PLAGIOGRANITIC ROCKS OF EVROS OPHIOLITE, NE GREECE

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Published: Jan 1, 2007
DOI: https://doi.org/10.12681/bgsg.16742
Keywords:
Plagiogranite trondhjemite petrogenesis partial melting epidosite
A. Magganas
National and Kapodistrian University of Athens, Faculty of Geology and Geoenvironment, Department of Mineralogy and Petrology
Abstract

Dykes or small stocks of plagiogranitic rocL· occur below the extrusive sequence and in mutually interpenetrating association with the sheeted dyke complex of the Evros Ophiolite, NE Greece. They are classified as tonalités, low silica trondhjemites (LST) and high silica trondhjemites (HST). Pétrographie and geochemical data suggest they resemble oceanic plagiogranites ofSSZ origin. Their normalized rock/ORG diagrams reveal ORG compatible element values, slightly depleted relative to ORG incompatible elements and Ba, Ta and Nb negative anomalies. Plagiogranites also show subparallel, relatively flat REE patterns with variable Eu anomaly. As such geochemical features are also found in the dacitic to rhyodacitic lavas of Evros Ophiolite, it is assumed that plagiogranitic melts, especially of LST composition, presumably fed them. As a first approximation to plagiogranites origin, it is suggested tonalité and HST could have been generated by 5-15 % partial melting of oceanic gabbros, whereas LST may possibly derive by fractional crystallization of a MORB type source. In a later stage, intense hydrothermal metamorphism affected the plagiogranites causing formation of peculiar epidositic spherical clots and veinlets

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  • Mineralogy-Petrology-Geochemistry-Economic Geology
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