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 1?, 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. © 2019 Geological Society of America.China University of Geosciences, Wuhan 113Y412 Mersin Üniversitesi GPMR201702 National Natural Science Foundation of China: 91755213Alastair Robertson, Benxun Su, and Associate Editor Erdin Bozkurt are thanked for their constructive and very valuable comments that improved the quality of the paper. We would like to thank Seher Kuru and Aynur G?rb?z for their help during cathodoluminescence imaging of zircons at Mersin University. G?zide ?nal is thanked for drawing the figures. This work was funded by T?BITAK (Project no. 113Y412) awarded to O. Parlak, and Chinese National Natural Science Foundation grant 91755213, awarded to T. Kusky. O. Parlak acknowledges the Open Fund (GPMR201702) of State Key Lab of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan for additional support