Geostatistical Assessment of Ore Reserve Estimation Accuracy in the Hired Gold Deposit

Document Type : Original Article

Authors

1 Department of Mining Engineering, Faculty of Engineering, University of Birjand, Birjand, Iran

2 Department of Mining Engineering, Isfahan University of Technology, Isfahan, Iran

10.22077/jgm.2025.10207.1060

Abstract

Accurate ore reserve estimation is essential for effective mine planning, particularly in deposits with highly skewed grade distributions, such as gold. This study focuses on the Hired gold deposit (Anomaly 3), located south of Birjand, where 1,583 trench and borehole samples were composited into 2,124 data points for geostatistical analysis. Three estimation techniques—Ordinary Kriging (OK), Full Indicator Kriging (FIK), and Sequential Gaussian Simulation (SGS)—were employed to model grade distribution and estimate ore tonnage. Data normalization, variogram modeling, and block modeling were performed to construct three-dimensional representations of the deposit. Model accuracy and reliability were evaluated using grade–tonnage curves and cross-validation analyses. The results indicate that FIK provides more robust estimates than OK and SGS, closely reflecting the actual grade distribution while minimizing the impact of high-grade outliers. At a cut-off grade of 0.1 g/t, the deposit contains an estimated 3.42 Mt of ore with an average grade of 0.75 g/t. Overall, the study demonstrates the effectiveness of FIK for resource estimation in gold deposits characterized by pronounced grade variability and skewed statistical distributions.

Keywords

Journal of Geomine
Volume 3, Issue 3
September 2025
Pages 155-164

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