25 August 2024, Volume 43 Issue 3

    

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  Geochemical characteristics, formation time and geological significance of Late Triassic⁃⁃Early Jurassic granites in southern Xiao Hinggan Ling (Mts. ) 

  YU Yuejiang , LI Xinpeng , WU Wei , LIU Jikai , MA Liling , WEN Dan , FENG Ruiguang

  Global Geology. 2024, 43(3): 319-335.

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  To investigate the magmatic activity and tectonic evolution of Late Triassic⁃⁃Early Jurassic in south⁃ ern Xiao Hinggan Ling (Mts. ), and to identify its petrogenesis, formation time and tectonic setting, petrology, geochemistry and isotopic chronology of Late Triassic⁃⁃Early Jurassic monzogranites and syenogranites in Xiao Hing⁃ gan Ling (Mts. ) have been studied. The results show that the zircons of monzogranites and syenogranites are mag⁃ matic zircons with obvious magmatic oscillations and growth belts. The LA⁃⁃MC⁃⁃ICP MS zircons have U⁃⁃Pb dates of (202. 5 ± 1. 9) Ma and (191. 5 ± 1. 4) Ma, respectively, being Late Triassic to Early Jurassic. The geochemical characteristics show that the rocks are high silicon, rich potassium, rich alkali and low sodium, which is a I⁃⁃type granite of aluminous high potassium calc⁃alkaline series. Enrichment of Rb, K, Th, Hf, and deficit of Ba, Sr, Ti, Nb, P. Light rare earth elements are more abundant than heavy rare earth elements with an obvious negative anomaly (δEu = 0. 37 ~ 0. 58). Based on regional correlation and comprehensive study, it is preliminarily concluded thatthe tectonic setting of the granites in southern Xiao Hinggan Ling (Mts. ) is an active continental margin environ⁃ ment formed by the subduction of the paleo⁃⁃Pacific plate to Eurasia. 
  

  
  
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  Nature and tectonic implications of Mesozoic magmatic rocks in Zhangguangcai Ling (Mts. ) , Northeast China

  LI Chengqiang , ZHOU Jianbo , WANG Hongyan , CHEN Zhuo , LI Gongyu

  Global Geology. 2024, 43(3): 336-352.

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  During Late Paleozoic to Early Mesozoic, it was found that the tectonic evolutionary history of the Zhangguangcai Ling (Mts. ) in Northeast China can be divided into 3 stages: ① Late Permian⁃⁃Middle Triassic (266⁃⁃234 Ma), the westward subduction of Heilongjiang Ocean formed I⁃⁃type grantic rocks; ② Late Triassic⁃⁃ Early Jurassic (224⁃⁃194 Ma), the Jiamusi⁃⁃Khanka Block and the Songliao Block collided after the closure of Hei⁃ longjiang Ocean, forming I⁃⁃type with a few A⁃⁃type granitic rocks; ③ Early⁃⁃Middle Jurassic (194⁃⁃163 Ma), A2 ⁃⁃ type and I⁃⁃type granites were developed under the complex influence of the extensional environment after the colli⁃ sion of the two blocks and the westward subduction of the Paleo⁃⁃Pacific Ocean. Combined with new evolution on the Heilongjiang Complex and the Nadanhada Terrane, the authors consider that the transition between the Paleo⁃⁃ Asian Ocean and the Paleo⁃⁃Pacific Ocean in eastern Eurasia occurred in the Late Triassic⁃⁃Early Jurassic, and the Heilongjiang Ocean was an important hinge linking up the tectonic transition between these two domains. 
  

  
  
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  Geological characteristics and its genetic model of tanzanite deposit at Merelani, Tanzania 

  SUN Guofeng , ZHANG Mingyun , YAN Hongpu , ZHANG Meng , ZHANG Weijie , LLOYD Shawarira

  Global Geology. 2024, 43(3): 353-362.

