modelling of the evolution of ground waters in a granite system at low temperature the stripa ground waters sweden abstract from chemical data collected by nordstrom and his colleagues on stripa ground waterswe have tried to model the evolution of the chemical composition of a ground water in a granitic system at low temperature the existence of two end member ground water compositions made it possible first to test the conventional model of a geothermal system according to which an overall equilibrium between the waters and a given mineral assemblage can be defined and then to show that such a model could be extended to low temperatures 10 c conversely if we know the mineral assemblage the equilibration temperature and the charge of the mobile ions in this case cl the composition of the solution is entirely fixed in our model of the stripa ground waters the existence of two end member ground water compositions can be explained by an evolution from a kaolinite albite laumontite equilibrium to a prehnite albite laumontite equilibium the latter requiring less al than the former we have also emphasized the importance of the cl ion concentrions ofof the ground waters because they cab be considered as indicators of the degree of reaction progress between rock and water thus determining the degree of equilibration of the system

fluid inclusions in the stripa granite and their possible influence on the groundwater chemistry fluid inclusions in quartz and calcite of the proterozoic stripa granite central sweden demonstrate that the rock and its fracture fillings have a complex evolutionary history the majority of inclusions indicate formation during a hydrothermal stage following emplacement of the stripa pluton total salinities of quartz inclusions range from 0 18 eq wt nacl for unfractured rock and from 0 10 eq wt for fractured rock vein calcites contain up to 25 eq wt nacl but the inclusion size is larger and the population density is lower homogenization temperatures are 100 150 c for unfractured rock and 100 250 for fractured rock pressure corrections assuming immediate post emplacement conditions of 2 kbar give temperatures about 160 c higher measurements of fluid inclusion population densities in quartz range from about 108 inclusions cm3 in grain quartz to 109 inclusions cm3 in vein quartz residual porosity from inclusion densities has been estimated to be at least 1 which is two orders of magnitude greater than the flow porosity breakage and leaching of fluid inclusions is proposed as an hypothesis for the origin of major solutes na ca cl in the groundwater evidence for the hypothesis is based on 1 mass balance only a small fraction of the inclusions need to leak to account for salt concentrations in the groundwater 2 chemical signatures brcl ratios of fluid inclusion leachates 0 0101 match those ratios for the deep groundwaters 0 0107 3 leakage mechanisms micro stresses from isostatic rebound or mining activities acting on irregular shaped inclusions could cause breakage and provide connection with the flow porosity and 4 experimental studies water forced through low permeability granites leach significant quantities of salt this hypothesis is consistent with the available data although alternate hypotheses cannot be excluded

rheological modelling and deformation instability of lithosphere under extension ii depth dependent rheology summary bassi bonnin 1988 have recently discussed the stability of continental lithosphere in extension they examine the hypothesis that thickness inhomogeneities can be amplified during extension and be responsible for lithospheric necking we carry our analysis one step further by accounting for the increase of strength with depth in brittle layers namely the upper crust and in some cases the upper part of the mantle this variation had been neglected in the previous study to simplify the mathematical formulation rather than a constant the equivalent viscosity is now a linear function of depth as predicted by byerlee s friction law which is postulated to control the mechanical behavior of brittle layers this more realistic rheological model confirms the results of the original analysis specifically that the interfaces between layers tend to flatten during extension unless they correspond to an inversion of density therefore extension of continental lithosphere appears to be stable if there is no other initial defect susceptible of localizing the deformation

origin of saline groundwaters in the carnmenellis granite cornwall england natural processes and reaction during hot dry rock reservoir circulation saline groundwaters up to 19 100 mg 1 1 total mineralisation issue in tin mines in the carnmenellis granite in cornwall u k at depths up to 800 m their stable isotope composition rules out seawater as a contributor to salinity circulation experiments carried out during hot dry rock hdr reservoir development in the same granite also produce return fluids with enhanced salinities acid hydrolysis of plagioclase and biotite are proposed as the main sources of salinity in the groundwater experimental studies carried out on biotites from a borehole used for hdr evaluation demonstrate the reactivity of the biotite and confirm the hypotheses of the field studies mg li k and silica levels in reacted solutions reflect the stoichiometric composition of the biotite chloride na and ca in solution on the other hand are enriched between 1 and 3 orders of magnitude over that of biotite reflecting the strongly incongruent nature of the reaction quartz and chalcedony saturation of the groundwaters encourages silica or silicate deposition rather than dissolution of rock forming quartz this argues against fluid inclusions as the source of salinity and suggests that new inclusions might be formed the proposed model for the genesis of saline water therefore links together or explains several processes groundwater movement convective heat transport the chemistry of the water water rock interaction secondary mineral including kaolinite formation and fluid inclusion formation and stability

armoured sponge spicules from panarea island italy implications for their fossil preservation abstract a variety of calcareous and siliceous skeletal components are associated with exceptional still active deposits of modern iron ooids off panarea one of the volcanic islands of the aeolian arc tyrrhenian sea italy both ooids and skeletal components occur as loose sediments influenced by submarine hydrothermal fluid vents whereas iron ooids are exclusively made of goethite laminae primarily nucleated on volcaniclastic material sponge spicules that represent most of the siliceous skeletal component develop laminated coatings concretions of varying sizes this partial or total coating consists of regularly banded fe rich layers exhibiting the same textural features and mineralogical composition goethite of the ooid cortex developed around inorganic cores spicules did not reveal any obvious attaching structure or interfingering with the surrounding coating and did not undergo bioerosion or any other evidence of biological intervention during their development a hydrothermal origin compatible with the general setting is therefore proposed for these armoured sponge spicules we believe that this unique modern case of iron concretions produced on siliceous spicules can contribute to explain other known fossil cases as well as to understand the taphonomy of this type of biogenic silica that seems rarely to have been preserved in such an extreme habitat

a new technique for sampling water and gas from deep drill holes a new technique for sampling water and gas from deep 500 1500 m drill holes is described the principle of the technique is to raise a continuous column of water inside a thin polyamide tube with a back pressure valve at the lower end and with shutoff valves every 50 m the equipment is easily assembled from standard parts sampling can be performed by three people without mechanical apparatus descent to 1000 m takes 2 hours and retrieval 1 hour the method makes it possible to obtain a practically undisturbed continuous water profile from a drill hole dissolved gases remaining inside the tube can be sampled at the surface to demonstrate the efficiency of the technique selected results from the deepest drill hole in finland having a vertical depth of 1100 m are presented

major and trace element geochemistry of neutral and acidic thermal springs at el chichon volcano mexico implications for monitoring of the volcanic activity abstract four groups of thermal springs with temperatures from 50 to 80 c are located on the s sw w slopes of el chichon volcano a composite dome tephra edifice which exploded in 1982 with a 1 km wide 160 m deep crater left very dynamic thermal activity inside the crater variations in chemistry and migration of pools and fumaroles drastic changes in the crater lake volume and chemistry contrasts with the stable behavior of the flank hot springs during the time of observations 1974 2005 all known groups of hot springs are located on the contact of the basement and volcanic edifice and only on the w sw s slopes of the volcano at almost same elevations 600 650 m asl and less than 3 km of direct distance from the crater three groups of near neutral ph 6 springs at sw s slopes have the total thermal water outflow rate higher than 300 l s and are similar in composition the fourth and farthest group on the western slope discharges acidic ph 2 saline 10 g kg of cl water with a much lower outflow rate water rock interaction modeling of main types of the el chichon thermal waters using regular log q k graphs saturation indices vs temperature showed maximum equilibrium temperature slightly higher than 200 c acidic waters are equilibrated with some clay minerals at about 120 c three main sources of the salinity of thermal water are suggested on the basis of mixing plots and isotopic data a magmatic source for co2 boron sulfur and a limited part of cl volcanic rock source for the major cations and trace elements the oil bearing evaporitic basement source oil field brine for nacl br a part of ca and some trace elements all flank thermal springs end up in the river rio magdalena that has a variable seasonal flow rates from 4 to 20 m3 s any changes in the chemistry of springs must notably change the composition of the streams draining hot springs and eventually rio magdalena a monthly geochemical monitoring of rio magdalena and streams draining main hot springs would be a useful tool for surveying the activity of the volcano

vapour discharges on nevado del ruiz during the recent activity clues on the composition of the deep hydrothermal system and its effects on thermal springs abstract the nevado del ruiz volcano is considered one of the most active volcanoes in colombia which can potentially threaten approximately 600 000 inhabitants the existence of a glacier and several streams channelling in some main rivers flowing downslope increases the risk for the population living on the flank of the volcano in case of unrest because of the generation of lahars and mudflows indeed during the november 1985 subplinian eruption a lahar generated by the sudden melting of the glacier killed twenty thousand people in the town of armero moreover the involvement of the local hydrothermal system has produced in the past phreatic and phreatomagmatic activity as occurred in 1989 therefore the physico chemical conditions of the hydrothermal system as well as its contribution to the shallow thermal groundwater and freshwater in terms of enthalpy and chemicals require a close monitoring the phase of unrest occurred since 2010 and culminated with an eruption in 2012 after several years of relative stability still maintains a moderate alert as required by the high seismicity and so 2 degassing in october 2013 a sampling campaign has been performed on thermal springs and stream water located at 2600 5000 m of elevation on the slope of nevado del ruiz analyzed for water chemistry and stable isotopes some of these waters are typically steam heated low ph and high sulfate content by the vapour probably separating from a zoned hydrothermal system by applying a model of steam heating based on mass and enthalpy balances we have estimated the mass rate of hydrothermal steam discharging in the different springs the composition of the hottest thermal spring botero londono is probably representative of a marginal part of the hydrothermal system having a temperature of 250 c and low salinity cl 1500 mg l which suggest along with the retrieved isotope composition a chiefly meteoric origin the vapour discharged at the steam vent nereidas 3600 m asl is hypothesized to be separated from a high temperature hydrothermal system based on its composition and on literature data on fluid inclusions we have retrieved the p t x conditions of the deep hydrothermal system as well as its ph and f o 2 the vapour feeding nereidas would separate from a biphasic hydrothermal system characterized by the following parameters t 315 c p 15 mpa nacl 10 wt co 2 5 wt and similar proportion between liquid and vapour considering also the equilibria involving s bearing gases and hcl ph would approach the value of 1 5 while f o 2 would correspond to the feo fe 2 o 3 buffer chlorine content is estimated at 10 300 mg l changes in the magmatic input into the hydrothermal system could modify its degree of vapourization and or p t x conditions thus inducing corresponding variations in vapour discharges and thermal waters these findings paralleled by contemporary measurements of water flow rates could give significant clues on risk evaluation

from symmetric necking to localized asymmetric shearing the role of mechanical layering we study the formation of localized shear zones during the layer parallel extension of viscous multi layers using two dimensional numerical simulations based on the finite difference method for power law viscous layers and a linear viscous embedding medium the extended multi layer develops boudins due to necking for power law viscous layers embedded in a power law viscous medium the extended multi layer develops first distributed necks and subsequently a localized shear zone with a vertical offset with a size of several layer thicknesses along the multi layer during the extension the deformation style switches from distributed and symmetric necking to localized and asymmetric shearing a localized shear zone develops in the viscous multi layer although the rheology is everywhere strain rate hardening power law stress exponent 1 and no material softening and or energy feedback mechanism e g shear heating combined with a temperature dependent viscosity is applied the shear localization is caused by structural softening because the formation of a localized shear zone decreases the bulk resistance and hence the work required to deform the multi layer a localized shear zone forms in the multi layer when the distance between the stiff layers is approximately equal to or less than the layer thickness the shear localization was observed in multi layers with nine and with only three stiff layers

