Phase transformation of hydrous ringwoodite to the lower-mantle phases and the formation of dense hydrous silica

Chen, Huawei; Leinenweber, Kurt; Prakapenka, Vitali; Kunz, Martin; Bechtel, Hans A.; Liu, Zhenxian; Shim, Sang-Heon

doi:10.2138/am-2020-7261

Title: Phase transformation of hydrous ringwoodite to the lower-mantle phases and the formation of dense hydrous silica

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Abstract

In order 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 1.1wt% H₂O) at pressures between 29 and 59 GPa and temperatures between 1200 and 2400 K. Our experimental 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 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 Brd + Pc + Stv mineralogy. Our experiments may provide an explanation for the enigmatic coexistence of Stv and Fp inclusions in lower-mantle diamonds

Authors:

Chen, Huawei ^[1]; Leinenweber, Kurt ^[1]; Prakapenka, Vitali ^[2]; Kunz, Martin ^[3]; Bechtel, Hans A. ^[3]; Liu, Zhenxian ^[4];

^[1]

Arizona State Univ., Tempe, AZ (United States)
Univ. of Chicago, IL (United States)
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Carnegie Inst. of Washington, Washington, DC (United States)

Publication Date:: Sun Sep 20 00:00:00 EDT 2020

Research Org.:: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Sponsoring Org.:: USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:: 1780748

Grant/Contract Number:: AC02-05CH11231

Resource Type:: Accepted Manuscript

Journal Name:: American Mineralogist

Additional Journal Information:: Journal Volume: 105; Journal Issue: 9; Journal ID: ISSN 0003-004X

Publisher:: Mineralogical Society of America

Country of Publication:: United States

Language:: English

Subject:: 58 GEOSCIENCES; stishovite; ringwoodite; bridgmanite; periclase; water; mantle

Citation Formats


                    Chen, Huawei, Leinenweber, Kurt, Prakapenka, Vitali, Kunz, Martin, Bechtel, Hans A., Liu, Zhenxian, and Shim, Sang-Heon. Phase transformation of hydrous ringwoodite to the lower-mantle phases and the formation of dense hydrous silica.  United States: N. p., 2020. 
Web.  doi:10.2138/am-2020-7261.

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                    Chen, Huawei, Leinenweber, Kurt, Prakapenka, Vitali, Kunz, Martin, Bechtel, Hans A., Liu, Zhenxian, & Shim, Sang-Heon. Phase transformation of hydrous ringwoodite to the lower-mantle phases and the formation of dense hydrous silica.  United States.  https://doi.org/10.2138/am-2020-7261

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                    Chen, Huawei, Leinenweber, Kurt, Prakapenka, Vitali, Kunz, Martin, Bechtel, Hans A., Liu, Zhenxian, and Shim, Sang-Heon. Sun .  
"Phase transformation of hydrous ringwoodite to the lower-mantle phases and the formation of dense hydrous silica".  United States.  https://doi.org/10.2138/am-2020-7261.  https://www.osti.gov/servlets/purl/1780748.

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@article{osti_1780748,

  title        = {Phase transformation of hydrous ringwoodite to the lower-mantle phases and the formation of dense hydrous silica},

  author       = {Chen, Huawei and Leinenweber, Kurt and Prakapenka, Vitali and Kunz, Martin and Bechtel, Hans A. and Liu, Zhenxian and Shim, Sang-Heon},

  abstractNote = {In order 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 1.1wt% H2O) at pressures between 29 and 59 GPa and temperatures between 1200 and 2400 K. Our experimental 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 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 Brd + Pc + Stv mineralogy. Our experiments may provide an explanation for the enigmatic coexistence of Stv and Fp inclusions in lower-mantle diamonds},

  doi          = {10.2138/am-2020-7261},

  journal      = {American Mineralogist},

  number       = 9,

  volume       = 105,

  place        = {United States},

  year         = {Sun Sep 20 00:00:00 EDT 2020},

  month        = {Sun Sep 20 00:00:00 EDT 2020}

}

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