numerical modelling of strata movement at footwall induced by underground mining abstract during metal mining the deformation and failure of rock mass are very important factors that dominate rock movement and zoning numerical modelling provides a feasible way to study the deformation and failure of rock mass in this study a numerical method of udec was adopted to study strata movement mechanism influenced by nww trending joints at the footwall at chengchao iron mine and the mohr coulomb model and the coulomb slip model with residual strength were adopted as the constitutive models of rock masses and joints respectively the whole strata movement process was simulated and the strata movement mechanism at footwall and zoning phenomenon was clarified in the chimney caving development stage gravity is the driving force and surface deformations are mainly subsidence deformation of the surface above the ore body in the post chimney deformation stage horizontal tectonic stress is the driving force and surface deformation and subsidence are dominated by horizontal deformation of the hanging wall and footwall in the mining area after the level 395 0 m is mined out the deformation characteristics of deep surrounding rock were revealed by means of numerical modelling the maximum failure depth of the cantilever beam and the spatial distribution of deep surrounding rock zones can be determined at last the influencing boundary of surface deformation expands rapidly in a linear way with the excavation step and the expanding velocity of the horizontal deformation is greater than that of the subsidence in the post chimney deformation stage

mapping and quantifying the clay aggregate microporosity in medium to coarse grained sandstones using the 14c pmma method abstract microporous aggregates of kaolin minerals and illite are common products filling the intergranular volume igv of deeply buried sandstones using bsei backscattered electron imaging a full analysis of igv is difficult and time consuming since it necessitates a two step process at the scales of 1 macroporosity between the detrital grains and 2 microporosity within the clay aggregates the 14c pmma method permits the mapping and quantification of the connected porosity in sandstone core samples across scales this method is based on the complete impregnation of the connected porosity by 14c labeled methylmethacrylate mma monomer and its subsequent in situ polymerization imaging the spatial distribution of the radioactive tracer within a section of an impregnated sample allows an integrated analysis of igv from the core scale to the nanometer scale this technique is illustrated through analysis of the clay cement of a medium to coarse grained sandstone from the athabasca basin canada the measured connected porosity distributions of kaolin mineral aggregates average porosity 42 and illite fillings average porosity 70 are in accordance with gaussian distributions this method also permits quantification of the relative volumetric amounts of the both illite and kaolin aggregate

the cooling kinetics of plagioclase feldspar as revealed by electron microprobe mapping in this study we have used electron microprobe mapping to investigate plagioclase compositional evolution due to cooling kinetics we re analyzed five run products from a prior study iezzi et al 2011 crystallized by cooling a natural andesitic melt from 1300 to 800 c at 25 12 5 3 0 5 and 0 125 c min under atmospheric pressure and air redox state as the cooling rate decreases the texture of large plagioclases changes from skeletal to hollow to nearly equant in this study we use x ray map data to obtain a database of 12 275 quantitative chemical analyses the frequency of an rich plagioclases showing disequilibrium compositions substantially increases with increasing cooling rate at 25 and 12 5 c min the distribution is single mode and narrow at 0 5 and 0 125 c min is single mode but very broad whereas at the intermediate cooling rate of 3 c min two distinct plagioclase populations are present this intermediate cooling rate is fast enough to cause departure from equilibrium for the crystallization of the an rich population but also sufficiently slow that an poor plagioclases nucleate from the residual melt we interpret our findings in the context of time temperature transformation ttt diagrams and infer the crystallization kinetics of plagioclase in the experiments compositional trends and our inferences regarding ttt systematics are consistent with two discrete nucleation events that produced separate populations of plagioclase i e an rich and an poor populations at 3 c min using plagioclase melt pairs as input data for the thermometric reaction between an and ab components we find that plagioclase mirrors very high near liquidus crystallization temperatures with increasing cooling rate these results have important implications for the estimate of post eruptive solidification conditions lava flows and intrusive bodies from centimeters to a few meters thick are characterized by a short solidification time and a significant thermal diffusion under such circumstances it is possible to crystallize plagioclases with variable and disequilibrium chemical compositions simply by cooling a homogeneous andesitic melt x ray element maps enrich the study of plagioclase compositional variations generated under conditions of rapid cooling

on the connected porosity of mineral aggregates in crystalline rocks the 14 c pmma impregnation of rock samples and mineral staining methods provide the connected porosity map and the spatial distribution of mineral aggregates respectively combined image analysis of mineral and porosity maps allows quantification of the connected porosity distribution in rock forming mineral aggregates after the two maps have been superimposed numerically the 14 c pmma method provides an indication of the extent of pore connectivity for each pixel in the analyzed area which can be used to obtain the porosity distribution as a function of modal mineralogy when applied to undeformed and deformed kivetty granodiorite samples from finland the method allows for a detailed analysis of the rock porosity porosity distributions related to the undeformed rock are unimodal and approximately identical to each other on the other hand porosity distributions of the deformed granodiorite are multimodal and vary significantly constituent porosity sets of the deformed samples were albite crystals free of alkali feldspar patches and alkali feldspar phenocrysts average porosity 0 21 albite containing alkali feldspar patches 0 59 rapakivi albitic mantles 1 15 quartz 0 39 and mafic minerals 5 8 moreover the analysis indicates that the numerous micropores observed under sem within alkali feldspar phenocrysts and albite crystals free of alkali feldspar patches are unconnected in 3d

weathering indices for rhyolitic tuff and granite in hong kong a series of chemical analyses and dry density tests of rhyolitic tuff and granitic samples have been carried out the test results have been interpreted using a newly developed theoretical weathering model for calculating a mobility index of major elements in rock and soil it is found that this index is useful for describing changes of rock and soil during weathering and classifying the degrees of weathering based on the theoretical model a new parameter called the volume index which combines chemical and physical data is suggested this index appears to be a good indicator for classifying the degree of weathering in hong kong a quantitative classification scheme is suggested

a lightweight extruder for accurate sectioning of soft bottom lake sediment cores in the field a new extrusion device is described for time efficient sectioning of high quality cores of soft bottom lake sediments in particular piston cores and core samples that include the undisturbed sediment water interface the instrument is lightweight versatile and easy to operate in the field while maintaining maximum accuracy in sectioning a sediment profile in predefined increments

comparison between the wintertime and summertime dynamics of the misa river estuary abstract the misa river on the italian adriatic coast is typical of the rivers that drain the apennine mountain range the focus of this study conducted in the late summer of 2013 and mid winter of 2014 was to contrast the general wintertime summertime dynamics in the misa river estuarine system rather than investigate specific dynamical features e g offshore sediment transport channel seiche and flocculation mechanisms summertime conditions of the misa river estuary are characterized by low freshwater discharge and net sediment deposition whereas in the wintertime the misa river and estuary is characterized by high episodic freshwater discharge and net erosion and sediment export major observed differences between wintertime summertime dynamics in the misa river and estuary are a result of seasonal scale differences in regional precipitation and forcing conditions driven largely by the duration and intensity of prevailing wind patterns that frequently change direction in summertime while keep almost constant directions for much longer periods in wintertime thus generating major sea storms sediment deposition was observed in the final reach of the misa river and estuary in the summertime however in the wintertime large flood events led to sediment erosion and export in the final reach of the misa river and estuary that in conjunction with storm wave induced mud transport led to sediment deposition at the river entrance and in the adjacent nearshore region the seasonal cyclic pattern of erosion and deposition was confirmed with bathymetric surveys of the final reach of the estuarine region a critical component for the balance between summertime deposition and wintertime erosion was the presence of an underlying mat of organic deposits that limited the availability of sediments for erosion in winter when massive debris transport occurs further suspended cohesive sediments flocs were subjected to smaller hydrodynamic stresses in the summertime favoring deposition within the estuary conversely during wintertime storms flocs were subjected to larger hydrodynamic stresses favoring breakup into smaller flocs and deposition outside the estuary

geological geochronological and mineralogical constraints on the genesis of the chengchao skarn fe deposit edong ore district middle lower yangtze river valley metallogenic belt eastern china abstract the edong ore district is located within the westernmost middle lower yangtze river valley metallogenic belt mlyrb and hosts the largest concentration of skarn fe deposits in china although the origin of these deposits remains controversial the chengchao deposit is the largest skarn fe deposit so far discovered within the mlyrb and provides a good opportunity to address the debate surrounding the origin of these skarn fe deposits here we present geological geochronological and mineralogical data from the chengchao skarn deposit and associated intrusions and discuss the relationships between granitoids and mineralization in the chengchao deposit the nw se striking orebodies in the study area have porphyritic quartz monzonite and or granite footwalls and triassic marble or diorite hangingwalls indicating a spatial relationship between these intrusions and fe mineralization zircon u pb data from the granite porphyritic quartz monzonite diorite and porphyritic diabase dike within the deposit show ages of 129 1 128 1 140 1 and 126 1 ma respectively these ages and the previously reported ages on the timing of mineralization suggest that the porphyritic quartz monzonite and granite are coeval with the formation of the skarn fe deposit our data confirm that the granitic rocks are temporally associated with fe mineralization the prograde substage of skarn development is characterized by two stages of andradite adr98 38grs61 2prp2 0sps1 0alm1 0 and diopside di95 61hd37 5jo3 0 including an early stage of garnet and pyroxene formation that is genetically associated with the mineralization the early stage garnets are more andradite rich adr98 50grs49 2prp1 0sps1 0alm0 than the late veinlet garnets characterized by intermediate grandite compositions adr67 37grs61 31prp2 0sps1 0alm1 0 the early stage pyroxenes di95 74hd26 5jo1 0 are compositionally distinct from the late stage pyroxenes di84 61hd37 16jo3 0 compositional variations of early stage garnets in the zoned skarns indicate that skarn formation and fe mineralization are genetically associated with the porphyritic quartz monzonite and granite intrusions the geological geochronological and mineralogical evidence indicates that the porphyritic quartz monzonite and granite intrusions in the chengchao fe deposit are spatially temporally and genetically associated with fe mineralization

controls over the strontium isotope composition of river water abstract strontium concentrations and isotope ratios have been measured in river and ground waters from the ganges orinoco and amazon river basins when compared with major element concentrations the data set has allowed a detailed examination of the controls over the strontium isotope systematics of riverine input to the oceans in the following environments 1 1 typical drainage basins containing limestones evaporites shales and alumino silicate metamorphic and igneous rocks 2 2 shield terrains containing no chemical or biogenic sediments and 3 3 the floodplains that constitute the largest areas of many large rivers the strontium concentration and isotope composition of river waters are largely defined by mixing of strontium derived from limestones and evaporites with strontium derived from silicate rocks the strontium isotope composition of the limestone endmember generally lies within the phanerozoic seawater range which buffers the 87 sr 86 sr ratios of major rivers a major exception is provided by the rivers draining the himalayas where widescale regional metamorphism appears to have led to an enrichment in limestones of radiogenic strontium derived from coexisting silicate rocks the strontium isotope systematics of rivers draining shield areas are controlled by the intense transportlimited nature of the weathering reactions and thereby limits variations in the strontium flux from these terrains floodplains are only a minor source of dissolved strontium to river waters and precipitation of soil salts in some floodplains can reduce the riverine flux of dissolved strontium to the oceans the most effective mechanisms for altering the isotope ratio and flux of riverine strontium to the oceans are increased glaciation and large scale regional metamorphism of the type produced during continental collision both mechanisms provide a means for increasing the 87 sr 86 sr ratio of the global riverine flux

alteration of the callovo oxfordian clay from meuse haute marne underground laboratory france by alkaline solution i a xrd and cec study the reaction of the clay fraction of the callovo oxfordian hard shale formation hosting the french underground laboratory site with high ph naoh koh and ca oh 2 solutions has been investigated through closed system experiments at 60 90 and 120 c over 6 24 and 168 h the mineralogical composition of the run samples has been determined using x ray diffraction xrd of randomly oriented powders showing the formation of different species of zeolites analcime chabazite phillipsite and ca silicates tobermorite katoite the phyllosilicates were studied using xrd of oriented preparations and cation exchange capacity measurements detrital or diagenetic mica and chlorite in the 2 m fraction remain unchanged on the contrary the smectite and random illite smectite mixed layer minerals are strongly reactive the expandable layers of montmorillonite type are selectively dissolved while beidellitic ones survive or are transitionally formed

