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Abstract:

Trace elements and rare earth elements (REEs) were studied to determine the formation of chert and siliceous limestones, which are predominantly observed in the Okçular formation. Cherts are divided into four types according to their varying forms depending on the deposition and diagenesis stages: (Type-I) layered cherts formed by direct precipitation from sea water, (Type-II) nodular cherts with rim formed by replacement, (Type-III) homogeneous chert nodules without rim, (Type-IV) chert micro nodules with high porosity. The porosity of stylolite-fracture networks and the chemical composition of seawater played a role in the formation of different types and sizes in cherts. The rim of Type II nodular cherts has significant color changes and porosity up to 20%. Anomalies of major and trace elements, especially La, Y, Sc, Ce, Th, U and Gd values, indicate direct deposition and replacement of early diagenetic pelagic deposits of cherts in the oxidized marine environment. Total (REE)+Y values, high LREE/HREE ratio and low Ce values indicate that dissolved seawater of chemical or biogenetic origin has a role in silicification. According to the similarity of the hierarchical cluster analysis of the chemical contents of the Okçular formation and the ophiolites, the silicon in the chert formation originates from the ophiolites.