Abstract
The experimental study on the electrical conductivities of schists with various contents of alkali ions (CA = K2O + Na2O = 3.94, 5.17, and 5.78 wt.%) were performed at high temperatures (623–1073 K) and high pressures (0.5–2.5 GPa). Experimental results indicated that the conductivities of schist markedly increased with the rise of temperature. Pressure influence on the conductivities of schist was extremely weak at the entire range of experimental temperatures. Alkali ion content has a significant influence on the conductivities of the schist samples in a lower temperature range (623–773 K), and the influence gradually decreases with increasing temperature in a higher temperature range (823–1073 K). In addition, the activation enthalpies for the conductivities of three schist samples were fitted as being 44.16–61.44 kJ/mol. Based on the activation enthalpies and previous studies, impurity alkaline ions (K+ and Na+) were proposed as the charge carriers of schist. Furthermore, electrical conductivities of schist (10−3.5–10−1.5 S/m) were lower than those of high-conductivity layers under the Tibetan Plateau (10−1–100 S/m). It was implied that the presence of schist cannot cause the high-conductivity anomalies in the middle to lower crust beneath the Tibetan Plateau.
Highlights
Electrical conductivity of geological material combined with magnetotelluric (MT) data is very significant in exploring material compositions and temperature–pressure conditions in the
The mineral compositions in the schist samples were detected by the scanning electron microscope (SEM) at the State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences (CAS), Guiyang, China
The major element content of the schist samples was analyzed by X-ray fluorescence (XRF) by Australian Laboratory Services, Shanghai, China
Summary
Electrical conductivity of geological material combined with magnetotelluric (MT) data is very significant in exploring material compositions and temperature–pressure conditions in theEarth’s interior. Electrical conductivity of geological material combined with magnetotelluric (MT) data is very significant in exploring material compositions and temperature–pressure conditions in the. For most dominant minerals and rocks of the Earth’s crust, upper mantle, and transition zone, the electrical properties have been researched in detail [1,2,3,4,5,6,7,8,9,10,11]. A large amount of metamorphic rocks was widely distributed in the surface of Tibetan Plateau [12,13,14], recording the past geological processes at different depths of the subduction zone. Electrical conductivity, an important physical parameter, can be applied to reveal the material compositions and thermodynamic state beneath the Tibetan Plateau.
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