Late Paleozoic volcanic rocks of the Intra-Sudetic Basin, Bohemian Massif: petrological and geochemical characteristics |
| |
| Authors: | J Ulrych F Fediuk P Martinec |
| |
| Institution: | a Institute of Geology, Academy of Science of the Czech Republic, Rozvojová 135, Prague 6 165 02, Czech Republicb Geohelp, Prague, Czech Republicc Institute of Geonics, Academy of Science of the Czech Republic, Ostrava, Czech Republic |
| |
| Abstract: | Late Paleozoic volcanic rocks in the Intra-Sudetic Basin of the Bohemian Massif in the Czech Republic can be subdivided into two series: (I) a minor bimodal trachyandesite-rhyolite series of Upper Carboniferous age with initial 87Sr/86Sr of ca. 0.710 and εNd values of −6.1 also characteristic of volcanics of the near Krkonoše Piedmont Basin (0.707 and −6.0, Ulrych et al., 2003) and (II) a major differentiated basaltic trachyandesite-trachyandesite-trachyte-rhyolite series of Lower Permian age with lower initial 87Sr/86Sr of ca. 0.705-0.708 and εNd values ranging from −2.7 to −3.4/−4.1/. The newly recognized volcanic rocks of trachytic composition indicate that the rocks were formed by magmatic differentiation of similar parental melts rather than constituting a bimodal mafic-felsic sequence from different sources. Both series are generally of subalkaline affinity and calc-alkaline character with some tholeiitic tint (FeO/MgO vs. SiO2, presence of orthopyroxene). The magmatic activity occurred in cycles in a layered chamber, each starting primarily with felsic volcanics and ending with mafic ones. The mafic rocks represent mantle-melt(s) overprinted by crust during assimilation-fractional crystallization. The Sr-Nd isotopic data confirm a significant crustal component in the volcanic rocks that may have been inherited from the upper mantle source and/or from assimilation of older crust during magmatic underplating and shallow-level melt fractionation. |
| |
| Keywords: | Late Paleozoic volcanics Continental basin Intra-Sudetic Basin Bohemian Massif Underplating Crustal anatexis |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
