rare earth elements in the sediments of the north atlantic ocean amazon delta and east china sea reinterpretation of terrigenous input patterns to the oceans

smnd isotopic and geochemical characterisation of the paleoproterozoic torngat orogen labrador canada abstract the torngat orogen is a paleoproterozoic granulite facies belt that welds the archean components of the nain and rae provinces in eastern labrador sm nd isotopic and supporting bulk rock major trace and rare earth element data help elucidate the sources of the main paleoproterozoic lithologies that comprise the orogen in the foreland paleoproterozoic ramah group metasediments intercalated with reworked nain province gneiss show variable trace element and nd 1 9 ga from 2 9 to 12 0 ranging between nain province crust and paleoproterozoic mugford group basalts compositions the ramah group data suggest derivation of ramah detritus from archean nain province gneisses and from the mugford group in the lac lomier complex rae province hinterland metasediments with variable trace element distribution patterns akin to rae province crust and nd 1 9 ga from 2 9 to 10 5 suggest derivation from rae province crust and from an unspecified juvenile component in the core of the orogen pelitic and psammitic protoliths of the tasiuyak gneiss nd 1 9 ga from 1 9 to 2 6 were derived from crustal sources unknown in both nain and rae provinces and may have been deposited in a trench environment starved of adjacent cratonic debris dioritic to granitic eastern and western metaplutonic suites intruding the tasiuyak gneiss and the lac lomier complex display contrasting geochemical and sm nd isotopic compositions the eastern metaplutonic suite has a tendency toward lower sio2 total alkalis less fractionated ree and higher mgo cao and tio2 relative to the western metaplutonic suite the eastern suite yields nd 1 9 ga from 3 8 to 6 7 and negative f sm nd suggesting igneous precursors from rae crust and a a lree enriched juvenile component the western suite yields nd 1 9 ga from 1 5 to 8 5 suggesting an important contribution from rae crustal sources in the petrogenesis of the igneous protoliths the presence of rae province nd isotopic compositions and the absence of nain province signatures in these intrusions favors the eastern rae province as the active margin during nain rae convergence

rare earth element geochemistry of colour lake an acidic freshwater lake on axel heiberg island northwest territories canada a lake column profile was collected in 24 m of water from colour lake axel heiberg island northwest territories canada in early june of 1991 beneath 1 8 m of lake ice the rare earth element ree concentrations of the acidic fresh waters of colour lake were analyzed along with the major solute chemistry in order to investigate ree distribution and speciation in the low ph waters previous studies indicate the lake is dominated by ca2 mg2 and so42 and has no measurable carbonate alkalinity shale normalized ree patterns for the lake waters are all enriched in the middle ree s mree s as compared to the light ree s lree s and heavy ree s hree s dissolved ree concentrations in colour lake e g 2 3 22 nmol kg 1 for nd mean value of 20 nmol kg 1 are typically less than values obtained for the acid saline waters of the lake tyrrell playa system in australia as well as the slightly acidic groundwaters of the carnmenellis region of england but greater than ree concentrations measured in the alkaline saline waters of mono lake california u s a the speciation of the ree s in colour lake was modelled based on the major solute chemistry using a combined specific ion interaction and ion pairing model these calculations suggest that in the relatively high sulfate low ph waters of colour lake the ree s exist as either free metal so42 or f complexes our calculations indicate that so42 complexes dominate over the free metal and fluoride species for the majority of the ree s in the lake water and that in general for acidic high sulfate waters sulfate complexes with the ree s may increase the dissolved concentrations of the ree s over natural waters where relatively low sulfate concentrations prevail

acid drainage at the inactive santa lucia mine western cuba natural attenuation of arsenic barium and lead and geochemical behavior of rare earth elements abstract a detailed geochemical study was conducted at the inactive zn pb mine of santa lucia in western cuba the studied mine wastes are characterized by high total concentrations of potentially toxic elements pte with average values of 17 4 fe 5 47 ba 2 27 pb 0 83 zn 1724 mg kg as and 811 mg kg cu oxidation of sulfide minerals in mine waste dumps and in the open pit produces acid mine effluents ph 2 5 2 6 enriched in dissolved so 4 2 up to 6754 mg l fe up to 4620 mg l and zn up to 2090 mg l low ph values 2 5 2 8 and high dissolved concentrations of the same pte were found in surface waters up to 1500 m downstream from the mine nevertheless concentrations of as ba and pb in acid mine effluents and impacted surface waters are relatively low 0 01 0 3 mg l as 0 002 0 03 mg l ba and 0 3 4 3 mg l pb analysis by x ray diffraction and electron microscopy revealed the occurrence of lead bearing barite and beudantite and the more common solid phases reported elsewhere in similar environments including fe oxyhydroxides jarosite anglesite and plumbojarosite because the reported solubilities for barite and beudantite are very low under acidic conditions these minerals may serve as the most important control in the mobility of as ba and pb in contrast fe oxyhydroxides are relatively soluble under acidic conditions and therefore they may have a less significant role in pte on site immobilization mine wastes and stream sediments show a light ree lree and middle ree mree enrichment relative to heavy ree hree in contrast acid mine effluents and surface waters are enriched in hree relative to lree these results suggest that the lree released during the oxidation of sulfides are captured by secondary weathering minerals while the mree are removed from the altered rocks the low concentrations of lree in acid stream water suggest that these elements can be retained in the sediments more strongly than hree and mree one possible explanation for the sharp decrease in dissolved lree might be their retention by low solubility secondary minerals such as anglesite barite and jarosite

heterogeneous rare earth element ree patterns and concentrations in a fossil bone implications for the use of ree in vertebrate taphonomy and fossilization history abstract a bone fragment cgdq 3 of falcarius utahensis a therizinosaur from the early cretaceous cedar mountain formation utah contained within a carbonate nodule was analyzed by laser ablation inductively coupled plasma mass spectrometry la icp ms in order to investigate ree variability within a thin walled phalanx previous studies have found depth related ree pattern variations however in cgdq 3 variation occurs along the circumference of the bone nasc normalized ree patterns and concentrations vary between two apparent end members a light ree enriched lree pattern similar to solution icp ms analysis of this bone characterizes approximately two thirds of the bone fragment total ree concentrations are high and do not vary significantly from the periosteal surface to the medullar surface conversely the remaining one third of the bone has ree patterns that are mree depleted and low in total ree concentrations ree concentrations in this part of the bone do not vary significantly from the periosteal to the medullar surface a positive ce anomaly is found throughout the entire bone and is greatest within the lree enriched portion of the bone this in combination with the lree enrichment suggests that the bone fossilized under reducing conditions the distance between the lree enriched and mree depleted regions is less than 1 mm isotopic and petrographic analyses of the bone and surrounding carbonate matrix suggest the ree patterns in the bone were the result of partial fossilization incomplete filling of micro pore spaces around bone crystallites in an environment with changing redox conditions the lower mree depleted part of the bone fossilized contemporaneously with a pendant cement that formed on the underside of the bone in the vadose zone formation of the pendant cement restricted water flow through the bone isolating the lower portion which incorporated a mree depleted pattern the upper part of the bone lree enriched side fossilized under more reducing conditions than the lower part this resulted in reductive dissolution of minerals such as hydrous ferric oxides and manganese oxides which were lree enriched with positive ce anomalies these ree were then incorporated into the upper part of the bone this likely occurred after the bone entered the saturated zone below the water table the thinness of the bone and presence of a pendant cement helped facilitate partial fossilization of the bone preserving the ree signature of an earlier fluid as demonstrated by this case study differences in ree patterns within a fossil may record changes in geochemical conditions during fossilization particularly when bones are encased in a material that reduces fluid permeability such as micritic vadose calcite analysis of such bones may offer the opportunity to decipher complex fluid histories that occur during fossilization la icp ms should be utilized to confirm solution icp ms analysis if it yields high ree variability prior to an interpretation of reworking or time averaging

rare earth element complexation behavior in circumneutral ph groundwaters assessing the role of carbonate and phosphate ions rare earth element ree concentrations were determined in circumneutral ph 7 ph 9 groundwaters from south central nevada and the mojave desert in eastern california u s a the inorganic speciation of the rees in these water were evaluated primarily to assess the relative importance of carbonate lnhco32 lnco3 and ln co3 2 and phosphate lnh2po42 lnhpo4 ln hpo4 2 and lnpo40 complexes other ree complexes with sulfate hydroxyl chloride and fluoride ions were also assessed as was the significance of the free metal ion species i e ln3 our speciation calculations indicate that ree carbonate complexes dominate and typically account for more than 99 of each ree in solution moreover carbonato complexes lnco3 were predicted to be the dominant species for the light rees and dicarbonato complexes ln co3 2 were predicted to increase in importance with increasing atomic number all other complexes were predicted to be negligible furthermore the combined percentage of all ree phosphate complexes never accounted for more than 0 1 of the dissolved rees and generally much less than 0 1 phosphate complexes can not compete with carbonate complexes in these groundwaters because of the low po43 concentrations 0 3 1 58 mol kg the much lower concentrations of the free phosphate ion i e po43 f 10 9 10 6 mol kg due to ion pair formation with ca2 and mg2 and the much higher free carbonate ion concentrations co32 f 0 32 87 mol kg

