We assembled approximately 328 seismic records. The data set was from 4 digitally recording long-period and broadband stations of CDSN. We carried out the inversion based on the partitioned waveform inversion (PWI). I...We assembled approximately 328 seismic records. The data set was from 4 digitally recording long-period and broadband stations of CDSN. We carried out the inversion based on the partitioned waveform inversion (PWI). It partitions the large-scale optimization problem into a number of independent small-scale problems. We adopted surface waveform inversion with an equal block (2((2() discretization in order to acquire the images of shear velocity structure at different depths (from surface to 430 km) in the crust and upper-mantle. The resolution of all these anomalies has been established with (check-board( resolution tests. These results show significant difference in velocity, lithosphere and asthenosphere structure between South China Sea and its adjacent regions.展开更多
Both evolution of the Asian monsoon system and the Cenozoic global cooling are thought to be closely linked to the Himalayan—Tibetan orogen. The South China Sea (SCS) with its high sedimentation rates of carbonate\|r...Both evolution of the Asian monsoon system and the Cenozoic global cooling are thought to be closely linked to the Himalayan—Tibetan orogen. The South China Sea (SCS) with its high sedimentation rates of carbonate\|rich hemipelagic sediments offers a unique opportunity to study the variability of the East Asian monsoon, the erosion and weathering of tectonic orogens as well as its possible impact on global and regional climate.Leg 184, the first deep\|sea drilling leg to the seas off China, cored 17 holes at 6 sites in the northern and southern parts of the SCS and recovered 5463m of sediment. The drilling of hemipelagic sediments was exceptionally successful, with core recovery averaging 83%～101%. The 32Ma sequence of deep\|sea sediments recovered during Leg 184 covers almost the entire environmental history of the SCS since its opening. The abnormally high sediment accumulation rates in the Oligocene section are correlative with the incipient sea floor spreading. The bathyal nature of the Oligocenefauna implies that rifting occurred in the Eocene or earlier. Faunal changesfrom the early to late Oligocene are indicative of basin deepening, a trend thatis even more evident in the Miocene section. Sediment deformation, abruptlithologic changes, and a hiatus occur near the Oligocene/Miocene boundary,representing one of the most significant events in the tectonic andenvironmental history of the SCS.展开更多
An integrated sedimentological, sequence stratigraphic, tectonic\|stratigraphic, isotope chronostratigraphic and isotope (element) geochemical analysis indicates that the Neoproterozoic basins in South China are chara...An integrated sedimentological, sequence stratigraphic, tectonic\|stratigraphic, isotope chronostratigraphic and isotope (element) geochemical analysis indicates that the Neoproterozoic basins in South China are characteristic of rift basins, and their formation and evolution are closely related to the breakup of the supercontinent Rodinia. (1) Neoproterozoic basins in South China can be divided into three major provinces: the southeastern Yangtze province, the Kangdian province along the western margin of the Yangtze block, and the Cathaysia province. They can be further subdivided into five subprovinces and eleven microprovinces on the basis of tectonic settings, sedimentary facies and palaeogeography,and outcrop sequence stratigraphy.(2) Four genetic facies associations and two environmental facies associations can be recognized in the Neoproterozoic basins. The former include① continental volcanic eruptive genetic facies association; ② submarine volcanic eruptive genetic facies association; ③ tillite genetic facies association; and ④ eustatic event deposits genetic facies association. The latter comprise: ① continental environmental facies association, and ② marine environmental facies association.展开更多
Carbon and oxygen isotope and dating analyses of foraminiferan in sediment cores collected from three different areas of the northern slope of the South China Sea were conducted, in order to examine the records of the...Carbon and oxygen isotope and dating analyses of foraminiferan in sediment cores collected from three different areas of the northern slope of the South China Sea were conducted, in order to examine the records of the gas hydrate decomposition events since the late Quaternary under the conditions of methane seepage. The results show that： 1） the δ13C values of the benthic foraminiferan Uvigerina spp. （size range of 0.25-0.35 ram） are from -0.212% to -0.021% and the δ180 values of the planktonic foraminiferan Globigerinoides