Site U1446(19°50’N,85°44’E,at water depth 1430 m)was drilled during Expedition 353(Indian monsoon rainfall)of the International Ocean Discovery Program(IODP).It is located in the Mahanadi offshore basin,on...Site U1446(19°50’N,85°44’E,at water depth 1430 m)was drilled during Expedition 353(Indian monsoon rainfall)of the International Ocean Discovery Program(IODP).It is located in the Mahanadi offshore basin,on the northern Bay of Bengal.Sedimentation rates and contents of biocarbonates are high at this relatively shallow site.Using a micropaleontological approach,we examined planktonic and benthic foraminifera in the upper around 40 m of this site,spanning the last around 190 ka.A striking feature of the foraminiferal record is the occurrence of strong but varying dissolution although the site is located well above the modern lysocline.Such strong dissolution has never been reported in this area.We estimated the flux of foraminifera and quantified the ratio of benthic foraminifera over total foraminifera(benthic/total foraminifera)along with the foraminifer fragmentation index in order to characterize past changes in this above-lysocline dissolution.This study reveals a clear glacialinterglacial contrast,with a stronger dissolution during marine isotope stages(MISs)1 and 5 than during MISs 2–4 and 6.Such a difference in preservation is likely to have a strong impact on geochemical proxies measured on foraminifera.Our new observations call for an in-depth study of the causes of such above-lysocline dissolution in the region,and an evaluation of its impact on the foraminifera-based proxies used for paleoenvironmental reconstruction.展开更多
This study assesses the capability of a coarse-resolution ocean model to replicate the response of the Southern Ocean Meridional Overturning Circulation(MOC) to intensified westerlies,focusing on the role of the eddy ...This study assesses the capability of a coarse-resolution ocean model to replicate the response of the Southern Ocean Meridional Overturning Circulation(MOC) to intensified westerlies,focusing on the role of the eddy transfer coefficient(κ).κ is a parameter commonly used to represent the velocities induced by unresolved eddies.Our findings reveal that a stratification-dependent κ,incorporating spatiotemporal variability,leads to the most robust eddy-induced MOC response,capturing 82% of the reference eddy-resolving simulation.Decomposing the eddy-induced velocity into its vertical variation(VV) and spatial structure(SS) components unveils that the enhanced eddy compensation response primarily stems from an augmented SS term,while the introduced VV term weakens the response.Furthermore,the temporal variability of the stratification-dependent κ emerges as a key factor in enhancing the eddy compensation response to intensified westerlies.The experiment with stratification-dependent κ exhibits a more potent eddy compensation response compared to the constant κ,attributed to the structure of κ and the vertical variation of the density slope.These results underscore the critical role of accurately representing κ in capturing the response of the Southern Ocean MOC and emphasize the significance of the isopycnal slope in modulating the eddy compensation mechanism.展开更多
Wind load is a control load that affects the safety of structures in the design of ocean platforms. It has not only direct and powerful effects that may cause structure resonance but also has indirect effects causing ...Wind load is a control load that affects the safety of structures in the design of ocean platforms. It has not only direct and powerful effects that may cause structure resonance but also has indirect effects causing waves or currents in the ocean. By analyzing the domestic and international norms, this study <span style="letter-spacing:0.1pt;font-family:Verdana;font-size:12px;">pre<span style="font-family:Verdana;font-size:12px;">sents a review of calculation methods of wind load on ocean platforms, which <span style="letter-spacing:-0.15pt;font-family:Verdana;font-size:12px;">belongs to large-scale non-entity structure used in the open sea while sur<span style="font-family:Verdana;font-size:12px;">round<span style="letter-spacing:-0.1pt;font-family:Verdana;font-size:12px;">ing wind has no fixed direction. Current computations according to the<span style="font-family:Verdana;font-size:12px;"> norms are not accurate, which even not takes the force of the wind against the surf<span style="letter-spacing:-0.1pt;font-family:Verdana;font-size:12px;">ace perpendicular to the structure into consideration. Additionally, thi<span style="font-family:Verdana;font-size:12px;">s study also introduces and compares the lift model of platforms based on different <span style="letter-spacing:-0.1pt;font-family:Verdana;font-size:12px;">theories, such as vortex-excitation and vibration, engineering structure dy<span style="font-family:Verdana;font-size:12px;">namics, gas flow pressure theory, analyzing their applicability, advantages, and disadvantages. This paper analyzes the limitations and applicable conditions of the existing calculation method itself, such as the lift model is suitable for the existence of stable vortex wake;the calculation method of the structural dynamics of marine engineering must be combined with the wind tunnel test and consider the mistakes caused by the position relationship;the numerical simulation method is accurate but tedious. This study provides an insight into the calculation methods of lift in designing ocean platforms, including the <span style="letter-spacing:0.1pt;font-family:Verdana;font-size:12px;">finite element method for simulating fluid force and updating formulas in<span style="font-family:Verdana;font-size:12px;"> Chinese norms.展开更多
With their suitable habitats significantly affected by climate change and human activities,most of the seven globally recognized sea turtles are facing endangerment.In order to predict their present and future(2090−21...With their suitable habitats significantly affected by climate change and human activities,most of the seven globally recognized sea turtles are facing endangerment.In order to predict their present and future(2090−2100)potentially suitable habitats,we utilized the MaxEnt model,incorporating occurrence data for various sea turtle species and environmental datasets under current conditions,as well as under two climate scenarios from the Shared Socioeconomic Pathways(SSP1-2.6 and SSP5-8.5).Our findings showed that the key environmental variables,such as temperature and distance from shore predominantly influence the prediction on the potentially suitable habitat for sea turtles.The most highly suitable habitats for sea turtles are predominantly found in the tropical coastal waters bordering continents,including South and North America,Asia,and Australia.Under the climate scenarios of SSP1-2.6 and SSP5-8.5 for 2090−2100,the anticipated loss of potential suitable habitats is expected to surpass any potential gains for all sea turtle species.The Kemp’s ridley sea turtle(Lepidochelys kempii)is especially vulnerable,with its potentially suitable habitat area projected to decrease by 0.43%under SSP1-2.6 scenario to 6.15%under SSP5-8.5 scenario.In contrast,the most resilient Dermochelys coriacea is projected with a reduction of 1.02%under SSP1-2.6 and 0.57%under SSP5-8.5 in its potentially suitable habitat.These varying responses to climate change inferred the necessity for species-specific conservation strategies.However,only 9.9%of the integrated potentially suitable habitat is protected within the World Database on Protected Areas(WDPA),which suggested the extending of WDPA for more efficiency on the sea turtle conservation.展开更多
Ecological water supplement projects have been implemented in many coastal wetlands,influencing saltmarsh vegetation restoration by altering tidal creek development.To clarify the effectiveness of ecological water sup...Ecological water supplement projects have been implemented in many coastal wetlands,influencing saltmarsh vegetation restoration by altering tidal creek development.To clarify the effectiveness of ecological water supplement on tidal creek development and saltmarsh vegetation restoration,time series of high-resolution remote sensing images from2000 to 2021 were used to extract and analyze tidal creeks and saltmarsh vegetation in the Diaokou Estuary Reserve.The results are summarized as follows:(1)All tidal creek indices,except curvature,exhibited a significant linear increase with time,while curvature initially decreased and increased afterwards.The 5-year cumulative ecological water supplement volume was significantly positively correlated(R^(2)>0.7)with all tidal creek indices.(2)During the same period,most landscape pattern metrics of Phragmites australis increased,while those of Tamarix chinensis initially increased and then declined.Although the class area(CA)of Suaeda salsa increased with time,its perimeter-area fractal dimension(PAFRAC)and aggregation index(AI)fluctuated.(3)The CA of P.australis and S.salsa was significantly positively correlated with most tidal creek indices except curvature,while that of T.chinensis showed no significant correlation with any tidal creek index.Moreover,the AI and PAFRAC of P.australis were significantly positively correlated with fractal dimension,frequency/curvature of tidal creeks,respectively,while those of S.salsa and T.chinensis exhibited no significant correlation.In summary,the ecological water supplement project enhanced tidal creek development in coastal wetlands,promoting the restoration of P.australis and S.salsa,while having little impact on the restoration of T.chinensis.展开更多
