Three-dimensional geologic block models were used to evaluate the Kutcho Creek volcanogenic massive sulfide deposit in north-central British Columbia. This stratiform deposit dips 45° and contains significant amounts of copper, zinc, silver, and gold mineralization. Over 16,000 m of drill core information and 1000 m of assays for each of the four metals and for specific gravity were used. Geologic contacts from directionally drilled holes were available for each of nine interpreted horizons.

Separate three-dimensional models were built for each metal and for specific gravity. Each model contained approximately 3.1 million cells, with cell dimensions of 10 m by 10 m (horizontal) by 2 m (vertical). Grids were used to define rock-unit boundaries and the correlations within those rock units. These grids controlled three-dimensional interpolation of assay values from the drill holes to the model cells.

Individual metal models were combined into a single copper-equivalent model using current milling and market costs for each metal. Sections through the model were used to quality check the model and to design several open-pit mine configurations. Geologic and mine-recoverable reserves, including average grade, tonnage, and waste/ore ratios, were determined for the entire deposit and on a bench-by-bench basis for the final pit. The calculations were used to fine-tune the final pit design and for mine planning.

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