Brittle faults record tectonic deformations of the Earth's surface and interior. Constraining their active timing is crucial for reconstructing geotectonic evolution, constraining seismicity models, and assessing seismic hazards. However, the low temperature and pressure conditions of brittle fractures and the fast strain rate of rocks pose significant challenges for dating brittle faults. Recently, in situ U-Pb dating of calcite has emerged as an important method due to its high resolution, low detection limits and short detection periods. This method requires identifying calcite characteristics and determining its genetic types in the field. Here, we summarise the main methods for constraining the timing of brittle fracture activity, the basic principles of in situ U-Pb calcite dating, and the field types and petrographic characteristics of syntectonic calcite. We also present case studies of in situ U-Pb dating of calcite in major fault zones as reference points. This study provides a overview of in situ U-Pb calcite dating techniques, highlighting the critical role of field and petrographic characteristics in accurately dating brittle fault activity and demonstrating their application in constraining the timing of tectonic events, which offers valuable insights for understanding tectonic evolution and assessing seismic hazards.

As a significant component of fossil plants, fossil wood is a key proxy for reconstructing ancient floras and terrestrial palaeoclimates. Although palaeoxylology has advanced markedly over the past two decades, Jurassic wood records from the Qinghai–Xizang Plateau remain sparse, and detailed anatomical studies are lacking. Here, we describe an exceptionally preserved fossil wood specimen from the Middle Jurassic Xiali Formation in Shuanghu County, Qiangtang terrane, Xizang (Tibet), China. This fossil exhibits the typical Shimakuroxylon Philippe, Boura, Oh et Pons anatomy, that is, shimakurean radial tracheid pitting and araucarioid cross-field pitting, thereby expanding the known diversity of Middle Jurassic fossil wood in Qinghai–Xizang Plateau, refining the vegetational composition of the Xiali Formation, and providing new palaeobiogeographic evidence for understanding the distribution of Shimakuroxylon and floristic connections across eastern Asia during the Jurassic.

The Ngwi area, along the central Cameroon shear zone (CCSZ), features two-mica granite and hornblende–biotite granite intrusive into paragneisses and amphibolites. This work provides insights into the kinematic evolution and emplacement mechanism of the Ngwi pluton, highlighting the complex tectonic history of the region, with implications for understanding the Pan-African tectonics. Structural data analysis reveals: (i) D₁ flattening (∼622–613 Ma) defined by NW- to WNW-striking S₁ foliation in paragneisses; (ii) D₂ sinistral shearing (∼613–590 Ma) with NE–SW to NNE–SSW and NW–SE rotational evolution, developed S₂ foliation in host-rocks and S_m2 magmatic fabric in pluton; (iii) D₃ dextral shearing (∼585–540 Ma) with NE–SW to ENE–WSW and NW–SE rotational evolution, induced a mylonitic fabric towards the pluton margins. Microstructural and kinematic data analysis suggest the Ngwi pluton emplaced into a high-strain sheared crustal domain during the D₂–D₃ phases, with a continuous evolution from magmatic to solid-state deformation (i.e., 700°C ≤ T ≤ 300°C) under high-grade amphibolite to low-grade greenschist conditions. The pluton's emplacement likely occurred within tension gashes opened in the paragneiss host rocks under a sinistral transpressive tectonics along the CCSZ, consistent with similar shear zones in Chad, Central African Republic and northeastern Brazil.

The northern margin of the North China Block preserves multiple regional unconformities that archive accretion-subduction processes within the Central Asian Orogenic Belt. To constrain their timing and origin, we conducted integrated petrographic and geochronologic analyses on two newly identified unconformity sections in the Chifeng area. Our findings reveal two distinct tectonic episodes: (1) At the Shidafen section, the Xibiehe gravelly sandstone (432 ± 2 Ma, tuff) unconformably overlies granitic gneiss basement (2556 ± 5 Ma) of the North China Craton. Paleogeographic evidence excludes Paleoproterozoic–Ordovician hiatuses, instead linking this unconformity to the Silurian collision between the Bainaimiao arc and North China Craton. (2) Yangshuwan section records a Carboniferous unconformity where the Qingfengshan gravelly sandstone (≤327 Ma, detrital zircon) disconformably overlies the Chaotugou tuff (355 ± 2 Ma). This unconformity (355–327 Ma) correlates with Carboniferous unconformities on the eastern segment of the northern North China Block, representing a regional response to the transition from retreating to advancing subduction of the Paleo-Asian Ocean slab. These two regional unconformities document Silurian arc–continent collision and Carboniferous subduction-mode switch in the Central Asian Orogenic Belt, providing critical insights into accretion-to-subduction processes in accretionary orogens.

