Modelling of mineralisation zones formed by oxidation and enrichment processes in porphyry copper deposits using multiple-point geostatistics: the case of Ali-Abad deposit, Iran

Oxidation and enrichment processes as a secondary phenomenon lead to forming a vertical arrangement of leached, enriched, and hypogene mineralisation zones in porphyry copper deposits. Generating a suitable geological model of these zones can enable a more accurate resource estimation. This research introduces a multiple-point geostatistics simulation (MPS) based workflow to simulate the geological model of such ineralisation zones. The main goal of this workflow is to generate realisations in which: i) the proportions of zones, ii) the vertical arrangement of zones, iii) spatial geometry of the zones, iv) non-stationarity in local proportions are reproduced accurately. Among various MPS algorithms, single normal equation simulation (SNESIM) is used in this study. The proposed workflow includes three main steps: i) constructing an appropriate training image, ii) selecting the best values for SNESIM input parameters, iii) calculating the soft probabilities in order to control the non-stationarity of local proportions. Finally, this workflow was applied to the Ali-Abad porphyry deposit case, and one hundred realisations were generated. The validations have illustrated the acceptance of the realisations in terms of the zones' proportions, the indicator variograms, and vertical mineralogical order of zones, and the local proportion of zones.