Based on the published data of structure geology,geochronology,petrology and isotope geochemistry,the authors of this paper have conducted studies on the tectonic evolution history of Japan arc system and Kyushu-Palau...Based on the published data of structure geology,geochronology,petrology and isotope geochemistry,the authors of this paper have conducted studies on the tectonic evolution history of Japan arc system and Kyushu-Palau ridge(KPR) . The studies show that the initial Japan arc system was resulted from the subduction of ancient Pacific plate beneath Eurasian Plate in Permian. It was part of an Andean-type continental volcanic arc which occurred in the offshore in the east of Asian during late Mesozoic era. The formation of tertiary back-arc basin(Japan Sea) resulted in the fundamental tectonic framework of the present arc system. Since Quaternary the system has been lying at E-W compression tectonic setting due to the eastward subduction of Amur Plate. It is expected that Japan arc system will be juxtaposed with Asian continent,which is similar to the present Taiwan arc system. The origin of Philippine Sea Plate(PSP) is still in debate. Some studies argued that it is a trapped oceanic crust segment,while the others insisted that it is a back-arc basin accompanied with ancient IBM arc. However,it is all agreed that the tectonic evolution of PSP started since 50 Ma,i.e.,PSP has drifted from the site around equator at 50 Ma to the present site,and the subduction of PSP along Nankai trough-Ryukyu Trench beneath the Japan arc system during 6–2 Ma led to the formation of the present Ryukyu arc system. Of the PSP,the KPR has been found with the oldest rocks formed at 38 Ma. Combining with its geochemical characteristics of oceanic arc tholeiite,it is suggested that KPR is an intraoceanic volcanic arc,more specifically,a relic arc(i.e.,rear arc of the ancient IBM) after rifting of ancient IBM. In addition,Amami-Daito province is of arc tectonic affinity,but has been affected by mantle plume. Therefore,based on their respective tectonic evolution history and geochemical characteristics of rock samples,it is inferred that there is no genetic relationship between Japan arc system and KPR. It is noted that rocks reflecting continental crust basement feature have been collected on the northern tip of KPR,which may be related to the process of KPR accreting on Japan arc,but the arc-continent accretion process are still at initial stage of modern continental crust accretion model. However,due to the scarcity of data of the northern tip of KPR,crustal structure of this location and its adjacent Nankai trough need to be further constrained by geophysical studies in the future.展开更多
A P-wave tomographic traveltime inversion was applied to obtain a new model of seismic velocity anomalies beneath the New Guinea-Solomon arc system(PN-SL).The P-wave traveltime data,obtained from the revised Internati...A P-wave tomographic traveltime inversion was applied to obtain a new model of seismic velocity anomalies beneath the New Guinea-Solomon arc system(PN-SL).The P-wave traveltime data,obtained from the revised International Seismological Center catalog,were recorded by 82 seismic stations in the PN-SL.Under the constraints of the epicenter distance,magnitude,and the number of stations recorded,15009 effective P-wave traveltime data were selected from 2011 teleseismic events.The obtained model showed that the Solomon Sea Plate subducted beneath the New Britain Island along the New Britain Trench at an angle of>70°and that the slab can be traced down to a depth of approximately 800 km.Conversely,we cannot observe a high-velocity anomaly exhibited by the subducted Solomon Sea Plate in the deep mantle at the Trobriand Trench,and the slab stopped at a depth of<200 km.The double subduction of the Solomon Sea Plate strongly modified the subduction patterns of the early subducted Pacific and Australian plates in the mantle along the West Melanesian Trench and the Pocklington Trough,respectively.In addition,the subducted Solomon Sea Plate induced the melting of the upper mantle to form a low-velocity anomaly,which provided the deep dynamic source for the expansion of the Bismarck Sea.Based on the joint consideration of the tomography results and a petrological analysis,the low-velocity anomalies beneath the Solomon Sea and Woodlark Basin are closely related to the early subduction of the Pacific and Australian Plates,respectively.展开更多
