Pennsylvania

Prospects, Inactive

Alternative names

Keystone

Commodities and mineralogy

Main commodities Au
Other commodities Ag; Cu; Pb; W; Zn
Ore minerals arsenopyrite; galena; gold; pyrite; scheelite; sphalerite; tetrahedrite
Gangue minerals ankerite; calcite; dolomite; quartz

Geographic location

Quadrangle map, 1:250,000-scale MM
Quadrangle map, 1:63,360-scale C-2
Latitude 63.5429
Longitude -150.9256
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Pennsylvania and Keystone prospects are on patented, adjacent claims in the canyon of Iron Gulch, a south-flowing tributary to Eureka Creek. The location is at the center of the end line between the two claims. It is about 150 feet west of Iron Gulch, and about 0.24 mile west-northwest of the center of section 7, T. 16 S., R. 17 W., Fairbanks Meridian. The location is accurate within 300 feet. The prospects are number 30 of Bundtzen (1981) and 39 of Thornsberry, McKee, and Salisbury (1984), and are included in location 12 of MacKevett and Holloway (1977).

Geologic setting

Geologic description

The area of the Pennsylvania-Keystone claims is underlain mainly by 'quartz-eye' metafelsite of the Spruce Creek sequence (Thornsberry, McKee, and Salisbury, 1984, fig. K-2; v. 2 occurrence 39; Hawley and Associates, 1978, fig. 4.1-(A)1). The claims are close to the axis of the Kantishna antiform (see record MM091).
Two main veins, the Pennsylvania and the Keystone, have been explored on the claims. The Pennsylvania vein crosses the west end line of the Pennsylvania claim about 100 feet north of the center of the claim. The vein strikes N 65 E and dips 85 S. It continues easterly (uphill) for about 500 feet and strikes toward the Pittsburgh vein (MM109), with which it probably correlates (Davis, 1923, p. 129; Thornsberry, McKee, and Salisbury, 1984, v. 2, no. 39). The Keystone vein is about 100 feet south of the Pennsylvania vein at the west end of the Pennsylvania claim. It strikes about N 50 E, and dips 60 S. The Keystone vein continues southwest for about 800 feet on the Keystone claim, and intersects the Pennsylvania vein on the Pennsylvania claim. Its total strike length is at least 1200 feet.
A third vein, which crops out between the Pennsylvania and Keystone veins, appears to intersect both of the them (Davis, 1923, p. 130), and a fourth vein is suggested by quartz float near the north boundary of the claims (Thornsberry, McKee, and Salisbury, 1984, v. 2, no. 39).
The Pennsylvania vein consists mainly of quartz and calcite, and contains pyrite and free gold. The Keystone vein consists mainly of quartz, along with arsenopyrite and pyrite and lesser amounts of galena and sphalerite (Capps, 1919, p. 122-23). Spectacular dendritic gold occurred in a shallow pit on a thin quartz vein that may be part of the Keystone vein (Capps, 1919; Davis, 1923, p. 130; Moffit, 1933, p. 131-132). Other minerals in the veins include chalcopyrite, scorodite, jamesonite(?), tetrahedrite, and scheelite (Bundtzen, 1981; Thornsberry, McKee, and Salisbury, 1984).
Geologic map unit (-150.927886040027, 63.5423941927706)
Mineral deposit model Low-sulfide gold-quartz vein (Cox and Singer, 1986; model 36a).
Mineral deposit model number 36a
Age of mineralization The deposit is assumed to be Eocene (see record MM091).
Alteration of deposit Oxidation of arsenopyrite to scorodite.

Production and reserves

Workings or exploration The veins were explored by numerous open cuts, short adits, and shafts, currently (2001) mostly inaccessible. Considerable development occurred prior to 1922 (Davis, 1923), and a little work was done in subsequent years. In 1983, the U.S. Bureau of Mines drilled three diamond core holes (K-8, -9, and -10). Between 132 and 135 feet, drill hole K-8 intersected vein quartz, chalcedonic quartz and dolomite, and mineralized metafelsite. Core recovery was only fair, and one section was lost. The best intersection was 147 to 150 feet, which assayed 0.294 ounce of gold per ton and 0.276 ounce of silver per ton. From 34.5 to 43.5 feet, drill hole K-9 intersected quartz-dolomite vein material and possible stope fill that assayed 0.10 ounce of gold per ton. Hole K-10 intersected quartz-dolomite-ankerite? vein material containing traces of gold and silver. Drill hole K-8 probably intersected the Pennsylvania vein (Thornsberry, McKee, and Salisbury, 1984, v. 2, occurrence 39 and drill logs).
Indication of production Undetermined
Production notes Production is unknown but small quantities of dendritic gold were almost certainly taken from the claims.

Additional comments

The claims are in Denali National Park and Preserve.

References

MRDS Number A011226; A011244

References

Bundtzen, T.K., 1981, Geology and mineral deposits of the Kantishna Hills, Mt. McKinley quadrangle, Alaska: M. S. Thesis, University of Alaska, College, Alaska, 238 p.
Reporters C.C. Hawley
Last report date 4/27/2001