Gondwana dispersion and Asian accretion: Tectonic and palaeogeographic evolution of eastern Tethys

Present-day Asia comprises a heterogeneous collage of continental blocks, derived from the Indian–west Australian margin of eastern Gondwana, and subduction related volcanic arcs assembled by the closure of multiple Tethyan and back-arc ocean basins now represented by suture zones containing ophiolites, accretionary complexes and remnants of ocean island arcs. The Phanerozoic evolution of the region is the result of more than 400 million years of continental dispersion from Gondwana and plate tectonic convergence, collision and accretion. This involved successive dispersion of continental blocks, the northwards translation of these, and their amalgamation and accretion to form present-day Asia. Separation and northwards migration of the various continental terranes/blocks from Gondwana occurred in three phases linked with the successive opening and closure of three intervening Tethyan oceans, the Palaeo-Tethys (Devonian–Triassic), Meso-Tethys (late Early Permian–Late Cretaceous) and Ceno-Tethys (Late Triassic–Late Cretaceous). The first group of continental blocks dispersed from Gondwana in the Devonian, opening the Palaeo-Tethys behind them, and included the North China, Tarim, South China and Indochina blocks (including West Sumatra and West Burma). Remnants of the main Palaeo-Tethys ocean are now preserved within the Longmu Co-Shuanghu, Changning–Menglian, Chiang Mai/Inthanon and Bentong–Raub Suture Zones. During northwards subduction of the Palaeo-Tethys, the Sukhothai Arc was constructed on the margin of South China–Indochina and separated from those terranes by a short-lived back-arc basin now represented by the Jinghong, Nan–Uttaradit and Sra Kaeo Sutures. Concurrently, a second continental sliver or collage of blocks (Cimmerian continent) rifted and separated from northern Gondwana and the Meso-Tethys opened in the late Early Permian between these separating blocks and Gondwana. The eastern Cimmerian continent, including the South Qiangtang block and Sibumasu Terrane (including the Baoshan and Tengchong blocks of Yunnan) collided with the Sukhothai Arc and South China/Indochina in the Triassic, closing the Palaeo-Tethys. A third collage of continental blocks, including the Lhasa block, South West Borneo and East Java–West Sulawesi (now identified as the missing “Banda” and “Argoland” blocks) separated from NW Australia in the Late Triassic–Late Jurassic by opening of the Ceno-Tethys and accreted to SE Sundaland by subduction of the Meso-Tethys in the Cretaceous.     

Palaeozoic and Mesozoic tectonic evolution and palaeogeography of East Asian crustal fragments: The Korean Peninsula in context

East and Southeast Asia comprises a complex assembly of allochthonous continental lithospheric crustal fragments (terranes) together with volcanic arcs, and other terranes of oceanic and accretionary complex origins located at the zone of convergence between the Eurasian, Indo-Australian and Pacific Plates. The former wide separation of Asian terranes is indicated by contrasting faunas and floras developed on adjacent terranes due to their prior geographic separation, different palaeoclimates, and biogeographic isolation. The boundaries between Asian terranes are marked by major geological discontinuities (suture zones) that represent former ocean basins that once separated them. In some cases, the ocean basins have been completely destroyed, and terrane boundaries are marked by major fault zones. In other cases, remnants of the ocean basins and of subduction/accretion complexes remain and provide valuable information on the tectonic history of the terranes, the oceans that once separated them, and timings of amalgamation and accretion. The various allochthonous crustal fragments of East Asia have been brought into close juxtaposition by geological convergent plate tectonic processes. The Gondwana-derived East Asia crustal fragments successively rifted and separated from the margin of eastern Gondwana as three elongate continental slivers in the Devonian, Early Permian and Late Triassic–Late Jurassic. As these three continental slivers separated from Gondwana, three successive ocean basins, the Palaeo-Tethys,. Meso-Tethys and Ceno-Tethys, opened between these and Gondwana. Asian terranes progressively sutured to one another during the Palaeozoic to Cenozoic. South China and Indochina probably amalgamated in the Early Carboniferous but alternative scenarios with collision in the Permo–Triassic have been suggested. The Tarim terrane accreted to Eurasia in the Early Permian. The Sibumasu and Qiangtang terranes collided and sutured with Simao/Indochina/East Malaya in the Early–Middle Triassic and the West Sumatra terrane was transported westwards to a position outboard of Sibumasu during this collisional process. The Permo–Triassic also saw the progressive collision between South and North China (with possible extension of this collision being recognised in the Korean Peninsula) culminating in the Late Triassic. North China did not finally weld to Asia until the Late Jurassic. The Lhasa and West Burma terranes accreted to Eurasia in the Late Jurassic–Early Cretaceous and proto East and Southeast Asia had formed. Palaeogeographic reconstructions illustrating the evolution and assembly of Asian crustal fragments during the Phanerozoic are presented.     

