Structures and geodynamics of the Mongolian tract of the Central Asian Orogenic Belt constrained by potential field analyses

Abstract

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Paleozoic Geodynamics and Architecture of the Southern Part of the Mongolian Altai Zone

“…The southern part of the Mongolian Altai Zone east of the studied region was interpreted as an early Permian rift, characterized by rhyolite and basaltic extrusions and associated siliciclastic sedimentation (Kovalenko et al., 2004; Yarmolyuk et al., 2013) and granitoid intrusions (Kröner et al., 2010). Similar rift zones were also described at the northern margin of the Mongolian Altai Zone and in the Trans‐Altai Zone to the south and were well imaged by potential field methods (Guy et al., 2014, 2020, 2021). The whole Bodonch‐Tseel domain likely represents a lower crustal expression of this giant Permian rift system that was shortened during the subsequent mid‐Permian to Triassic collision as documented in the Chinese Altai Zone (Jiang et al., 2012, 2019; Figure 16e).…”

“…530 to 460 Ma granitic plutons (Rudnev, Babin, et al., 2013; Rudnev et al., 2012; Soejono et al., 2017), called the later Ikh Mongol arc (Janoušek et al., 2018), which are connected to regional high temperature‐low pressure H T ‐L P metamorphism (Kozakov et al., 2012). Further to the south, the Chinese and Mongolian Altai zones occur, bounded by the Bulgan/Erquis fault zones from the Trans‐Altai Zone and East Junggar domain, both consisting of Devonian and Carboniferous volcanic‐sedimentary sequences imbricated with Cambrian to Devonian ophiolites (Guy et al., 2021; Lehmann et al., 2010). Finally, the southernmost part of the Mongolian Collage System is formed by the South Gobi Zone with Grenvillean‐age continental crust and its early Paleozoic volcanic‐sedimentary cover (Rojas‐Agramonte et al., 2011).…”

Petrostructural and Geochronological Constraints on Devonian Extension‐Shortening Cycle in the Chinese Altai: Implications for Retreating‐Advancing Subduction

“…This Devonian retreat has been repeatedly documented in recent years but the related tectono‐metamorphic evolution and structural patterns remain obscure. The succession of Devonian structures and metamorphism has recently been described and dated (Broussolle et al., 2018; Jiang et al., 2019; Xu et al., 2021; Zhang et al., 2015), however, the effects of Permian deformation related to the collision of the Chinese Altai with the southerly Junggar arc domain (Jiang et al., 2019; Li et al., 2017; Xu et al., 2021) complicates their restorations (Guy et al., 2020, 2021).…”

Paleomagnetic, tectonic and geochronological constraints for Permian–Triassic oroclinal bending of the Mongolian collage

“…The internal deformation of the southern limb of the Mongolian orocline–sinistral wrenching and pure shear shortening of the LZ, MAW and the TAZ belts (the shear corridor of Guy et al. [ 8 ] accommodating A1–A2 and A2–B rotations is portrayed together with the scissor-like closure of the Mongol Okhotsk Ocean and clockwise rotation of the Siberia). (e) Satellite image of the MAW with 280–260 Ma dyke swarm and S-shaped folds showing the first pure shear shortening stage.…”

“…1e ) indicating initial pure shear shortening of the PAO units [ 7 ]. These dykes and hosting units were later asymmetrically folded and transposed by sinistral shear zones forming a structural and geophysical corridor between the TNC and MB [ 8 ]. The 40 Ar/ 39 Ar and K–Ar data show three peaks at ∼270–260, 250–230 and 220–160 Ma [ 9–11 ] that are all related to: (i) mid-Permian shortening and pegmatite dyke intrusion and (ii) Triassic sinistral shearing associated with the shortening and anticlockwise rotation of pure shear dominated ‘S’-shaped lithons (Fig.…”