Old Man Diorite

Prospect, Inactive

Commodities and mineralogy

Main commodities Ag; Au; Mo
Other commodities As; Ba
Ore minerals arsenopyrite; chalcopyrite; gold; molybdenite; pyrite; pyrrhotite; sphalerite
Gangue minerals carbonate; chlorite; quartz

Geographic location

Quadrangle map, 1:250,000-scale TY
Quadrangle map, 1:63,360-scale D-7
Latitude 61.91
Longitude -152.32
Nearby scientific data Find additional scientific data near this location
Location and accuracy 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.

Geologic setting

Geologic description

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 Gold ranges from ten's of ppb to 0.122 oz/ton (Cominco American Incorporated, unpublished reports, 1986-1987).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.
Geologic map unit (-152.322219435925, 61.9094260321348)
Mineral deposit model Polymetallic veins
Age of mineralization The host rock is late Cretaceous/Early Tertiary(?)diorite; the veins may be related to the diorite intrusion.
Alteration of deposit Carbonate, pyrite, sericite, quartz

Production and reserves

Workings or exploration 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.
Indication of production None