The Mesozoic tectonic framework of the eastern South China is mainly controlled by subduction,turning toward,and rollback of the Pacific Plate.Recent studies of receiver function imaging and ambient noise tomography h...The Mesozoic tectonic framework of the eastern South China is mainly controlled by subduction,turning toward,and rollback of the Pacific Plate.Recent studies of receiver function imaging and ambient noise tomography have revealed the“Yshaped”thinnest crustal belt in the eastern South China under the overall extension of the lithosphere.However,the deep dynamic environment and formation mechanisms of the thin crustal belt remain debatable.Here we obtained high-resolution images of the crustal thickness and Poisson’s ratio in the eastern South China Block applying the recently proposed H-κ-c receiver function method,using data recorded by 305 dense portable broadband stations and 219 permanent stations surrounding.Additionally,we discussed the deep dynamic formation mechanism of the“Y-shaped”thinnest crustal belt coupled with two common conversion point stacked images at key locations.Results show that the average crustal thickness of the study area is 33 km(thin crust)and the average Poisson’s ratio is 0.24(low ratio).The overall crustal thinning toward the continental margin is likely because eastern South China was in a back-arc extension environment,which was induced by the rollback of the subducted plate in the Early Cretaceous.The crustal thickness of the“Y-shaped”thinnest crustal belt is<30 km,which is 3-5 km thinner than that outside the zone.The eastern branch is distributed along the trajectory of Nanchang-Ji’an-Ganzhou-Shaoguan-Guangzhou,and the western branch is around the Jianghan-Xiangzhong Basin,both of which intersect in Nanling.The eastern branch of the thin crustal zone indicates the potential location of the Pacific subduction slab breakoff,and the formation mechanism may be related to the interaction of deep-shallow processes,including the upwelling of mantle heat flow through the slab window and transtensional pre-existing faults.We developed a dynamic model that combines subduction-breakoff-rollback processes of the Paleo-Pacific Plate and accompanying deep fluid upwelling to explain the regional extension of the South China lithosphere,the formation mechanism of the thinnest crustal belt,and the distribution of granitic plutons.展开更多
The granitic dykes in the Badu Group, Zhejiang Province, South China provide important insights on tectonic setting and crustal evolution of the South China Block （SCB） and the Indochina Block during Triassic. Here ...The granitic dykes in the Badu Group, Zhejiang Province, South China provide important insights on tectonic setting and crustal evolution of the South China Block （SCB） and the Indochina Block during Triassic. Here we report LA-ICP-MS U-Pb data of granitic rocks from the Hucun and Kengkou which show early Triassic ages of 242 ± 2 and 232 ± 3 Ma, respectively, representing their timing of emplacement. The dyke rocks are enriched in K, AI, LREE, Rb, Th, U, and Pb, and are depleted in Nb, Ta, St, and Ti. The rocks are characterized by highly fractionated REE patterns with （La/Yb）N ratios of 28.46 -38.07 with strong negative Eu anomalies （Eu/Eu＊ = 0,65-0.73）. In situ Hf isotopic analyses of zircons from the Hucun granite yielded CHf（t） values of -13.9 to -6.4 and two-stage depleted mantle Hf model ages of 1.68-2.15 Ga, which indicate that the magma was formed by partial melting of the Paleo- proterozoic metasedimentary protoliths in the Cathaysia Block. The zircons from the Kengkou granite have eHf（t） values ranging from -40.7 to 31.5 and yield two-stage depleted mantle Hf model ages of 0.99 -2.49 Ga, indicating magma origin from a mixed source. The Hucun and Kengkou dykes, together with the Triassic A-type granites in SE China were probably generated during magmatism associated with crust-mantle decoupling along the convergent plate boundary between SCB and the Indochina Block.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 time series NDVI distribution maps of the study area were calculated with AVHRR images acquired from May 1999 to April 2000 on the North-South transect of Eastern China. Based on the analysis of the characteristic...The time series NDVI distribution maps of the study area were calculated with AVHRR images acquired from May 1999 to April 2000 on the North-South transect of Eastern China. Based on the analysis of the characteristics and their contributions to NPP on the transect, the RS NPP distribution maps were created by zones and the quantitative models were established between NDVI maps and field measured NPP sample data collected from Central and South China for forest and cultivated land. Furthermore, the spatial distribution and quantitative result were obtained through an overlapping and fitting analysis between the NPP maps and DEM. The result shows that the NPP distribution features are not only distinguished on detail zonation of natural vegetation in vertical, latitudinal and longitudinal distribution but also reflected an obvious effect from the crop growing period of agricultural area. According to the results above, an opposite opinion was given that the NPP values for the forest and agricultural areas vary greatly in different regions, with the forest areas having a higher value than the agricultural areas in Southern China. In the Huang, Huai and Hai Plains, agricultural regions have higher NPP values than the surrounding low mountains. In Northeastern China, the NPP values form a gradient across the mid-to-high mountain forest zone to plains and low mountain areas. Further, for most of the agricultural areas, NPP values range between 25—35 t·hm2·a-1 and do not show significant areal differentiation.展开更多
Numerical experiments with a low resolution atmospheric general circulation model (AGCM) were conducted to investigate the influences of SST anomalies (SSTA) over the South China Sea- tropical eastern indian Ocean (SC...Numerical experiments with a low resolution atmospheric general circulation model (AGCM) were conducted to investigate the influences of SST anomalies (SSTA) over the South China Sea- tropical eastern indian Ocean (SCS-TEIO) on the onset of the South China Sea summer Monsoon (SCSM).With positive SSTA over the SCS-TEIO,the anomalous cyclones appear over both sides of the equator at low layer,which weakens the Somali and Australian cross-equatorial SW flow. The anomalous anticyclone in the east of Phillips strengthens the subtropical high with its ridge southwestward shifted.The anomalous anticyclones over both sides of equator at high layer strengthen the South Asia high,thus weaken the SCSM and delay its onset.With negative SSTA over the SCS-ETIO,the anomalous anticyclones appear over both sides of the equator at low layer,which strengthen the Australian but weaken the Somali cross-equatorial SW flow.The anomalous cyclone in northeast of Phillips will weaken the subtropical high.The stronger monsoon meridional circulation over the tropical western Pacific will strengthen the cross-equatorial southerly flow,and the anomalous cyclones over both sides of equator at high layer will weaken the South Asia high,hence strengthen the SCSM and advance its onset.展开更多
From July 2008 to August 2008, 72 leaf samples from 22 species and 81 soil samples in the nine natural forest ecosystems were collected, from north to south along the North-South Transect of Eastern China （NSTEC）. B...From July 2008 to August 2008, 72 leaf samples from 22 species and 81 soil samples in the nine natural forest ecosystems were collected, from north to south along the North-South Transect of Eastern China （NSTEC）. Based on these samples, we studied the geographical distribution patterns of vegetable water use efficiency （WUE） and nitrogen use efficiency （NUE）, and analyzed their relationship with environmental factors. The vegetable WUE and NUE were calculated through the measurement of foliar δ 13C and C/N of predominant species, respectively. The results showed： （1） vegetable WUE, ranging from 2.13 to 28.67 mg C g-1 H2O, increased linearly from south to north in the representative forest ecosystems along the NSTEC, while vegetable NUE showed an opposite trend, increasing from north to south, ranging from 12.92 to 29.60 g C g-1 N. （2） Vegetable WUE and NUE were dominantly driven by climate and significantly affected by soil nutrient factors. Based on multiple stepwise regression analysis, mean annual temperature, soil phosphorus concentration, and soil nitrogen concentration were responding for 75.5% of the variations of WUE （p0.001）. While, mean annual precipitation and soil phosphorus concentration could explain 65.7% of the change in vegetable NUE （p0.001）. Moreover, vegetable WUE and NUE would also be seriously influenced by atmospheric nitrogen deposition in nitrogen saturated ecosystems. （3） There was a significant trade-off relationship between vegetable WUE and NUE in the typical forest ecosystems along the NSTEC （p0.001）, indicating a balanced strategy for vegetation in resource utilization in natural forest ecosystems along the NSTEC. This study suggests that global change would impact the resource use efficiency of forest ecosystems. However, vegetation could adapt to those changes by increasing the use efficiency of shortage resource while decreasing the relatively ample one. But extreme impacts, such as heavy nitrogen deposition, would break this trade-off mechanism and give a dramatic disturbance to the ecosystem biogeochemical cycle.展开更多
基金geological survey project of China Geological Survey(Grant Nos.12120114067701,DD20179357,and DD20160082)the National Natural Science Foundation of China(Grant No.41574092)supported by the National Natural Science Foundation of China(Grant Nos.91962110,41774113,42174069,41874055,and 42104099).
