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The Central Asian Orogenic Belt (CAOB) was generated through multiple collisional and accretionary events in the Paleo-Asian Ocean, a major global ocean that existed from the late Neoproterozoic into the late Paleozoic. Nevertheless, the question of when the Paleo-Asian Ocean finally closed has notoriously been enigmatic, especially due to the absence of large-scale investigations. The South Tianshan-Solonker Suture, is the largest and southernmost suture within the CAOB, and records the ultimate collision between the Tarim-North China cratons with the Siberia craton, and is commonly interpreted as marking the eventual closure of the Paleo-Asian Ocean. In this paper, we synthesize and evaluate relevant Chinese papers on the area, which are not readily available to an international audience, and extend this across the full length of the suture zone. Based on this review, we can divide the suture zone into four distinct segments, which are, from west to east: the South Tianshan Belt, the Beishan Belt, the Solonker Belt and the Yanji Belt. This enables us to provide a more systematic understanding of the nature and development of the South Tianshan-Solonker suture. Geochronological data from Paleozoic cover rocks and high-pressure metamorphic rocks show that during the late Carboniferous, the western section of the Paleo-Asian Ocean closed when the Tarim Craton moved northward to collide with the Kazakhstan-Yili Block, thus marking the initial development of the South Tianshan Belt. The Beishan Belt to the east formed when the Dunhuang-Alxa blocks were transported northward to collide with the Tuva-Mongolia Block, with the youngest zircon U Pb data from ophiolites indicating that closure of the local Beishan Ocean was in the early-middle Permian, although its final closure may not have been until the early late Permian along the northern margin of the Alxa Block, thus making it slightly younger than the South Tianshan Belt. Further to the east, the available petrographic, geochronological and paleontological data from the Solonker Belt indicate that this belt was formed in the middle-late Permian, during which time bi-directional subduction occurred and the North China and Siberia cratons were amalgamated during an 'Appalachian-type' orogeny. Furthermore, we observe that a transition in polarity from northward to bi-directional subduction occurred along the boundary between the Beishan and Solonker belts, which may be related to the East Gobi Transform Fault. In contrast, under the influence of the westward subduction of the Paleo-Pacific Ocean, the Jiamusi-Khanka Block moved southwestward along the Yilan-Yitong Fault in the middle-late Triassic (230–220 Ma) to amalgamate with the North China Craton. The formation of the South Tianshan-Solonker Suture can be characterized by four distinct west-to-east accretion/collision events that lasted from the late Carboniferous to the late Permian. The South Tianshan Belt, the Beishan Belt and the Solonker Belt therefore demarcate, respectively, the amalgamation between the Tarim Craton and the Kazakhstan-Yili Block, the Dunhuang-Alxa Block and the Tuva-Mongolia Block, and the North China Craton with the Siberia Craton, representing the final closure of the Paleo-Asian Ocean. During the middle-late Triassic, the Yanji Belt in the far east was influenced by the Paleo-Pacific tectonic domain as a result of amalgamation between the Jiamusi-Khanka Block and the North China Craton. • South Tianshan-Solonker Suture marks the final collision between Tarim-North China and Siberian cratons. • The Suture includes four segments, and closed form Late Carboniferous to Middle Triassic from west to east, respectively. • The Yanji belt was influenced by the Paleo-Pacific tectonic domain during the Middle Triassic. [ABSTRACT FROM AUTHOR]

Craton is an important geological unit of the continental lithosphere, which can provide significant information about the Earth's geological history, especially, composition, structure and evolution of continental lithosphere. Magnetotellurics (MT) is a useful tool to image the composition and structure of continental lithosphere because electrical conductivity is sensitive to temperature, bulk composition, volatile (H 2 O or CO 2) and/or melt/fluid content, and the presence of highly conductive minerals. In this paper, we reviewed the conductivity features and electrical discontinuities revealed by MT surveys in the worldwide cratonic lithospheres. By integrating various geophysical and petrological observations including surface heat flow, bulk composition, thermal conductivity, electrical conductivity, and xenolith data, the thermal structure and conductivity-depth profiles were constructed in the continental lithosphere. The plausibility of water in nominally anhydrous minerals (NAMs), silicate melt, and carbonate melt to account for the high conductivity anomalies observed in the cratonic lithosphere was evaluated based on the geothermal structure and composition within the cratonic lithosphere, and laboratory measurements of mineral physics. Our modelled results clearly indicate that the thermal structure of the cratonic lithosphere acts as a primary