Economic Trade-offs of Strategic Fragmentation Coarsening: An Integrated Mine-to-Crusher Assessment

Persistent economic and operational pressures require mining operations to reduce energy use and production costs across increasingly interconnected unit processes. Although finer blast-induced fragmentation can lower downstream comminution demand, achieving it generally requires denser drilling patterns and greater explosive consumption. This study evaluates whether controlled fragmentation coarsening through blast-pattern widening can improve the economic performance of an integrated drill-to-crush system. Full-scale trials at a large gold mine in the Tarkwa Basin, Ghana, compared 4.0 m × 4.0 m, 4.0 m × 4.5 m, and 4.5 m × 4.5 m patterns. Fragmentation measurements were integrated with drilling requirements, explosive consumption, primary-crusher energy demand, and activity-based costs. Widening the pattern to 4.5 m × 4.5 m reduced blasthole requirements, drilling meterage, and powder factor by approximately 21%, while increasing the volume broken per hole by 27%. These upstream gains were accompanied by coarser fragmentation: blast P80 increased from 244 to 293 mm, crusher-feed F80 increased from 269.14 to 332.79 mm, and specific crushing energy rose from 25.89 to 30.32 kWh/t. Under the reported cost assumptions, total drill-to-crush cost increased from $5.82/t for the baseline to $5.91/t and $6.42/t for the intermediate and widest patterns, respectively. Thus, the reduction in drilling-and-blasting expenditure did not offset the fragmentation-dependent crushing penalty. The results demonstrate that minimum powder factor and minimum drilling cost do not necessarily correspond to minimum system cost. The study provides a field-based framework for quantifying cost transfer across drilling, blasting, and primary crushing and shows that the economically preferred fragmentation distribution must be identified through integrated value-chain optimisation rather than isolated unit-process targets.