Why do continents break-up parallel to ancient orogenic belts?

The frequently observed parallelism between rifts and the preexisting orogenic fabric of continents suggests that the inherited tectonic fabric of the lithosphere influences the rupture of continents. We propose that the existence of a pervasive fabric in the lithospheric mantle induces an anisotropic strength in the lithosphere, that guides the propagation of continental rifts. Subcrustal mantle mechanical anisotropy is supported by (i) the anisotropic strength of olivine, (ii) an ubiquitous tectonic fabric in exposed mantle rocks, and (iii) measurements of seismic and electrical anisotropy. During major episodes of continent assembly, a pervasive deformation of the lithosphere induces a lattice-preferred orientation of olivine in mantle rocks. Later on, this crystallographic fabric is ‘frozen-in’ and represents the main source of shear wave splitting. This olivine fabric may entail a mechanical anisotropy in the lithospheric mantle. During subsequent tectonic events, especially during rifting, mechanical anisotropy may control the tectonic behaviour of the lithosphere     

Passive and active margin history of the northern Tatricum (Western Carpathians,Slovakia)

The Tatricum, an upper crustal thrust sheet of the Central Western Carpathians, comprises pre-Alpine crystalline basement and a Late Paleozoic-Mesozoic sedimentary cover. The sedimentary record indicates gradual subsidence during the Triassic, Early Jurassic initial rifting, a Jurassic-Early Cretaceous extensional tectonic regime with episodic rifting events and thermal subsidence periods, and Middle Cretaceous overall flexural subsidence in front of the orogenic wedge prograding from the hinterland. Passive rifting led to the separation of the Central Carpathian realm from the North European Platform. A passive margin, rimmed by peripheral half-graben, was formed along the northern Tatric edge, facing the Vahic (South Penninic) oceanic domain. The passive versus active margin inversion occurred during the Senonian, when the Vahic ocean began to be consumed southwards below the Tatricum. It is argued that passive to active margin conversion is an integral part of the general shortening polarity of the Western Carpathians during the Mesozoic that lacks features of an independent Wilson cycle. An attempt is presented to explain all the crustal deformation by one principal driving force - the south-eastward slab pull generated by the subduction of the Meliatic (Triassic-Jurassic Tethys) oceanic lithosphere followed by the subcrustal subduction of the continental mantle lithosphere.     

构造动力体制与复合造山作用——兼论三江复合造山带时空演化

构造动力体制是研究区域大地构造演化和成矿地质环境的基础,而造山带作为全球金属矿产资源集中产出的地带,同时保留了地球地质构造演化最为丰富的记录,因而是用来解剖不同构造动力体制及相关成矿环境和成矿作用的主要对象.板块构造源于大洋,描述和解释的是以水平运动为主导的板块构造导致的大陆边缘增生和大洋板块消失及与其相关的地质现象,其动力学体制称为大洋动力体制;大陆构造描述和解释的主要是大陆内部而不是边缘发生的以垂直运动(壳幔相互作用)为主导的的大陆物质增生和消失及其相关的地质现象,其动力学体制称为大陆动力体制;而洋陆转换则是水平和垂直运动相互耦合、共同作用的动力学体制,描述和解释的是洋陆转换及其相关的地质现象,可以将其称为转换动力体制.不同构造动力体制在全球范围内具有同区转承和异区并存特点.每一种构造动力体制都可以激发造山作用,因此,地球上同时存在着不同类型的造山作用和造山带,可以归结为俯冲造山(带)、碰撞造山(带)、伸展造山(带)和陆内造山(带)等完整反映造山带演化过程的4种类型.复合造山概念科学地描述了全球不同造山带的复杂性.它具有三种涵义,一是不同时期相同或不同类型造山带在空间上的复合(叠置);二是同一造山带在不同地质历史阶段、不同构造动力体制下造山作用的时间复合(叠加);三是同时具有时空复合特征的复合造山带.对三江造山带时空结构的解析表明,它是具有时空复合特征的巨型复合造山带的典型代表.     

