Structural evolution of the Irtysh Shear Zone (northwestern China) and implications for the amalgamation of arc systems in the Central Asian Orogenic Belt

Li, Pengfei; Sun, Min; Rosenbaum, Gideon; Cai, Keda; Yang, Yu

doi:10.1016/j.jsg.2015.08.008

Cited by 71 publications

(107 citation statements)

References 94 publications

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“…Synthesizing previous structural studies (Broussolle et al, 2018; Jiang et al, 2015; P. Li et al, 2015; P. Li, Sun, et al, 2016; Qu & Zhang, 1994; Wei et al, 2007; Zhang et al, 2015), Broussolle et al (2019) came to the conclusion that three Paleozoic deformation phases affected the Chinese Altai rocks. Originally horizontal metamorphic fabric S1 associated with extensive Early to Mid‐Devonian syntectonic magmatism was deformed by upright NE/SW‐oriented F2 folds of Late Devonian age cored by migmatites and granites (Jiang et al, 2015, 2019).…”

Section: Discussionmentioning

confidence: 91%

Revision of the Chinese Altai‐East Junggar Terrane Accretion Model Based on Geophysical and Geological Constraints

et al. 2020

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Potential field data analysis, geology, and geochemistry are used to revise the terrane accretion model of the Chinese Altai and East Junggar. Major gradients of potential field data demarcate significant crustal structures and their continuity in depth. These data demonstrate that the distribution of geophysical anomalies does not match with terranes boundaries defined previously. Instead, heterogeneously developed NE/SW-trending gravity and NW-SE magnetic anomalies in both units correlate with Devonian and Permian tectonometamorphic zones, respectively. Geophysical data also indicate a dense lower crust of the East Junggar confirmed by previous igneous petrology studies and seismic experiment. The northern tip of this dense crust coincides with the main gravity gradient beneath the Chinese Altai and a prominent magnetic high located above a NW/SE-trending zone of Permian granulites. This zone forms a boundary between north-and south-dipping gravity and magnetic anomalies that are interpreted as reflecting quasi-symmetrical extrusion of the Chinese Altai crust. In contrast, all geophysical data show the absence of a prominent deep-seated discontinuity which can be correlated with the Erqis Zone. These data are compared with corresponding data sets from southern Mongolia allowing the proposition of a new geodynamic model for the studied area. This model involves (1) accretionary stage characterized by Late Devonian joint evolution of the East Junggar and Chinese Altai characterized by N-S trending orogenic fabrics and (2) Early Permian oroclinal bending associated with underthrusting of the dense Junggar basement beneath the Chinese Altai and the development of NW-SE trending deformation zones in both units.

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Section: Discussionmentioning

confidence: 91%

Revision of the Chinese Altai‐East Junggar Terrane Accretion Model Based on Geophysical and Geological Constraints

et al. 2020

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“…40 Ar/ 39 Ar dating of major subvertical ductile shear zones across central Asia produces ages ranging from 290–245 Ma, indicating widespread deformation during the Permian and into the Triassic (e.g. Briggs et al, ; Laurent‐Charvet et al, ; Li, Sun, et al, ; Rolland et al, ; Shu et al, ; Wang et al, ). This deformation was dominantly strike‐slip throughout central Asia, but was often accompanied by a component of contractional or extensional deformation depending on the location and orientation of the structure.…”

Section: Geological Backgroundmentioning

confidence: 99%

“…Sinistral‐reverse shearing along the steeply NE dipping mylonitic Irtysh shear zone occurred between ∼ 290 and 252 Ma according to 40 Ar/ 39 Ar dating and the ages of cross cutting dykes (Briggs et al, , ; Laurent‐Charvet et al, ; Li, Yuan, et al, ; Li, Sun, et al, ; Li, Sun, Rosenbaum, Cai, et al, ; Li, Sun, Rosenbaum, Jiang, & Cai, ). This transpressional event was accompanied by regional uplift in the southern Chinese Altai at ∼ 270 Ma as a result of convergence between the Chinese Altai and the East and West Junggar terranes (Li, Sun, et al, ). Dextral slip along structures to the southwest, such as the Chingiz‐Alakol‐North Tianshan fault, Junggar fault, and Central Kazakhstan fault, was coeval with sinistral slip along the Irtysh shear zone (e.g.…”

