Jyro

Occurrence, Inactive

Alternative names

Bloomer Peak

Commodities and mineralogy

Main commodities Ag; Au
Other commodities As; Cu; Hg; Pb; Zn
Ore minerals pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale PM
Quadrangle map, 1:63,360-scale A-2
Latitude 55.2189
Longitude -160.5664
Nearby scientific data Find additional scientific data near this location
Location and accuracy The map site of this occurrence is at an elevation of 1,100 feet on the northeast spur of Bloomer Peak. The site is 4,000 feet northeast of the top of the peak (Wilson and others, 1988, locality 36). Location is accurate to within 500 feet.

Geologic setting

Geologic description

Peterson and opthers (1982) described small quartz veins near Bloomer Peak that assayed as much as 3.90 ppm gold. Followup led to the discovery of the Jyro vein system and numerous other quartz veins and silicified zones. The host rock is porphyritic quartz-feldspar tuff of the late Eocene to early Oligocene Popof volcanics (Wilson and others, 1995).
The Jyro vein system crops out on the crest of Bloomer Peak. It stikes N60E and can be followed on the surface for 3,000 feet. It is a vein-quartz breccia averaging 12 feet wide, and forms the core of the mineralized system. It is broken and iron stained and exhibits at least three periods of silicification (Peterson and others, 1982). The tuff hostrock intensely silicified, iron stained and locally argillized as much as 200 feet from the vein system. Some of the altered tuff contains quartz veins and stringers as much as 4 inches thick.
The Jyro vein and enclosing silicified tuff are sporadically enriched in gold. Grab samples contained as much as 0.62 ppm gold and 1.1 ppm silver, and trench samples as much as 0.31 ppm gold. Mean assay values of samples from the trench were 0.041 ppm gold, 0.225 ppm silver, 2.8 ppm molybdenum, 83 ppm arsenic, 0.145 ppm mercury, and 65 ppm Cu+Pb+Zn (Peterson and others, 1982). Small quartz veins elsewhere in the area assayed as much as 6.4 ppm gold.
Battle Mountain Exploration Company mapped and sampled the site in 1990. They determined that the northeast-trending veins and northwest-trending faults are consistently anomalous in gold, with values from 0.5 to 5.0 ppm. Arsenic values ranged from 50 to 900 ppm and mercury values were as much as 2 ppm (Ellis and Apel, 1990).
Geologic map unit (-160.568434589998, 55.2180710651458)
Mineral deposit model Epithermal gold veins (Cox and Singer, 1986; model 25)
Mineral deposit model number 25
Age of mineralization Eocene or younger.
Alteration of deposit Alteration includes silicification and minor argillization.

Production and reserves

Workings or exploration In 1982 UNC Teton Exploration Drilling Company mapped the site, cut 300 feet of trenches, collected 47 grab and 60 trench channel samples, and conducted a VLF-EM survey. Grab samples contained as much as 0.62 ppm gold and trench samples as much as 0.31 ppm gold. The U.S. Geological Survey collected a sample of the deposit (82ASH 27) in the mid-1980s. Battle Mountain Exploration Company mapped and sampled it in 1990. Gold values in their samples generally ranged from 0.5 to 5.0 ppm (Ellis and Apel, 1990).
Indication of production None

Additional comments

This site is on land patented by, or interim-conveyed to, the Aleut Corporation.

References

MRDS Number 10308136

References

Ellis, W.T., and Apel, R.A., 1990, Unga/Alaska Peninsula 1990 final report: Battle Mountain Exploration Company report, 49 p., 29 map sheets at various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)
Peterson, R.J., Lemmers, J., Handverger, P., Gallagher, J., Pilcher, R., East, J., Macleod, T., Bartels. E., 1982, Geology and precious metals potential Unga, Popof, and Korovin Islands, Shumagin Group, Aleutian Chain, Alaska: UNC Teton Exploration Drilling Company report, 127 p., 5 map sheets, various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)
Reporters S.H. Pilcher
Last report date 1/13/2001