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Our current knowledge regarding the distribution patterns of ancient and recent recycled materials, as well as the origin of intraplate basalts in the eastern Asia Big Mantle Wedge (BMW), is limited. To address this, we conducted a detailed geochemical analysis of olivine melt inclusions (OLMI) in nephelinite samples. The normal OLMIs detected in our investigation exhibit geochemical features that closely resemble those of the hosting nephelinite, indicating a consistent association with a carbonated mantle source. Additionally, we identified a distinct group of anomalous OLMIs that displayed different geochemical characteristics from the hosting nephelinite but showed similarities to regional alkali basalts sourced from pyroxenite. The observed geochemical diversity in the nephelinite OLMIs suggests an interaction between deeply derived carbonated melts originating from the flattened Pacific slab in the mantle transition zone and pyroxenite in the lithospheric mantle. Carbonated fluid‐fluxed melting is key to basalt formation in the BMW. Plain Language Summary: The Big Mantle Wedge (BMW) refers to the mantle regions situated between the flattened subducted slab in the mantle transition zone (MTZ) and the overlying plates. In order to better understand the distribution patterns of recycled materials and the origin of intraplate basalts within the Eastern Asia BMW, we have focused on studying the Cenozoic basalts from the eastern North China region. Initially, it was believed that these basalts were formed through decompression melting of the mantle caused by back‐arc extension associated with the subduction of the Pacific plate. However, recent studies have revealed unique characteristics of these basalts, such as high water content and isotopic values that differ from those of the depleted mantle. This suggests a possible connection between the basalts and decarbonation and dehydration processes occurring within the stagnant subducted slab in the MTZ. According to the proposed model, carbonated melts/fluids released from the stagnant slab interacted with the lithospheric mantle, resulting in the transformation of the melts and the involvement of pyroxenite in the lithospheric mantle. The pyroxenite forms through ancient melt metasomatism events. This interaction ultimately leads to the generation of basalts with a wide range of SiO2 content. Key Points: The olivine melt inclusions (OLMI) originate from either a carbonated mantle source or ancient pyroxenite in the lithosphereThe geochemical diversity in the OLMI reflects the interaction between deeply derived carbonated melts and pyroxeniteCarbonated fluid‐fluxed melting stands as a crucial mechanism in the formation of basalt within the Big Mantle Wedge [ABSTRACT FROM AUTHOR]

Charge disproportionation of ferrous iron has been considered as one of the mechanisms for the formation of metallic iron on the lunar surface. However, the detailed mechanism of the disproportionation reaction on the Moon is yet to be elucidated. We provide direct evidence for the ferrous disproportionation reaction that produces nano phase metallic iron (npFe0) during a rapid cooling process after splash melting from a lunar sample returned by China's Chang'e‐5 mission. Space weathering processes have resulted in the formation of three distinct zones at the rim of a pyroxene fragment, as observed through transmission electron microscopy. These zones, made up of splashed melts, newly formed melts from the substrate, and the mineral, are distinguished as I, II, and III. Quantitative analyses of the iron valence state by electron energy loss spectroscopy show that disproportionation reactions occurred in zone II at a low temperature of <570°C during a rapid cooling process. The reaction led to the production of α‐structure npFe0 and Fe3+ reserve in the glass phase. The npFe0 produced by the disproportionation reaction has a larger grain size than those formed from solar wind irradiation, implying that micrometeoroid impacts mainly contribute to the darkening of visible and near‐infrared reflectance. These findings reveal a novel rim structure by repeated space weathering and a universal formation mechanism of npFe0 during micrometeoroid impacts, suggesting that the disproportionation reaction could be widespread on airless bodies with impact‐induced splash processes. [ABSTRACT FROM AUTHOR]

How eclogite/pyroxenite‐derived melts evolve through the refractory lithosphere above a plume remains poorly understood. Here we conducted layered experiments of reaction between tholeiitic melts and harzburgite at 2–3 GPa, 1,400–1,500°C, with a run duration ranging from 2 to 24 hr. The resulting residual melts exhibit lower SiO2, TiO2, Al2O3, FeO, CaO, and total alkali contents, higher Ni, MgO, and Mg#, and almost constant CaO/Al2O3 compared to the initial tholeiitic melts. The compositions of the residual melts are influenced by factors such as the melt/harzburgite mass ratio, temperature, and run duration. Decreasing the melt/rock ratio or increasing temperature and run duration leads to a greater extent of assimilation. Under disequilibrated conditions (2 hr), the residual melts have higher SiO2, FeO, and MgO, and lower CaO, Al2O3, and total alkali contents compared to those under equilibrated conditions. The results suggest that interface reactions involving olivine dissolution and orthopyroxene precipitation, and chemical diffusion occur simultaneously during the interaction process. The compositions of the residual melts are largely controlled by interface reactions within 2 hr, followed by dominant chemical diffusion between the melts and refertilized harzburgite from 2 to 24 hr. Based on the experimental results, we propose a two‐stage model for the origin of Hawaiian shield stage parental magmas. Eclogite/pyroxenite‐derived tholeiitic melts first react with harzburgite, with varying melt/rock ratios, to produce residual melts in the deep lithosphere. These residual melts subsequently mix with plume peridotite‐derived melts at shallow depths, contributing to the geochemical diversity observed in Hawaiian shield stage lavas. Plain Language Summary: We conducted experiments to understand how melts derived from subducted oceanic crust interact with surrounding rocks during their journey through the Earth's lithosphere. By simulating melt‐rock reaction along wall‐rock boundary under high‐pressure and high‐temperature conditions, we found that the interaction mechanism involves olivine dissolution and orthopyroxene precipitation. The extent of interaction between the melts and rocks depends on factors such as the amount of melt present and the duration of the interaction. We also observed that certain chemical reactions took place at the interface between the melts and rocks, which affect the composition of the resulting melts. Our findings suggest that the formation of magmas with specific chemical compositions, similar to those observed in Hawaiian shield stage lavas, can be elucidated by the reaction between tholeiitic melts derived from eclogite/pyroxenite and harzburgite. The harzburgite was generated through prior high‐degree melting of peridotite influenced by the high temperatures in the plume setting. We propose a two‐stage model involving initial reactions in the deep lithosphere followed by mixing of the melts in shallower depths. This model provides insights into the processes that contribute to the diversity of magmas observed in Hawaiian volcanic islands. Key Points: Eclogite melts reacting with harzburgite produce high SiO2, MgO, and Ni tholeiitic meltsResidual melt composition is influenced by melt size and reaction time, involving interface reactions and diffusionEclogite melt interaction with harzburgite, followed by mixing with peridotite melts, accounts for Hawaiian shield stage lava generation [ABSTRACT FROM AUTHOR]

The increase in initial Hf isotopes identified in early Mesoarchean detrital zircon is commonly interpreted as a reflection of the geodynamic transition from stagnant‐lid to mobile‐lid tectonics. However, given the lack of petrogenetic context, interpreting detrital zircon may lead to spurious conclusions. In this contribution, we use zircon U‐Pb‐Hf‐O isotopic and bulk rock compositions of newly identified 3.05–2.9 Ga granitoids from the SW Yangtze Block to posit petrogenesis within an isotopically juvenile magmatic system. A statistical analysis of these data with a global igneous zircon Lu‐Hf isotopic compilation reveals an increase in average initial radiogenic Hf isotopes during the Paleoarchean to Mesoarchean transition. We posit that the Earth's continental crust underwent a global rejuvenation across the Paleo‐Mesoarchean transition. This rejuvenation can be explained by an independently observed increase in mantle temperatures resulting from mantle thermal evolution and does not require a change in tectonic style. Plain Language Summary: In this study, we explore the Earth's continental crust evolution before 3.0 billion years ago, a period characterized by limited preserved ancient rocks. We focus on zircon from igneous rocks, which provides a more reliable petrogenetic record than detrital zircon. Our study challenges the widely observed increase in detrital zircon initial Hf isotopes during the Paleo‐to Mesoarchean transition, often interpreted as a shift in tectonic regimes. We present new data from 3.05 to 2.9 billion‐year‐old granitoids in the Yangtze Block, suggesting isotopically juvenile magmatic activity. Statistical analysis of a global database of igneous zircon Hf isotopes reveals a state‐shift increase in εHf(t) across the Paleo‐to Mesoarchean transition, indicating global crustal rejuvenation at that time. Contrary to prevailing theories, we propose that this rejuvenation can be attributed to elevated mantle temperatures, challenging the notion of a significant geodynamic change during this period. Our findings emphasize the need to consider mantle thermal evolution in understanding continental crust growth on early Earth. Key Points: 3.05 and 2.9 Ga granitoids derived from juvenile crust are identified in the SW Yangtze BlockGlobal crust rejuvenation occurred across the Paleo‐to Mesoarchean transitionThis period of rejuvenation resulted from the effects of peak mantle temperatures [ABSTRACT FROM AUTHOR]