effective porosity measurements of poorly consolidated materials using non destructive methods abstract the porosity characterization of poorly consolidated sediments or soils is a key factor in understanding fluid flow and geochemical processes in surface and subsurface environments however porosity quantification is a challenging task due to the low cohesion of the extracted sample in this study we proposed and assessed a method combining x ray computed micro tomography ct and he gas pycnometry for the measurement of connected porosity in unconsolidated subsurface sands the principle is based on the calculation of the total sample volume from reconstructed ct volume and the measurement of the solid volume from he gas pycnometry disaggregation of the sample may occur during handling and is taken into account by correcting the ct volume using image processing the measurements obtained for reference consolidated sandstone were compared with those obtained from water absorption under vacuum the use of such non destructive techniques offers the advantage of preserving loose sample structure moreover it is a rapid and simple method that requires no sample preparation and could be easily implemented as routine analysis

coupled hydrogeochemical modelling using kirmat to assess water rock interaction in a saline aquifer in central eastern tunisia abstract to quantify water rock interactions and forecast their spatiotemporal evolution in the shallow aquifer of sidi el hani located in central eastern tunisia the numerical code kirmat was used based on available geological mineralogical thermodynamic kinetic and hydrodynamic data the model was built and calibrated on two transects of the aquifer oriented along the flow lines of groundwater the numerical results show that the interactions between water and rock are responsible for groundwater salinity which is strongly dominated by chlorides sodium and sulphates the variations of dissolved species in space and time are the result of halite dissolution anhydrite and gypsum dissolution and precipitation calcite dissolution and dolomite precipitation the precipitation of dolomite can locally induce a reduction in permeability and further enhance an increase in leaching because the residence time between rock and water will be amplified three numerical sensitivity studies have been conducted to evaluate the influence of water rock interactions on groundwater salinization the study highlights the finding that the modelled fate of dissolved species in the unconfined aquifer is rather sensitive to the darcy velocity but not very sensitive to the initial volume fractions of minerals in the two transects and the composition of groundwater injected at the upstream boundary

ree and nd isotope stratigraphy of a late jurassic carbonate platform eastern paris basin france abstract rare earth elements ree and nd isotopes on the labile fraction of the callovian oxfordian to tithonian jurassic carbonate platform of the eastern paris basin were used to reconstruct the composition of the contemporaneous waters from which the labile fraction may have originated this sedimentary record shows a remarkable change in the manganese content between the clayey deposits at the top and bottom of the succession and the carbonate platform deposits the combined analyses of ree and nd isotope ratios record the influence of emerged land and the tethys ocean the ree patterns are similar to those of seawater in the middle part of the sedimentary record suggesting ree removal by marine carbonate while bell shaped ree patterns are observed above and below reflecting continent derived ree carried by fe mn coatings on detrital particles therefore the ree patterns and their evolution through the sedimentary record highlight the roles played in the ree budget by fe mn coatings on detrital particles and by marine carbonates the predominant sources of nd during platform evolution are characterized by the nd isotope variations in the sediments the nonradiogenic values end t between 12 and 10 strongly suggest that the predominant source of nd on the platform was the continental crust through weathering and river inputs whereas some more radiogenic nd end t 5 values are more typical of the tethys seawater signature

isotopic and morphological features of fracture calcite from granitic rocks of the tono area japan a promising palaeohydrogeological tool this study aimed to develop a methodology for assessing the hydrochemical evolution of a groundwater system using fracture filling and fracture lining calcite fracture calcite in deep to ca 1000 m granitic rocks of the tono area central japan was investigated by optical and electron microscopy and chemical and isotopic analysis coupled with geological evidence these new data imply 3 main origins for the waters that precipitated calcite 1 relatively high temperature hydrothermal solutions precipitating calcite distinguished by 18osmow from 3 to ca 10 and with 13cpdb from ca 18 to 7 2 seawater probably partly of miocene age which precipitated calcite distinguished by 13cpdb of ca 0 and 18osmow ca 20 3 fresh water with a variable 13cpdb composition but which precipitated calcite distinguished by 13cpdb that was significantly ca 17 data for 14c suggest that at least some of the fresh water calcite formed within the last 50 ka the present day hydrogeological regime in the tono area is also dominated by fresh groundwater however the marine calcite of probable miocene age found at depth has shown no evidence for dissolution and many different calcite crystal forms have been preserved studies of other groundwater systems have correlated similar crystallographic variations with variations in the salinity of coexisting groundwaters when this correlation is applied to the tono observations the calcite crystal forms imply a similar range of groundwater salinity to that inferred from the isotopic data thus the present study suggests that even in presently low salinity groundwater systems calcite morphological variations may record the changing salinity of coexisting groundwaters it is suggested that calcite morphological data coupled with isotopic data could provide a powerful palaeohydrogeological tool in such circumstances

thermodynamic and kinetic constraints on reaction rates among minerals and aqueous solutions iv retrieval of rate constants and activation parameters for the hydrolysis of pyroxene wollastonite olivine andalusite quartz and nepheline

applications of fluorescence microscopy to study of pores in tight rocks observation of pore structures in thin section by traditional impregnation with blue dyed epoxy becomes difficult when the pores are smaller than about 1 micrometer and or linear in shape these types of pores are common in many low permeability gas reservoirs such as coal shale and tight sandstone incident light fluorescence microscopy can be used to observe small narrow pore structures in tight rocks this common medical technique can be adapted to petrography by staining the impregnation epoxy with fluorescent rhodamine b dye along with the usual blue dye and using an incident light microscope equipped for epifluorescence to observe the prepared thin section under excitation of green light at a wavelength of 5 400 angstroms rhodamine fluoresces a brilliant reddish orange clearly showing impregnated pore spaces a dichromatic interference filter in the light path passes the reddish orange light and blocks nonfluorescing mineral grains so that only the pore structure is visible fluorescing epoxy behaves as an emission source and even submicron size pores which may be narrower than the wavelengths of visible light become visible if they are impregnated the incident light configuration of the microscope also allows the observation of impregnated pore spaces in opaque materials such as coal fluorescence microscopy not only has potential for studying pore structures in tight sedimentary rocks but also can be applied to crystalline rock and other materials with narrow linear or small pores

hydrochemical disturbances measured in groundwater during the construction and operation of a large scale underground facility in deep crystalline rock in japan changes in the hydrochemical conditions of groundwater were evaluated following the construction of a large scale underground facility at the mizunami underground research laboratory miu japan the facility was constructed to a depth of 500 m in sedimentary and granitic rocks drawdown of the groundwater level in the range of several tens to hundreds of meters was observed up to hundreds of meters away from the shafts during the first ten years of facility construction and operation subsequent changes in groundwater chemistry occurred due to upconing of high salinity groundwater from the deepest part of the shaft and the infiltration of low salinity shallow groundwater we predict that future deep groundwater chemistry in the vicinity of the miu facility will resemble that of the present day shallow groundwater multivariate statistical analysis provides fundamental insights into such a site we found that the extent of hydrochemical variability related to miu construction and operation was dependent on the distance from the facility shafts and galleries and on hydrogeological compartmentalization resulting from lithological boundaries such as permeable conglomerates vs more compact lithological units and other features such as faults or clay layers we conclude that hydrochemical impact assessment of groundwater in low permeability rock is essential prior to the construction of such a facility this should include characterization of hydrogeological structures and compartments to propose suitable location of shafts and galleries

marine origin of savannah river estuary sediments evidence from radioactive and stable isotope tracers to determine the origin of sediments in the savannah river estuary we have measured 137 cs and stable isotope ratios of c n and s in suspended particles and bottom sediments at several sites in the savannah river and estuary and offshore on the continental shelf the 137 cs and stable isotope data were used with a two endmember mixing model to partition the suspended and bottom sediments at sites along a salinity gradient into riverine and marine fractions results from the 137 cs measurements indicated that 65 of inorganic sediments in suspension or in the top 5 cm of bottom deposits in the estuary were of marine origin stable carbon isotope ratios indicated that 74 of the organic sediments in suspension or on the bottom of the estuary were of marine origin except for sediments at the lowest salinity estuarine site

constancy of silicate mineral weathering rate ratios between natural and experimental weathering implications for hydrologic control of differences in absolute rates abstract inverse models which apportion watershed effluxes geochemical mass balance over estimated mineral surface area give weathering rates for individual silicate minerals e g feldspar 1 3 orders of magnitude slower than laboratory rates comparisons of rates calculated from several recent watershed geochemical mass balance studies with experimentally determined rates reveal that the ratio of mineral weathering rates for a given silicate mineral pair determined in an internally consistent field study equals the ratio of rates for the same minerals in any internally consistent set of laboratory experimental data thus the coefficient which corrects the weathering rate for any mineral from a laboratory data set to a field setting is identical to the corresponding coefficient for any other mineral in the same data sets the correction factor linking experimental and natural rates must be independent of composition physical e g hydrologic controls rather than compositional or chemical controls cause the difference between weathering rates in nature and the laboratory because flow in natural weathering profiles is spatially heterogeneous not all of the potentially available surface in natural systems actually participates in reactions with pore fluids

in situ stress field inversion and its application in mining induced rock mass movement abstract based on a series of experiments in numerical simulation the model boundary conditions for in situ stress field inversion and excavation are discussed study results indicate that roller boundary conditions are reasonable for the in situ stress field inversion before excavation simulation while as a closed system changing the roller boundary conditions to fixed boundary conditions in the subsequent excavation is optimal when the dimensions of the model borders are greater enough than the zone of influence of the excavation as a case study a comparative study of the mining induced ground movement in a steeply dipping mine is carried out in two different stress fields the results show that the mining induced ground movement in the high level tectonic stress field clearly differs from that in the ideal self weight stress field because of the steep occurrence and large thickness of the ore body the mining induced ground subsidence exhibits different characteristics at different mining stages in the practical tectonic environment further studies elucidate the causes of these differences and clarify the effects of high level tectonic stresses on rock mass movement and deformation finally based on gps monitoring results on the ground surface the current ground subsidence is evaluated and its development trend is predicted

strontium dissolved and particulate loads in fresh and brackish waters the baltic sea and mississippi delta a study was conducted of the isotopic composition and concentration of sr and of major elements in dissolved and suspended loads of fresh and brackish waters the purpose was to establish the contributions of different parent rocks and minerals to sr during weathering and transport and to identify the role of fe mn oxyhydroxides in the redistribution of sr in the water column during the sedimentary cycle studies were conducted on a profile across an oxic anoxic boundary in the baltic and on rivers covering behavior over an annual cycle in general the 87sr 86sr ratios differ between particulate and dissolved loads with more radiogenic sr in the particulate loads these differences are attributed to differential weathering of minerals where high rb sr minerals dominate the particulate load and low rb sr the dissolved load there is broad correlation of 87 sr 86 sr with k al in the suspended load the differences in 87 sr 86 sr between suspended and dissolved load are highly variable and are related to the fe or mn concentration on the particulates in samples with high fe al the difference becomes small a good correlation was found between sr al and fe al or mn al in the particulates both in brackish and fresh waters sr is removed from solution both in rivers and in the baltic sea whenever there is formation of fe mn oxyhydroxide particulates this precipitation greatly diminishes the difference in isotopic composition of the dissolved and suspended loads as the particles containing fe mn oxyhydroxides settle they dissolve in anoxic zones and release sr this provides a mechanism for sr redistribution in the water column sr is thus only quasi conservative in environments where fe mn oxyhydroxides form or dissolve from consideration of the isotopic differences in sr between dissolved and suspended loads it follows that the net sr input depends upon weathering characteristics of the contributing mineral phases changes in weathering mechanisms due to climate change may cause sr isotopic shifts in the marine environment

the influences of mining subsidence on the ecological environment and public infrastructure a case study at the haolaigou iron ore mine in baotou china the scope and extent of mine subsidence caused by exploitation of metal ores are usually low however in some cases owing to such factors as special geological conditions in ore body backward mining technology and unsound management systems exploitation of metal ores would also lead to a large area of mine subsidence causing great damages to the mining environment and infrastructure a serious mine subsidence happened in january 2007 at the haolaigou iron ore mine has caused a huge collapse pit on the earth s surfaces this provides a suitable place to study the influence of mine subsidence based on former research results a 3d geological model is constructed using the rock model software developed by authors group based on in situ geological conditions the range of orebody mining and the physical and mechanical parameters of rock and soil mass were determined by inverse analysis creep analysis of the collapse pit was also performed furthermore the elastoplastic and creep of the secondary collapse were computed and the final range of the collapse pit was predicted finally the influences of mining subsidence on the ecological environment and public infrastructure are discussed and control measures were proposed the results indicate that the collapse pit would not affect the road even if creep is considered however the secondary collapse would influence the road so the collapse pit should be dealt with as soon as possible

