Journals
  Publication Years
  Keywords
Search within results Open Search
Please wait a minute...
For Selected: Toggle Thumbnails
Pore Structure Characteristics and Influencing Factors of Deep Sandstone Reservoirs: A Case Study of Guaizihu Depression in Yin’e Basin
PENG Mou, LI Jianghai, YANG Bo
Acta Scientiarum Naturalium Universitatis Pekinensis    2024, 60 (2): 249-264.   DOI: 10.13209/j.0479-8023.2024.001
Abstract55)   HTML    PDF(pc) (42297KB)(14)       Save
This paper takes the deep sandstone of Bayingebi Formation in Guaizihu Sag of Yin’e Basin as the research object. Based on the basic characteristics of the reservoir, this article uses the constant rate mercury intrusion method to distinguish pores and throats and quantitatively characterize the characteristic parameters of pores and throats. Combined with scanning electron microscopy and casting thin section method, the morphological characteristics of pores and throats are qualitatively characterized, and the differences in microscopic pore structure are analyzed. In addition, different pore types are classified according to the fractal dimension of pore throat, and the main factors affecting the development of reservoir pores are discussed. The results show that the reservoir rock types in this area are mainly feldspar lithic sandstone with low compositional maturity. The average porosity of sandstone reservoir in the study area is 10.8%, and the average permeability is 1.17 mD, which belongs to low porosity and ultra-low permeability reservoir. Reservoir space types are mainly primary intergranular pores, dissolution pores and microfractures. The average pore radius is 195 μm, and the average throat radius is 3.5 μm. The pore structure types of the reservoir are divided into micro pore small throat type, small pore small throat type and large pore coarse throat type. The study area generally has the characteristics of relatively large pore-throat ratio, good pore-throat configuration relationship is an important factor affecting reservoir physical properties, and the main controlling factors affecting pore development are the combined effects of early diagenesis, organic acid dissolution and hydrocarbon filling. After relatively weak compaction and cementation transformation, the original debris provides a material and spatial basis for later dissolution, and the thick organic-rich mudstone at the top and bottom of the reservoir provides a source of organic acid dissolution and hydrocarbon filling. 
Related Articles | Metrics | Comments0
Paleo-sandblows and Their Represented Paleoseismic Events in the Taoyuan Basin, Yunnan Province
CHANG Zufeng, LUO Lin, LIU Changwei, LI Jianlin
Acta Scientiarum Naturalium Universitatis Pekinensis    2024, 60 (2): 227-238.   DOI: 10.13209/j.0479-8023.2023.097
Abstract49)   HTML    PDF(pc) (66194KB)(23)       Save
Based on the results of field geological surveys and stratigraphic dating data, the paleo-sandblows and their represented paleoseismic events developed in the upper strata of the Taoyuan Basin were analyzed. More than ten paleo-sandblow traces were outcropped in the 7-km-range from Taoyuan to Xialinong region in the Taoyuan Basin. The sandblows and their deposits are featured by mushroom-shape, umbrella-shape, sac-shape and skewed cup shape. Their large scale and wide distribution indicated that there was a strong sandblow eruption events related to paleoearthquake. The width of sandflow depositsis several meters, and the thickness is tens of centimeters to one meter. The largest one is 8 meters wide, and 1–1.5 m in the thickness. It is common to observe 1.0–4.5 m long, 0.25–0.35 m in diameter, and 0.8 m in width sand veins. The paleosol layer with good continuity is generally developed at the depth of 1.5–3.0 m below the ground, which is the ground surface at that time. These sand veins and sandflow deposits are generally developed above and below this layer. According to the 14C dating results of the top of the paleosol layer and the bottom of the overlying strata of the sandflow deposits, it is speculated that the time of the paleoseismic event forming the sandblows is 13030±40–12120±40 aBP, and its magnitude is at least greater than 7. The Chenghai-Binchuan fault was a strong active fault in the late Quaternary period, which triggered this Taoyuan earthquake.
Related Articles | Metrics | Comments0
Habitat Creation Modes Based on Balance between Water and Soil and Its Application in Ecological Restoration Engineering
WANG Zhiyong, LI Jianing, PENG Xiao, HONG Min, ZHANG Kai
Acta Scientiarum Naturalium Universitatis Pekinensis    2024, 60 (1): 165-174.   DOI: 10.13209/j.0479-8023.2023.092
Abstract81)   HTML    PDF(pc) (53797KB)(42)       Save
Methods for regulating the relationship between water and soil were summed up in 23 traditional waterscape and farmland design wisdom. Creating a reciprocal and mutually reinforcing relationship between water and soil in local area is the core of creating habitats through collection and diversion of water by cutting and filling earthwork. Moreover, two habitat creation modes, named collection mode and diversion mode, were put forward. Collection mode means building water catchment by cutting earthwork in land slope. Diversion mode means building dividing ridge by filling earthwork in inundation area. At the same time, spatial distribution pattern of two modes in river basin scale was proposed based on dynamic spatial relationship between slope and runoff inundation area. It presented a multiscale mosaic structure among diverse dividing ridges and water catchments. Potential in regulating the balance between water and soil and creating habitats being suitable for planting were shown clearly by the applications in ecological engineering practices. It could provide method and technology reference for ecological engineering practices in China.