Whether Mn carbonates can be used as a proxy for the oxygenation event is debated. Here we examined the Early Cretaceous lacustrine Mn carbonates from North China, which contain abundant microbial fossils. The extremely positive δ13C (up to +15‰ relative to Vienna Peedee belemnite) and micro‐area enrichment of Ni strongly indicate a methanogenic archaea origin of these microorganisms. Transmission electron microscope and electron energy loss spectroscopy show the nanoscale transformation of Mn‐oxides (Mg‐exchanged phyllomanganate) to Mn carbonates (kutnohorite), on extracellular polymeric substances. The reaction of the Mn oxides with organic matter resulted in increasing pH and alkalinity, together with the fluctuating pH, offering a suitable micro‐environment for the transformation processes. These Mn carbonates are therefore indicative of an oxidized, sulfate‐absent environment. The depicted scenario serves as a reference to ocean of the early Earth and provides a referable Mn oxide tracer for determining the emergence of the Great Oxidation Event. Plain Language Summary: Microbial‐mineral interactions have played an important role in the evolution of the Earth. Active methanogenesis exists in submerged sediments, and the biological activity of methanogen is directly or indirectly involved in the process of geochemical cycling and mineral precipitation. In modern ocean environments, the methanogenesis zone and the manganese reduction zone are respectively, located in the lower and upper layers of a chemical zone, so it is difficult for them to interact directly with each other. This study documents evidence for the direct reaction between them in the Early Cretaceous lacustrine sediment cores from north China. Precipitation of Mn carbonates was likely mediated by methanogenesis in couple with Mn oxide reduction. Such an environment resembles the oxygen oases in the ocean before the Great Oxidation Event and thus provides new insights into the marine environment at that time. Key Points: Abundant methanogen microfossils in Mn carbonates with positive δ13CNanoscale transformation from Mn oxides to Mn carbonatespH fluctuations due to changes in redox conditions promote the formation of kutnohorite [ABSTRACT FROM AUTHOR]

Changbaishan volcano (China/North Korea) is one of the most active and hazardous volcanic centers in Northeast Asia. Despite decades of intensive research, the eruption history of this stratovolcano remains poorly constrained. One of the major puzzles is the timing of the eruption that produced the Tianwen Yellow Pumice (TYP) deposit at the caldera rim. Here we identify a new cryptotephra layer in sediment core 13PT‐P4 from the East Sea. Grain‐specific major, minor, and trace element analyses of glass shards allow a clear correlation of this distal tephra to the proximal TYP deposit of Changbaishan. Age‐depth modeling using radiocarbon (14C) dates of sediment bulk organic fractions and other tephrochronological markers from the sediment sequence constraints the age of the cryptotephra and thus the TYP eruption to 29,948–29,625 cal yr BP (95.4% confidence interval). Our findings lead to a revision of the history of Changbaishan explosive activity, and show that the volcano has been particularly active during ca. 51–24 ka BP in the last 100 ka. Using high resolution palaeo‐proxy records, we find the TYP tephra almost coeval with regional to hemispheric‐scale climatic changes known as Heinrich Event 3 (H3). With its precise age determination and wide geographic dispersion, the tephra offers a key isochron for dating records of past climatic changes and addressing the phasing relationships in environmental response to H3 across East Asia. Plain Language Summary: Improving the knowledge of past volcanism is critical for volcanic hazard mitigation. Changbaishan volcano is one of the most dangerous volcanic centers in Northeast Asia, but its eruption history is not clearly understood. A classic example is the eruption that produced the magnificent Tianwen Yellow Pumice (TYP) deposited at the crater rim. Previous studies suggested a range of very different ages for this major eruption. In this study we trace its volcanic ash into a marine sediment core from the East Sea. By radiocarbon age‐depth modeling we are able to say with a high level of certainty that the eruption occurred sometime between 29,948 and 29,625 cal yr BP. The new results demonstrate the dispersal potential of ash from the eruption and shed light on the history and frequency of Changbaishan explosive activity. In addition, the TYP eruption is found to coincide with hemispheric‐scale and regional environmental changes. As a consequence, the volcanic ash can be used as a key time mark for dating sediment sequences and for investigating past environmental changes in East Asia. Our study also demonstrates the potential of using distal volcanic ash in reconstructing past explosive volcanism. Key Points: Timing of the Changbaishan Tianwen Yellow Pumice (TYP) eruption is resolved through proximal‐distal tephra correlation and radiocarbon age‐depth modelingEruption history of the Changbaishan volcano is revised, and dispersal potential of the TYP tephra is shown for the first timeA demonstration that the TYP tephra, as a regional marker, has great potential for sediment sequence‐based palaeoenvironmental studies [ABSTRACT FROM AUTHOR]

Mantle metasomatism, which affects the geochemical and lithological properties of the Earth, is crucial to the evolution and modification of the Earth's interior. Variations in chemical proxy of metasomatism, including high‐field strength elements (HFSE, e.g., Zr‐Ti isotopes and isovalent Zr‐Hf), have been commonly utilized as a tool to unravel the processes associated with the evolution of the Earth. However, the impact of mantle metasomatism by diverse agents on the Zr isotopic compositions of metasomatized mantle remains poorly understood. Here we carried out high‐precision double‐spike δ94/90Zr measurements for a suite of basalts, which were derived from the mantle sources metasomatized by typical metasomatic agents of fluid, silicate melt and carbonate melt originating from the deep mantle or recycled crustal materials. Mantle metasomatism results in lithological diversities within the mantle, ranging from hybridized peridotites to pyroxenite/eclogite and carbonated eclogite, which can significantly fractionate the isovalent HFSEs. However, our data show that these basalts have primitive mantle‐like δ94ZrNIST values (−0.033–0.043 ‰), regardless of their superchondritic Zr/Hf. The primitive mantle‐like δ94ZrNIST, irrelevant to any proxy of metasomatism (e.g., Sr‐Nd isotopes, Zr/Hf and La/Sm), indicate that mantle metasomatism and subsequence melting produce no measurable Zr isotopic variations in metasomatized mantle‐derived basalts. The δ94ZrNIST of basalts thus can be representative of the mean metasomatized mantle compositions. Combined with previously reported komatiites and oceanic basalts, we show that the Earth's mantle displays consistent δ94ZrNIST (−0.013 ± 0.053 ‰), even if it has a secular dynamic evolution with the interaction between Earth's exterior and interior. Plain Language Summary: Mantle metasomatism has a significant impact on the geochemical and lithological properties of the Earth's interior. The chemical variations, including the high‐field strength elements (HFSE), caused by this process, could provide key insights into such modification. However, the variation of Zr isotopes during mantle metasomatism remains enigmatic. Here, we analyzed the Zr isotopes of fresh basalts derived from mantle sources metasomatized by diverse metasomatic agents. We find that although mantle metasomatism leads to the substantial fractionation of Zr (Nb) from Hf (Ta), no measurable Zr isotopic variation occurs for metasomatized mantle‐derived melts, as reflected by the homogeneous and primitive mantle‐like Zr isotopic compositions of different samples. Combining our findings with previous data, we conclude that the Earth's mantle, from large‐scale and secular perspectives, maintains a consistent Zr isotopic composition, although the Earth underwent complex and dynamic evolution. Key Points: A first comprehensive investigation of Zr isotopes of mantle metasomatized by diverse agents of fluid, silicate melt and carbonate meltBasalts derived from metasomatized mantle show variable radiogenic isotopes and trace element patterns, but limited Zr isotope variationThe Earth's mantle exhibits consistent δ94Zr, despite its secular dynamic evolution with interaction between Earth's exterior and interior [ABSTRACT FROM AUTHOR]

