Unnamed (on Geyser Creek)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Au
Other commodities As; Cu; Hg; Pb; S; Zn
Ore minerals gold; pyrite; sulfur
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale UK
Quadrangle map, 1:63,360-scale A-2
Latitude 53.21
Longitude -168.45
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site is located in central Umnak Island along the drainage of Geyser Creek about midway between Geyser Bight and Russian Bay (Nye and others, 1992, locality H; Christie, 1974, anomaly 36?). Site location is accurate to within 1/2 mile.

Geologic setting

Geologic description

This site is an active geothermal area along Geyser Creek in which hot springs, fumaroles, and mud pots are common (Randolph and Ellis, 1989). Pleistocene volcanic flows, tuffs, and volcaniclastics of andesitic composition have been intensely argillized by the geothermal activity (Nye and others, 1992).
Four exploration companies have examined and sampled this site at various times. This sampling of the altered rocks has produced values of up to 418 ppm arsenic, 652 ppm copper, 0.64 ppm gold, 92 ppm lead, > 5 ppm mercury, 4 ppm molybdenum, 4.7 ppm silver, and 345 ppm zinc.
Nye and others (1992) report that the thermal waters are rich in boron (60 ppm) and arsenic (6 ppm).
Geologic map unit (-168.452001405089, 53.209069090291)
Mineral deposit model Hot-spring Au-Ag (Cox and Singer, 1986; model 25a)
Mineral deposit model number 25a
Age of mineralization Quaternary.
Alteration of deposit Byers (1959) described the alteration as consisting of fine-grained aggregates of quartz, chlorite, pyrite, and adularia(?). Simpson (1985) and Randolph and Ellis (1989) described the alteration as advanced argillic with up to 10 percent pyrite. Randolph (1990) also noted silica seen locally as veinlets, vugs, and rare calcedonic stockworks.

Production and reserves

Workings or exploration
This site has been examined and sampled by Duval-Quintana, Kennecott, Amax, and Battle Mountain Exploration. Christie (1974) reported values of up to .02 ppm gold, 4 ppm molybdenum, 1.2 ppm silver, and 47 ppm zinc from 6 samples of altered rock. Nine samples collected by Kennecott contained up to 250 ppm arsenic, 0.2 ppm gold, and 2.8 ppm mercury (Simpson, 1986).
Randolph and Ellis (1989) sampled this site as well as a zone along a north-flowing tributary which flows into Geyser Creek at this site (named Fumarole Creek by Nye and others, 1992). They reported values in 20 samples of up to 418 ppm arsenic, 652 ppm copper, 638 ppb gold, 92 ppm lead, > 5 ppm mercury, 1.5 ppm silver, and 345 ppm zinc. Six samples of quartz plus clay gave values to up to 72 ppm arsenic, 186 ppb gold, 2.6 ppm mercury, and 4.7 ppm silver. A panned sample taken at the intersection of the two drainages contained 5 small colors and 2 samples of nearby altered rocks contained 140 and 638 ppb gold.
Randolph and Ellis (1989) state that the samples collected by Amax were similar in value to those collected by Battle Mountain Exploration.
Indication of production None

Additional comments

Simpson (1986) considered this an active system, still depositing gold and altering country rocks. He found no ore grade zones and concluded it was unlikely that a deposit of significant size exists at the site. Battle Mountain Exploration (Randolph and Ellis, 1989) located numerous geochemically anomalous areas within the occurrence, but essentially agreed with previous interpretations.
This site is on land selected by the Aleut Native Corporation.

References

MRDS Number 10308465

References

Christie, J.S., 1974, Aleut-Quintana-Duval 1974 joint venture, final report: Unpublished Quintana Minerals Corporation report, 24 p., 3 appendices, 2 maps. (Report held by the Aleut Corporation, Anchorage, Alaska.)
Randolph, D.B., 1990, Unalaska, 1990 final report: Battle Mountain Exploration Company, 72 p. (Report held by the Aleut Native Corporation, Anchorage, Alaska).
Randolph, D.B., and Ellis, W.T., 1989, Unalaska project, 1989 final report: Battle Mountain Exploration Company, Alaska District, 41 p., 5 appendices, 11 plates, various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)
Simpson, D.F., 1986, Aleutian Islands project, 1985 final report: Kennecott-Alaska Exploration Company, 54 p. (Report held by the Aleut Native Corporation, Anchorage, Alaska).
Reporters S.H. Pilcher (Anchorage)
Last report date 1/27/2000