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The mantle transition zone (MTZ) is a layer between the upper and lower mantle that plays a crucial role in Earth's deep structure and material circulation. It is increasingly recognized as a potential repository for volatiles, such as water, which can have significant effects on mantle dynamics, melting processes, diamond formation, volcanic activity, and volatile cycling. The presence of water in the MTZ has been a topic of debate, but recent evidence suggests that it may be hydrous to some extent. Other volatiles, such as halogens, sulfur, nitrogen, and noble gases, also have important roles in the MTZ. Understanding the behavior and effects of these volatiles in the MTZ is essential for advancing deep Earth science. Further research and advanced analytical techniques are needed to fully understand the volatile budget in the deep Earth. [Extracted from the article]

Rare-Earth Elements (REE) are key geochemical tracers of crust–mantle differentiation, but there are few direct data on REE-rich minerals in mantle rocks. Here, we report the combined petrography and comprehensive chemical and isotopic characterization of three coesite- and kyanite-bearing eclogite xenoliths from the Udachnaya kimberlite pipe (Siberian craton), which are unusual in that two xenoliths (one with diamond and graphite) contain discrete, idiomorphic crystals of allanite at the grain boundaries of garnet and omphacite. Another xenolith contains allanite as part of a complex aggregate of calcite, apatite, barite, and celestine hosted by serpentine, which is a low-temperature secondary minerals likely result from metasomatic reaction at shallower depths during the transport of eclogite by the erupting kimberlite melt. The bulk rock composition reconstructed from the trace element composition of garnet and omphacite show marked depletion in LREE, precluding equilibration with kimberlite melt, whereas the measured bulk compositions show chondrite-normalized REE patterns with conspicuous depletions of Ce–Pr–Nd relative to La and Sm. The presence of 0.005 to 0.008 wt % of allanite, texturally and chemically out of equilibrium with the rock-forming minerals, allows balancing the LREE and Sm–Nd budget of the rock, whereas Th and U require additional hosts. This not only highlights the utility of measuring bulk eclogite xenoliths in bringing this unusual component to light, but also demonstrates that the long-known incompatible element enrichment in bulk eclogites reflects the deposition of discrete phases rather than merely bulk kimberlite melt addition. Although allanite is stable in metabasalts at the pressure–temperature conditions of 1025°C to 1080°C and 3.6 to 4.8 GPa recorded by the eclogite xenoliths, its association with Ba-Sr minerals suggests its formation via reaction of the host eclogites with kimberlite melt. This is supported by the similarity in 143Nd/144Nd ratios between bulk eclogite (0.51227–0.51249) and the host kimberlite at eruption, whereas clinopyroxene in part retains unradiogenic Sr (87Sr/86Sr = 0.70205 ± 0.00011) related to ancient depletion. The discovery of allanite in the Udachnaya eclogites demonstrates that this REE mineral can form when omphacite and grossular-rich garnet in eclogite breakdown in contact with REE- and alkali-rich carbonatite/kimberlite melt, and may be more common than hitherto recognized. Crystallization of allanite in the cratonic mantle eclogite reservoir may also help explain the difference in LREE abundances between the more strongly enriched carbonatite/kimberlite at depth and the final erupted product. It is likely that allanite is overlooked at eclogites xenoliths, while it is common accessory mineral, hosting REE in orogenic UHP/HP eclogites. Further studies are required to deciphered the peculiarities in metamorphic history recorded in eclogites xenoliths and orogenic eclogites, as well as the differences ancient (Archean/Proterozoic) and Phanerozoic subduction processes. [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]

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 type of lithosphere subducted between India and Tibet since the Paleocene remains controversial; it has been suggested to be either entirely continental, oceanic, or a mixture of the two. As the subduction history of this lost lithosphere strongly shaped Tibetan intraplate tectonism, we attempt to further constrain its nature and density structure with numerical models that aim to reproduce the observed history of magmatism and crustal thickening in addition to present-day plateau properties between 83°E and 88°E. By matching time-evolving geological patterns, here we show that Tibetan tectonism away from the Himalayan syntaxis is consistent with the initial indentation of a craton-like terrane at 55 ± 5 Ma, followed by a buoyant tectonic plate with a thin crust, e.g., a broad continental margin (Himalandia). This new geodynamic scenario can explain the seemingly contradictory observations that had led to competing hypotheses like the subduction of Greater India versus largely oceanic subduction prior to Indian indentation. By evaluating model predictions with multiple geological data, the study shows that Tibetan tectonism is most consistent with the initial indentation of a cratonic terrane, followed by subduction of a buoyant tectonic plate resembling a continental margin. [ABSTRACT FROM AUTHOR]

How subduction-related magmatism starts at convergent plate margins is still poorly understood. Here we show that boron isotope variations in early-formed boninites from the Izu-Bonin arc, combined with radiogenic isotopes and elemental ratios document rapid (~0.5 to 1 Myr) changes in the sources and makeup of slab inputs as subduction begins. Heterogeneous hornblende-granulite facies melts from ocean crust gabbros ± basalts fluxed early melting to generate low silica boninites. Hydrous fluids from slab sediments and basalts later fluxed the low silica boninites mantle source to produce high silica boninites. Our results suggest that initially the uppermost parts of the slab were accreted near the nascent trench, perhaps related to early low-angle subduction. The rapid changes in slab inputs recorded in the boninites entail a steepening subduction angle and cooling of the plate interface, allowing for subduction of slab sediment and basalt, and generating hydrous fluids at lower slab temperatures. The geochemical record of subduction initiation is still not well understood, despite >50 years of study. Here, the authors use boron isotopes in Izu-Bonin boninites to document rapid changes in slab inputs to melting at the start of subduction, related to the steepening and cooling of the downgoing Pacific plate. [ABSTRACT FROM AUTHOR]

