The calc-alkaline and adakitic volcanism of the Sabzevar structural zone (NE Iran): Implications for the Eocene magmatic flare-up in Central Iran

• Published in: Lithos 2016-04, Vol.248-251, p.517-535
• Main Authors: Moghadam, Hadi Shafaii, Rossetti, Federico, Lucci, Federico, Chiaradia, Massimo, Gerdes, Axel, Martinez, Margarita Lopez, Ghorbani, Ghasem, Nasrabady, Mohsen
• Format: Article
• Language: English
• Subjects: Adakitic rocks; Cenozoic magmatism; Flare-up; Iran; Sabzevar; Sr–Nd–Pb isotopes
• ISSN: 0024-4937; 1872-6143
• DOI: 10.1016/j.lithos.2016.01.019

A major magmatic flare-up is documented along the Bitlis–Zagros suture zone in Eocene–Oligocene times. The Cenozoic magmatism of intraplate Central Iran is an integrant part of this tectono-magmatic scenario. The Cenozoic magmatism of the Sabzevar structural zone consists of mostly intermediate to felsic intrusions and volcanic products. These igneous rocks have calc-alkaline and adakitic geochemical signatures, with nearly coincident zircon U–Pb and mica Ar–Ar ages of ca. 45Ma. Adakitic rocks have quite low HREE and high Sr/Y ratio, but share most of their geochemical features with the calc-alkaline rocks. The Sabzevar volcanic rocks have similar initial Sr, Nd and Pb isotope ratios, showing their cogenetic nature. Nd model ages cluster tightly around ~0.2–0.3Ga. The geochemistry of the Sabzevar volcanic rocks, along with their isotopic signatures, might strangle that an upper mantle source, metasomatized by slab-derived melts was involved in generating the Sabzevar calc-alkaline rocks. A bulk rock trace element modeling suggests that amphibole–plagioclase–titanite-dominated replenishment-fractional crystallization (RFC) is further responsible for the formation of the middle Eocene Sabzevar adakitic rocks. Extensional tectonics accompanied by lithospheric delamination, possibly assisted by slab break-off and melting at depth was responsible for the Eocene formation of the Sabzevar magmatic rocks and, more in general, for the magmatic “flare-up” in Iran. •Sabzevar volcanic rocks show both calc-alkaline and adakitic signature.•Sabzevar rocks have identical U–Pb and Ar–Ar ages of ca. 45–47Ma.•Mantle sources metasomatized by slab-derived melts/fluids contribute to the Eocene flare-up in Iran.