Bull Ridge

Prospect, Active

Commodities and mineralogy

Main commodities Cu; Zn
Ore minerals chalcopyrite; pyrrhotite

Geographic location

Quadrangle map, 1:250,000-scale RB
Quadrangle map, 1:63,360-scale D-4
Latitude 64.95494
Longitude -154.89719
Nearby scientific data Find additional scientific data near this location
Location and accuracy Bull Ridge is located at about 3,500 foot elevation on an 8-mile-long east-west-trending ridge system in the Kokrines Hills. It is about 1/4 mile southwest of VABM 3669. Horner hotsprings, now abandoned, are about 4 miles southeast of the site. Suprise (RB004) lies 2 1/2 miles north of this prospect. Coordinates are given for the approximate center of prospecting activity, in section 19, T. 6 S., R. 20 E. of the Kateel River meridian. The location is accurate. Bull Ridge lies within Doyon, Ltd. selected land.

Geologic setting

Geologic description

The northeast side of Bull Ridge is underlain by a northeast-trending, vertical to northwest dipping package of hornfelsed quartz biotite gneiss and biotite-amphibolite gneiss (DiMarchi and others, 1990). The southern side of the ridge is underlain by coarse grained biotite granite and granitic gneiss. Undifferentiated gneissic rocks are commonly cut by 3- to 4-foot-thick dikes of felsic biotite porphyry and aplite, and by discordant quartz tourmaline veins up to 2 inches thick. Disseminated pyrrhotite and minor chalcopyrite occur in undifferentiated gneiss as concordant stratiform layers. The spatial relationship of this mineralization to the hornfelsed zones suggests that mineralization is related to the granitic intrusion; the stratiform nature of the sulfide may be due to preferential replacement of certain favorable beds or metamorphic mineral bands, or pre-intrusive sulfides may have been remobilized or upgraded by a contact metamorphic event (DiMarchi and others, 1990).
The prospect was first discovered by WGM Inc. in 1976 when reconnaissance work detected elevated zinc and copper values in disseminated sulfide mineralization in hornfelsed gneiss. WGM Inc. also identified an airborne radiometric anomaly and anomalous uranium in stream sediment samples. In 1989 Central Alaska Gold Company (CAGC) completed 1:24,000 scale geologic mapping and geochemical sampling on the three ridges immediately north of Bull Ridge, and stream sediment sampling of the first-order drainages to the north (DiMarchi and others, 1990). Soil samples collected in 1989 by CAGC and 1998 by North Star Exploration contain weakly elevated base-metal values of copper and zinc (DiMarchi and others, 1990; Northstar Exploration Company, 1999 [99-33]).
Geologic map unit (-154.899681727376, 64.9543539343284)
Mineral deposit model Plutonic-related Cu-Zn.

Production and reserves

Workings or exploration The prospect was first discovered by WGM Inc. in 1976 when reconnaissance work detected disseminated sulfide mineralization with elevated zinc and copper values in hornfelsed gneiss (DiMarchi and others, 1990). WGM Inc. also identified an airborne radiometric anomaly and anomalous uranium in stream sediment samples. In 1989, Central Alaska Gold Company completed 1:24,000-scale geologic mapping and geochemical sampling on the three ridges immediately north of Bull Ridge, and stream sediment sampling of the first-order drainages to the north (DiMarchi and others, 1990).
Indication of production None

Additional comments

Bull Ridge lies within Doyon, Limited selected land. For more information, contact Doyon, Limited.

References

References

DiMarchi, J., Weglarz, T.B., Dickey, C.F., Laux, D.P., Smith, M.T., Toro, J., and Kurtz, J.P., 1990, Central Alaska Gold Company 1990 Annual Report, Alaska Field Operations - Doyon Option Volume 1: held by Doyon, Limited, Fairbanks, Alaska.
Reporters C.E. Cameron (Alaska Division of Geological and Geophysical Surveys)
Last report date 3/22/2000