Tephra layers in the western Philippine Sea,characterized by abundant volcanic glass shards,may provide crucial evidence on the eruption history of volcanoes and tectonic evolution of the western Pacific.A 220-ka sedi...Tephra layers in the western Philippine Sea,characterized by abundant volcanic glass shards,may provide crucial evidence on the eruption history of volcanoes and tectonic evolution of the western Pacific.A 220-ka sediment core from the Benham Rise in the western Philippine Sea offers new insights into the provenance of four intercalated tephra layers(T1–T4,in chronological order)containing either colorless or brown glass shards.Relative to primitive mantle,all glass shards are enriched in large-ion lithophile elements,such as Rb,Cs,and Pb,and depleted in high field-strength elements,such as Th,Nb,and Ta,indicating a subduction-related origin.The colorless glass shards are characterized by high SiO_(2)(>78%)and light rare earth element(LREE)contents as well as high La/Sm ratios(>9),low FeO and MgO contents(<1%),low Sr/Y(<15)and high Ba/Th ratios(>100),pointing to a rhyolitic composition and a medium-K calc-alkaline serial affinity.In contrast,the brown glass shards are characterized by lower SiO_(2)(<63%)and LREE contents,higher FeO,MgO,and CaO contents,lower La/Sm(<6)and Ba/Th(<75),and similar Sr/Y ratios(<15),indicating derivation from medium to high-K calc-alkaline andesite magma.Brown glass shards from layers T3(152 ka)and T4(172 ka)were correlated with volcanic deposits from the Taal and Laguna Caldera in the Maccolod Corridor,respectively,while the colorless glass shards from layers T1(36.5 ka)and T2(61.2 ka)were likely sourced from the Irosin Caldera in the Bicol Arc.Establishing the provenance of late Pleistocene tephra layers in the western Philippine Sea is helpful to complement a Philippine volcanic history and establish a regional tephrochronostratigraphy.展开更多
Early Cretaceous A-type granitic plutons are widely distributed in Shandong Peninsula,which are of great significance to understanding the regional tectonic evolution.Here we report geochemical characteristics,geochro...Early Cretaceous A-type granitic plutons are widely distributed in Shandong Peninsula,which are of great significance to understanding the regional tectonic evolution.Here we report geochemical characteristics,geochronological results,and zircon Hf-O isotope compositions of Wulian granites to reveal its origin and geological significance.Wulian granites share most characteristics of the A_(2)-type granite.Zircon U-Pb LA-ICPMS analysis for Wulian A-type granites yields average age of 116.6±2.1 Ma.Zircon O isotope values range from 4.20‰to 5.57‰,and these values are marginally identical to or slightly lower than those of mantle zircon(5.3‰±0.3‰).Zirconε_(Hf)(t)values(-26.1--23.5)indicate an enriched source.Integrated zircon Hf-O isotope compositions indicate that the source region of Wulian granites involves the components of ancient oceanic crust.Apatites from Wulian granites have the lower chlorine(0.06 wt.%-0.15 wt.%)and higher fluorine contents(2.11 wt.%-2.48 wt.%)compared with Haiyang pluton,together with their high(La/Gd)_(N),(La/Yd)_(N) and low(Gd/Yb)_(N) ratios and high oxygen state magma reflected from zircon,signifying that slab derived component was added into the overlying mantle region through fluid/melt.The geochemical characteristics of Wulian granites could be explained by the ridge(between the Izanagi and Pacific plates)subduction model,which began to influence the tectonic evolution of the Xuhuai region and Shandong Peninsula since~130±5 Ma.The following slab window between two plates plausibly explains regional extension,resulting in hot magma upwelling and the formation of the A-type granite belt.Integrating the Lower Yangtze River belt and Shandong Peninsula A-type granite proves the northward movement of the ridge between the Pacific Plate and Izanagi Plate.展开更多
The Hawaiian-Emperor seamount chain has shown two subparallel geographical and geochemical volcanic trends,Loa and Kea,since-5 Ma,for which numerous models have been proposed that usually involve a single mantle plume...The Hawaiian-Emperor seamount chain has shown two subparallel geographical and geochemical volcanic trends,Loa and Kea,since-5 Ma,for which numerous models have been proposed that usually involve a single mantle plume sampling different compositional sources of the deep or shallow mantle.However,both the dramatically increased eruption rate of the Hawaiian hotspot since-5 Ma and the nearly simultaneous southward bending of the Hawaiian chain remain unexplained.展开更多
