Bornite

Prospect, Active

Alternative names

Ruby Creek

Commodities and mineralogy

Main commodities Co; Cu
Other commodities Ag; Au; Ge; Pb; U; Zn
Ore minerals bornite; carrollite; chalcocite; chalcopyrite; cymrite; galena; germanite; marcasite; pyrite; pyrrhotite; renierite; sphalerite; tennantite-tetrahedrite
Gangue minerals barite; dolomite

Geographic location

Quadrangle map, 1:250,000-scale AR
Quadrangle map, 1:63,360-scale A-2
Latitude 67.0624
Longitude -156.948
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Bornite prospect is near the Bornite locality shown on the 1:63,360-scale topographic map. The prospect is near the center of section 8, T. 19 N., R. 9 E., of the Kateel River Meridian, and about 1.6 miles north-northeast of Bannock Mountain. The location is well known and accurate within 500 feet.

Geologic setting

Geologic description

The mineralization at the Bornite prospect consists of sulfide minerals in a matrix of brecciated, intensely folded and faulted dolomite and limestone of the Devonian Bornite marble, a 3000-ft.-thick unit of carbonate rocks (Hitzman and others, 1986). The main ore minerals are bornite and chalcopyrite but carrollite, chalcocite, galena, germanite, renierite, sphalerite, and tennantite-tetrahedrite also occur in smaller amounts. The deposit is structurally and stratigraphically confined to the Devonian dolomite, limestone, and calcareous phyllite along the fault (?) -controlled margin of a carbonate bank adjacent to a shale-filled graben. Hitzman and others believed the deposit to have formed along a rifted continental margin in Late Devonian time. Rigby and others (2011), however, describe Bornite as a copper-cobalt deposit with Mississippi Valley and Olympic Dam affinities.
From the 1950s and into the 1980s, Kennecott Exploration Co. explored the Bornite deposit underground from a shaft and workings on two levels and also extensive surface drilling. In 2011 NovaGold Resources Inc. and the NANA Native Corporation, who owns the land, reached an agreement to explore the deposit (Petsel and others, 2011). NovaGold drilled 6 holes in 2011 totaling about 2,600 meters to verify Kennecott's earlier work and 9 other exploration holes totaling 3,500 meters (NovaGold Resources Inc., 2011a, 2011b). The NovaGold drilling not only verified the earlier data in several high-grade intercepts, it also identified a new South Reef zone that significantly increases the the size of the deposit. Some notable intercepts were: 1) four intervals that totaled 111.3 meters in one hole that averaged 2.1 percent copper; 2) 26.3 meters that averaged 6.7 percent copper; 3) 93.2 meters that averaged 2.1 percent copper, 4) 31.9 meters that averaged 5.4 percent copper; 5) 110.6 meters that averaged 2.6 percent copper; 6) 153.1 meters that averaged 1.2 percent copper, and 7) 178 meters that averaged 4.0 percent copper and this included 59.2 meters that averaged 12.0 percent copper.
Hitzman (1986) estimated Bornite to have a resource of 90 million tons with a grade of 1.2 percent copper.
As reported in 2014, the Bornite Project is estimated to contain 2.16 billion pounds of copper (6.8 million tonnes grading 1.19 percent copper) in the indicated category and 3.3 billion pounds of copper (90.8 million tonnes grading 1.64 percent copper) in the inferred category (Davis and others, 2014).
Geologic map unit (-156.95074776096, 67.0618536222609)
Mineral deposit model Mississippi Valley or Olympic Dan similarities? Kipushi Cu-Co deposit? (Cox and Singer, 1986, model 32c).
Mineral deposit model number 32c?
Age of mineralization Late Devonian by analogy with other deposits in the Ambler mineral belt (Davis and others, 2014).
Alteration of deposit Dolomitization (Davis and others, 2014).

