A total of 111 mudstone samples from the southern Songliao Basin of China were analyzed to clarify how slow CO2 leakage influences mudstone seal capacity through diagenetic overprint diagenetic processes. Petrography and isotope data show that CO2-affected mudstones contain authigenic Dawsonite, ankerite, and calcite, whose carbon isotopic compositions consistently indicate a mantle-magmatic CO2 source. These carbonates precipitated later than Dawsonite in the underlying sandstones, demonstrating a progressive upward migration of CO2-charged fluids. CO2 leakage induced dissolution of feldspar, precipitation of authigenic carbonates, and formation of minor authigenic clays. Breakthrough pressure measurements reveal that ankerite has the strongest positive influence on mudstone seal capacity, whereas Dawsonite and calcite provide only limited improvements. The results indicate that CO2 leakage produces a vertical shift from carbonate dissolution zones to carbonate-cemented zones, enhancing long-term caprock integrity in the Songliao Basin. This study provides direct petrographic and isotopic evidence for the vertical migration of mantle-magmatic CO2 in mudstone caprocks, which is crucial for reconstructing the long-term CO2 leakage history of sedimentary basins and optimizing risk assessment frameworks of CO2 geological storage in similar continental petroliferous basins worldwide.

The late Mesozoic evolution of Northeast China was dominantly controlled by the Mongol-Okhotsk and the Paleo-Pacific tectonic regimes. Their superposition during the Early Cretaceous profoundly influenced magmatic activity, volcanic assemblages, sedimentary basin development, and extensional structures, ultimately establishing the present-day tectonic framework of Northeast China. This comprehensive study focuses on the formation processes of sandstones and volcanic rocks of the northern Great Xing'an Range, highlighting the transitional processes between these two tectonic regimes in the Early Cretaceous. Geochemistry and framework analysis of sandstones, along with detrital zircon U-Pb ages and provenance studies, consistently suggest a transitional tectonic setting during the deposition of the Early Cretaceous Jiufengshan Formation. Comparative geochemical analysis of volcanic rocks and zircon Hf isotopes reveals a fundamental shift in magma generation processes for volcanic rocks formed before and after the Jiufengshan Formation. Zircon trace element systematics document two distinct episodes of crustal thickening and thinning during the Early Cretaceous, genetically linked to the final closure of the Mongol-Okhotsk Ocean followed by post-collisional extension, as well as low-angle subduction and subsequent slab rollback of the Paleo-Pacific plate. This paper demonstrates that the postcollisional extension of the Mongol-Okhotsk tectonic regime primarily governed the tectonic evolution recorded in the Baiyingaolao, Meiletu, Longjiang, and Guanghua formations, with its influence progressively diminishing during the deposition of Jiufengshan Formation. Synchronously, far-field effects induced by the low-angle subduction of the Paleo-Pacific plate had already propagated into the northern Great Xing'an Range, where subsequent slab rollback triggered the formation of bimodal volcanic rocks in the Ganhe and Gushanzhen formations. The transition between these two competing tectonic regimes is precisely constrained to the interval between 116 Ma and 111 Ma, based on integrated chronostratigraphic evidence.

