structural evolution of the laurentian margin revisited southern quebec appalachians implications for the salinian orogeny and successor basins the laurentian margin of the appalachians is divided into external and internal zones on the basis of metamorphic and structural contrasts in the southern quebec internal zone silurian to early devonian southeast verging structures are superimposed on northwest verging structures whereas most of the external zone lacks such overprints regional backthrust faults define a major upper plate lower plate boundary the external zone rocks are in the hanging wall and internal zone rocks are in the footwall metamorphic rocks with silurian early devonian 40 ar 39 ar ages 430 410 ma characterize the lower plate to the east the saint joseph fault and the baie verte brompton line are southeastdipping normal faults that crosscut the upper plate lower plate boundary metamorphic rocks with middle ordovician 40 ar 39 ar ages 469 461 ma and rocks of the external zone both occur in the downthrown side of the saint joseph fault and the baie verte brompton line u pb and 40 ar 39 ar ages suggest that the northwest verging structures are related to ophiolite obduction and crustal thickening during the taconian orogeny ca 480 445 ma whereas the southeast verging structures formed during silurian early devonian backthrusting and normal faulting the revised structural interpretation has implications for the salinian orogeny and involves 1 southeast directed transport of the taconian crustal wedge of the upper plate followed by normal faulting and juxtaposition with the lower plate along the saint joseph fault and the baie verte brompton line and 2 the forma

characterization of deep saline aquifers in the becancour area st lawrence lowlands quebec canada implications for co2 geological storage the present paper provides a case study of the assessment of the potential for co2 storage in the deep saline aquifers of the becancour region in southern quebec this assessment was based on a hydrogeological and petrophysical characterization using existing and newly acquired core and well log data from hydrocarbon exploration wells analyses of data obtained from different sources provide a good understanding of the reservoir hydrogeology and petrophysics profiles of formation pressure temperature density viscosity porosity permeability and net pay were established for lower paleozoic sedimentary aquifers lateral hydraulic continuity is dominant at the regional scale whereas vertical discontinuities are apparent for most physical and chemical properties the covey hill sandstone appears as the most suitable saline aquifer for co2 injection storage this unit is found at a depth of more than 1 km and has the following properties fluid pressures exceed 14 mpa temperature is above 35 c salinity is about 108 500 mg l matrix permeability is in the order of 3 10 16 m2 0 3 mdarcy with expected higher values of formation scale permeability due to the presence of natural fractures mean porosity is 6 net pay reaches 282 m available pore volume per surface area is 17 m3 m2 rock compressibility is 2 10 9 pa 1 and capillary displacement pressure of brine by co2 is about 0 4 mpa while the containment for co2 storage in the becancour saline aquifers can be ensured by appropriate reservoir characteristics the injectivity of co2 and the storage capacity could be limiting factors due to the overall low permeability of aquifers this characterization offers a solid basis for the subsequent development of a numerical hydrogeological model which will be used for co2 injection capacity estimation co2 injection scenarios and risk assessment

hydrochemical and isotopic δ18o δ2h 87sr 86sr δ37cl and δ81br evidence for the origin of saline formation water in a gas reservoir abstract the permo triassic kangan gasfield in southern iran is composed of an aquifer the kangan aquifer ka and an overlying gas reservoir it is located in the kangan and dalan formations and consists predominantly of limestone and dolomite the kangan gasfield is exploited from 36 wells at depths from 2300 to 2860 m the quality of the produced formation waters pfw varies from fresh to saline with salinities of up to 60 000 mg l the present study aims to identify the origin of the salinity of the pfws the concentration of major ions li sr and br as well as 18o d 87sr 86sr 37cl and 81br isotope compositions of the ka water and pfw samples a fresh and a brine spring and the persian gulf water were all measured the suite of isotopic 37cl and 81br and hydrochemical data li cl and br concentrations and cf index in this study indicates that the salinity origin of the pfws is evaporated seawater which could be either the ka water or the intergranular saturated brine in the kangan gas reservoir kgr both derived from permo triassic evaporated seawater 18o and 87sr 86sr data exclude the ka water as the source of the saline pfw leaving the intergranular brine of the kgr as the most likely source although further isotopic and geochemical tests are needed to verify this this work also proposes for the first time the use of a li cl versus br cl diagram to distinguish between evaporate formation water water modified by halite dissolution and fresh water it is recommended to apply these comprehensive methods to deep brine aquifers especially related to gasfields

topography of the variscan orogen in europe failed not collapsed the variscan orogenic collage consists of three subduction collision systems rheno hercynian saxo thuringian and massif central moldanubian devonian to early carboniferous marine strata are widespread not only in the individual foreland fold and thrust belts but also in post tectonic basins within these foreland belts and on the cadomian crust of peri gondwanan microcontinental fragments which represent the upper plates of the subduction collision zones these marine basins preclude high elevations in the respective areas and also in their neighbourhood widespread late carboniferous intra montane basins with their coal bearing sequences are likewise incompatible with high and dry plateaus while narrow belts with high elevations remain possible along active margins within the orogen comparison of the variscides with the himalaya tibetan plateau is unfounded plausible reasons for the scarcity of high variscan relief include subduction of oceanic and even continental crust subduction erosion orogen parallel extension and most important lithospheric thinning accompanied by high heat flow and magmatism in many areas timing and areal array of magmatism and ht metamorphism are not compatible with a model of tectonic thickening and subsequent gravitational collapse it is suggested instead that lithospheric thinning and heating are due to mantle activities caused by the tethys rift the lower and middle crust were thermally softened and rendered unfit for stacking and isostatic uplift in terms of topography the variscides represent a failed orogen the ht regime also explains the abundance of granitoids and ht lp metamorphic rocks typical of the variscides melting in the ht regime extracted mafic components from variscan and cadomian crust as well as from cadomian metasomatized lithospheric mantle thus mimicking subduction related magmatism the onset of the ht regime at c 340 ma may also have triggered the final ascent of hp uhp felsic metamorphic rocks

the palaeozoic variscan oceans revisited abstract geological evidence supported by biogeographical data and in accord with palaeomagnetic constraints indicates that one ocean models for the variscides should be discarded and confirms instead the existence of three gondwana derived microcontinents which were involved in the variscan collision avalonia north armorica franconia and thuringia subdivided by a failed vesser rift and south armorica central iberia armorica bohemia all divided by small oceans in addition parts of south eastern europe including adria and apulia are combined here under the new name of palaeo adria which was also peri gondwanan in the early palaeozoic oceanic separations were formed by the break up of the northern gondwana margin from the late cambrian onwards most of the oceans or seaways remained narrow but much like the alpine cenozoic oceans gave birth to orogenic belts with hp uhp metamorphism and extensive allochthons the saxo thuringian ocean between north and south armorica and the galicia moldanubian ocean between south armorica and palaeo adria only the rheic ocean between avalonia and peri gondwana was wide enough to be unambiguously recorded by biogeography and palaeomagnetism and its north western arm closed before or during the emsian in europe ridge subduction under the northernmost part of armorica in the emsian created the narrow and short lived rheno hercynian ocean it is that ocean and not the rheic whose opening and closure controlled the evolution of the rheno hercynian foldbelt in south west iberia south west england germany and moravia czech republic devonian magmatism and sedimentation set within belts of early variscan deformation and metamorphism are probably strike slip related the first arrival of flysch on the forelands and or the age of deformation of foreland sequences constrains the sequential closure of the variscan seaways galicia moldanubian in the givetian saxo thuringian in the early famennian rheno hercynian in the tournaisian additional mid to late devonian and partly early carboniferous magmatism and extension in the rheno hercynian saxo thuringian and galicia moldanubian basins overlapped with variscan geodynamics as strictly defined the early carboniferous episode was the start of episodic anorogenic heating which lasted until the permian and probably relates to tethys rifting

a strontium oxygen and hydrogen isotopic composition of brines michigan and appalachian basins ontario and michigan abstract 87 sr 86 sr ratios of brine from samples from the michigan and appalachian basins in ontario and michigan covering the stratigraphic interval from the cambrian to mississippian vary from 0 708 to 0 711 with the exception of the salt units of the salina formation silurian most values are greater than seawater for the time in question indicating water rock interaction the sources of the radiogenic sr has not been identified all samples plot below the gmwl in 18 o 2 h space with the cambrian and ordovician samples closest to the line mixing of brines meteoric and glacial pleistocene water is indicated in some cases the more concentrated brines from each stratigraphic unit show a very narrow spread in values all the ordovician brines show a narrow range over a 200 km area for sr o and h isotopes indicating extensive lateral migration of the fluids strontium in the brine has not equilibrated isotopically with its host rock in some cases the late stage minerals saddle dolomite calcite and anhydrite have the same 87 sr 86 sr ratios as the brine indicating that they precipitated from the brine in isotopic equilibrium

mantle helium in ground waters of eastern north america time and space constraints on sources mantle helium in continental environments is generally considered to be the result of active volcanism and or active extension the latest episodes of volcanism in northeastern north america are the track of the new england hotspot 95 190 ma and the closure of the iapetus sea before 300 ma thus the identification of mantle helium in young ground waters of central new england is counter to the conventional wisdom on the basis of evaluation of helium evolution in emplaced magmas we postulate an aged mantle source for the excess helium component in ground waters of central new england that is either 1 a local near surface emplaced gas rich magma that has retained significant volatiles e g in fluid inclusions or 2 a deeply emplaced gas rich magma with high initial 2 he 4 he 10 5 and helium transport with dispersion through the crust over time this gas rich initial condition may support the concept of a volatile enriched mantle wedge and thus explain the increased buoyancy flux of the new england hotspot as it traversed eastern north america as has been suggested by others