hydrogeochemical evolution of groundwaters with excess fluoride concentrations from dashtestan south of iran hydrogeochemical investigations were carried out in the dashtestan the eastern part of borazjan with a focus on fluoride content the study area is underlain by a complex geology that is dominated by three lithological units namely marl alluvial sediments and carbonate rocks to assess the major geochemical factors controlling the fluoride enrichment in water 37 groundwater and 12 surface water samples were collected from the three lithological units fluoride concentrations ranged up to 3 mg l and average concentrations varied from 1 12 in carbonate aquifers to 1 73 in alluvial aquifers to 1 82 mg l in marl aquifers to study the influence of rocks and soils on groundwater quality an additional 41 soil and rock samples were also taken and analyzed for fluoride the order of average fluoride content in both rocks and soils is marl alluvial sediments limestone which confirms that marl is a likely source of fluoride

cementation of kerogen rich marls by alkaline fluids released during weathering of thermally metamorphosed marly sediments part i isotopic c o study of the khushaym matruk natural analogue central jordan abstract the khushaym matruk site in central jordan may represent a natural analogue depicting the interaction of alkaline solutions with a clayey sedimentary formation or with clay rich confining barriers at the interface with concrete structures in waste disposal sites in this locality past spontaneous combustion of organic matter in a clayey biomicritic formation produced a ca 60 m thick layer of cement marble containing some of the high temperature phases usually found in industrial cements e g spurrite brucite and ca aluminate a vertical cross section of the underlying sediments was used in order to study the interaction between cement marbles and neighbouring clayey limestones under weathering conditions a thermodynamic approach of the alteration parageneses calcite jennite afwillite brucite and csh phases in the cement marbles constrains the interacting solutions to have had ph values between 10 5 and 12 over 3 m the sediments located beneath the metamorphic unit were compacted and underwent carbonation they display large c and o isotopic variations with respect to pristine sediments from the bottom of the section low 13c values down to 31 4 pdb show the contribution of co2 derived from the oxidization of organic matter and from the atmosphere to the intense carbonation process affecting that particular sedimentary level the size of the c isotopic anomalies their geometrical extent and their coincidence with the variations of other markers like the zn content the structure of organic matter the mineralogical composition all argue that the carbonation process was induced by the percolation of high ph solutions which derived from the alteration of cement marbles the temperature of the carbonation process remains conjectural and some post formation o isotopic reequilibration likely affected the newly formed carbonate carbonation induced a considerable porosity reduction both in fractures and matrixes the khushaym matruk site may have some bearing to the early life of a repository site when water saturation of the geological formations hosting the concrete structures is incomplete enabling simultaneous diffusion of alkaline waters and gaseous co2 in the near field

strontium isotope record of seasonal scale variations in sediment sources and accumulation in low energy subtidal areas of the lower hudson river estuary abstract strontium isotope 87sr 86sr profiles in sediment cores collected from two subtidal harbor slips in the lower hudson river estuary in october 2001 exhibit regular patterns of variability with depth using additional evidence from sediment ca sr ratios 137cs activity and al carbonate caco3 and organic carbon ocsed concentration profiles it can be shown that the observed variability reflects differences in the relative input and trapping of fine grained sediment from seaward sources vs landward sources linked to seasonal scale changes in freshwater flow during high flow conditions the geochemical data indicate that most of the fine grained sediments trapped in the estuary are newly eroded basin materials during lower base flow conditions a higher fraction of mature materials from seaward sources with higher carbonate content is trapped in the lower estuary results show that high resolution multi geochemical tracer approaches utilizing strontium isotope ratios 87sr 86sr can distinguish sediment sources and constrain seasonal scale variations in sediment trapping and accumulation in dynamic estuarine environments low energy subtidal areas such as those in this study are important sinks for metastable short to medium time scale sediment accumulation these results also show that these same areas can serve as natural recorders of physical chemical and biological processes that affect particle and particle associated material dynamics over seasonal to yearly time scales

the effects of a shaft excavation experiment on the hydrology of the tono research field japan abstract in order to understand the groundwater flow deep underground and its long term evolution in the future it is necessary to develop a comprehensive hydrological evaluation system including in situ investigation methodology instrumentation for measurement and an assessment method such as numerical simulation a hydrological evaluation system was developed and a project was planned to confirm the efficiency of the system the project named the shaft excavation effect project in which a shaft 6 m in diameter and 150 m in depth was excavated and the system was applied to evaluate the shaft excavation effect on groundwater flow the following results were obtained 1 1 the recharge rate from the unconsolidated formation into the rock mass underneath was calculated to be 0 57 mm day 2 2 the hydrogeological model was classified into 12 groups according to the results from a geological survey geophysical logging and in situ hydraulic tests 3 3 the predictive simulation and the subsequent observation showed good agreement namely the area where pore water pressure was considerably influenced by the excavation was within a range of 100 m around the shaft the inflow into the pre existing shaft and the drift was not affected by the excavation of the new shaft 4 4 the efficiency of the hydrological evaluation system has been confirmed

quantitative micro porosity and orientation analysis in soils and sediments a technique to quantify the fabric of soils and sediments involving image processing and analysis is described in this paper such techniques are becoming popular in the earth sciences but unlike most other studies which investigate the porosity of coarse grained sediments this method examines the fine porosity between clay size particles to be investigated the usual problems associated with thresholding a grey level image to provide the necessary binary image for analysis are partly overcome by the use of wiener filtering methods to remove much of the degradation inherent in all imaging systems a new algorithm based on the relative contrast histogram method is then used to determine the optimum value at which to set the threshold the micro porosity determined is in good agreement with gravimetric porosity measurements unlike normal methods once the procedure has been initiated no further action is required from the operator and the method can thus be used for batch processing of large numbers of images thereby enhancing the statistical reliability of the results extensions of the technique allow for the variation in micro porosity from one region of a specimen to another to be studied further by segmenting the original image into domains of sub parallel particles it is possible to examine the intra domain porosity contrary to expectations the porosity in horizontal domains is greater than that in the vertical domains

hydrochemical baseline condition of groundwater at the mizunami underground research laboratory miu abstract hydrochemical conditions up to depths of 1000 m below ground level around the mizunami underground research laboratory were investigated to construct a baseline condition model describing the undisturbed hydrochemical environment prior to excavation of the underground facilities at mizunami gifu japan groundwater chemistry in this area was classified into a na ca hco 3 type of groundwater in the upper part of sedimentary rock sequence and a na ca cl type of groundwater in the deeper part of the sedimentary rock sequence and basement granite the residence time of the groundwaters was estimated from their 14 c contents to be approximately 9 3 ka in the middle part of the sedimentary rock and older than 50 ka in the deep part of the granite the evolution processes of these groundwaters were inferred to be water rock interactions such as weathering of plagioclase dissolution of marine sulphate sulphide minerals and carbonate minerals in the na ca hco 3 type of groundwater and mixing between low salinity water in the shallow part and higher salinity water in the deeper part of the granite in the na ca cl type of groundwater the source of salinity in the deeper part of the granite was possibly a palaeo hydrothermal water or a fossil seawater that recharged in the miocene subsequently being modified by long term water rock interaction the cl depth trend in granitic groundwater changes at a depth of 400 m below sea level the hydrogeological properties controlling the groundwater flow and or mixing processes such as advection and diffusion were inferred to be different at this depth in the granite this hydrochemical conceptual model is indispensable not only when constructing the numerical model for evaluating the hydrochemical disturbance during construction and operation of the miu facility but also when confirming a hydrogeological model

analysis of the surface deformation characteristics and strata movement mechanism in the main shaft area of chengchao iron mine the surface deformation and strata movement caused by underground mining in a metal mine often exceeds the designed range which can destroy main shafts and other key structures causing huge economic losses and affecting production safety here the main shaft area of chengchao iron mine affected by tectonic stress is analyzed detailed monitoring data from the past 11 years were used to analyze the surface deformation characteristics and the strata movement mechanism the results show that the surface deformation in the main shaft area shows s shaped curve characteristics comprising a stable deformation stage a rapid deformation stage and a stable deformation stage the surface horizontal displacement vector in the main shaft area points to the western mining area indicating that the surface deformation in the main shaft area is mainly affected by underground mining in the western area from december 2007 to december 2009 the expansion of the movement line varepsilon 2 mm m was small in december 2009 the expansion of the movement line increased significantly the expansion law of the break line varepsilon 6 mm m was similar to that of the movement line furthermore the movement angle decreased significantly from december 2009 to december 2011 and the break angle sharply decreased from december 2010 to december 2012 the cantilever beam mechanics model revealed that the fractured width of footwall in the direction of the main shaft area was 266 m when exploitation reaches a horizontal depth of 600 m the fracture width is predicted to reach 402 m

comparative isotopic and chemical geochronometry of monazite with implications for u th pb dating by electron microprobe an example from metamorphic rocks of the eastern wyoming craton u s a polygenetic monazite grains in diverse precambrian crystalline rocks from the black hills south dakota have been analyzed in situ by ion and electron microprobe methods shrimp and emp to evaluate the accuracy and precision of emp ages determined using a new analytical protocol that incorporates improved background acquisition and interference corrections parallel evaluations were conducted by comparing emp chemical and shrimp isotopic ages at regional rock and grainscales the monazite data set includes 354 emp chemical analyses from 26 grains in six metamorphic rocks which resolve into 54 age composition domains and 31 shrimp isotopic ages from 13 grains in one of the rocks with six grains microanalyzed in common by the two methods the data set also includes monazite bearing garnets in two of the rocks whose isotopic compositions were analyzed using pb stepwise leaching pbsl methods both the emp and shrimp data sets reveal a continuum of apparent monazite ages spanning a 1790 1680 ma timeframe with a relatively high probability of ages at 1755 and 1715 ma that correspond spatially to core and rim domains pbsl ages of 1742 and 1734 ma obtained from monazite bearing garnet in two rocks are intermediate compared to the corresponding emp ages and are thereby interpreted as mixed ages emp data for two grains in the structurally deepest of the six rocks record 1785 and 1755 ma ages in the cores and higher y and lower th rims respectively and these results are duplicated by shrimp ages in these and or other grains from the same rock overall the emp shrimp and pbsl ages are internally consistent at the various scales of observation which serves to validate emp chemical dating as an accurate and precise method of discerning monazite age populations in polymetamorphic terrains the emp data set is interpreted geologically as res ecting multiple episodes of monazite growth that are provisionally related to known metamorphic events in the black hills taking the most precise emp data at face value it is possible to resolve the timing of the two older events at 1784 4 ma or 1786 6 ma and 1756 3 ma or 1753 4 ma with 95 con dence these events are considered to be related to sequential episodes of n directed thrusting and e w compression associated with paleoproterozoic crustal assembly in the mid continent a younger metamorphism related to granite intrusion known to have occurred at 1715 3 ma is dated independently at 1717 2 ma from the emp monazite ages

