Klukwan Prospect, Skagway District, Juneau District, Haines Borough, Alaska, USA
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Location: The prospect is approximately 1.5 miles north, northeast of the village of Klukwan at an elevation of 1,200 feet in a canyon on the southwest side of Iron Mountain. It is the approximate center of a 4-mile-long deposit that extends to the northwest and southeast and is about 1 mile wide. It is shown as location 16 of Cobb (1972 [MF 424]) and location SE22 of Nokleberg and others (1987).
Geology: The Klukwan mafic/ultramafic complex lies within the Taku Terrane of Berg (1978) and forms the north end of the Klukwan-Duke belt (Brew and Morrell, 1978) of concentrically zoned, mafic/ultramafic complexes of probable middle Cretaceous age. The Klukwan ultramafic, a pyroxenite which hosts the deposit (MacKevett and others, 1974), is surrounded by hornblende diorite which is in contact with Cretaceous metabasalt to the west and Tertiary quartz diorite to the east. The pyroxenite is approximately 4 miles long in a northwest-southeast direction and up to 1.5 miles wide (Still, 1984 [OF 21-84]). The pyroxenite is composed principally of augite and hornblende with lesser amounts of feldspar, epidote, chlorite, magnetite, ilmenite, and at some locations, sulfides. Accessory to trace silicates include hematite, spinel, and leucoxene (MacKevett and others, 1974). The sulfides are mostly chalcopyrite, but pyrrhotite, pyrite, and bornite occasionally occur (Still, 1984 [OF 21-84]). The magnetite, which is titaniferous, and ilmenite occur as disseminations and as lenses of almost pure magnetite-ilmenite. Magnetite is typically interstitial to pyroxene and idiomorphic against hornblende, indicating that it formed after pyroxene but before hornblende (MacKevett and others, 1974). According to Taylor and Noble (1969), textural evidence indicates that the titaniferous magnetite recrystallized prior to crystallization of the hornblende. Robertson (1956) estimates the pyroxenite to contain from 5% to 51% magnetite and ilmenite. He also noted that the greatest concentration of titaniferous magnetite occurs in the lower portions of the pyroxenite. Taylor and Noble (1969), however, report a relatively uniform titaniferous magnetite content of 15 to 20% for the pyroxenite. Still (1984 [OF 21-84]) noted: 1) elevated gold, platinum, and palladium values in the Klukwan mafic/ultramafic complex are generally associated with sulfides, predominantly chalcopyrite, and are generally not associated with magnetite; 2) intermittent low grade mineralization averaging an estimated 750 to 1,500 ppm copper occurs along the basal contact of the pyroxenite near its southern end; and 3) hydrothermal pinch and swell veins, thought to be residual material from the ultramafic, that contain irregular sulfide mineralization occupy northerly striking, steeply dipping, shear zones near the southeastern margin of the pyroxenite. Assays of these veins contained up to 0.14 ounces of gold per ton, 0.003 ounces of platinum per ton, 0.008 ounces of palladium per ton, and 6.5% copper. Clark and Greenwood (1972), based on analyses of 10 samples from the Klukwan mafic/ultramafic complex indicate that it has an average platinum and palladium contents of 0.046 and 0.040 ppm respectively, with maximum values for both platinum and palladium of 0.100 ppm. According to Still (1984 [OF 21-84]), samples assay a maximum of 46.2% iron, 6.5% copper, 4.95% titanium, 0.0156 ounces of gold per ton, 0.031 ounces of platinum per ton, 0.011 ounces of palladium per ton, and 2,730 ppm vanadium. In their metallurgical study, Wells and Thorne (1953) commented that most of the titanium occurs as sphene. Other workers do not mention the presence of sphene (MacKevett and others, 1974; Robertson, 1956; Still, 1984 [OF 21-84]) and refer to magnetite and ilmenite as the main titanium-bearing minerals.
Workings: According to Still (1984 [OFR 21-84]), claims covering both the alluvial (SK031) and lode occurrences were staked in 1946. The Alaska Iron Mines company was created to develop the deposit. Work through 1961 included sampling and diamond drilling of the lode, pit sampling and churn drilling of the placer, aeromagnetic and ground magnetic surveys, and surface mapping. A pilot mill was constructed and copper concentrates were produced for metallurgical testing. The claims were leased to Columbia Iron Mining Company in 1961 and some claims were patented in 1964. The property reverted back to Alaska Iron Mines in 1972. Wells and Thorne (1953) reported that the most effective metallurgical treatment resulted from wet magnetic separation of ore ground to minus-20 mesh, followed by grinding and retreatment of the rougher concentrate. This produced concentrates with 62% to 64% iron and total iron recoveries of 45% to 97%, depending on the head grades of the samples. These recoveries corresponded to a recovery of about 98% of the magnetic iron. The titanium-oxide content of the concentrates from low-grade ores averaged about 2.2%. Concentrates from higher-grade samples contained up to 4.2% titanium dioxide.
