Abstract In this study, we develop a 3D S‐wave velocity model extending to 120 km depth beneath Northeast China, featuring high resolution for the crust and uppermost mantle, based on physics‐informed neural network framework for eikonal tomography. Notably, this model provides a characterization of the transitional lithosphere‐asthenosphere boundary (LAB) beneath the volcanic regions, while also illuminating its connections to the formation of Quaternary intraplate volcanoes in the region. Key observations include a prominent large‐scale high‐velocity anomaly beneath the Songliao Basin (SLB), which suggests a thicker lithosphere in that area. In addition, we identify undulations in the LAB, as well as diverse low‐velocity features underlying the volcanoes. Drawing from a schematic representation of lithospheric and upper mantle convection, we interpret these patterns as stemming from regional variations in the water‐carbon cycle and lithospheric thickening within the SLB. For instance, inputs from the deep Big Mantle Wedge not only promote lithospheric thickening beneath the SLB, but also enhance asthenospheric mobility, facilitating sodic volcanism in the southeastern and western sectors. In contrast, the Wudalianchi (WDLC) and Nuominhe (NMH) volcanoes, which lack intense deep convection, produce potassic lavas instead. Overall, these insights improve our understanding of intraplate volcanic mechanisms in this region.

A northwest-southeast trending high-density seismic array was deployed in the southern Xing'an-Mongolian Orogenic Belt, spanning the Songliao basin, the North-South gravity gradient lineament, the Great Xing'an Mountains, and the Erlian basin. The high-density seismic array included 1000 stations with an interval of -0.5 km. We image the lithospheric structure using the teleseismic receiver function method. Our results show that the Moho depth gradually increases from -35 km beneath the Songliao basin to -40 km beneath the Great Xing'an Mountains. In the vicinity of the North-South gravity lineament, the Moho is slightly inclined with a continuous depth of -5 km, which forms a transition zone from the basin to the orogenic belt. A middle crustal discontinuity, or the Conrad discontinuity, is imaged beneath the Songliao-Xilinhot block and the northern margin of the North China Craton. The Conrad and Moho discontinuities beneath the suture zones show traces of bidirectional subduction of the Paleo-Asian Ocean plate. Meanwhile, we find subtle changes in the receiver functions due to variations in the sedimentary layer thickness. The sedimentary layer beneath the southern Songliao basin is estimated to be -1.2 km thick and it thins toward its edge. Moreover, we find a middle lithospheric discontinuity below the Moho under the Songliao-Xilinhot block. Combining with previous findings, we deem that the middle lithospheric discontinuity reflects a high-temperature layer in the upper lithosphere mantle associated with hot and wet upwelling flows in the big mantle wedge under NE China.

Ambient noise surface wave exploration is one of the fields of interest in geophysical research. Extracting dispersion curves and inverting the S-wave velocity structure from the dispersion characteristics is also of primary importance. The accuracy of dispersion curves has great significance for the subsequent inversion result and its interpretation. The phase-shift method is widely used in dispersion imaging of surface waves. This method possesses advantages on stability but also suffers a lot from low resolution and low noise resistance. Therefore, we propose an improved phase-shift method based on semblance coefficients. This method replaces linear stacking in the traditional phase-shift method by calculating semblance coefficients and, therefore, can effectively improve the resolution and noise resistance of surface wave dispersion spectrum imaging. Tests are implemented on both synthetic ambient noise data and field data recorded by a short-period dense seismic array located in the ChangbaiShan region to evaluate the proposed method. The dispersion spectrum imaging results of the model and field data show that the semblance phase-shift (SPS) method has better noise resistance and computational accuracy than the traditional phase-shift method. The inversion results indicate that it is possible to obtain a reasonable S-wave velocity structure by inverting the dispersion curves resulting from the semblance phase-shift method. By constructing a 3 km deep and 4.8 km long S-wave velocity image, the velocity structure and abnormal conditions beneath the array in the ChangbaiShan region are presented. The results indicate a significant low-velocity anomaly at a depth of 1 km. It is inferred that it may be a fluid-rich structure.

