neoproterozoic adakitic plutons in the northern margin of the yangtze block china partial melting of a thickened lower crust and implications for secular crustal evolution abstract numerous neoproterozoic felsic and mafic ultramafic intrusions occur in the hannan region at the northern margin of the yangtze block among these the wudumen and erliba plutons consist of granodiorites and have shrimp zircon u pb ages of 735 ma the rocks have high k 2 o 0 8 3 6 wt and na 2 o 4 4 6 4 wt and low mgo 0 4 1 7 wt they also have high sr y 32 209 and la yb n ratios 4 4 38 6 their e nd values range from 0 41 to 0 92 and zircon initial 176 hf 177 hf ratios from 0 282353 to 0 282581 these geochemical features are similar to those of adakitic rocks produced by partial melting of a thickened lower crust our new analytical results combined with the occurrence of voluminous arc related mafic ultramafic intrusions emplaced before 740 ma lead us to propose that the crustal evolution in the northern margin of the yangtze block during neoproterozoic involved 1 rapid crustal growth and thickening by underplating of mafic magmas from the mantle which was modified by materials coming from the subducting oceanic slab from 1 0 to 0 74 ga and 2 partial melting of the thickened lower crust due to a thermal anomaly induced by upwelling of asthenosphere through an oceanic slab window producing the 735 ma adakitic wudumen and erliba plutons our model suggests that the crustal thickness was more than 50 km at the northern margin of the yangtze block at 735 ma and rule out the possibility of a mantle plume impact causing the 735 ma magmatism in the region

dehydration melting of amphibolite at 10 kbar the effects of temperature and time we have simulated the dehydration melting of a natural low k calcic amphibolite 67 4 hornblende 32 5 anorthite in piston cylinder experiments at 10 kbar and 750 1000 c for 1 9 days the solidus temperature is lower than 750 c garnet appears at 850 c the overall reaction is hb p l cpx al hb ca hb ga opx three stages of reaction are 1 melting dominated by the growth of clinopyroxene and garnet with little change in composition of liquid or garnet 2 a reversal of this reaction between 875 c and 900 c with decreases in the amounts of liquid and garnet and 3 a large increase in liquid along with the loss of hornblende and decrease of plagioclase while clinopyroxene and garnet increase garnet is enriched in pyrope and zoned from fe cores to mg edges range 3 mol pyrope liquid composition is enriched first in an to 950 c and then in ab the liquids are more calcic and aluminous than natural tonalites which is attributed to the plagioclase composition an90 the formation of peraluminous liquid from the metaluminous amphibolite is caused by anorthite not h2o saturated conditions the results are consistent with an amphibolite phase diagram with relatively high solidus temperatures in the garnet absent field 900 1000 c but with a solidus backbend at 7 9 kbar coincident with the garnet in boundary hornblende breakdown due to garnet formation in a closed system must make h2o available for h2o undersaturated melting right down to the h2o saturated solidus below 700 c which defines a large low temperature pt area where hydrous granitoid melts can be generated with residual garnet and hornblende

a coupled flow stress damage model for groundwater outbursts from an underlying aquifer into mining excavations abstract uncontrolled groundwater outbursts from underlying limestone aquifers into mining excavations present a significant safety challenge for underground coal mining in china although these mining hazards have been known for decades the mechanism for groundwater outbursts remains elusive a fully coupled flow stress damage model is presented to simulate the progressive development of fractures and the associated groundwater flow under incremental loading conditions resulting from mining processes the model is based on classical theories of porous media flow and damage mechanics and importantly links changes in permeability with the accumulation of damage in following the complete stress strain process this coupled flow stress damage model is applied to examine the influence of mining advance on the initiation extension and evolution of an outburst conduit as it develops adjacent to the mine panel fractures are shown to initiate both from the wings of the excavation in shear and from the center of the floor span in extension the growth of the extensile fractures is stunted by the presence of a high stress abutment but the wing fractures extend with one fracture becoming dominant as the dominant fracture develops into the underlying over pressured zone water pressures transmitted along the now open conduit reduce effective stresses and develop rapid heave displacements within the floor the result is a groundwater outburst the modeling is tuned to the results of laboratory experiments and follows the evolution of a viable outburst path observations corroborate with field measurements of permeability pre and post mining and are strong indicators of the veracity of the approach

