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.     

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.     

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 Early Triassic Indosinian orogeny in Vietnam (Truong Son Belt and Kontum Massif); implications for the geodynamic evolution of Indochina

New structural field data at various scale and ⁴⁰Ar–³⁹Ar geochronological results, from the basement rocks in the Truong Son belt and Kontum Massif of Vietnam, confirm that ductile deformation and high-temperature metamorphism were caused by the Early Triassic event of the Indosinian Orogeny in the range of 250–240 Ma. A compilation of isotopic data obtained in other countries along the Sibumasu–Indochina boundary broadly indicates same interval of ages. This tectonothermal event is interpreted as the result of a synchronous oblique collision of Indochina with both Sibumasu and South China, inducing dextral and sinistral shearing along E–W to NW–SE and N–S fault zones, respectively. The collision along Song Ma follows the northwards subduction of Indochina beneath South China and the subsequent development of the Song Da zone which in turn was affected by the Late Triassic Indosinian phase of shortening. Within the Indochina plate, internal collisions occurred coevally in the Early Triassic, as along the Poko suture, at the western border of the Kontum Massif.     

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.     

Tectonic implications of the Nan Suture Zone and its relationship to the Sukhothai Fold Belt, Northern Thailand

The Nan Suture and the Sukhothai Fold Belt reflect the processes associated with the collision between the Shan-Thai and Indochina Terranes in southeast Asia. The Shan-Thai Terrane rifted from Gondwana in the Early Permian. As it drifted north a subduction complex developed along its northern margin. The Nan serpentinitic melange is a thrust slice within the Pha Som Metamorphic Complex and in total this unit is a Late Permian accretionary complex containing offscraped blocks from subducted oceanic crust of Carboniferous and Permian age. The deformational style within the Pha Som Metamorphic Complex supports a west-dipping subduction zone. The Late Permian to Late Triassic fore-arc basin sediments are preserved in the Sukhothai Fold Belt and include a near continuous sedimentary record, at least locally. The whole sequence was folded and complexly thrust in the Late Triassic as a result of the collision. Late syn- to post-kinematic granites place an upper limit of 200 Ma on the time of collision. Post-orogenic sediments prograded across the suture in the Jurassic.     

The closure of Palaeo-Tethys in Eastern Myanmar and Northern Thailand: New insights from zircon U–Pb and Hf isotope data

Two of the major granite belts of Southeast Asia are the Main Range and Eastern Province. Together, these are interpreted to represent the magmatic expression of the closure of Palaeo-Tethys during Late Palaeozoic to Early Mesozoic times. Recent geochronological and geochemical work has better delineated these belts within Peninsular Malaysia, thereby providing important constraints on the timing of Palaeo-Tethys suturing. However, the northern extension of this Palaeo-Tethyan suture is less well understood. Here we present new ion microprobe U–Pb zircon age data from northern Thailand and eastern Myanmar. Measured ages of 219 and 220 Ma from the Kyaing Tong granite imply northern extension of the Main Range Province into eastern Myanmar. The Tachileik granite in far eastern Myanmar yields an age of 266 Ma, consistent with published Eastern Province ages, and this therefore constrains the northern extension of the Palaeo-Tethys suture in eastern Myanmar. We further discuss how this suture may extend northwards into Yunnan. A Late Cretaceous age (70 Ma) measured in Thailand represents later magmatic activity, and is similar to published magmatic ages from central Myanmar. This younger magmatism is interpreted to be related to the subduction of Neo-Tethys prior to India–Asia collision. Further, we present new laser ablation zircon Hf isotope data from eastern Myanmar which suggest that Palaeoproterozoic crust underlies both the Main Range and Eastern Province granites. Our εHf model age of ca. 1750 Ma from Sibumasu, the basement underlying eastern Myanmar, lies within the range of other model ages reported thus far for the Baoshan Block north in Yunnan, interpreted by some to be the northern extension of Sibumasu.     