occurrence and formation of high fluoride groundwater in the hengshui area of the north china plain although high f groundwater was observed in the hengshui of the north china plain the depth dependence of groundwater f and its relation to aquifer sediments remains unknown both shallow groundwater and deep groundwater were collected for chemical and isotopic characterization sediments were taken from different depths down to 130 m for total element analysis and f form determination with sequential extraction procedure results show that f concentration ranges from 0 37 to 3 28 mg l and from 0 28 to 3 6 mg l in shallow and deep groundwater respectively high f water from shallow aquifers are of cl so4 na mg hco3 cl so4 na and so4 cl na mg types while hco3 so4 cl na and cl so4 na types are from deep aquifers high f waters are mainly found at the depths of 50 200 and 300 m along the flow path groundwater shows an increasing trend in f concentration from the northwest to the southeast isotopes of 18o and d in deep groundwater are more depleted in comparison with shallow groundwater suggesting that shallow and deep groundwater replenish through different ways with longer retention time of deep groundwater 13c of dissolved inorganic carbon are between 11 9 and 8 8 in shallow groundwater and between 10 6 and 7 5 in deep groundwater respectively which indicates that groundwater dic comes from both rock weathering and biodegradation of organic matter fluoride content in the sediment ranges from 140 to 1690 mg kg showing a decreasing trend with depth good correlations between f and al2o3 and fe2o3 are observed demonstrating that f contents in sediments are significantly influenced by the minerals containing fe2o3 and al2o3 in terms of adsorption sequential extraction procedure shows that exchangeable f form f1 and fe mn oxides bound f f3 generally decrease with depths while organic matter or sulfide bound f f4 keeps relatively stable and carbonate bound f f2 exhibits highly variable the relationships between f concentration and fe or mn imply that f in f1 is more inclined to be scavenged by fe and mn oxides hydroxides which have a stronger affinity for f although a variety of hydrogeochemical processes affected f concentrations dissolution precipitation is a vital process in the study area in comparison with shallow groundwater cation exchange may exhibit more significantly effect on f enrichment in deep groundwater competitive adsorption of hco3 and oh with f leads to the release of f from aquifer matrix into solution which increases groundwater f concentration evaporation is another control on f concentration especially in shallow groundwater

a leaning historical monument formed by underground mining effect an example from czech republic abstract as causes of underground mining activities subsidences and slope deformations are very important problems in most countries if the slope deformation or subsidence cannot be effectively controlled then it will cause damages on buildings particularly tall buildings and even a disaster however surface impact of underground mining activity is very well known and reasonably well understood as a result of the effect of underground mining activities many hazards undesired structural and environmental problems on the surface are being addressed in many countries in this article deformations on the church of st peter of alcantara which is one of the most dominant monuments of karvina city czech republic were identified and discussed by means of the effect of underground mining activities on the buildings the results of this article will be useful in order to better understand the nature and magnitude of displacements that can affect surface infrastructures

characteristics of an unusual highly alkaline water from the maqarin area northern jordan abstract an unusual highly alkaline natural water ph 12 5 is recorded in adits and wells from the maqarin area northern jordan it is a calcium hydroxide sulfate type of water rich in base metals concentration the hydration of lime is responsible for the high ph value of this water the high calcium and base metals concentration is related to the effect of spontaneous combustion of organic matter in the bituminous marl formation a low temperature transformation process is still active as a result of reaction of these waters with the rocks

numerical simulation of porosity and permeability evolution of mount simon sandstone under geological carbon sequestration conditions abstract a numerical model was developed with the use of reactive transport code crunchflow to estimate porosity permeability and mineral composition changes of mount simon sandstone under typical geological carbon sequestration conditions p 23 8 mpa and t 85 c the model predicted a permeability decrease from 1 60 md to 1 02 md for the mount simon sandstone sample in a static batch reactor after 180 days of exposure to co 2 saturated brine which is consistent with measured permeability results model predicted solution chemistry results were also consistent with laboratory measured solution chemistry data sio 2 am was the primary mineral that causes permeability decrease followed by kaolinite both sio 2 am formation and kaolinite formation were attributed to the dissolution of quartz and feldspar this study shows that the formation of sio 2 am and kaolinite in the pore space of host rock is possible under typical co 2 sequestration conditions sio 2 am and kaolinite precipitation at the co 2 plume extent could reduce the permeability of host rock and improve lateral containment of free phase co 2 contributing to overall security of co 2 storage

metallogeny of copper and iron deposits in the eastern yangtse craton east central china abstract the eastern yangtse craton of central to eastern china is an important fe cu metallogenic province based on studies of the regional geology and tectonic evolution this metallogenic belt is controlled by faults and aulacogens in the continental plate in the early yanshan epoch jurassic the dominant west northwest and east west lithospheric faults controlled the distribution of cu mo and au mineralization whereas in the late yanshan epoch cretaceous the north northeast and northeast lithospheric faults controlled cu fe mineralization in a mineral district the distribution of ore fields is under the dual control of basement fault s and near surface fault s based on the relation of ring and lineament faults to intrusions a three level model of vertical zonation is proposed systematic petrochemical studies of mesozoic igneous rocks and mineralization identify three subseries 1 a calc alkaline intermediate to silicic subseries rich in potassium 2 a calc alkaline intermediate to felsic subseries rich in sodium and 3 a calc alkaline intermediate to mafic subseries rich in sodium genetic types of ore deposits are diverse including fe and cu skarns cu porphyries fe ore magma injections ningwu luzong fe deposits from late orthomagmatic to pegmatitic pneumato hydrothermal and to mesothermal epithermal associated with subvolcanic rocks and remobilized sedimentary fe and or cu deposits the genetic types of ore deposits form two metallogenic series 1 a sedimentary metallogenic series active mainly in the paleozoic and 2 a magmatic hydrothermal metallogenic series consisting of three subseries active predominantly in the jurassic and cretaceous with the latter being more important in this region the superposition and compounding of these two metallogenic series contribute to many styles of mineralization in this mineral province

polycyclic aromatic hydrocarbon distribution within lower hudson river estuarine sediments physical mixing vs sediment geochemistry abstract sediments and porewaters from two cores one from the east river new york and one from newark bay new jersey were sampled for polycyclic aromatic hydrocarbons pahs and other geochemical markers including 210 pb specific activities despite what appears to be similar sources of pahs to sediments within each core as inferred by ratios of alkylated to non alkylated pahs and pah isomer ratios sediments and associated pahs have undergone distinctly different depositional processes at each site sediments from the core in the east river appear to have been subject to intense physically driven resuspension resulting in selective depletion of low molecular weight pahs within the core presumably due to processes such as enhanced desorption and scouring of particle surfaces although sediment pah concentrations were higher in the east river core compared to the newark bay core porewaters were depleted of the majority of pahs analysed in the east river core relative to the newark bay core precluding quantifying sediment porewater pah distribution coefficients in this core sedimentary variables such as c n ratio particle surface area and sedimentary soot carbon were not related to organic carbon normalized pah distribution coefficients k oc obs rather in the core from the newark bay site k oc obs were influenced by sediment mixing and porewater dissolved organic carbon doc results indicate that in urban coastal areas the physical factors influencing time scales of sediment resuspension and deposition may be of primary importance over particle geochemistry in determining whether pahs will likely equilibrate between sediments and pore waters

two dimensional reactive transport modeling of the alteration of a fractured limestone by hyperalkaline solutions at maqarin jordan abstract two dimensional reactive transport modeling of the maqarin eastern springs site a natural analogue for the alteration of a fractured limestone by high ph portland cement waters has been performed using the crunchflow code these 2d calculations included transport by advection dispersion diffusion along a single fracture and diffusion in the wall rock solute transport was coupled to mineral dissolution and precipitation a limited sensitivity analysis evaluated the effect of different values of primary mineral surface areas flow velocity and sulfate concentration of the inflowing high ph solution major secondary minerals include ettringite thaumasite c s h c a s h and calcite c s h c a s h precipitation is controlled by the dissolution of primary silicates ettringite precipitation is controlled by diffusion of sulfate and aluminum from the wall rock to the fracture with aluminum provided by the dissolution of albite calcite precipitation is controlled by diffusion of carbonate from the wall rock extents of porosity sealing along the fracture and in the fracture wall rock interface depend on assumptions regarding flow velocity and composition of the high ph solution the multiple episodes of fracture sealing and reactivation evidenced in the fracture infills were not included in the simulations results can qualitatively reproduce the reported decrease in porosity in the fractures and in the wall rock next to the fractures instances of porosity increase next to fractures caused by carbonate dissolution were not reproduced by the calculations

geomedical assessment of an area having high fluoride groundwater in southeastern turkey the high fluoride concentration in groundwater has been yet determined in two villages sarim and karatas of western anliurfa turkey where it is the only source of drinking water to assess medical and hydrogeological dimensions of this problem principally including fluoride concentrations as well as electrical conductivity temperature and ph values were measured in groundwater wells of 65 villages including these two villages on site and a dental examination was performed on 451 children the fluoride concentrations in the groundwater of four villages determined as greater than 1 20 mg l causing dental fluorosis among children of these villages results revealed that dental fluorosis cases can develop even at low fluoride levels finally the prepared geomedical map demonstrated that medical and hydrogeological evidences were compatible with each other

influence of reaction kinetics and mesh refinement on the numerical modelling of concrete clay interactions large quantities of cements and concretes need to be incorporated in geological disposal facilities for long lived radwaste an alkaline plume diffusing from an aged concrete ph 12 5 through argillite type rocks has been modelled considering feedback of porosity value variations on transport properties using the reactive transport code toughreact the mineralogical composition of the argillite is modified at the interface with the concrete diffusion of cementitious elements leads to rapid and strong porosity occlusion in the argillite numerical results show that both reaction rates and spatial refinement affect mineralogical transformation pathways the variations in porosity and the extension of the zone affected by the alkaline perturbation are compared at different times the major effects of mineral precipitation under kinetic constraints rather than local equilibrium are a delay in the porosity clogging and an increase in the extension of the alkaline perturbation in the clay formation the same time delay rise for the porosity occlusion also appears for the roughest spatial resolutions a simulation as representative as possible of temporal and spatial scales of cementation processes must then be supported by more comparative data such as long term experimental investigations or natural analogues

geochemistry of wellbore integrity in co2 sequestration portland cement steel brine co2 interactions geochemistry and wellbore integrity in co2 sequestration effective geologic sequestration of co2 requires long term storage with very low leak rates injection wells are an obvious leakage pathway for co2 because they perforate the confining caprock in addition sequestration sites are likely to use monitoring wells to assess performance and in the case of depleted oil and gas fields may contain 10s to 1000s of older operating and abandoned wells all wells may have leakage pathways due to faulty construction or other defects however it is the subject of this chapter to consider whether geochemical reactions induced by co2 could result in damage to wells and the development of leaks this concern is based on the thermodynamic incompatibility of co2 saturated fluids with the portland cement and steel used to prevent fluid migration to the surface portland cement is an alkaline substance with ph 12 5 and is not in equilibrium with co2 bearing fluids ph 6 low carbon steel used as well casing is subject to aggressive corrosion by carbonic acid as a result well integrity has been a central issue in risk analysis of sequestration sites gasda et al 2004 ipcc 2005 viswanathan et al 2008 nordbotten et al 2009 at the outset it is important to bear in mind that geochemical reactions alone do not yield insight into wellbore integrity which is governed primarily by the effective permeability of the portland cement seal and the mechanical integrity of the system thus the significance of chemical reactions must be considered with respect to their impact to changes in permeability or in strength there is an unfortunate tendency in the literature to not distinguish between reaction and impact often co2 reactions are described as degradation of cement or corrosion of cement without adequately defining what these terms

alteration of the callovo oxfordian clay from meuse haute marne underground laboratory france by alkaline solution ii modelling of mineral reactions abstract one of the french options for the final disposal of high level radioactive waste is a deep geological repository the callovo oxfordian formation in the meuse and haute marne france was proposed by the french agency for the management of radioactive wastes andra to be the site of a research laboratory in order to evaluate in situ the interaction between the host formation and the engineered barriers in the previous experimental part secondary minerals such as zeolites tobermorite and katoite have been observed after the alteration of the callovo oxfordian clay under alkaline conditions three different reactions of phyllosilicates alteration have been proposed as a function of both ph and chemical composition of the reacting solutions the aim of this work was to simulate the reaction between the callovo oxfordian clay and high ph solutions in order to validate the proposed alteration reactions from experimental data the thermodynamic modelling of stability relationships among minerals in the callovo oxfordian clay was performed using the solution speciation solubility modelling code kindis at 120 c for different chemical media naoh koh and ca oh 2 input data were the mineralogical composition of the

