Sources and evolution of miocene-pleistocene alkaline magmatism in the north-east part of the arabian plate (data from Sr–Nd–Pb isotopic systematics and K–Ar geochronometry)

Abstract

A geochronological and isotope-geochemical study of alkaline basalts from three areas of young magmatism within the northeastern part of the Arabian Plate (Southeastern Turkey), Batman, Kurtalan and Alemdağ, was carried out. The obtained isotope data have indicated that the volcanism in the studied region developed over 5 mln years from the end of Miocene to the mid of Pleistocene during four pulses separated by breaks in magmatic activity: 6.1-4.9 Ma (Batman area, hawaiites), ~3.0 Ma (Alemdağ plateau, phase I, basalts), 2.0-1.9 Ma (Alemdağ plateau, phase II, tephrites), and 1.5-1.3 Ma (Alemdağ plateau, phase III, basalts; Kurtalan area, basalts). A comparison of spatial-temporal regularities of magmatic activity evolution in the studied part of the Arabian Plate and within the largest basalt plateau of Arabian foreland, Karacadağ plateau, located to the west, was carried out. The results of Sr-Nd-Pb isotope-geochemical studies show that the development of young basalt volcanism within the northern part of the Arabian Plate was characterized at different time by participation of various mantle sources in magma generation under this region. Initial pulses of magmatic activity are associated with melting of Arabian subcontinental lithospheric mantle (SCLM). The processes of fractional crystallization combined with crustal assimilation (AFC) have played an important role in the petrogenesis of lavas as well. In the subsequent time, a deep mantle source (PREMA) with a depleted isotopic composition of Sr and Pb played a leading role in the formation of basaltic magmas of increased alkalinity. The melts generated by this source were mixed with the SCLM material in various proportions at different stages of magmatism with a limited participation of AFC processes in the petrogenesis of the rocks. It was concluded that young basalt volcanism of elevated alkalinity in the northeast of the Arabian Plate is not related to the collision of the Eurasian and Arabian plates genetically, but presumably manifested here as a result of the migration of the initial rift geodynamic set from the Red Sea basin to the north along Levantine and East Anatolian transform faults with associated convective wave flows in the lower part of mantle under this part of the Earth.