The interaction between the Izanagi-Pacific ridge and the northeastern Eurasian Plate during the Eocene remains controversial. We focus on oceanic crust-derived adakitic rocks due to their potential for reconstructing the slab window associated with spreading ridges. New and previously published age data suggest that these adakitic rocks can be divided into three main episodes: Early Ypresian (ca. 55 Ma), Lutetian (ca. 46 Ma), and Bartonian (ca. 36–38 Ma). These rocks, which range from andesitic to dacitic in composition, are characterized by pronounced depletions in heavy rare earth elements (HREEs), low Y, high Sr, and high Sr/Y ratios. Variations in Mg, Mg#, Cr, and Ni values indicate partial melting of the subducted slab, followed by interaction with the surrounding mantle during ascent through the mantle wedge. Spatially, the first stage is localized as a ‘spot’ in NE China, suggesting a limited ridge-trench intersection. The subsequent two stages occur in two narrow belts, indicating large-scale ridge-trench intersections subparallel to the NE Eurasian margin. The temporal and spatial variations in adakitic rocks related to slab windows are best explained by changes in the scale of the Pacific-Izanagi ridge Subduction, possibly reflecting the variations in Pacific Plate movement during the Early Eocene.

Sediments play an important role in the evolution of convergent plate margins. Thermo-mechanical models have proposed that sediments can laterally migrate, especially in a diachronous subduction zone; however, there are no known arc-magmatism records of the lateral transport of sediment. The thermo-mechanical models can best be exemplified within an ancient diachronous convergence zone accompanied by along-trench arc lavas. We report Mg-Ba-Sr-Nd isotope compositions for late Paleozoic mafic arc rocks along the northern margin of the North China craton because of their potential to trace the different origins of metasomatism components corresponding to the diachronous process of the Paleo-Asian Ocean closure. The studied samples have large variations in δ26Mg (−0.28‰ to −0.16‰) and δ138/134Ba (−0.1‰ to +0.33‰) values with highly variable Sr-Nd isotopic compositions compared with the primitive mantle. Shallow-level geological processes cannot explain such large isotopic variations. Instead, the geochemical features of our samples reveal the prominent differences in the contributions of subduction sediments. Modeling results indicate that, spatially, subduction sediment flux gradually increased toward the ongoing arc magmatism in the scissor-like Paleo-Asian Ocean−North China craton convergence zone, corresponding to lateral sediment migration. This process is not smooth and has the potential not only to control the diverse composition of arc magmatism but also to cause episodic production and migration of mantle-derived arc magmatism in diachronous convergence zones. Consequently, Mg-Ba isotopes are reasonably considered as powerful tools to trace lateral sediment transport and its effects on arc magmatism diversity in extinct subduction systems.

Garnet pyroxenite provides crucial lithological and geochemical evidence for understanding mantle properties and processes. It can be formed via reaction of peridotites with silicate melts at moderate to high pressures. However, the formation mechanisms of garnet pyroxenites in the orogenic mantle and the origins of variations in their mineral compositions are unclear. To better understand the effects of water on the lithology and mineral chemistry of garnet pyroxenites, we carried out experiments of reactions between a hydrous basaltic andesite (4 wt % water) and a spinel lherzolite at 2-3 GPa and 1300-1375 degrees C using the reaction couple method. Control experiments without water in the melt were also conducted under the same conditions. The hydrous melt-peridotite reaction produced melt-bearing orthopyroxenites. In particular, a melt-bearing garnet orthopyroxenite and garnetite were formed at the melt-rock interface and on the melt side of the reaction couple, respectively, and the lherzolite transformed to garnet lherzolite at 3 GPa. In contrast, the control experiments produced garnet and clinopyroxene layers at 2 GPa and an eclogite at 3 GPa. Presence of water in melt stabilizes garnet relative to clinopyroxene on the liquidus, and intensifies the assimilation of reacting melt by the peridotite partial melt, which are the effects leading to the formation of garnetite and garnet orthopyroxenite, respectively. The thickness of garnet orthopyroxenite in the 3-GPa hydrous reaction experiments increases with temperature (from 1325 to 1375 degrees C) and run duration; garnet-rich and garnet-poor sections were generated at the higher temperature. Compared with previous hydrous melt-peridotite reaction experiments conducted at relatively high pressures (>= 3 GPa) and low temperatures (<= 1200 degrees C), high temperature is needed for the reaction to form and to develop garnet orthopyroxenite. The orthopyroxenite-peridotite assembly produced in our experiments is similar to garnet orthopyroxenite dikes in orogenic peridotites, which highlights the importance of hydrous melt-peridotite reactions in the formation of such dikes. The comparison of mineral chemistry between experimental products and natural samples suggests that subsolidus re-equilibration plays a significant role in causing the variations in mineral composition. Re-equilibration via intergranular diffusion between the constituent minerals can explain the low Mg# [atomic 100 x Mg/(Mg + Fe)] values of garnet and high Mg# values of orthopyroxene, as well as the low temperatures calculated using geothermometers. The processes of melt-peridotite reaction at high temperatures and subsolidus re-equilibration also govern trace element distributions among minerals in garnet orthopyroxenites from the orogenic massifs.

