The Las Cruces deposit is located within the Iberian Pyrite Belt and classed as a Volcanogenic Massive Sulphide (VHMS) deposit. VHMS mineralisation results from precipitation of metals associated with circulating hydrothermal fluids in volcanically active sub-marine areas. The metals precipitate as sulphides (pyrite/phyrrohtite with variable base metal sulphides such as chalcopyrite, sphalerite and galena) and are inter-layered to varying degrees with volcanic sediments.

The Las Cruces deposit, as per many other VHMS deposits, is characterised by a dipping massive sulphide horizon underlain by a stockwork vein system which are both hosted within shales and felsic volcanics. However, at Las Cruces, post deposition tectonism uplifted the deposit, exposing it to erosion and weathering with partial oxidation of some of the primary sulphides. This resulted in a copper leached gossan, which retained the relatively immobile gold and silver and overly the secondary sulphide horizons. The zones of primary sulphide mineralisation are the source of the current gossan and secondary sulphide zones and are key horizons for defining continuous volumes of similar geology and metal tenor. The zones of gossan, secondary sulphide, primary sulphide and stockwork are used as key domains for Mineral Resource estimation.

Mineralisation is characterised by a notable iron oxide gossan which occurs directly above a welldeveloped, flat lying secondary sulphide zone followed by a ........

Since early 2009, Cobre Las Cruces (CLC) operations have mined and processed 14.9 million tonnes of secondary sulfide reserves at 5.12% copper grade from its open pit operation. The available secondary sulfide Mineral Reserve is now depleted. In addition, available stockpiles have 5.0 million tonnes of PPS mineralisation with a copper grade of 1.19%, a zinc grade of 2.21% and a lead grade of 1.63%. There are 2.7 million tonnes of gossan mineralisation stockpiles at 2.58 g/t gold grade. CLC has been in operation for twelve years with all six phases of open pit mining now complete.

The CLC secondary sulfide copper reserves were depleted by end of February 2021. Process performance has been successful and designed copper recoveries were improved upon from several plant modifications developed by CLC. During 2019, CLC committed to extending its activity by re-processing tailings from the secondary copper ore operation. Laboratory test work was completed on old tailings with Cu grades above 1%. Metallurgical performance for copper recovery and consumables were good enough to consider this material amenable for leaching processing in the existing facilities. An economic evaluation was followed by copper cathode production from selected old tailings. An estimated 6.3 million tonnes of tailings with 1% copper will be processed by the plant through to 2023 using existing infrastructure.

The updated Mineral Resource estimate provides for an underground mining opp ........

The ore processing facility is designed to operate 365 days per year, 24 hours per day and process 1.5 Mtpa of ore to produce 72,000 tpa of cathode copper. The ore from the open pit mine ranges in grade from 5% to 10% copper and the design grade is 6.02% Cu. The copper in the ore is primarily found in chalcocite with some minor amounts found in chalcopyrite, tennantite-tetrahedrite complex, and enargite.

The metallurgical plant relies on an atmospheric leaching process to recover copper from the rich secondary sulphide chalcocite mineralisation. A unique feature of the plant is the use of eight OKTOP agitated reactor tanks to dissolve the copper under conditions of high temperature and high acidity. Oxygen is also added into the reactors to complete the reaction. The feed to the leaching reactor tanks is mined ore that has passed through three stages of crushing, a single stage of grinding and has then been thickened to eliminate as much process water as possible and three m ........