Metals and polymetals
The economic ore bodies targeted for the surface mining of metals and polymetals cover a wide range of mineralisation shapes and structures from steep dipping to bowl-shaped, and from vein-type to tabular and lenses amongst others; in addition to the different styles of mineralisation.
Pits targeting metals and polymetals can be large in size, and irregular in shape to fit the geometry of the mineralised zones and can reach an economic depth of up to 900m (and in special cases even more). Based on the shape of the mineralised zone and the economic cut-off grades applied, a high degree of mining selectivity could be required. Appropriate equipment selection, blasting practices and grade control practices are critical in these cases.
We regularly work on large, high production rate pits (1 million tonnes of rock moved per day). To allow for such high production rates and manage these operational risks appropriately, pushbacks with multi-pit accesses would be considered. Generally, in-pit backfill opportunities are limited, depending on the pushback strategy. This means that significantly large external waste stockpiles are required, and optimal pit, pushback, waste dump and hauling design can make a significant impact on the cost profile of the operation, specifically considering the trend of energy costs. In-pit crushing and conveying systems and trolley-assist lines are frequently applied, where it is practically possible, and where the operational cost savings outweigh the capital investment requirements.