查看更多>>摘要：Carbonates are viewed as the principal oxidized carbon carriers during subduction,and thus the stability of subducted carbonates has significant implications for the deep carbon cycle.Here we investigate the high pressure-temperature behaviors of rhodochrosite in the presence of iron up to～34 GPa by in-situ X-ray diffraction and ex-situ Raman spectroscopy.At relatively low temperature be-low～1500 K,MnCO3 breaks down into MnO and CO2.Upon heating to～1800 K,however,the Mn-CO3-Fe0 reactions occur with the formation of Mn3O4,FeO and reduced carbon.A'three-stage'reac-tion mechanism is proposed to understand the kinetics of the carbon-iron-manganese redox coupling.The results suggest that Fe0 can serve as a reductant to greatly affect the stability of rhodochrosite,which implies that the effect of Fe-metal should be seriously considered for the high pressure-temperature behaviors of other predominant carbonates at Earth's mantle conditions,particularly at depths greater than～250 km.
查看更多>>摘要：The Meso-neoproterozoic Bayan Obo rift is located along the northern margin of the North China Craton,and was associated with the break-up of the Columbia supercontinent.During rift evolution,syn-sedimentary deformation occurred due to tectonic activity and earthquakes.Seismic events are recorded in the Jianshan Formation of the Bayan Obo Group,Inner Mongolia,as soft sedi-ment deformation structures in the central Bayan Obo rift.Druse calcite crystals and collapse breccias in the Jianshan Formation may provide information on the rift evolution.The druse calcite crystals are idiomorphic-columnar in shape and associated with graphite,pyrite,and quartz.δ13C values of the graphite are-20‰,indicative of biogenic deoxygenation and formation in water.The druse calcite crys-tals are inorganic in origin and formed in water at a temperature of 55℃,based on calcite δ13C and δ18O data.The calcite grew in paleo-caves containing fault breccias,with heat derived from faulting.As such,the druse calcite crystals are important evidence for seismic events.The collapse breccias(i.e.,fault breccias)and other indicators of slip show that displacement occurred from NE to SW,which is different from the paleocurrent direction in the Jianshan Formation.The thickness of the collapse brec-cia is～200 m,which represents the height of the fault scarp.The strike of the fault scarp was NE-SW,based on the distribution of the collapse breccia.The Bayan Obo and Yanliao rifts experienced rapid NW-SE extension,and developed similar deformation structures at ca.1.6 Ga related to break-up of the Columbia supercontinent.
Lin LiangGuibin ZhangShengxuan HuangJingjing Niu...
525-535页
查看更多>>摘要：Ferromagnesite(Mg,Fe)CO3 with 20 mol%iron is a potential host mineral for carbon transport and storage in the Earth mantle.The high-pressure behavior of synthetic ferromagnesite(Mg0.81Fe0.19)CO3 up to 53 GPa was investigated by synchrotron X-ray diffraction(XRD)and Raman spectroscopy.The iron bearing carbonate underwent spin transition at around 44-46 GPa accompa-nied by a volume collapse of 1.8%,which also demonstrated a variation in the dνi/dP slope of the Ra-man modes.The pressure-volume data was fitted by a third-order Birch-Murnaghan equation of state(BM-EoS)for the high spin phase.The best-fit K0 = 108(1)GPa and K'0 = 4.2(1).Combining the dνi/dP and the K0,the mode Grüneisen parameters of each vibrational mode(T,L,ν4 and ν1)were calculated.The effects of iron concentration on the Mg1-xFexCO3 system related to high-pressure compressibility and vibrational properties are discussed.These results expand the knowledge of the physical properties of carbonates and provide insights to the potential deep carbon host.
查看更多>>摘要：The Getang is a representative Carlin-type gold deposit in Southwest China.It has a proven reserve of about 30 tonnes at an average grade of 5.1 g/t Au.The orebodies occur as strat-abound lenses,and are structurally controlled by shallow NWW-and NE-trending fold-fault systems and the unconformity between the Upper and Middle Permian.In this study,the regional-and deposit-scale structural investigations,joints and finite strain measurements,and stress and dynamic analysis were conducted with an aim to reveal the structural process of the Getang gold deposit and clarify the relationship between the gold mineralization and structures.Three phases of deformation were identi-fied in the deposit:(1)paleokarst was generated by a crustal uplift when the Youjiang Basin experi-enced extension at the end of the Middle Permian,laying the foundation for the unconformity;(2)the NW-trending structures were formed under a NNE-SSW compression during the Indochina-South Chi-na collision(Indosinian orogeny)in Triassic;(3)the NE-trending structures were generated or reacti-vated under a NW-SE-oriented compression during the Yanshanian intracontinental orogeny.The un-conformity recorded two episodes of tectonic evolution in the NNE-SSW and NW-SE directions.Struc-tural analyses and geochronology data suggest that the Getang gold deposit was formed as a result of tectonic transition from compression to extension during the Yanshanian intracontinental orogeny.
