| Summary: | With extraction of low-grade and high throughput deposits, elimination of tonnes of uneconomic material is highly desired to reduce energy consumption and water usage in the mine/mill production cycle. Even though technologies such as sensor-based sorting has wide application for pre-concentration purposes, effectiveness of sorter systems and key parameters for sortability of a material are still in the developmental stage. Number of factors such as grade variability, mineralogical alteration and ore blending scenarios during material handling will significantly affect contents of a material resulting in unforeseen changes in downstream processes. For these reasons, the ‘ore heterogeneity’ parameter is studied to evaluate sortability of an ore material under varying mine production scenarios.
Production data, drillhole data and representative drawpoint samples were provided from the New Afton copper-gold mine located near Kamloops, BC. The New Afton mine utilizes the block caving method for extraction of ore from the copper-gold alkali-porphyry deposit.
The distribution heterogeneity (DH) parameter is estimated for the data sets and the quantity of potentially removable material ahead of delivery to mill is studied. The DH is defined by variation of grade of a group of samples that constitute a lot, i.e. a group being an equal tonnage of material drawn from a drawpoint and the lot being the drawpoint. With this approach, the DH is analyzed across drawpoints, vertically within a drawpoint and along drill holes with changing vertical intervals of 0.5m – 10m. The DH values are compared with copper grades and an inverse relationship is found. This finding indicated that sortability of ore material can be defined by a heterogeneity parameter, especially the information can be obtained earlier from drillcore samples. The drillcore information can indicate a measure of heterogeneity and related copper grade of an in-situ material in advance of assay samples or sensor detection where a certain degree of mixing has occurred.
Overall, 27% of the sample data from the New Afton historical production record has grades less than 0.4% Cu, which is the current cut-off grade, and it correlates with relatively high heterogeneity and presents an opportunity for sorting and feed grade upgrade. === Applied Science, Faculty of === Mining Engineering, Keevil Institute of === Graduate
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