Tectonic evolution of the Malay Peninsula

The Malay Peninsula is characterised by three north–south belts, the Western, Central, and Eastern belts based on distinct differences in stratigraphy, structure, magmatism, geophysical signatures and geological evolution. The Western Belt forms part of the Sibumasu Terrane, derived from the NW Australian Gondwana margin in the late Early Permian. The Central and Eastern Belts represent the Sukhothai Arc constructed in the Late Carboniferous–Early Permian on the margin of the Indochina Block (derived from the Gondwana margin in the Early Devonian). This arc was then separated from Indochina by back-arc spreading in the Permian. The Bentong-Raub suture zone forms the boundary between the Sibumasu Terrane (Western Belt) and Sukhothai Arc (Central and Eastern Belts) and preserves remnants of the Devonian–Permian main Palaeo-Tethys ocean basin destroyed by subduction beneath the Indochina Block/Sukhothai Arc, which produced the Permian–Triassic andesitic volcanism and I-Type granitoids observed in the Central and Eastern Belts of the Malay Peninsula. The collision between Sibumasu and the Sukhothai Arc began in Early Triassic times and was completed by the Late Triassic. Triassic cherts, turbidites and conglomerates of the Semanggol “Formation” were deposited in a fore-deep basin constructed on the leading edge of Sibumasu and the uplifted accretionary complex. Collisional crustal thickening, coupled with slab break off and rising hot asthenosphere produced the Main Range Late Triassic-earliest Jurassic S-Type granitoids that intrude the Western Belt and Bentong-Raub suture zone. The Sukhothai back-arc basin opened in the Early Permian and collapsed and closed in the Middle–Late Triassic. Marine sedimentation ceased in the Late Triassic in the Malay Peninsula due to tectonic and isostatic uplift, and Jurassic–Cretaceous continental red beds form a cover sequence. A significant Late Cretaceous tectono-thermal event affected the Peninsula with major faulting, granitoid intrusion and re-setting of palaeomagnetic signatures.     

An alternative plate tectonic model for the Palaeozoic–Early Mesozoic Palaeotethyan evolution of Southeast Asia (Northern Thailand–Burma)

An alternative model for the geodynamic evolution of Southeast Asia is proposed and inserted in a modern plate tectonic model. The reconstruction methodology is based on dynamic plate boundaries, constrained by data such as spreading rates and subduction velocities; in this way it differs from classical continental drift models proposed so far. The different interpretations about the location of the Palaeotethys suture in Thailand are revised, the Tertiary Mae Yuam fault is seen as the emplacement of the suture. East of the suture we identify an Indochina derived terrane for which we keep the name Shan–Thai, formerly used to identify the Cimmerian block present in Southeast Asia, now called Sibumasu. This nomenclatural choice was made on the basis of the geographic location of the terrane (Eastern Shan States in Burma and Central Thailand) and in order not to introduce new confusing terminology. The closure of the Eastern Palaeotethys is related to a southward subduction of the ocean, that triggered the Eastern Neotethys to open as a back-arc, due to the presence of Late Carboniferous–Early Permian arc magmatism in Mergui (Burma) and in the Lhasa block (South Tibet), and to the absence of arc magmatism of the same age East of the suture. In order to explain the presence of Carboniferous–Early Permian and Permo-Triassic volcanic arcs in Cambodia, Upper Triassic magmatism in Eastern Vietnam and Lower Permian–Middle Permian arc volcanites in Western Sumatra, we introduce the Orang Laut terranes concept. These terranes were detached from Indochina and South China during back-arc opening of the Poko–Song Ma system, due to the westward subduction of the Palaeopacific. This also explains the location of the Cathaysian West Sumatra block to the West of the Cimmerian Sibumasu block.     