Clastic sedimentary rocks offer crucial insights for deciphering the Precambrian crustal evolution. Paleo-Mesoproterozoic sedimentation is widely developed in the southern margin of the North China Craton (SNCC). Previous research has primarily concentrated on magmatism, while the information of Precambrian crustal evolution revealed by sedimentary rocks was less concerned. Hence, we present the zircon U-Pb ages, zircon Hf isotopes and whole-rock geochemical data of the quartz sandstones from the Beidajian Formation of the Ruyang Group, the Sanjiaotang Formation of the Luoyu Group and the Ma'anshan and Luotuopan formations of the Wufoshan Group within the SNCC. The detrital zircon dating, Hf isotope data and geochemical features of these formations indicate that their sediments were primarily sourced from the Neoarchean-Paleoproterozoic rock units in the SNCC, with the characteristics of mature crustal materials. Their detrital zircon age spectra and depositional environment combined with geological evidence indicate that the SNCC was in an extensional environment during the late Paleoproterozoic to early Mesoproterozoic. The Hf isotope data combined with geological evidence suggest that the crustal growth was dominant in the SNCC during the early Neoarchean (2.80-2.70 Ga), and the crustal reworking played a dominant role during the mid-to late Paleoproterozoic (2.00-1.72 Ga), while the crustal growth and reworking coexisted during the late Neoarchean (ca. 2.50 Ga) and early to mid-Paleoproterozoic (2.46-2.02 Ga).

The timing, petrogenesis, and tectonic setting of the Paleo-Mesoproterozoic (similar to 1.6 Ga) alkaline magmatism and associated rare earth element (REE) mineralization in the southern North China Craton (SNCC) remain contentious. The Longwangzhuang (LWZ) deposit is a recently discovered REE deposit in the SNCC. It is hosted within the region's largest Late Paleoproterozoic granite pluton, namely the LWZ REE-bearing granite. In this study, we present an integrated study of zircon U-Pb geochronology, whole-rock geochemistry, and Sm-Nd and zircon Lu-Hf isotopes on the LWZ REE-bearing granite. Zircon U-Pb dating yields a crystallization age of 1613 +/- 6 Ma, implying that the pre-enrichment of REEs occurred in the late Paleoproterozoic. The granite exhibits A-type characteristics, including high SiO2, alkalis, and FeOT/(FeOT + MgO) ratios, with strong enrichment in LREEs and strong negative Eu anomalies. Whole-rock epsilon(Nd) (t) values range from -6.2 to -4.9, and zircon epsilon(Hf)(t) values vary from -4.8 to +0.8, indicating derivation primarily from the partial melting of ancient Mesoarchean crustal sources (Taihua Group). Geochemical tectonic discrimination diagrams consistently suggest an intraplate extensional setting. We conclude that the LWZ A-type granite formed during the Columbia supercontinent breakup. The primary enrichment of REEs was governed by extensive fractional crystallization of the magma, with late-stage hydrothermal activity contributing to the final ore-grade mineralization. This study not only clarifies the origin of the LWZ granite but also establishes a link between Proterozoic intracontinental rifting and REE metallogeny in the SNCC.