precipitation of secondary minerals in acid sulphate chloride waters traced by major minor and rare earth elements in waters the case of purace volcano colombia abstract major minor and rare earth elements were analyzed in the acid sulphate chloride thermal springs associated to purace volcano hydrothermal system the waters of purace were classified in 2 different groups as a function of the physico chemical parameters and element distributions group 1 is characterized by the highest ph 3 5 an outlet temperature of 81 c and a strong depletion of fe al si and ba with respect to the isochemical dissolution of the average volcanic local rock group 2 waters have lower ph values 1 9 and temperature 48 c compared with group 1 moreover group 2 is not characterized by a typical pathway representing the congruent dissolution of the rock and shows a distribution of major and minor elements that is more close to the near congruent dissolution of the average volcanic local rock with respect to group 1 these geochemical features of major and minor elements allow to propose that the chemical composition of the waters of group 1 is strongly affected by the precipitation of secondary minerals such as alunite jarosite kaolinite barite and polymorphs of sio2 the grouping of waters is also supported by the distribution of dissolved ree normalized to the average volcanic local rock group 1 shows ree patterns strongly depleted in light rare earth elements lree typical of water that formed alunitic and or kaolinitic rocks on the contrary group 2 is characterized by flat patterns in according to the near congruent dissolution of the rocks ree dissolved in waters of purace were compared with ree in the acidic waters of nevado del ruiz and azufral colombian volcanoes and with ree in minerals recognized in advanced argillic alteration alunite gypsum and kaolinite precipitation of secondary minerals is proposed as a common process depleting lree in acidic sulphate chlorine waters in volcano hydrothermal systems furthermore the chemical fractionation of the major and minor elements was interpreted together with the corresponding distributions of ree in order to trace the water rock interaction processes saturation indexes of most common secondary minerals identified in advanced argillic alterations were calculated using phreeqc software in a range of temperature from 25 to 250 c this geochemical approach allows to identify the possible mineral precipitation or dissolution of secondary minerals as well as the temperature at which the water reached equilibrium with a given set of minerals in group 1 the precipitation of secondary minerals lree enriched alunite minerals and kaolinite was traced at temperature of precipitation higher than 101 c

contrasting styles of rifting models and examples from the eastern canadian margin we present the results of a dynamical model of lithospheric rifting and rupture which show that a wide range of crustal thinning patterns across rifted passive margins can be produced by varying the steady state geotherm lithospheric composition dry versus wet materials and strain rate the basic mechanism of continental rupture is assumed to be passive rifting and necking we use a numerical thermomechanical model of lithosphere extension based on a finite element approach when plasticity is significant i e at lower temperatures or for harder materials deformation is unstable and thinning takes place abruptly over a narrow area conversely a progressive thinning across the margin is observed when creep is dominant i e in warm or ductile conditions cooling and associated hardening of the thinned area can occur during extension and cause the locus of extension to migrate laterally in these circumstances rupture is likely to take place asymmetrically along one edge of the thinned area producing a narrow margin and a very wide conjugate the eastern margins of canada and their conjugates across the north atlantic provide examples which cover this range of theoretical profiles the crustal thinning patterns inferred from deep seismic data and the duration of rifting compare well with model results we discuss also the constraints that these geodynamical models provide on such current issues as the seismic reflectivity of the lower crust or the location of the ocean continent boundary in wide areas supposedly underlain by 5 km thin continental crust

groundwater chemistry and water rock interactions at stripa groundwaters from near surface to a depth of 1232 m in the stripa granite have been sampled and analyzed for major and trace constituents the groundwater composition consists of two general types a typical recharge water of ca hco3 type 700 m depth of high ph 8 10 that reaches a maximum of 1250 mg l in total dissolved solids tds intermediate depths show mixtures of the two types that are highly fracture dependent rather than depth dependent any borehole can vary significantly and erratically in tds for either a horizontal or vertical direction the general transition from ca hco3 type to na ca cl type correlates with the depth profile for hydraulic conductivity that drops from 10 8 m s to 10 11 m s or lower thermomechanical stress from heater experiments clearly shows an effect on the groundwater composition that could be caused by changing flow paths leakage of fluid inclusions or both dissolution and precipitation of calcite fluorite and barite aluminosilicate hydrolysis and addition of a saline source possibly fluid inclusion leakage play the major roles in defining the groundwater composition the low permeability of the stripa granite has produced a groundwater composition that appears intermediate between the dilute shallow groundwaters typical of recharge in a crystalline rock terrain and the saline waters and brines typical of cratonic shield areas at depth

uptake of elements from seawater by ferromanganese crusts solid phase associations and seawater speciation marine fe mn oxyhydroxide crusts form by precipitation of dissolved components from seawater three hydrogenetic crust samples one phosphatized and two hydrothermal mn oxide samples were subjected to a sequential leaching procedure in order to determine the host phases of 40 elements those host phase associations are discussed with respect to element speciation in seawater the partitioning of elements between the two major phases mn oxide and fe oxyhydroxide can in a first order approximation be explained by a simple sorption model related to the inorganic speciation of the elements in seawater as has been proposed in earlier models free and weakly complexed cations such as alkali and alkaline earth metals mn co ni zn tl i and partly y are sorbed preferentially on the negatively charged surface of the mno2 in hydrogenetic crusts the driving force is a strong coulombic interaction all neutral or negatively charged chloro cd hg tl carbonate cu y pb and u and hydroxide be sc ti fe zr nb in sn sb te hf ta bi th and tl iii complexes and oxyanions v cr as se mo and w bind to the slightly positively charged surface of the amorphous feooh phase while coulombic interaction can explain the sorption of the negatively charged species the binding of neutral species is based on specific chemical interaction organic complexation of elements in deep ocean water seems to be at most of minor importance surface oxidation can explain some strong metal associations e g of co and tl with the mno2 and te with the feooh sorption reactions initially driven by coulombic forces are often followed by the formation of specific bonds between the adsorbate and the atoms of the oxide surface differences in the associations of some metals between the non phosphatized and phosphatized hydrogenetic crusts and between the hydrogenetic and the hydrothermal samples reflect the different physico chemical environments of formation and speciations in oxic seawater vs less oxic fluids especially for the redox sensitive metals such as mo and v these environmental related differences indicate that the methodology of chemical speciation used here in combination with spectroscopic methods may allow for the detection of changes in paleoceanographic conditions recorded during the several tens of millions of years of crust growth

behaviour of rare earth elements and yttrium in ferromanganese concretions gibbsite spots and the surrounding terra rossa over dolomite during chemical weathering abstract the behaviour of rare earth elements rees and yttrium y during chemical weathering processes has been investigated on a 4 05 m thick terra rossa profile over dolomite on the yunnan guizhou plateau china in this profile ferromanganese concretions and gibbsite spots coexist in the terra rossa solum analyses of rees y zr f s and toc as well as mineralogical studies were conducted on a suite of ferromanganese concretions gibbsite spots terra rossas dolomites and insoluble residues from the underlying dolomite these analyses helped us to understand the mobilization redistribution and fractionation of rees and y during chemical weathering the rees and y are mobilized and redistributed during the terra rossa formation rees except for ce are removed from the upper and middle profiles transferred downwards and then precipitated in the base profile resulting in remarkable enrichment in the terra rossa near the weathering front the significant increase of ph near the weathering front was responsible for ree excluding ce and y enrichment in the base profile y is quite mobile during extreme chemical weathering and most of it was carried away from the profile because of very efficient oxidative fractionation of ce a significant positive ce anomaly in terra rossa was found in the middle of the profile whereas the terra rossa near the weathering front exhibited notably negative ce anomalies moreover the presence of cerianite and its content in the ferromanganese concretions can explain the markedly positive ce anomaly and the variation of ce ce values with depth in profile these ce anomalies are characteristic of the geochemical environment especially the redox condition studies of ree distribution in the ferromanganese concretions gibbsite spots and surrounding terra rossa revealed that significant ree fractionation occurred rees and y were preferentially concentrated in the ferromanganese concretions rather than in the gibbsite spots the water rock interaction resulted in m type tetrad effects in some of the ferromanganese concretions gibbsite spots and terra rossa samples in addition the tetrad effect in terrestrial weathering processes likely played an important role in the fractionation of rees and y such as y ho sm nd and the eu anomaly change

geochemistry and origin of saline groundwaters in the fennoscandian shield chemical and isotopic analyses of water from drill holes and mines throughout the fennoscandian shield show that distinct layers of groundwater are present an upper layer of fresh groundwater is underlain by several sharply differentiated saline layers which may differ in salinity relative abundance of solutes and o h sr and s isotope signature saline groundwater can be classified into four major groups based on geochemistry and presumed origin brackish and saline waters from 50 200 m depth in coastal areas around the baltic sea exhibit distinct marine chemical and isotopic fingerprints modified by reactions with host rocks these waters represent relict holocene seawater inland three types of saline groundwater are observed an uppermost layer of brackish and saline water from 300 900 m depth saline water and brines from 1000 2000 m depth and superdeep brines which have been observed to a depth of at least 11 km in the drill hole on the kola peninsula u s s r electrical and seismic studies in shield areas suggest that such brines are commonly present at even greater depths the salinity of all inland groundwaters is attributed predominantly to water rock interaction the main solutes are cl ca na and mg in varying proportions depending on the host rock lithology the abundance of dissolved gases increases with depth but varies from site to site the main gas components are n2 ch4 up to 87 vol and locally h2 the 13c value for methane is highly variable 25 to 46 and it is suggested that hydrothermal or metamorphic gases trapped within the surrounding rocks are the most obvious source of ch4 the uppermost saline water has meteoric oxygen hydrogen isotopic compositions whereas values from deeper water plot above the meteoric water line indicating considerably longer mean residence time and effective low temperature equilibration with host rocks geochemical and isotopic results from some localities demonstrate that the upper saline water cannot have been formed through simple mixing between fresh water and deep brines but rather is of independent origin the source of water itself has not been satisfactorily verified although superdeep brines at least may contain a significant proportion of relict precambrian hydrothermal or metamorphic fluids

genesis of karst bauxite bearing sequences in baofeng henan china and the distribution of critical metals abstract bauxite bearing sequences are not only the main economic sources of aluminum but also of many critical metals the distribution of critical metals was determined from six bauxite profiles in baofeng and an evolution model was proposed for the formation of bauxite bearing sequences following a terrestrial deposition of the lower pisolitic bauxite horizon and the underlying clayey layer transportation and redeposition of bauxitic materials during submergence led to the formation of the upper bauxite horizon presenting finely clastic and oolitic textures as well as the intercalated clayey layers both bauxite ores and clay samples contain highly elevated contents of li b sc v ga zr nb w and total rees li contents are extremely low in high grade bauxite ores 10 92 44 77 ppm compared to highly elevated values in low grade bauxite ores 35 81 1601 ppm and clay samples 38 54 1965 ppm enlightening a new potential resource for li the bauxite bearing sequences resting on karstified carbonate the distribution pattern of ga is similar to that of li and the correlation analysis indicates that ga is primarily associated with silicates i e clay minerals the vertical distribution of li b v cr and ga shares the same pattern similar to that of k2o and sio2 being highly enriched in clayey layers relative to bauxite horizons both sc and total rees are also highly enriched in baofeng bauxite profiles highlighting a potential sc and rees resource

saline groundwaters in the canadian shield a first overview abstract the chemical and isotopic compositions of saline groundwaters and brines in the canadian shield are described the occurrence of such waters is very widespread not related to any specific rock type or mineralization and generally can be expected at depths below 1 km the most saline brines have salinities exceeding 200 g l 1 dissolved solids and their chemistries tend to suggest that in the past saline waters penetrated the canadian shield the original chemistry of these solutions was subsequently modified through strong rock water interactions and it appears that their final chemical compositions are independent of the original chemistries stable isotope analyses indicate that these waters are not simple evaporated seawater sedimentary basin brines hydrothermal solutions or residual ore forming fluids although any of these could be a precursor of the brines secondary isotope exchange reactions and the hydration of primary silicates accompanied by the formation of clay minerals could have modified not only the primary isotopic composition but may have also profoundly influenced the chemistries of these brines to be effective these processes would have had to occur in closed systems