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

the role of condensation in the evolution of dissolutional forms in gypsum caves study case in the karst of sorbas se spain abstract the karst of sorbas se spain is one of the most important gypsum areas worldwide its underground karst network comprises over 100 km of cave passages rounded smooth forms condensation cupola and pendant like features appear on the ceiling of the shallower passages as a result of gypsum dissolution by condensation water meanwhile gypsum speleothems formed by capillarity evaporation and aerosol deposition such as coralloids gypsum crusts and rims are frequently observed closer to the passage floors the role of condensation dissolution mechanisms in the evolution of geomorphological features observed in the upper cave levels has been studied by means of long term micro erosion meter mem measurements direct collection and analysis of condensation waters and micrometeorological monitoring monitoring of erosion at different heights on gypsum walls of the cueva del agua reveals that the gypsum surface retreated up to 0 033 mm yr 1 in mem stations located in the higher parts of the cave walls the surface retreat was negligible at the lowest sites suggesting higher dissolution rates close to the cave ceiling where warmer and moister air flows monitoring of microclimatic parameters and direct measurements of condensation water were performed in the covadura cave system in order to estimate seasonal patterns of condensation direct measurements of condensation water dripping from a metal plate placed in the central part of the el bosque gallery of covadura cave indicate that condensation takes place mainly between july and november in coincidence with rainless periods the estimated gypsum surface lowering due to this condensation water is 0 0026 mm yr 1 microclimatic monitoring in the same area shows differences in air temperature and humidity of the lower parts of the galleries colder and drier with respect to the cave ceiling warmer and wetter this thermal sedimentation controls the intensity of the condensation evaporation mechanisms at different heights in the cave

isotopic geochemistry of the saratoga springs implications for the origin of solutes and source of carbon dioxide we report the results of an isotopic study designed to determine the source of solutes and carbon dioxide in the famed saratoga springs new york mineral waters these waters have thousands of milligrams per liter total dissolved solid concentrations and are highly charged with carbon dioxide gas the spring waters are cold 12 c and there is no local deep seated thermal anomaly they emerge through thick shale caprock along the surface expression of normal faults the 13c 5 8 to 0 8 vienna peedee belemnite of the dissolved inorganic carbon and elevated 3he 4he ratios suggest that the source of the co2 is the mantle or an ancient deep crystallized igneous melt the stable isotopic content of the spring waters defines a mixing line between modern local meteoric waters 70 and a component with heavier d but similar 18o values this trend and that of 87sr 86sr of dissolved strontium versus 1 sr are consistent with the hypothesis that canadian shield type brines contribute salinity to the springs these brines plausibly migrate from the adirondack mountains to the topographically low mcgregor fault system in the hudson river lowlands where the saratoga springs discharge

geostatistical analysis on the spatial variation of radiogenic elements in the crystalline basement of grenville province in the southwestern quebec accurate assessment of deep geothermal resources remains a challenge from the practical point of view parameter uncertainties and partial knowledge of initial conditions limit the prediction of subsurface temperatures using a variety of thermal models strongly unreliable and the temperature is highly dependent on the radiogenic heat production in the geological layers mainly affected by a number of factors including the concentrations of uranium thorium and potassium and rock density in this paper geostatistical methods were applied to investigate the spatial distribution of radiogenic elements e g uranium thorium potassium and their corresponding concentrations and radiogenic heat production a representative region measuring 35 km 80 km in the southwestern quebec and covering the domains of portneuf mauricie morin terrane and parc des laurentides in the grenville province was selected for this study because of its easy accessibility analysis results show that the concentrations of uranium thorium and potassium for most rocks of the grenville basement in the research region are in the range of 1 2 ppm 3 10 ppm and 1 4 respectively furthermore 90 of the total samples analysed in this study show a uranium concentration of less than 3 ppm 64 of the samples show a thorium concentration of less than 5 ppm and 56 of the samples show a potassium concentration of less than 3 this paper engaged both the ordinary kriging interpolation and sequential gaussian simulation sgs methods to study the spatial distribution of radiogenic elements using density data for specific rocks the distribution of radiogenic heat production in the study area of the southwestern grenville province was also simulated using the sgs method conclusively results show that the difference between the minimum and the maximum value of radiogenic heat production is 30 considering a significant proportion of heterogeneity in rock density

fracturing induced release of radiogenic 4he and 234u into groundwater during the last deglaciation an alternative source to crustal helium fluxes in periglacial aquifers external 4he sources have been invoked to explain 4he concentrations in groundwater greater than those expected from in situ u and th production in a fractured aquifer of ordovician age located in the st lawrence lowlands quebec canada 4he concentrations of up to 4 48 x 10 5 cm3 stp gh20 1 were measured such concentrations are ca 1000 times higher than would be expected from in situ production a concomitant increase in 4he concentration and 234u 238u activity ratio is shown suggesting a common release process in groundwater for 234u and 4he this process has tentatively been identified as glaciation induced rock fracturing following the laurentide ice sheet retreat the resulting increase in exposed grain surface facilitates 234u release by recoil and that of radiogenic 4he by diffusion using a model of helium diffusion from a spherical grain it is shown that rock fracturing facilitated the release of accumulated 4he at rates ranging from 4 2 x 10 10 cm3stp gh20 1 yr 1 to 1 06 x 10 8 cm3stp gh20 1 yr 1 these release rates are between 1 000 and 30 000 times higher than the local u and th steady state production rate of 3 5 1 4 x 10 13 cm3stp grock 1 yr 1 integration of 4he release rates over time yields a radiogenic 4he concentration of between 3 85 x 10 6 cm3stp gh20 1 and 7 12x 10 5 cm3stp gh20 1 in the range of concentrations measured in the st lawrence lowlands fractured aquifers results support the occurrence of a local radiogenic helium source to explain the excesses measured in groundwater without requiring a significant external he crustal flux

carbon and noble gases in archean chert abstract in order to study the origin and evolution of volatiles trapped in archean and early proterozoic cherts we have measured contents and isotopic compositions of carbon and noble gases using step heating and mass spectrometry the observed negative correlation between the 13c value and nitrogen carbon ratio in the samples suggests that trapped carbon in archean cherts is a mixture of carbonate sedimentary organic matter and an atmospheric component elemental abundance patterns of noble gases show a slight depletion of 20ne and excess of 132xe relative to air which is explained by atmospheric noble gases dissolved in water at relatively low temperature the 3 he 4 he ratios indicate an apparent crustal value of 1 3 10 3 consistent with the in situ radiogenic production ratio significant excess 21ne 131xe and 132 136xe as well as slight enrichment of 38ar and 86kr relative to atmosphere are found in the onverwacht chert at the 800 and 1200 c steps similar but small isotope anomalies are detected in the frere formation chert at the 1800 c step excess 21ne shows positive correlations with 38ar 86kr and 132xe 136xe enrichments while excess 131xe has no relation with the other isotope anomalies the 21ne anomaly can be attributable to the nuclear reaction 18o n 21ne the enrichments of 86kr and 132xe 136xe are derived from spontaneous fission of 238u in the cherts the slight excess 38ar may be due to the 35cl p 38ar reaction based on the positive correlation between 21 ne 22 ne and 38 ar 36 ar ratios but should be verified in future work

using gravestones to assess changing rates of weathering in the united kingdom weathering rates were calculated using the height difference between lead lettering and marble on gravestones at three sites in the uk comparison of their regression lines and residuals suggested that two of the sites portsmouth and wolverhampton had similar amounts and rates of weathering over the last 100 150 years gravestones in swansea appear to have weathered much more and much faster than gravestones at the other two sites these differences may be the result of the differing pollution and rainfall histories of the three sites

micro erosion meter measurements of rock wear on the otway coast of southeast australia abstract the use of the micro erosion meter mem has been refined by providing 1 a base plate on which to check the relationship of legs and probe and 2 a micrometer level to check the relationships of the three studs countersunk in the rock at each site along 50 km of the otway coast lines of mem stations were installed across shore platforms normal to the shore and surveyed to mean low water readings were made bimonthly from 1978 to 1980 average site downwear ranged from 0 02 to 1 8 mm yr 1 according to rock type and the amount of exposure to the almost continuous swell waves the results of this study combined with other information available are used to discuss the origin and evolution of otway coastal morphologies

weathering of coastal defensive structures in southwest england a 500 year stone durability trial historic structures can be viewed as exposure trials of the stone of which they are constructed as such they represent a geomorphological weathering experiment several structures of henrician sixteenth century and greater age on the coast of southwest england have been exposed to coastal salt weathering for 500 600 years long term weathering rates on five different rock groups are derived from careful study of weathering depths and forms there is significant variation in weathering rate between five major rock groups rank ordering of weathering rate values reveals a durability order of these rock groups which is confirmed by local juxtapositions controls on rock durability in the coastal weathering environment include both mechanical and mineralogical characteristics specific density and combined quartz and muscovite content are positively related to durability high feldspar and chlorite content are associated with low durability copyright 2000 john wiley sons ltd

origin of brine in the kangan gasfield isotopic and hydrogeochemical approaches the kangan permo triassic brine aquifer and the overlying gas reservoir in the southern iran are located in kangan and dalan formations consisting dominantly of limestone dolomite and to a lesser extent shale and anhydrite the gasfield 2 900 m in depth and is exploited by 36 wells some of which produce high salinity water the produced water gradually changed from fresh to saline causing severe corrosion in the pipelines and well head facilities the present research aims to identify the origin of this saline water brine as a vital step to manage saline water issues the major and minor ions as well as 2h 18o and 37cl isotopes were measured in the kangan aquifer water and or the saline produced waters the potential processes causing salinity can be halite dissolution membrane filtration and evaporation of water the potential sources of water may be meteoric present or paleo seawater the na cl and i cl ratios versus cl concentration preclude halite dissolution concentrations of cl na and total dissolved solid were compared with br concentration indicating that the evaporated ancient seawater trapped in the structure is the cause of salinization 18o isotope enrichment in the kangan aquifer water is due to both seawater evaporation and interaction with carbonate rocks the 37cl isotope content also supports the idea of evaporated ancient seawater as the origin of salinity membrane filtration is rejected as a possible source of salinity based on the hydrochemistry data the 18o value and incapability of this process to dramatically enhance salinity up to the observed value of 330 000 mg l the overlaying impermeable formations high pressure in the gas reservoir and the presence of a cap rock above the kangan gasfield all prevent the downward flow of meteoric and persian gulf waters into the kangan aquifer the evaporated ancient seawater is autochthonous because the kangan brine aquifer was formed by entrapment of brine seawater during the deposition of carbonates gypsum and minor clastic rocks in a lagoon and sabkha environment the reliability of determining the source of salinity in a deep complicated inaccessible high pressure aquifer can be improved by combining various methods of hydrochemistry isotope hydrodynamics hydrogeology and geological settings

