Subduction-related mafic to felsic magmatism in the Malayer-Boroujerd plutonic complex, western Iran

Deevsalar, R., Shinjo, R., Liégeois, J. P., Valizadeh, M. V., Ahmadian, J., Yeganehfar, H. and Neill, I. (2018) Subduction-related mafic to felsic magmatism in the Malayer-Boroujerd plutonic complex, western Iran. Swiss Journal of Geosciences, 111(1-2), pp. 269-293. (doi: 10.1007/s00015-017-0287-y)

Abstract

The Malayer–Boroujerd plutonic complex (MBPC) in western Iran, consists of a portion of a magmatic arc built by the northeast verging subduction of the Neo-Tethys plate beneath the Central Iranian Microcontinent (CIMC). Middle Jurassic-aged felsic magmatic activity in MBPC is manifested by I-type and S-type granites. The mafic rocks include gabbroic intrusions and dykes and intermediate rocks are dioritic dykes and minor intrusions, as well as mafic microgranular enclaves (MMEs). MBPC Jurassic-aged rocks exhibit arc-like geochemical signatures, as they are LILE- and LREE-enriched and HFSE- and HREE-depleted and display negative Nb–Ta anomalies. The gabbro dykes and intrusions originated from metasomatically enriched garnet-spinel lherzolite [Degree of melting (fmel) ~ 15%] and exhibit negative Nd and positive to slightly negative εHf(T) (+ 3.0 to − 1.6). The data reveal that evolution of Middle Jurassic magmatism occurred in two stages: (1) deep mantle-crust interplay zone and (2) the shallow level upper crustal magma chamber. The geochemical and isotopic data, as well as trace element modeling, indicate the parent magma for the MBPC S-type granites are products of upper crustal greywacke (fmel: 0.2), while I-type granites formed by partial melting of amphibolitic lower crust (fmel: 0.25) and mixing with upper crustal greywacke melt in a shallow level magma chamber [Degree of mixing (fmix): 0.3]. Mixing between andesitic melt leaving behind a refractory dense cumulates during partial crystallization of mantle-derived magma and lower crustal partial melt most likely produced MMEs (fmix: 0.2). However, enriched and moderately variable εNd(T) (− 3.21 to − 4.33) and high (87Sr/86Sr)i (0.7085–0.7092) in dioritic intrusions indicate that these magmas are likely experienced assimilation of upper crustal materials. The interpretations of magmatic activity in the MBPC is consistent with the role considered for mantle-derived magma as heat and mass supplier for initiation and evolution of magmatism in continental arc setting, elsewhere.

• Item Type: Articles
• Keywords: Zagros Orogen, Tethyan subduction zone setting, Middle Jurassic, mantle melting, magma mixing, crustal anatexis.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Neill, Dr Iain
• Authors: Deevsalar, R., Shinjo, R., Liégeois, J. P., Valizadeh, M. V., Ahmadian, J., Yeganehfar, 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: Swiss Journal of Geosciences
• Publisher: Springer
• ISSN: 1661-8726
• ISSN (Online): 1661-8734
• Published Online: 25 January 2018
• Copyright Holders: Copyright © 2018 Swiss Geological Society
• First Published: First published in Swiss Journal of Geosciences 111(1-2): 269-293
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher