The Cretaceous Horsethief Batholith intrudes Middle Proterozoic sediments of the Purcell Supergroup. The intrusion is zoned from fine-grained/medium-grained granodiorite to coarse-grained quartz monzonite. East trending aplite dykes cut the intrusion.

Molybdenite occurs in at least three outcrops within 500 metres of each other on the upper reaches of Welsh Creek. The three showings occur along a northwest trend.

The northwest showing is an occurrence of molybdenite in two quartz veins, 5 centimetres apart. Intense k-feldspar alteration and strong sericite alteration characterizes the showing. A sample of the showing yielded 0.039 per cent molybdenum (Assessment Report 3223, Map 3).

The central showing consists of molybdenite occurring in fissures 1 to 2.5 centimetres apart, with quartz, pyrite and sericite. Channel samples range up to 0.005 per cent molybdenum (Assessment Report 3223, Map 3).

The southeast showing consists of an area of intense rusty joints with assays averaging 0.005 per cent molybdenum (Assessment Report 3223, Map 3).

Canadian Johns-Manville Company Limited staked and investigated a number of claims in the area in 1970, including the Slide, Annette and Blue. It is reported that 739 geochemical samples were taken in 1970 (Geology, Exploration and Mining in BC 1970, page 469). In 1971, Canadian Johns-Manville completed further geochemical, geological and geophysical surveys on its Slide group of claims (Geology, Exploration and Mining in BC 1971, page 426). In 1972, the company completed further surveys on its Slide group including mapping and geochemical sampling (Geology, Exploration and Mining in BC 1972, page 74). The company returned in 1973 and conducted further surveys including some detailed mapping on the Blue claims (Geology, Exploration and Mining in BC 1973, page 92).