Summit Prospect, Chandalar Mining District, Yukon-Koyukuk Census Area, Alaska, USAi

Regional Level Types
Summit Prospect	Prospect
Chandalar Mining District	Mining District
Yukon-Koyukuk Census Area	Census Area
Alaska	State
USA	Country

See also: Mikado (CH045), Little Squaw(CH040), Star(CH042).
Location: The Summit lode is at an elevation of about 4,800 feet, approximately 1/2 mile south of Little Squaw Peak, between Little Squaw Peak and peak 5072 (St. Marys Peak as labeled on fig. 2 in Chipp, 1970) in SW1/4 sec. 3, T. 31 N., R. 3 W., of the Fairbanks Meridian. The location is accurate.
Geology: Maddren (1913) reported a 54-foot-deep shaft and a 72-foot drift along the vein. Prospect pits have been dug along the Summit fault/vein system as far east as the pass between Big Creek and McClellan Creek and west along the spur going into Big Squaw Creek. Heiner and Wolff (1968) report that there was some development work in the 1950s and a small mill was established for the ore in the headwaters of Big Creek. It may not have milled any ore. In 2004, Little Squaw Gold Mining Company controlled 8,550 acres of patented and unpatented mining claims in the Chandalar district which includes the Summit prospect. This company contracted a district-scale analysis of the placer and lode gold potential of the district by Pacific Rim Geological Consulting, Inc. This study was completed in April, 2004 (Barker and Bundtzen, 2004). The Summit lode is one of the four principal auriferous quartz vein systems in the Chandalar area. The Summit vein system, like the others in the area, is localized along steeply-dipping, northwest-trending normal faults in Devonian quartz-muscovite schist, phyllite, and quartzite, intruded by Devonian mafic sills and dikes (Chipp, 1970). In general, the veins in the Chandalar area are less than 10 feet thick and are discontinuous, pinching out within a few hundred feet or less. The veins are composed principally of white crystalline to microcrystalline quartz, and their sulfide content is generally less than 5 percent. The principal sulfides (in relative order of abundance) are arsenopyrite, galena, sphalerite, and pyrite. Scorodite and limonite occur commonly as oxidation products. The quartz veins exhibit evidence of shearing, indicating that the veins were emplaced before or during fault movement. Major structural features in the area include large-scale northeast-trending anticlines and synclines, northeast-trending thrusts, and the northwest-trending, high-angle cross faults. The Summit lode follows the Summit fault, strikes N80W, and dips 75 to 80 degrees south. Early workings on the property exposed a vein 1.5 to 2 feet wide. A sample from these workings was reported to have assayed $54 of gold per ton (Maddren,1913). Dump samples of vein material collected by Chipp (1970) contained abundant arsenopyrite and scorodite in sheared and brecciated quartz; assays of these samples returned values of 0.5 to 6.6 parts per million gold. Ashworth (1983) described two generations of quartz at the Summit lode. The older generation is coarsely crystalline, massive, white quartz. It is in the hanging wall and is as much as 4 feet wide. It contains less than 5 percent sulfides and little gold. The younger generation pinches and swells; it adjoins the older veins, but typically follows in the footwall. It is generally finer grained and contains bands accentuated by smeared graphite and arsenopyrite. Scorodite is common, and free gold occurs as blebs and occasional wires. The genesis of the gold deposits in the Chandalar district is still in question. Various authors have hypothesized genetic links to a variety of felsic and mafic igneous rocks from which the gold was remobilized during metamorphism (Mertie, 1925; Boadway, 1933; Chipp, 1970; Dillon, 1982).
Workings: Maddren (1913) reported a 54-foot-deep shaft and a 72-foot drift along the vein. Prospect pits have been dug along the Summit fault/vein system as far east as the pass between Big Creek and McClellan Creek and west along the spur going into Big Squaw Creek. Heiner and Wolff (1968) report that there was some development work in the 1950s and a small mill was established for the ore in the headwaters of Big Creek. It may not have milled any ore. In 2004, Little Squaw Gold Mining Company controlled 8,550 acres of patented and unpatented mining claims in the Chandalar district which includes the Summit prospect. This company contracted a district-scale analysis of the placer and lode gold potential of the district by Pacific Rim Geological Consulting, Inc. This study was completed in April, 2004 (Barker and Bundtzen, 2004).
Age: Middle Cretaceous(?) based on arguments by Dillon (1982) that the age of emplacement of the gold-bearing quartz veins of the Koyukuk and Chandalar districts was between the Neocomian metamorphism of the Devonian host rocks and their erosional unroofing and cooling in Albian time.
Alteration: Oxidation of vein material produces scorodite and limonite.

Commodities (Major) - Ag, Au; (Minor) - Cu, Pb, Sb
Development Status: Undetermined
Deposit Model: Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a)

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Link to USGS - Alaska:	CH041

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References