LKAB's Kiruna Mine, located above the Arctic Circle in northern Sweden, is one of the world's largest most modern underground mines. The orebody is a high-grade magnetite iron ore and contains two distinct ore types, a high phosphorous content ore usually located against the hangingwall and a low phosphorous ore. Phosphorous is the major ore contaminant. The cave rock contains large amounts of high phosphorous ore remnants that are mixed with the low phosphorous in-situ rock during extraction. The grades of the cave rock must be accounted for when estimating the run-of-mine grades for each production blast. Since it is not possible to directly sample the cave rock, indirect methods must be used. An algorithm has been developed which uses principles of gravity flow to estimate the cave rock ore grades from the in-situ geologic block model. These estimates are then used in the model for prediction run of mine grades.
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