measuring stone weathering in cities surface reduction on marble monuments the purpose of this study was to establish whether measurements of stone weathering recorded by different observers could be aggregated into a single data base for evaluating pollution effects on calcareous building stone apparent differences in recorded weathering rates on marble tombstones were here found to be partly a result of lettering size measured measuring devices used and individual observers

towards an improved understanding of erosion rates and tidal notch development on limestone coasts in the tropics 10 years of micro erosion meter measurements phang nga bay thailand knowledge and understanding of shore platform erosion and tidal notch development in the tropics and subtropics relies mainly on short term studies conducted on recently deposited carbonate rocks predominantly holocene and quaternary reef limestones and aeolianites this paper presents erosion rates measured over a 10 year period on notches and platforms developed on the permian ratburi limestone at phang nga bay thailand in so doing it contributes to informing a particular knowledge gap in our understanding of the erosion dynamics of shore platform and tidal notch development in the tropics and subtropics notch erosion rates on relatively hard ancient limestones measured directly on the rock surface using a micro erosion meter mem over time periods of a decade or more the average intertidal erosion rate of 0 231 mm yr is lower than erosion rates measured over 2 3 years on recent weaker carbonate rocks average erosion rates at phang nga vary according to location and site and are in rank order from highest to lowest mid platform 0 324 mm yr notch floor 0 289 mm yr rear notch wall 0 228 mm yr lower platform 0 140 mm yr notch roof 0 107 mm yr and supratidal 0 095 mm yr the micro relief of the eroding rock surfaces in each of these positions exhibits marked differences that are seemingly associated with differences in dominant physical and bio erosion processes the results begin to help inform knowledge of longer term shore platform erosion dynamics models of marine notch development and have implications for the use of marine notches as indicators of changes in sea level and the duration of past sea levels copyright 2014 john wiley sons ltd

natural gas association with water and oil as depicted by atmospheric noble gases case studies from the southeastern mediterranean coastal plain a model for the equilibrium distribution of atmospheric noble gases ang between natural gas and water phases was extended to include the gas oil relationship the basic assumption is that the ang are introduced into hydrocarbon systems via recharge or seawater theoretical ang patterns of natural gas at equilibrium with water fall between the air pattern and that of air saturated water theoretical ang patterns of natural gas degassed from oil which had previously equilibrated with a water phase cover a wide range including the range calculated for gas water equilibration ang patterns in natural gas which fall outside the overlapping range may thus indicate association of the gas with oil the model was tested in the case of hydrocarbon systems of the southeastern mediterranean coastal plain other geochemical evidence indicates that the ashdod sadot shallow gas wells are not related to oil the relative ang abundances in gas samples from these wells lie within the range predicted for gas water association the relative ang abundances in samples degassed from oils of the helez kokhav oilfield are similar to specific patterns predicted for the degassing of oil which was previously associated with water published and new analyses of methane dominated natural gas samples from california japan and northern israel also reveal ang patterns of the type predicted by the model the results of the case studies support our hypothesis that water is responsible for transport of atmospheric noble gases into subsurface hydrocarbon systems this forms the basis for identification of oil associated natural gases via ang study

the micro erosion meter use and limitations detection of anomalies in measurements of low rates of limestone surface lowering with a traversing micro erosion meter mem led to temperature controlled laboratory and field investigations of some sources of error in the method regressions for the correction of temperature change in the instrument and in the stud rock interface were obtained probe erosion tests permitted a correction to be devised and also provided information whereby a measure of operational irregularity was adopted corrections and error terms were applied to field measurements from two southern new south wales karsts and a collection of australian limestone slabs exposed at one site examination of these results and of published mem rates from other parts of the world validated the mem method marine platforms are lowered at such gross rates that these error sources may be neglected there however limestone lowering in terrestrial environments cannot be assumed to proceed at rates which permit this and recommendations are made about procedures to ensure that investigations are prosecuted within the limitations of the method

quantifying the helium and hydrocarbon accumulation processes using noble gases in the north qaidam basin china abstract limited reserves and insecure resource supply have led to global shortage crises in helium a vital gas for cryogenic engineering and other countless industrial manufacturing processes despite the attention drawn by global supply disruptions the helium accumulation mechanism in natural gas fields remains poorly understood noble gases are excellent tracers for studying migration and accumulation processes of fluids in the subsurface and can be used to investigate the influence of subsurface fluids on helium accumulation we present noble gas isotope and abundance data as well as major gas compositional data from 10 producing wells in three gas fields in the north qaidam basin china helium is more concentrated in the mabei and dongping gas fields 2 06 48 4 10 4 cm3 stp cm3 than in the niudong gas field 1 15 1 42 10 4 cm3 stp cm3 the helium is mainly radiogenic with 3he 4he ratios of 0 01 0 05 ra where ra is the atmospheric value of 3he 4he and lacks significant contribution from the mantle 0 03 0 67 the noble gases derived from air saturated water 20ne 36ar 84kr and 130xe can be explained by an oil modified groundwater exsolution model with excess heavy noble gases the calculated voil vwater and vgas vwater ratios indicate that the mabei region is the most oil rich area and the dongping region has the driest natural gas which is consistent with the geological context these ratios further support the fractionation models the strong linear relationship between 4he and 20ne r2 0 98 suggested that 4he was dissolved into groundwater before migrating into the oil or gas phase the initial 4he concentrations in groundwater can accumulate within 0 31 2 78 myr assuming a 4he flux from the entire crustal section according to the fractionation model helium in groundwater partitions into the gas phase when contacting hydrocarbons the different volume ratios among oil gas and water during the equilibration process cause much greater variability in the helium concentrations in the gas phase e g 6 08 10 4 to 2 01 10 3 cm3 stp cm3 in mabei than those in the groundwater phase e g 9 18 10 3 to 1 39 10 2 cm3 4he stp cm3 h2o in mabei hydrocarbons play a critical role in helium accumulation and dilution helium rich natural gas fields are characterized by old groundwater systems and moderate hydrocarbon abundance this study has succeeded in quantitatively assessing the helium accumulation process in natural gas fields in the north qaidam basin and revealed that both groundwater and hydrocarbon phases control the helium accumulation in the subsurface environment this outcome has broad implications for the prediction of hydrocarbon and helium as resources

measuring erosion with the micro erosion meter contributions to understanding landform evolution abstract we review the contribution made to understanding landform evolution through the use of the micro erosion meter mem and the variant the traversing micro erosion meter tmem the mem has allowed the direct measurement of bedrock erosion in terrestrial and coastal settings as well as of building stone as recorded in mem measurements world wide the average rate of surface lowering on shore platforms is 1 486 mm a 1 and on terrestrial rock surfaces measured lowering rates are on average 0 903 mm a 1 reported means obscure significant variation in rates from a range of environmental settings and lithologies the mem has in a number of examples allowed the identification of the contribution of individual processes in polygenetic settings particularly in shore platform studies the dynamic nature of rock weathering has been highlighted where the tmem has revealed rock surfaces swelling and contracting at time scales ranging from hours to years the mem will continue to provide useful data on erosion rates and processes but the most fruitful investigations will be those that combine the t mem with other techniques that transcend time and space scale issues in erosion and process measurement

using 81kr and noble gases to characterize and date groundwater and brines in the baltic artesian basin on the one million year timescale abstract analyses for 81 kr and noble gases on groundwater from the deepest aquifer system of the baltic artesian basin bab were performed to determine groundwater ages and uncover the flow dynamics of the system on a timescale of several hundred thousand years we find that the system is controlled by mixing of three distinct water masses interglacial or recent meteoric water 18 o 10 4 with a poorly evolved chemical and noble gas signature glacial meltwater 18 o 18 with elevated noble gas concentrations and an old high salinity brine component 18 o 4 5 90 g cl l with strongly depleted atmospheric noble gas concentrations the 81 kr measurements are interpreted within this mixing framework to estimate the age of the end members deconvoluted 81 kr ages range from 300 ka to 1 3 ma for interglacial or recent meteoric water and glacial meltwater for the brine component ages exceed the dating range of the atta 3 instrument of 1 3 ma the radiogenic noble gas components 4 he and 40 ar are less conclusive but also support an age of 1 ma for the brine based on the chemical and noble gas concentrations and the dating results we conclude that the brine originates from evaporated seawater that has been modified by later water rock interaction as the obtained tracer ages cover several glacial cycles we discuss the impact of the glacial cycles on flow patterns in the studied aquifer system

supracrustal faults of the st lawrence rift system quebec kinematics and geometry as revealed by field mapping and marine seismic reflection data abstract the st lawrence rift system from the laurentian craton core to the offshore st lawrence river system is a seismically active zone in which fault reactivation is believed to occur along late proterozoic to early paleozoic normal faults related to the opening of the iapetus ocean the rift related faults fringe the contact between the grenvillian basement to the nw and cambrian ordovician rocks of the st lawrence lowlands to the se and occur also within the grenvillian basement the st lawrence rift system trends ne sw and represents a se dipping half graben that links the nw se trending ottawa bonnechere and saguenay river grabens both interpreted as iapetan failed arms coastal sections of the st lawrence river that expose fault rocks related to the st lawrence rift system have been studied between quebec city and the saguenay river brittle faults marking the st lawrence rift system consist of ne and nw trending structures that show mutual crosscutting relationships fault rocks consist of fault breccias cataclasites and pseudotachylytes field relationships suggest that the various types of fault rocks are associated with the same tectonic event high resolution marine seismic reflection data acquired in the st lawrence river estuary between rimouski the saguenay river and forestville identify submarine topographic relief attributed to the st lawrence rift system northeast trending seismic reflection profiles show a basement geometry that agrees with onshore structural features northwest trending seismic profiles suggest that normal faults fringing the st lawrence river are associated with a major topographic depression in the estuary the laurentian channel trough with up to 700 m of basement relief a two way travel time to bedrock map based on seismic data from the st lawrence estuary and comparison with the onshore rift segment suggest that the laurentian channel trough varies from a half graben to a graben structure from sw to ne it is speculated that natural gas occurrences within both the onshore and offshore sequences of unconsolidated quaternary deposits are possibly related to degassing processes of basement rocks and that hydrocarbons were drained upward by the rift faults