We determine high‐resolution tomographic models of isotropic P‐wave velocity (Vp) and tilting‐axis anisotropy of the Alaska subduction zone using a large number of local and teleseismic data recorded at many portable and permanent network stations in and around Alaska. We find a flat high‐Vp slab in the mantle transition zone (410–670 km depths) beneath western Alaska, which is connected with the subducting Pacific slab at 0–410 km depths, suggesting that a big mantle wedge has formed under western Alaska. Our tilting‐axis anisotropy model reveals complex mantle flows in the asthenosphere. Corner flow in the mantle wedge above the subducting Pacific slab and toroidal flow in the big mantle wedge are revealed, which may cause the Cenozoic intraplate volcanoes in western Alaska and the Bering Sea. In central Alaska, the mantle wedge beneath the Denali volcanic gap is characterized by high‐Vp and subhorizontal fast velocity directions normal to the volcanic arc, which may reflect a remnant of the subducted Yakutat slab. In SE Alaska, the shallow subduction of the Wrangell slab is visible above 150 km depth, and hot mantle upwelling through the Wrangell‐Yakutat slab gap may contribute to the Wrangell volcanic field. Plain Language Summary: Alaska is home to over 100 Cenozoic volcanoes, but their formation mechanism is still puzzling. Here we use a large number of seismic data and a novel tomographic technique to obtain high‐resolution images of isotropic P‐wave velocity (Vp) and anisotropy down to 800 km depth beneath Alaska. Our results show that a flat high‐Vp slab exists in the mantle transition zone (410–670 km depths) beneath western Alaska, where a big mantle wedge has formed above the flat slab. Fluids in the big mantle wedge and large‐scale mantle flow around it have caused Cenozoic intraplate volcanoes near the Bering Sea. The Denali volcanic gap, different from its neighboring Buzzard Creek‐Jumbo Dome volcanoes, has a high Vp mantle wedge with arc‐normal fast anisotropy, which may reflect a cool fluid barrier from the Yakutat slab. The high‐Vp Wrangell slab is revealed down to ∼100 km depth beneath the Wrangell volcanic field, Mount Churchill and Prindle volcano. Hot upwelling flows near the Wrangell slab edge may cause these volcanoes. Key Points: A big mantle wedge (BMW) has formed above a flat slab in the mantle transition zone under western AlaskaIntraplate volcanism in western Alaska and the Bering Sea is caused by hot upwelling flows in the BMWThe Wrangell volcanic field and Denali volcanic gap are caused by subduction of the Wrangell and Yakutat slabs, respectively [ABSTRACT FROM AUTHOR]

The Cascadia margin is an unusual subduction zone characterized by the downdip movement of young and thin oceanic plates, where mantle flow and intraslab deformation are still unclear. Here we present new anisotropic tomography of the Cascadia subduction zone, in which the hexagonal symmetry axis of anisotropy is tilting rather than horizontal or vertical as assumed in previous studies of seismic anisotropy. Subduction‐induced entrained and toroidal flows under the Cascadia margin are discriminated well by the spatial relationship between tilting‐axis anisotropy and slab geometry. The obliquely entrained flow is trapped in a narrow zone (<100 km wide) above and below the subducting slab and reaches ∼200 km depth, which is surrounded by large‐scale sub‐horizontal toroidal flow. The intraslab anisotropy is trench‐normal above 80 km depth but changes to trench‐parallel at 100–400 km depths, which may reflect fossil anisotropy overprinted by deep deformation beneath the arc, or joint effect of serpentinization and hydrous faulting. Plain Language Summary: The slab deformation and mantle flow under the Cascadia margin are controversial. We obtain new anisotropic tomography of the Cascadia subduction zone, which can reveal tilting 3‐D fast velocity directions (FVDs) and planes. Because the observed trench‐normal FVD in the Cascadia margin can be explained by both 3‐D toroidal and 2‐D entrained flows, we discriminate the two types of mantle flow with 3‐D FVDs that contain dip angle information. The 2‐D entrained flow above and below the subducting slab is trapped in a narrow zone of ∼100 km wide and is surrounded by large‐scale sub‐horizontal toroidal flow. The slab anisotropy above 80 km depth is consistent with that in the Juan de Fuca plate before subduction, but it is reshaped beneath the arc due to the slab deformation or phase transition. Key Points: Tilting‐axis anisotropy can reconcile contradictory assumptions of azimuthal and radial anisotropiesEntrained flow occurs within ∼100 km depth above and below the subducting slab and is surrounded by toroidal flowFossil anisotropy in the slab is overprinted beneath the arc due to intraslab deformation or phase transition [ABSTRACT FROM AUTHOR]

In subduction zones with slab‐slab interactions, the pattern of mantle convection is very complex and still unclear. In this study, we jointly invert a large number of P and S wave arrival time data of local earthquakes for 3‐D isotropic and anisotropic velocity structures of the Banda subduction zone. Along the curved Banda arc, the subducting Indo‐Australian slab is detected clearly as a high‐velocity zone, and its azimuthal anisotropy changes along the arc strike, representing fossil anisotropy within the slab and modified anisotropy by the subduction processes. Around the northern edge of the Banda slab, a semi‐toroidal pattern of anisotropy appears in low‐velocity anomalies, representing mantle flow extruded from the Banda arc and escaped from a gap of the Banda‐Molucca slab toward the northeast. Our 3‐D anisotropic tomography uncovers the mantle convection pattern induced by the slab‐slab interactions, shedding new light on the complex dynamical processes in this curved subduction zone. Plain Language Summary: The study of mantle convection pattern can improve our understanding of plate tectonics and geodynamics. The mantle convection pattern is affected by several factors, including the subducting slab geometry and slab‐slab interactions. The tectonics in the Banda area is rendered particularly complex due to the subduction and interactions of multiple slabs. Hence, this region is an ideal natural laboratory to study the mantle flow pattern associated with slab‐slab interactions. Here we invert both P and S wave arrival times of local earthquakes for 3‐D anisotropic structure of the upper mantle beneath the Banda region. Our results show that in this curved subduction zone, the mantle convection pattern is different from that in normal subduction zones. Trench‐parallel anisotropy is revealed beneath Banda, which reflects extruded material flow in the curved subduction zone. Our results provide new insight into subduction dynamics and mantle convection. Key Points: The first P and S wave anisotropic tomography of the Banda subduction zone is obtainedTrench‐parallel anisotropy along the Banda arc reflects lateral mantle flow caused by the highly curved Banda slabSemi‐toroidal anisotropy around the northern edge of the Banda arc reflects extruded mantle flow from the arc [ABSTRACT FROM AUTHOR]