西南三江地区洋板块地层特征及构造演化

以大地构造研究为主导,初步梳理了三江地区洋板块地层系统的分布及其构造演化规律。本文阐述了三江地区经历原-古特提斯大洋连续演化、分阶段拼贴增生至最终俯冲消亡的地质演化历程。甘孜-理塘弧后洋盆于早石炭世打开,二叠纪—中三叠世进入顶峰扩张期,晚三叠世洋盆萎缩引起向西俯冲,最终在晚三叠世末局部地区保留残留海。哀牢山弧后洋盆不晚于早石炭世形成,早石炭世—早二叠世整体扩张发育,早二叠世末或晚二叠世初开始向西俯冲,晚三叠世最终完全关闭。金沙江洋盆早石炭世时已扩张成洋,到早二叠世晚期开始俯冲,石炭纪—早二叠世早期是金沙江洋盆扩张的主体时期,早二叠世晚期至早、中三叠世俯冲消亡。澜沧江弧后洋盆中晚泥盆世开始扩张,在石炭纪—早二叠世发育为成熟洋盆,早二叠世晚期洋内俯冲形成洋内弧,晚二叠世—早、中三叠世双向俯冲消亡。昌宁-孟连洋为特提斯洋主带,具有原-古特提斯洋连续演化的地质记录,晚奥陶世开始向东俯冲消减,二叠纪末、早三叠世发生弧-陆碰撞作用,昌宁-孟连洋盆闭合。     

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.     

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.     

Tectonic framework and Phanerozoic evolution of Sundaland

Sundaland comprises a heterogeneous collage of continental blocks derived from the India–Australian margin of eastern Gondwana and assembled by the closure of multiple Tethyan and back-arc ocean basins now represented by suture zones. The continental core of Sundaland comprises a western Sibumasu block and an eastern Indochina–East Malaya block with an island arc terrane, the Sukhothai Island Arc System, comprising the Linchang, Sukhothai and Chanthaburi blocks sandwiched between. This island arc formed on the margin of Indochina–East Malaya, and then separated by back-arc spreading in the Permian. The Jinghong, Nan–Uttaradit and Sra Kaeo Sutures represent this closed back-arc basin. The Palaeo-Tethys is represented to the west by the Changning–Menglian, Chiang Mai/Inthanon and Bentong–Raub Suture Zones. The West Sumatra block, and possibly the West Burma block, rifted and separated from Gondwana, along with Indochina and East Malaya in the Devonian and were accreted to the Sundaland core in the Triassic. West Burma is now considered to be probably Cathaysian in nature and similar to West Sumatra, from which it was separated by opening of the Andaman Sea basin. South West Borneo and/or East Java-West Sulawesi are now tentatively identified as the missing “Argoland” which must have separated from NW Australia in the Jurassic and these were accreted to SE Sundaland in the Cretaceous. Revised palaeogeographic reconstructions illustrating the tectonic and palaeogeographic evolution of Sundaland and adjacent regions are presented.     

Early Middle Triassic mafic dikes from the Baoshan subterrane,western Yunnan: implications for the tectonic evolution of the Palaeo-Tethys in Southeast Asia

The time of final closure of the Palaeo-Tethys and the Sibumasu-Indochina collision in Southeast Asia represents a major unresolved geologic problem. Here, we present zircon chronology, whole-rock elemental, Sr–Nd, and zircon Hf isotopic geochemistry for newly discovered mafic dikes from the northern segment of the Sibumasu terrane, to provide constraints on this issue. Zircon U–Pb data indicate that the dikes were emplaced at 240 ± 3 Ma. These are the earliest Mesozoic magmatic rocks reported so far in the Sibumasu terrane, the late Palaeozoic passive margin of the Palaeo-Tethys. They are subalkaline tholeiites, showing geochemical characteristics similar to those of enriched mid-ocean ridge basalts (E-MORBs). They have ⁸⁷Sr/⁸⁶Sr(t) ratios of 0.703161–0.703826, ?Nd(t) of +4.8 to +7.5, and zircon ?Hf(t) of +9.2 to +13.3, implying strong mantle depletion. They were derived by partial melting of asthenospheric mantle and underwent subsequent fractional crystallization and lithospheric assimilation. The geologic–petrologic evidence suggests that the mafic dikes were generated in a collisional setting, when suturing of the Baoshan and Simao subterranes (the two subterranes are part of the Sibumasu and Indochina terranes, respectively) occurred. These early Middle Triassic mafic dikes provide an upper limit for Sibumasu–Indochina collision. In conjunction with previous work, we conclude that the final closure of the Palaeo-Tethys and collision of the Sibumasu and Indochina terranes took place during the late Permian to Early Triassic.     

