Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Pb; Zn
Ore minerals galena; sphalerite

Geographic location

Quadrangle map, 1:250,000-scale CH
Quadrangle map, 1:63,360-scale D-4
Latitude 67.88
Longitude -148.68
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of about 4,500 feet on a ridge approximately 1 1/2 miles southwest of the headwater lake on Thru Creek (NE1/4 sec. 9, T. 35 N., R. 5 W., of the Fairbanks Meridian). The location is accurate within a 1/2-mile radius.

Geologic setting

Geologic description

The Bob prospect is one of several Pb-Zn-Ag plus or minus Cu prospects near this site (DeYoung, 1978). Information specific to the property is sparse and only describes the prospect as galena and sphalerite with silver values in skarn associated with limestone (Grybeck, 1977). Newberry and others (1997) include the Bob prospect in a group of calcic Zn-Pb skarns and replacement bodies. These Zn-Pb skarns are described by Newberry and others (1986) as distal to Devonian(?) porphyry Cu-Mo systems associated with the Horace Mountain plutons in the Chandalar copper belt. The bedrock near of the prospect is mapped as Devonian Hunt Fork Shale near its contact with Skajit Limestone (Brosgé and Reiser, 1964). Intercalated diorite sills and andesitic flows(?) are also present in the section.
Geologic map unit (-148.682769039402, 67.8796143793321)
Mineral deposit model Zn-Pb skarn deposits? (Cox and Singer, 1986; model 18c?).
Mineral deposit model number 18c?
Age of mineralization Devonian(?) based on reported Early Devonian Pb/Pb zircon ages from the associated Baby Creek batholith and Horace Mountain plutons (Dillon and others, 1996).
Alteration of deposit Calc-silicate.

Production and reserves

Workings or exploration Claims were located in 1972 and 1976 by Placid Oil. No other information is available.
Indication of production None

Additional comments

See also: Bibban prospect (CH090). Alaska Kardex No. 031-61A (Kardex is a card file mining claim information system located at the State of Alaska DNR Public Information Center in Fairbanks).


MRDS Number A012134


Newberry, R.J., Allegro, G.L., Cutler, S.E., Hagen-Levelle, D.D., Adams, D.D., Nicholson, L.C., Weglarz, T.B., Bakke, A.A., Clautice, K.H., Coulter, G.A., Ford, M.J., Myers, G.L., and Szumigala, D.J., 1997, Skarn deposits of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 355-395.
Newberry, R.J., Dillon, J.T., and Adams, D.D., 1986, Regionally metamorphosed calc-silicate-hosted deposits of the Brooks Range, northern Alaska: Economic Geology, v. 81, p. 1728-1752.
Reporters J.M. Britton (Anchorage)
Last report date 11/17/1999