Cretaceous rift basin evolution was an important part of the tectonic history of northeast Asia in the late Mesozoic. Three types of rift basins are identified—active, passive and wide rift basins—and they developed in different regions. Passive rift basins in the eastern North China craton are thought to be the consequence of crustal stretching and passive asthenospheric upwelling. Wide rift basins in the eastern Central Asian orogen are assumed to originate from gravitational collapse of the thickened and heated orogenic crust. Active rift basins in the northern North China craton are attributed to uprising of asthenospheric materials along a lithospheric-scale tear fault. Slab tearing of the subducting paleo-Pacific plate is postulated and well explains the spatial distribution of different types of rift basins and the eastward shifting of magmatism in the northern North China craton. The Late Cretaceous witnessed a period of mild deformation and weak magmatism, which was possibly due to kinematic variation of the paleo-Pacific plate. [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]

The North China Craton (NCC) was originally formed by the amalgamation of the eastern and western blocks along an orogenic belt at ∼1.9 Ga. After cratonization, the NCC was essentially stable until the Mesozoic, when intense felsic magmatism and related mineralization, deformation, pull-apart basins, and exhumation of the deep crust widely occurred, indicative of destruction or decratonization. Accompanying this destruction was significant removal of the cratonic keel and lithospheric transformation, whereby the thick (∼200 km) and refractory Archean lithosphere mantle was replaced by a thin (<80 km) juvenile one. The decratonization of the NCC was driven by flat slab subduction, followed by a rollback of the paleo-Pacific plate during the late Mesozoic. A global synthesis indicates that cratons are mainly destroyed by oceanic subduction, although mantle plumes might also trigger lithospheric thinning through thermal erosion. Widespread crust-derived felsic magmatism and large-scale ductile deformation can be regarded as petrological and structural indicators of craton destruction. ▪ A craton, a kind of ancient continental block on Earth, was formed mostly in the early Precambrian (>1.8 Ga). ▪ A craton is characterized by a rigid lithospheric root, which provides longevity and stability during its evolutionary history. ▪ Some cratons, such as the North China Craton, can be destroyed by losing their stability, manifested by magmatism, deformation, earthquake, etc. [ABSTRACT FROM AUTHOR]

The subduction of the Paleo-Pacific Plate played an important role in the regional evolution of the eastern margin of the Eurasian continent, but the timing and extent of this event remain ambiguous. To address these issues, we examine the geochronology and geochemistry of Early Jurassic intrusive rocks in eastern Jilin Province, NE China. The Early Jurassic gabbro–diorites, diorites, granodiorites, and monzogranites are found to have been emplaced at 183–185 Ma and are characterized by enrichment in large ion lithophile elements and depletion in high field strength elements, similar to calc-alkaline arc-type igneous rocks. The Early Jurassic gabbroic and dioritic rocks have εHf (t) values of +2.1 to +10.1 and Hf single-stage (T DM1 ) model ages of 430–774 Ma, whereas the monzogranites have εHf (t) values of +6.7 to +8.9 and Hf single-stage (T DM1 ) ages of 597–718 Ma. The gabbro–diorites, diorites, and granodiorites described in this study are genetically linked and they represent the products of the fractional crystallization of a common mafic magma that was in turn derived from the partial melting of a mantle source that was metasomatized by subduction-related fluids. In contrast, the Early Jurassic monzogranites were generated by partial melting of a depleted lower crustal block that was probably accreted during the Neoproterozoic. More importantly, the Early Jurassic calc-alkaline igneous rocks in the east part of NE China form a NE-trending belt that is oriented perpendicular to the direction of Paleo-Pacific Plate movement at that time. West of this belt, contemporaneous bimodal igneous rocks occur in the Lesser Xing’an–Zhangguangcai Ranges. This magmatic configuration is best explained by continental arc magmatism along the continental margin and extensional magmatism in a back-arc setting, in each case triggered by the initial subduction of the Paleo-Pacific Plate beneath Eurasia in the Early Jurassic. [ABSTRACT FROM AUTHOR]

Contributions from fluid and melt inputs from the subducting Pacific slab to the chemical makeup of intraplate basalts erupted on the eastern Eurasian continent have long been suggested but have not thus far been geochemically constrained. To attempt to address this question, we have investigated Cenozoic basaltic rocks from the western Shandong and Bohai Bay Basin, eastern North China Craton (NCC), which preserve coherent relationships among the chemistries of their melt inclusions, their hosting olivines and their bulk rock compositions. Three groups of samples are distinguished: (1) high-Si and (2) moderate-Si basalts (tholeiites, alkali basalts and basanites) which were erupted at ∼23–20 Ma, and (3) low-Si basalts (nephelinites) which were erupted at <9 Ma. The high-Si basalts have lower alkalies, CaO and FeO T contents, lower trace element concentrations, lower La/Yb, Sm/Yb and Ce/Pb but higher Ba/Th ratios, and lower ε Nd and ε Hf values than the low-Si basalts. The olivines in the high-Si basalts have higher Ni and lower Mn and Ca at a given Fo value than those crystallizing from peridotite melts, and their corresponding melt inclusions have lower CaO contents than peridotite melts, suggesting a garnet pyroxenitic source. The magmatic olivines from low-Si basalts have lower Ni but higher Mn at a given Fo value than that of the high-Si basalts, suggesting more olivine in its source. The olivine-hosted melt inclusions of the low-Si basalts have major elemental signatures different from melts of normal peridotitic or garnet pyroxenitic mantle sources, pointing to their derivation from a carbonated mantle source consisting of peridotite and garnet pyroxenite. We propose a model involving the differential melting of a subduction-modified mantle source to account for the generation of these three suites of basalts. Asthenospheric mantle beneath the eastern NCC, which entrains garnet pyroxenite with an EM1 isotopic signature, was metasomatized by carbonatitic melts from carbonated eclogite derived from subducted Pacific slab materials present in the deeper mantle. High degree melting of garnet pyroxenites from a shallower mantle source produced the early (∼23–20 Ma) higher-Si basalts. Mixing of these materials with deeper-sourced melts of carbonated mantle source produced the moderate-Si basalts. A thicker lithosphere after 9 Ma precluded melting of shallower garnet pyroxenites, so melts of the deeper carbonated mantle source are responsible for the low-Si basalts. [ABSTRACT FROM AUTHOR]