Gondwanaland origin, dispersion, and accretion of East and Southeast Asian continental terranes

East and Southeast Asia is a complex assembly of allochthonous continental terranes, island arcs, accretionary complexes and small ocean basins. The boundaries between continental terranes are marked by major fault zones or by sutures recognized by the presence of ophiolites, mélanges and accretionary complexes. Stratigraphical, sedimentological, paleobiogeographical and paleomagnetic data suggest that all of the East and Southeast Asian continental terranes were derived directly or indirectly from the Iran-Himalaya-Australia margin of Gondwanaland. The evolution of the terranes is one of rifting from Gondwanaland, northwards drift and amalgamation/accretion to form present day East Asia. Three continental silvers were rifted from the northeast margin of Gondwanaland in the Silurian-Early Devonian (North China, South China, Indochina/East Malaya, Qamdo-Simao and Tarim terranes), Early-Middle Permian (Sibumasu, Lhasa and Qiangtang terranes) and Late Jurassic (West Burma terrane, Woyla terranes). The northwards drift of these terranes was effected by the opening and closing of three successive Tethys oceans, the Paleo-Tethys, Meso-Tethys and Ceno-Tethys. Terrane assembly took place between the Late Paleozoic and Cenozoic, but the precise timings of amalgamation and accretion are still contentious. Amalgamation of South China and Indochina/East Malaya occurred during the Early Carboniferous along the Song Ma Suture to form “Cathaysialand”. Cathaysialand, together with North China, formed a large continental region within the Paleotethys during the Late Carboniferous and Permian. Paleomagnetic data indicate that this continental region was in equatorial to low northern paleolatitudes which is consistent with the tropical Cathaysian flora developed on these terranes. The Tarim terrane (together with the Kunlun, Qaidam and Ala Shan terranes) accreted to Kazakhstan/Siberia in the Permian. This was followed by the suturing of Sibumasu and Qiangtang to Cathaysialand in the Late Permian-Early Triassic, largely closing the Paleo-Tethys. North and South China were amalgamated in the Late Triassic-Early Jurassic and finally welded to Laurasia around the same time. The Lhasa terrane accreted to the Sibumasu-Qiangtang terrane in the Late Jurassic and the Kurosegawa terrane of Japan, interpreted to be derived from Australian Gondwanaland, accreted to Japanese Eurasia, also in the Late Jurassic. The West Burma and Woyla terranes drifted northwards during the Late Jurassic and Early Cretaceous as the Ceno-Tethys opened and the Meso-Tethys was destroyed by subduction beneath Eurasia and were accreted to proto-Southeast Asia in the Early to Late Cretaceous. The Southwest Borneo and Semitau terranes amalgamated to each other and accreted to Indochina/East Malaya in the Late Cretaceous and the Hainanese terranes probably accreted to South China sometime in the Cretaceous.     

Development of the Khao Khwang Fold and Thrust Belt: Implications for the geodynamic setting of Thailand and Cambodia during the Indosinian Orogeny

The Indosinian Orogeny in Thailand is often viewed as having developed between strongly linear terranes, which today trend approximately N–S. The terranes were subsequently disrupted by later tectonics, particularly NW–SE trending Cenozoic strike-slip faults. The ENE–WSW to NE–SW striking thrusts and folds in the Khao Khwang Platform area of the Saraburi Group on the SW margin of the Indochina Terrane are not easily explained in the context of this traditional view. Reversal of the clockwise rotation shown to have affected the block north of the Mae Ping Fault zone only enhances the E–W orientation of structures in the fold and thrust belt, and moves the belt further east towards Cambodia. One solution for the trend that fits better with regional understanding from hydrocarbon exploration of the Khorat Plateau is that the Indochina Terrane was actually a series of continental blocks, separated by Permian rifting. During the Early Triassic the early stages of collision (South China-Cathaysian Terrane collision with Vietnam Indochina) resulted in the amalgamation of disparate blocks that now form the Indochina Terrane by closure along the rifts. At the same time or following on from the collision there was closure of the back-arc area between Indochina and the Sukhothai zone. The rift basins, were thrusted and inverted during the early stages of the Indosinian orogeny, and only underwent minor reactivated when later Sibumasu collided with Sukhothai Zone-Indochina Terrane margin during the Late Triassic. The scenario described above requires the presence of a (minor) E–W trending suture in NW Cambodia. Evidence for this suture is suggested by the presence of Permo-Triassic calc-alkaline volcanism.     

