mineral magnetic record of late quaternary climatic changes in a high alpine lake the magnetic properties of a sediment core from a high altitude lake in the swiss alps were compared with palynological and geochemical data to link climatic and mineral magnetic variations according to pollen data the sediments extend from the present to the younger dryas i e they cover more than 10 000 years of environmental change in the alps the major change in magnetic properties corresponds to the climatic warming of the early holocene high coercivity magnetic minerals that characterize the late glacial period almost disappeared during the holocene and the concentration of ferrimagnetic minerals increased sharply the contribution of superparamagnetic grains also decreased in the holocene sediments similar variations in sp content and coercivity of smaller magnitude are found in the holocene and are interpreted to represent minor climatic variations comparison with the historical record of the last 1000 years confirms this interpretation the magnetic mineralogy the superparamagnetic contents and the irm intensity in the coarse grained late glacial sediments are similar to those measured in the catchment bedrock this indicates a detrital origin the different properties and the higher concentration of magnetic minerals in the holocene sediments are due to authigenic phases magnetic properties provide a high resolution record of climatic change they are sensitive even to small variations that are not recorded in the pollen or loi data magnetic parameters show fine scale variation and constitute a valuable supplement to conventional climatic indicators 1999 elsevier science b v all rights reserved

comment on helium isotope fluxes and groundwater ages in the dogger aquifer paris basin by b marty t torgersen v meynier r k o nions and g de marsily

palaeclimatic significance of the xiantai fluvio lacustrine sequence in the nihewan basin north china based on rock magnetic properties and clay mineralogy summary here we report an increased cooling coupled with an intensified aridification for the xiantai fluvio lacustrine sequence of pleistocene age 1 9 0 1 ma in the nihewan basin north china known for the occurrence of several hominin sites the cooling is related to an up section decrease in propensity to chemical weathering as inferred from an increase in lowfield susceptibility after cycling to 700 c close to 700 c reacting chlorite is providing the iron source for newly formed very fine grained ferrimagnetic minerals which enhances the susceptibility signal the reactivity of chlorite after annealing at temperatures above 600 c is documented with x ray diffraction and the up section decrease in propensity to chemical weathering is confirmed by the up section declining illite chlorite ratios and increasing chlorite and illite contents based on x ray diffraction analysis on selected samples

sediment yields and sources in a welsh upland lake catchment during the past 800 years estimates of suspended sediment yield over the past 800 years have been derived from a whole basin study of lake sediments in llyn geirionydd north wales magnetic and physical sediment properties were used to correlate a suite of cores to a master chronology based on 210pb and 14c dates the sources of sediment within the catchment were identified by comparing the magnetic and heavy metal properties of sediments soils and stream sediments mean suspended sediment yields range from 6 to 18 t km 2 yr 1 with high yields in the periods 1765 1830 and 1903 1985 corresponding to mining activities in the catchment the impact of earlier deforestation agricultural expansion or climatic change on sediment yields is low although there is evidence that agricultural activities increased levels of peak stream discharge afforestation in the 20th century does not appear to have significantly increased sediment yield sediment sources have remained fairly constant through time they appear to be widespread and dominated by stream channel sides rather than point sources except during the mining phases when spoil material has dominated the sediment load sediment loads to the lake today are still dominated by sediment derived from unvegetated spoil heaps

magnetic properties of surface sediments from the pearl river estuary and its adjacent waters implication for provenance abstract environmental magnetism has been widely used as a rapid cost effective and non destructive method in various fields including sediment source identification nineteen surface sediments from ten transects in the pearl river estuary pre and its adjacent seas were studied for magnetic measurements combined with mineral analysis for representative samples magnetic implications for provenance are discussed the results indicate that concentration dependent magnetic parameters decrease gradually and change sharply between the pre and its adjacent waters the magnetic mineral assemblage is basically consistent at all sites i e consisting of magnetite and hematite however the grain size of magnetite particles is clearly different probably due to different material sources magnetic parameters allow separating the sediments from the pre and its adjacent seas into three groups more distinctively than deduced from clay mineral analysis these new findings indicate that magnetic properties of surface sediments bring complementary information of material source as well as marine geology

the randomness of major global earthquakes abstract on the basis of seismicity data compiled by bath and duda 1979 we infer that random occurrence is very unlikely for the fairly small global earthquakes m 7 6 when considering the period 1897 1977 if the earliest shocks 1897 1916 are excluded the question of randomness is still open but the support for poissonian independent behaviour is not very strong

helium 3 anomalies and crust mantle interaction in italy abstract the distribution of primordial 3he in the crust of italy has been investigated through a survey of groundwaters hot springs exploration and production geothermal wells the mantle derived component varies from 0 to 60 and reaches a maximum at vulcano in the eolian islands 3he anomalies occur where the conductive heat flow is relatively high but the relationships between heat flow and anomaly are uncertain the distribution of 3he in the main reservoir and cap rock to the larderello geothermal system shows that the mantle derived 3he varies from 5 to 40 of total he and reaches a maximum in fluids extracted from a depth of ca 3 km within the basement bomb produced tritiogenic 3he appears to make a near negligible contribution well 107 at larderello has been monitored over a period of 17 months and the 3 he 4 he ratio r varies from 1 4 to 1 6 times the atmospheric ratio ra whilst he ne varies from 9 to 160 a model is proposed for the larderello geothermal system whereby mantle derived heat and volatiles are advected to shallow 6 8 km depths in association with melts and released into the main geothermal reservoir at larderello in a non uniform manner possibly associated with fracturing isotopic and elemental equilibrium of gaseous species c o h appears to have taken place in the basement to the main reservoir from where fluid with r ra 3 2 has been extracted

helium isotopes tectonics and heat flow in the northern caucasus abstract 109 new measurements of 3he 4he r in subsurface fluids of the northern caucasus coupled with the data obtained previously allow regional regularities in the distribution of helium isotopic composition to be examined cis caucasian foredeeps show the lowest radiogenic r values the average rav value is slightly higher in gases of the scythian plate beyond the stavropol arch within the arch elevated r 1 6 4 5 10 7 indicates an input of mantle derived helium this input is even more evident to the south of starvropol arch in the caucasian mineral water area where the 8 ma old laccolithes occur and r values approach 5 11 10 7 the highest r values up to 0 7 0 9 10 5 are observed further to the south in the central segment of the greater caucasus where recent volcanism is manifested enhanced r values do not correlate with the crustal thickness but reflect degassing of magmatic reservoirs including those yet unknown according to the recent sr nd o data the young volcanic rocks are of mantle affinity but they are contaminated by a crustal component the average rav values in fluids and 87sr 86sr ratios in host magmatic rocks show an inverse correlation suggesting mixing of crustal and mantle materials r values vary inversely with apatite fission track ages of crystalline basement rocks the ages increase westward of the elbrus volcano most likely recording the thermal degradation of the greater caucasus since the pre cainozoic magmatic activity a direct correlation between rav values and background conductive heat flow densities implies that discharge of the mantle melts into the crust is the common cause of the geochemical geochronological and geothermal regularities observed elevated r values are generally observed in co2 bearing fluids low values are typical of ch4 gases a few n2 rich gases display highly variable r relationships between the major gas constituents and noble gas isotopes are discussed fractionation loss and gain of these species are considered as the processes controlling the compositions of underground fluids

helium isotopic fingerprints of the heavy land subsidence left in groundwater of the saga plain near beppu shimabara graben kyushu japan abstract the saga plain is near beppu shimabara graben a region of potential active volcanism in the graben mantle he which has a high 3he 4he ratio of 1 1 10 5 escapes easily from the underlying subduction zone in groundwater of the saga plain except in the shiroishi district this ratio gradually increased as the dissolved he content increased to a maximum of 5 10 6 in central shiroishi however the ratio reached a minimum of 8 7 10 7 with increasing dissolved he content suggesting that groundwater in central shiroishi has selectively accumulated radiogenic he which has a very low ratio of 1 10 8 rather than reflecting the regional he which is rich in mantle he this can be explained if groundwater in shiroishi has become mixed with fossil pore water drawn from impermeable marine clay aquitard layers the withdrawal of pore water has also caused severe land subsidence in central shiroishi

understanding and modelling dissolved gas transport in the bedrock of three fennoscandian sites summary the origin and transport of dissolved gases in the geosphere is of interest for assessment studies of nuclear waste repositories in this paper we analyse available field measurements of helium methane and hydrogen at three fennoscandian sites forsmark and laxemar in sweden and olkiluoto in finland the field data are interpreted using different analytical models all based on the one dimensional diffusion equation the results of the different models provide estimates about the amount of deep gas flux the in situ production and the groundwater residence time of the considered sites the computed helium fluxes which fall within the lower range of crustal degassing fluxes reported by torgersen 2010 are strictly related with the high tightness of the considered fracture media the very high estimates of groundwater residence time indicate that at the considered depths there are only very few flowing fractures while in the rest of the fractured domain groundwater has been almost motionless during a whole glacial cycle