The Shanan sag in the central-western Bohai Bay Basin hosts high-quality Paleogene source rocks within the Shahejie Formation’s third member(E_(2)s_(3)).Despite hydrocarbon indications in Cenozoic strata,no commercia...The Shanan sag in the central-western Bohai Bay Basin hosts high-quality Paleogene source rocks within the Shahejie Formation’s third member(E_(2)s_(3)).Despite hydrocarbon indications in Cenozoic strata,no commercial accumulations have been discovered.An integrated approach combining geochemical analysis,fluid inclusion thermometry,apatite fission-track(AFT)thermochronology,and basin modeling was employed to unravel the paleo-geothermal regime and hydrocarbon generation history of E_(2)s_(3) source rocks.AFT data from the Shahejie Formation’s second member(E_(2)s_(2))reveal a tectonothermal event at 25 Ma that accelerated E_(2)s_(3) maturation.Outside three sub-sag depocenters,current E_(2)s_(2) reservoir temperatures remain below the 25 Ma paleo-geothermal maxima despite subsequent Neogene burial.Hydrocarbon-bearing brine inclusions in E_(2)s_(2) reservoirs exhibit peak homogenization temperatures(Th)at 25 Ma,with minimal high-temperature signals,indicating that E_(2)s_(3) hydrocarbon generation peaked during the Paleogene thermal event,with limited late-stage accumulation.The regional effects of the Dongying Movement necessitate thick Neogene sedimentation to compensate for the 25 Ma paleo-geothermal anomaly.Our findings emphasize targeting Neogene depocenters in petroleum exploration to mitigate the inhibitory effects of high paleo-heat flow on late hydrocarbon generation,thereby enhancing current accumulation potential.展开更多
Taking the GY8HC well in the Gulong Sag of the Songliao Basin,NE China,as an example,this study utilized high-precision zircon U-Pb ages from volcanic ashes and AstroBayes method to estimate sedimentation rates.Throug...Taking the GY8HC well in the Gulong Sag of the Songliao Basin,NE China,as an example,this study utilized high-precision zircon U-Pb ages from volcanic ashes and AstroBayes method to estimate sedimentation rates.Through spectral analysis of high-resolution total organic carbon content(TOC),laboratory-measured free hydrocarbons(S_(1)),hydrocarbons formed during pyrolysis(S_(2)),and mineral contents,the enrichment characteristics and controlling factors of shale oil in an overmature area were investigated.The results indicate that:(1)TOC,S_(1),and S_(2)associated with shale oil enrichment exhibit a significant 173×10^(3)a obliquity amplitude modulation cycle;(2)Quartz and illite/smectite mixed-layer contents related to lithological composition show a significant 405×10^(3)a long eccentricity cycle;(3)Comparative studies with the high-maturity GY3HC well and moderate-maturity ZY1 well reveal distinct in-situ enrichment characteristics of shale oil in the overmature Qingshankou Formation,with a significant positive correlation to TOC,indicating that high TOC is a key factor for shale oil enrichment in overmature areas;(4)The sedimentary thickness of 12-13 m corresponding to the 173×10^(3)a cycle can serve as the sweet spot interval height for shale oil development in the study area,falling within the optimal fracture height range(10-15 m)generated during hydraulic fracturing of the Qingshankou shale.Orbitally forced climate changes not only controlled the sedimentary rhythms of organic carbon burial and lithological composition in the Songliao Basin but also influenced the enrichment characteristics and sweet spot distribution of Gulong shale oil.展开更多
Subduction zones are critical interfaces for lithospheric volatile fluxes,where complex tectonic and geochemical interactions facilitate the release of gases and fluids from deep-seated reservoirs within the Earth’s ...Subduction zones are critical interfaces for lithospheric volatile fluxes,where complex tectonic and geochemical interactions facilitate the release of gases and fluids from deep-seated reservoirs within the Earth’s crust.Mud volcanism,as a dynamic manifestation of these processes,contributes CH_(4)emissions that influence the global methane budget and impact marine ecosystems.Although∼2000 CH_(4)-rich mud extrusions have been documented in subduction zones globally,the geological origins and subduction-related geochemical and tectonic mechanisms driving these emissions remain poorly understood.This research examines the Makran subduction zone which hosts one of the world’s largest accretionary wedge and extensive CH_(4)-rich mud extrusions,as a model system.Integrated geochemical,geophysical,and geological observations reveal that thermogenic CH_(4)and clay-rich fluidized muds originate from deeply buried Himalayan turbidites(underthrusted sediments),driven by organic-rich sediment maturation and high fluid overpressure.Key tectonic features,including thrust faults,overburden pressure of wedge-top sediments,normal faults,brittle fractures,and seismicity,facilitate CH_(4)-rich mud extrusions into the hydrosphere and atmosphere.The extruded gases are predominantly CH_(4),with minor C_(2)H_(6),C_(3)H_(8),i-C_(4)H_(10),and n-C_(4)H_(10)while the mud breccia exhibits a chemical composition dominated by SiO_(2),Al_(2)O_(3),and Fe_(2)O_(3),enriched with trace elements(Rb,Zr,and V)and clay minerals,quartz,and carbonates.Geochemical indicators suggest intense chemical weathering and mature sediments classifying the mud breccia as litharenite and sub-litharenite,indicative of deep burial and compaction.These findings model the evolution of CH_(4)-rich mud extrusions through three geological stages:(i)Eocene to Early Miocene pre-thermogenic formation of the CH_(4)-rich source,(ii)Middle Miocene to Pliocene syn-thermogenic CH_(4)and fluidized mud generation,and(iii)Pleistocene to Recent post-thermogenic CH_(4)-rich fluidized mud migration.These findings underscore the critical yet often overlooked role of subduction-related geochemical and tectonic processes in CH_(4)generation and emission,with significant implications for the global CH_(4)budget and marine ecosystems.展开更多
Marine heat waves(MHWs), characterized by extreme warm sea surface temperature events, frequently occur in Chinese marginal seas. However, the seasonal variation and joint distribution of MHWs in the Bohai Sea have no...Marine heat waves(MHWs), characterized by extreme warm sea surface temperature events, frequently occur in Chinese marginal seas. However, the seasonal variation and joint distribution of MHWs in the Bohai Sea have not been fully described. Therefore, we conducted a systematic investigation of MHWs in this region. Our findings indicate that the frequency of MHW is low during winter, with long duration and weak intensity, while in summer, it is opposite, being high in the frequency, and shorter but stronger. Notably, in summer, the Laizhou and Liaodong bays exhibit a relatively long total day of MHWs compared to other areas in the Bohai Sea. Furthermore, our analysis of the joint distribution of MHWs, considering both duration and intensity, reveals significant seasonal variations. To provide practical insights for marine ranching, we have also investigated time series of MHWs at several specific stations and computed the correlation coefficients between MHW intensity and potential influential factors. Results suggest that sea surface height, cloud cover, wind stress, and wind stress curl are significantly correlated with MHW intensity, although these relationships vary geographically and seasonally. Overall, these findings elucidate the seasonal variation and potential influential factors of MHWs in the Bohai Sea and offer insights for decision-making and planning in marine ranching.展开更多
The Tarim basin experienced a complex tectonic evolutionary history from Sinian to Ceno zoic. Eight largescale and more than 20 subordinate unconformities defining tectonosequences of dif ferent protobasins formed in ...The Tarim basin experienced a complex tectonic evolutionary history from Sinian to Ceno zoic. Eight largescale and more than 20 subordinate unconformities defining tectonosequences of dif ferent protobasins formed in various tectonic settings have been identified within the Phanerozoic in the Tarim basin, their distribution determining the general characteristics of sequence stratigraphic framework of the basin. Tectonostratigraphic unit I （magasequence） consists mainly of the Sinian Sys tem, which formed in a rift or aulacogen setting and can been subdivided into two subordinate strati graphic units （supersequences）. Unconformity （Tgg） between Sinian and Cambrian with surface karsti fication is regarded as a postrift unconformity. Tectonostratigraphic unit II comprises the Cambrian and the Ordovician and can be divided into six subordinate tectonostratigraphic units, recording the tectonogeographic evolution of the prototype basins from Cambrian to Early Ordovician passive car bonate continental margin or cratonic depression and the Late Ordovician submarine to neritic ret roarc foreland and cratonic depressions. The tectonic uplift related to the formation of the unconformity Tg5-2 resulted in the remarkable change in basin tectonic setting from a passive divergent to an active convergent, with the development of the Tazhong （塔中） uplift, the Tangguzibasi （塘古孜巴斯）, and the northern depression at the end of the Middle to the early Late Ordovician. The widespread angular unconformity Tg5 formed by a relatively strong compressive deformation, which caused an abrupt tec tonogeographic change of the basin from abyssal to a neritic setting in response to the collision andassociated tectonic deformation of the North Kunlun （昆仑） orogenesis during the Late Ordovician to the Early Silurian. Tectono stratigraphic unit III is composed of the Silurian and the Lower to Middle Devonian and character ized by the development of fluvial or deltaic and clastic littoral and neritic deposits. Largescale terrigenous clastic depositional wedges progra dated from the north