iron hydroxide iron sulfate and hydrous silica coatings in acid mine tailings facilities a comparative study of their trace element composition abstract surface alteration layers often coat minerals in acid mine drainage systems and the characterization of their chemical composition is required to understand the uptake or release of potentially toxic elements samples with micrometer thick rock coatings were collected from bedrock in contact with three acidic tailings ponds and a small lake all located within the copper cliff mine tailings disposal area in sudbury ontario canada distribution and concentration of trace metals in the rock coatings were characterized with laser ablation inductively coupled plasma mass spectroscopy and micro x ray fluorescence spectroscopy the rock coatings are composed of goethite ferrihydrite schwertmannite jarosite and amorphous silica the latter phase is a product of the non stoichiometric weathering of the underlying siliceous rock layers within the coatings are distinguished on the basis of their atomic fe si ratios feo x coatings have fe si 4 1 si feo x coatings have fe si 4 1 to 1 1 and sio x coatings have si fe iron rich coatings feo x in contact with acidic tailings ponds ph x in contact with lake water at near neutral ph have similar trace metal concentrations than si feo x and sio x most likely the result of higher adsorption rates of metals at near neutral ph conditions high trace metal concentrations in si feo x and sio x are explained by the presence of jarosite group minerals which formed within si rich alteration layers through mixing of leached alkaline cations and trace elements from the underlying rock and fe 3 sulfate solutions from the pond calculated enrichment factors for trace metals and metalloids in the coatings relative to the pond indicate that the mobility for pb as cr and cu in the upper part of tailings ponds is commonly lower than the mobility for zn mn co and ni the environmental significance of these findings is discussed in terms of the attenuation of trace metals in the coatings and the widespread occurrences of silica gels and jarosite group minerals

distribution characterization and geochemical controls of elements of concern in uranium mine tailings key lake saskatchewan canada abstract the distribution of as mo ni and se in the aqueous and solid phases of u mine tailings in the deilmann tailings management facility dtmf located at the key lake mine in northern saskatchewan canada was defined using as discharged tailings samples collected monthly starting in 1996 and core samples collected from the dtmf from 3 locations on 3 occasions between 2004 and 2009 these data indicated that the dtmf can be divided into two geochemical zones tailings generated from the deilmann ore body between 1996 and 2000 and tailings from the mcarthur river ore body mined after july 2000 the deilmann tailings solids are generally characterized by greater elemental concentrations than those in the mcarthur river tailings particularly for as co and ni these elevated concentrations are attributed to the abundance of ni co as s minerals in this ore the mean aqueous concentrations of as mo ni and se are 3 7 23 2 0 14 and 0 02 mg l 1 respectively in the deilmann porewaters and 0 20 4 16 0 06 and 0 03 mg l 1 respectively in the mcarthur river porewaters similarly the mean as mo ni and se solid phase concentrations are 5 89 10 3 69 9 3 20 10 3 and 17 4 g g 1 respectively for the deilmann tailings and 440 13 6 551 and 3 03 g g 1 in the mcarthur river tailings statistically ph remained unchanged from the time of discharge while eh values have remained oxic with no significant change between the two tailings types over 15 a of residence time results from sequential extractions thermodynamic modeling and results of complimentary research indicated that ferrihydrite solubility is the dominant control on aqueous as concentrations and also plays a role in controlling dissolved mo ni and se

geochemistry of laterites stability of al goethite al hematite and fe super 3 kaolinite in bauxites and ferricretes an approach to the mechanism of concretion formation

uranyl phosphates and associated minerals in the koprubasi manisa uranium deposit turkey abstract the koprubasi uranium deposit is the largest known uranium deposits in turkey uranium mineralization is hosted in neogene fluvial sediments that consist of predominantly sandstone and conglomerate interlayered with siltstone claystone and mudstone sediments were primarily derived from metamorphic rocks adjacent to the basins of deposition with some volcanic contribution in the form of tuffs the sandstones and conglomerates are the most widespread sediments within the study area and host the majority of the u ore x ray diffraction xrd and scanning electron microscopy sem with energy dispersive x ray spectroscopy edx analysis were used to identify the ore and associated minerals the uranium ore minerals of the host sedimentary rocks are torbernite meta torbernite and meta autunite these coexist with jarosite various clays chlorite kaolinite illite and smectite and fe and mn hydr oxides with minor titanium oxide additionally quartz feldspars and a minor amount of mica muscovite and biotite are the main primary minerals in the sedimentary rocks the uranyl phosphates coat the surfaces of pebbles and some mineral grains fill cracks and are disseminated within the pores of the host sedimentary rocks uranyl phosphates are commonly associated with fe hydr oxides and clays although some were observed in millimeter or centimeter wide gaps within koprubasi sediments oxides of manganese are also locally abundant and associated with uranyl phosphates the uranyl phosphates in the sediments of the koprubasi area most likely formed when oxidizing groundwater moved through the host rock the common association of uranyl phosphates with fe hydr oxides and clays suggests that the precipitation of uranyl phosphate minerals is mainly due to adsorption of the uranyl and phosphate to the surface of fe hydr oxides and clays

the background concentrations of 13 soil trace elements and their relationships to parent materials and vegetation in xizang tibet china abstract the background concentrations of 13 soil trace elements copper cu lead pb zinc zn cadmium cd nickel ni chromium cr mercury hg arsenic as selenium se cobalt co vanadium v manganese mn and fluorine f from approximately 205 pedons in tibet china are reported here for the first time the 13 trace element concentrations follow an approximately log normal distribution while the mean concentrations of hg and se are lower and as is higher than the average concentration for all of china concentrations of the other trace elements are similar to the national average trace element concentrations are related to vegetation and human activity also played a notable role on the contents of trace elements in tibet the parent material relationship for all 13 soil trace element concentrations follows the pattern shale sandstone igneous rock limestone alluvial sediment glacial deposits lake sediments while for vegetation and human activity the concentration pattern is farmland shrub forests meadow prairie marsh and others the soil trace element concentrations on the tibetan plateau are related primarily to the parent material but were also affected by vegetation and human activity

redox control of arsenic mobilization in bangladesh groundwater abstract detailed hydrochemical measurements 34sso4 and 3h analyses were performed on 37 groundwater samples collected during february 1999 january and march 2000 from 6 locations in eastern and southeastern bangladesh to examine redox processes that lead to as mobilization in groundwater the study sites were chosen based on available nation wide as surveys to span the entire spectrum of as concentrations in bangladesh groundwater and to represent 3 of 5 major geological units of the ganges brahmaputra delta uplifted pleistocene terrace fluvial flood plain and delta plain arsenic was found to be mobilized under fe reducing conditions in shallow aquifers 50 g l or 0 7 m were always accompanied by high dissolved hco3 4 mm and were close to saturation with respect to calcite groundwater enriched in as 200 800 g l or 2 7 10 7 m and phosphate 30 100 m but relatively low in dissolved fe 5 40 m probably resulted from re oxidation of reducing as and fe enriched water this history was deduced from isotopic signatures of 34sso4 and 3h2o 3h to delineate the nature of redox changes for some of the reducing groundwaters in contrast as is not mobilized in presumed pleistocene aquifers both shallow 30 60 m and deep 150 270 m because conditions were not reducing enough due to lack of sufficient o2 demand

the mineralogy of arsenic in uranium mine tailings at the rabbit lake in pit facility northern saskatchewan canada a detailed investigation of the mineralogy of as in the tailings of the rabbit lake uranium ore processing facility was conducted the milling ore extraction process was sampled at three different locations to obtain information about when where and under what condition secondary as phases form these samples were compared with four samples of varying as content from the rabbit lake in pit tailings management facility tmf up to 20 as in the tailings are present in primary minerals that reach the tailings directly because they are not dissolved during the uranium extraction the remaining 80 constitute as that was dissolved during ore extraction and then re precipitated before being discharged into the tailings pond it was not possible to conclusively identify any individual re precipitated secondary as minerals in the rabbit lake tmf indirect evidence from sequential extraction analyses suggests the presence of an amorphous ca as phase and a possible but unlikely minor amount of an amorphous fe as phase however the close association between hydrous ferric oxide hfo and as could be clearly demonstrated hfo was identified to be 2 line ferrihydrite and its xrd pattern geometry indicates a substantial amount of adsorbed as this is in good agreement with sem tem and sequential extraction analyses that all showed the close association of hfo and as

geochemistry of arsenic in uranium mine mill tailings saskatchewan canada abstract the rabbit lake u mine in pit tailings management facility tmf 425 m long 300 m wide 91 m deep is located in northern saskatchewan canada the objectives of this study were to quantify the distribution of as phases in the tailings and evaluate the present day geochemical controls on dissolved as these objectives were met by analyzing pore fluid samples collected from the tailings body for dissolved constituents measuring eh ph and temperature of tailings core and pore fluid samples conducting sequential extractions on solid samples conducting geochemical modeling of pore fluid chemistry using available thermodynamic data and by reviewing historical chemical mill process records dissolved as concentrations in 5 monitoring wells installed within the tailings body ranged from 9 6 to 71 mg l pore fluid in the wells had a ph between 9 3 and 10 3 and eh between 58 and 213 mv sequential extraction analyses of tailings samples showed that the composition of the solid phase as changed at a depth of 34 m the as above 34 m was primarily associated with amorphous fe and metal hydroxides while the as below 34 m was associated with ca likely as amorphous poorly ordered calcium arsenate precipitates the change in the dominant as solid phases at this depth was attributed to the differences in the molar ratio of fe to as in the mill tailings below 34 m it was 4 the high ca as ratio during tailings neutralization would likely precipitate ca4 oh 2 aso4 2 4h2o type ca arsenate minerals geochemical modeling suggested that if the pore fluids were brought to equilibrium with this ca arsenate the long term dissolved as concentrations would range between 13 and 126 mg l

mineralogy and u pb pb pb and sm nd geochronology of the key lake uranium deposit athabasca basin saskatchewan canada the key lake deposit is one of several large high grade unconformity related uranium deposits located at the eastern margin of the athabasca basin in northern saskatchewan canada the deposit consists of the gaertner orebody now mined out and the deilmann orebody which is presently being mined in the past radiometric dating efforts yielded an age of oldest ore forming event of 1250 34 ma at the gaertner orebody and 1350 4 ma at the deilmann orebody this unlikely age difference called for further investigation innovative preparation techniques were used to separate the paragenetically oldest u mineral an anisotropic uraninite ore microscopy and u pb isotopic data show that the oldest event of uranium emplacement occurred simultaneously at the two orebodies at 1421 49 ma the primary ore forming phase was followed by younger generations of u mineralization and periods of remobilization sm nd data of key lake uraninite form an isochron corresponding to an age of 1215 ma this is interpret

microscale mineralogical characterization of as fe and ni in uranium mine tailings abstract uranium u ores can contain high concentrations of elements of concern eocs such as arsenic as and nickel ni present in sulfide and arsenide minerals the u in these ores is often solubilized by adding h2so4 to attain a ph 1 under oxic conditions this process releases some eocs from the primary minerals into solution the barren raffinate solution remaining after u extraction is subsequently neutralized with ca oh 2 to a terminal ph of 10 5 resulting in a reduction in the aqueous concentrations of the eocs these neutralized raffinates are mixed with the non reacted primary minerals and discharged as tailing into tailings management facilities tmfs to aid in the accurate characterization and quantification of the mineralogical controls on the concentrations of eocs in the tailings porewater their spatial distribution and speciation were studied at the micron scale in tailings samples collected from the deilmann u tailings management facility dtmf northern saskatchewan canada backscattered electron images of the tailings samples generated using an electron microprobe show the presence of nodules 10 200 m size surrounded by bright rims wavelength dispersive spectrometric wds and synchrotron based micro x ray fluorescence xrf elemental mapping show that the nodules are dominated by ca and s as gypsum and the bright rims are dominated by fe as and ni micro x ray absorption near edge structure xanes spectra collected within and near the rims indicate that the fe and ni are present mainly in the 3 and 2 oxidation states respectively for as the 5 oxidation state dominates but significant amounts of the 3 oxidation state are present in some areas linear combination fit analyses of the k edges for the fe as and ni xanes spectra to reference compounds suggest the fe in the rims is present as ferrihydrite with as and ni are adsorbed to it energy dispersive spectrometric eds data indicate that isolated highly reflective particles distributed throughout the tailings matrix are primary as cu fe and ni bearing minerals geochemical modeling of the neutralization process shows that the nodules gypsum formed at ph 1 and acted as a substrate for the precipitation of ferrihydrite at ph 3 4 the as and ni subsequently adsorb to the ferrihydrite overall the microscale data suggest that the as and ni adsorbed onto the ferrihydrite should remain stable for many years and continue to the control the fe as and ni concentrations in the tailings porewater

