Geochemistry and tectonic significance of ophiolitic units exposed in the Çelikhan-Adıyaman region

The Çelikhan ophiolite in the study area exhibits characteristics of an incomplete ophiolite sequence, represented by dunitic and harzburgitic tectonites, mafic cumulates, isotropic gabbros, a sheeted dyke complex, and basaltic-andesitic volcanic rocks. U-Pb zircon dating of gabbros, diorites, and basaltic volcanics from the Çelikhan ophiolite using the LA-ICP-MS (Laser Ablation Inductively Coupled Plasma Mass Spectrometry) method has determined the unit's age as Late Cretaceous. Geochemical analysis, including major, trace, and rare earth elements, along with mineral chemistry data from the sheeted dykes, indicates that the rocks formed from a common parental magma in a supra-subduction zone environment during the Late Cretaceous. The volcanic rocks in the Çelikhan area (Adıyaman) are represented by a narrow spectrum of compositions ranging from basaltic to neutral, and are geochemically consistent with formation in an intra-oceanic subduction zone, derived from tholeiitic magma. Syenitic-monzonitic rocks intruding the Çelikhan ophiolite have also been dated to the Late Cretaceous. The ophiolitic rocks in the study area yield ages ranging from 99.49 ± 1.5 Ma to 83.5 ± 0.79 Ma, indicating a Cenomanian-Santonian (Upper Cretaceous) age for the Çelikhan ophiolite. Pressure values calculated from mineral chemistry of amphiboles in the sheeted dykes suggest depths of 1.8 to 4.0 km (0.56 to 1.2 kbar). Based on the new geochronological data, geological mapping, structural, and geochemical analyses, it is concluded that the entire Çelikhan ophiolite formed in a northward-subducting intra-oceanic subduction zone in the Southern Neotethys during the Late Cretaceous. Keywords: Çelikhan ophiolite, Late Cretaceous, Subduction zone, Geochronology, Neotethys