on the possibility of determining rates of removal of uranium from crystalline igneous rocks using u series disequilibria 2 applicability of a u leach model to mineral separates abstract preliminary u series data are presented on the disequilibria of mineral separates of surface samples from the eye dashwa lakes granite canada most analyses of the ferromagnesian quartz plus feldspar and zircon plus sphene grains show that leaching of u has taken place such that 234 u 239 u 1 and 230 th 234 u 1 the simple leach model presented in a companion paper was used to explain these characteristic ratios it is suggested that the leach model may be used on zircon and sphere grains to estimate u leach rates and this is relevant to the suggestion of using sphene like hosts as the primary barrier in the safe disposal of nuclear waste a full analysis of u mobility within a given rock volume was not possible due to our limited data base and to our inability to monitor labile u directly

radiation damage halos in quartz radiation damage halos are present in quartz that surrounds or is adjacent to accessory minerals such as zircon these halos are not visible in transmitted light but are revealed by cathodoluminescence cl they extend up to 45 m away from the source of radioactivity some halos show concentric rings similar to those previously reported in pleochroic halos in biotite radiation damage halos occur in three main settings surrounding inclusions within quartz grains penetrating into quartz from adjacent radionuclide bearing grains and in quartz cement near such grains halos are more common in pre paleozoic rocks than in younger rocks except in cases of unusual enrichment in radioactive elements halos result from damage to quartz crystal structure identical to the process forming pleochroic halos in biotite damage is caused by alpha particles emitted by radioactive elements within mineral grains and is a partial function of time consequently radiation damage halos may have potential uses in geochronology

distribution of uranium thorium and rare earth elements in the eye dashwa lakes pluton a study of some analogue elements abstract the distribution of u th and rare earth elements ree s in the eye dashwa lakes pluton near atikokan ontario is examined materials analysed include a unaltered granite b altered granite c highly altered granite adjacent to open fractures and d fracture filling minerals distinct distribution patterns are noted for u and some ree s among the four types of samples th shows higher concentrations in materials c and d compared with unaltered and altered granite the highly altered granite and some fracture fillings have greater concentrations of u th and ree s the large concentrations of u th and ree s in these materials are due to both sorption on selective materials and precipitation as mineral phases containing these elements the occurrence of uraninite bastnaesite and thorogummite coatings on fracture fillings are examples of this precipitation

review of the modelling of radionuclide transport from u series disequilibria and of its use in assessing the safe disposal of nuclear waste in crystalline rock abstract u series disequilibia from crystalline rocks and u deposits have been used to estimate the timing of hydrogeological events for u and ra mobility and to model the transport rates of u and ra both with some sucess unfortunately activity ratio data alone are not unique to a given process or model and it is shown how inappropriate choice of the model can have quite diverse consequences for interpretation of the data information from other sources is needed to help minimise these non uniqueness problems but as yet the state of methodology is unadequate to assess completely the validity of the models in particular the rate of deposition of u in fractures seems highly dependent upon the availability of trivalent fe and other low temperature minerals whose rates of formation are largely unknown this review reinforces the need to assess closely the suggestion that chemisorption is an effective retardant of fracture borne borne repository source radionuclides

development of quartz cathodoluminescence for the geological grouping of archaeological ceramics firing effects and data analysis abstract cathodoluminescence cl spectrometry reveals genetic crystallographic and chemical characteristics of quartz grains specific to the thermodynamic conditions in which they crystallised and their mineralisation history these genetic characteristics have been used successfully to determine the provenance of sediments geological sediments are the raw material for archaeological ceramics which means quartz cl has a potential application in ceramic provenance studies particularly for fine wares and fabrics in which quartz is the only identifiable inclusion this paper demonstrates the viability of quartz cl for ceramic studies i by determining that the effect of thermal radiation heat does not alter the genetic defect structure of quartz up to 1100 c and ii using genetic quartz types to differentiate geological groups in an experimental ceramic assemblage which could not be identified using traditional methods inaa and ceramic petrography

comparison of 226ra 238u and 228th 228ra disequilibrium with weathering indices in beach sand sediments from greece weathering indices can be used to quantify weathering of rocks at various stages of weathering processes and provide a better understanding of element mobility during weathering various weathering indices have been proposed in the literature worldwide in the present work radioactive secular disequilibrium has been used to determine weathering extent thirty seven samples from kavala and thirty from sithonia beach sands all of them being the weathering products of the local granitic plutons are studied for their secular disequilibrium in both 238u and 232th series 226ra 238u and 228ra 228th respectively the results are compared to weathering indices already in use worldwide and suggest a consistent correlation with wip alkaline and alkaline earth element leaching and pwi silica leaching for the well and very well sorted sands and for the heavy minerals of kavala this study suggests that with an appropriate choice of the weathering index and samples both u series and weathering index can recover the extent of chemical weathering

radiation damage in diopside and calcite crystals from uranothorianite inclusions combining observation and simulation radiohalos formed around urano thorianite uth from the tranomaro granulitic skarns se madagascar were studied these structures consist of uth grains surrounded by both aluminous diopside cpx and calcite cc1 crystals optical microscope and scanning electron microscope sem images revealed 1 the presence of radiating cracks around the uth probably due to swelling of the metamict uth 2 a diffuse optical halo at the cc1 uth interface and 3 a wide reaction zone at the cpx uth interface composed of secondary calcite cc2 with low temperature sheet silicate from the smectite group samples prepared across various interfaces using focused ion beam fib were investigated by transmission electron microscope tem in contrast to sem observations there is no direct contact between cc1 and uth from cc1 to uth we found 1 a large 200 300 nm amorphous zone a enriched in u th and ca but without si 2 a chain b of very small 20 nm tho2 crystals 3 another amorphous zone c which in contrast to zone a is enriched in si and 4 another zone d made of small amorphous si rich bubbles the organization is similar for the uth cc2 interface the presence of hydrous minerals smectite and carbonate calcite in reaction zone and in cracks the presence of pb rich inclusions in secondary calcite the abundance of fluid inclusions in the porous layer in calcite the dissociation of u and th in the calcite uranothorianite layer and the tho2 chains along interfaces are strong indications that low temperature crystallization was promoted by a fluid phase srim simulation was used to calculate the effect of and recoil particles of the three decay chains in cpx cc and uth the thickness of the damaged area calculated for in cpx and cc are similar to the widths of the recrystallized areas observed in thin section 30 m corrected with the wandering recoil effect the size of the damaged area calculated for recoil nuclei in cc 50 60 nm is multiplied by 3 and is in rather good agreement with the thickness of the totally amorphous layer at the cc uth interface 200 nm finally it is emphasized that radiohalos are a point of chemical and physical weakness in a rock and probably a starting point for alteration