The tectonic m & eacute;lange belts along the northeastern margin of the North China Craton (NCC) provide critical insights into the closure of the Paleo-Asian Ocean (PAO) and the formation and evolution of the Central Asian Orogenic Belt (CAOB). Due to the lack of early Late Palaeozoic geological records in this region, understanding the initiation and polarity of PAO subduction remained unclear. Recently identified Middle Devonian and Lower Carboniferous meta-clastic rocks and Upper Devonian meta-volcanic rocks from the "Xia'ertai" tectonic complex in the northeastern margin of the NCC have provided new evidence. Comprehensive geological surveys, mineralogical and petrographic studies, geochemistry, and zircon U-Pb isotopic dating were conducted. The Middle Devonian meta-clastic rocks (muscovite two-feldspar gneiss) exhibit high SiO2 and Al2O3 contents, notable REEs fractionation, and negative Eu anomalies. Zircon U-Pb dating reveals ages between 384 and 443 Ma. These rocks, with sandstone as the protolith and granitic rocks as their provenance, formed in a basin along the continental margin during the extensional stage after arc-continent collision. The Upper Devonian meta-volcanic rocks (biotite plagioclase gneiss) belong to the high-K calc-alkaline series, are metaluminous to weakly peraluminous, and show a pronounced REEs fractionation and negative Eu anomalies. Zircon U-Pb dating gives a weighted average age of 381 Ma. These rocks are classified as highly differentiated I-type magmatic rocks, originated from partial melting of the lower crust, and formed in an active continental margin environment. The Lower Carboniferous meta-clastic rocks (two-mica quartz schist) have high SiO2 and Al2O3 contents, distinct REE patterns, and negative Eu anomalies. Zircon U-Pb ages range from 324 to 370 Ma. These rocks, with sandstone as the protolith and felsic volcanic rocks as their sole provenance, formed in an active continental island arc environment. Integrating these findings with previous research, we propose a four-stage tectonic evolution model for the northeastern margin of the NCC from the Early-Middle Devonian to Late Carboniferous: (1) Extensional phase following an arc-continent collision (Early-Middle Devonian); (2) Formation of an active continental margin arc due to the intensified southward subduction (modern coordinate system) of the PAO plate (Late Devonian); (3) Continued southward subduction of the oceanic lithosphere (Early Carboniferous); (4) Development of fore-arc and back-arc basins (Late Carboniferous).

Iron Formations (IFs) are critical records for reconstructing the surface environment and geochemical evolution of early Earth. As economically significant Precambrian sedimentary rocks, they serve as key archives for reconstructing early Earth's tectonic settings and paleoenvironmental conditions. This study focuses on a unique silicate IF at Nianpan (NP), Fushun area, northern Liaoning Province, which differs from typical Banded Iron Formations (BIFs) in its distinctive mineral assemblage. By integrating petrographic, mineral-chemical, geochemical, geochronological, and isotopic analyses, we reconstruct the protolith composition and depositional environment of this specific type of IF. The NP IF comprises two main rock types: magnetite-bearing two-pyroxene ore and banded ferrosilicate quartzite, both exhibiting a well-developed compositional banding. Thermobarometric calculations using the two-pyroxene thermometer and the garnet-orthopyroxene barometer constrain peak metamorphic conditions to granulite-facies (815 degrees C/1.05 GPa). Zircon U-Pb dating yields a depositional age of 2533.0 +/- 6.8 Ma and a metamorphic age of 2485.7 +/- 7.8 Ma. Systematic geochemical and isotopic analyses demonstrate that the protolith sediments were primarily derived from seawater, with a minor hydrothermal contribution (<0.1 %). The absence of a negative Ce anomaly (whole rock), coupled with significant enrichment in delta Fe-56 and the presence of pyrite, collectively suggest deposition occurred in a reducing, weakly acidic marine environment. Our results support a genetic model involving: (1) initial precipitation of ferruginous-siliceous sediments from seawater with minor hydrothermal input under anoxic conditions, followed by (2) regional granulite-facies metamorphism in the late Archean to early Paleoproterozoic, ultimately forming the distinctive silicate IF at NP in the Fushun area (northern Liaoning Province) of the North China Craton (NCC).

