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Journal Articles Journal of Volcanology and Geothermal Research Year : 2018

Electrical conductivity and induced polarization investigations at Kilauea volcano, Hawai'i

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Abstract

Two new datasets of core samples from Kilauea volcano have been used to conduct complex conductivity (induced polarization) measurements from 10 mHz to 45 kHz at 3 or 4 salinities (NaCl, 10-2 to 10 S m-1 at 25 °C) depending on the core samples. The first dataset corresponds to 15 core samples collected in 2015 at the ground surface in the caldera of Kilauea around the Halema'uma'u crater (dataset 1). The second data set (dataset 2) corresponds to 28 core samples from Keller's well (KW) in the south part of the caldera. A third dataset (dataset 3) corresponds to 28 core samples from Well PTA-2 from the Humu'ula Groundwater Research Project in Hawai'i. The electrical conductivity of these samples can be decomposed as the sum of a bulk conductivity and a surface conductivity associated with electrical conduction in the electrical double layer coating the surface of the grains. The variations of the in-phase conductivity with the pore water conductivity is used to infer the intrinsic formation factor and the surface conductivity, which is a good indicator of alteration. The surface conductivity, the normalized chargeability (determined from the dispersion of the in-phase conductivity curve as a function of frequency), and the quadrature conductivity scale with the cation exchange capacity. In addition, the normalized chargeability and the quadrature conductivity of unaltered core samples show a signature associated with the presence of (titano)magnetite. The quadrature conductivity (and therefore the normalized chargeability) depends on temperature according to an Arrhenius's law with an activation energy close to 16 kJ Mol-1. We observe that alteration yields a pronounced increase of surface conductivity, normalized chargeability, and quadrature conductivity. These data are in turn used to help in the interpretation of a DC electrical conductivity survey performed in the caldera of Kilauea. The conductivity response around Keller's KW-well is dominated by the surface conductivity contribution associated with alteration and temperature. We propose a new method to image equilibrium temperature from electrical conductivity tomography.
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Dates and versions

insu-03708962 , version 1 (29-06-2022)

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Cite

A. Revil, A. Ghorbani, L. S. Gailler, M. Gresse, N. Cluzel, et al.. Electrical conductivity and induced polarization investigations at Kilauea volcano, Hawai'i. Journal of Volcanology and Geothermal Research, 2018, 368, pp.31-50. ⟨10.1016/j.jvolgeores.2018.10.014⟩. ⟨insu-03708962⟩
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