Radioisotopic data and geodynamic interpretations in the eastern part of the Balkan Peninsula

Results of radiogeochronological studies on the igeous and metamorphic rock complexes can be effectively interpreted only when taking into account the possibilities and limitations of each method applied.
   Igneous rocks are comparatively easily dated when have not suffered superimposed thermal or tectonothermal (metamorphic) events after their cooling. Concordant ages are usually obtained using the Rb-Sr, U-Pb and K-Ar methods. The Ar-Ar method may be crucial for understanding the cooling history. U-Pb dating of zircon cores may supply information about the source rocks, and initial Rb-Sr ratios and Sm- Nd data are important for petrogenetic interpretations.
   When the igneous body has been subjected to post-intrusion tectonothermal events, its origin and evolution may be elucidated only with the aid of a complex of methods. The age of the intrusion may be obtained using isochrone methods: Rb-Sr whole-rock isochrone (the mineral isochrone reflect the time of superimposed metamorphism) and U-Pb zircon ages using the concordia-discordia diagram. In the second case, the upper concordia/discordia intercept is related to the intrusion age whereas the lower intercept gives the age of the superimposed metamorphism. In the most general case, K-Ar dates would be "mixed data" situated between the age of cooling and the time of superimposed metamorphism, and in case of full radiogenic Ar loss during the superimposed event, would date the latter. In such a case, the Ar-Ar method will supply information about the cooling history of this last tectonothermal event.
   A single metamorphic event (or cycle) imposed over a sedimentary or volcano-sedimentary sequence would result in concordant ages obtained by different isotopic methods. Considerable difficulties arise when trying to date polymetamorphic complexes with a long and controversial history. Unfortunately, such is the case with most of the polymetamorphic rocks exposed in the central parts of the Balkan Peninsula.
   The present overview aims to compare the information obtained during the last years when extensive new data have been published. The reference list contains (due to the very limited space) only a selected fraction of the various sources used. The author apologizes for the forceful omission of many valuable sources that will be fully cited in a following extended publication.