Cliff North

Prospect, Probably inactive

Commodities and mineralogy

Main commodities Ag; Cu; Pb; Zn
Ore minerals chalcopyrite; galena; pyrite; sphalerite
Gangue minerals calcite; quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale AR
Quadrangle map, 1:63,360-scale B-2
Latitude 67.295
Longitude -156.706
Nearby scientific data Find additional scientific data near this location
Location and accuracy Located equidistant between the Ambler and Shunghak Rivers, section 22 T. 22 N., R. 10 E., of the Kateel River Meridian at approximately 3,500 ft in elevation. The coordinates are accurate to within 500 ft.

Geologic setting

Geologic description

The Cliff South prospect is in a highly complex deformed sequence of predominantly country rock schists and greenstones. Exposures are found along a prominent north-south trending cliff. Two inter-layered sequences of metamorphosed Devonian-Mississippian volcanic, volcaniclastic, and sedimentary rocks have been identified; these contain the Cliff North/Horse Creek and Cliff South mineral showings. The structure is very complicated and all three prospects are different parts of a larger structure. The Horse Creek (AR029) occurrence is on the north limb of an north-dipping overturned syncline, the Cliff North occurrence is on the south limb of the overturned syncline, while Cliff South is on the open south limb of a corresponding overturned anticline between Cliff South and Cliff North (Ellis, 1980).
Mineralization is characterized by copper, lead, zinc, and silver occurring as massive, semi-massive, and disseminates sulfide found in outcrop and by diamond drilling. Detailed mapping of this zone indicated that the mineral horizons contain widespread mineralization, with locally calcareous lenses of massive sulfides up to 8 feet thick (Ellis, 1980).
Geologic map unit (, )
Mineral deposit model Kuroko massive sulfide (Cox and Singer, 1986; model 28a).
Mineral deposit model number 28a
Age of mineralization Devonian, based on age of host rock (Ellis, 1980).
Alteration of deposit Strong sulfide oxidation. Quartz, chlorite, calcite, and sericite alteration is associated with mineralization; there is also sericite-altered quartz -muscovite-schist (Ellis, 1980).

Production and reserves

Workings or exploration Initial exploration efforts started in the early 1970s. Exploration efforts to date includes geochemical surveys such as rock, soil, and stream sediment sampling, hand trenching, geophysical surveys that included induced polarity (IP) and electromagnetic (EM) surveys, and diamond core drilling. Most of the drill holes contained two mineralized zones that averaged 8 to 14 feet thick. They averaged from 0.3 to 1.4 percent copper, 0.6 to 1.9 percent lead, 2.5 to 5.5 percent zinc, and 0.5 to 2.0 ounces per ton silver. Rock chip samples have assayed as high as 2.7 percent copper, 3.9 percent lead, 8,4 percent zinc, and 4.6 ounces per ton silver. A high conductive geophysical anomaly correlates with anomalous geochemical samples. The majority of this work was completed between 1976 and 1980 by Sunshine Mining Company (Ellis, 1980).
Indication of production None
Reserve estimates In 1980, Sunshine Mining Company estimated a geologic reserve of 6.5 million tons ore grading 0.5 percent Cu, 1.0 opt Ag, 0.9 percent Pb, and 2.5 percent Zn (ELlis, 1980).

Additional comments

Cliff North is referred to under Horse Creek (AR029) generally as 'Cliff'. In 2014, Cliff North was created as a separate record from Horse Creek since both are on separate parts of a large overturned syncline and the prospects are separated by about a mile (W.T. Ellis, Vice President, Alaska Earth Sciences, Inc., oral communication, 2014).

References

References

Ellis, W.T., 1980, Ambler River Project, Alaska, Project Memorandum No. 7, Summary Report of Past Field Investigations and 1980 Field Investigations, Sunshine Mining Company, 114 p. (Report held at Alaska Earth Sciences, Inc., Anchorage, AK).
Ellis, W.T., 1983, Ambler River Project, Alaska, Project Memorandum No. 10, 1983 Field Investigations, Sunshine Mining Company, 49 p. (Report held at Alaska Earth Sciences, Inc., Anchorage, AK).
Reporters A. Angel (Alaska Earth Sciences, Inc.); V.C. Zinno (Alaska Earth Sciences, Inc.)
Last report date 3/11/2014