ruber （size range of 0.25-0.35 ram） are from -0.311% to -0.060%; 2） three cores （ZD2, ZD3 and ZS5） from the bottom of a hole are aged for 11 814, 26 616 and 64 090 a corresponding to the early oxygen isotope stage （MIS） Ⅰ, Ⅲ and Ⅳ final period, respectively; 3） a negative-skewed layer of carbon isotope corresponds to that of MIS II （cold period）, whose degree of negative bias is -0.2%0; and 4） the δ13C compositions of foraminiferans are similar to those of the Blake Ridge and the Gulf of Mexico sediments of the late Quaternary. According to the analysis, the reasons for these results are that the studied area is a typical area of methane seep environment in the area during MIS II due to the global sea-level fall and sea pressure decrease. Gas hydrate is decomposed and released, and a large number of light carbon isotopes of methane are released into the ocean, dissolved to inorganic carbon （DIC） pool and recorded in the foraminiferan shells. A pyrite layer developed in the negative bias layers of the foraminiferans confirms that the δ13C of foraminiferans is more affected by methane and less by the reduction of marine productivity and early diagenesis. The use of foraminiferan δ13C could accurately determine late Quaternary hydrate release events and provide evidence for both reconstructing the geological history of methane release events and exploring natural gas hydrate.展开更多
Previous studies on the Late Permian shallow-water ostracod faunas in South China have greatly increased our knowledge on the Late Permian ostracods.But the absence of data on contemporary deep-water ostracods makes i...Previous studies on the Late Permian shallow-water ostracod faunas in South China have greatly increased our knowledge on the Late Permian ostracods.But the absence of data on contemporary deep-water ostracods makes it difficult to comprehensively understand the Late Permian ostracods during the largest extinction among the"Big Five"in the Phanerozoic. During the past years,our work has been focused展开更多
Very high resolution seismic record were used to study the sedimentary processes and morphosedimentary features of the continental slope system since Miocene in Qiongdongnan Basin(QDNB),offshore Hainan,northern South ...Very high resolution seismic record were used to study the sedimentary processes and morphosedimentary features of the continental slope system since Miocene in Qiongdongnan Basin(QDNB),offshore Hainan,northern South China Sea.It can be divided into four types based on the sedimentary processes and morphology:wide and gentle slope,sigmoid-progradational slope,slumping slope and channeled slope.Different features of展开更多
The transition between Permian and Triassic(252.4 Ma) is marked by the most devastating extinction the biosphere ever went through.Although its cause stays unclear,it is admitted that this mass extinction originated i...The transition between Permian and Triassic(252.4 Ma) is marked by the most devastating extinction the biosphere ever went through.Although its cause stays unclear,it is admitted that this mass extinction originated in the conjunction of several global events: tectonic(Pangaea closing),volcanic(Siberian traps), magnetic(reversal of superchron),climatic(end of Permian glaciation) and eustatic(tecto-and ther-展开更多
The Qiongdongnan Basin lies in the west part of the northern South China Sea.To the west the basin is bound by the Red River Fault and the Yinggehai Basin,to the east by the Pearl River Mouth Basin,and to the south by...The Qiongdongnan Basin lies in the west part of the northern South China Sea.To the west the basin is bound by the Red River Fault and the Yinggehai Basin,to the east by the Pearl River Mouth Basin,and to the south by the Xisha Rise.In this study,the sequence stratigraphic framework was set up and 11 third-order sequences were distinguished.Based展开更多
Results are presented about the changes in chlorophyll a density, carbon fixation and nutrient levels in the surfacewaters of three transects of the southern South China Sea （SCS）, northern Java Sea （JS） and easte...Results are presented about the changes in chlorophyll a density, carbon fixation and nutrient levels in the surfacewaters of three transects of the southern South China Sea （SCS）, northern Java Sea （JS） and eastern Indian Ocean （IO） duringApril 5-16 of 2011. The in situ Chl a concentration and carbon fixation showed decreasing trends from high to low latitudealong the three transects, while the photosynthetic rate of phytoplankton estimated from 14C incorporation displayed no simplevariation with latitude. Chl a concentration and carbon fixation in the IO water was lower than that in the JS water. Highersalinity and lower contents of dissolved inorganic nitrogen （DIN） and silicate （SiO3^2-） characterized the IO water as comparedto the SCS or JS water, and the PO4^3- content was lower in the IO water than in the SCS or JS water in most cases. Our resultsalso indicate the importance of DIN and SiO3^2- concentrations for the geographical changes in phytoplankton biomass andprimary productivity among the three regions.展开更多