A detailed 3-D shear-wave velocity (Vs) model of the crust and upper mantle beneath the Changbai volcano and adjacent areas in NE China is obtained by conducting a joint inversion of group-velocity dispersion curves at periods of 5-30 s and phase-velocity dispersion curves at periods of 5-100 s from ambient noise and earthquake surface waves. We use 1602 group-velocity dispersion curves and 3125 phase-velocity dispersion curves, which were recorded at 57 permanent stations of the China Earthquake Administration and 27 portable stations of Jilin University during 2010 to 2014. Our results reveal strong heterogeneities in the crust and upper mantle beneath the study area. A remarkable low-Vs zone is revealed in the crust beneath the Changbai volcano, indicating a hot magma chamber. The Longgang volcano is also characterized by a low-Vs anomaly reflecting partial melt in the crust. In contrast, there is no notable low-Vs anomaly in the crust beneath the Jingpohu volcano. Previous geological results and our tomographic images suggest that Changbai is a composite volcano, whereas Jingpohu and Longgang are monogenetic volcanoes. Low-Vs zones are revealed in the upper mantle beneath the three active volcanoes, which are interconnected at different depths. Combining the present results with previous findings, we deem that the three active intraplate volcanoes are caused by hot and wet upwelling flows in the big mantle wedge associated with deep subduction of the western Pacific plate beneath NE Asia.

The nature of late Paleozoic metamorphism in the eastern Central Asian Orogenic Belt (CAOB) is controversial. This paper reports mineral chemistry, petrological, and zircon and titanite U-Pb age data for representative rocks in the Dongfengshan Group from the eastern margin of the Songnen Massif. We use these data to determine the rock associations, P-T conditions, and timing of metamorphism. The P-T conditions were estimated from 54 mineral pairs in representative rocks, including garnet-biotite schist, garnet-two-mica schist, garnet-biotite-plagioclase gneiss, and garnet amphibolite, and indicate the Dongfengshan Group experienced metamorphism at P = 5.5-7.1 kbar and T = 592-630 degrees C (i.e., a geothermal gradient ranging from 25 to 30 degrees C/ km) under medium-pressure lower amphibolite-facies conditions. The biotite-plagioclase gneiss and garnet amphibolite yielded titanite U-Pb ages of 251 and 260 Ma, respectively, which are interpreted to represent the regional metamorphic age (260-251 Ma). The consistency of these dates and ages of metamorphic rims in zircons from a biotite plagiogneiss (252 Ma) confirm that medium-pressure metamorphism occurred in the late Permian rather than the Neoproterozoic, as assumed previously. Based on metamorphic, magmatic, stratigraphic, and paleontological constraints, as well as the regional tectonic history, we propose that late Permian medium-pressure metamorphism in the Dongfengshan Group occurred during the collision and amalgamation of the Siberian and North China cratons following the final closure of the eastern Paleo-Asian Ocean.

The Songliao Basin is one of the largest non-marine petroliferous basins in the globally and contains nearly complete Cretaceous terrestrial sedimentary records. The Shahezi Formation is a thick terrestrial clastic sedimentary succession deposited during the rift period of the Songliao Basin. Accordingly, it is significant for research on initial basin history restoration and global continental–marine stratigraphic correlation, to certificate the deposition time of the Shahezi Formation. This formation is always met when wells are drilled in fault basins of the Songliao Basin, and its outcrops are discontinuously distributed along the southeastern margin of the basin. Limited by the discontinuous cores and outcrops, previous studies on the deposition time of the Shahezi Formation were lack of direct evidence. Borehole SK2 of ICDP was located in the thickest part of the Shahezi Formation in the northern Songliao Basin. It drilled into and traversed the Shahezi Formation from 3,335.99 m to 5,960.00 m, cored all the strata of this 2,624.01 m interval, and obtained 2,503.86 m of core with a coring rate of 95.79%. This core, which can be regarded as a continuous high-resolution terrestrial geological record, provides the basic material to study greenhouse climate events in the Cretaceous and interpret oil and gas generation processes in the basin. Based on centimeter-scale core observation, the Shahezi Formation is mainly composed of variegated conglomerate, gray sandstone, and black mudstone. It is a sedimentary succession of fan-delta facies and lake facies. One sedimentary tuff layer with a thickness of almost 1 m was found at a depth of 5,943.19 m, close to the bottom of the Shahezi Formation in SK2. The weighted mean age of 117.9 ± 1.6 Ma (MSWD = 0.15, N=15) provides a reference for the beginning of the deposition of the Shahezi Formation. One rhyolitic crystal tuff layer approximately 6 mm thick was found at a depth of 5,958.62 m at the bottom of the formation. The weighted mean age of 118.2 ± 1.5 Ma (MSWD = 0.18, N=19) is interpreted as the eruption age of the tuff sample. These weighted mean ages provide the best estimate of the beginning of deposition of the Shahezi Formation.Taking other studies into account, the deposition rate of the Shahezi Formation without compaction correction was calculated as about 460 m/Ma. This rate is much faster than the deposition rate of other periods in the Songliao Basin. The Shahezi Formation was deposited approximately from 118 to 111 Ma, from the middle Aptian to early Albian. The study of the high-resolution stratigraphic sequence and deposition time of the Shahezi Formation is a key to know the process of hydrocarbon generation in the basin. It provides a foundation for the correlation between terrestrial sedimentation in the Songliao Basin and global continental–marine stratigraphy. Also, it should have positive significance for other studies, such as CNS, OAE1a, OAE1b, ORB1, Cretaceous paleogeography and paleoclimate, change in the drifting direction of the subducting Pacific Plate, and other contemporaneous global geological events.

