A Generic Approach to Preliminary Economic Evaluation of Placer Gold Deposits In Ethiopia,

Abstract

Economic analysis for multiple hypothetical placer gold mine models was conducted and its result is plotted on four graphs, each represents deposits with specific stripping ratio. The analysis was conducted to prove economic feasibility on the hypothetical models and to provide graphs which will help estimate a mine project’s NPV. Existence of placer gold deposits and occurrences were investigated from the literatures and technical reports by the Geological Survey of Ethiopia. It is noted that placer deposits occur in four geographical regions in Ethiopia. These are in Adola area of Southern Ethiopia, in Benishangul and Wollega of Western Ethiopia, in the Akobo gold field of Southwestern Ethiopia, and also in the Mekele quadrangle of Northern Ethiopia. Hypothetical 64 mine models were prepared by simultaneously varying deposit stripping ratio, reserve size and production rate. The reserve sizes selected were Small 160,000 m3, Medium 400,000 m3, Large 800,000 m3 and Huge 1,600,000 m3. Four deposit types were modeled based on stripping ratio. These are Mine type-A with 1:1 Stripping ratio, Mine type B with 2:1, Mine type C with 4:1 SR, and Mine type D with 8:1 SR. And four production rates were used for analysis, these are 76, 190, 380 and 765 m3/day. The 64 models were reduced to 16 models by conducting economic analysis using cash flow tables and lump-sum costs of the models. Consequently, a production rate with maximum NPV for each stripping ratio/reserve size models was selected. Then detailed deposit and mine parameters were prepared and cost estimation was carried out for the 16 models based on their parameters. Again, using cash flow tables the grade requirements for the 16 mine models that would result in specific NPV values (10, 50, 100, and 200 million) were calculated. Reserve sizes and the grade requirements were represented by graph axes and NPV lines were drawn by connecting known points. Feasible scenarios were observed for all the hypothetical reserve sizes initially chosen. Finally a procedure was developed on how to use the resulting graphs of this study.