Eocene to Recent Volcanism Within the Rhenish Massif and the Northern Hessian Depression - Summary
The volcanism of the Rhenish Massif is associated with tectonic events related to the formation of the Rhine rift system. During the Tertiary, the beginning of volcanic activity shifts from west (Hocheifel, 46 Ma) to east (Northern Hessian Depression, 20 Ma). The Quaternary volcanism is restricted to two fields west of the Rhine. Except for the Siebengebirge, SiO2-undersaturated basaltoids predominate throughout the Tertiary. Their uniform major and trace element chemistry as well as their Sr (87Sr/86Sr = 0.7037 ± 0.0003) and Nd (143Nd/144Nd = 0.512858 ± 0.000055) isotope similarities are indicative of homogeneous mantle sources enriched in LIL elements prior to partial melting. Magma generation is believed to be a result of asthenosphere updoming for which evidence exists from geophysical observations and xenolith studies. Quaternary magmas presumably are related to a region of P-wave attenuation whose maximum elevation at 50 km depth is located beneath the West Eifel. From geochemical and isotopic evidence it can be concluded that these magmas in their majority come from mantle sources whose Sr (87Sr/86Sr = 0.7042 ± 0.0003) and Nd (143Nd/144Nd = 0.512695 ± 0.000045) isotopies and LIL element geochemistry are distinctly different from the Tertiary sources.
KeywordsPartial Melting Mantle Source Mantle Xenolith Volcanic Field Olivine Basalt
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