an updated insight into the natural attenuation of as concentrations in reigous creek southern france abstract the removal of metals and metalloids occurring in acid mine drainage has been studied on different scales years days dissolved and particulate concentrations of fe and as were monitored over a 4 a period along reigous creek an acid mine drainage from a former pb zn mine in southern france dissolved concentrations of fe 12 25 mmol l 1 as 0 9 3 5 mmol l 1 and so 4 2 10 70 mmol l 1 exhibited seasonal variations related to rainfall with an increase during the driest months about 30 of the as initially present in solution as as iii was coprecipitated with fe oxides in the first 40 m of reigous creek the corresponding as removal rate was 3 58 10 7 mol l 1 s 1 the mineralogy of resultant precipitates varied spatially and seasonally over the first 40 m amorphous as v fe iii phases and tooeleite were formed sediments deposited in the bed of the creek close to the spring contained both types of solid phases laminated concretions which consist of precipitates around bacterial structures were mainly constituted of tooeleite further downstream these fe oxide phases were replaced by schwertmannite and ferrihydrite on a daily basis concentrations of dissolved fe and as have been shown to vary up to 10 during the day as a result of photoreduction of fe oxide phases

source attenuation and potential mobility of arsenic at new britannia mine snow lake manitoba this study was to investigate the source mobility and attenuation of as at the new britannia mine snow lake manitoba one major source of as contamination was determined to be an arsenopyrite residue stockpile ars containing refractory au in a waste rock impoundment it appears that as is still moving through glacial clay at the base of the ars into a confined aquifer even though the pile was capped in the year 2000 arsenic is also being mobilized from a deposit of tailings which formed following spills by previous owners nor acme arsenic from the tailings is being mobilized by oxidation of arsenopyrite and reduction of arsenate to the more mobile arsenite by arsenate reducing bacteria this contamination is affecting a shallow unconfined aquifer and surface water flowing from the tailings through wetlands towards snow lake arsenic is being attenuated by adsorption to hydrated ferric oxides hfo in the tailings wetland soils and aquatic plants although as in surface water soils and plants along the flow path from the mine to snow lake are above canadian drinking water guidelines efficient natural attenuation by hfo in soils and plants of the wetlands have limited the concentration in snow lake to below drinking water standards

microbial control on the precipitation of modern ferrihydrite and carbonate deposits from the cezallier hydrothermal springs massif central france abstract actively precipitating hydrous iron oxides and carbonates are commonly associated with cool co2 rich spring waters in the massif central france chemical isotopic and mineralogical analyses and thermodynamic calculations were undertaken to elucidate the processes involved in the formation of these deposits hydrous iron oxide particles rich in al si ca and as are the first to form in the springs accompanying the iron oxides are layered carbonate deposits composed mainly of well crystallised calcite sem examination of both oxides and carbonates sampled at the outlet of the springs shows that they basically consist of grape shaped agglomerates of small 300 nm to 1 m anhedral crystals light acid etching of these agglomerates reveals colonies of spherical nannobacteria water trace partitioning between oxide and carbonate favours the hydrous oxide with as pb zn th concentration the microscopic features of both types of deposit indicate that microbial mediation probably contributes to their formation

geology and chemistry of hydrothermal deposits from active submarine volcano loihi hawaii high resolution bathymetric surveys bottom photography and sample analyses show that loihi seamount at the southernmost extent of the hawaiian hotspot is an active young submarine volcano that is probably the site of an emerging hawaiian island hydrothermal deposits sampled from the active summit rift system were probably formed by precipitation from cooling vent fluids or during cooling and oxidation of high temperature polymetallic sulphide assemblages no exotic benthic fauna were found to be associated with the presently active hydrothermal vents mapped

environmental arsenopyrite stability and dissolution theory experiment and field observations arsenopyrite has traditionally been considered to be chemically unstable in the surficial environment however field evidence demonstrates that arsenopyrite does not readily decompose under water saturated near surface conditions arsenopyrite occurs in the heavy mineral suite of a variety of thin sediments in southern new zealand with no evidence for chemical corrosion these sediments have been water saturated but within metres of the surface for 10 60 28000 and 2 million years these observations of long term arsenopyrite stability are in accord with geochemical predictions based on recent experimentally determined thermodynamic data for arsenopyrite calculations using the new thermodynamic data suggest that arsenopyrite has similar eh ph stability range to pyrite except under acid conditions ph 4 where arsenopyrite should transform to realgar or orpiment calculated as concentrations in equilibrium with the pyrite arsenopyrite assemblage in the surficial environment are 0 01 0 1 ppm similar to groundwater in arsenopyrite bearing rocks in this study 0 005 0 3 ppm and these waters may be in chemical equilibrium arsenopyrite decomposes in oxidised waters to yield up to 1100 ppm dissolved as in the laboratory and up to 400 ppm dissolved as in mine processing waters these concentrations of dissolved as are several orders of magnitude lower than equilibrium solubility of arsenopyrite because of kinetic effects and development of protective oxide coatings on arsenopyrite grains mine tailings containing arsenopyrite should be chemically stable during longterm storage provided they are kept water saturated and moderately reduced d 2003 elsevier science b v all rights reserved

precipitation of fe iii oxyhydroxide deposits from shallow water hydrothermal fluids in tutum bay ambitle island papua new guinea abstract previous research on sea floor fe iii oxyhydroxide deposits has focused primarily on deep sea hydrothermal systems found along volcanically active portions of the mid ocean ridges and on hydrogenetic deposits formed in deep basins and along continental shelves there is however not much known about their formation in shallow water settings associated with volcanic islands the hydrothermal system at ambitle island papua new guinea provides an excellent opportunity to study the formation of fe iii oxyhydroxides in a shallow water setting precipitation from the hydrothermal solution is caused by mixing with seawater based on a 87 sr 86 sr mixing model the calculated minimum and maximum seawater fractions are approximately 11 and 57 respectively thus precipitation of tutum bay fe iii oxyhydroxides takes place at a temperature range between approximately 60 and 93 c the chemical composition shows low mn contents fe mn 600 and elements that are usually enriched in fe iii oxyhydroxides such as co and v are below crustal abundance and well below their concentrations in island arc volcanics arsenic concentrations on the other hand are by two orders of magnitude higher than those in other marine deposits rare earth element ree concentrations reflect their concentration in the hydrothermal fluids rather than seawater the crystallinity of the deposits increases with age as protoferrihydrite is apparently altered to fe smectite and hematite and as bearing minerals are formed contact with seawater and therefore oxidizing conditions seems to be the factor increasing the crystallinity

effects of crustal field rotation on the solar wind plasma interaction with mars the crustal remnant field on mars rotates with the planet at a period of 24 h 37 min constantly varying the magnetic field configuration interacting with the solar wind until now there has been no self consistent modeling investigation on how this varying magnetic field affects the solar wind plasma interaction here we include the rotation of this localized crustal field in a multispecies single fluid mhd model of mars and simulate an entire day of solar wind interaction under normal solar wind conditions the mhd model results are compared with mars global surveyor mgs magnetic field observations and show very close agreement especially for the field strength along almost all of the 12 orbits on the day simulated model results also show that the ion escape rates slowly vary with rotation generally anticorrelating with the strength of subsolar magnetic crustal sources with some time delay in addition it is found that in the intense crustal field regions the densities of heavy ion components enhance significantly along the mgs orbit implying strong influence of the crustal field on the ionospheric structures

spatial variability of arsenic in some iron rich deposits generated by acid mine drainage abstract potential contamination of rivers by trace elements can be controlled among others by the precipitation of oxyhydroxides the streambed of the studied area located in la ch taigneraie district lot river basin france is characterised by iron rich ochreous deposits acidic ph 2 7 4 8 and so 4 mg waters beyond the acid mine drainage the presence of as both in the dissolved fraction and in the deposits is also a problem upstream at the gallery outlet as concentrations are high as max 2 6 mol l and up to 5 wt locally respectively in the dissolved and in the solid fractions downstream as concentrations decrease below 0 1 mol l in the dissolved fraction and to 1327 mg kg in the solid fraction this natural attenuation is related to the as retention within ochreous precipitates amorphous to poorly crystalline fe oxyhydroxides schwertmannite and goethite which have great affinities for this metalloid upstream schwertmannite is dominant while downstream goethite becomes the main mineral the transformation of schwertmannite into goethite is observed in the upstream deposits as schwertmannite is unstable relative to goethite furthermore thermodynamic calculations indicate that the downstream goethite is not able to precipitate in situ according to the water chemistry goethite mainly results from the transformation of schwertmannite and its solid transport downstream moreover as highlighted by leaching experiments carried out on the ochreous precipitates this transformation does not seem to affect the as retention in solids as no release of as was observed in the solution arsenic may either be strongly trapped by co precipitation in the present minerals or it may be quickly released and re adsorbed on the precipitate surface

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

effects of magnetic anomalies discovered at mars on the structure of the martian ionosphere and solar wind interaction as follows from radio occultation experiments the slopes of the electron density profiles obtained by radio occultation experiments at mars revealed different variations with solar zenith angle in comparison with behavior of the electron density profiles in the magnetic field free ionosphere of venus the results obtained by the mars global surveyor mgs spacecraft show the existence of highly variable and very localized magnetic fields of crustal origin at mars addressing the difference between the ionosphere at venus and mars the scale heights of electron density profiles obtained by radio occultation methods onboard mariner 9 and viking 1 are analyzed at altitudes higher than the topside boundary of the photoequlibrium region in the magnetic field free ionosphere the local increase of the mean scale height in the altitude region 180 250 km is assumed to be either an effect of a nonhorizontal magnetic field associated with the magnetic anomalies or diffusive equilibrium in the magnetic field free ionosphere the areas where the scale height of electron density profile is increased in comparison with average one have been selected the angle between the magnetic field measured by mgs mag er at altitudes 120 250 km and local zenith direction is investigated throughout these selected areas

mars ionopause a matter of pressures this study assesses under what circumstances the martian ionopause is formed on the dayside both in regions where there are strong crustal magnetic fields and areas where these fields are small 30 nt multiple data sets from three maven dayside deep dip campaigns are utilized between periapsis and 600 1 000 km as well as solar wind observations from mars express the ionopause is identified as a sudden decrease of the electron density with increasing altitude and a simultaneous increase of the electron temperature and variability below 400 km this is a physically robust approach as the electron temperature is a key parameter in determining the structure of the ionospheric profile and therefore also a strong indicator of the ionopause location we find that 36 54 of the electron density profiles over strong weak crustal magnetic field regions had an ionopause event we also evaluate the roles of ionospheric thermal and magnetic pressures on the ionopause formation as well as the presence of solar wind particles h down to the location of the ionopause we found that the topside ionosphere is typically magnetized at mostly all altitudes the ionopause if formed occurs where the total ionospheric pressure magnetic thermal equals the upstream solar wind dynamic pressure moreover the lower edge of the ionopause coincides with the altitude where the solar wind flow stops the thermal pressure suffers a significant reduction with increasing altitude and the solar wind proton density has a prominent increase

the legacy of arsenic contamination from mining and processing refractory gold ore at giant mine yellowknife northwest territories canada the case of the giant mine illustrates how a large long lived au mine has resulted in a complex regional legacy of as contamination and an estimated remediation cost of almost one billion canadian dollars aandc 2012 the mine located a few km north of the city of yellowknife on the shore of great slave lake figs 1 2 produced more than 7 million troy ounces of au approximately 220 tonnes from a largely underground operation giant mine was the largest producer in the yellowknife greenstone belt which produced more than12 million troy ounces 370 tonnes in total bullen and robb 2006 arsenopyrite bearing au ore was roasted from 1949 to 1999 as a pretreatment for cyanidation fig 3a poor or nonexistent emission controls in the early years resulted in the release of an estimated 20 000 tonnes of roaster generated as2o3 to the surrounding environment through stack emissions cpha 1977 wrye 2008 over the lifetime of the mine however most of the as2o3 237 000 tonnes was stored in underground chambers fig 3b and is a now an ongoing source of as to groundwater and surface water inac 2007 jamieson et al 2013 other roaster products include as bearing maghemite and hematite calcine were deposited with tailings and re mobilized into creek and lake sediments under reducing conditions post depositional remobilization of as associated with roaster generated fe oxides results in release of as to sediment pore water and reprecipitation of some as as a sulfide phase fawcett and jamieson 2011 however as iii in maghemite and as2o3 persists in the oxidizing conditions of near surface tailings and soils walker et al 2005 jamieson et al 2013 ore roasting increases the solubility toxicity and bioaccessibility of as by converting sulfide hosted as to oxide hosted as at giant

the magnetic field draping direction at mars from april 1999 through august 2004 using more than five years of data from the magnetometer and electron reflectometer mag er on mars global surveyor mgs we derive the draping direction of the magnetic field above a given latitude band in the northern hemisphere the draping direction varies on timescales associated with the orbital period of mars and with the solar rotation period we find that there is a strongly preferred draping direction when mars is in one solar wind sector but the opposite direction is not preferred as strongly for the other solar wind sector this asymmetry occurs at or below the magnetic pileup boundary mpb is observed preferentially on field lines that connect to the collisional ionosphere and is independent of planetary longitude the observations could be explained by a hemispherical asymmetry in the access of field lines to the low altitude ionosphere or possibly from global modification of the low altitude solar wind interaction by crustal magnetic fields we show that the draping direction affects both the penetration of sheath plasma to 400 km altitudes on the martian dayside and the radial component of the magnetic field on the planetary night side

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

the chemical characteristics of acid mine drainage with particular reference to sources distribution and remediation the witwatersrand basin south africa as a case study abstract water quality in the immediate vicinity of mine tailings in and around johannesburg south africa was investigated pollution is derived primarily from au mine tailings dumps that are disused or are undergoing retreatment to extract remaining au and is dispersed by way of groundwater plumes these discharge into perennial streams in the area pollution manifests itself in the form of low ph 2 and high so 4 2 concentrations exceeding 7 000 mg l 1 in some cases water quality improves away from the tailings area pollution loads were found to be higher at the end of the rainy season due to a rise in the water table and hence increased groundwater seepage polluted groundwater usually has low eh 300 mv and ph 2 3 and high ec up to 8 ms cm 1 in some instances oxidation of fe occurs as the groundwater emerges on surface further lowering ph and establishing an fe iii fe oh 3 redox equilibrium which operates for many kilometres downstream various processes that occur increase compositional heterogeneity in the water amongst which are evaporation dissolution of efflorescent crusts and dilution by unpolluted water wetland environments are characterised by high ph and low eh and appear to be influenced by a sulfide sulfate redox system under which so 4 2 and metals are removed and ph increased lakes in the mining area have normal water quality which arises from a combination of metal removal by wetlands most lakes have wetlands at their inlets and dilution by rain and unpolluted groundwater they offer a potential method for passively treating polluted water arising from tailings dumps

hydrothermal iron rich deposits from the teahitia mehitia and macdonald hot spot areas southwest pacific abstract during cruise so 47 of r v sonne iron oxyhydroxide crusts of restricted extent were recovered from teahitia and moua pihaa seamounts in the teahitia mehetia hot spot area and from macdonald seamount in the macdonald hot spot area the crusts show complex layering and incorporate volcanic ash layers they consist of goethite feldspar and pyroxene and display low contents of transition elements apart from fe it is believed that the crusts were deposited from relatively low temperature hydrothermal fluids these low temperatures preclude the formation of sulphide deposits the type of hydrothermal mineral recovered may be a function of the thermal regime of the system and the elevation which controls the pressure of the venting fluids the shallower depths of these seamounts compared to the axes of mid ocean ridges may therefore be responsible for the style of mineralization initially magmatic vapours migrating upwards through the hot spot volcano are thought to be absorbed into seawater at comparatively shallow levels to deposit sulphide minerals within the volcanic pile the fe oxyhydroxide deposits are the residual low temperature deposits formed when the spent hydrothermal fluid reached the crest of the seamount these deposits therefore differ fundamentally from those found at the crest of mid ocean ridges where sulphide mounds are deposited directly upon interaction of the boiling hydrothermal fluid with seawater the discovery of hydrothermal iron oxyhydroxide crusts in these two hot spot areas is only the second such finding after loihi seamount southeast of hawaii

ii using a borehole geophysical logging program in poorly consolidated sediments for a hazardous waste investigation i m a refugee from the oil industry i interpreted many seismic and other types of data in my time but because of the economic volatility of the oil industry i decided to find another area in which to employ my skills i soon discovered that the application of geophysical tools and techniques is steadily increasing in the hazardous waste industry and has now reached the level where it can be the cornerstone of a career

composition and origin of hydrothermal ironstones from central pacific seamounts abstract ironstones recovered from five late cretaceous seamounts in the central pacific region probably formed during late stage edifice building volcanism ironstones are dense and compact with the appearance of brown chert the ironstones are characterized by a goethite mineralogy with feooh contents up to 88 extreme fractionation of fe and mn low trace element and rare earth element abundances low co zn ratios and isotopic equilibration temperatures of about 20 45 c these characteristics indicate that the ironstones formed from hydrothermal fluids ironstones probably formed below the seawater seafloor interface as indicated by their occurrence as a proximal hydrothermal deposit presence of primary goethite cement pervasive replacement of rocks by goethite and absence of interbedded pyro clastic beds

nontronite from a low temperature hydrothermal system on the juan de fuca ridge abstract a deposit of fe rich al poor hydrothermal nontronite was recovered from the juan de fuca ridge analyses show the deposit to be mineralogically and chemically similar to nontronite described at other oceanic localities the deposit is located near the tip of a propagating segment of the juan de fuca ridge rare earth elements and sr isotopes indicate that the nontronite precipitated from seawater a formation temperature of 57 c is suggested by oxygen isotopic composition the low temperature nontronite deposits apparently form from newly established hydrothermal systems associated with the propagating rift segment more mature hydrothermal systems that deposit sulfide on the seafloor may develop from these low temperature systems

hydrothermal metallogenic processes off the islands of nisiros and kos in the hellenic volcanic arc abstract two submarine hydrothermal fields off nisiros and kos islands in the eastern sector of the hellenic volcanic arc have been investigated using analyses of submarine hydrothermal waters and sediments both the waters and the sediments were found to be enriched in fe mn and zn together with as mo and v in the sediments only resulting from seawater rock interaction processes similar to those described from mid ocean ridge systems differences found between the products of these processes in the two hydrothermal fields studied reflect differences between the rock types being leached the physiographic and geological conditions present including the thickness and composition of the sediment column above the volcanic rocks and the rates of mixing of hydrothermal solutions with normal seawater the geochemical features described support possible sub seafloor formation of metal sulphides at both of the hydrothermal fields studied

consolidation and incipient oxidation of alkaline arsenopyrite bearing mine tailings macraes mine new zealand abstract fine grained ca 15 m arsenopyrite bearing mine tailings have been exposed to drying and oxidation for 4 a pending relocation the tailings are still partly covered by a pond of decanted pore waters the water table in drying tailings has lowered by 1 3 m and desiccation cracks up to 2 cm wide have formed on the 1 m scale extending through the unsaturated zone tailings in the unsaturated zone have similar pore water contents to saturated tailings typically 16 32 wt water saturated tailings retain alkaline ph ca 10 from the mine cyanidation plant but ph lowers progressively towards ca 7 near the surface or near desiccation cracks in the unsaturated zone the redox state of the tailings changes in parallel with ph with an empirical relationship eh mv 55 ph 290 water in the remnant decant pond reflects this relationship also unsaturated tailings have variable but low permeabilities typically 10 3 to 10 4 m day and more permeable horizons have allowed incursion of oxygenated air and or rain water from desiccation cracks sulphide grains in all tailings examined are unaltered sulphides and solutions in the tailings are out of thermodynamic equilibrium predicted from the redox ph conditions due to kinetic constraints incursion of rain water locally facilitates deposition from pore waters of insoluble fe oxide and arsenate minerals thus fixing as in the dry unsaturated tailings

selective mineralization of microbes in fe rich precipitates jarosite hydrous ferric oxides from acid hot springs in the waiotapu geothermal area north island new zealand abstract a group of small springs that are informally called orange spring located near hakereteke stream in the northern part of the waiotapu geothermal area feed hot 80 c acidic ph 2 1 2 4 as rich sulfate waters into a discharge channel that is up to 25 cm deep submerged reddish brown precipitates on the channel floor are formed largely of noncrystalline as rich hydrous ferric oxide hfo mainly goethite poorly crystalline lepidocrocite and crystalline jarosite well preserved coccoid and rod shaped microbes are found in the as rich hfo but not in the lepidocrocite or jarosite the jarosite was probably precipitated when the water had a low ph 4 and lower so4 content the fluctuations in the ph and so4 content which led to precipitation of the different mineral phases may reflect mixing of the spring water with stream water that flowed through the channel when hakereteke stream was in flood stage the goethite probably formed when coccoid and rod shaped bacteria acidithiobacillus ferrooxidans mediated rapid oxidization of the fe2 to fe3 that was then immediately coprecipitated with the as such rapid precipitation promoted mineralization of the microbes the lack of mineralized microbes and the lower as in the lepidocrocite and jarosite may reflect precipitation rates that were slower than the decay rates of the microbes or ecological factors that limited their growth

submarine thermal springs associated with young volcanoes the teahitia vents society islands pacific ocean abstract hydrothermal solutions were sampled close to two summits of teahitia a submarine volcano from the southern extension of the society volcanic chain the temperatures measured within two vents were 30 c the vent solutions have a ph value around 5 3 and are enriched in fe mn si ba li and rees relative to ambiant seawater but show only a small decrease in mg and so4 concentrations the lowest measured 87sr 86sr is 0 70867 while the end is identical to those of the surrounding alkali basalt 2 5 the vent solutions from teahitia have chemical characteristics similar to pele s vents loihi seamount another mid plate volcano the exact temperature of seawater basalt interaction is difficult to constrain however the absence of positive eu anomaly in the fluids the particles and in the hydrothermal deposits from teahitia seems to exclude the participation of a high temperature component comparable as those involved in mid ocean ridge axis vents

control of pit lake water chemistry by secondary minerals summer camp pit getchell mine nevada abstract at the summer camp pit of the getchell mine in northern nevada the sulfate mineralogy is complex and includes gypsum jarosite pickeringite halotrichite copiapite melanterite langite and bukovskyite that occur along with scorodite mansfieldite and ca cu zn arsenate minerals leaching of these minerals by meteoric water seasonally contributes as fe ca trace metals sulfate and hydrogen ions to the lake during the early stages of pit lake refilling 1991 1993 this mechanism had an important control on water quality in the pit although over time the effect has lessened as groundwater inflow has increased the lake volume and diminished the relative importance of wall rock leachate the formation and reaction of secondary minerals around pit lakes in net evaporative environments are both a source and sink for metals

the natural attenuation of two acidic effluents in tharsis and la zarza perrunal mines iberian pyrite belt huelva spain the geochemical evolution of two acid mine effluents in tharsis and la zarza perrunal mines iberian pyrite belt huelva spain has been investigated in origin these waters present a low ph 2 2 and 3 1 and high concentrations of dissolved sulphate and metals fe al mn cu zn as cd co cr ni however the natural evolution of these acidic waters which includes the bacterial oxidation of fe ii and the subsequent precipitation of fe iii minerals represents an efficient mechanism of attenuation this self mitigating process is evidenced by the formation of schwertmannite which retains most of the iron load and by sorption toxic trace elements like as the later mixing with pristine waters rises the ph and favours the total precipitation of fe iii at ph 3 5 and subsequently al compounds at ph 4 5 along with the sorption of trace metals mn zn cu cd co ni until chemical equilibrium at circumneutral conditions is achieved

new sidescan sonar and gravity evidence that the nova canton trough is a fracture zone a 1990 sidescan sonar survey in the eastern region of the nova canton trough mapped 138 striking abyssal hill fabric trending into 70 striking trough structures the location and angle of intersection of the abyssal hills with the eastern nova canton trough effectively disprove a spreading center origin of this feature free air gravity anomalies derived from satellite altimetry data show continuity across the line islands of the nova canton trough with the clipperton fracture zone the canton clipperton trend is copolar about a pole at 30 s 152 w with other coeval pacific farallon fracture zone segments from the pau to marquesas fracture zones this copolarity leads us to postulate a pacific farallon spreading pattern for the magnetic quiet zone region north and east of the manihiki plateau with the nova canton trough originating as a transform fault in this system

hydrothermal clay mineral formation of east pacific rise and bauer basin sediments samples of surface metalliferous sediment recovered from the crest of the east pacific rise at 6 s and 10 s latitudes and from the adjacent bauer basin are characterized by an authigenically formed fe rich montmorillonite that dominates the non carbonate mineralogy of the clay fraction 2 m oxygen isotopic formation temperatures indicate that the fe montmorillonites are created by low temperature hydrothermal processes 30 50 c in the 10 s region of the east pacific rise and bauer basin possibly as a result of cooling and oxidation of unstable high temperature 380 30 c sulfide assemblages or as a result of the percolation of hydrothermally altered seawater solutions through underlying basalt and sediments the widespread sedimentation of the clay mineral is suggested to be caused by colloidal transport possibly as a result of erosion of hydrothermal mounds by bottom currents hydrothermal fe montmorillonite nontronite formation may act as a direct and significant oceanic sink for si and fe released by the high temperature hydrothermal alteration of basalt at ocean spreading centers

a transmission electron microscopy analysis of secondary minerals formed in tungsten mine tailings with an emphasis on arsenopyrite oxidation abstract grains of naturally oxidized arsenopyrite feass collected from the oxidation zone in w mine tailings were investigated primarily using transmission electron microscopy the grains are severely pitted and are surrounded by secondary minerals the pitted nature of the grains is related to mechanisms governing the electrochemical oxidation of sulfide minerals with prominent cusp like features occurring at cathodic regions of the surface and pits occurring at anodic regions in general the oxidation of arsenopyrite leads to the formation of an amorphous or nanocrystalline fe as o rich coating that contains small amounts of si ca cu zn pb and bi nanoscale variation in the as pb bi and zn contents of the coating was noted secondary cu sulfides thought to be chalcocite cu2s and or djurleite cu31s16 occur as a layer generally

seasonal variations in the formation of al and si rich fe stromatolites in the highly polluted acid mine drainage of agua agria creek tharsis sw spain abstract the study of the different biotic and abiotic processes involved in the current formation of fe stromatolites in rivers affected by acid mine drainage amd is essential not only to understand this unique and extreme environment but also to achieve a better understanding of the past iron formation on the earth and on mars the fe stromatolites studied in the highly polluted amd in tharsis sw spain revealed a unique mineral assemblage with jarosite and rostite as the most unexpected fe and al phases and goethite and schwertmannite as the main constituents seasonal variations in this region greatly affected the composition of the precipitates and the distribution of diatoms within the fe stromatolites drought and flood events were also recognized in the sedimentary textures and in the mineral assemblages observed of particular layers within the fe stromatolites the characterization of the chemical and mineralogical composition of fe stromatolites in tharsis as well as the different formation mechanisms proposed complement the existing literature on newly formed fe stromatolites and provides new observations to increase our understanding of those extreme environments

hydrogeochemistry of the tsumeb deposit implications for arsenate mineral stability the tsumeb base metal deposit contained one of the most diverse examples of mineralogical paragenesis ever observed within a single mineral deposit keller 1977 the deposit hosted approximately 307 minerals and 232 of those minerals are most likely formed in the oxidation zone of the total number 69 minerals were first described from the deposit arsenic minerals show the greatest diversity in the tsumeb deposit 63 arsenates 6 arsenites and 7 arseno sulfate minerals see appendix 1 typically as content was around 1 in the ore zone and was intermittently produced as a by product white as oxide mineralization is hosted in the otavi dolomite the main ore body is a pipe that comprises of massive peripheral ores manto style ores and disseminated and stringer ores these ores were subjected to extensive oxidation not just from surficial surface weathering but also along deep seated permeable faults that developed complex secondary mineral assemblages at depth due to the karstic nature of the host dolomite there has been considerable water flow through the deposit and during operations into the mine workings even during early mining as such water chemistry within the mine has a varied composition reflecting the different areas of the mine water source and geochemical reactions with host rock and the ore in addition to water which has been locally enriched from sulfide oxidation saline and dilute water can be observed in the mine with such a complex mineralogy and paragenesis it is possible to describe the geochemical conditions that influenced the mineral evolution of the deposit and predict interactions with groundwater the extent to which current mine water reflects mineral paragenesis and the observed as mineral assemblage in the mine is reviewed and used to provide an understanding of the formation of the oxide zone and the geochemical conditions at the time of formation compared

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 50 degree spherical harmonic model of the magnetic field of mars this paper presents a 50 degree and order spherical harmonic model of the magnetic field of mars derived at 120 km altitude using the three orthogonal components of the vector magnetic field data acquired by the mars global surveyor within the 80 to 200 km altitude range the downward continued vector magnetic field components to the surface of mars delineate details of the martian magnetic field the strong magnetic anomalies in the southern hemisphere do not show compelling evidence for magnetic lineations similar to those associated with the seafloor spreading on earth the anomalies are more or less equidimensional the magnetic signatures surrounding the impact basins hellas argyre and isidis show that the prominent magnetic anomalies are older than the impact events an average magnetization of 2 a m is estimated for the upper crust surrounding hellas basin four isolated magnetic anomalies are modeled by vertical prisms with circular cross sections of 170 to 190 km radius and 20 to 30 km thickness the magnetization of the model prisms is 5 a m more than that of the surroundings

solar wind interaction with the martian upper atmosphere crustal field orientation solar cycle and seasonal variations a comprehensive study of the solar wind interaction with the martian upper atmosphere is presented three global models the 3 d mars multifluid block adaptive tree solar wind roe upwind scheme mhd code mf mhd the 3 d mars global ionosphere thermosphere model m gitm and the mars exosphere monte carlo model adaptive mesh particle simulator m amps were used in this study these models are one way coupled i e the mf mhd model uses the 3 d neutral inputs from m gitm and the 3 d hot oxygen corona distribution from m amps by adopting this one way coupling approach the martian upper atmosphere ion escape rates are investigated in detail with the combined variations of crustal field orientation solar cycle and martian seasonal conditions the calculated ion escape rates are compared with mars express observational data and show reasonable agreement the variations in solar cycles and seasons can affect the ion loss by a factor of 3 3 and 1 3 respectively the crustal magnetic field has a shielding effect to protect mars from solar wind interaction and this effect is the strongest for perihelion conditions with the crustal field facing the sun furthermore the fraction of cold escaping heavy ionospheric molecular ions 2 and or 2 total are inversely proportional to the fraction of the escaping ionospheric and corona atomic ion o total whereas 2 and 2 ion escape fractions show a positive linear correlation since both ion species are ionospheric ions that follow the same escaping path

control of mars global atmospheric loss by the continuous rotation of the crustal magnetic field a time dependent mhd study we present a time dependent mhd study of the controlling effects of the mars crustal field on atmospheric escape we calculate globally integrated planetary ion loss rates under quiet solar conditions considering the continuous rotation of crustal anomalies with the planet it is found that the rotating crustal field plays an important role in controlling atmospheric escape significant time variation of 20 and 50 is observed during the entire rotation period for o and for o2 and co2 respectively the control is exerted mainly through two processes first the crustal magnetic pressure over the subsolar regime controls solar wind penetration and mass loading and therefore the escaping planetary ion source there is a strong negative correlation between the magnetic pressure and ion loss with a time lag of 1 h for o and 2 5 h for o2 and co2 second the crustal magnetic pressure near the terminator region controls the cross section area between the induced magnetospheric boundary and 100 km altitude at the terminator the change in day night connection regulates the extent to which planetary ions created on the dayside can be ultimately carried away by the solar wind and escape mars there is a strong positive correlation between the cross section area and ion loss with no significant time lag as the planet rotates the dayside process and the terminator process work together to control the total amount of escaping planetary ions however their relative importance changes with the local time of the strong crustal field region

magnetic field and plasma observations at mars initial results of the mars global surveyor mission the magnetometer and electron reflectometer investigation mag er on the mars global surveyor spacecraft has obtained magnetic field and plasma observations throughout the near mars environment from beyond the influence of mars to just above the surface at an altitude of 100 kilometers the solar wind interaction with mars is in many ways similar to that at venus and at an active comet that is primarily an ionospheric atmospheric interaction no significant planetary magnetic field of global scale has been detected to date 2 1021 gauss cubic centimeter but here the discovery of multiple magnetic anomalies of small spatial scale in the crust of mars is reported

hydrothermal venting within a coral reef ecosystem ambitle island papua new guinea shallow water 5 10 m hydrothermal venting in a nearshore coral reef environment at ambitle island in the tabar feni island arc east of papua new guinea occurs as focused discharge of boiling fluid from discrete ports 10 15 cm in diameter and as dispersed discharge of diffuse bubble streams that issue through the sandy mixed carbonate volcaniclastic sea floor abiotic aragonite and microcrystalline ferroan low mg calcite interlaminated with fe oxyhydroxides are the prominent hydrothermal precipitates geochemical attributes of aragonite 18o 13c and fluid inclusions suggest that cements formed from a solution with salinities 5 at temperatures of 100 c with probable contribution of hydrothermal co2 sr isotope ratios in abiotic hydrothermal aragonite 0 704 15 are similar to those in island arc basalt and denote considerable subsurface water rock interaction of meteoric water derived from the adjacent volcanic island the sr isotope ratio of a coral sample 0 707 46 collected adjacent to a vent portal suggests coral growth within a mixed seawater hydrothermal environment

spatial and temporal variability in crystallization of celadonites within the troodos ophiolite cyprus implications for low temperature alteration of the oceanic crust celadonite a low temperature 30 c hydrothermal alteration mineral is a predominant fracture and void filling phase within the volcanic rocks of the troodos ophiolite the combined chemical and structural properties of celadonite i e high k2o and ar retentive along with its common occurrence provide a valuable tracer for studying the temporal and spatial variability of low temperature hydrothermal fluid circulation and alteration within this ancient oceanic crust some 54 new k ar age determinations of celadonites from various geographic and stratigraphic locations within the extrusive rocks of troodos yield crystallization ages ranging from 90 9 1 0 to 49 8 0 5 ma with the oldest in close agreement with the estimated 91 92 ma crystallization age of troodos igneous rocks the youngest age indicates that low temperature water rock chemical exchange continued for at least 40 m y after crustal formation this represents a 100 increase over previous estimates based on limited numbers of k ar dates of celadonite of the duration of low temperature mineral precipitation in troodos correlation between celadonite ages and field relationships suggests the following 1 there is no apparent relationship between celadonite crystallization and stratigraphic depth 2 celadonite crystallization occurs homogeneously on an outcrop scale with adjacent samples from a single flow unit yielding equivalent k ar ages 3 flow units with relatively high primary permeabilities e g pillows and breccias yield celadonites with younger k ar ages 4 celadonite precipitation at distinct locations occurred rapidly with little or no age difference between rim and core sections of single large deposits the above correlations suggest that low temperature hydrothermal fluid circulation and secondary mineral precipitation are controlled by the local alteration conditions such as intrinsic permeability degree of fracturing and water rock ratios and are independent of time and space integration of these local heterogeneities over the entire extrusive sequence suggests that the upper oceanic crust undergoes relatively homogeneous closure to hydrothermal fluid circulation no evidence is found to support a progressive upward sealing of the oceanic crust

waveform tomography at a groundwater contamination site surface reflection data wehaveappliedacoustic waveformtomographyto452d seismic profiles to image the 3d geometry of a buried paleochannel at a groundwater contamination site at hill air force base in utah the paleochannel which is incised into an alluvium covered clay aquitard acts as a trap for dense nonaqueous phase liquids dnapls that contaminate the shallowest groundwater system in the study area the 2d profiles were extracted from a 3d surface reflection data set first arrival traveltime tomography provided initial velocity models for the waveform tomography we inverted for six frequency components in the band 30 90 hz of the direct and refracted waves to produce 45 2d velocity models the flanks and bottom of a channel with a maximum depth of about 15 m were well modeled in most of the 45 parallel 2d slices whichallowedustoconstructa3dimageofthechannel by combining and interpolating between the 45 image slices the 3d model of the channel will be useful for siting extraction wells within the site remediation program the alluvium that fills the channel showed marked vertical and lateral velocity heterogeneity traveltime tomography and waveform tomography can be complementary approaches used together they can provide high resolution images of complicatedshallowstructures

pressure oxidation autoclave as an analogue for acid sulphate alteration in epithermal systems gold extraction at the macraes gold mine in new zealand involves concentration of pyrite and arsenopyrite oxidation of those sulphides then cyanidation the ore concentrate is predominantly otago schist host rock andesitic composition with up to 15 sulphides the oxidation step is conducted on ore concentrate slurry in an autoclave at 225 c and 3 800 kpa oxygen gas pressure with continuous feed the slurry takes ca 1 h to pass through the autoclave during which time the sulphides are almost completely oxidised sulphide oxidation causes strong acidification of the slurry which is maintained at ph of 1 2 by addition of caco3 scales form on walls in the autoclave with minerals reflecting progressive oxidation and alteration of the ore through the system the schist in the ore feed has mineralogy similar to propylitically altered andesite quartz albite muscovite chlorite and pyrite muscovite undergoes almost complete dissolution with associated precipitation of quartz and alunite kal3 so4 2 oh 6 other principal minerals deposited and discharged include anhydrite and or gypsum jarosite kfe3 so4 2 oh 6 hematite and or amorphous iron oxyhydroxide and amorphous arsenates dissolved ferrous iron passes right through the autoclave and variably hydrated fe2 and fe3 sulphate minerals including rozenite and szomolnokite both feso4 hydrate and ferricopiapite fe5 so4 6o oh hydrate are formed along the way the autoclave chemical system resembles acid sulphate hydrothermal activity in geothermal systems and high sulphidation epithermal mineral deposits formed in arc environments these natural acid sulphate systems are pervaded by volcanic vapours in the near surface environment where widespread dissolution of host rocks occurs and deposition of quartz alunite and anhydrite is common some of the volume loss associated with these natural systems may be due to dissolution of soluble sulphate minerals by later stage groundwater incursion

comparison of contrasting gold mine processing residues in a temperate rain forest new zealand abstract processing residues high in metallic elements are the legacy of historic gold processing sites concentrating naturally occurring metalloids in the ore as sb as well as chemicals and metals added during processing to recover the gold zn pb hg this study uses electron microscopy to investigate the link between variations in processing residue mineralogy and the processing technique used to extract the gold semi cemented amorphous ferric arsenate and as bearing iron oxyhydroxides attenuating as zn and pb are the products of the simplest processing technique of crushing sulphide concentration and gold recovery through hg amalgamation zinc pb and ca added during cyanidation form zn rich carbonate and zn oxide mineralogy ore roasting concentrates as to elevated levels 35 wt as well as concentrating sb from the ore and hg from the amalgamation process roasting rapidly oxidises sulphide concentrates producing toxic and highly mobile arsenolite as2o3 as3 roaster tailings processed by all of these techniques crushing roasting and cyanidation are largely comprised of as hematite and quartz mine residue weathering causes localised acidification and leaching of metallic elements along with the high rainfall on these site remobilising elements lime added during processing and the carbonate host rock neutralises this acidification the formation of secondary fe3 oxyhydroxide minerals formed during residue weathering and oxidisation sequesters as zn and pb redox conditions and the ph of a site will control the stability of these secondary minerals the toxicity of a site processing residue can be correlated to the processing technique used with characterisation of processing residue mineralogy having important implications for site remediation and management

arsenic mobility in alteration products of sulfide rich arsenopyrite bearing mine wastes snow lake manitoba canada abstract the arsenopyrite residue stockpile ars in snow lake manitoba contains approximately 250 000 tons of cyanide treated refractory arsenopyrite ore concentrate the residue was deposited between 1950 and 1959 in an open waste rock impoundment and remained exposed until 2000 when the pile was capped with layers of waste rock and clay during the time when the ars was exposed to the atmosphere arsenopyrite pyrrhotite pyrite and chalcopyrite were oxidized producing scorodite jarosite and two generations of amorphous fe sulfo arsenates aisa these secondary phases attenuated some of the as released to pore water during oxidation in the upper layers of the ars the imposition of the cap prevented further oxidation the secondary as minerals are not stable in the reduced environment that currently dominates the pile therefore as currently is being released into the groundwater water in an adjacent monitoring well has concentrations of 20 mg l total as with relative predominance of as iii

refraction tomography over a buried waste disposal site determining the depth and geometry of a landfill s lower boundary is a difficult task potential field methods generally lack the necessary depth resolution and seismic reflection data are usually contaminated by source generated noise in the time range of interest 50 ms to address this problem we have developed a surface 2 d tomographic refraction scheme that is based on a fast finite difference eikonal solver and an inversion method that incorporates appropriate damping and smoothing constraints this new scheme has been applied to a first arrival traveltime data set collected across adjacent landfills in northern switzerland high quality seismic data were collected along five profiles that crossed the landfills and two that sampled undisturbed natural sediments seismic waves generated from multiple shots were recorded on large numbers of closely spaced receivers during quiet evening periods reliability of the resultant velocity tomograms was estimated on the basis of 1 ray diagrams 2 plot

low energy electron current in the martian tail due to reconnection of draped interplanetary magnetic field and crustal magnetic fields 1 we observe seasonal nighttime clustering of significant enhancements in the mars global surveyor electron omnidirectional flux data at low energy levels over a specific geographical region at the west edge of the crustal fields at around 70 s and between 30 e and 150 e we propose that photoelectrons generated over the crustal sources on the martian dayside are transported along lines of the reconnected interplanetary magnetic field to the nightside and populate currents formed in the magnetotail comparison of the draping direction estimated from the dayside data between 50 and 60 n latitude band over the northern hemisphere at the closest time of the enhancements with the crustal fields at 150 e and 65 s shows the existence of favorable conditions for the reconnection seasonal variation observed in the draping direction accounts for the seasonal nature of the phenomenon moreover a nearly 25 d periodic variation of the draping direction due to solar rotation strictly coincides with the periodic variation observed in the strength of the enhancements we also demonstrate the effect of the sun on the electron flux variations over two regions 1 closed crustal fields and 2 the enhancement clustering region finally we propose a model for the distribution of current sources on the nightside that accounts for the perturbations observed in the magnetic field data

ree fe variations in hydrothermal sediments implications for the ree content of seawater seafloor hydrothermal vent solutions exhibit rare earth element ree enrichments ranging between one to three orders of magnitude greater than average seawater to assess the impact of these hydrothermal inputs on ocean chemistry we have examined the behavior of rees for hydrothermal sediments collected adjacent to two pacific spreading ridge sites the east pacific rise at 19 s and the southern juan de fuca ridge at 4s n in general the ree fe ratios for both proximal and distal hydrothermal sediments are greater than vent solutions by a factor of 2 to 500 and these ratios increase with increasing distance away from the ridge axis an evaluation of these results in the context of previous models of ree behavior indicates that in fact seawater experiences a net depletion in rees as a result of hydrothermal activity this is due primarily to the large scavenging capacity of iron oxyhydroxides which precipitate from these solutions such an interpretation explains why the ree content of seawater collected in the vicinity of hydrothermal vents is anomalously lower than normal seawater sampled from a comparable depth

the environmental geochemistry of arsenic an overview arsenic is one of the most prevalent toxic elements in the environment the toxicity mobility and fate of arsenic in the environment are determined by a complex series of controls dependent on mineralogy chemical speciation and biological processes the element was first described by theophrastus in 300 b c and named arsenikon also arrhenicon caley and richards 1956 referring to its potent nature although it was originally considered an alternative form of sulfur boyle and jonasson 1973 arsenikon is believed to be derived from the earlier persian zarnik online etymology dictionary http www etymonline com index php term arsenic it was not until the thirteenth century that an alchemist albertus magnus was able to isolate the element from orpiment an arsenic sulfide as2s3 the complex chemistry required to do this led to arsenic being considered a bastard metal or what we now call a metalloid having properties of both metals and non metals as a chemical element arsenic is widely distributed in nature and can be concentrated in many different ways in the earth s crust arsenic is concentrated by magmatic and hydrothermal processes and has been used as a pathfinder for metallic ore deposits particularly gold tin copper and tungsten boyle and jonasson 1973 cohen and bowell 2014 it has for centuries been considered a potent toxin is a common poison in actual and fictional crimes and has led to significant impacts on human health in many areas of the world cullen 2008 wharton 2010 the potential issues associated with elevated as concentrations in water supplies have led to a large body of published research in the last few years related to

hydrothermal oxide and nontronite deposits on seamounts in the eastern pacific deposits of fe oxide mud nontronite and fe mn crusts were sampled from the summits of two seamounts in the eastern pacific where low temperature 0 15 c hydrothermal fluids are issuing the deposits consist of x ray amorphous fe oxyhydroxide and are rich in fe 43 wt contain minor si and p 4 and 3 5 respectively and have very low mn 0 01 and other trace element contents other deposits where no current hydrothermal activity was observed consist of mud and crusts composed of amorphous material and poorly crystalline hematite goethite and smectite these deposits have slightly higher mn up to 2 and other trace element contents the mineralogical and chemical differences between the active and inactive deposits and crusts are interpreted to be due to recrystallization and contamination with detrital biogenic hydrogenous and possibly hydrothermal sulfide material nontronite deposits capped by fe mn oxides were sampled from one of the seamounts these deposits have compositions similar to other seafloor nontronite deposits and formed at low temperatures 30 c during mixing of low temperature hydrothermal fluids with seawater the oxide deposits consist almost entirely of long delicate filaments remarkably similar in morphology to genera of fe oxidizing bacteria such bacteria were probably important in catalyzing the oxidation and precipitation of iron from hydrothermal fluids on the seamounts the occurrence of nearly identical filament rich oxide deposits on two widely separated seamounts suggests that this type of deposit may be common on seamounts but previously unrecognized