RARE EARTH ELEMENT MOBILITY DURING HYDROTHERMAL ALTERATION IN ASAREL PORPHYRY COPPER DEPOSIT, CENTRAL SREDNOGORIE

This study presents the REE behaviour during different hydrothermal alterations accompanying the formation of Asarel porphyry copper deposit. REE are relatively inert during propylitization and become partly mobile with increasing of alteration degree in intermediate argillic and sericitic types. In advanced argillic alteration MREE and HREE are strongly depleted while LREE are immobile. LREE are concentrated in the new-forming minerals - alunite, APS minerals and clay minerals. The mobility of REE is controlled mainly by pH, the concentration of complexing ions (SO42-, Cl-, F-) in the hydrothermal fluids and the presence of appropriate minerals to host them in their structures.