tracing interactions between natural argillites and hyper alkaline fluids from engineered cement paste and concrete chemical and isotopic monitoring of a 15 years old deep disposal analogue abstract samples of toarcian argillite were collected both next to and far from a cem ii cement paste and a cem ii concrete within the specific context of a 15 a old borehole located in the tournemire experimental platform aveyron france the objectives were evaluation of the mineralogical and geochemical changes of the claystone at the contact with the cementitious materials and determination of the spatial extent of the interactions the approach includes the examination of the mineralogical xrd sem tem chemical major trace rare earth elements and isotopic sr c o compositions of argillite whole rocks and of various soluble phases at two scales in the rock matrix p1 scale and along micro cracks p2 scale the two study scales outline nearly similar mineralogical modifications shown by the presence of ca silicate hydrates c s h and newly formed caco 3 within 10 15 mm of the cement paste and concrete chemical data from whole rock argillites indicate few changes in a slightly thicker zone 18 20 mm mainly consisting of an increase in the cao wt and a decrease in sr contents the other elementary contents remained quite constant except for mgo which suggests redistribution with precipitation of a mg rich mineral phase at 20 mm from cement paste concrete interface acetic acid leachates had more pronounced variations including a decrease of the total elementary content in the same geochemical disturbed zone gdz together with a significant increase of the sr isotopic ratios a combination of sr and c o isotopic patterns was used to distinguish the behavior of secondary cementitious phases in the clay rich rock i calcite dissolution and re precipitation is supported by c o isotopic data and ii c s h neoformation is evidenced by the 87 sr 86 sr ratios this tool also contributes to determine the origin of the fluids the proportion of newly formed c s h in the matrix and in the micro cracks of the argillite is modeled

self healing of cement fractures under dynamic flow of co2 rich brine fractures and defects in wellbore cement can lead to increased possibilities of co2 leakage from abandoned wells during geological carbon sequestration to investigate the physicochemical response of defective wellbore cement to co2 rich brine we carried out a reactive flow through experiment using an artificially fractured cement sample at a length of 224 8 mm a brine solution with dissolved co2 at a ph of approximately 3 9 was injected through the sample at a constant rate of 0 0083 cm3 s surface optical profilometry analysis and 3 d x ray microtomography imaging confirmed fracture closure and self healing behavior consistent with the measured permeability decrease visual inspection of the reacted fracture surface showed the development of reactive patterns mapping the flow velocity field inside the fracture as well as restricted flow toward the sample outlet the postexperiment permeability of the core sample was measured at half of its initial permeability a reactive transport model was developed with parameters derived from the experiment to further examine property evolution of fractured cement under dynamic flow of co2 rich brine sensitivity analysis showed that residence time and the size of initial fracture aperture are the key factors controlling the tendency to self healing or fracture opening behavior and therefore determine the long term integrity of the wellbore cement longer residence time and small apertures promote mineral precipitation fracture closure and therefore flow restriction this work also suggests a narrow threshold separating the fracture opening and self sealing behavior

geochemical tracers of sediment sources to san francisco bay river inflow and suspended sediment flux to san francisco bay are dominated by the sacramento and san joaquin river systems suspended sediments collected from rivers within the sacramento and san joaquin drainage basinsshow distinct chemical and sr isotope signatures reflecting their distinct bedrock lithologies concentrations of sm nd k and rb and 8 7 sr 8 6 sr ratios in suspended sediments increase from north to south in sierra nevada rivers and are significantly higher in the san joaquin drainage than in the sacramento drainage we show that variations in the geochemistry of fine grained detrital sediments cored beneath the bay can be used to assess the relative contributions of suspended sediment and inflow from these two major drainages in california for the sampled intervals over the past 1850 yr the proportion of suspended sediment from the sacramento drainage relative to the san joaquin drainage ranged between 5 and 85 average value of 55 compared with a modern value of 91 the current predominance of sediment entering san francisco bay from the sacramento drainage may be the result of greater trapping of sediments by reservoirs within the san joaquin drainage basin changes in the relative proportion of sediment from the sacramento and san joaquin drainages may reflect changes in the position of the storm track over california

rock alteration in alkaline cement waters over 15 years and its relevance to the geological disposal of nuclear waste the interaction of groundwater with cement in a geological disposal facility gdf for intermediate level radioactive waste will produce a high ph leachate plume such a plume may alter the physical and chemical properties of the gdf host rock however the geochemical and mineralogical processes which may occur in such systems over timescales relevant for geological disposal remain unclear this study has extended the timescale for laboratory experiments and shown that after 15 years two distinct phases of reaction may occur during alteration of a dolomite rich rock at high ph in these experiments the dissolution of primary silicate minerals and the formation of secondary calcium silicate hydrate c s h phases containing varying amounts of aluminium and potassium c a k s h during the early stages of reaction up to 15 months have been superseded as the systems have evolved after 15 years significant dedolomitisation mgca co3 2 2oh mg oh 2 caco3 co32 aq has led to the formation of magnesium silicates such as saponite and talc containing variable amounts of aluminium and potassium mg al k silicates and calcite at the expense of the early formed c a k s h phases this occured in high ph solutions representative of two different periods of cement leachate evolution with little difference in the alteration processes in either a koh and naoh or a ca oh 2 dominated solution but a greater extent of alteration in the higher ph koh naoh leachate the high ph alteration of the rock over 15 years also increased the rock s sorption capacity for u vi the results of this study provide a detailed insight into the longer term reactions occurring during the interaction of cement leachate and dolomite rich rock in the geosphere these processes have the potential to impact on radionuclide transport from a geodisposal facility and are therefore important in underpinning any safety case for geological disposal

assessing textural variation in laminated sands using digital image analysis of thin sections although between laminae parameter variations in sediments have been studied in the past measured parameters were generally limited to grain size distribution and total porosity the magnitude and directional characteristics of physical properties of laminated sediments also depend on the shape and orientation of particles packing pore size characteristics and properties of the pore network leaving out a complete characterization of granular sediment in models of physical properties could result in a systematic mismatch between modeled and measured values however tools for high resolution quantification of these spatial variable parameters are not readily available in order to provide such a tool an image analysis procedure is presented based on digital images of thin sections the procedure defines a sequence of rectangular measurement windows with their long sides oriented parallel to stratification and measures the sediment characteristics for each window logs of parameters values oriented perpendicular to stratification are thus created after verification of the image analysis procedure using comparative laboratory measurements the procedure is applied to two thin section images of unconsolidated fine grained laminated sands the quantitative variations observed in the logs of grain and pore characteristics correlate well with bedding observed on the original images overall the image analysis procedure proved to be a useful and versatile tool for quantifying variations of textural characteristics on sub lamina scale

a new method for quantitative petrography based on image processing of chemical element maps part i mineral mapping applied to compacted bentonites most natural rocks or engineered materials display a multi scale heterogeneity ranging from the nanometer to the centimeter their spatial textural heterogeneity can be approached from chemical element maps acquired using various techniques sem epma sxam synchrotron xrf tem depending on the chosen magnification chemical map processing that yields quantitative petrographic information is improved here according to newly developed mineral thresholding methods that accommodate mixtures and solid solutions the complex case of an mx80 compacted bentonite is used as a test case the 14 major chemical elements of this sample were mapped using an electron probe microanalyzer and chemical map processing yielded a quantitative map of the 18 mineral species of bentonite with a spatial resolution of a few micrometers the textural heterogeneity of the solid part of the sample is thus visualized and quantified on an area ranging between 0 1 1 cm2 the method also provides a complete modal analysis of the sample the methodology is expected to have broad applications in earth and materials sciences

investigation on the characteristics of overlying strata caving in the chengchao iron mine china in this study a comprehensive assessment of the overlying strata caving characteristics of mental mines is conducted for the non pillar sublevel caving method especially considering the geological features and rock mass characteristics in general the overlying strata caving process can be divided into four stages the intermittent roof caving stage the crack extension and surface subsidence stage the karst collapse stage and the mining induced collapse stage roof caving is an intermittent process with higher caving occurring in stronger rock masses and occurs more easily in weaker rock masses due to gaps generated in the overlying rock mass the bulking coefficient of the overlying strata is much greater than the laboratory measured value it also varies with the mining advance lines during the crack extension and surface subsidence stage the surface deformation is less extensive when the rock strength is greater and the gradient of surface deformation is lower when the rock mass integrity is lower thus higher mining height and lower rock mass quality result in greater surface deformation furthermore weak planes such as faults and joints can help to generate fissures in weathered rock masses these fissures create passageways for groundwater flow which accelerates crack extension and connection in reverse in addition surface collapses can be divided into karst collapses and mining induced collapses because a large number of fissures and a high karst rate create favorable conditions for karst collapse significant variations in groundwater levels can induce karst collapse at the surface with high negative pressure forming in the karst caves mining induced collapses are mainly related to the mining depth mining height and the properties of the overlying rock mass underground mining is a major factor in surface collapse and heavy rainfall can induce a delayed but sudden collapse

wellbore cement alteration during decades of abandonment and following co2 attack a geochemical modelling study in the area of potential co2 reservoirs in the pannonian basin abstract in east central europe the sedimentary rocks and saline reservoirs of the pannonian basin provide the greatest potential for geological sequestration of co2 however there is no knowledge about the integrity of cement casing and plugs in abandoned wellbores drilled in the last century which surround the potential co2 geological storage sites thermodynamic and kinetic batch and 1d kinetic reactive transport models have been built up in phreeqc to estimate the present composition of hydrated cement in different depths 106 1478 2136 and 2718 m of these abandoned wellbores and to access cement reactivity for the effect of potentially injected co2 the wellbore cements are all predicted to presently consist of mainly calcium silicate hydrate csh and portlandite but differences occur due to the stability of ettringite connected to the temperature of the geological environment with the depth the amount of potentially dissolved co2 increases which induces the breakdown of portlandite and csh in the cement and the major precipitation of calcite and amorphous silica the transformation affects the whole width of the cement casing after about 2 3 years in most of the depths however the calculated mass transfer among minerals indicate a 2 6 porosity drop which raises the attention to potential pore clogging this process significantly reduces the risks of abandoned wellbores when implementing co2 geological storage

reactive transport modeling of the interaction between a high ph plume and a fractured marl the case of wellenberg abstract in the context of the proposed low and intermediate level radioactive waste repository at wellenberg switzerland calculations simulating the interaction between hyperalkaline solutions and a fractured marl at 25 c have been performed the aim of these calculations is to evaluate the possible effects of mineral dissolution and precipitation on porosity and permeability changes in such a fractured marl and their impact on repository performance solute transport and chemical reaction are considered in both a high permeability zone fracture where advection is important and the wall rock where diffusion is the dominant transport mechanism the mineral reactions are promoted by the interaction between hyperalkaline solutions derived from the degradation of cement a major component of the engineered barrier system in the repository and the host rock both diffusive dispersive and advective solute transport are taken into account in the calculations mineral reactions are described by kinetic rate laws the fluid flow system under consideration is a two dimensional porous medium marl 1 porosity with a high permeability zone simulating a fracture 10 porosity crossing the domain the dimensions of the domain are 6 m per 1 m and the fracture width is 10 cm the fluid flow field is updated during the course of the simulations permeabilities are updated according to kozeny s equation the composition of the solutions entering the domain is derived from modeling studies of the degradation of cement under the conditions at the proposed underground repository at wellenberg two different cases have been considered in the calculations these 2 cases are representative of 2 different stages in the process of degradation of cement ph 13 5 and ph 12 5 in both cases the flow velocity in the fracture diminishes with time due to a decrease in porosity this decrease in porosity is caused by the precipitation of calcite replacement of dolomite by calcite and other secondary minerals brucite sepiolite analcime natrolite tobermorite however the decrease in porosity and flow velocity is much more pronounced in the lower ph case the extent of the zone of mineral alteration along the fracture is also much more limited in the lower ph case the reduction of porosity in the fractures would be highly beneficial for repository performance since it would mean that the solutions coming from the repository and potentially carrying radionuclides in solution would have to flow through low conductive rock before they would be able to get to higher conductive features the biggest uncertainty in the reaction rates used in the calculations arises from the surface areas of the primary minerals additional calculations making use of smaller surface areas have also been performed the results show that the smaller surface areas and therefore smaller reaction rates result in a smaller reactivity of the system and smaller porosity changes

