regional variations in fluid formation and metal sources in mvt mineralization in the pennine orefield uk implications from rare earth element and yttrium distribution sr nd isotopes and fluid inclusion compositions of hydrothermal vein fluorites abstract the pennine orefield is one of the most important ore fields for pb zn ba f mineralization in great britain it is subdivided into the northern pennine orefield npo consisting of the alston and askrigg blocks and the southern pennine orefield spo the alston block is underlain by the early devonian weardale granite and the askrigg block by the coeval wensleydale granite the potential relationship between the batholiths and the mineralization is a matter of debate we here studied the rare earth elements and y rey geochemistry sr nd isotopes and fluid inclusion fi compositions of fluorites from the two structural blocks in the npo and found that the fluorite mineralization in these blocks differ substantially the rey in askrigg fluorites show features that are characteristic for leaching of adjacent lower carboniferous limestones in contrast alston fluorites have significantly higher rey concentrations lack reysn limestone signatures and show a decoupling of redox sensitive eu from its trivalent rey neighbours neodymium isotopes indicate a similar crustal source of rey in both blocks but higher rey concentrations and lower y ho ratios suggest lower carboniferous shales as potential rey source in the alston block the fluids that precipitated the alston fluorites experienced temperatures 250 c prior to mineral formation as evidenced by eu geothermometry fluorite formation however occurred at much lower temperatures as suggested by homogenization temperatures in fi that fall within ranges of 105 159 c in alston and 99 160 c in askrigg fluorites mineralization of the mississippi valley type usually lack association with igneous activity we show that some of the fluids responsible for the npo mineralization were influenced by magmatic sources the rey systematics in alston fluorites may be linked to an interaction of the permian age whin sill dolerite with the basement granite which heated fluids and focussed fluid flow into the overlying sedimentary rocks in the askrigg block where such a dolerite intrusion was not described fluorites lack any positive eusn anomalies indicating that these fluids had never been subjected to temperatures exceeding 200 250 c

oxidative mobilization of cerium and uranium and enhanced release of immobile high field strength elements from igneous rocks in the presence of the biogenic siderophore desferrioxamine b abstract polyvalent trace elements such as the high field strength elements hfse are commonly considered rather immobile during low temperature water rock interaction hence they have become diagnostic tools that are widely applied in geochemical studies we present results of batch leaching experiments focused on the mobilization of certain hfse y zr hf th u and rare earth elements from mafic intermediate and felsic igneous rocks in the presence and absence respectively of the siderophore desferrioxamine b dfob our data show that dfob strongly enhances the mobility of these trace elements during low temperature water rock interaction the presence of dfob produces two distinct features in the rare earths and yttrium rey patterns of leaching solutions regardless of the mineralogical and chemical composition or the texture of the rock type studied bulk rock normalized rey patterns of leaching solutions with dfob show i a very distinct positive ce anomaly and ii depletion of la and other light rey relative to the middle rey with a concave downward pattern between la and sm these features are not observed in experiments with hydrochloric acid acetic acid or deionized water in dfob bearing leaching solutions ce and u are decoupled from and selectively enriched relative to light rey and th respectively due to oxidation to ce iv and u vi oxidation of ce3 and u4 is promoted by the significantly higher stability of the ce iv and u vi dfob complexes as compared to the ce iii and u iv dfob complexes this is similar to the relationship between the ce iv and ce iii pentacarbonate complexes that cause positive ce anomalies in alkaline lakes however while formation of ce iv carbonate complexes is confined to alkaline environments ce iv dfob complexes may produce positive ce anomalies even in mildly acidic and near neutral natural waters siderophore promoted dissolution processes also significantly enhance mobility of other immobile hfse and may not only cause or modify ce anomalies and th u fractionation but also mobilization of and fractionation between zr hf th and redox insensitive rey during weathering pedogenesis diagenesis and incongruent dissolution of particles in seawater and freshwater siderophores may significantly affect the use of hfse as geochemical tools concave downward light rey patterns may be used as a biosignature for water rock interaction in the presence of siderophores enhanced and preferential mobilization of u relative to th in the presence of siderophores may produce th u signals comparable to those indicative of weathering under oxidized conditions which might constrain the use of u concentrations and th u ratios as a paleoredox proxy the enhanced mobilization of zr and especially hf from igneous rocks in the presence of dfob might have implications for the use of the latter as a tracer for the impact of continental weathering on seawater chemistry because siderophore complexes affect the particle reactivity of hf and zr they may prevent effective removal of terrigenous hf and zr during aggregation coagulation of riverine particles in estuaries siderophore promoted solubilization and stabilization might hence be an additional way to transport continental hf and zr to the oceans furthermore siderophore enhanced mobilization may also have implications for the remediation techniques employed to immobilize hfse such as u th and rey at nuclear waste and reprocessing sites and at rey ore processing plants where soils are commonly contaminated with these sometimes radioactive heavy metals

mountain ordering a method for classifying mountains based on their morphometry a new method for classifying mountain morphology mountain ordering is proposed and quantitative expressions for various morphological parameters of two ordered mountains in northern japan were obtained using this method mountain order was defined in terms of the closed contour lines on a topographic map a set of closed concentric contour lines defines a first order mountain higher order mountains can be defined as a set of closed contour lines that contain lower order mountains and that have only one closed contour line for each elevation they are identified as m 1th order mountains where m represents the order of the enclosed lower order mountains the geomorphometry for a mountain ordered according to this definition permits the identification of systematic relationships between various morphological parameters the relationships between mountain order and these morphological parameters follow a form similar to that of horton s laws and permit the calculation of the ratios of number area and height these parameters are sufficient to express the magnitude of a mountain s dissection the size frequency distribution for area and height shows self similarity for ordered mountains and determines their fractal dimensions furthermore the relationship between area and height which has the form of a power function describes the relief structure of ordered mountains copyright 1999 john wiley sons ltd

petrology and oxygen isotope geochemistry of a fossil seawater hydrothermal system within the solea graben northern troodos ophiolite cyprus hydrothermal mineral zonations and o isotope patterns of the northern troodos complex do not parallel the ophiolite pseudostratigraphy but reflect the convective geometry of an upper cretaceous seawater hydrothermal system large areas of the sheeted intrusive complex sic including the subaxial region of the solea graben are composed of 18o rich subgreenschist mineral assemblages and may represent regions of diffuse seawater recharge other areas of the sic are recrystallized to distinctive epidosite rocks granular high variance assemblages of epidote quartz chlorite that are depleted in 18o al2o3 na2o k2o zr cu and zn and are enriched in cao and sr compared with other mafic volcanic and dike rocks of the solea graben epidosite alteration occurred at temperatures of 310 370 c and involved fluids with 18o values and salinities similar to those of upper cretaceous seawater the epidosite zones are discordant with earlier mineral o isotope zonations and with the axis of spreading in the solea graben suggesting a postspreading off axis origin the seawater hydrothermal system responsible for solea graben massive sulfide deposits was probably driven by hypabyssal intrusions not exposed emplaced in a terminal failed spreading episode the geometries of o isotope surfaces within the solea graben imply that the epidosites formed in fossil upflow and deep recharge conduits depletions in base metals show that epidosite alteration liberated cu and zn to mineralizing fluids within the fossil upflow zone

methods for determining deformation history for chocolate tablet boudinage with fibrous crystals abstract chocolate tablet boudinage with fibrous crystal growths between the boudinaged plates from two localities were studied in one from leytron valais switzerland the deformation history was found to be a succession of plane strain increments with the shortening direction perpendicular to the boudinaged sheet and the extension direction showing a progressive change in orientation within the sheet the incremental and finite strains were evaluated the other specimen from parys mountain anglesey great britain was found to have a more complex history with diachronous break up of the competent layer and flattening strain increments it was found that under these circumstances the direct graphical methods of determining finite and incremental strains gave inconsistent results a numerical model was developed which allowed the simulation of chocolate tablet structure with a complex deformation history the model was applied to the anglesey specimen and three possible strain histories for this structure were tried

characterization of lacustrine mixed fine grained sedimentary rocks using coupled chemostratigraphic petrographic analysis a case study from a tight oil reservoir in the jimusar sag junggar basin abstract mixed deposits are sediments consisting of external clastic epiclastic or terrigenous intrabasinal components and pyroclastic components the mixture comprising variable amounts of the three components is defined as mixed sedimentary rocks the permian lucaogou formation p2l in the jimusar sag of the junggar basin is a promising tight oil target in western china the fine grained mixed sedimentary rocks of which are rich in organic matter om and two sweet spot intervals with relatively high porosity however the sediment composition provenance and deposition environmental settings have not been studied in detail in this study coupled chemostratigraphic petrographic analysis were used to reconstruct their depositional environments the results show that the fine grained sedimentary rocks have three major sediment sources external clastic input terrigenous clastics intrabasinal autochthonous to parautochthonous components carbonates siliceous skeletal debris and om and pyroclastic input main lithofacies include siltstone fine sandstone mudstone dolomite and tuffite the silt sandstones were mainly sourced from rocks with calc alkaline composition while the tuffaceous sedimentary rocks were sourced from high k calc alkaline rocks elemental proxies suggest that the carbonate rocks were generally deposited under warm and arid conditions whereas the fine grained clastic sediments were deposited under relatively humid conditions the muddy or silty tuffaceous mixed rocks were deposited under relatively reducing conditions compared with carbonates and sandstones variations of lithofacies and om accumulation of different intervals reflect changing deposition environmental settings and the frequently altered high toc content rocks and good reservoirs are benefit for tight oil formation the work may provide some useful insights and serve as a reference for studying other mixed fine grained sedimentary rocks and tight oil plays in similar lacustrine basins elsewhere