The Shilu Fe-polymetallic ore deposit,a famous hematite-rich Fe-ore deposit,is situated at the western Hainan Province of south China.The deposit characterizes the upper Fe ores and the lower Co-Cu ores,which are main...The Shilu Fe-polymetallic ore deposit,a famous hematite-rich Fe-ore deposit,is situated at the western Hainan Province of south China.The deposit characterizes the upper Fe ores and the lower Co-Cu ores,which are mainly hosted within a low-grade to medium-grade,dominantly submarine metamorphosed siliciclastic and carbonate sedimentary succession of the Neoproterozoic Shilu Group.Three facies types of metamorphosed BIFs,i.e.the oxide facies,the silicate-oxide facies and the sulfide-carbonate facies BIFs,are identified within the sixth sequence of the Shilu Group.The oxide facies BIF(i.e.the Fe-rich itabirites or ores)consists of alternating hematite-rich microbands with quartz-rich microbands;the silicate-oxide facies BIF(i.e.the Fe-poor itabirites or ores)comprises alternating millimeter-to a few tens meter-scale,magnetite-hematite-rich bands with calcsilicate-rich(garnet+actinolite+diopside+epidote+quartz)meso-to microbands;and the sulfide-carbonate facies BIF(i.e.the Co-Cu ores)contains alternating macro-to mesobands of Co-bearing pyrite and pyrrhotite,and chalcopyrite with mesobands of dolomite+calcite+diopside+quartz and/or chlorite+sericite+quartz.The blastooolitic,blastopelletoid blastocolloidal and blastopsammitic textures,and blasobedding structures which most likely represent primary sedimentation are often observed in these BIF facies.The interbedded host rocks with the BIFs mainly are the pyroxene-amphibole rocks and the banded or impure dolostones,and also contain banded or laminated structures,and lepido-gra-noblastic,nematoblastic and/or blastoclastic textures.Compositionally,the main host rocks,the pyroxene-amphibole rocks contain basic-intermediate SiO_2(~54.00 wt.%),CaO(~14.19 wt.%),MgO(~9.68 wt.%)and Al_2O_3(~8.49 wt.%)with a positive correlation between Al_2O_3 and TiO_2.The UCC-like Zr and Hf abundances,high Ba content andεNd(t)value(^-5.99)as well as the ratios of La/YbPAAS(0.17~1.00),δEuPAAS(0.88~1.12)andδCePAAS(0.93~1.13)commonly reveal that the protoliths to this type rocks are hydrogenic with a large contribution of terrigenous sediments and minor hydrothermal input.The high CaO+MgO+LOI contents and the extremely low trace element and REEconcentrations as well as the ratios of Y/Ho(44~45),δEuPAAS(1.13~1.57)andδCePAAS(0.69~0.98)reflect a marine origin with minor terrigenous materials for the banded or impure dolostones.Moreover,this type rocks also account for a negativeεNd(t)value(^-7.49).The oxide facies BIF is dominated by Fe_2O_3+FeO(~75.59wt.%)and SiO_2(~20.47 wt.%)with aεNd(t)value of^-6.10.The variable contents in Al_2O_3,TiO 2,K2O,Na2O,Zr,Hf and∑REE,and variable ratios of Y/Ho(24~39)andδEuPAAS(0.86~11.07)suggest the precursor sediments to this facies BIF are admixtures of sea-floor hydrothermal fluids and seawaters with minor involvement of detrital components.Compared to the oxide facies BIF,the silicate-oxide facies BIF is lower in Fe_2O_3+Fe O(~39.81wt.%)and Ba but higher in SiO_2(~42.54 wt.%),Al2O3(~3.60 wt.%),TiO_2(~0.19 wt.%),MgO(~1.12 wt.%),CaO(~9.06 wt.%),K_2O(~0.98 wt.%),Mn and Zr.The ratios of Y/Ho(25~34),La/YbPAAS(0.14-0.74)andδEuPAAS(0.91~1.12)most likely are linked to higher degree of detrital contamintants.While the sulfide-caronate facies BIF is main but variable in Fe_2O_3+Fe O(15.79~57.91 wt.%),SiO 2(0.54~61.52 wt.%),MgO(0.12~16.09wt.%),CaO(0.17~23.41 wt.%)and LOI(8.28-30.06 wt.%).The generally low contents in trace elements(including REE)except for an obvious enrichment in Pb,and the positive Ce anomalies(δCePAAS=1.04~1.95)and negative Pr anomalies(δPrPAAS=0.67~0.93),as well as the variable ratios ofδEuPAAS(0.72~1.71),La/YbPAAS(0.26~1.60)and Y/Ho(26~57)suggest that the precursors to the sulfide-carbonate facies BIF mainly are metalliferious sediments from deep-marine hydrotheral source with minor detrital components.The T2DM ages(ca.2.0 Ga)imply that the Shilu BIFs and interbedded host rocks contain a component with Paleoproterozoic crustal residence age due to a significant crustal accretion event at ca.2.0 Ga in Hainan Island.In connection with the petrographical and mineralogical relationship,we conclude that the precursor precipitates to the Shilu BIFs are variable degree of admixtures of the Fe-Co-Cu-(Si)-rich hydrothermal fluids and detrital components from seawater and fresh water carring continental landmass;whereas the protolith to the main interbedded host rocks,i.e.the pyroxene-amphibole rocks,most likely was terrigenous,fine-grained clastic-sediments but with significant input of hydrothermal fluids in a seawater environment.As a result,a continent marginal marine basin is proposed for deposition of the Shilu BIFs and interbedded host rocks.Sea-level fluctuations caused by marine transgression–regressions possibly contributed to changes in the composition and varied input of the terrigenous sediments.展开更多
