lithofacies associations and evolution of the volcanic host succession to the minifie ore zone ladolam gold deposit lihir island papua new guinea the 46 million ounce ladolam gold deposit the largest alkalic epithermal gold deposit in the world in terms of contained gold is composed of four ore zones minifie lienetz kapit and coastal this detailed lithofacies study of the minifie ore zone recognized three evolutionary stages 1 volcanosedimentary strata part of an alkalic composite volcanic island 2 a porphyry style breccia dike and 3 epithermal style breccias the plio pleistocene volcanosedimentary stratigraphy reflects the transition from subaerial deposition of pyroclastic surge deposits close to vent to a subaqueous quiet depositional environment into which a cryptodome was emplaced the stratigraphy is predominantly composed of polymictic matrix supported breccia and sandstone interbedded with lavas and shallow intrusions the minifie strata have a shallow southward dip as a result of quaternary uplift overprinting the volcanosedimentary stratigraphy are three hydrothermally cemented breccia facies one deposited in the porphyry environment and two deposited in the epithermal environment porphyry style alteration assemblages and a 3 to 5 m wide biotite k feldspar calcite anhydrite cemented breccia dike are focused around the central minifie shear fault the porphyry alteration assemblages are overprinted by shallow level and deeper level epithermal style features the deeper level below the present mining surface 140 m below sea level epithermal vein stockwork is composed of quartz calcite adularia anhydrite cemented breccias and shallowly northward to near horizontal dipping veins that have gold grades of 1 to 60 g t au shallow level epithermal facies adularia quartz pyrite cemented breccias veins and associated alteration host the bulk mineable gold ore and typically yield 4 g t au over 12 m blast hole samples

mineralogy and geochemistry of alluvium contaminated by metal mining in the rio tinto area southwest spain the rio tinto in sw spain drains cu and pyrite mines which have been in operation since at least the bronze age extensive metal mining especially from 1873 to 1954 has resulted in contamination of the rio tinto alluvium with as cu pb ag and zn x ray diffraction xrd wavelength dispersive x ray mapping scanning electron microscope petrography and x ray energy dispersive edx analysis has revealed that 4 major groups of contaminant metal and as bearing minerals including sulphides fe as oxides fe oxides hydroxides oxyhydroxides and fe oxyhydroxysulphates occur in the alluvium sulphide minerals including pyrite chalcopyrite arsenopyrite and sphalerite occur in alluvium near the mining areas iron hydroxides and oxyhydroxides such as goethite and possibly ferrihydrite occur in cements in both the mining areas and alluvium downstream and carry minor amounts of as cu and zn iron oxyhydroxysulphates including jarosite plumbojarosite and possibly schwertmannite are the most common minerals in alluvium downstream of the mining areas and are major hosts of cu pb zn and of as next to the fe as minerals this work and other field observations suggest that 1 the extreme acidity and elevated metal concentrations of the river water will probably be maintained for some time due to oxidation of pyrite and other sulphides in the alluvium and mine waste tips and from formation of secondary oxide and oxyhydroxysulphates 2 soluble fe oxyhydroxysulphates such as copiapite which form on the alluvium are a temporary store of contaminant metals but are dissolved during periods of high rainfall or flooding releasing contaminants to the aqueous system 3 relatively insoluble fe oxyhydroxysulphates and hydroxides such as jarosite and goethite may be the major long term store of alluvial contaminant metals and 4 raising river ph will probably cause precipitation of fe oxyhydroxides and oxides hydroxides oxyhydroxides and thus have a positive effect on water quality but this action may destabilise some of these contaminant metal bearing minerals releasing metals back to the aqueous system

influence of the temperature of co2 rich springs on their aluminium and rare earth element contents abstract in a set of thermomineral waters of about constant major element composition al fe and rare earth element ree concentrations are strongly dependent on the spring temperature al and ree concentrations are not affected by co2 degassing at the outflow of the waters al concentrations vary by one order of magnitude between the coldest and the hottest waters this change in total concentration is related to a change in the speciation fluoride complexes mainly alf03 are the dominant species in cold waters hydroxide or fluoro hydroxide complexes are more important at higher temperature ree patterns vary smoothly as a function of the atomic number from a regular decrease for the hottest water ce yb 30 to a large increase from ce to dy followed by a slight decrease from dy to yb for the coldest waters ce yb 0 3 ce dy 0 15

estimation of deep reservoir temperature of co2 rich springs in kangwon district south korea abstract weakly acid to neutral co 2 rich springs ph 5 5 to 6 7 with high concentrations of dissolved ions tds 419 to 3091 mg l and bicarbonate 249 to 2470 mg l occur in kangwon district south korea they are grouped into three chemical types na hco 3 ca na hco 3 and ca hco 3 the na hco 3 type waters correspond to mature or partially equilibrated waters while the other two types show the hydrochemical characteristics of immature waters in this study we examined the applicability of chemical geothermometers and multiple mineral equilibrium approach to estimate potential deep reservoir temperatures the application of silica na k and na k ca thermometers to a representative na hco 3 type water yielded a reasonable temperature estimate 115 157 c for a deep geothermal reservoir the multiple mineral equilibrium approach yielded a similar temperature estimate about 140 160 c on the other hand the ca hco 3 type waters showed a relatively low and wide range of temperature estimates about 60 130 c which suggests that their disequilibrium state is possibly due to surface water mixing we believe that deep reservoir temperatures of co 2 rich groundwaters in kangwon district can be estimated from the chemistry of na hco 3 type waters and possibly approach 140 160 c

rare earth element geochemistry in soils developed in different geological settings of cuba abstract the increased exploitation of rare earth elements rees over the past few decades and the disposal of various products containing these elements have prompted numerous environmental studies and the need to establish regulatory guidelines we determined the concentration of rees in topsoil samples of 33 soil profiles collected from areas of different geological settings in cuba the average ree concentrations revealed the following chemical abundances in decreasing order ce nd la pr sm er yb dy tb lu ho gd eu tm the significant variation in ree levels reflects the geological diversity of cuba the highest ree concentrations were observed in typic rhodudalf and rhodic eutrodox which are derived from hard limestone in contrast the lowest ree concentrations were detected in the typic kandiustalf which originated from mica schist the lower light ree lree contents in cuban soils compared with soils from other countries is related to the low abundance of felsic rocks on the island we also observed a strong positive correlation between rees and some major elements in soils this finding implies that the distribution of rees in soils is partly governed by phosphates and aluminosilicates the low fractionation between lrees and heavy rees is likely related to the predominance of soils developed from carbonates this finding was also supported by the low lan smn and gdn ybn ratios and principal component analysis the spatial distribution of rees normalized to upper continental crust coupled with univariate and multivariate statistical techniques indicated that parent materials control the prevalence of rees in cuban soils the data presented here represent the first national wide survey of rees in cuban soils

strontium isotopes and rare earth elements as tracers of groundwater lake water interactions lake naivasha kenya abstract strontium isotope compositions and rare earth element ree concentrations are presented for groundwater and surface water samples collected from the lake naivasha watershed in the east african rift kenya the chief objective of the study is to test the suitability of rees in conjunction with sr isotopes as tools for investigating groundwater lake water interactions in general the ree concentrations and 87 sr 86 sr ratios support the authors earlier investigations where cl mass balance 18 o d and he isotopes were employed to study groundwater lake water interactions in the naivasha watershed the ree data suggest that a significant amount of the groundwater south of lake naivasha i e 50 85 consists of lake water recharge to the aquifer system specifically mixing calculations conducted using ree data of lake naivasha water and groundwaters indicate that between 70 and 85 of groundwater directly south of the lake is likely lake water these values are somewhat higher than the authors previous estimates determined with conservative stable h isotopes d 50 70 for both cases however the data demonstrate that water originating in lake naivasha contributes significantly to the underlying groundwater flow system hence supporting earlier evidence that the lake s freshness reflects rapid loss of water and dissolved solutes to the local groundwater system overall lake and groundwater sr isotope compositions support seepage of lake water into the underlying aquifer along the lake s south shore the 87 sr 86 sr data also provide additional insight into the geochemical evolution of waters of the lake naivasha watershed indicating that the initial source of sr to these waters is likely chemical weathering reactions involving basaltic rocks within the recharge zones of the watershed along the rift valley flanks furthermore with increasing residence time of groundwaters within the aquifer system and flow down and along the rift valley floor sr isotope compositions of groundwaters become more radiogenic reflecting rock water interactions with chemically differentiated and radiogenic peralkaline rhyolite volcanic rocks the importance of the longer aquifer residence times and radiogenic source rocks is especially apparent for geothermal waters of the olkaria geothermal field that have 87 sr 86 sr ratios i e 0 70747 similar to local comendites

the rotokawa geothermal system new zealand an active epithermal gold depositing environment the rotokawa geothermal system is less than 20 000 yrs old and is situated in a sequence of pleistocene and recent volcanic rocks and underlying mesozoic graywacke basement in the taupo volcanic zone a region dominated by extensional tectonics at lease 12 different hydrothermal explosition breccias are preserved in surface outcrops the largest eruptive site being a crater of 1 5 km in diameter which formed about 6 060 years ago and is presently occupied by an acid lake lake rotokawa with a ph approximately 2 significant bedded sulfur deposits which formed in an earlier crater lake exist beneath the present lake the deep fluids are dilute chloride 0 022 mole kg waters having higher reduced sulfur concentrations h 2 s approximately 7x10 super 3 mole kg than any previously studied active geothermal system a maximum temperature of 320 degrees c has been measured in the system water rock interaction has given rise to a zone of propylitic alteration at depth which is overlain by a region of advanced and intermediate argillic alteration extensive boiling occurs at depth an sulfide minerals such as sphalerite galena chalcopyrite and argentite occur sporadically with ubiquitous pyrite argentiferous alunite occurs in the advanced argillic alteration zone clasts of silicified lake beds in the hydrothermal explosion breccias commonly contain pyrite and carry subeconomic gold values of up to 0 1 g metric ton thermal waters discharging on the northeast shore of the lake are depositing gold ore grade arsenic and antimony sulfide rich muds which also contain high concentrations of tungsten thallium mercury silver and gallium this surface deposit is estimated to contain about 250 kg 8 000 oz of gold and has been deposited during the past 1 800 yrs since the formation 6 060 yrs ago of the large hydrothermal explosion crater in which lake rotokawa is now situated about 12 0 million oz 370 metric tons of gold may have been transported into the environment beneath the crater it is estimated that 1 7 to 3 3 million oz of gold may have been deposited in the upper 300 to 400 m underlying lake rotokawa from hydrothermal fluids initially saturated with gold

uranium and rare earth elements in co2 rich waters from vals les bains france abstract waters from springs at vals les bains result from the mixing of a co2 rich highly mineralized water with dilute shallow subsurface water total content of dissolved species vary from 5 mmol 1 to 100 mmol 1 for many elements mixing of these waters is non linear non conservative and further water rock reactions take place the ph is controlled by co2 outgassing redox conditions are controlled by both the iron hydroxide siderite buffer and the introduction of oxygen with shallow subsurface waters among the major elements concentrations of ca mg mn fe are related to mixing co2 outgassing and carbonate precipitation uranium shows a complex behaviour controlled by carbonate complexing redox conditions mixing of waters and leaching from the rocks the 234 u 238 u activity ratio is near secular equilibrium in the more dilute waters dissolved rare earth element ree patterns are almost flat with a slight negative eu anomaly in the concentrated waters heavy rare earth elements gd yb hree are strongly enriched relative to light rare earth elements ce eu lree we relate the enrichment in hree to water chemistry and to complexing with carbonate species

influence of the mediterranean outflow on the isotopic composition of neodymium in waters of the north atlantic the isotopic composition of neodymium in the water column of the eastern north atlantic near the strait of gibraltar has been determined for several depths the data show that the mediterranean outflow results in a significant shift in e nd 0 toward more radiogenic values of 143 nd 144 nd in the water column at a 1000 m depth this corresponds to a depth in the neighborhood of the salinity maximum associated with the mediterranean outflow the core of the mediterranean outflow gives e nd 0 9 8 as compared to e nd 0 12 in overlying and underlying waters demonstrating that the mediterranean waters are distinct from the atlantic from mixing considerations we estimate that pure mediterranean waters have e nd 0 6 possible sources of this relatively radiogenic nd could be from drainage of young continental terranes or the injection of remobilized nd from deep sea sediments that have a young radiogenic volcanic component new data from a depth profile in the western atlantic is presented comparison of nd data for the eastern north atlantic with that for the western north atlantic shows fundamental differences in the water column structures for e nd 0 while both regions show a pronounced maximum in e nd 0 the western basin maximum occurs at the near surface rather than at 1000 m in addition deep waters of the eastern basin are found to be more radiogenic than the western basin these differences indicate several sources of isotopically distinct nd in the north atlantic the deep waters of the north atlantic 1000 m have the lowest values of e nd 0 measured in the oceans we believe that the source of these low e nd 0 values which we associate with north atlantic deep water is either from freshwater drainage off the precambrian shields of north america and asia into the arctic ocean or from the injection of older continentally derived ree from deep sea sediments sm and nd concentrations are found to increase with depth and e nd 0 changes with depth indicating both vertical and lateral transport processes from different sources this suggests a surface source of nd and injection of ree into the water column from deep sea sediments or large scale bottom currents with high ree concentrations

rare earth element distribution in lake tyrrell groundwaters victoria australia abstract the rare earth element ree geochemistry of the saline to hypersaline acidic brines of lake tyrrell victoria australia were analyzed in order to determine the relative importance of concentration and modification processes in the lake system several types of brines were identified on the basis of different ree patterns and concentrations regional groundwater flowing into lake tyrrell yields the highest concentrations of ree while a transitional water group is identified on the basis of lower ree concentrations a third water group the reflux brine is characterized by extremely low ree concentrations the ree patterns suggest that ree are introduced to the lake tyrrell system by the regional groundwater which has concentrated ree from the aquifer material in its acidic waters eventually ree are removed from the evolving water mass as higher levels of ph are reached the data of the study strongly suggest that ree are scavenged from solution by fe oxyhydroxide phases which precipitate as the ph of the system rises water rock interactions probably control ph in the lake system and therefore ultimately control the concentration of ree in solution in this system our results are directly correlated with studies of hydrothermal vents and geothermal solutions which have shown the concentration of ree in solution to be dominantly controlled by ph

hydrothermal processes at the axi epithermal au deposit western tianshan insights from geochemical effects of alteration mineralization and trace elements in pyrite abstract as the largest low sulfidation ls epithermal deposit in the tulasu basin western tianshan nw china the axi gold deposit has a poorly understood geologic history it is not clear whether hydrothermal mineralization occurred during a single event or multiple events in this paper new data consist of whole rock geochemistry and mass change calculations for hydrothermal alteration la icp ms trace element analysis of pyrite was conducted in order to develop a comprehensive metallogenic model the pyrite sericite quartz alteration at the axi deposit is characterized by replacement of plagioclase and mafic phenocrysts by sericite quartz pyrite py1 smectite and illite indicating slightly acidic and reducing conditions during the early ore stage medium subhedral pyrite crystals py1 with porous texture are typically sited adjacent to iron rich minerals e g hornblende and are characterized by co ni mn enrichment with high ratios of co ni avg 1 114 and cu as avg 0 655 implying preferential sulfidation reactions in magmatic hydrothermal systems the quartz calcite pyrite adularia assemblages in silicified rocks and the strong mobility of lree both reflect a slightly acidic chloride rich solution phase during the later ore stage coarse anhedral pyrites with cataclastic texture py2 and medium euhedral pyrites py3 have a mixed hydrothermal origin and were deposited with quartz during au pyrite quartz and au polysulfide quartz stages respectively py2 and py3 both have significantly lower cu as ratios avg 0 103 and avg 0 088 respectively than py1 indicating the input of meteoric fluid during the later ore stage the three generations of pyrite especially py3 have significant lattice bound gold contents py1 0 01 38 86 ppm median 1 51 ppm py2 0 03 234 37 ppm median 1 21 ppm py3 3 31 231 56 ppm median 42 72 ppm gold precipitation is associated with the destabilization of au bearing chlorine au cl 2 and bisulfide complexes au hs 2 via sulfidation and fluid boiling all of these characteristics indicate the axi epithermal deposit is the result of two stages of mineralization

rare earth elements as geochemical tracers of regional groundwater mixing abstract the rare earth elements ree were analyzed in a groundwater system from south central nevada i e ash meadows national wildlife refuge the spring mountains pahranagat national wildlife refuge and the nevada test site in order to investigate their potential use as tracers of regional groundwater flow previous investigations using conservative tracers e g deuterium and uranium isotopes identified recharge in local mountains as the primary source 60 70 of total discharge for the springs in the regional discharge zone i e ash meadows with the remaining contribution being interbasin flow from the northeast initial mixing calculations for these groundwaters using shale normalized ree patterns agreed well with the previous studies however because the rees are not expected to behave conservatively in natural waters the effect of both solution complexation which acts to enhance the stability of the rees in solution as well as surface complexation responsible for the particle reactive behavior of the rees were examined in subsequent mixing calculations in order to assess the roles of solution and surface complexation relative partitioning coefficients were estimated for each ree in each groundwater by evaluating the ratio of the ionic strength corrected co 3 1 ree co 3 2 ree and co 3 2 f to the first hydrolysis binding constants for the rees the relative partitioning coefficients were then used to calculate ree patterns expected to develop and persist in solution as a consequence of solution and surface complexation the calculated ree values closely resembled the actual measured ree concentrations suggesting that the rees are in fact controlled by solution and surface complexation in these groundwaters the calculated ree concentrations were subsequently used to determine mixing ratios the results of which coincided with the initial calculations as well as the previous studies the results of this study suggest that solution complexation of the rees is sufficient to overcome to a certain degree the affinity of the rees to be adsorbed onto surface sites in the aquifers such that distinctive ree signatures develop and persist in solution in groundwaters from different aquifers the ability of solution complexation to overcome surface complexation is likely related to the formation of the negatively charged dicarbonato complex i e ln co 3 2 where ln is any ree which accounts for significant fractions of each ree in these groundwaters

rare earth elements yttrium and h o c sr nd and pb isotope studies in mineral waters and corresponding rocks from nw bohemia czech republic the sparkling waters from the area of kyselka near karlovy vary at the western slope of the doupovske hory bohemia czech republic and co2 poor waters from two underground boreholes at jachymov krusne hory bohemia have been studied with the aim of characterizing the distribution of rare earth elements yttrium and h o c sr nd pb isotopes during the low temperature alteration processes of the host rocks additionally leaching experiments were performed at ph 3 on the granitic and basaltic host rocks from kyselka and the granite of jachymov all ree patterns of the granite and the basalt derived waters from the kyselka area are different from those of their source rocks and the leachates of the latter this elucidates the inhomogeneous distribution of ree and y among the solid phases in the altered magmatic rocks the eu and ce anomalies in granite derived waters are inherited the y anomaly is achieved by fluid migration yttrium is always preferentially leached by mineral waters whereas y ho ratios of rocks and their leachates are very similar the ree abundances in waters from the wells in jachymov are derived from rocks intensely leached and depleted in easily soluble ree bearing minerals whereas the granites and basalts from kyselka still contain soluble ree bearing minerals a comparison of ree ca patterns of the experimental leachates with those of the mineral waters elucidate the high retention of ree in rocks during water rock interaction in strongly altered rocks sr isotope ratios of mineral waters and rocks differ widely whereas the corresponding nd isotope ratios are very similar 207pb 208pb 206pb 208pb and 206pb 207pb ratios in mineral waters are independent from u th ratios in the rocks 206pb 208pb and 206pb 207pb are lower in mineral waters than in their source rocks and their leachates which indicates that pb is primarily derived from solid phases that do not contain significant contents of leachable u and th thus mineral waters although co2 rich only interact with surface films on minerals and not with the bulk of the minerals as in the leaching experiments calculation of mixing ratios of waters from the granitic and basaltic sources of the waters from the kyselka area yield about 40 of water from the underlying granite in water recovered from the basalt whereas the granite derived water is mixed with only about 5 of the water from the basalt

snow metamorphism under alternating temperature gradients morphology and recrystallization in surface snow 1 the composition of the lower atmospheric boundary layer can be strongly influenced by snow photochemistry surface snow where air snow interactions take place is viewed as slowly changing quasi isothermal snow implied by the observation of mainly rounded snow crystals the role of snow for photochemistry is therefore expected to be purely geometric however large temperature gradients are often observed in these layers which would imply high recrystallization and faceting in controlled laboratory experiments we showed that temperature gradients on the order of 100 k m 1 do not lead necessarily to faceting if their sign changes with a daily cycle the shape of snow crystals does not reflect necessarily the metamorphic process with time lapse x ray tomography recrystallization rates as high as 60 of the total ice mass were observed during 12 hours the high recrystallization rates in apparently isothermal snow not only contradict the current understanding of snow metamorphism they also might influence chemical air snow interactions

rare earth element and heavy metal behaviour associated with the epithermal gold deposit on lihir island papua new guinea a thick sequence of alkaline intrusions and volcanic rocks underlies a quaternary caldera on lihir island the sequence is host to a still active subaerial hydrothermal system and associated epithermal gold mineralization chondrite normalized la lu cn and la sm cn ratios progressively increase up the alteration sequence from the potassic alteration zone to the argillic zone to the advanced argillic zone tb lu cn ratios only significantly increase in argillic and advanced argillic assemblages surface oxide alteration lithologies and acid sulphate water precipitates possess distinctly lower la lu cn and tb lu cn ratios than the underlying subsurface alteration units the changes in the ree lree and hree fractionation trends from subsurface to surface alteration zones reflect the transition from a magmatic hydrothermal neutral chloride fluid regime at depth to acid sulphate meteoric waters in the upper portion of the alteration profile boiling of the lree eu enriched magmatic fluids occurred at a depth of at least 750 m it is proposed that pronounced differential flow rates of the vapour and liquid phases and solution chemistry changes approximately above 300 350 m caused the incorporation of lree and eu into anhydrite calcite veins and the deposition of lree and hree into wallrocks of upper parts of the potassic alteration unit condensation of the vapour phases into meteoric waters gave rise to low temperature acid fluids that deposited large amounts of lree within argillic and advanced argillic alteration units this was also accompanied by hree mobility due to large fluid volumes acid fluid conditions and abundant sulphate complexes within the solutions the hree were either lost from the hydrothermal system or deposited in oxide assemblages and acid sulphate water precipitates

isotopic composition of neodymium in waters from the drake passage the isotopic composition of neodymium has been determined in seawaters from the drake passage the antarctic circumpolar current which controls interocean mixing flows through this passage the parameter e nd 0 which is a function of the ratio of neodymium 143 to neodymium 144 is found to be uniform with depth at two stations with a value which is intermediate between the values for the atlantic and the pacific and indicates that the antarctic circumpolar current consists of about 70 percent atlantic water cold bottom water from a site in the south central pacific has the neodymium isotopic signature of the waters in the drake passage by using a box model to describe the exchange of water between the southern ocean and the ocean basins to the north together with the isotopic results an upper limit of approximately 33 million cubic meters per second is calculated for the rate of exchange between the pacific and the southern ocean concentrations of samarium and neodymium were also determined and found to increase approximately linearly with depth these results suggest that neodymium may be a valuable tracer in oceanography and may be useful in paleo oceanographic studies

behaviour of rare earth elements during hydrothermal alteration at the buena esperanza copper silver deposit northern chile abstract a study of the ree behaviour in alteration zones of the buena esperanza subvolcanic cu ag deposit located in the coastal range of northern chile reveals that the elements are mobile in the rocks during alteration the ore forming process developed in three different stages of alteration mineralization the hydrothermal alteration of the early and middle stages affected basaltic fragments of a breccia pipe la and ce were leached from the rock fragments located at the bottom and at the middle part of the breccia pipe and partly redeposited at the top during alteration sm eu and tb were released selectively and the heavy ree behaved as relatively immobile elements sericite is the most important alteration mineral for fixing the ree during this stage the incoming fluids had low ree contents the late stage of hydrothermal alteration happened simultaneously with the intrusion of a gabbroic volcanic neck affecting mainly these subvolcanic rocks ree patterns of samples from the top and bottom of the alteration zone exhibit roughly parallel trends but are systematically enriched in ree in comparison to unaltered samples this enrichment seems to be more intensive at the top of the altered area coinciding with the enrichment of rb k and cu in these rocks epidote plays the most important role for fixing this hydrothermal input of ree during the latest stage of alteration

helium and argon isotope geochemistry of alkaline intrusion associated gold and copper deposits along the red river jinshajiang fault belt sw china abstract the red river jinshajiang strike slip fault zone on the eastern margin of the tibetan plateau was originally produced by the india eurasia collision 60 70 myr ago numerous post collisional mantle derived alkaline igneous rocks with ages of 40 30 ma have been intruded along this fault zone in recent years several copper and gold deposits associated with the alkaline intrusions of this region were discovered such as the yao an and beiya gold deposits and the yulong and machangqing copper deposits studied in this paper the mineralised intrusions are felsic with sio 2 ranging from 61 4 to 67 7 wt k 2 o na 2 o from 8 1 to 11 5 wt and k 2 o na 2 o 1 the deposits are located at both the exo and endo contact zones of the intrusions the mineral deposits are of hydrothermal origin with the ore forming temperatures mainly in the range 150 450 c this paper presents he and ar isotope analyses of these four deposits the concentrations of 4 he trapped in fluid inclusions of pyrites from the ores are 0 7 54 1 10 6 cm 3 stp g 1 and those of 40 ar are 0 6 7 3 10 6 cm 3 stp g 1 3 he 4 he ratios are 0 3 2 5 ra ra represents the 3 he 4 he ratio of air 1 39 10 6 40 ar 36 ar ratios are 316 1736 and 3 he 36 ar ratios are 0 2 11 2 10 3 generally the 3 he 4 he 40 ar 36 ar and 3 he 36 ar ratios for the gold deposits are higher than those for the copper deposits we suggest that the ore forming fluids of both gold and copper deposits were differentiated from the mantle derived alkaline magmas but were diluted by modified air saturated water masw that experienced intensive interaction with crustal rocks however the magmatic fluids responsible for the gold deposits were less extensively diluted by masw resulting in higher 3 he 4 he 40 ar 36 ar and 3 he 36 ar ratios than the copper deposits

the behaviour of the rare earth elements during mixing of river and sea waters rare earth element concentrations have been measured in organic rich luce river water and coastal sea water concentrations e g 350 1850 pmol kg nd in the water of luce and 45 350 pmol kg nd in luce bay are related to the presence of particles with 30 60 of the ree associated with 0 4 0 7 m particles and to riverine fe concentrations ree fractionation occurs in the river water the submicrometre river water is heavy ree enriched whereas the coarser fraction has a more shale like ree pattern laboratory experiments show that the ree in organic rich river waters are chiefly associated with feorganic matter colloids which flocculate during estuarine mixing preferential removal of heavy ree 95 relative to light ree 60 occurs but no ce anomaly is developed in contrast no ree removal occurs during estuarine mixing with organic poor river water

clay mineral weathering and contaminant dynamics in a caustic aqueous system ii mineral transformation and microscale partitioning microscopic and spectroscopic studies were conducted to assess mineral transformation processes in aqueous suspensions of illite il vermiculite vm and montmorillonite mt that were subjected to weathering in a simulated high level radioactive tank waste leachate 0 05 m alt 2 m na 1 m no3 p h 14 cs and sr 2 present as co contaminants time series 0 to 369 d experiments were conducted at 298 k with initial cs 0 and sr 0 concentrations from 10 5 to 10 mol kg incongruent clay dissolution resulted in an accumulation of secondary aluminosilicate precipitates identified as nitrate sodalite nitrate cancrinite and zeolite x by molecular spectroscopy and electron microscopy xrd ir nmr sem eds and tem eds contaminant fate was dependent on competing uptake to parent clays and weathering products tem eds results indicated that high il affinity for cs was due to adsorption at frayed edge sites the il system also comprised sr rich aluminous precipitates after 369 d reaction time in mt systems cs and sr were co precipitated into increasingly recalcitrant spheroidal precipitates over the course of the experiment whereas contaminant association with montmorillonite platelets was less prevalent in contrast cs and sr were found in association with weathered vm particles despite the formation of spheroidal aluminosilicate precipitates that were comparable to those formed from mt dissolution copyright 2005 elsevier ltd

cerium anomalies in lateritic profiles the ree geochemistry and mineralogy have been studied in four lateritic profiles one derived from a syenite akongo sw cameroon the others being developed on a gneissic basement and located along a soil toposequence goyoum e cameroon there is a fractionation between lree and hree in the lateritic samples during weathering the weathered residual products being enriched in lree from la to eu and depleted in hree from gd to lu sampled waters are enriched in hree in relation to the syenite host rock a positive ce anomaly has been found systematically at the top of the saprolite beneath a zone of iron oxide accumulation in the laterite up to 2000 ppm ce may be present in the akongo profile cerianite ceo2 is present as very fine coatings in non ferruginous clayey domains primary ree bearing accessory minerals are weathered at the bottom of the profile specifically allanite and apatite are transformed into florencite and rhabdophane but these phases have no ce anomaly all the data are interpreted as the result of the following processes 1 1 ree leaching in a reducing environment 2 2 oxidation of ce3 to ce4 in an oxidizing environment 3 3 deposition of cerium as cerianite whereas the other ree remain in solution

ree systematics in hydrothermal fluorite abstract ree patterns of fluorite from 63 post variscan hydrothermal veins of the schwarzwald area germany can be divided into two major groups type a fluorite shows roof shaped paas normalized patterns with enriched mree the turning point of the curvature is at ho or er position all patterns of type a show a distinct positive eu anomaly type b fluorite shows roof shaped patterns with enriched mree and strongly depleted hree and a characteristic steep slope between nd and sm the turning point of the curvature is at gd to dy all patterns of type b show negative or no eu anomalies laser ablation icp ms traverses through single grains combined with cathodoluminescence imagery revealed either i identical ree patterns and total ree concentrations from core to rim ii identical ree patterns but concentration gradients or iii variable ree patterns and concentration gradients from core to rim these features are explained by different degrees of supersaturation or different fluid fluorite ratios during crystallization and by complexly controlled precipitation processes under closed system conditions petrographically late fluorites from several deposits show the characteristics of new fluid batches rather than the expected remobilization features lree enrichment close to the crystal faces in some grains may result from the copreciptiation of a submicrometer sized lree enriched phase or from lree clustering in late cool fluids by comparison with literature data on natural waters from gneissic and granitic aquifers and of leachates of granites and gneisses we show that the hydrothermal vein fluorite preserves the characteristic source related ree feature of the hydrothermal fluid that migrated through either gneissic type a or granitic type b host rocks the immediate host rocks of the veins however are not the source rocks of the ree which indicates large scale fluid convection in the basement gneiss related type a fluorite shows tb ca tb la trends of primary hydrothermal crystallization whereas granite related type b fluorite indicates remobilization of possibly pegmatitic or variscan fluorite

monitoring of co2 rich waters with low ph and low ec an analogue study of co2 leakage into shallow aquifers the geochemistry of co2 rich springs and wells was monitored as a natural analogue study of co2 leakage into shallow aquifers in result within the relatively small study area diluted co2 rich waters dcws concentrated cw ccw and ordinary groundwaters were observed dcws showed an exceptionally low ph mean 4 8 and low ec mean 150 s cm the low ph and ec as well as the time invariant geochemistry of dcws were probably due to continuous co2 inputs into the open system which had a short reaction time and rarely consisted of reactive minerals dcws showed the low concentrations of sio2 mean 20 4 mg l and the average tritium concentration of 3 4 tu which indicates the low co2 h2o rock interaction in addition delta 13 text c text co 2 text g in equilibrium with water was estimated using the mass balance equation and 13cdic measured in water samples the results of the stable carbon isotope analysis showed that the co2 originated from a deep seated source to the shallow dcw aquifer 80 m deep below the surface whereas the deeper ccw aquifer was affected by soil organic co2 near the surface to detect the co2 leakage from co2 storage sites the geochemistry of shallow aquifers should be monitored this study result suggests that at least ph ec dic and carbon isotopes should be monitored because the monitoring of ph is helpful in an aquifer with low buffering capacity while ec can be low despite co2 leakage and the subsequently low ph at early stages depending on the subsurface environment above all this present study indicates that understanding the characteristics of aquifer conditions is of great importance for co2 leakage detection

fractionation of fe and cu isotopes in acid mine tailings modification and application of a sequential extraction method abstract sulfidic mine tailings have a high potential for contamination of the environment by triggering acid mine drainage hence it is crucial to understand metal mobilization processes and to develop monitoring tools metal isotope fingerprinting as a potential monitoring tool for metal sulfide oxidation processes was in the focus of this study by using stable isotope signatures of cu and fe for fe a six step sequential extraction method was applied in order to separate potential fe bearing minerals water soluble exchangeable fraction fe iii oxyhydr oxides fe oxides sulfides and organic compounds and residual silicates for cu this method was modified into a four step extraction method water soluble exchangeable fraction oxalate fraction bound to fe oxides and sulfides residual to verify accuracy and precision of the sequential extraction method for metal isotope analysis isotope fractionation during the extraction procedure was investigated employing minerals for which the mineral composition and the isotopic composition was known the developed procedure is suitable to separate target minerals with only a small loss in the elemental budget no significant isotope fractionation was observed during the extraction procedure application of this method on two sites of porphyry copper mine tailings in the atacama desert in chile chanaral bay revealed several implications about the mobilization of fe and cu in an environmental setting iron contents and fe isotope compositions are homogeneous with depth 0 61 cm 56fe 0 2 0 3 for the bulk and the fe hyr oxide fraction and only the deepest samples at 60 cm exhibited lower 56fe values 0 which are likely related to the occurrence of an alluvium at this depth the fe silicate fraction shows higher 56fe values 0 6 0 9 most likely because of preferential leaching of the light fe isotopes this consequently indicates a more pronounced fe isotope fractionation with depth as is expected from longer weathering the fe sulfide fraction is isotopically lighter compared to the fe hydr oxide fraction because during sulfide oxidation the heavy fe isotopes prefer the oxidized forms and oxidative precipitation results in an enriched fe isotopic signature for fe hydr oxides the cu isotope compositions of all bulk samples and individual fractions except the cu sulfides of one site ch1 exhibited a decrease of the 65cu values from the depth towards the surface which is potentially related to cu mobilization during capillary water rise in the arid climate a correlation of 65cu with ph indicates preferential adsorption of 65cu on fe oxy hydroxides at site ch1 which is evident by a change of 65cu from 0 5 to 0 7 in the water soluble fraction at another site ch12 where ph at depths was potentially not high enough for the formation of fe minerals that could adsorb cu only minor cu isotope fractionation was observed in the water soluble fraction the cu sulfide fraction at site ch1 exhibits higher 65cu values with an increase from the bottom 0 42 to the surface 0 92 which might be related to preferential leaching of the light isotopes e g by microorganisms

rare earth element systematics in hydrothermal fluids abstract rare earth element concentrations have been measured in hydrothermal solutions from geothermal fields in italy dominica valles caldera salton sea and the mid atlantic ridge the measured abundances show that hydrothermal activity is not expected to affect the ree balance of either continental or oceanic rocks the ree enrichment of the solutions increases when the ph decreases high temperature solutions 230 c percolating through different rock types may show similar ree patterns

rare earth elemental concentrations in some pacific northwest rivers abstract soluble rare earth element ree concentrations have been measured for five pacific northwest rivers columbia fraser klamath rogue and sacramento using radiochemical neutron activation analysis the relative abundances of the ree in river water resemble the ree abundance pattern in average sedimentary type rocks the la material balance in the oceans is discussed

rare earth elements neodymium and strontium isotopic systematics in mineral waters evidence from the massif central france abstract rare earth elements rees and sr and nd isotope distributions have been studied in mineralized waters from the massif central france the co 2 rich springs are characterized by a neutral ph 6 7 associated with total dissolved solids tds from 1 to 7 g l 1 the waters result from the mixing of very mineralized water pools thought to have equilibrated at a temperature of around 200 c with superficial waters these two mineral water pools evidenced by sr isotopes and dissolved rees could reflect 2 different stages of water rock interaction and an equilibrium with different mineral assemblages the concentrations of individual dissolved rees and total dissolved rees ree in the mineral waters examined vary over several orders of magnitude but are not dependent on the main parameters of the waters tds t c ph total organic c the dissolved ree concentrations presented as upper continental crust normalized patterns show hree enrichment in most of the samples the time evolution of ree patterns does not show significant fluctuations except in 1 borehole located in the limagne d allier area which was sampled on 16 occasions over an 18 month period ten samples are hree enriched whereas 6 samples show flat patterns the aqueous speciation of rees shows that co 2 3 complexes dominate 80 over the free metal f so 2 4 and hco 3 complexes the detailed speciation demonstrates that the fractionation of rees i e the hree enrichment in co 2 rich and ph neutral fluids is due essentially to the predominance of the co 2 3 complexes the sr isotopic composition of the mineral waters in the massif central shows different mixing processes in the cezallier area at least 3 end member water types exist the most dilute end member is likely to originate as poorly mineralized waters with minimal groundwater circulation two other mineralized end members are identified although the link between the geographical location of spring outflow and the mixing proportion between the 2 end members is not systematic the range in nd 0 for mineralized waters in the massif central correlates well with that of the known parent rocks except for 4 springs one way to explain the nd 0 in these instances is a contribution from drainage of volcanic rocks the isotopic systematics help to constrain the hydrogeological models for this area

the alkaline porphyry associated yao an gold deposit yunnan china rare earth element and stable isotope evidence for magmatic hydrothermal ore formation the yao an vein type gold deposit is located in the ailaoshan jinshajiang alkaline intrusive belt yunnan province china and is associated both in time and space with 33 5 1 0 ma old alkaline intrusions the gold mineralization is associated with potassic wall rock alteration the ree distribution patterns of secondary k feldspar are generally similar to those of the igneous perthite but with about seven times higher total ree abundances the alteration is ascribed to a high ree magmatic fluid derived from the yao an alkaline intrusive suite the hydrothermal yao an gold deposit formed during two gold bearing stages i e a sulfide pyrite stage and a sulfide oxide stage pyrite specularite the ree abundance of early stage i pyrite is relatively high with strong enrichment in lree la yb n of 40 290 generally positive eu anomalies eu eu 0 86 1 55 and ree patterns very similar to those of secondary feldspar in contrast the later stage ii pyrite has much lower ree concentrations and lower la yb n of 5 5 11 8 eu eu of 0 49 0 76 and flat chondrite normalized spidergram patterns the stage i pyrite has 34s in the range of 2 2 to 3 2 and overlaps with regionally distributed pyrite in least altered syenite porphyry in contrast stage ii pyrite has much higher 34s values between 7 8 and 16 5 carbon isotope data for four samples from stage ii revealed 13c pdb values between 6 and 8 these stable isotope and ree data suggest that magmatic fluids of the alkaline intrusions caused both potassic alteration and stage i sulfide mineralization the system evolved from stage i to stage ii mineralization by influx of meteoric fluids with relatively heavier sulfur although calcite carbon isotope data suggest that the co2 remained dominantly of magmatic origin

genesis of the oxidized sn ores in the gejiu district yunnan province sw china abstract the gejiu sn ore district one of the largest sn producing area 300mt 1 wt sn in the world is located in the western margin of the cathaysia block sw china there are five types of sn ores in the gejiu district including greisen skarn veined tourmaline massive sulfide and oxidized among these types of sn ores the genesis of the oxidized sn ores is most controversial such as magmatic hydrothermal origin and sedimentary exhalative sedex or hot water deposition red sea type this paper reports u pb ages fluid inclusions trace elements and h o isotopes of cassiterite from the oxidized sn ores aiming to solve this issue la mc icpms cassiterite u pb dating yielded an age of 86 7 2 8 ma which is accordant with the formation ages 86 ma of granitic intrusions in the gejiu district two types of fluid inclusions in cassiterite from the oxidized sn ores were observed one type is co2 rich inclusions type 1 and the other type is aqueous inclusions type 2 the homogenization temperatures range from 220 to 366 c and the salinities range from 10 9 to 21 wt nacl equiv for the two types of fluid inclusions furthermore fluid inclusions in cassiterite from the oxidized sn ores located at 300 m far away from granitic intrusions have higher temperatures 357 366 c than those located at 500 m 273 330 c hence the ore forming temperatures tend to decrease with the distance far away from the magmatic hydrothermal center the vapor components for the two types of fluid inclusions are co2 and h2o respectively and the liquid phase compositions of them are all h2o the co2 in the ore forming fluids may source from marble by decarbonization this indicates that the precipitation of cassiterite is resulted from fluid immiscible the 18o values of fluid inclusions in cassiterite range from 6 1 to 7 7 and the d values range from 135 to 153 indicating a mixture of magmatic and meteoric waters trace elements show that cassiterite is rich in in rb and u but ba nb and ti are depleted in addition the lower sr 0 4 2 1 ppm and higher sc 35 9 53 7 ppm contents reflect that the formation of cassiterite is related to f rich intermediate acid magma cassiterite has a relatively low total ree contents 2 7 9 2 ppm with negative eu eu 0 14 0 76 and ce ce 0 1 0 6 anomalies indicating that the ore forming environment is oxidized this is consistent with the cassiterite precipitation conditions hence all the evidence supports that the oxidized sn ores are genetically associated with the gejiu granitic magmatism

the behaviour of trace and rare earth elements ree during hydrothermal alteration in the rangan area central iran the rhyolitic dome in the rangan area has been subjected to hydrothermal alterations by two different systems 1 a fossil magmatic hydrothermal system with a powerful thermal engine of a deep monzodioritic magma 2 an active hydrothermal system dominated by meteoric water based on mineralogical and geochemical studies three different alteration facies have been identified phyllic advanced argillic and silicic with notable differences in ree and other trace elements behaviour in the phyllic alteration zone with assemblage minerals such as sericite pyrite quartz kaolinite lree are relatively depleted whereas hree are enriched the advanced argillic zone is identified by the presence of alunite jarosite and pyrophyllite as well as immobility of lree and depletion in hree in the silicic zone most of lree are depleted but hree patterns are unchanged compared to their fresh rock equivalents all the ree fractionation ratios la yb cn la sm cn tb yb cn ce ce cn and eu eu cn are low in the phyllic altered facies eu eu cn in both advanced and silicic facies is low too in all alteration zones high field strength elements hfse e g ti zr nb are depleted whereas transition elements e g v cr co ni fe are enriched geochemically speaking trace and rare earth elements behave highly selective in different facies

ree chemistry and sm nd systematics of late archean weathering profiles in the fortescue group western australia two weathering profiles each consisting of an upper sericite rich zone and a lower chlorite rich zone are preserved between flows of the mt roe basalt in the fortescue group hamersley basin western australia ree concentrations in samples from these two profiles which originally developed ca 2 760 ma show large variations depending on stratigraphic position lree abundances and la yb n are greatest at depths of 3 6 m below the paleosurface of the mt roe 1 profile and are somewhat lower in samples above this level the lrees reach concentrations 6 9 times greater than in the underlying basalt and thus appear to have been mobilized downward in the paleosol and concentrated in its middle part lree concentrations in the 2 profile show a similar distribution but with a sharp increase in all ree concentrations within 50 cm of the paleosurface the distinction between the ree profiles in the two paleosols may be related to the difference in the overlying material the 1 paleosol is overlain by a few meters of sediments and then by basalt whereas the 2 paleosol is directly overlain by basalt the lrees appear to have been mobilized both during chemical weathering of the parental basalt and during later lower greenschist facies metamorphism and metasomatism of the paleosols remobilization of the rees during the regional metamorphism of the fortescue group is confirmed by a whole rock sm nd reference isochron of mt roe 1 samples with an age of 2 151 360 ma variable initial 143nd 144nd values of unweathered basalt samples which may represent the paleosol protolith prevents a confident determination of the magnitude of lree mobility both the initial mobilization of the rees during weathering and the metasomatic remobilization appear to have taken place under redox conditions where ce was present dominantly as ce3 because ce anomalies are not developed within the sericite zone samples regardless of concentration europium anomalies in the paleoweathering profile are somewhat variable and were probably modified by mobilization of eu2 at metamorphic conditions in all samples the hrees appear to have been relatively immobile and correlate with al ti cr v zr and nb sm nd systematics and ree patterns of four unweathered basalt samples indicate derivation of the mt roe basalts from a heterogeneous and enriched source having epsilon nd between 4 0 and 7 4 initial 143nd 144nd values of these basalts are even lower than those reported by nelson et al 1992 for fortescue group basalts and indicate a substantial crustal component in the generation of mt roe basalts

changes in lead and zinc lability during weathering induced acidification of desert mine tailings coupling chemical and micro scale analyses desert mine tailings may accumulate toxic metals in the near surface centimeters because of low water through flux rates along with other constraints metal toxicity precludes natural plant colonization even over decadal time scales since unconsolidated particles can be subjected to transport by wind and water erosion potentially resulting in direct human and ecosystem exposure there is a need to know how the lability and form of metals change in the tailings weathering environment a combination of chemical extractions x ray diffraction micro x ray fluorescence spectroscopy and micro raman spectroscopy were employed to study pb and zn contamination in surficial arid mine tailings from the arizona klondyke state superfund site initial site characterization indicated a wide range in ph 2 5 to 8 0 in the surficial tailings pile ligand promoted dtpa extractions used to assess plant available metal pools showed decreasing available zn and mn with progressive tailings acidification aluminum shows the inverse trend and pb and fe show more complex ph dependence since the tailings derive from a common source and parent mineralogy it is presumed that variations in ph and bioavailable metal concentrations result from associated variation in particle scale geochemistry four sub samples ranging in ph from 2 6 to 5 4 were subjected to further characterization to elucidate micro scale controls on metal mobility with acidification total pb ranging from 5 13 g kg 1 was increasingly associated with fe and s in plumbojarosite aggregates for zn both total 0 4 6 g kg 1 and labile fractions decreased with decreasing ph zinc was found to be primarily associated with the secondary mn phases manjiroite and chalcophanite the results suggest that progressive tailings acidification diminishes the overall lability of the total pb and zn pools

