Crack control of basement roof slab is a key technical challenge to ensure building safety and durability.Based on the requirements of“General Specification for Concrete Structures”(GB55008-2021),this paper systemat...Crack control of basement roof slab is a key technical challenge to ensure building safety and durability.Based on the requirements of“General Specification for Concrete Structures”(GB55008-2021),this paper systematically analyses the causes of cracks,and puts forward a whole-process prevention and control system covering design optimization,low-shrinkage material proportioning,fine control of construction technology,and dynamic monitoring and repair.Through structural finite element simulation,wireless sensor network real-time monitoring,and carbon fibre fabric reinforcement test,the effectiveness of the multi-technology synergistic control framework is verified,and the engineering cases show that the crack width after repair is stable within 0.1mm,and the bearing capacity is increased by more than 30%.The study provides theoretical support for crack prevention and control in super-long underground projects,and looks forward to the direction of integration application of BIM technology and intelligent materials.展开更多
With the rapid development of heavy haul railway transportation technology,tunnel foundation defects and their effects on structural performance have attracted wide attention.This paper systematically investigates the...With the rapid development of heavy haul railway transportation technology,tunnel foundation defects and their effects on structural performance have attracted wide attention.This paper systematically investigates the evolution mechanism of tun-nel foundation defects in heavy haul railway tunnels and their impact on structural stiffness degradation through experiments and numerical simulations.A heavy haul train-ballasted track-tunnel basement-surround rock dynamic interaction model(TTTR model)is constructed.Firstly,the study reveals the four-stage evolution process of initial defects in the tunnel base-ment under complex environmental conditions.Experiments were conducted to measure the load-bearing capacity and stiff-ness degradation of the tunnel basement structure under different defect states.It is found that foundation defects,especially under the coupling of loose fill in the basement with the water-rich environment of the surrounding rock,significantly reduce the stiffness of the tunnel bottom structure and increase the risk of structural damage.Then,based on refined simulation of wheel-rail interaction and multi-scale coupled modeling technology,the TTTR dynamic interaction model was successfully constructed,and its validity was proven through numerical validation.A time-varying coupling technique of constrained boundary substructures(CBS technique)was adopted,significantly improving computational efficiency while ensuring calculation accuracy.The study also analyzes the effects of different degrees of void defects on the dynamic behavior of the train and the dynamic characteristics of the tunnel structure.It finds that foundation defects have a significant impact on the train’s operational state,track vibration displacement,and vibration stress of the tunnel lining structure,especially under the coupling effect of basement voids and the water-rich environment,which has the greatest impact.The research results of this paper provide a theoretical basis and technical support for the maintenance and reinforcement of tunnel foundation structures.展开更多
The basement was located at the bottom of the building,which not only affected the quality of the whole construction project but also had special requirements for construction technology and construction requirements....The basement was located at the bottom of the building,which not only affected the quality of the whole construction project but also had special requirements for construction technology and construction requirements.In modern times,with the increasing height of the building,the pressure on the ground has grown,and the demands for basements in construction projects have also steadily increased.With the development of modern technology,various construction techniques for basements emerged within the construction industry.Thus,this paper analyses the type of basement floor construction technologies,highlighting the application of these methods,and points out critical issues to consider.By examining frequent basement leakage problems,the paper proposed several measures to improve the quality if basement construction,aiming to better protect the service life of the building and further improve overall quality,and offering valuable insights for future projects.展开更多
Based on the global basement reservoir database and the dissection of basement reservoirs in China,the characteristics of hydrocarbon accumulation in basement reservoirs are analyzed,and the favorable conditions for h...Based on the global basement reservoir database and the dissection of basement reservoirs in China,the characteristics of hydrocarbon accumulation in basement reservoirs are analyzed,and the favorable conditions for hydrocarbon accumulation in deep basement reservoirs are investigated to highlight the exploration targets.The discovered basement reservoirs worldwide are mainly buried in the Archean and Precambrian granitic and metamorphic formations with depths less than 4500 m,and the relatively large reservoirs have been found in rift,back-arc and foreland basins in tectonic active zones of the Meso-Cenozoic plates.The hydrocarbon accumulation in basement reservoirs exhibits the characteristics in three aspects.First,the porous-fractured reservoirs with low porosity and ultra-low permeability are dominant,where extensive hydrocarbon accumulation occurred during the weathering denudation and later tectonic reworking of the basin basement.High resistance to compaction allows the physical properties of these highly heterogeneous reservoirs to be independent of the buried depth.Second,the hydrocarbons were sourced from the formations outside the basement.The source-reservoir assemblages are divided into contacted source rock-basement and separated source rock-basement patterns.Third,the abnormal high pressure in the source rock and the normal–low pressure in the basement reservoirs cause a large pressure difference between the source rock and the reservoirs,which is conducive to the pumping effect of hydrocarbons in the deep basement.The deep basement prospects are mainly evaluated by the factors such as tectonic activity of basement,source-reservoir combination,development of large deep faults(especially strike-slip faults),and regional seals.The Precambrian crystalline basements at the margin of the intracontinental rifts in cratonic basins,as well as the Paleozoic folded basements and the Meso-Cenozoic fault-block basements adjacent to the hydrocarbon generation depressions,have favorable conditions for hydrocarbon accumulation,and thus they are considered as the main targets for future exploration of deep basement reservoirs.展开更多
The Songliao Basin(SLB)covers an area of approximately 260,000 km2in northeastern Asia and preserves a continuous and complete Cretaceous terrestrial record(Wang et al.,2021).The region is the most important petrolife...The Songliao Basin(SLB)covers an area of approximately 260,000 km2in northeastern Asia and preserves a continuous and complete Cretaceous terrestrial record(Wang et al.,2021).The region is the most important petroliferous sedimentary basin in China because of its continual annual oil and gas equivalent production of tens of millions of tons(ca.220–440 million barrels per year)since 1959.The SLB was previously thought to have developed on Hercynian basement and accumulated continuous sedimentary deposits during the Late Jurassic and Cretaceous(Wan et al.,2013;Wang et al.,2016).展开更多
