Table of Content

15 August 2023, Volume 29 Issue 4

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The Petrogenesis of Baishuizhai Granitic Pluton and Its Significance to Uranium Mineralization in the Xiazhuang Area, Guangdong Province

LI Kun, CHEN Weifeng, GAO Shuang, SHEN Weizhou, HUANG Guolong, LIU Wenquan, FU Shuncheng, LING Hongfei

2023, 29(4):  497-513.  DOI: 10.16108/j.issn1006-7493.2021117

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The Baishuizhai pluton is one of the main ore-bearing wall rocks of the Zutongjian uranium deposit in the northwestern part of the Xiazhuang granite-related uranium ore filed, yet its petrogenetic mechanisms and its relationship with uranium mineralization are still unclear. Thus, in this study, we present zircon SHRIMP U-Pb ages, whole-rocks and mineral geochemical data for the Baishuizhai granite. Field and petrographic investigations show that the Baishuizhai granitic pluton was emplaced into the Xiazhuang granitic batholith, mainly composed of fine-grained two-mica granite and muscovite granite, and the zircon SHRIMP U-Pb dating reveals that both granites were formed during the Indochina period with ages of 229.4 Ma and 231.8 Ma, respectively. They show typical peraluminous S-type granitic geochemical characteristics that are high SiO₂ contents, total alkalis contents and ACNK values ( ≥ 1.1), low FeOt+MgO+TiO₂ contents and P₂O₅ contents, enriched in Rb, Th and U, depleted in Ba, Sr, P and Ti, and enriched in aluminum-rich minerals. Compared with the Xiazhuang granite, both types of granites in the Baishuizhai pluton show enriched in inherited zircon, higher SiO₂ contents and Rb/Sr ratios, but lower FeOt+MgO+TiO₂ contents, P₂O₅ contents, Zr/Hf ratios, and Fe²⁺/(Fe²⁺+Mg) ratios of biotites, indicating that they were derived from low partial melting of reducing material-rich feldspathic meta-pelites, and are not formed by the differentiation evolution of the parent magma of the mafic meta-pelites-derived Xiazhuang granite. Furthermore, compared with the two-mica granite, the muscovite granite display significant tetrad REE patterns, lower REE, Zr/Hf ratios and Eu/Eu* values, indicating that an interaction of F-rich fluids with the magma occurred in the formation of the muscovite granite. Both types of granites in the Baishuizhai granitic pluton are enriched in uranium and can be important uranium-bearing granites in the region. Relative to the 2-mica granite in the Baishuizhai pluton, the muscovite granite is more enriched in uranium and more favorable to be uranium source rocks for hydrothermal uranium mineralization.

Regional Comparative Study on Mineralogy and Geochemistry of Carbonate Rocks from the Upper Carboniferous in Tongling Ore District

WANG Jiayu, XU Liang, XIE Qiaoqin, LIU Tong, ZHOU Yuefei, LI Zhensheng, XU Xiaochun, CHEN Tianhu

2023, 29(4):  514-526.  DOI: 10.16108/j.issn1006-7493.2022008

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This paper presents a mineralogical and element geochemical study of carbonate rocks of the Upper Carboniferous Huanglong-Chuanshan Formation section from Tongling and Chaohu, Anhui Province. The results show that (1) the base of Huanglong Formation in Tongling is a set of dolostone containing framboidal pyrite; (2) the lower part of Huanglong Formation to the top of Chuanshan Formation are limestones; and (3) from bottom to top of section, mineral associations are dolomite+kaolinite +pyrite+quartz at the bottom of the Huanglong Formation → calcite+kaolinite+quartz (the middle and lower Huanglong Formation) → calcite+illite+quartz (the upper Huanglong Formation and the Chuanshan Formation), respectively. However the Huanglong-Chuanshan Formation in Chaohu are limestones composed of calcite with kaolinite and quartz, and the content of kaolinite tends to increase from the bottom of Huanglong Formation to the top of Chuanshan Formation. Also, carbonates of the Huanglong-Chuanshan Formation in Tongling (especially the dolomites at the bottom of the Huanglong Formation) show much higher V/Cr, Ni/Co, and V/Sc ratios, and Ce and Fe, Mn are uncorrelated while these parameters are positively correlated for Chaohu carbonates. Mineralogical and geochemical features suggest that carbonates at the bottom of the Huanglong Formation in Tongling were deposited in a relatively stable reducing environment, whereas carbonates in the middle and upper Huanglong Formation and Chuanshan Formation were deposited in a stable and weak oxidizing environment, and carbonates in Chaohu were formed in a more oxidizing and high-energy volatile environment. Combined with the previous studies, this study suggests that the existence of the ancient island in Tongling may be the main reason why the sedimentary environment of Tongling is different from that in Chaohu. Also, the sedimentary environment in Tongling area is favorable for the formation of colloform Pyrite.

