicified sediments (quartzite and argillite) and an altered diorite, near the intersection of the Grassy Mountain and St. Mary’s faults, host quartz veins with precious and base metal values. Aplite dikes are also reported in the area, while the diorite also hosts disseminated pyrite. Diamond drilling has identified massive pyrite pods or lenses, up to 30 centimetres wide, and 0.4-metre wide “blood red” gouge material assumed to be the St. Mary’s fault. Galena mineralization is also reported.
In 1989, a rock sample (Angus No.3) assayed 9.7 grams per tonne gold and 276.3 grams per tonne silver, whereas another sample (No. 5-M) assayed 884.1 grams per tonne silver and 55.14 per cent lead (Assessment Report 18708).
The area has been historically explored in conjunction with the nearby Leader A (MINFILE 082FNE060) occurrence. In 1983, Hawk Resources completed a ground electromagnetic survey on the area as the Leader 2 claim. In 1985, Geotech Resources and Tunstall Resources completed a program of soil sampling and ground electromagnetic surveys on the area as the Well claims. In 1989 and 1990, programs of prospecting, sampling and trenching and three drill holes, totalling 53.0 metres, were completed on the area as the Sylvan 1 claim. During 1998 through 2002, programs of prospecting, rock sampling and geological mapping and a 9.3 line-kilometre ground electromagnetic survey were completed on the area as Intrepid and Tick claims. In 2007, Ruby Red Resources prospected and soil sampled the area. In 2009, a further program of soil and rock sampling and geological mapping was completed.