hydrocarbon potential and depositional environment of the lower cretaceous black mudstones and shales in the coastal guangdong province china abstract the mesozoic especially the cretaceous sequences in the northern south china sea scs are important potential targets of oil and gas exploration however they are currently poorly understood we use organic petrology and geochemistry to evaluate the hydrocarbon potential and study depositional environment of the cretaceous black mudstones and shales from the dayawan section in the guangdong province china these mudstones and shales yield total organic carbon toc contents of 0 63 2 76 and most samples meet the requirement for higher toc source rocks organic matters in the mudstones and shales were sourced mainly from higher plants as well as subordinate benthic macroalgae organic petrology and geochemical data suggested that the organic matters were dominated by type iii and minor type ii and generally have low thermal maturity thus we evaluated the black mudstones and shales have a potential for hydrocarbon generation especially gas prone pr ph trace elements and mixture source of organic matter suggested that these black mudstones and shales formed in a coastal lacustrine environment characterized by weakly oxidizing weakly reducing conditions and low salinity a marine transgression developing in the middle part of the section was recognized generally the northern scs which exhibits the more marine influence likely contains source rocks with higher toc contents and better organic matter types the cretaceous source rocks with higher liquid hydrocarbon generation potential may occur locally in the pearl river mouth basin

englacial deltaic sediments as evidence for basal freezing and marginal shearing leirbreen southern norway analyse des depots de geles de limons sables et graviers pres du front du glacier leirbreen les structures demontrent une origine deltaique les sediments ayant ete geles avant leur incorporation au glacier et n ayant pas subit de cisaillement pendant le transport glaciaire on en deduit les mecanismes de variation du glacier

electron microprobe and la icp ms study of monazite hydrothermal alteration implications for u th pb geochronology and nuclear ceramics this paper presents new data that quantify the response of magmatic monazite to three main types of hydrothermal alteration namely sericitization chloritization and greisenization the samples were taken from three paleozoic granites the st nectaire granite massif central france the carnmenellis granite cornwall england and the skiddaw granite lake district england fluid inclusion thermometry and hydrothermal parageneses indicate that alteration took place at temperatures ranging from 260 to 340 c and salinities from 3 to 18 wt nacl equivalent possible monazite alteration mechanisms found in the course of this study using backscattered scanning electron microscopy bse sem electron microprobe laser raman spectroscopy and laser ablation inductively coupled plasma mass spectrometry la icp ms include cationic substitutions monoclinic to hexagonal structure transition accompanied by chemical exchanges selective th removal dissolution reprecipitation and dissolution with replacement by a different mineral these results show that despite the compositional and crystallographic simplicity of monazite it exhibits varied chemical responses to different mineral fluid interactions elemental and isotopic measurements by la icp ms for the unaltered monazites yield statistically significant 232th 208pb and 238u 206pb magmatic crystallization ages in some cases it was possible to give a reasonable estimate of the age of mineral fluid interaction using the altered parts of the monazites or newly precipitated crystals for other minerals 232th 208pb and 238u 206pb systematics were strongly disturbed by variable inputs and or depletions of u th and pb the data suggest that monazite like nuclear waste forms would be good hosts for tetravalent actinides but may release the lanthanides and actinides with lower and higher valencies especially if the fluids are oxidizing or tend to dissolve monazite

vertical geochemical variations and arsenic mobilization in the shallow alluvial aquifers of the chapai nawabganj district northwestern bangladesh implication of siderite precipitation core sediments from three disturbed boreholes jor ghat and raj and two undisturbed boreholes dw1 and dw2 were collected in the study area of the chapai nawabganj district of northwestern bangladesh for geochemical analyses in the study area groundwater samples from fourteen as contained private wells and five nested piezometers at both the dw1 and dw2 boreholes were also collected and analyzed the groundwater arsenic concentrations in the uppermost aquifer 10 40 m of depth range from 3 to 315 g l mean 47 73 73 41 g l while the arsenic content in sediments range from 2 to 14 mg kg mean 4 36 3 34 mg kg an environmental scanning electron microscope esem with an energy dispersive x ray spectrometer was used to investigate the presence of major and trace elements in the sediments groundwaters in the study area are generally the ca hco3 type with high concentrations of as but low levels of fe mn no3 and so 4 2 the concentrations of as fe mn decrease with depth in the groundwater showing vertical geochemical variations in the study area statistical analysis clearly shows that as is closely associated with fe and mn in the sediments of the jor core r 0 87 p 0 05 for fe and r 0 78 p 0 05 for mn and ghat core r 0 95 p 0 05 for fe and r 0 93 p 0 05 for mn while as is not correlated with fe and mn in groundwater the comparatively low fe and mn concentrations in some groundwater and the esem image revealed that siderite precipitated as a secondary mineral on the surface of the sediment particles the correlations along with results of sequential extraction experiments indicated that reductive dissolution of feooh and mnooh represents a mechanism for releasing arsenic into the groundwater

mobility of arsenic and trace element inventories in sediment cores from masuda city southwestern japan the vertical distribution of arsenic and other trace and major elements has been studied in four sediment cores from masuda city nagashima and okite in the shimane prefecture of southwestern japan the sediment cores were also subjected to leaching techniques and 14c dating the stratigraphic sequences in the cores consist of silt and sandy silt at top passing downward into gray to black clays elevated values of as pb zn cu ni cr and v are present in several horizons while abundances of these elements tend to be higher in the black and gray clays probably due to adsorption onto clay sediments higher concentrations of fe and total sulfur ts occur in black clays the correlations of the trace metals with iron suggest their adsorption onto fe oxy hydroxides whereas correlations with sulfur in some cores indicate that they were precipitated as fe sulfides age determinations suggest that clay horizons at 5 m depth were deposited at around 5 000 and 6 000 years bp 14c ages during the transgressive phase of sea level change the results of the leaching techniques in the core samples show that higher amounts of as were extracted with deionized water even at neutral ph as can be released from sediments to groundwater and therefore groundwater pollution is a concern in masuda city and the surrounding area

strontium isotope variations in single ostracod valves from the gulf of carpentaria australia a palaeoenvironmental indicator the gulf of carpentaria is a shallow 70 m epicontinental sea which was partially and at times fully isolated from the ocean due to changing sea levels in the late quaternary in an attempt to elucidate the palaeoenvironment of this marine lacustrine system and hence constrain the rates of sea level changes high precision measurements 0 0036 of 87sr86sr ratios are reported for individual fossil ostracod valves these valves were extracted from two piston cores taken from the deepest part of the gulf of carpentaria single valves weighing 20 g 40 g and containing a total of 10 8 g to 2 10 8 g of sr have been analysed at the bottom of the main core in a depth interval equivalent to an age of 36 000 to 40 000 years valves from the ostracod species cyprideis have 87sr86sr ratios of from 0 70955 2 to 0 70967 2 sr 6 1 to 7 9 from 26 000 years to 22 000 years slightly higher but relatively constant 87sr86sr ratios of from 0 70998 2 to 0 71016 2 sr 12 2 to 14 9 are present the highest sr ratios are found in ostracod valves of 13 000 years age which have values from 0 71034 2 to 0 71039 2 sr 17 2 to 18 0 all these values are significantly greater than that of contemporary seawater and are indicative of continental sources with high 87sr86sr ratios significantly lower 87sr86sr ratios of from 0 70918 2 to 0 70961 2 sr from 0 8 to 7 0 are found in ostracods younger than 12 000 years and ratios identical to modern seawater 87sr86sr 0 70912 2 sr 0 0 are present in the upper 2 cm of core which is 5 000 years in age the variations in 87sr86sr ratios in ostracod valves from the carpentaria basin are consistent with a lacustrine environment from 36 000 years to 12 000 years followed by a transgressive marine sequence which commenced in the gulf of carpentaria 12 000 years ago this marine transgression was a result of sea level rising above the 53 m relative to present day sea level arafura sill sr isotope ratios identical to that of modern seawater were however only obtained when the 12 m torres strait sill was opened to the coral sea which occurred 8 000 to 7 000 years ago the marked decrease in sr isotopic ratios at the bottom of the core may be due to flow of the fly river from new guinea prior to its diversion into the coral sea or more probably a transitory input of marine water into the carpentaria basin during a relatively high sea level 40 000 years ago it is suggested that the highest asr values present 13 000 years ago reflect increased rainfall in the gulf area of northern australia which is attributed to a southwards migration of the monsoonal rainfall pattern at that time in contrast to some other chemical indicators of palaeoenvironments the asr results of this study provide definitive and unambiguous resolution of marine versus non marine environments and can thus be used to resolve with great accuracy transgressive regressive sequences

fission track analysis of uranium distribution in granitic rocks abstract the natural uranium concentration and distribution in three granitoids from australia has been used to develop an understanding of the geochemical processes which control its behaviour in the natural environment and the potential behaviour of some analogue elements within a crystalline high level radioactive waste hlw repository environment in the coles bay granite olympic dam granite and the kambalda granodiorite fission track micromapping has been used to identify primary and secondary distribution between four main mineralogical locales 1 background u 2 resistate u 3 secondary u and 4 fracture u minor concentrations of total u are present as background u in the major rock forming minerals whereas resistate u contributed by the accessory minerals comprises up to 60 of total u two modes of redistribution of primary u are evident 1 in the secondary minerals particularly fe and ti hydroxides and 2 on alteration minerals which infill microfractures the association of u with these secondary and fracture infilling minerals indicates that it has been redistributed during post magmatic hydrothermal alteration and possibly by recent groundwater rock interaction the most important geochemical processes involved in this u redistribution include mobilisation and fixation through complex decoupling and redox reactions and retention by secondary minerals through adsorption and ionic exchange the effect of these processes upon natural u redistribution may be considered as an analogue of geochemical processes around a hlw repository this work shows that a degree of post magmatic alteration of a granite increases the proportion of secondary minerals of high sorption capacity present which may thus enhance the radionuclide retardation capability of the granitoids

geochemistry and anthropogenic inputs of metals in a tropical lake in venezuela lake valencia is a tropical lowland lake in north central venezuela lake bottom sediments were collected from 25 locations in april 1988 at 2 locations water ph conductivity dissolved o2 and temperature were measured at successive depths after drying 5 sediment samples were sieved into 5 mechanical fractions each was extracted with 1 m hno3 and analysed for ai ca cd co cr cu fe k mg mn na ni pb and zn the 63 m fraction of all samples was similarly analysed water temperatures declined with depth 1 c 25 m from approximately 26 c conductivity varied little with depth but dissolved o2 contents indicated anoxic conditions 25 m water ph 8 8 9 4 was consistent with high dissolved carbonates there was little consistent relationship between grain size and sediment metal contents approximate baseline metal contents were calculated from 21 of 25 samples the average composition of the sediments corresponded to an ideal mixture of shales carbonate rocks as 0 5 0 7 0 5 0 3 five samples from alluvial fans near the mouths of rivers traversing urban industrial zones had compositions different from the other sediments generally ph zn ni cd and cu were anthropogenically enriched by factors of 2 16 the major sources of pollutants were identified as domestic and industrial activities affecting the rivers that traverse the lakeside cities of maracay and valencia sodium mg ca mn and co3 showed natural enrichment arising from carbonate precipitation following a physical mixing of 2 sedimentary components biogenic carbonate and terrigenous material low geochemical mobility of metallic elements in neutral basic and reducing waters a processes of bury and mixture of sediments and precipitation of carbonate result in only 10 of the lake area being affected by contamination isoline plots of elements in the bottom sediments supported a hypothesis that material mixing physical transport and carbonate precipitation are the main controls of spatial distribution patterns

