chemical and physical denudation in the amazon river basin we present major and trace element data on the suspended and dissolved phases of the amazon river and its main tributaries the sr isotopic composition of the dissolved load is also reported special attention is paid to the abundances of ree and to their fractionation between the dissolved and suspended phase the rivers of the amazon basin are among the richest in dissolved ree and are similar to the rivers of the congo system however a greater range of fractionation between lree and hree is reported here at a global scale the rivers have intermediate patterns between those of the congo system and those of high ph rivers such as the indus and mississippi rivers only few elements rb u ba k na sr and ca are mobilized by silicate weathering these elements are strongly depleted in the suspended phase with respect to upper continental crust in the dissolved load these elements are controlled by atmospheric inputs and the weathering of the main lithologies we propose a model based on mass budget equations that allow the proportions derived from the different sources to be calculated as a consequence silicate carbonate and evaporite weathering rates can be estimated as well as the consumption of co2 by weathering of each of these lithologies physical weathering rates can be estimated by two complementary approaches on the one hand the multi year average of suspended sediments yields can be used to estimate physical denudation on the other hand we have developed a steady state model of erosion that allows us to calculate physical erosion rates on the basis of the dissolved load of rivers a mean crustal composition is assumed in this model for the rock sources of the drainage basins comparison of the rates predicted by the model to the observed rates shows good agreement for the lowland rivers but a strong discrepancy for the rivers derived from the andes andean rivers solimoes madeira and amazon have observed sediment yields much greater than those predicted according to the steady state model of chemical and physical weathering two interpretations can account for this inconsistency the first is that these rivers are not in steady state and hence that the soils are being destroyed the second requires that the local continental crust is different from the average continental crust of taylor and mclennan and contains a large proportion of sedimentary rocks using the measured sediment yields and assuming a steady state we can estimate the amount of sediment recycling for each drainage basin for the amazon at santarem we find that at least 25 of the mass of the upper continental crust of the amazon drainage basin is constituted of recycled material

chemistry of rainwater in the massif central france a strontium isotope and major element study atmospheric aerosols sea salt crustal dust and biogenic aerosols are the primary source of dissolved species in rainwater as well as one of the sources of dissolved species in river water chemical weathering studies require quantification of this atmospheric input the crustal component of atmospheric input can have various origins both distant and local the proportions of the various inputs marine distant or local are determined in this study strontium isotope ratios and ca na k mg al cl so4 no3 and sr concentrations were measured in rainwater samples collected in the massif central france over a period of one year each sample collected automatically represents a monthly series of rain events chemical composition of the rainwater samples varied considerably and the 87sr 86sr ratios ranged between 0 709198 and 0 713143 using na as an indicator of marine origin and al for the crustal input in rain samples the proportion of marine and crustal elements was estimated from elemental ratios a marine origin of 4 to 100 of cl of 0 6 to 20 of the so4 of 1 to 10 of ca 1 to 40 of k 4 to 100 of mg and 1 to 44 of sr was determined strontium isotopes were used to characterize the crustal sources the 87sr 86sr ratios of the crustal sources varied considerably from 0 7092 to 0 71625 and indicate the occurrence of multiple sources for the crustal component in the analysed rainwaters

dissolved constituents and sr isotopes in river waters from a mountainous island the danshuei drainage system in northern taiwan abstract taiwan is a typical active orogenic belt situated at the collision boundary between the eurasian continental plate and the philippine sea plate dissolved major and trace constituents as well as sr and sr isotopes in river waters collected from the danshuei river basin in northern taiwan have been studied to evaluate chemical weathering processes the results of principal component analysis show that the ion sources in these river waters can be categorized into 3 major components chemical weathering seasalt contribution and local anthropogenic input the chemical weathering is the most dominant factor that contributes about 85 of total variances significantly increased na cl and ca cl as well 87 sr 86 sr were observed in most upper stream samples the na cl and ca cl ratios in the dahan stream however are much higher than the shindien stream even though average rainfall is stronger in the shindien drainage basin chemical evidence from river waters supports less intense weathering in the region selective dissolution of secondary calcites explains the observed high ca cl sr cl and ca na in the dahan stream these results highlight the potential importance of tectonic factors such as uplift and physical erosion in studying chemical weathering in an active orogenic belt the variations of 87 sr 86 sr in the danshuei river are quite large reflecting some strata that released sr most of the upstream waters exhibit more radiogenic 87 sr 86 sr 0 713243 0 714338 due to weathering of ambient low grade metamorphic rocks 0 71678 0 72216 the distributions of cl sr and 87 sr 86 sr in the main stream were affected by somewhat conservative mixing with sources varing between ambient rocks and seasalt in the upper dahan stream heavy 87 sr 86 sr ratios were coincident with large deviations of na cl from the average seawater value as high as 40 the degree of chemical weathering in ambient rocks plays a dominant role in affecting the distribution of sr and 87 sr 86 sr in the danshuei river this isotopic characteristic makes 87 sr 86 sr an invaluable tracer for studying source mixing migration pathways and chemical weathering in an active orogenic belt

chemical weathering in high sediment yielding watersheds new zealand 1 we have determined the chemical erosion yields for fifteen watersheds in new zealand ranging in size from 12 2 to 2928 km2 these rates coupled with previously measured physical erosion yields allow us to compare these two modes of landscape denudation the physical erosion yields are some of the highest measured in the world although in most instances the chemical erosion yields are only a small fraction of the total erosion yields the absolute values are very high our data strongly support the notion that chemical erosion rates are greatly influenced by the yield of physical erosion and that the rapid production of fresh surfaces as a result of high physical erosion rates and subsequent denudation is critical to the high chemical erosion yields observed

characterising the stable δ88 86sr and radiogenic 87sr 86sr isotopic composition of strontium in rainwater rainwater plays a major role in determining the transfer of elements and pollutants to soils and hydrological catchments with compositional variations reflecting the extent of mixing between marine sea salt terrestrial dust and vegetation and anthropogenic aerosols while the radiogenic strontium isotope system 87sr 86sr is often used to help constrain the different sources of atmospheric sr the degree of variability in the stable strontium isotope system 88 86sr remains unresolved in order to determine how atmospheric sr affects the 88 86sr composition of water entering the hydrological cycle this study analysed a suite of rainwater samples collected over the course of a year in central paris rainwater 88 86sr compositions were found to range from 0 13 to 0 32 with 87sr 86sr ratios varying between 0 70796 and 0 71093 no seasonality was observed in 88 86sr whereas 87sr 86sr ratios were observed to be generally more radiogenic in the summer and less radiogenic in the winter strontium enrichment factors significantly above seawater implied a predominantly terrestrial non sea salt origin of sr in rainwater with the 88 86sr and 87sr 86sr composition of this terrestrial fraction consistent with a mixture of sr derived from carbonate dust and agricultural fertiliser evidence for a 0 1 decrease in the 88 86sr composition of the river seine as it passes through paris suggests that anthropogenic pollutants may contribute to significant regional variations in the composition of sr in the hydrological cycle together these results demonstrate that there is significant potential for both temporal and spatial variations in the 88 86sr and 87sr 86sr composition of rainwater that need to be taken into consideration when studying 88 86sr variations in localised catchments

serpentinization of oceanic peridotites 2 kinetics and processes of san carlos olivine hydrothermal alteration 1 the kinetics of the reaction mg fe olivine h 2 o serpentine magnetite brucite h 2 were investigated at 500 bars in the 250 350 c range using natural olivine san carlos fo 91 with grain sizes between 1 and 150 mm and for run durations up to 514 d the amount of magnetite produced which directly relates to reaction progress was accurately monitored using up to 24 time resolved magnetic measurements per experiment eighty percent of serpentinization was achieved after 60 d for olivine grain sizes of 5 15 mm and after 500 d for grain sizes of 50 63 mm serpentinization kinetics were found to be inversely proportional to the geometrical surface area of the starting olivine grains they were one or two orders of magnitude slower than serpentinization kinetics commonly used for modeling serpentinization related processes the nature of the serpentine mineral product depended on the initial olivine grain size igs for igs in the 5 150 mm range lizardite formed and olivine dissolution was the rate limiting process at igs below 5 mm chrysotile crystallized instead of lizardite and the relationship between olivine surface area and reaction kinetics no longer held we infer that for such small olivine grain sizes dissolution is no longer the rate limiting process serpentinization in our experiments was associated with the creation of new reactive surface area according to two cooperative processes etch pits formation associated with dissolution and grain fracturing for igs above 20 mm interestingly fractures and etch pits with similar geometry and sizes were also observed for residual olivine with a typical grain size of 50 mm in serpentinized peridotite samples from the southwest indian ridge this suggests that the processes governing olivine serpentinization kinetics in our experiments are similar to those prevailing in natural systems we therefore suggest that the new kinetic data set that we present here which encompasses a range of olivine grain sizes and reaction temperatures is relevant to the serpentinization of olivine in the oceanic crust insofar as water is available

tracing surface water mixing and groundwater inputs using chemical and isotope fingerprints δ18o δ2h 87sr 86sr at basin scale the loire river france abstract the spatial and temporal distributions of major elements stable isotopes of water molecule and strontium isotope ratios were investigated in the surface waters of the loire river basin the present study using a coupled hydrological and geochemical approach focuses on surface water mixing and the interactions between ground and surface water stable isotopes 18o 2h provide good evidence for the complex hydrological behavior of the loire river system at the basin scale and if binary mixing of surface water masses explain the longitudinal evolution of the loire signature in the upstream part of the basin groundwater contributions are required to explain locally the loire signature the water chemistry in the different zones of the basin shows large variations in major element contents the no3 content in the loire river roughly increases from up to downstream and is mainly controlled by the input from tributaries the highest concentrations are observed in the middle part of the loire basin in close relation with the diffuse agricultural sources in terms of water rock interaction using na as the reference element the loire basin data are scattered between the three main end members representing the major lithologies i e basalts granite gneiss and carbonate strontium isotope ratios measured in water range from 0 70691 to 0 71395 and plotted vs the ca na ratios the 87sr 86sr ratios clearly discriminate the three main lithological endmembers in the middle loire section the loire flow rate increases without significant inputs of surface water previous studies attributed this increase to groundwater inputs the relationship between 87sr 86sr and the cl sr ratios clearly shows the groundwater inputs from the beauce carbonate aquifer along a 90 km river profile between orleans and amboise these conservative tracers can be used to calculate up to 20 groundwater mixing during low flow period

upper mantle structure along a profile from oslo noress to helsinki to leningrad based on explosion seismology abstract waveforms from the noress array were analyzed for 147 industrial explosions during the 1985 to 1988 period along a profile running east from oslo noress to helsinki to leningrad ohl profile the events were 250 to 1300 km from noress and had local magnitude in the range 2 0 to 3 5 event locations and origin times constrained by the university of helsinki9s regional seismic network provide a reliable basis for travel time estimation at noress we also used data recorded by norsar in 1979 for three shots on the fennolora north south long range seismic profile which were near the ohl profile analysis of mantle p wave signals from the explosions showed that first arrivals could be traced continuously to a distance of 750 to 800 km where there is a cutoff and shift of approximately 2 0 to 2 5 sec in the travel time curve and an increase in average apparent velocity interpretation of the observed travel times and waveforms for this profile suggests a low velocity zone from approximately 105 to 135 km depth combined analysis of the seismic data with a bouguer gravity map indicates the presence in the upper mantle of a high velocity high density body of linear extent approximately from 200 to 300 to 500 to 600 km east of the noress array it is postulated that this body may represent the root of an ancient volcanic system in which lighter silicic constituents were depleted from the upper mantle during the eruptive phase

