Petrology of the Paleogene shoshonitic volcanism in north Sarab area, NW Iran: Geochemical, Ar-Ar dating and Sr-Nd-Pb isotopic constraints

IF 1.7 Q3 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Asian Earth Sciences: X Pub Date : 2022-12-01 DOI:10.1016/j.jaesx.2022.100109

Somaye Heidari , Amir Ali Tabbakh Shabani , Shohreh Hassanpour , Reza Maghdour-Mashhour

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Abstract

This study reports the earliest presumably known collisional magmatism of the NW Iran–eastern Turkey–Caucasus region from the north of Sarab city in East Azarbaijan province, NW Iran. Volcanic rocks of the area comprise alternating lava flows of mainly alkalibasalt, andesite, trachyandesite, dacite and pyroclastics (tuff and ignimbrite) affiliated with high-K calk-alkaline to shoshonitic magmatic series. Ar–Ar geochronology of the glass, matrix and plagioclase laths revealed crystallization time restricted to Late Eocene to Early Oligocene (34.90–30.69 Ma) which is coincident with the onset of the Arabian-Eurasian continental collision. Geochemical data show LREE enrichment compared with HREE and Nb and Ti depletion, indicating that they are subduction related. The Sr-Nd-Pb isotopic data reflect the incorporation of oceanic sediment into the magma source. We suggest that the volcanic rocks were generated from a metasomatised subcontinental lithospheric mantle source through 5 to 10 vol% partial melting in an extensional back arc basin by the Neotethys slab roll-back under the Iranian plateau.

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伊朗北部Sarab地区古近系松玄岩火山岩岩石学:地球化学、Ar-Ar测年和Sr-Nd-Pb同位素约束

本研究报告了伊朗西北部-土耳其东部-高加索地区从伊朗西北部东阿扎拜詹省萨拉布市北部已知的最早碰撞岩浆作用。该地区的火山岩包括交替的熔岩流，主要是碱性玄武岩、安山岩、粗安岩、英安岩和火山碎屑岩（凝灰岩和熔结凝灰岩），属于高钾碱性至浅玄质岩浆系列。玻璃、基质和斜长石板条的Ar–Ar地质年代学显示，结晶时间限制在始新世晚期至渐新世早期（34.90–30.69 Ma），这与阿拉伯-欧亚大陆碰撞的开始相吻合。地球化学数据显示，LREE富集与HREE相比，Nb和Ti贫化，表明它们与俯冲有关。Sr-Nd-Pb同位素数据反映了海洋沉积物与岩浆源的结合。我们认为，火山岩是由交代的次大陆岩石圈地幔源通过伊朗高原下的新特提斯板块回滚在伸展弧后盆地中5至10体积%的部分熔融而产生的。

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