Roy Creek

Prospect, Active?

Commodities and mineralogy

Main commodities Au; Cu
Ore minerals chalcopyrite; pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale CR
Quadrangle map, 1:63,360-scale A-1
Latitude 55.20173
Longitude -132.01673
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Roy Creek prospect is exposed along road cuts about a mile south of Halibut Creek and about 0.6 mile southwest of hill 980. It is about 0.5 mile southwest of the center of section 9, T. 77 S., R. 89 E.

Geologic setting

Geologic description

The Roy Creek prospect is one of the deposits in the Kael-7 Mile Trend (CR188), a belt of mineralization about 4 miles long and 0.5 mile wide. The rocks in the area consist mainly of marble and minor chlorite schist, cut by greenstone dikes and sills. They are part of the Wales Group of Late Proterozoic and Cambrian age (Eberlein and others, 1983; Brew, 1996). The mineralization is stratiform and and consists of breccia veins or zones (Hedderly-Smith, 1993, 1999 [Inventory]). The clasts in the breccia vary from fresh marble to ferroan(?) dolomite to silicified marble. The matrix is mainly quartz; locally the matrix may contain up to 50 percent pyrite and chalcopyrite, but it generally contains only a few percent of sulfides.
The mineralization in the Kael-7 Mile Trend was discovered in 1988 by a Sealaska geologist. The discovery (CR 186) was soon leased to the American Copper and Nickel Company, who mapped and sampled the belt, and drilled 26 shallow holes in 1990 and 1991, mainly on geochemical anomalies. Three holes totaling 2,837 feet were drilled in 1994, one at the Roy Creek prospect at the east end of the belt, and two at the west end. The drill hole at the Roy Creek prospect did not cut mineralization better than that at the surface.
Hedderly-Smith (1999 [Inventory]) originally described the deposit at the Roy Creek prospect as two quartz veins that strike about N50W and dip vertically. They are in road cuts about 1,000 feet apart. The veins, one 2 to 3 inches thick and the other 4 to 6 inches thick, contain pyrite and chalcopyrite; the host rock is chlorite-quartz greenschist. Later work indicated that there is only one vein that was sampled in two places. Four samples contained 0.4 to 74 parts per million (ppm) silver, 0.847 to 27.8 ppm gold, and 6.0 to 8.1 percent copper.
The prospect was also sampled by Maas and others (1991), who describe it as a quartz-pyrite-chalcopyrite vein exposed for about 15 feet in a roadcut. The vein cuts chlorite-quartz schist that strikes N65E and dips 67NW. It is about 0.1 to 0.2 feet thick, strikes about N20-40W, and dips 78N to vertical. Two samples contained 1.379 and 4.506 ounces of gold per ton, 11.5 and 17.6 ounces of silver per ton, and 2.24 and 4.80 percent copper. About 500 feet to the east, a similar quartz-stringer zone is exposed in a roadcut. A 3.7-foot-long sample contained 695 parts per billion gold and 242 ppm copper.
Geologic map unit (-132.01840445004, 55.2013753741051)
Mineral deposit model Au-Cu quartz vein or stratiform Au-Cu breccia zones in marble.
Age of mineralization Younger than the Late Proterozoic or Cambrian host rock.
Alteration of deposit Marble is silicified and dolomitized in the mineralized breccia zones.

Production and reserves

Workings or exploration Extensive surface sampling by government and industry geologists. One hole was drilled in 1994. Hedderly-Smith (1999 [Inventory]) collected four samples that contained 0.4 to 74 parts per million (ppm) silver, 0.847 to 27.8 ppm gold, and 6.0 to 8.1 percent copper. Maas and others (1991) collected two samples that contained 1.379 and 4.506 ounces of gold per ton, 11.5 and 17.6 ounces of silver per ton, and 2.24 and 4.80 percent copper. They also collected a 3.7-foot-long sample that contained 695 parts per billion gold and 242 ppm copper.
Indication of production None

References

References

Hedderly-Smith, D.A., 1989, Report of the 1988 field season - Sealaska Mineral Reconnaissance Project: Sealaska Corporation, 66 p. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.)
Hedderly-Smith, D.A., 1992, Report of 1992 work in the Kael-Dolomi area-Sealaska minerals project: Sealaska Corporation, 60 p. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.)
Hedderly-Smith, D.A., 1993, Report of the 1992 field season-Sealaska minerals reconnaissance project: Sealaska Corporation, 60 p. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.)
Hedderly-Smith, D.A., 1999, Inventory of metallic mineral prospects, showings and anomalies on Sealaska lands, 1988 through 1998: Sealaska Corporation, Juneau, Alaska, 217 p. (internal report held by Sealaska Corporation, Juneau, Alaska).
Reporters D.J. Grybeck (Applied Geology)
Last report date 5/1/2004