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Inversion of two-phase extensional basin systems during subduction of the Paleo-Pacific Plate in the SW Korean Peninsula:Implication for the Mesozoic “Laramide-style” orogeny along East Asian continental margin 被引量:1
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作者 Seung-Ik Park Jungrae Noh +4 位作者 Hee Jun Cheong Sanghoon Kwon Yungoo Song Sung Won Kim M.Santosh 《Geoscience Frontiers》 SCIE CAS CSCD 2019年第3期909-925,共17页
During subduction, continental margins experience shortening along with inversion of extensional sedimentary basins. Here we explore a tectonic scenario for the inversion of two-phase extensional basin systems, where ... During subduction, continental margins experience shortening along with inversion of extensional sedimentary basins. Here we explore a tectonic scenario for the inversion of two-phase extensional basin systems, where the Early-Middle Jurassic intra-arc volcano-sedimentary Oseosan Volcanic Complex was developed on top of the Late Triassic-Early Jurassic post-collisional sequences, namely the Chungnam Basin. The basin shortening was accommodated mostly by contractional faults and related folds. In the basement, regional high-angle reverse faults as well as low-angle thrusts accommodate the overall shortening, and are compatible with those preserved in the cover. This suggests that their spatial and temporal development is strongly dependent on the initial basin geometry and inherited structures.Changes in transport direction observed along the basement-sedimentary cover interface is a characteristic structural feature, reflecting sequential kinematic evolution during basin inversion. Propagation of basement faults also enhanced shortening of the overlying sedimentary cover sequences. We constrain timing of the Late Jurassic-Early Cretaceous(ca. 158-110 Ma) inversion from altered K-feldspar 40 Ar/39 Ar ages in stacked thrust sheets and K-Ar illite ages of fault gouges, along with previously reported geochronological data from the area. This "non-magmatic phase" of the Daebo Orogeny is contemporaneous with the timing of magmatic quiescence across the Korean Peninsula. We propose the role of flat/low-angle subduction of the Paleo-Pacific Plate for the development of the "Laramide-style" basement-involved orogenic event along East Asian continental margin. 展开更多
关键词 TWO-PHASE extensional basin SYSTEMS paleo-pacific plate INVERSION tectonics “Laramide-style” OROGENY East Asian continental margin
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Characterization of subduction initiation 被引量:2
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作者 Weidong SUN Lipeng ZHANG 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2023年第1期72-74,共3页
Compression is required for all kinds of subduction initiations,which may cause either subsidence or uplift,depending on the ages of the oceanic plates.Subduction initiations associated with the old oceanic crust tend... Compression is required for all kinds of subduction initiations,which may cause either subsidence or uplift,depending on the ages of the oceanic plates.Subduction initiations associated with the old oceanic crust tend to amplify preexisting subsidence by compression,whereas those associated with young oceanic plates may result in uplift. 展开更多
关键词 subduction initiation induced and spontaneous west Pacific plate tectonics
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Plate subduction, oxygen fugacity, and mineralization 被引量:13
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作者 LIU He LIAO Renqiang +2 位作者 ZHANG Lipeng LI Congying SUN Weidong 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2020年第1期64-74,共11页
Plate subduction is the largest natural factory that processes elements,which controls recycling and mineralization of a variety of elements.There are three major ore deposit belts in the world:the circumPacific,the c... Plate subduction is the largest natural factory that processes elements,which controls recycling and mineralization of a variety of elements.There are three major ore deposit belts in the world:the circumPacific,the centralAsian,and the Tethys belts.All the three belts are closely associated with plate subductions,the mechanism remains obscure.We approached this problem from systematic studies on the behaviours of elements during geologic processes.This contribution summaries the recent progress of our research group.Our results suggest that porphyry Cu deposits form through partial melting of subducted young oceanic crust under oxygen fugacities higher than AFMQ^+1.5,which is promoted after the elevation of atmospheric oxygen at ca.550 Ma.Tin deposits are associated with reducing magmatic rocks formed as a consequence of slab rollback.The Neo-Tethys tectonic regime hosts more than 60%of the world's total Sn reserves.This is due to the reducing environment formed during the subduction of organic rich sediments.For the same reason,porphyry Cu deposits formed in the late stages during the closure of the Neo-Tethys Ocean.Tungsten deposits