Controlling operational dilution in open-pit mining

Abstract

Dilution and ore loss are important factors that can affect costs and profitability of a mining operation by lowering the quantity of mineral or metal that can be produced from each ton of processed ore. When discussing open-pit mining, dilution and ore loss are sometimes assumed as fixed factors in geostatistical block models and cut-off grade calculations, without considering specific particularities of the deposit and operation. This paper proposes to quantify the dilution caused by operational inefficiency through identifying the ore blocks that are a part of the short-term plans and mapping their neighbourhood, considering the nature of the contacts and the differences in grades. This technique enables the operational dilution to be calculated. It is applicable for operations using mechanical excavation and/or blasting. The results demonstrate that operational dilution can be measured and controlled to improve the tonnage and grade reconciliation between planning and production.

Accounting for operational dilution by incorporating geological uncertainties in short-term mine planning

“…The methodology developed by [16,20] consisted of an automated routine for calculating operational dilution through the analysis of short-term mine plans (subsets of blocks to be extracted), analysing blocks' grades, contacts and neighbourhoods to verify if there were differences between the planned grades and the measured data. This work proposes improving the mentioned methodology by incorporating the information of grade uncertainty to calculate the operational dilution.…”

“…1) incorporated in the ore block. The ore loss is not considered at this stage because the methodology assumes that it is better to recover more ore tonnage, even with the consequence of generating higher dilution, than having ore losses [16]. Crawford [21] also showed that reducing dilution through more selective mining often resulted in higher ore losses.…”

“…2) will be added to the total block mass and the mass of the triangular prism designated ore loss (eq. 3) will be subtracted from it [16].…”

“…According to Câmara et al [16], in open-pit mining, dilution is generally accounted for only as a misclassification of blocks in the block model estimates. Rossi [17] showed the importance of incorporating an appropriate amount of dilution in the "undiluted" resource model such that a recoverable reserves model would eventually be obtained.…”

“…This paper will show how the use of information of geological uncertainties can contribute to control the operational dilution in open-pit mining, besides enabling the development of mine plans seeking to minimize dilution. To this end, the proposed methodology will present an evolution of the routine presented in [16].…”