The Nanyili （南一里）, Laohegou （老河沟）, and Shaiziyan （筛子岩） granitic intrusions are located in the southern margin of the Bikou （碧口） block in Pingwu （平武） area, Northwest Sichuan （四川）. The petrogr...The Nanyili （南一里）, Laohegou （老河沟）, and Shaiziyan （筛子岩） granitic intrusions are located in the southern margin of the Bikou （碧口） block in Pingwu （平武） area, Northwest Sichuan （四川）. The petrography and geochemical characteristics of the granitic intrusions as well as their source and tectonic settings are reported and discussed in this article. The Laohegou and Shaiziyan granites are with high SiO2 （69.89 wt.%-73.05 wt.%） and Al2O3 contents, and A/CNK=1.04-1.12. They are typical strongly peraluminous granites, with supersaturation in AI and Si. The abundance of ∑REE varies in the range of （33.13-89.12）×10^-6. The rocks show an LREE enrichment pattern and obvious Eu negative anomaly. The trace element geochemistry is characterized evidently by a negative anomaly of Ta, Nb, Ti, etc. and a positive anomaly of Rb, Ba, Sr, etc.. Zircons of the Nanyili granite have higher Th/U ratios, and their CL images have internal oscillatory zoning, suggesting that the zircons of the samples are igneous in origin. The LA ICP-MS zircon U-Pb isotopic concordia diagram yields an age of 223.1±2.6 Ma （MSWD=1.4）, which indicates that the granodiorite intrusions formed in the early Late Triassic. The Nanyili, Laohegou, and Shaiziyan granites have the characteristics of post-collisional granites and are regarded as post-orogenic granites. Thus, the granite intrusions are interpreted as syn-collisional granites that resulted from the crustal thickening caused by the collisions between the North China plate and the Yangtze plate during the Indosinian. The granitic intrusions formed in a transitional environment from syn- （compressional environment） to post-collision （extensional environment）.展开更多
Homret Ghannam alkali feldspar granite(HGAFG)in the central Eastern Desert(CED)of Egypt represents a distinctive example of late Neoproterozoic magmatism in the Arabian-Nubian Shield(ANS).This study integrates field o...Homret Ghannam alkali feldspar granite(HGAFG)in the central Eastern Desert(CED)of Egypt represents a distinctive example of late Neoproterozoic magmatism in the Arabian-Nubian Shield(ANS).This study integrates field observations,petrography,mineral chemistry(EMPA),and whole-rock geochemistry to investigate its petrogenesis,geodynamic evolution,and rare-metal potential.HGAFG comprises two cogenetic varieties,alkali feldspar granite and riebeckite-bearing granite,hosting rare-metal minerals such as zircon,fluorite,columbite and apatite.HGAFG exhibits diagnostic A-type geochemical characteristics,including high SiO₂contents(73.81-77.86 wt%),metaluminous to mildly peralkaline composition(ASI:0.92-1.03),enrichment in HFSE(Zr≈791.80 ppm,Nb≈68.12 ppm,Y≈90.81 ppm)andΣREE(103.40-475.57 ppm),and pronounced negative Eu anomalies(Eu/Eu^(*)=0.07-0.20).Zircon saturation thermometry yields high crystallization temperatures(TZr≈908.87℃)and low emplacement pressures(1.46 kbar)under reducing conditions(ƒO_(2)≈−11.5).The mineralogical and geochemical results reveal that HGAFG originated from a hybrid,fluorine-rich magma generated by anatexis of lower crust,followed by extensive fractional crystallization,during late post-collisional extension associated with lithospheric delamination.The reduced nature and fluorine enrichment of HGAFG magma promoted the mineralization of Nb-Ta-REE phases,highlighting its significance as a fertile,high-temperature product of the terminal magmatic stage in ANS evolution.展开更多
Investigating the damage evolution of surrounding rock under thermal shock cycles is crucial for ensuring the stability of engineering rock masses.This study performed Brazilian splitting tests on granite specimens un...Investigating the damage evolution of surrounding rock under thermal shock cycles is crucial for ensuring the stability of engineering rock masses.This study performed Brazilian splitting tests on granite specimens under varying temperature and cycle conditions,employing acoustic emission monitoring,digital image correlation,and three-dimensional scanning technology.A systematic analysis was conducted on the patterns of damage evolution,failure precursor,and response mechanisms under combined thermal and cyclic loading.Experimental results show that both P-wave velocity and tensile strength degrade significantly with increasing temperature and cycle count,with temperature having a more pronounced effect than cycle count.Notably,damage evolution exhibits a dual-threshold behavior in which degradation accelerates markedly above 400℃ and stabilizes after 5 thermal cycles.Fracture surfaces evolve from initially planar to rugged morphologies,with peak-valley height differences at 600℃ being approximately three times greater than those at 200℃.Furthermore,based on acoustic emission energy entropy analysis,we introduce a novel failure precursor indicator where the sustained increase and critical surge in average entropy serve as reliable early-warning signals for impending rock failure.These findings establish a solid theoretical basis and practical methodology for damage assessment and instability early-warning systems in high-temperature rock engineering.展开更多
The Mianhuakeng uranium deposit,characterized by uranium-rich granite,serves as a key site for research into crustal radioactive heating.Based on 45 rock samples,this study reviews that the host granite in the Mianhua...The Mianhuakeng uranium deposit,characterized by uranium-rich granite,serves as a key site for research into crustal radioactive heating.Based on 45 rock samples,this study reviews that the host granite in the Mianhuakeng uranium deposit has a high radioactive heat production rate(avg.5.50μW/m³)and a low Th/U ratio(avg.2.62).Uranium-rich granite and its alteration zone within the upper crust(0-5 km depth)contribute about 45%of the total radioactive heat production,wich is crucial for controlling geothermal resource distribution.For uranium-thermal at tectonic plate margins,a symbiotic geological model was proposed:Firstly,subduction of the Pacific Plate caused upwelling of the asthenosphere,generating a high heat-flow background.Secondly,heat transfer is enhanced by major faults such as the Youdong and Mianhuakeng faults.Subsequently,uranium was mobilized,transported,and enriched within the granite through deep siliceous hydrothermal activity and associated alteration.Ultimately,the uranium enrichment in granite leads to increased radioactive heat production,resulting in local thermal anomalies.This model provides a theoretical support for exploring and developing uranium-thermal symbiotic resources in South China.展开更多
The Shenshan Group provides important geological information which is vital in unraveling the amalgamation and subsequent rifting processes of South China.While conventional studies have asserted its formation in a su...The Shenshan Group provides important geological information which is vital in unraveling the amalgamation and subsequent rifting processes of South China.While conventional studies have asserted its formation in a subduction setting,the distinct investigation reveals the necessity for reassessment.To address this,the authors employ integrated methods encompassing petrological,zircon U-Pb geochronological,Lu-Hf isotopic and geochemical methods for sedimentary rocks from the upper Shenshan subgroup and Banxi Group.The geochemical results indicate that they were formed through the recycling deposition of intermediate-acidic igneous source material and experienced moderate chemical weathering.Additionally,both sedimentary sequences exhibit characteristics consistent with those formed in an intracontinental extensional rift setting since ca.810 Ma.The provenance analysis indicates that the upper Shenshan subgroup primarily originates from the Yangtze Domain,while the Banxi Group from both the Yangtze and Cathaysia domains.Synthesizing with previous studies,the Shenshan Group should be subdivided into the lower and upper subgroups which represent distinct tectonic backgrounds.The lower subgroup is inferred to have formed in an Early Neoproterozoic fore-arc setting,akin to the Zhoutan group.The upper subgroup corresponds to the Banxi Group,representing the Middle Neoproterozoic postorogenic rift setting,responding to the breakup of Rodinia.展开更多
