The mineralogy of the Kokchetav 'lamproite': Implications for the magma evolution

Yongfeng Zhu, Yoshihide Ogasawara, T. Ayabe

    Research output: Contribution to journalArticle

    12 Citations (Scopus)

    Abstract

    Kokchetav 'lamproite' occurs in the east end of Kokchetav massif and consists of phenocryst (mainly clinopyroxene) and matrix (mainly feldspar). The compositions of clinopyroxene, magnetite and biotite phenocryst were determined using wavelength dispersive spectrometry on a JEOL Super-probe 8900 electron microprobe for the purpose of revealing the process of magma evolution. Analyses revealed a core-rim variation, which is consistent with three stages of magmatic evolution: Mg-rich clinopyroxene cores (diopside) and biotite cores (phlogopite) crystallized in a deep magma chamber (stage I); Fe-rich clinopyroxene rim (salite) and biotite rim crystallized at low pressure in a shallow magma chamber (stage II); Magnetite phenocryst core also crystallized in a shallow magma chamber, and coexists with Fe-rich clinopyroxene rim and biotite rim. The magnetite rims probably formed during magma eruption at the same time when groundmass crystallized (stage III). The calculated temperatures for ilmenite-magnetite pair range from 679 to 887°C, log fO2 values range from - 11.1 to 14.9 log units. These values represent the latest conditions of magma as ilmenite exsolution in magnetite probably occured during magma eruption from the shallow chamber to surface.

    Original languageEnglish
    Pages (from-to)35-61
    Number of pages27
    JournalJournal of Volcanology and Geothermal Research
    Volume116
    Issue number1-2
    DOIs
    Publication statusPublished - 2002 Jul

    Fingerprint

    Ferrosoferric Oxide
    lamproite
    Mineralogy
    mineralogy
    clinopyroxene
    magma
    rims
    magnetite
    phenocryst
    biotite
    magma chamber
    chambers
    ilmenite
    volcanic eruption
    volcanic eruptions
    exsolution
    phlogopite
    diopside
    electron probe analysis
    Spectrometry

    Keywords

    • Clinopyroxene
    • Kokchetav
    • Lamproite
    • Magnetite
    • Mantle petrology

    ASJC Scopus subject areas

    • Geochemistry and Petrology
    • Geophysics

    Cite this

    The mineralogy of the Kokchetav 'lamproite' : Implications for the magma evolution. / Zhu, Yongfeng; Ogasawara, Yoshihide; Ayabe, T.

    In: Journal of Volcanology and Geothermal Research, Vol. 116, No. 1-2, 07.2002, p. 35-61.

    Research output: Contribution to journalArticle

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