Mining operations are predominantly focused on the Callie and Auron ore bodies in the underground mine at Dead Bullock Soak (“DBS”). Tanami consists of sediment hosted sheeted quartz vein mineralization.

The Project lies in the eastern part of the Early Proterozoic Granites-Tanami Inlier. The basement geology of the Project is predominantly comprised of the sedimentary rocks of the Tanami Group. The remaining basement is predominantly composed of granitic intrusions. The Tanami Group consists of two Formations; the Dead Bullock Formation and the overlying Killi Killi Formation.

The Killi Killi Formation is the most widespread unit across the Project tenements. It is dominated by a thick interval of turbidites, with a felsic volcanic component and a distinctive unit of jasper chert.

The Dead Bullock Formation has been informally divided by the geologists of the Project into two Members; the Callie Member and underlying Ferdies Member. These units host all the known gold mineralisation on the project tenements.

At DBS there are two sub-units (Members) within the Dead Bullock Formation; the Callie Member (which includes SHIM, Orac and the Callie Laminated Beds) and the Ferdies Member (which includes the Lower Auron Beds). Post-mineralization faulting has repeated parts of the stratigraphy and mineralization.

The Callie mineralization is developed in the DBS anticlinorium which is an upright isoclinal fold with local complex parasitic folding. Mineralization is present in the Lantin and Callie Anticlines, the Challenger Syncline and their respective limbs. The Auron deposit sits stratigraphically below the Callie deposit. The Federation deposit represents an un-mined mineralization envelope hosted predominantly within the hinge and southern limb of the Federation Anticline which is parallel to the Callie and Lantin Anticlines.

The Callie deposit has a complex shape, which is a function of the difference in strike of the quartz vein corridors (070°) and the plunge of the folded sequence (100°). The gold mineralization occurs in steeply dipping sheeted veins within the folded sequence. The orientation of the veins is 65° towards 154°, hence they are locally referred to as “70/70” veins. Vein density in the ore zone averages five veins per meter; however, it can reach more than 12 veins per meter in “corridors” that range in thickness from 20 to 50 meters (m). The width of mineralization varies significantly due to the interaction of the fold, fault and quartz vein corridor geometries, at its thickest point it is ~200 m wide in the hinge of the Callie Anticline. Mineralization has a down-plunge extent of at least 2,800 m from the surface to the easternmost deepest drill intercept. The mineralization currently remains open at depth. Gold is characteristically nuggety and occurs exclusively within the veins as grains from submillimeter sizes through to >20 millimeters (mm).

Auron shares the same structural, metamorphism, alteration and vein generations as Callie, and the mineralized quartz vein corridors that control the Callie mineralization are continuous through Auron. The majority of the economic Auron mineralization is represented by the Callie-style 70/70 sheeted vein mineralization. Auron shows a similarly complex shape as the Callie deposit due to the intersection of the folded sequence and the vein corridors. This is further complicated by fault repetitions. The Auron mineralization has been demonstrated to have a plunge extent of at least 2,500 m and remains open to the east. Like Callie, the width of the Auron mineralization varies significantly due to the interaction of the fold, fault and quartz vein corridor geometries, at its thickest point it is ~150 m wide. It gradually thins out up-plunge and is attenuated on the fold limbs.

Gold at Federation is hosted by a similar sheeted 70/70 vein set. The Federation mineralization has been demonstrated to have a plunge extent of at least 1,000 m. Mineralization has reduced widths relative to intersections within Callie and Auron.

Exploration drilling conducted during 2015 confirmed a new discovery in the Federation Anticline. The new orebody, referred to as Liberator, was similar to Federation in its structure and geometry but hosted in a rock mass similar to that of the Auron orebody.

Three types of gold mineralization have been recognized within the Project area:
• Callie-style mineralization is characterized by coarse and readily visible gold occurring in quartz veins hosted in carbonaceous siltstone. These contain very minor sulfides and are generally discordant to bedding. Mineralization is in subparallel, sheeted quartz veins within a structural corridor. Example deposits and prospects include Callie, Auron and Federation;

• Villa-style mineralization is associated with Au-sulfide (arsenopyrite, pyrite and pyrrhotite) ± quartz ± carbonate veins in BIF and chert. The veins follow a stratigraphic horizon of iron-rich, cherty metasedimentary rocks within the Dead Bullock Formation. While generally associated with veining, a vein is not necessary for gold deposition and gold may be disseminated throughout the host. Example deposits and prospects include Triumph, Colliwobble, Sleepy Hollow, Dead Bullock Ridge, and Villa–Fumerole;

• East Bullakatchie mineralization that developed in Au–carbonate–sulfide ± quartz veins. These are unique to the East Bullakitchie deposit and occur as concordant and discordant veins within metamorphosed sedimentary rock, which probably had a carbonate precursor.

Currently the Project comprises no active open pit operations. All mining production is from the Callie underground mine.

The levels are named based on the surface Reduced Level of 1,400 m, so 400mRL is located 1,000 m below surface.