Related Articles | Metrics | Comments0
General Method Framework of Designed Ecosystem and Its Application in Typical Habitat Creation Modes
WANG Zhiyong, LI Jianing, LIU Jiaju, PENG Xiao
Acta Scientiarum Naturalium Universitatis Pekinensis    2023, 59 (3): 501-512.   DOI: 10.13209/j.0479-8023.2022.113
Abstract236)   HTML    PDF(pc) (34349KB)(137)       Save
Based on the principles of ecology and design, the general method framework of designed ecosystem was put forward. The framework is guided by the provision of integrated ecosystem services and based on the basic laws of the ecosystem, which aims to create a balanced habitat of soil and water, configure a stable and orderly local biological network, and design recreation facilities with minimum intervention. At the same time, according to the practice of ecological restoration design and the classical ecological engineering design guides, this study summarized the key design parameters of the designed ecosystem from three aspects: structure, materials and auxiliary measures, a total of 31 items. On this basis, to engineer the traditional ecological wisdom, specific design methods and quantitative parameters of terrace, impounding-pond, dike-pond and stacking-fields habitat creation modes in the aspects of basic model characteristics, habitat unit shaping, water cycle regulation, soil environment regulation, biological community allocation and recreation facilities construction were put forward. This result provides an engineering and replicable method for the practice of large area ecosystem restoration engineering in China.
Related Articles | Metrics | Comments0
Late-Quaternary Activity of Tongdian-Madeng Basin Segment of Weixi-Qiaohou Fault
CHANG Zufeng, LI Jianlin, CHANG Hao, LUO Lin, LIU Changwei, HE Shufang
Acta Scientiarum Naturalium Universitatis Pekinensis    2022, 58 (5): 875-887.   DOI: 10.13209/j.0479-8023.2022.057
Abstract373)   HTML    PDF(pc) (111524KB)(307)       Save
Based on the field survey results, the geological and geomorphic evidences of Late Quaternary activity and paleoseismic events in Tongdian-Madeng basin section of Weixi-Qiaohou fault are studied. The results show that the segment is active during Holocene and dominated by dextral strike slip. Its horizontal slip rate is 1.8-2.4 mm/a, and vertical slip rate is 0.30-0.35 mm/a since the Holocene. The OSL ages of faulted strata revealed by Yushuiping trench are 5.1±0.6, 5.3±0.2, 7.5±0.5 and 10.3±0.9 ka respectively, belonging to Holocene accumulation. Several faults developed on T2 terrace of a small river in Xiataiping offset all the strata under the modern loam layer, and the OSL age of the upper stratum is 5.3±0.6 ka. The activity of fault since Pliocene resulted in strong tectonic deformation of the Pliocene sediments, and its property also changed from thrust to dextral strike slip. Seismic phenomena such as seismic wedge, sand vein and soft sedimentary structural deformation are exposed at Xinmin, Gaichang and other trenches and the offset amount is mostly about 1 m. It is considered to be caused by the same seismic event, with an occurrence time of about 28000 aBP and a magnitude of seven.
Related Articles | Metrics | Comments0
Main Controlling Factors of Uplift Deformation of Longmenshan Structural Belt: Insight from Discrete Element Method
WANG Ying, LI Jianghai, MA Changming, SONG Juechen
Acta Scientiarum Naturalium Universitatis Pekinensis    2022, 58 (5): 850-860.   DOI: 10.13209/j.0479-8023.2022.056
Abstract924)   HTML    PDF(pc) (11642KB)(201)       Save
 In order to explore the main controlling factors of uplift deformation of Longmenshan structural belt, based on the differences in the properties of lower crust material layer between the east and west sides of Longmenshan structural belt, three groups of PFC2D discrete element numerical simulation are carried out to realize quantitative analysis. The experimental deformation results and the model particle motion vector map show that under the condition of no obvious difference in the material properties of the lower crust, the existence of plate collision and compression stress and crustal thickness difference will not form a huge topographic elevation difference in the Longmenshan structural belt. When there are obvious differences in the viscosity coefficient of the lower crust, the relative value of the particle movement rate of the weak lower crust material layer is 1.5?2.94 m/s, and the average movement rate is 1.62 m/s, which is about 54 times of the average movement rate of the particles of the hard lower crust layer. Uplift deformation occurs in the middle of the model (Longmenshan structural belt), with a vertical influence range of 94.74% and a uplift amplitude of 19.85%. The particles of the middle crust and upper crust overlying the weak lower crust have a large upward velocity component, and the upward trend of the material layer of the upper crust is obvious. There is a 20 km thickness difference between Bayankala block and the crust of Sichuan Basin, which increases the uplift amplitude of Longmenshan structural belt from 14.79% to 19.85%. Based on the comprehensive analysis of three discrete element simulation experiments, it is concluded that the viscosity difference between the material layer of the lower crust of Bayan Kara block and the material layer of the underground block of Sichuan Basin is the most key control factor for the vertical uplift deformation of Longmenshan structural belt. On the premise that there are obvious differences in the viscosity structure of the lower crust, the crustal thickness differences between the Bayan Kara block and the Sichuan Basin significantly promote the vertical thrust uplift amplitude of the Longmenshan structural belt. 
Related Articles | Metrics | Comments0
Synthesis of Pyrite FeS2 Nanospheres and Study on the Supercapacitor Performance
LI Jianzhuo, CHUAN Xiuyun
Acta Scientiarum Naturalium Universitatis Pekinensis    2021, 57 (4): 623-631.   DOI: 10.13209/j.0479-8023.2021.058
Abstract590)   HTML    PDF(pc) (2351KB)(177)       Save
Pyrite FeS2 nanospheres was synthesized through a simple solvothermal method in one step, and the electrochemical performance as the electrode material of supercapacitor was studied. The structure, morphology, specific surface area and pore volume of the material were characterized and measured experimentally, and its supercapacitor performances in three common electrolytes (6 M KOH, 6 M NaOH and 1 M Na2SO4) were tested by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS). The results show that the product is homogeneous pyrite FeS2 nanospheres with a diameter of about 300?600 nm, showing obvious pseudocapacitance characteristics in all three electrolytes. When the electrolyte is KOH, it shows the highest specific capacitance, reaching 732.9 F/g at the current density of 2 A/g and 307.1 F/g at the current density of 20 A/g with the capacity retention rate of 41.9%. It is demonstrated that the synthesized FeS2 nanospheres is an excellent electrode material for supercapacitors. 
Related Articles | Metrics | Comments0
Analysis of Formation and Evolution of Salt Diapir in the Contractional Domain of Central Lower Congo Basin Based on Analogue and Discrete Element Modeling
CHENG Peng, LI Jianghai, LIU Zhiqiang
Acta Scientiarum Naturalium Universitatis Pekinensis    2021, 57 (3): 470-480.   DOI: 10.13209/j.0479-8023.2021.025
Abstract732)   HTML    PDF(pc) (9244KB)(176)       Save
Based on the seismic profile, analogue modeling and discrete element modeling method were carried out to study the deep genetic mechanism of the gravity instability structure and evolution process of the salt diapirs in the contractional zone of central Lower Congo Basin in the passive continental margin of Angola in West Africa. The effect of salt diapir activity on the migration of the sedimentary center of the mini-basin between the diapirs was further studied. The results show that the evolution process of salt diapirs in the contractional domain of central Lower Congo Basin is related to the stress conditions. In the early stage, it was mainly controlled by the effect of gravity spreading, and in the later stage, it was controlled by the effect of squeezing. According to the comparison between the results of analogue modeling and discrete element modeling and the seismic sections, the evolution process of salt diapir can be divided into the following three stages: 1) The early stage, the extended reactive diapir stage; 2) The mid stage, the passive diapir stage; 3) The late stage, squeezed active diapir stage. The sedimentary center of the mini-basin between the salt diapirs migrated to the diapirs with strong activities during the same period.
Related Articles | Metrics | Comments0
Preparation and Pyrolysis Kinetics of Phenolic Resins of Main Phenols in Semi-coking Wastewater
WANG Yali, WANG Yufei, LI Jian, PENG Jiajia, CAO Shuai, YAN Long
Acta Scientiarum Naturalium Universitatis Pekinensis    2020, 56 (6): 975-982.   DOI: 10.13209/j.0479-8023.2020.030
Abstract1051)   HTML    PDF(pc) (1292KB)(305)       Save
The composition and concentration of organic compounds in semi-coking wastewater were determined by GC-MS. The mixtures of a few of the five most representative phenolic substances (phenol, m-cresol, 2,3-dimethylphenol, catechol and 2,6-dimethylphenol) were utilized to simulate semi-coking wastewater. Phenolic resins in the simulated semi-coking wastewater were prepared in the presence of formaldehyde. The phenolic resins were characterized by in-situ infrared and thermal analysis. The pyrolysis kinetic parameters obtained from analyzing thermogravimetric analysis data indicated that a mixture of phenolic compounds had higher crosslinking degree and the phenolic resin was more stable. This study provides a theoretical basis for optimizing of semicoking wastewater treatment by utilizing formaldehyde.
Related Articles | Metrics | Comments0
Synoptic Characteristics Associated with Aerosol Pollution during the Same Period of Beijing Olympic and Paralympic Winter Games in History
MIAO Yucong, PENG Yanyu, LI Jian, ZHANG Gen
Acta Scientiarum Naturalium Universitatis Pekinensis    2020, 56 (5): 815-823.   DOI: 10.13209/j.0479-8023.2020.062
Abstract1096)   HTML    PDF(pc) (2833KB)(206)       Save
To understand the complicated relationships between synoptic forcing, regional transport and aerosol pollution during the same period of the Beijing Olympic and Paralympic Winter Games in history from 2015 to 2019, long-term meteorological observations, aerosol measurements and radiosonde data in Beijing and Zhangjiakou were analyzed, in combination with numerical simulation and objective synoptic classification. It’s found that the heavy aerosol pollution in both Beijing and Zhangjiakou is associated with warm, moist, and calm wind situations at the ground level. At the upper level, the heavy pollution events in Beijing are related to the 850 hPa southwest winds, and the heavy pollutions in Zhangjiakou are typically associated with the southwest and south winds. Although the distance between the centers of Beijing and Zhangjiakou is around 160 km, the increasing aerosol concentrations and occurrence of thermal inversion aloft are often synchronously observed in those two cities, which are relevant to certain large-scale synoptic patterns. When there is a high-pressure system in eastern China at the 850 hPa level, the warmer air mass in the southern regions can be brought to Beijing and Zhangjiakou, enhancing the thermal inversion and suppressing the development of boundary layer to some extent. Meanwhile, the aerosols emitted from the south Hebei, the north Shanxi and middle Inner Mongolia can be transported to Beijing, leading to the exacerbation of pollution. With a higher altitude, the polluted air masses advected to Zhangjiakou are mainly from the western upstream regions, which can deteriorate the air quality in addition to the local emissions. Thus, under the unfavorable synoptic conditions, joint efforts to reduce emissions in Beijing, Zhangjiakou, and those upstream regions should be considered to effectively mitigate the heavy pollution.
