CO2 distribution in CO2-rich melanophlogite from Fortunillo, Tuscany, Italy

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    CO2 distribution in M12 and M14cages of CO2-rich melanophlogite from Fortunillo, Tuscany, Italy was studied using synchrotron powder X-ray diffraction. Original and two heat-treated samples at 500 and 1000 °C were studied at room temperature. The diffraction patterns of these samples can be indexed as a cubic cell (Pm3n). For the non-heated sample, CO2 occupancy for M14 cage is close to unity, whereas about 0.85 for M12 cage. For the 500 °C-heated sample, the occupancies for M14 and M12 cages are reduced to 0.79 and 0.57, respectively. Present study showed that CO2 has preference to M14 cage, but substantial CO2 occupies M12 cage. The electron distributions obtained by MEM analysis clearly reveal orientationally ordered CO2 distribution in M12 and M14 cages. Present result is also used to clarify a recently proposed interpretation for the splitting of CO2 Raman vibrational peak for the heat-treated melanophlogite.

    Original languageEnglish
    Pages (from-to)471-478
    Number of pages8
    JournalJournal of Mineralogical and Petrological Sciences
    Issue number6
    Publication statusPublished - 2020


    • CO2
    • Crystal structure
    • Melanophlogite
    • Powder X-ray diffraction
    • Site distribution

    ASJC Scopus subject areas

    • Geophysics
    • Geology


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