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Karst regions are characterized by unique geological formations that pose challenges to soil fertility and plant nutrition. In this study, we investigated the distribution and interactions of selenium (Se) in soils of Zheng'an County, a representative karst region in subtropical China. The results showed that the Se enrichment in the soils of Zheng'an County was high, with total contents ranging from 0.49 to 3.87 mg/kg and an average of 1.22 mg/kg, making the area Se-rich. Despite the abundance of Se, the effective percentage of Se uptake by plants was relatively low due to the generally moderately acidic nature of the soils in the region (pH: 5.98–6.60), which encourages the conversion of the available Se into forms that are not readily accessible. In addition, the high organic matter (OM) content (21.92–127.66 g/kg) promoted Se retention by interacting with Ca2+ in carbonate rocks. In addition, the clay content (50.73% to 76.19%) enhanced Se adsorption and limited Se availability. In conclusion, this study provides a basis for soil management and ecological restoration strategies in karst landscapes, highlights new insights into the dynamics of Se, and calls for further research to elucidate the Se availability mechanism and improve the efficiency of Se uptake by plants. Meanwhile, this study provides the first systematic study of Se transport and transformation, as well as Se-enriched Gastrodia elata in karst regions, and provides a preliminary understanding of the geochemical behavior of Se in karst regions. [ABSTRACT FROM AUTHOR]

The central Sichuan Basin, located in western China, holds great significance in terms of hydrocarbon production, especially in relation to complex carbonate reservoirs, notably the Qixia Formation of the Middle Permian epoch. However, the comprehensive evaluation of this geological formation presents considerable challenges due to complex lithology, limited availability of reservoir property data at various scales, inadequacies in data integration, and the absence of a reliable reservoir ranking system for development decision making. Previous studies primarily relying on conventional data at the reservoir level, such as well logs and geological information, have proven insufficient in accurately characterizing the reservoir. This is especially evident without precise lithological information and detailed knowledge of microscale properties, which are crucial for effective reservoir evaluation. To address these challenges, this study integrates advanced technologies like X-ray diffraction, micro-CT and scanning electron microscope (SEM) techniques in digital drill cutting analysis at the microscale. A novel scoring system has been developed using a prominent component analysis (PCA) approach and an expert scoring system, which incorporates existing conventional well log data and digital cutting analysis. This scoring system has been validated using actual production data, thus establishing a robust evaluation methodology for assessing the exploration potential and optimizing development strategies for carbonate gas reservoirs in the Qixia Formation. The innovative approach, which incorporates parameters at both micro- and macroscales, holds promising potential in facilitating future exploration and development efforts. [ABSTRACT FROM AUTHOR]

The three-dimensional (3D) visualization of geological structures and the dynamic simulation of geological evolutionary processes are helpful when studying the formation of renowned geological features. However, most of the existing 3D modeling software is based on raster models, which are unable to generate smooth geological boundaries. This work proposes a 3D temporally dynamic (i.e., four-dimensional (4D)) modeling method using parametric functions and vector data structures, which can dynamically build geological evolutionary vector models of well-known geological features. First, we extract the typical features of different kinds of geological formations and represent them using different parameters. Next, we select appropriate parametric functions to simulate these geological formations according to the characteristics of the individual structures. Then, we design and develop 4D vector modeling software to simulate the geological evolution of these features. Finally, we simulate an area with complex geological structures and select six real-world geological features, such as the Piqiang Fault in China and the Eye of the Sahara in the Sahara Desert, as case studies. The modeling results show that a regional geological evolutionary model that contains smooth boundaries can be established within minutes using this method. This work will support studies into the formation of renowned geological features in terms of providing visualizations and will make the representation of geological processes more intuitive in 3D. [ABSTRACT FROM AUTHOR]

Long-runout landslides occur frequently in the sandstone and mudstone mountainous areas in southwestern China under heavy rainfall conditions. This has been a key issue in the field of disaster prevention and reduction. Considering the Niuerwan landslide in Wulong, Chongqing, on 13 July 2020, as an example, we employed technical methodologies, including unmanned aerial vehicle (UAV) images, field investigation, geological condition analysis (including geomorphology and topography, stratigraphic structure and formation lithology, etc.), interferometric synthetic aperture radar (InSAR) monitoring and Particle Flow Code 3D (PFC3D) simulations to study failure mechanism and a long-runout motion model of flow-like landslides induced by the heavy rainfall. The results showed that (1) the large differences between the upper and lower strata are the root cause of the instability and long-runout fluidization movement; (2) heavy rainfall is the key driving factor of slope instability and deep-seated landslides, leading to long-distance movement of the upper saturated residual soil; (3) the long-runout fluidization model of bedding landslides is mainly divided into the overall sliding in the lower layer, the mixing of coarse and fine particles in the middle layer, and saturation fluidization in the upper layer; and (4) the long-runout fluidization process of bedding landslides is composed of three stages: overall instability, mixed acceleration, and fluidization accumulation. In view of these findings, in the risk evaluation and prediction of long-runout fluidization landslides in sandstone and mudstone mountainous areas, this particular disaster model can be used to provide quantitative references for disaster prevention and mitigation. [ABSTRACT FROM AUTHOR]

Conduction between the unique geological formation karst collapse pillar (KCP) and the fractures caused by mining in the coal seam floor can lead to catastrophic water inrush disasters in many coalmines in Northern China. It is widely recognized that seepage mutation induced by the migration/loss of KCP fillings (highly broken rocks filling the fractured rocks) happens during occurrence of the KCP-related water inrush. However, roles of fluid path (mining-induced fracture) scale and KCP filling porosity in seepage mutation evolution remain unclear. Here, we conducted seepage tests on natural KCP fillings containing rock particles of different sizes. The filling specimens were deformed to different porosities from 14 to 26% through axial compression, and small to large fluid paths were simulated by seepage plates with distinct pore sizes from 2.5 to 12.5 mm. We found that seepage mutation occurs with significant permeability enhancement by 2 orders of magnitude under a pore diameter of 12.5 mm and a specimen porosity of 26%. There is a strong linear relationship between specimen permeability and Reynolds number (Re) over seepage mutation. The mutation is caused by the sudden collapse of the specimen skeleton and subsequent quick outflow of the particles. Therefore, it is inferred that the KCP-related water inrush is more likely to happen when highly porous KCP fillings are present and mining-induced fractures are well developed. [ABSTRACT FROM AUTHOR]

Lithological mapping is a crucial tool for exploring minerals, reconstructing geological formations, and interpreting geological evolution. The study aimed to investigate the application of the back propagation neural network (BPNN) and particle swarm optimization (PSO) algorithm in lithological mapping. The study area is the Beiliutumiao map-sheet (No. K49E011021) in Inner Mongolia, China. This area was divided into two parts, with the left side used for training and the right side used for validation. Fifteen geological relevant factors, including geochemistry (1:200,000-scale) and geophysics (1:50,000-scale), were used as predictor variables. Taking one lithology as an example, the lithological binary mapping method was introduced in detail, and then the complete lithology was mapped. The model was compared with commonly used spatial data mining methods using the E-measure, S-measure, and Weighted F-measure values. In diorite testing, the accuracy and kappa of the optimized model were 92.11% and 0.81, respectively. The validation results showed that our method outperformed the traditional BPNN and weights-of-evidence approaches. In the extension of the complete lithological mapping, the accuracy, recall, and F1-score were 82.66%, 74.54%, and 0.76, respectively. Thus, the proposed method is useful for predicting the distribution of one lithology and completing the whole lithological mapping at a fine scale. In addition, the trained network can be extended to an adjacent area with similar lithological features. [ABSTRACT FROM AUTHOR]

Thermo‐hydro‐mechanical‐chemical (THMC) interactions are prevalent during CO2 geological sequestration (CGS). In this study, a sequential coupling THMC numerical simulation program was constructed, which can be used to explore the following issues of CGS: fluid and heat flow, solute transport; stresses, displacements and rock failures related to geo‐mechanical effects; equilibrium and kinetic chemical reactions; chemical damage to mechanical properties of the rock. Then, the coupling program was applied to the Ordos CGS Project to study the formation response under the multi‐field interaction caused by CO2 injection. The simulation results show that the mechanical process dominates the short CO2 injection period. Specifically, the formation's permeability near the injection well increases by 43%, due to the reduction of effective stress, which significantly promotes the lateral migration of CO2. When the injection rate exceeds 0.15 million tons per year, the cohesion of the reservoir rock is not enough to resist the shear force inside the rock and rock failure may occur. During the subsequent long‐term sequestration period (200 years), the influence of mineral reactions gradually increases. Due to calcite dissolution, the shear modulus of caprock is predicted to decrease by 7.6%, which will to some extent increase the risk of rock failure. [ABSTRACT FROM AUTHOR]