noble gases dissolved in groundwater in a volcanic aquifer helium isotopes in the kumamoto plain this study investigates a tracing method using dissolved noble gases to survey the groundwater flow in a large groundwater basin the tracing method is based on measuring the concentrations of noble gases and the ratio of helium isotopes in groundwater samples since it is very difficult to detect trace amounts of noble gases and helium with high accuracy in a 15 ml groundwater sample dissolved gases were extracted and purified then a high resolution mass spectrometer was used for measurement and comparison with standard samples we used this method with samples from a confined aquifer formed by the deposition of pyroclastic flow in the kumamoto plain on the west side of mt aso in central kyushu japan the groundwater basin under the plain is divided into four small basins based on the helium concentrations and isotope ratios with two major groundwater flows one flow is buried by the aso pyroclastic flow along the old kase river the other is along the tsuboi river valley these two groundwater flows were identified from the different helium isotope ratios the helium component from the deep mantle is mixed into the groundwater under the kumamoto plain finally data on the concentrations and ratios of3he to4he in groundwater samples were used to determine the location of faults in the volcanic aquifer

changes in isotope ratio and content of dissolved helium through groundwater evolution abstract the dissolved he content and he isotope ratio are proxy indicators of groundwater evolution in the shimokita peninsula the record of 3h and excess bomb tritiogenic 3he reveals the intrusion depth of shallow and young groundwater into deep groundwater the record of tritiogenic 3he suggests that prior to the period of nuclear testing the natural production level of 3h irradiated by cosmic rays was probably 6 tu helium isotope ratios in the groundwater converge to that of the regional crustal he with increasing depth and dissolved he content the regional degassed he has a 3he 4he r ratio of 7 24 10 7 which consists of 6 mantle he with r 1 1 10 5 and 94 radiogenic he with r 1 10 8 the magnitude of degassing he flux is 5 10 9 m3 m2 a based on the accumulation of he and taking into consideration the degassing he flux groundwater at depths greater than 300 m below sea level is estimated to be stagnant exhibiting residence times in excess of 102 ka

the bayesian probabilistic prediction of strong earthquakes in the hellenic arc abstract the bayesian probability theory in conjunction with the poisson process model is used to develop a bayesian discrete distribution to estimate or predict the inter arrival times tj for strong earthquakes in the hellenic arc the bayesian posterior probabilities may be computed from the relationship p t r m t r e t r 1 e t r j 1 m t j e t j 1 e t j where p t r m is the conditional probability of the event tr given that an earthquake of magnitude m has occurred the bayesian discrete analysis is performed first by using the poisson process to determine the prior probability distribution for tj and the likelihood function we can imagine the random earthquake experiment involved in the application of bayes theorem to earthquake prediction to be a two stage experiment the first stage was initiated a long time ago when the real time arrival dates of strong earthquakes were first recorded the second stage was initiated in 1935 when the earthquake magnitude scale was introduced by richter 1935 in southern california richter probably never thought that this measure of the earthquake magnitude then will be an experiment designed to give us information about the outcome of the earthquake inter arrival times the first stage the earthquake data analyzed in this study have been taken from the earthquake catalog for the hellenic arc prepared by ambraseys 1981 the discrete bayesian analysis suggests determining the most likely outcomes for the length of earthquake inter arrival times by using some maximum values of the final bayesian probabilities the following inferences concerning future strong earthquake occurrences in the hellenic arc area may be drawn 1 1 our western northwestern zone is a seismic region which approximately coincides with the region studied by wyss and baer therefore we agree with the geographic location of the expected earthquake forecasted by wyss and baer 1981 2 2 using probability theory bayes theorem poisson process we concluded that a period of strong earthquake activity is expected to occur in the same geographic location during the decade 1992 2002 this conclusion supports ambraseys conclusion however it should be noted that our conclusion indicates that the period of strong earthquake activity will occur anyway a decade later than predicted by wyss and baer

sources of radiogenic helium in a clay till aquitard and its use to evaluate the timing of geologic events abstract concentrations of dissolved gases he ne ar and n 2 were measured in pore waters collected from a pleistocene 0 80 m depth and cretaceous 80 156 m depth aged clay rich aquitard system using both a conventional copper tube method and in situ diffusion samplers both methods yielded similar results he data revealed a well defined increase in concentration with depth from 1 7 10 8 cm 3 he stp g 1 water near the water table at 2 3 m below ground surface to 6 9 10 6 cm 3 he stp g 1 water at 80 m below ground surface b g the concentration at depth greatly exceeded values for atmospheric solubility at in situ temperatures and could not be attributed to steady state production from decay of u and th within the aquitard system trends in he isotope ratios and concentrations suggest accumulation as a result of both release of residual 4 he from within the pleistocene clay rich till ca 87 and an ascending radiogenic helium flux from underlying cretaceous age sediments ca 13 one dimensional transport modeling of the he data suggests that between 15 ka and 25 ka were required to produce the observed profile this time frame agrees with studies utilizing isotope tracers i e d h and 14 c dic to estimate the timing of deposition for the till at this site our results demonstrate the utility of using helium a nonreactive tracer for delineating hydrogeologic processes in slow permeability geologic strata and also support the contention that thick clay rich surficial aquitards can provide long term containment of contaminants including hazardous wastes

noble gases in crude oils from the paris basin france implications for the origin of fluids and constraints on oil water gas interactions in order to investigate the potential of noble gases to trace the dynamics of oil reservoirs we have analysed the abundance and isotopic composition of all noble gases he ne ar kr and xe in crude oils from the paris basin france using a new extraction and purification procedure the main oil reservoirs are presently located in the jurassic dogger limestone and in the triassic keuper sandstone but hydrocarbons originated from a common source rock formation located in the interbedded liassic sequence despite this common origin the abundance and isotopic ratios of the noble gases differ between the dogger and the keuper the isotopic compositions of kr and xe are indistinguishable from that of air 3he 4he ratios higher than those predicted from radiogenic production in the sediments or in the crust are attributed to the occurrence of mantle derived 3he in the basin each sedimentary sequence is characterised by well defined and homogeneous 21ne 22ne and 40ar 36ar ratios which average 0 0306 0 0008 and 312 10 for the dogger and 0 0367 0 0012 and 664 30 for the keuper respectively the main source of radiogenic noble gases appears to be the continental crust underlying the basin with possible regional contributions of noble gas isotopes produced in the sediments the helium and argon isotopic ratios of the dogger oils are very similar to those observed in geothermal waters flowing in the dogger aquifer throughout the basin demonstrating that noble gases in oils derive from associated groundwaters oil reservoirs in the paris basin therefore accumulate noble gases from wide regions of the continental crust through cross formational flow of groundwaters and subsequent partitioning into oil this observation implies that noble gases cannot be directly used to date oils but can provide time constraints if 1 water oil interactions are quantified and 2 the residence time as well as the noble gas characteristics of associated groundwaters are known oil water gas partitioning processes are well recorded in the fractionation of noble gas elemental abundance two distinct processes have been identified 1 accumulation of atmosphere derived ang and radiogenic noble gases both initially dissolved in groundwaters resulting in a positive correlation between absolute amount of ang and the extent of heavy noble gas fractionation and 2 subsequent fractional degassing resulting in a negative correlation between ang abundance and heavy noble gas fractionation degassing is particularly evident for the keuper oils and might have occurred in the reservoirs following hydrodynamic gas stripping the ang abundance in the dogger reservoirs requires that about one order of magnitude more water than presently observed has interacted with the oil given current estimates of the residence time for groundwaters in the dogger aquifer the duration of oil water interaction is in qualitative agreement with a palaeocene oligocene age for the major episode of secondary oil migration in the paris basin high xenon contents in keuper reservoirs suggest that they have experienced hydrodynamic interactions between flowing waters and oils for long time and that the trias might have reached hydrostatic condition only recently

helium transfer from water into quartz crystals a new approach for porewater dating several important fundamental and applied problems require a quantification of slow rates of groundwater flow to resolve these problems helium appears to be a promising tracer in this contribution we discuss a new approach which gives the helium inventory in a rock pore water system by using the relevant mineral record i e without extraction and investigation of the porewater samples some u and th poor minerals such as quartz quartz separates from permo carboniferous formation sandstone shale interlayering molasses basin northern switzerland hereafter pcf are used in this study contain excessive helium having migrated into their internal helium accessible volume hav from the surrounding porewater i n tolstikhin b e lehmann h h loosli a gautschi helium and argon isotopes in rocks minerals and related groundwaters a case study in northern switzerland geochim cosmochim acta 60 1996 1497 1514 these volumes are estimated by using helium as a nano size penetrating tool i e by saturation of the minerals with helium under controlled pressure temperature conditions and subsequent measurements of the helium saturated concentrations in the quartz separates hav total volume ratios vary from 0 017 to 0 16 along with the measured initial unsaturated he concentration the hav gives the internal helium pressure the mean value obtained for 7 samples 25 sample aliquots is p 0 45f0 15 atm 1 r the product of helium pressure and solubility 7 35 10 3 cc stp he cc h2o for the temperature and salinity of pcf aquifers reported in f j pearson w balderer h h loosli b e lehmann a matter t peters h schmassmann a gautschi applied isotope hydrogeology a case study in northern switzerland elsevier amsterdam 1991 439 pp is the mineral derived he concentration in the respective porewater cpw 0 0035f0 0017 cc he cc h2o this value is in full accord with measured he concentrations in pcf aquifers cpcf varying from 0 0045 to 0 0016 cc he cc h2o this agreement validates the proposed approach and also shows that the mineral porewater helium concentration equilibrium has been established indeed estimates of the he migration rates through our quartz samples show that in 6000 years the internal pressure should equilibrate with he concentration in related porewater of pcf and this time interval is short compared to independent estimates i n tolstikhin b e lehmann h h loosli a gautschi helium and argon isotopes in rocks minerals and related groundwaters a case study in northern switzerland geochim cosmochim acta 60 1996 1497 1514 the helium inventory in the rock porewater assemblage shows that helium abundance in pore waters is indeed important in shale samples with 15 porosity porewaters contain more helium than the host minerals altogether porewater heliumconcentration profiles available from the mineral record along with helium production rates are input parameters allowing model s of helium migration through a hydrological structure to be developed quite high helium concentrations in pcf porewaters imply slow removal mechanisms which will be discussed elsewhere

