The Indosinian and Yanshanian orogenic movements are both important Mesozoic orogenies in eastern China. The resulted tectonic belts are neither products of the third stage of crustal evolution, as proposed by Chen Guoda, nor intra-continental (or intraplate) orogenic belts generated by intraplate dynamics, as argued by some scholars —rather, they are superposed orogenic belts formed on the pre-existing continental crust in eastern China due to Mesozoic Paleo-Pacific dynamic system. In the past, these orogenic belts were called the marginal Pacific epicontinental activation belts of eastern China. In the Mesozoic, under the effect of Paleo-Pacific dynamic system, the East Asia margin orogenic system formed along Northeast Russia-Sikhote Alin (Russia)-Japan-Ryukyu-Taiwan (China)-Palawan (Philippines) regions, while simultaneously the Mesozoic superposed orogenic system formed in the pre-existing continental crust in eastern China adjacent to the East Asia continental margin. The two orogenic systems, both driven by Mesozoic Paleo-Pacific dynamic system, developed synchronously to form the giant Mesozoic orogenic system in the Pacific tectonic domain in eastern Asia, radically changing the pre-Indosian tectonic framework of the area.
The combined application of mineral fertilizer and biochar significantly improves the passivation of heavy metal-contaminated soil, surpassing the effects of individual application. This study has reinforced the validation of their passivation competence as soil remediation agents by examining the multifaceted role of potassium-silicon-calcium mineral fertilizer combined with rice husk-based biochar generated at different pyrolysis temperatures. The soil leaching column experiment, conducted based on the adsorption experiments, has facilitated our scrutiny of the passivation impacts of cadmium (Cd) and lead (Pb) when introducing different proportions of mineral fertilizers and biochar into the soil. These results indicate that biochar's adsorption efficiency for Cd and Pb is significantly improved at escalated pyrolytic temperature conditions in a single solution. The biochar generated at 700°C (C700) renders adsorption effectiveness of approximately 84.24% for Cd and 99.74% for Pb. Biochar conspicuously registers superior adsorption efficiency towards Pb relative to Cd. The mineral fertilizer, which achieves an adsorption efficiency of 97.76% for Cd, is identified as the main adsorbent for Cd, although its competence is slightly lower compared to C700 for Pb adsorption. Within a complex solution, biochar and mineral fertilizer show reduced Cd and Pb adsorption levels compared to single solutions. There is a keen competition for adsorption surfaces witnessed between Cd and Pb, with Pb's distribution coefficient (Kd) notably outpacing that of Cd. The isothermal adsorption analyses depict that the mineral fertilizer follows the Langmuir model for Cd adsorption, while C700 conveys the Freundlich model for Pb adsorption. The soil leaching column experiment's results signify that the composite passivation agents significantly outperform the individual passivation agents in efficiency. The combined application of biochar and mineral fertilizer minimizes the cumulative leaching of Cd and Pb, with the optimal soil remedy proportion for heavy metal contamination being 7∶3. In practical application, mindful consideration should be accorded to the deployment ratios of different passivation agents.
The largest Tan-Lu active fault system in northeastern Asia, spans approximately 3500 km in length and varies in width from 10 km to 200 km. In 1668, an earthquake with a magnitude of 8.5 occurred in Tancheng, causing the loss of over 50000 lives. To constrain the timing and process of the Tan-Lu fault system on eastern Asian margin, this study presents the field mapping, thin section observation, geochronology, and microanalysis of Weiyuanpu-Yehe ductile shear zone (WYSZ) of the northern Tan-Lu fault system. Kinematic indicators and microstructures suggest a sense of sinistral strike-slip. The deformation temperature of the mylonite is mediate to high based on the quartz deformation, c-axis fabrics. The differential stress of the shear zone is 20‒40 MPa using quartz paleopiezometry. The dikes within the shear zone yielded zircon U-Pb ages of 165‒163 Ma. However, due to the ambiguous geological relationship between the dikes and shear zone, additional geochronology is warranted. Since the Mesozoic era, based on the exposure of mylonite and dikes, the upper crust has been extensively eroded, exposing the ductile shear zone. Moreover, the understanding of the geometry and process of pre-existing structures has fundamental implications for predicating the potential earthquakes for the Tan-Lu fault system.
