针对复杂地质背景下的大陆架划界问题,提出了一种新的大陆坡脚点(foot point of the continental slope,FOS)确定方法。该方法基于水深平均梯度变化计算坡脚点所在位置,并结合相反证明以及凸包性、分段性、连续性原则进行优化。以莫桑...针对复杂地质背景下的大陆架划界问题,提出了一种新的大陆坡脚点(foot point of the continental slope,FOS)确定方法。该方法基于水深平均梯度变化计算坡脚点所在位置,并结合相反证明以及凸包性、分段性、连续性原则进行优化。以莫桑比克南部陆缘为研究区域,利用2021年实测的高精度多波束地形数据,应用该方法提取了大陆架划界最关键的依据——FOS,并与联合国大陆架界限委员会使用的Geocap软件提取的结果进行对比,确认了相同的FOS位置,证明该方法是准确有效的。展开更多
The Philippine Basin,surrounded by a series of oceanic trenches,is an independent deep ocean basin in the West Pacific Ocean.Its middle part is divided into three marginal sea sub-basins by the Kyushu-Palau and West M...The Philippine Basin,surrounded by a series of oceanic trenches,is an independent deep ocean basin in the West Pacific Ocean.Its middle part is divided into three marginal sea sub-basins by the Kyushu-Palau and West Mariana Ridges,namely,the West Philippine Basin,the Shikoku and Parece Vela Basins and the Mariana Trough.This paper,through the analysis of the geomorphologic features and gravity and magnetic characteristics of the basin and identification of striped magnetic anomalies,suggests that the entire Philippine Basin developed magnetic lineation of oceanic nature,and therefore,the entire basin is of the nature of oceanic crust.The basin has developed a series of special geomorphic units with different shapes.The KPR runs through the entire Philippine Basin.From the view of geomorphologic features,the KPR is a discontinuous seamount chain （chain-shaped seamounts） and subduction beneath the Japanese Island arc at the Nankai Trough which is the natural boundary between the basin and the Japanese Island arc.At the positions of 25 N,24 N,23 N and 18 N,obvious discontinuity is shown,which belongs to natural topographic discontinuity.Therefore,the KPR is topographically discontinuous.展开更多
Spreading rate is a primary factor of mantle melting and tectonic behavior of the global mid-ocean ridges. The spreading rate of the Gakkel ridge decreases gradually from west to east. However, the Gakkel ridge can be...Spreading rate is a primary factor of mantle melting and tectonic behavior of the global mid-ocean ridges. The spreading rate of the Gakkel ridge decreases gradually from west to east. However, the Gakkel ridge can be divided into four thick-and-thin zones with varying crustal thicknesses along ridge axis. This phenomenon indicates that mantle melting of the Gakkel ridge is not a simple function of spreading rate. Mantle temperature, water content, mantle composition, and other factors are important in crustal accretion processes. Based on gravity-derived crustal thickness and wet melting model, we estimate that the mantle potential temperatures of the four zones are 1 270, 1 220, 1 280, and 1 280℃ （assuming that mantle water content equals to global average value）, with corresponding mantle water contents of 210, 0, 340, and 280 mg/kg （assuming that mantle potential temperature is 1 260℃）, respectivly. The western thinned crust zone is best modeled with low mantle temperature, whereas the other zones are mainly controlled by the enhanced conduction caused by the slower spreading rate. Along the Gakkel ridge, the crustal thickness is consistent with rock samples types. Predominated serpentinized peridotite and basalt are found in the area with crustal thickness 〈1.5 km and 〉2.5 km, respectively. The rock samples are including from basalt to peridotite in the area with crustal thickness between 1.5 and 2.5 km. Based on this consistency, the traditional magmatic accretion zone accounted for only 44% and amagmatic accretion accounted for 29% of the Gakkel ridge. The amagmatic accretion is a significant characteristic of the ultra-slow spreading ridge.展开更多
Polymetalic sulfide is the main product of sea-floor hydrothermal venting, and has become an important sea-floor mineral resources for its rich in many kinds of precious metal elements. Since 2007, a number of investi...Polymetalic sulfide is the main product of sea-floor hydrothermal venting, and has become an important sea-floor mineral resources for its rich in many kinds of precious metal elements. Since 2007, a number of investigations have been carried out by the China Ocean Mineral Resources Research and Development Association（COMRA）cruises（CCCs） along the Southwest Indian Ridge（SWIR）. In 2011, the COMRA signed an exploration contract of sea-floor