Geochemical study of volcanic host rocks and argillic alteration mineralogy in Sarcheshmeh porphyry copper deposit: based on new data

Sarcheshmeh porphyry copper deposit lies within volcanic belt of Urumieh-Dokhtar, the most important mettalogenic belt of Iran. Based on petrography and petrology, the volcanic rocks are generally andesite and dacite. The magma has calcalkaline affinities and the amount of MgO and FeOt show a negative correlation with SiO2 which is a sign of fractional crystallization of clinopyroxene from magama. The CaO content also decreases which can be related with composition changes of plagioclase from calcic to sodic. The situation of such volcanic rocks is within magmatic arcs related to subduction of oceanic crust under continental crust. Based on XRD analysis, the major minerals of argillic alteration in sarcheshmeh deposit includes: kaolinite, montmorilonite, illite-mica, chlorite, quartz and pyrite, in which pyrite is the only sulfide in this barren zone. Finally, according to these studies, changes of clay minerals in western outcrop outward the deposit is constant, but in northern outcrop the amount of clay minerals changes from inside to margins of the deposit. By which in interior samples and adjacent to the stock, kaolinite is dominant and in margins plus exterior zones of algillic alteration, the montmorilonite dominates