Proterozoic rocks in the northeastern Jiangxi-southern Anhui may fall into three rock associations whichbelong to different but interrelated tectono-palaeogeographic units. The field geological and petrochemicalcharac...Proterozoic rocks in the northeastern Jiangxi-southern Anhui may fall into three rock associations whichbelong to different but interrelated tectono-palaeogeographic units. The field geological and petrochemicalcharacteristics of the northeastern Jiangxi-western Zhejiang volcanic zone indicate that it was once an islandarc zone. An analysis of the sedimentary characteristics of Proterozoic turbidites lying north of the zone has re-vealed the history of development of a back-arc basin. According to the type of the Proterozoic rock formationsouth of the zone, it may be deduced that the formation might represent the fore-arc and trench areas. Bymeans of various tectono-palaeogeographic analyses, the relation between the island arc zone and the back-arcbasin is inferred and the Late Proterozoic tectono-palaeogeographic development is discussed by using themodel of the trench-arc-basin system.展开更多
The late Archean(~3.0-2.5 Ga)was a key period of continental growth globally,which is widely considered to reflect the onset of vigorous plate tectonic activity,although related continental growth modes remain content...The late Archean(~3.0-2.5 Ga)was a key period of continental growth globally,which is widely considered to reflect the onset of vigorous plate tectonic activity,although related continental growth modes remain contentious.Here we investigate a suite of late Neoarchean metavolcanic rocks from the southwest Qixia area of the Jiaobei terrane in the North China Craton.The rocks in this suite include amphibolites,clinopyroxene amphibolites,and hornblende plagioclase gneisses.We present zircon U-Pb isotopic data which indicate that the protoliths of these rocks formed during~2549-2511 Ma.The(clinopyroxene)amphibolites correspond to meta-basaltic rocks,with some containing high modal content of titanite.These rocks show moderate to high FeO_(T)(8.96-13.62 wt.%)and TiO_(2)(0.59-1.59 wt.%),flat to less fractionated REE patterns,and mildly negative Th,Nb,and Ta anomalies,resembling those of Fe-tholeiites.In addition,they display positive zirconε_(Hf)(t)values(+2.6 to+8.7),and are devoid of crustal contamination or fractional crystallization.Combined with the low Nb/Yb(mostly<1.60)and(Hf/Sm)_N(mostly<0.95),low to moderate Th/Yb(0.08-0.54),and low V/Sc(5.53-9.19)ratios,these basaltic rocks are interpreted to have been derived from a relatively reduced and depleted mantle source that was mildly metasomatized by hydrous fluids.The hornblende plagioclase gneisses are meta-andesitic rocks,and occur interlayered with the basaltic rocks.They are transitional between tholeiitic and calc-alkaline rock series,and show fractionated REE patterns with evidently negative Th,Nb,and Ta anomalies.The depleted zirconε_(Hf)(t)values(+2.4 to+8.4)and quantitative chemical modeling suggest that the andesitic rocks were most likely generated by injection and mixing of juvenile felsic magmas with the tholeiitic basaltic magmas.In general,the chemical features and genesis of late Neoarchean meta-basaltic rocks in our study area resemble those of Mariana back-arc basin basalts.Combined with regional geological data,it is proposed that the Jiaobei terrane witnessed late Neoarchean crustal growth under a paired continental arc-back arc setting.On a regional context,we propose two distinct geodynamic mode of late Neoarchean continental growth across North China Craton(particularly the Eastern Block),i.e.,(1)arc-continent accretion along northwestern part of the Eastern Block;and(2)paired continental arc-back arc system surrounding the~3.8-2.7 Ga continental nuclei to the southeast.展开更多
The southern São Francisco Paleocontinent(SFP)comprises Archean nuclei and Paleoproterozoic complexes encompassing magmatic arcs juxtaposed during a Rhyacian to Orosirian orogenic event.The Juiz de Fora Complex(J...The southern São Francisco Paleocontinent(SFP)comprises Archean nuclei and Paleoproterozoic complexes encompassing magmatic arcs juxtaposed during a Rhyacian to Orosirian orogenic event.The Juiz de Fora Complex(JFC)represents an imbricated thrust system that comprises orthogranulites with a wide compositional range formed in an intra-oceanic setting during the Siderian to the Orosirian and later accreted to the southeastern margin of the SFP.Here we report new petrological,geochemical,whole-rock Nd and Sr data,as well as zircon U–Pb ages from felsic and mafic orthogranulites from the JFC.The new data is combined with a regional compilation that enables an evaluation of the interaction between magmatism and orogenetic episodes in the context of the consolidation of São Francisco Paleocontinent during the Rhyacian–Orosirian.Pre collisional Island Arc tholeiites(IAT),Tonalites-Tron dhjemites-Granodiorites(TTGs)and sanukitoid magmatism occurred from 2200 Ma to 2085 Ma.This was followed by post-collisional magmatism,which is represented by hybrid granitoids coeval with the emplacement of E-MORB basic rocks.Crustal signatures for the Rhyacian to Orosirian evolution are highlighted by the dominance of negativeεNd(t)associated with Meso-to Neoarchean Nd TDMmodel ages as well as inherited zircon grains from the hybrid granitoids.The JFC is extensively highlighted in the literature as a primitive intra-oceanic arc,but here we propose the reworking or recycling of ancient crustal segments within the mature arc stage of the JFC,suggesting a Mesoarchean crustal source involved in the JFC evolution.展开更多
肯倍对焊接程序、焊工资质以及焊接设备实行的有效管理能够带来良好的焊接生产表现,实现EBIT增长,提高成本竞争力并缩短生产前置时间。肯倍推出的Kemppi ARC System 3是一款全新的模块化软件解决方案,能够更好地进行焊接管理。客户...肯倍对焊接程序、焊工资质以及焊接设备实行的有效管理能够带来良好的焊接生产表现,实现EBIT增长,提高成本竞争力并缩短生产前置时间。肯倍推出的Kemppi ARC System 3是一款全新的模块化软件解决方案,能够更好地进行焊接管理。客户可以在度身定制的工具箱中选择模块,用于质量、项目管理或生产效率等生产流程任何部分的开发。展开更多
The bidirectional subduction system,island arc magmatic activities,and thermal structure of the forearc basin in the Molucca Sea are taken into consideration in this study.The active volcanic arcs on both sides of the...The bidirectional subduction system,island arc magmatic activities,and thermal structure of the forearc basin in the Molucca Sea are taken into consideration in this study.The active volcanic arcs on both sides of the bidirectional subduction zone in the Molucca Sea are undergoing arc-arc collisions.We applied a finite element thermal simulation method to reconstruct the thermal evolution history of the Molucca Sea Plate based on geophysical data.Then,we analyzed the thermodynamic characteristics of island arc volcanism on both sides of the bidirectional subduction zone.The results showed that at 10Myr,the oceanic ridge of the Molucca Sea Plate was asymmetrically biased to the west,causing this bidirectional subduction to be deeper in the west than in the east.Furthermore,the oceanic ridge subducted under the Sangihe arc at 5.5Myr,causing intermittent cessation of volcanic activities.Due to the convergence of bidirectional subduction,the geothermal gradient in the top 3km depth of the forearc area between the Sangihe and Halmahera arcs decreased from about 60℃km^(−1) at 4Myr to about 38℃km^(−1) today.Finally,within the 45–100 km depth range of the sliding surface of the subduction,anomalously high-temperature zones formed due to shear friction during the bidirectional subduction.展开更多
The initial shape of the secondary arc considerably influences its subsequent shape.To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence,theoretical and experi...The initial shape of the secondary arc considerably influences its subsequent shape.To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence,theoretical and experimental analysis of the evolution process of the short-circuit arc to the secondary arc is critical.In this study,an improved charge simulation method was used to develop the internal-space electric-field model of the short-circuit arc.The intensity of the electric field was used as an independent variable to describe the initial shape of the secondary arc.A secondary arc evolution model was developed based on this model.Moreover,the accuracy of the model was evaluated by comparison with physical experimental results.When the secondary arc current increased,the arcing time and dispersion increased.There is an overall trend of increasing arc length with increasing arcing time.Nevertheless,there is a reduction in arc length during arc ignition due to short circuits between the arc columns.Furthermore,the arcing time decreased in the range of 0°-90°as the angle between the wind direction and the x-axis increased.This work investigated the method by which short-circuit arcs evolve into secondary arcs.The results can be used to develop the secondary arc evolution model and to provide both a technical and theoretical basis for secondary arc suppression.展开更多
基金The China Ocean Mineral Resources R & D Association (COMRA),The Basic Research Project of the Ministryof Science and Technology under contract No. 2008 FY220300the National Natural Science Foundation of China undercontract No. 40609034
文摘Based on the published data of structure geology,geochronology,petrology and isotope geochemistry,the authors of this paper have conducted studies on the tectonic evolution history of Japan arc system and Kyushu-Palau ridge(KPR) . The studies show that the initial Japan arc system was resulted from the subduction of ancient Pacific plate beneath Eurasian Plate in Permian. It was part of an Andean-type continental volcanic arc which occurred in the offshore in the east of Asian during late Mesozoic era. The formation of tertiary back-arc basin(Japan Sea) resulted in the fundamental tectonic framework of the present arc system. Since Quaternary the system has been lying at E-W compression tectonic setting due to the eastward subduction of Amur Plate. It is expected that Japan arc system will be juxtaposed with Asian continent,which is similar to the present Taiwan arc system. The origin of Philippine Sea Plate(PSP) is still in debate. Some studies argued that it is a trapped oceanic crust segment,while the others insisted that it is a back-arc basin accompanied with ancient IBM arc. However,it is all agreed that the tectonic evolution of PSP started since 50 Ma,i.e.,PSP has drifted from the site around equator at 50 Ma to the present site,and the subduction of PSP along Nankai trough-Ryukyu Trench beneath the Japan arc system during 6–2 Ma led to the formation of the present Ryukyu arc system. Of the PSP,the KPR has been found with the oldest rocks formed at 38 Ma. Combining with its geochemical characteristics of oceanic arc tholeiite,it is suggested that KPR is an intraoceanic volcanic arc,more specifically,a relic arc(i.e.,rear arc of the ancient IBM) after rifting of ancient IBM. In addition,Amami-Daito province is of arc tectonic affinity,but has been affected by mantle plume. Therefore,based on their respective tectonic evolution history and geochemical characteristics of rock samples,it is inferred that there is no genetic relationship between Japan arc system and KPR. It is noted that rocks reflecting continental crust basement feature have been collected on the northern tip of KPR,which may be related to the process of KPR accreting on Japan arc,but the arc-continent accretion process are still at initial stage of modern continental crust accretion model. However,due to the scarcity of data of the northern tip of KPR,crustal structure of this location and its adjacent Nankai trough need to be further constrained by geophysical studies in the future.
基金the National Natural Science Foundation of China(Nos.91858215 and 41906048)the Fundamental Research Funds for the Central Universities(No.201964015)Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology(No.MMRZZ201801)。
文摘A P-wave tomographic traveltime inversion was applied to obtain a new model of seismic velocity anomalies beneath the New Guinea-Solomon arc system(PN-SL).The P-wave traveltime data,obtained from the revised International Seismological Center catalog,were recorded by 82 seismic stations in the PN-SL.Under the constraints of the epicenter distance,magnitude,and the number of stations recorded,15009 effective P-wave traveltime data were selected from 2011 teleseismic events.The obtained model showed that the Solomon Sea Plate subducted beneath the New Britain Island along the New Britain Trench at an angle of>70°and that the slab can be traced down to a depth of approximately 800 km.Conversely,we cannot observe a high-velocity anomaly exhibited by the subducted Solomon Sea Plate in the deep mantle at the Trobriand Trench,and the slab stopped at a depth of<200 km.The double subduction of the Solomon Sea Plate strongly modified the subduction patterns of the early subducted Pacific and Australian plates in the mantle along the West Melanesian Trench and the Pocklington Trough,respectively.In addition,the subducted Solomon Sea Plate induced the melting of the upper mantle to form a low-velocity anomaly,which provided the deep dynamic source for the expansion of the Bismarck Sea.Based on the joint consideration of the tomography results and a petrological analysis,the low-velocity anomalies beneath the Solomon Sea and Woodlark Basin are closely related to the early subduction of the Pacific and Australian Plates,respectively.
