Abstract
Underground working at the Fazenda Brasileiro gold mine started in 1988. Initially, surface declines served both access and production needs, but as the mine deepened the development of a central ore-hoisting shaft became necessary. The effects of increased mining costs in recent years have been made worse by falls in the gold price. Steps that have been taken in response to improve the long-term economic future of the mine include the development of a declining cutoff-grade strategy. The main objective of this strategy, for implementation over the life of the mine, is to increase its net present value. Incorporation of an opportunity cost element in cutoff-grade calculations has led to higher cutoff grades than were previously adopted. The application of a declining cutoff-grade methodology also assists in short-term decision-making with respect to major variations in the gold price. Additonally, operational cutoff grades have been calculated, for both mine-limited and mill-limited situations, to aid the evaluation of different situations. Finally, the overall long-term planning model developed for the cutoff-grade study provides a means to analyse the sensitivity of other mining parameters.
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