Deciphering the polyphase evolution of long-lived accretionary orogens is essential for understanding how the continental lithosphere responds to fundamental geodynamic transitions. A major challenge remains in quantifying the rheological evolution and stress field reorganization that accompany the overprinting of kinematically distinct deformation events. NE China provides a natural laboratory to investigate these complex processes, as it records the crucial Mesozoic transition from the Paleo-Asian orogenic to the Paleo-Pacific tectonic regime. This study investigates the polyphase ductile deformation in the Changchun-Taiping area, which is situated at the strategic tectonic junction of these two regimes. By integrating field and microstructural analysis, calcite EBSD fabric analysis and twin paleostress inversion, and zircon U-Pb geochronology, we reconstruct a two-stage deformation history and quantify the rheological parameters characteristic of each stage. The early stage (D-1) is characterized by E-W-trending, dextral strike-slip shearing under low-temperature (190-260 degrees C) conditions. Deformation was accommodated by intracrystalline plasticity, primarily through basal slip in calcite and the development of Type I and Type II mechanical twins. Differential stresses of 33-56 MPa and strain rates of 10(-11.59)-10(-8.9) s(-1) were estimated, consistent with a NNW-SSE compressional regime. This event is inferred to be Late Triassic in age and is interpreted to record post-collisional intracontinental convergence and lateral extrusion following the closure of the Paleo-Asian Ocean, with additional far-field influence from the Mongol-Okhotsk convergent system. The later stage (D-2) is marked by NE-SW-trending, sinistral strike-slip shearing that overprinted the D-1 fabrics under mid-greenschist facies conditions (310-360 degrees C). Deformation was dominated by the dynamic recrystallization of quartz and calcite, with activation of rhomb and prism slip systems, reflected in a shift in crystallographic preferred orientations from c-axis maxima to Y-axis maxima. D-2 deformation occurred under increased differential stress (52-75 MPa) and significantly higher strain rates (10(-8.52)-10(-6.79) s(-1)). Paleostress inversion reveals a fundamental reorganization of the stress field into a continental margin transtensional regime, characterized by a subvertical sigma(1), a near N-S horizontal sigma(2), and subhorizontal E-W sigma(3). Zircon U-Pb dating of a syn-kinematic diorite porphyrite dike constrains D-2 to the Late Jurassic (ca. 159 Ma), indicating a rollback-dominated Paleo-Pacific slab, with additional far-field stresses from the Mongol-Okhotsk convergent regime overprinting the transtensional stress field. Our findings demonstrate that the Mesozoic tectonic transition in NE China involved a shift from multi-directional convergence-dominated compression to a transtensional regime primarily driven by Paleo-Pacific slab rollback and locally modified by far-field tectonic overprinting.

Northeast China consists of several microcontinents and accretionary terranes, providing valuable insights into how different tectonic units amalgamate during orogeny. The Hegenshan-Nenjiang Ocean (HNO) is a branch of the Paleo-Asian Ocean located between the Xing'an and Songliao accretionary terranes. However, the geodynamic setting of these terranes, as well as the timing of the final closure of the HNO, remains uncertain. Here, we present an integrated study of field and microstructural observations, electron backscatter diffraction (EBSD), zircon U-Pb dating, Lu-Hf isotopes and geochemistry of the hitherto poorly dated low-grade metamorphic Xiqiuhe and Tongshan formations located in the northeastern Xing'an Accretionary Terrane (XAT). The results indicate that the Xiqiuhe Formation was deposited in the Late Silurian (ca. 425 Ma), constrained by the crystallization age of an interbedded rhyolite layer and the youngest detrital zircon population, whereas the Tongshan Formation has a maximum depositional age of the Early Carboniferous (ca. 330 Ma). The detrital zircons in both formations show similar U-Pb ages and eHf(t) value distribution patterns. The primary sources are the Erguna Massif and the Paleozoic magmatic arcs within the XAT. Rhyolites from the Xiqiuhe Formation are characterized by high SiO2 and Al2O3 concentrations and low MgO, Fe2O3T , Cr, Co and Ni concentrations. Their positive eHf(t) values (9.57-12.89) and two-stage model ages (805-593 Ma) indicate that they were derived from partial melting of a juvenile accreted lower crust. In addition, two deformation phases have been identified in the Xiqiuhe and Tongshan formations. Microstructures and quartz EBSD fabrics demonstrate that they developed at mid-crustal levels with deformation temperatures ranging from 400 to 500 degrees C. The early deformation (D1) is characterized by top-to-the-NNW thrusting, followed by the development of open folds and crenulation cleavage (D2) resulting from NW-SE shortening. Both deformation phases are associated with the final closure of the HNO. Our new data alongside with previously published data on the HNO, suggest that the Xiqiuhe and Tongshan formations formed in a Paleozoic back-arc basin setting related to the slab roll-back of the HNO. The back-arc basin initiated prior to the Late Silurian (ca. 425 Ma), showed alongstrike variations, and began closing between the Late Devonian and Early Carboniferous. The HNO finally closed between the late Early Carboniferous and middle Late Carboniferous (ca. 330-310 Ma), accompanied by transpressional structures in the XAT. (c) 2026 China University of Geosciences (Beijing) and Peking University. Published by Elsevier B.V. on behalf of China University of Geosciences (Beijing). Thi s is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

