Record details

Title
    The nature of radiohaloes in biotite: Experimental studies and modeling
Statement of responsibility
    Lutz Nasdala, Marita Wenzel, Michael Andrut, Richard Wirth, Peter Blaum
Author
    Andrut, Michael
    Blaum, Peter
    Nasdala, Lutz
    Wenzel, Marita
    Wirth, Richard
Language
    anglicky
Source title - serial
    American mineralogist
Vol./nr.
    Vol. 86, no. 4
Pages
    p. 498-512
Year
    2001
Notes
    9 obr., 2 fot., 5 tab., 2 s.bibl.
    il.
    Zkr. název ser.: Amer. Mineralogist
Subject group
    biotit
    chemismus minerálů
    inkluze minerální
    izotopy radioaktivní
    krušnohorský pluton
    krystalochemie
    křemenný diorit
    mikroskopie elektronová transmisní
    model matematický
    monazit
    pleochroismus
    radiační poškození
    rula
    spektrometrie Ramanova
    standard
    thorium
    titan
    uran
    zirkon
    železo
Geographical name
    ČR-Čechy
    Horní Slavkov (Sokolov)
    SRN-Bayern
Keyword
    Biotite
    Experimental
    Modeling
    Nature
    Radiohaloes
    Studies
Abstract (in english)
   Several micro-techniques (confocal laser-Raman microprobe, optical absorption micro-spectroscopy, high-resolution transmission electron microscopy, electron microprobe analysis) were employed in the detailed characterization of radiohaloes in biotites from two variscan rocks from Germany. The studied biotites are intermediate members of the phlogopite-annite series with Mg/Fe2+ ratios in the range 1.6-1.0. Radiohaloes in biotite resulted from the impact of 4He cores (particles) emitted from actinite-bearing inclusions. Monte Carlo simulations yielded (238U, 235U, and 232Th series) penetration ranges in biotite between 12.5 and 37.3 um, which are in resonable agreement with the observed radii of radiohaloes in natural biotites. The coloration pattern of a radiohalo closely correlates with the calculated distribution pattern of point defects generated in displacive events.
   Calculated point defect densities in the range from <10-5 to at most 10-2 dpa (displacement per lattice atom) suggest that there are only scattered point defects in a mainly preserved biotite lattice. This is consistent with HRTEM studies that did not reveal any indication for initial volume amorphization in the haloes. However, general Raman band broadening and intensity loss suggest that the short-range order in radiohaloes is significantly disturbed. The darkened color of radiohaloes, when compared with the un-irradiated host biotite, is caused by increased light absorption over the complete visible range due to increased point defect density
Contributor
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
    U
Entered date
    21. 8. 2007
Import date
    8. 8. 2012