Lithosphere最新文献

{"title":"The Late Cambrian to Neogene Evolution of the Khanom Core Complex (Peninsular Thailand)","authors":"Urs S. Klötzli, Bernhard Neugschwentner, Jolanta Burda, Pitsanupong Kanjanapayont, Qiu-Li Li, Yu Liu, Patrik Konečný, Punya Charusiri","doi":"10.2113/2024/lithosphere_2023_272","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_272","url":null,"abstract":"The Khanom Core Complex in Peninsular Thailand is a part of the crystalline basement of Sundaland and plays a key role in our understanding of the evolution of Thailand and SE Asia. The complex comprises ortho- and paragneisses, schists, meta-volcanics, subordinate calcsilicate rocks, and postkinematic granitoids. New petrochronological data reveal that the sedimentation and metamorphism of the paragneiss precursors (Haad Nai Phlao complex, Khao Yoi paragneisses) occurred in the Late Cambrian at the latest. A syn- to postsedimentary andesitic intrusion/extrusion in the Haad Nai Phlao complex at 495 ± 10 Ma defines a minimum age for the former event(s). In the Early Ordovician (477 ± 7 Ma), the Haad Nai Phlao complex and the Khao Yoi paragneisses were intruded by the Khao Dat Fa granite. During the Indosinian orogenic events, the Laem Thong Yang (211 ± 2 Ma) and Haad Nai Phlao (210 ± 2 Ma) granitoid plutons were intruded. Immediately afterward (ca. 208–205 Ma), the first metamorphic overprinting of the Laem Thong Yang granite and the Haad Nai Phlao complex including the Khao Dat Fa granite occurred. A second metamorphic overprinting of all lithological units and the contemporaneous intrusion of the Khao Pret granite followed in the Late Cretaceous and Early Paleogene (ca. 80–68 Ma). The tectonic formation of the core complex took place in the Eocene (<42 Ma), followed by exhumation and regional cooling below ca. 450°C and the latest cooling to ca. 120°C in the Miocene (ca. 20 Ma). The evolutionary data show that the Khanom Core Complex is part of Sibumasu, and its Late Cretaceous-Neogene cooling pattern and exhumation history can be directly related to the northward drift of India.Thailand is located on the geological entity known as Sundaland, which consists of Gondwana-derived continental terranes that accreted over time to build the present-day mainland of Indochina [1, 2]. Two main continental terranes can be distinguished, Sibumasu in the west and Indochina in the east, along with an interjacent arc, called Sukhothai. Both terranes are crucial to understand the geological evolution of Gondwana, the various Tethys oceanic domains, Sundaland, and Southeast Asia. However, there is no agreement on the nature and exact locations of their boundaries, the characteristics of the basement evolution, or the tectonic models of their amalgamation (References [2-5] and references therein). This problem is accentuated by the scarcity of crystalline basement exposures. The available basement data are limited to three regions of exposure in northern and southeast Thailand and on the Thai peninsula.The first description of crystalline basement rocks in Thailand was published by Heim and Hirschi [6]. These rocks are typically high- to medium-temperature low-pressure metamorphic and intermediate to acidic plutonic rocks [1, 7, 8]. Often, they are overlain by fossiliferous Phanerozoic sediments [1, 9]. Consequently, the first to assign a Precambrian age to the g","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"17 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139501765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study of the Effect of Drying and Wetting Cycles and Water Content on the Shear Characteristics of Tailing Sands","authors":"Yakun Tian, Zhijun Zhang, Min Wang, Lingling Wu, Lin Hu, Rong Gui","doi":"10.2113/2024/lithosphere_2023_320","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_320","url":null,"abstract":"The mechanical characteristics of tailing sands have an important impact on the safety and stability of the tailing dams. Fully understanding the effect of drying and wetting cycles (DWC) and water content on the characteristics of tailing sands is urgently needed. In this study, direct shear tests were first carried out to analyze the effect of DWC and water content on the macroscopic mechanical characteristics of tailing sands. Then, the mesoscopic mechanical behavior of tailing sands with different water contents under the action of DWC was studied by using PFC2D particle flow software. The results showed that the effect of DWC on the shear properties of tailing sands is more pronounced than water content. The cohesive force and the internal friction angle increase first and then decrease with the increasing water content. With the increasing number of DWC, the cohesive force and the internal friction angle all decreased to varying degrees. The results of the mesoscopic mechanical analysis indicated that after experiencing the DWC, the force chain of the sample gradually thickens to form a coarse force chain network area, and