The Curvicubitidae is a Triassic cicada family with some taxa systematically debatable. Here a new curvicubitid species,Beaconiella tongchuanensis sp. nov., is established from the Middle Triassic Tongchuan Entomofauna in NW China. Restudy of the two Australian species of Beaconiella Evans, 1963 (B. fennahi and B. multivenata) confirms that they are different species and first reveals the hindwing venation of B. multivenata. A detailed restudy of Curvicubitus triassicus Hong, 1984 confirms the treatment of Curvicubitus as a junior synonym of Beaconiella. A key to all the six species of Beaconiella in Curvicubitidae is first given. Although reported from only three sites, the family Curvicubitidae potentially was globally distributed during the Middle–Late Triassic, implying that this family probably originated as early as the Early Triassic or even the Permian.
Permian sedimentary successions, widely distributed in the eastern Junggar Basin, may record key details on the closure of the Paleo-Asian Ocean in this region. Results of boreholes show that Permian strata is mainly composed of mudstone, sandy mudstone, siltstone, sandstone, sandy conglomerate, dolomite, and limestone. Detrital zircon U-Pb dating results of three sandstone samples yielded the calculated maximum ages of 296 Ma, 278 Ma and 293 Ma, indicating they possibly deposited during the Early Permian. Permian strata in the eastern Junggar Basin show similar rock associations and detrital zircon age data distribution patterns. Our new and compiled age data for sandstone samples in the eastern Junggar Basin and Bogda region yield predominant Paleozoic ages, close to their sedimentary ages. Such detrital zircon age data distribution patterns support the hypothesis that these Early Permian meta-clastic rocks in the eastern Junggar Basin and Bogda region were deposited in a subduction-related basin, and indicate an Early Permian Ocean prevented Precambrian detritus from the Central Tianshan block from depositing in the eastern Junggar Basin and Bogda region.
The evolution and reforming history of the Cenozoic basins in the northeastern Tibetan Plateau (NETP) are significant for understanding the northeastward growth of the Tibetan Plateau. The sediments in these basins archived the spatial-temporal patterns of the surface uplift and deformation processes in response to remote effects of growth of the NETP. Here, we present an integrated provenance analysis of the Ningnan basin in the NETP to provide direct insights into the basin evolution and further constraints of the Tibetan Plateau’s northeastward growth. In this study, the Cenozoic strata (Sikouzi, Qingshuiying, Zhang’enpu and Ganhegou formations) in the Ningnan basin yield complex detrital zircon age distributions featured by predominant age populations at 200–360 Ma and 360–540 Ma with minor Precambrian ages. Detrital zircon U-Pb ages indicate that the southwestern Ordos Block, the western Qinling orogenic belt, and the eastern Qilian orogenic belt are primary source areas. Additionally, adjacent local paleo-uplifts (e.g., Xihua, Nanhua, Xiangshan, Liupan Mts.) also provided minor volumes of sediment. In addition, conglomerates and paleocurrent directions of the Sikouzi–Ganhegou formations exhibit an apparent change since the late Miocene, revealing an obvious provenance shift. The quantitatively determined mixing proportions of the surrounding source areas also reveals that the early source-to-sink system was replaced during the deposition of the Ganhegou Formation. Combined with previous studies, we suggest that the formation of the Ningnan basin was controlled by normal faults in extension setting and experienced continued sediment accumulation during the Qingshuiying–Zhang’enpu period; since the late Miocene, the significant provenance shift reflects the obvious northeastward growth of the NETP and led to the extinction of the Ningnan basin.
Sparse felsic microgranitoid enclaves (FMEs) in the Shangshuiquan granite of the Zhangjiakou district, the north margin of the North China Craton, are fine-grained, dark-colored and exhibit subangular to subspherical shapes. They share similar mineral assemblages, chemical compositions, and zircon Hf isotope compositions to the host granite. New zircon U-Pb geochronology reveals that the FMEs crystallized at 156–153 Ma, while the Shangshuiquan granite formed at ca. 146 Ma. The FEMs are, therefore, 10 to 7 Ma older than the host granite. Combined with petrological evidence, we suggest that the FMEs are fragments of rapidly crystalized magmas, which were captured by the younger Shangshuiquan magma. Magmas of the FMEs and Shangshuiquan granite originated from the same reservoir. The Shangshuiquan granite is the result of small batches of magma being built up incrementally, and the FMEs belong to the earlier batches of magma. The lifespan of the Shangshuiquan magma reservoir exceeds 10 Ma. FMEs derived from cogenetic fragments have the potential to offer critical information about the formation process and timescale of granitic plutons.