初论苏门答腊（印尼）的岩浆一构造旋回及其板块构造背景

本文将晚古生代以来苏门答腊火成岩划分出四个岩浆-构造旋回或岩浆活动期次（海西期、印支期、燕山期和喜山期）,并讨论其板块构造背景。结果表明：分布于西苏门答腊地体海西期酸性侵入岩属于碰撞后地壳的火山弧I-型花岗岩带,其火山岩为大陆拉张带（初始裂谷）中的安山．玄武岩系列,而分布在东苏门答腊地体的大多数酸性侵入岩具有s-型花岗岩的性质。印支期西苏门答腊地体侵入岩为I-型花岗岩,属于火山弧花岗岩。印支期碰撞后板内岩浆活动带（廖内群岛-班加岛-勿里洞岛）的侵入岩以含锡s-型花岗岩为特色。燕山期以后的深成岩-火山岩活动的岩石类型和分布特征,受大陆拉张带（初始裂谷）及其相邻的洋岛的控制。燕山早期细碧岩属于陆缘裂谷火山岩。喜山期火山岩属于陆缘火山弧,其中橄榄玄粗岩落在洋岛玄武岩与洋中脊玄武岩（MORB）交界线附近。     

The origin of the Woyla Terranes in Sumatra and the Late Mesozoic evolution of the Sundaland margin

The Jurassic–Cretaceous Woyla Group of northern Sumatra includes fragments of volcanic arcs and an imbricated oceanic assemblage. The arc rocks are intruded by a granitic batholith and are separated from the original continental margin of Sundaland by the oceanic assemblage. Rocks of the arc assemblage are considered to be underlain by a continental basement because of the occurrence of the intrusive granite and of tin anomalies identified in stream sediments. Quartzose sediments associated with the granite have been correlated with units in the Palaeozoic basement of Sumatra. From these relationships a model has been proposed in which a continental sliver was separated from the margin of Sundaland in the Late Jurassic to Early Cretaceous in an extensional strike-slip faulting regime, producing a short-lived marginal basin. The separated continental fragments have been designated the Sikuleh and Natal microcontinents. In the mid-Cretaceous the extensional regime was succeeded by compression, crushing the continental fragments back against the Sundaland margin, with the destruction of the marginal basin, now represented only by the imbricated oceanic assemblage. Modifications of this scenario are required by subsequent studies. Age-dating of the volcanic assemblage and intrusive granites in the Natal area showed that they formed part of an Eocene–Oligocene volcanic arc and are not relevant to the model. Thick-bedded radiolarian chert and palaeontological studies in the oceanic Woyla Group rocks of the Natal and Padang areas showed that they formed part of a more extensive and long-lived ocean basin which lasted from at least Triassic until mid-Cretaceous. This raised the possibility that the Sikuleh microcontinent might be allochthonous to Sumatra and encouraged plate tectonic reconstructions in which the Sikuleh microcontinent originated on the northern margin of Gondwanaland and migrated northwards across Tethys before colliding with Sundaland. Since these models were proposed, the whole of Sumatra has been mapped and units correlated with the Woyla Group have been recognised throughout western Sumatra. These units are reviewed and the validity of their correlation with the Woyla Group of northern Sumatra is assessed. From this review a revised synthesis for the Late Mesozoic tectonic evolution of the southwestern margin of Sundaland is proposed.     

Myanmar and Asia united,Australia left behind long ago

It is well known that western Myanmar is underlain by a continental fragment, the West Burma Block, but there are arguments about its origin and the time of its arrival in SE Asia. This study presents the first petrological, XRD diffraction, heavy mineral and detrital zircon U-Pb age data from turbidite sandstones in the Chin Hills that were deposited on West Burma crust in the Triassic. These sandstones contain detritus derived from areas surrounding West Burma and thus help resolve arguments about its location in the Palaeozoic and Mesozoic. West Burma, Sibumasu and Western Australia have similar populations of Archean zircons derived from Western Australian cratons. Until the Devonian all formed part of the Gondwana supercontinent. The abundance of Archean zircons decreases from Western Australia to West Burma and then to Sibumasu. This is consistent with their relative positions in the Gondwana margin, with Sibumasu furthest outboard from Western Australia. Differences in zircon populations indicate that Indochina was not close to West Burma or Sibumasu in Gondwana. West Burma contains abundant Permian and Triassic zircons. These are unknown in Western Australia and different from those of the Carnarvon Basin; they were probably derived from SE Asian tin belt granitoids. Cr spinel is present in most West Burma sandstones; it is common in SE Asia but rare in Western Australia. These new data show that West Burma was part of SE Asia before the Mesozoic and support suggestions that the Argo block that rifted in the Jurassic is not West Burma.     