numerical investigation of groundwater outbursts near faults in underground coal mines permeable geologic faults in the coal seam can cause intermittent production problems or unexpected amounts of groundwater outburst from the underlying aquifers with the acknowledgment of the basic mechanism for groundwater outbursts the groundwater outburst along the fault zones in coal mines are numerically investigated using rfpa a numerical code based on fem the fracture initiation propagation and coalescence in the stressed strata and the seepage field evolution in the stress field are represented visually during the whole process of groundwater outburst the numerically obtained damage evolution shows that the floor strata could be classified as three zones i e mining induced fracture zone intact zone and fault reactivation zone in which the intact zone is the key part for resisting groundwater outburst and directly determines the effective thickness of water resisting rock layer with understanding of the evolution of stress field and seepage flow in floor strata the groundwater outburst pathway is calibrated and the transformation of floor rock mass from water resisting strata to outburst pathway is clearly illuminated moreover it is shown that geometrical configuration including inclination angle of faults and seam drop along faults have an important influence on groundwater outburst finally based on geological hydrogeology survey and numerical results the mechanism analysis of groundwater outburst in an engineering case is studied which can provide significantly meaningful guides for the investigation on mechanism and prevention of groundwater outburst induced by faults in practice

simulation analysis of water resource damage feature and development degree of mining induced fracture at ecologically fragile mining area mining induced water damage has become one of wide concerned issues in contemporary society knowing the main causes to water resource damage especially the superficial aquifer damage as well as the damage mode is the basis for realizing water conservation in this paper the mining height and position of aquifuge are regarded as the main influencing factors in analyzing the change of aquifer taking the geological conditions of yili no 4 coal mine as an example a total of 18 numerical analysis models with different mining heights 3 5 8 10 15 20 m and different positions of aquifuge upper middle and bottom as changing conditions were established using universal distinct element code discrete element simulation software the variation characteristics of water resources in aquifers after disturbance were studied the variation of water pressure with mining height and position of aquifuge was analyzed the variation of water pressure in aquifer was proposed as a novel criterion for distinguishing the development degree of mining induced fracture the criterion for determining the failure of aquifer was established based on the ratio of water pressure change and mining height p h which is a pioneering research on the relationship between mining induced fracture and aquifer failure this study provides a reference for evaluating the development degree of mining induced fracture and provides theoretical basis for analyzing the coupling relationship between mining and water resource change in aquifer and for water conservation at ecologically fragile mining area

the length of pre existing fissure effects on the dilatancy behavior acoustic emission and strength characteristics of cracked sandstone under different confining pressures it is significant to study the dilatancy behavior and strength characteristic of cracked rock to ensure the stability and safety of engineering rock mass consequently the effects of the length of pre existing fissures and confining pressure on the strength characteristic of sandstone specimens were analyzed and the dilatancy and acoustic emission ae behaviors of sandstone specimens with different lengths of pre existing fissures under different confining pressures were discussed the rationality of the stress of dilatancy onset can be as the strength parameter of rock is explained from the cohesion and internal friction characteristics of rock material and its dilatancy behavior the results show that the strength parameters of sandstone specimens are negative related to the length of pre existing fissures but positive related to the confining pressure the difference between the stress of dilatancy onset and peak strength decreases with the increase of length of pre existing fissures but increases with confining pressure which is related to the internal friction characteristic of rock material under the condition of uniaxial compression or low confining pressure the obvious stress drop easily occurs after the dilatancy onset and the frequency of this phenomenon is positive related to the length of pre existing fissures however this phenomenon gradually decreases with the increase of confining pressure it correspondingly transforms to the emergence of yield platform no matter what occurrence of stress drop or yield platform all the cracked rock specimens show the special characteristics of drastic increase of volume dilatancy active ae signals and full evolution of cracks after the dilatancy onset it seems to be more insecure from the way to obtain the higher strength parameters by the frequent occurrence of cohesive particles fracture in rock and the rock material can still rely on crack friction to load in addition from the dilatancy behavior of rock material it seems that the large deformations always appear after the dilatancy onset which is more likely to cause the potential engineering danger