Oceanic‐plates vertical tearing is seismically identified in the present‐day Earth. This type of plate tearing is frequently reported in horizontally‐oblique subduction zones where transform‐faulted oceanic plates are subducting (or subducted). However, the mechanisms behind vertical slab tearing are still poorly understood, thus we utilize 3D time‐dependent Stokes' flow thermo‐mechanical numerical models to further study this problem. We find that (a) the age offset of transform fault and (b) the horizontal obliqueness of subduction fundamentally control the tearing behavior of two generic, materially homogeneous oceanic slabs separated by a low‐viscosity zone. The two slabs sequentially bend, which combined with the age‐thickness difference between slabs, causes the differential sinking of them. Based on the modeling results, well‐developed slabs vertical tearing would happen when the oblique angle of subduction is ≥30° or the age ratio of the secondly bent to firstly bent slab being ∼<0.6. Quantifying the horizontal distance‐vector between sinking slabs, we find that subduction at medium‐low horizontal‐obliqueness angles (≤40°) of young lithosphere (slabs‐average ∼15 Myr) tends to produce fault‐perpendicular tearing. Contrastingly, old‐age slabs (average ≥ 30 Myr) with medium‐large obliqueness angles (∼>20°) tend to produce fault‐parallel tearing, related to differential slab‐hinge retreat or rollback. Correlations between slabs' (a) computed tearing horizontal‐width and (b) scaling‐theory forms of their subduction‐velocity differences, are reasonable (0.76–0.97). Our numerically predicted scenarios are reasonably consistent with plate‐tear imaging results from at least four natural subduction zones. Our modeling also suggests that continual along‐trench variation in subduction dip angle may be related to a special case of oblique subduction. Plain Language Summary: Oceanic tectonic plates can tear‐off through time as they plunge and sink into the Earth's mantle and are especially favored when plates have preexisting fault‐weak zones. Two primary conditions promote oceanic tectonic slabs' tearing: (a) Obliqueness of a plate's horizontal velocity with respect to the overriding‐plate coastline and trench, leading to the two slabs sequentially bending yet having differences in deformation; (b) Differences in slab‐age between two sides of a displaced fault‐zone that created an offset in plate age and thickness. To understand these processes, we present 3D numerical models that simulate tectonic evolution and deformations, and we compare model results with analytical studies as well as with natural observations from seismic imaging. Age differences across fault‐zones combined with subduction horizontal obliqueness control the generation and development of vertical tearing. Furthermore, two geometrical patterns of vertical tearing are largely consistent with observations. Our findings suggest that along‐trench changes in the steep angle between the slab and surface (dip angle) may be related to a special case of oblique subduction. Observing the age contrast across faults and the horizontal obliqueness of plates' motion allows predictions of the tearing pattern, evolution, and local mantle flow. Key Points: 3‐D numerical models are conducted to study the vertical tearing mechanism of the transform‐faulted oceanic slabs during oblique subductionThe horizontal obliqueness and slab transform age difference play dominant roles in determining the style of vertical slab tearingCorrelations between slabs' computed tearing width and scaling‐theory forms of subduction‐velocity difference, are useful and strong [ABSTRACT FROM AUTHOR]

The East Kunlun Shan (EKLS) in northern Tibet occupies boundaries of the low‐relief topography and lower crustal low‐velocity zone in the interior plateau, making it ideal for exploring the relationship of surface deformation with underlying geodynamic processes. We used previous and new apatite (U‐Th)/He data to analyze the exhumation history and pattern throughout the EKLS and link surface deformation to deep structures. Integrated (U‐Th)/He ages reveal the rapid exhumation at 27–25 Ma, due to the coeval orogen‐scale tilting of the EKLS. Along with the crustal structures beneath the EKLS, it is inferred that orogen‐scale tilting is the isostatic response of the nonuniform crustal thickening related to northward injection of the Tibetan lower crust. This study highlights the role of ductile deformation within the lower crust in mountain building in northern Tibet, which shares a similarity with mountain building pattern in the eastern plateau margin. Plain Language Summary: How deep geodynamic process affects shallow crustal deformation in Tibet is one of the key issues in understanding continental dynamics. The East Kunlun Shan (EKLS) defines northern boundaries of low‐relief topography and crustal low‐velocity zone in the interior plateau. In this study, we explore the relationship between surface deformation and underlying geodynamic processes in the EKLS by analyzing the shallow crustal exhumation pattern in conjunction with deep structures. Amounts of apatite (U‐Th)/He ages across the EKLS reveal the late Oligocene orogen‐scale tilting, indicating the involvement of indistinctive shallow crustal shortening in the mountain building process. Such a regional tilting may be the reflection of nonuniform crustal thickening related to the injection of the Tibetan lower crust when considering the crustal structures beneath the EKLS. By comparing the mountain building patterns in the northern and eastern margins of Tibet, we conclude that ductile deformation in the lower crust may be a common phenomenon to mountain building in plateau margins. Key Points: Apatite (U‐Th)/He data reveal the accelerated exhumation at 27‐25 Ma and southward increasing exhumation across the East Kunlun Shan (EKLS)The EKLS has experienced the orogen‐scale tilting during the late OligoceneOrogen‐scale tilting of the EKLS may be the isostatic response of northward injection of the Tibetan weak lower crust [ABSTRACT FROM AUTHOR]

We present high‐resolution 3‐D tomographic models of isotropic P‐wave velocity (Vp), azimuthal anisotropy, and radial anisotropy down to 1,300 km depth beneath the central and eastern United States (CEUS), which are obtained by inverting a great number of local and teleseismic data and making a whole‐mantle correction to teleseismic travel‐time data recorded by the USArray. Trade‐offs between azimuthal and radial anisotropies occur due to the correlation between the azimuthal and incidence angles of seismic rays, but the use of uniform and crisscrossing rays can reduce the trade‐off effect. Our tomographic images reveal the North American Craton with layered anisotropy and strong anisotropies in the lower mantle related to the deeply subducted Farallon slab and passage of the Bermuda hotspot. In the upper mantle, low‐velocity anomalies with significant seismic anisotropy are revealed beneath three intraplate seismic zones in New Madrid, East Tennessee, and South Carolina, suggesting that hot and wet mantle upwelling occurs under the seismic zones, and the related fluids affect the earthquake generation. The most important dynamic processes in the mantle beneath the CEUS are the deep subduction of the Farallon plate and the passage of the Bermuda hotspot, which have caused strong structural heterogeneities, seismic anisotropy, as well as thermal anomalies and fluids that contributed to the formation of intraplate seismic zones in the CEUS. Plain Language Summary: In the central and eastern United States (CEUS), the North American Craton has been stable for over ∼1.3 Ga, whereas three intraplate seismic zones exist in New Madrid, East Tennessee and South Carolina. Their locations coincide well with the track of the passed Bermuda hotspot and the deeply subducted Farallon slab in the lower mantle, but related mantle dynamics are poorly understood. Here, we adopt two types of seismic anisotropy (directional dependence of seismic wave speed) to describe the mantle dynamics beneath the CEUS. We obtain high‐resolution 3‐D anisotropic images down to 1,300 km depth by inverting high‐quality travel‐time data of local and teleseismic events recorded by the USArray seismic network. Our results reveal detailed mantle structure and dynamics beneath the CEUS, including the layered North American Craton, weak lithosphere beneath the three seismic zones, and seismic anisotropies in the mantle transition zone (410–660 km depths) and the lower mantle. The New Madrid Seismic Zone is affected by asthenospheric upwelling beneath the Mississippi Embayment. A narrow low‐velocity pillar is revealed in the thick lithosphere beneath the East Tennessee Seismic Zone. The South Carolina Seismic Zone is affected by mantle convection under the passive continental margin. The deep subduction of the Farallon plate and the passage of the Bermuda hotspot are the most critical dynamic processes in the mantle beneath the CEUS, which have caused significant structural variations, strong seismic anisotropy, as well as thermal anomalies and fluids that contributed to the formation of the intraplate seismic zones in the CEUS. Key Points: 3‐D P‐wave anisotropic tomography down to 1,300 km depth beneath the central‐eastern USA is obtainedDifferent upper‐mantle structures and dynamics are revealed beneath the three intraplate seismic zonesAnisotropies in the upper part of the lower mantle are related to the subducted Farallon slab and passage of the Bermuda hotspot [ABSTRACT FROM AUTHOR]