Mafic enclaves in granites are generally considered to represent coeval mafic melts that derived from metasomatized mantle, which can provide valuable information about crust–mantle interaction. Exploring the genetic links between the mafic enclaves and their host monzogranite from the Triassic Zhashui Pluton, Qinling orogenic belt. The enclaves (220 ± 4.6 Ma) and the monzogranite (220 ± 2.8 Ma) display identical zircon U-Pb ages, and they also share similar trace element and zircon Lu-Hf isotopes, indicating a cognate source. The monzogranite displays zircon εHf(t) values of –0.99 to +1.98, while the mafic enclaves show similar values of –0.45 to +3.26; however, differences in mineral chemistry reveal different crystallization conditions. The amphibole from the mafic enclaves has higher temperature and pressure (757°C; 2.65 kbar) compared to those of the host monzogranite (733°C; 1.96 kbar), suggesting that mafic minerals in the enclaves crystallized at an early stage. Moreover, apatite in the mafic enclaves displays slightly higher volatile contents (0.72 wt%) than those of the monzogranite (0.66 wt%), indicating a volatile-rich condition. These results suggest that the mafic enclaves represent early hydrous mafic cumulates in the granitic chamber, and subsequent magma convection would have led to the formation of the mafic enclaves.
The Zaozigou gold deposit lies south of the Xiahe–Hezuo regional fault zone in the western Qinling orogenic belt and contains many intermediate to felsic dikes. Diorite porphyry, quartz diorite porphyry and biotite diorite porphyry are mineral-bearing dikes, whereas granite porphyry is unrelated to gold mineralization. To compare the relationship between different dikes and mineralization, this study analyzed the cathodoluminescence (CL) of zircon crystals in all four types of dikes exposed in the Zaozigou deposit, using a zircon typological classification. The formation temperature of the granite porphyry (734°C) was higher than the average temperature of the other three types of dikes (704°C), whereas the former’s alkalinity index (395) was lower than the average alkalinity index of the other three dikes (425). The ΣREE amount of granite porphyry (147.18 ppm) was smaller than the average ΣREE amount of the other three dikes (246.80 ppm) and its δEu value (0.33) was larger than the average δEu values of the other three dikes (0.30). The U-Pb ages of zircon in the four types of dikes were relatively consistent with the crystallization ages of approximately 240 Ma, which indicates that all four types of dikes intruded in the Middle Triassic. Compared to the other three ore-bearing dikes, the morphology of the zircon crystals in the barren dikes evolved from S13 to S5 and then returned to S13. These results indicate that the barren dike underwent an increase in temperature and a decrease in alkalinity, which may be an important reason for the absence of mineralization.
Iddingsitization is an aqueous alteration that is known to take place in meteorites and continental basalts providing a potential habitat for microbial life. However, little is known about the exact mode by which this reaction occurs in the hadal seafloor and its implication for the deep subsurface biosphere. A comprehensive investigation of hadal basalts from the southern Mariana Trench (SMT) conducted with microscopic examinations shows that iddingsite occurs as augite-hosted veins, rims, and mineral grains formed completely in place of augite within the SMT basalts. Carbon geochemistry indicates that organic matter with homogenous δ13C values between -27.8‰ and -27.2‰ might be biogenically accumulated in the SMT basalts. Furthermore, the close spatial relationships between carbonaceous matter (CM) and goethite in iddingsite point to microbial attachment to iddingsite minerals. Thus, iddingsitization might have fueled H2-utilizing microorganisms inhabiting the hadal oceanic crust, thereby leading to the formation of CM, as implied by oxygen isotopic compositions revealing low alteration temperatures (32–83°C) favorable for microbial growth. In all, microbial biosignatures associated with iddingsite in the SMT basalts are highlighted, and these results could pave the way for deciphering the deep subsurface biosphere at hadal zones.
