The basic tenet of the plate tectonic paradigm is that a newly generated oceanic plate is subducted at a trench. However, it is widely accepted today that some material is not subducted, but is accreted to form an accretionary wedge or prism, within which there may be a preserved section of the oceanic crust/mantle, known as an ophiolite.

Intraplate compressional features, such as inverted extensional basins, upthrust basement blocks and whole lithospheric folds, play an important role in the structural framework of many cratons. Although compressional intraplate deformation can occur in a number of dynamic settings, stresses related to collisional plate coupling appear to be responsible for the development of the most important compressional intraplate structures. These can occur at distances of up to 1600 km from a collision front, both in the fore-arc (foreland) and back-arc (hinterland) positions with respect to the subduction system controlling the evolution of the corresponding orogen. Back-arc compression associated with island arcs and Andean-type orogens occurs during periods of increased convergence rates between the subducting and overriding plates. For the build-up of intraplate compressional stresses in fore-arc and foreland domains, four collision-related scenarios are envisaged: (1) during the initiation of a subduction zone along a passive margin or within an oceanic basin; (2) during subduction impediment caused by the arrival of more buoyant crust, such as an oceanic plateau or a microcontinent at a subduction zone; (3) during the initial collision of an orogenic wedge with a passive margin, depending on the lithospheric and crustal configuration of the latter, the presence or absence of a thick passive margin sedimentary prism, and convergence rates and directions; (4) during post-collisional over-thickening and uplift of an orogenic wedge. The build-up of collision-related compressional intraplate stresses is indicative for mechanical coupling between an orogenic wedge and its fore- and=or hinterland. Crustal-scale intraplate deformation reflects mechanical coupling at crustal levels whereas lithosphere-scale deformation indicates mechanical coupling at the level of the mantle-lithosphere, probably in response to collisional lithospheric over-thickening of the orogen, slab detachment and the development of a mantle back-stop. The intensity of collisional coupling between an orogen and its fore- and hinterland is temporally and spatially variable. This can be a function of oblique collision. However, the build-up of high pore fluid pressures in subducted sediments may also account for mechanical decoupling of an orogen and its fore- and=or hinterland. Processes governing mechanical coupling=decoupling of orogens and fore- and hinterlands are still poorly understood and require further research. Localization of collision-related compressional intraplate deformations is controlled by spatial and temporal strength variations of the lithosphere in which the thermal regime, the crustal thickness, the pattern of pre-existing crustal and mantle discontinuities, as well as sedimentary loads and their thermal blanketing effect play an important role. The stratigraphic record of collision-related intraplate compressional deformation can contribute to dating of orogenic activity affecting the respective plate margin.

The following structural elements have been recognized to constitute the tectonic demarcation of Central Asian Foldbelt: (1) The Kazakhstan–Baikal composite continent, its basement formed in Vendian–Cambrian as a result of Paleoasian oceanic crust, along with Precambrian microcontinents and Gondwana-type terranes, subduction beneath the southeastern margin of the Siberian continent (western margin in present-day coordinates). The subduction and subsequent collision of microcontinents and terranes with the Kazakhstan–Tuva–Mongolia island arc led to crustal consolidation and formation of the composite-continent basement. In Late Cambrian and Early Ordovician, this continent was separated from Siberia by the Ob’–Zaisan ocean basin. (2) The Vendian and Paleozoic Siberian continental margin complexes comprising the Vendian–Cambrian Kuznetsk–Altai island arc and the rock complexes of Ordovician–Early Devonian passive margin and Devonian to Early Carboniferous active margin. Fragments of Vendian–Early Cambrian oceanic crust represented by ophiolite and paleo-oceanic mounds dominate in the accretionary wedges of island arc. The Gondwana-type continental blocks are absent in western Siberian continental margin complexes and supposedly formed at the convergent boundary of a different ocean, probably, Paleopacific. (3) The Middle–Late Paleozoic Charysh–Terekta–Ulagan–Sayan suture-shear zone separating the continental margin complexes of Siberia and Kazakhstan–Baikal. It is composed of fragments of Cambrian and Early Ordovician oceanic crust of the Ob’–Zaisan basin, Ordovician blueschists and Cambrian–Ordovician turbidites, and Middle Paleozoic metamorphic rocks of shear zones. In the suture zone, the Kazakhstan–Baikal continental masses moved westward along the southeastern margin of Siberia. In Late Devonian and Early Carboniferous, the continents amalgamated to form the North Asian continent. (4) The Late Paleozoic strike-slip faults forming an orogenic collage of terranes, which resulted from Late Devonian to Early Carboniferous collision between Kazakhstan–Baikal and Siberian continents and Late Carboniferous to Permian and Late Permian to Early Triassic collisions between East European Craton and North Asian continent. As a result, the Vendian to Middle Paleozoic accretion-collisional continental margins of Siberia and the entire Kazakhstan–Baikal composite continent became fragmented by large-amplitude (up to a few thousand kilometers) strike-slip faults and conjugate thrusts into several strike-slip terranes, which mixed with each other and thus disrupted the original geodynamic, tectonic, and paleogeographic demarcation.