Related Articles | Metrics | Comments0
Change of Vegetation and Contribution of Ecological Construction Projects in Hebei Province
ZHU Lijun, MENG Jijun, LI Jiangfeng
Acta Scientiarum Naturalium Universitatis Pekinensis    2020, 56 (4): 755-764.   DOI: 10.13209/j.0479-8023.2020.047
Abstract944)   HTML    PDF(pc) (9746KB)(155)       Save
This study analyzed the characteristics of vegetation change, and built spatial econometric models to identify the affecting factors of vegetation change in Hebei Province with topographic, meteorological, and socio-economic data. On this basis, the hotspot analysis and artificial neural network were used to further quantify the specific impact extent of the ecological projects on vegetation change. The results showed that vegetation index in the southern and northeastern regions of Hebei Province was higher than that in the northwestern areas. Vegetation improved in most areas during the study period and the area proportion of NDVI sustained regions, increased regions and decreased regions is 15.14%, 61.75% and 23.11%, respectively. The main influencing factors of NDVI were elevation, per capita GDP and population density in 2000, which had a negative effect on vegetation in Hebei Province, while NDVI in 2015 was also affected by the additional factors, precipitation and ecological construction program, which had a positive effect. The impacts of ecological construction projects on NDVI were positive in most areas, and most of them were slightly improved. The areas with significant improvement were distributed in Chengde City and Zhangjiakou City, which were also hot spots of NDVI change and EPA (Ecological Project Area) change. The negative impact of ecological construction project on NDVI mainly occurred in the northwest of Zhangjiakou City, the east of Qinhuangdao and Tangshan, and the urban built-up area in the south of Hebei Province. The research results provide a basis for the scientific evaluation of the performance of national ecological construction projects and support for ecological protection and vegetation restoration of Hebei Province.
Related Articles | Metrics | Comments0
Paleoenvironment Interpretation of Early Cambrian Yurtus Formation, Tarim Basin, and Its Mechanism for Organic Carbon Accumulation
WANG Zhihong, DING Weiming, LI Jian, HAO Cuiguo, LIU Hui, LI Tong, DONG Lin
Acta Scientiarum Naturalium Universitatis Pekinensis    2020, 56 (4): 667-678.   DOI: 10.13209/j.0479-8023.2020.045
Abstract1266)   HTML    PDF(pc) (26226KB)(113)       Save
This study scrutinizes the petrological and geochemical signatures by systematically sampling three sections of Yurtus Formation, which deposited during the early Cambrian in the western margin of Tarim Basin. The redox conditions together with the intensity of primary productivity during Yurtus Formation deposition are reconstructed, which provide theoretical basis for the distribution of source rocks and evaluation of reservoir potentials. The extremely high Ba content (>1000 μg/g) and appearance of barite in the lower part of Yurtus Formation implies high primary productivity, which explains the substantive organic matter in the surface ocean and is also consistent with the abundant phytoplankton fossil record and high TOC content. The large positive excursion of δ15N (>8‰) in the lower parts of Yurtus Formation probably is resulted from denitrification or annamox, both of which occur only when O2 is depleted. It may indicate that organic matter transporting from the surface ocean to deeper ocean could consume dissolved oxygen by the process of degradation, which would drive the condition of deeper ocean more reduced. Meanwhile, low Ge/Si values of cherts in the lower part of Yurtus Formation indicate normal seawater origin of Si input. Oversaturation state of silica promotes the organic matter preservation due to relatively fast cementation. 
Related Articles | Metrics | Comments0
Study of Partial Nitritation and Annmmox Process Treating Mainstream Municipal Wastewater with SASMBR
LI Jianqi, YU Daodao, LÜ Yufeng, LIU Sitong
Acta Scientiarum Naturalium Universitatis Pekinensis    2020, 56 (2): 331-340.   DOI: 10.13209/j.0479-8023.2020.010
Abstract737)   HTML    PDF(pc) (1257KB)(126)       Save
Based on the reactor unstable and low nitrogen removal rate when Partial Nitritation and Anammox (PN/A) process treat municipal wastewater, a new composite bioreactor named sequencing batch-baffled-separate membrane bioreactor (SASMBR) was designed and manufactured. This reactor was applied to the treating of municipal wastewater using PN/A process to explore the performance and analyze the operating costs of the reactor. The results showed that highly efficient and stable denitrification processes had been achieved using PN/A process in this reactor, with TN removal rate up to 80%–85%, nitrogen removal rate (NRR) up to 0.20–0.22 kgN/(m3·d) and the effluent TN concentration was below 8 mg/L. 16SrRNA gene sequencing analysis found that the baffles set inside the bioreactor could enrich ammonia oxidation bacteria (AOB), which ensuring a good treating performance of the reactor. Non-woven fabrics in the SASMBR could effectively retain anaerobic ammonium oxidizing bacteria (AnAOB), and the increasing abundance of AOB in the SASMBR could provide anaerobic environment and NO2--N substrate for the growth of AnAOB. As such, the combination inevitably accelerated the quick startup of the reactor and maintained its highly efficient and stable running. The operating costs was 0.307 yuan/m3 which was significantly lower than the traditional municipal wastewater treatment plants.
Related Articles | Metrics | Comments0
Meteorological Characteristics of Prolong Low-Visibility Events in Haikou during February 2018
YAN Yan, MIAO Yucong, LI Jian, GUO Jianping
Acta Scientiarum Naturalium Universitatis Pekinensis    2019, 55 (5): 899-906.   DOI: 10.13209/j.0479-8023.2019.056
Abstract912)   HTML    PDF(pc) (1431KB)(168)       Save
To understand the meteorological characteristics associated with the prolong low-visibility events occurring in Haikou and Qiongzhou Strait during February 2018, we systematically analyzed the visibility data, surface meteorological observations, sounding data and reanalysis data. It’s found that the low-visibility events in winter in Haikou typically occurred under relatively warmer and moister conditions. In winter, the visibility of Haikou was significantly anti-correlated with relative humidity, temperature and thermal stability, and was significantly correlated with wind speed and boundary layer height. No significant correlation was found between visibility and PM2.5 concentration. At the 925 hPa level, when Haikou was located to the south of high-pressure system, good visibility could be observed associated with the northeasterly winds; in contrast, when Haikou was controlled by the southeasterly winds, the warm and moisture air mass could be brought to Haikou, favoring the occurrence of low-visibility events.
Related Articles | Metrics | Comments0
Sedimentary Characteristics and Tectonic Segmentation of the Passive Continental Margin of the South Atlantic Ocean
PAN Xiangru, LI Jianghai, TAO Chongzhi, ZHANG Yu, YANG Menglian
Acta Scientiarum Naturalium Universitatis Pekinensis    2019, 55 (4): 654-662.   DOI: 10.13209/j.0479-8023.2019.049
Abstract751)   HTML    PDF(pc) (6884KB)(133)       Save
Seven major sediment centers were recognized based on the Total Sediment Thickness of the World’s Oceans and Marginal Seas (NCEI, NOAA), integrated with the research on the passive margin basins, oceanic plateaus, main transform faults. It could be revealed that the western and the northern parts of the South Atlantic Ocean have much thicker sedimentary than the eastern and the southern parts. The nature of sedimentary and tectonic of the passive continental margin and passive continental margin basins were discussed in four segments of South Atlantic Ocean Margin: equatorial segment, central segment, southern segment and Falkland segment. The Equatorial segment was controlled by large transform faults, where the Triassic salt layer developed. The Aptian salt layer was found in the Central segment, which was the key area of oil and gas exploration. Volcanism deeply influenced the Southern segment with the Seaward Dipping Reflectors.
Related Articles | Metrics | Comments0
Seafloor Bathymetry Response to Different Time Scale of Magmatic Supply Fluctuation
YUN Xiaorui, LI Jianghai, WU Tongwen, SONG Juechen
Acta Scientiarum Naturalium Universitatis Pekinensis    2019, 55 (3): 437-444.   DOI: 10.13209/j.0479-8023.2018.025
Abstract668)   HTML    PDF(pc) (9575KB)(97)       Save
The finite-difference numerical simulation is used to reproduce the seafloor bathymetry near mid-ocean ridges. The magma supply in the model changes regularly with fluctuation period and amplitude. The results indicate that only when the magmatic supply fluctuation period is greater than the time interval between the formation of two faults on the same side of mid-ocean ridge, the formation process of the seafloor bathymetry can be influenced and recorded. Combined with numerical simulation results and different types of ocean ridge topography, this paper considers that the fast spreading mid-ocean ridge is the only ridges type that can record three magmatic supply fluctuation period of Milankovich cycles (eccentricity (100 ka), obliquity (41 ka) and precession (23 ka)) on the bathymetry. Bathymetry in mid-speed mid-ocean ridges and part of slow spreading midocean ridges with sufficient magmatic supply may be related to the magmatic supply fluctuation period on the 100 ka time scale. seafloor bathymetry in most of the slow-spreading mid-ocean ridges is not affected by magmatic supply fluctuation period of 100 ka or less.
Related Articles | Metrics | Comments0
Geomorphological Characteristics of the Quaternary Volcanoes and Their Tectonic Implications in Aershan Region, Central Greater Khingan Range
MA Yuxuan, LI Jianghai, CHEN Yaohua
Acta Scientiarum Naturalium Universitatis Pekinensis    2019, 55 (2): 289-298.   DOI: 10.13209/j.0479-8023.2019.012
Abstract1119)   HTML    PDF(pc) (33266KB)(196)       Save

Based on ZY-3 high resolution satellite image and digital elevation model (DEM), the authors obtained volcanic geomorphology features in Aershan volcanic region by means of satellite image interpretation, the relief degree of surface and surficial-slope analysis. According to the results of the study, 19 Quaternary volcanos were found. They could be divided into five categories. The landforms can be divided into four classes according to relief degree of surface. Low position middle mountain is the main type (39.61%), followed by low position low mountain (36.24%). 80% of the long axis direction of the elliptical volcanic cones are ranging from 45° to 75° with a median value of 58.5°. It is parallel to the NE-trending volcanic chain of Xiaodonggou volcano-Shihaogou basin volcano-Yanshan-Gaoshan. The horseshoe-shaped craters are in the direction of NE, SW and NW. The median difference between NE and SW horseshoe-shaped craters is about 180°. The NW horseshoe craters are almost parallel to NW faults. The authors predict that there are NE faults controlling volcanic eruption and distribution. Thereby an inference can be drawn that the NE-trending fractured zones were controlled by Mesozoic basement faults in the study area, and provided the channel for magma to approach. Fracture controlled the magma ascending and the formation of NE-trending volcanic apparatus, and eventually affected the distribution of volcanic cones and morphology.

Related Articles | Metrics | Comments0
Salt Structure Formation Modeling Controlled by Structure Inclination Angle: Take the Lower Congo Basin as an Example
WANG Dianju, LI Jianghai, CHENG Peng, LIU Zhiqiang, YU Fahao
Acta Scientiarum Naturalium Universitatis Pekinensis    2019, 55 (2): 277-288.   DOI: 10.13209/j.0479-8023.2018.095
Abstract698)   HTML    PDF(pc) (28196KB)(132)       Save

Based on the data of three seismic work areas in the Lower Congo Basin, nine typical salt-related tectonic patterns are summarized in the basin and the distribution pattern of salt structures is confirmed. Established with the base tilt angle as a single variable based on the discrete element numerical simulation method, and evolution results of the structure and motion vectors are obtained. With the increase of the basement inclination angle, the flow velocity of salt rock and its overlying sediments gradually increases, and the subsequent terrigenous sediment transport distance is also longer. The basement inclination mainly has three kinds of control effects on the salt rock flow: differential compaction as the master control, differential compaction and gravity gliding combined, gravity gliding as master control. These three control effects are all affected by the basement inclination angle and appear in turn with the change of the angle. Based on the analysis results above, control pattern of basement inclination on salt rock flow in the passive margin basin of the South Atlantic is established.

Related Articles | Metrics | Comments0
The Aeolian Bedforms and the Reconstruction of Late Holocene Wind Direction in Qaidam Basin
WU Tongwen, LI Jianghai, YANG Menglian
Acta Scientiarum Naturalium Universitatis Pekinensis    2018, 54 (5): 1021-1027.   DOI: 10.13209/j.0479-8023.2018.042
Abstract1480)   HTML    PDF(pc) (41209KB)(179)       Save

Using remote sensing image for the aeolian morphology and high resolution ancient monsoon indicators, the authors restore how the wind blows in Qaidam Basin since late Holocene. The results show that the prevailing winds of the basin were northwest winds, at the same time there were a small amount of westerly and north wind, with the summer monsoon and westerly circulation having little effect on the wind models. The eastern dune and Yardang landforms of the basin recorded the westerly winds of the last glacial, but the landforms in the midwest indicated that the Asian winter monsoon developed from the northwest during late Holocene. The changes in the atmospheric circulation model took place around 4000 aBP years ago, which was an important node, basin climate shifting from warm and humid to cold and dry.

Related Articles | Metrics | Comments0
Identification of Supercooled Water Clouds by Using Micro Pulse Lidar
SONG Jiye, TAN Wangshu, LI Chengcai, YU Yingli, LI Jian, CHU Yiqi
Acta Scientiarum Naturalium Universitatis Pekinensis    2018, 54 (5): 961-969.   DOI: 10.13209/j.0479-8023.2018.022
Abstract1335)   HTML    PDF(pc) (5225KB)(150)       Save

On the basis of a previous algorithm of cloud detection, clouds and aerosols are distinguished by analyzing the backscatter signals of a micro pulse lidar. In this way, the content of clouds are classified into ice, water, mixed-phase clouds and horizontal oriented ice flakes. Finally, the supercooled water clouds are distinguished from water clouds by the information of temperature profiles. The monthly changes of the appearance heights and proportions of the various clouds are also calculated with one-year observations over the lidar site. The supercooled clouds are found to appear at 9.84% of all the cloudy time, and 11.99% of all the time for clouds at from 0℃ to − 40℃.

Related Articles | Metrics | Comments0
Characteristics and Genesis of Geoheritage Resources of Taihang Mountain
WANG Hui, LI Jianghai, WU Tongwen
Acta Scientiarum Naturalium Universitatis Pekinensis    2018, 54 (3): 546-554.   DOI: 10.13209/j.0479-8023.2017.098
Abstract1880)   HTML20)    PDF(pc) (7748KB)(665)       Save

Based on field investigation, the previous scientific research and studies of genesis, shapes, scales of geoheritage resources, the authors divided the geoheritage resources of Taihang Mountain into 5 categories, i.e., geological profiles, geological structure, paleontology, geomorphologic landscape and water landscape. The most typical geological heritages are tectonic landform, fluvial landform, rock landform and waterfall landform. Combined with Cenozoic geological background of Taihang Mountain, the interrelationship and genesis of planation surface, canyon landform, waterfall landform and karst landform was studied in detail. The results have great significance in promoting the scientific value of the geological heritage and provide lots of materials for the study of the evolution of Taihang Mountain.

Related Articles | Metrics | Comments0
Petroleum Geology and Exploration Potential of Vienna Basin
ZHANG Hongwei, LI Jianghai, ZHANG Liwei
Acta Scientiarum Naturalium Universitatis Pekinensis    2016, 52 (5): 881-890.   DOI: 10.13209/j.0479-8023.2016.047
Abstract1366)   HTML    PDF(pc) (1820KB)(1236)       Save

The oil geology feature of Vienna Basin was summarized and potential of exploration was discussed by analysising the strata of Vienna Basin and fracture development characteristics. Vienna Basin is a pull-apart basin located between the East Alps and West Carpathian. Its basement is composed of the Hercynian Bohemian Massif and Paleozoic and Mesozoic strata. The tectonic evolution can be divided into three stages, including Jurassic extensional rifting, Cretaceous-Early Miocene over-thrusting and Middle Miocene pull-parting stage. There are three structural lays from top to bottom, Jurassic-Cretaceous autochthonous, Permian-Paleogene allochthonous Alpine nappes and Neogene sediments. There are two sets of source rocks: the upper Jurassic marls and Paleogene shale, among which, the Upper Jurassic Kimmeridgian Malmian marls are considered to be the major source rocks. Reservoirs occur at various horizons from Triassic to Neogene Miocene strata, among which, the most important reservoirs are Miocene sandstones that deposit in shallow-water delta environment and contain 76% of all reserves, and the minor reservoirs are the Triassic dolosparite. Neogene shales provide the regional top-seal. After evaluation, it is considered that Mesozoic allochthonous napps (flysch turbidite and Triassic dolomite) and Mesozoic autochthonous succession (the second and the third structural layer) are the most prospective for exploration.

Related Articles | Metrics | Comments0
Strain and Kinematic Vorticity Analysis of the Liaonan Metamorphic Core Complex Ductile Detachment Zone
LI Jianbo, GUO Lei, OUYANG Zhixia, ZENG Tao, DING Yuanjun, ZHANG Ying
Acta Scientiarum Naturalium Universitatis Pekinensis    2015, 51 (6): 1078-1090.   DOI: 10.13209/j.0479-8023.2015.111
Abstract1102)      PDF(pc) (2298KB)(727)       Save

The Liaonan metamorphic core complex (MCC) developed a NNE trend, NWW-dipped, low-angle detachment fault. Ductile shear zone occurred in the lower part and mainly consists of mylonitic granitic gneisses, which indicated a top-to-NWW shearing. Finite strain measurement of feldspar strain markers were estimated by the Rf /φ method. It suggested that strain intensities of mylonites (Es) changed from 0.36 to 1.0 with an average of 0.75. Fulin and Hossack diagrams indicated strain types were close to flattening strain (lod parameter υ=0.11-0.98). Kinematic vorticity of mylonitic foliations and stretching lineations were estimated by Mohr diagram method and long and short axis method. The results indicated that kinematic vorticity ranged from 0.74 to 0.96 with an average of 0.85, which suggested that the foliations and lineations of mylonites recorded a bulk simple-dominated general shearing. The Kinematic vorticity during formation of extensional crenulation cleavage estimated by C′ method ranged from 0.10 to 0.84 with 0.58 on average. It recorded a later bulk pure-dominated general shearing. Based on the strain measurement, kinematic vorticity and thickness of the detachment fault, the quantification of thinning for the ductile shearing were calculated, which ranged from 130 to 705 m. All results suggested that the deformation mechanism of the Liaonan MCC was represented by earlier simple-dominated shearing and later pure-dominated shearing.

Related Articles | Metrics | Comments0
Estimating Air Pollutants Emissions from Open Burning of Crop Residues in Jianghan Plain
LI Jianfeng;SONG Yu;LI Mengmeng;HUANG Xin
   2015, 51 (4): 647-656.   DOI: 10.13209/j.0479-8023.2015.088
Abstract1094)      PDF(pc) (1058KB)(478)       Save
To investigate the emissions from open burning of crop residues in Jianghan Plain by using the Emission Factor Method, household surveys were conducted to obtain the percentages of crop residues burned in fields. Household survey statistics, GLC2000-China product and MODIS active fire products (MOD/MYD14A1) were used to analyze the temporal-spatial distribution of crop residues burning emissions in Jianghan Plain. The results gave a total emission of 73.3 Gg PM2.5, 18.6 Gg OC, 3.27 Gg BC, 7763 Gg CO2, 238 Gg CO, 10.6 Gg CH4, 28.6 Gg NMHCs, 0.382 Gg N2O, 5.74 Gg NH3, 8.26 Gg SO2 and 17.1 Gg NOx from the open burning of crop residues, in 2010, which happened most frequently in May, September and October. Among all subregions, Jianli County contributed the most to the total crop burning emissions, followed by Xiantao and Tianmen City, while Jingzhou municipal district had the highest PM2.5 emissions per unit area. Rice straw was the dominant source of crop burning emissions among all types of crop residues, followed by rape straw and wheat straw.
Reference | Related Articles | Metrics | Comments0
Geochronology, Geochemistry, Hf Isotope of Xiaojinggou Pluton in the Northern Margin of North China Craton and Its Tectonic Implications
MO Nan,GUO Lei,TONG Ying,WANG Tao,LIU Jiang,LI Jianbo
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract693)      PDF(pc) (2261KB)(757)       Save
In order to enhance the understanding of the late Paleozoic tectonic settings of northern margin of the north China craton (NNCC) and closure time of the Paleo-Asian Ocean, the zircon U-Pb age, geochemistry and zircon Hf isotope of the Xiaojinggou granite are conducted by LA-MC-ICP-MS, ICP-AES and ICP-MS. The zircon U-Pb dating results indicate that the Xiaojinggou pluton was intruded at Permian (275±1 Ma, MSWD=0.93). All the granite have high contents of SiO2 (70.72%?to?72.64%), K2O (4.19% to 4.23%) with moderate A/CNK values (averaged at 1.1), suggesting that Xiaojinggou pluton is slightly peraluminous and belongs to the high-K calc-alkaline series. The concentrations of rare earth elements (ΣREE) varies in the range of 87.67 to 101.51 μg/g. The Xiaojinggou pluton is characterized by enriched LREE patterns with slightly negative Eu anomalies. It is enriched in large ion lithophile elements (LILE, e.g. Rb, Ba, K, Sr), but depleted in high field strength elements (HFSEs, e.g. Nb, Ta, Y, Yb, Lu), which suggest this plutou may be derived from partial melting of the lower crust. Zircon εHf(t) value varies from -9.56 to -5.00 and TDM2 varies in the range of 1.91 to 1.61 Ga. All these characters indicates that the Xiaojinggou pluton is probably generated by partial melting of Lower Proterozoic crust of the NNCC, accompanied by the possible assimilation of mantle-derived magmas. In view of the evolution of the Permian granitic magmatism in the NNCC, middle Permian Xiaojinggou pluton formes in the transition period from subduction to collision/post-collision, and the Paleo-Asian Ocean should close before late Permian.