南秦岭及邻区大陆动力成矿系统 及成矿系列特征与找矿方向

以南秦岭及邻区为例, 从大陆岩石圈地幔尺度上探讨了早古生代以来４ 种大陆动力学成矿系统及其１４ 种不同的成矿系列, 并指出了具有重要经济价值的主要成矿系列及今后的找矿方向。在早古生代大陆岩石圈地幔垂向构造扩展动力成矿系统中, 陆缘主动裂谷盆地中, 陆缘主动裂谷盆地中Ｎｉ－Ｖ－Ｍｏ－Ａｕ－Ｕ－Ｓｅ等是主要成矿系列。晚古生代岩石圈地幔俯冲收缩导生大陆壳伸展形成的伸展动力学成矿系统中, 形成的４种成矿系列是具有重大经济价值的主要成矿系列。印支期陆陆碰撞造山期形成的含金剪切型金成矿系列及燕山期－ 喜马拉雅期陆内造山期热泉型金矿成矿系列中, 常形成大型－超大型金矿矿集区。     

West Pacific and North Indian Ocean Seafloor and Their Ocean-Continent Connection Zones: Evolution and Debates

The Indian Ocean and the West Pacific Ocean and their ocean-continent connection zones are the core area of "the Belt and Road". Scientific and in-depth recognition to the natural environment, disaster distribution, resources, energy potential of “the Belt and Road” development, is the cut-in point of the current Earth science community to serve urgent national needs. This paper mainly discusses the following key tectonic problems in the West Pacific and North Indian oceans and their ocean-continent connection zones (OCCZs): 1. modern marine geodynamic problems related to the two oceans. Based on the research and development needs to the two oceans and the ocean-continent transition zones, this item includes the following questions. (1) Plate origin, growth, death and evolution in the two oceans, for example, 1) The initial origin and process of the triangle Pacific Plate including causes and difference of the Galapagos and West Shatsky microplates; 2) spatial and temporal process, present status and trends of the plates within the Paleo- or Present-day Pacific Ocean to the evolution of the East Asian Continental Domain; 3) origin and evolution of the Indian Ocean and assembly and dispersal of supercontinents. (2) Latest research progress and problems of mid-oceanic ridges: 1) the ridge-hot spot interaction and ridge accretion, how to think about the relationship between vertical accretion behavior of thousands years or tens of thousands years and lateral spreading of millions years at 0 Ma mid-oceanic ridges; 2) the difference of formation mechanisms between the back-arc basin extension and the normal mid-oceanic ridge spreading; 3) the differentials between ultra-slow dian Ocean and the rapid Pacific spreading, whether there are active and passive spreading, and a push force in the mid-oceanic ridge; 4) mid-oceanic ridge jumping and termination: causes of the intra-oceanic plate reorganization, termination, and spatial jumps; 5) interaction of mantle plume and mid-oceanic ridge. (3) On the intra-oceanic subduction and tectonics: 1) the origin of intra-oceanic arc and subduction, ridge subduction and slab window on continental margins, transform faults and transform-type continental margin; 2) causes of the large igneous provinces, oceanic plateaus and seamount chains. (4) The oceanic core complex and rheology of oceanic crust in the Indian Ocean. (5) Advances on the driving force within oceanic plates, including mantle convection, negative buoyancy, trench suction and mid-oceanic ridge push, is reviewed and discussed. 2. The ocean-continent connection zones near the two oceans, including: (1) Property of continental margin basement: the crusts of the Okinawa Trough, the Okhotsk Sea, and east of New Zealand are the continental crusts or oceanic crusts, and origin of micro-continent within the oceans; (2) the ocean-continent transition and coupling process, revealing from the comparison of the major events between the West Pacific Ocean seamount chains and the continental margins, mantle exhumation and the ocean-continent transition zones, causes of transform fault within back-arc basin, formation and subduction of transform-type continental margin; (3) strike-slip faulting between the West Pacific Ocean and the East Asian Continent and its temporal and spatial range and scale; (4) connection between deep and surface processes within the two ocean and their connection zones, namely the assembly among the Eurasian, Pacific and India-Australia plates and the related effect from the deep mantle, lithosphere, to crust and surface Earth system, and some related issues within the connection zones of the two oceans under the super-convergent background. 3. On the relationship, especially their present relations and evolutionary trends, between the Paleo- or Present-day Pacific plates and the Tethyan Belt, the Eurasian Plate or the plates within the Indian Ocean. At last, this paper makes a perspective of the related marine geology, ocean-continent connection zone and in-depth geology for the two oceans and one zone.     

