characteristics of mud diapirs and mud volcanoes and their relationship to oil and gas migration and accumulation in a marginal basin of the northern south china sea mud diapir and mud volcano have the same formation mechanism and similar development and evolution characteristics but different geological features and forms in this study the development and characteristics of a mud diapir in yinggehai basin northwestern south china sea and a mud volcano in southwest taiwan basin northeastern south china sea were investigated the geochemical characteristics of their associated natural gases were also analyzed the results indicated that the yinggehai basin mud diapir is mainly distributed in the deep and large depression of the central basin and presents five lines in echelon arrangement along a northwest direction its development and evolution characteristics are low density and speed and abnormally high temperature and overpressure in contrast the southwest taiwan basin mud volcano is mainly distributed in a deep water slope area of the south sag and tainan kaohsiung onshore mud volcanoes are mainly distributed along the deep and large fault zone and their morphological characteristics are similar to venting volcanoes the seabed morphology of offshore mud volcano seems similar but current research is still insufficient there are many types of associated hydrocarbon gases in mud diapir and mud volcano but the high maturity coal type hydrocarbon gas is the main one the associated non hydrocarbon gas is rich in co2 and n2 which is mainly derived from a co2 source from inorganic crust the source of both diapir and volcano is thick marine miocene and pliocene age mud with hydrocarbon generating potential the mature hydrocarbon generation mud diapir mud volcano migration and deposition into an appropriate reservoir as well as diapir associated structures constitute a unique oil gas migration and accumulation system which thus adds to our understanding of the distribution of such mud diapir volcano type oil gas reservoir

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

fluorine surface speciation in south andean volcanic ashes abstract fresh volcanic ash samples collected during the eruptions of the hudson 1991 chaiten 2008 puyehue 2011 calbuco 2015 and copahue 2016 volcanoes were analyzed in order to identify the fluorine f bearing phases xps and hr tem was used to determine the solid speciation of f in order to decrease the surface differential charging of samples xps data have been collected using an electron flood gun during spectral acquisition ash leaching at different ph conditions was also performed with the aim of understanding the factors that control the fluoride release to aqueous reservoirs the results indicates that in the studied patagonian ashes f is concentrated onto the ash surface likely in the form of f na and f ca salts but also within the glass lattice forming f si and f al bonds although the main f source in the studied volcanic ashes is the aluminosilicate glass this phase is stable at the neutral ph that dominates the aqueous reservoirs thus the contribution to the pool of dissolved fluoride is minor higher contributions are associated with soluble fluoride salts in addition the presence of coatings of f ca compounds inhibits the release of fluoride within the volcanic glass lattice at least during the initial stages of the ash water interaction

sedimentological maps of the typical loessic units in north pampa argentina abstract application of grain size data allowed the construction of maps of two typical loessic formations of north pampa a sand sea covering the central argentine plain and a peripheral loess belt to the northeast compose the pampean aeolian system a region of 20 000 km 2 in the loess belt santa fe and cordoba provinces was studied thick loess outcrops are located in this region the tezanos pinto loess upper pleistocene lower holocene in age and the san guillermo fm late holocene in age are analysed in this article the silt content has been taken as the main parameter for mapping in general the pattern of the isoplethic curves is similar in both maps these maps show that the silt content in both loessic units progressively increases from ssw to nne in the loess belt the silt content increases from 55 to 60 in the ssw at the transition belt to the sand sea up to 75 80 in the nne along a distance of 120 200 km other sedimentological data of the outcropping loess paleosols sequences are presented as complementary information

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

observed and numerically simulated structure of a mature supercell thunderstorm abstract through the interactive use of doppler radar analyses and a three dimensional numerical storm simulation the detailed structure of a supercell tornadic storm is analyzed this storm named the del city storm occurred in central oklahoma on 20 may 1977 the storm exhibits certain important features which are essential to maintaining its longevity and which promote the storm s transition to its tornadic phase these features are strongly influenced by the rotational character of the storm separates the precipitation from the updraft and which orients the resulting downdrafts to which reinforce low level convergence along the gust front and sustain the storm analyses of air parcel and rain trajectories within the storm provide a detailed visualization of this internal structure these trajectories reveal that air parcels rising through the cyclonically rotating updraft actually turn anticyclonically with height owing to the influence of the storm relative environmental wind field downdraft traj

