Old Man Diorite Prospect, Yentna Mining District, Matanuska-Susitna Borough, Alaska, USAi

Regional Level Types
Old Man Diorite Prospect	Prospect
Yentna Mining District	Mining District
Matanuska-Susitna Borough	Borough
Alaska	State
USA	Country

Location: Alaska Department of Natural Resources claim records show the prospect located approximately 3000 to 3500 feet in elevation on the south side of Old Man Creek, about five miles up stream from the confluence of Old Man Creek and the Skwentna River in Section 13, T. 21 N., R. 17 W.
Geology: At this locality a Late Cretaceous/Early Tertiary(?) diorite is cut by shallow (10-30 degree) veins less than 1 foot to 5 foot thick, and poorly developed stockwork veins. Mineralization consists of varying amounts of quartz, chlorite, arsenopyrite, pyrite, pyrrhotite, molybdenite, and carbonate. The best gold grades are associated with zones of sub-parallel veins. Gold ranges from ten's of ppb to 0.122 oz/ton (Cominco American Incorporated, unpublished reports, 1986-1987). The diorite is probably one of the late Cretaceous/Early Tertiary Kichatna plutons (TKk) described by Reed and Nelson (1980) in the Talkeetna quadrangle to the north. A K-Ar age of 67.4 +/-2 m.y. suggests that these plutons may be slightly older than the 65-km belt of composite plutons to the west. The veins may be related to the diorite intrusion.
Workings: Exploration work included silt and rock chip geochemical sampling, mapping, and diamond drilling. The property is steep and technical climbers with Dihedral Exploration were employed to conduct geologic and geochemical surveys.
Age: The host rock is late Cretaceous/Early Tertiary(?)diorite; the veins may be related to the diorite intrusion.
Alteration: Carbonate, pyrite, sericite, quartz

Commodities (Major) - Ag, Au, Mo; (Minor) - As, Ba
Development Status: None
Deposit Model: Polymetallic veins

Other Databases

Link to USGS - Alaska:	TY026

Other Regions, Features and Areas containing this locality

References