Mineralogy and geochemistry of the Avin kaolin deposit, northeast of Mianeh, East-Azarbaidjan Province, NW Iran

The Avin kaolin deposit is located about 35km of northeast of the Mianeh town, East-Azarbaidjan Province, NW Iran. Field evidence and petrographic studies indicate that development and formation of this deposit is genetically related to alteration of dacite rocks of Eocene- Oligocene age. In attention to mineralogical data, this deposit consists of minerals such as kaolinite, quartz, muscovite-illite, cristobalite, rutile, orthoclase, and goethite. Investigation of some geochemical parameters such as values of TiO2, Ba+Sr, and Ce+Y+La show that development of this deposit is related to function of two processes of  hypogene and supergene. Incorporation of the obtained results from mineralogical studies, mass changes geochemistry, and variations trend of elemental ratios indicate that chemistry of altering fluids (pH and Eh), surface adsorption, scavenging by metallic oxides, fixation in neomorphic mineralogical phases, ratio of fluid to rock, and amount of availibility to complexing ions are six effetive parameters in mobilization, distribution, and enrichment of trace and rare earth elements in this deposit. Geochemical analysis indicates that decrease of  Eu anomalies in kaolinized samples was related to destruction of plagioclase minerals of the dacitic rocks by high temperature hydrothermal fluids and decrease of negative Ce anomalies is due to development of kaolinization process by fluids with acidic-oxidizing nature.