Publication Date:
2007-10-08
Description:
The pre-Alpine evolution of the external Hellenides is poorly constrained because of the Alpine impact which largely erased the older orogenic imprints. Only a few outcrops with pre-Alpine basement exist, one of which is located in eastern Crete. The pre-Alpine basement, part of the Phyllite-Quartzite Unit, is composed of four sub-complexes, which are different in protolith age, type and age of metamorphism, and postmetamorphic cooling history. The lowermost, Kalavros crystalline complex (KCC) underwent Permian amphibolite-facies metamorphism related to top-to-the-NE shearing. The KCC exhibits a four-stage garnet zonation and a late, high-temperature event associated with the growth of K-feldspar. The KCC is overlain by the Myrsini crystalline complex (MCC), which underwent Carboniferous amphibolite facies metamorphism associated with top-to-the-north shearing. Late cooling of the MCC is documented by Jurassic fission track ages of zircon. The Chamezi crystalline complex underwent upper greenschist-facies metamorphism related to top-to-the-north shearing. In addition, the Vai crystalline complex, in an uncertain structural position, is characterized by Triassic emplacement of granite, followed by amphibolite-facies top-to-the-NW shearing and cooling, as is indicated by Jurassic fission-track ages of zircon. A preliminary tectonic model is presented, which invokes south-directed subduction, collision and accretion of the crystalline complexes to the northern margin of Gondwana.
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