The Shirley adit is located on the western shore of Phillips Arm, southwest of the mouth of Shirley Creek.

The area is underlain by a persistent band, greater than 12 kilometres long, of stratified metavolcanic and metasedimentary rocks of the Upper Triassic Quatsino and Karmutsen formations (Vancouver Group). The band trends northwest and separates Jurassic to Cretaceous Coast Plutonic Complex rock of two different compositions, diorite and granodiorite.

Locally, two adits expose a 120 metre wide, east- striking, band of relatively unaltered limestone hosting molybdenite mineralization across 3 metres near the contact of the limestone and quartz monzonite intrusive. In 1969, samples assayed up to 0.03 per cent molybdenum over 1.5 metres (Property File - Bacon and Crowhurst Ltd. [1969-07-15]: Letter RE: Shirley Creek Prospect, Powell River Area).

In 1969, Avija Mines prospected and sampled the area. 1983, Du Pont of Canada Exploration completed a program of rock and silt sampling and geological mapping on the area.