Mineralogy and geochemistry of REEs in Anbagh alterd sketch, east of Ahar, NW Iran

Anbagh altered sketch is located about 25 km east of Ahar, within Ahar-Jolfa metallogenic belt and laid by a widespread Eocene andesite to basalt volcanic rocks affected by Oligocene granite- granodiorite igneous bodies which altered them to silicic, argillic, phyllic and propylitic zones. The low pH and high acidity of SO4-2 ligands in fluid resulting in loses of REEs in silicic zone. Loss of LREEs in argillic zone caused by reduce in adsorption ability of clay minerals in low pH. The HREEs enrichment in phyllic zone is due to the abundance of sericite (±Fe oxides). A significant reduction of Eu/Eu* ratio in silicic zone can be attributed to the rare hydrothermal sulfides and clay minerals as an effective agents in sorption of released Eu+2. Decrease in pH caused by pyrite oxidation made negative Eu anomaly in argillic alteration zone. Factors such as changes in pH, the abundance of absorptive neomorph mineral phases, type and abundance of ligands play an important role in the distribution  concentration of REE in the play Anbagh alteration system.