The final closure time of the Paleo-Asian Ocean (PAO) is key to understanding the evolution of the Central Asian Orogenic Belt, and it has remained highly controversial for a long time. Here, we conduct structural investigations and zircon U-Pb and ⁴⁰Ar/³⁹Ar dating on the Hulan Metamorphic Complex (HMC) in central Jilin Province to determine the final closure time and direction of the eastern PAO. The metamorphic complexes are composed mainly of schists, marbles, gneisses, quartzites, metamorphosed plutons and dikes, which were involved in a nearly NEE-directed ductile thrusting and deformed to mylonites at a temperature of 550–450°C. Protolith ages of 262–252 Ma from three metamorphosed igneous rocks, emplacement ages of 229–221 Ma from two unmetamorphosed igneous intrusions and metamorphic ages of 243–238 Ma from three gneisses are yielded based on the zircon U-Pb dating. Three muscovite samples and one biotite sample yield ⁴⁰Ar/³⁹Ar plateau ages of 230–228 and 222 Ma, respectively. By integrating the dating results from this study and previous studies, the timing of metamorphism of the HMC is constrained to an interval between 248 and 229 Ma, and its peak metamorphism is reached at 243–238 Ma (Middle Triassic). During the period of 230–220 Ma, the HMC has already been uplifted to a geothermal level of 350–300°C. We consider that the metamorphism and shortening ductile deformation of the HMC is related to the final closure of the eastern PAO along the eastern Solonker Suture in an NEE–SWW closure direction. The Middle Triassic closure time of the eastern segment suggests a west-to-east scissor-style closure model for the PAO.

The prolonged subduction history of the Palaeo-Asian Ocean remains pivotal to reconstructing the accretion history of the Central Asian Orogenic Belt, yet its duration and tectonic evolution are debated due to ambiguous ophiolite records. Here, we identified Early Cambrian and Early Permian gabbros in the Jijitaizi ophiolite of the Beishan orogen, obtaining zircon U-Pb ages of 514 ± 3, 292 ± 3 and 289 ± 2 Ma. Early Cambrian gabbros exhibit back-arc basin affinities: N-MORB-like REE patterns (∑REE = 22.55–30.11 ppm) with subduction-fluid imprints (Th/Ta > 1 and negative Nb anomalies), indicating derivation from depleted MORB mantle metasomatised by slab fluids. Early Permian gabbros show ultra-depleted forearc cumulate signatures: extreme REE depletion (∑REE = 3.48–4.81 ppm), high ε_Nd(t) (+10.49 to +14.07), low Ti/V (4.62–6.08), high Ca^# and anorthitic plagioclase (An_80–93). The regional data collectively constrain the Jijitaizi–Xiaohuangshan and Hongliuhe–Xichangjing ophiolites as a unified back-arc system in the Early Cambrian, also providing evidence for long-term subduction from Early Cambrian to Early Permian.

The main lithologies of the volcanic rocks in the Erlanghe Formation of the southern Zhangguangcai Range are andesite and rhyolite. Zircon laser ablation multi-collector inductively coupled plasma mass spectrometer (LA-MC-ICP–MS) isotopic dating yields weighted average ages of 190 ± 2.8 and 187 ± 1.7 Ma, indicating their formation during the Early Jurassic. The Erlanghe Formation volcanic rocks exhibit geochemical characteristics, including enrichment in large-ion lithophile elements (LILEs) and depletion in high-field-strength elements (HFSEs). In situ zircon Hf isotopic results show that andesite and rhyolite samples have consistent Hf isotopic compositions, with high positive ε_Hf(t) values (+6.5 to +9.6, +8.5 to +11.8) and similar two-stage model ages (T_DM2 = 619−818 and 477−684 Ma). The intermediate volcanic rocks are derived from a depleted mantle source and formed by partial melting of the thickened lower crust—a process induced by the underplating of depleted mantle-derived magmas. In contrast, the felsic volcanic rocks form via partial melting of crustal materials. The discovery of the 190−187 Ma calc-alkaline volcanic assemblage reveals a compositional polarity of volcanic rocks along the transect from the continental margin to the continental interior. This finding provides reliable constraints on the initiation timing of Paleo-Pacific Plate subduction within the tectonic system of the southern Zhangguangcai Range.

Siderite concretions formed in different depositional settings exhibit distinct mineral paragenesis and can offer important clues to paleoenvironmental conditions. In this study, we conducted PLM, XRD, XRF and SEM–EDS analyses on the nucleus, mantle and wallrock of concretions found at Longtan Formation in the Chaohu area (Eastern China), with the aim of establishing a formation model for the concretions. The concretions are composed of a black nucleus, a grey mantle, white stockwork and a brown annular vein. The nucleus is primarily composed of apatite and the mantle is siderite-rich. The stockwork comprises mainly ankerite and the annular vein consists primarily of pyrite. The apatite nucleus is formed through the combination of phosphate ions with calcium ions. The siderite mantle developed subsequently, resulting from the association of carbonate ions with ferrous ions. The ankerite stockwork is probably related to the increased alkalinity of the pore waters induced by the oxidation of organic matter. The pyrite annular vein is interpreted as a product of sulphate-reduction zones. Comparative analysis indicates that the siderite concretions were mainly formed around bivalve fossils in the suboxic zone within sediments, while the sediments of the Longtan Formation (at Guibeitan, Chaohu) were formed under oxic conditions in a marginal marine–terrestrial transitional environment.

