|Quadrangle map, 1:250,000-scale||CH|
|Quadrangle map, 1:63,360-scale||C-5|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The Eva prospect is at an elevation of about 3,300 feet on the east side of the ridge between Big Spruce Creek and Mathews River. It is about 1.1 mile north-northwest of peak 4737 and about 0.6 mile west-northwest of the center of section 29, T. 33 N., R. 8 W. A map showing the geology of the area and the location this and the other deposits of the Chandalar Copper Belt is Figure C-1 of Kurtak and others (2002).|
The Eva prospect was discovered by Bear Creek Mining Company in 1967 along what would would become known as the Chandalar Copper Belt (Kurtak and others, 2002). Bear Creek and several other companies (Midwest Oil Company, WGM Inc., Arctic Resources Inc., and Venture Resources Corp.) explored the property into the 1990s. Their work included geological mapping, sampling, and geochemical and geophysical surveys.
The Eva prospect is one of several Cu deposits in the Chandalar area which have been described by Newberry and others (1986) as mostly copper skarn deposits. They are all northwest of a belt of Devonian(?) metamorphosed granodioritic rocks informally named the Horace Mountain plutons that are probably genetically related to these deposits. Many of these copper skarns exhibit both prograde garnet and pyroxene and retrograde epidote and actinolite mineral assemblages. Newberry and others (1986) stated that the mineralogy, mineralization, and alteration of these skarns tend to place them in the category of continental-margin, porphyry-related copper skarns.
Some of the descriptions of the Eva prospect include it with the nearby Victor (CH064) and Venus prospects (CH065) (DeYoung, 1978; Cobb and Cruz, 1983). The Venus prospect in particular is characterized as a porphyry deposit. Cobb and Cruz (1983) classify the Eva deposit as either a porphyry or skarn, whereas Newberry and others, (1086) classify it as a copper skarn, and the Eva prospect thus has been characterized as a porphyry copper and (or) copper skarn deposit (Cobb and Cruz, 1983). Newberry and others (1986), however, classified it as a Cu skarn.
Kurtak and others (2002) de-emphasize the skarn interpretation and describe the Eva prospect as restricted to a belt about a half mile long of conspicuous red-stained muscovite schist, associated with quartz-sericite schist, calcareous schists, calc-silicate schist, and some small metamorphosed igneous bodies. The mineralization is concentrated in the muscovite schist and consists of erratically-distributed, malachite-and-azurite-stained pods and lenses with disseminated chalcopyrite. A select sample contained 68 parts per billion (ppb) gold, 2.1 parts per million (ppm) silver, 2,835 ppm copper, 306 ppm lead, and 93 ppm zinc. The mineralization in the quartz-sericite schist, calcareous schist, and calc-silicate schist is relatively weak and spotty. However, a sample of calcareous schist with pyrite stringers contained 9.7 ppm silver, 3,395 ppm lead, 3,933 ppm zinc, and 23 ppb gold. A sample of calc-silicate schist contained an average of 64 ppb gold, 2.45 ppm silver, and 4,740 ppm copper. The metamorphosed igneous rocks contain only a trace of sulfide minerals.Nicholson (1990) estimated that the Eva and nearby Victor(CH064) prospects have a resource of 50,000 tons with an average grade of 2 percent copper. However, Kurtak and others (2002) note that the mineralization at the Eva prospect appears to be 'limited to small, discontinuous outcrops'.
|Geologic map unit||(-149.427160383177, 67.6598962527859)|
|Mineral deposit model||Pods and lenses of copper mineralization in muscovite schist and copper skarn.|
|Age of mineralization||Probably related to a belt of Devonian(?) intrusive rocks.|
|Alteration of deposit||Propylitic and sericitic alteration of the meta-granodiorite and retrograde epidote/actinolite alteration of the skarns.|
|Workings or exploration||The Eva prospect was discovered by Bear Creek Mining Company in 1967 along what would would become known as the Chandalar Copper Belt (Kurtak and others, 2002). Bear Creek and several other companies (Midwest Oil Company, WGM Inc., Arctic Resources Inc., and Venture Resources Corp.) explored the property into the 1990s. Their work included geological mapping, sampling, and geochemical and geophysical surveys.|
|Indication of production||None|
|Reserve estimates||Nicholson (1990) estimated that the Eva and nearby Victor(CH064) prospects have a resource of 50,000 tons with an average grade of 2 percent copper. However, Kurtak and others (2002) note that the mineralization at the Eva prospect appears to be 'limited to small, discontinuous outcrops'.|
This prospect is on Doyon Ltd. selected lands; for more information, contact Doyon Ltd., Fairbanks, Alaska.MAS No. 0020310140
Cobb, E.H., and Cruz, E.L., 1983, Summaries of data and lists of references to metallic and selected nonmetallic mineral deposits in the Chandalar quadrangle, Alaska: U.S. Geological Survey Open-File Report 83-278, 91 p.
DeYoung, J.H., Jr., 1978, Mineral resources map of the Chandalar quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-878-B, 2 sheets, scale 1:250,000.
Dillon, J.t., Reifensuthl, R.R., and Harris, G.W., 1996, Geologic map of the Chandalar C-5 quadrangle, southeastern Brooks Range, Alaska: Alaska Division of Geological and Geophysical Surveys, Professional Report 104, 2 sheets, scale 1:63.360.
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.
Ventures Resource Corp., 1999, 1999 Annual report: Ventures Resource Corporation, 36 p.
WGM Inc., 1973, Progress report 1973, Chandalar district: Unpublished report for Midwest Oil Corporation, 46 p.
WGM inc., 1974, Chandalar district progress report 1974: Unpublished report for AMOCO Minerals, 37 p.
WGM Inc., 1977, 1077 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., 1980, 1979 annual profess report, Block 5-Wiseman Chandalar Copper 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|