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Defining the spatial distribution of geological structures and rock properties is important for understanding how fluid flow is controlled in a geothermal reservoir. Here, we present a procedure to examine the potential fluid pathways. By combining 3‐D resistivity models derived from audio‐magnetotelluric (AMT) data with available rock properties (porosity and permeability) and fluid sample data (fluid resistivity, salinity, and temperature), we investigated the relationship between electrical resistivity and fluid flow in an active volcanic system. Different petrophysical models and empirical relations are evaluated to determine the relationship between the fluid flow system at Mount Meager, British Columbia, and the resistivity model. In addition, we utilized porosity and permeability measured in the laboratory to define the porosity‐permeability relationship. The porosity of the volcanic core samples showed a range of 2.6%–23.2% and the permeability was in a range of 0.001–5,186.57 mD. The results showed the potential of 3‐D inversion of AMT data to map the fluid pathways at Mount Meager. These pathways are correlated with loss circulation zones in boreholes and can account for porosity up to 8.5%, which using the porosity‐permeability relationship translates to permeability of the order 0.249 mD. Not only are the fault and fracture zones important for reservoir exploitation, but they also provide permeability for the circulation of meteoric water. Our studies suggest that a set of fractures with 0.1 m spacing and 20 mm aperture can keep 40% fluid in pores and transmit fluid with possible permeability of 666 mD. Plain Language Summary: Geothermal is the natural heat within the Earth. Heat passes to the near‐surface by the magma intrusion into the crust and circulation of groundwater through fluid flow pathways. This paper evaluates the fluid flow pathways, structure, and physical properties beneath the Mount Meager Volcanic Complex (MMVC; Canada). The audio‐magnetotelluric (AMT) method (natural‐source electromagnetic geophysical technique) was used to produce the 3‐D resistivity model. Moreover, utilizing laboratory experiments, we modified rock‐physical and fluid chemistry relationships to focus on the MMVC rather than using relations adapted to other volcanic settings. The AMT model shows correlations between the locations of conductors and faults and suggests that faults act as flow pathways. A porosity of up to 8.5% is expected in the potential reservoir zone. By combining the resistivity model with rock and fluid properties, we mapped potential flow pathways and rock properties. Results showed that in rocks with low porosity and permeability, fractures provide the primary way of flow with porosity and permeability up to 40% and 666 mD, respectively. This project contributes to the development of conceptual models of the hydrothermal flow, which could be used to reduce the risk of future exploitation of geothermal resources. Key Points: Audio‐magnetotelluric data have been used to model the conductivity distribution beneath an active volcanic system in southwestern CanadaUtilizing 3‐D Inversion, we provide details on the structure, physical properties, and flow pathways of a volcano‐hosted geothermal systemPermeability can increase up to five orders of magnitude in fractured rocks beneath Mount Meager [ABSTRACT FROM AUTHOR]

Surface electrical and electromagnetic geophysical methods can map enhanced electrical conductivity caused by acid mine drainage in mine tailings piles. In this case study, we investigate quantitative relationships between geophysical responses and the electrical conductivity, acidity and salinity of tailing samples at the Central Manitoba Mine tailings in Manitoba, Canada. Previous electromagnetic surveys at the site identified zones of enhanced conductivity that were hypothesized to be caused by acid mine drainage. In the present study, high-resolution EM31 and DC-resistivity measurements were made on a profile through a zone of enhanced conductivity and laboratory measurements of salinity and pH were made on saturation paste extracts from an array of tailing samples collected from the upper 2 m of tailings along the profile. Observed spatial correlation of pH and pore-fluid salinity in the tailings samples confirms that the enhanced conductivity in the Central Manitoba Mine tailings is due to acid mine drainage. Contoured cross-sections of the data indicate that the acid mine drainage is concentrated near the base of the oxidized zone in the thicker parts of the tailings pile. The zone of increased acidity extends to the surface on sloping margins causing an increase in apparent conductivity in shallow penetrating geophysical responses. The quantitative relationship between measured pH and salinity shows that the conductivity increase associated with the acid mine drainage is due only in part to conduction by ions produced from dissociation of sulfuric acid. Comparison of the observations with fluid conductivity estimates based on statistical relationships of pH and ion concentrations in water samples from across the tailings pile shows that Ca 2 + and Mg 2 + ions also make significant contributions to the conductivity at all values of pH and Cu 2 + , Al 3 + and Fe 3 + ions make additional contributions at low pH. Variability in the measured conductivity at constant values of pH is explained by variations in the contribution of the SO 4 2 − to the measurements. The results of the study demonstrate the feasibility of using electromagnetic geophysical surveys to map acid mine drainage, and related ionic concentration, in mine tailings. [ABSTRACT FROM AUTHOR]

Electrical conductivity (EC) is used for monitoring different types of aqueous systems. The measured EC value at any temperature needs to be corrected for a standard temperature, for reporting or comparison, since EC is dependent on temperature. A temperature compensation factor has been derived for conductivity correction from anaerobic digester supernatant/centrate samples of five different wastewater treatment plants in western Canada. For a temperature compensation factor of 0.0198°C-1, corresponding to the standard temperature at 25°C, the estimated EC25 values were found to be reasonably accurate, with a maximum error of 2.01%. The estimated EC values, based on any standard temperature, were found to be statistically similar to each other. Considering the temperature dependence of EC, a relationship between EC and ionic strength was developed in this study for anaerobic digester supernatant/centrate samples. This relationship can be used to estimate the ionic strength of the solution in a system associated with struvite formation from anaerobic digester supernatant/centrate and effectively monitor the system performance. [ABSTRACT FROM AUTHOR]

