Summary

Deposit type

• Carlin-type
• Breccia pipe / Stockwork
• Hydrothermal

Summary:

The mineral deposits along the Carlin Trend form a suite of deposits known as Carlin type deposits.

Carlin mineral systems are a unique class of epigenetic ore deposits with enigmatic origins. They are unique due to the size and scale of deposits that formed exclusively within NE Nevada during the middle-Eocene period (42-35 Ma), establishing this area as a world-class gold complex. Carlin mineral systems are enigmatic due to their unknown, distal source of gold, as well as deposit characteristics and hydrothermal conditions that culminate to being atypical of most documented mineral systems.

South Arturo is a regionally distal Carlin-type deposit located in far north of the Carlin Trend that forms three structurally discrete ore bodies; the west, east and north. The western ore body (Phase 1) has an active open pit operation named South Arturo OP, which contains Mineral Resources and Mineral Reserves. Phase 1 was historically mined as both an open pit and underground. The eastern ore body (Phase 2) is an active underground operation named South Arturo UG (locally known as El Niño), which contains Mineral Resources and Mineral Reserves. Phase 2 was previously mined as an open pit.

South Arturo is a regionally distal Carfin-type deposit characterized by prolate mineralization geometries that are dominantly structurally controlled. Stratabound mineralization is apparent but far less continuous than similar deposits on the Carlin Trend. This likely reflects relatively lower hydrothermal fluid-rock interaction coupled with less favorable host rocks where planar faulting and fold features were the most permeable traps. Thus, mineralization orientations are highly variable due to the locally complex structural controls.

Mineralization is primarily hosted within the shelf-facies Rodeo Creek Formation. Discontinuous zones of mineralization occur within the allochthonous sequence of Vinini Formation but are minor. The platform-facies Bootstrap limestone is not a major host to mineralization but plays an important chemical and rheological competency contrast focusing fluid flow along its contact with Rodeo Creek Formation. This lithological contact is highly attenuated by pre-mineral deformation causing significant fault and dissolution breccias forming a highly permeable pathway.

The complex deformation history resulted in two oppositely plunging asymmetric anticlines. The intersection lineation of the two axial planes steeply plunges to the NW, which is the dominant control on the prolate mineralization geometries hosted within favorable Rodeo Creek sub-units of Phase 1. Conversely, Phase 2 mineralization is hosted within the brecciated contact of Rodeo Creek and Bootstrap, of which the widest zones of high-grade gold focuses in the apex of the local NE-trending anticlinal axial plane.

Mineralization also focuses in discrete dissolution breccia within high-angle normal faults that activate on the steep limb of the two regional anticlines, with highest grades focused in the Rodeo Creek Formation. Jurassic and Eocene dikes locally trend NW, and host volumetrically minor mineralization. All mineralization is associated with variable intensities of decalcification and argillization alteration. Mineralization occurs as oxide, sulfide refractory and carbonaceous refractory.

The South Arturo gold-silver deposits can be divided into five mineralized areas. These areas are the South Arturo, West Button Hill, Southwest Dee pit, Deep North, and Hinge. The majority of these deposits are classified as “Meikle Type” breccia hosted Carlin type deposits. A complex set of breccias occur at the upper contact of the Bootstrap limestone. These breccias can be generalized into four basic types: silicified heterolithic breccias, silica-Sulfide breccia, dolomite breccia, and cavity- fill breccias. While mineralization is widespread throughout the South Arturo Mine area, localized high-grade gold mineralization drives the economics and mine locations.

The dimensions and orientations of the modelled mineralized domains for South Arturo deposits:
Length - 520 – 1,500 m
Width - 70 – 550 m
True Thickness - 25 – 170 m
Approximate Strike Direction - NNW.

South Arturo
The northern extent of South Arturo mineralization lies approximately 200 feet southeast of the Dee pit and under 600 feet of waste rock. An overall north-south orientation to mineralization is inferred from the grade thickness contours, which define an area 1,700 feet in a north-south direction by 300 feet to 350 feet wide in an east-west direction. The mineralization and Tertiary contact dip 15° to 20° to the south. Drilling has shown that rocks are oxidized to a depth of up to 2,000 feet. Paleozoic rocks host the mineralization mainly in multi-stage, multi-lithic breccias with gold values ranging from 0.006 opt Au. These breccias are commonly formed by karsting or dissolution of carbonate rock and subsequent collapse and cavity fill. In general, decalcification is followed by weak to strong silicification with local argillization. Silver to gold ratios are generally 1:1 at grades of greater than 0.06 opt Au but increase to 5:1 at lower gold grade values.

