Water-rock interaction in the Sangan deposit, northeastern Iran

Huge iron ores and two distinct skarn zones were formed in the carbonate rocks by late Eocene granitic batholith in the Sangan area. A total of 48 samples mainly from the carbonates and the granitic rocks were analyzed for oxygen and carbon isotopes. The marbles have relatively high delta O-18 and delta C-13 values whereas the granitic rocks have low delta O-18 values. The delta O-18 and delta C-13 values from other carbonate types are between these two sources. The isotopic mass-balance calculations suggest the presence of magmatic water in the Sangan deposit. The delta O-18 values of the igneous rocks can be explained by isotopic exchange with a magmatic water and the gradual decrease of the delta O-18 and delta C-13 values from marbles to calcite and dolomite skarns can be ascribed to interaction of hydrothermal fluids with carbonate rocks in the area as water to rock ratio increased.