Rum North

Prospect, Inactive

Commodities and mineralogy

Main commodities Cu; Pb; Zn
Other commodities Ag
Ore minerals arsenopyrite; chalcopyrite; galena; gold; magnetite; pyrite; pyrrhotite; sphalerite
Gangue minerals chlorite; quartz

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-1
Latitude 63.2385
Longitude -144.1239
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Rum North prospect is at an elevation of about 5,500 feet approximately 1.75 miles east of Rumble Creek. It is about 0.7 mile east of peak 7405 and in the SW1/4 section 20, T. 17 N., R. 7 E., Copper River Meridian. The location is accurate to within 150 feet.

Geologic setting

Geologic description

The Rum North prospect is in a west-northwest-trending, steeply south dipping sequence of metavolcanic and metasedimentary rocks that have been intruded by gabbroic sills in the central and basal part of the Drum unit. The Rum North prospect is about 1,000 feet away from the Rum South prospect (MH343) and separated from it by an inferred fault (R.A. Blakestad and others, unpublished Resource Associates of Alaska Inc. report, 1978). The Drum unit that hosts the Rum prospects consists of white to pale gray-green, rusty weathering, quartz-sericite(-chlorite-pyrite) schist with minor gray to black carbonaceous phyllite and rare interbeds of chloritic phyllite. The schist commonly contains 1 to 5 percent quartz eyes but may contain more. The protoliths of the schist are about two-thirds of volcanic origin and one-third of sedimentary origin. The schist has a phyllitic parting in many places (Dashevsky and others, 2003).
The Rum North massive sulfide deposit is poorly exposed near the top of a steep talus-covered slope. A train of sparse sulfide float below it contains both copper-rich and lead-zinc-rich cobbles that suggest the presence of a strongly zoned sulfide horizon. Cobbles of massive sulfide found in Rum Creek are generally fairly small, rarely as large as 12 inches. The limited outcrop exposure shows two bands of massive sulfide, each less than 1 foot thick. Representative assays have 3.9 percent copper, 5.5 percent lead, 10.1 percent zinc, 20.5 parts per million (ppm) silver, and 0.2 ppm gold (Lange and others, 1993; S.S. Dashevsky, written communication, 2003).
Nine grab samples of massive sulfide from the Rum North and Rum South zones average 4.21 percent copper, 7.07 percent lead, 8.95 percent zinc, 2.89 ounces of silver per ton, and traces of gold. The highest grade samples contain 37.2 percent combined copper, lead, and zinc with as much as 11.7 ounces of silver per ton (J.K. Muntzert and others, unpublished Resource Associates of Alaska Inc. report, 1977).
The rocks at the Rum prospect include fairly thin, discontinuous, interbedded metarhyolite tuffs, rhyodacite and dacite tuffs, and tuffaceous sedimentary rocks that have characteristic undulating graphitic phyllite layers throughout the section. Massive sulfide float boulders are found at what appears to be the top of a thick, predominantly felsic sequence of rocks that includes crystal and lapilli tuffs and lesser rhyodacite, dacite, and metasedimentary rocks. The basal part of this sequence that consists of thin, cherty, siliceous schists and thin, pyritic rhyolite flows is oxidized to form a spectacular color anomaly north of Rum Creek. The rocks above the massive sulfide float train are generally more chloritic, finer grained, and probably have a greater metasedimentary component (J.K. Muntzert and others, unpublished Resource Associates of Alaska Inc. report, 1977).
Geologic map unit (-144.126149259954, 63.2381233263655)
Mineral deposit model Kuroko massive sulfide (Cox and Singer, 1986; model 28a).
Mineral deposit model number 28a
Age of mineralization The Drum unit, which is part of the metamorphic sequence that includes the rocks at this deposit, has been dated at the Devonian-Mississippian boundary on the basis of one SHRIMP U-Pb zircon age of 359 +/- 6 Ma at the nearby DD South prospect (MH325).
Alteration of deposit The massive sulfides are associated with an intensely chloritized layer or unit with peripheral sericite-quartz-pyrite +/- chalcopyrite alteration (Lange and others, 1993).

Production and reserves

Workings or exploration One hole was drilled to 1,173 feet in the Rum North prospect; no massive sulfides were intersected (American Copper and Nickel Company, unpublished data, 1998). Field work has also included detailed geologic mapping, trenching, and magnetic and soil geochemistry surveys over the mineralized area (Rodney A. Blakestad and others, unpublished Resource Associates of Alaska Inc. report, 1979).
Indication of production None

Additional comments

The unpublished data that is cited can be seen by contacting Grayd Resources Inc. in Vancouver, B.C., Canada (www.grayd.com), or Northern Associates Inc. in Fairbanks, Alaska.

References

References

Lange, I. M., Nokleberg, W.J., Newkirk, S. R., Aleinikoff, J.N., Church, S.E., and Krouse, R.H., 1993, Devonian volcanogenic massive sulfide deposits and occurrences, southern Yukon-Tanana terrane, eastern Alaska Range, Alaska: Economic Geology, v. 88, p. 344-376.
Reporters W.T. Ellis (Alaska Earth Sciences) and A.W. Wyatt and S.S. Dashevsky (Northern Associates Inc.)
Last report date 3/20/2003