The history of the Hawaiian hotspot is of enduring interest in studies of plate motion and mantle flow,and has been investigated by many researchers using the detailed history of the Hawaiian-Emperor Seamount chain.On...The history of the Hawaiian hotspot is of enduring interest in studies of plate motion and mantle flow,and has been investigated by many researchers using the detailed history of the Hawaiian-Emperor Seamount chain.One of the unexplained aspects of this history is the apparent offset of several Emperor seamounts from the Hawaii plume track.Here we show that the volcanic migration rates of the Emperor seamounts based on existing data are inconsistent with the drifting rate of the Pacific plate,and indicate northward and then southward “absolute movements”of the seamounts.Numerical modeling suggests that attraction and capture of the upper part of the plume by a moving spreading ridge led to variation in the location of the plume’s magmatic output at the surface.Flow of the plume material towards the ridge led to apparent southward movement of Meiji.Then,the upper part of the plume was carried northward until 65 Ma ago.After the ridge and the plume became sufficiently separated,magmatic output moved back to be centered over the plume stem.These changes are apparent in variations in the volume of seamounts along the plume track.Chemical and isotopic compositions of basalt from the Emperor Seamount chain changed from depleted(strong mid-ocean ridge affinity)in Meiji and Detroit to enriched(ocean island type),supporting declining influence from the ridge.Although its surface expression was modified by mantle flow and by plume-ridge interactions,the stem of the Hawaiian plume may have been essentially stationary during the Emperor period.展开更多
Following the popularity of digital video application,video copying and dissemination have become very easy;however,this makes video hacking and piracy a potential threat in video communication.Video watermarking tech...Following the popularity of digital video application,video copying and dissemination have become very easy;however,this makes video hacking and piracy a potential threat in video communication.Video watermarking technology can solve the problem of copyright protection,and thus,it has been extensively researched.The robustness of the video watermarking algorithm in the bitstream domain is poor,especially the anti-recompression ability,since the watermarked video may be compressed again before transmitting.Considering this,this paper proposes a video watermarking algorithm in the bitstream domain based on moving object detection.To increase the robustness of the watermarking scheme,the moving macroblocks that belong to the moving object in each P frame can be identified via the moving object detection algorithm.Then,watermark embedding in the moving macroblocks is performed using codeword substitution to ensure the consistency of the bitstream.Moving object detection and watermark embedding are independent and are both carried out in the bitstream domain by partially decoding the bitstream;this avoids the complete decoding and reconstruction of the video,making the method to be highly efficient.The simulation results confirm that the proposed method is robust against recompression and has little impact on the video visual quality and no influence on the bit rate.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.42076049,42376050)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB42000000)the Laoshan Laboratory(No.LSKJ202204201)。
文摘Tephra layers in the western Philippine Sea,characterized by abundant volcanic glass shards,may provide crucial evidence on the eruption history of volcanoes and tectonic evolution of the western Pacific.A 220-ka sediment core from the Benham Rise in the western Philippine Sea offers new insights into the provenance of four intercalated tephra layers(T1–T4,in chronological order)containing either colorless or brown glass shards.Relative to primitive mantle,all glass shards are enriched in large-ion lithophile elements,such as Rb,Cs,and Pb,and depleted in high field-strength elements,such as Th,Nb,and Ta,indicating a subduction-related origin.The colorless glass shards are characterized by high SiO_(2)(>78%)and light rare earth element(LREE)contents as well as high La/Sm ratios(>9),low FeO and MgO contents(<1%),low Sr/Y(<15)and high Ba/Th ratios(>100),pointing to a rhyolitic composition and a medium-K calc-alkaline serial affinity.In contrast,the brown glass shards are characterized by lower SiO_(2)(<63%)and LREE contents,higher FeO,MgO,and CaO contents,lower La/Sm(<6)and Ba/Th(<75),and similar Sr/Y ratios(<15),indicating derivation from medium to high-K calc-alkaline andesite magma.Brown glass shards from layers T3(152 ka)and T4(172 ka)were correlated with volcanic deposits from the Taal and Laguna Caldera in the Maccolod Corridor,respectively,while the colorless glass shards from layers T1(36.5 ka)and T2(61.2 ka)were likely sourced from the Irosin Caldera in the Bicol Arc.Establishing the provenance of late Pleistocene tephra layers in the western Philippine Sea is helpful to complement a Philippine volcanic history and establish a regional tephrochronostratigraphy.
基金supported by the National Natural Science Foundation of China(No.91958110)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB42020203)。
文摘Early Cretaceous A-type granitic plutons are widely distributed in Shandong Peninsula,which are of great significance to understanding the regional tectonic evolution.Here we report geochemical characteristics,geochronological results,and zircon Hf-O isotope compositions of Wulian granites to reveal its origin and geological significance.Wulian granites share most characteristics of the A_(2)-type granite.Zircon U-Pb LA-ICPMS analysis for Wulian A-type granites yields average age of 116.6±2.1 Ma.Zircon O isotope values range from 4.20‰to 5.57‰,and these values are marginally identical to or slightly lower than those of mantle zircon(5.3‰±0.3‰).Zirconε_(Hf)(t)values(-26.1--23.5)indicate an enriched source.Integrated zircon Hf-O isotope compositions indicate that the source region of Wulian granites involves the components of ancient oceanic crust.Apatites from Wulian granites have the lower chlorine(0.06 wt.%-0.15 wt.%)and higher fluorine contents(2.11 wt.%-2.48 wt.%)compared with Haiyang pluton,together with their high(La/Gd)_(N),(La/Yd)_(N) and low(Gd/Yb)_(N) ratios and high oxygen state magma reflected from zircon,signifying that slab derived component was added into the overlying mantle region through fluid/melt.The geochemical characteristics of Wulian granites could be explained by the ridge(between the Izanagi and Pacific plates)subduction model,which began to influence the tectonic evolution of the Xuhuai region and Shandong Peninsula since~130±5 Ma.The following slab window between two plates plausibly explains regional extension,resulting in hot magma upwelling and the formation of the A-type granite belt.Integrating the Lower Yangtze River belt and Shandong Peninsula A-type granite proves the northward movement of the ridge between the Pacific Plate and Izanagi Plate.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA22050103)the Marine S&T Fund of Shandong Province for Pilot National Laboratory for Marine Science and Technology(Qingdao)(2022QNLM050201)and the National Natural Science Foundation of China(92258303)to W.S.L.L.acknowledges NSF grant EAR1554554.
文摘The Hawaiian-Emperor seamount chain has shown two subparallel geographical and geochemical volcanic trends,Loa and Kea,since-5 Ma,for which numerous models have been proposed that usually involve a single mantle plume sampling different compositional sources of the deep or shallow mantle.However,both the dramatically increased eruption rate of the Hawaiian hotspot since-5 Ma and the nearly simultaneous southward bending of the Hawaiian chain remain unexplained.
基金supported by the National Key Research & Development Program of China (2016YFC0600408)the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (XDB18020000)the Programme National de Planétologie (PNP) of the Institut des Sciences de l’Univers (INSU) of the French National Centre for Scientific Research (CNRS),co-funded by the French Space Centre (CNES) (BFC 221950)。
文摘The history of the Hawaiian hotspot is of enduring interest in studies of plate motion and mantle flow,and has been investigated by many researchers using the detailed history of the Hawaiian-Emperor Seamount chain.One of the unexplained aspects of this history is the apparent offset of several Emperor seamounts from the Hawaii plume track.Here we show that the volcanic migration rates of the Emperor seamounts based on existing data are inconsistent with the drifting rate of the Pacific plate,and indicate northward and then southward “absolute movements”of the seamounts.Numerical modeling suggests that attraction and capture of the upper part of the plume by a moving spreading ridge led to variation in the location of the plume’s magmatic output at the surface.Flow of the plume material towards the ridge led to apparent southward movement of Meiji.Then,the upper part of the plume was carried northward until 65 Ma ago.After the ridge and the plume became sufficiently separated,magmatic output moved back to be centered over the plume stem.These changes are apparent in variations in the volume of seamounts along the plume track.Chemical and isotopic compositions of basalt from the Emperor Seamount chain changed from depleted(strong mid-ocean ridge affinity)in Meiji and Detroit to enriched(ocean island type),supporting declining influence from the ridge.Although its surface expression was modified by mantle flow and by plume-ridge interactions,the stem of the Hawaiian plume may have been essentially stationary during the Emperor period.
基金supported by the National Natural Science Foundation of China(No.61702563)。
文摘Following the popularity of digital video application,video copying and dissemination have become very easy;however,this makes video hacking and piracy a potential threat in video communication.Video watermarking technology can solve the problem of copyright protection,and thus,it has been extensively researched.The robustness of the video watermarking algorithm in the bitstream domain is poor,especially the anti-recompression ability,since the watermarked video may be compressed again before transmitting.Considering this,this paper proposes a video watermarking algorithm in the bitstream domain based on moving object detection.To increase the robustness of the watermarking scheme,the moving macroblocks that belong to the moving object in each P frame can be identified via the moving object detection algorithm.Then,watermark embedding in the moving macroblocks is performed using codeword substitution to ensure the consistency of the bitstream.Moving object detection and watermark embedding are independent and are both carried out in the bitstream domain by partially decoding the bitstream;this avoids the complete decoding and reconstruction of the video,making the method to be highly efficient.The simulation results confirm that the proposed method is robust against recompression and has little impact on the video visual quality and no influence on the bit rate.