the isotopic composition of radiogenic helium and its use to study groundwater movement in confined aquifers abstract the 3 he 4 he ratio for radiogenic he is shown to be primarily determined by the abundance of li and neutron absorbing elements in the host formations and is almost independent of the radioelement abundance the 3 he 4 he ratios have been computed for various li contents in rock matrices with average abundances of other elements the 3 he 4 he ratio is specific for each formation and may therefore be used to study crustal diffusion of he it is shown however that both the 3he and 4he contents of continental basements are likely to exceed those of the mantle so that diffusion of mantle he through continental crust is not likely to occur changes in the 3 he 4 he ratio for dissolved he have potential for studying groundwater movement and mixing processes atmospheric he which was dissolved at recharge is progressively diluted by radiogenic he with an isotopic ratio characteristic of the aquifer as the groundwater migrates down dip mixing proportions for formation he and atmospheric he in aquifers for which there is admixture of fracture borne water and interstitially stored water can also be estimated from isotopic measurements these processes are discussed in relation to two aquifers in eastern england

210pb geochronology of sediment accumulation rates in mexico city metropolitan zone as recorded at espejo de los lirios lake sediments abstract a sedimentary sequence from the espejo de los lirios lake in the metropolitan zone of mexico city mzmc was analyzed in detail for 210 pb and 137 cs activities allowing to assess the evolution of the accretion rates in the lake during the last 84 4 years the core revealed the deposition of contemporaneously indigenous lake sediments to the site interspersed with eroded bedrock from the catchment evidencing episodic increases in sediment accretion which varied from 0 14 to 0 93 cm year 1 increasing trends in sedimentation rates were found to be closely related to demographic expansion of the metropolitan zone of mexico city and explained on the basis of the erosive processes produced as a result of deforestation created as a consequence of the urban and industrial development of the mzmc

normalized magnetic parameters and their applicability to paleomagnetism and environmental magnetism using simple theory one can show that normalized magnetic parameters i e one primary magnetic measurement divided by a second are not independent of the concentration of magnetic minerals in an assemblage except in a few special cases in the common situation when the number of minerals in an assemblage is unknown these parameters can only be used to show a lack of change in domain size or mineralogy

etude geochimique de la nappe du dogger du bassin parisien abstract waters from the dogger nappe of the paris basin which are utilized for heating have a chlorinity in the range 0 07 0 6 mole litre and a temperature in the range 48 80 c we present here a geochemical study of waters sampled in about 25 boreholes except chloride and sulfates elements seem to be controlled by equilibrium with minerals commonly encountered in hydrothermal systems calcite disordered dolomite chalcedony ca montmorillonite disordered kaolinite albite and adularia a chalcedony geothermometer indicates temperatures close to the observed temperatures whereas the na k geothermometer gives a mean value close to the mean observed temperature but na k variations do not follow local variations of temperature the cl br ratio 420 suggests that the chlorinity of dogger water is related to sea water dogger water can be the result of interaction between a mixture of evolved sea water and fresh water and minerals of the reservoir

helium accumulation in groundwater ii a model for the accumulation of the crustal 4he degassing flux abstract a model of 4 he accumulation in a confined aquifer is presented which includes in situ production and a crustal degassing flux of 4 he into the bottom of a confined aquifer the model is consistent with the measurements of 4 he concentration in the great artesian basin australia torgersen and clarke 1985 and also with the measurements of 4 he concentration in the auob sandstone of namibia heaton 1981 the measured value of the crustal degassing flux of 4 he from these two areas is comparable with the 4 he degassing flux calculated from the atmospheric budget of 4 he wasserburg et al 1963 ozima and podosek 1983 a literature review suggests that a crustal degassing 4 he source may account for the 4 he accumulation in many other groundwater systems it is concluded from the literature review the detailed modelling of 4 he accumulation in gab and the auob sandstone and the atmospheric budget that crustal degassing of 4 he may be a common and widespread phenomena

geochemical control of magnetite dissolution in subarctic lake sediments and the implications for environmental magnetism geochemical and mineral magnetic studies of lake sediments from the karsa valley in north sweden demonstrate that down core variations in magnetic properties have been determined by post depositional magnetite dissolution rather than by sediment source changes a low sediment accumulation rate during times of climatic amelioration combined with a higher organic carbon content produced intense reducing conditions with almost complete magnetite loss an increase in the sedimentation rate and a reduction in the organic carbon content primarily due to glacier reformation allowed magnetite preservation thus the mineral magnetic profiles record lake sediment palaeoredox conditions brought about by climate change this new interpretation of mineral magnetic transformations in freshwater sediments may have far reaching implications for other mineral magnetic studies concerned with the alternation between glacial stadial and interglacial interstadial episodes during the quaternary period

magnetic mineralogy and its implication of contemporary coastal sediments from south china magnetic parameters have been widely used as a rapid cost effective and non destructive method to assess whether their magnetic properties reflect the development history in the pearl river delta three sediment cores collected from south china coastal waters were selected for magnetic research the results indicate that the predominant ferrimagnetic mineral is magnetite with an additional smaller amount of surprisingly high coercive greigite fine grained superparamagnetic and single domain particles of magnetite and the relative contribution of greigite are increased when the total concentration of ferrimagnetic minerals is higher three well known stages of the chinese history i e iron smelting cultural revolution and the latest phase of opening and reforming were identified in the vertical variation of magnetic concentration parameters although the record of the three cores is not completely consistent the results point out that magnetic concentration parameters can reflect the development and pollution history in surrounding coastal areas

radiogenic helium in shallow groundwater within a clay till southwestern ontario 1 profiles of 4he in pore water were measured in clay aquitards in sw ontario the 4he distributions are consistent with groundwater velocities that are 70 of initial 4he for 50 to 60 ka prior to incorporation into the till

helium diffusivity and fluxes from a sedimentary basin permo carboniferous trough northern switzerland abstract abundances of radiogenic he and ar isotopes observed in ground waters of the permian carboniferous terrigenous sediments pct in northern switzerland exceed those in the overlaying muschelkalk and underlying crystalline basement aquifers eliminating external sources of these species in this case a comparison of the observed abundances with those in situ generated sheds light on mobility of noble gases generated in the pct detailed studies of the parent element and he isotope concentrations in the pct rocks mineral separates pore and ground waters along with the data on logging and porosity allow he isotope production and redistribution in the pct rock water system to be understood and quantified the pct shales generate most of 3he and 4he and both isotopes are almost completely released from the shales into pore space and migrate either into the aquifers with movable waters and further out of the pct or into gas fluid inclusions of the rock forming minerals quartz and plagioclase here we present a he concentration profile based on i helium measured concentrations in ground water samples from 5 aquifers available within the cross section studied ii helium concentrations in 15 pct pore water samples derived from the he partial pressure in gas fluid inclusions recovered by special extraction saturation experiments in order to estimates the rates of he migration through the pct we compare the produced and observed abundances within the frame of 1d diffusion model only two parameters the diffusion coefficient for the whole sequence dall 4 1 10 3 m2 year 1 and the rate of he removal from the crystalline aquifers cr 1 4 10 6 year 1 are required to obtained a good agreement between the observed and calculated he concentrations in pct waters the minimal square deviations are 2 to 3 10 8 mol cm 3 h2o comparable with the accuracy of measurements the following parameters were derived from the modeling the reduction factor dall d0 0 013 the he diffusion fluxes into the overlaying muschelkalk and underlying crystalline aquifers fmu 1 4 10 7 mol m 2 year 1 and fcr 0 24 10 7 mol m 2 year 1 respectively from these values we calculated the mean helium residence times in pct 120 ma and in muschelkalk aquifer 6 ka the relationships between he diffusivities of the pct and the underlying crystalline basement are discussed we further compare our results with other estimates of he mobility in low permeable sediments

geographical distribution of 3he 4he ratios in japan implications for arc tectonics and incipient magmatism the 3he 4he and 4he 20ne ratios of 115 natural gas samples including various types of gases from volcanoes hot springs mineral springs water wells petroleum fields and natural gas fields were measured using a mass spectrometer the observed 3he 4he and 4he 20ne ratios range from 7 47 10 8 to 9 65 10 6 and from 0 26 to 1100 respectively the 3he 4he ratios reflect well the geotectonic structure of the japanese islands in northeastern ne japan there is a clear geographical difference in the 3he 4he ratios between the frontal arc forearc and volcanic arc back arc regions lower ratios were found in the trench side region and higher ratios in the back arc side this result suggests that the mantle derived helium in the volcanic arc region is associated with the diapiric uprise of a magma lower 3he 4he ratios in the frontal arc region may be due to radiogenic he produced by radioactive decay of u and th in the crustal and sedimentary rocks in southwestern sw japan there is no clear geographical contrast in the 3he 4he ratios some samples in the frontal arc region show quite high 3he 4he ratios the tendency of the 3he 4he ratios agrees with the distribution of terrestrial heat flow data and reflects geotectonic structures different from ne japan the high 3he 4he ratios observed in the frontal arc region in sw japan may be indicative of renewed or incipient magmatism due to a descending young and warm slab

modelling of helium transport in groundwater along a section in the pannonian basin underground water flow in sedimentary basins controls the distribution of dissolved salts and gases and their concentrations may therefore be used as indicators of the flow direction recent measurements of the 4he concentration in deep waters of the pannonian basin have great importance in this respect this paper presents an example of the simultaneous computation of water flow and helium distribution along a section crossing the great hungarian plain the model consists of three permeable layers the boundaries of the layers are prescribed using geologic sections constrained by ample borehole and seismic data the results of the finite difference calculations are fitted to the observed helium concentrations using a least squares algorithm that varies the model parameters the significance of the model is that it reconstructs the structure and flux of the groundwater flow and estimates the poorly known hydrogeological parameters of the flow regime such as hydraulic conductivities conductivity anisotropy and dispersion coefficients the statistical uncertainty of the estimated parameters is around half an order of magnitude an estimate of the regional average of the incoming helium flux is also obtained the total helium flux in the great hungarian plain at the surface is within the range observed in old stable continental areas of the earth

helium accumulation in groundwater iii limits on helium transfer across the mantle crust boundary beneath australia and the magnitude of mantle degassing abstract the groundwaters of the great artesian basin australia have been previously shown to be accumulating in situ production helium for groundwaters ages 100 kyr 1 2 new helium isotope measurements show that the observed in situ production helium 3he 4he 1 6 10 8 is isotopically distinct from the crustal degassing helium flux 3he 4he 6 6 10 8 furthermore the crustal degassing helium isotope ratio is marginally in excess of the whole crustal production ratio 3he 4he 3 5 10 8 and the production ratio in a variety of continental rock types this suggests that the upper limit on volatile transport across the mantle crust boundary beneath the relatively stable and complacent australian continent can be characterized by a conductive diffusive helium heat flux ratio of 2 6 1064he atoms mw 1 s 1 which is two orders of magnitude less than the intrusive volcanic ratio of 2 9 1084he atoms mw 1 s 1 measured at the galapagos 16 these results constrain the transcrustal mantle degassing fluxes of4he and40ar to be much less than the mid ocean ridge degassing fluxes which are much less than the degassing of4he and40ar from continental crust thus the degassing of the earth s interior is dominated by magmatic processes but the dominant fluxes of4he and40ar to the atmosphere must come from the continental crust

a simple model for the interpretation of magnetic records in lacustrine and ocean sediments abstract many sources of magnetic minerals have been implicated as potential influences on the magnetic record of lake and ocean sediments the state of the art of our knowledge of these sources and their properties has been used to define a model which indicates those sedimentary environments where specific magnetic mineral sources may influence the magnetic record authigenically formed magnetic minerals are only likely to be found in estuaries and eutrophic lakes cosmic deposition eolian deposition and magnetic bacteria may be important in low accumulation rate deep ocean sediments whereas catchment derived material is only likely to be the sole source of the magnetic record in high accumulation rate low productivity lakes fly ash is only likely to be a dominant source in very low accumulation rate lake and ocean sediments

quantitative study of geochemical processes in the dogger aquifer paris basin france the quantification of geochemical reactions in hydrothermal aquifers requires an exhaustive approach because of their interdependence all chemical elements likely to have a quantitative influence on dissolution or precipitation reactions have to be taken into account geochemical constraints the number of which equals the number of the chemical elements were determined with the help of chemical analyses of the solution in the case study of the dogger aquifer paris basin france 12 elements are taken into account al c cl ca f h k mg na o s si three constraints apply to water activity neutrality and conservation of chloride in aqueous solutions the determination of the remaining constraints was based on saturation indices stability diagrams of minerals and partial pressure of carbon dioxide pco2 the present day solutions are at equilibrium with respect to nine minerals albite anhydrite chalcedony calcite dolomite fluorite kaolinite k feldspar and illite or chlorite thus it was demonstrated that the composition of these solutions including computed pco2 is only a function of temperature and chloride content moreover it was possible to test the validity of the geochemical system by computing its speciation and comparing these theoretical results with actual chemical analyses ph and concentrations finally geochemical simulations were used in predicting what quantities would be dissolved or precipitated as either the temperature or the chlorinity varied although the rock is predominantly calcareous these quantities could not be determined if the influence of the aluminosilicates were neglected this chemical component approach with which one can pose and solve rigorously the chemical equilibrium problem constitutes a prerequisite for the quantitative study of geochemical processes related to fluid flow

sulphur and oxygen isotopes of dissolved sulphur species in formation waters from the dogger geothermal aquifer paris basin france isotopic analyses of the s in sulphides and sulphates from formation waters were made at 35 geothermal wells exploiting the dogger geothermal aquifer of the paris basin isotopic analyses of the o of the dissolved sulphates were also made on 12 of these the results show a distribution of the 34s of the sulphates according to geographic zones that also correspond to variations in the geochemistry of the fluids in particular the sulphide content samples taken in the seine st denis area and in the areas north and west of paris show high 34s values ranging from 26 3 to 48 9 values of 34s for sulphides range from 8 5 to 5 and are interpreted as reflecting the effect of bacterial reduction in a confined part of the basin modelling this reduction by a rayleigh distillation mechanism made it possible to calculate a value of 1 038 0 003 for the coefficient of fractionation between the sulphates and sulphides we show that an important part of the sulphides formed by bacterial reduction has been subtracted from the fluid by deposition south of paris and in the val de marne the 34s values for the sulphates are more uniform ranging between 22 4 and 26 6 despite the existence of bacterial activity this is most probably due to a higher rate of flow of the waters entailing renewal of the sulphate stock the isotopic composition of the o of the sulphates for the seine st denis area and the areas west and north of paris is very uniform between 16 1 and 17 1 despite the wide range in 34s 26 3 to 48 9 for the same samples the calculated isotopic temperatures are close to those measured in situ these results suggest either that sulphate water isotopic equilibrium was established after the reduction or that the coefficient of o fractionation is very low 1 003 during bacterial reduction

3h 3he 14c and u th he groundwater ages in the st lawrence lowlands quebec eastern canada abstract this study attempts to place constraints on groundwater residence times using helium isotopes and 14c of a regional groundwater flow system the becancour river watershed located midway between montreal and quebec city quebec canada this densely populated region is one of the main targets for shale gas exploitation in eastern canada for this reason this watershed has been the focus of a detailed aquifer study to gain a better understanding of groundwater resources both in terms of availability and quality in the current study noble gases were sampled and analyzed in twenty eight wells from a quaternary granular aquifer and a regional bedrock aquifer of ordovician age tritium 3h and radiocarbon a14c activities were measured on selected wells helium isotopic ratios 3he 4he r normalized to that of the atmosphere ra 1 386 10 6 range from r ra 0 039 0 003 to 3 109 0 065 the helium isotopic signatures point to the presence of three water bodies 1 modern infiltration water with nearly atmospheric helium isotopic ratio and little post bomb tritium recharging the shallower granular aquifer 2 mid 50s tritium rich water slightly mineralized and 3 an older water component rich in terrigenic helium flowing in from the bedrock fractured aquifer uncorrected 14c ages range from 15 ka to modern 14c is affected by several dead carbon reservoirs related to carbonate dissolution cations exchange oxidation of organic matter and methanogenesis adjusted 14c ages calculated with netpath range from 7 ka to modern older 14c ages correspond to the end of the regional re organization of the hydrological system following deglaciation and isostatic rebound noble gas recharge paleotemperatures are 4 9 c colder than the present temperatures although no clear relation with ages has been found the relationship between the helium isotopic ratios and 14c ages suggests that the regional bedrock aquifer is affected by mixing between these three water sources calculated u th 4he ages can be partially explained by in situ production of 4he in the aquifer rock and the addition of a radiogenic helium source external to the aquifer calculated minimum helium fluxes of 1 0 10 8 to 1 8 10 7 cm3 stp cm 2 yr 1 are tens to hundreds of times lower than the average continental crust flux of 3 3 10 6 cm3 stp cm 2 yr 1 suggesting local sources possibly from production of radiogenic helium in the shale gas formations underlying the studied aquifers the occurrence of old groundwater in this aquifer system clearly limits the renewable resource and increases the risk of overexploitation in the case of increased use or in the case of pollution from different sources