late quaternary environments of the carpentaria basin australia abstract quaternary variations in the level of the sea have exposed the shallow 29 000 km2 but shallow maximum depth s 4 0 kyr the pollen assemblages closely resemble the black soil plains presently found along the southern gulf thus the biogeographic and climatic barrier across the australia papua new guinea land bridge has remained largely intact in spite of the range of environmental conditions that have occured during the last

late quaternary hydrological changes in the gulf of carpentaria the gulf of carpentaria is a shallow epicontinental sea between australia and papua new guinea fig 1 it has a maximum depth of 69 m and is connected to the arafura sea across a 53 m sill1 in the east the connection to the coral sea through torres straits is 12 m ref 1 we propose here that low sea levels during the pleistocene2 3 fig 2 resulted in subaerial exposure of the gulf of carpentaria thereby reducing the regional input of moisture and latent heat to the atmosphere and tropical cyclogenesis as a result the climate of the carpentaria basin may have been significantly drier than at present4 5 even so previous workers6 7 have reported the presence of lacustrine sediments in the gulf that could have been deposited when the sea level dropped below the 53 m contour1 during 1982 the extent of lake carpentaria was defined by high resolution seismic profiles and cores the size and development of lake carpentaria and its dependence on the hydrological balance are discussed below

contrasted monazite hydrothermal alteration mechanisms and their geochemical implications in spite of the major importance of monazite as a repository for the rare earths and th in the continental crust for u th pb geochronology and as a possible form for high level nuclear waste very little work has been carried out so far on the behaviour of this mineral during fluid rock events this contribution describes two contrasting examples of the hydrothermal alteration of monazite the first case comes from a sample of the carnmenellis granite cornwall southwest england chloritized at 284 16 c whereas the other occurs in the skiddaw granite lake district northwest england which underwent greisenization at 200 30 c an integrated study involving backscattered scanning electron microscopy electron microprobe analyses and laser ablation inductively coupled plasma mass spectrometry la icp ms reveals that the chloritization event was characterized by the coupled substitution 2ree3 th4 ca2 in the altered parts of the monazite thus leaving the p o framework of the crystal untouched in contrast greisenization led to the coupled substitution ree3 p5 th4 si4 and therefore involved a partial destruction of the phosphate framework the resulting rare earth element patterns are quite different for these two examples with a maximum depletion for dy and er in the altered parts of the carnmenellis monazite whereas the skiddaw monazite shows a light rare earth depletion but an yb and er enrichment during alteration this latter enrichment accompanied by an increase in u but roughly unchanged pb concentrations probably resulted from a decrease in the size of the 9 coordinated site in monazite thereby favouring the smaller rare earths these contrasted styles of monazite alteration show that the conditions of fluid rock interaction will not only affect the aqueous geochemistry of the lanthanides actinides and lead and the relative stability of the different minerals holding these elements variations in these conditions will also lead to various possible chemical exchanges between the crystalline phases and the hydrothermal fluids the occurrence of common lead along penetrative cracks in the carnmenellis monazite shows that only a leaching prior to the u pb analyses of the whole grain will permit an accurate determination of the magmatic crystallization age in contrast for the skiddaw case it may be possible to date the fluid rock event by in situ 207pb 206pb geochronology the observation that the altered parts of both monazite examples display nd leaching and no significant sm nd fractionation indicates that they should not affect the host whole rock nd isotopic signatures finally it appears that monazite like ceramics designed for the containment of high level nuclear wastes will retain th and the geochemically equivalent transuranic elements during fluid rock events similar to those documented in this study but may release nd u and the corresponding radionuclides to the environment

stratigraphic control of the geochemistry of holocene inner shelf facies great barrier reef received 15 august 1994 revision accepted 28 june 1995 abstract cleveland bay and halifax bay are adjacent embayments situated on the inner shelf region o 20 m of the central great barrier reef shelf off townsville northeast australia these bays contain holocene sediments up to 5 m in thickness deposited during the last stages of the post glacial sea level rise x ray diffraction and x ray fluorescence techniques were used to examine the mineralogy and geochemistry of the main holocene facies sampled in 40 vibrocores the sediments of southern halifax bay and cleveland bay consist mainly of quartz ca 50 alkali feldspars ca 20 clay minerals ca 20 consisting of mixed layer clays smectite kaolinite and illite and carbonate ca 10 including aragonite and calcite the holocene facies sequence comprises in order of increasing age modern bay shoreline and mangrove sediments the oxides of the major components sioz a o fe203 mgo cao k o na o p o in halifax bay show the predicted linear correlations with geochemically related minor elements pb rb sr y zr ga zn ni co mn cr ti sc v ba and can be used to discriminate holocene facies however in cleveland bay these elements are poorly correlated within each facies and provide very poor facies discrimination these findings probably result from the presence of sandy shoreline sediments up to 2 m in thickness in the holocene sequence of cleveland bay with the consequent development of a weak oxic zone and migration of elements between adjacent facies a similar oxic zone is poorly developed in halifax bay because the shoreline facies there is either thin or absent that the chemical signatures of holocene inner shelf facies are spatially variable and are strongly influenced by the stratigraphy has wide implications for geochemical studies of marine sediments