to south in the southeast ern slope of the basin indicate the continuously shallowing and uplifting along the northern basin margin. Tectonostratigraphicunit IV includes the Upper Devonian, Carboniferous, and Permian and can be classified into two sub ordinate tcctonostratigraphic sequences. The angular unconformity （Tg3） at the base of the unit is the most widespread unconformity and the strong compression and uplift of the basin during this period has been suggested to be related to the collision of the Tianshan （天山） orogenesis and resulted in fun damental change in tectonic geomorphology with higher to the northeast and lower to the southwest. Tectonostratigraphic unit IV records another tectonic cycle from weak extension to compression in ba sin setting and is composed mainly of nearshore elastic deposits of embayment basin f＇flls. From the Triassic, the Tarim basin evolved into a period characteristic of development of intracontinental de pressions and marginal foreland basins and experienced several cycles from rapid subsidence to strong uplift and deformation, resulting in superimposition and reformation of differently orientated proto basins filled with a series of regional depositional cycles bounded by major unconformities and consist ing of extremely thick alluvial and lacustrine deposits. The Kuqa foreland depression in the northwest ern basin margin developed since the Triassic and deposited a elastic wedge of the Mesozoic to Cenozoic more than I00 000 m in thickness, which progradated and thin towards the southern Tabei （塔北） forebulge. The largescale sedimentary cycles from alluvial, fluvial to lacustrine, and finally fluvial deposits are attributed to the results of foreland tectonisim from active to relatively quiet stages. The foreland tectonisim was active during the Triassic, relatively quiet during the Jurassic, and active again from the Late Jurassic to the Cretaceous. To the Eogene, the depression subsided again and the com pression intermittently increased, resulting in a series of faulted and folded structural belts.展开更多
A Discrete Element Method （DEM） model is developed to study the particle break- age effect on the one-dimensional compression behavior of silica sands. The ＇maximum tensile stress＇ breakage criterion considering m...A Discrete Element Method （DEM） model is developed to study the particle break- age effect on the one-dimensional compression behavior of silica sands. The ＇maximum tensile stress＇ breakage criterion considering multiple contacts is adopted to simulate the crushing of circular particles in the DEM. The model is compared with published experimental results. Com- parison between the compression curves obtained from the numerical and experimental results shows that the proposed method is very effective in studying the compression behavior of silica sands considering particle breakage. The evolution of compression curves at different stress levels is extensively studied using contact force distribution, variation of contact number and particle size distribution curve with loading. It is found that particle breakage has great impact on com- pression behavior of sand, particularly after the yield stress is reached and particle breakage starts. The crushing probability of particles is found to be macroscopically affected by stress level and particle size distribution curve, and microscopically related to the evolutions of contact force and coordination number. Once the soil becomes well-graded and the average coordination number is greater than 4 in two-dimension, the crushing probability of parent particles can reduce by up to 5/6. It is found that the average contact force does not always increase with loading, but increases to a peak value then decreases once the soil becomes more well-graded. It is found through the loading rate sensitivity analysis that the compression behavior of sand samples in the DEM is also affected by the loading rate. Higher yield stresses are obtained at higher loading rates.展开更多
Two kinds of basalts with different chemical compositions were obtained in the Sanshui Basin,they share the same eruption period. Although they have significant differences in major and trace element concentrations,th...Two kinds of basalts with different chemical compositions were obtained in the Sanshui Basin,they share the same eruption period. Although they have significant differences in major and trace element concentrations,their isotopic ratios suggest a similar magma source. Based on mineral geochemical analysis,orthopyroxene with reaction rim and zoned clinopyroxene are observed in Zidong(ZD)basalts,but not found in Wangjiegang(WJG) basalts. Linear scanning of these minerals suggests compositional variation between within-plate tholeiite and within-plate alkali-basalt. Presence of a doublelayer magma chamber under the Sanshui Basin,and occurrence of magma mixing between upper and lower chambers is proposed. This magma mixing leads to different chemical composition and mineral constitution of two kinds of basalts,as well as reaction rim and compositional variation of minerals in ZD basalts.展开更多
Using the occurrence characteristics of bubble plumes in the South China Sea as a reference, this paper continues to study the seismic responses produced by bubble plumes in the cold seepage active region. To make the...Using the occurrence characteristics of bubble plumes in the South China Sea as a reference, this paper continues to study the seismic responses produced by bubble plumes in the cold seepage active region. To make the plume modelling scheme more reasonable, we modified the original modelling scheme and reconstructed a plume water body model based on the variation of its radius as bubbles rise in seawater. The plume seismic records of shot gathers were obtained by forward simulation. The seismic records of single shot show obvious characteristics of a scattering wave field and the periodic characteristics of the model. Seismic records of shot gathers were processed using prestack depth migration. The boundary of its imaging section has a good convergence effect. The migration sections can be imaged distinctly with higher accuracy. The aforementioned studies once again laid a foundation for the further study of the seismic responses produced by plumes. They also gradually probed a more suitable seismic data processing method for plumes and provided a theoretical guidance for the identification of plumes.展开更多
The transesterification of palm oil and methanol catalyzed by Br?nsted acidic ionic liquids was investigated. Four eco-friendly Br?nsted acidic ionic liquids were prepared and their structures were characterized by NM...The transesterification of palm oil and methanol catalyzed by Br?nsted acidic ionic liquids was investigated. Four eco-friendly Br?nsted acidic ionic liquids were prepared and their structures were characterized by NMR, FT-IR and TG–DTG. The results demonstrated that [CyN_(1,1)PrSO_3H][p-TSA] was more efficient than the other ionic liquids and chosen as catalyst for further research. The influences of various reaction parameters on the conversion of palm oil to biodiesel were performed, and the orthogonal test was investigated to seek the optimum reaction conditions, which were illustrated as follows: methanol to oil mole ratio of 24:1, catalyst dosage of 3.0 wt% of oil, reaction temperature of 120 °C, reaction time of 150 min, and the biodiesel yield achieved 98.4%. In addition, kinetic study was established for the conversion process, with activation energy and preexponential factor of 122.93 k J·mol^(-1) and 1.83 × 10^(15), respectively. Meanwhile, seven-time recycling runs of ionic liquid were completed with ignorable loss of its catalyst activity. The refined biodiesel met the biodiesel standard EN 14214.展开更多
Environmental load is the primary factor in the design of offshore engineering structures and ocean current is the principal environmental load that causes underwater structural failure. In computational analysis, the...Environmental load is the primary factor in the design of offshore engineering structures and ocean current is the principal environmental load that causes underwater structural failure. In computational analysis, the calculation of current load is mainly based on the current profile. The current profile model, which is based on a structural failure criterion, is conducive to decreasing the uncertainty of the current load. In this study, we used prototype monitoring data and the empirical orthogonal function(EOF) method to investigate the current profile in the South China Sea and its correlation with the design of underwater structural strength and the dynamic design of fatigue. The underwater structural strength design takes into account the size of the structure and the service water depth. We propose profiles for the overall and local designs using the inverse first-order reliability method(IFORM). We extracted the characteristic profile current(CPC) of the monitored sea area to solve dynamic design problems such as vortex-induced vibration(VIV). We used random sampling to verify the feasibility of using the EOF method to calculate the CPC from the current data and identified the main problems associated with using the CPC, which deserve close attention in VIV design. Our research conclusions provide direct references for determining current load in this sea area. This analysis method can also be used in the analysis of other sea areas or field variables.展开更多