大陆边缘增生造山作用

文章评述了增生造山作用的研究历史和进展,认为增生造山作用贯穿地球历史,是大陆增生的重要方式。用大陆边缘多岛弧盆系构造理解造山带的形成演化,提出巨型造山系的形成与长期发育的大洋岩石圈俯冲制约的两侧或一侧的多岛弧盆系密切相关。在多岛弧盆系演化过程中的弧 弧和弧 陆碰撞,弧前和弧后洋盆的消减冲杂岩的增生,洋底高原、洋岛/海山、外来地块(体)拼贴等一系列碰撞和增生造山作用形成大陆边缘增生造山系。大洋岩石圈最终消亡形成对接消减带,大洋岩石圈两侧的多岛弧盆系转化的造山系对接形成造山系的联合体。拼接完成后往往要继续发生大陆之间的陆 陆碰撞造山作用、陆内汇聚(伸展)作用,后者叠加在增生造山系上,使造山过程更加复杂。对接消减带是认识造山系形成演化的关键。大洋两侧多岛弧盆系经历的各种造山过程可以从广义上理解为一个增生造山过程。多岛弧盆系研究对于划分造山带细结构非常重要,是理解造山系物质组成、结构和构造的基础,并制约了造山后陆内构造演化。大陆碰撞前大洋两侧多岛弧盆系及陆缘系统更完整地记录了威尔逊旋回,记录的信息更加丰富。根据多岛弧盆系的思路对特提斯大洋演化提出新的模式,认为西藏冈底斯带自石炭纪以来受到特提斯大洋俯冲制约,三叠纪发生向洋增生造山作用,特提斯大洋于早白垩世末最终消亡。     

南海北部及其沿岸中、新生代壳幔相互作用与构造演化——纪念“陆缘扩张带”概念的倡导者陈国达教授

新生代火山岩中的深源捕虏体资料反映,南海北部及其沿岸地区岩石圈地幔的主体由主量元素易熔组分相对饱满的、同位素组成类似MORB-OIB型的、高温型的二辉橄榄岩所组成;但在其顶部残留有古老的岩石圈地幔,它由主量元素易熔组分相对贫瘠的、同位素组成类似EM型的、较低温的方辉橄榄岩组成。在下地壳底部,分布着由晚中生代幔源岩浆分离结晶和堆晶的基性麻粒岩。由此提出了该区中、新生代壳 -幔或岩石圈 -软流圈相互作用与构造演化的简略模式: (1)印支期 -燕山早期为地壳岩石圈厚度增大的华夏型后地台活化造山带环境;(2)燕山晚期岩石圈快速减薄(如拆沉作用),造山带拉伸塌陷,地壳深处并发生广泛的底侵作用; (3)始新世 -渐新世软流圈再次上涌(如地幔柱的影响),岩石圈地幔发生底蚀减薄,地壳也因为下部层的塑性流展和上部层的张裂拉伸而减薄; (4)中新世以来,由于地幔热源在拉伸环境中被释放,壳幔发生冷却,部分软流圈地幔转化为“新生的”岩石圈地幔。研究进一步说明,南海北部陆缘扩张是该区大陆构造演化到大陆活化造山带后期,在深部壳 -幔的相互作用下,岩石圈所发生的垂向减薄和侧向伸展,既不同于弧后扩张,也不是受控于大西洋式的海底扩张。     

Marginal basins of the NW Pacific and Eastern Eurasia

ABSTRACT

The broad zone between old oceanic lithosphere of the NW Pacific and Eastern Eurasian continental lithosphere is home to a chain of marginal basins. Different from oceans, marginal basins are more influenced by the underlying subduction zone both geophysically and geochemically and are more likely to be blanketed by sediments from the nearby continent. This special issue collects 19 papers that explore the tectonic, magmatic, sedimentary and fluid activity features of marginal basins during rifting, spreading and post-spreading stages. Most papers in this special issue focus on South China Sea marginal basins, where abundant research provides interesting insights into how marginal sea basins evolve. Because South China Sea basins are fully evolved and their key features have not been overprinted by younger deformation, the results of this special issue are very useful for understanding the evolution of other marginal basins.     