Teleseismic tomography is a powerful tool to study the 3‐D structure of the upper mantle beneath a local seismic network, but the robustness of its images has been challenged by the increasing size of the study volume in recent studies. This is because teleseismic tomography uses relative travel‐time residuals (RTTRs) that are contaminated more by the whole‐mantle heterogeneity for a larger study region. In this work, we correct the RTTRs of teleseismic events for the mantle heterogeneities outside the study volume using two global tomographic models. Our results show that the whole‐mantle correction is necessary when a study region is wider than ∼10°, and the maximum outside residual reaches 1.2 s for a study region of ∼35° wide. After the whole‐mantle correction, those teleseismic events with a large ray spread angle are still useful for tomographic imaging. Applying this approach to teleseismic travel‐time data recorded by the USArray, we obtain a high‐resolution 3‐D P‐wave velocity (Vp) model beneath the central and eastern United States. It shows three low‐velocity anomalies beneath the New Madrid Seismic Zone, the East Tennessee Seismic Zone, and the South Carolina Seismic Zone, suggesting that lithospheric weakness induced by fluids may play an important role in reactivating the intraplate seismic zones. The passage of the Bermuda hotspot and remnants of the subducted Farallon slab in the lower mantle might be responsible for the fluid release and lithospheric weakening, which reactivated ancient rifts and suture zones in the crust and facilitated the formation of the intraplate seismic zones. Plain Language Summary: Teleseismic tomography is a widely used method exploiting travel‐time data of distant earthquakes to study the three‐dimensional seismic velocity structure of the upper mantle beneath a study region covered by a seismograph network. We find that the size of the study volume significantly affects teleseismic tomography and the data should be corrected for the whole‐mantle heterogeneity outside the study volume. We obtain a reliable tomographic model beneath the central and eastern US by making the whole‐mantle correction to high‐quality travel‐time data of teleseismic events recorded by the USArray seismic network. Our results reveal three low‐velocity anomalies beneath the New Madrid Seismic Zone, the East Tennessee Seismic Zone, and the South Carolina Seismic Zone in the central and eastern US, as well as remnants of the subducted Farallon plate in the lower mantle under the region. Hot and wet mantle upwelling flow may contribute to reactivation of ancient rifts and suture zones, which can cause the intraplate seismic zones. In addition, the passage of the Bermuda hotspot and the deeply subducted Farallon plate may have facilitated the formation of the three intraplate seismic zones. Key Points: Teleseismic tomography is affected by the inversion volume sizeTeleseismic data should be corrected for the whole‐mantle heterogeneity before using them in tomographic imaging of a large study regionThe passage of the Bermuda hotspot and the subducted Farallon slab facilitated the formation of seismic zones in the central‐eastern USA [ABSTRACT FROM AUTHOR]

A high‐resolution velocity and anisotropy model of the uppermost mantle under the Hainan Island and surrounding areas is obtained by a tomographic inversion of 8192 Pn arrival‐time data hand‐picked from high‐quality seismograms recorded at a total of 137 seismic stations of our recently deployed HAVESArray portable seismic network and Chinese provincial stations. Our new model shows obvious velocity and anisotropic structural features related to the distribution of Quaternary volcanic rocks on the surface. Extensive low Pn velocity anomalies are detected under the Weizhou Island, northern Hainan Island, southern Leizhou Peninsula, southern South China, and around the Pearl River Mouth Basin (PRMB), whereas high Pn velocity anomalies are imaged under the PRMB and areas of 108°–109°E and between the Baise‐Hepu fault and the Wuchuan‐Sihui fault. The Pn fast propagation directions exhibit a radiated pattern around the PRMB. Integrated with previous global and regional tomographic models, our present results indicate that the Hainan plume is upwelling around the PRMB in the upper mantle, and then plume‐related flow is split into several branches under the volcanoes in the northern Hainan Island, southern Leizhou Peninsula and Weizhou Island. This flow pattern could be associated with the westward deep subduction of the Philippine Sea and Pacific plates and eastward deep subduction of the Indian plate. Our results provide new insights into the formation mechanism of the Hainan‐Leizhou and Weizhou volcanoes. Plain Language Summary: The Quaternary volcanism in the Hainan and surrounding areas was very intense, and there were many periods of volcanic eruptions in the geologic history. The link among the Hainan, Leizhou, and Weizhou volcanoes is still unclear. Pn wave glides in the uppermost mantle and first arrives at a station within a certain epicentral distance. Therefore, Pn tomography has obvious advantages for revealing high‐quality velocity and anisotropy structural features of the uppermost mantle in the study region. Extensive low Pn velocity anomalies are revealed under the northern Hainan Island, southern Leizhou Peninsula, Weizhou Island, southern South China Block and around the Pearl River Mouth Basin (PRMB), whereas a radiated pattern of Pn fast‐propagation directions around the high‐V PRMB is revealed. These results suggest that multiple branches of mantle flows may exist under the Hainan, Leizhou, and Weizhou volcanoes from the Hainan mantle plume, probably due to the westward deep subduction of the Pacific plate and eastward deep subduction of the Indian plate. Key Points: A high‐resolution Pn anisotropy tomographic model in Hainan Island and surrounding areas is obtained with manually picked travel‐time dataSignificant low‐V anomalies are revealed in the northern Hainan Island, southern Leizhou Peninsula and Weizhou IslandA radiated pattern of anisotropy around the PRMB suggests the existence of multiple branches of the Hainan mantle plume [ABSTRACT FROM AUTHOR]

Water is essential for the formation of granites, but its origin and role in granite generation (i.e., dehydration vs. water‐fluxed melting) remain uncertain. These issues are addressed by combining water abundances and other geochemical indices in zircons from Late Mesozoic granites generated during the destruction of the North China Craton (NCC). The water contents in zircons from the NCC Early Cretaceous granites (763 ppm, median) are much higher than those of the NCC Jurassic granites (424–513 ppm), upper mantle and continental arc magmas (92–477 ppm). More importantly, the higher water contents in the voluminous Early Cretaceous granites also have higher zircon saturation temperatures, εHf(t), and lower δ18O values. These observations suggest a predominantly mantle origin for the water, and water‐fluxed crustal melting, in which larger water ingression produced more voluminous melts. The high‐water flux was likely related to the subduction of the Paleo‐Pacific Plate, which ultimately destabilized the NCC. Plain Language Summary: The fact that water is essential in generating granites has been known for a long time. However, its detailed role is poorly understood due to heterogeneous source and complex melting reactions involved in the generation of granites. As a fundamental issue of granite genesis, it remains a long‐standing problem to distinguish the two major mechanisms, that is, hydrous‐mineral‐dehydration melting versus external‐water‐added melting. In this study, the water content of zircon combined with other lines of clues of I‐type granites that generated during the destruction of North China Craton (NCC) in Late Mesozoic collectively points to water‐added crustal melting rather than dehydration melting. The isotope composition of zircon suggests a mantle provenance of water. The highest water contents occurred in the Early Cretaceous granites, corresponding to the climax of the NCC destruction. Higher zircon water contents in Early Cretaceous granites indicate higher water‐flux into thelithospheric mantle and overlying crust by the subduction of the paleo‐Pacific plate. Accordingly, water played a significant role in cratonic destruction. Key Points: Water contents of zircons from North China Craton Jurassic granites are comparable with continental arc magmasHigher zircon water contents are found in voluminous Early Cretaceous granites generated during the climax of cratonic destructionEarly Cretaceous granites were generated by water‐fluxed crustal melting, the water in which has a predominant mantle origin [ABSTRACT FROM AUTHOR]