Section: Geological Backgroundmentioning

confidence: 99%

Late Paleozoic Exhumation of the West Junggar Mountains, NW China

et al. 2020

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The Tianshan and Altai mountain belts dominate the present-day topography of central Asia and are major constituents of the Central Asian Orogenic Belt. These mountain belts have been extensively studied using low-temperature thermochronology to understand their uplift and exhumation history. In comparison, few studies have focused on the spatial extent and timing of intracontinental deformation in the intervening ranges, such as the West Junggar Mountains. Apatite fission track (AFT) and apatite U-Pb dating of igneous samples from the West Junggar Mountains reveals AFT central ages ranging from latest Carboniferous to Middle Jurassic and mean confined track lengths between 14.1 and 12.0 μm, which are negatively correlating to AFT central ages. Apatite U-Pb dating produced mid-Carboniferous-early Permian ages within uncertainty of zircon U-Pb crystallization ages, indicating cooling to below ∼ 450-550 • C immediately following emplacement. Thermal history modeling of our AFT data combined with published (U-Th)/He data predicts rapid cooling to <60 • C during the early-middle Permian (285-260 Ma), followed by slower cooling rates during the Mesozoic-Cenozoic. The rapid cooling event coincides with (1) the timing of major basinward thrusting in the Junggar Basin adjacent to the study area and (2) exhumation in the Chinese Altai to the north. In contrast to previous studies, our results imply that the West Junggar Mountains do not record significant exhumation during the Mesozoic-Cenozoic. This suggests that Mesozoic deformation of the Central Asian Orogenic Belt was less pervasive and widespread than previously assumed.

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“…The Early Palaeozoic granitic rocks are characterized by negative ε Nd (t) and ε Hf (t) values, likely implying crust components contributed to their magma source (Yu et al, 2019). The Devonian granitoids are widely distributed throughout the orogen and mainly comprise metaluminous I-type granites and minor peraluminous Stype granites, such as the Kuerti pluton, Kuwei batholiths, Kurmutu, and Hemu plutons (Cai et al, 2011a;Li, Sun, Rosenbaum, Cai, & Yu, 2015;Wang et al, 2006;Yuan et al, 2007). Geochemically, they exhibit enrichment of light rare earth elements (LREE) and large-ion lithophile elements (LILE; such as Sr, K, Rb, and Ba) relative to highfield-strength elements (HFSE; such as Nb, Ta, and Ti), indicating an origin derived from arc-related magma source (Hawkesworth, Turner, McDermott, Peate, & van Calsteren, 1997).…”

Section: Geological Settingmentioning

confidence: 99%

Geochronology, geochemistry, and petrogenesis of the Kezijiaer gabbros, southern Chinese Altai: Evidence for ridge subduction

Wang

Yang

et al. 2020

Geological Journal

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The Chinese Altai as a key part of the Central Asian Orogenic Belt is characterized by wide outcrops of Palaeozoic granitoids and minor mafic plutons. It is widely accepted that Devonian ridge subduction played an important role in the tectonic evolution of the Chinese Altai. However, Carboniferous magmatism related to ridge subduction has received little attention. Here, we report zircon U–Pb age and whole‐rock geochemistry of the Kezijiaer gabbros in the southern Chinese Altai, aiming to elucidate their emplacement age and petrogenesis and tectonic setting. Laser ablation inductively coupled plasma mass spectrometry zircon U–Pb dating shows that the Kezijiaer gabbros were emplaced in the Early Carboniferous with a crystallization age of 348 ± 3 Ma (mean square of weighted deviates = 0.46). Geochemically, the Kezijiaer gabbros exhibit low SiO2, high MgO, Fe2O3, Ni, and Cr concentrations, as well as enrichments of light rare earth elements and large‐ ion lithophile elements (e.g., Rb, Ba, Th, and U) relative to high‐field‐strength elements and heavy rare earth elements. Meanwhile, they have high TiO2, Nb/Ta, Zr/Hf, and Ti/V and low La/Yb values. These features show that the gabbros share geochemical signatures of both island arc basalt and mid‐ocean ridge basalt. Together with low La/Sm, Sm/Yb, and Dy/Yb ratios, it is suggested that the Kezijiaer gabbros mainly originated from partial melting of a spinel lherzolite mantle wedge metasomatized by subduction‐related fluids and sediment melts with input of asthenospheric components, subsequently followed by fractional crystallization of olivine and clinopyroxene. Taking into account regional geology and published data, we argue that an Early Carboniferous ridge subduction regime responsible for the Kezijiaer gabbros might have also exerted a pivotal role in the tectonic evolution processes of the Chinese Altai in the Palaeozoic.

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Structural evolution of the Irtysh Shear Zone (northwestern China) and implications for the amalgamation of arc systems in the Central Asian Orogenic Belt

Cited by 71 publications

References 94 publications

Revision of the Chinese Altai‐East Junggar Terrane Accretion Model Based on Geophysical and Geological Constraints

Revision of the Chinese Altai‐East Junggar Terrane Accretion Model Based on Geophysical and Geological Constraints

Late Paleozoic Exhumation of the West Junggar Mountains, NW China

Geochronology, geochemistry, and petrogenesis of the Kezijiaer gabbros, southern Chinese Altai: Evidence for ridge subduction

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