Podrobnosti záznamu

    Review of geochemical variation in Lower Palaeozoic metabasites from the NE Bohemia Massif: intracratonic rifting and plumeridge interaction
Údaj o odpovědnosti
    P.A. Floyd, Q.G. Crowley
Další názvy
    Orogenic Processes: Quantification and Modelling in the Variscan Belt (Variant.)
    Crowley, Q. G.
    Floyd, P. A.
    Kryza, Ryszard
    Seston, R.
    Winchester, J. A.
Zdrojový dokument - seriál
    Geological society special publication
    Vol. 179
    p. 155-174
    12 obr., 4 s.bibl.
    Zkr. název ser.: Geol. Soc. spec. Publ. (London).
Předmětová skupina
    alkalický bazalt
    chemismus hornin
    plášťový chochol
    tholeiitický bazalt
    západosudetská oblast
    zóna riftová
Geografické jméno
    Polsko - jihozápad
    Železný Brod (Jablonec nad Nisou)
Klíčové slovo
Abstrakt (anglicky)
   During early Palaeozoic time the Cadomian basement of the northern margin of Gondwana underwent extensive rifting with the formation of various crustal blocks that eventually became separated by seaways. Attenuation of the continental lithosphere was accompanied by the emplacement of anatecic granites and extensive mafic-dominated bimodal magmatism, often featuring basalts with an ocean crust chemistry. Intrusive metabasites in deep crustal segments (associated with granitic orthogneisses) or extrusive submarine lavas at higher levels (associated with pelagic and carbonate basinal sediments) show a wide range of chemical characteristics dominated by variably enriched tholeiites. Most crustal blocks show the presence of three main chemical groups of metabasites: Low-Ti tholeiitic metabasalts, Main Series tholeiitic metabasalts and alkalic metabasalt series.
   They differ in the degree of incompatible element enrichment (depleted to highly enriched normalized patterns), in selected large ion lithophile (LIL) to high field strength element (HFSE) ratios, and abundances of HFSE and their ratios. Both the metatholeiite groups are characterized by a common enrichment of light REE-Th-Nb-Ta. High Th values (or Th/Ta ratios) and associated low eNd values (especially in the Low-To tholeiitic metabasalts) reflect sediment contamination in the mantle sources rather than at crustal levels, although this latter feature cannot be ruled out entirely. The range of chemical variation exhibited is a consequence of the melting of (a) a lithospheric source contaminated by a sediment component (which generated the Low-Ti tholeiites), and (b) a high-level asthenospheric midocean ridge basalt (MORB)-type source that mixed with a plume component (which generated the range of enriched Main Series tholeiites and the alkali basalts).
   It is considered that a plume played an important role in the generation of both early granites and the enriched MORB-type compositions in the metabasites
    Česká geologická služba
Kód přispěvatele
    ČGS (UNM)
Zdrojový formát
Datum vložení
    30. 4. 2007
Datum importu
    8. 8. 2012