Zohreh Hossein Mirzaei Beni, Ebrahim Panahpour
Department of Geology, Science and Research Branch, Islamic Azad University (IAU), Teheran, Iran
Department of Soil Science, College of Agriculture, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran
Key words: Chah basheh, Tuff rhyolite, Volcanic rocks, Porphyric texture, Precambrian.
The age of Chah Basheh rhyolite and tuff rhyolite is Precambrian and are located in the Central Iran, 115 km from east Isfahan and S Naein. Rhyolites of Chah Basheh are containing large crystals of quartz, plagioclase with high rate of albite and alkali feldspar. The phenocryst of quartz can be seen in the field and also as microcrystal and are often subhedral to euhedral and is the most frequent phenocryst in these rocks. Large quantities of quartz have corrosion Gulf. Plagioclases often have euhedral phenocryst, sodice composition and albite to oligoclase combination. Two generations of plagioclase can be seen in these rocks. Most plagioclases changed to secondary minerals such as serysyty and some of them are filled by chlorite, penin and calcite. Alkali feldspar finds as fine crystal and often changed to kaolinite. These volcanic rocks have a felsophyric texture with SiO2 and k-feldspar.