solute sources and chemical weathering in the owens lake watershed eastern california 1 chemical and strontium isotope analyses of solutes in a series of streams representing the bulk of the water reaching the 8500 km2 owens lake watershed provide a unique opportunity to evaluate factors that control stream chemistry on a regional scale the streams drain terrain that is dominated by mesozoic granitoids of the sierra nevada batholith but that also contains irregularly distributed roof pendants of paleozoic metasedimentary sequences mass balance modeling indicates that plagioclase feldspar weathering is the dominant contributor to stream chemistry and that carbonate dissolution is also a significant source of solutes for most streams the calculated ratio of plagioclase to carbonate is highly sensitive to the assumed weathering product of plagioclase kaolinite versus smectite and we suggest that the importance of carbonate could be exaggerated in cases where only the plagioclase to kaolinite reaction is considered strontium isotope 87sr 86sr ratios range from 0 70685 to 0 71958 with a flow weighted mean of 0 70911 to the extent that this value represents the water that would be flowing into owens lake were it not diverted by the los angeles aqueduct system the flow weighted mean 87sr 86sr ratio is consistent with ratios measured in owens lake core carbonates ranging in age up to 25 kyr the overall sr budget of the watershed is determined by the relative contributions of carbonate dissolution and plagioclase feldspar weathering and is dominated by reactions related to pyrite oxidation and hydrothermal fluid input from just two subbasins the impact of these processes needs to be considered when modeling regional and global riverine sr budgets climate related shifts in the relative importance of silicate mineral weathering reactions appear to be only second order effects on a regional scale

large scale erosion rates from in situ produced cosmogenic nuclides in european river sediments abstract we have calculated long term erosion rates of 20 100 mm kyr from quartz contained 10be in the bedload of middle european rivers for catchments ranging from 102 to 105 km2 these rates average over 10 40 kyr and agree broadly with rock uplift incision and exhumation rates historic soil erosion rates and erosion rates calculated from the measured sediment loads of the same rivers moreover our new erosion rate estimates correlate well with lithology and relief however in the regen neckar loire and meuse catchments cosmogenic nuclide derived erosion rates are consistently 1 5 4 times greater than the equivalent rates derived from measured river loads this may be due to the systematic under representation of high magnitude low frequency transport events in the gauging records which cover less than a century alternatively the discrepancy may derive from spatially non uniform erosion and preferential tapping of deeper sections of the irradiation profile a third explanation relates the high cosmogenic nuclide derived erosion rates to inheritance of an elevated pleistocene erosion signal uncertainties associated with the cosmogenic nuclide derived erosion rate estimates are not greater than the potential errors in conventional estimates therefore the cosmogenic nuclide approach is an effective tool for rapid catchment wide assessment of time integrated rates of bedrock weathering and erosion and we anticipate its fruitful application to the quaternary sedimentary record

surface water groundwater interactions in an alluvial plain chemical and isotopic systematics our work on the loire river forms part of a french national research program dedicated to wetlands and aims to better understand the global functioning of the system from the hydrological geochemical ecological and sociological aspects the present study using a coupled hydrological and geochemical stable and sr isotopes approach focuses on the soulangy site with its secondary anastomosing channels just below the confluence of the loire and allier rivers and also on the dorna nt site with two unconnected oxbow lakes 50 km upstream of the confluence the stable isotopes of water 18o 2h show that the alluvial or riverbank aquifer feeds the loire river during the summer but is not recharged by the river during flood periods in the winter the alluvial groundwater thus has a purely local origin from precipitation the major elements reveal an anthropogenic input of cl and more importantly of no3 especially near farms the 87sr 86sr isotopes identify different groundwater layers in the alluvium i e an upper and a lower alluvial aquifer and a perched aquifer at dornant that have relatively complex relationships with the surface water the two main rivers loire and allier present distinct geochemical characteristics reflecting the different lithologies that they drain upstream in addition the secondary channels lying parallel to the loire main stream at the soulangy site give different geochemical signatures which shows that they are not fed by the same overflows of the loire they are more or less well connected to the upper level of the alluvial plain and a longitudinal study of one of these channels has revealed a loire river influence progressively replaced by a water contribution from the upper alluvial aquifer similarly the two oxbow lakes at the dornant site are not supplied by the same water during the summer months a conceptual scheme of the loire hydrosystem based on 18o and 87sr 86sr suggests that the isotopic variations of the loire river can be related to a massif central surface water supply for the loire and allier main streams and to a groundwater supply from the alluvial plains

variations of chemical features in a monsoon glacier watershed southeastern tibet plateau the ph ec electric conductivity 18o and major ions in melt water precipitation runoff and groundwater samples which were collected in baishui basin were analyzed based on chemical analysis the characteristic variations are analyzed in this paper the melt water precipitation runoff and groundwater were ca2 mg2 hco3 type with similar ion compositions but showed different ion concentrations normally the content is high in groundwater and runoff water but low in melt water and precipitation from the upper basin glacier downward there was a general increasing trend for the total ion concentrations in basin hco3 and ca2 accounted for more than 80 of total ions in samples indicating that ions mainly came from limestone and water typical of carbonate solution water water rock interaction is the significant contributor to water geochemistry the concentration of inorganic ion in melt water had an obvious diurnal variation with temperature change the 18o values increases with the altitude decrease the similarity of 18o in runoff and groundwater samples was due to their frequent transformation in karst regions

water exchange mixing and transient storage between a saturated karstic conduit and the surrounding aquifer groundwater flow modeling and inputs from stable water isotopes water exchanges between a karstic conduit and the surrounding aquifer are driven by hydraulic head gradient at the interface between these two domains the case study presented in this paper investigates the impact of the geometry and interface conditions around a conduit on the spatial distribution of these exchanges isotopic 18o and d discharge and water head measurements were conducted at the resurgences of a karst system with a strong allogenic recharge component val d orleans france to estimate the amounts of water exchanged and the mixings between a saturated karstic conduit and the surrounding aquifer the spatio temporal variability of the observed exchanges was explored using a 2d coupled continuum conduit flow model under saturated conditions feflow the inputs from the water heads and stable water isotopes in the groundwater flow model suggest that the amounts of water flowing from the aquifer are significant if the conduit flow discharges are less than the conduit flow capacity this condition creates a spatial distribution of exchanges from upstream where the aquifer feeds the conduit recharge area to downstream where the conduit reaches its maximum discharge capacity and can feed the aquifer discharge area in the intermediate transport zone no exchange between the two domains takes place that brings a new criterion to delineate the vulnerable zones to surface water on average 4 of the water comes from the local recharge 80 is recent river water and 16 is old river water during the november 2008 flood both isotopic signatures and model suggest that exchanges fluctuate around this steady state limited when the river water level increases and intensified when the river water level decreases the existence of old water from the river suggests a transient storage at the aquifer conduit interface that can be considered as an underground hyporheic zone

the origin of faceted garnets in sandstones dissolution or overgrowth faceted garnets from a wide range of geological ages environments and locations have been studied in polished grain mounts by a combination of backscattered electron microscopy and elemental mapping using energy dispersive x ray analysis in all cases the areas apparently showing positive relief on the faceted garnet surfaces are compositionally identical to the adjacent grain cores despite a wide variation in detrital garnet compositions in one case zoning within the grain core can be traced into the faceted areas on the grain surface thus faceted areas must be considered to form part of the original detrital grains together with previously published studies on experimental garnet etching thermodynamic conditions for garnet growth textural relationships between faceted garnets and authigenic and detrital phases and distribution of faceted garnets in the subsurface this paper provides conclusive proof that faceted garnet surfaces form as a result of dissolution not overgrowth

hydrogeochemistry and strontium isotopes in the arno river basin tuscany italy constraints on natural controls by statistical modeling summary in this paper the chemistry of major and trace elements and for the first time strontium isotopic ratios measured in running waters from the arno river basin tuscany central northern italy and thermal springs discharging in the same hydrographic system are presented and discussed classical graphical methods e g mixing diagrams have here been improved to identify in a correct statistical sample space extreme chemical compositions attributable to the action of geochemical processes and or inherited from specific lithologies namely contributions or components 1 2 and 3 to be used in inverse modeling procedures due to the absence of clear end members a linear least squares problem with non negativity constraints and distances as required for compositional data convex linear mixing was solved by considering the contribution of the most discriminant variables given by the 87 sr 86 sr isotopic ratios and the concentration of ca 2 mg 2 sr and rb following such approach it can be assumed p 2 mg 2 hco 3 radiogenic rich 87 sr 86 sr 0 71274 rb sr 0 039 represents a dominant feature at basin scale with a weight ranging from 69 to 100 much lower percentages are related to component 2 represented by a ca 2 mg 2 so 4 2 facies with intermediate 87 sr 86 sr 0 70874 and low rb sr 2 8 10 4 ratios and component 3 identified by ca 2 hco 3 facies with less radiogenic 87 sr 86 sr 0 70827 and low mg 2 ca 2 0 011 ratios these components are mainly dominated by the dissolution of evaporitic rocks and or mixing with thermal waters in the southern part of the arno river basin and by dissolution of the carbonatic fraction kinetically favored with respect to that of the silicatic minerals in the upper reaches of the main course and its tributaries respectively

the structure of the baltic shield region on the basis of dss and earthquake data the lithospheric models obtained for the baltic shield by using deep seismic soundings are discussed and results from different parts of the shield are compared with models achieved by the investigation of surface waves and of p to s converted waves the results are found to agree rather well with each other particularly with regard to the first interface at a depth of 10 15 km and the whole thickness of the crust c 40 km the macroseismic focal depth determinations of regional earthquakes are correlated with lithospheric structure the main maximum in the focal depth distributions of finnish earthquakes occur at a depth of 10 12 km the geographical distribution of the earthquake epicentres suggests several seismo active zones in the northern baltic shield one new finding in this field concerns the lapland zone which runs in a north westerly direction

geochemistry of the upper han river basin china 3 anthropogenic inputs and chemical weathering to the dissolved load abstract the study focuses on the chemical and trace element compositions of the dissolved load in the upper han river the water source area of the middle route of china s south to north water transfer project water samples were collected in the high flow period and analyzed for cations by inductively coupled plasma atomic emission spectrometer and anions by ionic chromatography respectively in order to understand the contributions of anthropogenic activities and rock weathering to river solutes as well as the associated co2 consumption in the carbonate dominated basin the river waters have a mean tz of 2674 eq l ranging from 1034 3 to 4611 6 eq l which is significantly higher than that of the global river waters calcium and hco3 followed by mg2 and so42 dominate the chemical composition of major species in the basin there are three major reservoirs carbonates silicates and agriculture urban effluents contributing to the dissolved load in the river chemical weathering rate is approximately 53 1 t km2 yr with respective carbonate and silicate weathering rates of 47 5 t km2 yr 19 8 mm kyr and 5 6 t km2 yr 2 1 mm kyr the co2 consumption is estimated to be 64 69 109 mol yr and 9 69 109 mol yr by carbonate and silicate weathering respectively the contribution of the anthropogenic inputs to the dissolved load is estimated to be 16 7 demonstrating the strong impacts of human activities on water chemistry