文摘Proterozoic rocks in the northeastern Jiangxi-southern Anhui may fall into three rock associations whichbelong to different but interrelated tectono-palaeogeographic units. The field geological and petrochemicalcharacteristics of the northeastern Jiangxi-western Zhejiang volcanic zone indicate that it was once an islandarc zone. An analysis of the sedimentary characteristics of Proterozoic turbidites lying north of the zone has re-vealed the history of development of a back-arc basin. According to the type of the Proterozoic rock formationsouth of the zone, it may be deduced that the formation might represent the fore-arc and trench areas. Bymeans of various tectono-palaeogeographic analyses, the relation between the island arc zone and the back-arcbasin is inferred and the Late Proterozoic tectono-palaeogeographic development is discussed by using themodel of the trench-arc-basin system.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.41530207 and 41872196)Central University Basic Scientific Research Business Expenses of China University of Geosciences(Beijing)(Grant Nos.2-9-2019-055 and 2-9-2016-006)support by the undergraduate innovation and entrepreneurship program(X201911415003)。
文摘The late Archean(~3.0-2.5 Ga)was a key period of continental growth globally,which is widely considered to reflect the onset of vigorous plate tectonic activity,although related continental growth modes remain contentious.Here we investigate a suite of late Neoarchean metavolcanic rocks from the southwest Qixia area of the Jiaobei terrane in the North China Craton.The rocks in this suite include amphibolites,clinopyroxene amphibolites,and hornblende plagioclase gneisses.We present zircon U-Pb isotopic data which indicate that the protoliths of these rocks formed during~2549-2511 Ma.The(clinopyroxene)amphibolites correspond to meta-basaltic rocks,with some containing high modal content of titanite.These rocks show moderate to high FeO_(T)(8.96-13.62 wt.%)and TiO_(2)(0.59-1.59 wt.%),flat to less fractionated REE patterns,and mildly negative Th,Nb,and Ta anomalies,resembling those of Fe-tholeiites.In addition,they display positive zirconε_(Hf)(t)values(+2.6 to+8.7),and are devoid of crustal contamination or fractional crystallization.Combined with the low Nb/Yb(mostly<1.60)and(Hf/Sm)_N(mostly<0.95),low to moderate Th/Yb(0.08-0.54),and low V/Sc(5.53-9.19)ratios,these basaltic rocks are interpreted to have been derived from a relatively reduced and depleted mantle source that was mildly metasomatized by hydrous fluids.The hornblende plagioclase gneisses are meta-andesitic rocks,and occur interlayered with the basaltic rocks.They are transitional between tholeiitic and calc-alkaline rock series,and show fractionated REE patterns with evidently negative Th,Nb,and Ta anomalies.The depleted zirconε_(Hf)(t)values(+2.4 to+8.4)and quantitative chemical modeling suggest that the andesitic rocks were most likely generated by injection and mixing of juvenile felsic magmas with the tholeiitic basaltic magmas.In general,the chemical features and genesis of late Neoarchean meta-basaltic rocks in our study area resemble those of Mariana back-arc basin basalts.Combined with regional geological data,it is proposed that the Jiaobei terrane witnessed late Neoarchean crustal growth under a paired continental arc-back arc setting.On a regional context,we propose two distinct geodynamic mode of late Neoarchean continental growth across North China Craton(particularly the Eastern Block),i.e.,(1)arc-continent accretion along northwestern part of the Eastern Block;and(2)paired continental arc-back arc system surrounding the~3.8-2.7 Ga continental nuclei to the southeast.
