Emplacement history of the Central Anatolian Ophiolites: insights from the Felahiye Ophiolite in Central Türkiye

The Central Anatolian Crystalline Complex (CACC) is represented by Late Cretaceous Barrovian-type metamorphism, ophiolite obduction and numerous intrusive granitoid rocks. The Felahiye Ophiolite, which is a part of the Central Anatolian Ophiolites (CAOs), represents a significant remnant of the Late Cretaceous oceanic lithosphere in the eastern CACC. However, the exact origin and polarity of the subduction zones involved in the formation of these ophiolites and mélanges remain unclear. This study presents new field, geochemical, and geochronological data from the Felahiye Ophiolite to address these critical questions. The integration of geochemical, petrographic, and field data supports the interpretation that the Felahiye Ophiolite is a remnant of the Late Cretaceous supra-subduction type oceanic crust. U-Pb zircon crystallization age of 92.0 ± 1.1 Ma was obtained from a cumulate gabbro of the Felahiye Ophiolite. Hafnium isotope compositions of these zircons (εHf_(t) =  +8 to + 12) suggest a depleted mantle source. ⁴⁰Ar/³⁹Ar dating of amphibole from a gabbro provided a cooling age of 69.4 ± 3.2 Ma, suggesting thermal influence of granitoid intrusions following ophiolite emplacement. We propose a new model for the origin of the CAOs, emphasizing eastward subduction of an ocean basin located both east and west of the CACC. This is consistent with the CAOs forming on N-S trending ridges within an eastward-subducting ocean, leading to westward obduction onto the CACC, N-S trending magmatic arc development in the CACC, and distinct geological histories from those of the Tauride Belt Ophiolites.

安纳托利亚中部结晶杂岩（Central Anatolian Crystalline Complex, CACC）以晚白垩世巴罗式变质作用（Barrovian-type metamorphism）、蛇绿岩仰冲（ophiolite obduction）及大量侵入型花岗岩类岩石（intrusive granitoid rocks）为特征。费拉希耶蛇绿岩（Felahiye Ophiolite）作为安纳托利亚中部蛇绿岩群（Central Anatolian Ophiolites, CAOs）的组成部分，是CACC东部区域晚白垩世海洋岩石圈（oceanic lithosphere）的重要残片。然而，参与形成此类蛇绿岩与混杂岩（mélanges）的俯冲带（subduction zones）的确切成因及极性仍不明确。本研究通过获取费拉希耶蛇绿岩的全新野外、地球化学及地质年代学数据，以解答上述关键科学问题。综合地球化学、岩石学与野外调查数据的分析结果，支持费拉希耶蛇绿岩属于晚白垩世俯冲带之上型洋壳（supra-subduction type oceanic crust）残片的认识。对该蛇绿岩中堆晶辉长岩（cumulate gabbro）的U-Pb锆石结晶年龄测定结果显示，其年龄为92.0±1.1 Ma。这些锆石的铪同位素组成（Hafnium isotope compositions）为εHf(t) = +8至+12，表明其源区为亏损地幔源区（depleted mantle source）。对辉长岩中角闪石（amphibole）开展的⁴⁰Ar/³⁹Ar测年获得冷却年龄为69.4±3.2 Ma，指示蛇绿岩侵位（ophiolite emplacement）后受到了花岗岩类侵入作用的热影响。本研究提出了关于安纳托利亚中部蛇绿岩群成因的全新模型，强调发育于CACC东西两侧的海盆发生向东俯冲（eastward subduction）。该模型与以下认识一致：安纳托利亚中部蛇绿岩群形成于向东俯冲洋盆内的南北向海岭（N-S trending ridges）之上，随后向西仰冲到CACC之上，在CACC内部形成南北向展布的岩浆弧（magmatic arc），且其地质演化历史与陶里德带蛇绿岩（Tauride Belt Ophiolites）存在显著差异。