Late Paleozoic – Mesozoic subduction-related magmatism at the southern margin of the Siberian continent and the 150 million-year history of the Mongol-Okhotsk Ocean

The paper reviews geological, geochronological and geochemical data from the Late Paleozoic – Mesozoic magmatic complexes of the Siberian continent north of the Mongol-Okhotsk suture. These data imply that these complexes are related to the subduction of the Mongol-Okhotsk Ocean under the Siberian continent. We suggest that this subduction started in the Devonian, prior to the peak of magmatic activity. Studied magmatic complexes are of variable compositions possibly controlled by changes of the subduction regime and by possible input from enriched mantle sources (hot spots).The oceanic lithosphere of the Mongol-Okhotsk Ocean had shallowly subducted under the Siberian continent in the Devonian. Steeper subduction in the Early – Late Carboniferous led to switching from an extensional to compressional tectonic regime resulting in fold-thrust deformation, to the development of duplex structures and finally to the thickening of the continental crust. This stage was marked by emplacement of voluminous autochthonous biotite granites of the Angara-Vitim batholith into the thickened crust. The igneous activity in the Late Carboniferous – Early Permian was controlled by the destruction of the subducted slab. The allochthonous granitoids of the Angara-Vitim batholith, and the alkaline granitoids and volcanics of the Western Transbaikalian belt were formed at this stage. All these complexes are indicative of extension of the thickened continental crust. A normal-angle subduction in the Late Permian – Late Triassic caused emplacement of various types of intrusions and volcanism. The calc-alkaline granitoids of the Late Permian – Middle Triassic Khangay batholith and Late Triassic Khentey batholith were intruded near the Mongol-Okhotsk suture, whereas alkaline granitoids and bimodal lavas were formed in the hinterland above the broken slab. The Jurassic is characterized by a significant decrease of magmatic activity, probably related to the end of Mongol-Okhotsk subduction beneath the studied area.The spatial relationship of the Late Permian – Middle Triassic granitoids, and the Late Triassic granitoids is typical for an active continental margin developing above a subduction zone. All the Late Carboniferous to Late Jurassic mafic rocks are geochemically similar to subduction-related basalts. They are depleted in Nb, Ta, Ti and enriched in Sr, Ba, Pb. However, the basaltoids located farther from the Mongol-Okhotsk suture are geochemically similar to a transition type between island-arc basalts and within-plate basalts. Such chemical characteristics might be caused by input of hot spot related enriched mantle to the lithospheric mantle modified by subduction. The Early Permian and Late Triassic alkaline granitoids of southern Siberia are of the A₂-type geochemical affinities, which is also typical of active continental margins. Only the basaltoids generated at the end of Early Cretaceous are geochemically similar to typical within-plate basalts, reflecting the final closure of the Mongol-Okhotsk Ocean.     

华南印支期碰撞造山--十万大山盆地构造和沉积学证据

十万大山盆地是云开造山带前陆地区的一个窄长的晚二叠世—中三叠世沉积盆地,位于扬子与华夏陆块拼接位置的西南端。十万大山盆地晚二叠世—中三叠世沉积由巨厚的磨拉石建造组成,并构成多个向上变粗和向上变细的构造-地层层序。云开造山带及前陆冲断带上泥盆统至下二叠统中发育了大量的印支期形成的薄皮褶皱和冲断构造。这些指示扬子和华夏陆块在印支期发生了强烈陆内碰撞与会聚及前陆盆地的沉积作用。P2 /P1 之间的不整合面是伸展构造向挤压构造转换的转换面,为华南印支期碰撞挤压造山或活化造山的序幕。T3 /T2 之间不整合面是挤压构造向伸展构造转换的转换面,是印支期活化挤压造山结束的界面,标志着晚二叠世开始的碰撞造山作用的结束。华南内部晚二叠世—中三叠世构造运动性质及转换与当时华南南缘存在的古特提斯洋的闭合及印支板块与华南陆块的碰撞作用有关。     

