Late Paleocene – Middle Eocene magmatic flare-up in western Anatolia

Abstract

A 3000-km long magmatic belt of predominantly Eocene age extends from Anatolia into Iran representing a major magmatic flare-up. We present new zircon U-Pb, Ar/Ar mica and apatite fission-track ages for this magmatism from northwestern Turkey, and review its geochemistry and geodynamic setting. The new age data show that magmatism started at the Late Paleocene (58 Ma) during the final stages of continental collision and continued into the early Middle Eocene (45 Ma) with most of the magmatism taking place in the Early-Middle Eocene (54 to 45 Ma). The Late Paleocene-Middle Eocene magmatism is separated from Late Cretaceous and Oligo-Miocene magmatic flare-ups by periods of magmatic quiescence. The Late Paleocene-Middle Eocene magmatism consists of plutonic and volcanic belts. The plutonic belt cuts across and post-dates the İzmir-Ankara suture. The plutonic rocks are mainly middle- to high-K calc-alkaline I-type granodiorite and granite, and the volcanic rocks are middle- to high-K calc-alkaline basalt, basaltic andesite and andesite. Geochemically, all the rocks are similar to those found in subduction-related environments. Crustal thicknesses calculated based on geochemistry suggest a thickened crust (60–70 km) at 58 to 54 Ma, and a relatively thin crust (ca. 40 km) at 54 to 45 Ma, which match with uplift and erosion during the Late Paleocene, and marine sedimentation during the Early-Middle Eocene in northwest Anatolia, respectively. The Late Paleocene-Middle Eocene magmatism is tentatively assigned to subduction of the southern branch of the Neo-Tethys.