The Dongfanghong hornblende gabbro is located in the western part of the Wandashan Orogen and to the east of the Jiamusi Block in NE China. It was emplaced into Early Paleozoic oceanic crust (i.e. Dongfanghong ophiolite) at ~ 275 Ma and both later collided with the eastern margin of the Jiamusi Block. The Dongfanghong gabbro is sub-alkaline with high Na 2 O contents and is characterized by enrichment in light rare earth elements (LREE), large ion lithosphile elements (LILE), Sr, Eu, and Ba, and depletion in high field strength elements (HFSE). The enriched isotopic signatures ( 87 Sr/ 86 Sr i = ~ 0.7065, εNd(t) = ~− 0.5, 208 Pb/ 204 Pb i = ~ 38.05, 207 Pb/ 204 Pb i = ~ 15.56, 206 Pb/ 204 Pb i = ~ 18.20 and zircon εHf(t) = ~+ 5.8) indicate an enriched mantle (EM2) source, with some addition of continental material. It has arc geochemical affinities similar to Permian arc igneous rocks in the eastern margin of the Jiamusi Block, the Yakuno Ophiolite in SW Japan, arc rocks along the western margin of the North America Craton, and also the Gympie Group in eastern Australia. All these features, together with information from tectonic discrimination diagrams, suggest that the Dongfanghong gabbro formed in an immature island arc. The spatial configuration of ~ 290 Ma immature continental arc rocks in the eastern part of the Jiamusi Block and the ~ 275 Ma immature island arc Dongfanghong gabbro in the Wandashan Orogen to the east is best explained by eastward arc retreat and slab roll-back of the Paleo-Pacific Plate. This model is also supported by the Carboniferous–Permian stratigraphic transition in the Jiamusi Block from oceanic carbonate rocks to coal-bearing terrestrial clastic rocks and andesites. We thus suggest that both Paleo-Pacific subduction and roll-back occurred in the Early Permian along the eastern margin of Asia. [ABSTRACT FROM AUTHOR]

Abstract: Despite considerable efforts, the Paleozoic tectonic setting (subduction vs. post-collision vs. mantle plume) in the Central Asian Orogenic Belt (CAOB) remains controversial. With aims of solving this issue, we examined zircon saturation temperatures of granitoids emplaced in different settings, and demonstrated that zircon saturation thermometry of felsic igneous rocks, especially when integrated with their lithology and geochemistry, can be a simple and powerful tool for tectonic discrimination. This method is then applied in northern Xinjiang where the Early Permian granitoids have higher saturation temperatures (>800°C) than the Silurian–Carboniferous granitoids (mainly <800°C). Moreover, the latter are mainly of I-type and are characterized by relatively narrow range of uniformly higher εNd. Consistent with high εHf in zircons from contemporaneous ultramafic–mafic complexes, they were most likely derived from subduction-related processes. In contrast, the high-temperature Early Permian granitoids and associated ultramafic–mafic rocks show a wide range in εNd and εHf in zircons, consistent with the involvement of a great variety of crustal and mantle materials in magma genesis. The thermal anomaly and diversity of Permian magmatic rocks in the CAOB can be ascribed to a mantle plume activity, in agreement with widespread contemporaneous flood basalts, and associated mafic dykes and ultramafic complex in Tarim. Therefore, the temporal variation in temperature and geochemistry of Paleozoic granitoids in northern Xinjiang mirrors a significant change in tectonic setting from a subduction–collision setting during Silurian–Carboniferous to an intra-plate setting since Early Permian. [Copyright &y& Elsevier]

Abstract: Basaltic rocks from Shuangliao, northeast China include basanite, alkali olivine basalt, transitional basalt and sub-alkaline diabase. Ar–Ar dating shows that the basanites and alkali olivine basalts formed earlier (48.5–51Ma) than the transitional basalts and diabases (43–41.6Ma). These rocks have the highest Fe2O3 contents (13.4–14.6wt.%) and lowest (87Sr/86Sr)i ratios (<0.703) among the Cenozoic basalts from eastern China. On a primitive-mantle normalized variation diagram, they show positive Eu, Sr, Nb and Ta anomalies, and depletion in very incompatible elements (Rb, Ba, Th, U), reminiscent of HIMU-type oceanic island basalts. In particular, the basanites possess noticeable negative K anomalies. Nevertheless, their Pb isotopic compositions (206Pb/204Pb=18.13–18.34) do not show the high time-integrated 238U/204Pb mantle component expected for a HIMU basalt. On a 206Pb/204Pb versus 207Pb/204Pb diagram, most samples straddle the Northern Hemisphere Reference Line (NHRL), in salient contrast to the majority of Chinese Cenozoic basalts, which plot above the NHRL. These data, as well as a comparison with high-pressure experimental melts, are consistent with the presence of young subducted oceanic crust (SOC) in the source of Shuangliao basalts. Varying (87Sr/86Sr)i, La/Nb and Eu/Eu* with rock-type suggests that the upper oceanic crust (with variable amount of lower oceanic crust) was preferentially sampled by earlier (51–48Ma), highly alkaline rocks, whereas the lower oceanic crust was predominantly sampled in later (41–43Ma) transitional basalts and diabases. This temporal trend is attributed to the differential melting of a heterogeneous source in association with lithospheric thinning, during which fusible upper oceanic crust melted earlier than lower oceanic crust and peridotites. We postulate that the SOC components may have been derived from the seismically detected stagnant Pacific slab within the mantle transition zone. This hypothesis is supported by the same Indian MORB-like isotopic composition being found in the Shuangliao basalts and in the extinct Izanaghi–Pacific plate of NW Pacific. The latter has been subducting underneath the eastern Asian continent since the early Cretaceous. [Copyright &y& Elsevier]

