The Variable Zone Modeling (VZM) concept was introduced to resolve the problem of accurate estimation of mineral concentrations in an epigenetic deposit where concentration of an attribute is a function of local and small-scale geologic variations. VZM not only allows block height variation from one stack to the next, but it also allows block height changes within each stack. This approach provides the ability to fit the blocks exactly to geologic units (zones and subzones). A computer program was designed to automatically generate the subzone definitions through the use of predefined criteria.

VZM was applied to the Athabasca oil sand deposits of Alberta, Canada, which contain many depositional facies. Use of VZM in modeling these sand units produced excellent results in estimating bitumen content where previous models have failed. The application of VZM to these deposits in the vicinity of a surface mine at Fort McMurray, Alberta, is discussed in detail in this paper.

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