Haile gold mineralization occurs as an en echelon 5 km long by 1.5 km wide cluster of moderately to steeply-dipping ore lenses within a ENE-trending anticlinorium. Eleven named gold deposits are recognized at Haile. From west to east these include Champion, 601, Small, Mill Zone, Haile, Ledbetter, Mustang, Red Hill, Palomino, Snake and Horseshoe. Ore body geometry, depth, size, grade, mineralogy and alteration are variable between deposits. Ore zone geometry is strongly controlled by post-mineral folding and position within the Haile anticlinorium. Some of the deposits coalesce, especially in the central part of the district around the large Ledbetter deposit. Ore lenses are typically 50 to 300 m long, 20 to 100 m wide, and 5 to 30 m thick.

Gold mineralization at Haile is mostly hosted by folded laminated siltstone and greywacke of the upper Persimmon Fork Formation and is capped by less permeable volcanic rocks. Mineralization is typically within 100 meters of the sediment-volcanic contact. Mineralized zones at Ledbetter, Red Hill and Snake are partly hosted in volcanic rocks.

Gold mineralization at Haile is disseminated and occurs in silicified and pyrite-rich metasediments with local K feldspar and molybdenite. Mineral zonation is a quartz-sericite-pyrite+-K feldspar+- gold (QSP), sericite +- pyrrhotite propylitic (chlorite-calcite-epidote) haloes. QSP mineralized zones are tens of meters wide. Sericite envelopes range in thickness from tens to hundreds of meters and are controlled by protolith, structural permeability and post-mineral folding. Within the mineralized zones, quartz is dominant (60% to 80%), pyrite is moderate (1% to10%), and sericite is variable at 5% to 20%. Two silicification events are observed in the mineralized zones. Early massive silicification is finely disseminated to diffuse. Later silicification is manifested as matrix fill in tectonic and hydrothermal breccias and as stock work veinlets. Sericite alteration is commonly expressed as sericite schists due to sericite replacement of micaceous layers in metasediments, imparting a tannish white color. Bleaching and/or argillisation is weakly developed within and adjacent to sericite zones. Propylitic alteration is characterized by increased chlorite (5% to 20%) and a mottled texture with blebs of 3 to 5 mm calcite aggregates. Late calcite +- quartz veining is focused along fault zones.

High-grade zones >3 g/t Au are characterized by intense silicification, anastomosing quartz veins, hydrothermal breccias and >1% fine-grained pyrite. Pyrite grain size is typically <20 microns and occurs as stringers, lenses and banded layers, including graded beds and reworked sulfide sediment. High grade zones are focused where ENE faults coincide with anticline axes in folded metasediments adjacent to the overlying metavolcanic rocks. The Horseshoe deposit averages over 4 g/t and occurs within a tight anticline dissected by ENE-trending, NW-dipping faults.

Oxidation at Haile extends to depths of 20 to 60 meters and is deepest along faults and in folded volcanic rocks. Hematite and goethite are strongest near surface, accompanied by saprolite, and decreased at depth to weak joint stains.

Gold spatially correlates with molybdenite, silver, arsenic, antimony, molybdenum, and tellurium at Haile (Mobley et al., 2014). Arsenopyrite, chalcopyrite, galena, and sphalerite are rarely associated with gold mineralization.

Haile is currently being mined using conventional open pit methods. The open pit is located in gently undulating topography intersecting natural drainages that will require diversion to withstand high rainfall events during the summer months. Waste dumps are managed according to the AP and are located on high ground and lined for control of drainage (contact water) if required.

The open pit that forms the basis of open pit reserves and life of mine (LoM) production schedule is approximately 2.5 km from east to west, 1.25 km north to south with a maximum depth of 370 m. Total material movement is estimated at 536 Mt comprised of 55 Mt of ore and 481 Mt waste giving a strip ratio of 8.74 (Waste:Ore). Ore grade averages 1.71 g/t Au yielding over 3 Moz of gold in situ. SRK have created 13 pit/pushbacks that are approximately 150 m to 300 m wide with the minimum mining width of 60 m. Bench sinking rates are approximated to one 5 m bench per month.

2017 production rates are 2.1 million tonnes per annum (Mtpa) of ore delivered to the mill and 22.3 Mtpa of total material movement. Over the next 18 months, open pit production will ramp up to 3.3 Mtpa of ore and 44.0 Mtpa of total material movement. Open pit ore production will increase to 4.0 Mtpa in 2027, after the Horseshoe underground has been exhausted.

The Horseshoe underground mine production schedule is based on the productivity assumptions. The schedule was completed using iGantt scheduling software and is based on mining operations occurring 365 days/year, 7 days/week, with two 12-hr shifts each day. A production rate of 1,924 t/d was targeted with ramp-up to full production as quickly as possible.

Stopes will be mined using the sublevel open stoping method. Individual stope blocks are designed to be 15 m wide, up to 30m long, and will have a transverse orientation. Levels are spaced 25 m apart and each stope block will have a top and bottom access (5 m x 5 m flat back drifts).

