Glenn Gulch

Prospect, Inactive

Alternative names


Commodities and mineralogy

Main commodities Ag; Au; Sb
Other commodities Bi; Cu; Hg; Pb; W; Zn
Ore minerals arsenopyrite; diaphorite; kermesite; stibnite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale ID
Quadrangle map, 1:63,360-scale B-4
Latitude 62.4496
Longitude -157.92656
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is south of Otter Creek valley about 0.4 mile east of the mouth of Black Creek. It is at an elevation of about 480 feet, about 0.6 mile northeast of the center of section 11, T. 27 N., R. 47 W., of the Seward Meridian. The location is accurate.

Geologic setting

Geologic description

The Glen Gulch prospect is a steeply-inclined quartz-sulfide vein that is exposed in the Otter Creek placer mine (ID111). The lode consists of sulfide-quartz mineralization in a N5-8E steeply dipping shear zone that cuts monzonite of the 68.7 Ma, Black Creek stock (Bundtzen and others, 1992; Miller and Bundtzen, 1994). The zone can be traced along strike for about 180 feet where it is buried under placer tailings on one end and under vegetation on the other. Major stibnite and arsenopyrite are readily identified in the field. Microprobe studies by Bundtzen and others (1992) also indicates the presence of the silver-antimony-lead sulfosalt, diaphorite, as well as kermesite, and two other unidentifiable silver sulfosalt minerals (Bart Cannon, oral communication, 1991). The mineralization formed during multiple hydrothermal events. Early arsenopyrite is brecciated and cut by stibnite and diaphorite. Brooks (1916) also identified minor cinnabar. Chip and channel samples from the vein contain up to 8.6 parts per million (ppm) gold, 1,019 ppm silver, 36.7 percent antimony, 2,101 ppm copper, 999 ppm lead, more than 2,000 ppm arsenic, 15 ppm bismuth, 135 ppm tungsten, more than 5.0 ppm mercury, and 516 ppm zinc (Bundtzen and others, 1992).
Geologic map unit (-157.928961979721, 62.4489155499546)
Mineral deposit model Polymetallic vein (Cox and Singer, 1986; model 22c).
Mineral deposit model number 22c
Age of mineralization Unknown; the Black Creek stock that hosts the vein is 68.9 Ma (Bundtzen and others, 1992).
Alteration of deposit Silicification.

Production and reserves

Workings or exploration The Glenn Gulch prospect was first described by Brooks (1916), and later by Mertie and Harrington (1924), who referred to the prospect as the Mohawk Lode. The U.S. Geological Survey and Alaska Division of Geological and Geophysical Surveys mapped and sampled the site in 1988 (Bundtzen and others, 1992).
Indication of production None
Production notes No lode production; the gold mined from placers above the lode is included with Otter Creek placer mine (ID111).