CO 2 sequestration is an effective technology for reducing greenhouse gas effect. To ensure the safety, assessment of well applicability should be conducted before CO 2 sequestration. However, current studies mainly focus on identifying which barrier has the highest risk of leakage rather than selecting a target well for injection in specific geological formation. To further investigate, this paper proposes well applicability assessment method combining reservoir and wellbore properties together for CO 2 sequestration. A novel assessment system combing Fuzzy comprehensive evaluation and Analytic hierarchy process has been established. Twenty-nine indexes subjected to seven categories (i.e., formation, well, cement sheath, cementing quality, casing, tubing, and wellhead properties) are taken into consideration. The weighting factors of these seven categories are 0.0673, 0.0552, 0.096, 0.1537, 0.2283, 0.2637 and 0.1369, respectively. Tubing and casing properties have the greatest influence on safety injection. Furthermore, the proposed system has been applied to S gas reservoir, China. Results show that Wells #P1 and #P2 are suitable for injection. Since more comprehensive indicators are considered comparing with previous studies, the results are more accuracy and objective. The findings of this paper could help efficiently and effectively evaluating well applicability for CO 2 sequestration and reducing the risk of CO 2 leakage. [ABSTRACT FROM AUTHOR]

The three-dimensional (3D) visualization of geological structures and the dynamic simulation of geologic evolutionary processes are helpful when studying the formation of renowned geologic features. However, most of the existing 3D modelling software is based on raster models, which is unable to generate smooth geologic boundaries. This work proposes a three-dimensional and temporally dynamic (i.e., 4D) modelling method using parametric functions and vector data structures, which can dynamically build geologic evolutionary vector models of well-known geologic features. First, we extract the typical features of different kinds of geologic formations and represent them using different parameters. Next, appropriate parametric functions are selected to simulate these geologic formations according to the characteristics of the individual structures. Then, we designed and developed a 4D vector modelling software to simulate the geologic evolution of these features. Finally, we simulated an area with complex geologic structures and selected six real-world geologic features, such as the Piqiang Fault in China and the Eye of the Sahara in the Sahara Desert, as case studies. The modelling results show that a regional geologic evolutionary model that contains smooth boundaries can be established quickly using this method. This work will support studies into the formation of these renowned geological features and make the representation of geologic processes more intuitive. [ABSTRACT FROM AUTHOR]

With its high mountains, deep valleys, and complex geological formations, the Jiuzhaigou County has the typical characteristics of a disaster-prone mountainous region in southwestern China. On August 8, 2017, a strong Ms 7.0 earthquake occurred in this region, causing some of the mountains in the area to become loose and cracked. Therefore, a survey and evaluation of landslides in this area can help to reveal hazards and take effective measures for subsequent disaster management. However, different evaluation models can yield different spatial distributions of landslide susceptibility, and thus, selecting the appropriate model and performing the optimal combination of parameters is the most effective way to improve susceptibility evaluation. In order to construct an evaluation indicator system suitable for Jiuzhaigou County, we extracted 12 factors affecting the occurrence of landslides, including slope, elevation and slope surface, and made samples. At the core of the transformer model is a self-attentive mechanism that enables any two of the features to be interlinked, after which feature extraction is performed via a forward propagation network (FFN). We exploited its coding structure to transform it into a deep learning model that is more suitable for landslide susceptibility evaluation. The results show that the transformer model has the highest accuracy (86.89%), followed by the random forest and support vector machine models (84.47% and 82.52%, respectively), and the logistic regression model achieves the lowest accuracy (79.61%). Accordingly, this deep learning model provides a new tool to achieve more accurate zonation of landslide susceptibility in Jiuzhaigou County. [ABSTRACT FROM AUTHOR]

Diagenesis is the primary cause of the densification of the Fuyu reservoir in Sanzhao sag, Songliao Basin. In this paper, the types of diagenesis, the influence of diagenesis on reservoir physical properties and the formation reasons of tight reservoir in Fuyu oil layer were studied by means of ordinary thin sections, casting thin sections, cathodoluminescence and scanning electron microscope. Results show that the diagenesis of the Fuyu reservoir in Sanzhao sag mainly includes compaction, cementation, metasomatism, and dissolution. Compaction and cementation are the main reasons for the compactness of the Fuyu reservoir in Sanzhao sag. The compactness causes also vary in different parts of the Fuyu reservoir. At the bottom of the Fuyu oil layer, the porosity reduction rate of early calcite cementation is 77%, and that of compaction is 9.23%. Cementation is the primary cause of reservoir compactness, and compaction is the secondary factor. In the middle and upper sections of the Fuyu reservoir, the porosity reduction rate of compaction is 50%, and that of cementation is 32.31%. Compaction is the main reason causing reservoir compactness, and cementation is the secondary factor. This work extensively analyzes the diagenesis characteristics of the Fuyu reservoir and its influence on the reservoir physical properties, providing a scientific basis for the study of the reservoir physical properties and the prediction of high-quality reservoirs. [ABSTRACT FROM AUTHOR]

Hydrogen, as a clean and efficient energy source, is important in achieving zero-CO 2 targets. This paper explores the potential of hydrogen geologic storage (HGS) in China for large-scale energy storage, crucial for stabilizing intermittent renewable energy sources and managing peak demand. Despite its promise, HGS faces challenges due to hydrogen's low density and viscosity, and its complex interactions with geological formations and microorganisms. This review offers a comprehensive overview of the current research status for HGS, with a particular focus on highlighting the main challenges confronting China. These difficulties and challenges primarily arise from complex geological conditions and the absence of fundamental parameters within potential reservoirs, including depleted oil/gas fields, salt caverns, and brine aquifers. Additionally, we have synthesized the current applications of machine learning (ML)as a potential solution. Key challenges are examined, such as the effects of operational parameters (e.g., cyclical injection-production and injection rates) on HGS efficiency, which can influence phenomena such as hydrogen fingering and caprock integrity. This review also looks into the insufficiently understood hydrogen-water-rock geochemical reactions under diverse temperatures and pressures, a gap that hampers the development of predictive numerical simulations and raises concerns about hydrogen leakage due to changes in porosity and permeability. Additionally, the paper addresses the limited knowledge about the metabolic mechanisms of subsurface microorganisms under extreme conditions, highlighting potential risks of hydrogen leakage and groundwater contamination. These microorganisms can metabolize hydrogen, producing gases such as CH 4 and H 2 S, which may cause steel corrosion. Furthermore, the study assesses the distribution and prospects of three primary methods for pure hydrogen storage in China, considering the current state of hydrogen development and relevant government policies. The role of ML in advancing HGS is also discussed, offering insights into future research directions. This review not only scrutinizes the scientific challenges of HGS but also underscores its potential, guiding future simulation and practical engineering applications in this field. • HGS is feasibility in China through policy examination and potential site analysis. • Geochemical and microbial reactions jeopardize to reservoir integrity and H 2 quality. • Elucidating the present application and future prospective for ML in HGS. • Summarizing the key challenges associated with achieving large-scale HGS. [ABSTRACT FROM AUTHOR]

• Novel approach: our study proposes a 3D U-shaped neural network that can accurately simulate the temperature field of hot dry rocks in both space and time dimensions. This approach is a significant advancement as previous methods have addressed these tasks separately, presenting challenges. • Improved accuracy: by incorporating an attention mechanism and residual structure, our neural network captures the nonlinear relationship between the temperature field and rock strata parameters more accurately. This leads to more precise temperature field simulations of hot dry rocks and enhances our understanding of the system. • Practical implications: the simulated temperature field provides valuable insights into the effects of different geological formations on hot dry rocks. This information is crucial for predicting and exploiting hot dry rock geothermal reserves. Our findings lay the foundation for further research and development in this field and offer practical implications for the utilization of hot dry rock geothermal resources. Hot dry rock has emerged as a crucial renewable resource with a potential to provide significant energy to China. Accurately simulating the temperature field of hot dry rocks in space is essential in estimating their reserves. Moreover, predicting the temperature change curve of hot dry rocks over time is crucial for research in the field. Although these tasks are interrelated and share a common ground of simulating the temperature of hot dry rocks, previous approaches have dealt with them separately, each being challenging. In this study, we propose a 3D U-shaped deep-time neural network that can extract the nonlinear relationship between the temperature field and rock strata parameters, thereby enabling the simulation of the temperature field of hot dry rocks in both space and time dimensions. The proposed neural network, which incorporates an attention mechanism and residual structure, can incorporate multiple rock parameters and geological structures, leading to more accurate simulation of the temperature field of hot dry rocks. To train the network, we constructed extensive datasets based on granite rock parameters and actual geological structures, with the temperature fields simulated by the finite element method serving as labels. The resulting trained network model can successfully emulate the complex hot dry rock model, reducing the workload by combining the two networks into one. Furthermore, the simulated temperature field allows the observation of the effect of different geological activities on hot dry rocks. Network simulation has shown notable advancements in efficiency compared to traditional finite element methods. Moreover, it offers the advantage of exploring the impact of distinct geological structures on geothermal reservoirs in a spatial context. Additionally, it allows for the observation of temporal variations in the temperature distribution across different geological strata during different time periods. Thereby laying the groundwork for further prediction and exploitation of hot dry rock geothermal reserves. [ABSTRACT FROM AUTHOR]