Tengchong Cenozoic volcanics that have record key information on the tectonic evolution and mantle features of the southeast margin of the Tibetan Plateau are of great importance because of its unique eruption history...Tengchong Cenozoic volcanics that have record key information on the tectonic evolution and mantle features of the southeast margin of the Tibetan Plateau are of great importance because of its unique eruption history spanning the entire Quaternary period. Magma origin and evolution of Tengchong Cenozoic volcanic rocks were studied on the basis of Nd-Sr-Pb isotope and major and trace element data from different eruptions in the Ma＇anshan area. Different samples within one eruption show relative identical lithologies, chemical and isotopic compositions. However, the geochemical features for the five eruptions are distinct from each other. These volcanic rocks show low Mg# values （〈45）, moderate to high fractionation of LREEs and HREEs, and enrichment of Pb and Ba and depletion of Nb. Tengchong Cenozoic volcanic rocks were derived from an enriched mantle based on Nd-Sr-Pb isotopic studies. And lines of evidence show that crustal contamination should be involved before the eruption of different periods of Tengchong Cenozoic volcanic rocks. Older subducted components may be responsible for adakite recycling at various stages of evolution, which results in the origin of the enriched mantle source magma accounting for the isotopic features of Tengchong Cenozoic volcanic rocks. Segregated primitive magma pulsating injected into magma chamber, fractional crystallized and contaminated with crust component. Finally, magmas with distinct chemical and isotopic compositions for each eruption formed. The extension of the northeast segment of the Yingjiang tectonic belt triggered the pulsating eruption of the Cenozoic volcanics in the Tengchong area.展开更多
To study the bubble plume's seismic response characteristics,the model of a plume water body has been built in this article using the bubble-contained medium acoustic velocity model and the stochastic medium theor...To study the bubble plume's seismic response characteristics,the model of a plume water body has been built in this article using the bubble-contained medium acoustic velocity model and the stochastic medium theory based on an analysis of both the acoustic characteristics of a bubble-contained water body and the actual features of a plume.The finite difference method is used for forward modelling,and the single-shot seismic record exhibits the characteristics of a scattered wave field generated by a plume.A meaningful conclusion is obtained by extracting seismic attributes from the pre-stack shot gather record of a plume.The values of the amplitude-related seismic attributes increase greatly as the bubble content goes up,and changes in bubble radius will not cause seismic attributes to change,which is primarily observed because the bubble content has a strong impact on the plume's acoustic velocity,while the bubble radius has a weak impact on the acoustic velocity.The above conclusion provides a theoretical reference for identifying hydrate plumes using seismic methods and contributes to further study on hydrate decomposition and migration,as well as on distribution of the methane bubble in seawater.展开更多
Compared with the laboratory acoustic measurement of sediment samples, the in-situ acoustic measurement in marine sediment is considered more accurate and rehable, because it covers all of the surrounding environment ...Compared with the laboratory acoustic measurement of sediment samples, the in-situ acoustic measurement in marine sediment is considered more accurate and rehable, because it covers all of the surrounding environment factors and avoids the disturbance during the course of sampling and transporting of sediment samples. A new multi-frequency in-situ geoacoustic measurement system （MFIS^AMS） has been developed. The system can provide acoustic vdocity （compressional wave） and attenuation profiles of the uppermost 4 - 8 m sediment in the seafloor. It consists of 8 channels with 12 frequencies （multi-frequencies） and 0.5 - 2 MHz sampling rates. The data collected can be transmiuted in real-time. Associated with inclinometer and altimeter, it can provide the data for depth emendation. Acoustic velocity and attenuation data have been obtained from two in-situ experiments conducted in the Hangzhou Bay.展开更多
In this paper, incised valley filling deposits, which formed an important pathway system for long-distance hydrocarbon migration, are discussed in detail based on core and logging data. The sequence SQy23 of the Creta...In this paper, incised valley filling deposits, which formed an important pathway system for long-distance hydrocarbon migration, are discussed in detail based on core and logging data. The sequence SQy23 of the Cretaceous Yaojia Formation is the main hydrocarbon-bearing layer in the Fulaerji Oilfield. The hydrocarbon source of the oilfield is the Qijia-Gulong Sag which is about 80 km away from the Fulaerji Oilfield. The transport layer of long-distance hydrocarbon migration is the overlapped sandstone complex which fills the incised valley. The incised valley developed during the depositional period from the late Qingshankou Formation to the early Yaojia Formation of Cretaceous （SQqna-SQy0 was about 70 km long and 20 km wide, and extended in the NW-SE direction. The overlapped filling of the incised valley mainly occurred in the expanding system tract of the third-order sequence SQy23 （ESTy23）. Towards the basin, incised valley filling deposits overlapped on the delta developed in the early period, and towards the basin margin, incised valley filling deposits were covered by the shore-shallow lacustrine sandy beach bar developed in the maximum flooding period. All of the delta, the incised valley filling and the shore-shallow sandy beach bar are sandstone-rich, and have high porosity and permeability, and can form an effective hydrocarbon migration and accumulation system. Deltaic sand bodies collected and pumped hydrocarbon from the active source, incised valley filling depositional system completed the long-distance hydrocarbon migration, and lithological traps of shore-shallow lacustrine sandy beach bar accumulated hydrocarbon. The incised valley filling sequences are multi-cycle： an integrated shortterm filling cycle was developed on the erosion surface, and the sequences upward were mud-gravel stone, medium-fine sandstone containing terrigenous gravels and muddy pebbles with cross bedding, silty mudstone with ripple bedding, and mudstone. The incised valley filling deposits are characterized by a strong heterogeneity and the main hydrocarbon migration pathway is the medium-fine sandstone interval.展开更多
A micromechanical investigation on simple shear behavior of dense granular assemblies was carried out by discrete element method.Three series of numerical tests were performed to examine the effects of initial porosit...A micromechanical investigation on simple shear behavior of dense granular assemblies was carried out by discrete element method.Three series of numerical tests were performed to examine the effects of initial porosity,vertical stress and particle shape on simple shear behavior of the samples,respectively.It was found that during simple shear the directions of principal stress and principal strain increment rotate differently with shear strain level.The non-coaxiality between the two directions decreases with strain level and may greatly affect the shear behavior of the assemblies,especially their peak friction angles.The numerical modelling also reveals that the rotation of the principal direction of fabric anisotropy lags behind that of the major principal stress direction during simple shear,which is described as fabric hyteresis effect.The degrees of fabric and interparticle contact force anisotropies increase as particle angularity increases,whereas the orientations of these anisotropies have not been significantly influenced by particle shape.An extended stress–dilatancy relationship based on ROWE-DAVIS framework was proposed to consider the non-coaxiality effect under principal stress rotation.The model was validated by present numerical results as well as some published physical test and numerical modelled data.展开更多
基金The National Natural Science Foundation of China under contract No.41976060the Fund of Research on Paleoclimate in the Eastern Indian Ocean under contract No.GASI-04-01-03+1 种基金the Foreign Cultural and Educational Experts Employment Program under contract No.GDW20181100256the Fund of Laboratoire des Sciences du Climat et de l’Environnement under contract No.7437
文摘Site U1446(19°50’N,85°44’E,at water depth 1430 m)was drilled during Expedition 353(Indian monsoon rainfall)of the International Ocean Discovery Program(IODP).It is located in the Mahanadi offshore basin,on the northern Bay of Bengal.Sedimentation rates and contents of biocarbonates are high at this relatively shallow site.Using a micropaleontological approach,we examined planktonic and benthic foraminifera in the upper around 40 m of this site,spanning the last around 190 ka.A striking feature of the foraminiferal record is the occurrence of strong but varying dissolution although the site is located well above the modern lysocline.Such strong dissolution has never been reported in this area.We estimated the flux of foraminifera and quantified the ratio of benthic foraminifera over total foraminifera(benthic/total foraminifera)along with the foraminifer fragmentation index in order to characterize past changes in this above-lysocline dissolution.This study reveals a clear glacialinterglacial contrast,with a stronger dissolution during marine isotope stages(MISs)1 and 5 than during MISs 2–4 and 6.Such a difference in preservation is likely to have a strong impact on geochemical proxies measured on foraminifera.Our new observations call for an in-depth study of the causes of such above-lysocline dissolution in the region,and an evaluation of its impact on the foraminifera-based proxies used for paleoenvironmental reconstruction.