地体的单向和多向聚合与离散

地体构造是对板块构造理论的发展和补充,它受控于全球板块动力学体系,因此不能将地体与板块割裂开来去研究.其相对于刚性板块的小规模、多样性和广泛性,对了解全球板块的离散和大陆的拼贴增生过程具有十分重要意义.地体构造无处不在,它不仅存在于中、新生代陆缘造山带中,也存在于古老造山带中,一些古老的克拉通实际上也是由不同的地体拼合...     

Consolidation of the American Cordilleras

The continental margin orogenic systems of the western Americas are enormous features that formed along the Pacific margins of the North and South American plates during late Mesozoic through Cenozoic time. There has been considerable debate concerning their origin, and they are often compared with intra-oceanic fringing arc-trench systems more typical of the Australasian margins of the Pacific Ocean, in that both involve the subduction of oceanic lithosphere, often with similar convergent relative motion vectors. The onset of orogenesis in the two Cordilleras, as shown in reversal of sedimentary polarity from sources generally on the continent to sources along the Pacific margin, seems to date from shortly after emplacement of the oldest oceanic crust in that part of the Atlantic Ocaen east of each continent — i.e., about 170 Ma, or Middle Jurassic, in the case of the Central Atlantic, and about 135 to 100 Ma, or Early to mid-Cretaceous, in the case of the South Atlantic. These ages also seem to mark the onset of westward motion of the two continents over the Pacific Ocean basin and subsequent crustal thickening and uplift, with development of thrust belts, foreland basins, and foredeeps. Prior to this prolonged westward drift, both margins had been convergent for at least several hundred million years, but no massive mountain building had taken place. Instead, the margins were tectonically “neutral”, with typically submarine fringing arc-trench systems or shallow marine to continental margin arcs which stood “outboard” of shallow marine platformal shelves or basins whose main sedimentary polarity was from the continent. Although accretion of “suspect” terranes, high rates of convergence, and age of subducting lithosphere all may have influenced particularly local tectonic response and/or phases of orogenic activity in the two chains, the absolute motion of the two continental margins over the Pacific Ocean basin is considered to have been the dominant factor in Cordilleran tectonic evolution.     

The variation of crustal stretching and different modes of rifting along the Australian southern continental margin

The southern margin of Australia is a passive continental margin, formed during a Late Jurassic–Cretaceous rifting phase. The development of this passive margin is mainly associated with extensional processes that caused crustal thinning. In this work, we have measured the amount of extension and the stretching factor (β factor) across seven transect profiles approximately evenly distributed across the margin. The obtained results show that the amount of extension and the β factor along the margin vary from west to east. The lowest amount of extension, low–intermediate β factors and a very narrow margin are observed in the western part with 80 km of extension and is underlain mostly by the Archean Yilgarn Craton and the Albany–Fraser Orogen. The Gawler Craton in the centre of the south Australian margin is another region of low extension and low–intermediate β factor. The largest amount of extension (384 km) and the largest β factor (β = 1.88) are found in the eastern part of the passive margin in an area underlain by Phanerozoic Tasman Orogen units. Our results imply that there is a strong control of the age and thickness of the continental lithosphere on the style of rifting along the Australian passive margin. Rifting of old and cold lithosphere results in a narrow passive margin, with the formation of relatively few faults with relatively wide spacing, while rifting of younger, warmer lithosphere leads to wide rifting that is accommodated by a large number of faults with small spacing.     

Wilson cycle passive margins: Control of orogenic inheritance on continental breakup

Rifts and passive margins often develop along old suture zones where colliding continents merged during earlier phases of the Wilson cycle. For example, the North Atlantic formed after continental break-up along sutures formed during the Caledonian and Variscan orogenies. Even though such tectonic inheritance is generally appreciated, causative physical mechanisms that affect the localization and evolution of rifts and passive margins are not well understood.We use thermo-mechanical modeling to assess the role of orogenic structures during rifting and continental breakup. Such inherited structures include: 1) Thickened crust, 2) eclogitized oceanic crust emplaced in the mantle lithosphere, and 3) mantle wedge of hydrated peridotite (serpentinite).Our models indicate that the presence of inherited structures not only defines the location of rifting upon extension, but also imposes a control on their structural and magmatic evolution. For example, rifts developing in thin initial crust can preserve large amounts of orogenic serpentinite. This facilitates rapid continental breakup, exhumation of hydrated mantle prior to the onset of magmatism. On the contrary, rifts in thicker crust develop more focused thinning in the mantle lithosphere rather than in the crust, and continental breakup is therefore preceded by magmatism. This implies that whether passive margins become magma-poor or magma-rich, respectively, is a function of pre-rift orogenic properties.The models show that structures of orogenic eclogite and hydrated mantle are partially preserved during rifting and are emplaced either at the base of the thinned crust or within the lithospheric mantle as dipping structures. The former provides an alternative interpretation of numerous observations of ‘lower crustal bodies’ which are often regarded as igneous bodies. The latter is consistent with dipping sub-Moho reflectors often observed in passive margins.     