rare earth distributions with a positive ce anomaly in the western north atlantic ocean from the vertical distributions of the rare earth elements ree in the sargasso sea we now report the first profiles of pr tb ho tm and lu in seawater together with profiles for la ce sm eu and yb the first observations of positive ce anomalies in seawater are ascribed to reducing inshore sediments as a source for ce ref 1 all vertical profiles are consistent with adsorption of trivalent rare earths by settling particles possibly siliceous or calcareous followed by their release at or near the sea floor on dissolution of the carriers the very different ce profile demonstrates the additional effects of oxidation reduction reactions

iron and aluminum hydroxysulfates from acid sulfate waters acid sulfate waters are produced mostly by the oxidation of common sulfide minerals such as pyrite chalcopyrite pyrrhotite and marcasite in rocks soils sediments and industrial wastes this spontaneous process of mineral weathering plays a fundamental role in the supergene alteration of ore deposits the formation of acid sulfate soils and the mobilization and release of acidity and metals to surface and ground waters the purely natural process of acid rock drainage is often intensified by human activities related to mining mineral processing construction soil drainage and dredging geochemical reaction rates are accelerated because physical disturbance gives greater exposure of mineral surfaces to air and water and to microbes that catalyze the reaction process large quantities of reactive sulfides are also concentrated and exposed to air as a result of mining and mineral processing acid sulfate waters produce a number of fairly insoluble hydroxysulfate and oxyhydroxide minerals that precipitate during oxidation hydrolysis and neutralization the objective of this chapter is to describe the formation properties fate and environmental implications of the nano to microphase hydroxy sulfates of fe and al that are precipitated from acid sulfate waters these minerals are commonly of poor crystallinity and difficult to characterize much remains to be learned about their occurrence formation and properties mine drainage the best known examples of acid sulfate waters are those released from mines where coal and metallic sulfide ores have been exploited ash et al 1951 barton 1978 nordstrom 1982a rose and cravotta 1998 nordstrom and alpers 1999 there may be as many as 500 000 inactive or abandoned mine sites in the united states alone lyon et al 1993 although most of these pose no immediate water quality problem kleinmann 1989 estimated that about 19 300 km of streams and more than 72 000 ha of lakes and reservoirs have been

secondary mineralogy and microtextures of weathered sulfides and manganoan carbonates in mine waste rock dumps with implications for heavy metal fixation the secondary mineralogy and microtextures of weathered waste rock dumps derived from the mining of galena sphalerite ore in quartz veins containing manganoan carbonates were examined using back scattered electron imaging x ray diffraction and chemical analysis sphalerite pyrrhotite and arsenopyrite were coated or replaced by iron oxyhydroxides in the earliest stage of the weathering and were then replaced by sulfur galena shows a thin alteration rim of anglesite oxidation of pyrite has resulted in porous boxworks of fe oxyhydroxides the relative resistance to oxidation from most resistant to least resistant was observed to be pyrite galena arsenopyrite sphalerite pyrrhotite rhodochrosite dissolved to form hydrohetaerolite pseudomorphs and manganoan calcite has an outer alteration rim of hydrohetaerolite and an inner zone of smithsonite rock and mineral fragments were cemented by fine aggregates of plumbojarosite fe oxyhydroxides sulfates and manganates microchemical analysis and sequential extractions showed a close association of as with fe oxyhydroxides sulfates of pb cu zn and as with plumbojarosite and of pb and zn with manganates despite their lower acid neutralizing capacity manganoan carbonates played an important role in the fixation of pb and zn by the formation of manganates

solid phase control on the mobility of potentially toxic elements in an abandoned lead zinc mine tailings impoundment taxco mexico detailed mineralogical and geochemical investigations were conducted within abandoned pb and zn flotation tailings at el fraile impoundments in taxco guerrero central southern mexico these tailings are divided into an active oxidation zone near the surface an underlying transition zone and an unoxidized zone although these tailings have undergone 30 a of sulfide oxidation the active oxidation zone has only penetrated to a depth of 0 2 m in the settling pond and to 0 6 1 2 m in the dam the oxidation of sulfide minerals and the insufficiency of ph buffering minerals have produced low ph conditions ph 1 9 4 4 and high concentrations of dissolved so42 as and heavy metals so42 1534 10086 mg l 1 fe 1 5 2568 mg l 1 zn 36 7 2435 mg l 1 cd 0 4 30 6 mg l 1 pb 0 01 0 6 mg l 1 cu 0 5 38 2 mg l 1 and as 0 01 164 mg l 1 these concentrations of dissolved constituents are attenuated by a series of precipitation and sorption reactions precipitation of secondary phases gypsum goethite hematite and k jarosite has led to the formation of cemented layers within the active oxidation zone in the tailings dam these cemented layers act as a trap for released potentially toxic elements from the overlying oxidized tailings adsorption and coprecipitation on fe precipitates play an important role in the mobilization and attenuation of zn cd cu and as within the el fraile tailings additionally to the well known ability of fe precipitates to strongly trap as and heavy metals this study shows that precipitation of beudantite pbfe3aso4so4 oh 6 appears to be one of the solid phase controls on the natural attenuation of as and pb and other heavy metals in these tailings

rare earth elements in thermal water from the sob 1 well murska sobota ne slovenia thermal water produced from the sob 1 well is a water mixture contributed from several stratified aquifers that belong to two hydrogeological subsystems termed middle and upper subsystem the subsystems thermal waters differ appreciably in the ree and y signatures ree y averages to about 10 and 0 2 ppb for the middle and upper subsystem respectively as the sob 1 well experiences pressure cycling the inflow from the subsystems aquifers is not constant but cycles as well causing the cycling of chemical composition of abstracted thermal water mixture including rees and y paas normalized cycling ree and y distribution for thermal water mixture from the sob 1 well indicates that the abundance of rees and y is mainly controlled by solubility of their carbonate and bicarbonate species and therefore by availability of free and dissolved carbon dioxide in the aquifer

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

redistribution of fissiogenic and non fissiogenic ree th and u in and around natural fission reactors at oklo and bangombe gabon abstract elemental abundances and isotopic compositions of rare earth elements ree th and u of twenty eight samples from four kinds of natural fission reactors at the oklo and bangombe uranium ores were determined by mass spectrometry fissiogenic and non fissiogenic ree components of each sample were calculated from the isotopic compositions the geochemical distribution of both fissiogenic and non fissiogenic ree differs among the four reactors each reactor shows the following features possibly associated with the local geochemical conditions 1 reactor 9 at the shallow depth of the oklo deposit contains higher amounts of non fissiogenic ree than the other reactors the distribution of non fissiogenic ree does not reflect the primordial ree abundance patterns and might have been disturbed in and around the reactor due to supergene alteration our results suggest that significant amounts of fissiogenic lighter ree lree such as la ce and pr were mobile in the reactor 2 reactors 10 and 13 located deep underground have much lower contents of non fissiogenic ree than reactor 9 all fissiogenic ree show high retention in the reactors non fissiogenic ree of reactor 10 inform of the primordial ore formation without any geochemical disturbance little redistribution of both fissiogenic and non fissiogenic ree in the reactor 10 was observed and 3 the bangombe reactor located at shallow depth has apparently well preserved fissiogenic ree non fissiogenic ree in the bangombe reactor might have been disturbed possibly by hydrothermal processes the distribution behavior of fissiogenic ree is considered to be related with physico chemical reactor conditions such as nuclear reaction temperature and chemical compositions of each reactor but clear relationship between nuclear parameters and the ree distribution could not be obtained in this study