We determine high‐resolution 3‐D tomographic images of P‐wave isotropic velocity, radial anisotropy and azimuthal anisotropy beneath NE Asia down to 800 km depth. Our results show negative radial anisotropy (i.e., Vhorizontal < Vvertical) in the asthenosphere of the big mantle wedge (BMW), which may reflect mineral alignment caused by vertical flow in the asthenosphere. Across the Tanlu fault zone (TLF), the western and eastern parts of the BMW exhibit high and low P‐wave velocities, respectively. Combining our tomographic results with surface geological features, we speculate that convection in the BMW includes upwelling asthenosphere beneath the Japan Sea and the Korean Peninsula and downwelling asthenosphere beneath the Songliao and North China basins. The downwelling asthenosphere beneath the two basins is associated with diminishing volcanism and anomalous tectonic subsidence since ∼110 Ma. The great TLF is an important boundary for the BMW structure and dynamics. Plain Language Summary: The subducting Pacific plate becomes flat in the lower part of the mantle transition zone beneath NE Asia, and a big mantle wedge (BMW) has formed above the flat slab. The BMW controls tectonic and geological activities in NE Asia, which are characterized by large‐scale sedimentary basins, lithospheric thinning, large strike‐slip faults, deep earthquakes and intraplate volcanism. However, the convection pattern in the BMW is still unclear. We determine the first 3‐D P‐wave radial anisotropy model down to 800 km depth beneath NE Asia, as well as high‐resolution tomographic images of isotropic P‐wave velocity and azimuthal anisotropy. We find predominant negative radial anisotropy in the BMW and east‐west variations of velocity structure. Combining the tomographic results with surface geological features, we speculate that convection in the BMW may include upwelling flows beneath the SW Japan Sea and the southern Korean Peninsula and downwelling flows beneath the Songliao and North China basins. Key Points: The first 3‐D radial anisotropy model beneath NE Asia is obtainedEast‐west structural variations in the big mantle wedge (BMW) are revealedA possible convection pattern in the BMW is proposed [ABSTRACT FROM AUTHOR]

Active volcanoes in East Asia pose potential threats to the surrounding areas. The eruptive history of many of the Japanese volcanoes are well understood, but their dispersal pathways are often based on visible tephra. Additionally, other important volcanoes in the region still require a deeper understanding of their eruptive potential. Here, we explore the Holocene cryptotephra record preserved in a marine core 13PT‐P4 in the southwestern East Sea, in order to better reconstruct past eruptive events and their dispersal. Six widespread tephra layers are identified and correlated to their source volcanoes in S Korea (Ulleungdo), China/N Korea (Changbaishan) and Japan (Kikai), with their dispersal ranges updated. Our results rank the 13PT‐P4 sequence the most intensively tephra‐constrained Holocene record in the East Sea, which permits synchronization of this mid‐latitude archive with records in the Arctic and tropical regions. Terrestrially based tephra ages are used to constrain the marine reservoir effect and the age‐depth model of the record. The average reservoir age in the region is estimated to be 1150 ± 30 14C yr at ca. 7.3–5.6 cal ka BP and 1565 ± 30 14C yr at ca. 1.0 cal ka BP. These observed changes in reservoir age could indicate active upwelling at a regional scale. Additionally, we provide a detailed age estimate and glass geochemistry for a previously poorly understood eruption (U‐1) from the Ulleungdo volcano, thus refining its Holocene eruptive history. The U‐1 eruption is dated to 3354‐3080 cal yr BP (95.4%), and has glass composition that is distinct from other Ulleungdo tephras. Plain Language Summary: Explosive volcanic eruptions are one of the most important natural hazards in East Asia. The study of eruptive history and volcanic ash dispersal are the key to understand the behavior of certain volcanoes over time and to better identify the level of risk from different volcanoes. We studied the microscopic volcanic ash layers preserved in a marine core from the southwestern East Sea. Geochemical and stratigraphic evidence allow us to pinpoint the source volcanoes and eruptive events for these ash layers. The results indicate that several ash layers in the region are more widely dispersed than what we have learned from visible ash studies. We provide chronological and geochemical data for a previously poorly understood eruption from Ulleungdo volcano, S Korea, thus refining its Holocene eruptive history. We use terrestrial ages of the ash layers to aid the dating of the marine record and the assessment of marine reservoir effect. Using the identified ash layers, we can now synchronize the marine record with sedimentary archives in the Arctic and the tropical regions. This is also one of the first studies of microscopic volcanic ash layers in marine records in the region and shows the potential of this approach for future studies. Key Points: Widespread cryptotephra layers identified in the East Sea sediments permit hemispheric synchronization of sedimentary archivesHolocene eruptive history of the Ulleungdo volcano is refined and the U‐1 eruption is dated for the first time and geochemically characterizedSea‐land tephra correlations allow for the establishment of marine age models and the assessment of marine reservoir ages [ABSTRACT FROM AUTHOR]

A detailed 3‐D model of P wave isotropic velocity and azimuthal anisotropy beneath SE Asia is obtained by jointly inverting local earthquake arrival times and teleseismic relative travel‐time residuals. Our results show that the high‐velocity (high‐V) subducting Australian slab has penetrated through the mantle transition zone (MTZ) and reached a depth of ∼1,200 km beneath Sumatra, whereas the high‐V slab has subducted toward the north and trapped within the MTZ beneath Java. The Hainan mantle plume is revealed clearly as a significant low‐velocity anomaly beneath the MTZ, which extends down to the bottom of our model (∼1,600‐km depth). The upwelling of the Hainan plume is resisted by the stagnant slab in the MTZ, resulting in divergent fast‐velocity directions of azimuthal anisotropy beneath the stagnant slab. The detailed results of seismic tomography and azimuthal anisotropy provide important new information on the complex mantle structure and dynamics of the SE Asian region, in particular, the subducting slabs and the Hainan plume, as well as their interactions. Plain Language Summary: The SE Asia curved subduction system is an ideal region to study plate tectonics and subduction dynamics due to the coexistence and interactions of the Hainan mantle plume and subducting slabs. However, detailed geometries and structures of the plume and slabs are still unclear because of the uneven distribution of seismic stations and earthquakes in SE Asia. In this work, we study the 3‐D seismic velocity structure beneath SE Asia by conducting P wave seismic tomography. We find that the Hainan plume upwelling is resisted by a stagnant slab in the mantle transition zone (MTZ, at depths of 410–660 km), generating divergent azimuthal anisotropies that are centered in significant low‐velocity zones beneath the MTZ. The coexistence of the mantle plume and the stagnant slab may have caused the complex tectonic history and geological features in SE Asia, such as many arc and back‐arc volcanoes, active intraplate volcanism, and widely distributed Cenozoic basalts. Key Points: A high‐resolution 3‐D model of P wave velocity and azimuthal anisotropy beneath SE Asia is determinedDifferent slab geometries beneath Sumatra and Java are related to the lithosphere age of the subducting slabThe Hainan plume upwelling is resisted by a stagnant slab in the MTZ, causing divergent shape azimuthal anisotropies [ABSTRACT FROM AUTHOR]

