A Paleogene extensional arc flare‐up in Iran

Abstract

[1] Arc volcanism across Iran is dominated by a Paleogene pulse, despite protracted and presumably continuous subduction along the northern margin of the Neotethyan ocean for most of Mesozoic and Cenozoic time. New U-Pb and 40 Ar/ 39 Ar data from volcanic arcs in central and northern Iran constrain the duration of the pulse to ∼17 Myr, roughly 10% of the total duration of arc magmatism. Late Paleocene-Eocene volcanic rocks erupted during this flare-up have major and trace element characteristics that are typical of continental arc magmatism, whereas the chemical composition of limited Oligocene basalts in the Urumieh-Dokhtar belt and the Alborz Mountains which were erupted after the flare-up ended are more consistent with derivation from the asthenosphere. Together with the recent recognition of Eocene metamorphic core complexes in central and east central Iran, stratigraphic evidence of Eocene subsidence, and descriptions of Paleogene normal faulting, these geochemical and geochronological data suggest that the late Paleocene-Eocene magmatic flare-up was extension related. We propose a tectonic model that attributes the flare-up to decompression melting of lithospheric mantle hydrated by slab-derived fluids, followed by Oligocene upwelling and melting of enriched mantle that was less extensively modified by hydrous fluids. We suggest that Paleogene magmatism and extension was driven by an episode of slab retreat or slab rollback following a Cretaceous period of flat slab subduction, analogous to the Laramide and post-Laramide evolution of the western United States.

Long-lived, stationary magmatism and pulsed porphyry systems during Tethyan subduction to post-collision evolution in the southernmost Lesser Caucasus, Armenia and Nakhitchevan

“…1), is attributed to decompression melting of metasomatised lithospheric mantle during extension and thinning of the crust, and the adakitic composition is interpreted in terms of mantle metasomatism by slab-derived adakitic melts (Aghazadeh et al, 2011;Castro et al, 2013). This geodynamic evolution is comparable with the extensional flare-up evolution and asthenospheric upwelling scenario proposed by Verdel et al (2011) (Fig. 1), the geodynamic significance and the age of which remain uncertain .…”

“…The Talysh mountains and the adjoining Alborz range are interpreted as back-arc systems during the Eocene, followed by Late Eocene to Early Oligocene basin inversion, uplift and transpression attributed to the initiation of the Arabian-Eurasian collision (Ismail-Zadeh et al, 1995;Brunet et al, 2003;Vincent et al, 2005;Adamia et al, 2010;Ballato et al, 2010;Verdel et al, 2011;Asiabanha and Foden, 2012). In the Lesser Caucasus, Paleocene to late-Middle Eocene thick molasse series were deposited in a foreland basin to the southwest of the Somkheto-Karabagh belt ( Fig.…”

Geochemistry and geodynamics of the Mawat mafic complex in the Zagros Suture zone, northeast Iraq

“…K-Ar and Ar-Ar dating show 107-95 Ma [61] for metamorphism in the Late Cretaceous. According to our model, the Mawat igneous complex is not produced by the obduction on the Arabian passive margin during Zagros Orogeny, because most recent works confirm that the collision between the Arabian and Iranian Plates occurred in the Late Miocene [30,[62][63][64][65]. During the collision between the Arabian and Iranian plates in the Late Miocene the Mawat complex was overthrust on the Red Bed Series.…”

The Sanandaj–Sirjan Zone in the Neo-Tethyan suture, western Iran: Zircon U–Pb evidence of late Palaeozoic rifting of northern Gondwana and mid-Jurassic orogenesis

“…2) and reflect subduction of Neo-Tethyan oceanic crust prior to collision (Alavi, 1994;Agard et al, 2011;Verdel et al, 2011). Volcanic rocks of a similar age are widely distributed throughout most of the rest of Iran east and north of the Urumieh-Dokhtar Magmatic Arc (Verdel et al, 2011).…”