Unnamed Occurrence (ARDF - MF043; area near Fall Creek; Mudside Creek; Coal Creek; and upper Topsy Creek), Yakutat Mining District, Hoonah-Angoon Census Area, Alaska, USAi

Regional Level Types
Unnamed Occurrence (ARDF - MF043; area near Fall Creek; Mudside Creek; Coal Creek; and upper Topsy Creek)	- not defined -
Yakutat Mining District	Mining District
Hoonah-Angoon Census Area	Census Area
Alaska	State
USA	Country

The Tertiary and Mesozoic country rocks of the hydrothermal zones are in the Lituya terrane of Brew and others (1978). The sites are in Glacier Bay National Park and Preserve.
Location: A lode containing gold is in Fall Creek about 1.25 miles upstream from its mouth into Lituya Bay. The coordinates are for the approximate location of the best sample collected by Rossman (1959, fig. 9) from a hydrothermal zone about 0.5 mile long that approximately parallels Fall Creek. The location is accurate to about 0.1 mile. This site also includes lodes described by Rossman in Mudslide Creek (about 58.639; 137.492), also in the north fork of Fall Creek, Coal Creek, and in the upper Topsy Creek drainage area.
Geology: Red- and yellow-stained hydrothermally altered zones as much as one-half mile long occur in sedimentary and volcanic rocks of Tertiary and Mesozoic age southeast of Lituya Bay (Brew and others, 1978). The zones, which are rich in clay, possibly are the result of alteration by thermal springs localized by faults. The faults subsequently localized Fall Creek and other drainages. Rossman (1959) found a maximum of 0.24 ounce per ton gold in one sample from the zone in Fall Creek. The Bureau of Mines found 0.02 ounce per ton silver in a jasper-rich zone in greenstone in upper Fall Creek. The rock contained fine disseminated pyrite and a trace of powellite (Kimball and others, 1978, p. C94).
Workings: Hydrothermal zones were first observed by D.J. Miller of the U.S. Geological Survey in mapping of the Lituya area (Miller, 1953); the mapping was followed up by sampling in 1954 (Rossman, 1959). In addition to the location in Fall Creek that assayed 0.24 ounce per ton gold and 0.06 ounce per ton silver, Rossman found 0.06 ounce per ton gold about 0.5 mile upstream in Fall Creek and at another location in the north fork of Fall Creek. Miller reported addtional hydrothermal zones in upper Topsy Creek about 1 mile to the SE; these occurrences are in rocks of Mesozoic age and were shown by Rossman in his report (fig. 9). In later follow up, the U.S. Bureau of Mines detected silver in one sample in upper Fall Creek; the sample contained fine disseminated pyrite and a trace of powellite in jasperoid in greenstone (Kimball and others, 1978, p. 94).
Age: Tertiary.
Alteration: Solfataric (?) hydrothermal alteration.

Commodities (Major) - Au; (Minor) - Ag, Mo, W
Development Status: No
Deposit Model: Epithermal (?) low-sulfide gold deposit.

Other Databases

Link to USGS - Alaska:	MF043

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References