Economic evaluation of mineral deposit: A bottom-up approach

Proper economic evaluation of a mineral deposit is critical to effective investment decision-making in a mineral project. However, this often requires detailed mine production scheduling to produce a schedule that reflects the actual cash flow when the project comes on stream. Because of the dexterity required for this task  many mine planners and explorationist attempt to use statistical formulas that approximate the mine scheduling and value of the project. The mathematical model developed for production scheduling often produces a constant production rate schedule over an approximate life span of the project. In this paper, we have attempted to apply a bottom-up approach that begins with geometrical modelling and equipment deployment pattern to define the number of equipment required for each sequence of operation based on available workfront in the development of each bench. Then, based on the number of equipment and the production rate at each sequence of operations, a production schedule is developed. This production schedule therefore will reflect annual cash flow since it is based on the sequence of operation. Application of this method on the west pit of Itakpe mine shows a considerable net present value and internal rate of return of the deposit compared with the evaluation made using statistical models. The NPV of the west pit was found to be USD621 million as against USD122.41 million using Nwosu’s formula and USD123.85 million Taylor’s formula. The above value of NPV using the proposed method shows the maximum expected NPV of the mineral project-based technical restrictions. An understanding of this value can guide the mineral property owner in decision-making.