东亚陆缘扩张带──一条离散式大陆边缘成因的探讨

亚洲东部大陆边缘，介于大陆与大洋之间，存在着一条巨型的“沟弧盆”地带。该构造带的出现是亚洲大陆岩石圈演化－运动史上的重大事件之一，它的成因问题流行假说颇多，本文侧重从亚洲东部壳体演化运动历史背景的分析入手，探讨该构造带形成时期的历史动力环境，地壳结构及性质、壳体演化过程的特点，以及壳体增生扩展过程等，阐明了它是由于东亚陆缘扩张所成。并探讨了该陆线扩张带的形成与壳体演化运动的关系及其扩张机因。研究表明：亚洲陆缘扩张带的形成机理，并非“洋壳俯冲、弧后引张”所致。它们主要是陆缘壳体上的大陆类型活动区（华夏地洼型造山带），在其发展的余动期，由于陆缘扩张及陆壳薄化所致。作者认为，从壳体大地构造学这一新思路入手，对该陆缘扩张带成因的深入研究，有助于正确认识该大陆架上广泛分布的有色、稀有金属内生矿床，以及泥炭、褐煤、油气田的构造类型、特点、分布规律及其经济价值。     

The origin and pre-Cenozoic evolution of the Tibetan Plateau

Different hypotheses have been proposed for the origin and pre-Cenozoic evolution of the Tibetan Plateau as a result of several collision events between a series of Gondwana-derived terranes (e.g., Qiangtang, Lhasa and India) and Asian continent since the early Paleozoic. This paper reviews and reevaluates these hypotheses in light of new data from Tibet including (1) the distribution of major tectonic boundaries and suture zones, (2) basement rocks and their sedimentary covers, (3) magmatic suites, and (4) detrital zircon constraints from Paleozoic metasedimentary rocks. The Western Qiangtang, Amdo, and Tethyan Himalaya terranes have the Indian Gondwana origin, whereas the Lhasa Terrane shows an Australian Gondwana affinity. The Cambrian magmatic record in the Lhasa Terrane resulted from the subduction of the proto-Tethyan Ocean lithosphere beneath the Australian Gondwana. The newly identified late Devonian granitoids in the southern margin of the Lhasa Terrane may represent an extensional magmatic event associated with its rifting, which ultimately resulted in the opening of the Songdo Tethyan Ocean. The Lhasa−northern Australia collision at ~ 263 Ma was likely responsible for the initiation of a southward-dipping subduction of the Bangong-Nujiang Tethyan Oceanic lithosphere. The Yarlung-Zangbo Tethyan Ocean opened as a back-arc basin in the late Triassic, leading to the separation of the Lhasa Terrane from northern Australia. The subsequent northward subduction of the Yarlung-Zangbo Tethyan Ocean lithosphere beneath the Lhasa Terrane may have been triggered by the Qiangtang–Lhasa collision in the earliest Cretaceous. The mafic dike swarms (ca. 284 Ma) in the Western Qiangtang originated from the Panjal plume activity that resulted in continental rifting and its separation from the northern Indian continent. The subsequent collision of the Western Qiangtang with the Eastern Qiangtang in the middle Triassic was followed by slab breakoff that led to the exhumation of the Qiangtang metamorphic rocks. This collision may have caused the northward subduction initiation of the Bangong-Nujiang Ocean lithosphere beneath the Western Qiangtang. Collision-related coeval igneous rocks occurring on both sides of the suture zone and the within-plate basalt affinity of associated mafic lithologies suggest slab breakoff-induced magmatism in a continent−continent collision zone. This zone may be the site of net continental crust growth, as exemplified by the Tibetan Plateau.     

