Record details

    Halloysite from karst sediments of the Koněprusy area: evidence for acid hydrothermal speleogenesis in the Bohemian Karst, Czech Republic
Statement of responsibility
    Melka K., Suchý V., Zeman A., Bosák P., Langrová A.
Other titles
    Sixteenth Conference on Clay Mineralogy and Petrology in Karlovy Vary (Czech Republic), August 27-31, 2000 (Variant.)
    Bosák, Pavel, 1951-
    Langrová, Anna
    Melka, Karel, 1930-
    Suchý, Václav
    Zeman, Antonín, 1943-
Source title - serial
    Acta Universitatis Carolinae. Geologica
    Vol. 44, no. 2-4
    p. 117-124, [2] l. příl.
    3 obr., 2 diagr., 2 fot. v textu, 2 pl. v příl.
    Bibliografie na s. 123-124
    Zkr. název ser.: Acta Univ. Carol., Geol.
Classfication no.
Conspectus category
Subject group
    analýza termická
    metoda prášková
    mikroskopie elektronová
    minerály jílové
Geographical name
    Český kras
    Koněprusy (Beroun, Beroun)
Abstract (in english)
   (Pre)-Cretaceous sediments that fill extensive hydrothermal dissolution cavities in Devonian limestones in the Čertovy schody Quarry contain locally abundant halloysite clays. In most samples halloysite coexist with metahalloysite and kaolinite that form snowy-white and blue-green masses intimately intergrown with manganese oxides. The determination of members of kaolinite group minerals was the main purpose of this study. X-ray diffraction method and thermal analyses enabled to differentiate halloysite from metahalloysite and kaolinite. Tubular morphology of halloysite form over interstratified states (mixed-layer halloysite-metahalloysite crystal structure) to metahalloysite. Field observations indicate that halloysite formed due to selective in situ hydrothermal alteration of clayey matrix of quartz sandstone and/or breccias of unclear original compositional that occur within the sedimentary fill.
   The proposed model for halloysite formation formation involves alteration by arm (<80°C) acid solutions that migrated through the system of tectonic fractures, dissolved limestone host and altered overlying sedimentary memebrs that collapsed into the resulting hydrothermal depressions. Since halloysite partially replaced also Cenomanian sediments, the hydrothermal alteration must have occurred only during post-Cenomanian time
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
Entered date
    16. 9. 2008
Import date
    8. 8. 2012