Record details

Title
    Formation conditions of various calcite types an unusual alteration pproducts of wollastonite in calcite marble near Nezdice (Varied Group of Moldanubicum), Czech Republic
Statement of responsibility
    Karel Žák, Petr Dobeš, Stanislav Vrána
Other titles
    Podmínky vzniku různých typů kalcitu a pseudomorfóz po wollastonitu v kalcitickém mramoru u Nezdic (pestrá skupina moldanubika)
Author
    Dobeš, Petr
    Vrána, Stanislav
    Žák, Karel, 1957-
Language
    anglicky
Source title - serial
    Journal of the Czech Geological Society
Vol./nr.
    Vol. 42, no. 1-2
Pages
    p. 17-25
Year
    1997
Notes
    3 diagr., 1 pl., 5 tab., 11 bibl.
    České resumé
    Zkr. název ser.: J. Czech geol. Soc.
Subject group
    inkluze fluidní
    izotopy C
    izotopy O
    kalcit
    moldanubikum Šumavy
    mramor
    parageneze
    pseudomorfóza
    wollastonit
Geographical name
    ČR-Čechy
    Nezdice na Šumavě (Klatovy)
Keyword
    Alteration
    Calcite
    Conditions
    Czech
    Formation
    Group
    Marble
    Moldanubicum
    Near
    Nezdice
    Pproducts
    Republic
    Types
    Unusual
    Varied
    Various
    Wollastonite
Abstract (in english)
   Extensive calcite-rich replacements after wollastonite have been found in an abandoned marble quarry near Nezdice, Šumava Mts., southern Czech republic. Because any natural reversals of wollastonite reaction both in high-temperature and low-temperature environment are rare, combined mineralogical and stable isotope study of these pseudomorphs was performed. Other types of calcite observed in the quarry include marble in the zones of metamorphic decarbonation, hydrothermal vein calcite and calcite related to karstification process. Stable isotope and fluid inclusion methods were used to study the other types of calcite for comparison purposes.
   A plausible scenario of the formation of the calcite pseudomorphs involves the following two step evolution mode: (1) transformation of wollastonite to optically and X-ray amorphose phase (which could probably result from a high-rate tectonic deformation or shock wave compression), (2) reaction of the relatively unstable amorphose phase with water having high contents of CO2 to CaCO3, mainly in the zone of supergene alteration. Formation of the secondary carbonates during weathering is strongly indicated by oxygen and carbon isotope composition. The carbonate-rich pseudomorphs after wollastonite still contain relics of the optically and X-ray amorphose phase which formed by transformation of wollastonite and retains its accicular crystal shape. Associated diopside, quartz, and primary calcite show no replacement by secondary calcite.
   Stable isotope analyses and fluid inclusion study of calcite crystals coating some open fractures in the marble quarry indicate that this hydrothermal acivity has no connection with formation of the pseudomorphs after wollastonite
Contributor
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
    U
Entered date
    21. 2. 2008
Import date
    8. 8. 2012