Higher Himalayan Crystalline (HHC) rocks often show metamorphic zonations from lower greenschist facies to migmatites associated with leucogranite intrusions that are classically described as examples of Tertiary inve...Higher Himalayan Crystalline (HHC) rocks often show metamorphic zonations from lower greenschist facies to migmatites associated with leucogranite intrusions that are classically described as examples of Tertiary inverted metamorphism. The present study, based on structural, petrological and geochronological investigations in the Kinnar Kailas Granite (KKG) and surrounding HHC sequence, evidences a discordant intrusive contact of the Ordovician KKG with respect to Pre\|Alpine high grade deformed HHC sequence in the Sutlej valley.Four main phases of deformation are recorded in this HHC sequence and pre\|Ordovician sediments. The first three phases of deformation occurred under high\|grade metamorphic conditions, before the intrusion of the KKG. The geometry of the main progressive ductile deformation (D2—D3) results from SW vergent doming and migmatisation. The latest deformation is expressed by local shearing under greenschist facies conditions. This late D4 deformation corresponds to N—S oriented ductile normal faults lowering the eastern blocks. The KKG is a shallow depth intrusion, showing discordant contacts with the surrounding basement rocks and large scale magmatic stoping. The KKG crosscuts the high\|grade deformation structures (D2—D3) but is locally affected by the local late D4 extensional deformation. The granite textures reflect only slight orientation related to magmatic deformation and even at few centimetres from the intrusion contact, the granite appears undeformed in contrast to the surrounding highly foliated rocks. Furthermore, xenoliths of Kyanite\|Sillimanite bearing basement rocks are present within the KKG.展开更多
Objective More and more evidence suggests that the Kwangsian orogen is probably an intraplate orogen, which is one of the few examples of intraplate orogenesis worldwide. However, the initiation time, size and scope ...Objective More and more evidence suggests that the Kwangsian orogen is probably an intraplate orogen, which is one of the few examples of intraplate orogenesis worldwide. However, the initiation time, size and scope of the Kwangsian orogeny have not been determined yet. This study analyzed the Silurian A-type granites in northeastern Guangxi, South China Block, which may provide new evidence for the transition from compression to post- orogenic extension of the Kwangsian orogen.展开更多
The petrogenesis and genetic link to polymetallic mineralization of the granites in the Dayishan complex,southern Hunan province remain debated.Here,we present an integrated study on the petrology,zircon U-Pb ages and...The petrogenesis and genetic link to polymetallic mineralization of the granites in the Dayishan complex,southern Hunan province remain debated.Here,we present an integrated study on the petrology,zircon U-Pb ages and whole-rock geochemistry for this complex.Our findings indicate that the southern complex consists of(amphibole-bearing)biotite granites and muscovite granites emplaced at 153-151 Ma,and the central and northern complex consists of two-mica granites and tourmaline-bearing muscovite granites,respectively with the former emplaced at 164 Ma and the latter at 150 Ma.The(amphibole-bearing)biotite granites have SiO_(2) contents of 68.0-73.8 wt% and are enriched in alkalis and rare earth elements and depleted in Sr and Ba.They display Zr+Y+Ce+Nb>350 ppm and 10000×Ga/Al>2.6 along with high zircon saturation temperatures(821-883oC).The two-mica granites and(tourmaline-bearing)muscovite granites have high SiO_(2)(74.4-77.3 wt%)and low Ga/Al,Zr+Nb+Ce+Y,K/Rb,Zr/Hf,and Nb/Ta along with low zircon saturation temperatures(709-817℃).Geochemical characteristics suggest that the(amphibole-bearing)biotite granites are A-type granites generated through shallow dehydration melting of early Paleozoic granitoids,and that the two-mica granites and(tourmaline-bearing)muscovite granites are fractionated A-type granites produced through fractionation crystallization from the(amphibole-bearing)biotite granites accompanied by fluid fractionation.展开更多
Both fractional crystallization and fluid-melt-crystal interaction are involved in the formation of highly fractionated granites.This paper assessed those two processes using geochemistry of muscovite and tourmaline a...Both fractional crystallization and fluid-melt-crystal interaction are involved in the formation of highly fractionated granites.This paper assessed those two processes using geochemistry of muscovite and tourmaline and bulkrock chemistry of multi-phase Wangxianling granitoids,South China.Compositional variations suggest the coarse-grained muscovite granite is produced from fractional crystallization of the two-mica granite whereas the fine-grained muscovite granite represents a distinct magma pulse.Progressive fractionation of quartz,feldspar and biotite leads to elevated boron and aluminum content in melt which promoted muscovite and tourmaline to crystallize,which promotes two-mica granite evolving towards tourmaline-bearing muscovite granite.Fluid-melt-crystal interaction occurred at the magmatichydrothermal transitional stage and resulted in the textural and chemical zonings of tourmaline and muscovite in finegrained muscovite granite.The rims of both tourmaline and muscovite are characterized by the enrichment of fluid mobile elements such as Li,Mn,Cs and Zn and heavierδ^(11)B values of the tourmaline rims(-15.0‰to-13.6‰)compared to cores(-15.7‰to-14.3‰).Meanwhile,significant M-type REE tetrad effects(TE_(1,3)=1.07-1.18)and low K/Rb ratios(48-52)also correspond to fluid-melt-crystal interaction.This study shows zoned muscovite and tourmaline can be excellent tracers of fractional crystallization and late-stage fluid-melt-crystal interaction in highly evolved magmatic systems.展开更多
In the western segment of the East Kunlun Orogen(WEKO),muscovite granite and garnet granite from the Hureguole intrusion exhibit zircon U-Pb ages of 435-442 Ma.Geochemically,these rocks contain high concentrations of ...In the western segment of the East Kunlun Orogen(WEKO),muscovite granite and garnet granite from the Hureguole intrusion exhibit zircon U-Pb ages of 435-442 Ma.Geochemically,these rocks contain high concentrations of SiO_(2),K_(2)O and Al_(2)O_(3),with low concentrations of TiO_(2)and MgO,indicating a peraluminous high-K calc-alkaline affinity.They are enriched in Rb,Th,U and LREE,depleted in Eu,Ba,Sr and Ti,being classified as S-type granites.Negative whole-rockε_(Nd)(t)values(-9.8 to-9.1)and zirconε_(Hf)(t)values(-11.6 to-8.2)for those granites indicate that they were derived from partial melting of pelitic rocks in the Paleoproterozoic Baishahe Formation of the Jinshuikou Group.Based on the collected zircon ages,Cambrian-Devonian magmatic activity in the WEKO was divided into three stages:early(446-520 Ma),middle(427-441 Ma)and late(372-424 Ma)stages.Statistically,whole-rock Nd and zircon Hf isotope data(ε_(Nd)(t)/T_(DM)^(Nd),ε_(Hf)(t)/T_(DMC)^(Hf))from Paleozoic igneous rocks in the WEKO reveal a magma source that was initially dominated by depleted mantle components in the northward subduction stage of the Proto-Tethy an Ocean plate(446-520 Ma),shifting to predominantly crustal sources during the closure period of the North Qimantagh back-arc basin(427-441 Ma),then to crust-mantle mixed sources in the post-collision stage(372-424 Ma).展开更多
The roughness of the fracture surface directly affects the strength,deformation,and permeability of the surrounding rock in deep underground engineering.Understanding the effect of high temperature and thermal cycle o...The roughness of the fracture surface directly affects the strength,deformation,and permeability of the surrounding rock in deep underground engineering.Understanding the effect of high temperature and thermal cycle on the fracture surface roughness plays an important role in estimating the damage degree and stability of deep rock mass.In this paper,the variations of fracture surface roughness of granite after different heating and thermal cycles were investigated using the joint roughness coefficient method(JRC),three-dimensional(3D)roughness parameters,and fractal dimension(D),and the mechanism of damage and deterioration of granite were revealed.The experimental results show an increase in the roughness of the granite fracture surface as temperature and cycle number were incremented.The variations of JRC,height parameter,inclination parameter and area parameter with the temperature conformed to the Boltzmann's functional distribution,while the D decreased linearly as the temperature increased.Besides,the anisotropy index(Ip)of the granite fracture surface increased as the temperature increased,and the larger parameter values of roughness characterization at different temperatures were attained mainly in directions of 20°–40°,60°–100°and 140°–160°.The fracture aperture of granite after fracture followed the Gauss distribution and the average aperture increased with increasing temperature,which increased from 0.665 mm at 25℃to 1.058 mm at 800℃.High temperature caused an uneven thermal expansion,water evaporation,and oxidation of minerals within the granite,which promoted the growth and expansion of microfractures,and reduced interparticle bonding strength.In particular,the damage was exacerbated by the expansion and cracking of the quartz phase transition after T>500℃.Thermal cycles contributed to the accumulation of this damage and further weakened the interparticle bonding forces,resulting in a significant increase in the roughness,anisotropy,and aperture of the fracture surface after five cycles.展开更多
