Three Development Options for Exeter’s Caspiche Au-Cu Deposit


Acquisition of adequate water resources will be a crucial factor in development of Exeter’s Caspiche gold-copper
deposit in northern Chile. A recent PEA presents both surface-only and surface-underground mining options.
Exeter Resource Corp. has reported the results of a new preliminary economic assessment (PEA) of its Caspiche goldcopper deposit in northern Chile. The PEA reviews a low-capex, stand-alone, open-pit heap-leach oxide gold operation, as well as two other staged mine plans that include expanded open-pit mining and underground mining of the central, higher-grade gold-copper zone at Caspiche. The options are, in descending order of choice:

• A stand-alone, heap-leach oxide option that would process 30,000 metric tons per day (mt/d) to produce 122,000 gold equivalent oz/y over a mine life of about 10 years, including 148,000 oz/y during the first five years of operation. Initial capex would be $251 million, including $41 million for contingencies. All-in sustaining cash costs would be $676/gold equivalent oz.

• An accelerated 60,000-mt/d, open-pit heap-leach operation producing approximately 240,000 oz/y over a six-year mine life. Gold-copper sulphide mineralization would be mined from an extension of the oxide open pit, with concentrator operations beginning in year six. Sulphide mineral would be mined from the open pit for an additional 12 years at a rate of 27,000 mt/d. Mineralized gold-coppersilver material would be treated in a conventional copper flotation concentrator, with a cyanide leach-SART-carbon column plant to recover additional gold and copper from one of the flotation circuit tailings streams.

• An accelerated 60,000-mt/d, open-pit heap-leach operation producing approximately 250,000 oz/y over a five-year mine life. Large sub-level open-stope underground mining would start in year three, targeting the Caspiche gold-copper sulphide higher-grade core.

Initially a single ramp would be advanced into the top of the higher-grade core. By year seven, underground mining operations would ramp up to full capacity of 27,000 mt/d with the development of a second ramp. Sulphide processing would be as in option 2.

The Exeter announcement noted that, “Critical for any mine development in the Caspiche region is securing adequate water resources. Exeter continues a program to establish an independently owned water supply to minimize the cost of water procurement to the project. Exeter is optimistic that its current water program could provide quantities of water to meet all of the mining options outlined in the PEA.”

Conclusion of final feasibility and environmental impact studies for the top option is contingent on establishing secured water resources.

As featured in Womp 2014 Vol 06 - www.womp-int.com