Subduction-driven recycling of volatiles plays a crucial role in shaping our planet. Nevertheless, the mechanisms for the transfer of carbon from a subducting slab into the overlying arc lithosphere remain enigmatic. In this study, we present novel findings using Li-Mg-Zn isotopic systematics along with radiogenic Sr-Nd-Hf isotopes from four Late Jurassic (emplaced at 157-150 Ma) subduction-related mafic igneous rocks in the eastern North China Craton. We aim to investigate the role of carbonated oceanic slabs in generating mafic arc magmatism. These mafic rocks show lighter Li (67Li = -3.67%0 to-0.67%0) isotopic compositions relative to the mantle. They exhibit light Mg (626Mg = -0.38%0 to-0.32%0) and normal mantle-like Zn (666Zn = 0.26%0-0.30%0) isotopic compositions, indicating "Mg-Zn isotopic decoupling." Modeling requires a complex mantle source region encompassing 4.5%-14.0% dehydrated altered oceanic crust and 0.3%-6.0% carbonate-bearing silicate sediments. Abundant amphibole phenocrysts, arc-like trace element patterns, and enriched Sr-Nd-Hf isotopic compositions suggest a hybridized subcontinental lithospheric mantle source with significant slab-derived hydrous carbonatitic liquid contributions. We propose that water significantly depresses the thermal stability of Mgrich carbonates and facilitates the generation of hydrous carbonatitic liquids at sub-arc depths. Consequently, our findings elucidate that arc magmatism originates from a mantle source infiltrated by hydrous carbonatitic liquids from subducting slabs. The combined analysis of Li-Mg-Zn isotopes provides a case study for identifying the recycling of carbon in subduction zones.

Water is an essential element for life and plays a pivotal role in shaping our planet. However, the behavior of water in relatively "dry" magmatic systems and its influence on crystallization processes remain enigmatic. This study delves into the micro-analytical examination of amphibole-bearing gabbroic intrusions in the northeastern North China Craton, exploring their petrogenetic relationship with contemporaneous amphibole-rich appinites. The majority of pressure data cluster at similar to 1.17-4.01 kbar, indicating that these crystallization processes occurred near the roof of a magma chamber at shallow crustal levels. The paragenetic assemblages comprising olivine (forsterite similar to 72), clinopyroxene%orthopyroxene, bytownite (anorthite[An]similar to 87), pargasite, and phlogopite denote a middle-pressure system characteristic of the olivine gabbro. The associations of clinopyroxene%orthopyroxene, andesine (An similar to 45), and magnesio-hornblende record a shallow-pressure level for the gabbro. A peritectic relationship between clinopyroxene and amphibole suggests that the crystallization of amphibole in these gabbroic rocks is facilitated by a hydrous reaction involving water-rich residual melts and anhydrous pyroxene-dominated residues within a closed-system evolution. The source of the "damp" mantle, characterized by low water contents, is responsible for generating amphibole-bearing gabbroic rocks. The "wet" magma system, with high water contents, facilitates the crystallization of amphibole-rich appinites. Varying amounts of water from the shallow oceanic crust can be recycled into the deep upper mantle via the subduction of the Paleo-Pacific Plate, causing a heterogeneous hydrous lithospheric mantle. In conclusion, the coexistence of two distinct types of mafic intrusions, each defined by varying proportions of hydrous minerals, reveals the heterogeneity of deep-Earth water cycling.

