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This paper presents new zircon U–Pb ages and Hf isotope data, and whole‐rock major and trace element geochemical data of Permian igneous rocks from the eastern Songnen Massif (SM) and the western Jiamusi Massif (JM), NE China, to constrain their tectonic evolution. Zircon U–Pb dating indicates that Permian magmatism within the eastern SM can be subdivided into two stages: early Permian (ca. 293 Ma) and middle to late Permian (272–257 Ma). The early Permian igneous rocks comprise a bimodal association of rhyolites, basaltic andesites, and gabbros. The middle to late Permian igneous rocks are dominated by gabbro–diorites, monzodiorites, quartz diorites, monzonites, quartz monzonites, granodiorites, monzogranites, syenogranites, and alkali feldspar granites, along with minor bodies of A‐type quartz trachytes. The Permian felsic magmas originated mainly from partial melting of a relatively juvenile lower crust, whereas the coeval mafic rocks were probably derived from partial melting of a relatively depleted lithospheric mantle that was modified by fossil subduction‐related fluids. The igneous rock associations and their geochemical features, together with data from coeval sedimentary and volcanosedimentary successions, indicate that Permian magmatism within the eastern Songnen and western Jiamusi massifs formed in an extensional environment, similar to a back‐arc setting, related to westward subduction of a Palaeo‐oceanic plate beneath the eastern margin of the Jiamusi Massif. We find no evidence for double‐sided subduction of the Mudanjiang oceanic plate during the Permian. [ABSTRACT FROM AUTHOR]

The Carboniferous tectonic history of the northern West Junggar of NW China is of key importance for understanding the tectonics of the Altaids. This paper presents a systematic study of the emplacement of the E'min ophiolite, the ages of turbidites, and a stitching granite dike in order to constrain the late Carboniferous oceanic evolution of northern West Junggar. Our field investigation reveals that the Tarbagatay subduction–accretion complex formed by imbrication of turbidites and ophiolitic slices in the Western Tarbagatay Mountain, which is considered as the forearc of the Saur arc in northern West Junggar. Field relationships and zircon geochronology suggest that the emplacement of the E'min ophiolite was later than the minimum time of deposition of hanging wall turbidites, which have a zircon age of 324 Ma, and must be earlier than the crystallization time of a 311‐Ma stitching granite dike that intruded the younger turbidites. The turbidites become younger from north to south, with minimum deposition ages varying from 324 to 309 Ma. The 311‐Ma dike has an adakitic affinity suggesting that it may have formed by magma melted from a subduction slab wedge and from accreted material at ~310 Ma. Therefore, we propose an accretionary arc setting for the Saur arc, with southward migration of the trench and magma front. The 311‐Ma dike has a high Al enrichment and arc‐related geochemical signature suggesting that it was generated by melting of accreted trench sediments. This may indicate that subduction of the Saur arc may have lasted to at least the late Carboniferous. The development of such arc accretion suggests that the formation of the southern Altaids was fundamentally similar to that of accretionary orogens in the western Pacific. [ABSTRACT FROM AUTHOR]

Outcrops of early Palaeozoic mafic rocks are limited in the South China Block (SCB), which become a barrier to unlock the related tectonic evolutionary history. We present a new report of early Palaeozoic Pengxi hornblendite at Xiajiang County, Jiangxi Province, in this paper. The Pengxi hornblendite has a concordant zircon U–Pb age of 433 ± 2 Ma (40 grains) which could represent its formation time. It is characterized by high MgO content (16.8–19.6 wt.%) and Mg# (78–80), compatible elements concentration (Ni = 280–506 ppm, Cr = 1,580–1,780 ppm), and evident depletions of Nb, Ta, and Ti which are similar to the arc‐related magmatism. Combining with the enriched Nd (εNd(t) = −5.3 to −7.8) isotopic feature, we suggest that the hornblendite was derived from partial melting of metasomatized subcontinental lithospheric mantle (SCLM). The lack of other field geological evidences in the study and adjacent areas, such as volcanic rocks, pyroclastic sedimentary rocks, and turbidites, did not support the contemporaneous subduction model. The study area is located near the boundary of the Yangtze and Cathaysia blocks which was a Neoproterozoic subduction belt characterized by ophiolites, volcanic rocks, and turbidites. Mafic rocks formed at different periods (e.g., 800, 500, and 430 Ma) in the SCB have similar enriched Nd isotopic compositions and La/Nb ratios which suggest that the Silurian hornblendite with arc‐like geochemical features may not be the result of contemporaneous subduction but likely inherited from the Neoproterozoic subduction. During Silurian post‐orogenic collapse event, the partial melting of enriched SCLM generated the Pengxi hornblendite. This work can provide new data to the further discussion of the controversies in the tectonic background of the SCB. [ABSTRACT FROM AUTHOR]