diel behavior of rare earth elements in a mountain stream with acidic to neutral ph abstract diel 24 h changes in concentrations of rare earth elements ree were investigated in fisher creek a mountain stream in montana that receives acid mine drainage in its headwaters three simultaneous 24 h samplings were conducted at an upstream station ph 3 3 an intermediate station ph 5 5 and a downstream station ph 6 8 the ree were found to behave conservatively at the two upstream stations at the downstream station ree partitioned into suspended particles to a degree that varied with the time of day and concentrations of dissolved ree were 2 9 to 9 4 fold 190 to 830 higher in the early morning vs the late afternoon the decrease in dissolved ree concentrations during the day coincided with a corresponding increase in the concentration of ree in suspended particles such that diel changes in the total ree concentrations were relatively minor 27 to 55 increase at night across the lanthanide series the heavy ree partitioned into the suspended solid phase to a greater extent than the light ree filtered samples from the downstream station showed a decrease in shale normalized ree concentration across the lanthanide series with positive anomalies at la and gd and a negative eu anomaly as the temperature of the creek increased in the afternoon the slope of the ree profile steepened and the magnitude of the anomalies increased the above observations are explained by cyclic adsorption of ree onto suspended particles of hydrous ferric and aluminum oxides hfo hao conditional partition coefficients for each ree between the suspended solids and the aqueous phase reached a maximum at 1700 hours and a minimum at 0700 hours this pattern is attributed to diel variations in stream temperature possibly reinforced by kinetic factors i e slower rates of reaction at night than during the day estimates of the enthalpy of adsorption of each ree onto suspended particles based on the field results averaged 82 kj mol and are similar in magnitude to estimates in the literature for adsorption of divalent metal cations onto clays and hydrous metal oxides the results of this study have important implications to the use of ree as hydrogeochemical tracers in streams

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

an overview of the upb geochronology of the paleoproterozoic torngat orogen northeastern canada abstract the paleoproterozoic torngat orogen northern labrador and northeastern quebec canada is the result of oblique collision between the nain north atlantic and rae cratons a comprehensive set of u pb ages allows the chronology of events to be closely bracketed subduction occurred below the nain craton from ca 1910 1870 ma and collision between the cratons may have occurred between 1869 and 1844 ma sinistral deformation continued along the intervening abloviak shear zone until ca 1824 ma and convergence was ultimately impeded by the partial subduction of the southern rae craton post collisional isostatic uplift of the southern rae craton initiated deformation in the komaktorvik zone ca 1798 ma a prominent bend in the abloviak shear zone may be the result of differential uplift of the western side of the orogen in the south sinistral strike slip and east as well as west side up deformation continued episodically in the komaktorvik zone until at least 1710 ma the tectonic development of the orogen can be explained in terms of modern plate tectonic processes

geochemistry of rare earth elements in a neutral mine drainage environment anjir tangeh northern iran abstract this study investigates the geochemical characteristics of rare earth elements and yttrium ree y in the neutral mine drainage nmd and river water in the vicinity of the anjir tangeh coal washing plant mazandaran province northern iran the nmd water had a neutral ph along with high sulphate and bicarbonate concentrations the total concentrations of ree in the nmd water were lower than in the river water according to the north american shale composite nasc normalised concentrations the patterns of nmd showed heavy ree hree enrichment while the river water represented middle ree mree enhancement both negative europium eu and positive gadolinium gd anomalies were observed in the drainage and river water within the study area the sum of ree concentration increased gradually downstream of the discharging point of the plant reject water in contrast to decreasing of al fe mn and cu pb zn concentrations the river sediment with high fe concentrations was enriched with lanthanum la and cerium ce the overall ree pattern of the nmd approximates those of coal except for the depletion in light ree lree and the enrichment of eu dominant inorganic ree species in the river water included ln co3 2 and lnco3 while lnco3 ln co3 2 and ln so4 were the main complexes in the nmd the saturation index indicated that al and fe were both oversaturated in the drainage and river water which can control the fractionation of ree by the sorption process according to both hierarchical cluster analysis hca and principal component analysis pca ph al and p were the significant parameters in the ree distribution

isotopic and trace element constraints on the origin and evolution of saline groundwaters from central missouri na ca cl groundwaters with salinities of 1 to 30 discharge from natural springs and artesian wells in mississippian carbonates and ordovician sandstones and carbonates in central missouri carbonate saturation and quartz supersaturation are maintained throughout the salinity range major and trace element and isotopic variations in the waters are used to place constraints on models for rock water interaction and regional hydrology the groundwaters have d values that range from 108 to 45 and 18 o values that range from 14 7 to 6 5 smow these data lie approximately along the meteoric water line ranging from values similar to local recharge in missouri to significantly lower values that are similar to 18 o and d for meteoric recharge in high altitude and high latitude regions of north america the more saline samples have the lowest 18 o and d contents a trend that is opposite to that observed in most other studies of saline waters the h o isotopic correlation and the range in salinity and several major and trace element concentrations in central missouri groundwaters are readily explained by a saline dilute water mixing model 87sr 86sr ratios for the groundwaters range from 0 7155 to 0 7161 these values are significantly higher than previously published values for 1 estimates of 87 sr 86 sr in phanerozoic seawater 0 7068 0 7092 and 2 carbonates of the mississippian burlington keokuk fm 0 7075 0 7105 through which some of the waters migrate as they pass to the surface nd 0 values in the groundwaters range from 10 9 to 8 1 and 147 sm 144 nd ratios range from 0 108 to 0 128 these values are similar to or lower than previously published analyses of carbonates and other authigenic phases from the burlington keokuk fm mean nd 0 7 8 0 8 1 mean 147 sm 144 nd 0 141 the h o sr and nd isotopic data and the results of model calculations preclude 1 models involving the modification of ancient seawater for the origin of the saline waters and 2 extensive interaction between the groundwaters and their host carbonates the waters apparently acquired their 18 o and d values as meteoric recharge and their 87sr 86sr and rare earth element signatures from extraformational crustal sources high 87 sr 86 sr low nd 0 low 147sm 144nd and largely preserved these isotopic signatures during subsequent migration through the carbonates chemical exchange via rock water interaction is required for isotopic exchange to occur therefore the present state of chemical equilibrium between the groundwaters and carbonate aquifer minerals may serve to limit rock water interaction and hence preserve the extraformational isotopic signatures in the waters the integration of geochemical isotopic and hydrologic data on a local and regional scale suggests a history for the central missouri groundwaters involving 1 meteoric recharge in the front range of colorado 2 dissolution of permian halite in the subsurface of kansas 3 interaction with predominantly silicate mineral assemblages in paleozoic strata and possibly precambrian basement with aquisition of crustal sr and ree signatures 4 dilution and migration to shallow aquifer levels in central missouri and 5 mixing with local meteoric recharge through mississippian carbonates with no significant change of the isotopic signatures acquired in stage 3

geochemistry of the rare earth elements in hypersaline and dilute acidic natural terrestrial waters complexation behavior and middle rare earth element enrichments rare earth element ree speciation was modelled in acid 2 9 ph 3 5 hypersaline groundwaters from australia and from the palo duro basin in texas usa using a combined specific ion interaction pitzer model and ion pairing model the free metal ion species i e ln3 is the dominant form of dissolved rees in these systems accounting for 40 70 of the dissolved metal in groundwater from lake tyrrell victoria australia 50 90 of the rees in groundwater from lake gilmore western australia and always 90 of each ree in the texas groundwaters lakes tyrrell and gilmore are actually dry lakes that act as groundwater discharge zones the abundance of the free metal ion species increases in these waters with increasing ionic strength and with decreasing ph the free metal ion species is followed in abundance by ree sulfate and ree chloride complexes that account for 20 50 and 10 15 respectively of the dissolved rees in the groundwaters from lake tyrrell 15 30 and 5 20 respectively in the groundwaters from lake gilmore and 3 and 7 respectively in the palo duro basin groundwaters the groundwaters of the lake tyrrell system and the palo duro basin are enriched in the middle rees mrees compared to both the light rees lrees and the heavy rees hrees only nd sm and dy were determined in the lake gilmore groundwaters and consequently it is unclear whether these acid groundwaters are also enriched in the mrees previous investigators suggested that fe rich organic flocs ree phosphate complexation and solid liquid exchange reactions between terrestrial waters and mree enriched surface fe mn coatings suspended particulates or secondary mineral phases within aquifer materials may promote the development of mree enrichments in natural waters we propose that organic colloids and ree phosphate complexes are insignificant in acidic natural waters in regards to mree enrichments instead solid liquid exchange reactions or dissolution of surface coatings suspended particulates and or secondary phases as well as sulfate complexation more likely controls the development of mree enrichments in acidic natural terrestrial waters

light rare earth elements enrichment in an acidic mine lake lusatia germany abstract the distribution of rare earth elements ree was investigated in the acidic waters lake and groundwater of a lignite mining district germany the fe and so4 rich lake water ph 2 7 displays high ree contents e g la 70 g l ce 160 g l and an enrichment of light ree lree in the nasc normalised pattern considering the hydrodynamic model and geochemical data the lake water composition may be calculated as a mixture of inflowing quaternary and mining dump groundwaters the groundwater of the dump aquifer is lree enriched nevertheless the leachates of dump sediments generally have low ree contents and display flat nasc normalised patterns however geochemical differences and ree pattern in undisturbed lignite lree enriched pattern and low water soluble ree contents and the weathered lignite of the dumps flat ree pattern and high water soluble ree contents suggest that lignite is probably the main ree source rock for the lake water

