Polybaric melting of a single mantle source during the Neogene Siverek phase of the Karacadağ Volcanic Complex, SE Turkey

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 Baenrichment. Neither fractional crystallisation nor crustal contamination can account for the differences in trace element enrichment observed between the two groups. Group 1 are 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 is migrated northwards during the Neogene.

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

“…Arabian magmatic activity is predominantly intraplate in nature and expressed in several basaltic volcanic fields exhibiting alkaline characteristics. Intraplate magmatism was active from 30 to 16 Ma and from 13 to 8 Ma in southern Turkey (e.g., Karacadağ, Gaziantep, and Kilis; Ekici et al, 2012Ekici et al, , 2014Gürsoy et al, 2009;Lustrino et al, 2010Lustrino et al, , 2012, northwestern Syria (e.g., Al Ghab and Homs regions; Krienitz et al, 2006;Lustrino & Sharkov, 2006;Ma et al, 2011), and southern Syria/Jordan (Harrat Ash Shaam; Krienitz et al, 2007;Shaw et al, 2003), increasingly so since the Pliocene (Ilani et al, 2001). Most volcanism occurred in close proximity to tectonic structures such as the Dead Sea Fault Zone, Esdraelon Valley, Euphrates Graben, Sirhan Graben, and Karak Graben (Ekici et al, 2014).…”

“…The magmatic source for Miocene-Quaternary volcanism in the Karacadağ Volcanic Complex has been identified as resembling predominantly OIB-like asthenosphere (Lustrino et al, 2012;Şen et al, 2004), though possibly metasomatized and compositionally heterogeneous, involving metasomatic networks in the local upper lithospheric mantle (Lustrino et al, 2012;Pearce et al, 1990). Isotope data further suggest a mantle source possibly distinct from that of magmatism attributed to the Afar plume (Ekici et al, 2012(Ekici et al, , 2014, although some authors have noted similarities (Faccenna et al, 2013;Keskin et al, 2012b).…”

“…Additionally, plume head spreading (van Hinsbergen et al, 2011), or entrainment of plume material due to mantle flow (Faccenna et al, 2013), may produce diachronous trends in volcanism. The absence of a nearby flood basalts, or seismological evidence for a plume, or direct involvement of a deep-seated melt in the intraplate volcanics of Anatolia make that previously, correlation to a major plume was considered unlikely (e.g., Aldanmaz et al, 2000Aldanmaz et al, , 2006Arger et al, 2000;Ekici et al, 2012Ekici et al, , 2014McKenzie & O'Nions, 1995;Pearce et al, 1990;Polat et al, 1997)-one of the key reasons why local deformation and slab edge formation have previously been invoked as triggers for melting in the first place. Faccenna et al (2013) postulated that a northward younging trend of intraplate volcanism may exist from the Afar plume toward Anatolia, driven by mantle flow toward the Aegean rollback system, but at least on the scale of Anatolia, no clear diachronicity is visible.…”

“…Upper Neogene intraplate-type volcanics are found in several places in western and eastern Anatolia and occur throughout different styles of tectonic provinces, from extensional in western Anatolia to transpressional and transcurrent in eastern, northern, and central Anatolia (Şengör et al, 1985;Şengör & Yilmaz, 1981). Such types of volcanics are often associated with mantle plumes, but no such plume appears to be present below Anatolia, nor is evident from the young volcanic's petrogenesis (e.g., Aldanmaz et al, 2000Aldanmaz et al, , 2006Arger et al, 2000;Ekici et al, 2012Ekici et al, , 2014McKenzie & O'Nions, 1995;Pearce et al, 1990;Polat et al, 1997), although large-scale mantle flow associated with the distant Afar plume may have played a role (Faccenna et al, 2013).…”

“…In summary, Late Neogene alkaline volcanism is interpreted to result from very different local tectonic and geodynamic processes throughout Anatolia. Previous studies of Anatolian intraplate volcanics have predominantly used bulk-rock geochemical and isotope data (e.g., Aldanmaz et al, 2006;Alıcı et al, 2001Alıcı et al, , 2002Arger et al, 2000;Bağcı et al, 2011;Chakrabarti et al, 2012;Ekici et al, 2012Ekici et al, , 2014Italiano et al, 2017;Klaver et al, 2016;Lustrino et al, 2012;Polat et al, 1997;Sölpüker, 2007;Yurtmen et al, 2000) to investigate the generation of alkaline magmas across various tectonic settings. However, in view of the complex history of the region following late-stage subduction or collision of the African, Eurasian, and Arabian plates, the nature and interaction of mantle and subduction components are difficult to decipher using bulk-rock geochemistry alone.…”