polymetallic sulfides of 10 000 km2 on the SWIR with the International Seabed Authority. Based on the multibeam data and shipborne gravity data obtained in 2010 by the R/V Dayang Yihao during the leg 6 of CCCs21, together with the global satellite surveys, the characteristics of gravity anomalies are analyzed in the Duanqiao hydrothermal field（37°39′S, 50°24′E）. The ＂subarea calibration＂ terrain-correcting method is employed to calculate the Bouguer gravity anomaly, and the ocean bottom seismometer（OBS） profile is used to constrain the two-dimensional gravity anomaly simulation. The absent Moho in a previous seismic model is also calculated.The results show that the crustal thickness varies between 3 and 10 km along the profile, and the maximum crustal thickness reaches up to 10 km in the Duanqiao hydrothermal field with an average of 7.5 km. It is by far the most thicker crust discovered along the SWIR. The calculated crust thickness at the Longqi hydrothermal field is approximately 3 km, 1 km less than that indicated by seismic models, possibly due to the outcome of an oceanic core complex（OCC）.展开更多
Marine geophysical survey by the Chinese National Antarctic Research Expedition （CHINARE） began with the first science expedition in 1984/1985, although only four cruises were performed in the vicinity of the Antar...Marine geophysical survey by the Chinese National Antarctic Research Expedition （CHINARE） began with the first science expedition in 1984/1985, although only four cruises were performed in the vicinity of the Antarctic Peninsula between then and 1991/1992. After a 20 year hiatus, Antarctic marine geophysical research was relaunched by the Chinese Polar Environmental Comprehensive Investigation and Assessment Programs （known simply as the Chinese Polar Program） in 2011/2012. Integrated geophysical surveys have been carried out annually since, in Prydz Bay and the Ross Sea. During the last 5 years, we have acquired about 5500 km of bathymetric, gravimetric, and magnetic lines; more than 1800 km of seismic reflection lines; and data from several heat flow and Ocean Bottom Seismometer （OBS） stations. This work has deepened understandings of geophysical features and their implications for geological tectonics and glacial history in Antarctica and its surrounding seas. Compiled Antarctic Bouguer and Airy isostatic gravity anomalies show different features of tectonics between the East Antarctic stability and West Antarctic activity. Calculated magnetic anomalies, heat flow anomalies and lithospheric anisotropy offshore of Prydz Bay may imply high heat capacity of mantle shielded by the continental shelf lithosphere, but high heat dissipation of mantle due to the Cretaceous breakup of Gondwana along the continent and ocean transition （COT）, where large sediment ridges would be brought about by the Oligocene ice sheet retreat and would enlarge free-air gravity anomalies. In the western Ross Sea, CHINARE seismic profiles indicate northern termination of the Terror Rift and deposition time of the grounding zone wedge in the northern JOIDES Basin.展开更多
To understand the rheology,structure,and tectonics of the lithosphere in the Mariana subduction zone and surrounding regions,we calculated the effective elastic thickness of the lithosphere(Te)in these areas using the...To understand the rheology,structure,and tectonics of the lithosphere in the Mariana subduction zone and surrounding regions,we calculated the effective elastic thickness of the lithosphere(Te)in these areas using the improved moving window admittance technique(MWAT)method.We find that smaller data grid spacing can better reflect Te variations in the subduction zone.The Te of the study region ranges from 0 to 47 km.The Te is reduced from 40 km on the seaward side of the outer-rise region to 1-2 km along the trench axis.The lithospheric breaking distance from the trench axis ranges from 0 to 250 km.We suggest that the intermediate Te values in seamounts and high Te values on the seaward side of the outer-rise region respectively reflect the‘fossil’rheological state and current lithospheric strength of the Pacific plate.The faulting induced by the downward bending of subducting plate not only ruptures the lithosphere but also contributes to the mantle serpentinization,significantly reducing the lithospheric strength.The largest breaking distance of the Ogasawara Plateau may be due to the increase in the mass load of the subducting plate in the Ogasawara Plateau and the significant horizontal bending force in the plate caused by the resistance of seamounts to subduction.Furthermore,a good positive correlation exists between the breaking distance and subduction dip angle along the trench axis.We suggest that the subducting plate with a larger breaking distance is likely to form a larger subduction angle.展开更多