fossil brines preserved in the st lawrence lowlands quebec canada as revealed by their chemistry and noble gas isotopes abstract brines in cambrian sandstones and ordovician dolostones of the st lawrence lowlands at becancour quebec canada were sampled for analysis of all stable noble gases in order to trace their origin and migration path in addition to quantifying their residence time major ion chemistry indicates that the brines are of na ca cl type possibly derived from halite dissolution 87 sr 86 sr ratios and ca excess indicate prolonged interactions with silicate rocks of the proterozoic grenville basement or the cambrian potsdam sandstone the brines constrain a 2 3 contribution of mantle 3 he and large amounts of nucleogenic 21 ne and 38 ar and radiogenic 4 he and 40 ar 4 he 40 ar and 21 ne 40 ar ratios corrected for mass fractionation during incomplete brine degassing are identical to their production ratios in rocks the source of salinity halite dissolution plus the occurrence of large amounts of 40 ar in brines constrain the residence time of becancour brines as being older than the cretaceous evaporites in the st lawrence lowlands likely existed only during devonian silurian time brines might result from infiltration of devonian water leaching halite penetrating into or below the deeper cambrian ordovician aquifers during the devonian the basin reached temperatures higher than 250 c allowing for thermal maturation of local gas prone source rocks utica shales and possibly facilitating the release of radiogenic 40 ar into the brines the last thermal event that could have facilitated the liberation of 40 ar into fluids and contributed to mantle 3 he is the cretaceous monteregian hills magmatic episode for residence times younger than the cretaceous it is difficult to find an appropriate source of salinity and of nucleogenic radiogenic gases to the becancour brines

mineral magnetic properties of holocene lake sediments and soils from the karsa valley lappland sweden and their relevance to palaeoenvironmental reconstruction a mineral magnetic study of lacustrine sediments and soils from the karsa valley in lappland sweden was undertaken to estimate the potential of mineral magnetic techniques in elucidating the variability of climate recorded by glacier fluctuations and soil development sediment cores from two lake basins receiving sediment input from a glacial outflow stream and their respective catchments show a mineral magnetic record that can be interpreted in terms of glacial activity and soil development dissolution of magnetite is indicated during periods of climatic amelioration and causes a high s ratio during periods of glacial advance and colder wetter climate the minerogenic sediment supply is increased and magnetite is preserved in the sediment resulting in a low s ratio variations in the s ratio can then be used as a proxy climate indicator

thermal evolution of the intracratonic paris basin insights from 3d basin modelling abstract the thermal evolution of the paris basin pb has been widely studied using 1d 2d and more rarely 3d thermal models it is well documented that the pb experienced higher temperatures in the past compared to what is currently observed however a quantitative analysis of the main processes and parameters that affect the temperature distribution at the basin scale and over time is still not available in this study through basin modeling which accounts for the main processes of the thermal evolution of sedimentary basins we analyze and quantify the role of the different geological mechanisms by discriminating the causes of abnormal temperatures during the late mesozoic this is done with a 3d basin model built from base moho to present day topography using the temisflow basin modelling software the model includes thermal processes within an evolving upper crust defined by three main structural domains each crustal sector presents radiogenic heat production conductivity and thickness values which are used as input parameters to reproduce the paleo and present day basal heat flow variations observed in the basin the model calculates heat flow through time in both crust and sedimentary column where the crust is coupled with the geological evolution of the basin this approach allows estimating the eroded thickness during the main tertiary uplift event and therefore the maximum temperature in the late cretaceous the model is constrained by different types of paleo thermo chronometers and by 52 wells that are regionally distributed over the entire basin resulting in a new regional thermal history of the pb the amount of missing section in the cretaceous chalk which mainly affected the eastern part of the basin is increased by up to 500m compared with previous studies and constitutes the key controlling factor of the temperature evolution this new regional thermal history of the paris basin may be important for further analysis of the hc generation from the lower jurassic toarcian source rock and bring new insights into the geothermal potential of the basin

chlorine 36 dating of very old groundwater 1 the great artesian basin australia chlorine 36 has many advantages as a dating tool for very old groundwater these advantages include a suitable half life 3 01 x 10 sup 5 years simple geochemistry conservative behavior in groundwater and a general absence of subsurface sources at levels comparable to the atmospheric input recent advances in tandem accelerator mass spectrometry have permitted the analysis of sup 36 cl at low abundance expected following residence in the subsurface for 10 sup 6 years or more in order to test the suitability of sup 36 cl for dating very old groundwater the sup 36 cl cl ratios of 26 groundwater samples from the great artesian basin of australia have been measured groundwater ages calculated from the sup 36 cl data compare favorably with ages computed independently from hydrodynamic simulations

crustal helium in deep pacific waters we have analyzed deep helium isotope data from world ocean circulation experiment section p17 along 135 w in the pacific ocean combining these data with neon data we have derived the isotopic ratio rt of the nonatmospheric part of helium terrigenic helium the calculated rt values are significantly lower than helium isotope ratios from mid ocean ridge mor sources rmor 8ra ra 3he 4he air which are generally presumed to dominate the isotope characteristics of helium of nonatmospheric origin for the depths most influenced by the southern east pacific rise epr helium plume the isotopic ratio of terrigenic helium is 7 4 ra however both the northern epr plume and the juan de fuca ridge jdfr plume show significantly lower rt values of 6 8 ra we find minimum rt values of 5 6 ra at about 20 n to 30 n from 2000 m depth to the ocean floor we conclude that in addition to the epr and jdfr helium sources having mor isotope characteristics there is a flux of radiogenic 4he out of deep sea sediments and the oceanic crust which causes a significant deviation of rt toward values lower than rmor using our calculated terrigenic 4he concentrations and isotope ratios rt and the helium isotope ratios of the two end members mor helium and crustal helium we derive concentrations and ocean bottom fluxes of crustal 4he 4hecrust maximum concentrations of 4hecrust up to 30 pmol kg 1 are found at about 20 n to 30 n between 2000 m and 4000 m along the p17 section the mean crustal 4he flux is obtained as 1 0 0 4 109 atoms m 2earth s 1

time lag of the earthquake energy release between three seismic regions three complete data sets of strong earthquakes m 5 5 which occurred in the seismic regions of chile mexico and kamchatka during the time period 1899 1985 have been used to test the existence of a time lag in the seismic energy release between these regions these data sets were cross correlated in order to determine whether any pair of the sets are correlated for this purpose statistical tests such as thet test the fisher s transformation and probability distribution have been applied to determine the significance of the obtained correlation coefficients the results show that the time lag between chile and kamchatka is 2 which means that kamchatka precedes chile by 2 years with a correlation coefficient significant at 99 80 level a weak correlation between kamchatka mexico and noncorrelation for mexico chile

correlation between dissolved 4he concentration and 36cl in groundwater at aspo sweden abstract tunnel excavation at aspo island sweden has caused severe groundwater disturbance gradually extending deeper into the tunnel as present day baltic seawater intrudes through fractures connecting to the surface however the paleo hydrogeochemical conditions have remained in the deep highly saline waters that have avoided mixing a correlation has been observed between dissolved 4he concentration and cl ion concentration measured every two years from 1995 to 2001 at aspo groundwater mixing conditions can be examined by the correlations between 1 cl 36cl cl and 3h concentrations subsurface production is responsible for the majority of the 36cl and excess dissolved 4he of interstitial groundwater in fractures the secular equilibrium ratio of 36cl cl in rock was theoretically estimated to be 5 05 0 82 10 14 based on the neutron flux intensity a value comparable to the measured 36cl cl ratio in rock and groundwater the degassing crustal 4he flux was estimated to be 2 9 10 8 1 3 10 6 ccstp cm2a using the hto diffusion coefficient for the aspo diorite the 4he accumulation rate ranges from 6 8 10 10 for the in situ accumulation rate to 7 0 10 9 ccstp gwater a considering both 4he in situ production and the degassing flux assuming 4he is accumulated constantly in groundwater by comparing the subsurface 36cl increase with 4he concentrations in groundwater the 4he accumulation rate was determined from data for groundwater arriving at the secular equilibrium of 36cl cl the 4he accumulation rate was found to be 1 83 0 72 10 8 ccstp gwater a without determining the magnitude of degassing 4he flux

dating very old pore waters in impermeable rocks by noble gas isotopes the sup 4 he sup 40 ar and sup 136 xe content dissolved in the pore water of sedimentary rock samples was measured on samples from borehole cores near the repository for nuclear waste in morsleben germany due to the very low permeabilities of the rock formations conventional groundwater sampling was almost impossible hence the authors developed a new sampling method for noble gases in the pore water of freshly drilled rock cores this method provides vertical noble gas profiles in high depth resolution even in impermeable rocks by application of the new technique quantitative age information of groundwater and pore water have been derived the authors find palaeowaters from the last glaciation depleted in delta d and delta sup 18 o with a sup 4 he age of about 55 kyr the high saline pore solutions below are at least 6 mio years old this has been concluded from the profiles of radiogenic sup 4 he and sup 40 ar close to diffusion in steady state and from xenon isotopes produced by spontaneous fission of sup 238 u in the rocks a sup 4 he flux of 2 center dot 10 sup minus 7 cc stp cm sup 2 yr is derived from the profile which is due to local sup 4 he production within the investigatedmore sediments less

loess stratigraphy in central china abstract the loess deposits in central china record world wide climate changes of the last 2 5 ma numerous climatic oscillations are marked by alternating loess and soil units with continuous coverage of the matuyama and brunhes epochs magnetic susceptibility of the deposits correlates closely with the oxygen isotope record of the deep sea sediments and provides an independent measure of climate and time the key marker bed of the chinese loess sequence is the paleosol s5 the time equivalent of the mid brunhes oxygen isotope stages 13 14 and 15 it marks a prolonged interval of warm humid climate lasting from approximately 615 to 470 thousand years ago several episodes of river downcutting coincide with deposition of the exceptionally thick loess units l1 oceanic oxygen isotope stages 2 to 4 l2 stage 6 l5 stage 12 l6 stage 16 l9 stage 22 l15 stage 38 about 1 15 ma and ws4 about 2 3 ma these erosional events are interpreted as a result of episodic uplift of the loess plateau the deposition of the earliest loess layers between 2 5 and 2 3 ma ago marks a first order shift from warm and humid environments toward harsh continental steppes comparable to those of the middle and late pleistocene little if any lithologic or paleontologic changes were noted within or above the olduvai magnetozone so that the proposed plio pleistocene boundary at approximately 1 65 ma has no lithostratigraphic and biostratigraphic representation in the chinese loess series comparison with the deep sea drilling program core 552a in the north atlantic and with the santerno river section near bologna shows that the occurrence of the earliest loess in china coincides with the timing of the first significant ice rafting in the north atlantic and with the appearance of cold water foraminifers in the marine deposits of northern italy an extension of the stage system of the oxygen isotope signal extended back to the gauss matuyama boundary is proposed

canadian shield brine from the con mine yellowknife nt canada noble gas evidence for an evaporated palaeozoic seawater origin mixed with glacial meltwater and holocene recharge abstract dissolved noble gas concentrations were measured in high salinity 270 g l ca na cl groundwaters from the con mine yellowknife canada in an effort to discriminate between two possible origins as either a brine generated by evaporative enrichment in a paleozoic inland sea or marine water concentrated by freezing during glacial times major ion and isotope geochemistry indicate that brines from the deepest level remain relatively undisturbed by mixing with modern water introduced by mining mixing calculations are used to quantify fractions of brine glacial meltwater and modern water from this noble gas concentrations were corrected for excess air with ne and normalized to 100 brine solution over pressuring of helium and argon in the brine provide age constraints based on the accumulation of geogenic 4he and 40ar radiogenic age calculations together with the local geological history suggest brine emplacement during early palaeozoic time likely during the devonian when evaporitic inland seas existed in this region the concentrations of the atmospherically derived noble gases in the brine fraction kr 1 4e 8 xe 8 5e 10 cc stp cc h 2 o are close to atmospheric equilibrium for brine at 25 c kr 7 3e 9 xe 8 0e 10 cc stp cc h 2 o but are far lower than would be expected for closed system concentration of seawater by freezing kr 2 8e 6 xe 4 2e 7 cc stp cc h 2 o thus despite the complicated mixing history of the brine the atmospheric and geogenic noble gases provide strong evidence for an origin as air equilibrated brine from evaporated paleozoic seawater which infiltrated via density displacement through existing fractures and faults into the canadian shield

mineral magnetic characterization of sediment sources from an analysis of lake and floodplain sediments in the catchments of the old mill reservoir and slapton ley south devon uk research on suspended sediment transport in the catchments of the old mill reservoir and slapton lower ley south devon has attempted to discriminate changing catchment sources on the basis of downcore variations in the mineral magnetic properties of lake reservoir and floodplain sediments here we examine these downcore variations and also explore the variability in catchment sources and the influence of topographic controls on mineral magnetic signatures of topsoils and subsoils particle size controls on the mineral magnetic signatures are explored by an analysis of a fractionated sediment sample whilst the possible impact of diagenesis is assessed by an examination of the mn profiles in the lake and reservoir sediments from this analysis it is evident that the mineral magnetic signatures of well sorted floodplain deposits are more likely to reflect the particle size composition of the transported material by contrast the mineral magnetic record in the sediment of slapton ley appears to be most strongly influenced by dissolution of magnetic minerals the sediment of the old mill reservoir provides the only suitable record for the application of a simple mixing model which is developed in order to quantify changes in the relative contribution of topsoil and subsoil through time the research has important implications for attempting to reconstruct sediment sources in highly eutrophic lakes and emphasizes the uncertainty in the application of simple mixing models 1998 john wiley sons ltd

environmental magnetism past present and future environmental magnetism involves the application of rock and mineral magnetic techniques to situations in which the transport deposition or transformation of magnetic grains is influenced by environmental processes in the atmosphere hydrosphere and lithosphere the first explicit description of environmental magnetism as a distinct field was in 1980 since that time environmental magnetism has become a broad field that is finding application in an ever increasing array of scientific disciplines in this review of the present state of environmental magnetic studies we divide the field into three broad but arbitrary categories the first involves the use of mineral magnetic assemblages in the geological record to study physical processes in depositional environments this category includes the correlation of sediment cores using magnetic susceptibility measurements studies of geomagnetic field behavior the analysis of depositional and postdepositional mechanical processes that affect sediments and the examination of magnetic parameters that might represent proxies for paleoclimatic variation the second category encompasses studies of the processes responsible for variations in the magnetic minerals brought into a sedimentary environment these provenance investigations include studies of changes in catchment derived sediment in lakes fluctuations in contributions from terrigenous aeolian and glaciogenic components in deep sea sediments and the origin of atmospheric particulates the final category addresses in situ changes and transformations of magnetic minerals in sedimentary environments including pedogenesis authigenetic diagenetic formation of ferrimagnetic phases dissolution of magnetic minerals due to reductive diagenesis and contributions of biomagnetism to sedimentary magnetism because environmental magnetism can address problems in so many disciplines and because many of these problems may be inaccessible to other techniques it is likely that the scope of environmental magnetism will continue to expand rapidly environmental magnetism is capable of providing important data for studies of global environmental change climatic processes and the impact of humans on the environment all of which are major research initiatives in the international scientific community these factors suggest that environmental magnetism has a bright and diverse future

3 he 4 he ratios in ch 4 rich natural gases suggest magmatic origin natural gas and oil fields commercially exploited since the 1950s are distributed in the zonal area facing the sea of japan in north east japan we report here measurements of the 3he 4he ratios in 27 ch4 rich natural gases obtained from commercial oil and gas wells in the area we observed extraordinarily high 3he 4he ratios up to 8 65 10 6 in gases from wells drilled into deep reservoirs in volcaniclastic rock formations the so called green tuff fig 1 these values are almost identical to those of volcanic fumaroles in the japanese islands in contrast gases in shallower sedimentary rock reservoirs have low 3he 4he ratios with a minimum value of 0 3 10 6 these low values are similar to those of natural gases originating from biological materials this suggests that the formation of natural gas reservoirs in the volcaniclastic rock may be attributed to large scale magmatic activities which occurred in the middle miocene

water circulation control on carbonate δ18o records in a low permeability clay formation and surrounding limestones the upper dogger oxfordian sequence from the eastern paris basin france abstract upper dogger to oxfordian formations in the eastern part of the paris basin france are currently being investigated by the french nuclear waste management agency andra testing the feasibility of long term deep nuclear waste disposal in the callovo oxfordian claystones characterising the hydrogeological behaviour of the callovo oxfordian claystones is therefore essential in evaluating its potential as a geological barrier in order to evaluate and quantify water rock interactions experienced over geological time by these formations bulk carbonate 13 c and 18 o were measured and calculations of water rock ratios were used to explain carbonate 18 o changes meteoric porewater and a maximum temperature reached of about 40 c were considered the jurassic marine carbonate 13 c was preserved in the callovo oxfordian claystones and in the overlying limestones 0 28 to 3 39 pdb while the 18 o values are lower by 0 5 6 25 to 1 32 pdb calculations show that upper dogger and oxfordian limestone 18 o data i have random like distribution through theoretical 18 o w r curves and ii suggest that water rock ratios 0 08 0 4 needed to explain 18 o changes are higher by a factor of about 2 20 compared to the present day water rock ratio these features indicate advection in both aquifers according to the history of the paris basin this hydrogeological behaviour could have been effective since jurassic cretaceous transition times inversely the carbonate 18 o content trends observed for the callovo oxfordian data show that changes were controlled by post depositional fluid rock interaction with water rock ratio 0 02 0 15 similar to the present day porewater rock ratio the 130 m thick callovo oxfordian claystone appears remarkably homogenous regarding its hydrogeological properties this study suggests an initial marine porewater replacement by meteoric water only after porosity was reduced to its present value thus demonstrating that the callovo oxfordian clay has mainly been isolated from advective meteoric water circulation only the upper 20 m of the callovo oxfordian claystone formation underwent heterogeneous water rock exchange w r from 0 01 to 0 3 probably as a result of its mineralogical heterogeneity and proximity to the advective oxfordian limestone aquifer this study of carbonate 18 o confirms the hydrogeological barrier properties of the callovo oxfordian clay and suggests that it has been a natural hydrological barrier since the earliest times of its diagenesis