It is critical to recognize and reproduce aquifer heterogeneity properly in groundwater modeling and management due to its impacts in groundwater flow, transport, mixing and reaction. It is widely reported that attributes of geologic formations often exhibit statistical scaling with probability distribution of non-Gaussian type. To capture those features in a unified and self-consistent manner, a general geostatistical model termed Generalized sub-Gaussian (GSG) model was proposed by Riva et al. (Water Resour Res 51:4623–4634, 2015. https://doi.org/10.1002/2015WR016998). One may wonder whether GSG also works on a broader variety of environmental systems having attributes of different types. Geophysical data are playing growingly significant role in aquifer characterization mainly due to its ease of implementation and low cost. This study focuses on assessing the applicability and transferability of GSG model via a dataset of electrical resistivity collected in three deep boreholes in the northern Ordos Basin in China. By analyzing statistical scaling behaviors, frequency distributions and model fittings of resistivity data, it is found that resistivity data from each borehole indeed can be characterized by GSG model. Though three neighboring boreholes are in a same formation and bear similar geological texture, their corresponding GSG models seem distinct. Cross-validation results further suggest that GSG model calibrated using two boreholes are different from that based on the remaining borehole, though large-lag increments exhibit similar frequency distributions. It is found that GSG is able to characterize well log resistivity in three boreholes but with distinct parameters. Attention should be paid when transferring a calibrated GSG model to the vicinity even within a single sedimentary structure. [ABSTRACT FROM AUTHOR]

• Statistical analysis of the parameters of soft and hard strata in China, as well as subway cross-sections and construction methods. • Stability grading criteria for subway stations in soft and hard strata. • Propose instability prevention measures for each stability grade of subway stations in soft and hard strata. In congested urban underground space, a subway station may have to be constructed within an unfavorable complex geological formation comprising upper-soft and lower-hard strata, at a higher risk of structure damage and ground surface subsidence during the construction process. When the subway station is constructed using the undercutting method in a complex urban environment, there is currently lack of theory or guidance on the selection of appropriate construction method for subway stations in different upper-soft and lower-hard strata conditions. This paper conducted a series of numerical simulation, model test, and field test to specifically investigate the stability classification of large-span underground subway stations in upper-soft and lower-hard strata. Results indicate the following: (1) The thickness of the overlying soft rock serves as an indicator for the stability classification of large-span subway stations in upper-soft and lower-hard strata. (2) The stability of large-span subway stations in upper-soft and lower-hard strata can be generally divided into five levels (W-I, W-II, W-III, W-IV, and W-V) from very stable to unstable. (3) For each classification, appropriate construction method was proposed and validated through typical engineering case studies. The research conclusions of this paper can provide effective reference for the selection of construction safety and stability methods for subway station excavation. [ABSTRACT FROM AUTHOR]

Over the past decade, the exploration and development of deep coalbed methane (CBM) resources in China have attracted significant attention for their immense potential. Typically found in geological conditions marked by high formation temperature, reservoir pressure, and in-situ stress, exploring and developing these resources present a multitude of challenges. As the coal seams extend to greater depths, adsorption behavior, pore-fracture structure, and mechanical properties of deep coal seams become increasingly intricate, impacting properties such as gas content, permeability, and fracability. Despite the presence of significant free gas in deep CBM reservoirs, production remains challenging due to the extremely low permeability of coal seams. Additionally, high in-situ stress and complex mechanical parameters of deep coal seams can significantly reduce hydraulic fracturing performance, further complicating the development of deep CBM. This comprehensive review provides a detailed analysis of the geological conditions and formation property variations at different depths for CBM reservoirs, illuminating the distinctions between deep and shallow CBM reservoirs. Furthermore, this review summarizes the pilot tests and research perspectives in China to address the challenges associated with exploring and developing deep CBM resources. By raising awareness of the particularities of deep CBM and offering practical and accessible references, this review aims to contribute to the better exploration and development of these valuable resources. • Deep CBM reservoirs present complex geological features influenced by high temperature, pressure, and stress conditions. • Accurate depth definition of deep CBM resources requires thorough understanding of geological and engineering attributes. • Deep CBM wells display distinct production patterns: minimal water, initial gas peak, and stable adsorbed gas production. • "Large-scale, large-displacement, multiple-rounds" fracturing boosts gas in deep CBM wells. • Pilot tests in China confirm substantial development potential for deep CBM resources. [ABSTRACT FROM AUTHOR]

This paper provides newly found and profound insight into the initiation mechanism of the first Baige landslide occurred on the upper reaches of the Jinsha River in October 10, 2018. The detailed geological characteristics are interpreted by comprehensive field surveys in the past year, which indicate that the Baige landslide developed in the Jinsha River tectonic suture zone, and the active tectogenesis significantly contributes to broken stratigraphic structures and complex spatial distribution of lithologies. The initiation is considered to be long-term creep under the exogenic and endogenic integration, while the active tectogenesis and the influence of serpentinite and foliation, respectively, are the primary exogenic and endogenic factors. In addition, this creep process can be analyzed within three stages: evolution and formation of failure-prone geological structures, progressive deformation and fracturing, and shear failure of the locking section. The distribution and easily degraded behavior of the serpentinite are the fundamental, enabling the formation of failure-prone structures and also responsible for the subsequent deformation evolution. The foliation controls the toppling deformation-failure mode and direction. Furthermore, this catastrophic landslide further reminds us to pay attention to the landslides along the upper reaches of the Jinsha River, and our preliminary results indicate that the distribution characteristics of landslides significantly depend on the Jinsha River tectonic suture zone and the serpentinite mélange belt and thus are always associated with tectonically induced damage. [ABSTRACT FROM AUTHOR]

The 2015 earthquakes in Nepal killed more than 9,000 people, displaced millions of people and deeply affected the economy. The earthquakes and reconstructions processes also transformed Nepal into a complex terrain of geoeconomic accumulation and geopolitical manoeuvring, including major international capital flows, the promulgation of a new constitution, an economic blockade by India and the expansion of trade corridors with China. Building on critiques of 'disaster capitalism', we propose and mobilize the concept of 'geo-logics of power' to draw further attention to the materialities of geopolitical and geoeconomic processes shaping reconstruction in post-earthquake Nepal. Focusing on two trans-Himalayan corridors connecting Nepal and China, we argue that the Nepal experienced a particular form of disaster capitalism: one in which the geo-logics of power – including trans-Himalayan discourses, practices, and materialities – came to shape political and economic transformations of a country long portrayed as a 'buffer' state between Indian and China. More broadly, we suggest that geo-logics of power result from a combination of geopolitical and geoeconomic power dynamics informed by geological formations and associated socio-natural processes. [ABSTRACT FROM AUTHOR]

A geological stratum is a rock or soil layer that has internally consistent characteristics and is distinguishable from adjacent layers. A stratigraphic section contains reference information for the strata of an associated sedimentary area. In this paper, the thermal properties of 36 rock formations in a succession of the Yangtze plate in China are studied. Thermal properties are analyzed with an emphasis on rock formations, rock lithological types and dry/saturated conditions. The results show that thermal conductivity varies dramatically with different rock lithological types, which range from 0.72 W m−1 K−1 to 4.49 W m−1 K−1. The analysis of biochemical sedimentary rocks shows that silicate has the highest thermal conductivity, followed by dolomite and limestone; this variation is due to the differences in rock-forming minerals. The thermal conductivity of the clastic rocks is mainly determined by the type of minerals, the porosity and the water content. Compared to dry samples, the thermal conductivity and volumetric heat capacity of saturated samples are higher. Moreover, the thermal conductivity data of nine other locations in the Yangtze plate are compared with the stratigraphic data. This analysis shows that thermal conductivity matches very well for most of the geological formations, with the exception of sandstone, which exhibits a significant deviation across formations. Finally, the thermal properties for the Yangtze plate are mapped for insight on their spatial distribution. • Thermal properties of 36 rock formations in a sedimentary succession are measured. • Thermal conductivity varies dramatically with lithological types of rocks. • Two categories rocks are studied with emphasis on sedimentogenesis. • Thermal properties of Yangtze plate are mapped for insights on spatial distribution. [ABSTRACT FROM AUTHOR]

Geothermal resource is green and clean energy, and geothermal field is widely distributed in the world. Its development and utilization has little harm to the environment, can change the current situation of energy consumption mainly based on fossil energy, reduce carbon emissions, and promote the development of techniques for sustainable processing of natural resources. However, each geothermal field has its own characteristic structure, origin, and storage, so it is necessary to carry out targeted research. In this paper, the geothermal characteristics and geological characteristics of the geothermal belt in Lushan County, China are analyzed by means of remote sensing interpretation, field investigation and observation, geophysical exploration, long-term observation, pumping test, and hydrochemical analysis. Result of this study shows that the geothermal belt of Lushan geothermal fields is as a result of primary thermal control and heat conduction structures of the near east-west Checun-Xiatang deep fault as well as secondary thermal control and heat conduction structures of near north-east and north-west secondary faults; and annual recoverable geothermal energy of whole geothermal field is 4.41 × 1011 MJ. The research results will be beneficial for the development and utilization of Lushan hot springs. At the same time, it also provides reference for more geothermal research. [ABSTRACT FROM AUTHOR]

