Early Palaeozoic sedimentary record and provenance of flysch sequences in the Hovd Zone (western Mongolia): Implications for the geodynamic evolution of the Altai accretionary wedge system

Soejono, Igor; Čáp, Pavel; Míková, Jitka; Janoušek, Vojtěch; Buriánek, David; Schulmann, Karel

doi:10.1016/j.gr.2018.07.005

Cited by 29 publications

(35 citation statements)

References 74 publications

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“…Volcanic rocks dated at Middle Devonian show bimodal geochemical characteristics indicating a back‐arc extensional regime (Wan et al, ; Xu et al, ). Further north, Middle Devonian sedimentary basins situated on the former Ordovician accretionary wedge were interpreted as extension‐related basins based on their generally siliciclastic sedimentary infill (Soejono et al, ). Taken together, a significant crustal extension phase affected mainly the orogenic lower and upper crustal sections of the Altai accretionary wedge.…”

Section: Discussionmentioning

confidence: 99%

“…The lithological content of this unit led Xiao et al () to interpret it as a giant “Altai” accretionary wedge. Together with the Ikh‐Mongol arc system (Janoušek et al, ), it represents a huge early Paleozoic Altai accretionary system, rimming the active margin of the Precambrian Zavhan and Baydrag ribbon continents to the northeast (Figure ; Jiang et al, ; Soejono et al, ). This accretionary system developed above a long‐lasting and retreating Pacific‐type oceanic plate that produced Devonian to Carboniferous oceanic assemblages further south (Jiang et al, ; Nguyen et al, ; Xiao et al, ).…”

Section: Geological Settingmentioning

confidence: 99%

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Structural and Geochronological Constraints on Devonian Suprasubduction Tectonic Switching and Permian Collisional Dynamics in the Chinese Altai, Central Asia

et al. 2019

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Kinematic significance and time scales of geodynamic processes forming the Altai OrogenicBelt are addressed through structural and petrological analysis combined with zircon and monazite geochronology. The study area is composed of orogenic lower crust represented by a Devonian migmatite-magmatite complex and orogenic middle and upper crust formed by an amphibolite-facies Ordovician sedimentary sequence and a weakly to unmetamorphosed Devonian volcano-sedimentary cover, respectively. The orogenic lower and middle crust were first affected by moderate thickening, which formed subhorizontal Barrovian metamorphic schistosity. This fabric was reworked by deep crustal melting and intrusion of granite sheets during horizontal extension at 400-380 Ma. Soon after, this horizontal fabric was affected by NW-SE shortening generating crustal-scale upright folding associated with subvertical flow of still partially molten orogenic lower crust. During this event, the orogenic lower and middle crust were tightly juxtaposed with upper crustal sedimentary rocks. The last event was related with a NE-SW oriented convergence resulting in large-scale folding and megafold interference pattern in the Permian at 280-273 Ma. Combined with existing regional data, our results allow proposing a Devonian tectonic switching from compression to extension and back to compression, as a response to variations of subduction dynamics between slab advance and retreat in a Pacific-type suprasubduction system. The Permian folding was associated with the progressive northward exhumation of thermally softened crust. This tectonic evolution is in response to the indentation of the rigid Junggar arc domain into the weak Altai wedge.

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Section: Discussionmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Structural and Geochronological Constraints on Devonian Suprasubduction Tectonic Switching and Permian Collisional Dynamics in the Chinese Altai, Central Asia

et al. 2019

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“…490 Ma and a broad minor peak in the interval of 1,200–700 Ma. Such a detrital pattern was interpreted as clastic material derived mainly from the northerly Proterozoic Lake Zone and margins of Precambrian Mongolian microcontinents (e.g., Janoušek et al, 2018; Jiang et al, 2017; Soejono et al, 2018). The difference in amplitude of the ca.…”

Section: Geological Background Of the Chinese Altai And The East Junggarmentioning

confidence: 99%

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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“…1). The sediments are ascribed to Zuun Nuruu (Ordovician), Tsetseg (Silurian) and Sagsai (Lower Devonian) formations (Soejono et al 2018). The age of these sediments decreases generally westwards, but the stratigraphic record is complicated due to strong deformation so that the same part of the sequence may be repeated (Žáček et al 2017a).…”

Section: Introductionmentioning

confidence: 99%

“…The entire unit subsequently underwent an Early Devonian metamorphism reaching up to amphibolite-facies conditions and polyphase deformation. Finally, it was exhumed along deep-seated, NW-SE striking faults (Soejono et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Anorogenic Early Permian dykes in the western Mongolian Altai - petrography, geochemistry and K-Ar geochronology

et al. 2019

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A variety of felsic and mafic dykes grouped into swarms intruded the Lower Palaeozoic volcano-sedimentary sequences (flysch) and Late Devonian to Early Carboniferous plutonic rocks in the Hovd and Altai zones of the Central Asian Orogenic Belt (CAOB), western Mongolian Altai. The dykes reach a thickness of 0.5-20 m, length of approximately 50-2,500 m and strike mostly SW-NE or E-W. The felsic rocks chemically correspond to high-K calc-alkaline to alkaline rhyolites. Compositional trends of mafic rocks pass from alkaline-and calc-alkaline basalts to trachyandesite. The bimodal nature of the association and the transitional calc-alkaline to alkaline character of the dykes indicate magma production through partial melting of the mantle and continental crust in an intra-plate (rift) geodynamic setting. The new conventional whole-rock K-Ar dating of mafic and felsic dykes yielded ages ranging from 300 ± 9 to 281 ± 9 Ma (1σ). This indicates anorogenic volcanic activity associated with Late Carboniferous to Early Permian extension coeval with magmatism in the Gobi-Altai Rift and in the adjacent parts of the Chinese Altai. The calculated crystallization pressures of 1-2 kbar and 0.3-0.4 kbar for felsic and mafic rocks, respectively, indicate emplacement at shallow levels.

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Early Palaeozoic sedimentary record and provenance of flysch sequences in the Hovd Zone (western Mongolia): Implications for the geodynamic evolution of the Altai accretionary wedge system

Cited by 29 publications

References 74 publications

Structural and Geochronological Constraints on Devonian Suprasubduction Tectonic Switching and Permian Collisional Dynamics in the Chinese Altai, Central Asia

Structural and Geochronological Constraints on Devonian Suprasubduction Tectonic Switching and Permian Collisional Dynamics in the Chinese Altai, Central Asia

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

Anorogenic Early Permian dykes in the western Mongolian Altai - petrography, geochemistry and K-Ar geochronology

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