geochemistry of dissolved gases from the eastern carpathians transylvanian basin boundary abstract we show the results of a study on the volatiles dissolved in mineral waters discharged over a 200 km long transect along the rodna b rg u area and c limani gurghiu harghita volcanic chain eastern carpathians romania all of the collected mineral water samples carry dissolved gas with carbon dioxide content up to 1 99 cm 3 stp gh 2 o and helium content up to 2 3 10 5 cm 3 stp gh 2 o carbon 13 c tdic total dissolved inorganic carbon ranging from 15 6 to 5 32 vs vpdb he systematics he isotopes in the range of 0 38 0 99 ra ra air normalized 3 he 4 he ratio and co 2 3 he ratio spanning over four orders of magnitude from morb like values of 2 92 10 9 to crustal type values of 3 02 10 13 coherently indicate the presence of fluids from different crustal sources e g sediments hydrocarbon reservoirs besides minor but detectable contributions of mantle magmatic derived fluids up to 16 45 our investigations show that the wide range of chemical and isotopic composition can be explained in terms of mixings among different gas sources feeding the groundwater and the contemporary occurrence of gas water interactions like degassing and deposition of carbonates affecting the circulating waters after their infiltration

influence of co2 dynamics on the longitudinal variation of incision rates in soluble bedrock channels feedback mechanisms we use measurements of dissolution rates of limestone tablets placed along a cave stream to estimate rates of modern incision dissolution rates within the stream display a systematic decrease with downstream distance we discuss a variety of mechanisms that could be responsible for the longitudinal decrease in dissolution rates and develop simple mathematical models for each the dissolutional length scales that arise from each model allow a first order estimate of the plausibility of each mechanism and motivate further field studies to test each possibility water chemistry and other field data suggest that a decrease in the concentration of co2 along the cave stream is responsible for the observed decrease in dissolution rates we propose two potential mechanisms that could trigger this reduction in dissolved co2 and discuss the plausibility of each mechanism in light of the field data collected either of these mechanisms introduces a feedback loop whereby the stream profile of a channel in soluble bedrock indirectly influences co2 concentrations in the water via either microbial or hydraulic processes the co2 concentration in turn effects the incision rates and therefore the future stream profile this study illustrates the importance of co2 dynamics in determining incision rates in a soluble channel and points to further modeling and field work that are needed in order to enable the development of realistic stream incision models in soluble strata

short term microscale topographic changes of coastal bedrock on shore platforms we report a series of short term diurnal rock surface monitoring studies on inter and supra tidal shore platforms using a traversing micro erosion meter at two sites kaikoura peninsula new zealand and apollo bay victoria australia statistically signi cant day to day changes were measured surface rise and lowering occurred at rates above instrument error with a maximum range of 3 378 mm between 1 697 mm lowering and 1 681 mm rise individual measurements showed rises greater than 2 mm these daily variations reveal that surface lowering and rise occur at a much shorter time scale than previously reported from other studies the patterns observed suggest wetting and drying is the most likely process causing surface changes at these temporal scales we argue that traversing micro erosion meter studies operating at a short term time scale of day to day provide meaningful results that open new opportunities for studying rock weathering and erosion in a coastal environment copyright 2004 john wiley sons ltd

deducing the ancestry of terranes shrimp evidence for south america derived gondwana fragments in central europe we present here an example of how the sensitive high resolution ion microprobe shrimp zircon dating method can provide a terrane specific geochronological fingerprint for a rock and thus help to reveal major tectonic boundaries within orogens this method applied to inherited zircons in a ca 580 ma metagranitoid rock from the eastern bohemian massif has provided for the first time in the central european variscan basement unequivocal evidence for mesoproterozoic and late paleoproterozoic geologic events ca 1 2 ga 1 5 ga and 1 65 1 8 ga the recognition of such zircon ages has important consequences because it implies that parts of the precambrian section of variscan central europe were originally derived from a grenvillian cratonic province as opposed to the common assumption of an african connection a comparison with previously published shrimp data suggests however that these mesoproterozoic and late paleoproterozoic zircon ages may be restricted to the moravo silesian unit in the eastern variscides whereas the saxothuringian and moldanubian zones appear to contain a typical north african i e neoproterozoic plus eburnian inherited zircon age spectrum this finding supports new tectonic concepts according to which variscan europe is composed of a number of completely unrelated terranes with extremely different paleogeographic origins the moravo silesian unit can be best interpreted as a peri gondwana terrane which was situated in the realm of the amazonian cratonic province by the late precambrian comparable to the avalonian terranes of north america and the united kingdom

geochemical and isotopic evidence for a genetic link between canadian shield brines dolomitization in the western canada sedimentary basin and devonian calcium chloridic seawater hypersaline brines of marine origin deep within fractured crystalline rocks of the canadian shield are characterized by calcium chloride compositions with relatively low concentrations of magnesi

decadal scale micro erosion rates on shore platforms abstract knowledge of the long term rates of erosion of shore platforms are needed to assist modeling platform development understand rates and modes of development and decipher issues of inheritance from former sea level few studies report rates from more than 2 years of monitoring we report decadal scale erosion rates using both a micro erosion meter and a traversing micro erosion meter with measurements from 30 years and 10 years respectively gross mean surface lowering rates measured over 10 years with a traversing micro erosion meter were 0 901 s e 0 116 mm yr compared with 1 130 s e 0 217 mm yr over two years over thirty years 1973 2003 12 micro erosion meter sites provide a mean surface lowering rate of 1 09 s e 0 126 mm yr compared to 1 43 s e 0 128 mm yr calculated over twenty years 1973 1993 from 15 bolt sites and 1 53 s d 1 45 mm yr from 31 bolt sites rates calculated over longer time periods are reduced compared to short term rates as a result of faster eroding bolt sites being removed from the data set comparison of means between short and long time periods for existing bolts show no significant difference that is short term measurements over two years are representative of decadal scale erosion rates in fact decadal scale rates may under represent rates of platform development because of the loss of faster eroding bolt sites the loss of such bolts means that obtaining long term erosion rates is problematic future modeling of shore platform development can use mem rates with more certainty but we recommend using higher rates from shorter term studies unless longer records are complete

pre early ordovician cadomian arc type granitoids the bolu massif west pontides northern turkey geochemical evidence the west pontides tectonic belt of northern turkey comprises a lower ordovician lower carboniferous transgressive sequence a stratigraphic basement to this paleozoic sequence is exposed in the bolu area the tectono stratigraphy of the basement closely resemble that of the cadomian belt of western europe three rock units forming the basement imply development of an andean type active continental margin during the pre early ordovician period high grade metamorphics the sunnice group granitoids the bolu granitoid complex and evolved felsic meta volcanic rocks the casurtepe formation are exposed unconformably beneath the lower ordovician fluvial clastics between the bolu yedigoller area to the north of bolu the bolu granitoid complex comprises a group of intrusive rocks of variable composition and size generated through multiple episodes of magmatism and is represented by two separate intrusive bodies within the study area the tullukiris pluton in the west and the kapikaya pluton in the east both plutons are mainly tonalite and granodiorite in composition more felsic and mafic compositional varieties also occur major and trace element chemical characteristics of the granitoids as well as biotite chemistry indicate that these are volcanic arc type granitoids and are products of an immature arc developed during early stages of a subduction furthermore textural and chemical characteristics of the plutons show that these are subvolcanic intrusions emplaced at shallow depths and are calc alkaline in composition the granitoidic plutons intrude the casurtepe formation the casurtepe formation is represented by arc type volcanics and volcaniclastics both the casurtepe formation and the granitoids represent subduction zone magmatism constructed on a continental crust represented by the sunnice group the history is very similar to cadomian active margins as exposed in western europe i e the north armorican and bohemia massifs and therefore the basement to the paleozoic of the west pontides is considered to be a preserved remnant of the cadomian belt

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

simulation of the dissolution of weathered versus unweathered limestone in carbonic acid solutions of varying strength a simulation was undertaken within a climatic chamber to investigate limestone dissolution under varied carbonic acid h2co3 strengths as a possible analogue for future increases in atmospheric co2 arising from global warming twenty eight samples cut from a block of bath box hill limestone from somerville college oxford which had been removed during restoration after 150 years in an urban environment were weighed and placed in closed bottles of thin plastic containing varying concentrations of h2co3 half of the stone samples were derived from exposed surfaces of the stone block weathered while the others were obtained from the centre of the block on unexposed surfaces unweathered the purpose of this was to compare dissolution of previously weathered versus unweathered surfaces in strong ph 4 73 versus weak ph 6 43 solutions of h2co3 a temperature of c 19 c was maintained within the chamber representing a plausible future temperature in oxford for the year 2200 given current warming scenarios the simulation lasted 25 days with a few stone samples being removed midway stone samples show reduced weight in all cases but one there was greater dissolution of stone samples in a strong h2co3 solution as conveyed by higher concentrations of total hardness and ca2 in the water samples as well as enhanced microscopic dissolution features identified using sem the simulation confirms that enhanced atmospheric co2 under global warming given adequate moisture will accelerate dissolution rates particularly of newly replaced limestone building stones however previously weathered surfaces such as those on historical stone exposed for a century or more appear to be less susceptible to the effects of such increased rainfall acidity conservation techniques which remove weathered surfaces such as stone cleaning may accelerate future decay of historical limestone structures by increasing their susceptibility to dissolution copyright 2006 john wiley sons ltd

