With the development of economy,the impact of human activities on ecological environment is increasing,and environmental protection work is important.Trace elements(Co,Ni,Cu,Pb,Zn,Cd,Cr,and Sc)in surface fi ne-grained...With the development of economy,the impact of human activities on ecological environment is increasing,and environmental protection work is important.Trace elements(Co,Ni,Cu,Pb,Zn,Cd,Cr,and Sc)in surface fi ne-grained sediment samples from the Jiaozhou Bay catchment were selected to evaluate their 2015 environmental background values and the environmental quality.Using statistical analysis,the environmental background values(ranges)of Sc,Co,Ni,Cu,Pb,Zn,Cd,and Cr were calculated,being 13.1(10.8-15.4),12.4(8.6-16.2),32.0(22.9-41.2),29.6(13.5-64.9),24.1(13.0-44.6),77.6(38.5-156.5),0.07(0.02-0.20),and 82.5(66.5-104.0)mg/kg,respectively.The enrichment factor,contamination factor,and pollution load index were used to evaluate the pollution status of the Jiaozhou Bay catchment.The environmental background values of most elements are higher than those of the upper continental crust and lower than those of global shale.At present,the pollution in the eastern Jiaozhou Bay is much higher than that in the western part.The results shall be helpful for future management for trace element pollution monitoring in the Jiaozhou Bay catchment.展开更多
The Bohai Sea is influenced by numerous extreme oceanic wave events in history.However,it is often difficult to determine the types of these events due to the lack of detailed historical records,causing uncertainty in...The Bohai Sea is influenced by numerous extreme oceanic wave events in history.However,it is often difficult to determine the types of these events due to the lack of detailed historical records,causing uncertainty in the reconstruction of historical coastal disasters.We investigated an anomalous sand layer in the Xiliyu Village by the coast of Laizhou Bay,Shandong,from which an extreme event deposit was identified using a multi-proxy approach including grain size distribution,geochemistry,and magnetic susceptibility.This event was dated 2700–3100 a bp,and caused inundation of a large coastal area of Laizhou Bay.By comparing historical records with instrumental data,we believe that the event deposit was generated by a severe storm surge with wind speed of>34.9 m/s.展开更多
Natural gas hydrate is a potential clean energy source and is related to submarine geohazard,climate change,and global carbon cycle.Multidisciplinary investigations have revealed the occurrence of hydrate in the Qiong...Natural gas hydrate is a potential clean energy source and is related to submarine geohazard,climate change,and global carbon cycle.Multidisciplinary investigations have revealed the occurrence of hydrate in the Qiongdongnan Basin,northern South China Sea.However,the spatial distribution,controlling factors,and favorable areas are not well defined.Here we use the available high-resolution seismic lines,well logging,and heat flow data to explore the issues by calculating the thickness of gas hydrate stability zone(GHSZ)and estimating the inventory.Results show that the GHSZ thickness ranges between mostly~200 and 400 m at water depths>500 m.The gas hydrate inventory is~6.5×109-t carbon over an area of~6×104 km2.Three areas including the lower uplift to the south of the Lingshui sub-basin,the Songnan and Baodao sub-basins,and the Changchang sub-basin have a thick GHSZ of~250-310 m,250-330 m,and 350-400 m,respectively,where water depths are~1000-1600 m,1000-2000 m,and2400-3000 m,respectively.In these deep waters,bottom water temperatures vary slightly from~4 to 2℃.However,heat flow increases significantly with water depth and reaches the highest value of~80-100 mW/m2 in the deepest water area of Changchang sub-basin.High heat flow tends to reduce GHSZ thickness,but the thickest GHSZ still occurs in the Changchang sub-basin,highlighting the role of water depth in controlling GHSZ.The lower uplift to the south of the Lingshui sub-basin has high deposition rate(~270-830 m/Ma in 1.8-0 Ma);the thick Cenozoic sediment,rich biogenic and thermogenic gas supplies,and excellent transport systems(faults,diapirs,and gas chimneys)enables it a promising area of hydrate accumulation,from which hydrate-related bottom simulating reflectors,gas chimneys,and active cold seeps were widely revealed.展开更多