基金supported by the National Key R&D Program for Developing Basic Sciences(2022YFC3104802)the National Natural Science Foundation of China(Nos.42306219 and 42106020)+3 种基金the Tai Shan Scholar Pro-gram(Grant No.tstp20231237)Part of computing resources are financially supported by Laoshan Laboratory(No.LSKJ202300301)Dr.Eric P.CHASSIGNET is supported by the CAS President’s International Fellowship Initiative(PIFI)NOAA Climate Program Office MAPP Program(Award NA15OAR4310088).
文摘This study assesses the capability of a coarse-resolution ocean model to replicate the response of the Southern Ocean Meridional Overturning Circulation(MOC) to intensified westerlies,focusing on the role of the eddy transfer coefficient(κ).κ is a parameter commonly used to represent the velocities induced by unresolved eddies.Our findings reveal that a stratification-dependent κ,incorporating spatiotemporal variability,leads to the most robust eddy-induced MOC response,capturing 82% of the reference eddy-resolving simulation.Decomposing the eddy-induced velocity into its vertical variation(VV) and spatial structure(SS) components unveils that the enhanced eddy compensation response primarily stems from an augmented SS term,while the introduced VV term weakens the response.Furthermore,the temporal variability of the stratification-dependent κ emerges as a key factor in enhancing the eddy compensation response to intensified westerlies.The experiment with stratification-dependent κ exhibits a more potent eddy compensation response compared to the constant κ,attributed to the structure of κ and the vertical variation of the density slope.These results underscore the critical role of accurately representing κ in capturing the response of the Southern Ocean MOC and emphasize the significance of the isopycnal slope in modulating the eddy compensation mechanism.
文摘Wind load is a control load that affects the safety of structures in the design of ocean platforms. It has not only direct and powerful effects that may cause structure resonance but also has indirect effects causing waves or currents in the ocean. By analyzing the domestic and international norms, this study <span style="letter-spacing:0.1pt;font-family:Verdana;font-size:12px;">pre<span style="font-family:Verdana;font-size:12px;">sents a review of calculation methods of wind load on ocean platforms, which <span style="letter-spacing:-0.15pt;font-family:Verdana;font-size:12px;">belongs to large-scale non-entity structure used in the open sea while sur<span style="font-family:Verdana;font-size:12px;">round<span style="letter-spacing:-0.1pt;font-family:Verdana;font-size:12px;">ing wind has no fixed direction. Current computations according to the<span style="font-family:Verdana;font-size:12px;"> norms are not accurate, which even not takes the force of the wind against the surf<span style="letter-spacing:-0.1pt;font-family:Verdana;font-size:12px;">ace perpendicular to the structure into consideration. Additionally, thi<span style="font-family:Verdana;font-size:12px;">s study also introduces and compares the lift model of platforms based on different <span style="letter-spacing:-0.1pt;font-family:Verdana;font-size:12px;">theories, such as vortex-excitation and vibration, engineering structure dy<span style="font-family:Verdana;font-size:12px;">namics, gas flow pressure theory, analyzing their applicability, advantages, and disadvantages. This paper analyzes the limitations and applicable conditions of the existing calculation method itself, such as the lift model is suitable for the existence of stable vortex wake;the calculation method of the structural dynamics of marine engineering must be combined with the wind tunnel test and consider the mistakes caused by the position relationship;the numerical simulation method is accurate but tedious. This study provides an insight into the calculation methods of lift in designing ocean platforms, including the <span style="letter-spacing:0.1pt;font-family:Verdana;font-size:12px;">finite element method for simulating fluid force and updating formulas in<span style="font-family:Verdana;font-size:12px;"> Chinese norms.
基金The National Key Research and Development Program of China under contract No.2023YFC2811400.
文摘With their suitable habitats significantly affected by climate change and human activities,most of the seven globally recognized sea turtles are facing endangerment.In order to predict their present and future(2090−2100)potentially suitable habitats,we utilized the MaxEnt model,incorporating occurrence data for various sea turtle species and environmental datasets under current conditions,as well as under two climate scenarios from the Shared Socioeconomic Pathways(SSP1-2.6 and SSP5-8.5).Our findings showed that the key environmental variables,such as temperature and distance from shore predominantly influence the prediction on the potentially suitable habitat for sea turtles.The most highly suitable habitats for sea turtles are predominantly found in the tropical coastal waters bordering continents,including South and North America,Asia,and Australia.Under the climate scenarios of SSP1-2.6 and SSP5-8.5 for 2090−2100,the anticipated loss of potential suitable habitats is expected to surpass any potential gains for all sea turtle species.The Kemp’s ridley sea turtle(Lepidochelys kempii)is especially vulnerable,with its potentially suitable habitat area projected to decrease by 0.43%under SSP1-2.6 scenario to 6.15%under SSP5-8.5 scenario.In contrast,the most resilient Dermochelys coriacea is projected with a reduction of 1.02%under SSP1-2.6 and 0.57%under SSP5-8.5 in its potentially suitable habitat.These varying responses to climate change inferred the necessity for species-specific conservation strategies.However,only 9.9%of the integrated potentially suitable habitat is protected within the World Database on Protected Areas(WDPA),which suggested the extending of WDPA for more efficiency on the sea turtle conservation.
基金National Key Research and Development Program of China,No.2022YFC3204302China National Admin-istration of Coal Geology,No.ZMKJ-2021-ZX04。
文摘Ecological water supplement projects have been implemented in many coastal wetlands,influencing saltmarsh vegetation restoration by altering tidal creek development.To clarify the effectiveness of ecological water supplement on tidal creek development and saltmarsh vegetation restoration,time series of high-resolution remote sensing images from2000 to 2021 were used to extract and analyze tidal creeks and saltmarsh vegetation in the Diaokou Estuary Reserve.The results are summarized as follows:(1)All tidal creek indices,except curvature,exhibited a significant linear increase with time,while curvature initially decreased and increased afterwards.The 5-year cumulative ecological water supplement volume was significantly positively correlated(R^(2)>0.7)with all tidal creek indices.(2)During the same period,most landscape pattern metrics of Phragmites australis increased,while those of Tamarix chinensis initially increased and then declined.Although the class area(CA)of Suaeda salsa increased with time,its perimeter-area fractal dimension(PAFRAC)and aggregation index(AI)fluctuated.(3)The CA of P.australis and S.salsa was significantly positively correlated with most tidal creek indices except curvature,while that of T.chinensis showed no significant correlation with any tidal creek index.Moreover,the AI and PAFRAC of P.australis were significantly positively correlated with fractal dimension,frequency/curvature of tidal creeks,respectively,while those of S.salsa and T.chinensis exhibited no significant correlation.In summary,the ecological water supplement project enhanced tidal creek development in coastal wetlands,promoting the restoration of P.australis and S.salsa,while having little impact on the restoration of T.chinensis.
基金the National Natural Science Foundation(41802169)Key Laboratory of Polar Geology and Marine Mineral Resources Foudation(HNPY-202506)for supporting this study.
文摘The Shanan sag in the central-western Bohai Bay Basin hosts high-quality Paleogene source rocks within the Shahejie Formation’s third member(E_(2)s_(3)).Despite hydrocarbon indications in Cenozoic strata,no commercial accumulations have been discovered.An integrated approach combining geochemical analysis,fluid inclusion thermometry,apatite fission-track(AFT)thermochronology,and basin modeling was employed to unravel the paleo-geothermal regime and hydrocarbon generation history of E_(2)s_(3) source rocks.AFT data from the Shahejie Formation’s second member(E_(2)s_(2))reveal a tectonothermal event at 25 Ma that accelerated E_(2)s_(3) maturation.Outside three sub-sag depocenters,current E_(2)s_(2) reservoir temperatures remain below the 25 Ma paleo-geothermal maxima despite subsequent Neogene burial.Hydrocarbon-bearing brine inclusions in E_(2)s_(2) reservoirs exhibit peak homogenization temperatures(Th)at 25 Ma,with minimal high-temperature signals,indicating that E_(2)s_(3) hydrocarbon generation peaked during the Paleogene thermal event,with limited late-stage accumulation.The regional effects of the Dongying Movement necessitate thick Neogene sedimentation to compensate for the 25 Ma paleo-geothermal anomaly.Our findings emphasize targeting Neogene depocenters in petroleum exploration to mitigate the inhibitory effects of high paleo-heat flow on late hydrocarbon generation,thereby enhancing current accumulation potential.
基金Supported by the National Natural Science Foundation of China(42372162,4244205C)Project of"Solving Problems by Listing Talents"in Heilongjiang Province(2022-JS-1740,2022-JS-1853)Project on the Theory of Oil and Gas Enrichment from the Interaction of Earth's Multiple Spheres(THEMSIE04010103).
文摘Taking the GY8HC well in the Gulong Sag of the Songliao Basin,NE China,as an example,this study utilized high-precision zircon U-Pb ages from volcanic ashes and AstroBayes method to estimate sedimentation rates.Through spectral analysis of high-resolution total organic carbon content(TOC),laboratory-measured free hydrocarbons(S_(1)),hydrocarbons formed during pyrolysis(S_(2)),and mineral contents,the enrichment characteristics and controlling factors of shale oil in an overmature area were investigated.The results indicate that:(1)TOC,S_(1),and S_(2)associated with shale oil enrichment exhibit a significant 173×10^(3)a obliquity amplitude modulation cycle;(2)Quartz and illite/smectite mixed-layer contents related to lithological composition show a significant 405×10^(3)a long eccentricity cycle;(3)Comparative studies with the high-maturity GY3HC well and moderate-maturity ZY1 well reveal distinct in-situ enrichment characteristics of shale oil in the overmature Qingshankou Formation,with a significant positive correlation to TOC,indicating that high TOC is a key factor for shale oil enrichment in overmature areas;(4)The sedimentary thickness of 12-13 m corresponding to the 173×10^(3)a cycle can serve as the sweet spot interval height for shale oil development in the study area,falling within the optimal fracture height range(10-15 m)generated during hydraulic fracturing of the Qingshankou shale.Orbitally forced climate changes not only controlled the sedimentary rhythms of organic carbon burial and lithological composition in the Songliao Basin but also influenced the enrichment characteristics and sweet spot distribution of Gulong shale oil.
基金funded by the National Natural Science Foundation of China(Grants No.92058213 and No.U22A20581)the Specific Research Fund of the Innovation Platform for Academicians of Hainan Province(Grant No.YSPTZX202204)key R&D projects of Hainan Province(ZDYF2024GXJS022).
文摘Subduction zones are critical interfaces for lithospheric volatile fluxes,where complex tectonic and geochemical interactions facilitate the release of gases and fluids from deep-seated reservoirs within the Earth’s crust.Mud volcanism,as a dynamic manifestation of these processes,contributes CH_(4)emissions that influence the global methane budget and impact marine ecosystems.Although∼2000 CH_(4)-rich mud extrusions have been documented in subduction zones globally,the geological origins and subduction-related geochemical and tectonic mechanisms driving these emissions remain poorly understood.This research examines the Makran subduction zone which hosts one of the world’s largest accretionary wedge and extensive CH_(4)-rich mud extrusions,as a model system.Integrated geochemical,geophysical,and geological observations reveal that thermogenic CH_(4)and clay-rich fluidized muds originate from deeply buried Himalayan turbidites(underthrusted sediments),driven by organic-rich sediment maturation and high fluid overpressure.Key tectonic features,including thrust faults,overburden pressure of wedge-top sediments,normal faults,brittle fractures,and seismicity,facilitate CH_(4)-rich mud extrusions into the hydrosphere and atmosphere.The extruded gases are predominantly CH_(4),with minor C_(2)H_(6),C_(3)H_(8),i-C_(4)H_(10),and n-C_(4)H_(10)while the mud breccia exhibits a chemical composition dominated by SiO_(2),Al_(2)O_(3),and Fe_(2)O_(3),enriched with trace elements(Rb,Zr,and V)and clay minerals,quartz,and carbonates.Geochemical indicators suggest intense chemical weathering and mature sediments classifying the mud breccia as litharenite and sub-litharenite,indicative of deep burial and compaction.These findings model the evolution of CH_(4)-rich mud extrusions through three geological stages:(i)Eocene to Early Miocene pre-thermogenic formation of the CH_(4)-rich source,(ii)Middle Miocene to Pliocene syn-thermogenic CH_(4)and fluidized mud generation,and(iii)Pleistocene to Recent post-thermogenic CH_(4)-rich fluidized mud migration.These findings underscore the critical yet often overlooked role of subduction-related geochemical and tectonic processes in CH_(4)generation and emission,with significant implications for the global CH_(4)budget and marine ecosystems.
基金Supported by the National Natural Science Foundation of China (Nos. 92358302, 42227901)。
文摘Marine heat waves(MHWs), characterized by extreme warm sea surface temperature events, frequently occur in Chinese marginal seas. However, the seasonal variation and joint distribution of MHWs in the Bohai Sea have not been fully described. Therefore, we conducted a systematic investigation of MHWs in this region. Our findings indicate that the frequency of MHW is low during winter, with long duration and weak intensity, while in summer, it is opposite, being high in the frequency, and shorter but stronger. Notably, in summer, the Laizhou and Liaodong bays exhibit a relatively long total day of MHWs compared to other areas in the Bohai Sea. Furthermore, our analysis of the joint distribution of MHWs, considering both duration and intensity, reveals significant seasonal variations. To provide practical insights for marine ranching, we have also investigated time series of MHWs at several specific stations and computed the correlation coefficients between MHW intensity and potential influential factors. Results suggest that sea surface height, cloud cover, wind stress, and wind stress curl are significantly correlated with MHW intensity, although these relationships vary geographically and seasonally. Overall, these findings elucidate the seasonal variation and potential influential factors of MHWs in the Bohai Sea and offer insights for decision-making and planning in marine ranching.
