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.
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.
<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,
The breakup of Pangea in the Mesozoic placed the South American and African plates under horizontal extension, which triggered rifting and the formation of intracontinental basins in NE Brazil. The ...subsequent geodynamic evolution changed the forces acting upon the South American plate because of the simultaneous development of the Mid-Atlantic Ridge (MAR) and the Andes. The problem we address in this work is the effect of the changing stress field on intracontinental deformation in NE Brazil, and we used the intracontinental Rio do Peixe Basin (RPB) as case study. We used remote sensing, shuttle radar topography, geophysical data, and detailed structural geology to address this problem. Based on the integrated analysis of brittle deformation within the basin, at the basin boundaries, and in the host basement, we conclude the following: (1) In the Cretaceous, the Rio do Peixe Basin formed from an approximately NW–SE tension, as deduced from brittle deformation in sedimentary rocks within the RPB and bounding master faults. (2) Subsequently, the maximum compressive stress that acted upon the study area shifted from vertical to horizontal, and was oriented approximately ENE–WSW. The new compressive stress field inverted the RPB, which is recorded in the basin at all scales. (3) The inversion of the RPB is consistent with the stress field imposed by the MAR push (to the west) and the Andean push (to the east), which have kept the South American plate under ENE–WSW horizontal compression since the late Cretaceous.
•We describe the evolution of the Rio do Peixe Basin, Brazil.•The stress field evolved from Cretaceous extension to Cenozoic compression.•Inversion is reported for the first time in the basin.•Tectonic inversion has a close relationship with the Andes rise and tectonics.•Inversion in intraplate South America modified basin structures and topography.
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