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The Neoproterozoic Jiangnan orogenic belt records the accretion and collision between the Yangtze and Cathaysia blocks in South China. The orogen is divisible into three units: a northeastern domain (also referred to as the Huaiyu or Shuangxiwu domain), a central domain (Jiuling domain) and an undifferentiated southwestern domain. Detrital zircons from the oldest sequences (Shuangqiaoshan, Lengjiaxi, Fanjingshan and Sibao groups) in the central and southwest domains yield similar age spectra with major age populations at c. 875–820 Ma, along with minor Palaeo- to Mesoproterozoic and Archaean ages. The dominance of detrital ages close to the deposition ages of the units, along with juvenile zircon Hf isotopic compositions and arc-like whole-rock compositional data, indicate the sedimentary units accumulated adjacent to a convergent plate margin magmatic arc. The presence of Mesoproterozoic and older zircons, both as detritus in the units and as xenocrysts within igneous rocks displaying a subduction-related signature, along with the compositional data, place the magmatic arc along a continental margin. In the northeastern domain, the oldest coeval sequence (Shuangxiwu and Qigong groups) and arc igneous suites are dated at c. 970–850 Ma, and lack older detritus and xenocrysts, indicating they represent an accreted oceanic arc system.

The Jiangnan orogenic belt in South China, formed by the collision of the Yangtze and Cathaysia sub-blocks, represents a key to reconstruct the assembly of the Rodinia supercontinent. Here we investigated the Fuchuan ophiolite melange and Shexian magmatic units in the eastern Jiangnan belt, and report the first findings of anorthosite and leucogranite that are dated at 848 ± 4 and 840 ± 5 Ma, respectively. The anorthosites yield positive eNd(t) values (2.3–4.2) and lower initial 87Sr/86Sr ratios (0.704616–0.704679), along with zircon eHf(t) of ∼9.2, suggesting a depleted mantle contribution with minor crustal assimilation. The mafic-ultramafic rocks and anorthosite within the Fuchuan ophiolite display N-MORB & E-MORB signatures, likely generated in back-arc marginal sea spreading center and metasomatized by subduction-related fluids. The intermediate-felsic igneous suites from Shexian area in the eastern margin of the Zhanggong Terrane were formed at 850–830 Ma and display continental-arc-related geochemical features. Zircons within these rock suites mostly show eHf(t) values of 3–12, whereas inherited grains yielded negative eHf(t) values with model ages of 2.7–1.9 Ga, implying an active continental marginal environment. Overall relations and data indicate that the disrupted Fuchuan mafic-ultramafic rocks, anorthosite and leucogranite constitute the remnants of an 860–830 Ma ophiolite, whereas the northwestward subduction beneath the Zhanggong terrane occurred at ca. 870–860 Ma to ca. 830 Ma. A ca. 817 Ma muscovite-bearing K-granitic pluton dated at 817 ± 5 Ma emplaced in a post-collisional setting constrains the upper age limit of continental assembly along the Shaoxing- Jiangshan- Pingxiang- Qidong-Quanzhou- Longsheng-Yongfu fault zone. The timing of the final assembly of South China occurred at 830–800 Ma as referred from a collisional-type granitic magmatism ca. 830–815 Ma and an external dynamic process of uplifting-erosion-transpotation-deposition presented by the regional-scale unconformity with ages 820–795 Ma. Age and nature of the Jiangnan orogenic belt, along with sedimentary records and paleomagnetic constraints, indicate that the South China Block was possibly located along the northern Rodinia margin, adjacent to the Tarim and northwestern Australia blocks.

The Neoproterozoic amalgamation and timing of collision between the Yangtze and Cathaysia sub-blocks along the Jiangnan Orogen in South China remain disputed. With a view to constrain the crustal evolution in this major orogen, here we present new results from petrology, geochemistry, zircon U-Pb chronology and Lu-Hf isotopes, on a suite of meta-sedimentary rocks from the Shuangqiaoshan Group and tuffaceous rock from the Liantuo Formation in the Jiuling terrane of central Jiangnan Orogen. Magmatic zircon grains in meta-sedimentary and sedimentary samples from the bottom to top part of the lower and upper Shuangqiaoshan groups constraints the deposition during 863–820 Ma and 797–780 Ma, respectively. The unconformities were formed during 820–797 Ma, reflecting the final amalgamation of Yangtze with Cathaysia sub-blocks along the central Jiangnan Orogen. Our data also identify four major events at 1000–800, 1500–1900, 1900–2200, 2300–2600 Ma. The Neoproterozoic detrital zircons in the lower Shuangqiaoshan Group possess variable eHf(t) values of −44.0 to +13.4. Combined with the geochemical features, these data suggest that the lower Shuangqiaoshan Group was deposited in a back-arc basin with a mixed provenance of granitic and felsic volcanic components, whereas the upper Shuangqiaoshan Group was formed in a rift basin with more granitic or felsic components in the source region. Integrating the results presented in this study with those from previous works, a five-stage crustal evolution model is proposed for the Neoproterozoic Jiangnan Orogen involving (1) intra-oceanic subduction beneath the Huaiyu oceanic island arc (1000–880 Ma), (2) collision between Huaiyu arc and Yangtze Sub-block (880–860 Ma), (3) back-arc extension beneath the Yangtze Sub-block (860–830 Ma), (4) collision between Cathaysia and Yangtze sub-blocks (830–800) and (5) intracontinental rifting throughout South China Block (800–750 Ma).

International audience; The South China Block is situated in the Eastern Asian margin. Since the Neoproterozoic, its tectonic evolution was constrained by successive consumption-closure processes of the Paleo-South China, Proto-Tethys, Paleo-Tethys, and Paleo-Pacific oceans. Studies suggest that this block was initially formed by the Neoproterozoic assembly of the Yangtze and Cathaysia blocks following the subduction-accretion of the Paleo-South China Ocean. Then after, it experienced three tectonic-magmatic events in the Phanerozoic. Among these events, the Late Mesozoic tectonism-magmatism was linked with the consumption of the Paleo-Pacific Ocean, while the Silurian and Early to Middle Triassic events took place in intracontinental settings that were related to far-field effects of the closure of the remote Proto-Tethys and Paleo-Tethys oceans, respectively. The subduction-accretion of the Paleo-South China Ocean, and collision at 980–820 Ma between the Yangtze and Cathaysia blocks formed the Jiangnan Orogenic Belt and the Proto-South China Continent, followed by a rifting tectonics and bimodal volcanism at 810–760 Ma. From 760 Ma to 460 Ma, the South China Block was situated under shore, shallow sea to slope depositional environments. During Late Ordovician to Early Devonian (460–400 Ma), an intracontinental orogeny occurred mainly in the Cathaysia Block as a response to the closure of the Proto-Tethys Ocean. Shortly afterwards, this block underwent a stable carbonate deposition during Early Devonian- Middle Triassic (400–230 Ma) and was thus under a shore or shallow sea environment. In the Middle-Late Triassic (240–220 Ma), the South China Block was affected by the closure of the Paleo-Tethys Ocean, intracontinental deformation and S-type granitic magmatism. During the Cretaceous, a multi-stage basin-and-range framework occurred in the western shore of the Paleo-Pacific Plate.

South China Block is situated in the Eastern Asian margin. Its tectonic process was constrained by convergences of the ancient South China, paleo-Asian, paleo-Tethys and paleo-Pacific oceans with d...

Widespread late Mesozoic Yanshanian magmatic rocks exposed in the South China Block are of critical importance for unravelling the geodynamic setting of palaeo-Pacific subduction. However, available information on magmatic rocks from inland South China is inadequate to constrain the petrogenesis and tectonic setting of late Mesozoic magmatism. This study focuses on the late Jurassic granitic batholiths and stocks exposed in NW Guangdong, and further inland areas at the boundary region of Hunan (Xiang), Hubei (E) and Jiangxi (G) (abbreviated as XEG). Zircon U–Pb geochronology reveals that the studied granitic rocks were emplaced during latest Jurassic at 153 – 145 Ma. Geochemically, the Daping and Taibao plutons in NW Guangdong exhibit features of adakite-like melts, such as high Sr, SiO 2 , Al 2 O 3 contents, and low Yb content, without an Eu anomaly. This suggests that these rocks were most likely derived from partial melting of a high Sr/Y source at a normal lower continental crustal depth (30–40 km). Combined with the data from the coeval A-type granites in the late Mesozoic Qinhang metallogenic zone, we suggest that the Daping and Taibao adakitic granites were probably generated in low pressure environments related with the extension of the Qinhang zone in response to the late Jurassic roll-back of the palaeo-Pacific slab. The XEG granites, characterized by peraluminous geochemical signatures and enrichment of light rare earth elements and negative eHf(t) values, are classified as highly fractionated I- and S-types, I-type to S-type, formed at an intraplate setting. If correct, this interpretation indicates that the slab roll-back of the palaeo-Pacific plate probably has not reached the XEG region, updating current models for the subduction of the palaeo-Pacific plate. Supplementary Material: Analytical procedures, representative field photographs and photomicrographs of samples, U-Pb geochronological data, zircon Lu-Hf isotopic compositions, bulk rock major and trace element data are available at: https://doi.org/10.6084/m9.figshare.c.4029982