苏门答腊岛（印尼）岩浆旋回中的成矿作用

本文阐述了东苏门答腊地体和西苏门答腊地体白海西期岩浆旋回以来各自的金属矿产分布特征。海西期东苏门答腊地体以裂陷盆地的层控型铅-锌矿为主,而矽卡岩型Ag、cu和Pb．zn矿化产于西苏门答腊地体。印支期sn矿成矿作用主要与s-型花岗岩类（220～195Ma）侵入和苏门答腊岛中部的梅迪亚苏门答腊深大断裂走滑活动有关。燕山早期铜．金成矿作用为陆缘夭折古裂谷和岛弧环境。燕山晚期为弧-陆碰撞的火山弧的Sn-Au-Ag成矿作用。喜山期发育的岩浆弧Au—Ag成矿与苏门答腊深大断裂活动和巴厘散构造带有关,归因于印度-澳大利亚洋壳斜向俯冲于苏门答腊岛之下。     

Geotectonic evolution of the Western Cordillera of Colombia: New aspects from geochemical data on volcanic rocks

The Western Cordillera of Colombia (WCC) is part of the Basic Igneous Complex (BIC), which is one of the world's largest ophiolitic complexes, extending from Costa Rica through Panama and Colombia to Ecuador. Major and trace element data on 32 volcanic rocks from the central and northern parts of the Western Cordillera are presented; no data have been available to date for volcanic rocks from the northern parts of the Western Cordillera. Petrographical and geochemical investigations show that the rocks are altered and have undergone low-grade metamorphism. The subalkaline rocks are represented by tholeiitic basalts, calc-alkaline basic andesites, andesites, and one dacite. It is concluded that a mature oceanic island arc existed in the Cretaceous, in what is now the northern part of the Western Cordillera. The tectonics of the region, particularly the intensive imbrication of the chain, indicates the presence of a paleo-subduction zone with an oceanic island arc that accreted on the old continental margin. These new data, combined with new and previous data from the central part of the BIC of Colombia, suggest that volcanic rocks of the Western Cordillera can be interpreted as allochthonous slabs. These slabs were imbricated with back-arc and fore-arc sediments and tonalitic bodies during the closing of a back-arc basin in northwestern South America and accretion of an oceanic island arc. Oblique subduction accreted these different areas to the continental margin during Late Cretaceous and early Tertiary times. Two plate-tectonic models are proposed: a) development of the calc-alkaline volcanic rocks in the northern parts of the Western Cordillera, separated by tholeiitic rocks, formed along a transform fault represented by the tholeiitic basalts of the central and southern parts of the Western Cordillera; or b) development of an oceanic island arc along the Cretaceous continental margin of northwestern South America. In the central and southern parts of this island arc, accretion took place early and therefore only an island-arc tholeiitic suite was formed.     

The Bentong–Raub Suture Zone

It is proposed that the Bentong–Raub Suture Zone represents a segment of the main Devonian to Middle Triassic Palaeo-Tethys ocean, and forms the boundary between the Gondwana-derived Sibumasu and Indochina terranes. Palaeo-Tethyan oceanic ribbon-bedded cherts preserved in the suture zone range in age from Middle Devonian to Middle Permian, and mélange includes chert and limestone clasts that range in age from Lower Carboniferous to Lower Permian. This indicates that the Palaeo-Tethys opened in the Devonian, when Indochina and other Chinese blocks separated from Gondwana, and closed in the Late Triassic (Peninsular Malaysia segment). The suture zone is the result of northwards subduction of the Palaeo-Tethys ocean beneath Indochina in the Late Palaeozoic and the Triassic collision of the Sibumasu terrane with, and the underthrusting of, Indochina. Tectonostratigraphic, palaeobiogeographic and palaeomagnetic data indicate that the Sibumasu Terrane separated from Gondwana in the late Sakmarian, and then drifted rapidly northwards during the Permian–Triassic. During the Permian subduction phase, the East Malaya volcano-plutonic arc, with I-Type granitoids and intermediate to acidic volcanism, was developed on the margin of Indochina. The main structural discontinuity in Peninsular Malaysia occurs between Palaeozoic and Triassic rocks, and orogenic deformation appears to have been initiated in the Upper Permian to Lower Triassic, when Sibumasu began to collide with Indochina. During the Early to Middle Triassic, A-Type subduction and crustal thickening generated the Main Range syn- to post-orogenic granites, which were emplaced in the Late Triassic–Early Jurassic. A foredeep basin developed on the depressed margin of Sibumasu in front of the uplifted accretionary complex in which the Semanggol “Formation” rocks accumulated. The suture zone is covered by a latest Triassic, Jurassic and Cretaceous, mainly continental, red bed overlap sequence.     

