Controlling dilution and costs in narrow-vein underground gold mines is essential to ensure the economic viability of the projects. Dilution, meaning the entry of unwanted material during ore extraction, has a significant impact on the operational costs, which must be managed to secure long-term profitability and sustainability of operations throughout the life of the mine.
Common underground mining methods in narrow vein mines include cut and fill, room and pillars, and sublevel stoping. The choice of the mining method depends on deposit characteristics, such as the competence of the ore and wall rocks, thickness and ore dip, aiming to optimize mining recovery and minimize dilution. Veins where the dip is shown at intermediate values bring greater complexity to the choice of mining method. Methods based on stopes tend to be more productive but depend on a minimum ore dip that enables flow through the side walls of the stopes. Often, the presence of material not mucked from the stopes leads to a mistaken understanding of underbreak. In these cases, it is appropriate to use auxiliary equipment that allows fine material cleaning.
The selection of mining equipment is also critical for dilution. Standard equipment, offering higher productivity, requires larger drift sections, leading to significant dilutions ranging from 100% to up to 400% depending on the ore thickness, making the operation uneconomical in many cases. An alternative to reducing dilution in wide sections of development is the practice of split blasting, where the waste rock at the base of the face is blasted and mucked first, followed by ore blasting and mucking. Conversely, low-profile equipment favors dilution reduction but may negatively impact operational productivity. Striking a balance between equipment efficiency, productivity, and dilution minimization is essential to ensure the profitability and sustainability of underground mining operations.
During mine development, geological-structural mapping and sampling play a crucial role in ensuring the correct positioning of the auriferous vein on the heading faces to prevent unplanned dilutions and excavation instability, which may arise from inaccuracies in ore vein positioning during excavation. Workforce quality for production drilling and effective excavation monitoring is also fundamental to guaranteeing efficient and safe operations in adherence to mine design standards.
Precise and comprehensive management is required for dilution and cost control in narrow vein underground gold mines. From mining methods and equipment selection to geological and structural control and workforce quality, the industry can improve efficiency, reduce dilution, and enhance economic sustainability in underground gold mining.