kinematic constraints on buckling a lithospheric scale orocline along the northern margin of gondwana a geologic synthesis abstract the paleozoic variscan orogeny was a large scale collisional event involving amalgamation of multiple continents and micro continents existing data suggests oroclinal buckling of an originally near linear convergent margin during the last stages of variscan deformation in the late paleozoic closure of the rheic ocean resulted in e w shortening present day coordinates in the carboniferous producing a near linear n s trending east verging belt subsequent n s shortening near the carb permian boundary resulted in oroclinal buckling this late stage orogenic event remains an enigmatic part of final pangea amalgamation the present day arc curvature of the variscan has inspired many tectonic models with little agreement between them while there is general consensus that two separate phases of deformation occurred various models consider that curvature was caused by dextral transpression around a gondwana indentor strike slip wrench tectonics or a change in tectonic transport direction due to changing stress fields more recent models explain the curvature as an orocline with potentially two opposite facing bends caused by secondary rotations deciphering the kinematic history of curved orogens is difficult and requires establishment of two deformation phases an initial compressive phase that forms a relatively linear belt and a second phase that causes vertical axis rotation of the orogenic limbs historically the most robust technique to accurately quantify vertical axis rotation in curved orogens is paleomagnetic analysis but recently other types of data including fracture geochemical petrologic paleo current and calcite twin data have been used to corroborate secondary buckling a review of existing and new variscan data from iberia is presented that argues for secondary buckling of an originally linear orogenic system together these data constrain oroclinal buckling of the cantabrian orocline to have occurred in about 10 ma during the latest carboniferous which agrees well with recent geodynamical models and structural data that relate oroclinal buckling with lithospheric delamination in the variscan

factors controlling carbonate dissolution rates quantified in a field test in the austrian alps carbonate dissolution rates were investigated by measuring the mass difference of carbonate tablets exposed to natural dissolution for 1 year 70 tablets were distributed over 13 test sites on the north slope of the hochschwab massif in the austrian alps the influences of altitude subsoil vs sub aerial exposure vegetation karst morphology soil humidity sample lithology and sample surface morphology were investigated the observed dissolution rates varied between 13 and 40 m a for subcutaneous samples and about 11 m a for sub aerial exposure outstandingly high rates of 48 m a were observed in a doline and nearly zero rates were measured at a site influenced by seeping spring water a mass balance using high resolution hydrological data was calculated for the klaffer spring which has an average outflow of 4 8 m3 s it indicated a loss of 21 106 kg of carbonate rock per year which gives an average dissolution rate of 95 m a for the catchment area of 83 km2 the dissolution rates of 10 m a from the sub aerially exposed samples are comparable to values from limestone pedestals which were protected from dissolution by glacial erratics for the past 15 ka

paleozoic evolution of the armorica plate on the basis of paleomagnetic data new paleomagnetic data support the contention that armorica and gondwana formed a coherent block until ordovician time however by early devonian time armorica collided with the north american northern european assembly to form the old red continent and the collision itself was responsible for the acadian orogeny not for the earlier taconic orogeny as postulated previously the carboniferous collision of gondwana with the old red continent subsequently formed pangaea and produced the appalachian hercynian orogeny

comparison of the sr isotopic signatures in brines of the canadian and fennoscandian shields abstract a synthesis of sr isotope data from shallow and deep groundwaters and brines from the fennoscandian and canadian shields is presented a salinity gradient is evident in the water with concentrations varying from approximately 1 75 g l 1 below 1500 m depth in the fennoscandian shield and from 10 up to 300 g l 1 below 650 m depth in the canadian shield strontium isotope ratios were measured to assess the origin of the salinity and evaluate the degree of water rock interaction in the systems in both shields the sr concentrations are enriched relative to cl defining a positive trend parallel to the seawater dilution line and indicative of sr addition through weathering processes the depth distribution for sr concentration increases strongly with increasing depth in both shields although the variation in sr isotope composition does not mirror that of sr concentrations strontium isotope compositions are presented for surface waters and groundwaters in several sites in the fennoscandian and canadian shields numerous mixing lines can be drawn reflecting water rock interaction a series of calculated lines links the surface end members surface water and shallow groundwater and the deep brines these mixing lines define a range of 87 sr 86 sr ratios for the deep brines in different selected sites all sites show a specific 87 sr 86 sr signature and the occurrence of large 87 sr 86 sr variations is site specific in both shields in canadian shield brines the sr isotope ratios clearly highlight large water rock interaction that increases the 87 sr 86 sr ratio from water that could have been of marine origin in contrast to the canadian shield groundwater does not occur in closed pockets in the fennoscandian and the well constrained 87 sr 86 sr signatures in deep brines should correspond to a large well mixed and homogeneous water reservoir whose sr isotope signature results from water rock interaction

monteregian hotspot track a long lived mantle plume the monteregian hills the younger white mountains and the new england seamounts constitute a well defined hotspot track the evolution of the plume through time is obtained from the marine track the buoyancy flux of the plume when it made the new england seamounts was about 2 mg s 1 which would make it the seventh or eighth most active plume today the hotspot declined in activity after it made nashville seamount the buoyancy flux when it made corner seamounts and today is less than 0 5 mg s 1 the changes in the flux of the marine hotspot limit how far the marine flux can be extrapolated to the west onto the continental track and what can be learned in general about vulnerability of the continental lithosphere to hotspots the lack of an obvious track west of montreal may be due either to failure of the plume to penetrate the canadian shield to the lack of recognizable intrusions or to strengthening of the plume when it approached montreal

4he diffusion in 40ar retentive minerals abstract 4he vacuum diffusion experiments were carried out by stepwise degassing minerals normally used in k ar chronometry such as hornblende nepheline and others the study aims at 4he diffusion parameters for uppermost crustal temperatures and thus at he retentivities of the minerals the results indicate long time near quantitative 4he retention in hornblende pyroxene langbeinite and perhaps nepheline for 0 5 mm grains at least at temperatures below about 70 c sanidine and muscovite lose 4he over geologic periods at lower temperatures only the minerals of the first group are possible u th he chronometers or geothermometers provided that other dating problems such as alpha loss and u migration can be settled closure temperatures for rapidly cooling 2 mm hornblende crystals are found to be in the range of 190 to 170 c tentative u he indices indicate that diffusion parameters of the same order of magnitude as determined for the he retentive minerals may be used to select minerals to be further examined for their u th he datability e g ore minerals

exploring the influence of biofilm on short term expansion and contraction of supratidal rock an example from the mediterranean previous geomorphological investigations using the traversing micro erosion meter tmem have identified daily and hourly contractions and expansions of littoral rock on a range of lithologies while organic influences on these patterns have been inferred this has rarely been tested in a controlled way here a tmem was used to measure micro scale mm topographic changes on supratidal limestone of the massif des calanques southern france four tmem monitoring sites each 64 cm2 were set up in total two in the calanque de morgiou and two in the presqu ile de cassis on both shores one tmem bolt site was positioned on bare rock and the other on colonized rock tmem data were collected and the surface micro topography mapped for each site at two hourly intervals from early morning to late evening across one day in mid summer significant relative expansion and contraction was observed between measurement periods at all four sites regardless of biofilm colonization p 0 001 in all instances and sometimes between adjacent zones on the rock surface at a scale of centimetres rock with and without biofilm behaved broadly similarly but the magnitude of topographic change varied average movement from one interval to the next was 0 03 mm on bare sites and 0 06 mm on biofilm colonized sites as expected patterns of surface change related largely to insolation with greatest movement occurring in the morning and evening when thermal gradients were steepest interestingly the presence of a biofilm intensified rock expansion but delayed surface response to microclimatic variability we largely attribute this effect to biofilm influences on surface albedo and hypothesize that episodes of contraction and expansion are superimposed onto longer annual to decadal episodes of surface movement and downwearing short term tmem studies therefore need to be coupled with longer term seasonal and annual measurements to improve understanding of rock surface dynamics copyright 2014 john wiley sons ltd

inscription legibility method for estimating rock weathering rates abstract relative legibility of dated inscription is closely associated with measured surface recessions for 3895 vermont marble tombstones and the resulting ordinal to ratio transfer function allows weathering rates to be computed for many exposed rock surfaces that cannot be measured by more accurate methods case studies demonstrate applications of the technique 1 surfaces of horizontal ground level marble plaques have dissolved at steady rates of 1 3 mm 100 yr in providence ri and 1 1 mm 100 yr in richmond va despite reports of increasing acid rain 2 vertical faces of century old marble tombstones in upper midwestern united states small towns have receded 10 times faster 1 4 mm 100 yr than have stones in less polluted environments 3 vertical faces of limestone monuments have receded at half the rate 0 5 mm 100 yr of vermont marble tombstones 0 9 mm 100 yr in louisville ky 4 aspect differences have not affected recession rates of marble pillar surfaces near philadelphia pa 5 aspect is important to sandstone granular weathering rates at inscription rock nm where north facing cliffs recede 3 times faster 0 9 mm 100 yr than do southeast facing cliffs 6 horizontal pre weathered quartizite surfaces at a scenic overlook in maryland recede at 0 6 mm 100 yr

air xe enrichments in elk hills oil field gases role of water in migration and storage hydrocarbons from the elk hills naval petroleum reserve npr 1 bakersfield ca are enriched in heavy noble gases the 132xe 36ar ratios are as high as 576 times the ratio in air and represent the largest relative xe enrichments ever observed in terrestrial fluids the xe isotopic composition is indistinguishable from air we show that these samples cannot be explained by equilibration of oil with air saturated water and secondary enrichment via a rayleigh distillation gas stripping process based on laboratory studies of others with potential petroleum source rocks we believe the source of this enriched heavy noble gas component was adsorbed air initially trapped in on the source rocks that was expelled and mixed with the hydrocarbons during expulsion and primary migration kr and xe enrichments decrease with increasing 36ar concentration we propose a model in which an initial kr xe enriched hydrocarbon becomes diluted with noble gases extracted from air saturated groundwater during expulsion migration and storage the model generates an integrated water hydrocarbon ratio for the production fluid which indicates a minimal role for water in hydrocarbon expulsion and migration the results are interpreted to provide time geometrical constraints on the mechanisms by which hydrocarbons can migrate as a separate phase

