Influence of FeO and H on the electrical conductivity of olivine

Geochem Geophys Geosyst

et al. 2016

Self Cite

The electrical conductivity of eclogite was measured at temperatures of 873–1173 K and pressures of 1.0–3.0 GPa within a frequency range of 0.1–106 Hz using a YJ‐3000t multianvil press and Solartron‐1260 impedance/gain‐phase analyzer. Three solid‐state oxygen buffers (Cu + CuO, Ni + NiO, and Mo + MoO2) were employed to control the oxygen fugacity. Experimental results indicate that the electrical conductivity of the samples tended to increase with increasing temperature, conforming to an Arrhenius relation. Under the control of a Cu + CuO oxygen buffer, the electrical conductivity of the eclogite decreased with a rise in pressure, and its corresponding activation volume and activation energy at atmospheric pressure were calculated as −2.51 ± 0.29 cm3/mole and 0.86 ± 0.12 eV, respectively. At 2.0 GPa, the electrical conductivity of the eclogite increased with increasing oxygen fugacity, and the preexponential factor increased while the activation enthalpy decreased. The observed positive exponential factor for the dependence of electrical conductivity on oxygen fugacity, as well as the negative activation volume, confirm that the hopping of small polarons is the dominant conduction mechanism in eclogite at high temperatures and pressures. Our results suggest that the electrical conductivity of dry eclogite under various redox conditions cannot explain the high anomalies in conductivity under stable midlower continental crust and under the Dabie‐Sulu ultrahigh‐pressure metamorphic belt of eastern China.

Section: Discussionsupporting

confidence: 91%

{Fe}_{Mg}^{\times} + h_{}^{•} \overset{}{⇌} {Fe}_{Mg}^{•}

where

{Fe}_{Mg}^{\times}

and

{Fe}_{Mg}^{•}

are respectively the ferrous and ferric ions on the site of the magnesium ion in the lattice. The dominant charge carrier is the small polaron,

{Fe}_{Mg}^{•}

(Fe 3+ at Mg site).…”

Section: Discussionmentioning

confidence: 99%

Section: Conduction Mechanismsmentioning

confidence: 99%

See 1 more Smart Citation

Influence of temperature, pressure, and oxygen fugacity on the electrical conductivity of dry eclogite, and geophysical implications

Geochem Geophys Geosyst

et al. 2016

Self Cite

“…The presence of small amounts of water in nominally anhydrous minerals has a considerable influence on the electrical conductivity of single crystal olivine and polycrystalline olivine aggregates at high temperature and high pressure [2,17,18]. To precisely determine the water content for the hot-pressed sintered olivine aggregates, we conducted the Fourier transform infrared (FTIR) analysis in the Key Laboratory of High-temperature and High-pressure Study of the Earth's Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China.…”

Section: Sample Preparation and Characterizationmentioning

confidence: 99%

Influence of High Conductive Magnetite Impurity on the Electrical Conductivity of Dry Olivine Aggregates at High Temperature and High Pressure

Sun

et al. 2019

Minerals

Self Cite

The electrical conductivity of dry sintered olivine aggregates with various contents of magnetite (0, 3, 5, 7, 10, 20, and 100 vol. %) was measured at temperatures of 873–1273 K and a pressure of 2.0 GPa within a frequency range of 0.1–106 Hz. The changes of the electrical conductivity of the samples with temperature followed an Arrhenius relation. The electrical conductivity of the sintered olivine aggregates increased as the magnetite-bearing content increased, and the activation enthalpy decreased, accordingly. When the content of interconnected magnetite was higher than the percolation threshold (~5 vol. %), the electrical conductivity of the samples was markedly enhanced. As the pressure increased from 1.0 to 3.0 GPa, the electrical conductivity of the magnetite-free olivine aggregates decreased, whereas the electrical conductivity of the 5 vol. % magnetite-bearing sample increased. Furthermore, the activation energy and activation volume of the 5 vol. % magnetite-bearing sintered olivine aggregates at atmospheric pressure were calculated to be 0.16 ± 0.04 eV and −1.50 ± 0.04 cm3/mole respectively. Due to the high value of percolation threshold (~5 vol. %) in the magnetite impurity sample, our present results suggest that regional high conductivity anomalies in the deep Earth’s interior cannot be explained by the presence of the interconnected magnetite-bearing olivine aggregates.

“…Dry silicate minerals and rocks cannot result in high‐conductivity anomalies in the Earth's interior (Dai et al, 2014, 2016, 2019; Fuji‐ta et al, 2004; Hu et al, 2013; Yang et al, 2012). In contrast, geophysicists have shown that the high‐conductivity anomalies in the Earth's lithosphere can be caused by the presence of water in nominally anhydrous minerals (Dai & Karato, 2014; Karato, 2019; H. Y. Liu et al, 2019; Wang et al, 2006; Yang et al, 2011), interconnected aqueous fluids (Amiguet et al, 2012; X. Z. Guo et al, 2015; Li et al, 2018; Manthilake et al, 2015, 2016; Shimojuku et al, 2014; Sinmyo & Keppler, 2017), partial melting (Freitas et al, 2019; Gaillard, 2005; X. Guo et al, 2018; Laumonier et al, 2015, 2017; Maumus et al, 2005; H. W. Ni et al, 2011), and interconnected secondary high‐conductivity phases (Bagdassarov et al, 2009; Glover et al, 1996; Kawano et al, 2012; Manthilake et al, 2016; Wang et al, 2013; Zhang & Yoshino, 2016).…”

Section: Introductionmentioning

confidence: 99%

Electrical Conductivity of Clinopyroxene‐NaCl‐H₂O System at High Temperatures and Pressures: Implications for High‐Conductivity Anomalies in the Deep Crust and Subduction Zone

Sun

et al. 2020

JGR Solid Earth

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Electrical conductivities of the clinopyroxene (Cpx)-NaCl-H 2 O system with various salinities (5, 10, 15, 20, 25 wt%) and fluid fractions (5, 10, 15, 20, 25 vol%) were measured at 1 GPa and 673-973 K. For comparison with electrical properties of the Cpx-NaCl-H 2 O system, the conductivities of dry Cpx, hydrous Cpx, and a Cpx-H 2 O system were researched at the same temperature and pressure. The experimental results included (1) the electrical conductivities of all samples that were associated with Cpx and the temperatures conform to the Arrhenius relationship that is used to fit the activation enthalpy, which decreased with increasing salinity (mass fraction of NaCl in saline fluids) and fluid fraction (volume fraction of saline fluids in the Cpx-NaCl-H 2 O system); (2) at a fixed fluid fraction of 10 vol%, the conductivities of the Cpx-NaCl-H 2 O system increased slightly with an increase in salinity, and the gap between the conductivities of the systems with 5 and 25 wt% saline fluids was approximately 1 order of magnitude;(3) at a fixed salinity of 5 wt%, the conductivity of the Cpx-NaCl-H 2 O system with 25 vol% saline fluids was approximately 1.5 orders of magnitude higher than that of the system with 5 vol% saline fluids. Furthermore, it was proposed that the unusually high conductivities of southern Tibetan Plateau, Dabie Orogen, Grenville province and central New Zealand can be caused by clinopyroxene with interconnected saline fluids with corresponding salinities and fluid fractions.