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Alternative names

Ambler 4-B

Commodities and mineralogy

Main commodities Ag; Cu; Pb; Zn
Other commodities Au
Ore minerals chalcopyrite; galena; owyheeite; pyrite; sphalerite
Gangue minerals calcite; chlorite; muscovite; quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale AR
Quadrangle map, 1:63,360-scale B-3
Latitude 67.298
Longitude -157.1609
Nearby scientific data Find additional scientific data near this location
Location and accuracy Located on ridge east of VABM Sleet in NW1/4 NW1/4, 0.6 mile from the center of section 20, T. 22 N., R. 8 E., of the Kateel River Meridian. Prospect at approximately 1,400 ft in elevation. Accurately located to within 300 ft.

Geologic setting

Geologic description

Layered sulfide zone 9 ft to 27 ft. (3 m to 9 m) thick, continuos for at least 6000 ft (2000 m) along strike, consists of banded, fine to medium grained pyrite, sphalerite, galena, chalcopyrite and minor owyheeite in a silica-calcite-pyrite matrix. The country rocks are characteristic of the Devonian-Mississippian Ambler sequence and consist dominantly of well-foliated porphyroblastic quartz-feldspar-muscovite-chlorite schist interlayered with quartz-muscovite-chlorite phyllite, graphitic phyllite, calcite-mica schist and marble. Mineralized zone is repeated by complex folding (Nana Development Corp., written communication, 1997).
Geologic map unit (-157.169784713409, 67.2914608862254)
Mineral deposit model Kuroko massive sulfide (Cox and Singer, 1986; model 28a).
Mineral deposit model number 28a
Age of mineralization Devonian (Hitzman and others, 1986).
Alteration of deposit No hydrothermal alteration of wall rock evident (Hitzman and others, 1986).

Production and reserves

Workings or exploration Surface geologic mapping, geochemical sampling (soil grids), electromagnetic measurements, magnetometer measurements, and eight drill holes by 1984 (Nana Development Corp., written communication, 1997). According to Mayfield and Grybeck (1978) two drill samples 2400 ft (820 m) apart intersected layered sulfide zones 9 ft. to 27 ft. (3 m to 9 m) thick assaying 100 g/ton Ag, 2-8 percent Zn and 1-1.6 percent Pb. Grades from drill samples indicated 3.8 percent Zn, 1.2 to 1.6 percent Pb, 69-514 g/ton Ag.
Indication of production None
Reserve estimates Hitzman and others (1986) report greater than eight million metric tons grading 0.8 percent Cu, 6.8 percent Zn, 2.3 percent Pb, 200 g/ton Ag. Bundzten (1996) reported 'significant' tonnage grading 1.5 percent Pb, 5 percent-10 percent Zn, 103-343 g/ton Ag, and minor Au.

Additional comments

Excellent example of stratiform volcanogenic sulfide deposit typical of the Ambler sequence in the southern Brooks Range. This is the westernmost known occurrence of this type deposit in the southern Brooks Range. All available data suggest Smucker to be relatively significant in size (Hitzman and others, 1986).
This location was changed in 2014 from the 1997 version of this record. The 1997 version was mislocated (W.T. Ellis, Vice President, Alaska Earth Sciences, Inc., oral commun., 2014).


MRDS Number A011883


Reporters K.R. Leonard (USGS), R.L. Elliott (USGS), J.M. Schmidt (USGS), S.W. Nelson (USGS retired); A. Angel (Alaska Earth Sciences, Inc.); V.C. Zinno (Alaska Earth Sciences, Inc.)
Last report date 3/11/2014