establishing constraints on groundwater ages with 36cl 14c 3h and noble gases a case study in the eastern paris basin france abstract groundwaters from the tithonian kimmeridgian oxfordian and upper dogger aquifers within the eastern part of the paris basin france were characterised using 3 h 14 c and 36 cl and noble gases tracers to evaluate their residence times and determine their recharge period this information is an important prerequisite to evaluating the confinement properties of the callovo oxfordian clay formation sandwiched between the oxfordian aquifer and the dogger aquifer currently being investigated by the french nuclear waste management agency andra for radioactive waste disposal data presented in this paper are used to test 4 hypotheses 1 the oxfordian limestone is isolated from the overlying tithonian kimmeridgian surface aquifer this first hypothesis is supported by the presence of measurable 3 h activities in groundwaters from the surface aquifer 6 11 tu and by its absence in groundwaters derived from deeper aquifers 2 the callovo oxfordian clay sequence in the vicinity of the url serves as an effective barrier to advective flow and transport between the underlying upper dogger aquifer and the overlying oxfordian limestone aquifer this second hypothesis is supported by relatively low concentrations of cl 3 5 78 mg l 1 na 15 145 mg l 1 br 0 08 0 4 mg l 1 and 4 he rad 0 2 2 3 ccstp g 1 and slightly higher 36 cl cl ratios 2 7 59 10 15 at at 1 in groundwaters from the oxfordian aquifer compared to those from the upper dogger aquifer 345 4027 mgcl l 1 402 2390 mgna l 1 1 8 22 2 mgbr l 1 1 6 37 2 ccstp he g 1 1 5 10 15 at 36 cl at 1 cl 3 groundwaters from the oxfordian aquifer in the vicinity of url are pre holocene with residence times exceeding 10 ka geochemical and isotopic lines of evidence for this hypothesis include a 13 c values measured on oxfordian aquifer waters that are close to 13 c of the aquifer matrix reflecting strong isotopic exchange over several thousand years b noble gas temperatures that indicate recharge temperatures between 3 and 8 6 c lower by 2 7 c than the modern average temperature in this area c radiogenic 4 he concentrations between 0 16 10 5 and 2 3 10 5 ccstp g 1 of water about 2 3 orders of magnitude greater than the 4 he concentration of air equilibrated water 4 groundwater residence time for the upper dogger aquifer in the vicinity of the url probably exceed several hundred thousand years such long residence times are indicated by the accumulation of radiogenic he up to 37 10 5 ccstp g 1 assuming a closed system primary contributors to uncertainties in interpretation of the data presented in this paper are the lack of well defined 36 cl cl input ratio knowledge about the 4 he rad sources for oxfordian and dogger aquifers knowledge about transport processes occurring through the dogger aquifer and the extensive dilution of initial 14 c activities by dissolution exchange with aquifer matrix overall however although the data presented in this paper remain semi quantitative due to inevitable intrinsic limitations of the methods none contradict the hypotheses of long residence times and aquifer isolation in the vicinity of the url

geochemical evidence for efficient aquifer isolation over geological timeframes aquitards layers of rock having low permeability have been suggested as potential long term reservoirs for toxic materials such as nuclear or chemical waste but information about the isolation properties of aquitard layers is essential to evaluate whether they can indeed be used safely as reservoirs here we investigate the long term mobility of groundwaters between two aquifers surrounding an aquitard layer in the eastern recharge area of the paris basin france using helium isotopes as a geochemical tracer the deeper trias sandstone aquifer which lies above the crystalline basement accumulates radiogenic 4he and primordial 3he from large regions of the crust and mantle at rates comparable to the degassing of the whole crust1 and of mid ocean ridges2 we show that the overlying carbonate dogger aquifer which is separated from the trias aquifer by an aquitard layer consisting of a 600 m succession of shales and clays is stagnant and has been extremely well isolated from the trias over the past several million years this finding together with previous studies at the centre of the paris basin3 4 shows that diffusive mass transfer across aquitards is negligible and that cross formational flow in basins takes place preferentially in faulted areas

basin scale thermal and fluid flow histories revealed by carbonate clumped isotopes δ47 middle jurassic carbonates of the paris basin depocentre the reconstruction of past diagenetic conditions in sedimentary basins is often under constrained this results from both the analytical challenge of performing the required analyses on the minute sample amounts available from diagenetic mineral phases and the lack of tracers for some of the diagenetic parameters the carbonate clumped isotopes thermometry 47 opens new perspectives for unravelling the temperatures of diagenetic phases together with the source of their parent fluids two parameters that are otherwise impossible to constrain in the absence of exploitable fluid inclusions here is reported the study of a large number of sedimentary and diagenetic carbonate phases from middle jurassic reservoirs of the paris basin depocentre by combining detailed petrographic observations with a large number of 47 data n 45 on a well documented paragenetic sequence including calcite and dolomite burial cements the data reveal carbonate crystallization at temperatures between 29 c and 98 c from fluids with 18owater values between 7 and 2 in response to the progressive burial and uplift of the paris basin throughout 165 myr of basin evolution coupled to the time temperature evolution previously estimated from thermal maturity modelling these temperatures allow determining the timing of four successive cementation episodes the overall dataset indicates a history of complex water mixing with a significant contribution of hypersaline waters from the triassic aquifers migrated upward along faults during the cretaceous subsidence of the basin subsequent large scale infiltrations of meteoric waters induced a dilution of these pre existing brines in response to the paris basin uplift in the tertiary overall the data presented here allow proposing an integrated approach to characterize the cementation events affecting the studied carbonate reservoir units based on temperature oxygen isotope composition and salinity of the parent fluids as well as on petrographic grounds this article is protected by copyright all rights reserved

atmosphere derived noble gas evidence for the preservation of ancient waters in sedimentary basins hydrological modeling of the middle jurassic carbonate aquifer of the paris basin indicated fluid residence time from 1 k y to 100 k y whereas the chemistry of waters suggested longer residence time here we report independent water age estimates on the basis of atmosphere derived noble gas recharge paleotemperatures the calculated paleotemperatures range from 15 to 26 c and are related to the stable isotope composition and the salinity of the waters and the distance from the recharge the spatial distribution of the paleotemperatures suggests 1 occurrence of old saline waters in the center of the basin which infiltrated during the warmer climate interval in the tertiary eocene and 2 dilution by recent fresh waters early pleistocene flowing from the recharge these results strongly suggest that deep aquifers in sedimentary basins can store waters for very long periods of time in contrast to the conclusions reached from hydrological modeling

helium isotope fluxes and groundwater ages in the dogger aquifer paris basin the dogger aquifer of the paris basin has been shown to be first order homogeneous in its helium concentration and its helium isotopic ratio although slight differences are noted in relation to specific chemical water types the helium isotopic composition of the dogger aquifer contains a small component of mantle helium that is associated with a magmatic input although the heat accompanying this magma is small constraints on the age of the overlying albien aquifer are used to calculate the flux of helium out of the dogger this constraint allows a calculation of the residence time of waters in the dogger aquifer of 4 myr 50 which is significantly longer than estimates derived from hydrologic models and hydrologic testing it is possible that the hydrologic ages and the helium ages can be reconciled by a vertically layered dogger aquifer with gradients in he salinity and fluid flow vertical profiles of fluid composition helium concentration and permeability are required in the paris basin to resolve this question

diagenesis of magnetic minerals in the recent sediments of a eutrophic lake magnetic mineral assemblages in lake sediments are usulally interpreted as reflecting changing catchment erosion magnetic and chemical assemblages in a small eutrophic lake lough augher northern ireland suggest diagenetic dissolution of fine grained magnetite however probably as a result of changing redox conditions associated with eutrophication water column results show internal cycling of mn and fe from the sediments into the armxic hypolimnion calculations suggest that late summer hypolimnetic fe concentrations are controlled by formation of aulhigenic vivianite sedimentary pore water concentrations of total soluble fe and p suggest a similar process in the sediments the loss of mn from the lake by diffusion from the sediment and washout at overturn is indicated by mn budget calculations and by it marked decrease in its sedimentary concentration reflecting onset of eutrophication as indicated by diatom biostratigraph y the changes in the sediment mn profile are coincident with and in some cases identical to changes in several rnagnctic parameters the changes in magnetic stratigraphy suggest a coarsening of the magnetic grain size and reduction in the total concentration agreement with chemical profiles indicative of changing rcdox suggest that this coarsening results from dissolution of fine grained magnetite catchment stability together with other stratigraphic profiles of eutrophication and changing redox supports the conclusion that the magnetic profiles are reflecting in situ diagenetic changes rather than altered catchment processes with the data available it is not possible to identify the actual clissolution process involved or to determine whether it is chemically or bacterially controlled