文摘The Mesozoic tectonic framework of the eastern South China is mainly controlled by subduction,turning toward,and rollback of the Pacific Plate.Recent studies of receiver function imaging and ambient noise tomography have revealed the“Yshaped”thinnest crustal belt in the eastern South China under the overall extension of the lithosphere.However,the deep dynamic environment and formation mechanisms of the thin crustal belt remain debatable.Here we obtained high-resolution images of the crustal thickness and Poisson’s ratio in the eastern South China Block applying the recently proposed H-κ-c receiver function method,using data recorded by 305 dense portable broadband stations and 219 permanent stations surrounding.Additionally,we discussed the deep dynamic formation mechanism of the“Y-shaped”thinnest crustal belt coupled with two common conversion point stacked images at key locations.Results show that the average crustal thickness of the study area is 33 km(thin crust)and the average Poisson’s ratio is 0.24(low ratio).The overall crustal thinning toward the continental margin is likely because eastern South China was in a back-arc extension environment,which was induced by the rollback of the subducted plate in the Early Cretaceous.The crustal thickness of the“Y-shaped”thinnest crustal belt is<30 km,which is 3-5 km thinner than that outside the zone.The eastern branch is distributed along the trajectory of Nanchang-Ji’an-Ganzhou-Shaoguan-Guangzhou,and the western branch is around the Jianghan-Xiangzhong Basin,both of which intersect in Nanling.The eastern branch of the thin crustal zone indicates the potential location of the Pacific subduction slab breakoff,and the formation mechanism may be related to the interaction of deep-shallow processes,including the upwelling of mantle heat flow through the slab window and transtensional pre-existing faults.We developed a dynamic model that combines subduction-breakoff-rollback processes of the Paleo-Pacific Plate and accompanying deep fluid upwelling to explain the regional extension of the South China lithosphere,the formation mechanism of the thinnest crustal belt,and the distribution of granitic plutons.
基金supported by the Central Fundamental Research(Grant No.DZLXJK201504)
文摘The granitic dykes in the Badu Group, Zhejiang Province, South China provide important insights on tectonic setting and crustal evolution of the South China Block （SCB） and the Indochina Block during Triassic. Here we report LA-ICP-MS U-Pb data of granitic rocks from the Hucun and Kengkou which show early Triassic ages of 242 ± 2 and 232 ± 3 Ma, respectively, representing their timing of emplacement. The dyke rocks are enriched in K, AI, LREE, Rb, Th, U, and Pb, and are depleted in Nb, Ta, St, and Ti. The rocks are characterized by highly fractionated REE patterns with （La/Yb）N ratios of 28.46 -38.07 with strong negative Eu anomalies （Eu/Eu＊ = 0,65-0.73）. In situ Hf isotopic analyses of zircons from the Hucun granite yielded CHf（t） values of -13.9 to -6.4 and two-stage depleted mantle Hf model ages of 1.68-2.15 Ga, which indicate that the magma was formed by partial melting of the Paleo- proterozoic metasedimentary protoliths in the Cathaysia Block. The zircons from the Kengkou granite have eHf（t） values ranging from -40.7 to 31.5 and yield two-stage depleted mantle Hf model ages of 0.99 -2.49 Ga, indicating magma origin from a mixed source. The Hucun and Kengkou dykes, together with the Triassic A-type granites in SE China were probably generated during magmatism associated with crust-mantle decoupling along the convergent plate boundary between SCB and the Indochina Block.
