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The Mezcala gold district, Guerrero, Mexico, is a Cretaceous to early Paleocene oxidized Fe-Au skarn deposit, genetically associated with an adakitic magmatic event of 63±2 Ma, dated by ion-probe U/Pb on zircons.

The inner and outer alteration patterns and the mineralogical sequence (high garnet/pyroxene ratio, high ferric/ferrous ratio >1, predominance of Fe-poor garnet and pyroxene, low total sulfides) found in Mezcala are compatible with the description of an oxidized gold skarn type. Carbon and oxygen isotope analyses of the inner calcite zone (−9.98 to −11.64 and +13.21 to +14.59‰, respectively) unequivocally support a magmatic signature of the hydrothermal fluid. Carbon and oxygen isotopes from the outer calcite zone (−8.81 to +3.45 and +12.95 to +22.77‰, respectively) suggest a complex mechanism of degassing and subsequent cooling/dilution of the resulting magmatic brine with …