age mapping and dating of monazite on the electron microprobe deconvoluting multistage tectonic histories high resolution x ray mapping and dating of monazite on the electron microprobe are powerful geochronological tools for structural metamorphic and tectonic analysis x ray maps commonly show complex th u and pb zoning that reflects monazite growth and overgrowth events age maps constructed from the x ray maps simplify the zoning and highlight age domains microprobe dating offers a rapid in situ method for estimating ages of mapped domains application of these techniques has placed new constraints on the tectonic history of three areas in western canada age mapping has revealed multiphase monazite with older cores and younger rims included in syntectonic garnet microprobe ages show that tectonism occurred ca 1 9 ga 700 m y later than mylonitization in the adjacent snowbird tectonic zone in new mexico age mapping and dating show that the dominant fabric and triple point metamorphism occurred during a 1 4 ga reactivation not during the 1 7 ga yavapai mazatzal orogeny in norway monazite inclusions in garnet constrain high pressure metamorphism to ca 405 ma and older cores indicate a previously unrecognized component of ca 1 0 ga monazite in all three areas microprobe dating and age mapping have provided a critical textural context for geochronologic data and a better understanding of the complex age spectra of these multistage orogenic belts

an imaging method for the porosity of sedimentary rocks adjustment of the pmma method example of a characterization of a calcareous shale abstract porosity of sedimentary rocks can be mapped and quantified by a new technique the 14c polymethylmethacrylate pmma method this imaging technique provides a porosity map drawn from physical information including porosity details stemming from 10 9 m dimensions on sample surface dimensions of up to 10 1 m the pmma porosity value is similar to that obtained by standard methods of porosity determination scanning electron microscope sem images of the same rock cross section reveal the relationships between pore spaces and bounding minerals this information is important in order to take porosity heterogeneities into account when interpreting various physical problems such as transport properties determined by laboratory measurements and in situ tracer experiments

in situ interaction of cement paste and shotcrete with claystones in a deep disposal context in situ sampling was performed in the andra meuse haute marne france underground research laboratory url allowing the study of two cement based materials claystone interfaces that have undergone 4 to 5 years of interaction the first interface concerned a shotcrete that was sprayed on the wall of an access drift at the laboratory level and the second one a class g cement paste that was injected in a borehole filled from the surface and was intercepted during the excavation of a new gallery in the first case the hydrodynamic conditions were controlled by the ventilation of the drift while in the second the cement paste and claystone materials were considered saturated and far from any mechanical perturbation a multi scale investigation was carried out to identify any evidence of alkaline perturbation in the cement based materials and the claystone chemical mineralogical and textural measurements were thus performed on the different materials in contact at the nanometer to a centimeter scale results showed that all the perturbations resulting from the geochemical contrast between the cement materials and the claystone were limited to a m scale on each side of the interfaces carbonation was observed in the cement materials leading to an opening or a clogging of the porosity according to the hydrodynamic conditions and the formulation of the cement material the distribution of the cation exchange population was also modified in the claystone in contact with the cement paste where a potassium saturation of the exchangeable fraction was identified the originality of the present work is that realistic field controlled samples from the andra url were studied hereby allowing the evaluation of the impact of natural heterogeneities of the in situ experimental conditions that is hydrodynamic conditions engineered damage zone mineralogical variations on the perturbations at the cement paste claystone interfaces an important result is that the clogging of porosity was not homogenous along the interfaces

coupled reactive transport model study of pore size effects on solubility during cement bicarbonate water interaction abstract we investigate the interaction between ca rich cementitious materials and bicarbonate rich clay pore water with the primary focus on pore size effect on the dissolution of the main hydration products portlandite and calcium silicate hydrates c s h and the precipitation of the secondary mineral calcite in a coupled reactive transport modelling framework the concept of pore size dependent solubility is extended to reactive transport modelling within cementitious materials for the two pore sizes 1e 6 and 1e 8 m considered here the effect of pore size on the solubility of portlandite c s h and calcite is different with portlandite and calcite less affected and c s h more affected due to a higher water c s h interfacial tension this difference leads to a different evolution of porosity at the interface of a cementitious material and bicarbonate enriched pore water between systems with large or small pores in systems with mixed large and small pores if diffusion through large pores is much faster than through small pores precipitation will only occur in large pores because the pore solution diffused into small pores has already become under saturated with respect to calcite due to precipitation in large pores first these results might also explain why cementation of porous rocks occurs preferentially in large pores relative to small pores observed in nature

mining induced ground deformation in tectonic stress metal mines a case study abstract in situ monitoring data of ground deformation in the western area of chenchao iron mine were collected over eight years results were analysed to conduct a preliminary investigation into the ground movement induced by underground mining 1 in the northeastern area the ratios of horizontal to vertical displacement increase gradually and the horizontal displacement may be as much as an order of magnitude larger than the vertical displacement at a large distance which induces regional horizontal movement curves of the ratio of horizontal to vertical displacement with respect to time can be categorised as fluctuation fallback convergence and increase types 2 in the mine road stack site and southern area around the high voltage tower ground deformation can be divided into two stages stable deformation and rapid deformation while in the southeastern area of the transport tunnel service shaft and road tunnel it can be divided into three stages stable deformation rapid deformation and subsequent stable deformation three categories are found in the time displacement curves folding s and linear types 3 the ground deformation of the footwall underwent a significant change in january 2010 because the large horizontal tectonic stress in the mine was released at that time surrounding rock masses were subjected to toppling deformation along the major structural plane in the northeastern area while tensile deformation occurred perpendicular to the major structural plane in the northern area

chemical dynamics of the st lawrence riverine system δdh2o δ18oh2o δ13cdic δ34ssulfate and dissolved 87sr 86sr chemical and stable isotope analyses of the st clair detroit niagara and st lawrence rivers st lawrence system and their tributaries show that the chemical and isotopic compositions of the waters are strongly controlled by the geology of their drainage basins tributaries draining the canadian shield have very low tds hco3 so42 ca2 mg2 no3 sr2 higher si and fetotal and high 87sr 86sr ratios 0 710 0 713 the grand and thames rivers that drain paleozoic limestones dolostones and evaporites are characterized by opposite attributes the st lawrence and the tributaries draining the canadian appalachians fall between these two endmembers the st clair detroit and niagara rivers do not show any pronounced seasonal variations in major component chemistry due to buffering by the great lakes in contrast pronounced seasonal variations characterize the lower st lawrence mainly because of significant tributary inputs into the overall water budget the d and 18o in the st lawrence range from 60 9 to 44 5 and from 8 5 to 6 1 smow respectively much heavier than the comparative values measured for the tributaries 92 8 to 58 3 and 13 1 to 8 5 this is a consequence of evaporative loss that over the residence time of water of 102 years equals about 7 of the water volume in the great lakes the strontium and sulfur isotopic values for the st lawrence system are relatively uniform with measured values from 0 70927 to 0 71112 for 87sr 86sr and from 4 3 to 5 6 for sulfate 34s their seasonal variations are also minor the strontium and sulfur fluxes of the st lawrence river are calculated to be 7 84 108 and 1 09 1011 mol a respectively the relative contributions of the great lakes tributaries and other sources to these fluxes are 73 16 11 for strontium and 64 13 23 for sulfur isotopic composition of dissolved inorganic carbon 13cdic in the st lawrence system ranges from 4 7 to 0 7 considerably heavier than the values for the tributaries 16 5 to 6 7 the light 13cdic values for the tributaries suggest that co2 from bacterial respiration plays an important role in the isotopic composition of riverine dic however in the main stem river s this bacterial signal is masked by isotopic equilibration with atmospheric co2 due to the long residence time of water in the great lakes seasonally the main stem river s have heavier 13c values in the fall than in the spring a consequence of preferential 12c consumption by photosynthetic plants in the epilimnion of the great lakes during the growth season in the down stream portion of the st lawrence river influx of isotopically light tributary waters causes progressive 13c depletion from 1 3 to 2 0 and 1 4 to 3 0 in the fall and spring respectively the total dic carbon flux of the st lawrence river is calculated to be 3 9 1011 mol a mass balance calculations show that the relative contributions of the great lakes tributaries decay of organic matter exchange with the atmosphere and dissolution of carbonates to this total dic flux are 81 13 2 6 10 in the spring and 83 15 2 4 0 in the fall respectively

15 years of in situ cement argillite interaction from tournemire url characterisation of the multi scale spatial heterogeneities of pore space evolution the solution selected by some countries to isolate radioactive wastes from the biosphere for up to one million years in deep geological repositories includes a multi barrier disposal design with steel canister bentonite and cement materials the geochemical contrast between such materials and the host rock formation creates perturbations potentially altering the confinement properties of the formation in this context the french institute for the radiological protection and nuclear safety irsn have developed an in situ experimental programme based on the study of cement argillaceous formation interfaces in their underground research laboratory at tournemire aveyron france an in situ engineered analogue of a cement clay rock interface which has undergone 15 years of interaction has been characterised such important interaction time for an in situ engineered analogue provides a bridge between laboratory derived data and the long time scale of safety assessment modelling as the mineralogical and petrological investigations have already been published this work presents for the first time a quantitative characterisation of the spatial distribution of the porosity in the cement and the clay rock in terms of time scale and design interfaces have been characterised using an autoradiography technique in addition to petrophysical measurements this technique enables visualisation and quantification of the spatial distribution of the porosity using 2d mapping of decimetric scale specimens thus autoradiographs allow highlighting the relationship between the field heterogeneities and the pore space evolution in each material in contact moreover the porosity measurements show a clogging of the porosity in the clay rock while the porosity increases in the cement the extension of the porosity evolution extends to a centimetre on both sides of the interface but is heterogeneously distributed in space as a function of the fissure network and interface geometries the connected fissure network visualised using autoradiography in the clogged area could permit solute e g radionuclide transport and may also be interpreted as an evolution of the mechanical properties of the clay rock formation upon alkaline perturbation this set of data with the spatial quantification of the porosity in both cement and clay materials will be useful to constrain reactive transport modelling and thus to predict long term evolution of an engineered barrier

variability in spatial distribution of mineral phases in the lower bowland shale uk from the mm to μm scale quantitative characterization and modelling the microstructure of a highly laminated lower bowland shale sample is characterized at the micron to millimeter scale to investigate how such characterization can be utilized for microstructure based modelling of the shale s geomechanical behavior a mosaic of scanning electron microscope sem back scattered electron bse images was studied mineral and organic content and their anisotropy vary between laminae with a high variability in fracturing and multi micrometer aggregates of feldspars carbonates quartz and organics the different microstructural interface types and heterogeneities were located and quantified demonstrating the microstructural complexity of the bowland shale and defining possible pathways for fracture propagation a combination of counting box dispersion covariance and 2d mapping approaches were used to determine that the total surface of each lamina is 3 to 11 times larger than the scale of heterogeneities relative to mineral proportion and size the dispersion approach seems to be the preferential technique for determining the representative elementary area rea of phase area fraction for these highly heterogeneous large samples supported by 2d quantitative mapping of the same parameter representative microstructural models were developed using voronoi tessellation using these characteristic scales these models encapsulate the microstructural features required to simulate fluid flow through these porous bowland shales at the mesoscale

seasonal variation of sediment deposition in the hudson river estuary abstract during and following the spring freshet rapid rates of sediment deposition were observed in the hudson river estuary side scan sonar surveys and sediment coring studies revealed a large amount of spatial variability in sedimentation within the estuary and a distinct seasonal progression during the freshet sediment was deposited in the seaward reaches of the estuary in the two month period after the freshet this sediment was eroded and sedimentation occurred 10 30 km further landward at the estuarine turbidity maximum etm zone the thickness of the new freshet deposit was as great as 40 cm in the etm indicating intense trapping and rapid deposition the location of this depocenter corresponded to a frontal zone where water column observations and modeling studies have indicated enhanced sediment trapping the mass of the new deposits was estimated at 300 000 metric tons during both 1998 and 1999 with similar spatial distributions in 1998 the estimated fluvial input was 560 000 metric tons significantly greater than the 120 000 metric tons estimated for 1999 thus the mass of the observed deposits appear to be more influenced by the redistribution of sediment within the estuary due to seasonal variations in erosion deposition conditions rather than by the direct input of sediment from the watershed

