The Central Asian Orogenic Belt (CAOB) evolved through complex closure of the Paleo-Asian Ocean from the Neoproterozoic to the late Phanerozoic. This caused the Chinese cratons to collide with ...Eurasia and led to the formation of the world's largest Phanerozoic orogenic belt. Ocean closure commenced in the west and was completed in the east near Changchun. Closure of the Paleo-Asian Ocean in NE China was along the Solonker–Xar Moron–Changchun–Yanji suture and this was likely completed in the Late Permian, although associated activity continued into the Triassic. There was an overlap in the latest Permian–Early Triassic between terminal activity associated with Paleo-Asian Ocean closure and the onset of tectonism associated with subduction of the Paleo-Pacific plate. This switch in geodynamic setting occurred at ~260–250Ma, and is reflected by a relaxing of north–south directed compression and the onset of east–west directed processes related to Paleo-Pacific subduction. By the Early Jurassic, events associated with the westward advance of the Paleo-Pacific plate dominated, leading to extensive development of I-type granites as far inland as the Great Xing'an Range. From ~140Ma, the Paleo-Pacific plate retreated eastward, resulting in an extensional setting in the Early Cretaceous, the effects of which were enhanced by regional thinning of the lithosphere, commonly attributed to delamination. Throughout this period, the eastern Asian margin was tectonically complex. The north–south oriented Jiamusi–Khanka(–Bureya) block was rifted away from the eastern margin of the CAOB in the Late Triassic, but was then re-united in the Jurassic by westward-advancing subduction that affected both the western and eastern margins of the block. Accretionary complexes continued to evolve in the Cretaceous along the whole eastern margin of Asia, with final accretion of the Nadanhada Terrane (part of the Sikhote–Alin accretionary terrane) with the CAOB at ~130Ma, followed by the emplacement of S-type granites.
•Paleo-Asian Ocean closed diachronously along Solonker suture.•Closure completed in late Permian•Paleo-Pacific subduction affected eastern CAOB.•Precambrian rocks rare in CAOB of NE China•Chinese terranes originated in Siberia
The microcontinental blocks in the CAOB include the combined NE China blocks (comprising the Erguna, Xing'an, Songliao and Jimusi-Khanka blocks) in the eastern segment of the CAOB, the ...Kazakhstan-Yili-Central Tianshan and Junggar blocks in the western segment of the CAOB, and the Tuva-Mongolia blocks and Beishan block in the central segment of the CAOB. The basement in these microcontinental blocks mainly consists of Archean to Paleoproterozoic crystalline rocks and/or Meso-Neoproterozoic granitoids and metamorphic complexes, indicating that most of the so-called blocks in the CAOB can be regarded as microcontinental fragments. Zircon age spectra from the eastern segment of the CAOB reveal four age peaks at 495Ma, 780Ma, 1825Ma and 2600Ma, which is similar to those recorded in the central and western segments of the CAOB. In addition, evidence of the global ‘Grenvillian’ tectonic event at 1000Ma is also present in most blocks, indicating that the microcontinents in the CAOB have a common tectonic history. Furthermore, late Pan-African metamorphism at ~500Ma affects all the microcontinents in the CAOB, with this granulite-facies event forming a single metamorphic belt that extends for >1300km across NE China, and named the “NE China Khondalite Belt” in the eastern segment of the CAOB. There is also a corresponding >1000km-long Sayang–Baikal orogenic belt along the southern margin of the Siberia Craton. We propose that the microcontinents of the CAOB originated as part of Rodinia along the global Grenville Orogenic Belt (1100–750Ma). At 750–600Ma, after the break-up of Rodinia, the various microcontinental blocks were located along the margin of Gondwana, close to the South China and Tarim cratons. At ~600Ma, these blocks became detached from eastern Gondwana and, together with accreted complexes, drifted to the north (present-day co-ordinates) across the Paleo-Asian Ocean to the southern margin of the Siberia Craton, where collision took place during the late Pan-African.