Origin and Genetic Mechanism of the Early Cretaceous Metabasite from the Ramba Area, Tethyan Himalaya

YU Youzhi, LIU Zhichao

2023, 29(4):  527-542.  DOI: 10.16108/j.issn1006-7493.2022007

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A large number of Early Cretaceous mafic rocks are widely exposed in the Tethyan Himalaya, southern Tibet, China. These rocks provide an important record of the tectonic-magmatic evolution of the north margin of the Indian continent before the Cenozoic Indian-Eurasian collision. Their genesis is critical for reconstructing the evolution history of the Indian passive margin. This paper presents systematical petrographic and geochemical data of the Early Cretaceous metabasites from the Ramba area, eastern Tethyan Himalaya. The Ramba metabasites include amphibolitie-amphibolitic gneisses, which occurred as dikes and lenses in the low-medium grade metasedimentary rocks of the Ramba dome. These Ramba metabasites display tholeiitic affinity and low contents of SiO₂ (44.78-47.42 wt%), relatively high contents of MgO (7.31-9.60 wt%) and FeOt (9.68-15.87 wt%) with variable TiO₂ contents (0.73-2.16 wt%) and medium to high Mg# values (46.4-63.9). The radiogenic Nd isotopic compositions of the Ramba metabasites (ε_Nd(t) values range from 5.7 to 6.5) are comparable with that of the Indian Oceanic MORB. However, the REEs distribution patterns of the Ramba metabasites are similar to that of the E-MORB, indicating involvement of enriched components in their origin. It is worth noting that the Ramba metabasites do not show depletion in high-field-strength elements (HFSE), and their Nb/U ratios are similar to that of the mantle-derived rocks. Therefore, it can be inferred that the continental crust contamination is not significant in the formation of Ramba metabasites and their enrichment components should be mainly attributed to an enriched mantle source. Consequently, it is speculated that the Ramba metabasites were products of the interaction between magma derived from a depleted asthenospheric mantle and an enriched continental lithospheric mantle. They were generated during the early stage of the breakup of eastern Gondwana (~140 Ma) and were originated from the asthenosphere upwelling that was triggered by early activity of the Kerguelen mantle plume.

Advances on the Analogue Modeling of the Emplacement of Granitic Magma

LI Yingying, WANG Bo, CAO Tingting

2023, 29(4):  543-558.  DOI: 10.16108/j.issn1006-7493.2022055

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Regional tectonics not only facilitate the ascent and emplacement of the granitic intrusions but also control the final shapes of the intrusions. Analogue modeling is a critical method to study the magma emplacement. This paper reviewed the experimental set-up, materials and scaling used in previous analogue models related to magma emplacement, and summarized the influence of various parameters on the geometry of the intrusions in various tectonic settings. We suggested that: (1) the intrusion geometry is controlled by the characteristics of the country rocks in pre-kinematic static settings during tectonic quiescent stage. (2) In syn-kinematic settings during tectonic active stage, the intrusion geometry and deformation patterns of plutons are influenced by several parameters, including the thickness and rheological layering of the country rocks, velocity and total distance of displacement, velocity and total volume of magma injection, position of the injection inlet (magma channel), relative timing of tectonic activity and magma emplacement. Deformation can in turn control the shape of intrusions. (3) The parameters, such as
displacement velocity and injection velocity in different settings, have similar impact on the intrusion geometry. In addition, some limitations of analogue modeling method are also discussed. The CT technique and numerical modeling methods are suggested to be profitable supplementation of analogue modeling for the study in magma emplacement. 


