The tectonomagmatic evolution of the Rhodope area, Bulgaria
Final Report Abstract
The aim of the research project was to examine metamorphic and igneous rocks from the Rhodope area in Southern Bulgaria. This region constitutes a highly suited terrain to investigate processes active in a late- to post-collisional tectonic regime. As part of a broader project (DFG Bündelantrag), the aim of the proposed project was to examine (1) HP ophiolites and (2) post-collisional high-K volcanic rocks. Lu-Hf garnet dating of metamorphic basement rocks revealed a metamorphic event during the Cretaceous affecting the highest nappe unit (Upper Allochthon) and an Eocene event for the Middle Allochthon. This provides evidence for two separate subduction events in the Rhodopes, in support of previous findings. New major, trace element and Sr-Nd-Hf-Pb isotope data was obtained for K-rich postcollisional Teriary lavas from Bulgaria, and as possible recent analogue for Quaternary lavas from Santorini. The isotope signatures found in the Bulgarian lavas indicate lithospheric mantle refertilization by subduction components similar to presently subducted continentderived sediments and subsequent post-collisional melting. Notably, the Bulgarian lavas record a more enhanced influx of fluid-like subduction components in comparison to the Santorini lavas. As K-rich lavas like those investigated here are an important endmember of subduction-related volcanism worldwide, we performed a more in-depth study of the behaviour of the extended high-field-strength element group (Nb, Ta, Zr, Hf, W, and Mo) in the Santorini and Bulgarian lavas using high-precision techniques. Likewise, such measurements were performed in a set of sediment samples (DSDP Leg 13 and ODP Leg 160) to characterize possible subduction components. In general, ratios of HFSE in the lavas largely mirror HFSE compositions of the subducted sediments, and there is little evidence for a role of residual mineral phases in the subducting slab and in the lithospheric mantle that are capable of fractionating HFSE ratios.
Publications
- (2012). Tectonomagmatic constraints on the sources of Eastern Mediterranean K-rich lavas. Journal of Petrology, 53(1), 27-65
Kirchenbaur, M., Münker, C., Schuth, S., Garbe-Schönberg, D. & Marchev, P.
(See online at https://doi.org/10.1093/petrology/egr055) - (2012). Timing of high-pressure metamorphic events in the Bulgarian Rhodopes from Lu-Hf garnet geochronology. Contributions to Mineralogy and Petrology, 163(5), 897-921
Kirchenbaur, M., Pleuger, J., Jahn-Awe, S., Nagel, T.J., Froitzheim, N., Fonseca, R.O.C. & Münker, C.
(See online at https://doi.org/10.1007/s00410-011-0705-5) - (2015). The behaviour of the extended HFSE group (Nb, Ta, Zr, Hf, W, Mo) during the petrogenesis of mafic K-rich lavas: the Eastern Mediterranean case. Geochimica et Cosmochimica Acta, 165: 178-199
Kirchenbaur, M. & Münker, C.
(See online at https://doi.org/10.1016/j.gca.2015.05.030)
