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Electrical Conductivity of Omphacite as a Function of Water Content and Implications for High Conductivity Anomalies in the Dabie‐Sulu UHPM Belts and Tibet
- Source :
- Journal of Geophysical Research: Solid Earth. 124:12523-12536
- Publication Year :
- 2019
- Publisher :
- American Geophysical Union (AGU), 2019.
-
Abstract
- Magnetotelluric surveys revealed high‐conductivity layers in the lower crust beneath Tibet and in the shallow part of the upper mantle relevant to continental collision extending to the Dabie‐Sulu ultrahigh‐pressure metamorphic (UHPM) belts of eastern China, which have been interpreted by the presence of aqueous fluids/partial melts or hydrous phases. However, these explanations are not consistent with their petrological features and seismic properties. Hydrogen‐bearing omphacite could be a probable candidate to explain such high‐conductivity anomalies due to its high water‐partitioning coefficient versus coexisting garnet in eclogite. In this study, we investigated electrical conductivities of Fe‐free and Fe‐bearing omphacite as a function of water content (0.005–0.122 wt.%) at 3 GPa and 500–1300 K. Our results show that water significantly enhances the electrical conductivity of omphacite, while iron facilitates conductivity by accelerating hydrogen diffusivity and lowering its activation enthalpy. Assuming a heat flow of 70 mW/m2, the high electrical anomalies observed beneath the Dabie‐Sulu UHPM belts and the Tibetan Plateau can be reasonably explained by omphacite containing 0.07 wt.% water since water content higher than 0.07 wt.% in omphacite was frequently reported in naturally collected eclogite.
- Subjects :
- geography
Plateau
geography.geographical_feature_category
Continental collision
Metamorphic rock
Crust
Conductivity
engineering.material
Geophysics
Space and Planetary Science
Geochemistry and Petrology
Electrical resistivity and conductivity
Earth and Planetary Sciences (miscellaneous)
engineering
Eclogite
Omphacite
Petrology
Geology
Subjects
Details
- ISSN :
- 21699356 and 21699313
- Volume :
- 124
- Database :
- OpenAIRE
- Journal :
- Journal of Geophysical Research: Solid Earth
- Accession number :
- edsair.doi...........f3f4eed1c0070c6f2f7af5ee455405ba