The Neoproterozoic Jiangnan accretionary orogenic belt recorded the accretion and collision of the Yangtze and Cathaysia blocks to form a stablized South China Block, but related geometry and kinematics is poorly constrained, leading to largely varied tectonic models. Here, we present detailed field investigation and kinematic analysis of the plutonic-metamorphic complexes in the Yuanbaoshan and Sanfang areas of the west Jiangnan orogenic belt, which enables identification of extensional granite-cored domes. In the dome margins, down-dipping lineations display a radial pattern and dome dominated foliations are extensively developed. The shearing structures within the plutonic-metamorphic complexes display extensional shearing surrounding the Yuanbaoshan and Sanfang granitic dome cores. Gneissic granites and massive ones from both the Yuanbaoshan and Sanfang plutons yield comparable crystallization ages of ca. 835–823 Ma that are within age errors of each other, as are the sheared recrystallized asymmetric quartz veins and mylonites dated at 831 Ma. Overall ages of the deformed Sibao Group and the undeformed overlying Danzhou Group, along with those of the granite plutons and mylonites, suggest formation of the granite-cored domes at ca. 835–823 Ma, coeval to the timing of emplacement of the granitic plutons. Locally, top-to-the-E thrusting structures are also observed in the west Yuanbaoshan and Sanfang areas and are inferred as at ca. 860–835 Ma, coinciding well with E- or SE- directed structures developed elsewhere in the Jiangnan orogenic belt, but in contrast with doming extensional shearing structures. Therefore, overall geometry and kinematics in the west Jiangnan belt indicate development of granitic dome related extensional ductile shearing deformation dated at ca. 835–823 Ma and a possible top-to-the-E compressional ductile thrusting deformation within 860–835 Ma. Given the previously inferred regional geology observations, along with age and chemical data across the Jiangnan orogenic belt, the dominant extensional shearing deformation in the region argue for a slab roll-back event within an accretionary belt, typical of domes-and-basins structures formed in accretionary convergent continental margin. The top-to-the-E thrusting is here interpreted as corresponding to compressional regime generated by the west directed subduction of oceanic crust beneath the northern Guangxi continental margin arc in the west Jiangnan orogenic belt.

The formation and tectonic evolution of the Jiangnan orogenic belt in South China have been debated in the context of plate subduction-collision versus mantle plume. Here we present new results from petrology, whole rock geochemistry, zircon U-Pb chronology and Hf isotopes, on three magmatic suites ranging in composition from felsic to mafic from the Jiuling terrane of the central Jiangnan orogenic belt in the southeastern margin of Yangtze Block. Suite 1 including meta-diorites and meta-basites are dated at 849.9 ± 4.9, 848.8 ± 4.5 and 846.3 ± 3.5 Ma. The meta-diorites and some of the meta-basites display enrichment of LREE, Rb and K and depletions of Nb, Ta and Ti anomalies, with distinctive geochemical features of continental arc setting. The eHf(t) values of zircons from meta-diorites range from 0.17 to 6.10. The other meta-basites have LREE depleted REE patterns, similar to N-MORB and intra-oceanic island arc settings, suggesting a fore-arc environment. Suite 2 consists of foliated granitoids dated at 816.8 ± 4.2, 814.6 ± 3.6, 812.5 ± 3.5 and 810.3 ± 3.5 Ma, with the A/CNK values >1.1, and are classified as post-collisional granites in the Rb/(Y + Nb) diagram. Zircon grains from the granitoids show eHf(t) values in the range of −1.99 to 8.49 and Hf model ages of 1835–1041 Ma. Suite 3 is composed of meta-diabase dated at 792.1 ± 2.8 Ma, with zircon eHf(t) values of 8.46–13.83. This suite shows E-MORB REE patterns, and plot within continental rift field. Their zircon Hf model ages mainly clustered at 1046–811 Ma, indicating magma sourced through partial melting of early Neoproterozoic lithosphere mantle. These data suggest that the three Neoproterozoic Jiuling magmatic suites in the Jiuling terrane correlate with (1) the continental arc, fore-arc, (2) collision and (3) continental rift settings in the interval from 850 Ma to 790 Ma. These tectonic settings are consistent with a geodynamic process from the oceanic subduction beneath the Yangtze Block (850 Ma), collision between Cathaysia and Yangtze Blocks (820 Ma) and intracontinental rift (790 Ma). This tectono-magmatic cycle in the Jiangnan orogenic belt is >200 Ma later than the global Grenville orogeny in response to Rodinia supercontinent assembly, and challenges some of the existing models.

The Longyou garnet amphibolite is exposed on the southeast of the Neoproterozoic Jiangshan-Shaoxing fault zone of South China. Some recent studies propose that the Longyou garnet amphibolite was retrograded from an Early Paleozoic collision-related eclogite, which is inconsistent with previous numerous studies. Here we carry out a systematic study including field investigation, petrography, mineral chemistry, zircon geochronology and bulk rock geochemistry to ascertain its genesis. Our results indicate that a small amount of plagioclase inclusions found in garnet and clinopyroxene are anorthite, while plagioclase that largely distribute in the outer part of garnet and clinopyroxene porphyroblasts are andesine and labradorite (with An values of 44–66). No sodium-rich plagioclase (albite or oligoclase) which is indicative of omphacite symplectite has been found. The zircon CL images and Th/U ratios indicate that, apart from some newborn-metamorphic small zircons, a number of large zircon crystals exhibit obvious core-rim structures. Zircon U-Pb dating results indicate that the zircon cores yield concordant weighted average age of 879 ± 11 Ma and the zircon metamorphic rims yield weighted average age of 446 ± 5 Ma. Furthermore, the bulk rock geochemical features of garnet amphibolite suggest that its protolith is basic igneous rock (the SiO2 content within 46.8–48.2%), and its trace elements exhibit E-MORB geochemical affinity. This study also constrains the P-T pseudosection for Longyou garnet amphibolite (LGA), which revealing that the LGA at least experienced three stages of metamorphism in Silurian: the prograde metamorphism stage with P-T condition of 0.67–0.75 G Pa/685–719 °C (M1), the peak-metamorphism with P-T condition of 0.9–1.1 G Pa/760–778 °C (M2), and the retrograde metamorphism stage with P-T condition of ∼0.68G Pa/∼767 °C (M3). In combination with regional geological setting, this study constrains the formation process for the LGA.

The Neoproterozoic sedimentary strata in the central Jiangnan Orogen of South China are separated into the Lengjiaxi and Banxi groups by a mid-Neoproterozoic angular unconformity. This unconformity, previously interpreted as the evidence of continental collision between the Yangtze and Cathaysia blocks, is crucial for understanding the Neoproterozoic tectonic regime in the South China Craton. Here we report U-Pb ages and in situ Lu-Hf isotopes of detrital zircon grains from the sedimentary rocks near this unconformity. Zircon grains in meta-sandstone samples collected from the top part of Lengjiaxi Group yield maximum depositional ages of ∼827 Ma, ∼828 Ma and 836 Ma, and combined with other available age data, we suggest that the upper limit of the sedimentation for Lengjiaxi Group is at ca. 825 Ma. Zircon U-Pb analysis for two sandstone samples collected from the bottom of Banxi Group and Nanhuan strata yields two youngest ages of 797 Ma and 719 Ma, marking the initial depositional ages for these strata. All the samples contain abundant Neoproterozoic euhedral zircon grains, suggesting their near-source provenance. The Hf isotopic model ages of detrital zircons with positive eHf(t) values reveal two periods of juvenile crustal growth at 1.5–0.9 Ga and 2.8–1.6 Ga in the Yangtze Block. Several grains display core-rim structure with ages of rim part ranging from 864 to 851 Ma. We correlate these metamorphic ages with the amalgamation of Yangtze and Cathaysia blocks in the central segments. Our data in combination with those from other studies suggest that a back-arc basin existed in the central Jiangnan belt during ca. 860 Ma to ca. 825 Ma. We propose a four-phase crustal evolution model for the central Jiangnan belt.

The Yili Block represents the easternmost segment of the Kazakhstan–Yili microcontinent. Late Paleozoic magmatic rocks are extensively exposed in the Yili Block and are essential in understanding the tectonic development of the SW Central Asia Orogenic Belt (CAOB). We conducted field investigations, zircon U–Pb dating, whole-rock geochemical and Sr–Nd isotopic studies on the magmatic rocks from the Wusun Range, southern Yili Block. The Late Paleozoic volcanic and plutonic rocks of the Wusun Range show geochemical features consistent with that of calc-alkaline series, and they have positive eNd(t) values (0.9 to 5.6), Neo- to Mesoproterozoic single-stage Nd model ages (0.80 ~ 1.33 Ga), and variable initial 87Sr/86Sr ratios (0.7041–0.7059), suggesting that these magmatic rocks are likely derived from partial melting of a moderately depleted mantle wedge with minor involvement of a Precambrian continental crust. These new data, combined with previously published results put constraints on the Late Paleozoic magmatic and geodynamic evolution of the Balkhash–Yili active continental margin. The Late Paleozoic arc magmatism initiated from ~ 386 Ma along the northern Yili Block, and migrated southward to have occurred since ~ 340 Ma along its southern margin. Subsequently, the arc-related magmatism moved back northward and terminated at 310 Ma in the south and at ~ 295 Ma in the north. The OIB-like geochemical features of some volcanic rocks indicate incipient marginal rifting occurred along the southern Yili Block during Late Carboniferous. Taking into account the regional structural and tectonic data, the Carboniferous Yili magmatic arc may be laterally correlated with the Balkhash–Yili active margin of the Kazakhstan microcontinent, which was likely resulted from the southward subduction of the Junggar – North Tianshan Ocean.