The summer and winter circulations in the South China Sea (SCS) including the surface elevation and water temperature are simulated using the model described by Cai and Li (1996) with the monthly mean wind stress and ...The summer and winter circulations in the South China Sea (SCS) including the surface elevation and water temperature are simulated using the model described by Cai and Li (1996) with the monthly mean wind stress and air temperature field at the 1000 mb level from the European Centre for Medium-Range Weather Forecasts as inputs. The boundary conditions at Bashi Channel and Taiwan Strait are taken from the simulation results of the Kuroshio using the same numerical model with a grid size of 0.5°×0.5° and the results of Cai and Li (1996) as boundary conditions. The computational domain for the present paper is between 100°E and 123°E and between 4.5°N and 27°N. The horizontal resolution is 0.25°×0.25° and the vertical variations of the velocity components are resolved by 6 layers The computed steady flow, temperature and elevation fields are consistent with the corresponding fields observed. In particular, the temperature and elevation fields of the South China Sea Warm Current (SCSWC) have been successfully simulated. The paths of the branch of the Kuroshio entering the South China Sea (SCSBK) through Bashi Channel in winter and summer are discussed It is found that the SCSBK flows southward to the southern SCS from the coast of the Guangdong Province. A portion of the SCSBK returns to the Bashi Channel and subdivides again in deep waters in winter with a branch flows to the south along the coast of the Philippines instead of flowing back to the Pacific In addition, our results confirm the existence of a eastward current to the northeast of Dongsha in summer with the Kuroshio as its source as suggested by Huang et al. Since the value of the eddy viscosity adopted for the simulation of the Kuroshio is on the high side, resulting in a weaker west boundary current in the western Pacific as the boundary conditions for the present simulations, some deviations from the actual situations are expected although the results are in general consistent with observations.展开更多
Ⅰ. An analysis of the development trend of the economy in the north,middle aud south coastal regions or China since China began to implementreform and open
The Shilu iron ore deposit,located in the western Hainan Province,South China,is one of the most important iron-ore mining districts in China not only for its huge reserves of hematite-rich ores,but also for its poten...The Shilu iron ore deposit,located in the western Hainan Province,South China,is one of the most important iron-ore mining districts in China not only for its huge reserves of hematite-rich ores,but also for its potentially economic significance of associated metals of copper,cobalt,nickel,silver,lead and zinc,and of non-metals of dolomite,quartzite,barite,gypsum and sulfur.展开更多
There have been a number of applications of satellite altimetry to seasonal and interannual sea level variability in the South China Sea. However, these applications usually exclude shallow waters along the coast, wit...There have been a number of applications of satellite altimetry to seasonal and interannual sea level variability in the South China Sea. However, these applications usually exclude shallow waters along the coast, with one of the concerns being large aliased tide-correction error. In this study the authors analyzed 14 years of merged satellite altimeter data to obtain the amplitude and phase of the semi-annual cycle and to examine the variation at the K1 alias frequency (close to the semi-annual frequency). The results indicate that the amplitude of the semi-annual cycle ranges from 3-7 cm, substantial compared with that of the annual cycle; while the amplitude at the K1 alias frequency (error of the K1 tidal correction) is essentially 1 cm only. Altimeter-derived semi-annual cycle is in good agreement with that from independent tide-gauge observations, pointing to the competent ability of satellite altimetry in observing semi-annual sea level variations in the South China Sea.展开更多
基金State Natural Scientific Foundation (49734150) and National High Performance Computation Foundation.
文摘We assembled approximately 328 seismic records. The data set was from 4 digitally recording long-period and broadband stations of CDSN. We carried out the inversion based on the partitioned waveform inversion (PWI). It partitions the large-scale optimization problem into a number of independent small-scale problems. We adopted surface waveform inversion with an equal block (2((2() discretization in order to acquire the images of shear velocity structure at different depths (from surface to 430 km) in the crust and upper-mantle. The resolution of all these anomalies has been established with (check-board( resolution tests. These results show significant difference in velocity, lithosphere and asthenosphere structure between South China Sea and its adjacent regions.
文摘Both evolution of the Asian monsoon system and the Cenozoic global cooling are thought to be closely linked to the Himalayan—Tibetan orogen. The South China Sea (SCS) with its high sedimentation rates of carbonate\|rich hemipelagic sediments offers a unique opportunity to study the variability of the East Asian monsoon, the erosion and weathering of tectonic orogens as well as its possible impact on global and regional climate.Leg 184, the first deep\|sea drilling leg to the seas off China, cored 17 holes at 6 sites in the northern and southern parts of the SCS and recovered 5463m of sediment. The drilling of hemipelagic sediments was exceptionally successful, with core recovery averaging 83%～101%. The 32Ma sequence of deep\|sea sediments recovered during Leg 184 covers almost the entire environmental history of the SCS since its opening. The abnormally high sediment accumulation rates in the Oligocene section are correlative with the incipient sea floor spreading. The bathyal nature of the Oligocenefauna implies that rifting occurred in the Eocene or earlier. Faunal changesfrom the early to late Oligocene are indicative of basin deepening, a trend thatis even more evident in the Miocene section. Sediment deformation, abruptlithologic changes, and a hiatus occur near the Oligocene/Miocene boundary,representing one of the most significant events in the tectonic andenvironmental history of the SCS.
文摘An integrated sedimentological, sequence stratigraphic, tectonic\|stratigraphic, isotope chronostratigraphic and isotope (element) geochemical analysis indicates that the Neoproterozoic basins in South China are characteristic of rift basins, and their formation and evolution are closely related to the breakup of the supercontinent Rodinia. (1) Neoproterozoic basins in South China can be divided into three major provinces: the southeastern Yangtze province, the Kangdian province along the western margin of the Yangtze block, and the Cathaysia province. They can be further subdivided into five subprovinces and eleven microprovinces on the basis of tectonic settings, sedimentary facies and palaeogeography,and outcrop sequence stratigraphy.(2) Four genetic facies associations and two environmental facies associations can be recognized in the Neoproterozoic basins. The former include① continental volcanic eruptive genetic facies association; ② submarine volcanic eruptive genetic facies association; ③ tillite genetic facies association; and ④ eustatic event deposits genetic facies association. The latter comprise: ① continental environmental facies association, and ② marine environmental facies association.