The Yanshanian Movement (or Yanshanian Orogeny) has been a topic of study for nearly a century, with ongoing interests. This study reviews its origin, tectonic subdivision, development and dynamic mechanisms, and associated magmatic-tectonic activity in Western Liaoning, northeastern North China Craton (NCC). By analyzing rock assemblages, petrogenesis, and magma sources of Mesozoic volcanic rocks, and combining with available data on deformation, basin formations, mineralization, and evolution of biota, we propose a new dynamic mechanism of the Yanshanian Movement in Western Liaoning, particularly during its initial stage and pulsation pattern. The initial stage (Early to Middle Jurassic, 190-165 Ma) is defined by abundant magmatism, mineralization and compressional structures, likely associated with the multi-plate (Mongol-Okhotsk, Paleo-Pacific, and Meso-Tethys) convergence around the East Asian continent. The pulsation pattern is characterized by alternating tectonic settings in the northeastern NCC during the Jurassic to Early Cretaceous, featuring stages of both compression and extension. The first N(W)-S(E) compression stage (165-160 Ma) is marked by an unconformity above the Jiulongshan/Haifanggou Formation and associated (N)E-(S)W fold-and-thrust structures, influenced by WNW-directed subduction of the Paleo-Pacific Plate (PPP) and the far-field effect of the N-S closure of the Mongol-Okhotsk Ocean (MOO). The subsequent first extension stage (160-145 Ma) is small-scale and local, dominated by NE-SW and NW-SE structural trends, with NE-SW extension indicated by magnetic lineations of granitic plutons and top-to-the-NE ductile shear zones in the northern NCC, likely correlating with short-term stress relaxation from the MOO regime. This NW-SE extension is confirmed by the Late Jurassic basin-and- range-type tectonics in the northeastern NCC, possibly linked to the localized high-angle subduction and rollback of the PPP. The second N(W)-S(E) compression stage (145-135 Ma) corresponds to the Yanshanian Bepisode, illustrated by the syn-tectonic deposition and the unconformity from Upper Jurassic to lowermost Cretaceous. The NE-SW-trending compressional structures were controlled by rapid low-angle NNW-directed subduction of the PPP, alongside with subordinate E-W-trending structures associated with the final N-S closure of the MOO. The following second NW-SE extension in the late Early Cretaceous (135-100 Ma) is recorded by metamorphic core complexes, extensional domes and rift basins, and large-scale magmatic-tectonic activity, driven by asthenospheric material upwelling, lithospheric delamination, and thinning of the NCC lithosphere due to the rapid retreat and rollback of the PPP.