the number of cracks inside the sample is significantly larger than that of the sample that has not experienced the DWC. The results of this study are of great significance for understanding the macroscopic and mesoscopic shear failure mechanism of tailing sands under the effects of DWCs and water content.The tailing dam is a man-made debris flow hazard with high potential energy, and there are many unstable factors in its operation process. The collapse of the tailing dam not only affects the production of mining enterprises but also brings huge disasters to the inhabitants. Due to periodic changes in water conditions (i.e., rainfall infiltration, water evaporation, and repeated elevation and decline of the infiltration line), the tailing dam is subjected to long-term drying and wetting cycles (DWCs) during operation. It was found that the DWCs will lead to a decrease in the mechanical properties of the soil, and the changes in water content also affect the microstructure and mechanical properties of the soil. Under the action of DWC and water content, the matric suction and shear strength of the soil will change, thus affecting the stability of the soil structure. Therefore, a comprehensive understanding of the influence of the DWC and water content on the characteristics of tailing sands is of great significance for the long-term safety and stability of the tailing dam.A substantial effort has been made on the changes in the physical properties and mechanical behavior of rock materials under the action of cyclic wetting and drying [1-21]. The properties of rock materials (i.e., porosity, longitudinal wave velocity, compressive strength, shear strength, etc.) are significantly influenced by DWCs. Zhou et al. [7] studied the dynamic tensile strength characteristics of rocks after cyclic drying and wetting. They inferred ","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"278 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140072332","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental and Numerical Investigation of Rock Failure Process under Hydromechanical Coupling Action","authors":"Zeqi Zhu, Xiancheng Mei, Jianhe Li, Qian Sheng","doi":"10.2113/2024/lithosphere_2023_317","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_317","url":null,"abstract":"In order to study the initiation mechanism of rocks under hydromechanical coupling, hydromechanical coupling triaxial tests and acoustic emission tests were carried out on basalt in the Xiluodu hydropower station dam site area in southwestern China. The test results indicate that the basalt displays typical hard brittle behavior, and its peak strength increases as confining pressure rises. Conversely, the peak strength decreases gradually as the initial water pressure increases, which leads to decreased hardness. Meanwhile, tensile failure is the main crack initiation mode under hydromechanical coupling action. During the stable crack growth stage, tensile failure is predominant, complemented by shear failure, with failures mainly occurring in the rock middle position. Contrary to this, during the unstable stage, the rock failure is mainly due to shear failure. The critical pore water pressure failure criterion of rock crack initiation under hydromechanical coupling conditions is derived based on the test results and introduced into the numerical simulation. The hydromechanical coupling failure process and pore water pressure distribution law of basalt are analyzed, and the rationality of the critical pore water pressure failure criterion is verified. These findings are significant for understanding the rock failure process under hydromechanical coupling action and provide a valuable reference for future research.Hydroelectric engineering projects often involve structures such as underground power stations, water diversion tunnels, and sloping dam foundations, which are subjected to the combined action of high-ground stress and strong osmotic pressure. Therefore, research on the mechanical properties of rocks or rock masses under hydromechanical coupling has become a pressing issue in geotechnical engineering. Several scholars, including Song et al. [1], Zhu et al. [2], Yu et al. [3], Xu et al. [4], Wang et al. [5], and Wang et al. [6], have conducted hydromechanical coupling triaxial tests on limestone [1-3], sandstone [4-6], and granite [7, 8] to investigate the relationship between rock permeability, stress, strain, and pore water pressure. They have discussed the influence of pore water pressure on rock strength characteristics, deformation laws, and damage evolution. Moreover, Li et al. [9], Zhao [10], and Guo et al. [11] have employed acoustic emission (AE) signals to analyze the AE characteristics during the process of rock cracking under hydromechanical coupling.The aforementioned research has extensively demonstrated that hydromechanical coupling induces pore water pressure within the internal cracks of a rock, which significantly impacts the cracking