The Kunlun Orogen is generally divided into the East Kunlun Orogenic Belt (E-KOB) and the West Kunlun Orogenic Belt (W-KOB) by the Altyn Tagh fault. The E-KOB forms part of the western segment of the ...Central China Orogenic System (CCOS), and is considered to have formed by the collision between the Qaidam Block and Qiangtang or Bayanhar Terrane as a consequence of the closure of the Kunlun Ocean (branch of the Paleo-Tethyan Ocean). Based on a compilation recently published high-quality data, this contribution provides an overview of the composition, nature and ages of the principal tectonic elements, including ophiolitic mélanges and related volcanic rocks, intrusive plutons and sedimentary cover sequences in the E-KOB. According to multiple lines of evidence from these tectonic elements, we proposed herewith a Paleozoic–Triassic subduction and accretionary tectonic model to interpret the spatiotemporal tectonic framework, plate subduction polarity, and tectonic processes from accretion to collision of the E-KOB. Three main ophiolitic mélange zones are identified in the E-KOB, from north to south, they are the Qimantagh–Xiangride ophiolitic mélange zone (QXM), the Aqikekulehu–Kunzhong ophiolitic mélange zone (AKM) and the Muztagh–Buqingshan–Anemaqen ophiolitic mélange zone (MBAM). According to these ophiolitic mélange zones, the E-KOB is divided into four major tectonic units: the North Qimantagh belt, the Central Kunlun belt, the South Kunlun belt and the Bayanhar Terrane. Based on several lines of evidence from geology, geochemistry and geochronology, the South Kunlun belt is interpreted as a Paleozoic to Triassic fore-arc and accretionary complex related to northward subduction of the Kunlun Ocean during the Ordovician–Triassic time. The AKM, MABM and the South Kunlun belt constitute a wide accretionary complex along the Kunlun Suture zone that marks final closure of the major Paleo-Tethyan Ocean, while the QXM represents the best expression of another suture that records final closure of the Qimantagh back-arc basin. The Central Kunlun Belt, as a long-lived island-arc terrane from Ordovician to Triassic times, rifted from the Qaidam Block due to the spreading of the Qimantagh back-arc basin during the period of ca. 485–425Ma. Taken into all the geological, geochemical and geochronological lines of evidence together, a trench / arc / back-arc basin tectonic system in the E-KOB was built up, and evolved into a protracted and long-lived northward-subduction and accretion along the Kunlun Suture during Paleozoic and Triassic time.
Defining the structural style of fold–thrust belts and understanding the controlling factors are necessary steps towards prediction of their long-term and short-term dynamics, including seismic ...hazard, and to assess their potential in terms of hydrocarbon exploration. While the thin-skinned structural style has long been a fashionable view for outer parts of orogens worldwide, a wealth of new geological and geophysical studies has pointed out that a description in terms of thick-skinned deformation is, in many cases, more appropriate. This paper aims at providing a review of what we know about basement-involved shortening in foreland fold–thrust belts on the basis of the examination of selected Cenozoic orogens. After describing how structural interpretations of fold–thrust belts have evolved through time, this paper addresses how and the extent to which basement tectonics influence their geometry and their kinematics, and emphasizes the key control exerted by lithosphere rheology, including structural and thermal inheritance, and local/regional boundary conditions on the occurrence of thick-skinned tectonics in the outer parts of orogens.
The Qinling Orogenic Belt (QOB) is located between the North China and South China Blocks, and has been considered to have formed by the collision between these blocks. This contribution provides an ...overview of the composition, nature and ages of the principal tectonic elements including ophiolitic mélanges and related volcanic rocks, gabbroic–granitic intrusions, metamorphic basement, sedimentary cover and its provenance in this orogen. The QOB represents a composite orogenic belt that witnessed four major episodes of accretion and collision between discrete continental blocks, such as the North China Block, North Qinling Block and the South China Block. The available geology, geochemistry and geochronology of these tectonic elements together with those of the adjacent regions, can be used to trace the polarity of the four stages of plate subduction, accretion, collision and the related tectonic history as follows. (1) The Grenvillian-aged orogeny along the Kuanping suture between the North Qinling Terrane and North China Block is associated with the southward subduction of Mesoproterozoic Ocean, which led to the amalgamation of the North Qinling Terrane and the North China Block at ca. 1.0Ga. (2) The Neoproterozoic subduction/accretion as represented by the widely distributed terranes and volcanic–sedimentary rocks, resulted in a wide accretionary wedge formed by the southward accretion to the South China Block. (3) The Paleozoic orogeny along the Shangdan suture between the North and South Qinling Blocks is characterized by Early Paleozoic ocean–continent subduction and a long-lived Late Paleozoic continent–continent subduction. The polarity and detailed evolutionary process of the Early Paleozoic ocean–continent subduction have been constrained by the ophiolitic mélange, island-arc related volcanics and intrusions in the North Qinling Belt, as well as the evolutionary history of the Erlangping back-arc basin. The northward subduction and destruction of the Shangdan Ocean during Early Devonian was succeeded by continent–continent subduction beneath the North Qinling Terrane from Middle Devonian to Early Triassic. (4) The Triassic collisional orogeny occurred between the South Qinling Block and South China Block along the Mianlue suture. Silurian rifting along the present Mianlue zone marks the precursor of the eastern Mianlue Ocean, which separated the South Qinling Block from the South China Block during Late Paleozoic. The northward subduction of the ocean led to the Middle Triassic collision between the South China Block and the South Qinling Block. (5) After the collision, the whole QOB evolved into an intra-continental orogen, including Early Jurassic differential tectonics, Late Jurassic to Early Cretaceous compression and thrusting, and Late Cretaceous to Paleogene orogen collapse and depression. These multiple orogenies resulted in abundant mineralization, the genetic types, spatial distribution and metallogenic epochs which correlate well with the tectonics and evolutionary history of the QOB.