a hot spring in granite of the western tianshan china the western tianshan range is a major cenozoic orogenic belt in central asia exposing predominantly paleozoic rocks including granite ongoing deformation is reflected by very rugged topography with peaks over 7000 m high active tectonic deformation is tied to an e w trending fracture and fault system that sections the mountain chain into geologically diverse blocks that extend parallel to the orogen in the muzhaerte valley upwelling hot water follows such a fault system in the muza granite about 20 l min 1 na so4 cl water with a temperature of 55 c having a total mineralization of about 1 g l 1 discharge from the hot spring the water is used in a local spa that is frequented by the people of the upper ili river area its waters are used for balneological purposes and the spa serves as a therapeutic institution the major element composition of the hot water is dominated by na and by so4 and cl ca is a minor component dissolved silica 1 04 mmol l 1 corresponds to a quartz saturation temperature of 116 c and a corresponding depth of the source of the water of about 4600 m this temperature is consistent with na k and na li geothermometry the water is saturated with respect to fluorite and contains 7 5 mg l 1 f as a consequence of the low ca concentration the water is undersaturated with respect to the primary minerals of the reservoir granite at reservoir temperature causing continued irreversible dissolution of granite the waters are oversaturated with respect to ca zeolite minerals such as stilbite and mesolite and it is expected that zeolites precipitate in the fracture pore space and in alteration zones replacing primary granite the stable isotope composition of o and h supports a meteoric origin of the water the cl br mass ratio of 1500 suggests that the salinity results from halite dissolution salts leached from powders of muza granite show the same cl br signature as the hot spring water sodium chloride is stored in fluid and solid inclusions in the granite which have been introduced to quartz by ductile shearing and faulting related to ongoing orogenesis the hot water remobilizes the salt that is continuously liberated by the tectonic deformation water granite interaction contributes a thenardite component na2so4 to the major element composition by albite dissolution in h2so4 the water rock interaction along faults and fractures transforms and alters muza granite to a low temperature epigranite

rare earth elements in river waters we measured rare earth element ree concentrations in river waters to characterize the suspended and dissolved river flux of the ree to the oceans the ree pattern of river suspended materials is sensitive to drainage basin geology a positive correlation is observed between la yb ratios and nd model ages for the rivers studied major rivers have light ree enriched patterns relative to the north american shale composite nasc with la yb n 1 6 2 7 river water dissolved material 0 2 m is heavy ree enriched relative to suspended material and the most pronounced negative ce anomalies occur in rivers of high ph light ree concentrations vary by approximately 3 orders of magnitude and are inversely related to ph and major cation concentrations from these data we estimate that typical major river runoff has heavy ree depleted suspended material with la yb n 1 9 we conclude that the terrigenous input to the oceans from major rivers is heavy ree depleted relative to shales from the available data average river water dissolved material appears to be heavy ree enriched with la yb n 0 4 estuarine removal processes lower the dissolved ree river flux by approximately 60 and result in a flux that is more heavy ree enriched with la yb n 0 2 calculated oceanic residence times with respect to river input range from 2300 to 21 000 years are shortest for ce and greatest for the heavy ree and la such long residence times may suggest the presence of additional sources of ree in seawater

comparison of surface aquifer and pore waters from a mesozoic basin and its underlying palaeozoic basement southeast france chemical evolution of waters and relationships between aquifers abstract as part of the deep geology of france gpf ardeche project water samples were collected along the ardeche margin of the massif central crystalline shield water is contained within various rocks including early jurassic carbonate triassic sandstone and evaporite permian continental deposits and the crystalline basement three sample types were studied surface water from streams and springs formation water sampled from fractured zones aquifers at various depths and pore water from rocks cored in the morte merie scientific borehole drilled to a depth of 980 m in 1993 as part of the ardeche project three main water chemistry signatures are associated with the three major geological groups 1 hco 3 ca mg water occurs in early jurassic carbonate and late triassic sandstone with dolomitic cement 2 ca so 4 water occurs in triassic sulphated shale and sandstone 3 na cl water occurs in permian sandstone and crystalline basement the samples enable a comparison between waters that flow on the surface those that have been in the underlying geological formations for a short time and those that have resided in closed pores of the host rock for a long time saturation indices computed for surface and formation waters show that dissolution reactions progressively increase the concentration of elements until saturation is reached surface waters were saturated for quartz and carbonate and formation waters for quartz carbonate gypsum muscovite and k feldspar saline water 12 g l tds from the permian rocks is controlled by a mineralogical assemblage of quartz calcite anhydrite muscovite k feldspar and albite at temperatures 80 90 c although equilibrium was reached for the formation waters concentrations in the pore waters reflect a general enrichment as compared to free formation waters from the fractured zones of the corresponding formation which suggests introduction of mobile elements in the solution only in permian rocks was a stable equilibrium observed since pore waters show no enrichment as compared to formation waters no water mixing was observed except along faults that form pathways for the fluid between formations each geological group generally behaves as a closed system except the permian rocks that seem to be or were exposed to circulation from the crystalline basement

porosity and fluid velocities in the upper continental crust 2 to 4 km inferred from injection tests at the soultz sous forets geothermal site a heat exchanger was created at the french hot dry rock geothermal site using a doublet of boreholes at a depth of 3600 3800 m after hydraulic stimulation this exchanger was tested during a long term circulation trial from july to november 1997 tracer tests were carried out during the circulation trial an analysis of the tracers indicates a connected porous volume in the range of 0 5 to 2 5 10 6 m 3 with a connected porosity of the order of 0 9 to 2 3 these values are one order of magnitude higher than values obtained by extrapolation from petrophysical investigation of the boreholes this result is interpreted as being due to the connection of the major faults to a dense network of 2 nd order structures fluid circulation velocities inferred from the tracer test are of the order of 0 25 to 0 36 m h velocities derived from observation of the migration of fresh fluids after injection into the granite during stimulation tests are of the same order of magnitude 0 02 to 0 17 m h yielding hydraulic conductivity estimates of 6 6 10 8 to 2 3 10 6 m s 1 both the pressure gradient during the circulation test and the density gradient are related to freshwater injection and can be considered as possibly equivalent to temperature and hydraulic gradients in the rhine graben at least during some specific geological events such as the alpine uplift phases thus the test shows that fluid migration can occur in the upper continental crust exhibiting reservoir properties and these should be taken into account in large scale modelling these properties are in good agreement with a proposed scenario of evolution involving active fluid migration during the eocene alpine uplift phase it also supports the hypothesis of seawater derived saline fluids stored in old fractured shield rocks which implies deep seawater circulation in the continental crust

trace metal remobilization in the interstitial waters of red clay and hemipelagic marine sediments interstitial water samples from the guatemala basin and the coast of baja california have been analyzed for manganese iron copper nickel and nitrate the data provide a systematic look at changes in trace metal diagenesis proceeding from red clay to highly reducing nearshore sediments in red clay sediments the nitrate concentrations suggest that only aerobic respiration is occurring manganese and iron are below detection nickel concentrations remain the same as in bottom seawater but copper shows a pronounced maximum just at the sediment water interface proceeding to hemipelagic sediments denitrification becomes increasingly important and manganese and iron remobilization occur in the sediments the linear manganese and nitrate profiles suggest regions of production or consumption separated by zones of diffusion this differs from the conventional picture of a continuous series of reactions within the sediments manganese reduction always occurs before iron reduction the pore water nickel correlates well with manganese in these sediments suggesting that nickel is associated with mno2 in the solid phase the pore water flux ratio of manganese and nickel agrees well with the ratio in solid phase authigenic oxides copper still displays a core top concentration maximum as well as a second maximum associated with the remobilized manganese the calculated ratio of the cu c flux ratios support the argument for copper remobilization during organic carbon oxidation comparison of the upward and downward diffusive fluxes with the rate of copper buried by sedimentation shows that at least half of the copper buried must be of diagenetic origin and less than 25 of the copper reaching the sediments is buried

hydrogeochemistry and rare earth element behavior in a volcanically acidified watershed in patagonia argentina abstract the rio agrio watershed in northern patagonia argentina is naturally acidic due to discharges of volcanic h 2 so 4 hcl and hf at its headwaters near the summit of copahue volcano a suite of water samples was collected from the summit of the volcano to a point roughly 40 km downstream where the ph of the rio agrio rose above 6 0 this suite included a sample of the hyperacidic ph the concentrations of ree in the rio agrio decreased by several orders of magnitude through the study area as a result of dilution and chemical attenuation a subtle shift in the slope of shale normalized profiles of dissolved ree concentration was observed from being weakly positive near the source of the rio agrio to showing a weak middle ree enrichment trend in lake caviahue to being weakly negative in the lower reaches of the river the trend to a negative slope across the lanthanide series in the lower river is explained by selective partitioning of the heavier ree to hydrous oxides of fe and al suspended in the water column and accumulating on the riverbed most of the decrease in ree load occurred immediately downstream of the confluence with a tributary that increased the ph of the rio agrio from 4 3 to 6 1 although the mixed water was supersaturated with ree phosphate compounds precipitation of lnpo 4 is not believed to have been a dominant process because the predicted pattern of inter element fractionation from phosphate deposition is inconsistent with the observed trends instead ree attenuation most likely occurred from adsorption onto freshly precipitated hydrous aluminum oxide the behavior of ree in the rio agrio watershed is broadly similar to what has been observed in watersheds that owe their acidity to oxidation of sulfide minerals

the behaviour of zirconium hafnium and rare earth elements during the crystallisation of halite and other salt minerals abstract halite crystals from messinian and tortonian evaporites from sicily and spain and current precipitated halite crystals and the relative parent brines active evaporation systems were investigated in order to evaluate the zr hf and rare earth element ree behaviour halite crystallisation from evaporating brines fractionates zr hf and ree through a two step process during the first step dissolved complexes of studied elements are scavenged onto the surfaces of crystallising halite during the second step elements are co precipitated into the crystal lattice as it grows the first step mechanism is determined by the dissolved ree speciation in saltworks where carbonate ree complexes occur surface complexation of ree onto halite crystals does not occur on the contrary surface ree complexes onto halite crystals are forming in the dead sea water where aqueous ree speciation is dominated by chloride complexes under the latter conditions halite crystallises with cubic and cubic octahedral composite habitus octahedral planes involve the formation of strong coulombic interactions mainly with hf h 2 o 3 oh 5 rather than with zr h 2 o 4 oh 4 0 complexes as a consequence newly formed halite in the dead sea shows strong subchondritic zr hf ratios based on these indications analyses carried out on salt minerals from messinian and tortonian evaporites in sicily and spain show that their overall ree content can be considered a discriminating parameter between authigenic minerals and diagenetic modified materials however features of shale normalised ree patterns are driven by the mineralogical composition of evaporites rather than their authigenic or secondary nature on the contrary the zr hf signature of salt minerals is influenced by their origin indeed subchondritic zr hf values are found in primary salt minerals whereas larger zr hf values are recognised in those diagenetically modified calculated distribution coefficients of zr hf and ree are employed for modelling the ree distribution in halite equilibrated with the deep sea brines from typo medee and thetis basins eastern mediterranean the obtained indications allow us to discriminate brines formed by dissolution of evaporites relative to those representing relics of fossil evaporated seawater

rare earth elements concentrations and speciation in rainwater from guiyang an acid rain impacted zone of southwest china abstract rare earth elements rees and major ions were determined in rainwater samples collected from guiyang in the acid rain impacted zone of southwest china the concentrations of total dissolved and acid soluble rees in rainwater are higher than those of most of the world s cities as well as the local surface water the dissolved ree concentrations are negatively correlated to ph in rainwater this is consistent with acidification of rainwater resulting in increasing ree concentrations speciation calculations using the phreeqc model predict that the free ree metal ion i e ln3 sulfate lnso4 oxalate lnox and lnox2 and fluoride lnf2 complexes were relatively important forms of dissolved ree although the contribution to rainwater acidity of oxalic acid is much lower than that of sulfuric acid the proportion of ree oxalate complexes is not lower than that of ree sulfate complexes in rain waters the rainwater is enriched in the middle rees mree compared to both the light rees lree and heavy rees hree ree phosphate complexes phosphatic minerals and a fe mn oxyhydroxide coating are more likely controls on the development of mree enrichment in the rainwater complexation of sulfate and ree played little role in the development of mree enrichment even though sulfate is the most important anion in acidic rainwater in the shale normalized ree pattern plot la showed a clear positive anomaly la might have two main anthropogenic sources in rainwater one of the important sources could be automobile emission another main source of excess la in rainwater could be the ree fertilizer that has been widely used in the agriculture of china for approximately 30 years

the chemistry of geothermal waters in iceland iii chemical geothermometry in geothermal investigations abstract new data from geothermal wells in iceland have permitted empirical calibration of the chalcedony and na k geothermometers in the range of 25 180 c and 25 250 c respectively the temperature functions are t c 1112 4 91 log sio 2 273 15 t c 933 0 993 log na k 273 15 concentrations are expressed in ppm these temperature functions correspond well with the chalcedony solubility data of fournier 1973 and the thermodynamic data for low albite microcline solution equilibria of heloeson 1969 a new co2 geothermometer is proposed which is considered to be useful in estimating underground temperatures in fumarolic geothermal fields its application involves analysis of co2 concentrations in the fumarole steam the temperature function which applies in the range 180 300 c is logco2 37 43 73192 t 11829 103 t2 0 18923t 86 187 logt where t is in k and co2 in moles per kg of steam

zirconium hafnium and rare earth element signatures discriminating the effect of atmospheric fallout from hydrothermal input in volcanic lake water geochemical behaviour of rare earth elements ree zr and hf was investigated in co2 rich waters circulating in pantelleria island also including specchio di venere lake within a calderic depression a wide range of total dissolved ree concentrations was found 2 77 12 07 nmol l 1 with the highest contents in the lake the main ree complexes in the co2 rich waters are ree co3 2 and reeco3 showing changeable proportions as a function of ph the ree normalized to post archean australian shale paas showed similar features with heavy ree hree enrichments in co2 rich waters collected from springs and wells whereas a different ree pattern was found in the specchio di venere lake water with middle ree mree enrichments the paas normalized concentration ratios lree hree n and mree hree n in waters are 1 positive eu anomalies were found in the investigated waters owing to water rock interactions with less evolved host rocks ce anomalies as a function of eh values were recognized with the highest ce anomaly occurring in the lake water with respect to the co2 rich waters the y ho and zr hf molar ratios are higher in the investigated waters except for lake water than that in the local rocks with values ranging from 35 4 to 77 9 and from 76 3 to 299 respectively the precipitation of authigenic phases was considered to be responsible for the increase in the y ho and zr hf ratios owing to enhanced hf and ho removal with respect to zr and y

crustal structure of the baltic shield based on off fennolora refraction data abstract since the early 1960s deep seismic sounding experiments have been carried out on the baltic shield in this study we will mainly concentrate on the results obtained from two international profiles sveka and baltic carried out in finland in 1981 and 1982 results from these profiles are shown and discussed and compared with those obtained from the fennolora and from the other recent refraction profiles of the baltic shield in fennoscandia according to the results from sveka and baltic and average crustal velocity is 6 6 6 7 km s which is rather high several distinct reflection boundaries have been found within the crust in the lower part of the crust a high velocity layer with a p wave velocity of 7 0 7 5 km s has been found in some cases in addition the results indicate that the crustal structure has a clear block like character different blocks being separated from each other by deep fractures the crustal thickness in the baltic shield is about 45 km on average whereas around the ladoga bothnian bay zone in central finland it is about 10 km thicker than this thus there is a large scale depression in the moho boundary in the central part of the baltic shield

the rare earth element geochemistry of acid sulphate and acid sulphate chloride geothermal systems from yellowstone national park wyoming usa rare earth element ree concentrations have been determined by inductively coupled plasma mass spectrometry icp ms in acid sulphate and acid sulphate chloride waters and the associated sinters and volcanic rocks from the yellowstone national park ynp wyoming usa geothermal system ree concentrations in the volcanic rocks range from 222 to 347 ppm their chondite normalised ree patterns are typical of upper continental crust with lree hree and negative eu anomalies total ree concentrations in the fluids range from 3 to 1133 nmol kg 1 162 ppm and ree concentrations in sinter are 181 ppm ree abundances and patterns in drill core material from ynp indicate some ree mobility normalisation of ree concentrations in altered lava creek tuff lct from y 12 drill core to ree concentrations in fresh lct indicate that the ree overall have been depleted with the exception of eu which has been decoupled from the ree series and concentrated in the altered rocks relative to the host rocks the ree patterns of the fluids are variably depleted in hrees and lrees and usually have a pronounced positive eu anomaly this decoupling of eu from the ree suite suggests that 1 eu has been preferentially removed either from the host rock glass or from the host rock minerals or 2 the waters are from a high temperature or reducing environment where eu2 is more soluble than the trivalent rees since the latter is inconsistent with production of acid sulphate springs in a low temperature oxidising near surface environment we suggest that the positive eu anomalies in the fluids result from preferential dissolution of a eu rich phase in the host rock spatial and temporal variations in major element chemistry and ph of the springs sampled from norris geyser basin and crater hills accompany variations in ree concentrations and patterns of individual geothermal springs these are possibly related to changes in subsurface plumbing which results in variations in mixing and dilution of the geothermal fluids and may have lead to changes in the extent and nature of ree complexing

the behavior of rare earth elements zr and hf during biologically mediated deposition of silica stromatolites and carbonate rich microbial mats abstract venere lake in the pantelleria island thermal system central mediterranean sea consists of a mix of seawater and hydrothermal volcanic fluids containing high levels of dissolved sio 2 close to the lake s thermal springs siliceous stromatolites are deposed under high bacterial activity conditions whereas roughly interlaminated ca carbonates and microbial mats are widely scattered in the lake the dissolved ree speciation in lake waters is dominated by ree co 3 2 ree co 3 and ree h 3 sio 4 2 complexes on the contrary the most abundant zr and hf species are hydroxyl and fluoride complexes the behavior of ree zr and hf in the venere lake waters is controlled by precipitation of amorphous silica carbonates and bacterial activity chondrite normalized ree patterns in stromatolites are characterized by positive la anomalies superchondritic y ho ratios and negative eu anomalies the eu depletion is also found in microbial mats where is associated to a chondritic y ho signature zr and hf differently behave in dissolved phase and in newly formed siliceous and carbonatic material hf reacts easily into amorphous silica surfaces whereas zr is preferentially partitioned onto phosphate binding sites on microbial cell surfaces similar to the observed behavior of heavy ree hree we suggest that the zr hf relationship reflect the interface processes between mineral phases and bacterial membranes or compounds produced by bacterial activity

geochemistry of metal rich brines from central mississippi salt dome basin u s a abstract oil field brines are the most favored ore forming solutions for the sediment hosted mississippi valley type ore deposits detailed inorganic and organic chemical and isotope analyses of water and gas samples from six oil fields in central mississippi one of the very few areas with high metal brines were conducted to study the inorganic and organic complexes responsible for the high concentrations of these metals the samples were obtained from production zones consisting of sandstone and limestone that range in depth from 1900 to 4000 m 70 120 c and in age from late cretaceous to late jurassic results show that the waters are dominantly bittern brines related to the louann salt the brines have extremely high salinities that range from 160 000 to 320 000 mg l total dissolved solids and are na ca cl type waters with very high concentrations of ca up to 48 000 mg l and other alkaline earth metals but with low concentrations of aliphatic acid anions the concentrations of metals in many water samples are very high reaching values of 70 mg l for pb 245 mg l for zn 465 mg l for fe and 210 mg l for mn the samples with high metal contents have extremely low concentrations 2 s samples obtained from the smackover formation limestone have low metal contents that are more typical of oil field waters but have very high concentrations up to 85 mg l of h 2 s computations with the geochemical code solmineq 87 give the following results 1 both pb and zn are present predominantly as aqueous chloride complexes mainly as pbcl 4 2 and zncl 4 2 respectively 2 the concentrations of metals complexed with short chained aliphatic acid anions and reduced s species are minor 3 organic acid anions are important in controlling the concentrations of metals because they affect the ph and buffer capacity of the waters at subsurface conditions and 4 galena and sphalerite solubilities control the concentrations of pb and zn in these waters

extreme alteration in an acid sulphate geothermal field sulphur springs saint lucia abstract sulphur springs is a vigorous geothermal field associated with the soufriere volcanic centre in southern saint lucia intensely altered rocks occur over an area of at least 200 400 m together with bubbling hot pools and fumaroles the pools are sodium calcium sulphate type with phs of 3 7 and temperatures of 41 97 c fumaroles have temperatures up to and at times above 100 c gases collected from both fumaroles and bubbling pools have high contents of co2 601 993 mmol mol and commonly high h2s 3 190 mmol mol least altered host rocks surrounding sulphur springs comprise calc alkaline feldspar quartz porphyritic dacites of near uniform chemical composition these rocks which form massive domes and volcaniclastic units were emplaced 13 30 ka ago lindsay et al 2013 within the geothermal field the dacites have been moderately to highly altered to acid sulphate assemblages of kaolinite illite smectite alunite natroalunite cristobalite opaline silica native sulphur jarosite and amorphous compounds muddy sediments from grey to blackish thermal pools additionally contain iron sulphides despite intense alteration of the volcanic rocks and derived volcaniclastic sediments zr and ti have remained essentially immobile which allows identification of the precursors dacites and calculation of mass changes many of the altered rocks and sediments show major depletions of fe mg ca na extremely altered samples additionally show notable losses of al p k ree and y implying leaching by highly acidic waters a few of the highly altered rocks however have gained al together with p presumably due to neutralization or evaporation of acidic thermal waters also present within the geothermal field are metre scale zones with very high contents of silica and native sulphur and surface thermal waters define a linear trend in a plot of 18o vs d and reach high levels of isotopic enrichment the enrichment trend is ascribed to progressive evaporation in the thermal pools the low slope of the isotopic trend 1 4 is interpreted as being due to surficial mixing between meteoric waters and steam condensates derived at about 230 c from the deep brine that underlies the geothermal field the whole rock o h isotopic composition of four highly altered samples kaolinite smectite opal sulphates can be accounted for if the alteration fluid was a 50 50 mixture of steam and meteoric water and alteration occurred at 50 125 c whole rock 34s values of samples containing variable amounts of sulphates sulphides and native s are all notably negative 5 to 16 consistent with derivation of sulphur from volcanic gases such as so2 and h2s altered rocks and thermal pool sediments in the geothermal field are commonly enriched in hg and se up to 50 mg kg at sulphur springs primary dacitic rocks have been chemically and mineralogically transformed by reaction with acidic waters that formed when uprising volcanic gases condensed into neutral meteoric waters in many cases this has led to substantial mass losses or gains in al p and rees regardless of the degree of alteration however the precursor rocks can still be identified using ti zr relations

factors controlling the style of continental rifting insights from numerical modelling passive continental margins similarly formed by lithospheric stretching and rifting can differ significantly in terms of width ranging from 50 to 400 km or subsidence history our interest lies in determining what properties of the lithosphere and what stress and strain boundary conditions control this regional variability and the siting of rupture continental breakup occurs probably as the result of a stretching instability which develops in a zone of material or geometrical heterogeneity to analyze the factors controlling these instabilities we use a numerical thermo mechanical model of lithosphere extension based on a finite element program the particular program was chosen because it combines constitutive models appropriate to our knowledge of lithosphere rheology elasticity plasticity and nonlinear temperature dependent creep with a kinematic formulation for large inelastic strain we choose to weaken the plate by locally increasing the crustal thickness by a very small amount and examine how this defect or perturbation acts to localize the deformation we compare the geometry and timing of necking for relatively wet versus dry rheology cold versus warm geotherm and fast versus slow strain rate we examine as well how the width and amplitude of the perturbation itself affects the deformation history since a velocity boundary condition is applied the required extensional forces are evaluated and compared to estimates of plate driving forces conditions that favor deformation by plasticity rather than creep cold geotherms dry rheologies lead to a more localized extension and rapid rupture but the forces involved 1013 n m are larger than typical plate driving forces increasing the amplitude of the defect i e crustal thickness contrasts accelerates necking as well cooling of the thinned area becomes significant at low extension rates depending on the initial rheology cooling simply delays the moment when deformation becomes unstable or conversely inhibits necking