process [12, 13]. Once the pore water pressure attains a critical level, it instigates the inception, expansion, and penetration of rock cracks, commonly referred to as hydromechanical fracturing [14]. This phenomenon is a significant factor that causes a range of engineering disasters, inc","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"10 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139553739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of Lithology on the Characteristics of Wave Propagation and Dynamic Response in Rocky Slope Sites Subject to Blasting Load Via the Discrete Element Method","authors":"Danqing Song, Xuerui Quan, Zhuo chen, Dakai Xu, Chun Liu, Xiaoli Liu, Enzhi Wang","doi":"10.2113/2024/lithosphere_2023_302","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_302","url":null,"abstract":"To investigate the dynamic response and attenuation law of rock slope sites subjected to blasting, three lithological numerical models, including slate (hard rock), tuff (relatively soft rock), and shale (soft rock), are established by using MatDEM. By analyzing the wave field, velocity, and acceleration response of the models and their Fourier spectrum, combined with stress and energy analysis, their dynamic response characteristics are investigated. The results show that blasting waves propagate from near field to far field in a circular arc, and the attenuation effect of waves in soft rock is less than that in hard rock. The influence of lithology on the dynamic response of the ground surface and bedrock is different. Blasting waves mainly affect the dynamic response in the near-field area of the blasting source. In addition, the dynamic amplification effect of slopes is as follows: hard rock > relatively soft rock > soft rock. The slope surface has an elevation attenuation effect. A dynamic amplification effect appears in the slope interior within the relative elevation (0.75, 1.0). The Fourier spectrum has an obvious predominant frequency, and that of the slope crest and interior is less than that of the slope surface. Moreover, the total energy generated by the rocky sites gradually changes into kinetic energy, gravitational potential energy, elastic potential energy, and heat. Energy-based analysis shows that the attenuation effect of blasting waves in hard rock is larger than that in soft rock overall. This work can provide a reference for revealing the blasting vibration effect of rock sites.Because of the advantages of fast construction, low cost, and high efficiency, the blasting method has become the main construction method of slope and tunnel engineering [1]. Nevertheless, due to the influence of the propagation medium, the waveforms and propagation characteristics of blasting seismic waves become very complicated [2]. Blasting seismic waves will lead to slope instability and other geological disasters; in particular, in coal mining areas, under the influence of human blasting over the years, geological disasters, such as mountain cracking and creep, will occur on slopes, seriously threatening the safety of people’s lives and property [3, 4]. Moreover, seismic exploration blasting technology is an important method in geophysical exploration [5]. The seismic effect of explosive blasting has become a key problem in land oil and gas exploration and foundation construction. The propagation law and damage effect of seismic waves in different geological bodies are the main basis of engineering blasting design [6, 7]. Therefore, explosion-induced seismic waves have been one of the most active subjects in the field of civil engineering blasting.Blasting seismic waves are a complex physical phenomenon [8, 9]. It is affected by many factors, such as the location of the source of detonation, the amount of explosive, the mode of explosion, the ","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"162 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139690006","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gravity-Seismic Joint Inversion of Lithospheric Density Structure in the Qiongdongnan Basin, Northwest South China Sea","authors":"Chaoyang Li, Wei Gong, Lihong Zhao, Zhonghua Li, Pengyao Zhi, Jiayu Ge","doi":"10.2113/2024/lithosphere_2023_124","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_124","url":null,"abstract":"Qiongdongnan Basin (QDNB), located at the northwestern corner of the South China Sea (SCS), is a key juncture between the extensional tectonic regime in the northern continental margin and the shear tectonic regime in the western continental margin. Analyzing the crustal density structure and tracking the thermodynamic controlling factors are effective approaches to reveal the nonuniform breakup process of the northwestern SCS. Herein, focusing on the obvious tectonic deformation with distinct eastern and western parts in the QDNB, we present the crustal density structures of five profiles and identify the high-density anomaly related to the synrifting mantle underplating and postrifting magmatic intrusions. The crustal density model was constructed from the Bouguer gravity anomaly, ocean bottom seismic profiles, and multichannel seismic reflection profiles. The northern part of QDNB, with normal crustal density, lower surface heat flow of <55 mW/m2, and limited extension factor of 1.25–1.70, is recognized as the initial nonuniform extension continental crust. The mantle underplating beneath the QDNB is identified as a high mantle density of 3.30–3.40 g/cm3 and a high lower crustal density of 2.92–2.96 g/cm3, which is usually recognized by the high-velocity layers in the northeastern margin of SCS. The magmatic intrusions are identified as the high-density bodies ranging from 3.26 g/cm3 at the base to 2.64 g/cm3 at the top, which become stronger from the west to east. The central part of Xisha Trough is featured by the cooling of the heavily thinned lower crust in the final continental rifting stage, which is close to the cold and rigid oceanic crust. Lateral variations in the deep magmatic anomaly should be the crucial factor for the nonuniform breakup process in the northwestern margin of SCS.As the largest Cenozoic marginal basin located in the western Pacific region, the South China Sea (SCS) was formed in a complex tectonic setting due to the strong interaction among the Indo-Australian, Eurasian, and Pacific plates [1, 2] (Figure 1). Because of the stretching stress introduced by the rollback of the paleo-Pacific plate and the slab pull of the paleo-SCS, the SCS shows the ununiform continental rifting and progressive seafloor spreading from east to west, featuring highly inhomogeneous crustal structure and asymmetric magmatism beneath the marginal basins [3-5]. It is generally accepted that the SCS might represent a “plate-edge or Pacific-type” extensional basin, and the passive upwelling of the fertile asthenospheric mantle induced by the surrounding subductions could be primarily responsible for these inhomogeneous features [6, 7]. Some scholars even believed that the SCS had experienced a “magma-rich”-type breakup process in its middle-eastern part, but a “magma-poor” one is observed in the west [4, 8].In the case of the northern continental margin of SCS, the compositional or structural east–west heterogeneity has been observed by vario","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"7 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139553743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of the Advance Jacked Pipe on the Jacking Force of the Subsequent Pipe Based on Pipe–Soil Full Contact Model","authors":"Yu Zhang, Xu Zhao, Fei Guo, Lianjin Tao, Jun Liu, Weizhang Liao, Lei Tan, Xiaohui Yang","doi":"10.2113/2024/lithosphere_2023_216","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_216","url":null,"abstract":"In pipe jacking engineering, accurate prediction of jacking force is the key to pipe jacking design. Based on a project of the Beijing Daxing Airport Line, the influence of the advance jacked pipes on the jacking force of the subsequent pipe is carried out in the present work. First, the verified numerical model of practical engineering was established, and the jacking force and radial stress of different pipes were analyzed. Then, the two pipes were taken as research object, and the parameters of spacing, angle, buried depth, and pipe diameter were investigated, respectively. The results show that in the actual project, the advance jacked pipes have amplification and superposition effects on friction resistance of the subsequent pipe, and the maximum growth rate is 37.2%. The friction resistance of the subsequent pipe presents a trend of first increasing and then decreasing with the change of the layout angle of advance jacked pipe from 0° to 180°. With the increase of buried depth and pipe diameter, the absolute value of incremental friction resistance of the subsequent pipe increases gradually, but the growth rate remains constant. Finally, the empirical formulas for predicting the friction resistance growth rate of subsequent pipes under different angles are proposed. The research results can provide some reference for the design of pipe jacking.In recent years, rapid urbanization resulted in a great development in underground space. The pipe jacking method has been widely used in energy transportation engineering, water conservancy, and tunnel engineering because of its advantages of fast construction speed, little disturbance to the surrounding environment, and easy-to-control jacking accuracy [1-12]. Besides, pipe jacking is also used in pipe roof engineering. For example, the Xinle Ruin station of Shenyang subway line 2 was built with the pipe roof method. The pipe roof structure consists of 19 steel pipes with a diameter of 2000 mm and 2 steel pipes with a diameter of 2300 mm [13]. The Gongbei tunnel was built by 36 steel pipes with a diameter of 1620 mm [14].The core problem of pipe jacking is still the calculation of friction resistance. The magnitude of the jacking force is directly determined by the friction resistance, and the radial stress of the pipe–soil interface determines the distribution and magnitude of friction resistance stress. At present, the existing literatures have done a lot of research on the friction resistance. The numerical simulation and laboratory test methods have been adopted to study the pipe–soil interaction under different types of lubricants and their combinations by Shou et al. [15]. They concluded that the reduction of the jacking force is closely related to the decrease of friction coefficient, and the effect of lubrication is slightly more significant in the case of curved pipe than in the case of linear pipe. Yen and Shou [16] took the obtained average friction coefficient as the input parameter of t","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"33 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139951551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Controls of Multi-Scale Fractures in Tight Sandstones: A Case Study in the Second Member of Xujiahe Formation in Xinchang Area, Western Sichuan Depression","authors":"Junwei Zhao, Yingtao Yang, Gongyang Chen, Xiaoli Zheng, Senlin Yin, Lei Tian","doi":"10.2113/2024/lithosphere_2023_343","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_343","url":null,"abstract":"Different scales of fractures affect the reservoir quality in tight sandstone. There are more studies on macroscopic tectonic fractures but less on bedding fractures and microfractures. The control factors of multi-scale fractures are unclear. In this paper, we analyzed the types and controls of fractures in the second member of the Xinchang region in Western Sichuan. We use core and outcrops observations, imaging logging, scanning energy spectra, and rock slices. Natural fractures can be classified into tectonic, bedding, and microscopic types. The tectonic fractures are mainly low- to medium-angle tensile fractures. The bedding fractures are nearly horizontally distributed along the bedding surface, including parallel, dark mineral interface, and carbonaceous fragments interface bedding fractures. The microfractures develop intra-grain, edge-grain, and inter-grain types. The intra-grain microfractures are inside quartz or feldspar grains, whereas inter-grain types penetrate multiple grains with larger extension lengths. The tectonic fractures are related to the stress, grain size, mineral component, argillaceous content, and lithologic thickness. Parallel bedding fractures are controlled by the coupling of water depth and flow velocity. Bedding fractures at the interface are controlled by rock component. The microfractures are controlled by the length-width axis ratio of the grain, grain element content, and brittleness index. Fractures of different scales form a three-dimensional fracture system that has a substantial impact on the gas production.Tight sandstone gas is an unconventional natural resource dominated by low-porosity and low-permeability reservoirs with porosity less than 10% and air permeability less than 1 × 10–3 μm2 [1-4]. It has been discovered in many basins in China [5-8] and accounts for a relatively large proportion of the gas production, such as in the Ordos, Sichuan, Junggar, and Tarim basins [9-16]. The Xinchang gas field in the Sichuan Basin was first discovered in 1988. The exploration progress was slow owing to the insufficient understanding of geological and fracking processes. After 2,000 years, a few exploration wells were drilled in close to the fracture system, and gas production was increased [17-21]. Exploration showed that the fractures play an important role in controlling the gas production of the Xinchang gas field. However, the distribution of fractures in this zone is complex with different fracture geneses, scales, and occurrences. Nevertheless, there is a lack of the systematic understanding of fractures.Tectonic fractures in tight sandstones have been extensively studied [22, 23]. The factors affecting them include the stress heterogeneity in different tectonic zones [24-31] and lithologic heterogeneity [32-34]. Sedimentation controls differences in the lithology and layer thickness, and heterogeneity in the mineral composition and structure of reservoirs influence fracture development [35-40]. Bedding","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"15 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140017254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrogenesis and Tectonic Implication of Jurassic Granites in Central Guangdong, SE China: Constraints from Zircon U-Pb-Hf-O and Whole-Rock Geochemical and Sr-Nd Isotopic Data","authors":"Zhiguang Lai, Yongxin Xu, Chunbo Xin, Xuewen Luo","doi":"10.2113/2024/lithosphere_2023_327","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_327","url":null,"abstract":"The origin and tectonic regime responsible for the inland Jurassic granites in Southeast (SE) China remain controversial. This study presents