twenty year weathering remeasurements at st paul s cathedral london microerosion meter mem measurements of the surface height of the balustrade of st paul s cathedral london have been repeated in the year 2000 following earlier measurements in 1980 1981 1985 and 1990 methodological sources of error mean that while the measurements were made to 0 0001 mm the data are reliable to two decimal places there was a reduction in the mean erosion rate on horizontal sites from 0 045 mm a1 in the period 1980 1990 to 0 025 mm a1 in 1990 2000 decreases in atmospheric so2 levels from 20 25 ppb in 1980 1982 to around 10 ppb in 1990 2000 offer a causal explanation the surface topography evolved more erratically in 1990 2000 than before with much but not all of the more microelevated areas showing greater and often more variable erosion there are also indications of less erosion and more surface rises in low lying microareas on horizontal sites which is interpreted as possible deposition and or microfloral growth in wetter depressions the pattern being largely absent on a well drained vertical site

geomorphology s role in the study of weathering of cultural stone abstract great monumental places petra giza angkor stonehenge tikal macchu picchu rapa nui to name a few are links to our cultural past they evoke a sense of wonderment for their aesthetic fascination if not for their seeming permanence over both cultural and physical landscapes however as with natural landforms human constructs are subject to weathering and erosion indeed many of our cultural resources suffer from serious deterioration some natural some enhanced by human impact groups from the united nations to local civic and tourism assemblies are deeply interested in maintaining and preserving such cultural resources from simple rock art to great temples geomorphologists trained in interacting systems process and response to thresholds rates of change over time and spatial variation of weathering processes and effects are able to offer insight into how deterioration occurs and what can be done to ameliorate the impact review of recent literature and case studies presented here demonstrate methodological and theoretical advances that have resulted from the study of cultural stone weathering because the stone was carved at a known date to a baseline or zero datum level some of the simplest methods e g assessing surface weathering features or measuring surface recession in the field provide useful data on weathering rates and processes such data are difficult or impossible to obtain in natural settings cultural stone weathering studies demonstrate the importance of biotic and saline weathering agents and the significance of weathering factors such as exposure microclimate and human impact more sophisticated methods confirm these observations but also reveal discrepancies between field and laboratory studies this brings up two important caveats for conservators and geomorphologists for the conservator are laboratory and natural setting studies really analogous and useful for assessing stone damage for the geomorphologist does cultural stone data have any real relevance to the natural environment these are questions for future research and debate in any event cultural stone weathering studies have been productive for both geomorphologists and conservators continued collaboration and communication between the geomorphic historic preservation archaeological and engineering research communities are encouraged

geochemistry and origin of formation brines from the paris basin france 2 saline solutions associated with oil fields abstract oil fields from the paris basin are located in three geological levels dogger middle jurassic rhaetian and keuper upper triassic the origin of water and dissolved salts in saline solutions associated with oil is investigated using the hypothesis that cl and br are conservative in solution in a diagram of cl br ratios vs cl the points of the dogger and the keuper aquifers lie in the zone of primary brines whereas those of the rhaetian are located in the zone of secondary brines the na cl ratio is very high in all of the saline solutions suggesting either a relatively poorly evolved brine at the beginning of halite deposition or some halite dissolution all of the saline solutions especially those from the dogger aquifer are clearly diluted dilution by meteoric waters would not alter the cl br ratio high concentrations of lithium rubidium and boron are attributed to the presence of an extremely evolved brine of marine origin in mixtures of secondary brines formed by dissolution of halite and small amounts of sylvite and ca sulphate mass balance calculations of the excess of cl with respect to na k allows the fraction x of water derived from the primary brine to be calculated assumptions are that all na and k is derived from the secondary brine and that the cl content of the primary brine is constrained by bischofite saturation at 11 000 mmol kg 1 the typical proportion of water from the primary brine waters is 0 7 in the dogger formation and 2 4 in the keuper values of the concentration factor cf expressed as the ratio of the molal concentration of a conservative ion in the evolved brine to its concentration in seawater have been calculated for lithium solutions from the dogger and keuper aquifers have cfli values of 1 8 103 and of 7 7 103 respectively in the rhaetian aquifer the linear relationship between heavy isotope contents of the brine 2h and 18o and the cl content indicates a mixture of two water sources the first one is meteoric water as defined by the intersection of the formation water line with the global meteoric water line 2 h 65 18 o 9 3 the other end member is enriched in heavy isotopes and in cl and is attributed to seawater that has dissolved evaporites mainly halite however the presence of small amounts of an extremely evolved brine is required to account for the bromide lithium rubidium and boron contents of the formation brine from the rhaetian aquifer as this contribution is very limited in amount it cannot affect the heavy isotope content of the formation water mass balance equations are solved for ternary mixtures of meteoric water seawater and brine the same constraints as above no na and k supplied by the primary brine and clbrine 11 000 mmol kg 1 are applied it is also assumed that the seawater component has the same ionic contents as modern seawater and that the salt content of the meteoric component is negligible the fraction of primary brines is x 1 4 according to the cl balance this estimate agrees with that obtained from the lithium balance assuming that the primary brine component was the same as that of the keuper formation water mass balance calculations also indicate that the so42 content of the rhaetian formation water is exclusively due to the secondary brine component in the three saline solutions the very high ca2 contents and high ca 2 mg 2 ratios may be attributed to reaction of the very evolved brine free of so2 4 with gypsum or anhydrite the result is an exchange of mg2 for ca2 which causes a release of ca2 to the solution and a precipitation of secondary mg sulphate this process can also account for the high strontium contents of the analysed samples values of the ratio 87 sr 86 sr are very high in the keuper formation water due to close contact of the solutions with the granitic basement or with granite derived detrital deposits values in the rhaetian and dogger aquifers equal those of upper triassic marine deposits the stable isotope 34s and 18o content of the dissolved aqueous so2 4 indicates a triassic origin for the bulk of sulphate involved in the evolution of formation waters from the rhaetian and from the dogger all geochemical indicators thus show a vertical migration of triassic brines however aqueous so2 4 from the keuper has a permian isotopic signature suggesting a reworking in solution of salts from this period

the relationship between he and cl as a criterion for the formation of groundwater composition abstract the analysis of the relationship between 1611 parallel determinations of helium and chloride concentrations in the groundwater of crystalline shields and sedimentary basins was performed the comparison showed that groundwaters have helium and chlorides concentrations in the range of 1 8 10 8 to 6 8 mol m3 and of 5 6 10 3 to 6488 mol m3 respectively and relatively stable he rcl ratios equal to 5 5 10 5 in sedimentary basins and 7 5 10 4 in crystalline shields such behavior of helium and chlorides shows that the formation of the groundwater composition is determined primarily by the processes of mixing fresh meteoric and saline sea waters with ancient brines from great depths during sedimentation sea water penetrates the subsurface and mixes with ancient brines on land fresh meteoric waters dilute the mixtures of seawater and ancient brines most of the radiogenic 4he and chlorides comes from the subsurface ancient brine the radiogenic 4he in the host rocks plays a secondary role therefore the concentration of 4he in saline groundwater reflects the size of the impurities of the ancient brine with a very high content of 4he rather than the residence time within the subsurface

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

assessing compositional variability and migration of natural gas in the antrim shale in the michigan basin using noble gas geochemistry abstract this study uses stable noble gases he ne ar kr xe volume fractions and isotopic ratios from antrim shale natural gas to assess compositional variability and vertical fluid migration within this reservoir in addition to distinguishing between the presence of thermogenic versus biogenic methane r ra values where r is the measured 3he 4he ratio and ra is the atmospheric value of 1 384 0 013 10 6 vary from 0 01 to 0 34 suggesting a largely dominant crustal 4he component with minor atmospheric and mantle contributions crustal 21ne 40ar and 136xe contributions are also present but the atmospheric component is largely dominant for these gases crustal contributions for 21ne 40ar and 136xe vary between 1 1 and 12 5 between 0 7 and 19 and between 0 1 and 2 7 respectively a few samples present higher than atmospheric 20ne 22ne ratios pointing to the presence of a small mantle ne component high horizontal and vertical variability of noble gas signatures in the antrim shale are observed these are mainly due to variable noble gas input from deep brines and to a smaller extent variable in situ production within different layers of the antrim shale in particular the lachine and norwood members estimated 4he ages considering external 4he input for antrim shale water vary between 0 9 ka and 238 2 ka and match well for most samples with the timing of the major wisconsin glaciation suggesting that antrim shale water was influenced by glaciation induced recharge consistency between measured and predicted 40ar 36ar ratios assuming ar release temperatures 250 c supports a thermogenic origin for most of the methane in these samples this thermogenic methane is likely to originate at greater depths either from the deeper portion of the antrim shale in the central portion of the michigan basin or from deeper formations given that the thermal maturity of the antrim shale in the study area is rather low

halogens and noble gases in sedimentary formation waters and zn pb deposits a case study from the lennard shelf australia abstract halogen ratios br cl and i cl and concentrations provide important information about how sedimentary formation waters acquire their salinity but the possible influence of organic br derived from sedimentary wall rocks is rarely quantified here it is demonstrated that br cl versus i cl mixing diagrams can be used to deconvolve organic br contributions that organic matter has a limited range of br i ratios and that organic br is a more significant component in zn pb deposit ore fluids than previously recognised the significance of these findings is illustrated for the lennard shelf zn pb deposits of western australia fluid inclusions related to lennard shelf zn pb mineralisation have variable salinity and hydrocarbon contents the halogen data from these fluid inclusions require mixing of three fluid end members 1 an evaporated seawater bittern brine 30 wt nacl equiv with greater than seawater br cl ratio 2 a lower salinity pore fluid 5 wt nacl equiv with moderately elevated br cl and i cl and 3 fluids with br cl ratios of 5 times seawater and extremely elevated i cl ratios of 11 500 times seawater the first two fluids have 40 ar 36 ar of 300 400 and greater than air saturated water 36 ar concentrations that are typical of fluid inclusions related to zn pb mineralisation the third organic rich fluid has the highest 40 ar 36 ar ratio of up to 1500 and a depleted 36 ar concentration mineralisation is interpreted to have resulted from mixing of zn rich evaporitic brines and h 2 s present in hydrocarbons it is suggested that aqueous fluids acquired organic br and i from hydrocarbons and that hydrocarbons exsolving from the aqueous fluid removed noble gases from solution interaction of variably saline brines and hydrocarbons could account for the variable br cl and i cl composition and 36 ar concentrations recorded by lennard shelf fluid inclusions the distinct 40 ar 36 ar signature of the fluid with the highest i cl ratio suggests the hydrocarbons and brines were sourced independently from different parts of the sedimentary basin these data indicate the complementary nature of halogen and noble gas analysis and provide new constraints on important mixing processes during sediment hosted zn pb mineralisation