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

groundwater arsenic in the chaco pampean plain argentina case study from robles county santiago del estero province in large parts of rural argentina people depend on groundwater whose as content exceeds the argentine drinking water standards 0 05 mg l 1 the most affected areas are located in the chaco pamp

hydrocarbon seeps in petroliferous basins in china a first inventory abstract natural hydrocarbon seepage is a widespread phenomenon in sedimentary basins with important implications in petroleum exploration and emission of greenhouse gases to the atmosphere china has vast petroleum oil and gas bearing sedimentary basins but hydrocarbon seepage has rarely been the object of systematic studies and measurements based on the available chinese literature we report a first inventory of 932 hydrocarbon seeps or seepage zones 710 onshore seeps and 222 offshore seeps including 81 mud volcanoes 449 oil seeps 215 gas seeps and 187 solid seeps bitumen outcrops the seeps are located within the main 20 mesozoic cenozoic petroliferous sedimentary basins especially along the marginal regional and local faults the type of manifestations oil gas or mud volcano reflects the type and maturity of the subsurface petroleum system and the sedimentary conditions of the basin oil seeps are particularly abundant in the junggar basin gas seeps mostly developed in the lunpola basin in smaller basins of the eastern guizhou and yunnan provinces onshore taiwan and in the offshore yinggehai basin mud volcanoes developed in basins junggar qaidam qiangtang onshore and offshore taiwan that experienced rapid sedimentation which induced gravitative instability of shales and diapirism in comparison to available global onshore seep data bases china results to be the country with the highest number of seeps in the world the massive gas seepage in china could represent a considerable natural source of methane to the atmosphere and a key process that may drive future hydrocarbon exploration

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

late miocene provenance change on the eastern margin of the yinggehai song hong basin south china sea evidence from u pb dating and hf isotope analyses of detrital zircons abstract understanding the provenance of the reservoir in a sedimentary basin is of great importance in hydrocarbon exploration and production the yinggehai song hong basin is one of the most important cenozoic petroliferous basins in the south china sea to better understand the provenance characteristics of the upper miocene huangliu formation tortonian messinian on the eastern margin of the basin and test the influence of uplift of the tibetan plateau in the south china sea 172 single zircons from two sandstone samples in the lingtou gas field were dated by u pb chronometer and 54 of these grains were spot analyzed for hf isotopes the results indicate that the upper member of the huangliu formation in this gas field shows two major peaks of u pb ages at ca 250 ma and ca 432 ma along with four subordinate peaks at ca 757 ma ca 1926 ma ca 2529 ma and ca 2775 ma the initial hf isotope ratios ehf t of these zircons are negative to positive for each age group suggesting that existing crustal materials were mixing with new mantle melts in some magmatic episodes in contrast the lower member of the huangliu formation show two major age peaks at ca 98 ma and 248 ma with a subordinate peak at ca 1453 ma the ehf t values are concentrated between 11 6 and 3 4 revealing that they were derived from older crust comparing with the source characteristics of tectonic units surrounding the basin the source of the upper member in the gas field was mainly from the southern yangtze block whereas the lower member was derived from the hainan uplift together with the change of climate and sedimentation rate after 10 ma on the northern margin of the south china sea we attribute the provenance change to the uplift of the tibetan plateau at the same time

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

the structure and formation of diapirs in the yinggehai song hong basin south china sea abstract the occurrence of shale diapirs in the yinggehai song hong ygh sh basin is well documented as is their association with big petroleum fields in order to better understand how and why the diapirs form we performed a detailed geophysical analysis using a new regional compilation of high resolution two and three dimensional seismic reflection data as well as drilling data that cover the diapirs in ygh sh basin as many as 18 diapirs were identified and are arranged in six n s striking vertical en echelon zones on seismic reflection sections gas chimney structures diapiric faults and palaeo craters are genetically linked with the process of diapirism here we use geophysical and geological observations to propose a three stage model for diapirism initiation emplacement and collapse during these three stages different diapiric structure styles are formed which we describe in detail these include buried diapirs piercing diapirs and collapsed diapirs we link the diapirism to activity on the offshore continuation of the red river fault as shown on our high resolution seismic reflection data which is also related to a high paleogeothermal gradient caused by crustal thinning we also recognize the role of loading by the very large volume of sediment eroded from the edges of the tibetan plateau and delivered by the red river to the basin

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

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

the dependence of numerically simulated convective storms on vertical wind shear and buoyancy abstract the effects of vertical wind shear and buoyancy on convective storm structure and evolution are investigated with the use of a three dimensional numerical cloud model by varying the magnitude of buoyant energy and one directional vertical shear over a wide range of environmental conditions associated with severe storms the model is able to produce a spectrum of storm types qualitatively similar to those observed in nature these include short lived single cells certain types of multicells and rotating supercells the relationship between wind shear and buoyancy is expressed in terms of a nondimensional convective parameter which delineates various regimes of storm structure and in particular suggests optimal conditions for the development of supercell type storms applications of this parameter to well documented severe storm cases agree favorably with the model results suggesting both the value of the model in studying these modes of convection as well as the value of this representation i

