Origin and Development of Skarn-Forming Fluids from the Band-e-Narges Skarn Iron Ore- Central Iran

Abstract

The Band-e-Narges magnetite deposit is located in the central part of Urumieh–Dokhtar Magmatic Arc. Wide I-type calk-alkaline and alkalin magmatic activity in the Koh-e Latif region has been reported due to Eocene intrusive processes in UDMA. Five stages of paragenesis have been observed in the mineralization in this area: prograde stage, retrograde stage, sulfide- quartz stage, carbonate stage and Oxidation stage.The result of all δ34S values of pyrite and anhydrite + pyrite shows values are positive with a magmatic sulfur origin in these deposits. fluid inclusions have been observed according to the petrographic and microtermometric inclusions within garnet, quartz, and calcite minerals at various stages. According to high temperature and middle salinity of fluid inclusions in prograde skarn-stage, the fluid inclusions shows reaction with the calcareous wall rock and fluid inclusions were trapped at pressures of 400 to 500 bars, corresponding to depths of 1.5 to 2 km .Fluid inclusions in quartz have moderate temperatures and low salinity indicating quartz-sulfide stage and late retrograde stage. fluid inclusions with moderate homogenization temperature (300 to 350 oC ) suggest that reboiling coccurred under hydrostatic pressure of 150 to 250 bars, equivalent to a depth of 1 to 1.5 km in the late retrograde skarn and quartz-sulfide stages. Fluid inclusions in calcite have moderate temperatures and low to high salinities . The geology, mineralogy, geochemistry, salinities and homogenization-temperatures from the fluid inclusions populations at the Band-e-Narges iron deposit are follows a model of boiling as a result of decrease pressure, mixing and cooling.