geodynamic evolution of a cadomian arc region the northern ossa morena zone iberian massif abstract ductile deformation and polyphase metamorphism in the ossa morena zone of the iberian massif are related to two major tectonothermal episodes of cadomian late neoproterozoic to early cambrian and variscan age middle to late paleozoic the available petrological structural and geochronological data suggest that a number of tectono metamorphic and magmatic episodes occurred during the 620 480 ma interval that would comprise a complete cadomian wilson cycle the geodynamic scenario was that of an andean type continental margin an evolutionary model is presented for this orogeny comprising stages of volcanic arc generation crustal thickening back arc extension tectonic inversion and cratonization a correlation with comparable areas from pre mesozoic massifs elsewhere in europe is proposed in particular with the armorican massif of northern france

isotope fractionation of neon during stepheating extraction a comment on re interpretation of the existence of a primitive plume under australia based on neon isotope fractionation during step heating by gautheron and moreira 2003 using a rayleigh distillation fractionation model we calculate that the maximum isotope fractionation potentially achievable is less than 5 during the early stages of gas release from a sample our calculation corrects the erroneous conclusions of gautheron and moreira 2003 who re interpreted the plume like neon isotopic compositions found in metasomatic apatite from a south eastern australian xenolith matsumoto et al 1997 to be the result of rayleigh type isotope fractionation of originally morb type neon during stepheating gas extraction we stress that the modelling of neon isotopic fractionation by gautheron and moreira 2003 is incorrect and that the finding of a plume like neon isotopic composition in the apatite by matsumoto et al 1997 remains a quite valid and robust conclusion

millennium long recession of limestone facades in london historical data on the temperature and precipitation data for london has been combined with output from the hadley model to estimate the climate of london for the period 1100 2100 ce this has been converted to other parameters such as freeze thaw frequency and snowfall relevant to the weathering of stone facades the pollutant concentrations have been estimated for the same period with the historical values taken from single box modelling and future values from changes likely given current policy within the metropolis these values are used in the lipfert model to show that the recession from karst weathering dominates across the period while the contributions of sulphur deposition seem notable only across a shorter period 1700 2000 ce observations of the late seventeenth century suggest london architects witnessed a notable increase in the recession rate and attributed fretting quality to smoaks of the sea coal the recession rates measured in the late twentieth century lend some support to the estimates from the lipfert model the recession looks to increase only slightly and frost shattering will decrease while salt weathering is likely to increase

the distribution of igneous rocks beneath mont megantic the easternmost monteregian as revealed by gravity at the surface mont megantic the easternmost and most imposing of the monteregian hills is composed of 77 5 leucogranite and syenite and 22 5 gabbro nonetheless the intrusion is characterized by a major positive bouguer anomaly of 20 mgal a computed three dimensional gravity adumbration is consonant with the intrusion having the form of a vertical prismatic column with a flat base at a depth of 10 km the base appears to coincide with the unconformity atop precambrian basement rocks gabbro composes 96 of the adumbration leucogranite and syenite make up the remainder and are confined to an uppermost layer no more than about 1 km thick the subvolcanic texture of the granite and presence of miarolitic cavities at megantic show the shallow level of the intrusion the present surface perhaps having been no deeper than 1 or 2 km this is the same as the depth of emplacement elucidated at mont royal at the opposite end of the monteregian chain which in turn points to uniform uplift and erosion sin

rates and patterns of bedrock denudation by coastal salt spray weathering a seven year record rapid surface lowering of bedrock is taking place in the supratidal zone by salt spray weathering a seven year run of data demonstrates a mean rate of lowering of 0 625 mm a 1 considerable variation exists in annual point lowering values within measurement sites although between site variation is not significant aggregate year to year variations in surface lowering are not significant spatial variation in individual point values may be compensated by temporal variation over an 11 year period there is a marked summer maximum in surface lowering rate and this is strongly correlated with monthly air temperature spatially and temporally episodic swelling of the rock surface is demonstrated this does not correlate statistically with any available climatic variable and is deemed to be a real and largely stochastic phenomenon it is interpreted as rock bursting at the granular scale due to haloclasty the processes most likely to be responsible for the observed rapid denudation are crystallization and thermal expansion of halite both of which are enhanced by high summer temperatures

thermal constraints on crustal rare gas release and migration evidence from alpine fluid inclusions the palfris marl of the helvetic alpine nappes contains four distinct vein fill generations ch4 rich gas is found in abundant fluid inclusions within these carbonate veins while free ch4 gas has also been produced from exploratory boreholes through this formation the stable isotope and helium neon and argon isotopic composition of these fluids has been determined a constant radiogenic 40ar concentration of 1 25 0 13 1 ppm in these differently sited fluids requires an intimate association between the 40arrad source and the hydrocarbon phase this can only be reasonably explained if the 40arrad was input into the hydrocarbon phase during hydrocarbon generation migration or storage prior to entrapment in the fluid inclusions stable isotope results constrain the maturity of hydrocarbon production while fluid inclusion formation pressures and temperatures record values of up to 2 5 kbars and 250 c these values place limits on the range of thermal conditions in which the hydrocarbon 40arrad relationship was established all fluids within inclusions also contain radiogenic 4he40ar values at predicted crustal production ratios these observations provide the first evidence that both 4herad and 40arrad can be quantitatively released on a regional scale bounded by the thermal conditions required to produce the hydrocarbon phase and the conditions under which the fluid inclusions were formed t 190 250 c these results require that negligible quantities of excess 40arrad decoupled from 4herad have been released into this system given the wide array of mechanisms which can potentially cause decoupling of these two species this result provides an important constraint on the role of these processes within the sedimentary fluid regime in contrast the free borehole gas contains excess radiogenic 4he and 21ne relative to 40arrad in proportions which can be accounted for by local production and subsequent diffusion from the surrounding marl the latter pattern is consistent with rare gas migration in lower temperature environments a conceptual model which considers both diffusional and metamorphic release of helium and argon and the ability of the surrounding fluid regime to transport the rare gases from their respective mineral production sites is consistent with both these results and data from regional rare gas studies

maturation thermique de la matiere organique dans un bassin du paleozoique inferieur basses terres du saint laurent quebec canada the organic matter om sampled in 15 oil exploration wells and 102 outcrops of cambrian ordovician rocks in the st lawrence lowlands consists of zooclasts chitinozoans graptolites and scolecodonts and solid bitumen mainly pyrobitumen the reflectance of pyrobitumen transformed in vitrinite equivalent ro std b indicates that the upper part of the platform sequence is mature condensate zone in the quebec area but overmature in the montreal area the platform is divided into three domains based on optical texture of om and types of bitumen domain 1 south of montreal contains a highly reflecting and coked pyrobitumen showing alteration rims domain 3 east of trois rivieres contains low reflecting late solid bitumen commonly associated with oil impregnations domain 2 located midway contains a pyrobitumen with moderate reflectance and locally fine mosaic texture the thermal maturation in the autochthonous sequences of the st lawrence lowlands and in the appalachian allochthons increas

micro topographic change on calcarenites grand cayman island west indies changes in micro topography as a result of varying erosion rates have been monitored on a calcarenite ridge on grand cayman island west indies using a traversing model of the micro erosion meter erosion takes place through the solution of a calcitic cement and solutional disintegration results in a rapid change of micro relief where a protective crust is present surface lowering is slower and also more uniform thus the original relative relief is maintained

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

helium and argon isotopes in rocks minerals and related ground waters a case study in northern switzerland abstract to address the problems related to the transfer of helium and argon isotopes from rocks into related aquifers the concentrations of u th li and k and helium and argon isotopes were measured in a sedimentary sequence from tertiary to permo carboniferous and in crystalline rocks in northern switzerland in addition to whole rock samples mineral separates have also been investigated the observed concentrations of 3 he 4 he and 40 ar in rocks minerals and groundwaters are compared to calculated values which would result from in situ radiogenic production in a closed system this comparison shows that the rocks and minerals have almost completely lost radiogenic in situ produced helium loss of 3 he and 4 he has been controlled by different retention capacities of the rock forming and accessory minerals and fillings therefore measured 3 he 4 he ratios in these rocks can differ from the calculated production ratios the deviation is generally less than a factor of 3 however in certain chemical sediments e g anhydrites elevated ratios of 3 he 4 he up to 15 10 8 which is 20 times the production ratio were observed it is postulated that 3 h the precursor of 3 he might be chemically bound in such sediments during the 12 3 years half life of 3 h and that the beta decay energy of 3 h is too small to liberate 3 he the calculated closed system concentrations of helium in groundwater exceed the measured ones by up to three orders of magnitude implying that the water rock system has not been a closed system since the time of sedimentation and that movable waters have removed helium to a discharge area and to the atmosphere stagnant old waters however could contain high concentrations of helium and supply it to younger movable waters aquitards with low permeability permian shales appear to be a more important source of helium isotopes than water bearing rocks permian sandstones high abundances of all parent elements in the shales almost complete loss of radiogenic helium and the enhanced production ratio of 3 he 4 he 7 2 10 8 in these rocks similar to the ratio observed in the neighbour permian aquifer 9 4 10 8 suggest the shale as a major source of helium isotopes for this aquifer and diffusion as a principal process for helium transfer from the stagnant porewaters in shales into the movable waters in sandstones some sedimentary rocks e g permian sandstones and shales contain more helium than could have been produced since the time of sedimentation while permian sandstones mainly have retained this excess rare gas component they have released radiogenic helium the difference in the retention of these two components most probably demonstrates that migration of radiogenic helium from damage tracks along crystal imperfections to grain boundaries is an important process controlling its loss the abundances of excess 3 he and 4 he in rocks cannot be predicted by in situ production calculations studies of rocks and minerals are required the average ratio of 40 ar 36 ar 385 in groundwaters collected from permian sediments from the weiach borehole is much higher than that in the aquifers from the crystalline basement below the sediments radiogenic 40 ar in permian sediments is mainly liberated by diagenetic water rock interactions the low contribution of radiogenic 40 ar in deep aquifers of the crystalline basement and the fact that chlorine concentrations in groundwaters from the basement are also much lower than in the overlaying permian aquifer eliminates a hypothetical upwards fluid flux from this study we envisage intrabasin sources for helium and argon isotopes in groundwaters with mainly lateral migration of waters through sedimentary layers at different rates and diffusion of helium from slower velocity older waters in more stagnant zones shales into flow passes with highervelocity younger waters in sections with higher permeability sandstones an external source for noble gases is not required in such a model