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

a proposed new type of arsenian pyrite composition nanostructure and geological significance this report describes a new form of arsenian pyrite called as3 pyrite in which as substitutes for fe fe as s2 in contrast to the more common form of arsenian pyrite as1 pyrite in which as1 substitutes for s fe as s 2 as3 pyrite has been observed as colloformic overgrowths on as free pyrite in a hydrothermal gold deposit at yanacocha peru xps analyses of the as3 pyrite confirm that as is present largely as as3 empa analyses show that as3 pyrite incorporates up to 3 05 at of as and 0 53 at 0 1 at 0 27 at 0 22 at 0 08 at and 0 04 at of pb au cu zn ni and co respectively incorporation of as3 in the pyrite could be written like as3 y au 1 y 2 fe2 where au and vacancy help to maintain the excess charge hrtem observations reveal a sharp boundary between as free pyrite and the first overgrowth of as3 pyrite 20 40 nm thick and co linear lattice fringes indicating epitaxial growth of as3 pyrite on as free pyrite overgrowths of as3 pyrite onto as free pyrite can be divided into three groups on the basis of crystal size 8 20 nm 100 300 nm and 400 900 nm and the smaller the crystal size the higher the concentration of toxic arsenic and trace metals the yanacocha deposit in which as3 pyrite was found formed under relatively oxidizing conditions in which the dominant form of dissolved as in the stability field of pyrite is as3 in contrast reducing conditions are typical of most environments that host as1 pyrite as3 pyrite will likely be found in other oxidizing hydrothermal and diagenetic environments including high sulfidation epithermal deposits and shallow groundwater systems where probably kinetically controlled formation of nanoscale crystals such as observed here would be a major control on incorporation and release of as3 and toxic heavy metals in oxidizing natural systems

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

origin and migration of hydrocarbon gases and carbon dioxide bekes basin southeastern hungary the bekes basin is a sub basin within the pannonian basin containing about 7000 m of post cretaceous sedimentary rocks natural gases are produced from reservoirs precambrian to tertiary in age located on structural highs around the margins of the basin gas composition and stable carbon isotopic data indicate that most of the flammable gases were derived from humic kerogen contained in source rocks located in the deep basin the depth of gas generation and vertical migration distances were estimated using quantitative source rock maturity carbon isotope relationships for methane compared to known neogene source rock maturity depth relationships in the basin these calculations indicate that as much as 3500 m of vertical migration has occured in some cases isotopically heavy 7 0 co2 is the predominant species present in some shallow reservoirs located on basin margin structural highs and has probably been derived via long distance vertical and lateral migration from thermal decompositon of carbonate minerals in mesozoic and older rocks in the deepest parts of the basin a few shallow reservoirs 2000m contain isotopically light 50 to 60 0 methane with only minor amounts of c2 homologs 3 v v this methane is probably mostly microbial in origin above normal pressures occuring at depths greater than 1800 m are believed to be the principal driving force for lateral and vertical gas migration these pressures are caused in part by active hydrocarbon generation undercompaction and thermal decomposition of carbonates

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

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

multiphase natural gas migration and accumulation and its relationship to diapir structures in the df1 1 gas field south china sea abstract the dongfang1 1 df1 1 gas field is the largest commercial gas field yet discovered in the yinggehai basin south china sea the gas reservoirs in the field are normally pressured pliocene shallow marine facies fine grained sandstones and the main source rocks are highly over pressured miocene mudstones and shales the natural gases in the reservoirs consist mainly of hydrocarbon gas co 2 and n 2 geochemical data for the natural gases show that the hydrocarbon rich gases except for a small amount of biogas were derived from these source rocks distributed within over pressured zones but gases rich in co 2 mainly originate from the thermal decomposition of miocene calcareous shales and pre tertiary carbonates at higher temperature fluid inclusion data for the reservoirs were used together with the regional geology distribution of different types of reservoirs and the evolution of diapir structures to determine the episodes of gas migration and accumulation in the df1 1 gas field we believe that the field was formed by four episodes of gas migration and accumulation fluid paleopressure simulation software designed and developed by cnooc china limited was used to simulate the paleopressure history of the strata at the top of the present day high pressure zone a depth of 2800 m in the df1 1 gas field it predicts that the first episode occurred before about 2 ma the second and the third episodes between 2 and 0 5 ma and that the co 2 rich gases migrated into the reservoirs after 0 5 ma the formation and evolution of diapir structures in the yinggehai basin had an important influence on the migration and accumulation of natural gases in the df1 1 gas field rapid deposition gas generation in the source rocks and thermal expansion of pore fluids caused over pressuring in the miocene shales in the center of the depression this over pressuring together with active faulting formed diapir structures during 5 0 5 ma the faults and fractures related to the diapir structures provided a pathway for gas vertical migration from the deep source rocks into the df1 1 reservoirs and controlled the geological distribution of different types of natural gases on this basis a model for gas migration and accumulation is suggested for the df1 1 gas field