Access to the mine is via the Callie Decline located in the footwall of the Callie mine area. At the end of December 2018, the decline had reached the elevation of M20mRL, where “M” represents levels located below 0 mRL (“Minus”). Nominal level spacing is 40 m, with additional sub-levels in the upper part of the mine. For many years, mine production has focused on the Callie mine area and peripheral extensions. The Auron orebody was identified relatively recently, with production activities commencing in 2013. Development of an independent decline system for Auron commenced in 2013 and production activities started late in the same year.

The mining method used at the Tanami is long-hole open stoping with paste or rock backfill, using a 92.5% mine recovery factor and a stope dilution factor that varies according to geotechnical recommendations (7% to 20%).

Mine development is drilled using twin boom electric hydraulic jumbos. The jumbos are also used to install ground support.

The mine is accessed using a 5.5 m wide x 5.8 m high fully arched 1:8 to 1:7 decline. The decline spirals down following the plunge of the ore body on the footwall side. Levels are generally accessed every 40 m with the occasional intermediate sub-level in the upper levels. Level development typically consists of an access drive 5.0 m wide x 5.5 m high running along the footwall of the ore body

Drill drives 5.0 m wide x 5.6 m high are developed off the access drive into the ore body. Stopes typically have one drill drive per level and two draw points drives (5.5 m wide x 5 m high) on their extraction level.

Haulage efficiency is a key factor in the design basis and overall mining strategy and truck haulage was previously identified as one of the main mining constraints at the Project. The Auron Decline link from 1200RL to 425RL was completed in 2016 to create a one-way traffic haulage loop to support mining down to -260RL, which decongested the access network for the mine.

The stopes targeted for mining in the early years are from material in the upper levels of the mine, above 0RL because areas are diamond-drilled to a higher drill density and confidence level. Balancing and sequencing tonne-kilometers (tkms) between upper levels and lower levels is an important strategy so that the mine continues to be economic and well exploited. This strategy is mainly based on the availability of work areas for the stoping sequence.

To achieve higher recoveries, primary stopes need to be filled using engineered fill. This allows extraction of adjacent ore in secondary stopes. Secondary and tertiary stopes are filled with rock fill.

Large services contracts include:
Explosives storage, mixing and transport – Orica;
Underground drilling – Swick Mining Services.

Crushing and Ore Handling
Underground ore is transported 44 km by trucks to The Granites processing plant site and stockpiled on a ROM pad adjacent to the crushing plant. The ROM ore is crushed in a 3-stage crushing circuit to an approximately P80 of 12 mm. The equipment utilised to crush the ore is as follows:
• Primary Jaw Crusher (Vicker Reiwoldt 42” x 30” double toggle);
• Secondary Cone Crusher (Symonds 7’ SXHD);
• Tertiary Cone Crusher (Symonds 7’ SXHD).

The primary jaw crusher is fed ROM ore that is smaller than 800 mm.

The secondary crusher is fed with the product from the primary jaw crusher and continues to reduce the ore size. Ore from the secondary crusher then passes to the tertiary crushers.

The undersize is the final product from the crushing circuit and is conveyed into a large ore holding bin (with a 3,500 t capacity) for storage. The oversize is conveyed back to the tertiary crusher for further size reduction.

Grinding
Crushed ore is recovered from the ore bin via two apron feeders and then ground in a Primary overflow ball mill (4,700 kW installed power) operated in closed circuit with a hydrocyclone distributor consisting of ten 400CVXFB Weir Warman Cavex Flat Bottom cyclones. Quicklime is added to the mill feed conveyor via a screw feeder located beneath a lime silo. Trommel oversize is discharged into a scats bay and periodically recycled back to the ball mill via an emergency feeder located adjacent to the ore bin.

The primary ball mill circuit cyclone overflow is fed to a secondary grate discharge ball mill (2700 kW installed power). This mill is in closed circuit with ten 400CVX10 Weir Warman cyclones. The targeted liberation grind size from the grinding circuit is within a P80 range of 50 µm to 80 µm, when both the primary and secondary ball mills are operating. The cyclone overflow is sampled via an automated, cross-stream sampler and reports to a pre-leach thickener ahead of the leach/CIP circuit.

The Granites processing plant comprises a three-stage crushing circuit followed by two stage series ball milling to grind the ore to a cyclone overflow P80 of typically 60 to 100 µm ahead of gravity concentration, cyanide leaching, and gold recovery. All gold recovered is processed on site to produce gold doré bars.

Within the grinding circuit, gravity concentration is used to recover liberated gold, utilizing rougher and cleaner spirals and Wilfley tables as well as a Knelson centrifugal concentrator to produce a gold concentrate. The gravity recoverable gold concentrate is cyanide leached using an intensive leach reactor (Acacia reactor), producing an eluate solution suitable for electrowinning.

Gold which is present in the ore but not gravity recoverable (e.g. present in cyclone overflow) is further processed in a conventional CIP circuit. Lime is added to the ore to increase the pH to greater than 10, sodium cyanide solution and oxygen are added to leach the g ........