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New 40Ar/39Ar ages are presented for volcanic rocks from the Karacadağ Volcanic Complex (KVC) in SE Anatolia. These extend the oldest age recognised for the KVC for lavas from the Siverek Phase plateau basalt back to at least 17 Ma. Our data agree with prior studies that the second, Karacadağ Phase of igneous activity began at about 4.5 Ma with a peak between 2 and 1 Ma, but in contrast to previous work we find that this included volcanism on the Mt. Karacadağ ridge from the earliest part of this phase. Construction of the Mt. Karacadağ ridge coincided with development of the prominent east-west striking Abd El Aziz and Sinjar compressional antiforms, which lie approximately 100 km to the south. These provide complementary evidence for the orientation of compressional deformation across a broad zone of the leading edge of the Arabian Plate as it collided with Anatolia between 4 and 1 Ma. The new data also indicate that the compression-aligned deformation of the foreland magmatism may have permitted tapping of melts from greater depth in the probably asthenospheric mantle than occurred prior to 4 Ma. However, magmas from throughout the history of the KVC contain some components derived from the lithospheric mantle. [ABSTRACT FROM AUTHOR]

Pliocene to Quaternary magmatism in the Karacadağ Volcanic Complex in SE Turkey occurred in the foreland region of the Arabia–Eurasia collision and can be divided into two phases. The earlier Karacadağ phase formed a north–south-trending volcanic ridge that erupted three groups of lavas. The same range of mantle sources contributed to the younger Ovabağ phase lavas, which were erupted from monogenetic cones to the east of the Karacadağ fissure. As at several other intraplate localities across the northern Arabian Plate this magmatism represents mixtures of melt from shallow, isotopically enriched mantle and from deeper, more depleted mantle. The deep source is similar to the depleted mantle invoked for other northern Arabian intraplate volcanic fields but at Karacadağ this source contained phlogopite. This source could be located in the shallow convecting mantle or may represent a metasomatic layer in the base of the lithosphere. There is no evidence for a contribution from the Afar mantle plume, as has been proposed elsewhere in northern Arabia. Melting during the Karacadağ and Ovabağ phases could have resulted from a combination of upwelling beneath weak or thinned lithosphere and restricted local extension of that weakened lithosphere as it collided with Eurasia. Tension associated with the collision focused magma of the Karacadağ phase into the elongate shield volcano of Mt. Karacadağ. The northern end of the fissure accommodated more extensive differentiation of magma, with isolated cases of crustal contamination, consistent with greater stress in the lithosphere closest to the collision. Most magma batches of the Karacadağ and Ovabağ phases differentiated by fractional crystallization at ∼5 MPa, near the boundary between the upper and lower crust. Magma batches dominated by melt from garnet lherzolite show evidence for restricted amounts of differentiation at ∼22·5 MPa, which is close to the base of the lithospheric mantle. [ABSTRACT FROM AUTHOR]

Abstract: Siverek plateau basalts represent the Neogene activity of the Karacadağ Volcanic Complex in southeast Turkey and can be divided into two groups based on incompatible element concentrations. Group 1 is largely basaltic, containing some alkali basalts, while Group 2 consists of alkali basalts, trachybasalts and tephrites. The lavas display a range in major element concentrations that are consistent with restricted amounts of differentiation in the crust. Melts from both groups have experienced variable, small amounts of interaction with crustal rocks, which is responsible for most of the isotopic heterogeneity and caused significant Ba-enrichment. Neither fractional crystallisation nor crustal contamination can account for the differences in trace element enrichment observed between the two groups. Group 1 is derived mainly from the spinel lherzolite field by >1% partial melting. Group 2 lavas were derived from very similar mantle but by smaller degrees of melting and contain a larger relative contribution from garnet-lherzolite. The Siverek plateau lavas are indistinguishable from contemporaneous magmatism in the Karasu Valley of southern Turkey and in northernmost Syria. Together, these plateau basalt fields represent mantle upwelling and melting beneath the thinned and/or weakened Arabian Plate as it migrated northwards during the Neogene. [Copyright &y& Elsevier]