基金Project(40976035) supported by the National Natural Science Foundation of ChinaProject(2009CB219501) supported by the National Basic Research Program of ChinaProject(908-ZC-I-07) supported by the Special Program of Comprehensive Survey and Assessment Offshore China Sea
文摘Carbon and oxygen isotope and dating analyses of foraminiferan in sediment cores collected from three different areas of the northern slope of the South China Sea were conducted, in order to examine the records of the gas hydrate decomposition events since the late Quaternary under the conditions of methane seepage. The results show that： 1） the δ13C values of the benthic foraminiferan Uvigerina spp. （size range of 0.25-0.35 ram） are from -0.212% to -0.021% and the δ180 values of the planktonic foraminiferan Globigerinoides ruber （size range of 0.25-0.35 ram） are from -0.311% to -0.060%; 2） three cores （ZD2, ZD3 and ZS5） from the bottom of a hole are aged for 11 814, 26 616 and 64 090 a corresponding to the early oxygen isotope stage （MIS） Ⅰ, Ⅲ and Ⅳ final period, respectively; 3） a negative-skewed layer of carbon isotope corresponds to that of MIS II （cold period）, whose degree of negative bias is -0.2%0; and 4） the δ13C compositions of foraminiferans are similar to those of the Blake Ridge and the Gulf of Mexico sediments of the late Quaternary. According to the analysis, the reasons for these results are that the studied area is a typical area of methane seep environment in the area during MIS II due to the global sea-level fall and sea pressure decrease. Gas hydrate is decomposed and released, and a large number of light carbon isotopes of methane are released into the ocean, dissolved to inorganic carbon （DIC） pool and recorded in the foraminiferan shells. A pyrite layer developed in the negative bias layers of the foraminiferans confirms that the δ13C of foraminiferans is more affected by methane and less by the reduction of marine productivity and early diagenesis. The use of foraminiferan δ13C could accurately determine late Quaternary hydrate release events and provide evidence for both reconstructing the geological history of methane release events and exploring natural gas hydrate.
基金Instrument Developing Project of the Chinese Academy of Sciences(YZ201136)National Natural Science Foundation of China(41106086,41474065,41376059,41376061,91428205,41576036,41076028,41476167,and 41606080)Chinese Academy of Sciences Scholarship,the Strat
文摘Previous studies on the Late Permian shallow-water ostracod faunas in South China have greatly increased our knowledge on the Late Permian ostracods.But the absence of data on contemporary deep-water ostracods makes it difficult to comprehensively understand the Late Permian ostracods during the largest extinction among the"Big Five"in the Phanerozoic. During the past years,our work has been focused
文摘Very high resolution seismic record were used to study the sedimentary processes and morphosedimentary features of the continental slope system since Miocene in Qiongdongnan Basin(QDNB),offshore Hainan,northern South China Sea.It can be divided into four types based on the sedimentary processes and morphology:wide and gentle slope,sigmoid-progradational slope,slumping slope and channeled slope.Different features of
文摘The transition between Permian and Triassic(252.4 Ma) is marked by the most devastating extinction the biosphere ever went through.Although its cause stays unclear,it is admitted that this mass extinction originated in the conjunction of several global events: tectonic(Pangaea closing),volcanic(Siberian traps), magnetic(reversal of superchron),climatic(end of Permian glaciation) and eustatic(tecto-and ther-
文摘The Qiongdongnan Basin lies in the west part of the northern South China Sea.To the west the basin is bound by the Red River Fault and the Yinggehai Basin,to the east by the Pearl River Mouth Basin,and to the south by the Xisha Rise.In this study,the sequence stratigraphic framework was set up and 11 third-order sequences were distinguished.Based
基金National Natural Science Foundation of China(41206132,41276162,41130855)Chinese Academy of Sciences Strategic Pilot Science and Technology(XDA11020202,XDA05030403)+2 种基金National Project of Basic Sciences and Technology(2012FY112400,2013FY111200)Chinese Academy of Sciences Knowledge Innovation Program(SQ201115)Natural Science Foundation of Guangdong Province(S2011040000151)
文摘Results are presented about the changes in chlorophyll a density, carbon fixation and nutrient levels in the surfacewaters of three transects of the southern South China Sea （SCS）, northern Java Sea （JS） and eastern Indian Ocean （IO） duringApril 5-16 of 2011. The in situ Chl a concentration and carbon fixation showed decreasing trends from high to low latitudealong the three transects, while the photosynthetic rate of phytoplankton estimated from 14C incorporation displayed no simplevariation with latitude. Chl a concentration and carbon fixation in the IO water was lower than that in the JS water. Highersalinity and lower contents of dissolved inorganic nitrogen （DIN） and silicate （SiO3^2-） characterized the IO water as comparedto the SCS or JS water, and the PO4^3- content was lower in the IO water than in the SCS or JS water in most cases. Our resultsalso indicate the importance of DIN and SiO3^2- concentrations for the geographical changes in phytoplankton biomass andprimary productivity among the three regions.