the behaviour of rees in thailand s mae klong estuary suggestions from the y ho ratios and lanthanide tetrad effects abstract the concentrations of rare earth elements and yttrium rey were measured in dissolved phase in suspended particulate matter spm and in sediments in seven sampling stations in the mae klong estuarine system inner thailand gulf in order to study their behaviour and distribution pattern the analysed samples generally show high rare earth element ree content in the dissolved phase with high medium rare earth elements mrees and y enrichments in the shale normalized pattern versus paas these chemical features are interpreted in terms of direct influences of weathering processes of ree rich minerals e g phosphates which abundantly out crop in the mae klong watershed these large mree enrichments also suggest that dissolved sulphate complexes play an important role in the dissolved ree fate close to the marine coastal system the shale normalized rees and y ho ratios additionally indicate a direct rey co precipitation with fe oxyhydroxides along the river path and consequent adsorption as coating onto feooh surfaces the rey behaviour in spm appears strongly influenced by al fe and mn content suggesting that the formation of an authigenic fe mn oxyhydroxides and aluminosilicate particulate leads to rey adsorption and or co precipitation the observed variations in the y ho ratios suggest that different y ho fractionation processes take place in the studied estuarine system strong similarities among chondrite normalized ree patterns in both sediments and granitic rocks out cropping in the surrounding regions suggest a generic relationship between the two groups of materials

feasibility of estimating cementation rates in a brittle fault zone using sr ca partition coefficients for sedimentary diagenesis abstract cement phases such as calcite or quartz often incorporate trace elements from the parent fluids as they crystallize experimental sedimentary diagenesis indicates that trace element partition coefficients reflect rates of cementation the applicability of these findings to fault zone cementation is examined as we make a preliminary attempt to estimate calcite cementation rate in a brittle fault zone directly from the fault rock composition data samples for this study were collected from the knoxville outcrop of the saltville fault in tennessee the cementation rates for the fault rock samples range from 1 10 12 to 3 10 13 m 3 h per m in agreement with some experimental rates and the rates reported for samples from the dsdp sites when applied to a non responsive pore system model these rates result in rapid precipitation sealing indicating the influence exerted by the surface area volume ratio of the pore network we find it feasible to obtain a reasonable range of values for the cementation rate using the trace element partition method however the study also indicates the need for relatively accurate values for the trace carrier element ratio in the fault zone syntectonic pore fluid and exhumed cement

characterization of gases in sedimentary formations through monitoring during drilling and core leaching balazuc borehole deep geology of france programme abstract continuous analysis of the drilling fluids and core sampling formed a major part of the ardeche theme of the deep geology of france programme when drilling the balazuc 1 borehole in 1991 the analyses of gas concentrations in the drilling fluids are compared to those of core leaching both data sets show good agreement although higher concentrations are obtained in the drilling fluids the drilling to core ratio shows a relatively constant value these higher concentrations are due to crushing of the rock during drilling and the influence of the sediments surrounding the borehole the characterization of the gases with depth indicates 3 different zones 1 the jurassic carbonates with high ch 4 and co 2 concentrations 2 the triassic upper sandstone and middle evaporitic units with average concentrations of he co 2 n 2 and low ch 4 and 3 the triassic lower sandstone unit and the carboniferous silts with high he n 2 and low co 2 and ch 4 concentrations these trends indicate that diffusion is not a major process at balazuc and that the formations remained relatively independent from each other nitrogen and co 2 which are the main constituents show a reverse correlation the high co 2 zones are related to the carbonate formations in the hettangian carbonates a zone of black shales has preserved a high hydrocarbon content due to its very low permeability whilst in the other formations any hydrocarbons originally present have escaped the he record in the continuous measurement mainly reflects the fractured levels and the paleoporous zones this is correlated to major fluid transfer in the formations of the lower part of the borehole along the uzer fault

c o h n fluids in quartz segregations from a major ductile shear zone the berzosa fault spanish central system the berzosa fault is a major ductile shear zone the berzosa shear zone bsz which separates the ollo de sapo anticline from the inner higher grade crystalline axis of the iberian hercynian belt this shear zone is the site of abundant early kinematic quartz al silicates segregations rich in fluid inclusions host rocks are medium grade staurolite schists and sillimanite gneisses fluid inclusions in selected quartz segregations across the berzosa shear zone have been studied by microthermometric methods as well as in some instances by raman analysis the recorded fluid inclusion history begins at the end of an intense secondary recrystallization period during late peak metamorphic conditions and lasts until late in the uplift history of the zone three types of inclusions have been found which in a time sequence are co2 h2o h2o salt b type and n2 ch4 three types of b inclusion may be distinguished in turn depending on whether they were trapped during an earlier dynamic recovery phase b1 type formed later as intergranular trails b2 type or were trapped apparently along with n2 ch4 in clusions from a heterogeneous fluid b3 type considerations from isochores confirm that co2 h2o inclusions were trapped during late peak and high t retrograde metamorphic conditions in the range 650 500 c and 5 2 kbar whilst n2 ch4 inclusions along with the b3 type of inclusions formed at low pressures 1 kbar and temperatures 300 c b2 type inclusions were trapped chronologically between these two in a period in which strong inverse lateral thermal gradients developed in the zone inferred p t paths for the area are convex to the t axis

the chemistry of fumarolic vapor and thermal spring discharges from the nevado del ruiz volcanic magmatic hydrothermal system colombia on the basis of three sets of gas samples taken during the three months preceding the november 13 1985 eruption of nevado del ruiz from fumaroles on the crater floor the composition of the vapors discharged following minor eruptive activity in september corresponded to that of an essentially magmatic gas during the subsequent quiet period in october the proportion of a hydrothermal component in the vapor discharge increased steadily up until the major eruption the gases were found to be exceptionally high in total sulfur and are super saturated with respect to elemental sulfur their thermodynamic equilibration temperatures range from 200 to 600 c gases and waters from fumaroles and thermal springs on the flanks of the volcano are likely to be derived from a two phase vapor brine envelope surrounding the magmatic system the chemistry of the fumarole discharges is compatible with the assumption of an eruptive mechanism involving the build up of pressure in an extensive vapor zone by gas released from an essentially stagnant already extensively degassed body of magmatic material at depth production of such a residual gas over extended periods may account for the large amount of so2 discharged from the volcano in relation to the small amount of ejected solids

estuarine distributions of zr hf and ag in the hudson river and the implications for their continental and anthropogenic sources to seawater 1 zirconium and hf in seawater are derived from continental weathering and are transported to the oceans by rivers but the modification of this flux with estuaries is largely unknown furthermore there is no information as to whether there is a pollutant source of these metals that might affect their budget calculations in the modern ocean to address the riverine flux and potential anthropogenic sources the distributions of dissolved zr and hf have been measured in surface and bottom water through the hudson river estuary the distribution of ag is included because it is sensitive to urban sources and has partial similarities in its distribution to those of zr and hf there is about 50 removal of zr and hf in surface water relative to their freshwater end member concentrations of 243 and 3 1 pmol kg as salinity starts to increase but an urban source of these metals midestuary may obscure greater removal silver concentrations in surface water are below the detection limit until salinity of 3 5 is reached the concentrations of zr and hf 0 5 m above the bottom are 1 5 to 3 times higher than their surface water concentrations throughout the estuary and may result from input of groundwater diffusion from pore fluids or inclusion of colloidal phases in our analyses downstream of the turbidity maximum bottom water ag concentrations are high due to release from particles that originally formed within the estuary and were moved inland following the spring freshet this process may also affect zr and hf the increase in the freshwater atomic zr hf ratio from 70 to 80 characteristic of terrestrial rocks to the elevated zr hf 110 ratio of seawater takes place at middle to high salinity due to enhanced release of zr from resuspended particles and slower removal rates compared to hf a main implication of this study is that estuaries are a sink for zr and hf the reduction of the predicted export of continental zr and hf to the oceans increases their previously calculated seawater residence by as much as 2 to 4 times assuming rivers dominate the supply of zr and hf to seawater

geochemical evolution of ground water in smith creek valley a hydrologically closed basin in central nevada u s a abstract smith creek valley is a hydrologically closed basin in which ground water is recharged by subsurface inflow from sorrounding mountains and infiltration of streamflow into alluvial fan deposits near the mountains ground water is discharged by evapotranspiration from shallow ground water areas in the central part of the basin dominant ions in the dilute recharge water are na ca and hco 3 dissolved solids concentration increases during flow through the basin fill sediments with na becoming increasingly dominant in the discharge area a bare soil playa sorrounded by phreatophytic vegetation ground water salinity dominated by na and cl increases markedly the main processe controlling geochemical evolution of ground water in the basin fill aquifer were identified using major ion chemistry mass balance calculations thermodynamic calculations stable isotopes and mineral identification these processes are 1 dissolution of volcanic tuff and tuff derived basin fill deposits 2 cation exchange of ca and mg in the water for na in clay minerals 3 weathering of plagioclase to montmorillonite 4 precipitation of zeolite minerals 2 concentration of dissolved constituents by evapotranspiration 6 dissolution of cl and so 4 evaporative salts 7 precipitation of calcite

rare earth element systematics in hydrothermal fluids abstract rare earth element concentrations have been measured in hydrothermal solutions from geothermal fields in italy dominica valles caldera salton sea and the mid atlantic ridge the measured abundances show that hydrothermal activity is not expected to affect the ree balance of either continental or oceanic rocks the ree enrichment of the solutions increases when the ph decreases high temperature solutions 230 c percolating through different rock types may show similar ree patterns

application of continuum models to deformation of the aleutian island arc continuum models were constructed to describe large scale deformation of the aleutian island arc over the past 5 m y these models consider the island arc as a continuum in the horizontal plane with the velocity boundary condition at the pacific edge stated as a fraction of pacific plate convergence transferred to the arc first a simple model of uniformly distributed strain is formulated to illustrate the mechanics of continuous deformation lineaments along the arc massif rotated about a vertical axis are matched by small element rotation calculated from the model however this model does not predict across arc variations in deformation and produces an unrealistic amount of crustal thickening after 5 m y a physically more meaningful model of deformation is the thin viscous sheet model based on averages of stress and rheology throughout the lithosphere the amount of motion transferred from the pacific plate to the arc is constrained by the rotated lineaments while the effective stress strain exponent n and the ability the lithosphere has to sustain crustal thickness contrasts the argand number are independent variables primarily bathymetry earthquake focal mechanisms and styles of faulting are used to evaluate the models the preferred model is one where the amount of motion transferred from the pacific plate is greater in an arc parallel direction than in an arc normal direction producing stresses consistent with strike slip faulting at the far western end of the arc and tensional stresses consistent with transverse normal faulting elsewhere in the arc massif this model agrees with observations of slip vectors by ekstr6m and engdahl 1989 who conclude that a portion of the arc parallel component of relative plate motion is taken up in the overriding plate this model implies that compressive stress transferred to the arc is small in comparison to along arc shear stress and that stresses conducive to strikeslip faulting are prevalent throughout the arc