We acknowledge the financial support by the Major State Research Development Program of China (Grant No. 2016YFC0600202), National Natural Science Foundation of China (Nos. 41330208 and 41572200) and State Key Laboratory for Mineral Deposits Research (Nanjing University) (ZZKT-201603). The Cathaysia Block of the South China Craton includes a Proterozoic basement that experienced a prolonged Precambrian crustal evolution but to date lacks evidence of Proterozoic metamorphic ages. At Lichuan and Jianning, in the Wuyi Domain of the eastern Cathaysia Block, Proterozoic rock units include migmatized paragneiss of the Wanyuan Group and minor amphibolite of the Tianjingping Formation, which are enveloped by schist of Mayuan Group, and all are intruded by Paleozoic and Mesozoic igneous rocks. Detrital zircon grains from the Wanyuan paragneiss display metamorphic rims that yield concordant weighted average 206Pb/238U ages of 860 ± 6 Ma and 435 ± 5 Ma, along with variably disconcordant ages with lower intercept ages of 442 ± 41 Ma. The zircon core ages range from 3015 Ma to 851 Ma, with three major age populations at 930–865 Ma, 1850–1200 Ma and 2650–2400 Ma. Detrital zircon grains from Mayuan schist samples at Jianning generally lack core-rim structures and yield three main age populations at 860–736 Ma, 1835–1775 Ma and 2720–2500 Ma. Metamorphic ages of ca. 860 Ma and ca. 435 Ma for the Wanyuan paragneiss along with the youngest detrital zircon constrain the depositional age of the protolith to ca. 865–860 Ma, whereas the Mayuan Group is younger and probably deposited after ca. 736 Ma. Characteristics of detrital zircon age populations along with regional geological data suggest accumulation of the Wanyuan Group in a convergent and/or collisional setting. Metamorphism and a possible subduction -collision process within the Cathaysia Block at around 860 Ma suggest it was not a unified block in early Neoproterozoic. The growth of ca. 440 Ma metamorphic rims is likely related to granitic magmatism, such as that exposed in the Lichuan region. The sparse evidence for early Neoproterozoic metamorphism likely reflects widespread overprinting by the Paleozoic tectonothermal event at around 440 Ma. Postprint

The Early Mesozoic tectonic and magmatic events in South China are considered to represent intracontinental orogeny, although the mechanism and geodynamic setting remain debated. Here we report zircon U–Pb geochronology, Hf isotopes and whole-rock geochemistry from four granitic plutons in the Nanling and Yunkai domains. The zircon data define seven groups of weighted mean 206 Pb/ 238 U ages as 218 ± 2, 222 ± 4, 225 ± 3, 227 ± 3, 221 ± 2, 224 ± 3 and 231 ± 3 Ma, representing the magmatic crystallization ages. These intrusions are characterized by a peraluminous nature, with high A/CNK values (>1.1), negative Eu, Ba, Sr, Nb and Ti anomalies, and enrichment in LREE, Rb, Th, U and Pb. Zircon grains from all the samples show variably negative e Hf ( t ) values (−3.8 to −18.6) with two-stage Hf model ages clustered in the range 1.4–2.5 Ga. Our data indicate that the Early Mesozoic granitic magmas were generated by the partial melting of crustal rocks with insignificant input of mantle materials. In conjunction with other geological evidence, we suggest that Triassic intracontinental deformation was triggered by far-field stress propagation from the plate boundary of South China. Supplementary materials: U–Pb geochronological data, zircon Lu–Hf isotopic compositions, major and trace element data, and 40 Ar/ 39 Ar ages are available at https://doi.org/10.6084/m9.figshare.c.3672838.

The Yangtze and Cathaysia blocks in South China are separated by the ca. 1500 km long Jiangnan Orogen. The Lianyunshan complex, located in the central segment of Jiangnan Orogen, includes wide exposures of late Mesozoic granites. Here we report geological, geochronological and geochemical data from the Lianyunshan late Mesozoic granites and their Neoproterozoic host rocks belonging to the Lengjiaxi Group. Detrital zircon U–Pb ages reveal a single prominent peak at ca. 840 Ma in the metamorphosed and deformed Lengjiaxi Group samples. Ten of the youngest zircon grains in these rocks have a weighted mean age of 828.8 ± 7.1 Ma, which is tentatively interpreted as the maximum depositional age of the Lengjiaxi Group. Two stages of late Mesozoic S-type granites are dated at ca. 150 Ma and ca. 140 Ma from the Lianyunshan domain. From early to late, these rocks show decreasing MgO, CaO, Fe2O3T, TiO2 contents and increasing SiO2, K2O, Eu/Eu*, Rb/Sr ratios and differentiation index, suggesting continuous magmatic evolution dominated by fractional crystallization. The eHf(t) values of zircons with late Mesozoic ages are all negative, with their two-stage model ages mainly ranging from 1.9 to 1.4 Ga, which is significantly different from the model age of the host rocks belonging to the Lengjiaxi Group. These results indicate that the late Mesozoic granites were mainly derived from the partial melting of Paleo-Mesoproterozoic basement rocks that are older than Lengjiaxi Group. Major and trace element features suggest that the protoliths of these early stage granites in Lianyunshan are probably mixed greywacke and shale. The arc-like trace elements signature of all the late Mesozoic granites were possibly inherited through crustal contamination during the magma genesis caused by slab rollback associated with Paleo-Pacific subduction during 150- to 140 Ma beneath the central Jiangnan belt.

International audience; The South China Block was built up by the assembly of the Yangtze and Cathaysia blocks along the Neoproterozoic Jiangnan Orogenic Belt. The timing of the Jiangnan Orogeny remains controversial. The widespread orogeny–related Neoproterozoic angular unconformity that separates the underlying folded Sibao (ca.1000–820 Ma) and overlying Danzhou (ca.800–720 Ma) Groups was investigated. Six sedimentary samples, below and above the unconformity in three distal localities (Fanjingshan, Madiyi, and Sibao) yield detrital zircon with UPb ages ranging from 779 ± 16 Ma to 3006 ± 36 Ma, with a prominent peak at ca. 852 Ma. The youngest ages of 832 ± 11 Ma and 779 ± 16 Ma are revealed for the underlying Sibao and overlying Danzhou Groups, respectively. The detrital zircon UPb age relative probability plot of the Jiangnan Orogen matches well with those of the Yangtze and Cathaysia blocks since ca. 865 Ma. Integrating geological, geochemical and geochronological results, we suggest that the Paleo–South China Ocean began to subduct under the Yangtze block at ca. 1000 Ma, and was partly closed at ca. 865 Ma. Afterwards, the Yangtze and Cathaysia blocks initially collide at 865 Ma, forming the Jiangnan Orogen. This collision resulted in not only the folding of the Sibao Group, but also sediment deposition in a syn-collisional setting, which makes the upper part of the Sibao Group. The youngest S-type granite dated at ca. 820 Ma that intruded in the Sibao Group marks the late stage of the Jiangnan Orogeny.

The link between two tectono-magmatic events during Early and Late Mesozoic periods in the Nanling Belt of South China remains debated. Here we present zircon U–Pb geochronology, Hf isotopes and whole-rock geochemistry of granitic intrusions from Zhuguangshan in the Nanling Belt. The zircon data exhibit two magmatic episodes with 206Pb/238U ages of ca. 230 Ma and 150 Ma, representing the Indosinian (Early–Middle Triassic period) and Early Yanshanian (Jurassic–Cretaceous period) events, respectively. The Indosinian granites are characterized by strongly peraluminous nature with high A/CNK values (> 1.1), whereas the Early Yanshanian granites are weakly peraluminous (average A/CNK value of 1.06). Although the Early Yanshanian granites bear higher HREE contents and lower LREE/HREE ratios, the two-phase granites show enrichment in LREE, Rb, Th, U and Pb, depletion in Eu and negative Ba, Sr, Nb and Ti anomalies. All samples show variably negative eHf(t) values (− 5 to − 16) with two-stage Hf model ages clustered around 1.8–2.1 Ga. Our data indicate that the two-phase granitic magmas were generated from the partial melting of early Paleoproterozoic basement rocks with no input of mantle material. Combined with other geological evidence, we infer that the Indosinian tectono-magmatic event was closely related to intracontinental orogeny triggered by collisions along the boundaries of South China Craton, in relation to processes associated with the E–W trending Tethys tectonic domain. We envisage that the Early Yanshanian event might be a response to the back-arc extension of NW-directed paleo-Pacific plate subduction. The Nanling Belt is a critical zone that records the transformation from Tethys to paleo-Pacific tectonic regimes.

A paper titled as “Retrograde garnet amphibolite from eclogite of the Zhejiang Longyou area: New evidence of the Caledonian orogenic event in the Cathaysia block” was recently published in Chinese Science Bulletin (Chen et al., 2015). However, the petrographic features and mineral compositions that authors provided cannot demonstrate that high-pressure or ultra-high pressure metamorphism occurred in the area in Early Paleozoic. Moreover, this conclusion is inconsistent with regional geological background. Combined with our field survey and petrographic observations, it can be inferred that this garnet amphibolite did not experience eclogite-facies metamorphism, and cannot be taken as evidence for the Caledonian collisional orogeny.

