Mineralogy and petrogenesis of Chalu iron skarn deposit (SE Damghan)

The Chalu Fe skarn developed at the contacts of the part of intrusive body with monzodiorite composition and Cretaceous carbonate rocks. Endoskarn which occurs in a limited area is characterized by andradite rich garnet (Ad90Gr5Sp3) and clinopyroxene. The calcic exoskarn shows a continuous mineralogical evolution and zonation with increasing distant from contact. It is composed mainly of coarse- grained vesuvianite and garnet (Ad53Gr43Py2), in proximal zone to fine grained calcite, garnet (Ad27Gr71Py2) and vesuvianite in distal zone. The chemical compositions of garnet and vesuvianite in different parts of exoskarn indicate an evolutionary trend of increasing CO2 and H2O in the fluid, decreasing fO2, decreasing temperature. Hematite flakes (specularite) and magnetite which contain the main ore mineralization accompanied by Fe sulphides (pyrite and chalcopyrite) and secondary malachite, limonite and goethite.