Geology, petrography and geochemistry of ophiolitic rocks observed to the north of Kulp (Diyarbakır)

The ophiolitic units observed to the north of Kulp (Diyarbakır) have a tectonic contact relationship with both Bitlis Metamorphics and Çüngüş Formation. Kulp Ophiolite mainly consists of mantle tectonites, ultramafic and mafic cumulates, sheeted dikes, volcanics and intercalated pelagic sediments. Geochemical studies carried out on oceanic crust rocks (volcanics, sheet dikes and isolated dikes) exhibit that these rocks are basic in composition. The major and trace element contents of the rocks suggest that the volcanics and sheeted dikes are more akin to normal mid-ocean ridge basalt (N-MORB) type mantle, while isolated dikes were derived from a mantle source between normal mid-ocean ridge basalt (N-MORB) and enriched mid-ocean ridge basalt (E-MORB) type mantle. It is clearly seen in both Ta/Yb – Th/Yb and Nb/Th – Y diagrams that no subduction component is observed in the development of oceanic crustal rocks of the Kulp Ophiolite. In addition, tectonic environment discrimination diagrams such as V-Ti and Ta-Hf-Th also indicate that these rocks were formed in the mid-ocean ridge environment. The Cr-Y diagram shows that the volcanics, sheeted dikes and isolated dikes in the study area are the product of approximately 20-25% partial melting of the normal mid-ocean ridge mantle source. The geochemical data summarized above indicate that the oceanic crust rocks (volcanics, sheeted dikes and isolated dikes) belonging to the ophiolitic units observed in the north of Kulp (Diyarbakır) were formed by the partial melting of a heterogeneous mantle source at different degrees in the mid-ocean ridge (MOR) tectonic environment due to the opening regime in the Late Triassic-Early Cretaceous period in the Southern Neotethyan oceanic basin. It is observed that the oceanic crustal rocks belonging to the ophiolitic units observed in the north of Kulp (Diyarbakır) have great similarities to the Masirah (Oman) Ophiolite in terms of geochemical properties. Keywords: Ophiolite, sheeted dike, basalt, isolated dike, cumlates