distribution of helium and tritium in lake baikal the 3 h 3 he age of a water mass is a measure of the time that has passed since the water mass was last in contact with the atmosphere between 1992 and 1995 a detailed study of 3 h 3 he ages was conducted in lake baikal the deepest and largest lake by volume on earth to investigate deep water renewal in its three major basins maximum 3 h 3 he ages are 14 17 years in the southern basin 16 18 years in the central basin and 10 11 years in the northern basin rates of renewal of deep water with surface water deduced from volume weighted mean 3 h 3 he ages below 250 m depth are about 10 yr 1 in the southern and central basins and 15 yr 1 in the northern basin in the southern basin the mean 3 h 3 he age below 250 m depth increased steadily from 9 6 years in 1992 to 11 years in 1995 indicating a slight diminution in deep water renewal during this time bottom water renewal by large scale advection was estimated from the mass balance of 3 he in the 200 m thick bottom layer of each basin bottom water renewal rates in the northern basin were found to be between 80 and 150 km 3 yr 1 and in the central basin between 10 and 20 km 3 yr 1 whereas in the southern basin they were practically zero correlating oxygen and dissolved helium 4 concentrations with 3 h 3 he age allowed us to determine the mean hypolimnetic oxygen depletion rate in the water column 4 5 mol l 1 yr 1 as well as mean helium fluxes from the lake bottom 2 8 x 10 11 atoms m 2 s 1 in the northern basin and 1 3 x 10 11 atoms m 2 s 1 in the central and southern basins the helium isotope ratio of the terrigenic helium component injected from the lake bottom determined from measurements of water from hydrothermal springs in the vicinity of the lake was found to be 2 2 x 10 7

magnetic and chemical characterisation of a diagenetic magnetic mineral formed in the sediments of productive lakes abstract measurement of low frequency magnetic susceptibility in sediments from several lakes showed that a diagenetically formed magnetic mineral can contribute a significant amount to the intensity of bulk magnetic measurements on anaerobic sediments from productive lakes a single ferrimagnetic mineral containing stable single domains is responsible sequential chemical extraction showed that the mineral is not a carbonate phosphate or partially reduced oxide comparison of changes in magnetic properties with changes in sulphide concentrations suggests that the mineral concentration covaries with sulphide but is not actually a simple iron monosulphide

mantle helium in sacramento basin natural gas wells abstract helium isotope ratios in sacramento basin natural gas wells show a strong mantle signal the3he 4he ratios range from 0 11 times the atmospheric ratio 0 11 ra in the rio vista field to 2 75 ra in the moon bend field indicating that 1 to 34 of the helium is mantle derived 3he 4he versus ch4 4he ratios provide evidence of two component mixing between crustal and magmatic end members extrapolation of the linear regression line to ch4 4he 0 gives a hypothetical magmatic end member 3he 4he ratio of 3 84 ra half the typical mantle ratio this indicates that the magmatic end member may actually represent a mixture of mantle and crustal helium gases which deviate from the simple two component mixture can be explained by addition of pure methane radiogenic 4he or a high n2 he component with 3he 4he 0 6 ra to 1 0 ra the ch4 3he ratio of the magmatic end member remains poorly constrained 0 to 3 109 and one cannot rule out the possibility that a significant proportion of the methane in some fields may be of deep earth origin however fields with the highest 3he 4he ratios are associated with buried plio pleistocene intrusives which have up arched sediments to form hydrocarbon traps the methane in these fields may have been produced by rapid thermal alteration of the intruded sediment elsewhere the methane appears either to have migrated from deeply buried sediments in the western basin or to have been produced by local microbial activity

recent research on the physical aspects of earthquakes abstract recent developments in the field of physical aspects of earthquakes which encompasses in present day terminology the analysis of focal dynamics and of catastrophic effects of earthquakes are reviewed in particular individual sections of this review deal with the earthquake source effects of earthquakes on the ground the geographic and temporal distribution of earthquakes the characterization of seismic risk earthquake prediction and with the artificial release of earthquakes in this instance the review supplements earlier information by the author 1975 by new data published mainly between 1975 and 1984

origin of ore fluids in the muruntau gold system constraints from noble gas carbon isotope and halogen data abstract hydrothermal vein minerals directly associated with native gold mineralization in the muruntau vein system uzbekistan have been studied for noble gas carbon isotope and halogen chemistry of the trapped ore related fluids helium trapped in early arsenopyrite 1 which has preserved the original fluid signature better than associated scheelite and quartz indicates a small input from a mantle source 5 of total he however the overwhelming majority of the he in the fluid 95 is from crustal sources the noble gases ne kr and xe in the sample fluids are dominated by gases of atmospheric origin the carbon isotope 13 c 2 1 to 5 3 and halogen characteristics of the fluids log br cl 2 64 to 3 23 lend further support for the activity of juvenile fluids during the main ore stage the high proportion of crustal components in the ore forming fluids may be explained by intense fluid rock interaction and is also supported by previous nd and sr isotope studies the involvement of a juvenile fluid component during the main stage of hydrothermal activity at muruntau 275 ma can be linked to the emplacement of lamprophyric dikes at muruntau due to apparently overlapping ages for high temperature alteration related ore vein formation and intrusion of the dikes the input of mantle derived fluids possibly related to the hercynian collisional event in the western tien shan stimulated intense fluid rock interaction in the crust in this context the mantle derived fluid should be considered as one possible carrier of metals significant amounts of external meteoric fluids circulating in fracture systems are interpreted to have modified the noble gas signature of fluid in quartz mostly during late low temperature fluid circulation

cross checking groundwater age by 4he and 14c dating in a granite tono area central japan abstract groundwater dating was performed simultaneously by the 4he and 14c methods in granite of the tono area in central japan groundwater was sampled at 30 packed off sections of six 1000 m boreholes 4he concentrations increased and 14c concentrations decreased along a groundwater flow path on a topographic gradient 4he ages were calculated by using the in situ 4he production rate derived from the porosity density and u and th content of the rock neglecting external flux 14c ages were calculated with a noncorrected model in which the initial 14c content was 100 percent of the modern radiocarbon level co 100 pmc a statistical model using the average 14c content of tritium bearing samples co 46 4 pmc and a 13c model based on the isotopic mass balance although the absolute 14c ages calculated by the models were different the relative 14c ages were almost identical the relative 14c ages were considered reliable because dissolved inorganic carbon has no significant geochemical reactions in granite the relation between the 4he ages and the noncorrected 14c ages was 4he age 1 15 14c age 7200 r2 0 81 except in the discharge area the slope of this relation was equivalent to unity which indicates that the 4he accumulation rate is confirmed by the relative 14c ages moreover the accumulated 3he 4he ratio was equivalent to that derived from the 6li n 3h reaction in granite these results show that the accumulated he is of crustal origin produced in situ without external flux except in the discharge area the intercept value of 7200 a implies that the 14c concentrations were diluted due to geochemical reactions tritium bearing samples supported this result simultaneous measurements make it feasible to estimate the accumulation rate of 4he and initial dilution of 14c which cannot be done with a single method cross checking groundwater dating has the potential to provide more reliable groundwater ages the circulation time of the groundwater flow in the tono area may be several tens of thousands of years and the groundwater age calculated from the 4he and 14c ages appears to be consistent with geochemical information such as groundwater types d and 18o

dynamic changes in hydrogeochemical conditions caused by tunnel excavation at the aspo hard rock laboratory hrl sweden abstract hydraulic changes caused by tunneling at the aspo hard rock laboratory hrl in sweden have been investigated over a period of 2a using different hydrochemical approaches i e noble gas content isotopic measurements and major ion concentrations the dissolved noble gases 4he and ne contents and the ratio of 3he 4he 40ar 36ar stable isotopes chemical concentrations of major ions and 36cl cl ratios were determined in groundwater samples collected in the tunnel from borehole sections isolated by inflated packers groundwater was categorized into 3 groups based on 4he and cl contents undisturbed groundwater i e prior to tunnel construction with high 4he and cl contents groundwater that has been gradually changed by mixing with baltic seawater and whose 4he and cl contents have gradually increased with increasing depth and groundwater that has been totally changed due to a rapid mixing of baltic seawater and or shallow groundwater and whose 4he and cl contents are extremely low compared with other samples collected at the same surrounding depth the oldest groundwater with a high salinity of more than 14 000 mg l 1 of cl is estimated to be more than 1 8 ma old the groundwater residence time ranges from 0 9 to 900 ka in the mixing zone groundwater in the disturbed zone where rapid mixing has occurred is hard to date reliably and its primary hydrochemical character has already been lost