control on its internal melting state and electrical conductivity and thereby its dynamic evolution. When the craton has anomalous high surface heat flow (for example the North China Craton), the origin of the enhanced conductivity may be explained by the presence of silicate melt or carbonate melt, rather than water in NAMs. However, because of low temperature, silicate melt can be ruled out as a candidate for cratons with relatively low surface heat flow. Instead, either a small amount of carbonate melt or water in NAMs may explain the high conductivity anomalies observed in the deep part of the cratonic lithosphere. Although metasomatism products (i.e., phlogopite or amphiboles) or sulfides may produce conductivity anomalies as well at the shallow lithosphere, they require the formation of interconnected pathways over large scales, which rarely occurs in the deep cratonic lithosphere. • Craton is an important geological unit of the continental lithosphere, which is characterized by low surface heat flow, low density, high viscosity, thick lithospheric root, and high conductivity anomaly. • Many electrical anomalies and discontinuities have been detected in the worldwide cratonic lithospheres by magnetotelluric (MT) observations. However, the causes of the conductivity anomalies in the cratonic lithosphere remain unclear. • The thermal structure of the cratonic lithosphere acts as a primary control on its internal melting state and electrical conductivity and thereby its dynamic evolution. Graphite films cannot explain electrical anomalies located in the deep lithosphere for thermodynamic reasons. • When the craton has anomalous high surface heat flow, the origin of the enhanced conductivity may be explained by the presence of silicate melt or carbonate melt. • Silicate melt can be ruled out as a candidate for cratons with relatively low surface heat flow. Instead, either a small amount of carbonate melt or water in NAMs may explain the high conductivity anomalies observed in the deep part of the cratonic lithosphere. [ABSTRACT FROM AUTHOR]

Abstract The amalgamation of Gondwana and its subsequent fragmentation has been a subject of several studies over the past five decades, yet the very important question of the initial geometry of the supercontinent remains enigmatic. Current reconstruction models of the Indian Ocean are characterized by large gaps, overlaps and misfits of major structural and Cratonic bodies in their fit, and positions of tectonic blocks that are inconsistent with field observations, a phenomenon sustained by inadequate data, long standing debates and a lack of consensus on the nature of major structures and basins in the ocean. Past attempts to reconstruct the initial fit of the ocean has led to varied and complex models, with their own logic and different geographical limits, whose validity and underlying assumptions require testing in the light of current global geological and geophysical data. Our analysis of these models and their consequences on the continental passive margins brings to the fore critical scientific questions and the incoherencies that exist between them. This paper presents a compressive study of the structure of the Precambrian basement, Paleozoic marginal and rift basins of the plates constituting the Indian Ocean, examining the architecture and geochronological composition of their composing Cratons and crustal blocks, and delineating important structural markers to juxtapose them in full-fit reconstructions. We introduce a new holistic model from Gondwana's initial geometry to Chron 34, achieved through a combination of onshore and offshore geological and geophysical data. Our new model is coherent with current data interpretations of major structures across the Indian Ocean. Consistent with the interpretation of the Beira High as continental crust, and recent seismic refraction interpretation of the Pamela MOZ3-5 expedition in the Northern Mozambique Ridge and Northern Natal Valley. The model also permits full extent of major cratonic, volcanic and sedimentary structures within the supercontinent, and presents a new synthesis upon which further work may be projected. [ABSTRACT FROM AUTHOR]

Establishing how tectonic plates have moved since deep time is essential for understanding how Earth's geodynamic system has evolved and operates, thus answering longstanding questions such as what "drives" plate tectonics. Such knowledge is a key component of Earth System science, and has implications for wide ranging fields from core-mantle-crust interaction and evolution, geotectonic phenomena such as mountain building and magmatic and basin histories, the episodic formation and preservation of Earth resources, to global sea-level changes, climatic evolution, atmospheric oxygenation, and even the evolution of life. In this paper, we take advantage of the rapidly improving database and knowledge about the Precambrian world, and the conceptual breakthroughs, both regarding the presence of a supercontinent cycle and possible dynamic coupling between the supercontinent cycle and mantle dynamics, in order to establish a full-plate global reconstruction from 540 Ma back to 2000 Ma. We utilise a variety of global geotectonic databases to