The Whitehorse Copper Belt is located west of Whitehorse and contains 30+ mines, deposits and showings. Many of the occurrences in the Copper Belt are skarns. The skarns form on or near the contact between the Whitehorse batholith and the Lewes River group. The Whitehorse batholith is commonly a grey coarse-grained hornblende granite and ranges from quartz monzonite to granodiorite to diorite. The Lewes River group contains numerous different rock types, most importantly of which is the limestone group, which is essential in the formation of skarns in the area.  A small number of occurrences within the Copper Belt are vein and/or replacement and occur within the Whitehorse batholith granite.

The Middle Chief and Big Chief deposits are within 2000 ft (610 m) of the Little Chief deposits. Therefore, although there is little detailed work done on the Middle and Big Chief deposits, it is assumed that they display much of the same characteristics. The Middle and Big Chief deposits are considered a faulted northward extension of the Little Chief deposit. The description below is from the Little Chief Deposit:

"The Little Chief deposit is within the Hancock member of the Aksala formation in the Lewes River Group.  The skarn occurs along the northwest trending contact between the granodiorite and the limestone and the ore is about 600 ft. (182.88 m) along strike and an average of 80 ft. (24.384 m) in width.

The Little Chief mine display features of both endoskarns and exoskarns however, the endoskarn is subordinate to the exoskarn. The skarns of the contact zone developed in three stages; the pyroxene Stage, The Magnetite-Andradite Stage, and the Serpentine-Chlorite-Epidote Stage. The skarn is believed to have formed between 525-300 °C with early contact metamorphic minerals forming  in a high CO₂ environment and skarn minerals forming in a low CO₂ environment. The deposit shows characteristics of both infiltrational and diffusional metasomatic features. The deposit has been described as a bimetasomatic skarn in calcareous rocks onto which an infiltrational skarn has been imposed.

Ore minerals present within the deposit include bornite, chalcopyrite, valeriite and magnetite.  During drilling, encouraging copper values have been intersected down to an elevation of 1430 ft (435.9 m). Total production at the Little Chief mine between operating years 1967-1982 was 8 536 400 tonnes (Includes production from the Middle Chief deposit)  and the reported grade between 1972-1982 was 1.53 Cu%, 0.75 g/t Au and 9.16 g/t Ag."