This paper presents an overview of the thermal studies dealing with heat flow data, lithospheric thermal thickness, basin thermal history, and thermal modeling in the North China Craton (NCC), with ...aim to provide ideas for geodynamical mechanism on the NCC destruction. Heat flow investigations show that only a small cold core is still preserved in the Ordos, western NCC, with low heat flow value of <50mW/m2. The mean heat flow in the eastern NCC is ~64mW/m2, close to the global continental average. The thermal lithosphere beneath the NCC thins eastward from ~140km in the west to ~80km in the east, with similar trend as the seismic lithosphere. However, there is a disparity in thickness between the thermal and seismic lithosphere, which is ~80km in the western NCC and decreases eastward. It implies an eastward thinning of the rheological boundary layer (RBL), which could be attributed to the lowering of asthenospheric viscosity due to dehydration of the subducted Pacific Plate. The geothermal regime confirms that the destruction occurred mainly in the eastern NCC, whereas the western NCC was only locally modified.
The sedimentary basins in the NCC have recorded distinct thermal histories since the Mesozoic. The Ordos Basin located in the western NCC experienced its maximum paleo-temperature in the Mesozoic, associated with compression, uplift and erosion. In contrast, most depressions of the Bohai Bay Basin in the eastern NCC experienced their maximum heat flow at the Cenozoic era, accompanied by episodic extension, rapid subsidence and sedimentation. Few boreholes in the Jiyang Depression recorded high heat flow of >80mW/m2 and surface denudation of ~2km in the Mesozoic.
The paper summarizes several dynamical models related to lithospheric thinning, including the mantle plume, delamination, subduction and lithospheric extension, and analyzes their near-surface tectono-thermal responses. Present results suggest that the regional thermal–chemical erosion by vigorous mantle convection within the big mantle wedge (BMW), possibly together with local delamination, may play a key role in the Mesozoic thinning, and the Cenozoic thinning is probably related to rifting and/or mantle plume. The thermal regime, combined with magmatism and numerical modeling, indicates that the NCC evolution has involved four distinct stages: modification in the Jurassic by Pacific Plate subduction; destruction during the Early Cretaceous under combined convective erosion, peridotite–melt interaction, and possible local delamination; multi-phase extension perhaps together with plume in the Late Cretaceous–Cenozoic; and cooling since the Late Cenozoic.
The Sichuan Basin, adjacent to the Emeishan large igneous province (ELIP), is one of the large petroliferous basins in China. The effects of the ELIP on the basin thermal history and hydrocarbon ...generation have attracted much attentions. A 2D viscoplastic model is applied to simulate the evolution of the Emeishan mantle plume, and then the effects of the plume on the Sichuan Basin are discussed. Constrained by the pre-eruption uplift and volcanic activity, the modeling infers that the initial hemispherical Emeishan plume had a radius of 85–150 km and an excess temperature of 150–300 K. The plume head extended laterally after reaching the bottom of the lithosphere. The plume head-lithosphere interaction led to lithosphere erosion and partial melting atop the plume head. Near the junction between the inner and intermediate ELIP zones, the lithosphere erosion was the most serious and the mantle melting degree was the highest. There the basalt might erupt from the Xiaojing-Qiaojia fault, and flow to the intermediate ELIP zone due to terrain. That can explain the concentration of Emeishan basalts in the intermedia ELIP zone and the abnormal high paleo-heat flow in the southwestern Sichuan Basin. Thermal convection induced in the upper mantle prevented the plume head from spreading beneath the lithosphere, and the lateral extent of the plume head was 1200–1300 km. Only a few unmelted plume materials could reach the central Sichuan Basin, which should be the boundary of the outer ELIP zone. The Permian basalts and high paleo-heat flow anomalies in the central Sichuan basin might be derived from the subsequent lithospheric extension, which led to the upwelling and decompression melting of both the plume and asthenosphere materials. Since the plume head couldn't migrate to the northeastern Sichuan Basin, the surface observations there should be independent of the Emeishan plume.
