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Remnants and fragments of the subducted paleo-Pacific plate:Constraints from geochemistry and geophysics

Science China earth sciences 2024年第10期67卷 3041-3061页

作者： Xisheng XU Zhouchuan HUANG Dingsheng JIANG Gang ZENG Li-Qun DAI State Key Laboratory for Mineral Deposits Research School of Earth Sciences and EngineeringNanjing UniversityNanjing 210023China school of earth and space sciences University of Science and Technology of ChinaHefei 230026China

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 ***, 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 ***, following the rollback of the paleo-Pacific plate(began at ~145 Ma), a Cretaceous BMW system would also form above

关键词： Paleo-Pacific plate Big mantle wedge Late Mesozoic Remnants and fragments Geochemistry Geophysics

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An envelope-based machine learning workflow for locating earthquakes in the southern Sichuan Basin

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earthquake Research Advances 2024年第2期4卷 45-54页

作者： Kang Wang Jie Zhang Ji Zhang Zhangyu Wang Ziyu Li school of earth and space sciences University of Science and Technology of ChinaHefei230026China

The development of machine learning technology enables more robust real-time earthquake monitoring through automated implementations. However, the application of machine learning to earthquake location problems faces challenges in regions with limited available training data. To address the issues of sparse event distribution and inaccurate ground truth in historical seismic datasets, we expand the training dataset by using a large number of synthetic envelopes that closely resemble real data and build an earthquake location model named ENVloc. We propose an envelope-based machine learning workflow for simultaneously determining earthquake location and origin time. The method eliminates the need for phase picking and avoids the accumulation of location errors resulting from inaccurate picking results. In practical application, ENVloc is applied to several data intercepted at different starting points. We take the starting point of the time window corresponding to the highest prediction probability value as the origin time and save the predicted result as the earthquake location. We apply ENVloc to observed data acquired in the southern Sichuan Basin, China, between September 2018 and March 2019. The results show that the average difference with the catalog in latitude, longitude, depth, and origin time is 0.02°,0.02°, 2 km, and 1.25 s, respectively. These suggest that our envelope-based method provides an efficient and robust way to locate earthquakes without phase picking, and can be used in earthquake monitoring in near-real time.

关键词： Waveform envelope earthquake location Local seismicity Synthetic data Sparse stations

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Monitoring seismicity in the southern Sichuan Basin using a machine learning workflow

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earthquake Research Advances 2024年第1期4卷 59-66页

作者： Kang Wang Jie Zhang Ji Zhang Zhangyu Wang Huiyu Zhu school of earth and space sciences University of Science and Technology of ChinaHefei230026China

Monitoring seismicity in real time provides significant benefits for timely earthquake warning and *** this study,we propose an automatic workflow based on machine learning(ML)to monitor seismicity in the southern Sichuan Basin of *** workflow includes coherent event detection,phase picking,and earthquake location using three-component data from a seismic *** combining Phase Net,we develop an ML-based earthquake location model called Phase Loc,to conduct real-time monitoring of the local *** approach allows us to use synthetic samples covering the entire study area to train Phase Loc,addressing the problems of insufficient data samples,imbalanced data distribution,and unreliable labels when training with observed *** apply the trained model to observed data recorded in the southern Sichuan Basin,China,between September 2018 and March *** results show that the average differences in latitude,longitude,and depth are 5.7 km,6.1 km,and 2 km,respectively,compared to the reference *** Loc combines all available phase information to make fast and reliable predictions,even if only a few phases are detected and *** proposed workflow may help real-time seismic monitoring in other regions as well.

关键词： earthquake monitoring Machine learning Local seismicity Gaussian waveform Sparse stations

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The effects of local variations in conditions on carbon storage and release in the continental mantle

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National Science Review 2024年第6期11卷 22-36页

作者： Stephen F.Foley Chunfei Chen Dorrit E.Jacob school of Natural sciences Macquarie University Research school of earth sciences Australian National University State Key Laboratory of Geological Processes and Mineral Resources School of Earth Sciences China University of Geosciences

Recent advances indicate that the amount of carbon released by gradual degassing from the mantle needs to be revised upwards, whereas the carbon supplied by plumes may have been overestimated in the *** in rock types and oxidation state may be very local and exert strong influences on carbon storage and release mechanisms. Deep subduction may be prevented by diapirism in thick sedimentary packages,whereas carbonates in thinner sequences may be subducted. Carbonates stored in the mantle transition zone will melt when they heat up, recognized by coupled stable isotope systems(e.g. Mg, Zn, Ca). There is no single ‘mantle oxygen fugacity’, particularly in the thermal boundary layer(TBL) and lowermost lithosphere, where very local mixtures of rock types coexist. Carbonate-rich melts from either subduction or melting of the uppermost asthenosphere trap carbon by redox freezing or as carbonate-rich dykes in this zone. Deeply derived, reduced melts may form further diamond reservoirs, recognized as polycrystalline diamonds associated with websteritic silicate minerals. Carbon is released by either edge-driven convection,which tears sections of the TBL and lower lithosphere down so that they melt by a mixture of heating and oxidation, or by lateral advection of solids beneath rifts. Both mechanisms operate at steps in lithosphere thickness and result in carbonate-rich melts, explaining the spatial association of craton edges and carbonate-rich magmatism. High-pressure experiments on individual rock types, and increasingly on reactions between rocks and melts, are fine-tuning our understanding of processes and turning up unexpected results that are not seen in studies of single rocks. Future research should concentrate on elucidating local variations and integrating these with the interpretation of geophysical signals. Global concepts such as average sediment compositions and a uniform mantle oxidation state are not appropriate for small-scale processes; an increa

关键词： lithospheric mantle carbonate melts deep carbon cycle craton destruction continental rifts

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The great catastrophe: causes of the Permo-Triassic marine mass extinction

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National Science Review 2024年第1期11卷 37-50页

作者： Paul B.Wignall David P.G.Bond school of earth & Environment University of Leeds school of Environmental sciences University of Hull

The marine losses during the Permo-Triassic mass extinction were the worst ever experienced. All groups were badly affected, especially amongst the benthos(e.g. brachiopods, corals, bryozoans, foraminifers,ostracods). Planktonic populations underwent a fundamental change with eukaryotic algae being replaced by nitrogen-fixing bacteria, green-sulphur bacteria, sulphate-reducing bacteria and prasinophytes. Detailed studies of boundary sections, especially those in South China, have resolved the crisis to a ～55 kyr interval straddling the Permo-Triassic boundary. Many of the losses occur at the beginning and end of this interval painting a picture of a two-phase extinction. Improved knowledge of the extinction has been supported by numerous geochemical studies that allow diverse proposed extinction mechanisms to be studied. A transition from oxygenated to anoxic-euxinic conditions is seen in most sections globally, although the intensity and timing shows regional variability. Decreased ocean ventilation coincides with rapidly rising temperatures and many extinction scenarios attribute the losses to both anoxia and high *** kill mechanisms include ocean acidification for which there is conflicting support from geochemical proxies and, even less likely, siltation(burial under a massive influx of terrigenous sediment) which lacks substantive sedimentological evidence. The ultimate driver of the catastrophic changes at the end of the Permian was likely Siberian Trap eruptions and their associated carbon dioxide emissions with consequences such as warming, ocean stagnation and acidification. Volcanic winter episodes stemming from Siberian volcanism have also been linked to the crisis, but the short-term nature of these episodes(

关键词： ocean anoxia ocean acidification siltation productivity collapse volcanic winter

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Rethinking the egg

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National Science Review 2024年第6期11卷 81-82页

作者： Michael J.Benton school of earth sciences University of Bristol

Our image of early dinosaur eggs must change. Early dinosaur eggs are portrayed as soft-shelled, like those of modern lizards or snakes [1], and yet all the evidence is that early dinosaurs at least laid leathery-shel...

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Solar energetic particles intensity variations associated with a tilted-dipole 3D corotating interaction region

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earth and Planetary Physics 2024年第5期8卷 797-810页

作者： YuJi Zhu Fang Shen Xi Luo Yang Wang BoFeng Tang State Key Laboratory of space Weather National Space Science Center Chinese Academy of Sciences Shandong Institute of Advanced Technology (SDIAT) College of earth and Planetary sciences University of Chinese Academy of Sciences school of Science Harbin Institute of Technology

The effect of a tilted-dipole three-dimensional corotating interaction region(CIR) on the transport and acceleration of solar energetic particles(SEPs) is *** this work,we discussed how the particle intensity longitudinal and radial dependence might be influenced by the background ***,we investigate how the spectral index distribution is modulated by the CIR structure We use the focused transport equation(FTE) to describe the propagation and acceleration of SEPs in a tilt-dipole 3D CIR,generated by the high-resolution 3D magnetohydrodynamic(MHD) *** forward stochastic differential method is used to solve the *** protons with theE～(-4.4)spectrum from 0.5 to 15 MeV are injected uniformly at the heliographic equator of 0.15 *** quantities are extracted along each interplanetary magnetic field(IMF) line to show the *** the tilted-dipole CIR background,if injected from the solar equator at the inner boundary,particles in the slow flow are transported to higher latitudes due to the extension of the IMF lines to higher *** longitudinal patterns of the particles are dominated by the density of IMF *** focusing effect modulates the longitudinal variation of the particle intensity and gives rise to new longitudinal intensity *** adiabatic effect largely increases the intensity fluctuation along the *** structure of the solar wind can also lead to the difference of the index α in the empirical functionI＿(max)=kR～(-α),describing the radial variation of peak intensity according to our *** the influence of the CIR structure,the index α varies from 1.9 to 3.4 at 0.3-1.0 *** variation of the solar wind speed should be considered when estimating the radial dependence of the SEP peak *** spectra indices rise near the CIR boundaries and drop near the stream interface(SI).The adiabatic effect makes the spatial variability of the spectral index *** spectral index could be sim

关键词： solar energetic particle (SEP) corotating interaction regions (CIR) magnetohydrodynamic (MHD)

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Influence of upstream solar wind on magnetic field distribution in the Martian nightside ionosphere

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earth and Planetary Physics 2024年第5期8卷 728-741页

作者： JiaWei Gao ZhaoJin Rong Qi Zhang Anna Mittelholz Chi Zhang Yong Wei Key Laboratory of earth and Planetary Physics Institute of Geology and Geophysics Chinese Academy of Sciences College of earth and Planetary sciences University of Chinese Academy of Sciences Swedish Institute of space Physics Department of earth sciences Center for space Physics and Department of Astronomy Boston University

Using over eight years of Mars Atmosphere and Volatile Evolutio N （MAVEN） data,from November 2014 to May 2023,we have investigated the Martian nightside ionospheric magnetic field distribution under the influence of upstream solar wind drivers,including the interplanetary magnetic field intensity (∣BIMF∣),solar wind dynamic pressure （PSW）,solar extreme ultraviolet flux （EUV）,and Martian seasons （Ls）.Our analysis reveals pronounced correlations between magnetic field residuals and both∣BIMF∣and *** observed with EUV flux and Lswere weaker—notably,magnetic field residuals increased during periods of high EUV flux and at Mars *** find that the IMF penetrates to an altitude of 200 km under a wide range of upstream conditions,penetrating notably deeper under high∣BIMF∣*** analysis also indicates that EUV flux and IMF cone angle have minimal impact on IMF penetration *** findings provide useful constraints on the dynamic nature of Martian atmospheric escape processes and their evolution,suggesting that historical solar wind conditions may have facilitated deeper IMF penetration and higher rates of ionospheric escape than are observed ***,by establishing criteria for magnetic‘quiet’conditions,this study offers new insights into the planet’s magnetic environment under varying solar wind influences,knowledge that should help refine models of the Martian crustal magnetic field.