Related Articles | Metrics | Comments0
Genesis of High Aeromagnetic Anomaly Zone in Central Tarim Basin: New Evidence from Seismic Profiles
LI Wenshan,LI Jianghai,ZHOU Xiaobei,LI Weibo,WANG Honghao,YANG Jingyi
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract839)      PDF(pc) (3995KB)(756)       Save
Based on a comprehensive analysis of borehole and structural features, the authors interpreted 2D seismic data in East Tarim and 3D seismic data in Central Tarim area. Under the layer of Sinian, a sag-depression dual structure intracontinental rift was identified. The rift zone consists of 4 east-west sags, and its plane distribution is consistent with the hige aeromagnetic anomaly zone. The structural and stratigraphic analysis shows that there are bimodal volcanic rock in a typical intracontinental syn-rift sags, and it is the direct reflection of the high aeromagnetic anomaly; the boundary faults of 4 sags are consistent with axial trace of high aeromagnetic anomaly zone, from which it can be inferred that the anomaly source has a vertical downward channel, and it relates to basement faults and upwelling of hypomagma. Further research involving calculation of the magnetic anomaly confirmed the Nanhua rift zone model. The east segment of high aeromagnetic anomaly zone is formed by rift zone, while it weakened until disappears to the middle and west; high aeromagnetic anomaly in Bachu segment is mainly caused by Permian basalt and the west segment belongs to North Tarim landmass.
Related Articles | Metrics | Comments0
Research on the Characteristics of Wind Energy Resources over Huangang Wind Farm in Jiangsu Province
WANG Yefang,LI Chengcai,SHI Guangming,LI Jian,LI Wusheng,LI Shuyong,WANG Wei
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract642)      PDF(pc) (776KB)(341)       Save
Based on the analysis of wind data measured at one wind measurement tower over Huangang Wind Farm in Jiangsu Province from Dec. 2010 to Nov. 2011, it was calculated that at 10, 50, 70 and 80 m heights the annual average wind speed was 4.0?6.1 m/s, the annual average wind power density was 80.4?238.4 W/m2, the annual effective wind power density was 116.5?262.5 W/m2, the annual effective hours were 5777?7845 h, and the annual effective wind energy density was 679.3?2041.5 (kW?h)/m2. In addition, the dominant wind directions were NNE, N and NE, the sum of them took up nearly 30% of the full year wind directions, the wind energy density of the dominant wind directions accounted for almost 50% of the full year wind energy density, and the wind speed was mainly ranging from 3 to 8 m/s, about 80% of the full year wind speeds. Overall, wind energy resource was abundant in this region. Especially the hub height of the already built wind turbines had the wind power density of more than 250 W/m2, and the effective hours took up nearly 90% of the full year. Therefore, wind energy resource had a great value of development and utilization in this region.
Related Articles | Metrics | Comments0
Emergy-Ecological Footprint Integrated Model for Eco-city Evaluation: A Case of Tianjin City
ZHANG Xuehua,LI Jian,ZHANG Hongwei
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract565)            Save
In order to avoid some shortages of traditional ecological footprint model, the authors proposed an integrated model by using emergy theory, which is named as Emergy-Ecological Footprint Integrated Model. In ecological carrying capacity calculation, the proposed model adds the carrying capacity of actual product output and virtual product supply based on material input-output theory and people ’s innovation. In ecological footprint calculation, the proposed model considers waste ecological footprint into evaluation system. Finally, the proposed model is applied in Tianjin eco-city evaluation from 2001 to 2008. The calculating result shows that the ecological carrying capacity is higher than ecological footprint, and ecological surplus is in rising tendency which expresses that Tianj in is in sustainable state.
Related Articles | Metrics | Comments0
Geochemistry of the Carboniferous Volcanic Rocks of Benbatu Formation in Sonid Youqi, Inner Mongolia and Its Geological Significance
TANG Wenhao,ZHANG Zhicheng,LI Jianfeng,FENG Zhishuo,CHEN Chen
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract703)            Save
The Carboniferous volcanic rocks of Benbatu Formation at Chagannuoer in Sonid Youqi, Inner Mongolia, consist of basalts with pillow and massive structure and dacites. The SiO2 content of the volcanic rocks mainly fallen in two ranges 48. 20% -51. 11% and 64. 66% -65. 42% , showing a bimodal distribution composition. The mafic volcanic rocks are mainly alkaline basalt series, with Na-rich and potassium-deficient. The felsic volcanic rocks belong to calc-alkaline series with high alkali content and about 3% K2O content. The pillow basalts are characterized by slightly loss LREE, enriched HREE, slightly positive Eu anomalies and high abundances in Hf, Zr and Th (HFSE). The massive basalts are characterized by enriched Rb, Th, Zr, Hf and loss Ta, Nb. The dacites have obvious severity of REE fractionation with Eu negative anomalies significantly, enriched Rb, Th, Pb, Hf, Zr and loss Eu, Sr, Nb, Ta. According to Rb-Sr isochron age, SHRIMP U-Pb zircon dating data and paleontological data, Chagannuoer bimodal volcanic rocks formed in Late Carboniferous, about 313-308 Ma. The characteristics of geochemistry and regional geology suggest that Chagannuoer bimodal volcanic rocks formed in post-collisional extensional setting, so it can be inferred that the Solonker suture zone had ever been closed before the Late Carboniferous.
Related Articles | Metrics | Comments0
On the Design of Trivium
TIAN Yun,CHEN Gongliang,LI Jianhua
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract794)            Save
In order to discuss the design principles of stream ciphers, Trivium, a candidate cipher in eSTREAM, is studied. Research about its security and efficiency is summarized. Based on the modeling structure of the algorithm and the definition of k-order primitive polynomials, new design principles of stream ciphers are illustrated. Improvements and new design of Trivium are given according to the principles.
Related Articles | Metrics | Comments0