geochemical implications of rare earth element patterns in hydrothermal fluids from mid ocean ridges abstract rare earth element data are reported for vent fluids collected from eight deep sea hydrothermal areas including samples from sediment hosted and bare rock hydrothermal systems the morb normalized ree patterns from these diverse settings are remarkably similar to each other but distinctly different than seawater or basalt being lree enriched and possessing a strikingly positive eu anomaly the ree concentrations making up these patterns vary widely however both on a spatial and temporal basis when plotted against ionic radii these fluid trends are remarkably linear and show the same fractionation patterns exhibited by plagioclase during magma segregation this analysis suggests that the partitioning of the ree between fluid and rock during high temperature hydrothermal alteration of morb is dominated by crystochemical exchange during dissolution and recrystallization reactions at the exposed surfaces of plagioclase phenocrysts a comparison of ree ionic radii in eight coordination indicate that the partitioning of 3ree and 2eu are dominated by chemical substitution for ca 2 and sr 2 respectively these considerations predict that the total 3ree content of vent fluid varies in a systematic way during the transition from an rich morb plagioclase to ab rich hydrothermal plagioclase and that these parameters can be used as indicators of the average extent of alteration inside active hydrothermal systems

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

trace and rare earth element ree characteristics of mudstones from eocene pinghu formation and oligocene huagang formation in xihu sag east china sea basin implications for provenance depositional conditions and paleoclimate abstract the interpretation of depositional conditions provenance and paleoclimate provide important information to understand hydrocarbon source rock formation and distribution the concentrations of trace elements and rare earth elements rees of fifty mudstone samples from eocene pinghu formation and oligocene huagang formation in xihu sag east china sea basin were determined by inductively coupled plasma mass spectrometry icp ms to test the depositional conditions provenance and paleoclimate evidences from the visual comparisons of the simple bivariate plots diagrams and statistical comparisons of the mann whitney rank sum test suggest that there may be a common source for the pinghu formation and huagang formation mudstones sedimentary provenance from bivariate plots diagrams of hf versus la th and la sc versus co th shows that pinghu formation mudstones are mainly composed of mixed felsic basic source and acidic source whereas huagang formation is mainly acidic source additionally the ree vs la yb discrimination diagram shows that the property of the provenance for the pinghu formation mudstones consists sedimentary rock alkaline basalt and a small amount of continent tholeiitic basalts whereas that of the huagang formation is mainly alkaline basalt and sedimentary rock discriminant diagrams consisting of la th sc and th co zr 10 suggest that the mudstones of two formations were deposited in continental island arc and active continental margin tectonic setting redox proxies v ni v v ni and ce indicate that most of the mudstones of two formations were deposited in a relatively dysoxic anoxic condition the cool and humid climate represented by sr cu and rb sr ratios were prevailing in xihu sag during the eocene and oligocene period and the oligocene was cooler than eocene moreover five long term base level cycles siii1 siii5 and four sequence boundaries sb2 sb5 were recognized in the pinghu formation and huagang formation based on the previous research we find that the abnormal surfaces of geochemical parameters such as v ni sr ba u ti v ti ti and ree to some extent agree with sequence boundaries sb2 sb3 sb4 and sb5 in mudstones additionally the increment of ti and ree concentrations and the decrease of sr ba v ni u ti and v ti ratios above the sb4 indicates that terrigenous clast grew significantly and the sea level dropped after late eocene which is related with the late eocene tectonic movement

