Mantle lithosphere control of crustal tectonics and magmatism of the western ohře (Eger) rift

Abstract

This paper summarizes our recent research on the relationship between tectonics of the mantle lithosphere and of the upper crust in the western Bohemian Massif. The rejuvenated Variscan junction of three mantle domains, the Saxothuringian, Moldanubian and Teplá-Barrandian, delimited by different orientation of seismic anisotropy reflecting a consistent fossil olivine orientation and belonging to originally separated microplates, plays important role in the crustal architecture of the region. The crust above the mantle junction is the most active part of the BM characterized by periodic earthquake swarms and mofettes emitting gases of mantle origin. Detected offsets of surface boundaries of the three units from their mantle counterparts indicate a detachment of the rigid upper crust from the mantle lithosphere. Locations of major tectonic features like the Ohře (Eger) Rift, the West Bohemian Shear Zone and the Mariánské Lázně Fault were probably predisposed by the boundaries of the mantle lithosphere domains. We have suggested that the sublithospheric mantle of the western BM acted as a major provider for heat and partial melts and the Variscan mantle boundaries served as magma conduits for the late-orogenic granitic magmatism and, after their rejuvenation, also for the Cenozoic volcanism. Similarly, the boundaries may have pre-determined the subsequent locations of sedimentary basins. It is possible that also in other regions some of these so called intra-plate phenomena can be related to partly healed up and later rejuvenated microplate boundaries. List of abbreviations: BM - Bohemian Massif, BOHEMA - International project BOhemian Massif HEterogeneity and Anisotropy, BP - Bor Pluton, CHB - Cheb Basin, DEKORP Deutsches Kontinentales Reflexionsseismisches Programm, DP - Doupovskě hory Mts., DU - Dyleň Unit, ECC - Erzgebirge (Krušné hory) Crystalline Complex, ECRIS - European Cenozoic Rift System, ER - Ohře (Eger) Rift, HSU - Horní Slavkov Unit, KH - Komorní Hůrka, KHF - Krušné Hory (Erzgebirge) Fault, KU - Kladská Unit, KVP - Karlovy Vary Pluton, MD - Moldanubian Unit, MLC - Mariánské Lázně Complex, MLF - Mariánské Lázně Fault, PF - Plesná Fault, SB - Sokolov Basin, SP - Smrčiny (Fichtelgebir-ge) Pluton, ST - Saxothuringian Unit, T-junction - triple junction of the ST/TB/MD mantle lithospheres, TB - Teplá-Barrandian Unit, TCC - Teplá Crystalline Complex, TP - Tirschenreuth Pluton, WBSZ - West Bohemian Shear Zone, ZEV - Zone of Erbendorf-Vohenstrauss, ZH - Železná Hůrka, ŽP - Žandov (also Lesny̌-Lysina or Kynžvart) Pluton.