Production and reserves

Workings or exploration
From the 1950s into the 1980s, Kennecott Exploration Co. explored the Bornite deposit underground from a shaft and workings on two levels and also by extensive surface drilling. In 2011 NovaGold Resources Inc. and the NANA Native Corporation who own the land reached an agreement to explore the deposit (Petsel and others, 2011). NovaGold drilled 6 holes in 2011 totaling about 2,600 meters to verify the Kennecott's earlier work and 9 other exploration holes totaling 3,500 meters (NovaGold Resources Inc., 2011a, 2011b).
The NovaGold drilling not only verified the earlier data in several high-grade intercepts, it also identified a new South Reef zone that significantly increases the the size of the deposit. Some notable intercepts were: 1) 4 intervals that totaled 111.3 meters in one hole that averaged 2.1 percent copper; 2) 26.3 meters that averaged 6.7 percent copper; 3) 93.2 meters that averaged 2.1 percent copper, 4) 31.9 meters that averaged 5.4 percent copper; 5) 110.6 meters that averaged 2.6 percent copper; 6) 153.1 meters that averaged 1.2 percent copper, and 7) 178 meters that averaged 4.0 percent copper and this included 59.2 meters that averaged 12.0 percent copper.
In 2012, NovaCopper captured extensive physical property data at Bornite including resistivity, chargeability, specific gravity, and magnetic susceptibility data for use in modeling the existing ground induced polarity (IP) and gravity surveys, and the airborne electromagnetic (EM) and magnetic surveys. In general, some broad comments can be made concerning geophysical domains in and around mineralization at Bornite. Mineralization is characterized by low resistivity, less than 20 ohms, ambiguous but elevated, often irregular chargeability highs (greater than 35 milliradians) marginal to the mineralization, and 3 to 5 milligal gravity anomalies. Mineralization appears to lie along the flanks of 20 to 150 nanoteslas long wave magnetic anomalies (Davis and others, 2014).
As reported in 2014, the Bornite Project is now estimated to contain 2.16 billion pounds of copper (6.8 million tonnes grading 1.19 percent copper) in the indicated category and 3.3 billion pounds of copper (90.8 million tonnes grading 1.64 percent copper) in the inferred category (Davis and others, 2014).
Indication of production None
Reserve estimates
As reported in 2014, the Bornite Project is now estimated to contain 179 million pounds of copper (6.8 million tonnes grading 1.19 percent copper) in the indicated category and 3.3 billion pounds of copper (90.8 million tonnes grading 1.64 percent copper) in the inferred category (Davis and others, 2014).
The historic resource estimate from Hitzman (1986) was 90 million tons with an average of 1.2 percent copper (Hitzman and others, 1986).
On April 19, 2016, Trilogy Metals Inc. released an updated resource estimate, and on May 16, 2016, filed a NI 43-101 technical report for the Bornite deposit (Davis and others, 2016). The updated resource resulted in contained copper in indicated resources increasing from 334 to 913 million pounds, constituting a 173 percent increase in contained metal over the previous resource estimate. Total contained copper in inferred resources decreased from 5,696 to 5,450 million pounds copper (1,768 million pounds in-pit at 0.5 percent copper cut-off grade; 3,683 million pounds below-pit at 1.5 percent copper cut-off grade), which constitutes a 4 percent decrease in contained metal due principally to moving in-pit inferred resources to the indicated category. The resource update incorporated a new, 3D lithology, alteration, and structural model for the Bornite deposit, as well as results from previously un-sampled or partially sampled historical Kennecott drill core. Trilogy continued environmental baseline data collection, but no exploration or drilling was conducted in 2016 at Bornite (Athey and Werdon, 2017).

References

MRDS Number A010661

References

Reporters J.M. Schmidt (USGS); S.W. Nelson (USGS retired); D.J. Grybeck (Contractor, USGS); A. Angel (Alaska Earth Sciences, Inc.); V.C. Zinno (Alaska Earth Sciences, Inc.); M.B. Werdon (DGGS)
Last report date 8/26/2017