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

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

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

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

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

dongfang 1 1 gas field in the mud diapir belt of the yinggehai basin south china sea abstract the dongfang 1 1 df1 1 mud diapir field is the largest gas field discovered in the yinggehai basin up to now with a proven gas reserve of 99 68 10 9 m 3 the gas pay zones are within the pliocene fine sandstones and siltstones of the littoral and sand bar facies with normal pressure regimes the gases include variable amounts of co 2 and n 2 in addition to hydrocarbon gases the hydrocarbon gases with the exception of biogenic methane and nitrogen originated from the marine source rocks within the overpressured lower to middle miocene strata while co 2 is most likely the product of thermal decomposition of the tertiary calcareous mudstones and pre tertiary carbonates through relatively long distance vertical migration the field has received at least four phases of natural gas charging occurring relatively late most likely during the post pliocene himalayan orogeny diapiric faults act as the main conduit for upward movement of fluids released from the deep high pressure system with abnormally high pressures providing the significant driving force for gas migration because of the episodic nature of the deep high pressured fluid release and the diapir fault activity this shallow diapir gas field is characterized by multiple gas sources and episodic fluid accumulation

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

molecular nitrogen in natural gas accumulations generation from sedimentary organic matter at high temperatures the occurrence of natural gas accumulations with high percentages up to 100 of molecular nitrogen in various hydrocarbon provinces represents a largely unresolved problem and a serious exploration risk in this context a geochemical and basin modeling study was performed to evaluate the potential of sedimentary organic matter to generate molecular nitrogen the masses of nitrogen present in coals if converted into molecular nitrogen are sufficient to fill commercial gas reservoirs a calculation for gas accumulations in northern germany where percentages of molecular nitrogen range from less than 5 to greater than 90 reveals that the molecular nitrogen generated in underlying coal bearing strata is sufficient to account for the nitrogen gas even in the largest fi lds in addition much of the total nitrogen in clay rich rock types such as shales and mudstones is fixed in sedimentary organic matter and may add to the nitrogen generation capacity of the coals a kinetic interpretation of the nitrogen and methane generation characteristics of humic coals during laboratory pyrolysis indicates that nitrogen is generated from organic matter in sedimentary basins at higher temperatures than methane minimum temperatures for preferential nitrogen generation are in excess of 300 c for extremely low heating rates or isothermal conditions lasting over 300 m y thus nitrogen rich gases are mainly formed in the final stage of gas generation when sedimentary rocks grade into metamorphic rocks applications of the kinetic parameters for the generation of nitrogen and methane from coaly organic matter in carboniferous sedimentary rocks are presented for part of the northwest german basin in this area immense volumes of the methane rich gas gener ted during the late paleozoic and mesozoic were lost to the atmosphere the present gas composition mainly reflects the latest cenozoic gas generation this cenozoic gas is nitrogen rich where the carboniferous source rock sequences are highly mature and deeply buried

geochemistry and accumulation of carbon dioxide gases in china we propose the following identification indicators for co2 of different origins based on data obtained from analyzing the molecular composition of 1198 gas samples the co2 carbon isotope values of 390 samples and the helium isotope composition of 256 samples collected from wells of 16 oil and gas bearing basins and gas seepages in china and reviewing literature on organic and inorganic co2 throughout the world co2 is of organic origin if co2 content 13cco22 is of inorganic origin if dgr13cco2 8 pmil or co2 60 and co2 is of either organic or inorganic origin or a mixtur of organic and inorganic origins if 10 pmil 13cco213cco2 values of organic co2 mainly range from 10 to 22 pmil in tectonically stable oil and gas bearing basins where deep faults and magmatism are undeveloped organic co2 occurs almost exclusively in tectonically active oil and gas bearing basins where active faults and magmatism are present or in areas of modern volcanic activity the dgr13cco2 values of inorganic co2 range from 2 to 8 pmil and are distributed along faults the inorganic co2 with a dgr13cco2 value of 0 3 pmil is of metamorphic origin and that with dgr13cco2 values of 6 2 pmil is mantle derived and of magmatic origin in china the dgr13cco2 values of inorganic co2 gas pools range from 3 41 to 8 44 pmil and the helium ratio r ra is 1 which indicates that these gases are typically derived from the mantle

characteristics and predictability of a supercell during hymex sop1 an analysis is presented here of intense convection affecting the friuli venezia giulia region fvg northeastern italy during the intensive observation period 2b iop2b in the first special observation period sop1 of hymex hydrological cycle in mediterranean experiment the present study focuses on the first of three severe convection episodes that affected fvg on the morning of 12 september 2012 in the first episode a supercell which produced hail and severe damage to trees and buildings was observed on the plain of fvg the available observations are analysed together with a high resolution mesoscale model in order to identify the relevant mechanisms for the formation and development of the cell six different simulations were performed starting at three different initial times using respectively two different analysis forecasts as initial boundary conditions a large spread in forecast precipitation is found among the six simulations only a few of the simulations were able to reproduce intense rainfall on the plain of fvg during the morning although with significant differences in the rainfall distribution among them one of the six simulations well reproduces the observed elongated distribution of the intense rainfall maximum the characteristics of the cell responsible for this distribution are consistent with those expected for a supercell and its simulated evolution near the adriatic coast agrees well with the other observations some instability parameters over the fvg plain and offshore over the northern adriatic sea are analysed every 5 min showing that during this event the potential instability varies significantly over small space and time intervals and among the simulations the best simulations have the best match to the observed potential instability calculated using the mean characteristics of the lowest 500 m layer

geochemistry origin and accumulation of co2 in natural gases of the yinggehai basin offshore south china sea geochemical and isotopic data indicate the presence of co2 of both organic and inorganic origin in the natural gas reservoirs of the yinggehai basin the natural gases with inorganic co2 commonly show a high content of co2 ranging from 15 to 85 a heavier carbon isotope value of co2 from 0 56 to 8 16 and a lower 3he 4he ratio ranging from 0 20 to 6 79 107 indicating a crustal origin these gases occur locally commonly related to diapir structures natural gases rich in hydrocarbons occur widely and are characterized by a low co2 content from 0 1 to 5 0 and a lighter c1 carbon isotope value from 10 59 to 20 7 indicating an organic origin geological background and geochemical data indicate that the sanya and meishan formations are the main source of hydrocarbon gases and the organic co2 pyrolysis experiments on tertiary calcareous shales and thermal history modeling both suggest that the calcareous shales occurring in the lower miocene strata are the main source of the inorganic co2 gas whereas thermal contact metamorphism of the paleozoic carbonates and or magmatic co2 may have made only a small contribution abnormally high paleogeothermal gradients 4 25 4 56c 100 m 12 09 12 26f 100 ft and a rapid heating rate caused the lower miocene calcareous shales to reach the threshold temperature about 300c 570f of their thermal decomposition at the burial depth of about 6500 m 21 300 ft and to generate great volumes of inorganic co2 gas diapir faults acted as the main pathways for the upward migration of deep inorganic co2 gases into reservoirs connected with shale diapirism along the central yinggehai basin the heavier carbon isotope values of associated methanes and a strong thermal anomaly in the co2 rich gas reservoirs provide evidence that the inorganic co2 gas migrated into the reservoirs later than their associated hydrocarbon rich gases this suggests that the earlier formed traps and sandstone reservoirs distant from shale diapir structures may have greater potential in the exploration for hydrocarbon rich gases

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

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

loess of southern south america abstract loess and loessoid loess like reworked loess sediments extend across the chaco pampean plains and the nw mountain environments of argentina and in neighbouring countries paraguay brazil uruguay bolivia loessoid sediments are much more abundant than primary loess the beginning of the loessoid sedimentation cycle was related to a phase of late miocene orogeny in the andes the plio pleistocene record is mostly composed of loessoid sediments modified by pedogenesis which produced welded palaeosols the late pleistocene holocene loess record reveals a heterogeneous composition across the region coarse textures and an andean derived volcanic composition prevail in the southern pampas finer textures and material coming from the andes and the other two sources sierras pampeanas and the parana basin characterize the loess deposits of the northern pampas and the eastern chaco a southern patagonian source is also suggested for the mountain valley loess of tucuman although a western andean provenance has been proposed it is believed that the material in the western chaco was derived from the bolivian andes loess deposition was related to a multistage transport mechanism involving fluvial and aeolian processes inferred westerly and southwesterly wind directions as dominant carriers of the aeolian deposits are in agreement with westerly palaeowind simulations using climate models however the role played by westerly tropospheric winds and northerly winds remains to be established

effects of the alps and apennines on forecasts for po valley convection in two hymex cases two intensive observation periods iops of the hydrological cycle in the mediterranean experiment hymex are examined in this study iop6 and iop13 were characterized by troughs with associated cold fronts entering the western mediterranean and in both cases organized frontal convection in the po valley was observed these similarities notwithstanding predictability of the po valley convection was limited for iop6 for most of the forecast models available during hymex but not for iop13 using the weather research and forecast wrf model in research mode the present study confirms the relatively good forecast for frontal convection in iop13 is not very sensitive to modeling assumptions in contrast it is found that only a two way nested simulation initialized close to the event was able to produce a realistic representation of the squall line in the po valley for iop6 a comparison between a successful and an unsuccessful simulation of the po valley convection in iop6 suggests the sensitivity lies with the orographic flow modification which was at the threshold between flow over and flow around responses to the maritime alps in particular in the flow over regime downslope winds from the maritime alps and apennines suppress the convergence uplift where the front encounters the barrier wind in the po valley while in the flow around regime it is unimpeded a delicate balance between the competing mechanisms of orographically induced subsidence on the lee side of the apennines and frontal uplift in the po valley is found to be crucial for squall line survival

the influence of the shear induced pressure gradient on thunderstorm motion abstract in the present investigation we propose a simple theory to explain how a veering environmental wind shear vector can cause an initially symmetric updraft to grow preferentially to the right of the shear vector and acquire cyclonic rotation the explanation offered is based on linear theory which predicts that interaction of the mean shear with the updraft produces favorable vertical pressure gradients along its right flank to asses the validity of linear theory for large amplitude updrafts the three dimensional shallow anelastic equations are numerically integrated using a simple parameterization for latent heating within a cloud and the linear and nonlinear forcing terms are separately analyzed these results suggest that although the nonlinear effects strongly promote splitting of the updraft the linear forcing remains the dominant factor in preferentially enhancing updraft growth on the right flank we believe this differential forcing is a major contributor to the observed predominance o

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

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

arsenic associations in sediments from the loess aquifer of la pampa argentina groundwater from the quaternary loess aquifer of la pampa central argentina has significant problems with high concentrations of as up to 5300 g l 1 as well as other potentially toxic trace elements such as f b mo u se and v total as concentrations in 45 loess samples collected from the aquifer have a range of 3 18 mg kg 1 with a mean of 8 mg kg 1 these values are comparable to world average sediment as concentrations five samples of rhyolitic ash from the area have as concentrations of 7 12 mg kg 1 chemical analysis included loess sediments and extracted porewaters from two specially cored boreholes results reveal a large range of porewater as concentrations being generally higher in the horizons with highest sediment as concentrations the displaced porewaters have as concentrations ranging up to 7500 g l 1 as well as exceptionally high concentrations of some other oxyanion species including v up to 12 mg l 1 the highest concentrations are found in a borehole located in a topographic depression which is a zone of likely groundwater discharge and enhanced residence time comparison of sediment and porewater data does not reveal unequivocally the sources of the as but selective extract data acid ammonium oxalate and hydroxylamine hydrochloride suggest that much of the as and v is associated with fe oxides primary oxides such as magnetite and ilmenite may be partial sources but given the weathered nature of many of the sediments secondary oxide minerals are probably more important extract compositions also suggest that mn oxide may be an as source the groundwaters of the region are oxidising with dissolved o2 no3 and so4 normally present and as v usually the dominant dissolved as species under such conditions the solubility of fe and mn oxides is low and as mobilisation is strongly controlled by sorption desorption reactions desorption may be facilitated by the relatively high ph conditions of the groundwaters in the region 7 0 8 8 and high concentrations of potential competitors e g v p hco3 phreeqc modelling suggests that the presence of v at the concentrations observed in the pampean porewaters can suppress the sorption of as to hydrous fe iii oxide hfo by up to an order of magnitude bicarbonate had a comparatively small competitive effect oxalate extract concentrations have been used to provide an upper estimate of the amount of labile as in the sediments a near linear correlation between oxalate extractable and porewater as in one of the cored boreholes investigated has been used to estimate an approximate kd value for the sediments of 0 94 l kg 1 this low value indicates that the sediments have an unusually low affinity for as

