Geochemical characteristics of the komatiites

The geochemical characteristics of the komatiites that occur on the Baltic Shield show that they all represent an Al- undepleted (Yilgarn) type with CaO-Al ratios less than 1 and Al2O3 - Ti02 ratios about 20. Major differences in petrogenic oxides are apparent as the higher Fe and Ti content of Kola komatiites.

  • Jensen (Cation %) plot for the komatiites from the Baltic Shield

  • TiO2-Al203 plot for Karelia and Kola komatiites

  • TiO2-FeO plot for Karelia and Kola komatiites

  • Th-Nb plot for Karelian komatiites

  • REE plot for komatiites from Vedlozero-Segozero greenstone belt

  • Melt ejection and magma generation temperatures

  • Sm-Nd isotopic system

  • Rare earth spectra were used to subdivide Archean komatiites from Baltic Shield into 4 groups:
    1. komatiites showing a chondritic nonfractionated REE distribution:{(La/Sm)n=0.8-1.1, (Gd/Yb)n=0.9-1.2, (Ce/Yb)n=0.9-1.1} Palaselga,Ura-Guba, Polmos-Poros, Kamennoozero;
    2. LREE-depleted komatiites:{(La/Sm)n=0.4-0.7, (Gd/Yb)n=0.89-1.4, (Ce/Yb)n=0.6-0.8} Kuhmo (Finland);
    3. LREE-enriched komatiites:{(La/Sm)n=1.4-1.6, (Gd/Yb)n=1.1-1.4, (Ce/Yb)n=1.1-1.2} Sovdozero, Hautavaara;
    Proterozoic Windy Belt komatiites do not differ substantially in major petrogenic oxides from Archean komatiites and represent the same Al-undepleted type, but they are more intensely enriched in LREE and are higher at a general level than Archean komatiites.
    Sm-Nd isotopic study of the Vedlozero-Segozero greenstone belt, Koikary and Palaselga domains.

    Komatiites of the Baltic Shield:
    Kola peninsula:
    North Karelia:
    Cenral Karelia:

    1. Introduction
    2. Geology
    3. Layered flows
    4. Structures
    5. Petrography
    6. Geochemistry
    7. Mantle sources
    8. References
    9. Researcher (Sergei Svetov)

    Последние изменения: 20 октября 2006