Dee Deep North
Dee Deep North is a north-northeast trending pod of mineralization that plunges slightly north and is approximately 600 feet long, 150 feet wide, and 150 feet thick. The majority of high-grade refractory mineralization is in silica-Sulfide breccia within a flat to west-dipping silicified, multilithic breccia body above the Bootstrap limestone between 4,900 FASL and 5,100 FASL. The principal controls are the north-northeast trending high angle EB fault and southwest dipping low-angle structures.

Southwest Dee
The Southwest Dee pit mineralization is along the north-northeast trending, west dipping Dee Fault Zone. The mineralization is carbonaceous, partially oxidized, variably silicified mudstone/siltstone breccia approximately 300 feet in a north-south strike length, 100 feet wide, and 150 feet in thickness. The mineralization sits between 4,900 FASL and 5,100 FASL, with a small portion exposed along the southwest high wall at the bottom of the Dee pit.

West Button Hill
The West Button Hill mineralization trends north-northeast for over 2,000 feet in strike length, in pods that vary up to 600 feet wide and 50 feet thick. The majority of high-grade refractory mineralization is in the lower Rodeo Creek Formation and multi-lithic breccias above the Bootstrap limestone. The principal controls are the north-northeast and north-south trending high-angle structures and favorable host rocks. The mineralization has been shown to extend 1,230 feet below pre-mining surface elevation, as it is offset on the northeast striking, down-to-the-east Tara West fault.

Hinge
The Hinge zone is a north-south striking zone that lies between the Arturo zone to the south west and West Button Hill to the northeast and is due east relative to the existing Dee pit. It is approximately 1,400 feet long and up to approximately 300 feet wide, lying between elevations of 4,750 FASL and 5,250 FASL at depths from 330 feet to 900 feet below surface. Mineralization is hosted in the lower portion of the Rodeo Creek Formation and silicified breccias of the Basal Rodeo Creek and Popovich Upper Mud units. Breccia bodies drape the Bootstrap limestone. Mineralization in the Hinge zone is controlled by the Hinge fault, a steeply east dipping northsouth structure that appears to be a northerly extension of faults in Newmont’s Bootstrap pit to the south. Intersecting faults that influence mineralization have not been clearly identified. Much of the mineralization is partially to completely oxidized, even in the more deeply buried zones.

Mining Methods

• Drift & Fill
• Longhole open stoping
• Transverse open stoping
• Longitudinal open stoping

Summary:

South Arturo (El Nino) is a high-grade underground deposit situated down plunge of the Phase 2 pit, where mining was concluded in 2017. Underground mining is successfully extracting mineralization below the Phase 2 Pit.

South Arturo (El Nino) mine utilize Longhole open stoping, as primary mining method, and underhand Drift and Fill, as secondary mining method. Mining in South Arturo will be finished in 2027.

El Nino underground is accessed via a portal located at 1,536 m (5,040 ft) elevation above mean sea level ("amsl") within the South Arturo Phase 2 pit. Two portals were connected via a looped decline to access the ore deposit. The current mine depth for reserves extends down to 1,477 m (4,845 ft) amsl elevation and exploration potential exists down dip to the east and down plunge to the north.

Typical Mining Dimensions: 6.1m Wide, 22.9m high, length varies;
Backfill Type: Cemented Aggregate Fill (locally referred to as Cemented Rock Fill), Mine Waste;
Access type: 2 x Portal to South Arturo Open Pit.

Ore is hauled to ore pads on surface for temporary storage. The ore is subsequently transported to the Goldstrike Roaster facility for processing.

