Petrography and Geochemistry of the Kocali Ophiolitic Complex and the Karadut Formation (Kahramanmaras, SE Türkiye)

The Kahramanmaras region (Turkey) is located between the Arabian Plate and the Tauride-Anatolide tectonic belt, making it a study area where lithological units of different ages and origins are found together. The petrography and geochemistry of ophiolitic complex units (Kocali Complex) located in northern Kahramanmaras and the sedimentary units (Karadut Formation) that tectonically overlie them were examined to reveal their roles within the tectonic system. Samples taken from the working area were examined under a polarizing microscope for their mineral composition, textural properties, and alteration degrees; major element contents were determined by XRF analysis, and trace and rare earth element contents were determined by ICP-MS analysis. 
The basalts of the Kocali Complex are generally altered basalts, with some samples being almost completely carbonated. The conglomerates of the unit are predominantly composed of angular clasts, which include rock fragments of both magmatic and sedimentary origin. Petrographic examinations indicate that the serpentinites are rich in opaque minerals and locally contain ore minerals; in addition, they exhibit a pronounced sieve texture accompanied by carbonation-type alteration. The Cenozoic Karadut Formation consists of sandy and carbonate-rich limestones, marls, and mudstones. Carbonate limestones are fine to medium-grained and display a homogeneous fabric, whereas sandy limestones are distinguished by their light to dark gray coloration. These units commonly crop out as beds with variable dip angles and occur in alternation with marls. The marls are whitish to beige in color and locally characterized by manganese coatings. Microscopic observations reveal that the siltstones and mudstones of the formation contain feldspar and very fine-grained quartz, accompanied by iron oxide precipitation and opaque minerals.
Chemical analyses show that the SiO₂ contents of the Kocali Complex rocks range from 2.41 to 87.60 wt.%, Fe₂O₃ contents from 0.60 to 11.82 wt.%, and CaO contents from 0.32 to 42.92 wt.%. In contrast, the Karadut Formation rocks display SiO₂ contents between 61.31 and 95.24 wt.%, Fe₂O₃ contents of 0.42–3.02 wt.%, and CaO contents ranging from 0.33 to 16.59 wt.%. These results indicate that the units of the Kocali Complex exhibit considerable chemical heterogeneity. The SiO₂, Fe₂O₃, and MgO values are consistent with the characteristic geochemical signature of an ophiolitic mélange. In comparison, the Karadut Formation units are characterized by elevated SiO₂ and CaO contents, reflecting a carbonate-rich sandstone geochemistry. The observed chemical contrasts point to a genetic relationship between ophiolitic source rocks and sedimentary environments. In conclusion, the observed geochemical differences between the Kocali Mélange and the Karadut Formation reveal not only lithological and source-rock diversity but also provide important clues to the geodynamic evolution of the region. In this context, the study makes a significant contribution to the understanding of geodynamic processes by demonstrating the interaction between ophiolitic rocks and the sedimentary basin.

Keywords: Geochemistry; Mélange; Ophiolite; Petrography; Türkiye