Petrography studies of the volcaniclastic rocks in the Kooshk-e Nosrat and Aliabad, of Hoze Soltan Lake in north of Qom reveal that these rocks could be divided into five facies assemblages:1-Tuffs (vitric, lithic and crystal) 2-Lapilli tuffs,lapillistone, tuff- breccia ,volcanic breccia 3- Ignimbrite 4-Andesite porphyry and 5-tuffites. It is also shown that the chemical composition and mineralogy has been played an important role in the diagenetic evolution of these rocks such as:compation ,cementation ,zeolite formation and altration of metastable glasses.
The existance of foraminifer a (e.g. Nummulites) in sedimentary rock intercalations would attribute the age of the formation these indicates a Tertiary age for these rocks.