Overpressure is widely developed in deep petroliferous strata in the hinterland of the Junggar Basin. However, a comprehensive understanding of its origin and effect on hydrocarbon distribution and enrichment remains lacking. In this study, we employ five empirical methods and comprehensive geological analysis to identify the origin of overpressure, and uncover the effect of overpressure on hydrocarbon enrichment. The results indicate that disequilibrium compaction is not a significant factor in overpressure generation. Instead, hydrocarbon generation, pressure transfer and diagenesis are the primary causes. The empirical methods support this conclusion. There is a positive correlation between overpressure intensity and source rock thickness and maturity. Notably, widespread cross-formational migration of hydrocarbon bearing fluid occurred, with sandstone overpressure exceeding that of adjacent shale in non-source strata. Furthermore, there is a distinct transformation from smectite to illite near the top of overpressure. Hydrocarbon generation pressurization and pressure transfer significantly effect hydrocarbon enrichment. The overpressure caused by hydrocarbon generation drives hydrocarbon migration and accumulation, establishing an optimal energy configuration between reservoir and cap rock. Faults play a crucial role in hydrocarbon vertical migration and pressure relief. The overpressure in reservoirs can reduce the porosity and permeability thresholds and enhance the charging capacity of oil and gas.
Hyperpycnal deposits has gradually emerged as a current research hotspot, with a special focus on lacustrine hyperpycnal deposits. However, our understanding of the formation mechanism and distribution of high-quality reservoirs in hyperpycnal deposits remains insufficient. In this study, the formation mechanism and distribution of high-quality reservoirs in the second member of the Sangonghe Formation are studied through sedimentology, petrology, and geochemistry, and 10 types of lithofacies were identified in the depositional sequences of the hyperpycnal flow. These can be summarized as gravelly bed to suspended load lithofacies association (GBS), gravelly reverse to normal compound-graded (GNR), coarse-grained sandy suspended load (CSS), and fine-grained sandy suspended load (FSS) lithofacies associations. The hyperpycnal system can be divided into four individual units: restricted channel, unrestricted channel, lobe, and levee. The reservoir quality varies with lithofacies. Gravelly bed load lithofacies has coarse grain sizes, high content of rigid minerals, and soluble components, such as magmatic rock fragments. Therefore, the gravelly bed load lithofacies reservoir has developed dissolution pores and well-preserved pore throats. Its reservoir quality is good. GBS and GNR are the main lithofacies associations in the restricted channel, where type I and type II reservoirs developed. The unrestricted channel is dominated by the CSS lithofacies association, with type III reservoirs developed. The lobe is dominated by the CSS and FSS lithofacies associations, with type III and type IV reservoirs developed. High-quality reservoirs mainly develop in the restricted and unrestricted channels, whereas reservoirs in the lobe have poor quality. The levees are dominated by siltstone and gray mudstone and are generally nonreservoirs.
Fracture effectiveness plays a key role in gas productivity of ultra-deep tight sandstone reservoirs, Kuqa depression, Tarim Basin. Based on cores, thin sections, well logging, well testing and production data, the study evaluated fracture effectiveness and illustrated its impacts on gas productivity. High-angle and vertical shear fractures are the most important types. Distribution of effective fractures shows great heterogeneous. Fracture effectiveness is influenced by tectonism, diagenesis and in-situ stress. Earlier fractures or fractures in close to gypsum rock are easier to be filled. Completely filled fractures can be reopened under late tectonism. Dissolution improves local fracture effectiveness. Minerals spanning fracture surfaces protect fracture effectiveness from late compression. Fractures filled with calcite can be activated by acidification. Effective fractures parallel to maximum horizontal principal compressive stress direction show larger aperture. Overpressure can decrease the effective normal stress to maintain fracture effectiveness. With exploitation, decline in pore pressure reduces fracture effectiveness. Linear density, aperture, and strike of effective fractures influence gas productivity. Effective fractures greatly enhance matrix permeability. Therefore, more abundant and larger aperture fractures are always corresponded to higher productivity. However, effective fractures also facilitate late water invasion, especially, both mutually parallel. Intense water invasion leads to rapidly declines in productivity.
In this study, the abundance of trace elements in the Baiyinhua depression coal and its relationship with the coal depositional environment was examined. (1) The content of arsenic in the Baiyinhua depression coal is that of a typically high arsenic coal from the late Mesozoic of China. The average arsenic content of Baiyinhua coal is 24.93 times, the highest being 132.71 times, that of Chinese coal. Coal rank is not a controlling factor affecting arsenic enrichment in coal. (2) Arsenic is primarily enriched in the syngenetic and diagenetic stages, the enrichment being most obvious in the syngenetic stage, with the intrusion of a magmatic-hydrothermal solution in the epigenetic stage also providing rich sources of arsenic. (3) The Baiyinhua coal-forming plant material is mainly woody plants. The coal seam was covered with deep water, the oxygen supply was very weak, the bacteria very few, the sedimentary environment of the swamp relatively calm and the degree of damage to the woody plants is very low. The minerals in the coal are mainly quartz and clay minerals. The coal ash yield of Baiyinhua is small, with SiO2, Al2O3, MgO, K2O, TiO2, MnO and P2O5 mainly being combined in the inorganic minerals of the coal.