The Ordovician-Silurian organic-rich shales in the Wufeng and Longmaxi Formations are widespread in southern China and are the most important shale gas producers in China. The shales display varying total organic carbon content ranging from 0.2% to 6% and are composed of black siliceous mudstone, shelly limestone, siliceous clay-rich mudstone, gray silty-shaly interlaminated mudstone, gray argillaceous mudstone, and calcareous or dolomitic mudstone. Detailed stratigraphic correlation of these formations was achieved, and a high-resolution sequence stratigraphy was constructed based on the integration of welllog data, mineralogical, geochemical, and petrophysical analyses. The Wufeng Formation and the Guanyinqiao Bed were interpreted to be a condensed section with four cycles of sea-level fluctuation. The Longmaxi Formation consists of three members. The Long-1 Member was interpreted to be a thirdorder depositional sequence that can be subdivided into a transgressive systems tract, an early highstand systems tract, and a late highstand systems tract. Within the constructed isochronal stratigraphic framework, the characteristics and genetic mechanism of different shale lithofacies were studied. The deposition of black siliceous mudstone of high total organic carbon in the Wufeng Formation and the Long-1 transgressive systems tract was likely influenced by volcanic activity. The Guanyinqiao shelly limestone or calcareous mudstone was associated with the Ordovician-Silurian transition when glaciation and mass extinction took place. The gray silty-shaly interlaminated mudstone of moderate total organic carbon in the Long-1 early highstand systems tract was the product of bottom flow intrusion. The deposition of gray argillaceous mudstone and calcareous or dolomitic mudstone with low total organic carbon in the Long-1 late highstand systems tract resulted from enhanced terrigenous input from peripheral uplifts. The distribution pattern of different lithofacies varies greatly in the Upper Yangtze area, and this difference is a result of dissimilar sediment provenances and variable hydraulic restriction levels that were controlled by basin geometry. A better understanding of the distribution pattern and depositional history of the Wufeng and Longmaxi Formations might provide guidance for future profitable shale gas exploration. [ABSTRACT FROM AUTHOR]

Impedance inversion performed on post-stack seismic data is one approach to reservoir prediction. Conventional post-stack seismic data inversion has two main stages. Stage one involves deconvolution to estimate reflectivities and stage two is estimation of the impedance section from these reflectivities. These two stages are ill-posed inverse problems due to the nature of seismic inversion. An alternative method has been proposed that combines the two stages to estimate seismic impedance directly. Because it is less sensitive to noise in the seismic data, the proposed method decreases the inherent ill-posedness of impedance inversion. To regularise this merged inverse problem, L0 gradient minimisation of impedance has been used. L0 gradient minimisation regularisation provides a blocky impedance solution that makes formation interfaces and geological edges more precise and keeps the inversion procedure robust even if random noise exists in the seismic data. A split-Bregman-like algorithm has been used to solve the L0 gradient minimisation problem. The results of numerical examples show that the proposed inversion method can generate more accurate impedance models compared with conventional methods. Finally, the proposed method is applied to real seismic data from east China to test its applicability in practice. The inversion results confirm that the proposed method is effective at inverting real seismic data. [ABSTRACT FROM AUTHOR]

The upper reaches of the Minjiang River are in the eastern margin of the Tibetan Plateau, where active faults are well developed and earthquakes frequently occur. Anomalous climate change and the extremely complex geomechanical properties of rock and soil have resulted in a number of geohazards. Based on the analysis of remote sensing interpretations, geological field surveys, geophysical prospecting and geological dating results, this paper discusses the developmental characteristics of the Gamisi ancient landslide in Songpan County, Sichuan Province, and investigates its geological age and formation mechanism. This study finds that the Gamisi ancient landslide is in the periglacial region of the Minshan Mountain and formed approximately 25 ka BP. The landslide initiation zone has a collapse and slide zone of approximately 22.65×106–31.7×106 m3 and shows a maximum sliding distance of approximately 1.42 km, with an elevation difference of approximately 310 m between the back wall of the landslide and the leading edge of the accumulation area. The landslide movement was characterized by a high speed and long runout. During the sliding process, the landslide body eroded and dammed the ancient Minjiang River valley. The ancient river channel was buried 30‐60 m below the surface of the landslide accumulation area. Geophysical prospecting and drilling observations revealed that the ancient riverbed was approximately 80‐100 m thick. After the dam broke, the Minjiang River was migrated to the current channel at the leading edge of the landslide. The Gamisi ancient landslide was greatly affected by the regional crustal uplift, topography, geomorphology and paleoclimatic change. The combined action of periglacial karstification and climate change caused the limestone at the rear edge of the landslide fractured, thus providing a lithological foundation for landslide occurrence. Intense tectonic activity along the Minjiang Fault, which runs through the middle and trailing parts of the Gamisi ancient landslide, may have been the main factor inducing landsliding. Studying the Gamisi ancient landslide is of great significance for investigating the regional response to paleoclimatic change and geomorphologic evolution of the Minjiang Fault since the late Pleistocene and for disaster prevention and mitigation. [ABSTRACT FROM AUTHOR]

On 12 May 2008, a devastating mega-earthquake of magnitude 8.0 struck the Wenchuan area, northwestern Sichuan Province, China. Following this earthquake event, many areas in the affected areas were susceptible to geological disasters, such as debris flows, landslides and other secondary disasters. To better understand the mechanism of the formation processes of geological disasters, and to reduce the economic loss caused by the disasters, a comprehensive analysis is required. With the aim of obtaining the characteristics of unfavourable geological bodies, and analysing their stability, we choose the Gengda Township as an example (there are many unfavourable geological bodies distributed in this area, including landslides and deformation bodies). Field investigations and computational models are employed to analyse the stability of the unfavourable geological bodies. Through preliminary analysis and model calculation, the following conclusions can be drawn: under natural conditions, the stability factor of the landslide ranges from about 1.02–1.03, which means that the landslide is in a basically stable or less stable condition. Under the effect of continuous heavy rainfall, the stability factor of the landslide will be significantly reduced, and the corresponding value ranges from 0.9–0.96, which signifies that the landslide is in an unstable condition. For No 1 and No 2 deformation bodies (named by local inhabitants), the stability varied from less stable to unstable, and basically stable to unstable, respectively. On the basis of the results of the calculation, some countermeasures are proposed to mitigate the effects of these disasters probably caused by geological bodies. [ABSTRACT FROM AUTHOR]

• Resource-Richness Analogy Approach used in less explored reservoirs is proposed. • Genesis-Statistics Assessment Approach for heterogeneous tight oil is proposed. • The parameter criteria of lacustrine tight oil resource assessment are established. • In-place tight oil resources in China's major basins are estimated of 12.6 × 109 t. • 15 most favorable plays are outlined with in-place resources of 5.3 × 109 t. Large-scale commercial development of shale gas and tight oil resources in North American and continuous discoveries of tight oil in China lead to the recognition of the importance of assessment on tight oil resources. Based on the characteristics of China's tight oil reservoirs and exploration status, this paper discusses a workflow focusing on in-place resource evaluation. In the workflow, a Resource-Richness Analogy Approach (RR-AA) is proposed for assessment of tight oil resources in less explored areas, a Genesis-Statistics Assessment Approach (GS-AA) for lacustrine tight oil resources with strong heterogeneity and regions where more delicate assessment is required, and an EUR Analogy Approach (EUR-AA) for assessment on recoverable tight oil by fully using available EUR data of production wells. After analyzing the geological characteristics of the formation of tight oil in the Ordos, Bohai Bay, Songliao, Junggar, Sichuan and other major Basins, the distributions of essential parameters such as reservoir thickness, area and porosity have been defined, and the parameter evaluation criteria have been established. Finally, the tight oil resource potentials in the major basins in China have been evaluated using one of the three methods and the prospective areas of high resource abundance are outlined in each of basins. The results from this study show that China's tight oil resources have a large potential and good exploration future. The estimated in-place tight oil resources are 12.580 × 109 tons, mainly distributed in the Ordos, Songliao, Bohai Bay and Junggar Basins. 15 most favorable zones are proposed having in-place resources of 5.296 × 109 tons. [ABSTRACT FROM AUTHOR]

Chancelloriid sclerites from the lowermost Cambrian Xinji Formation (Series 2, Stage 3), southern margin of the North China platform, are systematically described. Thousands of isolated sclerites from three sections are assigned to three genera and four species, including Chancelloria cf. eros , Allonnia tripodophora , Archiasterella pentactina , and Ar. tetraspina. To accurately document the taxonomic significance of the sclerite structure, modified formulas (m+nC, m+nA, and m+0) are put forward to represent the full series and variation of sclerite forms. Based on the sclerite construction, statistical analysis on the proportions of different sclerite forms in the rock samples and the composition of sclerites in previously described chancelloriid scleritomes, a new scheme for identification and classification of isolated sclerites reconciled within the framework of the complete scleritome, is proposed. [ABSTRACT FROM AUTHOR]

