MINERALOGICAL AND GEOCHEMICAL PROPERTIES OF THE Na- AND Ca-BENTONITES OF ORDU (NE TURKEY)

A number of different types of bentonite deposits formed by hydrothermal alteration and diagenetic processes are to be found in the Ordu area of the Eastern Black Sea region. The Ca- and Na-bentonite deposits are related to Upper Cretaceous tholeitic to calc-alkaline volcanites, predominantly dacite and andesite, and also include rhyodacite with lesser basalt and their pyroclastic equivalents. In the present study, dacite (PR1), perlite (PR2), moderately altered rocks (MPR), and Na- and Ca-bentonites were studied to describe and compare their mineralogical and geochemical properties and their conditions of formation by means of X-ray diffraction, optical microscopy, scanning electron microscopy, and chemical analytical techniques.