Identification of the meta-instable stress state and study of its mechanism and evolution of relevant physical fields would be of great significance for determination of potential seismic risks and estimation of criti...Identification of the meta-instable stress state and study of its mechanism and evolution of relevant physical fields would be of great significance for determination of potential seismic risks and estimation of critical times. In laboratory experiments, that the specimen enters the meta-instable is marked by accelerated stress release. Could we use the experimental result to identify the earthquake in natural conditions? Because the observational data from one station can only reflect the stress state beneath this station, the key problem for identification of the meta-instability is how to recognize regional stress state through observational data from many stations. In this work, we choose the evolution of the temperature field over varied deformation stages during a stick-slip event on a 5 bending fault as an example, and attempt to find the response features of the physical quantity when the fault enters the meta-instable state. We discuss the characteristics of stages for the stress build-up, stress-time process deviating from linearity before instability, meta-instability, instability, and post-instability, respectively. The result shows that the fault instability slide is a conversion process from independent activities of each fault segment to synergism activity. The instability implies completion of the synergism. The stage deviating from linearity is the onset of stress release, and it is also the onset of the synergism. At the meta-instability stages, stress release becomes dominant, while the synergism tends to finish. Therefore, the analysis of the regional overall stress state should not start from individual stations, and instead it should begin with the evolution of the whole deformation field.展开更多
At GMT time 13：19, August 8, 2017, an M1.0 earthquake struck the Jiuzhaigou region in Sichuan Province, China, causing severe damages and casualties. To investigate the source properties, seismogenic structures, and ...At GMT time 13：19, August 8, 2017, an M1.0 earthquake struck the Jiuzhaigou region in Sichuan Province, China, causing severe damages and casualties. To investigate the source properties, seismogenic structures, and seismic hazards, we systematically analyzed the tectonic environment, crustal velocity structure in the source region, source parameters and rupture process, Coulomb failure stress changes, and 3-D features of the rupture plane of the Jiuzhaigou earthquake. Our results indicate the following： （1） The Jiuzhaigou earthquake occurred on an unmarked fault belonging to the transition zone of the east Kunlun fault system and is located northwest of the Huya fault. （2） Both the mainshock and aftershock rupture zones are located in a region where crustal seismic velocity changes dramatically. Southeast to the source region, shear wave velocity at the middle to lower crust is significantly low, but it rapidly increases northeastward and lies close to the background velocity across the rupture fault. （3） The aftershock zone is narrow and distributes along the northwest-southeast trend, and most aftershocks occur within a depth range of 5-20 km. （4） The focal mechanism of the Jiuzhaigou earthquake indicates a left-lateral strike-slip fault, with strike, dip, and rake angles of 152~, 74~ and 8~, respectively. The hypocenter depth measures 20 km, whereas the centroid depth is about 6 kin. The co-seismic rupture mainly concentrates at depths of 3-13 km, with a moment magnitude （Mw） of 6.5. （5） The co-seismic rupture also strengthens the Coulomb failure stress at the two ends of the rupture fault and the east segment of the Tazang fault. Aftershocks relocation results together with geological surveys indicate that the causative fault is a near vertical fault with notable spatial variations： dip angle varies within 660-89~ from northwest to southeast and the average dip angle measures -84~. The results of this work are of fundamental importance for further studies on the source character展开更多
A growing body of evidence shows that volcanism near the Permian-Triassic boundary（PTB） may be crucial in triggering the Permian–Triassic（P–Tr） mass extinction. Thus, the ash beds near the PTB in South China may...A growing body of evidence shows that volcanism near the Permian-Triassic boundary（PTB） may be crucial in triggering the Permian–Triassic（P–Tr） mass extinction. Thus, the ash beds near the PTB in South China may carry information on this event. Three volcanic ash layers, altered to clay, outcropped in the PTB beds in Zunyi Section, Guizhou Province, Southwest China. The U-Pb ages, trace elements, and Hf-isotope compositions of zircon grains from these three ash beds were analyzed using LA-ICPMS and LA-MC-ICPMS. The zircons are mainly magmatic in origin（241-279 Ma） except for two inherited/xenocrystic zircons（939 and 2 325 Ma）. The ages of these magmatic zircons indicate three episodes of magmatism which occurred around the MiddleLate Permian boundary（-261.5 Ma, MLPB）, the Wuchiapingian-Changhsingian boundary（-254.5 Ma, WCB）, and the PTB（-250.5 Ma）, respectively. The first two episodes of magmatism near the MLPB and WCB may be attributed to magmatic inheritance or re-deposition. All magmatic zircons share similar trace-element and Hf-isotope compositions. They have Y, Hf, Th and U contents and Nb/Ta ratios are typical of zircons from silicic calc-alkaline magmas. These zircons also exhibit enriched Hf-isotope compositions with _（εHf）（t） values of-11.4 to ＋0.2, which suggests that the three magmatic episodes involved melting of the continental crust. The more enriched Hf-isotope composition （_（εHf）（t）=-11.4--4.8） of Bed ZY13（-250.5 Ma） implies more input of ancient crustal material in the magma. Integration of the Hf-isotope and trace-element compositions of magmatic zircons suggest that these three episodes of magmatism may take place along the convergent continent margin in or near southwestern South China as a result of the closure of the Palaeo-Tethys Ocean.展开更多
Granite is the dominant rock type in Earth’s continental crust.The origin of granite can be directly or indirectly related to the fractional crystallization of mantle-derived basaltic melt or the reworking of pre-exi...Granite is the dominant rock type in Earth’s continental crust.The origin of granite can be directly or indirectly related to the fractional crystallization of mantle-derived basaltic melt or the reworking of pre-existing continental or oceanic crust, which contribute to the growth of continental crust. Among the various types of granites, the peraluminous leucogranites in the Himalayan orogen, which are high in SiO_2(>73%) and low in mafic minerals (<5%),展开更多