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•Qinling orogen formed by four episodes of accretion–collision between discrete blocks•Grenvillian orogeny along Kuanping suture between North Qinling and North China•South Qinling represents southward Neoproterozoic subduction/accretion wedge.•Two-stage subduction between the NQB and SQB occurred during Palaeozoic.•Triassic collisional orogeny between SQB and SCB took place along the Mianlue suture.
Geodynamics of the South China Sea Sibuet, Jean-Claude; Yeh, Yi-Ching; Lee, Chao-Shing
Tectonophysics,
12/2016, Letnik:
692, Številka:
Part.B
Journal Article
Recenzirano
Odprti dostop
The beginning of seafloor spreading in the South China Sea (SCS) is now established from IODP drilling Leg 349 at 33Ma. Chron 12 (32Ma) is the oldest chron identified in the SCS. The nature of the ...crust of the northeastern part of the SCS located north of chron C12, where chrons 15 to 17 were previously identified, is not oceanic but thinned continental crust intruded by volcanic elongated features emplaced 17–22Ma ago. Based on magnetic anomaly identifications, the end of the SCS spreading could be either 15.5, 20.5Ma (Briais et al., 1993; Barckhausen et al., 2014) or something else. However, as post-spreading magmatic activity (~13–3.5Ma) largely masks the spreading fabric in particular near the axis of the east sub-basin, published locations of the axial magnetic anomaly (extinct spreading axis) and spreading rates are not reliable. A contoured map of the extremely dense set of magnetic data shows that a few magnetic lineations belonging to the magnetic seafloor spreading fabric are still preserved and parallel to the N055° bathymetric seafloor spreading trends identified on swath-bathymetric maps in the central part of the SCS, suggesting that the extinct ridge axis is N055° trending with potential N145° transform faults. Based on published swath-bathymetric data, oceanic domains with different seafloor spreading lineaments have been delimited (N055°, N075° and N085°) and provide important constraints used to propose a kinematic sketch of the SCS opening. As a consequence, the Zhongnan faults zone, located between the east and southeast sub-basins, acted as a major fracture zone system during the SCS opening, with horizontal offsets varying from ~50km to ~140km.
The flow-line pattern defined from the seafloor spreading lineaments and the few identified FZs have been used to highlight conjugate segments of continental margins. During the first phases of opening of the SCS, from the fit of continents to chron C10 (30Ma), the N175° extension observed in the Xisha trough and eventually south of the Macclesfield Bank extends to the Qui Nhon ridge, located along the eastern margin of Vietnam, in the southward prolongation of the Red River fault system. Normal faults curve toward the south with a horsetail geometry interpreted as evidence for a few tens of kilometers of dextral motion along the Qui Nhon ridge. Since chron 10 and until the end of SCS opening, the plate boundary located between the southern South China Sea (SSCS) and EU plates jumped westward several times from the location of the Ulugan fault near Palawan to the western limit of the southwest basin, explaining the progressive formation of the SCS from east to west and giving the characteristic V-shape of the SCS. The opening of the whole SCS is linked and occurred simultaneously with the northward subduction of the proto-SCS whose suture is located south of Palawan and extends westwards in north Borneo.
•Northeastern South China Sea crust is thinned continental crust intruded by volcanics.•Post-spreading magmatic activity (<13Ma) largely masks the spreading fabric.•N055°, N075° and N085° seafloor spreading oceanic domains are identified.•Extension in Xisha trough and south of Macclesfield Bank extends to Qui Nhon ridge.•South China Sea (SCS) opening is compensated by northward proto-SCS subduction.
<正>The Dongbo ophiolite in the western part of the Yarlung-Zangbo suture zone in southern Tibet rests tectonically on the middle-late Triassic and Cretaceous flysch units,and consist mainly of ...peridotites,mafic dikes,
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