Granite residual soil (GRS) is a type of weathering soil that can decompose upon contact with water, potentially causing geological hazards. In this study, cement, an alkaline solution, and glass fiber were used to re...Granite residual soil (GRS) is a type of weathering soil that can decompose upon contact with water, potentially causing geological hazards. In this study, cement, an alkaline solution, and glass fiber were used to reinforce GRS. The effects of cement content and SiO_(2)/Na2O ratio of the alkaline solution on the static and dynamic strengths of GRS were discussed. Microscopically, the reinforcement mechanism and coupling effect were examined using X-ray diffraction (XRD), micro-computed tomography (micro-CT), and scanning electron microscopy (SEM). The results indicated that the addition of 2% cement and an alkaline solution with an SiO_(2)/Na2O ratio of 0.5 led to the densest matrix, lowest porosity, and highest static compressive strength, which was 4994 kPa with a dynamic impact resistance of 75.4 kN after adding glass fiber. The compressive strength and dynamic impact resistance were a result of the coupling effect of cement hydration, a pozzolanic reaction of clay minerals in the GRS, and the alkali activation of clay minerals. Excessive cement addition or an excessively high SiO_(2)/Na2O ratio in the alkaline solution can have negative effects, such as the destruction of C-(A)-S-H gels by the alkaline solution and hindering the production of N-A-S-H gels. This can result in damage to the matrix of reinforced GRS, leading to a decrease in both static and dynamic strengths. This study suggests that further research is required to gain a more precise understanding of the effects of this mixture in terms of reducing our carbon footprint and optimizing its properties. The findings indicate that cement and alkaline solution are appropriate for GRS and that the reinforced GRS can be used for high-strength foundation and embankment construction. The study provides an analysis of strategies for mitigating and managing GRS slope failures, as well as enhancing roadbed performance.展开更多
The undrained mechanical behavior of unsaturated completely weathered granite(CWG)is highly susceptible to alterations in the hydraulic environment,particularly under uniaxial loading conditions,due to the unique natu...The undrained mechanical behavior of unsaturated completely weathered granite(CWG)is highly susceptible to alterations in the hydraulic environment,particularly under uniaxial loading conditions,due to the unique nature of this soil type.In this study,a series of unconfined compression tests were carried out on unsaturated CWG soil in an underground engineering site,and the effects of varying the environmental variables on the main undrained mechanical properties were analyzed.Based on the experimental results,a novel constitutive model was then established using the damage mechanics theory and the undetermined coefficient method.The results demonstrate that the curves of remolded CWG specimens with different moisture contents and dry densities exhibited diverse characteristics,including brittleness,significant softening,and ductility.As a typical indicator,the unconfined compression strength of soil specimens initially increased with an increase in moisture content and then decreased.Meanwhile,an optimal moisture content of approximately 10.5%could be observed,while a critical moisture content value of 13.0%was identified,beyond which the strength of the specimen decreases sharply.Moreover,the deformation and fracture of CWG specimens were predominantly caused by shear failure,and the ultimate failure modes were primarily influenced by moisture content rather than dry density.Furthermore,by comparing several similar models and the experimental data,the proposed model could accurately replicate the undrained mechanical characteristics of unsaturated CWG soil,and quantitatively describe the key mechanical indexes.These findings offer a valuable reference point for understanding the underlying mechanisms,anticipating potential risks,and implementing effective control measures in similar underground engineering projects.展开更多
Exploring dynamic mechanical responses and failure behaviors of hot dry rock(HDR)is significant for geothermal exploitation and stability assessment.In this study,via the split Hopkinson pressure bar(SHPB)system,a ser...Exploring dynamic mechanical responses and failure behaviors of hot dry rock(HDR)is significant for geothermal exploitation and stability assessment.In this study,via the split Hopkinson pressure bar(SHPB)system,a series of dynamic compression tests were conducted on granite treated by cyclic thermal shocks at different temperatures.We analyzed the effects of cyclic thermal shock on the thermal-related physical and dynamic mechanical behaviors of granite.Specifically,the P-wave velocity,dynamic strength,and elastic modulus of the tested granite decrease with increasing temperature and cycle number,while porosity and peak strain increase.The degradation law of dynamic mechanical properties could be described by a cubic polynomial.Cyclic thermal shock promotes shear cracks propagation,causing dynamic failure mode of granite to transition from splitting to tensile-shear composite failure,accompanied by surface spalling and debris splashing.Moreover,the thermal shock damage evolution and coupled failure mechanism of tested granite are discussed.The evolution of thermal shock damage with thermal shock cycle numbers shows an obvious S-shaped surface,featured by an exponential correlation with dynamic mechanical parameters.In addition,with increasing thermal shock temperature and cycles,granite mineral species barely change,but the length and width of thermal cracks increase significantly.The non-uniform expansion of minerals,thermal shock-induced cracking,and water-rock interaction are primary factors for deteriorating dynamic mechanical properties of granite under cyclic thermal shock.展开更多
The corrosion of waste canisters in the deep geological disposal facilities(GDFs)for high-level radioactive waste(HLRW)can generate gas,which escapes from the engineered barrier system through the interfaces between t...The corrosion of waste canisters in the deep geological disposal facilities(GDFs)for high-level radioactive waste(HLRW)can generate gas,which escapes from the engineered barrier system through the interfaces between the bentonite buffer blocks and the host rock and those between the bentonite blocks.In this study,a series of water infiltration and gas breakthrough experiments were conducted on granite and on granite-bentonite specimens with smooth and grooved interfaces.On this basis,this study presents new insights and a quantitative assessment of the impact of the interface between clay and host rock on gas transport.As the results show,the water permeability values from water infiltration tests on granite and granite-bentonite samples(10−19-10−20m^(2))are found to be slightly higher than that of bentonite.The gas permeability of the mock-up samples with smooth interfaces is one order of magnitude larger than that of the mock-up with grooved interfaces.The gas results of breakthrough pressures for the granite and the granite-bentonite mock-up samples are significantly lower than that of bentonite.The results highlight the potential existence of preferential gas migration channels between the rock and bentonite buffer that require further considerations in safety assessment.展开更多
Microwave-assisted rock-breaking technology,as a novel hybrid approach,is anticipated to facilitate the efficient excavation of complex rock formations.It is therefore crucial to understand the damage and failure mech...Microwave-assisted rock-breaking technology,as a novel hybrid approach,is anticipated to facilitate the efficient excavation of complex rock formations.It is therefore crucial to understand the damage and failure mechanisms of rocks that have been subjected to irradiation.In this study,uniaxial compression experiments were conducted on granite specimens after 1.4 kW microwave irradiation for varying durations.Furthermore,a numerical method was proposed to solve electromagnetic-thermal-mechanical coupling problems by integrating finite and discrete elements.The results demonstrated a differential temperature distribution(high temperature in the middle and low-temperature areas at the ends)in the granite specimens under microwave irradiation,which resulted in a notable reduction in their physical and mechanical properties.As the duration of irradiation increased,the rate of heating and the extent of strength reduction both diminished,while the morphology and distribution of cracks at ultimate failure became increasingly complex.The numerical method effectively addresses the simulation challenges associated with the electromagnetic selective heating of granite containing multiple polar minerals under microwave irradiation.This approach accounted for the non-uniform thermal expansion of the minerals and provided a comprehensive model of damage progression under compression.展开更多
