Mantle peridotite xenoliths in alkali basalts from the East Thrace region (NW Turkey)

This paper represents the first report on the peridotitic mantle xenoliths including spinel harzburgites and spinel lherzolites found in the Late Miocene-Pliocene basaltic rocks (Thracean alkaline basalts - TAB) of the Thrace region, northwestern Turkey. The lavas formed and extruded during the north-south extension of western Anatolia, are olivine basalts and basanites displaying within-plate affinity. The estimated modal mineralogy of the peridotite xenoliths is olivine (58-84 %) + orthopyroxene (12-35 %) + clinopyroxene (0-12 %) + spinel (1-5 %). They are characterized mainly by protogranular and also transitional protogranular to porphyroclastic and fine-grained equigranular textures. Melt pockets are recognized in only one sample. Deformation features in olivine and pyroxenes are zoning, twinning, including inclusions, kink banding, triple junction and undulatory extinction. Bulk-rock analyses indicate that the xenoliths are depleted in basaltic components (e.g. CaO - 0.39-1.50 wt. %, Al₂O₃ - 0.80 - 1.78 wt. %). Light rare-earth element (LREE) enrichment is significant (e.g. La_n 2-6), which suggests a cryptic metasomatic history.