geochemistry and origins of natural gases in the yinggehai and qiongdongnan basins offshore south china sea abstract four gas fields and a number of gas bearing structures have been discovered in the yinggehai and qiongdongnan basins offshore south china sea chemical and isotopic data indicate the presence of at least three genetic groups of gases in these basins biogenic gas thermogenic gas and gases with mixed origin thermogenic gases produced from the yacheng field are characterized by relatively high contents of benzene and toluene relatively low 13c values of toluene and high abundance of bicadinanes and oleanane in the associated condensates showing good correlation with the coal bearing sequence of the yacheng formation in the qiongdongnan basin in contrast the gases from the df1 1 and ld gas fields contain high amounts of n2 and co2 low to moderate amounts of benzene and toluene with relatively high 13c values of toluene these characteristics correlate well with the miocene neritic shales in the yinggehai basin analyses on potential source rock samples indicate excellent gas source potential for both the coal bearing sequence in the yacheng formation and the miocene neritic shales containing type iii ii2 kerogens as the result of recent rapid subsidence and sedimentation high temperature and overpressure systems are well developed in the yinggehai and qiongdongnan basins the rapid heating resulted in advanced maturation of organic matter deposited in normally pressured and overpressured strata whereas the strongly overpressured systems led to retarded organic matter maturation postponing the time when the source rocks reached peak gas generation results of 1 d modeling indicate that the coal bearing yacheng formation in the yacheng sag reached peak gas generation during mid miocene pliocene time after the deposition of upper oligocene to lower miocene reservoir rocks the lower mid miocene marine shales reached their peak gas generation stage during the pliocene quaternary in the central yinggehai basin supplying abundant gases to charge the pliocene reservoirs more importantly focused episodic gas migration significantly increased the hydrocarbon expulsion efficiencies of source rocks and thus provided favorable conditions for the accumulation of large amounts of gases in the diapiric structures in a very short geological time the gas source relationship for the yacheng field suggests dominantly short distance gas migration and thus strong source facies controls on the geographic distribution of gas fields within the qiongdongnan basin

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

provenance of upper miocene to quaternary sediments in the yinggehai song hong basin south china sea evidence from detrital zircon u pb ages abstract the yinggehai song hong y sh basin located on the northwestern shelf of the south china sea is one of the world s largest pull apart basins in order to identify the provenance of the upper miocene to quaternary sediments of the basin ten sediment samples were collected from drill cores in the dongfang gas field u pb dating of detrital zircon grains extracted from the ten samples using a laser ablation inductively coupled mass spectrometer la icp ms yields ages ranging from the archean to cenozoic 2898 46 ma to 26 1 ma the zircon u pb age spectra of the upper miocene to quaternary show a similar pattern with major peaks clustered at ca 32 ma ca 99 ma ca 160 ma ca 247 ma ca 422 ma and three broad age groups 600 1000 ma 1700 2100 ma and 2200 2800 ma suggestive of a wide range of igneous rock ages in the source areas the detrital zircon ages provide diagnostic criteria for identification of the various source areas and reveal that the detritus was derived from multiple sources comparison of the results with the rock types and their ages surrounding the potential source areas indicates that the clastic material was derived from three dominant age sources 1 yangtze craton 2 hainan island and 3 indochina block the yangtze craton was a major and continuous source area contribution to the basin comparing the age characteristics and its source areas since 10 ma the largely stable provenance also suggests that if the red river capture ever existed it should have happened before the late miocene

mechanisms producing different precipitation patterns over north eastern italy insights from hymex sop1 and previous events during the first hymex special observation period sop1 field campaign the target site of north eastern italy nei experienced a large amount of precipitation locally exceeding the climatological values and distributed among several heavy rainfall episodes in particular two events that occurred during the last period of the campaign drew our attention these events had common large scale patterns and a similar mesoscale setting characterised by southerly low level flow interacting with the alpine orography but the precipitation distribution was very different during intensive observing period iop18 31 october 1 november 2012 convective systems were responsible for intense rainfall mainly located over a flat area of the eastern po valley well upstream of the orography conversely during iop19 4 5 november 2012 heavy precipitation affected only the alpine area in addition to iop18 and iop19 the present study analyses other heavy precipitation episodes that display similar characteristics and which occurred over nei during the autumn of recent years a high resolution 2 km grid spacing non hydrostatic nwp model and available observations are used for this purpose the two different observed precipitation patterns are explained in terms of interaction between the impinging flow and the alps depending on the thermodynamic profile convection can be triggered when the impinging flow is forced to rise over a pre existing cold air layer at the base of the orography in this situation a persistent blocked flow condition and upstream convergence are responsible for heavy rain localized over the plain conversely if convection does not develop flow over conditions are established and heavy rain affects the alps numerical parameters proposed in the literature are used to support the analysis finally the role of evaporative cooling beneath the convective systems is evaluated it turns out that the stationarity of the systems upstream of the alps is mainly attributable to persistent blocked flow conditions while convective outflow slightly modifies the location of precipitation