alteration of as bearing phases in a small watershed located on a high grade arsenic geochemical anomaly french massif central at a watershed scale sediments and soil weathering exerts a control on solid and dissolved transport of trace elements in surface waters and it can be considered as a source of pollution the studied subwatershed 1 5 km sup 2 was located on an as geochemical anomaly the studied soil profile showed a significant decrease of as content from 1500 mg kg sup 1 in the 135 165 cm deepest soil layer to 385 mg kg sup 1 in the upper 0 5 cm soil layer directly in the stream suspended matter and the 63 micro m fraction of bed sediments had as concentrations greater than 400 mg kg sup 1 in all these solid fractions the main representative as bearing phases were determined at two different observation scales bulk analyses using x ray absorption structure spectroscopy xas and microanalyses using scanning electron microscope sem and associated electron probe microanalyses epma as well as micro raman spectroscopy and synchrotron based micro scanning x ray diffraction micro sxrd characterization three main as bearing phases were identified i arsenates mostly pharmacosiderite the most concentrated phases as in both the coherent weathered bedrock and the 135 165 cm soil layer but not observed in the river solid fraction ii fe oxyhydroxides with in situ as content up to 15 4 wt in themore deepest soil layer and iii aluminosilicates the least concentrated as carriers the mineralogical evolution of as bearing phases in the soil profile coupled with the decrease of bulk as content may be related to pedogenesis processes suggesting an evolution of arsenates into as rich fe oxyhydroxides therefore weathering and mineralogical evolution of these as rich phases may release as to surface waters less

the first stage in the formation of the uranium deposit of arlit niger role of a new non continental organic matter abstract the uranium deposits of arlit are located in fluvial sandstone rich in organic matter of continental origin type iii deposited in palaeochannels previous studies on arlit deposits documented that organic matter of continental origin type iii was the main contributor to the reduction of uranium from the oxidation state of uranium vi u vi to uranium iv u iv this study shows that migrated oils of non continental origin strongly contributed to the genesis of uranium mineralization the petrographic analyses showed that i solid bitumen resulting from the polymerization of migrated oils is present in abundance in the porosity of the sandstone and fractures at the level of the channels of the tarat formation tamou takriza southern taza and guezouman formation mine sector of akouta and ii uranium mineralization is mainly associated with this migrated organic matter currently expressed in the form of solid bitumen the association occurs at an infra micrometric scale in the solid bitumen the geochemical analysis rock eval py gc ms and gc ms and the analysis of different indicators and biomarkers n alkanes pr ph steranes indicate the presence of a second organic matter with a different signature to type iii the oils present in the porosity of the sandstone of the guezouman and tarat formations confirm that channels of these two formations are the traps of the oil migration

a slow thrust slip event following the two 1996 hyuganada earthquakes beneath the bungo channel southwest japan we report a slow thrust slip event that occurred beneath the bungo channel region southwestern japan on oct and dec 1996 two hyuganada earthquakes both mw 6 7 followed by afterslips occurred in addition a crustal movement characterized by an extremely slow rise was observed around the bungo channel about 200 km north from the epicenters and continued for about 300 days long assuming a slow slip on the plate boundary we estimate its duration and surface displacements from gps time series data by curve fitting and then determine the fault slip distribution we found that a slow slip without any earthquakes continued for nearly one year and released the seismic moment comparable to that of the hyuganada earthquakes occurrence of the slow thrust slip event suggests that this kind of event may be a characteristic mode of stress release at a transition region of interplate coupling

arsenic readily released to pore waters from buried mill tailings abstract at the mcclean lake operation in the athabasca basin of northern saskatchewan the untreated acid raffinate solutions associated with u mill tailings contain up to 700 mg l dissolved as to reduce the concentration of as and other contaminants in acid tailing slurries at the jeb mill at mcclean lake ferric sulfate may be added to the acid raffinates to assure that their molar fe as ratio equals or exceeds 3 tailings slurries are then neutralized with lime to ph 4 and subsequently to ph 7 8 the neutralized tailings contain minerals from the original ore which are chiefly quartz illite kaolinite and chlorite and precipitated secondary minerals that include gypsum scorodite annabergite hydrobasaluminite and ferrihydrite most of the as is associated with the secondary arsenate minerals scorodite and annabergite however a few percent is adsorbed and or co precipitated mainly by ferrihydrite of major concern to provincial and federal regulators is the risk that significant amounts of as might be released from the tailings to pore waters after their subaqueous disposal in the tailings management facility a laboratory study was performed to address this issue measuring readily desorbed as using a method known as equilibrium partitioning in closed systems epics the epics method was selected because it employs a leaching solution that except for its as concentration is identical in composition to the neutralized raffinate in contact with the tailings laboratory experiments and modeling results demonstrated that the as that could be readily released to pore waters is about 0 2 of the total as in the tailings long term such releases may contribute no more than a few mg l of dissolved as to tailings pore waters

hydrothermally precipitated mixed layer illite smectite in recent massive sulfide deposits from the sea floor mixed layer illite smectite i s in recent massive sulfide deposits from a seamount near the east pacific rise has been studied by x ray powder diffraction xrd and scanning and transmission electron microscopy sem tem the i s fills pore space between quartz and sulfides and xrd and tem analyses indicate that the i s contains 25 45 smectite with r1 type ordering isisis microprobe and analytical electron microscope analyses indicate a rectorite like composition k being the dominant interlayer cation the occurrence of the i s within a hydrothermally precipitated sulfide deposit the pore filling texture and the internal structure of the i s are all consistent with direct precipitation from hydrothermal solutions direct precipitation of i s from solution has two important implications first some sericite in ancient volcanogenic massive sulfide deposits may have similarly originated as hydrothermal precipitates rather than as alteration products with implications for mobility and transport of al second direct precipitation of r1 ordered i s from fluid implies that during diagenetic evolution of smectite to illite the sequence of smectite random i s ordered i s illite may not be followed

understanding of hydraulic properties from configurations of stochastically distributed fracture networks a systematic investigation of the effect of configurations of stochastically distributed fracture networks on hydraulic behaviour for fractured rock masses could provide either quantitative or qualitative correlation between the structural configuration of the fracture network and its corresponding hydraulic behaviour and enhance our understanding of appropriate application of groundwater flow and contaminant transport modelling in fractured rock masses in this study the effect of block sizes intersection angles of fracture sets standard deviations of fracture orientation and fracture densities on directional block hydraulic conductivity and representative elementary volume is systematically investigated in two dimensions by implementing a numerical discrete fracture fluid flow model and incorporating stochastically distributed fracture configurations it is shown from this investigation that the configuration of a stochastically distributed fracture network has a significant quantitative or qualitative effect on the hydraulic behaviour of fractured rock masses compared with the deterministic fracture configurations that have been extensively dealt with in a previous study this investigation is expected to be more practical and adequate since fracture geometry parameters are inherently stochastically distributed in the field moreover the methodology and approach presented in this study may be generally applied to any fracture system in investigating the hydraulic behaviours from configurations of the fracture system while establishing a bridge from the discrete fracture network flow modelling to equivalent continuum modelling in fractured rock masses copyright 2007 john wiley sons ltd

on the cause of long period crustal movement abstract it has been found by continuous observation in the vaults of crustal movement observatories that the progress of crustal deformation is accompanied by a long period fluctuation the migration of this fluctuation between the adjacent stations and its simultaneity over a wide area has also been recognized some interpretations of the cause have been proposed from the viewpoint that fluctuations originate substantially from the tectonic source in this paper it is concluded that this long period strain fluctuation is fairly well explained by precipitation changes at each site the simultaneity may be explained by the identical precipitation conditions over a wide area while the migration may be deceptive attributed to the differences in the response to the precipitation at each station in other words prior to the discussion of the long period crustal movement in relation to tectonics the effect of precipitation on the crustal strain at that station should be carefully examined

arsenic mobility in mildly alkaline drainage from an orogenic lode gold deposit bralorne mine british columbia abstract the historical 1932 1971 bralorne mine produced over 87 million grams of au from an archetypal orogenic lode gold deposit in southwest british columbia high concentrations of as in mine drainage however represent an on going environmental concern prompting a detailed study of effluent chemistry the discharge rate at the mine portal was monitored continuously over a fourteen month period during which effluent samples were collected on a quasi weekly basis water samples were also collected on synoptic surveys of the adit between the portal and the main source of flow in the flooded workings total concentrations of as in the mildly alkaline ph 8 7 portal drainage average 3034 g l whereas at the source they average 5898 g l as emergent waters from the flooded workings flow toward the portal their dissolved oxygen content and ph increase from 0 to 10 mg l and from 7 7 to 9 respectively near the emergence point dissolved fe precipitates rapidly sorbing both as iii and as v with increasing distance from the emergence point dissolved as iii concentrations drop to detection limits through sorption on hydrous ferric oxide and through oxidation to as v concentrations of dissolved as v on the other hand increase and stabilize reflecting lower sorption at higher ph and the lack of available sorbent nonetheless based on synoptic surveys approximately 35 of the source as load is sequestered in the adit resulting in as sediment concentrations averaging 8 5 wt the remaining average as load of 1 34 kg d is discharged from the portal partitioning of as v between dissolved and particulate phases in portal effluent is characterized by a sorption density of 0 37 mol as mol fe 1 and by a distribution coefficient k d of 130 l g hfo the relatively high sorption density may reflect co precipitation of as with fe oxyhydroxides rather than a purely adsorption controlled process results of this study show that the as self mitigating capacity of drainage from orogenic lode gold deposits may be poor in high ph and fe limited settings

source and fate of inorganic solutes in the gibbon river yellowstone national park wyoming usa ii trace element chemistry the gibbon river in yellowstone national park receives inflows from several geothermal areas and consequently the concentrations of many trace elements are elevated compared to rivers in non geothermal watersheds water samples and discharge measurements were obtained from the gibbon river and its major tributaries near norris geyser basin under the low flow conditions of september 2006 allowing for the identification of solute sources and their downstream fate norris geyser basin and in particular tantalus creek is the largest source of many trace elements al as b ba br cs hg li sb tl w and rees to the gibbon river the chocolate pots area is a major source of fe and mn and the lower gibbon river near terrace spring is the major source of be and mo some of the elevated trace elements are aquatic health concerns as sb and hg and knowing their fate is important most solutes in the gibbon river including as and sb behave conservatively or are minimally attenuated over 29 km of fluvial transport some small attenuation of al fe hg and rees occurs but primarily there is a transformation from the dissolved state to suspended particles with most of these elements still being transported to the madison river dissolved hg and rees loads decrease where the particulate fe increases suggesting sorption onto suspended particulate material attenuation from the water column is substantial for mn with little formation of mn as suspended particulates

