A comparison of ordinary and simple kriging on a PGE resource in the Eastern limb of the Bushveld complex
Date
2015-05-19
Authors
Mpanza, Mbalenhle
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Abstract
The selection of an appropriate estimation method is one of the fundamental decisions in resource estimation. The effects of selecting an inappropriate estimation method can lead to ± 50% error in the estimate (Dominy et al., 2002). In selective mining, for example it is the mining block estimates that determine which of the ore blocks are to be mined and processed and which of the ore blocks are waste. The choice of the estimation method amongst others is based on the geology and complexity of grade distribution within the deposit. For example polygonal estimation methods are suitable for producing a volume weighted global mean grade, and in this estimation method there is one fixed and biased answer. The inverse distance method is unbiased but does not minimise the estimation variance, while kriging is subject to certain conditions, such as providing the best estimate possible by a linear combination of the available weighted data as well as minimising the error variance of the estimate.
This dissertation presents a detailed study of the application of two linear geostatistical estimation techniques; Ordinary and Simple Kriging. Included in this study is a detailed discussion on variography and its necessity in resource estimation. The theory of kriging as well as the kriging equations is discussed in great detail. The differences between Ordinary and Simple Kriging estimation techniques are drawn from this study by the consideration of the kriging variance, kriging efficiency, kriged estimate, kriging neighbourhood as well as the block variance.
The suitability of the application of both Ordinary and Simple Kriging estimation techniques is highlighted by this study. The two techniques are applied on a PGE (4E) deposit from an undisclosed locality due to confidentiality. This dissertation highlights the differences that are not discussed in most literature between Ordinary and Simple Kriging and the way that these techniques influence the outcomes of mineral resource estimation.