Compositing and regularisation of drillhole of data for geostatistical resource estimation
DOI:
https://doi.org/10.17159/Abstract
Compositing or regularisation of drillhole data is common practice as part of modern resource estimation and is deemed a necessary step in producing unbiased estimates of mineral resources and reserves. Commonly, data is collected over irregular distances due to the varying relative thicknesses of lithologies drilled or sampling/assaying strategies. This necessitates data transformation to regular lengths of equal size to ensure that all data has the same statistical support.
However, there has been little recent detailed study of the effect that this process has on the data that is subsequently taken forward for the estimation process. In this paper the currently available methods of compositing will be reviewed and the possible effects of inappropriate compositing presented. It is shown through a case study that compositing of data to different lengths can result in significant changes to the average and variance of datasets which can lead to differences in the final estimated value. These differences are exacerbated by breaks or gaps in data where for a variety of reasons there has been no data collection or data has been lost. The importance of treating blank and zero data appropriately is also presented. Globally, these differences may be minimal, but locally substantial, affecting the efficiency of estimation and thus mine planning, reconciliation and other operations. Further detailed investigation of compositing is required if the full implications of compositing is to be understood and the bias that can be induced effectively defined.
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