Among gold deposits of the Tintina Gold Belt, Livengood mineralization is most similar to the dike and sillhosted mineralization at the Donlin Creek deposit, where gold occurs in narrow quartz veins associated with dikes of similar composition (Ebert, et al., 2000). The age of the intrusions and the coincidence of mineralization and intrusive rocks are typical of those of other nearby gold deposits of the Tintina Gold Belt, which have been characterized as intrusion-related gold systems (Newberry and others, 1995; McCoy and others, 1997). For these reasons Livengood is best classified with these deposits.

Gold mineralization is associated with disseminated arsenopyrite and pyrite in volcanic, sedimentary and intrusive rocks, and in quartz veins cutting the more competent lithologies, primarily volcanic rocks, sandstones, and to a lesser degree, ultramafic rocks. Mineralization appears to be contiguous over a map area approximately 2.5 km2; a 0.1 g/mt grade shell averages 280 m thick and drilling has not closed off the deposit at depth. The stronger zones of mineralization are associated with areas of more abundant dikes. South of the Lillian Fault individual mineralized envelopes are tabular and follow stratigraphic units, particularly the Devonian volcanics, or lie in envelopes that dip up to 45° to the south, mimicking the structural architecture and attitude of the diking. On the north side of the Lillian fault mineralization is similar in style and orientation and hosted primarily in steeply dipping Upper Sediments. Three principal stages of alteration are currently recognized; in order from oldest to youngest, these are characterized by biotite, albite, and sericite. Arsenopyrite and pyrite were introduced primarily during the albite and sericite stages. Gold correlates strongly with arsenic and occurs primarily within and on the margins of arsenopyrite and pyrite grains. Carbonate was introduced with and subsequent to these stages. Dating of the sericite alteration (Athey, Layer, and Drake, 2004) indicates that mineralization and alteration were contemporaneous with the emplacement of the dikes.

The Livengood Gold Project is a conventional surface mine that will utilize large-scale mining equipment for standard open pit mining of a blast/load/haul operation. Mining was scheduled to provide a mill feed of 52,600 t/d (47,700 mt/d). Preproduction stripping of 86.7 Mt (78.6 Mmt) of waste rock material is required for the construction of process facilities and site infrastructure. Mineralized material mined during preproduction will be stockpiled for mill feed later in the production period, after mill start-up.

All pits were designed with bench heights of 65.6 ft (20 m) and bench face angles of 70°. As the mining height is 32.8 ft (10 m) a bench, the mining of the pit walls will be double benched; catch benches were designed on alternating mining benches. Catch bench width varies depending upon the pit wall’s relation to the ultimate pit. The inter-ramp slope angle (ISA) for the ultimate pit is 42°, requiring a catch bench width of 48.9 ft (14.9 m). Pit phases that are internal to the ultimate pit were designed with a steeper ISA of 47°, giving a 37.4 ft (11.4 m) catch bench width. These internal pits are mined earlier in the production sequence and the internal pit walls are mined out by subsequent phase pushbacks, until the final pit slope of the ultimate pit is reached. The internal pits are scheduled to be mined in a period of around three years to minimize the time exposed to the steepened slopes. Slope heights for the internal pits were also limited to 395 to 525 ft (120 to 160 m) maximum between haul roads, step outs, and areas of shallower slopes. The pit designs also accounted for haul road access to all mining areas and minimum practical mining widths, based on the specified mining equipment. Haul roads were designed at a grade of 10% with a width of 100 ft (30.5 m), which is 3.5 times the width of the selected 320 t (290 mt) haul trucks (28.5 ft or 8.7 m). The haul road network internal to the ultimate pit limits was designed to one pit exit location.

The optimized production schedule provides an operating life of 23 years. A two-year preproduction period is required for removal of waste rock material and site construction. Mine production will produce mill feed mineralized material for 16 years. During the mine production period, low grade mineralized material will be stockpiled to be used for future mill feed, while waste rock material will be placed in a waste rock stockpile. Portions of the low grade, stockpiled, mineralized material will be sent to the mill during the mine production period, supplementing direct mine production tonnes to maintain constant mill throughput. After mining is complete, the mill will be fed from the remaining low grade stockpile for seven years.

The recovery methods for the Project were established on the basis of previously noted laboratory-scale testwork programs, information from equipment suppliers and on BBA’s experience on similar projects. Significant process plant configuration changes implemented within the PFS compared to the FS include the addition of secondary crushing ahead of the SAG mill for more efficient use of power, inclusion of a single line SAG/ball mill configuration, and simplification of the mill foundation and pebble re-grind circuit. Recent metallurgical testwork completed has also resulted in the grind size being coarsened from 90 to 180 µm (P80), as well as a reduced leach circuit retention time from 32 to 24 hours.