are also controlled by slab rollback,but is not so sensitive to oxygen fugacity.Subduction related W/Sn deposits are mostly accompanied by abundant accessory fluorites due to the breakdown of phengite and apatite.Decomposition of phengite is also significant for hard rock lithium deposits,whereas orogenic belt resulted from plate subduction promote the formation of Li brine deposits.Cretaceous red bed basins near the Nanling region are favorable for Li brines.Both Mo and Re are enriched in the oxidationreduction cycle during surface processes,and may get further enriched once Mo-,Re-enriched sediments are subducted and involved in magmatism.During plate subduction,Mo and Re fractionate from each other.Molybdenum is mainly hosted in porphyry Mo deposits and to a less extent,porphyry Cu-Mo deposits,whereas Re is predominantly hosted in porphyry Cu-Mo deposits and sedimentary sulfide deposits. 展开更多
关键词 plate subduction oxygen FUGACITY ORE DEPOSITS GEOCHEMICAL behaviors subduction factory
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Global kinematics of tectonic plates and subduction zones since the late Paleozoic Era 被引量:10
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作者 Alexander Young Nicolas Flament +4 位作者 Kayla Maloney Simon Williams Kara Matthews Sabin Zahirovic R.Dietmar Müller 《Geoscience Frontiers》 SCIE CAS CSCD 2019年第3期989-1013,共25页
Detailed global plate motion models that provide a continuous description of plate boundaries through time are an effective tool for exploring processes both at and below the Earth's surface. A new generation of n... Detailed global plate motion models that provide a continuous description of plate boundaries through time are an effective tool for exploring processes both at and below the Earth's surface. A new generation of numerical models of mantle dynamics pre-and post-Pangea timeframes requires global kinematic descriptions with full plate reconstructions extending into the Paleozoic(410 Ma). Current plate models that cover Paleozoic times are characterised by large plate speeds and trench migration rates because they assume that lowermost mantle structures are rigid and fixed through time. When used as a surface boundary constraint in geodynamic models, these plate reconstructions do not accurately reproduce the present-day structure of the lowermost mantle. Building upon previous work, we present a global plate motion model with continuously closing plate boundaries ranging from the early Devonian at 410 Ma to present day.We analyse the model in terms of surface kinematics and predicted lower mantle structure. The magnitude of global plate speeds has been greatly reduced in our reconstruction by modifying the evolution of the synthetic Panthalassa oceanic plates, implementing a Paleozoic reference frame independent of any geodynamic assumptions, and implementing revised models for the Paleozoic evolution of North and South China and the closure of the Rheic Ocean. Paleozoic(410-250 Ma) RMS plate speeds are on average ~8 cm/yr, which is comparable to Mesozoic-Cenozoic rates of ~6 cm/yr on average.Paleozoic global median values of trench migration trend from higher speeds(~2.5 cm/yr) in the late Devonian to rates closer to 0 cm/yr at the end of the Permian(~250 Ma), and during the Mesozoic-Cenozoic(250-0 Ma) generally cluster tightly around ~1.1 cm/yr. Plate motions are best constrained over the past 130 Myr and calculations of global trench convergence rates over this period indicate median rates range between 3.2 cm/yr and 12.4 cm/yr with a present day median rate estimated at~5 cm/yr. For Paleozoic times(410-251 Ma) our model results in median convergence rates largely~5 cm/yr. Globally,~90% of subduction zones modelled in our reconstruction are determined to be in a convergent regime for the period of 120-0 Ma. Over the full span of the model, from 410 Ma to 0 Ma,~93% of subduction zones are calculated to be convergent, and at least 85% of subduction zones are converging for 97% of modelled times. Our changes improve global plate and trench kinematics since the late Paleozoic and our reconstructions of the lowermost mantle structure challenge the proposed fixity of lower mantle structures, suggesting that the eastern margin of the African LLSVP margin has moved by as much as ~1450 km since late Permian times(260 Ma). The model of the plate-mantle system we present suggests that during the Permian Period, South China was proximal to the eastern margin of the African LLSVP and not the western margin of the Pacific LLSVP as previous thought. 展开更多
关键词 TECTONIC reconstruction PALEOZOIC plate VELOCITIES subduction zone KINEMATICS Lower MANTLE structure South China
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Dynamic subduction process of local plate revealed by Ibaraki earthquake sequence of 1982 in Japan 被引量:2
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作者 DIAO Gui-ling 《Acta Seismologica Sinica(English Edition)》 EI CSCD 2001年第2期141-147,共7页