trace metal and as solid phase speciation in sulphide mine tailings indicators of spatial distribution of sulphide oxidation in active tailings impoundments abstract redistribution of potentially harmful metals and as was studied based on selective extractions in two active sulphide mine tailings impoundments in finland the hitura tailings area contains residue from ni ore processing while the luikonlahti site includes tailings from the processing of cu co zn ni and talc ores to characterize the element solid phase speciation with respect to sulphide oxidation intensity and the water saturation level of the tailings drill cores were collected from border zones and mid impoundment locations the mobility and solid phase fractionation of ni cu co zn cr fe ca al as and s were analysed using a 5 step non sequential parallel selective extraction procedure the results indicated that metal redistribution and sulphide oxidation intensity were largely controlled by the disposal history and strategy of the tailings sorting exposure of sulphides due to delayed burial impoundment structure and water table and reactivity of the tailings metal redistribution suggested sulphide weathering in the tailings surface but also in unsaturated proximal areas beside the earthen dams and in water saturated bottom layers where o 2 rich infiltration is possible sulphide oxidation released trace metals from sulphide minerals at both locations in the hitura tailings with sufficient buffering capacity ph remained neutral and the mobilized metals were retained by secondary fe precipitates deeper in the oxidized zone in contrast sulphide oxidation induced acidity and rise in the water table after oxidation apparently remobilized the previously retained metals in luikonlahti in general continuous disposal of tailings decreased the sulphide oxidation intensity in active tailings unless there was a delay in burial and the reactive tailings were unsaturated after deposition

alteration adsorption and nucleation processes on clay water interfaces mechanisms for the retention of uranium by altered clay surfaces on the nanometer scale abstract nano scale processes on the solid water interface of clay minerals control the mobility of metals in the environment these processes can occur in confined pore spaces of clay buffers and barriers as well as in contaminated sediments and involve a combination of alteration adsorption and nucleation processes of multiple species and phases this study characterizes nano scale processes on the interface between clay minerals and uranyl bearing solution near neutral ph samples of clay minerals with a contact ph of 6 7 are collected from a u mill and mine tailings at key lake saskatchewan canada the tailings material contains cu as co mo ni se bearing polymetallic phases and has been deposited with a surplus of ca oh 2 and na2co3 slaked lime small volumes of mill process solutions containing sulfuric acid and u are occasionally discharged onto the surface of the tailings and are neutralized after discharge by reactions with the slaked lime transmission electron microscopy tem in combination with the focused ion beam fib technique and other analytical methods sem xrd xrf and icp oes are used to characterize the chemical and mineralogical composition of phases within confined pore spaces of the clay minerals montmorillonite and kaolinite and in the surrounding tailings material alteration zones around the clay minerals are characterized by different generations of secondary silicates containing variable proportions of adsorbed uranyl and arsenate species and by the intergrowth of the silicates with the uranyl minerals cuprosklodowskite cu uo2 2 sio3oh 2 h2o 6 and metazeunerite cu uo2 aso4 2 h2o 8 the majority of alteration phases such as illite illite smectite kaolinite and vermiculite have been most likely formed in the sedimentary basin of the u ore deposit and contain low amounts of fe 10 at formed most likely in the limed tailings at high contact ph 10 5 and their structure is characterized by a low degree of long range order adsorption of u and nucleation of metazeunerite and cuprosklodowskite are strongly controlled by the presence of the adsorbed oxy anion species arsenate and silica on the fe enriched silicates heterogeneous nucleation of nano crystals of the uranyl minerals occurs most likely on adsorption sites of binary uranyl arsenate and silica complexes as well as on ternary uranyl arsenate or uranyl silicate complexes the uranyl minerals occur as aggregates of misoriented nano size crystals and are the result of supersaturated solutions and a high number of nucleation sites that prevented the formation of larger crystals through oswald ripening the results of this study provide an understanding of interfacial nano scale processes between uranyl species and altered clay buffers in a potential nuclear waste repository as similar alteration conditions of clays may occur in a multi barrier system

clay mineral weathering and contaminant dynamics in a caustic aqueous system ii mineral transformation and microscale partitioning microscopic and spectroscopic studies were conducted to assess mineral transformation processes in aqueous suspensions of illite il vermiculite vm and montmorillonite mt that were subjected to weathering in a simulated high level radioactive tank waste leachate 0 05 m alt 2 m na 1 m no3 p h 14 cs and sr 2 present as co contaminants time series 0 to 369 d experiments were conducted at 298 k with initial cs 0 and sr 0 concentrations from 10 5 to 10 mol kg incongruent clay dissolution resulted in an accumulation of secondary aluminosilicate precipitates identified as nitrate sodalite nitrate cancrinite and zeolite x by molecular spectroscopy and electron microscopy xrd ir nmr sem eds and tem eds contaminant fate was dependent on competing uptake to parent clays and weathering products tem eds results indicated that high il affinity for cs was due to adsorption at frayed edge sites the il system also comprised sr rich aluminous precipitates after 369 d reaction time in mt systems cs and sr were co precipitated into increasingly recalcitrant spheroidal precipitates over the course of the experiment whereas contaminant association with montmorillonite platelets was less prevalent in contrast cs and sr were found in association with weathered vm particles despite the formation of spheroidal aluminosilicate precipitates that were comparable to those formed from mt dissolution copyright 2005 elsevier ltd

the arsenic source term for an in pit uranium mine tailings facility and its long term impact on the regional groundwater abstract detailed field sampling and analyses and laboratory based diffusion cell experiments were used in conjunction with 3 d reactive transport modeling modflow and mt3d99 to quantify the fate and long term 10 ka transport of as in the rabbit lake in pit tailings management facility rlitmf northern saskatchewan canada the rlitmf 300 m 425 m 90 m thick was engineered to ensure solute transport within the rlitmf is dominated by diffusion concentrations of as in the tailings pore fluids ranged from 0 24 to 140 mg l n 43 arsenic speciation analyses indicate 90 of this arsenic exists as as 5 this observation is supported by ph eh measurements of pore fluids n 135 geochemical analyses yielded a strong inverse correlation between the fe as molar ratio in the tailings solids and the corresponding concentration of dissolved as which is attributed to the adsorption of as to secondary 2 line ferrihydrite present in the tailings diffusion cell testing yielded values for the effective diffusion coefficient sorption coefficient and effective porosity of as in the tailings of 4 5 10 10 m 2 s 2 4 cm 3 g and 0 36 respectively reactive transport simulations using the field and laboratory data show adsorption of as to the tailings and diffusive transport of dissolved as in the tailings should reduce the source term concentration of as to between 40 and 70 of the initial concentrations over the 10 ka simulation period based on these simulations the as concentrations in the regional groundwater 50 m down gradient of the tailings facility should be maintained at background concentrations of 0 001 mg l over the 10 ka period these findings suggest the engineered in pit disposal of u mine tailings can provide long term protection for the local groundwater regime from as contamination

geological environment of the cigar lake uranium deposit the cigar lake uranium deposit occurs within the athabasca basin of northern saskatchewan canada like other major uranium deposits of the basin it is located at the unconformity separating helikian sandstones of the athabasca group from aphebian metasediments and plutonic rocks of the wollaston group the athabasca group was deposited in an intra continental sedimentary basin that was filled by fluviatile terrestrial quartz sandstones and conglomerates the group appears undeformed and its actual maximum thickness is about 1500 m on the eastern side of the basin the detrital units correspond to the manitou falls formations where most of the uranium deposits are located the lower pelitic unit of the wollaston group which lies directly on the archean basement is considered to be the most favourable horizon for uranium mineralization during the hudsonian orogeny 1800 1900 ma the group underwent polyphase deformation and upper amphibolite facies metamorphism the hudsonian orogeny was followed by

distribution of arsenic and nickel in uranium mill tailings rabbit lake saskatchewan canada abstract the rabbit lake u mine in pit tailings management facility tmf is located in northern saskatchewan canada the tailings body is approximately 425 m long 300 m wide and 91 m thick at its centre an investigation of the tmf was performed to collect tailings samples from depth to quantify the distribution of as and ni in the tailings with respect to ore type and assess the distribution of as and ni with respect to tailings mineralogy the tailings body consists of alternating layers of ice frozen tailings and unfrozen tailings which varied in texture from a slurry to a firm silty sand the tailings solids are predominately composed of quartz 16 36 calcium sulphate 0 3 54 and illite 3 and 14 arsenic and ni concentrations in the tailings show similar patterns with depth which were strongly related to historical changes in as and ni concentrations in the mill feed mineralogy of the ore bodies indicated that as and ni in the mill feed occurred primarily as 1 1 molar ratio arsenides such as niccolite and gersdorffite arsenic and ni concentrations in the tailings were also measured at a near 1 1 molar ratio mill process records showed that an average of 71 of the as in the mill feed was solubilized during leaching sem analysis suggested that solubilized as is precipitated as ca2 fe3 and ni2 arsenates during the neutralization process mill records indicated that 17 000 tonnes of as were discharged to the tmf of which approximately 88 was as arsenates and 12 as primary arsenides

geothermal spring causes arsenic contamination in river waters of the southern tibetan plateau china large numbers of as enriched geothermal springs are distributed at the southern tibetan plateau and their influence on river water is still not clear lhasa river and its tributary duilong qu located at downstream of the largest geothermal spring of the tibetan plateau were selected for sampling during monsoon and non monsoon seasons dissolved trace elements b cr ni cu zn as cs ba and u were measured in river water samples by icp ms the results show that due to contribution of geothermal spring as levels of duilong qu 205 6 g l and lhasa river 12 7 g l were higher during non monsoon season than that of who guideline for drinking water 10 g l accordingly as level of river water was lower during the monsoon season than that of the non monsoon season due mainly to dilution process therefore although tibetan rivers are generally considered as free of contamination geothermal springs cause as contamination of river water at some local regions and may harm the local residents further research is needed in other parts of the plateau to determine whether as level of groundwater of the related region is high

a review of the source behaviour and distribution of arsenic in natural waters the range of as concentrations found in natural waters is large ranging from less than 0 5 g l 1 to more than 5000 g l 1 typical concentrations in freshwater are less than 10 g l 1 and frequently less than 1 g l 1 rarely much higher concentrations are found particularly in groundwater in such areas more than 10 of wells may be affected defined as those exceeding 50 g l 1 and in the worst cases this figure may exceed 90 well known high as groundwater areas have been found in argentina chile mexico china and hungary and more recently in west bengal india bangladesh and vietnam the scale of the problem in terms of population exposed to high as concentrations is greatest in the bengal basin with more than 40 million people drinking water containing excessive as these large scale natural as groundwater problem areas tend to be found in two types of environment firstly inland or closed basins in arid or semi arid areas and secondly strongly reducing aquifers often derived from alluvium both environments tend to contain geologically young sediments and to be in flat low lying areas where groundwater flow is sluggish historically these are poorly flushed aquifers and any as released from the sediments following burial has been able to accumulate in the groundwater arsenic rich groundwaters are also found in geothermal areas and on a more localised scale in areas of mining activity and where oxidation of sulphide minerals has occurred the as content of the aquifer materials in major problem aquifers does not appear to be exceptionally high being normally in the range 1 20 mg kg 1 there appear to be two distinct triggers that can lead to the release of as on a large scale the first is the development of high ph 8 5 conditions in semi arid or arid environments usually as a result of the combined effects of mineral weathering and high evaporation rates this ph change leads either to the desorption of adsorbed as especially as v species and a range of other anion forming elements v b f mo se and u from mineral oxides especially fe oxides or it prevents them from being adsorbed the second trigger is the development of strongly reducing conditions at near neutral ph values leading to the desorption of as from mineral oxides and to the reductive dissolution of fe and mn oxides also leading to as release iron ii and as iii are relatively abundant in these groundwaters and so4 concentrations are small typically 1 mg l 1 or less large concentrations of phosphate bicarbonate silicate and possibly organic matter can enhance the desorption of as because of competition for adsorption sites a characteristic feature of high groundwater as areas is the large degree of spatial variability in as concentrations in the groundwaters this means that it may be difficult or impossible to predict reliably the likely concentration of as in a particular well from the results of neighbouring wells and means that there is little alternative but to analyse each well arsenic affected aquifers are restricted to certain environments and appear to be the exception rather than the rule in most aquifers the majority of wells are likely to be unaffected even when for example they contain high concentrations of dissolved fe

evaluation of arsenic sorption and mobility in stream sediment and hot spring deposit in three drainages of the tibetan plateau abstract enrichment of arsenic as in sediment 12 227 mg kg in the upstream tributaries of the indus and brahmaputra rivers originating from the tibetan plateau where hot springs were abundant has been found sandy sediment samples from the nu salween river lantsang mekong river and jinsha yangtze river also originating from the tibetan plateau were collected in july 2012 and were found to contain 6 8 mg kg to 30 5 mg kg as average17 3 6 5 mg kg n 12 deposits collected within 1 m of two hot springs in changdu tibet displayed significantly higher as levels 263 7 mg kg in ld 2 with 65 quartz and 101 8 mg kg in nud 1 with 82 calcite to evaluate the valence states of as and also the phases responsible for sorption x ray absorption spectroscopy xas was employed to analyze the two hot spring deposits and three river sediment samples coarse sand nud 6 as 14 6 mg kg fine sand nud 4 as 17 8 mg kg and silty sand ld 1 as 30 5 mg kg the x ray absorption near edge spectrum xanes data indicate that 70 of as from 3 samples in the nu salween river drainage nud 1 nud 4 and nud 6 is as v or arsenate with the rest being as 0 or as fe sulfides the proportion of as v is 90 for 2 samples in the lantsang mekong river drainage ld 1 and ld 2 linear combination fit of the iron extended x ray fine structure spectrum exafs show that 3 samples from the nu salween river contain 20 ferrihydrite and 10 goethite without any hematite being detected but 2 samples from the lantsang mekong river contain

changes in the as solid speciation during weathering of volcanic ashes a xas study on patagonian ashes and chacopampean loess abstract x ray absorption spectroscopy xas was used to determine the oxidation state of as local chemical coordination and the relative proportion of different as species in recent and ancient andean volcanic ashes as well as in chaco pampean loess as k edge xanes analysis indicates that in loess sediments the dominant species is as v i e 91 conversely as iii is dominant in all ash samples in the puyehue sample only as iii species were determined while in both the chaiten and the ancient tephra samples as iii species accounts for 66 of the total as the remaining 34 corresponds to as 1 in the chaiten sample and to as v in the weathered tephra the proposed exafs models fit well with the experimental data suggesting that in ancient and recent volcanic ashes as iii is likely related to as atoms present as impurities within the glass structure forming hydroxide species bound to the al si network in addition the identified as 1 species is related to arsenian pyrite while in the ancient volcanic ash as v was likely a product of incipient weathering in loess sediments the identified as v species represents arsenate ions adsorbed onto fe oxy hydr oxides forming inner sphere surface complexes in a bidentate binuclear configuration

natural immobilization of uranium by phosphate mineralization in an oxidizing saprolite soil profile chemical weathering of the coles hill uranium deposit virginia abstract geochemical and mineralogical studies of the 15 to 20 m thick soil and saprolite profile developed over the coles hill uranium deposit demonstrate that uranium transport may be inhibited or naturally attenuated by the precipitation of u vi phosphate minerals in oxidizing and saturated soil environments this study examines geochemical conditions in which these secondary uranium phosphates are formed and remain stable for hundreds of thousands of years we also describe geochemical conditions that may lead to their dissolution the lower part of the weathering profile which consists of groundwater saturated saprolite contains up to 1300 mg kg uranium within the solid this concentration is approximately 1 5 times greater than the average ore grade of the deposit indicating that the saturated saprolites are enriched relative to the underlying primary ore uranium within this zone is dominantly associated with u vi phosphates of the meta autunite mineral group groundwaters from this zone contain less than 14 g l uranium suggesting that the u vi phosphate minerals present within the coles hill saprolites are capable of buffering dissolved uranium concentrations to values significantly lower by a factor of 2 or more than the us epa maximum contaminant level of 30 g l above the water table u vi phosphates of the type found in the saturated saprolite zone are not present and the soil uranium concentration drops to an average value of 250 mg kg thus the zone of water table fluctuation represents a major transition zone in uranium mineralogy mineralogical characterization of the upper part of the profile suggests that geochemical conditions in the unsaturated zone are not conducive to uranium stabilization by meta autunite group minerals uranium within the vadose zone however is associated with phosphate e g al phosphate minerals and sorption with phosphate to ferric oxyhydroxides as a whole the coles hill soil profile is interpreted to have reached a steady state with respect to uranium transport and immobilization results of this study suggest that uranium is leached from the unsaturated part of the profile meta autunite unstable and reprecipitated below the water table where the measured activity ratio of dissolved phosphate to carbonate is higher based on estimates of weathering rates for this region the processes responsible for the dispersal of uranium within the coles hill system are estimated to have been active on a time scale of hundreds of thousands of years this system thus represents an excellent natural laboratory for understanding the long term mineralogical and geochemical processes involved in the coupling of uranium and phosphorus in natural fluid rich systems

icp ms a powerful tool for high precision trace element analysis in earth sciences evidence from analysis of selected u s g s reference samples abstract inductively coupled plasma mass spectrometry icp ms is a powerful analytical technique with considerable application to geochemistry in this paper we demonstrate the power of icp ms as a tool in petrogenetic studies data for 28 elements in seven u s g s basalt and andesite reference samples agv 1 bcr 1 bhvo 1 bir 1 dnc 1 w 1 and w 2 are presented accuracy and precision standard deviation for 26 of these elements is either excellent a detailed description of the icp ms technique we have developed is given a simple hf hno 3 dissolution in screwtop teflon bombs was used for sample preparation icp ms instrumental sensitivity was measured by external solutions with surrogate calibration for 4 elements matrix correction was made by use of standard addition naturally occurring internal standards rb y ce and pb were used to correct for instrumental drift between sample and spiked sample measurements we report data for the elements li cs rb sr ba zr hf nb ta y sc u th pb and all 14 of the ree in addition the procedure acquired data for be mo w tl and bi many elements in this array are crucial for the evaluation of petrogenetic models and source tracing herein lies the real power of icp ms one technique one dissolution small sample size good limits of detection good to excellent accuracy and good precision for many geochemically important elements

an attempt to correct strain data measured with vault housed extensometers under variations in temperature abstract strain data obtained by vault housed extensometers have precisions on the order of nanostrains but they are distorted by variations in temperature which cause two types of noise actual variations due to the thermo elastic effect of the earth s crust and false variations due to the thermal expansion of extensometer which occurs when the extensometers themselves are subjected to variations in temperature here i explore a method of removing false variations which are severe when the vault is located at shallow depths if variations in temperature at arbitrary points inside a vault are estimated false variations can be removed from the recorded variations in strain i derive formulae that enable variations in temperature to be estimated at various points in a vault based on measured variations at reference points the formulation is valid if some simplification is allowed i examined whether variations in temperature inside a vault can be estimated in terms of the derived formulae and obtained the following results when the reference temperature data are obtained from adequate points in the vault variations in temperature at another point can be estimated with an accuracy of 0 1 c however when the reference temperature data are obtained from outside the vault estimated variations in temperature are rather inaccurate which means that the false variations in strain cannot be removed accurately moreover the data indicate that the thermal diffusivity of the ground is temporally variable and this introduces another difficulty in correcting false variations in strain data these results indicate that correcting the distortions in strain data due to variations in temperature is much more difficult than anticipated

post collisional crustal extension setting and vhms mineralization in the jinshajiang orogenic belt southwestern china abstract the jinshajiang orogenic belt job of southwestern china located along the eastern margin of the himalayan tibetan orogen includes a collage of continental blocks joined by paleozoic ophiolitic sutures and permian volcanic arcs three major tectonic stages are recognized based on the volcanic sedimentary sequence and geochemistry of volcanic rocks in the belt westward subduction of the paleozoic jinshajiang oceanic plate at the end of permian resulted in the formation of the chubarong dongzhulin intra oceanic arc and jamda weixi volcanic arc on the eastern margin of the changdu continental block collision between the volcanic arcs and the yangtze continent block during early middle triassic caused the closing of the jinshajiang oceanic basin and the eruption of high si and al potassic rhyolitic rocks along the permian volcanic arc slab breakoff or mountain root delamination under this orogenic belt led to post collisional crustal extension at the end of the triassic forming a series of rift basins on this continental margin arc significant potential for vhms deposits occurs in the submarine volcanic districts of the job mesozoic vhms deposits occur in the post collisional extension environment and cluster in the late triassic rift basins

newly recognized hosts for uranium in the hanford site vadose zone abstract uranium contaminated sediments from the u s department of energy s hanford site have been investigated using electron microscopy six classes of solid hosts for uranium were identified preliminary sediment characterization was carried out using optical petrography and electron microprobe analysis empa was used to locate materials that host uranium all of the hosts are fine grained and intergrown with other materials at spatial scales smaller than the analytical volume of the electron microprobe a focused ion beam fib was used to prepare electron transparent specimens of each host for the transmission electron microscope tem the hosts were identified as 1 metatorbernite cu uo2 2 po4 2 8h2o 2 coatings on sediment clasts comprised mainly of phyllosilicates 3 an amorphous zirconium oxyhydr oxide found in clast coatings 4 amorphous and poorly crystalline materials that line voids within basalt lithic fragments 5 amorphous palagonite surrounding fragments of basaltic glass and 6 fe and mn oxides these findings demonstrate the effectiveness of combining empa fib and tem to identify solid phase contaminant hosts furthermore they highlight the complexity of u geochemistry in the hanford vadose zone and illustrate the importance of microscopic transport in controlling the fate of contaminant metals in the environment

remobilization of u and ree and the formation of secondary minerals in oxidized u deposits the hydrothermal uranium vein type deposits of menzenschwand and wittichen in the schwarzwald in southwestern germany have been investigated with regards to their primary and secondary mineralization primary magmatic uraninite i from the host granite of menzenschwand primary hydrothermal uraninite ii and secondary supergene uranyl silicates uranophane and cuprosklodowskite uranyl phosphates torbernite and uranocircite and uranyl arsenates zeunerite heinrichite novacekite walpurgite and uranospinite were analyzed for their ree contents by la icp ms together with uraninite ii samples from other known schwarzwald uraninite ii occurrences for comparison water samples were taken from drillings and abandoned mines and were analyzed for their major and trace element composition including u and ree the ree patterns of uraninite show significant eu anomaly variations negative eu anomalies are related to granitic host rocks whereas positive eu anomalies imply a gneissic ree source this is in agreement with the observation of eu anomalies in granite and gneiss derived waters which display negative and positive eu anomalies respectively rare earth element distributions in the secondary uranyl minerals provide information about the sequence of mineral precipitation and the degree of remobilization of u cerium anomalies or their absence imply that uranyl silicates formed during an earlier stage of weathering under more reduced conditions than the uranyl arsenates and phosphates the ree patterns of the uranyl silicates in wittichen are similar to those of uraninite ii suggesting a very local redistribution on the millimeter to centimeter scale in contrast the ree patterns of uranyl arsenates and phosphates are different from uraninite ii patterns and resemble those of the waters this shows that the uranyl phosphates and arsenates are formed not only by redistribution of u in the hydrothermal veins but are influenced by waters from the host rock implying that u was probably transported over a greater distance these conclusions are supported by field observations where uranyl silicates are often found in the vicinity of uraninite ii whereas uranyl phosphates and arsenates are commonly found on fissures in the host rock to explain specific features in the sulfide rich pyrite chalcopyrite menzenschwand deposit we conducted thermodynamic reaction modeling using the phreeqc computer code sulfide oxidation was modeled by reaction of a u rich water in equilibrium with atmospheric oxygen with fes2 and cufes2 a water that initially precipitates uranophane gradually evolves to more acidic ph values thereby reaching torbernite saturation this is in agreement with observed paragenetic sequences ongoing reaction results in a further decrease of ph and in the destabilization of uranophane and torbernite since goethite precipitates even at low ph values these calculations can explain observed pseudomorphs of goethite after both uranophane and torbernite which are frequently observed at menzenschwand if the reaction proceeds and f o2 in the system is buffered by the surrounding minerals u6 can be reduced to u4 and uraninite can form and replace pyrite and earlier formed secondary uranium minerals such as ianthinite also these textures have been observed we show that the combination of ree geochemistry careful paragenetic observations and thermodynamic modeling allows to reconstruct the formation and weathering of uranium deposits in great detail

geochemical and mineralogical aspects of sulfide mine tailings abstract tailings generated during processing of sulfide ores represent a substantial risk to water resources the oxidation of sulfide minerals within tailings deposits can generate low quality water containing elevated concentrations of so 4 fe and associated metal loid s acid generated during the oxidation of pyrite fes 2 pyrrhotite fe 1 x s and other sulfide minerals is neutralized to varying degrees by the dissolution of carbonate oxy hydroxide and silicate minerals the extent of acid neutralization and therefore pore water ph is a principal control on the mobility of sulfide oxidation products within tailings deposits metals including fe iii cu zn and ni often occur at high concentrations and exhibit greater mobility at low ph characteristic of acid mine drainage amd in contrast hydr oxyanion forming elements including as sb se and mo commonly exhibit greater mobility at circumneutral ph associated with neutral mine drainage nmd these differences in mobility largely result from the ph dependence of mineral precipitation dissolution and sorption desorption reactions cemented layers of secondary oxy hydroxide and hydroxy sulfate minerals referred to as hardpans may promote attenuation of sulfide mineral oxidation products within and below the oxidation zone hardpans may also limit oxygen ingress and pore water migration within sulfide tailings deposits reduction oxidation redox processes are another important control on metal loid mobility within sulfide tailings deposits reductive dissolution or transformation of secondary oxy hydroxide phases can enhance fe mn and as mobility within sulfide tailings production of h 2 s via microbial sulfate reduction may promote attenuation of sulfide oxidation products including fe zn ni and tl via metal sulfide precipitation understanding the dynamics of these interrelated geochemical and mineralogical processes is critical for anticipating and managing water quality associated with sulfide mine tailings

a two step homogenization based permeability model for deformable fractured rocks with consideration of coupled damage and friction effects abstract the permeability variation induced by anisotropic damage of rock blocks and nonlinear deformation of fractures is modeled with a two step homogenization technique for deformable fractured rocks containing arbitrarily distributed penny shaped microcracks in rock blocks separated by multiple sets of critically orientated fractures of much large scales the proposed model accounts for the influences of the microstructural alteration of rock blocks and fractures at the laboratory scale and the development pattern of the fracture system as well as the rock fracture interaction at the field scale on the permeability of a fractured rock under mechanical loading or excavation condition the proposed model was first validated by laboratory data of compression tests with permeability measurements on the beishan granite coupled shear flow tests with hydraulic conductivity measurements on a granite fracture and anisotropic strength tests on the martinsburg slate with good agreement between the model predictions and the laboratory measurements numerical simulations were finally performed to examine the excavation induced permeability change in the surrounding granitic rock of the stripa tunnel demonstrating the importance in considering both the damage of rock blocks and the deformation of fractures for better understanding the excavation induced permeability change in the surrounding rock near the excavation surface

hydrogeochemistry and environmental impact of geothermal waters from yangyi of tibet china abstract the yangyi geothermal field located 72 km northwest to lhasa city capital of tibet has a high reservoir temperature up to at least 207 2 c the geothermal waters from both geothermal wells and hot springs belong to the hco 3 co 3 na type factor analysis of all the chemical constituents shows that they can be divided into two factors f 1 factor receives the contributions of so 4 2 cl sio 2 as b na k and li whereas f 2 factor is explained by hco 3 f co 3 2 ca 2 and sr 2 the f 1 factor can be regarded as an indicator of the reservoir temperature distribution at yangyi but its variable correlation with the results of different geothermometers na k quartz and k mg does not allow one to draw further inferences different from f 1 the f 2 factor is an indicator of a group of hydrogeochemical processes resulting from the co 2 pressure decrease in geothermal water during its ascent from the deep underground including transformation of hco 3 to co 3 2 precipitation of ca 2 and sr 2 and release of f from some fluoride bearing minerals of reservoir rocks the plot of enthalpy vs chloride prepared on the basis of na k equilibrium temperatures suggests that a parent geothermal liquid pgl with cl concentration of 185 mg l that of sample yyt 8 and enthalpy of 1020 j g corresponding to a temperature of 236 237 c i e somewhat higher than that of sample yyt 6 is present in the geothermal reservoir of the yangyi area below both the qialagai valley and the bujiemu valley although the samples less affected by mixing and cooling yyt 6 and yyt 7 come from the second site the discharge of geothermal waters with high contents of toxic elements such as b as and f into the luolang river the only drinking water source for local residents has caused slight pollution of the river water great care should therefore be taken in the geothermal water resource management at yangyi

slow earthquakes linked along dip in the nankai subduction zone we identified a strong temporal correlation between three distinct types of slow earthquakes distributed over 100 kilometers along the dip of the subducting oceanic plate at the western margin of the nankai megathrust rupture zone southwest japan in 2003 and 2010 shallow very low frequency earthquakes near the nankai trough as well as nonvolcanic tremor at depths of 30 to 40 kilometers were triggered by the acceleration of a long term slow slip event in between this correlation suggests that the slow slip might extend along dip between the source areas of deeper and shallower slow earthquakes and thus could modulate the stress buildup on the adjacent megathrust rupture zone

aseismic slip and low frequency earthquakes in the bungo channel southwestern japan 1 analysis of global positioning system gps data has shown transient crustal deformation in the bungo channel in southwestern japan since late august 2003 six years after a similar event in 1996 1997 considering the southeastward motion at many of the gps sites and the similarity between the 1996 1997 and 2003 events it is highly likely that the transients were caused by aseismic interplate slip between the philippine sea plate and the amurian plate the 2003 aseismic slip is estimated beneath the bungo channel and the relative slip increased with time on the west side with a moment magnitude mw amounting to 7 0 in contrast to the gradual subsidence of low frequency earthquakes which began and ended in coincidence with the 2003 event the 2003 transient crustal deformation proceeded at a roughly constant rate until the end of november 2003 the bungo channel area may release energy accumulated from the subduction of the philippine sea plate by aseismic slip

the behavior of arsenic and antimony at pezinok mining site southwestern part of the slovak republic arsenic and antimony contamination is found at the pezinok mining site in the southwest of the slovak republic investigation of this site included sampling and analysis of water mineralogical analyses sequential extraction in addition to flow and geochemical modeling the highest dissolved arsenic concentrations correspond to mine tailings up to 90 000 g l and the arsenic is present predominately as as v the primary source of the arsenic is the dissolution of arsenopyrite concentration of antimony reaches 7 500 g l and its primary source is the dissolution of stibnite pore water in mine tailings is well buffered by the dissolution of carbonates ph values between 6 6 and 7 0 and arsenopyrite grains are surrounded by reaction rims composed of ferric iron minerals based on sequential extraction results most solid phase arsenic is in the reducible fraction i e ferric oxyhydroxides sulfidic fraction and residual fraction distribution of antimony in the solid phase is similar but contents are lower the principal attenuation mechanism for as v is adsorption to ferric oxide and hydroxides but the adsorption seems to be limited by the competition with sb v produced by the oxidation of stibnite for adsorption sites water in mine tailings is at equilibrium with gypsum and calcite but far from equilibrium with any arsenic and antimony minerals the concentrations of arsenic and antimony in the surrounding aquifer are much lower with maximum values of 215 and 426 g l respectively arsenic and antimony are transported by ground water flow towards the blatina creek but their loading from ground water to the creek is much lower compared with the input from the mine adits in the blatina creek arsenic and antimony are attenuated by dilution and by adsorption on ferric iron minerals in stream sediments with resulting respective concentrations of 93 and 45 g l at the site boundary south of mine tailing ponds

thermoelastic strain in a half space covered by unconsolidated material an algorithm to predict crustal thermoelastic strain from observed local atmospheric temperature is given and applied to a 24 month crustal strain record of one test strainmeter site located near bouquet reservoir in southern california we use a crustal model that consists of an elastically decoupled layer overlying a uniform elastic half space and a thermal source that is given by a stationary temperature wave whose wavelength is related to local topography and or lateral material heterogeneity the decoupled layer delays attenuates and low pass filters the source temperature field the thermoelastic strain in the underlying half space resulting from the temperature variations at the base of the decoupled layer is calculated using the berger 1975 solution for thermoelastic strain in a uniform half space applying our model to the test data we obtain a good fit between predicted and observed strains if we filter the surface thermal signal through a 63 cm thick decoupled layer much of the remaining strain variations clearly correspond to other environmental sources reservoir loading and rainfall our analysis suggests that the horizontal thermoelastic strain is inversely proportional to the wavelength of local topography and or lateral material heterogeneity thus the horizontal thermoelastic strain will be greater in areas of local topography and or lateral material heterogeneity and smaller in more homogeneous and flat areas an upper layer of loose material natural or artificial acts as a thermoelastic strain insulator burial of strainmeters in places where such a layer exists can reduce the thermoelastic strain noise considerably even for shallow strainmeter emplacements

uranium bearing opals products of u mobilization diffusion and transformation processes understanding the retention mechanism of u by amorphous silica i e opal in the environment is of great importance to nuclear waste disposal because opals can retain u for millions of years uraniferous opals from spor mountain and the thomas range utah u s a are examined in terms of their mineralogical chemical and isotopic compositions uranium rich zones composed of most likely vorlanite cauo 4 occur in fibrous opal ct termed lussatite along the interface of the phase with microcrystalline quartz red to black colored precipitates of vorlanite also occur in the interstices between fibers and grains in lussatite and massy opals respectively the high abundance of vorlanite in certain growth zones can be explained by the diffusion of ca and u along boundaries of layers grains and fibers and by the release of ca and u through the transformation of opal a into opal ct and from opal ct into microcrystalline quartz similar o isotope compositions of opal ct and associated microcrystalline quartz indicate that crystallization processes and deposition of subsequent layers of opal occurred from fluids of similar origin and t differences in the isotope and chemical composition between uraniferous opals microcrystalline quartz the sio 2 polymorph moganite and pyrolusite indicate the past occurrence of various alteration processes involving fluids of different composition and t the results of this study indicate that assemblages of opal and microcrystalline quartz can retain u for millions of years as long as confined pore spaces between different generations of opal and quartz or between growth features of opal provide space for the nucleation and adsorption of u bearing phases and species

repetitive long term slow slip events beneath the bungo channel southwestern japan identified from leveling and sea level data from 1979 to 2008 1 leveling and sea level data for the period from 1979 to 2008 around the bungo channel southwestern japan were investigated to characterize vertical deformation patterns we found evidence of discrete events that may have occurred beneath the bungo channel before the two most recent long term slow slip events sses 1996 1997 and 2003 detected from gps data gps derived steady state vertical displacements related to ongoing subduction of the philippine sea plate were subtracted from the vertical displacements observed by leveling surveys the spatial pattern of the residual vertical displacements observed by leveling was similar to that observed by gps in the periods including recent long term sses this suggests that discrete vertical displacements which might represent long term sses have occurred in each of four intervals between leveling surveys before gps deployment we calculated differences of sea level between tidal stations near the bungo channel after some corrections and then cross correlated them with the gps derived vertical displacements of the recent long term sse to estimate the timing of the events these cross correlations and the discrete vertical displacements derived from leveling suggest that long term sses may have occurred around 1980 around 1985 1986 and around 1991

arsenic and lead mobility from tailing materials to the aqueous compartment this study concerns the mineralogy of the tailings of a former ag pb mine auzelles district france and the contribution of the waste materials to the heavy metal dissemination in the environment accumulation of metals in fish flesh was reported and this pollution is attributed to past mining activities tailings were studied to establish the major transfer schemes of as and pb in order to understand their mobility that leads to contamination of a whole ecosystem mineralogical investigation solubility and compliance tests were performed to assess the stability of the metal bearing phases among the various metallic elements measured as and pb show the highest bulk concentrations up to 0 7 and 6 3 respectively especially for samples presenting near neutral ph values according to x ray diffraction xrd scanning electron microscopy sem edx electron probe micro analysis epma and micro raman spectrometry rs tailings mineralogy still contain primary minerals such as sulfides e g galena pyrite phosphates monazite apatite and or carbonates e g hydro cerussite dolomite siderite sulfates e g anglesite lanarkite plumbojarosite and beudantite are the main secondary metal bearing phases with other interesting phases accounting for metals mobility such as fe and or pb and or mn oxides e g lepidocrocite goethite up to 15 wt of pb was measured plumboferrite type phase mimetite the lowest pb solubilities were obtained at ph 8 9 and at a larger range than for as for which the lowest solubilities are reached around ph 6 7 at this minimum solubility ph value pb concentrations released still over exceed the national environmental quality standards neqs whatever the samples the highest solubility is reached at ph 2 for both elements whatever the considered sample this represents up to 51 of total pb and up to 46 of total as remobilized and concentrations exceeding the neqs as and pb released mainly depends on the fe mn oxides e g goethite lepidocrocite and carbonates cerussite which are the less stable phases compliance tests also show that pb concentrations released are higher than the upper limit for hazardous waste landfills determination of the mineralogy allows understanding both the solubility and leaching test experiments results as well as to forecast the impact of the residues on the water quality at a mid term scale

arsenic in contaminated soils and anthropogenic deposits at the mokrsko roudný and kasperske hory gold deposits bohemian massif cz soil mine tailing and waste dump profiles above three mesothermal gold deposits in the bohemian massif with different anthropogenic histories have been studied their mineralogical major element and arsenic as contents and the contents of secondary arsenic minerals were analyzed the as bearing minerals were concentrated and determined using x ray diffraction xrd analysis the debye scherrer powder method scanning electron microscopy sem and energy dispersive microanalysis edax the amorphous hydrous ferric oxides hfo as bearing goethite k ba or ca fe and fe arsenates pharmacosiderite arseniosiderite and scorodite and sulfate arsenate pitticite were determined as products of arsenopyrite or arsenian pyrite oxidation the as behaviour in the profiles studied differs in dependence on the surface morphology chemical and mineralogical composition of the soil mine wastes or tailings oxidation conditions ph presence of or distance from primary as mineralization in the bedrock and duration of the weathering effect although the primary as mineralization and the bedrock chemical composition are roughly similar there are distinct differences in the as behaviour amongst the mokrsko roudn and kasperske hory deposits

characterization of geosynthetic clay liner bentonite using micro analytical methods in barrier design familiarity of the structure and composition of the soil material at the micron scale is necessary for delineating the retention mechanisms of introduced metals such as the formation of new mineral phases in this study the mineralogical and chemical makeup of the bentonite from a geosynthetic clay liner gcl was extensively characterized using a combination of conventional benchtop x ray diffraction xrd and micro x ray diffraction mu xrd with synchrotron generated micro x ray fluorescence mu xrf elemental mapping and mu xrd s mu xrd these methods allow for the non destructive in situ investigation of a sample with micro m spatial resolution synchrotron based hard x ray microprobes are specifically advantageous to the study of trace metals due to higher spatial resolution 10 micro m and higher analytical sensitivity femtogram detection than is possible using normal laboratory based instruments minerals comprising less than 5 of the total bentonite sample such as gypsum goethite and pyrite were identified that were not accessible by other conventional methods for the same gcl bentonite two dimensional general area diffraction detector system gadds images proved to be particularly advantageous in differentiating between the microcrystalline clay which appeared as homogeneous debye rings and the spotty or grainy appearance of primary more coarsely crystalline accessory minerals for s mu xrd themore tunability of the synchrotron x rays allowed for efficient distinction of both clay minerals at low scattering angles and in identifying varying fe oxide minerals at higher angles gcl samples permeated with metal bearing mining solutions were also examined in order to consider how mechanisms of metal attenuation may be identified using the same techniques in addition to the cation exchange capacity from the montmorillonite clay tests showed how minerals comprising only 1 2 of the bentonite such as goethite could potentially play a significant role in sequestering a range of metals specifically ni zn and cu less

a review of existing methods used to evaluate the hydraulic conductivity of a fractured rock mass we review the existing methods for evaluating the hydraulic conductivity of a rock mass rock mass permeability may be assessed using empirical analytical and numerical approaches empirical methods use data from in situ field tests to derive the relationship between depth and permeability by applying a curve fitting method and establishing the relationship between hydraulic conductivity and a geological index analytical methods rely on darcy and cubic laws to estimate the permeability of a rock mass by taking into account the geometrical characteristics of the joint sets analytical equations of the flow rate into underground excavations are also developed by solving the laplace equation for homogeneous and isotropic aquifers under various boundary conditions numerical modeling can evaluate the outcomes of both empirical and analytical approaches and vice versa and can provide a sensitivity analysis of the parameters that affect rock mass permeability the importance of stress and joint set characteristics is often investigated via numerical modeling as are the scale effect and directional permeability in this review paper we provide a comprehensive review of these approaches for studying rock mass permeability we summarize the advantages and disadvantages of existing methods and highlight potential future research directions

clay mineral formation and transformation in rocks and soils three mechanisms for clay mineral formation inheritance neoformation and transformation operating in three geological environments weathering sedimentary and diagenetic hydrothermal yield nine possibilities for the origin of clay minerals in nature several of these possibilities are discussed in terms of the rock cycle the mineralogy of clays neoformed in the weathering environment is a function of solution chemistry with the most dilute solutions favouring formation of the least soluble clays after erosion and transportation these clays may be deposited on the ocean floor in a lateral sequence that depends on floccule size clays undergo little reaction in the ocean except for ion exchange and the neoformation of smectite therefore most clays found on the ocean floor are inherited from adjacent continents upon burial and heating however dioctahedral smectite reacts in the diagenetic environment to yield mixed layer illite smectite and finally illite with uplift and weathering the cycle begins again

depositional characteristics of uranium tailings from saskatchewan canada the management of uranium tailings generated as a by product of ore processing is particularly important to minimize the environmental footprint of the industry a clear understanding of tailings slurry behavior is required at the time of deposition to help evaluate the storage capacity and life span of the containment facilities the main purpose of this study was to investigate the segregation and self weight settling properties of uranium tailings detailed laboratory investigations were conducted on tailings from 4 5 and 6 nominal mill feeds high grade mcarthur river ores blended with special wastes on site from the cameco key lake operation the results indicate that the three uranium tailings can be characterized as a sandy silt material with a negligible amount of clay their depositional behavior is governed by the initial solids content of the slurry the investigated tailings showed insignificant segregation between 25 and 40 initial solids content the initial hydraulic conductivity during settling was about 10 4 m s at a void ratio of 4 and was increased by half an order of magnitude for the 4 mill feed and by almost two orders of magnitude for the 5 and 6 mill feeds at a void ratio of 8 over the same range of initial void ratio the settling potential increased threefold from 8 to 24 for the 4 mill feed and from 12 to 36 for the 5 and 6 mill feeds the better rate and amount of dewatering of future high mill feed tailings as compared to the current low mill feed tailings means that the onsite containment facility can store more tailings thereby supporting a longer life span of the mill

investigating arsenic speciation in the jeb tailings management facility at mcclean lake saskatchewan using x ray absorption spectroscopy abstract areva resources canada operates the mcclean lake operation mlo a uranium mine and processing facility located in northern saskatchewan uranium containing ores processed at the mlo contain high concentrations of arsenic that is oxidized to soluble arsenite and arsenate species when leaching and recovering uranium to reduce the environmental impact of areva s mining operations areva has developed a tailings preparation process designed to trap arsenic in a mineral form before the tailings are permanently deposited in the jeb tailings management facility tmf scorodite feaso 4 2h 2 o is predicted to be the primary arsenic species produced from the tailings preparation process however scorodite has never been observed in aged tailings samples confirming the presence of scorodite in the tailings is important in verifying that the tailings preparation process at the mlo can isolate high concentrations of arsenic from the environment in the form of stable minerals herein x ray absorption near edge structure xanes spectroscopy was used to investigate arsenic speciation in a series of samples collected from the jeb tmf in 2013 arsenic k edge xanes analysis confirmed that most 86 wt of the arsenic content in the tailings samples consisted of iron containing arsenates of these crystalline scorodite was the most abundant arsenate species followed by poorly crystalline arsenates in the form of poorly crystalline ferric arsenate feaso 4 xh 2 o and arsenate adsorbed on ferrihydrite aso 4 feooh arsenite adsorbed on ferrihydrite aso 3 feooh and gersdorffite niass were also identified as minor arsenic species in the tailings samples the abundance and distribution of scorodite in the tmf suggests that it is the major arsenic species produced in the tailings preparation process

arsenic and iron speciation in uranium mine tailings using x ray absorption spectroscopy abstract in northern saskatchewan canada high grade u ores and the resulting tailings can contain high levels of as an environmental concern in the u mining industry is the long term stability of as within tailings management facilities tmfs and its potential transfer to the surrounding groundwater to mitigate this problem u mill effluents are neutralized with lime to reduce the aqueous concentration of as this results in the formation of predominantly fe 3 as 5 secondary mineral phases which act as solubility controls on the as in the tailings discharged to the tmf because the speciation of as in natural systems is critical for determining its long term environmental fate characterization of as bearing mineral phases and complexes within the deposited tailings is required to evaluate its potential transformation solubility and long term stability within the tailings mass in this study synchrotron based bulk x ray absorption spectroscopy xas was used to study the speciation of as and fe in mine tailings samples obtained from the deilmann tmf at key lake saskatchewan comparisons of k edge x ray absorption spectra of tailings samples and reference compounds indicate the dominant oxidation states of as and fe in the mine tailings samples are 5 and 3 respectively largely reflecting their generation in a highly oxic mill process deposition in an oxidized environment and complexation within stable oxic phases linear combination fit analyses of the k edges for the fe x ray absorption near edge spectra xanes to reference compounds suggest fe is predominantly present as ferrihydrite with some amount of the primary minerals pyrite 8 15 in some samples and chalcopyrite 5 15 in some samples extended x ray absorption fine structure exafs analysis of as k edge spectra indicates that as 5 arsenate present in tailings samples is adsorbed to the ferrihydrite though an inner sphere bidentate linkage

major hydrogeochemical processes in the two reservoirs of the yangbajing geothermal field tibet china abstract the yangbajing geothermal field with the highest reservoir temperature in china is located about 90 km northwest to lhasa city capital of tibet where high temperature geothermal fluids occur both in shallow and deep reservoirs the geophysical survey by the indepth international deep profiling of tibet and the himalayas project group proved the existence of magmatic heat source at yangbajing in the study area the hydrochemistry of cold surface waters and groundwaters and that of thermal groundwaters from both reservoirs are distinctively different however analysis of the relationship between enthalpy values and cl concentrations of cold groundwaters and geothermal fluids indicates that the geothermal fluids from the shallow reservoir were formed as a result of mixing of cold groundwaters with geothermal fluids from the deep reservoir in other words the geothermal fluids from the deep reservoir flowed upwards into the shallow reservoir where it was diluted by the shallow cold groundwaters to form the shallow geothermal fluids with much lower temperature a binary mixing model with two endmembers the cold groundwaters and the deep geothermal fluids was proposed and the mixing ratios for the geothermal fluid from each shallow well were estimated using the mixing ratios the concentrations of some constituents in shallow geothermal fluids such as as b sio 2 so 4 2 and f were calculated and their differences with the actual concentrations were estimated the results show that the differences between estimated and actual concentrations of as and b are small the average absolute values being only 1 9 and 7 9 respectively whereas those of sio 2 so 4 2 and f are much bigger indicating that other hydrogeochemical processes are responsible for the concentrations of these constituents it is postulated that sio 2 precipitation due to water temperature decrease h 2 s oxidation and ion exchange between oh in geothermal waters and exchangeable f in fluoride bearing silicate minerals during the geothermal fluid upflow might be the causes for the observed concentration differences