The Lesser Xing'an–Zhangguangcai Range is located in the eastern part of the Central Asian Orogenic Belt (CAOB). Early Mesozoic igneous rocks in this area can place constraints on the crustal growth mechanism in the Northeastern China. This paper reports a suite of Late Triassic high‐Mg diorites and mafic dikes from the southern Lesser Xing'an–Zhangguangcai Range. The mafic dikes have younger zircon U–Pb ages of 195 ± 2 Ma. They display intermediate SiO2 (50.58% to 58.20%) and high Na2O/K2O ratios of 1.90 to 3.20, low A/CNK ratios of 0.75 to 0.84, low (87Sr/86Sr)i ratios of 0.7045 to 0.7046, and high εNd(t) values of +3.1 to +3.5. Most zircons in the mafic dikes exhibit positive εHf(t) values from +8.6 to +16.0, with single‐stage Hf model ages ranging from 0.2 to 0.5 Ga in combination with their enrichment in LREE and LILEs and depletion in HFSEs. They are considered to be formed by melting of metasomatized subarc lithosphere mantle. The diorite and quartz diorite have older zircon U–Pb ages of 200 ± 3 and 202 ± 2 Ma, respectively. They have SiO2 = 54.45% to 61.18%, Al2O3 = 17.16% to 19.10%, TiO2 = 0.74% to 1.13%, and Mg# = 46.6 to 49.5, and they also display moderately depleted Sr–Nd (εNd(t) = +2.3 to +4.3) and zircon Lu–Hf (εHf(t) = +8.6 to +16.0) isotopic compositions. These features suggest that they were formed by melting of juvenile arc crust in active continental margin. Considering the occurrence of the contemporaneous and latter igneous rocks in the Zhangguangcai Range, we argue that the diorite, quartz diorite, and mafic dikes from the Lengshan area were also related to the westward subduction of Palaeo‐Pacific Plate (Izanagi Plate) beneath the Eurasian Plate. The strike‐like fault along the eastern margin of the Songneng–Zhuangguangcai Block may play an important role in the genesis of diorite melt. [ABSTRACT FROM AUTHOR]

Carboniferous volcanic rocks are widely distributed in the Junggar Basin and may provide a unique insight into the tectonic history of this basin. In this paper, we focus on the tectonic evolution of the northern Junggar Basin (NJB) using geochronological and geochemical data to establish the diachronous closure model for the Keramaili oceanic basin. The Lower Carboniferous strata in the eastern part (well WC‐1) and the Upper Carboniferous strata in the western part (well Y‐2) of the NJB are composed of a mix of compositional and rock‐type forms. These volcanic rocks are mostly high‐K assemblages characterized by high K (1.73–6.48%), high alkali (Na2O + K2O = 5.04–7.45%), and low TiO2 (0.57–1.06%). They also exhibit various REE concentrations (68.44–168.19 ppm), an enrichment of LREE (LaN/YbN = 4.54–8.09), and small negative Eu anomalies (δEu = 0.74–0.90). The depletion of HFSE and relevant tectonic setting discrimination diagrams demonstrate that these two volcanic associations were formed in a subduction‐related environment. The data also indicate that the high‐K volcanic rocks are derived from a mix of melted subducted sediments and mantle metasomatized by silica‐rich fluids. Although these two sets of volcanic rocks formed in Early and Late Carboniferous, the similar petrographic and geochemical natures suggest similar magma source and tectonic setting. Along with different regional tectonic settings in the NJB during the Carboniferous, we propose an asynchronous subduction of Keramaili oceanic basin, resulting in the inconsistent temporal and spatial distribution of Upper Carboniferous volcanic rocks in the NJB. [ABSTRACT FROM AUTHOR]

In this paper, we report on LA‐ICP‐MS zircon U–Pb dates of 14 Mesozoic volcanic rocks from the central Great Xing'an Range (CGXR). These data are integrated with the temporal and spatial distribution of local magmatism‐related Mesozoic mineralization, in an effort to develop an understanding of the geodynamic evolution of the region. Periodic magmatic events in the GXR date from ~1,703 through ~145 Ma. Mesozoic volcanism in the CGXR can be subdivided into three episodes: Triassic (250–205 Ma), Early–Middle Jurassic (182–165 Ma), and Late Jurassic–Early Cretaceous (155–115 Ma). A revision of the previously defined volcanic sequence is offered using a combination of our zircon U–Pb ages and published Mesozoic geological and geophysical evidence from northeast China. We propose that (a) Early–Middle Triassic volcanism in the CGXR resulted from subduction of the Paleo‐Asian oceanic plate; (b) Late Triassic volcanism was related to subduction of the Mongol–Okhotsk oceanic plate (especially near the Erguna Block) and subsequent extension after the closure of the Paleo‐Asian Ocean; (c) Early–Middle Jurassic volcanism was mainly controlled by the southward subduction of the Mongol–Okhotsk oceanic plate; (d) Late Jurassic–initial Early Cretaceous magmatism was initiated by closure of the Mongol–Okhotsk Ocean; and (e) late Early Cretaceous volcanism was induced following the final closure of the Mongol–Okhotsk Ocean and rollback of the Paleo‐Pacific oceanic plate. [ABSTRACT FROM AUTHOR]