origin of rare earth element signatures in groundwaters of circumneutral ph from southern nevada and eastern california usa concentrations of the rare earth elements ree were measured in circumneutral ph groundwaters from southern nevada and death valley ca groundwaters from the regional lower paleozoic carbonate rock aquifer cambrian devonian have flat shale normalized patterns that closely resemble the shale normalized patterns of the aquifer rock samples principally cambrian groundwaters associated with younger carbonate rocks chiefly permian in the study region exhibit heavy ree hree enriched shale normalized ree patterns with substantial negative ce anomalies that also mimic these carbonate rocks in addition groundwaters from the felsic volcanic rock aquifers have the same flat to light ree lree enriched shale normalized patterns with large negative eu anomalies as the felsic volcanic rocks the similar ree patterns of all the groundwaters and associated aquifer rocks studied suggest that the groundwaters inherited ree signatures from the host rocks through which they flow because negative ce anomalies are not an uncommon feature of carbonate rocks of marine origin the negative ce anomalies reported here for these groundwaters may reflect a permian marine ce signature previously we demonstrated that carbonate complexes dominate ree speciation in southern nevada and death valley groundwaters moreover solid liquid partitioning coefficients kd indicate that the affinity of lrees to sorb to aquifer surface sites is substantially greater than for the hrees in the southern nevada carbonate and felsic volcanic rock alluvial aquifers consequently the hrees enrichments reported here for groundwaters associated with younger paleozoic carbonate rocks compared to these source rocks is consistent with ree carbonate complexation and preferential removal of lrees to aquifer surface sites

rare earth elements geochemistry in springs from taftan geothermal area se iran abstract concentrations of rare earth elements rees were determined in springs and andesitic dacitic rocks of taftan geothermal field hydrochemical results of major ions indicate that thermal springs are na so 4 cl and ca so 4 cl types concentrations of rees are in ranges of 10 4 to 1 2 and 49 to 62 times of chondrite for springwater and rock samples respectively the thermal sts and tts and the cold aps springs with low ph values exhibit a very high ree contents 0 64 to 3 15 mg l saturation index indicates that fe and al phases can control dissolved ree concentration in fts and pf cold springs the speciation of ree complexes indicates dominant presence of lnso 4 and free ion in the taftan thermal springs in aps cold spring with ph 4 fluoride complexes are dominate over the free ion and sulfate species while in pf and fts cold springs with ph 6 4 and 7 respectively carbonate complexes lnco 3 are predominant species chondrite normalized pattern for the low ph waters show very distinctive gull wing patterns characteristic feature of acid sulfate geothermal systems and are similar to those of the host rocks chemical characteristics of rare earth elements in spring and volcanic rock samples indicate that rees are originated from the andesitic dacitic host rocks whole rock normalized ree patterns and petrographic evidences show that rare earth elements leached mainly from marginal alteration of minerals and matrix decomposition in volcanic rocks in chondrite normalized ree patterns significant negative eu anomaly in the cold springs compare to the thermal and acidic springs indicates that alteration of plagioclase is more intense in the later corresponding to increasing in temperature and acidic state of reactant water

crustal and upper mantle electrical conductivity structures in west africa geodynamic implications abstract measurements of the electrical and magnetic fields at the surface of the earth have been carried out in west africa in the period range 10 10 000 s in this area the method of magnetotelluric mt sounding finds its application in a variety of geological problems such as the deep shape of sedimentary basins the geometry of orogenic belts and craton deep structures the present article is an attempt to correlate the conductivity model with large scale tectonics mt surveys have revealed the presence of several areas where electrical resistivity is abnormally low at crustal and upper mantle depths and the existence of lateral electrical conductivity inhomogeneities within the lithosphere subsurface electrical conductivity distribution is in good relation with the geological features and its variation associated with lithological and structural changes a major discontinuity found at a depth of several hundred kilometers in the lithosphere separates two structural blocks the eastern one with higher resistivities being the west african craton the lithosphere derived from this work has a maximum thickness of 300 km under the senegalo mauritanian basin and more than 400 km beneath the craton the electrical asthenosphere is certainly not well developed under the craton a sketch of electric structures across west africa is presented and a geodynamic interpretation is proposed to explain the present structural pattern of the southern segment of the mauritanides belt

the geochemistry of rare earth elements in groundwater from the carnmenellis area southwest england shallow groundwater samples from the carnmenellis area of southwest england collected from wells boreholes springs adits and stream baseflow represent recently recharged waters of low salinity their major ion concentrations closely reflect the lithology of their host rocks which comprise the carnmenellis granite and devonian metasediments and metabasite of greenschist grade groundwaters from the granite are predominantly na cl or na ca cl type whilst those from the metasediment are na ca mg cl hco3 waters with a larger range of compositions the major ion compositions are predominantly a function of water rock interaction processes and the larger range of metasediment water compositions probably reflects the greater lithological variation the ph of groundwater samples circulating through granite is typically lower than that of groundwater in the metasediments the range being 4 3 to 7 2 median 5 7 and 4 7 to 8 0 median 6 6 respectively rare earth element ree concentrations of 0 45 m filtered groundwater samples have been determined by inductively coupled plasma mass spectrometry icp ms a large range of concentrations exists and many are below detection limits but levels reach up to 229 g 1 1 6 m total rees the rees are strongly controlled by ph with higher levels in groundwaters of ph 6 chondrite normalised profiles are light rare earth element lree enriched compared to heavy rare earths hrees with a common slight negative eu anomaly both features reflecting the compositions of their host rocks ree profiles therefore appear to be controlled by water rock interactions involving predominantly ree enriched minerals in the granite the rees are probably derived mainly from the accessory minerals monazite and apatite as well as the high ree framework minerals biotite and muscovite the source of rees in groundwater from the metasediments is more uncertain but probably includes clay minerals chlorite and carbonate ree compositions normalised to shale have flatter profiles although many are slightly convex with higher normalised sm eu and gd values a few metasediment derived waters with high total ree concentrations have lree enriched shale normalised patterns it is suggested that the bulk of the rees in these few samples is colloidal rather than totally dissolved groundwaters from the metasediments have a notable depletion in ce which is distinct from waters in the granite this depletion is problematic in that it is difficult to see how redox processes could be the dominant control since groundwaters from the metasediments are unlikely to be more oxidising than those from the granite likewise variations in ph fail to totally explain the distinctions in ce concentration and la ce ratios between the two water types it is therefore suggested that the ce contents are largely source related rather than process related the observed ree compositions of granite and metasedimentderived groundwaters from the carnmenellis area are so distinctive that the rees in general and ce in particular might be useful as future tracers in studies of water rock interaction and groundwater provenance

hydrogeochemistry and rare earth element behavior in a volcanically acidified watershed in patagonia argentina abstract the rio agrio watershed in northern patagonia argentina is naturally acidic due to discharges of volcanic h 2 so 4 hcl and hf at its headwaters near the summit of copahue volcano a suite of water samples was collected from the summit of the volcano to a point roughly 40 km downstream where the ph of the rio agrio rose above 6 0 this suite included a sample of the hyperacidic ph the concentrations of ree in the rio agrio decreased by several orders of magnitude through the study area as a result of dilution and chemical attenuation a subtle shift in the slope of shale normalized profiles of dissolved ree concentration was observed from being weakly positive near the source of the rio agrio to showing a weak middle ree enrichment trend in lake caviahue to being weakly negative in the lower reaches of the river the trend to a negative slope across the lanthanide series in the lower river is explained by selective partitioning of the heavier ree to hydrous oxides of fe and al suspended in the water column and accumulating on the riverbed most of the decrease in ree load occurred immediately downstream of the confluence with a tributary that increased the ph of the rio agrio from 4 3 to 6 1 although the mixed water was supersaturated with ree phosphate compounds precipitation of lnpo 4 is not believed to have been a dominant process because the predicted pattern of inter element fractionation from phosphate deposition is inconsistent with the observed trends instead ree attenuation most likely occurred from adsorption onto freshly precipitated hydrous aluminum oxide the behavior of ree in the rio agrio watershed is broadly similar to what has been observed in watersheds that owe their acidity to oxidation of sulfide minerals

the properties of reservoir water in post mining excavations of cambrian and devonian quartzite sandstones holy cross mountains in the holy cross mountains southern poland there are numerous disused quarries some of these are filled with water and some despite their nearby location have extremely diverse physicochemical and chemical properties of their waters one such object is the wi niowka mala reservoir its waters contain large amounts of sulfates 700 mg l and iron 24 mg l which are weathering products of rocks containing metal sulfides mainly pyrite in the direct drainage zone as a consequence there is an increase in the electrolytic conductivity of the water supplying the reservoir resulting in very low ph values 4 this article presents the detailed limnological characteristics of this reservoir and explains the process that led to its water acidification a control reservoir barcza was also selected for the tests although it is also a post mining excavation it has a neutral ph and a low concentration of sulfates and iron the examined reservoirs differ in the hydrochemical type of waters the wi niowka mala reservoir represents a sulfate calcium double ion type so42 ca2 and the barcza reservoir a bicarbonate calcium type hco3 ca2 the concentrations of the main ions occurring here are shaped by the lithological features of the surrounding rocks respectively upper cambrian quartzite sandstones with pyrite mineralization zones lower devonian sandstones cut by mudstones and claystones with tuffite inserts

trace elements and their isotopes in bones and teeth diet environments diagenesis and dating of archeological and paleontological samples fossil biogenic apatites display trace element te compositions that can record environmental and biological signals give insights into past water compositions or be used for dating paleontological and archeological bones and teeth processes of te incorporation into apatites of skeletal phosphatic tissues are described ranging from those active in living organisms to those active during diagenesis abiotic incorporation mechanisms have been modeled theoretically and experimentally and include crystallographic controls on te partitioning coefficients inorganic surface adsorption and adsorption mediated through chelation and diffusion adsorption processes each leading to specific fractionation patterns predictions from models and experiments have been tested against te concentration and isotopic composition data on remains of contemporary wild or raised animals and on fossils of various ages and environments in living organisms tes incorporated in apatite are separated in two categories non essential elements whose concentration is compared to that of an essential element with similar behavior e g sr ca to reconstruct trophic chains and essential elements whose isotopic ratios are used to trace metabolic activity diet etc in fossils elements are incorporated during diagenesis such as rare earth elements rees and trace diagenetic processes ranging from very early quantitative adsorption likely mediated by chelators protracted diagenesis through inorganic adsorption and fractionation through diffusion adsorption to low grade metamorphism associated with intense redistribution under crystal chemical control these different steps are also identified as steps of radionuclide incorporation only samples where the earliest steps can be deciphered are useful for determining stratigraphic and archeological ages other samples will date late diagenetic events that have obliterated the paleoenvironmental signals but may be of geological significance e g tectonic events

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

mineralogical control of rare earth elements in acid sulfate soils abstract major trace and rare earth element concentrations were measured in porewater surface water and sediments at an acid sulfate soil site the concentrations of la and ce in porewater are up to 1 3 ppm there is a strong correlation between ree concentration and acidity except that the maximum concentrations were consistently found below the horizon of maximum acidity associated with an increase in ph to ca 4 and change in mineralogy from jarosite dominated to goethite dominated mottles jarosite replacement by goethite is as expected with the rise in ph which in turn is due to the occurrence of a fossil shell bed just below the rare earth element patterns in the porewaters are enriched in the mree with respect to post archaean australian shale paas measurements and calculations show that this is in accord with experiments on low degree partial dissolution of jarosite even when the jarosite itself is highly enriched in lree there is a clear fractionation in the patterns between the clay rich soil matrix which is slightly depleted in the lree when normalized to paas la ybpaas 0 5 and the secondary mineral phase jarosite which is enriched in the lree la ybpaas 15 50 the ree pattern in the porewater changes with the transition from jarosite to goethite rich mottles becoming relatively more enriched in the lree compared to the hree which is consistent with the incongruent dissolution of jarosite to form goethite and the release of greater amounts of jarosite ree to solution including proportionately more of the jarosite compatible lree maximum surface water ree concentrations in acidic water were 100 200 ppb la and ce ree patterns in surface water were very similar to the porewater transition zone enriched in the mree but asymmetric relatively enriched in the lree compared to the hree

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

rare earth elements in foraminifera tests abstract the concentrations of nine rare earth elements ree la ce nd sm eu gd dy er and yb have been determined in mixed species assemblages of foraminifera tests taken from atlantic ocean sediment core tops reductive cleaning techniques have revealed that ree are present in three phases in foraminifera tests collected from sea floor sediments ree included in the foraminiferal calcite matrix termed lattice ree ree associated with an authigenic femn rich phase adsorbed onto the surface of the test following the death of the organism termed coating ree and ree associated with alumino silicate detritus termed detrital ree which commonly infills the test chambers after burial in the sediment the concentrations of ree in the nondetrital lattice plus coating and lattice phases have been measured in this study approximately 90 of the ree measured in the non detrital phase reside in the coating phase the remainder being present in the lattice phase these data have been used to investigate the relationship between the distribution of dissolved ree in the ocean and in the coating and lattice phases in addition to the ree the concentrations of mn fe cu al and po4 have been measured as an aid to characterisation of the various phases

wide angle seismic imaging of a mesoproterozoic anorthosite complex the nain plutonic suite in labrador canada the mesoproterozoic nain plutonic suite nps of labrador canada one of the largest anorogenic plutonic terranes was studied by a refraction wide angle seismic experiment four ocean bottom seismometers and 18 land stations were deployed along a 330 km profile and recorded air gun shots from the easternmost 160 km with the nps located in the center of the line at the suture of the nain and churchill provinces p and s wave velocity models were developed by forward modeling of travel times and amplitudes upper and middle crustal p wave velocities outside and beneath the nps range from 5 9 to 6 5 km s lower crustal p wave velocities range from 6 55 to 7 0 km s within the anorthositic rocks velocities are as high as 6 8 km s and reflections define the base of the nps to be 8 km deep in the se churchill province and 11 km in the nain province a variation that may be the result of lateral density changes within the country rocks or the anorthosites the total crustal thickness is 39 km west of the nps but is only 32 34 km beneath the nps some 5 km less than nain province crust distal from the nps the inferred crustal thinning is possibly related to anatexis of the lowermost crust by a thermal plume that generated the plutonism the poisson s ratios are 0 275 within the anorthosite plutons 0 27 in the upper and middle crust and 0 285 in the lower crust these values are some 0 03 higher than in the archean nain crust distal to the nps indicating a higher plagioclase content at all crustal levels as result of the plutonism we postulate that a crustal root similar to the root observed farther north in the torngat orogen was completely removed by anatexis and the silicic and basic magmas probably ascended to midcrustal levels along preexisting zones of weakness at the nain churchill boundary

rare earth elements in chloride rich groundwater palo duro basin texas usa rare earth element ree data for groundwater samples from the deep basin brine aquifer of the palo duro basin texas usa illustrates the potential use of ree for inferring groundwater flow paths through different geologic materials the ree content of the groundwaters range over 2 5 orders of magnitude and are depleted by 102 to 105 relative to aquifer materials the shale normalized ree patterns for groundwater that have primarily interacted with arkosic sandstones granite wash are flat with similar heavy ree hree enrichments lula n 0 60 to 0 80 the samples with highest ree contents and ree patterns which are enriched in the intermediate rees irees sm tb reflect variable degrees of interaction with carbonate rocks the iree enrichment is the result of fluid interaction with fe mn coatings on carbonate minerals and or secondary minerals in fractures and vugs the chloride complex lncl2 and free ions are the predominant ree species accounting for over 95 of the rees carbonate and sulfate species account for the other 5 and have very little influence on the behavior of the rees although this study indicates a potentially important role for the rees in understanding geochemical transport and groundwater movement it also indicates the necessity for developing a better understanding of ree speciation in high ionic strength solutions

the development of acidic groundwaters in coal bearing strata part i rare earth element fingerprinting abstract this study examines the rare earth element ree pattern of acidic mine discharges in the durham basin ne england as a means of fingerprinting their sources and understanding the water rock interactions although whole rock compositions proved to be unhelpful mimicking acid mine water generation in a series of selective leachates of the coal and coal bearing strata gave ree patterns similar to those measured in the emergent waters ree ratios and anomalies were used as indicators of specific interactions in the development of acidic groundwater the implications of the findings for the classification and evolution of acid mine discharges are discussed

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 element and nd isotopic variations in regionally extensive dolomites from the burlington keokuk formation mississippian implications for ree mobility during carbonate diagenesis abstract marine carbonates of the burlington keokuk fm miss of the midcontinent region have been subject to two major episodes of regionally extensive 100 000 km2 dolomitization previous studies of the cathodoluminescent petrography sr c and o isotopic compositions and sr fe mn and ca concentrations of burlington keokuk dolostones outline a diagenetic history in which lime mud was pervasively dolomitized by a seawater dominated fluid at many localities this early dolomite generation dolomite i was recrystallized by nonmarine diagenetic fluids at shallow burial depths to produce dolomite ii dolomites i and ii have similar rare earth element ree patterns and abundances and a narrow range of initial 143nd 144nd isotope ratios of 0 511906 0 000025 1 this consistency in the nd isotope ratios and ree patterns along with the presence of anomalously low abundances of cerium in the dolomites cherts glauconite pellets fish apatite and crinoids suggests that 1 seawater derived ree dominated the system and 2 the extensive water rock interaction that produced profound textural and compositional changes during the formation of dolomite ii did not significantly alter the ree patterns or nd isotopic signatures of the dolomites the results of quantitative modeling of isotopic and trace lement exchange during water rock interaction in carbonate systems indicate that extremely large water rock ratios are required to alter the ree signatures of diagenetic carbonates such large water rock ratios can reflect either 1 large extents of fluid flow during carbonate recrystallization or 2 minimal interaction between diagenetic fluids and host rocks during carbonate cement crystallization late vug filling calcite and dolomite have low sm nd and high ce nd n ratios relative to the dolostones such distinct ree signatures probably reflect limited interaction between late diagenetic fluids and burlington keokuk host rocks penecontemporaneous clastic sediments have similar initial 143nd 144nd isotope ratios 0 511857 0 511877 and lower sm nd ratios compared to the dolomites suggesting 1 a common crustal source of ree for the clastics and carbonates and 2 ree fractionation during the formation of carbonate apatite glauconite and other authigenic phases in the marine environment