The Chinese Central Tianshan constitutes the centric and vital component of the Tianshan orogen, it contains important information for understanding the accretionary orogeny of the Central Asian Orogenic Belt (CAOB). To better constrain the Paleozoic evolution of the Chinese Central Tianshan, we present new field observations, fabric analyses, zircon U–Pb ages, zircon Lu–Hf isotopic and whole rock geochemical data of mafic, intermediate and felsic intrusive rocks in the Baluntai area, Chinese Central Tianshan. Field-scale and microscopic structural patterns of the intrusive rocks reveal that the early Paleozoic gabbro-diorite intrusions underwent multistage structural reworking, and generally exhibit gently south- or north-dipping foliations and microscopic kinematic fabrics indicating top-to-the-north shearing. These ductilely deformed intrusive rocks were intruded by granitic sills or dikes that are generally sub-parallel or with low angle to the main foliations of the host rocks. Gentle foliations and top-to-the-north kinematics can be rarely noticed within the granitic intrusions. At the sites close to the Baluntai Fault, locally intense mylonitization occurred in the felsic intrusions and deformed mafic-intermediate ones, where earlier shallow foliations were completely or partially transformed to steep ones bearing sub-horizontal stretching lineations, and asymmetric kinematic indicators suggest dextral shearing. Zircon LA-ICP-MS U–Pb datings constrain the emplacement ages of the gabbroic and dioritic intrusive rocks at 452–420 Ma, and the crystallization age of one mylonitic K-granite at 417 Ma. Two samples of granitic sill contain plenty of zircons inherited from the host gabbroic and dioritic rocks, and a few such zircons have dark rims probably formed during granitic injection, dating on these rims roughly constrains the crystallization ages of the felsic sills at ca. 370–360 Ma. The eHf(t) values of a gabbro (420 Ma), two diorite samples (425 and 445 Ma) and a mylonitic granite (417 Ma) vary from −15.45 to −2.06, corresponding to two-stage crustal model ages (TDM)C ranging from ∼2.4 Ga to ∼1.5 Ga, suggesting variable degrees of involvement of the Proterozoic crustal basement and the juvenile mantle components during the early Paleozoic magmatic generation. The geochemical data of the mafic-intermediate plutons exhibit features of magmatic rocks formed in continental arcs. The mylonitic granite and one undeformed granite resemble A-type granite in terms of geochemical features, suggesting that these granites were produced in a post-collisional/extensional environment. Considering the previously published data, the early Paleozoic arc-type magmatic rocks within the Chinese Central Tianshan likely resulted from the southward subduction of an oceanic basin located to the north, and ceased progressively during 420–400 Ma. The amalgmation between Chinese Central Tianshan and Tarim most likely completed at ca. 360 Ma following the closure of the South Tianshan back-arc basin. This event reworked the Chinese Central Tianshan arc and formed the top-to-the-north kinematics. Thereafter, the Chinese Central Tianshan was affected by the early Permian dextral strike-slip faulting due to the regional large-scale transcurrent tectonics and overprinted by the Permian mafic magmatism.

In view of the recent issue proposed by some researchers that “the garnet amphibolite in Longyou county of Zhejiang was retrograded from Caledonian collision-related eclogite”. Based on detailed field geological investigation, we carried out a systematic study including petrography, mineral chemistry, zircon geochronology and bulk rock geochemistry. Our results indicate that, the relatively small amounts of plagioclase which only found in interior of garnet or clinopyroxene metacryst are anorthite, while plagioclase that largely distribute in the outer part of garnet or clinopyroxene metacryst are andesine and labradorite (with their An value within 44–66), and no sodium-rich plagioclase (albite or oligoclase) which imply omphacite decomposition structure are found. The CL images of zircon exhibit obvious core-rim structure. U-Pb dating results indicate that the weighted average age of the zircon core part is 879±11 Ma, with Th/U ratio values ranging from 0.20–1.23 which suggest their magmatic origin; while the age of the rim is 446±5 Ma, and lots of their corresponding Th/U ratio show low values ( £ 0.1), suggesting their metamorphic origin. Moreover, the bulk rock geochemistry feature of garnet amphibolite suggest that its protolith is basic (the SiO2 content within 46.8%–48.2%), and its trace element exhibit E-MORB geochemical affinity. Based on the effective bulk rock composition and EPMA analysis results, as well as the mineral association we found, the P-T pseudosection for Longyou garnet amphibolite was worked out. And this figure reveals that the Longyou garnet amphibolite at least experienced three stages of metamorphism: the prograde metamorphism stage with P-T condition of 0.67–0.75 GPa/685–719°C; the peak-metamorphism with P-T condition of 0.91–0.97 GPa/766–782°C; and the retrograde metamorphism stage with P-T condition of ~0.68 GPa/~767°C (by traditional P-T thermobarometer, we also get a P-T condition of 0.66–0.67 GPa/720–740°C for retrograde metamorphism stage). Whichever stage, its pressure is medium-pressure but not high- pressure. In combination with regional geological setting, we prefer the following genetic model for Longyou garnet amphibolite: the paleo-South China Ocean subduction under Yantze plate in Neoproterozoic→trigger back-arc extension→mantle-derived magma upwelling and forming E-MORB type basic rocks in Neoproterozoic→medium to high-grade metamorphism in Silurian.

The Jiangnan Orogen and Cathaysia Block constitute integral components in the geological framework of the South China Craton. However, the tectonic attributes of these two regions remain controversial. In this study we present LA–ICP–MS zircon U–Pb ages, Lu–Hf isotopes, and major and trace elements data from a suite of clastic rocks. Two hundred and forty seven zircon U–Pb ages obtained from the Neoproterozoic meta-sandstones in western Jiangnan Orogen define three major age populations: 2564–2395 Ma, 2068–1849 Ma and 963–730 Ma, corresponding to the early Paleoproterozoic crustal growth, amalgamation of the supercontinent Columbia and tectonics associated with Rodinia. Two hundred and forty three zircon U–Pb age data from Cambrian and Ordovician sandstones in the western Cathaysia yield five age populations: 2626–2392 Ma, 2050–1518 Ma, 1173–904 Ma, 857–708 Ma and 630–502 Ma, which can be correlated to the Neoarchean–early Paleoproterozoic continental growth, the tectono-thermal events associated with the Columbia supercontinent, the assembly and breakup of Rodinia, as well as the Pan-African event. The 630–502 Ma population correlates with the assembly of Gondwana supercontinent during late Neoproterozoic to early Paleozoic, although direct geological evidence for this event has not yet been reported from this region. These results suggest that the western Jiangnan belt and western Cathaysia Block have distinct crustal evolution histories albeit with close affinities. The REE geochemisty and Lu–Hf isotope data also indicate that the provenances of the Neoproterozoic and early Paleozoic detritus in western Jiangnan belt and western Cathaysia are mostly composed of reworked crustal materials. The metamorphic rims of zircon grains with core–rim structures yield ages of 912–891 Ma and 853–835 Ma, suggesting two phases of metamorphic events during Neoproterozoic in the source areas. These two events are likely associated with the tectonics related to the collision of Yangtze and Cathaysia blocks in the western and eastern segments, respectively.

Analytical procedures, representative field photographs and photomicrographs of samples, U–Pb geochronological data, zircon Lu–Hf isotopic compositions, bulk rock major and trace element data.

International audience; Modes of magma emplacement may provide key information on geodynamic-tectonic settings of magmatism, when the threshold of magma volume and duration of emplacement process is crossed, brittle/ductile crustal deformation behavior, and volumes and rates of magma transfer in the crust. The majority of upper-crustal granitic intrusions are incrementally emplaced as laccoliths or sills, while midcrustal or deeper-level granitic intrusions appear to be predominantly emplaced as sills or lopoliths, but relatively few examples have been studied. We present a case study on the Jurassic Qitianling pluton from South China, which was constructed in the upper part of the middle crust (at a depth of ~10-15 km). To characterize its emplacement mechanism and evolution, we have combined field and microscopic observations, Anisotropy of Magnetic Susceptibility measurements and Bouguer gravity anomaly modeling. The main findings are (1) the generally undeformed granite-country rock contacts with a narrow thermal aureole, (2) irregularly wavy and gradational contacts between the main granite facies, (3) dominant subhorizontal magnetic fabrics in the granites with a scattered magnetic foliation, (4) rare occurrence of dykes, and (5) a subcircular surface and lopolith-like pluton geometry. Accordingly, we suggest that the Qitianling pluton forms an ~25-km wide and ~5-km thick lopolith that was incrementally emplaced during a period of tectonic quiescence, most likely by under-accretion of multiple magma sheets deflected from magma pulses that ascended through pipe-like channels. The mineralogical and compositional variation of the pluton may be the result of in situ fractionation, fractionation at deeper crustal level, or variation in source-derived melt compositions.

International audience; We conducted a paleomagnetic study on the Early Permian volcanic and sedimentary rocks, and the Neoproterozoic mafic dikes in the Yili Block, NW China. Magnetite and hematite were proven to be the principal magnetic remanence carriers. Demagnetizations revealed stable characteristic remanence magnetizations with a sole reversed magnetic polarity. The magnetic remanence of only the Early Permian strata turned out to be primary based on positive fold tests; meanwhile, the magnetic remanence age of the mafic dikes is ambiguous. Accordingly, the first Early Permian paleomagnetic pole for the Yili Block is calculated at λ = 81.5°N, φ = 256.5°E, N = 11, and A95 = 10.9°. Comparisons of this new pole with published ones from the Yili, Tarim, and South Junggar blocks provide new quantitative constraints on late Paleozoic kinematic evolution of the SW Central Asian Orogenic Belt: (1) Between the Yili and Tarim blocks, significant relative movement took place along major strike‐slip faults during the Late Carboniferous to Early Permian (580 ± 290 km) and the Early to Late Permian (585 ± 340 km), and the displacement rate increased from the Late Carboniferous to Early Permian (~19.3 ± 9.7 mm/yr) to the Early to Late Permian (~29.3 ± 17.0 mm/yr); (2) a significant relative rotation of 28.3° ± 18.3° in the Late Permian, and a lateral displacement of 630 ± 295 km after the Late Permian occurred between the Yili and South Junggar blocks. The significant strike‐slip movements played an important role in the formation of the Central Asian Orogenic Belt and should be considered with great attention in tectonic and paleogeographic reconstructions.