It has previously been postulated that the Earth's hydrous mantle transition zone may play a key role in intraplate magmatism, but no confirmatory evidence has been reported. Here we demonstrate that ...hydrothermally altered subducted oceanic crust was involved in generating the late Cenozoic Chifeng continental flood basalts of East Asia. This study combines oxygen isotopes with conventional geochemistry to provide evidence for an origin in the hydrous mantle transition zone. These observations lead us to propose an alternative thermochemical model, whereby slab-triggered wet upwelling produces large volumes of melt that may rise from the hydrous mantle transition zone. This model explains the lack of pre-magmatic lithospheric extension or a hotspot track and also the arc-like signatures observed in some large-scale intracontinental magmas. Deep-Earth water cycling, linked to cold subduction, slab stagnation, wet mantle upwelling and assembly/breakup of supercontinents, can potentially account for the chemical diversity of many continental flood basalts.
The basement rocks in parts of NE China constitute a khondalitic sequence of sillimanite- and garnet-bearing gneisses, hornblende–plagioclase gneiss and various felsic paragneisses. Zircon U–Pb ...dating of garnet–sillimanite gneiss samples from the Erguna, Xing'an, Jiamusi and Khanka blocks indicates that high-grade metamorphism occurred at ~500Ma. Evidence from detrital zircons in Paleozoic sediments from the Songliao Block also indicates the former presence of a ~500Ma component. This uniformity of U–Pb ages across all crustal blocks in NE China establishes a >1300km long Late Pan-African khondalite belt which we have named the ‘NE China Khondalite Belt’. This indicates the blocks of NE China were amalgamated prior to ~500Ma, contrary to current belief. One scenario is that this amalgamated terrane had a tectonic affinity to the Siberia Craton, once forming part of the Late Pan-African (~500Ma) Sayang–Baikal orogenic belt extensively developed around the southern margin of the Siberia Craton. This belt was the result of collision between currently unidentified terranes with the Southeastern Angara–Anabar Province at about 500Ma, where the rocks were deformed and metamorphosed to granulite facies. It appears likely that at sometime after ~450Ma, the combined NE China blocks rifted away from Siberia and moved southward to form what is now NE China. The combined block collided with the North China Craton along the Solonker–Xar Moron–Changchun suture zone at ~230Ma rather than in the end-Permian as previously thought. Local rifting at the eastern extremity of the developing Central Asian Orogenic Belt (CAOB) resulted in the splitting away of the Jiamusi/Khanka(/Bureya) blocks. However, this was only transient and sometime between 210 and 180Ma, these were re-united with the CAOB by the onset of Pacific plate subduction, which has dominated the tectonic evolution of the region since that time.
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► Basement of NEC contain ~500Ma khondalitic sequence. ► Collision between NCC and SC along X -C zone during Triassic. ► Onset of PO subduction at 210–180Ma.
Columbia is a Palaeo-Mesoproterozoic supercontinent that was assembled during global 2.0-1.8 Ga collisional events, underwent long-lived, subduction-related accretion at key continental margins in ...the period 1.8-1.3 Ga, commenced to fragment ∼1.6 Ga ago, and finally broke up at ∼1.3 Ga. Similar to most other cratonic blocks (Laurentia, Baltica, Siberia, Amazonia, West African, South Africa, India, Australia, and Antarctica), the North China Craton records the history of assembly, accretion, and break-up of the Columbia supercontinent. New data indicate that the Archaean to Palaeoproterozoic basement of the North China Craton was assembled by microcontinental blocks along three Palaeoproterozoic collisional belts: the Khondalite Belt, the Jiao-Liao-Ji Belt, and the Trans-North China Orogen. The Khondalite Belt was formed by collision between the Yinshan and Ordos blocks and was amalgamated to form the Western Block at ∼1.95 Ga. The Eastern Block underwent Palaeoproterozoic rifting at 2.2-1.9 Ga to break-up into the Longgang and Nangrim blocks; then the rift basin/incipient ocean closed attending subduction and collision to form the Jiao-Liao-Ji Belt at ∼1.9 Ga. Finally, the Western and Eastern blocks collided along the Trans-North China Orogen to form the coherent basement of the North China Craton at ∼1.85 Ga. Following this final assembly, the North China Craton underwent subduction-related accretion at its southern margin during the period 1.78-1.45 Ga, forming the Xiong'er volcanic belt. At 1.6-1.2 Ga, the northern margin of the North China Craton underwent a rifting event that led to separation of the craton from other cratonic blocks of the supercontinent Columbia, forming the 1.6-1.2 Ga Zhaertai-Bayan Obo rift zone and associated 1.35 Ga mafic sills along the northern margin of the craton. These data indicate that in any configuration of Columbia, the southern margin of the North China Craton must have faced an open ocean, whereas its northern margin was connected to another continental block.
