Mineralogy and geochemistry of major and trace elements in argillic alteration zone of the Kamar district, NW Iran

The action of alteration processes on the Eocene tuffs has led to the formation of a spread argillic alteration zone in the Kamar district (south of Ardebil, Tarom-Hashtjin Zone). The aim of this study is to determine the factors controlling argillic alteration, using mineralogical studies and chemical alteration indices. Quartz, kaolinite, muscovite (sericite), rutile, anatase, illite, diaspore, alunite, albite, clinochlore, jarosite, gypsum, pyrite, orthoclase and dolomite are the mineral assemblage of this alteration zone. The mineralization of sulfides includes pyrite (predominantly), chalcopyrite, borneite, chalcocite, galena, and sphalerite. The chemical index of alteration (CIA) values are between 51.55 to 74.3 %, and the mineralogical index of alteration (MI) values vary from 8.22 to 48.3%. The mafic index of alteration (MIA(O)) ranges from 55.88% to 87.48%, Depletion of a large number of elements, including some immobile elements (Zr, Y, LREEs, Al2O3), the presence of minerals indicating acidic pH, such as jarosite and alunite, and high-temperature minerals such as rutile and anatase, the presence of the vuggy quartz in some altered regions, and concomitant enrichment of As, Sb and Mo, in the Kamar argillic zone, bear similarities to the hot fluid alterations of high-sulfidation epithermal deposits.