Electrical conductivity of tremolite under high temperature and pressure: implications for the high-conductivity anomalies in the Earth and Venus

Shen, Kewei; Wang, Duojun; Liu, Tao

doi:10.1007/s00410-020-01688-y

Cited by 17 publications

(38 citation statements)

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“…We also noted that the electrical conductivity of our diopside-tremolite-albite sample is higher than that of pure clinopyroxene (Yang et al, 2011) or pure tremolite (Shen et al, 2020) by a factor of 10 3 -10 4 , especially when the temperature is lower than 1000 K (Figure 3). These electrical conductivity experiments on clinopyroxene, plagioclase, and amphibole were conducted at different pressures.…”

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confidence: 69%

“…However, a recent experimental study found that the electrical conductivity of tremolite amphibole is much lower than previously thought, about 10 3 -10 5 lower than that of hornblendite. It only exceeds the conductivity of olivine by one order of magnitude at temperatures <1123 K, i.e., the melting temperature (Shen et al, 2020). Therefore, the role of amphiboles in the electrical conductivity of the mantle is ambiguous and it certainly requires further study.…”

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confidence: 99%

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Electrical conductivity of metasomatized lithology in subcontinental lithosphere

Peng

Manthilake

Mookherjee

2022

American Mineralogist

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A plausible origin of the seismically observed mid-lithospheric discontinuity (MLD) in the subcontinental lithosphere is mantle metasomatism. The metasomatized mantle is likely to stabilize hydrous phases such as amphiboles. The existing electrical conductivity data on amphiboles vary significantly. The electrical conductivity data on hornblendite is much higher than the recent data on tremolite. Thus, if hornblendite truly represents the amphibole varieties in MLD regions, then it is likely that amphibole will cause high electrical conductivity anomalies at MLD depths. However, this is inconsistent with the magnetotelluric observations across MLD depths. Hence, to better understand this discrepancy in electrical conductivity data of amphiboles and to evaluate whether MLD could be caused by metasomatism, we determined the electrical conductivity of a natural metasomatized rock sample. The metasomatized rock sample consists of ~87% diopside pyroxene, ~9% sodium-bearing tremolite amphibole, and ~3% albite feldspar. We This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America.The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.

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confidence: 69%

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confidence: 99%

Electrical conductivity of metasomatized lithology in subcontinental lithosphere

Peng

Manthilake

Mookherjee

2022

American Mineralogist

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“…The light orange region corresponds to the high electrical conductivity of subduction zones from MT observations. The purple solid line represents the electrical conductivity of amphibole at 2.0 GPa (Hu et al, 2018), the magenta dotted line represents the conductivity of epidote (Hu et al, 2017), the light blue hatched region and light blue dashed line indicate the conductivity of antigorite (Reynard et al, 2011; Wang et al, 2017), the red solid line denotes the conductivity of talc (Wang & Karato, 2013), the green dashed line and orange hatched region represent the conductivity of lawsonite (Manthilake et al, 2015; Pommier et al, 2019), the green solid line is the electrical conductivity of chlorite (Manthilake et al, 2016), the gray and pink hatched regions are the electrical conductivity of talc rocks and serpentinite at 3.0 GPa, respectively (X. Guo et al, 2011), and the wine red dashed line is the electrical conductivity of tremolite (Shen et al, 2020). Note that Amp = amphibole, Atg = antigorite, Chl = chlorite, Epi = epidote, Law = lawsonite, Srp = serpentinite, Tr = tremolite, and Tlc = talc.…”

Section: Resultsmentioning

confidence: 99%

Electrical Conductivity of Talc Dehydration at High Pressures and Temperatures: Implications for High‐Conductivity Anomalies in Subduction Zones