The early continental lithosphere of the Earth has experienced complex tectonic-magmatic processes, leading to significant change of its thermal structure and rheological properties, which are highly heterogeneous. The Qingyuan area in northern Liaoning Province in NE China is a natural laboratory for studying the rheological properties and deformation mechanisms of high-grade metamorphic rocks in the middle and lower crust, characterized by widespread amphibolite-granulite facies metamorphic rocks and associated structural phenomena and varying rheology. This study presents detailed investigations of the middle-lower crustal rocks of Jingjiagou Formation in the Qingyuan area, including field and microstructures, EBSD (Electron Back Scatter Diffraction) analysis, zircon U-Pb dating and electron microprobe analyses. The peak P-T conditions are constrained at 1 similar to 1.25 GPa/910 to 1050 degrees C for garnet pyroxenite, 0.8 similar to 1.1 GPa/800 to 870 degrees C for pyrigarnite, and 0.85 similar to 1.0 GPa/770 to 800 degrees C for amphibolite. Crystallographic preferred orientation statistics of pyroxene, amphibole and plagioclase indicate that deformation in the amphibolite-granulite facies rocks was dominated by dislocation creep of clinopyroxene and orthopyroxene during the peak metamorphic stage, with (110)[001]/(010)[001] and (100)[001] slip systems, respectively. During retrogression, amphibole deformation shifted to diffusion creep along (100)[001] slip system, with plagioclase also developing diffusion creep. At the Neoarchean/Paleoproterozoic boundary (2494 +/- 12 Ma), these deformation mechanisms reflect the flow deformation characteristics of high-grade metamorphic rocks in the Jingjiagou Fm. under the influence of vertical tectonics. Supracrustal rocks subducted into TTG magmas and were transformed within amphibolite-granulite facies conditions, with deformation driven by dislocation creep. As TTG magma ascended and temperatures and pressures dropped, rock deformation transitioned to diffusion creep at various crustal levels. This shift in mineral deformation mechanisms influenced the macroscopic structural patterns and associated deformation processes in the Jingjiagou Fm. of the Qingyuan area, NE China.

The late Archean (3.0-2.5 Ga) marks a significant transformation period in the continental crust and geodynamic processes. Representative Archean records in the North China Craton (NCC), including basaltic rocks, trondhjemite-tonalite-granite (TTG) gneisses and potassic granites, are essential for understanding the formation of the Archean continental crust. The Western Liaoning (WLN) in northern NCC preserves valuable Neoarchean geological records, providing a natural laboratory for studing crustal development and geodynamics. Based on mineralogy, petrology, geochronology, and geochemistry, this study investigates the Neoarchean mafic and felsic rocks in WLN. The 2549-2531 Ma old mafic rocks are derived from partial melting of the ultramafic lithospheric mantle, influenced by crustal contamination and metasomatic exchange with subduction fluids. TTG gneisses dated 2526-2509 Ma are classified as peraluminous calc-alkaline granites, generated by the partial melting of garnet amphibolites in thickened arc root. Potassic granites belong to the weakly peraluminous shoshonite-series are S-type granites, originated from partial melting of upper crustal metamorphic argillaccous rocks. This study also identifies a crustal growth episode in WLN between 2.8 and 2.7 Ga, through a comprehensive analysis of Hf model ages of mafic and felsic rocks. Late Neoarchean geodynamic evolution in WLN involved a transition from mid-ocean ridge (N-MORB-type) to intra-oceanic island arc (boninite-type), then to Andean-type active continental margin (adakite-and high-alumina TTG-type), and ultimately to an extensional tectonic phase (the potassic granite-type). Collectively, WLN preserves a complex geodynamic history of crust-mantle interactions related to subduction during the late Neoarchean.

During Early Cretaceous,NNE-trending extensional basins filling with various volcanic-sedimentary formations developed in the northeastern Da Hinggan Ling(Mts.),northeastern China.This study investigates the formation age and geological background of Jiufengshan Formation,providing insights into its tectonic setting and formation mechanisms.Detrital zircons from four sandstone samples of Jiufengshan Formation in Nenjiang area indicate a maximum depositional age of 116±1 Ma,corresponding to late Early Cretaceous.Petrographic analysis and zircon age peak comparisons suggest these sandstones originated from proximal deposits with nearby provenances of earlier and contemporaneous volcanic rocks.Further research on the sandstone framework and trace elements in detrital zircons indicates that the formation process of Jiufengshan Formation was likely related to the low-angle subduction of the Paleo-Pacific plate.