The late Early Paleozoic and Early Mesozoic tectonic events in South China have been central to the debate over plate subduction versus intracontinental orogeny. Here we present zircon U–Pb geochronology, Hf isotopes and whole-rock geochemistry of six representative granitic plutons from South China. The zircon data show two groups with 206Pb/238U ages of ca. 430 Ma and 225 Ma, representing the crystallization ages of magma. The six plutons investigated in this study are characterized by peraluminous nature with high A/CNK values (> 1.1) and the presence of aluminous minerals like muscovite. They exhibit enrichment in LREE, depletion in Eu, negative Ba, Sr, Nb and Ti anomalies and enrichment in Rb, Th, U and Pb. All samples show variably negative eHf(t) values (− 2 to − 16) with two-stage Hf model ages clustered around 1.5–1.8 Ga. These data indicate that both the Early Paleozoic and Early Mesozoic granitic magmas were generated by the partial melting of early-middle Paleoproterozoic basement rocks without significant input of mantle material. The distribution of all the plutons with ages around 430 Ma and 225 Ma are unrelated to subduction tectonic regime. Combining with other geological evidence, our study suggests that the tectono-magmatic events during late Early Paleozoic and Early Mesozoic were largely related to intracontinental orogeny triggered by interactions between the Yangtze and Cathaysia continental blocks. The far-field stress propagation derived from the South China plate boundary might have played a crucial role as the primary cause of the stress field within the continental interior of the South China Craton.

The geodynamic framework of the South China Craton in the Early Paleozoic and Early Mesozoic has been modeled as developing through either oceanic convergence or intracontinental settings. On the basis of an integrated structural, geochemical, zircon U-Pb and Hf isotopic, and mica 40Ar/39Ar geochronologic study we establish that an intracontinental setting is currently the best fit for the available data. Our results suggest that widespread tectonomagmatic activity involving granite emplacement and mylonitic deformation occurred during two distinct stages: ~435–415 Ma and ~230–210 Ma. The coeval nature of emplacement of the plutons and their ductile deformation is corroborated by the subparallel orientation of the mylonitic foliation along the pluton margins, gneissose foliation in the middle part of pluton, the magmatic foliation within the plutons, and the schistosity in the surrounding metamorphosed country rocks. The 435–415 Ma granitoids exhibit peraluminous, high-K characteristics, and zircons show negative eHf(t) values (average −6.2, n = 66), and Paleoproterozoic two-stage model ages of circa 2.21–1.64 Ga (average 1.84 Ga). The data suggest that the Early Paleozoic plutons were derived from the partial melting of the Paleoproterozoic basement of the Cathaysia Block. The 230–210 Ma granites are potassic and have zircons with eHf(t) values of −2.8–−8.7 (average −5.4, n = 62), corresponding to TDM2 ages ranging from 2.0 to 1.44 Ga (average 1.64 Ga), suggesting that the Early Mesozoic partial melts in Cathaysia were also derived from basement. The geochemical distinction between the two phases of granites traces continental crustal evolution with time, with the Early Mesozoic crust enriched in potassium, silicon, and aluminum, but deficient in calcium, relative to the Paleozoic crust. Kinematical investigations provide evidence for an early-stage ductile deformation with a doubly vergent thrusting pattern dated at 433 ± 1 to 428 ± 1 Ma (40Ar/39Ar furnace step-heating pseudoplateau ages obtained on muscovite and biotite from mylonite and deformed granite) and a late-stage strike-slip movement with sinistral sense of ductile shearing at 232 ± 1 to 234 ± 1 Ma (40Ar/39Ar furnace step-heating pseudoplateau ages) along an E-W direction. The geological, geochemical, and isotopic signatures likely reflect far-field effects in response to continental assembly events at these times.

The multiphase emplacements of granitoids and well-developed depositional sequences from Neoproterozoic to Mesozoic are exposed widely in the Wugongshan domain of South China provide important keys for the reconstruction of the pre-Mesozoic tectonic evolution of the Cathaysia Block. Here we present the results from geological investigations, detrital zircon U–Pb geochronology, in situ Hf-isotope and REE composition of the Ordovician meta-sandstones, together with the U–Pb age data on a Mesozoic pluton with an attempt to evaluate the petrogenesis and crustal evolution history. A group of 276 detrital zircon U–Pb ages are reported from four meta-sandstones which show five major age populations: 2630–2350 Ma with a peak of 2440 Ma, 1890–1540 Ma (peak of 1680 Ma), 1120–870 Ma (peak of 980 Ma), 810–700 Ma (peak of 760 Ma) and 660–510 Ma (peak of 550 Ma). Among these, the most prominent age at 980 Ma fits well with the collisional event of Yangtze and Cathaysia Blocks. The second prominent age at 760 Ma correlates with a breakup of Rodinia, and the third one at 1680 Ma corresponds to the initial breakup of Columbia. For the fourth (peak of 2440 Ma) and fifth (peak of 550 Ma) ages, no corresponding magmatic rocks are exposed in the study area or in the adjacent regions, although the age populations broadly correspond to the global continental growth in the early Paleoproterozoic and the latest Neoproterozoic ‘Pan-African’ orogeny. We obtained 132 in situ Hf isotope compositions, among which 98 show negative eHf(t) values (− 36.88 to − 0.3) with two-stage model ages (T DM2 ) of 3.5–1.7 Ga (peak of 2.2 Ga), and 34 display positive eHf(t) values (+ 0.3 to + 9.89) with crystallization ages of 1.5–1.1 Ga (peak of 1.4 Ga). Zircons from two Mesozoic granitic samples yield rather similar late Jurassic ages of 158.1 ± 2.1 Ma and 154.0 ± 3.9 Ma. All the corresponding eHf(t) values of zircons are negative (− 24.2 to − 4.2) and the Hf two-stage model ages range from 1.5 to 3.0 Ga with a peak of 1.68 Ga. Combined with previous age data on 120 Ma massive granitoids and 230 Ma on ductile sheared plutons, we consider that the magmatism in the Wugong complex started from the late Triassic, and reached a peak in the late Jurassic, but was gradually weakened since the early Cretaceous (130 Ma) and culminated at 120 Ma. Almost all the Wugongshan granitic plutons were derived from the partial melting of Mesoproterozoic crustal material, with little mantle components. We also discuss the provenance of the metasedimentary rocks and pre-Mesozoic crustal evolution of Cathaysia.

The Jiangnan orogenic belt in South China defines a subduction-collisional zone between the Yangtze and the Cathaysia blocks. The eastern part of this belt comprises the oceanic Huaiyu terrane, the northeast Jiangxi suture zone and the continental Jiuling terrane. We report zircon U–Pb and Hf isotope data and whole rock geochemistry on the arc magmatic rocks of andesite and basalt occurring as olistostromal blocks, as well as conglomerate in the Dengshan Group above the unconformity between cover sequence and the volcanic arc units. The andesites yield weighted mean ages of 864 Ma, 868 and 871 Ma, whereas the detrital zircons from the conglomerate yield a major age population of 863–810 Ma (peak of 833 Ma), with two minor ones of 1120–940 Ma (peak at 960 Ma) and 1780–1560 Ma (1670 Ma). A post-ca. 810 Ma depositional age is thus suggested for the Dengshan Group. The influx of olistostromal deposits into the Dengshan Group must post-date the youngest detrital zircon age of 810 Ma and is possibly related to the widespread Nanhua rifting associated with the breakup of Rodinia. Furthermore, the age distribution of detrital zircons from the phyllite associated with the arc units compared to its depositional age also suggest a convergent setting, and those from the conglomerate are plotted into a similar field. The andesite and basaltic trachyandesite have LREE enriched patterns, with minor negative Eu anomaly, and negative Nb, Ta, Cs and Ti anomalies. However, the basalt displays only minor LREE enrichment, with no Eu anomaly, and almost flat spidergram trace element patterns, except for a minor positive Sr, Ba and Ti anomaly and negative Rb anomaly. The andesite and basaltic trachyandesite are all plotted in the field of volcanic arc, suggesting an arc setting. The basalt is plotted between EMROB and volcanic arc domains, suggesting magma generation from metasomatised sub-arc sources with subducted oceanic components. The Hf isotopic data on zircons from the andesite yield positive ɛ Hf( t ) values of 2.79–15.51 and late Mesoproterozoic model ages, suggesting that the Neoproterozoic arc sources include reworking of subducted late Mesoproterozoic materials. Our results show that the amalgamation of the Yangtze and Cathaysia blocks in the eastern part occurred at some time between ca. 864 Ma and ca. 810 Ma.

We present U–Pb–Hf isotopic and elemental data for granitoid intrusions formed during the early Permian in Eastern Tianshan (eastern part of Chinese Tianshan), with the aim of deciphering their magma sources and geodynamic evolution. These granitoids were formed at ca. 300–270 Ma and generally exhibit alkali-calcic to alkali compositions, and metaluminous and high-K calc-alkaline to shoshonitic characteristics. Commonly, steep REE patterns with significant enrichment of LREE relative to HREE showing (La/Yb)CN (4.4–43), distinctive negative Eu anomalies and depletion of Nb, Ta and Ti are noteworthy features of these granitoids, akin to the typical I-type granitoids implying an influx of mantle-derived magma. The tectonic setting of these granitoids in combination with the regional geology, suggests that the granitoids were generated in a post-collisional setting. The eHf(t) values from − 10 to + 14 (with four peaks at ca. − 4, + 5, + 8.5 and + 12) and TDMC model ages (with four populations at ca. 1500, 970, 720 and 500 Ma) imply that the reworking of early Mesoproterozoic ancient crust related to Columbia and Neoproterozoic crust associated with Rodinia along with the early Permian input of juvenile material were variably sourced during the generation of the magmas studied herein. During the post-collisional process, the slab breakoff played a key role in the genesis of the granitoids and involved the reworking of ancient crust and mantle-derived sources, consistent with the Hf isotopic compositions.