Abstract
The coexistence of divergent (spreading ridge) and convergent (subduction zone) plate boundaries at which lithosphere is respectively generated and destroyed is the hallmark of plate ...tectonics. Here, we document temporally- and spatially-associated Neoarchean (2.55–2.51 Ga) rock assemblages with mid-ocean ridge and supra-subduction-zone origins from the Angou Complex, southern North China Craton. These assemblages record seafloor spreading and contemporaneous subduction initiation and mature arc magmatism, respectively, analogous to modern divergent and convergent plate boundary processes. Our results provide direct evidence for lateral plate motions in the late Neoarchean, and arguably the operation of plate tectonics, albeit with warmer than average Phanerozoic subduction geotherms. Further, we surmise that plate tectonic processes played an important role in shaping Earth’s surficial environments during the Neoarchean and Paleoproterozoic.
The Dharwar Craton is a composite Archean cratonic collage that preserves important records of crustal evolution on the early Earth. Here we present results from a multidisciplinary study involving ...field investigations, petrology, zircon SHRIMP U–Pb geochronology with in-situ Hf isotope analyses, and whole-rock geochemistry, including Nd isotope data on migmatitic TTG (tonalite-trondhjemite-granodiorite) gneisses, dark grey banded gneisses, calc-alkaline and anatectic granitoids, together with synplutonic mafic dykes along a wide Northwest – Southeast corridor forming a wide time window in the Central and Eastern blocks of the Dharwar Craton. The dark grey banded gneisses are transitional between TTGs and calc-alkaline granitoids, and are referred to as ‘transitional TTGs’, whereas the calc-alkaline granitoids show sanukitoid affinity. Our zircon U–Pb data, together with published results, reveal four major periods of crustal growth (ca. 3360-3200 Ma, 3000-2960 Ma, 2700-2600 Ma and 2570-2520 Ma) in this region. The first two periods correspond to TTG generation and accretion that is confined to the western part of the corridor, whereas widespread 2670-2600 Ma transitional TTG, together with a major outburst of 2570–2520 Ma juvenile calc-alkaline magmatism of sanukitoid affinity contributed to peak continental growth. The transitional TTGs were preceded by greenstone volcanism between 2746 Ma and 2700 Ma, whereas the calc-alkaline magmatism was contemporaneous with 2570–2545 Ma felsic volcanism. The terminal stage of all four major accretion events was marked by thermal events reflected by amphibolite to granulite facies metamorphism at ca. 3200 Ma, 2960 Ma, 2620 Ma and 2520 Ma. Elemental ratios (La/Yb)N, Sr/Y, Nb/Ta, Hf/Sm) and Hf-Nd isotope data suggest that the magmatic protoliths of the TTGs emplaced at different time periods formed by melting of thickened oceanic arc crust at different depths with plagioclase + amphibole ± garnet + titanite/ilmenite in the source residue, whereas the elemental (Ba–Sr, (La/Yb)N, Sr/Y, Nb/Ta, Hf/Sm) and Hf-Nd isotope data εHf(T) = −0.67 to 5.61; εNd(T) = 0.52 to 4.23; of the transitional TTGs suggest that their protoliths formed by melting of composite sources involving mantle and overlying arc crust with amphibole + garnet + clinopyroxene ± plagioclase + ilmenite in the residue. The highly incompatible and compatible element contents (REE, K–Ba–Sr, Mg, Ni, Cr), together with Hf and Nd isotope data εHf(T) = 4.5 to −3.2; εNd(T) = 