Granite origin is crucial to understanding the evolution of continental crust,yet many concerns about granite genesis remain yielding ongoing debates.A new integrated study of petrology,geochronology,mineral chemistry...Granite origin is crucial to understanding the evolution of continental crust,yet many concerns about granite genesis remain yielding ongoing debates.A new integrated study of petrology,geochronology,mineral chemistry and whole-rock geochemistry of the Dupangling granitic complex in South China,indicate that the granites in the western complex were emplaced during the Caledonian(418 Ma);they have SiO_(2)contents of 68.1-70.4 wt%,and are calc-alkaline and strongly peraluminous with high maficity[(TFe_(2)O_(3)+MgO)>4.0 wt%]and exhibit^(87)Sr/^(86)Sr(t)of 0.7234-0.7311 andε_(Nd)(t)of-9.0 to-6.7.The granites in the eastern complex,emplaced during the Indosinian(212 Ma),have high SiO_(2)contents(73.3-79.8 wt%)and exhibit affinities with A-type granites,such as enrichment in alkalis and rare earth elements(REEs),and depletion in Sr and Ba along with high TFeO/(TFeO+MgO),Ga/Al and Zr+Y+Ce+Nb;these granites exhibit^(87)Sr/^(86)Sr(t)of 0.7221 andε_(Nd)(t)of-9.2 to-7.5.Geochemical characteristics suggest that the older Caledonian granites were derived through dehydration melting of Paleoproterozoic metasedimentary rocks plus additional(~20%-32%)input from mafic magma,whereas the Indosinian granites were generated through shallow dehydration melting of the Caledonian granitoids.展开更多
A systematic study of early Paleozoic S-type granites in Pinghe enhances our understanding of the tectonic evolution of proto-Tethys and provides a foundation for exploring rare metal deposits in the region.The Pinghe...A systematic study of early Paleozoic S-type granites in Pinghe enhances our understanding of the tectonic evolution of proto-Tethys and provides a foundation for exploring rare metal deposits in the region.The Pinghe granites consist of monzogranite and leucogranite.Zircon U-Pb dating shows that the emplacement ages of the monzogranite and leucogranite are 502.0 Ma and 500.9 Ma,respectively.All samples have high SiO_(2) content and a weakly to strongly peraluminous character(A/CNK=1.08-1.23),consistent with S-type granites.The monzogranite has relatively high CaO,Sr,Ba,and CaO/Na_(2)O ratios but lower Rb.In contrast,the leucogranite has lower CaO,Sr,Ba,and CaO/Na_(2)O ratios but higher Rb.The similar ε_(Nd)(t)values(−9.3 to−8.4)and Pb isotopic compositions((^(206)Pb/^(204)Pb)t=18.03-19.36,(^(207)Pb/^(204)Pb)t=15.66-15.76,(^(208)Pb/^(204)Pb)t=37.97-38.55)suggest that the monzogranite formed through partial melting of crustal greywacke,while the leucogranite originated from partial melting of crustal pelite.Regional geological studies suggest that these S-type granites in Pinghe were emplaced in an active continental margin setting,associated with the westward subduction of the proto-Tethys oceanic slab.The geochemical characteristics of leucogranite are consistent with those of tungsten-tin-related granites,indicating significant metallogenic potential for W and Sn deposits.展开更多
The Tong’an-Baishuidong mining district(TBMD),located in the eastern section of the Jiangnan Orogen,is a newly discovered granite-type lithium mining district.Thisstudy presents new monazite U-Pb chronological,whole-...The Tong’an-Baishuidong mining district(TBMD),located in the eastern section of the Jiangnan Orogen,is a newly discovered granite-type lithium mining district.Thisstudy presents new monazite U-Pb chronological,whole-rock geochemical,and Nd-Pb isotopic data to reveal the petrogenesis and geodynamic setting of the Wutang granites in the TBMD.The monazite U-Pb age of 145.8±1.0 Ma indicates that the granites were emplaced at the end of the Late Jurassic.Whole-rock geochemical results demonstrate that the Wutang granites are enriched in SiO_(2)(72.80-73.40 wt%)but depleted in CaO(0.44-0.90 wt%)and MgO+TiO_(2)+TFeO(1.79-2.05 wt%).These granites exhibit negative Eu anomalies(δEu=0.3−0.4)and high aluminum saturation indexes(A/CNK=1.2−1.6),differentiation indexes(DI=90-92),and Rb/Sr ratios(4.7-8.1).They also have moderate Ba contents(239-278 ppm)and low Sr contents(52.7-82.0 ppm)as well as low Nb/Ta(2.2-5.3)and Zr/Hf(21.3-31.5)ratios.All these indicate that they are highly fractionated granites.Additionally,these granites contain 5-10 wt%muscovite but no hornblende,with calculated corundum contents of 2.3-5.5 wt%.They have low high-field strength element(HFSE)contents(Zr+Nb+Ce+Y=182-202 ppm)and zircon saturation temperatures(700-770℃),with Th and Y negatively linked with Rb.These petrographic and geochemi-cal features further reveal that the Wutang granites belong to highly fractionated S-type granites.TheεNd(t)values of these granites range from−9.03 to−8.23,corresponding to two-stage model ages(T DM2)of 1488-1553 Ma.The initial Pb isotope ratios are:(206 Pb/^(204)Pb)i=18.38-18.55,(^(207)Pb/^(204)Pb)i=15.67-15.68,and(^(208)Pb/^(204)Pb)i=38.62-38.67.These Nd-Pb isotopic results demonstrate that the parental magma originated from the partial melting of ancient crustal materials.In the meantime,the TBMD in the eastern section of the Jiangnan Orogen was in a compression-extension transitional setting associated with the episodic subduction of the Paleo-Pacific Plate.展开更多
Colloids are prevalent in nuclear waste repositories,with bentonite colloids posing an uncontrollable risk factor for nuclide migration processes.In this study,static adsorption experiments were coupled with dynamic s...Colloids are prevalent in nuclear waste repositories,with bentonite colloids posing an uncontrollable risk factor for nuclide migration processes.In this study,static adsorption experiments were coupled with dynamic shower experiments to comprehensively investigate the influence of bentonite colloids on Sr^(2+)migration in granite,considering adsorption capacity.Bentonite colloids have a considerably greater adsorption capacity than both bentonite and granite,with a maximum adsorption of 30.303 mg/g.The adsorption behavior of bentonite colloids on Sr^(2+)is well described by the Langmuir isotherm and pseudo-second-order kinetic models,indicating that a single-layer chemical adsorption process is controlled by the site activation energy.The adsorbed Sr^(2+)is unevenly distributed on the colloids,and the adsorption mechanism may involve ion exchange with Ca.Bentonite colloids exhibit superior adsorption in neutral environments.The cations in groundwater inhibit Sr^(2+)adsorption,and the inhibition efficacy decreases in the order Fe^(3+)>Ca^(2+)>Mg^(2+)>K^(+).The presence of bentonite colloids in a granite column slightly influences the retention of Sr^(2+)in the column while markedly reducing the Sr^(2+)penetration time from 70 h to 18 h.However,the coexistence of Co^(2+),Ni^(2+),and Cs^(+)in a multinuclide system weakens the ability of the colloids to promote Sr^(2+)migration.In comigration of colloid and multinuclide systems,the adsorption of nuclides by bentonite colloids causes the nuclide migration speed to decrease in the order Sr^(2+)>Cs^(+)>Ni^(2+)>Co^(2+).This study provides insights into Sr^(2+)migration in cave repositories for low-and medium-level radioactive waste.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 40572121 and 40234041)MOST Special Fund from the State Key Laboratory of Continental Dynamics, Northwest University
文摘The Nanyili （南一里）, Laohegou （老河沟）, and Shaiziyan （筛子岩） granitic intrusions are located in the southern margin of the Bikou （碧口） block in Pingwu （平武） area, Northwest Sichuan （四川）. The petrography and geochemical characteristics of the granitic intrusions as well as their source and tectonic settings are reported and discussed in this article. The Laohegou and Shaiziyan granites are with high SiO2 （69.89 wt.%-73.05 wt.%） and Al2O3 contents, and A/CNK=1.04-1.12. They are typical strongly peraluminous granites, with supersaturation in AI and Si. The abundance of ∑REE varies in the range of （33.13-89.12）×10^-6. The rocks show an LREE enrichment pattern and obvious Eu negative anomaly. The trace element geochemistry is characterized evidently by a negative anomaly of Ta, Nb, Ti, etc. and a positive anomaly of Rb, Ba, Sr, etc.. Zircons of the Nanyili granite have higher Th/U ratios, and their CL images have internal oscillatory zoning, suggesting that the zircons of the samples are igneous in origin. The LA ICP-MS zircon U-Pb isotopic concordia diagram yields an age of 223.1±2.6 Ma （MSWD=1.4）, which indicates that the granodiorite intrusions formed in the early Late Triassic. The Nanyili, Laohegou, and Shaiziyan granites have the characteristics of post-collisional granites and are regarded as post-orogenic granites. Thus, the granite intrusions are interpreted as syn-collisional granites that resulted from the crustal thickening caused by the collisions between the North China plate and the Yangtze plate during the Indosinian. The granitic intrusions formed in a transitional environment from syn- （compressional environment） to post-collision （extensional environment）.
