The Late Permian was marked by a series of important geological events and widespread organic-rich black shale depositions,acting as important unconventional hydrocarbon source rocks.However,the mechanism of organic m...The Late Permian was marked by a series of important geological events and widespread organic-rich black shale depositions,acting as important unconventional hydrocarbon source rocks.However,the mechanism of organic matter(OM)enrichment throughout this period is still controversial.Based on geochemical data,the marine redox conditions,paleogeographic and hydrographic environment,primary productivity,volcanism,and terrigenous input during the Late Permian in the Lower Yangtze region have been studied from the Putaoling section,Chaohu,to provide new insights into OM accumulation.Five Phases are distinguished based on the TOC and environmental variations.In Phase I,anoxic conditions driven by water restriction enhanced OM preservation.In Phase II,euxinic and cycling hydrological environments were the two most substantial controlling factors for the massive OM deposition.During Phase III,intensified terrestrial input potentially diluted the OM in sediment and the presence of oxygen in bottom water weakened the preservation condition.Phase IV was characterized by a relatively higher abundance of mercury(Hg)and TOC(peak at 16.98 wt%),indicating that enhanced volcanism potentially stimulated higher productivity and a euxinic environment.In Phase V,extremely lean OM was preserved as a result of terrestrial dilutions and decreasing primary productivity.Phases I,II and IV are characterized as the most prominent OM-rich zones due to the effective interactions of the controlling factors,namely paleogeographic,hydrographic environment,volcanism,and redox conditions.展开更多
Marine strata are widely exposed in the Hushan and Chaohu areas, Lower Yangtze region. As biomarker geochemistry of the strata has not been well documented, this paper deals with the biomarker composition of represent...Marine strata are widely exposed in the Hushan and Chaohu areas, Lower Yangtze region. As biomarker geochemistry of the strata has not been well documented, this paper deals with the biomarker composition of representative samples collected from the Silurian, Carboniferous and Triassic systems and their geological implications, thus providing clues to marine organic matter. On the basis of experimental results, it is shown that abundant biomarkers (e.g. n-alkanes, isoprenoids, terpanes and steranes) were detected. As organic matter in the strata is highly to over mature in general based on petrologic microobservation, some biomarkers (mainly n-alkanes) except terpanes and steranes cannot reflect the source, depositional environment and maturity of organic matter. Thus, primarily based on analyses of the terpanes and steranes, it is suggested that organic matter in the Silurian and Carboniferous strata is derived mainly from lower organisms, while higher plants are predominant in the Triassic organic matter. This further indicates that the depositional environment may have transformed from the marine to continental facies in the Late Triassic. These results provide new evidence for the study of regional depositional evolution, and have enriched the study of biological composition of organic matter. In addition, the biomarker geochemistry of organic matter at high to over maturation stage is addressed.展开更多
The middle and lower Yangtze River basin(MLYRB)suffered persistent heavy rainfall in summer 2020,with nearly continuous rainfall for about six consecutive weeks.How the likelihood of persistent heavy rainfall resembli...The middle and lower Yangtze River basin(MLYRB)suffered persistent heavy rainfall in summer 2020,with nearly continuous rainfall for about six consecutive weeks.How the likelihood of persistent heavy rainfall resembling that which occurred over the MLYRB in summer 2020(hereafter 2020PHR-like event)would change under global warming is investigated.An index that reflects maximum accumulated precipitation during a consecutive five-week period in summer(Rx35day)is introduced.This accumulated precipitation index in summer 2020 is 60%stronger than the climatology,and a statistical analysis further shows that the 2020 event is a 1-in-70-year event.The model projection results derived from the 50-member ensemble of CanESM2 and the multimodel ensemble(MME)of the CMIP5 and CMIP6 models show that the occurrence probability of the 2020PHR-like event will dramatically increase under global warming.Based on the Kolmogorov-Smirnoff test,one-third of the CMIP5 and CMIP6 models that have reasonable performance in reproducing the 2020PHR-like event in their historical simulations are selected for the future projection study.The CMIP5 and CMIP6 MME results show that the occurrence probability of the 2020PHR-like event under the present-day climate will be double under lower-emission scenarios(CMIP5 RCP4.5,CMIP6 SSP1-2.6,and SSP2-4.5)and 3-5 times greater under higher-emission scenarios(3.0 times for CMIP5 RCP8.5,2.9 times for CMIP6 SSP3-7.0,and 4.8 times for CMIP6 SSP5-8.5).The inter-model spread of the probability change is small,lending confidence to the projection results.The results provide a scientific reference for mitigation of and adaptation to future climate change.展开更多
Fault geometry, kinematics, geophysics, the tectonic stress field and tectonic evolution of the Zhouwang fault in the southern Jiangnan tectonic transition zone of the Lower Yangtze region, eastern China are examined....Fault geometry, kinematics, geophysics, the tectonic stress field and tectonic evolution of the Zhouwang fault in the southern Jiangnan tectonic transition zone of the Lower Yangtze region, eastern China are examined. Field observations show the fault is composed of a series of nearly E–W trending, N–S dipping faults, and four stages of tectonism(sinistral strike-slip, thrust nappe, normal fault, and dextral strike-slip) developed in turn. Geophysical data show that the fault trends almost linearly E–W along a flat, steep gravity gradient at shallow depth, with distinct gravity anomalies to the north and south and different in the north and south. Also, the deep part is characterized by northward dip and a gradual slowing down. Tectonic stress field analysis indicates that the fault experienced four tectonic movements: NNE–SSW compression, NNW–SSE compression, NEE–SWW extension, and E–W compression. Combined with regional tectonic background and previous research results, this indicates that:(1) the Zhouwang fault experienced sinistral strike-slip movement during the Indosinian Period(260–200 Ma);(2) thrust nappes developed during the early Yanshanian Period(163–145 Ma);(3) a normal fault occurred in the late Yanshanian Period(125–65 Ma);and(4) dextral strike-slip movement occurred in the Himalayan Period(ca. 50–37 Ma). The results reveal the tectonic evolution of the fault during Mesozoic deformation in the area, and also reveal the geological evolution and tectonic transformation of the Lower Yangtze region, which is key to our understanding of intracontinental deformation in eastern China.展开更多
During Ching dynasty from 1644 to 1911, an interval of 268 years, there occurred in the lower Yangtze valley 197 floods and 156 droughts. The most serious droughts came in 1785, 1814, and 1856; and the most disastrous...During Ching dynasty from 1644 to 1911, an interval of 268 years, there occurred in the lower Yangtze valley 197 floods and 156 droughts. The most serious droughts came in 1785, 1814, and 1856; and the most disastrous floods in 1680,展开更多
The Wuwei Basin is one of the most important oil-and gas-bearing basins in the Meso-Cenozoic basin groups in the Lower Yangtze River region.It has great shale gas resource prospects.The formation mechanism of this bas...The Wuwei Basin is one of the most important oil-and gas-bearing basins in the Meso-Cenozoic basin groups in the Lower Yangtze River region.It has great shale gas resource prospects.The formation mechanism of this basin is poorly studied for lack of constraining data for deep structures.In this paper,a crustal electrical structure model of the Wuwei Basin and the adjacent areas is constructed based on the two-dimensional inversion of a magnetotelluric(MT)sounding profile achieved with the nonlinear conjugate gradient method.The results show that large-scale low-resistance bodies have developed in the underlying middle and lower crust of the Wuwei Basin,and are different from the uplifts on the two sides according to their high-resistance electrical characteristics.The electrical structure and regional geological and geophysical data suggest that the peak zone of the Chuzhou-Chaohu foreland fold-and-thrust belt is located on the east bank of the Yangtze River(Wuhu Section),which,together with the main thrust fault belt in the east,forms a typical thrust structure belt.An early Yanshanian sinistral strike-slip fault developed in the deep part of the Wuwei Basin,which may have controlled the formation and evolution of the basin,whereas the tectonic inversion of the early-developed thrust faults is relatively weak.These findings provide a geophysical basis for future studies of basin tectonic evolution and regional tectonic frameworks.展开更多