constrain our reconstruction, and use palaeomagnetically recorded true polar wander events and global plume records to help evaluate competing geodynamic models and also provide new constraints on the absolute longitude of continents and supercontinents. After revising the configuration and life span of both supercontinents Nuna (1600—1300 Ma) and Rodinia (900—720 Ma), we present a 2000—540 Ma animation, starting from the rapid assembly of large cratons and supercratons (or megacontinents) between 2000 Ma and 1800 Ma. This occurred after a billion years of dominance by small cratons, and kick-started the ensuing Nuna and Rodinia supercontinent cycles and the emergence of stable, hemisphere-scale (long-wavelength) degree-1/degree-2 mantle structures. We further use the geodynamicly-defined type-1 and type-2 inertia interchange true polar wander (IITPW) events, which likely occurred during Nuna (type-1) and Rodinia (type-2) times as shown by the palaeomagnetic record, to argue that Nuna assembled at about the same longitude as the latest supercontinent Pangaea (320—170 Ma), whereas Rodinia formed through introversion assembly over the legacy Nuna subduction girdle either ca. 90° to the west (our slightly preferred model) or to the east before the migrated subduction girdle surrounding it generated its own degree-2 mantle structure by ca. 780 Ma. Our interpretation is broadly consistent with the global LIP record. Using TPW and LIP observations and geodynamic model predictions, we further argue that the Phanerozoic supercontinent Pangaea assembled through extroversion on a legacy Rodinia subduction girdle with a geographic centre at around 0°E longitude before the formation of its own degree-2 mantle structure by ca. 250 Ma, the legacy of which is still present in present-day mantle. • Two alternative 2000—540 Ma full-plate global reconstructions linked to global geodynamics. • Revised reconstruction of supercontinents Nuna and Rodinia. • Two types of inertia interchange true polar wander (IITPW) linked to geodynamics. • Palaeolongitude options determined by true polar wander and LIP records. • Transition of global tectonic regime from pre-1.8 Ga cratonic and supercraton assembly to post-1.8 Ga supercontinent cycle. • Multiple geotectonic databases and palaeomagnetic data all in GIS-compatible formats. [ABSTRACT FROM AUTHOR]

Kimberlites represent magmas derived from great mantle depths and are the principal source of diamonds. Kimberlites and their xenolith cargo have been extremely useful for determining the chemical composition, melting regime and evolution of the subcontinental mantle. The late-Devonian Udachnaya (means Fortuitous ) pipe hosts the largest diamond deposit in Russia (> 60% diamond quantity and value) and one of the largest in the world, supplying gem-quality diamonds (~ 12% of world production). Since its discovery in 1956, the Udachnaya kimberlite pipe has become a “type locality” for geochemists and petrologists studying mantle rocks and mantle physical–chemical conditions. Apart from hosting a diverse suite of extremely well-preserved mantle xenoliths, the host kimberlite (East body) is the only known occurrence of fresh kimberlite, with secondary serpentine almost absent and uniquely high Na 2 O and Cl (up to 6.2 wt.%) and low H 2 O (< 1 wt.%) contents. The discovery of such compositional features in the only unaltered kimberlite has profound implications for models of parental kimberlite magma compositions, and the significance of the high Na and Cl abundances in the Udachnaya-East pipe has therefore been subjected to vigorous criticism. The main argument against a primary magmatic origin of high Na-Cl levels involves the possibility of contamination by salt-rich sedimentary rocks known in the subsurface of the Siberian platform, either by assimilation into the parental magma or by post-intrusion reaction with saline groundwaters. In this paper we review evidence against crustal contamination of Udachnaya-East kimberlite magma. This evidence indicates that the kimberlitic magma was not contaminated in the crust, and the serpentine-free varieties of this kimberlite owe their petrochemical and mineralogical characteristics to a lack of interaction with syn- and post-magmatic aqueous fluids. The groundmass assemblage of this kimberlite, as well as earlier-formed melt inclusions, contains alkali carbonate, chloride and other Na- and Cl-bearing minerals. This mineralogy reflects enrichment of the parental melt in carbonate, chlorine and sodium. The combination of low H 2 O, high alkali-Cl abundances, lack of serpentine, and the presence of alteration-free mantle xenoliths all indicate that the Udachnaya-East kimberlite preserves pristine compositions in both kimberlite and mantle xenoliths. Evidence for broadly similar chemical signatures is found in melt inclusions from kimberlites in other cratons (South Africa, Canada and Greenland in our study). We demonstrate that two supposedly “classic” characteristics of kimberlitic magmas – low sodium and high water contents – relate to postmagmatic alteration. A “salty” carbonate composition of the kimberlite parental melt can account for trace element signatures consistent with low degrees of partial melting, low temperatures of crystallisation and exceptional rheological properties that enable kimberlite magmas to rise with high ascent velocities, while carrying a large cargo of entrained xenoliths and crystals. Our empirical studies are now supported by experimental data which suggest that carbonate-chloride fluids and melts derived by liquid immiscibility are a crucial factor of diamond formation. [ABSTRACT FROM AUTHOR]

