25 November 2024, Volume 43 Issue 4

    

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  Geochemical characteristics,petrogenesis,and tectonic environment of Middle Jurassic diorite in Daomuhe,central Jilin Province

  TAI Yande, LIU Dawei, PAN Zhongcui, LIU Zhe, CAO Zhongyuan, ZHANG Yong, SUN Lingyun

  Global Geology. 2024, 43(4): 463-478.

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  To explore the magmatism and tectonic background of the central Jilin Province during the Middle Jurassic,the Daomuhe diorite was selected as the research subject. Through zircon U-Pb dating and whole-rock major oxides and trace element analysis,the study investigates the geochronology,geochemical composition,petrogenesis and tectonic setting. The LA-ICP-MS zircon U-Pb dating results show that the age of the diorite is 174.5 Ma,indicating that the intrusion crystallized during the Middle Jurassic. The rocks are characterized by low Si content,high Al and relative Na enrichment. They are enriched in light rare earth elements (LREE) and large ionic lithophile elements (LILE) such as Rb,K,Th,and U,but relatively depleted in high field strength elements (HFSE) such as Nb,Ta,P,and Ti. The Nb/Ta,La/Nb,and Th/Nb ratios indicate that the magmas of the diorite have characteristics of a mixed source from the crust and mantle,potentially related to fluid interaction from the subducting slab. Combined with the geochemical characteristics and data from previous studies,it is suggested that the Daomuhe diorite likely formed in an active continental margin environment associated with the subduction of the Paleo-Pacific Plate.
  

  
  
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  Petrogenesis and geotectonic setting of Early Jurassic granodiorites in Yeniugou，eastern Kunlun，Qinghai Province

  ZHANG Wanhui, CAO Shoulin, LI Xiaoliang, YAN Zhengping, YANG Le, LI Zhengdong, YANG De, DANG Yuanyuan, LI Liang

  Global Geology. 2024, 43(4): 479-495.

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  In order to ascertain the petrogenesis，geotectonic setting and genetic connection with Late Triassic granites of the Early Jurassic granodiorites in Yeniugou area of Golmud City，the authors systematically conducted whole-rock geochemical，zircon U-Pb dating and Lu-Hf isotopic studies on the above issues. The results show that the zircons of Yeniugou granodiorites exhibit typical magmatic zircon oscillatory zoning and Th/U values (0.25-1.28，>0.10)，with weighted average age and εHf(t) value of (198.4±1.6) Ma and 4.99-7.50，respectively. In geochemistry，the Yeniugou granodiorites show the geochemical properties of C-type adakitic rock，including high Sr [(400×10-6)-(420×10-6)] but low Mg [w(MgO)=0.95%-1.19%]，Y [(6.93×10-6)-(7.87×10-6)] and Yb [(0.65×10-6)-(0.77×10-6)] contents，with typical low Na2O/K2O ratios (1.12-1.34，<2)，relative depletion of heavy rare earth elements and high field strength elements. Based on the geotectonic evolution，it can be inferred that the primary magma of Yeniugou granodiorites originated from the partial melting of Neopro-terozoic lower crustal amphibolite (TDM2=919-759 Ma). It is a continual magmatism of the Late Indosinian，and emplaced within the same geodynamic setting as the Late Triassic granitoids in a strong extensional background that was caused by the lower crustal delamination after the closure of Paleo-Tethys Ocean and orogeny.
  

  
  
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  Analysis of tight reservoirs characteristics and main control factors of high-quality reservoirs in Denglouku Formation in Fulongquan area，southeastern Songliao Basin#br#

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  HAO Tiantian, LI Lili, HAN Fengzhu, LOU Renxing, ZHANG Yiming, LIU Yingmei, ZHANG Yanan, JIA Huanan

  Global Geology. 2024, 43(4): 496-508.

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  Previous studies on tight reservoirs in Denglouku Formation in Fulongquan area，southeastern Songliao Basin，were relatively weak，which restricted the deployment of oil and gas exploration and development in this area. The authors use rock-mineral determination，scanning electron microscopy，mineral X-ray diffraction analysis， conventional mercury injection and other technologies to conduct a detailed study on its physical properties and the main control factors of high-quality reservoirs. The results show that the general characteristics of the clastic grain composition of tight sandstones are Q30.3 F34.3R35.4，and both the compositional maturity and structural maturity are low. The reservoirs are dominated by primary intergranular pores and dissolution pores. The pore throat is mainly composed of low to ultra-low pores and ultra-low permeability and compactness. The pore throat is generally fine，mainly submicron and nanometer pore throat. According to the characteristics of conventional mercury injection，tight reservoirs are classified into Ⅰ，Ⅱ and Ⅲ types. The main controlling factors of high-quality reservoirs mainly include favorable lithology(coarse clastic rock and well sorted fine sandstone and siltstone)，favorable sedimentary microfacies(marginal beach，central beach and crevasse fan microfacies) and favorable microscopic pore structure(relative coarse pore throat radius and high movable fluid saturation).
  