文摘Homret Ghannam alkali feldspar granite(HGAFG)in the central Eastern Desert(CED)of Egypt represents a distinctive example of late Neoproterozoic magmatism in the Arabian-Nubian Shield(ANS).This study integrates field observations,petrography,mineral chemistry(EMPA),and whole-rock geochemistry to investigate its petrogenesis,geodynamic evolution,and rare-metal potential.HGAFG comprises two cogenetic varieties,alkali feldspar granite and riebeckite-bearing granite,hosting rare-metal minerals such as zircon,fluorite,columbite and apatite.HGAFG exhibits diagnostic A-type geochemical characteristics,including high SiO₂contents(73.81-77.86 wt%),metaluminous to mildly peralkaline composition(ASI:0.92-1.03),enrichment in HFSE(Zr≈791.80 ppm,Nb≈68.12 ppm,Y≈90.81 ppm)andΣREE(103.40-475.57 ppm),and pronounced negative Eu anomalies(Eu/Eu^(*)=0.07-0.20).Zircon saturation thermometry yields high crystallization temperatures(TZr≈908.87℃)and low emplacement pressures(1.46 kbar)under reducing conditions(ƒO_(2)≈−11.5).The mineralogical and geochemical results reveal that HGAFG originated from a hybrid,fluorine-rich magma generated by anatexis of lower crust,followed by extensive fractional crystallization,during late post-collisional extension associated with lithospheric delamination.The reduced nature and fluorine enrichment of HGAFG magma promoted the mineralization of Nb-Ta-REE phases,highlighting its significance as a fertile,high-temperature product of the terminal magmatic stage in ANS evolution.
基金supported by National Natural Science Foundation of China (Nos.52264006,52364004,and 52464005)the Guizhou Provincial Science and Technology Foundation (No.GCC[2022]005-1)。
文摘Investigating the damage evolution of surrounding rock under thermal shock cycles is crucial for ensuring the stability of engineering rock masses.This study performed Brazilian splitting tests on granite specimens under varying temperature and cycle conditions,employing acoustic emission monitoring,digital image correlation,and three-dimensional scanning technology.A systematic analysis was conducted on the patterns of damage evolution,failure precursor,and response mechanisms under combined thermal and cyclic loading.Experimental results show that both P-wave velocity and tensile strength degrade significantly with increasing temperature and cycle count,with temperature having a more pronounced effect than cycle count.Notably,damage evolution exhibits a dual-threshold behavior in which degradation accelerates markedly above 400℃ and stabilizes after 5 thermal cycles.Fracture surfaces evolve from initially planar to rugged morphologies,with peak-valley height differences at 600℃ being approximately three times greater than those at 200℃.Furthermore,based on acoustic emission energy entropy analysis,we introduce a novel failure precursor indicator where the sustained increase and critical surge in average entropy serve as reliable early-warning signals for impending rock failure.These findings establish a solid theoretical basis and practical methodology for damage assessment and instability early-warning systems in high-temperature rock engineering.
基金supported by the National Natural Science Foundation of China(41902310,42372348,42372286)Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project(2024ZD1003607)+2 种基金China Geological Survey Projects(DD20230700802,DD20221819)the Basic Research Fund of the Chinese Academy of Geological Sciences(JKYQN202306)Key Research and Development Program of Shanxi Province,China(202102090301009).
文摘The Mianhuakeng uranium deposit,characterized by uranium-rich granite,serves as a key site for research into crustal radioactive heating.Based on 45 rock samples,this study reviews that the host granite in the Mianhuakeng uranium deposit has a high radioactive heat production rate(avg.5.50μW/m³)and a low Th/U ratio(avg.2.62).Uranium-rich granite and its alteration zone within the upper crust(0-5 km depth)contribute about 45%of the total radioactive heat production,wich is crucial for controlling geothermal resource distribution.For uranium-thermal at tectonic plate margins,a symbiotic geological model was proposed:Firstly,subduction of the Pacific Plate caused upwelling of the asthenosphere,generating a high heat-flow background.Secondly,heat transfer is enhanced by major faults such as the Youdong and Mianhuakeng faults.Subsequently,uranium was mobilized,transported,and enriched within the granite through deep siliceous hydrothermal activity and associated alteration.Ultimately,the uranium enrichment in granite leads to increased radioactive heat production,resulting in local thermal anomalies.This model provides a theoretical support for exploring and developing uranium-thermal symbiotic resources in South China.
基金supported by the National Natural Science Foundation of China(42372250,42102262 and 41972235)National Key Research and Development Program Project(2023YFF0803701)+1 种基金Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(SML2023SP206)the program of China Scholarship Council。
文摘The Shenshan Group provides important geological information which is vital in unraveling the amalgamation and subsequent rifting processes of South China.While conventional studies have asserted its formation in a subduction setting,the distinct investigation reveals the necessity for reassessment.To address this,the authors employ integrated methods encompassing petrological,zircon U-Pb geochronological,Lu-Hf isotopic and geochemical methods for sedimentary rocks from the upper Shenshan subgroup and Banxi Group.The geochemical results indicate that they were formed through the recycling deposition of intermediate-acidic igneous source material and experienced moderate chemical weathering.Additionally,both sedimentary sequences exhibit characteristics consistent with those formed in an intracontinental extensional rift setting since ca.810 Ma.The provenance analysis indicates that the upper Shenshan subgroup primarily originates from the Yangtze Domain,while the Banxi Group from both the Yangtze and Cathaysia domains.Synthesizing with previous studies,the Shenshan Group should be subdivided into the lower and upper subgroups which represent distinct tectonic backgrounds.The lower subgroup is inferred to have formed in an Early Neoproterozoic fore-arc setting,akin to the Zhoutan group.The upper subgroup corresponds to the Banxi Group,representing the Middle Neoproterozoic postorogenic rift setting,responding to the breakup of Rodinia.
