Geochemical and Sr–Nd–Hf isotopic evidence for Cenozoic partial melting of mantle beneath Natanz, Central Iran

Author(s): Shahrouz Babazadeh, Massimo D'Antonio, Davood Raeisi, Tanya Furman, M. Santosh, Valeria Di Renzo, Urs Klötzli, Sung Hi Choi, Jalil Ghalamghash, John M. Cottle, Richard M. Palin
Abstract: The products of Cenozoic continental arc magmatism in Iran provide an outstanding natural laboratory for investigating subduction-related processes. Here we present whole rock, Sr[sbnd]Nd isotopic, zircon U–Pb–Hf age, and mineral composition data for Cenozoic intrusive rocks from the Natanz area, central Urumieh–Dokhtar magmatic arc (UDMA), with a view to re-evaluate spatial–temporal variations in arc magmatism, magma petrogenesis and mantle source characteristics. The suite investigated in this study ranges from less evolved (gabbro) to highly evolved (granite) rocks with calc-alkaline affinity and an age range from 23.2 to 19.7 Ma. Their εNd_(t) values vary from −0.32 to 2.73, initial ⁸⁷Sr/⁸⁶Sr values range from 0.7049 to 0.7075, and zircon εHf_(t) values range from −2.2 to +8.9. Combined modelling of trace element and isotopic data suggests that the most mafic Natanz magmas could have formed through ∼5% melting of a source comprising 99% depleted mantle +1% sediment, with the melts modified subsequently by ∼3% contamination by Cadomian upper crustal components. We postulate that Natanz magmatism originated during a flare-up event instigated by retreat of the subducted slab prior to or in conjunction with the collision between the Arabian and Eurasian plates. The spatial–temporal associations in central UDMA (i.e., 33° 30′ N to 34° N) mirror three distinct flare-up episodes that occurred between 57 and 36 Ma, 26–15 Ma, and < 10 Ma; these events have not been reported previously from the northwestern and southeastern portions of the UDMA. Our results argue against any lull in magmatic activity in central UDMA during Eocene to Miocene times.
Organisation(s): Department of Lithospheric Research
External organisation(s): Chungnam National University (CNU), Consorzio di Ricerca per l’Energia, l’Automazione e le Tecnologie dell’Elettromagnetismo, University of Tehran, Pennsylvania State University, Chinese Academy of Geological Sciences, University of Adelaide, Geological Survey of Iran, University of California, Santa Barbara, University of Oxford
Journal: Lithos
Volume: 468-469
ISSN: 0024-4937
DOI: https://doi.org/10.1016/j.lithos.2024.107489
Publication date: 03-2024
Peer reviewed: Yes
Austrian Fields of Science 2012: 105105 Geochemistry, 105127 Geochronology
Keywords
ASJC Scopus subject areas: Geology, Geochemistry and Petrology
Portal url: https://ucrisportal.univie.ac.at/en/publications/0bfa600b-0aba-4515-b8ee-65c7ff8865b9

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