Lithosphere最新文献

{"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":null,"pages":null},"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":"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":null,"pages":null},"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}

{"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":null,"pages":null},"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":"Asymmetrical Microfracture Density Across an Active Thrust Fault: Evidence from the Longmen Shan Fault, Eastern Tibet","authors":"Hu Wang, Peisheng Luo, Yi Liang, Dongming Li, Kaijin Li, Lin Deng, Lichun Chen","doi":"10.2113/2024/lithosphere_2023_193","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_193","url":null,"abstract":"Microfracture density in fault damage zones can reflect spatial variability that decays in intensity as a function of distance from the fault, which is crucial in understanding the mechanical, seismological, and fluid-flow properties of the fault system. However, few studies explored the characteristics of fracture density between the two sides of active dip-slip faults due to rare field observations. Here, we measured and modeled microfractures across an active thrust fault associated with the 2008 Mw 7.9 Wenchuan earthquake in the Longmen Shan, eastern Tibetan Plateau. The results showed that the microfracture density at the Qingping site developed more intensely in the hanging wall than in the footwall for an exposed thrust fault, indicating an asymmetrical pattern. The hidden thrust fault at the Jushui site showed that microfractures developed more intensely in vertical planes in the hanging wall than in the footwall, whereas microfractures developed similarly in horizontal planes within the two sides, indicating a quasiasymmetrical pattern. Comparing the data at the two sites with computational modeling, we suggest that fault geometry might exert a first-order control of the asymmetrical microfracture density pattern, which is helpful for revealing different deformational behaviors of rock masses in the fault damage zones and better understanding the hanging-wall effect for evaluating seismic hazards on active thrust faults.A fault damage zone, expressed as a zone with numerous fractures surrounding a narrow fault core, has been considered to be related to coseismic loading and, therefore, has the potential to reveal the rock deformational mechanics and past earthquake rupture conditions [1-7]. Moreover, such a damage zone is expected to act as conduits, barriers, or combined conduit-barrier systems that play a fundamental role in crustal fluid flow [8-10]. Therefore, quantitative determination of characteristics of fractures in the fault damage zone is critical to understand the mechanical and seismological properties of the fault system.Geometrically, fracture density is one of the key parameters in evaluating the spatial variability that decays in intensity as a function of distance from the fault [11, 12]. Many studies have measured micro/mesofracture density on fault-perpendicular transects to show that fracture density decreases gradually away from the fault core, which can be simplified to fit either an exponential decay model [13] or a power law decay model [14, 15] in the fault damage zone. Moreover, previous studies have suggested that the characteristics of fracture density might be influenced by the amount of slip across the fault, the size of the fault, lithology, rupture processes, and movement history [8, 13, 16]. For example, Caine et al. [8] suggested that a wide damage zone may indicate the effect of more repeated seismic events with greater accumulative deformation than that of a narrow damage zone. Ostermeijer et al. [12]","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139500784","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":"Data-Driven Dynamic Inversion Method for Complex Fractures in Unconventional Reservoirs","authors":"Ruixue Jia, Xiaoming Li, Xiaoyong Ma, Liang Zhu, Yangdong Guo, Xiaoping Song, Pingde Wang, Jiantao Wang","doi":"10.2113/2024/lithosphere_2023_347","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_347","url":null,"abstract":"Hydraulic fracturing is a crucial technology for enhancing the recovery of oil and gas from unconventional reservoirs. Accurately describing fracture morphology is essential for accurately predicting production dynamics. This article proposes a new fracture inversion model based on dynamic data-driven methods, which is different from the conventional linear elastic fracture mechanics model. This method eliminates the need to consider complex mechanical mechanisms, resulting in faster simulation speeds. In the model, the fracture morphology is constrained by combining microseismic data and fracturing construction data, and the fracture tip propagation domain is introduced to