Unnamed (Gulf of Alaska coast)

Mines, Probably inactive

Commodities and mineralogy

Main commodities Au; Fe; PGE; Ti
Other commodities Cr; Zr
Ore minerals ilmenite; magnetite; native gold; pge; rutile; zircon
Gangue minerals garnet

Geographic location

Quadrangle map, 1:250,000-scale MF
Quadrangle map, 1:63,360-scale C-5
Latitude 58.61
Longitude -137.66
Nearby scientific data Find additional scientific data near this location
Location and accuracy
Beach placers, related inland buried beaches, and probably related offshore marine deposits extend from the north edge of land on the Mt. Fairweather quadrangle at 59.000 and 138.164 southeasterly for about 64 miles to 58.383 and 136.889 at the head of Astrolabe Bay. The placers are interrupted by occasional inlets, especially Lituya Bay, a few bold headlands and by La Perouse glacier, but they are remarkably continuous.
The coordinates for this site are for Harbor Point on the southeast side of the entrance to Lituya Bay--the approximate center of the beach placer deposits on the Mt. Fairweather 1:250,000 quadrangle. Two individual placer deposits, immediately northwest and southeast of Lituya Bay (respectively MF041 and MF 042), are also described separately.
The deposits extend southeasterly from the Mt. Fairweather C-5 quadrangle into the B-4 and B-3 quadrangles, the latter point at the head of Astolobe Bay. They extend northwesterly into the C-6, D-6, and D-7 quadrangles, thence into the Yakutat 1:250,000 quadrangle.
The presence of extensive placers in the Mt. Fairweather quadrangle was noted by MacKevett and others, 1971, p. 83, pl. 1, locations 87 and 88, also by Cobb, 1972 (MF-436), and by Kimball and others, 1978.

Geologic setting

Geologic description

A series of beach placer deposits extends for about 64 miles from the north edge of the Mt. Fairweather quadrangle south to the head of Astrolobe Bay on the Mt. Fairweather B-3 quadrangle (Rossman, 1957; Rossman, 1963, B 1121-F, p. F45-47; Kimball and others, 1978, p. C28-C91). Related deposits formed at higher sea stands extend inland, in places for more than one mile. Economic production from the beaches has been limited to transient deposits rich in gold that form lenses and layers as much as 1-foot thick, especially after heavy spring and winter storms. More common economic heavy minerals, such as ilmenite, magnetite, and zircon, are enriched in layers up to several feet thick, that locally extend along the beach for miles and in widths of several hundred feet. Similar deposits are locally preserved in back beaches.
The ultimate source of heavy minerals, particularly ilmenite, magnetite, PGEs and some of the gold is in the layered mafic complexes of the Fairweather Range. Gold and other resistant minerals as zircon were also derived from other bedrock sources. Littoral processes winnowed out light minerals and left layers and lenses of black and ruby sands that contain most of the valuable dense minerals. The deposits are products of a dynamic, high-energy coastal environment, essentially single cycle (Foley and others, 1995).
The beaches range in sedimentary character from well-sorted sandy to gravelly sand to sandy cobble and sandy boulder. Dunes cover some ancient beaches in the back beach area, and forested terraces mark the location of beaches that either formed at higher sea-stands or were uplifted tectonically (Yehle, 1979).
The beach deposits were exploited on a small scale from at least as early as 1894 until World War II, with lesser activity since then.
Geologic map unit (-137.661944763387, 58.6096500096853)
Mineral deposit model Modern and fossil beach placers.
Age of mineralization Holocene.