geochemical processes assessed by rare earth elements fractionation at laguna verde acidic sulphate crater lake azufral volcano colombia abstract the geochemical behaviour of major elements fe al mn and rare earth elements ree was investigated in the laguna verde acidic crater lake of azufral volcano colombia the cold lake water t close to 10 c is sulphate dominated due to absorption and oxidation of h2s ph 2 1 2 7 eh 196 260 mv and na enriched total dissolved solids 0 79 g l 1 the total amount of ree dissolved in the lake ranges from 3 3 to 9 1 ppb the ree patterns normalized to the local rocks show a light rare earth elements lree depletion quite constant in the 15 samples similar patterns were already found in the acidic sulphate springs of nevado del ruiz volcano hydrothermal system caused by the precipitation of alunite and jarosite absorbing lree and hence removing them from solution alunite and jarosite minerals are not oversaturated at chemical physical conditions within the lake itself but alunite becomes oversaturated for temperatures above 100 c reigning in the underlying hydrothermal system water temperatures close to 75 c were found in the northern part of the lake coupling the distribution of ree in lake water lree depleted and the saturation indexes we suggest that the distribution of ree in the lake water is the result of the alunite precipitation in the northern part of the lake and or in the deeper hydrothermal system the acidic hydrothermal fluids mobilize the ree with contents up to 5 orders of magnitude higher than seawater acidic hydrothermal systems such as acidic crater lakes can hence be considered potential ree reservoirs

tracing thermal aquifers of el chichon volcano hydrothermal system mexico with 87sr 86sr ca sr and ree abstract the volcano hydrothermal system of el chichon volcano chiapas mexico is characterized by numerous thermal manifestations including an acid lake steam vents and boiling springs in the crater and acid and neutral hot springs and steaming ground on the flanks previous research on major element chemistry reveals that thermal waters of el chichon can be divided in two groups 1 neutral waters discharging in the crater and southern slopes of the volcano with chloride content ranging from 1500 to 2200 mg l and 2 acid to neutral waters with cl up to 12 000 mg l discharging at the western slopes our work supports the concept that each group of waters is derived from a separate aquifer aq 1 and aq 2 in this study we apply sr isotopes ca sr ratios and ree abundances along with the major and trace element water chemistry in order to discriminate and characterize these two aquifers waters derived from aq 1 are characterized by 87 sr 86 sr ratios ranging from 0 70407 to 0 70419 while sr concentrations range from 0 1 to 4 mg l and ca sr weight ratios from 90 to 180 close to average values for the erupted rocks waters derived from aq 2 have 87 sr 86 sr between 0 70531 and 0 70542 high sr concentrations up to 80 mg l and ca sr ratio of 17 28 aquifer 1 is most probably shallow composed of volcanic rocks and situated beneath the crater within the volcano edifice aquifer 2 may be situated at greater depth in sedimentary rocks and by some way connected to the regional oil gas field brines the relative water output l s from both aquifers can be estimated as aq 1 aq 2 30 both aquifers are not distinguishable by their ree patterns the total concentration of ree however strongly depends on the acidity all neutral waters including high salinity waters from aq 2 have very low total ree concentrations 4 ground waters draining fresh and old pyroclastic deposits rich in magmatic anhydrite it is suggested that the main mechanism controlling the concentration of ree in waters of el chichon is the acidity as low ph results from the shallow oxidation of h 2 s contained in hydrothermal vapors ree distribution in thermal waters reflects the dissolution of volcanic rocks close to the surface or lake sediments as is the case for the crater lake

bathymetric and geochemical investigation of kawah ijen crater lake east java indonesia abstract a bathymetric survey of kawah ijen crater lake was conducted by acoustic sounding in 1996 to compare the lake morphology with those measured in 1922 1925 and 1938 and to calculate the present lake volume even though the lake experienced several hydrothermal eruptions the maximum depth became shallower 182 m than before 200 m resulting in a reduced lake volume 3 0 10 7 m 3 fifty two major and minor constituents including rare earth elements and polythionates pt of the lake waters at various depths were determined by icp aes icp ms and hplc respectively these ions except for several volatile elements are taken up by lake fringe through congruent dissolution of pyroclastics of kawah ijen volcano most ions are homogeneously distributed throughout the lake although pt showed a considerable vertical variation rare earth elements ree in the kawah ijen water as well as those from other hyper acidic crater lakes show distribution patterns likely due to the three rock dissolution preferential congruent and residual types and their logarithmic concentrations linearly depend upon the ph values of the lake waters using the pt degradation kinetics data production rates of pt injection rates of so 2 and h 2 s into the lake were estimated to be 114 86 and 30 tons day respectively also travel time of the spring water at the banyupahit riverhead from kawah ijen was estimated to be 600 1000 days through the consideration of decreasing rates of pt molten sulfur stocks containing sn cu bi sulfides and pb barite exposed on the inner crater slope were presumed to be extinct molten sulfur pools at the former lake bottom this was strongly supported by the barite precipitation temperature estimated through the consideration of the temperature dependence of pb chlorocomplex formation

evolution of interstitial waters along the passive margin of the southeast basin of france welcom well chemical on line monitoring applied to balazuc 1 well ardeche abstract as part of the geologie profonde de la france gpf deep geology of france programme investigating the passive margin of the southeast basin of france studies are being made on the possibility of modelling mass transfer in the summer of 1990 when the first hole in the area balazuc 1 was being drilled along a basement rooted fault chemical monitoring of the drilling fluids welcom enabled the composition of the interstitial fluids contained within the intersected rocks to be reconstructed the computations were compared to on core leaching carried out during the drilling following which the welcom results were calibrated the interstitial fluids from the drilled formations show very contrasted compositions from the top to the bottom of the hole it has been possible to distinguish diagenetically evolved seawater within the hettangian limestone modified continental fluids within the upper part of the triassic sandstone reservoirs and evaporated seawater within the middle triassic evaporites several zones of intensive fluid circulation are also indicated by dolomitization of the basal hettangian limestone circulation of fluids expelled from the evaporites within the upper part of triassic sandstone reservoirs and continental derived hydrothermal fluid flow within the lower triassic sandstone reservoir and carboniferous silty shale the results show that chemical logging of drilling fluids can provide valuable data concerning interstitial fluids where other techniques are not available

spacing of faults at the scale of the lithosphere and localization instability 1 theory 1 large scale tectonic structures such as orogens and rifts commonly display regularly spaced faults and or localized shear zones to understand how fault sets organize with a characteristic spacing we present a semianalytical instability analysis of an idealized lithosphere composed of a brittle layer over a ductile half space undergoing horizontal shortening or extension the rheology of the layer is characterized by an effective stress exponent ne the layer is pseudoplastic if 1 ne 0 and forms localized structures if 1 ne 0 two instabilities grow simultaneously in this model the buckling necking instability that produces broad undulations of the brittle layer as a whole and the localization instability that produces a spatially periodic pattern of faulting the latter appears only if the material in the brittle layer weakens in response to a local perturbation of strain rate as indicated by 1 ne 0 fault spacing scales with the thickness of the brittle layer and depends on the efficiency of localization localization is more efficient for more negative 1 ne leading to more widely spaced faults the fault spacing is related to the wavelength at which different deformation modes within the layer enter a resonance that exists only if 1 ne 0 depth dependent viscosity and the model density offset the instability wavelengths by an amount al that we determine empirically the wave number of the localization instability is kjl j al 1 ne 1 2 h with h the thickness of the brittle layer j an integer and 1 4 al 1 2 if the strength of the layer increases with depth and the strength of the substrate decreases with depth

flow behavior of fine grained synthetic dunite in the presence of 0 5 wt h2o the deformation behavior of synthetic dunite mg forsterite plus 2 5 vol enstatite with a grain size of 1 m has been investigated in combined constant displacement rate and temperature stepping experiments at temperatures of 850 to 1000 c strain rates of 10 7 to 10 5 s 1 and a confining pressure of 600 mpa nominally dry material behaved purely elastically in contrast samples with 0 5 wt added water flowed at stresses between 9 and 81 mpa reaching strains up to 12 fitting a dorn type power law to the wet data yielded stress exponents n of 1 7 0 4 and apparent activation energies in the range 302 22 kj mol 1 the wet deformed samples showed polygonal grains no crystallographic preferred orientation no subgrains low dislocation densities and evidence for grain boundary cavitation grain growth was minor it is concluded that the wet samples probably deformed by a grain size sensitive grain boundary sliding dominated mechanism though the nature of the accommodation process remains unclear and the possibility of transitional behavior between dislocation creep and diffusion creep cannot be eliminated application of the results to upper mantle shear zones supports previous speculation that the presence of such zones can lead to a significant weakening of the top 10 to 20 km of the upper mantle during extension of the continental lithosphere

rheological modelling and deformation instability of lithosphere under extension summary continental break up which precedes oceanic accretion probably results from an unstable extension of the lithosphere analogous to necking of metals when they are submitted to tension by reason of complexity of the rheology no conclusion about lithospheric extension stability may be reached by an a priori analysis we thus examine directly the evolution when the lithosphere is stretched of lateral inhomogeneities represented in our example by small scale variations of thickness the rheological model is derived from the hypotheses of brace kohlstedt 1980 and is consistent with the results of rock mechanics the lithosphere consists of three or four layers of varying thicknesses and mechanical properties the brittle upper crust and eventually the brittle part of the mantle are assimilated to perfectly plastic media and are described in a state of uniform extension by a constant viscosity in the lower crust and ductile mantle lithosphere the effective viscosity is supposed to be exponential the mechanical model relies on a perturbation method developed by fletcher hallet 1983 among others contrary to previous published results no unstable behaviour of the lithosphere is observed unless the latter is more dense than the asthenosphere in which case a gravitational instability may develop this discrepancy can be explained by differences in assumptions concerning the variation of strength in the lithosphere as yet poorly constrained by the data we observe a great sensitivity of the results to the strength stratification and to the artificial discontinuities of density or viscosity implied by the models

chemical constraints and origins of four groups of gulf coast reservoir fluids discussion the authors take to task stoessell and moore s 1983 review of some previous ideas on the origin of gulf coast formation fluids taking specific exception to their interpretation of data from the edwards formation six points are emphasized edwards brines are significantly enriched in bromide relative to chloride over seawater evaporated to halite saturation edwards brines have significantly higher k c1 and ca mg c1 ratios than seawater evaporated to halite saturation edwards brines cannot achieve molar ca mg ratios of 16 by dolomization progressive stabilization of metastable dolomite by updip fluid cannot raise the magnesium content of edwards water in the absence of dolomite dissolution the volume of brine contained in the cretaceous section exceeds any reasonable volume of hypothetical connate mesozoic brine and isotopic differences between edwards brines and jurassic seawater evaporated to halite saturation are extreme and therefore preclude recognition of any primary jurassic component in the current brines

cored section of the balazuc well southeastern basin of france geologic and geochemical approach deep geology of france programme abstract the ardeche project of the geologie profonde de la france gpf or deep geology of france programme aims at quantifying mass transfer along the margin of the southeastern basin of france using drilling data a very comprehensive geologic study has been made of the cores from the balazuc well including lithology sedimentology mineralogy and petrography this enabled the determination of several lithologic units and of the evolution of their depositional environment petrographic study showed that the diagenetic evolution can be divided into four phases from syn sedimentary diagenesis to a late faulting related phase in order to provide a framework for these observations at the scale of the units a geochemical investigation was carried out as well it consisted of the unusual procedure of total rock analyses on core slabs up to 60 cm long each sample representing a rocktype in this paper we compare the geologic results with the chemical logs that were obtained from these analyses the lithology and mineralogy of the formations give a specific chemical signature the evolution with depth of the major elements defines trends that can be correlated with first and second order major and minor stratigraphic cycles indicating that the base level evolution has been recorded by these logs through detrital control using minor elements fe mn sr and ba the evolution with depth of several specific mineralogical phases indicates that the depositional environment and tectonic control of the sedimentation remained guides for the chemical composition of diagenetic deposits comparison with petrographic results shows that diagenesis occurred extremely rapidly leading to a complete decrease in permeability of the series the results show that this type of geochemistry can be a powerful tool to complete geologic observations

oceanography chemical twins separated how the chemical composition of sea water changes on its journey through the world s oceans is poorly understood systematic measurements of dissolved trace metals across the pacific ocean suggest that these metals may help track sources and mixing of water masses

