Petrology and LA-ICP-MS zircon geochronology for Late Cretaceous felsic dikes and intermediate volcanic rocks hosted in Mersin ophiolite, South Turkey and its implications


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NURLU N.

GEOSCIENCES JOURNAL, no.1, 2020 (SCI İndekslerine Giren Dergi) identifier identifier

Özet

LA-ICP-MS U-Pb geochronology of zircons, whole-rock (main, trace, and REE) geochemistry, and mineral chemistry (feldspars) are constrained for felsic dikes and intermediate volcanic rocks of the Mersin ophiolite in the Inner Tauride Suture Zone (Southern Turkey). The geochronological research, dependent on LA-ICP-MS U-Pb zircon analyses from examined rocks, has yielded a concordia age of 87.38 +/- 0.32 Ma for a microgranular felsic dike, stating a Coniacian (Late Cretaceous) age. The felsic dikes show mainly hemicrystalline, aphanitic, porphyritic textures and petrographic analyses from the felsic dikes, and volcanic rocks exhibit that they are mainly dacite, rhyodacite, andesite and basaltic andesite, which are poor in mafic minerals. The mineral chemistry of the dacite and rhyodacite dikes present that plagioclases have a wide range of contents, from andesine (An(31.1-497)) to albite (An(03-28.15)) and K-feldspars represented by sanidine (Or(42.5-93.3)). Dacite/aplite dikes cutting mainly andesitic volcanic rocks present island arc tholeiite-like geochemistry. These felsic intrusive rocks are depleted in HFSE (high-field-strength elements), enriched in LILE (large-ion lithophile elements) and present flat-type REE trends; these patterns furthermore verify their supra-subduction zone geodynamic setting. The initial phase of arc-type volcanics formed above, as can be observed in most of the ophiolites in the Inner Tauride Suture Zone. The arctype volcanics and SSZ-type slab (of metamorphic rock and ophiolite) are cut by dacitic rocks (Coniacian). From the geochronology, field relations, and geochemical evidence from the felsic dikes and volcanics, it can be concluded that the Mersin ophiolite occurred in a tectonic environment (subduction zone) in the southern branch of the Neo-Tethys, located in modern Southern Anatolia.