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The assessment of mineralogical properties and hydrological or physicochemical controls on the drainage chemistry of mine waste rock

University of British Columbia

Mining exploitation produces a substantial amount of waste rock that, when exposed to water and oxygen, may liberate metals and acidity in mine drainage. Waste rock and mine drainage should therefore be carefully managed to avoid the propagation of harmful elements in the environment. Proper management strategies include geochemical characterization of waste rock, water quality monitoring, long-term predictions, and thorough knowledge of mobility controls of solutes in mine waste. This study investigates the relationship between waste rock weathering, processes controlling mineral reactivity or solute mobility, and drainage chemistry in field barrel kinetic tests or within the full-scale waste-rock pile. The main findings of this work are that: 1) Waste rock reactivity, evaluated from mineral liberation and association indices that are calculated from automated mineralogy data, complements bulk geochemistry and lithological characterization and improves drainage quality predictions; 2) Mechanisms of secondary mineral precipitation, sorption, surface passivation and galvanic reactions are linked to potential mobilization or inhibition of metals in the drainage data; 3) Mineralogical composition and weathering patterns are interrelated with hydrological responses, providing an initial qualitative indication of hydrological and geochemical processes controlling drainage chemistry in field barrels; 4) Reactive transport modeling provides site-specific calibrated mineral weathering rates illustrating the control of hydrological, physicochemical, and mineralogical processes on drainage chemistry; 5) High-resolution sampling and analyses of waste rock weathering and drainage of reactive zones within the waste-rock pile reveal high degrees of physicochemical heterogeneity that can hardly be described by static laboratory testing or sensor measurements alone. Overall, this thesis is facilitating the interpretation of waste-rock reactivity using waste-rock quantitative mineralogical evaluations; providing mineralogical perspectives on geochemical and hydrological processes; expanding the identification of mechanisms affecting metal mobility from waste-rock drainage; and, providing information to achieve more accurate drainage prediction models. As improvements are made to the automation of mining operations at large scales, more information can be gathered cost-effectively. This novel mineralogical approach, adding new perspectives on weathering processes impacting mine drainage, could therefore be applied to other mine sites, ultimately allowing for the optimization of waste-rock management as well as long-term drainage predictions.

Text

2020-04-14

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/73989

Mining Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/