The South Arturo Mine is located in the northern end of the Carlin Trend, a 60 km long northnorthwest alignment of sedimentary rock-hosted gold deposits. These deposits are generally known as Carlin-type deposits named after the Carlin deposit. More than 50 million ounces of gold have been mined from the Carlin Trend since 1980. Characteristically, the gold mineralization in Carlin-type gold deposits is dispersed, micron-sized, and found commonly on the rims of pyrite grains in predominately carbonate-bearing host rocks. Decalcification, silicification, and dolomitization are the most dominant alteration features. Generally, there is negligible base metal content, low silver to gold ratios, and a geochemical enrichment in arsenic, antimony, and mercury.

The South Arturo gold-silver deposits can be divided into five mineralized areas. These areas are the South Arturo, West Button Hill, Southwest Dee pit, Deep North, and Hinge. The majority of these deposits are classified as “Meikle Type” breccia-hosted Carlin-type deposits. A complex set of breccias occur at the upper contact of the Bootstrap limestone. These breccias can be generalized into four basic types: silicified heterolithic breccias, silica-sulphide breccia, dolomite breccia, and cavity-fill breccia. The oldest breccias are the silicified heterolithic breccias and the dolomite breccias which have been crosscut and replaced by mineralized silica-sulphide breccias. The youngest breccias are the post mineral cavity-fill breccias.

The northern extent of South Arturo mineralization lies approximately 60 m southeast of the Dee pit and under 180 m of waste rock. An overall north-south orientation to mineralization is inferred from the grade thickness contours, which define an area 520 m in a north-south direction by 100 m to 115 m wide in an east-west direction. The mineralization and Tertiary contact dip 15° to 20° to the south. Drilling has shown that rocks are oxidized to a depth of up to 600 m. Paleozoic rocks host the mineralization mainly in multi-stage, multi-lithic breccias with gold values ranging from 0.2 g/t Au to more than 35 g/t Au with an average grade of approximately 2.0 g/t Au. These breccias are commonly formed by karsting or dissolution of carbonate rock and subsequent collapse and cavity fill. In general, decalcification is followed by weak to strong silicification with local argillization. Silver to gold ratios are generally 1:1 at grades of greater than 2.06 g/t Au but increase to 5:1 at lower gold grade values.

Dee Deep North is a north-northeast trending pod of mineralization that plunges slightly north and is approximately 180 m long, 45 m wide, and 45 m thick. The majority of high-grade refractory mineralization is in silica-sulphide breccia within a flat to west-dipping silicified, multilithic breccia body above the Bootstrap limestone between 1,494 MASL and 1,554 MASL. The principal controls are the north-northeast trending high angle EB fault and southwest dipping low angle structures.

The Southwest Dee pit mineralization is along the north-northeast trending, west dipping Dee Fault Zone. The mineralization is carbonaceous, partially oxidized, variably silicified mudstone/ siltstone breccia approximately 100 m in a north-south strike length, 30 m wide, and 45 m in thickness. The mineralization sits between 1,494 MASL and 1,554 MASL, with a small portion exposed along the southwest high wall at the bottom of the Dee pit.

The West Button Hill mineralization trends north-northeast for over 600 m in strike length, in pods that vary up to 120 m wide and 15 m thick. The majority of high-grade refractory mineralization is in the lower Rodeo Creek Formation and multi-lithic breccias above the Bootstrap limestone. The principal controls are the north-northeast and north-south trending high angle structures and favorable host rocks.

The Hinge zone is a north-south striking zone that lies between the Arturo zone to the south west and West Button Hill to the northeast and is due east relative to the existing Dee pit. It is approximately 425 m long and up to approximately 90 m wide, lying between elevations of 1,450 MASL and 1,600 MASL at depths from 100 m to 270 m below surface. Mineralization is hosted in the lower portion of the Rodeo Creek Formation and silicified breccias of the Basal Rodeo Creek and Popovich Upper Muds units.

The South Arturo operation is an open pit mine with production sourced from several interconnected phased pits that are designed to optimize both mill feed and dewatering campaigns. The average mining rate will be 110,000 tpd of ore plus waste over the mine life. The current mine life is five years (2018-2022), however, if the price of gold increases, the mine life will be re-evaluated. Mining of the West Button Hill pit was completed in 2017.

Mining is carried out with a Barrick owned fleet of mining equipment including 263 t (302 st) class rear dump haul trucks, electric shovels, hydraulic excavators, a front-end loader, and blast hole drills for 222 mm to 251 mm (8-3/4 in. to 9-7/8 in.) diameter blast holes. Pit benches are 6.1 m (20 ft) in height in ore and 12.2 m (40 ft) in waste. Track dozers, graders, front end loaders, and service vehicles support the mining operation.

