Record details

Title
    The beryllian cordierite + beryl + spessartine assemblage, and secondary beryl in altered cordierite, Greer Lake granitic pegmatites, southeastern Manitoba
Statement of responsibility
    Scott Jobin-Bevans, Petr Černý
Other titles
    Granitic pegmatites: The Černý - Foord volume (Variant.)
Author
    Černý, Petr
    Jobin-Bevans, Scott
Language
    anglicky
Source title - serial
    Canadian mineralogist
Vol./nr.
    Vol. 36, no. 2
Pages
    p. 447-462
Year
    1998
Notes
    7 obr., 4 fot., 3 tab., 3 s. bibl.
    Francouzské resumé
    il.
    Zkr. název ser.: Canad. Mineralogist
Subject group
    berthierit
    beryl
    cordierit
    granáty
    krystalizace
    leukogranit
    metasomatóza
    pegmatit
    podmínky P-T
    pseudomorfóza
    slídy
Geographical name
    Biskupice (Třebíč)
    ČR-Morava
    Dolní Bory (Žďár nad Sázavou)
    Kanada-Manitoba
    Věžná (Žďár nad Sázavou)
Keyword
    Altered
    Assemblage
    Beryl
    Beryllian
    Cordierite
    Granitic
    Greer
    Lake
    Manitoba
    Pegmatites
    Secondary
    Southeastern
    Spessartine
Abstract (in english)
   seudomorphs after beryllian cordierite (possibly beryllian sekaninaite) occur along core margins of Archean peraluminous granitic pegmatites of the beryl - columbite subtype at Greer Lake, southeastern Manitoba, and in analogous position in pegmatitic pods of the parent leucogranite. The pseudomorphs are locally intergrown with primary columnar beryl I, and studded by spessartine that contains subparallel inclusions of beryl II. The muscovite biotite > berthierine assemblage of the pseudomorphs after cordierite contains anhedral fine-grained beryl III, locally attaining &20 vol. per cent of the breakdown products. This complex mineral association is interpreted as a product of two processes, (i) Magmatic crystallization from a Be-rich and Mn-enriched melt yielded cordierite and beryl I at &550°C and <2.8 kbar.
   Increased activity of Mn triggered intermittent stabilization of spessartine + beryl II during the crystallization of cordierite; this assemblage probably represents a Be-rich substitute for spessartine + aluminosilicate + quartz, the low-pressure equivalent of "manganocordierite", which is unstable above 1 kbarP(H2O). (ii) Subsolidus metasomatic alteration of cordierite by alkali- and F-bearing residual aqueous fluids at about 500-450°C, -2.7-2.6 kbar generated biotite > muscovite » beryl III along the basal parting planes, followed by severaltextural varieties of muscovite > biotite » beryl III, which replaced the bulk of the cordierite crystals. Low-temperature alteration of biotite yielded berthierine. The proportion of beryl III (up to &20 per cent) in the micaceous matrix of the pseudomorphs indicates up to -2.6 wt.
   per cent BeO in the cordierite precursor, which closely corresponds to the experimentally established maximum value at the given P,T conditions of magmatic crystallization
Contributor
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
    U
Entered date
    26. 9. 2007
Import date
    8. 8. 2012