The Early Eocene Ekmekçi granodiorite porphyry in the Karacabey region (Sakarya Zone, NW Turkey)

Abstract

The Ekmekçi granodiorite porphyry is a unit in the E-W trending, postcollisional Eocene magmatic rocks of northern Anatolia. It occurs as a relatively small stock, but represents a link between plutonic and volcanic rocks. This Early Eocene granodiorite porphyry intruded into the Upper Triassic rocks of the Karakaya complex in the Sakarya Zone. In this study we present geochemical and zircon U-Pb LA-ICP-MS age data to contribute to understanding the Early Tertiary postcollisional tectonic setting of NW Anatolia. The granodiorite porphyry includes plagioclase, quartz, hornblende, K-feldspar, biotite, and minor zircon, apatite, sphene, and opaque minerals. The stock displays medium-K calc-alkaline I-type and metaluminous affinity. Similar to other Eocene magmatic rocks, it displays characteristic features of subduction-related magmatism, such as enrichment in large-ion lithophile elements relative to highfield strength elements and enrichment of light rare earth elements relative to heavy rare earth elements with a lack of significant Eu anomalies. They are characterized by homogeneous initial Sr and Nd isotopic compositions of 0.7044-0.7049 and 0.51255-0.51260, respectively. Zircon U-Pb data indicate that the Ekmekçi granodiorite porphyry was emplaced at 5.1 ± 1 Ma (2s Ypresian). Geochemically, the Ekmekçi granodiorite porphyry is similar to mafic volcanic rocks rather than the plutonic rocks of the same age. It was emplaced to the north of the İzmir-Ankara-Erzincan Suture (northern plutonic belt of NW Anatolia) and can be correlated with southern plutons such as Orhaneli, Topuk, Tepeldağ, Gürgenyayla, and Sivrihisar in the Anatolide-Tauride block in terms of age.