Record details

Title
    Cryptic trace-element variation as an indicator of reverse zoning in a granitic pluton: the Říčany granite, Czech Republic
Statement of responsibility
    Vojtěch Janoušek, Graeme Rogers, D.R. Bowes, Věra Vaňková
Author
    Bowes, D. R.
    Janoušek, Vojtěch, 1968-
    Rogers, Graeme
    Vaňková, Věra
Language
    anglicky
Source title - serial
    Journal of the Geological society
Vol./nr.
    Vol. 154, no. 5
Pages
    p. 807-815
Year
    1997
Notes
    8 obr., 3 tab., 32 bibl.
    Zkr. název ser.: J. Geol. Soc. (London)
Subject group
    anatexe
    chemismus hornin
    granit
    izotopy Nd
    izotopy Sr
    petrogeneze
    prvky stopové
    složení peraluminické
    středočeský pluton
    vmístění
    vzácné zeminy
    zonálnost
Geographical name
    ČR-Čechy
    Říčany (Praha-východ)
Keyword
    Cryptic
    Czech
    Granite
    Granitic
    Indicator
    Pluton
    Republic
    Reverse
    Říčany
    Trace-element
    Variation
    Zoning
Abstract (in english)
   Cryptic variation recognized on the basis of trace-element patterns shows the Říčany granite in the northeastern part of the Hercynian Central Bohemian Pluton to be a reversely zoned, high-level intrusion. Unlike many other reversely zoned plutons, there are no marked differences in modal composition between the margins and the centre of the intrusion. The granite is generally peraluminous and geochemically evolved, as demonstrated by its restricted and high SiO2 range and low K/Rb ratio, coupled with a c. two-fold variation in Ba an Sr concentrations. Modelling shows that the geochemical variations can be most readily explained by K-feldspar-dominated fractionation in a magma chamber below the present level of exposure. The reverse zoning is interpreted as the product of emplacement of an essentially single pulse of magma from a deeper level magma chamber in which fractionation has led to a vertical compositional gradient.
   The least evolved magma was emplaced in the centre of the high-level pluton with the more evolved magma around it. Recognition of cryptic reverse zoning in granites has major implications for granite petrogenesis in that the magmatic evolution of such bodies has to be established before assessing potential mechanisms of emplacement
Contributor
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
    U
Entered date
    3. 7. 2008
Import date
    8. 8. 2012