Source melting and origin of the basaltic rocks situated along the active East Anatolian and Dead Sea Transform Faults, Southeastern Türkiye

Magmatic activity associated with active transform faults in the Eastern Mediterranean region is widely observed around Toprakkale (Osmaniye), Ceyhan (Adana), and Hatay. This magmatic activity is associated with the Toprakkale Fault (East Anatolian Fault Zone) to the west, the Amanos Segment (East Anatolian Fault Zone) and Yesemek Segment (Dead Sea Fault Zone), which border the Karasu Valley to the east.

Lavas from the western sector (Toprakkale region) are represented by predominantly alkaline mafic compositions, plotted within the basanite and basalt fields in total alkaline-silica (TAS) diagram and displaying SiO₂ and MgO contents of 43.70–48.77 wt% and 5.98–10.46 wt%, respectively. Furthermore, in the eastern sector (Karasu Valley) of the study area, mafic lavas similarly show alkaline affinities and mainly represented by basalts and trachybasalts with SiO₂ and MgO values ranging from 44.89–51.01 wt% and 4.53–9.21 wt% respectively.

Primitive mantle–normalized [1] multi-element patterns of basaltic rocks display LIL element enrichment relative to HFS elements and have broadly OIB-like affinities, but these rocks differ from OIB signature by the depletion in LIL element contents. In contrast, samples from the Karasu Valley are represented by enrichment in LIL and depletion of HFS elements, and are distinct from the OIB signature by enrichment in Cs, Ba, and Pb, along with depletion in Sm, Zr, and Hf. Incompatible element ratios of the mafic lavas show systematic similarities between the western (Toprakkale) and eastern (Karasu Valley) parts of the study area. Ba/La ratios from Toprakkale region range 7.29-9.41 whereas lavas from the Karasu Valley are characterized by higher values that range between 9.76-18.70. Similarly, both sectors are represented by elevated Th/U (3.02–9.16) and consistently high Dy/Yb ratios (>2) [2].

These geochemical features may indicate that the basaltic rocks were derived from a garnet-bearing mantle source. Decompression process appears to be related to the transform fault activities, and the upwelling of the asthenosphere is capable of producing alkaline magmatism within both sectors of the fault zones.

1. Sun, S., McDonough, W.F., 1989. In Magmatism in the Ocean Basins Geological Society London Special Publications, pp. 313–345.

2. Peters, et al., 2008. Lithos, 102(1-2), 295–315.

ACKNOWLEDGEMENTS

This research has been founded by TUBITAK COST project 125Y257

This research is financially supported by TUBITAK 2224-A