PERIDODITIC XENOLITHS IN ALKALINE BASALTS ATTEKlRDAG REGION (THRACE)

Abstract

In basaltic volcanics at Tekirdağ region (Thrace), peridodit(ic) xenoliths such as harzburgite and dunite thought as parts of upper mantle has been found. Petrographically, the bazaltic lavas are olivine-basalts showing a primary paragenesis including mainly plagioclaze. olivine. augite. magnetite and scarcely hypersthene as well the secondary minerals at important degrees locally. On the other hand, geochemically they correspond to the alkaline basalt, trachybasalt basanitic rock types. Peridodite xenolithenclosing Hacıköy and Balabanlı and excluding Muratlı basalts also differ in both major and trace element contents. Including olivine (forsterite). enstatite, Cr-spinel and scarcely diopside, the peridodite xenoliths are typically protogranular and partly grading into porphyroclastic in fabric. Magmatic textures are well preserved. Displaying no foliation or lineation. those have coarseto huge grain sizes. Bandings resembling twinning and deformation lamellas imply the mechanical effec and are characteristic for the olivines and pyroxenes. Whether, the presence of relations depicting partially melting of original mantle, between major elements of the peridodite xenoliths is a fact, the melting point is probably not high. They were uneffected by metasomatism and submit a somewhat consumpted composition compared to primitive mantle.