In this study,we report for thefirst time an Early Palaeozoic basement diorite from the drilled well Nirona-A in the Banni Half-Graben of the Kutch basin,western India.The 40Ar–39Ar dates provided a plateau age of 441...In this study,we report for thefirst time an Early Palaeozoic basement diorite from the drilled well Nirona-A in the Banni Half-Graben of the Kutch basin,western India.The 40Ar–39Ar dates provided a plateau age of 441.84±2.66 Ma and another pseudo plateau of 441.28±5.82 to 388.08±16.65 Ma for the basement diorite.These ages constrain the basement formation age to the Late Ordovician-Early Silurian period.The obtained basement ages are correlatable with the later part of Cambro-Ordovician alkaline magmatism that has been reported from the Huqf area in Central Oman,whereas their lithological and petrographic correlativity with base-ment diorites occurring in the Dinsi Body of Nagar Parkar igneous complex in Pakistan can also be envisaged.The geochemical studies characterized the diorite with enrich-ment of LILE(Rb,Ba,and K)and LREE(La,Ce,Nd),strong depletion of HFSE(Nb,Sr,P,and Ti),along with weakly negative Eu anomalies.The geochemical signatures indicate their petrogenetic affiliation with mantle-derived magmas,as well as their tectonic setting to be arc-related,having post-collisional continental-arc type affinity.The*440 Ma basement of Kutch,therefore,appears to rep-resent the later thermal event associated with the reworked Neoproterozoic subduction-related suite from Greater India’s northwest edge,which has implications for Gond-wana assembly in the northwest Indian subcontinent.展开更多
Introduction: Located in the central-western part of Côte d’Ivoire, the subsoil of the Gagnoa region is made up of sedimentary volcano formations and granitoids with developed fracturing. This complex Precambria...Introduction: Located in the central-western part of Côte d’Ivoire, the subsoil of the Gagnoa region is made up of sedimentary volcano formations and granitoids with developed fracturing. This complex Precambrian basement contains most of the region’s water resources. This is at the origin of the high failure rate during the various hydrogeological prospecting campaigns. Methodology: The database consists of resistivities from 42 holes and 51 trails drilled as part of the implementation of high-throughput drilling in the study area. The objective of this study is to deepen the knowledge of the fissured basement by interpreting profile curves and electrical soundings. It will be a question of classifying the different types of anomalies obtained on the profiles and their shapes. The orientation of the lineaments observed on the profiles was determined. Results: The interpretation of the geophysical data revealed various anomalies, the main ones being of the CC (Conductor Compartment) and CEDP (Contact between two bearings) types. These types of anomalies are mainly expressed in various forms: the “V”, “W” and “U” shapes. From these anomalies and the appearance of the electrical profiles, lineaments and their orientations were identified with N90-100, N130-140, N170-180 as major orientations. Conclusion: These results could contribute to a better understanding of the fractured environment of the Gagnoa region.展开更多
Water is an essential element for all forms of life. The quantity and quality of water are a problem in places. In Kouba Adougoul and its surroundings in south guera, water-related health problems are reported. That i...Water is an essential element for all forms of life. The quantity and quality of water are a problem in places. In Kouba Adougoul and its surroundings in south guera, water-related health problems are reported. That is why this study focuses on the quality of water in the basement areas, of Kouba Adougoul. Our objective is to contribute to a better understanding of water of human consumption in these areas for this, we carried out a physicochemical and bacteriological control on a number water point. Ten water points were collected during May 2022 for analysis. To achieve this objective, we made the in-situ analysis of physical parameters such as pH, electrical conductivity, and temperature. These measurements were made using the multi-parameter kit. The result shows that, the water temperatures vary from 24.4˚C to 27.4˚C proving that the waters are from deep depths. For the use of these waters, it is necessary to take certain precautions. The pH values varied between 6.15 and 7.78, an average of 6.77 giving some waters an aggressive character. It was low mineralized, with electrical conductivity averages ranging from 182.1 to 2100 μS/cm−1 an average of 586.36 μS/cm−1. For the chemical parameters, it is by hydrometric titration that the content of the ions was determined. The determination of the various coliforms in these waters was carried out by its various methods which led to detecting that the waters of Kouba Adougoul are turbid, and present high proportions of nitrates, iron and ammonium. The presence of pathogenic germs, such as total coliforms and thermo-tolerant coliforms in these waters, has been demonstrated. For their consumption, these waters deserve treatment beforehand. In the study area, the anthropogenic activities are considered the most serious sources of groundwater.展开更多
Seafloor extension and associated rifting in the North Atlantic Area, which started in Early Paleogene (from −62 Ma), resulted in a few micro-continents being isolated and submerged below sea levels. Published isotopi...Seafloor extension and associated rifting in the North Atlantic Area, which started in Early Paleogene (from −62 Ma), resulted in a few micro-continents being isolated and submerged below sea levels. Published isotopic data for sunken offshore continental materials (basement) in the North Atlantic area are quite sparse, but a few do exist for the Rockall Plateau, or more precisely the Rockall Bank. Isotopic data for Early Paleogene basaltic materials, covering basement rocks of the Rockall Plateau, have hitherto only been publicised for the NW margin of the Hatton bank. The Early Paleogene basaltic archipelago of the Faroe Islands, on which some isotopic data do exist, rests on an ancient sunken continental crust of unknown geochemical and isotopic compositions. The objective of this contribution is to assess potential lead isotopic relationships between the Rockall Plateau and the Faroese sub-basaltic basement, based on the sparse available isotopic data existing for the former and using available isotopic data for slightly contaminated Faroese basaltic rocks. The results reached in this contribution point to a likely association between the Faroese sub-basaltic basement and the basement of the Rockall Bank and hence the Rockall Plateau and potentially also between Faroese basaltic rocks and contemporaneous counterparts from the Hatton Bank.展开更多
Episodes of tectonic activities since Archaean time in one of the oldest craton,the eastern Yilgarn Craton of Western Australia,have left a complex pattern in the architectural settings.Insights of the crustal scale a...Episodes of tectonic activities since Archaean time in one of the oldest craton,the eastern Yilgarn Craton of Western Australia,have left a complex pattern in the architectural settings.Insights of the crustal scale architectural settings of the Craton have been made through geophysical data modelling and imaging using high resolution aeromagnetic and Bouguer gravity data.The advanced technique of image processing using pseudocolour composition,hill-shading and the multiple data layers compilation in the hue,saturation and intensity(HSI)space has been used for image based analysis of potential field data.Geophysical methods of anomaly enhancement technique along with the imaging technique are used to delineate several regional and as well as local structures.Multiscale analysis in geophysical data processing with the application of varying upward continuation levels,and also anomaly enhancement techniques using spatial derivatives are used delineating major shear zones and regional scale structures.A suitable data based interpretation of basement architecture of the study area is given.展开更多
Based on the data of seismic reflection, seismic refraction and magnetism collected in the research area and geology obtained from adjacent areas, this paper deals with the issue of basement constitution of the southe...Based on the data of seismic reflection, seismic refraction and magnetism collected in the research area and geology obtained from adjacent areas, this paper deals with the issue of basement constitution of the southern part of the Okinawa Trough. In the shelf basin of the East China Sea, Taiwan folded belt and Ryukyu Islands folded belt which surround the trough, outcrop Later Paleozoic, Mesozoic and Eogene strata. In the southern trough, multichannel seismic reflection data indicate that the overlying strata are composed of Neogene and Quaternary deposits, and the acoustic basement consists of Eogent and even older strata. Seismic refraction profiles show that there are Eogene and Mesozoic velocity layers with longitudinal velocities of 4.7 - 5.3 km/s and 6.3 km/s respectively beneath the Quaternary-Miocene Layers. Qualitative analysis and forward and reversed calculation of magnetic data show that the magnetic basement is mainly formed by metamorphic rocks, the Yanshanian neutral-acid magmatic rocks and the Himalayan neutral-basic magmatic rocks being the next components, and the magnetic basement is mostly corresponding to the acoustic basement. Comprehensive analyses demonstrate that the basement of the southern Okinawa Trough is mainly formed by Eogene system and Mesozoic and Upper Paleozoic groups metamorphosed in varying degrees, and the basic magmatic rocks of Himalayan epoch have been formed in some parts of the basin.展开更多