geochemical and mineralogical impacts of h2so4 on clays between ph 5 0 and 3 0 natural and constructed clay liners are routinely used to contain waste and wastewater the impact of acidic solutions on the geochemistry and mineralogy of clays has been widely investigated in relation to acid mine drainage systems at ph 1 0 the impact of h2so4 leachate characterized by ph 1 0 and potentially negative ph values on the geochemistry and mineralogy of clays is however not clear thus laboratory batch experiments were conducted on three natural clay samples with different mass ratios of smectite illite and kaolinite to investigate the impact of h2so4 on the geochemistry and mineralogy of aluminosilicates from ph 5 0 to 3 0 batch testing was conducted at seven ph treatments 5 0 3 0 1 0 0 0 1 0 2 0 and 3 0 using standardized h2so4 solutions for four exposure periods 14 90 180 and 365 d aqueous geochemical and xrd analyses showed increased dissolution of aluminosilicates with decreasing ph and increasing exposure period that smectite was more susceptible to dissolution than illite and kaolinite precipitation of an amorphous silica phase occurred at ph 0 0 and anhydrite precipitated in ca rich clays at ph 1 0 in addition global dissolution rates were calculated for the clays and showed good agreement to literature smectite illite and kaolinite dissolution rates which suggests global dissolution rates for complex clays could be determined from monomineralic studies a stepwise conceptual model of the impact of h2so4 on aluminosilicate geochemistry and mineralogy between ph 5 0 and 3 0 is proposed

association of hydrogeological factors in temporal variations of fluoride concentration in a crystalline aquifer in india the major part of groundwater in india is found in granitic aquifers fluoride in groundwater from a crystalline aquifer in a semi arid region of granitic rocks in india known as maheshwaram watershed was analyzed for spatial and temporal variability during 1999 2002 to assess the effect of hydrogeological factors on fluoride concentration samples were collected from 32 representative wells in the area for the pre and post monsoon seasons and analyzed for f content the chess computer program was used to calculate ionic activities of aqueous species and the mineral saturation index si for calcite and fluorite the gardenia computer program was used to calculate the recharge values in the study area the influences of dissolution kinetics of fluoride minerals and recharge from rainfall on fluoride concentration were of interest and results clearly indicate that fluoride content in groundwater depends on the interaction period of groundwater with host rock results could also be utilized for designing remedial measures particularly with dilution method in an optimal way

reaction and diffusion at the reservoir shale interface during co2 storage impact of geochemical kinetics abstract we use a reactive diffusion model to investigate what happens to co2 injected into a subsurface sandstone reservoir capped by a chlorite and illite containing shale seal the calculations simulate reaction and transport of supercritical sc co2 at 348 15 k and 30 mpa up to 20 000 a given the low shale porosity 5 chemical reactions mostly occurred in the sandstone for the first 2000 a with some precipitation at the ss sh interface from 2000 to 4000 a ankerite dolomite and illite began replacing mg fe chlorite at the sandstone shale interface transformation of chlorite to ankerite is the dominant reaction occluding the shale porosity in most simulations from 4000 to 7500 a this carbonation seals the reservoir and terminates reaction overall the carbonates calcite ankerite dolomite chlorite and goethite all remain close to local chemical equilibrium with brine quartz is almost inert from the point of its dissolution precipitation however the rate of quartz reaction controls the long term decline in aqueous silica activity and its evolution toward equilibrium the reactions of feldspars and clays depend strongly on their reaction rate constants microcline is closer to local equilibrium than albite the timing of porosity occlusion mostly therefore depends on the kinetic constants of kaolinite and illite for example an increase in the kaolinite kinetic constant by 0 25 logarithmic units hastened porosity closure by 4300 a the earliest simulated closure of porosity occurred at approximately 108 a for simulations designed as sensitivity tests for the rate constants these simulations also emphasize that the rate of co2 immobilization as aqueous bicarbonate solubility trapping or as carbonate minerals mineral trapping in sandstone reservoirs depends upon reaction kinetics but the relative fraction of each trapped co2 species only depends upon the initial chemical composition of the host sandstone for example at the point of porosity occlusion the fraction of bicarbonate remaining in solution depends upon the initial na and k content in the host rock but the fraction of carbonate mineralization depends only on the ca mg fe content since ankerite is the dominant mineral that occludes porosity the dissolved concentration of ferrous iron is also an important parameter future efforts should focus on cross comparisons and ground truthing of simulations made for standard case studies as well as laboratory measurements of the reactivities of clay minerals

hangingwall surface subsidence at the kiirunavaara mine sweden large scale surface subsidence has been experienced at the kiirunavaara mine since sublevel caving was implemented as a mining method surface disturbances are affecting part of the city of kiruna the railway and the power station continuous and discontinuous subsidences characterize the hangingwall deformation which is periodically monitored using surveying techniques and mapping of surface cracks a historic review of subsidence prognoses has been carried out and the results compared with the actual condition of the hangingwall the review showed discrepancies between different prognoses in addition limit equilibrium analyses indicated that break angles flatten while the mining depth increases however this tendency is not clear in the field where break angles show a large dispersion of values by using surveying data two different analyses have been performed the time dependent movements of the hangingwall have been described using time displacement curves and strain analysis has been performed for different sections of the hangingwall three different stages of the time displacement behavior have been identified and described it has been concluded that extension strain can reach values which may damage civil structures before surface crack can be observed

equilibrium partial pressure of co 2 in callovian oxfordian argillite as a func tion of relative humidity experiments and modelling having previously demonstrated that the mineral assemblage of claystone can impose its pco2 under saturated conditions we here study the effect of rock desaturation i e the evaporation of pore water on the partial pressure of co2 pco2 in callovian oxfordian argillite from the paris basin france in this new study which combines experiments at room temperature and geochemical modelling we examine the primary role of capillary forces on chemical equilibria for relative humidity values ranging between 50 and 100 in particular we are able without any fitting parameters to model the experimental decrease of pco2 as a function of decreasing water content in the argillite this application to a complex natural system not only confirms the theoretical concepts of geochemistry in capillary contexts but is promising with respect to other systems both natural soil rock and industrial ceramics granular material

the origin of fluoride rich groundwater in mizunami area japan mineralogy and geochemistry implications abstract the aim of this paper was to explore new factors that might be reasons for the occurrence of fluoride rich groundwater in the area around a construction site during the construction of two deep shafts of the mizunami underground research laboratory miu in mizunami city central japan a large quantity of groundwater with high fluoride concentration was charged into the shafts chemical investigation carried out during the excavation revealed that fluoride concentrations in the area around the miu site greatly exceeded those prescribed by japanese standards therefore the origin of fluoride ion was experimentally investigated samples were collected from the core of a deep borehole drilled in the study area the weathering and alteration levels of the collected granites varied greatly granitic powders were used to measure fluoride content in the granitic rock mass the fluoride content ranged between 200 and 1300 mg kg the powders were reacted with purified water for 80 days the results of water rock interaction showed granitic rock to be one of the main sources of fluoride rich groundwater in mizunami area fluoride concentrations in these solutions that were shaken for 80 days varied between 2 and 7 mg l this change may have occurred as a result of the spatial distribution of fluoride ions in the granite mass as evidenced by mineralogical analysis of fluoride content in several specimens x ray powder diffraction analysis of the rock before and after the water rock interaction tests manifested that the presence of fluorite mineral was relatively small compared to other minerals the degree of weathering and alteration might be an additional factor causing dissolution of fluoride rich minerals however it was difficult to interpret the change in fluorite composition by x ray diffraction analysis

investigation on the distribution characteristics of ground cracks in the chengchao iron mine china in this study a comprehensive assessment of the distribution characteristics of ground cracks in the chengchao iron mine was conducted by field investigation and monitoring in general ground cracks are initially distributed around collapse pits and subsequently extend outwards centered on the mined out area greater ground deformation leads to more developed ground cracks ground cracks can be divided into cut through crack deep crack and shallow crack based on their downward extension depths furthermore the formation of ground cracks is controlled by both underground mining and geological structures ground cracks can be divided into mining induced crack and tectonic crack based on their main influencing factors moreover many types of ground cracks are caused by different failure modes including tensile failure shear failure and mixed failure ground cracks can be divided into vertical shear crack vertical shear and horizontal tensile crack horizontal tensile crack horizontal shear crack and mixed crack based on their formation mechanisms in particular the movement line and the break line defined as e 2 mm m and 6 mm m respectively can be reasonably regarded as disturbance boundary and crack boundary in a metal mine the disturbance zone caused by underground mining can be divided into collapse zone break zone and movement zone based on the size of ground deformation and the characteristics of ground cracks increases in ground crack width and length exert different degrees of stress release on the rock masses outside and inside the crack thus increasing their deformation difference in addition the extension of ground cracks is related to the ground topography and the strength and integrity of the rock masses and soil cracks on hilltop are more developed than those on flat land and cracks will initially appear in rock mass and soil rather than on a concrete structure due to the lower strain resistance of the rock mass and soil however concrete structures are more sensitive to cracking than rock mass and soil because of the better integrity of concrete structures

a new method for quantitative petrography based on image processing of chemical element maps part ii semi quantitative porosity maps superimposed on mineral maps visualizing and quantifying the spatial heterogeneity of rock textures i e mineral and porosity distributions is of great interest in petrology or for understanding petrophysical properties spatial heterogeneities are not accurately revealed by usual techniques based on microscopy or bulk physical measurements detailed mineral mapping is already available from processing of chemical element maps acquired using an electron probe microanalyzer part i the present paper is devoted to developing a new coupled method for obtaining porosity maps from the same initial data according to the difference between measured and theoretical sums of oxide weight percentages a mean porosity is semi quantitatively estimated for each pixel of the map i e not fully absolute or accurate all pores including nanometer size ones are taken into account whereas a sample area of several square millimeters is analyzed spatial resolution of a few micrometers the textural heterogeneities are thus visualized from the complementary maps of solids and voids by superimposing these two maps both the mean porosity and a porosity histogram associated with each rock forming mineral are obtained such porosity measurements integrate the pore amounts within mono crystals larger than the x ray emission volume or between nanometer size crystals of a matrix when porosity changes are associated with a given mineral various crystal arrangements dissolution etc pluri modal distributions appear on porosity histograms thresholding each histogram mode then allows these processes to be localized we used the mx80 bentonite to test this methodology which represents a useful tool to study the local deformations and alteration of each rock forming mineral as well as to model transport properties

tracing the distribution of erosion in the brahmaputra watershed from isotopic compositions of stream sediments bank sediments and suspended loads of the brahmaputra river and its important tributaries were collected from the himalayan front to bangladesh along with most of the important tributaries chemical and isotopic compositions of the sediments are used to trace sediment provenance and to understand erosion patterns in the basin overall isotopic compositions range from 0 7053 to 0 8250 for sr and nd from 20 5 to 6 9 this large range derives from the variable proportions of sediments from himalayan formations with high sr isotopic ratios and low nd and transhimalayan plutonic belt with lower sr isotopic ratios and higher nd the latter are exposed to erosion in the tsangpo and in the eastern tributary drainages overall erosion of the himalayan rocks is dominant representing ca 70 of the detrital influx compositions of the brahmaputra main channel are rather stable between 0 7177 and 0 7284 for sr and between 14 4 and 12 5 for nd throughout its course in the plain from the siang tsangpo at the foot of the himalayan range down to the delta this stability despite the input of large himalayan rivers suggests that the siang tsangpo river represents the major source of sediment to the whole brahmaputra geochemical budget implies that erosion of the namche barwa zone represents about 45 of the total flux at its outflow before confluence with the ganga from only 20 of the mountain area higher erosion rates in the eastern syntaxis compared to the other himalayan ranges is related to the rapid exhumation rates of this region possibly triggered by higher precipitation over the far eastern himalaya and the high incision potential of the tsangpo river due to its very high water discharge

the dynamics of a partially mixed estuary measurements of velocity density and pressure gradient in the lower hudson river estuary were used to quantify the dominant terms in the momentum equation and to characterize their variations at tidal and spring neap timescales the vertical momentum flux assumed to be due mainly to turbulent shear stress was estimated indirectly based on the residual from the acceleration and pressure gradient terms the indirect estimates of stress compared favorably to bottom stress estimates using a quadratic drag law supporting the hypothesis that the tidal momentum equation involves a local balance between tidal acceleration pressure gradient and stress divergence estimates of eddy viscosity indicated that there was significant tidal asymmetry with flood tide values exceeding ebb values by a factor of 2 as a consequence of the asymmetry the vertical structure of the tidally averaged stress bore no resemblance to the tidally averaged shear in spite of the asymmetry of vertical mixing the tidally averaged estuarine circulation was found to depend simply on the intensity of bottom turbulence which could be parameterized by a rayleigh drag formulation based on the tidal velocity magnitude and the tidally averaged near bottom flow this seemingly paradoxical result indicates that the estuarine circulation can be modeled without detailed knowledge of the effective eddy viscosity only requiring an estimate of the bottom drag coefficient the tidal forcing conditions and the baroclinic pressure gradient a notable characteristic of this solution is an inverse dependence of the estuarine circulation on the amplitude of the tides