neoproterozoic high k granites produced by melting of newly formed mafic crust in the huangling region south china abstract the huangling igneous complex in the central yangtze block south china consists of the 850 ma tonalite and trondhjemite which were intruded by the 826 13 ma high k granite the granites are composed of plagioclase 30 60 alkali feldspar 10 30 quartz 20 30 biotite 2 63 1 73 3 wt k 2 o 2 58 4 79 wt and na 2 o 3 90 5 89 wt and low mgo 0 49 1 78 wt and are magnesian alkali calcic in composition their chondrite normalized ree patterns are characterized by enrichment of lree la yb n 14 5 32 8 and mostly negative eu anomalies eu eu 0 5 1 1 they have moderately high sr 202 698 ppm and low y 6 13 18 7 ppm with sr y ratios of 14 64 these large elemental variations probably resulted from fractional crystallization they also have negative whole rock nd 9 75 to 11 73 and zircon hf values 7 1 to 15 8 which are similar to those of the neoproterozoic mafic rocks in the same region suggesting that the granites may have been produced by melting of newly emplaced mafic rocks tonalites and trondhjemites of the huangling complex previously were considered as products by differentiation of water rich basaltic magmas and melting of the thickened archean continental crust in an arc setting respectively therefore the crustal growth and reworking of the yangtze block were probably wholly controlled by the subduction system which resulted in formation of the stable continent during the neoproterozoic

non boussinesq gravity currents propagating on different bottom slopes i0 exists between the front location measured from the virtual origin xf c x0 and time t in the early deceleration phase for both the boussinesq and non boussinesq cases where km is a measured empirical constant b 0 is the total released buoyancy and ti0 is the t intercept our results show that km not only increases as the relative density difference increases but also assumes its maximum value at 6 for sufficiently large relative density differences in the late deceleration phase the front location data deviate from the 3 2 power law and the flow patterns on d 6 9 slopes are qualitatively different from those on d 0 2 in the late deceleration phase we showed that viscous effects could become more important and another power law xfcx0 2 dk 2 v b 0 2 3 a 1 3 0 1 3 tctv0 applies for both the boussinesq and non boussinesq cases where kv is an empirical constant a0 is the initial volume of heavy fluid per unit width is the kinematic viscosity of the fluids and tv0 is the t intercept our results also show that kv increases as the relative density difference increases and kv assumes its maximum value at 6

effect of confining presurre pore pressure and specimen dimension on permeability of yinzhuang sandstone abstract tests on yinzhuang sandstone for measuring permeability under different confining pressure pore pressure and specimen dimensions were carried out with an orthogonal experimental design table l 16 4 3 having 3 experimental factors and 4 levels a total of 16 tests had been performed the permeability of yinzhuang sandstone was found as a function of the axial stress and strain strongly but the effect of confining pressure pore pressure and specimen dimensions on permeability was not obvious for most regions in a complete stress strain path only in some individual regions some individual factors discovered its own significant effect for example the confining pressure gave most significant influence on permeability in the strain softening region whereas the ratio of pore pressure to confining pressure discovered an obvious effect only on the value of highest permeability

theoretical models for simulating the failure range and stability of inclined floor strata induced by mining and hydraulic pressure abstract there is a risk of floor failure within mining of coal seams above aquifers therefore investigating the processes involved is of great significance for the prediction and prevention of mine water hazards with consideration of the effects of mining pressure and non uniformly distributed hydraulic pressure the two dimensional 2d hydraulic mechanical calculation hm model and the key strata stability analysis ks model were proposed to analyze the theoretical range of failure and the stability of inclined floor strata after mining to validate the model a numerical simulation of the failure characteristics of inclined floor above a confined aquifer was conducted along with an in situ investigation the results showed approximate agreement between the theoretical and simulated failure ranges of the inclined floor along the strike and inclination with their characteristics being approximate to spoon shaped and inverted saddle shaped with upper small lower large respectively the theoretical failure depths of the floor around the mining face side and the upper and lower parts were 13 m 12 5 m and 14 m respectively with general agreement between simulated and measured results moreover the zones prone to water intrusion were indicated to be mainly distributed near the upper end lower end and mining face side of the inclined key strata in good agreement with the distribution of the area disturbed by mining and the risk of groundwater inrush induced by the vertical failure depth the research results could provide an improved understanding of the mechanism of water inrush from underlying aquifers