the nain churchill boundary and the nain plutonic suite a regional perspective on the geologic setting of the voisey s bay ni cu co deposit northern labrador is the site of two major lithotectonic elements of eastern canadian shield geology first it encompasses a paleoproterozoic continental suture zone archean rocks of the nain province tectonically juxtaposed against paleoproterozoic and reworked archean rocks of the churchill province the nain churchill suture evolved between 1860 and 1740 ma impressing upon the archean and paleoproterozoic rocks a regional metamorphic and tectonic signature referred to as the torngat orogen an important component of the torngat orogen is the tasiuyak gneiss a paleoproterozoic metasedimentary unit that occupies most of the eastern margin of the churchill province second northern labrador is the site of a world renowned terrane of mesoproterozoic anorogenic igneous rocks the nain plutonic suite that sits astride the suture and acts as a stitching batholith between the nain and churchill provinces the nain plutonic suite comprising amalgamated granitic anorthositic dioritic and troctolitic intrusions largely obscures the suture for nearly half of its total length the suite evolved between 1350 and 1290 ma and is interpreted as a product of magmatism associated with limited intracontinental rifting of the conjoined nain churchill crust above a mantle plume the voisey s bay ni cu co deposit serendipitously discovered in 1993 resides within one of the oldest troctolitic intrusions of the nain plutonic suite a 1334 ma intrusion that transgresses a contact between archean and paleoproterozoic gneisses genetic controls on the setting of mineralization have been built upon the nain churchill boundary as a zone of weakness that was exploited by mantle magmas and have implicated the tasiuyak gneiss as a crustal sulfur source although the archean paleoproterozoic junction at voisey s bay is presently interpreted as representing the nain churchill boundary in reality the provincial affinity of the archean gneisses is equivocal this uncertainty dictates caution in assigning the nain churchill boundary as the convenient transcrustal conduit that allowed the voisey s bay mafic intrusions rapid transit from their mantle staging area modeling the sulfide deposit as being solely a result of sulfur saturation of mafic magma by proximal paleoproterozoic tasiuyak paragneisses is also questionable because other genetic processes may have been responsible for example desilication of gneiss is strongly indicated by aluminous refractory minerals in vestiges of fused tasiuyak gneiss the spatial distribution of the mineralized rock at voisey s bay apparently within the subchamber plumbing system feeding a larger intrusion and within remnants of the larger intrusion itself may serve as a paradigm for similar deposits in the nain area but the preerosional comparative morphology of that larger intrusion relative to the better preserved ones may never be known a thorough understanding of the setting and genesis of the voisey s bay deposit will better facilitate establishing exploration targets in other parts of the nain region in labrador as a whole and in other geologically similar regions of the world

behavior of rare earth elements in groundwater during flow and mixing in fractured rock aquifers an example from the dandenong ranges southeast australia a previously defined flow system is used to investigate ree behavior at different stages along groundwater flow paths in fractured basalt and sedimentary aquifers results from this study indicate that ree concentrations and patterns predominantly reflect different types and rates of reactions taking place to those controlling major ion chemistry in areas where recharge is through sediments ree concentrations are high nd 8 62 31 61 ng l and localised processes such as source heterogeneity control ree patterns and concentrations increased concentrations of rees in these groundwaters where ph 6 1 is a result of early stage ree mobilisation in the flow system in contrast where groundwater recharges through basalt ree concentrations are low nd 2 40 4 75 ng l and ree concentrations are relatively constant along groundwater flow paths indicating steady state conditions groundwater from both the sediment and basalt aquifer systems flows into the local discharge area in contrast to tds contents and major ion ratios groundwater from the discharge area has ree concentrations nd 1 84 4 18 ng l and patterns that reflect a larger component of flow from the basalt aquifer lower ree concentrations of groundwater from the regional sedimentary aquifer may result from progressive ree sorption or co precipitation as indicated by an increase in y ho cl cn ratios and hree enrichment for groundwater with ph not vert similar 7 1 due to greater abundances of hree vs lree dicarbonato complexes

neodymium and strontium isotopic dating of diagenesis and low grade metamorphism of argillaceous sediments the behaviour of the rb sr and sm nd isotopic systems with increasing degree of hercynian metamorphic overprint was studied along a transect in cambrian shales of northwestern morocco clay fractions of 0 2 to 2 6 m size from five samples were investigated representing a range from nonmetamorphic to epizonal metamorphic conditions the samples were washed in cold l n hc1 prior to digestion to separate soluble exchangeable rb sr sm and nd from amounts of these elements fixed in the crystallographic sites of the minerals and to analyze both components separately the results reveal that the rb sr isotopic system is dominated by sr hosted by clay mineral phases both detrital and authigenic illite and chlorite and carbonate hosted soluble sr isotopic homogenization of sr occurred during hercynian metamorphism yielding ages between 309 and 349 ma the sm nd isotopic system on the other hand is dominated by cogenetic apatite and fe oxide hydroxide both having high contents of leachable rees the leachates yield a sm nd isochron age of 523 72 ma indicating diagenetic equilibrium between apatite and fe oxide hydroxide fine grained clay fractions of 0 2 m show inheritance of a detrital nd component the study demonstrates that the diagenesis of the investigated argillaceous sediments can be dated by the sm nd chronometer in authigenic cement phases the isotopic system of these minerals apatite fe hydroxide oxide was homogenized during authigenic mineral growth in a sediment that was flushed by diagenetic fluids and had abundant primary or secondary interconnected pore space the hercynian metamorphic overprint caused partial isotopic rehomogenization of the adsorbed and clay hosted portion of the sr as well as of the carbonate hosted sr the sm nd system in the cement phases survived this metamorphism this results in decoupling of the two isotopic systems and allows the dating of diagenesis on the one hand sm nd and metamorphism on the other hand rb sr

crustal scale flexural slip folding during late tectonic amplification of an orogenic boundary perturbation in the paleoproterozoic torngat orogen northeastern canada large variations in metamorphic grade over short distances disparate orientations and diverse kinematics of contemporaneous structures and a previously unexplained 90 counterclockwise bend in the orogenic boundary of the amphibolite to granulite facies northern segment of the paleoproterozoic torngat orogen are shown to be the result of multiple tectonic events acting upon an orogenic boundary perturbation the perturbation was initiated when a promontory on the nain province margin composed of a 1910 1885 ma continental magmatic arc burwell domain indented the rae province hinterland during the onset of collisional orogeny at ca 1870 ma dn 1 sinistral transpression at ca 1845 1822 ma dn 2 caused formation of the orogen parallel abloviak shear zone and oblique burial of the nain province margin beneath a tilted section of the hot buoyant magmatic arc reactivation of the orogen at ca 1798 1770 ma dn 3 involved crustal scale flexural slip folding of the perturbation and simultaneous exh

depth of the conductosphere under the indian shield abstract the depth at which the highly conducting layer of the upper mantle the conductosphere begins under the indian shield is estimated to do this the geomagnetic daily variations measured north of the magnetic equator are separated into contributions of internal and external origin and from the latter an analytical representation for the ionospheric current system is inferred the external field produced by this current and the field induced by it in a two layer conductivity model of the earth consisting of an insulator overlying a perfect conductor are obtained the total field thus calculated is compared with the data to obtain the conductosphere depth the conductosphere below the indian shield is found to be located at approximately 1000 km well below the average global value in agreement with previous findings below the african shield this result supports the hypothesis that there is a correlation between the deep conducting structure of the earth and some tectonic features

the southeastern churchill province synthesis of a paleoproterozoic transpressional orogen the paleoproterozoic southeastern churchill province secp is located in the northeastern canadian shield of labrador and quebec the secp formed through the oblique collisions of the archean nain and superior cratons with a third intervening archean block the core zone the belt has a tripartite structure comprising the torngat orogen to formed by nain craton core zone collision in the east the core zone in the centre and the new quebec orogen nqo formed by superior craton core zone collision in the west the secp thus records transpressional development on the flanks of the superior and nain cratons as they indented northwards to form the larger trans hudson nagssugtoqidian orogenic belt to the north principal stages of tectonic development were 1 2 2 2 1 ga crustal rifting of nain and superior cratons 2 ca 1 9 ga subduction under eastern nain craton 3 ca 1 87 1 85 ga collision of nain craton and core zone to form the to 4 1 845 1 820 ga sinistral transpression in the to and subduction under the western core zone and 5 1 82 1 77 ga collision of superior craton and core zone to form the nqo in association with dextral transpression crustal scale cross sections of the secp have been developed from reflection and refraction seismic data the western part of the nqo is dominantly west vergent and associated with an imbricate thick skinned thrust stack that ramps from the base of the crust the core zone is characterized by a 35 40 km thick crust and pervasive east dipping fabrics related to westerly thrusting the to is a narrow doubly vergent belt associated with a 48 km thick crust that forms a crustal root with a moho relief of 12 km the root is interpreted to result from attempted subduction of the core zone under the nain craton possibly as a result of mid crustal wedging by the nain craton the to was the site of intense convergence that resulted in excision of juvenile crust possibly including tectonic removal of the axial magmatic arc as a result the middle to lower levels of the secp consist largely of refractory archean lithosphere this may account for the lack of widespread post collisional plutonism in the secp and the preservation of the to root

rare earth element fractionation during the precipitation and crystallisation of hydrous ferric oxides from anoxic lake water abstract an enrichment of light rare earth elements lree is characteristic for most of the acidic fe and so 4 rich pit lakes and groundwaters in the lignite mining area of lower lusatia germany one of these acidic lakes the pit lake rl 1223 has a strong thermal and chemical stratification the upper water layer 0 9 m shows ph values of about 3 during all seasons the monimolimnion 10 17 m of the lake is anoxic and has ph values of about 7 the rare earth element ree patterns of the upper lake water show enriched lree la n yb n 1 6 whereas the opposite patterns depletion of lree la n yb n 0 4 are found in the anoxic water of the monimolimnion experiments were conducted to observe the behaviour of ree during fe oxidation in water from the monimolimnion depth 14 m the sampled monimolimnion water was placed in plastic bottles and the changing water chemistry was observed for 40 weeks after sampling due to the initial anoxic conditions almost all fe precipitated in the investigated water and the ph value decreased from about 7 to 3 during the oxidation the fe precipitates are identified as ferrihydrite which is transformed into goethite within the oxidation process stable ph conditions ph 3 0 were reached after about 10 weeks of oxidation the original ree patterns of the investigated water are generally reflected in the fe precipitates collected at the beginning of the experiment as well as after up to 40 weeks of oxidation however in the corresponding water lree were temporally enriched with a maximum la n yb n ratio of 1 0 and a maximum la n sm n ratio of 2 3 after 6 weeks of oxidation time ph 3 8 4 9 although complex geochemical changes took place between the start and the end of the experiment ree patterns observed at these points in time are nearly identical these differences of the ree pattern can be explained by the sampling procedure the experimental findings can be transmitted to the mining dump aquifers of the study area where geochemical conditions comparable to the experimental oxidation time from 3 to 6 weeks are found and hydrous ferric oxides are precipitating groundwater passing through the mining dumps can preferentially desorb lree from the fe precipitates and display the typical lree enrichment and carry it to the epilimnion of the acidic pit lakes in lower lusatia