Three different conceptual models have been proposed for the Cenozoic subduction style in South Asia, including Greater India, Intra‐oceanic Arc, and Continental Terrane (or Greater Indian basin). Since these models imply distinctive origins for the Tethyan–Greater Himalayan (TGH) sequences, for example, as a relic of the subducted Greater India or Gondwana–affiliated continental terrane, quantitively reproducing the relic TGH crustal mass with numerical models could help further constrain the debated Cenozoic subduction history between India and Eurasia. Based on the modeling results, we show that the subducted plate since the Paleocene should consist of a significant oceanic portion that is, ∼1,000 km long for the Intra‐oceanic Arc model and up to 2,000 km long for the Terrane model. Our results do not support the existence of a continuous >3,000 km long continental Greater India before the early Eocene collision in South Asia. Plain Language Summary: Approximately 55 million years ago, the Indian Subcontinent was in the Southern Hemisphere, >3,000 km away from Tibet. However, it remains unknown what tectonic units were between them. Previous studies suggest that this region was composed of either pure land or with parts being oceans. By now, this region has mostly foundered into the deep Earth, with its surface relics forming the Himalayan Mountains. Because land and ocean contribute differently to the relic materials, the mass of the Himalayan Mountain can provide essential information about this lost tectonic region. This study uses numerical models to replicate the relic Himalayan mass while evaluating the earlier proposed models. We found that to match the Himalayan mass, the region between Tibet and India ∼55 million years ago could not be purely continental and should include >1,000 km long oceanic plate. Key Points: Different models of Cenozoic subduction history in South Asia imply distinctive origins for the Tethyan–Greater Himalayan sequencesQuantitively reproducing the Tethyan–Greater Himalayan mass helps constrain the Cenozoic subduction history in South AsiaBoth the Intra‐oceanic Arc and Terrane models, but not the Greater India model, could have been operating during the Cenozoic subduction [ABSTRACT FROM AUTHOR]

Olivine‐hosted melt inclusions have the potential to provide direct evidence about the nature of the mantle sources of magmas. In this study, we report the major and trace element and Sr–Nd–Pb–Hf isotope compositions of the Lijiang picrites from the Emeishan large igneous province, as well as major and trace element and Pb isotopic compositions of olivine‐hosted melt inclusions in the picrites. Using these data, we infer the nature of the mantle sources for the Lijiang high‐Ti picrites (Ti/Y = 645–654), and compare them with the Dali low‐Ti picrites (Ti/Y = 351–408). Lijiang melt inclusions have highly heterogeneous Pb isotope compositions (208Pb/206Pb = 2.015–2.201, 207Pb/206Pb = 0.812–0.882, 260 Ma age‐corrected) that overlap the majority of the fields from FOZO to enriched mantle 1 (EM1). The primitive mantle‐normalized trace element patterns of these melt inclusions reveal an enriched composition with depletions in Ba, Nb, Ta, Zr, and Hf. We suggest that an old recycled GLOSS II‐like sediment was probably the main component that imparted the EM1 signature into the sources of the Lijiang picrites. Furthermore, we reverse calculated the mantle potential temperature (Tp) beneath Lijiang and Dali using the Al‐in‐ol temperature. The estimated mantle Tp beneath Lijiang is lower than Dali. We infer that the Lijiang picrites might have originated from the mantle plume with lower thermal energy, corresponding to the waning stage of the axis of the Emeishan mantle plume. Our study suggest that high‐Ti magmas of the Emeishan large igneous province were derived from those parts or stages of the mantle plume with lower thermal energy. Key Points: Highly heterogeneous Pb isotope compositions of olivine‐hosted melt inclusions are found in the Lijiang picritesGLOSS II‐like subduction sediments are responsible for the enriched mantle 1‐like component in the source of the Emeishan large igneous province (LIP)Thermal variation of the mantle plume controlled the types and distribution of basaltic magmas in the Emeishan LIP [ABSTRACT FROM AUTHOR]

The southeastern Tibetan Plateau experienced intense Cenozoic shortening and extrusion along the western Yangtze Craton, SW China, where the Permian Emeishan flood basalts were emplaced. Seismic anisotropy along a dense E–W‐trending linear seismic array across the west Yunnan is determined by shear‐wave splitting analysis to characterize the deformation associated with these processes. Interestingly, a strong N–S‐oriented anisotropic zone collocated with the Eocene–Oligocene potassic magmatism is observed between two weak anisotropic zones in the Three‐River Orogenic Zone and the western Yangtze Craton, respectively. The lateral anisotropy variation and distinct upper mantle structures collectively suggest that the western most Yangtze Craton, strengthened by the Permian mantle plume, acted as a rigid barrier to divert the Cenozoic Tibetan mantle flow into the Three‐River Orogenic Zone. Consequently, the western edge of the Yangtze Craton has been partially eroded and its anisotropic orientation was realigned to the direction of the mantle flow. This observation indicates that both the remodeled anisotropy in the lithosphere and the dynamic flow in the asthenosphere contribute to the mantle anisotropy at the lateral lithosphere‐asthenosphere transition, which is usually hard to seismologically resolve from the vertical lithosphere‐asthenosphere boundary. Plain Language Summary: The India‐Asia collision has resulted in substantial continental extrusion in the Cenozoic. Associated with this extrusion process, the Tibetan mantle flowed along the west edge of the Yangtze Craton where the Permian Emeishan Large Igneous Province was emplaced. Here, we use seismic anisotropy to inspect footprints left by the interaction between the mantle flow and the cratonic lithosphere. Shear‐wave splitting analysis was performed along a dense E–W‐trending linear seismic array across the west Yunnan, SW China, and delineates a strong N–S‐oriented anisotropic zone spatially overlapping with the Eocene‐Oligocene potassic magmatism. Interestingly, this strong anisotropic zone is laterally sandwiched by two weak anisotropic zones, the Three‐River Orogenic Zone to the west and the western Yangtze Craton to the east. There is a prominent slow‐speed anomaly in the upper mantle beneath the Three‐River Orogenic Zone, whereas a thick fast‐speed anomaly beneath the western Yangtze Craton. Such lateral variations of seismic anisotropy and wave speed can be best accounted for the interaction between the southward Tibetan mantle flow and the plume‐strengthened Yangtze Craton. This observation well inspects the remodeled anisotropy in the lithosphere and the dynamic flow in the asthenosphere and yields new insights into the nature of seismic anisotropy at the lithosphere‐asthenosphere boundary. Key Points: Salient lateral variations of seismic anisotropy in the west Yunnan are revealed by shear‐wave splitting analysisThe plume‐strengthened western Yangtze Craton diverted the Cenozoic Tibetan mantle flow into the Three‐River Orogenic ZoneThe western edge of the Yangtze Craton has been partially eroded away and its fabric was remodeled to align with the mantle flow [ABSTRACT FROM AUTHOR]

The Earth's mantle shows large‐scale geochemical heterogeneities bounded by several identifiable end‐member compositions. However, the origin of extreme mantle reservoirs, for example, high 238U/204Pb (HIMU), and their location in the Earth's interior remains poorly constrained. Clinopyroxenes from late Cenozoic Wudi lavas in eastern China have heterogeneous Pb isotopic compositions, even though the erupted lavas are isotopically homogeneous. Our new results provide, to our knowledge, the first evidence for the existence of a HIMU‐like component in the sources of late Cenozoic lavas. Analyses of olivines and their host lavas indicate that the basaltic melts are derived from partial melting of carbonated peridotite. The HIMU source is likely to be younger than 700 Ma old and related to subduction events of the Paleo‐Asian ocean. In addition to deep and ancient recycling, storage of a metasomatically produced mantle reservoir in the mantle transition zone may be an important mechanism for developing extreme isotopic signatures. Key Points: We provide the first evidence for the presence of HIMU component in the magma sourceSubduction‐related, carbonatite‐metasomatized mantle is a likely candidate for the HIMU reservoirThe transition zone may be an important reservoir in the development of mantle heterogeneities [ABSTRACT FROM AUTHOR]

