| 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. |