radiation damage rims in quartz from uranium bearing sandstones abstract using cathodoluminescence cl mode of a scanning electron microscope sem radiation damage in quartz is made visible in uranium vanadium bearing sandstones located in the salt wash member of the morrison formation jurassic from the colorado plateau u s a detrital quartz grains surrounded by uranium minerals display radiation damage rims three concentric rims with thicknesses of 37 m 24 m and 16 m have been observed the rims are similar to halos surrounding uranium and thorium rich accessory minerals observed by owen 1988 they are due to alpha particles which create damage when penetrating a medium the width of the rims agrees well with the bragg kleeman rule and corresponds to the most energetic alpha particles in the 238u decay series sandstones entirely cemented by vanadium clays also exhibit radioactive rims which demonstrates that uranium has been removed during diagenesis these results have important implications for the uranium ore genesis in the salt wash sandstones because they imply an ancient episode of uranium leaching prior to recent weathering therefore cathodoluminescence in sandstones may be useful in recognizing ancient zones or episodes of accumulation and leaching of alpha emitting nuclides from the uranium series

distribution of radon sources and effects on radon emanation in granitic soil at ben lomond california the abundance and distribution of radioelements on bulk and microscopic scales were investigated in residual granitic derived soil at a facility for investigating the movement of radon into structures in bulk soil samples ra concentrations range from 0 6 to 1 3 pci g and variations in ra th and k appear to be controlled mainly by heterogeneities inherited from the parent granitic rock which contains abundant dikes and inclusions u in soil and parent rock is concentrated in primary minerals mainly zircon and sphene and in secondary sites that are of greater importance for rn emanation the main u bearing secondary sites are weathered sphene grain boundary coatings weathered biotite and plagioclase as well as dense fe rich coatings and a ree phosphate mineral present in near vertical fracture zones in saprolite underlying shallow loam elevated u in these sites generally correlates with high ti al fe and or p preferential distribution of u and ra on grain boundaries and porous weathered minerals is reflected in relatively high rn emanation rates in the soil highest emanation occurs between 1 3 and 2 3 m depth where fine pedogenic phasesgibbsite and amorphous silica and fe ooh are most abundant it is related to fixation of ra by these phases which precipitate close to the surface and accumulate at these depths by illuviation separation of ra from u may occur locally given remobilization of u series elements from secondary sites and large differences between ra and u sorption capabilities of several phases present in the soil concentration of u along permeable fracture zones in saprolite suggests that contribution of soil gas rn from depth 2 m could be significant to rn availability near the surface

an improved method for ra isotope 226ra 228ra 224ra measurements by gamma spectrometry in natural waters application to co2 rich thermal waters from the french massif central abstract an improved method was developed to measure 226 ra 228 ra and 224 ra in freshwaters by gamma spectrometry radium was selectively extracted from acidified samples using specific filters 3m empore radium rad disks the latter was subsequently analysed by gamma spectrometry simultaneous and direct determination of the activities of the three isotopes was performed by comparison of gamma rays of the radium rad disks with those of a calibrated standard disk this efficient and reliable method allowed a reduction of sample processing to a few hours this technique was applied to analyse the ra isotope compositions of several co 2 rich hydrothermal springs of the western border of the limagne graben french massif central the studied springs emerge from a succession of granitic outcrops lined up along a major fault their chemical compositions evolve from calcic and magnesian chloro bicarbonated to sodic bicarbonated all the springs display high ra activities probably linked to high co 2 content and or high cation content of these waters with various ra isotope ratios 226 ra activity ranges from 588 to 2287 mbq l and 228 ra activity from 260 to 1590 mbq l whereas 224 ra displays an activity between 245 and 1808 mbq l four of the six analysed springs have 228 ra 226 ra activity ratios lower than 0 7 thus significantly lower than the ratio expected from an interaction with a calc alkaline granitoid typically having 232 th 238 u activity ratio between 1 and 2 low 228 ra 226 ra ratio 0 27 of the northern water montpensier suggests the existence in this area of a zone of u concentration possibly resulting from u mobilization and accumulation induced by previous hydrothermal events the 224 ra 228 ra ratios display smaller variations they suggest short transit times from the zone of ra leaching to the surface a few days or a very shallow addition of 224 ra e g from a localised zone where 228 th could be preferentially adsorbed on the mineral surfaces in some cases these ratios might be used to infer differences in transit times of waters between neighboring springs

airborne measurements of gravity wave breaking at the tropopause 1 a breaking atmospheric gravity wave was investigated with a combination of airborne in situ dynamical measurements and ground based vhf radar observations the wave was generated by flow over mountains and it was observed to break near the tropopause the measurements reveal that the wave was overturning at the tropopause and that the initial breakdown into turbulence involved the generation of smaller oscillations with a horizontal wavelength of around 500 m there was also evidence that the turbulence associated with the wave breaking can cause substantial mixing in the tropopause region

metamorphic origin of ore forming fluids for orogenic gold bearingquartz vein systems in the north american cordillera constraints froma reconnaissance study of δ15n δd and δ18o the western north american cordillera hosts a large number of gold bearing quartz vein systems from the mother lode of southern california through counterparts in british columbia and southeastern alaska to the klondike district in central yukon these vein systems are structurally controlled by major fault zones which are often reactivated terrane bounding sutures that formed in orogens built during accretion and subduction of terranes along the continental margin of north america mineralization ages span mid jurassic to early tertiary and encompass much of the evolution of the cordilleran orogen nitrogen contents and 15n values of hydrothermal micas from veins are between 130 and 3 500 ppm and 1 7 to 5 5 per mil respectively these values are consistent with fluids derived from metamorphic dehydration reactions within the phanerozoic accretion subduction complexes which have 15n values of 1 to 6 per mil the 18o values of gold bearing vein quartz from different locations in the cordillera are between 14 6 and 22 2 per mil but are uniform for individual vein systems the d values of hydrothermal micas are between 110 and 60 per mil ore fluids have calculated 18o values of 8 to 16 per mil and d values of 65 to 10 per mil at an estimated temperature of 300 c d values of ore fluids do not show any latitudinal control these results indicate a deep crustal source for the ore forming fluids most likely of metamorphic origin low dh2o values of 120 to 130 per mil for a hydrous muscovite from the sheba vein in the klondike district reflect secondary exchange between recrystallizing mica and meteoric waters collectively the n h and o isotope compositions of ore related hydrothermal minerals indicate that the formation of these gold bearing veins involved dilute aqueous carbonic and nitrogen bearing fluids that were generated from metamorphic dehydration reactions at deep crustal levels these data are not consistent with either mantle derived fluids or granitoid related magmatic fluids nor do they support a model involving deeply circulated meteoric water

preferential leaching and the age of radiation damage from alpha decay in minerals preferential release into solution of radionuclides that result from alpha decay is a contributor to natural isotopic disequilibrium such release is critical to geochemical understanding of alpha decay products and would be an undesirable characteristic of solidified nuclear waste in deep geological formations spontaneous annealing of the radiation damage that is responsible for the preferential release is shown to diminish the effect in thorianite and uraninite which we have found to be 550 to 1000 m y old respectively leaching experiments and measurements of the thorium and uranium isotopes show that there is strongly enhanced release of short lived 228th relative to 232th but only slight enhancement of long lived 234u and 230th relative to 238u and 232th these results are interpreted in terms of natural annealing of damage occurring on a time scale between the 10 and 105 years of the alpha decay products with a simple assumption actual times for the survival of the enhanced leaching in these minerals are 15 000 years