造山带与前陆盆地结构构造及动力学研究思路和进展

运用大量的研究成果，综合分析了大陆岩石圈结构和动力学特征，在此基础上探讨了造山带研究的思路和方法，总结了造山带结构、构造及其形成演化研究的新进展。指出前陆盆地的研究是深入研究造山带的关键，前陆盆地是前陆冲断作用引起岩石圈挠曲变形的结果，阐述了前陆盆地形成机制的研究进展。     

Late Mesozoic and Cenozoic rifting and its dynamic setting in Eastern China and adjacent areas

During the Late Mesozoic and Cenozoic, extension was widespread in Eastern China and adjacent areas. The first rifting stage spanned in the Late Jurassic–Early Cretaceous times and covered an area of more than 2 million km² of NE Asia from the Lake Baikal to the Sikhot-Alin in EW direction and from the Mongol–Okhotsk fold belt to North China in NS direction. This rifting was characterized by intracontinental rifts, volcanic eruptions and transform extension along large-scale strike–slip faults. Based on the magmatic activity, filling sequence of basins, tectonic framework and subsidence analysis of basins, the evolution of this area can be divided into three main developmental phases. The first phase, calc-alkaline volcanics erupted intensely along NNE-trending faults, forming Daxing'anling volcanic belt, NE China. The second phase, Basin and Range type fault basin system bearing coal and oil developed in NE Asia. During the third phase, which was marked by the change from synrifting to thermal subsidence, very thick postrift deposits developed in the Songliao basin (the largest oil basin in NE China).Following uplift and denudation, caused by compressional tectonism in the near end of Cretaceous, a Paleogene rifting stage produced widespread continental rift systems and continental margin basins in Eastern China. These rifted basins were usually filled with several kilometers of alluvial and lacustrine deposits and contain a large amount of fossil fuel resources. Integrated research in most of these rifting basins has shown that the basins are characterized by rapid subsidence, relative high paleo-geothermal history and thinned crust. It is now accepted that the formation of most of these basins was related to a lithospheric extensional regime or dextral transtensional regime. During Neogene time, early Tertiary basins in Eastern China entered a postrifting phase, forming regional downwarping. Basin fills formed in a thermal subsidence period onlapped the fault basin margins and were deposited in a broad downwarped lacustrine depression. At the same time, within plate rifting of the Lake Baikal and Shanxi graben climaxed and spreading of the Japan Sea and South China Sea occurred. Quaternary rifting was marked by basalt eruption and accelerated subsidence in the area of Tertiary rifting. The Okinawa Trough is an active rift involving back-arc extension.Continental rifting and marginal sea opening were clearly developed in various kind of tectonic settings. Three rifting styles, intracontinental rifting within fold belt, intracontinental rifting within craton and continental marginal rifting and spreading, are distinguished on the basis of nature of the basin basement, tectonic location of rifting and relations to large strike–slip faults.Changes of convergence rates of India–Eurasia and Pacific–Eurasia may have caused NW–SE-trending extensional stress field dominating the rifting. Asthenospheric upwelling may have well assisted the rifting process. In this paper, a combination model of interactions between plates and deep process of lithosphere has been proposed to explain the rifting process in East China and adjacent areas.The research on the Late Mesozoic and Cenozoic extensional tectonics of East China and adjacent areas is important because of its utility as an indicator of the dynamic setting and deformational mechanisms involved in stretching Lithosphere. The research also benefits the exploration and development of mineral and energy resources in this area.     

造山带与前陆盆地结构构造及动力学研究思路和进展

运用大量的研究成果，综合分析了大陆岩石圈结构和动力学特征，在此基础上探讨了造山带研究的思路和方法，总结了造山带结构、构造及其形成演化研究的新进展。指出前陆盆地的研究是深入研究造山带的关键，前陆盆地是前陆冲断作用引起岩石圈挠曲变形的结果，阐述了前陆盆地形成机制的研究进展     