Horizontal and vertical distributions of δ^18 and δ^13 were investigated in shells of four planktonic foraminiferal species, Globigerinoides ruber, Globigerinoides sacculifer, Pulleniatina obliquiloculata and Neoglo...Horizontal and vertical distributions of δ^18 and δ^13 were investigated in shells of four planktonic foraminiferal species, Globigerinoides ruber, Globigerinoides sacculifer, Pulleniatina obliquiloculata and Neogloboquedrina dutertrei, from a total of 62 core-top sediment samples from the Indonesian throughflow region. Results were compared to modern hydrologic conditions in order to explore potential of proxies in reconstructing fluvial discharge and upper ocean water column characteristics in this region. Our results show that, in the Makassar Strait, both of depleted δ^18 and δ^13 of these four species were linked to freshwater input. In the Bali Sea,however, depleted δ^18 and δ^13 for these species may be due to different reasons. Depleted δ^18 was a result of freshwater input and as well influenced by along-shore currents while depleted δ^13 was more likely due to the Java-Sumatra upwelling. Comparison of shell δ^18 records and hydrographic data of World Ocean Atlas 2005 suggests that G. ruber and G. sacculifer calcify within the mixed-layer, respectively at 0–50 m and 20–75 m water depth, and P. obliquiloculata and N. dutertrei within the upper thermocline, both at 75–125 m water depth. N.dutertrei calcifies at slightly deeper water depth than P. obliquiloculata does. In general, δ^13 values of both G.ruber and G. sacculifer are larger than those of P. obliquiloculata and N. dutertrei at all sites, possibly related to depth habitats of these species and vertical distribution of nutrients in the Indonesian throughflow region.展开更多
The biogenic silica of sediment samples from Core CJ01-185 which is collected from the eastern India Ocean off the Sunda Strait is analyzed to evaluate the impact of the opening of the Sunda Strait on a paleoproductiv...The biogenic silica of sediment samples from Core CJ01-185 which is collected from the eastern India Ocean off the Sunda Strait is analyzed to evaluate the impact of the opening of the Sunda Strait on a paleoproductivity evolution. The new results indicate that the biogenic silica mass values of Core CJ01-185 show the lowest 0.86% in the last glacial period, and reach its maxima of 1.89% in the late Holocene. Furthermore, the biogenic silica mass accumulation rate(MARBSi) values also vary with much higher during the late Holocene than during the last glaciation. The input of additional terrigenous materials from the Java Sea has enhanced the paleoproductivity and increased the biogenic silica mass and MARBSi values after the opening of the Sunda Strait. It is suggested that the paleoproductivity in the study area is mainly influenced by the southeast monsoon and upwelling before the opening of the Sunda Strait. However, the paleoproductivity is dominated by the terrigenous materials input other than by the southeast monsoon or upwelling in the Holocene.展开更多
Large-scale Cenozoic magmatic rocks from the interplay between the Indian and Eurasian plate are exposed in the Yulong porphyry copper belt in the northern Jinshajiang-Ailaoshan domain.Alkali-rich magmas along the Yul...Large-scale Cenozoic magmatic rocks from the interplay between the Indian and Eurasian plate are exposed in the Yulong porphyry copper belt in the northern Jinshajiang-Ailaoshan domain.Alkali-rich magmas along the Yulong porphyry copper belt can reveal the tectono-magmatic processes in the Sanjiang region.In this study,we present new zircon U-Pb-Hf isotopes and whole rock geochemistry of Cenozoic granitoids from the Zhalaga area in the northern Yulong porphyry copper belt.The Zircon U-Pb dating results show that the Zhalaga granitic porphyry crystallized at ca.42-38 Ma.These porphyry deposits are depleted in Nb,Ta,Sr,and Ti enriched in alkaline and rare earth elements(REEs),and exhibit high zircon saturation temperatures,that strongly indicate A-type affinity.These data and the generally positiveεHf(t)values(2.0-4.5)suggest the magmas originated from a hybrid of partial melting of subduction-modified lithospheric mantle,possibly triggered by upwelling of the asthenospheric mantle.Geochronological and geochemical data of the current and previous studies distinguish three magmatic phases during the Cenozoic in the Jinshajiang-Ailaoshan region:(1)ca.62-48 Ma;(2)ca.44-30 Ma;and(3)ca.28-16 Ma.The strong collision between the Indian and Eurasian plates produced relatively fast convergence rates during the first episode(ca.62-48 Ma),whereas the subsequent right-lateral strike-slip faulting in the Jinshajiang fault zone initiated at ca.43 Ma is associated with the relatively low India-Eurasia convergence rates during ca.44-30 Ma.These significantly impacted the nature and spatial distribution of the magmatism and the large-scale metallogeny during the Cenozoic in the Sanjiang region.We suggest that the Zhalaga alkali-rich magmas occurred in a transition period from involving soft to hard collisional settings.This remarkable example demonstrates that alkali-rich magmas with A-type affinity are also generated in an orogenic tectonic setting.展开更多
