winter cascading of cold water in lake geneva 1 during the winters of 1998 and 1999 observations were made of the cascading of cold water from the nearshore shallow shelf zones and down the sloping sides of lake geneva cascading starts on the average 10 hours after the onset of surface cooling the draining cold water descends like a gravity current and the downslope speed of the head of these slugs of cold water u has a mean value of 5 2 cm s 1 with slugs persisting on the average for 8 hours when the monin obukov length scale at the water surface l is negative implying convection occurs and d over bar lg 1 where d is the mean shelf depth the nondimensionalized speed of the front of slugs u b 1 3 is found to be 1 3 0 4 where b is the surface buoyancy flux integrated over the time period from one slug to the next each slug is unsteady the head being followed by several fronts in which the temperature of the current decreases and its thickness increases these fronts travel faster than the mean flow by a factor of r 1 38 0 3 dynamical similarities are found with roll waves observed in turbulent open channel flows the circulation induced by the cascade is found to give a positive skewness to the time derivatives of near surface temperature in shallow waters in contrast with negative values close to the slope the volume of cold water carried by a slug increases with downslope distance as a consequence of turbulent entrainment and the contribution of convectively unstable plumes from the surface the average volume carried by the slug across the 21 m depth contour is about 1 9 times the volume of water in shallower water i e that on the shelf between shore and a depth of 21 m implying that cascading is an efficient means of flushing shelf water integrated around the lake the mean total volume flux amounts to 11 5 the average winter river inflow

lunar core formation new constraints from metal silicate partitioning of siderophile elements abstract analyses of apollo era seismograms lunar laser ranging data and the lunar moment of inertia suggest the presence of a small at least partially molten fe rich metallic core in the moon but the chemical composition and formation conditions of this core are not well constrained here we assess whether pressure temperature conditions can be found at which the lunar silicate mantle equilibrated with a fe rich metallic liquid during core formation to this end we combine measurements of the metal silicate partitioning behavior of siderophile elements with the estimated depletion due to core formation in those elements in the silicate mantle of the moon we also explore how the presence of the light element sulfur suggested by seismic models to be present in the core at concentrations of up to 6 wt in the lunar core affects core formation models we use published metal silicate partitioning data for ni co w mo p v and cr in the lunar pressure range 1 atm 5 gpa and characterize the dependence of the metal silicate partition coefficients d on temperature pressure oxygen fugacity and composition of the silicate melt and the metal if the core is assumed to consist of pure iron core mantle equilibration conditions that best satisfy lunar mantle depletions of five siderophile elements ni co w mo and p are a pressure of 4 5 0 5 gpa and a temperature of 2200 k the lunar mantle depletions of cr and v are also consistent with metal silicate equilibration in this pressure and temperature range if 6 wt s is incorporated into the lunar core our results therefore suggest that metal silicate equilibrium during lunar core formation occurred at depths close to the present day lunar core mantle boundary this provides independent support for both the existence of a deep magma ocean in the moon in its early history and the presence of significant amounts of sulfur in the lunar core

terrestrial origin of the moon abundance patterns of siderophile elements in the earth s mantle have been determined by complex processes connected with internal segregation of a metallic core amounting to 32 of the earth s mass although the lunar core may be only 2 of the lunar mass and formed in very different conditions to the earth s core the lunar siderophile pattern is closely related to that of the earth s mantle implying that the material in the moon derived mainly from the earth s mantle after core formation new models for the accretion of the earth which require impacts by large planetesimals in the presence of a corotating primitive terrestrial atmosphere provide a mechanism for transferring material from the earth s mantle into geocentric orbit as a ring of proto lunarplanetesimals from which the moon later accreted

flaws in the giant impact hypothesis of lunar origin abstract the currently popular giant impact hypothesis attempts to explain both the origin of the moon and the high angular momentum density of the earth moon system in terms of a single event in which the growing earth was struck by a martian sized planetesimal this hypothesis is implausible in its present form because 1 it possesses a low intrinsic dynamical probability 2 the collision would have melted and differentiated the earth causing geochemical signatures quite different to those actually observed and 3 the collision mechanics cause the moon to be derived mainly from the mantle of the impactor whereas geochemical evidence strongly indicates derivation of protolunar material mainly from the terrestrial mantle these problems can be resolved by requiring that a giant impact occurring after the earth had accreted to 70 of its present size was responsible for the high angular momentum density of the earth moon system but did not itself produce the moon collisions by much smaller e g 0 001 0 01 me high velocity planetesimals at a very late stage of accretion were probably responsible for ejecting protolunar material from the earth s mantle without causing gross melting and differentiation of the earth

a mechanism for the generation of the lunar mare basalts summary according to the magma ocean or magmasphere model of lunar formation rapid accretion would result in the formation of a solid primitive core of undifferentiated material surrounded by a spherical shell of molten silicate as the outer layers of the moon cool by radiation of heat to space the deep interior will warm due to the decay of trace radionuclides this will lead to compression of the remnant magmasphere producing excess pressure in the fluid magma it is proposed that relief of this excess pressure through vents opened by the excavation of the mascon basins was sufficient to drive the major episodes of mare volcanism between 3 9 3 2 ga thermal models of the moon are constructed and a range of initial conditions based on the magmasphere model are identified which satisfy known constraints on lunar evolution the rate at which radial thermoelastic stress accumulates within the moon is calculated and from this estimates of the maximum volume of basaltic magma which could be produced by this mechanism are obtained by comparing these calculated magma generation rates with estimates of the volume of mare basalts residing on the lunar surface we are able to identify a set of initial temperature profiles which both satisfy the known constraints on lunar evolution and are able to produce the observed volume of mare basalts these models are characterised by deep magmaspheres and or initially warm central temperatures

secondary copper enrichment in tailings at the laver mine northern sweden field and laboratory studies of the sulphide bearing tailings at laver northern sweden show that the present release of metals from the tailings is low especially with regard to cu a large part of the cu released by sulphide oxidation is enriched in a distinct zone just below the oxidation front the enrichment zone occurs almost all over the tailings area except in areas with a shallow groundwater table the cu enrichment is caused by formation of covellite and adsorption onto mineral surfaces the transport of zn co cd ni and s seems to be controlled mainly by adsorption no secondary zone or secondary minerals containing these metals have been found just below the groundwater table metals are released into solution when the enrichment zone reaches the groundwater due to the low ph an increased release of metals especially cu can be expected in the future since the enrichment zone is moving towards the groundwater table

mobility and retention of trace elements in hardpan cemented cassiterite tailings north queensland australia this study reports on the mobility and retention of trace elements in cassiterite tailings at the inactive jumna mill tropical north queensland since the 1980s the uncapped tailings have developed laterally discontinuous fe rich hardpans which are located in the higher parts of gently sloping tailings masses and at the top 50 cm of the tailings piles hardpan cemented tailings comprise thin layers typically 0 2 2 mm thick of hfo hydrous ferric oxides and sulfate efflorescences cementing tailings grains in comparison to the tailings the hardpan cemented tailings contain significantly higher median as ca cd co cu fe in mn mo stotal th u y and zn values partial leaching studies of tailings and pond water analyses indicate that wetting and acidification of fe cemented tailings removes significant proportions of trace elements into pore and surface waters tin shows no mobility due to the presence of weathering resistant cassiterite sno2 and as and pb display limited mobility possibly due to their coprecipitation with jarosite type phases and hfo materials at the top of the tailings profile by contrast the trace elements cd ce cu la ni pb u and zn display the greatest mobility possibly due to their incorporation in soluble sulfate efflorescences and sorption onto mineral and hfo surfaces hence the fe rich hardpans do not protect the sulfidic tailings from further oxidation nor do they cause permanent sequestration of trace elements

the earliest atmosphere of the earth walker j c g 1982 the earliest atmosphere of the earth precambrian res 17 147 171 this paper examines from the point of view of atmospheric physics the possibility that the initial complement of volatiles in the material that formed the earth was very much larger than that remaining the escape of large amounts of hydrogen into an interplanetary vacuum is possible only if the heat source in the upper levels of the atmosphere provided by solar extreme ultraviolet and particle emissions was much larger than it is today rapid escape of hydrogen would have swept heavy minor gases along with it if the rate of escape declined due to a decreasing upper atmospheric energy source minor gases would have been selectively retained by the earth beginning with the heaviest rotation would not have facilitated escape significantly because a rapidlyescaping atmosphere would have tended to conserve angular momentum if earth accreted in the presence of a gaseous nebula it would have acquired a dense hot atmosphere of nebular composition this primary atmosphere would probably have been convective and adiabatic at lower levels with the upper atmosphere approximately isothermal and devoid of turbulence planetary rotation would have imposed a global circulation on the upper atmosphere and overlying nebula with downwelling over the poles and upwelling over the equator this circulation would have carried away into the nebula any gases released from the solid phase during the course of accretion the primary atmosphere may not have dissipated completely after the disappearance of the nebula heavy gases particularly may have been retained by the earth to contribute to the present volatile inventory

earth moon system planetary science and lessons learned the origin and evolution of the moon is now well understood many bizarre theories were proposed to account for our satellite before these were swept away by the data from the apollo missions we now understand with the benefit of hindsight that we are looking at a very ancient object whose surface has changed little for the past 3 5 b y nevertheless the moon remains a unique body in the solar system the moon formed as the result of a glancing collision with the earth of a mars sized impactor late in the accretional history of the earth when both bodies had differentiated into metallic cores and silicate mantles the impactor is derived from the neighborhood of the earth as shown by similarities in o and cr isotopes our satellite is mostly derived from the mantle of the impactor rather than from the mantle of the earth the moon melted perhaps entirely and a thick 50 km feldspathic crust dated at 4460 40 ma floated on the ocean of magma the closest analogue may be the crust of mercury the interior crystallized into cumulate zones of differing mineralogy from which the mare basalts were later derived by partial melting the impact history of the lunar surface has provided insights into planetary accretion the planetesimal hypothesis and the bombardment history in the inner solar system debate continues whether the concentration of impact produced basins constitutes a cataclysm or the tail end of accretion a notable example and a target for future missions is the 2500 km diameter south pole aitken basin that may provide insights into the nature of the deep lunar crust remaining significant problems include whether the moon has a small metallic core while the deep interior structure is not well understood new seismic and heat flow data are an urgent priority

formation of sequences of cemented layers and hardpans within sulfide bearing mine tailings mine district freiberg germany abstract the roles of mineral dissolution precipitation transformation and mass transport processes related to formation of characteristic cemented layer hardpan sequences were studied in low sulfide and low carbonate freiberg polymetallic mine tailings using high resolution profiling combined geochemical geomicrobiological and geophysical methods allowed description of the process of weathering of reactive mineral phases and the position of the oxidation front in detail as well as revealing the mechanisms of cementation of tailings predominantly by the formation of gels poorly crystalline phases autochthonous and allochthonous gels reduced the porosity of cemented layers to values 1 whereas secondary crystalline phases were less efficient in filling the pore space electron microprobe analysis of cemented tailings showed that common jarosite group minerals contained up to about 8 wt pbo and 0 2 1 9 wt as 2 o 5 iron as si gels reached contents of up to 44 wt as 2 o 5 in gel rich cemented layers zinc was below the detection limit in the studied secondary phases sequential extraction of cemented and related oxidized brown silt layers confirmed that the bulk of as was bound to amorphous poorly crystalline hydrous oxides of fe whereas pb was often bound to jarosite zinc was found preferentially in the water soluble and the exchangeable fractions in the grey silt and the sand directly underlying the oxidized layers as pb and zn occurred as sulfide minerals the main effects of the cemented layer hardpan sequences at the studied site are 1 a temporary natural attenuation of the toxic compounds 2 a restriction of the downward movement of the oxidation front and 3 a reduction of the extent of the erosion of the surface of the tailings impoundment by wind and water the potential of a heap to form cemented layers and hardpans is greatly increased by a heterogeneous distribution of grain sizes and reactive materials in the topmost zone as well as by the occurrence of sulfide rich tailings on top of layers with low permeability

the characterization of arsenic in mine waste arsenic is dispersed widely in nature and is the 47th most abundant element among the 88 known natural elements the average crustal abundance is 1 5 ppm with higher concentrations in reduced shales and coals it is concentrated in many metal bearing mineral deposits being a chalcophile element it occurs in many metallic deposits including those of cu ag au zn hg u sn pb mo w ni co and pge arsenic is often more dispersed than ore minerals in those deposits and as such is a useful indicator in geochemical exploration boyle and jonasson 1973 hale 1981 cohen and bowell 2014 consequently elevated concentrations of as are common in mine waste and process waste from metal bearing ores bowell et al 1994 2013 thornton 1994 craw and pacheco 2002 lazareva et al 2002 in particular as is the main element of environmental concern in most hardrock mines in this chapter we outline the principal occurrences of as at mine sites and their environmental significance as an example of the detailed controls on as geochemistry in mine waste we focus on the gold mines in new zealand many mines are significant point sources for as in the environment and some mine sites have high concentrations of as locally often exceeding 1 in ore or waste for almost all of these mines the as is a natural but undesirable component of the ore and therefore the as is discarded with the rest of the mine wastes hence mine wastes especially mine tailings are major repositories of as and have to be managed carefully view this table table 1 major primary mineral hosts for as in mine waste arsenic is an especially common constituent of sulfide bearing mineral deposits where as typically occurs either as separate as minerals table 1 or in solid solution

hydrochemistry mineralogy and chemical fractionation of mine and processing wastes associated with porphyry copper mines a case study from the sarcheshmeh mine se iran abstract the sarcheshmeh is one of the largest oligo miocene porphyry cu deposits in the world comparative hydrochemical mineralogical and chemical fractionation associated with mining efflorescence salts and processing wastes of this mine are discussed hydrochemical results showed that rock waste dumps reject wastes and old impoundments of tailings are the main sources of acid mine drainage waters amd that contain potentially toxic metals such as cd co cu mn ni and zn as well as al episodic fluxes of highly contaminated acidic waters were produced in a tailings dam over a short period of time secondary soluble minerals provide important controls on the quality of amd produced especially in old dry tailings impoundments secondary sulfate minerals such as gypsum magnesiocopiapite hydronium jarosite kornelite and coquimbite were found in rock waste drainages and in old weathered reject wastes highly soluble secondary minerals such as gypsum eriochalcite and bonattite are also observed in an evaporative layer on old tailings impoundments chemical fractionation patterns of potentially toxic elements showed that the geochemical behavior of metals is primarily controlled by the mineralogical composition of waste samples elements such as co cr cu mn ni and zn are readily released into the water soluble fraction from efflorescence salts associated with rock waste drainages as well as from the evaporative layer of old tailings potentially toxic elements such as as mo and pb are principally adsorbed or co precipitated with amorphous and crystalline fe oxides but they may also be associated with oxidizing primary sulfides and residual fractions following the development of the dammed tailings pond the secondary minerals were dissolved producing acidic waters contaminated by al 154 mg l 1 cu 150 mg l 1 cd 0 31 m gl 1 co 2 13 mg l 1 mn 73 7 mg l 1 ni 1 74 mg l 1 zn 20 3 mg l 1 and cl 1690 mg l 1 therefore the potential use of recycled water from the sarcheshmenh dammed tailings pond is diminished by the presence of corrosive ions like cl in highly acidic fluids that promote corrosion of pipes and pumps in the water recycling system

major and trace metal mobility during weathering of mine tailings implications for floodplain soils abstract mine tailings discharged to river systems have the potential to release significant quantities of major and trace metals to waters and soils when weathered to provide data on the mechanisms and magnitudes of short and long term tailings weathering and its influence on floodplain environments three calendar year long column leaching experiments that incorporated tailings from potosi bolivia and soil from unaffected downstream floodplains were carried out these experiments were designed to model 20 cycles of wet and dry season conditions two duplicate columns modeled sub aerial tailings weathering alone a third modeled the effects of long term floodplain tailings contamination and a fourth modeled that of a tailings dam spill on a previously contaminated floodplain as far as was practical local climatic conditions were modeled chemical analysis of the leachate and column solids optical mineralogy xrd sem epma bcr and water soluble chemical extractions and speciation modeling were carried out to determine the processes responsible for the leaching of al ca cu k na mg mn sn sr and ti over the 20 cycles the ph declined to a floor of ca 2 in all columns calcium cu mg mn and na showed significant cumulative losses of up to 100 60 30 95 and 40 respectively compared to those of al k sr sn and ti which were up to 3 1 5 5 1 and 0 05 respectively the high losses are attributed to the dissolution of relatively soluble minerals such as biotite and oxidation of chalcopyrite and cu sulfosalts while low losses are attributed to the presence of sparingly soluble minerals such as svanbergite cassiterite and rutile these results strongly suggest that the release of tailings to floodplains should be limited or prohibited and that all tailings should be removed from floodplains following dam spills

molybdenum in eucrites evidence for a metal core in the eucrite parent body molybdenum concentrations from 15 to 70 ppb in eucrites have been determined with a new method of neutron activation these values are very low compared to chondrites and are in agreement with the large depletions of other siderophile elements in eucrites the eucrites have a mean mo la ratio of 0 0066 which is a factor of 570 lower than the ci chondritic ratio 3 75 the depletions of siderophiles in eucrites were presumably caused by segregation of metal molybdenum however is fractionated as an incompatible element similar to la among the individual eucrites the variable concentrations but roughly constant ratio of mo to la indicate that metal was absent during the fractionation that produced the eucrites and imply that core formation occurred before the fractionation the need for a relatively large degree of partial melting to completely segregate metal argues for a fractional crystallization model for the production of the eucrite magmas the amount of metal in the eucrite parent body epb required to obtain the observed depletion of the mo la ratio depends on the degree of partial melting during metal silicate equilibrium the depletion of co has a dependence on the degree of partial melting different from mo and w and using co together with mo and w the metal content and degree of partial melting can be estimated a metal content of 30 to 50 and metal segregation at approximately 50 partial melting of the silicates is consistent with the data if the epb had a ratio of co to refractory lithophile elements less than ci chondrites a metal content as low as 20 with metal segregation at 20 partial melting is possible a large metal core in the epb vesta may therefore be detectable from a spacecraft

accumulation of arsenic from acidic mine waters by ferruginous bacterial accretions stromatolites in the acidic stream ph 2 2 4 of the carnoules pb zn mine gard france very high as contents from 9 to 20 can be accumulated as ferric arsenate and arsenate sulphate precipitates in rapidly growing bacteria made structures the main bacterial forms are rod shaped and sheathed their sheath is made of fe as rich material and is coated with ferric arsenate colloidal particles or may be partially included in authigenic crystals living forms ofthiobacillus type bacteria have been recognized in the precipitates the cyclic development of bacterial colonies alternating with sand deposition and erosive episodes results in the formation of as rich ferruginous accretions these laminated and dome shaped bacterial constructions are similar to those of stromatolites the extremely high contents of solute as in upstream flow 250 mg 1 are lowered by 2 3 order of magnitude downstream lead is also precipitated and concentrated in this feas rich bacterial stromatolite 2500 ppm pb this accumulation and concentration of as and heavy metals via direct or induced microbial action limits pollution downflow but seasonal storms could erode these feaspb rich deposits and drastically increase pollution the accumulation of ferric arsenate by bacterial stromatolites suggests that possible microbial remediation strategies may be used in acid mine drainage environments

topographic hadley cells when a rotating fluid over sloping topography is heated from below and or cooled from above horizontal temperature gradients develop which drive convection cells aligned with isobaths we refer to these cells as topographic hadley cells laboratory experiments reveal that sinking occurs in small cyclonic vortices situated in relatively shallow regions this is balanced by slower upwelling in adjacent deeper regions the cross isobath motions which connect the upwelling and downwelling are accelerated by coriolis forces resulting in strong jets which follow isobathic contours for anticlockwise rotation the surface jets keep the shallows to their left when looking in the direction of flow which is opposite to both kelvin and rossby wave propagation

weathering fluxes of arsenic from a small catchment in slovak republic inputs of as to a small catchment due to chemical weathering of bedrock mechanical weathering of bedrock and atmospheric precipitation were 71 53 23 98 and 0 02 g ha 1 year 1 respectively the output fluxes of as due to mechanical erosion of soil biological uptake stream discharge and groundwater flow were 6 32 4 77 0 37 and 0 02 g ha 1 year 1 respectively the results indicate that arsenic accumulates in soil and regolith with a very high rate this is attributed to the selective weathering and erosion with respect to arsenic and fixation of arsenic in the secondary solids produced by weathering the output fluxes of as in stream and groundwater in vydrica catchment in slovak republic 0 39 g ha 1 year 1 based on muscovite biotite granites and granodiorites were much lower compared to catchments in a gold district in the czech republic these results may be ascribed to the low levels of arsenic pollution measured in vydrica catchment the arsenic fluxes were estimated by calculation of mechanical and chemical weathering rates of the bedrocks in vydrica catchment from mass balance data on sodium and silica the justification of the steady state of na and si is that neither of the elements is appreciably accumulated in plants and in exchangeable pool of ions in soil

influence of climate mineralogy and mineral processing on the weathering behaviour within two low sulfide high carbonate gold mine tailings in the eastern desert of egypt despite its importance within environmental management strategies little concern is shown to sulfide oxidation and or hardpan formation at neutral ph where dry condition prevails two gold mine tailings in egypt el sid and barramiya were studied for their geochemical mineralogical properties and climate influence on hardpan formation the tailings are characterised by homogeneous silt sized sediments 42 have high carbonate predominantly as calcite for el sid and dolomite ankerite for barramiya and low sulfide contents chiefly as pyrite galena and sphalerite for el sid and arsenopyrite pyrite for barramiya el sid is characterised by high average concentrations of pb 2 758 mg kg and zn 2 314 mg kg its lower part dominated by mafics overlaid by granitoids barramiya has higher as average 2 836 mg kg content and represents a mixture of mica schists mafics ultramafics during field investigations no hardpans were identified only bassanite and gypsum were found at the surface of el sid tailings forming thin layers and desiccation crack fillings column experiments showed a thin crust consisting of gypsum halite and sodium sulfate formed at the top of the column of el sid tailings after 2 weeks this was not recognized in the column from barramiya the homogenous thickened tailings deposition in both areas did not favour hardpan formation since the critical amounts of reacting sulfides were never achieved in individual lamina due to missing mineral grain size fractionation the high temperature low water availability characteristic for desert climate regions did not allow significant sulfides oxidation therefore both tailings will suffer from continuous erosion and spreading out of contaminants to the environment for a prolonged period of time by sporadic flash floods

the role of mining and agricultural activity in creating coexisting but divergent soils san luis valley colorado usa abstract application of irrigation water especially through flood or furrow methods can have profound impacts on soil morphological chemical and physical properties using a variety of field and laboratory techniques we examined the impact of both acidic and alkaline irrigation water on a host of soil properties in the san luis valley of southern colorado impacts on calcium carbonate clay content and gypsum to a depth of 1 m are presented for 4 sites a control two sites exposed to acidic irrigation water and one site exposed to alkaline irrigation water along with the increased water in this arid ecosystem water quality and sediment content have likely contributed to the pedologic changes observed in this system one of the most prominent changes is the removal of carbonate within the upper meter of soil at the site with the greatest exposure to acidic irrigation water changes in soil structure and color differences in clay mineralogy and rock fragment weathering and the presence of jarosite provide further evidence of accelerated weathering along this management gradient the sum of these changes has resulted in a shift in the soil classification and has potential implications on buffering capacity and soil productivity

release transport and attenuation of metals from an old tailings impoundment abstract the oxidation of sulfide minerals from mine wastes results in the release of oxidation products to groundwater and surface water the abandoned high sulfide camp tailings impoundment at sherridon manitoba wherein the tailings have undergone oxidation for more than 70 a was investigated by hydrogeological geochemical and mineralogical techniques mineralogical analysis indicates that the unoxidized tailings contain nearly equal proportions of pyrite and pyrrhotite which make up to 60 wt of the total tailings and which are accompanied by minor amounts of chalcopyrite and sphalerite and minute amounts of galena and arsenopyrite extensive oxidation in the upper 50 cm of the tailings has resulted in extremely high concentrations of dissolved so4 and metals and as in the tailings pore water ph 1 m thick geochemical modeling and mineralogical analysis indicate that the hardpan layer consists of secondary melanterite rozenite gypsum jarosite and goethite the minerals indicated mainly control the dissolved concentrations of so4 fe ca and k the highest concentrations of dissolved metals are observed directly above and within the massive hardpan layer near the water table at a depth of 4 m most metals and so4 sharply decline in concentration although dissolved concentrations of metals and so4 decrease below the water table these concentrations remain elevated throughout the tailings with up to 60 600 mg l 1 fe and 91 600 mg l 1 so4 observed in the deeper groundwater during precipitation events surface seeps develop along the flanks of the impoundment and discharge pore water with a geochemical composition that is similar to the composition of water directly above the hardpan these results suggest that shallow lateral flow of water from a transient perched water table is resulting in higher contaminant loadings than would be predicted if it were assumed that discharge is derived solely from the deeper primary water table the abundance of residual sulfide minerals the depletion of aluminosilicate minerals in the upper meter of the tailings and the presence of a significant mass of residual sulfide minerals in this zone after 70 a of oxidation suggest that sulfide oxidation will continue to release acid metals and so4 to the environment for decades to centuries

the partitioning of fe ni and co between olivine metal and basaltic liquid an experimental and thermodynamic investigation with application to the composition of the lunar core abstract the partitioning of fe ni and co between mg rich olivine lunar basaltic liquid and metal has been measured over a range of temperatures and pressures the results of the olivine metal partitioning may be compared to those predicted from thermodynamic calculation in general the agreement is good although the calculated distribution coefficients are slightly greater then those experimentally determined this discrepancy increases with increasing temperature and pressure but it is not possible to ascertain unambiguously which thermodynamic data might be responsible at lower temperatures inversion of the equilibria to yield cosmothermometers for measuring the temperature of equilibration between olivine and metal gives results for the pallasite meteorites in excellent agreement with independent estimates the results have been applied to apollo 15 green glass presumed to approximate a primitive melt from the lunar mantle to deduce the composition of fe ni co metal in equilibrium with the lunar mantle this composition is approximately by weight 54 60 fe 38 45 ni and 1 co consequently if metal has separated from the lunar mantle under equilibrium conditions to form a small lunar core this core will be nickel rich with a ni fe ratio of 0 7 0 15

dense water formation around islands 1 basic constraints on the dense water formation rate and circulation resulting from cooling around an island are discussed the domain under consideration consists of an island surrounded by a shelf a continental slope and a stratified ocean atmospheric cooling over the shelf forms a dense water that penetrates down the sloping bottom into the stratified basin strong azimuthal flows are generated over the sloping bottom as a result of thermal wind thermally direct and indirect mean overturning cells are also forced over the slope as a result of bands of convergent and divergent reynolds stresses associated with the jets the coriolis force associated with the net mass flux into the downwelling region over the slope is balanced by these nonlinear terms giving rise to a fundamentally different momentum budget than arises in semienclosed marginal seas subject to cooling a similar momentum balance is found for cases with canyons and ridges around the island provided that the terms are considered in a coordinate system that follows the topography both eddy fluxes and the mean overturning cells are important for the radial heat flux although the eddy fluxes typically dominate the properties of the dense water formed over the shelf temperature diapycnal mass flux are predicted well by application of baroclinic instability theory and simple heat and mass budgets it is shown that each of these quantities depends only on a nondimensional number derived from environmental parameters such as the shelf depth coriolis parameter offshore temperature field and atmospheric forcing

60025 relict of primitive lunar crust abstract new isotopic analyses are presented for 3 plagioclase rich fractions and one mafic fraction from ferroan anorthosite 60025 the observed206pb 204pb ratios vary between 52 5 and 60 5 all much higher than the ratio for terrestrial contamination in a207pb 206pb 204pb 206pb correlation diagram the plagioclase data define a model pb pb age of 4 520 0 007 ae using meteoritic primordial lead for the non radiogenic component in the concordia diagram the plagioclase data yield intersections at 4 503 0 007 and 0 28 ae the meaning of the lower intercept is obscure the earlier 60025 analysis of tera and wasserburg 1 with an observed206pb 204pb of 23 0 agrees closely with the new plagioclase data in the isotope correlation and concordia diagrams since the apparent age does not correlate with the206pb 204pb ratios and u contents of the samples it does not appear to be controlled by terrestrial lead contamination the time averaged values for the plagioclase leads are exceptionally low 16 55 and agree within factors of 2 with the observed values in the samples these are much lower than the values observed for mafic rocks or their sources showing that the anorthosite lead has never been associated for a substantial length of time with any high source in this way the 60025 data differ substantially from u pb data for two other lunar anorthosites 15415 and 60015 the results suggest that the averaged model pb ages of 4 51 0 01 ae closely approximate the crystallization age for the plagioclase fraction of the anorthosite and that it dates back to an early phase in lunar history one sample from the mafic fraction of 60025 yields a younger model pb age of 4 42 ae the age may have been lowered by post crystallization disturbances or perhaps this fraction is not coeval with the plagioclase fraction

the role of secondary minerals in controlling the migration of arsenic and metals from high sulfide wastes berikul gold mine siberia abstract the role of secondary minerals in controlling the migration of as cu zn pb and cd has been investigated in piles of high sulfide waste at the berikul au mine kemerovo region russia these wastes contain 40 45 wt sulfides and have been stored for approximately 50 a near the mokry berikul river sulfide oxidation generates acid pore solutions ph 1 7 with high concentrations of so42 190 g l fe 57 g l as 22 g l zn 2 g l cu 0 4 g l pb 0 04 g l and cd 0 03 g l from these solutions as is precipitated as amorphous non stoichiometric fe sulfoarsenates in the lower horizons of the waste piles during precipitation of the fe sulfoarsenates the concentration of fe in these phases decreases from 34 to 21 wt that of as increases from 11 to 22 wt while the s content remains approximately constant 5 4 5 8 wt arsenic is also accumulated in jarosite beudantite solid solutions up to 8 4 wt as which occur as inclusions in the amorphous fe sulfoarsenates in efflorescent crusts on the surface of the waste pile as co precipitates with the fe iii sulfates copiapite 0 27 wt as and rhomboclase 0 87 wt as zinc and cu are incorporated primarily into fe ii sulfates i e melanterite in the interior of the waste pile and rozenite in the efflorescent crust the zn mineral dietrichite is also formed at the surface of the waste pile as a result of evaporation of pore solutions and is the only fe ii sulfate containing detectable amounts of as 0 64 wt lead is mainly co precipitated with minerals of the jarosite group where the pb content may reach 4 3 wt co precipitation of toxic elements with sulfates and sulfoarsenates of fe is shown to be a significant mechanism in controlling the concentration of heavy metals in pore solutions of high sulfide mine wastes precipitation of secondary phases causes the formation of a hardpan layer with low permeability at a depth of 1 1 5 m below the surface of the waste pile rainwater accumulates above the hardpan horizons and slowly drains along these aquicludes to the bottom of the pile most of the rainwater evaporates during infiltration this leads to formation of the described efflorescent sulfate crusts dissolution of these crusts during the next rain storm produces highly acidic surface waters ph 1 1 rich in so42 30 g l fe 18 g l as 0 24 g l zn 0 12 g l cu 0 04 g l pb and cd 0 002 g l during the warm t 0 c period of the year which lasts about 7 months these surface waters transport a total of a few tens of kilograms of as and zn several kilograms of cu and a few hundred grams of pb and cd from the waste pile into the mokry berikul river as a result the concentrations of these metals in the river water increase by an order of magnitude thus reaching levels close to or exceeding the maximum values permissible for drinking water

a comparative mineralogical and geochemical study of sulfide mine tailings at two sites in new mexico usa a comparative study of sulfide mine tailings from two sites near silver city in southwest new mexico has shown the need for environmental monitoring in a geological context the cyprus pinos altos and cleveland deposits consist of cu and zn skarn mineralization in the pinos altos mountains of new mexico primary ore minerals in both deposits include chalcopyrite sphalerite and galena the cyprus pinos altos mine ceased operation in 1995 and the cleveland mill closed in 1950 the deposits have similar mineralogical characteristics however the tailings are different in terms of age degree of oxidation and method of disposal the cyprus pinos altos tailings cpat are stored in a lined bermed impoundment they are dominantly water saturated and exhibit no secondary phase formation the grains are not cemented and show no evidence of primary mineral dissolution the geochemical data show a predominantly primary signature the tailings pond water is neutral to slightly alkaline ph from 7 to 8 3 partly as a result of processing methods the cleveland mill tailings cmt were deposited in a valley at the headwaters of an ephemeral stream they are highly oxidized and differentially cemented they have undergone numerous wet dry cycles resulting in extensive oxidation secondary minerals predominate and consist mainly of jarosite goethite hematite and fe oxyhydroxides and oxyhydroxysulfates the ph of the stream draining the cmt is as high as 2 15 maximum metal contents in the stream immediately downstream from the tailings are 5305 ppm zn 454 ppm cu 1 16 ppm pb 17 5 ppm cd 1 4 ppm as and 0 01 ppm hg

mineralogy and environmental relevance of amd precipitates from the tharsis mines iberian pyrite belt sw spain abstract this paper documents the solid phases associated to acid mine drainage amd at the tharsis mines sw spain it provides an inventory of the amd precipitates describing their main modes of occurrence and mineral assemblages results indicate that iron aluminum and magnesium sulfates predominate in the assemblages they occur as efflorescences composed of complex mixtures of metallic salts and as ochres jarosite combined with goethite also their distributions illustrate two hydrochemical environments the open pits which reflect a proximal secondary paragenesis and the downstream river banks meca river which represent a more evolved paragenesis resulting from the evolution of amd produced throughout the system these environments can be differentiated by composition and variety of minerals which is considerably lower along the meca river the newly formed minerals have monitoring significance and proved capable of participating in cycles of retention liberation of hydrogen ions sulfate and metals in a semi arid climate the importance of the amd precipitates as environmental indicators is stressed they may help to understand the response of the system to the episodic rainfall events that occur after prolonged dry periods

heavy metal retention in secondary precipitates from a mine rock dump and underlying soil dalarna sweden this study investigates the retention of heavy metals in secondary precipitates from a sulfidic mine rock dump and underlying podzolic soils by means of mineralogical and chemical extraction methods the rock dump which is at least 50 years old consists of a 5 10 cm thick leached zone and an underlying 110 115 cm thick accumulation zone optical microscopy and electron microprobe analyses confirm that pyrrhotite weathering has proceeded much further in the leached horizon relative to the accumulation horizon the weathering of sulfides in the leached zone has resulted in the migration of most heavy metals to the accumulation zone or underlying soils where they are retained in more stable phases such as secondary ferric minerals including goethite and jarosite some metals are temporarily retained in hydrated ferrous sulfates e g melanterite rozenite

the meteorite component of apollo 16 noritic impact melt breccias noritic melt rocks alias lkfm and vha from apollo 16 have concentrations of ni approximately three to five times those of impact melt rocks of similar composition from other lunar landing sites the melt rock associated with apollo 16 dimict breccias has the highest mean concentration of ni of any lunar rock type 1150 g g in 11 samples the ni is contained in fe ni metal that is dissimilar in composition to metal from ordinary chondrites in having a lower ni concentration 6 and lower ni co ratio 17 it also has ir ni and ir au ratios of about one half and one third those of chondrites the metal in the noritic impact melts is the carrier of the siderophile element signature of ancient meteorite group 1h the composition of the fe ni metal is dissimilar to that of chondrites because it derives from metal rich meteorites probably irons that created the impact melts 3 9 ga ago the metal from these iron meteorites dominates the siderophile element concentrations of polymict samples at apollo 16 models that attempt to estimate indigenous concentrations of ni and co in apollo 16 materials overestimate their abundance by assuming that the meteoritic component has chondritic ratios of ir to ni and co the type 2 melt vha associated with the dimict breccias and the type 1 melt apollo 16 lkfm were most likely produced by impact of two related iron meteoroids that impacted near the apollo 16 site the type 2 melt found in samples from station 7 is probably from the same impact as that producing the dimict breccias although it could represent the impact of a third related iron

the groundwater recharge regime of some slightly metamorphosed neoproterozoic sedimentary rocks an application of natural environmental tracers isotope data of precipitation and groundwater in parts of the voltaian basin in northern ghana were used to explain the groundwater recharge regime in the area groundwater recharge is an important parameter in the development of a decision support system for the management and efficient utilization of groundwater resources in the area it is therefore important to establish the processes and sources of groundwater recharge 18o and 2h data for local precipitation suggest enrichment relative to the global meteoric water line gmwl and indicate that precipitation takes place at a relative humidity less than 100 the groundwater data plot on an evaporation line with a slope of 5 suggesting a high degree of evaporative enrichment of the precipitation in the process of vertical infiltration and percolation through the unsaturated zone into the saturated zone this finding is consistent with the observation of high evapotranspiration rates in the area and ties in with the fact that significant clay fraction in the unsaturated zone limits vertical percolation and thus exposes the percolating rainwater to the effects of high temperatures and low humidities resulting in high evapotranspiration rates groundwater recharge estimates from the chloride mass balance cmb method suggest recharge in the range of 1 8 32 of the annual average precipitation in the form of rainfall the highest rates are associated with areas where open wells encourage significant amount of groundwater recharge from precipitation in the area in the northern parts of the study area groundwater recharge is lower than 12 the recharge so computed through the application of the cmb methodology takes on a spatial distribution akin to the converse of the spatial pattern of both 18o and 2h in the area as such the locations of the highest recharge are associated with the most depleted values of the two isotopes this observation is consistent with the assertion that low vertical hydraulic conductivities slow down vertical percolation of precipitation down to the groundwater water the percolating precipitation water thus gets enriched in the heavier isotopes through high evapotranspiration rates at the same time the amount of water that finally reaches the water table is considerably reduced copyright 2013 john wiley sons ltd

rare earth elements as a tool for studying the formation of cemented layers in an area affected by acid mine drainage abstract in a profile with two cemented layers sampled in an area affected by acid mine drainage both have rare earth element ree signatures with positive ce anomalies in the post archean australian shale normalised patterns both cemented layers have higher contents of environmentally relevant metals cd co cu fe mn u and zn than the over and underlying unconsolidated quaternary sediments and are depleted of al ca k and mg the cemented layers are enriched in middle and heavy ree but only the bulk pattern of the lower cemented layer reveals a positive ce anomaly for the upper cemented layer this positive ce anomaly was only determined by spatially resolved laser ablation inductively coupled plasma mass spectrometry la icp ms studies only for segments with a high abundance of mn occurring as mn phases as proven by energy dispersive x ray spectroscopy the mn phases are formed secondarily to the ferric cement and are especially enriched in ce and co the ce anomaly of the lower cemented layer most probably is inherited from groundwater to the ferric cement whereas the ce anomaly of the upper cemented layer is the result of preferential scavenging of ce onto the mn phases compared to other ree

geochemical controls on arsenic distribution in the baccu locci stream catchment sardinia italy affected by past mining abstract the baccu locci stream catchment sardinia italy is affected by serious as contamination as a consequence of past mining the presence of both point and widespread sources of contamination waste rock dumps and flotation tailings respectively strongly affects surface water chemistry and produces high as concentrations hundreds of g l 1 in stream waters water chemistry of the baccu locci stream changes considerably over a distance of about 10 km as a consequence of various locally concomitant processes acting along the stream course 1 mixing with metal rich so 4 waters 2 dissolution precipitation of metal bearing phases 3 mixing with hco 3 dominated lake waters 4 gypsum dissolution coupled with calcite precipitation 5 mixing with dilute surface and or ground waters in contrast to metals e g pb cu zn and cd whose dissolved concentrations rapidly decrease downstream of the mined area through co precipitation adsorption mechanisms as concentrations tend to gradually increase up to 0 9 mg l 1 along the stream course as far as the alluvial plain though significant variations are locally observed this behaviour is mainly due to the higher mobility of as than metals under the near neutral oxidative conditions occurring in the baccu locci stream waters results of a leaching test indicate that part of the as contained in the flotation tailings occurs as as iii which is more mobile and less strongly sorbed than as v the as released to the waters by various mechanisms i e release desorption from the fe iii hydroxides coatings of silicate grains oxidation of residual arsenopyrite decomposition of scorodite tends to remain in solution and to be transported long distances as a consequence of the widespread presence of highly as contaminated flotation tailings all over the medium lower baccu locci stream catchment long term as contamination is expected

formation of a hardpan in the co disposal of fly ash and sulfide mine tailings and its influence on the generation of acid mine drainage abstract pilot scale field experiments were conducted to test a strategy for the treatment of acid mine drainage by addition of an alkaline cover of coal combustion fly ash on two sulfide mine tailings impoundments iberian pyrite belt sw spain during the pilot scale treatment calcium rich alkaline solutions from fly ash interacted with metal rich acidic solutions from the mine tailings leading to the massive precipitation of newly formed phases mainly in the fly ash close to the interface between both materials over time the interaction between fly ash and pyrite sludge promoted the formation of a chemically cemented zone or hardpan which was analyzed at high spatial resolution by micro x ray diffraction xrd and micro x ray fluorescence xrf based on synchrotron radiation these micro characterization techniques extensively identified poorly crystalline fe oxyhydroxysulfates jarosite and gypsum as newly formed phases in the hardpan and gypsum in the fly ash as deduced from principal component analysis of the fluorescence intensity data these phases seem to exert a significant mineralogical control on element mobility in particular jarosite showed high affinity for as whereas poorly crystalline fe rich assemblages selectively concentrated mn ni and pb sequential extractions indicated that the application of a fly ash cover significantly reduced the bioavailability of most of the elements by modification of their chemical speciation into less mobile forms under typical oxidizing conditions as an additional advantage the development of the hardpan hindered the penetration of oxidizing agents to sulfide mine tailings this effect significantly reduced the sulfide oxidation rates therefore attenuating the release of potentially pollutant elements to the environment

iron and arsenic rich nanoprecipitates associated with clay minerals in sulfide rich waste dumps abstract the relationships between clay minerals and associated iron and arsenic rich phases are a main scientific issue in reactive mine waste dumps therefore this paper documents the composition and morphology of the fine fraction the obtained results indicated that the study sites have similar relative proportions of the detrital materials however major differences were observed in the remainder phases which is in accordance with the mineralogy that was inherited from the respective ore deposits in general the clay mineral assemblage is dominated by the presence of illite halloysite 7 a and beidellite there are also associated minerals such as jarosite and goethite as well as amorphous as rich nanoprecipitates with specific morphologies moreover the results suggested that amd conditions control the physical chemical transformations namely constraining the stability of the secondary phases formed by weathering in the waste dumps acidity is responsible for the degradation of the clay minerals which is reflected in their crystalochemistry structural order disorder and morphology on the contrary jarosite is more stable being a dominant mineral in such environmental conditions the stability of amorphous ferric arsenates or its evolution to a more crystalline phase is dependent on the fe as ratio which is lower in penedono the study of the secondary products especially the nanoparticles puts in evidence their ability to control the mobility of trace elements suggesting potential applications in environmental technology including remediation of reactive mine waste dumps

influence of hardpan layers on arsenic mobility in historical gold mine tailings abstract hardpans or cemented layers form by precipitation and cementation of secondary minerals in mine tailings and may act as both physical and chemical barriers precipitation of secondary minerals during weathering of tailings can sequester metal loid s thereby limiting their release to the environment at montague gold mines in nova scotia tailings are partially cemented by the fe arsenate mineral scorodite feaso4 2h2o previous studies have shown that the formation of scorodite can effectively limit aqueous as concentrations due to its relatively low solubility

the formation and potential importance of cemented layers in inactive sulfide mine tailings abstract investigations of inactive sulfide rich tailings impoundments at the heath steele new brunswick and waite amulet quebec minesites have revealed two distinct types of cemented layers or hardpans that at heath steele is 10 15 cm thick occurs 20 30 cm below the depth of active oxidation is continuous throughout the tailings impoundment and is characterized by cementation of tailings by gypsum and fe ii solid phases principally melanterite hardpan at the waite amulet site is only 1 5 cm thick is laterally discontinuous 10 100 cm occurs at the depth of active oxidation and is characterized by cementation of tailings by fe iii minerals principally goethite lepidocrocite ferrihydrite and jarosite at heath steele an accumulation of gas phase co2 of up to 60 of the pore gas occurs below the hardpan the calculated diffusivity of the hardpan layer is only about 1 100 that of the overlying uncemented tailings the pore water chemistry at heath steele has changed little over a 10 year period suggesting that the cemented layer restricts the movement of dissolved metals through the tailings and also acts as a zone of metal accumulation generation of a cemented layer therefore has significant environmental and economic implications it is likely that in sulfide rich tailings impoundments the addition of carbonate rich buffering material during the late stages of tailings deposition would enhance the formation of hardpan layers

the effects of hardpan layers on the water chemistry from the leaching of pyrrhotite rich tailings material column leaching experiments were used to determine the effects of an iron rich hardpan layer on the rate of tailings oxidation and the composition of leachate waters from the renison bell tailings dams in western tasmania australia one meter long pvc columns filled with tailings cover material cassiterite flotation tailings and hardpan samples from the tailings dams were leached over a period of 14 weeks under dry cover conditions when hardpan was present the solute loads peaked at 21 49 days fe at 2 294 ppm and so42 at 4 700 ppm and stabilised at much lower concentrations after 9 weeks in contrast the solute loads steadily increased over time in the column where hardpan was absent so42 from 1 800 to 3 100 ppm and fe from 407 to 1 692 ppm under saturated cover conditions the solute concentrations in the leachate also increased with time so42 from 1 900 to 17 000 ppm and fe from 480 to 8 500 ppm the presence of a hardpan layer between the reactive tailings and cover material has been found to improve leachate water chemistry and lessen the rate of sulphide oxidation

experimental investigation of the partitioning of phosphorus between metal and silicate phases implications for the earth moon and eucrite parent body abstract the solid metal silicate melt partition coefficient for p d p has been determined experimentally at 1190 c and 1300 c the dependence of the partition coefficient on oxygen fugacity has been investigated and is consistent with a valence state of 5 for p in the silicate melt the experimental partition coefficients are given by log d p 1 21 log o 2 15 95 at 1190 c log d p 1 53 log o 2 17 73 at 1300 c the experimentally determined partition coefficients may be used to interpret the low p la ratios of the earth moon and eucrites relative to c1 chondrites the low p la ratios in the eucrites may be explained by partitioning of p into 5 to 25 of a sulfur bearing metallic liquid assuming equilibration and separation of the liquid metal from the silicates at low degrees of partial melting of the silicates the low w la ratios in the eucrites compared to c1 chondrites require the separation of an additional 2 to 10 solid metal the lowering of both p la and w la ratios in the moon may be explained by partitioning of p and w into metal during formation of a small core by separation of liquid metal from silicate at low degrees of partial melting of the silicates the w la ratios in the earth and moon are virtually indistinguishable while p la ratios differ by a factor of two the concentrations of feo also appear to be different these observations are difficult to reconcile with the hypothesis of a terrestrial origin of the moon following formation of the earth s core but are consistent with independent formation of the earth and moon

lunar heat flow regional prospective of the apollo landing sites 1 we reexamine the apollo heat flow experiment in light of new orbital data using three dimensional thermal conduction models we examine effects of crustal thickness density and radiogenic abundance on measured heat flow values at the apollo 15 and 17 sites these models show the importance of regional context on heat flux measurements we find that measured heat flux can be greatly altered by deep subsurface radiogenic content and crustal density however total crustal thickness and the presence of a near surface radiogenic rich ejecta provide less leverage representing only minor 1 5 mw m 2 perturbations on surface heat flux using models of the crust implied by gravity recovery and interior laboratory results we found that a roughly 9 13 mw m 2 mantle heat flux best approximate the observed heat flux this equates to a total mantle heat production of 2 8 4 1 1011 w these heat flow values could imply that the lunar interior is slightly less radiogenic than the earth s mantle perhaps implying that a considerable fraction of terrestrial mantle material was incorporated at the time of formation these results may also imply that heat flux at the crust mantle boundary beneath the procellarum potassium rare earth element and phosphorus kreep terrane pkt is anomalously elevated compared to the rest of the moon these results also suggest that a limited kreep rich layer exists beneath the pkt crust if a subcrustal kreep rich layer extends below the apollo 17 landing site required mantle heat flux can drop to roughly 7 mw m 2 underlining the need for future heat flux measurements outside of the radiogenic rich pkt region

silicon isotopes in lunar rocks implications for the moon s formation and the early history of the earth silicon isotopic data from a range of lunar samples are presented to assess the degree of heterogeneity of the lunar mantle and its similarity to bulk silicate earth bse multi collector inductively coupled plasma mass spectrometry mc icpms was used to analyse 24 samples including both high and low ti basalts as well as highland anorthosites and picritic glasses covering all the apollo sample return missions no systematic 30si differences are found between any of the bulk sample lithologies 2 sd 30silow ti basalt 0 29 0 06 30sihigh ti basalt 0 32 0 09 30silunar glass 0 29 0 05 and 30sihighland rocks 0 27 0 10 the average of the lunar samples is 30si 0 29 0 08 2 sd which is identical to the composition of bse 30si 0 29 0 08 2 sd from savage et al 2010 the bse si isotope composition is thought to be the result of si partitioning between metal and silicate and consequent isotopic fractionation during core formation the moon forming impactor would not be expected to share that composition because it is thought to have been relatively small 0 1 earth masses like mars and formed under relatively low temperatures and pressures that are insufficient for si to partition into the core therefore the identical lunar and bse si isotope data show that si isotopes like those of oxygen must have homogenised in the aftermath of the moon forming impact if smooth particle hydrodynamic simulations of the giant impact are correct in showing that most lunar material should have originated from the impactor rather than the earth the data presented here are in agreement with other isotope systems and experimental studies that indicate that the majority of core formation happened early and before the giant impact it has been predicted pahlevan et al 2011 that the moon and the bse should show a 0 14 offset in 30si for the moon to have an fe fe mg ratio twice that of bse the current resolution and sample population size of the si data for the moon and earth would allow such an offset to be detected the fact that is it not observed can put constraints on the element ratios and lunar budgets as modelled by pahlevan et al 2011 in particular it constrains the fe fe mg ratio of the moon to be only 1 1 3 bse

an experimental study of iron sulfides weathering under simulated calcareous soil conditions in calcareous sites hard rock mining activities release pyrite fes2 pyrrhotite fe1 xs and other sulfides to soils the sulfides then undergo weathering processes generating acid rock drainage and secondary compounds despite the potentially important environmental impacts very few studies have considered the mechanisms of pyrite and pyrrhotite weathering and the transformation of secondary compounds under neutral alkaline carbonated conditions in this study we used an experimental approach combining electrochemical microscopic and spectroscopic techniques to examine the interfacial processes involved in pyrite and pyrrhotite weathering under simulated calcareous soil conditions the results showed an initial oxidation step with the formation of variable amounts of surface sulfur compounds e g polysulfides sn2 and elementary sulfur s0 and acid generation leading to significant modification of the oxidative behavior of the minerals the surface changes that occurred as a result of mineral weathering provoked transient enhancement of pyrite reactivity and progressive passivation in the pyrrhotite system iron sulfides weathering was found to involve the formation of an intermediate siderite feco3 like compound preceding the predominant formation of k jarosite k fe3 so4 2 oh 6 and or ferric oxyhydroxide feooh compounds depending on the surface acid condition reached in the systems mechanisms of pyrite and pyrrhotite weathering in calcareous soils are suggested on the basis of surface characterization and chemical analysis of the leachates generated and the environmental implications are discussed

axisymmetric circulation driven by marginal heating in ice covered lakes below the temperature of maximum density tmd in freshwater lakes heating at the lateral margins produces gravity currents along the bottom slope akin to katabatic winds in the atmosphere and currents on continental shelves we describe axisymmetric basin scale circulation driven by heat flux at the shorelines in polar lake kilpisjarvi a dense underflow originating near the shore converges toward the lake center where it produces warm upwelling and return flow across the bulk of lake water column the return flow being subject to coriolis force creates a lake wide anticyclonic gyre with velocities of 2 4 cm s 1 while warm underflows are common on ice covered lakes the key finding is the basin scale anticyclonic gyre with warm upwelling in the core this circulation mechanism provides a key to understanding transport processes in semi enclosed basins subject to negative buoyancy flux due to heating or cooling at temperatures above tmd at their lateral boundaries

the pore water geochemistry and the mineralogy of the vadose zone of sulfide tailings waite amulet quebec canada low ph waters requiring treatment because of high concentrations of dissolved metals are being discharged from a decommissioned tailings impoundment at the former waite amulet zncu mine in northeastern quebec canada a detailed study of the vadose zone of the tailings comparing mineralogical and geochemical analyses of the tailings solids with geochemical analysis of the tailings pore water and pore gas indicates the presence of three zones within the tailings these zones include an upper sulfide depleted zone in which the sulfides have been extensively removed and oxidation is largely complete an intermediate zone where sulfide oxidation and acid neutralization reactions are occurring and an unoxidized zone below the depth of oxygen penetration where sulfides are unoxidized high aqueous concentrations of dissolved solids are being displaced downward from the sulfide depleted zone through the unoxidized zone toward the water table sulfide oxidation and acid neutralization reactions have generated concentrations of dissolved solids high enough to lead to the precipitation of a series of secondary solid phases precipitation dissolution reactions involving these solid phases control the concentrations of the major ions in the tailings pore water concentrations of dissolved metals are controlled by precipitation dissolution crystal structural replacement and adsorption coprecipitation reactions predictions based on the observed data and numerical simulations suggest that in the absence of an effective remedial program sulfide oxidation and h production will continue for several centuries

core formation in the earth and moon new experimental constraints from v cr and mn abstract the mantles of the earth and moon are similarly depleted in v cr and mn relative to the concentrations of these elements in chondritic meteorites the similar depletions have been used as evidence that the moon inherited its mantle from the earth after a giant impact event we have conducted liquid metal liquid silicate partitioning experiments for v cr and mn from 3 to 14 gpa and 1723 to 2573 k to understand the behavior of these elements during planetary core formation our experiments have included systematic studies of the effects of temperature silicate composition metallic s content metallic c content and pressure temperature has a significant effect on the partitioning of v cr mn with all three elements increasing their partitioning into the metallic liquid with increasing temperature in contrast pressure is not observed to affect the partitioning behavior the experimental results show the partitioning of cr and mn are hardly dependent on the silicate composition whereas v partitions more strongly into depolymerized silicate melts the addition of either s or c to the metallic liquid causes increased metal silicate partition coefficients for all three elements parameterizing and applying the experimental data we find that the earth s mantle depletions of v cr and possibly mn can be explained by core formation in a high temperature magma ocean under oxygen fugacity conditions about two log units below the iron wustite buffer though the depletion of mn may be due entirely to its volatility however more oxidizing conditions proposed in recent core formation models for the earth cannot account for any of the depletions additionally because we observe no pressure effect on the partitioning behavior the data do not require the mantle of the moon to be derived from the earth s mantle although this is not ruled out all that is required to create depletions of v cr and mn in a mantle is a planetary body that is hot enough and reducing enough during its core formation such conditions could have existed on the moon forming impactor