Rapid cooling history of a Neotethyan ophiolite: Evidence for contemporaneous subduction initiation and metamorphic sole formation

The Beyşehir-Hoyran Nappes, including Mesozoic carbonate platform rocks, deep-sea sediments, and ophiolite-related units, crop out extensively on the western limb of the Isparta Angle in the Central Taurides, Turkey. The ophiolite-related rocks are represented by variably serpentinized harzburgitic mantle tectonites, tectonically underlain by a subophiolitic metamorphic sole and mélange. The harzburgitic mantle tectonites and metamorphic sole are intruded by undeformed isolated dikes. Protoliths of the metamorphic sole are similar to within-plate alkali basalts and associated sediments. The isolated dikes were geochemically derived mainly from tholeiitic magma and, to a lesser extent, from alkaline magma. Five isolated dike samples yielded U-Pb ages ranging from 90.8 ± 1.6 Ma to 87.6 ± 2.1 Ma (zircon) and from 102.3 ± 7.4 Ma to 87.5 ± 7.9 Ma (titanite). Seven amphibolite samples yielded U-Pb age ranges of 91.1 ± 2.1–88.85 ± 1.0 Ma (zircon) and 94.0 ± 4.8–90.0 ± 9.4 Ma (titanite) and a 40Ar-39Ar age range of 93.7 ± 0.3–91.4 ± 0.4 Ma (hornblende). U-Pb and 40Ar-39Ar ages of mineral phases with different closure temperatures (∼900–500 °C) from the isolated dikes and metamorphic sole rocks are almost identical and overlapping within 1σ, suggesting that both the magmatic growth of oceanic crust and formation of metamorphic sole were contemporaneous and cooled very rapidly. Hence, all the data should be interpreted as the crystallization ages of the ophiolite and metamorphic sole pair. Genesis of suprasubduction zone–type oceanic crust, genesis and exhumation of the metamorphic sole, and postmetamorphic dike emplacement within the Inner Tauride Ocean can be best explained by subduction initiation and rollback processes during the Late Cretaceous based on petrological and geochronological data obtained from the ophiolitic rocks of the Beyşehir-Hoyran Nappes.

Polyphase tectonic evolution of the Aksu Basin, Isparta Angle (Southern Turkey)

The Aksu Basin, within the Isparta Angle, is located to the north of the intersection of the Aegean and Cyprus arcs and has been evolving since the Middle Miocene. Correlation of: (1) kinematic analysis of fault planes that cut the basin fill, (2) the reactivation/inversion of fault planes and (3) sedimentological data indicate that the Aksu Basin has evolved by four alternating compressional and extensional tectonic phases since its formation. The first phase was NW-SE oriented compression caused by the emplacement of the Lycian Nappe units which ended in Langhian. This compressional phase that induced the formation and the initial deformation of the basin was followed by a NW-SE extensional phase. This tectonic phase prevailed between the Langhian and Messinian and was terminated by a NE-SW compressional regime known as the Aksu Phase. The neotectonic period is characterized by NE-SW extension and began in the Late Pliocene. Correlation with the existing tectonic literature shows that the order of deformational phases proposed in this study might also be valid for the entire Isparta Angle area.