Western Yunnan is an important area for Mesozoic marine strata, development of which helps to reconstruct paleoenvironments in the eastern Tethys. To bring knowledge of eastern Tethys up to that of western Tethys, this study focuses on its sedimentary characteristics and paleoenvironmental significance concentrating on the Xiushan section of the Simao Basin with analyses of the petrology, element geochemistry, and C-O-Sr isotopes. Samples are micrite, bioclastic limestone, marl, and mixed calcareous clastic rocks with the 87Sr/86Sr values of limestone ranging from 0.708255 to 0.708933; the δ13C values of the limestone range from -5‰ to +1.5‰ and the δ18O values range from -13.7‰ to -9.1‰. Based on the results, it is concluded that the Middle Jurassic limestones in the Simao Basin were deposited in a tidal flat environment with a strong influence of terrigenous input. At least one transgression event occurred during the depositional period. The paleoclimate as a whole changed from dry hot to humid hot and back to dry hot again. These enriched and improved results provide further data support for a comparison of the paleoenvironments between the eastern and western Tethys.
The utilization of CO2-Enhanced Coal Bed Methane (CO2-ECBM) technology is pivotal in realizing the environmentally responsible and efficient exploitation of Coalbed Methane (CBM) energy resources. The optimization of carbon capture, utilization, and storage (CCUS) for carbon reduction mandates a nuanced understanding of the diverse geological attributes present in CBM reserves globally. Traditional estimations of CO2-ECBM’s carbon sequestration potential have predominantly relied on rudimentary empirical models, notably those proposed by the United States Department of Energy (DOE), which overlook the intrinsic geological conditions and the physicochemical properties of subsurface fluids. Addressing these limitations, our study implements the advanced DR/Henry mixed adsorption model in tandem with the Peng-Robinson equation of state (PR-EOS). This approach meticulously identifies the critical parameters governing the mass exchange ratios between CO2 and CH4, pertinent to in-situ geological environments. Subsequently, we have formulated a comprehensive carbon sequestration potential assessment framework. This innovative model adheres to the mass conservation principles for individual CO2 and CH4 components, taking into account the specific surface and stratigraphic conditions prevalent. Employing this refined methodology, we evaluated the CO2-ECBM carbon sequestration potential of the 40 evaluation units of extensional, compressive, and cratonic continental coal bearing basins in China’s three major temperature-pressure systems across different depth domains and coal ranks within 2000 m. Our findings reveal that the theoretical carbon sequestration capacity of China’s continental coal-bearing basins is approximately 59.893 billion tons. Concurrently, the potential ECBM output stands at an estimated 4.92 trillion cubic meters, underscoring the substantial environmental and energy benefits inherent in harnessing CO2-ECBM technology effectively. The regional analysis revealed that North and Northwest China hold the highest sequestration and recovery potential, followed by the Northeast and Southern regions, respectively. Specific areas, including the eastern edge of the Ordos Basin and southern Junggar Basin, Qinshui, Huoxi, Xishan, and other areas in Shanxi, present promising future prospects for geological carbon storage in unrecoverable coal seams.
The karst groundwater of Cambrian limestone may become an important water source for industry and agriculture in the Pingdingshan area, and is also a potential threat to mining safety. Therefore, to find out the origin, flow paths, and hydrogeochemical processes of karst groundwater beneath the Pingdingshan coalfield, a total of 16 water samples were collected. Our findings confirmed that the karst groundwater is mainly recharged by precipitation. The precipitation can directly supply the deep aquifer of the karst water system through the southwest limestone outcrops, and this area mostly includes the southern part of mines No. 11, No. 9, and the hidden outcrops in the southern part of mine No. 2. What is more, the areas adjacent to the synclinal axis, including mines No. 10, No. 12, and No. 8, may be the main discharge areas. A mixing model of 87Sr/86Sr and Sr showed that in the southwest Pingdingshan coalfield, the proportion of precipitation decreased gradually from the recharge area to the discharge area, ranging from 89.1% to 17.1%. Besides, the northeast Pingdingshan coalfield is another recharge area for the whole karst system, thus, the infiltrating groundwater will indirectly supply the deep aquifer through Quaternary deposition near the mine No. 13. Our research results can provide theoretical support for the prevention and control of groundwater disasters and the development and utilization of regional groundwater resources in the coalfield in Northern China.