the influence of seasonal and local weather conditions on rock surface changes on the shore platform at kaikoura peninsula south island new zealand abstract a traversing micro erosion meter tmem was used to measure micro scale surface changes in a 45 cm2 area of an intertidal mudstone shore platform on kaikoura peninsula new zealand with hourly readings taken over 5 days for two seasons within 4 h either side of low tide for all monitoring events the relative height of a total of 120 co ordinates were obtained resulting in 4200 and 4800 measurements for the summer and winter seasons respectively within seasons samples were grouped according to the presence of rain or no rain significant changes were found in the micro topography with variations in temperature and among rain and no rain sample groups for both seasons in the absence of rain there were positive linear relationships between rock surface temperatures and rock surface elevations and regression analysis explained 42 3 and 46 5 of this variation for the summer y 0 098 0 004x p value 0 007 and winter y 0 007 0 012x p value

processes controlling 234u and 238u isotope fractionation and helium in the groundwater of the st lawrence lowlands quebec the potential role of natural rock fracturing abstract the goal of this study is to explain the origin of 234 u 238 u fractionation in groundwater from sedimentary aquifers of the st lawrence lowlands quebec canada and its relationship with 3 he 4 he ratios to gain insight regarding the evolution of groundwater in the region 234 u 238 u activity ratios or 234 u 238 u act were measured in 23 groundwater samples from shallow quaternary unconsolidated sediments and from the deeper fractured regional aquifer of the becancour river watershed the lowest 234 u 238 u act 1 14 0 01 was measured in ca hco 3 type freshwater from the quaternary shallower aquifer where bulk dissolution of the carbonate allows u to migrate into water with little 234 u 238 u isotopic fractionation the 234 u 238 u act increases to 6 07 0 14 in na hco 3 cl type groundwater preferential migration of 234 u into water by recoil is the underlying process responsible for this isotopic fractionation an inverse relationship between 234 u 238 u act and 3 he 4 he ratios has been observed this relationship reflects the mixing of newly recharged water with 234 u 238 u act close to the secular equilibrium and containing atmospheric tritiogenic helium and mildly mineralized older water 14 c ages of 6 6 kyrs with 234 u 238 u act of 6 07 and large amounts of radiogenic 4 he in excess of the steady state amount produced in situ the simultaneous fractionation of 234 u 238 u act and the addition of excess 4 he could be locally controlled by stress induced rock fracturing this process increases the surface area of the aquifer matrix exposed to pore water from which produced 4 he and 234 u can be released by recoil and diffusion this process would also facilitate the release of radiogenic helium at rates greater than those supported by steady state u th production in the rock consequently sources internal to the aquifers could cause the radiogenic 4 he excesses measured in groundwater

acid rain damage to carbonate stone a quantitative assessment based on the aqueous geochemistry of rainfall runoff from stone an onsite experimental procedure was used to identify and quantify acid rain damage to carbonate stone based on the change in rain runoff chemical composition observed changes in runoff from stone are attributed to the interaction of acidic species present in the rain with the stone surface onsite data obtained during the summer and fall of 1984 at three locations in the northeastern united states indicate that carbonate stone surface recession is related to acid deposition although the study is continuing current data are not adequate to distinguish differences in the acid stone reaction between limestone and marble nor among the three study sites a single linear relation between carbonate stone surface recession the dependent variable and hydrogen ion loading to the stone surface the independent variable appears to describe the data set

u pb geochronology and sm nd isotopic composition of proterozoic gneisses channel islands uk gneissic units of the channel islands united kingdom have traditionally been considered to be palaeoproterozoic basement to the late neoproterozoic cadomia terrane based on lithological correlations and imprecise or ambiguous isotopic data a new precise u pb date of 2061 2 ma based on analyses of single zircons for the icart granitic orthogneiss of guernsey confirms a palaeoproterozoic age of its igneous protolith the nd depleted mantle model age t dm of this gneiss is 2220 ma only slightly older than its crystallization age indicating that it represents juvenile crust other gneisses from guernsey have similar t dm ages ranging from 2210 to 2370 ma suggesting that they are also exposures of juvenile palaeoproterozoic crust a component from a penetratively deformed orthogneiss from sark previously correlated with icartian gneisses on guernsey yields a u pb zircon date of 616 4 2 ma this crystallization age demonstrates that the protolith was a cadomian intrusion and that penetrative deformation and amphibolite facies metamorphism in the northern channel islands were cadomian in age the use of gneissic features as a means of invoking the antiquity of many other undated gneissic units in the region is thus considered unreliable the presence of 2170 7 ma zircon xenocrysts within the sark orthogneiss combined with its initial e nd 615 9 5 are strong evidence that pre cadomian basement was a significant source component and that documenting the extent and age of pre cadomian basement may be possible by indirect geochemical methods

transverse micro erosion meter measurements determining minimum sample size two transverse micro erosion meter tmem stations were installed in each of four rock slabs a slate shale basalt phyllite schist and sandstone one station was sprayed each day with fresh water and the other with a synthetic sea water solution salt water to record changes in surface elevation usually downwearing but with some swelling 100 measurements the pilot survey the maximum for the tmem used in this study were made at each station in february 2010 and then at two monthly intervals until february 2011 the data were normalized using box cox transformations and analyzed to determine the minimum number of measurements needed to obtain station means that fall within a range of confidence limits of the population means and the means of the pilot survey the effect on the confidence limits of reducing an already small number of measurements say 15 or less is much greater than that of reducing a much larger number of measurements say more than 50 by the same amount there was a tendency for the number of measurements for the same confidence limits to increase with the rate of downwearing although it was also dependent on whether the surface was treated with fresh or salt water about 10 measurements often provided fairly reasonable estimates of rates of surface change but with fairly high percentage confidence intervals in slowly eroding rocks however many more measurements were generally needed to derive means within 10 of the population means the results were tabulated and graphed to provide an indication of the approximate number of measurements required for given confidence limits and the confidence limits that might be attained for a given number of measurements

two hourly surface change on supra tidal rock marengo victoria australia a traversing micro erosion meter was used to measure rock surface micro topography over 40 cm2 on a supra tidal cliff face from early morning to late evening in late spring from 06 00 hours to 22 00 hours the relative heights of 188 coordinates were obtained using the meter at 2 hour intervals resulting in a data set of 1607 readings monitoring shows that rock surfaces are dynamic entities with significant rise and fall relative to the first measurement at shorter timescales than previously reported the maximum positive rise between readings was 0 261 mm and lowering was 0 126 mm the pattern of change did not relate as expected to environmental variables such as temperature or insolation rather the surface showed greater surface change in the early morning and late afternoon it is hypothesized that this pattern relates to the expansion and contraction of lichen thalli as moisture is absorbed during higher humidity in the morning and late afternoon the implications of these results for weathering studies are considered copyright 2006 john wiley sons ltd

morphometric comparison of weathering features on side by side carbonate rock surfaces with different exposure ages a case from the croatian coast this study presents the comparison of morphometry of karren features developed on two rock surfaces located side by side having different exposure times cosmogenic 36cl analyses were used to determine the age of a rock surface exposed after a rockslide that occurred 2400 years ago whereas the rock surface not affected by the slide was exposed to weathering for a longer time period clint and grikes trittkarren rillenkarren solution pits and kamenitzas were measured comparatively less density of grikes on the surface affected by the slide made it having a fresh appearance most of the grikes were inherited from previous weathering stage and exposure time since the rockslide event has not been sufficient to homogenize these features between both rock surfaces tritkarren and rillenkarren were preferentially found on the rockslide surface indicating that their genesis is likely to occur at decadal to centennial timescale solution pits and kamenitzas were found on both surfaces and some of their size parameters were indistinguishable between the populations of both rock surfaces area and depth parameters of both forms were clearly correlated and we define a morphometric index a d ratio as the slope between these two parameters within each population after an initial stage preferential weathering occurs along the vertical axis in solution pits and laterally in kamenitzas thus we suggest that the a d ratio is related to the evolution relative age of the karren features thus under rock surfaces affected by the same weathering conditions lower a d ratios of solution pits and higher a d ratios of kamenitzas indicate longer time exposed to weathering thus although solution pits and kamenitzas are likely to be developed in decadal to centennial timescales their morphology changes through time at millennial timescale and it can be tracked by morphometric analysis

a morphological study of greenschist weathering on dated coastal structures south devon uk three dated structures up to 450 years in age display the effects of coastal weathering of the greenschist of which they are constructed a variety of weathering forms is present the various topographic surfaces of the structures create variation in weathering environments and consequent weathering processes and rates weathering is enhanced by direct exposure to salt bearing spray and by humid conditions and apparently limited by direct exposure to solar radiation the maximum rates of weathering on the three surfaces approximate to 0 6 mm a 1 over this period consistent with measured contemporary weathering rates for a natural surface formed by this rock type in a nearby coastal location 1997 by john wiley sons ltd