J.D. Lyons Prospect, Chistochina Mining District, Valdez-Cordova Census Area, Alaska, USAi

Regional Level Types
J.D. Lyons Prospect	Prospect
Chistochina Mining District	Mining District
Valdez-Cordova Census Area	Census Area
Alaska	State
USA	Country

Location: The J.D. Lyons prospect (Cobb, 1979 [OF 79-1247,p. 18]) is at an elevation of about 4,400 feet on the ridge about 1/4 mile south of the confluence of the two headwater forks of Grubstake Creek . It is in the center of the N1/2, section 35, T. 12 N., R. 7 E., Copper River Meridian. Another geologically similar prospect is at an elevation of about 3,700 feet to the north, but south of Grubstake Creek. The location of these prospects is accurate; they are shown as locality 5 of Richter (1966, figure 5, p. 31), locality 16 of Richter and Matson (1972), and locality 15 of MacKevett and Holloway (1977).
Geology: The Lyons prospect is in hornfelsed, chlorite-hornblende volcanic rocks in the border phase of the Pennsylvanian to Permian, Ahtell pluton (Richter, 1964 and 1966; Richter and Matson, 1968). The hornfels is cut by irregular, discontinuous quartz veins as much as 6 inches thick. The veins and host rock is weakly copper stained (malachite?), and the quartz veins contain small amounts of pyrite and chalcopyrite (Richter 1966, p. 31).
Workings: The prospect on the ridge at an elevation of about 4,400 feet was developed prior to 1963 by prospect pits and by a 10-foot-long adit (Richter, 1964).
Age: The mineralization is probably related either to the Pennsylvanian to Permian, Ahtell intrusive or to mid-Jurassic dioritic rocks exposed east of the occurrence.
Alteration: Chlorite-hornblende hornfels in altered border phases of the Pennsylvanian to Permian, Ahtell pluton.

Commodities (Major) - Cu
Development Status: None
Deposit Model: Polymetallic vein (Cox and Singer, 1986; model 22c)

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Link to USGS - Alaska:	GU018

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References