Stable isotope (O, H and S) studies of the phyllic and potassic–phyllic alteration zones of Kahang porphyry copper- molybdenum deposit, NE-Isfahan


1 School of Geology, University College of Science, University of Tehran, Iran

2 Mining Engineering Department, Isfahan University of Technology, Isfahan, Iran


      Kahang porphyry Cu–Mo deposit, located northeast of Isfahan city in central of Iran, is associated with a composite Miocene stock and ranging from diorite through granodiorite to quartz-monzonite. Stable isotopes (S, O, H) studies were restricted to the phyllic and potassic- phyllic alteration zones, where numerous cross-cutting quartz, sulfides veinlets were present. The main objective of this research was to determine the origin of the ore-forming fluids, and their important components. The δ34S values of sulfides (pyrite and chalcopyrite) range from -1.5 to +0.25 percent. These value are almost analogous to those from Ajo and Twin Buttes porphyry copper deposits in Arizona. The δ18O and δD  values range from 8.1 to 8.6 percent (mean of 8.3 percent) and -65 to -78 percent relative to standard oceanic water, respectively. Based on the lowest obtained δD values, the calculated maximum exchangeable meteoric water that might be involved in the phyllic and potassic–phyllic alteration processes was ~20 percent. These isotopic investigations demonstrated that: (1) in contrast to some of the well-known PCDs, about 80 percent of the fluids involved in the phyllic and potassic–phyllic alterations at Kahang contains a magmatic O and H isotopic signature and (2) the sulfur also conatains a magmatic origin.


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