|Quadrangle map, 1:250,000-scale||PE|
|Quadrangle map, 1:63,360-scale||C-1|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||El Paso Natural Gas Company collected samples along a line about 1,900 feet long trending south-southwest, beginning near Peak 4326 at the head of Groundhog Basin. They then drilled a 149-foot hole about 0.1 mile southwest of Peak 4326; the coordinates for the prospect are at the drill hole. The prospect is about 0.6 mile east-southeast of the center of section 7, T. 62 S., R. 86 E. The location is accurate.|
The rocks in the prospect area are part of a belt of Mesozoic or Paleozoic sedimentary and volcanic rocks that have been metamorphosed to Tertiary or Cretaceous schist and gneiss. The belt is about 1 1/2 mile wide and strikes northwest (Brew, 1997; George and Wyckoff, 1973). The metamorphic rocks are bounded on the east by a thick, regionally extensive, 60 to 70 Ma tonalite sill and on the west by a 90 Ma granodiorite pluton (Brew, 1997 Still and others, 2002). On the north side of Groundhog Basin, the metamorphic rocks are intruded by a 16.3 Ma biotite 'tin' granite pluton about 1,000 by 2,0000 feet in size. The granite is probably the source of the numerous rhyolite dikes and sills that extend from it and the mineralization in the area (Newberry and Brew, 1989).El Paso Natural Gas Company worked in the area from 1971 to 1976 (George and Wyckoff, 1973). They collected more than 200 surface samples along a line about 1,900 feet long that extended south-southwest from Peak 4326. They also drilled a hole 149 feet deep about 0.1 mile southwest of Peak 4326. Still and others (2002) identified the mineralization as quartz veins and stringers up to 10 feet thick that follows the layering in the gneiss hostrock. Four samples contained up to 63.9 parts per million (ppm) silver, 1,417 ppm lead, and 1,089 ppm tin. In the samples El Paso Natural Gas Company collected, the 6 best surface samples contained 840 to 1,655 ppm zinc, and 320 to 2,720 ppm lead. A 32-foot intercept in the El Paso drill hole consisted of rhyolite and gneiss cut by quartz stringers with sphalerite and galena; the intercept averaged 0.7 percent zinc, 1.0 percent lead, and 0.3 ounce of silver per ton. The mineralization is almost certainly of the same origin and age as that at the nearby Groundhog Basin prospect (PE040).
|Geologic map unit||(-132.043281217737, 56.506665954064)|
|Mineral deposit model||Banded Ag-Cu-Sn-Pb-Zn tabular replacement bodies, veins, and stringers.|
|Age of mineralization||16.3 Ma based on a genetic tie to a nearby, zinnwaldite 'tin' granite (Newberry and Brew, 1989).|
|Alteration of deposit||None specifically noted.|
|Workings or exploration||El Paso Natural Gas Company worked in the area from 1971 to 1976. They collected more than 200 surface samples along a line about 1,900 feet long that extended south-southwest from Peak 4326. They also drilled a hole 149 feet deep about 0.1 mile southwest of Peak 4326.|
|Indication of production||None|
Brew, D.A., 1997, Reconnaissance geologic map of the Petersburg C-1 Quadrangle, Southeastern Alaska: U.S. Geological Survey Open-File Report 97-156-H, 23 p., 1 sheet, scale 1:63,360.
George, R.H., and Wyckoff, B.S., 1973, Whistlepig mineral exploration program, Alaska, Final report 1972 (with attached diamond drill hole logs and analyses): Unpublished El Paso National Gas Company report 109 p. 12 sheets (available at the Bureau of Land Management, Minerals Information Center, Juneau Alaska).
Newberry, R.J., and Brew, D.A., 1989, Epigenetic hydrothermal origin of the Groundhog Basin-Glacier Basin silver-tin-lead-zinc deposits, southeastern Alaska: U.S. Geological Survey Bulletin 1903, p. 113-121.3
Still, J.C., Bittenbender, P.E., Bean, K.W., and Gensler, E.G., 2002, Mineral assessment of the Stikine area, central southeast Alaska: Bureau of Land Management Technical Report 51, 560 p.
|Reporters||D.J. Grybeck (Port Ludlow, WA)|
|Last report date||3/4/2008|