electromagnetic evidence for lateral inhomogeneities within the earth s upper mantle abstract the composition of the upper mantle is of great significance to our understanding of plate tectonics and global evolution information about the physical properties of the earth at upper mantle depths including lateral variations in electrical conductivity can be deduced from measurements of the electric and magnetic fields at the earth s surface electromagnetic methods appear to give poorer resolution than do some other methods for example seismics but as they are sensitive to quite different properties of a medium they provide a different and complementary class of information the basic theory of electromagnetic sounding methods is briefly reviewed below and evidence regarding lateral conductivity inhomogeneities in the earth s upper mantle is examined while lateral electrical conductivity inhomogeneities appear to be the rule rather than the exception the interpretation of electromagnetic data still presents difficulties and the results from many regions are not as yet unambiguous where the data are of sufficient resolution a rapid increase in electrical conductivity can usually be identified within the upper mantle the depth to this highly conductive zone is different in different tectonic environments but is broadly consistent between analogous but widely separated tectonic environments a comparatively shallow conducting region is found beneath the ocean lithosphere the depth of this region is dependent on lithospheric age many of the more shallow conducting regions in both continental and oceanic environments are associated with high heat flow values and seismic low velocity zones these highly conducting regions may be zones of partial melt

use of the magnetotelluric method for a better understanding of the west african shield magnetotelluric soundings have been carried out in the republic of upper volta and in the niger republic to gain a better understanding of the structure of the west african shield the sounding stations are situated from east to west on a sedimentary basin on the central african mobile belt pan african orogeny at 550 100 m y and on the west african craton eburnean orogeny at 1850 250 m y the results show that the craton is characterized by a zone of high resistivity in the crust and uppermost mantle the absence of a conductive zone at the interface between the crust and the uppermost mantle is consistent with the hypothesis of hyndman and hyndman 1968 on the dehydration of the crust of the stable shields the first conductive layer of the craton is situated at a depth of 130 km with a temperature of about 860 c in the mobile belt and the basin the presence of a low resistivity layer at a depth of 30 40 km has been established if water is present in the lower crust it can explain the origin of this conductive zone a plausible explanation is that this layer may have been formed by the slow infusion of water from the mantle during the last thermal reactivation regional differences in electrical conductivity structure between the central african mobile belt and west african craton appear to extend deeper than 200 km modeled conductivity variations with depth in the upper mantle obtained from magnetotelluric results are compared to other continental models thermal model seismic structure in order to define a lower lithospheric boundary for west africa at the present stage the problem is not yet resolved mobile crustal plate or anchorage in the african plate

rapid development of negative ce anomalies in surface waters and contrasting ree patterns in groundwaters associated with zn pb massive sulphide deposits ground and surface waters collected from two undisturbed zn pb massive sulphide deposits the halfmile lake and restigouche deposits and active mines in the bathurst mining camp bmc nb canada were analysed for the rare earth elements ree ree contents are highly variable in waters of the bmc with higher contents typical of waters with higher fe and lower ph there are significant differences between ground and surface waters and between groundwaters from different deposits the ree contents of surface waters are broadly similar within and between deposit areas although there are spatial variations reflecting differences in ph and redox conditions surface waters are characterised by strong negative ce anomalies ce ce nasc as low as 0 08 produced by oxidation of ce3 to ce4 and preferential removal of ce4 from solution upon leaving the shallow groundwater environment groundwaters and seeps typically lack significant ce anomalies reflecting generally more reducing conditions in the subsurface environment and indicating that ce oxidation is a rapid process in the surface waters deeper groundwaters at the halfmile lake deposit are characterised by ree patterns that are similar to the host lithologies whereas most groundwaters at the restigouche deposit have lree depleted patterns compared to nasc halfmile lake deposit groundwaters have generally lower ph values whereas restigouche deposit groundwaters show greater heavy ree complexation by carbonate ions shallow waters at the halfmile lake and stratmat main zone deposits have unusual patterns which reflect either the adsorption of light ree onto colloids and fracture zone minerals and or precipitation of ree phosphate minerals middle ree enrichment is typical for ground and surface waters and is highest for neutral ph waters the labile portion of stream sediments are generally more middle ree enriched than total sediment and surface waters indicating that the ree are removed from solution by adsorption to fe and mn oxyhydroxides in the order middle ree light ree heavy ree

water rock interaction in an acidic mine discharge as indicated by rare earth element patterns abstract the rare earth element ree composition of an acidic spring discharging at ph 2 7 was studied in relation to the ree composition of selected extracts of the coal bearing strata hydrologically above the discharge the low ph of the discharge and the access to the strata through which it flows provides an excellent opportunity to study the use of rees as tracers of water rock interaction extraction techniques were used to mimic the process of acidic groundwater generation in coal bearing strata samples were treated to remove exchangeable ions and then treated sequentially with solutions buffered at ph 5 5 3 6 and 1 6 in order to mimic the natural buffering systems of groundwaters finally samples were oxidised with hydrogen peroxide in an attempt to remove the pyrite the results show that the composition of the spring is controlled by pyrite oxidation and buffering by fe oxy hydroxides the latter with compositions inherited from carbonates from within the sequence the similarity of ree patterns of the carbonate and the silicate extracts tends to obscure information concerning the relative roles of carbonate or silicate phases the source strata of the spring has evolved over time and shows that different coal seams have a unique contribution this distinct contribution appears more related to the mixture of sedimentary components i e carbonates silicates etc in the coal seam and the combination of shale and sandstone layers surrounding coal seams than the composition of the components themselves the similarity between ree compositions of the sequential extracts suggests that relationships discovered for this spring will be applicable elsewhere in the basin however this very property will hamper the use of such lithophilic elements in cases where characterisation of the source area is not possible

proterozoic orogens of the northeastern canadian shield new information from the lithoprobe ecsoot crustal reflection seismic survey as part of the eastern canadian shield onshore offshore transect ecsoot lithoprobe acquired 1250 km of deep seismic reflection data along the coast of labrador and across ungava bay to image evidence of proterozoic crustal accretion to the archean nuclei of the nain and superior provinces of the canadian shield the relatively pristine archean crust of the nain province has low reflectivity and generally lacks systematic reflector orientations reworking of archean crust on the margins of the makkovik province has little effect on this weak signature in contrast the archean crust in the eastern churchill rae province appears to have been overprinted by a strongly developed whole crustal easterly dipping reflection fabric interpreted to result from proterozoic collision of the nain and superior provinces in the paired new quebec and torngat orogens juvenile proterozoic crust in the makkovik and grenville provinces also shows strong whole crustal dipping reflection fabrics interpretable as outw

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

rare earth element speciation in geothermal fluids from yellowstone national park wyoming usa abstract elevated concentrations 20 1133 nmol kg of rare earth elements ree are present in acid sulphate and acid sulphate chloride hydrothermal waters of the yellowstone national park ynp we used recently estimated thermodynamic data haas et al 1995 to speciate seventeen ynp hydrothermal fluids with the eq3nr code the fluids show a range in ph 2 0 4 0 and temperature 70 93 c and are of varied chemistry with tds 155 2 075 ppm sulphate 100 10 325 mol kg chloride 190 24 580 mol kg fluoride 26 1 790 mol kg and so 4 f 0 8 323 field temperature and ph measurements were used in the modelling and saturation with kaolinite and quartz was assumed although quartz was actually supersaturated where possible oxygen fugacity was calculated from the analytical sulphate sulphide ratios otherwise it was set above the hematite magnetite buffer and pyrite saturation although speciation calculations show that this is not critical carbonate and phosphate levels were set at the analytical detection limit with the exception of 4 waters for which analytical data for phosphate existed the waters show little fractionation of ree relative to their host rhyolitic volcanics it appears that the ree abundances of hydrothermal fluids resulting from alteration of ynp rhyolites are unaffected by the presence of potential complexing species i e that acid alteration completely strips ree from the portion of the rocks that it affects without any fractionation across the ree series the main control over ree speciation is the relative abundances of potential complexing agents however ph and absolute abundances are also important in the most acidic waters ph 2 0 the free ion is the major species when salinity and so 4 cl are low 60 80 of each ree and ree complexes with chloride can be significant up to 5 for higher so 4 cl values sulphate complexes dominate 80 90 for less acid waters ph 2 8 4 0 fluoride is the main complexing agent in low so 4 f fluids but as the so 4 f ratio increases the sulphate species become dominant especially for the light ree lree

depth of the nonconducting layer at the nigerian dip equator the geomagnetic daily variations at the nigerian dip equator are analyzed to find the thickness of the nonconducting layer in this zone to do so the external current system was determined from the external part of the geomagnetic daily variations by using a method discussed in a previous work the field induced by this system was calculated assuming a two layer model for the earth conductivity fitting this induced field to the internal part of the geomagnetic daily variations yielded a thickness of 500 km for the nonconducting layer in the interval of 100 km south to 500 km north of the dip equator however there is evidence showing a latitudinal gradient in the thickness south of this interval

