The Red Chris deposit displays characteristics of both alkalic and calc-alkalic porphyry copper deposits.

Alkalic features are:
- the paucity of quartz in the pre-mineral monzodiorite and late-mineral porphyry phases,
- the relatively high K2O, Na2O lithogeochemistry of the Stuhini Group volcanics,
- its copper-gold metal signature (versus copper-molybdenum for most calc-alkalic systems),
- magnetite-bearing potassic alteration,
- the unusually high copper-gold grades, at least in part of the system (in contrast, calc-alkalic deposits tend to be bulk mineable lower grade ore bodies).
Calc-alkalic features are:
- the large tonnage of the deposit,
- the relatively simple and centralized alteration pattern,
- the intense quartz-sericite-pyrite or ‘phyllic’ alteration, which is generally underdeveloped in alkalic systems, especially in British Columbia,
- the strong association of copper sulfides with quartz veins.

Prospecting and drilling in the Red stock has delineated several zones of significant copper-gold mineralization in the central part of the stock. The two principal zones targeted for mine development currently are the East zone, and the Main zone, centred 800 metres to the west. The intervening area has been termed the Saddle zone, which is somewhat less well mineralized. At surface, East zone and Main zone mineralization extends at least 1,500 metres along the stock’s east-northeast axis; in width, it ranges from at least 200 metres in the East zone to 500 metres in the Main zone. The depth of significant mineralization is over 1,000 metres in the East zone and about 1,000 metres in the centre of the Main Zone.

A further 1.5 km to the west of the Main zone are the Gully and Far West zones. The Gully zone footprint is approximately 400-500 metres across, east-west. The Far West zone has a smaller footprint and has seen less drilling than the other zones. Some mineralization in the Far West zone is hosted in Stuhini Group country rocks close to the stock’s northern contact.

Prominent limonitic gossans and natural kill zones occur within the steep slopes and drainages over the Gully and Far West zones. However, in areas without drainage relief such as over the East and Main zones, weak limonite extends only 1 or 2 metres beneath the top of the bedrock. The overlying gravel till layer is often very limonitic or composed of ferricrete. Thus, it appears that glaciation has removed any of the supergene mineralization that might have existed over the Red Chris deposit. However, supergene chalcocite mineralization has reportedly been intersected in shallow drilling near the headwaters of the East Gully drainage. Chalcocite occurs along with malachite, azurite and manganese oxides in this oxidized zone.

Copper sulfide mineralization is disseminated, occurs in quartz veins, and in microfractures. Quartz veins range from microveinlets about a millimetre thick to domains of quartz flooding several centimetres thick. The veins can be wavy and anastomosing, or form intricate stockworks, and most may be characterized as A-veins. In mineralized A-veins, quartz forms fine and ‘sugary’ interlocking grains, hosting fine specks or coarser blebs of bornite and/or chalcopyrite, +/- magnetite. Zones of higher quartz vein density may represent composite A-veins due to repeated fissuring along vein margins or other zones of weakness. Some of these may have the appearance of ‘B-veins’ due to a central seam of bornite or chalcopyrite, but most are probably A-veins as they lack the vein-normal crystal growths and terminations associated with true B-veins; some B-veins have been recognized, but they are comparatively minor. In addition to the dominant quartz veinhosted and disseminated mineralization, a minor amount of moderate- to high-grade copper is associated with K-feldspar or biotite-altered halos around early fractures (early dark micaceous or ‘EDM’ veins; see Proffett, 2009).

Bornite and chalcopyrite frequently occupy mafic mineral sites due to the partial or complete replacement of hornblende or biotite. Bornite can be very finely disseminated and easily mistaken for dark red or blue-black specular hematite. Gold is present in microscopic inclusions in bornite and chalcopyrite. Fine molybdenite occurs locally in veinlets of various stages around the strongest Cu-Au zones, especially on the north side of the East zone. Sphalerite and galena occur very locally, usually in trace amounts, in veins or fracture coatings.