Long Hole Stoping
Long-hole stoping is used in areas with vertically continuous ore geometries which have fair to good ground conditions. Approximately 60% of the LOM plan for the Carlin Complex underground operations is scheduled to be mined using long-hole stoping. Multiple variants of the method are employed with transverse longhole open stoping being the most common. Other variations include:
• Longitudinal open stoping, for narrow ore zones where the stope strike is parallel to the orebody strike.
• Blind benching, similar to a traditional longhole stope, but a full bottom cut is not developed. This is used where the vertical extent of the ore is 9-13 m and requires sublevels to be on opposite sides of the orebody.
• Floor pulls, where after completing either a topcut or a drift and fill cut, short 2-9 m blastholes are drilled into the sill of the drift. The floor pull and drift are backfilled concurrently after mining. These are used around stopes to improve the overall recovery of the zone, and where there is insufficient ore to justify adding a deeper level.
• Uphole stoping, where a top cut is not driven to reduce costs. Both blasthole drilling and mucking occur from the bottom cut. This method is used in zones where paste backfill is available.

Planned stope level spacing is 10.6–30.5 m (35–100 ft) high based on ground conditions and
orebody geometry

Primary stopes are stopes that are mined first in the sequence. These stopes are backfilled with a cemented backfill (cemented rock fill (CRF)) and stopes mined between these areas are referred to as secondary stopes. Secondary stopes are backfilled with a combination of CRF and waste rock based on geotechnical requirements. Stopes are typically sequenced to be mined from the bottom up.

Generally, the CRF placed in the primary stopes has a greater strength than the host rock allowing the secondary stopes, with CRF on either side, to be mined with greater width and length parameters. Primary stopes have dimensions ranging from 4.6-9.1 m (15-30 ft) wide, while secondary stopes are 4.6-12.2 m (15-40 ft).

Stope strike length varies, typically from 9.1–21.3 m (30–70 ft) and is dictated by geotechnical criteria for wall exposure or the transverse width of the orebody, whichever is less. Multiple panels are taken with a backfill cycle in between where the orebody is wider than the maximum allowable strike length.

Drift and Fill
Drift and fill mining is a method of mining typically used for wide underground deposits with poor rock mass quality. A tunnel (drift) is mined into the orebody extracting the ore and backfilled, then another drift is mined adjacent to the first drift and then also backfilled. This continues until all of the ore at that elevation is extracted.

Underhand drift and fill is where the vertical progression is in a downwards direction; each new level of drifts occurs underneath the previously mined and backfilled drifts.

The underhand drifts are nominally designed as 4.6 m (15 ft) wide by 4.6 m (15 ft) high. The minimum width is 4.6 m (15 ft). The primary drift is driven with increased ground support to hold the ground open, then backfilled with a high strength cemented rock fill backhauled into the 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 enough headings to complete the full mining cycle.

The underhand drift and fill method provides a backfill roof for subsequent lifts in the mining cycle. A backfill plant, shotcrete plant, cement storage facilities, aggregate storage area and cement mixing pit are located on surface to support this mining method.

Blasting and Explosives
Each underground operation stores explosives underground in dedicated powder and cap magazines located away from active areas. The mines comply with Mine Safety and Health Administration (MSHA) and all other regulatory agencies. Both emulsion and ANFO are used as blasting agents based on loading conditions. Goldstrike, South Arturo UG, and sections of Leeville have reactive ground and utilize a buffered emulsion in those areas. Development rounds are timed with non-electric LP detonators and stope blastholes are timed with electronic detonators. Blasts occur twice per day during shift change and are initiated remotely from surface.

Backfil
Cement is added to backfill types to permit full orebody extraction by creating a self-supporting backfill product. Cemented backfill exposures can consist of both vertical and horizontal exposures. The determination of cemented backfill strength is dependent on the geometry of the exposure and assessed as part of the Geotechnical evaluation of excavation stability.

Materials used in the production of backfill are sourced from within the Carlin Complex. Waste rock is harvested from open pit operations where the product meets the hardness, friability, particle shape and chemical composition suitable for product selection. Parent rock is crushed at a facility within the Carlin Complex and distributed to each batching facility by surface trucks.

Equipment
The South Arturo UG mine mainly utilize diesel powered rubber tired equipment consisting of load-haul-dump (also referred to as LHD, loaders, or muckers), articulated haul trucks, longhole drills, jumbos and bolters. Additionally, there are ancillary/support equipment, including personnel carriers, forklifts, scissor lifts, explosives trucks, shotcrete sprayers, shotcrete remix trucks, lube trucks, graders, dozers and water trucks.