2-D and 3-D physical modelling of lithospheric convergence in the Luzon-Taiwan-Ryukyu region is performed with properly scaled laboratory models. The lithospheric model consists of two pails, continental (the Asian Plate, AP) and oceanic (the Philippine Sea Plate, PSP). The oceanic lithosphere has one layer, while the continental lithosphere includes both mantle and crustal layers. The continental margin is covered by sediments. A low-viscosity asthenosphere underlies the lithosphere. The opposing Luzon and Ryukyu subduction zones are initiated by inclined cuts made within the PSP. The subduction/collision is driven by a piston. Pre-collisional intraoceanic subduction along the Luzon and Ryukyu boundaries results in the formation of a transform zone between them, with two tear faults at the ends. The PSP undergoes strong compression along this zone. Subduction of the Chinese margin under the Luzon boundary further increases the compression. Compressive stresses reach the yield limit of the PSP in the arc area, which is a weak zone in the experiments. The plate fails at the western side of the arc along an eastward dipping fault, the Longitudinal Valley Fault. Underthrusting of the frontal wedge of the PSP along this fault results in the closure of the fore arc basin and is then blocked. The PSP fails at the opposite side of the Luzon arc along the westward dipping fault. The failure releases lithospheric compression in this region and results in the initiation of southward-propagating subduction of the PSP under northeastern Taiwan. The incipient subduction zone becomes part of the southeastward-retreating Ryukyu subduction zone, which allows the Okinawa back arc rift to propagate into Taiwan. The Taiwan collision thus includes the following succession of major processes over time, or from south to north: (1) an L-W shortening of the PSP in the Luzon arc; (2) a failure of this plate at the western side of the arc and the formation of the eastward-dipping Longitudinal Valley Fault (the transient plate boundary); O) a closure of the fore arc basin and a rapid uplift of the orogen; i4) a failure of the PSP at the eastern side of the Luzon arc partly overthrusting the orogen, and the initiation of westward (WN-ward) subduction of the PSP; (5) and finally 'back arc' rifting in the rear of this incipient subduction zone (i.e. in northern Taiwan). All these processes commence with some delay with respect to the preceding ones and propagate southwards.

The North Kokchetav tectonic zone is located between the Kokchetav HP-UHP metamorphic belt and the Stepnyak zone of Ordovician island arc and oceanic complexes. The Kokchetav zone is a collage of nappes (thrust sheets) that consist of basement gneiss and sedimentary rocks of the Kokchetav microcontinent, granite gneiss, mica schists with eclogite blocks, the Shchuch’e ophiolite, Middle Proterozoic felsic volcanics, and Arenigian siliceous-terrigenous sediments with olistostromes. The latter are of gravity-sliding origin and their clastic material includes quartz-muscovite and quartz-garnet-muscovite schists, gneiss, dolomite, and amphibolite. The sheet boundaries are marked by mylonite and Early Ordovician mica schists (40Ar/39Ar ages of syntectonic muscovite are 489–469 Ma). The North Kokchetav collage of compositionally diverse thrust sheets can be interpreted as a collisional zone. According to geological evidence, tectonic activity in the zone lasted as late as the Middle Ordovician. Syncollisional thrusting in the North Kokchetav zone was coeval with the latest dynamic metamorphic event in the history of the Kokchetav belt. All events of retrograde metamorphism and exhumation of HP and UHP rocks in the belt have Cambrian ages, i.e., the rocks had been exhumed prior to the Early–Middle Ordovician collisions and the related orogeny.