velocity and temperature structure functions in the upper troposphere and lower stratosphere from high resolution aircraft measurements abstract high resolution measurements obtained from noaa best atmospheric turbulence bat probes mounted on an egrett high altitude research aircraft were used to characterize turbulence in the upper troposphere and lower stratosphere at scales from 2 m to 20 km focusing on three dimensional behavior in the sub kilometer scale range data were analyzed for 129 separate level flight segments representing 41 h of flight time and 12 600 km of wind relative flight distances the majority of flights occurred near the tropopause layer of the winter subtropical jet stream in the southern hemisphere second order structure functions for velocity and temperature were analyzed for the separate level flight segments individually and in various ensembles a 3d scaling range was observed at scales less than about 100 m with power law exponents for the structure functions of the velocity component in the flight direction varying mostly between 0 4 and 0 75 for the separate flight segments but close to for the

repetitive hydraulic fracturing and shear zone inflation in an archean granitoid hosted ribbon banded au quartz vein system renabie area ontario canada abstract economically significant tonalite 2722 ma and trondhjemite 2728 ma hosted archean au quartz vein mineralization in the renabie area ontario located in a marginal part of the 10 15 km thick wawa domal gneiss terrane shows strong structural control major ore zones occur in e w and nw nnw striking ductile brittle high strain zones that are superimposed on an earlier regional foliation mineralized zones are up to 20 30 m wide mineable to a depth of 1300 vertical metres and dip typically at 60 80 angles production and reserves for the renabie mine totalled 6 million tonnes at 6 6 g t au and 2 g t ag net shear from kinematic indicators is oblique reverse south side up sinistral on e w structures e g nudulama renabie main zone depth 2475 level and west side up sinistral on nw nnw structures e g braminco 21 zone the strain features of the shear zone hosted mineralization together with evidence of reaction enhanced ductility associated with hydrothermal fluid wallrock interaction indicate that mineralization and hydrothermal alteration occurred synchronously with shear deformation the characteristic banded appearance book ribbon structure of the renabie veins which is typical of many archean and cordilleran au quartz vein systems is interpreted to be the result of inflationary vein formation by repeated increments of hydraulic fracturing and mineral deposition 250 750 associated with hydrothermal fluid overpressuring within and below the actively deforming ductile brittle shear zones crack seal type process fracture orientation was largely controlled by the anisotropy in rock tensile strength associated with the approximately planar shear fabric the element mineral association of renabie is typical of oxidized archean au quartz vein systems containing anhydrite hematite carbonate and tourmaline with a chalcophile association consisting of mos 2 cu pb sulphides native au ag and pb bi au ag tellurides key factors in the development of significant mineralization at renabie as compared with other usually small low grade archean granitoid hosted au quartz vein systems include the repetitive nature of the mineralizing process and the focusing of au bearing fluids within the actively deforming shear zones a specific and sufficiently large reservoir of overpressured hydrothermal archean au bearing fluid was generated at some location not yet identified in the archean crustal structure represented by the kapuskasing section

stratospheric gravity wave fluxes and scales during deepwave abstractduring the deep propagating gravity wave experiment deepwave project in june and july 2014 the gulfstream v research aircraft flew 97 legs over the southern alps of new zealand and 150 legs over the tasman sea and southern ocean mostly in the low stratosphere at 12 1 km altitude improved instrument calibration redundant sensors longer flight legs energy flux estimation and scale analysis revealed several new gravity wave properties over the sea flight level wave fluxes mostly fell below the detection threshold over terrain disturbances had characteristic mountain wave attributes of positive vertical energy flux efz negative zonal momentum flux and upwind horizontal energy flux in some cases the fluxes changed rapidly within an 8 h flight even though environmental conditions were nearly unchanged the largest observed zonal momentum and vertical energy fluxes were mfx 550 mpa and efz 22 w m 2 respectively a wide variety of disturbance scales were found at flight level over

arsenic mobility in mildly alkaline drainage from an orogenic lode gold deposit bralorne mine british columbia abstract the historical 1932 1971 bralorne mine produced over 87 million grams of au from an archetypal orogenic lode gold deposit in southwest british columbia high concentrations of as in mine drainage however represent an on going environmental concern prompting a detailed study of effluent chemistry the discharge rate at the mine portal was monitored continuously over a fourteen month period during which effluent samples were collected on a quasi weekly basis water samples were also collected on synoptic surveys of the adit between the portal and the main source of flow in the flooded workings total concentrations of as in the mildly alkaline ph 8 7 portal drainage average 3034 g l whereas at the source they average 5898 g l as emergent waters from the flooded workings flow toward the portal their dissolved oxygen content and ph increase from 0 to 10 mg l and from 7 7 to 9 respectively near the emergence point dissolved fe precipitates rapidly sorbing both as iii and as v with increasing distance from the emergence point dissolved as iii concentrations drop to detection limits through sorption on hydrous ferric oxide and through oxidation to as v concentrations of dissolved as v on the other hand increase and stabilize reflecting lower sorption at higher ph and the lack of available sorbent nonetheless based on synoptic surveys approximately 35 of the source as load is sequestered in the adit resulting in as sediment concentrations averaging 8 5 wt the remaining average as load of 1 34 kg d is discharged from the portal partitioning of as v between dissolved and particulate phases in portal effluent is characterized by a sorption density of 0 37 mol as mol fe 1 and by a distribution coefficient k d of 130 l g hfo the relatively high sorption density may reflect co precipitation of as with fe oxyhydroxides rather than a purely adsorption controlled process results of this study show that the as self mitigating capacity of drainage from orogenic lode gold deposits may be poor in high ph and fe limited settings

the relationship between riverine u series disequilibria and erosion rates in a basaltic terrain u series isotopes have been measured in the dissolved phase suspended load and bedload of the main rivers draining basaltic catchments in iceland for the dissolved phase 234u 238u and 238u 230th range between 1 08 and 2 2 and 7 4 and 516 respectively for the suspended load and bedload 234u 238u and 238u 230th range from 0 97 to 1 09 and from 0 93 to 1 05 respectively chemical erosion rates calculated from dissolved major elements range between 13 and 333 t km 2 yr 1 physical erosion rates have also been estimated from existing data and range between 21 and 4864 t km2 yr with an average of 519 t km 2 yr 1 u series disequilibria indicate that weathering in iceland operates at close to steady state conditions a model of continuous weathering indicates a maximum weathering timescale of 10 kyr with an average rate of uranium release into water of 1 6 10 4 yr 1 which is significant when compared to granitic terrains located at similar latitudes and to tropical basaltic terrains all river waters display 234u 238u greater than secular equilibrium consistent with the effects of alpha recoil the same dissolved phase 234u 238u exhibit a negative trend with physical erosion rates explained by the dominant effect of close to congruent chemical weathering of hyaloclastites in the younger basaltic terrains therefore chemical erosion rate and mineral weathering susceptibility play a major role in determining 234u 238u disequilibria in basaltic river waters comparison of global data for river basins in which weathering was recently strongly limited indicates a negative correlation between silicate weathering rates estimated with major elements and the age of weathering estimated with u series disequilibria this strongly suggests a key role of time and soil thickness on the chemical erosion of silicates