The Early Cretaceous aluminous A-type granites in the Lower Yangtze River belt(LYRB)can provide important insights into the Mesozoic magmatism in eastern China,but their origin remains highly controversial.In this stu...The Early Cretaceous aluminous A-type granites in the Lower Yangtze River belt(LYRB)can provide important insights into the Mesozoic magmatism in eastern China,but their origin remains highly controversial.In this study,radiogenic Ca-Nd isotopic analysis was performed for syenite porphyry and alkali-feldspar granite porphyry of the Yangshan pluton,a typical aluminous A-type granitic intrusion in the LYRB,to constrain its source and geodynamic setting.The results show thatε_(Ca)(126 Ma),ε_(Nd)(126 Ma)and K/Ca_(source) of the syenite porphyry range from-0.24 to+0.96,-7.2 to-6.0,and 0.31 to 1.26,respectively.The corresponding values for the alkali-feldspar granite porphyry range from 0.26 to 0.84,-8.0 to-6.1,and 0.79 to 1.08,respectively.Binary mixing modeling indicates that they were originated from the same sources with different proportion,namely,a mixing of 50%to 75%Neoproterozoic crust and 50%to 25%asthenospheric mantle.Together with previous works,we propose that the Early Cretaceous subduction of the ridge between the Pacific and Izanagi plates was responsible for the formation of the aluminous A-type granites in the LYRB.展开更多
Studies of the Pb, Sr and Nd isotopic composition of Mesozoic intrusive rocks indicate that the basement of the copper-gold metallogenic belt of the middle and lower reaches of the Yangtze River has 'two-layer str...Studies of the Pb, Sr and Nd isotopic composition of Mesozoic intrusive rocks indicate that the basement of the copper-gold metallogenic belt of the middle and lower reaches of the Yangtze River has 'two-layer structure' and partly has 'multi-layered structure', and is inhomogeneous and shows the distinct feature of E-W provincialism. The calculated model lead ages (t1) are mostly greater than 2600 Ma, and the model neodymium ages (TDM) vary from 953 to 2276 Ma and concentrate in two time intervals: 1800-2000 Ma and 1200-1600 Ma. It is concluded that the basement of the MBYR is composed of the Late Archaeozoic to Middle Proterozoic metamorphic series and that the crust was initiated in the Archaean and continued to grow in the Early and Middle Proterozoic, and the proportion of new crust formed by mantle differentiation during the Late Proterozoic is low.展开更多
In this study,we compiled and analyzed 69310 P-wave travel-time data from 6639 earthquake events.These events(M≥2.0)occurred from 1980 s to June 2019 and were recorded at 319 seismic stations(Chinese Earthquake Netwo...In this study,we compiled and analyzed 69310 P-wave travel-time data from 6639 earthquake events.These events(M≥2.0)occurred from 1980 s to June 2019 and were recorded at 319 seismic stations(Chinese Earthquake Networks Center)in the study area.We adopted the double-difference seismic tomographic method(tomo DD)to invert the 3-D P-wave velocity structure and constrain the crust-upper mantle architecture of the Middle and Lower Reaches of the Yangtze River Metallogenic Belt(MLYB).A 1-D initial model extracted from wide-angle seismic profiles was used in the seismic tomography,which greatly reduced the inversion residual.Our results indicate that reliable velocity structure of th e uppermost mantle can be obtained when Pn is involved in the tomography.Our results show that:(1)the pattern of the uppermost mantle velocity structure corresponds well with the geological partitioning:a nearly E-W-trending low-velocity zone is present beneath the Dabie Orogen,in contrast to the mainly NE-trending low-velocity anomalies beneath the Jiangnan Orogen.They suggest the presence of thickened lower crust beneath the orogens in the study area.In contrast,the Yangtze and Cathaysia blocks are characterized by relatively high-velocity anomalies;(2)both the ultra-high-pressure(UHP)metamorphic rocks in the Dabie Orogen and the low-pressure metamorphic rocks in the Zhangbaling dome are characterized by high-velocity anomalies.The upper crust in the Dabie Orogen is characterized by a low-velocity belt,sandwiched between two high velocity zones in a horizontal direction,with discontinuous low-velocity layers in the middle crust.The keel of the Dabie Orogen is mainly preserved beneath its northern section.We infer that the lower crustal delamination may have mainly occurred in the southern Dabie Orogen,which caused the mantle upwelling responsible for the formation of the granitic magmas emplaced in the middle crust as the low-velocity layers observed there.Continuous deep-level compression likely squeezed the granitic magma upward to intrude the upper crustal UHP metamorphic rocks,forming the'sandwich'velocity structure there;(3)high-velocity updoming is widespread in the crust-mantle transition zone beneath the MLYB.From the Anqing-Guichi ore field northeastward to the Luzong,Tongling,Ningwu and Ningzhen orefields,high-velocity anomalies in the crust-mantle transition zone increase rapidly in size and are widely distributed.The updoming also exists in the crust-mantle transition zone beneath the Jiurui and Edongnan orefields,but the high-velocity anomalies are mainly stellate distributed.The updoming high-velocity zone beneath the MLYB generally extends from the crust-mantle transition zone to the middle crust,different from the velocity structure in the upper crust.The upper crust beneath the Early Cretaceous extension-related Luzong and Ningwu volcanic basins is characterized by high velocity zones,in contrast to the low velocity anomalies beneath the Late Jurassic to Early Cretaceous compression-related Tongling ore field.The MLYB may have undergone a compressive-to-extensional transition during the Yanshanian(Jurassic-Cretaceous)period,during which extensive magmatism occurred.The near mantle-crustal boundary updoming was likely caused by asthenospheric underplating at the base of the lower crust.The magmas may have ascended through major crustal faults,undergoing AFC(assimilation and fractional crystallization)processes,became emplaced in the fault-bounded basins or Paleozoic sequences,eventually forming the many Cu-Fe polymetallic deposits there.展开更多
Anomalous characteristics of the atmospheric water cycle structure are highly significant to the mechanisms of seasonal-scale meteorological droughts.They also play an important role in the identification of indicativ...Anomalous characteristics of the atmospheric water cycle structure are highly significant to the mechanisms of seasonal-scale meteorological droughts.They also play an important role in the identification of indicative predictors of droughts.To better understand the causes of seasonal meteorological droughts in the middle and lower reaches of the Yangtze River(MLRYR),characteristics of the atmospheric water cycle structure at different drought stages were determined using standardized anomalies.The results showed that the total column water vapor(TCWV)was anomalously low during drought occurrence periods.In contrast,there were no anomalous signals at the drought persistence and recovery stages in the MLRYR.Moreover,there was no significant temporal correlation between the TCWV anomaly and seasonal-scale drought index(the 3-month standardized precipitation index(SPI_(3))).During drought events,water vapor that mainly originated from the Bay of Bengal was transported southwest of the MLRYR.Meanwhile,the anomalous signal of water vapor transport was negative at the drought appearance stage.At the drought persistence stage,the negative anomalous signal was the most significant.Water vapor flux divergence in the MLRYR showed significant positive anomalous signals during drought events,and the signal intensity shifted from an increasing to a decreasing trend at different drought stages.In addition,a significant positive correlation existed between the anomaly of water vapor flux divergence and regional SPI_(3).Overall,water vapor flux divergence is more predictive of droughts in the MLRYR.展开更多
Based upon the summer (June-August) precipitation data from 30 stations in the middle and lower reaches of Yangtze River in China, the spatial and temporal distribution of summer precipitation in the Yangtze River Bas...Based upon the summer (June-August) precipitation data from 30 stations in the middle and lower reaches of Yangtze River in China, the spatial and temporal distribution of summer precipitation in the Yangtze River Basin was analyzed. As was shown in the results, the distribution of summer precipitation in the middle and lower reaches of Yangtze River was mainly composed of four types: northern type (2005 and 2007), southern type (2001 and 2003), intermediate type (2000, 2004 and 2006) and integral type (2002). According to the correlation analysis of summer precipitation and atmospheric circulation in East Asia, the precipitation in the Yangtze River Basin and high-low level circulation anomalies were significantly related. In other words,with the increase of the meridional degree of circulation at mid-high latitudes in the middle and upper troposphere as well as anomaly by south of subtropical high at low latitudes,the center or ridge line remained steady in the south of 30° N,thus the precipitation in the Yangtze River Basin was obviously on the high side. The study could provide better guidance for the diagnosis and forecasting of precipitation in the Yangtze River Basin in the future.展开更多
The extreme floods in the Middle/Lower Yangtze River Valley(MLYRV)during June−July 2020 caused more than 170 billion Chinese Yuan direct economic losses.Here,we examine the key features related to this extreme event a...The extreme floods in the Middle/Lower Yangtze River Valley(MLYRV)during June−July 2020 caused more than 170 billion Chinese Yuan direct economic losses.Here,we examine the key features related to this extreme event and explore relative contributions of SST anomalies in different tropical oceans.Our results reveal that the extreme floods over the MLYRV were tightly related to a strong anomalous anticyclone persisting over the western North Pacific,which brought tropical warm moisture northward that converged over the MLYRV.In addition,despite the absence of a strong El Niño in 2019/2020 winter,the mean SST anomaly in the tropical Indian Ocean during June−July 2020 reached its highest value over the last 40 years,and 43%(57%)of it is attributed to the multi-decadal warming trend(interannual variability).Based on the NUIST CFS1.0 model that successfully predicted the wet conditions over the MLYRV in summer 2020 initiated from 1 March 2020(albeit the magnitude of the predicted precipitation was only about one-seventh of the observed),sensitivity experiment results suggest that the warm SST condition in the Indian Ocean played a dominant role in generating the extreme floods,compared to the contributions of SST anomalies in the Maritime Continent,central and eastern equatorial Pacific,and North Atlantic.Furthermore,both the multi-decadal warming trend and the interannual variability of the Indian Ocean SSTs had positive impacts on the extreme floods.Our results imply that the strong multi-decadal warming trend in the Indian Ocean needs to be taken into consideration for the prediction/projection of summer extreme floods over the MLYRV in the future.展开更多
Our knowledge about the interaction between human activities and the environment in the middle-late Holocene remains incomplete.Core C1 in Lake Chaohu from the middle and lower reaches of Yangtze River (MLYR),eastern ...Our knowledge about the interaction between human activities and the environment in the middle-late Holocene remains incomplete.Core C1 in Lake Chaohu from the middle and lower reaches of Yangtze River (MLYR),eastern China,provides an opportunity to investigate vegetation and climate changes,human activities,and East Asian summer monsoon(EASM) evolution since 5100 cal.yr BP.These variables are assessed based on radiocarbon dating,pollen and charcoal records,and magnetic susceptibility (χ_(lf)),median grain size and TP.Results reveal a hiatus in sedimentation between 2080 and 730 cal.yr BP in the western part of Lake Chaohu,which is common in most lakes in the MLYR.Evergreen and deciduous broadleaved mixed forest retreated gradually after 3650 cal.yr BP,and was replaced by secondary Pinus forest after at least 730 cal.yr BP.Intense agricultural activities and vegetation clearance are first detected at 2520 cal.yr BP.Human settlements expanded from the lake front wetlands (during the period 2520–2080 cal.yr BP) to remote high-altitude areas(2080–400 cal.yr BP),and then returned to the lake front to reclaim the wetlands and lake (after 400 cal.yr BP).A gradual trend of recessional EASM strength from 4300 cal.yr BP and centennial-scale variations of EASM during the period5100–3650 cal.yr BP are revealed.The reduction of summer insolation,southward shift of the ITCZ,and El Ni?o Southern Oscillation may control the intensity of EASM and climate on a large regional scale.展开更多
The Shimensi deposit is a recently discovered W-Cu-Mo polymetallic deposit located in the Jiangnan porphyry-skarn W belt in South China.The deposit has a resource of 0.74×10^(6)t of WO_(3)accompanied by 0.4×...The Shimensi deposit is a recently discovered W-Cu-Mo polymetallic deposit located in the Jiangnan porphyry-skarn W belt in South China.The deposit has a resource of 0.74×10^(6)t of WO_(3)accompanied by 0.4×10^(6)t Cu and 28000 t Mo and other useful components like Ga,making it one of the largest W deposits in the world.This paper is aimed to reveal the ore-controlling mechanisms of the Shimensi deposit,involving the role of the ore-related granites,the tectonic background for its formation,and the metallogenesis model.The systematic geological survey suggests multi-types of alteration are developed in the deposit,mainly including greisenization,potassic-alteration,sericitization,chloritization,and silicification.Drilling engineering data and mining works indicate that the Shimensi deposit consists of two main orebodies of I and II.Therein,the W resource has reached a supergiant scale,and the accompanied Cu,Mo,Au,Bi,Ga,and some other useful components are also of economic significance.The main ore-minerals consist of scheelite,wolframite and chalcopyrite.Disseminated mineralization is the dominant type of the W-Cu-Mo polymetallic orebodies,and mainly distributes in the inner and external contact zone that between the Neoproterozoic biotite granodiorite and the Yanshanian granites.The main orebody occurs at the external contact zone,and the pegmatoid crust near the inner contact zone is an important prospecting marker of the W mineralization.Of them,the disseminated W ores within the wall rock of the Neoproterozoic biotite granodiorite is a new mineralization type identified in this paper.Combining previous geochronological and isotopic data,we propose that the mineralization of the Shimensi deposit is closely related to the intruding of the Yanshanian porphyritic biotite granite and granite porphyry.Geochemical data suggest that the biotite granodiorite is rich in Ca and had provided a large amount of Ca for the precipitation of scheelite in this area.Thus,it is a favorable wall rock type for W mineralization.The Shimensi deposit belongs to granitic-type W polymetallic deposit related to post-magmatic hydrothermal,and the ore-forming fluid was initially derived from the Yanshanian magmas.展开更多
To investigate the multi-scale features in two persistent heavy rainfall(PHR) events in the middle and lower reaches of the Yangtze River(MLRYR) in June of 1982 and 1998, this study examines the impact of multi-scale ...To investigate the multi-scale features in two persistent heavy rainfall(PHR) events in the middle and lower reaches of the Yangtze River(MLRYR) in June of 1982 and 1998, this study examines the impact of multi-scale oscillations in the north and south of 30?N on the PHR events by performing sensitivity experiments with the Weather Research and Forecast(WRF) model. It is found that the 60-day lowpass perturbation made a trivial contribution to the MLRYR precipitation during the PHR event in 1982.This PHR event resulted mainly from the combined effects of 30–60-day oscillation at low latitudes and10–30-day oscillation at both high and low latitudes. The southwesterly anomalies associated with the 30–60-day anticyclonic anomaly over the northwestern Pacific facilitated moisture transport from the ocean to the MLRYR and enhanced the low-level convergence and ascending motion in the MLRYR. This similarly occurred in the 10–30-day oscillation as well. Moreover, the 10–30-day anomalies at high latitudes played a role in strengthening the large-scale low-level convergence over the MLRYR. The PHR event in 1998 was mainly related to the 60-day oscillation at both high and low latitudes and 30–60-day oscillation at low latitudes. The 60-day low-pass filtered anomalous cyclone at high latitudes in the north of 30?N contributed to the development of low-level convergence and ascending motion in northern MLRYR while the anomalous anticyclone at low latitudes in the south of 30?N not only increased the moisture in the MLRYR but also preconditioned the dynamical factors favorable for PHR over the whole area. The 30–60-day perturbations located north and south of 30?N worked together producing positive moisture anomaly in the MLRYR.In addition, the anomalous circulation in the south of 30?N tended to favor the development of ascending motion and low-level convergence in the MLRYR.展开更多
Fish-bearing-nodules are found in Early Triassic marine strata in many regions, including East Greenland, East Spitsbergen, Northwest Madagascar, Canada, Angola, and South China. A new Olenekian(Early Triassic) conodo...Fish-bearing-nodules are found in Early Triassic marine strata in many regions, including East Greenland, East Spitsbergen, Northwest Madagascar, Canada, Angola, and South China. A new Olenekian(Early Triassic) conodont biostratigraphic study for stratum that contains fish-bearing-nodule levels is conducted based on the Longtan(LT) Section of Nanjing City and the Qingshan(QS) Section of Jurong County, Jiangsu Province, South China. A total of 101 samples were collected at the two sections and three conodont zones were recognized: in ascending order, they are Scythogondolella(Sc.) milleri Zone, Novispathodus(Nv.) pingdingshanensis Zone, and Triassospathodus(Tr.) aff. homeri Zone. The Scythogondolella milleri Zone is globally recognized as the uppermost conodont zone of the Smithian and the base of the Novispathodus pingdingshanensis Zone was previously suggested as the marker of the Smithian-Spathian boundary in the Yangtze region. The fish-bearing-nodule levels of Nanjing and Jurong are within the conodont Scythogondolella milleri Zone, laterally correlated well with the upper part of the Novispathodus waageni Zone in Chaohu of Anhui Province that also contains fish-bearing-nodule levels. The conodont biostratigraphic correlation confirms the Early Triassic fish-bearing-nodule levels in the Lower Yangtze region are coeval, with an end-Smithian in age.展开更多
A varied class method is applied to calculate the effective discharges and their variations after the Three Gorges Dam(TGD)construction based on the mean daily flow discharge and suspended sediment concentration field...A varied class method is applied to calculate the effective discharges and their variations after the Three Gorges Dam(TGD)construction based on the mean daily flow discharge and suspended sediment concentration field data from 1981 to 2016.For comparison,the bankfull discharges are also determined according to the cross-section profiles and flow discharge-stage relations.Our results show that a bimodal effective discharge curve usually exists at the fixed sites,which generates two effective discharges(Q_(e1) and Q_(e2))within the moderate flow range.Under the quasi-equilibrium circumstances of the pre-dam period,effective discharges are closely related to the mean annual runoff,with a narrow range of regional variations in occurrence frequency.Our analyses draw the conclusion that the relatively higher unsaturation degrees of the pre-dam effective discharges caused by dam interception and riverbed coarsening are the primary cause of the increase in effective discharges from Yichang to Shashi,while the more frequent low and medium discharges due to flow regulation drive the decrease in effective discharges from Jianli to Datong.The slightly elevated flood levels and descending bankfull levels collaboratively result in the decrease of bankfull discharges from Yichang to Shashi,while the lowered bed elevation causes the increase in bankfull discharges from Luoshan to Datong.Overall,the bankfull discharge in the Middle and Lower Yangtze River is larger than effective discharge and approaches the 1.5-year recurrence interval discharge.展开更多
Deep-water navigation channels in the tidal reaches of the lower Yangtze River are affected by water and sediment fluxes that produce complex shoals and unstable channel conditions.The Fujiangsha reach is particularly...Deep-water navigation channels in the tidal reaches of the lower Yangtze River are affected by water and sediment fluxes that produce complex shoals and unstable channel conditions.The Fujiangsha reach is particularly difficult to manage,as it has many braided channels within the tidal fluctuation zone.In this study,hydrologic and topographic data from the Fujiangsha reach from 2012 to 2017 were used to examine the variations in deposition and erosion,flow diversion,shoals,and channel conditions.Since the Three Gorges Dam became operational and water storage was initiated,the Fujiangsha reach has shown an overall tendency toward erosion.Channels deeper than 10 m accounted for 83.7% of the total erosion of the Fujiangsha reach during 2012-2017.Moreover,the dominant channel-forming sediments have gradually changed from suspended sediments to a mixed load of suspended and bed-load sediments.Deposition volumes of these sediments has varied significantly among different channels,but has mainly occurred in the Fubei channel.Furthermore,periodic variations in the Jingjiang point bar have followed a deposition-erosion-deposition pattern,and the downstream Shuangjian shoal mid-channel bar has been scoured and shortened.Approximately 44.0% of the bed load from the upstream Fujiangsha reach is deposited within the 12.5-m deep Fubei channel.The increased erosion and river flow from the Jingjiang point bar and the Shuangjian shoal during the flood season constituted 59.3% and 40.7%,respectively,of the total amount of siltation in the Fubei channel.展开更多
To investigate the geodynamic processes of Mesozoic large-scale mineralization in South China,we deployed a 350-km-long,wide-angle seismic reflection/refraction sounding profile between Yingshan in Hubei and Changshan...To investigate the geodynamic processes of Mesozoic large-scale mineralization in South China,we deployed a 350-km-long,wide-angle seismic reflection/refraction sounding profile between Yingshan in Hubei and Changshan in Zhejiang.This profile traverses the Cu-Au metallogenic belt in the middle and lower reaches of the Yangtze River(YMB),the Jiangnan W-polymetal metallogenic belt(JNMB),and the Qinhang Cu-polymetal metallogenic belt(QHMB).Our imaging results reveal various interesting velocity features along the profile.(1)The velocity structure is characterized by vertical layering and horizontal blocking;(2)the YMB is marked by high velocity and high V_(p)/V_(s) ratios in general with a significantly uplifted Moho interface and a thin crust of~31 km,and the lower crust contains high-velocity anomalies and has the characteristics of a crustmantle transition zone;(3)the JNMB is bounded by the Jiangnan fault and Jingdezhen-Huangshan fault and has low-velocity anomalies and low V_(p)/V_(s) ratios;and(4)the QHMB is characterized by high-velocity anomalies and high V_(p)/V_(s) ratios.The highvelocity anomalies in the YMB and QHMB represent relatively Cu-Au-rich mafic juvenile lower crust.The formation of this kind of crust is considered to be related to mantle-derived magma underplating or residues of Neoproterozoic oceanic crustal materials,and it also provided sources for large-scale Cu-Au mineralization in the Mesozoic.The JNMB has features similar to those of ancient crusts enriched in W-Sn,the partial melting of which played a leading role in the formation of the superlarge W deposits in this belt.Considering these results and other regional geological data,we propose that a large-scale oblique upwelling of the asthenosphere along the collisional belt of the Yangtze and Cathaysia blocks during the Mesozoic was the deep driving mechanism for the explosive mineralization of Cu,Au,and W in northeastern South China.The boundaries of the blocks or terrains and discontinuities of the lithosphere were the main channels for deep heat and magmas and therefore controlled the spatial distribution of the metallogenic belt.展开更多
基金supported by the Fundamental and Commonwealth Geological Survey of Oil and Gas of China(Grant No.DD 20221662)the National Natural Science Foundation of China(NSFC)Program(Grant No.42302124).
文摘The Late Permian was marked by a series of important geological events and widespread organic-rich black shale depositions,acting as important unconventional hydrocarbon source rocks.However,the mechanism of organic matter(OM)enrichment throughout this period is still controversial.Based on geochemical data,the marine redox conditions,paleogeographic and hydrographic environment,primary productivity,volcanism,and terrigenous input during the Late Permian in the Lower Yangtze region have been studied from the Putaoling section,Chaohu,to provide new insights into OM accumulation.Five Phases are distinguished based on the TOC and environmental variations.In Phase I,anoxic conditions driven by water restriction enhanced OM preservation.In Phase II,euxinic and cycling hydrological environments were the two most substantial controlling factors for the massive OM deposition.During Phase III,intensified terrestrial input potentially diluted the OM in sediment and the presence of oxygen in bottom water weakened the preservation condition.Phase IV was characterized by a relatively higher abundance of mercury(Hg)and TOC(peak at 16.98 wt%),indicating that enhanced volcanism potentially stimulated higher productivity and a euxinic environment.In Phase V,extremely lean OM was preserved as a result of terrestrial dilutions and decreasing primary productivity.Phases I,II and IV are characterized as the most prominent OM-rich zones due to the effective interactions of the controlling factors,namely paleogeographic,hydrographic environment,volcanism,and redox conditions.
基金funded by the National Natural Science Foundation of China (Grant Nos. 41072090 and 40872086)the Undergraduate Innovation Program of Nanjing Universitythe Open Project Program of Key Laboratory of Tectonics and Petroleum Resources (China University of Geosciences), Ministry of Education (Grant No. TPR-2010-26)
文摘Marine strata are widely exposed in the Hushan and Chaohu areas, Lower Yangtze region. As biomarker geochemistry of the strata has not been well documented, this paper deals with the biomarker composition of representative samples collected from the Silurian, Carboniferous and Triassic systems and their geological implications, thus providing clues to marine organic matter. On the basis of experimental results, it is shown that abundant biomarkers (e.g. n-alkanes, isoprenoids, terpanes and steranes) were detected. As organic matter in the strata is highly to over mature in general based on petrologic microobservation, some biomarkers (mainly n-alkanes) except terpanes and steranes cannot reflect the source, depositional environment and maturity of organic matter. Thus, primarily based on analyses of the terpanes and steranes, it is suggested that organic matter in the Silurian and Carboniferous strata is derived mainly from lower organisms, while higher plants are predominant in the Triassic organic matter. This further indicates that the depositional environment may have transformed from the marine to continental facies in the Late Triassic. These results provide new evidence for the study of regional depositional evolution, and have enriched the study of biological composition of organic matter. In addition, the biomarker geochemistry of organic matter at high to over maturation stage is addressed.
基金supported by the National Natural Science Foundation of China(Grant No.42088101)the National Key Research and Development Program of China(2020YFA0608901 and 2019YFC1510004)+1 种基金the Natural Science Foundation of Jiangsu(BK20190781),the National Natural Science Foundation of China(Grant No.42005020)the General Program of Natural Science Foundation of Jiangsu Higher Education Institutions(19KJB170019).
文摘The middle and lower Yangtze River basin(MLYRB)suffered persistent heavy rainfall in summer 2020,with nearly continuous rainfall for about six consecutive weeks.How the likelihood of persistent heavy rainfall resembling that which occurred over the MLYRB in summer 2020(hereafter 2020PHR-like event)would change under global warming is investigated.An index that reflects maximum accumulated precipitation during a consecutive five-week period in summer(Rx35day)is introduced.This accumulated precipitation index in summer 2020 is 60%stronger than the climatology,and a statistical analysis further shows that the 2020 event is a 1-in-70-year event.The model projection results derived from the 50-member ensemble of CanESM2 and the multimodel ensemble(MME)of the CMIP5 and CMIP6 models show that the occurrence probability of the 2020PHR-like event will dramatically increase under global warming.Based on the Kolmogorov-Smirnoff test,one-third of the CMIP5 and CMIP6 models that have reasonable performance in reproducing the 2020PHR-like event in their historical simulations are selected for the future projection study.The CMIP5 and CMIP6 MME results show that the occurrence probability of the 2020PHR-like event under the present-day climate will be double under lower-emission scenarios(CMIP5 RCP4.5,CMIP6 SSP1-2.6,and SSP2-4.5)and 3-5 times greater under higher-emission scenarios(3.0 times for CMIP5 RCP8.5,2.9 times for CMIP6 SSP3-7.0,and 4.8 times for CMIP6 SSP5-8.5).The inter-model spread of the probability change is small,lending confidence to the projection results.The results provide a scientific reference for mitigation of and adaptation to future climate change.
基金supported by the Second-level Project of Nanjing Geological Survey Center of the China Geological Survey(Grant No.DD20190043)the National Natural Science Foundation of China(Grant Nos.41572177,41272213,41573023,41072161,41502193,41272222)。
文摘Fault geometry, kinematics, geophysics, the tectonic stress field and tectonic evolution of the Zhouwang fault in the southern Jiangnan tectonic transition zone of the Lower Yangtze region, eastern China are examined. Field observations show the fault is composed of a series of nearly E–W trending, N–S dipping faults, and four stages of tectonism(sinistral strike-slip, thrust nappe, normal fault, and dextral strike-slip) developed in turn. Geophysical data show that the fault trends almost linearly E–W along a flat, steep gravity gradient at shallow depth, with distinct gravity anomalies to the north and south and different in the north and south. Also, the deep part is characterized by northward dip and a gradual slowing down. Tectonic stress field analysis indicates that the fault experienced four tectonic movements: NNE–SSW compression, NNW–SSE compression, NEE–SWW extension, and E–W compression. Combined with regional tectonic background and previous research results, this indicates that:(1) the Zhouwang fault experienced sinistral strike-slip movement during the Indosinian Period(260–200 Ma);(2) thrust nappes developed during the early Yanshanian Period(163–145 Ma);(3) a normal fault occurred in the late Yanshanian Period(125–65 Ma);and(4) dextral strike-slip movement occurred in the Himalayan Period(ca. 50–37 Ma). The results reveal the tectonic evolution of the fault during Mesozoic deformation in the area, and also reveal the geological evolution and tectonic transformation of the Lower Yangtze region, which is key to our understanding of intracontinental deformation in eastern China.
文摘During Ching dynasty from 1644 to 1911, an interval of 268 years, there occurred in the lower Yangtze valley 197 floods and 156 droughts. The most serious droughts came in 1785, 1814, and 1856; and the most disastrous floods in 1680,
基金jointly supported by China Geological Survey(Nos.DD20190030,DD20201164,DD20221638)China National Nonprofit Institute Research(Nos.JKYZD202329,AS2017Y05,JYYWF20180902).
文摘The Wuwei Basin is one of the most important oil-and gas-bearing basins in the Meso-Cenozoic basin groups in the Lower Yangtze River region.It has great shale gas resource prospects.The formation mechanism of this basin is poorly studied for lack of constraining data for deep structures.In this paper,a crustal electrical structure model of the Wuwei Basin and the adjacent areas is constructed based on the two-dimensional inversion of a magnetotelluric(MT)sounding profile achieved with the nonlinear conjugate gradient method.The results show that large-scale low-resistance bodies have developed in the underlying middle and lower crust of the Wuwei Basin,and are different from the uplifts on the two sides according to their high-resistance electrical characteristics.The electrical structure and regional geological and geophysical data suggest that the peak zone of the Chuzhou-Chaohu foreland fold-and-thrust belt is located on the east bank of the Yangtze River(Wuhu Section),which,together with the main thrust fault belt in the east,forms a typical thrust structure belt.An early Yanshanian sinistral strike-slip fault developed in the deep part of the Wuwei Basin,which may have controlled the formation and evolution of the basin,whereas the tectonic inversion of the early-developed thrust faults is relatively weak.These findings provide a geophysical basis for future studies of basin tectonic evolution and regional tectonic frameworks.