neoproterozoic tonalite and trondhjemite in the huangling complex south china crustal growth and reworking in a continental arc environment the huangling igneous complex in the central yangtze block of south china is composed of 850 ma tonalite and trondhjemite intruded by 820 ma granite tonalites mainly consist of plagioclase and quartz with abundant hornblende and biotite and contain fine to coarse grained hornblende rich igneous enclaves they have variably low sio2 56 4 67 5 wt and sr 230 517 ppm and high mgo 1 47 4 02 wt and high y 8 87 15 7 ppm with low sr y 17 43 unlike archean tonalites their whole rock end values range from 8 3 to 10 3 and zircon ehf values from 3 9 to 12 6 similar to those of spatially associated neoproterozoic mafic rocks the tonalites are thus proposed to have been produced by three stages involving partial melting of subduction modified lithospheric mantle 5 to 20 percent crustal contamination of hydrous basaltic magmas in the middle to lower crust and fractional crystallization of amphibole plagioclase biotite magnetite trondhjemites are composed of plagioclase quartz and alkali feldspar with minor biotite and hornblende they have high sio2 67 3 75 6 wt and sr 340 840 ppm and low mgo 0 09 0 78 wt and y 4 8 11 2 ppm with high sr y 32 162 similar to archean trondhjemites and high pressure partial melts of mafic rocks these rocks have extremely negative end 18 7 to 19 9 and zircon ehf values 18 9 to 49 2 with two stage hf isotope model ages of 2 46 to 3 90 ga indicating their formation in the lower crust by melting of archean amphibolites and granulites which were probably widely distributed beneath the yangtze block their highly variable chemical compositions also resulted from fractional crystallization of plagioclase hornblende biotite thus the association of the tonalite and trondhjemite is different from the archean ttg series this difference may reflect different geothermal gradients however modeling using tonalitic and trondhjemitic samples of the huangling complex suggests that mixing of the two magmas can generate a typical ttg affinity series suggesting that the origin of some ttg series may have involved both crustally derived and mantle derived melts the generation of the huangling igneous complex was linked to slab subduction beneath the northern margin of the yangtze block during the neoproterozoic similar to the cenozoic arc magmatism in the andes therefore melting of metasomatized hydrous mantle in arc settings can generate mafic magmas that not only under plated and contributed to continental crustal growth but also caused melting of thickened ancient crust and newly formed lower mafic crust

late archaean granites a typology based on the dharwar craton india abstract extensive field work in the eastern dharwar craton associated with petrographic and geochemical major and trace elements investigations allows four main types of late archaean granitoids to be distinguished 1 na rich granitoids of trondhjemitic tonalitic and granodioritic composition ttg that are characterised by strongly fractionated ree patterns and low hree contents and generally interpreted as slab melts generated by partial melting of metamorphosed hydrated basalt most likely in a subduction environment 2 sanukitoids which are k and mg rich monzonites and granodiorites with ttg like ree patterns associated with marked lile enrichment and considered to result from the reaction of slab melts generated in a subduction environment with and assimilation of mantle wedge peridotite 3 uncommon high hfse mg and k granites with strongly ree and lile enrichment that probably formed by partial melting of an enriched mantle source unlike in the genesis of sanukitoids in this case the slab melt is considered to be wholly consumed by reaction with mantle minerals resulting in mantle enrichment subsequent melting of this enriched mantle probably in a post subduction setting gives rise to high hfse mg and k magmas as demonstrated for the closepet granite dharwar craton the hot mantle derived magma can induce melting of continental crust and then mix with the anatectic products 4 k rich mg poor anatectic biotite granites with ree patterns that are less fractionated and show negative eu anomalies these granites result from the remelting of old basement or recently accreted plutons both with ttg compositions such anatexis can occur either in a subduction or in a post subduction environment this typology based on the well exposed dharwar craton can be extended to late archaean granitoids from all over the world about such 500 analysis were compiled and a number of discriminant diagrams based on both major and trace elements are proposed the most likely tectonic setting for the observed rock types is an accretionary orogen with accretion of continental blocks above a subduction system followed by thermal reworking of the newly accreted continental material however it has been found that archaean subduction related granitoids are significantly different from their modern counterparts implying progressive changes in the modes of magma generation at convergent margins from the archaean to the present

