Geochemistry of phonolitic-trachytic magmas: their sources and fractionation trends (examples from the Bohemian Massif)

Geochemical charakteristics of the AFC processes resulting in evolved trachyte/phonolite derivates of alkaline magmas: (a) serie nephelinite/tephrite-phonolite/trachyte-(carbonatite), and (b) serie olivine nephelinite/basanite - trachyandesite - trachyte/phonolite - (rhyolite) will be investigated. Petrochemical modeling for evaluation of parental magma source is proposed. On basis of the Sr-Nd isotopic data, the magmatic source and a level of crustal magma contamination will be established. For detailed geochemical evaluation of sample set, the great number of indicative elements is needed; it will be ensured by the sensitive analytical mathods of instrumental neutron and gamma(photon)-activation analyses (INAA + IGAA). The determination of radiogenic Ar and K by means of NAA would contribute to the more precise geochronological dating.