To enhance the prediction accuracy of landslides in in Longyan City, China, this study developed a methodology for geologic hazard susceptibility assessment based on a coupled model composed of a Geographic Information System (GIS) with integrated spatial data, a frequency ratio (FR) model, and a random forest (RF) model (also referred to as the coupled FR-RF model). The coupled FR-RF model was constructed based on the analysis of nine influential factors, including distance from roads, normalized difference vegetation index (NDVI), and slope. The performance of the coupled FR-RF model was assessed using metrics such as Receiver Operating Characteristic (ROC) and Precision-Recall (PR) curves, yielding Area Under the Curve (AUC) values of 0.93 and 0.95, which indicate high predictive accuracy and reliability for geological hazard forecasting. Based on the model predictions, five susceptibility levels were determined in the study area, providing crucial spatial information for geologic hazard prevention and control. The contributions of various influential factors to landslide susceptibility were determined using SHapley Additive exPlanations (SHAP) analysis and the Gini index, enhancing the model interpretability and transparency. Additionally, this study discussed the limitations of the coupled FR-RF model and the prospects for its improvement using new technologies. This study provides an innovative method and theoretical support for geologic hazard prediction and management, holding promising prospects for application.
Addressing global warming, a common change today, requires achieving peak carbon dioxide emissions and carbon neutrality (also referred to as the dual carbon goals). Enhancing research on the carbon cycle is urgently needed as the foundation. Water, a key carrier in the carbon cycle, necessitates investigation into groundwater carbon pools’ contribution to atmospheric carbon sinks. This study assessed carbon stocks in the Yinchuan Basin's soil and groundwater carbon pools. Findings indicate the basin's surface soils contain approximately 24.16 Tg of organic carbon and a total of 60.01 Tg of carbon. In contrast, the basin’ s groundwater holds around 4.90 Tg of carbon, roughly one-fifth of the organic carbon in surface soils. Thus, groundwater and soil carbon pools possess comparable carbon stocks, underscoring the importance of the groundwater carbon pool. Studies on terrestrial carbon balance should incorporate groundwater carbon pools, which deserve increased focus. Evaluating groundwater carbon pools’ contributions is vital for achieving the dual carbon goals.
Several conjugate components represent the aquatic ecosystem of Lake Baikal: Baikal water (surface and deep water), groundwater from boreholes, water of numerous Baikal tributaries, cold and hot mineral springs around Lake Baikal, and the Angara River, the only runoff reflecting all this aquatic diversity. River waters in the Baikal region are known to be deficient in some vital elements, including fluorine. This article discusses the features of the fluorine distribution in the water from the conjugate components of the Baikal ecosystem. Fluorine ion concentrations in the water of the Baikal ecosystem was determined using the potentiometric method. The study represents the monitoring that was carried out between 1997 and 2022 years. We determine likely causes of high and low fluorine concentrations in the water from different components, propose and substantiate the fluorine sources, geological and geochemical model of its influx and distribution features in the water of the Baikal ecosystem.
To assess the effect of mining activity on heavy metal pollution and associated health risks in tin mining regions, water and soil sampling was conducted near a tin mining site in Hunan Province. The content and distribution of heavy metals were determined. Pollution, ecological risks, and potential health hazards were evaluated using the ground accumulation index, potential ecological risk index, and health risk assessment models, respectively. The results indicated elevated levels of heavy metals in water and soil samples compared to acceptable background values. Ground accumulation index assessment revealed extreme pollution of soil with As and Cd and moderate pollution with Cu, Pb, and Zn. Cr and Hg were categorized as non-pollutants. Water samples exhibited extreme pollution levels of Hg, Cr, Cd, and As; moderate pollution levels of Pb; and moderate to high pollution levels of Cu and Zn. The tin mining area demonstrated a significantly high level of potential ecological risk, where As and Cd were the primary risk elements in soil, whereas Cr, Cd, and As contributed predominantly to water ecological risk. The human health risk assessment highlighted As, Cd, Cr, Hg, Pb, and Cu in water and As and Pb in soil as the principal non-carcinogenic factors. The primary carcinogenic factors were As, Cr, and Cd in water and As in soil, with As posing the greatest risk for non-carcinogenic and carcinogenic effects. Furthermore, oral intake was the primary exposure route, with children being particularly vulnerable to the adverse effects of heavy metal pollution.
The Triassic Xujiahe Formation in the slope zone of the Sichuan foreland basin is a new field of continental tight gas exploration in recent years. The fourth member of the Xujiahe Formation (Xu4 Member), the major interval in the Jianyang Block of the Tianfu gas field in the basin, is characterized by considerable buried depth, tight reservoirs, and strong heterogeneity. By using cast thin section, X-ray diffraction (XRD), scanning electron microscopy (SEM), fluid inclusion thermometry, and core analysis, the reservoir rock types, dominant diageneses, diagenetic history, and controls on high-graded reservoirs were investigated. It is found that the Xu4 Member in Jianyang mainly consists of lithic feldspar sandstones and feldspar lithic sandstones, followed by lithic quartz sandstones. High-energy hydrodynamic conditions in the microfacies of underwater distributary channels and mouth bars are beneficial to the preservation of primary pores and the occurrence of secondary pores, and there are no significant differences in petrophysical properties between these two microfacies. Compaction and calcareous cementation are the dominant controls on reservoir porosity decrease in the Xujiahe Formation; corrosion is the major contributor to porosity increase by generating secondary dissolved pores, e.g. intragranular dissolved pores and intergranular dissolved pores, as major reservoir space in the study area. Fracture zones around the faults inside the Xujiahe Formation (fourth−order faults) are favorable for proximal tight gas accumulation, preservation, and production. The research findings have been successfully applied to explore the Xujiahe Formation in the slope zone of the Sichuan foreland basin. They can be referential for other similar tight sandstone gas accumulations.