The East China Sea Shelf Basin (ECSSB) is a typical Meso-Cenozoic superimposed basin characterized by different tectonic frameworks, suffering multi-stage tectonism (e.g. the Indosinian, the Yanshanian and the Himalayan) since the Mesozoic. The Mesozoic ECSSB is a key place to our understanding of the tectonic evolution and dynamic mechanism in eastern South China and the subduction of the Izanagi Plate. Based on geological and geophysical results acquired over the last 10 years, this paper provides a summary of the distribution of Mesozoic strata, ascertains boundaries of the Mesozoic basin and proposes the division of the Mesozoic tectonic units in the ECSSB. The Mesozoic ECSSB was subdivided into the Western Fault Depression (WFD) characterized by dispersed Cretaceous half-grabens and the East Depression (ED) characterized by depressions at the early stage and grabens at the later stage. The WFD is composed of half-grabens formed under transtension, and the ED is composed of depression zones on the pre-Mesozoic basement under regional compression, indicating different dynamic mechanisms from the Cenozoic basins. Formation of the Mesozoic tectonic framework was controlled by the collision, compression and subduction of the Izanagi Plate and the Pacific Plate and also affected by the Indian Plate at a later stage. By comparison, this paper preliminarily proposes that the northern South China Sea and the ED of the ECSSB were originally a unified basin and jointly constituted a huge Mesozoic proto-basin in the East Asian continental margin. The Mesozoic tectonic unit division is helpful not only to discuss and resolve problems of ocean-continent differences and boundaries in southeastern South China but also to understand the tectonic nature of the East Asian continental margin, the dynamic mechanism of the Mesozoic basins and the transition of continental margin types. It also provides scientific support for petroleum exploration of the Mesozoic strata in the East China Sea. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The recognition of unconformities is important for stratigraphic subdivision and correlation and for determining the timing of tectonic activity and the ocean‐continent transition process. Here, we have identified a Late Palaeozoic disconformity in the Moqinwula area of the northern Junggar Block, NW China. Integrated field relationship observations and sedimentological, biostratigraphical, geochemical and detrital zircon geochronological data, suggest that the underlying Hongliugou Formation is of Devonian age and was deposited in a passive continental margin setting. The overlying Tamugang Formation formed in the Early Carboniferous and was deposited in a foreland basin setting. Integrating the published data and our new work, we suggest a new tectonic evolution model related to the Karamaili ocean‐continent transition process. During the Early Devonian, northward subduction of the Karamaili Ocean plate beneath the East Junggar Belt formed the Yemaquan arc. At this time, a passive margin sequence was deposited on the northern Junggar Block. During the Early Carboniferous, the closure of the Karamaili Ocean resulted from the collision between the Junggar Block and the East Junggar Belt. Foreland basins subsequently developed, forming an extensive unconformity in the accretionary wedge to the north and a disconformity in the relatively rigid and stable Junggar Block to the south. This significant difference in stratigraphic contact relationships confirms that regional convergence‐induced shortening deformation had no significant influence on the northern margin of the Junggar Block, suggesting the existence of a relatively rigid basement, probably an oceanic plateau, under the cover sediments of the Junggar Block. [ABSTRACT FROM AUTHOR]

The Hailar Basin, located in north‐east China, is a typical continental rifted basin that contains oil and gas. The basin formation process comprised several stages of construction and reformation with complex formation mechanisms. The Bayanhushu (BYHS) Sag is a secondary structural unit in the south‐west Hailar Basin with a significant resource potential, but its current poor exploration and insufficient understanding of the structural evolution characteristics are restricting further oil and gas exploration. Therefore, the study of the structural evolution of the BYHS Sag plays a pivotal role in the future exploration and development of oil and gas. There are different hypotheses on the formation mechanisms and structural evolution of the BYHS Sag. To further understand the evolutionary history of the BYHS Sag, a structural physical simulation experiment was used based on the structural interpretation and geometric analysis of a seismic section. Inversion validation was then undertaken by the 2DMove equilibrium profile recovery technology. It was found that the formation process of the BYHS Sag was mainly controlled by the western Adunchulu Fault. Faults on the section developed in succession from top to bottom. The fault plane experienced multiple changes, thus forming a special seat‐shaped structural pattern. Structural inversion occurred twice during the evolution of the sag. The compressive stress during the tectonic inversion mainly acted in a SE direction. It is inferred that this was related to the subduction of the Palaeo‐Pacific Plate under the Eurasian Plate and the intermittent compression caused by the transmission of stress of the arc–continent collision. [ABSTRACT FROM AUTHOR]