Plate tectonics plays a critical role in modulating atmospheric CO_(2)concentration on the geological timescale(≥106year).A growing consensus on tectonic and Earth’s CO_(2)history in the Cenozoic and deeper time pro...Plate tectonics plays a critical role in modulating atmospheric CO_(2)concentration on the geological timescale(≥106year).A growing consensus on tectonic and Earth’s CO_(2)history in the Cenozoic and deeper time provides solid restrictions and standards for testing tectonic carbon processes against global measurements.Despite this,modeling the causal relationship between tectonic events and atmospheric CO_(2)levels remains a challenge.We examine the current state of the global tectonic CO_(2)research and suggest a conceptual workflow for numerical experiments that integrates plate tectonics and deep carbon dynamics.Future tectonic carbon cycle modeling should include at least four modules:(1)simulation of carbon-carrying processes,such as carbon ingassing and outgassing at the scale of minerals;(2)calculation of CO_(2)fluxes in tectonic settings like subduction,mantle plume,and plate rifting;(3)reconstruction of carbon cycling within the plates-scale tectonic scenario,particularly involving the processes of supercontinent convergence and dispersion;and(4)comparison with atmospheric CO_(2)history data and iterations,aiming to find the coincidental link between different tectonic carbon fluxes and climate changes.According to our analysis,the recent advancements in each of the four modules have paved the path for a more general assembly.We envision that the large variety of carbon transportation parameters across more than ten orders of magnitude in both time and space is the primary technical hurdle in simulating tectonic carbon dynamics.We propose a boundary-condition-connected approach for simulating the global carbon cycle to realize carbon exchange between the solid earth and surface spheres.展开更多
Lunar exploration is deemed crucial for uncovering the origins of the Earth-Moon system and is the first step for advancing humanity’s exploration of deep space.Over the past decade,the Chinese Lunar Exploration Prog...Lunar exploration is deemed crucial for uncovering the origins of the Earth-Moon system and is the first step for advancing humanity’s exploration of deep space.Over the past decade,the Chinese Lunar Exploration Program(CLEP),also known as the Chang’e(CE)Project,has achieved remarkable milestones.It has successfully developed and demonstrated the engineering capability required to reach and return from the lunar surface.Notably,the CE Project has made historic firsts with the landing and on-site exploration of the far side of the Moon,along with the collection of the youngest volcanic samples from the Procellarum KREEP Terrane.These achievements have significantly enhanced our understanding of lunar evolution.Building on this success,China has proposed an ambitious crewed lunar exploration strategy,aiming to return to the Moon for scientific exploration and utilization.This plan encompasses two primary phases:the first crewed lunar landing and exploration,followed by a thousand-kilometer scale scientific expedition to construct a geological cross-section across the lunar surface.Recognizing the limitations of current lunar exploration efforts and China’s engineering and technical capabilities,this paper explores the benefits of crewed lunar exploration while leveraging synergies with robotic exploration.The study refines fundamental lunar scientific questions that could lead to significant breakthroughs,considering the respective engineering and technological requirements.This research lays a crucial foundation for defining the objectives of future lunar exploration,emphasizing the importance of crewed missions and offering insights into potential advancements in lunar science.展开更多
Numerous new records of Ferganiella, Podozamites, and Schidolepium, including a new species, Ferganiella ivantsovii sp. nov., are described from the Early Jurassic(Toarcian) Middle Subformation of the Prisayan Formati...Numerous new records of Ferganiella, Podozamites, and Schidolepium, including a new species, Ferganiella ivantsovii sp. nov., are described from the Early Jurassic(Toarcian) Middle Subformation of the Prisayan Formation from the Euro-Sinian paleofloristic region in the Irkutsk Basin, Eastern Siberia, Russia. An analysis of the paleogeographic distribution of Ferganiella and Podozamites shows that both genera were the most diverse and numerous in the East Asian province of the Euro-Sinian region and in the Northern Chinese province of the Siberian region during the Early and Middle Jurassic. These phytochoria were located in the subtropical and temperate subtropical climate zones, which allows us to consider Ferganiella and Podozamites as thermophilic plants, which are important indicators of the Early Toarcian climatic optimum. Their abundance in the Irkutsk Basin thus may indicate Early Toarcian warming;further abundant Schidolepium cones, which produced Araucariacites pollen, typical for Euro-Sinian flora complement the scenario. Thus, the new finds are the first macrofloristic indicators of the Toarcian climatic optimum in the Irkutsk Basin.展开更多
Recent studies have shown that Cu-rich sulfide accumulates in the lower continental crust and serves as a critical reservoir to balance Cu depletion in the upper crust.Recycling of Cu in the lower crust is also assume...Recent studies have shown that Cu-rich sulfide accumulates in the lower continental crust and serves as a critical reservoir to balance Cu depletion in the upper crust.Recycling of Cu in the lower crust is also assumed to be a major metal source for non-arc setting porphyry Cu deposits.To test this hypothesis and further explore the behavior of Cu in the lower crust,we analyzed the elemental and Cu isotopic compositions of lower crustal rocks from different geological domains.The collected samples include hornblendites from the Kohistan arc,granulite xenoliths and hornblendites from the Gangdese arc,hornblendites and gabbros from the Laiyuan complex in the North China Craton,and hornblendite xenoliths from the western margin of the Yangtze Craton.These lower crustal rocks have experienced varying degrees of primary or secondary sulfide accumulation,with significantly varied Cu contents(11.2 to 145 ppm)andδδ^(65)(1.05‰to 1.40‰).Petrography and geochemistry reveal varying degrees of metasomatism and fluid interaction in these rocks,and based on this,they can be further divided into three groups:Group I includes the Gangdese granulites and Yunnan hornblendites,which perhaps experienced significant metasomatism.This suite of rocks shows enrichment ofδ^(65)(dδ^(65)=0.01‰to 1.40‰),positively correlated with metasomatism(dδ^(65)vs.Ce/Pb).We suggest the secondary sulfides which transformed from sulfates during the interaction between lower crust and arc magma are dominant in these rocks,so the feature of heavy isotope enrichment is inherited.Group II includes Laiyuan hornblendites and gabbros,derived from the same parental magma and emplaced at different depths(hornblendites,23.3–28.1 km;gabbros 8.4–11.1 km).The Cu isotopic compositions are strongly fractionated between these two kinds of rocks,with low dδ^(65)in the hornblendites(0.00‰to 0.28‰)and highly polarized dδ^(65)in the gabbros(1.05‰to 0.81‰).Geochemical indicators and mineral assemblages reveal that fluid interaction is most likely re展开更多