Based on geological, chronological, geochemical and Nd isotopic studies of the high-grade basement of the Qilian terrane, the authors have drawn the following main conclusions: (1) the high-grade basement of the Qilia...Based on geological, chronological, geochemical and Nd isotopic studies of the high-grade basement of the Qilian terrane, the authors have drawn the following main conclusions: (1) the high-grade basement of the Qilian terrane consists mainly of meta-argillo-arenaceous rocks and granites and its bulk part was formed in the period of 0.8–1.0 Ga (the Jinningian period); (2) most of the meta-argillo-arenaceous rocks and granitic rocks have strong negative Eu and Ba anomalies (Eu/Eu*= 0.47–0.71 and Ba/Ba*=0.16–0.64), with fDM and ENd (1.0 Ga) ranging from 1.87 to 2.26 Ga and from ?8.54 to ?4.06 respectively, showing relatively high maturity; and (3) the Jinningian granitic rocks are a typical product of continent-continent collision, being probably related to the formation of the supercontinent Rodinia. These studies, combined with the study of high-grade basement rocks near the Qilian terrane, suggest that before the Jinningian period, the Qilian-Qaidam northern-margin terrane and Dunhuang-Alxa terrane were separated from each other, belonging to different plate systems of the North China craton and Yangtze platform respectively. The Qilian orogenic belt was the same as or similar to the Qiling orogenic belt in terms of the geological evolution history at least before the Jinningian period.展开更多
A comprehensive geophysical profile stretching from Qingyijing at the southern edge of the Junggar Basin to Ubara on the northern margin of the Junggar Basin was conducted in an attempt to probe the crustal structure ...A comprehensive geophysical profile stretching from Qingyijing at the southern edge of the Junggar Basin to Ubara on the northern margin of the Junggar Basin was conducted in an attempt to probe the crustal structure of the western Junggar Basin(hereafter referred to simply as ‘the Basin'), and, in particular, the structure and property of the Basin's crystalline basement. A survey using seismically converted waves was conducted along this profile to determine the characteristics of the P-and Swave velocities typical of the crust and uppermost mantle. A joint inversion of gravitation and aeromagnetic data was also performed to acquire the density and magnetization intensity values found beneath the western Basin. This research revealed that the Basin is composed of the so-called Manasi terrain in the south, and the Wulungu terrain in the north. Their boundary is located along the WNW-trending Dishuiquan-Sangequan suture, linking the NE-striking Da'erbute suture(DS) in the west, and the WNWtrending Kalameili suture(KS) in the east. In its northern part, the Wulungu-type terrain has a doublelayered basement, of which the upper layer is a folded basement of Hercynian orogenic origin, and the lower layer is a crystalline basement of Middle–Upper Proterozoic age. The southern part of the Basin, i.e., the Manasi terrain, has a single-layered crystalline basement. The folded basement here is too thin to be clearly distinguished.展开更多
Basement membrane degradation and blood-brain barrier damage appear after cerebral infarc- tion, severely impacting neuronal and brain functioning; however, the underlying pathogenetic mechanisms remain poorly underst...Basement membrane degradation and blood-brain barrier damage appear after cerebral infarc- tion, severely impacting neuronal and brain functioning; however, the underlying pathogenetic mechanisms remain poorly understood. In this study, we induced cerebral infarction in stroke- prone spontaneously hypertensive rats by intragastric administration of high-sodium water （1.3% NaC1） for 7 consecutive weeks. Immunohistochemical and immunofluorescence assays demonstrated that, compared with the non-infarcted contralateral hemisphere, stroke-prone spontaneously hypertensive rats on normal sodium intake and Wistar-Kyoto rats, matrix metalloproteinase-9 expression, the number of blood vessels with discontinuous collagen IV expression and microvessel density were significantly higher, and the number of continuous collagen IV-positive blood vessels was lower in the infarct border zones of stroke-prone sponta- neously hypertensive rats given high-sodium water. Linear correlation analysis showed matrix metalloproteinase-9 expression was positively correlated with the number of discontinuously collagen IV-labeled blood vessels and microvessel density in cerebral infarcts of stroke-prone spontaneously hypertensive rats. These results suggest that matrix metalloproteinase-9 upregula- tion is associated with increased regional angiogenesis and degradation of collagen IV, the major component of the basal lamina, in stroke-prone spontaneously hypertensive rats with high-sodi- um water-induced focal cerebral infarction.展开更多
The basement of the South China Sea（SCS）and adjacent areas can be divided into six divisions（regions）-Paleozoic Erathem graben-faulted basement division in Beibu Gulf,Paleozoic Erathem strike-slip pull-apart in Yi...The basement of the South China Sea（SCS）and adjacent areas can be divided into six divisions（regions）-Paleozoic Erathem graben-faulted basement division in Beibu Gulf,Paleozoic Erathem strike-slip pull-apart in Yinggehai waters,Paleozoic Erathem faulted-depression in eastern Hainan,Paleozoic Erathem rifted in northern Xisha（Paracel）,Paleozoic Erathem strike-slip extending in southern Xisha,and Paleozoic-Mesozoic Erathem extending in Nansha Islands（Spratly）waters.The Pre-Cenozoic basement in the SCS and Yunkai continental area are coeval within the Tethyan tectonic domain in the Pre-Cenozoic Period.They are formed on the background of the Paleo-Tethyan tectonic domain,and are important components of the Eastern Tethyan multi-island-ocean system.Three branches of the Eastern Paleo-Tethys tectonic domain,North Yunkai,North Hainan,and South Hainan sea basins,have evolved into the North Yunkai,North Hainan,and South Hainan suture zones, respectively.This shows a distinctive feature of localization for the Pre-Cenozoic basement.The Qiongnan（i.e.South Hainan）Suture Zone on the northern margin of the South China Sea can be considered the vestige of the principal ocean basin of Paleo-Tethys,and connected with the suture zone of the Longmucuo-Shuanghu belt-Bitu belt-Changning-Menglian-Bentong-Raub belt,the south extension of Bitu-Changning-Menglian-Ching Mai belt-Chanthaburi-Raub-Bentong belt on the west of South China Sea,and with the Lianhua-Taidong suture zone（a fault along the east side of Longitudinal Valley in Taiwan）-Hida LP/HT（low pressure-high temperature）metamorphic belt-Hida -marginal HP/LT metamorphic belt in southwestern Honshu of Japan,on the east of the South China Sea.The Qiongbei（North Hainan）suture zone may eastwards extended along the Wangwu-Wenjiao fault zone,and connects with the Lufeng-Dapu-Zhenghe-Shangyu（Lianhuashan）deep fault zone through the Pearl River Mouth Basin.The Meso-Tethys developed on the south of the South China Sea.The Nansha Trough may be considered the vestige of the northern shelf of the Meso-Tethys. The oceanic crust of the Meso-Tethys has southwards subducted along the subduction-collision-thrust southern margin of the Nansha Trough with a subduction-pole opposite to those of the Yarlung Zangbo-Mytkyina-Bago zone on the west of the South China Sea,and the Meso-Tethyan（e.g.Northern Chichibu Ocean of the Meso-Tethys）suture zone＂Butsozo tectonic line＂in the outer belt of the Jurassic-Early Cretaceous terrene group in southwest Japan,on the east of the South China Sea.展开更多
