Mineralogy of the zeolitic-bentonitic sequences of the Kuh-e-Arshe, north Central Iran

The zeolitic-bentonitic sequences of the Kuh-e-Arshe,50 km east Semnan ,north Central Iran have been formed in a nearly closed chemical system, in a near surface condition in marine environments. The solution being resident in the rocks. Clinoptilolite, mordenite, smectite, trace amounts of illite, quartz, opal-CT, plagioclase, dolomite, calcite, together with rocks fragments were determined in this sequences. XRD data have been showed that zeolite minerals, smectite, illite, quartz and dolomite are major components. SEM images are indicated that zeolite and smectite, namely mordenite and clinoptilolite form mainly from volcanic glasses (shards). The data obtained indicate that this zeolitic-bentonitic sequences formed by the alteration of volcanic ash of rhyodacite/dacite composition.