The principal deposits within the Wafi-Golpu project are porphyry copper-gold mineralization and epithermal style mineralization.

The Wafi-Golpu Property contains a major mineralised system. Wafi-Golpu is a complex mutliphased mineralised system which comprises copper gold porphyry intrusives which are followed by later stage epithermal gold mineralization events.

The Wafi-Golpu project contains three major deposits localised around a Wafi Diatreme complex. These deposits include:
• Wafi Epithermal gold deposit
• Golpu Porphyry copper - gold deposit
• Nambonga porphyry gold - copper deposit.

The Wafi gold deposit is hosted in the metasedimentary units of the Owen Stanley Metamorphics and peripheral to the diatreme breccia complex. The Wafi mineralization has been defined over a surface area of dimensions approximately 1,100m x 800m and depth of up to 600m below surface with the majority of the material potentially exploitable by open pit mining.

Alteration at Wafi is typical of high sulphidation epithermal mineralised systems with advanced argillic minerals characterised by quartz-alunite grading outwards to dickitekaolinite then to minerals formed at the margins including carbonates-smectite chloritechalcedony. Weathering has affected the upper portion of the deposit but below the base of oxidation, primary sulphides are predominantly pyrite with lesser enargite and tennantite. Mineralization is sub-parallel to bedding and appears preferentially hosted in coarser grained sedimentary units.

The Golpu porphyry related copper gold deposit consists of a stockwork vein array hosted by altered hornblende porphyry intrusive and surrounding metasediments adjacent to the diatreme breccia.

The Golpu porphyry deposit is a major porphyry copper and gold deposit.

The overall dimensions of the mineralised system as currently defined is approximately 800m north-south x 500m west-east and of a vertical extent greater than 2,000m.

Mineralization is derived from either the porphyry or epithermal systems; within the porphyry environment, mineralization is disseminated, microfracture and stockwork vein controlled.

The Nambonga mineralization extends over an area of approximately 200m x 200m and to a vertical extent of 800m.

Mineralization at Nambonga consists of disseminated and vein style copper/gold mineralization structurally-controlled base metal mineralization in steeply dipping lodes.

Based on the geotechnical analysis of the data received from the 2016 Geotechnical Drilling Program, the updated Feasibility Study proposes utilisation of the following exploration, design, development and mining approach:
1. Initial underground access via the Nambonga Decline, offering the following advantages:
- Earlier and quicker access to underground drill platforms in support of an extensive underground drilling program (geology, geotechnical, hydrogeological, metallurgical)
- Affords access to an underground work front in support of developing the twin Watut Declines from both surface and from underground
- De-risks Project Execution and the critical path to achieving first production
- Has future use as a second means of egress, and replaces a blind-sunk intake ventilation shaft
2. Primary underground access via the Watut Portal and the twin Watut Declines to the underground block cave mine. The Watut Declines also form part of the primary ventilation circuit and materials handling system conveying ore to the Watut Process Plant
3. A ‘Cave Engineering Level’ established above the Reid Fault at 4,870 metres reduced level (mRL)12 for data gathering, further refinement of the rock mass, monitoring of the cave and potentially for dewatering
4. Ore extracted via three block caves producing ore at 17Mtpa (design capacity).

It is proposed that the first block cave, BC44, be situated at 4,400 mRL. The second block cave, BC42, will be situated at 4,200 mRL. These block caves are expected to be mined for 7 and 9 years respectively during the first 14 years of the mine life. The third block cave, BC40, proposed to be situated at 4,000 mRL, is expected to be mined for 16 years leading to a total mine life of 28 years from first production of the processing plant (excluding construction and closure phases). The ore body remains open at depth and ultimate life of mine is still to be determined.

During caving operations, ore from the block cave drawpoints is planned to be delivered by autonomous load-hauldump vehicles to underground crushers. The proposed Material Handling System (MHS) includes two crushers on each level, from which the crushed ore is to be conveyed to the surface via dedicated transfer conveyors. The ore conveyor emerging at the portal terrace on the surface will continue overland to deliver crushed ore to a coarse ore stockpile adjacent to the Watut Process Plant. The MHS is designed to manage 17Mtpa.

The process plant includes the following unit processes and facilities:
• crushed ore stockpiling and reclaim
• two parallel grinding lines
• SAG and ball mill grinding (SAB circuit) with allowance to retrofit a pebble crusher
• copper flotation comprising rougher flotation, concentrate regrind and three stage cleaning
• copper concentrate thickening and pumping
• tailings thickening, pumping and water recovery
• reagents mixing and distribution (including lime slaking, flotation reagents, water treatment and flocculants)
• grinding media storage and addition
• water services (including raw water, fire water, potable water, gland water, cooling water and process water)
• air services (including high pressure air and low pressure process air).