The North Yili Block is one of the major continental constituents of the Central Asian Orogenic Belt (CAOB), study of its basement evolution and tectonic origin is essential for the understanding of the accretionary history of the CAOB and the reconstruction of global supercontinent as well. We conducted field geological, geochronological and geochemical investigations on the mafic dikes intruding in the highly deformed Proterozoic carbonate in the North Yili Block, NW Chinese Tianshan. Zircon U–Pb dating results suggest that the gabbro and gabbroic diorite dikes and associated granitic vein formed in 776–778 Ma. Element and isotope geochemical data reveal that these intrusive rocks derived from an OIB-like mantle source, and were variably influenced by fraction crystallization and important crustal contamination, thus, a continental rifting setting is proposed for these dikes. Our new data provide the first evidence for a Neoproterozoic continental intra-plate magmatism occurred in the North Yili Block, this event can be linked with the coeval continental rifting-related magmatism in northern Tarim and in other microcontinents within the SW CAOB (e.g., Central Kazakhstan, Kyrgyzstan Middle Tianshan). Based on the comparison on the Neoproterozoic to early Paleozoic stratigraphic sequences between the North Yili and Tarim blocks, it is suggested that the North Yili Block most likely originated from the Tarim Block, and is potentially one additional constituent member of the Rodinia supercontinent.

We report detrital zircon ages for Precambrian and early Palaeozoic metasediments from the Tianshan orogen in Kyrgyzstan, an important component of the Central Asian Orogenic Belt and compare these with published ages from the Chinese Tianshan and the Tarim craton. These data provide information on possible source terrains and suggest that Precambrian basement is widespread in the Tianshan and may, at least in part, represent continental fragments rifted off the Tarim craton during the early history of the Central Asian Orogenic Belt. Distinct differences in the Precambrian zircon age distribution between the North and Middle Tianshan of Kyrgyzstan support earlier ideas that these two terranes had different crustal histories prior to their amalgamation in the early Palaeozoic. We envisage an archipelago-type scenario for the Palaeo-Asian Ocean south of the Siberian craton in the late Neoproterozoic to early Palaeozoic in which numerous island arcs and Precambrian crustal fragments derived from Tarim drifted northwards (in present coordinates) and were amalgamated and tectonically stacked together during several ocean closure and accretion–collision events. This is surprisingly similar to what has been envisaged for the evolution of Indonesia where Mesozoic rifting of fragments from the Australian margin was followed by Cretaceous collisions and Cenozoic collision of Australia with the SE Asian margin. In both Central Asia and Indonesia continental crust has arrived in the region in multiple episodes and has been fragmented and juxtaposed by subduction-related processes. Continental growth during this process was minimal.

The tectonic evolution of the Chinese Tianshan Belt which is located in the southern margin of the Central Asian Orogenic Belt remains controversial. In order to reveal the evolutionary history of this belt, we investigate metasedimentary rocks from the Tianshanmiao of Harlik domain and Xingxingxia area of central Tianshan domain in this study. The Permian siltstones from Xingxingxia contain six zircon populations with ages peak at 280, 815 and 910, 1590, 1855 and 2340 Ma, suggesting a diverse provenance. The 2544–2294 Ma ages correlate with the generation of continental nuclei in Tarim. The tectonothermal events during 1855, 1590, 910 and 815 Ma may correspond to the assembly and breakup of the Columbia and Rodinia supercontinents, respectively. Similar Precambrian age spectra and “event signature” curves suggest that the central Tianshan was most likely a part of the Tarim block in the Proterozoic. The detrital zircon U–Pb ages of Ordovician meta-greywackes from the Tianshanmiao sequence reveal six zircon populations with peaks at 460, 933, 1382, 1850, 2000 and 2462 Ma, among which the zircons with dominant age peaks (460 Ma and 930 Ma, more than 70%) are euhedral, low sphericity and exhibit clear oscillatory zoning, suggesting local derivation from the proximal Ordovician and Neoproterozoic granitoids. The range of eHf(t) values (−5.4 to +21) of zircon grains from Ordovician rocks suggests that these were derived from depleted mantle or through partial melting of juvenile crust, similar to the case for the Early Paleozoic magmatism in Chinese Altai. Our detrital zircon data suggest that the provenance of the Harlik was neither the Tarim nor the Junggar, and instead, we propose a connection with the Chinese Altai-Tuva–Mongol Arc along the southern margin of the Siberia craton at ∼500 Ma. The Harlik domain drifted southward and then collided with the central Tianshan in the Carboniferous-Permian as a result of the closure of Paleo-Tianshan Ocean.

The Central Asian Orogenic Belt (CAOB) is one of the largest accretionary orogens in the world. It was formed mainly by amalgamation of island arcs, accretionary wedges and microcontinents. Revealing the origins of the Precambrian continental blocks is essential for the understanding of the tectonic framework and geodynamic evolution of the CAOB. In this paper we present detrital zircon U–Pb ages of Precambrian meta-sedimentary rocks and late Paleozoic undeformed sandstone from the northern Yili Block, Chinese North Tianshan, in order to better understand the regional tectonic evolution. Two mica-schist samples from the Wenquan Metamorphic Complex (WMC) show similar zircon age distribution patterns with peaks at ∼0.43 Ga, ∼0.54 Ga, ∼0.65–0.68 Ga, ∼0.74–0.79 Ga, ∼0.89–0.92 Ga, ∼1.3–1.55 Ga and ∼1.69–1.70 Ga, respectively. Minor age peaks of ∼1.1 and ∼2.2 Ga are also separately recognized in individual samples. A phyllite from the Mesoproterozoic Changcheng System yielded detrital zircon ages mainly ranging from 855 to ∼1500 Ma with a single peak at ∼906 Ma. According to the analysis of age data and corresponding CL images of the dated zircon grains, protoliths of the mica-schists and phyllite should have deposited later than 645 Ma and 850 Ma, respectively, and were subjected to medium- to low-grade metamorphism during mid-late Silurian time. The good agreement between the age patterns of the meta-sediments and those of the nearby granitic and high-grade metamorphic rocks of the WMC indicates that the detrital zircon grains were mainly derived from the local metamorphic/crystalline basement. Occurrence of much older zircons (∼1.0–2.2 Ga) in the mica-schists and absence of such zircon populations in the phyllite suggest that (1) the protoliths of the mica-schists and phyllite had distinct sources and were deposited at different time, and (2) Mesoproterozoic to Paleoproterozoic rocks probably existed in the northern Yili Block. Three undeformed sandstone samples yielded consistent single age peak at ∼368–376 Ma and contain only a few Proterozoic detrital zircon grains. The peak age is in agreement with ages of neighboring late Paleozoic arc magmatic rocks in the Chinese North Tianshan. Thus, the sandstone was probably deposited during latest Devonian to earliest Carboniferous time in a forearc or interarc basin, around which Proterozoic basement was not exposed or completely isolated. A comparison between the zircon age patterns of the northern Yili Block and the surrounding cratons and microcontinents leads us to conclude that (1) the northern Yili Block had a Proterozoic basement similar to that of the Chinese Central Tianshan and Kyrgyz North Tianshan, and (2) these microcontinental blocks share the same origin as the Tarim Craton, but are distinguished from the Siberian Craton.

International audience; Highlights:• The Neoproterozoic Jiangnan collision of Cathaysia and Yangtze is responsible for the formation of the South China Block (SCB)• During the Early Paleozoic, the SCB was welded to the North China block along the Qinling belt, and also experienced an intracontinental orogeny that partly reworked the Jiangnan belt.• During the Middle Triassic, the SCB was welded to Indochina, the Qinling belt was reworked by N-directed intracontinental subduction.• The Xuefengshan belt is also a Middle Triassic intracontinental orogen.

International audience; Debate on whether the Early Paleozoic tectono-magmatic event in South China is related to a subduction–collision or an intracontinental orogen has been lasted for decades within the geoscience community. This study deals with LA-ICP-MS zircon U–Pb ages, whole-rock chemistry, rare earth elements, trace elements and Hf isotopes from granitoid samples collected in the Yunkai domain in order to better constrain the Early Paleozoic tectonic evolution of the South China Block. The weighted mean 206Pb/238U ages for eight samples range from 426 Ma to 443 Ma, representing the crystallization ages of the magma. Fourteen samples were analyzed for geochemistry, all of which are characterized by a peraluminous signature with A/CNK values greater than 1.0. The REE geochemistry reveals enrichment in light rare earth element. LREE/HREE values range from 2.81 to 30.36 and (La/Yb)N vary from 1.23 to 55.14 (mean of 14 analyses is 14.69). All the samples exhibit distinct negative Ba, Sr and Nb anomalies and enrichment in Rb, Th, U and Pb. Hf isotopic analyses indicate negative εHf (t) values mainly ranging from − 3 to − 12, corresponding to two model age distributing from 1637 Ma to 2208 Ma. The geochemical analyses indicate that the Silurian granitic magmas in the Yunkai domain were derived from partial melting of crustal materials with little or no input of mantle source. These new data support the intracontinental subduction model already proposed to account for the Early Paleozoic tectonic, metamorphic and magmatic event of South China.