annealing radiation damage and the recovery of cathodoluminescence the structural recovery upon heat treatment of a highly metamict actinide rich zircon u 6000 ppm has been studied in detail using a range of techniques including x ray powder diffraction raman spectroscopy shrimp ion probe electron microprobe transmission electron microscopy and cathodoluminescence analysis the structural regeneration of the amorphous starting material depends on random nucleation it starts between 800 and 950 c when amorphous zrsio4 decomposes to form crystalline zro2 and amorphous sio2 at around 1100 c well crystallised zrsio4 grows at the expense of the oxides u has been retained in the newly grown zircon whereas pb was evaporated during the heat treatment this process is in marked opposition to the reconstitution of moderately metamict minerals which experience a gradual recovery controlled by the epitaxial growth at the crystalline amorphous boundaries both of these recovery processes are not the direct inverse of metamictisation the structural regeneration was found to be connected with a significant increase in the emission of cl in all cases annealing heavily damaged zircon and moderately damaged zircon and monazite we observe that the final wellcrystallised annealing products emit more intense cl than their radiation damaged starting minerals although having almost identical elemental composition our observations are taken as evidence that the cl is not only determined by the chemical composition of the sample but is also strongly controlled by structural parameters such as crystallinity or the presence of defect centres

helium irradiation study on zircon synthetic zrsio4 and mildly to strongly radiation damaged natural zircon samples were irradiated with 8 8 mev 4he2 ions fluences in the range 1 1013 5 1016 ions cm2 for comparison an additional irradiation experiment was done with 30 mev 16o6 ions fluence 1 1015 ions cm2 the light ion irradiation resulted in the generation of new synthetic zrsio4 or additional mildly to strongly metamict natural samples damage the maximum extent of the damage is observed in a shallow depth range approximately 32 33 m 8 8 mev he and 12 m 30 mev o below the sample surface i e near the end of the ion trajectories these depth values and the observed damage distribution correspond well to defect distribution patterns as predicted by monte carlo simulations the irradiation damage is recognised from the notable broadening of raman active vibrational modes lowered interference colours i e decreased birefringence and changes in the optical activity i e luminescence emission at very low damage levels a broad band yellow emission centre is generated whereas at elevated damage levels this centre is suppressed and samples experience a general decrease in their emission intensity most remarkably there is no indication of notable structural recovery in pre damaged natural zircon as induced by the light ion irradiation which questions the relevance of alpha assisted annealing of radiation damage in natural zircon

geochemistry of mineralizing fluids in the bralorne pioneer mesothermal gold vein deposit british columbia canada gold quartz veins at the bralorne mesothermal vein deposit have extensive quartz ankeritic carbonate muscovite hydrothermal alteration envelopes that grade outward to chlorite calcite albite minor pyrite with traces of sphalerite galena and tetrahedrite are found in the veins with native gold more abundant pyrite and arsenopyrite with lesser pyrrhotite and chalcopyrite occur in altered wall rock adjacent to the veins envelopes are characterized by addition of k 2 o co 2 s as and au with corresponding depletion of na 2 o feo total and mgo sio 2 and cao are locally depleted and reconcentrated fluid inclusions suggest that deposition of gold was from dilute aqueous solutions 2 ch 4 at 350 degrees c and 1 75 kbars progressive dilution of this fluid by cooler meteoric water led to fluids at 250 degrees c and 0 5 to 1 kbar with 1 wt percent or less nacl equivalent and no detectable carbonic component sulfur isotope ratios of sulfides associated with gold mineralization range from 7 to 9 per mil clustering about a magmatic signature of 0 per mil the ore fluid had a delta 18 o value of 13 or 1 and delta 13 c of 11 or 2 per mil based on measurements in coexisting vein quartz carbonate and muscovite temperature of the mineralizing fluids appears to have increased with depth at a normal geothermal gradient of approximately 30 degrees c km gold sulfides and the associated alteration assemblages are modeled using observed mineralogy and thermodynamic data for chloride complexes as having been deposited from a slightly acid solution ph 4 5 with an na k ratio of at least 8 1 and a high content of dissolved co 2 log fugacity 2 5 conditions were strongly reducing as suggested by the log fugacity of ch 4 0 5 with f sub o 2 about 10 super 30 bars and f sub s 2 about 10 super 7 bars precipitation of gold in the immediately adjacent highly quartz sericite ankerite pyrite altered wall rock was due to reaction with carbonation of the wall rock that caused the ph of the ore fluid to rise destabilizing aurous chloride complexes such a shift is in the direction of slightly increasing or constant stability of gold thiosulfide ions and at a relatively constant f sub o 2 the most significant result of this modeling is that in detail the actual precipitation of gold is by reduction of aurous ions by electrons donated through concurrent oxidation of s super 2 in h 2 s to s super in pyrite fes 2 this explains the empirically observed correlation between pyrite and gold in this type of deposit and in the model between consumption of fe super 2 and production of pyrite on the one hand with precipitation of gold on the other

mobility of u series nuclides during basalt weathering an example from the deccan traps india abstract u series disequilibria have been measured by tims and mc icp ms in dissolved phases and suspended sediments of the main basaltic rivers from the deccan trap region india for dissolved phases 234u 238u 230th 238u and 226ra 238u range between 1 11 and 1 28 between 0 03 10 2 and 1 35 10 2 and between 0 02 and 0 16 respectively for suspended particles 234u 238u 230th 238u and 226ra 238u range from 0 95 to 1 1 from 1 23 to 1 59 and from 0 1 to 0 47 respectively 230th 238u and 234u 238u systems show direct links with indices of weathering the data also indicate possible redistributions between the solid and aqueous phases and indicate that erosion processes do not presently operate at steady state because present day physical erosion rates are higher than expected 100 400 mm ka versus 40 mm ka for a steady state process for the narmada and the tapti basins models assuming either discrete or continuous particle leaching yield timescales for chemical erosion of 40 90 ka in contrast with basins located in northern latitudes erosion in the deccan basins does not appear to have been significantly disturbed during the last glaciation 234u 238u disequilibria in the dissolved phase of large rivers world wide are also explored and two key factors are highlighted in this study the dissolution of carbonates releasing dissolved u at secular equilibrium and the silicate weathering rate estimated at the scale of the watershed in particular a positive correlation is found between dissolved 234u 238u and basaltic weathering rates for the deccan that could reflect a key role of physical erosion since for silicate monolithological basins chemical erosion rates are primarily controlled by physical erosion rates for basins with mixed lithology dissolved organic matter also plays a key role in the preferential release of 234u from silicate minerals 234u 238u ratios in rivers therefore reflect a mixture between u released by carbonate dissolution and 234u preferentially released from silicate minerals located in high physical erosion and peat areas

