Record details

    Boron-bearing 2M1 polylithionite and 2M1+1M boromuscovite from an elbaite pegmatite at Řečice, western Moravia, Czech Republic
Statement of responsibility
    Milan Novák, Petr Černý, Mark Cooper, Frank C. Hawthorne, Luisa Ottolini, Zhi Xu, Jiang-Jie Liang
    Cooper, Mark
    Černý, Petr
    Hawthorne, Frank C.
    Liang, Jiang-Jie
    Novák, Milan, 1952-
    Ottolini, Luisa
    Xu, Zhi
Source title - serial
    European journal of mineralogy
    Vol. 11, no. 4
    p. 669-678
    5 obr., 1 fot., 2 tab., 2 s.bibl.
    Zkr. název ser.: Eur. J. Mineral.
Subject group
    moldanubikum strážecké
    podmínky P-T
    spektrum hmotnostní
Geographical name
    Řečice (Žďár nad Sázavou)
Abstract (in english)
   An elbaite-subtype pegmatite Řečice, western Moravia, czech republic, carries abundant B-rich minerals: dominant tourmaline (shorl to elbaite and rare liddicoatite), and subordinate tusionite, B-bearing polylithionite and borumuscovite. The pegmatitic unit contains numerous, randomly distributed pockets lined with crystals of orthoclase, quartz, two generations, of red to pink elbaite, subordinate albite, minor polythionite and two generations of boromuscovite. Polylithionite, as previously unreported 2M1 polytype, contains - 80 mol.perc. polylithionite end-member K2(Li4Al2)Si8O20F4 and 20 mol.perc. of K2(LiAl3)Si8O20F4; the content of 0.44 wt.perc. B2O3 is the highest found so far in a lepidolite. Boromuscovite is compositionally variable from 50 to almost 100 mol.perc. of end-member boromuscovite. Dominant boromuscovite I consists of a mixture of 83 vol.perc. 2M1 and 17 vol.perc. 1M polytypes.
   Boromuscovite II forms rare overgrowths on larger flakes of boromuscovite I and is slightly Fe-, Mg-enriched NMR MAS spectra confirm the substitution IVB for IVAl in all three micas. Crustallization of B-bearing polylithionite after the abundant red elbaite I indicates that highly evolved residual melt attained saturation of a K-, l-, F-rich phase, while the high activity of B was maintained from early stages. The hydrothermal fluids which precipitated boromuscovite were relatively depleted in Li, Rb, Cs and F, but were B-rich. In agreement with experimental studies, Li and F are concentrated in late magmatic minerals (elbaite, polylithionite), but their activities are negligible in hydrothermal fluids and their precipitates. In contrast, high activity of B is maintained from the magmatic to the hydrothermal stage, as indicated from abundant early schorl to late Li-, F-poor boromuscovite.
   Crystallization of the massive pegmatite units and pockets including boromuscovite I seems to be a near-isobaric process in a closed system. Formation of late slightly Fe-, Mg-enriched boromuscovite II overgrowths indicates mixing of residual and metamorphic
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
Entered date
    14. 2. 2008
Import date
    8. 8. 2012