The Central Asian Orogenic Belt is the world's largest accretionary orogenic belt, associated with the closure of the Paleo-Asian Ocean (PAO). However, the final closure timing of the eastern PAO remains contentious. The Permian-Triassic sedimentary sequences in the Wangqing area along the Changchun-Yanji suture zone offer important clues into this final closure. New data on petrology, whole-rock geochemistry, zircon U-Pb geochronology and zircon Hf isotopes of sedimentary rocks from the Miaoling Formation and Kedao Group in Wangqing area provide new insights into the final closure of the eastern end of the PAO. The maximum deposition ages of the Miaoling Formation and Kedao Group have been constrained to the Late Permian (ca. 253 Ma) and early Middle Triassic (ca. 243 Ma), respectively. These sedimentary rocks exhibit similar geochemical characteristics, showing low textural and compositional maturities, implying short sediment transport, with all detrital zircons suggesting their origins from felsic igneous rocks. The epsilon Hf(t) values of the Miaoling Formation range from -6.09 to 12.43 and from -2.20 to 7.59 for the Kedao Group, implying these rocks originated from NE China. Considering our new data along with previously published data, we propose that a reduced remnant ocean remained along the Changchun-Yanji suture zone in the early Middle Triassic (ca. 243 Ma), suggesting the final closure of the eastern PAO likely occurred between the latest Middle Triassic and early Late Triassic.

The Archean supracrustal rock series in the Laojinchang area of Jilin Province, China provide valuable insights into the Precambrian geological evolution of the North China Craton. This study presents new results on petrography, geochemistry, mineralogy, isotope geochronology and phase equilibrium modeling of the Laojinchang granulite facies metamorphic rocks. The protolith ages of garnet two-pyroxene granulite and amphibolite from Sidaolazihe Formation, and two-pyroxene granulite from Laoniugou Formation are 2565 f 5.9 Ma, 2512 f 17 Ma, and 2509.2 f 8.6 Ma, respectively, with the metamorphic age recorded by amphibolite being 2475.6 f 9 Ma. New geochemical data indicates that TTGs (tonalite-trondhjemite-granodiorite) weathering in an island arc environment formed the protolith of argillaceous gneiss of Sidaolazihe Formation. Basaltic andesite, formed under an island arc environment, was the protolith of garnet two-pyroxene granulite of Sidaolazihe Formation; while calc-alkaline basalt was the protolith of amphibolite from the same formation and two-pyroxene granulite from Laoniugou Formation. All these Archean supracrustal rocks exposed in the Laojinchang area have recorded nearly isobaric cooling (IBC) anticlockwise P-T paths with distinct prograde, peak and post-peak stages. The peak P-T conditions reached granulite facies, suggesting a heat source from underplated magmas. A tectonic model involving an island-arc setting is proposed for the evolution of these Neoarchean supracrustal rocks in Laojinchang area.

The Erguna ductile shear zone is situated in the Erguna Massif, which has been exposed along the eastern bank of the Erguna River in northeastern China. The authors present comprehensive study results on the macro-and micro-structures, finite strain and kinematic vorticity, quartz electron backscatter diffraction（EBSD） fabrics, and geochronology of granitic rocks in the Erguna ductile shear zone. The deformed granitic rocks have experienced significant SE-trending dextral strike-slip shearing. Finite strain and kinematic vorticity in all deformed granitic rocks indicate that the deformation is characterized by simple sheardominated general shearing with S-L tectonites. Mineral deformation behaviors and quartz C-axis textures demonstrate that the deformed granitic rocks developed under greenschist to amphibolite facies conditions at deformation temperatures ranging from 450 to 550 ℃. New LA-ICP-MS zircon U-Pb ages indicate that these granitic rocks were formed in Early Triassic（～248.6 Ma） and Early Cretaceous（～136.7 Ma）. All the evidence indicates that this deformation may have occurred in Early Cretaceous and was related to the compression resulting from the final closure of the Mongol-Okhotsk Ocean.

