Arctic

Prospect, Active

Commodities and mineralogy

Main commodities Ag; Au; Cu; Pb; Zn
Other commodities Sb
Ore minerals arsenopyrite; barite; bornite; chalcocite; chalcopyrite; galena; pyrite; pyrrhotite; sphalerite; stibnite; tennantite-tetrahedrite
Gangue minerals calcite; quartz; talc

Geographic location

Quadrangle map, 1:250,000-scale AR
Quadrangle map, 1:63,360-scale A-1
Latitude 67.174
Longitude -156.3875
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Arctic prospect is about 1.2 miles east of VABM 3725 'Riley' on a ridge above the Kogoluktuk River in the Ambler district. The property is shown as a group of prospect symbols on the USGS 1:63,360-scale topographic map in the southeast quarter of section 34, T. 21 N., R. 11 E., of the Kateel River Meridian. The location is well-known and accurate to within 500 feet.

Geologic setting

Geologic description

Arctic is one of several volcanogenic deposits in the Ambler schist belt along the south flank of the Brooks Range. The deposits may be part of a rifted continental margin (Schmidt, 1981). Arctic is a syngenetic deposit hosted in the Ambler Schist Belt, a thick sequence of Devonian or Mississippian, low to medium-grade metamorphosed basaltic and rhyolitic rocks, submarine ash flow tuffs, volcaniclastic and minor plutonic rocks, and pelitic, carbonaceous, and calcareous metasedimentary rocks. These rocks are part of a large fold structure termed the Kalurivik arch. A Devonian or Mississippi age of mineralization is based both on fossil evidence and on U-Pb radiometric dating (Hitzman and others, 1986).
The Arctic polymetallic, stratabound, volcanogenic deposit consists of tabular bodies of banded massive and disseminated sulfides, one foot to more than 55 feet thick, composed of 20 percent to 90 percent pyrite, chalcopyrite and sphalerite, along with lesser amounts of pyrrhotite, chalcocite, bornite, galena, tennantite-tetrahedrite, arsenopyrite and stibnite (Schmidt, 1988). The sulfides are enclosed in calcareous talcose to quartzose lenses within a metavolcanic (rhyolitic) unit. The deposit is about 3,000 feet by 2,200 feet in area and about 270 feet thick. The massive sulfide occurrences are covered by a small gossan cap 9 to 15 feet deep.
Geologic map unit (-156.390238298231, 67.1734660796529)
Mineral deposit model Kuroko massive sulfide (Cox and Singer, 1986; model 28a).
Mineral deposit model number 28a
Age of mineralization Devonian-Mississippian, the age of the host rocks (Hitzman and others, 1986).
Alteration of deposit Chlorite-rich rocks in the footwall and surrounding the sulfides form an alteration zone containing a complex assemblage of barium fluorphlogopite, talc, Mg-chlorite, barite, phengite, quartz, and calcite (Schmidt, 1988).