comparison of hydrogeochemical logging of drilling fluid during coring with the results from geophysical logging and hydraulic testing example of the morte merie scientific borehole ardeche france deep geology of france programme abstract a 980 m deep well was cored on the ardeche border of the southeastern basin of france as part of the deep geology of france gpf programme hydrogeochemical logging was carried out during drilling which involved the monitoring of physico chemical parameters ph eh temperature and conductivity and chemical parameters concentrations of he rn co 2 ch 4 o 2 ca cl and sio 2 of the drilling fluid permanently circulating in the well this logging programme was complemented by geophysical logging and two hydraulic tests the combination of these measurements enabled identification of a transmissive interval due to fractures in the jurassic carbonates and of fluid inflow both at the base of the porous and slightly permeable triassic sandstones and from an open fracture in the permian conglomerates these intervals are marked by changes in the drilling fluid chemistry such as an increase in chemical species content or a drop in ph the degree of modification depends on the natural permeability of the fractures and the salinity of the fluids the porous and permeable intervals are also marked by he anomalies which act as a tracer for these zones comparison between the geophysical and hydrogeochemical logs reveals that the latter provide information on the liquid phase whether the fractures are productive or not whereas the geophysical logs are more directly related to the solid phase

geochemistry of ree zr and hf in a wide range of ph and water composition the nevado del ruiz volcano hydrothermal system colombia the geochemical behaviour of rare earth elements zr and hf was investigated in the thermal waters of nevado del ruiz volcano system a wide range of ph between 1 0 and 8 8 characterizes these fluids the acidic waters are sulphate dominated with different cl so4 ratios the important role of the ph and the ionic complexes for the distribution of ree zr and hf in the aqueous phase was evidenced the ph rules the precipitation of authigenic fe and al oxyhydroxides producing changes in ree zr hf amounts and strong anomalies of cerium the precipitation of alunite and jarosite removes lree from the solution changing the ree distribution in acidic waters y ho and zr hf twin pairs have a different behaviour in strong acidic waters with respect to the water with ph near neutral yttrium and ho behave as zr and hf in waters with ph near neutral to neutral showing super chondritic ratios the twin pairs showed to be sensitive to the co precipitation and or adsorption onto the surface of authigenic particulate fe al oxyhydroxides suggesting an enhanced scavenging of ho and hf with respect to y and zr leading to superchondritic values in acidic waters a different behaviour of twin pairs occurs with chondritic y ho ratios and sub chondritic zr hf ratios for the first time zr and hf were investigated in natural acidic fluids to understand the behaviour of these elements in extreme acidic conditions and different major anion chemistry zr hf molar ratio changes from 4 75 to 49 29 in water with ph 3 6 in strong acidic waters the fractionation of zr and hf was recognized as function of major anion contents cl and so4 suggesting the formation of complexes leading to sub chondritic zr hf molar ratios

rare earth element speciation in geothermal fluids from yellowstone national park wyoming usa abstract elevated concentrations 20 1133 nmol kg of rare earth elements ree are present in acid sulphate and acid sulphate chloride hydrothermal waters of the yellowstone national park ynp we used recently estimated thermodynamic data haas et al 1995 to speciate seventeen ynp hydrothermal fluids with the eq3nr code the fluids show a range in ph 2 0 4 0 and temperature 70 93 c and are of varied chemistry with tds 155 2 075 ppm sulphate 100 10 325 mol kg chloride 190 24 580 mol kg fluoride 26 1 790 mol kg and so 4 f 0 8 323 field temperature and ph measurements were used in the modelling and saturation with kaolinite and quartz was assumed although quartz was actually supersaturated where possible oxygen fugacity was calculated from the analytical sulphate sulphide ratios otherwise it was set above the hematite magnetite buffer and pyrite saturation although speciation calculations show that this is not critical carbonate and phosphate levels were set at the analytical detection limit with the exception of 4 waters for which analytical data for phosphate existed the waters show little fractionation of ree relative to their host rhyolitic volcanics it appears that the ree abundances of hydrothermal fluids resulting from alteration of ynp rhyolites are unaffected by the presence of potential complexing species i e that acid alteration completely strips ree from the portion of the rocks that it affects without any fractionation across the ree series the main control over ree speciation is the relative abundances of potential complexing agents however ph and absolute abundances are also important in the most acidic waters ph 2 0 the free ion is the major species when salinity and so 4 cl are low 60 80 of each ree and ree complexes with chloride can be significant up to 5 for higher so 4 cl values sulphate complexes dominate 80 90 for less acid waters ph 2 8 4 0 fluoride is the main complexing agent in low so 4 f fluids but as the so 4 f ratio increases the sulphate species become dominant especially for the light ree lree

the influence of the lithospheric thickness on bilateral slip summary a 2 d model of slip formation and dynamic propagation in an elastic lithospheric plate coupled to the asthenosphere and having a fault plane is investigated using a finite element method slip is nucleated at a weak portion of the fault plane and propagates bilaterally at the edges slip is assumed to develop according to a critical shear stress criterion combined with a slip weakening law except for the weak portion the slip resistance is constant along the fault plane the influence of resistive stresses from the asthenosphere at the bottom of the plate is taken into account the results indicate that bilateral slip lengths are limited to about the lithospheric plate thickness or somewhat larger such lengths will only be reached for sufficiently high tectonic loading after maximum slip length has been reached the slipping region is split into two regions of unidirectional slip moving in opposite directions the results thus illustrate one mechanism which limits the maximum amount of slip during an earthquake even in the absence of strong barriers

the precambrian continental crust its structure composition and evolution as revealed by deep drilling in the u s s r abstract petrologic geochemical studies of the kola superdeep and other deep borehole sections drilled in the precambrian basement of the east european platform are discussed proterozoic metasediments and metavolcanic rocks that constitute the pechenga palaeorift and the underlying archaean granite gneiss basement were detected by the kola borehole in the 0 6842 m and 6842 12064 m intervals respectively zones of density decrease by hydrofracture resulting from progressive metamorphism under closed system conditions were identified in the upper crust at a 4500 9000 m depth sharp textural variations of rocks an increase in porosity and the presence of mineralizing fluids are specific features of these zones which may have contributed to tectonic deformation and metamorphically produced ore formation deep boreholes drilled into the more eroded archaean basement of the tatar dome provided information that was used for constructing a petrologic geochemical model of the lower crust to a depth of 25 30 km adacitic trondhjemitic composition for the primeval continental crust was calculated by extrapolation of geochemical trends established for the lower crust we propose that the lower crust formed as a result of an initial melting of the earth s chondrite shell and only existed in pre archaean times we also present data on temperatures and distribution of radiogenic elements in the kola and some other borehole sections a heat production model is proposed for the archean crust according to the model the crustal contribution to the heat flow is 25 mw m 2 or 52 of the total heat flow and that of the mantle is 22 24 mw m 2 or 48 of the total flow

burial and thermal history of the west bashkirian sedimentary basins abstract the galo system is applied to the numerical reconstruction of burial and thermal histories of the west bashkirian lithosphere from the riphean to the present an analysis of the variation in tectonic subsidence of the basin during its development is utilized to estimate approximately the mantle heat flow variations our variant of basin evolution suggests that after cooling in the early riphean the rather weak thermal reactivations have not led to considerable heating of the lithosphere in the study region surface heat flow decreased from relatively high values in the early riphean 60 70 mw m 2 in the eastern area and 40 50 mw m 2 in the western part to present day values of 32 40 mw m 2 in spite of the relatively low temperature regime of the basin as a whole a syn rifting deposition of more than 10 km of limestone shale and sandstone in the riphean resulted in rather high temperatures 180 190 c at the base of present day sedimentary blanket in the eastern area in agreement with the observed data computed present day heat flow through the sediment surface increases slightly from 32 to 34 mw m 2 near the west boundary of the region to 42 mw m 2 near the boundary of the ural foldbelt whereas the heat flow through the basement surface decreases slightly from 28 32 to 24 26 mw m 2 in the same direction the mantle heat flow is only 11 3 12 7 mw m 2 which is considerable lower than mean heat flow of the russian platform 16 18 mw m 2 and comparable with the low heat flow of precambrian shields

fluid infiltration into fault zones chemical isotopic and mechanical effects fluid infiltration into fault zones and their deeper level counterparts brittle ductile shear zones is examined in diverse tectonic environments in the 2 7 ga abitibi greenstone belt major tectonic discontinuities with lateral extents of hundreds of kilometres initiated as listric normal faults accommodating rift extension and acted as sites for komatiite extrusion and locally intense metasomatism during reverse motion on the structures accommodating shortening of the belt these transcrustal faults were utilised as a conduit for the ascent of trondhjemitic magmas from the base of the crust and of alkaline magmas from the asthenosphere and for the discharge of thousands of cubic kilometres of hydrothermal fluids such fluids were characterised by 18o 6 2 d 50 20 13c 4 4 and temperatures of 270 to 450 c probably derived from devolatilisation of crustal rocks undergoing prograde metamorphism hydrothermal fluids were more radiogenic 87sr 86sr 0 7010 to 0 7040 and possessed higher than did contemporaneous mantle komatiites or tholeiites and thus carried a contribution from older sialic basement a provinciality of87sr 86sr and 13c is evident signifying that fault plumbing sampled lower crust which was heterogeneous at the scale of tens of kilometres mineralised faults possess enrichments of large ion lithophile lil lil elements including k rb ba cs b and co2 and rare elements such as au ag as sb se te bi and w fluids were characterised by xco2 0 1 neutral to slightly acidic ph low salinity 3 wt k na 0 1 they carried minor ch4 co and n2 and they underwent transient effervescence of co2 during decompression clastic sediments occupy graben developed at fault flexures the40ar 39ar release spectra indicate that fault rocks experienced episodic disturbance on time scales of hundreds of millions of years

dissolved zirconium and hafnium distributions across a shelf break in the northeastern atlantic ocean abstract dissolved zr and hf distributions have been determined for five stations located across the shelf break in the northeastern atlantic ocean on the celtic approaches for stations in deep water the range in zr concentrations has been found to be 70 180 pmol kg and the range in hafnium concentrations 0 4 1 1 pmol kg the distributions with depth are indicative of a nutrient like scavenging regeneration behavior in seawater although the dissimilarity with silicate and nitrate for samples below the nutricline suggest that other mechanisms are also important in defining the oceanic distribution of these elements in contrast the concentrations of zr and hf at the station located closest to land are highest in surface waters and decrease with depth although salinity does not indicate dilution of seawater with freshwater with high zr and hf concentrations the ratio of dissolved zr to hf in seawater is higher and more variable than is found for the majority of terrestrial rocks or predicted from thermodynamic considerations fractionation due to small differences in their interactions with particulate material is implicated

a dynamic model of extension in the baltimore canyon trough region a dynamic model of extension in the baltimore canyon trough region of the central north atlantic indicates that rifting proceeded in two stages and was controlled by laterally offset preexisting weaknesses within the middle crust and upper mantle beneath the appalachian orogen the crustal weakness is hypothesized to result from thin skinned thrust faulting in the appalachian foreland and the upper mantle weakness results from crustal thickening beneath the appalachian hinterland during the early stages of rifting 225 185 ma the loci of extension in the crust and mantle lie within the respective preweakened regions and are connected by a shear zone in the lower crust in a manner similar to whole lithosphere simple shear extension and thinning of the upper crust at this time results in the formation of late triassic early jurassic rift basins in the appalachian piedmont and in the development of a horizontal pressure gradient which drives widespread ductile flow in the lower crust the pressure gradient may also have influenced magma transport moving melt generated beneath the eastern baltimore canyon trough into the more westerly triassic basin province during the late stages of rifting 185 175 ma extension in the crust shifts to a position overlying the preexisting upper mantle weakness as a result of thermal weakening by the upwelling asthenosphere in this region the loci of extension in the crust and mantle are then coincident and the style of rifting becomes similar to whole lithosphere pure shear the shift in the locus of crustal extension is accompanied by the cessation of subsidence and volcanism in the triassic basins the onset of rapid subsidence in the baltimore canyon trough and the formation of a basement hinge zone separating the highly thinned crust beneath the baltimore canyon trough from moderately thinned crust beneath the triassic basin province extension becomes increasingly focused beneath the eastern edge of the baltimore canyon trough until the onset of seafloor spreading approximately 50 m y after rifting began the resulting conjugate margins are asymmetric with most of the region encompassing the triassic basins stranded on the north american plate