Petrogenesis and Tectonic Implications of the Indosinian Fengxian Pluton, Western Qinling Orogeny

NI Chunyu, JIANG Yaohui

2023, 29(4):  559-570.  DOI: 10.16108/j.issn1006-7493.2021121

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This paper reports systematically petrological and SHRIMP zircon U-Pb dating, whole-rock geochemical and Sr-Nd-Hf isotopic research for the Fengxian Pluton. We discussed the magmatic evolution, source characteristics, tectonic and geodynamic settings of these plutons. Our study shows that: 1. The Fengxian pluton is composed of granodiorite and quartz monzonite, invaded in the Middle Triassic (~237.5 Ma). The SiO₂ content of the rock is 61.7~66.7 wt %, belonging to the high potassium calc-alkaline series, with relatively high MgO content (1.49-2.43 wt%) and Mg# value (0.53-0.58), belonging to the high-K calc-alkaline series. They are enriched in light rare earth elements (LREE) and lack marked negative Eu anomalies. They are also enriched in LILE and depleted in HFSE. Their high Sr (474×10-6-629×10-6) low Y (6.85×10-6-7.60×10-6) and Yb (0.57×10-6- 0.72×10-6) value are similar to those of adakites. They show εNd(t) values of -4.2 to -5.8, initial ⁸⁷Sr/⁸⁶Sr ratios of 0.7072-0.7077 and ε_Hf(t) values of -1.1 to -4.3. We believe that the Fengxian pluton is mainly derived from subducted sediments in the continental margin environment of the northward subduction of the Paleo-Tethys oceanic slab. The origin of the Fengxian pluton suggests that the Animaqing-Mianlue oceanic crust had subducted under the West Qinling before 237.5 Ma, and the eastern segment of the West Qinling remains a continental arc till the Middle Triassic.

Reactive Transport Numerical Modeling for Deep Geological Sequestration of Brine Wastewater

DU Zhuoran, DU Song, YANG Yun, SONG Jian, WU Jianfeng, WU Jichun

2023, 29(4):  571-579.  DOI: 10.16108/j.issn1006-7493.2021110

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Brine wastewater deep well injection in China is still at the stage of access demonstration. The transport of liquid waste in deep reservoirs involves variable density drive, water-rock chemical reactions and variable-parameter synergistic physical-chemical interactions. How to quantitatively characterize these processes is one of the key scientific and technological challenges to be solved in deep well injection. Consequently, this paper selected a certain injection zone in Ordos Basin as prototype, used PFLOTRAN to construct a variable-density and variable-parameter reactive solute transport model to predict and evaluate the migration, transformation and evolution of reservoir minerals, as well as the change of reservoir properties after the brine wastewater injection to the deep geological body. As the simulation results showed, the injection of brine wastewater into the injection zone contributes to secondary minerals precipitation, such as anhydrite, calcite and fluorite; the geological storage capacity decreases by 1.51% approximately in the simulated 100 years; and the contamination area is around 2.57 km². This model provides a simulation tool to quantitatively characterize the migration and transformation process of brine wastewater components after the deep well injection.

Precipitation-induced Pressure Wave Propagation in Unsaturated Zone and Its Effect on Rapid Groundwater Discharge