major ion chemistry of the ganga brahmaputra river system weathering processes and fluxes to the bay of bengal the ganga brahmaputra one of the world s largest river systems is first in terms of sediment transport and fourth in terms of water discharge a detailed and systematic study of the major ion chemistry of these rivers and their tributaries as well as the clay mineral composition of the bed sediments has been conducted the chemistry of the highland rivers upper reaches of the ganga the yamuna the brahmaputra the gandak and the ghaghra are all dominated by carbonate weathering ca mg and hco3 account for about 80 of the cations and anions in the lowland rivers the chambal the betwa and the ken hco3 excess over ca mg and a relatively high contribution of na k to the total cations indicate that silicate weathering and or contributions from alkaline saline soils and groundwaters could be important sources of major ions to these waters the chemistry of the ganga and the yamuna in the lower reaches is by and large dictated by the chemistry of their tributaries and their mixing proportions illite is the dominant clay mineral about 80 in the bedload sediments of the highland rivers kaolinite and chlorite together constitute the remaining 20 of the clays in the chambal betwa and ken smectite accounts for about 80 of the clays this difference in the clay mineral composition of the bed sediments is a reflection of the differences in the geology of their drainage basins the highland rivers weather acidic rocks whereas the others flow initially through basic effusives the ganga brahmaputra river system transports about 130 million tons of dissolved salts to the bay of bengal which is nearly 3 of the global river flux to the oceans the chemical denudation rates for the ganga and the brahmaputra basins are about 72 and 105 tons km yr 1 respectively which are factors of 2 to 3 higher than the global average the high denudation rate particularly in the brahmaputra is attributable to high relief and heavy rainfall

the role of supergene sulphuric acid during weathering in small river catchments in low mountain ranges of central europe implications for calculating the atmospheric co2 budget abstract the geochemistry of dissolved and suspended loads in river catchments of two low mountain ranges in central europe allows comparison of pertinent chemical weathering rates distinct differences in lithology i e granites prevailing in the black forest compared to palaeozoic sediments in the rhenish massif provide the possibility to examine the influence of lithology on weathering here we determine the origin of river water using the stable isotope ratio 18oh2o and we quantify the geogenic proportions of sulphate from stable isotope ratios 34sso4 and 18oso4 particularly in catchments with abundant pyrite determination of the geogenic amount of sulphate is important since oxidation of pyrite leads to acidity which increases weathering our results show that spatially averaged silicate weathering rates are higher for the river catchments acher and gutach in the black forest 10 12 t km2 yr compared to the river catchments of the mohne dam and the aabach dam in the rhenish massif 2 6 t km2 yr correspondingly the co2 consumption by silicate weathering in the black forest 334 395 103 mol km2 yr is more than twice as high as in the rhenish massif 28 151 103 mol km2 yr these higher rates for watersheds of the black forest are likely due to steeper slopes leading to higher mechanical erosion with respective higher amounts of fresh unweathered rock particulates and due to the fact that the sediments in the rhenish massif have already passed through at least one erosion cycle carbonate weathering rates vary between 12 and 38 t km2 yr in the catchments of the rhenish massif the contribution of sulphuric acid to the silicate weathering is higher in the catchments of the rhenish massif 9 16 than in the catchments of the black forest 5 7 due to abundant pyrite in the sediments of the rhenish massif three times higher long term erosion rates derived from cosmogenic nuclides compared to short term erosion rates derived from river loads in central europe point to three times higher co2 consumption during the past 103 to 104 years

carbon flux and c s isotopic characteristics of river waters from a karstic and a granitic terrain in the yangtze river system abstract we analyzed dissolved major elements 13 c dic and 34 s so4 in river waters from a karstic and a granitic terrain to examine weathering processes and the influence of basin geology on water quality and associated riverine alkalinity transport results show that waters from the karstic terrain have higher total dissolved solids tds major ion concentrations and 13 c dic values but lower k na and si concentration and 34 s so4 values than that from the granitic terrain the compositions of major ions and isotopes indicate that the solutes of the granitic terrain are controlled by processes of silicate and carbonate dissolution by carbonic acid however carbonate dissolution by both carbonic and sulfuric acid are dominant processes in karstic terrain total erosion rates dissolved inorganic carbon dic flux and co 2 uptake were 28 0 t km 2 yr 1 2 9 10 5 mol km 2 yr 1 and 2 3 10 5 mol km 2 yr 1 for the granitic terrain and 70 2 t km 2 yr 1 11 9 10 5 mol km 2 yr 1 and 6 4 10 5 mol km 2 yr 1 for the karstic terrain respectively these results indicated the karstic area plays an important role in uptake of co 2 and dic flux along the yangzte river basin our results also revealed that co 2 uptake due to carbonate chemical weathering in both karstic and granitic terrain is very high and provide as much or more dic flux than that from silicate chemical weathering

glacial sedimentation in the late precambrian bebedouro formation bahia brazil abstract the possibility that diamictites of the late precambrian bebedouro formation of northern bahia brazil are glacial in origin has been based on the areal extent diversity of the lithology of the stones and the presence of outsize dropstones in rhythmites more detailed studies on the diamictites show that some of the stones are faceted and their shapes are typical of those developed by glacial transport additionally a small abraded pavement is described and garnets found in the matrix of the diamictite have chattermark trails taken in aggregrate these observations suggest a glacial origin for the bebedouro formation in the study area the texture of the diamictites range from stone rich to siltstones containing sporadic stones the stone rich diamictites are commonly found in layers up to a metre in thickness separated by poorly laminated siltstone the formation probably was deposited in a large lake or sea and the layered diamictites are debris flows which were derived from uneven piles of glacial debris deposited on the floor of the lake or sea

strontium isotopes as tracers of groundwater induced floods the somme case study france major ions trace elements and o h and sr isotopes have been determined for surface water and groundwater in the somme catchment northern france the present study using a coupled hydrological and geochemical stable and sr isotopes approach focuses on the interactions between ground and surface water stable water isotopes 18o 2h show that all waters have a purely local origin from precipitation without significant evaporation or water rock interaction as all points plot close to the general meteoric water line water chemistry in the different catchments shows large variations in major element contents plotting na vs cl contents and mg2 no3 k so42 sr2 concentrations reveals a slight variations in groundwater composition b agricultural input into surface waters and c some similarities between ground and surface waters suggesting the former to be responsible for the chemical signature of the dissolved river load strontium isotope ratios measured in groundwater range from 0 70769 to 0 70808 clearly higher than that of chalk matrix water 0 707337 variations of sr isotope signatures in groundwater from the chalk aquifer are significant and help identifying different groundwater bodies the different signatures in groundwater are better explained by matrix heterogeneity which can present lateral facies variations than by a strong anthropogenic influence the sr isotope compositional range in surface waters is very wide varying from 0 70775 to 0 70816 and defining a trend towards a more radiogenic sr isotope signature with high sr contents and high mg sr ratios the relationship between 87sr 86sr and the mg sr ratios allows different end members to be defined the rivers are influenced by anthropogenic disturbance even during flood periods and river water has geochemical characteristics very similar to those of groundwater indicating a strong influence from groundwater feeding the rivers

neutralization of atmospheric acidity by chemical weathering in an alpine drainage basin in the north cascade mountains the most important weathering reaction that neutralizes incoming atmospheric acidity in the south cascade lake basin is weathering of calcite which occurs in trace amounts in veins on joint surfaces and as a subglacial surficial deposit although the basin is underlain by igneous and high grade metamorphic rocks weathering of plagioclase is quantitatively negligible the principal silicate weathering reaction is alteration of biotite to vermiculite these conclusions are based on mass balance calculations involving runoff compositions and on mineralogical observations for predictive modeling of the effects of increased acid deposition it is essential to identify the relevant weathering reactions feldspar weathering is commonly not an important source of solutes in alpine basins underlain by granitic rocks 30 references 2 figures 1 table

water geochemistry of the xijiang basin rivers south china chemical weathering and co2 consumption abstract the xijiang river the mainstream of the zhujiang pearl river which is the second largest river in china in terms of discharge flows through a large carbonate rock region in south china the chemical and sr isotopic compositions of the xijiang waters were determined during the high flow season in order to understand the chemical weathering processes associated co2 consumption and anthropogenic influences within the carbonate dominated basin the major ion compositions of the river waters are characterized by the dominance of ca2 mg2 hco 3 and are significantly rich in so 4 2 the so 4 2 is mainly derived from the oxidation of sulfide minerals and acid precipitation caused by coal combustion chemical and sr isotopic compositions of the river waters indicate that four reservoirs carbonates silicates evaporites and anthropogenic inputs contribute to the total dissolved loads the chemical weathering rates of carbonates and silicates for the xijiang basin are estimated to be approximately 78 5 and 7 45 ton km 2 a 1 respectively the total chemical weathering rate of rocks for the xijiang basin is approximately 86 1 ton km 2 a 1 or 42 mm ka 1 which is much higher than global mean values the budgets of co2 consumption by carbonate and silicate weathering are estimated to be 284 109 and 54 3 109 mol a 1 respectively it would appear that h2so4 is involved as a proton donor in weathering reactions in the xijiang basin calculated results show that the contribution of cations from rock weathering induced by h2so4 accounts for approximately 11 2 results from this study show that the flux of co2 released into the atmosphere is approximately 0 1 106 mol c km 2 a 1 or 0 41 1012 g c a 1 produced by h2so4 induced carbonate weathering in the basin when extrapolated to the entire surface area of carbonate in sw china the flux of co2 released to the atmosphere by h2so4 induced carbonate weathering is about 1 41 1012 g c a 1

chattermarked garnets in pleistocene glacial sediments an examination of the surface textures on detrital garnets shows that conchoidal fractures v shaped etch pits and other marks of unknown origin can be modified by chemical etching to produce features which resemble chattermark trails produced by slip stick motion in order to differentiate false trails from those produced by glacial grinding it is recommended that the altered surfaces of garnets be examined under a scanning electron microscope an analysis of chattermark trails on garnets from glaciogenic deposits from nova scotia denmark and south central ontario shows that there is a wide variation in the percentage of garnets with chattermark trails in different glacial environments however after local anomalies in the percentage of chattermarked garnets are averaged out by recycling and dispersion there is evident a crude correlation between the type of glaciation and the average percentage of chattermarked garnets in glacial deposits

a global geochemical mass budget applied to the congo basin rivers erosion rates and continental crust composition rivers carry the products of continental denudation either in a dissolved form chemical erosion or in a solid form physical erosion we focus in this paper on the relationship between physical erosion and chemical erosion we establish the mass budget of the congo basin rivers using chemical complementarities between river suspended sediments sandy bedload and dissolved load of the congo basin rivers reported in a previous paper dupre et al 1995 a series of equations are presented assuming that the physical and chemical erosion processes are in a steady state during one year the total mass of river borne material dissolved and particulate transported in the river over a given period of time should balance the mass of upper continental crust eroded during this time we show that the local continental crust on each drainage basin can be estimated and solve our steady state weathering model using an inversion procedure the very good agreement between modelled and measured values of the river suspended sediment concentrations validates the steady state hypothesis in this wet tropical area consequently in this area the sediment yield provide a good estimate of the rates of mechanical denudation this result also validates the calculation of the chemical and isotopic composition of the local continental upper crust using the bulk river load erosion rates for the silicate upper crust and thus independent of the lithological variability silicates evaporites and carbonates of the drainage basins are calculated mechanical erosion rates and chemical erosion rates for the congo basin at brazzaville are 8 t km2 y and 5 t km2 y the corresponding consumption of atmospheric co2 by weathering process is estimated to 51 103 mol km2 an these weathering and consumption rates are low in spite of the severity of the weathering conditions of the high soil temperature and of the intensity of precipitations these conclusions indicate the limiting influence the dynamic equilibrium of soils for silicate weathering finally by estimating the local continental crust chemical composition before the onset of erosion processes especially for the most soluble elements we can test the model of taylor and mclennan

