AGE, GEOCHEMISTRY, AND TECTONIC SIGNIFICANCE OF QUATERNARY BASALTS ASSOCIATED WITH TRANSFORM FAULTS OF THE ANATOLIA-ARABIA-AFRICA TRIPLE JUNCTION

Mafic volcanism, active seismicity, vigorous geothermal fluid circulation and mineralization are commonly associated with triple junctions. In this study we demonstrate that ⁴⁰Ar/³⁹Ar dating of mafic volcanism associated with the Anatolia-Arabia-Africa triple junction (A³ triple junction) can also be used to constrain the onset of tectonic escape of the Anatolian plate. The A³ triple junction, located near the Gulf of İskenderun in the eastern Mediterranean, is a trench-transform-transform system that includes two major, dominantly left-lateral transform faults: the East Anatolian fault zone (the Anatolia-Arabia plate boundary) and the Dead Sea fault zone (the Arabia-Africa plate boundary). Quaternary alkaline basalt (including basanite) from the Toprakkale and Karasu volcanic fields are investigated within a broad zone of transtension associated with these plate boundary faults near the İskenderun and Amik Basins, respectively. Seismic velocities obtained primarily from the Continental Dynamics-Central Anatolian Tectonics project (CD-CAT) show abrupt contrasts in lithospheric thicknesses under the triple junction, from ~60 km beneath the Arabian margin to >100 km beneath central Anatolia. Here we present ⁴⁰Ar/³⁹Ar geochronology, whole rock geochemistry, Sr, Nd, Hf, and Pb isotopes of basalts from each volcanic field and compare their mantle source regions and equilibration depths to the seismically imaged lithosphere-asthenosphere boundary. These results will be discussed within a broader context of regional magmatism and mantle structure associated with the inception and migration of the triple junction, which also has implications for dating tectonic escape of the Anatolian microplate.