Parallel Tethyan sutures in mainland Southeast Asia: New insights for Palaeo-Tethys closure and implications for the Indosinian orogeny

Two contrasting parallel tectonic sutures can be recognised through the Yunnan–Thailand region of mainland Southeast Asia; they are sutures of the Devonian–Triassic Palaeo-Tethys Ocean and a Permian back-arc basin. The Changning–Menglian and Inthanon suture zones are regarded as the Palaeo-Tethys Suture Zone. The Jinghong–Nan–Sra Kaeo suture is regarded as a closed back-arc basin. The Sukhothai Zone is no longer treated as a part of the Sibumasu Terrane, but is defined as the core part of the Permian island-arc system developed on the western margin of the Indochina Terrane. Two tectonic events are interpreted from the parallel sutures; a Late Permian collapse of the back-arc basin and a mid-Triassic collision of Sibumasu to the Sukhothai Arc of Indochina (= closure of the Palaeo-Tethys). The Early–early Middle Triassic thermotectonism of Vietnam as linked to the Indosinian orogeny by some authors is incompatible with the suggested timing of Sibumasu collision, but instead it is temporally closer to the back-arc compression of western Indochina.     

The Mount Wright Arc: A Cambrian subduction system developed on the continental margin of East Gondwana,Koonenberry Belt,eastern Australia

The Mount Wright Arc, in the Koonenberry Belt in eastern Australia, is associated with two early to middle Cambrian lithostratigraphic groups developed onto the Late Neoproterozoic volcanic passive margin of East Gondwana. The Gnalta Group includes a calc-alkaline basalt-andesite-dacite suite (Mount Wright Volcanics), interpreted to represent the volcanic component of the arc. Volcaniclastic Gnalta Group rocks now buried in the Bancannia Trough represent the continental back-arc, developed immediately behind the arc in a manner analogous to the modern Taupo Volcanic Zone of New Zealand. East of the Gnalta Group is the Ponto Group, a deep marine sedimentary package that includes tholeiitic lavas (Bittles Tank Volcanics) and felsic tuffs, interpreted as part of a fore-arc sequence. The configuration of these units suggests the Mount Wright Arc developed on continental crust in response to west-dipping subduction along the East Gondwana margin, in contrast with some models for Cambrian convergence on other sections of the Delamerian Orogen, which invoke east-dipping subduction and arc accretion by arc-continent collision.This convergent margin was deformed by the middle Cambrian Delamerian Orogeny, which involved initial co-axial shortening followed by sinistral transpression, and oroclinal folding around the edge of the Curnamona Province.     

MULTI-ARC BASIN SYSTEM OF THE KUNLUN OROGENICBELT AND PAN-CATHYSIAN CONTINENTAL ACCRETION

After Rodinia supercontinent was disintegrated in Late Proterozoic, an ocean, namely, Tethys Ocean, occurred between Gondwana continental group and Pan-Cathaysian continental group from Late Proterozoic to Mesozoic. From Early Paleozoic to Mesozoic, Tethys Ocean was subducted toward Pan-Cathaysian block group, which results in backarc expansion, arc-land collision and forearc accretion. When the backarc basin expands and reaches the small oceanic basin, ophiolite melange will be generated. As accretion had already occurred in the south of the continental margin in the earlier stage, the succeeding backarc expansion and the frontal arc position were migrated toward south correspondingly. Therefore, multiple ophiolite belts and magmatic rock belts occurred, and show a trend of decreasing age from north toward south. As the continental margin was split and migrated toward south and reached a high latitude position, i.e., with the shortening and subduction of oceanic crust, the sedimentary bodies at high latitude was accreted continuously toward low latitude area together with the formation of oceanic island, mixing of cold-type and warm-type organism was generated. Moreover, blocks split and separated from Pan-Cathaysian or Gondwana continental group cannot traverse the oceanic median ridge and joins with another continental block. As a result, the Kunlun belt on the SW margin of the Pan-Cathaysian land was resulted from the multi-arc orogenesis such as the backarc seabed expansion, arc-arc collision, arc-land collision oceanic bed, and the continuous southward accretion process.     

