The Carlota mine is located in the western part of the United States in the Miami-Globe mining region, in the state of Arizona at an average elevation of 4,200 feet (1,300 metres) above sea level. The surrounding nature is characterized by its mountainous terrain and desert highlife.
Historic activity first occurred in the area in the early 1900’s. More recently the known deposit was developed in the mid-1990s. Several years after were spent collecting baseline environmental, social, and geological data to understand the feasibility of the project and study potential impacts. This information was used to develop robust mitigation plans and systems to avoid or minimize impacts and to obtain modern environmental permits to operate. KGHM International Ltd. acquired the project from Cambior Inc. in 2005 and mining commenced three years later in 2008 and the first copper harvested in Q4 2008. The mine operated for most it’s life at approximately 40,000 tonnes per day producing on average 11.2 thousand tonnes of copper cathodes per year. In 2013, the Carlota mine began concurrent reclamation and revegetation activities throughout the property and initiated detailed studies on the more complex facilities in preparation for mine closure. During 2013 sub-surface leach test work was undertaken to explore ways to extract additional economic copper from the heap leach pad. In 2014 mining operations from the open pit ceased. However, residual copper production continues at present utilizing surface and sub-surface leaching via injection wells. Development of injection wells continues to extract economic copper from the solution inventory within heap leach pad.
Mining of the copper ore from the Carlota site was by conventional open pit methods. This begins by blasting rock using explosives in an engineered and controlled setting. The resulting material that is of economic value (ore) is loaded into large haulage trucks and subsequently transported to the heap leach pad for conveyor stacking in fifteen foot (5 meter) lifts. At the Carlota mine, the ore was stacked on a heap leach pad comprised of a double lined surface, and a prepared and compacted sub-soil layer. This configuration prevents interaction between the solutions and mineralized rock with the sub-soils.
Carlota production was based on the solvent-extraction / electro-winning (SX/EW) method. This method involves exposing the ore to dilute sulfuric acid causing the copper to dissolve into solution. This copper bearing solution undergoes solvent extraction to extract the copper from the aqueous solution and concentrate into a high copper grade electrolyte solution prior to electro-winning. The copper is then plated onto stainless steel cathodes that produces 99.99% copper. Copper is stripped from the cathodes and prepared for shipment to manufacturers of copper rod, tube, and wire products.
Currently, the Carlota Mine runs the process of post-mine area recultivation along with underground leaching of the remaining heaps. This model of operation assumes stable production of copper since 2020, to the moment of final closure of the Carlota Mine.