25 May 2024, Volume 43 Issue 2

    

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   Petrogenesis and tectonic significance of gabbros from Erlangping unit in eastern segment of North Qinling: constrained by zircons U-Pb ages, geochemistry and Sr-Nd-Hf isotopes

  WANG Yue,CAO Huahua,ZHAO Shujuan,LI Xiyao

  . 2024, 43(2): 153-170.

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   The formation age and tectonic properties of Erlangping unit in North Qinling Orogenic Belt have long been the focus of controversy. The key to solve this problem is to precisely constrain the time and nature of the subduction、related magmatism. In this paper, the petrography, zircon U-Pb geochronology, whole、rock major andtrace elements geochemistry, and Sr-Nd-Hf isotopes analysis of the gabbros from Erlangping unit in eastern segment of the North Qinling Orogenic Belt have been studied. Geochemical characteristics show that the gabbros from the Erlangping unit has low w ( SiO2 ) (49. 61% - 50. 58% ), and enriched Na and depleted K (Na2O/ K2O = 8. 44 - 14. 09), with right?leaning chondrite normalized REE patterns, relatively enriched large ion lithophile elements (LILEs) and depleted high field strength elements (HFSEs), with negative anomalies of Nb, Ta, Zr and Hf, and slightly enriched Sr-Nd isotope compositions, exhibiting the characteristics of island arc igneous rocks with CAB properties. Their primary magmas could be mainly derived from the partial melting of amphibole?bearing garnet phase mantle metasomatized by subduction fluids, formed in the island arc setting. By zircon SIMS U??Pb dating technology, the weighted average age of the gabbros from Erlangping unit is (464 ± 2. 9) Ma, which defines the di? agenetic age belongs to Middle Ordovician. Based on the regional geological data and the previous research results, the authors propose that the gabbros from Erlangping unit is the product of the southward subduction of Kuanping Ocean underneath North Qinling Microcontinent, but the influence of the northward subduction of Shangdan Ocean underneath North Qinling Microcontinent could not be ruled out. 
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   Geochronology and geochemistry of Late Jurassic granodiorite in Huma area of northern segment of Da Hinggan Ling (Mts. ) : constraints on tectonic evolution of Mongolia-Okhotsk Ocean 

  KONG Jingui,ZHANG Guobin,ZHANG Wendong,WANG Qilin,DONG Jiasong,CHEN Xingkai,HE Yunlong

  . 2024, 43(2): 171-192.

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   In the northern segment of the Da Hinggan Ling (Mts. ), Late Mesozoic granites are highly deve? loped. However, the volcanic activity periods, rock compositions, and petrogenetic mechanism in this area have been controversial in the field of earth sciences. The authors systematically conducted zircon U??Pb isotope geo? chronological and whole?rock elemental composition studies on the medium?fine grained granodio?rite in the Huma area of the northern segment of the Da Hinggan Ling (Mts. ), and aimed to investigate rock genesis and magmatic source regions, analyze the tectonic setting of rock formation, and attempt to constrain the timing of the closure of the Mongol??Okhotsk Ocean. The research results indicate that the crystallization of the granodiorite is (149. 9 ± 1. 7 Ma), which is the Late Jurassic. The granodiorite is rich in Si and Al, but poor in Mg, Y and Yb (w(Y)≤18 × 10 - 6 , w(Yb)≤1. 9 × 10 - 6 ), has high Sr content (w(Sr) > 400 × 10 - 6 ) and A/ CNK of 1. 01 - 1. 15, belonging to the high - K calc?alkaline rock series. It is relatively enriched in Rb, Ba, K, La, Ce and Sr elements, and depleted in Ta, Nb, P, Ti, Y, Yb and Lu elements, with a weak positive Eu anomaly. It belongs to the “C” type Adakite. Combined with the regional magmatic zircon Nd isotopic composition characteristics, the data indicate that the magma originated from the partial melting of accretionary lower crustal amphibolite?facies material during the Late Neoproterozoic to Phanerozoic. Combining geochronological, geochemical characteristics, and regional tectonic evo? lution, it is suggested that the Late Jurassic granodiorite in the Huma area of the northern segment of the Da Hing? gan Ling (Mts. ) formed in a post?collision uplift tectonic environment and is closely related to the closure of the Mongol??Okhotsk Ocean. 

