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    20 December 2024, Volume 30 Issue 06
    The Origin of Orbicular Granitoids
    CAO Yufei, LI Shuting, ZHANG Shaobing, HUANG Fang
    2024, 30(06):  635-645.  DOI: 10.16108/j.issn1006-7493.2023067
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    Granitoids with orbicular structure are very rare because of their unique orbicular structure. They stand as unique objects to study magma processes. When high-temperature magma contacted or mixed with low-temperature magma, due to their difference in viscosity and temperature, high interfacial tension leads the high-temperature magma to form orbicules in low-temperature magma. The temperature of orbicules decrease rapidly and result in high degrees of supercooling. Induced by
    exsolution of volatiles or other factors, the orbicules begin to crystallize and branched or feathery crystals are formed. The rapid crystallization in orbicules results in rapid change of local melt and the alternating crystallization of different minerals, forming dark and light rings. During this process, the crystallized minerals can exhibit branched or feathery structures. However, it is still unclear how viscosity and temperature control spheroidization, and how minerals crystallize after spheroidization, and how long the crystallization process lasts. These issues are waiting to be studied and revealed.
    Mechanism Governing on Different Hydrochemical Evolution Processes for Two Types of Travertine and Silica Sinters in Shannan, Tibet
    CONG Tingting, TAN Hongbing, CONG Peixin, SHI Zhiwei, XUE Fei, ZHANG Yu
    2024, 30(06):  646-659.  DOI: 10.16108/j.issn1006-7493.2023073
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    The Tibet Plateau is rich in geothermal resources. Among them, in Chaka and Quzhuomu areas of Shannan, under similar background of geohistorical evolution, geothermal springs with significantly different water chemical compositions were formed, and two different types of springs, silica and travertine, were deposited on a large scale. In this paper, the causal mechanisms of the differences in hydrochemistry between the two types of geothermal systems are discussed through the comparative analysis of the parameters of the two types of geothermal springs, normal and trace chemical compositions, and the stable isotopes of H and O. The results show that Quzhuomu geothermal springs are recharged by meteoric water, and the components source is mainly water-rock interaction, and the water chemical type is mainly HCO3-Ca-Na type. Due to the long hydrochemical evolution process of Chaka and the mixing of a higher proportion of magma residual fluid, the water chemical type evolves into Cl-Na type. The estimation results of various geothermal thermometer show that the thermal reservoir temperature of Quzhuomu is between 98.8-181.3 ℃ , and the proportion of cold water mixing before excretion is 43.4%, while the thermal reservoir temperature of Chaka (183.2-204.3 ℃ ) is significantly higher than that of Quzhuomu. Compared with Quzhuomu, the longer water cycle evolution process of Chaka geothermal springs, the mixing of a higher proportion of magma residual fluid and the higher thermal reservoir temperature, are the main cause mechanism that controls the large-scale deposition of silica during the discharge process of geothermal springs and the abnormal enrichment of some typical incompatible elements in the water body.
    Variations Between Two Lower Cambrian Prof iles in the Upper Yangtze Region and Their Implications for Depositional Environments
    WANG Guozhi, ZHANG Can, LIU Dayong, QIU Linfei, LI Ziying, PENG Ping’an
    2024, 30(06):  660-667.  DOI: 10.16108/j.issn1006-7493.2023071
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    Sampling of two quarry sections occurred at Zunyi, Guizhou, and Youyang, southeastern Chongqing. These samples were systematically collected from organic-rich, polymetal-enriched shales at the base of the Lower Cambrian Niutitang Formation. Analysis encompassed organic geochemistry, mineralogy, and major and trace element compositions. Despite being approximately 300 kilometers apart, both sections are situated within the Upper Yangtze Platform, facilitating comparative study. Vertical variations in TOC, δ13Corg, and major and trace element abundances suggest that these sections occupy distinct positions on the continental shelf slope. Compared to the Songlin section, samples from the Danquan section indicate proximity to the source area, characterized by higher clastic input fluxes. Although multiple depositional environment changes occurred within less than a 9-meter range from the Niutitang Formation’s base upwards in both sections, the depositional environments tended to converge with rising sea levels. The relationship between shale organic matter abundance (TOC), organic carbon isotopes (δ13Corg), and certain trace elements associated with hydrothermal activity (e.g., As, Ni, Sb) in both sections indicates different mechanisms for trace element enrichment. In the Songlin section, organic matter adsorption primarily drives trace element enrichment at the Niutitang Formation’s base, whereas in the Danquan section, mixing with codepositional hydrothermal fluids is the primary mechanism.
    Exploration of the Adsorption Characteristics and Mechanisms of Heavy Metal Ni(II) by the Biochar Prepared from Crayfish Shell
    XU Xiaoqi, ZHOU Bin, LI Jinhui, CHEN Yang
    2024, 30(06):  668-677.  DOI: 10.16108/j.issn1006-7493.2023060
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    Crayfish shells are a common type of kitchen waste, and their transformation into biochar for the purpose of adsorbing heavy metal pollutants in water can mitigate pollution and facilitate resource utilization. The various processing methods applied to the raw materials may exert an influence on the adsorption of heavy metals by crayfish shell biochar. A comprehensive understanding of these underlying mechanisms can contribute to the optimization of crayfish shell biochar production and application, thereby offering valuable insights into the management of kitchen waste. In this study, crayfish shells were employed as the primary raw materials, and three types of biochar were obtained through diverse processing methods: raw crayfish shell biochar (CB), cooked and washed crayfish shell biochar (WCB), and cooked and unwashed crayfish shell biochar (CCB). Subsequent batch adsorption experiments were conducted, with a comprehensive exploration of biochar characteristics and adsorption mechanisms through analytical techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The findings revealed a hierarchy in specific surface area and equilibrium adsorption capacity as CB>WCB>CCB, while the maximum adsorption capacity displayed a sequence of CB>CCB>WCB. The adsorption kinetics of Ni(II) by all three biochar types conformed to the Elovich model, pseudo-first-order and pseudo-secondorder kinetic model. The adsorption isotherms followed the Langmuir and Freundlich models. The adsorption mechanisms included physical adsorption, ion exchange, and surface functional group complexation. Notably, cooked crayfish shells proved to be less conducive to resource utilization compared to their raw counterparts, and washing treatments had a negligible impact on adsorption capacity. Consequently, the utilization of unwashed cooked crayfish shells for biochar production emerges as a more economically and environmentally viable alternative.
    Strain Characteristics and Tectonic Significances of the Sanjiang Ductile Shear Zone in the Junction Area of Northern Guangxi and Western Hunan
    GUAN Rongfang, QIN Ya, FENG Zuohai, GOU Xiaofang, XING Quanli, KANG Zhiqiang, HU Qiaofan, WU Jie
    2024, 30(06):  678-693.  DOI: 10.16108/j.issn1006-7493.2023062
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    The strain characteristics and tectonic significance of the Sanjiang ductile shear zone are studied by analyzing the macro-micro structures, magnetic fabrics and quartz EBSD fabrics to constrain the Early Paleozoic orogenic processes of the Yangtze and Cathaysia block. The Sanjiang ductile shear zone has typical macro-micro scopic ductile deformation fabrics, including S-C fabric, tensile lineation, A-type fold, domino structure, mechanical twin, permeable foliation, core-mantle  structure and quartz dynamic recrystallization. The magnetic fabrics and macro-micro structure show that the Sanjiang ductile shear zone extends more than 40 km in NNE direction with a width of 3.7-7.5 km. The mylonitic C-foliation strikes 262°-321° with the dip at 31°-87° and the overall average is 295 °∠ 69°. The mean of 36 groups of magnetic foliations with susceptibil ity anisotropy (Pvalue)≥1.05 is 304°∠ 83°. The clockwise rotation of the magnetic foliation relative to the C-plane foliation of mylonite indicates a sinistral sense of the Sanjiang ductile shear zone. Macro-micro structures show that the Sanjiang ductile shear zone is dominated by sinistral thrust shear and dextral normal slip shear. The rock strain of the Sanjiang ductile shear zone is mainly flattening and tensile strain. At the same time, it shows both pure shear and simple shear. Quartz EBSD fabric analysis reveals that the Sanjiang ductile shear zone is characterized by the late mid-low temperature deformation (300-500 ℃ ) superimposed on the early midhigh temperature deformation (480-600 ℃ ). Based on the research of macro-micro structures, magnetic fabrics and quartz EBSD fabrics, combined with regional geological data, it is considered that the Sanjiang ductile shear zone was formed in the tectonic background of compression and extrusion of the Cathaysia block from SE toward the Yangtze block. In the early extrusion and collision stage, the Sanjiang ductile shear zone underwent mid-high temperature sinistral thrust shear. After the late orogenic extension, the Sanjiang ductile shear zone experienced dextral normal slip shear at mid-low temperature. The above analysis reveals the strain characteristics, deformation temperature and dynamic background of the Sanjiang ductile shear zone and provides new constraints for better understanding of the Early Paleozoic tectonic events in South China.

    The Occurrence State of Lithium in the Middle Mesoproterozoic Wumishan Formation Lithium-rich Rock Series in Eastern Hebei Province
    GENG Xiaolei, LI Wei, , WANG Kebing, CAI Yuanfeng, , REN Chao, JI Shichao, WANG Jingzhao, , GAO Yanfeng, WANG Yuguang, TONG Xinen, WANG Ruiqi
    2024, 30(06):  694-704.  DOI: 10.16108/j.issn1006-7493.2023072
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    In 2021, Hebei Geological Survey Institute discovered an extraordinary enrichment of lithium in the Middle Mesoproterozoic Wumishan Formation in the eastern Hebei, which is the first time that clay type lithium resources were found in Precambrian strata in China. The lithium-rich rock series has large thickness, wide distribution, stable horizon, Li2O grade of 0.1-0.42 wt%, and has great prospecting potential. As a new lithium-endowed horizon, the occurrence state of lithium is directly related to the exploration and development significance of the clay-type lithium resources discovered this time. By using X- ray diffraction (XRD), thermal analysis (TG-DTG) and Fourier transform infrared spectroscopy (FTIR), it is found that the lithium-rich rocks in the study area are mainly composed of dolomite, quartz and clay minerals such as illite and illite/smectite mixed layers. Through solid state nuclear magnetic resonance spectroscopy, time-of-flight secondary ion mass spectrometry (TOF-SIMS), clay mineral purification and Na ion exchange experiments, it is revealed that the lithium in the Wushan Formation lithium-rich rock series mainly exists in the illite and illite/smectite mixed layers in the form of isomorphic replacement, and a very small amount of lithium exists in the form of ion adsorption between the clay mineral layers or on the surface. The research results provide important theoretical basis and technical support for the selection, metallurgy and exploitation of clay-type lithium resources in eastern Hebei Province in the future.

    Suppression of Desiccation Cracking Behavior in Clayey Soils Using the Bio-carbonation of Reactive Magnesia Method
    ZHENG Hongyang, WANG Rui, LIU Yujia, TANG Chaosheng
    2024, 30(06):  705-713.  DOI: 10.16108/j.issn1006-7493.2023066
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    Upon drying, the generated cracks on the soil surface can greatly weaken the mechanical properties of soils, thereby causing various geological engineering problems. Based on the bio-carbonation of reactive magnesia (RMC) method, this study investigated the feasibility of the spraying method in suppressing desiccation cracking and explored the effects of curing agent composition, urea concentration, RMC dosage and spraying sequence on the anti-cracking performance of soils. The results show that: (1) The formation of hydrated magnesium carbonates (HMCs), and the bio-carbonation product of RMC could enhance the cementation of soil particles and establish a bio-carbonation layer on the sample surface, which enables to effectively inhibit the desiccation cracking behavior of soils through decreasing the evaporation rate of moisture in the soil and increasing the tensile strength of samples; (2) The elevated urea concentration could significantly facilitate the bio-carbonation of RMC. In the case of 2.0 mol/L urea concentration, the maximum penetration resistance of the bio-carbonized sample increased by 195.5% after three wetting-drying cycles in comparison to that of the raw sample; (3) Both high RMC dosage and the post-spraying treatment of RMC solution impeded the infiltration of RMC within the soil matrix, which negatively affected the improvement of cementation performance for soil samples. 
    Three-dimensional Geological Modeling and Numerical Study on Roof Crack Evolution in No. 3 Cave of Longyou Grottoes
    ZHANG Deyu, ZHOU Jian, ZHANG Luqing, YANG Zhifa, FU Yan, LI Ziyi
    2024, 30(06):  714-725.  DOI: 10.16108/j.issn1006-7493.2023074
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    The ancient underground caverns in Longyou Grottoes are immovable cultural relics under the key protection in China, with a history of thousands of years, but their rock mass strength shows a trend of deterioration. In the recent 20 years, many field investigations found that cracks in the surrounding rock of the roof of No.3 cavern developed rapidly, and local blocks fell off at the thin roof rock. In order to further analyze the evolution and expansion of cracks in the roof of No.3 cave in Longyou Grottoes, high-precision three-dimensional point cloud data of the cave contour were obtained by using three-dimensional laser scanning technology. Also highprecision geometric and geological models were established combined with rock mass structure information. The development process of cracks in the roof of No. 3 cave in Longyou Grottoes was numerically simulated and analyzed by using the strength reduction method. The research results show that, based on high-precision 3D laser scanning point cloud data combined with a geological survey, the 3D geological model of Longyou Cave 3 is constructed. The results of numerical simulation on this high-precision grid model can accurately reflect the evolution and expansion law of the roof crack of Cave 3. The cracks in the roof of No.3 cave in Longyou Grottoes were mainly generated around the entrance and rock column, and the expansion form is mainly annular. With the increase in the strength reduction
    coefficient of rock mass, the tensile stress concentration area of the roof surrounding rock is distributed at the tip of existing cracks and in the middle of multiple cracks, and the longitudinal expansion of tensile cracks mainly appear in the outermost surrounding rock of the tunnel roof. Variations of the displacement field of the roof rock body show the characteristics of spatial heterogeneity. The maximum displacement in the fracture concentration area on the northern side of No. 3-1 rock pillar is 6mm, while the maximum displacement in the fracture concentration area on the northern side of No.3-3 rock pillar is 12.14 mm. This study obtained the distribution, shape and development trend of cracks in the roof of Longyou Grottoes No.3 for the first time, which is generally consistent with the field survey data. Therefore, this study can provide a reference for the mechanical analysis and prediction of the surrounding rock of the cave and the long-term protection of the grottoes.
    Using the Thickness of Delta Foredeposits to Restore the Maximum Paleo-water Depth of Lakes: A Case Study of Qinnan Sag in Bohai Bay Basin and Huizhou Sag in Pearl River Mouth Basin
    DANG Zhaoqing, CHEN Ying, LYU Chengfu, BAI Zhizhao, XIAO Yueye, ZHOU Qianshan
    2024, 30(06):  726-736.  DOI: 10.16108/j.issn1006-7493.2023058
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    Water depth plays a decisive role in the redox conditions of a basin and plays an important role in the enrichment and preservation of organic matter in sedimentary basins. Previous studies mainly relied on paleontology, element geochemistry,
    stratigraphic thickness, and other methods for qualitative and semi-quantitative palaeodepth restoration. However, these methods have a high dependence on original samples and low prediction accuracy and are not suitable for Palaeogene Lake basin palaeodepth restoration in offshore basins. In this study, the depth of paleowater is mainly restored based on the thickness of the delta for deposits in seismic profiles. By using this method, the maximum palaeobathymetric during the sedimentary period of the third Member of the Shahejie Formation of the Eocene in Qinnan west subsag of Bohai Bay Basin is 595 m, and the maximum paleowater depth during the sedimentary period of Wenchang Formation in the southwest of Huizhou Sag of Pearl River Mouth Basin is 526 m. Combined with previous research results, it is found that the rate of sag-controlling fault activity is strong in the third Member of the Shahejie Formation period of Qinnan Sag and the Wenchang Formation period of Huizhou Sag, and they are during the strong rifting of the basin, which controls the formation of deep water lake basins. During this period, many Sags in Bohai Bay Basin and Pearl River Mouth Basin are in deep-water-ultra-deepwater environments, so it is inferred that the deep water environment is the result of strong fault activity. Then the redox conditions of the lake basin are controlled, and more organic matter is preserved in the lake basin to form high-quality source rocks. 
