Unnamed Occurrence (ARDF - SM060; eastern Chuilnuk Mountains), Aniak Mining District, Bethel Census Area, Alaska, USAi

Regional Level Types
Unnamed Occurrence (ARDF - SM060; eastern Chuilnuk Mountains)	- not defined -
Aniak Mining District	Mining District
Bethel Census Area	Census Area
Alaska	State
USA	Country

Location: This occurrence is in the eastern Chuilnuk Mountains, in the headwall cirque of an unnamed tributary of the Chuilnuk River. It is at an elevation of about 2,700 feet, about 0.6 mile east of peak 3310 and 0.6 mile north-northwest of peak 3110, in the SW1/4 sec. 8, T. 14 N., R. 47 W., of the Seward Meridian. The location is accurate.
Geology: This occurrence consists of a series of quartz-tourmaline-sulfide-bearing greisen veins in the 68-Ma-old Chuilnuk Mountains pluton (Cady and others, 1955). The Chuilnik Mountains pluton is a mesozonal intrusion composed of medium-grained, hornblende-biotite granodiorite that intrudes shale and sandstone of the Upper Cretaceous, Kuskokwim Group (Decker and others, 1995). The veins vary from 1 to 4 inches thick and occur at a density of about 1 vein per foot. The sulfide content of the veins is low, less than 2.0 percent, but tourmaline makes up as much as 20 percent of the vein material. The greisen veins can be traced perpendicular to its strike for about 1,300 feet across the cirque headwall. Individual veins strike N5-15E and dip nearly vertically and they extend up the headwalls of the cirque here for at least 300 feet. Two grab samples of the veins collected at the base of the cirque contained up to 63 parts per billion (ppb) gold, 2,300 ppb silver, 515 parts per million (ppm) arsenic, 405 ppm bismuth, 59 ppm antimony, and 123 ppm tin (T. K. Bundtzen, unpublished data, 1998).
Workings: The geology of the Chuilnik Mountains area was mapped by the U.S. Geological Survey in the 1940s and by the Alaska Division of Geological and Geophysical Surveys in the 1980s (Cady and others, 1955; Decker and others, 1995). This occurrence was discovered in 1998 (T.K. Bundtzen, unpublished data, 1998).
Age: Unknown. Decker and others (1995) report a 40K/40Ar biotite age of 68 Ma for the Chuilnuk Mountains pluton.
Alteration: Development of tourmaline-quartz-sulfide greisen.

Commodities (Major) - Ag, Bi, Sn; (Minor) - As, Au, Sb
Development Status: None
Deposit Model: Silver-polymetallic veins or tin veins (Cox and Singer, 1986; models 20b or 15b

Other Databases

Link to USGS - Alaska:	SM060

Other Regions, Features and Areas containing this locality

References