基金the State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang(No.2020Z03)the National Key R&D Program of China(Nos.2016YFC0600408,2019YFA0708400)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB41020102)。
文摘The Early Cretaceous aluminous A-type granites in the Lower Yangtze River belt(LYRB)can provide important insights into the Mesozoic magmatism in eastern China,but their origin remains highly controversial.In this study,radiogenic Ca-Nd isotopic analysis was performed for syenite porphyry and alkali-feldspar granite porphyry of the Yangshan pluton,a typical aluminous A-type granitic intrusion in the LYRB,to constrain its source and geodynamic setting.The results show thatε_(Ca)(126 Ma),ε_(Nd)(126 Ma)and K/Ca_(source) of the syenite porphyry range from-0.24 to+0.96,-7.2 to-6.0,and 0.31 to 1.26,respectively.The corresponding values for the alkali-feldspar granite porphyry range from 0.26 to 0.84,-8.0 to-6.1,and 0.79 to 1.08,respectively.Binary mixing modeling indicates that they were originated from the same sources with different proportion,namely,a mixing of 50%to 75%Neoproterozoic crust and 50%to 25%asthenospheric mantle.Together with previous works,we propose that the Early Cretaceous subduction of the ridge between the Pacific and Izanagi plates was responsible for the formation of the aluminous A-type granites in the LYRB.
基金This study was supported by the National Natural Science Foundation of China grant 49802007.
文摘Studies of the Pb, Sr and Nd isotopic composition of Mesozoic intrusive rocks indicate that the basement of the copper-gold metallogenic belt of the middle and lower reaches of the Yangtze River has 'two-layer structure' and partly has 'multi-layered structure', and is inhomogeneous and shows the distinct feature of E-W provincialism. The calculated model lead ages (t1) are mostly greater than 2600 Ma, and the model neodymium ages (TDM) vary from 953 to 2276 Ma and concentrate in two time intervals: 1800-2000 Ma and 1200-1600 Ma. It is concluded that the basement of the MBYR is composed of the Late Archaeozoic to Middle Proterozoic metamorphic series and that the crust was initiated in the Archaean and continued to grow in the Early and Middle Proterozoic, and the proportion of new crust formed by mantle differentiation during the Late Proterozoic is low.
基金funded by grants from the Key Project of the National Natural Science Foundation of China(No.41630320)the National Key Research and Development Program of China(No.2016YFC0600200)the Hefei Postdoctoral Science Foundation。
文摘In this study,we compiled and analyzed 69310 P-wave travel-time data from 6639 earthquake events.These events(M≥2.0)occurred from 1980 s to June 2019 and were recorded at 319 seismic stations(Chinese Earthquake Networks Center)in the study area.We adopted the double-difference seismic tomographic method(tomo DD)to invert the 3-D P-wave velocity structure and constrain the crust-upper mantle architecture of the Middle and Lower Reaches of the Yangtze River Metallogenic Belt(MLYB).A 1-D initial model extracted from wide-angle seismic profiles was used in the seismic tomography,which greatly reduced the inversion residual.Our results indicate that reliable velocity structure of th e uppermost mantle can be obtained when Pn is involved in the tomography.Our results show that:(1)the pattern of the uppermost mantle velocity structure corresponds well with the geological partitioning:a nearly E-W-trending low-velocity zone is present beneath the Dabie Orogen,in contrast to the mainly NE-trending low-velocity anomalies beneath the Jiangnan Orogen.They suggest the presence of thickened lower crust beneath the orogens in the study area.In contrast,the Yangtze and Cathaysia blocks are characterized by relatively high-velocity anomalies;(2)both the ultra-high-pressure(UHP)metamorphic rocks in the Dabie Orogen and the low-pressure metamorphic rocks in the Zhangbaling dome are characterized by high-velocity anomalies.The upper crust in the Dabie Orogen is characterized by a low-velocity belt,sandwiched between two high velocity zones in a horizontal direction,with discontinuous low-velocity layers in the middle crust.The keel of the Dabie Orogen is mainly preserved beneath its northern section.We infer that the lower crustal delamination may have mainly occurred in the southern Dabie Orogen,which caused the mantle upwelling responsible for the formation of the granitic magmas emplaced in the middle crust as the low-velocity layers observed there.Continuous deep-level compression likely squeezed the granitic magma upward to intrude the upper crustal UHP metamorphic rocks,forming the'sandwich'velocity structure there;(3)high-velocity updoming is widespread in the crust-mantle transition zone beneath the MLYB.From the Anqing-Guichi ore field northeastward to the Luzong,Tongling,Ningwu and Ningzhen orefields,high-velocity anomalies in the crust-mantle transition zone increase rapidly in size and are widely distributed.The updoming also exists in the crust-mantle transition zone beneath the Jiurui and Edongnan orefields,but the high-velocity anomalies are mainly stellate distributed.The updoming high-velocity zone beneath the MLYB generally extends from the crust-mantle transition zone to the middle crust,different from the velocity structure in the upper crust.The upper crust beneath the Early Cretaceous extension-related Luzong and Ningwu volcanic basins is characterized by high velocity zones,in contrast to the low velocity anomalies beneath the Late Jurassic to Early Cretaceous compression-related Tongling ore field.The MLYB may have undergone a compressive-to-extensional transition during the Yanshanian(Jurassic-Cretaceous)period,during which extensive magmatism occurred.The near mantle-crustal boundary updoming was likely caused by asthenospheric underplating at the base of the lower crust.The magmas may have ascended through major crustal faults,undergoing AFC(assimilation and fractional crystallization)processes,became emplaced in the fault-bounded basins or Paleozoic sequences,eventually forming the many Cu-Fe polymetallic deposits there.
基金supported by the National Key Research and Development Program of China(Grants No.2019YFC0409000,2017YFC1502403,and 2018YFC0407701)the Fundamental Research Funds for the Central Universities(Grant No.B200204045).
文摘Anomalous characteristics of the atmospheric water cycle structure are highly significant to the mechanisms of seasonal-scale meteorological droughts.They also play an important role in the identification of indicative predictors of droughts.To better understand the causes of seasonal meteorological droughts in the middle and lower reaches of the Yangtze River(MLRYR),characteristics of the atmospheric water cycle structure at different drought stages were determined using standardized anomalies.The results showed that the total column water vapor(TCWV)was anomalously low during drought occurrence periods.In contrast,there were no anomalous signals at the drought persistence and recovery stages in the MLRYR.Moreover,there was no significant temporal correlation between the TCWV anomaly and seasonal-scale drought index(the 3-month standardized precipitation index(SPI_(3))).During drought events,water vapor that mainly originated from the Bay of Bengal was transported southwest of the MLRYR.Meanwhile,the anomalous signal of water vapor transport was negative at the drought appearance stage.At the drought persistence stage,the negative anomalous signal was the most significant.Water vapor flux divergence in the MLRYR showed significant positive anomalous signals during drought events,and the signal intensity shifted from an increasing to a decreasing trend at different drought stages.In addition,a significant positive correlation existed between the anomaly of water vapor flux divergence and regional SPI_(3).Overall,water vapor flux divergence is more predictive of droughts in the MLRYR.
文摘Based upon the summer (June-August) precipitation data from 30 stations in the middle and lower reaches of Yangtze River in China, the spatial and temporal distribution of summer precipitation in the Yangtze River Basin was analyzed. As was shown in the results, the distribution of summer precipitation in the middle and lower reaches of Yangtze River was mainly composed of four types: northern type (2005 and 2007), southern type (2001 and 2003), intermediate type (2000, 2004 and 2006) and integral type (2002). According to the correlation analysis of summer precipitation and atmospheric circulation in East Asia, the precipitation in the Yangtze River Basin and high-low level circulation anomalies were significantly related. In other words,with the increase of the meridional degree of circulation at mid-high latitudes in the middle and upper troposphere as well as anomaly by south of subtropical high at low latitudes,the center or ridge line remained steady in the south of 30° N,thus the precipitation in the Yangtze River Basin was obviously on the high side. The study could provide better guidance for the diagnosis and forecasting of precipitation in the Yangtze River Basin in the future.
基金This work is supported by National Natural Science Foundation of China(Grant No.42030605 and 42088101)National Key R&D Program of China(Grant No.2020YFA0608004).
文摘The extreme floods in the Middle/Lower Yangtze River Valley(MLYRV)during June−July 2020 caused more than 170 billion Chinese Yuan direct economic losses.Here,we examine the key features related to this extreme event and explore relative contributions of SST anomalies in different tropical oceans.Our results reveal that the extreme floods over the MLYRV were tightly related to a strong anomalous anticyclone persisting over the western North Pacific,which brought tropical warm moisture northward that converged over the MLYRV.In addition,despite the absence of a strong El Niño in 2019/2020 winter,the mean SST anomaly in the tropical Indian Ocean during June−July 2020 reached its highest value over the last 40 years,and 43%(57%)of it is attributed to the multi-decadal warming trend(interannual variability).Based on the NUIST CFS1.0 model that successfully predicted the wet conditions over the MLYRV in summer 2020 initiated from 1 March 2020(albeit the magnitude of the predicted precipitation was only about one-seventh of the observed),sensitivity experiment results suggest that the warm SST condition in the Indian Ocean played a dominant role in generating the extreme floods,compared to the contributions of SST anomalies in the Maritime Continent,central and eastern equatorial Pacific,and North Atlantic.Furthermore,both the multi-decadal warming trend and the interannual variability of the Indian Ocean SSTs had positive impacts on the extreme floods.Our results imply that the strong multi-decadal warming trend in the Indian Ocean needs to be taken into consideration for the prediction/projection of summer extreme floods over the MLYRV in the future.
基金supported by the National Key Research and Development Program of China (Grant No.2022YFF0801101)the National Natural Science Foundation of China (Grant Nos.42077424,41877434,42171161)。
文摘Our knowledge about the interaction between human activities and the environment in the middle-late Holocene remains incomplete.Core C1 in Lake Chaohu from the middle and lower reaches of Yangtze River (MLYR),eastern China,provides an opportunity to investigate vegetation and climate changes,human activities,and East Asian summer monsoon(EASM) evolution since 5100 cal.yr BP.These variables are assessed based on radiocarbon dating,pollen and charcoal records,and magnetic susceptibility (χ_(lf)),median grain size and TP.Results reveal a hiatus in sedimentation between 2080 and 730 cal.yr BP in the western part of Lake Chaohu,which is common in most lakes in the MLYR.Evergreen and deciduous broadleaved mixed forest retreated gradually after 3650 cal.yr BP,and was replaced by secondary Pinus forest after at least 730 cal.yr BP.Intense agricultural activities and vegetation clearance are first detected at 2520 cal.yr BP.Human settlements expanded from the lake front wetlands (during the period 2520–2080 cal.yr BP) to remote high-altitude areas(2080–400 cal.yr BP),and then returned to the lake front to reclaim the wetlands and lake (after 400 cal.yr BP).A gradual trend of recessional EASM strength from 4300 cal.yr BP and centennial-scale variations of EASM during the period5100–3650 cal.yr BP are revealed.The reduction of summer insolation,southward shift of the ITCZ,and El Ni?o Southern Oscillation may control the intensity of EASM and climate on a large regional scale.
基金supported financially by the National Natural Science Foundation of China(No.41772069)projects of the China Geological Survey(1212011220737,121201004000150015,DD20190570).
文摘The Shimensi deposit is a recently discovered W-Cu-Mo polymetallic deposit located in the Jiangnan porphyry-skarn W belt in South China.The deposit has a resource of 0.74×10^(6)t of WO_(3)accompanied by 0.4×10^(6)t Cu and 28000 t Mo and other useful components like Ga,making it one of the largest W deposits in the world.This paper is aimed to reveal the ore-controlling mechanisms of the Shimensi deposit,involving the role of the ore-related granites,the tectonic background for its formation,and the metallogenesis model.The systematic geological survey suggests multi-types of alteration are developed in the deposit,mainly including greisenization,potassic-alteration,sericitization,chloritization,and silicification.Drilling engineering data and mining works indicate that the Shimensi deposit consists of two main orebodies of I and II.Therein,the W resource has reached a supergiant scale,and the accompanied Cu,Mo,Au,Bi,Ga,and some other useful components are also of economic significance.The main ore-minerals consist of scheelite,wolframite and chalcopyrite.Disseminated mineralization is the dominant type of the W-Cu-Mo polymetallic orebodies,and mainly distributes in the inner and external contact zone that between the Neoproterozoic biotite granodiorite and the Yanshanian granites.The main orebody occurs at the external contact zone,and the pegmatoid crust near the inner contact zone is an important prospecting marker of the W mineralization.Of them,the disseminated W ores within the wall rock of the Neoproterozoic biotite granodiorite is a new mineralization type identified in this paper.Combining previous geochronological and isotopic data,we propose that the mineralization of the Shimensi deposit is closely related to the intruding of the Yanshanian porphyritic biotite granite and granite porphyry.Geochemical data suggest that the biotite granodiorite is rich in Ca and had provided a large amount of Ca for the precipitation of scheelite in this area.Thus,it is a favorable wall rock type for W mineralization.The Shimensi deposit belongs to granitic-type W polymetallic deposit related to post-magmatic hydrothermal,and the ore-forming fluid was initially derived from the Yanshanian magmas.
基金Supported by the National Key Basic Research and Development(973)Program of China(2012CB417201)
文摘To investigate the multi-scale features in two persistent heavy rainfall(PHR) events in the middle and lower reaches of the Yangtze River(MLRYR) in June of 1982 and 1998, this study examines the impact of multi-scale oscillations in the north and south of 30?N on the PHR events by performing sensitivity experiments with the Weather Research and Forecast(WRF) model. It is found that the 60-day lowpass perturbation made a trivial contribution to the MLRYR precipitation during the PHR event in 1982.This PHR event resulted mainly from the combined effects of 30–60-day oscillation at low latitudes and10–30-day oscillation at both high and low latitudes. The southwesterly anomalies associated with the 30–60-day anticyclonic anomaly over the northwestern Pacific facilitated moisture transport from the ocean to the MLRYR and enhanced the low-level convergence and ascending motion in the MLRYR. This similarly occurred in the 10–30-day oscillation as well. Moreover, the 10–30-day anomalies at high latitudes played a role in strengthening the large-scale low-level convergence over the MLRYR. The PHR event in 1998 was mainly related to the 60-day oscillation at both high and low latitudes and 30–60-day oscillation at low latitudes. The 60-day low-pass filtered anomalous cyclone at high latitudes in the north of 30?N contributed to the development of low-level convergence and ascending motion in northern MLRYR while the anomalous anticyclone at low latitudes in the south of 30?N not only increased the moisture in the MLRYR but also preconditioned the dynamical factors favorable for PHR over the whole area. The 30–60-day perturbations located north and south of 30?N worked together producing positive moisture anomaly in the MLRYR.In addition, the anomalous circulation in the south of 30?N tended to favor the development of ascending motion and low-level convergence in the MLRYR.
基金funded by the Stratefic Priority Research Program of the Chinese Academy of Science(No.XDA14010404)the National Science Foundation of China(Nos.41572008,U1663201,41372016,40920124002,1402014)+2 种基金the Ministry of Science and Technology(No.2016YFC0503301)the State Key Laboratory of Palaeobiology and Stratigraphy(Nanjing Institute of Geology and Palaeontology,CAS)(Nos.123107,143108,173123)the China Geological Survey(No.121201102000150012-09)
文摘Fish-bearing-nodules are found in Early Triassic marine strata in many regions, including East Greenland, East Spitsbergen, Northwest Madagascar, Canada, Angola, and South China. A new Olenekian(Early Triassic) conodont biostratigraphic study for stratum that contains fish-bearing-nodule levels is conducted based on the Longtan(LT) Section of Nanjing City and the Qingshan(QS) Section of Jurong County, Jiangsu Province, South China. A total of 101 samples were collected at the two sections and three conodont zones were recognized: in ascending order, they are Scythogondolella(Sc.) milleri Zone, Novispathodus(Nv.) pingdingshanensis Zone, and Triassospathodus(Tr.) aff. homeri Zone. The Scythogondolella milleri Zone is globally recognized as the uppermost conodont zone of the Smithian and the base of the Novispathodus pingdingshanensis Zone was previously suggested as the marker of the Smithian-Spathian boundary in the Yangtze region. The fish-bearing-nodule levels of Nanjing and Jurong are within the conodont Scythogondolella milleri Zone, laterally correlated well with the upper part of the Novispathodus waageni Zone in Chaohu of Anhui Province that also contains fish-bearing-nodule levels. The conodont biostratigraphic correlation confirms the Early Triassic fish-bearing-nodule levels in the Lower Yangtze region are coeval, with an end-Smithian in age.
基金This work was supported by the National Key Research and Development Program of China(No.2016YFC0402101)the National Natural Science Foundation of China(Grant Nos.51779184).We would like to thank the Yangtze River Water Resources Commission for providing important field data.The instructive suggestions by the editors and anonymous reviewers are gratefully acknowledged.
文摘A varied class method is applied to calculate the effective discharges and their variations after the Three Gorges Dam(TGD)construction based on the mean daily flow discharge and suspended sediment concentration field data from 1981 to 2016.For comparison,the bankfull discharges are also determined according to the cross-section profiles and flow discharge-stage relations.Our results show that a bimodal effective discharge curve usually exists at the fixed sites,which generates two effective discharges(Q_(e1) and Q_(e2))within the moderate flow range.Under the quasi-equilibrium circumstances of the pre-dam period,effective discharges are closely related to the mean annual runoff,with a narrow range of regional variations in occurrence frequency.Our analyses draw the conclusion that the relatively higher unsaturation degrees of the pre-dam effective discharges caused by dam interception and riverbed coarsening are the primary cause of the increase in effective discharges from Yichang to Shashi,while the more frequent low and medium discharges due to flow regulation drive the decrease in effective discharges from Jianli to Datong.The slightly elevated flood levels and descending bankfull levels collaboratively result in the decrease of bankfull discharges from Yichang to Shashi,while the lowered bed elevation causes the increase in bankfull discharges from Luoshan to Datong.Overall,the bankfull discharge in the Middle and Lower Yangtze River is larger than effective discharge and approaches the 1.5-year recurrence interval discharge.
基金National Natural Science Foundation of China,No.51809131,No.U2040203Open Foundation of State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering,No.2017491211Fundamental Research Funds for Central Welfare Research Institutes,No.TKS20200404,No.TKS20200312。
文摘Deep-water navigation channels in the tidal reaches of the lower Yangtze River are affected by water and sediment fluxes that produce complex shoals and unstable channel conditions.The Fujiangsha reach is particularly difficult to manage,as it has many braided channels within the tidal fluctuation zone.In this study,hydrologic and topographic data from the Fujiangsha reach from 2012 to 2017 were used to examine the variations in deposition and erosion,flow diversion,shoals,and channel conditions.Since the Three Gorges Dam became operational and water storage was initiated,the Fujiangsha reach has shown an overall tendency toward erosion.Channels deeper than 10 m accounted for 83.7% of the total erosion of the Fujiangsha reach during 2012-2017.Moreover,the dominant channel-forming sediments have gradually changed from suspended sediments to a mixed load of suspended and bed-load sediments.Deposition volumes of these sediments has varied significantly among different channels,but has mainly occurred in the Fubei channel.Furthermore,periodic variations in the Jingjiang point bar have followed a deposition-erosion-deposition pattern,and the downstream Shuangjian shoal mid-channel bar has been scoured and shortened.Approximately 44.0% of the bed load from the upstream Fujiangsha reach is deposited within the 12.5-m deep Fubei channel.The increased erosion and river flow from the Jingjiang point bar and the Shuangjian shoal during the flood season constituted 59.3% and 40.7%,respectively,of the total amount of siltation in the Fubei channel.
基金supported by the National Key R&D Program of China(Grant Nos.2019YFA0708602,2019YFA0708603,and 2016YFC0600201)the National Natural Science Foundation of China(Grant Nos.42130807,42074099)the China Geological Survey(Grant No.1212011220243)。
文摘To investigate the geodynamic processes of Mesozoic large-scale mineralization in South China,we deployed a 350-km-long,wide-angle seismic reflection/refraction sounding profile between Yingshan in Hubei and Changshan in Zhejiang.This profile traverses the Cu-Au metallogenic belt in the middle and lower reaches of the Yangtze River(YMB),the Jiangnan W-polymetal metallogenic belt(JNMB),and the Qinhang Cu-polymetal metallogenic belt(QHMB).Our imaging results reveal various interesting velocity features along the profile.(1)The velocity structure is characterized by vertical layering and horizontal blocking;(2)the YMB is marked by high velocity and high V_(p)/V_(s) ratios in general with a significantly uplifted Moho interface and a thin crust of~31 km,and the lower crust contains high-velocity anomalies and has the characteristics of a crustmantle transition zone;(3)the JNMB is bounded by the Jiangnan fault and Jingdezhen-Huangshan fault and has low-velocity anomalies and low V_(p)/V_(s) ratios;and(4)the QHMB is characterized by high-velocity anomalies and high V_(p)/V_(s) ratios.The highvelocity anomalies in the YMB and QHMB represent relatively Cu-Au-rich mafic juvenile lower crust.The formation of this kind of crust is considered to be related to mantle-derived magma underplating or residues of Neoproterozoic oceanic crustal materials,and it also provided sources for large-scale Cu-Au mineralization in the Mesozoic.The JNMB has features similar to those of ancient crusts enriched in W-Sn,the partial melting of which played a leading role in the formation of the superlarge W deposits in this belt.Considering these results and other regional geological data,we propose that a large-scale oblique upwelling of the asthenosphere along the collisional belt of the Yangtze and Cathaysia blocks during the Mesozoic was the deep driving mechanism for the explosive mineralization of Cu,Au,and W in northeastern South China.The boundaries of the blocks or terrains and discontinuities of the lithosphere were the main channels for deep heat and magmas and therefore controlled the spatial distribution of the metallogenic belt.