Subduction-driven recycling of crustal components plays a crucial role in shaping the compositional heterogeneities of the mantle. However, determining the metasomatic proportion and age of sediment recycling remains challenging owing to the overprinting influence of other slab contributions. This study focuses on two Early Cretaceous (126-123 Ma) gabbroic intrusions from the northeastern North China Craton (NCC), China, which provide insights into how subducted sediments modulate mantle compositions. The olivine gabbro has higher MgO contents and lower FC3MS (FeOT/CaO - 3MgO/SiO2) values, suggesting peridotite-derived melts, relative to the gabbro that originates from pyroxenite mantle sources. The two gabbroic intrusions exhibit arc-like trace element distribution patterns, along with enriched whole-rock Sr-Nd and zircon Hf-O isotopic compositions. These characteristics indicate their derivation from fluxed melting of sub-continental lithospheric mantle sources hybridized by melts derived from similar to 5 % terrigenous sediments. Based on the three-stage Pb isotopic growth model, the metasomatized time of the mantle sources occurred in the Late Jurassic (160-150 Ma), which provides new geochemical evidence supporting the Late Mesozoic subduction of the Paleo-Pacific Plate beneath the Eurasian continent. Using the program ABS5, we conducted quantitative calculations to estimate the pressure and temperature of sediment melting, with 3.1-3.2 GPa and 838-842 degrees C. Thus, our findings not only illustrate the specific contributions (i.e., proportion and age) of sediments input into the mantle, while also highlight the significant role of mantle metasomatism driven by recycled sediments in creating mantle compositional heterogeneities.

This study presents LA–ICP–MS U–Pb dating and whole-rock geochemical analyses of the Late Triassic Gangshan harzburgite in the Qingyuan area, with the aim of elucidating its petrogenesis and further constraining the early Mesozoic tectonic evolution of the eastern segment of the northern margin of the North China Block（NCB）. Zircons from the harzburgites exhibit typical oscillatory growth zoning or striped absorption in cathodoluminescence images. U–Pb analyses of zircons yield ages ranging from 2 525 Ma to 225 Ma, with two youngest ages（225±7 Ma） indicating that the harzburgites were formed during Late Triassic. Geochemical analyses of the Gangshan harzburgites show that the rocks have low concentrations of SiO 2 （42.38%–42.85%） and Al2O3（3.31%–3.33%）, along with high concentrations of MgO（41.32%–41.76%）, Cr(4 856×10 -6 –5 191×10 -6 ) and Ni(1 942×10 -6 –2 041×10 -6 ). They also display low REE abundances(∑REE=4.38×10 -6 –4.69×10 -6 ) and fiat REE patterns with low（La/Yb） N ratios（1.24–1.56） and slightly positive Eu anomalies（δEu=1.13–1.16）. These features suggest that the Gangshan harzburgites are cumulates of basaltic magma derived from the depleted lithospheric mantle. Combined with previous studies, these Late Triassic mafic–ultramafic rocks, together with coeval granitoids in adjacent regions, constitute a typical bimodal association, suggesting that they formed in a post-orogenic extensional environment after the final closure of the Paleo-Asian Ocean.

The Paleo-Pacific Plate stagnated in the mantle transition zone beneath northeast Asia during the Late Mesozoic, resulting in the eastern Asian big mantle wedge (BMW). However, its formation mechanism remains unclear. Here, we analyzed elemental and isotopic compositions of 126–60 Ma intraplate basaltic rocks to map the mantle flow pattern and investigate the implications for the formation of the BMW. These rocks exhibit eastward an increase in Ba/Nb, Ba/La, 87Sr/86Sr, and 208Pb/204Pb ratios, while a decrease in Nb/Yb, Zr/Yb, Ta/Yb, and Nb/Nb* ratios, indicating mixing between the fertile mantle and the depleted mantle modified by slab material, implying the occurrence of trench-perpendicular mantle flow. The coeval mantle flow and formation of the BMW, the similar directions of mantle flow and Paleo-Pacific Plate subduction, and migration of basin depocenters indicate trench-perpendicular mantle flow was a key factor in the formation of the BMW. Moreover, these basaltic rocks have elevated δ66Zn values (0.22‰ to 0.52‰), indicating recycled carbonates have been added into their mantle source, which increased the mantle flow velocity. Combined with slab roll-back in the Late Mesozoic, it created the essential conditions for mantle flow to promote the formation of the eastern Asian BMW.