Wang

Shen

2020

JGR Solid Earth

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The dehydration of hydrous minerals is one of the causes of high-conductivity anomalies in subduction zones. To determine the origin of these anomalies, the trade-off between the dehydration and conduction mechanisms of hydrous minerals at high pressures and temperatures should be clarified. Talc is a typical hydrous mineral in hot subduction zones, and previous studies may have underestimated its contribution to high-conductivity anomalies. We report the new electrical conductivity results for talc, which were measured at 1.0-4.0 GPa and 523-1293 K using impedance spectroscopy. The pressure effect on conductivity of talc is obvious in the different heating stages. The pressure decreased the conductivity prior to dehydration and remarkably increased the conductivity during dehydration. A sharp conductivity increase was observed beyond the dehydration temperature, and the maximum conductivity was 0.1 S/m. The increase in conductivity associated with a high activation energy of 284.5 ± 11.8 kJ/mol and an activation volume of −6.2 ± 0.6 cm 3 /mol was attributed to an inhomogeneous dehydration model involving cation migration. The talc dehydration temperatures at different pressures derived from the conductivity inflection points are 1023-1093 K. The increased electrical conductivity produced by talc ongoing dehydration provides an explanation for the high-conductivity anomalies observed at deep depths in hot subduction zone. The silica-rich fluid released by talc may contribute to the silica deposition in plate interface and induce the high-conductivity anomalies observed at shallow depths in the hot subduction zones. Plain Language Summary Geophysical observations have revealed many anomalously high electrical conductivity regions in subduction zones. The dehydration of hydrous minerals may induce high-conductivity anomalies in subduction zones, but how the dehydration affects the electrical conductivity remains unclear. We report new results of high-pressure conductivity measurements on talc at 1.0-4.0 GPa and up to 1293 K. We found a sharp conductivity increase above the dehydration temperature, and the maximum conductivity was~0.1 S/m. We also found the increase in conductivity was attributed to cations migration. The experimental results were analyzed to interpret the geophysical observations in subduction zones. We conclude that dehydration provides an explanation for the high-conductivity anomalies observed in some hot subduction zones. These results will enhance our ability to figure out the distribution of hydrous minerals in slabs through interpretation of high-conductivity anomalies in subduction zones.

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“…In a first approximation, by neglecting the contribution of the low-frequency features and any deviation of the experimental data from the semicircular shape, a single R-CPE equivalent circuit could be roughly used to model the mica samples and derive their total (bulk) conductivity as a function of temperature. Oversimplified approaches as the aforementioned one and even the simpler R-C circuit in parallel have often been used to estimate the bulk conductivity of minerals [50][51][52]. However, as the recorded impedance spectra of the mica samples exhibit more complicated spectral features, we are obliged to analyze them in more detail, in order to separate different contributions to the overall bulk conductivity.…”

Section: Experimental Results and Analysismentioning

confidence: 99%

Complex Electrical Conductivity of Biotite and Muscovite Micas at Elevated Temperatures: A Comparative Study

2020

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The unique physicochemical, electrical, mechanical, and thermal properties of micas make them suitable for a wide range of industrial applications, and thus, the interest for these kind of hydrous aluminosilicate minerals is still persistent, not only from a practical but also from a scientific point of view. In the present work, complex impedance spectroscopy measurements were carried out in muscovite and biotite micas, perpendicular to their cleavage planes, over a broad range of frequencies (10−2 Hz to 106 Hz) and temperatures (473–1173 K) that have not been measured so far. Different formalisms of data representation were used, namely, Cole-Cole plots of complex impedance, complex electrical conductivity and electric modulus to analyze the electrical behavior of micas and the electrical signatures of the dehydration/dehydroxylation processes. Our results suggest that ac-conductivity is affected by the structural hydroxyls and the different concentrations of transition metals (Fe, Ti and Mg) in biotite and muscovite micas. The estimated activation energies, i.e., 0.33–0.83 eV for biotite and 0.69–1.92 eV for muscovite, were attributed to proton and small polaron conduction, due to the bound water and different oxidation states of Fe.

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Electrical conductivity of tremolite under high temperature and pressure: implications for the high-conductivity anomalies in the Earth and Venus

Cited by 17 publications

References 60 publications

Electrical conductivity of metasomatized lithology in subcontinental lithosphere

Electrical conductivity of metasomatized lithology in subcontinental lithosphere

Electrical Conductivity of Talc Dehydration at High Pressures and Temperatures: Implications for High‐Conductivity Anomalies in Subduction Zones

Complex Electrical Conductivity of Biotite and Muscovite Micas at Elevated Temperatures: A Comparative Study

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