|Quadrangle map, 1:250,000-scale||YA|
|Quadrangle map, 1:63,360-scale||C-5|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This deposit (a beach placer) extends northwesterly from the mouth of Lost River for about 10.5 miles to Ocean Cape, thence 1.5 miles to Pt. Carrew, thence 1.5 miles southeasterly along the south coast of Monti Bay to the Ankau tidal inlet. The deposit is about half on Yakutat quadrangle C-5 and half on B-5; the coordinate location point is the join of the two quadrangles. The Yakutat beach placer is number 5 of Cobb (1972); also see Cobb (1979).|
The Yakutat beach is developed on a wide band of unconsolidated sediments of Holocene age (MacKevett and Plafker, 1970; Foley and others, 1995; Wright, 1969; Wright, 1972). The deposit consists of transient modern beach concentrations and somewhat older and more stable layers and lenses of materials relatively rich in heavy minerals in the upland beach. Although less well known than some of the other Gulf of Alaska beaches (for example, Yakataga), the Yakutat beach is enriched in economic heavy minerals (ilmenite + zircon + rutile) relative to the Yakataga and Mt. Fairweather beaches studied by the U. S. Bureau of Mines (Foley and others, 1995). The Yakutat beach is the northwestward continuation of the Situk and Blacksand beach deposits.
Potentially productive segments of the beach consist mainly of medium coarse sand in relatively continuous layers as much as several feet thick. Native gold, platinum minerals, rutile, and scheelite occur locally in concentrates.Foley and others (1995) estimate about 3.4 percent total economic heavy minerals (ilmenite + rutile + zircon) in a prism averaging about 5.5 meters thick that extends for several kilometers along the coast. These investigators found gold in more than 10 percent of their samples of heavy- mineral concentrates. Thomas and Berryhill (1962) reported about 35 pounds of iron per cubic yard of material in their samples from the Yakutat beach.
|Geologic map unit||(-139.747665803398, 59.4996975770607)|
|Mineral deposit model||Beach placer: heavy-mineral ilmenite-rich. Characterized by small amounts of gold and PGEs. High energy beach processes.|
|Age of mineralization||Holocene|
|Workings or exploration||
The Yakutat beach has been extensively explored by the U.S. Bureau of Mines (Thomas and Berryhill, 1962; Foley and others, 1995) using hand and powered augers and excavation. Foley and others collected 213 samples (nos. 164-258) from the Yakutat beach as defined here. (Samples nos. 242-245 were collected on Tawah Creek, a tributary to Lost Creek.)
The two studies by the Bureau complement each other. The report by Thomas and Berryhill (1962) contains some data on scheelite and other trace minerals not given by Foley. Foley and his coinvestigators worked especially on total economic heavy metal minerals: ilmenite + zircon + rutile. Data on gold and platinum group minerals were gathered as part of the broader investigation and are not quantitative. Both gold and platinum metals would be recovered in a large-scale placer mining operation for titanium and zircon at Yakutat.Reconnaissance-type samples were collected by MacKevett and Plafker (1970) and Reimnitz and Plafker (1976) of the U.S. Geological Survey.
|Indication of production||Yes; small|
The beaches at Yakutat are broader than those in the Cape Yakataga area. Including a very small part of the Situk beach, Foley and others (1995, p. 56) assumed a wedge-shaped prism 0 to 11 meters deep, averaging 300 meters wide for a linear distance of 24 km down the coast. This prism contains 36 million cubic meters of beach sand, or approximately 57 million tonnes of sand. This mass contains from about 0.2 to 14.8 percent valuable heavy minerals (ilmenite + zircon + rutile) and averages about 3.4 percent valuable heavy metals.
Somewhat more than 10 percent of the samples collected by Foley and others contained gold, detected either in head samples or in spiral concentrates. The minimum limit of detection for gold in Foley's investigation was 0.028 grams/tonne (ppm).
Thomas and Berryhill (1962) reported about 35 pounds of iron, 20.5 pounds of titania and traces of gold and scheelite in the Yakutat and closely related beaches.Foley and others (1995, table 3) also investigated recovery of gold and PGEs by flotation.
|Production notes||Some gold has probably been recovered from the area.|
The Yakutat beach deposits are a significant resource of ilmenite-based titanium and associated other metals. Titanium mainly occurs in iron-rich minerals that probably were derived mostly from mafic-ultramafic rocks, not the metamorphic terranes that are the hosts of high-grade titanium (rutile) deposits. The placer deposits are essentially lag deposits produced in a young, high-energy environment (Foley and others, 1995, p. 56).The Yakutat area is within the Tongass National Forest and probably could be developed.
|MRDS Number||AO13400; D002751|
Cobb, E.H., 1972, Metallic mineral resources map of the Yakutat quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-408, 1 sheet, scale 1:250,000.
Cobb, E.H., 1979, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Bering Glacier, Icy Bay, Middleton Island, and Yakutat quadrangles, Alaska: U.S. Geological Survey Open-File Report 79-1246, 41 p.
Foley, J.Y., La Berge, R.D., Grosz, A.E., Oliver, F.S., and Hirt, W.C., 1995, Onshore titanium and related heavy-mineral investigations in the eastern Gulf of Alaska region, southern Alaska: U.S. Bureau of Mines Open-File Report 10-95, 125 p.
MacKevett, E.M., Jr., and Plafker, G., 1970, Geochemical and geophysical reconnaissance of parts of the Yakutat and Mount St. Elias quadrangles, Alaska: U.S. Geological Survey Bulletin 1312-L, p. L1-L12 p.
Reimnitz, Erk, and Plafker, George, 1976, Marine gold placers along the Gulf of Alaska margin: U.S. Geological Survey Bulletin 1415, 16 p., 1 plate.
Thomas, B.I., and Berryhill, R.V., 1962, Reconnaissance studies of Alaskan beach sands, eastern Gulf of Alaska: U.S. Bureau of Mines Report of Investigations 5986, 38 p., 7 sheets.
Wright, F.F., 1969, Sedimentation and gold distribution, Yakutat Bay, Alaska: University of Alaska Marine Science Report R69-9, 23 p.
|Reporters||C. C. Hawley (Hawley Resource Group)|
|Last report date||4/15/1999|