Petrogenesis of mafic collision zone magmatism: the Armenian sector of the Turkish-Iranian Plateau

Neill, I.; Meliksetian, K.; Allen, M.B.; Navasardyan, G.; Kuiper, K.

Abstract

The Turkish–Iranian Plateau grew after the Middle Miocene following the initial Paleogene Arabia–Eurasia collision. Authors attribute uplift to break-off of the southern Neo-Tethys slab beneath the Bitlis–Zagros Suture at ~ 15–10 Ma, coupled with continued plate convergence and regional crustal shortening. Since this time there has been an upsurge in mantle-derived collision magmatism over large parts of NW Iran, Eastern Anatolia and the Lesser Caucasus, potentially hundreds of kilometres from the site of southern Neo-Tethys slab break-off, > 10 Myr after the proposed break-off event. Whole rock elemental and Sr–Nd–Pb–Hf isotope data are presented for < 3 Ma trachy-basalt to trachy-basaltic andesite lavas erupted in Armenia in the South Caucasus. Samples formed by < 5% melting of fertile subduction-modified spinel-facies lithospheric mantle, and few display elemental or isotopic evidence for contamination by the 45-km thick Mesozoic–Paleogene arc crust or South Armenian Block continental crust. Recent magmatic activity in Armenia may not be a direct consequence of southern Neo-Tethys slab break-off 300–450 km away, beneath the Bitlis Suture. Late Miocene break-off of a second (northern Neo-Tethys) slab beneath the Pontide Arc may have allowed asthenospheric upwelling over a wider area than was affected by southern Neo-Tethyan break-off. However, whole-scale delamination of mantle lithosphere is ruled out due to the modest degrees of partial melting, a lack of asthenospheric components and limited crustal involvement in magmatism. Small-scale sub-lithospheric convection may be complementary to break-off, causing localised removal of lithospheric mantle and aiding the occurrence of melting for a significant time interval after the break-off event(s). Collision magmas such as those in Armenia represent mantle-derived additions to continental crust, enriched in incompatible elements but with Th/La ratios ≤ 0.2, much lower than those calculated for continental crust (0.25–0.3). Collision magmatism in Turkic-style orogens must be balanced by infra-crustal recycling and delamination to produce bulk continental crust.

Citation

Neill, I., Meliksetian, K., Allen, M., Navasardyan, G., & Kuiper, K. (2015). Petrogenesis of mafic collision zone magmatism: the Armenian sector of the Turkish-Iranian Plateau. Chemical Geology, 403, 24-41. https://doi.org/10.1016/j.chemgeo.2015.03.013

• Journal Article Type: Article
• Acceptance Date: Mar 12, 2015
• Publication Date: May 1, 2015
• Deposit Date: Mar 13, 2015
• Publicly Available Date: Apr 2, 2015
• Journal: Chemical Geology
• Print ISSN: 0009-2541
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 403
• Pages: 24-41
• DOI: https://doi.org/10.1016/j.chemgeo.2015.03.013
• Keywords: Arabia–Eurasia collision, Armenia, Continental crust, Orogenic plateau, Radiogenic isotopes, Sub-lithospheric convection
• Public URL: https://durham-repository.worktribe.com/output/1413482