measurements of cesium and strontium diffusion in biotite gneiss a significant retardation of radionuclides transported by flowing water from an underground repository can be expected if the nuclides are able to diffuse into the water filled micropores in the rock this diffusion into the pores will also increase the surface available to interactions between the nuclides in the ground water and the rock material such as sorption to calculate the retardation it is necessary to know the sorption properties and the diffusivities in the rock matrix for the radionuclides diffusion experiments with cesium and strontium in biotite gneiss samples have been performed both the transport of strontium and cesium through rock samples and the concentration profiles of cesium and strontium inside rock samples have been determined the result shows that diffusion of cesium and strontium occurs in the rock material a diffusion model has been used to evaluate the diffusivity both pore diffusion and surface diffusion had to be included in the model to give good agreement with the experimental data if surface diffusion is not included in the model the effective pore diffusivity that gives the best fit to the experimental data is found to be higher than expected from earlier measurement of iodide diffusion in the samemore type of rock material this indicates that the diffusion of cesium and strontium sorbing components in rock material is caused by both pore diffusion and surface diffusion acting in parallel less

listvenite and related rocks perspectives on terminology and mineralogy with reference to an occurrence at cregganbaun co mayo republic of ireland the rock listvenite is named and defined by reference to historical observations and recommendations are made so that listvenite s s can be distinguished from related carbonate rich alteration products of ultramafic rocks the mineralogy and tectonic setting of listvenite are reviewed taking into account the descriptions and classifications used in the literature the petrography of listvenite and related rocks at cregganbaun serves as a reference to illustrate the characteristics of true listvenite and closely related products of listvenitic alteration

on the possibility of determining rates of removal of uranium from crystalline igneous rocks using u series disequilibria 1 a u leach model and its applicability to whole rock data the removal of u from granitic rocks is characterised by234u 238u 1 and 230th 234u 1 it is notable from weathered eye dashwa lakes canada granite samples and from the published data that230th 234u ratios seldom exceed a limiting value of about 2 a u leach model is discussed in detail which may account for these observations the model assumes that 230th is practically immobile and that the removal of u can then be measured against the decay rate of the unsupported230th a property of the model is that the isotope ratios reach constant values reflecting a kind of secular equilibrium and this implies that u is seldom removed faster than the decay of230th if the limited230th 234u ratios from the data correspond to secular equilibrium ratios then this allows simple calculation of u leach rates from any given subsurface sample a test for the model using235u 231pa ratios is suggested a comparison of leach rates derivable from u th pb systematics of colorado and wyoming granite samples with the corresponding estimates from the model shows that the latter are high by a factor of 10 50 data from rapidly weathered surface rinds suggests that the presence of labile u restricts the application of the model to subsurface low weathered zones

the relative mobility of u th and ra isotopes in the weathered zones of the eye dashwa lakes granite pluton northwestern ontario canada radioisotope activity ratios of weathered surface rocks from the eye dashwa lakes granite pluton show that in the 238u decay series 226ra has been leached more rapidly than the grandparent 234u and 238u isotopes the observation of 238th232th disequilibria in the 232th decay series shows that either 228th half life of 1 9 yrs or 228ra half life of 5 75 yrs have been removed from these rocks very rapidly indeed isotope ratios of separated mineral fractions appear to show that whereas uranium tends to be removed from all mineral fractions ra is strongly readsorbed onto feldspars presumably as these undergo alteration to clay minerals this necessitates making a distinction between intermineral mobility of u or ra and the net loss of u or ra from the whole rock an attempt has been made to model quantitatively the transport rate of ra though with little success failure of the modelling appears to indicate that the mobility of 228ra is higher than might be predicted by the mobility of 226ra that is the two isotopes are not strict analogues of one another in their response to initial weathering

radionuclides in ground water of the carson river basin western nevada and eastern california u s a abstract ground water is the main source of domestic and public supply in the carson river basin ground water originates as precipitation primarily in the sierra nevada in the western part of carson and eagle valleys and flows down gradient in the direction of the carson river through dayton and churchill valleys to a terminal sink in the carson desert because radionuclides dissolved in ground water can pose a threat to human health the distribution and sources of several naturally occurring radionuclides that contribute to gross alpha and gross beta activities in the study area were investigated generally alpha and beta activities and u concentration increase from the up gradient to down gradient hydrographic areas of the carson river basin whereas222rn concentration decreases both226ra and228ra concentrations are similar throughout the study area alpha and beta activities and u concentration commonly exceed 100 pci l in the carson desert at the distal end of the flow system radon 222 commonly exceeds 2 000 pci l in the western part of carson and eagle valleys adjacent to the sierra nevada radium 226 and228ra concentrations are alpha emitting radionuclides in the ground water originated from the dissolution of u rich granitic rocks in the sierra nevada by co2 oxygenated water dissolution of primary minerals mainly titanite sphene in the granitic rocks releases u to the water dissolved u is probably removed from the water by adsorption on fe and mn oxide coatings on fracture surfaces and fine grained sediment by adsorption on organic matter and by coprecipitation with fe and mn oxides these coated sediments are transported throughout the basin by fluvial processes thus u is transported as dissolved and adsorbed species a rise in the water table in the carson desert because of irrigation has resulted in the oxidation of u rich organic matter and dissolution of u bearing coatings on sediments producing unusually high u concentration in the ground water alpha activity in the ground water is almost entirely from the decay of u dissolved in the water beta activity in ground water samples is primarily from the decay of40k dissolved in the water and ingrowth of238u progeny in the sample before analysis approximately one half of the measured beta activity may not be present in ground water in the aquifer but instead is produced in the sample after collection and before analysis potassium 40 is primarily from the dissolution of k containing minerals probably k feldspar and biotite radon 222 is primarily from the decay of226ra in the aquifer materials radium in the ground water is thought to be mainly from alpha recoil associated with the decay of th in the aquifer material some ra may be from dissolution or desorption or ra rich coatings on sediments

further study of terrain effects on the mesoscale spectrum of atmospheric motions abstract wind and temperature data collected on commercial airliners are used to investigate the effects of underlying terrain on mesoscale variability these results expand upon those of nastrom et al by including all available data from the global atmospheric sampling program gasp and by more closely focusing on the coupling of variance with the roughness of the underlying terrain over mountainous regions the earlier results showing that variances are larger over mountains than over oceans or plains with greatest increases at wavelengths below about 80 km are confirmed statistical tests are used to confirm that these differences are highly significant over mountainous regions the roughness of the underlying terrain was parameterized from topographic data and it was found that variances are highly correlated with roughness and in the troposphere with background wind speed average variances over the roughest terrain areas range up to about ten times larger than those over the oceans these re

small scale wind fluctuations in the tropical tropopause layer from aircraft measurements occurrence nature and impact on vertical mixing abstractthe contribution of turbulent mixing to heat and tracer transport in the tropical tropopause layer ttl is poorly constrained partly due to a lack of direct observations here the authors use high resolution 20 hz airborne measurements to study the occurrence and properties of small scale 100 m wind fluctuations in the ttl 14 19 km over the tropical pacific the fluctuations are highly intermittent and appear localized within shallow 100 m patches furthermore active turbulent events are more frequent at low altitude near deep convection and within layers of low gradient richardson number a case study emphasizes the link between the turbulent events and the occurrence of inertio gravity waves having small horizontal or vertical scale in order to evaluate the impact of the observed fluctuations on tracer mixing their characteristics are examined during active events they are in broad agreement with inertial range turbulence theory the motions are close to 3d isotropic and the sp