sediment facies and late holocene progradation of the mekong river delta in bentre province southern vietnam an example of evolution from a tide dominated to a tide and wave dominated delta abstract the mekong river delta southern vietnam is a typical mixed tide and wave energy delta with a wide delta plain formed during the last 6 ka and is one of the largest deltas in the world three cores were taken from bentre province in the lower delta plain with the objective to describe the sediment facies and to clarify the changes from tide dominated to tide wave dominated delta of the mekong river delta during the late holocene three cores bt1 bt2 and bt3 were obtained in 1997 holocene sediments in bt1 and bt3 with thickness ranging from 10 to 20 m were mainly composed of deltaic sediments unconformably overlying the late pleistocene sediments the bt2 core however consisted of transgressive estuarine sediments covered by deltaic sediments infilling the paleo mekong river incised valley which is more than 70 m deep and was formed during the last glacial period the deltaic sediment facies and succession in the bt2 and bt3 cores taken from the outer delta plain with beach ridges were different from those of the bt1 core taken from the inland delta plain the bt2 and bt3 cores provide a good example of tide and wave dominated delta sediments and were characterized by a coarsening upward delta front facies covered by a fining upward subtidal to intertidal flat facies followed by a coarsening upward foreshore dune facies these changes from the inland delta plain to the beach ridge delta plain were accompanied by changes in progradation rates and subaqueous delta topography caused by increased wave influence

chemical weathering in the three rivers region of eastern tibet abstract three large rivers the chang jiang yangtze mekong lancang jiang and salween nu jiang originate in eastern tibet and run in close parallel over 300 km near the eastern himalayan syntaxis seventy four river water samples were collected mostly during the summer season from 1999 to 2004 their major element compositions vary widely with total dissolved solids tds ranging from 31 to 3037 mg l reflecting the complex geologic makeup of the vast drainage basins the major ion distribution of the main channel samples primarily reflects the weathering of carbonates evaporite dissolution prevails in the headwater samples of the chang jiang in the tibetan plateau interior as evidenced by the high tds 928 and 3037 mg l and the na cl dominant major element composition local tributary samples of the mekong and salween draining the lincang batholith and the tengchong volcano show distinctive silicate weathering signatures we used five reservoirs rain halite sulfate carbonate and silicate in a forward model to calculate the contribution from silicate weathering to the total dissolved load and to estimate the consumption rate of atmospheric co 2 by silicate weathering carbonate weathering accounts for about 50 of the total cationic charge tz in the samples of the mekong and the salween exiting the tibetan plateau in the exit sample of the chang jiang 45 of tz is from halite dissolution inherited from the extreme headwater tributaries in the interior of the plateau and carbonates contribute only 26 to the tz the net rate of co 2 consumption by silicate weathering is 103 121 10 3 mol km 2 year 1 lower than the rivers draining the himalayan front gis based analyses indicate that runoff and relief can explain 52 of the spread in the rate of atmospheric co 2 drawdown by silicate weathering but other climatic temperature precipitation potential evapotranspiration and geomorphic elevation slope factors also show collinearity only qualitative conclusions can be drawn for the significance of lithology due to lack of digitized lithologic information the effect of the peculiar drainage pattern due to tectonic forcing is not readily apparent in the major element composition or in increased chemical weathering rates the 87 sr 86 sr ratios and the silicate weathering rates are in general lower in the three rivers than in the rivers draining the himalayan front

the fate of geothermal arsenic in the madison and missouri rivers montana and wyoming geothermal as from yellowstone national park causes high as concentrations 10 370 g l in the madison and missouri rivers in montana and wyoming arsenic transport is largely conservative in the upper basin as demonstrated by the near equivalence of dissolved and total recoverable as concentrations the constancy of as loads and consistent ratios of concentrations of as to conservative geothermal tracers diurnal cycling of as between aqueous and solid phases in response to ph induced changes in sorption equilibria causes small variations of about 10 20 in dissolved as concentrations hcl extractable as concentrations in river and lake sediment in the upper basin are variable depending on position relative to the as rich headwaters and geochemical and physical processes associated with lakes in the lower missouri river large quantities of suspended sediment from tributaries provide sufficient sorption sites for substantial conversion of as from the aqueous phase to the solid phase

biogeochemistry of u ni and as in two meromictic pit lakes at the cluff lake uranium mine northern saskatchewan open pits which remain after uranium u mining operations cease can form meromictic lakes that develop suitable conditions for the containment of dissolved and colloidal metals in this study t

numerical experiments on permeability tensor and its application to jointed granite at stripa mine sweden rock masses containing a large number of geological discontinuities called joints are treated as homogeneous anisotropic porous media a permeability tensor hydraulically equivalent to a flow network formed by joints is formulated in terms of two tensors and a nondimensional scalar both depending only on the geometrical aspects of joints such as the spacing size orientation and aperture two dimensional numerical analyses on seepage flow through the networks support the validity of the present theory the information about the geometry of joints which is obtained from the ventilation drift at stripa mine sweden is interpreted to give the corresponding permeability tensor the permeability tensor is compared with the result of the large scale hydraulic conductivity test with the conclusion that it provides a reasonable prediction for the hydraulic properties of stripa jointed granite

long period toroidal earth free oscillations from the great sumatra andaman earthquake observed by paired laser extensometers in gran sasso italy summary strain data recorded by two crossed laser extensometers operating in the gran sasso underground observatory recorded seismic free oscillations excited by the 2004 december 26 sumatra andaman earthquake the main source of instrumental noise can be mitigated by differencing data from the crossed strainmeter arms so that the resulting differential strain data set offers an unprecedented resolution of the seismic toroidal free oscillations with periods t 1000 s we reconstruct the time evolution of selected free oscillations for comparison with synthetic seismograms that include normal mode coupling effects from coriolis force attenuation and ellipticity envelopes estimated for the gran sasso differential data set for free oscillations with period t 1 mhz are approximated adequately by a composite centroid moment tensor cmt source with five subevents and an aggregate mw 9 3 moment magnitude envelopes for several toroidal free oscillations with t 1000 s are predicted less well the amplitude of the rarely observed mode 0t2 is overpredicted at gran sasso by roughly a factor of two and other modes are underpredicted the amplitude discrepancy for 0t2 is confirmed at selected exceptionally low noise seismic stations hypothetical explanations include a slow slip component of the seismic moment release errors in the composite cmt source model unmodelled coupling effects to earth s secular modes and feedback from the sumatra andaman tsunami on indian ocean coastlines of these hypotheses either an extended duration strain release or tsunami feedback seem most plausible the viability of the tsunami feedback mechansim deserves further investigation

natural arsenic contamination of holocene alluvial aquifers by linked tectonic weathering and microbial processes 1 linked tectonic geochemical and biologic processes lead to natural arsenic contamination of groundwater in holocene alluvial aquifers which are the main threat to human health around the world these groundwaters are commonly found a long distance from their ultimate source of arsenic where chemical weathering of as bearing minerals occurs we propose a gbh as model that ties together all of the important tectonic biologic and hydrologic processes that cause natural as release in groundwater in holocene terrestrial deposits processes highlighted by the gbh as model can explain the movement of arsenic from lithosphere to hydrosphere however we propose a factor that has increased dissolved as concentrations in holocene aquifers to levels where human health is threatened mechanical weathering associated with pleistocene glaciation our model invokes erosion of mountain belts aided by glaciers transport of arsenic by surface waters adsorption of as by stream sediments and deposition of stream sediments and organic matter in alluvial deposits subsequently fe iii reducing bacteria present in alluvial aquifers cause the release of sorbed as to groundwater under moderately reducing conditions

permeability tensor for discontinuous rock masses rock masses which commonly contain a large number of discontinuities are treated as homogeneous anisotropic porous media to formulate the corresponding permeability tensor this has been successfully achieved by introducing a symmetric tensor crack tensor which depends only on the geometry of the related cracks aperture size and orientation the principal directions associated with the symmetric crack tensor are coaxial with those of the permeability tensor the first invariant of the crack tensor is proportional to the mean permeability while the deviatoric part is related to the anisotropic permeability these results are well supported by numerical experiments on the permeability of cracked media by long remer wilson and witherspoon an actual rock mass moderately jointed granite was studied to see whether the crack tensor can be determined in situ stereology based on geometrical statistics provides a sound basis for determining the crack tensor in situ the crack tensor is obtained by

arsenic attenuation in tailings at a former cu w as mine sw finland nearly half a century after mine closure release of as from the ylojarvi cu w as mine tailings in groundwater and surface water run off was observed investigations by scanning electron microscopy sem electron microprobe analysis empa synchrotron based micro x ray diffraction xrd micro x ray absorption near edge structure xanes and micro extended x ray absorption fine structure exafs spectroscopy and a sequential extraction procedure were performed to assess as attenuation mechanisms in the vadose zone of this tailings deposit results of sem empa and sequential extractions indicated that the precipitation of as bearing fe iii oxy hydroxides up to 18 4 wt as2o5 and fe iii arsenates were important secondary controls on as mobility the xrd xanes and exafs analyses suggested that these phases correspond to poorly crystalline and disordered as bearing precipitates including arsenical ferrihydrite scorodite kankite and hydrous ferric arsenate hfa the ph within 200 cm of the tailings surface averaged 5 7 conditions which favor the precipitation of ferrihydrite poorly crystalline fe iii arsenates are potentially unstable over time and their transformation to ferrihydrite which contributes to as uptake has potential to increase the as adsorption capacity of the tailings arsenic mobility in tailings pore water at the ylojarvi mine will depend on continued arsenopyrite oxidation dissolution or transformation of secondarymore fe iii arsenates and the as adsorption capacity of fe iii oxy hydroxides within this tailings deposit less

field evidence for uranium nanocrystallization and its implications for uranium transport abstract high resolution transmission and scanning electron microscopies hrtem and sem both equipped with energy dispersive x ray spectrometers eds have been used to determine the chemical form of u vi in rocks and to examine u uptake mechanisms at low u concentrations 10 8 10 7 mol l in the downgradient of the koongarra u ore deposit in australia uranium was concentrated in fe hydr oxide nodules and veins that consisted mainly of goethite and hematite nanocrystals 20 100 nm in size of uranyl phosphates such as metatorbernite cu uo2 2 po4 2 8h2o were scattered between and firmly attached to nanocrystals 2 50 nm of goethite and hematite the environment where the nanocrystallization occurred was probably isolated from the koongarra groundwaters undersaturated with respect to the uranyl phosphates chemical analyses by eds showed that the uranyl phosphate nanocrystals contribute more to the u uptake than adsorbed u the presence of the uranyl phosphate nanocrystals between fe hydr oxides explains the u distribution previously studied in the macro and micro scale in koongarra our hrtem and sem observations suggest that during crystallization of goethite and hematite from ferrihydrite u p and cu or mg adsorbed onto ferrihydrite are released from ferrihydrite accumulated on the surface of forming goethite and hematite and finally form nanocrystals of uranyl phosphates thus uranyl phosphate nanocrystallization though initiated by adsorption is a dominating mechanism of the u uptake and controls long term u transport at low u concentrations

microscale controls on the fate of contaminant uranium in the vadose zone hanford site washington abstract an alkaline brine containing uranyl uo22 leaked to the thick unsaturated zone at the hanford site we examined samples from this zone at microscopic scale to determine the mode of uranium occurrence microprecipitates of uranyl uo22 silicate within lithic clast microfractures and constructed a conceptual model for its emplacement which we tested using a model of reactive diffusion at that scale the study was driven by the need to understand the heterogeneous distribution of uranium and the chemical processes that controlled it x ray and electron microprobe imaging showed that the uranium was associated with a minority of clasts specifically granitic clasts occupying less than four percent of the sediment volume xanes analysis at micron resolution showed the uranium to be hexavalent the uranium was precipitated in microfractures as radiating clusters of uranyl silicates and sorbed uranium was not observed on other surfaces compositional determinations of the 1 3 m precipitates were difficult but indicated a uranyl silicate these observations suggested that uranyl was removed from pore waters by diffusion and precipitation in microfractures where dissolved silica within the granite equilibrated solution would cause supersaturation with respect to sodium boltwoodite this hypothesis was tested using a reactive diffusion model operating at microscale conditions favoring precipitation were simulated to be transient and driven by the compositional contrast between pore and fracture space pore space conditions including alkaline ph were eventually imposed on the microfracture environment however conditions favoring precipitation were prolonged within the microfracture by reaction at the silicate mineral surface to buffer ph in a solubility limiting acidic state and to replenish dissolved silica during this time uranyl was additionally removed to the fracture space by diffusion from pore space uranyl is effectively immobilized within the microfracture environment within the presently unsaturated vadose zone