on the interpretation of the distinctive pattern of geomagnetic induction observed in northwest india the geomagnetic variation data from the 1979 indian array experiment have been reanalyzed and reexamined using the hypothetical event analysis technique the contour map of the z h ratio replicates distinctive anomaly in northwest india previously delineated in maps of the fourier coefficients the anomaly reveals the presence of a significant conductor under the ganga basin the contour map has been used to derive a response profile perpendicular to the strike of the anomaly for comparison with 2 d numerical models an excellent fit was found for a conductor at a depth of 32 km with a width of 110 km and a conductivity contrast of 1000 this result places the conductor deep within the lithosphere in the absence of supporting data the origin of the conductor is difficult to resolve however it is thought to be related to pressure released partial melting caused by fracturing of the indian crust during the collision of india with asia

the conductosphere depth at equatorial latitudes as determined from geomagnetic daily variations the structure of the conductosphere at equatorial latitudes is investigated by analyzing geomagnetic daily variations gdv data to do so the magnetic field induced in a multilayered model by an external source of finite size that reproduces the external part of these variations is computed latitudinal profiles of the total field produced at ground by the assumed external source are then found and compared with the measured gdv data results are applied to equatorial zones in peru africa and india

a three dimensional numerical model study of electromagnetic induction around the indian peninsula and sri lanka island abstract magnetic field variations recorded using an array of magnetometers have shown earlier significant anomalies at some southern stations of india e g annamalainagar adiramapatnam and trivandrum the nature of anomalous horizontal and vertical fields and their persistence to periods of the order of hours cannot be explained in terms of the usual coast effect alone some authors have suggested that these anomalies could be caused by the electric currents induced in the deep ocean but channelled through a good conductor situated below the palk strait and gulf of manowar between india and sri lanka to investigate the effect of such a deep conductor possibly in the lower crust or upper mantle a three dimensional model of india sri lanka and the surrounding coast lines has been studied using a numerical technique with the aid of the well known finite difference numerical method for partial differential equations solutions of the magnetic fields have been computed for two different models 1 without conductor and 2 with a conductor in the palk strait gulf of manowar region below the ocean floor the results are presented in the form of contour plots and spatial behaviour of the amplitudes of three magnetic field components h d z at the surface of the earth contour plots clearly reveal that when a highly conducting sub surface structure is introduced in the palk strait region the currents tend to flow along the direction of the conductor and contribute to enhancement of the magnetic field amplitudes along the east coast of the indian peninsula and west coast of sri lanka island the amplitude plots show that in general the numerical results for the model with the sub surface conductor tend to agree with the results of the magnetometer observations thereby supporting the hypothesis of a sub surface conducting structure between india and sri lanka

rare earth elements and neodymium isotopes in ferromanganese oxide coatings of cenozoic foraminifera from the atlantic ocean abstract an evaluation has been made of the method of establishing the ree contents and patterns and nd isotopic compositions of sea water over cenozoic time from their record in the femn oxide coatings of foraminiferal calcite using 0 60 ma samples from the rio grande rise dsdp site 357 it has been established that the ree contents of the coatings are generally similar to those of recent samples however in the cenozoic samples the surface coatings have been diagenetically modified under suboxic conditions resulting in a distinctly different ree pattern although the original 143 nd 144 nd ratios appear to have been preserved the nd isotopic curve for cenozoic sea water in the s atlantic shows clear temporal trends although these are not so extreme as to show 143 nd 144 nd ratios outside the range observed in modem sea water with the principal exception of the oldest samples there is an approximate inverse relationship between the nd and sr isotopic compositions of the foraminifera it is suggested that the changes reflect both global changes in the relative proportions of nd and sr derived from continental input and from the weathering of volcanic debris together with short term and local variations to which the sr curve is insensitive reflecting the different response times of the two elements to changes in oceanic input functions the nd isotope curve appears to be a potentially useful tracer of ocean palaeochemistry

environmental geochemistry of rare earth elements in cu porphyry mine tailings in the semiarid climate conditions of sarcheshmeh mine in southeastern iran abstract sarcheshmeh mine is one of the largest oligo miocene porphyry cu deposits in the world it is located in the kerman cenozoic magmatic arc in southeastern iran this paper discusses the geo environmental behavior of rare earth elements rees in the sarcheshmeh dammed tailing pond situated in semiarid climate for this purpose solid and water samples were collected to consider 1 weathering oxidation reactions and upward migration of soluble elements 2 super saturation and formation dissolution of the secondary evaporative phases 3 hydro geochemical changes of the surface and groundwater resources 4 flotation of the cu sulfide ore and tailing management strategies the mean values of the rees for fresh and weathered tailings and the evaporative phases were 113 0 103 7 and 74 6 mg kg respectively when compared with the fresh and weathered tailings the evaporative phases showed significant enrichment of hrees and a well depleted pattern of lrees except for that of eu this geochemical pattern suggests a higher solubility and mobility potential of hrees and eu compared with lrees resulting in good fractionation and enrichment of these elements in the surface evaporative layer formed on top of the weathered tailings the water samples showed a range of hydro geochemical features under acidic ph of 2 5 to 4 7 near neutral ph of 6 4 to 7 9 alkaline ph of 8 to 10 and highly alkaline ph 10 conditions the maximum concentration of rees was observed in the acidic waters produced by the weathered tailings after rainfall rees of 489 to 1903 g l although rees decreased as the ph value increased the general trend was compatible with the highest concentration of hrees rather than lrees the speciation calculations indicate that lnso4 ln so4 2 and ln3 are the primary forms of dissolved rees at acidic and near neutral ph and the dominant species was lnso4 lnco3 40 78 ln co3 2 31 68 and lnso4 31 07 were the dominant species under alkaline conditions at high alkaline ph the speciation pattern changed to lnoh2 53 15 ln co3 2 44 88 and lnco3 2 61 where ln denotes lanthanide based on the results and considering previous works it appears that ionic potential plays an important role in the geo environmental behavior of rees of adsorption tendency mobility potential and ionic substitution

the gravity field over the ungava bay region from satellite altimetry and new land based data implications for the geology of the area gravity data were obtained along two transects on the southern coast of ungava bay which provide continuous gravity coverage between leaf bay and george river the transects and the derived gravit

the trace metal geochemistry of the lake tyrrell system brines victoria australia abstract we have analyzed the waters of the lake tyrrell system for the trace metals fe mn pb cu and zn in a number of samples both dissolved fe t and fe 2 were also determined great care was exercized to minimize any contamination of the samples not surprisingly the highest metal concentrations occur in the low ph high eh regional groundwaters with much lower values observed in the reflux brines and the neutral wahpool timboram waters it is thought that the source of these metals to the groundwaters is the dissolution of a suite of heavy minerals within the aquifer the pliocene parilla sand as the acid groundwaters flow toward the lake some metals are removed near lake edge at depth the metal concentrations in the spring zone region indicate an extremely dynamic system where at different times of the year due to changes in the hydrologic regime metals can be either removed or solubilized

geochemical processes affecting the acidic groundwaters of lake gilmore yilgarn block western australia a preliminary study using neodymium samarium and dysprosium neodymium samarium and dysprosium concentrations were determined in groundwaters along a transect of lake gilmore sediments from the shoreline toward the playa center with the future intention of employing the whole suite of rare earth elements ree two different water bodies were identified in the groundwater playa system based on the neodymium samarium and dysprosium concentrations and associated ph and salinity values shallow groundwaters that discharge along the playa margins had the highest concentrations of these elements and the lowest ph and salinity a more saline entrained brine was identified toward the middle of the playa with higher ph values and the lowest observed concentrations of neodymium samarium and dysprosium groundwaters with transitional neodymium samarium and dysprosium values ph and salinity were also recorded along the transect the data suggest that the acidic shallow groundwaters remove ree from the surrounding granitic rocks of the yilgarn block and introduce them into the playa where they are removed from solution as the ph of the system increases evaporative concentration does not appear to have a significant effect on the ree concentrations in the lake gilmore system other factors such as increasing ph and scavenging of ree by iron oxyhydroxides which precipitate as ph rises appear to exert more control on ree concentrations in the groundwaters by removing them from solution

geophysical interpretation of the torngat orogen along the north river nutak transect labrador a 19 3 mgal 1 gal 1 cm s2 positive bouguer gravity anomaly and a broad aeromagnetic low coincide with the tasiuyak domain of the early paleo proterozoic torngat orogen the domain evolved during the collision of the western margin of the archean nain province with an inferred eastward facing platform to rise sedimentary wedge sited on a proto continent of churchill rae province a density contrast of 0 065 g cm 3 was measured between rocks of the tasiuyak domain and those of the flanking lac lomier complex of the orogen and nain province using this contrast a two and one half dimensional model shows that rocks of tasiuyak domain constitute a triangular prismatic body with maximum thickness of 13 km adjacent to nain province which thins westward to a feather edge the model is compatible qualitatively with the aeromagnetic anomaly and consonant with geological interpretation of an eastward facing and thickening continental slope deposit deep exhumation of the torngat orogen may account for t

ultimate removal mechanisms of elements from the ocean abstract the surface complex formation model can adequately explain the observed partitioning of most of the elements between seawater and pelagic clays and between river water and river suspended particles the adsorption of elements on the hydrous oxide surface of iron oxide manganese oxide and clay minerals is the most important ultimate removal mechanism of most of the elements from the ocean