The black shales of Wufeng and Longmaxi Formation (Late Ordovician-Early Silurian period) in Sichuan Basin are the main strata for marine shale gas exploration, which have a yearly shale gas production of 228×108 m3 and cumulative shale gas production of 919×108 m3. According to the lithological and biological features, filling sequences, sedimentary structures and lab analysis, the authors divided the Wufeng /Guanyinqiao and Longmaxi Formations into shore, tidal flat, shoal, shallow water shelf and deep water shelf facies, and confirmed that a shallow water deposition between the two sets of shales. Although both Formations contain similar shales, their formation mechanisms differ. During the deposition of Wufeng shale, influenced by the Caledonian Movement, the Central Sichuan and Guizhou Uplifts led to the transformation of the Sichuan Basin into a back-bulge basin. Coinstantaneous volcanic activity provided significant nutrients, contributing to the deposition of Wufeng Formation black shales. In contrast, during the deposition of Longmaxi shale, collisions caused basement subsidence, melting glaciers raised sea levels, and renewed volcanic activity provided additional nutrients, leading to Longmaxi Formation black shale accumulation. Considering the basic sedimentary geology and shale gas characteristics, areas such as Suijiang-Leibo-Daguan, Luzhou-Zigong, Weirong-Yongchuan, and Nanchuan-Dingshan are identified as key prospects for future shale gas exploration in the Wufeng-Longmaxi Formations.
Benthic bivalves, the most widely distributed mollusks since the Mesozoic era, often inhabited environments where their fossilized remains are found adjacent to or intermingled with organic-rich shale. Recent Jurassic shale oil exploration in the Sichuan Basin has revealed that bioclastic layers, composed of abundant fossil bivalves and closely associated with shales and, exhibit significant hydrocarbon potentials. However, the microscopic structures of these bivalve fossils and their role in hydrocarbon storage and migration remain poorly understood. In this study, we characterized the microporosity of bivalve shells within the Middle-Lower Jurassic bioclastic shale in the northeastern Sichuan Basin using a combination of 2D imaging (thin section, SEM), 3D reconstruction (FIB-SEM), and permeability simulation. The micropores within the shell fossils range from 100 to 1000 nm in radius and are uniformly distributed in a grid-like pattern within the shell interior, where they host liquid hydrocarbons. The bioclastic carbonate layers exhibit an overall porosity of approximately 0.8%. Comparative analysis with extant bivalve shells suggests that these micropores represent residual pores from the nacreous brick wall structure. Due to the regular orientation of the shells and their microporous nacres, permeability coefficients along the long bivalve fossil axes are three to five times higher than those along the short axes. These residual micropores within the bioclastic fossil shells have a positive influence on both the storage and migration of shale oil and gas, making bioclastic fossil-bearing shalespromising sweet spots for shale oil and gas exploration in similar sedimentary environments.
The Central Asian Orogenic Belt (CAOB) is one of the largest and best preserved accretionary type orogenic belts in the world. Due to its complex tectonic history, the timing and location of the final closure of the Paleo-Asian Ocean and its tectonic evolution have been hotly discussed. To determine the petrogenesis and tectonic characteristics of the poorly exposed Triassic volcanic-intrusive complex on the northern margin of the eastern North China Craton, the authors conducted a study of zircon Lu-Hf isotopes, integrated with zircon U-Pb dating and whole-rock geochemistry. Zircons from eight representative volcanic and intrusive samples yielded concordant U-Pb ages of 251-245 Ma. The volcanic and intrusive rocks are all characterized by enrichments in large ion lithophile elements and depletions in high field strength elements, and they have features similar to those of highly fractionated I-type granites. The εHf(t) values for the volcanic and intrusive rocks, respectively, range from -1.69 to +3.75 (mean=+1.22) and -2.17 to +3.15 (mean=+0.38), with two-stage model ages of 1035-1345 Ma (mean=1196 Ma) and 1073-1401 Ma (mean=1250 Ma). The Hf isotopic features indicate that these rocks were formed by partial melting of young crustal material that was newly accreted from the depleted mantle, together with a degree of contamination by other crustal material. The volcanic-intrusive complex was related to an active continental margin in a volcanic arc and syn-collisional setting, indicating that the Paleo-Asian Ocean was closed after the Middle Triassic (245 Ma) along the northern margin of the North China Craton. This provides a constraint on the timing of the change in tectonic setting in this area from compression to extension. The results enhance our understanding of the evolution of the Paleo-Asian Ocean.
