In the Central Anatolian Crystalline Complex (CACC) the Late Cretaceous post-collisional granitic magmatism is followed by Eocene extension, resulting in formation of roughly E-W trending transtensional basins. Formation of these basins was accompanied by calc- alkaline- mildly alkaline volcanism. The volcanic rocks, mainly subaques lava flows and subareal domes are concentrated along these basins and associated with Middle Eocene (Bartonian) Mucur Formation. They are basic to intermediate and are classified as basalt, basaltic andesite and rarely alkali basalt and trachy-andesite. All studied samples are strongly and variably LREE enriched relative to chondrite with the (La/Sm)N ratio of 2.26- to 6.17. They have negative Nb-Ta and Ti anomalies in the primitive mantle normalized diagram, and are characterized by low Nb/La (0.21 to 0.62), Ce/Pb (3.70-34.90) and Nb/U ratios (1.11-30), which may indicate an interaction with the Late Cretaceous granitic host rocks in the course of their ascent. The volcanic rocks display similar but variable ranges of Sr, Nd and Pb isotope values. Relatively high values of &epsilon / Nd (0.53 to 4.33) indicate an isotopically depleted mantle source. Combined trace element and isotope compositions of the Eocene samples suggest that they were derived from a heterogeneous lithospheric mantle source that had been metasomatized by subduction related agents such as fluids and/or melts during a previous geodynamic event. Geochemistry and geotectonic setting point out that lithospheric delamination was the most likely mechanism to generate these calc-alkaline to mildly alkaline volcanic rocks in the CACC.

Composition and texture of the Middle and Late Eocene volcanic, volcaniclastic, and volcanic-sedimentary rocks in the Bijgerd-Kuh e Kharchin area, in the Uromieh-Dokhtar zone northwest of Saveh, Iran, suggest the complexity of the magmatic system that involved multiple eruptions from one or more sources. Hydrated volcanic fragments in hyaloclastic rocks, and the presence of a sequence of shallow and intermediate-depth marine microfossils, suggest that the Middle Eocene units were erupted in a marine basin. The bimodal volcanism of the Late Eocene is distinguished by the presence of four alternating sequences of hyaloclastite lava and ignimbrite. The REE patterns show spatial homogeneity and temporal heterogeneity in the composition of all the Late Eocene sequences, suggesting origination of magma from varying sources that erupted at different times. The trace element distributions of the hyaloclastites and ignimbrites are compatible with those evolved through fractional crystallization of the lower and upper continental crust, respectively.