Mineralogy and REEs geochemistry of kaolinized zones of the Goorgoor area, North of Takab, NW Iran

Thekaolinizedzonesof the Goorgoor area (north of Takab, West-Azarbaidjan province) are alteration products of andesitic rocks of Miocene age in northwest of Iran. Based on the mineralogical studies, kaolinite, quartz, jarosite, montmorillonite, albite, muscovite-illite, anatase, chlorite, orthoclase, calcite, goethite and hematite are mineral phases in these zones. The silicic veins existing within these zones include metallic minerals such as pyrite, chalcopyrite, galena, sphalerite, bornonite, and stibnite. The mass change calculations of rare earth elements (REEs), with assumption of Sc as a monitor immobile element, reveal that development of kaolinization processes were accompanied by enrichment-depletion of La-Nd and depletion of Sm-Lu. Geochemical analyses show that the degree of differentiation of Al from Fe and destruction of zircon by hydrothermal fluids are the most important controlling factors for variation of Eu (0.84-1.06) and Ce (0.83-0.93) anomalies in these zones, respectively. Positive and strong correlations of (La/Lu)N and (LREEs/HREEs)N values with components such as P, S, LOI, and Sr establish the effective role of hypogene solutions in progression of kaolinization processes. The combination of the obtained results from mineralogical and geochemical investigations suggest that changes in chemistry of altering solutions (e.g., pH and Eh) and diversity in type of fixing minerals are two key factors affecting differentiation and distribution of REEs in the kaolinizedzones at Goorgoor.