基金the Rio de Janeiro State University and the Faculty of Geology(FGEL)for all the support from the LGPA and LAGIR labsFAPERJ,CNPq and CAPES,and joint projects with CPRM and Petrobras,are thanked for the financial support。
文摘The southern São Francisco Paleocontinent(SFP)comprises Archean nuclei and Paleoproterozoic complexes encompassing magmatic arcs juxtaposed during a Rhyacian to Orosirian orogenic event.The Juiz de Fora Complex(JFC)represents an imbricated thrust system that comprises orthogranulites with a wide compositional range formed in an intra-oceanic setting during the Siderian to the Orosirian and later accreted to the southeastern margin of the SFP.Here we report new petrological,geochemical,whole-rock Nd and Sr data,as well as zircon U–Pb ages from felsic and mafic orthogranulites from the JFC.The new data is combined with a regional compilation that enables an evaluation of the interaction between magmatism and orogenetic episodes in the context of the consolidation of São Francisco Paleocontinent during the Rhyacian–Orosirian.Pre collisional Island Arc tholeiites(IAT),Tonalites-Tron dhjemites-Granodiorites(TTGs)and sanukitoid magmatism occurred from 2200 Ma to 2085 Ma.This was followed by post-collisional magmatism,which is represented by hybrid granitoids coeval with the emplacement of E-MORB basic rocks.Crustal signatures for the Rhyacian to Orosirian evolution are highlighted by the dominance of negativeεNd(t)associated with Meso-to Neoarchean Nd TDMmodel ages as well as inherited zircon grains from the hybrid granitoids.The JFC is extensively highlighted in the literature as a primitive intra-oceanic arc,but here we propose the reworking or recycling of ancient crustal segments within the mature arc stage of the JFC,suggesting a Mesoarchean crustal source involved in the JFC evolution.
文摘肯倍对焊接程序、焊工资质以及焊接设备实行的有效管理能够带来良好的焊接生产表现,实现EBIT增长,提高成本竞争力并缩短生产前置时间。肯倍推出的Kemppi ARC System 3是一款全新的模块化软件解决方案,能够更好地进行焊接管理。客户可以在度身定制的工具箱中选择模块,用于质量、项目管理或生产效率等生产流程任何部分的开发。
基金supported by the Natural Science Foundation of Shandong Province(No.ZR2021MD069)the Strategic Pioneer Science and Technology Special Project of the Chinese Academy of Sciences(No.XDB42020104)+1 种基金the National Natural Science Foundation of China(No.42176052)the Project of Introducing and Cultivating Young Talents in the Universities of Shandong Province(No.LUJIAOKEHAN-2021-51).
文摘The bidirectional subduction system,island arc magmatic activities,and thermal structure of the forearc basin in the Molucca Sea are taken into consideration in this study.The active volcanic arcs on both sides of the bidirectional subduction zone in the Molucca Sea are undergoing arc-arc collisions.We applied a finite element thermal simulation method to reconstruct the thermal evolution history of the Molucca Sea Plate based on geophysical data.Then,we analyzed the thermodynamic characteristics of island arc volcanism on both sides of the bidirectional subduction zone.The results showed that at 10Myr,the oceanic ridge of the Molucca Sea Plate was asymmetrically biased to the west,causing this bidirectional subduction to be deeper in the west than in the east.Furthermore,the oceanic ridge subducted under the Sangihe arc at 5.5Myr,causing intermittent cessation of volcanic activities.Due to the convergence of bidirectional subduction,the geothermal gradient in the top 3km depth of the forearc area between the Sangihe and Halmahera arcs decreased from about 60℃km^(−1) at 4Myr to about 38℃km^(−1) today.Finally,within the 45–100 km depth range of the sliding surface of the subduction,anomalously high-temperature zones formed due to shear friction during the bidirectional subduction.
基金supported by National Natural Science Foundation of China(Nos.92066108 and 51277061)。
文摘The initial shape of the secondary arc considerably influences its subsequent shape.To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence,theoretical and experimental analysis of the evolution process of the short-circuit arc to the secondary arc is critical.In this study,an improved charge simulation method was used to develop the internal-space electric-field model of the short-circuit arc.The intensity of the electric field was used as an independent variable to describe the initial shape of the secondary arc.A secondary arc evolution model was developed based on this model.Moreover,the accuracy of the model was evaluated by comparison with physical experimental results.When the secondary arc current increased,the arcing time and dispersion increased.There is an overall trend of increasing arc length with increasing arcing time.Nevertheless,there is a reduction in arc length during arc ignition due to short circuits between the arc columns.Furthermore,the arcing time decreased in the range of 0°-90°as the angle between the wind direction and the x-axis increased.This work investigated the method by which short-circuit arcs evolve into secondary arcs.The results can be used to develop the secondary arc evolution model and to provide both a technical and theoretical basis for secondary arc suppression.