文摘The Shilu Fe-polymetallic ore deposit,a famous hematite-rich Fe-ore deposit,is situated at the western Hainan Province of south China.The deposit characterizes the upper Fe ores and the lower Co-Cu ores,which are mainly hosted within a low-grade to medium-grade,dominantly submarine metamorphosed siliciclastic and carbonate sedimentary succession of the Neoproterozoic Shilu Group.Three facies types of metamorphosed BIFs,i.e.the oxide facies,the silicate-oxide facies and the sulfide-carbonate facies BIFs,are identified within the sixth sequence of the Shilu Group.The oxide facies BIF(i.e.the Fe-rich itabirites or ores)consists of alternating hematite-rich microbands with quartz-rich microbands;the silicate-oxide facies BIF(i.e.the Fe-poor itabirites or ores)comprises alternating millimeter-to a few tens meter-scale,magnetite-hematite-rich bands with calcsilicate-rich(garnet+actinolite+diopside+epidote+quartz)meso-to microbands;and the sulfide-carbonate facies BIF(i.e.the Co-Cu ores)contains alternating macro-to mesobands of Co-bearing pyrite and pyrrhotite,and chalcopyrite with mesobands of dolomite+calcite+diopside+quartz and/or chlorite+sericite+quartz.The blastooolitic,blastopelletoid blastocolloidal and blastopsammitic textures,and blasobedding structures which most likely represent primary sedimentation are often observed in these BIF facies.The interbedded host rocks with the BIFs mainly are the pyroxene-amphibole rocks and the banded or impure dolostones,and also contain banded or laminated structures,and lepido-gra-noblastic,nematoblastic and/or blastoclastic textures.Compositionally,the main host rocks,the pyroxene-amphibole rocks contain basic-intermediate SiO_2(~54.00 wt.%),CaO(~14.19 wt.%),MgO(~9.68 wt.%)and Al_2O_3(~8.49 wt.%)with a positive correlation between Al_2O_3 and TiO_2.The UCC-like Zr and Hf abundances,high Ba content andεNd(t)value(^-5.99)as well as the ratios of La/YbPAAS(0.17~1.00),δEuPAAS(0.88~1.12)andδCePAAS(0.93~1.13)commonly reveal that the protoliths to this type rocks are hydrogenic with a large contribution of terrigenous sediments and minor hydrothermal input.The high CaO+MgO+LOI contents and the extremely low trace element and REEconcentrations as well as the ratios of Y/Ho(44~45),δEuPAAS(1.13~1.57)andδCePAAS(0.69~0.98)reflect a marine origin with minor terrigenous materials for the banded or impure dolostones.Moreover,this type rocks also account for a negativeεNd(t)value(^-7.49).The oxide facies BIF is dominated by Fe_2O_3+FeO(~75.59wt.%)and SiO_2(~20.47 wt.%)with aεNd(t)value of^-6.10.The variable contents in Al_2O_3,TiO 2,K2O,Na2O,Zr,Hf and∑REE,and variable ratios of Y/Ho(24~39)andδEuPAAS(0.86~11.07)suggest the precursor sediments to this facies BIF are admixtures of sea-floor hydrothermal fluids and seawaters with minor involvement of detrital components.Compared to the oxide facies BIF,the silicate-oxide facies BIF is lower in Fe_2O_3+Fe O(~39.81wt.%)and Ba but higher in SiO_2(~42.54 wt.%),Al2O3(~3.60 wt.%),TiO_2(~0.19 wt.%),MgO(~1.12 wt.%),CaO(~9.06 wt.%),K_2O(~0.98 wt.%),Mn and Zr.The ratios of Y/Ho(25~34),La/YbPAAS(0.14-0.74)andδEuPAAS(0.91~1.12)most likely are linked to higher degree of detrital contamintants.While the sulfide-caronate facies BIF is main but variable in Fe_2O_3+Fe O(15.79~57.91 wt.%),SiO 2(0.54~61.52 wt.%),MgO(0.12~16.09wt.%),CaO(0.17~23.41 wt.%)and LOI(8.28-30.06 wt.%).The generally low contents in trace elements(including REE)except for an obvious enrichment in Pb,and the positive Ce anomalies(δCePAAS=1.04~1.95)and negative Pr anomalies(δPrPAAS=0.67~0.93),as well as the variable ratios ofδEuPAAS(0.72~1.71),La/YbPAAS(0.26~1.60)and Y/Ho(26~57)suggest that the precursors to the sulfide-carbonate facies BIF mainly are metalliferious sediments from deep-marine hydrotheral source with minor detrital components.The T2DM ages(ca.2.0 Ga)imply that the Shilu BIFs and interbedded host rocks contain a component with Paleoproterozoic crustal residence age due to a significant crustal accretion event at ca.2.0 Ga in Hainan Island.In connection with the petrographical and mineralogical relationship,we conclude that the precursor precipitates to the Shilu BIFs are variable degree of admixtures of the Fe-Co-Cu-(Si)-rich hydrothermal fluids and detrital components from seawater and fresh water carring continental landmass;whereas the protolith to the main interbedded host rocks,i.e.the pyroxene-amphibole rocks,most likely was terrigenous,fine-grained clastic-sediments but with significant input of hydrothermal fluids in a seawater environment.As a result,a continent marginal marine basin is proposed for deposition of the Shilu BIFs and interbedded host rocks.Sea-level fluctuations caused by marine transgression–regressions possibly contributed to changes in the composition and varied input of the terrigenous sediments.