East Asia is exceptionally rich in diverse geological phenomena related to processes of major global significance in Earth history. Its tectonic evolution is closely related to the subduction of the Izanagi and Pacific plates and the India-Eurasia collision. Thus, this domain presents a vast natural laboratory within which some of the most topical and fundamental problems in Pacific-Asian Tectonics can be addressed. Recent breakthroughs in understanding the tectonic evolution of East Asia have been achieved, involving intraplate deformation, plate fragmentation, plate boundary processes, orogenic collapse, and craton destruction. These advances have been achieved via multidisciplinary work including structural geology, basin research, land and marine geophysics, thermochronology, numerical modeling, geochemistry and classical field geology. In the current context of research in East Asia the time is ripe for a thematic volume of review papers. This special issue is focused on the theme "Pacific-Asian Tectonics". It describes interdisciplinary methods adopted to study Meso-Cenozoic basin-forming mechanisms and evolutionary processes, unravels the timing and characteristics of major intraplate deformation, depicts the spatial-temporal distribution of Meso-Cenozoic igneous rocks, discusses the deep lithospheric structures overlying the subducting oceanic plates, and probes the natures and fates of subduction or collision processes. [ABSTRACT FROM AUTHOR]

Thermal regime and thermal history are of significant important in basin dynamics and hydrocarbon generation of source rocks. The sedimentary basins in three typical cratons of China, North China Craton (NCC), Yangtze Craton (YC) and Tarim Craton (TC), underwent completely different tectonic background and dynamic mechanism, which resulted in the differentials of their thermal regimes. In this paper, the thermal regimes of the Bohai Bay Basin in the eastern NCC, Tarim Basin in TC, and Sichuan basin in the Upper YC were studied. There has some lower thermal background in the area of western China than eastern side of the NCC. The mean heat flow value of Tarim basin is 42.5 mW/m2, 53.8 mW/m2 in the Sichuan basin and 66.7 mW/m2 in the eastern NCC. And the temperature at 10000 m ultra-depth in the Tarim Basin also shows lower values than that of Sichuan and Bohai Bay basins. The thermal history, modeled from thermal indicators of vitrinite reflectance (R o), equivalent vitrinite reflectance data (R equ), fission track and (U Th)/He data of apatite and zircon, evolved differently because of the different tectonic history in these basins. The Tarim basin underwent a cooling history with the heat flow of 55–65 mW/m2 in the Cambrian decreasing to the present-day of 40–50 mW/m2. The Meso-Cenozoic thermal history of the Bohai Bay basin experienced four evolutionary stages with two heat flow peaks in the late Early Cretaceous and in the Middle to Late Paleogene, which correspond to the destruction peaks of the eastern NCC and had heat flow values of 82–86 mW/m2 and 81–88 mW/m2, respectively. The Sichuan basin was stable with heat flow value of less than 65 mW/m2 from the Late Sinian to Late Paleozoic, and the heat flow increased rapidly to the peak value (75–100 mW/m2) at the end of Early Permian by thermal effect of the Emeishan mantle plume. From Mesozoic to present, the heat flow decreased to the present value (60–70 mW/m2). In addition, the comparation of thermal characteristics of typical cratons around the world, including heat flow, thermal history, lithospheric thermal structure and thermal lithospheric thickness, also have been caried out. The differential thermal histories of Tarim and Sichuan basins resulted in the different thermal evolution of Cambrian source rocks. This study may provide some new geothermal evidence for hydrocarbon generation and phase distribution of oil and gas in the deep and/or ultra-deep basin. Thermal regime and thermal history of typical sedimentary basins in three typical cratons of China underwent completely different evolution. The Tarim basin underwent a cooling history, the Bohai Bay basin experienced four evolutionary stages with two heat flow peaks, and the Sichuan basin was stable with heat flow but to a peak at the end of Early Permian. Nansheng Qiu, Chang Jian, Zhu Chuanqing, Liu Wen, Zuo Yinhui, Xu Wei, Li Dan. [Display omitted] • Three typical cratons of China show great differences in heat flow and deep-temperature. • Three typical cratons of China show great differences in lithospheric thickness from 76–170 km. • Thermal histories of Bohai Bay, Sichuan and Tarim basins are summarized. • Thermal regime between stable and destabilized cratons are compared. • Three thermal evolution patterns of source rocks are obtained. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, published data for granulite terrain rocks exposed at the surface, lower crustal xenoliths, and Mesozoic intermediate-felsic igneous rocks from the eastern North China craton (NCC) are integrated to constrain the nature and evolution of the lower crust in this area. U–Pb zircon dating shows that the protolith ages for most of the granulite terrain rocks are 2500 to 2600Ma and that many of them experienced 1800–1900Ma metamorphism. Lower crustal xenoliths entrained in volcanic rocks with ages varying from ~460 to ~10Ma suggest that the lower crust is dominated by Neoarchean rocks, although there may be minor rocks with ages of Meso- to Paleoarchean (>3000Ma), ~45Ma and possibly ~1900Ma locally. The Mesozoic intrusive rocks, although varying from diorite to granite and spanning from Triassic to Cretaceous, contain ~2500Ma inherited zircons and have magmatic zircons with Hf crust model ages (TDM Hf, C) ages of 2500–2700Ma and whole-rock Sr–Nd isotopic compositions falling within the field of the granulite terrain rocks, pointing to their derivation by the melting of Neoarchean lower crust. The combined data for the granulite terrain rocks, lower crustal xenoliths and Mesozoic intermediate-felsic igneous rocks indicate that the present lower crust is dominated by rocks with Neoarchean ages and is intermediate to mafic in composition (i.e., SiO2 <62%). The (87Sr/86Sr)i, εNd (t) and εHf (t) of the lower crust at 130Ma are considered to be 0.705 to 0.716, −10 to −28 and −13 to −28, respectively. The εNd (t) range is very different from that proposed previously (−32 to −44). The large range of εHf (t) for the lower crust implies that significant εHf (t) variations for magmatic zircons from the Mesozoic intermediate-felsic igneous rocks do not necessarily reflect mixing of mantle– and crustal–magmas as commonly thought, instead they may reflect heterogeneity in the ancient lower crust. Given that the voluminous Mesozoic intermediate to felsic igneous rocks in the eastern NCC are derived dominantly by partial melting of the Archean lower crust, it requires that a large amount of Archean lower crust be restitic. A restite origin can explain some of the Hannuoba granulite xenoliths having higher Mg# than the granulite terrains. It may be applicable to other parts of the world. [Copyright &y& Elsevier]

Young stresses that the Archaean-Proterozoic transition is one of the most important in geological history, being directly related to the onset of "modern-style" plate tectonics, massive palaeoclimatic upheavals, and the oxygenation of the palaeo-atmosphere; the early Palaeoproterozoic sedimentary record encompasses evidence for Earth's first widespread glacial episodes, defining the Huronian Glacial Event. Despite a change from poorly preserved pre-3.2 Ga fluvial deposits mainly confined to the flanks of volcanoes and volcanic plateaux of the "plume-lid tectonics" era, to the advent of "modern-style" plate tectonics in the Mesoarchaean which led to relatively large braided river systems, there was little change in fluvial style during the Archaean as a whole. The continued use of the "accepted" 2.5 Ga age for the Archaean-Proterozoic boundary can thus be brought into question, as is done in the final paper by Rajat Mazumder et al. based on a review of the Archaean-Palaeoproterozoic geology of Peninsular India. The concept of a gradual and globally diachronous Archaean-Proterozoic transition over some hundreds of million years (wherein a clear definition of a global ~2.5 Ga "boundary" becomes irrelevant), thus contrasts with the suggestion of redefining a new specific boundary globally, or as a possible compromise having a separate such boundary for each major craton. [Extracted from the article]

The Meso-Neoproterozoic period, sometimes referred to as the 'boring billion' or 'Earth's middle age', spans the interval between the formation of the Columbia and Rodina supercontinents. It is regarded as a stable era of the Earth. However, from a global perspective, there are many intensive events of mafic volcanism, dyke intrusions and formation of rift basins recorded in different cratons during this period. This paper focuses on rift basins that developed in three cratons in China (North China, South China and Tarim cratons), because large-scale primary gasfields, as one of the deep resources, have been discovered recently in rocks of Meso-Neoproterozoic age. The formation mechanisms and tectonic settings of these rift basins as the targets of Deep Earth are discussed, based on the restoration of global positions of the three cratons by pre-existing paleomagnetic data and plate reconstruction. We recognise that the rift basins of the North China Craton are related to extrusion tectonics in the southwest Ordos Block or are pull-apart basins along the northern and southern sides of the Ordos Block. The rift basins of the South China Craton are derived from mantle lithospheric delamination of the Jiangnan Orogen in the eastern South China Craton or subduction retreat and backarc opening in the western South China Craton, respectively. The rift basins of the Tarim Craton originated from the backarc opening along the margin of the Supercontinent Rodinia. [ABSTRACT FROM AUTHOR]