International audience; The Xu-Huai thrust-and-fold belt, located in the southeastern margin of the North China Block, consists mainly of thrust and folded pre-Mesozoic strata. Its geodynamic evolution and tectonic setting are topics of long debate. This paper provides new evidence from geological mapping, structural analysis, and making balance cross-sections, with restoration of cross-sections. Results suggest that this belt was subjected to two-phase deformation, including an early-phase regional-scale NW-ward thrust and fold, and a late-phase extension followed by the emplacement of dioritic, monzodioritic porphyrites dated at 131–135 Ma and locally strike-slip shearing. According to the mapping, field observations and drill-hole data, three structural units were distinguished, namely, (1) the pre-Neoproterozoic crystalline basement in the eastern segment, (2) the nappe unit or the thrust-and-fold zone in the central segment, which is composed of Neoproterozoic to Ordovician carbonate rocks and Carboniferous-Permian coal-bearing rocks, about 2600 m thick, and (3) the western frontal zone. A major decollement fault has also been identified in the base of the nappe unit, on which dozen-meter to km-scale thrust-and-fold bodies were commonly developed. All pre-Mesozoic depositional sequences were involved into a widespread thrust and fold event. Six uncompetent-rock layers with biostratigraphic ages (Nanjing University, 1996) have been recognized, and each uncompetent-rock layer occurred mainly in the top of the footwall, playing an important role in the development of the Xu-Huai thrust-and-fold belt. Geometry of the major decollement fault suggests that the nappe unit of this belt was rooted in its eastern side, near the Tan-Lu Fault Zone. Two geological cross-sections were chosen for structural balancing and restoration. From the balanced cross-sections, ramp-flat and imbricated faults as well as fault-related folds were identified. A shortening of 20.6–29.6 km was obtained from restoration of balanced sections, corresponding to a shortening rate of 43.6–46.4%. This shortening deformation was likely related to the SE-ward intracontinental underthrust of the North China Block beneath the South China Block during the Mesozoic.

The Central Asian Orogenic Belt is an accretionary orogen with many distinct terranes including the Chinese Central Tianshan, whose Precambrian tectonic affinity is not yet clearly known. We present Precambrian age spectra of inherited/xenocrystic zircons from magmatic rocks in the Chinese Central Tianshan, collected from published papers. The age patterns are dominated by zircons with ages ranging from 3261 to 541 Ma. These spectra provide robust clues regarding the Precambrian affinity of the Chinese Central Tianshan. The age spectra record two major tectonothermal events, represented by salient age peaks of c . 950 and 900 Ma within the ‘Grenville Orogeny’ period, and age peaks at c . 750 and 630 Ma, synchronous with magmatic events corresponding to Rodinia break-up. These results are consistent with the hypothesis that the Chinese Central Tianshan was part of the Tarim craton during Precambrian time as well as documenting its incorporation into, and separation from the Rodinia landmass.

The early Neoproterozoic Jiangnan orogenic belt, located in the southeastern margin of the Yangtze Block, is considered to mark the suture zone between the Yangtze and Cathaysia Blocks. The eastern part of this belt consists of the Huaiyu and Jiuling terranes, separated by the NE Jiangxi fault zone which represents the back-arc marginal sea. The western part of the Jiangnan orogenic belt is characterized by the Jiangnan arc and back-arc sea. Neoproterozoic mafic–ultramafic rock suites are exposed along both the Jiangshan-Shaoxing-Pingxiang-Shuangpai and the NE Jiangxi suture zones, whereas I-, S- and A-type granites occur widely in the Jiangnan region. Here, we present new LA–ICP–MS zircon U–Pb data, Hf isotopes and whole rock geochemistry for the mafic rocks and granite from the Jiangnan orogenic belt. The N-MORB (normal mid-ocean ridge basalts) type basalts from the Nanqiao of Liuyang area in the west Jiangnan orogenic belt show low K2O contents (0.74–0.16 wt.%), belonging to tholeiitic series, and display LREE (light rare earth element) depleted REE (rare earth element) patterns, with positive Pb, Sr anomaly and minor negative Ti anomalies. The other mafic suites in the Daolinshan, Yiyang and Liuyang areas exposed in the eastern and western segments of the Jiangnan orogenic belt show distinctive geochemical signatures of volcanic arc, with zircon U–Pb ages of 863 ± 6 Ma. Most of these rocks show negative Nb, Ta, Zr, Hf and Sr anomalies and have LREE enriched REE patterns, with minor negative Eu anomaly. These features coincide with those of the arc and fore-arc rock assemblages in the eastern Huaiyu Terrane and adjacent areas. Anorogenic granites of 790 ± 5 Ma are also found in the Daolinshang area. Our Hf isotopic data further reveal that the zircons from both the dolerite and A-type granite in the Daolinshan area possess positive ɛHf(t) values, yielding latest Mesoproterozoic to early Neoproterozoic model ages. Combined with previous studies, our data confirm the existence of an arc-trench system in the Jiangnan orogenic belt at ca. 863 Ma. Therefore, we infer that the amalgamation of the Yangtze and Cathaysia Blocks in the eastern part occurred at some time after ca. 863 Ma. This was followed by breakup at ca. 790 Ma which was triggered by mantle upwelling, as evidenced by the Daolinshan A-type granite with positive ɛHf(t) values

Granitoids are the predominant geological constituents of South China and important for the understanding of the formation and evolution of continental crust. We describe field structural features of four small-scale granitic plutons and their country rocks in southern Jiangxi Province and present new zircon U-Pb and mica 40Ar/39Ar ages that are used to discuss the tectonic-magmatic evolution and thermal overprint events, that is, the tectonic rejuvenation of continental crust of the Cathaysia Block. The muscovite-bearing granite of Mashuang pluton shows sub-north-south mylonitic foliation and stretching/mineral lineation that shallowly plunges to the northeast, generally consistent with fabrics in the host rocks that are composed of widely migmatized metasediments. Zircons and muscovites yielded U-Pb and 40Ar/39Ar ages at 457 ± 4 and 199 ± 1 Ma, which are considered to represent the ages of emplacement and postmylonitic thermal overprint, respectively. The undeformed granites of Tianjiu and Junme...

The Jiangnan Orogen is considered as the trace of the collisional suture between the Yangtze and Cathaysia Blocks in South China. Here we investigate the mafic–ultramafic suites and granitoids exposed in the Yuanbaoshan area along the western segment of the Jiangnan Orogen. We present new LA-ICP-MS zircon U–Pb data, Hf isotopes and whole rock geochemistry from a suite of granite, gabbro diorite and mafic–ultramafic rocks from this area. Zircons in the mafic rocks yield a U–Pb age of 854.7 ± 5.3 Ma, whereas those from the granites show ages of 822.6 ± 5.2, 830.7 ± 5.0, 823.8 ± 5.3 and 833.0 ± 5.9 Ma. The Neoproterozoic mafic–ultramafic rocks display dominantly tholeiitic features and are characterized by negative Ba, Nb, Ta, Zr, Hf and Sr anomalies and LREE enriched patterns, with a minor negative Eu anomaly. The gabbro diorite also exhibits similar geochemical characters. The mafic suite plots in the field of volcanic arc basalt in tectonic discrimination diagrams and displays distinctive geochemical signatures of an arc setting. The zircons from these rocks show ɛHf(t) values in the range of 3.9–13.8. The granitoids in northern Guangxi are typical S-type granites with high ACNK values (1.15–1.40), and are classified as collision-related granites in tectonic discrimination diagrams. The zircons from these rocks show negative ɛHf(t) values of −18.99 to −0.84. We correlate the granitoids with the continent–continent collisional orogeny between the Yangtze and Cathaysia Blocks. Our new results suggest a ∼854 Ma volcanic arc and an 840–820 Ma collisional setting in the western segment of the Jiangnan Orogen, which is different from previous proposals of plume and bimodal magmatic settings and place the timing of assembly of the Yangtze and Cathaysia Blocks at some time ca. 850–800 Ma.

The northern part of the Yili Block, located in the northwest of the Chinese Tianshan, extends westward to joint with the Aktau-Junggar domain in Kazakhstan, and is one of the major continental constituents of the Central Asian Orogenic Belt (CAOB). The nature and tectonic significance of the basement of the continental domains are important for understanding the continental evolution and geodynamic processes of the CAOB. We investigated the Wenquan metamorphic complex (WMC) that represents the basement and metamorphosed sedimentary cover of the northern Yili Block. The WMC is mainly composed of gneissic S-type granite, migmatite associated with amphibolite, paragneiss, micaschist, quartzite, marble, and intruding leucogranitic dykes. The migmatites display banded, schlieren and ptygmatic structures containing rootless, lensoid or layered leucosome and leucocratic sills, which are indicative of in situ partial melting of the country rocks and variable degrees of melt migration. Geochemical data suggest that the protoliths of the orthogneiss and gneissic K-granite belong to peraluminous S-type granites characterized by wide range of I (Sr) values (0.68324–0.72365), low ɛ Nd ( t ) values (−1.9 to −4.4) and two-stage Nd model ages ( t MD -2: 1.56–1.82 Ga). The S-type granites might have derived from both clay-poor and clay-rich source rocks that are probably meta-sedimentary and meta-volcanic rocks in the WMC. The leucogranites show relatively narrow range of I (Sr) values (0.70273–0.70419), more negative ɛ Nd ( t ) values (−6.9 to −9.1) and more consistent t MD -2 ages (1.51–1.55 Ga). The leucosome and leucocratic sills show variable Sr and Nd isotopic compositions probably due to localized and different degree of partial melting. Our new zircon SHRIMP and LA-ICPMS U–Pb ages, together with previously published data indicate that the migmatization occurred at 926–909 Ma, the gneissic S-type granites emplaced during 919–862 Ma, and the leucogranites emplaced in the period of 909–845 Ma. Inherited old zircons were found in all dated samples and may have come from their source rocks. Association of geochronologically overlapped and genetically linked migmatites, gneissic S-type granites and leucogranitic rocks is interpreted as the results of anatexis of the upper crustal rocks during an early Neoproterozoic tectonic/metamorphic event that needs to be further studied in the northern Yili Block. Such early Neoproterozoic migmatization and S-type granitic magmatism are considered as an important episode of reworking and cratonization of the continental crust of the Yili and adjacent continental blocks in Central Asia.