changes in chemical and 87sr 86sr signature distribution patterns of suspended matter and bed sediments in the upper loire river basin france abstract the mineralogy of the suspended particulate matter spm transported by the upper loire river consists mainly of quartz and k feldspar during periods of high river flow with an increase in calcite concentration during periods of low flow concurrently large fluctuations are observed in the levels of cao and fe2o3 the main oxides present in the spm along with sio2 the analysed trace elements also fluctuate significantly the bed sediments bs have a similar oxide content to the spm but lower zn and pb levels and higher zr levels fluctuations in the chemical element concentrations with river discharge are related to fluctuation in the mineral assemblages present in the spm thus k ti and rb levels increase with increasing in k feldspar abundance during high flow and ca and sr levels decrease with increasing discharge due to a decrease in calcite abundance these mineralogical and chemical variations relate to different sources of sediments under different flow conditions sources that can be distinguished by sr isotopic study the sr isotopic composition fluctuates according to the rate of river discharge i e the 87 sr 86 sr ratio increases with increasing discharge and reaches a maximum with peak flow and vice versa the 87 sr 86 sr ratio also increases with the combined increase in k feldspar abundance and decrease in calcite abundance these similarities suggest the existence of at least two particulate matter reservoirs one with detrital silicates and the other with carbonates finally the relationship between the 87 sr 86 sr ratios in the suspended and dissolved loads suggests the coexistence of authigenic calcite in the carbonate reservoir the spm flow is related to a specific mechanical erosion rate over the whole loire watershed ranging from 9 to 23 t km 2 yr 1 during the survey at orleans the spm flow of the loire river was 37 104 t yr 1 providing an estimate of the specific erosion rate of around 9 8 t km 2 yr 1 from the shift in the spm flux between the sampling point and the mouth of the loire river and the divergence in the mean annual discharge a calculation was made of the input of solid matter by the tributaries and by supplementary erosion processes along the river

chattermarked garnets found in soil profiles and beach environments an examination of the surface features on garnets from soil profiles developed on glacial sediments shows that the percentage of chattermarked garnets either remains unchanged throughout the profile or may decrease in the a and upper part of the b horizons it is possible that a decrease in chattermarked garnets up profile may result from dissolution of the garnets by humic and carbonic acids most etch features on garnets in soil profiles are inherited but fresh pits are found in the a and b horizon of a sangamon soil profile an analysis of the surface features of garnets from 17 beach environments shows that the degree of rounding varies markedly but on average they are better rounded than those found in glacial deposits less than 1 of the garnets in beach deposits have chattermark trails the results of these studies on garnets found in soil and beach environments confirm the usefulness of chattermarked garnets to authenticate and determine the nature of ancient glaciations

seasonally chemical weathering and co2 consumption flux of lake qinghai river system in the northeastern tibetan plateau the major cation and anion compositions of waters from the lake qinghai river system lqrs in the northeastern tibetan plateau were measured the waters were collected seasonally from five main rivers during pre monsoon late may monsoon late july and post monsoon middle october the lqrs waters are all very alkaline and have high concentrations of tds total dissolved solids compared to rivers draining the himalayas and the southeastern tibetan plateau seasonal variations in the water chemistry show that except the daotang river the tds concentration is high in october and low in july in the lqrs waters the forward models were used to quantify the input of three main rivers buha river shaliu river and hargai river from rain halite carbonates and silicates the results suggest that 1 atmospheric input is the first important source for the waters of the buha river and the shaliu river contributing 36 57 of the total dissolved cations 2 carbonate weathering input and atmospheric input have equal contribution to the hargai river water 3 carbonate weathering has higher contribution to these rivers than silicate weathering and 4 halite is also important source for the buha river the daotang river water is dominated by halite input owing to its underlying old lacustrine sediments the water compositions of the heima river are controlled by carbonate weathering and rainfall input in monsoon season and groundwater input may be important in pre monsoon and post monsoon seasons after being corrected the atmospheric input average co2 drawdown via silicate weathering in the lqrs is 35 103 mol km2 per year with highest in monsoon season lower than himalayas and periphery of tibetan plateau rivers but higher than some rivers draining shields

tracing water cycle in regulated basin using stable δ18o δ2h isotopes the ebro river basin spain abstract variations in the stable isotope compositions of o and h in a catchment s water balance are mainly caused by natural variations in the isotopic composition of rainfall through mixing with pre existing waters and evaporation stable isotopes were analysed in surface waters along the main course of the ebro river spain in its main tributaries and in some groundwaters as part of a year long monthly survey at the outlet meteoric input data over the basin from five iaea gnip stations surrounding the ebro catchment showed that the mean weighted 18 o 2 h rain input showing enriched values for four stations and a depleted value for the fifth most surface and ground waters collected in the ebro catchment plot close to the global and local meteoric water lines reflecting a meteoric origin and a lack of significant evaporation or oxygen isotope exchanges between water and the rock matrix although the main tributaries show large variations of 18 o and 2 h signatures respectively 5 0 to 9 6 and 38 5 to 63 6 only the guadalope river shows an evaporated signal all tributaries have more depleted 18 o and 2 h values than the mean rainwater 18 o and 2 h signal for the ebro catchment given by local rain monitoring stations the depleted values in the ebro tributaries originate from runoff from the pyrenees whereas normal mediterranean rains yield mostly enriched values the ebro river itself shows 18 o and 2 h values that fall between those of its tributaries and no variation is related to the location along the river course the river water at the outlet amposta display a range of 18 o 2 h values from respectively 7 2 to 8 4 and 47 5 to 53 9 though with a few enriched values there is no link between river discharge and cl content temporal 18 o 2 h variations at the ebro outlet reflect input of enriched water from mediterranean rains and of depleted waters from pyrenean runoff the geochemical signal at the ebro basin outlet was deconvolved through a conceptual scheme of the ebro hydro system highlighting the major role played by dam impoundments not only on water quantity but also on its quality

natural weathering mechanisms of almandine garnet the weathering of almandine garnet in the oxidized vadose zone of saprolite near otto north carolina begins at grain boundaries and along fractures traversing the garnet grains radially oriented fibrous intergrowths of gibbsite and goethite form layers of uniform thickness which grow by centripetal replacement as weathering proceeds the contact between the garnet surface and the layer of weathering products is sharp and smooth and garnet corners are rounded large well defined etch pits are absent on the underlying garnet surface these observations suggest that diffusion transport of reactants and or products through the gibbsite goethite layer is the rate limiting step in the weathering of almandine garnet in the oxidizing environment of the saprolite in soils overlying the saprolite garnet surfaces are directly exposed to weathering solutions without the intervening surface layer such unprotected grains in soils and stream sediments exhibit numerous large well developed etch pits surface reaction control rather than transport control prevails during weathering of almandine garnet in the absence of protective surface layers of weathering products biochemical or biological processes in the soil apparently prevent the gibbsite goethite layer from forming or persisting soil solutions can therefore react directly with the garnet surface rather than requiring reactants or products to diffuse through the gibbsite goethite coating as in the saprolite the mechanism and rate limiting step of almandine garnet weathering is apparently strongly dependent on the chemical environment in which weathering occurs

water geochemistry of rivers draining karst dominated regions guangxi province south china implications for chemical weathering and role of sulfuric acid abstract guangxi province located in south china is a typical karst region affected by acid depositions for a couple of decades water samples from the major river basins in this region were collected and the chemical compositions were measured with a main purpose to quantify chemical weathering rates and associated co2 budget the average total dissolved solids tds of the river waters 232 mg l are comparable with other karstic rivers the major ion compositions of the river waters are characterized by the dominance of ca2 mg2 hco3 and are significantly rich in so42 the chemical compositions of the river waters indicate that four major reservoirs atmospheric anthropogenic carbonate and silicate inputs contribute to the dissolved loads the carbonate chemical weathering rates range from 61 4 t km2 yr for the qingshuihe river basin to 93 3 t km2 yr for the zuojiang river basin the silicate chemical weathering rates range from 2 9 t km2 yr for the qingshuihe river basin to 7 9 t km2 yr for the liujiang river basin the co2 consumption rates by carbonate weathering range from 559 103 mol km2 yr for the qingshuihe river basin to 817 103 mol km2 yr for the zuojiang river basin the co2 consumption rates by silicate weathering range from 19 103 mol km2 yr for the zuojiang river basin to 85 103 mol km2 yr for the liujiang river basin sulfuric acid is involved as a proton donor in weathering reactions and about 9 15 of the chemical weathering rates of the river basins are sulfuric acid induced the co2 consumption rates are only 85 91 of the value when assuming carbonic acid provides all the protons in the weathering reactions the co2 released from sulfuric acid induced carbonate weathering would exceed the co2 consumed by silicate weathering making the river basins in guangxi net co2 sources on geological timescales the total net co2 releasing flux is approximately 15 7 109 mol yr 0 19 1012 gc yr this result quantitatively highlights the fact that co2 budget by chemical weathering will be largely modified by sulfuric acid especially in seriously acid deposition affected region

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

experimental formation and significance of etch patterns on detrital garnets the patterns found on the surfaces of etched detrilal garnets are formed by facets that resemble a series of elongated overlapping sharp edged rectangular or rhombohedral building blocks mammilla

origin of groundwater salinity current seawater vs saline deep water in a coastal karst aquifer based on sr and cl isotopes case study of the la clape massif southern france origin of groundwater salinity current seawater vs saline deep water in a coastal karst aquifer based on sr and cl isotopes case study of the la clape massif southern france a b s t r a c t in this study a typical coastal karst aquifer developed in lower cretaceous limestones on the western med iterranean seashore la clape massif southern france was investigated a combination of geochemical and isotopic approaches was used to investigate the origin of salinity in the aquifer water samples were collected between 2009 and 2011 three groundwater groups a b and c were identified based on the hydrogeological setting and on the cl a concentrations average and maximum cl a concentrations in the recharge waters were calculated cl ref and cl ref max to be 0 51 and 2 85 mmol l respectively group a includes spring waters with cl a concentrations that are within the same order of magnitude as the cl ref concentration group b includes groundwater with cl a concentrations that range between the cl ref and cl ref max concentrations group c includes brackish groundwater with cl a concentrations that are significantly greater than the cl ref max concentration overall the chemistry of the la clape groundwater evolves from dominantly ca hco 3 to nacl type on binary diagrams of the major ions vs cl most of the la clape waters plot along mixing lines the mixing end members include spring waters and a saline component current seawater or fossil saline water based on the br cl molar ratio the hypothesis of halite dissolution from triassic evaporites is rejected to explain the origin of salinity in the brackish groundwater groundwaters display 87 sr 86 sr ratios intermediate between those of the limestone aquifer matrix and current mediterranean seawater on a sr mixing diagram most of the la clape waters plot on a mixing line the end members include the la clape spring waters and saline waters which are similar to the deep geo thermal waters that were identified at the nearby balaruc site the 36 cl cl ratios of a few groundwater samples from group c are in agreement with the mixing hypothesis of local recharge water with deep saline water at secular equilibrium within a carbonate matrix finally phreeqc modelling was run based on cal cite dissolution in an open system prior to mixing with the balaruc type saline waters modelled data are consistent with the observed data that were obtained from the group c groundwater based on several trac ers i e concentrations and isotopic compositions of cl and sr calculated ratios of deep saline water in the mixture are coherent and range from 3 to 16 and 0 to 3 for groundwater of groups c and b respectively with regard to the la clape karst aquifer the extension of a lithospheric fault in the study area may favour the rise of deep saline water such rises occur at the nearby geothermal balaruc site along another lithospheric fault at the regional scale several coastal karst aquifers are located along the gulf of lion and occur in mezosoic limestones of similar ages the 87 sr 86 sr ratios of these aquifers tend toward values of 0 708557 which suggests a general mixing process of shallow karst waters with deep saline fossil waters the occurrence of these fossil saline waters may be related to the introduction of seawater during and after the flandrian transgression when the highly karstified massifs invaded by seawater formed islands and peninsulas along the mediterranean coast