文摘Higher Himalayan Crystalline (HHC) rocks often show metamorphic zonations from lower greenschist facies to migmatites associated with leucogranite intrusions that are classically described as examples of Tertiary inverted metamorphism. The present study, based on structural, petrological and geochronological investigations in the Kinnar Kailas Granite (KKG) and surrounding HHC sequence, evidences a discordant intrusive contact of the Ordovician KKG with respect to Pre\|Alpine high grade deformed HHC sequence in the Sutlej valley.Four main phases of deformation are recorded in this HHC sequence and pre\|Ordovician sediments. The first three phases of deformation occurred under high\|grade metamorphic conditions, before the intrusion of the KKG. The geometry of the main progressive ductile deformation (D2—D3) results from SW vergent doming and migmatisation. The latest deformation is expressed by local shearing under greenschist facies conditions. This late D4 deformation corresponds to N—S oriented ductile normal faults lowering the eastern blocks. The KKG is a shallow depth intrusion, showing discordant contacts with the surrounding basement rocks and large scale magmatic stoping. The KKG crosscuts the high\|grade deformation structures (D2—D3) but is locally affected by the local late D4 extensional deformation. The granite textures reflect only slight orientation related to magmatic deformation and even at few centimetres from the intrusion contact, the granite appears undeformed in contrast to the surrounding highly foliated rocks. Furthermore, xenoliths of Kyanite\|Sillimanite bearing basement rocks are present within the KKG.
基金supported by the National Science Foundation of China(grant No.41302046)China Geological Survey(grant No.12120113063600)
文摘Objective More and more evidence suggests that the Kwangsian orogen is probably an intraplate orogen, which is one of the few examples of intraplate orogenesis worldwide. However, the initiation time, size and scope of the Kwangsian orogeny have not been determined yet. This study analyzed the Silurian A-type granites in northeastern Guangxi, South China Block, which may provide new evidence for the transition from compression to post- orogenic extension of the Kwangsian orogen.
基金supported financially by the National Natural Science Foundation of China(Grant Nos.41872054 and 41272083)。
文摘The petrogenesis and genetic link to polymetallic mineralization of the granites in the Dayishan complex,southern Hunan province remain debated.Here,we present an integrated study on the petrology,zircon U-Pb ages and whole-rock geochemistry for this complex.Our findings indicate that the southern complex consists of(amphibole-bearing)biotite granites and muscovite granites emplaced at 153-151 Ma,and the central and northern complex consists of two-mica granites and tourmaline-bearing muscovite granites,respectively with the former emplaced at 164 Ma and the latter at 150 Ma.The(amphibole-bearing)biotite granites have SiO_(2) contents of 68.0-73.8 wt% and are enriched in alkalis and rare earth elements and depleted in Sr and Ba.They display Zr+Y+Ce+Nb>350 ppm and 10000×Ga/Al>2.6 along with high zircon saturation temperatures(821-883oC).The two-mica granites and(tourmaline-bearing)muscovite granites have high SiO_(2)(74.4-77.3 wt%)and low Ga/Al,Zr+Nb+Ce+Y,K/Rb,Zr/Hf,and Nb/Ta along with low zircon saturation temperatures(709-817℃).Geochemical characteristics suggest that the(amphibole-bearing)biotite granites are A-type granites generated through shallow dehydration melting of early Paleozoic granitoids,and that the two-mica granites and(tourmaline-bearing)muscovite granites are fractionated A-type granites produced through fractionation crystallization from the(amphibole-bearing)biotite granites accompanied by fluid fractionation.
基金funded by the National Natural Science Foundation of China(Grant Nos.42072089 and 41530206)。
文摘Both fractional crystallization and fluid-melt-crystal interaction are involved in the formation of highly fractionated granites.This paper assessed those two processes using geochemistry of muscovite and tourmaline and bulkrock chemistry of multi-phase Wangxianling granitoids,South China.Compositional variations suggest the coarse-grained muscovite granite is produced from fractional crystallization of the two-mica granite whereas the fine-grained muscovite granite represents a distinct magma pulse.Progressive fractionation of quartz,feldspar and biotite leads to elevated boron and aluminum content in melt which promoted muscovite and tourmaline to crystallize,which promotes two-mica granite evolving towards tourmaline-bearing muscovite granite.Fluid-melt-crystal interaction occurred at the magmatichydrothermal transitional stage and resulted in the textural and chemical zonings of tourmaline and muscovite in finegrained muscovite granite.The rims of both tourmaline and muscovite are characterized by the enrichment of fluid mobile elements such as Li,Mn,Cs and Zn and heavierδ^(11)B values of the tourmaline rims(-15.0‰to-13.6‰)compared to cores(-15.7‰to-14.3‰).Meanwhile,significant M-type REE tetrad effects(TE_(1,3)=1.07-1.18)and low K/Rb ratios(48-52)also correspond to fluid-melt-crystal interaction.This study shows zoned muscovite and tourmaline can be excellent tracers of fractional crystallization and late-stage fluid-melt-crystal interaction in highly evolved magmatic systems.
基金funded by the China Postdoctoral Science Foundation(Grant No.2019M663959XB)the Geological Survey and Development Bureau of Qinghai Province 2019 Geological Survey Project(2019[45])the Key Laboratory of Deep Dynamics of the Ministry of Natural Resources,Open Research Project 2019。
文摘In the western segment of the East Kunlun Orogen(WEKO),muscovite granite and garnet granite from the Hureguole intrusion exhibit zircon U-Pb ages of 435-442 Ma.Geochemically,these rocks contain high concentrations of SiO_(2),K_(2)O and Al_(2)O_(3),with low concentrations of TiO_(2)and MgO,indicating a peraluminous high-K calc-alkaline affinity.They are enriched in Rb,Th,U and LREE,depleted in Eu,Ba,Sr and Ti,being classified as S-type granites.Negative whole-rockε_(Nd)(t)values(-9.8 to-9.1)and zirconε_(Hf)(t)values(-11.6 to-8.2)for those granites indicate that they were derived from partial melting of pelitic rocks in the Paleoproterozoic Baishahe Formation of the Jinshuikou Group.Based on the collected zircon ages,Cambrian-Devonian magmatic activity in the WEKO was divided into three stages:early(446-520 Ma),middle(427-441 Ma)and late(372-424 Ma)stages.Statistically,whole-rock Nd and zircon Hf isotope data(ε_(Nd)(t)/T_(DM)^(Nd),ε_(Hf)(t)/T_(DMC)^(Hf))from Paleozoic igneous rocks in the WEKO reveal a magma source that was initially dominated by depleted mantle components in the northward subduction stage of the Proto-Tethy an Ocean plate(446-520 Ma),shifting to predominantly crustal sources during the closure period of the North Qimantagh back-arc basin(427-441 Ma),then to crust-mantle mixed sources in the post-collision stage(372-424 Ma).
基金funding support from the National Natural Science Foundation of China(Grant No.52274082)the Program of Qingjiang Excellent Young Talents,Jiangxi University of Science and Technology(Grant No.JXUSTQJBJ2020003)the Innovation Fund Designated for Graduate Students of Jiangxi Province(Grant No.YC2023-B215).
文摘The roughness of the fracture surface directly affects the strength,deformation,and permeability of the surrounding rock in deep underground engineering.Understanding the effect of high temperature and thermal cycle on the fracture surface roughness plays an important role in estimating the damage degree and stability of deep rock mass.In this paper,the variations of fracture surface roughness of granite after different heating and thermal cycles were investigated using the joint roughness coefficient method(JRC),three-dimensional(3D)roughness parameters,and fractal dimension(D),and the mechanism of damage and deterioration of granite were revealed.The experimental results show an increase in the roughness of the granite fracture surface as temperature and cycle number were incremented.The variations of JRC,height parameter,inclination parameter and area parameter with the temperature conformed to the Boltzmann's functional distribution,while the D decreased linearly as the temperature increased.Besides,the anisotropy index(Ip)of the granite fracture surface increased as the temperature increased,and the larger parameter values of roughness characterization at different temperatures were attained mainly in directions of 20°–40°,60°–100°and 140°–160°.The fracture aperture of granite after fracture followed the Gauss distribution and the average aperture increased with increasing temperature,which increased from 0.665 mm at 25℃to 1.058 mm at 800℃.High temperature caused an uneven thermal expansion,water evaporation,and oxidation of minerals within the granite,which promoted the growth and expansion of microfractures,and reduced interparticle bonding strength.In particular,the damage was exacerbated by the expansion and cracking of the quartz phase transition after T>500℃.Thermal cycles contributed to the accumulation of this damage and further weakened the interparticle bonding forces,resulting in a significant increase in the roughness,anisotropy,and aperture of the fracture surface after five cycles.