The southern Jiangxi Province is an important part of the fluorite mineralization belt in South China. Fluorite ore bodies are primarily in the contact zone between the Devonian Huitong granitic complex and the Late Cretaceous Ganzhou Formation, controlled by the NE‐trending faults. Zircon U–Pb dating of the Huitong granitic complex yields emplacement ages of 410.7 ± 1.4 Ma and 400.7 ± 4.6 Ma, while the Sm–Nd dating of the fluorite yields an isochron age of 94 ± 2 Ma, suggesting that the Huitong granitic complex is the host rock. Fluid inclusions in the fluorite show low homogenization temperatures (136–207°C), salinities (1.23–3.87 wt% NaCl), and densities (0.87–0.95 g/cm3), suggesting that the ore‐forming fluid is an NaCl‐H2O system of low temperature, salinity, and density. Raman spectroscopy showed that the fluid phase is dominated by water. The δDVSMOW values of the fluid inclusions in the Tongda fluorite ranged between −59.5 and −55.2‰, while the δ18OVSMOW values of the fluorite ranged from −7.2 to −5.6‰. Collectively, the ore‐forming fluid is dominated by meteoric water, possibly with a minor contribution of hydrothermal fluid. Both the interaction with host rocks and the cooling of hydrothermal fluids are the likely mechanisms of underlaying fluorite precipitation at low temperatures. The mineralization occurred in extensional faults during the Late Cretaceous related to the subduction of the Palaeo‐Pacific Oceanic Plate. [ABSTRACT FROM AUTHOR]

As numerous blocks of the Ediacaran‐Cambrian supra‐subduction zone ophiolites, seamounts, subduction‐related metamorphic rocks, and arc granitoids have been identified in the ophiolitic mélanges in the contiguous West Junggar (China) and Balkhash (Kazakhstan) area, the initial subduction of the Junggar‐Balkhash Ocean, a major branch of the southern Palaeo‐Asian Ocean is emerging as an interesting topic. In this study, we present new data from diabase and basalt xenoliths in an Ediacaran‐Early Cambrian quartz‐monzonite block within the Tangbale ophiolitic mélange and an isolated dacitic tufflava block within the Saleinuohai ophiolitic mélange in southern West Junggar, NW China, as another line of evidence for the Ediacaran initial subduction of the Junggar‐Balkhash Ocean and the Cambrian migration of arc magmatism in West Junggar. The diabase and dacitic tufflava yield concordant zircon U–Pb ages of 568 and 530 Ma, respectively. The diabase and basalt exhibit high Al2O3 (17.38–17.75 wt%) and low TiO2 (0.69–0.90 wt%), with Mg# = 47–55, whereas the dacitic tufflava is characterized by high Na2O (7.87–8.43 wt%), with Mg# = 46–49. All the samples display similar LREE and large‐ion lithophile element (LILE) enrichment and Nb, Ta, Ti, and varying Zr and Hf depletion, indicating that they were formed in an intra‐oceanic arc setting. An integration of the new and published data shows that the subduction of the Junggar‐Balkhash Ocean was initiated in the Late Ediacaran at least, followed by slab rollback and retreat of subduction zone, which would be responsible for the northward migration of arc magmatism. [ABSTRACT FROM AUTHOR]

The Jiaodong Peninsula in China underwent ultrahigh pressure (UHP) metamorphism in the Triassic and extensive magmatism in the Jurassic–Cretaceous, resulting in the formation of large‐scale gold deposits. This makes it an ideal site to study the destruction of the eastern North China Craton (NCC) as well as regional gold mineralization processes. The Weideshan granitoid suite is widely distributed in the Jiaodong Peninsula, with geochemical and isotopic data indicating that it formed through migmatization of crust‐derived silicic magma and mantle‐derived intermediate magma. This makes it different from the Jurassic Linglong suite, and the Cretaceous Guojialing and Laoshan suites in the Jiaodong Peninsula, although they have evolutionary continuity. U–Pb age estimates, from SHRIMP and LA‐ICP‐MS zircon dating, suggest that the Weideshan granitoid suite formed between 118.0 and 110.5 Ma, around the same time as the Jiaodong gold deposit, suggesting that the ore‐forming event was enabled during the stage of magmatic activity that formed the Weideshan suite, rather than during that which formed the Linglong or Guojialing suites. The initiation of Late Jurassic to Early Cretaceous magmatism reflects a regional switch from a collisional system with crustal thickening (compression) between the NCC and Yangtze Craton (YC) to lithospheric thinning (extension) during the subduction of the Pacific Plate. The upwelling of the Weideshan suite and the relevant extension structures that developed during this switching process provided favourable conditions for large‐scale gold mineralization. [ABSTRACT FROM AUTHOR]

The Hailar–Tamtsag Basin (HTB), an important component of the late Mesozoic extensional basin system in Northeast (NE) China, is characterized by episodic rifting, dramatic magmatism, and thick terrestrial sediments, which provides crucial opportunities to understand late Mesozoic tectonomagmatic events in NE China. However, the previously established late Mesozoic chronostratigraphic framework in the basin remains problematic due to limited isotopic chronological constraints. Here, we present 28 new zircon U–Pb ages for the volcanic rocks from the HTB, which allow us to establish a refined chronostratigraphic framework for the late Mesozoic terrestrial strata. Newly calibrated results indicate that the depositional ages of the Tamulangou and Tongbomiao formations are constrained to ca. 157–148 and ca. 142–137 Ma, respectively; the depositional ages of the Lower Nantun and Upper Nantun members are constrained to ca. 131–120 and ca. 117–111 Ma, respectively. Combining these results with previous studies on sedimentation, structural deformation, and magmatism, the Late Jurassic–Early Cretaceous tectonostratigraphic evolution of the HTB is reconstructed, and three major phases of intracontinental deformation are identified. The HTB experienced extensional deformation in the Late Jurassic due to the break‐off of the subducted oceanic slab of the Mongol–Okhotsk Ocean and subsequent gravitational collapse of orogenically thickened crust following the closure of the ocean basin. Then, in the latest Jurassic–earliest Cretaceous, the evolution of the HTB was dominated by compressional deformation related to flat‐slab subduction of the Paleo‐Pacific Plate. During the Early Cretaceous, an extensional regime resumed in the HTB in response to rollback of the subducting Paleo‐Pacific Plate. [ABSTRACT FROM AUTHOR]

