Sound velocities of Na0.4Mg0.6Al1.6Si0.4O4 NAL and CF phases to 73 GPa determined by Brillouin scattering method

Lidong Dai, Yuki Kudo, Kei Hirose, Motohiko Murakami, Yuki Asahara, Haruka Ozawa, Yasuo Ohishi, Naohisa Hirao

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    13 Citations (Scopus)

    Abstract

    The sound velocities of two aluminum-rich phases in the lower mantle, hexagonal new Al-rich phase (NAL) and its corresponding high-pressure polymorph orthorhombic Ca-ferrite-type phase (CF), were determined with the Brillouin scattering method in a pressure range from 9 to 73 GPa at room temperature. Both NAL and CF samples have identical chemical composition of Na0. 4Mg0. 6Al1. 6Si0. 4O4 (40 % NaAlSiO4-60 % MgAl2O4). Infrared laser annealing in the diamond anvil cell was performed to minimize the stress state of the sample and obtain the high-quality Brillouin spectra. The results show shear modulus at zero pressure G0 = 121. 960 ± 0. 087 GPa and its pressure derivative G' = 1. 961 ± 0. 009 for the NAL phase, and G0 = 129. 653 ± 0. 059 GPa and G' = 2. 340 ± 0. 004 for the CF phase. The zero-pressure shear velocities of the NAL and CF phases are obtained to be 5. 601 ± 0. 005 km/sec and 5. 741 ± 0. 001 km/sec, respectively. We also found that shear velocity increases by 2. 5 % upon phase transition from NAL to CF at around 40 GPa.

    Original languageEnglish
    Pages (from-to)195-201
    Number of pages7
    JournalPhysics and Chemistry of Minerals
    Volume40
    Issue number3
    DOIs
    Publication statusPublished - Mar 2013

    Keywords

    • CF phase
    • High pressure
    • MORB
    • NAL phase
    • Sound velocity

    ASJC Scopus subject areas

    • Materials Science(all)
    • Geochemistry and Petrology

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