It has been proposed by Zhang et al.[1] that the northern part of the North Chirm Craton (NCC) was connected to the north-western part of the North Australian Craton (NAC) in the Proterozoic, mainly based on the radia...It has been proposed by Zhang et al.[1] that the northern part of the North Chirm Craton (NCC) was connected to the north-western part of the North Australian Craton (NAC) in the Proterozoic, mainly based on the radial geometry of correlative -1.32 Ga dyke swarms in the two cratons (Fig. la). While the hypothetical connection between the NCC and the NAC was thought to be paleomagnetically permissible at ~1.80- 1.78Ga but w让h a slightly different configuration [2], the exact duration of either configuration is uncertain (e.g.,[2,3]).展开更多
Two new species of Eretmophyllum Thomas are described from the lower(Toarcian)and upper(Aalenian)Prisayan Formation of the Irkutsk Basin,Eastern Siberia,Russia based on distinct morphological and cuticular features of...Two new species of Eretmophyllum Thomas are described from the lower(Toarcian)and upper(Aalenian)Prisayan Formation of the Irkutsk Basin,Eastern Siberia,Russia based on distinct morphological and cuticular features of the leaves that distinguish them from other species of the genus.Eretmophyllum polypapillosum sp.nov.is characterized by the presence of 2-3 papillae on the lower and upper epidermis of ordinary cells.Taphonomically,the leaf burials of E.polypapillosum sp.nov.indicate that it preferred mesophilic forests developed on river terraces and/or low watersheds.Eretmophyllum yershowskiensis sp.nov.is represented exclusively by leaf cuticles extracted by coal maceration,and it probably inhabited the low banks of peat bogs.The presence of the genus Eretmophyllum in the Early Jurassic of France and Eastern Siberia shows that it was already widespread in the territory of Eurasia,distributed from Western Europe to Eastern Siberia.This indicates the possible existence of Eretmophyllum species elsewhere in the Early Jurassic such as Central Asia and Northwest China.展开更多
Recent geochronological studies in southern Siberia support a Siberian assembly between 2.1 and 1.8 Ga. This broadly coincides with major orogenic events in most other Precambrian continents including Laurentia. In th...Recent geochronological studies in southern Siberia support a Siberian assembly between 2.1 and 1.8 Ga. This broadly coincides with major orogenic events in most other Precambrian continents including Laurentia. In the Mesoproterozoic, Siberia was mainly an area of stable platform sedimentation whereas Laurentia underwent a continental growth from southeast. Lack of traces of the Grenville orogeny in Siberia suggests its peripheral position in Rodinia. The eastern （Uchur- Maya area） and western （Yenisei area） Siberian margins probably faced oceans during the Meso- and Neoproterozoic. Recent geological, geochronological, geochemical and paleomagnetic data suggest integrity of Siberia and Laurentia in the Meso- and early Neoproterozoic with the Siberian southern margin close to the northern margin of Laurentia. However, some ‘intervening＇ continental blocks were probably located between these two cratons. The 750-720 Ma igneous event was probably related to the rifting between Siberia and Laurentia and the opening of the Paleo-Asian Ocean, causing the development of a passive margin sedimentary succession in southern Siberia.展开更多
The Late Paleozoic–Early Mesozoic Mongol-Okhotsk Ocean extended between the Siberian and Amur–North China continents.The timing and modalities of the oceanic closure are widely discussed.It is largely accepted that ...The Late Paleozoic–Early Mesozoic Mongol-Okhotsk Ocean extended between the Siberian and Amur–North China continents.The timing and modalities of the oceanic closure are widely discussed.It is largely accepted that the ocean closed in a scissor-like manner from southwest to northeast(in modern coordinates),though the timing of this process remains uncertain.Recent studies have shown that both western(West Transbaikalia)and eastern(Dzhagda)parts of the ocean closed almost simultaneously at the Early–Middle Jurassic boundary.However,little information on the key central part of the oceanic suture zone is available.We performed U-Pb(LA-ICP-MS)dating of detrital zircon from wellcharacterized stratigraphic sections of the central part of the Mongol-Okhotsk suture zone.These include the initial marine and final continental sequences of the East Transbaikalia Basin,deposited on the northern Argun-Idemeg terrane basement.We provide new stratigraphic ages for the marine and continental deposits.This revised chronostratigraphy allows assigning an age of~165–155 Ma,to the collisionrelated flexure of the northern Argun-Idemeg terrane and the development of a peripheral foreland basin.This collisional process took place 5 to10 million years later than in the western and eastern parts of the ocean.We demonstrate that the northern Argun-Idemeg terrane was the last block to collide with the Siberian continent,challenging the widely supported scissor-like model of closure of the MongolOkhotsk Ocean.Different segments of the ocean closed independently,depending on the initial shape of the paleo continental margins.展开更多
The Early Cretaceous aluminous A-type granites in the Lower Yangtze River belt(LYRB)can provide important insights into the Mesozoic magmatism in eastern China,but their origin remains highly controversial.In this stu...The Early Cretaceous aluminous A-type granites in the Lower Yangtze River belt(LYRB)can provide important insights into the Mesozoic magmatism in eastern China,but their origin remains highly controversial.In this study,radiogenic Ca-Nd isotopic analysis was performed for syenite porphyry and alkali-feldspar granite porphyry of the Yangshan pluton,a typical aluminous A-type granitic intrusion in the LYRB,to constrain its source and geodynamic setting.The results show thatε_(Ca)(126 Ma),ε_(Nd)(126 Ma)and K/Ca_(source) of the syenite porphyry range from-0.24 to+0.96,-7.2 to-6.0,and 0.31 to 1.26,respectively.The corresponding values for the alkali-feldspar granite porphyry range from 0.26 to 0.84,-8.0 to-6.1,and 0.79 to 1.08,respectively.Binary mixing modeling indicates that they were originated from the same sources with different proportion,namely,a mixing of 50%to 75%Neoproterozoic crust and 50%to 25%asthenospheric mantle.Together with previous works,we propose that the Early Cretaceous subduction of the ridge between the Pacific and Izanagi plates was responsible for the formation of the aluminous A-type granites in the LYRB.展开更多
Several generations of mafic dyke swarms of different ages and geochemical characteristics cut Precambrian rocks of the southern part of the Siberian craton(Irkutsk Promontory).Each generation of dykes is related to a
Extreme and prolonged rainfall in the Tunka Ridge caused several debris flows in the vicinity of the Arshan village(Siberia, Russia) on June 28, 2014. These debris flows, in spite of similar geological conditions, had...Extreme and prolonged rainfall in the Tunka Ridge caused several debris flows in the vicinity of the Arshan village(Siberia, Russia) on June 28, 2014. These debris flows, in spite of similar geological conditions, had different velocity, peak discharge and alluvial fan volume values. The flow velocity was from 3.5 m/s to 19.6 m/s, the peak discharge ranged from 63 m3/s to 13566 m3/s, and the alluvial fan volume varied from 4.13×103 to 8.45×105 m3. Such a great range of values is due to the morphometric parameters of the debris flow basins. The article deals with the influence of morphometric parameters of debris flow basins, such as the basin area, the average slope, Melton ratio, relief ratio on the debris flow velocity, peak discharge and volume of alluvial fans. In this debris flow event the average values of slope angle and total basin relief of the debris flow basins did not affect the values of debris flow velocity, peak discharge and alluvial fan volume. The highest correlations were observed with the debris flow basin area that was connected with the water inflow volume into the debris flow basins during the rainfall. The unequal water distribution among debris flow basins also had an impact on the debris flow velocity, peak discharge and volume of alluvial fans.展开更多
We present a summary of late Paleoproterozoic to Neoproterozoic mafic magmatism in the Siberian craton which allows us distinguish following main pulses of mafic dyke emplacement:1)1860–1850 Ma mafic dykes are locali...We present a summary of late Paleoproterozoic to Neoproterozoic mafic magmatism in the Siberian craton which allows us distinguish following main pulses of mafic dyke emplacement:1)1860–1850 Ma mafic dykes are localized within the展开更多
The paper reviews goals and objectives, stages and components of a seismotectonic study conducted in Eastern Siberia, Russia. Based on a comprehensive analysis of geological and geophysical data, our study establishes...The paper reviews goals and objectives, stages and components of a seismotectonic study conducted in Eastern Siberia, Russia. Based on a comprehensive analysis of geological and geophysical data, our study establishes whether the local earthquakes are of tectonic origin and reveals relationships among earthquakes with recent geodynamic processes in the area under study. Seismic hazard assessment and evaluation of tectonic processes are the two major closely interrelated aspects of seismotectonic studies. A seismotectonic study is generally combined with a seismic study and conducted prior to the stage of detailed seismic zonation (DSZ) which is followed by seismic micro-zonation (SMZ). In three stages of the seismotectonic study, we analyze specific geological structures, reveal the regional dynamics of seismotectonic processes, clarify details of potential seismic hazard locations and identify sites of the potential instantaneous deformation of the crust which may take place due to active faulting. Based on results of our longterm studies, a seismotectonic zonation map of Eastern Siberia is compiled. The paper briefly reviews the methods of mapping and refers to data on active faults and neotectonic structures revealed in the area under study, which are closely related to regional earthquake sources.展开更多
The Mesozoic geodynamic evolution of Transbaikalia has been largely controlled by the scissors-like closure of the Mongol-Okhotsk Ocean that separated Siberia from Mongolia-North China continents.Following the oceanic...The Mesozoic geodynamic evolution of Transbaikalia has been largely controlled by the scissors-like closure of the Mongol-Okhotsk Ocean that separated Siberia from Mongolia-North China continents.Following the oceanic closure,the tectonic evolution of that region was characterized by collisional uplift and subsequent extension that gave rise to the formation of metamorphic core complexes.This complex tectonic setting prevailed simultaneously between 150 Ma and 110 Ma both in Transbaikalia,North Mongolia,and within the North China Craton.Published paleobotanical and paleontological data show that the oldest Mesozoic basins had formed in western Transbaikalia before the estimated age of extension onset.However no precise geochronological age is available for the onset of extension in Transbaikalia.The Tugnuy Basin,as probably the oldest Mesozoic basin in western Transbaikalia,is a key obj ect to date the onset of extension and following changes in tectonic setting.In this study,U-Pb(LA-ICP-MS)dating of detrital zircons from three key Jurassic sediment formations of the Tugnuy Basin are used to identify the potential source areas of the sediments,understand the changes in sediment routing and provide insights on the topographic evolution of western Transbaikalia.Our results show several significant changes in tectonic regime after the closure of the Mongol-Okhotsk Ocean.A wide uplifted plateau formed during the closure of the Mongol-Okhotsk Ocean,determining the Early Jurassic drainage system reaching the AngaraVitim batholith to the north and shedding sediments to the continental margin to the South.The following collisional event at the end of the Early Jurassic led to the uplift of the collision zone,which partially inverted the drainage system toward the North.A strike-slip displacement induced by the oblique collision initiated some of the early Transbaikalian depressions,such as the Tugnuy Basin at about 168 Ma.A phase of basin inversion,marked by folding and erosion of the Upper Jurassic sediments,could corre展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos. 40872129, 41172180)
文摘Identification of the meta-instable stress state and study of its mechanism and evolution of relevant physical fields would be of great significance for determination of potential seismic risks and estimation of critical times. In laboratory experiments, that the specimen enters the meta-instable is marked by accelerated stress release. Could we use the experimental result to identify the earthquake in natural conditions? Because the observational data from one station can only reflect the stress state beneath this station, the key problem for identification of the meta-instability is how to recognize regional stress state through observational data from many stations. In this work, we choose the evolution of the temperature field over varied deformation stages during a stick-slip event on a 5 bending fault as an example, and attempt to find the response features of the physical quantity when the fault enters the meta-instable state. We discuss the characteristics of stages for the stress build-up, stress-time process deviating from linearity before instability, meta-instability, instability, and post-instability, respectively. The result shows that the fault instability slide is a conversion process from independent activities of each fault segment to synergism activity. The instability implies completion of the synergism. The stage deviating from linearity is the onset of stress release, and it is also the onset of the synergism. At the meta-instability stages, stress release becomes dominant, while the synergism tends to finish. Therefore, the analysis of the regional overall stress state should not start from individual stations, and instead it should begin with the evolution of the whole deformation field.
基金funded by the Seismological Bureau Spark Program Project(Grant No.XH15007)the National Natural Science Foundation of China(Grant Nos.41604058,41574057,41621091)the Sichuan-Yunnan National Seismological Monitoring and Prediction Experimental Station Project(Grant No.2016CESE0204)
文摘At GMT time 13：19, August 8, 2017, an M1.0 earthquake struck the Jiuzhaigou region in Sichuan Province, China, causing severe damages and casualties. To investigate the source properties, seismogenic structures, and seismic hazards, we systematically analyzed the tectonic environment, crustal velocity structure in the source region, source parameters and rupture process, Coulomb failure stress changes, and 3-D features of the rupture plane of the Jiuzhaigou earthquake. Our results indicate the following： （1） The Jiuzhaigou earthquake occurred on an unmarked fault belonging to the transition zone of the east Kunlun fault system and is located northwest of the Huya fault. （2） Both the mainshock and aftershock rupture zones are located in a region where crustal seismic velocity changes dramatically. Southeast to the source region, shear wave velocity at the middle to lower crust is significantly low, but it rapidly increases northeastward and lies close to the background velocity across the rupture fault. （3） The aftershock zone is narrow and distributes along the northwest-southeast trend, and most aftershocks occur within a depth range of 5-20 km. （4） The focal mechanism of the Jiuzhaigou earthquake indicates a left-lateral strike-slip fault, with strike, dip, and rake angles of 152~, 74~ and 8~, respectively. The hypocenter depth measures 20 km, whereas the centroid depth is about 6 kin. The co-seismic rupture mainly concentrates at depths of 3-13 km, with a moment magnitude （Mw） of 6.5. （5） The co-seismic rupture also strengthens the Coulomb failure stress at the two ends of the rupture fault and the east segment of the Tazang fault. Aftershocks relocation results together with geological surveys indicate that the causative fault is a near vertical fault with notable spatial variations： dip angle varies within 660-89~ from northwest to southeast and the average dip angle measures -84~. The results of this work are of fundamental importance for further studies on the source character
基金supported by an aid grant from Chengdu Center, China Geological Survey (No. 12120113049100-1)the National Natural Science Foundations (Nos. 40572068, 40839903 and 41272044)+1 种基金the "111" Program (No. B08030)an aid grant (No. GBL11206) from the State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Wuhan), China
文摘A growing body of evidence shows that volcanism near the Permian-Triassic boundary（PTB） may be crucial in triggering the Permian–Triassic（P–Tr） mass extinction. Thus, the ash beds near the PTB in South China may carry information on this event. Three volcanic ash layers, altered to clay, outcropped in the PTB beds in Zunyi Section, Guizhou Province, Southwest China. The U-Pb ages, trace elements, and Hf-isotope compositions of zircon grains from these three ash beds were analyzed using LA-ICPMS and LA-MC-ICPMS. The zircons are mainly magmatic in origin（241-279 Ma） except for two inherited/xenocrystic zircons（939 and 2 325 Ma）. The ages of these magmatic zircons indicate three episodes of magmatism which occurred around the MiddleLate Permian boundary（-261.5 Ma, MLPB）, the Wuchiapingian-Changhsingian boundary（-254.5 Ma, WCB）, and the PTB（-250.5 Ma）, respectively. The first two episodes of magmatism near the MLPB and WCB may be attributed to magmatic inheritance or re-deposition. All magmatic zircons share similar trace-element and Hf-isotope compositions. They have Y, Hf, Th and U contents and Nb/Ta ratios are typical of zircons from silicic calc-alkaline magmas. These zircons also exhibit enriched Hf-isotope compositions with _（εHf）（t） values of-11.4 to ＋0.2, which suggests that the three magmatic episodes involved melting of the continental crust. The more enriched Hf-isotope composition （_（εHf）（t）=-11.4--4.8） of Bed ZY13（-250.5 Ma） implies more input of ancient crustal material in the magma. Integration of the Hf-isotope and trace-element compositions of magmatic zircons suggest that these three episodes of magmatism may take place along the convergent continent margin in or near southwestern South China as a result of the closure of the Palaeo-Tethys Ocean.
基金supported by the National Natural Science Foundation of China(41772058 and 41402055)
文摘Granite is the dominant rock type in Earth’s continental crust.The origin of granite can be directly or indirectly related to the fractional crystallization of mantle-derived basaltic melt or the reworking of pre-existing continental or oceanic crust, which contribute to the growth of continental crust. Among the various types of granites, the peraluminous leucogranites in the Himalayan orogen, which are high in SiO_2(>73%) and low in mafic minerals (<5%),
基金supported by the National Natural Science Foundation of China(Grant Nos.41888101 and 41625016)XPLORER PRIZE。
文摘Plate tectonics plays a critical role in modulating atmospheric CO_(2)concentration on the geological timescale(≥106year).A growing consensus on tectonic and Earth’s CO_(2)history in the Cenozoic and deeper time provides solid restrictions and standards for testing tectonic carbon processes against global measurements.Despite this,modeling the causal relationship between tectonic events and atmospheric CO_(2)levels remains a challenge.We examine the current state of the global tectonic CO_(2)research and suggest a conceptual workflow for numerical experiments that integrates plate tectonics and deep carbon dynamics.Future tectonic carbon cycle modeling should include at least four modules:(1)simulation of carbon-carrying processes,such as carbon ingassing and outgassing at the scale of minerals;(2)calculation of CO_(2)fluxes in tectonic settings like subduction,mantle plume,and plate rifting;(3)reconstruction of carbon cycling within the plates-scale tectonic scenario,particularly involving the processes of supercontinent convergence and dispersion;and(4)comparison with atmospheric CO_(2)history data and iterations,aiming to find the coincidental link between different tectonic carbon fluxes and climate changes.According to our analysis,the recent advancements in each of the four modules have paved the path for a more general assembly.We envision that the large variety of carbon transportation parameters across more than ten orders of magnitude in both time and space is the primary technical hurdle in simulating tectonic carbon dynamics.We propose a boundary-condition-connected approach for simulating the global carbon cycle to realize carbon exchange between the solid earth and surface spheres.
基金supported by the National Natural Science Foundation of China(L2224032)the Research Project on the Discipline Development Strategy of Academic Divisions of the Chinese Academy of Sciences(XK2022DXC004).
文摘Lunar exploration is deemed crucial for uncovering the origins of the Earth-Moon system and is the first step for advancing humanity’s exploration of deep space.Over the past decade,the Chinese Lunar Exploration Program(CLEP),also known as the Chang’e(CE)Project,has achieved remarkable milestones.It has successfully developed and demonstrated the engineering capability required to reach and return from the lunar surface.Notably,the CE Project has made historic firsts with the landing and on-site exploration of the far side of the Moon,along with the collection of the youngest volcanic samples from the Procellarum KREEP Terrane.These achievements have significantly enhanced our understanding of lunar evolution.Building on this success,China has proposed an ambitious crewed lunar exploration strategy,aiming to return to the Moon for scientific exploration and utilization.This plan encompasses two primary phases:the first crewed lunar landing and exploration,followed by a thousand-kilometer scale scientific expedition to construct a geological cross-section across the lunar surface.Recognizing the limitations of current lunar exploration efforts and China’s engineering and technical capabilities,this paper explores the benefits of crewed lunar exploration while leveraging synergies with robotic exploration.The study refines fundamental lunar scientific questions that could lead to significant breakthroughs,considering the respective engineering and technological requirements.This research lays a crucial foundation for defining the objectives of future lunar exploration,emphasizing the importance of crewed missions and offering insights into potential advancements in lunar science.
文摘Numerous new records of Ferganiella, Podozamites, and Schidolepium, including a new species, Ferganiella ivantsovii sp. nov., are described from the Early Jurassic(Toarcian) Middle Subformation of the Prisayan Formation from the Euro-Sinian paleofloristic region in the Irkutsk Basin, Eastern Siberia, Russia. An analysis of the paleogeographic distribution of Ferganiella and Podozamites shows that both genera were the most diverse and numerous in the East Asian province of the Euro-Sinian region and in the Northern Chinese province of the Siberian region during the Early and Middle Jurassic. These phytochoria were located in the subtropical and temperate subtropical climate zones, which allows us to consider Ferganiella and Podozamites as thermophilic plants, which are important indicators of the Early Toarcian climatic optimum. Their abundance in the Irkutsk Basin thus may indicate Early Toarcian warming;further abundant Schidolepium cones, which produced Araucariacites pollen, typical for Euro-Sinian flora complement the scenario. Thus, the new finds are the first macrofloristic indicators of the Toarcian climatic optimum in the Irkutsk Basin.
基金supported by the National Natural Science Foundation of China (41888101 and 41625016)the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) (311021003)the National Key Research and Development Program of China (2022YFF0802800)。
基金supported by National Key R&D Program of China(2022YFF0800902)National Natural Science Foundation of China(No.42121002)+3 种基金the Open Research Project from the State Key Laboratory for Mineral Deposits Research,Nanjing University(2022-LAMD-K11)SinoProbe Lab 202204,State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences(GPMR202110)the 111 Project(B18048)the Fundamental Research Funds for the Central Universities(2-9-2019-034).
文摘Recent studies have shown that Cu-rich sulfide accumulates in the lower continental crust and serves as a critical reservoir to balance Cu depletion in the upper crust.Recycling of Cu in the lower crust is also assumed to be a major metal source for non-arc setting porphyry Cu deposits.To test this hypothesis and further explore the behavior of Cu in the lower crust,we analyzed the elemental and Cu isotopic compositions of lower crustal rocks from different geological domains.The collected samples include hornblendites from the Kohistan arc,granulite xenoliths and hornblendites from the Gangdese arc,hornblendites and gabbros from the Laiyuan complex in the North China Craton,and hornblendite xenoliths from the western margin of the Yangtze Craton.These lower crustal rocks have experienced varying degrees of primary or secondary sulfide accumulation,with significantly varied Cu contents(11.2 to 145 ppm)andδδ^(65)(1.05‰to 1.40‰).Petrography and geochemistry reveal varying degrees of metasomatism and fluid interaction in these rocks,and based on this,they can be further divided into three groups:Group I includes the Gangdese granulites and Yunnan hornblendites,which perhaps experienced significant metasomatism.This suite of rocks shows enrichment ofδ^(65)(dδ^(65)=0.01‰to 1.40‰),positively correlated with metasomatism(dδ^(65)vs.Ce/Pb).We suggest the secondary sulfides which transformed from sulfates during the interaction between lower crust and arc magma are dominant in these rocks,so the feature of heavy isotope enrichment is inherited.Group II includes Laiyuan hornblendites and gabbros,derived from the same parental magma and emplaced at different depths(hornblendites,23.3–28.1 km;gabbros 8.4–11.1 km).The Cu isotopic compositions are strongly fractionated between these two kinds of rocks,with low dδ^(65)in the hornblendites(0.00‰to 0.28‰)and highly polarized dδ^(65)in the gabbros(1.05‰to 0.81‰).Geochemical indicators and mineral assemblages reveal that fluid interaction is most likely re
基金supported for Australia Research Council (ARC) Laureate Fellowship Project (FL150100133)the National Natural Science Foundation of China (41890833)
文摘It has been proposed by Zhang et al.[1] that the northern part of the North Chirm Craton (NCC) was connected to the north-western part of the North Australian Craton (NAC) in the Proterozoic, mainly based on the radial geometry of correlative -1.32 Ga dyke swarms in the two cratons (Fig. la). While the hypothetical connection between the NCC and the NAC was thought to be paleomagnetically permissible at ~1.80- 1.78Ga but w让h a slightly different configuration [2], the exact duration of either configuration is uncertain (e.g.,[2,3]).
基金carried out in the framework of the topic of the state task of the Institute of the Earth's Crust,Siberian Branch of the Russian Academy of Sciences(Project No.121042700218-2)this work involved the Centre of Geodynamics and Geochronology equipment at the Institute of the Earth's Crust(Grant No.075-15-2021682)。
文摘Two new species of Eretmophyllum Thomas are described from the lower(Toarcian)and upper(Aalenian)Prisayan Formation of the Irkutsk Basin,Eastern Siberia,Russia based on distinct morphological and cuticular features of the leaves that distinguish them from other species of the genus.Eretmophyllum polypapillosum sp.nov.is characterized by the presence of 2-3 papillae on the lower and upper epidermis of ordinary cells.Taphonomically,the leaf burials of E.polypapillosum sp.nov.indicate that it preferred mesophilic forests developed on river terraces and/or low watersheds.Eretmophyllum yershowskiensis sp.nov.is represented exclusively by leaf cuticles extracted by coal maceration,and it probably inhabited the low banks of peat bogs.The presence of the genus Eretmophyllum in the Early Jurassic of France and Eastern Siberia shows that it was already widespread in the territory of Eurasia,distributed from Western Europe to Eastern Siberia.This indicates the possible existence of Eretmophyllum species elsewhere in the Early Jurassic such as Central Asia and Northwest China.
文摘Recent geochronological studies in southern Siberia support a Siberian assembly between 2.1 and 1.8 Ga. This broadly coincides with major orogenic events in most other Precambrian continents including Laurentia. In the Mesoproterozoic, Siberia was mainly an area of stable platform sedimentation whereas Laurentia underwent a continental growth from southeast. Lack of traces of the Grenville orogeny in Siberia suggests its peripheral position in Rodinia. The eastern （Uchur- Maya area） and western （Yenisei area） Siberian margins probably faced oceans during the Meso- and Neoproterozoic. Recent geological, geochronological, geochemical and paleomagnetic data suggest integrity of Siberia and Laurentia in the Meso- and early Neoproterozoic with the Siberian southern margin close to the northern margin of Laurentia. However, some ‘intervening＇ continental blocks were probably located between these two cratons. The 750-720 Ma igneous event was probably related to the rifting between Siberia and Laurentia and the opening of the Paleo-Asian Ocean, causing the development of a passive margin sedimentary succession in southern Siberia.
基金conducted in the frame of the grant of the Ministry of Science and High Education of the Russian Federation No.075-15-2019-1883。
文摘The Late Paleozoic–Early Mesozoic Mongol-Okhotsk Ocean extended between the Siberian and Amur–North China continents.The timing and modalities of the oceanic closure are widely discussed.It is largely accepted that the ocean closed in a scissor-like manner from southwest to northeast(in modern coordinates),though the timing of this process remains uncertain.Recent studies have shown that both western(West Transbaikalia)and eastern(Dzhagda)parts of the ocean closed almost simultaneously at the Early–Middle Jurassic boundary.However,little information on the key central part of the oceanic suture zone is available.We performed U-Pb(LA-ICP-MS)dating of detrital zircon from wellcharacterized stratigraphic sections of the central part of the Mongol-Okhotsk suture zone.These include the initial marine and final continental sequences of the East Transbaikalia Basin,deposited on the northern Argun-Idemeg terrane basement.We provide new stratigraphic ages for the marine and continental deposits.This revised chronostratigraphy allows assigning an age of~165–155 Ma,to the collisionrelated flexure of the northern Argun-Idemeg terrane and the development of a peripheral foreland basin.This collisional process took place 5 to10 million years later than in the western and eastern parts of the ocean.We demonstrate that the northern Argun-Idemeg terrane was the last block to collide with the Siberian continent,challenging the widely supported scissor-like model of closure of the MongolOkhotsk Ocean.Different segments of the ocean closed independently,depending on the initial shape of the paleo continental margins.