Underground space resources are important for the purposes of urban sustainable development and are a significant means by which to realize three-dimensional urban development. A reasonable and scientific evaluation of underground space resources is the foundation for the rational use of land resources and urban planning. On the basis of the geological conditions used by preceding researchers, this study adds the analysis of two influencing factors of social and economic value, alongside existing facilities and protection needs. The evaluation index is quantified and the comprehensive quality evaluation system of underground space resources is constructed. Finally, taking the Nanshan District of Shenzhen as an example, the evaluation of underground space resources is carried out. The results show that for shallow underground space, the comprehensive quality of underground space resources development in Nanshan District is generally high. Nantou, Nanshan and Yuehai streets are recommended as areas to actively develop underground space, whereas the Qianhai and Houhai areas are recommended to be used with caution in the development and construction of their underground space. In addition, this study also provides a reference for the purposes of underground space planning in the Nanshan district of Shenzhen.
Horsetailing is an important feature to identify the strike-slip structure and indicates the movement mode of the fault. However, the formation mechanism of horsetailing in the extensional regime remains unclear. In this study, the formation process of horsetailing is reproduced through physical experiment, simulating the Linnan sag in the extensional regime. The results of the physical experiment demonstrates that the formation of the horsetailing in the extensional regime requires two phases of non-coaxial stretching plus the segment of the principal fault. The stretching distance in the early phase is slightly smaller than that in the middle–late phase. The segment point of the principal fault is only the intersection of the horsetailing structure and the principal fault. The horsetailing formed in the extensional regime is different from that in the strike-slip regime. For the formation of structure, the principal fault is dip-slip in the early phase and then becomes an oblique-slip in the middle–late phase, and the horsetailing is composed of the middle–late new tensile faults. The fault properties of the horsetailing in the extensional regime has important guiding significance for the longitudinal fluid migration along the fault in petroliferous basins.
Water inrush is a common disaster in submarine mining. The key to preventing this disaster is to restrict the water-conducting fissure propagation induced by mining from forming a flow channel to communicate with the overlying aquifer. The mechanical behavior of hydraulic fractures under stress disturbance lies at the heart of the problem. Hence, the multiple parallel bond—grain-based model (multi Pb-GBM) is introduced to explore the hydraulic fracture evolution law of crystalline granite under the influence of stress disturbance. The results show that: hydraulic fracturing under stress disturbance is clearly affected by the stress wave frequency; the higher the frequency is, the more difficult it is to crack, but the crack propagation speed is faster after crack initiation; the propagation direction of a crack is deflected towards the propagation direction of the stress wave and the crack dip angle is controlled by the maximum principal stress; the internal crystal boundary of the same mineral is the most stable one among the three contacts, the contact boundary between different minerals being the most fragile one. This research not only has a practical application value to seabed mining engineering, but also has important theoretical significance in enriching deep rock mechanics theory.
Depleted shergottites record unique information about the primary composition and differentiation of the mantle of Mars. Their petrology, geochemistry, and cosmic ray exposure and crystallization ages suggest that most of them were excavated by a single young impact in the Amazonian-aged lava flows of the Tharsis and Elysium volcanic provinces. However, the difficulties of deriving consistent model ages for individual craters and inadequate evaluation of 3–7 km craters capable of ejecting martian meteorites have not been settled. Here we perform detailed geological investigations and crater statistics in patches of impact melt deposits for potential source craters of depleted shergottites with D > 3 km, especially those in the Tharsis and Elysium volcanic provinces. By excluding the effect of heterogeneous textures across ejecta deposits, which hinder straightforward extraction of superposed production populations, our systematically updated model ages reveal that Chakpar crater at the northern flank of Ascraeus Mons is the best-fit candidate. The local context of this crater permits establishing a link between the meteorites and specific lava flows. The long-lived volcanic center here may experience an eruption and/or local deposition hiatus for about 1.8 billion years, and abundant subsurface water existed when the impact occurred at about 1.1 million years.