Original paper

Mineralogical and geochemical studies of acid-sulfate alteration in the Shahrzad area, east of Esfahan, Central Iran

Taghipour, Batoul; Mackizadeh, Mohammad Ali; Kasson, Arthur; Huertas, Antonio Delgado


In the Cenozoic magmatic belt of Central Iran, the Eocene volcanics and pyroclastics from the Shahrzad area underwent extensive hydrothermal alteration. Major alteration zones show inclusions of propylite, quartz sericite, advanced argillic and silicified zones. Shahrzad alunites are mainly porcelaneous and their compositions show a solid solution between alunite and jarosite. In alteration zones, the mineral assemblage is characterized by alunite-jarosite + quartz + sericite + alkali feldspars + chlorite ± turquoise ± barite ± iron oxides. There are numerous alunite and jarosite occurrences, mainly as veinlets, in parts of the advanced argillic zone. Alunite δ18O and δD values range from −1.76 to 8.81 ‰ and from −52.86 to −129.26 ‰ respectively. Field observations, mineralogical evidence and results from light element stable isotope data (δ18O, δD and δ34S) indicate that the Shahrzad alunitization is of supergene origin.


acid-sulphate alterationcentral iranalunitejarositestable isotope