Gabbroic-dioritic dykes from the Sanadaj-Sirjan Zone: windows on Jurassic and Eocene geodynamic processes in the Zagros Orogen, western Iran

Deevsalar, R., Shinjo, R., Wang, K.-L., Yaganehfar, H. and Neill, I. (2018) Gabbroic-dioritic dykes from the Sanadaj-Sirjan Zone: windows on Jurassic and Eocene geodynamic processes in the Zagros Orogen, western Iran. Journal of the Geological Society, 175(6), pp. 915-933. (doi: 10.1144/jgs2017-156)

Abstract

The Sanandaj-Sirjan Zone (SaSiZ) is a magmatic terrane within the Zagros Orogen, western Iran, marking the Tethyan suture zone between the Afro-Arabian Plate and the Central Iran Micro-Continent. Mafic-intermediate dyke swarms with Middle Jurassic (Group-1: hornblende gabbro and diorite) and Late Eocene (Group-2: hornblende-pyroxene gabbro) ages are recognized in the Malayer-Boroujerd Plutonic Complex of the northern SaSiZ. Group-1 dykes have elemental and isotopic signatures consistent with melting of a mantle source modified during Neo-Tethyan subduction. Some Group-1 magmas evolved to intermediate compositions through assimilation and fractional crystallization. Group-2 dykes have within-plate trace element geochemical signatures, modelled as deriving from low-degree melting of asthenospheric mantle without a subduction influence. Published models postulate either a Cretaceous-Eocene Neo-Tethyan flat-slab scenario, or a Latest Cretaceous-Palaeogene Neo-Tethyan break-off event beneath the SaSiZ. Such models do not reconcile with the Late Eocene presence of within-plate magmatism in westernmost Iran, very close to the Zagros Suture. We argue that a period of flat-slab subduction concluded with sub-parallel subduction of a Neo-Tethyan ridge to the trench. The resulting slab break-off event in the Late Eocene is responsible for generation of the distinct Mesopotamia and Zagros slabs in mantle tomography models. Break-off was followed by small volume within-plate type magmatism before short-lived re-establishment of Tethyan subduction prior to the final Arabia-Eurasia collision.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Neill, Dr Iain
• Authors: Deevsalar, R., Shinjo, R., Wang, K.-L., Yaganehfar, H., and Neill, I.
• Subjects: Q Science > QE Geology
• College/School: College of Science and Engineering > School of Geographical and Earth Sciences > Earth Sciences
• Journal Name: Journal of the Geological Society
• Publisher: Geological Society of London
• ISSN: 0016-7649
• ISSN (Online): 2041-479X
• Published Online: 12 June 2018
• Copyright Holders: Copyright © 2018 The Authors
• First Published: First published in Journal of the Geological Society 175:915-933
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher