Arid regions are vital components of Earth’s land surface.Clarifying the area/boundary of arid region is crucial for comprehending area changes and potential mechanisms.However,the accuracy and applicability of arid ...Arid regions are vital components of Earth’s land surface.Clarifying the area/boundary of arid region is crucial for comprehending area changes and potential mechanisms.However,the accuracy and applicability of arid region boundary delineated by different indices remain unclear.In this study,the annual precipitation(AP),humidity index(H),and aridity index(K)were calculated for delineating arid region of China using 106 meteorological stations during 1990–2019.The results suggest that AP and H can accurately delineate arid region,because they are consistent with the distribution of typical soil and vegetation in arid region,whereas K is not.Moreover,AP is the best index for delineating arid region in regions with limited meteorological data,especially in studying long-term patterns and mechanisms of area changes.The accuracy of delineating arid region using H is enhanced in regions with abundant meteorological data.Over the past 30 years,influenced by the increase of atmospheric moisture influx and precipitation,the area in arid region of northwestern China decreased by 70×10^(3)–90×10^(3)km^(2),resulting in the present area of approximately 1.55×10^(6)km^(2).This study provides appropriate indices for delineating arid region,contributing to improving our knowledge of regional responses difference to climate change.展开更多
Groundwater is essential for maintaining public health,promoting economic development,and ensuring ecosystem stability in arid and semi-arid regions.The northwestern Ordos Basin(China)primarily relies on groundwater f...Groundwater is essential for maintaining public health,promoting economic development,and ensuring ecosystem stability in arid and semi-arid regions.The northwestern Ordos Basin(China)primarily relies on groundwater from multilayered aquifer systems;however,our knowledge of the hydrochemical characteristics and water quality of groundwater in this region is limited.Here,we employed a newly collected dataset of 94 groundwater samples from different aquifers to constrain the source,controlling processes of fluoride in groundwater,and its potential health risk in the area.Groundwater is characterized by Na-Cl and Na-SO_(4) types with a minor Na-HCO_(3) type,which is primarily controlled by ion exchange,silicate weathering,and the dissolution of carbonate and evaporite minerals.Of the groundwater samples,42%exceeded the fluoride limit of 1.5 mg/L established by the World Health Organization(WHO).This is mainly attributed to geogenic sources,including fluorine-bearing mineral dissolution,cation exchange,evaporation,and competitive adsorption.The water quality index suggests that most samples are unsuitable for drinking.Health risk assessment results based on the Monte Carlo simulation indicate that children face significantly higher non-carcinogenic health risks from fluoride exposure than adults(both males and females).These findings provide new insights into the complex hydrogeochemical evolution of fluoride in groundwater and the groundwater quality status in multi-aquifer systems,contributing to the sustainable development and management of groundwater resources in the Ordos Basin.展开更多
Based on year-long mooring observations(January-December 2013)near the Xisha Islands in the northwestern South China Sea,this study investigates the characteristics of typhoon-induced near-inertial waves(NIWs)during t...Based on year-long mooring observations(January-December 2013)near the Xisha Islands in the northwestern South China Sea,this study investigates the characteristics of typhoon-induced near-inertial waves(NIWs)during three events(typhoons Wutip,Nari,and Haiyan).The influence of mesoscale eddies on NIWs and the interaction between NIWs and internal tides(ITs)were analyzed.Notably,near-inertial kinetic energy(NIKE)increased significantly following typhoon Haiyan,reaching a peak value of 40.60 J/m^(3),the highest recorded NIKE in 2013.This value was approximately threefold and fivefold larger than those generated by typhoons Wutip and Nari,respectively.NIKE generated by all three typhoons exhibited downward radiation.Power spectral analysis revealed significant frequency shifts in NIWs during each typhoon,with shifts linked to mesoscale eddies present at the observation site.Additionally,bicoherence analysis reveals that the fD_(1)(f+D_(1))and D_(2)−f waves(where f is the local inertial frequency,and D1 and D_(2)denote the frequencies of diurnal and semidiurnal ITs,respectively)in the power spectrum originate from the nonlinear interactions between NIWs and ITs during typhoons Wutip and Haiyan.Temporal analysis of kinetic energy and shear showed that the enhancement of nonlinear coupling between NIWs and ITs was primarily driven by the strong NIWs with strong vertical shear.This study provides valuable insights into the generation,propagation,and interaction of NIWs and ITs,contributing to a deeper understanding of ocean mixing processes in response to different typhoon conditions.展开更多
The Fengcheng Formation in the Hashan area,located on the northwestern margin of the Junggar Basin,represents a saline-alkaline lake facies with fine-grained mixed sedimentation.This formation is rich in alkaline mine...The Fengcheng Formation in the Hashan area,located on the northwestern margin of the Junggar Basin,represents a saline-alkaline lake facies with fine-grained mixed sedimentation.This formation is rich in alkaline minerals and serves as a high-quality source rock for hydrocarbon generation in alkaline lakes.However,its lithology is complex,and the origins of the salt minerals remain unclear.This study focuses on the salt minerals in the Fengcheng Formation of the Hashan area.Using core observation,thin section identification,scanning electron microscopy,electron probe micro-analysis,trace and rare earth element analysis,stable isotope analysis,fluid inclusion analysis,and zircon U-Pb dating,the sedimentary age of Fengcheng Formation and the mineralogical and geochemical characteristics of salt minerals were systematically studied.The salt minerals identified in the Fengcheng Formation include calcite,dolomite,eitelite,northupite,shortite,reedmergnerite,and Na-carbonate.According to the different types of salt minerals,the different contact relations between minerals,the different production positions and production styles of mineral combinations,the salt mineral assemblage in the study area is classified into three categories:The combination of calcite,dolomite,shortite,and reedmergnerite,The combination of Na-carbonates,eitelite,shortite,and reedmergnerite,The combination of dolomite,eitelite,shortite,and northupite.Two zircon U-Pb ages,307.8±2.7 Ma and 308.5±3.5 Ma,span the Carboniferous-Permian boundary,corresponding to an interglacial period within the Late Paleozoic Ice Age,aligning with the development of salt minerals.Salt minerals have the formation modes of sedimentation,replacement and hydrothermal transformation.Terrestrial weathering products,atmosphe ric,volcanic and hydrothermal processes,residual seawater,clay mineral transformation,thermal evolution of organic matter and tuffaceous alteration are material sources.The salt-forming fluid has the characteristics of weak acid-alkaline,medium-low temperature and high salinity,and is mainly driven by subduction zone high pressure,magmatic heat and gravity.The burial depth,temperature and CO_(2)concentration required for the formation of salt minerals were clarified,and the evolution sequence of salt-forming fluids from sedimentation to diagenesis and accompanied by hydrothermal(hot water)activities was summarized.The evolution model of salt minerals controlled by different genesis from the first member to the third member of Fengcheng Formation was established.The research findings are significant for understanding the paleoenvironment of the Fengcheng Formation,the formation mechanisms of high-salinity lakes,and the salt formation models.展开更多
Tropical cyclones(TCs)have profound impacts on socioeconomic conditions and pose substantial risks to lives and property.However,it is still unclear whether the multitimescale changes in TC activity over the past 2000...Tropical cyclones(TCs)have profound impacts on socioeconomic conditions and pose substantial risks to lives and property.However,it is still unclear whether the multitimescale changes in TC activity over the past 2000 years in the Northwestern Pacific(NWP)were regulated by Asian dust forcing.Here,we assessed the impact of Asian dust on TC activity using observational data and reconstructed records from the northern and southern NWP.Our correlation analysis of instrumental data from 1954 to 2017 reveals no significant relationship between observed TC activity and Asian dust forcing.Furthermore,we found a meridional dipole pattern of TC variation across the NWP in observations and reconstructions.These finding challenges current explanations that are based on the synchronous changes in TC activity and Asian dust forcing.Alternatively,we propose that the Western Pacific Subtropical High(WPSH)plays a crucial role in driving these meridional dipole patterns in TC variations,as supported by observations and reconstructions.The southwestward extension of an enhanced WPSH intensifies easterly flow,steering TCs westward along its southern edge.This leads to more TC activity in the southern NWP but less in the north,and vice versa when the WPSH is weakened.With the expected strengthening of the WPSH due to global warming,it is vital to consider its impact on NWP TC activity for effective risk-mitigation strategies.展开更多
A 28-year best track dataset containing size parameters that include the radii of the 15.4 m s^-1 winds （R15） and the 25.7 m s^-1 winds （R26） of tropical cyclones （TCs） in the Northwestern Pacific, the NCEP/ NCA...A 28-year best track dataset containing size parameters that include the radii of the 15.4 m s^-1 winds （R15） and the 25.7 m s^-1 winds （R26） of tropical cyclones （TCs） in the Northwestern Pacific, the NCEP/ NCAR reanalysis dataset and the Extended Reconstructed Sea Surface Temperature （ERSST） dataset are employed in this study. The climatology of size parameters for the tropical cyclones in the Northwestern Pacific from 1977 to 2004 is investigated in terms of the spatial and temporal distributions. The results show that the major activity of TCs in the Northwestern Pacific is from July to October. A majority of TCs lie over the ocean west of 150°E, and a few TCs can intensify to the Saffir-Simpson （S-S） categories 4, 5. Both R15 and R26 tend to increase as the tropical cyclones intensify. The values of R15 and R26 are larger for intense TCs in the Northwestern Pacific than in the North Atlantic generally. Both R15 and R26 peak in October, and before and after October, R15 and R26 decrease, which is different from the case in the North Atlantic. The smaller R15s and R26s occur in a large range over the Northwestern Pacific, while the larger R15s and R26s mainly lie in the eastern ocean from Taiwan Island to the Philippine Islands where many tropical cyclones develop in intense systems. The tropical cyclones with size parameters of R15 or R26 on average take a longer time to intensify than to weaken, and the weak tropical cyclones have faster weakening rates than intensification rates. From 1977 to 2004, the annual mean values of R15 increase basically with year; during the 28-year period, the value of R15 increases by 52.7 kin, but R26 does not change with year obviously.展开更多
The Lower Cretaceous strata in the Kuqa Basin in Xinjiang are marked by a set of arid red beds. Several types of sedimentary fades can be identified in this set of arid red beds: mudstones of the plaza and intracontin...The Lower Cretaceous strata in the Kuqa Basin in Xinjiang are marked by a set of arid red beds. Several types of sedimentary fades can be identified in this set of arid red beds: mudstones of the plaza and intracontinental sebkha, aeolian sandstones, sandy conglomerates of the intermittent river, conglomerates of the pluvial fan, etc. These types of sedimentary facies constitute a typical desert system. Therefore, the Cretaceous strata in the Kuqa Basin provide a favorable condition for studies of sequence stratigraphic divisions of the desert system. With the rise and fall of the base level of the sedimentary basin, cyclicity is clearly revealed in stratigraphic records, which helps the identification of the third-order sequences. Based on the cyclicity in stratigraphic records, 5 third-order sequences can be found in the strata of the Early Cretaceous in the Kuqa Basin. These sequences comprise a second-order tectonic sequence. The primary feature of these third-order sequences is of an upward-fining sedimentary succession formed by a succession of 'coarse sediments of the alluvial system-fine sediments of the lake system'. The result of this study shows that aeolian sandstones are the best reservoirs of natural gas in the Cretaceous strata in the Kuqa Basin, and that the Kela-2 gas field is the first large gas field dominated by aeolian sandstone reservoirs in China.展开更多
Based on in-situ time series data from the acoustic Doppler current profiler （ADCP） and thermistor chain in Wenchang area, a sequence of internal solitary wave （ISW） packets was observed in September 2005, propaga...Based on in-situ time series data from the acoustic Doppler current profiler （ADCP） and thermistor chain in Wenchang area, a sequence of internal solitary wave （ISW） packets was observed in September 2005, propagating northwest on the continental shelf of the northwestern South China Sea （SCS）. Corresponding to different stratification of the water column and tidal condition, both elevation and depression ISWs were observed at the same mooring location with amplitude of 35 m and 25 m respectively in different days. Regular arrival of the remarkable ISW packets at approximately the diurnal tidal period and the dominance of diurnal internal waves in the study area, strongly suggest that the main energy source of the waves is the diurnal tide. Notice that the wave packets were all riding on the troughs and shoulders of the internal tides, they were probably generated locally from the shelf break by the evolution of the internal tides due to nonlinear and dispersive effects.展开更多
The sequence stratigraphy of the Jurassic coal measures of northwestern China has been studied based on data from outcrop and borehole sections. Because of the geological background and the diversity of basin types, s...The sequence stratigraphy of the Jurassic coal measures of northwestern China has been studied based on data from outcrop and borehole sections. Because of the geological background and the diversity of basin types, such as isochronisms of coal seams and recognition of key sequence boundaries, it is rare to summarize and correlate sequence structure and framework. The types and recognition characteristics of the sequence boundaries of the Jurassic coal measures are revealed by comparing climatic characteristics, structural styles and the base level cycle. A total of five third-order sequences and 15 systems tracts have been subdivided and the sequence stratigraphic framework has been reconstructed confirming that the thick coals accumulated in the late stage of transgression system tracts of sequence I （SQ I） and sequence III （SQ III）. This idea is of important academic significance for instructing coal resources exploration, and enhancing geological effects of prospecting engineering. It is also of practical significance for guaranteeing construction of the large-scale coal production base in northwestern China, accelerating the westward development of the coal industry stratagem.展开更多
The Triassic-Jurassic （Tr-J） boundary marks a major extinction event, which （～200 Ma）resulted in global extinctions of fauna and flora both in the marine and terrestrial realms. There prevail great challenges in ...The Triassic-Jurassic （Tr-J） boundary marks a major extinction event, which （～200 Ma）resulted in global extinctions of fauna and flora both in the marine and terrestrial realms. There prevail great challenges in determining the exact location of the terrestrial Tr-J boundary, because of endemism of taxa and the scarcity of fossils in terrestrial settings leading to difficulties in linking marine and terrestrial sedimentary successions. Investigation based on palynology and bivalves has been carried out over a 1113 m thick section, which is subdivided into 132 beds, along the Haojiagou valley on the southern margin of the Junggar Basin of the northern Xinjiang, northwestern China. The terrestrial Lower Jurassic is conformably resting on the Upper Triassic strata. The Upper Triassic covers the Huangshanjie Formation overlaid by the Haojiagou Formation, while the Lower Jurassic comprises the Badaowan Formation followed by the Sangonghe Formation. Fifty six pollen and spore taxa and one algal taxon were identified from the sediments. Based on the key-species and abundance of spores and pollen, three zones were erected： the Late Triassic （Rhaetian） Aratrisporites-Alisporites Assemblage, the Early Jurassic （Hettangian） Perinopollenites-Pinuspollenites Assemblage, and the Sinemurian Perinopollenites-Cycadopites Assemblage. The Tr-J boundary is placed between bed 44and 45 coincident with the boundary between the Haojiagou and Badaowan formations. Beds with Ferganoconcha （？）, Unio-Ferganoconcha and Waagenoperna-Yananoconcha bivalve assemblages are recognized. The Ferganoconcha （？） bed is limited to the upper Haojiagou Formation,Unio- Ferganoconcha and Waagenoperna- Yananoconcha assemblages are present in the middle and upper members of the Badaowan Formation. The sedimentary succession is interpreted as terrestrial with two mainly lake deposit intervals within Haojiagou and Badaowan formations, yielding fresh water algae and bivalves. However, the presence of brackish water algae Tasmanites and the marine-littoral facies bivalve Waagenoperna from the Badaowan Formation indicate that the Junggar Basin was influenced by sea water caused by transgressions from the northern Tethys, during the Sinemurian.展开更多
A large number of autonomous profiling floats deployed in global oceans have provided abundant temperature and salinity profiles of the upper ocean. Many floats occasionally profile observations during the passage of ...A large number of autonomous profiling floats deployed in global oceans have provided abundant temperature and salinity profiles of the upper ocean. Many floats occasionally profile observations during the passage of tropical cyclones. These in-situ observations are valuable and useful in studying the ocean’s response to tropical cyclones, which are rarely observed due to harsh weather conditions. In this paper, the upper ocean response to the tropical cyclones in the northwestern Pacific during 2000–2005 is analyzed and discussed based on the data from Argo profiling floats. Results suggest that the passage of tropical cyclones caused the deepening of mixed layer depth (MLD), cooling of mixed layer temperature (MLT), and freshening of mixed layer salinity (MLS). The change in MLT is negatively correlated to wind speed. The cooling of the MLT extended for 50–150 km on the right side of the cyclone track. The change of MLS is almost symmetrical in distribution on both sides of the track, and the change of MLD is negatively correlated to pre-cyclone initial MLD.展开更多
Dissolved and particulate 234 Th, particulate organic carbon(PON), nitrogen, and chlorophyll-a concentrations in the upper 200 m of water columns from seven stations in the northwestern North Pacific Ocean were determ...Dissolved and particulate 234 Th, particulate organic carbon(PON), nitrogen, and chlorophyll-a concentrations in the upper 200 m of water columns from seven stations in the northwestern North Pacific Ocean were determined in the winter of 1997.The dissolved, particulate, and total 234 Th activities (dissolved plus particulate)show a pronounced deficiency with respect to its parent 238 U in the euphotic zone whereas the total 234 Th shows a near-equilibrium at the depth greater than 100 m.The 234 Th data are used to derive the mean residence time, export fluxes of 234 Th, and fluxes of particulate organic carbon and nitrogen out of the euphotic zone. In the Subarctic Current area, the residence time of dissolved 234 Th with respect to its removal onto particles is 40 ~50 d while the residence time of dissolved 234Th in the subtropical area is about 20 d due to the Kuroshio's influence.The particulate organic carbon(POC)and particulate organic nitroge(PON)fluxes in winter range over 3.8～8.2 and 0.50～0.98 mmol/(m2 ·d), respectively, and are higher in the west region than in the east, and higher in the south than in the north. The co-influence of Kuroshio-Oyashio Currents with supply of nutrient substances from the coastal area and the light condition are two factors determining the horizontal distribution of POC fluxes in winter.The depth distribution of the chlorophyll-a as well as the consistence of the ratio of POC to PON with the Redfield ratio suggest that phytoplankton is the main contributor to the export of POC in this area in winter.The POC fluxes in the northwestern North Pacific Ocean in winter are comparable to some areas in the world oceans in spring and summer seasons.展开更多
A typical HP/MT (high pressure/medium temperature) eclogite from Xiongdian, northwestern Dabie Mountains, has been geochronologically studied using the single-zircon U-Pb, 40Ar-39Ar and Sm-Nd methods. Prismatic zircon...A typical HP/MT (high pressure/medium temperature) eclogite from Xiongdian, northwestern Dabie Mountains, has been geochronologically studied using the single-zircon U-Pb, 40Ar-39Ar and Sm-Nd methods. Prismatic zircons occurring as inclusions within garnets define a minimum crystallization age of 399.5±1.6 Ma. 40Ar-39Ar dating on amphibole gives a plateau age.of 399.2 ± 4 Ma, which is interpreted as a retrogression age of amphibolite facies. This integrated study enables us to conclude that the age of high-pressure metamorphism is older than 399.5 ± 1.6 Ma, suggesting Caledonian collision between the North China and Yangtze plates. Round zircon within the aggregate of quartz and muscovite gives a concordant age of 301± 2 Ma, reflecting a later retrogression event. An age profile of post-eclogite metamorphism is documented, including amphibolite facies metamorphism at 399.2 Ma shortly after eclogitization and later retrogressive metamorphism at 301 Ma. Sm-Nd mineral isochron of garnet+omphacite gives an unreasonable age of 544 ± 23 Ma. which is quite older than that of prismatic zircon and may be attributed to isotopic disturbance by retrogression.展开更多
In order to reveal the characteristics and climatic controls on the stable isotopic composition of precipitation over Arid Northwestern China, eight stations have been selected from Chinese Network of Isotopes in Prec...In order to reveal the characteristics and climatic controls on the stable isotopic composition of precipitation over Arid Northwestern China, eight stations have been selected from Chinese Network of Isotopes in Precipitation(CHNIP).During the year 2005 and 2006, monthly precipitation samples have been collected and analyzed for the composition of δD and δ18O.The established local meteoric water line δD=7.42δ18O+1.38, based on the 95 obtained monthly composite samples, could be treated as isotopic input function across the region.The deviations of slope and intercept from the Global Meteoric Water Line indicated the specific regional meteorological conditions.The monthly δ18O values were characterized by a positive correlation with surface air temperature(δ18O(‰) =0.33 T(℃)-13.12).The amount effect visualized during summer period(δ18O(‰) =-0.04P(mm)-3.44) though not appeared at a whole yearly-scale.Spatial distributions of δ18O have properly portrayed the atmospheric circulation background in each month over Arid Northwestern China.The quan-titative simulation of δ18O, which involved a Rayleigh fractionation and a kinetic fractionation, demonstrated that the latter one was the dominating function of condensation of raindrops.Furthermore, the raindrop suffered a re-evaporation during falling processes, and the precipitation vapor might have been mixed with a quantity of local recycled water vapor.Multiple linear regression equations and a δ18O-T relation have been gained by using meteorological parameters and δ18O data to evaluate physical controls on the long-term data.The established δ18O-T relation, which has been based on the present-day precipitation, could be considered as a first step of quantitatively reconstructing the historical environmental climate.展开更多
Based on comprehensive petrological, geochronological, and geochemical studies, this study analyzed the relationships between the Beiya gold-polymetallic skarn deposit and quartz syenite porphyries, and discussed the ...Based on comprehensive petrological, geochronological, and geochemical studies, this study analyzed the relationships between the Beiya gold-polymetallic skarn deposit and quartz syenite porphyries, and discussed the source（s） and evolution of magmas. Our results suggest that syenite porphyries（i.e. the Wandongshan, the Dashadi, and the Hongnitang porphyries）, which formed between the Eocene and the early Oligocene epochs, are the sources for the gold-polymetallic ores at the Beiya deposit. Carbonate rocks（T2 b） of the Triassic Beiya Formation in the ore district provide favorable host space for deposit formation. Fold and fault structures collectively play an important role in ore formation. The contact zone between the porphyries and carbonates, the structurally fractured zone of carbonate and clastic rocks, and the zone with well-developed fractures are the ideal locations for ore bodies. Four types of mineralization have been recognized： 1） porphyry-style stockwork gold–iron（copper） ore, 2） skarn-style gold-iron（copper and lead） ore in the near contact zone, 3） strata-bound, lense-type lead–silver–gold ore in the outer contact zone, and 4） distal vein-type gold–lead–silver ore. Supergene processes led to the formation of oxide ore, such as the weathered and accumulated gold–iron ore, the strata-bound fracture oxide ore, and the structure-controlled vein-type ore. Most of these ore deposits are distributed along the axis of the depressed basin, with the hypogene ore controlling the shape and characteristics of the oxide ore. This study provides critical geology understanding for mineral prospecting scenarios.展开更多
The accumulation and productivity of shale gas are mainly controlled by the characteristics of shale reservoirs;study of these characteristics forms the basis for the shale gas exploitation of the Lower Cambrian Niuti...The accumulation and productivity of shale gas are mainly controlled by the characteristics of shale reservoirs;study of these characteristics forms the basis for the shale gas exploitation of the Lower Cambrian Niutitang Formation(Fm),Southern China.In this study,core observation and lithology study were conducted along with X-ray diffraction(XRD)and electronic scanning microscopy(SEM)examinations and liquid nitrogen(N2)adsorption/desorption and CH4 isothermal adsorption experiments for several exploration wells in northwestern Hunan Province,China.The results show that one or two intervals with high-quality source rocks(TOC>2 wt%)were deposited in the deep-shelf facies.The source rocks,which were mainly composed of carbonaceous shales and siliceous shales,had high quartz contents(>40 wt%)and low clay mineral(<30 wt%,mainly illites)and carbonate mineral(<20 wt%)contents.The SEM observations and liquid nitrogen(N2)adsorption/desorption experiments showed that the shale is tight,and nanoscale pores and microscale fractures are well developed.BJH volume(VBJH)of shale ranged from 2.144×10^-3 to 20.07×10^-3 cm^3/g,with an average of 11.752×10^-3 cm3/g.Pores mainly consisted of opened and interconnected mesopores(2–50 nm in diameter)or macropores(>50 nm in diameter).The shale reservoir has strong adsorption capacity for CH4.The Langmuir volume(VL)varied from 1.63 to 7.39 cm^3/g,with an average of 3.95 cm^3/g.The characteristics of shale reservoir are controlled by several factors:(1)A deep muddy continental shelf is the most favorable environment for the development of shale reservoirs,which is controlled by the development of basic materials.(2)The storage capacity of the shale reservoir is positively related to the TOC contents and plastic minerals and negatively related to cement minerals.(3)High maturity or overmaturity leads to the growth of organic pores and microfractures,thereby improving the reservoir storage capacity.It can be deduced that the high percentage of residual gas in Niutitang Fm results from the strong reservoir storage capacity of adsorbed gas.Two layers of sweet spots with strong storage capacity of free gas,and they are characterized by the relatively high TOC contents ranging from 4 wt%to 8 wt%.展开更多
Weighting values for different habitat variables used in multi-factor habitat suitability index (HSI) modeling reflect the relative influences of different variables on distribution of fish species. Using the winter-s...Weighting values for different habitat variables used in multi-factor habitat suitability index (HSI) modeling reflect the relative influences of different variables on distribution of fish species. Using the winter-spring cohort of neon flying squid (Ommastrephes bartramii) in the Northwestern Pacific Ocean as an example, we evaluated the impact of different weighting schemes on the HSI models based on sea surface temperature, gradient of sea surface temperature and sea surface height. We compared differences in predicted fishing effort and HSI values resulting from different weighting. The weighting for different habitat variables could greatly influence HSI modeling and should be carefully done based on their relative importance in influencing the resource spatial distribution. Weighting in a multi-factor HSI model should be further studied and optimization methods should be developed to improve forecasting squid spatial distributions.展开更多
Water demand increases continuously with an increasing population and economic development. As a result, the difference between water supply and demand becomes a sig- nificant issue, especially in arid regions. To fig...Water demand increases continuously with an increasing population and economic development. As a result, the difference between water supply and demand becomes a sig- nificant issue, especially in arid regions. To figure out the utilization of water resources in the arid region of northwestern China （ARNWC）, and also to provide methodologies to predict the water use in future, three models were established in this study to calculate agricultural irri- gation, industrial and domestic water use in the ARNWC from the late 1980s to 2010. Based on river discharges in the region, the supply and demand of water resources at the river basin level were analyzed. The results indicated that agricultural irrigation demand occupies more than 90% of the total water use in the ARNWC. Total water demand increased from 31.97 km3 in the late 1980s to 48.19 km3 in 2010. Most river basins in this arid region were under me- dium and high water stress. Severe-risk river basins, such as the Shiyang river basin and the eastern part of the northern piedmont of the Tianshan Mountains, were found in this region. It was revealed that the water supply became critical from April to May, which was the season of the lowest water supply as determined by comparing monthly water consumption.展开更多
The northwestern Pacific （NWP） is a fog-prone area, especially the ocean east of the Kuril Islands. The present study analyzes how the Pacific-Japan （PJ） teleconnection pattern influences July sea fog in the fog-p...The northwestern Pacific （NWP） is a fog-prone area, especially the ocean east of the Kuril Islands. The present study analyzes how the Pacific-Japan （PJ） teleconnection pattern influences July sea fog in the fog-prone area using independent datasets. The covariation between the PJ index and sea fog frequency （SFF） index in July indicates a close correlation, with a coefficient of 0.62 exceeding the 99% confidence level. Composite analysis based on the PJ index, a case study, and model analysis based on GFDL-ESM2M, show that in high PJ index years the convection over the east of the Philippines strengthens and then triggers a Rossby wave, which propagates northward to maintain an anticyclonic anomaly in the midlatitudes, indicating a northeastward shift of the NWP subtropical high. The anticyclonic anomaly facilitates the formation of relatively stable atmospheric stratification or even an inversion layer in the lower level of the troposphere, and strengthens the horizontal southerly moisture transportation from the tropical-subtropical oceans to the fog-prone area. On the other hand, a greater meridional SST gradient over the cold flank of the Kuroshio Extension, due to ocean downwelling, is produced by the anticyclonic wind stress anomaly. Both of these two aspects are favorable for the warm and humid air to cool, condense, and form fog droplets, when air masses cross the SST front. The opposite circumstances occur in low PJ index years, which are not conducive to the formation of sea fog. Finally, a multi-model ensemble mean projection reveals a prominent downward trend of the PJ index after the 2030s, implying a possible decline of the SFF in this period.展开更多
Tectonically, the northwestern South China Sea （SCS） is located at the junction between three micro-plates, i.e., the Indochina, South China and Zhongsha-Xisha micro-plates, and involves three basins, i.e., the Ying...Tectonically, the northwestern South China Sea （SCS） is located at the junction between three micro-plates, i.e., the Indochina, South China and Zhongsha-Xisha micro-plates, and involves three basins, i.e., the Yinggehai Basin, the Qiongdongnan Basin and Xisha Trough in the east, and the Zhongjiannan Basin in the south. Since the Pliocene （5.3 Ma）, the Yinggehai Basin has experienced repeated accelerating subsidence, high thermal fluid, and widely developing mud-rich overpressure chambers, abundant mud diapers and crust-mantle mixed CO2. While a large central canyon was developed in the Qiongdongnan Basin, new rift occurred in the Xisha ~rough. These characteristics demonstrate a single tectonic unit for the northwestern SCS, for which we have undertaken stress field modeling to understand its plate deformations and sedimen- tary responses. Our results demonstrate that an extension tectonic event occurred after 5.3 Ma in theYingge- hal-Qiongdongnan-Xisha trough area, which is characterized by thinner crust C〈16000 m）, half-graben or graben structural style and thicker sedimentary sequences （〉3 500 m）. A new rift system subsequently was developed in this area; this event was mainly driven by the combined effects of different movement veloc- ity and direction of the three micro-plates, and the far-field effect of the continental collision between the Indian Plate and the Tibetan Plateau, and subduction of the Pacific Plate underneath the Eurasian Plate.展开更多
基金supported by the National Natural Science Foundation of China(Nos.42271003,42301001)the Fundamental Research Funds for the Central Universities(No.lzujbky-2022-ey09)+1 种基金the China Postdoctoral Science Foundation(No.GZB20230275)Supercomputing Center of Lanzhou University。
文摘Arid regions are vital components of Earth’s land surface.Clarifying the area/boundary of arid region is crucial for comprehending area changes and potential mechanisms.However,the accuracy and applicability of arid region boundary delineated by different indices remain unclear.In this study,the annual precipitation(AP),humidity index(H),and aridity index(K)were calculated for delineating arid region of China using 106 meteorological stations during 1990–2019.The results suggest that AP and H can accurately delineate arid region,because they are consistent with the distribution of typical soil and vegetation in arid region,whereas K is not.Moreover,AP is the best index for delineating arid region in regions with limited meteorological data,especially in studying long-term patterns and mechanisms of area changes.The accuracy of delineating arid region using H is enhanced in regions with abundant meteorological data.Over the past 30 years,influenced by the increase of atmospheric moisture influx and precipitation,the area in arid region of northwestern China decreased by 70×10^(3)–90×10^(3)km^(2),resulting in the present area of approximately 1.55×10^(6)km^(2).This study provides appropriate indices for delineating arid region,contributing to improving our knowledge of regional responses difference to climate change.
基金supported by the Natural Science Foundation of Inner Mongolia Autonomous Region(2024QN04014)the Open Research Fund of Yinshanbeilu Grassland Eco-hydrology National Observation and Research Station,China Institute of Water Resources and Hydropower Research(Grant No.YSS202401)+2 种基金Scientific Research Support Program for Introducing Talents at the Inner Mongolia Autonomous Region of China(DC2400002177 and DC2400003177)Major Projects of Erdos Science and Technology(Project No.2022EEDSKJZDZX015)Applied technology research and development project in Jungar Banner of Inner Mongolia Autonomous Region of China(2023YY-13).
文摘Groundwater is essential for maintaining public health,promoting economic development,and ensuring ecosystem stability in arid and semi-arid regions.The northwestern Ordos Basin(China)primarily relies on groundwater from multilayered aquifer systems;however,our knowledge of the hydrochemical characteristics and water quality of groundwater in this region is limited.Here,we employed a newly collected dataset of 94 groundwater samples from different aquifers to constrain the source,controlling processes of fluoride in groundwater,and its potential health risk in the area.Groundwater is characterized by Na-Cl and Na-SO_(4) types with a minor Na-HCO_(3) type,which is primarily controlled by ion exchange,silicate weathering,and the dissolution of carbonate and evaporite minerals.Of the groundwater samples,42%exceeded the fluoride limit of 1.5 mg/L established by the World Health Organization(WHO).This is mainly attributed to geogenic sources,including fluorine-bearing mineral dissolution,cation exchange,evaporation,and competitive adsorption.The water quality index suggests that most samples are unsuitable for drinking.Health risk assessment results based on the Monte Carlo simulation indicate that children face significantly higher non-carcinogenic health risks from fluoride exposure than adults(both males and females).These findings provide new insights into the complex hydrogeochemical evolution of fluoride in groundwater and the groundwater quality status in multi-aquifer systems,contributing to the sustainable development and management of groundwater resources in the Ordos Basin.
基金The Natural Science Foundation of Jiangsu Province under contract No.BK20210885the National Natural Science Foundation of China under contract Nos 52372356,52371277,and 42076005.
文摘Based on year-long mooring observations(January-December 2013)near the Xisha Islands in the northwestern South China Sea,this study investigates the characteristics of typhoon-induced near-inertial waves(NIWs)during three events(typhoons Wutip,Nari,and Haiyan).The influence of mesoscale eddies on NIWs and the interaction between NIWs and internal tides(ITs)were analyzed.Notably,near-inertial kinetic energy(NIKE)increased significantly following typhoon Haiyan,reaching a peak value of 40.60 J/m^(3),the highest recorded NIKE in 2013.This value was approximately threefold and fivefold larger than those generated by typhoons Wutip and Nari,respectively.NIKE generated by all three typhoons exhibited downward radiation.Power spectral analysis revealed significant frequency shifts in NIWs during each typhoon,with shifts linked to mesoscale eddies present at the observation site.Additionally,bicoherence analysis reveals that the fD_(1)(f+D_(1))and D_(2)−f waves(where f is the local inertial frequency,and D1 and D_(2)denote the frequencies of diurnal and semidiurnal ITs,respectively)in the power spectrum originate from the nonlinear interactions between NIWs and ITs during typhoons Wutip and Haiyan.Temporal analysis of kinetic energy and shear showed that the enhancement of nonlinear coupling between NIWs and ITs was primarily driven by the strong NIWs with strong vertical shear.This study provides valuable insights into the generation,propagation,and interaction of NIWs and ITs,contributing to a deeper understanding of ocean mixing processes in response to different typhoon conditions.
基金funded by National Natural Science Foundation of China(Grant Nos.42172153)。
文摘The Fengcheng Formation in the Hashan area,located on the northwestern margin of the Junggar Basin,represents a saline-alkaline lake facies with fine-grained mixed sedimentation.This formation is rich in alkaline minerals and serves as a high-quality source rock for hydrocarbon generation in alkaline lakes.However,its lithology is complex,and the origins of the salt minerals remain unclear.This study focuses on the salt minerals in the Fengcheng Formation of the Hashan area.Using core observation,thin section identification,scanning electron microscopy,electron probe micro-analysis,trace and rare earth element analysis,stable isotope analysis,fluid inclusion analysis,and zircon U-Pb dating,the sedimentary age of Fengcheng Formation and the mineralogical and geochemical characteristics of salt minerals were systematically studied.The salt minerals identified in the Fengcheng Formation include calcite,dolomite,eitelite,northupite,shortite,reedmergnerite,and Na-carbonate.According to the different types of salt minerals,the different contact relations between minerals,the different production positions and production styles of mineral combinations,the salt mineral assemblage in the study area is classified into three categories:The combination of calcite,dolomite,shortite,and reedmergnerite,The combination of Na-carbonates,eitelite,shortite,and reedmergnerite,The combination of dolomite,eitelite,shortite,and northupite.Two zircon U-Pb ages,307.8±2.7 Ma and 308.5±3.5 Ma,span the Carboniferous-Permian boundary,corresponding to an interglacial period within the Late Paleozoic Ice Age,aligning with the development of salt minerals.Salt minerals have the formation modes of sedimentation,replacement and hydrothermal transformation.Terrestrial weathering products,atmosphe ric,volcanic and hydrothermal processes,residual seawater,clay mineral transformation,thermal evolution of organic matter and tuffaceous alteration are material sources.The salt-forming fluid has the characteristics of weak acid-alkaline,medium-low temperature and high salinity,and is mainly driven by subduction zone high pressure,magmatic heat and gravity.The burial depth,temperature and CO_(2)concentration required for the formation of salt minerals were clarified,and the evolution sequence of salt-forming fluids from sedimentation to diagenesis and accompanied by hydrothermal(hot water)activities was summarized.The evolution model of salt minerals controlled by different genesis from the first member to the third member of Fengcheng Formation was established.The research findings are significant for understanding the paleoenvironment of the Fengcheng Formation,the formation mechanisms of high-salinity lakes,and the salt formation models.
基金National Natural Science Foundation of China,No.42225105,No.42201176National Natural Science Foundation of China Basic Science Center for Tibetan Plateau Earth System Project(NSFC BSCTPES Project),No.41988101。
文摘Tropical cyclones(TCs)have profound impacts on socioeconomic conditions and pose substantial risks to lives and property.However,it is still unclear whether the multitimescale changes in TC activity over the past 2000 years in the Northwestern Pacific(NWP)were regulated by Asian dust forcing.Here,we assessed the impact of Asian dust on TC activity using observational data and reconstructed records from the northern and southern NWP.Our correlation analysis of instrumental data from 1954 to 2017 reveals no significant relationship between observed TC activity and Asian dust forcing.Furthermore,we found a meridional dipole pattern of TC variation across the NWP in observations and reconstructions.These finding challenges current explanations that are based on the synchronous changes in TC activity and Asian dust forcing.Alternatively,we propose that the Western Pacific Subtropical High(WPSH)plays a crucial role in driving these meridional dipole patterns in TC variations,as supported by observations and reconstructions.The southwestward extension of an enhanced WPSH intensifies easterly flow,steering TCs westward along its southern edge.This leads to more TC activity in the southern NWP but less in the north,and vice versa when the WPSH is weakened.With the expected strengthening of the WPSH due to global warming,it is vital to consider its impact on NWP TC activity for effective risk-mitigation strategies.
文摘A 28-year best track dataset containing size parameters that include the radii of the 15.4 m s^-1 winds （R15） and the 25.7 m s^-1 winds （R26） of tropical cyclones （TCs） in the Northwestern Pacific, the NCEP/ NCAR reanalysis dataset and the Extended Reconstructed Sea Surface Temperature （ERSST） dataset are employed in this study. The climatology of size parameters for the tropical cyclones in the Northwestern Pacific from 1977 to 2004 is investigated in terms of the spatial and temporal distributions. The results show that the major activity of TCs in the Northwestern Pacific is from July to October. A majority of TCs lie over the ocean west of 150°E, and a few TCs can intensify to the Saffir-Simpson （S-S） categories 4, 5. Both R15 and R26 tend to increase as the tropical cyclones intensify. The values of R15 and R26 are larger for intense TCs in the Northwestern Pacific than in the North Atlantic generally. Both R15 and R26 peak in October, and before and after October, R15 and R26 decrease, which is different from the case in the North Atlantic. The smaller R15s and R26s occur in a large range over the Northwestern Pacific, while the larger R15s and R26s mainly lie in the eastern ocean from Taiwan Island to the Philippine Islands where many tropical cyclones develop in intense systems. The tropical cyclones with size parameters of R15 or R26 on average take a longer time to intensify than to weaken, and the weak tropical cyclones have faster weakening rates than intensification rates. From 1977 to 2004, the annual mean values of R15 increase basically with year; during the 28-year period, the value of R15 increases by 52.7 kin, but R26 does not change with year obviously.
基金This study was supported by the Ministry of Sciences and Technology of China(2001CB209100),
文摘The Lower Cretaceous strata in the Kuqa Basin in Xinjiang are marked by a set of arid red beds. Several types of sedimentary fades can be identified in this set of arid red beds: mudstones of the plaza and intracontinental sebkha, aeolian sandstones, sandy conglomerates of the intermittent river, conglomerates of the pluvial fan, etc. These types of sedimentary facies constitute a typical desert system. Therefore, the Cretaceous strata in the Kuqa Basin provide a favorable condition for studies of sequence stratigraphic divisions of the desert system. With the rise and fall of the base level of the sedimentary basin, cyclicity is clearly revealed in stratigraphic records, which helps the identification of the third-order sequences. Based on the cyclicity in stratigraphic records, 5 third-order sequences can be found in the strata of the Early Cretaceous in the Kuqa Basin. These sequences comprise a second-order tectonic sequence. The primary feature of these third-order sequences is of an upward-fining sedimentary succession formed by a succession of 'coarse sediments of the alluvial system-fine sediments of the lake system'. The result of this study shows that aeolian sandstones are the best reservoirs of natural gas in the Cretaceous strata in the Kuqa Basin, and that the Kela-2 gas field is the first large gas field dominated by aeolian sandstone reservoirs in China.
基金The Key Program of Knowledge Innovation Project of Chinese Academy of Sciences under contract No.KZCX1-YW-12the National 863 Program under contract Nos 2008AA09A401 and 2006AA09A109
文摘Based on in-situ time series data from the acoustic Doppler current profiler （ADCP） and thermistor chain in Wenchang area, a sequence of internal solitary wave （ISW） packets was observed in September 2005, propagating northwest on the continental shelf of the northwestern South China Sea （SCS）. Corresponding to different stratification of the water column and tidal condition, both elevation and depression ISWs were observed at the same mooring location with amplitude of 35 m and 25 m respectively in different days. Regular arrival of the remarkable ISW packets at approximately the diurnal tidal period and the dominance of diurnal internal waves in the study area, strongly suggest that the main energy source of the waves is the diurnal tide. Notice that the wave packets were all riding on the troughs and shoulders of the internal tides, they were probably generated locally from the shelf break by the evolution of the internal tides due to nonlinear and dispersive effects.
基金supported by the Major National S&T(Science and Technology) Program of China(2011ZX05009-002)the National Natural Science Foundation of China (41002049, 41030213)the Fundamental Research Funds for the Central Universities in China (2010YD09)
文摘The sequence stratigraphy of the Jurassic coal measures of northwestern China has been studied based on data from outcrop and borehole sections. Because of the geological background and the diversity of basin types, such as isochronisms of coal seams and recognition of key sequence boundaries, it is rare to summarize and correlate sequence structure and framework. The types and recognition characteristics of the sequence boundaries of the Jurassic coal measures are revealed by comparing climatic characteristics, structural styles and the base level cycle. A total of five third-order sequences and 15 systems tracts have been subdivided and the sequence stratigraphic framework has been reconstructed confirming that the thick coals accumulated in the late stage of transgression system tracts of sequence I （SQ I） and sequence III （SQ III）. This idea is of important academic significance for instructing coal resources exploration, and enhancing geological effects of prospecting engineering. It is also of practical significance for guaranteeing construction of the large-scale coal production base in northwestern China, accelerating the westward development of the coal industry stratagem.
基金supported by Special Basic Research Program of Ministry of Science and Technology of China (Grant No. 2006FY120300)National Committee of Stratigraphy of China. V. Vajda acknowledges the financial support provided by Swedish Research Council (VR, Grant No. 2007-4509)+1 种基金V. Vajda is a Swedish Royal Academy of Sciences Research Fellow founded through the Knut and Alice Wallenbergs Foundationa contribution to UNESCO-IUGS IGCP Project 506
文摘The Triassic-Jurassic （Tr-J） boundary marks a major extinction event, which （～200 Ma）resulted in global extinctions of fauna and flora both in the marine and terrestrial realms. There prevail great challenges in determining the exact location of the terrestrial Tr-J boundary, because of endemism of taxa and the scarcity of fossils in terrestrial settings leading to difficulties in linking marine and terrestrial sedimentary successions. Investigation based on palynology and bivalves has been carried out over a 1113 m thick section, which is subdivided into 132 beds, along the Haojiagou valley on the southern margin of the Junggar Basin of the northern Xinjiang, northwestern China. The terrestrial Lower Jurassic is conformably resting on the Upper Triassic strata. The Upper Triassic covers the Huangshanjie Formation overlaid by the Haojiagou Formation, while the Lower Jurassic comprises the Badaowan Formation followed by the Sangonghe Formation. Fifty six pollen and spore taxa and one algal taxon were identified from the sediments. Based on the key-species and abundance of spores and pollen, three zones were erected： the Late Triassic （Rhaetian） Aratrisporites-Alisporites Assemblage, the Early Jurassic （Hettangian） Perinopollenites-Pinuspollenites Assemblage, and the Sinemurian Perinopollenites-Cycadopites Assemblage. The Tr-J boundary is placed between bed 44and 45 coincident with the boundary between the Haojiagou and Badaowan formations. Beds with Ferganoconcha （？）, Unio-Ferganoconcha and Waagenoperna-Yananoconcha bivalve assemblages are recognized. The Ferganoconcha （？） bed is limited to the upper Haojiagou Formation,Unio- Ferganoconcha and Waagenoperna- Yananoconcha assemblages are present in the middle and upper members of the Badaowan Formation. The sedimentary succession is interpreted as terrestrial with two mainly lake deposit intervals within Haojiagou and Badaowan formations, yielding fresh water algae and bivalves. However, the presence of brackish water algae Tasmanites and the marine-littoral facies bivalve Waagenoperna from the Badaowan Formation indicate that the Junggar Basin was influenced by sea water caused by transgressions from the northern Tethys, during the Sinemurian.
基金the Ministry of Science and Technology of China (No.2002CB714001 and 2001CCB00200)the Youth Fund of State Oceanic Administration (No. 2004203)
文摘A large number of autonomous profiling floats deployed in global oceans have provided abundant temperature and salinity profiles of the upper ocean. Many floats occasionally profile observations during the passage of tropical cyclones. These in-situ observations are valuable and useful in studying the ocean’s response to tropical cyclones, which are rarely observed due to harsh weather conditions. In this paper, the upper ocean response to the tropical cyclones in the northwestern Pacific during 2000–2005 is analyzed and discussed based on the data from Argo profiling floats. Results suggest that the passage of tropical cyclones caused the deepening of mixed layer depth (MLD), cooling of mixed layer temperature (MLT), and freshening of mixed layer salinity (MLS). The change in MLT is negatively correlated to wind speed. The cooling of the MLT extended for 50–150 km on the right side of the cyclone track. The change of MLS is almost symmetrical in distribution on both sides of the track, and the change of MLD is negatively correlated to pre-cyclone initial MLD.
基金the National Natural Science Foundation ofChina under contract No.40173027.
文摘Dissolved and particulate 234 Th, particulate organic carbon(PON), nitrogen, and chlorophyll-a concentrations in the upper 200 m of water columns from seven stations in the northwestern North Pacific Ocean were determined in the winter of 1997.The dissolved, particulate, and total 234 Th activities (dissolved plus particulate)show a pronounced deficiency with respect to its parent 238 U in the euphotic zone whereas the total 234 Th shows a near-equilibrium at the depth greater than 100 m.The 234 Th data are used to derive the mean residence time, export fluxes of 234 Th, and fluxes of particulate organic carbon and nitrogen out of the euphotic zone. In the Subarctic Current area, the residence time of dissolved 234 Th with respect to its removal onto particles is 40 ~50 d while the residence time of dissolved 234Th in the subtropical area is about 20 d due to the Kuroshio's influence.The particulate organic carbon(POC)and particulate organic nitroge(PON)fluxes in winter range over 3.8～8.2 and 0.50～0.98 mmol/(m2 ·d), respectively, and are higher in the west region than in the east, and higher in the south than in the north. The co-influence of Kuroshio-Oyashio Currents with supply of nutrient substances from the coastal area and the light condition are two factors determining the horizontal distribution of POC fluxes in winter.The depth distribution of the chlorophyll-a as well as the consistence of the ratio of POC to PON with the Redfield ratio suggest that phytoplankton is the main contributor to the export of POC in this area in winter.The POC fluxes in the northwestern North Pacific Ocean in winter are comparable to some areas in the world oceans in spring and summer seasons.
基金This paper is a partial result of a major tundamental project (No. 8502206) of the Ministry of Geology and Mineral Resources and a project (No. 9514) of the Foundation for Development of Science and Technology in Geology, and financially supported by the
文摘A typical HP/MT (high pressure/medium temperature) eclogite from Xiongdian, northwestern Dabie Mountains, has been geochronologically studied using the single-zircon U-Pb, 40Ar-39Ar and Sm-Nd methods. Prismatic zircons occurring as inclusions within garnets define a minimum crystallization age of 399.5±1.6 Ma. 40Ar-39Ar dating on amphibole gives a plateau age.of 399.2 ± 4 Ma, which is interpreted as a retrogression age of amphibolite facies. This integrated study enables us to conclude that the age of high-pressure metamorphism is older than 399.5 ± 1.6 Ma, suggesting Caledonian collision between the North China and Yangtze plates. Round zircon within the aggregate of quartz and muscovite gives a concordant age of 301± 2 Ma, reflecting a later retrogression event. An age profile of post-eclogite metamorphism is documented, including amphibolite facies metamorphism at 399.2 Ma shortly after eclogitization and later retrogressive metamorphism at 301 Ma. Sm-Nd mineral isochron of garnet+omphacite gives an unreasonable age of 544 ± 23 Ma. which is quite older than that of prismatic zircon and may be attributed to isotopic disturbance by retrogression.
基金National Natural Science Foundation of China,No.40830636 No.40671034Foundation of Isotopes in Precipitation of Chinese Ecosystem Research Network
文摘In order to reveal the characteristics and climatic controls on the stable isotopic composition of precipitation over Arid Northwestern China, eight stations have been selected from Chinese Network of Isotopes in Precipitation(CHNIP).During the year 2005 and 2006, monthly precipitation samples have been collected and analyzed for the composition of δD and δ18O.The established local meteoric water line δD=7.42δ18O+1.38, based on the 95 obtained monthly composite samples, could be treated as isotopic input function across the region.The deviations of slope and intercept from the Global Meteoric Water Line indicated the specific regional meteorological conditions.The monthly δ18O values were characterized by a positive correlation with surface air temperature(δ18O(‰) =0.33 T(℃)-13.12).The amount effect visualized during summer period(δ18O(‰) =-0.04P(mm)-3.44) though not appeared at a whole yearly-scale.Spatial distributions of δ18O have properly portrayed the atmospheric circulation background in each month over Arid Northwestern China.The quan-titative simulation of δ18O, which involved a Rayleigh fractionation and a kinetic fractionation, demonstrated that the latter one was the dominating function of condensation of raindrops.Furthermore, the raindrop suffered a re-evaporation during falling processes, and the precipitation vapor might have been mixed with a quantity of local recycled water vapor.Multiple linear regression equations and a δ18O-T relation have been gained by using meteorological parameters and δ18O data to evaluate physical controls on the long-term data.The established δ18O-T relation, which has been based on the present-day precipitation, could be considered as a first step of quantitatively reconstructing the historical environmental climate.
基金jointly financially supported by “Yunling Scholars” Research Project from Yunnan Province,China Geological Survey Project(No.DD20160124 and 12120114013501)the National Natural Science Foundation of China(grant No.41602103)the “Study on metallogenic regularities and metallogenic series of gold-polymetallic deposits,Northwestern Yunnan Province” research project(E1107)from Yunnan Gold&Mining Group Co.,Ltd
文摘Based on comprehensive petrological, geochronological, and geochemical studies, this study analyzed the relationships between the Beiya gold-polymetallic skarn deposit and quartz syenite porphyries, and discussed the source（s） and evolution of magmas. Our results suggest that syenite porphyries（i.e. the Wandongshan, the Dashadi, and the Hongnitang porphyries）, which formed between the Eocene and the early Oligocene epochs, are the sources for the gold-polymetallic ores at the Beiya deposit. Carbonate rocks（T2 b） of the Triassic Beiya Formation in the ore district provide favorable host space for deposit formation. Fold and fault structures collectively play an important role in ore formation. The contact zone between the porphyries and carbonates, the structurally fractured zone of carbonate and clastic rocks, and the zone with well-developed fractures are the ideal locations for ore bodies. Four types of mineralization have been recognized： 1） porphyry-style stockwork gold–iron（copper） ore, 2） skarn-style gold-iron（copper and lead） ore in the near contact zone, 3） strata-bound, lense-type lead–silver–gold ore in the outer contact zone, and 4） distal vein-type gold–lead–silver ore. Supergene processes led to the formation of oxide ore, such as the weathered and accumulated gold–iron ore, the strata-bound fracture oxide ore, and the structure-controlled vein-type ore. Most of these ore deposits are distributed along the axis of the depressed basin, with the hypogene ore controlling the shape and characteristics of the oxide ore. This study provides critical geology understanding for mineral prospecting scenarios.