The Jurassic tight sandstone oil and gas exploration and development in the eastern Yangxia Sag is a new field. To elucidate the origin, accumulation process and potential of tight oil and gas, the authors have conducted comprehensive analyses employing methodologies encompassing source rocks, oil geochemistry, and fluid inclusions. The results show that the abundance of organic matter of Jurassic source rocks is high, and the type of organic matter is of II-III and in mature evolution stage. The main source rocks of oil and gas are Huangshanjie Formation and Jurassic coal-bearing source rocks. Ahe Formation developed two stages of hydrocarbon charging, and the period is later than the reservoir densification time. Yangxia Formation oil charged before the reservoir densified, and the late gas charged after the reservoir densified. Hydrocarbon generation intensity of Jurassic source rocks has reached the basic conditions for the formation of tight gas reservoirs. Controlled by the difference of source rocks distribution and accumulation process, tight sandstone oil and gas accumulation conditions are better in the depression direction than in the southeast margin area. This study is of practical importance for expanding the exploration field and selecting favorable areas in the eastern Yangxia sag.
Zirconium, prized for its exceptional corrosion resistance, high melting point, and unique nuclear properties, plays a critical role in multiple industrial sectors globally. Zirconium deposits are categorized into endogenetic and exogenetic types in China. Endogenetic deposits - including alkaline rock-, alkaline granite-, and pegmatite-type mineralizations - predominantly occur along the Tarim Craton's northern margin, the North China Craton, the southern Greater Khingan metallogenic belt, and the Yangtze Craton's western margin. Exogenetic deposits, comprising clastic sedimentary, weathering crust, and fragmentation types, are concentrated in South China's coastal zones. Endogenetic mineralization formed during Permian-Cretaceous magmatic-hydrothermal events linked to evolved alkaline granitic systems, while exogenetic deposits developed in Quaternary periods through weathering of zirconium-rich protoliths. However, economic extraction of endogenetic deposits remains constrained by rare earth element (REE) associations and radioactive complexities. Currently, China's most economically significant reserves derive from clastic sedimentary systems, particularly coastal placer deposits. This study systematically synthesizes the spatial distribution and metallogenic mechanisms of Chinese zirconium deposits, offering strategic insights for resource exploration and sustainable utilization.
The giant Upper Yangtze Pb-Zn metallogenic province, also known as the Sichuan-Yunnan-Guizhou (SYG) Pb-Zn province hosting >500 carbonate-hosted epigenetic Pb-Zn deposits that contain >20 Mt Pb + Zn base metal reserves. The giant Maoping Pb-Zn deposit is the second largest deposit in this province and owns >5 Mt Pb + Zn metal reserves with ore grades of 12 wt.%-30 wt.% Pb + Zn. Such large tonnages and high grades make it among the top 100 similar mineral deposits in the world. The ore bodies are predominantly located within the strata of the Upper Devonian (Zaige Formation) and Lower (Baizuo Formation)-Upper (Weining Formation) Carboniferous. The principal ore minerals consist of galena (Gn), sphalerite (Sp), and pyrite (Py), while the primary gangue minerals include dolomite (Dol), calcite (Cal), and quartz (Qtz). Three mineralization stages of carbonate minerals have been identified: (1) pre-sulfide stage 1, (2) syn-sulfide stage 2, and (3) post-sulfide stage 3. Trace elements and C-O-Sr isotopes of three stages’ carbonate minerals, together with S-Pb isotopes of sulfides, revealing that the metamorphic basement rocks played the role of the metal source during the early stage of Pb-Zn mineralization, whereas the metal contribution of the sedimentary wall rocks found to be more prominent during the late stage of Pb-Zn mineralization. In addition, the dissolution of marine carbonate rocks and CO2 degassing may have also played an important role in the formation of the Maoping deposit. Furthermore, syn-sulfide stage 2 calcite has a U-Pb age of 214 ± 20 Ma obtained by LA-ICPMS in-situ analyses, suggesting that the hydrothermal mineralization occurred during the Triassic. Our study proposes a new coupled metallogenic model of fluid-structure-lithology assemblage and provides new insights about the formation and evolution of the Maoping deposit with significant implication for understanding and exploration of similar Pb-Zn deposits worldwide.