Record details

    Geochronologie a geologie granitu Zvůle (23-34 Jindřichův Hradec)
Statement of responsibility
    Susanna Scharbert, Karel Breiter
Other titles
    Geochronology and Geology of the Zvůle Granite
    Breiter, Karel, 1956-
    Scharbert, Susanna
Source title - serial
    Zprávy o geologických výzkumech v roce 1999
    s. 160-162
    2 obr., 1 tab.
    Anglické resumé
    Obsahuje bibliografické odkazy
    Zkr. název ser.: Zpr. geol. Výzk. v Roce 1999.
Subject group
    datování Rb/Sr
    geologie regionální
    granit dvojslídný
    mapa geologická
    mezinárodní spolupráce
    moldanubický pluton
    složení peraluminické
Geographical name
    Zvůle (Jindřichův Hradec)
Abstract (in english)
   The Zvůle granite (ZG, formerly termed also Landštejn granite, Fig. 1a) forms a circular-shaped stock in the axial part of the NE-branch of the South Bohemian Pluton (SBP). The extension of the stock was indicated by a Th-minimum in airborne gamma-ray spectrometry (Dědáček et al. 1991, Fig. 1c) and precisely located by new mapping (Fig. 1b). Deep roots of the stock are indicated by strong negative anomaly of gravity (Blížkovský, Novotný 1982). Petrographically, the ZG is a medium-to coarse-grained, equigranular to slightly porphyritic two-mica albite granite. In several samples, the biotite is chloritised. According to detailed geochemical sampling, the ZG is reversely zoned with the most evolved facies along the S. contact (Fig. 1d,e,). Six samples of the ZG were investigated by the Rb-Sr method. The contents of Rb and Sr were determined by the siotope dilution method with a VG MM30 solid source mass spectrometer.
   These six samples exhibit a good spread and allowed to calculate and construct a perect isochron according to Ludwig's (1992) model 1 (Tab. 1, Fig. 2). From geochronological investigation we conclude that emplacement and crystallisation of the ZG occurred 320.5˝2.7 Ma ago with an initial Sr ratio of 0.7126˝0.0007 (MSWD 0.63). The late-post-magmatic chloritisation of sample 2943 does not shift the results beyond the error limits. The ZG represents the isotopically most homogenous melt within the peraluminous suite of the SBP. The older members of this suite, the Číměř and Eisgarn s.s. granites (c. 330 Ma), are much less homogeneous: their scatter is strong in Sr isotope composition which makes it difficult to get precise age (Scharbert 1998). The evolvement of well mixed melts seems to be time dependent: The latest Zvůle intrusion could form in a lower, better homogenised magma chamber
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
Entered date
    21. 3. 2008
Import date
    8. 8. 2012