Tillson

Prospects, Undetermined

Alternative names

Kay
Bahrt

Commodities and mineralogy

Main commodities Au
Ore minerals gold; pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale SI
Quadrangle map, 1:63,360-scale C-7
Latitude 57.6734
Longitude -136.0957
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Tillson, Kay, and Bahrt prospects vary in elevation from about 500 feet to 1,500 feet, in a roughly elliptical, east-trending area about 0.2 mile long and 0.2 mile wide, on the east flank of Doolth Mountain. For this record, the site is plotted at the center of the area, about 0.2 mile northwest of the southeast corner of sec. 25, T. 48 S., R. 57 E. The Tillson prospect is location 27 of Cobb (1972, 1978). The location is accurate.

Geologic setting

Geologic description

Johnson and Karl (1985) map the rocks in the area of this prospect as Cretaceous graywacke and argillite interbedded with sparse, lenticular beds of basalt. The rocks are cut by numerous high-angle, mainly northwest-striking faults; these include the extensions of the faults at the Hirst (SI087) and Chichagof (SI093) mines, which control the mineralization there and straddle this prospect.
Reed and Coats (1941) report that the claims on the Tillson prospect were originally staked in 1912 and acquired by Tillson in 1915. The principal working is a 95-foot tunnel that follows two faults about 6 feet apart that strike N47W and dip 50SW. The tunnel exposed an auriferous quartz lens about 1.5 feet thick in one fault, and some quartz in the other. Claims on the Kay prospect were prospected by several pits that exposed quartz veins up to 2.5 feet thick in graywacke. The Bahrt prospects were explored around 1927 by pits and by approximately 40- and 90-foot tunnels. The workings exposed northwest-striking, generally steeply-dipping faults that contain up to 1.5 feet of quartz with considerable pyrite locally. There is no record of production, but the extent of the workings suggests some gold may have been produced.
Isotopic studies indicate that the gold-quartz veins in coastal southern and southeastern Alaska are Eocene, about 50 Ma in age (Haeussler, 1995; Goldfarb, 1997; Goldfarb and others, 1997). ARDF record SI087 provides an overview of the geology of auriferous quartz veins in the Chichagof Mining District.
Geologic map unit (-136.097525439806, 57.6730282199018)
Mineral deposit model Low-sulfide gold-quartz vein (Cox and Singer, 1986; model 36a).
Mineral deposit model number 36a
Age of mineralization Isotopic studies indicate that the gold-quartz veins in coastal southern and southeastern Alaska are Eocene, about 50 Ma in age (Haeussler and others, 1995; Goldfarb, 1997; Goldfarb and others, 1997).

Production and reserves

Workings or exploration The principal working on the Tillson claim is a 95-foot tunnel; the Kay prospect was explored by several pits. The Bahrt prospects were explored by pits and by two tunnels, 40 foot and 90 feet long.
Indication of production Undetermined
Production notes There is no record of production, but the extent of the workings suggests that some gold may have been produced.

Additional comments

The prospects are in West Chichagof-Yakobi Wilderness.

References

References

Goldfarb, R J., 1997, Metallogenic evolution of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 4-34.
Goldfarb, R.J., Miller, L.D., Leach, D.L., and Snee, L.W, 1997, Gold deposits in metamorphic rocks in Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 151-190.
Haeussler, P J., Bradley, D., Goldfarb, R., Snee, L., and Taylor, C., 1995, Link between ridge subduction and gold mineralization in southern Alaska: Geology, v. 23, no. 11, p. 995-998.
Reporters H.C. Berg (U.S. Geological Survey)
Last report date 10/16/2004