Apatite geochemistry in granitoids is controlled primarily by the original melt compositions and partition coefficients. However, additional factors (e.g., post-crystallization effects, mineral crystallization sequences, and crustal assimilation) can also contribute to variations in apatite compositions. In this study, we collected three groups of early Paleozoic granitoids from the North Qinling Orogen and obtained in situ geochemical data for apatite. The granitoids were formed by partial melting of oceanic arc crust (group A), recycling of ancient crust (group B), and melting of the lithospheric mantle and extensive fractionation (group C). Trace element and Nd isotope data show the apatite from the Taiping and Manziying plutons (group A) were affected by postcrystallization processes and crustal assimilation, respectively. In addition, crystallization of plagioclase/allanite and apatite resulted in the variable Eu anomalies and rare earth element contents of apatite in the group A granitoids. In contrast, apatite compositions in group C were controlled primarily by the fractionation of hornblende. However, the decoupling of Eu anomalies of apatite and their host rocks, particularly for group B, cannot be easily explained by the aforementioned factors. As such, the redox state may also have been an important factor. We used a ternary diagram (10 x [Eu/Eu*]N-V-Ga) to constrain the redox state from the apatite data, and provide insights into the types and petrogenesis of the host granitoids. Combined with the whole-rock and zircon geochemical data, we found that the apatite from the rocks derived from continental crust (group B and cratonic adakites) is generally reduced, whereas apatite from the mafic rocks and high Ba-Sr granitoids is highly oxidized. The highest degree of oxidation was found for the altered apatite from the group A granitoids and unaltered apatite in the orogenic adakites, possibly due to interactions with fluid derived from oceanic crust. Moreover, unaltered group A granitoids exhibit a transitional trend from an oxidized to a reduced state. Apatite geochemistry can be used to constrain the redox state of adakitic rocks and whether they have a continental or oceanic crustal origin. The high Sr contents of high Ba-Sr granitoids are inherited from their mantle source.

Magma mixing is the key to revealing deep geodynamic processes. High Ba-Sr granitoids (Ba > 500 ppm; Sr > 300 ppm) are initially defined as products that reflect the entrainment of mantle sources into the melting zone, which could provide constraints for magma mixing. Here, we collected a suite of spatiotemporally correlated high Ba-Sr granitoids (Ba = 831-1136 ppm; Sr = 991-1306 ppm) from the North Qinling Orogen, Central China, to constrain their petrogenesis based on whole-rock elemental and isotopic compositions, as well as zircon U-Pb, Lu-Hf, and O isotopes. High Ba-Sr granitoids in the North Qinling Orogen mainly formed during the early Paleozoic from ca. 450 to 420 Ma and exposed to a nearly east-west trend. In the Erlangping unit, they exhibited variable SiO2 and elevated Mg number (Mg-#, 42-55) and Cr (39-77 ppm) and Ni (13-54 ppm) contents. Simple simulations of trace elements indicated fractional crystallization of clinopyroxene, garnet, hornblende, and accessory minerals. They have depleted Sr-Nd-Hf and low O isotopes (4.89 parts per thousand-5.48 parts per thousand), and isotopic modeling constrains a depleted mantle, which was metasomatized by the oceanic sediments and altered oceanic crust-derived fluid. Spatially adjacent high Ba-Sr granitoids in the Kuanping unit have more "crustal/enriched" geochemical and isotopic characteristics, but distinctly higher total Mg-# (53-54) and Fe2O3 (3.77-4.90 wt%) and Ni (16.8-24.4 ppm) contents than typical crustal-derived melts, coupled with the occurrence of mafic microgranular enclaves (MMEs). The simulation of the fractional crystallization of coeval gabbroic intrusions well reproduced the trace element compositions of the MMEs. There was some complementarity in the composition of the simulated melt and neighboring crustal-derived melts (e.g., Nb, Ta, Zr, Hf, and heavy rare earth elements), supporting the mixing origin of the high Ba-Sr granitoids. Isotopic modeling constrained the mixing of mantle-derived melt and lower crust-derived melt to form high Ba-Sr granitoids. Although the host granitoids and MMEs shared an overlapping isotopic scope, the fractional crystallization process and initiation of local superheating of the felsic magmas provided the possibility for efficient magma mixing.

