Petrogenesis and the Evolution of Pliocene Timar Basalts in the East of Lake Van, Eastern Anatolia, Turkey: a Consequence of the Partial Melting of a Metasomatized Spinel-Rich Lithospheric Mantle Source

Abstract

The Eastern Anatolian region provides a good example for collision-related volcanic activity. This activity started during the Middle Miocene and continued through the Pliocene and Quaternary. The new K - Ar ages reveal that the post-collisional Pliocene Timar basalts located in the East Anatolian Accretionary Complex (EAAC) erupted between 4.72 (Zanclean) and 3.29-2.93 Ma (Piacenzian). The Pliocene Timar basalts consist of plagioclase, clinopyroxene (augite), and olivine minerals and have glomeroporphyritic, intergranular, and ophitic textures. They display enrichment in light rare earth elements (LREEs) with (La/Yb)(N) values that range between 3.19 and 6.66 to 21.63-5.61. Sr-87/Sr-86(i) and Nd-143/Nd-144(i) isotopic ratios of the Timar basalts are 0.70599-0.70436 and 0.51277-0.51259, respectively. The epsilon Nd(t) values of these rocks range between 1.0116 and 1.0121. Sr-87/Sr-86(i) and Nd(t) contents indicate crustal contamination during the emplacement of the Timar basalts. According to the Energy Constrained-Assimilation Fractional Crystallization (EC-AFC) model, this contamination rate is between similar to 1.4 and 4.4%. The melting model shows that the least evolved samples of the Timar basalts were formed by similar to 0.1-2% partial melting of the lherzolitic source. Primitive melts that constituent Timar basalts were occurred with partial melting of a magma source that has predominantly spinel bearing mineralogy. All data indicate that the origin of the parental melts of the Timar basalts is metasomatized lithospheric mantle source and then these melts reached the surface from the fissures that is related to extensional tectonics in Pliocene.