The Goldstrike deposits are Carlin style deposits. Carlin deposits comprise stratabound disseminated gold mineralization hosted by Silurian-Devonian carbonate rocks that have been metamorphosed to varying extents. The deposits are hydrothermal in origin and are usually structurally controlled. The carbonate host rocks are part of an autochthonous miogeoclinal carbonate sequence exposed as tectonic windows beneath the Roberts Mountains allochthon.

The gold mineralization is associated with silicification, argillization, and sulphide mineralization with little or no oxide mineralization remaining. In sulphide ore, the gold is intimately associated with very fine-grained pyrite and marcasite and is refractory. Over time, the pyrite oxidized, freeing the gold and making its extraction relatively easy, as in the historic Post Oxide deposit. Associated sulphide minerals include arsenopyrite, realgar, orpiment, and stibnite. Gangue minerals include quartz, calcite, and barite. Realgar and orpiment are generally low in abundance; however, these minerals are locally common in stockwork veinlets, fracture fillings, and breccia matrices.

OPEN PIT
The Betze-Post deposit, the largest on the Carlin Trend, is divided into sub-deposits which, from east to west, are the Deep Post, Post, Betze, West Betze, and Screamer. Other zones within the pit are North Betze, West Barrel, and North Screamer.

Five generations of pyrite mineralization have been recognized at the Betze-Post open pit. Early stages of diagenetic pyrite, and coarse-grained pyrite in the metamorphic aureole of the Goldstrike diorite, are barren. Early hydrothermal, very fine-grained pyrite and marcasite grains of the third generation are coated by a 25 µm thick rind and cut by micro-veinlets of arsenic and gold bearing pyrite of the fourth generation. Barren, late hydrothermal coarsegrained pyrite and marcasite is accompanied by barite and stibnite. Sulphides make up approximately 5% by weight of the ore, locally up to 20%.

The gold bearing arsenian pyrite may be subdivided into coarse grained sulphides at ±200 µm diameter and fined grained at 10 µm to 20 µm, with the latter carrying proportionately much more gold. Gold at 0.05 µm to 0.1 µm is occluded in the iron sulphides. Approximately 10% to 20% of the gold is free, 20% to 30% is held in the fine-grained pyrite/marcasite, a few percent is contained in coarse pyrite, and the balance is in very fine pyrite associated with clay.

UNDERGROUND
Gold mineralization in the underground mine is subdivided into East Banshee, West Banshee, Meikle, South Meikle, (East) Griffin, Extension, West Griffin, Rodeo, Barrel, West Rodeo, and North Post deposits and sub-deposits. The sulphide mineralization is associated with silicification and argillization, and there is little or no oxide mineralization. In sulphide mineralization, the gold is intimately associated with very fine-grained pyrite and marcasite. Associated sulphide minerals include arsenopyrite, realgar, orpiment, and stibnite. Gangue minerals include quartz, calcite, and barite. Realgar and orpiment are generally low in abundance; however, these minerals are locally common in stockwork veinlets, fracture fillings, and breccia matrices.

The orientation of the mineralization is different in each zone. East Banshee, Meikle, MeikleEast, Extension, Rodeo, North Post, and East-Griffin are characterized by steep and shallow angle east-dipping mineralization. South Griffin, West Banshee, and part of Lower Rodeo are more moderately west dipping. South Meikle, West Griffin, and Barrel mineralization are relatively flat lying.

The Goldstrike deposits with fine to very finely disseminated gold and arsenic bearing pyrite. The host rocks are generally sedimentary, mostly calcareous formations, frequently altered and decalcified. There is hydrothermal alteration and there are collapse structures which generated the breccias that host the deposits. The alteration and folding and faulting have led to poor rock quality in the deposits in generally and locally very poor ground conditions in the vicinity of the major faults.

The geometry of the deposits is variable from flat-lying to pipe-like, with irregular shapes due to the alteration.

UNDERGROUND ZONE DIMENSIONS
Length (ft) Thickness (ft) Comment (Attitude, Mineralization Type, etc.)

Banshee: Length - 1,750 ft, Thickness - 10 to 200 ft, (Fault and brecciated dykes);

Liberty: Length - 1,500 ft, Thickness - 10 to 150 ft, (Upper Mud and Wispy units, dykes and breccias along faults);

Meikle (main): 1,600 ft, Thickness - 10 to 380 ft, (Fault and breccia);

South Meikle: Length - 2,000 ft, Thickness - 10 to 70 ft, (Flat, faulted & brecciated dykes);

Extension: Length - 1,030 ft, Thickness - 10 to 70 ft, (Fault, brecciated dykes);

Griffin: Length - 1,100 ft, Thickness - 10 to 250 ft, (Fault, brecciated, dykes and Bazza Sand);

Griffin Bx: Length - 1,080 ft, Thickness - 10 to 150 ft, (Fault and brecciated);

West Griffin: Length - 1,400 ft, Thickness - 10 to 60 ft, (Bazza sand unit, Fault);

Barrel: Length - 1,600 ft, Thickness - 10 to 130 ft, (Upper Mud and Wispy units);

Rodeo: Length - 2,350 ft, Thickness 10 to 200 ft, (Upper Mud and Wispy units, dykes and breccias along faults);

North Post: Length - 2,400 ft, Thickness - 10 to 140 ft, (Wispy subunit, dykes and breccias along faults).