Pyrite occurs commonly as very fine- to coarse-grained, anhedral to euhedral disseminations, fracture fillings, and veins. Within the mineralized zones, pyrite content increases upwards, generally concomitant with a decrease in bornite. It ranges from less than 1% to over 10%, with the highest abundance in a halo peripheral to the higher grade copper mineralization (where it is not truncated by faulting). Pyrite is abnormally low or absent in the high-grade East zone except near the surface, but it is quite ubiquitous throughout the Main zone ore and elsewhere in the Red stock. Late-stage pyrite (± minor chalcopyrite) veins cut quartz vein stockworks, and are particularly common in the upper levels of the mineralized system in the sericitic-argillic alteration, and these represent classic D-veins. Pyrite commonly replaces hornblende sites, even in distal parts of the Red Chris deposit.

The Red Chris mine is a 30,000 t/d open pit conventional milling operation with mining rates of approximately 130,000 t/d. The mining fleet includes an Atlas Copco 351 Pit Viper rotary drill, a Komatsu PC 7000 electric hydraulic excavator, a P&H 2800 electric shovel, a Hitachi 3600 diesel hydraulic shovel, a Komatsu PC2000 diesel hydraulic excavator, a Caterpillar 994 wheel loader, ten Caterpillar 793 haul trucks, five Caterpillar 785 haul trucks, five Caterpillar 777 haul trucks, and associated support equipment. Other mining fleet equipment includes five Caterpillar D10 dozers, three Atlas Copco 780 DTH drills, one Caterpillar 988 wheel loader and one 40 tonne capacity articulated truck.


Mining is currently occurring in the Phase 4 pushback and the Phase 5 pushback, both of which are located in the Main zone portion of the ore body. Mining of NAG material (required for PAG dump foundation blanket, road and project requirements) is also being supplemented by targeted development within the Phase 6 pushback footprint. Pits are mined using 12 m high benches and combinations of single and double-benching at various slope angles. Run-of-mine barren rock from the open pit is placed north of the East zone in a rock disposal site where topography allows any runoff to be collected and directed to the processing plant for use and treatment, prior to reporting to the TIA.

Plant design is based on a standard porphyry copper flow sheet employing SAG and ball milling, flotation, regrinding, thickening and filtering to produce a concentrate for export averaging 27% copper at a moisture content of 8%. The grinding circuit would include a 10.36m x 4.72m x 11,200kW SAG mill feeding one 7.32m x 12.80m x 13,428kW ball mill providing a primary grind of K80 of -150µ. Coarse rejects from the SAG mill would be crushed in a 600kW pebble crusher. Ball mill discharge would feed one bank of 5 x 200m³ rougher flotation cells followed by 1 x 183m3 and 1 x 61m3 cleaner flotation columns and a bank of 5 x 100m³ cleaner scavenger flotation cells. Cyclone underflow would be fed to a 4.12 m x 6.93m x 2,200kW primary regrind ball mill and a 4.6m x 4.4m x 14.3m x 1,120kW secondary regrind vertical mill to provide a K80 of -24µ. The primary and regrind product sizes were determined by G&T Metallurgical Services Ltd. to provide the optimum conditions for copper recovery and concentrate grade. Concentrate would be thickened and filtered and then loaded on B-Train trucks of nominal 50 tonne capacity for hauling to the Port of Stewart for shipment to smelters in the Pacific Rim.

Plant design is based on a standard porphyry copper flow sheet employing SAG and ball milling, flotation, regrinding, thickening and filtering to produce a copper concentrate at a moisture content of 8% for export.

Ball mill product feeds a bank of six 200 m³ rougher flotation cells followed by a 180 m3 scavenger/sulphide tank cell. The cleaning circuit includes one 183 m3 and one 61 m3 cleaner flotation columns and a bank of five 100 m³ cleaner scavenger flotation cells. Regrind cyclone underflow is fed to a 2,200 kW primary regrind ball mill and a 1,120 kW secondary regrind vertical mill to provide a grind of approximately 80% passing 24 microns. The primary and regrind product sizes were determined by the AMEC Americas Ltd. feasibility study to provide the optimum conditions for copper recovery and concentrate grade. Concentrate is thickened and filtered, and then loaded on trucks of nominal 40 tonne capacity for hauling to the Port of Stewart, for subsequent shipment ........