The North Tianshan in NW China is a key to understanding the accretionary history of the southern Altaids. However, the tectonic setting of the North Tianshan in the Carboniferous‐Permian is debatable, and its amalgamation history is ambiguous. We report new data on the field relations, geochronology and geochemistry of Carboniferous–Jurassic volcanic rocks and sedimentary rocks from the Shichang area in order to constrain the late Palaeozoic–Early Mesozoic tectonic evolution of the North Tianshan. New LA‐ICP‐MS zircon U–Pb dates demonstrate that the Carboniferous–Permian stratigraphy is a tectonic imbrication of Carboniferous–Permian rocks and Carboniferous volcanic rocks were emplaced in Permian volcano‐sedimentary rocks. The 311 ± 2 Ma volcanic rocks are calc‐alkaline, enriched in Light Rare Earth Elements and large‐ion lithophile elements, depleted in high‐field‐strength elements, and have low initial 87Sr/86Sr ratios with positive εNd(t)(+0.3 to +8.6)values. The geochemical‐isotopic data suggest the volcanic rocks were generated in an intra‐oceanic island arc. The turbidite samples 18SC02 (~267 Ma to ~349 Ma) and 18SC09 (~299 Ma to ~369 Ma) have a relatively narrow age range with no Devonian or Precambrian peaks. Our detrital zircon data suggest the presence of a so far unrecognized intra‐oceanic arc, which was isolated from the main Yili‐Central Tianshan and Mosuowan arcs in the Shichang area of the North Tianshan during the Late Carboniferous to Permian. The compiled detrital zircon data from Carboniferous to Jurassic indicates that the North Tianshan intra‐oceanic arc was probably amalgamated with the Mosuowan arc by the Early Triassic, and then accreted to the Yili‐Central Tianshan arc by the Middle‐Late Triassic, as revealed by the changes of zircon provenance of Carboniferous, Permian, Triassic and Jurassic sedimentary rocks. All integrated data suggest that the southern Altaids most likely formed by processes of multiple subduction–accretion and convergence similar to that in the ongoing southwest Pacific. [ABSTRACT FROM AUTHOR]

The Bayan Nuru ductile shear zone is located in the Yabulai–Bayan Nuru tectonic belt of the middle part of the southern Central Asian Orogenic Belt (CAOB) and east of the Langshan tectonic belt. This article is the first report on the Bayan Nuru ductile shear zone, and provides dynamic, kinematic, and geochronological data of the shear zone. Accurately determining the shear orientation and estimating the shearing age of the Bayan Nuruductile shear zone, has important reference value and significance for understanding the tectonic evolution in Alxa during "Yanshan movement" period. All shearing signatures, including asymmetrical folds, rotated porphyroclasts, "domino" structures, "mica fishes," S–C fabrics, and asymmetric stress shadows, developed in the shear zone, indicate sinistral shear. The temperature environment at the time of formation of the shear zone was determined by the mineral deformation thermometer and EBSD quartz C‐axis fabric analysis. The temperature was 350–550°C. The differential stress (σ) was estimated to be 44.31–97.94 MPa and the strain rate(έ) to be 10−14 s−1(350°C) and 10−10s−1(550 °C). The average kinematic vorticity of the Bayan Nuru NNE‐trending ductile shear zone is 0.93, indicating that the shear zone was dominated by simple shear. The thickness of the ductile shear zone was reduced by 7%–22%. Combined with the age of granitic mylonite (289.53 ± 0.74 Ma) and the NNE‐trending spread feature, the Bayan Nuru ductile shear zone in the western part of the Langshan fault zone may have been formed in the context of continuous compressional intraplate deformation, caused by the subduction of the Paleo‐Pacific Plate at 170–150 Ma. [ABSTRACT FROM AUTHOR]