finite element modeling of stress distributions and problems for multi slice longwall mining in bangladesh with special reference to the barapukuria coal mine abstract this paper deals with current coal mining operations under a mega aquifer in nw bangladesh and presents a case study of underground mining in barapukuria the study uses numerical analyses to evaluate stress redistribution strata failure and water inflow enhancements that result from these coal extraction operations a total of three models a b and c are presented in this study two dimensional numerical modeling was performed to analyze the deformation and failure behavior of rock elements for two different models a and b for model a we used an elastic finite element software package considering a mohr coulomb failure criterion for model b we used boundary element method bem the first two models were applied to determine the stress patterns model a provides the tectonic stress pattern of the basin whereas model b represents the mining induced stress field the third model is a schematic model the results of model a show that tensional failure of rock elements is concentrated in the gondwana coal sequences as well as within the eastern boundary fault ebf and its surroundings failure occurs in the middle to lower part of the model and the magnitude of tensional stress in the shallow part is much greater than in the deeper part contours of max magnitudes are attributed to up bending of the overburden which would create numerous upward propagating fissures fractures the results of model b show that fracture propagation would be about 240 m upward for single slice height 3 m mining extraction from the contours of mean stress magnitudes it is observed that the high range of fracture propagation increased upward for multi slice extraction of coal it is apparent from the fracture heights that large amounts of caving would occur towards the roof due to the multi slice extraction of coal and finally would be linked with the water bearing dupi tila formation if this happened it would ultimately cause a major water inflow hazard in the mine

plutonism oblique subduction and continental growth an example from the mesozoic of california major episodes of mesozoic plutonism in california correlate with periods of oblique subduction and trench parallel transport of western california along intrabatholithic faults major episodes of plutonism occurred in the late jurassic during left oblique convergence and in the mid cretaceous during right oblique convergence in contrast a conspicuous lull in plutonism but continuation of volcanism in the earliest cretaceous coincides with a time when the north america farallon convergence vector although large in magnitude was oriented perpendicular to the trench this correlation suggests that plutonism is facilitated by strike slip faulting within the batholithic belt one explanation which helps to solve the plutonic room problem is that plutons are passively emplaced at releasing bends in the strike slip faults and volume is conserved by thrusting at the trench if this correlation is generally applicable then it implies that mid crustal plutonism is limited beneath areas in which the convergence vector is subperpendicular to the trench continental growth in such areas may occur dominantly by volcanism

