Electrical conductivity of anhydrous and hydrous gabbroic melt under high temperature and high pressure: implications for the high-conductivity anomalies in the mid-ocean ridge region
<p>The electrical conductivity of gabbroic melt with four different water contents (i.e., 0 %, 2.59 wt %, 5.92 wt %, and 8.32 wt %) was measured at temperatures of 873–1373 K and pressures of 1.0–3.0 GPa using a YJ-3000t multi-anvil high-pressure apparatus and Solartron-1260 impedance spectros...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-08-01
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| Series: | Solid Earth |
| Online Access: | https://se.copernicus.org/articles/14/847/2023/se-14-847-2023.pdf |
| Summary: | <p>The electrical conductivity of gabbroic melt with four different water
contents (i.e., 0 %, 2.59 wt %, 5.92 wt %, and 8.32 wt %) was measured at
temperatures of 873–1373 K and pressures of 1.0–3.0 GPa using a YJ-3000t
multi-anvil high-pressure apparatus and Solartron-1260 impedance
spectroscopy analyzer. At a fixed water content of 2.59 wt %, the
electrical conductivity of the sample slightly decreased with increasing
pressure in the temperature range of 873–1373 K, and its corresponding
activation energy and activation volume were determined as 0.87 <span class="inline-formula">±</span> 0.04 eV and <span class="inline-formula">−</span>1.98 <span class="inline-formula">±</span> 0.02 cm<span class="inline-formula"><sup>3</sup></span> molec.<span class="inline-formula"><sup>−1</sup></span>, respectively. Under the
certain conditions of 873–1373 K and 1.0 GPa, the electrical conductivity of
the gabbroic melts tends to gradually increase with a rise in water content
from 0 wt % to 8.32 wt %, and the activation enthalpy decreases from 0.93 to
0.63 eV accordingly. Furthermore, functional relation models for the
electrical conductivity of gabbroic melts with variations of
temperature, pressure, and water content were constructed at high-temperature
and high-pressure conditions. In addition, the dependence
relation of the electrical conductivity of melts with the degree of
depolymerization was explored under conditions of four different water
contents at 1373 K and 1.0 GPa, and three previously available reported
results on those of representative calc-alkaline igneous rock melts (i.e.,
dacitic melt, basaltic melt, and andesitic melt) were compared in detail. In
combination with our presently acquired electrical
conductivity data on gabbroic melt with four different water contents and
the available data on polycrystalline olivine, the electrical conductivity
of a gabbroic melt–olivine system with variation of the volume percentage of
anhydrous and hydrous melts was successfully constructed by using the
typical Hashin–Shtrikman upper-bound model. In light of the electrical
conductivity of the gabbroic melt–olivine system with previous magnetotelluric (MT) results,
we find that anhydrous and hydrous gabbroic melts can be employed to
reasonably interpret the high-conductivity anomalies in the Mohns Ridge of
the Arctic Ocean.</p> |
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| ISSN: | 1869-9510 1869-9529 |