  
  
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  Provenance-sedimentary system in the northern part of eastern depression in North Yellow Sea Basin

  GAO Dan, CHENG Rihui, SHEN Yanjie, TAN Xiao , WANG Liaoliang

  Global Geology. 2024, 43(4): 509-516.

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  To explore the basic characteristics of the provenance-sedimentary system in the northern part of the eastern depression of the North Yellow Sea Basin，the authors conducted a study of the lithology and facies of the eastern depression using a combination of microscopic identification of core samples and seismic reflection feature analysis. The results indicate that there are sand bodies deposited from the north towards the center of the depression，with clastic rock sedimentation predominating in the area. The rock composition is characterized by high contents of granitic and carbonate materials，with sediment coming from weathering and erosion of the basin’s peripheral uplift and the Pre-Mesozoic basement. The northern sedimentary system is primarily a fan delta sedimentary system during the Middle to Late Jurassic and Early Cretaceous，with varying scales of development during different periods. A comprehensive analysis suggests that the north is a weathered provenance，characterized by a (fan) delta-subsubaqueous fan sedimentary system.
  

  
  

  
  

  
  
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  Logging identification and productivity prediction method for low-saturation complex oil-water layers in X Oilfield#br#

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  WANG Aiyun, FU Chendong, ZHANG Zhiguo, WANG Fan, REN Li, ZHANG Weifeng, ZHANG Lihua, WANG Yumei

  Global Geology. 2024, 43(4): 517-525.

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  To address the challenge of identifying low-saturation oil layers and complex oil-water layers in the S reservoir group of X Oilfield，as well as predicting the productivity of two-phase fluids，the authors applied experimental data from core analysis and considered the effects of clay and calcium content to establish a variable exponent “new three-water saturation model”. At the same time，improvements were made to the traditional relative permeability calculation methods. Based on these improvements，several oil-water layer identification techniques were developed，including the dual saturation crossplot method，the dynamic saturation lower limit method，and the movable fluid oil saturation method. By integrating multiple parameters that reflect reservoir quality，crude oil properties，and fracturing scale，a two-phase fluid productivity prediction technology was established for both pre-fracturing and post-fracturing conditions. The verification results from ten wells showed that the fluid identification accuracy improved from 75.0% to 87.2%，and the productivity prediction accuracy reached 83.3%，achieving precise identification of oil and water within the same layer，graded evaluation，and quantitative assessment of the oil-water production ratio.
  

  
  
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  Seismic prediction and application of shallow gas reservoir in sparsely drilled deep water area of South China Sea#br#

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  SONG Peng, LI Fang, SUN Wanyuan, WU Qibin, LIU Guochang

  Global Geology. 2024, 43(4): 526-540.

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  To solve the problems of petrophysical modeling，seismic recognition and reservoir prediction caused by the lack of well logging data and low reliability in exploration of shallow/ultra-shallow gas reservoirs in the deep water area of the South China Sea. According to the geological characteristics in this area，the authors constructed a loose shallow petrophysical model，established a seismic response recognition template，and proposed the construction method of a low-frequency seismic inversion model in sparsely drilled area. The elastic parameters of shallow reservoir were effectively obtained. Using the petrophysical template，the gas-bearing property of the reservoir was predicted scientifically. The results show that the P-wave velocity of shallow gas reservoirs in the deep water area of the South China Sea is significantly affected by the gas saturation，but the effect is weakened when the saturation exceeds 10%. The shallow gas layer has low P-wave impedance and density，and the low-impedance region indicates potential gas reservoir，but the accuracy is limited in saturation prediction，and velocity ratio of P-wave and S-wave is better than that of gas saturation identification.
  

  
  
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  Noise suppression and uncertainty quantification in seismic imaging using normalizing flows#br#

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  SUN Changxiao, MAO Weijian, SHI Xingchen

  Global Geology. 2024, 43(4): 541-550.