A backfill plant, shotcrete plant, cement storage facilities, aggregate storage area and cement mixing pit are located on surface to support this mining method.

Comminution

Crushers and Mills

Summary:

Goldstrike Roaster
The Goldstrike roaster facility includes primary and secondary crushing followed by two parallel dry grinding.

Crushing
Ore is reclaimed from one of the roaster stockpiles and goes through two stages of open circuit crushing including a gyratory crusher, scalping screen and cone crusher for screen oversize. The screen undersize and the cone crusher product are combined in a coarse ore stockpile.

Dry Grinding
Ore is reclaimed from the coarse ore stockpile by apron feeders and conveyed to one of the two parallel dry grinding circuits. The ore is heated with natural gas and progresses toward the centre of the mill as it is being dried and ground where it is transported with air through grates, a static cyclone classifier and a dynamic classifier for size separation. Oversize is returned to the second stage of the grinding mill for further size reduction while undersize material is transferred to bag houses for further processing. Target grinding circuit product size to roasting is P80 of 74 µm.

Processing

• Calcining
• Carbon re-activation kiln
• Crush & Screen plant
• Thermal oxidation
• Counter current decantation (CCD)
• Agitated tank (VAT) leaching
• Carbon in leach (CIL)
• Elution
• Carbon adsorption-desorption-recovery (ADR)
• Dewatering
• Solvent Extraction & Electrowinning
• Cyanide (reagent)
• Roasting

Summary:

Ore from El Nino (South Arturo) underground mine is transported to the Goldstrike Roaster facility for processing. The carbon from Goldstrike Roaster CIL is then transferred to carbon handling circuit located within the Goldstrike Autoclave Facility. The Goldstrike Autoclave refinery produces doré bullion.

Double refractory ore is processed through the Goldstrike Roaster’s Dorr-Oliver bubbling fluid bed roasters. The sulphide sulphur (SS) and organic carbon (total carbonaceous material, TCM) holding the gold is oxidized to liberate the gold so it can be recovered through conventional cyanidation (CIL).

Goldstrike Roaster (Process capacity of 6.6 Mtpa)
The roaster facility includes primary and secondary crushing followed by two parallel dry grinding and dual stage roasters with combined calcine quenching, dust and gas handling, neutralization, and CIL circuits. The loaded carbon is acid washed, pressure stripped and regenerated at site to produce doré bullion which is shipped off site for further refining.

Two Stage Roasting
Material from the roaster silo is fed to the top of the roaster by a bucket elevator and a fluidized feeder. The fluidized feeder distributes ore continuously to the first stage (upper) bed of the two parallel roasters. The exothermic chemical reaction provides the heat required to maintain the first stage temperature between 524°C and 593°C with the addition of sulphur pellets as needed to maintain feed fuel value. Sulfide concentrates can also be used to maintain temperature within the roaster.

Solids flow by gravity to the second stage of the roaster through an inter-stage solid transfer system where material bed temperature is maintained between 524°C and 561°C. Oxidation is essentially complete after the second stage achieving approximately 99% sulphide sulphur oxidation and typically greater than 80% organic carbon oxidation. Calcine from the second stage of the roaster discharges by gravity to the calcine quench system.

High purity oxygen is injected at the bottom of the second stage of the roasters and flows upward, fluidizing the material and supporting the rapid oxidation of carbon, sulphide sulphur and other fuels within the feed.

The exhaust gas from each stage is classified using dry cyclones. The coarse material recovered from the exhaust gas is returned to the roaster for further treatment while the gas is forwarded to gas quenching and final dust scrubbing. The off-gas from the final dust scrubbers of both circuits are recombined for final off-gas cleaning.

Off-Gas Cleaning
The final gas cleaning circuit combines the dust free off-gas from both roasters to capture mercury, sulphur dioxide, carbon monoxide, and nitrous oxides. Mercury removal is achieved through chlorine sparging to produce calomel which is shipped off site for further processing. Sulphur dioxide gases are neutralized with lime and carbon monoxide is oxidized to carbon dioxide through heating of the gases after SO2 removal in a carbon monoxide incinerator. Nitrous oxides are removed by passing off-gases through a mist stream of ammonia in the presence of an iron oxide-titanium oxide catalyst and exit through a stack as nitrogen and water vapor to the atmosphere.

