Record details

    Geochemically anomalous olivine-poor nephelinite of Říp Hill, Czech Republic
Statement of responsibility
    Jaromír Ulrych, Edvín Pivec, Anna Langrová, Emil Jelínek, Erzsébet Árva-Sós, Axel Höhndorf, Jiří Bendl, Zdeněk Řanda
Other titles
    Geochemicky anomální olivínem chudý nefelinit z Řípu
    Árva-Sós, Erzsébet
    Bendl, Jiří
    Höhndorf, Axel
    Jelínek, Emil, 1943-
    Langrová, Anna
    Pivec, Edvín
    Řanda, Zdeněk
    Ulrych, Jaromír
Source title - serial
    Journal of the Czech Geological Society
    Vol. 43, no. 4
    p. 299-311
    2 obr., 7 diagr., 5 tab., 2 s.bibl.
    České resumé
    Zkr. název ser.: J. Czech geol. Soc.
Subject group
    chemismus hornin
    datování absolutní
    frakcionace chemická
    horniny vulkanické
    izotopy Nd
    izotopy Sr
    vulkanity Českého středohoří
    vzácné zeminy
Geographical name
    České středohoří-Říp
Abstract (in english)
   Sodalite olivine-poor nephelinite of Říp Hill substantially differs both from olivine nephelinite and olivine-free nephelinite of the Cenozoic volcanic province of the Bohemian Massif. Říp Hill represents an erosion-resistant neck 25.6 Ma in age located in the Teplá-Barrandian terrane block in contrast to the České středohoří Mts. volcanic complex in the saxothuringian terrane. The very low Mg-value (48.5), low contents of compatible elements as Cr (79ppm), Ni (31), Co (32), Sc (21) and lack of mantle-type xenoliths gives evidence of differentiation of primary mantle magma. Anomalous enrichment in incompatible elements particularly in REE (650 ppm), U (3.6), Th (15.6), Nb (154), Ta (12.1), is associated with late magmatic crystallization (mostly of apatite, Ti-magnetite hauyne). 87Sr/86Sr (0.7036-0.7038) and 143Nd/144Nd (0.51278) ratios of the olivine-poor nephelinite are consistent with HIMU IOB from a sublithospheric source; 1Nd (+3.4) value implies an depleted mantle source.
   Olivine-poor nephelinite could be derived from carbonated nephelinite magma with high CO2/H2O + CO2 volatile fraction resulting in high viscosity and thus stopping of magma associated with differentiation and contamination in crustal reservoir during its ascent to the surface. Such magma could be associated with high explosive pyroclast-rich locano of maar or stratovolcano type. The olivine-poor nephelinite of Říp Hill reveals common features in mineral paragenesis and chemical composition of minerals such as clinopyroxene, (Mg, Al, Ti) - magnetite, barite, ankerite with carbonate-bearing alkaline ultramafic lamprophyres in the vicinity. This fact suggests their mutual genetic association within the Říp Hill volcanic centre
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
Entered date
    18. 2. 2008
Import date
    8. 8. 2012