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 40 Ar/ 39 Ar 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°C to ca 60 °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 °C, between 24 and 13 Ma is related to exhumation along high-angle normal faults in the southern part of the CRMC.