Geochronological and geochemical constraints on the Erguna massif basement,NE China – subduction history of the Mongol–Okhotsk oceanic crust

We present new geochronological and geochemical data for granites and volcanic rocks of the Erguna massif, NE China. These data are integrated with previous findings to better constrain the nature of the massif basement and to provide new insights into the subduction history of Mongol–Okhotsk oceanic crust and its closure. U–Pb dating of zircons from 12 granites previously mapped as Palaeoproterozoic and from three granites reported as Neoproterozoic yield exclusively Phanerozoic ages. These new ages, together with recently reported isotopic dates for the metamorphic and igneous basement rocks, as well as Nd–Hf crustal-residence ages, suggest that it is unlikely that pre-Mesoproterozoic basement exists in the Erguna massif. The geochronological and geochemical results are consistent with a three-stage subduction history of Mongol–Okhotsk oceanic crust beneath the Erguna massif, as follows. (1) The Erguna massif records a transition from Late Devonian A-type magmatism to Carboniferous adakitic magmatism. This indicates that southward subduction of the Mongol–Okhotsk oceanic crust along the northern margin of the Erguna massif began in the Carboniferous. (2) Late Permian–Middle Triassic granitoids in the Erguna massif are distributed along the Mongol–Okhotsk suture zone and coeval magmatic rocks in the Xing’an terrane are scarce, suggesting that they are unlikely to have formed in association with the collision between the North China Craton and the Jiamusi–Mongolia block along the Solonker–Xra Moron–Changchun–Yanji suture zone. Instead, the apparent subduction-related signature of the granites and their proximity to the Mongol–Okhotsk suture zone suggest that they are related to southward subduction of Mongol–Okhotsk oceanic crust. (3) A conspicuous lack of magmatic activity during the Middle Jurassic marks an abrupt shift in magmatic style from Late Triassic–Early Jurassic normal and adakite-like calc-alkaline magmatism (pre-quiescent episode) to Late Jurassic–Early Cretaceous A-type felsic magmatism (post-quiescent episode). Evidently a significant change in geodynamic processes took place during the Middle Jurassic. Late Triassic–Early Jurassic subduction-related signatures and adakitic affinities confirm the existence of subduction during this time. Late Jurassic–Early Cretaceous post-collision magmatism constrains the timing of the final closure of the Mongol–Okhotsk Ocean involving collision between the Jiamusi–Mongolia block and the Siberian Craton to the Middle Jurassic.     

Geological history of the Sibumasu Block in Peninsular Thailand: report of a Geologists’ Association Field Meeting in 2007

It is widely accepted that Thailand consists of two principal blocks or terranes, both of Gondwana origin, which collided and fused in the Late Triassic. The western of the two is the Sibumasu Block, and the purpose of this field meeting was to examine Peninsular Thailand where the succession reveals the nature of Sibumasu's Late Palaeozoic rifting from Gondwana in the context of the overall Phanerozoic history of this block. Sedimentary rocks ranging from Cambrian to Miocene crop out in Peninsular Thailand, as well as granite plutons which are aligned in N-S chains, the western chain of Cretaceous–Palaeogene age and those further east of Triassic age. Of particular importance in that history was the NNE-SSW Khlong Marui Fault belt which coincides with the conspicuous bend of the Peninsula; it formed the (present day) eastern boundary of a Late Palaeozoic rift and has been active intermittently since.     

