Ophiolites and Related Formations in the Central Part of the Sabzevar Range (Iran) and Possible Geotectonic Reconstructions

Magma storage and plumbing of adakite-type post-ophiolite intrusions in the Sabzevar ophiolitic zone, northeast Iran

“…Neotethyan subduction gave rise to the Jurassic-Cretaceous Sanandaj-Sirjan subduction zone, trending parallel to the main Zagros thrust, as well as several back-arc oceanic seaways in central Iran (Omrani et al, 2008;Shafaii Moghadam et al, 2009;Rossetti et al, 2010). These back-arc oceanic domains (Sabzevar, Nain-Baft and Sistan) are thought to have opened during the Cretaceous period and closed during the transition from Paleocene to Eocene (Baroz et al, 1983;Arvin and Robinson, 1994;Shojaat et al, 2003;Babazadeh and de Wever, 2004). Iranian ophiolites as part of the Neotethyan oceanic region are the results of obduction processes of these minor oceanic seaways, showing discontinuous back-arc oceanic crust emplacement (Agard et al, 2011 and references therein).…”

Metamorphic history and geodynamic significance of the Early Cretaceous Sabzevar granulites (Sabzevar structural zone, NE Iran)

“…The timing of metamorphism in the Sabzevar structural zone has been constrained by K-Ar muscovite and Rb-Sr whole rock and mica geochronology. These data document that granitic magmatism occurred in the Early Eocene (at about 50 Ma), synchronous with the main greenschist-to-amphibolite retrograde metamorphism recorded in the metabasite blocks (Baroz et al, 1984).…”

“…105 Ma) (Rossetti et al, 2010). This metamorphic age thus contrasts with the Late Cretaceous formation age of the Sabzevar ophiolites and the Tertiary age of their structuration (Baroz et al, 1984;Shojaat et al, 2003). Consequently, the Sabzevar granulites have to be considered as allocthonous tectonic slivers preserved within the Tertiary nappe edifice, and this evidence imposes re-consideration of the current tectonic models for the Alpine convergence history of the region.…”

“…The blocks consist of serpentinised peridotites and intrusive and extrusive rocks, but foliated metabasites (blueschists, greenschists, and amphibolites) are also present. Syn-to-late tectonic, which are variably-sized granitic bodies, intrude the ophiolitic mélange, postdating main fabric development in the ophiolitic mélange and inducing contact metamorphism in the host rocks (Baroz et al, 1984). Another mélange unit underlies the tectonic mélange and consists of SE-verging imbricated thrust slices of red cherts and volcanic-volcaniclastic rocks, with features characteristic of a subduction-accretion complex (e.g.…”

“…It constitutes the largest ophiolitic massif (150 km long and 10-30 km wide) of north-eastern Iran and consists of a dismembered ophiolitic suite, with a tectonised and extensively serpentinised mantle section (harzburgite, dunite, and lherzolite) intruded by mafic magmas and a volcano-sedimentary sequence, Late Cretaceous to Paleocene in age (Alavi-Tehrani, 1977;Lensch et al, 1977;Delaloye and Desmons, 1980;Baroz et al, 1984;Shojaat et al, 2003). The geochemical signature of the ophiolitic rocks attests to a general MORB-like signature, suggesting that the oceanic lithosphere developed at an oceanic spreading centre (Baroz et al, 1984;Shojaat et al, 2003). These ophiolitic rocks dominantly occur dispersed as centimetre-to kilometre-size blocks into a highly sheared serpentinite matrix to form a major ophiolitic tectonic mélange.…”