Ore mineralogy and geochemistry of the productive intrusive bodies in Guydash Fe-Skarn deposit, East Azarbaijan Province

The Guydash Fe deposit is located in the south of East Azarbaijan Province, about 27 km southwest of Qara Aghaj city at the northwestern parts of the Sanandaj-Sirjan zone. This research was conducted to study the mineralogy of the ore and the geochemistry of the intrusive bodies producing skarn mineralization. A set of granitoids with porphyry diorite-monzodiorite and porphyry granodiorite-monzogranite compositions have intruded  into the Jurassic carbonate rocks and caused iron skarn mineralization. The ore is composed dominantly of magnetite with subordinate minerals including hematite, pyrite, chalcopyrite, tetrahedrite, tennantite and goethite. The skarn zone includes various minerals of garnet (grossular and andradite), pyroxene, chlorite, epidote, actinolite, calcite and quartz. This mineral assemblage indicates that the skarn is calcic. In the geochemical diagrams, skarn-producing igneous rocks locate in granite and monzodiorite fields. All of these rocks are calc-alkaline, diorite rocks are meta-aluminous, and granodiorite rocks are per-aluminous in nature. Granodioritic rocks are adakite-type with high silica, and dioritic rocks are ordinary calc-alkaline type. The enrichment of Rb, Th, Ba and U, and the depletion of Nb and Ti elements in these rocks relative to the primitive mantle is comparable to the rocks derived from subduction zones. The chondrite-normalized REE patterns are almost similar for the studied rocks, indicating their richness in light rare earth elements (LREE) compared to heavy rare earth elements (HREE). The LaN/YbN ratio in these rocks indicates the absence of garnet at the source site and the shallow depth of magma formation. Granodiorite-producing magma is obtained by melting of the thinned lower crust. The Nb/Zr and Sr/Ce ratios in these rocks reveal that magma was formed by melting of the subducted crust and the sediments on it. The studied rocks fall in the category of igneous intrusions relating to magmatic activity in the active continental margin, in a continental arc.