Comparative Study on Linear and Non-Linear Geostatistical Methods: A Case Study on Kalsaka Hill Gold Deposit, Burkina Faso

Abstract

Selecting an appropriate method to evaluate an ore deposit is imperative in resource estimation since it becomes the basis for reliable planning and development of a mine. Even though linear geostatistical methods such as Ordinary Kriging (OK) give reasonable estimates, there may be instances where recoverable resource estimates are difficult to obtain, particularly when the deposit is characterised by a positively skewed grade distribution with some outliers. Multiple Indicator Kriging (MIK), which is a non-linear estimation technique, is not based on any assumption about the distribution underlying the data and offers realistic solutions to problems associated with skewness and outliers. This paper looks at the use of MIK technique as an alternative method of recoverable resource estimation to OK by comparing the resource estimates obtained from MIK and OK models. OK model showed more smoothing effect on its estimates than the MIK model as evidenced in swath plots. Underestimated grades and tonnages were observed when OK was used to estimate a gold deposit at Kalsaka, according to the grade and tonnage reconciliation. MIK model yields estimates which are higher and closer to the actual than the OK model estimates.

Keywords: Gold, Multiple Indicator Kriging, Ordinary Kriging, Outlier, Variography