    Astronomical Forcing in the Middle-Upper Jurassic Walloon Coal Measures Cycles in the Surat Basin, Australia
    CUI Zehong, JING Yuhong, HUANG Wensong, LIU Lingli, ZHANG Yunfei
    2024, 30(06):  737-746.  DOI: 10.16108/j.issn1006-7493.2023061
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    The Walloon coal measures in the Surat Basin, Australia, has a huge amount of coalbed methane (CBM) resources, but the spatial heterogeneity of CBM production capacity varies significantly. Variable characteristics of multiple thin coal seams in the Walloon coal measures, and rapid lateral changes in lithology limit further research on the lateral differences of coal reservoirs. Therefore, fine-scale stratigraphic framework delineation of the Walloon coal measures in the Surat Basin is fundamental for understanding the temporal and spatial differences of coal reservoirs. The S-4 well, which has a complete and continuous sedimentary formation, is used as the main drilling well. Time series analysis of its natural gamma (GR) logging data is used for the cyclostratigraphic study. The power spectrum analysis results show that the Walloon coal measures in the Surat Basin recorded 15 sedimentary cycles of 405 kyr periodicity, and orbital forcing had a significant impact on its depositional process. The long eccentricity, short eccentricity, obliquity, and precession are represented by sedimentary cycles with thickness of 23.9 m, 6.3-9.3 m, 2.4-2.7 m, and 1.2-1.4 m, respectively. Correlation coefficient analysis indicates that the Walloon coal measures was driven by astronomical cycles at >99% confidence level. Using the zircon CA-TIMS U-Pb age of 162.54±0.05 Ma from the S-4 well coal-bearing tuff as a constraint, an astronomical calibration was performed using a stable 405 kyr cycle to establish an astronomical time scale for the Walloon coal measures. The duration of this formation was determined to be 5.7-6.1 Myr, mainly deposited during the Middle Jurassic Callovian to Late Jurassic Oxfordian. Based on the consistency between time series analysis and identification of cyclic interfaces, combined with the identified sedimentary cycles of 405 kyr periodicity, the Walloon coal measures was divided into 5 third-order sequences and 15 fourth-order sequences, establishing a high-frequency sequence stratigraphic framework for the study area. The stratigraphic framework provides a reference for high-precision isochronous correlation of the Walloon coal measures in the Surat Basin.
    Hydroclimate Changes in Southwestern China Over the Past 800 Years and its Dynamics
    ZHAO Bin, CUI Yingfang, KONG Xinggong, ZHAO Kan, WANG Yongjin
    2024, 30(06):  747-755.  DOI: 10.16108/j.issn1006-7493.2023063
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    Southwestern China is a high-risk area of drought. However, hydroclimate behavior and its mechanism on various timescales in southwestern China are still unclear, largely due to scarce long-term high-resolution hydrological reconstructions. Moreover, the speleothem-based oxygen isotope record shows an ambiguous relationship between Asian summer monsoon variation and regional hydrological change. Here, we present a nearly 800-yr-long (1180-1969 AD) annually resolved and accurately dated regional hydroclimate record based on annual laminae thickness data from a stalagmite (NO. DX1) in Dongge Cave, Guizhou Province. The regional climatic conditions are dominantly influenced by the Asian summer monsoon and the Intertropical Convergence Zone (ITCZ). In the continuously-growing section (from 0-58.2 mm), regular laminations can be observed under a microscope. The microscopic features of the lamina resemble those from Shihua and Hulu caves in the monsoonal regions of China. Therefore, we obtain a layer-counting timescale and an annual laminae thickness record from 1180 to 1969 AD. The close similarity between the annual laminae thickness and δ13C records suggests that annual laminae thickness of stalagmite DX1 can serve as a proxy for regional hydroclimate. Centennial-scale hydroclimate changes are broadly similar to the Northern Hemisphere (NH) temperature variations, with a significant drought event (-1540-1630 AD) during the Little Ice Age (LIA), supporting that the NH temperature has an important influence on low-latitude hydrological changes, via meridional shifts of the ITCZ. The mathematical analyses reveal that the regional hydrological changes display significant -3-year and -7-year periodicities (accounting for -44% of the total variance), likely related to the interannual El Niño-Southern Oscillation (ENSO) variations. In addition, the 31-yr running biweight variance for the regional hydroclimate gradually decreased from the Medieval Warm Period to the LIA, reached the minimum during the coldest LIA interval (-1540-1630 AD), then gradually increased, and became unusually high during the Current Warm Period. This hydroclimate variance is largely consistent with the reconstructed ENSO variance and further modulated by secular NH temperature background states. Our observation implies that the ENSO and low-latitude hydrological variance will increase, and the frequency and amplitude of extreme climate events will increase under the scenario of continuous global warming.