1.93 to −1.26; , of the sanukitoids and synplutonic dykes suggest their derivation from enriched mantle reservoirs with minor crustal contamination. Field, elemental and isotope data εHf(T) = −4.3 to −15.0; εNd(T) = −0.5 to −7.0 of the anatectic granites suggest their derivation through reworking of ancient as well as newly formed juvenile crust. Secular increase in incompatible as well as compatible element contents in the transitional TTGs to sanukitoids imply progressive enrichment of Neoarchean mantle reservoirs, possibly through melting of continent-derived detritus in a subduction zone setting, resulting in the establishment of a sizable continental mass by 2700 Ma, which in turn is linked to the evolving Earth. The Neoarchean geodynamic evolution is attributed to westward convergence of hot oceanic lithosphere, with continued convergence resulted in the assembly of micro-blocks, with eventual slab break-off leading to asthenosphere upwelling caused extensive mantle melting and hot juvenile magma additions to the crust. This led to lateral flow of hot ductile crust and 3D mass distribution and formation of an orogenic plateaux with subdued topography, as indicated by strain fabric data and strong seismic reflectivity along an E-W crustal profile in the Central and Eastern blocks of the Dharwar Craton.
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•Multi-stage Archean crustal growth ca. 3360-3200 Ma, ca. 3000-2960 Ma, ca. 2700-2600 Ma and ca. 2570-2520 Ma.•Secular changes in the composition of granitoids through time imply increasing involvement of enriched peridotitic mantle.•Convergence of oceanic lithosphere and eventual slab breakoff lead to asthenosphere upwelling.•Lateral flow of hot orogenic crust lead to orogenic plateau formation with subdued topography.
The Nadanhada Terrane, located along the eastern margin of Eurasia, contains a typical accretionary complex related to paleo‐Pacific plate subduction‐accretion. The Yuejinshan Complex is the first ...stage accretion complex that consists of meta‐clastic rocks and metamafic‐ultramafic rocks, whereas the Raohe Complex forms the main parts of the terrane and consists of limestone, bedded chert, and mafic‐ultramafic rocks embedded as olistolith blocks in a weakly sheared matrix of clastic meta‐sedimentary rocks. Geochemical data indicate that the Yuejinshan metabasalts have normal mid‐ocean ridge basalt (N‐MORB) affinity, whereas the Raohe basaltic pillow lavas have an affinity to ocean island basalts (OIB). Sensitive high‐resolution ion microprobe (SHRIMP) U‐Pb zircon analyses of gabbro in the Raohe Complex yield a weighted mean 206Pb/238U zircon age of 216 ± 5 Ma, whereas two samples of granite intruded into the complex yield weighted mean 206Pb/238U zircon ages of 128 ± 2 and 129 ± 2 Ma. Laser ablation inductively coupled plasma mass spectrometry (LA‐ICPMS) U‐Pb zircon analyses of basaltic pillow lava in the Raohe Complex define a weighted mean age of 167 ± 1 Ma. Two sandstone samples in the Raohe Complex record younger concordant zircon weighted mean ages of 167 ± 17 and 137 ± 3 Ma. These new data support the view that accretion of the Raohe Complex was between 170 and 137 Ma, and that final emplacement of the Raohe Complex took place at 137–130 Ma. The accretion of the Yuejinshan Complex probably occurred between the 210 and 180 Ma, suggesting that paleo‐Pacific plate subduction was initiated in the Late Triassic to Early Jurassic.