Melting of subducted m & eacute;lange can potentially transport mass from the slab-mantle interface to the mantle wedge in subduction zones. The m & eacute;lange diapir model was primarily proposed from the results of laboratory experiments and thermodynamic modeling. However, the melting mechanisms of m & eacute;lange diapirs in subduction zones remain unclear. To further constrain the mantle dynamics of a m & eacute;lange diapir, we studied Oligocene alkaline intermediate rocks on the northeast Asian continental margin. We report whole-rock geochemical and Sr-Nd-Pb-Mg-Zn isotope data and show that these rocks formed by partial melting of m & eacute;lange. We conclude that a diapir was the mechanism for Oligocene melting of the m & eacute;lange. We also identified younger rocks formed by melting of m & eacute;lange in the eastern part of northeast Asia, implying an eastward shift in such magmatism since the Oligocene. Our results and the tectonic setting indicate that melting of m & eacute;lange diapirs occurred preferentially during tectonic transitions, such as the formation of a back-arc basin triggered by trench-perpendicular mantle flow. The low-viscosity mantle with an incompressible stress field triggered melting of the m & eacute;lange diapirs. Interactions occurred between the m & eacute;lange diapirs and carbonated peridotites, constraining the depth of m & eacute;lange-mantle interactions to the asthenosphere, which is deeper than the depth inferred in previous studies.

The subduction of carbonate-bearing components into Earth's interior is a key part of the deep carbon cycle. However, the mechanisms of carbon transfer from the subducted slab to the sub-arc mantle remain unclear. Here we present a novel study using the Li-Mg-Zn isotopic systematics of Early Cretaceous olivine websterites from the northeastern North China Craton, China, to investigate cryptic carbonatite metasomatism. Clinopyroxene in the websterites has high Ca/Al and (La/Yb)N ratios, indicating their derivation from fluxed melting of a carbonated mantle peridotite. The samples exhibit lighter Li (67Li = -4.42%0 to 3.62%0) and Mg (626Mg = -0.40%0 to -0.36%0) isotopic compositions compared with the mantle, but similar Zn (666Zn = 0.25%0-0.29%0) isotopic compositions, suggesting the source was modified by similar to 14% dehydrated altered oceanic crust and similar to 6% carbonate-bearing silicate sediments. We propose that arc magmatism lacking high-67Li and-666Zn signatures does not necessarily indicate the absence of carbonates in the source. The combination of clinopyroxene and Li-Mg-Zn isotopic analyses can provide an improved understanding of deep carbon cycling.

Abundant subducted materials are recycled into the deep mantle during the plate subduction process and are further reflected in the postcollision mafic rocks. The Early Cretaceous Mid-Oceanic-Ridge-Basalt (MORB)-like mafic rocks in the southern margin of the North China Craton (SNCC) preserve significant information on recycled materials. These rocks provide a window for discussing the crust-mantle interaction and tracing the history of subduction. The studied rocks comprise the Jingwan metadiabase, Putaozhuang, Nianpanzhuang, and Niujiaowan metahornblende gabbro, with Early Cretaceous ages (140-129 Ma). They show large ion lithophile element enrichment in both the Enriched-MORB and Normal-MORB rare earth element patterns. They are characterized by slightly depleted isotopic compositions, high MgO, Cr, Ni and Mg-# values as well as the low SiO2, suggesting a depleted mantle source affinity. The enriched NdHf (epsilon(Nd)(t) = -14.50 to -13.47; epsilon(Hf)(t) = -9.27 to -8.82) and unradiogenic Pb isotopes imply that Jingwan samples originated from a depleted mantle source metasomatized by lower continental crustal materials. Their relatively enriched zircon epsilon(Hf)(t) values (-15.8 to -1.6) and delta O-18 values (4.82 parts per thousand-8.77 parts per thousand) along with their Paleoproterozoic to Neoproterozoic inherited zircons also argue for the contribution of low continental crustal materials from the North China Craton. In contrast, Putaozhuang, Nianpanzhuang, and Niujiaowan samples have positive whole-rock epsilon(Nd)(t) values (4.08-5.20) and epsilon(Hf)(t) values (3.23-5.62). Combined with the existence of Paleozoic zircons, high zircon epsilon(Hf)(t) values, and high Nb/U ratios, these materials suggest that they originated from a depleted mantle source metasomatized by juvenile crust and terrigenous sediments. This is corroborated by variable zircon delta O-18 values (5.57 parts per thousand-9.63 parts per thousand) and mantle-like delta O-18 values (5.08 parts per thousand-5.60 parts per thousand) of Paleozoic inherited zircons from Niujiaowan samples. The distinct geochemical characteristics of Early Cretaceous mafic rocks are induced by the incorporation of different components from subducted crust and sediments into the depleted mantle source. Paleo-Pacific Plate far-field effects controlled the intense lithospheric extension and thinning of the Early Cretaceous MORB-like rocks in the SNCC, which were placed in an immature back-arc basin setting.

