Record details

    Age-related Contrasting Alkaline Volcanic Series in North Bohemia
Statement of responsibility
    Jaromír Ulrych, Edvín Pivec
    Pivec, Edvín
    Ulrych, Jaromír
Source title - serial
    Chemie der Erde
    Vol. 57, no. 4
    p. 311-336
    11 obr., 3 s.bibl.
    Německé resumé
    Zkr. název ser.: Chem. d. Erde
Subject group
    chemismus hornin
    geochemie izotopická
    vzácné zeminy
    zóna riftová
Subject category
Geographical name
Abstract (in english)
   The Late Cretaceous-Tertiary volcanism of the north-eastern arm of the Ohře (Eger) Rift in North Bohemia displays characteristic features of two intraplate magmatic series. An older (79-50 Ma) unimodal ultramafic ultra-alkaline (melilititic) series, representing the precursor of rifting, occurs exclusively in external blocks of the Ohře Rift. A younger (40-18 Ma) bimodal (basanite-phonolite) rock series of alkaline character predominates in the internal blocks of the rift. The later series is characteristic of highly-volcanic active rifts. In addition the youngest picrobasaltic intrusions (9 Ma) occur there in association with regional faults. A similar, however, mildly alkaline bimodal alkali basalt/basanite-trachyte association prevails in the central part of the Ohře Rift, in the České středohoří Mts.
   Enrichment of the ultramafic rock series in incompatible elements (Rb, Cs, REE, Y, U, Th, Zr, Hf, Nb, Ta, P) can be explained by low-degree partial melting of metasomatically enriched mantle source and/or steady zone refining process of magma generation. Further enrichment during the postmagmatic process from the high level crustal reservoir source is likely. The 87Sr/86Sr (0.70327-0.70366) and 143Nd/144Nd (0.51267-0.51287) ratios of the (ultra)mafic rocks of both magmatic series are similar and close to those of HIMU OIB. The majority of phonolites (PH1-type) was derived from basanitic to olivine-poor nephelinitic magma and only a minority of the more evolved phonolites (PH2-type) probably represent extreme differentiates of the first mentioned phonolites. The addition of lithophile elements in post-magmatic process to evolved and anomalous phonolites is highly probable.
   Phonolites that originated by low-pressure crustal fractionation were affected by some crustal contamination (87Sr/86Sr = 0.70407-0.70534, 144Nd/143Sm = 0.51280)
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
Entered date
    21. 2. 2008
Import date
    8. 8. 2012