South Reef

Prospect, Active

Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Co; Zn
Ore minerals bornite; chalcocite; chalcopyrite
Gangue minerals barite; dolomite

Geographic location

Quadrangle map, 1:250,000-scale AR
Quadrangle map, 1:63,360-scale A-2
Latitude 67.065
Longitude -156.91
Nearby scientific data Find additional scientific data near this location
Location and accuracy Approximately 3,500 feet east southeast of Bornite (AR018) at an elevation of 1,200 feet; section 9, T. 19 N., R. 9 E., of the Kateel River Meridian. This location is accurate to within 500 feet.

Geologic setting

Geologic description

The geology of the South Reef deposit is composed of alternating beds of carbonate rocks (limestone and dolostone) and calcareous phyllite. Limestone transitions laterally into dolostone, which hosts the majority of the mineralization and is considered to be hydrothermal in origin. Spatial relationships and petrographic work establish dolomitization as genetically related to early stages of the copper mineralizing system (Hitzman, 1986).
Copper mineralization in the South Reef zone consists of one to three mineralized intervals (at a 0.5 percent cut-off) coalescing into a crudely stratiform body hosted in secondary dolomite developed at or near the Iron Mountain structure. The body, which is 250 to 300 meters wide and 750 meters long varies in true thickness from roughly 10 meters to as much as 170 meters (Davis and others, 2014).
The South Reef deposit is located within the Arctic Alaska Terrane, a sequence of mostly Paleozoic continental margin rocks that make up the Brooks Range and North Slope of Alaska (Moore, 1992). It is within the Phyllite Belt geologic subdivision, which together with the higher-grade Schist Belt, stretches almost the entire length of the Brooks Range and is considered to represent the hinterland of the Jurassic Brooks Range orogeny. The southern margin of the Phyllite Belt is marked by melange and low angle faults associated with the Kobuk River fault zone, while the northern boundary is thought to be gradational with the higher-grade metamorphic rocks of the Schist Belt (Till and others, 2008).
Geologic map unit (, )
Mineral deposit model Mississippi Valley or Olympic Dam similarities? Kipushi Cu-Co deposit? (Cox and Singer, 1986, model 32c).
Mineral deposit model number 32c?
Age of mineralization Sulfide mineralization (chalcopyrite, pyrite, and bornite) from Bornite (Ruby Creek) was dated by Re-Os techniques (Selby and others, 2009), producing an age of 384 ± 4.2 Ma for main stage copper mineralization.
Alteration of deposit Dolomitization (Davis and others, 2014).

Production and reserves

Workings or exploration South Reef was discovered during recent work (2006-2012) near the Bornite (AR018) prospect by NovaCopper. Twenty one drill holes have been completed at the South Reef deposit as of winter 2014. The 2012 drilling defined an approximately 250 to 300 meters wide by 750 meters long zone of mineralization at South Reef. Based on the drilling results, using a 1 percent copper cut-off, there is an inferred resource of 43.1 million tonnes of 2.54 percent copper (Davis and others, 2014).
Indication of production Undetermined
Reserve estimates The 2012 drilling defined an approximately 250 to 300 meters wide by 750 meters long zone of mineralization at South Reef. Based on the drilling results, using a 1 percent copper cut-off, there is an inferred resource of 43.1 million tonnes of 2.54 percent copper (Davis and others, 2014).

References

References

Reporters A. Angel and V.C. Zinno (Alaska Earth Sciences, Inc.)
Last report date 3/15/2016