chemo sedimentary facies analysis of fine grained sediment formations an example from the lucaogou fm in the jimusaer sag junggar basin nw china abstract fine grained sedimentary formations occupy about two thirds of the entire sedimentary sequences in nature they have recently received great attention owing to the boom of shale oil and gas exploration unlike their coarse counterparts detailed depositional features of fine grained sedimentary rocks are quite difficult to recognize directly by visual inspection at core or hand specimen scales a chemo sedimentary facies analysis csfa procedure has been developed by incorporating high resolution down to 30 m 2d elemental maps of rock slabs obtained by in situ xrf scanning with high resolution optical images the method enables one to unambiguously differentiate rock compositions and fine sedimentary structures and to generate core scale chemo sedimentary facies images the 2d chemo sedimentary facies map contains major elements with atomic numbers greater than 12 and some trace elements including ba v cr ni cu zn rb sr y zr nb mo th and u at individual pixels the csfa procedure was applied to study the lucaogou formation a key shale oil producing interval in the jimusaer sag junggar basin nw china to illustrate three key advantages of csfa in studying fine grained sedimentary formations 1 recognizing invisible sedimentary structures 2 determining sediment provenances 3 identifying subtle paleo environmental changes the lucaogou formation has been characterized in unprecedented fine details with sedimentary heterogeneities at centimeter millimeter scales seven chemo sedimentary facies were delineated in the lucaogou formation among them facies cs 1 was deposited under a relatively deep fresh to brackish water with strong energy and moist climate facies cs 2 was deposited under relatively shallow brackish water with weak energy arid climate facies cs 6 was deposited under relatively shallow brackish water arid climate with intermittent hydrodynamic enhancement facies cs 7 was deposited in semi deep fresh water with strong energy and moist climate facies cs 1 and cs 7 have relatively high porosities the dolomitic fragments in facies cs 6 was originally deposited in facies sc 2 but has higher porosities than that of facies cs 2 facies cs 6 and facies cs 7 commonly occur together the interval with well developed facies cs 1 facies cs 6 and facies cs 7 are identified to be the most favorable exploration intervals in the lucaogou formation

rare earth and trace element mobility in mid crustal shear zones insights from the mont blanc massif western alps the behaviour of rare earth elements ree during fluid rock interaction in mid crustal shear zones has received little attention despite their potential for mass balance calculation and isotopic tracing during deformation in this study several cases of large ree mobility during alpine fluid driven shear zone development in the pre alpine granitic basement of the mont blanc massif are considered on a regional scale the undeformed granite compositions range within 5 wt sio2 70 5 75 3 wt and magmatic chemical variations are of the order of 10 20 ascribed to minor effects of crystal fractionation major and trace element mobility observed in shear zones largely exceeds these initial variations shear zones developed a range of mineral assemblages as a result of shearing at mid crustal depths at not vert similar0 5 gpa 400 c five main shear zone assemblages involve muscovite chlorite epidote actinolite and calcite respectively as major phases in most cases selective enrichments of light or heavy ree and y ta hf are observed ree mobility is unrelated to deformation style cataclastic mylonitic the intensity of strain and to the shear zone s major metamorphic mineral assemblages instead the changes in ree concentrations are ascribed to the alteration of pre existing magmatic ree bearing minerals during deformation related fluid rock interaction and to the syntectonic precipitation of metamorphic ree bearing minerals mainly monazite bastnasite aeschynite and tombarthite minor proportions 2 of these accessory phases with grain sizes mostly 20 m account for enrichments of up to 5 1 compared to the initial granite whole rock ree budget the stability of the ree phases appears to be largely dependent on the altering fluid composition ree mobility is ascribed to changes in ph and to the availability of co32 po42 and so42 ligands in the fluid such processes are likely to influence the mobility of ree y hf and ta in shear zones

multi proxy analysis of organic matter accumulation in the upper ordovician lower silurian black shale on the upper yangtze platform south china abstract there is no doubt that organic matter plays an important role in shale gas accumulation and storage thus successful evaluation and production strategies of organic rich shale deposits require an understanding of the range of factors that contribute to the accumulation and preservation of organic matter in these deposits this paper reports results of a multi faceted study of two ordovician silurian transition sections of the upper yangtze platform of south china organic and inorganic geochemical data are used to reconstruct paleoenvironmental changes across this critical interval of earth history and to identify those factors that were most important to organic matter accumulation deposition of organic rich shale of the katian lower wufeng formation was favored by rising sea level and diminished clastic sediment content black shale of the upper wufeng preceded hirnantian glaciation whereas the overlying lower longmaxi formation accumulated in association with a post glacial rise of sea level as well as the peak of caledonian tectonism the carbonaceous deposits appear to reflect the combined effects of elevated primary productivity as suggested by si al and ti al ratios especially in the upper wufeng and consequent depletion of water column oxygen preservation consideration of the relationships of redox sensitive trace element concentrations and total organic carbon content suggest that bottom water conditions fluctuated between anoxic and euxinic during this period perhaps related to rapid oscillations of sea level moreover the basin appears to have remained connected with the global ocean in spite of caledonian uplift of bordering areas thus black shale sedimentation on the upper yangtze platform at the ordovician silurian boundary reflects the interplay of climate change and tectonism and their influences on sea level clastic sediment content and paleo productivity

the concept of cryo conditioning in landscape evolution comment to the paper published by ivar berthling and bernd etzelmuller quaternary research 75 2011 378 384 abstract the term cryo conditioning proposed by the authors for classifying specific landform association in periglacial landscapes needs to be defined more precisely a starting point could be the proper understanding of the term cryo in the various compound words found in various disciplines this is also important for a correct understanding of the proposed concepts since it concerns one of the most important processes in nature the phase transition of water between solid and liquid cold temperate transition surfaces in polythermal glaciers and at the permafrost base in their forelands can act as a specific hub between the glacial and periglacial domains

on the thermal regime of an arctic valley glacier a study of white glacier axel heiberg island n w t canada from 1974 to 1981 a total of 32 bore holes was drilled on white glacier and vertical ice temperature profiles measured the data obtained allowed the construction of three longitudinal and four transverse profiles of the two dimensional temperature distributions thus an extensive layer of temperate or near temperate ice was discovered close to the bedrock in the lowest part of the glacier tongue it was also found that the temperature distribution cannot be in a steady state since there is a temperature minimum 100 150 m below the glacier surface in the accumulation area a simple numerical model calculation shows that this minimum can be mostly explained by the general climatic warming since 1880 the 10 m temperatures show diffuse relations to climatic conditions and balance zones a simple scheme for extrapolating surface temperatures is discussed