基金supported by the National Natural Science Foundation of China(No.41130422)the National Basic Research Program of China(Nos.2011CB201100-03 and 2006CB202302)the Frontier Research Project of Marine Facies of the Oil Industry in China
文摘The Tarim basin experienced a complex tectonic evolutionary history from Sinian to Ceno zoic. Eight largescale and more than 20 subordinate unconformities defining tectonosequences of dif ferent protobasins formed in various tectonic settings have been identified within the Phanerozoic in the Tarim basin, their distribution determining the general characteristics of sequence stratigraphic framework of the basin. Tectonostratigraphic unit I （magasequence） consists mainly of the Sinian Sys tem, which formed in a rift or aulacogen setting and can been subdivided into two subordinate strati graphic units （supersequences）. Unconformity （Tgg） between Sinian and Cambrian with surface karsti fication is regarded as a postrift unconformity. Tectonostratigraphic unit II comprises the Cambrian and the Ordovician and can be divided into six subordinate tectonostratigraphic units, recording the tectonogeographic evolution of the prototype basins from Cambrian to Early Ordovician passive car bonate continental margin or cratonic depression and the Late Ordovician submarine to neritic ret roarc foreland and cratonic depressions. The tectonic uplift related to the formation of the unconformity Tg5-2 resulted in the remarkable change in basin tectonic setting from a passive divergent to an active convergent, with the development of the Tazhong （塔中） uplift, the Tangguzibasi （塘古孜巴斯）, and the northern depression at the end of the Middle to the early Late Ordovician. The widespread angular unconformity Tg5 formed by a relatively strong compressive deformation, which caused an abrupt tec tonogeographic change of the basin from abyssal to a neritic setting in response to the collision andassociated tectonic deformation of the North Kunlun （昆仑） orogenesis during the Late Ordovician to the Early Silurian. Tectono stratigraphic unit III is composed of the Silurian and the Lower to Middle Devonian and character ized by the development of fluvial or deltaic and clastic littoral and neritic deposits. Largescale terrigenous clastic depositional wedges progra dated from the north to south in the southeast ern slope of the basin indicate the continuously shallowing and uplifting along the northern basin margin. Tectonostratigraphicunit IV includes the Upper Devonian, Carboniferous, and Permian and can be classified into two sub ordinate tcctonostratigraphic sequences. The angular unconformity （Tg3） at the base of the unit is the most widespread unconformity and the strong compression and uplift of the basin during this period has been suggested to be related to the collision of the Tianshan （天山） orogenesis and resulted in fun damental change in tectonic geomorphology with higher to the northeast and lower to the southwest. Tectonostratigraphic unit IV records another tectonic cycle from weak extension to compression in ba sin setting and is composed mainly of nearshore elastic deposits of embayment basin f＇flls. From the Triassic, the Tarim basin evolved into a period characteristic of development of intracontinental de pressions and marginal foreland basins and experienced several cycles from rapid subsidence to strong uplift and deformation, resulting in superimposition and reformation of differently orientated proto basins filled with a series of regional depositional cycles bounded by major unconformities and consist ing of extremely thick alluvial and lacustrine deposits. The Kuqa foreland depression in the northwest ern basin margin developed since the Triassic and deposited a elastic wedge of the Mesozoic to Cenozoic more than I00 000 m in thickness, which progradated and thin towards the southern Tabei （塔北） forebulge. The largescale sedimentary cycles from alluvial, fluvial to lacustrine, and finally fluvial deposits are attributed to the results of foreland tectonisim from active to relatively quiet stages. The foreland tectonisim was active during the Triassic, relatively quiet during the Jurassic, and active again from the Late Jurassic to the Cretaceous. To the Eogene, the depression subsided again and the com pression intermittently increased, resulting in a series of faulted and folded structural belts.
基金Project supported by the National Natural Science Foundation of China(Nos.50909057,51208294 and 41372319)the Innovation Program of Shanghai Municipal Education Commission(No.15ZZ081)the Innovation Project of Shanghai Postgraduate Education(No.20131129)
文摘A Discrete Element Method （DEM） model is developed to study the particle break- age effect on the one-dimensional compression behavior of silica sands. The ＇maximum tensile stress＇ breakage criterion considering multiple contacts is adopted to simulate the crushing of circular particles in the DEM. The model is compared with published experimental results. Com- parison between the compression curves obtained from the numerical and experimental results shows that the proposed method is very effective in studying the compression behavior of silica sands considering particle breakage. The evolution of compression curves at different stress levels is extensively studied using contact force distribution, variation of contact number and particle size distribution curve with loading. It is found that particle breakage has great impact on com- pression behavior of sand, particularly after the yield stress is reached and particle breakage starts. The crushing probability of particles is found to be macroscopically affected by stress level and particle size distribution curve, and microscopically related to the evolutions of contact force and coordination number. Once the soil becomes well-graded and the average coordination number is greater than 4 in two-dimension, the crushing probability of parent particles can reduce by up to 5/6. It is found that the average contact force does not always increase with loading, but increases to a peak value then decreases once the soil becomes more well-graded. It is found through the loading rate sensitivity analysis that the compression behavior of sand samples in the DEM is also affected by the loading rate. Higher yield stresses are obtained at higher loading rates.
基金financial supported by the National Natural Science Foundation of China (Nos. 41276047, 41030853, 41572207, 41440041)the Special and Frontier Foundation for the Twelve Five Plan of the China Ocean Mineral Resources Research and Development Association (No. DY125-22-QY-21)
文摘Two kinds of basalts with different chemical compositions were obtained in the Sanshui Basin,they share the same eruption period. Although they have significant differences in major and trace element concentrations,their isotopic ratios suggest a similar magma source. Based on mineral geochemical analysis,orthopyroxene with reaction rim and zoned clinopyroxene are observed in Zidong(ZD)basalts,but not found in Wangjiegang(WJG) basalts. Linear scanning of these minerals suggests compositional variation between within-plate tholeiite and within-plate alkali-basalt. Presence of a doublelayer magma chamber under the Sanshui Basin,and occurrence of magma mixing between upper and lower chambers is proposed. This magma mixing leads to different chemical composition and mineral constitution of two kinds of basalts,as well as reaction rim and compositional variation of minerals in ZD basalts.
基金The National Natural Science Foundation under contract No.41306050the Science and Technology Project of Guangdong Province under contract No.2014A010103030+1 种基金the Natural Science Foundation of Guangdong Province under contract No.2015A030313617the National Marine Important Charity Special Foundation under contract No.201305019
文摘Using the occurrence characteristics of bubble plumes in the South China Sea as a reference, this paper continues to study the seismic responses produced by bubble plumes in the cold seepage active region. To make the plume modelling scheme more reasonable, we modified the original modelling scheme and reconstructed a plume water body model based on the variation of its radius as bubbles rise in seawater. The plume seismic records of shot gathers were obtained by forward simulation. The seismic records of single shot show obvious characteristics of a scattering wave field and the periodic characteristics of the model. Seismic records of shot gathers were processed using prestack depth migration. The boundary of its imaging section has a good convergence effect. The migration sections can be imaged distinctly with higher accuracy. The aforementioned studies once again laid a foundation for the further study of the seismic responses produced by plumes. They also gradually probed a more suitable seismic data processing method for plumes and provided a theoretical guidance for the identification of plumes.
基金Supported by the National Natural Science Foundation of China(21576053)the Natural Science Foundation of Fujian Province(2016J01689)the Young Teacher Education Research Foundation of Fujian Province(JAT160056)
文摘The transesterification of palm oil and methanol catalyzed by Br?nsted acidic ionic liquids was investigated. Four eco-friendly Br?nsted acidic ionic liquids were prepared and their structures were characterized by NMR, FT-IR and TG–DTG. The results demonstrated that [CyN_(1,1)PrSO_3H][p-TSA] was more efficient than the other ionic liquids and chosen as catalyst for further research. The influences of various reaction parameters on the conversion of palm oil to biodiesel were performed, and the orthogonal test was investigated to seek the optimum reaction conditions, which were illustrated as follows: methanol to oil mole ratio of 24:1, catalyst dosage of 3.0 wt% of oil, reaction temperature of 120 °C, reaction time of 150 min, and the biodiesel yield achieved 98.4%. In addition, kinetic study was established for the conversion process, with activation energy and preexponential factor of 122.93 k J·mol^(-1) and 1.83 × 10^(15), respectively. Meanwhile, seven-time recycling runs of ionic liquid were completed with ignorable loss of its catalyst activity. The refined biodiesel met the biodiesel standard EN 14214.
