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Neirod - East

Prospect, Active

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Commodities and mineralogy

Main commodities Au
Other commodities As; Cu; Hg; Pb; Sb; Zn
Ore minerals arsenopyrite; boulangerite; jamesonite; pyrite; zinkenite
Gangue minerals ferricrete breccia; quartz; tourmaline

Geographic location

Quadrangle map, 1:250,000-scale MD
Quadrangle map, 1:63,360-scale C-6
Latitude 63.536
Longitude -155.995
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Neirod-East prospect lies along a steep westerly slope of the Cripple Creek Mountains at an elevation of 2,350 feet (716 m) in Section 33, T. 22 S., R. 16 E., of the Kateel River Meridian. The reporter investigated the site in 1996.

Geologic setting

Geologic description

An extensive altered zone in border phase plutonic rocks and hornfels extends in a north-south direction for a distance of about 1,968 feet (600 m). The mineralization consists of: (1) ferricrete breccia in the border phase of the Cripple Creek Mountains pluton; (2) stockwork veins in hornfels; and (3) quartz stockwork in fine grained monzonite. The Neirod-East prospect falls within a north 40 degrees east alignment of several metallic lodes, including the Moose Jaw (MD019), Montana Saddle (MD018), and Wyoming Lode (MD016) prospects. Age of mineralization is inferred to be Late Cretaceous based on 71.0 Ma age of adjacent pluton (Bundtzen and others, 1997).
Microprobe analyses of mineralization from the Neirod-East prospect indicates the presence of boulangerite, jamesonite, and zinkenite in addition to the megascopic arsenopyrite observed in hand specimens. Gold is intimately intergrown with jamesonite - an uncommon association (Bart Cannon, written communication, 1998). Five chip channel samples collected along about 1,640 feet (500 m) strike of the zone contained up to 760 ppb gold, 1.00 percent arsenic, 5,360 ppb mercury, and 178 ppm copper (Bundtzen and others, 1997).
Geologic map unit (-155.997375209736, 63.5353890807644)
Mineral deposit model Porphyry Cu-Au (Cox and Singer, 1986; model 20c).
Mineral deposit model number 20c
Age of mineralization Late Cretaceous (inferred) based on 71.0 Ma age of adjacent pluton (Bundtzen and others, 1997).
Alteration of deposit Extensive sericitization of plutonic rocks; late tourmaline metasomatism.

Production and reserves

Workings or exploration Five chip channel samples collected along about 1,640 feet (500 m) strike of the zone contained up to 760 ppb gold, 1.00 percent arsenic, 5,360 ppb mercury, and 178 ppm copper (Bundtzen and others, 1997).
Indication of production None
Reserve estimates None.

Additional comments

See Montana Saddle prospect (MD018).

References

MRDS Number 10307773

References

Bundtzen, T.K., Pinney, D.S., and Laird, G.M., 1997, Preliminary geologic map and descriptive data tables from the Ophir C-1 and western Medfra C-6 quadrangles, Alaska: Alaska Division of Geological and Geophysical Surveys Public Data File Report 97-46, 10 p., 1 sheet, scale 1:63,360.
Patton, W.W. Jr., Moll, E.J., Dutro, J.T., Jr., Silberman, M.L., and Chapman, R.M., 1980, Preliminary geologic map of the Medfra quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-811-A, one sheet at 1:250,000 scale.
Reporters Bundtzen, T.K. (Pacific Rim Geological Consulting)
Last report date 6/3/1998