Multigaussian and plurigaussian simulation to quantify uncertainty in estimating ore grades and rock types in copper deposits [Simulación multigaussiana y plurigaussiana para cuantificar incertidumbre en la estimación de leyes de mineral y tipos de rocas en yacimientos cupríferos]

Abstract

The main objective of this researching was to quantify the uncertainty of a copper deposit using multigaussian simulation of grades of rock types. The developed algorithms for simulation of categorical variables, usgsim for continuous variables and algorithms programmed in Python 3.0. The dimensions of a block are 20x20x15m indexed 81x109x58 in xyz; making a total of 512 082 blocks. The results of the categorical simulations show that there is a probability (p.v. ≥ 0.8) of 19 987, 227 387 and 49 036 blocks for rock type 1, 2 and 3, respectively. Consequently, the quantified uncertainty for this threshold (0.8) is 20 %; representing 58 % of the blocks. On the other hand, the quantification of the uncertainty of continuous variables (associated with grades of Cu and Mo), not less than 90, 80 and 70 %, based on cut-off thresholds of variance per block, resulted in lithology One 353, 1900 and 7553 blocks with Cu grades, which represents 0.07, 0.37 and 1.49 % of the total blocks, respectively; a total of 24, 139 and 582 blocks with grades of Mo, representing 0.006, 0.027 and 0.114 % of the total blocks; for lithology Two there were 106, 648 and 2739 blocks with Cu grades, which represents 0.021, 0.127 and 0.535 % of the total blocks; a total of 32, 129 and 357 blocks with grades of Mo, which represents 0.006, 0.025 and 0.070 % of the total blocks; finally for lithology 3 there were 478, 2324 and 8804 blocks with Cu grades, which represents 0.093, 0.454 and 1.719 % of the total blocks; a total of 93, 355 and 982 blocks with grades of Mo, which represents 0.018, 0.069 and 0.192 % of the total blocks. 

Finally, it is concluded that it was possible to quantify the uncertainty in the estimation of mineral grades and rock types in a copper deposit.