Production and reserves

Workings or exploration
Kennecott completed 70 drill holes in the Arctic deposit in the 1970s and defined an inferred resource of 36.3 million tons of ore.
NovaGold Resources, Inc. (2007) reached an earn-in agreement with Kennecott Exploration Company and Kennecott Arctic Company (subsidiaries of Rio Tinto PLC) in March 2004. The agreement covers a 35,000 acre area in the Ambler district. Initial exploration by NovaGold in 2004 focused on the Arctic deposit and included new descriptions of existing core, structural geology studies, and drilling 11 infill holes totaling 9,768 feet. These holes confirmed previous drill results and helped refine the three-dimensional geologic model for the Arctic deposit. Some 2004 drill intercepts reported by NovaGold include: 1) hole AR04-80 had 6.5 meters with 3.36 percent copper, 0.91 gram of gold per tonne, 1.90 percent lead, and 7.93 percent zinc; 2) hole AR04-86 had 12.5 meters with 3.76 percent copper, 0.91 gram of gold per tonne, 52.4 grams of silver per tonne, 0.58 percent lead, and 6.01 percent zinc, or an 8.0 percent copper equivalent; 3) hole AR04-87 had 7.4 meters with 9.65 percent copper, 0.73 grams of gold per tonne, 108.2 grams of silver per tonne, 1.64 percent lead, and 10.35 percent zinc, or 16.9 percent copper equivalent.
In 2005, NovaGold drilled about 3,000 meters of core hole and carried out district-scale surface geology, geochemistry, and geophysical surveys (NovaGold Resources, Inc., 2007). In 2006, NovaGold drilled 12 holes to test geophysical anomalies near the Arctic deposit and outlined additional mineralization. They also carried out extensive detailed surface geologic mapping and geochemical surveying. As of May 2011, the deposit has been explored by 119 core holes totaling about 25,000 meters, 96 of which are in mineralization. In 2011, NovaGold commissioned a comprehensive NI 43-101 preliminary economic assessment of the deposit that included a statement of its resources (Rigby and others, 2011).
Assuming a net smelter return of $75 per ton, the deposit has an indicated resource of 16.845 million tons with an average grade of 4.14 percent copper, 6.03 percent zinc, 0.94 percent lead, 0.83 gram of gold per tonne, and 59.62 grams of silver per ton. It has an addition inferred resource of 12.087 million tons with an average grade of 3.53 percent copper, 4.94 percent zinc, 0.79 percent lead, 0.067 grams of gold per tonne, and 48.04 grams of silver per tonne.
In 2016, Trilogy Metals Inc. (formerly NovaCopper Inc.) drilled a total of 3,058 meters in 13 holes at their Arctic volcanogenic massive sulfide deposit. Significant results include: hole AR16-0155, which intersected 3 mineralized intervals, including 36.36 meters of 2.27 percent copper, 0.27 gram of gold per tonne, 25.3 grams of silver per tonne, 0.36 percent lead, and 2.54 percent zinc, and 8.48 meters of 6.14 percent Cu, 1.32 grams of gold per tonne, 96.6 grams of silver per tonne, 1.93 percent lead, and 8.27 percent zinc; hole AR16-0148, which intersected 4 mineralized intervals, including 21.22 meters of 3.79 percent copper, 0.85 gram of gold per tonne, 69.1 grams of silver per tonne, 0.99 percent lead, and 5.78 percent zinc; hole AR16-0150, which intersected 5 mineralized intervals, including 16.60 meters of 5.40 percent copper, 0.20 gram of gold per tonne, 46.0 grams of silver per tonne, 1.23 percent lead, and 6.69 percent zinc; and hole AR16-0153, which intersected 12.59 meters of 2.49 percent copper, 0.86 gram of gold per tonne, 56.6 grams of silver per tonne, 2.17 percent lead, and 9.64 percent zinc. Trilogy plans to complete a prefeasibility study and update the resource estimates for the Arctic deposit in 2017 (Athey and Werdon, 2017).
Indication of production None
Reserve estimates
Kennecott completed 70 drill holes in the Arctic deposit in the 1970s and estimated an inferred resource of 36.3 million tons grading 4.0 percent copper, 5.5 percent zinc, 0.8 percent lead, 0.7 gram of gold per tonne, and 54.9 grams of silver per tonne, or 8.0 percent copper equivalent (Eakins and others, 1985).
In 2011, NovaGold commissioned a comprehensive NI 43-101 preliminary economic assessment of the deposit that included a statement of its resources (Rigby and others, 2011). Assuming a net smelter return of $75 per ton, the deposit has an indicated resources of 16.845 million tonnes with an average grade of 4.14 percent copper, 6.03 percent zinc, 0.94 percent lead, 0.83 grams of gold per tonne, and 59.62 grams of silver per tonne. It has an addition inferred resource of 12.087 million tons with an average grade of 3.53 percent copper, 4.94 percent zinc, 0.79 percent lead, 0.067 grams of gold per tonne, and 48.04 grams of silver per tonne.
In 2013, NovaGold commissioned a comprehensive Preliminary Economic Assessment report (43-101 compliant). Using a constant net smelter return of $35.01 per tonne milled, they report 1) 23.848 million tonnes indicated with an average grade of 3.26 percent copper, 4.45 percent zinc, 0.76 percent lead, 0.71 gram of gold per tonne, and 53.2 grams of silver per tonne; and 2) 3.368 million tonnes inferred with an average grade of 3.22 percent copper, 3.84 percent zinc, 0.58 percent lead, 0.59 percent gold, and 41.5 percent silver (Wilkins and others, 2013).
As of 2016, the Arctic deposit has a total indicated and inferred resource of 27.2 million tonnes with 3.25 percent copper, 4.37 percent zinc, an in situ lead grade of 0.74 percent, 0.02 ounce of gold per tonne, and 1.51 ounces of silver per tonne, for contained metals of 1,952 million pounds of copper, 2.623 million pounds of zinc, 444 million pounds of lead, 610,000 ounces of gold, and 45.3 million ounces of silver (Wilkins and others, 2013).

References

MRDS Number A011889

References

Reporters J.M. Schmidt (USGS), S.W. Nelson (USGS retired); Travis Hudson (Applied Geology, Inc.); 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