Geochemical description and sulfur isotope data for Shahrak intrusive body and related Fe-mineralization (east Takab), northwest Iran

The Shahrak intrusive body (SIB) occurs at the intersection of the Urumieh-Dokhtar Volcanic Belt and the Sanandaj-Sirjan metamorphic belt in northwest Iran. This intrusive body consists of granodiorite, monzonite, monzodiorite, and monzogabbro, that intruded Oligo-Miocene sedimentary units and Cretaceous and Precambrian metamorphic rocks. Iron mineralization has occurred as magnetite skarn with hematite and pyrite in calcareous units at the contact with the SIB. The Rb-Sr age dating shows that the age of the SIB is about 24.9 Ma (Chattian). Whole rock geochemical studies indicate that the magma has calc-alkaline to high-K calc-alkaline affinities and is metaluminous. The multi-elements spider diagrams normalized to chondrite and primitive mantle show significant enrichment of light rare earth element against heavy rare earth element and depletion of Ti, P, Ta, and Nb, indicating characteristic features of the volcanic arc rocks in a subduction setting. Furthermore, the various types of tectonomagmatic diagrams show that these rocks are generated in an active continental margin. The parental magma of the rocks probably originated from an enriched mantle on the basis of the geochemistry of the REE elements. The average Sr isotopic composition of the SIB is Sr-87/Sr-86(i) = 0.706. Therefore, the parent magma of the SIB may be the result of partial melting of enriched mantle or subducted slab contaminated with the continental crust. The sulfur isotope composition of pyrite grains (ave., +5.29 %) in the Korkora-1 iron deposit indicates that the sulfides are formed from magma or due to in situ dissolution and leaching of igneous sources. Dehydration melting of the subducted part of oceanic crust has likely produced the fluids that are necessary for melting of the mantle wedge to produce mafic-intermediate melts. The generated melts penetrated into the crust, and during their ascent they underwent a little crustal contamination and eventually were emplaced as intrusive bodies comprising gabbrodiorite to granodiorite.