behaviour of li isotopes during regolith formation on granite massif central france controls on the dissolved load in water saprolite soil and sediment abstract lithium li contents and isotopes were studied in all environments of a small river catchment draining granite in the margeride mountains of the french massif central this covered surface waters primary and accessory minerals of the granites the whole rock and soil and sediment samples developed in the catchment completed with regional data for mineral waters and rainwater the integrated investigation aimed at evaluating the potential of li isotopes as effective tracers of water rock interaction processes within a granitic environment the 7li values and li concentrations were measured on sediment and soil samples following standard acid dissolution procedures and chemical purification of li using the cationic exchange resin protocol in a clean lab lithium isotope compositions were measured with a neptune mc icp ms and li concentrations by icp ms the samples represented different stages of granite weathering including fresh granite weathered rock surface saprolite and sediments in riverbanks and fields bordering the streams the extent of li mobility during granite weathering was first evaluated through determining the percentage change relative to ti with a range from 31 to 66 in the collected samples the weathered rock was depleted by 47 for li with negative 7li values ranging from 1 9 to 3 4 soil to riverbank sediment samples were characterized by less negative 7li values indicating that li is enriched in soil with fractionation of li isotopes and changes of the mineral abundance in the samples to complement this first view we i modelled the theoretical li isotope signature of water interacting with granite using a weathering model based on dissolution ii applied an atmospheric input correction to surface waters iii applied a raleigh equation for modelling the li isotope fractionation when compared with corrected surface water and mineral water and iv compared li isotopes with sr isotope data in a larger weathering framework

strontium isotopic composition of the po river dissolved load insights into rock weathering in northern italy abstract strontium isotopic composition 87sr 86sr of river water provides insight on the nature of rocks involved in the weathering processes and important constraints for reconstructing silicate versus carbonate weathering in large scale basins new data presented in the context of a geochemical map of the po river basin highlight that the po river water evolves from the upper part of the catchment where 87sr 86sr approaching 0 7097 relates to the weathering of igneous and metamorphic silicate rocks to the middle part where less radiogenic compositions 87sr 86sr 0 7089 are driven by the confluence of the tributaries draining mesozoic carbonate rocks of the south alpine domain and from inflow of apennine streams characterized by less radiogenic sr signatures due to weathering of marly sediments and mafic magmatic rocks down flow the sr isotopic compositions of po river water rises at 0 7091 either by the confluence of the last apennine tributary panaro 87sr 86sr 0 7095 and or by the possible contribution from hyporheic exchanges po river isotopic signatures reveal slightly more radiogenic 87sr 86sr in comparison to other important alpine river systems e g danube rhine and rhone likely suggesting that silicate rocks are comparatively contributing more weathering byproducts in the po basin

examining suspended sediment sources and dynamics during flood events in a drained catchment using radiogenic strontium isotope ratios 87sr 86sr soil erosion is recognized as one of the main processes of land degradation in agricultural areas high suspended sediment loads often generated from eroding agricultural landscapes are known to degrade downstream environments accordingly there is a need to identify suspended sediment sources and to investigate their dynamics here soil and sediment strontium isotopic ratios were used to examine suspended sediment sources and dynamics in a lowland drained catchment in france suspended sediment n 14 was collected in stream and at tile drain n 4 outlets during three flood events between december 2013 and february 2014 potential source soils n 28 representative of the carbonate and silicate substrates found in the catchment were sampled and analyzed strontium isotopic ratios 87sr 86sr were measured in different particle size fractions 2 m 63 m and 2 mm soil 87sr 86sr ratios significantly discriminated between source samples classified as carbonate 0 712625 to 0 717815 and silicate 0 719287 to 0 724631 soils 87sr 86sr ratios measured in suspended sediment 0 713660 to 0 720571 reflect variations in source contributions during different hydrological conditions the 87sr 86sr ratios varied in the different fractions of soil samples i e 2 m 63 m and 2 mm and in suspended sediment samples suspended sediment was interpreted as a mixture of two end members with the dominant contribution of the 2 m fraction of soil samples occurring during small scale flood events and the 2 mm fraction during more intense flood events modelling results indicate that carbonate source soil contributions are variable with their highest contributions occurring during the two first flood events compared to the last flood event the results also show that the tile drainage system enhances the connectivity between cultivated hillslopes and the river network providing a preferential pathway for fine 2 m particles this study demonstrates the potential of using strontium isotopic ratios to examine the variations of suspended sediment sources in drained catchments with contrasting carbonate and silicate sources more importantly the results highlight the need to improve the management of sediment exported from tile drains in similar agricultural environments as they were demonstrated to transfer very fine material to the riverine environment

formation waters from mississippian pennsylvanian reservoirs illinois basin usa chemical and isotopic constraints on evolution and migration we have analyzed a suite of seventy four formation water samples from mississippian and pennsylvanian carbonate and siliciclastic strata in the illinois basin for major minor and trace element concentrations and for strontium isotopic composition a subset of these samples was also analyzed for boron isotopic composition data are used to interpret origin of salinity and chemical and sr isotopic evolution of the brines and in comparison with a similar data set from an earlier study of basin formation waters from silurian devonian reservoirs systematics of cl br na show that present mississippian pennsylvanian brine salinity can be explained by a combination of subaerial seawater evaporation short of halite saturation and subsurface dissolution of halite from an evaporite zone in the middle mississippian st louis limestone along with extensive dilution by mixing with meteoric waters additional diagenetic modifications in the subsurface interpreted from cation br ratios include k depletion through interaction with clay minerals ca enrichment and mg depletion by dolomitization and sr enrichment through caco3 recrystallization and dolomitization ste genevieve limestone middle mississippian formation waters show 87sr86sr ratios in the range 0 70782 0 70900 whereas waters from the siliciclastic reservoirs are in the range 0 70900 0 71052 inverse correlations between 87sr86sr and b li and mg concentrations suggest that the brines acquired radiogenic 87sr through interaction with siliciclastic minerals completely unsystematic relations between 87sr86sr and 1 sr are observed sr concentrations in ste genevieve and aux vases middle mississippian waters appear to be buffered by equilibrium with respect to srso4 although there are many similarities in their origin and evolution these formation waters are distinguished from silurian devonian brines in the basin by elevated clbr and nabr ratios and by unsystematic sr isotope relationships thus waters from these two major segments of the illinois basin stratigraphic column form distinct geochemical regimes which are separated by the new albany shale group devonian mississippian regional aquitard geochemical evolution appears to have been influenced significantly by paleozoic and mesozoic hydrologic flow systems in the basin

chemical weathering under mid to cool temperate and monsoon controlled climate a study on water geochemistry of the songhuajiang river system northeast china abstract for the first time the river water geochemistry of the songhuajiang basin the third largest river system in china has been studied in order to understand chemical weathering and associated co2 consumption rate in a mid to cool temperate and monsoon controlled climatic zone the major ion compositions of the river waters are characterized by the dominance of ca2 and hco 3 accounting for 46 and 74 of major cations and anions respectively the average total dissolved solids tds 116 mg l 1 and total cation concentration tz 1388 eq l 1 of the river waters are similar to those of global major rivers the chemical weathering rates of carbonate silicate and evaporites in the whole songhuajiang basin are estimated to be approximately 5 15 2 23 and 0 40 t km 2 a 1 respectively the total rock weathering rate for the whole songhuajiang basin is approximately 7 78 t km 2 a 1 which is at the lower end of the spectrum for global major rivers and is comparable with that of the amur and the congo zaire river the estimated co2 consumption rates for the whole songhuajiang basin are 53 4 103 mol km 2 a 1 and 66 6 103 mol km 2 a 1 by carbonate and silicate weathering respectively as a sub basin the 2nd songhuajiang has the highest 18 9 t km 2 a 1 while the nenjiang river basin has the lowest total rock weathering rate 5 03 t km 2 a 1 which indicates important controls of regional climate and lithology compared to the large rivers of china total rock weathering rates increase from north to south supporting the idea that the climate acts as major control on global chemical weathering the co2 consumption rate by silicate weathering within the whole songhuajiang river basin though under mid to cool temperate climate is in the same order of magnitude as that of huanghe 82 4 103 mol km 2 a 1 and is not much lower than that of changjiang 112 103 mol km 2 a 1 which suggests that the role of songhuajiang river weathering in long term climate change cannot be neglected compared to those of the large rivers of china

nature and classification of waterlain glaciogenic sediments exemplified by pleistocene late paleozoic and late precambrian deposits this study of waterlain glaciogenic sediments is designed to present both a review and new information on glaciogenic subaquatic deposits of differing age in a number of localities in north and south america and south africa the late paleozoic glaciogenic deposits of the parana basin in brazil and the karoo basin of south africa are singled out for special attention as they show a reasonably complete lateral sequence of terrestrial to off shore glaciogenic sedimentation although the environment of subaquatic glaciogenic sedimentation varies from one area to the next certain common elements are found which can be used to develop a generalized model for both glaciomarine and glaciolacustrine sedimentation for descriptive purposes the model is divided into two broad categories a shelf facies and a basinal facies the shelf facies is marked by massive diamicton ite which may be 200 m or more in thickness and which is frequently overlain by a complex of clastic sediments consisting primarily of gravity and fluid flows the basinal facies is marked by products of subaquatic slumps and more distal turbidites and glaciomarine sediments new terminology is introduced the massive diamicton ite which is diagnostic of the shelf facies probably represents deposition from the base of active ice in a subaquatic environment and is termed undermelt diamicton ite the gravity and fluid flows which are usually found overlying undermelt diamicton ite and in the basinal facies are subdivided into six categories glaciogenic subaquatic outwash glaciogenic suspension flow glaciogenic chaotic debris flow glaciogenic subaquatic debris flow glaciogenic slurry flow and glaciogenic turbidity flow the relative abundance of undermelt diamicton ite and the various types of gravity and fluid flows can be used to define inner shelf outer shelf inner basin and outer basin facies of glaciomarine sedimentation

long term fluxes of dissolved and suspended matter in the ebro river basin spain summary the aim of this study was to evaluate over a long time period the export fluxes for dissolved and solid matter loads on the catchment scale of the ebro river basin in spain data are compiled from the databank of the confederacion hidrografica del ebro che the spatial and temporal distribution of physical and chemical parameters suspended particulate matter spm and major elements were investigated in the ebro basin upstream in mendavia and downstream in tortosa between 1981 and 2004 using the historical databank the mean interannual dissolved fluxes were estimated to be 1 6 106 t year 1 at mendavia and 5 9 106 t year 1 at tortosa respectively leading to evaluated specific export rates close to 93 t km 2 year 1 at mendavia and 69 t km 2 year 1 at tortosa respectively the spm flow related to the specific mechanical erosion rate over the whole basin was around 1 0 105 t year 1 providing an estimate of the specific export rates of around 5 1 t km 2 year 1 at mendavia and 1 2 t km 2 year 1 at tortosa thus highlighting the control of solid transport by the numerous dams within the ebro river basin calculations were also carried out for the respective contribution of carbonate and evaporite gypsum with respect to the total dissolved solids tds it appears that the tds over the whole catchment scale is mostly controlled by so4 na and ca concentrations reflecting the preferential contribution of both evaporite and carbonate dissolution during chemical weathering within the ebro river basin

faceted garnets from sandstones of the munising formation cambrian northern michigan petrographic evidence for their origin by intrastratal dissolution imbricate wedge marks facets on garnets in sandstones of the cambrian munising formation of northern michigan are associated with mouldic secondary porosity developed at the expense of garnet mouldic pores surrounding faceted garnets indicate that garnets in these sandstones have been affected by intrastratal dissolution retreat of the mineral surface from its original boundaries rather than by grain enlargement which would be expected if garnet overgrowths had formed the association of garnet facets with textural evidence of garnet dissolution proves that garnet facets form by intrastratal dissolution these results confirm similar findings in other recent studies and extend the geographic and stratigraphic range of proven occurrences of facet formation by intrastratal dissolution

glacimarine processes and inductive lithofacies modelling of ice shelf and tidewater glacier sediments based on quaternary examples abstract three variables control the type of glacial debris source and where and when debris is introduced to an ocean 1 type of glacial ice source ice sheet or valley glacier 2 condition of a grounded glacier melting freezing or frozen base and cold or warm internal ice and 3 type of glacier front ice shelf or tidewater using these variables in different combinations eight glacimarine regimes are postulated to exist by integrating information from holocene sediment and pleistocene glacimarine sequences with the eight inductive regimes lithofacies relationships are predicted and modelled the models show a complexity of glacimarine lithofacies the importance of recognizing this complexity lies in realistic interpretations of ancient sequences ice shelf sediment may be limited in the geologic record because of tectonic and climatic constraints required for ice shelf formation alternatively in some tidewater glacier regimes larger volumes of glacimarine sediment are produced than in ice shelf regimes ice proximal sediment is distinctive especially near subglacial meltwater stream effluxes ice shelves and tidewater glaciers may produce similar ice proximal lithofacies e g morainal bank associations and laminites in certain regimes however details of lithofacies may aid in distinguishing ice shelf from tidewater regimes ice shelf and tidewater iceberg zone sediment can be distinguished from each other if basal and high level englacial debris can be distinguished ice shelf zone sediment out from the grounding line has a basal debris source high level englacial debris is deposited in more distal ice shelf zones resulting in sediment by pass in corresponding positions of a tidewater glacier regime iceberg rafted debris comprises mixed basal and high level englacial debris deeper water zones receive large volumes of sediment when a melting freezing base grounding line is at the edge of a continental shelf when the grounding line retreats sediment supply may be drastically reduced because of a back sloping continental shelf and trapping by morainal banks cool water bioclastic carbonates may accumulate once a grounding line has retreated although ice shelf iceberg zones are more extensive than those in tidewater regimes ice shelf icebergs have low debris content and resulting ice rafted debris may be scarce the smallest volume of sediment is produced by a frozen base ice sheet ending as a tidewater front and the largest volume by a melting freezing base valley tidewater glacier glacimarine sediment has a relatively high preservation potential near continental interiors or margins however at continental margins mass flow olistostrome and tectonic melange deposits may be preserved with glacimarine diamictites these deposits may be difficult to distinguish from each other especially if metamorphosed such as at a convergent margin the models presented do not fully represent the glacimarine environment because many other variables are omitted however the principal concepts of generating glacimarine lithofacies associations are considered continued research will verify if each regime exists and will provide data on those regimes that exist today to compare and modify these models

riverine hydrochemistry and co2 consumption in the tropic monsoon region a case study in a granite hosted basin hainan island china to evaluate the carbon sink capacity caused by rock chemical weathering processes and its controlling factors in the tropical monsoon region the hydrochemistry of the granite hosted changhuajiang river chjr basin in hainan island china were systematically investigated by collecting water samples from the river mouth to headwater in the dry season and the wet season respectively the results show that na ca2 and hco3 are dominant in the chemical runoff of the chjr the spatial and temporal variations of major ions imply the influence of the multi sources the concentrations of ca2 mg2 hco3 and dsi mainly sourcing from rock silicates and carbonates weathering are lower in the wet season than those in the dry season however the concentrations of k cl so4 2 and no3 mainly sourcing from the atmospheric precipitation and human activities are significantly controlled by the monsoon rainfall and hydrological stage in the chjr basin the contributions of the silicates chemical weathering human activities atmospheric input evaporites dissolution and carbonates chemical weathering to the chemical runoff are 82 62 9 05 5 24 2 05 and 1 05 in the chjr respectively the chemical weathering rates of silicates carbonates and evaporites are 16 25 0 40 and 0 62 t km 2 year 1 respectively chemical weathering rates in global granite hosted basins significantly correlate with temperatures p 10 c on a regional scale we find that the chemical weathering rates in the southern china appear a weak positive correlation with normalized differential vegetation indexes ndvi which need to be confirmed by enough data the flux of atmospheric co2 consumption from rock weathering in the chjr basin is 2 71 105 mol km 2 year 1 by the discharge water of 2014 with being close to that 2 9 105 mol km 2 year 1 in the other tropical basins and far from that 5 06 105 mol km 2 year 1 calculated by the averaged discharge water of over years in the chjr the silicates weathering intensity lies at the moderate phase implying that the weathering processes are still developing in global tropical granite basins hence how the atmospheric co2 consumption from rock weathering will change with increasing the atmospheric co2 level and dam construction altering water cycle in the tropical monsoon area is expected to be deserved

major and trace element partition and fluxes in the rhone river dissolved and particulate major and trace element concentrations and suspended particulate contents were determined during three years on the lower rhone river france from subsurface water samples collected about twice a month and more regularly during flood events dissolved elements can be grouped into two sets showing similar relationship between concentration and water discharge related to dilution process and to local and diffuse inputs of dissolved elements in the rhone basin the variation of no 3 na and cl na ratios and the absence of correlation between no 3 and the enrichment in cl show that rhone river is not highly affected by fertilizer applications compared to other large french rivers seine and loire rivers in particulate phase ca sr u pb bi cd sb and zn displayed high enrichment factors over shale composition lead bi cd and zn enrichment could be related to the anthropogenic inputs while ca sr and u enrichment was explained by lithological composition of the rhone basin dominated by carbonate rocks distribution coefficients of elements kd are relatively stable with however some variations with increasing spm concentrations these variations were attributed to local and diffuse inputs and to a higher contribution of carbonate bedrock in the rhone basin during flood events dissolved and particulate major and trace elements and suspended particulate matter spm fluxes of the rhone river to the mediterranean sea were estimated for the period 2001 2003 spm and particulate element fluxes were highly dependent on flood events 69 to 91 of the annual fluxes were exported in less than 12 of the time rhone river inputs were the principal source of particulate elements except for cd and zn in the northwestern mediterranean sea while the major part of dissolved elements were carried out by atmospheric inputs except dissolved as for which rhone river contributed to more than 50 of the input to the marine system

evidence for slowly changing 87sr86sr in runoff from freshwater limestones of southern france abstract 87 sr 86 sr ratios have been determined in modern rivers and freshwater limestones dating from 65 ma to the present over an area extending from the pyrenees to the massif central southern france about 40 ma ago the alpine mountain range of the pyrenees was strongly uplifted by the alpine orogenic activity and its pre hercynian basement dominated by schists gneisses and granites was rapidly exposed from beneath its blanket of mesozoic marine limestones meanwhile the 87 sr 86 sr ratio of the rivers has remained remarkably constant in both space with the exception of the very few northernmost samples and time in this area extreme variations through the orogenic period are small with 87 sr 86 sr lying between 0 7073 and 0 7084 at 55 65 ma and 0 7077 0 7096 for the last 30 ma river sr is controlled by a nearly binary mixing of silicate 3 4 and 1 4 end members with negligible influence of evaporites it is inferred that the silicate sediment contribution ratio of the world average rivers to seawater sr changes at a very slow rate even taking major basaltic events into account does not alter this conclusion as their contribution to the river sr is very subordinated to other components it is inferred that the seawater 87 sr 86 sr secular main trend over the phanerozoic is controlled by hydrothermal alteration of oceanic basalts and slow variation of the limestone silicate contribution ratio to the riverine sr oceanic events changes in organic productivity and carbonate compensation depth ccd may produce intense short term variations but recovery of steady state seawater 87 sr 86 sr is delayed by 40 80 ma through diagenetic sr remobilization in carbonate sediments

the fluvial geochemistry and denudation rate of the guayana shield in venezuela colombia and brazil abstract the guayana shield is composed of early to mid precambrian igneous and metamorphic basement rocks with a quartzitic platform cover the complete absence of limestones and evaporites allows a clear chemical expression in the stream data of the primary weathering of the basement in a humid tropical environment total erosion rates are extremely slow 10 m m y with equal contributions from the dissolved and suspended loads however the former is largely silica with ratios of si to total cation equivalents si tz ranging to in excess of three weathering is complete to kaolinite and gibbsite i e the environment is one of active laterisation with a penetration rate of the weathering front into the fresh substrate about twice the denudation rate in basins of relatively homogeneous lithology rb sr isochrons constructed from the river data agree with the whole rock ages from the drainages thus all the common refractory rb containing minerals k feldspar mica are completely dissolved the thick lateritic regolith that is accumulating as a result of this intense weathering is a common relict feature on other southern hemisphere shields in the absence of active tectonics or greatly accelerated mechanical erosion the weathering rates of these basement rocks must be quite insensitive to environmental change

chattermark trails surface features on detrital quartz grains indicative of a tropical climate abstract with respect to weathering erosional processes and sediment transport quartz is one of the most stable minerals and makes up to 98 of the mineral volume of siliciclastic sands pettijohn et al 1987 although a major component in a wide variety of rocks quartz has almost no characteristic properties that allow determining parent rock types quartz does not contain characteristic cleavage planes and quartz grains react to impact or collision with other sediment particles by producing conchoidal fractures very similar to those observed for broken glass for sedimentologists physical geographers and soil scientists detrital quartz grains are poor in characteristic features except for a suite of surface features that may be indicative of various transport environments or even climate related alterations one of these surface features are chattermark trails chattermark trails are a series of linearly arranged rune like grooves on surfaces of minerals grains such as quartz and garnet lacking any type of cleavage these trails have been described from many unconsolidated sediments and are attributed mostly to glacial sediments laboratory experiments on polished quartz beads reveal that chattermark trails are not primary surface features but become visible after etching by dilute hydrofluoric acid comparison of the etched and non etched surface of the same quartz bead reveals that mechanically produced invisible cracks related to blunt collisions with other polished quartz beads became visible only after chemical etching chattermark trails on detrital quartz grains are the product of two processes the dynamic one is an invisible transport related blunt collision followed by a second stationary process which enables quartz dissolution to make the chattermarks visible in the broad field of laterite research it is well accepted that quartz dissolution in surface or near surface deposits is restricted to stationary chemical weathering in a wet tropical or at least subtropical climate drawing on this information chattermark trails are no longer considered a product of a specific sedimentary environment but reveal a distinct history of the quartz grain they are formed by blunt collisions in a sediment transport stage before experiencing some dissolution during a depositional stage in a tropical climate grains can be remobilized in an active sediment transport system collectively the results reveal that chattermark trails on quartz grains provide unique insights into the transport and climate history of sediments

geochemistry of trace metals from chinese river estuary systems an overview abstract based on the data from extensive estuarine studies over 10 years 1983 93 the present work provides an overview of the geochemical features of large chinese river estuary systems elevated concentrations of major elements are observed in chinese rivers from north to south which is attributed to intense weathering and erosion over the drainage basins trace metal levels in chinese rivers are relatively low and similar to those from large and less disturbed world aquatic systems e g amazon and orinoco in the estuaries particulate elements show stable distributions in the mixing zone especially when absolute concentrations are normalized to aluminium and or scandium dissolved trace metals may have either conservative and or active non conservative distributions or both in chinese estuaries wherever non conservative distributions are observed trace elements may be remobilized and or scavenged from solution depending upon river discharge sedimentary dynamics and element biological uptake and regeneration of trace metals becomes more important in high salinity areas further offshore the riverine effluent plumes than inside correlation of heavy metals with grain size and operational chemical forms reveals a high proportion of elements associated with the fine size fraction compared to total sediments and elevated labile fractions in bottom sediments in anthropogenically disturbed systems finally an estimate is made towards the chemical flux of trace metals to the ocean through chinese estuaries

structural regularities in the lithosphere of continents and plate tectonics abstract two fundamental but competing earth science concepts have been under discussion in russia the first one that of endogenous regimes is based on the assumption that permanent vertical relationships or long term interactions between the crust and upper mantle control crustal evolution significant horizontal movements of the lithosphere as required by the second concept that of global plate tectonics would destroy these crust mantle interactions certain regular features of the crust and upper mantle support the endogenous regime concept and are difficult to explain in terms of conventional plate tectonics in particular the close correlation between near surface features and deep 400 km mantle inhomogeneities suggests that many geological structures are deeply rooted in the mantle moreover geophysical studies have failed to reveal a well defined and continuous asthenosphere at relatively shallow depths 100 km that would allow lithospheric plates to be transported over large distances and the rheology of the lithosphere itself is found to be sufficiently inhomogeneous as to cast doubt on the principle of thin rigid plates in contrast palaeomagnetic and other data require that horizontal movements of many near surface geological structures must have taken place to explain this apparent contradiction it is suggested here that the crust and its connected deep root are capable of gliding along one of the deep mantle phase transition zones with respect to the inner earth

the indus river system india pakistan major ion chemistry uranium and strontium isotopes the indus river is one of the large river systems draining the himalaya we report in this paper the major ion chemistry sr and u isotope systematics of the indus system particularly its headwaters the results show that 1 on an average about a third of the cations in the waters can be from silicate weathering however most of the ca mg is likely to be from the weathering of carbonates and evaporites 2 the 87sr86sr of the waters ranges between 0 7085 and 0 7595 the higher values 0 72 are typical of the tributaries draining the precambrian granite gneissic terrains the 87sr86sr of the indus main channel throughout its entire stretch shows only minor variations 0 7104 0 7116 the indus transports 8 8 106 mol sr to the arabian sea annually with a 87sr86sr of 0 7111 if our results of sr concentration and 87sr86sr measured at thatta can be considered typical of the indus throughout the year and 3 the u concentration in the indus and its tributaries is generally high 0 37 10 3 g 1 1 the source for the high uranium can be the weathering of granites zones of uranium mineralisation and black shales the indus results when compared with our earlier data on the ganga brahmaputra show that in all these three river systems carbonate weathering is the dominant source of ca mg and hco3 and that u concentrations are high in the case of 87sr86sr the indus waters are less radiogenic however its tributaries draining the precambrian granites gneisses have 87sr86sr in excess of 0 72 similar to that in the rivers of the ganga system the low 87sr86sr of the indus 0 7111 suggests that its contribution to the sr isotope evolution of oceans since the cenozoic is less significant than that of the ganga brahmaputra

late proterozoic glaciation in central eastern brazil synthesis and model abstract in the surroundings of the middle proterozoic sao francisco craton of central eastern brazil numerous traces of an ancient glaciation can be found almost all criterua necessary to prove an ancient glaciation occur including scratched and facetted pebbles a striated surface quarrying outwash plains eskers varvites dropstones decollement structures etc poorly sorted tillites with varying pebble composition are widely distributed continental tillites and glaciomarine sequences interfinger in the east and southeast of the craton traces of ice movement suggest flow directions of the ice towards the east and the southeast of the craton at the coast the wet base glaciers passed over to floating shelf ice in the northeast glaciers also came from the serrinha craton in northeastern bahia the glaciation covered an area of at least 1300 700 km the sequences containing traces of glaciation discordantly overlie archean to middle proterozoic rocks they in turn are overlain by late proterozoic calcareous and psammopelitic sediments of the bambui group present data indicate that glaciation took place around 1000 ma ago

the sources and transport of sr and nd isotopes in the baltic sea we have determined the concentration and isotopic composition of sr and nd in waters from the baltic sea the baltic sea is an intracontinental stratified brackish water estuarine like system and the rivers emptying into it drain a suite of terranes ranging from proterozoic archean in the north to phanerozoic in the south the sampled brackish waters range in salinity from seawater sw at 35 289 to a minimum of 2 460 at the surface in the innermost part of the gulf of bothnia the sr concentrations show generally conservative behavior indicating a simple two component mixing however small deviations 3 70 from a perfect mixing line reveal that the imprints from rivers with different sr concentrations are preserved in the blending strontium concentrations from a depth profile across the redoxcline in the baltic proper indicate that vertical particle transport alters the sr concentration in the water our estimated concentration of sr in the average freshwater input to the baltic is 0 03 ppm which is only about 0 4 of the sw concentration the sr isotopic data range from e sr sw 0 in seawater to e sr bw sw 7 8 in the least saline baltic water bw sample in the gulf of bothnia the isotopic composition of sr versus 1 sr in the baltic sea follows an almost perfect mixing line which shows that seawater sr is mixed with much more radiogenic components calculated end member values of e sr sw for each sample show that the riverine input into the gulf of bothnia has e sr sw 120 200 and 10 50 e units in the baltic proper these values are in general agreement with direct measurements of river waters in each region however the calculated values in the gulf of bothnia are lower than the measured river water input in this region which indicates the presence of less radiogenic sr presumably originating from the river waters draining the southern part of the basin which are partially transported northward and mixed with sr from the gulf of bothnia rivers the nd concentration in the baltic sea is not conservative varying between 5 and 45 ppt with the highest concentrations in the bottom waters due to vertical particulate transport a plot of e nd o in baltic water yields a good correlation with the calculated freshwater end member e sr sw the data show that it is possible to unravel the different freshwater sources into the baltic and to identify the zones of particulate removal of both non conservative species such as the ree and of quasi conservative species such as sr the use of isotopic tracers in this estuarine environment may provide a much better insight into mixing and element transport it should also be possible to trace lateral movements of freshwater inputs

lead isotope signatures of holocene fluvial sediments from the loire river valley abstract the distribution of mn v th pb and isotopes of pb in the labile fraction of sediments from a channel infill in the middle loire alluvial plain are used to highlight some aspects of the basin evolution over the period from 0 to 10 ka bp the acid extractable matter aem in the sediment samples is variable in amount and in trace element contents iron mn oxyhydroxides are the principle trace element carrying phase in the labile fraction and carbonates are a secondary carrier vanadium and pb originate from the weathering of silicates and are used as a silicate erosion rate index in the fluviatile record most of the aem data plot along a general trend between 3 endmembers basalts cretaceous carbonate rocks and granites in the relationship between 207pb 206pb and 206pb 206pb these endmembers have been mixed in various proportions depending on natural holocene inputs erosion volcanic events or human influences mining and smelting of ore

source mechanisms of moderate size earthquakes and stress orientation in mid plate south america summary fault plane solutions of six mid plate earthquakes with magnitudes ranging from 4 8 to 5 5 mb were determined using p wave first motion data and the relative amplitudes of short period teleseismic depth phases pp and sp these results together with previous studies show a predominance of reverse and strike slip faulting indicating horizontal compressional stresses in mid plate south america the orientation of the p axes however is not uniform in western and southwestern brazil the p axes are oriented approximately e w probably due to the nazca south america plate convergence in eastern brazil the direction of the p axes show more scatter but an average e w direction is consistent with the available data on the contrary in northern brazil the p axes of two events in the amazon basin trend approximately n s a direction perpendicular to the direction of absolute plate motion as well as to the relative plate motions nazca south america and south america africa

seasonal variations of physical and chemical erosion a three year survey of the rhone river france abstract numerous studies of weathering fluxes have been carried out on major world rivers during the last decade to estimate co 2 consumption rates landscape evolution and global erosion rates for obvious logistical reasons most of these studies were based on large scale investigations carried out on short timescales by comparison much less effort has been devoted to long term monitoring as a means to verify the temporal variability of the average characteristics their trends and the representativeness of short term investigations here we report the results of a three year survey november 2000 to december 2003 of the major and trace element composition of dissolved and suspended matter in the lower rhone river france the largest river of the mediterranean area subsurface water samples were collected in arles about 48 km upstream of the estuary twice a month routinely and at higher frequency during flood events during each flood event the suspended particulate matter spm show the usual trend of clockwise hysteresis with higher spm concentrations on the rising limb of the flood than at the same discharge on the falling limb we show that the annual average spm flux of the rhone river to the mediterranean sea 7 3 0 6 10 6 tons yr 1 was largely controlled by the flood events 83 of the solid discharge occurred in less than 12 of the time and that the precision on the total output flux depends strongly on the precise monitoring of spm variations during the floods the chemical composition of water and spm are characterized by the predominance of ca 2 due to the abundance of carbonate rocks in the rhone watershed chemical budgets have been calculated to derive the contributions of atmospheric deposition carbonate silicate and evaporite weathering and anthropogenic inputs the chemical weathering rate of carbonates is estimated to be 89 5 t km 2 yr 1 compared to 14 4 3 t km 2 yr 1 from silicates by contrast the physical erosion rate of silicates is about 51 t km 2 yr 1 against 19 t km 2 yr 1 for carbonates the steady state model of gaillardet et al 1995 has been applied to the chemical composition of dissolved and solid products the results show that the rhone river currently exports much less material than produced at steady state by weathering in its watershed the sediment flux inferred from the steady state calculation 21 56 10 6 t yr 1 is on the same order as that estimated in literature for the 19th and the beginning of the 20th centuries this imbalance may suggest that the rhone is under a transient erosion regime following climate change i e significant decrease of the flooding frequency since the beginning of the 19th century on the other hand the imbalance may also be due to the trapping of alluvion by the numerous dams on the river and its tributaries our data corroborate with previous studies that suggest a strong coupling between chemical and physical erosion fluxes during the hydrological seasonal cycle of the rhone river the correlation between physical and chemical transport rates is however clearly different from that reported for global annual averages in large world rivers

weathering and anthropogenic influences on the water and sediment chemistry of wular lake kashmir himalaya this paper presents a study on the wular lake which is the largest fresh water tectonic lake of kashmir valley india one hundred and ninety six 196 water samples and hundred 100 sediment samples n 296 have been collected to assess the weathering and anthropogenic impact on water and sediment chemistry of the lake the results showed a significant seasonal variability in average concentration of major ions being highest in summer and spring and lower in winter and autumn seasons the study revealed that lake water is alkaline in nature characterised by medium total dissolved solids and electrical conductivity the concentration of the major ion towards the lake central showed a decreasing trend from the shore line the order of major cations and anions was ca2 mg2 na k and hco3 so4 2 cl respectively the geochemical processes suggested that the chemical composition lake water is mostly influenced by the lithology of the basin carbonates silicates and sulphates which had played a significant role in modifying the hydrogeochemical facies in the form of ca hco3 mg hco3 and hybrid type chemical index of alteration values of wular lake sediments reflect moderate weathering of the catchment area compared to upper continental crust and the post archean shale the sediments have higher si ti mg and ca contents and lower al fe na k p zn pb ni cu content geoaccumulation index igeo and us environmental protection agency sediment quality standards indicated that there is no pollution effect of heavy metals zn mn pb ni and co the study also suggested that wular lake is characterised by both natural and anthropogenic influences

controls on seasonal variations of silicate weathering and co2 consumption in two river catchments on the ne tibetan plateau abstract water samples from the buha and shaliu rivers located on the semi arid northeastern tibetan plateau were collected weekly over a one year period the major ionic compositions of water samples were measured and the daily contents of suspended particulate material spm were monitored in both rivers in order to investigate the influence of lithology climate and physical erosion on seasonal silicate weathering in the shaliu river weathering of trace amounts of calcite contributes more than 50 of the ca2 and hco 3 to the river water through high resolution variations of ca2 concentrations and elemental ratios the signal of carbonate precipitation is captured at the end of monsoon in this river the measured physical erosion rate is only 8 7 16 0 mm kyr in this semi arid region which is 2 3 orders of magnitude lower than that in the himalaya and nearby regions in contrast with several orders of magnitude in seasonal variations of silicate weathering rates in both catchments the distinct lithology between the catchments only leads to a 15 times difference of annual net co2 consumption the correlation analysis shows that seasonal silicate weathering is strongly dependent on water discharge in the semi arid area the most important observation is that unrecognized by the previous studies both physical erosion rate and air temperature exhibit two distinct trends with silicate weathering rates and net co2 consumption during the years the two trends might suggest that temperature plays a more important role on the co2 consumption rate before the mid monsoon under a condition of low water discharge than that after the monsoon with a high water discharge during the period before the mid monsoon the relationship between temperature and silicate weathering rate exhibits higher activation energy than after the mid monsoon suggesting a greater dissolution of uneasily weatherable minerals from groundwater frozen soil and or dust input the relationship between erosion and weathering during the period before the mid monsoon indicates a faster increase of silicate weathering rate because freezing erosion produces large amount of high surface area minerals

dissolved load of the loire river chemical and isotopic characterization the loire river with one of the largest watersheds in france has been monitored just outside the city of orleans since 1994 physico chemical parameters and major and trace elements were measured between 2 day and 1 week intervals according to the river flow the sampling site represents 34 of the total loire watershed with 76 silicate rocks and 24 carbonate rocks elements are transported mainly in the dissolved phase with the ratio of total dissolved salts tds to suspended matter sm ranging between 1 6 and 17 4 chemical weathering of rocks and soils are thus the dominant mechanisms in the loire waters composition the highest tds sm ratios are due to dissolved anthropogenic inputs the database shows no link between no3 content and river flow the na k mg2 so42 and cl concentrations are seen to decrease with increasing discharge in agreement with a mixing process involving at least two components the first component during low flow is concentrated and may be related with input from the groundwater and sewage station water the second component during high flow is more dilute and is in agreement with bedrock weathering and rainwater inputs a geochemical behaviour pattern is also observed for hco3 and ca2 species their concentrations increase with increasing discharge up to 300 m3 s after which they decrease with increasing discharge the sr isotopic composition of the dissolved load is controlled by at least five components a series of natural components represented by a waters draining the silicate and carbonate bedrock b groundwater and c rainwaters and two kinds of anthropogenic components the aim of this study is to describe the mixing model in order to estimate the contribution of each component finally specific export rates in the upper loire watershed were evaluated close to 12 t year 1 km 2 for the silicate rate and 47 t year 1 km 2 for the carbonate rate

water geochemistry of the qiantangjiang river east china chemical weathering and co2 consumption in a basin affected by severe acid deposition abstract the chemical composition of the qiantangjiang river the largest river in zhejiang province in eastern china was measured to understand the chemical weathering of rocks and the associated co2 consumption and anthropogenic influences within a silicate dominated river basin the average total dissolved solids tds 113 mg l 1 and total cation concentration tz 1357 eq l 1 of the river waters are comparable with those of global major rivers ca2 and hco3 followed by na2 and so42 dominate the ionic composition of the river water there are four major reservoirs carbonates silicates atmospheric and anthropogenic inputs contributing to the total dissolved load of the investigated rivers the dissolved loads of the rivers are dominated by both carbonate and silicate weathering which together account for about 76 3 of the total cationic load origin the cationic chemical weathering rates of silicate and carbonate for the qiantangjiang basin are estimated to be approximately 4 9 ton km 2 a 1 and 13 9 ton km 2 a 1 respectively the calculated co2 consumption rates with the assumption that all the protons involved in the weathering reaction are provided by carbonic acid are 369 103 mol km 2 a 1 and 273 103 mol km 2 a 1 by carbonate and silicate weathering respectively as one of the most severe impacted area by acid rain in china h2so4 from acid precipitation is also an important proton donor in weathering reactions when h2so4 is considered the co2 consumption rates for the river basin are estimated at 286 103 mol km 2 a 1 for carbonate weathering and 211 103 mol km 2 a 1 for silicate weathering respectively the results highlight that the drawdown effect of co2 consumption by carbonate and silicate weathering can be largely overestimated if the role of sulfuric acid is ignored especially in the area heavily impacted by acid deposition like qiantangjiang basin the actual co2 consumption rates after sulfuric acid weathering effect deduction is only about 77 of the value calculated with the assumption that carbonic acid donates all the protons involved in the weathering reaction

major and trace element geochemistry in upper ganga river in the himalayas india chemical weathering and resulting water compositions in the upper ganga river in the himalayas were studied for the first time temporal and spatial sampling for a 1 year period monthly intervals was carried out and analyzed for dissolved major elements trace elements rare earth elements ree and strontium isotopic compositions amounts of physical and chemical loads show large seasonal variations and the overall physical load dominates over chemical load by a factor of more than three the dominant physical weathering is also reflected in high quartz and illite mica contents in suspended sediments large seasonal variations also occur in major elemental concentrations the water type is categorized as hco3 so42 ca2 dominant which constitute 60 of the total water composition on an average only about 5 12 of hco3 is derived from silicate lithology indicating the predominance of carbonate lithology in water chemistry in the head waters of the ganga river more than 80 na and k are derived from silicate lithology the silicate lithology is responsible for the release of low sr with extremely radiogenic sr 87sr 86 sr 0 75 in bhagirathi at devprayag however there is evidence for other end member lithologies for sr other than carbonate and silicate lithology trace elements concentrations do not indicate any pollution although presence of arsenic could be a cause for concern high uranium mobilization from silicate rocks is also observed the ree is much less compared to other major world rivers such as the amazon perhaps because in the present study only samples filtered through 0 2 m were analysed negative eu anomalies in suspended sediments is due to the excess carbonate rock weathering in the source area

inversion of teleseismic p wave particle motions for crustal structure in fennoscandia abstract we test a model of the earth s crust by transforming the observed vertical component of the teleseismic p wave record into the synthetic radial component and comparing this with the observed radial component the optimum model can be found by minimizing the rms difference between the synthetic radial component and the observed one for a number of records in the time intervals several tens of seconds long we applied this method to long period records of norsar and some other seismograph stations in fennoscandia the search for the optimum models was performed by trial and error and by application of the iterative procedure based on the general method of solution of the ill posed inverse problems tikhonov and arsenin in comparison with the conventional spectral ratio analysis our techniques are more flexible and demonstrate a higher resolving power it is found that in the norsar siting area the crustal thicknesses are regulated by the variations of thickness of the granite layer which dominates in the crust this observation explains peculiarities of the gravity field in the oslo graben region a similar relation between the parameters of the crust is found in the eastern part of fennoscandia

development of garnet porphyroblasts by multiple nucleation coalescence and boundary misorientation driven rotations two types of garnet porphyroblast occur in the schneeberg complex of the italian alps type 1 porphyroblasts form ellipsoidal pods with a centre consisting of unstrained quartz decussate mica and small garnet grains and a margin containing large garnet grains orientation contrast imaging using the scanning electron microscope shows that the larger marginal garnet grains comprise a number of orientation subdomains individual garnet grains without subdomains are small 50 m faceted and idioblastic and have simple zoning profiles with ca rich cores and ca poor rims subdomains of larger garnet grains are similar in size to the individual small garnet grains type 2 porphyroblasts comprise only ellipsoidal garnet with small subdomains in the centre and larger subdomains at the margin each subdomain has its own ca high ca dropping towards subdomain boundaries garnet grains with or without subdomains all have the same ca poor composition at rims in contact with other minerals the compositional zonation patterns are best explained by simultaneous multiple nucleation followed by growth and amalgamation of individual garnet grains the range of individual garnet and garnet subdomain sizes can be explained by a faster growth rate at the porphyroblast margin than in the centre the difference between type 1 and type 2 porphyroblasts is probably related to the growth rate differential across the porphyroblast electron backscatter diffraction shows that small individual garnet grains are randomly oriented large marginal garnet grains and subdomain bearing garnet grains have a strong preferred orientation clustering around a single garnet orientation misorientations across subdomain boundaries are small and misorientation axes are randomly oriented with respect to crystallographic orientations the only explanation that fits the observational data is that individual garnet grains rotated towards coincident orientations once they came into contact with each other this process was driven by the reduction of subdomain boundary energy associated with misorientation loss rotation of garnet grains was accommodated by diffusion in the subdomain boundary and diffusional creep and rigid body rotation of other minerals quartz and mica around the garnet an analytical model in which the kinetics of garnet rotation are controlled by the rheology of surrounding quartz suggests that at the conditions of metamorphism the rotation required to give a strong preferred orientation can occur on a similar time scale to that of porphyroblast growth

use of sr isotopes as a tool to decipher the soil weathering processes in a tropical river catchment southwestern india river water composition major ion and sr 87 sr 86 ratio was monitored on a monthly basis over a period of three years from a mountainous river nethravati river of southwestern india the total dissolved solid tds concentration is relatively low 46 mg l 1 with silica being the dominant contributor the basin is characterised by lower dissolved sr concentration avg 150 nmol l 1 with radiogenic sr 87 sr 86 isotopic ratios avg 0 72041 at outlet the composition of sr and sr 87 sr 86 and their correlation with silicate derived cations in the river basin reveal that their dominant source is from the radiogenic silicate rock minerals their composition in the stream is controlled by a combination of physical and chemical weathering occurring in the basin the molar ratio of sio2 ca and sr 87 sr 86 isotopic ratio show strong seasonal variation in the river water i e low sio2 ca ratio with radiogenic isotopes during non monsoon and higher sio2 ca with less radiogenic isotopes during monsoon season whereas the seasonal variation of rb sr ratio in the stream water is not significant suggesting that change in the mineral phase being involved in the weathering reaction could be unlikely for the observed molar sio2 ca and sr 87 sr 86 isotope variation in river water therefore the shift in the stream water chemical composition could be attributed to contribution of ground water which is in contact with the bedrock weathering front during non monsoon and weathering of secondary soil minerals in the regolith layer during monsoon the secondary soil mineral weathering leads to limited silicate cation and enhanced silica fluxes in the nethravati river basin c 2015 elsevier ltd all rights reserved

sub critical fracture and associated retrogression of garnet during mylonitic deformation garnets from the alpine fault mylonites are fractured most fractures have a retrogressive fracture fill a small number have garnet fill a detailed sem study has been carried out to elucidate the mechanisms of fracture and associated retrogression wide fracture zones contain free floating islands of garnet in a retrogressive matrix electron channelling patterns show that segments of garnet across such fracture zones rarely show any relative rotations where rotations are observed they are small and systematic some large fractures show clearly that fracture and retrogression occurs by a replacement process fracture surface morphologies are indicative of surface dissolution a model is established where crack tips advance by a process of dissolution at a high stress crack tip whilst precipitation occurs as the tip and its associated stress field advance precipitation of retrogressive fracture fill occurs if fracture occurs out of the field of stability of garnet