Geochemistry and petrogenesis of Ghohroud Igneous Complex (Urumieh–Dokhtar zone): evidence for Neotethyan subduction during the Neogene

Abstract

The Oligo–Miocene Ghohroud granitoid is located in the north of Isfahan, in the Urumieh–Dokhtar magmatic arc (UDMA). The rock composition ranges from granodiorite to tonalite. Rocks mainly include quartz, plagioclase, and alkali feldspar with minor biotite and amphibole. Dacitic and basaltic rocks outcrop as dykes. Geochemical data show that these rocks are subalkaline, calc-alkaline, and metaluminous. Microgranular enclaves, sieve texture, oscillatory zoning in plagioclase, and clear roundness of quartz pieces demonstrated magma mixing. The magma has experienced fractional crystallization that has led to the presence of different petrological units. Large-ion lithophile element (LILE) and Pb enrichment is evidence of crustal contamination. Considering the clear negative anomaly of Nb and Ti, the magma has been formed in a volcanic arc environment. The geochemistry of major and rare earth elements reveals that initial magma has been formed by partial melting of lower crustal protoliths. An underplating magma can supply heat source for the dehydration melting of lower crust and generation of Ghohroud granitic melt by melting of a mafic source during the subduction of the Neotethyan oceanic plate and the Central Iran continental crust.