Tectonics of the eastern Arctic region

The Vendian (Baikalian), Late Devonian (Ellesmerian), and Mid-Cretaceous (Brookian) orogenies were three cardinal events in the history of formation and transformation of the continental crust in the eastern Arctic region. The epi-Baikalian Hyperborean Craton was formed by the end of the Vendian (660–550 Ma), when the Archean-Proterozoic Hyperborean continental block was built up by the Baikalian orogenic belt and concomitant collision granitoids. As judged from the localization of deepwater facies, the Early Paleozoic ocean occupied the western part of the Canadian Arctic Archipelago, western Alaska, and the southern framework of the Canada and Podvodnikov basins and was connected with the Iapetus ocean. The closure of the Early Paleozoic Arctic basins is recorded in two surfaces of structural unconformities corresponding to the pre-Middle Devonian Scandian orogenic phase and the Late Devonian Ellesmerian Orogeny; each tectonic phase was accompanied by dislocations and metamorphism. The Ellesmerian collision was crucial in the Caledonian tectogenesis. The widespread Late Devonian-Mississippian rifting probably was a reflection of postorogenic relaxation. As a result, the vast epi-Caledonian continental plate named Euramerica, or Laurussia, was formed at the Devonian-Carboniferous boundary. The East Arctic segment of this plate is considered in this paper. In the Devonian, the Angayucham ocean, which was connected with the Paleoasian and Uralian oceans [62], separated this plate from the Siberian continent. The South Anyui Basin most likely was a part of this Paleozoic oceanic space. The shelf sedimentation on the epi-Caledonian plate in the Carboniferous and Permian was followed by subsidence and initial rifting in the Triassic and Jurassic, which further gave way to the late Neocomian-early Albian spreading in the Canada Basin that detached the Chukchi Peninsula-Alaska microplate from the continental plate [25]. The collision of this microplate with the Siberian continent led to the closure of the South Anyui-Angayucham ocean and the development of the Mid-Cretaceous New Siberian-Chukchi-Brooks Orogenic System that comprised the back Chukchi Zone as a hinterland and the frontal New Siberian-Wrangel-Herald-Lisburne-Brooks Thrust Zone as a foreland; the basins coeval with thrusting adjoined the foreland. Collision started in the Late Jurassic; however, the peak of the orogenic stage fell on the interval 125–112 Ma, when ophiolites had been obducted on the margin of the Chukchi Peninsula-Alaska microplate along with folding and thrusting accompanied by an increase in the crust’s thickness, amphibolite-facies metamorphism, and growth of granite-gneiss domes. The magmatic diapir of the De Long Arch that grew within the continental plate in the Mid-Cretaceous reflected a global pulse of the lower mantle upwelling that coincided with the maximum opening of the Canada Basin. The present-day appearance of the eastern Arctic region arose in the Late Mesozoic and Cenozoic owing to the opening of the Amerasia and Eurasia oceans. Sedimentary basins of various ages and origins—including the Late Devonian-Early Carboniferous grabens, the spatially coinciding Late Jurassic-Early Cretaceous rifts related to the opening of the Canada Basin, the syncollision basins in front of the growing orogen, and the Cretaceous-Cenozoic basins coeval with strike-slip faulting and rifting at the final stages of orogenic compression and during the opening of the Eurasia ocean were telescoped on sea shelves.     

松辽盆地形成、发展与岩石圈动力学

根据区域构造环境、深部构造机制、火山活动的时间序列以及盆地几何学、运动学特征,分析了松辽盆地形成与发展的岩石圈动力学问题。提出古太平洋板块向欧亚大陆下俯冲引起热流上升,由此导致裂谷期前火山作用和岩石圈热与机械减薄,裂谷期上地壳伸展发育成裂谷盆地,火山活动减弱。随着陆缘陆块拼贴,俯冲带长距离后退,处于热异常的岩石圈开始向热平衡转化,盆地由伸展转化为坳陷。     

Thermal thickness of the Earth’s lithosphere: a numerical model

A technique is suggested and the thermal thickness of the lithosphere is calculated, as well as the temperature distribution in the lithosphere on the basis of data on topography, the age of the oceanic bottom, crustal composition and structure, gravity anomalies, and mean annual surface temperatures. The bottom of the lithosphere is determined as the 1300°C isotherm. The calculation resolution is 0.5°×0.5°. All first-order tectonic structures, such as mid-ocean ridges and plume areas in oceans, continental rifts, cratons, and orogenic belts, are expressed in the computed thermal thickness. The comparative analysis of the thermal thickness of oceanic and continental lithosphere, lithosphere of cratons and young platforms, ancient and young orogens, remnant oceanic basins and adjacent continental areas can be used in geodynamical analysis of the corresponding regions.