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

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

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

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

geochemistry of a late quaternary loess paleosol sequence in central argentina implications for weathering sedimentary recycling and provenance abstract a loess paleosol sequence in the pampean plain central argentina was analyzed geochemically in order to evaluate the weathering signature and sedimentary recycling as well as to analyze the origin of these loessic sediments corralito i sequence is composed of three paleosols and a buried soil separated by loess layers the loess paleosol sequence shows a similar geochemical composition throughout suggesting that pedogenesis has not been intense enough to mask the chemical signature of the parent material weathering indices cia ciw pia and lwi elemental ratios rb sr cao tio2 and na2o tio2 and the a cn k ternary diagram indicate incipient chemical alteration for this sequence compatible with a weathering limited regime as expected paleosols cias 60 exhibit a slightly higher chemical alteration than loess layers cias 58 mass balance calculations reveal the losses of some major oxides i e cao na2o and sr in the buried soil and paleosols compared to its loess mantles reflecting the weathering of plagioclase besides the losses of k2o and ba in the buried soil and paleosols i and ii when compared to its loess layers suggest the chemical alteration of k feldspar the chemical alteration of volcanic glass is evidenced by the relative losses of as in almost all levels conversely the relative gains of fe2o3 and mgo reveal that pyroxenes and amphiboles or fe oxy hydroxides are concentrated in paleosols and the buried soil compared to its loess mantles the geochemical approach used to constrain the origin of these pampean plain loessic sediments indicates they derive mainly from the andean region conversely the pampean ranges the parana river basin and uruguayan precambrian outcrops which were pointed out as minor local sources do not contribute significantly to the loess deposits this work also shows that corralito i loess paleosol sequence and other loess samples from argentina do not evidence sedimentary recycling suggesting that these pampean plain loess deposits are mainly composed by young materials derived from undifferentiated volcanic rocks

etude metallographique des differentes associations minerales et caracterisation chimique des mineraux uraniferes du gisement de cigar lake saskatchewan canada the cigar lake deposit discovered in 1981 represents one of the richest uranium occurrences known in the province of saskatchewan the eastern margin of the athabasca basin can be considered as o

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

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

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

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

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

dawsonite and ankerite formation in the ldx 1 structure yinggehai basin south china sea an analogy for carbon mineralization in subsurface sandstone aquifers abstract the geochemistry and petrology of the ldx 1 structure of the yinggehai basin a natural analog of a sedimentary carbon storage site was investigated to understand the consequences of the charging of co2 gas in this system the rocks in this structure are dominated by subarkose and sublitharenite sandstones the authigenic minerals formed after co2 injection are dawsonite microcrystalline quartz kaolinite and ankerite dawsonite and ankerite are formed just beneath a co2 bearing anticlinal structure due to the reactions between silicate minerals feldspars and clay minerals and the fluid phase carbon and oxygen isotopic analyses indicate that the main carbon source for dawsonite and ankerite formation was mantle magmatic co2 the aqueous activities of sodium and calcium the partial pressure of co2 ph and temperature are the key factors influencing the stability of the dawsonite and ankerite the presence of the anticlinal structure maintaining a locally high co2 partial pressure in the waters beneath this structure is likely responsible for the observed long term persistence of dawsonite and ankerite in this system

numerical study of convection observed during the winter monsoon experiment using a mesoscale two dimensional model abstract a two dimensional version of the pennsylvania state university mesoscale model has been applied to winter monsoon experiment data in order to simulate the diurnally occurring convection observed over the south china sea the domain includes a representation of part of borneo as well as the sea so that the model can simulate the initiation of convection also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle this allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck which typically occupies several hundred kilometers of the domain frank and cohen s cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area the major conclusions are ice phase processes are important in determining the level of maximum large scale heating and vertical motion because there is a strong anvil componen

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

chronology of late pleistocene pampa loess from the cordoba area in argentina in argentina loess palaeosol sequences were studied from the two sections at monte ralo and corralito located near to the city of cordoba in the east of the pampean ranges infrared optically stimulated luminescence irsl and thermoluminescence tl dating techniques were applied to set up a more reliable chronological framework for the upper pleistocene loess record irsl ages increase with depth and are stratigraphically consistent the oldest loess exposed correlates at least to the penultimate glaciation the luminescence dating study gives evidence for humid climate conditions with soil formation during the last interglacial period and the middle pleniglacial correlating to marine isotope stage mis 5 and 3 respectively three extended periods of soil formation are recorded in the loess palaeosol sequences at the corralito section these buried soils most likely correlate with the last interglacial and early last glacial period during the middle pleniglacial two palaeosols are intercalated in the loess successions in the cordoba area the periods of increased loess accumulation and deposition of loessic sediments correlate with more arid and glacial periods during the early pleniglacial the middle pleniglacial and the late glacial copyright 2009 john wiley sons ltd