development and application of a sensitive and rapid analytical method to determine the rare earth elements in surface waters abstract a new cost effective method to determine the 14 rare earth elements ree s in waters to levels as low as 0 2 1 0 ng l 1 ppt has been established inductively coupled plasma mass spectrometry icp ms is used for measurement following automated preconcentration using the dionex metpac cc 1 resin of iminodiacetate functionality the free ree ion is chelated onto the resin while alkali and alkaline earth elements are washed through and separated enabling the method to be applied to seawater as well as fresh water the eluant 0 8 m hno 3 provides an ideal medium for analysis by icp ms and the suite of elements determined can be expanded to include first row transition elements cd pb and u based on replicate analyses of control samples and data for field and laboratory duplicate samples lakes and streams relative standard deviations are better than 10 except where concentrations are below 5 ng l 1 application of this method to 135 lake waters in the baie d espoir region of newfoundland indicates a contamination is not introduced from sampling bottles nalgene lpe or during the filtering and acidification process even at low ng l 1 levels b there is a high degree of correlation in element distribution patterns between lake waters and their corresponding centre lake sediments for yb and tb c the chondrite normalized plots for water and sediment are similar in shape and show consistent patterns within geological units but are distinct between such units and d the powerful potential of ree concentrations in surface water for geochemical mapping

geophysical correlations in the ungava bay area we used gravity and magnetic data to extend geological features across ungava bay and hudson strait from northern quebec and labrador to baffin island tectonic domains identified on land were extended offshore by visual inspection of the potential fields the boundaries identified on colour shaded relief maps were drawn on the original marine magnetic profiles to verify the robustness of the conclusions our interpretation in ungava bay remains speculative but gives some insight into the architecture of the northeastern canadian shield onshore where trends are well marked the magnetic fabric of the superior province reappears east of the new quebec orogen in the western core zone geochronology and geochemical data also suggest the affinity of the western core zone with the superior province on the gravity map the new quebec orogen appears to vanish offshore a major trend in magnetic and gravity gradients can be followed offshore possibly as far north as hudson strait it has been identified as the extension of the george river and moonbase shear zones the de pas batholith is associated with a linear trend west of this shear zone to the east several features appear distinctly in the magnetic map a narrow northwest trending anomaly can be followed from quebec all the way to baffin island on land this feature marks the western limit of the lake harbour group two wide north trending bands that can be followed from the torngat orogen all the way to baffin island are interpreted as the extensions of the lac lomier complex and tasiuyak domain resume nous avons utilise des donnees gravimetriques et magnetiques pour prolonger les caracteristiques geologi ques a travers la baie d ungava et le detroit d hudson du nord du quebec et du labrador jusqu a l ile de baffin les domaines tectoniques identifies sur terre ont ete prolonges au large par une inspection visuelle des champs de poten tiels les limites indiquees sur des cartes topographiques en couleurs ont ete tracees sur les profils magnetiques marins originaux afin de verifier la solidite des conclusions dans la baie d ungava notre interpretation demeure speculative mais elle donne un apercu de l architecture du nord est du bouclier canadien sur terre ou les tendances sont bien marquees la texture magnetique de la province du superieur reapparait a l est de l orogene du nouveau quebec dans la zone noyau occidentale la geochronologie et les donnees geochimiques suggerent aussi une affinite entre la zone noyau occidentale et la province du superieur sur la carte gravimetrique l orogene du nouveau quebec semble dispa raitre vers le large une tendance majeure dans les gradients magnetiques et gravimetriques peut etre suivie au large possiblement aussi loin que le detroit d hudson cette tendance a ete identifiee comme la prolongation des zones de ci saillement de la riviere george et de moonbase le batholite de depas est associe a une tendance lineaire a l ouest de cette zone de cisaillement vers l est plusieurs caracteristiques sont distinctes sur la carte magnetique une etroite ano malie a tendance nord ouest peut etre suivie de quebec jusqu a la terre de baffin sur terre cette caracteristique marque la limite ouest du groupe de lake harbour deux larges bandes a tendance nord qui peuvent etre suivies de l orogene torngat jusqu a l ile de baffin sont interpretees comme etant des extensions du complexe du lac lomier et du domaine de tasiuyak

mobility and fractionation of rare earth elements during supergene weathering and gossan formation and chemical modification of massive sulfide gossan primary massive sulfide gossans msg in the bathurst mining camp bmc new brunswick canada are characterized by relative enrichment of au sb and as formation of jarosite group minerals jarosite plumbojarosite and argentojarosite and little or no fractionation in the rare earth elements ree including preservation of large positive eu anomalies average eu eu nasc 4 14 in msg 6 61 in massive sulfide mineralization 0 60 in host rocks the chemical and mineralogical characteristics of msg e g halfmile lake deposit imply low ph 3 and relatively oxidizing conditions during gossan formation oxidation of a volcanogenic massive sulfide body comprising pyrite pyrrhotite sphalerite galena and chalcopyrite with a falling water table the lack of light ree or heavy ree fractionation and preservation of positive eu anomalies characteristic of the original 465 ma hydrothermal fluid is consistent with relatively large water rock ratios during massive sulfide mineralization oxidation and removal of the ree predominantly as sulfate complexes lnso4 ln so4 2 low ph groundwaters recovered from past producing mines in the bmc display ree patterns reflecting those inferred to have occurred during gossan formation gossan at the restigouche deposit in contrast to the halfmile lake deposit displays mineralogical and chemical evidence for having been chemically reworked since primary gossan formation evidence for chemical reworking includes loss of primary massive sulfide mineralization textures replacement of plumbojarosite with anglesite almost complete removal of jarosite minerals loss of au sb and as and apparent preferential removal of eu resulting in loss of positive eu anomalies for most samples average eu eu nasc 1 21 in the gossan with many displaying strong negative anomalies 3 65 in massive sulfide mineralization 0 54 in host rocks based on geochemical modeling conditions inferred for the chemical reworking of the restigouche deposit include near neutral conditions and either relatively oxidizing conditions with eu2 hosted in a preferentially weathered mineral host possibly through substitution for pb in plumbojarosite and beudantite or cycling between reduced and oxidized conditions during gossan reworking

hydrochemistry on the yilgarn block western australia ferrolysis and mineralisation in acidic brines abstract in the southeastern part of western australia internal drainage and a semi arid climate have resulted in extensive development of playas the brines beneath the playas wedge outwards and force local infiltration to crop out at playa margins as discharge zones the discharging water contains dissolved fe2 oxidation and hydrolysis ferrolysis of which generates very acidic water ph 2 8 at least some of the alkalinity generated by the original reduction of fe3 has been sequestered as subsurface calcrete within local soils the acidity causes the dissolution of kaolinite which is abundant in playa sediments and as a thick capping on weathered bedrock giving water with a low ph and high concentrations of dissolved al and si evaporation and mixing with playa brines containing high concentrations of k and so4 causes alunite to precipitate as ph rises from a minimum of 2 8 at chlorinities of 1 to 2 m to 6 at chlorinities of 4 8 m the alunite deposits formed by this process are many orders of magnitude larger than occurrences elsewhere in the world the large scale mobilisation of si during this process may be one mechanism for the formation of silica cemented rocks silcrete that are widespread in the australian regolith

the geochemistry of rare earth elements ree in acid mine drainage from the sitai coal mine shanxi province north china abstract in this paper geochemical characteristics of rare earth elements ree in acid mine drainage amd from the sitai coal mine of shanxi province north china were investigated by determining concentrations of dissolved rees and major solutes in the amd samples concentrations of rees in the amd precipitate samples and country rock samples mudstone and coal and modeling rees species in the amd the results show that amd in the sitai coal mine have high rees and so42 concentrations in comparison with several terrestrial waters worldwide the ree speciation modeling indicates that sulfate complexes lnso4 60 and free metal species ln3 20 40 are dominant rees species in the amd amd of the sitai coal mine also shows a middle ree enriched nasc north american shale composite normalized pattern the authors suggest that both ree sulfates lnso4 in the amd and country rock of coal measures are possible reasons for middle ree enriched nasc normalized pattern of the sitai coal mine amd further work on the amd precipitates is needed to obtain more information on the origin of the middle ree enriched nasc normalized patterns

naturally acid waters from copahue volcano argentina volcanic acid sulfate chloride brines form through absorption of volcanic vapors in shallow reservoirs of meteoric water reaction with surrounding volcanic rocks leads to partial neutralization of the fluids and precipitation of secondary minerals chemical data of such acid waters from copahue volcano argentina covering 8 years of observations show evidence for changes in composition related to water rock interaction at depth prior to emergence of the fluids at the surface the chemical composition changed dramatically during the 2000 eruption of copahue with enhanced concentrations and fluxes of mg na fe and al followed in 2001 by rapidly declining concentrations and element fluxes the subsequent 5 years saw more variable element ratios and strong depletions in k and al most incompatible elements are released from the rock matrix stochiometrically whereas some elements are enriched through vapor input from the magma as pb zn most fluids have lree enrichments relative to the rock matrix but during periods of new magma intrusion the lree enrichment decreases as does the magnitude of the negative eu anomaly in the fluids these observations are interpreted assuming early dissolution of plagioclase olivine and volcanic glass that occurs during intrusion of new magma into the hydrothermal system the high field strength elements are virtually immobile even in these hot acid fluids with nb and ta more so than hf and zr the mobility of u and th in these fluids is comparable at variance with th behavior in neutral fluids the local rivers and lakes of copahue are fertilized by volcanic dissolved p and most surface waters with ph 3 have high levels of as the acid fluids from copahue may be surficial analogs for deep subduction fluids that evolve below zones of arc magma generation as well as for early mars environments that are thought to have had large acid lakes