Electrical conductivity of wadsleyite at high temperatures and high pressures

Dai, Lidong; Karato, Shun‐ichiro

doi:10.1016/j.epsl.2009.08.012

Cited by 104 publications

(82 citation statements)

References 29 publications

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“…7). Although previous studies have examined the electrical conductivity of the (dry) dominant minerals in the upper mantle (e.g., olivine, pyroxene, and garnet) and assessed their pressure dependences (Xu et al 2000a;Dai et al 2005Dai et al , 2009a, no study has assessed the influence of pressure on the electrical conductivity of hydrous minerals. According to Eq.…”

Section: Influence Of Pressure and Chemical Compositionmentioning

confidence: 99%

“…Previous measurements of the electrical conductivity of garnet only considered the effect of chemical composition or water content (Romano et al 2006;Dai and Karato 2009c). Recently, a novel technique has been established to control oxygen fugacity during high-pressure conductivity measurements using the Kawai-1000t multi-anvil apparatus at Yale University (USA) and using the YJ-3000t equipment at the Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China Dai and Karato 2009a).…”

Section: Introductionmentioning

confidence: 99%

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The effect of chemical composition and oxygen fugacity on the electrical conductivity of dry and hydrous garnet at high temperatures and pressures

Dai

et al. 2011

Contrib Mineral Petrol

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The in situ electrical conductivity of hydrous garnet samples (Py 20 Alm 76 Grs 4 -Py 73 Alm 14 Grs 13 ) was determined at pressures of 1.0-4.0 GPa and temperatures of 873-1273 K in the YJ-3000t apparatus using a Solartron-1260 impedance/gain-phase analyzer for various chemical compositions and oxygen fugacities. The oxygen fugacity was controlled by five solid-state oxygen buffers ). Experimental results indicate that within a frequency range from 10 -2 to 10 6 Hz, electrical conductivity is strongly dependent on signal frequency. Electrical conductivity shows an Arrhenius increase with temperature. At 2.0 GPa, the electrical conductivity of anhydrous garnet single crystals with various chemical compositions (Py 20 Alm 76 Grs 4 , Py 30 Alm 67 Grs 3 , Py 56 Alm 43 Grs 1 , and Py 73 Alm 14 Grs 13 ) decreases with increasing pyrope component (Py). With increasing oxygen fugacity, the electrical conductivity of dry Py 73 Alm 14 Grs 13 garnet single crystal shows an increase, whereas that of a hydrous sample with 465 ppm water shows a decrease, both following a power law (exponents of 0.061 and -0.071, respectively). With increasing pressure, the electrical conductivity of this hydrous garnet increases, along with the pre-exponential factors, and the activation energy and activation volume of hydrous samples are 0.7731 ± 0.0041 eV and -1.4 ± 0.15 cm 3 /mol, respectively. The results show that small hopping polarons Fe Á Mg andprotons (H Á ) are the dominant conduction mechanisms for dry and wet garnet single crystals, respectively. Based on these results and the effective medium theory, we established the electrical conductivity of an eclogite model with different mineral contents at high temperatures and high pressures, thereby providing constraints on the inversion of field magnetotelluric sounding results in future studies.

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Section: Influence Of Pressure and Chemical Compositionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The effect of chemical composition and oxygen fugacity on the electrical conductivity of dry and hydrous garnet at high temperatures and pressures

Dai

et al. 2011

Contrib Mineral Petrol

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“…Based on these studies, the water storage capacity in the upper mantle and transition zone has been estimated [Hirschmann et al, 2005]. Constraints on the water content in these regions were also inferred based on the results of electrical conductivity measurements on olivine [Wang et al, 2006], orthopyroxene [Dai and Karato, 2009b], wadsleyite and ringwoodite [Dai and Karato, 2009c;Huang et al, 2005]. However, these studies are incomplete since these minerals occupy only $40-80% of these regions, and the robustness of results of these studies hinges upon the degree to which the remaining mineral phases influence the hydrogen solubility and distribution.…”