The kinematics and dynamics of plate tectonics are frontal subjects in geosciences and the strong earthquake occurred along the plate boundary result directly from plate movement. By analyzing Ibaraki earthquake seque... The kinematics and dynamics of plate tectonics are frontal subjects in geosciences and the strong earthquake occurred along the plate boundary result directly from plate movement. By analyzing Ibaraki earthquake sequence, it has been found that the focal fault plane shows a special image of grading expansion along the direction of strike and adjustment along the dip direction respectively. With the consideration of strike, dip and slip directions of focal mechanism, we have confirmed that Ibaraki earthquake belongs to a thrust fault earthquake occurred under the Japan Trench. The cause of the earthquake sequence is discussed in the paper. The study on the temporal-spatial distribution of the earthquake sequence with a time-scale between the year-scale spatial geodetic data and the second-scale moment tensor of the strong earthquake has indicated the dynamic process of Pacific Plate subduction under the Eurasia Plate. According to the average slip distance of earthquake and the velocity of plate movement, it is predicted that a strong earthquake might occur in recent years. 展开更多
关键词 earthquake sequence plate tectonics subduction zone dynamic process
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Reviewing subduction initiation and the origin of plate tectonics:What do we learn from present-day Earth? 被引量:5
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作者 Gang Lu Liang Zhao +2 位作者 Ling Chen Bo Wan FuYuan Wu 《Earth and Planetary Physics》 CSCD 2021年第2期123-140,共18页
The theory of plate tectonics came together in the 1960s,achieving wide acceptance after 1968.Since then it has been the most successful framework for investigations of Earth’s evolution.Subduction of the oceanic lit... The theory of plate tectonics came together in the 1960s,achieving wide acceptance after 1968.Since then it has been the most successful framework for investigations of Earth’s evolution.Subduction of the oceanic lithosphere,as the engine that drives plate tectonics,has played a key role in the theory.However,one of the biggest unanswered questions in Earth science is how the first subduction was initiated,and hence how plate tectonics began.The main challenge is how the strong lithosphere could break and bend if plate tectonics-related weakness and slab-pull force were both absent.In this work we review state-of-the-art subduction initiation(SI)models with a focus on their prerequisites and related driving mechanisms.We note that the plume-lithosphere-interaction and mantleconvection models do not rely on the operation of existing plate tectonics and thus may be capable of explaining the first SI.Reinvestigation of plate-driving mechanisms reveals that mantle drag may be the missing driving force for surface plates,capable of triggering initiation of the first subduction.We propose a composite driving mechanism,suggesting that plate tectonics may be driven by both subducting slabs and convection currents in the mantle.We also discuss and try to answer the following question:Why has plate tectonics been observed only on Earth? 展开更多
关键词 subduction initiation plate tectonics mantle convection driving force mantle drag
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Density Structure of the Papua New Guinea-Solomon Arc Subduction System
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作者 XU Chong XING Junhui +3 位作者 GONG Wei ZHANG Hao XU Haowei XU Xiaoyu 《Journal of Ocean University of China》 SCIE CAS CSCD 2023年第5期1269-1276,共8页
The Papua New Guinea-Solomon(PN-SL)arc is one of the regions with active crustal motions and strong geological actions.Thus,its complex subduction system makes it an ideal laboratory for studying the initiation mechan... The Papua New Guinea-Solomon(PN-SL)arc is one of the regions with active crustal motions and strong geological actions.Thus,its complex subduction system makes it an ideal laboratory for studying the initiation mechanism of plate subduction.However,the PN-SL subduction system has not yet been sufficiently studied,and its density structure has yet to be revealed.In this paper,we used the free-air gravity data,Parker-Oldenburg density surface inversion method,and the genetic algorithm density inversion method to obtain the density structure of an approximately 1000-km-long northwest-southeast line crossing the PN-SL subduction system under the constraints of the CRUST1.0 global crustal model,onshore seismic data,and the LLNL-G3Dv3 global P-wave velocity model.The density structure shows that density differences between the plates on the two sides of the trench could play a significant role in plate subduction. 展开更多
关键词 Papua New Guinea-Solomon plate subduction gravity anomaly density structure genetic algorithm
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New Zircon U-Pb Age of the Babu Ophiolites in Southeast Yunnan,China and Constrains of Plate Subduction Time 被引量:4
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作者 HUANG Hu DU Yuansheng +1 位作者 YANG Jianghai YU Wenchao 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2017年第3期1151-1152,共2页
Objective The Babu ophiolite in Malipo County of southeastern Yunnan is interpreted as remanant ocean crust and represents a possible branch of Paleo-Tethyan Ocean in South China. It consists mainly of mafic and ultra... Objective The Babu ophiolite in Malipo County of southeastern Yunnan is interpreted as remanant ocean crust and represents a possible branch of Paleo-Tethyan Ocean in South China. It consists mainly of mafic and ultramafic rocks. These rocks are very important to understand the evolution of the Paleo-Tethyan Ocean. However, the Babu ophiolite is still disputed and the mafic and ultramafic rocks have been inferred to be part of the Emeishan large igneous province (LIP) by some researchers. In this paper, we present zircon U-Pb data on the metabasalts in Malipo to reveal the formation time of mafic and ultramafic rocks and their tectonic nature. 展开更多
关键词 PB ICP MS Th is New Zircon U-Pb Age of the Babu Ophiolites in Southeast Yunnan China and Constrains of plate subduction Time of in
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Remnants and fragments of the subducted paleo-Pacific plate:Constraints from geochemistry and geophysics
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作者 Xisheng XU Zhouchuan HUANG +2 位作者 Dingsheng JIANG Gang ZENG Li-Qun DAI 《Science China Earth Sciences》 SCIE EI CAS CSCD 2024年第10期3041-3061,共21页
The subduction and rollback of the paleo-Pacific plate during Mesozoic time was the key engine for the evolution of the continental margin in eastern China. It led to lateral accretion of continental crust in Northeas... The subduction and rollback of the paleo-Pacific plate during Mesozoic time was the key engine for the evolution of the continental margin in eastern China. It led to lateral accretion of continental crust in Northeast China, lithospheric destruction beneath the North China Craton, and the generation of huge volumes of felsic magmatic rocks in South China. This had a profound influence on deep material cycles and the evolution of epigenetic environmental systems along the continental margin of East Asia. To fully understand the transformation of the dynamic mechanism during the subduction and rollback of the paleoPacific plate, we have attempted to trace the remnants and fragments of the subducted paleo-Pacific plate at great depths. Such remnants in both temporal and spatial dimensions can be tracked by using geochemical and geophysical approaches. Studies of the trace elements, Mg-Zn isotopes and Os-Nd-Hf-Pb-O isotopes in continental basalts from eastern China reveal a significant number of the remnants of subduction of the paleo-Pacific plate, and the initial subduction can be traced back to the Early Jurassic. Large-scale geophysical imaging unveils a multitude of high-velocity anomalies in the lower mantle of East Asia.Notably, many high-velocity bodies, aptly referred to as “slab graveyards”, are nestled at the base of the lower mantle. Numerous isolated high-velocity anomalies are also present in the upper part of the lower mantle, creating conduits for the descent of the subducted slabs into the lower mantle. However, a resolution of the remnants for the subducted slabs within the lower mantle are quite low. Consequently, their impact on the lower mantle's dynamics is yet to be thoroughly investigated. Finally, the presently observed big mantle wedge(BMW) in East Asia has developed through subduction of the Pacific plate in the Cenozoic.However, following the rollback of the paleo-Pacific plate(began at ~145 Ma), a Cretaceous BMW system would also form above the mantle transition zone in East Asia. There are significant differences in tectonic-magmatic processes and basinforming and hydrocarbon-accumulation processes among different regions along the East Asian continental margin. Such differences may be controlled by variations in the speed and angle of rollback of the paleo-Pacific plate. 展开更多
关键词 paleo-pacific plate Big mantle wedge Late Mesozoic Remnants and fragments GEOCHEMISTRY GEOPHYSICS
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Formation of the adakite-like granitoid complex and porphyry copper-gold deposit in Shaxi from southern Tancheng-Lujiang fault belt: A clue to the West Pacific plate subduction 被引量:2
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作者 YANG Xiaoyong 《Chinese Journal Of Geochemistry》 EI CAS 2009年第1期28-43,共16页
On the basis of the geological and geochemical studies, including chemical analysis of bulk rocks, rare-earth and trace element studies, fluid inclusion, and S and O isotopic analyses, the authors described the geolog... On the basis of the geological and geochemical studies, including chemical analysis of bulk rocks, rare-earth and trace element studies, fluid inclusion, and S and O isotopic analyses, the authors described the geological background of the deposit in detail and presented significant proofs for the conditions of formation of the Shaxi porphyry copper-gold deposit. Compared with other large and supper-large porphyry copper deposits in China and the adjacent Cu-Au mineralized areas, the ore-forming processes and conditions were analyzed; and the possibility of forming large porphyry copper deposits in the Shaxi area was discussed. The present study indicated that the ore-forming fluid and material were mainly of magmatic origin, while meteoric water played a certain role in the ore-forming processes. Interactions between subducting and overriding plates provided a major driving force for the formation of igneous rocks and the deposition of metal elements in East China since Jurassic. Based on the geo- chemical data of the Shaxi intrusive, it is found that the copper (gold) mineralization is closely related to the genesis of adakite-like intrusive in the Shaxi area. This adakite-like intrusive was formed in the subduction environment as a result of the subduction of the West Pacific plate toward the East China continent, where there is a great potentiality to form a large porphyry copper deposit. 展开更多
关键词 斑岩 金成矿 物化环境 温度
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Characteristics of Paleoproterozoic Subduction System in Western Margin of Yangtze Plate
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作者 Zhang Hongxiang Liu Congqiang Xu Zhifang Geology and Geophysics Institute, Chinese Academy of Sciences, Beijing 100101 Huang Zhilong Geochemistry Institute, Chinese Academy of Sciences, Guiyang 550002 《Journal of Earth Science》 SCIE CAS CSCD 2000年第1期58-67,共10页
Paleoproterozoic subduction strongly occurred in the western margin of Yangtze plate. The basalticandesite volcanics of Ailaoshan Group and Dibadu Formation had been formed during paleo QinghaiTibet oceanic plate s... Paleoproterozoic subduction strongly occurred in the western margin of Yangtze plate. The basalticandesite volcanics of Ailaoshan Group and Dibadu Formation had been formed during paleo QinghaiTibet oceanic plate subduction under the paleoYangtze plate. Their trace element geochemistry suggests that their forming environments are continentalmarginarc and back arcbasin respectively. Consequently, the Paleoproterozoic subduction system in the western margin of Yangtze plate was established. Ailaoshan Group and Dibadu Formation came from an enriched mantle source that was contaminated by crustal sediments carried by subducted slab, and formed the Paleoroterozoic metamorphic basement of western margin of Yangtze plate. Ailaoshan Group is actually western boundary of Yangtze plate. 展开更多
关键词 western margin of Yangtze plate Paleoproterozoic subduction system Ailaoshan Group (AG) Dibadu Formation (DF) incompatible element (IE) large ion lithospheric element (LILE) high field strengthen element (HFSE).
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Causes of Cretaceous subduction termination below South China and Borneo:Was the Proto-South China Sea underlain by an oceanic plateau? 被引量:1
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作者 Suzanna H.A.van de Lagemaat Licheng Cao +4 位作者 Junaidi Asis Eldert L.Advokaat Paul R.D.Mason Mark J.Dekkers Douwe J.J.van Hinsbergen 《Geoscience Frontiers》 SCIE CAS CSCD 2024年第2期100-124,共25页
The South China,Indochina,and Borneo margins surrounding the South China Sea contain long-lived arcs that became inactive at approximately 85 Ma,even though an embayment of oceanic crust(the‘Proto-South China Sea’)r... The South China,Indochina,and Borneo margins surrounding the South China Sea contain long-lived arcs that became inactive at approximately 85 Ma,even though an embayment of oceanic crust(the‘Proto-South China Sea’)remained in the intervening region.This oceanic crust eventually subducted in the Cenozoic below Borneo and the Cagayan arc,while the modern South China Sea opened in its wake.To investigate the enigmatic cessation of Mesozoic subduction below South China and Borneo,we studied a fragment of oceanic crust and overlying trench-fill sediments that accreted to NW Borneo during the final stages of Paleo-Pacific subduction.Based on radiolarian biostratigraphy of cherts overlying the pillow basalts and detrital zircon geochronology of the trench-fill,we constrained the minimum age of the oceanic crust during accretion to 40 Ma.This shows that subduction cessation was not related to ridge subduction.Geochemical analysis of pillow basalts revealed an enriched mid-ocean ridge basalt signature comparable to oceanic plateaus.Using paleomagnetism,we show that this fragment of oceanic crust was not part of the Izanagi Plate but was part of a plate(the‘Pontus’Plate)separated from the Izanagi Plate by a subduction zone.Based on the minimum 40 Ma age of the oceanic crust and its geochemistry,we suggest that Mesozoic subduction below South China and Borneo stopped when an oceanic plateau entered the trench,while the eastern plate margin with the Izanagi Plate remained active.We show how our findings offer opportunities to restore plate configurations of the Panthalassa-Tethys junction region. 展开更多
关键词 Proto-South China Sea PALEOMAGNETISM Geochemistry BORNEO paleo-pacific Izanagi plate
