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Local structure variations observed in orthoenstatite at high pressures

Zhang, Dongzhou and Jackson, Jennifer M. and Sturhahn, Wolfgang and Xiao, Yuming (2011) Local structure variations observed in orthoenstatite at high pressures. American Mineralogist, 96 (10). pp. 1585-1592. ISSN 0003-004X.

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The site-specific behavior of iron in an orthoenstatite-structured ^(57)Fe-enriched (M1)(M2)Si_(2)O_(6) powdered sample was explored using synchrotron Mössbauer spectroscopy and diamond-anvil cells in two independent experiments at ambient temperature. In one experiment, NaCl was used as the pressure-transmitting medium (ambient pressure to 36 GPa), and in the other experiment, Ne surrounded the sample (4.1 to 26.8 GPa). The hyperfine parameters of the M1 and M2 sites at room pressure are in excellent agreement with previous literature values obtained using conventional Mössbauer spectroscopy and yield (Mg_(0.980)Fe_(0.020(5))(Mg_(0.760)Fe_(0.240))Si_(2)O_6 as the chemical formula. Analyses of both data sets reveal a change in the trend or discontinuity in the hyperfine parameters around 10 GPa, indicative of a transformation in orthopyroxene. However, the detailed behaviors of the iron sites with pressure appear to depend on the local stress conditions provided by the different pressure media. Our observations may help explain the reported variations in structural transition behavior for orthopyroxenes at high pressures.

Item Type:Article
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URLURL TypeDescription
Zhang, Dongzhou0000-0002-6679-892X
Jackson, Jennifer M.0000-0002-8256-6336
Sturhahn, Wolfgang0000-0002-9606-4740
Additional Information:© 2011 Mineralogical Society of America. Manuscript received: October 14, 2010; manuscript accepted: June 17, 2011; manuscript handled by Jennifer Kung. We thank E.A. Hamecher, C.A. Murphy, and J.K. Wicks for help in conducting experiments, Y. Fei for synthesizing the sample, and the following for support: NSF-EAR-0711542, CAREER EAR-0956166, and Caltech. Use of the Advanced Photon Source was supported by the U.S. D.O.E., O.S., O.B.E.S. (DE-AC02-06CH11357). Sector 3 operations and the gas-loading system at GSE-CARS are supported in part by COMPRES under NSF Cooperative Agreement EAR 06-49658. Use of HPCAT is supported by DOE-BES, DOE-NNSA, NSF, and the W.M. Keck Foundation. We thank Jennifer Kung for handling our manuscript and an anonymous reviewer for helpful comments.
Funding AgencyGrant Number
Department of Energy (DOE)DE-AC02-06CH11357
NSF Cooperative AgreementEAR 06-49658
Department of Energy (DOE) Basic Energy Sciences (BES)UNSPECIFIED
Department of Energy (DOE) NNSAUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:Orthoenstatite; pyroxene; upper mantle; Mössbauer spectroscopy; nuclear resonant scattering
Issue or Number:10
Record Number:CaltechAUTHORS:20111031-111356518
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:27521
Deposited By: Jason Perez
Deposited On:31 Oct 2011 21:08
Last Modified:24 Jan 2020 17:58

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