Crushed ore is delivered to a single conical, open stockpile via the material handling systems. The stockpile has a ‘live’ capacity of approximately 60 kt, while ‘dead’ capacity can be recovered using a bulldozer or excavator.

Coarse ore is reclaimed from the stockpile by four apron feeders, two for each grinding line. Each feeder is designed to provide up to the full feed rate to the SAG mill, but will generally operate at 50% capacity for even draw-down of the stockpile.

Each pair of apron feeders discharges onto a SAG mill feed conveyor (one conveyor per grinding train), which transports the crushed ore to the SAG mill feed chute.

Lime is added to the SAG mill feed conveyor, to maintain the pH at a design level (above pH 7).

The grinding circuit consists of two parallel lines of grinding mills, each with nominal 1370 t/h capacity. Each grinding line consists of a single SAG mill, followed by a single ball mill operating in closed circuit with a cyclone cluster. SAG and ball mills are driven by a 14 MW twin pinion drive assembly. The SAG mills are 10.4m diameter by 6.0m effective grinding length (EGL). The ball mills are 7.6m diameter by 12.2m EGL.

The SAG mills are fitted with trommel screens to separate oversize pebbles and scats. Trommel oversize from each SAG mill reports to the respective SAG mill feed conveyor via two transfer conveyors prior to Year 7. From Year 7 onward, pebbles are conveyed to separate pebble surge bins and pebble crushers, with crushed pebbles conveyed to the SAG mill feed conveyors. SAG mill trommel undersize gravitates to the primary cyclone feed hopper where it is combined with the discharge from the ball mill.

The flotation circuit consists of two parallel trains of rougher flotation cells followed by rougher concentrate regrind, cleaner scalping via Jameson cells, three stages of cleaning in separate banks of tank cells and cleaner scavenger cells. The cleaner scavenger bank is operated in open circuit.

Trash screen underflow gravitates to the rougher flotation circuit, which consists of two parallel trains of seven 200 m³ forced-air tank cells. The level in each stage is controlled by an internal dart valve arrangement. Lime slurry is added to the head of the rougher bank for pH control.

Collector and frother are added at the head of the rougher circuits and in stages down the banks.

The copper rougher tailings flow from the parallel trains to the tailings thickener distribution box, where they combine with cleaner 1 tailings, for distribution to the two tailings thickeners.

The regrind circuit consists of two ball mills with dedicated cyclone clusters in closed circuit. Discharge from both regrind mills gravitates to a single discharge hopper, where rougher concentrate and cleaner scavenger concentrate are added to the circuit. Slurry is pumped from the regrind mill discharge hopper to two cyclone clusters by dedicated pumps. Regrind cyclone overflow (at P80 30 µm) from both cyclone clusters is combined and gravitates initially to cleaner 1, and after Year 4 to the cleaner scalper cell(s) (two B6500/24 Jameson cells). Cleaner scalper concentrate is pumped to the concentrate thickener.

Lime slurry is added to both the cleaner scalping and cleaner 1 feed streams to maintain the slurry at pH 10. Collector, frother and depressant (sodium cyanide) can also be added to cleaner 1 feed.

Concentrate recovered from cleaner 1 is pumped to the cleaner 2 flotation bank for further upgrading. Cleaner 1 tailings gravitate to the cleaner scavenger cells. The cleaner 1 bank consists of four 200 m³ forced-air tank cells arranged in series.

Cleaner scavenger cells recover a low grade concentrate that is pumped to the regrind circuit. Cleaner scavenger tailings are pumped to the tailings thickener feed distribution box. The cleaner scavenger unit consists of two 200 m³ forced-air tank cells arranged in series.

Cleaner 2 concentrate is pumped to the cleaner 3 flotation bank for further upgrading. Cleaner 2 tailings report back to the head of cleaner 1. The cleaner 2 bank consists of four 150 m³ forced-air tank cells arranged in series.

Cleaner 3 concentrate is transferred to the concentrate thickener. Cleaner 3 tailings gravitate to the head of the second copper cleaner bank. The cleaner 3 bank consists of three 150 m³ forced-air tank cells arranged in series with wash water to reduce entrained gangue.

Concentrate is pumped from the copper flotation circuit to a 25m diameter high-rate copper concentrate thickener in each train.

Flocculant is added to the thickener feed stream to enhance settling. The concentrate thickener overflow reports to the process water pond. Copper concentrate solids settle to a density of 60% solids. The thickener underflow stream is pumped to two agitated concentrate storage tanks, which provide 24 hours surge capacity for the concentrate pumping system.

The pumping station consists of two positive displacement pumps operated in a duty/standby arrangement. The concentrate pipeline transports concentrate approximately 100 km from the process plant to port facility in the Lae area, and includes a test loop and pipeline monitoring instrumentation.