acid sulfate chloride volcanic waters formation and potential for monitoring of volcanic activity abstract this paper deals mainly with acidic sulphate chloride asc waters that are discharged at volcanic edifices generally not associated with crater lakes geographically the largest number of such manifestations were found on japanese and kuril islands these waters are formed by 1 condensation of magmatic vapor under shallow conditions and or 2 dissolution of magmatic gases in underground waters 3 near surface mixing of steam heated sulphate waters with sodium chloride waters of deeper formation 4 interaction of sodium chloride waters with the rocks undergone by argillic and advanced argillic alteration including hydrolysis of elemental sulfur 5 a combination of several of the listed processes criteria to assess the nature of such waters using their chemical and isotopic composition are based on the relative abundances of major species and trends in isotopic compositions generally controlling by mixing of magmatic host rock meteoric endmembers an overview of available data on temporal chemical variations of such waters shows that usually volcanic activity is marked by an increase in the so4 cl ratio during or after the eruptive event the response on the volcanic activity depends on hydrogeological conditions that control the appearance of the asc springs

ree fractionation during the gypsum crystallization in hyperacid sulphate rich brine the poas volcano crater lake costa rica exploited as laboratory abstract the critical role of rare earth elements lanthanides plus yttrium hereafter ree in high tech technologies and consequently their increasing demand from the industry in addition to the capability of ree to trace water rock interaction processes boosted the study of ree in unconventional extreme environments this study is focused on the geochemical behaviour of ree in the hyperacid sulphate rich brine of the crater lake of poas volcano costa rica where the precipitation of gypsum occurs this system can hence be considered as a natural laboratory to evaluate the fractionation of ree between the lake water mother brine and the precipitating gypsum mineral total ree concentrations dissolved in waters range from 1 14 to 2 18 mg kg 1 calculated distribution coefficients kd for ree between the gypsum and the mother brine indicate a preferential removal of the light ree lree with respect to the heavy ree hree with kd values mainly decreasing from la to lu during the observation period 2007 2009 the distributions of ree concentrations dissolved in lake water normalized to the average local volcanic rock show two different trends i lree depleted patterns and ii flat patterns the identification of the lree depleted pattern is justified by the kd calculated in this study we demonstrate that the precipitation of gypsum is able to strongly fractionate the ree in hyperacid sulphate rich brine inducing changes in ree concentrations and distributions over time x ray computed tomography imaging was performed on gypsum crystal precipitated from the lake waters to gain insights on crystal scale processes possibly controlling the ree geochemistry i e surface processes vs structural substitution accordingly the heavy metals and possibly the ree seem to be mainly located on the crystal surface rather than inside the crystal suggesting that a surface process could be the major process controlling ree removal from the water to the crystal

chemical constraints and origins of four groups of gulf coast reservoir fluids pitzer s method for computing activity coefficients has been applied to reported fluid compositions in four groups of gulf coast reservoirs the mississippi and arkansas smackover formation the texas edwards group the texas frio formation and the louisiana miocene sequence the activity quotients in fluids from carbonate reservoirs imply a reaction relation between calcite and disordered dolomite in which ordering increases at higher temperatures this relationship indicates that an increasing mg ca molality ratio with decreasing temperature does not necessarily imply dolomite dissolution by an updip moving fluid instead it may reflect an approach to equilibrium between calcite and metastable dolomite activity quotients in fluids from clastic reservoirs imply a rea tion relation between chlorite illite potassium feldspar and quartz at temperatures above 100 c 212 f present fluid compositions in the smackover and the edwards appear to be related to the updip movement of louann brines from the gulf coast basin accompanied by dolomitization in particular bromide plots for the edwards fluids indicate simple dilution of louann brines with interstitial fluids similar plots for fluids from the smackover show the complicating effects of illite formation sylvite dissolution and halite recrystallization albitization may have occurred during fluid movement through clastics prior to entering the smackover and edwards present fluid compositions in the frio and miocene are apparently not related to louann brines the compositional data reflect the effects of halite dissolution the subsequent albitization of plagioclase and potassium feldspar and the dissolution of carbonates during secondary porosity formation

water rock interaction in tertiary sandstones san joaquin basin california u s a diagenetic controls on water composition three water types are recognized among petroleum associated waters of the southern san joaquin basin 1 meteoric water 2 diagenetically modified connate water and 3 mixed meteoric modified connate water the diagenetically modified connate marine water can be further subdivided into three types 1 fully mg depleted mg 1 mole of the sum of na k ca and mg 2 partially mg depleted and 3 ca enriched enrichment in ca which is the sharpest chemical divide found for the diagenetically modified connate water is the result of feldspar albitization the ca enriched waters are also rich in total dissolved al up to 6 mg l 1 and exhibit lighter 18o values than other diagenetically modified connate waters the total dissolved al abundance in these waters may be due to the presence of organic complexing agents simple and aromatic organic acids and phenolics the lighter 18o values are probably due to both albitization and the lack of substantial clay diagenesis illitization of smectite

identification of connate water in interstitial solution of chalk sediment interstitial solution was recovered from core samples of a borehole through 472 m of the upper cretaceous chalk formation in eastern england the solution has been analysed for major and some minor components and also for oxygen and hydrogen isotopic composition samples of the carbonate rock have also been analysed following acid dissolution the general feature of interstitial solution chemistry is a progressive dilution of dissolved species with decreasing depth from a near marine composition found in the deepest samples which are identified as connate water departures from the expected dilution trend are interpreted as evidence for diagenetic reactions during burial or as a result of freshwater circulation following subaerial uplift sr2 li and f have been enriched in interstitial solution and k has been slightly depleted the profile of chalk chemistry with depth shows no conclusive evidence for changes in the mg and sr content of the bulk carbonate due to freshwater diagenesis the 18o and d of the interstitial water reflect the same mixing as that shown by dissolved species however an apparent depletion of 18o and d in the deepest fluids with respect to the expected marine isotopic composition is tentatively explained as a result of the differences in diffusion rates of aqueous oxygen and hydrogen and of ionic solutes

periodic instabilities during compression or extension of the lithosphere 1 deformation modes from an analytical perturbation method we argue that the plastic rheology of the lithosphere rather than its recoverable elastic properties is responsible for the systematic development of periodic instabilities during compression or extension we use a linear perturbation model with analytical solutions to calculate the instability modes for various rheologies the growth of such periodic instabilities is enhanced by the highly nonlinear stress strain rheologies encountered in the brittle layers of the lithosphere on the contrary ductile layers deforming according to high temperature creep flow laws tend to inhibit these instabilities for oceanic domains we assume that the only brittle layer is the upper part of the lithosphere in compression the only valid instability is a buckling whose wavelength is around 4 times the thickness of the brittle layer calculated wavelengths and growth rates are consistent with observations available for the indian ocean for continental domains a reasonable assumption is the existence of two plastic layers one in the upper crust the other in the upper mantle for moho temperatures between 450 c and 600 c in compression and extension two instabilities develop a long wavelength instability involving the whole lithosphere coupling mode and a short wavelength instability involving the crust and controlled by the upper brittle layer intrinsic crustal mode in compression the coupling mode is a whole lithosphere buckling with a wavelength about 4 times the thickness of the active lithosphere the two plastic layers plus the intermediate ductile layer in extension the coupling mode is a boudinage of opposite phase in the two plastic layers and a folding of the intermediate ductile layer the intrinsic crustal mode is a crustal buckling in compression crustal boudinage in extension neither deflects the moho the intrinsic crustal mode is favored by an increase in thermal gradient and by a decrease in strength of the ductile lower crust

stretching instabilities and lithospheric boudinage a competent layer with a nonlinear rheology can under extension exhibit pinch and swell instabilities such instabilities can explain small scale regular deformations of rock recently they have also been invoked in relation to the distribution of basins and ranges fletcher and hallet 1983 and the undulation of the bouguer map froidevaux 1986 in the western part of north america for the case of a simple stratified structure different authors have expressed mathematical solutions describing these instabilities in this paper we elucidate the general physical meaning of these nonhomogeneous deformations in the simplest case where the competent layer is fully embedded in a softer material a fundamental mode develops with a preferred wavelength equal to 4 times the thickness of a competent layer the novelty is the occurrence of overtones with alternate symmetrical and antisymmetrical deflections of the interfaces between layers these modes have a large amplitude when the rheology tends to perfect plasticity the presence of a free surface like the earth s surface for the upper crust is shown to double the preferred wavelength of the fundamental mode and to forbid one overtone out of two this new effect is caused by gravity which inhibits the growth of surface topography another shift is of opposite sign to that caused by a free surface numerical solutions for multilayer structures can elucidate the nature of couplings between various layers the case of a three layer lithosphere having a soft lower crust and overlying a mantle asthenosphere has been analyzed in some detail it shows that in the range of wavelengths larger than 30 km up to five preferred modes may be superimposed this should encourage further analysis of the western u s topography and gravity pattern which is known to contain at least two wavelengths about 40 km for the individual basins and ranges and about 200 km for the bouguer troughs in nevada and their associated broad topographies

extension of continental lithosphere a model for two scales of basin and range deformation we develop a model for deformation in an extending continental lithosphere that is stratified in density and strength assuming a rheology consistent with seismic focal depths and experimental flow laws the model demonstrates that necking instabilities at two wavelengths will arise due to the presence of a strong upper crust and upper mantle separated by a weak lower crust the magnitudes of the instabilities are directly related to strength contrasts within the lithosphere while the dominant wavelengths of necking are controlled mainly by the thicknesses of the strong layers the results are applied to the basin and range province of the western united states where two scales of deformation can be recognized one corresponding to the spacing of ranges and the other to the width of tilt domains a bouguer gravity anomaly and associated regional topography with a wavelength comparable to the width of tilt domains has also been recognized for plausible density and strength stratifications our results show that the horizontal scale of short wavelength necking is consistent with the spacing of individual basins and ranges while that of the longer wavelength necking is consistent with the width of tilt domains we thus suggest that basin and range deformation may be controlled by two scales of extensional instability extension in the weak lower crust in this model is laterally displaced from regions of upper crustal extension the resultant horizontal shearing in the lower crust may be a mechanism for the initiation of low angle extensional detachments

naturally acid waters from copahue volcano argentina volcanic acid sulfate chloride brines form through absorption of volcanic vapors in shallow reservoirs of meteoric water reaction with surrounding volcanic rocks leads to partial neutralization of the fluids and precipitation of secondary minerals chemical data of such acid waters from copahue volcano argentina covering 8 years of observations show evidence for changes in composition related to water rock interaction at depth prior to emergence of the fluids at the surface the chemical composition changed dramatically during the 2000 eruption of copahue with enhanced concentrations and fluxes of mg na fe and al followed in 2001 by rapidly declining concentrations and element fluxes the subsequent 5 years saw more variable element ratios and strong depletions in k and al most incompatible elements are released from the rock matrix stochiometrically whereas some elements are enriched through vapor input from the magma as pb zn most fluids have lree enrichments relative to the rock matrix but during periods of new magma intrusion the lree enrichment decreases as does the magnitude of the negative eu anomaly in the fluids these observations are interpreted assuming early dissolution of plagioclase olivine and volcanic glass that occurs during intrusion of new magma into the hydrothermal system the high field strength elements are virtually immobile even in these hot acid fluids with nb and ta more so than hf and zr the mobility of u and th in these fluids is comparable at variance with th behavior in neutral fluids the local rivers and lakes of copahue are fertilized by volcanic dissolved p and most surface waters with ph 3 have high levels of as the acid fluids from copahue may be surficial analogs for deep subduction fluids that evolve below zones of arc magma generation as well as for early mars environments that are thought to have had large acid lakes