The Jiamusi Block is an important tectonic unit in the Chinese segment of the CAOB. Its eastern margin became an active continental margin in the period of Late Carboniferous. However, the tectonic affinity of this section has not been resolved yet. The Early Permian andesites within the Erlongshan Formation in the eastern Jiamusi Block provide a critical record for the active continental margin setting. Precise LA‐ICP‐MS U–Pb zircon dating on four andesite samples gave ages of 280 ± 3 Ma, 282 ± 3 Ma, 286 ± 4, and 284 ± 2 Ma, respectively, defining an Early Permian age for the crystallization of the andesites. The andesites have medium‐K and calc‐alkaline compositions, with variable SiO2 (54.70–57.46 wt%), TiO2 (0.87–1.12 wt%), TFe2O3 (6.52–8.13 wt%), MgO (2.62–3.33 wt%), Al2O3 (15.96–17.83 wt%), Na2O (3.28–4.10 wt%), and K2O (1.16–1.95 wt%) contents. They are relatively enriched in LREEs ((La/Yb)N = 5.0–7.1) and LILEs (e.g., Ba, Th, Sr, and U), deleted in HREEs and HFSEs (e.g., Nb, Ta, Zr, and Y) and have weak or no Eu anomalies (Eu/Eu* = 0.87–1.02). These geochemical features indicate that the andesites within the Erlongshan Formation originated from an active continental margin setting, and their magma source was produced by partial melting of a mantle material that had been metasomatized by subduction‐related melts and subsequently underwent the removal of mafic minerals and accumulation of plagioclase. Integrated with previous studies on the igneous and sedimentary rocks, we thus propose that the Jiamusi Block was in an active continental margin setting in the period of the Late Carboniferous to Early Permian (310–280 Ma), and it is more likely related to the subduction of the Mongol‐Okhotsk Ocean. [ABSTRACT FROM AUTHOR]

New zircon U–Pb age data, Hf isotopes, whole‐rock major and trace elements, and Sr–Nd isotopic data for Early–Middle Triassic intrusive rocks from the Jiawula and Tsagenbulagen area in the southern part of the Erguna Massif provide valuable constraints on the southward subduction of the Mongolia–Okhostk Ocean lithosphere. The Jiawula–Tsagenbulagen granitoids mainly consist of granodiorite, quartz monzonite, and biotite granite. These granitoids, long believed to be mainly Late Jurassic–Early Cretaceous (ca. 150–139 Ma) and minor Permian (ca. 278 Ma and 254–253 Ma), are newly found to contain a latest Early Triassic to Middle Triassic generation (zircon U–Pb age: ca. 248–244 Ma). Geochemically, the Early to Middle Triassic granitoids are characterized by high SiO2 (74–77 wt.%) and Al2O3 (12.2–15.95 wt.%), low Mg# values (12.98–37.32), and variable Na2O/K2O ratios (0.62–1.75). They are metaluminous to peraluminous and belong to the high‐K calc‐alkaline series. Moreover, they show enrichment in light rare earth elements and large‐ion lithophile elements and depletion in heavy rare earth elements and high‐field‐strength elements (e.g., Nb, Ta, and Ti). They have an increased amount of SiO2/Al2O3 but lower V/Th ratios and negative correlations between V/Th and SiO2/Al2O3 ratios, indicating that the magmas experienced various degrees of biotite and/or plagioclase fractional crystallization. Their whole‐rock εNd(t) and zircon εHf(t) values ranged from +1.07 to +4.15 and from +0.5 to +2.9, respectively, indicating that the primary magmas were probably generated by partial melting of juvenile crustal material with the help of mantle‐derived mafic magmas. These magmas subsequently underwent fractional crystallization, magma mixing, and a small amount of crustal contamination during their emplacement. The geochemical characteristics of these Early–Middle Triassic intrusive rocks have affinities with intrusive rocks from active continental margin settings. Therefore, we conclude that the Early–Middle Triassic magmatism in the Erguna Massif was generated within an Andean‐type arc setting related to the southwards subduction of the Mongol–Okhotsk oceanic plate beneath the Erguna Massif. We summarized previous age data of the Early to Late Triassic magmatic rocks from Erguna and Central Mongolia and identified arc setting granites and post‐orogenic granites. Thus, a tectonic evolutionary model was proposed for the geological observations in the Erguna and Central Mongolia massifs, involving the Triassic continuous southward subduction in the Erguna Massif and the Late Triassic slab‐rollback and back‐arc basin extension in the south‐eastern Central Mongolia Massif. [ABSTRACT FROM AUTHOR]

We present the results of our study on 16 Cretaceous granitoid plutons along the south‐east coast of continental China. The zircon U–Pb ages and the bulk‐rock Rb–Sr isochron age (R2 = 0.935) indicate that the granitoids represent the last episode of magmatism (119–92 Ma) associated with the paleo‐Pacific Plate subduction beneath continental China. These granitoids show large compositional variation that is to a first‐order consistent with varying extents of magma evolution, which is best expressed by a large SiO2/MgO range and correlated trends of SiO2/MgO with the abundances and ratios of major and trace elements. The correlated Nd (εNd(t) = −6.1 to −1.2) and Hf (εHf(t) = −4.7 to +3.4) isotopic variation reflects parental magma compositional differences as a result of varying sources and processes. The Nd–Hf isotope data indicate that these granitoids were produced by mature continental crust melting with significant mantle input (~20–60%). Rhyolite‐MELTS modelling shows that relative to the less evolved (i.e., low SiO2/MgO) granitoid plutons, the progressively more evolved (i.e., varying larger SiO2/MgO) plutons can be explained by varying extents (~24% to 67%) of fractional crystallization. The origin of the magmas parental to the granitoids is best explained by a two‐stage process: (a) subducting slab dehydration‐induced mantle wedge melting for basaltic magmas and (b) ascent and underplating/intrusion of the basaltic magmas caused the mature crustal melting for the granitoid magmas. The systematic northward decrease in εNd(t) and εHf(t) suggests progressively more enriched crustal material towards the north, but it may very well indicate northward crustal thickening, permitting a greater extent of crustal assimilation. [ABSTRACT FROM AUTHOR]

