Record details

    Structural properties of ferromagnesian cordierites
Statement of responsibility
    Thomas Malcherek, M. Chiara Domeneghetti, Vittorio Tazzoli, Luisa Ottolini, Catherine McCammon, Michael A. Carpenter
    Carpenter, Michael A.
    Domeneghetti, M. Chiara
    Malcherek, Thomas
    McCammon, Catherine
    Ottolini, Luisa
    Tazzoli, Vittorio
Source title - serial
    American mineralogist
    Vol. 86, no. 1-2
    p. 66-79
    8 diagr., 9 tab., 37 bibl.
    Zkr. název ser.: Amer. Mineralogist
Subject group
    chemismus minerálů
    metoda monokrystalová
    mřížkové parametry
    stupeň uspořádanosti
    zpřesňování struktury
Geographical name
    Dolní Bory (Žďár nad Sázavou)
    Srí Lanka
    Velká Británie-Scotland
Abstract (in english)
   A set of natural and heat-treated cordierite crystals has been analyzed using single-crystal X-ray diffraction, EMPA, SIMS, and 57 FE Mössbauer-spectroscopy. Struture determination of natural cordierite shows that the average size of the tetrahedrally coordinated T1 1 cation increase systematically by about 0.01 A as the Fe content of the solid solution decrease toward the Mg end-member. For fe-rich compositions, the mean tetrahedral bond lengths T1 1-0 is close to 1.749 A, a value expected for an A1O4 tetrahedron is an alumosilicate framework structure. it is suggested that the structural dilation of the tetrahedral sites, which is driven by the decreasing average size of the octahedral cation, is sustained by substitution of the large cations Mg and Fe2 for Al. Mössbauer spectroscopy shows that up to 11% of Feř+ can be attributed to tetrahedral coordination in Mg-rich cordierite.
   Charge balance for the substitutions is either provided by introduction of Na+ into vacant Ch2 (0,,) channel sites or substitution of an additional Al3+ by Si4+. tetrahedral site occupancies and corresponding Al, Si order parameters are calculated on the basis of a simple hard sphere model, based on refined cation-oxygen mean bond length, chemical composition, and Fe site-occupancy refinements. Almost complete Al, Si ordering among ring sites T2 is encountered fro most natural cordierite samples. Al, Si ordering among the T1 tetrahedra is less pronounced for Fe-rich compositions. Partial disorder is attributable to Al/Si ratios in excess of 4/5
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
Entered date
    21. 8. 2007
Import date
    8. 8. 2012