Mine-to-Pad in Gold Mining: A Case Study (1996-2008) on Fragmentation for Run-of-Mine (ROM) Leaching in Peru

Abstract

In the context of open-pit mining in Peru, this study presents the experience of a gold operation that, since 1994, has implemented a leaching process without crushing or grinding stages (Run-of-Mine). The present work constitutes a case study of a specific mine, with the main objective of demonstrating, through metallurgical plant validation, how an optimal fragmentation near 4 inches can prove suitable for leaching in this particular context, given the geological characteristics of the deposit.

Covering the period from 1996 to 2008, the study evaluates various techniques aimed at optimizing ore microfracturing, including non-electric and electronic initiation systems, air decking, and the use of gassed emulsions. The methodology is based on operational analysis and P80 particle size distribution in leaching heaps, along with cost indicators related to drilling, blasting, loading, and plant processing.

The choice of an average particle size close to 4 inches is justified because it provides a balance between heap permeability, mineral surface exposure, and control of fines generation. This size improved metallurgical recovery without excessively increasing drilling and blasting costs, validating it as the optimal point in this case study.

The results evidence that an adequate blasting sequence increases heap permeability and improves gold recovery, even in low-grade materials. Furthermore, it is observed that a moderate increase in drilling and blasting costs results in a reduction of overall mining costs.

It is concluded that the "Mine-to-Pad" approach is technically feasible, economically profitable, and environmentally favorable, as it eliminates crushing stages, reduces energy consumption, and maintains a closed-loop process in the plant. This model represents an efficient alternative for operations with complex or low-grade mineralizations.