226ra 238u and 228th 228ra disequilibrium as weathering indices in beach sand sediments associated with granitoids from cyclades greece abstract radioactive secular disequilibrium measured as the absolute difference from 1 of the 226ra 238u and 228ra 228th ratios have been used to determine weathering extent twenty eight samples from beach sands of cyclades islands all of them being the weathering products of the local granitic plutons are studied for their secular disequilibrium in both 238u and 232th series 226ra 238u and 228th 228ra respectively the results are compared to weathering indices already in use worldwide and suggest a significant linear correlation of u series disequilibrium with wip alkaline and alkaline earth element leaching and pwi silica leaching for the beach sands studied and significant non linear correlations with cia chemical index of alteration and pia plagioclase index of alteration considering only the heavy mineral enriched samples significant correlations exist between u series disequilibrium and cia ciw chemical index of weathering and pia therefore with an appropriate choice of the weathering index and samples both u series and weathering index can recover the extent of chemical weathering on the other hand the use of th series disequilibrium as a weathering index is limited due to 228th and 228ra geochemistry and especially due to their short radionuclide half lives u series disequilibrium can therefore be used as a relatively sensitive weathering index in sediments consistent with cia ciw and pia indices however the mineralogical composition must be considered more specifically the mineral content of the sediments should involve considerable amounts of sensitive to weathering minerals e g fe mg minerals as well as feldspars

in situ radionuclide transport and preferential groundwater flows at ineel idaho decay series disequilibrium studies uranium and thorium decay series disequilibria in groundwater occur as a result of water rock interactions and they provide site specific natural analog information for assessment of in situ long term migration of radionuclides in the far field of a nuclear waste disposal site in this study a mass balance model was used to relate the decay series radionuclide distributions among solution sorbed and solid phases in an aquifer system to processes of water transport sorption desorption dissolution precipitation radioactive ingrowth decay and recoil isotopes of u 238u 234u th 232th 230th 228th 234th ra 226ra 228ra 224ra and rn 222rn were measured in 23 groundwater samples collected from a basaltic aquifer at the idaho national engineering and environmental laboratory ineel idaho the results show that groundwater activities of th and ra isotopes are 2 4 orders lower than those of their u progenitors which average 1 35 0 40 dpm 238u l with 234u 238u ratios of 1 6 3 0 222rn activities range from 20 to 500 dpm l modeling of the observed disequilibria places the following constraints on the time scale of radionuclide migration and water rock interaction at ineel 1 time for sorption is minutes for ra and th time for desorption is days for ra and years for th and time for precipitation is days for th years for ra and centuries for u 2 retardation factors due to sorption average 106 for 232th 104 for 226ra and 103 for 238u 3 dissolution rates of rocks are 70 to 800 mg l y 4 ages of groundwater range from 10 to 100 years contours of groundwater age as well as spatial patterns of radionuclide disequilibria delineate two north south preferential flow pathways and two stagnated locales relatively high rates of dissolution and precipitation and recoil of 222rn occur near the groundwater recharging sites as well as in the major flow pathways decay of the sorbed parent radionuclides e g 226ra and 228ra on micro fracture surfaces constitutes an important source of their daughter 222rn and 228th activities in groundwater

a fluid inclusion study of au bearing quartz vein systems in the central and north deborah deposits of the bendigo gold field central victoria australia the central and north deborah gold deposits with a production of about 7 tons au are located in one of 15 domes in the bendigo gold field central victoria australia an important mesothermal lode gold province the gold bearing quartz vein systems are hosted predominantly by reverse faults in lower ordovician turbidites which underwent lower greenschist facies metamorphism in the central and north deborah mines there are six stages of quartz veins that developed in the following sequence 1 laminated veins with a metal association of au as sb pb zn ni 2 spurs au 3 massive barren veins main dilation stage 4 brecciated veins with au as 5 quartz ankerite veinlets and 6 late pure quartz or calcite veinlets of the three mineralized vein stages 1 2 and 4 only the first one predated or was coeval with the main deformation event whereas stages 2 and 4 postdated the main deformation the vein structures indicate that vein development was controlled by repeated fluctuations of fluid pressure inducing hydraulic fracturing fluid inclusions in vein quartz contain c o h fluids of variable compositions three main types of fluid inclusions are recognized at room temperature type i two phase primary ch4 v h2o l fluid inclusions type ii two or three phase primary pseudosecondary co2 v or l ch4 v or l h2o l fluid inclusions including iia ch4 co2 h2o and iib co2 h2o fluid inclusions and type iii h2o v h2o l fluid inclusions type iii fluid inclusions are further divided into three groups iiia primary pseudosecondary vapor rich iiib primary pseudosecondary liquid rich and iiic secondary liquid rich data from fluid inclusion distribution microthermometry and raman spectroscopy indicate that fluids associated with au mineralized quartz veins stages 1 2 and 4 have moderate salinity ranging from 0 to 12 wt percent nacl equiv modeled salinities around 7 8 wt nacl equiv these veins formatted at temperatures from 325 to 375 c and pressures of 200 to 300 mpa with emplacement depths of about 8 to 12 km fluids associated with barren quartz veins stages 3 5 and 6 have a low salinity of about 0 to 3 wt percent nacl equiv modeled salinities about 2 3 wt nacl equiv and lower temperatures there is evidence of fluid immiscibility in all vein stages and mixing between fluids of the same souce but differing fo2 may also have influenced gold deposition cox et al 1995 hydrothermal ore forming fluids responsible for gold mineralization are in the ch2 co2 h2o nacl system whereas those of massive barren veins stage 3 and veinlets stages 5 and 6 are in the co2 h2o nacl and h2o nacl systems respectively the carbonic phases of type i and ii fluid inclusions range from pure ch4 through mixed ch4 and co2 to pure co2 gold ore forming fluids were weakly acidic with f o2 estimated to have been 10 25 to 10 37 bars and generally above the co2 ch4 and below the so2 h2s buffer boundaries throughout gold mineralization the relatively reduced mineralizing fluids are similar to those of other turbidite hosted lode gold deposits and counterparts in volcanic plutonic terranes

