Oceanic plateaus are a significant type of large igneous provinces in the oceans,providing insights to regional tectonic events and mantle behavior.The three world's largest oceanic plateaus,the Ontong Java Platea...Oceanic plateaus are a significant type of large igneous provinces in the oceans,providing insights to regional tectonic events and mantle behavior.The three world's largest oceanic plateaus,the Ontong Java Plateau,the Kerguelen Plateau and the Shatsky Rise,are representatives in displaying extraordinary fluxes of magma from mantle to lithosphere.Detailed description incorporating transdisciplinary observations on marine geology,geophysics and geochemistry allow us to test the two lively-debated oceanic plateau formation hypotheses(mantle plume and plate boundary models).Predictions from either hypothesis merely obtain partial support.It is therefore unclear to differentiate one model from another one regarding the oceanic plateau formation.Careful comparisons of the three oceanic plateaus show many commonalities and even more differences in their formation and evolution.This diversity signifies one may not be typical of all.Notably,several key common features,i.e.,massive and rapid eruption and near-ridge formation setting,imply that the lithospheric volcanic emplacement of oceanic plateaus was controlled by seafloor spreading despite a mantle plume exists peripherally.If a coincidence of mantle plume and spreading ridge occurs,it may indicate a plume-ridge interaction.One possible mechanism is that spreading ridge is dragged by a plume and migrates to the location of the plume.Another possibility is that the asthenosphere is fed by a plume nearby and generates melting anomalies along the spreading ridge.展开更多
Redox-sensitive elements in sediments, such as manganese （Mn）, vanadium （V）, molybdenum （Mo）, and uranium （U）, are promising indicators of past redox conditions during sedimentation and early diagenesis. Howev...Redox-sensitive elements in sediments, such as manganese （Mn）, vanadium （V）, molybdenum （Mo）, and uranium （U）, are promising indicators of past redox conditions during sedimentation and early diagenesis. However, in the Ontong Java Plateau, west equatorial Pacific, there are sparse datasets of redox-sensitive elements in sediment cores. Here, we present a 250 ka record of redox sensitive elements from a 460 cm gravity core at site WP7 （3~56＇S, 156^.E, water depth 1 800 m）, which was recovered from the southwest Ontong Java Plateau during the 1993 cruise of R/V Science I of the Institute of Oceanology, Chinese Academy of Sciences （IOCAS）. Relative to the Post-Archean Australian Shale （PAAS）, authigenic Mn, cobalt （Co）, nickel （Ni）, Mo, V, U, and cadmium （Cd） were found at constantly low levels except when peaks occurred at several depth intervals. Manganese, Co, Ni, and Mo concentrations were elevated at 25-35 cm due to Mn redox cycling. The core was divided into three distinct sections, the top 0-25 cm being oxic, a suboxic section at 25-35 cm and from 35-460 cm which was anoxic. Differential authigenic enrichments of Co, Ni, Mo, V, U, and Cd at the same depth intervals were observed indicating that the enrichments happened during sedimentation or diagenesis and suffered no post settlement redox changes. Therefore, no significant changes in redox conditions during sedimentation must have happened. The water at depth on the Ontong Java Plateau during past 250 ka must have been well oxygenated, possibly resulted from the more or less continuous presence of oxygen-rich deep water like the modem Antarctic Intermediate Water （AAIW） and Antarctic Circumpolar Water （ACW）; while it＇s slightly less oxygenated in glacial intervals, possibly due to ventilation weakening and/or the surface productivity increase.展开更多
The eruption of large igneous provinces usually has major geodynamic in fluence sonoverriding plates.Seamount chains indicate that the drifting direction of the Pacific Plate changed by~80°in the Early Cretaceous...The eruption of large igneous provinces usually has major geodynamic in fluence sonoverriding plates.Seamount chains indicate that the drifting direction of the Pacific Plate changed by~80°in the Early Cretaceous when the Ontong Java Plateau formed.This,however,is not fully consistent with the magnetic anomalies.Here we show that there is an angle of~25°between the magnetic anomaly lines M_(0)and 34 of both the Japanese and the Hawaiian lineations,suggesting that the orientations of both spreading ridges changed by roughly the same angle towards the same direction.The configurations of the Shatsky Rise,the Papanin Ridge and the Osbourn Trough suggest that the eruption of the Ontong Java plume head uplifted the southeastern corner of the Pacific Plate,and pushed its east part northward by~700 km within 2 Ma.Meanwhile,the west part of the Pacific Plate was subducting southwestward underneath the eastern Asian Continent.These two forces together rotated the Pacific Plate anticlockwisely by ca 50°.Consequently,the drifting direction of the Pacific Plate also changed from southwestward to northwestward,which plausibly explains the ca 80°bending of the Shatsky Rise and the Papanin Ridge.The ridge between the Pacific and the Izanagi/Kula plates was pointed towards the~300°orientation,whereas the Pacific Plate was subducting towards the~250°orientation before~125 Ma,and towards~280°afterward.展开更多
基金supported by the National Key R&D Program of China(No.2018YFC0309800)the National Natural Science Foundation of China(Nos.91628301,U1606401,41606069,41776058,41890813)+3 种基金the Natural Science Foundation of Guangdong Province in China(No.2017A030313243)the Chinese Academy of Sciences(Nos.Y4SL021001,QYZDY-SSW-DQC005,133244KY SB20180029)the China Association of Marine Affairs(No.CAMAZD201714)the Asia-Pacific Economic Cooperation(No.12119016)
文摘Oceanic plateaus are a significant type of large igneous provinces in the oceans,providing insights to regional tectonic events and mantle behavior.The three world's largest oceanic plateaus,the Ontong Java Plateau,the Kerguelen Plateau and the Shatsky Rise,are representatives in displaying extraordinary fluxes of magma from mantle to lithosphere.Detailed description incorporating transdisciplinary observations on marine geology,geophysics and geochemistry allow us to test the two lively-debated oceanic plateau formation hypotheses(mantle plume and plate boundary models).Predictions from either hypothesis merely obtain partial support.It is therefore unclear to differentiate one model from another one regarding the oceanic plateau formation.Careful comparisons of the three oceanic plateaus show many commonalities and even more differences in their formation and evolution.This diversity signifies one may not be typical of all.Notably,several key common features,i.e.,massive and rapid eruption and near-ridge formation setting,imply that the lithospheric volcanic emplacement of oceanic plateaus was controlled by seafloor spreading despite a mantle plume exists peripherally.If a coincidence of mantle plume and spreading ridge occurs,it may indicate a plume-ridge interaction.One possible mechanism is that spreading ridge is dragged by a plume and migrates to the location of the plume.Another possibility is that the asthenosphere is fed by a plume nearby and generates melting anomalies along the spreading ridge.
基金Supported by the Pilot Project of the National Knowledge Innovation Program of the Chinese Academy of Sciences(No.KZCX2-YW-221)the National Basic Research Program of China(973 Program)(No.2007CB815903)+2 种基金the Pilot Project of the National Knowledge Innovation Program of Institute of Oceanology,Chinese Academy of Sciences(No.2007-10)the National Natural Science Foundation of China(No.40906038)the Open Foundation of the State Key Laboratory of Marine Geology(No.MG0903)
文摘Redox-sensitive elements in sediments, such as manganese （Mn）, vanadium （V）, molybdenum （Mo）, and uranium （U）, are promising indicators of past redox conditions during sedimentation and early diagenesis. However, in the Ontong Java Plateau, west equatorial Pacific, there are sparse datasets of redox-sensitive elements in sediment cores. Here, we present a 250 ka record of redox sensitive elements from a 460 cm gravity core at site WP7 （3~56＇S, 156^.E, water depth 1 800 m）, which was recovered from the southwest Ontong Java Plateau during the 1993 cruise of R/V Science I of the Institute of Oceanology, Chinese Academy of Sciences （IOCAS）. Relative to the Post-Archean Australian Shale （PAAS）, authigenic Mn, cobalt （Co）, nickel （Ni）, Mo, V, U, and cadmium （Cd） were found at constantly low levels except when peaks occurred at several depth intervals. Manganese, Co, Ni, and Mo concentrations were elevated at 25-35 cm due to Mn redox cycling. The core was divided into three distinct sections, the top 0-25 cm being oxic, a suboxic section at 25-35 cm and from 35-460 cm which was anoxic. Differential authigenic enrichments of Co, Ni, Mo, V, U, and Cd at the same depth intervals were observed indicating that the enrichments happened during sedimentation or diagenesis and suffered no post settlement redox changes. Therefore, no significant changes in redox conditions during sedimentation must have happened. The water at depth on the Ontong Java Plateau during past 250 ka must have been well oxygenated, possibly resulted from the more or less continuous presence of oxygen-rich deep water like the modem Antarctic Intermediate Water （AAIW） and Antarctic Circumpolar Water （ACW）; while it＇s slightly less oxygenated in glacial intervals, possibly due to ventilation weakening and/or the surface productivity increase.
基金supported by the National Key R&D Program of China(No.2016YFC0600408)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA22050103)+1 种基金the Taishan Scholar Program of Shandong Province(No.ts201712075)the Aoshan Talents Cultivation Program supported by Pilot National Laboratory of Marine Science and Technology(No.2017ASTCP-OS07)。
文摘The eruption of large igneous provinces usually has major geodynamic in fluence sonoverriding plates.Seamount chains indicate that the drifting direction of the Pacific Plate changed by~80°in the Early Cretaceous when the Ontong Java Plateau formed.This,however,is not fully consistent with the magnetic anomalies.Here we show that there is an angle of~25°between the magnetic anomaly lines M_(0)and 34 of both the Japanese and the Hawaiian lineations,suggesting that the orientations of both spreading ridges changed by roughly the same angle towards the same direction.The configurations of the Shatsky Rise,the Papanin Ridge and the Osbourn Trough suggest that the eruption of the Ontong Java plume head uplifted the southeastern corner of the Pacific Plate,and pushed its east part northward by~700 km within 2 Ma.Meanwhile,the west part of the Pacific Plate was subducting southwestward underneath the eastern Asian Continent.These two forces together rotated the Pacific Plate anticlockwisely by ca 50°.Consequently,the drifting direction of the Pacific Plate also changed from southwestward to northwestward,which plausibly explains the ca 80°bending of the Shatsky Rise and the Papanin Ridge.The ridge between the Pacific and the Izanagi/Kula plates was pointed towards the~300°orientation,whereas the Pacific Plate was subducting towards the~250°orientation before~125 Ma,and towards~280°afterward.