基金granted by the National Natural Science Foundation of China (41603046)the Natural Science Foundation of Hunan Province (2017JJ1034)
文摘The accumulation and productivity of shale gas are mainly controlled by the characteristics of shale reservoirs;study of these characteristics forms the basis for the shale gas exploitation of the Lower Cambrian Niutitang Formation(Fm),Southern China.In this study,core observation and lithology study were conducted along with X-ray diffraction(XRD)and electronic scanning microscopy(SEM)examinations and liquid nitrogen(N2)adsorption/desorption and CH4 isothermal adsorption experiments for several exploration wells in northwestern Hunan Province,China.The results show that one or two intervals with high-quality source rocks(TOC>2 wt%)were deposited in the deep-shelf facies.The source rocks,which were mainly composed of carbonaceous shales and siliceous shales,had high quartz contents(>40 wt%)and low clay mineral(<30 wt%,mainly illites)and carbonate mineral(<20 wt%)contents.The SEM observations and liquid nitrogen(N2)adsorption/desorption experiments showed that the shale is tight,and nanoscale pores and microscale fractures are well developed.BJH volume(VBJH)of shale ranged from 2.144×10^-3 to 20.07×10^-3 cm^3/g,with an average of 11.752×10^-3 cm3/g.Pores mainly consisted of opened and interconnected mesopores(2–50 nm in diameter)or macropores(>50 nm in diameter).The shale reservoir has strong adsorption capacity for CH4.The Langmuir volume(VL)varied from 1.63 to 7.39 cm^3/g,with an average of 3.95 cm^3/g.The characteristics of shale reservoir are controlled by several factors:(1)A deep muddy continental shelf is the most favorable environment for the development of shale reservoirs,which is controlled by the development of basic materials.(2)The storage capacity of the shale reservoir is positively related to the TOC contents and plastic minerals and negatively related to cement minerals.(3)High maturity or overmaturity leads to the growth of organic pores and microfractures,thereby improving the reservoir storage capacity.It can be deduced that the high percentage of residual gas in Niutitang Fm results from the strong reservoir storage capacity of adsorbed gas.Two layers of sweet spots with strong storage capacity of free gas,and they are characterized by the relatively high TOC contents ranging from 4 wt%to 8 wt%.
基金supported by the National 863 project (2007AA092201 2007AA092202)+4 种基金National Development and Reform Commission Project (2060403)"Shu Guang" Project (08GG14) from Shanghai Municipal Education CommissionShanghai Leading Academic Discipline Project (Project S30702)supported by the National Distantwater Fisheries Engineering Research Center, and Scientific Observing and Experimental Station of Oceanic Fishery Resources, Ministry of Agriculture, ChinaYong Chen’s involvement in the project was supported by the Shanghai Dongfang Scholar Program
文摘Weighting values for different habitat variables used in multi-factor habitat suitability index (HSI) modeling reflect the relative influences of different variables on distribution of fish species. Using the winter-spring cohort of neon flying squid (Ommastrephes bartramii) in the Northwestern Pacific Ocean as an example, we evaluated the impact of different weighting schemes on the HSI models based on sea surface temperature, gradient of sea surface temperature and sea surface height. We compared differences in predicted fishing effort and HSI values resulting from different weighting. The weighting for different habitat variables could greatly influence HSI modeling and should be carefully done based on their relative importance in influencing the resource spatial distribution. Weighting in a multi-factor HSI model should be further studied and optimization methods should be developed to improve forecasting squid spatial distributions.
基金National Key Project on Basic Research(973),No.2010CB951003The National Science and Technology Project,No.2014BAD10B06
文摘Water demand increases continuously with an increasing population and economic development. As a result, the difference between water supply and demand becomes a sig- nificant issue, especially in arid regions. To figure out the utilization of water resources in the arid region of northwestern China （ARNWC）, and also to provide methodologies to predict the water use in future, three models were established in this study to calculate agricultural irri- gation, industrial and domestic water use in the ARNWC from the late 1980s to 2010. Based on river discharges in the region, the supply and demand of water resources at the river basin level were analyzed. The results indicated that agricultural irrigation demand occupies more than 90% of the total water use in the ARNWC. Total water demand increased from 31.97 km3 in the late 1980s to 48.19 km3 in 2010. Most river basins in this arid region were under me- dium and high water stress. Severe-risk river basins, such as the Shiyang river basin and the eastern part of the northern piedmont of the Tianshan Mountains, were found in this region. It was revealed that the water supply became critical from April to May, which was the season of the lowest water supply as determined by comparing monthly water consumption.
基金supported by a "973" project (Grant No. 2012CB955602) Natural Science Foundation of China and the Shandong Joint Fund for Marine Science Research Centers (Grant No. U1406401)the NSFC (Grant No. 41175006)supported by the Fundamental Research Funds for the Central Universities
文摘The northwestern Pacific （NWP） is a fog-prone area, especially the ocean east of the Kuril Islands. The present study analyzes how the Pacific-Japan （PJ） teleconnection pattern influences July sea fog in the fog-prone area using independent datasets. The covariation between the PJ index and sea fog frequency （SFF） index in July indicates a close correlation, with a coefficient of 0.62 exceeding the 99% confidence level. Composite analysis based on the PJ index, a case study, and model analysis based on GFDL-ESM2M, show that in high PJ index years the convection over the east of the Philippines strengthens and then triggers a Rossby wave, which propagates northward to maintain an anticyclonic anomaly in the midlatitudes, indicating a northeastward shift of the NWP subtropical high. The anticyclonic anomaly facilitates the formation of relatively stable atmospheric stratification or even an inversion layer in the lower level of the troposphere, and strengthens the horizontal southerly moisture transportation from the tropical-subtropical oceans to the fog-prone area. On the other hand, a greater meridional SST gradient over the cold flank of the Kuroshio Extension, due to ocean downwelling, is produced by the anticyclonic wind stress anomaly. Both of these two aspects are favorable for the warm and humid air to cool, condense, and form fog droplets, when air masses cross the SST front. The opposite circumstances occur in low PJ index years, which are not conducive to the formation of sea fog. Finally, a multi-model ensemble mean projection reveals a prominent downward trend of the PJ index after the 2030s, implying a possible decline of the SFF in this period.
基金The major project of the China National Science and Technology "Large Oil and Gas Fields and Coal bed Gas Development" under contract No.2011ZX05023-003-003the Fundamental Research Funds for the Central Universities under contract No.1350219123
文摘Tectonically, the northwestern South China Sea （SCS） is located at the junction between three micro-plates, i.e., the Indochina, South China and Zhongsha-Xisha micro-plates, and involves three basins, i.e., the Yinggehai Basin, the Qiongdongnan Basin and Xisha Trough in the east, and the Zhongjiannan Basin in the south. Since the Pliocene （5.3 Ma）, the Yinggehai Basin has experienced repeated accelerating subsidence, high thermal fluid, and widely developing mud-rich overpressure chambers, abundant mud diapers and crust-mantle mixed CO2. While a large central canyon was developed in the Qiongdongnan Basin, new rift occurred in the Xisha ~rough. These characteristics demonstrate a single tectonic unit for the northwestern SCS, for which we have undertaken stress field modeling to understand its plate deformations and sedimen- tary responses. Our results demonstrate that an extension tectonic event occurred after 5.3 Ma in theYingge- hal-Qiongdongnan-Xisha trough area, which is characterized by thinner crust C〈16000 m）, half-graben or graben structural style and thicker sedimentary sequences （〉3 500 m）. A new rift system subsequently was developed in this area; this event was mainly driven by the combined effects of different movement veloc- ity and direction of the three micro-plates, and the far-field effect of the continental collision between the Indian Plate and the Tibetan Plateau, and subduction of the Pacific Plate underneath the Eurasian Plate.