Section: Introductionmentioning

confidence: 99%

Solubility of water in pyrope‐rich garnet at high pressures and temperature

Mookherjee

Karato

2010

Geophysical Research Letters

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[1] The water solubility in pyrope-rich garnet was determined between pressures of 5-9 GPa and temperatures of 1373 -1473 K under silica activity and oxygen fugacity similar to those expected in the Earth's upper mantle. We found that pyrope-rich garnet has substantial water solubility up to $0.1 wt% under these conditions. In addition, the water content in garnet varied as a function of chemical conditions. In particular, the variation in water fugacity (and Mg#) caused a variation in water partitioning with olivine (D H 2 O ol/py ). The substantial water solubility in pyrope-rich garnet under deep upper mantle conditions might have significant influence on physical and transport properties.Citation: Mookherjee, M., and S. Karato (2010), Solubility of water in pyrope-rich garnet at high pressures and temperature, Geophys. Res. Lett., 37, L03310,

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“…Current knowledge of mantle mineral conductivity with dissolved hydrogen is focused on olivine -the major phase (60%) in the upper mantle -due to a lack of compelling data on the conductivity of other nominally anhydrous phases, such as pyroxenes, for upper mantle conditions [Dai and Karato, 2009]. Such focus limits most MT studies to assume that hydrous olivine is the dominant conducting phase when considering a subsolidus mechanism.…”

Section: Dissolved H2o Contributionmentioning

confidence: 99%

Geophysical and petrological constraints on ocean plate dynamics

Sarafian¹

2017

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This thesis investigates the formation and subsequent motion of oceanic lithospheric plates through geophysical and petrological methods. Ocean crust and lithosphere forms at mid-ocean ridges as the underlying asthenosphere rises, melts, and flows away from the ridge axis. In Chapters 2 and 3, I present the results from partial melting experiments of mantle peridotite that were conducted in order to examine the mantle melting point, or solidus, beneath a mid-ocean ridge. Chapter 2 determines the peridotite solidus at a single pressure of 1.5 GPa and concludes that the oceanic mantle potential temperature must be ~60 ºC hotter than current estimates. Chapter 3 goes further to provide a more accurate parameterization of the anhydrous mantle solidus from experiments over a range of pressures. This chapter concludes that the range of potential temperatures of the mantle beneath mid-ocean ridges and plumes is smaller than currently estimated. Once formed, the oceanic plate moves atop the underlying asthenosphere away from the ridge axis. Chapter 4 uses seafloor magnetotelluric data to investigate the mechanism responsible for plate motion at the lithosphere-asthenosphere boundary. The resulting two dimensional conductivity model shows a simple layered structure. By applying petrological constraints, I conclude that the upper asthenosphere does not contain substantial melt, which suggests that either a thermal or hydration mechanism supports plate motion. Oceanic plate motion has dramatically changed the surface of the Earth over time, and evidence for ancient plate motion is obvious from detailed studies of the longer lived continental lithosphere. In Chapter 5, I investigate past plate motion by inverting magnetotelluric data collected over eastern Zambia. The conductivity model probes the Zambian lithosphere and reveals an ancient subduction zone previously suspected from surface studies. This chapter elucidates the complex lithospheric structure of eastern Zambia and the geometry of the tectonic elements in the region, which collided as a result of past oceanic plate motion. Combined, the chapters of this thesis provide critical constraints on ocean plate dynamics.

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Electrical conductivity of wadsleyite at high temperatures and high pressures

Cited by 104 publications

References 29 publications

The effect of chemical composition and oxygen fugacity on the electrical conductivity of dry and hydrous garnet at high temperatures and pressures

The effect of chemical composition and oxygen fugacity on the electrical conductivity of dry and hydrous garnet at high temperatures and pressures

Solubility of water in pyrope‐rich garnet at high pressures and temperature

Geophysical and petrological constraints on ocean plate dynamics

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