   
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   Geochronology and tectonic significance of Early Cretaceous volcanic rocks in Wuchuan area, Inner Mongolia

   

  ZHANG Chunlin,CAO Huahua,SHAO Enqing,BU Xuejiao,WANG Yue

  . 2024, 43(2): 193-203.

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   This article mainly focuses on the Early Cretaceous volcanic rocks in the Wuchuan area of Inner Mongolia, western part of the northern margin of the North China Craton. LA??ICP??MS zircon U??Pb dating of the volcanic rocks has been studied, and the dating results showed that the weighted average age of the basaltic coarse andesite is (123 ± 3) Ma (MSWD = 2. 63, n = 16), forming in the Early Cretaceous. And the weighted average age of rhyolite is (121 ± 3) Ma (MSWD = 0. 02, n = 13), also forming in the Early Cretaceous. The Early Creta? ceous basaltic coarse andesite and rhyolite form a typical bimodal volcanic association, which should be formed in the intra?continental rift environment. This tectonic environment is mainly due to the remote extension of the weak zone on the northern margin of the North China Craton by the gravity collapse event after the Early Cretaceous Mongolia??Okhotsk orogen, and is not related to the subduction of the ancient Pacific Plate.

   
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   Geochemical characteristics and tectonic significance of diabase of Es3 Member in Linnan Subsag, Bohai Bay Basin 

  LI Yuanzhe,BIAN Weihua,ZHAO Lanquan,JI Jinjiao,BAI Jiawei,LU Guochao

  . 2024, 43(2): 204-215.

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   As an important unconventional oil and gas reservoir unit, the formation and distribution of diabase are often controlled by their tectonic settings. Using petrology, geochemistry, and Sr??Nd isotopes geochemistry, the authors discuss the geochemical characteristics and geodynamic background of diabase of Es3 Member in Linnan Subsag, Bohai Bay Basin. The results show that the diabase belongs to the series of alkaline basalts with high Al, low Ti and enriched Na. The large ion lithophile elements (Rb, Ba, Pb, Sr) and light rare earth elements are relatively enriched, while the high field strength elements (Th, U) are relatively depleted, exhibiting a positive Eu anomaly. The diabase in the study area originates from the asthenosphere mantle, which is the result of mixingbetween different crust?mantle boundary zones. The formation of diabase is associated with intraplate magmatic ac? tivities, which suffered contamination by crustal materials during magma emplacement, occurring under a continen? tal extensional tectonic setting. The Cenozoic extension in the Bohai Bay Basin occurred under an active rift envi? ronment, where the upwelling of the asthenosphere mantle was closely associated with the subduction of the Pacific Plate beneath the Eurasian Plate and the development of an intraplate mantle plume. 

   
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   Geochemical characteristics and significance of platinum group elements in No. 2 ore body of Jinchuan Cu-Ni sulfide deposit 

  HUA Zhaofu, LU Jilong, HOU Yaru, ZHAO Wei, LI Chao, SUN Xiaohan

  . 2024, 43(2): 216-227.

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   Taking No. 2 ore body of Jinchuan Cu-Ni sulfide deposit as the research object, the geochemical characteristics of major elements, trace elements and platinum group elements (PGE) were studied to explore the magma evolution and metallogenic mechanism of Jinchuan deposit. The results show that the ( La / Yb) N value of rock and ore in the study area is 4. 1, enriched in LREE; the (La / Lu) N value is 3. 8, fractionated in LREE and HREE; and depleted in high field?strength elements Nb, Th and Zr, indicating that there is crustal contamination in the formation process of the ore body. The content of PGE in ore of No. 2 ore body is higher than that in rock, which is due to the enrichment of PGE caused by mineralization. There is PGE differentiation in the rock and ore, mainly enriched in low melting point PGE (Rh, Pt, Pd). Based on the research results, it is inferred that the parent magma in the study area is basaltic magma formed by moderately partial melting of the mantle, and the main metallogenic mechanism is deep liquation and injection. 

   
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   Diagenetic facies and development model of tuffaceous sandstone reservoirs in Wenchang Formation in Lufeng Sag, Pearl River Mouth Basin

  LI Xiaoyan, DING Lin, LI Xiaoping, XIAO Zhangbo, WU Qiongling, ZHANG Yuexia, LIU Jinliang

  . 2024, 43(2): 228-241.

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    The deep sandstone reservoirs of Wenchang Formation in Lufeng Sag is one of the most important reservoir rocks in Zhuyi Depression of the Pearl River Mouth Basin, and the development of tuff leads to tight reser? voir with low permeability and ultra?low permeability. Due to the influence of tuff, the diagenesis and its distribu? tion in this area exhibit special characteristics. Based on the detailed observation of the diagenesis, transformation of authigenic minerals, and pore types of tuffaceous sandstone reservoirs using a polarizing microscope, combined with the analysis of scanning electron microscopy, pore permeability testing, logging data, the diagenetic facies anddevelopment model of the Wenchang Formation tuffaceous sandstone reservoir in the Lufeng Sag were studied. The results indicate that tuffaceous alteration is the main diagenetic process affecting reservoir properties, followed by compaction and dissolution. According to the intensity and combination of various diagenetic processes, the reser? voir can be divided into five diagenetic types: ①medium compaction??weak cementation??medium tuffaceous dissolu? tion phase (type Ⅰ); ②medium strong compaction??weak cementation??strong tuffaceous dissolution phase (type Ⅱ); ③medium strong compaction??medium strong apatite cementation??medium dissolution phase (type Ⅲ); ④ medium strong compaction??medium strong kaolinite cementation??weak dissolution phase ( type Ⅳ) and ⑤strong compaction??weak cementation??weak dissolution phase (type Ⅴ). Among them, the type Ⅰ is high?quality diage? netic facies (with an average porosity of 13. 4% and permeability of 5. 4 × 10 - 3 μm 2 ), the Type Ⅱ is favorable di? agenetic facies (with an average porosity of 15. 4% and permeability of 1. 5 × 10 - 3 μm 2 ). The type Ⅲ and Ⅳ are potential favorable diagenetic facies (with an average porosity of 15. 0% and permeability of 1. 0 × 10 - 3 μm 2 ), and the Type Ⅴ is unfavorable diagenetic facies. Affected by atmospheric water leaching and organic acid dissolution, the deep sandstone reservoirs in the Wenchang Formation of the Lufeng Sag mainly develop two types of diagenetic facies combinations: Ⅱ-Ⅲ-Ⅳ-Ⅴ, and Ⅰ-Ⅴ. Diagenetic facies are closely related to reservoir quality. Identif? ying high?quality diagenetic facies can predict the distribution of favorable reservoirs and provide geological basis for oil and gas exploration.

   
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   Prediction of Lower Cambrian effective source rocks and favorable oil-gas accumulation areas in eastern Sichuan Basin 

   

  SUN Ziming,BIAN Changrong,SUN Wei,LIU Guangxiang,DONG Tian

  . 2024, 43(2): 242-254.

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   To evaluate gas exploration prospect of Sinian- Lower Cambrian in eastern Sichuan Basin, the Lower Cambrian effective source rocks were predicted based on the analysis of regional sedimentary?tectonic back-ground, combined with the analysis of measured total organic carbon content (TOC) of source rocks, well logging and two?dimensional seismic data. The favorable accumulation areas for oil and gas were predicted through integra? tion with the paleo?structure of top Sinian and the distribution of Lower Cambrian hydrocarbon generation centers at the end of the Middle Triassic in eastern Sichuan Basin. The results show that the strongly sedimentary-tectonic differentiation from the Late Sinian to the Early Cambrian led to the formation of intra-platform fault depressions / rift troughs, intra?platform sags and intra-platform uplifts in the Middle-Upper Yangtze region. The eastern Sichuan Basin is mainly located in the intra?platform uplift, with an effective source rock thickness of 50 - 150 m. Thethickness of effective source rocks in the Xishui-Nanchuan-Shizhu zone is less than 30 meters, and the degree of development is poor. From a plane view, four source rock development centers and corresponding hydrocarbon generation centers controlled by rift troughs and intra-platform sags have developed around the eastern Sichuan Basin. These centers could provide sufficient oil and gas sources for the Sinian-Lower Cambrian in the eastern Sichuan Basin. In conclusion, the eastern Sichuan Basin has a great potential for natural gas, and the central Sichuan paleo-uplift and its surrounding areas are favorable areas. 

   
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   Facies architecture and reservoir significances of subaqueous lava flow: a case study of Cretaceous Yixian Formation in Yixian area 

   

  ZHANG Ying,LIU Zhifeng,ZHU Wenqi,WANG Jian,BIAN Haiyue,ZHANG Jinming,TANG Huafeng

  . 2024, 43(2): 255-262.