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•Lateral extent of the Emeishan plume head was predicted to be 1200–1300 km.•The 120 km-thick thermal lithosphere thinned to ~70 km due to plume erosion.•Mantle flow induced in the upper mantle prevent the plume head from spreading.•The farthest reach of the Emeishan plume head was the central Sichuan Basin.
The Upper Yangtze Craton (UYC) has stayed in a long-term stabilization state. Its thermal history can be portioned into two parts: secular evolutionary trend and short-lived thermal perturbations. ...The former is simulated by a two-dimensional forward transient thermal model, and the latter is discussed by reviewing previous studies. The numerical modeling indicates the UYC tended to be cooling as it adjusted to the asynchronous rates of change in the internal radiogenic heat production and in the convecting mantle temperature below the cratonic root. The average cooling rate of the UYC has been ~58 °C/Ga since the end of Archean, faster than that of the convecting mantle. The surface heat flow presents a decreasing trend from ~82 mW/m2 at 2.5 Ga to ~53 mW/m2 at present-day, which constructs the long-term evolutionary path. The thermal perturbations derived from the occasional tectono-thermal events, such as mantle plume activity and regional lithosphere extension, serves as paroxysmal factors. The thermal effects of the Emeishan mantle plume were very strong, yielding to the maximum heat flow anomaly of ~100 mW/m2 at the Late Permian. In contrast, the influences of regional lithosphere extension during both the early Paleozoic period and the Early Permian-Middle Triassic period were rather weak, resulting in a surface heat flow increase of <10 mW/m2. These thermal anomalies disappeared after a time period depending on the thermal relaxation without altering the stability of the UYC, and then the thermal evolution of craton returned to its original cooling route. The thermal history of the UYC, the overprinting of the secular cooling and the short-lived perturbations, helps better understand the craton evolution and provide the fundamental thermal data for petroliferous-basin analysis.
•Upper Yangtze Craton (UYC) is stable with surface heat flow of ~53 mW/m2.•Modeling shows surface heat flow has decreased from ~82 mW/m2 at 2.5 Ga to date.•Historic UYC remained warmer relative to the global average geotherm for cratons.•Secular cooling was perturbed by mantle plume activity and lithosphere extension.
•A thermochemical model is constructed to model the water transport in the process of slab flattening.•Water can be brought and released in the transition zone by slab under specific ...conditions.•Water transport behavior depends on the viscosity contrast between the hydrous layer and o mantle.•Melting at the lithospheric base by wet plume from flattening slab can explain the intraplate volcanoes.
Geophysical observations imply the intraplate volcanism in East Asia is related to dehydration of slab stagnating in the transition zone. To better understand the dynamics of such process, a thermochemical mantle convection model is constructed to simulate numerically the thermal evolution of slab and the transportation of water in the process of slab downgoing, flattening and stagnation. Equation of water transfer is included, and water effects on density and viscosity are considered. Model results indicate the warming of slab by surrounding mantle is rather slow. Water could be successfully dragged into the transition zone if the reference viscosity of the hydrous layer (with initial water of 2wt%) is higher than 1017Pas and that of mantle is 1021Pas. Wet plumes could then originate in the flat-lying part of the slab, relatively far from the trench. Generally, the viscosity of the hydrous layer governs the initiation of wet plume, whereas the viscosity of the overlying mantle wedge controls the activity of the ascending wet plumes – they are more active in the weaker wedge. The complex fluid flow superposed by corner flow and free thermal convection influences greatly the water transport pattern in the upper mantle. Modeling results together with previous modeling infer three stages of water circulation in the big mantle wedge: 1) water is brought into the mantle transition zone by downward subducting slab under some specific thermo-rheological conditions, otherwise water is released at shallow depth near wedge tip; 2) wet plume generates from surface of the flattening slab warmed by surrounding mantle, and 3) water spreads over the big mantle wedge. Wet plume from the flattening Pacific Plate arrives at the lithospheric base and induces melting, which can explain the intraplate Cenozoic volcanoes in East Asia.