The Galinge Fe-Co deposit in the East Kunlun orogenic belt is a large skarn iron deposit associated with critical metal cobalt. This study elucidates its two-period magmatism and mineralisation and their genetic links on the basis of petrography, geochronology and geochemistry. The early granodiorite (236.1 ± 1.4 Ma) is associated with the early magnetite-sulphide period (major metallogenic event), whereas later intermediate–mafic dikes (227.1 ± 1.7 Ma) correspond to the late veined magnetite period. Petro-geochemical results show that both intrusions are metaluminous I-type granites with similar geochemical signatures (parallel REE patterns, high Mg^#, LILE enrichment, HFSE depletion), suggesting derivation from partial melting of the lower crust with mantle and a postcollisional setting. H-O-S isotopes show that ore-forming fluid and ore materials during the major metallogenic period were predominantly from a deep magmatic source. EPMA and LA-ICP-MS analyses classify two-period magnetite as skarn-type magnetite. Early magnetite formed at higher temperatures with Co incorporated via isomorphism, while late magnetite crystallised under more reduced conditions with Co mainly in sulphide inclusions. Co/Ni ratios for magnetite (< 1) indicate deep magmatic origins. Collectively, temporal–spatial correlations, shared deep magmatic provenance and geochemical coherence demonstrate that both magnetite formations are related to two periods of magmatic intrusion activity.

Buried-hill reservoirs represent crucial deep hydrocarbon targets. However, their characteristics and genesis in a compressional–extensional tectonic setting remain poorly constrained because of complex interplay among tectonic compression, weathering and extensional faulting. The Baiyun Sag in the northern South China Sea (SCS) underwent a Meso–Cenozoic transition from compression to extension. Integrating petrological observations, wireline logging and 3D seismic datasets, this study confirms that its basement is predominantly composed of Yanshanian intermediate–acid intrusive rocks. Three buried-hill reservoir types were identified: Type I (gradually changing reservoir), formed by prolonged weathering following Late Mesozoic compression is widely distributed at the tops of buried hills and consists of a weathering crust and an inner fractured zone. Type II (interbedded reservoir), featuring alternating weathered and tight zones (TZs), occurs on the flanks of buried hills. It formed through weathering along reactivated faults during late Mesozoic and Cenozoic extension. Type III (transitional reservoir), located on the tops of buried hills proximal to boundary faults, comprises a weathering crust and multiple alternating weathered and TZs. These reservoirs formed through differential tectonism and weathering responses to late Mesozoic compression from Paleo-Pacific Plate subduction and Cenozoic extension from SCS opening. Differential tectonism primarily controls buried-hill reservoir types in such settings.

The Darriwilian Age, marked by the Great Ordovician Biodiversification Event (GOBE), represents a key interval of global environmental change and widespread organic-rich sedimentation. However, the nature of contemporaneous climatic–oceanographic conditions and the mechanisms governing organic matter (OM) enrichment in South China remain poorly constrained. Here, we present an integrated petrological and geochemical investigation of organic-rich successions from the Ningkuo–Hulo formations in the AY1 core, Lower Yangtze region. Our results identify two distinct phases of OM accumulation. Phase I is characterized by relatively low total organic carbon (TOC) contents and developed under warm, humid climatic conditions, intensified chemical weathering, enhanced terrigenous input, weak upwelling and predominantly suboxic to oxic bottom waters, collectively limiting OM preservation. In contrast, Phase II records markedly higher TOC contents and corresponds to a transition toward cooler and drier climatic conditions, strengthened upwelling and the establishment of anoxic–euxinic bottom waters. These changes promoted nutrient recycling, enhanced primary productivity, reduced sediment dilution and more efficient OM preservation. This study systematically reveals two successive stages of climatic–oceanic evolution during the Darriwilian Age, providing new insights into the coupled evolution of palaeoclimate and palaeomarine processes in regulating organic carbon burial in South China.

The Jiamusi Block in Northeast Asia provides a critical window for investigating the subduction of the Pacific Plate beneath the Western Pacific Orogenic Belt during the Mesozoic and Cenozoic. To constrain the structure and evolution of the lithosphere–asthenosphere system, this study integrates regional gravity and magnetic surveys with two NW–SE-trending magnetotelluric (MT) profiles of lengths 250 and 150 km across the block. Two-dimensional nonlinear conjugate gradient inversion derived the electrical structure to a depth of 200 km. The inversion models reveal distinct crustal and mantle low-resistivity bodies (labelled C1–C8) that spatially correlate with abrupt positive gravity and aeromagnetic anomalies. These low-resistivity features are interpreted as signatures of mantle-derived fluids and partial melts, indicative of asthenospheric upwelling and lithospheric thinning. We attribute these processes to the westward subduction of the Pacific Plate, which induced significant crust–mantle interaction and fluid metasomatism. Furthermore, a comparative analysis reveals that the lithospheric thickness of the Jiamusi Block (70–95 km) is intermediate between that of the Songnen Block (65–80 km) and the Xing'an Block (100–120 km). This variation suggests that lithospheric thickness in the region is primarily controlled by the geometry of the subducting slab's mantle wedge and the intensity of the associated fluid metasomatism.