The origin, age and evolution of the Precambrian metamorphic basement of southern China provide useful insights into early crustal development. Here, we present new laser ablation-inductively coupled plasma-mass spect...The origin, age and evolution of the Precambrian metamorphic basement of southern China provide useful insights into early crustal development. Here, we present new laser ablation-inductively coupled plasma-mass spectrometry （LA-ICP-MS） U-Pb age data for detrital zircons from five samples of the Precambrian metamorphic basement of the Xiangshan uranium orefield. Two of these samples, from the northern Xiangshan volcanic basin, yielded a total of 140 U-Pb ages that cluster within the Neoproterozoic （773-963 Ma; 79.3% of data points）, with the rest being scattered through the Paleoproterozoic and Mesoproterozoic, along with a single Archean age. These ages indicate that this basement material is associated with the Cathaysia Block. In comparison, the 172 concordant ages from the other three samples from the southern part of the Xiangshan volcanic basin cluster within the Neoproterozoic （767-944 Ma; 59.8%） as well as the Proterozoic （37.8%） and the Archean （2502-2712 Ma; 14.5%）. These samples are also free of zircons with Grenvillian ages, indicating that these units are associated with the southeastern Yangtze Block. Combining these data with the geochemistry of these units, which suggests that the metamorphosed sedimentary rocks within the northern and southern parts of the Xiangshan basin have a common component from a magmatic island arc that formed during the early Neoproterozoic, we infer that the basin was located along the boundary between the Cathaysian and Yangtze blocks. In addition, the zircons within the samples from the southern and northern parts of the Xiangshan basin show different pre-Neoproterozoic （963 Ma） age populations but similar post- Neoproterozoic zircon populations, indicating that the amalgamation of the Cathaysian and Yangtze blocks occurred after the Neoproterozoic （960 Ma）, with magmatism peaking at 830 Ma and rifting starting at -770 Ma, leading to the subsequent deposition （from bottom to top） of the Shenshan, Kuli, and Shangshi formations.展开更多
The pre-Cenozoic northern South China Sea(SCS)Basin basement was supposed to exist as a complex of heterogeneous segments,divided by dozens of N-S faulting.Unfortunately,only the Hainan Island and the northeastern SCS...The pre-Cenozoic northern South China Sea(SCS)Basin basement was supposed to exist as a complex of heterogeneous segments,divided by dozens of N-S faulting.Unfortunately,only the Hainan Island and the northeastern SCS region were modestly dated while the extensive basement remains roughly postulated by limited geophysical data.This study presents a systematic analysis including U-Pb geochronology,elemental geochemistry and petrographic identification on granite and meta-clastic borehole samples from several key areas.Constrained from gravity-magnetic joint inversion,this interpretation will be of great significance revealing the tectono-magmatic evolution along the southeastern margin of the Eurasian Plate.Beneath the thick Cenozoic sediments,the northern SCS is composed of a uniform Mesozoic basement while the Precambrian rocks are only constricted along the Red River Fault Zone.Further eastern part of the northern SCS below the Cenozoic succession was widely intruded by granites with Jurassic-to-early Cretaceous ages.Further western part,on the other hand,is represented by meta-sedimentary rocks with relatively sporadic granite complexes.To be noted,the western areas derived higher-degree and wider metamorphic zones,which is in contrast with the lowerdegree and narrower metamorphic belt developed in the eastern region.Drastic collisions between the Indochina Block and South China continent took place since at least late Triassic,resulting in large-scale suturing and deformation zones.At the westernmost part of the northern SCS,the intracontinental amalgamation with closure of the Meso-Tethys has caused fairly stronger and broader metamorphism.One metamorphic biotite granite is located on the suturing belt and yields a Precambrian U-Pb age.It likely represents the relict from the ancient Gondwana supercontinent or its fringes.Arc-continental collision between the Paleo-Pacific and the southeast China Block,on the other hand,results in a relatively narrow NE–SW trending metamorphic belt during the late Mesozoic.Within the overall geological setting,the Cenozoic SCS oceanic basin was subsequently generated from a series of rifting and faulting processes along the collisional-accretionary continental margin.展开更多
A gravity survey was conducted one month after the 2010 Yushu earthquake in the epicenter area. The cross-fauh survey line was 500 km long, from Langqian county to Qingshuihe county, in a transition zone between Bayan...A gravity survey was conducted one month after the 2010 Yushu earthquake in the epicenter area. The cross-fauh survey line was 500 km long, from Langqian county to Qingshuihe county, in a transition zone between Bayan Har block and Qiangtang block, in an area of high elevation, large undulating terrain, and complex geological features. An interpretation of the data was carried out together with other kinds of data, such as seismic exploration and magnetic exploration. The result shows that gravity is sensitive to fault bounda- ry ; the geologic structure of the region is complex at middle and upper depths, and the density profile reveals an eastward-pushing fault movement.展开更多
The Early Paleozoic evolution of the northern margin of Gondwana is characterized by several episodes of bimodal magmatism intruded or outpoured within thick sedimentary basins. These processes are well recorded in th...The Early Paleozoic evolution of the northern margin of Gondwana is characterized by several episodes of bimodal magmatism intruded or outpoured within thick sedimentary basins. These processes are well recorded in the Variscan blocks incorporated in the Ligurian Alps because they experienced low temperature Alpine metamorphism. During the Paleozoic, these blocks, together with the other Alpine basements, were placed between the Corsica-Sardinia and the Bohemian Massif along the northern margin of Gondwana. In this framework, they host several a variegated lithostratigraphy forming two main complexes(Complexs I and II) that can be distinguished by both the protoliths and their crosscutting relationships, which indicate that the acidic and mafic intrusives of Complex II cut an already folded sequence made of sediments, basalts and granitoids of Complex I. Both complexes were involved in the Variscan orogenic phases as highlighted by the pervasive eclogite-amphibolite facies schistosity(foliation II). However, rare relicts of a metamorphic foliation at amphibolite facies conditions(foliation I)is locally preserved only in the rocks of Complex I. It is debatable if this schistosity was produced during the early folding event e occurred between the emplacement of Complex I and II e rather than during an early stage of the Variscan metamorphic cycle.New SHRIMP and LA ICP-MS Ue Pb zircon dating integrated with literature data, provide emplacement ages of the several volcanic or intrusive bodies of both complexes. The igneous activity of Complex I is dated between 507 ± 15 Ma and 494 ± 5 Ma, while Complex II between 467 ± 12 Ma and 445.5 ± 12 Ma.The folding event recorded only by the Complex I should therefore have occurred between 494 ± 5 Ma and 467 ± 12 Ma. The Variscan eclogite-amphibolite facies metamorphism is instead constrained between ~420 Ma and ~300 Ma. These ages and the geochemical signature of these rocks allow constraining the Early Paleozoic tectono-magmatic evolution of the Ligurian blocks, from a middleeupper Cambrian rifting stage, through the formation of an Early Ordovician volcanic arc during the Rheic Ocean subduction, until a Late Ordovician extension related to the arc collapse and subsequent rifting of the PaleoThetys. Furthermore, the ~420-350 Ma ages from zircon rims testify to thermal perturbations that may be associated with the Silurian rifting-related magmatism, followed by the subduction-collisional phases of the Variscan orogeny.展开更多
文摘Crack control of basement roof slab is a key technical challenge to ensure building safety and durability.Based on the requirements of“General Specification for Concrete Structures”(GB55008-2021),this paper systematically analyses the causes of cracks,and puts forward a whole-process prevention and control system covering design optimization,low-shrinkage material proportioning,fine control of construction technology,and dynamic monitoring and repair.Through structural finite element simulation,wireless sensor network real-time monitoring,and carbon fibre fabric reinforcement test,the effectiveness of the multi-technology synergistic control framework is verified,and the engineering cases show that the crack width after repair is stable within 0.1mm,and the bearing capacity is increased by more than 30%.The study provides theoretical support for crack prevention and control in super-long underground projects,and looks forward to the direction of integration application of BIM technology and intelligent materials.
基金funded by the National Natural Science Foundation of China (Grant No. 52178402 & 52378468)the Open Foundation of MOE Key Laboratory of Engineering Structures of Heavy Haul Railway (Central South University) (Grant No. 2022JZZ01)+1 种基金the National Engineering Research Center for High-Speed Railway Construction Technology for their project supportthe support from the MOE Key Laboratory of Engineering Structure of Heavy Haul Railway (Central South University)
文摘With the rapid development of heavy haul railway transportation technology,tunnel foundation defects and their effects on structural performance have attracted wide attention.This paper systematically investigates the evolution mechanism of tun-nel foundation defects in heavy haul railway tunnels and their impact on structural stiffness degradation through experiments and numerical simulations.A heavy haul train-ballasted track-tunnel basement-surround rock dynamic interaction model(TTTR model)is constructed.Firstly,the study reveals the four-stage evolution process of initial defects in the tunnel base-ment under complex environmental conditions.Experiments were conducted to measure the load-bearing capacity and stiff-ness degradation of the tunnel basement structure under different defect states.It is found that foundation defects,especially under the coupling of loose fill in the basement with the water-rich environment of the surrounding rock,significantly reduce the stiffness of the tunnel bottom structure and increase the risk of structural damage.Then,based on refined simulation of wheel-rail interaction and multi-scale coupled modeling technology,the TTTR dynamic interaction model was successfully constructed,and its validity was proven through numerical validation.A time-varying coupling technique of constrained boundary substructures(CBS technique)was adopted,significantly improving computational efficiency while ensuring calculation accuracy.The study also analyzes the effects of different degrees of void defects on the dynamic behavior of the train and the dynamic characteristics of the tunnel structure.It finds that foundation defects have a significant impact on the train’s operational state,track vibration displacement,and vibration stress of the tunnel lining structure,especially under the coupling effect of basement voids and the water-rich environment,which has the greatest impact.The research results of this paper provide a theoretical basis and technical support for the maintenance and reinforcement of tunnel foundation structures.
文摘The basement was located at the bottom of the building,which not only affected the quality of the whole construction project but also had special requirements for construction technology and construction requirements.In modern times,with the increasing height of the building,the pressure on the ground has grown,and the demands for basements in construction projects have also steadily increased.With the development of modern technology,various construction techniques for basements emerged within the construction industry.Thus,this paper analyses the type of basement floor construction technologies,highlighting the application of these methods,and points out critical issues to consider.By examining frequent basement leakage problems,the paper proposed several measures to improve the quality if basement construction,aiming to better protect the service life of the building and further improve overall quality,and offering valuable insights for future projects.
基金Supported by the Science and Technology Project of China National Petroleum Corporation(2021DJ02).
文摘Based on the global basement reservoir database and the dissection of basement reservoirs in China,the characteristics of hydrocarbon accumulation in basement reservoirs are analyzed,and the favorable conditions for hydrocarbon accumulation in deep basement reservoirs are investigated to highlight the exploration targets.The discovered basement reservoirs worldwide are mainly buried in the Archean and Precambrian granitic and metamorphic formations with depths less than 4500 m,and the relatively large reservoirs have been found in rift,back-arc and foreland basins in tectonic active zones of the Meso-Cenozoic plates.The hydrocarbon accumulation in basement reservoirs exhibits the characteristics in three aspects.First,the porous-fractured reservoirs with low porosity and ultra-low permeability are dominant,where extensive hydrocarbon accumulation occurred during the weathering denudation and later tectonic reworking of the basin basement.High resistance to compaction allows the physical properties of these highly heterogeneous reservoirs to be independent of the buried depth.Second,the hydrocarbons were sourced from the formations outside the basement.The source-reservoir assemblages are divided into contacted source rock-basement and separated source rock-basement patterns.Third,the abnormal high pressure in the source rock and the normal–low pressure in the basement reservoirs cause a large pressure difference between the source rock and the reservoirs,which is conducive to the pumping effect of hydrocarbons in the deep basement.The deep basement prospects are mainly evaluated by the factors such as tectonic activity of basement,source-reservoir combination,development of large deep faults(especially strike-slip faults),and regional seals.The Precambrian crystalline basements at the margin of the intracontinental rifts in cratonic basins,as well as the Paleozoic folded basements and the Meso-Cenozoic fault-block basements adjacent to the hydrocarbon generation depressions,have favorable conditions for hydrocarbon accumulation,and thus they are considered as the main targets for future exploration of deep basement reservoirs.
基金supports from the International Continental Scientific Drilling Programfunded by the National Natural Science Foundation of China(Grant Nos.41790453,41472304,42102129,42102135 and 41972313)+2 种基金Natural Science Foundation of Jilin Province(Grant No.20170101001JC)the National Key Research&Development Program of China(Grant No.2019YFC0605402)China Geological Survey(Grant No.DD20189702)。
文摘The Songliao Basin(SLB)covers an area of approximately 260,000 km2in northeastern Asia and preserves a continuous and complete Cretaceous terrestrial record(Wang et al.,2021).The region is the most important petroliferous sedimentary basin in China because of its continual annual oil and gas equivalent production of tens of millions of tons(ca.220–440 million barrels per year)since 1959.The SLB was previously thought to have developed on Hercynian basement and accumulated continuous sedimentary deposits during the Late Jurassic and Cretaceous(Wan et al.,2013;Wang et al.,2016).
文摘In this study,we report for thefirst time an Early Palaeozoic basement diorite from the drilled well Nirona-A in the Banni Half-Graben of the Kutch basin,western India.The 40Ar–39Ar dates provided a plateau age of 441.84±2.66 Ma and another pseudo plateau of 441.28±5.82 to 388.08±16.65 Ma for the basement diorite.These ages constrain the basement formation age to the Late Ordovician-Early Silurian period.The obtained basement ages are correlatable with the later part of Cambro-Ordovician alkaline magmatism that has been reported from the Huqf area in Central Oman,whereas their lithological and petrographic correlativity with base-ment diorites occurring in the Dinsi Body of Nagar Parkar igneous complex in Pakistan can also be envisaged.The geochemical studies characterized the diorite with enrich-ment of LILE(Rb,Ba,and K)and LREE(La,Ce,Nd),strong depletion of HFSE(Nb,Sr,P,and Ti),along with weakly negative Eu anomalies.The geochemical signatures indicate their petrogenetic affiliation with mantle-derived magmas,as well as their tectonic setting to be arc-related,having post-collisional continental-arc type affinity.The*440 Ma basement of Kutch,therefore,appears to rep-resent the later thermal event associated with the reworked Neoproterozoic subduction-related suite from Greater India’s northwest edge,which has implications for Gond-wana assembly in the northwest Indian subcontinent.
文摘Introduction: Located in the central-western part of Côte d’Ivoire, the subsoil of the Gagnoa region is made up of sedimentary volcano formations and granitoids with developed fracturing. This complex Precambrian basement contains most of the region’s water resources. This is at the origin of the high failure rate during the various hydrogeological prospecting campaigns. Methodology: The database consists of resistivities from 42 holes and 51 trails drilled as part of the implementation of high-throughput drilling in the study area. The objective of this study is to deepen the knowledge of the fissured basement by interpreting profile curves and electrical soundings. It will be a question of classifying the different types of anomalies obtained on the profiles and their shapes. The orientation of the lineaments observed on the profiles was determined. Results: The interpretation of the geophysical data revealed various anomalies, the main ones being of the CC (Conductor Compartment) and CEDP (Contact between two bearings) types. These types of anomalies are mainly expressed in various forms: the “V”, “W” and “U” shapes. From these anomalies and the appearance of the electrical profiles, lineaments and their orientations were identified with N90-100, N130-140, N170-180 as major orientations. Conclusion: These results could contribute to a better understanding of the fractured environment of the Gagnoa region.
文摘Water is an essential element for all forms of life. The quantity and quality of water are a problem in places. In Kouba Adougoul and its surroundings in south guera, water-related health problems are reported. That is why this study focuses on the quality of water in the basement areas, of Kouba Adougoul. Our objective is to contribute to a better understanding of water of human consumption in these areas for this, we carried out a physicochemical and bacteriological control on a number water point. Ten water points were collected during May 2022 for analysis. To achieve this objective, we made the in-situ analysis of physical parameters such as pH, electrical conductivity, and temperature. These measurements were made using the multi-parameter kit. The result shows that, the water temperatures vary from 24.4˚C to 27.4˚C proving that the waters are from deep depths. For the use of these waters, it is necessary to take certain precautions. The pH values varied between 6.15 and 7.78, an average of 6.77 giving some waters an aggressive character. It was low mineralized, with electrical conductivity averages ranging from 182.1 to 2100 μS/cm−1 an average of 586.36 μS/cm−1. For the chemical parameters, it is by hydrometric titration that the content of the ions was determined. The determination of the various coliforms in these waters was carried out by its various methods which led to detecting that the waters of Kouba Adougoul are turbid, and present high proportions of nitrates, iron and ammonium. The presence of pathogenic germs, such as total coliforms and thermo-tolerant coliforms in these waters, has been demonstrated. For their consumption, these waters deserve treatment beforehand. In the study area, the anthropogenic activities are considered the most serious sources of groundwater.
文摘Seafloor extension and associated rifting in the North Atlantic Area, which started in Early Paleogene (from −62 Ma), resulted in a few micro-continents being isolated and submerged below sea levels. Published isotopic data for sunken offshore continental materials (basement) in the North Atlantic area are quite sparse, but a few do exist for the Rockall Plateau, or more precisely the Rockall Bank. Isotopic data for Early Paleogene basaltic materials, covering basement rocks of the Rockall Plateau, have hitherto only been publicised for the NW margin of the Hatton bank. The Early Paleogene basaltic archipelago of the Faroe Islands, on which some isotopic data do exist, rests on an ancient sunken continental crust of unknown geochemical and isotopic compositions. The objective of this contribution is to assess potential lead isotopic relationships between the Rockall Plateau and the Faroese sub-basaltic basement, based on the sparse available isotopic data existing for the former and using available isotopic data for slightly contaminated Faroese basaltic rocks. The results reached in this contribution point to a likely association between the Faroese sub-basaltic basement and the basement of the Rockall Bank and hence the Rockall Plateau and potentially also between Faroese basaltic rocks and contemporaneous counterparts from the Hatton Bank.
基金supported by Spaceage Geoconsulting,a research oriented consulting firm.
文摘Episodes of tectonic activities since Archaean time in one of the oldest craton,the eastern Yilgarn Craton of Western Australia,have left a complex pattern in the architectural settings.Insights of the crustal scale architectural settings of the Craton have been made through geophysical data modelling and imaging using high resolution aeromagnetic and Bouguer gravity data.The advanced technique of image processing using pseudocolour composition,hill-shading and the multiple data layers compilation in the hue,saturation and intensity(HSI)space has been used for image based analysis of potential field data.Geophysical methods of anomaly enhancement technique along with the imaging technique are used to delineate several regional and as well as local structures.Multiscale analysis in geophysical data processing with the application of varying upward continuation levels,and also anomaly enhancement techniques using spatial derivatives are used delineating major shear zones and regional scale structures.A suitable data based interpretation of basement architecture of the study area is given.
文摘Based on the data of seismic reflection, seismic refraction and magnetism collected in the research area and geology obtained from adjacent areas, this paper deals with the issue of basement constitution of the southern part of the Okinawa Trough. In the shelf basin of the East China Sea, Taiwan folded belt and Ryukyu Islands folded belt which surround the trough, outcrop Later Paleozoic, Mesozoic and Eogene strata. In the southern trough, multichannel seismic reflection data indicate that the overlying strata are composed of Neogene and Quaternary deposits, and the acoustic basement consists of Eogent and even older strata. Seismic refraction profiles show that there are Eogene and Mesozoic velocity layers with longitudinal velocities of 4.7 - 5.3 km/s and 6.3 km/s respectively beneath the Quaternary-Miocene Layers. Qualitative analysis and forward and reversed calculation of magnetic data show that the magnetic basement is mainly formed by metamorphic rocks, the Yanshanian neutral-acid magmatic rocks and the Himalayan neutral-basic magmatic rocks being the next components, and the magnetic basement is mostly corresponding to the acoustic basement. Comprehensive analyses demonstrate that the basement of the southern Okinawa Trough is mainly formed by Eogene system and Mesozoic and Upper Paleozoic groups metamorphosed in varying degrees, and the basic magmatic rocks of Himalayan epoch have been formed in some parts of the basin.
基金supported by China National Natural Science Foundation Grant 49732070.
