Secondary leaching of supergene copper was piloted at Quebrada Blanca. Injection wells were used to leach in-situ the residual copper from a 3,200 m? sector of an abandoned heap. The sulfide material had been subjected to crushing, agglomeration, and heap leaching some 18 years previously but still assayed 0.4 % sequential copper. Electro-resistivity tomography surveys were used to map the underlying heap primary liner and to track solution movement within the abandoned heap. Inflows and outflows from the test area were monitored and sampled on a regular basis to determine copper recovery and leaching performance. Drilling campaigns before and after the test allowed reconciliations of material and solution balances. Key operating parameters such as well spacing and injection flow rates were determined. Hydrodynamic and metallurgical monitoring indicated chemical ferric leaching and some bacterial leaching of the residual secondary sulfides. After five months of injecting leaching solution, copper recovery stood at more than 13 %. The results of the field trial were encouraging, allowing for further scale-up in a much larger area.
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