Mineralogical, Petrographical and Geochemical Characteristics of Eldivan Ophiolite (Çankırı) Harzburgitic Tectonites

Abstract

The Eldivan Ophiolite is located at the central part of the İzmir-Ankara-Erzincan Ophiolitic Belt which is between Şabanözü, Eldivan and Korgun towns. From bottom to top, units forming the ophiolite consist of volcano sedimentary and metamorphic series, tectonites, cumulates and sheeted dikes. Tectonites, which are the main subject of the study, are generally represented by harzburgites and occasionally consist of dunite, pyroxenolite and chromitite levels. In harzburgites which have traces of plastic deformation (foliation, lineation and folding), the minerals display a distinct orientation as a result of intra crystallographic dislocation and grinding mechanism. The degree of deformation decreases upwards. Less amount of clinopyroxene is encountered at lower levels of harzburgites which are composed of olivine (60-90%) and orthopyroxene (10-35%). There is also observed a decrease in the amount of orthopyroxene and an increase in chromite ratio towards upper levels. The composition of olivines is usually forsteritic and orthopyroxene is enstatitic and displays a slight impoverishment in Mg content towards upper levels. However, there is observed a decrease in the amount of chrome but an increase in aluminium amount in the upward direction. This situation can be explained as a result of the primary composite of upper mantle and partial melting processes.