Crash; Sheep Creek 2 Prospect, Yukon-Koyukuk Census Area, Alaska, USAi

Regional Level Types
Crash; Sheep Creek 2 Prospect	Prospect
Yukon-Koyukuk Census Area	Census Area
Alaska	State
USA	Country

The Crash prospect contains anomalous gold, which is atypical of most sulfide occurrences and prospects in the Farewell Mineral Belt. The Crash zone is in a splay structure associated with a regional fault that hosts the Dahl prospect (MG053).
Location: The Crash prospect is located in an unnamed east-flowing tributary of Sheep Creek, 4.0 kilometers northwest of Smith Lake; it is at an elevation of 2,800 feet (853 m) in the SW1/4 sec. 7, T. 26 N., R. 24 W., of the Seward Meridian. The Crash occurrence is 3.0 kilometers north of the Dahl Prospect (MG053). The reporter visited the site in 1981.
Geology: The Crash prospect consists of two siliceous cataclastic breccias similar to those that host mineralization at the Dahl prospect (MG053). Exposed mineralization in one shale hosted breccia zone contains massive chalcopyrite, sphalerite, and traces of galena near the contact between the Lower Ordovician to Lower Silurian, Post River Formation and the mid- to Upper Silurian Terra Cotta Mountains Sandstone; both are units of the Dillinger subterrane (Bundtzen, Harris, and Gilbert, 1997). Another siliceous cataclastic breccia contains abundant arsenopyrite. Both sulfide bearing zones range from 3 to 30 centimeters thick, appear stratiform or parallel to sedimentary bedding, and are isoclinally folded, which suggests sulfides were formed prior to Lower Cretaceous compressive deformation (Bundtzen, Harris, and Gilbert, 1997). The mineralization at the Crash prospect might also be related to younger plutons. The larger massive sulfide-bearing breccia contained up to 16.5 percent copper and 926.8 grams/tonne silver (Brewer and others, 1992). The second cataclastic zone contains a 0.2 to 2.0 meter pod of massive arsenopyrite that contains 6.8 grams/tonne gold. Three samples collected by Smith and Albanese (1985) contain up to 316 ppm copper, 86 ppm lead, 940 ppm zinc, and 10.5 grams/tonne silver.
Workings: Tom Smith and Mary Albanese first sampled the Sheep Creek-2 occurrence in 1982 during mineral investigations by the Alaska Division of Geological and Geophysical Surveys in the area (Smith and Albanese, 1985). One breccia zone with massive sulfide mineralization contained up to 16.5 percent copper and 926.8 grams/tonne silver. Another smaller siliceous breccia zone with massive arsenopyrite contained 6.5 grams/tonne gold (Brewer and others, 1992). Three random grab samples contained up to 316 ppm copper, 86 ppm lead, 940 ppm zinc, and 10.5 grams/tonne silver.
Age: Undated; inferred to be Lower Ordovician to Lower Silurian, based on graptolites found in mineralized area (Bundtzen, Harris, and Gilbert, 1997).
Reserves: None.

Commodities (Major) - Ag, Cu, Zn; (Minor) - Au, Pb
Development Status: No
Deposit Model: Uncertain; either sedimentary exhalitive lead-zinc (?) or polymetallic vein (Co

Other Databases

Link to USGS - Alaska:	MG049

Other Regions, Features and Areas containing this locality

References