characterize the multi-directionality of fracture propagation. The simulated fracture exhibits a multi-branch fracture network morphology, aligning more closely with geological understanding. In addition, the influence of microseismic signal intensity on the direction of fracture propagation is considered in this study. The general stochastic approximation (GSA) algorithm is employed to optimize the direction of fracture propagation. The proposed method is applied to both the single-stage fracturing model and the whole well fracturing model. The research findings indicate that in the single-stage fracturing model, the inverted fracture morphology aligns closely with the microseismic data, with a fitting rate of the fracturing construction curve exceeding 95%, and a microseismic data fitting rate exceeding 93%. In the whole well fracturing model, a total of 18 sections were inverted. The fitting rate between the overall fracture morphology and the microseismic data reached 90%. The simulation only took 5 minutes, demonstrating high computational efficiency and meeting the needs of large-scale engineering fracture simulation. This method can effectively support geological modeling and production dynamic prediction.The world has abundant shale gas reservoir resources; however, due to the influence of reservoir rock properties, its development poses significant challenges [1-4]. Hydraulic fracturing technology can effectively enhance the physical properties of reservoirs and form complex fracture networks within the reservoir, thereby promoting oil and gas production [5-7]. In order to assess the development impact of shale gas reservoirs and devise appropriate development plans, it is necessary to establish a numerical model that is specific to the shale gas reservoir in question. Accurately describing the post-fracturing fracture morphology is crucial for model construction and subsequent flow simulations, as it is a key factor in ensuring the accuracy of model calculation results [8]. Moreover, the morphology of fractures post-fracturing is often highly complex, characterized by a network structure of fractures [9, 10]. Many existing fracture propagation models only consider a simplified quasi-three-dimensional or three-dimensional straight fracture structure. However, these mo","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140313388","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":"Effects of Stress on Transport Properties in Fractured Porous Rocks","authors":"Jing Ba, Jinyi Min, Lin Zhang, José M. Carcione","doi":"10.2113/2024/lithosphere_2023_103","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_103","url":null,"abstract":"The nonlinear characteristics of the rock transport properties (permeability and electrical conductivity in this study) as a function of stress are closely related to the geometry of the pore space, which consists of stiff pores, microcracks, or microfractures. We consider two behaviors of the pore space, one linear and the other exponential, related to the stiff pores and microfractures, respectively, where the relation between stress and strain can be described by the Two-Part Hooke’s Model. With this model, the relations between porosity, transport properties, and effective stress (confining minus pore pressure) can be obtained and validated with the experimental data of four tight sandstones collected from the Shaximiao Formation of Sichuan Basin, southwest China. The agreement is good. At low effective stresses, the closure of cracks is the main mechanism affecting the transport properties, whose behavior is similar in terms of their parameters. Subsequently, experimental data of nine tight sandstones from the Yanchang Formation, collected from the Ordos Basin, west China, are employed to confirm the previous results, indicating that the fluid and electrical current follow the same path in the pore space.Reservoir rocks have pores, cracks, or microfractures and are generally heterogeneous [1-4]. The deformation under loading is different in stiff pores and microfractures, which affects the elastic and transport properties, especially in low-permeability rocks. Since cracks provide a permeability path for the flow of reservoir fluids [5-9], understanding of the relationships between the transport properties and effective stress is important for detecting and monitoring reservoir fluids.Previous studies revealed that the exponential function describes the behavior of permeability and conductivity as a function of effective stress [10-20]. However, an important point is to describe the behavior of the sharp decrease of these transport properties when the effective stress increases at low values, especially for low-permeability rocks [21, 22]. The power law has also been adopted to describe such variation [23-27]. For instance, Jones and Owens [28] and Walsh [29] reformulated the expression of power law. On the other hand, Kaselow and Shapiro [30] applied a four-parameter exponential equation to analyze the electrical conductivity as a function of the effective pressure.The closure of cracks with increasing effective stress leads to lower porosity, and permeability or electrical conductivity shows a similar behavior. The transport properties as a function of porosity can be studied with a power law [31, 32] or by analyzing experimental data [21]. Archie [33] established an empirical relation between the formation factor (the ratio between bulk resistivity and that of water) and porosity. Subsequently, some researchers investigated the relationships between electrical conductivity and porosity [34, 35], clay content [36-38], crack radii, aspect r","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139589747","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":"Production Dynamic Characteristic of Fractured Wells in Multilayer Reservoirs Considering the Effect of Non-Uniform Flux Distribution","authors":"Yanzhong Liang, Bailu Teng, Wanjing Luo","doi":"10.2113/2024/lithosphere_2023_173","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_173","url":null,"abstract":"Hydraulic fracturing stimulation, which improves matrix permeability and reduces production costs, has been extensively used in the exploitation of multilayer reservoirs. However, little research on the production dynamic characteristics of vertically fractured wells in stratified reservoirs has been done in the literature. The influence of flux variation along the fracture on the pressure transient behavior has been ignored in these previous works. Therefore, this paper introduces a novel semi-analytical model for fractured wells in multilayer reservoirs, in which the finite difference method is used to characterize fluid flow in the fracture and the Green’s function method is used to characterize fluid flow in the matrix. With the aid of the model, the production dynamic characteristics of fractured wells in multilayer reservoirs can be readily investigated. In addition, based on the assumption of nonuniform flux distribution along the fracture, we successfully recognize four flow regimes occurring in the pressure drop and pressure derivative curves. Following that, the influences of several parameters on the pressure dynamics and layered flux contribution are studied. The calculation results indicate that a larger storability ratio, as well as a larger permeability ratio, can increase the values of the pressure drop and the pressure derivative; the greater the fracture height, the greater the fluid flow into each layer of the fracture. During the production of this model, increasing the fracture conductivity can reduce the pressure drop and pressure derivative, which means lower flow resistance in the fracture.With the growing dependence on fossil energy, deep and ultra-deep areas have steadily evolved into the next main potentials of resource exploration and development. Recently, China has consistently discovered a huge number of deep-layer reservoirs, such as the Puguang, Tahe, Shunbei, and Anyue oilfields, showing great resource potentialities and considerable economic benefits [1]. Considering the influence of the complex sedimentary environment, most deep reservoirs are composed of several layers with different stratigraphic characteristics. Commingling production is commonly adopted to increase producing profit for stratified reservoirs in oil and gas fields [2]. Given this, extensive literature was related to the pressure dynamics of a vertical well in stratified reservoirs [3-6]. Rahman and Mattar [7] derived a new analytical solution for the commingled-layered reservoir with unequal initial pressures in the Laplace domain. Onwunyili and Onyekonwu [8] developed a coupled model that can more accurately simulate the commingled production behavior of multilayer reservoirs. Shi et al. [9] investigated the impact of the vertical inhomogeneous closed boundary radii on pressure transient behaviors of the multilayered commingled reservoir. These previous researches give us a basic understanding of the production dynamic characteristics for th","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140151178","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":"Lithospheric Conductivity Structure in the Middle Segment of the Jiangnan Orogenic Belt: Insights into Neoproterozoic Tectonic–Magmatic Processes","authors":"Jiayong Yan, Hui Chen, Juzhi Deng, Hui Yu, Yuexin You, Yidan Wen, Min Feng","doi":"10.2113/2024/lithosphere_2023_325","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_325","url":null,"abstract":"The Jiangnan Orogenic Belt (JOB) evolved from the Yangtze and Cathaysia blocks through multi-stage oceanic-continental subduction, collisional orogeny, and intracontinental