文摘针对复杂地质背景下的大陆架划界问题,提出了一种新的大陆坡脚点(foot point of the continental slope,FOS)确定方法。该方法基于水深平均梯度变化计算坡脚点所在位置,并结合相反证明以及凸包性、分段性、连续性原则进行优化。以莫桑比克南部陆缘为研究区域,利用2021年实测的高精度多波束地形数据,应用该方法提取了大陆架划界最关键的依据——FOS,并与联合国大陆架界限委员会使用的Geocap软件提取的结果进行对比,确认了相同的FOS位置,证明该方法是准确有效的。
基金973 Jointly funded by Cenozoic Sequence Stratigraphy and Sedimentary Evolution of Continental Margin of the East China Sea under contract No.2007CB41170301Research on Sedimentary Features and Sedimentary Filling of the Lower Slope Basin in the Deep Water Area of the Middle and Northern South China Sea of the Special Fund Program of Basic Scientific Research Expenses under contract No.JG1007Supporting Technologies for Delimitation of Continental Shelves and Exclusive Economic Zones under contract Nos 200805078,201205037 and 201205003
文摘The Philippine Basin,surrounded by a series of oceanic trenches,is an independent deep ocean basin in the West Pacific Ocean.Its middle part is divided into three marginal sea sub-basins by the Kyushu-Palau and West Mariana Ridges,namely,the West Philippine Basin,the Shikoku and Parece Vela Basins and the Mariana Trough.This paper,through the analysis of the geomorphologic features and gravity and magnetic characteristics of the basin and identification of striped magnetic anomalies,suggests that the entire Philippine Basin developed magnetic lineation of oceanic nature,and therefore,the entire basin is of the nature of oceanic crust.The basin has developed a series of special geomorphic units with different shapes.The KPR runs through the entire Philippine Basin.From the view of geomorphologic features,the KPR is a discontinuous seamount chain （chain-shaped seamounts） and subduction beneath the Japanese Island arc at the Nankai Trough which is the natural boundary between the basin and the Japanese Island arc.At the positions of 25 N,24 N,23 N and 18 N,obvious discontinuity is shown,which belongs to natural topographic discontinuity.Therefore,the KPR is topographically discontinuous.
基金Chinese Polar Environment Comprehensive Investigation and Assessment Programmes under contract Nos CHINARE2013-03-03 and 2013-04-03the National Natural Science Foundation of China under contract No.41106049
文摘Spreading rate is a primary factor of mantle melting and tectonic behavior of the global mid-ocean ridges. The spreading rate of the Gakkel ridge decreases gradually from west to east. However, the Gakkel ridge can be divided into four thick-and-thin zones with varying crustal thicknesses along ridge axis. This phenomenon indicates that mantle melting of the Gakkel ridge is not a simple function of spreading rate. Mantle temperature, water content, mantle composition, and other factors are important in crustal accretion processes. Based on gravity-derived crustal thickness and wet melting model, we estimate that the mantle potential temperatures of the four zones are 1 270, 1 220, 1 280, and 1 280℃ （assuming that mantle water content equals to global average value）, with corresponding mantle water contents of 210, 0, 340, and 280 mg/kg （assuming that mantle potential temperature is 1 260℃）, respectivly. The western thinned crust zone is best modeled with low mantle temperature, whereas the other zones are mainly controlled by the enhanced conduction caused by the slower spreading rate. Along the Gakkel ridge, the crustal thickness is consistent with rock samples types. Predominated serpentinized peridotite and basalt are found in the area with crustal thickness 〈1.5 km and 〉2.5 km, respectively. The rock samples are including from basalt to peridotite in the area with crustal thickness between 1.5 and 2.5 km. Based on this consistency, the traditional magmatic accretion zone accounted for only 44% and amagmatic accretion accounted for 29% of the Gakkel ridge. The amagmatic accretion is a significant characteristic of the ultra-slow spreading ridge.
基金The National Basic Research Program(973 Program)of China under contract No.2012CB417305the China Ocean Mineral Resources Research and Development Association Twelfth Five-Year Major Program under contract Nos DY125-11-R-01 and DY125-11-R-05+2 种基金the International Cooperative Study on Hydrothermal System at Ultraslow Spreading SWIRthe Natural Science Foundation of Zhejiang Province of China under contract No.LY12D06006the Scientific Research Fund of Second Institute of Oceanography,State Oceanic Administration under contract No.JG1203
文摘Polymetalic sulfide is the main product of sea-floor hydrothermal venting, and has become an important sea-floor mineral resources for its rich in many kinds of precious metal elements. Since 2007, a number of investigations have been carried out by the China Ocean Mineral Resources Research and Development Association（COMRA）cruises（CCCs） along the Southwest Indian Ridge（SWIR）. In 2011, the COMRA signed an exploration contract of sea-floor polymetallic sulfides of 10 000 km2 on the SWIR with the International Seabed Authority. Based on the multibeam data and shipborne gravity data obtained in 2010 by the R/V Dayang Yihao during the leg 6 of CCCs21, together with the global satellite surveys, the characteristics of gravity anomalies are analyzed in the Duanqiao hydrothermal field（37°39′S, 50°24′E）. The ＂subarea calibration＂ terrain-correcting method is employed to calculate the Bouguer gravity anomaly, and the ocean bottom seismometer（OBS） profile is used to constrain the two-dimensional gravity anomaly simulation. The absent Moho in a previous seismic model is also calculated.The results show that the crustal thickness varies between 3 and 10 km along the profile, and the maximum crustal thickness reaches up to 10 km in the Duanqiao hydrothermal field with an average of 7.5 km. It is by far the most thicker crust discovered along the SWIR. The calculated crust thickness at the Longqi hydrothermal field is approximately 3 km, 1 km less than that indicated by seismic models, possibly due to the outcome of an oceanic core complex（OCC）.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 41576069, 41306201, 41776189, 41706212 and 41706215)the Chinese Polar Environment Comprehensive Investigation & Assessment Programs (Grant Nos. CHINARE2017-01-03 and CHINARE2017-04-01)the Special Foundation of the Second Institute of Oceanography, SOA (Grant No. 14260-10)
文摘Marine geophysical survey by the Chinese National Antarctic Research Expedition （CHINARE） began with the first science expedition in 1984/1985, although only four cruises were performed in the vicinity of the Antarctic Peninsula between then and 1991/1992. After a 20 year hiatus, Antarctic marine geophysical research was relaunched by the Chinese Polar Environmental Comprehensive Investigation and Assessment Programs （known simply as the Chinese Polar Program） in 2011/2012. Integrated geophysical surveys have been carried out annually since, in Prydz Bay and the Ross Sea. During the last 5 years, we have acquired about 5500 km of bathymetric, gravimetric, and magnetic lines; more than 1800 km of seismic reflection lines; and data from several heat flow and Ocean Bottom Seismometer （OBS） stations. This work has deepened understandings of geophysical features and their implications for geological tectonics and glacial history in Antarctica and its surrounding seas. Compiled Antarctic Bouguer and Airy isostatic gravity anomalies show different features of tectonics between the East Antarctic stability and West Antarctic activity. Calculated magnetic anomalies, heat flow anomalies and lithospheric anisotropy offshore of Prydz Bay may imply high heat capacity of mantle shielded by the continental shelf lithosphere, but high heat dissipation of mantle due to the Cretaceous breakup of Gondwana along the continent and ocean transition （COT）, where large sediment ridges would be brought about by the Oligocene ice sheet retreat and would enlarge free-air gravity anomalies. In the western Ross Sea, CHINARE seismic profiles indicate northern termination of the Terror Rift and deposition time of the grounding zone wedge in the northern JOIDES Basin.
基金This research was supported by the National Natural Science Foundation of China(Nos.41676039 and 4207061006)the Shandong Young Teacher Growth Program.
文摘To understand the rheology,structure,and tectonics of the lithosphere in the Mariana subduction zone and surrounding regions,we calculated the effective elastic thickness of the lithosphere(Te)in these areas using the improved moving window admittance technique(MWAT)method.We find that smaller data grid spacing can better reflect Te variations in the subduction zone.The Te of the study region ranges from 0 to 47 km.The Te is reduced from 40 km on the seaward side of the outer-rise region to 1-2 km along the trench axis.The lithospheric breaking distance from the trench axis ranges from 0 to 250 km.We suggest that the intermediate Te values in seamounts and high Te values on the seaward side of the outer-rise region respectively reflect the‘fossil’rheological state and current lithospheric strength of the Pacific plate.The faulting induced by the downward bending of subducting plate not only ruptures the lithosphere but also contributes to the mantle serpentinization,significantly reducing the lithospheric strength.The largest breaking distance of the Ogasawara Plateau may be due to the increase in the mass load of the subducting plate in the Ogasawara Plateau and the significant horizontal bending force in the plate caused by the resistance of seamounts to subduction.Furthermore,a good positive correlation exists between the breaking distance and subduction dip angle along the trench axis.We suggest that the subducting plate with a larger breaking distance is likely to form a larger subduction angle.