Stopes will be drilled downward from the top access using 114 mm diameter holes (stope slots will be drilled with a DTH drill and stope production rings will be drilled with a tophammer drill). A bottom up, primary/secondary extraction sequence will be followed. Primary stopes will be backfilled with CRF(Cemented rock fill) and secondary stopes will be backfilled with RoM waste from the underground and open pit operations.

Stope extraction will occur in two steps. During the first step, a slot will be mined at the far end the stope using a drop raise and 28 fan-drilled slash holes. The slot is required to create sufficient void space for the remainder of the stope to be blasted. During the second step, production rings will be blasted three rows at a time (13 blast holes per ring) until the stope is completely extracted. The number of three-row blasts in a given stope will depend on the length of the stope. All blasting will be performed with bulk emulsion.

Ore will be remotely mucked from the bottom stope access using a 14-t LHD (6.2m3 ). Cable bolts will be installed at the stope brow to ensure stability. The LHD will transport the ore to a muck bay to maximize the efficiency of the stope mucking operations. A second 14-t LHD and a fleet of 40-t haul trucks will be used to transport ore from the muck bays to the surface. Multiple muck bays will be used on each level to avoid interference between the stope loader and the haul trucks. At the surface, the haul trucks will dump onto a RoM ore stockpile and will then travel to an adjacently located backfill plant to be loaded with CRF. After being loaded, the haul trucks will return to the underground mine and will dump the CRF into a muck bay near the top of an empty primary stope. After dumping the load of CRF at the muck bay, the haul truck will return to the producing level to once again be loaded with ore. A 7-t LHD will be used to transport the CRF from the muck bay to a dumping point at the top access of the empty stope.

A mine access and material handling tradeoff study was completed for the Horseshoe deposit. Options considered included shaft access with ore hoisting, decline access with conveyor haulage, and decline access with truck haulage. The tradeoff study demonstrated that, given the deposit depth, production rate, and anticipated mine life, the economically superior option is decline access with truck haulage.

The upper portion of the 5.0 m wide by 5.5 m high access decline is expected to be in weathered rock and therefore will require an increased level of ground support. After the decline has passed through the weathered rock, a less intensive level of ground support will be required. The decline is designed at a maximum gradient of 14%. A turning radius of 25 m was used, which is suitable for the underground haul trucks contemplated for the operation.

The portal for the access decline will be located on an open pit bench approximately 80 m below the natural surface, thereby eliminating the need to develop the access decline through saprolite. The portal construction will consist of scaling and bolting/screening and application of shotcrete as necessary to support and create a safe surface above the mine portal. A structurally sound corrugated pipe style liner with supports as necessary will be constructed for the first 200 feet of portal or as dictated by the rock conditions. Ventilation, power, water discharge, supply water, and communications will be installed at the portal and carried down the decline to support the development operation. An all weather gravel surface will be established at the portal and portal bench area and drainage will be maintained away from the portal entrance to minimize water entering the portal and decline from the bench area.

Secondary egress will be via 5.0 m diameter raisebored ventilation raises equipped with emergency hoisting.

The mine will utilize CRF in the primary stopes and either rock fill or low strength CRF in the secondary stopes. CRF will be generated in a surface plant located at the underground storage yard that includes a 160 t/hr portable crushing/screen plant that will create two specification grade aggregate piles and an oversize pile. The specification grade aggregate will be transported to the CRF plant by a front-end loader where it will be loaded into one of two hoppers, a large aggregate (4 inch to 3/16 inch) and fine aggregate (3/16 inch minus), that will in turn batch feed into a mixer that combines specified quantities of cement, water, and aggregate to create the required high strength CRF. A conveyor moves the CRF mixture to a bin that stores the CRF for loading of the underground trucks. The CRF plant has a capacity of 100 m3 /hr with a batch mixer, cement silo with screw conveyor and weigh hopper, water weigh hopper, and the aforementioned two loss-in-weight aggregate bins. The 40-t underground haul truck pulls under the bin after dumping its ore on the stockpile and loads the CRF. Once loaded, the truck hauls the CRF underground to an open stope where backfilling is taking place. The truck dumps the load either directly into the stope or in a staging area where an LHD hauls the CRF to the stope for placement.

The processing methods will remain the same as the currently operating plant for the proposed expansion. A conventional flotation and cyanide leaching flow sheet will continue to be used at Haile.

The existing Haile facilities have an ample site footprint to expand to a capacity of 4.0 Mtpa.

RoM ore will continue to be fed from the existing tip bin using the installed apron feeder and will pass over the existing vibrating grizzly where fines will be scalped out and oversize material will feed the existing primary (jaw) crusher operating in open circuit exactly as per the current arrangement.

The primary crushed ore stream will be able to diverted by a modified chute from the head of the first extant crusher area conveyor onto a new conveyor and delivered via a scalping screen into a secondary crusher operating in open circuit. Screen undersize and secondary crushed ore will be combined and conveyed back to the existing coarse ore bin and stockpile arrangement.

A twin parallel screen and crusher arrangement was developed but it is anticipated that only a single line will be equipped initially and the second set of equipment installed later once an assessment of crushing equipment availability and productivity is able to be made.