Test geochemistry of planktonic foraminifera is an indispensable tool in reconstructing past ocean hydrological changes. It is essential to investigate region-specific implications of test geochemistry,although those ...Test geochemistry of planktonic foraminifera is an indispensable tool in reconstructing past ocean hydrological changes. It is essential to investigate region-specific implications of test geochemistry,although those established from other regions can be broadly applied. In this study, characteristics of6180 and Mg/Ca from tests of four planktonic foraminiferal species, Globigerinoides ruber sensu stricto(s.s.), Globigerinoides sacculifer, Pulleniatina obliquiloculata and Neogloboquadrina dutertrei, from 60 coretop sediment samples retrieved from the Indonesian Throughflow(ITF) region were studied. These geochemical data were compared with modern hydrographic profiles in order to assess their relations and to investigate potential implications of test geochemical parameters in reconstructing past oceanographic change in the ITF region. Calcification depths of these four species were first estimated based on comparison between measured test δ180 and predicted calcite δ^(18)O that was calculated from modern temperature and salinity. The results indicate that G. ruber s.s. and G. sacculifer calcify within the mixedlayer at 0-50 m and 20-75 m, respectively, whereas P. obliquiloculata and N. dutertrei calcify within the thermocline at around 75 to 125 m. A combined study of excess Mg/Ca(difference between measured and predicted Mg/Ca) and salinity suggests that salinity exerts a negligible impact on test Mg/Ca of these foraminiferal species in the ITF region. Comparison of test Mg/Ca-derived temperatures with temperature profiles of the upper 200 m of the water column from the seas of the ITF region also indicate calcification depths of these species, which match well with the above estimations using test δ^(18)O. It further indicates that G. sacculifer may be more sensitive in reflecting changes in the depth of the mixedlayer, highlighting a potential use of Mg/Ca temperature difference between G. ruber s.s. and G. sacculifer in reconstructing the depth of the mixed-layer in the ITF region.展开更多
In the past few decades, the (1 + 1)-dimensional nonlinear Schr6dinger (NLS) equation had been derived for envelope Rossby solitary waves in a line by employing the perturbation expansion method. But, with the de...In the past few decades, the (1 + 1)-dimensional nonlinear Schr6dinger (NLS) equation had been derived for envelope Rossby solitary waves in a line by employing the perturbation expansion method. But, with the development of theory, we note that the (1+1)-dimensional model cannot reflect the evolution of envelope Rossby solitary waves in a plane. In this paper, by constructing a new (2+1)-dimensional multiscale transform, we derive the (2+1)-dimensional dissipation nonlinear Schrodinger equation (DNLS) to describe envelope Rossby solitary waves under the influence of dissipation which propagate in a plane. Especially, the previous researches about envelope Rossby solitary waves were established in the zonal area and could not be applied directly to the spherical earth, while we adopt the plane polar coordinate and overcome the problem. By theoretical analyses, the conservation laws of (2+ 1)-dimensional envelope Rossby solitary waves as well as their variation under the influence of dissipation are studied. Finally, the one-soliton and two-soliton solutions of the (2+ 1)-dimensional NLS equation are obtained with the Hirota method. Based on these solutions, by virtue of the chirp concept from fiber soliton communication, the chirp effect of envelope Rossby solitary waves is discussed, and the related impact factors of the chirp effect are given.展开更多
