Vein deposits hosted by plutonic rocks in the Croesus Stock and Hailey gold belt mineralized areas, Blaine County, Idaho

Mineral deposits in the Croesus and Hailey gold belt mineralized
areas in Blaine County, south-central Idaho, are preciousand
base-metal quartz veins that are part of a family of vein
deposits spatially and temporally associated with the Idaho
batholith. Historic production from these veins has been mainly
gold and silver. Host rocks are older border phase plutons of the
Idaho batholith that are characterized by more potassium and
less sodium as compared to rocks from the main body of the
batholith to the west. Host structures are reverse faults that have
moderate to shallow dips to the northeast and high-angle normal
faults that also strike northwest.
The veins are characterized by several generations of quartz
and generally sparse sulfide minerals; gold is associated with
late-stage comb quartz. The precious-metal ore bodies are in a
series of shoots, each of which is as much as 8 ft in width, 400 ft
in breadth, and 1,000 ft in pitch length.