Petrogenesis of Miocene alkaline volcanic suites from western Bohemia. Whole rock geochemistry and Sr-Nd-Pb isotopic signatures.

0459103 - GLÚ 2017 RIV DE eng J - Článek v odborném periodiku
Ulrych, Jaromír - Krmíček, Lukáš - Tomek, Č. - Lloyd, F. E. - Ladenberger, A. - Ackerman, Lukáš - Balogh, K.
Petrogenesis of Miocene alkaline volcanic suites from western Bohemia. Whole rock geochemistry and Sr-Nd-Pb isotopic signatures.
Chemie der Erde-Geochemistry. Roč. 76, č. 1 (2016), s. 77-93. ISSN 0009-2819. E-ISSN 1611-5864
Institucionální podpora: RVO:67985831
Klíčová slova: Bohemian Massif * Cenozoic alkaline volcanism * Geochemistry * K-Ar ages * Sr-Nd-Pb isotopes
Kód oboru RIV: DD - Geochemie
Impakt faktor: 1.380, rok: 2016

The Mid to Late Miocene intraplate alkaline volcanic suites of western Bohemia are relict of the intensive voluminous volcanism accompanied by large-scale uplift and doming. The association with the uplift of the NE flank of the Cheb–Domažlice Graben (CDG) is uncertain in view of the mostly transpressional tectonics of the graben. The volcanism is most probably of the Ohře/Eger Rift off-rift settings. Two cogenetic volcanic suites have been recognised: (i) silica-saturated to oversaturated consisting of olivine basalt – trachybasalt – (basaltic) trachyandesite – trachyte – rhyolite (13.5 to 10.2 Ma) and (ii) silica-undersaturated (significantly Ne-normative) (melilite-bearing) olivine nephelinite – basanite – tephrite (18.3 to 6.25 Ma). A common mantle source is assumed for the near-primary mantle-derived compositions of both suites, i.e., olivine basalt and olivine nephelinite. Apparently, they were generated by different degrees of partial melting of a common mantle source, with garnet, olivine and clinopyroxene in the residuum. Negative Rb and K anomalies indicate a residual K-phase (amphibole/phlogopite) and melting of partly metasomatised mantle lithosphere. The evolution of the olivine basalt – trachybasalt – (basaltic) trachyandesite – trachyte – rhyolite suite suggests the presence of an assimilation–fractional crystallization process (AFC). The magmas were probably sourced by both sub-lithospheric and lithospheric partly metasomatised mantle. The evolution of the (melilite-bearing) olivine nephelinite – basanite – tephrite suite is less clear because of its limited extent. The Sr-Nd-Pb isotopic composition of primitive volcanic rocks of both suites is similar to that of the European Asthenospheric Reservoir (EAR). Initial Pb isotopic data plot partly above the northern hemisphere reference line at radiogenic ²⁰⁶Pb/²⁰⁴Pb ratios of ~19 to 20, and indicate the presence of a Variscan crustal component in the source.
Trvalý link: http://hdl.handle.net/11104/0259376