The Carrapateena Project is located within the highly prospective Olympic Dam copper-gold (Cu-Au) Province. This is a metallogenic belt along the eastern margin of the Gawler Craton in South Australia, which hosts the Prominent Hill Mine, Olympic Dam mine and the Moonta-Wallaroo historic mining district. The Craton comprises variably deformed and metamorphosed sedimentary, volcanic and plutonic rock, spread from the late Archean to Mesoproterozoic, and it has been subdivided into a series of domains – the Carrapateena deposit being part of the Olympic Domain. The age of the iron oxide copper gold (IOCG) mineralisation in the Gawler Craton is uncertain, though it is interpreted in the literature to be associated with Mesoproterozoic magmatism of the Hiltaba Suite and the Gawler Range Volcanics.

The Carrapateena copper-gold mineral deposit is hosted in a brecciated granite complex, with both bornite and chalcopyrite copper mineralisation present – the bornite being a distinct higher grade zone of mineralisation.

The vast majority of copper and gold mineralisation within the deposit is hosted by hematite-dominated breccias with moderate mineralisation occurring within hematite altered granite breccias (Eastern Cu domain). Sulphides are the primary copper-bearing minerals in the Carrapateena Breccia Complex. Copper and gold mineralisation is structurally and chemically controlled, with subsequent alteration destroying mineralising structures. The most abundant sulphides are chalcopyrite, pyrite and bornite, and these constitute the majority of sulphides at Carrapateena. The less common sulphides are chalcocite, digenite and covellite, and in smaller amounts sphalerite and galena.

Gold mineralisation at the Carrapateena orebody is almost exclusively hosted by hematite altered breccias. Gold grains are usually very small (10 µm), and when seen in polished section, are often intimately associated with copper sulphides. Gold grains are commonly a combination of gold and minor silver (electrum).

Mining Methods
The current mining method of SLC is based on the 2017 Carrapateena Feasibility Study and further refinements since accessing the orebody. The mine is currently in production from its two uppermost level, and production from the orebody to date reflects expectations in terms of mining and milling recovery. If the decision to transition to a block cave mining method is made, the lowest three levels of the SLC will be mined at a declining shut-off value (to as low as $70/tonne on the bottom level 4230 RL), in order to improve overall mine economics. If the mine continues to be mined as an SLC to the bottom of the orebody, the shut-off value strategy will be different. The average grade of the top 10 SLC levels is 1.5% copper and 0.73 g/t gold.

The SLC Ore Reserve is made up of tunnel development which makes up approximately 10% of the SLC Ore Reserve Estimate component, and the remainder comprised of blasted production rings from the SLC. Flow modelling for the SLC production is done using Power Geotechnical Cellular Automata (PGCA) Code, operated by OZ Minerals personnel. The fragmentation of the Lower Whyalla and Woomera Shales units has been determined to be finer than the other rock masses, due to their lower rock strength. It is generally accepted that fine material travels more quickly to the draw point than coarse material, therefore to simulate this preferential propagation, the Lower Whyalla and Woomera shales are given a propagation rate of double that of the ore and the other rock masses. Calibration of this mobility through site observation and flow model calibration will be key to the management of this risk.

Transition to Block Cave
Block caving is a mining method that involves the establishment of a stable extraction level using ground support such as rock bolts and cable bolts. An undercut level is mined above the extraction level, and the undercut material is removed through drill and blast. Once the undercut is complete, the extraction level can be mined, and broken ore is removed from draw points on the extraction level. As the ore is removed from the draw points, the rock mass above breaks under stress and moves downwards via gravity, allowing more ore to be removed from draw points on the extraction level. The block cave design at Carrapateena incorporates two blocks called macro blocks – Block Cave 1 and Block Cave 2 (BC1 and BC2). The timing of mining these macro blocks are scheduled to maximise the grade in the early years of the Carrapateena block cave, allowing improved financial returns. BC1 incorporates eight extraction drives and 196 draw points (see Figure 5) and can sustain a production rate of 12 Mtpa. BC2 comprises the five eastern extraction drives, and 149 draw points, and can sustain a production rate of 8 Mtpa.

The design characteristics of BC1 and BC2 are:
• Primary access is through a decline access from the portal shared with the SLC
• Ore is crushed underground and transported to surface using conveyor haulage
• Cave establishment utilising an advanced undercut sequence
• Straight-through draw point layout (“El Teniente” layout)
• Preconditioning level located 400 m above the extraction level that will be used for preconditioning the rock mass and cave monitoring
• Average heights of draw of 580 m for BC1 and 280 m for BC2
• Maximum capped heights of draw of 600 m for BC1 and 400 m for BC2

The minerals processing plant is designed to treat of crushed ore to produce a copper-gold flotation concentrate. Ore is primary crushed underground to a product size P80 of 106 mm. The Project FS base case assumes a start-up 4 Mtpa throughput rate increasing to 4.25 Mtpa after ramp-up.

The current FS base case now includes a third permanent crusher located five levels below the top of the orebody. This additional permanent crusher removes the PFS requirement for a mobile surface crushing unit for ore mined before the commissioning of the then second permanent crusher. Configuration of the new first permanent crushing station allows crushing/conveying of all material types, which reduces haulage costs and haulage constraints for the mine prior to commissioning of the second crusher.

The minerals processing plant will include the following processing stages:
• Grinding in an SABC (SAG mill, ball mill and pebble crusher) in closed circuit with cyclones producing a grind size P80 of 75 µm

Ore Processing
The current processing plant at Carrapateena is designed to produce at a rate of 4.25 Mtpa. Debottlenecking studies have been identified to increase the plant capacity to a throughput rate of 5 Mtpa. The current copper concentrator is a standard semi-autogenous, ball mill and flotation circuit. While the block cave is being established, a second process plant will be built using vertical roller mills for comminution and copper flotation, producing a concentrate that will then be transported to port and subsequently to smelters by ships.

Metallurgical test work has been completed during the previous studies for Carrapateena. The test work has resulted in adequate metallurgical characterisation of five flotation domains. Copper and gold recoveries for the life of mine average 90% for copper and 66% for gold for the entirety of this reserve statement. Higher recovery is expected for the SLC due to higher grades. The study has identified that dry ........