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Two-dimensional Numerical Modeling Research on Continent Subduction Dynamics 被引量:4
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作者 WANGZhimin XUBei +2 位作者 ZHOUYaoqi XUHehua HUANGShaoying 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2004年第1期313-319,共7页
Continent subduction is one of the hot research problems in geoscience. New models presented here have been set up and two-dimensional numerical modeling research on the possibility of continental subduction has been ... Continent subduction is one of the hot research problems in geoscience. New models presented here have been set up and two-dimensional numerical modeling research on the possibility of continental subduction has been made with the finite element software, ANSYS, based on documentary evidence and reasonable assumptions that the subduction of oceanic crust has occurred, the subduction of continental crust can take place and the process can be simplified to a discontinuous plane strain theory model. The modeling results show that it is completely possible for continental crust to be subducted to a depth of 120 km under certain circumstances and conditions. At the same time, the simulations of continental subduction under a single dynamical factor have also been made, including the pull force of the subducted oceanic lithosphere, the drag force connected with mantle convection and the push force of the mid-ocean ridge. These experiments show that the drag force connected with mantle convection is critical for continent subduction. 展开更多
关键词 continent subduction application of ANSYS software dynamic mechanism modeling plate tectonics
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Why primordial continents were recycled to the deep:Role of subduction erosion 被引量:6
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作者 S.Azuma S.Yamamoto +1 位作者 H.Ichikawa S.Maruyama 《Geoscience Frontiers》 SCIE CAS CSCD 2017年第2期337-346,共10页
Geological observations indicate that there are only a few rocks of Archean Earth and no Hadean rocks on the surface of the present-day Earth.From these facts,many scientists believe that the primordial continents nev... Geological observations indicate that there are only a few rocks of Archean Earth and no Hadean rocks on the surface of the present-day Earth.From these facts,many scientists believe that the primordial continents never existed during Hadean Earth,and the continental volume has kept increasing.On the other hand,recent studies reported the importance of the primordial continents on the origin of life,implying their existence.In this paper,we discussed the possible process that could explain the loss of the primordial continents with the assumption that they existed in the Hadean.Although depending on the timing of the initiation of plate tectonics and its convection style,subduction erosion,which is observed on the present-day Earth,might have carried the primordial continents into the deep mantle. 展开更多
关键词 subduction erosion Hadean plate tectonics Archean
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Decadal Seismicity Prior to Great Earthquakes at Subduction Zones: Roles of Major Asperities and Low-Coupling Zones 被引量:3
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作者 Lynn R. Sykes 《International Journal of Geosciences》 2021年第9期845-926,共82页
Decadal forerunning seismic activity of magnitude Mw ≥ 5.0 is mapped for all 45 mainshocks of Mw 7.7 to 9.1 at subduction zones of the world from 1993 to mid 2020. The zones of high slip in nearly all great earthquak... Decadal forerunning seismic activity of magnitude Mw ≥ 5.0 is mapped for all 45 mainshocks of Mw 7.7 to 9.1 at subduction zones of the world from 1993 to mid 2020. The zones of high slip in nearly all great earthquakes were nearly quiescent beforehand and are identified as the sites of great asperities and zones of strong seismic coupling. Much forerunning activity occurred at smaller asperities along the peripheries of the rupture zones of many great and giant mainshocks. Those sizes of great asperities as ascertained from forerunning activity generally agree with the areas of high seismic slip as determined by others from geodetic and tide-gauge data and finite-source seismic modeling. Asperities are strong, well-coupled portions of plate interfaces. Different patterns of forerunning activity on time scales of about 5 to 45 years are attributed to either the sizes and spacing of asperities (or lack of). This permits many great asperities to be mapped decades before they rupture in great and giant shocks. Several poorly coupled subduction zones such as Java, Lesser Sunda, Marianas, Tonga and Kermadec are characterized by few great thrust earthquakes and little, in any forerunning activity. Rupture zones of many great and giant earthquakes are bordered either along strike, updip, or downdip by zones of lower plate coupling. Several bordering regions were sites of forerunning activity, aftershocks, and slow-slip events. The detection of forerunning and precursory activities of various kinds should be sought on the peripheries of great asperities as well as within zones of high co-seismic slip. 展开更多