Production and reserves

Workings or exploration
The beaches in the Mt. Fairweather quadrangle were probably first exploited by the Russians. The most extensive American mining occurred from about 1894 to 1917 (Mertie, 1933), but small scale mining took place almost continuously until World War II. Essentially continuous small-scale mining is documented in the annual resource reports prepared by the U.S. Geological Survey, including the 1904, 1918, 1919, 1922, 1923, and 1925 reports of Brooks, also the resource reports of Brooks and Martin in 1921 and Brooks and Capps in 1924. Brook's successor, P. S. Smith documented activity in 1926, 1934, including B 857-A, also 1936, 1937, 1938, 1939 (B 910A), and 1941 and 1942. Much of the mining was by small scale methods, but from 1901 to 1903 Lituya Bay Gold Mining Co. used hydraulic lifts that fed sluice boxes, the process water was brought down down to the beach in timbered flumes (Wright and Wright, 1907). There was some claim activity in the 1960s, and Kimball and others (1978) reported 136 twenty-acre placer claims still active in 1978 .
The area has also been explored by the USGS and USBM. In 1952, Rossman (1957) examined the area between Sea Otter Creek and Dixon Harbor. Miller (1961) reported on the geology of Lituya district, after earlier reporting on the Tertiary rocks that are a possible intermediate source of the placer materials (Miller, 1953). Thomas and Berryhill (1962) sampled beaches between Sea Otter Creek and Icy Point in 1957 and 1958. Kimball and others (1987) studied the entire area between 1975-1977. Because of budget and permitting limits, only the modern beaches were studied, but 26 sample lines at 20 localities and 241 holes were drilled over the approximate 64 mile length of the deposits, in addition to collecting surface channel and grab samples. The core samples were collected with small diameter (0.17 to 0.25 foot) augers or split tubes. Swell factor was measured in the field. The samples were processed following a standard flow sheet, that included size splitting at 20 mesh. The minus-20-mesh fraction was stripped with a hand magnet to separate magnetite, then further separated by electromagnetic and heavy liquid methods. In the coarser fraction gold was determined by fire assay of a panned concentrate (Kimball and others, 1978, p. C49-53). The sample size was recognized as too small to give reliable average gold contents. Ilmenite was determined accurately. In 1992 and 1993, the Bureau again sampled the area. This work by Foley and others (1995) concentrated on 'valuable heavy minerals' (defined as ilmenite + rutile + zircon) but obtained data on other heavy minerals including gold and PGEs. Earlier, the content of PGEs reported from beach and other deposits in the province were summarized by Foley and others (1989).
Indication of production Yes; small
Reserve estimates
Kimball and others, 1978 (p. C86-89) estimated 6 million cubic yards of material in resource blocks scattered along the 64-mile length of the placer field. The material had an average grade of 1 percent ilmenite and less than 2 cents per cubic-yard of gold, assuming a gold price of $300/ounce.
Extrapolating to the unsampled areas outside the blocks suggested a resource of 90 million cubic yards of material in the belt, with grades similar to those determined by Kimball and associates. Locally some beaches are appreciably richer.
Foley and others (1995) determined an average of 2.43 percent ilmenite and 0.01 percent rutile in their Fairweather samples (p. 2). Zircon is less abundant in the Fairweather than the Yakutat and Yakataga areas (p. 48).
A sample collected east of Icy Point near the mouth of Kaknau River contained 14.88 percent titanium in the spiral concentrates. Sample 310, collected northwest of LaPerouse Glacier, contained significant gold in the head and spiral concentrate samples.
Production notes Mertie (1933) estimated that about 4000 ounces of gold were produced between 1890 and 1917. Probably at least 1000 more ounces were produced between 1917 and World War II when there was small-scale placer activity almost every year. Total PGE production has been about 100 ounces or less.

Additional comments

The ilmenite from the beach placers is a high-iron type that needs special processing (Foley and others, 1995). Much of the gold is very fine-grained and difficult to recover. Cook (1969) studied the recovery of the very fine gold of the beach placers by less conventional methods, including flotation.
The beach placers in the Fairweather area are part of the extensive Pacific Coast heavy-mineral placer system recognized by Clifton and Luepke (1987). The entire beach placer resource centered on Lituya Bay in the Mt. Fairweather quadrangle is in Glacier Bay National Park and Preserve. The Park extends offshore to about 3 miles northerly to about Sea Otter Creek; north of that point, offshore lands out to the three-mile limit belong to the State of Alaska.

References

MRDS Number 10307814

References

Clifton, H.E., and Luepke, G., 1987, Heavy-mineral placer deposits of the continental margin of Alaska and the Pacific Coast States, Chapter 30 in Scholl, D.W., Grantz, Arthur, and Vedder, J.G., eds., Geology and resource potential of the continental margin of western North America and adjacent ocean basins, Beaufort Sea to Baja California: Circum-Pacific Council for Energy and Mineral Resources, Earth Science Series, v. 6, p. 691-738.
Reporters C.C. Hawley (Hawley Resource Group)
Last report date 4/4/1999