the mechanisms of petrogenesis of the archaean continental crust comparison with modern processes the petrographic and chemical composition of magmatic rocks generated during the archaean appears to be different from that of post archaean rocks komatiites are widespread before 2 5 ga and rarely occur afterwards in addition the archaean continental crust is primarily ttg tonalitic trondhjemitic and granodioritic in composition exhibiting typical trondhjemitic differentiation trends whereas modern equivalents are granodioritic to granitic following classical calc alkaline differentiation trends this distinction becomes more prominent when rare earth elements ree are taken into account archaean ttg are yb poor ybn 8 5 and have high layb ratios 5 layb n 150 in comparison the post 2 5 ga granitoids emplaced in subduction zone geodynamic environments have high yb content 4 5 ybn 20 with very low layb n ratios 20 theoretical calculations and experimental petrology have shown that the ttg can be produced by partial melting of an archaean tholeiite transformed into garnet bearing amphibolite consequently the low heavy ree content of the ttg is explained by the influence of both residual garnet and hornblende in their source after 2 5 ga the role of these minerals in calc alkaline magma genesis becomes progressively less important which is interpreted in terms of a cooling earth model in modern subduction zone environments the subducted oceanic slab is relatively old and cold and the geothermal gradient along the benioff plane in low ca 10 c km consequently the down going lithosphere undergoes dehydration before partial melting is able to occur the liberated fluids are light ree and lile enriched and ascend into the overlying mantle wedge where they induced partial fusion the produced magmas separate from their mantle source region leaving a residue mainly composed of olivine and pyroxenes mantle derived magmas typically exhibit high yb contents due to low kdyb values for olivine and pyroxenes during the archaean the subducted lithosphere was relatively young and hot providing high geothermal gradients along the benioff zone thus partial melting of the subducted slab was possible at lower temperatures before dehydration would take place garnet and hornblende are the main residual phases accounting for the low yb contents of the archaean ttg this model can be tested using a modern analogue of archaean like subduction processes in south chile an oceanic ridge has subducted and all thermodynamic calculations indicate that this creates locally high geothermal gradients along the benioff zone thus in very small areas archaean like environments may be simulated in modern subduction zones the modern andesites produced in this environment show archaean geochemical characteristics with low ybn 5 whereas the majority of andesites along the andean arc have modern patterns with ybn ranging from 8 to more than 17 this conclusion was generalised to all young subducted lithospheres all over the world in conclusion it appears that since the archaean there has been a change in the site of continental crust genesis the location of calc alkaline magma source in subduction zone environments has migrated through time from the subducted slab to the mantle wedge this is a direct consequence of the progressive cooling of the earth

damage induced permeability changes in granite a case example at the url in canada abstract this paper concerns both in situ measurements of permeability and numerical modelling of changes in permeability induced by microcrack growth hydraulic experiments including pulse tests with the seppi probe are in progress these tests are a part of the tunnel sealing experiment tsx at the 420 m level of canada s underground research laboratory whose aim is to estimate the in situ hydraulic properties of lac du bonnet granite based on laboratory investigations the anisotropic damage model developed by homand et al comput geotech 22 1998 135 and recently reviewed by shao et al int j rock mech min sci 36 1999 1001 has been extended in order to account for changes in permeability induced by microcrack growth we have implemented this extension in the three dimensional code flac 3 d triaxial compression tests with permeability measurements carried out on two different granites provide a verification of the numerical implementation with a good agreement between experiments and predictions comparison between in situ measurements of permeability and predictions indicates that both the results of numerical modelling and observations are globally in agreement finally numerical modelling as well as the in situ measurements indicate that a depth of 50 70 cm is a good estimation of the extent of excavation disturbed zone in the tsx tunnel

hydrogeological analysis and salvage of a deep coalmine after a groundwater inrush this paper presents a case history of the permanent salvage of the sanhejian coalmine in china after a sudden groundwater inrush which includes emergency responses hydrogeological analyses and design and performance of bulkheads the inrush accident occurred in october 2002 in the mined out area with a high water pressure of 7 6 mpa and a high water temperature of 51 c the emergency response quickly followed up to provide the time required to perform a detailed hydrogeological analysis to identify the source and pathway of groundwater the sanhejian coalmine is geologically located in the tengxian anticline hydrogeological setting the sunshidian fault the northern boundary of the mine was assumed impermeable in the original hydrogeological report after the accident and hydrogeological analysis this assessment was revised and the fault was considered to be permeable the sunshidian fault connects the strata in the mine and the excellent water productive middle ordovician majiagou formation in the core of the tengxian anticline it was concluded that the water inrush was from the underlying ordovician karst aquifer and the pathway was a hidden tectonic structure in the strata overlying the aquifer this assessment served as the guideline for salvaging the mine in this project after a detailed technical and economic analysis a concrete bulkhead design was selected from several alternatives including dewatering and surface grouting the performance of the bulkheads has been sufficient for the last 6 years since their construction this case history shows that the hydrogeological analysis plays an essential role in successfully salvaging the coalmine from the water inrush by identifying the source and pathway of groundwater

