The Nahlin showing is hosted by the Upper Mississippian to Permian Nahlin ultramafic body, part of the Cache Creek Complex. The Nahlin body is 100 kilometres long and up to 8 kilometres wide and is the largest alpine-type ultramafic in the Canadian Cordillera. On the southwest it is faulted against Lower Jurassic sedimentary rocks (Inklin Formation, Laberge Group and Upper Triassic Stuhini Group volcanic rocks) and on the northeast against Upper Paleozoic rocks of the Cache Creek Complex. This ultramafic body consists of oceanic crustal ultramafic rocks consisting of: peridotite, dunite, pyroxenite, which is in general serpentinized, and locally includes pods of nephrite jade and small bodies of listwanite, rodingite, and talc. The rocks weather uniformly reddish brown and are generally devoid of vegetation. Middle Jurassic diorite stocks of the Three Sisters Plutonic Suite intrude to the immediate south and to the west. In general, the ultramafic consists of hard, dark green to black peridotite. The principal variation in the body is the degree of serpentinization which is most intense along contacts and sheared or brecciated zones.
On the southern flanks of Nahlin Mountain, along the Nahlin River, faulted blocks of serpentinized peridotite are in contact with Permian Horsefeed limestone, dolomitic limestone, and argillite. Locally, the peridotite contains small veinlets up to 1.5 centimetres wide of chrysotile and serpentine. The peridotite is chloritized and sheared. The limestones are deeply weathered, and powdery argillaceous carbonates are common on all rock surfaces.
Small quartz-carbonate veinlets hosting disseminated pyrite occur within the altered peridotite adjacent to a Jurassic hornblende diorite intrusive. In 1977, a sample taken from a quartz-carbonate vein assayed 0.003 per cent zinc (Assessment Report 7610). Occasionally small veinlets of hematite are present, probably due to the oxidation of magnetite.
In 1977, Mattagami Lake Mines Limited conducted exploration for uranium in the Canadian Cordillera. Map areas covered included 104J, K and N. During the program a total of 95 stream sediments, 131 stream waters and 71 rock samples were analyzed. Few significant uranium anomalies were found in map areas 104 J and 104 K. Nine rock samples were collected on Traverse No. 8., Nahlin Mountain (page 16,17, Assessment Report 7610).
In 1989, an exploration program was undertaken by a geological field crew of 2 men employed by Stetson Resource Management Corp. Geological and geochemical surveys were carried out over 3 days in August. Twelve rock chip samples were collected from ankeritic alteration zones, and quartz breccias and stockwork. Four bulk heavy mineral concentrate stream sediment and four silt samples were collected from major property drainages. No significant results were obtained from the 12 rock samples collected from the property. No significant results were returned from the silt samples collected from property drainages.