关键词 EARTHQUAKES subduction Prediction plate Coupling ASPERITIES
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A-type granites induced by a breaking-off and delamination of the subducted Junggar oceanic plate,West Junggar,Northwest China 被引量:1
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作者 Chu Wu Tao Hong +2 位作者 Xing-Wang Xu Cheng-Xi Wang Lian-Hui Dong 《China Geology》 CAS 2022年第3期457-474,共18页
The A-type granites with highly positiveε_(Nd)(t)values in the West Junggar,Central Asian Orogenic Belt(CAOB),have long been perceived as a group formed under the same tectonic and geodynamic setting,magmatic sourceq... The A-type granites with highly positiveε_(Nd)(t)values in the West Junggar,Central Asian Orogenic Belt(CAOB),have long been perceived as a group formed under the same tectonic and geodynamic setting,magmatic sourceq and petrogenetic model.Geological evidence shows that these granites occurred at two different tectonic units related to the southeastern subduction of Junggar oceanic plate:the Hongshan and Karamay granites emplaced in the southeast of West Junggar in the Baogutu continental arc;whereas the Akebasitao and Miaoergou granites formed in the accretionary prism.Here the authors present new bulk-rock geochemistry and Sr-Nd isotopes,zircon U-Pb ages and Hf-O isotopes data on these granites.The granites in the Baogutu continental arc and accretionary prism contain similar zirconε_(Hf)(t)values(+10.9 to+16.2)and bulk-rock geochemical characteristics(high SiO_(2)and K_(2)O contents,enriched LILEs(except Sr),depleted Sr,Ta and Ti,and negative anomalies in Ce and Eu).The Hongshan and Karamay granites in the Baogutu continental arc have older zircon U-Pb ages(315-305 Ma)and moderate^(18)O enrichments(δ^(18)_(O_(zircon))=+6.41‰-+7.96‰);whereas the Akebasitao and Miaoergou granites in the accretionary prism have younger zircon U-Pb ages(305-301 Ma)with higher^(18)O enrichments(δ^(18)_(O_(zircon))=+8.72‰-+9.89‰).The authors deduce that the elevated^(18)O enrichments of the Akebasitao and Miaoergou granites were probably inherited from low-temperature altered oceanic crusts.The Akebasitao and Miaoergou granites were originated from partial melting of low-temperature altered oceanic crusts with juvenile oceanic sediments below the accretionary prism.The Hongshan and Karamay granites were mainly derived from partial melting of basaltic juvenile lower crust with mixtures of potentially chemical weathered ancient crustal residues and mantle basaltic melt(induced by hot intruding mantle basaltic magma at the bottom of the Baogutu continental arc).On the other hand,the Miaoergou charnockite might be sourced from a deeper partial melting reservoir under the accretionary prism,consisting of the low-temperature altered oceanic crust,juvenile oceanic sediments,and mantle basaltic melt.These granites could be related to the asthenosphere's counterflow and upwelling,caused by the break-off and delamination of the subducted oceanic plate beneath the accretionary prism Baogutu continental arc in a post-collisional tectonic setting. 展开更多
关键词 A-type granite plutons Sr-Nd-Hf-O isotopes Breaking-off and delamination subducted Junggar oceanic plate West Junggar Central Asian Orogenic Belt
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Effective Elastic Thickness of the Lithosphere in the Mariana Subduction Zone and Surrounding Regions and Its Implications for Their Tectonics
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作者 LING Zilong ZHAO Lihong +2 位作者 WU Zhaocai ZHI Pengyao DING Renwei 《Journal of Ocean University of China》 SCIE CAS CSCD 2022年第4期827-836,共10页
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
关键词 effective elastic thickness moving window admittance technique Mariana subduction zone plate bending
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Seismic-gravimetric analysis of the subducted Nazca plate 1 between 32°S and 36°S
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作者 Lujan Eckerman Alejo Agüero +2 位作者 Silvana Spagnotto Patricia Martinez Silvina Nacif 《Geodesy and Geodynamics》 2018年第1期57-66,共10页
The study region is seismically and tectonically characterized by the angle variations in the subduction of the Nazca plate. The results obtained from earthquakes location between 32° and 36°S latitude and67... The study region is seismically and tectonically characterized by the angle variations in the subduction of the Nazca plate. The results obtained from earthquakes location between 32° and 36°S latitude and67°-71°W longitude are presented in this work. The presence of a wedge of asthenospheric materials and the partial or total eclogitization of the subducted Nazca plate and its relation with isostatic cortex models published was analyzed. In addition, a gravimetric profile obtained from gravity forward modeling is presented at 33.5°S, proposing a new configuration at depths for the main tectonic components: Nazca plate, asthenospheric wedge and South American plate. Also, a new density scheme using recently published velocity models was obtained. 展开更多
