Location: The Big Lake prospect is at an elevation of 1,200 feet, about 0.7 mile from the northeast side of Johnson Creek and 1 mile northwest of Berners Bay. It is in the NE1/4 section 14, T. 35 S., R. 62 E. of the Copper River Meridian. The location is accurate.
Geology: The Big Lake prospect was discovered in 1988 by International Curator Resources, Ltd. It consists of a series of parallel quartz veins in Jualin Diorite that strike northwest and dip 70 NE. The veins crop out along the ridge crest for nearly 1,300 feet; they extend toward the Yankee Boy prospect (JU051), about 2,300 feet away. The Big Lake and Yankee Boy veins are probably part of the same vein system that consists of a zone about 300 feet wide. There are two distinct types of Big Lake quartz veins; one is massive and the other consists of thin, white, veinlets. The massive veins are distinguished by a pervasive yellow-brown iron stain, sheared margins, and 1% to 10% pyrite; they are in sheared, chloritic diorite that contains about 1% disseminated pyrite. The small, white, veinlets range in thickness from one-eighth inch to three feet, and lay parallel to each other in zones up to fifty feet wide. The veins contain isolated blebs of pyrite, chalcopyrite, malachite, and specular hematite. Alteration adjacent to the veins is characterized by sericite, pervasive interstitial carbonate, and moderate to strong silicification (Barnett and others, 1989). In 1988, International Curator Resources Ltd. collected numerous samples of the Big Lake veins and Placer Dome U.S. drilled one core hole in 1989. The average for twenty grab samples collected along strike for 1200 feet was 0.454 ounce of gold per ton (Barnett, 1989). The drill hole had several anomalous intercepts; one 2.5-foot interval assayed 0.109 ounce of gold per ton (Barnett and others, 1989). The Big Lake prospect is in the Jualin mine area (see JU044), currently (2001) controlled by Coeur Alaska. It is in the Berners Bay district at the north end of the Juneau Gold Belt. The district is characterized by a series of structurally-controlled, mesothermal, gold-bearing quartz veins. Most of the veins are in Early Cretaceous (105 Ma) Jualin Diorite, which intrudes Mesozoic (Upper Triassic) metabasalt. Both extensional and shear vein are present that generally strike north to northwest and dip east. Discrete vein systems are defined by one or more through-going quartz veins, many of which are in shear zones (Miller and others, 1995). Hydrothermal muscovite from veins in the Jualin mine are 53.2 Ma to 55.5 Ma (Miller and others, 1994). This coincides with the 55 Ma age of the other mesothermal gold veins in the Juneau Gold Belt (Goldfarb and others, 1997).
Workings: The Big Lake prospect was discovered in 1988. International Curator Resources, Ltd. collected numerous samples of the veins and Placer Dome U.S. drilled one core hole in 1989. The prospect is currently (2001) controlled by Coeur Alaska.
Age: Hydrothermal muscovite from veins in the Jualin mine are 53.2 Ma to 55.5 Ma (Miller and others, 1994). This coincides with the 55 Ma age of the other mesothermal gold veins in the Juneau Gold Belt (Goldfarb and others, 1997).
Alteration: Alteration adjacent to the veins is characterized by sericite, pervasive interstitial carbonate, and moderate to strong silicification. Local oxidation of copper minerals.

Commodities (Major) - Au; (Minor) - Ag, Cu, Pb, Zn
Development Status: None
Deposit Model: Low-sulfide Au-quartz vein (Cox and Singer, 1986; model 36a)

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Commodity List

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Mineral List

7 valid minerals.