reappraisal of the ages of neoproterozoic strata in south china no connection with the grenvillian orogeny the jiangnan fold belt separates the yangtze and cathaysia blocks in south china and has long been considered grenvillian in age in order to place south china in central rodinia it consists of deformed early neoproterozoic strata that are unconformably overlain by undeformed late neoproterozoic strata and intruded by undeformed and unmetamorphosed granitic plutons zircons from the early neoproterozoic strata yield u pb ages as young as 830 ma and one granitic pluton has a zircon u pb age of ca 827 ma the 830 ma mafic rocks along the southeastern margin of the yangtze block have arc affinity geochemical characters whereas mafic rocks younger than 830 ma have typical ocean island basalt oib like compositions thus we suggest that the early neoproterozoic strata were deposited on an active continental margin prior to amalgamation of the yangtze and cathaysia blocks at ca 830 ma the overlying late neoproterozoic strata were deposited in the intracontinental rifted nanhua basin at 820 730 ma and probably reflect backarc spreading above the long lived 950 735 ma oceanic subduction zone along the northern and western margin of the yangtze block this model is consistent with the secular tectonic evolution of south china during the neoproterozoic the jiangnan fold belt is therefore not a grenvillian feature as previously suggested and there is no evidence to place south china in central rodinia instead we believe that south china was located in a marginal position relative to this supercontinent

fluid permeability of sedimentary rocks in a complete stress strain process abstract the permeability of sedimentary rocks during triaxial compression tests was investigated to relate it to the complete strain stress process it was found that the permeability was not constant but varied with the stress and strain states in the rocks prior to the peak strength the permeability decreases with increasing load a dramatic increase in permeability occurs during the strain softening period in the present study in situ measurements of fluid flow and pressure in floor strata was carried out in a double longwall mining face in the yangzhuang colliery these measurements show that both the strata pressure and the position with respect to the mining face influence the hydrogeologic properties the permeability increased in the floor strata behind the mining face because those mining induced fractures opened as the strata pressure decreased to better understand this change in hydraulic behavior around the mining faces 3 d numerical modeling was carried out the model provides the general picture of the stress distribution and failure zone both in the floor and roof strata the field and model results demonstrate the importance of changes in the stress and strain states on the hydrogeology of a site

hydrogeochemical analysis of multiple aquifers in a coal mine based on nonlinear pca and gis hydrogeochemical characteristic analysis of multiple categorical aquifers including the delineation of hydrogeochemical spatial distributions can provide a basic understanding of the groundwater flow system necessary for the prevention and control of groundwater damage associated with coal mines nonlinear principal component analysis pca was used to analyse the groundwater chemical characteristics of water samples from five aquifers in gubei coal mine anhui province china in particular ca2 mg2 na k hco3 cl so4 2 and ph were analysed to analyse the spatial distribution of groundwater chemistry in this permian fractured aquifer interpolation of principal component 1 pc1 scores obtained from the nonlinear pca was performed using the inverse distance weighting idw method additionally concentrations of the hydrogeochemical variables were plotted against depth the relationships between water samples variables and water samples with variables were simultaneously analysed by nonlinear pca the results show 1 nonlinear pca explains more variability than standard pca in the first two principal components pcs 2 the cenozoic top aquifer has low concentrations of na k and cl the cenozoic middle aquifer and cenozoic bottom aquifer are characterised by high concentrations of ca2 and mg2 and low concentrations of hco3 the shallow groundwater of the permian fractured aquifer is recharged by the cenozoic bottom aquifer while other parts have high concentrations of hco3 and low concentrations of ca2 and mg2 the taiyuan limestone aquifer has similar groundwater chemistry to that of the cenozoic bottom aquifer and thus it may be recharged by the cenozoic bottom aquifer in outcropping taiyuan formation strata 3 the wide south western and north western areas of the permian fractured aquifer may be recharged by the cenozoic bottom aquifer and 4 concentrations of ca2 and mg2 in the permian fractured aquifer are negatively correlated with sampling depth while the concentrations of na k and hco3 are positively correlated with sampling depth which verifies that the shallow groundwater of this permian fractured aquifer is recharged by the cenozoic bottom aquifer the findings demonstrate that combining nonlinear pca with gis can be a powerful approach for conducting spatial nonlinear analysis of hydrogeochemical characteristics

