In order to understand the role of serpentine minerals in the global carbon cycle, high-pressure X-ray diffraction (XRD) experiments were performed on chrysotile (Mg3Si2O5(OH)4) using carbon dioxide (CO2) as a pressure medium. Synchrotron XRD patterns revealed the formation of magnesite and high-pressure chrysotile after heating at 170 °C for 1 h at 2.5(1) GPa. The Rietveld refinement suggests that the unit cell composition of the original chrysotile changes to Mg2.4(1)Si2O5(OH)2.4(1) upon the formation of magnesite, which appears to be driven by the dehydrogenation of the innermost hydroxyl group, OH3, and the rearrangement of magnesium (Mg) at the M1 site, leading to the formation of metastable monodehydroxylated chrysotile. Metastable chrysotile is observed up to 5.0(1) GPa and 500 °C, which corresponds to the slab Moho geotherms for the South Sumatra and Ryukyu subduction zone. After recovery to ambient conditions, the characteristic fibrous morphology of the original chrysotile was found to have changed to an earthy form. These results can help us to understand deep carbon cycling along the subduction zones, and may prompt the design of a novel method of asbestos detoxification using pressure and temperature.
Bibliographical noteFunding Information:
This research was supported by the project Crustal Evolution of Victoria Land, Antarctica and Formative Process of Planets (20140409 and PM18030) funded by the Ministry of Ocean and Fisheries, Korea. The authors also thank the partial supports by the Leader Researcher program (NRF-2018R1A3B1052042) of the Korean Ministry of Science and ICT and the NRF grant 2016K1A4A3914691.
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All Science Journal Classification (ASJC) codes
- Computer Science(all)
- Environmental Engineering
- Chemical Engineering(all)
- Materials Science (miscellaneous)
- Energy Engineering and Power Technology