Podrobnosti záznamu

    Śleza Ophiolite: geochemical features and relationship to Lower Palaeozoic rift magmatism in the Bohemian Massif
Údaj o odpovědnosti
    Peter A. Floyd, Ryszard Kryza, Quentin G. Crowley, John A. Winchester, M. Abdel Wahed
Další názvy
    Palaeozoic Amalgamation of Central Europe (Variant.)
    Crowley, Quentin G.
    Floyd, Peter A.
    Kryza, Ryszard
    Wahed, M. Abdel
    Winchester, John A.
Zdrojový dokument - seriál
    Geological society special publication
    Vol. 201
    p. 197-215
    11 obr., 1 tab., 3 s. bibl.
    Zkr. název ser.: Geol. Soc. spec. Publ. (London).
Předmětová skupina
    chemismus hornin
    krkonošsko-jizerské krystalinikum
    mariánskolázeňský bazický komplex
    původ plášťový
Geografické jméno
    Mariánské Lázně (Cheb)
    Polsko - jihozápad
Klíčové slovo
Abstrakt (anglicky)
   The Śleza Ophiolite is one of several thrust-bounded crustal slices dominated by metabasites in the western Sudetes. The apparent field association of serpentinites, gabbros and amphibolitic components led previous workers to consider that this lithological assemblage represented an ophiolite sequence. Fieldwork suggests that the ophiolite is now highly inclined, partly overturned, so that an ophiolitic pseudostratigraphy can be deduced, grading from serpentinites and gabbros in the south to metabasite lavas in the north. The recent discovery of pillow lava structures (at Gozdnica Hill, to the west of Sobótka town) confirms that the volcanic top of the ophiolite lies in the northern section, as might be expected from the ophiolite model. The gabbros have undergone greenschist facies metamorphism with the random development of low-grade amphibole.
   The volcanic portion of the sequence comprise metamorphosed dolerites and basalts partly within the contact aureole of the Variscan Strzegom-Sobótka granite. Previous work dated plagiogranites associated with the gabbros at about 400-420 Ma (U-Pb zircon ages). Geochemical data suggest that the gabbros are distinct and apparently not comagmatic with the volcanic section of sheeted dykes and lavas. The gabbros, in particular, although very depleted in incompatible elements are dissimilar to supra-subduction zone ophiolites, exhibiting instead N-MORB-like light REE depleted patterns. Depletion is both a feature of the cumulate character of many of the gabbros, as well as a source effect (especially the uniformly low Nb content). The metabasalts and metadolerites, on the other hand, are a well-evolved single comagmatic suite with high incompatible element contents, Zr/Y approximately 3-4, and generally flat to light REE-depleted patterns.
   The geochemical dichotomy of the plutonic and volcanic segments calls into question a simple interpretation of the body as a single-stage coherent stratiform ophiolite. Chemical comparison with Sudetic metabasites from within the nearby Rudawy-Janowickie and Kaczawa Complexes shows that the Śleza metabasites have a number of features in common, including the presence of both low-Ti (gabbros) and high-Ti (dykes and lavas) chemical groups. The correlation of the gabbros, dykes and lavas with the low-Ti and high-Ti (Main Series) metatholeiites respectively, seen throughout the Bohemian Massif, as well as the Sudetes, places them within the regional collage of Palaeozoic crustal blocks separated by the Saxothuringian Seaway. Comparison with Bohemian Massif metabasites also indicates that sediment contamination of the Śleza Ophiolite sources was not an important process and that an enriched plume source played no part in the generation of the ophiolitic melts.
   The two Śleza chemical groups were derived from variably depleted asthenospheric mantle sources. Simple modelling suggests that the volcanic segment could have been derived by 10-15 per cent partial melti
    Česká geologická služba
Kód přispěvatele
    ČGS (UNM)
Zdrojový formát
Datum vložení
    24. 10. 2007
Datum importu
    8. 8. 2012