Abstract

Ivan S. Zagorèev writes: Koukouvelas & Pe-Piper (1991) have presented interesting evidence and interpretations about the Oligocene intrusion of the Xanthi pluton. Several problems concerning the regional setting remain, however, either unexplained or wrongly treated due to insufficient knowledge of Bulgarian and latest Greek publications. The main problems may be summarized as follows.

(1) The Xanthi pluton was emplaced mostly within amphibolite-facies metamorphic rocks of the Thermes (lower amphibolite-marble series (G) and Boz Dag (D) marble formations (Dimadis & Zachos 1989) which represented equivalents of the Rupèos Group and Dobrostan Marble Formation (Kozhoukharov 1988) respectively. The protolith of these formations was most probably (after acritarchs) of Precam-brian age (Kozhoukharov 1988), and their amphibolite facies regional metamorphism and synmetamorphic folding predated (Zagorèev 1981) the intrusion of the Palaeozoic south Bulgarian granitoids (340–240 Ma; Zagorèev & Moorbath 1986) such as the Kavala pluton (Kokkinakis 1980).

The site of the Xanthi pluton coincides not only with the ENE-striking Kavala–Komotini normal fault but also (Fig. 1) with the older SW-vergent Meso-Rhodopean overthrust (Dimadis & Zachos 1989) of the Central Rhodope (Sidironero) unit over the Pirin-Pangaion unit (Papanikolaou & Panagopoulos 1981; Zagorèev 1981, 1989). This overthrust is probably of a Mid-Cretaceous age similarly to the Strimon overthrust; the latter cuts through the superimposed schistosity in the Spancevo pluton, and is older than the Late Cretaceous Dautov (North Pirin) granitoid pluton (Zagorèev & Moorbath 1983).

Interpretations of Palaeogene amphibolite-facies regional metamorphism (e.g. Liati 1986) are based almost exclusively on K-Ar data. The latter represent mostly ‘

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