SUPRA-SUBDUCTION ZONE OPHIOLITES OF CENTRAL ANATOLIA - GEOCHEMICAL EVIDENCE FROM THE SARIKARAMAN-OPHIOLITE, AKSARAY, TURKEY

The Central Anatolian Crystalline Complex (CACC), situated between the northern and southern oceanic strands of Neotethys, contain a number of little-studied ophiolitic bodies of late Cretaceous age that have a bearing on the Mesozoic development of this region. The pillow lavas and sheeted dykes of the Sarikaraman Ophiolite were originally a comag matic differentiated series of vesicular, aphyric and olivine-poor, pl agioclase-clinopyroxene phyric tholeites, but now exhibit greenschist facies assemblages. A set of late dolerite dykes cross-cutting the who le volcanic sequence are more chemically evolved and were probably der ived from a different source. Relative to N-MORB the lavas and dykes a re enriched in some LIL elements (K, Rb, Cs, U, Th and Sr) and deplete d in HFS elements (Nb, Ta, Hf, Zr, Ti and Y) and light REE. In terms o f immobile elements the ophiolitic basalts have the broad chemical cha racteristics of island are tholeiites that were formed in a supra-subd uction zone setting, whereas the late dykes are more akin to N-MORB. I n this respect the Sarikaraman Ophiolite is similar to other ophiolite s found in the eastern Mediterranean region and emphasizes the preserv ation of this particular environment in the CACC. If all the Central A natolian Ophiolites (of which the Sarikaraman Ophiolite is one example ) were derived via southward thrusting from the Vardar-Izmir-Ankara-Er zincan Ocean branch to the north, age relationships suggest that this segment of ocean crust was relatively short-lived before obduction ont o the CACC.