Abstract: Considerable progress has recently been made regarding temporal and spatial distribution of magmatism in the Lhasa Terrane. However the eastward and southeastward correlation of these Tibetan magmatic suites in western Yunnan and Burma remains poorly constrained. This paper reports zircon U–Pb dating and Hf isotopic compositions of granites in the Gaoligong–Tengliang–Yingjiang area, west Yunnan. It reveals three episodes of plutonism, and more importantly a southwestward magmatic migration. The Gaoligong batholiths in the northeast were mainly emplaced during early Cretaceous (126–121Ma) and comprised predominantly S-type granites with negative zircon εHf values (εHf =−2∼−12). The Tengliang granites, situated southwest of the Gaoligong belt, were emplaced in late Cretaceous (68–76Ma) and also displayed a strong peraluminous affinity and negative εHf (−5∼−14), indicating a provenance from a Proterozoic sedimentary source with little mantle contribution. The youngest phase of magmatism (52–66Ma) occurred in Yingjiang, southwestmost of the study area. It is composed of S-type granites (εHf=−2∼−12) in east Yingjiang and I-type granites (εHf =−4∼+6) in west Yingjiang, near the China–Burma border. The late Cretaceous–early Cenozoic plutons in the Tengliang and Yingjiang area are thus considered as the northern continuation of the late Cretaceous magmatic arc (west), which comprises I-type granites and andesitic rocks, and of the belt of predominant S-type granites (east) in Burma, Thailand and Malaysia. Such a chemical polarity of the dual I-type and S-type granites is strongly reminiscent of the northern American Cordillera, indicating a Cordilleran-style continental margin during the late Cretaceous–early Cenozoic. While the magmatic arc was related to eastward subduction of the Neo-Tethys beneath the Asian continent, the S-type granites represented the melting products of thickened crust in the hinterland, in response to subduction-induced decrease in lithospheric strength and compressive plate-convergence forces and to a less degree to the collision between Burma and Sundaland blocks. The Gaoligong early Cretaceous granites, which bear strong similarities in lithology, geochemistry and emplacement age to those in the northern magmatic belt in the Lhasa Terrane, are also the magmatic expression of crustal thickening. This crustal thickening may have stemmed from the collision between the Lhasa Block and the Qiangtang Block in late Jurassic and Early Cretaceous. The magmatism in western Yunnan thus recorded a long-term subduction of the Neo-Tethyan plate, enhanced by continental collisions at different time. [Copyright &y& Elsevier]

Gravity lineaments are well recognized along plate boundaries and in the interiors of oceanic plates. However, the formation mechanism of intracontinental gravity lineaments remains poorly understood. The North–South Gravity Lineament (NSGL), which extends >4000 km from Russia to South China, is characterized by an abrupt change in the observed Bouguer gravity anomaly, ranging from −100 mGal in the west to −40 mGal in the east over a distance of <100 km. Here we employ gravity modeling along a deep seismic sounding profile that transects the NSGL to delineate the relative contributions of the thickness and composition of the crustal and upper mantle and the stagnant slab in the mantle transition zone to the observed gravity anomaly, and to ultimately constrain the formation mechanism of the NSGL. Our results indicate that crustal thickness is the dominant factor in the formation of the NSGL, with lithospheric composition also playing a role. Combining our results with those of previous studies, lateral variations in the lithospheric mantle composition and crustal/lithospheric thickness across the NSGL can be attributed to lithospheric thinning and mantle replacement in the eastern part of the North China Craton during the late Mesozoic. This was triggered by the subduction of the Paleo-Pacific plate and subsequently led to the persistence of a stagnant slab and big mantle wedge. This study highlights the fundamental need for integrated geophysical–petrological analyses to better understand the surface response to deep tectonic processes. • Gravity modeling along a seismic profile across the north-south gravity lineament in eastern China. • Using the stagnant slab to explain the formation of the intracontinental gravity lineament. • Integration of geophysical and geochemical data sheds light on the surface response to deep processes. [ABSTRACT FROM AUTHOR]

