Thomson, Andrew;
Hao, Ming;
Pommier, Anne;
(2024)
Electrical Conductivity and Sound Velocities of Talc Under High Pressure and High Temperature Conditions and Application to the Subducting Cocos Plate.
Journal of Geophysical Research: Solid Earth
, 129
(11)
, Article e2024JB029824. 10.1029/2024JB029824.
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Abstract
Talc is expected to be an important water carrier in Earth's upper mantle, and understanding its electrical and seismic properties under high pressure and temperature conditions is required to detect possible talc-rich regions in subduction zones imaged using geophysical observations. We conducted acoustic and electrical experiments on natural talc aggregates at relevant pressure-temperature conditions. Compressional wave velocity (Vp) was measured using ultrasonic interferometry in a Paris-Edinburgh press at pressures up to 3.4 GPa and temperatures up to 873 K. Similar Vp values are obtained regardless of the initial crystallographic preferred orientation of the samples, which can be explained by talc grain reorientation during the experiment, with the (001) plane becoming perpendicular to the uniaxial compression axis. Electrical conductivity of the same starting material was determined using impedance spectroscopy in a multi-anvil press up to 6 GPa and 1263 K. Two conductivity jumps are observed, at ∼860–1025 K and ∼940–1080 K, depending on pressure, and interpreted as talc dehydroxylation and decomposition, respectively. Electrical anisotropy is observed at low temperature and decreases with increasing pressure (∼10 at 1.5 GPa and ∼2 at 3.5 GPa). Comparison of acoustic and electrical results with geophysical observations in central Mexico supports the presence of a talc-bearing layer atop the subducted Cocos plate.
| Type: | Article |
|---|---|
| Title: | Electrical Conductivity and Sound Velocities of Talc Under High Pressure and High Temperature Conditions and Application to the Subducting Cocos Plate |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1029/2024JB029824 |
| Publisher version: | https://doi.org/10.1029/2024JB029824 |
| Language: | English |
| Additional information: | This version is the author accepted manuscript. For information on re-use, please refer to the publisher's terms and conditions. |
| Keywords: | talc, seismic velocity, electrical conductivity, dehydration, Cocos plate, central Mexico |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10200382 |
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