Yongle atoll in the Xisha(Paracel) Archipelago is an isolated carbonate platform developed on Precambrian metamorphic and Mesozoic volcanic rocks since the early Miocene. To identify the 3D stratigraphic architecture ...Yongle atoll in the Xisha(Paracel) Archipelago is an isolated carbonate platform developed on Precambrian metamorphic and Mesozoic volcanic rocks since the early Miocene. To identify the 3D stratigraphic architecture and evolution of this platform, 13 high-resolution seismic profiles and shallow-to-deep water multi-beam data were processed and analyzed to reveal seismic facies, sequence boundary reflectors, seismic units, and platform architecture. Nine types of seismic facies were recognized based on their geometry, which included seismic amplitude, continuity, and termination patterns;additionally, six reflections, i.e., Tg, T60, T50, T40, T30, and T20, were identified in the Cenozoic strata. Five seismic units, SQ1(lower Miocene), SQ2(middle Miocene), SQ3(upper Miocene), SQ4(Pliocene), and SQ5(Quaternary), were identified from bottom to top across the platform. The platform grew rapidly in the middle Miocene and backstepped in the late Miocene–Pliocene. Here, we discuss the developmental characteristics and evolution of the Yongle Atoll, in combination with drilling wells, which can be divided into four stages: the initiation stage in the early Miocene, the flourishing stage in the middle Miocene, the partial-drowning stage in the late Miocene–Pliocene, and modern atoll in the Quaternary.展开更多
The late Quaternary shallow-water carbonates have been altered by a variety of diagenetic processes,and further influenced by high-amplitude global and regional sea level changes.This study utilizes a new borehole dri...The late Quaternary shallow-water carbonates have been altered by a variety of diagenetic processes,and further influenced by high-amplitude global and regional sea level changes.This study utilizes a new borehole drilled on the Yongxing Island,Xisha Islands to investigate meteoric diagenetic alteration in the late Quaternary shallowwater carbonates.Petrographic,mineralogical,stable isotopic and elemental data provide new insights into the meteoric diagenetic processes of the reef limestone.The results show the variation in the distribution of aragonite,high-Mg calcite(HMC)and low-Mg calcite(LMC)divides the shallow-water carbonates in Core SSZK1 into three intervals,which are UnitⅠ(31.20-55.92 m,LMC),UnitⅡ(18.39-31.20 m,aragonite and LMC)and UnitⅢ(upper 18.39 m of core,aragonite,LMC and HMC).Various degrees of meteoric diagenesis exist in the identified three units.The lowermost UnitⅠhas suffered almost complete freshwater diagenesis,whereas the overlying UnitsⅡandⅢhave undergone incompletely meteoric diagenesis.The amount of time that limestone has been in the freshwater diagenetic environment has the largest impact on the degree of meteoric diagenesis.Approximately four intact facies/water depth cycles are recognized.The cumulative depletion of elements such as strontium(Sr),sodium(Na)and sulphur(S)caused by duplicated meteoric diagenesis in the older reef sequences are distinguished from the younger reef sequences.This study provides a new record of meteoric diagenesis,which is well reflected by whole-rock mineralogy and geochemistry.展开更多
基金Supported by the Shandong Provincial Natural Science Foundation of China(No.ZR2020MD061)the Construction of Public Scientifi c Research Platform for Hydrobiology and Biotechnology,a Central-Government-Led Local Science and Technology Development Foundation(No.ZY2021HN04)the Independent Project of Hainan Provincial Key Laboratory of Marine Geological Resources and Environment(Nos.ZZ[2020]2019256-01,2019256[2020]HNHSKC-01)。
文摘With the development of economy,the impact of human activities on ecological environment is increasing,and environmental protection work is important.Trace elements(Co,Ni,Cu,Pb,Zn,Cd,Cr,and Sc)in surface fi ne-grained sediment samples from the Jiaozhou Bay catchment were selected to evaluate their 2015 environmental background values and the environmental quality.Using statistical analysis,the environmental background values(ranges)of Sc,Co,Ni,Cu,Pb,Zn,Cd,and Cr were calculated,being 13.1(10.8-15.4),12.4(8.6-16.2),32.0(22.9-41.2),29.6(13.5-64.9),24.1(13.0-44.6),77.6(38.5-156.5),0.07(0.02-0.20),and 82.5(66.5-104.0)mg/kg,respectively.The enrichment factor,contamination factor,and pollution load index were used to evaluate the pollution status of the Jiaozhou Bay catchment.The environmental background values of most elements are higher than those of the upper continental crust and lower than those of global shale.At present,the pollution in the eastern Jiaozhou Bay is much higher than that in the western part.The results shall be helpful for future management for trace element pollution monitoring in the Jiaozhou Bay catchment.
基金Supported by the National Natural Science Foundation of China(Nos.41706096,41530962,41771218)the Research Start-up Project of Jiangsu Normal University(No.19XSRX006)the Opening Foundation of Hainan Key Laboratory of Marine Geological Resources and Environment(No.HNHYDZZYHJKF005)。
文摘The Bohai Sea is influenced by numerous extreme oceanic wave events in history.However,it is often difficult to determine the types of these events due to the lack of detailed historical records,causing uncertainty in the reconstruction of historical coastal disasters.We investigated an anomalous sand layer in the Xiliyu Village by the coast of Laizhou Bay,Shandong,from which an extreme event deposit was identified using a multi-proxy approach including grain size distribution,geochemistry,and magnetic susceptibility.This event was dated 2700–3100 a bp,and caused inundation of a large coastal area of Laizhou Bay.By comparing historical records with instrumental data,we believe that the event deposit was generated by a severe storm surge with wind speed of>34.9 m/s.
基金Supported by the K.C.Wong Education Foundation(No.GJTD-2018-13)the Youth Innovation Promotion Association of Chinese Academy of Sciences+7 种基金the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(Nos.GML2019ZD0104,GML2019ZD0205)the Guangzhou Municipal Science and Technology Program(No.201904010285)the National Natural Science Foundation of China(No.42076077)the Innovation Academy of South China Sea Ecology and Environmental Engineering,Chinese Academy of Sciences(No.ISEE2018PY02)the National Key Research and Development Program of China(No.2021YFC3100604)the Hainan Key Laboratory of Marine Geological Resources and Environment(No.HNHYDZZYHJKF003)the Guangdong Basic and Applied Basic Research Foundation(No.2021A1515011298)the Guangdong Special Support Talent Team Program(No.2019BT02H594)。
文摘Natural gas hydrate is a potential clean energy source and is related to submarine geohazard,climate change,and global carbon cycle.Multidisciplinary investigations have revealed the occurrence of hydrate in the Qiongdongnan Basin,northern South China Sea.However,the spatial distribution,controlling factors,and favorable areas are not well defined.Here we use the available high-resolution seismic lines,well logging,and heat flow data to explore the issues by calculating the thickness of gas hydrate stability zone(GHSZ)and estimating the inventory.Results show that the GHSZ thickness ranges between mostly~200 and 400 m at water depths>500 m.The gas hydrate inventory is~6.5×109-t carbon over an area of~6×104 km2.Three areas including the lower uplift to the south of the Lingshui sub-basin,the Songnan and Baodao sub-basins,and the Changchang sub-basin have a thick GHSZ of~250-310 m,250-330 m,and 350-400 m,respectively,where water depths are~1000-1600 m,1000-2000 m,and2400-3000 m,respectively.In these deep waters,bottom water temperatures vary slightly from~4 to 2℃.However,heat flow increases significantly with water depth and reaches the highest value of~80-100 mW/m2 in the deepest water area of Changchang sub-basin.High heat flow tends to reduce GHSZ thickness,but the thickest GHSZ still occurs in the Changchang sub-basin,highlighting the role of water depth in controlling GHSZ.The lower uplift to the south of the Lingshui sub-basin has high deposition rate(~270-830 m/Ma in 1.8-0 Ma);the thick Cenozoic sediment,rich biogenic and thermogenic gas supplies,and excellent transport systems(faults,diapirs,and gas chimneys)enables it a promising area of hydrate accumulation,from which hydrate-related bottom simulating reflectors,gas chimneys,and active cold seeps were widely revealed.
基金The National Natural Science Foundation of China under contract No.41176044Shaanxi Provincial Technology Foundation for Selected Overseas Chinese Scholar under contract Shaan Renshe[2015]No.1190
文摘Horizontal and vertical distributions of δ^18 and δ^13 were investigated in shells of four planktonic foraminiferal species, Globigerinoides ruber, Globigerinoides sacculifer, Pulleniatina obliquiloculata and Neogloboquedrina dutertrei, from a total of 62 core-top sediment samples from the Indonesian throughflow region. Results were compared to modern hydrologic conditions in order to explore potential of proxies in reconstructing fluvial discharge and upper ocean water column characteristics in this region. Our results show that, in the Makassar Strait, both of depleted δ^18 and δ^13 of these four species were linked to freshwater input. In the Bali Sea,however, depleted δ^18 and δ^13 for these species may be due to different reasons. Depleted δ^18 was a result of freshwater input and as well influenced by along-shore currents while depleted δ^13 was more likely due to the Java-Sumatra upwelling. Comparison of shell δ^18 records and hydrographic data of World Ocean Atlas 2005 suggests that G. ruber and G. sacculifer calcify within the mixed-layer, respectively at 0–50 m and 20–75 m water depth, and P. obliquiloculata and N. dutertrei within the upper thermocline, both at 75–125 m water depth. N.dutertrei calcifies at slightly deeper water depth than P. obliquiloculata does. In general, δ^13 values of both G.ruber and G. sacculifer are larger than those of P. obliquiloculata and N. dutertrei at all sites, possibly related to depth habitats of these species and vertical distribution of nutrients in the Indonesian throughflow region.
基金The National Programme on Global Change and Air-sea Interaction under contract Nos GASI-GEOGE-06-03 and GASI-02-IND-CJ01the China-Indonesia Joint Project under contract No."BENTHIC"the Third Institute of Oceanography,Ministry of Natural Resources Research Grant under contract No.2015015
文摘The biogenic silica of sediment samples from Core CJ01-185 which is collected from the eastern India Ocean off the Sunda Strait is analyzed to evaluate the impact of the opening of the Sunda Strait on a paleoproductivity evolution. The new results indicate that the biogenic silica mass values of Core CJ01-185 show the lowest 0.86% in the last glacial period, and reach its maxima of 1.89% in the late Holocene. Furthermore, the biogenic silica mass accumulation rate(MARBSi) values also vary with much higher during the late Holocene than during the last glaciation. The input of additional terrigenous materials from the Java Sea has enhanced the paleoproductivity and increased the biogenic silica mass and MARBSi values after the opening of the Sunda Strait. It is suggested that the paleoproductivity in the study area is mainly influenced by the southeast monsoon and upwelling before the opening of the Sunda Strait. However, the paleoproductivity is dominated by the terrigenous materials input other than by the southeast monsoon or upwelling in the Holocene.
基金supported by the National Natural Science Foundation of China(No.41776056)Natural Science Foundation of Guangdong Province(Nos.2017A030310395,2018B030311030)China Postdoctoral Science Foundation(grant No.2020M672671)。
文摘Large-scale Cenozoic magmatic rocks from the interplay between the Indian and Eurasian plate are exposed in the Yulong porphyry copper belt in the northern Jinshajiang-Ailaoshan domain.Alkali-rich magmas along the Yulong porphyry copper belt can reveal the tectono-magmatic processes in the Sanjiang region.In this study,we present new zircon U-Pb-Hf isotopes and whole rock geochemistry of Cenozoic granitoids from the Zhalaga area in the northern Yulong porphyry copper belt.The Zircon U-Pb dating results show that the Zhalaga granitic porphyry crystallized at ca.42-38 Ma.These porphyry deposits are depleted in Nb,Ta,Sr,and Ti enriched in alkaline and rare earth elements(REEs),and exhibit high zircon saturation temperatures,that strongly indicate A-type affinity.These data and the generally positiveεHf(t)values(2.0-4.5)suggest the magmas originated from a hybrid of partial melting of subduction-modified lithospheric mantle,possibly triggered by upwelling of the asthenospheric mantle.Geochronological and geochemical data of the current and previous studies distinguish three magmatic phases during the Cenozoic in the Jinshajiang-Ailaoshan region:(1)ca.62-48 Ma;(2)ca.44-30 Ma;and(3)ca.28-16 Ma.The strong collision between the Indian and Eurasian plates produced relatively fast convergence rates during the first episode(ca.62-48 Ma),whereas the subsequent right-lateral strike-slip faulting in the Jinshajiang fault zone initiated at ca.43 Ma is associated with the relatively low India-Eurasia convergence rates during ca.44-30 Ma.These significantly impacted the nature and spatial distribution of the magmatism and the large-scale metallogeny during the Cenozoic in the Sanjiang region.We suggest that the Zhalaga alkali-rich magmas occurred in a transition period from involving soft to hard collisional settings.This remarkable example demonstrates that alkali-rich magmas with A-type affinity are also generated in an orogenic tectonic setting.
基金supported by the National Natural Science Foundation of China(Grant Nos.41176044 and 41576045)Shaanxi Provincial Technology Foundation for Selected Overseas Chinese Scholar(Grant No.Shaan Renshe[2015]No.1190)
文摘Test geochemistry of planktonic foraminifera is an indispensable tool in reconstructing past ocean hydrological changes. It is essential to investigate region-specific implications of test geochemistry,although those established from other regions can be broadly applied. In this study, characteristics of6180 and Mg/Ca from tests of four planktonic foraminiferal species, Globigerinoides ruber sensu stricto(s.s.), Globigerinoides sacculifer, Pulleniatina obliquiloculata and Neogloboquadrina dutertrei, from 60 coretop sediment samples retrieved from the Indonesian Throughflow(ITF) region were studied. These geochemical data were compared with modern hydrographic profiles in order to assess their relations and to investigate potential implications of test geochemical parameters in reconstructing past oceanographic change in the ITF region. Calcification depths of these four species were first estimated based on comparison between measured test δ180 and predicted calcite δ^(18)O that was calculated from modern temperature and salinity. The results indicate that G. ruber s.s. and G. sacculifer calcify within the mixedlayer at 0-50 m and 20-75 m, respectively, whereas P. obliquiloculata and N. dutertrei calcify within the thermocline at around 75 to 125 m. A combined study of excess Mg/Ca(difference between measured and predicted Mg/Ca) and salinity suggests that salinity exerts a negligible impact on test Mg/Ca of these foraminiferal species in the ITF region. Comparison of test Mg/Ca-derived temperatures with temperature profiles of the upper 200 m of the water column from the seas of the ITF region also indicate calcification depths of these species, which match well with the above estimations using test δ^(18)O. It further indicates that G. sacculifer may be more sensitive in reflecting changes in the depth of the mixedlayer, highlighting a potential use of Mg/Ca temperature difference between G. ruber s.s. and G. sacculifer in reconstructing the depth of the mixed-layer in the ITF region.
基金supported by the National Natural Science Foundation of China(Grant No.41406018)
文摘In the past few decades, the (1 + 1)-dimensional nonlinear Schr6dinger (NLS) equation had been derived for envelope Rossby solitary waves in a line by employing the perturbation expansion method. But, with the development of theory, we note that the (1+1)-dimensional model cannot reflect the evolution of envelope Rossby solitary waves in a plane. In this paper, by constructing a new (2+1)-dimensional multiscale transform, we derive the (2+1)-dimensional dissipation nonlinear Schrodinger equation (DNLS) to describe envelope Rossby solitary waves under the influence of dissipation which propagate in a plane. Especially, the previous researches about envelope Rossby solitary waves were established in the zonal area and could not be applied directly to the spherical earth, while we adopt the plane polar coordinate and overcome the problem. By theoretical analyses, the conservation laws of (2+ 1)-dimensional envelope Rossby solitary waves as well as their variation under the influence of dissipation are studied. Finally, the one-soliton and two-soliton solutions of the (2+ 1)-dimensional NLS equation are obtained with the Hirota method. Based on these solutions, by virtue of the chirp concept from fiber soliton communication, the chirp effect of envelope Rossby solitary waves is discussed, and the related impact factors of the chirp effect are given.