Despite numerous studies, the origin of intraplate basalts from eastern Asia is still elusive. This includes the relative importance of subducted oceanic crust and metasomatized lithospheric mantle in generation of these lavas. To address this important issue, we have carried out an integrated Mg-Sr-Nd isotope study of Jiaohe garnet pyroxenite xenoliths and Cenozoic basalts from the Changbaishan-baoqing volcanic belt (CVB), NE China. The Jiaohe garnet pyroxenite xenoliths exhibit low Hf/Hf* ((Hf N /(Sm N × Nd N)0.5, 0.7–0.9), depleted Sr Nd isotopic compositions (87Sr/86Sr i = 0.7035–0.7041; ε Nd = +2.9 − +8.6) and low δ26Mg (−0.61 to −0.39‰). These features reflect both protolith heterogeneity and the effect of isotopic exchange with carbonates during subduction. The CVB basalts display variable Mg isotopic compositions. Low-Si basalts are characterized by low δ26Mg (−0.27 to −0.44‰), variable Hf/Hf* (0.7–1.4) and depleted Sr Nd isotopic compositions (87Sr/86Sr i = 0.7039–0.7050; ε Nd = +1.0 − +4.7), which were attributed to partial melting of upwelling asthenospheric mantle containing recycled oceanic crustal components. In contrast, high-Si basalts display low Hf/Hf* (0.6–0.9), EM1-like Sr Nd isotopic compositions (87Sr/86Sr i = 0.7047–0.7054; ε Nd = −2.4 - -0.2) and normal mantle-like δ26Mg values (−0.18 to −0.33‰). Such features can be explained by participation of metasomatized lithospheric mantle in their source. The transition from low-Si melts with low-δ26Mg to high-Si melts with normal mantle-like δ26Mg for the CVB basalts are genetically related to continental rifting, asthenospheric mantle upwelling and mechanical-chemical erosion of basal metasomatized lithosphere induced by subduction of the Pacific oceanic slab. Recycled oceanic crust and basal lithospheric mantle both played a fundamental role in generation of the intraplate basalts in eastern Asia. [Display omitted] • The Jiaohe garnet pyroxenite xenoliths exhibit low δ26Mg values. • Low-Si basalts with low δ26Mg were derived from recycled oceanic crust. • High-Si basalts with normal δ26Mg were derived from enriched lithospheric mantle. [ABSTRACT FROM AUTHOR]

• Non-collisional piston-like volcanotectonic cycles are distributed broadly on Earth. • Subduction interrupted by buoyant fragments explains typical piston-like cycles. • Terrane-bearing plates can also subduct continuously, causing piston-like cycles. • Multi-terrane arrivals induce frequent slab break-off, rebound, and trench jump. • Isobaric heating after exhumation represents a key feature of piston-like cycles. Pulsing volcanotectonic cycles characterized by short-lived (10 s Myr) switches in magmatic and tectonic patterns have been broadly identified in active margins. However, the specific mechanism that causes these switches remains ambiguous, i.e. , whether the subduction continuity and/or terrane arrival (accretion, underthrusting, or subduction of buoyant continental/oceanic blocks with a thicker crust than their surrounding oceanic plate) plays a crucial role in controlling the observed volcanotectonic cycles remains controversial. Here, by modeling subduction processes involving the sequential arrival of buoyant terranes, we show that 1) in scenarios where the oceanic plate is weakly coupled with terranes, the entraining of the terrane into the subduction induces slab breakup to occur between the partially subducted terrane and its adjacent oceanic slab, with the terrane then rebounding and moving away from the trench. This evolution causes switches in the magmatic and tectonic patterns within the overriding plate. 2) In these models, the exposed terrane materials can preserve characteristic pressure-temperature-time trajectories, i.e., nearly isothermal compression to isothermal decompression and/or isobaric heating after partial exhumation. 3) slab breakup does not guarantee the occurrence of a trench jump; only when the terrane has a medium scale (∼300 km) will a new trench tend to develop prominently behind the rebounded terrane. 4) in scenarios where the composite slab (terrane and oceanic portions) resists yielding deformation and the terrane density is close to that of the oceanic plate (<0.6% density contrast), continuous subduction will occur. In this latter scenario, slab deformation (revealed by subduction angle and slab curvature), instead of slab breakup, will control the magmatic and tectonic patterns in the overriding plate. By further comparing model results with observations, we demonstrate that intermittent subduction interrupted by the subduction of terranes can be a tectonic driver for episodes of compression-to-extension transformations and magmatism (or piston-like volcanotectonic cycles) in two representative accretionary belts — with or without trench jumps (exemplars in south-central-Tibet and eastern-Mediterranean). In contrast, continuous subduction with strongly coupled upper and subducting plates could have contributed to similar cycles in the example without accretion (e.g. , the Altiplano in the Central Andes). Therefore, over 10 s of Myr, the scale and frequency of terrane arrivals could essentially control the specific motion pattern of the subducting plate, creating the observed short-lived volcanotectonic switches at these three subtypes of active margins. [ABSTRACT FROM AUTHOR]

Eastern China provides a precious opportunity to explore how subduction drives evolution of the overlying continental lithosphere and to understand the fate of subducted plates. In this study, a synthesis of geochronological, whole-rock geochemical and zircon Hf isotopic data is used to examine temporal and spatial variations in distribution, composition and generation of Mesozoic magmas in the northern North China Craton. A compilation of age data reveals over 1000 km of inland-ward migration of a magmatic belt during 185– 145 Ma and then back again after 145– 140 Ma, coincident with the transition from contractional to extensional deformation regime in the very early Cretaceous. Distinct trends in lithologies, geochemistry and Nd Hf isotopes as a function of age and location are also observed in these magmas. The Mesozoic magmatism and deformation, as well as the lithospheric destruction, across the northern North China Craton is interpreted as the consequence of a change in subduction geodynamic regime of the Paleo-Pacific slab and its interaction with overlying continental lithosphere, which involves an active continental arc at Korean and Liaodong Peninsulas in the early-middle Jurassic, progressive shallowing of the subducting Paleo-Pacific plate in the middle-late Jurassic, and subsequent slab rollback in the early Cretaceous. Considering that trench retreat and slab-roll back are demonstrated as the pre-request of slab stagnation in the mantle transition zone, we further propose that the big mantle wedge structure in East Asia was probably initiated at 145– 140 Ma and was likely fully developed by ~120 Ma. Such a peculiar deep mantle structure governed the post-Cretaceous evolution of the Asian continental lithosphere by mediating the chemical and physical properties of upper mantle. [ABSTRACT FROM AUTHOR]