Temporal geochemical comparisons are conducted for representative magmatism from western Northern Luzon to reconstruct the Cenozoic tectonics. Oligo‐Pleistocene magmas from western Northern Luzon display elemental and Sr‐Nd‐Hf‐Pb‐O isotope geochemistry similar to intraoceanic arc magmatism, consistent with derivation from the mantle wedge, coupled with fractional crystallization. Specifically, the Oligo‐Miocene (~26.8–15.6 Ma) Central Cordillera diorite complex samples exhibit a negative correlation between Sr‐Nd isotopes, consistent with mantle metasomatism by fluids/melts released from pelagic sediments. The Mio‐Pleistocene samples (<~9 Ma) exhibit consistent 87Sr/86Sr ratios with variable εNd and partially overlap with those of Scarborough seamount basalts, consistent with mantle metasomatism by fluids/melts released from the Scarborough seamount basalts, which are being subducted beneath Northern Luzon with the South China Sea fossil ridge. Temporal changes in Sr‐Nd‐Hf‐Pb isotopes are also observed for the Taiwan‐Luzon arc magmatism. The Oligo‐Miocene (>~9 Ma) magmatism exhibit intraoceanic arc isotopic signatures, suggestive of a chemical imprint from subducted pelagic sediments. The Mio‐Pleistocene (<~9 Ma) lavas display enriched mantle‐type isotope compositions, consistent with an input of terrigenous sediment in the mantle. The temporal variations in Sr‐Nd‐Hf‐Pb isotopes for the Taiwan‐Luzon magmatism, combined with paleomagnetic evidence, mirror a transition from the Proto‐South China Sea to the South China Sea fossil ridge subduction beneath western Northern Luzon at ~9 Ma. In addition, this study also highlights the importance of relatively enriched components in the lower plate in the maturation of overriding juvenile oceanic crust in an arc‐continent collision system. Key Points: Oligo‐Miocene Central Cordillera diorite complex exhibit Sr‐Nd isotope composition controlled by pelagic sedimentsMio‐Pleistocene igneous rocks exhibit Sr‐Nd isotope composition controlled by the subducted Scarborough Seamount Chain basaltsTemporal variations in isotope geochemistry for the Taiwan‐Luzon magmatism mirror a tectonic transition and crustal maturation [ABSTRACT FROM AUTHOR]

It remains unclear why some cratonic lithospheres like the North China Craton (NCC) have undergone significant thinning and catastrophic destruction. Here we provide evidence for a dense Phanerozoic cratonic keel beneath the NCC that provides a reason for the craton destruction during the late Mesozoic. We observed two long‐lasting (>100 Myr) episodes of surface subsidence that formed the saucer‐shaped basin topography on the NCC from the Paleozoic to early Mesozoic, which was not associated with lithosphere stretching or a high sea level. Based on a detailed geological and geochemical analysis and 2‐D numerical experiments, we show that this subsidence most likely reflects the secular cooling and eclogitization of iron‐rich materials infiltrated into the cratonic mantle since the early Phanerozoic, a process that is the most prominent over the eastern NCC. This result implies that the lithosphere beneath the eastern NCC became gravitationally unstable prior to its Mesozoic destruction as its keel became progressively denser during the Paleozoic. An early Mesozoic partial removal of this dense keel possibly led to widespread surface uplift of the NCC, as indicated by regional basin inversion. We conclude that the long‐term subsidence of a cratonic basin reflects a gradual increase of the lithospheric density and that this type of subsidence should not be considered a characteristic of stable cratons as previously assumed. Key Points: The reason for cratonic lithosphere destruction remains enigmaticThe extensive Phanerozoic NCC subsidence suggests temporal increase of lithospheric densityThermal‐chemical evolution of cratonic lithosphere could be a norm of continental evolution [ABSTRACT FROM AUTHOR]

Picrites are potentially near‐primary melts that offer rare insights into the earliest stages of magmatic evolution. However, without detailed investigation of magmatic processes, robust records of early melt evolution and mantle melting behavior cannot be acquired. Here petrological and geochemical interrogations of the Dali picrites were conducted to investigate the magmatic processes. Compositional variation observed in the Dali picrites is dominated by variable accumulation of a wehrlitic assemblage, transported by a low MgO carrier melt. Groundmass clinopyroxenes were produced by direct crystallization of the carrier melt. In contrast, compositions of olivine‐hosted melt inclusions and clinopyroxene macrocrysts indicate that olivine and clinopyroxene macrocrysts crystallized from diverse melt batches that are genetically related to the carrier melt, which formed as a consequence of magma mixing. The compositional range of melts in equilibrium with clinopyroxene macrocrysts with Mg# < 88 (> 88) is similar to (notably smaller than) the range of melt inclusions hosted in olivine macrocrysts with equivalent forsterite values. This observation can be explained by coupling between major and trace elements during partial melting in the mantle. Overall, a process involving periodic magma replenishment, tapping, and fractional crystallization in deep magma chamber(s) can explain the compositional variations recorded in the Dali macrocryst assemblage. Close genetic relationships between macrocrysts and carrier melts appear to be common to many primitive mafic rocks, which may reflect common deep magma chamber processes whereby diverse mantle‐derived melts are injected and evolved, and the primitive macrocrysts thus formed are subsequently transported by mixed liquids, producing macrocryst‐bearing primitive mafic rocks. Key Points: Compositional variation in the Dali picrites is dominated by variable accumulation of olivine and clinopyroxene macrocrystsThe macrocrysts crystallized from multiple parental magmas and are genetically related to the carrier meltPeriodic RTX processes in the magma chamber(s) dominate the compositional evolution of the diverse parental melts [ABSTRACT FROM AUTHOR]

Evidence for post-Archaean crustal growth via magma underplating is largely based on U-Pb dating of zircons from granulite-facies xenoliths. However, whether the young zircons from such xenoliths are genetically related to magma underplating or to anatexis remains controversial. The lower-crustal xenoliths carried by igneous rocks in the Chifeng and Ningcheng (North China Craton) have low SiO2 and high MgO, indicating that parental melts of their protoliths were of unambiguous mantle origin. The xenoliths contain abundant magmatic zircons with late-Palaeozoic ages, and have more radiogenic zircon Hf-isotope compositions and hence younger model ages than ancient crustal magmas and the 'reworking array' of the basement rocks. Our data suggest that the granulites represent episodic magmatic underplating to the lower crust of this craton in Phanerozoic time. Considering the observation that regional lowermost crust (~5 km) is mafic and characterized by Phanerozoic zircons, this work reports an example of post-Archaean crustal growth via magma underplating. [ABSTRACT FROM AUTHOR]

A novel target-enriched multiplex polymerase chain reaction (Tem- PCR) assay for the simultaneous detection of S almonella spp., L isteria monocytogenes and E scherichia coli O157: H7 was developed in the present study. The invA, hly and rfbE genes were selected as target genes for identifying S almonella spp., L. monocytogenes and E. coli O157: H7, respectively. Three pairs of target-enriched long primers with a composition of pathogen-specific PCR primer combined with a universal oligonucleotide sequence at 5′ segment of each pathogen-specific PCR primer were designed. Following optimization of reaction conditions, the Tem- PCR assay for detecting S almonella spp., L. monocytogenes and E. coli O157: H7 was successfully developed, which was able to simultaneously detect the three foodborne pathogens from pure cultures with an analytical detection limit of ca. <110 cfu/mL for each target. The Tem- PCR assay showed a high specificity to the target bacteria without specific priming observed in nontarget bacteria and also showed a potential diagnostic capability in practice. Compared with conventional multiplex PCR assay, the Tem- PCR assay does need not to optimize the concentration of each pair of primers, suggesting an efficient detection method for foodborne pathogens in laboratory diagnosis. Practical Applications Applying the target-enriched multiplex polymerase chain reaction assay to 355 food samples, including poultry meat, raw pork, raw milk, egg, sausage, raw beef, milk powder and frozen meat, revealed that 21 food samples were positive in this assay, in accordance with the testing results of conventional culture-based method, indicating a rapid and reliable tool for efficient screening of S almonella spp., L isteria monocytogenes and E scherichia coli O157: H7 from food. [ABSTRACT FROM AUTHOR]