The Kokchetav subduction-collision zone (KSCZ) hosting ultrahigh- and high-pressure (UHP-HP) rocks underwent the multistage Vendian-Early Ordovician geodynamic evolution. The subduction of the Paleoasian oceanic lithosphere bearing blocks of continental crust and the collision of the Kokchetav microcontinent with the Vendian-Cambrian island-arc system ultimately led to the formation and exhumation of UHP-HP rocks. In the Vendian-Early Cambrian the margin of the Kokchetav microcontinent deeply subsided into the subduction zone (150–200 km), which led to UHP-HP metamorphism (the maximum at about 535 Ma) and to partial melting of its rocks. In next stage (535–528 Ma), the generated acidic melts including blocks of UHP-HP rocks quickly, at a rate of 1 m/year, ascended to depths of 90 km for 1 Myr. During subsequent 5 Myr, the UHP-HP rocks ascending at a rate of 0.6–1 cm/year reached the base of the accretionary prism (depths of 60–30 km). Then, in the period from 528 to 500 Ma, the UHP-HP rocks ascended along the faulting structures of the lower crust as a result of jamming the subduction zone by the Kokchetav microcontinent. During the period from 500 to 480 Ma, the UHP-HP rocks became part of the upper crust. This process led to the KSCZ, which comprises terranes of the Vendian-Early Arenigian subduction zone occurring at different depths, separated by zones of garnet-mica and mica schists, blastomylonites and mylonites. In the same period there was a jump of subduction zone, which led to the formation of the Ordovician Stepnyak island arc. As a result of the Late Arenigian-Early Caradocian microcontinent-island arc collisions (480–460 Ma), the KSCZ overrided upon the fore-arc trough of the Stepnyak island arc to form a thick accretion-collision orogen, which having experienced anatectic melting was intruded by collisional granites of the Zerenda complex 460–440 Ma in age.

Проведены исследования метаморфических комплексов Хадарта, Хобой и Орсо, принадлежащих Ольхонскому террейну Западного Прибайкалья. Установлено, что субстратом для метаморфитов комплексов Хадарта, Хобой и Орсо могли быть породы активной континентальной окраины (система островная дуга—задуговый бассейн). U-Pb датирование цирконов (SHRIMP-II) из гнейсов комплекса Орсо показало, что начальные стадии развития задугового бассейна в пределах активной окраины отвечают интервалу времени 840—800 млн лет. Получены аргументы в пользу того, что значительная часть тектонических единиц, составляющих Ольхонский террейн, является фрагментами активной континентальной окраины Баргузинского микроконтинента, отколовшегося в раннем неопротерозое от Алданской провинции Сибирского кратона. Причленение Баргузинского микроконтинента к кратону сопровождалось проявлением высокоградного метаморфизма, индикаторами которого являются гранулиты комплексов Хадарта и Хобой. Возраст этих комплексов составляет 507 ± 8 и 498 ± 7 млн лет соответственно (U-Pb датирование цирконов, SHRIMP-II). Этот временной рубеж может быть обозначен как начальный этап формирования Ольхонского метаморфического террейна. Новые данные, полученные для Ольхонского террейна, хорошо соотносятся с результатами датирования ряда других высокометаморфизован-ньгх комплексов, локализованных вдоль южного фланга Сибирского кратона (Слюдянка, Китойкин, Дерба) и отражают ранние стадии становления Центрально-Азиатского складчатого пояса. Совокупность полученных результатов позволяет интерпретировать Ольхонский метаморфический террейн как ран-непалеозойский коллизионный композит различных фрагментов неопротерозойской активной окраины Баргузинского микроконтинента.

