Trace element and oxygen isotope study of eclogites and associated rocks from the Münchberg Massif (Germany) with implications on the protolith origin and fluid-rock interactions

Eclogites, metagabbros, and paragneisses from the Variscan Münchberg Massif record a complex succession of igneous, hydrothermal metamorphic processes. The geodynamic setting related to protolith formation impact different types fluid-rock interactions have been uncertain up now. We use major trace element chemistry as well oxygen isotopes disentangle geochemical signatures stages rocks' history. In Massif, dark eclogites (kyanite-free; Fe-Ti-MORB signature) are distinguished light (kyanite-bearing; higher Mg#, Al 2 O 3 , Cr; lower incompatible contents; positive Eu anomalies; MORB arc basalt signature). δ 18 values for both (+5.0 +10.8‰) equal to, or than those MORB. Amphibolite facies metagabbros more enriched, almost OIB-like signature high (+9.4 +10.3‰). Good linear correlations between fluid-immobile elements throughout eclogite confirm their derivation common, N-MORB E-MORB-like parental magma. interpret former plagioclase-rich cumulates complementary differentiates. This relationship is partly obscured by variable degrees magma contamination sediments, which also affected metagabbros. However, originated enriched mantle source eclogites. Following intrusion, were subjected alteration under influence seawater, indicated Li, B, Sb, O. Metamorphic appear be mostly limited extent, probably due lack lawsonite dehydration fluid source. Nevertheless, contents at least some fluid-mobile elements, such LILE, Pb, modified during subduction-exhumation cycle crustal magmas argues against typical oceanic crust. Instead, rift-drift transition opening Rheic Saxothuringian Ocean seems most likely. alongside with similar rocks in Mariánské Lázně other resembling high-pressure massifs, may this transition.