文摘Based on geological, chronological, geochemical and Nd isotopic studies of the high-grade basement of the Qilian terrane, the authors have drawn the following main conclusions: (1) the high-grade basement of the Qilian terrane consists mainly of meta-argillo-arenaceous rocks and granites and its bulk part was formed in the period of 0.8–1.0 Ga (the Jinningian period); (2) most of the meta-argillo-arenaceous rocks and granitic rocks have strong negative Eu and Ba anomalies (Eu/Eu*= 0.47–0.71 and Ba/Ba*=0.16–0.64), with fDM and ENd (1.0 Ga) ranging from 1.87 to 2.26 Ga and from ?8.54 to ?4.06 respectively, showing relatively high maturity; and (3) the Jinningian granitic rocks are a typical product of continent-continent collision, being probably related to the formation of the supercontinent Rodinia. These studies, combined with the study of high-grade basement rocks near the Qilian terrane, suggest that before the Jinningian period, the Qilian-Qaidam northern-margin terrane and Dunhuang-Alxa terrane were separated from each other, belonging to different plate systems of the North China craton and Yangtze platform respectively. The Qilian orogenic belt was the same as or similar to the Qiling orogenic belt in terms of the geological evolution history at least before the Jinningian period.
基金supported by the Major Program of the National Natural Science Foundation of China (No. 41490611)the Joint Research Projects between the Pakistan Science Foundation and the National Natural Science Foundation of China (No. 41661144026)the Detailed Lithospheric Structure and Deep Processes of the Tibetan Main Collision Zone (No. 2016YFC0600301)
文摘A comprehensive geophysical profile stretching from Qingyijing at the southern edge of the Junggar Basin to Ubara on the northern margin of the Junggar Basin was conducted in an attempt to probe the crustal structure of the western Junggar Basin(hereafter referred to simply as ‘the Basin'), and, in particular, the structure and property of the Basin's crystalline basement. A survey using seismically converted waves was conducted along this profile to determine the characteristics of the P-and Swave velocities typical of the crust and uppermost mantle. A joint inversion of gravitation and aeromagnetic data was also performed to acquire the density and magnetization intensity values found beneath the western Basin. This research revealed that the Basin is composed of the so-called Manasi terrain in the south, and the Wulungu terrain in the north. Their boundary is located along the WNW-trending Dishuiquan-Sangequan suture, linking the NE-striking Da'erbute suture(DS) in the west, and the WNWtrending Kalameili suture(KS) in the east. In its northern part, the Wulungu-type terrain has a doublelayered basement, of which the upper layer is a folded basement of Hercynian orogenic origin, and the lower layer is a crystalline basement of Middle–Upper Proterozoic age. The southern part of the Basin, i.e., the Manasi terrain, has a single-layered crystalline basement. The folded basement here is too thin to be clearly distinguished.
基金supported by the China Medical Board Project,No.82-143
文摘Basement membrane degradation and blood-brain barrier damage appear after cerebral infarc- tion, severely impacting neuronal and brain functioning; however, the underlying pathogenetic mechanisms remain poorly understood. In this study, we induced cerebral infarction in stroke- prone spontaneously hypertensive rats by intragastric administration of high-sodium water （1.3% NaC1） for 7 consecutive weeks. Immunohistochemical and immunofluorescence assays demonstrated that, compared with the non-infarcted contralateral hemisphere, stroke-prone spontaneously hypertensive rats on normal sodium intake and Wistar-Kyoto rats, matrix metalloproteinase-9 expression, the number of blood vessels with discontinuous collagen IV expression and microvessel density were significantly higher, and the number of continuous collagen IV-positive blood vessels was lower in the infarct border zones of stroke-prone sponta- neously hypertensive rats given high-sodium water. Linear correlation analysis showed matrix metalloproteinase-9 expression was positively correlated with the number of discontinuously collagen IV-labeled blood vessels and microvessel density in cerebral infarcts of stroke-prone spontaneously hypertensive rats. These results suggest that matrix metalloproteinase-9 upregula- tion is associated with increased regional angiogenesis and degradation of collagen IV, the major component of the basal lamina, in stroke-prone spontaneously hypertensive rats with high-sodi- um water-induced focal cerebral infarction.
基金funded by the State Fund for Natural Science of China(No40976029)the National Basic Research Program of China("973")(2007CB411700 and 2009CB2194)+2 种基金the Major Knowledge Innovation Programs of the Chinese Academy of Sciences(kzcx2-yw- 203-01)the National Program of Sustaining Science and Technology(2006BABl 9B02)the Program of the Ministry of Land and Resources,China(GT-YQ-QQ-2008-1-02 and 2009GYXQ06)
文摘The basement of the South China Sea（SCS）and adjacent areas can be divided into six divisions（regions）-Paleozoic Erathem graben-faulted basement division in Beibu Gulf,Paleozoic Erathem strike-slip pull-apart in Yinggehai waters,Paleozoic Erathem faulted-depression in eastern Hainan,Paleozoic Erathem rifted in northern Xisha（Paracel）,Paleozoic Erathem strike-slip extending in southern Xisha,and Paleozoic-Mesozoic Erathem extending in Nansha Islands（Spratly）waters.The Pre-Cenozoic basement in the SCS and Yunkai continental area are coeval within the Tethyan tectonic domain in the Pre-Cenozoic Period.They are formed on the background of the Paleo-Tethyan tectonic domain,and are important components of the Eastern Tethyan multi-island-ocean system.Three branches of the Eastern Paleo-Tethys tectonic domain,North Yunkai,North Hainan,and South Hainan sea basins,have evolved into the North Yunkai,North Hainan,and South Hainan suture zones, respectively.This shows a distinctive feature of localization for the Pre-Cenozoic basement.The Qiongnan（i.e.South Hainan）Suture Zone on the northern margin of the South China Sea can be considered the vestige of the principal ocean basin of Paleo-Tethys,and connected with the suture zone of the Longmucuo-Shuanghu belt-Bitu belt-Changning-Menglian-Bentong-Raub belt,the south extension of Bitu-Changning-Menglian-Ching Mai belt-Chanthaburi-Raub-Bentong belt on the west of South China Sea,and with the Lianhua-Taidong suture zone（a fault along the east side of Longitudinal Valley in Taiwan）-Hida LP/HT（low pressure-high temperature）metamorphic belt-Hida -marginal HP/LT metamorphic belt in southwestern Honshu of Japan,on the east of the South China Sea.The Qiongbei（North Hainan）suture zone may eastwards extended along the Wangwu-Wenjiao fault zone,and connects with the Lufeng-Dapu-Zhenghe-Shangyu（Lianhuashan）deep fault zone through the Pearl River Mouth Basin.The Meso-Tethys developed on the south of the South China Sea.The Nansha Trough may be considered the vestige of the northern shelf of the Meso-Tethys. The oceanic crust of the Meso-Tethys has southwards subducted along the subduction-collision-thrust southern margin of the Nansha Trough with a subduction-pole opposite to those of the Yarlung Zangbo-Mytkyina-Bago zone on the west of the South China Sea,and the Meso-Tethyan（e.g.Northern Chichibu Ocean of the Meso-Tethys）suture zone＂Butsozo tectonic line＂in the outer belt of the Jurassic-Early Cretaceous terrene group in southwest Japan,on the east of the South China Sea.