关键词： Martian magnetic field external magnetic field upstream solar wind drivers IMF penetration altitude magnetic field activity indices

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Concise extraction and characterization of the pore-throat network in unconventional hydrocarbon reservoirs: A new perspective

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Petroleum Science 2024年第3期21卷 1474-1487页

作者： Shu-Heng Du Yong-Min Shi State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing100190China school of Engineering Science University of Chinese Academy of SciencesBeijing100049China school of earth and space sciences Peking UniversityBeijing100871China

In this study,a new image-based method for the extraction and characterization of pore-throat network for unconventional hydrocarbon storage and exploitation is proposed.“Pore-throat solidity”,which is analogous to particle solidity,and a new method for automatic identification of pores and throats in tight sandstone oil reservoirs are ***,the“pore-throat combination”and“pure pore”are defined and distinguished by drawing the cumulative probability curve of the pore-throat solidity and by selecting an appropriate cutoff *** the discrete grid set is recognized as a pore-throat combination,Legendre ellipse fitting and minimum Feret diameter are *** the pore and throat grid sets are identified as pure pores,the pore diameter can be directly *** the new method,the analytical results for the physical parameters and pore radius agree well with most prior *** results comparing the maximum ball and the new model could also prove the accuracy of the latter's in micro and nano *** new model provides a more practical theoretical basis and a new calculation method for the rapid and accurate evaluation of the complex processes of oil migration.

关键词： Hydrocarbon exploitation Pore Throat Porous media Identification

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A holistic perspective on earth system science

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Science China earth sciences 2024年第10期67卷 3013-3040页

作者： Yongfei ZHENG Zhengtang GUO Nianzhi JIAO Mu MU Shilong PIAO Suiyan FU Dinghui YANG Maoyan ZHU State Key Laboratory of Lithospheric and Environmental Coevolution School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei 230026China State Key Laboratory of Lithospheric and Environmental Coevolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China school of Ocean and earth sciences Xiamen UniversityXiamen 361102China Department of Atmospheric and Oceanic sciences Fudan UniversityShanghai 200438China school of Environment Peking UniversityBeijing 100871China school of earth and space sciences Peking UniversityBeijing 100871China Department of Mathematical sciences Tsinghua UniversityBeijing 100084China Nanjing Institute of Geology and Palaeontology Chinese Academy of SciencesNanjing 210008China

earth system can be categorized into three parts, solid earth system, surface earth system, and Sun-earth space system. These three subsystems not only have mutual transmission and coupling relationships in both energy and matter but also involve multiple scales from microscopic to macroscopic. earth system science is characterized by its globality and unity with a holistic view and a systematic view at multiple scales in both space and time. It focuses not only on the physical, chemical and biological interactions between various geospheres but also on the properties, behaviors, processes, and mechanisms of the entire earth and its spheres. Although significant progress has been made in the study of internal disciplines of these three subsystems,there is still insufficient understanding of their overall behavior and interactions between individuals, thus facing challenges of different types and levels. The solid earth system is composed of the crust, mantle, and core. Existing observational techniques struggle to penetrate deep into the mantle, making direct observation and data acquisition difficult;the extreme environments within earth, such as high temperature, high pressure, and strong magnetic fields, also pose great challenges to observational equipment and scientific experiments. The surface earth system is an open complex mega-system, in which there are complex interactions and feedback mechanisms among its geospheres(such as atmosphere, hydrosphere, biosphere, pedosphere and lithosphere), leading to difficulties in understanding of its overall behavior and long-term evolution. Biological activities have become increasingly significant in affecting the surface earth system. The coupling between the internal and external earth systems becomes more complex. Distinguishing and quantifying the impacts of earth spherical interactions and biological activities on the surface earth system is a major challenge. The Sun-earth space system involves multiple physical

关键词： earth's interior earth's exterior Geospheres Energy exchange Material transfer

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