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

Abstract

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.

Slabitization: Mechanisms controlling subduction development and viscous coupling

“…Together with deformation patterns, the consistency of deformation temperatures experienced by basal peridotites and HT metamorphic soles, near 850-900°C, has been reported in most ophiolites (e.g., Spray, 1984Harper et al, 1994;Suhr and Cawood, 1993;Parlak et al, 2019). Deformation features relate to either coupling or strain localization.…”

“…This is testified by the welding of metamorphic soles, which represent portions stripped from the downgoing slab at ~30 km depth during subduction infancy (Figs. 1b,2a,b), to banded peridotites lying at the base of ophiolites (e.g., Williams and Smyth, 1973;Dewey, 1976;Searle and Malpas, 1982;Spray, 1984;Gnos, 1998;Wakabayashi andDilek, 2000, 2003;Searle and Cox, 2002;Agard et al, 2016;Guilmette et al, 2018;Parlak et al, 2019). As shown below, they allow investigating the complex feedbacks between reactions, deformation and fluids at a warm subduction interface.…”

Subduction Initiation During Collision‐Induced Subduction Transference: Numerical Modeling and Implications for the Tethyan Evolution

“…Thus, the timing of collision is a bit varied among different studies (Aitchison et al, 2007;DeCelles et al, 2014;Najman et al, 2010;Searle, 2019;Yin & Harrison, 2000;Zhu et al, 2015). On the other hand, the geological records for SI are even more complex (Guilmette et al, 2018;Hall, 2018;Pandey et al, 2019;Parlak et al, 2019;Patriat et al, 2019;Searle, 2019;Stern, 2004;Stern et al, 2012). The emplacement of magmatic rock is generally later, by several million years, than the exact time of SI (Arculus et al, 2019;Hall, 2018;Shervais et al, 2019).…”

History of Subduction Polarity Reversal During Arc‐Continent Collision: Constraints From the Andaman Ophiolite and its Metamorphic Sole

“…spreading rates are of several tens of kilometer per million years. It means that the ages of magmatic rocks in narrow ophiolite bodies like on Andaman are typically within 1-2 Myr (e.g., in Oman, Rioux et al, 2016Rioux et al, , 2013or Turkey, van Hinsbergen et al, 2016;and reference therein;Parlak et al, 2019). Instead, the minimal 5-Myr transition between SSZ and arc magmatism that are found within a few meters in Andaman suggests a more or less stationary magma source after the SSZ ophiolite is formed.…”