the effect of high ph alkaline solutions on the mineral stability of the boom clay batch experiments at 60 c abstract boom clay is currently viewed as a reference host formation for studies on deep geological disposal of radioactive waste in belgium the interactions between bulk rock boom clay and 0 1 m koh 0 1 m naoh 0 1 m ca oh 2 young cement water and evolved cement water solutions ranging in ph from 12 5 to 13 2 were examined as static batch experiments at 60 c to simulate alkaline plume perturbations which are expected to occur in the repository due to the presence of concrete both liquids and solids were investigated at specific times between 90 and 510 days in order to control the elemental budget and to search for potential mineralogical alterations also the clay fraction was separated from the whole rock boom clay at the end of each run and characterized for its mineralogical composition thereby the importance of the mineral matrix to buffer the alkaline attack and the role of organic matter to protect clay minerals were also addressed the results indicate that the degree of geochemical perturbation in boom clay is dependent on the initial ph of the applied solution together with the nature of the major cation in the reactant fluids the higher the initial ph of the media the stronger its interaction with boom clay no major non clay mineralogical alteration of the boom clay was detected but dissolution of kaolinite smectite and illite occurred within the studied experimental conditions the dissolution of clays is accompanied by the decrease in the layer charge followed by a decrease in the cation exchange capacity the highest toc values coincide with the highest total elemental concentrations in the leachates and correspondingly the highest dissolution degree however no quantitative link could be established between the degree of organic matter decomposition and clay dissolution

groundwater control and stability in an excavation in magnesian limestone near sunderland ne england abstract a case history is presented of a 22 m deep excavation for a storm sewage pumping station in the very variable and water bearing upper magnesian limestone adjacent to the english northeast coast considerable effort was expended during several phases of ground investigation to try to characterise the rock in engineering terms prior to construction in addition to conventional double barrel cored drilling valuable data on the condition of the weathered dolomites and limestones and on the localised nature of groundwater inflows were obtained by examining coastal exposures and from two trial shafts and a heading constructed as advanced works on the incoming sewer these helped in predicting many of the difficulties that might need to be overcame during construction a full scale pumping test at the site of the excavation also determined the bulk permeability of the strata and led to the conclusion that preconstruction groundwater control measures would be needed a peripheral grout curtain and basal grout blanket were constructed by low pressure techniques and their combined efficacy was tested by further pumping tests in the event construction of the excavation was relatively trouble free and was accompanied by maximum groundwater inflows of about 8 l s 1 at full depth induced internal erosion of the weathered rock was minimal some difficulties were caused however by the presence of a zone of gash breccia in one corner of the excavation and by persistent minor instability in the overlying glacial till these were overcome by special support measures overall the rock mass was less weathered and more competent than predicted by the initial ground investigation the coastal exposures subsequent triple tube coring and the two trial shafts helped to give a more realistic indication of the actual ground conditions

in situ investigations and reactive transport modelling of cement paste argillite interactions in a saturated context and outside an excavated disturbed zone abstract the interactions between cementitious materials and a clayey deep formation were investigated by studying the specific in situ context of the tournemire underground research laboratory url of the french institute for radioprotection and nuclear safety and by reactive transport modelling using the hytec code the study forms part of the safety assessment framework for the deep geological disposal of high to intermediate level long lived radioactive waste the in situ context investigated in the tournemire url corresponds to an engineered cemented borehole crosscutting the toarcian argillite formation the argillite cem ii cement paste contacts have been in place over 18 a and were sampled in a saturated context outside the excavated disturbed zone edz studies of the mineralogy xrd carbonatometry sem and tem petrophysical properties bet and geochemistry toc sr contents c o and sr isotopes eds analyses were carried out both on the argillite and on the cement paste in contact alteration of the cement paste is clearly expressed by decalcification and the opening of macroporosity these modifications are mainly due to the dissolution of portlandite the neoformation of c s h phases was identified in the first few micrometre next to the argillite interface along with secondary carbonates at the outermost contact geochemical measurements argue for the introduction of a sedimentary fluid into the macroporosity of the cement paste to explain the formation of part of these secondary phases this hypothesis is considered and tested using the hytec code which indicates that such transport could have occurred near the argillite cement paste contact at a very early stage after this stage the transport was reversed and cementitious fluids flowed from the cement paste to the argillite the changes brought about by these fluids are observed over a thickness of 11 13 mm in a so called black rim in which carbonates and c s h secondary phases are identified in the matrix of the sediment an illitization process may also be observed in this altered rim reaching its maximum development towards the inner part geochemical analyses show that the argillite disturbances are strictly confined to the black rim theoretical mineralogical profiles based on thermodynamic equilibria defined by the hytec code are in good agreement with the observations and are used to achieve a better understanding of transport processes

investigation of the ground movement due to underground mining at the jinshandian iron mine in china to investigate the mechanism responsible for mining induced ground movement at the jinshandian iron mine in china the vertical and horizontal deformations of the ground surface were monitored in situ over a period of 8 years the results were analyzed and combined with subsidence results derived from laser scanning measurements and collapse cracking behavior of the ground the results show that the horizontal displacement mainly occurs in the rock masses surrounding the mined voids moreover several obvious onset points can be found in the displacement time curves that are indicative of rapid increases in displacement currently the scope of the ground movement of the footwall is larger than that of the hanging wall this behavior is distinctive and distinguishes the jinshandian iron mine from others it can be attributed to the sliding toppling failure of the column shaped rock masses in the footwall under the combined effect of the in situ horizontal stress and high dip angles of the discontinuities

concepts of sediment deposition and accumulation applied to the continental shelf near the mouth of the yangtze river a fundamental understanding of how sedimentary strata form requires distinction between deposition and accumulation of particles deposition refers to the temporary emplacement of particles on the seabed accumulation is the net sum of many episodes of sediment deposition and removal the difference between rates of deposition and accumulation affects the ability of an environment to record sedimentary events radionuclide profiles of 234 th and 210 pb within the seabed can be used to determine 100 day deposition rates and 100 yr accumulation rates respectively on the continental shelf near the mouth of the yangtze river short term deposition rates are about 4 4 cm month whereas accumulation rates integrated over a century are an order of magnitude less about 5 4 cm yr

a tectono genetic model for porphyry skarn stratabound cu au mo fe and magnetite apatite deposits along the middle lower yangtze river valley eastern china abstract the middle lower yangtze river valley metallogenic belt yrb situated along the northern margin of the yangtze craton is characterized by porphyry skarn stratabound cu au mo fe deposits in the areas of uplift and magnetite apatite deposits in cretaceous fault basins following detailed field investigations and a review of published data we recognize two episodes of magmatism and mineralization in the yrb 1 156 137 ma high k calc alkaline granitoids associated with 148 135 ma porphyry skarn stratabound cu au mo fe deposits and 2 135 123 ma shoshonitic series associated with 134 9 122 9 ma magnetite apatite deposits a type granitoids and associated alkaline volcanic have a small age range from 126 5 to 124 8 ma and are temporally spatially and genetically associated with the second episode the geodynamic history of the yrb did not experience the paleozoic to mesozoic lithospheric thickening that took place in the north china craton this process is inferred to be linked to partial melting of the delaminated lower crust at high pressures resulting in the development of c type adakitic rocks the petrochemical and sr nd isotopic data show that both the shoshonitic series and a type granitoids are quite different from adakites with only some of the k calc alkaline granitoids having adakitic signatures previous ore genesis models were established based on an assumed relationship with adakites and a continuous tectono thermal evolution from 150 to 100 ma all data obtained for the middle lower yangtze river region consistently show that the tan lu regional strike slip fault zone initiated at 233 6 to 225 6 ma from the collision between the north china and yangtze cratons and was reactivated at ca 160 ma the tan lu fault was caused by the oblique subduction of the izanagi plate which along the yrb the low angle subducted slab and the overlying crust was disrupted or broken due to the disharmonious movement of the two blocks the high k calc alkaline granitoids magmas were derived from melting of the subducted slab with some input of crustal material these magmas were emplaced at the intersections between ne and ew trending faults and formed porphyry skarn stratabound cu au mo fe deposits between 156 and 137 ma after 135 ma the subducted plate changed its direction of motion to northeast now running parallel to the eurasian continental margin and leading to large scale continental extension the shoshonitic series and subsequent a type granitoids magmatism and the development of magnetite apatite ores in the yrb took place in both fault basins and ne trending rifts between 135 and 124 ma

experimental assessment of well integrity for co2 geological storage a numerical study of the geochemical interactions between a co2 brine mixture and a sandstone cement steel sample geologic storage of co2 is one option for avoiding co2 emissions from a large scale point source such as a thermal power plant and a gas refinery the alteration of well materials by co2 under reservoir conditions requires characterization because the wells are the main possible leakage pathways for co2 from a geological reservoir this paper presents a numerical modeling of interaction experiments involving a composite well sample formed from steel casing surrounded by portland cement itself surrounded by sandstone and co2 saturated brine at 10 mpa and 50 c during a period of up to 8 weeks as reported by mito et al 2015 a reactive transport model was developed to simulate diffusion of the co2 saturated brine in the well sample and the resulting successive dissolution precipitation reactions in the sandstone cement and steel the observed changes in mineralogy which primarily consist of dissolution of portlandite and ca rich csh phases and precipitation of calcite amorphous silica and zeolite and the associated evolution in brine composition were reproduced by the model a buffering role of sandstone on the cement degradation was evidenced thus avoiding the re dissolution of calcite usually observed in experiments with direct interaction between cement and co2 saturated brine interestingly the model results also noted a possible perturbation in the measured ph and ca content due to co2 outgassing during solution sampling the si behavior control linked with the uncertainty in zeolite stability is also discussed

engineering geology ground surface movement and fissures induced by underground mining in the jinchuan nickel mine the jinchuan nickel mine is the largest underground mine with cut and fill mining in china in 1999 there appeared evident ground surface movement and many ground fissures in jinchuan no 2 mine following an introduction to the engineering geology and mechanical properties of the rock mass in the jinchuan mine areas this paper reveals the features of the measured in situ stresses and puts emphasis on an analysis of the mechanism of surface movement and ground fissures induced by the underground mining with backfill it is indicated that both the fault structures and the alteration contact zones are well developed as the dominant engineering geological characteristics in the jinchuan mine areas the stress redistribution in surrounding rocks resulting from the mining the low stiffness of the filling body the existence of the void space and the influence of on going mining activities is the main reason for the occurrence of surface movement and ground fissures

a methodology based on strain analysis for identifying potential discontinuous deformation zones in sublevel caving mines abstract underground mining operations using the sublevel caving method often result in discontinuous ground deformations involving surface cracks determining the limit of the discontinuous deformation zone is important for the relocation of neighbouring residential areas mining infrastructure and the planning of underground mining operations the limit of the discontinuous deformation zone is characterised by the outermost surface crack which is a tensile crack when it occurs and is correlated with the horizontal ground tensile strain in this study a mathematical procedure combining the horizontal displacement as periodically monitored by total station and gps multiquadric radial basis function mq rbf interpolation and continuum mechanics is provided to calculate the strain state at any point on the ground then the relationship between a new tensile crack and horizontal ground tensile strain is studied to determine the criterion representing the presence of a new tensile crack this means that when the criterion at any point on the ground is satisfied the point will have the potential to crack based on this the potential discontinuous deformation zone where surface cracks may occur can be identified potential break angles at representative sections can then be determined a case study is presented to illustrate the results given by the above methodology the result shows that when major principal horizontal ground strain e1 at any point on the ground reaches the potential cracking major principal strain pcmps 6 mm m in this case study the point will have the potential to crack subsequently the area within the outermost contour of the pcmps can be defined as the potential discontinuous deformation zone moreover the approximate matching of the limits of potential discontinuous deformation zones and surface cracks verifies the reliability of the mathematical procedure and the rationality of the pcmps in identifying the discontinuous deformation zone additionally in this case study the potential break angles at two respective sections are significantly different indicating that the break angles should be further studied and care taken in design of works in these two zones respectively