Compositional Block Cokriging

Estimates of a whole block composition may be useful for improving the assessment and mining of resources, especially if the economic viability depends on more than just one metal or component. Banded Iron Formation (BIF) represents such a case, where optimal exploitation requires evaluation of Fe content, as well as waste and penalty elements. Block cokriging of the whole composition may yield these estimates. To avoid the spurious correlation problem, this should be based on log-ratios of the composition. But due to the non-linearity of the log-ratio transformations, this does not yield a direct change-of-support model. This contribution explores the approximation of this block average compositional cokriging by means of geostatistical simulation within the block. This methodology is illustrated with a BIF deposit of Western Australia.