Options
Byrdina, Svetlana
Loading...
Preferred name
Byrdina, Svetlana
ORCID
3 results
Now showing 1 - 3 of 3
- PublicationOpen AccessThree-Dimensional Electrical Resistivity Tomography of the Solfatara Crater (Italy): Implication for the Multiphase Flow Structure of the Shallow Hydrothermal System(2017-11-27)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The Solfatara volcano is the main degassing area of the Campi Flegrei caldera, characterized by 60 years of unrest. Assessing such renewal activity is a challenging task because hydrothermal interactions with magmatic gases remain poorly understood. In this study, we decipher the complex structure of the shallow Solfatara hydrothermal system by performing the first 3-D, high-resolution, electrical resistivity tomography of the volcano. The 3-D resistivity model was obtained from the inversion of 43,432 resistance measurements performed on an area of ~0.68 km2. The proposed interpretation of the multiphase hydrothermal structures is based on the resistivity model, a high-resolution infrared surface temperature image, and 1,136 soil CO2 flux measurements. In addition, we realized 27 soil cation exchange capacity and pH measurements demonstrating a negligible contribution of surface conductivity to the shallow bulk electrical conductivity. Hence, we show that the resistivity changes are mainly controlled by fluid content and temperature. The high-resolution tomograms identify for the first time the structure of the gas-dominated reservoir at 60mdepth that feeds the Bocca Grande fumarole through a ~10mthick channel. In addition, the resistivity model reveals a channel-like conductive structure where the liquid produced by steam condensation around the main fumaroles flows down to the Fangaia area within a buried fault. The model delineates the emplacement of the main geological structures: Mount Olibano, Solfatara cryptodome, and tephra deposits. It also reveals the anatomy of the hydrothermal system, especially two liquid-dominated plumes, the Fangaia mud pool and the Pisciarelli fumarole, respectively.363 49 - PublicationOpen AccessElectrical resistivity tomography and time-domain induced polarization field investigations of geothermal areas at Krafla, Iceland: comparison to borehole and laboratory frequency-domain electrical observations(2019)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ;Interaction of H2S and basaltic rocks in volcanic geothermal areas can originate from natural up-flow of magmatic fluids or H2S artificial re-injection in relation to geothermal exploitation, both causing pyrite mineralization. We study the possibility to track these processes with electrical impedance field measurements. Electrical Resistivity Tomography (ERT) and Time-Domain Induced Polarization (TDIP) measurements were performed along thirteen 1.24 km long profiles, at three different sites around the eastern caldera rim of the Krafla caldera: (i) a ‘cold altered’ site affected by past hydrothermal circulations, (ii) a hot active site and (iii) a ‘cold un-altered’ site, unaffected by hydrothermal circulations. We present 2-D inversions of direct current (DC) resistivity, maximum phase angle of the electrical impedance (MPA) and relaxation time. The maximum depth of investigation for the MPA is 200 m, obtained in zones of high resistivity, corresponding to fresh and recent unaltered basalt. At the hot and cold altered sites, the field resistivities are compared to in situ borehole logs and laboratory complex resistivity measurements on rock samples from the boreholes. The laboratory complex resistivity was measured at six different pore water conductivities, ranging from 0.02 to 5 S m−1, and frequency in the range 10−2 − 106 Hz. The time-range investigated in our field TDIP measurements was approximately 0.01–8 s.At the cold altered site, the inverted resistivity is consistent with both borehole observations and laboratory measurements. At the hot site, resistivity from field inversion and borehole logs are consistent. Comparing inversion results and borehole logs to laboratory resistivity measured on core samples at room temperature reveals that a correction coefficient for the effect of temperature on resistivity of 6 per cent per °C is appropriate at investigated depths. This exceptionally high temperature correction coefficient suggests a dominant influence of interface and interfoliar conduction, characteristic of smectite-rich rocks, compared to electrolyte conduction. High MPA is attributed to the presence of pyrite at the hot site and of iron-oxides at the cold unaltered site, through joint consideration of MPA together with DC resistivity and relaxation time. TDIP measurements offer the possibility to detect the presence of metallic minerals at shallow depth and distinguish between pyrite and iron-oxides. The abundance of highly conductive smectite in altered volcanic rocks represents a challenge for resolving IP parameters, because the low resistivity created by abundant smectite limits the data quality of the measured voltage discharge.247 21 - PublicationOpen AccessAnatomy of a fumarolic system inferred from a multiphysics approach(2018-05-15)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ;; ;; ; ;Fumaroles are a common manifestation of volcanic activity that are associated with large emissions of gases into the atmosphere. These gases originate from the magma, and they can provide indirect and unique insights into magmatic processes. Therefore, they are extensively used to monitor and forecast eruptive activity. During their ascent, the magmatic gases interact with the rock and hydrothermal fluids, which modify their geochemical compositions. These interactions can complicate our understanding of the real volcanic dynamics and remain poorly considered. Here, we present the first complete imagery of a fumarolic plumbing system using three-dimensional electrical resistivity tomography and new acoustic noise localization. We delineate a gas reservoir that feeds the fumaroles through distinct channels. Based on this geometry, a thermodynamic model reveals that near-surface mixing between gas and condensed steam explains the distinct geochemical compositions of fumaroles that originate from the same source. Such modeling of fluid interactions will allow for the simulation of dynamic processes of magmatic degassing, which is crucial to the monitoring of volcanic unrest.462 79