Neogene calc-alkaline volcanism in Bobak and Sikh Kuh, Eastern Iran: Implications for magma genesis and tectonic setting

• Published in: Mineralogy and petrology Vol. 117; no. 1; pp. 63 - 77
• Main Authors: Biabangard, Habib, Sepidbar, Fatemeh, Palin, Richard M., Boomeri, Mohammad, Whattam, Scott A., Homam, Seyed Masoud, Shahraki, Omol Banin
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01.03.2023; Springer Nature B.V
• Subjects: Assimilation; Continental crust; Crystallization; Earth and Environmental Science; Earth Sciences; Eocene; Fractional crystallization; Fractionation; Geochemistry; Inorganic Chemistry; Isotopes; Lava; Magma; Mineralogy; Neogene; Original Paper; Rocks; Signatures; Strontium 87; Strontium isotopes; Tectonics; Trace elements; Volcanic activity; Volcanic rocks; Volcanism; Iran; Geochemistry; Partial melting; Sr–Nd isotopes; High-Na volcanic rocks
• ISSN: 0930-0708; 1438-1168
• DOI: 10.1007/s00710-022-00798-8

The Neogene post-collisional volcanism in eastern Iran is represented by the Sikh Kuh and Bobak high-Na rocks including trachybasalt, trachyandesite, trachydacite, and dacite. We report whole rock geochemistry and Nd–Sr isotopic data which constrain the characteristics of the mantle source. The rocks are highly enriched in incompatible trace elements, suggesting a metasomatized subcontinental lithospheric mantle (SCLM) as the magma source. Felsic rocks record abundant petrographic evidence, major and trace element data, and isotopic ( 87 Sr/ 86 Sr(i) = 0.70727–0.70902) signatures indicative of fractional crystallization, and potentially, crustal assimilation. Such processes however, have not significantly affected the isotopic signatures ( 87 Sr/ 86 Sr(i) = 0.70417–0.70428) of the mafic members, suggesting that they are derived from a mantle source. The geochemical and isotopic data for the Sikh Kuh and Bobak volcanic rocks suggest that these Neogene magmas were derived from a small degree of partial melting (~ 2–10 vol%) of a spinel-bearing subcontinental lithospheric mantle source in a post-collisional setting. The generated more unfractionated mafic magmas erupted during an episode of extensional tectonics, presumably caused by extension that followed Eocene collision between the Lut and Afghan continental blocks. These melts interacted with continental crust during ascent, experiencing crystal fractionation, and crustal assimilation, to produce more evolved felsic volcanic rocks.