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
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 time series NDVI distribution maps of the study area were calculated with AVHRR images acquired from May 1999 to April 2000 on the North-South transect of Eastern China. Based on the analysis of the characteristics and their contributions to NPP on the transect, the RS NPP distribution maps were created by zones and the quantitative models were established between NDVI maps and field measured NPP sample data collected from Central and South China for forest and cultivated land. Furthermore, the spatial distribution and quantitative result were obtained through an overlapping and fitting analysis between the NPP maps and DEM. The result shows that the NPP distribution features are not only distinguished on detail zonation of natural vegetation in vertical, latitudinal and longitudinal distribution but also reflected an obvious effect from the crop growing period of agricultural area. According to the results above, an opposite opinion was given that the NPP values for the forest and agricultural areas vary greatly in different regions, with the forest areas having a higher value than the agricultural areas in Southern China. In the Huang, Huai and Hai Plains, agricultural regions have higher NPP values than the surrounding low mountains. In Northeastern China, the NPP values form a gradient across the mid-to-high mountain forest zone to plains and low mountain areas. Further, for most of the agricultural areas, NPP values range between 25—35 t·hm2·a-1 and do not show significant areal differentiation.
基金National Climbing Programme"South China Sea Monsoon Experiment"National Key Programme for Developing Basic Sciences G1998040900
文摘Numerical experiments with a low resolution atmospheric general circulation model (AGCM) were conducted to investigate the influences of SST anomalies (SSTA) over the South China Sea- tropical eastern indian Ocean (SCS-TEIO) on the onset of the South China Sea summer Monsoon (SCSM).With positive SSTA over the SCS-TEIO,the anomalous cyclones appear over both sides of the equator at low layer,which weakens the Somali and Australian cross-equatorial SW flow. The anomalous anticyclone in the east of Phillips strengthens the subtropical high with its ridge southwestward shifted.The anomalous anticyclones over both sides of equator at high layer strengthen the South Asia high,thus weaken the SCSM and delay its onset.With negative SSTA over the SCS-ETIO,the anomalous anticyclones appear over both sides of the equator at low layer,which strengthen the Australian but weaken the Somali cross-equatorial SW flow.The anomalous cyclone in northeast of Phillips will weaken the subtropical high.The stronger monsoon meridional circulation over the tropical western Pacific will strengthen the cross-equatorial southerly flow,and the anomalous cyclones over both sides of equator at high layer will weaken the South Asia high,hence strengthen the SCSM and advance its onset.
基金National Natural Science Foundation of China No.30590381 No.31000211 National Basic Research Program of China No.2010CB833504
文摘From July 2008 to August 2008, 72 leaf samples from 22 species and 81 soil samples in the nine natural forest ecosystems were collected, from north to south along the North-South Transect of Eastern China （NSTEC）. Based on these samples, we studied the geographical distribution patterns of vegetable water use efficiency （WUE） and nitrogen use efficiency （NUE）, and analyzed their relationship with environmental factors. The vegetable WUE and NUE were calculated through the measurement of foliar δ 13C and C/N of predominant species, respectively. The results showed： （1） vegetable WUE, ranging from 2.13 to 28.67 mg C g-1 H2O, increased linearly from south to north in the representative forest ecosystems along the NSTEC, while vegetable NUE showed an opposite trend, increasing from north to south, ranging from 12.92 to 29.60 g C g-1 N. （2） Vegetable WUE and NUE were dominantly driven by climate and significantly affected by soil nutrient factors. Based on multiple stepwise regression analysis, mean annual temperature, soil phosphorus concentration, and soil nitrogen concentration were responding for 75.5% of the variations of WUE （p0.001）. While, mean annual precipitation and soil phosphorus concentration could explain 65.7% of the change in vegetable NUE （p0.001）. Moreover, vegetable WUE and NUE would also be seriously influenced by atmospheric nitrogen deposition in nitrogen saturated ecosystems. （3） There was a significant trade-off relationship between vegetable WUE and NUE in the typical forest ecosystems along the NSTEC （p0.001）, indicating a balanced strategy for vegetation in resource utilization in natural forest ecosystems along the NSTEC. This study suggests that global change would impact the resource use efficiency of forest ecosystems. However, vegetation could adapt to those changes by increasing the use efficiency of shortage resource while decreasing the relatively ample one. But extreme impacts, such as heavy nitrogen deposition, would break this trade-off mechanism and give a dramatic disturbance to the ecosystem biogeochemical cycle.