Abstract A single species of fossil conifer with well-preserved cuticles from multiple layers of the Dalong Formation in two sections in Duanshan Town, Guizhou Province, Southwest China has been used to reconstruct palaeo-atmospheric p CO 2. The age of these layers can be dated back to the late Changhsingian (latest Permian), corresponding to the Clarkina changxingensis and Clarkina yini conodont Zones. Two calibration approaches were employed in this study. Using the stomatal ratio method, the p CO 2 curves of the two sections showed matching trends, with levels decreasing in the middle of the profiles, and similar ranges at ca. 340–510 ppm and ca. 300–440 ppm. Similar values (ca. 360–520 ppm), yet with wider error ranges, were obtained when the mechanistic model proposed by Franks et al. in 2014 was applied to one of the sections. Our values are lower than the mean p CO 2 values from coeval palaeosols, but partly overlap with them when error ranges are taken into consideration, thus more independent studies are needed to evaluate the discrepancies between the two proxy methods. The low atmospheric CO 2 concentrations in this study suggest a cool climate rather than extensive glaciation for the brief period of late Changhsingian, which is supported by the oxygen isotope record of conodont apatite and a major restructuring of Late Permian flora and fauna. Highlights • Fossil conifers from the late Changhsingian strata of two sections were firstly used to reconstruct atmospheric p CO 2. • The stomatal ratio method and a mechanistic gas exchange model have been applied to this study. • The result of p CO 2 is ca. 300–500 ppm, suggesting a cool climate shortly before the mass extinction event. [ABSTRACT FROM AUTHOR]

Assessment of fractured rock aquifers in many parts of the world is complicated given their strong heterogeneity. Delineation of the subsurface geological formation in the weathered terrain is essential for groundwater exploration. To achieve this goal, 2D electrical resistivity tomography (ERT) and self-potential (SP) in combination with joint profile method (JPM) and boreholes have been carried out to delineate the subsurface geological units, detect the fracture/fault zones in hard rock, monitor the groundwater flow, and estimate the groundwater reserves contained within the weathered terrain at a complex heterogeneous site of Huangbu, South Guangdong of China. The integration of resistivity images with the borehole lithology along three profiles delineates three subsurface distinct layers namely topsoil cover, weathered and unweathered layers. The incorporation of ERT and SP with JPM reveal five fractures/faults, i.e., F1, F2, F3, F4 and F5. 2D ERT models interpret the less resistive anomalies as the fractures/faults zones, and high resistive anomalies as the fresh bedrock. The inversion program based on the smoothness-constraint is used on the resistivity field data to get more realistic three layered model. SP measurements are obtained along the same electrical profiles which provide the negative anomalies clearly indicating the groundwater preferential flow pathways along the fracture/fault zones. Hydraulic parameters namely hydraulic conductivity and transmissivity were determined to estimate the groundwater resources contained within the fractures/faults. The integrated results suggest that the fractures/faults zones are most appropriate places of drilling for groundwater exploration in the investigated area. Geophysical methods coupled with the upfront borehole data provides better understanding about the conceptual model of the subsurface geological formations. The current investigation demonstrates the importance of the integrated geophysical methods as a complementary approach for groundwater assessment in the hard rock weathered areas. [ABSTRACT FROM AUTHOR]

Highlights • Heterogeneities in organic matter, porosity, permeability, minerals, laminae, and natural fracture are characterized. • Organic matter and porosity are the primary controlling factors of shale gas accumulation. • Transgressive systems tracts are more favorable for gas accumulation. • The shale gas resources are mainly concentrated in the shelf depocenter. Abstract Shale gas as an unconventional gas has made a significant impact on worldwide energy supply. The heterogeneity of the shale reservoir has a dramatic effect on the shale gas accumulation. The heterogeneity characterization of the Paleozoic Wufeng-Longmaxi Formation Shale in the Upper Yangtze Region is studied within a sequence stratigraphic framework by testing in situ gas content, organic matter, minerals, porosity, permeability, and the observation and description of core and thin sections, and data statistics. Results show that the shelf depocenter has higher porosity than the shelf margin and the permeability is obviously lower at the transitional zone compared to neighboring areas. The most obvious characteristic of organic matter and mineral composition is that the TOC and quartz content at the lower section of the formation deposited during transgressive systems tract is higher than that at the upper section of the formation deposited during highstand systems tract throughout the whole deposition zone. The laminae are primarily developed at the upper section of the formation. The natural fracture is mainly developed at the Qiyueshan fault zone and the Xuefeng Mountain fault zone. The primary controlling factors of shale gas accumulation are organic matter and porosity. The transgressive systems tracts with high organic matter content and porosity at the lower section of the formation are more favorable for gas accumulation. The shale gas resources and exploration potential are mainly concentrated in the shelf depocenter. [ABSTRACT FROM AUTHOR]

Two tridactyl footprints from the Chuanjie Formation (Middle Jurassic) of Yunnan Province, China are morphological characteristics of thyreophoran tracks. They show some similarities to Shenmuichnus, known from the Early Jurassic strata of both Shaanxi and Yunnan provinces, but are somewhat larger, thereby resembling the ichnogenus Stegopodus. Based on their general morphology and size being congruent with this ichnogenus, they are tentatively assigned here to cf. Stegopodus. This is the fourth report of large ornithischian (probably thyreophoran) tracks from the Lower-Middle Jurassic of China that indicates relatively large trackmakers that were likely to be taxonomically distinct from much smaller and gracile Anomoepus trackmakers, also of ornithischian affinity. The larger tracks indicate a hitherto unreported abundance, size range and diversity of track types attributed to this group. The parallel orientation of the two best preserved trackways may indicate gregariousness. [ABSTRACT FROM AUTHOR]

Abstract Three shale samples, which were from MF-1 well (a) and MF-2 well (b) in the northern Ordos Basin of China and Yan'an Formation of Jurassic coal measure strata of J601 well (c) in the western edge of the Ordos Basin, were taken for thermal simulation and rock pyrolysis experiments. The rules of hydrocarbon generation production and S 2 varied with the increase in thermal maturity (R o), and the relationship between S 2 and gaseous hydrocarbon generation production were analyzed. The analytical results indicated that as the R o increased, the liquid hydrocarbon production of the shale samples first increased and then decreased, while the gaseous hydrocarbon production and total hydrocarbon production increased, and the S 2 gradually decreased. Gaseous hydrocarbon production increased as S 2 decreased, and there was a two-stage negative linear correlation between S 2 and gaseous hydrocarbon production. The gaseous hydrocarbon production increased slowly when the R o value was below 0.8% and rapidly increased after this threshold was met. During the process of the hydrocarbon generation of the shale in the Ordos Basin, the evolution phase could be divided into three stages: the immature stage of producing liquid hydrocarbon, the mature stage of producing gaseous and liquid hydrocarbon, and the overmature stage of gaseous hydrocarbon thermal cracking. Considering the hydrocarbon expulsion efficiency of the shale samples, the total organic carbon (TOC) content had a positive logarithmic correlation with the shale gas content (the gaseous hydrocarbon production minus the expulsed gaseous hydrocarbon production). The hydrocarbon generation potential and gas content increased with the increase of TOC. With the knowledge of the shale samples' TOC content, the shale gas content of the sampling layer could be preliminarily determined based on the regression equations of TOC and gas content. The exploration potential of the shale layer could be evaluated according to the gas content calculation, after considering the standards for the shale gas favorable area and the target area gas content. Graphical abstract After analyzing the rules of hydrocarbon generation production with the increase in thermal maturity (Ro), a corresponding mode of the process of shale hydrocarbon-generating was established and the maximum generated gas amount of shale samples could be calculated. Considering the hydrocarbon expulsion efficiency of the shale samples, the total organic carbon (TOC) content had a positive logarithmic correlation with the shale gas content. A new and reliable methods to estimate coal measures strata shale gas content was proposed which provided a reliable basis for the evaluation of shale gas resources and optimization of favorable areas. Image 1 Highlights • We performed thermal simulation and rock pyrolysis experiments on coal measure strata shale samples. • There is a two-stage linear negative correlation between S 2 and gaseous hydrocarbon production. • A corresponding mode of the process of shale hydrocarbon-generating was established. • A new and reliable methods to estimate coal measures strata shale gas content was presented. [ABSTRACT FROM AUTHOR]

This paper reports results from detrital zircon U-Pb geochronology, Hf isotopic geochemistry, sandstone modal analysis, and palaeocurrent analysis of the early Mesozoic strata within the Ningwu basin, China, with the aims of constraining the depositional ages and sedimentary provenances and shedding new light on the Mesozoic tectonic evolution of the northcentral North China Craton (NCC). The zircons from early Mesozoic sandstones are characterized by three major populations: Phanerozoic (late Palaeozoic and early Mesozoic), late Palaeoproterozoic (with a peak at approximately 1.8 Ga), and Neoarchaean (with a peak at approximately 2.5 Ga). Notably, three Phanerozoic zircons in the Early Triassic Liujiagou Formation were found to have positive εHf(t) values and characteristics typical of zircons from the Central Asian Orogenic Belt (CAOB). Therefore, the CAOB began to represent the provenance of sediment in the sedimentary basins in the northern NCC no later than the Early Triassic (261 Ma), implying that the final amalgamation of the NCC and CAOB occurred before the Early Triassic. The U-Pb geochronologic and Hf isotopic results show that the Lower Middle Triassic sediments were mainly sourced from the Yinshan-Yanshan Orogenic Belt (YYOB), and that a sudden change in provenances occurred, shifting from a mixed YYOB and CAOB source in the Middle Jurassic to a primarily YYOB source in the Late Jurassic. The results of the sandstone modal analysis suggest that the majority of the samples from the Lower Middle Jurassic rocks were derived from either Continental Block or Recycled Orogen sources, whereas all the samples from the Upper Jurassic rocks were derived from Mixed sources. The change in source might be ascribed to the southward subduction and closure of the Okhotsk Ocean and the resulting intense uplift of the YYOB during the Late Jurassic. This uplift likely represents the start of the Yanshan Orogeny. [ABSTRACT FROM AUTHOR]