基金the support provided by the National Natural Science Foundation of China(Grant Nos.52278336 and 42302032)Guangdong Basic and Applied Research Foundation(Grant Nos.2023B1515020061).
文摘Granite residual soil (GRS) is a type of weathering soil that can decompose upon contact with water, potentially causing geological hazards. In this study, cement, an alkaline solution, and glass fiber were used to reinforce GRS. The effects of cement content and SiO_(2)/Na2O ratio of the alkaline solution on the static and dynamic strengths of GRS were discussed. Microscopically, the reinforcement mechanism and coupling effect were examined using X-ray diffraction (XRD), micro-computed tomography (micro-CT), and scanning electron microscopy (SEM). The results indicated that the addition of 2% cement and an alkaline solution with an SiO_(2)/Na2O ratio of 0.5 led to the densest matrix, lowest porosity, and highest static compressive strength, which was 4994 kPa with a dynamic impact resistance of 75.4 kN after adding glass fiber. The compressive strength and dynamic impact resistance were a result of the coupling effect of cement hydration, a pozzolanic reaction of clay minerals in the GRS, and the alkali activation of clay minerals. Excessive cement addition or an excessively high SiO_(2)/Na2O ratio in the alkaline solution can have negative effects, such as the destruction of C-(A)-S-H gels by the alkaline solution and hindering the production of N-A-S-H gels. This can result in damage to the matrix of reinforced GRS, leading to a decrease in both static and dynamic strengths. This study suggests that further research is required to gain a more precise understanding of the effects of this mixture in terms of reducing our carbon footprint and optimizing its properties. The findings indicate that cement and alkaline solution are appropriate for GRS and that the reinforced GRS can be used for high-strength foundation and embankment construction. The study provides an analysis of strategies for mitigating and managing GRS slope failures, as well as enhancing roadbed performance.
基金Project(42202318)supported by the National Natural Science Foundation of ChinaProject(252300421199)supported by the Natural Science Foundation of Henan Province,ChinaProject(2024JJ6219)supported by the Hunan Provincial Natural Science Foundation of China。
文摘The undrained mechanical behavior of unsaturated completely weathered granite(CWG)is highly susceptible to alterations in the hydraulic environment,particularly under uniaxial loading conditions,due to the unique nature of this soil type.In this study,a series of unconfined compression tests were carried out on unsaturated CWG soil in an underground engineering site,and the effects of varying the environmental variables on the main undrained mechanical properties were analyzed.Based on the experimental results,a novel constitutive model was then established using the damage mechanics theory and the undetermined coefficient method.The results demonstrate that the curves of remolded CWG specimens with different moisture contents and dry densities exhibited diverse characteristics,including brittleness,significant softening,and ductility.As a typical indicator,the unconfined compression strength of soil specimens initially increased with an increase in moisture content and then decreased.Meanwhile,an optimal moisture content of approximately 10.5%could be observed,while a critical moisture content value of 13.0%was identified,beyond which the strength of the specimen decreases sharply.Moreover,the deformation and fracture of CWG specimens were predominantly caused by shear failure,and the ultimate failure modes were primarily influenced by moisture content rather than dry density.Furthermore,by comparing several similar models and the experimental data,the proposed model could accurately replicate the undrained mechanical characteristics of unsaturated CWG soil,and quantitatively describe the key mechanical indexes.These findings offer a valuable reference point for understanding the underlying mechanisms,anticipating potential risks,and implementing effective control measures in similar underground engineering projects.
基金The authors are grateful for the financial support from the National Natural Science Foundation of China(Grant Nos.52225904 and 52039007)the Natural Science Foundation of Sichuan Province(Grant No.2023NSFSC0377)supported by the New Cornerstone Science Foundation through the XPLORER PRIZE.
文摘Exploring dynamic mechanical responses and failure behaviors of hot dry rock(HDR)is significant for geothermal exploitation and stability assessment.In this study,via the split Hopkinson pressure bar(SHPB)system,a series of dynamic compression tests were conducted on granite treated by cyclic thermal shocks at different temperatures.We analyzed the effects of cyclic thermal shock on the thermal-related physical and dynamic mechanical behaviors of granite.Specifically,the P-wave velocity,dynamic strength,and elastic modulus of the tested granite decrease with increasing temperature and cycle number,while porosity and peak strain increase.The degradation law of dynamic mechanical properties could be described by a cubic polynomial.Cyclic thermal shock promotes shear cracks propagation,causing dynamic failure mode of granite to transition from splitting to tensile-shear composite failure,accompanied by surface spalling and debris splashing.Moreover,the thermal shock damage evolution and coupled failure mechanism of tested granite are discussed.The evolution of thermal shock damage with thermal shock cycle numbers shows an obvious S-shaped surface,featured by an exponential correlation with dynamic mechanical parameters.In addition,with increasing thermal shock temperature and cycles,granite mineral species barely change,but the length and width of thermal cracks increase significantly.The non-uniform expansion of minerals,thermal shock-induced cracking,and water-rock interaction are primary factors for deteriorating dynamic mechanical properties of granite under cyclic thermal shock.
基金The Royal Society,UK,Grant/Award Number:IEC\NSFC\211366Fundamental Research Funds for the Central Universities(China University of Mining and Technology),Grant/Award Number:2023ZDPY11National Natural Science Foundation of China,Grant/Award Numbers:51809263,52174133。
文摘The corrosion of waste canisters in the deep geological disposal facilities(GDFs)for high-level radioactive waste(HLRW)can generate gas,which escapes from the engineered barrier system through the interfaces between the bentonite buffer blocks and the host rock and those between the bentonite blocks.In this study,a series of water infiltration and gas breakthrough experiments were conducted on granite and on granite-bentonite specimens with smooth and grooved interfaces.On this basis,this study presents new insights and a quantitative assessment of the impact of the interface between clay and host rock on gas transport.As the results show,the water permeability values from water infiltration tests on granite and granite-bentonite samples(10−19-10−20m^(2))are found to be slightly higher than that of bentonite.The gas permeability of the mock-up samples with smooth interfaces is one order of magnitude larger than that of the mock-up with grooved interfaces.The gas results of breakthrough pressures for the granite and the granite-bentonite mock-up samples are significantly lower than that of bentonite.The results highlight the potential existence of preferential gas migration channels between the rock and bentonite buffer that require further considerations in safety assessment.
基金funded by the Postgraduate Research and Practice Innovation Program of Jiangsu Province(Grant No.KYCX23_2744)the Fundamental Research Funds for the Central Universities(Grant No.2023XSCX051)the Graduate Innovation Program of China University of Mining and Technology(Grant No.2023WLKXJ182).
文摘Microwave-assisted rock-breaking technology,as a novel hybrid approach,is anticipated to facilitate the efficient excavation of complex rock formations.It is therefore crucial to understand the damage and failure mechanisms of rocks that have been subjected to irradiation.In this study,uniaxial compression experiments were conducted on granite specimens after 1.4 kW microwave irradiation for varying durations.Furthermore,a numerical method was proposed to solve electromagnetic-thermal-mechanical coupling problems by integrating finite and discrete elements.The results demonstrated a differential temperature distribution(high temperature in the middle and low-temperature areas at the ends)in the granite specimens under microwave irradiation,which resulted in a notable reduction in their physical and mechanical properties.As the duration of irradiation increased,the rate of heating and the extent of strength reduction both diminished,while the morphology and distribution of cracks at ultimate failure became increasingly complex.The numerical method effectively addresses the simulation challenges associated with the electromagnetic selective heating of granite containing multiple polar minerals under microwave irradiation.This approach accounted for the non-uniform thermal expansion of the minerals and provided a comprehensive model of damage progression under compression.