Files included as Supplemental Material consist of Supplemental Text S1 (12 Figures and 5 Texts) and Supplemental Tables (11 Tables). They contain additional information regarding analytical methods and results.

Accretionary orogens are sites of extensive continental crustal growth and modification. The mechanism by which mafic crust is transformed into silicic melts (i.e., maturation of continental crust) is important for understanding the formation of the continental crust. The North Qinling Orogen (NQO) is a composite orogenic belt and contains an early Paleozoic accretion-dominated orogenic system, which is ideal for investigating continental crustal maturation. We obtained zircon and monazite U–Pb age and O isotope data, zircon Lu–Hf isotope data, and whole-rock major- and trace-element and Sr–Nd isotope data for early Paleozoic granitoids of the NQO. The granitoids are divided into three groups. Group 1 includes the Taiping tonalite (445 ± 3 Ma), the Manziying syenogranite (445 ± 2 Ma), and the Huoshenmiao granodiorite (436 ± 2 Ma). The Taiping and Huoshenmiao plutons have relatively high SiO2 contents (68.64–71.67 wt.%) and Na2O/K2O ratios (1.15–4.19), with enrichments in Rb, Ba, Th, and U and depletions in Nb, Ta, P, and Ti, and they are geochemically similar to sodic arc magmas. The Manziying syenogranite is a peraluminous potassic granite with high K2O contents (4.59–5.27 wt.%). Grantioids from Group 1 have similarly depleted Sr–Nd–Hf–O isotopic features (εHf[t] = +5.9 to +8.8; δ18O = 3.98‰–5.41‰), indicative of derivation via partial melting of oceanic arc crust, which suggests that partial melting of oceanic arc crust in a subduction system contributes to the generation of continental crust and causes its maturation. Group 2 consists of the Wuduoshan monzogranite (418 ± 2 Ma) and the Sikeshu granodiorite (423 ± 3 Ma). These plutons have relatively high SiO2 (65.59–72.06 wt.%), K2O (3.26–4.79 wt.%), and Al2O3 (14.65–16.12 wt.%) contents and Sr/Y (33–87) and (La/Yb)N (23–48) ratios. The Wuduoshan monzogranite has positive zircon εHf(t) (+0.4 to +3.1) and uniform δ18O (6.38‰–8.07‰) values, but the Sikeshu granodiorite has more variable isotopic compositions (εHf[t] = −1.9 to +5.0; δ18O = 6.37‰–10.60‰). The Wuduoshan monzogranite and Sikeshu granodiorite have similar whole-rock Sr–Nd isotopic compositions to basement rocks of the NQO. These features indicate that the two plutons formed by partial melting of basement rocks (i.e., subducted into the lower crust) of the North Qinling unit, along with juvenile crustal material. Group 3 is represented by the Xiaguan monzogranite, which formed at 434–430 Ma, and can be subdivided into heavy rare earth element (REE)-depleted and -enriched units. The former has high Sr/Y (56–98) and (La/Yb)N (34–73) ratios and low MgO (0.13–0.24 wt.%), Cr (0.37–1.69 ppm), and Ni (0.32–1.09 ppm) contents, similar to adakites derived from metabasaltic sources. The heavy REE-enriched nature of the Xiaguan monzogranite may reflect modification of its source by melt or fluid. Our results show that partial melting of enriched oceanic arc crust contributed to crustal maturation in an accretionary orogen. The addition of evolved crustal material also facilitated this process; therefore, the basement rocks and crustal thickness should be considered when assessing crustal dynamics in an accretionary orogen.

