@article{fdi:010076616,
  title = {{E}lectrical resistivity tomography and time-domain induced polarization field investigations of geothermal areas at {K}rafla, {I}celand : comparison to borehole and laboratory frequency-domain electrical observations},
  author = {{L}evy, {L}. and {M}aurya, {P}. {K}. and {B}yrdina, {S}vetlana and {V}andemeulebrouck, {J}. and {S}igmundsson, {F}. and {A}rnason, {K}. and {R}icci, {T}. and {D}eldicque, {D}. and {R}oger, {M}. and {G}ibert, {B}. and {L}abazuy, {P}.},
  editor = {},
  language = {{ENG}},
  abstract = {{I}nteraction of {H}2{S} and basaltic rocks in volcanic geothermal areas can originate from natural up-flow of magmatic fluids or {H}2{S} artificial re-injection in relation to geothermal exploitation, both causing pyrite mineralization. {W}e study the possibility to track these processes with electrical impedance field measurements. {E}lectrical {R}esistivity {T}omography ({ERT}) and {T}ime{D}omain {I}nduced {P}olarization ({TDIP}) measurements were performed along thirteen 1.24 km long profiles, at three different sites around the eastern caldera rim of the {K}rafla 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. {W}e present 2-{D} inversions of direct current ({DC}) resistivity, maximum phase angle of the electrical impedance ({MPA}) and relaxation time. {T}he maximum depth of investigation for the {MPA} is 200 m, obtained in zones of high resistivity, corresponding to fresh and recent unaltered basalt. {A}t 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. {T}he 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)-10(6) {H}z. {T}he time-range investigated in our field {TDIP} measurements was approximately 0.01-8 s. {A}t the cold altered site, the inverted resistivity is consistent with both borehole observations and laboratory measurements. {A}t the hot site, resistivity from field inversion and borehole logs are consistent. {C}omparing 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 degrees {C} is appropriate at investigated depths. {T}his exceptionally high temperature correction coefficient suggests a dominant influence of interface and interfoliar conduction, characteristic of smectite-rich rocks, compared to electrolyte conduction. {H}igh {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. {T}he 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.},
  keywords = {{H}ydrogeophysics ; {H}ydrothermal {S}ystems ; {E}lectrical {R}esistivity {T}omography ; {ISLANDE}},
  booktitle = {},
  journal = {{G}eophysical {J}ournal {I}nternational},
  volume = {218},
  numero = {3},
  pages = {1469--1489},
  ISSN = {0956-540{X}},
  year = {2019},
  DOI = {10.1093/gji/ggz240},
  URL = {https://www.documentation.ird.fr/hor/fdi:010076616},
}