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   Subaqueous emplacement lava flow is an important type of basin filling, and its facies architecture, reservoir distribution patterns and potential characteristics are still unclear. In this paper, the subaqueous emplace? ment lava flow of Yixian Formation in Yixian area is taken as an example to study the rock types, lithofacies and reservoir characteristics by using the methods of geological survey, rock and mineral identification and image analy? sis. The results show as follows: ①the lithology of the subaqueous lava flow includes lava and hyaloclastite, which can be divided into two kinds of microfacies: composite lava flow microfacies (CLFM) and in situ deposition of clastic microfacies (SDCM) of subaerial erpuptive - subaqueous emplacement lava flow subfacies in effusive facies. There are three overlapping type of CLFM and SDCM, namely dominated by CLFM, dominated by SDCM, and theequal proportion of CLFM and SDCM. ②the vertical facies sequence is SDCM to CLFM or only SDCM. The lateral facies sequence is CLFM to SDCM. ③4 types and 8 subtypes of porosities were identified. The pore of CLFM is dominated by vesicles and quenched fractures, and the pore of SDCM is dominated by secondary dissolution pore. The value of surface porosity of SDCM is higher than that of CLFM. It is inferred that the reservoir in the front part of the subaqueous lava flow should be better than that in root part. 

   
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   Heat accumulation mechanism of Songnan central uplift belt and its influence on geothermal resources exploitation in Qingshankou Formation 

   

  XU Xiaohong,XIAO Hangzhou,LI Yingjiu,JIA Xuefeng,ZHAO Rongsheng

  . 2024, 43(2): 263-270.

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   Through analysis of core thermal property and geothermal well production data, combining with nu? merical simulation technology, the heat accumulation mechanism of Qingshankou Formation in Songnan central up? lift belt and the temperature recovery rule of geothermal wells were studied. After comparing the similarities and differences of geothermal reservoirs and production wells in different structural positions and burial depths, the au? thors summarized the heat accumulation mechanism of basin?type geothermal resources and its influence on produc? tion wells. The results show that the temperature in the middle part of Qingshankou Formation ranges from 45 ℃ to 165 ℃ , and the temperature in the uplift is obviously higher than that in the depression, with a maximum of 100 ℃ . At the same time, the exploitation simulation shows that the fluid temperature of geothermal well in uplift decreases more slowly than that in the depression during 30 years of continuous exploitation with a decreasing ampli?tude of about 7 ℃ . Based on the analysis of geological structure, fault system and tectonic pattern, it is concluded that the uplift and depression tectonic units are the main heat accumulation mechanism of Qingshankou Formation reservoir in Songnan central uplift belt. In addition, under similar conditions, the temperature decreasing rate of geothermal well exploitation in the structural uplift area is lower than that in the structural depression area, and the sustainable time of exploitation in the uplift is longer. 

   
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   Cooperative inversion method of gravity and its gradient data based on physical consistency 

   

  LI Lili, HE Zhaokun, MA Guoqing, WANG Taihan, LI Zongrui, MENG Qingfa

  . 2024, 43(2): 271-281.

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   Gravity and its gradient data can effectively reflect changes in the underground density. To obtain high resolution density results, the authors propose a cooperative inversion method based on the physical consisten-cy characteristics of gravity and its gradient data, which takes the inversion results of single component data as con-straints for the joint inversion of gravity and its gradient data, and can better utilize the resolution characteristics of different component data. Model experiments have shown that compared with single component inversion and cross gradient inversion methods, the proposed method can obtain higher resolution inversion results and has strong noise resistance. It has been proven that the cooperative inversion of gravity and its calculated gradient data based on physical consistency can still obtain high resolution results. The density inversion results obtained by applying this method to satellite gravity and its calculated gradient data in Changbai Mountain reveal the magma system in the re-gion. 

   
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   Simulating surface vegetation biomass in Jilin Province based on multi?source remote sensing data 

   

  GONG Liwei,YANG Xuegang,WU Qiong

  . 2024, 43(2): 282-289.

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   Surface vegetation biomass is an important index to characterize soil carbon stocks. In order to clarify the temporal and spatial distribution of surface vegetation biomass in Jilin Province and the main driving fac-tors, the authors calculated the surface vegetation biomass in Jilin Province based on multi-source remote sensing data. Using normalized difference vegetation index, land surface temperature, soil wet, land cover data, digital elevation model, slope gradient and aspect as the driving factors of the model, the model coupled with random forest and cellular automata was constructed to simulate the spatial distribution of surface vegetation biomass for 2020 and 2025, respectively, in Jilin Province based on the changes of surface vegetation biomass from 2010-2015 and 2015-2020. The importance ranking of random forest indicats that the normalized difference vegetation index, land surface temperature, soil wet and land cover data are the key driving factors affecting the distribution of surface vegetation biomass in Jilin Province. 

   
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   Application of gravity exploration in investigation of active fracture tectonics in Yinchuan Plain 

   

  ZHANG Yuan,AN Baizhou,ZHU Dan,CHEN Shaoze,YAN Zhaotao,CHEN Xiaojing,SUN Boyang

  . 2024, 43(2): 290-298.

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   Active faults are direct inducement of geological disasters, such as earthquakes and landslides. In order to find out the influence of the spatial distribution of active faults on shallow surface activities, and evaluate the risk of geological hazards and the location of urban construction areas, based on 1 ∶ 200 000 gravity data of Yin-chuan Plain, 6 gravity profiles are cut off by wavelet analysis in the study area. The selected profiles pass through the main fault structures in the study area. Boundary identification, Euler inversion, human-computer interactive inversion and other methods were used to process the gravity anomal data. According to the processing results, the faults structures in the study area were interpreted, and specific parameters such as top burial depth, dip angle and location of the Yinchuan Fault and Luhuatai Fault were identified, it further complements and perfects the under? standing of active fault system in Yinchuan Plain. 
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   Design of distribution jet joint at inlet port of reverse circulation pneumatic DTH hammer and analysis of its structure parameters

   

  LI Linghao,WANG Qingyan,FAN Liming,SHENG Jie,ZHONG Weiling

  . 2024, 43(2): 299-307.

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   In order to solve the problems of repeated rock crushing and inefficient rock debris discharge during the drilling process of reverse circulation pneumatic down-the-hole hammer, the authors designed a distribution jet joint at the inlet port based on NGQ -320 reverse circulation pneumatic down-the-hole hammer. This joint can realize the dynamic adjustment of the air supply of the down-the-hole hammer, and its injection structure can intro? duce part of the compressed gas into the center channel, which can improve the power supply of the impact mecha-nism and conduct pumping effect on the flow field at the bottom of the well at the same time. The authors used CFDtechnology to study the flow field of the distribution jet joint, discussed the impact of injection hole angle, injection opening depth, injection hole diameter and injection hole deflection angle on the suction performance of the center channel, and determined the optimal values of the various structural parameters. The results show that the distribu-tion jet joint has better suction performance with the injection hole opening depth of 320-330 mm, injection hole deflection angle of 30°-35°, injection hole diameter of 12 mm, and injection hole deflection angle of 11°-13°. 

   
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   Experimental study on decomposition of natural gas hydrate in Shenhu area of South China Sea using ferromagnetic particle-assisted microwave heating 

   

  LI Xuhui,LIU Baochang,ZHU Yue,PENG Saiyu,ZHAO Chuang,DAI Wenhao

  . 2024, 43(2): 308-317.

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   The Shenhu area on the northern slope of the South China Sea is the first trial extraction area for natural gas hydrate in China, with over 90% of hydrate reserves located in muddy fine sand strata. To achieve efficient development of natural gas hydrate, it is essential to improve the average gas production rate and the energy efficiency ratio in muddy fine sands. Using muddy fine sand as the base for hydrate synthesis, the authors conducted microwave heating decomposition experiments on synthesized methane hydrate, investigating the effects of adding different types of ferromagnetic particles on the decomposition of methane hydrate. The experimental results showed that the group with added iron?cobalt alloy powder performed the best in terms of average gas production rate and energy efficiency ratio, with a 22. 66% improvement compared to the blank group. The addition of nano?bari? um ferrite particles significantly enhanced the decomposition efficiency in the early stages of the reaction. The small particle size and large specific surface area of the nanoparticles contributed to their uniform distribution, optimizing wettability and surface tension, and reducing the “Jarmin effect”. Analysis using the Avrami model indicated that ferromagnetic particles effectively promoted the microwave decomposition of hydrate, with nano?barium ferrite showing the most significant effect.