Delineation of the spatial variability of carbonate and sulfide minerals in mine waste-rock piles using geostatistics

Social and environmental consequences associated with sulfide-bearing mine wastes (i.e., waste rock and mill tailings) and acid mine drainage constitute growing threats to sustainable mining and development, biodiversity of ecosystems, and global water quality. Spatial heterogeneity of geochemically important parameters in wasterock piles is well-known and is important to incorporate in environmental impact assessments; however, quantitative characterization of spatial heterogeneity remains under investigation. Here, we show the integrated results from trans-disciplinary waste-rock studies at three mine sites in northern Canada, conducted over the past 20 years. These studies focus on diverse projects, including an experimental-scale test pile study, characterization of medium-scale stockpiles, and an examination of an operational-scale pile. Through geostatistical analyses, we observed that spatial heterogeneity of geochemically important parameters, including the abundances of carbonate and sulfide minerals, in field-scale waste-rock piles can be represented by random distributions using lognormal scaling. Our findings are foundational for forecasting waste-rock weathering and for environmental risk assessments, and can be applied to enhance the development of long-term waste-rock management strategies and improve reclamation measures of waste-rock piles throughout the world.