The metasedimentary Lujiapuzi Formation crops out along the northeastern margin of the North China Craton, close to the Yan‐Liao Rift. The age and tectonic setting of the formation, and its relationship with the Yan‐Liao Rift are currently unclear. Here we present detrital zircon U‐Pb ages, and Hf isotopic and geochemical data for the Lujiapuzi Formation to constrain the timing of deposition, the provenance of the formation, and the regional stratigraphy relationship. Zircon U‐Pb dating constrains the timing of deposition of the Lujiapuzi Formation to younger than 1780 Ma, and indicates that most grains were sourced from the Longgang Block and the Paleoproterozoic Liao‐Ji Belt. Detailed field investigations and a correlation of the regional stratigraphy reveal that much of the Lujiapuzi Formation is equivalent to the Tuanshanzi Formation in the Yan‐Liao Rift; the lower section may represent the earliest sediments deposited within the Fanhe Basin. Based on these results and the findings of previous studies, we suggest that the base of the Changcheng System has an age of 1.80 Ga. Zircon Hf isotopic data indicate that the main period of crustal growth along the northeastern margin of the North China Craton occurred at 3.2–2.5 Ga, with a peak at 2.9–2.7 Ga. [ABSTRACT FROM AUTHOR]

Reconstructing the evolution of paleofluid pressure in carbonate reservoirs is a challenging problem, particularly when no oil-bearing fluid inclusions are available to provide barometric constraints on the fluid system. To recover the paleofluid pressure in the Sinian Dengying Formation (Z 2 dn) and the Cambrian Longwangmiao Formation (Є 1 l) of the central paleo-uplift of the Sichuan Basin, we conducted a comprehensive analysis combining the inclusion pressure-volume-temperature simulation, inclusions in situ Raman shifts, and basin modeling. The results showed that the evolution of the pore pressure could be divided into four stages. Prior to the end of the late Triassic, the whole central paleo-uplift was in a normal pressure state. During the Jurassic, a moderate overpressure prevailed in the dolomitic reservoirs of the Gaoshiti-Moxi area and decreased in the adjacent units. At the end of the early Cretaceous, the overpressure reached a maximum in the whole region and was strongest in the Longnüsi area, decreasing to the west. From the late Cretaceous to the present day, the central area of the basin has uplifted rapidly with the overpressure significantly decreasing. Z 2 dn has been restored to normal pressure during the Neogene, while Є 1 l remains moderately overpressurized. Based on an analysis of the structural background and preservation conditions, the types of sedimentary facies, the preservation condition of the traps, and the differential weathering process are the primary reasons for the different pressure states in Z 2 dn and Є 1 l during the last stages. [ABSTRACT FROM AUTHOR]

In order to explore the marine redox structure on the earliest Cambrian (ca. 542–529 Ma) Yangtze Platform, South China, new Fe-Mo-C-S geochemical data from the slope Xugongping section for the Liuchapo and the base of Niutitang Formation are reported here. Integrated Fe speciation and Mo abundance data from the Xugongping section, in combination with previously published data from slope-basinal Longbizui section and others, suggest oxic surface waters and ferruginous deep waters coexisting with occasional mid-depth euxinic waters during the Fortunian Stage, and with widespread euxinic waters during the early Stage 2 marine transgression. A compilation of new and published sulfur isotope data of pyrite for the Liuchapo and the base of Niutitang Formations presents high isotopic values (mostly >+10‰) and distinctly different spatiotemporal gradient characteristics during the Fortunian Stage and the beginning of the Stage 2. We propose that redox stratification developed in the earliest Cambrian protected basin, and eustatic change and the connectivity of the protected basin with the open ocean controlled the materials supply from riverine input and open ocean reservoir and thus spatiotemporal variability of ocean chemistry. [ABSTRACT FROM AUTHOR]

The ongoing exploration for shale oil and gas has focused sedimentological research on the transport and deposition mechanisms of fine-grained sediments, and more specifically on fine-grained mass-flow deposits. It appears, however, that no easily applicable classification scheme for gravity-flow deposits exists, and that such classifications almost exclusively deal with sandy and coarser sediments. Since the lack of a good classification system for fine-grained gravity flow deposits hampers scientific communication and understanding, we propose a classification scheme on the basis of the mud content in combination with the presumed transport mechanism. This results in twelve types of gravity-flow deposits. In order to show the practical applicability of this classification system, we apply it to the Triassic lacustrine Yanchang Formation in the southern Ordos Basin (China), which contains numerous slumps, debris–flows deposits, turbidites and hyperpycnites. The slumps and debrites occur mostly close to a delta front, and the turbidites and hyperpycnites extend over large areas from the delta slopes into the basin plain. The case study shows that (1) mud cannot only be transported but also deposited under active hydrodynamic conditions; (2) fine-grained gravity-flow constitute a significant part of the lacustrine mudstones and shales; (3) muddy gravity flows are important for the transport and deposition of clastic particles, clay minerals and organic matter, and thus are important mechanisms involved in the generation of hydrocarbons, also largely determining the reservoir capability for unconventional petroleum. [ABSTRACT FROM AUTHOR]

• During the Early Triassic, the study area is dominated by fine-grained mixed rocks that formed in a storm-controlled neritic shelf environment. • Mixed sediments formed via facies mixing and punctuated mixing. • From southeast to northwest, the South Yellow Sea Basin contains four paleogeographic units: coast, carbonate platform, shallow shelf, and deep-water basin. • The Qinglong Formation strata exhibit weak hydrocarbon generation and strong sealing. Drilling results from borehole CSDP-2 show that typical fine-grained mixed rocks occur in the Lower Triassic succession in the Central Uplift of the South Yellow Sea Basin, which reveals the storm event and possible double-provenance supply, and advances the previous understanding. We document the rock types, sedimentary structures and textures, and formation mechanisms of fine-grained mixed rocks on the basis of core and thin-section observations, XRD whole-rock geochemical, major and trace element, and laser particle-size analyses. During the Early Triassic, a storm-controlled neritic shelf and restricted platform were the main sedimentary environments of the Central Uplift, and the deposition was dominated by fine-grained mixed rocks, with some argillaceous siltstone and silt-bearing limestone. Formation of the fine-grained mixed rocks is attributed to facies mixing and punctuated mixing under the comprehensive influence of the paleogeographic background, paleoclimate variations, eustatic sea-level change, sediment supply, and storm events. Facies mixing is apparent in the succession as alternations of restricted platform, evaporated platform, brackish platform, and lagoon deposits. Mixed rocks formed by punctuated mixing exhibit an orderly succession of turbidity current, debris flow, storm current, and weak tractive current sediments. The geological significances of this research are twofold. In the South Yellow Sea Basin, the neritic shelf that formed in the Central Uplift gradually changed to a shallow-water carbonate platform in the Southern Depression and Wunansha Uplift. A deep-water basin formed in the Northern Depression. This palaeogeographic pattern is consistent with that of the Lower Yangtze continental region, revealing that two possible ancient provenances, the Cathaysia Wuyi Terrane and the North China Craton, may exist simultaneously. The Lower Triassic strata are characterized by weak hydrocarbon generation and strong sealing, and could act as caprocks for the underlying Permian hydrocarbon system. [ABSTRACT FROM AUTHOR]

The roof, floor and gangue samples of coal seams were collected from a borehole in the Gujiao mining area. The vertical distribution of major elements, trace elements and rare earth elements (REEs) was tested through X-ray fluorescence spectrometry and inductively coupled plasma-mass spectrometry (ICP-MS). The formation environment and material source of the strata were analysed. The results showed that the major elements of the coal seam roof, floor and gangue are Si and Al, followed by Fe, K, and Ti. In the Shanxi Formation, Sn, B, Ta, Bi, Th, U, Li, Be, Nb, In, Cs and Hf are enriched. In the Taiyuan Formation, B, Bi, U, Li, Sr, Mo and Sb are enriched. Sn, B, Th, U, and Be of the Shanxi Formation and B, U, Mo, and Sb of Taiyuan Formation are enriched hazardous elements. The ratios of Sr/Ba, U/Th, Ni/Co and V/Cr could indicate the paleosalinity and redox conditions. The Shanxi Formation was mainly formed in an oxic environment. The roof and floor of the No. 7 coal and the roof of the No. 8 coal are limestone, indicating anoxic and suboxic to dysoxic environments. The lithology of the Shanxi Formation and Taiyuan Formation material source is complex, including sedimentary rocks, granite and alkaline basalt. Most samples are distributed at the intersection of the granite and alkaline basalt, indicating dual sourcing from the granite and alkaline basalt. [ABSTRACT FROM AUTHOR]