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  Through the field geological mapping, the geological setting and its mineralization characteristics for tanzanite deposit at Merelani area, Tanzania are described in details, especially the occurrences of orebodies and characteristics of gemstone are analyzed and reviewed, further its genetic model is discussed preliminarily. It is considered that tanzanite has been formed in the altered graphite gneiss which distributed in the Neoproterozoic Mo⁃ zambique metamorphic belt at proximately 500 Ma when the Pan⁃⁃African movement was taken place. Being a skarn deposit related to the contact metasomatism, the lithostratigraphic and tectonic deformation are two main controlling factors. 
  

  
  
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  Comprehensive exploration method and deep prospecting prediction in Nanzhaobeigou shallow overburden area of Nanyang City, Henan Province 

  QUAN Zhixin, LI Xiangzi, XIE Guoxing, WANG Qiuyun, ZHANG Meng, GAO Pengfei

  Global Geology. 2024, 43(3): 363-377.

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  In order to find a rapid and effective comprehensive method for ore prospecting in overburden area, a 1 ∶ 10 000 high⁃precision magnetic survey, a IP mid⁃gradient profile and a wide⁃area electromagnetic sounding geophysics were carried out in Nanzhaobeigou gold polymetallic deposit of Nanyang City, Henan Pro⁃vince. The re⁃ sults show that: ① 1 ∶ 10 000 high magnetic survey reflects the distribution characteristics of geological body and fault structure. ② The low resistance and high polarization zone identified by the IP mid⁃gradient profile is caused by mineralization alteration of metals. ③ Wide⁃area electromagnetic sounding shows that the deep anomaly corre⁃ sponds well with the mineralization alteration zone. A large⁃scale lead⁃zinc⁃tungsten orebody has been found through drilling engineering. 
  
  
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  Lithofacies types and cycle patterns of shale layers of Qingshankou Formation in Gulong Sag, Songliao Basin 

  LIN Tiefeng , FU Xiuli , AI Xin , BAI Yunfeng

  Global Geology. 2024, 43(3): 378-389.

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   Based on core observation, thin section identification, geochemical test and Markov chain analy⁃ sis, the lithofacies types and cycle patterns of shale layers of Qingshankou Formation in Gulong Sag are discussed. According to the classification standard of “organic matter abundance⁃⁃sedimentary structure⁃⁃mineral composition⁃⁃ lamination density⁃⁃lithology”, the shale layers of Qingshankou Formation in Gulong Sag are divided into 7 lithofa⁃ cies, including high TOC⁃⁃high density laminae⁃⁃clay shales (A), high TOC⁃⁃high density laminae⁃⁃felsic shales (B), medium TOC⁃⁃low density laminae⁃⁃felsic shales (C), low TOC⁃⁃low density laminae⁃⁃felsic shales (D), lowTOC ⁃⁃layered⁃⁃siltstones (E), low TOC⁃⁃layered⁃⁃ostracoid limestonse (F) and low TOC⁃⁃layered⁃⁃dolomites (G). Based on lithofacies combination patterns and their distribution characteristics, three cycle patterns are divided: ① the static water cycle pattern (A⁃⁃B⁃⁃C⁃⁃A) is mainly developed in the highstand system tract; ② the turbidite cycle pattern (A⁃⁃B⁃⁃C / D/ E / F⁃⁃A) is mainly developed in the transgressive system tract and the regressive system tract; ③ the dolomite cycle pattern (A⁃⁃B⁃⁃C⁃⁃D/ G⁃⁃A) is developed in all three system tracts. The west of Gulong Sag mainly developed turbidite cycle, the center of Gulong Sag mainly developed static water cycle, and the Sanzhao Sag on east side mainly developed static water⁃⁃dolomite cycle. The distribution of cycle models is mainly affected by provenance, paleoclimate and paleosalinity. 
  

  
  
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  Sedimentary facies characteristics and source rocks evaluation of Mesoproterozoic Hongshuizhuang Formation in Lingyuan area, western Liaoning 

  ZHANG Liya

  Global Geology. 2024, 43(3): 390-402.

