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.

Petrology, petrogenesis, and geochronology review of the Cenozoic adakitic rocks of northeast Iran: Implications for evolution of the northern branch of Neo‐Tethys

“…This collision between two plates resulted in numerous magmatic events in the CISZ (Yousefi, Sadeghian, Samyari, & Ghasemi, 2017). These volcanic and intrusive rocks in this region of the CISZ are definitely the result of subduction of Neo‐Tethys Ocean (Sabzevar branch) and the post‐Eocene magmatism that occurred in the Oligocene to Miocene (Asiabanha & Foden, 2012; Ghasemi & Rezaei Kahkhaei, 2015; Jamshidi et al, 2015, 2018; Shabanian, Acocella, Gioncada, Ghasemi, & Bellier, 2012; Yousefi et al, b). According to the ages obtained by U–Pb geochronology, these hypabyssal intrusive and volcanic rocks in Qouchan‐Esfarayen magmatic belt have a lower age than the rocks of the other two adjacent regions.…”

“…These Middle Eocene to Miocene–Pliocene igneous rocks are evidence of subduction of the Sabzevar branch of the Neo‐Tethys Ocean. The association of these hypabyssal magmatic rocks and melting Neo‐Tethys oceanic plate has been widely accepted by researchers (Ghasemi & Rezaei Kahkhaei, 2015; Jamshidi et al, 2015; Yousefi, Sadeghian, Samyari, & Ghasemi, 2017; Yousefi, Sadeghian, Wanhainen, et al, 2017). According to geothermobarometry of some phenocrysts, such as amphibole, plagioclase, and pyroxene, in these adakites in some of these regions, the depth of the beginning of magma crystallization (before shallow emplacement) is estimated to be <30 km (Jamshidi et al, 2015; Yousefi, Sadeghian, Wanhainen, et al, 2017).…”

Geochemical and Nd-Sr Isotopic Compositions of Hypabyssal Adakites in the Torud-Ahmad Abad Magmatic Belt, Northern Central Iran Zone: Analysis of Petrogenesis and Geodynamic Implications

“…The northern part of the Central Iran zone includes several magmatic belts, e.g., Davarzan-Abbasabad Eocene volcanic magmatic belt in the northern part of the Sabzevar City investi-*Corresponding author: f.yousefi87@gmail.com Manuscript received May 21, 2020. Manuscript accepted November 27, 2020. gated by Ghasemi and Rezaei-Kahkhaei (2015) and the Torud-Ahmad Abad magmatic belt (TAMB), South-Southeast Shahrood (Fig. 1), presented by Yousefi et al (2017a).…”

“…12. The model presents the dominance of a compressional tectonic regime and continuation of subduction of the Neo-Tethys oceanic slab in the Middle-Upper Cretaceous, opening of a sedimentary-volcanic basin reflecting an extensional regime (Late Paleocene-Early Eocene) (e.g., Ghasemi and Rezaei-Kahkhaei, 2015), melting of modified mantle under the influence of dehydration of subducted oceanic slab (LSA) (Fig. 12a), and continuation of subduction and melting of subducted oceanic lithosphere creating the acidic and intermediate magmas, emplaced as small subvolcanic intrusions or dikes (HSA) (Fig.…”

“…1), presented by Yousefi et al (2017a). The Davarzan-Abbasabad Eocene magmatic belt consists of arc-like Paleocene to Eocene magmatism and post-subduction Oligocene to Quaternary magmatism (Ghasemi and Rezaei-Kahkhaei, 2015). The TAMB consists of intermediate to felsic subvolcanic domes and dikes that cut Eocene volcano-sedimentary rocks (Yousefi et al, 2017a, b) (Fig.…”