对小兴安岭东风山群红林组中黑云母混合片麻岩进行了岩相学、年代学和Hf同位素研究,以确定这套岩石的原岩性质、形成时代以及岩石成因.岩相学特征表明这套混合片麻岩主要由片麻状二长花岗岩和片麻状正长花岗岩两种岩性组成,局部保留的变余半自形粒状结构或变余似斑状结构指示其原岩为花岗岩.片麻状二长花岗岩和片麻状正长花岗岩中的锆石多呈自形-半自形柱状,具有明显的振荡环带结构,Th/U比值较高(0.11～1.16)指示其岩浆成因.对岩浆锆石LA-ICP-MS U-Pb定年结果表明,片麻状二长花岗岩和片麻状正长花岗岩分别形成于479 Ma和499 Ma,即早奥陶世和晚寒武世.片麻状二长花岗岩和片麻状正长花岗岩的Hf同位素组成相似且变化范围小,锆石εHf(t)值分别为-6.6～-10.6和-6.4～-8.6,两阶段模式年龄分别为1698～1958 Ma和1692～1831 Ma,表明片麻状花岗岩的岩浆源区为古老地壳物质,其原始岩浆可能源自于古元古代地壳的部分熔融.结合前人研究成果讨论了东风山群的物质组成及原岩性质,认为东风山群具有构造混杂岩属性,其组成不仅包括新元古代、早古生代和晚古生代等具有地层性质的变质碎屑岩(副变质岩),而且存在新元古代和早古生代由岩浆侵位形成的花岗质岩石(正变质岩).

The Paleozoic tectonic evolution of Northeast (NE) China was dominated by the amalgamation of multiple microcontinental massifs and the closure of the Paleo-Asian ocean, whereas in the Mesozoic and Cenozoic, NE China experienced the overprinting of circum-Pacific and Mongol-Okhotsk tectonic systems, which finally resulted in the very complex tectonic features of NE China. In addition, there exists a big dispute on whether the tectonic evolution of Great Xingan gravity lineament (GXGL) and the region on its west was affected by the subduction of the Pacific plate. In this study, we determined a 3-D P-wave structure down to 1000 km depth beneath NE China using a great number of high-quality arrival-time data of local, regional and teleseismic events recorded by dense seismic networks in NE China, North China, South Korea and Japan. Our tomographic images show some new features in the subsurface of this region. The subducting Pacific slab is imaged clearly by high-velocity anomalies extending from the Japan Trench to the deep GXGL, stagnating in the mantle transition zone. The Changbaishan intraplate volcano is underlain by a significant low-V anomaly from the mantle transition zone and a big mantle wedge (BMW) is present up to the surface, which may reflect that the deep subduction dehydration of the Western Pacific plate resulted in lower melting point of the rock in the upper mantle, and further caused large-scale upwelling of partially molten material. Complex geodynamic processes occur in the BMW due to large-scale deep subduction of the Pacific Plate, such as the deep dehydration process of the subducting slab and upwelling of low-velocity and hot materials. The uneven mantle flow in the upper mantle driven by the subducting slab front poses strong action on the upper lithosphere, which has an important influence on the tectonic evolution of crust and upper mantle structure beneath NE China and even on the formation and evolution of the GXGL.

We investigate three-dimensional (3-D) temperature distribution of the upper mantle at depths of 50-200 km beneath the North China Craton (NCC) and surrounding areas using high-resolution P- and S-wave velocity models as well as mineral physics and geothermal data and methods. The thickness of thermal lithosphere is also estimated assuming its bottom has a mantle adiabatic temperature of 1300 degrees C. Our results show that the study area exhibits an alternate distribution pattern with three weak zones and two stable blocks. The Qilian orogen, the Shanxi rift system and the Tanlu fault system are characterized by lower seismic velocity, higher temperature, higher heat flow, and thinner thermal lithosphere. The three mechanically weak zones may be related to subductions of the Indian plate and the Pacific plate beneath the Eurasian continent, resulting in thermochemical erosion of the upwelling asthenospheric material, which have played an important role in the Cenozoic partial destruction of the lithosphere beneath the NCC. The Ordos block and part of the North China Basin have higher seismic velocity, lower temperature and thicker thermal lithosphere, suggesting that the two relatively stable blocks have suffered from less damage and still kept a remanent Archean lithospheric keel.