Metasomatism of the lithospheric mantle by subduction-related fluids/melts is recorded in the Early Cretaceous Xinkailing high magnesium andesites (HMAs) from Western Liaoning. Olivine-hosted melt inclusions within the Xinkailing HMAs are alkaline and record a much lower SiO 2 content and higher Al 2 O 3 and CaO contents than the sub-alkaline bulk rock compositions. These observed compositional differences between bulk rocks and melt inclusions suggest that a crustally derived, high-SiO 2 melt was incorporated in the Xinkailing HMAs within the pre-eruptive magma chamber. The process of this incorporation accounts for the compositional differences between upper (HMAs) and lower (high magnesium basalts) successions of the Yixian Formation. Olivine phenocrysts also record unusually high Ni and Ni/MgO contents with high Fo values. Based on the fact that bulk rocks record low Ni contents, whereas olivine crystals record a steep correlation between Fo and Ni and low CaO and CaO/FeO contents, in addition to the likely considerable depression of the olivine liquidus temperature, we argue that a hydrous (2–6% H 2 O) orthopyroxene-rich pyroxenite source was formed by the reaction between subducted slab-released SiO 2 -rich fluids and overlying mantle peridotite. We further propose that during a series of Phanerozoic successive subduction events around the Eastern NCC, a significant amount of water may have been transported to the lithospheric mantle, thus lowering its viscosity and ultimately destabilizing the cratonic lithosphere. [ABSTRACT FROM AUTHOR]

This paper reports new zircon LA–ICP–MS and SIMS U–Pb ages and Hf isotope data, and whole-rock major and trace element data for Late Triassic igneous rocks of eastern Heilongjiang Province, NE China. These data provide new insights into the timing of the initiation of subduction of the Paleo-Pacific Plate beneath the Eurasian continent. The zircon U–Pb age data indicate that a suite of Late Triassic (228–202 Ma) igneous rocks is present within the Songnen–Zhangguangcai Range Massif and within the western margin of the Khanka Massif. The Late Triassic igneous rocks within the Songnen–Zhangguangcai Range Massif consist of basalts, basaltic andesites, gabbro-diabases, and rhyolites, whereas coeval igneous rocks in the western margin of the Khanka Massif consist of hornblende gabbros and syenogranitic porphyries. These Late Triassic rocks constitute a geochemically bimodal igneous rock association that contains mafic rocks enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), and depleted in heavy rare earth elements (HREE) and high field strength elements (HFSE) such as Nb, Ta, Zr, Hf, and Ti. Zircons from these mafic rocks have ε Hf ( t ) values and T DM1 ages of +2.8 to +9.8 and 477–733 Ma, respectively, suggesting that they formed from a primary magma generated by the partial melting of depleted lithospheric mantle material that had been previously modified by subduction-related fluids. The coeval felsic rocks are characterized by enrichments in LREEs and LILEs, and depletions in HREEs and HFSEs (including Nb, Ta, and Ti), and their zircons have ε Hf ( t ) values and T DM2 ages of +0.6 to +7.9 and 766 to 1461 Ma, respectively, implying that these rocks were generated during the partial melting of juvenile crustal material. The Late Triassic bimodal igneous rocks in eastern Heilongjiang Province, combined with the regional geologic information, therefore record a post-orogenic extensional environment related to the final late Permian–Early Triassic closure of the Paleo-Asian Ocean. In addition, the presence of Late Triassic bimodal igneous rocks within the eastern margin of the Eurasian continent suggests that the subduction of the Paleo-Pacific Plate beneath the Eurasian continent began after the Late Triassic. [ABSTRACT FROM AUTHOR]

The primary driver of magmatism, crustal deformation and metallogeny of the North China Craton in the Jurassic remains actively debated, either attributed to the subduction of the Paleo-Pacific (i.e., Izanagi) plate in the east or to the closure of the Mongol-Okhotsk Ocean in the north. This issue is addressed here by examining temporal and spatial variation of the contemporary volcanic rocks (i.e., Tiaojishan Formation) of the Yanshan belt in the northern part of the craton. These rocks are mainly calc-alkaline and intermediate-felsic in composition and show a highly coherent geochemical composition and unradiogenic zircon Hf isotope, indicating that they have similar origins and formed in a subduction-related setting. The eruption age of the Jurassic volcanic rocks decreases westward (i.e., inland-ward) from Western Liaoning (166–153 Ma), through Pingquan-Chengde-Luanping (162–153 Ma) and Jingxi-Xuanhua (158–149 Ma), to Yuxian (157–142 Ma). This temporal and spatial variation is consistent with the motion of the subducted Paleo-Pacific plate over that time. In addition to the westward migration, the earliest volcanic rocks in the Yanshan belt formed earlier than those in the adjacent southern Great Xing'an Range in the north. These observations suggest that the southward subduction and closure of the Mongol-Okhotsk plate played a limited role in generation of these volcanic rocks. Two episodes of Middle-Late Jurassic volcanism (166–153 Ma and 150–139 Ma) are observed in the northern Great Xing'an Range. They are interpreted as results of closure of the Mongol-Okhotsk Ocean and subduction of the Paleo-Pacific plate, respectively. Temporal-spatial variation of volcanic activity in the northern North China Craton and adjacent region demonstrates that the Paleo-Pacific subduction was the principal cause of the evolution of Eastern China during the late Mesozoic, whereas the Mongol-Okhotsk tectonic regime is largely confined to the northern Great Xing'an Range and the area north to it. • Age of Tiaojishan volcanic rocks decreases inlandward from east to west. • Subduction of Izanagi plate controlled Jurassic magmatism of Eastern China. • Mongol-Okhotsk tectonic regime is confined to northern GXAR in the Jurassic. [ABSTRACT FROM AUTHOR]

