Employing non-linear geostatistical estimation methods for grade modeling and ore reserve estimation of Yazd, Aliabad copper deposit based on selecting optimal size of blocks

In the present research, grade modeling and ore reserve estimation of Yazd, Aliabad copper deposit were carried out using two high accurate non-linear geostatistical methods called log- kriging and multiple indicator kriging through Datamine. Variography of the transformed data in the variety of directions revealed that most empirical variograms are fitted with the spherical type of theoretical models, whereas the deposit has geometric anisotropy. To determine optimal block size of the deposit, kriging efficiency and kriging variance criteria were also employed obtaining the optimal block size of 20*20*7.5m. Based on validation of estimation results through cross-validation method for measured assay data against estimated values, determination coefficients were attained about 0.67 and 0.68 for log-kriging and multiple indicator kriging methods, respectively which are favorite results. Ore reserve estimation for various cutoff grades of 0.1, 0.15, 0.2, 0.25 and 0.3% showed that calculated reserve by indicator kriging method for cutoff grades of 0.1, 0.15 and 0.2% are less than log-kriging method about 6, 26 and 21%, respectively. The value for cutoff grade of 0.25% is equal for the both methods while in the case of 0.3% is about 13% higher. In general, the results of the indicator kriging method are more accurate due to the better resolution to separate ore deposit and waste. The results of the present study, can be generalized and used for all metallic ore deposits with geological and exploration conditions almost similar to Yazd, Aliabad copper deposit.