Mineralogical study of bentonites in Taştepe (Göre - Nevşehir) and its surroundings

This study aims to reveal the mineralogical-petrographic and geochemical properties of bentonites detected in the Göre (Nevşehir) region within the Central Anatolian Volcanic Province (CAVP). In this regard, optical and electron microscopes, X-ray diffraction, Xray fluorescence spectrometry, and inductively coupled plasma-mass spectrometry examinations were carried out. In the study area, Aşıklıdağ Andesite, Kavak Ignimbrite, and Kumtepe Ignimbrite units are generally observed. The alteration, which mostly affects pyroclastic (İgnimbrite) and partly lava products, has resulted in gray-yellowishwhitish siliceous and grayish-green clay mineral formations. Altered samples mainly include silica minerals (Quartz, Cristobalite, Opal-CT), Clay (Smectite, Montmorillonite, ± İllite), biotite ± pyroxene mineral as a ferromagnesian mineral, and feldspar group minerals (K-feldspar and plagioclase). Cation exchange capacity (CEC) values are in the range of 0,190-0,761 meq/g and increase in direct proportion to the smectite contents. According to major and trace element compositions, low-medium grade alteration product ignimbrites and high-grade alteration product bentonites are derived from alkaline magma with trachy-andesitic (İntermediate) composition. Keywords: Bentonite, cation exchange capacity (cec), ıgnimbrite, smectite