Petrochemistry and tectonic setting of the Davarzan-Abbasabad Eocene Volcanic (DAEV) rocks, NE Iran

Abstract

The Davarzan–Abbasabad Eocene Volcanics (DAEV) is located at the northeastern edge of the volcanic–plutonic belt of the Central Iran structural zone. DAEV start with continental to shallow marine sediments of the Paleocene–Eocene and then continue extensively with shallow submarine to sub-aerial basaltic and andesitic volcanics, related volcaniclastics and sedimentary rocks during the Middle–Upper Eocene. The volcanics are olivine basalts, basaltic andesites and andesites in composition and show porphyric, hyaloporphyritic, glomeroporphyric, fluidal, and seriate textures. The geochemistry of DAEV points to a fractional series from olivine basalt to andesite with transitional and medium to high K calc–alkaline nature. Their primitive mantle and chondrite-normalized trace element patterns show that these rocks have high light- and low heavy rare earth elements and are enriched in large-ion lithophile elements and depleted in high field strength elements (Nb, Ti, P, and Zr). Integration of geochemical and petrological data with regional studies indicates that the magma(s) forming the DAEV rocks were derived from 14 to 16 % partial melting of an enriched mantle source in 70–100 km depths during Middle–Upper Eocene time in an intra-arc extensional setting. This mantle source had been previously metasomatized by fluids derived from Sabzevar Neo–Tethyan-subducted slab during the Upper Cretaceous–Paleocene.