|Quadrangle map, 1:250,000-scale||LH|
|Quadrangle map, 1:63,360-scale||C-1|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This prospect is on a west tributary to the upper Styx River in the Alaska Range about 16.5 miles northeast of Snowcap Mountain in the northeast quarter of section 24, T. 17 N., R. 22 W., of the Seward Meridian. The location site is centered where potassic alteration with A-veins and chalcopyrite has been found in outcrop along the creek.|
As originally described by Reed and Elliott (1970), iron-stained and altered intrusive rocks are present along about 200 feet of a creek. The altered rocks consist dominantly of quartz and sericite with minor potassium feldspar and biotite. These rocks generally contain less than one percent sulfide minerals, including pyrite, sphalerite, and galena, which are disseminated and in quartz veins as much as 2 inches wide. Sphalerite and galena also occur as thin veinlets and disseminations in felsite. Shear zones in the altered intrusions are also mineralized with sulfides. Besides zinc and lead values, rock samples contained as much as 15 parts per million (ppm) silver and 300 ppm molybdenum. The altered intrusive rocks are probably Late Cretaceous or Tertiary components of the Alaska-Aleutian Range batholith (Reed and Lanphere, 1973).
Float boulders contained chalcopyrite. Potassic alteration with quartz-magnetite stockworks and disseminated chalcopyrite extends over an area of about 1 kilometer by 3 kilometers, and intense phyllic alteration extends outward about another 2.5 kilometers. Kennecott did a ground magnetic survey that defined a magnetic high about 1.0 by 1.9 kilometers in area that trends northeast from the mineralization. Rock samples contained up to 0.73 percent copper, 0.415 grams of gold per tonne, and 0.125 percent molybdenum (Kiska Metals Corporation, 2010).In 2016, First Quantum Minerals funded a single, 806-meter-long, exploratory drill hole targeting the center of a 1.4-kilometer-wide magnetotelluric anomaly, which is coincident with other geological, geochemical, and geophysical anomalies, at Kiska Metals Corp.’s Copper Joe porphyry copper property in southwest Alaska. The drill hole into the Evening Star target intercepted more than 400 meters of hydrothermal breccia with strong phyllic alteration, abundant pyrite, sparse early quartz veins, magnetite-anhydrite-pyrite-chalcopyrite veins, and banded molybdenite veins. No significant copper grades were intersected but extensive brecciation and strong alteration suggests a robust hydrothermal porphyry system; additional drilling is required to determine if ore-grade mineralization exists. First Quantum Minerals withdrew from the project at the end of the season. In December 2016, AuRico Metals Inc. announced a definitive agreement to acquire Kiska Metals, subject to customary closing conditions including Kiska shareholder approval, expected in the first quarter of 2017 (Athey and Werdon, 2017).
|Geologic map unit||(-153.159907531456, 61.5384781614177)|
|Mineral deposit model||Copper-gold-molybdenum porphyry? (Cox and Singer, 1986, model 20c or 21a).|
|Mineral deposit model number||20c? or 21a?|
|Age of mineralization||Probably Late Cretaceous or Tertiary based on similarities with other mineralized intrusives of the Alaska-Aleutian Range batholith (Reed and Elliott, 1970; Reed and Lanphere, 1973).|
|Alteration of deposit||A core zone of potassic and magnetite alteration associated with porphyry dikes and an extensive 4.5 by 2.5 kilometer zone of moderate to intense phyllic alteration peripheral to the core zone (Roberts, 2014).|
|Workings or exploration||
In 2006, Kennecott Exploration staked 100 State of Alaska mining claims over this prospect, which they interpreted to have porphyry-style alteration in porphyritic monzodiorite rocks (Kiska Metals Corporation, 2010). Kennecott did a ground magnetic survey that defined a magnetic high about 1.0 by 1.9 kilometers in area that trends northeast from the mineralization. Rock samples contained up to 0.73 percent copper, 0.415 grams of gold per tonne, and 0.125 percent molybdenum.
In 2010, Kiska Metals Corp. (Kiska) signed an option agreement with Kennecott to explore the Copper Joe claims. Exploration work conducted by Kiska consisted of geological mapping, rock, soil and stream sediment geochemistry sampling, and an induced-polarization (IP) survey and ground magnetics around a prospective area defined in previous work by AMAX and Kennecott. In 2011, a short follow-up program was conducted on Copper Joe that consisted of geological mapping, rock geochemistry sampling, and prospecting. At this time, new claims were staked (Shogun Claims) to the northwest of the Copper Joe claims covering drainages with anomalous copper and gold in stream sediment samples collected in 2010 (Roberts, 2014).Kiska and First Quantum Minerals Ltd. (First Quantum) drilled two holes totalling 885 meters at Copper Joe in 2014. Drilling did not return any significant assay results but did confirm a large porphyry-hydrothermal system. One drill hole intersected two zones of heterolithic, magnetite breccia cross-cutting a porphyritic quartz monzonite and the other drill hole intersected a moderately to strongly chlorite-epidote altered quartz monzonite breccia intruded by a weakly altered biotite-feldspar porphyry (Kiska Metals Corp., 2014). Exploration work in 2015 includes a geophysical survey and infill geologic mapping (Kiska Metals Corp., 2015).
|Indication of production||None|
Cox, D.P., and Singer, D.A., eds., 1986, Mineral deposit models: U.S. Geological Survey Bulletin 1693, 379 p.
Roberts, M., 2014, Copper Joe Executive Summary, Kiska Metals Corporation. (Released January 26, 2014): http://www.kiskametals.com/i/pdf/Kiska_CopperJoe_ExecutiveSummary_26Jan2014.pdf (as of July 11, 2014).
|Reporters||Travis L. Hudson (Applied Geology) and Madelyn A. Millholland Millholland & Associates); D.J. Grybeck (Contractor, USGS); V.C. Zinno (Alaska Earth Sciences, Inc.); N.V. King (Alaska Earth Sciences, Inc.); M.B. Werdon (DGGS)|
|Last report date||8/26/2017|