基金supported financially by the National Natural Science Foundation of China(Grant Nos.41872054 and 41272083)。
文摘Granite origin is crucial to understanding the evolution of continental crust,yet many concerns about granite genesis remain yielding ongoing debates.A new integrated study of petrology,geochronology,mineral chemistry and whole-rock geochemistry of the Dupangling granitic complex in South China,indicate that the granites in the western complex were emplaced during the Caledonian(418 Ma);they have SiO_(2)contents of 68.1-70.4 wt%,and are calc-alkaline and strongly peraluminous with high maficity[(TFe_(2)O_(3)+MgO)>4.0 wt%]and exhibit^(87)Sr/^(86)Sr(t)of 0.7234-0.7311 andε_(Nd)(t)of-9.0 to-6.7.The granites in the eastern complex,emplaced during the Indosinian(212 Ma),have high SiO_(2)contents(73.3-79.8 wt%)and exhibit affinities with A-type granites,such as enrichment in alkalis and rare earth elements(REEs),and depletion in Sr and Ba along with high TFeO/(TFeO+MgO),Ga/Al and Zr+Y+Ce+Nb;these granites exhibit^(87)Sr/^(86)Sr(t)of 0.7221 andε_(Nd)(t)of-9.2 to-7.5.Geochemical characteristics suggest that the older Caledonian granites were derived through dehydration melting of Paleoproterozoic metasedimentary rocks plus additional(~20%-32%)input from mafic magma,whereas the Indosinian granites were generated through shallow dehydration melting of the Caledonian granitoids.
基金funded by the Science and Technology Department of Yunnan Province(202303AA080006)the National Natural Science Foundation of China(41972312 and 41672329).
文摘A systematic study of early Paleozoic S-type granites in Pinghe enhances our understanding of the tectonic evolution of proto-Tethys and provides a foundation for exploring rare metal deposits in the region.The Pinghe granites consist of monzogranite and leucogranite.Zircon U-Pb dating shows that the emplacement ages of the monzogranite and leucogranite are 502.0 Ma and 500.9 Ma,respectively.All samples have high SiO_(2) content and a weakly to strongly peraluminous character(A/CNK=1.08-1.23),consistent with S-type granites.The monzogranite has relatively high CaO,Sr,Ba,and CaO/Na_(2)O ratios but lower Rb.In contrast,the leucogranite has lower CaO,Sr,Ba,and CaO/Na_(2)O ratios but higher Rb.The similar ε_(Nd)(t)values(−9.3 to−8.4)and Pb isotopic compositions((^(206)Pb/^(204)Pb)t=18.03-19.36,(^(207)Pb/^(204)Pb)t=15.66-15.76,(^(208)Pb/^(204)Pb)t=37.97-38.55)suggest that the monzogranite formed through partial melting of crustal greywacke,while the leucogranite originated from partial melting of crustal pelite.Regional geological studies suggest that these S-type granites in Pinghe were emplaced in an active continental margin setting,associated with the westward subduction of the proto-Tethys oceanic slab.The geochemical characteristics of leucogranite are consistent with those of tungsten-tin-related granites,indicating significant metallogenic potential for W and Sn deposits.
基金funded by the Program of Science and Technology Department of Jiangxi Province(2023KDG01002 and 2023KDG01003)the National Natural Science Foundation of China(42062006 and 41962007)+1 种基金the Key Research and Development Program of Jiangxi Province(20223BBG71015)the Personnel Training Project of Jiangxi Bureau of Geology(2023JXDZKJRC02,2022JXDZKJRC04,and 2024JXDZKJRC05).
文摘The Tong’an-Baishuidong mining district(TBMD),located in the eastern section of the Jiangnan Orogen,is a newly discovered granite-type lithium mining district.Thisstudy presents new monazite U-Pb chronological,whole-rock geochemical,and Nd-Pb isotopic data to reveal the petrogenesis and geodynamic setting of the Wutang granites in the TBMD.The monazite U-Pb age of 145.8±1.0 Ma indicates that the granites were emplaced at the end of the Late Jurassic.Whole-rock geochemical results demonstrate that the Wutang granites are enriched in SiO_(2)(72.80-73.40 wt%)but depleted in CaO(0.44-0.90 wt%)and MgO+TiO_(2)+TFeO(1.79-2.05 wt%).These granites exhibit negative Eu anomalies(δEu=0.3−0.4)and high aluminum saturation indexes(A/CNK=1.2−1.6),differentiation indexes(DI=90-92),and Rb/Sr ratios(4.7-8.1).They also have moderate Ba contents(239-278 ppm)and low Sr contents(52.7-82.0 ppm)as well as low Nb/Ta(2.2-5.3)and Zr/Hf(21.3-31.5)ratios.All these indicate that they are highly fractionated granites.Additionally,these granites contain 5-10 wt%muscovite but no hornblende,with calculated corundum contents of 2.3-5.5 wt%.They have low high-field strength element(HFSE)contents(Zr+Nb+Ce+Y=182-202 ppm)and zircon saturation temperatures(700-770℃),with Th and Y negatively linked with Rb.These petrographic and geochemi-cal features further reveal that the Wutang granites belong to highly fractionated S-type granites.TheεNd(t)values of these granites range from−9.03 to−8.23,corresponding to two-stage model ages(T DM2)of 1488-1553 Ma.The initial Pb isotope ratios are:(206 Pb/^(204)Pb)i=18.38-18.55,(^(207)Pb/^(204)Pb)i=15.67-15.68,and(^(208)Pb/^(204)Pb)i=38.62-38.67.These Nd-Pb isotopic results demonstrate that the parental magma originated from the partial melting of ancient crustal materials.In the meantime,the TBMD in the eastern section of the Jiangnan Orogen was in a compression-extension transitional setting associated with the episodic subduction of the Paleo-Pacific Plate.
基金supported by the General Project of the National Natural Science Foundation of China(No.42377413).
文摘Colloids are prevalent in nuclear waste repositories,with bentonite colloids posing an uncontrollable risk factor for nuclide migration processes.In this study,static adsorption experiments were coupled with dynamic shower experiments to comprehensively investigate the influence of bentonite colloids on Sr^(2+)migration in granite,considering adsorption capacity.Bentonite colloids have a considerably greater adsorption capacity than both bentonite and granite,with a maximum adsorption of 30.303 mg/g.The adsorption behavior of bentonite colloids on Sr^(2+)is well described by the Langmuir isotherm and pseudo-second-order kinetic models,indicating that a single-layer chemical adsorption process is controlled by the site activation energy.The adsorbed Sr^(2+)is unevenly distributed on the colloids,and the adsorption mechanism may involve ion exchange with Ca.Bentonite colloids exhibit superior adsorption in neutral environments.The cations in groundwater inhibit Sr^(2+)adsorption,and the inhibition efficacy decreases in the order Fe^(3+)>Ca^(2+)>Mg^(2+)>K^(+).The presence of bentonite colloids in a granite column slightly influences the retention of Sr^(2+)in the column while markedly reducing the Sr^(2+)penetration time from 70 h to 18 h.However,the coexistence of Co^(2+),Ni^(2+),and Cs^(+)in a multinuclide system weakens the ability of the colloids to promote Sr^(2+)migration.In comigration of colloid and multinuclide systems,the adsorption of nuclides by bentonite colloids causes the nuclide migration speed to decrease in the order Sr^(2+)>Cs^(+)>Ni^(2+)>Co^(2+).This study provides insights into Sr^(2+)migration in cave repositories for low-and medium-level radioactive waste.