Fore-arc crust and mantle wedge serpentinite, dragged down by the subducting slab, play a critical role in enriching the sub-arc mantle source of arc magmas. However, discriminating between these two components in arc magmas remains challenging because the fore-arc crust may contain serpentinite components inherited from previous subduction event(s). Here we present molybdenum concentration and isotope data, coupled with reanalyzed and published geochemical data, for common representatives of circum-Pacific high-Mg andesites and adakites. Elevated δ98/95Mo values (−0.13‰ to 0.00‰) in the Kamchatka and Aleutian high-Mg andesites are associated with elevated Mo/Ce (0.026 to 0.075), Ba/Th (138 to 808), and Sb/Ce (0.0026 to 0.0192) ratios, as well as Sr-Nd-Hf-Pb isotope compositions close to the depleted mantle and moderated δ18O values (+6.6‰ to +7.8‰). These characteristics are consistent with compositional contributions from slab-derived aqueous fluids via fore-arc serpentinites. In contrast, decreasing δ98/95Mo values (−0.07‰ to −0.48‰) in the Cascadia and Setouchi high-Mg andesites as well as four adakites from Fiji and the Austral Volcanic Zone, are generally accompanied by decreasing Mo/Ce (0.036 to 0.002) and Sb/Ce (0.0066 to 0.0002) ratios, increasing Sr/Y ratios (15 to 207), and Sr-Nd-Hf-Pb-O isotopic variations ranging from values reflecting altered oceanic crust to those resembling sediment input. These features can be accounted for by an increasing melt contribution from the subducted oceanic crust. Nine adakites from the Aleutians, Fiji, Panama, and the Austral Volcanic Zone exhibit δ98/95Mo values (−0.19‰ to −0.04‰) higher than the depleted mantle but lower Mo/Ce ratios (0.007 to 0.018) and low to moderate Sb/Ce ratios (0.0002 to 0.0025), indicating a potential serpentinite contribution. However, elevated Sr/Y ratios (57 to 295), unradiogenic Sr-Pb isotopes, radiogenic Nd-Hf isotopes, and moderate δ18O values (+6.3‰ to +6.5‰) suggest that these adakites are derived from fore-arc crust dragged down by the descending oceanic crust. The circum-Pacific adakites in this study show a decrease in δ98/95Mo with decreasing Mo/Ce, consistent with partial melting of oceanic crust and 98Mo pre-enriched fore-arc crust, respectively, having lost 98Mo during subduction dehydration. Thus, our study not only distinguishes the components between eroded fore-arc crust and wedge serpentinite but also indicates a major role of both dehydration and melting in facilitating material transfer in subduction zones. • High δ98/95Mo in high-Mg andesites reflect eroded fore-arc serpentinite. • Low δ98/95Mo in adakites represent the slab melt component. • High δ98/95Mo in adakites represent eroded fore-arc crust. • Mo isotopic data support a liquid-dominated mass transfer mode in subduction zones. [ABSTRACT FROM AUTHOR]

The widespread Middle Jurassic to Early Cretaceous (J2-K1) intraplate tectonism of East Asia has recently been proposed to reflect the flat subduction of the Izanagi plate, whose mechanism, however, remains poorly constrained. Here, we compare these geological records with those within the western United States (U.S.) during the Laramide flat subduction. Two prominent differences are identified during slab advance: 1) western U.S. witnessed continental-scale subsidence and marine inundation, while East Asia experienced mostly basin inversion implying uplift; 2) the landward migrating magmatism in western U.S. quickly evolved into a regional magmatic lull that lasted for >40 Myr, but the East Asian magmatism was largely continuous in space and time. Assisted with numerical models, we show that a flat slab could indeed reproduce the observed East Asian crustal deformation and topographic history during the advance and retreat of the slab. We further find that 1) this slab should be more buoyant than the Laramide slab so that the former oceanic slab could break off which led to surface uplift instead of subsidence, and 2) the crust of the flat slab melted more easily than an oceanic one. The observation that the J2-K1 tectonism was largely contemporary with the assembly (ca. 180–137 Ma) of exotic terranes along the east coast implies that the flat sab underplating North China and Northeast China likely represented subduction of the buoyant continental lithosphere associated with these terranes. The terrane slab could have carried and flattened portions of the nearby oceanic slab with it, forming a giant composite flat slab that defined the J2-K1 intraplate tectonism within East Asia. Unlabelled Image [ABSTRACT FROM AUTHOR]

The control of redox conditions on the geochemical recycling process in subduction zones is still poorly understood due to large uncertainties in oxygen fugacity (f O 2) for subducted slabs. We present the first systematic geochemical and B-Mo-Sr-Nd-Hf-Pb isotopic data for continental arc basalts (CABs) and back-arc basalts (BABs) from Sumatra to investigate the relationships between oxygen fugacity and B Mo isotopic fractionation processes during subduction. The Sumatran CABs and BABs yield high FeOT/MgO ratios and low K 2 O contents (0.48–1.42 wt%) and can be classified as tholeiitic. They have variable Sr-Nd-Hf-Pb isotopic compositions, consistent with the input of different amounts of melt from subducted terrigenous sediments into mantle sources. The BAB samples show much lower δ11B (−9.0‰ to −7.3‰) values than the CABs (δ11B = −7.0‰ to +0.17‰), reflecting significant B isotopic fractionation during multistage melting of subducted sediments. This is distinct from the similar δ98/95Mo values for the Sumatran CABs (−0.21‰ to −0.01‰) and BABs (−0.17‰ to −0.08‰), suggesting limited Mo isotopic fractionation during subduction. The Sumatran CABs show low V/Yb ratios, suggesting that melts from subducted sediments were possibly generated at f O 2 values lower than FMQ + 1.5. The limited Mo isotopic fractionation could be induced by the relatively low f O 2 during melting of subducted sediments, which would significantly decrease the mobility of Mo but have no influence on B. Alternatively, rocks from highly oxidized arcs, such as the Izu arc (e.g., >FMQ + 3), exhibit across-arc lightening trends for both B and Mo isotopes, which is consistent with enhanced Mo isotopic fractionation due to elevation of f O 2 during subduction. Thus, the B Mo isotopes of arc rocks could provide diagnostic indicators for distinct geochemical recycling processes controlled by changes in redox conditions in subduction zones. • Mantle wedge beneath Sumatra is metasomatized by melts from subducted sediments. • Structure of subducted slab influences melting of subducted sediments. • Change of f O 2 causes different B Mo isotopic fractionation processes in subduction zones. [ABSTRACT FROM AUTHOR]