europium redox equilibria in aqueous solution thermochemical data and recent advances in theoretical aqueous solution chemistry enable prediction of the relative stabilities of aqueous eu2 and eu3 over a wide range of temperatures and pressures at low temperatures near earth surface conditions the aqueous geochemistry of europium should be dominated by the trivalent state except possibly in the most reducing alkaline pore waters of anoxic marine sediments however at temperatures greater than about 250 c and elevated pressures divalent europium should predominate even with significant amounts of complexing trivalent europium is not stable at elevated temperatures and pressures consequently under most hydrothermal and metamorphic conditions europium in aqueous solution should be divalent at intermediate temperatures around 100 c significant activities of both eu2 and eu3 and related complexes can occur in aqueous solutions depending on the oxidation state and the ph of the solutions and the activities of potential ligands such as sulfate carbonate and chloride the predicted stability of divalent europium in aqueous solution at elevated temperatures is consistent with the large positive europium anomalies in rare earth element patterns of high temperature barites of hydrothermal and metamorphic origin reported by guichard et al 5 and with the observed depletion of europium as a result of high temperature sericitization of feldspar bearing assemblages discovered by alderton et al 1 it is suggested that significant fractionation of europium relative to the other rare earth elements may take place during high temperature hydrothermal alteration processes such as in the mid oceanic ridge systems because of the expected stability of divalent europium during these processes

a review on the potentiality of rare earth elements to trace pedogenetic processes abstract this review aims at considering the use of rees to trace pedogenetic processes in order to quantify the respective contribution of the successive processes on pedogenesis we first consider the origins and contents of rees in soils to assess their natural occurrence and tackle the common data treatment used to interpret their concentrations we review subsequently the impact of the different pedogenetic processes on the fate of rees in soils from their release into a soil solution by primary mineral heavy minerals phosphates silicates and carbonates dissolution during weathering to their fixation on or into main ree bearing secondary minerals clay minerals fe mn oxides and carbonates then their mobilization by plant recycling and organic matter and finally the impact of argilluviation and redox processes on their fractionation we conclude that rees much more than other trace elements can interestingly trace the considered processes that are encountered in a large diversity of non polluted soils arising from diverse parent materials weathering generally fractionates rees and accounts for a significant part of the variation in the initial ree stock of the soils plant recycling induces a weak mobilization of rees and their accumulation in topsoil argilluviation can be traced using the mree enrichment and the eu anomaly of the clay minerals redox processes can be traced by the ce anomaly caused by the precipitation of cerium on mn oxides to use rees as tracers of pedogenetic processes we recommend to i precisely characterize the ree bearing minerals ii adapt the choice of reference s for normalization and iii perform mass balance calculations

the ree content of some hydrothermal fluids ree concentrations were determined in solutions from submarine hydrothermal vents on the east pacific rise and for the first time from continental geothermal fields in tibet and bulgaria they indicate that in hydrothermal systems ree are immobile at temperatures below 350 c and for water rock ratios of 105 nd values of submarine solutions and anhydrites 4 7 to 6 2 suggests recharge on the sedimentcovered flanks of the ridge carbonate anions as measured by alkalinity appear to increase the solubility of heavy ree somewhat but not to the extent that substantial amounts of ree could be driven out from rocks by hydrothermal activity

geochemical behavior of rare earth elements during the evolution of co2 rich groundwater a study from the kangwon district south korea abstract a hydrochemical study of co 2 rich groundwaters in the kangwon district south korea was conducted to elucidate the behavior of rare earth elements ree as a result of mixing of co 2 rich waters the ree fractionation during the formation of carbonate precipitates was also investigated the co 2 rich waters can be classified into three chemical types na hco 3 ca na hco 3 and ca hco 3 with characteristic isotope compositions chemical and isotope data indicate that the na hco 3 waters were influenced by a deep co 2 supply at depth while other waters were formed by mixing between na hco 3 water and less saline shallow groundwater concentrations of total dissolved ree ree in co 2 rich waters varied according to the water types and were highest in the na hco 3 waters up to 3456 ng l their ree concentrations showed excellent correlations with parameters such as tds ph alkalinity 18 o and tritium indicating progressive mixing with shallow groundwater the distribution of dissolved ree concentration showed different patterns dependent upon water type the na hco 3 waters displayed an s shape pattern with strong heavy ree hree enrichment in contrast the ca na hco 3 water was characterized by a slight hree enrichment while the ca hco 3 water exhibited a relatively flat scattered low ree lree enrichment pattern the ree patterns of the precipitates formed from the original waters and of the residual waters after removal of the precipitates were similar to those of the original co 2 rich waters indicating that no ree fractionation occurred between precipitates and residual waters

rare earth elements and hydrothermal ore formation processes abstract the geochemical behaviour of ree is influenced by nearly all important hydrothermal ore formation processes including fluid rock interactions fluid precipitations adsorption and scavenging onto particles and changes in fluid temperature pressure ph eh alkalinity and ligand concentration destabilization of ree complexes in response to these physicochemical changes and possible chemical crystallographic controls determine the concentration and distribution of ree within hydrothermal minerals mineraloids and amorphous phases alteration assemblages of intrusive related mineralisations may exhibit a wide range of ree distributions and ree fractionation trends the ree distribution within these hydrothermally altered lithologies will depend on the ree concentration in the rock and the fluid the partitioning behaviour of the ree between the rock phases and the fluid and the types of alteration reactions which take place reactive rocks such as carbonate rich lithologies of skarn deposits may gain or loose significant amounts of ree during fluid rock interactions ree geochemical investigations combined with fluid inclusion and stable isotope studies may point to the origin of alteration products and the source s of ore fluids ancient massive sulphide ores commonly exhibit anomalous eu concentrations similar to many recent submarine hydrothermal precipitates the recognition of hydrothermal fluid seawater sedimentary or volcanically derived ree distributions within ores chemical sediments and hydrothermally altered lithologies may help to constrain genetic modelling of massive sulphide deposits care should be taken with the interpretation of ree distributions from metamorphosed hydrothermal ore deposits becase metamorphic and diagenetic alteration reactions may change the ree distributions mobility of ree may occur during diagenesis of carbonate rich rocks and during the development of shear zones and migmatites in contrast very large fluid rock ratios are necessary to cause significant changes in ree patterns of silicate rich rocks during diagenesis and regional metamorphism

rare earth element geochemistry and the tetrad effect abstract the tetrad effect is found in the rare earth elements la lu and results from increased stability at quarter half three quarter and complete filling of the 4f electron shell suggestions that this effect is observed in ree patterns of seawater and other geological samples marine phases the mineral kimuraite late stage granitic rocks the mineral uraninite and siliciclastic sediments are not compelling in the cases of seawater and the carbonate mineral kimuraite a discontinuity at gd may be attributed to the tetrad effect but the complexity of the overall controls on these ree distributions leaves such an interpretation uncertain at best unusual ree patterns in leucogranites and pegmatites are best explained by fractionation of trace minerals notably apatite apparent tetrad anomalies in uraninite rees disappear when normalised to upper crustal i e shale abundances analytical difficulties probably explain apparent tetrad effects in some seawater limestone and siliciclastic ree patterns

rare earth element trends and cerium uranium manganese associations in weathered rock from koongarra northern territory australia at koongarra australia three drill cores form the cahill schist formation containing u ore and regolith above it containing secondary u ore were studied to ascertain the distribution of rare earth elements rees and u the unaltered schist has a ree trend similar to the post archaean australian shale paas which is therefore used as a normalising standard unweathered rock from the zone of primary u mineralisation contained strong enrichment of the heavy rees and this pattern is retained during most of the weathering strongly bleached and very weathered shallow samples from this zone do not show enrichment of hrees in general however weathering appears to have little effect on the pattern of rees in the bulk rock at this site zones rich in mn oxy hydroxides occurring as coatings on fissure surfaces contain large concentrations of ce and u with a clear ce anomaly ce ce 3 8 the ce and u apparently occur together as microcrystalline oxides within 1 2 mu m diameter globules on mineral surfaces in the mn rich zones 46 refs 10 figs 2 tabs