Petrography and mineral chemistry of alteration zones in the Kahang porphyry Cu-Mo deposit (Northeast of Isfahan)

The study area is located in the Uromieh-Dokhtar volcanic belt and composed of andesite-basalt، andesite، dacite and quartz-monzonite as volcanic and subvolcanic. The occurrence of phyllic، argillic and propyllitic alterations point to the presense of hydrothermal fluids. The studied amphiboles have tschermakite and ferro-edenite composition. The compositional changes from core (Fe-Mg-Mn) to rim (calcic) refer to the variation of physico-chemical condition of magma in the last stage of crystallization. The biotites are assumed to be primary، their Fe/Fe+Mg ratio is over than 0. 33% and they are iron enriched. The composition of the chlorites plotted in the repidolite field with Fe and Si in the range of 6. 56% to 6. 76% and 5. 19% to 5. 61% respectively. The low content of Al+Fe3+ in sphene، can be the result of high temperature of its formation. The potassium content of the Kahang jarosites is more than that of the sodium indicating the hydrothermal-magmatic condition of these phases formation.