Key words Bohemian Massif
Central Bohemian Pluton
Springer Online Journal Archives 1860-2000
Abstract The Sr-Nd isotopic data for selected granitoids of the Central Bohemian Pluton show a broad negative correlation with the total range of (87Sr/ 86Sr)330=0.7051–0.7129 and ε330 Nd =+0.2 to –8.9. The older intrusions have more depleted Sr-Nd compositions and calc-alkaline geochemistry (Sázava suite), whereas the younger intrusions shift towards K-rich calc-alkaline (Blatná suite) and shoshonitic rocks (Říčany and Čertovo břemeno suites) with more evolved isotopic signatures. The distribution of the data is interpreted as reflecting a diversity of sources and processes, rather than a single progressive crustal contamination trend. The Sázava suite could have originated by partial melting of metabasites, or of a mantle source with an isotopic composition close to bulk earth, or by hybridization of crustally-derived tonalitic and mantle-derived magmas. Variation within the Blatná suite is modelled by mixing between a moderately enriched (87Sr/86Sr)330∼0.708, ε330 Nd∼–3] mantle component with either an isotopically evolved metasedimentary component, or with more evolved magmas of the suite. The Říčany suite was most probably produced by partial melting of peraluminous lithologies, possibly of the adjacent Moldanubian unit. The Čertovo břemeno suite evolved from strongly enriched mantle-derived magmas [(87Sr/86Sr)330∼0.7128, ε330 Nd∼–7], either through closed-system fractional crystallization or interaction with magma corresponding to leucogranites of the Central Bohemian Pluton.
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