DANG Lei, XIE Yueqing, WANG Chuan, CHANG Yang, ZENG Xiankui, WU Jichun

2023, 29(4):  580-589.  DOI: 10.16108/j.issn1006- 7493.2021104

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A large number of studies, using water chemistry and stable isotopes to conduct hydrograph separation, indicate that majority of stream water during rainfall is derived from ‘old water’ that is stored in the catchment before the rainfall. This phenomenon is known as ‘old water paradox’. Pressure wave in unsaturated zone driven by precipitation is regarded as a potential underlying mechanism. In this study, we established four numerical soil column experiments with different soil types (sand, loamy sand, sandy loam and loam). We attempted to explore pressure wave propagation and the possibility of rapid groundwater discharge driven by the pressure wave with demonstrative experiments. Our results show that after the first intensive rainfall, pressure wave were generated in the four columns and were observed at the bottom after 1.86, 2.84, 5.24 and 7.46 days. In comparison, the relevant soil water arrived at the bottom after 6.12, 10.33, 18.05 and 30.00 days. The differences between celerities and velocities are 74.71, 51.05, 27.08 and 20.13 cm/d. Our study indicates that celerities and velocities are strongly affected by soil hydraulic conductivities and soil retention curves, and pressure waves in sand can be propagated more easily than those in other soil types. As the thickness of unsaturated zone is usually linearly proportional to the distance from river bank, pressure wave generated during precipitation can propagate into groundwater and drive rapid groundwater discharge. This process would be easier in more permeable soils. Overall, this study advances our understanding of catchment hydrology and helps discover underlying mechanisms in a theoretical manner. 

Analysis of Deformation Characteristics and Parameters of Clay Layers in South Subsidence Area of Beijing

YOU Binhao, YE Shujun, TIAN Fang, LUO Yong

2023, 29(4):  590-599.  DOI: 10.16108/j.issn1006-7493.2021083

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The land subsidence in Beijing is divided into north and south areas, and the southern area mainly includes Lixian-Yufa subsidence zone. The subsidence rate in this area has accelerated in recent years and reached 50-75 mm/a during 2017-2019, showing new subsidence characteristics. Based on the subsidence and water level observation data of 7-year time series from 2011 to 2017 at Yufa Subsidence Monitoring Station, the only subsidence observation station in the south subsidence area. The deformation characteristics of soil layers, especially clay layers, are systematically analyzed. Then the elastic and inelastic specific storage, vertical hydraulic conductivities and deformation lag time of the clay layers are estimated by the stress-strain diagram method and the type curve method. The results show that there are both elastic deformation and plastic deformation in each soil layer, and the plastic deformation is the main deformation with obvious deformation hysteresis. However, the deformation rate of each soil layer presents different characteristics. The results of the stress-strain diagram method show that the inelastic specific storage of the first and second clay layers is between 1.49×10^-5 and 2.10×10^-5, the elastic specific storage is between 3.93×10^-5 and 8.38×10^-5, the inelastic specific storage is 2-4 times of the elastic specific storage, the vertical hydraulic conductivity is between 6.20×10 ^-6~4.39×10^-5 m/d, and the soil deformation lag time is 2.1-12.8 years. The specific storage of the shallow layers in the study area estimated by the type curve method is about 4.8×10^-4, and that of the deep layer is between 1.08×10^-4 and 2.05×10^-4. The specific storage of shallow layer is 2-4 times of that of deep layer, and the vertical hydraulic conductivities are 1-2 orders of magnitude larger than that of the deep layers.

