Age and mantle sources of Quaternary basalts associated with leaky transform faults of the migrating Anatolia-Arabia-Africa triple junction

Toprakkale basalts and basanites have 40Ar/39Ar plateau ages ranging from 810 +/- 60 ka to 46 +/- 13 ka, and Karasu volcanic field basalts have 40Ar/39Ar plateau ages ranging from 2.63 +/- 0.17 Ma to 52 +/- 16 ka. Two basanite samples within the Toprakkale volcanic field have isotopic characteristics of a depleted mantle source, with Sr-87/Sr-86 of 0.703070 and 0.703136, Nd-143/Nd-194 of 0.512931 and 0.512893, Hf-176/Hf-177 of 0.283019 and 0.282995, Pb-206/Pb-204 of 19.087 and 19.155, and Pb-208/Pb-204 of 38.861 and 38.915. The Hf-176/Hf-177 ratios of Toprakkale basalts (0.282966-0.283019) are more radiogenic than Karasu basalts (0.282837-0.282965), with some overlap in Nd-143/Nd-194 ratios (0.512781-0.512866 vs. 0.512648-0.512806). Toprakkale Pb-206/Pb-204 ratios (19.025 +/- 0.001) exhibit less variation than that observed for Karasu basalts (18.800-19.324), and Pb-206/Pb-204 values for Toprakkale basalts (38.978-39.103) are slightly lower than values for Karasu basalts (39.100-39.219). Melting depths estimated for the basalts from both volcanic fields generally cluster between 60 and 70 km, whereas the basanites record melting depths of similar to 90 km. Depth estimates for the basalts largely correspond to the base of a thin lithosphere (similar to 60 km) observed by seismic imaging. We interpret the combined radiogenic isotope data (Sr, Nd, Hf, Pb) from all alkaline basalts to reflect partial melting at the base of the lithospheric mantle. In contrast, seismic imaging indicates a much thicker (>100 km) lithosphere beneath southern Anatolia, a substantial part of which is likely subducted African lithosphere. This thicker lithosphere is adjacent to the surface locations of the basanites. Thus, the greater melting depths inferred for the basanites may include partial melt contributions either from the lithospheric mantle of the attached and subducting African (Cyprean) slab, or from partial melting of detached blocks that foundered due to convective removal of the Anatolian lithosphere and that subsequently melted at similar to 90 km depth within the asthenosphere. Toprakkale basalts and basanites have 40Ar/39Ar plateau ages ranging from 810 +/- 60 ka to 46 +/- 13 ka, and Karasu volcanic field basalts have 40Ar/39Ar plateau ages ranging from 2.63 +/- 0.17 Ma to 52 +/- 16 ka. Two basanite samples within the Toprakkale volcanic field have isotopic characteristics of a depleted mantle source, with Sr-87/Sr-86 of 0.703070 and 0.703136, Nd-143/Nd-194 of 0.512931 and 0.512893, Hf-176/Hf-177 of 0.283019 and 0.282995, Pb-206/Pb-204 of 19.087 and 19.155, and Pb-208/Pb-204 of 38.861 and 38.915. The Hf-176/Hf-177 ratios of Toprakkale basalts (0.282966-0.283019) are more radiogenic than Karasu basalts (0.282837-0.282965), with some overlap in Nd-143/Nd-194 ratios (0.512781-0.512866 vs. 0.512648-0.512806). Toprakkale Pb-206/Pb-204 ratios (19.025 +/- 0.001) exhibit less variation than that observed for Karasu basalts (18.800-19.324), and Pb-206/Pb-204 values for Toprakkale basalts (38.978-39.103) are slightly lower than values for Karasu basalts (39.100-39.219). Melting depths estimated for the basalts from both volcanic fields generally cluster between 60 and 70 km, whereas the basanites record melting depths of similar to 90 km. Depth estimates for the basalts largely correspond to the base of a thin lithosphere (similar to 60 km) observed by seismic imaging. We interpret the combined radiogenic isotope data (Sr, Nd, Hf, Pb) from all alkaline basalts to reflect partial melting at the base of the lithospheric mantle. In contrast, seismic imaging indicates a much thicker (>100 km) lithosphere beneath southern Anatolia, a substantial part of which is likely subducted African lithosphere. This thicker lithosphere is adjacent to the surface locations of the basanites. Thus, the greater melting depths inferred for the basanites may include partial melt contributions either from the lithospheric mantle of the attached and subducting African (Cyprean) slab, or from partial melting of detached blocks that foundered due to convective removal of the Anatolian lithosphere and that subsequently melted at similar to 90 km depth within the asthenosphere. Toprakkale basalts and basanites have 40Ar/39Ar plateau ages ranging from 810 +/- 60 ka to 46 +/- 13 ka, and Karasu volcanic field basalts have 40Ar/39Ar plateau ages ranging from 2.63 +/- 0.17 Ma to 52 +/- 16 ka. Two basanite samples within the Toprakkale volcanic field have isotopic characteristics of a depleted mantle source, with Sr-87/Sr-86 of 0.703070 and 0.703136, Nd-143/Nd-194 of 0.512931 and 0.512893, Hf-176/Hf-177 of 0.283019 and 0.282995, Pb-206/Pb-204 of 19.087 and 19.155, and Pb-208/Pb-204 of 38.861 and 38.915. The Hf-176/Hf-177 ratios of Toprakkale basalts (0.282966-0.283019) are more radiogenic than Karasu basalts (0.282837-0.282965), with some overlap in Nd-143/Nd-194 ratios (0.512781-0.512866 vs. 0.512648-0.512806). Toprakkale Pb-206/Pb-204 ratios (19.025 +/- 0.001) exhibit less variation than that observed for Karasu basalts (18.800-19.324), and Pb-206/Pb-204 values for Toprakkale basalts (38.978-39.103) are slightly lower than values for Karasu basalts (39.100-39.219). Melting depths estimated for the basalts from both volcanic fields generally cluster between 60 and 70 km, whereas the basanites record melting depths of similar to 90 km. Depth estimates for the basalts largely correspond to the base of a thin lithosphere (similar to 60 km) observed by seismic imaging. We interpret the combined radiogenic isotope data (Sr, Nd, Hf, Pb) from all alkaline basalts to reflect partial melting at the base of the lithospheric mantle. In contrast, seismic imaging indicates a much thicker (>100 km) lithosphere beneath southern Anatolia, a substantial part of which is likely subducted African lithosphere. This thicker lithosphere is adjacent to the surface locations of the basanites. Thus, the greater melting depths inferred for the basanites may include partial melt contributions either from the lithospheric mantle of the attached and subducting African (Cyprean) slab, or from partial melting of detached blocks that foundered due to convective removal of the Anatolian lithosphere and that subsequently melted at similar to 90 km depth within the asthenosphere.

Automated summary

The study reveals a wide range of ages for the volcanic rocks from Toprakkale and Karasu volcanic fields, ranging from different epochs. Isotopic analysis of basanite samples from Toprakkale volcanic field suggests a depleted mantle source. Melting depths of the volcanic rocks are estimated to reflect partial melting at the base of the lithospheric mantle.