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.

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.

Underground mine production comes from the Rodeo, Meikle, North Post, and Banshee areas.

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.

Two main mining methods are used underground at the Goldstrike Mine, 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.

Transverse longhole stopes are designed at various heights ranging from 35 ft to 100 ft, based on the existing and planned sill development levels used in the active mining areas. Stope widths are designed at 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 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 45 ft. Transverse longhole stopes are designed with at least 60° hanging walls and with subvertical footwalls.

Longitudinal stopes are utilized in areas of the mine where the geometry and ground conditions allow. The stopes are accessed from a footwall drive and then driven parallel to the strike of ore. If the strike length of the ore is greater than 60 ft, the development is driven to the end and the stope is mined in a retreat fashion in sections no longer than 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.

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 an 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 POX
• Two p ........