Many data have been reported from the Early Palaeozoic subduction complex belt and accretionary arc to the south of the Solonker‐Xar Moron‐Changchun‐Yanji Suture (SXCYS) zone. However, as the suture is covered to the east by the Mesozoic–Cenozoic Songliao Basin, there have yet been no related reports about the Early Palaeozoic igneous rocks in this area. The authors discovered an Early Palaeozoic granitoid intrusion in the Fangjiatun area, northern Liaoning, and performed petrologic, geochemical, zircon U–Pb dating and Hf isotopic analyses on it. Zircon SHRIMP U–Pb dating results show that the intrusion formed at 437–432 Ma, that is, in the late stage of the Early Silurian. Petrogeochemical analysis indicates that the intrusion records 63.14%–66.45% SiO2, with Na2O/K2O ratios of 1.01–6.12 and magnesian index (Mg#) values of 32.42–40.82. The REEs show a certain degree of LREE/HREE fractionation and slightly lower ΣREE contents. The trace elements are relatively enriched in Rb, Ba, Th, K, and Sr (large‐ion lithophile elements [LILEs]) and depleted in Nb, Ta, P, and Ti (high‐field‐strength elements [HFSEs]), displaying continental magmatic arc characteristics. The rocks have high Sr mass fractions, low Y and Yb mass fractions, and high Sr/Y ratios, which are consistent with the geochemical signatures of typical adakites. Zircon Hf isotopic analyses indicate that their εHf(t) values range from 0.29–6.56, reflecting the relatively depleted signatures of the source area. Based on its occurrence location and emplacement time, the intrusion is interpreted to have been produced by tectonic thermal events during the subduction of the Palaeo‐Asian oceanic crust beneath the northern margin of the North China Craton (NCC), thus reflecting the existence of an Early Palaeozoic continental marginal accretionary arc in the eastern segment of the NCC along the south of the SXCYS and provide new evidence for the tectonic evolution of the northern margin of the NCC in the Early Palaeozoic. [ABSTRACT FROM AUTHOR]

The Tongcheng ultrapotassic rocks intrude in Mesoproterozoic limestones in Chongxin County, Gansu Province, China, at the south‐western margin of the Ordos Block. They are characterized by high K2O and Al2O3 but low SiO2, FeOT, MgO, and CaO. The ultrapotassic rocks are relatively depleted in Nb, Ta, Ti, Zr, and Hf and enriched in the large‐ion lithophile elements Rb, Ba, and Th. Zircons from the ultrapotassic rocks yield an Early Cretaceous U–Pb age of 120 Ma. The slightly enriched whole‐rock Sr and Nd isotopic compositions ((87Sr/86Sr)i = 0.705–0.706; εNd = −4.9 to −5.2) indicate an enriched lithospheric mantle source. Combined with regional tectonic data, the Tongcheng ultrapotassic rocks were generated in an extensional environment, which were caused by the upwelling of asthenospheric mantle. Subduction of the palaeo‐Pacific Plate in Early Cretaceous resulted in large‐scale lithospheric thinning in the eastern North China Craton (NCC), which may have also occurred in the western part of the NCC, but the scale of thinning was smaller compared with that of the eastern NCC. [ABSTRACT FROM AUTHOR]

The Tan–Lu Fault Zone (TLFZ) is the largest continental‐scale strike‐slip fault zone in East China. It experienced a complex Meso‐Cenozoic deformation and controlled the development and evolution of the Bohai Bay Basin (BBB). Though its Mesozoic sinistral and Cenozoic dextral motions have been well documented, its strike‐slip transition history and mechanism from sinistral to dextral motions in the Early Paleogene remain poorly understood. To investigate these issues, we made a thorough analysis on the fault geometry and kinematics as well as the response of depocentre in the Early Paleogene of the sags adjacent to the TLFZ across the southeast BBB. The results show that the WNW‐/NW‐, E‐W‐, and ENE‐/NE‐trending extensional faults developed in the Early Paleogene of those sags share almost the same geometrical and kinematic features. Such features indicate that the TLFZ is sinistral in Ek3‐Ek2 depositional stage, extension dominated in Ek1 depositional stage, and dextral in Es4L depositional stage. Such strike‐slip transition of the TLFZ is a comprehensive effect of the plate events around the Eurasian Plate. The NNW‐directed subduction of the Pacific to the Eurasian plates triggers the sinistral motion of the TLFZ during 65–55 Ma, but this sinistral motion is terminated by the far‐field effect of the NNE‐directed India–Eurasia collision initiating at 55 Ma. Then, the kinematic adjustment of the Pacific Plate from NNW to WNW breaks the stress balance exerted on the TLFZ by the subduction of the Pacific to Eurasian plates and the India–Eurasia collision and makes it turn into dextral motion gradually during 48–42 Ma. [ABSTRACT FROM AUTHOR]