The Mongol-Okhotsk suture belt represents the result of the final closure of the Mongol-Okhotsk Ocean between the Siberian Craton and Erguna Block (also called Amuria), which played an essential role in the formation and tectonic evolution of eastern Eurasia during Mesozoic times. However, the timing of the final closure and subduction polarity of the Mongol-Okhotsk Ocean are still debated. In this study, provenance analysis of Multidimensional scaling and crustal thickness variation based on zircon Eu anomaly were used for the first time to reveal the tectonic evolution of the Mongol-Okhotsk Ocean during Mesozoic times. The results show that the evolution of the Mongol-Okhotsk Ocean can be divided into several stages. From Early Triassic (-245 Ma) onwards, the Mongol-Okhotsk Ocean started to shrink due to southward subduction beneath the Erguna Block. The closure of western segments of the Mongol-Okhotsk Ocean occurred in the Late Triassic, leading to a weakening or cessation of oceanic plate subduction, and the prevalence of an extensional environment during 225-215 Ma. Subsequently, after the Late Triassic (starting at ca. 205 Ma), subduction of the Mongol-Okhotsk Ocean continued until the middle segments closed during Middle Jurassic (-165 Ma). From 165 to 155 Ma, many magmatic arc rocks and metamorphic core complexes formed in the central and western segments of the Mongol-Okhotsk suture belt within a post-orogenic extensional setting. The eastern part of the Mongol-Okhotsk Ocean rapidly closed in a scissor-like manner, resulting in the collision between the Erguna Block and the Siberian Craton during the Late Jurassic (-150-145 Ma). Collision also caused uplift of the southern margin of the Siberian Craton and the sediment deposition in the Mohe Basin. The subsequent crustal shortening associated with the collision led to the formation of nappes and the emplacement of adakites along the northern margin of Greater Xing'an Mountains. Since the Early Cretaceous, the compressional environment transitioned into a postorogenic extensional tectonic environment influenced by the west-directed slab rollback of the Paleo-Pacific Plate and detachment of the subducted Mongol-Okhotsk oceanic plate after closure of the Mongol-Okhotsk Ocean.

The Neoarchean Qingyuan greenstone belt (QGB) is located at the northeastern margin of the North China Craton (NCC) and has experienced amphibolite- to granulite-facies metamorphism. The supracrustal rock assemblage is composed of biotite-hornblende (Bt-Hb) monzonitic gneiss, garnet-biotite-hornblende (Grt-Bt-Hb) monzonitic gneiss, Grt-Bt-Hb plagioclase gneiss, amphibolite and orthopyroxene-biotite-hornblende (Opx-Bt-Hb) plagioclase gneiss. This study involves thorough field and petrographic observations, whole-rock geochemistry and LA-ICP-MS zircon U‒Pb ages of these rocks to constrain the Neoarchean geodynamic setting of the QGB. Zircon U‒Pb dating indicates that these metavolcanic rocks formed during 2.57‒2.52 Ga and experienced subsequent regional metamorphism at 2.52‒2.47 Ga. Lithological and geochemical characteristics show that the QGB protoliths were tholeiitic to calc-alkaline basalts, andesites, dacites and rhyolites. The andesite-dacite-rhyolite assemblage exhibits high SiO2 and Mg# values, low Yb and Y contents, strongly fractionated chondrite-normalized REE patterns and depletion in Nb, Ta, Ti and P, resembling Phanerozoic adakites. These geochemical characteristics suggest an origin from the partial melting of a subducted slab interacting with mantle wedge material. The tholeiitic to calc-alkaline basalts exhibit slightly LREE-enriched chondrite-normalized REE patterns and negative Nb and Ti anomalies, like island arc basalts. These basalts might have originated by partial melting of a mantle source affected by metasomatism from subduction-derived fluids and melts. The lithological associations and geochemical characteristics imply that the Qingyuan greenstone belt developed in a continental margin arc setting.

