Elements variations and the origin of fluids during the hydrothermal alterations in the Astaneh-Arak granitoid

Seven distinct hydrothermal alteration zones developed within the Astaneh granitoid. The phyllic and silicic alterations have a wide extension in the study area. In the phyllic alteration, La in comparison to other REEs, is much more enriched which may be the result of sericite formation. The enrichment of LREE in the propylitic alteration, due to their accommodation in secondary minerals, is more than that of unaltered sample. The REE normalized pattern in the argillic alteration shows a considerable leaching of REE during the alteration process. The Eu/Eu* ratio in the altered samples is less than one and in comparison to unaltered sample displays positive anomaly. Generally, the chondrite normalized pattern in altered and unaltered sample is similar. The stable isotopes, δO18 and δD, data indicate that magmatic-metamorphic waters were responsible for fluids involved in phyllic and silicic alterations.