Gondwana and Cathaysian blocks,palaeotethys sutures and cenozoic tectonics in South-east Asia

The Triassic Indosinian Orogeny followed extinction of the Palaeotethys Ocean resulting in suturing of Gondwana affinity and Cathaysian blocks.The Gondwana affinity Sinoburmalaya block of Peninsular Malaysia, characterized by Carboniferous—Permian mudstones containing glacial dropstones and sparse fauna and flora, is traced extensively into Sumatra. This mudstone facies is flanked on the east by a sandstone-dominated facies and by carbonate localized in the Kinta Valley. The muddy and sandy facies both begin with a basal Carboniferous condensed red bed sequence, which unconformably overlies the older formations of Sinoburmalaya. Both facies also demonstrate a Late Permian conformable transition into overlying limestone. The Cathaysian block of East Malaya is characterized by Late Permian Gigantopteris flora and fusulinid limestones associated with andesitic volcanism. It is similar but not identical to the West Sumatra Carboniferous—Permian block, characterized by Early Permian volcanism, fusulinid limestones and early Cathaysian Jambi flora.The South to SSE trending central Peninsular Malaysian Triassic orogenic belt swings south-east from Singapore to Bangka, then east to Billiton. The Palaeotethys suture (Bentong—Raub Line) forms the western margin of this belt and is therefore unlikely to continue south along the Palaeogene Bengkalis Graben, which transects the north-west—south-east orogenic fabric of Sumatra.The oroclinal bending of the Indosinian Orogen, from a north-west—south-east grain in Sumatra to a northerly grain through Peninsular Malaysia, is attributed to the Palaeocene collision of India and its subsequent indentation into Eurasia. The bending was accomplished by clockwise rotation and right-lateral shear parallel to the orogenic grain. The Mesozoic Palaeotethyan sutures were transformed into Palaeocene and younger shear zones. The outer zones of the orocline experienced pull apart tectonics (Andaman Sea and Sumatra basins) while the inner part (East Malaya to Billiton), being compressional, lacks Cenozoic basins.     

Contemporaneous assembly of Western Gondwana and final Rodinia break-up: Implications for the supercontinent cycle

Geological, geochronological and isotopic data are integrated in order to present a revised model for the Neoproterozoic evolution of Western Gondwana. Although the classical geodynamic scenario assumed for the period 800–700 Ma is related to Rodinia break-up and the consequent opening of major oceanic basins, a significantly different tectonic evolution can be inferred for most Western Gondwana cratons. These cratons occupied a marginal position in the southern hemisphere with respect to Rodinia and recorded subduction with back-arc extension, island arc development and limited formation of oceanic crust in internal oceans. This period was thus characterized by increased crustal growth in Western Gondwana, resulting from addition of juvenile continental crust along convergent margins. In contrast, crustal reworking and metacratonization were dominant during the subsequent assembly of Gondwana. The Río de la Plata, Congo-São Francisco, West African and Amazonian cratons collided at ca. 630–600 Ma along the West Gondwana Orogen. These events overlap in time with the onset of the opening of the Iapetus Ocean at ca. 610–600 Ma, which gave rise to the separation of Baltica, Laurentia and Amazonia and resulted from the final Rodinia break-up. The East African/Antarctic Orogen recorded the subsequent amalgamation of Western and Eastern Gondwana after ca. 580 Ma, contemporaneously with the beginning of subduction in the Terra Australis Orogen along the southern Gondwana margin. However, the Kalahari Craton was lately incorporated during the Late Ediacaran–Early Cambrian. The proposed Gondwana evolution rules out the existence of Pannotia, as the final Gondwana amalgamation postdates latest connections between Laurentia and Amazonia. Additionally, a combination of introversion and extroversion is proposed for the assembly of Gondwana. The contemporaneous record of final Rodinia break-up and Gondwana assembly has major implications for the supercontinent cycle, as supercontinent amalgamation and break-up do not necessarily represent alternating episodic processes but overlap in time.     