The NNW striking Wudalianchi Cenozoic volcanic belt (WVB) in NE China is mainly composed of volcanoes in Menlu River area, Keluo, Wudalianchi and Erkeshan. K–Ar radiometric dating suggests two episodes of volcanism in the WVB. Specifically, the Pliocene to early Pleistocene volcanism is distributed only in the northern part of WVB, whereas middle Pleistocene to Holocene volcanism occurred over the entire WVB. Geomorphological analyses further delineate four northeast-striking linear alignments of cones in the Wudalianchi and Keluo volcanic fields, probably related to magma feeding fractures with en echelon arrangement. No age progression is observed along these alignments. We propose that a NNW-trending rift may have controlled the eruption from Pliocene to early Pleistocene and a dextral transpression stress field may have influenced the volcanism from middle Pleistocene to Holocene. We suggest that the Pliocene and early Pleistocene volcanism is associated with far effect of the India–Eurasia collision, while the middle Pleistocene to Holocene volcanism in WVB may have resulted from interaction between the India–Eurasia collision and the subduction of the Pacific plate. [ABSTRACT FROM AUTHOR]

Abstract: Whether or not mantle plumes and plate subduction are genetically linked is a fundamental geoscience question that impinges on our understanding of how the Earth works. Late Cenozoic basalts in Southeast Asia are globally unique in relation to this question because they occur above a seismically detected thermal plume adjacent to deep subducted slabs. In this study, we present new Pb, Sr, Nd, and Os isotope data for the Hainan flood basalts. Together with a compilation of published results, our work shows that less contaminated basaltic samples from the synchronous basaltic eruptions in Hainan–Leizhou peninsula, the Indochina peninsula and the South China Sea seamounts share the same isotopic and geochemical characteristics. They have FOZO-like Sr, Nd, and Pb isotopic compositions (the dominant lower mantle component). These basalts have primitive Pb isotopic compositions that lie on, or very close to, 4.5- to 4.4-Ga geochrons on 207Pb/204Pb versus 206Pb/204Pb diagram, suggesting a mantle source developed early in Earthʼs history (4.5–4.4 Ga). Furthermore, our detailed geochemical and Sr, Nd, Pb and Os isotopic analyses suggest the presence of 0.5–0.2 Ga recycled components in the late Cenozoic Hainan plume basalts. This implies a mantle circulation rate of >1 cm/yr, which is similar to that of previous estimates for the Hawaiian mantle plume. The identification of the ancient mantle reservoir and young recycled materials in the source region of these synchronous basalts is consistent with the seismically detected lower mantle-rooted Hainan plume that is adjacent to deep subducted slab-like seismic structures just above the core–mantle boundary. We speculate that the continued deep subduction and the presence of a dense segregated basaltic layer may have triggered the plume to rise from the thermal–chemical pile. This work therefore suggests a dynamic linkage between deep subduction and mantle plume generation. [Copyright &y& Elsevier]

Igneous rocks related to abnormal high heat flow preserved in ancient convergent margins provide direct clues to identify fossil ridge-subduction. The Khanka Massif, as a witness of the final termination of the Paleo-Asian Ocean in Late Paleozoic, provides an ideal opportunity to trace the fossil ridge-subduction. Different types of Permian igneous rocks (282–255 Ma) were identified in composition from mafic to felsic. The mantle-derived mafic rocks are further subdivided into two groups. Group I are arc-featured rocks with normal mantle-like features in Mg isotopes. Permian subduction setting was therefore proposed within western margin of Khanka Massif, supported by the coeval arc-featured granitoids and the detrital zircon cumulative proportion curves. By contrast, Group II are tholeiitic and have more depleted Sr-Nd-Pb-Hf isotopic compositions similar to MORB of Paleo-Asian Ocean. In addition, the decoupling between Sr-Nd-Pb-Hf and Mg isotopes indicate isotope exchange between MORB and magnesite. High heat condition is therefore required because of the decomposition reactions of magnesite. The crust-derived felsic rocks exhibit the prominent difference in Sr-Nd-Pb-Hf-Mg isotopic compositions, implying synchronous melting of the continental and oceanic crusts, which are supported by the high zircon saturation temperatures (855–935 °C). Consequently, an 'abnormal high-heat condition' caused by ridge subduction and resultant slab window is the most likely model to reconcile the diversiform magmatism and tectonic evolution along the west margin of the Khanka Massif in the Permian. Sr-Nd-Pb-Hf-Mg isotopes are therefore verified as an integrated tracer to decipher the magmatic response to the ridge-subduction in ancient subduction zone. • 'Abnormal' Permian igneous rocks were identified in easternmost CAOB. • Permian Ridge subduction was responsible for these 'abnormal' igneous rocks. • Integrated Sr-Nd-Pb-Hf-Mg isotopes were valid to trace fossil ridge-subduction. [ABSTRACT FROM AUTHOR]