Structure of the acid hydrothermal system of Papandayan volcano, Indonesia, investigated by geophysical methods

Heat and Mass Transport in a Vapor‐Dominated Hydrothermal Area in Yellowstone National Park, USA: Inferences From Magnetic, Electrical, Electromagnetic, Subsurface Temperature, and Diffuse CO2 Flux Measurements

“…By combining petrophysical laws (Archie, ; Llera et al, ; Revil, ; Waxman & Smits, ), values of petrophysical parameters (Ghorbani et al, ) measured on samples from the SPTA and from drill holes in hydrothermal areas of Yellowstone National Park (White et al, ), and values of electrical conductivity measured in thermal waters from Yellowstone National Park (Bergfeld et al, ), we show that the higher conductivity in the interior of the plume (10 −1 S/m) with respect to its surroundings (10 −3 S/m) may result from a combination of several effects (Figures S7 and Text S7): higher temperature, lower pH (e.g., Byrdina et al, ) and/or higher salinity (resulting in higher pore water electrical conductivity), and hydrothermal alteration of the rock matrix (resulting in higher cationic exchange capacity; e.g., Revil et al, ). The very low near‐surface electrical conductivity (10 −4 S/m) in the model below areas of higher topography likely results from lower liquid saturation.…”

“…The strong correlation between the distributions of SP anomalies and magnetic susceptibility and the lack of spatial correlation with the distribution of CO 2 flux, heat flux, subsurface temperature, and shallow electrical conductivity (Figure S6) suggests that the distribution of the SP anomalies is decoupled from the thermal plume structure and more likely related to a process that also affects the magnetic susceptibility. Therefore, we propose that the negative SP anomalies result from the low pH near the ground surface around the mud pool, affecting the sign of the streaming coupling coefficient (e.g., Aizawa et al, ; Byrdina et al, ; Revil & Pezard, ; Text S5). The low pH is also consistent with the decrease in magnetic susceptibility due to dissolution of magnetic minerals in presence of acid‐sulfate waters.…”

“…Our goal was to take advantage of the expected large contrasts in electrical conductivity and magnetization to delineate different domains within the vapor‐dominated system. Electrical conductivity is significantly influenced by, among other effects, fluid saturation and salinity, pH, temperature, and rock alteration (e.g., Archie, ; Byrdina et al, ; Llera et al, ; Palacky, ) and magnetization by hydrothermal rock alteration (e.g., Hochstein & Soengkono, ). We supplemented the geophysical surveys with measurements of rock magnetic properties in the field and in the laboratory to better constrain the magnetic signature related to rock alteration.…”

Hydrothermal system of the active crater of Aso volcano (Japan) inferred from a three-dimensional resistivity structure model

“…Using the compositional data shown in Miyabuchi and Terada (2009), we estimated the electrical conductivity of lake water in the Nakadake first crater to be ~ 40 S/m by the same method (details are shown in Additional file 2: Appendix B). Although this exceptionally high value is likely to be an overestimate as pointed out by Byrdina et al (2018) for waters of high ion concentrations, the order of magnitude would not be different because high values exceeding 10 S/m were sometimes measured for hot-spring waters in the volcanic area (e.g., Seki et al 2016). If such high-conductivity fluids infiltrate the inter-connected fractures, the influence of sulfur or sulfates with high resistivity to the bulk conductivity of rocks can be neglected (e.g., Guinea et al 2012;Byrdina et al 2018).…”

“…Although the electrical conductivity of lake water has not been measured so far, it is expected to have a considerably high value due to its high ion concentration and low pH (e.g., Ohsawa et al 2010). Byrdina et al (2018) estimated the theoretical electrical conductivity of spring waters sampled at Papandayan volcano (Indonesia) to be extremely high values of 20-25 S/m from their chemical compositions and pH values. Using the compositional data shown in Miyabuchi and Terada (2009), we estimated the electrical conductivity of lake water in the Nakadake first crater to be ~ 40 S/m by the same method (details are shown in Additional file 2: Appendix B).…”