В течение прошедшего десятилетия в пределах Бурея-Ханкайского и Солонкерского орогенных поясов, охватывающих (на российской территории) нынешние Западное Приморье и Юг Центрального Приамурья, было выполнено палеомагнитное изучение метаморфических пород протерозоя, а также осадочных комплексов нижнего и среднего палеозоя, которые отнеcены к тектоно-стратиграфическим террейнам различного возраста и происхождения – Малохинганскому, Матвеевско-Нахимовскому, Кабаргинскому, Спасскому, Вознесенскому и Лаоэлин-Гродековскому [3]. По результатам полевых и лабораторных палеомагнитных исследований выделенные «первичные» (доскладчатые) ChRM-компоненты намагниченности, которые в этих породах характеризуются пологими векторными наклонениями (единицы и первые десятки градусов) прямого и обратного знака, преимущественно в ЮЗ-СЗ (реже – антиподальных к ним СВ-ЮВ) румбах стереографической проекции. Первые из них приняты за направления прямой полярности. Соответствующие графо-аналитические тесты, определяющие степень сохранности доскладчатой компоненты намагниченности в породах [4-6] – положительны. Расчет позиций среднего палеомагнитного полюса для каждого террейна производился по значениям координат соответствующих изученных геологических разрезов [1, 2]. В таблице представлены основные палеомагнитные данные для изученных опорных проте-розойско-кембрийских, силурийских и девонских разрезов Бурея-Ханкайского и Солонкерского орогенных поясов Амурской плиты. Рассчитанные позиции палеополюса для Амурской плиты и ее террейнов в протерозое – кембрии в пределах статистической погрешности не отличаются друг от друга и образуют рой направлений, приуроченных к району нынешнего Индийского океана юго-западнее Австралии (для выбранной ChRM-полярности). Для силура и девона подобная картина практически сохраняется – позиции палеомагнитного полюса лишь смещаются к западу, в сторону нынешней Северной Африки и Средиземноморья. В целом, для всех террейнов палеомагнитные широты не выходят за пределы экваториальной области обоих полушарий, колеблясь от 6.0° ю.ш. до 14.6° с.ш. При сравнении позиций палеомагнитного полюса для различных комплексов пород этих террейнов на протяжении раннего-среднего фанерозоя наблюдается их отчетливый разброс по склонению вдоль дуги большого круга с центром вращения (эйлеровым полюсом).

Central Mongolia is geologically characterized by close juxtaposition of an accreted oceanic terrane with an arc-microcontinent collision zone. We present new U–Pb zircon ages and geochemical data for the Bayankhongor ophiolite mélange from the oceanic terrane and for a syenite porphyry pluton from the arc-microcontinent zone, providing critical constraints on the regional evolution in late Neoproterozoic to early Cambrian times. An anorthosite (655±4 Ma) associated with layered gabbro, a rodingite (metasomatized layered gabbro) (647±6 Ma), and a high-level isotropic amphibole gabbro (647±7 Ma) yielded the oldest zircon ages for the plutonic part of the ophiolite. A plagiogranite dike in the amphibole gabbro yielded an age of 636±6 Ma, which is the youngest date obtained for the ophiolitic rocks. We suggest that the long duration (ca. 20 Ma) for formation of this plutonic sequence characterizes the sea-floor spreading evolution, and the Nd–Sr isotopic composition (εNd(t) = +7.6 to +4.7; initial 87Sr/86Sr ratio = 0.70279–0.70327) points to a mid-ocean-ridge origin. The syenite porphyry, dated at 523±2 Ma, records the terminal or post-collisional phase of orogeny. The Bayankhongor oceanic lithosphere experienced at least 92Ma of drift between its formation and accretion.