Definition of Operational Mining Unit (OMU) Size

Abstract

The estimation of recoverable mineral resources and reserve curves is generally based on selective mining units (SMUs) represented by a block model. The size or support of the block estimate is characterized by its volume, shape, and orientation by which it is assigned a grade that directly impacts variance and resulting confidence intervals. However, local geology variations associated with operational mining configuration and production rates are commonly disregarded when defining an SMU. This paper aims to present an operational practice for defining mining recovery curves. A methodology to achieve realistic values through an operational mining unit (OMU) that matches the expected production distribution of volumes and grades is proposed. This process computes expected actual production by considering mining sequencing and production rates, applied to a regular SMU using a common geostatistical resource estimation model. Planned dilution is calculated and implemented for a range of block sizes, and one OMU is selected that is a reasonable match to the actual production. Operational mining unit size (or sizes, if variable) will yield tonnes, grades, and metal of ore at given cutoffs (ore and waste) considering operating selectivity. Different orebody domains, mining configurations, and production rates affecting the OMU are also described. Examples are shown to illustrate the methodology using the Walker Lake public dataset and a real (Cu-Au) operational mining case.