Age: Coeval with the Cretaceous pyroxenite (Still, 1984 [OF 21-84]).
Alteration: Epidote alteration of hornblende diorite near contact with pyroxenite.
Reserves: Robertson (1956) estimates the deposit to contain between 1 and 5 billion tons of pyroxenite with an average grade of about 13% iron. This estimated resource includes a zone in the lower part of the pyroxenite that he estimates to contain 500 million tons that contain 20% +5% iron. Berg and Cobb (1967) cite several billion tons of rock containing about 13% magnetic iron. Still (1984 [OFR 21-84]) cites a 1972 unpublished report by the Henry J. Kaiser Company that estimates a reserve of 3.5 billion tons with a soluble iron content of 16.8%. Page and others (1973) refer to a published reserve of 500 million tons of titaniferous magnetite with an average platinum group metals content of 0.0027 ounces per ton. However, Still's observation (1984 [OFR 21-84]) that gold, platinum, and palladium are associated with sulfides and not with magnetite does not support that reserve figure.
Commodities (Major) - Fe,Ti; (Minor) - Au, Cu, Pd, Pt, V
Development Status: No
Deposit Model: Disseminated magmatic PGE-Fe-Ti minerals in a zoned ultramafic body (Cox and Si
8 entries listed. 7 valid minerals.
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Berg, H.C., 1984, Regional geologic summary, metallogenesis, and mineral resources of southeastern Alaska: U.S. Geological Survey Open-file Report 84-572, 298 p., 1 plate, scale 1:600,000. Berg, H.C., and Cobb, E.H., 1967, Metalliferous lode deposits of Alaska: U.S. Geological Survey Bulletin 1246, 254 p. Clark, A.L., and Greenwood, W.R., 1972, Geochemistry and distribution of platinum-group metals in mafic to ultramafic complexes of southern and southeastern Alaska: U.S. Geological Survey Professional Paper 800-C, p. C157-C160. Cobb, E.H., 1972, Metallic mineral resources map of the Skagway quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-424, 1 sheet, scale 1:250,000. Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Mt. Fairweather and Skagway quadrangles, Alaska: U.S. Geological Survey Open-File Report 78-316, 123 p. MacKevett, E.M., Jr., Robertson, E.C., and Winkler, G.R., 1974, Geology of the Skagway B-3 and B-4 quadrangles, southern Alaska: U.S. Geological Survey Professional Paper 832, 33 p., 1 plate. Page, N.J., Clark, A.L., Desborough, G.A., and Parker, R.L., 1973, Platinum-group metals, in Brobst, D.A., and Pratt, W.P., eds., United States mineral resources: U.S. Geological Survey Professional Paper 820, p. 537-545. Robertson, E.C., 1956, Magnetite deposits near Klukwan and Haines, southeast Alaska: U.S. Geological Survey Open-File Report 132, 37 p. Still, J.C., 1984, Copper, gold, platinum and palladium sample results from the Klukwan mafic/ultramafic complex, southeast Alaska: U.S. Bureau of Mines Open-File Report 21-84, 53 p. Still, J.C., 1991, Bureau of Mines mineral investigations in the Juneau mining district, Alaska, 1984-1988; Volume 2, Detailed mine, prospect, and mineral occurrence descriptions, Section A, Haines-Klukwan-Porcupine subarea: U.S. Bureau of Mines of Mines Special Publication, 214 p. Still, J.C., Hoekzema, R.B., Bundtzen, T.K., Gilbert, W.G., Wier, K.R., Burns, L.E., and Fechner, S.A., 1991, Economic geology of Haines-Klukwan-Porcupine area, southeastern Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 91-4, 156 p., 5 sheets, scale 1:63,360. Wells, R.R., and Thorne, R.L., 1953, Concentration of Klukwan, Alaska, magnetite ore: U.S. Bureau of Mines Report of Investigations 4984, 15 p. Winkler, G.R., and MacKevett, E.M., Jr., 1970, Analyses of bedrock and stream-sediment samples from the Haines-Porcupine region, southeastern Alaska: U.S. Geological Survey Open-File Report 369, 91 p., 1 sheet, scale 1:125,000.