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  Based on the cores, field sections, thin sections and organic geochemical data, the sedimentary facies characteristics of the Mesoproterozoic Hongshuizhuang Formation and the evaluation of source rocks were carried out. The results show that the Mesoproterozoic Hongshuizhuang Formation is mainly deposited by trough facies and carbonate plat⁃ form facies, the bottom⁃up low⁃level system tract is mainly composed of deep⁃water trough facies and shallow shelf facies sedimentation, the transgression system tract is mainly composed of deep⁃water trough facies and deep⁃water slope facies sedimentation, and the high⁃level system tract is mainly composed of deep⁃water gentle slope and tidal margin shore beach facies deposits. The average abundance of total organic carbon in the source rocks of Hongshuizhuang Formation was 4. 75% and (S1 + S2 ) was 6. 9 mg / g, which were generally good⁃very good source rocks, and the organic matter types were mainly Ⅰ⁃⁃Ⅱ1 type kerogen with great oil production potential, and the average Tmax was 438. 3 ℃ and the kerogen was brown, indicating that it was in the stage of mature oil production. On the whole, the trough facies black mudstone in the low⁃level system and transgression system tracts has great oil and gas potential, which is thefocus of the next exploration and research. 
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  Thermogravimetric characteristics and its influencing factors of oil shales in Middle Permian Lucaogou Formation in Santanghu Basin, NW China 

  CHEN Guibiao , XU Yinbo

  Global Geology. 2024, 43(3): 403-412.

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  In order to study the thermogravimetric characteristics, pyrolysis process and its influencing factors of oil shales during heating, the oil yield, total organic carbon, pyrolysis, major elements and thermogravimetric analysis of oil shales from the Lucaogou Formation in Santanghu Basin were tested. The results show that oil shales from the Lucaogou Formation in Santanghu Basin are medium quality oil shales with high organic matter abun⁃ dances, high ash contents and medium calorific values. The main elements of ashes are SiO2 , Al 2O3 and CaO, which belong to high melting ashes. Thermogravimetric analysis of oil shale shows that the pyrolysis process is mainly divided into three stages, including low temperature, medium temperature and high temperature weight loss stages. The medium temperature weight loss stage is the main weight loss stage and pyrolysis reaction stage of oil shales, with the temperature of 300 - 580 ℃ . Among them, the temperature of large amount of oil and gas genera⁃ tion stage in oil shale pyrolysis process is 430 - 500 ℃ , which is the key stage of oil generation. While 500 -580 ℃ is the gas generation stage, which can form a certain amount of shale gas. 
  

  
  
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  Lithology classification of L⁃band SAR data by combining backscattering and polarization characteristics 

  GUO Senmiao , JIANG Qigang , LIANG Shichen , WANG Peng

  Global Geology. 2024, 43(3): 413-423.

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  Taking Mindoro Island in Philippines as the study area, and selecting ALOS PALSAR dual⁃polariza⁃ tion data (polarization mode of HH and HV polarization) as the source data, the authors used the maximum likeli⁃ hood classification method to classify the rock units and geological mapping in study area by extracting the backscat⁃ tering coefficients (Sigma0 HH and Sigma0 HV) and the polarization decomposition parameters (entropy, angle and anisotropy). With the inclusion of polarization decomposition parameters, the overall accuracy increased from 36. 706% to 65. 000% , comparing to the result using only backscattering coefficients. The F1 scores of the coastal marsh and coral reef exceeded 0. 80, and those of the gabbro and Mansalay Formation exceeded 0. 75. After adding polarization features, the rock unit boundaries were better extracted and increased separability of the Mansalay Forma⁃ tion and Mindoro metamorphic rocks from other rocks. Three polarization decomposition parameters compensate for the similarity of backscattering coefficients of multiple rock units and significantly improve the separability of rock units. It is shown that the combination of polarization decomposition parameters and backscattering coefficients of L⁃bandSAR data can improve the classification accuracy of rock units in vegetation⁃covered areas. 
  
  
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  Research on groundwater activity in Ningjiang District, Songyuan City, Jilin Province based on InSAR time⁃series 

  DU Bing, ZHANG Xuqing, SUN Tao, CHEN Feng, WANG Linwei

  Global Geology. 2024, 43(3): 424-433.

