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American Mineralogist

Journal of Earth and Planetary Materials

Ed. by Baker, Don / Xu, Hongwu / Swainson, Ian


IMPACT FACTOR 2017: 2.645

CiteScore 2017: 2.31

SCImago Journal Rank (SJR) 2017: 1.440
Source Normalized Impact per Paper (SNIP) 2017: 1.059

Online
ISSN
1945-3027
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Volume 88, Issue 10

Issues

Structural systematics of hydrous ringwoodite and water in earth’s interior

Joseph R. Smyth / Christopher M. Holl / Daniel J. Frost / Steven D. Jacobsen / Falko Langenhorst / Catherine A. McCammon
Published Online: 2015-03-31 | DOI: https://doi.org/10.2138/am-2003-1001

Abstract

Seven separate samples of hydrous ringwoodite with compositions ranging from Fo100 to Fo89 and hydrogen contents from 0.2 to 1.1 wt% were synthesized in the 5000 ton multi-anvil press at the Bayerisches Geoinstitut. Synthesis conditions ranged from 18 to 22 GPa and 1400 to 1500 °C. The crystals were characterized by single-crystal X-ray diffraction, electron microprobe, IR and Mössbauer spectroscopy, and by analytical and high-resolution transmission electron microscopy. The crystals are optically isotropic, and the Fe-bearing samples are deep blue in color. Mössbauer spectroscopy and ELNE spectroscopy applied to the Fe-bearing samples indicates about 10% of the iron is in the ferric state. High-resolution TEM examination of one of the Fe-bearing samples indicates that the crystals are homogeneous and free of significant inclusions or exsolution features. Infrared spectra show a broad absorption band extending from about 2500 to 3600 cm-1 with maxima ranging from 3105 for the pure magnesian samples to 3150 cm-1 for the Fo89 samples. The crystal structures of the seven ringwoodite samples were refined by X-ray single-crystal diffraction. Refinement of cation site occupancies indicates full occupancy of the tetrahedral site for all samples, whereas the occupancy of the octahedral site appears to decrease systematically with H content. The principal hydration mechanism involves octahedral cation vacancies. The IR spectra are consistent with protonation of the short O-O approach on the tetrahedral edge, which would imply partial Mg-Si disorder.

About the article

Received: 2002-08-24

Accepted: 2002-12-27

Published Online: 2015-03-31

Published in Print: 2003-10-01


Citation Information: American Mineralogist, Volume 88, Issue 10, Pages 1402–1407, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am-2003-1001.

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© 2015 by Walter de Gruyter Berlin/Boston.

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