基金support for this work by the National Natural Science Foundation of China (No. 15572072)the National Key Basic Research and Development Program (No. 2016ZX05028-002-005)
文摘Environmental load is the primary factor in the design of offshore engineering structures and ocean current is the principal environmental load that causes underwater structural failure. In computational analysis, the calculation of current load is mainly based on the current profile. The current profile model, which is based on a structural failure criterion, is conducive to decreasing the uncertainty of the current load. In this study, we used prototype monitoring data and the empirical orthogonal function(EOF) method to investigate the current profile in the South China Sea and its correlation with the design of underwater structural strength and the dynamic design of fatigue. The underwater structural strength design takes into account the size of the structure and the service water depth. We propose profiles for the overall and local designs using the inverse first-order reliability method(IFORM). We extracted the characteristic profile current(CPC) of the monitored sea area to solve dynamic design problems such as vortex-induced vibration(VIV). We used random sampling to verify the feasibility of using the EOF method to calculate the CPC from the current data and identified the main problems associated with using the CPC, which deserve close attention in VIV design. Our research conclusions provide direct references for determining current load in this sea area. This analysis method can also be used in the analysis of other sea areas or field variables.
基金supported by the Chinese Ministry of Science and Technology(Sinoprobe-05-03)Doctoral Fund of Ministry of Education of China(20110022120003)+1 种基金the Fundamental Research Funds for the Central UniversitiesOpen Fund of State Key Laboratory of Geological Processes and Mineral Resources(GPMR2011)
文摘Tengchong Cenozoic volcanics that have record key information on the tectonic evolution and mantle features of the southeast margin of the Tibetan Plateau are of great importance because of its unique eruption history spanning the entire Quaternary period. Magma origin and evolution of Tengchong Cenozoic volcanic rocks were studied on the basis of Nd-Sr-Pb isotope and major and trace element data from different eruptions in the Ma＇anshan area. Different samples within one eruption show relative identical lithologies, chemical and isotopic compositions. However, the geochemical features for the five eruptions are distinct from each other. These volcanic rocks show low Mg# values （〈45）, moderate to high fractionation of LREEs and HREEs, and enrichment of Pb and Ba and depletion of Nb. Tengchong Cenozoic volcanic rocks were derived from an enriched mantle based on Nd-Sr-Pb isotopic studies. And lines of evidence show that crustal contamination should be involved before the eruption of different periods of Tengchong Cenozoic volcanic rocks. Older subducted components may be responsible for adakite recycling at various stages of evolution, which results in the origin of the enriched mantle source magma accounting for the isotopic features of Tengchong Cenozoic volcanic rocks. Segregated primitive magma pulsating injected into magma chamber, fractional crystallized and contaminated with crust component. Finally, magmas with distinct chemical and isotopic compositions for each eruption formed. The extension of the northeast segment of the Yingjiang tectonic belt triggered the pulsating eruption of the Cenozoic volcanics in the Tengchong area.
基金financially supported by the National Natural Science Foundation of China(No.41306050)the Science and Technology Project of Guangdong Province of China(No.2014A010103030)+1 种基金the Natural Science Foundation of Guangdong Province under contract(No.2015A030313617)the National Marine Important Charity Special Foundation of China(No.201305019)
文摘To study the bubble plume's seismic response characteristics,the model of a plume water body has been built in this article using the bubble-contained medium acoustic velocity model and the stochastic medium theory based on an analysis of both the acoustic characteristics of a bubble-contained water body and the actual features of a plume.The finite difference method is used for forward modelling,and the single-shot seismic record exhibits the characteristics of a scattered wave field generated by a plume.A meaningful conclusion is obtained by extracting seismic attributes from the pre-stack shot gather record of a plume.The values of the amplitude-related seismic attributes increase greatly as the bubble content goes up,and changes in bubble radius will not cause seismic attributes to change,which is primarily observed because the bubble content has a strong impact on the plume's acoustic velocity,while the bubble radius has a weak impact on the acoustic velocity.The above conclusion provides a theoretical reference for identifying hydrate plumes using seismic methods and contributes to further study on hydrate decomposition and migration,as well as on distribution of the methane bubble in seawater.
基金supported by the National High Technology Research and Development Program of China(863 Pro-gram, Grant No.2005AA615040)the National Natural Science Foundation of China(Grant No.40776038)+2 种基金Open Fund of Key Laboratory of Geo-detection(China University of Geosciences,Beijing),Ministry of Education (GrantNo. GDL0802)the Ocean Public Welfare Scientific Research Special Appropriation Project(Grant Nos.200805079and 200805005)the Open Fund of Key Laboratory of Submarine Geoscience,State Oceanic Administration(Grant No. KCSG0803)
文摘Compared with the laboratory acoustic measurement of sediment samples, the in-situ acoustic measurement in marine sediment is considered more accurate and rehable, because it covers all of the surrounding environment factors and avoids the disturbance during the course of sampling and transporting of sediment samples. A new multi-frequency in-situ geoacoustic measurement system （MFIS^AMS） has been developed. The system can provide acoustic vdocity （compressional wave） and attenuation profiles of the uppermost 4 - 8 m sediment in the seafloor. It consists of 8 channels with 12 frequencies （multi-frequencies） and 0.5 - 2 MHz sampling rates. The data collected can be transmiuted in real-time. Associated with inclinometer and altimeter, it can provide the data for depth emendation. Acoustic velocity and attenuation data have been obtained from two in-situ experiments conducted in the Hangzhou Bay.
文摘In this paper, incised valley filling deposits, which formed an important pathway system for long-distance hydrocarbon migration, are discussed in detail based on core and logging data. The sequence SQy23 of the Cretaceous Yaojia Formation is the main hydrocarbon-bearing layer in the Fulaerji Oilfield. The hydrocarbon source of the oilfield is the Qijia-Gulong Sag which is about 80 km away from the Fulaerji Oilfield. The transport layer of long-distance hydrocarbon migration is the overlapped sandstone complex which fills the incised valley. The incised valley developed during the depositional period from the late Qingshankou Formation to the early Yaojia Formation of Cretaceous （SQqna-SQy0 was about 70 km long and 20 km wide, and extended in the NW-SE direction. The overlapped filling of the incised valley mainly occurred in the expanding system tract of the third-order sequence SQy23 （ESTy23）. Towards the basin, incised valley filling deposits overlapped on the delta developed in the early period, and towards the basin margin, incised valley filling deposits were covered by the shore-shallow lacustrine sandy beach bar developed in the maximum flooding period. All of the delta, the incised valley filling and the shore-shallow sandy beach bar are sandstone-rich, and have high porosity and permeability, and can form an effective hydrocarbon migration and accumulation system. Deltaic sand bodies collected and pumped hydrocarbon from the active source, incised valley filling depositional system completed the long-distance hydrocarbon migration, and lithological traps of shore-shallow lacustrine sandy beach bar accumulated hydrocarbon. The incised valley filling sequences are multi-cycle： an integrated shortterm filling cycle was developed on the erosion surface, and the sequences upward were mud-gravel stone, medium-fine sandstone containing terrigenous gravels and muddy pebbles with cross bedding, silty mudstone with ripple bedding, and mudstone. The incised valley filling deposits are characterized by a strong heterogeneity and the main hydrocarbon migration pathway is the medium-fine sandstone interval.
基金Projects(50909057,51208294,41372319)supported by the National Natural Science Foundation of ChinaProject(15ZZ081)supported by Innovation Program of Shanghai Municipal Education Commission,ChinaProject(20131129)supported by Innovation Program of Shanghai Postgraduate Education,China
文摘A micromechanical investigation on simple shear behavior of dense granular assemblies was carried out by discrete element method.Three series of numerical tests were performed to examine the effects of initial porosity,vertical stress and particle shape on simple shear behavior of the samples,respectively.It was found that during simple shear the directions of principal stress and principal strain increment rotate differently with shear strain level.The non-coaxiality between the two directions decreases with strain level and may greatly affect the shear behavior of the assemblies,especially their peak friction angles.The numerical modelling also reveals that the rotation of the principal direction of fabric anisotropy lags behind that of the major principal stress direction during simple shear,which is described as fabric hyteresis effect.The degrees of fabric and interparticle contact force anisotropies increase as particle angularity increases,whereas the orientations of these anisotropies have not been significantly influenced by particle shape.An extended stress–dilatancy relationship based on ROWE-DAVIS framework was proposed to consider the non-coaxiality effect under principal stress rotation.The model was validated by present numerical results as well as some published physical test and numerical modelled data.