基金financially supported by the National Natural Science Foundation of China(Grant No.41602069 and 41572185)the Fundamental Science on Radioactive Geology and Exploration Technology Laboratory(Grant No.RGET1402)+1 种基金the Natural Science Foundation of Jiangxi Province(Grant No.20171BAB213026)Science and technology research projectfrom the Education Department of Jiangxi Province(Grant No.GJJ150554)
文摘The origin, age and evolution of the Precambrian metamorphic basement of southern China provide useful insights into early crustal development. Here, we present new laser ablation-inductively coupled plasma-mass spectrometry （LA-ICP-MS） U-Pb age data for detrital zircons from five samples of the Precambrian metamorphic basement of the Xiangshan uranium orefield. Two of these samples, from the northern Xiangshan volcanic basin, yielded a total of 140 U-Pb ages that cluster within the Neoproterozoic （773-963 Ma; 79.3% of data points）, with the rest being scattered through the Paleoproterozoic and Mesoproterozoic, along with a single Archean age. These ages indicate that this basement material is associated with the Cathaysia Block. In comparison, the 172 concordant ages from the other three samples from the southern part of the Xiangshan volcanic basin cluster within the Neoproterozoic （767-944 Ma; 59.8%） as well as the Proterozoic （37.8%） and the Archean （2502-2712 Ma; 14.5%）. These samples are also free of zircons with Grenvillian ages, indicating that these units are associated with the southeastern Yangtze Block. Combining these data with the geochemistry of these units, which suggests that the metamorphosed sedimentary rocks within the northern and southern parts of the Xiangshan basin have a common component from a magmatic island arc that formed during the early Neoproterozoic, we infer that the basin was located along the boundary between the Cathaysian and Yangtze blocks. In addition, the zircons within the samples from the southern and northern parts of the Xiangshan basin show different pre-Neoproterozoic （963 Ma） age populations but similar post- Neoproterozoic zircon populations, indicating that the amalgamation of the Cathaysian and Yangtze blocks occurred after the Neoproterozoic （960 Ma）, with magmatism peaking at 830 Ma and rifting starting at -770 Ma, leading to the subsequent deposition （from bottom to top） of the Shenshan, Kuli, and Shangshi formations.
基金The National Natural Science Foundation of China under contract Nos 42076066,92055203 and 41874076the National Science and Technology Major Project under contract Nos 2016ZX05026004-002 and 2017ZX05026005-005the Fund of China Association for Science and Technology under contract No.2018CASRQNJL18
文摘The pre-Cenozoic northern South China Sea(SCS)Basin basement was supposed to exist as a complex of heterogeneous segments,divided by dozens of N-S faulting.Unfortunately,only the Hainan Island and the northeastern SCS region were modestly dated while the extensive basement remains roughly postulated by limited geophysical data.This study presents a systematic analysis including U-Pb geochronology,elemental geochemistry and petrographic identification on granite and meta-clastic borehole samples from several key areas.Constrained from gravity-magnetic joint inversion,this interpretation will be of great significance revealing the tectono-magmatic evolution along the southeastern margin of the Eurasian Plate.Beneath the thick Cenozoic sediments,the northern SCS is composed of a uniform Mesozoic basement while the Precambrian rocks are only constricted along the Red River Fault Zone.Further eastern part of the northern SCS below the Cenozoic succession was widely intruded by granites with Jurassic-to-early Cretaceous ages.Further western part,on the other hand,is represented by meta-sedimentary rocks with relatively sporadic granite complexes.To be noted,the western areas derived higher-degree and wider metamorphic zones,which is in contrast with the lowerdegree and narrower metamorphic belt developed in the eastern region.Drastic collisions between the Indochina Block and South China continent took place since at least late Triassic,resulting in large-scale suturing and deformation zones.At the westernmost part of the northern SCS,the intracontinental amalgamation with closure of the Meso-Tethys has caused fairly stronger and broader metamorphism.One metamorphic biotite granite is located on the suturing belt and yields a Precambrian U-Pb age.It likely represents the relict from the ancient Gondwana supercontinent or its fringes.Arc-continental collision between the Paleo-Pacific and the southeast China Block,on the other hand,results in a relatively narrow NE–SW trending metamorphic belt during the late Mesozoic.Within the overall geological setting,the Cenozoic SCS oceanic basin was subsequently generated from a series of rifting and faulting processes along the collisional-accretionary continental margin.
基金supported by the Key Director Foundation Project,Institute of Seismology,CEA(IS200916004)
文摘A gravity survey was conducted one month after the 2010 Yushu earthquake in the epicenter area. The cross-fauh survey line was 500 km long, from Langqian county to Qingshuihe county, in a transition zone between Bayan Har block and Qiangtang block, in an area of high elevation, large undulating terrain, and complex geological features. An interpretation of the data was carried out together with other kinds of data, such as seismic exploration and magnetic exploration. The result shows that gravity is sensitive to fault bounda- ry ; the geologic structure of the region is complex at middle and upper depths, and the density profile reveals an eastward-pushing fault movement.
基金supported by Italian 1:50,000 Geological Mapping (CARGdR egione Liguria Project, University of Pavia grants)
文摘The Early Paleozoic evolution of the northern margin of Gondwana is characterized by several episodes of bimodal magmatism intruded or outpoured within thick sedimentary basins. These processes are well recorded in the Variscan blocks incorporated in the Ligurian Alps because they experienced low temperature Alpine metamorphism. During the Paleozoic, these blocks, together with the other Alpine basements, were placed between the Corsica-Sardinia and the Bohemian Massif along the northern margin of Gondwana. In this framework, they host several a variegated lithostratigraphy forming two main complexes(Complexs I and II) that can be distinguished by both the protoliths and their crosscutting relationships, which indicate that the acidic and mafic intrusives of Complex II cut an already folded sequence made of sediments, basalts and granitoids of Complex I. Both complexes were involved in the Variscan orogenic phases as highlighted by the pervasive eclogite-amphibolite facies schistosity(foliation II). However, rare relicts of a metamorphic foliation at amphibolite facies conditions(foliation I)is locally preserved only in the rocks of Complex I. It is debatable if this schistosity was produced during the early folding event e occurred between the emplacement of Complex I and II e rather than during an early stage of the Variscan metamorphic cycle.New SHRIMP and LA ICP-MS Ue Pb zircon dating integrated with literature data, provide emplacement ages of the several volcanic or intrusive bodies of both complexes. The igneous activity of Complex I is dated between 507 ± 15 Ma and 494 ± 5 Ma, while Complex II between 467 ± 12 Ma and 445.5 ± 12 Ma.The folding event recorded only by the Complex I should therefore have occurred between 494 ± 5 Ma and 467 ± 12 Ma. The Variscan eclogite-amphibolite facies metamorphism is instead constrained between ~420 Ma and ~300 Ma. These ages and the geochemical signature of these rocks allow constraining the Early Paleozoic tectono-magmatic evolution of the Ligurian blocks, from a middleeupper Cambrian rifting stage, through the formation of an Early Ordovician volcanic arc during the Rheic Ocean subduction, until a Late Ordovician extension related to the arc collapse and subsequent rifting of the PaleoThetys. Furthermore, the ~420-350 Ma ages from zircon rims testify to thermal perturbations that may be associated with the Silurian rifting-related magmatism, followed by the subduction-collisional phases of the Variscan orogeny.
