Optimizing ore sampling procedure of drill holes at Miduk porphyry copper deposit and its effects on processing plant recovery

One of the major concerns, when dealing with consignments received from mining sites, is the reliability of data obtained from samples of the ore, which is crucial in operational conditions in processing plant. Sampling in open pits is particularly significant due to the fact that extraction design and grade fluctuations are based on the results obtained from blast holes samples. Thus, optimization of sampling procedure is essential to improve processing plant efficiency. In this work, sampling variance components including composition, distribution, preparation and analysis along with estimation variance of different mining blocks were determined to be utilized in sampling optimization using classical statistical methods. Using a statistical multifactor analysis the total copper grade, the ratio of iron oxide to copper oxide and the ratio of chalcocite to chalcopyrite mineral contents in the ore, were found to be the main factors affecting recovery in processing plant. To reduce sampling error of blast holes on the basis of geostatistical and statistical methods, the centre of ore blocks was determined to be the best location for the blast holes, with the optimum increment weight and the number of increments for each blast hole being 8.2 kg and 4, respectively. Eventually, statistical analysis of the factors affecting processing recovery resulted in the ranges (Fe ≤4%, 10% < CuO ≤ 12, 0.95 < Cu ≤1.00) at confidence level 95%. The coefficients of effectiveness of these factors were determined in equation: Recovery = 90.195 + 0.215A – 2.350B – 2.110C where A, B and C corresponds to 7 levels of Cu grade, 3 levels of copper oxide percent and 3 levels of Fe percent, respectively