Key Points
Nadanhada Terrane is an accretionary complexBasaltic rocks have OIB and N‐MORB affinitiesOnset of Pacific accretion at 210–180 Ma, final emplacement at 137–130 Ma
The Tarim Craton, located in the center of Asia, was involved in the assembly and breakup of the Rodinia supercontinent during the Neoproterozoic and the subduction‐accretion of the Central Asian ...Orogenic Belt (CAOB) during the Paleozoic. However, its tectonic evolution during these events is controversial, and a link between the Neoproterozoic and Paleozoic tectonic processes is missing. Here we present zircon U‐Pb ages, Hf isotopes, and whole‐rock geochemical data for the extensive granitoids in the western Kuruktag area, northeastern Tarim Craton. Three distinct periods of granitoid magmatism are evident: circa 830–820 Ma, 660–630 Ma, and 420–400 Ma. The magma sources, melting conditions (pressure, temperature, and water availability), and tectonic settings of various granitoids from each period are determined. Based on our results and the geological, geochronological, geochemical, and isotopic data from adjacent areas, a long‐lived accretionary orogenic model is proposed. This model involves an early phase (circa 950–780 Ma) of southward advancing accretion from the Tianshan to northern Tarim and a late phase (circa 780–600 Ma) of northward retreating accretion, followed by back‐arc opening and subsequent bidirectional subduction (circa 460–400 Ma) of a composite back‐arc basin (i.e., the South Tianshan Ocean). Our model highlights a long‐lived accretionary history of the southwestern CAOB, which may have initiated as part of the circum‐Rodinia subduction zone and was comparable with events occurring at the southern margin of the Siberian Craton, thus challenging the traditional southward migrating accretionary models for the CAOB.
Key Points
Three periods of granitoids intrusion and tectonic settings are determined
A long‐lived accretionary orogenic model is proposed for southwest CAOB
The model links the early history of the CAOB with Rodinia evolution
Mesozoic volcanic rocks and granitoids are widespread in the Great Xing'an Range, which is part of a large igneous province in the eastern China. However, the ages of the volcanic rocks, especially ...those in the southern segment of the range, are poorly constrained. Here we present zircon U–Pb and whole rock Ar–Ar ages of 43 volcanic rocks from the four recognized formations (Manketouebo, Manitu, Baiyingaolao and Meiletu) in the southern Great Xing'an Range. The volcanic rocks of the Manketouebo Formation have a large span of ages ranging from 174 to 122
Ma, while those of the Manitu Formation exhibit a smaller age range from 156 to 125
Ma. The Baiyingaolao and Meiletu volcanic rocks both have Early Cretaceous ages between 139 and 124
Ma. These data indicate that the mapped units are not strictly ‘formations’ and further studies are required to resolve this issue. However, when taken together, these new data define two episodes of magmatism (Late Jurassic and Early Cretaceous) with the Early Cretaceous volcanic rocks being dominant. Combined with previously published data from the northern Great Xing'an Range, and available age data from other parts of northeastern China and surrounding regions, two stages of magmatism, i.e., Jurassic and Early Cretaceous, can be identified throughout this part of Asia. The Jurassic rocks mainly comprise granites, while volcanic rocks are dominant in the Early Cretaceous. These two stages of magmatism form opposite spatial trends, that is, the Jurassic rocks become younger to the west, whereas the Cretaceous rocks become younger to the east. Between the two stages of magmatism, the ‘magma gap’ increases eastward in duration from less than 10
Ma in the Great Xing'an Range to more than 40
Ma in Japan. These trends can be explained by westward subduction of the Paleo-Pacific oceanic Plate and its control on subsequent geodynamic processes. Jurassic subduction of the oceanic slab caused crustal shortening and thickening, and formed the westward decrease in age of the granites with characteristics of an active continental margin, while volcanism was rare. By the end of the Jurassic, westward flat-slab subduction of the Paleo-Pacific Oceanic plate changed its direction to the north or northwest. This subsequently caused a transformation in tectonic regime from compression to extension in the Cretaceous and induced large-scale delamination of the thickened lower crust and lithospheric mantle. Delamination was initiated at the western margin of the subducting slab, and migrated eastward. Delamination and consequent upwelling of the asthenosphere triggered extensive volcanic eruption, with only minor granite emplacement. Similar age trends are also observed for other parts of eastern China, suggesting this model can also be applied to explain the geodynamic setting of the Mesozoic large igneous events in China and adjacent regions.
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