multivariate statistical analysis of water chemistry in evaluating groundwater geochemical evolution and aquifer connectivity near a large coal mine anhui china major ion chemistry of groundwater from main aquifers near the dingi coal mine anhui china was analyzed with a suite of statistical techniques in an effort to understand aquifer connectivity and groundwater geochemical evolution fifty seven groundwater samples were analyzed from four aquifers the cenozoic top middle bottom aquifers and a permian coal strata aquifer with increasing depth of the aquifers groundwater became more mineralized showing greater hardness and salinity the dissolutions of halite and sylvite carbonate sulfate and silicate minerals were the primary processes controlling groundwater chemical compositions in the cenozoic bottom and coal strata aquifers while k na and hco3 originating from silicate mineral weathering were more enriched in the coal strata aquifer principal component analysis pca identified two principal components with the first component representing hardness variation and accounting for 57 5 of total variance and the second component 23 5 of total variance controlled primarily by salinity and sulfate reduction process the cenozoic bottom aquifer had greater hardness than other aquifers whereas the coal strata aquifer was characterized by higher salinity and larger influences of sulfate reduction cluster analysis revealed that the coal strata aquifer was largely isolated from the cenozoic aquifers with possible infiltration at discrete locations indicating that the high yield thick cenozoic aquifers may serve as a potential additional source for groundwater inrush into coal mines

study of the hydrogeological characteristics and permeability of the xinli seabed gold mine in laizhou bay jiaodong peninsula china this paper presents a case study investigation into the hydrogeological characteristics and permeability of rock mass in a seabed mine following an introduction to the geology and hydrogeological conditions in the xinli mine area we reveal the features of the preferred structural planes dynamic characteristics of mine water seepage and the permeability of the fractured rock mass in the pit the permeability of the pit rock mass shows varied characteristics at different geotectonic locations because of the different degrees to which the structural planes developed the fractured rock mass generally shows low permeability and the main composition of water seepage is high salinity brine future large scale undersea mining may induce rock mass movement destroy water resistant layers and enhance water transmissibility and the probability of water gushing into the pit thus strengthening the quality of the filling mass protecting the stope roof and the water resistant layers as well as regular monitoring of water seepage discharge and identification of water sources are critical to work safety and the prevention of seawater gushing in the mine

petrology of the chilliwack batholith north cascades washington generation of calc alkaline granitoids by melting of mafic lower crust with variable water fugacity calc alkaline granitoid rocks of the oligocene pliocene chilliwack batholith north cascades range from quartz diorites to granites 57 78 sio2 and are coeval with small gabbroic stocks modeling of major element trace element and isotopic data for granitoid and mafic rocks suggests that 1 the granitoids were derived from amphibolitic lower crust having ree rare earth element and sr nd isotopic characteristics of the exposed gabbros 2 lithologic diversity among the granitoids is primarily the result of variable water fugacity during melting the main effect of fh 2 o variation is to change the relative proportions of plagioclase and amphibole in the residuum the ree data for intermediate granitoids quartz diorite granodiorite eu eu 0 84 0 50 are modeled by melting with fh 2 o 1 kbar leaving a plagioclase pyroxene residuum in contrast data for leucocratic granitoids leuco granodiorites and granites eu eu 1 0 0 54 require residual amphibole in the source and are modeled by melting with fh 2 o 2 3 kbar consistent with this model isotopic data for the granitoids show no systematic variation with rock type 87sr 86sri 0 7033 0 7043 end 0 3 3 to 5 5 and overlap significantly with data for the gabbroic rocks 87sr 86sri 0 7034 0 7040 end 0 3 3 to 6 9 the fh 2 o variations during melting may reflect additions of h2o to the lower crust from crystallizing basaltic magmas having a range of h2o contents chillwack gabbros document the existence of such basalts one dimensional conductive heat transfer calculations indicate that underplating of basaltic magmas can provide the heat required for large scale melting of amphibolitic lower crust provided that ambient wallrock temperatures exceed 800 c based on lithologic and geochemical similarities this model may be applicable to other cordilleran batholiths