deformation, which is an important region to study the formation and evolution of the South China Continent (SCC). Magnetotelluric soundings were collected along a 520-km-long northwest (NW)-trending profile across the middle segment of the JOB to explore the possible remnants of ancient tectonic–magmatic processes beneath the central SCC by combining with the satellite gravity and magnetic data. The resistivity model reveals that the crust in the middle segment of the JOB and its adjacent area is characterized by high resistivity anomalies, while the uppermost mantle is characterized as medium resistivity anomalies and separated by several subvertical, lithospheric-scale conductors. Two trans-crust anomalies of high conductivity and low density beneath the Jiujiang–Shitai Buried fault (JSBF) and Jiangshan–Shaoxing fault (JSF) extend south-eastward to the lithosphere, which are attributed to the NW and southeast boundaries of the middle segment of the JOB. The imaged NW-trending of JSF reflects the tectonic process of the JOB subducting under the Cathaysia Block. Two lower-crustal conductors also imaged beneath the Jiuling area are interpreted as the partial melting of the lower crust, which may be related to the deep southeast subduction of the Paleo-south China Ocean during 970 to 860 Ma. In addition, the trans-lithosphere high conductivity adjacent to the ancient collisional zone of the Jinning period II (ACZII) is probably related to the asthenosphere upwelling caused by the soft collision between the Yangtze and Cathaysia Blocks, which triggered the contemporaneous magmatism in the Jiuling area. This work provides a new insight into the lithospheric evolution in SCC during the Neoproterozoic.The South China Continent (SCC) is located at the junction of the Paleo-Asian Ocean, Tethys, and Pacific tectonic domains, bordered by the North China Block to the north, the Indochina Block to the south, the Qinghai-Tibet Plateau to the west, and the West-Pacific Plate to the east [1] . Its present status comes from the composite evolution of multi-stage plate tectonics in the Paleo-south China Block, making it one of the most complex geological evolution history areas since the Neoproterozoic [2, 3]. The Jiangnan Orogenic Belt (JOB) in the middle of SCC is spread in a NE-NEE direction, with the Yangtze Block on the northwest (NW) and the Cathaysia Block on the southeast (Figure 1). This area records the collisional assembly of these two ancient microplates, which is of great significance for understanding the crustal accretion, tectonic evolution in the SCC, and the breakup of supercontinent Rodinia [4, 5].Previously proposed models for the tectonic evolution of the JOB include (1) plate subduction collision model [6, 7]; (2) plume model [8]; and (3) plate-rift model [9]. The first ","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140036800","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 Investigation on the Grouting Performance of Foam-CNT Composite Grouts in Vertical Inclined Fractures Under Flowing Condition","authors":"Yaohui Liu, Fang Lv, Zebin Ouyang, Tao Wang","doi":"10.2113/2024/lithosphere_2023_341","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_341","url":null,"abstract":"Grouting is an effective method to solve the problem of water inrush in tunnel and underground engineering. However, rock fractures are often simplified as horizontal and smooth fractures in most grouting studies, while studies on vertical inclined fractures are still rare. To investigate the diffusion law in vertical inclined fractures, a vertical inclined fracture grouting simulation device was developed. A new type of cement slurry with low weight and high flowing water resistance was developed by combining carbon nanotube (CNT) slurry with foamed cement. Physical simulation experiments were conducted to investigate various factors (initial flowing water, inclination angle, sand content, and grouting rate) on the sealing efficiency of grouting. Results show that the high foam content has a negative effect on the compressive strength of the slurry, and has a positive effect on the fluidity and water resistance. The optimum ratio of slurry is 30% foam content, 1.0% CNT content, 1.3 water/cement ratio, and 3% additive content. The inclination angle and inclination direction of the fracture have a great influence on the sealing efficiency of grouting. Foam-CNT composite grouts can meet the requirement of flowing water grouting in vertical inclined fractures.Water inrush is a common problem in tunneling and underground engineering. Water inrush will delay the project and result in high personal injury and property damage [1, 2]. Grouting is an effective method to solve the problem of water inrush [3]. Grouting can improve the strength and reduce the permeability of the rock by injecting slurry into the rock fractures [4-7]. Considerable progress has been made in the area of flowing water grouting in recent years [8-10]. However, the theory of grouting still cannot meet the requirements of practical engineering.Many scholars studied the sealing and diffusion law of flowing water grouting [11-14]. Sui et al. [15] investigated the effects of fracture width, initial flowing rate, grouting time, and grouting amount on the sealing efficiency of flowing water grouting through laboratory simulation experiments. Liang et al. [16] demonstrated that the inclination of fracture has a significant effect on the sealing efficiency and the diffusion law of flowing water grouting. Depending on the relation between the direction of flowing water and fracture, rock fractures can be divided into horizontal fractures, horizontally inclined fractures, and vertically inclined fractures (Figure 1). However, in most studies on flowing water grouting, rock fractures are simplified as horizontal fractures [17, 18], and studies on the vertical inclined fracture grouting are still rare.Many scholars have proved that the diffusion law of liquid in inclined fractures and horizontal fractures is completely different [19]. Graf et al. [20] proposed a numerical method to discretize inclined nonplanar two-dimensional (2D) fractures within a three-dimensional (3D) finite element grid","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140301026","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":"Numerical Modeling of Melting Processes During Slab Break-off: Insights Into Tectonic Setting for Massif-Type Anorthosites","authors":"Qian Yuan","doi":"10.2113/2024/lithosphere_2023_344","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_344","url":null,"abstract":"The concept that lithosphere detachment or break-off has long been conceived as a viable mechanism to explain prominent geological phenomena in Earth’s crust and the surface. One of the strengths of slab delamination mechanism is that it can account for the extensive magmatism in active orogenic belts due to the upwelling of the asthenosphere after the slab break-off. However, in the last 20 years, geodynamic simulations show that the inflow of the asthenosphere upon slab break-off is insufficient to cause significant melting of the overriding lithosphere adjacent to the slab window. The primary reasons include the occurrence of slab break-off at a location that is too deep to effectively heat the overriding lithospheric mantle. Another factor is the presence of a thin film of crustal material that is retained during the slab break- off, inhibiting a significant thermal perturbation within the lithosphere. In this work, we couple petrological–thermomechanical simulations with magmatic melting processes to examine the lithospheric melting and surface lithological expression associated with slab break-off. Our work shows that in the early Earth when the mantle temperature is relatively higher, shallow slab break-off can give rise to significant lithospheric melting during the development of slab break-off. Moreover, because the slab becomes weaker in the earlier hotter mantle, it may break-off prior to the stage of continental collision, thus the magmatism it induced may not give a direct constraint on the time of continental collision. Our study has implications for the interpretation of geological and tomography studies in orogenic belts. It also provides insights into reconciling conflicts between geodynamic and geological studies regarding slab break off-induced melting and magmatism.One of the most peculiar lithologies in Earth’s middle age is Proterozoic massif-type anorthosites (PMAs), a plutonic batholith-forming rock type temporally restricted to the Proterozoic [1-4]. Formally, PMAs are composed of at least 90% plagioclase feldspar accompanied by minor mafic silicates and Fe-Ti oxides [5]. PMAs are areally and volumetrically extensive, with the largest PMA being the Kunene Complex in SW Angola, which covers an area of 18,000 km2 [6]. A consensus has been largely reached on the mechanism by which anorthosites were concentrated. They formed through the accumulation of magmatic plagioclase at the top of a magma chamber due to the low density of plagioclase compared to coexisting melt [7]. However, despite their simple mineralogy and have been studied for over a century, the geodynamic setting accounting for PMAs remains hotly debated [1, 2, 8, 9].A variety of tectonic settings have been proposed for PMAs, including Andean-type continental arc, post-orogenic, anorogenic, and continental rift settings [2, 4, 10, 11]. In recent years, a new tectonic regime—slab break-off—has been adopted accounting for the origin of several PMAs in Asia based o","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140313461","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}