Cenozoic thermal evolution of the Central Rhodope Metamorphic Complex (Southern Bulgaria)

We have combined new titanite, zircon, and apatite fission-track and apatite [U-Th-(Sm)]/He analyses with previously published U-Pb, Rb-Sr, and 40Ar/39Ar thermochronological data to reconstruct the Cenozoic thermal evolution of the Central Rhodope Metamorphic Complex (CRMC), exposed mainly in southern Bulgaria and to a lesser extent in northern Greece. Results reveal two phases of cooling. During the first phase, between 37 and 33 Ma, the CRMC experienced rapid cooling from partial melting at > 650 degrees C to ca 60 degrees C. Multiple generations of low-angle ductile-to-brittle fault zones accommodated the exhumation of the migmatitic core together with parts of its high-grade periphery. Oligocene volcanism and associated local elevation of the geothermal gradient is responsible for the resetting of some fission-track ages in the CRMC. The second cooling phase to temperatures of about 40 degrees C, between 24 and 13 Ma, is related to exhumation along high-angle normal faults in the southern part of the CRMC.