spatiotemporal evolution of aseismic interplate slip between 1996 and 1998 and between 2002 and 2004 in bungo channel southwest japan 1 interplate aseismic slip in the bungo channel area southwest japan occurred during 1996 1998 and 2002 2004 we employed a square root information filter following the time dependent inversion technique to time series of daily coordinates of global positioning system gps sites the results show that aseismic interplate slip occurred beneath the southwestern part of shikoku island from late 1996 then shifted southwestward to the bungo channel area from may 1997 to february 1998 and subsided over time with a moment magnitude mw of 7 1 in contrast the 2002 2004 event shows slip in the area beneath the bungo channel in an early stage from march 2003 to august 2003 from august 2003 to january 2004 the slip area expanded by around 30 km northeastward to the southwestern part of shikoku island and the northern part of the bungo channel and then decayed over time with mw reaching 7 1 in the 2002 2004 event the start of the northeastward expansion and acceleration of the aseismic slip coincided with the occurrence of a short term slow slip event and low frequency earthquakes in a deep area this is a different spatiotemporal evolution from that of the 1996 1998 event despite having occurred in almost the same area with similar moment magnitudes a balance of slip deficit and forward aseismic slip on the plate boundary suggests that part of the bungo channel area releases strain energy mainly by episodic long term slow slip events

late cenozoic to holocene deformation in southwestern sichuan and adjacent yunnan china and its role in formation of the southeastern part of the tibetan plateau from at least 2 4 ma to present crust in the southeastern part of the tibetan plateau west of the convex east xianshuihe xiaojiang fault system has deformed internally and rotated clockwise around the eastern himalayan syntaxis the northwest striking ganzi fault zone bounds the rotating crust on the north and has a total left slip of 78 100 km of which 60 km is transferred to the xianshuihe fault zone across a diffuse transfer zone and 22 40 km is absorbed by bending of older structures and crustal shortening crustal shortening is expressed along and east of the eastern end of the ganzi fault zone by mountains capped by permanent glaciers locally rising nearly 1000 m above the average elevation of the tibetan plateau a similar transfer of left slip into shortening occurs farther south across the xianshuihe fault in the high mountains around and east of gongga shan 7556 m the northwest striking convex east left lateral litang fault zone lies southwest of the ganzi xianshuihe xiaojiang fault zone and appears to be less well developed but otherwise similar to the ganzi fault zone the batang chenzhi and other northeast striking right lateral faults of small displacement occur within the rotating crustal fragment together with the left slip faults they accommodate east west shortening northeast of the eastern himalayan syntaxis south of this region of shortening the crust is extending to form grabens within the dali and southern xiaojiang fault systems and in the tengchong volcanic province the progressive change from shortening southward into extension is related to variations in strain that characterize the region from northeast to southeast of the eastern himalayan syntaxis the assemblage of structures in southwestern sichuan geometrically resembles structures of eocene to miocene age in southern yunnan that were positioned northeast of the eastern himalayan syntaxis similar to present day southwestern sichuan at the time of their development the similarity in the structural development in the two areas indicates that crust northeast of the syntaxis underwent a common evolution as the syntaxis migrated northward during the past 50 m y structures in sichuan are less fully developed than older structures in southwestern yunnan and can serve as a guide to reconstruct the progressive tectonic development in the region of the syntaxis deformation in these areas indicates that plateau formation has been complex inhomogeneous and diachronous at scales from 1000 km to less than 100 km

mobility of uranium during weathering mineralogical and geochemical mechanisms of u fixation under oxidizing conditions in the vicinity of the secondary u ore deposit at koongarra australia were examined using transmission and scanning electron microscopy and thermodynamic calculations the formation of saleeite mg uo 2 2 po 4 2 1oh 2 o is the predominant mechanism for u fixation upstream from the deposit where saleeite replaces sklodowskite and granular apatite within the deposit and further downstream u is fixed in microcrystals 10 50 nm of saleeite and meta torbernite scattered within veins of fine grained 2 50 nm fe super 3 minerals primarily goethite and hematite thermodynamic calculations indicate the groundwater is undersaturated with respect to saleeite and metatorbernite and that these minerals should precipitate at higher u or p concentrations than observed this suggests that the upstream saleeite precipitated at the reaction interfaces of dissolving sklodowskite and apatite under local saturation conditions observed textural relationships of saleeite and meta torbernite microcrystals with the fe minerals combined with thermodynamic calculations suggest surface precipitation as the formation mechanism for saleeite and meta torbernite microcrystals within and downstream from the secondary ore deposit phosphorous released during the aging of ferrihydrite and u adsorbed onto fe minerals are probably the sources of the major components of the microcrystals downstream the microcrystals exist where groundwater u concentrations are as low as 10 30 mu g l once released from the ore deposit u is fixed in uranyl phosphates even where measured groundwater is undersaturated with respect to uranyl phosphates the surface precipitation is an important example of long term post adsorption u fixation in a natural system the fully crystalline and radiation damaged microstructures of saleeite indicate uranyl phosphates have formed continuously or intermittently for the last few million years

holocene delta evolution and sediment discharge of the mekong river southern vietnam abstract evolutionary changes delta progradation and sediment discharge of the mekong river delta southern vietnam during the late holocene are presented based on detailed analyses of samples from six boreholes on the lower delta plain sedimentological and chronostratigraphic analyses indicate clearly that the last 3 kyr were characterized by delta progradation under increasing wave influence southeastward sediment dispersal decreasing progradation rates beach ridge formation and steepening of the face of the delta front estimated sediment discharge of the mekong river for the last 3 kyr based on sediment volume analysis was 144 36 million t yr 1 on average or almost the same as the present level the constant rate of delta front migration and stable sediment discharge during the last 3 kyr indicate that a dramatic increase in sediment discharge owing to human activities as has been suggested for the yellow river watershed did not occur although southeast asian rivers have been considered candidates for such dramatic increases in discharge during the last 2 kyr the mekong river example although it is a typical large river of this region does not support this hypothesis therefore estimates of the millennial scale global pristine sediment flux to the oceans must be revised

synergies in elemental mobility during weathering of tetrahedrite cu fe zn 12 sb as 4s13 field observations electron microscopy isotopes of cu c o radiometric dating and water geochemistry abstract tetrahedrite cu fe zn 12 sb as 4s13 is commonly present in many ore deposits and may be transferred to mining waste here we describe the behavior of all elements in tetrahedrite during oxidative dissolution in a natural oxidation zone at piesky slovakia this being a long term analogue of weathering of tetrahedrite rich mining wastes electron microprobe work identified initial early advanced and mature stages of weathering the initial stages include formation of secondary covellite and chalcocite the following stages only oxidic products divided into greenish masses and brown veinlets both of them are nanocrystalline mixtures of minerals the masses are cu sb as rich and consist of a nanocrystalline pyrochlore phase the veinlets are fe sb as rich and contain tripuhyite goethite and pyrochlores quantitative elemental budgets show that some elements zn s ni co are rapidly lost whereas others especially cu and as are retained and form copper arsenates in the mature stages of weathering about 10 as and almost 50 of sb are lost during weathering likely released into water some sb is stored in secondary minerals such as camerolaite cualstibite or tripuhyite light carbon isotopic composition 13c down to 11 1 document significant biological contribution for c in the secondary minerals copper isotopes become progressively heavier during weathering from initial 65cu of 2 45 in tetrahedrite up to 4 3 in some azurite samples but 6 3 in covellite and chalcocite documenting cyclic removal of light copper isotopes into covellite and chalcocite the observation of elemental synergies during weathering of tetrahedrite shows that the solubility and mobility of as is controlled by copper arsenates not by iron oxides in an environment rich in tetrahedrite but poor in pyrite antimony another element of environmental concern is mostly released into water and creates low concentration anomalies in stream sediments and soils

significance of aluminum phosphate sulfate minerals associated with u unconformity type deposits the athabasca basin canada aluminum phosphate sulfate aps minerals formed around the athabasca unconformity type deposits and those from their australian counterparts are chemically very similar showing the same continuum between the diagenetic sr rich aps minerals of the barren sandstones and the lree rich composition of the aps minerals in the hydrothermally altered sandstone the p and lree rich compositions were controlled by the transport and the redistribution of p and lree elements released from the dissolution of phosphate minerals principally monazite in the basement rocks and in the basin during the syn ore alteration processes the s sr ratio measured in the aps minerals from unaltered sandstone away from the unconformity and any mineralization is preserved during the syn ore alteration processes suggesting that the fluids involved in both the deep burial diagenetic processes and the syn ore alteration system were derived from a similar diagenetic reservoir in both the athabasca and kombolgie regions the trioctahedral chlorite host rock alteration around the australian basement hosted u deposits as compared to the illite and sudoite associated with the athabasca basement hosted along with the more lree rich aps compositions in the australian deposits suggests that the ph and oxygen fugacity f o 2 of the syn ore fluids differed in the alteration systems of the two regions at the time of the u deposition

estimating the intensity of rock discontinuities this paper presents an approach for estimating the intensity of discontinuities and formulating intensity and orientation as a fracture tensor specifically the size distribution and the number of discontinuities are estimated first from which the fracture tensor is then derived discontinuity size distribution is inferred from the trace data sampled in circular windows by using a general stereological relationship between the true trace length distribution and the discontinuity diameter distribution assuming circular shaped discontinuities because the measured trace lengths are biased a method is proposed to estimate the true trace length distribution for circular window sampling circular window sampling has the advantage of automatically eliminating the orientation bias when estimating the true trace lengths a method is then presented with which the total number of discontinuities in an objective volume can be estimated from the number of discontinuities observed in normal size boreholes and using the inferred discontinuity diameter from the circular window sampling on the rock surface with the derived size distribution and number of discontinuities the intensity of discontinuities which is the total surface area of discontinuities per unit volume can then be calculated and included in a new definition of a fracture tensor an application of the approach to analyze simulated discontinuities produces satisfactory results

uranium bearing phases in a u mill disposal site in northern canada products of the interaction between leachate raffinate and tailings material abstract the above ground tailings management facility agtmf is a licensed tailings receiving facility at the key lake mine site northern saskatchewan canada tailings within the agtmf were deposited between 1983 and 1995 and are derived from mining and milling of the gaertner and deilmann ore bodies at key lake the tailings are primarily composed of quartz phyllosilicate and clay gangue minerals minor amounts of ni co s arsenides iron oxide minerals and gypsum they typically contain u concentrations on the order of between 50 and 300 ug g u a small area of the agtmf receives occasional mill process upset solutions with an initial ph range of 2 6 the solutions contain elevated activities of u bearing aqueous species and are rapidly buffered to neutral and sub alkaline ph values during interaction with surroundings tailings solids having a ph of approximately 10 this buffering and neutralization process results in the precipitation of gypsum and minor amounts of uranyl minerals phases of the autunite group chernikovite h3o uo2 po4 h2o 3 and troegerite h3o uo2 aso4 h2o 3 with minor nh 4 occur predominantly in the gypsum matrix but can also occur as crusts on silicates the occurrence of troegerite is due to elevated concentrations of as within the deposited tailings solids surface alteration on phyllosilicates within tailings affected by the mill process solutions results in elevated concentrations of k at the phyllosilicate water interface which are ideal nucleation sites for the formation of single crystals of zippeite k3 h2o 3 uo2 4 so4 2o3 oh use of nh4 sulfates and ammonia in the extraction and yellow cake precipitation cycles and subsequent entrainment of nh4 species in the tailings results in the occurrence of nh4 bearing phases of the zippeite and autunite group literature data on dissolution features dissolution kinetics and mineral solubilities suggests that the minerals of the autunite group control the mobility of u in the contact zone between the mill process solutions and the tailings