Petrology and evolution of the Hercynian Pieria Granitoid Complex (Thessaly, Greece): paleogeographic and geodynamic implications

The Upper Carboniferous Pieria Granitoid Complex (PGC) and associated Pelag onian basement units are remnants of a Hercynian orogenic belt incorporated into the alpine nappe systems of the central Hellenides. The granitoid roc ks range from tonalite to granite and are mildly peraluminous. The lack of significant negative Eu and Sr anomalies suggests insignificant high-level crystal fractionation involving plagioclase. Meta-diorite sheets that cut a nd are deformed with the granitoids are characterized by metamorphic fabric s. Their trace element signatures are similar to enriched MORE and the high Ba/La is typical of subduction-related mafic rocks. They are interpreted a s representing predominantly asthenosphere-derived melts intruded into the granitoids. The bimodal mafic-felsic association observed in the PGC is als o found in other plutonic complexes throughout the Flambouron unit of the P elagonian terrane. Geochemically and isotopically, these plutons resemble H ercynian plutons of western Europe interpreted to result from melting of lo wer crustal orthogneisses. The Flambouron unit plutons were situated paleog eographically on the northern margin of Gondwana. Mantle enrichment resulte d from shea-lived subduction during Devonian to early Carboniferous collisi on of Gondwana and Laurasia, whereas plutonism occurred during regional ext ension as Gondwana rotated clockwise with respect to Laurasia in the late C arboniferous. (C) 2000 Elsevier Science B.V. All rights reserved.