Podrobnosti záznamu

Název
    Zircon ages for high pressure granulites from South Bohemia, Czech Republic, and their connection to Carboniferous high temperature processes
Údaj o odpovědnosti
    Alfred Kröner, Patrick J. O'Brien, A.A. Nemchin, R.T. Pidgeon
Autor
    Kröner, Alfred
    Nemchin, A. A.
    O'Brien, Patrick J.
    Pidgeon, R. T.
Jazyk
    anglicky
Zdrojový dokument - seriál
    Contributions to mineralogy and petrology
Svazek/č.
    Vol. 138, no. 2
Strany
    p. 127-142
Rok
    2000
Poznámky
    3 obr., 2 fot., 2 tab., 4 s.bibl.
    il.
    Zkr. název ser.: Contr. Mineral. Petrology
Předmětová skupina
    datování U/Pb
    granulit
    metamorfóza vysokostupňová
    moldanubikum Šumavy
    složení granitické
    vrásnění variské
    zirkon
Geografické jméno
    ČR-Čechy
    Kleť (Český Krumlov)
    Prachatice
Klíčové slovo
    Ages
    Bohemia
    Carboniferous
    Connection
    Czech
    Granulites
    High
    Pressure
    Processes
    Republic
    South
    Temperature
    Zircon
Abstrakt (anglicky)
   etrological and isotopic investigations were undertaken on high pressure granulites of granitic to mafic composition from the Prachatice and Blanský les granulite complexes of southern Bohemia, Czech Republic. The predominant felsic granulites are quartz+ternary feldspar (now mesoperthite)-rich rocks containing minor garnet, kyanite and rutile, and most show a characteristic mylonitic fabric formed during retrogression along the exhumation path. Three high temperature reaction stages at distinctly different pressures are recognized. Rare layers of intermediate to mafic composition, containing clinopyroxene, best record a primary high pressure-high temperature stage (15 kbar, >900°C), and a well-defined overprint at medium pressure granulite facies conditions (6-8 kbar, 700-800°C) during which orthopyroxene (+plagioclase) formed from garnet and clinopyroxene. A further high temperature overprint at lower pressure (ca.
   4 kbar) is reflected in the development of cordierite- and/or andalusite-bearing partial-melt patches in some felsic granulites). Conventionally separated zircons from the granulites were measured on a SHRIMP II ion microprobe. Near-spherical, multifaceted grains interpeted to be metamorphic, and short prismatic grains from the cordierite-bearing melt patch, are all concordant and yielded indistinguishable results producing an average age, for 83 individual grain spots, of 339.8˝2.6 Ma(2ň). Metamorphic grains from a meta-granodiorite associated with the granulites gave the same age (339.6˝3.1 Ma, mean of 9), whereas inherited magmatic grains of the same sample yielded 367.8˝1.4 Ma. A mean age of 469.3˝3.8 Ma was obtained for two short prismatic concordant grains in one of the granulites, whereas several of the rounded grains with ca. 340 Ma metamorphic zircon overgrowths had much older (207Pb/206Pb minimum ages up to 1771 Ma) discordant cores
Přispěvatel
    Česká geologická služba
Kód přispěvatele
    ČGS (UNM)
Zdrojový formát
    U
Datum vložení
    19. 3. 2007
Datum importu
    8. 8. 2012