Relics of Devonian oceanic lithosphere in Byala Reka dome, Eastern Rhodopes: Evidence from zircon U-Pb dating and Hf-isotope tracing

Zircon U-Pb isotope dating and tracing of amphibolitized eclogites from the metaophiolitic part of the Byala Reka Unit near Chernichevo village in the Eastern Rhodopes of Bulgaria give evidence for a Paleozoic protolith age (Concordia age for most zircons at 380.9 ± 1.9 Ma). Hafnium isotope data ( ε Hf ~ 10) of these zircons argue for their mantle source. The high pressure mineral assemblages in the metaeclogites suggest transition of the metamorphism from blue schist to eclogite facies. Retrogression by almost isothermal decompression with replacement of glaucophane/barroisite by Ca-amphiboles, plagioclase and epidote results in the formation of common epidote amphibolites. Partial recrystallization of the zircons during the metamorphism is suggested by trace element distribution, CL imaging and age data.