calcareous nannofossil changes in response to the spreading of the south china sea basin during eocene oligocene abstract numerous models have been proposed to constrain the process of the south china sea formation yet the paleogene paleoenvironmental researches are hindered by the paucity of long continuous well dated geological records in this work eocene to oligocene nannofossil biostratigraphy and assemblage changes in a sediment section from the northern south china sea were studied to shed light on these issues we established an age model to confine the studied section between 40 and 22 ma based on 17 calcareous nannofossil datum levels the age model enabled to date the most prominent seismic reflector t60 centered at 26 8 ma a regional tectonic event interpreted as corresponding to the ridge jump event in the early phase of south china sea spreading changes in nannofossil abundance and assemblage compositions imply continuous transgression and deepening of water depth from the late eocene to early miocene during the late eocene the studied area was a neritic sea with relatively eutrophic conditions supporting abundant r lockeri group and c pelagicus from 34 ma to 27 ma during the oligocene the earlier neritic environment was replaced by relative warm and oligotrophic conditions in a shallow sea as indicated by higher concentration of c floridanus sphenolithus spp and helicosphaera spp since 26 ma pelagic conditions prevailed small reticulofenestra

history of actinide and minor element mobility in an archean granitic batholith in manitoba canada abstract surface and borehole core samples from the lac du bonnet granite manitoba canada have been analysed for major element concentrations fe 3 fe total ratios rare earth element ree content and actinide isotopic abundances this work forms part of the geological investigations of the canadian nuclear fuel waste management program performed by atomic energy of canada limited aecl the study attempts to understand the history of and processes governing mobilisation of elements and naturally occurring radionuclides during high and low temperature alteration events in fluid bearing fractures in the granite one surface sample and two core samples from 150 m and 730 m are each in contact with fractures in the granite and show evidence of alteration events that penetrated the rock matrix over distances of at least 3 cm loss of ca and na is seen in cores from a depth of 150 m from the highly altered hematite rich rock adjacent to sub horizontal fracture zones at the underground research laboratory url of aecl near lac du bonnet in contrast k fe fe 3 fe and u concentrations increase towards the fracture surface due to formation of illite and association of u with hematite and the illite at the fracture surface u continues to increase but fe and thefe 3 fe ratio decrease indicating fe removal by reduction the ree also show some enrichment in more altered rock at intermediate depths but the total ree concentration is lower than in the surface and deep core samples no clear trends are visible for parent and fracture surface ree in surface and deep core samples however disequilibrium values of 234 u 238 u and 230 th 234 u ratios in surface and intermediate depth core samples indicate that u has been mobilised in recent geological time the last ma but th has remained relatively immobile high th u and 230 th 234 u ratios in surface samples are indicative of rapid leaching of u but little isotopic fractionation probably within the last 10 5 a apparently unaltered rock several centimetres distant from the fracture in surface and intermediate depth samples has lost appreciable u but evidence from u series disequilibrium studies suggests that this process occurred more than one million years ago perhaps during deuteric or hydrothermal alteration core from a fracture at depth in the granite shows little hematite or clay formation and lacks evidence of ree and recent or ancient actinide mobilisation the u series results are correlated with the observed concentrations and isotope activity ratios of u in groundwaters sampled from the same or adjacent fractures analyses of samples of highly altered rubble recovered from centre portions of fracture zones at the url show both excesses and deficiencies of 234 u and 230 th in neighbouring locations possibly due to the presence of a redox front whose position is controlled by modern groundwater composition the implications of these results are discussed for the concept of disposal of nuclear fuel waste at depth in plutonic rock on the canadian shield

comparison of radio echo sounding 30 1000 mhz and high resolution borehole temperature measurements at finsterwalderbreen southern spitsbergen svalbard

distribution of arsenic and other trace elements in the holocene sediments of the meghna river delta bangladesh geochemical study of the holocene sediments of the meghna river delta chandpur bangladesh was conducted to investigate the distribution of arsenic and related trace and major elements the work carried out includes analyses of core sediments and provenance study by rare earth element ree analysis results showed that the cores pass downward from silty clays and clays into fine to medium sands the uppermost 3 m of the core sediments are oxidized average oxidation reduction potential orp 230 mv and the orp values gradually become negative with depths 45 to 170 mv indicating anoxic conditions prevail in the meghna sediments the ree patterns of all lithotypes in the study areas are similar and are comparable to the average upper continental crust arsenic and other trace elements pb zn cu ni and cr have greater concentrations in the silts and clays compared to those in the sands positive correlation between as and fe was found in the sediments indicating as may be adsorbed on fe oxides in aquifer sediments

molybdenum and other heavy metals of the mecca quarry and logan quarry shales pennsylvanian age mecca quarry shale from illinois and indiana contains enriched values of mo and other heavy metals average values range up to 1 160 ppm mo 8 970 ppm zn 160 ppm u 320 ppm pb 250 ppm se 420 ppm cu 450 ppm ni and 5 970 ppm v for full thicknesses pennsylvanian logan quarry shale of indiana carries similar enrichments of heavy metals for both shales trace element contents correlate markedly with specific lithologies most samples were analyzed by quantitative x ray fluorescence near shore deposition in brackish waters for the indiana locations deeper more characteristically marine environment for illinois despite high trace element values in both shales e g near ore grades for mo their thinness generally less than 1 m and the fine grained dispersed nature of their host phases relegate these shales to the status of long term resources unless improved beneficiation techniques can be devised or appreciably higher grades can be found the association of these shales with subjacent minable coals however improves their economic outlook modified journal abstract

u series in fe u rich fracture fillings from the oxidised cap of the mina fe uranium deposit spain implications for processes in a radwaste repository abstract within the framework of the enresa spain natural analogue programme the u ore deposit of mina fe is being studied as a natural analogue of radioactive spent fuel behaviour in this context the knowledge of the role played by fracture minerals as scavengers of certain analogue elements mainly u and the establishment of the time scale of the rock water interaction processes controlling the uptakes or losses of u in the system are two relevant objectives fracture infill materials from the site have first been mineralogically characterised then the upper part of the u series determined in both bulk samples and u rich leachates obtained by sequential leaching uranium series of the bulk samples indicate that most of the fractures remained as closed systems in the last 1 6 ma while in other fractures water rock interaction processes affecting the upper part of the u series have been identified these processes indicate recent or rapid u accumulation or losses 102 ka or 234u 230th recoil gain the apparently random distribution in depth of fractures where these processes occurred corroborates the different hydraulic behaviour of fractures as a result of their varying degree of sealing uranium concentrations and 234u 238u ars of the leachates obtained with morgan s solution and 6n hcl indicate that minerals dissolved with these reagents u iv vi oxyhydroxides and goethite clays respectively are responsible for the retention of almost all of the u in the bulk samples furthermore the 234u lost by the u minerals dissolved with morgan s solution seems to be fixed onto goethite clay mixtures the intersticial water being the vehicle for the isotopic transfer which in turn is a recent or recent past process

dissolved vanadium in rivers and estuaries abstract new measurements of dissolved vanadium in a variety of rivers and estuaries are presented here the data indicate that the average concentration of dissolved vanadium in major rivers entering the ocean is 15 nmol kg weathering rate and type of source rock rather than solution chemistry or anthropogenic influences appear to be the important factors in determining fluvial dissolved vanadium concentrations laboratory experiments suggest that in oxic waters vanadium is found predominantly in its most oxidized anionic form v v complexation with organic matter and formation of large colloidal species appear to be unimportant adsorption also appears to be a less important influence for vanadium than for some other trace elements such as zinc in estuaries vanadium behaves as a bioactive element showing a close correspondence with the distribution of phosphate the extent of estuarine vanadium removal is presently uncertain but may be low due to rapid remineralization of this element based on the river flux the oceanic residence time for dissolved vanadium is estimated to be 100 000 years

trace metals in lacustrine and marine sediments a case study from the gulf of carpentaria northern australia abstract sediment cores taken from the shallow the data form remarkably linear covariation trends suggesting physical mixing of two sedimentary components as the predominant process controlling the compositions of both lacustrine and marine sediments one component has high ca sr and mn suggestive of biogenic carbonate the other component contributes virtually all of the sedimentary budget of the other elements and is probably terrigenous clay either water borne or aeolian minor contributions from heavy minerals such as zircon may account for the higher values of zr and y for some horizons in the core anomalously high concentrations of zircon may have been brought into the gulf as dust particles during episodes of increased aeolian activity carbonate is most abundant in the marine sediments resulting in the higher observed ca and sr concentrations v and mn seem to be the metallic elements most sensitive to depositional environment and water chemistry environmental conditions had little or no effect on sedimentation of the other metals v and mn were delivered to the lacustrine sediments more efficiently than to the marine sediments probably reflecting changes in solubility as slightly acid lacustrine waters gave way to more neutral oceanic conditions metal organic complexing was not an important process in these oxidised sediments

ice and environment a terminological discussion abstract this article discusses the terminological and disciplinary problems associated with the point of view that ice is a rock resulting from a dynamic development of earth sciences which have begun the research into other planets as well such a position necessitates a revision of the definitions of the hydrosphere atmosphere and lithosphere it is the state that determines which particular sphere ice belongs to water is understood to be a triphase substance as a result permafrost should now include the cold layer of polythermal glaciers rock glaciers are features that integrate glacial and periglacial permafrost this facilitates the research into the interaction between the glacial and the periglacial environment by recognizing the leading role of the isotherm 0 c as the physical feature integrating these fields

debris entrainment and transfer in polythermal valley glaciers hambrey mj bennett mr dowdeswell ja et al 1999 debris entrainment and transfer in polythermal valley glaciers journal of glaciology 45 149 69 86 published 1999

the thermal regime of sub polar glaciers mapped by multi frequency radio echo sounding radio echo soundings provide an effective tool for mapping the thermal regimes of polythermal glaciers on a regional scale radar signals of 320 370 mhz penetrate ice at sub freezing temperatures but are reflected from the top of layers of ice which are at the melting point and contain water radar signals of 5 20 mhz on the other hand see through both the cold and the temperate ice down to the glacier bed radio echo soundings at these frequencies have been used to investigate the thermal regimes of four polythermal glaciers in svalbard kongsvegen uversbreen midre lovenbreen and austre broggerbreen in the ablation area of kongsvegen a cold surface layer 50 160m thick was underlain by a warm basal layer which is advected from the temperate accumulation area the surface ablation of this cold layer may be compensated by freezing at its lower cold temperate interface this requires that the free water content in the ice at the freezing interface is about 1 of the volume the cold surface layer is thicker beneath medial moraines and where cold based hanging glaciers enter the main ice stream on uversbreen the thermal regime was similar to that of kongsvegen a temperate hole was found in the otherwise cold surface layer of the ablation area in a surface depression between kongsvegen and uversbreen where meltwater accumulates during the summer near the subglacial lake setevatnet 250 m a s l lovenbreen was frozen to the bed at the snout and along all the mountain slopes but beneath the central part of the glacier a warm basal layer up to 50m thick was fed by temperate ice from two cirques on austre broggerbreen a temperate basal layer was not detected by radio echo soundings but the basal ice was observed to be at the melting point in two boreholes

