TY - JOUR

T1 - Laboratory SIP signatures associated with oxidation of disseminated metal sulphides

AU - Placencia-Gómez, Edmundo

AU - Slater, Lee

AU - Ntarlagiannis, Dimitrios

AU - Binley, Andrew

N1 - Date of Acceptance: 17/02/2013

PY - 2013/5

Y1 - 2013/5

N2 - Oxidation ofmetal sulfideminerals is responsible for the generation of acidic waters rich in sulfate and metals. When associated with the oxidation of sulfide ore mine waste deposits the resulting pore water is called acid mine drainage (AMD); AMD is a known environmental problem that affects surface and ground waters. Characterization of oxidation processes in-situ is challenging,particularly at the field scale. Geophysical techniques, spectral induced polarization (SIP) in particular, may provide a means of such investigation.We performed laboratory experiments to assess the sensitivity of the SIP method to the oxidation mechanisms of common sulfideminerals found in mine waste deposits, i.e., pyrite and pyrrhotite, when the primary oxidant agent isdissolved oxygen. We found that SIP parameters, e.g., phase shift, the imaginary component of electrical conductivity and total chargeability, decrease as the time of exposure to oxidation and oxidation degree increase. This observation suggests that dissolution–depletion of the mineral surface reduces the capacitive properties and polarizability of the sulfide minerals. However, small increases in the phase shift and imaginary conductivity do occur during oxidation. Thesetransient increases appear to correlatewith increases of soluble oxidizing products, e.g., Fe2+ and Fe3+ in solution; precipitation of secondary minerals and the formation of a passivating layer to oxidation coating the mineral surface may also contribute to these increases. In contrast, the real component of electrical conductivity associated with electrolytic, electronic and interfacialconductance is sensitive to changes in the pore fluid chemistry as a result of the soluble oxidation products released (Fe2+ and Fe3+), particularly for the case of pyrrhotite minerals.

AB - Oxidation ofmetal sulfideminerals is responsible for the generation of acidic waters rich in sulfate and metals. When associated with the oxidation of sulfide ore mine waste deposits the resulting pore water is called acid mine drainage (AMD); AMD is a known environmental problem that affects surface and ground waters. Characterization of oxidation processes in-situ is challenging,particularly at the field scale. Geophysical techniques, spectral induced polarization (SIP) in particular, may provide a means of such investigation.We performed laboratory experiments to assess the sensitivity of the SIP method to the oxidation mechanisms of common sulfideminerals found in mine waste deposits, i.e., pyrite and pyrrhotite, when the primary oxidant agent isdissolved oxygen. We found that SIP parameters, e.g., phase shift, the imaginary component of electrical conductivity and total chargeability, decrease as the time of exposure to oxidation and oxidation degree increase. This observation suggests that dissolution–depletion of the mineral surface reduces the capacitive properties and polarizability of the sulfide minerals. However, small increases in the phase shift and imaginary conductivity do occur during oxidation. Thesetransient increases appear to correlatewith increases of soluble oxidizing products, e.g., Fe2+ and Fe3+ in solution; precipitation of secondary minerals and the formation of a passivating layer to oxidation coating the mineral surface may also contribute to these increases. In contrast, the real component of electrical conductivity associated with electrolytic, electronic and interfacialconductance is sensitive to changes in the pore fluid chemistry as a result of the soluble oxidation products released (Fe2+ and Fe3+), particularly for the case of pyrrhotite minerals.

KW - Spectral induced polarization

KW - Sulfide minerals

KW - Oxidative-weathering

KW - Dissolution–depletion

KW - Oxidation products

KW - AMD

U2 - 10.1016/j.jconhyd.2013.02.007

DO - 10.1016/j.jconhyd.2013.02.007

M3 - Journal article

VL - 148

SP - 25

EP - 38

JO - Journal of Contaminant Hydrology

JF - Journal of Contaminant Hydrology

SN - 0169-7722

ER -