The high‐pressure Heilongjiang Complex belongs to a Jurassic accretionary complex in Yilan area, NE China. The complex is located in the junction of three orogenic systems in the NE Asia: the E‐W‐striking Central Asian Orogenic Belt (CAOB), the N‐S‐striking Paleo‐Pacific system, and the ENE‐WSW‐striking Mongol‐Okhotsk system. Thus, a detailed tectono‐metamorphic analysis coupled with accurate radiometric dating of the Heilongjiang Complex provided in this study represent important evidence for understanding the complex interactions between the three orogenic systems in the Late‐Palaeozoic to Mesozoic. New structural and microstructural data combined with the strain analysis highlight the presence of three distinct deformation events affecting the high‐pressure Heilongjiang Complex. The first deformation event D1 is related to development of blueschist facies prolate to plane strain fabrics that were subsequently reworked by the blueschist‐amphibolite facies event D2 that transposed all previous structures by the main west‐dipping schistosity. This planar fabric was folded by upright F3 folds and heterogeneously reworked by greenschist facies E‐W‐striking vertical cleavage during large scale N‐S shortening. Each deformation event was related to specific strain fabrics and metamorphic conditions highlighting dynamic evolution of the subduction complex during burial, exhumation, and final shortening. The first D1 event is related to westward directed prograde constrictional flow and progressive dismembering of competent mafic, ultramafic layers, and quartzites in highly stretched meta‐sedimentary matrix. This mélange was folded by recumbent detachment folds resulting in emplacement of the exhumed unit progressively reaching amphibolite facies conditions atop of W‐WSW‐dipping channel. This event is associated with dominant flattening implying increasing mechanical coupling between the colliding Songliao and Jiamusi blocks. Subsequently, the accreted subduction complex was reworked during N‐S‐directed horizontal shortening. This event was associated with an important post‐buckle flattening of fold limbs and rotation of competent blocks with inherited D1 and D2 strain ellipsoids along F3 fold axes. Our new 40Ar‐39Ar plateau ages on muscovite and phengite (173–177 Ma), together with previous radiometric data, are interpreted as reflecting exhumation of subduction channel during the blueschist‐amphibolite facies event while the N‐S shortening (D3) probably operated in Late Jurassic as indicated by some previously published cooling ages (~140–160 Ma). The westward‐oriented subduction and exhumation fabrics of the high‐pressure Heilongjiang accretionary complex followed by N‐S‐directed upright folding are interpreted to reflect transition from E‐W Pacific subduction regime to N‐S‐directed shortening related to the closure of the Mongol‐Okhotsk Ocean. [ABSTRACT FROM AUTHOR]

East Asia suffered an important transformation from the Tethys to the Pacific tectonic domain during the early Mesozoic. Moreover, the South China Block (SCB) in East Asia has an obvious change from an Indosinian syn-orogenic compression to a post-orogenic extensional tectonic setting. The dynamic evolution of the SCB that caused this change is still unclear. Here, we combine the petrology and whole-rock geochemistry of the Daoxian mafic granulite xenoliths in basalts from South Hunan Province and the structural features of the Xuefengshan tectonic belt, to propose a late Triassic tectonic model in the central SCB. The Daoxian region is located in the eastern part of the Xuefengshan basement uplift belt. The Daoxian mafic granulite xenoliths, forming in the late Triassic, have high Mg# value, high MgO and low SiO2 contents. They have flat REE patterns with a positive Eu anomaly, enriched in Rb, Ba, and depleted in Th, U, Nb, Zr and Hf. These xenoliths are the product of pyroxene and plagioclase accumulation of the mafic melts. The mafic melts originated from the asthenosphere and then underplated to the bottom of the lower crust. In the Xuefengshan belt, it is observed that the unconformities during the Late Triassic changed from high-angle unconformity, through low-angle unconformity and para-unconformity, to conformity, from the central to western parts of the SCB. The detachment layer beneath the Xuefengshan belt displaying NW-trending thrusts cross-cuts the late Palaeozoic strata. We suggest that orogenic collapse happened beneath the central SCB during the Late Triassic, which was accompanied by lithospheric extension and asthenospheric upwelling. These dynamic processes induced different effects on the SCB. Beneath the central SCB, the mantle-derived melt underplated the lower crust, and subsequently influenced the deep crust. From central to western SCB, the regular westward change of the stratal unconformities is related to the weakening of the lithospheric extension. In the central and eastern SCB, the orogenic collapse and the subsequent asthenosphere upwelling could have contributed to the mantle disturbance to enhance the roll-back of the Palaeo-Pacific slab. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]