Klukwan Fan

Prospect, Active

Commodities and mineralogy

Main commodities Au; Cu; Fe; Pd; Pt; Ti; V
Ore minerals chalcopyrite; gold; ilmenite; hematite; titaniferous magnetite; palladium; platinum

Geographic location

Quadrangle map, 1:250,000-scale SK
Quadrangle map, 1:63,360-scale B-3
Latitude 59.41
Longitude -135.9
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is an alluvial fan on the southwest side of Iron Mountain; it is about 1 mile north of the village of Klukwan. The alluvial fan extends for a radius of approximately 1 mile around the location. It is shown as location 15 by Cobb (1972; MF-424).

Geologic setting

Geologic description

The following description is summarized from MacKevett and others (1974). The Klukwan fan is a Holocene alluvial deposit consisting of pyroxenite, gabbro, and diorite detritus that ranges from silt to large boulders in size. Parts of the fan are almost entirely pyroxenite while others are as much as 50% diorite and gabbro. The iron and the titanium are primarily in titaniferous magnetite that is widely distributed in the pyroxenite, both as disseminations and as nearly pure fragments. This alluvial material has been eroded from the mid-Cretaceous zoned mafic/ultramafic complex at Iron Mountain (SK030), which includes a core of pyroxenite surrounded by hornblende diorite. The northwest-trending Chilkat Fault, which separates the Taku terrane on the east from the Alexander terrane on the west, lies under the alluvial fan.
Wells and Thorne (1953) comment that much of the titanium occurs in sphene, but later workers (MacKevett and others, 1974; Still, 1984 [OF 21-84]) refer only to titaniferous magnetite and ilmenite as the titanium-bearing minerals.
Geologic map unit (-135.90185431244, 59.4096681929544)
Mineral deposit model A placer iron deposit in an alluvial fan eroded from a magnetite-bearing pyroxenite body.
Age of mineralization The deposit is a Holocene alluvial fan (MacKevett and others, 1974).

Production and reserves

Workings or exploration
According to Still (1984 [OF 21-84]), claims covering both the alluvial and lode occurrences (SK030) were staked in 1946. The Alaska Iron Mines company was created to develop the deposit(s). 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.
Indication of production None
Reserve estimates Williams (1953) notes that the alluvial fan is a nearly perfect cone that contains about 600 million tons of material. He indicates that sampling showed the alluvial fan to average about 12% iron. Based on volume calculation for the alluvial fan and a density of 20 cubic feet per ton, Robertson (1956) estimates the fan to contain 500 million tons of broken rock that averages 10% magnetite. Still (1984 [OFR 21-084]) cites an unpublished 1972, Henry J. Kaiser Company report that estimates the fan contains 989,761,000 tons of material with 10.8% soluble iron.

Additional comments

The Haines Highway crosses this alluvial fan and provides good accessibility. However, the alluvial fan lies partly in, and adjacent to, the Alaska, Chilkat Bald Eagle Preserve.

References

MRDS Number A013095; D000232

References

Reporters T.C. Crafford (T. Crafford & Associates, Anchorage)
Last report date 2/4/2001