The nominal Livengood process plant capacity at 92% is 52,600 t/d (47,700 mt/d) resulting in an annual capacity of 19.2 Mt/y (17.4 Mmt/y). Run of mine ore is transported to the primary gyratory (54/75) crusher, where it is crushed and stockpiled in a covered pile, then conveyed to the secondary crushing (1000 hp) building. Crushed product (1.65 in (42 mm)) will then be conveyed and processed in a comminution circuit (SABC) consisting of wet grinding in a single semiautogenous (SAG) mill ((D×L) 36 ft × 20 ft /18,774 hp) in closed circuit with a pebble crusher (1,000 hp) and a single ball mill (26 ft × 40.5 ft / 20,115 hp). The ball mill is in closed circuit with hydro-cyclones. A pulp stream will be bled from the cyclone feed and treated with a bank of eight centrifugal gravity gold separators. The gravity tails will be pre-treated with oxygen and lead nitrate and then leached in a conventional CIL circuit (2 rows of 7 tanks). The gravity gold will be intensively leached from the gravity concentrate with an intensive leach reactor (ILR) system.

The hydrocyclone overflow product will be pumped to a trash screen, before discharging into the pre-leach high rate thickener with a diameter of 131.2 ft (40 m). This thickener will thicken the slurry to 50 wt% in the thickener underflow stream. The thickener overflow will report to the process water tanks. The underflow from the thickener will feed CIL lines 1 and 2 at the preconditioning stage.

Pre-conditioning with oxygen and lead nitrate will be conducted in four large tanks. The designed retention time is four hours when the plant operates at 52,600 t/d (47,700 mt/d).

The CIL circuit is comprised of two lines of 7 large CIL tanks each and all within their own concrete containment areas. The designed retention time is 21 hours when the plant operates at 52,600 t/d (47,700 mt/d). The average design carbon loading remains 4000 g/mt from the FS, but is to be confirmed by additional CIL testwork and simulation.

The slurry will flow counter-currently to the carbon from tank 1 through to tank 7. Fresh carbon will be added to tank 7 and flow to tank 1, by way of the carbon advance pumps located in each CIL tank. Slurry will exit tank 7 over the carbon safety screens, before heading to the pre-detox thickeners. Loaded carbon exiting tank 1 will report to the carbon stripping system (ADR) for recovery of the adsorbed metals.

Loaded carbon from the CIL tanks reports to the loaded carbon stripping circuit, where gold will be stripped and the carbon reactivated for recycle to the CIL circuit. Based on the information available, it is assumed that one strip per day will be sufficient to recover the gold loaded onto the carbon.

The ADR circuit includes an acid wash stage (two vessels) and High Pressure “modified” Zadra process for gold stripping from the loaded carbon. The Zadra stripping circuit (4 vessels) is considered “modified”, as the electrowinning is done in-line, with no pregnant tank between stripping and electrowinning. The barren solution is collected in two 31,700 gal (120 m3) barren tanks. The stripping cycle will be two stages, in which copper is stripped first, followed by gold. The stripped copper is converted to copper sulfate for use in the cyanide detoxification circuit downstream.

The stripped carbon will flow to the carbon regeneration kilns (4) that each possess the same carbon capacities and conservatively include provision for 100% regeneration of the carbon. The regenerated carbon will be combined with fresh carbon, making up for carbon losses that occur through the process. This regenerated/fresh carbon mixture will maintain an adequate supply to the CIL circuits.

The flow of pregnant solution from the Zadra circuit and the gravity ILR is split to feed a total of seven electrowinning cells. The refining equipment is designed to handle both the gold from the stripping circuit and from the gravity recovery system. The electrowinning sludge is filtered, dried, and mixed with fluxes, before being smelted in an induction furnace.

Gold from the leach circuit will be recovered by an adsorption-desorption-recovery (ADR) circuit, where the final product will be doré. Two thickeners (131 ft / 40 m diameter) (Pre leach and PreDetox) will be used to maximize water and cyanide recovery. The Inco SO2/air cyanide detoxification method will be used to reduce the cyanide content of the process tailings to acceptable concentrations prior to being discharged to the tailings management facility (TMF). A preliminary water balance indicates that approximately 286 gpm (65 m3 /hr) of fresh water will be required during operations.

Process plant reagents, including cyanide, lime, elemental sulphur, hydrochloric acid, lead nitrate, carbon and flocculants, will be delivered to site by transport truck and stored in the process facility as required.