文摘The summer and winter circulations in the South China Sea (SCS) including the surface elevation and water temperature are simulated using the model described by Cai and Li (1996) with the monthly mean wind stress and air temperature field at the 1000 mb level from the European Centre for Medium-Range Weather Forecasts as inputs. The boundary conditions at Bashi Channel and Taiwan Strait are taken from the simulation results of the Kuroshio using the same numerical model with a grid size of 0.5°×0.5° and the results of Cai and Li (1996) as boundary conditions. The computational domain for the present paper is between 100°E and 123°E and between 4.5°N and 27°N. The horizontal resolution is 0.25°×0.25° and the vertical variations of the velocity components are resolved by 6 layers The computed steady flow, temperature and elevation fields are consistent with the corresponding fields observed. In particular, the temperature and elevation fields of the South China Sea Warm Current (SCSWC) have been successfully simulated. The paths of the branch of the Kuroshio entering the South China Sea (SCSBK) through Bashi Channel in winter and summer are discussed It is found that the SCSBK flows southward to the southern SCS from the coast of the Guangdong Province. A portion of the SCSBK returns to the Bashi Channel and subdivides again in deep waters in winter with a branch flows to the south along the coast of the Philippines instead of flowing back to the Pacific In addition, our results confirm the existence of a eastward current to the northeast of Dongsha in summer with the Kuroshio as its source as suggested by Huang et al. Since the value of the eddy viscosity adopted for the simulation of the Kuroshio is on the high side, resulting in a weaker west boundary current in the western Pacific as the boundary conditions for the present simulations, some deviations from the actual situations are expected although the results are in general consistent with observations.
文摘Ⅰ. An analysis of the development trend of the economy in the north,middle aud south coastal regions or China since China began to implementreform and open
文摘The Shilu iron ore deposit,located in the western Hainan Province,South China,is one of the most important iron-ore mining districts in China not only for its huge reserves of hematite-rich ores,but also for its potentially economic significance of associated metals of copper,cobalt,nickel,silver,lead and zinc,and of non-metals of dolomite,quartzite,barite,gypsum and sulfur.
基金Canadian Space Agency Government Research Initiative ProgramNASA Ocean Surface Topography Science Team Program
文摘There have been a number of applications of satellite altimetry to seasonal and interannual sea level variability in the South China Sea. However, these applications usually exclude shallow waters along the coast, with one of the concerns being large aliased tide-correction error. In this study the authors analyzed 14 years of merged satellite altimeter data to obtain the amplitude and phase of the semi-annual cycle and to examine the variation at the K1 alias frequency (close to the semi-annual frequency). The results indicate that the amplitude of the semi-annual cycle ranges from 3-7 cm, substantial compared with that of the annual cycle; while the amplitude at the K1 alias frequency (error of the K1 tidal correction) is essentially 1 cm only. Altimeter-derived semi-annual cycle is in good agreement with that from independent tide-gauge observations, pointing to the competent ability of satellite altimetry in observing semi-annual sea level variations in the South China Sea.
