Petrogenesis of Cenozoic high-Mg (picritic) volcanic rocks in the České středohoří Mts. (Bohemian Massif, Czech Republic)

Petrogenesis of Cenozoic high-Mg (picritic) volcanic rocks in the České středohoří Mts. (Bohemian Massif, Czech Republic)

WoS Article

Representative samples of high-Mg (picritic) rocks of Eocene to Oligocene age (38 to 21 Ma) from the České středohoří Mts. (CSM) in the Ohře/Eger Rift were studied and compared with Cenozoic high-Mg rocks from the Bohemian Massif. The picritic rocks of the CSM correspond to picrite, meimechite and basanite to tephrite. Individual petrographic types are characterised by the association of mafic minerals: magnesian olivine (Fo86-80) + clinopyroxene (aluminian diopside) +/- amphibole (pargasite/kaersutite) +/- dark mica (ferroan phlogopite). The contents of incompatible elements, such as Nb, Ta, U, Th, the La-N/Yb-N ratios, and the overall Sr-Nd-Pb isotope signatures of the high-Mg rocks partly overlap the basanites of the usti Formation, also showing a similar age (44-21 Ma). The Pb isotope signature for all recognised high-Mg rock types is compatible with a variable contribution from an inherited (Variscan) orogenic Pb component preserved in their lithospheric mantle source. Both the high-Mg volcanic rocks from the CSM and from other areas of the Bohemian Massif require the involvement of a heterogenous lithospheric source. Their parental melts were generated by variable degree of melting of an olivine-rich peridotitic mantle, containing clinopyroxene-amphibole (+/- phlogopite) vein assemblages with highly radiogenic Sr and Pb signatures.

Representative samples of high-Mg (picritic) rocks of Eocene to Oligocene age (38 to 21 Ma) from the České středohoří Mts. (CSM) in the Ohře/Eger Rift were studied and compared with Cenozoic high-Mg rocks from the Bohemian Massif. The picritic rocks of the CSM correspond to picrite, meimechite and basanite to tephrite. Individual petrographic types are characterised by the association of mafic minerals: magnesian olivine (Fo86-80) + clinopyroxene (aluminian diopside) +/- amphibole (pargasite/kaersutite) +/- dark mica (ferroan phlogopite). The contents of incompatible elements, such as Nb, Ta, U, Th, the La-N/Yb-N ratios, and the overall Sr-Nd-Pb isotope signatures of the high-Mg rocks partly overlap the basanites of the usti Formation, also showing a similar age (44-21 Ma). The Pb isotope signature for all recognised high-Mg rock types is compatible with a variable contribution from an inherited (Variscan) orogenic Pb component preserved in their lithospheric mantle source. Both the high-Mg volcanic rocks from the CSM and from other areas of the Bohemian Massif require the involvement of a heterogenous lithospheric source. Their parental melts were generated by variable degree of melting of an olivine-rich peridotitic mantle, containing clinopyroxene-amphibole (+/- phlogopite) vein assemblages with highly radiogenic Sr and Pb signatures.

Ohře/Eger rift; Picrite; Meimechite; Basanite/tephrite; K-Ar ages; Sr-Nd-Pb isotopes

Ohře/Eger rift; Picrite; Meimechite; Basanite/tephrite; K-Ar ages; Sr-Nd-Pb isotopes

KRMÍČEK, L.; ULRYCH, J.; JELÍNEK, E.; SKÁLA, R.; KRMÍČKOVÁ, S.; KORBELOVÁ, Z.; BALOGH, K.

2022

15.04.2021

SPRINGER WIEN

WIEN

0930-0708

MINERALOGY AND PETROLOGY

115

2

Republic of Austria

193

211

19

https://link.springer.com/article/10.1007/s00710-020-00729-5

http://hdl.handle.net/