The Sulphurets-Mitchell Creek area is underlain by rocks of the Lower Jurassic Hazelton Group. These rocks include green to grey volcanic epiclastics, and a sequence of dominantly fine-grained marine sediments. A third sequence of massive red and green volcanic sandstones and conglomerates form the highest peaks capping the stratigraphic sections.

The Kerr L mineral occurrence is reported to lie entirely within a "tectonic shear zone". This zone contains all of the significant gold anomalies. This zone covers an elongated northern trending area, 800 to 900 metres wide and 2 kilometres long. The zone is flanked by comparitively unaltered or weakly altered, fine-grained, brownish green clastic sediments and submarine volcanic rocks on the east, and by a thick unit of basaltic andesite on the west. This tectonic zone is typically composed of moderately to strongly altered and sheared rocks, interpreted to be of volcanic, subvolcanic or plutonic origin. Most of the altered zone can be described as a sericite schist, how- ever, andesitic tuffs and flows, and feldspar porphyry dykes and possibly flows, can be recognized in the less altered zone. A later formed "swarm" of fine-grained, weakly altered andesite dykes cuts across the schistosity. Both the altered zone and dykes have been cut by faults. Minor sections of silty shale and siltstone occur on the western and eastern margin of the altered zone.

The L Zone lies within the same fault-bounded block as the C Zone (104B 188) and the two mineral zones may be connected by sub-economic mineralization and alteration. The west bounding fault is the B Zone fault; the east bounding fault is the Camp Fault.

Gold mineralization in the Kerr L Zone occurs in quartz-cemented breccia in silicified ash tuff to cherty tuff. The gold probably occurs as free gold or electrum within quartz veins and silica cemented breccias. Alteration consists of pervasive silica, sericite and carbonate.

One trench sample (L1, 16860) assayed 29.0 grams per tonne gold, 17.9 grams per tonne silver and 0.03 per cent copper over 1.5 metres (Assessment Report 16616).