w and m type tetrad effects in ree patterns for water rock systems in the tono uranium deposit central japan abstract abundances of rare earth elements plus y ree were determined for granitic rocks tertiary sedimentary rocks and related groundwater in the tono area central japan tetrad effects concave curves in ree patterns were found for these rocks and groundwater samples conjugate m and w types of tetrad effects were simultaneously observed in these specimens which constitute the water rock system the granitic rocks show the m type tetrad effects while the groundwater and the sedimentary rocks exhibit the w type tetrad effects non chondritic y ho ratios were found especially in the groundwater y ho ratios showed larger values than the chondritic value for the samples showing w type tetrad effects and vice versa these results suggest that 1 preference of the groundwater for a w type tetrad effect and larger y ho ratio than chondrite produces an m type tetrad effects and lower y ho ratios in the granitic rocks during weathering processes 2 the w type tetrad effect and larger y ho ratio for the sedimentary rocks is brought about by the fixation of groundwater ree onto the sedimentary rocks the variation of the tetrad effect and y ho ratio was confirmed by laboratory experiments on the leaching of ree from the granitic rocks the w type tetrad effect and large y ho ratio in the u mineralization zone in the sedimentary rocks were also found by sims analysis which is consistent with the w type tetrad effect and larger y ho ratio in the whole rock abundances of the sedimentary rocks disequilibrium of the u series 234 u 238 u analyzed by sims in the u mineralization zone suggests that the u bearing minerals were formed through precipitation from groundwater as it became reducing these results suggest that the ree in the sedimentary rocks were transported by the groundwater from the granitic rocks in the tono area based on this study it is implied that the degree of the tetrad effects and the variation of y ho ratio can be valuable tools to investigate the migration of ree during water rock interactions in natural systems

downstream changes in antimony and arsenic speciation in sediments at a mesothermal gold deposit in british columbia canada abstract this study investigates sb speciation in sediments along the drainage of the upper peter adit at the bralorne au mine in southern british columbia canada and compares the behavior of sb with that of as the upper peter mineralization consists of native au in quartz carbonate veins with 1 wt sulfides dominated by pyrite and arsenopyrite although stibnite the primary sb bearing sulfide mineral can be locally significant dissolved sb concentrations can reach up to 349 g l 1 in the mine pool sediments were collected for detailed geochemical and mineralogical characterization at locations along the 350 m flow path which includes a 100 m shallow channel within the adit a sediment settling pond about 45 m beyond the adit portal and an open wetland another 120 m farther downstream from the mine pool to the wetland outlet dissolved sb in the drainage drops from 199 g l 1 to below the detection limit due to the combined effect of dilution and removal from solution speciation analyses using x ray absorption near edge structure xanes spectroscopy indicate that sb iii s accounts for around 70 of total sb in the sediments in the main pool at the far end of the adit at a short distance 24 m downstream of the main adit pool however sb iii o and sb v o species represent 50 of total sb in the bulk sediments indicating significant oxidation of the primary sulfides inside the adit although sb appears largely oxidized in the bulk samples collected near the portal sb iii s species are nevertheless present in the

geochemistry of syntectonic crustal fluid regimes along the lithoprobe southern canadian cordillera transect in conjunction with the lithoprobe southern canadian cordillera program an extensive examination of geochemical indicators of origins movement chemical evolution and economic significance of paleocrustal fluids was conducted the study area covers approximately 360 000 km2from the canadian rockies to vancouver island research incorporated petrological mineralogical fluid inclusion 18o d 13c and rb sr studies of samples of quartz carbonate veins and other rock types the results of the study document a variety of pre syn and postorogenic crustal fluid events in the rockies a major pre laramide hydrothermal event was identified which was comprised of a west to east migration of warm saline brines this was followed by a major circulation of meteoric water in the rockies during laramide uplift in the southern omineca extensional zone convecting surface fluids penetrated to the brittle ductile transition at 350 450 c and locally into the underlying more ductile rocks a principal c

uranium series disequilibrium studies of granitic rocks abstract igneous plutons of the canadian shield which are to be considered as possible storage sites for radioactive waste should be free from any evidence of past mobility of chemical species through the rock however cores taken from some plutons to depths of up to 1 km reveal the presence of hydrous low temperature alteration along joints and fractures and within the body of the rock to test whether such rocks or any others have been subjected to chemical transport in geologically recent times we may study the state of radioactive equilibrium between 238 u 235 u and 232 th and their short lived daughterisotopes members of the decay series of these parent isotopes have half lives ranging from a few hours to 0 25 ma also the chemical characteristics of the various daughters vary significantly allowing us to test the mobility of isotopes of similar half life but differing chemistry if the rock has been chemically undisturbed for 10 ma or more then the activity in d p m g of each daughter in these decay schemes will be equal to that of its parent isotope conversely if the rock was chemically disturbed 10 n a ago then some daughter isotopes with half lives t 10 n a will be out of equilibrium with their parents preliminary results are presented showing disequilibrium effects in samples from atikokan ontario

radiation induced defects in drusy quartz athabasca basin canada a new aid to exploration of uranium deposits room temperature powder electron paramagnetic resonance epr spectra of drusy quartz i e euhedral quartz crystals as coatings on or infillings in cavities and fractures from five uranium mineralized areas in the eastern athabasca basin saskatchewan canada reveal a suite of radiation induced defects these epr spectra also show that radiation induced defects in drusy quartz from different geologic occurrences are similar in nature but vary widely in abundance for example radiation induced defects in drusy quartz from altered basement rocks significantly below mineralization are close to or below detection limits providing the first line of direct evidence for previous suggestions that fluids from the underlying basement rocks were uranium deficient drusy quartz in ore samples and those from alteration haloes around uranium orebodies are characterized by elevated levels of radiation induced defects similarly drusy quartz from less altered sandstones near the present day surface hundreds of meters above mineralization where uranium rich minerals are generally absent contains abundant radiation induced defects comparison of epr spectra of drusy quartz from less altered sandstones before and after hf treatments reveals that radiation induced defects are uniformly distributed in individual crystals in contrast to the preferred concentration in the grain margins and along fractures in detrital quartz these results suggest that radiation induced defects in drusy quartz were most likely formed by bombardment of alpha particles emitted by uranium bearing fluids during crystal growth therefore detection of radiation induced defects in drusy quartz from less altered sandstones represents a new near surface technique for exploration of uranium mineralization in the athabasca basin

an analogue validation study of natural radionuclide migration in crystalline rocks using uranium series disequilibrium studies abstract concentrations and isotope ratios of natural decay series radionuclides have been studied in three contrasting crystalline rock drillcore sections intersecting water conducting fractures deep in the bedrock radioactive disequilibria resulting from rock water interactions were observed in two of the cores these indicated u migration along distances of 40 cm or more on a time scale of 1 myr in conjunction with th immobility under the same conditions fracture surface minerals showed a high affinity for radionuclide retardation and a limit of 3 cm is suggested for the migration of radionuclides from fracture fluids into the saturated rock this limit may correspond to enhanced matrix porosities resulting from earlier hydrothermal activity along the same channels

