Foreland Magmatism during the Arabia–Eurasia Collision: Pliocene–Quaternary Activity of the Karacadağ Volcanic Complex, SW Turkey

Abstract

Pliocene to Quaternary magmatism in the Karacadağ Volcanic Complex in southeast 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. Like 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 focussed 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 crystallisation 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.

Mantle Sources of Recent Anatolian Intraplate Magmatism: A Regional Plume or Local Tectonic Origin?

“…More widely known, and sampled in the present study, are the volcanic products of late Miocene to Quaternary age (e.g., Ekici et al, ; Ercan et al, ; Lustrino et al, , ; Pearce et al, ; Şen et al, ). This younger volcanic activity is divided into two distinct stages on the basis of stratigraphic and geochronological studies.…”

Petrogenesis of mafic collision zone magmatism: The Armenian sector of the Turkish–Iranian Plateau

“…Fluids derived from Arabian Platform sediments, ultimately reflecting juvenile Pan-African continental crust, may have high Pb isotope ratios, leading to a fertilised sub-Armenian mantle significantly more radiogenic than that responsible for the preceding arc magmatism. Like Ekici et al (2014), we recognise that there are few if any appropriate elemental and isotopic studies of the Arabian Platform with which to test this hypothesis. …”

Petrogenesis of OIB-like basaltic volcanic rocks in a continental collision zone: Late Cenozoic magmatism of Eastern Iran

“…Most studies agree that these rocks form by low-degree melting of enriched asthenospheric mantle (e.g., Macpherson et al, 2010). An alternative model is that melts are formed in the lithospheric mantle, but that the mantle source was enriched by small-volume melts derived from the convecting asthenosphere (e.g., Ekici et al, 2014). Previous workers have stated that the Eastern Iranian OIBlike rocks formed by melting of the convecting asthenosphere (Pang et al, 2012;Saadat and Stern, 2012;Su et al, 2014) although this information needs to be reconciled with geophysical and xenolith-based evidence for lithospheric thickness (see Section 6.2).…”

“…Saal et al (2005). Karacadag (Ekici et al, 2014) is an OIB-type volcano in S Turkey on the Arabian Plate and appears to be derived at least in part from an asthenospheric source which is nevertheless more enriched than the Iranian samples. Suphan volcano in Eastern Anatolia (Özdemir and Güleç, 2014), which has been argued to have mixed with asthenospheric components, falls around the EMII end member on Pb isotope plots so is not plotted here.…”

“…The anomaly is also unlikely to represent higher than ambient mantle temperatures. Recent isotopic studies have disproven a link between the closest within-plate foreland magmatism to Turkey and Iran at the Karacadag volcanic centre in Northern Arabia, and the Afar plume (Ekici et al, 2014). Secondly, OIB-like output in Iran is extremely limited, with only small-volume cones and flows as opposed to more extensive magmatic outpourings which might be expected with a hotter-thanambient mantle source.…”