Geochronological, Geochemical and Sr-Nd-Pb Isotope Characteristics of the Meydan Ophiolite, SE Turkey: Petrogenesis and Implications for Mesozoic Tectonic Evolution


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GEOCHEMISTRY INTERNATIONAL, cilt.58, ss.639-669, 2020 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 58
  • Basım Tarihi: 2020
  • Doi Numarası: 10.1134/s0016702920060099
  • Dergi Adı: GEOCHEMISTRY INTERNATIONAL
  • Sayfa Sayıları: ss.639-669

Özet

Gabbros, sheeted dikes and volcanic rocks of the Meydan ophiolite in the South-east Anatolian orogenic belt were examined to determine their U-Pb zircon ages, whole-rock, mineral chemistry and Nd-Sr-Pb isotope compositions. The new U-Pb dating of zircon separates yielded a 88.3 +/- 1.3 Ma crystallization age for gabbroic rocks of Meydan ophiolite. The ophiolite includes tectonites, ultramafic-mafic cumulates, isotropic gabbros, isolated mafic dikes, sheeted dikes, plagiogranites and rare basalts. The sheeted dikes and volcanics of the Meydan ophiolite exhibit near-flat rare earth element (REE) patterns, flat high field strength element trends and negative Nb anomalies that are similar to other SSZ-type eastern Mediterranean ophiolites. The whole-rock and mineral chemistry of the Meydan ophiolite/volcanic rocks suggests that they formed a supra-subduction zone and the dismembered ophiolite metamorphic sole formed beneath the ophiolite in a subduction trench setting. Isotopic ratios, i.e.,Sr-87/Sr-86 versus(206)Pb/Pb-204 and(143)Nd/Nd-144 versus(87)Sr/Sr-86, show only limited variations, whereas(143)Nd/Nd-144 versus(206)Pb/Pb-204,Sr-87/Sr-86 ratios are much more variable. The isotopic ratios are indicative of mixed magmatic contributions from DMM/MORB and EMII reservoirs that probably reflect the overall recycling of mantle wedge, pelagic sediment, oceanic crust and continentally derived sediment. The Meydan ophiolite, inferred arc volcanics and accretionary melange are all intruded by Late Cretaceous (87.7 +/- 0.47 to 80.1 +/- 0.46 Ma; zircon U-Pb) granitic rocks which are evaluated as the product of continental margin arc magmatism. The available regional comparisons suggest that the rocks studied were derived from the Berit Ocean to the north of the Bitlis Puturge continent, in which the Komurhan, Ispendere and Goksun ophiolites also formed during the Late Cretaceous.