Calcine Quenching/Neutralization
The calcine product from the roaster is cooled rapidly with recycled process water in the quench tanks. The cooled quench tank discharge from both roasters is combined and the resulting slurry feeds two neutralization tanks where milk-of-lime is used to adjust slurry alkalinity to pH 10. Neutralization circuit slurry is dewatered in a thickener with excess water recycled for reuse in the quench tanks. The thickener underflow reports to the roaster CIL circuit.

Roaster CIL
The slurry from neutralization thickener underflow is pumped to a CIL circuit, which has eight agitated tanks. Cyanide is added to the first tank, with the flexibility to add supplementary cyanide further down the train. Slurry flows through the series of tanks, from Tank 1 through Tank 8. Activated carbon is transferred with recessed impeller pumps counter-current to slurry flow from the eighth tank to the first tank. When loaded carbon is transferred out of the first tank, it passes over a screen that separates the carbon from the slurry.

The carbon is then transferred to a loaded carbon holding bin and into a truck that transports it for elution, acid washing and regeneration in a carbon handling circuit located within the Autoclave Facility. The slurry exiting the final CIL tank is sent to a cyanide detoxification reactor before being transferred for impoundment in the TSF.

Goldstrike Autoclave - stripping circuit
Loaded activated carbon is stripped and regenerated at an existing stripping circuit.

The Goldstrike Autoclave refinery produces doré bullion.

Water Supply

Summary:

Carlin Complex
Water is withdrawn from dewatering and production wells onsite where it is then distributed through various infrastructure for use in process plants, water stands and other mine facilities. Excess water not used for mining or process is then routed to infiltration, irrigation, storage structures, and various discharge sites.

Process and Mining Water
Process water at the Carlin Complex is provided through existing well fields. In the North Area these well fields have been used historically to provide all the process water for the mills and heap leach facilities.

At the current dewatering pumping rates, water is diverted to the various processes when needed and any excess dewatering water is discharged to Maggie Creek via a permitted water discharge facility. During irrigation season some of the discharge water is utilized by the NGM-owned Hadley Ranch, Leeville and Goldstrike process water is from UG and Open Pit Dewatering systems. Any water not consumed by mining or process is then discharged to Boulder Valley. North Area potable water is provided by permitted potable water wells and supporting treatment and infrastructure facilities.

Potable Water
Domestic water is provided by four potable wells in the North Area. EW-14 is operating in Goldstrike, Gen 3 is operating in Genisis, HDDW6 and HDDW8 are in Leeville. The Leeville wells are treated by an on-site treatment plant.

Carlin Complex processing plants
Reclaim
Water Solution is reclaimed from process tailings facilities and pumped back to each plant to be used to make up water lost to heat transfer.

Process Water
Process water from plant thickeners is reused through processes. At the roasting facilities, thickener overflow water is cooled in cooling towers and reused in the roaster quenching circuits.

Fresh Water
Fresh water is dewatered from dewatering wells around the Carlin facility and generally discharged to the environment. A small portion of the fresh water is used in the processing facilities where reclaim water is not appropriate due to high scaling potential, including roaster off-gas, lime slaking, and heat exchangers.

Water Treatment
The Goldstrike Autoclave facility operates a water treatment facility to treat reclaim water to replace freshwater use and improve water quality for boilers. In late 2024, NGM obtained approval to discharge this treated water.

Processing facilities Water Consumption:
Goldstrike Roaster - Fresh Water 450-680 m3/hr; Reclaim Water 680-900 m3/hr.
Goldstrike Autoclave - Fresh Water 270-360 m3/hr; Reclaim Water 270-450 m3/hr.

Commodity Production

Operational metrics

Personnel

Job Title	Name	Profile	Ref. Date
General Manager	Gavin Ferguson		Apr 25, 2025
Health & Safety Manager	Chris Torres		Apr 23, 2025
Maintenance Superintendent	Ben Lupercio		Apr 25, 2025
Mineral Resource Manager	Graeme Stroker		Apr 25, 2025
Process Manager	Amanda Steensen		Apr 25, 2025
Processing Superintendent	Craig Gardner		Apr 25, 2025