Luna

Prospect, Active

Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Au; Co; Zn
Ore minerals arsenopyrite; bornite; chalcopyrite; magnetite; pyrite; pyrrhotite; sphalerite
Gangue minerals actinolite; chlorite; epidote; garnet; pyroxene; quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale CH
Quadrangle map, 1:63,360-scale D-5
Latitude 67.76
Longitude -149.1633
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Luna prospect is about 6.5 miles at an azimuth of 6 degrees from the west peak of Horace Mountain. It covers much of the northeast quarter of section 20, T. 34 N., R. 7 W. Kurtak and others (2002) include detailed maps of the geology of the prospect, the regional geology of the area, and the location of this and other deposits of the Chandalar Copper Belt.

Geologic setting

Geologic description

The Luna prospect was discovered by Bear Creek Mining Company in 1968 and they explored it until 1973 by detailed mapping, geochemical and geophysical surveys, trenching, and sampling. Exploration continued at intervals until at least 1997 by Midwest Oil Company; by WGM Inc. who core drilled 5 holes totaling 1,500 feet in 1978-1979; and by Arctic Resources Inc. and Ventures Resource Corp. in 1997. The prospect has been mapped and sampled in detail several times and is covered by several generations of geochemical and geophysical surveys.
The rocks in the vicinity of the Luna prospect are interbedded Cambrian or Ordovician schist, marble, and skarn, overlain by Silurian and Devonian, Skajit Limestone. Quartz-sericite schist closely associated with the ore bodies is thought to be the sheared margin of a metamorphosed igneous body (Kurtak and others, 2002). The structure of the area is complex with thrust faulting and at least two generations of folding. The schists are isoclinally folded with shallow-plunging northeast-trending axes and they form a broad synform, which follows Roberts Creek.
Most of the mineralization is in quartz-sericite schist and calcareous quartz(+/-sericite)-chlorite schist. It consists of bodies of massive pyrrhotite, pyrite, chalcopyrite, magnetite, and sphalerite, in stringers and disseminations (Kurtak and others, 2002). Several notable intercepts were cut in the five, 1978-1979 drill holes: 1) 6.1 feet that contained 6.3 percent copper, 0.5 percent zinc, and 1.0 ounce of silver per ton; 2) 2.2 feet that contained 1.9 percent copper, and 1.0 percent zinc; and 3) 3.6 feet that contained 2.0 percent copper and 7.0 percent zinc. Samples collected by Nicholson (1990) contained up to 1,129 parts per billion (ppb) gold, 10.2 percent copper, and 8,447 ppm zinc. Kurtak and others (2002) collected samples of the same tenor and Ventures Resource Alaska reported samples over widths of 20 to 30 feet with 3 percent or more copper (Swainbank and others, 1997).
There are several interpretations of the mineralization at the Luna prospect. Newberry and others (1986, 1997) group it with the many skarn deposits of the Chandalar Copper Belt that is northwest of and genetically related to the Devonian(?) granitic plutons at Horace Mountain. Many of those skarns exhibit both garnet-pyroxene prograde and epidote-actinolite retrograde mineral assemblages. They conclude that the mineralogy, mineralization, and alteration indicate that most of them are continental-margin, porphyry-related copper skarns. In particular, they classify the Luna deposit as a copper-zinc-silver skarn or a calcic copper skarn.
Nicholson (1990) suggests that at least part of the mineralization is volcanogenic based on the presence of massive, stringer, and disseminated sulfides, even if there are 'distal' copper-zinc skarns at Luna as well. Ventures Resource Corporation (1999) conclude that the mineralization at Luna is stratabound and consists principally of chalcopyrite and lesser amounts of bornite and sphalerite in altered calc-silicate schist associated with small bodies of meta-diorite and granodiorite. Ventures describes the deposit as including: a) stratabound volcanogenic sulfides; b) strata-controlled massive pyrite-chalcopyrite-magnetite skarns; c) strata- and shear-controlled massive chalcopyrite-bornite-sphalerite replacements; and d) a 2-foot-thick massive pyrrhotite-arsenopyrite replacement(?) in marble.
Using two different models, Nicholson (1990) estimated that the Luna deposit contains a resource of 1.8 million tons or 70,000 tons, in both cases with an average grade of 0.9 percent copper, 0.03 percent zinc, and 0.25 ounce of silver per ton.
Geologic map unit (-149.166064300583, 67.7596033514971)
Mineral deposit model Cu skarn deposit or Kuroko massive sulfide? (Cox and Singer, 1986; models 18b? and 28a?).
Mineral deposit model number 18b? or 28a?
Age of mineralization Devonian(?) based on Early Devonian Pb/Pb zircon ages from the nearby Baby Creek batholith and Horace Mountain plutons (Dillon and others, 1996).
Alteration of deposit Chloritic alteration of schists and silicic alteration of metamorphosed dikes and sills.