基金financially supported by Natural Science Foundation of China (U1701245)Research Program of Sanya Yazhou Bay Science and Technology City (No. SKJC-2020-01-009)+2 种基金Natural Science Foundation of China (91958206, 41876044)National Key Research and Development Program of China (2018YFC0308301)Strategic Priority Research Program of Chinese Academy of Sciences (XDA22040105)。
文摘Yongle atoll in the Xisha(Paracel) Archipelago is an isolated carbonate platform developed on Precambrian metamorphic and Mesozoic volcanic rocks since the early Miocene. To identify the 3D stratigraphic architecture and evolution of this platform, 13 high-resolution seismic profiles and shallow-to-deep water multi-beam data were processed and analyzed to reveal seismic facies, sequence boundary reflectors, seismic units, and platform architecture. Nine types of seismic facies were recognized based on their geometry, which included seismic amplitude, continuity, and termination patterns;additionally, six reflections, i.e., Tg, T60, T50, T40, T30, and T20, were identified in the Cenozoic strata. Five seismic units, SQ1(lower Miocene), SQ2(middle Miocene), SQ3(upper Miocene), SQ4(Pliocene), and SQ5(Quaternary), were identified from bottom to top across the platform. The platform grew rapidly in the middle Miocene and backstepped in the late Miocene–Pliocene. Here, we discuss the developmental characteristics and evolution of the Yongle Atoll, in combination with drilling wells, which can be divided into four stages: the initiation stage in the early Miocene, the flourishing stage in the middle Miocene, the partial-drowning stage in the late Miocene–Pliocene, and modern atoll in the Quaternary.
基金The National Natural Science Foundation of China-Guangdong Joint Foundation under contract No.U1701245the Hainan Provincial Natural Science Foundation of China under contract No.418QN306+2 种基金the Land and Georesource Bureau of Hainan Province under contract No.SQ2016KJHZ0027the Pioneer Hundred Talents Program under contract No.Y910091001the Guangzhou Marine Geological Survey Project under contract No.GZH201400210.
文摘The late Quaternary shallow-water carbonates have been altered by a variety of diagenetic processes,and further influenced by high-amplitude global and regional sea level changes.This study utilizes a new borehole drilled on the Yongxing Island,Xisha Islands to investigate meteoric diagenetic alteration in the late Quaternary shallowwater carbonates.Petrographic,mineralogical,stable isotopic and elemental data provide new insights into the meteoric diagenetic processes of the reef limestone.The results show the variation in the distribution of aragonite,high-Mg calcite(HMC)and low-Mg calcite(LMC)divides the shallow-water carbonates in Core SSZK1 into three intervals,which are UnitⅠ(31.20-55.92 m,LMC),UnitⅡ(18.39-31.20 m,aragonite and LMC)and UnitⅢ(upper 18.39 m of core,aragonite,LMC and HMC).Various degrees of meteoric diagenesis exist in the identified three units.The lowermost UnitⅠhas suffered almost complete freshwater diagenesis,whereas the overlying UnitsⅡandⅢhave undergone incompletely meteoric diagenesis.The amount of time that limestone has been in the freshwater diagenetic environment has the largest impact on the degree of meteoric diagenesis.Approximately four intact facies/water depth cycles are recognized.The cumulative depletion of elements such as strontium(Sr),sodium(Na)and sulphur(S)caused by duplicated meteoric diagenesis in the older reef sequences are distinguished from the younger reef sequences.This study provides a new record of meteoric diagenesis,which is well reflected by whole-rock mineralogy and geochemistry.