zircon secondary ion mass spectrometry (SIMS) U-Pb ages, in situ zircon Hf-O isotopes, and whole-rock geochemical and Sr-Nd isotopic data for the Fogang and Xinxing Batholiths in central Guangdong. Mineralogical and geochemical features indicate that these granites are high-K (>4.8 wt% K2O at 72 wt% SiO2), calc-alkaline I-type granites. SIMS U-Pb analyses on magmatic zircons yield consistent ages ranging from 158 to 163 Ma, suggesting that the Fogang and Xinxing granites were emplaced in the period of 163–158 Ma. In addition, these granites have whole-rock initial Sr87/Sr86 ratios of 0.6802–0.7072 and negative εNd(t) values of −9.5 to −8.2, zircon negative εHf(t) values of −12.34 to −0.56, and high δ18O values of 7.64‰–10.08‰. The above features imply that the granites were most likely generated through the mixture of supracrustal sedimentary components with minor addition of mantle-derived magmas. Granites from the Fogang and Xinxing Batholiths in SE China should be derived from the Proterozoic crustal reworking due to asthenosphere upwelling or underplating and intrusion of mafic magmas. These Jurassic granites reflect anorogenic magmatism probably formed in an intraplate extensional setting resulted from the foundering of the flat slab beneath SE China.Granite is a primary component of continental crust, preserving abundant information about the formation, evolution, and accretion of crust, as well as interactions between the crust and mantle. Multiperiod Mesozoic granites are widely distributed in Southeast (SE) China, with a concentration in the Triassic, Jurassic, and Cretaceous, respectively Figure 1(a) [1-3]. Among them, the Nanling region is mainly characterized by Jurassic granite, while the coastal areas are dominated by Cretaceous granite (see Figures 1(a) and 1(b)) [4]. The coexistence of multiperiod rocks from different origins is of great significance for understanding the genesis of the granite, crust-mantle interaction, magma differentiation, and mixing processes [5-8]. Previous researchers have reported the geochronology, petrology, mineralogy, and geochemistry of the Nanling granites. However, there has been ongoing debate regarding their petrogenesis and tectonic mechanism.The Fogang and Xinxing Batholiths represent Late Mesozoic basements in the Nanling region, with Fogang Batholith being the largest and most representative granite basement in the region (Figures 1(c) and 1(d)) [4, 7]. Due to intense fractional crystallization, the batholiths exhibit complex geochemical characteristics, making their genetic types difficult to determine [9]. Different scholars have classified the Fogang Batholith as I-type [8, 9], A-type [5], S-type [6], or high-fractionated I-type granites [10]. Similarly, there are different views on the genetic type of the Xinxing Batholith, such as I-type [11], A-typ","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"43 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139465141","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Long-Lasting Exhumation History of the Ötztal-Stubai Complex (Eastern European Alps): New Constraints from Zircon (U–Th)/He Age-Elevation Profiles and Thermokinematic Modeling","authors":"Kyra Hölzer, Reinhard Wolff, Ralf Hetzel, István Dunkl","doi":"10.2113/2024/lithosphere_2023_174","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_174","url":null,"abstract":"The Eastern European Alps formed during two orogenic cycles, which took place in the Cretaceous and Cenozoic, respectively. In the Ötztal-Stubai Complex—a thrust sheet of Variscan basement and Permo-Mesozoic cover rocks—the record of the first (Eoalpine) orogeny is well preserved because during the second (Alpine) orogeny, the complex remained largely undeformed. Here, new zircon (U–Th)/He (ZHe) ages are presented, and thermokinematic modeling is applied to decipher the cooling and exhumation histories of the central part of the Ötztal-Stubai Complex since the Late Cretaceous. The ZHe ages from two elevation profiles increase over a vertical distance of 1500 m from 56 ± 3 to 69 ± 3 Ma (Stubaital) and from 50 ± 2 to 71 ± 4 Ma (Kaunertal), respectively. These ZHe ages and a few published zircon and apatite fission track ages were used for inverse thermokinematic modeling. The modeling results show that the age data are well reproduced with a three-phase exhumation history. The first phase with relatively fast exhumation (~250 m/Myr) during the Late Cretaceous ended at ~70 Ma and is interpreted to reflect the erosion of the Eoalpine mountain belt. As Late Cretaceous normal faults occur at the margins of the Ötztal-Stubai Complex, normal faulting may have also contributed to the exhumation of the study area. Subsequently, a long period with slow exhumation (<10 m/Myr) prevailed until ~16 Ma. This long-lasting phase of slow exhumation suggests a rather low topography with little relief in the Ötztal-Stubai Complex until the mid-Miocene, even though the Alpine orogeny had already begun in the Eocene with the subduction of the European continental margin. Accelerated exhumation since the mid-Miocene (~230 m/Myr) is interpreted to reflect the erosion of the mountain belt due to the development of high topography in front of the Adriatic indenter and repeated glaciations during the Quaternary.Mountain belts with thick continental crust, such as the European Alps, the Himalaya, or the North American Cordillera, are formed during long-lasting plate convergence with crustal shortening by nappe stacking and folding [1-3]. Due to the isostatic uplift of the thickened crust, the internal parts of such orogens become the locus of erosion, which removes material at the Earth’s surface and leads to the cooling and exhumation of metamorphic rocks [4, 5]. Apart from erosion, another important mechanism that may cause rock exhumation and cooling is normal faulting because tectonic slip along normal faults transports rocks in their footwalls toward the Earth’s surface [6-9].To quantify the cooling history of metamorphic rocks, it is necessary to determine the temperature conditions in rocks through time, which is possible by applying geochronological methods such as Sm/Nd, Rb/Sr, or Ar/Ar dating to minerals with different closure temperatures [10-12]. The final cooling in the upper crust from temperatures of ~250°C to ~60°C can be constrained with low-temperature ther","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"57 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139476961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigating the Mechanism of Strong Roof Weighting and Support Resistance Near Main Withdrawal Roadway in Large-Height Mining Face","authors":"Junwu Du, Qingxiang Huang","doi":"10.2113/2024/lithosphere_2023_288","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_288","url":null,"abstract":"Aiming at investigating the strong roof weighting when the large height mining face is nearing the main withdrawal roadway, the 52,304 working face (WF) nearly through the main withdrawal roadway mining in a colliery of Shendong coalfield was taken as the research background. The ground pressure, roof structure, and superposition effect of stress in the last mining stage were studied by field measurement, physical simulation, and numerical calculations. The obtained results demonstrated that the main roof formed the “long step voussoir beam” structure under the influence of the main withdrawal roadway. The superposition effect of the front abutment pressure of the WF and the concentrated stress of the main withdrawal roadway caused the stress asymmetrical distribution on the two sides -level hard rock straof the main withdrawal roadway, and the stability of the pillar on the mining side decreases. The initial average periodic weighting interval was 20.7 m. While the WF approaches the main withdrawal roadway, the pillar near the WF of the main withdrawal roadway collapsed, the main roof was broken ahead of the WF, and the actual roof control distance of support and the periodic weighting interval increased by 2.56 and 1.26 times the normal state, respectively. Consequently, the “static load” of the immediate roof and the “dynamic load” of the sliding unsteadiness of the long step voussoir beam increased. The structural model of the “long step voussoir beam” under the superposition of “static and dynamic load” was established concerning those results, and an expression was proposed to compute the support resistance. Meanwhile, the mechanism of strong roof weighting was revealed when the WF was nearly through the main withdrawal roadway. The research conclusion is expected to provide a guideline for the safe withdrawal of the large-height mining faces under similar conditions.To increase the withdrawal speed and yield efficacy of the working face (WF) and avoid the tense connection between face mining and entry driving, predriving double withdrawal roadway is widely used in coal mines to reinforce the withdrawal operation [1]. In this scheme, the main and auxiliary withdrawal roadways are advance driven at the stop-mining line of the WF. After the primary withdrawal roadway is connected with the WF, the reinforcements are withdrawn through the connecting entry between the primary and secondary withdrawal roadways. Consequently, the withdrawal speed of the WF increases 3–5 times compared with the traditional methods, thereby increasing the production rate and improving the mining efficiency [2, 3]. Although this method has remarkable advantages, it has some shortcomings, including low mining speed in the last mining stage, concentrated mining-induced stress field, and high roof pressure [4]. More specifically, the superposition effect of the lateral and front abutment pressure of the main withdrawal roadway and the WF near the main withdrawal roadway","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"35 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139758627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}