The Yeba Formation volcanic rocks in the Gangdese arc recorded important information regarding the early history of the Neo-Tethyan subduction. To explore their magmatic evolution and tectonic significance, we performed a systematic petrological, geochronological and geochemical study on these volcanic rocks. Our data indicated that the Yeba Formation documents a transition from andesite-dominated volcanism (which started before 182 Ma and continued until ~176 Ma) to bimodal volcanism (~174–168 Ma) in the earliest Middle Jurassic. The early-stage andesite-dominated volcanics are characterized by various features of major and trace elements and are interpreted as the products of interactions between mantle-derived arc magmas and lower crustal melts. Their positive ε Nd (t) and ε Hf (t) values suggest a significant contribution of asthenosphere-like mantle. The late-stage bimodal volcanism is dominated by felsic rocks with subordinate basalts. Geochemical signatures of the basalts indicate a composite magma source that included a “subduction component”, an asthenosphere-like upper mantle domain and an ancient subcontinental lithospheric mantle component. The felsic rocks of the late stage were produced mainly by the melting of juvenile crust, with some ancient crustal materials also involved. We suggest that the occurrence and preservation of the Yeba Formation volcanic rocks were tied to a tectonic switch from contraction to extension in the Gangdese arc, which probably resulted from slab rollback of the subducting Neo-Tethyan oceanic slab during the Jurassic. [ABSTRACT FROM AUTHOR]

During the Early Carboniferous, the northeastern Qaidam Basin probably formed in an active continental margin setting. Due to marine regression after the late Early Carboniferous, the marginal shelf began to receive more terrestrial clastic sediments, and alternating occurrence of carbonates and siliciclastics characterized this region. Consequently, shales or mudstones with considerable thickness were deposited in the Upper Carboniferous, especially in the Keluke Formation. In order to illuminate a more accurate sedimentary environment of shales and further evaluate the shale gas potential, multidisciplinary traditional methods were conducted including rock core examinations and laboratory analysis. Results reveal that the sedimentary microfacies of shales in the Keluke Formation can be divided into the upper shoreface, the lower shoreface, and the upper to transition offshore. These microfacies developed on a homoclinal carbonate ramp with a gentle slope. The thickest succession of mudstone develops in the lower shoreface, which is a counterpart with the lagoonal setting of a stationary hydraulic system. The quartz content of shale samples ranges from 30% to 66% and clay minerals from 24% to 43% by bulk compositional analysis, which indicates the content of brittle minerals and shales fissility to some extent. The total organic carbon content ranges from 0.5% to 7.6% by weight, with an average value of 2.69% in ZK1‐1 and 1.11% in ZK3‐2, indicating abundant organic matter richness. The kerogen is mainly of type II, which indicates that source for the organic matter is a mixture of higher terrestrial plants and acquatic organisms. The vitrinite reflectance ranges from 1.22% to 1.55%, indicating a moderate to high thermal maturity. Three types of pores are recognized in the shales, including organic pores, intrapartical pores, and interparticle pores. The significance of this work emphasizes two aspects. First, it gives a more detailed classification of sedimentary environment of the mudstone succession; second, it acquires the preliminary subsurface data regarding to the shale gas potential evaluation. [ABSTRACT FROM AUTHOR]

The North Qilian orogenic belt is the key in the exploration of the formation and assembly of Asia. The Early–Middle Devonian Xueshan Formation, which is deposited in the north area of North Qilian Orogenic Belt, is the most important for revealing the evolution basin–mountain transition of the North Qilian Belt. In order to reveal the tectonic evolution of the central orogenic belt in China and Paleozoic global plate reconstruction, it is necessary to perform provenance analysis of the Xueshan Formation. Eighteen samples were collected from Yumen and Yongchang profiles in the west of North Qilian Belt (WN), and 16 samples were obtained from Gulang and Jingtai profiles in the east of North Qilian Belt (EN). The compositions of clastic conglomerates and the sandstones suggested that felsic volcanic was the main source of the WN Xueshan Formation deposits and that the sedimentary and metamorphic rocks were the main source of the EN sediments. According to major geochemistry indexes, such as Al2O3/SiO2 ratio ranging from 0.08 to 0.37 and the chemical index of alteration less than 80, the source rocks were moderately weathered and of moderately matured. The samples from the EN were relatively enriched in Cr, Ni, Sc, and V elements and depleted in Hf element. However, those from the WN were enriched in Hf without the enrichment of Cr, Ni, Sc, or V. The samples from WN showed a strong negative Eu anomaly, but the samples from EN showed a weak negative Eu anomaly or a positive Eu anomaly. All the above geochemical characteristics suggested the prominent input of felsic clasts with granitic rocks into the WN. Meanwhile, the discrimination diagrams of trace elements implied that WN rocks were derived from continental island arc and that the EN rocks were derived from orogenic belt and the passive continental margin. The North China Plate subducted southwards and formed subduction‐related arc magmatism along the southern margin of the North Qilian Terrane during the Early–Middle Devonian. In conclusion, the WN is a fore‐arc basin, but EN is a foreland basin. [ABSTRACT FROM AUTHOR]

A new campterophlebiid damsel-dragonfly, Honghea xui gen. et sp. nov., is described from the Lower Jurassic Badaowan Formation of the Junggar Basin, NW China. This is the second Chinese Campterophlebiidae recorded for the earliest Jurassic, reflecting the quick diversification and radiation of the damsel-dragonflies during this period. H . nouveau onghea gen. nov. is closely related to Chinese genera Zygokaratawia and Ctenogampsophlebia , both from the Middle Jurassic of the Daohugou Biota; but differs from these genera in having a larger wing size, RP2 slightly distal of Sn, and a narrower area between IR2 and RP3/4. [ABSTRACT FROM AUTHOR]

Integration of the geological context, core analysis, and petrographic investigation, together with data from wireline logs, resulted in the recognition of petrofacies types and the representation of facies models characterizing the X-XII sand groups of the K2qn3 Formation in the Daqingzijing area of the Songliao Basin, China. The results show that the lithology of the reservoir’s X-XII sand groups includes shale calcium-bearing siltstone and sandstone, calcareous siltstone and silty sandstone. The petrofacies consist mainly of quartz, feldspar and rock fragments cemented by clay, and some samples include calcite. The studied interval was deposited onto a delta front. Four types of petrofacies were recognized: subaqueous distributary channel, mouth bar, distal bar and subaqueous interdistributary bay. According to background investigation, the study area’s X-XII sand groups have experienced a large-scale decline in lake level. There are many subaqueous distributary channels in layers 36-40, while other layers were mainly deposited in a subaqueous interdistributary bay. [ABSTRACT FROM AUTHOR]

The South Anhui ophiolite (SAO) and the Northeast Jiangxi ophiolite (NJO) are the only two known Precambrian ophiolite suites within the eastern segment of the Jiangnan Orogen, South China. These ophiolites may provide significant insights into the convergence history of the South China Block during the Rodinia supercontinent cycle. SHRIMP zircon U–Pb dating indicates that the SAO formed at 831 ± 5 Ma whereas the NJO formed at ca. 1000 Ma. Modal mineral assemblages and the preservation of relict primary mineral assemblages indicate that serpentinized peridotites from both ophiolites were mainly harzburgite in protolith. Relict olivine and orthopyroxene fragments within both ophiolite suites yield similarly high Mg# values. The serpentinized peridotite samples yield U-shaped rare earth element patterns and contain high-Cr# spinel, both of which are indicative of supra-subduction zone ophiolites. However, serpentinized peridotites within the SAO contain olivine and clinopyroxene with slightly higher Mg# values, and have lower platinum-group element (PGE) and trace element concentrations than peridotites from the NJO. The SAO peridotites are also depleted in Ir, Pt, and Pd, in contrast to the flat and chondrite-like PGE patterns of the NJO peridotites. These observations indicate that compared with the NJO, SAO peridotites were subjected to a greater degree of melt extraction prior to emplacement. Furthermore, gabbro and basalt from the SAO have N-MORB- or arc-like geochemical characteristics that reflect the incorporation of crustal materials into the mantle source, suggesting that this ophiolite formed in a continental marginal back-arc basin setting. In comparison, the less pronounced depletions in trace elements and PGEs, as well as the restricted 187 Os/ 188 Os isotopic compositions of NJO serpentinized peridotites, suggest that they formed in a fore-arc setting. The contrasting geochemical characteristics of the two ophiolite suites indicate that they were generated during distinct stages of convergence along the southeastern margin of the Yangtze Block. Our results show that ophiolite suites produced within a single orogenic cycle could preserve diverse geochemical characteristics, and may provide insights into the initiation and cessation of continental amalgamation. [ABSTRACT FROM AUTHOR]

