The Salt Chuck Mine is in a mafic pluton about 4.5 miles long and up to a mile wide in outcrop. The pluton consists of gabbro, clinopyoxenite, and diorite; most workers believe that the pluton is roughly cogenetic with the mineral deposit (Gault, 1945; Sainsbury, 1961; Gault and Wahrhaftig, 1992; Loney and others, 1987). Detailed studies by Watkinson and Melling (1992) and by Loney and Himmelberg (1992) describe the rocks in the vicinity of the mine as layered gabbro intruded by magnetite-bearing pyroxenite. The host rocks at the deposit are variably altered to epidote, actinolite, chlorite, sericite, titanite, and calcite. The pluton has been dated at 429 Ma (Loney and others, 1987). It intrudes metamorphosed volcanic and sedimentary rocks of the Descon Formation of Silurian and Devonian age (Eberlein and others, 1983; Brew, 1996).
The deposit consists chiefly of bornite, chalcopyrite, and platinum-group minerals that occur as disseminations or as veinlets and irregular masses in the gabbro and clinopyroxenite (Wright 1915; Mertie, 1921; Buddington and Chapin, 1929; Gault, 1945; Sainsbury, 1961; Page and others, 1973). The ore bodies are generally pods, lenses, and irregular masses with higher-grade cores. Numerous small faults cut the ore bodies. Most of the sulfides are in clinopyroxenite near its contact with gabbro. The ore minerals include varying amounts of digenite, chalcocite, and covellite that often rim bornite and chalcopyrite; they are mainly in irregular disseminated masses but some are in pyrite-pyrrhotite veins, and in epidote or calcite veinlets. The platinum-group minerals are mainly kotulskite (PdTe) or sperrylite (PtAs2), with minor amounts of the palladium-antimony minerals stibiopalladonite and isomertieite.
The deposit probably formed in two stages: 1) magmatic deposition of sulfides and platinum-group minerals, probably near the contact between layered gabbro and clinopyroxenite; and 2) remobilization of the sulfides and platinum-group minerals by low-temperature deuteric, or externally derived, chlorine-rich fluids with redeposition near gabbro-clinopyroxenite contacts.
Mine Site Workings
A good deal of development was performed by Goodro (the discoverer) with ore shipments sent to the smelter, but most of the development was started after the Alaska Palladium Company took over the property in 1919. Extensive underground work permitted mining of the ore by the glory hole method, and a modern flotation mill of 300-ton capacity was installed. Concentrates were snipped on the motor vessel to Prince Rupert, British Columbia, Canada and from there by rail road to the smelter in Irvington, New Jersey. Due to heavy surface construction in late 1925, more than 70 men were on the payroll.
The workings of the Salt Chuck Mine are shown in detail on the maps and diagrams of Gault (1945) and Gault and Wahrhaftig (1992). The deposit was mined in three glory holes connected by an intricate network of raises, stopes, and drifts at three levels. The workings connected to a main haulage tunnel at the 300-foot level that led to a mill (described in detail by Mertie, 1921) on the shore of the salt chuck at the head of Kasaan Bay. The main drift of the 300 level is 1,380 feet long. The west drift of the 300 level is turned west at 1,000 feet from the portal, and the 315 and 316 drifts are turned west at 1,150 feet. There are several other drifts as detailed in this document. The 200 and 300 levels are also connected by a corkscrew raise from the 311 drift which enters the 308 stope on the south side and a short raise at the northeast corner of the 308 stope which leads to the southeast end of the 200 level. The 200 level is connected with the surface by a raise starting from a point near the raise from the 200 level from the northeast corner of the 300 stope. The 200 level is 110 feet above the 300 level and includes remnants of several drifts around the small glory holes as well as a north drift, a west drift and a drift along the east side of the mine. A third raise from the 300 level, at the intersection of the 300 and 314 drifts, opens into a small grizzly chamber which connects with the stope directly below glory hole No. 1. A fourth raise from the 300 level connects the 313 drift with two small stopes below the 308 stope and with the No. 5 stope. The 100 level is 90 feet above the 200 level.
Historical Exploration and Sampling
During World War II, the U.S. Geological Survey and the U.S. Bureau of Mines studied the deposit in detail, drilled 13 holes, and reinterpreted 7 holes that had been drilled earlier by Solar Development Company (Gault, 1945; Holt and others, 1948; Gault and Wahrhaftig, 1992). Drilling results lead to delineation of a mineral resource estimate in 1945.
In 1948, geologists from the US Bureau of Mines (Holt, S.P., Shepard, J.G., Thorne, R.L., Tolonen, A.W., and Fosse, E.L., 1948) completed an investigation of the Salt Chuck Mine. During the investigation it became apparent that additional information on the factors controlling successful concentration of the ore to marketable products was desirable. Analysis of the mine ore sample is 0.68% Cu, 8.6% Fe, and 0.06% V205. No gold, platinum, or palladium was detected spectroscopically in the samples, but a trace of silver was found. Fire-assay fusions were made on the mine ore and later on the composite mill tailing. The treatment procedure involved tests on the flotation of the copper minerals and magnetic separation of the iron minerals. The flotation tailing was treated in a Davis tube to remove the magnetite. Results of the concentration testing are detailed in this document.
Further mapping, sampling and investigations of the Salt Chuck Mine were undertaken by the US Bureau of Mines in 1992 and 1995. Selected rock samples shows up to 40 g/t (1.28oz oz/t) gold, 150 g/t (4.82 oz/t) silver, >20% (20,000 ppm) copper, 40 g/t (1.28 oz oz/t) palladium, 0.60 g/t platinum, 0.07% (700 ppm) vanadium and 1,860 ppm strontium. The resource estimate was reported by USBM in 1995 (Maas, K.M., Bittenbender, P E., and Still, J.C., 1995) from previous drilling and work undertaken in 1945.
In 2007, as part of a larger company reverse-take-over merger, Pure Nickel Inc. (2007) completed surface mapping and sampling, targeting the North Pole Hill prospect which formed part of the Salt Chuck mine and unpatented claims held in the area. In December 2012, 2000m of drilling undertaken by Pure Nickel confirmed a new gold discovery at North Pole Hill. Intersections of 29.1 g/t gold over 2.58m and 1.2 g/t over 5.49 m were encountered. The gold discovery was associated with previously untested soil geochemical and IP anomalies on the Salt Chuck property; and IP and soil geochemical sampling extend 1.5 km along strike to the east and west, and a second gold in soil anomaly splays southward and continues a further 1.7 km. The reported anomalies extend to the limits of the surveys – therefore the potential mineralized structure is open in all directions. North Pole Hill anomalies were hypothesized to reflect the presence of the same style of remobilized magmatic Cu‐Au‐Pd‐Ag mineralization found at the historic Salt Chuck mine, located 2 km to the southeast. In addition to the remobilized gold‐copper mineralization, broad zones of anomalous palladium concentrations were encountered at greater depths in the westernmost drill holes, including NPH‐12‐02 where a weighted average concentration of 234 ppb Pd was intersected over 12.85 m apparent width. These anomalous Pd intersections appear to reflect primary magmatic mineralization, and they raise the possibility that remobilized Pd mineralization, such as at the Salt Chuck mine, may be associated with other structures not yet encountered in the North Pole Hill area. Pure Nickel proposed further drilling at the Salt Chuck property in 2014, but the project claims expired in 2016 due to other projects having higher priority.