查看更多>>摘要：In rock engineering,the shear strength of the basalt-concrete bonding interface is a key factor affecting the shear performance of hydroelectric dam foundations,embedded rock piles and rock bolts.In this study,30 sets of in-situ direct shear tests were conducted on the basalt-concrete bond interface in the Baihetan dam area to investigate the shear strength characteristics of the basalt-concrete bonding interface.The bonding interface contains two states,i.e.,the bonding interface is not sheared,termed as se(symbolic meaning see Table 1);the bonding interface is sheared with rupture sur-face,termed as si.The effects of lithology,Joints structure,rock type grade and concrete compressive strength on the shear strength of the concrete-basalt contact surface were investigated.The test results show that the shear strength of the bonding interface(se&si)of columnar jointed basalt with concrete is greater than that of the bonding interface(se&si)of non-columnar jointed one with the same rock type grade.When the rock type grade is Ⅲ2,fcol is 1.22 times higher than fncol and ccol is 1.13 times great-er than cncol.The shear strength parameters of the basalt-concrete bonding interface differ significantly for different lithologies.The cohesion of the bonding interface(si)of cryptocrystalline basalt with con-crete is 2.05 times higher than that of the bonding interface(si)of breccia lava with concrete under the same rock type grade condition.Rock type grade has a large influence on the shear strength of the non-columnar jointed basalt-concrete bonding interface(se&si).cnol increases by 33%when the grade of rock type rises from Ⅲ1 to Ⅱ1.the rock type grade has a greater effect on bonding interface(si)cohe-sion than the coefficient of friction.When the rock type grade is reduced from Ⅲ2 to Ⅲ1,f'ncol increases by 2%and c'ncol improves by 44%.The shear strength of the non-columnar jointed basalt-concrete bonding interface(se&si)increases with the increase of the compressive strength of concrete.When concrete compressive strength rises from 22.2 to 27.6 MPa,the cohesion increases by 94%.
查看更多>>摘要：Block-flexure toppling failure is frequently encountered in interbedded anti-inclined rock(IAR)slopes,and seriously threatens the construction of hydropower infrastructure.In this study,we first investigated the Lean Reservoir area's geological setting and the Linda landslide's characteris-tics.Then,uniform design and random design were used to design 110 training datasets and 31 testing datasets,respectively.Afterwards,the toppling response was obtained by using the discrete element code.Finally,support vector regression was used to obtain the influence weights of 21 impact factors.The results show that the influence weight of the slope angle and rock formation dip angle on the top-pling deformation among tertiary impact factors is 25.96%and 17.28%,respectively,which are much greater than the other 19 impact factors within the research range.For the primary impact factors,the influence weight is sorted from large to small as slope geometry parameters,joints parameters,and rock mechanics parameters.Joints parameters,especially the geometric parameters,cannot be ignored when evaluating the stability of IAR slopes.Through numerical simulation,it was qualitatively deter-mined that failure surfaces of slopes were controlled by cross joints and that the rocks in the slope toe play a role in preventing slope deformation.
查看更多>>摘要：In the context of global warming and intensified human activities,glacier instability in plateau regions has increased,and glacier debris flows have become active,which poses a significant threat to the lives and property of people and socioeconomic development.The mass movement process of glacier debris flows is extremely complex,so this paper uses the 2018 Sedongpu glacier debris flow event on the Qinghai-Tibet Plateau as an example and applies a numerical simulation method to invert the whole process of mass movement.In view of the interaction between phases in the process of mo-tion,we use the fluid-solid coupling method to describe the mass movement.The granular-flow model and drift-flux model are employed in FLOW3D software to study the mass movement process of gla-cier debris flows and explore their dynamic characteristics.The results indicate that the glacier debris flow lasted for 700 s,and the movement process was roughly divided into four stages,including initia-tion,scraping,surging and deposition;the depositional characteristics calculated by the fluid-solid cou-pling model are consistent with the actual survey results and have good reliability;strong erosion oc-curs during the mass movement,the clear volume amplification effect,and the first wave climbs 17.8 m across the slope.The fluid-solid coupling method can better simulate glacier debris flows in plateau re-gions,which is helpful for the study of the mechanism and dynamic characteristics of such disasters.
查看更多>>摘要：Water and sand leakage disasters are likely to occur during construction in water-rich sand layer areas,resulting in ground collapse.The stress-strain action characteristics of discontinuous graded sand under different internal erosion degrees,and the evolution mechanism of water and sand leakage disasters caused by the internal erosion need to be further explored.Therefore,this paper takes the discontinuous graded sand in a water rich sand layer area in Nanchang City of China as the research object.Considering the influence of different fine particle losses(0,10%,20%and 30%)un-der the internal erosion of sand,the salt solution method is used to realize the specified loss of fine par-ticles in the internal erosion.The stress-strain behavior after the loss of fine particles due to internal erosion is studied by triaxial shear test.Meanwhile,the physical model test and PFC-CFD method are both used to study the evolution rules of water and sand leakage disaster considered the influence of in-ternal erosion degrees.Results show that:(1)under the same confining pressure,the peak failure strength of sand samples decreases along with the increase of fine particle loss.(2)In the water and sand leakage test of saturated sand,a natural filter channel is formed above the observed soil arch.The greater the loss of fine particles,the steeper and wider the collapse settlement area.(3)The relationship between the cumulative amount of water and sand leakage and time is nonlinear.The total mass loss of sand increases along with the increase of internal erosion degree.(4)After the soil arch is formed around the damaged opening,the sand continues to converge above the soil arch under the action of water flow,resulting in the dense convergence of contact force chains.
查看更多>>摘要：The Bozhong19-6(BZ19-6)condensate gas reservoirs,located in the southwestern Bo-zhong sub-basin,Bohai Bay Basin,China,were paleo-oil reservoirs in the geological past and have un-dergone at least three successive hydrocarbon charging events.The hydrocarbon migration and accu-mulation process of"early oil and late gas"has occurred in the current reservoirs.At the end of the sedimentation of the Guantao Formation(N1g,～12 Ma),the reservoirs began to fill with first stage low-moderate mature crude oil.At the late stage of the Lower Minghuazhen Formation(N1ml)(～6.7 Ma),the reservoirs were largely charged with second stage high mature crude oil.Since the deposition of the upper Minghuazhen Formation(N2mu,～5.1 Ma),the paleo-oil reservoirs were transformed into shallow Neogene reservoirs due to the reactivation of basement faults.From the late stage of the N2mu to the present day(～2.8‒0 Ma),the reservoirs were rapidly filled by natural gas within a short period.In ad-dition,analysis of the formation of the reservoir bitumen and the conspicuous loss of the lower molecu-lar weight n-alkanes in the crude oil reveal that the injection of a large amount of gas in the late stage caused gas flushing of the early charged oil.
查看更多>>摘要：Due to the complex conditions and strong heterogeneity of tight sandstone reservoirs,the reservoirs should be classified and the controlling factors of physical properties should be studied.Cast thin section observations,cathodoluminescence,scanning electron microscopy(SEM),X-ray diffrac-tion(XRD),and high-pressure mercury injection(HPMI)were used to classify and optimize the reser-voir.The Brooks-Corey model and stepwise regression were used to study the fractal dimension and main controlling factors of the physical properties of the high-quality reservoir.The results show that the reservoirs in the study area can be divided into four types,and the high-quality reservoir has the best physical properties and pore-throat characteristics.In the high-quality reservoir,the homogeneity of transitional pores was the best,followed by that of micropores,and the worst was mesopores.The porosity was controlled by depth and kaolinite.The model with standardized coefficients is y = 12.454-0.778×(Depth)+0.395×(Kaolinite).The permeability was controlled by depth,illite/montmorillonite,and siliceous cement,and the model with standardized coefficients is y = 1.689-0.683×(Depth)-0.395×(Illite/Montmorillonite)-0.337×(Siliceous Cement).The pore-throat evolutionary model shows that the early-middle diagenetic period was when the reservoir physical properties were at their best,and the kaolinite intercrystalline pores and residual intergranular pores were the most important.
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