Paleozoic evolution of the External Crystalline Massifs of the Western Alps

The External Crystalline Massifs (ECMs) of the Alps record, during the Paleozoic, the progressive closure of oceanic domains between Gondwana, Armorica and Avalonia in three contrasting tectonic domains. The eastern one shows the Early Devonian closure of the Central-European Ocean between Armorica and Gondwana along a northwest dipping subduction zone. The western domain is marked by Lower Ordovician rifting followed by Mid-Devonian obduction of the back-arc Chamrousse ophiolite. The central domain underwent Late Devonian to Dinantian extension in a back arc setting associated with southeast dipping subduction of the Saxo-Thuringian Ocean. Based on tectonostratigraphic correlations, we propose that the western domain shows an affinity to the Barrandian domain while the eastern and central domains correspond to the north-eastward extension of the Moldanubian zone, to the south of the present-day Bohemian Massif. From Mid-Carboniferous to Permian, the eastern and central domains of the ECMs, including the internal parts of the Maures Massif, Sardinia and Corsica were stretched towards the south-west along the ca. 1500 km long dextral ECMs shear zone preceding the opening of the Palaeo-Tethys ocean.     

Stratigraphy and palaeoenvironmental evolution of the mid- to upper Palaeozoic succession in Northwest Peninsular Malaysia

The stratigraphy of the Devonian to Permian succession in Northwest Peninsular Malaysia is revised. The Timah Tasoh Formation consists of black mudstone containing graptolites and tentaculitids indicating a Pragian or earliest Emsian age. The Sanai Limestone overlies the Timah Tasoh Formation at Sanai Hill B and contains conodonts indicating a Late Devonian (Frasnian to possibly early Famennian) age. In other places, Late Tournaisian chert of the Telaga Jatoh Formation overlies the Timah Tasoh Formation. The overlying Kubang Pasu Formation is predominantly composed of mudstone and sandstone, and can be divided into 3 subunits, from oldest to youngest: (1) Chepor Member; (2) Undifferentiated Kubang Pasu Formation; (3) Uppermost Kubang Pasu Formation. The ammonoid Praedaraelites tuntungensis sp. nov. is reported and described from the Chepor Member of Bukit Tuntung, Pauh. The genus indicates a Late Viséan age for part of the subunit. Dropstones and diamictites from the Chepor Member indicate a glacial marine depositional environment. The Carbo-Permian, undifferentiated Kubang Pasu Formation consists of similar interbedded mudstone and sandstone. The uppermost Kubang Pasu Formation of Kungurian age consists of coarsening upward cycles of clastics, representing a shallow marine, wave- and storm-influenced shoreline. The Permian Chuping Limestone also represents shallow marine, wave- and storm-influenced deposits. A Mid-Palaeozoic Unconformity separating Early–Late Devonian rocks from overlying Late Devonian–Carboniferous deposits probably marks initiation of rifting on Sibumasu, which eventually led to the separation of Sibumasu from Australian Gondwana during the late Sakmarian (Early Permian).     

Paleomagnetism of Peninsular Malaysia

Paleomagnetic results from Upper Jurassic to Paleocene rocks in Peninsular Malaysia show counter clockwise (CCW) rotations, while clockwise rotations (CW) are predominantly found in older rocks. Continental redbeds of the Upper Jurassic to Lower Cretaceous Tembeling Group have a post folding remagnetization, giving a VGP at N54°E29°, corresponding to approximately 40° of CCW rotation relative to Eurasia and 60° CCW relative to the Indochina block (Khorat Plateau). Samples from Cretaceous to Paleocene mafic volcanics of the Kuantan dike swarm and the Segamat basalts give VGPs at N59°E47° and N34°E36°, respectively. These Malayasian data are indistinguishable from the Late Eocene and Oligocene VGPs reported for Borneo and the Celebes Sea and are similar to the Eocene VGPs reported for southwest Sulawesi and southwest Palawan. The occurrence of CCW deflected data over this large region suggests that much of Malaysia, Borneo, Sulawesi, and the Celebes Sea rotated approximately 30° to 40° CCW relative to the Geocentric Axial Dipole (GAD) between the Late Eocene and the Late Miocene, although not necessarily synchronously, nor as a single rigid plate. These regional CCW rotations are not consistent with simple extrusion based tectonic models. CW declinations have been measured in Late Triassic granites, Permian to Triassic volcanics, and remagnetized Paleozoic carbonates. The age of this magnetization is poorly understood and may be as old as Late Triassic, or as young as Middle or Late Cretaceous. The plate, or block rotations, giving rise to these directions are correspondingly weakly constrained.