The Longgang Block is one of the most important parts of the eastern North China Craton, characterized by extensive Late Neoarchean（～2.5 Ga） granulite facies metamorphism. However, it remains uncertain whether it was influenced by Paleoproterozoic magmatism-metamorphism. The authors provide a comprehensive analysis of amphibolite in Laojinchang area, southern Jilin Province, through petrographic, geochemical, mineralogical, and zircon dating. The main findings are as follows: The mineral assemblage of amphibolite is Hb+Pl+Cpx+Bi+Kf+Q, characteristic of amphibolite facies; zircon U-Pb dating indicates that the metamorphic age of amphibolite is 1 834±33 Ma; the amphibolite has geochemical characteristics of calcium alkaline, with depletion of Nb, Ta, Ti and P. The plagioclase in the amphibolite is oligoclase, belonging to acidic plagioclase. It is speculated that the protolith of the amphibolite is diorite; using geothermobarometer, the peak metamorphic P-T conditions of amphibolite are determined to be 536–593 ℃/3.4–5.0 kbar, and the post-peak conditions are 429–566 ℃/1.3–3.1 kbar. The above results indicate that the Paleoproterozoic metamorphism has been superimposed on Longgang Block, linked to a new orogenic event on the northern edge of North China Craton.

The Sand River area is in the northeastern part of the Central Zone (CZ) of the Limpopo Belt, and represents a key terrane to reveal early Precambrian tectonic processes in southern Africa. Based on petrology, U–Pb zircon ages, and major and trace element data of high-pressure (HP) mafic granulites from the Sand River area, the tectonic evolution of the Central Zone of the Limpopo Belt is re-evaluated here that allows revision of previous interpretations. The protoliths of the HP mafic granulites and amphibolites are sub-alkaline tholeiitic basalts similar to those formed at a mid-ocean ridge and intruded at 2.8 Ga. Based on the distinct mineral assemblages, three metamorphic stages (M1–M3) are recognized in the studied samples: (1) a peak HP granulite facies stage M1 (~1.17–1.32 GPa/~825–870°C), (2) a post-peak near-isothermal decompression stage M2 (~0.70–0.73 GPa/~835–880°C), and (3) a later, independent metamorphic stage M3 (~0.53–0.69 GPa/~793–801°C). M1 and M2 define together a clockwise P–T path. It reveals important information related to the Neoarchean collisional orogeny, and its later overprinted by an independent orogeny with subsequent exhumation and cooling. U–Pb zircon dating of two mafic granulites samples yielded protolith formation of the mafic granulites is prior to ~2.72 Ga, and the two metamorphic age peaks of ~2.72 (M1) and ~2.0 Ga (M3), which present the peak and post-peak cooling stages, respectively. The metamorphic evolution of HP mafic granulites in the Sand River area as reconstructed in this study suggests the Neoarchean collision of the Kaapvaal and Zimbabwe cratons and a discrete Paleoproterozoic orogenic overprint followed by post-orogenic exhumation and cooling.

Accessible silicate reservoirs on Earth (i.e., the depleted mantle and continental crust) are depleted in Nb relative to chondrites, as expressed by their subchondritic Nb/Ta ratios. Mixtures of continental crust and depleted mantle cannot produce chondritic Nb/Ta ratios; therefore, another geochemical reservoir with a superchondritic Nb/Ta ratio is necessary to balance the low Nb contents of the continental crust. We investigated alkaline igneous rocks with superchondritic Nb/Ta ratios (20.4-24.8). Their high Nb/Ta ratios were inherited from their lithospheric mantle source rather than being produced by magmatic differentiation. Geochemical data show that an enriched mantle domain with superchondritic Nb/Ta ratios can be produced by the interaction of subducted carbonate-rich sediment-derived melts with the lithospheric mantle, and the enriched lithospheric mantle is a potential superchondritic reservoir.