An integrated study of zircon U-Pb geochronology and geochemistry, together with Nd-Hf isotopes, have been carried out on the rhyodacite and rhyolitic tuff of the Jingtan Formation in the eastern part of the Jiangnan orogen. SIMS zircon U-Pb dating of two samples yielded weighted mean 206 Pb/ 238 U ages of 784 ± 6 Ma and 788 ± 6 Ma, respectively. Geochemically, they are peraluminous (A/CNK mostly around 1.2) and are characterized by enrichments in Rb, Th, REEs and HFSEs (e.g. Zr and Y) but depletions in Ba, Sr, P, Eu and Ti. The volcanic rocks show a clear A-type granite geochemical signature with high total alkalis (K 2 O + Na 2 O = 5.3–7.64 wt%), FeO t /MgO ratios and low CaO, MgO and TiO 2 contents. They have negative whole-rock ε Nd (t) (−4.2 to −1) and positive zircon ε Hf (t) (+1.26 to +11.6) values, illustrating decoupled Nd-Hf isotopes which may be genetically related to their petrogenesis process. The positive ε Hf (t) values and juvenile T Hf DM1 (0.89–1.3 Ga) of zircons indicate that the volcanic rocks may have been derived from the partial melting of the Neoproterozoic to late Mesoproterozoic crustal materials. Combined with the occurrence of significant volumes of contemporary bimodal volcanic rocks in eastern section of the Jiangnan orogen, it is inferred that the Jingtan felsic volcanic rocks formed during post-collisional extension shortly after the final amalgamation of Yangtze and Cathaysia blocks. [ABSTRACT FROM AUTHOR]

Numerous ∼830 Ma dikes intruded into the Neoproterozoic Tongde mafic-intermediate intrusion at the western margin of the Yangtze Block, providing an ideal opportunity for examining petrogenesis of high-Mg diorites during the breakup of the supercontinent Rodinia. Rocks from the dikes are composed of fine to medium grained diorites which have high Mg # (40–69), low SiO 2 (50.98–61.01 wt%), and variable Na 2 O contents (1.94–5.50 wt%). They show right inclined REE patterns with slightly negative to positive Eu anomalies (Eu/Eu ∗ = 0.90–1.35). Their primitive mantle-normalized trace element patterns are characterized by enrichment of Ba and Pb and depletion of Nb, Ta and Ti. They also show high and variable Sr/Y (12–115) and (La/Yb) N ratios (3–21). The high-Mg diorites have relatively constant initial 87 Sr/ 86 Sr ratios (0.704862–0.706320) and positive εNd values (+0.6–+2.0). These geochemical features reveal that the Tongde high-Mg dioritic dikes were not produced by partial melting of subducted oceanic slab or enriched mantle source. Rather, they were more likely formed by fractional crystallization of garnet and hornblende-bearing mineral assemblages from hydrous mafic magmas under high pressure conditions. The dikes intruded along the fractures resulted from magma thermal contraction after emplacement of the Tongde intrusion. The new model proposed for the petrogenesis of the high-Mg dioritic dikes suggest that the western margin of the Yangtze Block was in an active continental arc setting during the early Neoproterozoic. [ABSTRACT FROM AUTHOR]

The diagenetic evolution and chemical changes of mudstones have a significant influence on the reservoir quality of the mudstones and their interbedded sandstones. To investigate, a variety of methods were applied to the mudstones in the middle of the third member of the Shahejie Formation (Es3z), which were formed in a lacustrine basin during 43.7–38.2 Ma. Optical microscopy and XRD analysis show that the mudstones are dominated by clay minerals (56.8%) followed by carbonate (18.2%), quartz (14.9%), feldspar (8.4%), pyrite (0.9%), anhydrite (0.8%), and total organic carbon (TOC: 2.4%). Cementation and replacement are the main diagenetic events in the mudstone of Es3z. Carbonates and clay minerals are the most common cements, but occasionally authigenic pyrite, albite, and quartz are also present. At the eogenetic stage, the diagenetic events comprised precipitation of pyrite, siderite, dolomite, and calcite besides transformation of K-feldspar into kaolinite. During the mesogenetic stage, the main diagenetic events included precipitation of fracture-filling calcite, ferroan calcite, ankerite, microcrystalline quartz, quartz overgrowth, and transformation of K-feldspar into illite and albite. The limited variation of the Nb/Ta and Zr/Hf ratios and the almost identical distribution pattern of the REE and trace elements indicate that the detrital material in the mudstones was sourced by a common provenance of felsic igneous rocks. The CIA values of Es3z mudstones vary from 50.59 to 65.05 and the PIA values vary from 50.86 to 75.58, which confirm a low-intensity weathering of the source area. Thus, the variation in the bulk-rock geochemical composition of the mudstones may not be primary, but instead a result of mass transfer with the interbedded sandstones during diagenesis. Changes ratios between aim elements (Al, Si, Ca and K) and immobile elements with burial depth in combination with mass balance calculation indicate that aluminum and silicon were retained by the precipitation of authigenic minerals in the mudstone. The mudstones have received progressively more potassium with increasing depths, whereas calcium has been expelled. The reservoir quality of the Es3z sandstones has mainly been affected by the diagenetically induced decrease in the carbonate content in the mudstones causing carbonate cementation in the sandstones. [ABSTRACT FROM AUTHOR]

The fourth member of the Lower Cretaceous Quantou Formation in Southern Fuxin Uplift zone of the Southern Songliao Basin is typical tight oil reservoir which has recently been explored and produced. For effective exploration and development, the evaluation and control factors of the reservoir quality of the K 1 q 4 sandstones should be thoroughly studied. The study focused on the control of the combination of sequence stratigraphy, depositional facies and diagenesis on the reservoir quality, and identified the impact of CO 2 charging, based on the core and thin section observation, XRD, SEM, fluid inclusion and isotope testing and analysis. The fourth member of the Lower Cretaceous Quantou Formation consists of lowstand system tracts (LST), transgressive system tracts (TST) and highstand system tracts (HST). The K 1 q 4 sandstones were mostly deposited in distributary channels and crevasse splays of a delta plain within the LST and TST, and underwater distributary channels and sheet sands of a delta front within the HST. The K 1 q 4 sandstones, mostly silt to medium grained, medium to well sorted, and are mostly lithic arkoses and feldspathic litharenites, have undergone significantly diagenetic alterations, such as compaction, quartz cementation, unstable grains (feldspar and volcanic fragments) dissolution, carbonate cementation and clay minerals cementation. The reservoir quality of the K 1 q 4 sandstones are poor with low porosity and permeability, showing variations among the different system tracts and depositional facies, and are influenced by the charging of CO 2 and controlled by the combination of sequence stratigraphy, depositional facies and diagenesis. The sandstones with high reservoir quality are mostly deposited in high energy environments, including the (underwater) distributary channel sandstones, especially the LST distributary channel sandstones with the best reservoir quality among the LST, TST and HST sandstones, which can be ascribed to larger grain size and better sorting resulting in larger intergranular pore space after compaction, and less content of carbonate cements, illite and mixed-layer I/S, and more pore-lining chlorite and more effectively dissolution. The poor reservoir quality of sandstones from crevasse splay and sheet sand is due to the small grain size and bad sorting which resulted in extensive compaction and the resulting weak dissolution. The charging of CO 2 has dual impact on the reservoir quality of the K 1 q 4 sandstones. The CO 2 charging can induce the dissolution of unstable detrital grains and the precipitation of dawsonite. The former create new secondary pore space, while the latter occupy the intergranular pore space. The CO 2 charging is harmful to the reservoir quality when the dawsonite content exceeds a threshold of 5%. [ABSTRACT FROM AUTHOR]

The tight sandstone reservoir of the Donghetang Formation underwent complex diagenetic processes for which the controlling factors remain unknown. Here, we present a case study of the lower member of this formation and show that this part of the reservoir consists mostly of lithic quartz sandstone with poor physical characteristics. Using core observation, thin section identification, electronic microprobe, scanning electronic microscopy, X-ray diffraction, and inclusion fluorescence microscopy, we identified five major diagenetic processes: compaction, cementation, dissolution, metasomatism, and hydrocarbon charging. Compaction and cementation have negative effects on petrophysical properties (referred to porosity and permeability of sandstone in this paper), and dissolution improves these properties. Diagenesis is affected by the depositional environment, and clastic constituents control compaction and dissolution; burial history and the geotemperature field control diagenesis at the macroscopic scale, while hydrocarbon charging affects the degree of cementation and dissolution. As oil saturation increases, the percentage of calcareous cements decreases and the development of secondary dissolved pores improves. [ABSTRACT FROM AUTHOR]

Two anatomically preserved calamitean axes are reported for the first time from the Late Permian Wutonggou Formation in the southern Bogda Mountains, Xinjiang Uygur Autonomous Region, Northwest China. Based on the anatomical features, these axes are assigned to Arthropitys. A new species Arthropitys taoshuyuanensis sp. nov. is established. A. taoshuyuanensis sp. nov. possesses a large pith and comprises large pith cavity and a narrow perimedullary zone at the nodes and diaphragms at the internodes. Carinal canals are circular and surrounded by a single layer of metaxylem tracheids. Secondary xylem is divided into interfascicular rays and fascicular wedges. Interfascicular rays are initially four to five cells wide and taper abruptly centrifugally. Fascicular wedge consists of thick-walled tracheids and thin-walled fascicular ray cells. Radial tracheid walls have uniseriate or biseriate circular pits, or scalariform pits. The absence of growth rings in the Arthropitys specimens indicates that they probably lived in the wetland area under stable annual temperature and water sufficient conditions. [ABSTRACT FROM AUTHOR]