Secondary crushed ore will similarly either be reclaimed from either the surge bin or stockpiled and re-fed by FEL into the reclaim bin and delivered to the upgraded grinding circuit.

The existing conveyors are suitably sized for the increased plant feed rate but some will require a speed increase to reduce loading per unit length to avoid spillage. A minor upgrade to the SAG mill feed conveyor drive is required to cope with the increased circuit capacity for new feed and the design pebble recycle rate.

The existing 2-stage grinding circuit that consists of a primary SAG and secondary ball mill will be supplemented with a pebble crusher and tertiary vertical tower mill to meet the increased throughout.

The SAG mill discharge grates design will be changed to include pebble ports and mill discharge is still fed to the existing vibrating horizontal screen. The screen is adequately sized for expansion and the screen oversize will be conveyed to a new pebble crushing circuit. A magnet is provided for tramp steel removal. The crushed pebbles will be delivered back onto the SAG mill feed conveyor.

Since plant start-up the lack of a pebble crushing capability has been identified as a key weakness in the design and plans have been initiated to fast track the installation of these specific modifications urgently during 2017 rather than delay until the plant expansion project is started.

The SAG discharge screen undersize is fed to the existing ball mill which will continue to operate in closed circuit, but with a modified hydrocyclone cluster. The overflow slurry from this cyclone cluster will feed a new tertiary grinding circuit.

A portion of the existing ball mill hydrocyclone underflow will still be treated in a flash rougher flotation cell and the flash flotation concentrate pumped to a trash screen and flash flotation tails returning to the secondary ball mill.

The tertiary grinding circuit envisaged consists of a vertical ball mill (tower mill) operated in reverse closed circuit with its own hydrocyclone cluster.

The tertiary mill model was selected as conservatively sized with a generous installed power due to the uncertainty over the LOM variation in ore competency given the lack of detail in the mining schedule at the time. A smaller unit is potentially suitable and this is more likely if the design criteria for the circuit product particle size is altered based on operating experience gained in the near term.

The grinding circuit product slurry from the overflow of the tertiary tower mill’s hydrocyclones will pass through a new trash screen and slurry sampler to feed the flotation circuit.

The design flotation circuit residence time could be maintained with the installation of a new prerougher flotation cell located in place of the existing conditioning tank which would be removed.

However, since plant operations have started up at Haile, rougher flotation kinetics appear to be faster than expected and the extra flotation cell is not considered to be likely to be necessary at the time of compilation of this report.

The existing rougher flotation cell configuration can also be modified to allow operation of the last two cells in a scavenger configuration if required as part of the expansion though this is not a critical action.

The flotation tailings slurry will still be dewatered in the existing flotation tails thickener; an additional hi-rate thickener could be installed, operating in parallel, to meet the expanded plant capacity. However, the extant high-rate thickener capacity is limited primarily by the undersized feed launder and feed well arrangement and the obsolescent design of these components as opposed to the installed area.

It is expected that replacement of these components with a design specified for the flowrates expected for upgraded plant capacity using more appropriate modern technology will suffice and a complete new thickener may not be necessary.

The existing pre-aeration thickener, which was installed to dewater reground concentrate slurry prior to leaching, will be repurposed to instead dewater the combined flash and rougher flotation concentrate slurry streams prior to regrind. The significantly coarser size distribution of the “as floated” concentrate is expected to display enhanced settling rates, improve overflow clarity and the extant thickener dimension is suitable for the increased design throughput.

Oxidized concentrate slurry could be pumped to a new carbon in leach (CIL) circuit with the residue from the concentrate CIL circuit pumped to the existing to the existing CIL tanks and combined with thickened flotation tailings slurry.

This was believed necessary to ensure sufficient residence time would be retained for the float tails leaching by converting the first in train single large concentrate CIL tank to be the first of eight flotation tails CIL stages.

This represents a high cost option and as such is non-preferred. Operational experience infers the concentrate leach kinetics are faster than predicted and preg-robbing is not anticipated to be of any significance.

In place of the proposed CIL a hybrid Concentrate leach arrangement is preferred obviating the requirement for carbon to be present, removes the cost for interstage screens, carbon transfer pumps etc.

As well as these key changes, general pump and piping upgrades would be required.

To manage the extra volume of loaded carbon produced from both the concentrate and flotation tailings CIL circuits in the expanded plant, the installation of an additional acid wash and elution column was allowed for. The current plant elution area structural steel was designed to readily accept an additional column for each application.

Since start-up, reasonable metal loading values were noted. Also, lower than anticipated plant feed silver grades compared to the geological resource model predictions and most importantly faster batch turnarounds in the elution circuit operation have been performed. This supports the deduction that the extra vessels would not necessarily be required. A second batch per day can be completed to make maximum use of the existing installed elution capacity then the second columns are redundant.

The extant electrowinning cells were sized based on the flowrate through the strip so running a second strip per day (one at a time), will not require any additional cells to operate. The existing regeneration kiln was sized to handle a maximum throughput that is believed adequate for the plant expansion.