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  To quantify the uncertainty of seismic imaging，reduce imaging artifacts and improve resolution，the authors use a technique known as normalizing flows，which employs invertible neural networks，to both enhance the images and estimate the posterior distribution of imaging results. By sampling from the estimated posterior distribution and conducting statistical analysis on these samples，the authors perform uncertainty quantification for seismic imaging. In comparison to traditional sampling methods like Markov Chain Monte Carlo，the normalizing flows method allows to predict the posterior distribution directly，instead of relying on random sampling. Therefore，it demonstrates significant advantages in terms of computational efficiency and adaptability. The authors apply this method to denoise and enhance imaging results from sparse acquisition. The tests on synthetic data show improvements in the migration imaging results of the sparse ocean bottom node acquisition data，with reduced noise，enhanced event continuity and improved depth illumination. Furthermore，by statistically analyzing the posteriors，the authors provide uncertainty quantification in the imaging results.
  
  
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  CSA-PointNet：a tree species classification model for coniferous and broad-leaved mixed forests#br#

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  HUO Yanping, LENG Liang, WANG Minshui, JI Xue, WANG Mingchang

  Global Geology. 2024, 43(4): 551-556.

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  LiDAR technology is able to quickly acquire 3D structural information of trees，and when combined with deep learning algorithms，it can achieve tree species classification at the single plant level. In order to solve the problem of losing the vertical structure，canopy shape and spatial distribution information of trees when converting point clouds into 2D images or 3D voxels，the authors propose CSA-PointNet based on PointNet，which can directly take the point cloud of an individual tree as input. By introducing both the channel-attention mechanism and the spatial-attention mechanism，it enhances the extraction of detailed features and spatial distribution characteristics，thereby improving the accuracy of tree classification. The Jingyue forest dataset is used to train and test CSA-PointNet and mainstream models (VoxNet and PointNet)，respectively. The results show that the overall classification accuracy of CSA-PointNet is 74.69%，and the kappa coefficient is 0.51，both of which are higher than those of VoxNet and PointNet.
  

  
  
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  Helium-generating potential evaluation of bauxite in Linxing area based on natural gamma-ray spectral logging#br#

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  WANG Lidang, YANG Zhanjun, WEI Boyang, ZHAO Yang, LI Ang, FU Xuehai

  Global Geology. 2024, 43(4): 557-565.

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  To investigate the helium-generating potential of bauxite in the Benxi Formation of Linxing area in the eastern margin of Ordos Basin，the authors conducted a study on the helium-generating potential of different lithologies using the natural gamma-ray spectral logging method. The results indicate that the volcanic rock source and the closed coastal shallow marine sedimentary environment provide abundant enrichment conditions of U and Th for the bauxite of the Benxi Formation in the study area. The bauxite reservoirs of the Benxi Formation show the logging characteristics of ultra-high natural gamma，high U and high Th. The bauxite layer has very high helium-generating potential，while the hydrocarbon gas produced by adjacent coal formation can serve as effective carriers for forming helium-containing natural gas reservoirs. The tight sandstone above the bauxite of the Benxi Formation demonstrates good gas-bearing capacity，with gas tests showing a helium content of 0.148%，indicating industrial mining value.
  

  
  
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  Numerical simulation of GPR based on finite-difference time-domain method and its application in tunnel geological forecasting#br#

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  YAN Yuan, CHAI Lunwei, HUANG Yong, FU Wei, ZHAO Wen, WANG Peng

  Global Geology. 2024, 43(4): 566-573.

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  To accurately identify the reflection waveform characteristics of ground penetrating radar (GPR)，the authors employed the finite-difference method to establish models for karst model，lithologic contact zone model，and fault fracture zone model. These models simulate typical unfavorable geological bodies encountered in tunnel geological forecasting. By analyzing the waveform characteristics of reflected waves，the study compares forecast results of karst structures and fault fracture zones in the engineering cases of the Xi’an-Kunming High-Speed Railway and the New Xi’an-Chengdu High-Speed Railway. Results indicate that the simulated radar waveform characteristics can serve as reference wave features for forecasting typical unfavorable geological bodies using GPR，thereby enhancing the accuracy of forecast results.
  

  
  
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  Surface subsidence monitoring and spatial-temporal evolution patterns analysis based on InSAR of Jiaohe mining area，Jilin Province#br#

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  XU Siyu, ZHANG Yibin, XU Yuwei, SONG Jinhong

  Global Geology. 2024, 43(4): 574-585.

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  The authors utilized SBAS-InSAR technology to monitor surface subsidence in the Jiaohe mining area，obtaining surface subsidence rates and cumulative subsidence results. The reliability of the monitoring results was verified through accuracy assessments and field investigations，allowing for an analysis of the spatio-temporal evolution patterns of surface subsidence in the area. The results indicate that during the monitoring period from January 2017 to December 2021，significant surface subsidence occurred in the Jiaohe mining area，primarily concentrated around Hongsheng Village，Gongye Village，and Jianshe Village. The subsidence zone S1，located in Hongsheng Village，experienced the most severe subsidences，accounting for 58.02% of the total subsidence areas in the Jiaohe mining area，with a maximum subsidence rate of -99.64 mm/a and a maximum cumulative subsidence of -499.7 mm. The average subsidence rate in the southern part of Hongsheng Village exceeded -80 mm/a.
  