基金the State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang(No.2020Z03)the National Key R&D Program of China(Nos.2016YFC0600408,2019YFA0708400)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB41020102)。
文摘The Early Cretaceous aluminous A-type granites in the Lower Yangtze River belt(LYRB)can provide important insights into the Mesozoic magmatism in eastern China,but their origin remains highly controversial.In this study,radiogenic Ca-Nd isotopic analysis was performed for syenite porphyry and alkali-feldspar granite porphyry of the Yangshan pluton,a typical aluminous A-type granitic intrusion in the LYRB,to constrain its source and geodynamic setting.The results show thatε_(Ca)(126 Ma),ε_(Nd)(126 Ma)and K/Ca_(source) of the syenite porphyry range from-0.24 to+0.96,-7.2 to-6.0,and 0.31 to 1.26,respectively.The corresponding values for the alkali-feldspar granite porphyry range from 0.26 to 0.84,-8.0 to-6.1,and 0.79 to 1.08,respectively.Binary mixing modeling indicates that they were originated from the same sources with different proportion,namely,a mixing of 50%to 75%Neoproterozoic crust and 50%to 25%asthenospheric mantle.Together with previous works,we propose that the Early Cretaceous subduction of the ridge between the Pacific and Izanagi plates was responsible for the formation of the aluminous A-type granites in the LYRB.
文摘Several generations of mafic dyke swarms of different ages and geochemical characteristics cut Precambrian rocks of the southern part of the Siberian craton(Irkutsk Promontory).Each generation of dykes is related to a
文摘Extreme and prolonged rainfall in the Tunka Ridge caused several debris flows in the vicinity of the Arshan village(Siberia, Russia) on June 28, 2014. These debris flows, in spite of similar geological conditions, had different velocity, peak discharge and alluvial fan volume values. The flow velocity was from 3.5 m/s to 19.6 m/s, the peak discharge ranged from 63 m3/s to 13566 m3/s, and the alluvial fan volume varied from 4.13×103 to 8.45×105 m3. Such a great range of values is due to the morphometric parameters of the debris flow basins. The article deals with the influence of morphometric parameters of debris flow basins, such as the basin area, the average slope, Melton ratio, relief ratio on the debris flow velocity, peak discharge and volume of alluvial fans. In this debris flow event the average values of slope angle and total basin relief of the debris flow basins did not affect the values of debris flow velocity, peak discharge and alluvial fan volume. The highest correlations were observed with the debris flow basin area that was connected with the water inflow volume into the debris flow basins during the rainfall. The unequal water distribution among debris flow basins also had an impact on the debris flow velocity, peak discharge and volume of alluvial fans.
文摘We present a summary of late Paleoproterozoic to Neoproterozoic mafic magmatism in the Siberian craton which allows us distinguish following main pulses of mafic dyke emplacement:1)1860–1850 Ma mafic dykes are localized within the
文摘The paper reviews goals and objectives, stages and components of a seismotectonic study conducted in Eastern Siberia, Russia. Based on a comprehensive analysis of geological and geophysical data, our study establishes whether the local earthquakes are of tectonic origin and reveals relationships among earthquakes with recent geodynamic processes in the area under study. Seismic hazard assessment and evaluation of tectonic processes are the two major closely interrelated aspects of seismotectonic studies. A seismotectonic study is generally combined with a seismic study and conducted prior to the stage of detailed seismic zonation (DSZ) which is followed by seismic micro-zonation (SMZ). In three stages of the seismotectonic study, we analyze specific geological structures, reveal the regional dynamics of seismotectonic processes, clarify details of potential seismic hazard locations and identify sites of the potential instantaneous deformation of the crust which may take place due to active faulting. Based on results of our longterm studies, a seismotectonic zonation map of Eastern Siberia is compiled. The paper briefly reviews the methods of mapping and refers to data on active faults and neotectonic structures revealed in the area under study, which are closely related to regional earthquake sources.
基金supported by grants from the Russian Foundation for Basic Research(Grant No.17-05-00191)joint programme of Russian Foundation for Basic Research,Russia(No.13-05-91052)CNRS,France(PICS 4881)。
文摘The Mesozoic geodynamic evolution of Transbaikalia has been largely controlled by the scissors-like closure of the Mongol-Okhotsk Ocean that separated Siberia from Mongolia-North China continents.Following the oceanic closure,the tectonic evolution of that region was characterized by collisional uplift and subsequent extension that gave rise to the formation of metamorphic core complexes.This complex tectonic setting prevailed simultaneously between 150 Ma and 110 Ma both in Transbaikalia,North Mongolia,and within the North China Craton.Published paleobotanical and paleontological data show that the oldest Mesozoic basins had formed in western Transbaikalia before the estimated age of extension onset.However no precise geochronological age is available for the onset of extension in Transbaikalia.The Tugnuy Basin,as probably the oldest Mesozoic basin in western Transbaikalia,is a key obj ect to date the onset of extension and following changes in tectonic setting.In this study,U-Pb(LA-ICP-MS)dating of detrital zircons from three key Jurassic sediment formations of the Tugnuy Basin are used to identify the potential source areas of the sediments,understand the changes in sediment routing and provide insights on the topographic evolution of western Transbaikalia.Our results show several significant changes in tectonic regime after the closure of the Mongol-Okhotsk Ocean.A wide uplifted plateau formed during the closure of the Mongol-Okhotsk Ocean,determining the Early Jurassic drainage system reaching the AngaraVitim batholith to the north and shedding sediments to the continental margin to the South.The following collisional event at the end of the Early Jurassic led to the uplift of the collision zone,which partially inverted the drainage system toward the North.A strike-slip displacement induced by the oblique collision initiated some of the early Transbaikalian depressions,such as the Tugnuy Basin at about 168 Ma.A phase of basin inversion,marked by folding and erosion of the Upper Jurassic sediments,could corre