松辽盆地大陆科学钻探"松科2井"连续获取登娄库组二段岩芯105.05 m,岩芯收获率为99.1％,是迄今获取的最连续完整的沉积记录.笔者对该段岩芯进行了厘米级沉积地质描述(分层厚度2～5 cm),揭示其岩性-岩相沉积序列.登娄库组二段共识别9种岩石类型,为辫状河相的废弃河道和河道亚相,并且进一步划分为河道淤积、沙滩、心滩3种沉积微相.碎屑锆石LA-ICP-MS U-Pb测年结果中登娄库组二段最年轻碎屑锆石年龄为102±4 Ma,表明松辽盆地徐家围子断陷该时期已经进入阿尔必晚期.

We study the detailed 3‐D crustal and upper mantle structure beneath the active Changbai intraplate volcano in Northeast China by conducting a trans‐dimensional Bayesian inversion of teleseismic receiver functions and Rayleigh‐wave group velocity dispersions from ambient noise. More than 12,000 teleseismic receiver functions recorded at 78 seismic stations and 1,573 group velocity dispersions are used in this study. Receiver‐function H‐κ stacking measurements reveal a thick crust (~40 km) with a high Vp/Vs ratio (~1.8) beneath the Changbai volcano. Our joint inversion results show a heterogeneous crustal structure in the study region. A low‐velocity body at depths of 8–15 km is revealed directly beneath the Changbai volcano, which has a lateral extent of ~100 km in the north–south direction and may reflect a large magma chamber in the midcrust. Our results also reveal a 5–10 km depressed Moho and a low‐velocity anomaly in the uppermost mantle beneath the Changbai volcano. These features may indicate an upwelling channel of the asthenospheric material with a high mafic composition, and the mafic intrusion attaches to the bottom of the crust and thus deepens the Moho beneath the volcano. Our results support the notion that the Changbai volcanism is caused by hot and wet mantle upwelling associated with subduction‐driven corner flow in the big mantle wedge above the stagnant Pacific slab in the mantle transition zone.

为精确划分松辽盆地沙河子组层序地层,限定断陷期沙河子组与营城组地层时代,进而研究断陷期盆地的演化,笔者利用松辽盆地大陆科学钻探松科2井获取的下白垩统地层岩芯资料,从岩芯尺度对沙河子组与营城组界面进行揭示,结合过松科2井地震剖面解释、 松科2井及邻井测井响应特征分析和岩芯精细描述,总结出沙河子组顶界面在不同尺度的具体特征:①在地震剖面尺度,其表现为明显上超的特征;②在测井曲线上,界面附近表现为由下到上自然伽马曲线变化幅度增大,双侧向电阻率曲线由低值变为中高值的特征;③岩芯尺度上,表现为细粒沉积的砂泥岩突变为砾岩或火山岩.

中国白垩纪大陆科学钻探松科2井连续获取营城组岩心365.32 m,岩心直径为214 mm,岩心收获率达98.47％,是迄今直径最大,收获率最高且保存最为完整的营城组岩心,这些宝贵资料为营城组研究提供了前所未有的机遇.营城组时期与Aptian-Albian对应.通过对松科2井营城组岩心的精细描述,揭示了营城组火山-沉积序列及其建造过程.营城组主要包括沉积岩与火山岩两大岩类,共计17种岩石类型,其中沉积岩9种(砾岩、粗砂岩、中砂岩、细砂岩、粉砂岩、粉砂质泥岩、泥岩,含角砾凝灰质砂岩、凝灰质砂岩)、火山岩类8种(流纹岩、流纹质角砾集块岩、流纹质角砾集块熔岩、流纹质熔结凝灰熔岩、流纹质含角砾熔结凝灰熔岩、隐爆角砾岩、安山质集块熔岩与凝灰岩).沉积相为扇三角洲相,具体分为扇三角洲平原亚相、扇三角洲前缘亚相与前扇三角洲亚相,分流河道微相、扇间沼泽微相,水下分流河道微相、河口砂坝微相与静水泥质沉积微相.火山岩相包括爆发相和喷溢相,具体分为空落亚相、热碎屑流亚相、啧溢相中部亚相和上部亚相.沉积岩与火山岩交替出现于营城组中,主要发育3期沉积岩与3期火山岩,自下而上形成3个完整的沉积-火山旋回,即沉积岩Ⅰ-火山岩Ⅰ、沉积岩Ⅱ-火山岩Ⅱ和沉积岩Ⅲ-火山岩Ⅲ.这一发现对于重新认识营城组时期构造-火山-盆地充填规律,可能具有重要启示.文中精细的描述资料为今后相关的深入研究提供了迄今最精准的基本地质素材.