The Cambrian Ross Orogeny in northern Victoria Land (Antarctica) and New Zealand: A synthesis

In the Cambrian, the paleo-Pacific margin of the East Gondwana continent, including East Antarctica, Australia, Tasmania and New Zealand, was affected by the Ross–Delamerian Orogeny. The evidence from geochemistry of volcanic rocks and petrography of clastic sediments in northern Victoria Land (Antarctica) reveals that orogenesis occurred during a phase of oblique subduction accompanied by the opening and subsequent closure of a back-arc basin. A similar sequence of events is recognized in New Zealand. In both regions Middle Cambrian volcanic rocks are interpreted as arc/back-arc assemblages produced by west-directed subduction; sediments interbedded with the volcanic rocks show provenance both from the arc and from the Gondwana margin and therefore place the basin close to the continent. Rapid back-arc closure in the Late Cambrian was likely accomplished through changes to the subduction system.     

Arc–continent collision and orogenesis in western Tasmanides: Insights from reactivated basement structures and formation of an ocean–continent transform boundary off western Tasmania

Crustal architecture in formerly contiguous basement terranes in SE Australia, Tasmania and northern Victoria Land is a legacy of late Neoproterozoic–Cambrian subduction-related processes, culminating in formation of the Delamerian–Ross orogen. Structures of Delamerian–Ross age were subsequently reactivated during late Mesozoic–Cenozoic Gondwana breakup, strongly influencing the geometry of continental rifting and providing clues about the origins and configuration of the pre-existing basement structures. An ocean–continent transform boundary developed off western Tasmania follows the trace of an older Paleozoic strike-slip structure (Avoca–Sorell fault system) optimally oriented for reactivation during the final separation of Australia from Antarctica. This boundary cuts across rocks preserving an earlier record of arc–continent collision during the course of which continental crust was subducted to mantle depths and Cambrian mafic–ultramafic island arc rocks were thrust westwards over late Neoproterozoic–Cambrian passive margin sequences. Collision was accompanied by development of a foreland basin into which 520–600 Ma arc-derived detrital zircons were shed. Following a reversal in subduction polarity, and change to transcurrent motion along the Gondwana margin, Tasmania migrated northward along the proto-Avoca fault system before entering a subduction zone located along the Heathcote–Governor fault system, precipitating a second collision, south-vergent thrusting, and tectonic reworking of the already accreted Cambrian arc–forearc assemblages and underlying passive margin sequences.     

Tectonic evolution of the southern margin of Laurasia in the Black Sea region

The Black Sea region comprises Gondwana-derived continental blocks and oceanic subduction complexes accreted to Laurasia. The core of Laurasia is made up of an Archaean–Palaeoproterozoic shield, whereas the Gondwana-derived blocks are characterized by a Neoproterozoic basement. In the early Palaeozoic, a Pontide terrane collided and amalgamated to the core of Laurasia, as part of the Avalonia–Laurasia collision. From the Silurian to Carboniferous, the southern margin of Laurasia was a passive margin. In the late Carboniferous, a magmatic arc, represented by part of the Pontides and the Caucasus, collided with this passive margin with the Carboniferous eclogites marking the zone of collision. This Variscan orogeny was followed by uplift and erosion during the Permian and subsequently by Early Triassic rifting. Northward subduction under Laurussia during the Late Triassic resulted in the accretion of an oceanic plateau, whose remnants are preserved in the Pontides and include Upper Triassic eclogites. The Cimmeride orogeny ended in the Early Jurassic, and in the Middle Jurassic the subduction jumped south of the accreted complexes, and a magmatic arc was established along the southern margin of Laurasia. There is little evidence for subduction during the latest Jurassic–Early Cretaceous in the eastern part of the Black Sea region, which was an area of carbonate sedimentation. In contrast, in the Balkans there was continental collision during this period. Subduction erosion in the Early Cretaceous removed a large crustal slice south of the Jurassic magmatic arc. Subduction in the second half of the Early Cretaceous is evidenced by eclogites and blueschists in the Central Pontides and by a now buried magmatic arc. A continuous extensional arc was established only in the Late Cretaceous, coeval with the opening of the Black Sea as a back-arc basin.