a study of differentiation pattern and rare earth elements migration in geochemical and hydrogeochemical environments of airekan and cheshmeh shotori areas central iran the airekan and cheshmeh shotori areas are located about 60 km northeast of khour in isfahan province from central iran research on characteristics and rare earth elements ree pattern in hydrogeochemical environments of these areas suggests the same origin for the elements dissolved in groundwater in these areas investigation of migration pattern of ree in hydrogeochemical environments shows that the migration and transportation of ree has occurred through chloride complexes rees leached by water rock interaction from the airekan granite are transported by groundwater and then precipitated in the cheshmeh shotori area study of the cheshmeh shotori sediments shows the presence of a sequence of red oxidized and dark layers geochemical characteristics of these sediments reveal that their ree characteristics are mainly inherited from the airekan granite changes in the ree pattern of these sediments with depth show that changes in oxidation and reduction process have not played a significant role in controlling their behavior it is crucial to note that adsorption of rees dissolved in water by hydrosilicate increases these elements in depth the ree behavior shows water rock interaction between the granitic rocks and groundwater as the main factor of solution migration and precipitation of rees in the cheshmeh shotori area

the migration of radionuclides in granite a review based on natural analogues abstract the characterization of a geological formation for nuclear waste disposal should be carried out on a site by site basis however the study of analogous granitic formations all around the world gives a few general guidelines for a better understanding of elemental migration processes in this review focused on mineralogical petrological and geochemical phenomena it is shown that fractures should play a dominant role in transport through granites moreover mineralogical transformations as well as their textural and petrophysical consequences e g permeability changes should be reliably predicted finally this review confirms that water rock interactions do mobilize many elements including analogues of actinides u th ree however most alteration minerals of granite e g clay minerals carbonates exhibit a high capability for efficiently trapping these heavy elements it is concluded that natural analogues are very useful for specifying the appropriate approach for the characterization of a geological site they have also proved essential for developing and validating geochemical models of mass transfers around a repository in granite

dispersion of u th and ree by water rock interaction around an intragranitic u vein jalerys mine morvan france abstract the dispersion of u th and ree from a u vein type deposit localized in an intragranitic vein through the surrounding host rock has been characterized by combining petrological mineralogical and geochemical major and trace elements radiogenic isotopes studies the different stages of hydro thermal alteration have been identified including those leading to changes in the major or trace element concentrations the distances over which u th and ree have migrated are estimated and correlated with the main water rock interaction processes the role of co precipitation with secondary minerals in the retention of these elements is stressed these processes are considered as analogous to those which could take place around a radioactive waste repository in a similar rock type the main geochemical implications of this work for the safety assessment of such a disposal are discussed

an account of the techniques using ostracodes in palaeolimnology in australia abstract ostracodes are common in australian waters especially in saline lakes where they are particularly diverse this makes them indispensable tools for australian palaeolimnological studies especially since many australian lakes are saline the following types of subjective information can be obtained from the study of australian fossil ostracode faunas without knowledge of the ecology or taxonomy of their living representatives the search for a life assemblage can lead to detection of the presence of water currents and the effects of reworking in addition to the identification of particular facies such as a lake shoreline or a desiccation phase rate of sedimentation can be estimated as well as the amount of sediment compaction of drying information on water oxygenation and acidification can be obtained and finally presence of seasonality affecting lakes can be identified with additional reference to the ecology of particular species permanency of lake water can be assessed and so can the variability of rainfall and even at times the detection of whether a lake was close to a summer winter rainfall boundary shell ornamentation can inform on water depth in addition salinity data can be obtained as well as some information on water chemistry and temperature the latter from trace elements mg sr and stable isotope 18 o studies of ostracode shells

general bathymetry of the gulf of carpentaria and the quaternary physiography of lake carpentaria abstract a generalized bathymetric map of the gulf of carpentaria has been prepared from royal australian navy sounding data the results confirm earlier work of nix and kalma and indicate that a closed basin lake carpentaria below 53 m present water depth could have existed during quaternary low sea level stands an evaluation of previous and present work shallow seismic records of the canadian superior mining co australia and oil company fathometer profiles indicate the preservation of lake sediments at 65 m and 53 m water depth preserved shoreline feature at 19 m 29 m and 65 m as well as extensive underlying erosion and incision these findings are consistent with erosion and incision of gulf sediments during sea level lowering aeolian infilling and dune formation on the present arafura sill during the dry phase of maximum glaciation and subsequent lake carpentaria formation and lacustrine sediment deposition most probably during the sea level rise phase lake carpentaria clearly dominates the physiography and climatology of this land bridge during quaternary time

rare earth element geochemistry of the woxi w sb au deposit hunan province south china the woxi w sb au deposit in hunan south china is hosted by proterozoic metasedimentary rocks a turbiditic sequence of slightly metamorphosed greenschist facies gray green and purplish red graywacke siltstone sandy slate and slate the mineralization occurs predominantly 70 as stratabound stratiform ore layers and subordinately as stringer stockworks the former consists of rhythmically interbedded banded to finely laminated stibnite scheelite quartz pyrite and silty clays whereas the latter occurs immediately beneath the stratabound ore layers and is characterized by numerous quartz pyrite gold scheelite stringer veins or veinlets that are typically either subparallel or subvertical to the overlying stratabound ore layers the deposit has been the subject of continued debate in regard to its genesis rare earth element geochemistry is used here to support a sedimentary exhalative sedex origin for the woxi deposit the ree signatures of the metasedimentary rocks and associated ores from the woxi w sb au deposit remained unchanged during post depositional processes and were mainly controlled by their provenance the original ore forming hydrothermal fluids as demonstrated by fluid inclusions in quartz from the banded ores are characterized by variable total ree concentrations 3 5 to 136 ppm marked lree enrichment lan ybn 28 248 lree hree 16 to 34 and no significant eu anomalies eu eu 0 83 to 1 18 they were most probably derived from evolved seawater that circulated in the clastic sediment pile and subsequently erupted on the seafloor the bulk banded ores are enriched in hree lan ybn 4 6 11 4 lree hree 3 to 14 and slightly depleted in eu eu eu 0 63 to 1 14 relative to their parent fluids this is interpreted as indicating the influence of seawater rather than a crystallographic control on ree content of the ores within a single ore layer the degree of hree enrichment tends to increase upward while the total ree concentrations decrease reflecting greater influence and dilution of seawater there is a broad similarity in chondrite normalized ree patterns and the amount of ree fractionation of the bandedoresinthisstudyandexhalitesfromothersedex typepolymetallicoredeposits suggestingasimilargenesisforthesedeposits

