Podrobnosti záznamu

Název
    Compositional variations in the sodalite-bearing nepheline phonolite from Želenický vrch Hill, North Bohemia
Údaj o odpovědnosti
    Paula Pazdernik
Autor
    Pazdernik, Paula
Jazyk
    anglicky
Zdrojový dokument - seriál
    Acta Universitatis Carolinae, Geologica
Svazek/č.
    Vol. 41, no. 2
Strany
    p. 65-79
Rok
    1997
Poznámky
    1 obr., 19 diagr., 11 tab., 2 s.bibl.
    Zkr. název ser.: Acta Univ. Carol., Geol.
Předmětová skupina
    chemismus hornin
    fonolit
    minerály horninotvorné
    nefelin
    prvky hlavní
    prvky stopové
    sodalit
    tektosilikáty
    vulkanity Českého středohoří
    vzácné zeminy
Geografické jméno
    České středohoří-Želenický vrch
    ČR-Čechy
Klíčové slovo
    Bohemia
    Compositional
    Hill
    Nepheline
    North
    Phonolite
    Sodalite-bearing
    Variations
    Vrch
    Želenický
Abstrakt (anglicky)
   The sodalite-bearing nepheline phonolite of Želenický vrch Hill near Most, reveals only indistinct compositional variations. Modal composition of the rock (phenocrysts of alkali feldspars, nepheline and microphenocrysts of crystalochemistry of the main rock-forming minerals were established: (a) increased Na and Ba contents in alkali feldspar towars the marginal parts of the body as the top; (b) higher amount of Si and Na both in rims of nephenite phenocrysts and in nephelines from the matrix; (c) lower Na contents in clinopyroxenes in the outer parts of the hill. A differentiation trend from Ca (Na) pyroxenes (Ca-rich aegirine-augites) through Na (Ca) pyroxenes (Na-rich aegirine-augites) to Na-pyroxenes (aegirines) was established.
   Major and trace element composition of the phonolite indicates strong differentiation of a parental magma caused by feldspar fractionation but also by fractionation of Ti-oxides, sphene, olivine, clinopyroxene, and apatite: there is a notable enrichment in incompatible elements (Rb, Zr, Hf, Nb, Ta) and a depletion in Sr, Ba, P, Ti and compatible Mg as well. The trace element patterns of the sodalite-bearing nepheline phonolite are remarkably similar to the average crust composition, however the phonolite patterns show increased peaks of magnitudes of enrichment or depletion respectively, compared with the normalized values of average crust. The high (La/Yb)N-ratios (15-24) point to a substantial LREE enrichment. The amount of MREE depletion (due to crystallization of plagioclasses is indicated by Gd/Gd*-ratios (0.26-0.36). The most evident effects on compositional variation, esp. in marginal parts of the intrusion, are attributed to alteration-processes
Přispěvatel
    Česká geologická služba
Kód přispěvatele
    ČGS (UNM)
Zdrojový formát
    U
Datum vložení
    21. 3. 2008
Datum importu
    8. 8. 2012