Global water cycling involves interactions between Earth's interior and its surface environment. Geophysical and mineral physics studies have suggested that the mantle transition zone is hydrous, at least locally. However, there are poor constraints on whether water in the transition zone is sourced internally from primordial materials or from Earth's surface via subduction-related processes. Cenozoic volcanism in Northeast Asia is triggered by hot and wet upwelling flows above the stagnated Pacific slab and has produced mantle transition zone-derived volcanic rocks. Potassium behaves geochemically similarly to water during magmatic processes, and hence can potentially be used to constrain the nature of water in the mantle transition zone. Here we report potassium isotopes in a set of well-characterized Cenozoic volcanic rocks in Northeast Asia. Their K isotope ratios (-0.83 parts per thousand to -0.36 parts per thousand) are lower than primitive mantle (-0.42 parts per thousand +/- 0.08 parts per thousand), suggesting crustal potassium inputs and modifications of the mantle transition zone by subducted slab materials. Decoupling of potassium isotopes from radiogenic Sr-Nd-Pb isotopes, combined with a geophysically identified low-resistivity anomaly above the transition zone, requires the input of surficial water from the stagnated subducted slab into the transition zone. This water can then be cycled back to the surface in Northeast Asian volcanics. Water in the mantle transition zone beneath Northeast Asia is sourced from the Earth's surface and introduced by the subducted Pacific slab, according to a study of potassium isotopes from Cenozoic volcanics.

Compositional variations of apatite are mainly determined by parameters such as partition coefficients and the composition of parental magma. However, the relative importance of these parameters in relation to apatite geochemistry in different lithologies of magmatic rocks is not well constrained. In this study, six Mesozoic (219-154 Ma) mafic-felsic intrusions from the eastern North China Craton, were selected for detailed apatite microanalyses (trace elements and Nd isotopes). Apatite from the studied intrusions has uniform textures in the cathodoluminescence image. They exhibit high abundances of rare earth elements (REE) and are characterized by light REE enriched patterns, indicative of a magmatic origin. Alongside compiled apatite data, these findings suggest that compositional variations of REE + Y in apatite from mafic to felsic magmatic rocks are controlled primarily by elemental partitioning between apatite and melts. The competitive crystallization of other accessory minerals prior to apatite can be responsible for compositional variations of Sr, Pb, Th, and U. New Nd isotope data for apatite are discussed and compared with whole-rock Nd and zircon Hf isotope data for the same sample. The Nd isotopic compositions between the whole-rock and apatite are identical. The integrated dataset provides an alternative interpretation for the isotopic decoupling between apatite Nd and zircon Hf isotope systems. In conclusion, apatite REE concentrations and Nd isotopes have the potential to serve as geological indicators.

晚白垩世是古太平洋俯冲板块运动变化的关键时期.本文总结了东北亚陆缘晚白垩世火成岩的时空分布特征,结合火成岩地球化学数据,探讨该时期岩浆作用与古太平洋俯冲及气候变化之间的潜在联系.东北亚陆缘晚白垩世火成岩分布范围由陆内至陆缘明显收缩,指示古太平洋板块俯冲-后撤过程.火成岩展布方向发生小角度偏转,可能是俯冲板块在深部地幔流影响下发生变形以及不同位置后撤速率差异所致.该时期东北亚陆缘经历了地壳减薄和岩浆初始温度上升,暗示板块后撤诱发陆缘向地幔流,引起地壳减薄并形成具有较高初始温度的岩浆.晚白垩世东北亚陆缘地区经历了由升温到降温的过程,与岩浆作用变化相对应,暗示岩浆活动与区域古气候变化具有潜在协同性.