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Metal deportment and ore variability of the Bolcana porphyry Au–Cu system (Apuseni Mts, Romania) – Implications for ore processingBlannin, R.; Tusa, L.; Birtel, S.; Gutzmer, J.ORC; Gilbricht, S.; Ivascanu, P.
The maiden resource estimate for the Bolcana gold-copper porphyry defines 381 Mt at 0.53 g/t gold and 0.18% copper. The early stage of exploration provides the perfect opportunity for the application of geometallurgical studies, to enable optimisation of future mine and plant operations. Quantitative mineralogy and microfabric characterisation of crushed material and thin sections from seven 40 m drill core intervals were accomplished by Scanning Electron Microscopy based Mineral Liberation Analysis, complemented by X-ray Powder Diffraction. The mineralogy of the studied samples is highly variable, depending on lithology, mineralisation and alteration. The main Cu-bearing mineral is chalcopyrite, predominantly occurring in B and C veins. At shallow depths, secondary bornite and covellite form rims around chalcopyrite. Primary bornite occurs at greater depths in the system. Native gold grains are typically <10 μm and hosted by chalcopyrite or, to a lesser extent, pyrite. Electron Probe Microanalysis on four samples determined that gold concentrations in solid solution in selected sulphide minerals are <100 ppm. Copper and associated gold should be recoverable by flotation of chalcopyrite. The recovery of free gold and gold associated with pyrite may require additional processing steps.
15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 27.08.2019, Glasgow, United Kingdom