geochemistry and lithofacies of permo carboniferous carbonaceous rocks from the southwestern edge of the bohemian massif germany a contribution to facies analysis of continental anoxic environments abstract the permo carboniferous schmidgaden weiden erbendorf and stockheim basins from southern germany host discontinuous seams of high ash coal and carbargillites which were mined for hard coal explored for uranium and only recently have proved their source rock potential for gaseous and fluid hydrocarbons alteration and facies of these carbonaceous beds were geologically and chemically investigated during silicification which is exclusively confined to the carbonaceous interbeds of pyroclastic depositions element depletion prograded except for zn pb u the anoxic environments under consideration may be subdivided into fluvial swamp upper westphalian beds from schmidgaden weiden erbendorf and stockheim and lacustrine depositions upper stephanian and upper autunian carbargillites from erbendorf weiden bechtsrieth sio 2 mgo cao mo and zr have proved to be most suitable for recognition of these environments whereas u k 2 o and notably cu zn are less appropriate in the ternary plots displaying the organic chemistry of extracts of these carbonaceous beds fluvial swamps have low and lacustrine beds high contents of saturated hydrocarbons all samples show a pronounced oep odd even predominance of n alkanes which partly are environment controlled terrestrial origin partly maturity controlled the high iso and cyclo alkanes of schmidgaden and bimodal n alkyl distribution point to a contribution of algal material finally four basin types bearing carbonaceous rocks are discussed with respect to their economic potential and compared with basins elsewhere cerilly lodeve st hippolyte uinta type i intramontane fault bounded basin swamp type ii volcanic depression with steep relief swamps type iii halfgraben lake type iv volcanic depression with smooth relief lake types i and ii are of interest for hard coal organic hosted u deposits and mainly gasprone types iii and iv however show good source rock potential for crude oil

variations in organic geochemistry of anoxic oxic black shale carbonate sequences in the pennsylvanian of the midcontinent u s a abstract two cores containing thin organic rich phosphatic black shale members the excello and little osage shale and transitional lithologies from pennsylvanian cyclothems of southeast kansas and northeast oklahoma were characterized by geochemical and organic petrographic methods by very detailed sampling geochemical analyses included organic carbon determination rock eval pyrolysis bitumen extraction and chromatographic separation into saturated aromatic and nonhydrocarbon fractions gas chromatography of saturated hydrocarbons carbon isotope analysis of coexisting saturated and aromatic fractions and whole rock v and ni analyses organic petrography included maceral identification on polished whole rock fragments and vitrinite reflection and thermal alteration index tai determinations of kerogen concetrates the analytical results demonstrate large and systematic variations in geochemical properties within the black shale units in both cases an abrupt increase in toc 20 25 level and hi 400 level at the initiation of phosphatic black shale deposition is followed by a gradual decline to values of less than 1 toc and 100 hi organic constituents include both liptinitic algal derived and humic terrestrial components variations in their relative amounts control the nature and quality of the organic profile of the little osage shale level of anoxia varied within this sequence and influenced several geochemical parameters pr ph ratios decrease nonhydrocarbons increase relative to hydrocarbons saturated hydrocarbons decline relative to aromatics carbon isotopic composition of coexisting saturated and aromatic hydrocarbons converge and v and ni and the v ni v ratio increase with increased anoxia eustatic rise of sea level and rapid marine transgression over the continental craton with consequent flooding of adjacent extensive brackish marine peat swamps and the resultant influx of a large supply of nutrients and humic detritus appear to be the key geologic control of black shale deposition

sea level and environmental changes since the last interglacial in the gulf of carpentaria australia an overview abstract the gulf of carpentaria is an epicontinental sea maximum depth 70 m between australia and new guinea bordered to the east by torres strait currently 12 m deep and to the west by the arafura sill 53 m below present sea level throughout the quaternary during times of low sea level the gulf was separated from the open waters of the indian and pacific oceans forming lake carpentaria an isolation basin perched above contemporaneous sea level with outlet channels to the arafura sea a preliminary interpretation is presented of the palaeoenvironments recorded in six sediment cores collected by the images program in the gulf of carpentaria the longest core approx 15 m spans the past 130 ka and includes a record of sea level lake level changes with particular complexity between 80 and 40 ka when sea level repeatedly breached and withdrew from gulf lake carpentaria evidence from biotic remains foraminifers ostracods pollen sedimentology and geochemistry clearly identifies a final marine transgression at about 9 7 ka radiocarbon years before this transgression lake carpentaria was surrounded by grassland was near full and may have had a surface area approaching 600 km 300 km and a depth of about 15 m the earlier rise in sea level which accompanied the marine isotopic stage 6 5 transgression at about 130 ka is constrained by sedimentological and biotic evidence and dated by optical and thermoluminescence and amino acid racemisation methods

late quaternary cyclic aridity in tropical australia abstract during the numerous quaternary sea level fluctuations the vast gulf of carpentaria in northern australia was more often a large lacustrine basin than a shallow sea recovery of aeolian quartz particles in a core spanning the last 40 000 calibrated years of sedimentation identifies a 2 600 year cyclic pattern of aridity the most pronounced period peaks around 21 500 calibrated years bp corresponding to the onstart of the period of lowest global sea level and glacial advance in new zealand the following peak of aeolian dust activity in carpentaria just precedes the termination of the low sea level stand at 19 300 calibrated years bp the timing of aeolian activity in northern australia does not coincide with heinrich events he 1 to 3 recognised in the atlantic ocean nor with the cyclicity of chilean glacial activity thus suggesting that separate forces engender those different phenomena

spatial pattern and stability of the cold surface layer of storglaciaren sweden the mechanisms controlling the spatial distribution and temporal fluctuations of the thermal structure in polythermal glaciers have to date been poorly investigated and are not fully understood