The area is underlain by intermediate to acid volcanics of the Lower-Middle Jurassic Harrison Lake Formation. The volcanics are intruded by a Late Jurassic (Arthur, 1987) quartz diorite to monzonite stock, which forms the resistant peak and part of the east flank of Mount Klaudt. A linear feature, thought to be a fault, forms the east boundary of the intrusion and parallels the southern tributary of Brett Creek. East of this fault, rhyolite and rhyodacite consisting of massive to pyroclastic (lapilli) beds, have undergone pyritic and argillic alteration with some silicification.

A zone of alteration and mineralization is present where the main logging road crosses Brett Creek. The complex fault zone passes through here parallel to the creek. Strata within the zone trend northeast and dip gently to the southeast. A massive rhyodacite breccia with rounded clasts and a pervasively silica-pyrite altered matrix is exposed in the creek. An overlying dacitic flow unit contains quartz-carbonate (and possibly barite) stringers and veins of black sphalerite and minor chalcopyrite. A composite chip sample yielded 2 per cent zinc and 0.1 per cent copper (Assessment Report 17350). Extending eastward from here is a pervasively pyrite-silica altered andesite tuff with local stringer veins.