Podrobnosti záznamu

    Chemical characteristics of zircon from A-type granites and comparison to zircon of S-type granites
    Breiter, Karel
    Dall'Agnol, R.
    Krás Borges, R. M.
    Lamarão, C. N.
Typ dokumentu
    článek v odborném periodiku
Zdrojový dokument - seriál
    1192/195, April
    s. 208-225
    Rozsah: 18 s. : P
Předmětová kategorie
    A-type granites
    Krušné hory/Erzgebirge
    S-type granites
    Wiborg batholith
Klíčové slovo
Abstrakt (anglicky)
   The trace element content in zircons was investigated using back-scattered electron images and electron microprobe analyses. The studied Proterozoic (Wiborg batholith, Finland and Pará, Amazonas and Goiás states, Brazil) and Variscan (Krušné Hory/Erzgebirge, Czech Republic and Germany) plutons cover a wide range of rocks, from large rapakivi-textured geochemically primitive plutons to small intrusions of rare-metal granites. The zircon from the non-mineralized plutons is poor in minor and trace elements; the zircon in moderately fractionated granite varieties is slightly enriched in Hf, Th, U, Y, and HREEs; whereas the zircon in highly fractionated ore-bearing granites may be strongly enriched in Hf (up to 10 wt% HfO2), Th (up to 10 wt% ThO2), U (up to 10 wt% UO2), Y (up to 12 wt% Y2O3), Sc (up to 3 wt% Sc2O3), Nb (up to 5 wt% Nb2O5), Ta (up to 1 wt% Ta2O5), W (up to 3 wt% WO3), F (up to 2.5 wt% F ), P (up to 11 wt% P2O5), and As (up to 1 wt% As2O5).
   Metamictized zircons may also be enriched in Bi, Ca, Fe, and Al. The increase in the Hf content coupled with the decrease in the Zr/Hf value in zircon is one of the most reliable indicators of granitic magma evolution. The contents of Hf and U in zircon are dependent mainly on the degree of granite fractionation and the nature and volume of the volatile phases and are independent of the A- or S-character of the parental melt. The zircon Zr/Hf ratios 55 and 25 are proposed to approximately distinguish common, moderately evolved and highly evolved granites. Zircons from the moderately and highly evolved granites of A- and S-type can be discriminated on the basis of their HREE content and the U/Th ratios. Nb, Ta, and W are present in zircon from the highly evolved granites from all studied areas, while high As, Bi, and Sc contents are typical only for the Erzgebirge.
    AV ČR Brno, Geologický ústav
Kód přispěvatele
    AV ČR, GLÚ
Zdrojový formát
Datum importu
    23. 10. 2014