geochemistry and genesis of aps minerals in advanced argillic alteration zone, northwest of shir-kuh, yazd

northwest of shir-kuh batholith, a number of leucocratic granitic and granodioritic plutons have intruded sedimentary hosts including shale-sandstone (triassic-jurassic) and sandstone-conglomerate (lower cretaceous). contact metamorphism and hydrothermal alterations are widespread. late alteration assemblage mainly occurs in arkosic sandstones of sangestan formation and includes propylitic, quartz-sericitic, advanced argillic and silicific zones. quartz-sericite zone is the most widespread. advanced argillic alteration is characterized by the following assemblage: jarosite, alunite, turquoise, from the al-phosphate-sulfate group (aps). considering this mineral assemblage and probable interactions taking place between the minerals, a geochemical environment with high fo2 and low ph is thought to be prevailing at the time of alteration and formation of alunite, jarosite and turquoise.