Degradation of Trichloroethylene in Activated Sodium Persulfate System

HAO Tian, ZHANG Yun

2023, 29(4):  600-607.  DOI: 10.16108/j.issn1006-7493.2021076

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Trichloroethylene (TCE) was taken as a target pollutant to study its degradation characteristics in the environmentally friendly chelating agents, sodium citrate (TCD) and citric acid (CA), chelating ferrous ion (Fe²⁺)-catalyzed sodium persulfate (Na₂S₂O₈) system. The effects of the proportion of sodium persulfate, chelating agents, and pH value on the degradation of TCE were investigated, and the optimal proportion of all components and suitable pH value were obtained. Both TCD and CA had effectively chelated Fe²⁺-catalyzed sodium persulfate, which degraded TCE in water, and the degradation of TCE abided by the first-order kinetic reaction model. The optimal proportion in mole was 20:10:10:1 for Na₂S₂O₈/TCD/Fe²⁺/TCE and 20:5:10:1 for  Na₂S₂O₈/CA/Fe²⁺/TCE, respectively, at which both the degradation rate and the first-order reactive rate constant reached their
maximum values. The maximal degradation rate was 96.7% and 97.6% and the maximal reactive rate constant was 2.48×10^-2 and 2.68×10^-2 min-1 for the two reactive systems, respectively. Additionally, the usage of CA for the optimal proportion was only half of TCD. For small proportion, both degradation rate of TCE and the first-order reaction rate constant increased with the increasing amount of TCE, CA, or Na₂S₂O₈. However, excessive chelating agents could form an over-stabilized chelate with Fe²⁺, which reduced the catalytic effect of Fe²⁺ and the oxidative capacity of Na₂S₂O₈. Excessive amount of Na2S2O8 could generate much more sulfate radicals, and these sulfate radicals could consume internally, refraining the degradation reaction of TCE. In the system of Na₂S₂O₈/ Fe²⁺/TCE being 20:10:1, the catalytic effect would dwindle if the proportion in mole was greater than 10 for TCD and 5 for CA. In the system of TCD/Fe²⁺/TCE being10:10:1or CA/Fe²⁺/TCE being 5:10:1, the reaction would be refrained if the proportion in mole was greater than 20 for Na₂S₂O₈. A suitable range of pH value was necessary for the degradation of TCE in activated sodium persulfate system. Alkaline condition refrained the degradation reaction of TCE, while acid to neutral condition was helpful for the reaction.

Influence of Fuel Pollution on Hydrogeological Parameters of Porous Media

YANG Pengfei, CHEN Yudao, JIANG Yaping, YAN Jianing, ZHENG Gao, ZOU Zhikun, LIU Quan, QIN Jiaxiao

2023, 29(4):  608-616.  DOI: 10.16108/j.issn1006-7493.2021108

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Influence of fuel pollution on groundwater environment is an important subject. Investigating the hydrogeological parameters of contaminated sites will be helpful to understand the changes of hydrogeological parameters before and after pollution, as well as changes of the migration behavior of contaminants in groundwater. To compare the differences of parameters before and after gasoline contamination and evaluate the impacts of gasoline contamination on hydrogeological parameters, three stages of quantitative tracer experiments in sand-tank were performed. The results show that: (1) the accumulation of gasoline contamination leads to the occurrence of bioclogging, and the degree of bioclogging tends to slow down with the increasing percolation distance; there exist differences in solute dispersion in different regions of porous media, and increased solute flux in the dominant flow on the central line and the mass recovery rate ; the solute Breakthrough Curves show a lean-high pattern and a clear trailing. (2) by monitoring the gasoline contamination for 6 years, it is found that the permeability coefficients of traditional gasoline tank (TG-tank) and ethanol gasoline tank (EG-tank) were 25.4 and 20.5 m/d, respectively, which decreased to 61% and 49% of the initial permeability coefficient KII before the sand tank was contaminated; the effective porosity of TG-tank and EGtank was reduced from the initial value of 0.30 to 0.28 and 0.26, respectively. Hydrodynamic dispersion coefficient also tended to decrease. The permeability of porous media is reduced more significantly by ethanol gasoline pollution. The accumulation of organic contamination will change the hydrogeological parameters of the contaminated site, and strengthening studies of hydrogeological parameters after contamination can provide a reasonable basis for evaluating the contamination risk.

Physical Analogue Modeling Research on the Relationship Between Longmenshan Fault Zone and Longriba Fault Zone

GE Jiacheng, JIA Dong, YIN Hongwei, YAN Bing, CHEN Zhuxin, FAN Xiaogen, YANG Shuang, CUI Jian, ZHONG Cheng

2023, 29(4):  617-629.  DOI: 10.16108/j.issn1006-7493.2021119

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In the eastern part of Songpan-Ganzi block about 150 km northwest of Longmenshan fault zone in the eastern Tibetan Plateau, there is a NE-trending Longriba fault zone featured with dextral transpressive shearing. Due to its special geographical location, it has attracted widespread attention. In order to study the relationship between these two similar fault zones, three groups of physical analogue modeling are designed according to the actual geological conditions of the region and the similarity principles. The influence of the Bikou terrane and the bottom detachment is mainly considered, and the Particle Image Velocimetry is used to monitor the surface deformation. The experimental model shows that NE-trending Longmenshan fault zone and Longriba fault zone with thrust and right-lateral strike-slip component and Minshan uplift zone with north-south strike are developed under EW compression stress. According to the experimental results, we conclude that only with the existence of the Bikou terrane, faults develop along the boundary of the detachment, otherwise arc faults develop within the detachment layer. The Longmenshan fault zone is connected with the Longriba fault zone in the deep detachment to form a pop-up structure.The results of this study show the development process of fault zone under the influence of Bikou terrane, and provide a possible structural model for understanding the relationship between Longmenshan fault zone and Longriba fault zone.

Study on Genetic Mechanism and Lower Limit of Deep Effective Reservoirs in the Xihu Sag

XIAO Xiaoguang

2023, 29(4):  630-643.  DOI: 10.16108/j.issn1006-7493.2022004

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In order to clarify the formation mechanism of effective reservoir in the Xihu sag and implement the strategy for the development of marine economy effective exploration, we used thin section identification, scanning electron microscopy, constant rate mercury injection, X-ray diffraction and DST tests to analyze the genesis and development of effective reservoirs in the Xihu sag from three aspects including source, sink, and lithology, and discusses the lower limit of their development depth. The result shows that the formation of effective reservoir is controlled by provenance, sedimentation, and diagenesis. The igneous (especially granite) and metamorphic rocks occur around the Xihu Sag. The strong hydrodynamics of large braided river-delta- tidal flat sedimentary environment provides conditions for the development of effective reservoirs under deep low permeability in the Xihu Sag, while transformation of pore throat structures by diagenesis determines vertical distribution of effective reservoirs. Favorable sedimentary microfacies, strong dissolution and early chlorite development are the main factors controlling effective reservoir development in the Xihu Sag. Clean medium-coarse and gravel-bearing medium-coarse sandstone reservoirs under low geothermal and overpressured development determine the lower limit of effective reservoir development.


Research on the Control of CBM Well Reservoir Geological Engineering Characteristics on Productivity

LI Quanzhong, SHEN Jian, HU Haiyang, JI Xiaofeng

2023, 29(4):  644-656.  DOI: 10.16108/j.issn1006-7493.2021118

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In order to improve the single well gas production of CBM well，the influencing factors of CBM well gas production are studied from the geological static parameters and engineering dynamic parameters of CBM development. Based on a block of Shanxi Qinshui Basin 12 reservoir parameters and geological characteristics of typical CBM Wells and development data， starting from the geological control factors, engineering control, detailed analysis of seven aspects of 24 kinds of factors, including coal bed methane resource characteristics，coal reservoir seepage characteristics，structures，energy，drilling，fracturing，drainage，we study the degree to which these factors control the CBM gas production. The results show that the gas production of CBM Wells in the same block is different, which is affected by both geological factors and engineering factors; Also, coalbed methane resources and coalbed methane reservoir seepage, structures and energy characteristics clearly influence coalbed methane production, and when the permeability of coalbed methane reservoir is more than 0.7 mD，it is favorable for coalbed methane well to yield increased gas production. In addition, faults affect the gas content of coal reservoir and fluid migration in the process of drainage and production. In the development of CBM, faults should be avoided and a safe distance of 400 m should be maintained. Furthermore, the higher the casing pressure and gas release pressure of CBM well，the more conducive to expanding the desorption radius of coal reservoir, which results in high and stable production of a CBM well. The scale of fracturing operation in coal reservoir also has great influence on gas production, and the scale of fluid injection is more significant than that of sand injection in the study area. The pressure drop rate and gas production rising rate should be reasonably controlled in each stage of CBM well, and the pressure drop rate should be controlled within 10 kPa/d in the pressure control and production raising stage. These will allow to enlarge the pressure drop funnel radius of Coal Reservoir. The analysis of the geological and engineering
factors of CBM Wells in the study area provides a theoretical basis for the geological selection and geological selection of CBM. It
may also serve as technical guidance for the development of other CBM projects.