关键词 subducted Nazca plate seismicity Intermediate earthquakes Gravimetric profile
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Ripple Tectonics—When Subduction Is Interrupted
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作者 Zvi Ben-Avraham Gerald Schubert +1 位作者 Emanuele Lodolo Uri Schattner 《Positioning》 2020年第3期33-44,共12页
Subduction plays a fundamental role in plate tectonics and is a significant factor in modifying the structure and topography of the Earth. It is driven by convection forces that change over a >100 Myr time scale. H... Subduction plays a fundamental role in plate tectonics and is a significant factor in modifying the structure and topography of the Earth. It is driven by convection forces that change over a >100 Myr time scale. However, when an oceanic plateau approaches, it plugs the subduction, and causes slab necking and tearing. This abrupt change may trigger a series of geodynamic (tectonic, volcanic) and sedimentary responses recorded across the convergence boundary and its surrounding regions by synchronous structural modifications. We suggest that a large enough triggering event may lead to a ripple tectonic effect that propagates outwards while speeding up the yielding of localized stress states that otherwise would not reach their threshold. The ripple effect facilitates tectonic, volcanic, and structural events worldwide that are seemingly unrelated. When the world’s largest oceanic plateau, Ontong Java Plateau (OJP), choked the Pacific-Australian convergence zone at ~6 Myr ago, it induced kinematic modifications throughout the Pacific region and along its plate margins. Other, seemingly unrelated, short-lived modifications were recorded worldwide during that time window. These modifications changed the rotation of the entire Pacific plate, which occupies ~20% of the Earth’s surface. In addition, the Scotia Sea spreading stopped, global volcanism increased, the Strait of Gibraltar closed, and the Mediterranean Sea dried up and induced the Messinian salinity crisis. In this paper, we attribute these and many other synchronous events to a new “ripple tectonics” mechanism. We suggest that the OJPincipient collision triggered the Miocene-Pliocene transition. Similarly, we suggest that innovative GPS-based studies conducted today may seek the connectivity between tectonic, seismic, and volcanic events worldwide. 展开更多
关键词 plate Tectonics subduction-Collision Transition Miocene-Pliocene Transition
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An Orthogonal Collision Dynamic Mechanism of Wave-Like Uplift Plateaus in Southern Asia
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作者 Weihong Qian Jeremy Cheuk-Hin Leung Banglin Zhang 《Open Journal of Geology》 2023年第8期828-846,共19页
In southern Asia, there are three large-scale wave-like mountains ranging from the Tibetan Plateau westward to the Iranian Plateau and the Armenian Plateau. On the southern side between plateaus, there are the Indian ... In southern Asia, there are three large-scale wave-like mountains ranging from the Tibetan Plateau westward to the Iranian Plateau and the Armenian Plateau. On the southern side between plateaus, there are the Indian Peninsula and the Arabian Peninsula. What dynamic mechanisms form the directional alignment of the three plateaus with the two peninsulas remains a mystery. In the early stages of the Earth’s geological evolution, the internal structure of the Earth was that the center was a solid core, and the outmost layer was a thin equatorial crust zone separated by two thick pristine continents in polar areas, while the middle part was a deep magma fluid layer. Within the magma fluid layer, thermal and dynamic differences triggered planetary-scale vertical magma cells and led to the core-magma angular momentum exchange. When the core loses angular momentum and the magma layer gains angular momentum, the movement of upper magma fluids to the east and the tropical convergence zone (TCZ) drives the split and drift of two thick pristine continents, eventually forming the current combination of these plateaus and peninsulas and their wave-like arrangement along the east-west direction. Among them, the horizontal orthogonal convergence (collision) of upper magma fluids from the two hemispheres excited the vertical shear stress along the magma TCZ, which is the dynamic mechanism of mountain uplifts on the north side and plate subductions on the south side. To confirm this mechanism, two examples of low-level winds are used to calculate the correspondence between cyclone/anticyclonic systems generated by the orthogonal collision of airflows along the atmospheric TCZ and satellite-observed cloud systems. Such comparison can help us revisit the geological history of continental drift and orogeny. 展开更多
关键词 plateau Uplift plate subduction Tibetan plateau Iranian plateau Armenian plateau
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