The Goldstrike Mine consists of operating open pit and underground mines.

The Betze-Post open pit is a truck and shovel operation. With completion of the 3rd NW phase targeted for March 2019, the open pit has three remaining phases (4th NW, West Barrel, and 5th NW). The ultimate pit will measure approximately two miles east to west, 1.5 miles north to south, and have an average depth of approximately 1,300 ft.

The underground mine consists of 11 separate production areas stretching over a length of 12,000 ft, and a vertical distance from approximately 600 ft to 2,000 ft below surface. At the southern end of the underground zones, the pit workings cut the underground zones.

SHAFTS
There are two access shafts for the mine - the Meikle shaft and the Rodeo shaft. Both are used for personnel and materials, while, ore is only hoisted via the Meikle shaft. The Meikle shaft is approximately 1,800 ft deep, extending to the 3,700 ft level, while the Rodeo shaft is 1,300 ft deep and extends to the 4,100 ft level.

Hoist operation in both shafts is automated with human oversight provided. There are ventilation shafts and boreholes for ventilation in both the Meikle and Rodeo mines.

RAMPS
There are three ramps to surface, all three are accessed through the open pit. The Betze No. 1 portal is a fresh air intake and used for both vehicular traffic and movement of ore to the pit. The Betze No. 2 portal is an emergency exit and a fresh air intake for the North Post. The third access to surface, the North Post portal, is also used for vehicular and material supply traffic, and as air exhaust. Some ore from the underground is hauled by truck to a dump area in the pit and subsequently moved by open pit haulage trucks to the mill area.

Goldstrike underground operations use two mining methods for extraction: long hole open stoping and underhand drift & fill, both of which rely on cemented backfill for support.

In relatively good to fair ground conditions, where longhole stoping methods are used, the wall and back instability is reduced by mining smaller, longhole sections and filling before mining the next section. In poor ground, the underhand drift and fill method provides a backfill roof for subsequent lifts in the mining cycle.

The underhand drift and fill method is utilized in areas of fair to poor ground conditions regardless of the width of the zone. The underhand drifts are nominally designed as 4.6 metres (15 ft) wide by 4.6 metres (15 ft) high. The minimum width is 4.6 metres (15 ft) (one drift). The primary drift is driven with increased ground support to hold the ground open, then backfilled with a high strength cemented rock fill at the Meikle mine, paste fill at the Rodeo and North Post 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 a sufficient number of headings to complete the full mining cycle.

Transverse longhole stopes are designed at various heights ranging from 10.7 m (35 ft) to 30.5 m (100 ft), based on the existing and planned sill development levels used in the active mining areas. Stope widths are designed at 6.1 to 7.6 metres (20 ft to 25 ft), based on the ground conditions. In secondary stopes, the width is dictated by the actual dimensions of the adjacent primary stopes. Development of the secondary sills may be reduced to 4.0 metres (13 ft) leaving a rock “skin” to account for poor quality backfill in the adjacent stopes. The overall stope length is based on the transverse dimension of the ore; however, individual stopes can be limited to 13.7 metres (45 ft). Transverse longhole stopes are designed with at least 60° hanging walls and with subvertical footwalls.

Transverse longhole stoping is used where the mineralized zone has a significant width. Footwall drifts are driven parallel to the strike of the ore to provide access for stoping. Mining with transverse stopes requires a primary, secondary, and sometimes tertiary extraction to completely mine out the area.

Longitudinal stopes are utilized in areas of the mine where the geometry and ground conditions allow. The stopes are accessed from a footwall drive driven parallel to the strike of ore. If the strike length of the ore is greater than 18.3 metres (60 ft), the development is driven to the end and the stope is mined in a retreat fashion in sections no longer than 18.3 metres (60 ft). Each section is mined and filled before the next section is mined. If ground conditions are poor, the longhole stope section length can be reduced.

Overhand drift and fill, back stoping, and benching are all used to a much lesser extent, based on ground conditions and the geometry of the ore zones.

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Goldstrike process facilities provide the capability to treat single refractory ore (sulphidic) and double refractory ore (sulphidic and carbonaceous) through roasting or pressure oxidation. The roaster circuit accommodates Goldstrike open-pit and underground ore as well as Cortez Hills Open Pit (CHOP) and Cortez Hills Underground (CHUG) ore. A blended feed to the roaster is required to control the circuit heat balance. Pressure oxidation also receives a blended feed from stockpiles and operates as either alkaline or acid POX dependent upon feed carbonate/sulphide ratios. Pressure oxidation is followed by CaTS leaching, also referred to as the Thiosulphate Leach Conversion (TLC) with a Resin in leach (RIL) adsorption circuit for gold recovery. Respective facilities include:

1. An autoclave circuit consisting of:
• Primary crushing;
• Two parallel SAG Mill-Ball Mill grinding circuits with pebble crushing;
• Five parallel autoclaves capable of alkaline or acid ( ........