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  The surface cumulative deformation data of Ningjiang District in Songyuan City, Jilin Province from 2017 to 2021 have been monitored by SBAS⁃⁃InSAR technology. It systematically analyzes the impact of groundwater activity on surface subsidence in the area, combined with actual groundwater level measurement data. The InSAR mo⁃ nitoring results show that there is a significant subsidence in study area, with obvious seasonal periodic subsidence characteristics over time. This study constructs a multivariate linear regression model through incorporating factors such as groundwater level changes, geological conditions, and precipitation to quantitatively analyze the relationship among these factors and surface deformation. The results reveal a significant influence of groundwater level changes on surface deformation. Furthermore, when combined with land use data, it is found that agricultural water usage pri⁃ marily influences surface deformation in the subsidence area. 
  
  
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  Application of semi⁃airborne transient electromagnetic data processing and interpretation in exploration of water hazards in Hesigula open⁃pit coal mine 

  ZHAI Hao , LI Tonglin , KANG Xinze , WU Yuhao

  Global Geology. 2024, 43(3): 434-443.

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   In order to reduce the impact of underground water on coal mines and ensure the safety mining of the Hesigula open⁃pit coal mine in Xilingol League of Inner Mongolia, the authors use the semi⁃airborne transient electromagnetic method to conduct groundwater exploration of coal mines. Through the Occam inverse discrimination, the distribution of underground low⁃resistance electrical abnormalities is obtained, and comparison with the results of the nuclear magnetic and drilling results, the following main conclusions are obtained: ① The water⁃bearing sand layers of the Quaternary loose rocks exhibit relatively high resistance, while the porosity and fractures within the clastic rock layers and coal seams of the Cretaceous Damoguaihe Formation demonstrate low electrical resistance. Conversely, the strata of the Damoguaihe Formation display relatively high resistance as a whole. ② In the study are⁃ a, underground water seepage channels are primarily distributed within the aquifers of porosity and fractures in the clastic rock layers of the Cretaceous strata. ③ Underground water⁃rich areas are mainly concentrated in the range from 840 m to 880 m. As the depth increases, the area of the water⁃rich zones gradually decreases. 
  

  
  
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  Semi supervised identification of surface cracks in stone carvings based on improved VGG16 network 

  ZHANG Yinghao, FENG Xuan, ZHAO Pengfei, DONG Zejun, ZHOU Haoqiu, ZHANG Minghe, AN Yafei, YANG Jiarun, WANG Yuheng, WANG Liulei

  Global Geology. 2024, 43(3): 444-451.

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   In order to quickly and accurately detect the surface cracks in stone carvings, the authors establish an improved VGG16 network model, which changes the original three fully connected layers to two fully connected layers, adds dropout regularization, and combines it with the semi supervised learning algorithms to apply deep learning to intelligent recognition research of surface cracks in stone carvings. In order to test the performance and accuracy of the improved model, Unet, ResNet and the original models were selected for comparison. The improved VGG16 network model achieved an accuracy of 93. 6% and the training time is reduced by 18% compared with the original models, which has the advantage of lightweight operation. The model can meet the basic needs of surface crack recognition and has good robustness. 
  

  
  
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  Study on geological disaster characteristics and prevention measures of debris landslide in Yixing area of Jiangsu 

  ZHANG Jixing, SONG Jinglei, LIU Hong, WANG Yashan, LIU Baosheng

  Global Geology. 2024, 43(3): 452-461.

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   Aiming at the typical geological disasters of debris landslide in Yixing area, Jiangsu Province, the basic characteristics of debris landslide are analyzed, and the reliability of the prevention measures are verified through some examples. The results show that the debris landslides in Yixing area are mainly occurred in the pied⁃ mont gentle slope area of southern mountains. The gradient is below 15° of natural slope. The landslide body has the dual structure characteristics of upper soil and lower rock. The landslide is a retrogressive landslide with retru⁃ sive and progressive general deformation failure which shows as topography reform and rainfall induction. The axial horizontal distance of the landslide body is 10. 0 to 12. 0 times of the altitude difference of the cutting slope. Through comprehensive measures such as repairing slope surface, anti⁃slide pile, backfilling and presser foot, re⁃ taining wall, and drainage ditch, the potential hazard of landslide is eliminated, the horizontal displacement and vertical displacement of the slope converges to a fixed value, and the slope is stable.