High-pressure phase transitions of clinoenstatite

Lazarz, John D.; Dera, Przemyslaw; Hu, Yi; Meng, Yue; Bina, Craig R.; Jacobsen, Steven D.

doi:10.2138/am-2019-6740

Title: High-pressure phase transitions of clinoenstatite

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Abstract

Clinoenstatite (Mg₂Si₂O₆) undergoes a well-known phase transition from a low-pressure form (LPCEN, space group P2₁/c) to a high-pressure form (HPCEN, space group C2/c) at similar to ~ 6 GPa. High-pressure structure refinements of HPCEN were carried out based on single-crystal X-ray diffraction experiments between 9.5 and 35.5 GPa to determine its P-V equation of state and structural evolution over an expanded pressure range relevant to pyroxene metastability. The best-fit isothermal equation of state to our data combined with the five data points between 5.34 and 7.93 GPa from Angel and Hugh-Jones (1994) yields a second-order Birch-Murnaghan equation with K_T0 = 121(2) GPa and V₀ = 403.9(5) Å³ (with $$K^{'}_{T0}$$ = 4 implied). Further reduction of misfit upon fitting a third-order Birch-Murnaghan equation is not significant at the 90% confidence level. At ~45 GPa, a transition from HPCEN to a P21/c-structured polymorph (HPCEN2) was observed in our study, which is isostructural to the P2₁/c phase recently observed in diopside (CaMgSi₂O₆) at 50 GPa (Plonka et al. 2012) and in clinoferrosilite (Fe₂Si₂O₆) at 30–36 GPa (Pakhomova et al. 2017). Observation of HPCEN2 in Mg₂Si₂O₆ completes the third apex of the pyroxene quadrilateral wherein HPCEN2 is found, facilitating a broader view of clinopyroxene crystal chemistry at conditions relevant to metastability in the Earth’s mantle along cold subduction geotherms.

Authors:

Lazarz, John D. ^[1]; Dera, Przemyslaw ^[2]; Hu, Yi ^[3]; Meng, Yue ^[4]; Bina, Craig R. ^[5]; Jacobsen, Steven D. ^[5]

Northwestern Univ., Evanston, IL (United States). Dept. of Earth and Planetary Sciences; Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Univ. of Hawai'i at Manoa, Honolulu, HI (United States). School of Ocean and Earth Science and Technology, Hawaii Inst. of Geophysics and Planetology
Univ. of Hawai'i at Manoa, Honolulu, HI (United States). School of Ocean and Earth Science and Technology, Hawaii Inst. of Geophysics and Planetology and Dept. of Geology and Geophysics
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Proton Source, HPCAT
Northwestern Univ., Evanston, IL (United States). Dept. of Earth and Planetary Sciences

Publication Date:: Sat Jun 01 00:00:00 EDT 2019

Research Org.:: Argonne National Lab. (ANL), Argonne, IL (United States); George Washington Univ., Washington, DC (United States)

Sponsoring Org.:: National Science Foundation (NSF); USDOE Office of Science (SC); Carnegie/DOE Alliance Center (CDAC); USDOE National Nuclear Security Administration (NNSA), Office of Defense Programs (DP)

OSTI Identifier:: 1542639

Alternate Identifier(s):: OSTI ID: 1599885

Grant/Contract Number:: AC02-06CH11357; NA0003858

Resource Type:: Accepted Manuscript

Journal Name:: American Mineralogist

Additional Journal Information:: Journal Volume: 104; Journal Issue: 6; Journal ID: ISSN 0003-004X

Publisher:: Mineralogical Society of America

Country of Publication:: United States

Language:: English

Subject:: 58 GEOSCIENCES; MgSiO3; clinoenstatite; enstatite; pyroxene; single-crystal X-ray diffraction

Citation Formats


                    Lazarz, John D., Dera, Przemyslaw, Hu, Yi, Meng, Yue, Bina, Craig R., and Jacobsen, Steven D. High-pressure phase transitions of clinoenstatite.  United States: N. p., 2019. 
Web.  doi:10.2138/am-2019-6740.

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                    Lazarz, John D., Dera, Przemyslaw, Hu, Yi, Meng, Yue, Bina, Craig R., & Jacobsen, Steven D. High-pressure phase transitions of clinoenstatite.  United States.  https://doi.org/10.2138/am-2019-6740

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                    Lazarz, John D., Dera, Przemyslaw, Hu, Yi, Meng, Yue, Bina, Craig R., and Jacobsen, Steven D. Sat .  
"High-pressure phase transitions of clinoenstatite".  United States.  https://doi.org/10.2138/am-2019-6740.  https://www.osti.gov/servlets/purl/1542639.

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@article{osti_1542639,

  title        = {High-pressure phase transitions of clinoenstatite},

  author       = {Lazarz, John D. and Dera, Przemyslaw and Hu, Yi and Meng, Yue and Bina, Craig R. and Jacobsen, Steven D.},

  abstractNote = {Clinoenstatite (Mg2Si2O6) undergoes a well-known phase transition from a low-pressure form (LPCEN, space group P21/c) to a high-pressure form (HPCEN, space group C2/c) at similar to ~ 6 GPa. High-pressure structure refinements of HPCEN were carried out based on single-crystal X-ray diffraction experiments between 9.5 and 35.5 GPa to determine its P-V equation of state and structural evolution over an expanded pressure range relevant to pyroxene metastability. The best-fit isothermal equation of state to our data combined with the five data points between 5.34 and 7.93 GPa from Angel and Hugh-Jones (1994) yields a second-order Birch-Murnaghan equation with KT0 = 121(2) GPa and V0 = 403.9(5) Å3 (with $K^{'}_{T0}$ = 4 implied). Further reduction of misfit upon fitting a third-order Birch-Murnaghan equation is not significant at the 90% confidence level. At ~45 GPa, a transition from HPCEN to a P21/c-structured polymorph (HPCEN2) was observed in our study, which is isostructural to the P21/c phase recently observed in diopside (CaMgSi2O6) at 50 GPa (Plonka et al. 2012) and in clinoferrosilite (Fe2Si2O6) at 30–36 GPa (Pakhomova et al. 2017). Observation of HPCEN2 in Mg2Si2O6 completes the third apex of the pyroxene quadrilateral wherein HPCEN2 is found, facilitating a broader view of clinopyroxene crystal chemistry at conditions relevant to metastability in the Earth’s mantle along cold subduction geotherms.},

  doi          = {10.2138/am-2019-6740},

  journal      = {American Mineralogist},

  number       = 6,

  volume       = 104,

  place        = {United States},

  year         = {Sat Jun 01 00:00:00 EDT 2019},

  month        = {Sat Jun 01 00:00:00 EDT 2019}

}

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