lack of bedrock grain size influence on the soil production rate abstract our study deals with the part played by bedrock grain size on soil formation rates u and th series disequilibria were measured in two soil profiles developed from two different facies of the same bedrock i e fine and coarse grain size granites in the geomorphically flat landscape of the experimental breuil chenue forest site morvan france the u and th series disequilibria of soil layers and the inferred soil formation rate 1 2 mm ky 1 are nearly identical along the two profiles despite differences in bedrock grain size variable weathering states and a significant redistribution of u and th from the uppermost soil layers this indicates that the soil production rate is more affected by regional geomorphology than by the underlying bedrock texture such a production rate inferred from residual soil minerals integrated over the age of the soil is consistent with the flat and slowly eroding geomorphic landscape of the study site it also compares well to the rate inferred from dissolved solutes integrated over the shorter time scale of solute transport from granitic and basaltic watersheds under similar climates however it is significantly lower than the denudation or soil formation rates previously reported from either cosmogenic isotope or u series measurements from similar climates and lithologies our results highlight the particularly low soil production rates of flat terrains in temperate climates moreover they provide evidence that the reactions of mineral weathering actually take place in horizons deeper than 1 m while a chemical steady state of both concentrations and u series disequilibria is established in the upper most soil layers i e above 70 cm depth in such cases the use of soil surface horizons for determining weathering rates is precluded and illustrates the need to focus instead on the deepest soil horizons

relation between u series nuclide migration and microstructural properties of sedimentary rocks abstract natural radionuclide migration in miocene sedimentary rocks has been studied at the tono u deposit in japan which is a potentially useful analogue of radioactive waste isolation in geological environments uranium series disequilibrium studies have revealed that natural radionuclides have been redistributed during the past 3 5 105 a in the u mineralized zone permeability tests using core samples of the u mineralized zone have shown that the microfabrics of sedimentary rocks such as the connectivity of pores which control the groundwater movement directly influence the redistribution of nuclides detailed observations using cathodoluminescence cl and electron probe microanalysis epma were carried out after a dye impregnation test in order to improve the understanding of the importance of microfabrics in relation to nuclide migration results of the observations show that u has migrated within detrital grains such as biotite and quartz as well as between these grains uranium series disequilibrium studies of each detrital quartz and biotite grain have been shown that these detrital minerals behave differently in respect of the migration of u owing to their different textural properties the detrital biotite flakes especially along the 001 cleavage planes appear to have fixed u for a long period of time whereas the u has remained mobile within the microfractures in detrital quartz grains

geochemistry of mine waters draining a low sulfide gold quartz vein deposit bralorne british columbia abstract the bralorne and pioneer mines now inactive produced over 4 million ounces of au from an orogenic lode au deposit located on the eastern edge of the coastal mountains of sw british columbia between 2007 and 2009 drainage from a recently developed exploration adit was investigated in order to better understand and anticipate potential environmental management issues associated with the development of this type of deposit in the future portal discharge rate and specific conductance were monitored continuously over a 14 month period during which 36 water samples were collected additional samples were collected from flooded workings within the adit concentrations of as and sb at the portal range as high as 1738 and 316 g l respectively while those in the mine pool reach 3304 and 349 g l respectively effluent chemistry is mildly alkaline ph 8 7 and is dominated by na ca mg hco3 and so4 geochemical inverse modeling of effluent composition indicates weathering of albite 2515 kg a ferroan dolomite 718 kg a pyrite 456 kg a arsenopyrite 23 kg a and stibnite 2 kg a modeled sulfide reaction coefficients normalized by their corresponding host rock concentrations suggest that oxidation of arsenopyrite is 25 times slower than that of pyrite whereas oxidation of stibnite is 1 5 times faster oxidative dissolution of arsenopyrite and stibnite releases 10 6 kg a of as and 1 1 kg a of sb of which 57 and 46 respectively are sorbed to ferrihydrite and gibbsite on the bed of the shallow channel through which the mine pool drains to the portal although mass balance calculations predict the formation of sufficient ferrihydrite to sorb 100 of the as dissolved in the mine pool this attenuation process was ineffective possibly because the precipitated sorbents settled to the bottom of the water column or because of competition for sorption sites from ca and hco3 the dissolved sb as molar ratio in portal effluent 0 082 is much greater than the sb as ratio of the mineralization 0 002 because of slower arsenopyrite oxidation and somewhat lesser sorption of sb

the use of autoradiography in determining the distribution of radionuclides sorbed on thin sections of plutonic rocks from the canadian shield abstract autoradiography coupled with classical petrographic techniques has been used to determine the distribution of radionuclides sorbed under oxic conditions onto rock thin sections representative of the four major types of plutons in the canadian shield to determine which minerals are most effective in removing radionuclides from aqueous solutions kodak spectroscopic and ilford k 5 nuclear emulsion plates were investigated the ilford film was found to give higher resolution and required a shorter exposure time than the kodak film sorption was found to be negligible on quartz and strongest on the mafic minerals the pyroxenes micas hornblende and opaques and on alteration minerals chlorite and sphene precipitation of am and pm was observed indicating that for actinides and rare earths experimentally obtained static sorption coefficients may reflect precipitation as well as sorption and must be used with caution in modelling studies

actinide and rare earth element characteristics of deep fracture zones in the lac du bonnet granitic batholith manitoba canada the history of major trace and actinide element mobility and fluid infiltration has been studied in two deep fractures 1 km in the lac du bonnet batholith as part of the canadian nuclear fuel waste management program core samples collected from two fracture zones fr1 and fr2 1175 m deep containing saline groundwater tds 50 g l were investigated mineralogically chemically and isotopically 238u series o and h several sequentially overprinting alteration stages were identified from early high temperature to later low temperature hydrothermal alteration k feldspar illite chlorite and later kaolinite formed during these stages subsequent infiltration of oxidizing fluids produced alteration of the chlorite to hydrous iron oxides fracture zone fr1 contains predominantly hematite coating fracture zone fr2 is characterized by the formation of a breccia and by an intense alteration of the granite in contact with this breccia to illitic clay alteration occurred during infiltration either of formation brines or of isotopically evolved meteoric water where 18o 8 to 12 and d 65 to 20 at calculated temperatures between 250 and 25 c loss of ca na and sr and to some extent ba was observed in all the altered samples relative to fresh granite a sharp increase in k mg u th and ree was observed in the illitic clay rich zone pronounced disequilibria of 234u238u 0 5 230th234u 0 7 and 226ra230th 0 9 exist in the illitic clay indicating loss of 234u 230th and 226ra to the groundwater within the last 1 5 ma in contrast an excess of 234u 230th and 226ra was measured in the brecciated samples the disequilibria are consistent with a model involving loss of 234u 230th and 226ra to groundwater by recoil from u deposited on the illitic clay surfaces these radionuclides were deposited subsequently in the nearby brecciated zone