@article{5ed88e8698b5426699cc93dc8c6b2b00,
title = "Phase transformation of hydrous ringwoodite to the lower-mantle phases and the formation of dense hydrous silica",
abstract = "To understand the effects of H2O on the mineral phases forming under the pressure-temperature conditions of the lower mantle, we have conducted laser-heated diamond-anvil cell experiments on hydrous ringwoodite (Mg2SiO4 with 1.1 wt% H2O) at pressures between 29 and 59 GPa and temperatures between 1200 and 2400 K. Our results show that hydrous ringwoodite (hRw) converts to crystalline dense hydrous silica, stishovite (Stv) or CaCl2-type SiO2 (mStv), containing 1 wt% H2O together with Brd and MgO at the pressure-temperature conditions expected for shallow lower-mantle depths between approximately 660 to 1600 km. Considering the lack of sign for melting in our experiments, our preferred interpretation of the observation is that Brd partially breaks down to dense hydrous silica and periclase (Pc), forming the phase assembly Brd + Pc + Stv. The results may provide an explanation for the enigmatic coexistence of Stv and Fp inclusions in lower-mantle diamonds.",
keywords = "Bridgmanite, Mantle, Periclase, Ringwoodite, Stishovite, Volatile Elements in Differentiated Planetary Interiors, Water",
author = "Huawei Chen and Kurt Leinenweber and Vitali Prakapenka and Martin Kunz and Bechtel, {Hans A.} and Zhenxian Liu and Shim, {Sang Heon}",
note = "Funding Information: We thank two anonymous reviewers and the editor. This work was supported by NSF grants (EAR1321976 and EAR1401270) and NASA grant (80NSSC18K0353) to S.H.S. H.C. has been supported by the Keck foundation (PI: P. Buseck). The results reported herein benefit from collaborations and/ or information exchange within NASA{\textquoteright}s Nexus for Exoplanet System Science (NExSS) research coordination network sponsored by NASA{\textquoteright}s Science Mission Directorate. We acknowledge the use of facilities within the Eyring Materials Center at Arizona State University. The synchrotron experiments were conducted at GSECARS, Advanced Photon Source (APS), Advanced Light Source (ALS), and National Synchrotron Light Source (NSLS). GSECARS is supported by NSF-Earth Science (EAR-1128799) and DOE-GeoScience (DE-FG02-94ER14466). The Multi-Anvil Cell Assembly Project, DAC gas loading, and the U2A beamline at the NSLS are supported by COMPRES under NSF EAR 11-43050. APS, ALS, and NSLS are supported by DOE, under contracts DE-AC02-06CH11357, DE-AC02-05CH11231, and DE-SC0012704, respectively. The experimental data for this paper are available by contacting SHDShim@asu.edu or hchen156@asu.edu. Funding Information: We thank two anonymous reviewers and the editor. This work was supported by NSF grants (EAR1321976 and EAR1401270) and NASA grant (80NSSC18K0353) to S.H.S. H.C. has been supported by the Keck foundation (PI: P. Buseck). The results reported herein benefit from collaborations and/ or information exchange within NASA's Nexus for Exoplanet System Science (NExSS) research coordination network sponsored by NASA's Science Mission Directorate. We acknowledge the use of facilities within the Eyring Materials Center at Arizona State University. The synchrotron experiments were conducted at GSECARS, Advanced Photon Source (APS), Advanced Light Source (ALS), and National Synchrotron Light Source (NSLS). GSECARS is supported by NSF-Earth Science (EAR-1128799) and DOE-GeoScience (DE-FG02-94ER14466). The Multi-Anvil Cell Assembly Project, DAC gas loading, and the U2A beamline at the NSLS are supported by COMPRES under NSF EAR 11-43050. APS, ALS, and NSLS are supported by DOE, under contracts DE-AC02-06CH11357, DEAC02-05CH11231, and DE-SC0012704, respectively. The experimental data for this paper are available by contacting SHDShim@asu.edu or hchen156@asu.edu. Publisher Copyright: {\textcopyright} 2020 De Gruyter. All rights reserved.",
year = "2020",
month = sep,
day = "25",
doi = "10.2138/am-2020-7261",
language = "English (US)",
volume = "105",
pages = "1342--1348",
journal = "American Mineralogist",
issn = "0003-004X",
publisher = "Mineralogical Society of America",
number = "9",
}