  
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  Risk assessment of geological disasters based on ArcGIS in Shanwei City，Guangdong Province#br#

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  LI Yunan, ZHEN Junwei, QU Xiangyang, LU Xingyu

  Global Geology. 2024, 43(4): 586-599.

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  To provide a scientific basis for disaster prevention，reduction management and land spatial planning in Shanwei，the authors conducted a geological disaster risk assessment and zoning using the information value method based on the ArcGIS platform，and proposed risk management and control recommendations based on the results. The results indicate that the types of geological disasters in Shanwei include collapses，landslides，and debris flows，primarily on a small scale. In terms of timing，geological disasters mainly occur from April to October，and spatially，they are predominantly distributed in Luhe County. The areas of high-risk，medium-risk，and low-risk zones account for 6.59%，29.81%，and 63.60%，respectively，with the high-risk zone covering an area of 289.81 km2，primarily located in the northern low mountain area，southwestern hilly areas，and central-eastern low mountain areas. The recommendations for geological disaster risk management and control include strengthening the identification of geological disaster risks，improving geological disaster risk assessment work，and fully implementing preventive measures during critical periods for geological disasters.
  
  
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  Determination of exchangeable base calcium，magnesium，sodium and potassium in calcareous soil by modified inductively coupled plasma optical emission spectrometry#br#

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  ZHANG Yajing, LU Yuhan, NIE Xitao, ZHANG Jianan, ZHANG Yuting

  Global Geology. 2024, 43(4): 600-607.

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  To improve the analysis efficiency and accuracy of exchangeable base calcium，magnesium，sodium， potassium in calcareous soils，inductively coupled plasma optical emission spectrometry (ICP-OES) was used to determine their contents. The results showed that the optimal conditions were repeatedly washed with 70% ethanol solution，and then treated with the mixture of 0.1 mol/L ammonium chloride and 70% ethanol，8.5 in pH，several times for extraction. After drying，10 mL of 20% to 30% nitric acid solution was added for acidification. The solution preparation process was improved by replacing the traditional single standard solution with a mixed standard configuration. The selected spectral lines were calcium at 317.933 nm，magnesium at 279.553 nm，sodium at 589.592 nm，and potassium at 766.491 nm. The recovery rate of the standard samples was 98.0%-100.7%，and the detection limits were 0.008，0.005，0.004，and 0.007 mg/L，respectively. The relative standard deviation (RSD) was 0.29%-0.98% (n=5) for the two national standard samples GBW(E)070337 and GBW(E)070341. There was no significant difference between the measured results of the Jilin soil (sample 1) and those of the flame photometer and atomic absorption spectrophotometry. The results showed that this method is suitable for the analysis of exchangeable calcium，magnesium，sodium，and potassium in calcareous soils.
  

  
  
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  Geothermal geological characteristics and genetic model of sandstone thermal reservoirs in northwestern plain of Shandong#br#

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  DING Pengpeng, JIA Chao, WANG Mingzhu, WANG Hui, FENG Keyin, WEI Maojie

  Global Geology. 2024, 43(4): 608-618.

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  To analyze the geothermal geological characteristics and formation model of the sandstone geothermal reservoirs in the northwestern plain of Shandong，the authors used a combination of data collection and experimental testing methods to study the characteristics of geothermal reservoirs，geothermal gradient，hydrochemistry，and dynamic changes in water levels. The results show that the sandstone geothermal reservoirs in the northwestern plain of Shandong are mainly of the Neogene Guantao Formation and Paleogene Dongying Formation，with the deepest burial depth of the reservoir top and maximum formation thickness located in Linyi County，Liaocheng. The geothermal gradient is generally below 3.4 ℃/100 m，except in the uplifted area of Pingyuan County，where the gradient exceeds 4.0 ℃/100 m. The geothermal water is primarily of the Cl-Na type，characterized by an enrichment of Na+，K+，and Cl- ions. The geothermal water temperature ranges from 54.4 to 85.9 ℃，with the highest reservoir temperatures observed in Linqing，Liaocheng. There is minimal hydraulic connectivity between the geothermal water in the sandstone reservoir and deep groundwater，and changes in geothermal water levels are mainly influenced by artificial extraction and recharge activities.