Production and reserves

Workings or exploration The Luna prospect was discovered by Bear Creek Mining Company in 1968 and they explored it until 1973 by detailed mapping, geochemical and geophysical surveys, trenching, and sampling. Exploration continued at intervals until at least 1997 by Midwest Oil Company; by WGM Inc. who core drilled 5 holes totaling 1,500 feet in 1978-1979; and by Arctic Resources Inc. and Ventures Resource Corp. in 1997. The prospect has been mapped and sampled in detail several times and is covered by several generations of geochemical and geophysical surveys.
Indication of production None
Reserve estimates Using two different models, Nicholson (1990) estimated that the Luna deposit contains a resource of 1.8 million tons or 70,000 tons, in both cases with an average grade of 0.9 percent copper, 0.03 percent zinc, and 0.25 ounce of silver per ton.
Production notes None.

Additional comments

This prospect is on Doyon Ltd. selected lands; for more information, contact Doyon Ltd., Fairbanks, Alaska.
MAS No. 0020310109

References

MRDS Number 10307342

References

Arctic Resources Inc., 1981, Doyon Ltd. exploration program, Block 4, 5, 8, and 22: Unpublished report 81-27 for Doyon Ltd., p. 1-36 (
Dashevsky, S.S., 1986, Mines, prospects, and geochemical anomalies on Doyon Ltd. regional overselection lands, Alaska Blocks 1 - 8, v; I of II: Unpublished report 86-01A for Doyon Ltd., 42 p. (on file at Doyon Ltd., Fairbanks, Alaska).
Kurtak, J.M., Klieforth, R.F., Clark, J.M., and Maclean, E.A., 2002, Mineral investigations in the Koyukuk mining district, northern Alaska, 2 vols.: Bureau of Land Management, Alaska Technical Report 50, 845 p.
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.
Nicholson, L.M., 1990, Porphyry copper, copper skarn, and volcanogenic massive sulfide occurrences in the Chandalar copper district, Alaska: Fairbanks, University of Alaska, M.Sc. thesis, 164 p.
Nicol, D.L., 1983, Evaluation of the mineral potential of Doyon Ltd.'s Block 5 and 22 (unpublished report 83-04 for Doyon Ltd., (on file at Doyon Ltd., Fairbanks, Alaska).
Ventures Resource Corporation, 1999, 1999 Annual report: Ventures Resource Corporation, 36 p.
WGM Inc., 1978, 1977 Annual progress report, Doyon Ltd. project, v. II, Luna area: Unpublished report 78-04 for Doyon Ltd., 15 p. (on file at Doyon Ltd., Fairbanks, Alaska).
WGM Inc., 1979, 1978 Doyon Ltd. annual progress report, Block 5 Luna volcanogenic massive sulfide and associated base-metal deposits and anomalies of the Chandalar Copper Belt: Unpublished report 79-21 for Doyon Ltd., 35 p. (on file at Doyon Ltd., Fairbanks, Alaska).
WGM Inc., 1980, 1979 annual profess report, Block 5-Wiseman Chandalar Cop[er Belt: Unpublished report 80-06 for Doyon Ltd., 28 p. (on file at Doyon Ltd., Fairbanks, Alaska).
Reporters J.M. Britton (Anchorage, Alaska); D.J. Grybeck (Contractor, U.S. Geological Survey)
Last report date 4/18/2010