Overburden is transported by off-highway, 263 t (302 st) trucks from the open pit to adjacent overburden storage areas, which are approximately 0.9 km from the pit exit. Mined ore is trucked over existing and proposed haul roads to appropriate stockpiles, depending on ore type. Ore that requires milling is transported to a pre- determined stockpile location for transportation to Barrick’s Goldstrike facilities for processing located approximately five kilometers from the South Arturo Mine. Mill-grade ore is transported to Barrick’s Goldstrike facilities. Approximately 1.63 million tonnes of refractory ore are planned to be transported from South Arturo to Goldstrike. Sub-grade ore material may be placed in stockpiles, or on a selected portion of the overburden storage areas for possible future processing. Oxide mill ore is transported by truck to Barrick’s Cortez operation for processing, which is located approximately 118 km (73 mi) from South Arturo.

Diesel-powered rotary drills will be used for drilling blast holes. Typical drilling penetration rates will range from 29 m/hr (95 ft/hr) to 46 m/hr (150 ft/hr). For 12.2 m (40 ft) high benches, the typical subdrill will be 1.2 m (4 ft) and stemming lengths will average approximately 6.1 m to 6.7 m (20 ft to 22 ft). Average drill availability and utilization are 82% and 44%, respectively.

Vertical blast holes are loaded with ammonium nitrate and fuel oil (ANFO) or emulsion, which subsequently is detonated. Powder factors vary due to the changing lithological units and geological structures/conditions. Powder factors range from 0.09 kg of explosive per tonne to 0.31 kg/t (0.18 lb/st to 0.62 lb/st). Unconsolidated gravels and growth media that do not require the use of blasting techniques prior to removal are ripped with a dozer, as needed. Explosives and blasting agents are handled by licensed haulers and stored on site in compliance with the required regulations of the Bureau of Alcohol, Tobacco, and Firearms, Mine Safety and Health Administration, and the Department of Homeland Security. Federal, state, and county roads/highways are used to transport explosives and other mining materials by licensed trucking companies.

El Nino Underground will be accessed via a portal located at 1,536 MASL (5,040 ft) elevation within the South Arturo Phase-2 pit. The current design includes a twin portal decline for accessing the ore deposit. The current mine depth for reserves is planned to extend down to 1,477 MASL (4,845 ft) elevation.

The primary method of mining will be underhand cut and fill with cemented rockfill as the fill material. The underhand drifts are nominally designed as 4.6 m (15 ft) wide by 4.6 m (15 ft) high. The minimum width is 4.6 m (15 ft). The primary drift is driven with increased ground support to hold the ground open, then backfilled with a high strength cemented rock fill backhauled into the mine. Where the ore width exceeds the nominal drift width, subsequent drifts are developed (parallel or at oblique angles to the primary drift) and then backfilled. This process continues until the entire ore shape at a given elevation has been excavated and filled. Successive lifts are taken beneath the primary workings, utilizing the backfill as an engineered back. This method can provide a consistent production rate from a mining area given enough headings to complete the full mining cycle.

The underhand drift and fill method provides a backfill roof for subsequent lifts in the mining cycle. A backfill plant, shotcrete plant, cement storage facilities, aggregate storage area, and cement mixing pit will be located on surface to support this mining method.

Ore from South Arturo will be processed via one of three possible routes: ROM heap leaching (possible in the future if economics warrant), milling and CIL, or roasting and CIL.

Ore from South Arturo will be routed based on the maximum net cash flow that can be achieved. The majority of the precious metal production will come from ore that will be trucked to existing Barrick’s processing circuits located approximately 12.9 km away over improved gravel roads.

ROM HEAP LEACHING
ROM material is segregated in the waste dump for future possible heap leach process if economics warrant. ROM material will be placed on a permanent leach pad by haul trucks. Cyanide solution will be distributed by drip emitters. The pregnant solution will then be collected and pumped to a carbon adsorption circuit. The cyanide concentration and pH of the barren solution will be adjusted, and the solution will be re- circulated via pumping to the heap leach pads. Loaded carbon will be trucked to the existing autoclave carbon processing circuit for stripping and refining to recover the precious metals and the carbon will be regenerated prior to being returned to the carbon adsorption columns at South Arturo for reuse.

OXIDE ORE MILLING/CIL
The grinding and CIL circuits in the existing circuit at Cortez will be utilized to process the oxidized mill grade South Arturo ore on a campaign basis. The treatment plant currently includes crushing, semi-autogenous grinding (SAG), ball milling, grind thickening, carbon-in-column (CIC) circuit for the grind thickener overflow solution, CIL circuit, tailings countercurrent decantation (CCD) wash thickener circuit, carbon stripping and reactivation circuits, and a refinery to produce gold doré.

ROASTER/CIL
Ore that is scheduled for roaster/CIL processing will be toll processed in the existing roaster circuit at Goldstrike on a campaign basis. The roaster pre-oxidizes ore that contains refractory carbonaceous and sulphidic material, so it can be effectively processed in a traditional CIL circuit. Metallurgical recovery is based on the BTR test results and Goldstrike Roaster predicted recovery curve.