Petrogenesis of the Cenozoic alkaline volcanic rock series of the České Středohoří Complex (Bohemian Massif), Czech Republic: A case for two lineages

0476474 - GLÚ 2018 RIV US eng J - Journal Article
Dostal, J. - Schellnutt, J. G. - Ulrych, Jaromír
Petrogenesis of the Cenozoic alkaline volcanic rock series of the České Středohoří Complex (Bohemian Massif), Czech Republic: A case for two lineages.
American Journal of Science. Roč. 317, June (2017), s. 677-706. ISSN 0002-9599. E-ISSN 1945-452X
Institutional support: RVO:67985831
Keywords : Bohemian Massif * Central European volcanic province * continental alcaline volcanism * fractional crystallization * magmatic fluids
OECD category: Geology
Impact factor: 3.893, year: 2017

Cenozoic volcanic rocks of the Ceske Stredohori volcanic complex (CSVC) of the Bohemian Massif form the eastern part of the Central European Volcanic Province. The main pulse of the magmatic activities took place from Late Eocene to Middle Miocene and peaked from ~32 to ~24 Ma. CSVC is composed of lava flows, volcanic clastic deposits and subvolcanic intrusions. The volcanic rocks are sodic (Na₂O>K₂O) alkaline silica-undersaturated types, which form two main bimodal associations: (1) basanite-phonolite and (2) subordinate trachybasalt-trachyte series, which differ particularly in the alkali-silica space and by the variations particularly of TiO₂. The mafic rocks strongly predominate over the felsic types (~6%). The intermediate rocks are rare. Petrological modelling using MELTS software shows that both suites were generated from two distinct parental magmas (basanitic and trachybasaltic) by a fractional crystallization without a noticeable crustal contamination. Some phonolites, particularly their abundances of several incompatible trace elements such as heavy REE and Zr were modified by late- to post-magmatic fluids. The compositional differences among the mafic rocks are, in part, related to variably metasomatically enriched lithospheric mantle. The Nd-Sr isotopic and trace element composition of the mafic magma indicates that the mantle source was slightly heterogeneous amphibole-and/or phlogopite-bearing garnet peridotite. The presence of garnet, amphibole and/or phlogopite indicates lithospheric melting took place close to the asthenosphere-lithosphere boundary. The lithospheric mantle source was probably metasomatically enriched by fluids or melts from an upwelling asthenospheric mantle. The enrichment took place probably during the later stages of the Variscan orogeny. The two mafic parent rock types may be derived from a similar source which showed subtle differences in the source mineralogy mode.
Permanent Link: http://hdl.handle.net/11104/0273013