Significance of Nain-Baft ophiolitic belt (Iran): Short-lived, transtensional Cretaceous back-arc oceanic basins over the Tethyan subduction zone

Abstract

Four dismembered massifs belonging to the Nain-Baft ophiolitic belt (Central Iran) stretch in a NW-SE direction parallel to the fossil active margin of the Iranian Continental Block (Sanandaj-Sirjan Zone). They are separated by huge transcurrent faults. The Nain, Dehshir, Shahr-e-Babak and Baft massifs are composed of associated slices of harzburgites, small bodies of gabbros and dike swarm complexes, accompanied by various extrusives from basaltic-andesitic lava flows and breccias to dacites and rhyolites. Trace element geochemistry of these lavas displays calc-alkaline and arc-tholeiite signatures, suggesting a back-arc origin for these ophiolites. This is in accordance with the position of these massifs, to the North of the Mesozoic Magmatic Arc crosscutting the Sanadaj-Sirjan Zone. Conventional K-Ar datings on amphibole within amphibolite and gabbros deliver ages between 93 Ma and 67 Ma. These ages are in good agreement with the stratigraphic age of the conformably Cenomanian to Maastrichtian sedimentary cover of the extrusives. The closure of these back-arc basins occurred in the Middle Paleocene as testified by the presence of neritic limestones, sealing all the tectonic contacts. The general geological setting of the Nain-Baft belt suggests that these massifs generated in a transtensional small back-arc basins separated by transcurrent faults. These short-lived transtensional basins result from the oblique subduction of the Tethyan Ocean under the Iranian Continental Block.

Evidence for mantle exhumation along the Arabian margin in the Zagros (Kermanshah area, Iran)

“…During the late Cretaceous time also, limited short-lived back-arc oceanic basins developed in the Central Iran block forming the Nain-Baft ophiolites described by Moghadam et al (2009). On the other side of the Tethys, an Albian rifting episode led to the formation of the so-called periArabian trench system and was accompanied by basalts flooding in Syria, Israel, and Liban (Kazmin 2002).…”

The long‐term evolution of the Doruneh Fault region (Central Iran): A key to understanding the spatio‐temporal tectonic evolution in the hinterland of the Zagros convergence zone

“…The Mesozoic-Cenozoic tectonic evolution of CEIM is dominated by the polyphase opening and closure of various back-arc oceanic basins formed in the upper-plate domain of the Neotethyan subduction system (i.e., the Sabzevar, Nain-Baft, Sistan oceans; Arvin & Robinson, 1994;Barrier et al, 2008;McCall, 1997;Rossetti et al, 2014;Şengör et al, 1988;Shafaii Moghadam, Whitechurch, Rahgoshay, & Monsef, 2009;Shafaii Moghadam, Corfu, & Stern, 2013;Stampfli & Borel, 2002;Stöcklin, 1974). Such domains presently form the various ophiolitic sutures zones that surround the CEIM (Figure 1).…”

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Neogene to Present paleostress field in Eastern Iran (Sistan belt) and implications for regional geodynamics

“…The Sistan ocean opened between two microcontinental blocks, the Lut block to the west and the Afghan block to the east, although its exact orientation is still somewhat speculative (Figures 1 and 2) [Barrier and Vrielynck, 2008;Saccani et al, 2010]. Rifting between the Lut and Afghan blocks may have started during the early (to middle) Cretaceous [Delaloye and Desmons, 1980;Babazadeh and De Wever, 2004], as for Sabzevar or Nain-Baft microoceans [Moghadam et al, 2009;Agard et al, 2011;Shafaii Moghadam et al, 2014]. A recent paleomagnetic study [Mattei et al, 2015] shows that Central Iran (defined by the Yadz, Tabas, and Lut blocks) suffered a homogeneous counterclockwise rotation of about 30°between the Late Jurassic to the Early Cretaceous supporting the idea of a coherent Central Iranian block at that time.…”