The deep subduction of the Pacific Plate underneath East Asia is thought to have played a key role in the destruction of the North China Craton (NCC). To test this hypothesis, this paper presents a ...new 2-D model that includes an initial stable equilibrated craton, the formation of a big mantle wedge (BMW), and erosion by vigorous mantle convection. The model shows that subduction alone cannot thin the cold solid craton, but it can form a low-viscosity BMW. The amount of convective erosion is directly proportional to viscosity within the BMW ( eta sub(0bmw)), and the rheological boundary layer thins linearly with decreasing log sub(10)( eta sub(0b mw)), thereby contributing to an increase in heat flow at the lithospheric base. This model also differs from previous modeling in that the increase in heat flow decays linearly with t super(1/2), meaning that the overall thinning closely follows a natural log relationship over time. Nevertheless, convection alone can only cause a limited thinning due to a minor increase in basal heat flow. The lowering of melting temperature by peridotite-melt interaction can accelerate thinning during the early stages of this convection. The two combined actions can thin the craton significantly over tens of Myr. This modeling, combined with magmatism and heat flow data, indicates that the NCC evolution has involved four distinct stages: modification in the Jurassic by Pacific Plate subduction and BMW formation, destruction during the Early Cretaceous under combined convective erosion and peridotite-melt interaction, extension in the Late Cretaceous, and cooling since the late Cenozoic. Key Points * Craton destruction related to subduction is tested by numerical modeling * The overall thinning closely follows a natural log relationship over time * Combined convective erosion and peridotite-melt interaction cause destruction
In order to study the effects of the crystallinity of polyethylene with different densities on breakdown strength and conductance properties, this paper mainly tests the X-ray diffraction (XRD), ...different scanning calorimeter (DSC), direct current (DC) breakdown and conductance properties of low-density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), and high-density polyethylene (HDPE), and further analyzes the experimental results separately. The results show that an increase in the density of polyethylene leads to the continuous improvement of crystallinity, and an increase in crystallinity causes a significant decrease in the conduction current at the same field strength. The field strength corresponding to the two turning points in the conductance characteristic curve increases simultaneously.
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•Western North China Craton is stable but heat flow is not low.•Some tectonothermal events only heat and thin cratons and others can destroy them.•Cratons in Western China have long ...cooling histories disturbed by mantle plume.•Cratons in Eastern China were destroyed due to Pacific Plate subduction.
Craton’s thermal state is one of the main gateways to understand the craton dynamics. Three cratons in China, the Tarim, North China, and Yangtze cratons, are in different thermal states and differ in their stabilities. Low heat flow usually corresponds to stable craton butnotviceversa. The Tarim Craton is cold (∼44 mW/m2) and still keeps its stability now. The western North China Craton and the upper Yangtze Craton are not too cold (50–60 mW/m2) but also remain stable. The eastern North China Craton and the Middle-Lower Yangtze Craton are relatively hot with heat flow of 60–70 mW/m2, both have been heated and destroyed in the Mesozoic. All these cratons have experienced complex tectonothermal events since their formation. Some tectonothermal events only thin and heat craton but others can destroy craton. Several sedimentary basins are developed in these cratons, which recorded individual thermal histories. These thermal records could help to understand the thermal evolution of these cratons and provide constraints on craton dynamics including stability or destruction. The thermal results indicate parts of craton in western China (Tarim and Sichuan) have secular cooling histories, which were locally disturbed by mantle plume activities in the Permian. The Middle-Lower Yangtze Craton has undergone similar thermal evolution as the eastern North China Craton. All parts of cratons in eastern China might all have been destroyed due to subduction and dehydration of the Pacific Plate during the Mesozoic.