Abstract: We studied hidden periodicities and trends in the temporal dynamics of soil salinity in the Canadian prairies at a field scale. Singular spectrum analysis (SSA) was applied to time series of the groundwater depth (Dgw), total precipitation, groundwater electrical conductivity (ECgw), and soil electrical conductivity (ECe). We found that the temporal variability of soil salinity is determined by its seasonal and quasi-3-yr oscillations controlled by similar cycles of Dgw and ECgw, which are controlled by the precipitation. In the seasonal cycle, the system “precipitation – groundwater depth – groundwater salinity – soil salinity” proceeds as follows: The maximal level of the precipitation is reached in late May. The water table peaks 2 months after the maximal level of precipitation was reached. The seasonal oscillation of ECgw is in phase with that of Dgw. ECe peaks 1.5 months after the maximal level of ECgw was reached. In the quasi-3-yr cycle, ECe peaks about 14 months after the maximal rise of the groundwater. Most likely, this cycle of Dgw is a response to the 3-yr periodicity of the precipitation observed in the region. SSA is the effective tool to detect hidden oscillations in soil processes handling relatively short time series with missing records. [Copyright &y& Elsevier]

Long-period magnetotelluric data have been used to image the deep electrical structure of the Cascadia subduction zone in British Columbia, Canada. Zones of elevated electrical conductivity were found in both the forearc and backarc regions and are interpreted as a consequence of the fluid release from subducting slab. A shallow zone of high conductivity beneath Vancouver Island is likely due to fluids that are trapped above the subducting plate. East of this structure is a conductive (∼0.03 S/m) forearc mantle wedge that also exhibits low seismic velocities and may be serpentinized. A free fluid phase is required to account for this enhanced conductivity. Elevated conductivities are observed in the upper mantle throughout the backarc (∼0.01 S/m) and strongly support the hypothesis of a shallow, convecting asthenosphere. This enhanced upper mantle conductivity can be explained by either hydrogen ion diffusion in olivine minerals, or by a few percent partial melting (<4%). [ABSTRACT FROM AUTHOR]

Abstract: Using laboratory-derived temperature dependences of the electrical conductivity of mantle minerals coupled with appropriate mixing laws, we determine the bulk conductivity of mantle mineral assemblages for the ternary olivine–orthopyroxene–clinopyroxene (Ol–Opx–Cpx) system. We calculate physical property bounds (Hashin–Shtrikman bounds) as a function of the fraction of different phases present; these limits correspond to the extreme situations where the most conducting phase is either fully interconnected or fully disconnected. The relationships we present between temperature, mineral composition and bulk electrical conductivity allow constraining one of them given the other two. We apply this approach to an area of the North American Cordilleran Intermontane Belt in the Yukon Territory, northern Canada, where xenolith evidence indicates bimodal upper mantle mineral assemblages (harzburgite and lherzolite). This locality coincides spatially with an upper mantle region of low electrical conductivity determined by long period magnetotelluric data. Given the mantle mineral composition and the maximum and minimum bounds on the electrical conductivity, deduced by non-linear model appraisal, we determine the permitted extremal temperature bounds of the Intermontane belt mantle rocks directly below the Moho to a depth of some 80 km. We show that the mantle in this region is at a minimum temperature of 820 °C and a maximum temperature of 1020 °C; the latter is some 200 °C colder than that suggested in a recent interpretation of an observed collocated low velocity zone from a teleseismic survey. [Copyright &y& Elsevier]

• Deciduous angiosperm trees increased pH of throughfall water in mixed stands with evergreen conifers. • Deciduous angiosperm trees reduced electrical conductivity of throughfall in mixed stands with evergreen conifers. • Persistent acidifying air pollution at low levels on Eastern Cape Breton Island, Canada. • High Na+ proportion on base cation sum in throughfall water. • Hyper-accumulation of Zn in foliage of Betula alleghanensis. Forest management objectives in public water supply areas are designed to optimize water quality. We employed a paired-tree sampling approach within mixed stands to test the effects of evergreen conifer versus deciduous angiosperm taxa on water chemistry beneath canopies (i.e., throughfall; TF) in a post-industrial region with Ca-impoverished acidic soils and pronounced coastal weather conditions. Reduced concentrations of protons and sea salt were two discernable benefits of deciduous angiosperm trees. These effects became more pronounced during fall recharge when tree physiological dormancy coincided with onshore storm events and increasing seasonal demand for industrial and residential coal combustion. Taxon differences however, did not exert any significant effect on base cation proportions in soil leachates and on soil cation exchange complexes. Thus, ecosystem-based management of stand-level tree diversity in public water supply areas should monitor pH and electrical conductivity of TF water to mitigate adverse water quality effects of persistent acidifying air pollution and the preponderance and high concentration of Na+ in coastal regions. Results largely corroborated previous observations of a decreasing trend in acidifying air pollution at the northeastern periphery of the Eastern Deciduous Forest biome, although elevated SO 4 2−/Cl− – ratios above seawater levels were still noted in TF water chemistry. Electrical conductivity was a reliable predictor of Cl− concentration in TF water regardless of taxon, phenology, and stand location (R 2 = 0.99). [ABSTRACT FROM AUTHOR]