A suite of Paleozoic granitoids in Central Tianshan was studied for both geochemistry and geochronology in an effort to constrain their origin and tectonic setting. We combined LA-ICP-MS dating of zircon, standard geochemical analyses and Hf-isotopic studies of zircon to develop our tectonic model. Based on our analysis, the granitoids formed in three distinctive stages: ~ 450–400 Ma, ~ 370–350 Ma and ca. 340 Ma. The first stage (450–400 Ma) granitoids exhibit metaluminous, magnesian, high-K to shoshonitic characteristics of I-type granitoids (arc-setting), that are enriched in LREE relative to HREE with high (La/Yb)CN values, show negative Eu anomaly and are depleted in Nb, Ta and Ti. This phase of granitoid emplacement was most likely related to the southward subduction of the Paleo-Tianshan Ocean beneath the Tarim block and the subsequent Central Tianshan arc. In contrast, the second stage granitoids (370–350 Ma) are distinctly different and are classified as calc-alkaline or shoshonitic plutons with a weak positive Eu anomaly. Within the second stage granitoids, it appears that the earlier (~ 365 Ma) granitoids fit within the A-type field whereas the younger (~ 352 Ma) granitoids plot within the post-collisional potassic field. These granitoids formed during collisions between Central Tianshan and the Tuha terrane that occurred along the northern margin of Central Tianshan. Lastly, the ca. 340 Ma granitoids are typical of volcanic arc granitoids again that probably formed during the northward subduction of the South Tianshan Ocean beneath the Central Tianshan landmass or the subsequent southward subduction of the residual Paleo-Tianshan Ocean. The Hf isotopic data of zircons from all the studied granitoids were pooled and yielded three prominent Hf TDMC model age populations: ca. 2400 Ma, ca. 1400 Ma and ca. 1100 Ma. The Hf-data shows a significant input of juvenile crust in addition to crustal recycling. We interpret these three phases of juvenile crustal addition to phases of global growth of continental crust (~ 2400 Ma), the addition of juvenile crust during the breakup of the Columbia supercontinent (~ 1400 Ma) and the assembly of Rodinia (~ 1100 Ma).

The protoliths of the metamorphic suite of the Chencai Group in the northeastern margin of the Cathaysia Block in South China are composed of Neoproterozoic argillaceous–arenaceous rocks of turbidite facies, marine carbonates, gabbro and basalt. Here, we present zircon U–Pb ages, Hf isotopes, and whole-rock geochemical data on migmatites and metagabbros from the Chencai Group and the surrounding hornblende gneisses. The gabbroic enclaves in the migmatites and hornblende gneiss are characterized by subduction-related geochemical characteristics, which differentiate them from the migmatites. Zircons from the hornblende gneiss, migmatite and gabbro yielded weighted mean 206 Pb/ 238 U ages of 879 ± 10 Ma, 438 ± 3 Ma and 453.2 ± 3.5 Ma, respectively. Hf isotopic analysis reveals ϵHf(t) values of +0.02 to −2.55 for zircons from the migmatite, whereas those from the hornblende gneisses and gabbros show positive ϵHf(t) values (+3.41 to +13.36 and +1.80 to +5.25, respectively). Our data correlate the protoliths of the hornblende gneiss and metagabbros to subduction-related magmatism prior to the assembly of the Yangtze and Cathaysia blocks. The migmatite and gabbro record a Palaeozoic tectonothermal event that led to migmatization and resetting of Neoproterozoic ages. Our results suggest that the Palaeozoic event was initiated before c . 453 Ma with metamorphism at c . 438 Ma.

International audience; The early Paleozoic geological evolution of the South China Craton composed of the Yangtze and Cathaysia Blocks has been the focus of long debate. The Cathaysia block has been central to the controversy regarding convergent margin versus intraplate environment in the early Paleozoic. In order to address the early Paleozoic evolution of Cathaysia, we undertook a systematic study of the stratigraphic sequences, deformational features and geochronology of magmatic event. Our results show that (1) during the early Paleozoic, the Jiangnan domain of the SE Yangtze block was characterized by a carbonate platform and the Cathaysia block by a graptolitefacies clastic rock assemblage, (2) in the Cathaysia block, a littoral-neritic depositional environment prevailed in Cambrian whereas a neritic-bathyal setting dominated during the early-middle Ordovician, and (3) the Late Ordovician depositional sequence in Cathaysia witnessed a period of transition from neritic-bathyal to littoral-land environment, marking the initial uplift process. Paleo-current measurements on the crossbeds revealed northwestward and westward transport directions, suggesting a source area to the east-southeast. All samples collected from the Cambrian-Ordovician strata show similar chemical characteristics; they have negative Nd(t) values ( 9.7 to 13.7) and two-stage Nd(t) model ages at ca.2.04 to 2.36 Ga. This suggests that the early Paleozoic rocks were derived from the eroded Paleoproterozoic basement, and little or no mantle component was identified. During the Silurian, the Cathaysia block underwent strong folding, thrusting, weak metamorphism and large-scale anatexis accompanied by granitoid emplacement, building the South China Fold Belt. The maximum shortening is estimated at 67 percent. A kinematic analysis of the ductile sheared rocks revealed a fan-shape thrust pattern, with top-to-the southeast in the southeastern and top-to-the northwest in the northwestern Cathaysia block. Zircon U-Pb dating of four granitic plutons yielded 206Pb/238U ages of 435 4 Ma, 424 5 Ma, 428 3 Ma and 427 2 Ma. All the zircon Hf(t) values are negative ( 6 to 9) and show a peak of two-stage Hf model ages around 1.9 Ga, indicating that the Silurian granitic magma was derived from the recycling of Paleoproterozoic basement. Major features of the early Paleozoic South China Fold Belt include the lack of early Paleozoic ophiolites and volcanic rocks, the absence of coeval HP-type blueschists, and the absence of mantle-derived juvenile magmatic rocks. Consequently, a subductioncollision- type orogeny is excluded. The magmatism most probably took place in an intraplate tectonic setting with little or no input of mantle components. We therefore conclude that the South China Fold Belt was an intraplate orogen, and is possibly related to the global early Paleozoic continental assembly.

Authors thank the Major State Research Development Program of China (Grant No. 2016YFC0600202) for financial support, as well as financial support from National Natural Science Foundation of China (Nos. 41330208, 41572200 and 41190070) and State Key Laboratory for Mineral Deposits Research (Nanjing University) (ZZKT–201603). Peter A. Cawood acknowledges support from Australian Research Council grant FL160100168. The Neoproterozoic Jiangnan Orogen in South China records a succession of arc-trench-basin assemblages culminating in accretion of the bounding Yangtze and Cathaysia blocks to form the stabilized South China Craton. The orogen can be traced over some 1500 km and extends up to 100 km across strike. It is divisible into three domains: the northeast domain (also referred to as the Huaiyu or Shuangxiwu Terrane), the central domain (Jiuling Terrane), and an undifferentiated southwest domain. The northeast domain contains arc type volcanic suites and I-type granitoids dated at ca. 970–850 Ma. It is interpreted as an intra–oceanic terrane based on the juvenile radiogenic isotopic signature of the igneous rocks, the absence of older detritus and inherited xenocrysts, and the presence of ophiolites along its southwestern and western margins. The central and southwest domains contain trench-arc-basin assemblages of clastic sedimentary units, mappable magmatic arc suites and ophiolitic mélanges (Sibao and equivalent groups) that range in age from ca. 880 to 820–815 Ma. The presence of old zircon grains within these two domains, both as detritus within sedimentary units and as inherited zircon in arc basalt, suggest they formed at convergent continental margins. S-type granites dated at 845–815 Ma are a distinctive element of the central and southwest domains. The ages of these granites overlap with convergent plate magmatism in the two domains, arguing against previous models for plume-rift and post-collisional geodynamic settings. Instead, these bodies likely formed in an accretionary orogenic margin setting in which granitic magmatism occurred in an extensional regime triggered by slab rollback. The slab-rollback process triggered mantle-sourced thermal input and partial melting of the older and buried arc-bounding basin sediments. Early Paleozoic S-type granites in the Lachlan and New England belts in eastern Australia and Jurassic ones in the Cordillera belt of the western US provide analogous geodynamic environments. Isotopic data indicate that the central Jiangnan domain experienced significant crustal growth, whereas in the southwest domain there was a greater degree of crustal reworking. The character and distribution of the early Neoproterozoic sedimentary and igneous succession in the orogen suggests it represents a ca. 970–820 Ma accretionary orogen. Upper age limits on the Jiangnan Orogen are provided by a regional angular unconformity in the central and southwest domains at ca. 810–805 Ma, and in the northeast domain at ca. 825 Ma, along with the overlying bimodal volcanic and clastic sedimentary successions mostly dated at ca. 810–730 Ma. Thus, timing of final assembly of South China displays variations across the Jiangnan Orogen, from ca. 825 Ma in the northeast to ca. 820–805 Ma in the central and southwest of the orogen. Post-assembly successions are parts of the Nanhua Basin and are interpreted to have formed during regional lithospheric extension across the eastern and central South China Craton. The age patterns across the South China Craton are indicative of northwest directed accretion of fragments and suggest an external rather than an internal position of the craton within the assembled Rodinia supercontinent. Paleomagnetic data, regional correlations and sedimentary records are consistent with a position along the northern margin of Rodinia, adjacent to India and Australia. The Jiangnan Orogen recorded the accretion of trench-arc assemblages and ultimately the Yangtze Block to the Cathaysia Block that was already located on the margin of Rodinia. The Panxi-Hanan belt, which lies along the western and northwestern margin of the Yangtze Block, formed on the upper plate to a subduction system that both overlaps with, and is younger than, the Jiangnan Orogen. The belt provides a record of ongoing accretion on the Rodinia margin until the mid-Neoproterozoic. Postprint