This retrospective cohort study aimed to determine the prevalence of anemia among patients with gynecological cancer prior to any treatment and to identify contributing factors associated with anemia ...in this group. We retrospectively analyzed data from female patients aged 18 and above, diagnosed with various forms of gynecological cancer at The Affiliated Hospital of Southwest Medical University between February 2016 and March 2021. Anemia was assessed based on the most recent CBC results before any cancer treatment. Eligibility was based on a definitive histopathological diagnosis. Key variables included demographic details, clinical characteristics, and blood counts, focusing on hemoglobin levels. Statistical analysis was conducted using logistic regression models, and anemia was defined as hemoglobin levels below 12 g/dL for women, according to WHO criteria. Of the 320 participants, a significant prevalence of anemia was found. Correlations between anemia and factors like age, educational level, and biological markers (iron, folic acid, and vitamin B12 levels) were identified. In our study, we found that the prevalence of anemia among patients with gynecological cancer prior to any treatment was 59.06%, indicating a significant health concern within this population. The study highlights a significant prevalence of anemia in patients with gynecological cancer, emphasizing the need for regular hemoglobin screening and individualized management. These findings suggest the importance of considering various characteristics and clinical variables in anemia management among this patient group. Further studies are needed to explore the long-term effects of these factors on patient outcomes and to develop targeted interventions.
Surface Heat flow (HF) can be calculated from the accumulation of radiogenic heat production (RHP) of arbitrarily subdivided thin layers of the crust and the residual HF. However, geothermal studies ...of scientific drilling projects around the world do not have clear vertical correspondence between HF and RHP, which has created a great controversy for the relationship between the two. For the first time, continuous temperature data, thermal conductivity and RHP measurements from the 3,008‐m‐deep Lujiang‐Zongyang Scientific Drilling in the northeastern Yangtze Craton, demonstrate that the abnormal HF is determined by high RHP rock (mean value, 10 μW/m3). The detailed spatial‐temporal study of magmatic activity in the Lujiang‐Zongyang basin shows the high RHP rock are concentrated in the early syenite‐monzonite period (133–131 Ma) in the northern basin. Two enrichment processes caused by late Neoproterozoic and Mesozoic subduction contribute to the formation.
Plain Language Summary
Heat flow (HF) is the most important parameter to characterize the thermal state of the Earth's interior. The surface HF can be calculated from the accumulation of heat production of subdivided thin layers of the crust and residual HF. However, no direct evidence of HF and heat production vertical variation has been found in the present continental scientific drilling wells. In this study, the contribution of the vertical variation of heat production to the surface HF is confirmed for the first time, and the HF values significantly higher than the regional background are determined by the high heat production rock. The study of the genesis of the high heat production rock concluded that they likely underwent two enrichment processes in the Late Neoproterozoic and Mesozoic, respectively, with the Late Mesozoic enrichment process being completed in a very short period of time.
Key Points
First direct evidence was found to confirm that surface heat flow is determined by the heat production
The relationship between natural gamma‐ray and heat production is reconstructed
The formation of rocks with high heat production result from two enrichment processes
The Bohai Bay Basin is the largest Cenozoic rift basin in eastern China, which exhibits a high rate of post‐rift subsidence deviating from the theoretical exponentially decay trend of thermal ...subsidence. The driving force for this phenomenon remains an outstanding question. Here we quantify the spatial and temporal distribution of the anomalous post‐rift subsidence by removing the thermal subsidence related to earlier stretching events from the observed tectonic subsidence. A multi‐episodic finite extension model is employed to estimate the stretching factors during rifting for nine profiles and 48 wells covering the basin. Our results show that the anomalous subsidence commenced at 12 Ma and the average anomalous subsidence rate accelerated from ∼19 m/Myr during the late Miocene to ∼75 m/Myr during the Quaternary, reaching ∼400 m at present. The anomalous subsidence is compared with published changes in dynamic topography arising from mantle flow. The temporal evolution of the dynamic topography generally fits the evolution of the anomalous subsidence, whereas variation in dynamic topography exhibits smaller amplitude and larger wavelength than our results. Small‐scale convection in the shallow mantle might play a role in generating short‐wavelength topography disturbances in the past tens of million years. Besides, the spatial distribution of the Quaternary anomalous subsidence generally coincides with fault movements in the past ∼2 Myr. We suggest mantle processes as well as fault activities might be possible mechanisms accounting for additional accommodation in the basin.
Key Points
We employ multi‐episodic extension modeling to quantify spatial and temporal patterns of the anomalous post‐rift subsidence
The anomalous subsidence commenced at 12 Ma and reaches ∼400 m at present, compatible with temporal changes in dynamic topography
Dynamic topography induced by mantle convection as well as fault activities may contribute to the anomalous subsidence
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