rare earth element distribution in 400 c hot hydrothermal fluids from 5 s mar the role of anhydrite in controlling highly variable distribution patterns abstract two submarine hydrothermal vent fields at 5 s mid atlantic ridge mar turtle pits and comfortless cove emanate vapor phase fluids at conditions close to the critical point of seawater 407 c 298 bars in this study the concentration and distribution of rare earth element ree and yttrium y has been investigated independent of the major element composition the fluids display a strong temporal variability of their ree y concentrations and relative distributions at different time scales of minutes to years chondrite normalized distributions range from common fluid patterns with light ree enrichment relative to the heavy ree accompanied by positive eu anomalies type i to strongly ree y enriched patterns with a concave downward distribution with a maximum enrichment of sm and weakly positive or even negative eu anomalies type ii the larger the sum of ree the smaller cecn ybcn and eu eu we also observed a strong variability in fluid flow and changing fluid temperatures correlating with the compositional variability as evident by the positive correlation of total ree ca and sr concentrations in turtle pits and comfortless cove fluids precipitation dissolution of hydrothermal anhydrite controls the variability in ree concentrations and distributions in these fluids and the transformation of one fluid type to the other the variable distribution of ree can be explained by the accumulation of particulate anhydrite with concave downward ree distribution and negative eu anomaly into a fluid with common ree distribution type i followed by the modification of the ree fluid signature due to dissolution of incorporated anhydrite a second model in which the type ii fluids represent a primary ree reaction zone fluid pattern which is variably modified by precipitation of anhydrite can also explain the observed correlations of total ree fractionation of lree hree and size of eu anomaly as well as ca sr the emanation of such a fluid may be favored in a young hydrothermal system in its high activity phase with short migration paths and limited exchange with secondary minerals however this model is not as well constrained as the other and requires further investigations the strongly variable ree fluid signature is restricted to the very hot actively phase separating hydrothermal systems turtle pits and comfortless cove at 5 s and has not been observed at the neighboring red lion vent field which continuously emanates 350 c hot fluid and displays a stable ree distribution type i

the aqueous geochemistry of the rare earth elements and yttrium 4 monazite solubility and ree mobility in exhalative massive sulfide depositing environments abstract although there is considerable evidence that rare earth elements ree and particularly the light ree lree have been mobile in the alteration zones below many massive sulfide deposits there is some disagreement over the cause of this mobility most researchers have argued or implied that the ree were mobilized by analogues of modern seafloor hydrothermal vent fluids however the few measurements that have been made of the ree concentrations of these modern fluids suggest that their ability to mobilize ree is negligible in order to shed further light on this problem we have carried out calculations of monazite solubility monazite is thought to be the principal host for the lree in a model vent fluid at temperatures from 200 to 300 c these calculations show that at 300 c the model fluid will contain 0 08 ppb ce 0 07 ppb la and 0 03 ppb nd at 200 c the concentrations increase to 0 54 ppb 0 37 ppb and 0 15 ppb respectively a decrease in ph of one unit at 300 c also increases ree solubility significantly 7 4 ppb ce 5 7 ppb la and 1 1 ppb nd these solubilities are similar to the concentrations of ree measured in seafloor hydrothermal vent fluids however they are considerably lower than required to account for the scale of ree mobility in alteration zones associated with massive sulfide deposits if the mass ratio of typical hydrothermal vent fluid to rock reached 1000 concentrations of ree in the altered rock the predicted to be in the range

experimental geochemical mineralogical and o isotope constraints on the late magmatic history of the fichtelgebirge granites germany mineralogical experimental geochemical and stable isotope data give evidence for an aqueous late stage fluid which develops increasingly from the less to the more highly evolved granites of the fichtelgebirge g1 g4 in less evolved granites particularly g1 only minor chloritization and sericitization minor hydration and corrosion of zircons low leachable fractions of sr and zr the nearly chondritic ratios of zr hf and y ho and rare earth element ree patterns lacking the tetrad effect provide evidence of a less differentiated granitic melt system poor in complexing agents and water with insignificant late magmatic fluid rock interaction the subsequent low temperature alteration which is suggested by oxygen isotope composition of quartz and biotite did not affect the whole rock chemical composition in the highly evolved granites particularly g4 albitization sericitization and fluoritization ubiquitous hydration and corrosion of zircons high leachable fractions of sr and zr zr hf and y ho ratios very different from the chondritic ratios and ree patterns showing a marked tetrad effect point to the presence of a highly specialized fluid system rich in water and complexing agents such as fluorine leading to a marked magmatic hydrothermal alteration the oxygen isotopes also indicate alteration by high temperature fluids which were likely exsolved during the final stage of crystallization

geochemical characterization of highly diverse hydrothermal fluids from volcanic vent systems of the kermadec intraoceanic arc abstract during the r v sonne cruise so253 in 2016 2017 hydrothermal vent sites along the kermadec intraoceanic arc were sampled for hydrothermal fluids at four active volcanoes macauley haungaroa brothers and rumble iii respectively water depths ranged between 290 m and 1700 m a new vent field was discovered at haungaroa the samples were taken from diffuse flow sites as well as from white and black smokers rich in metals and gases with discharge temperatures as high as 311 c their fluid composition is very variable but basically divides into two types one that indicates distinct magmatic input and another that shows evidence for intense water rock interaction under hot acidic conditions fluid samples from macauley the shallowest sampling site 300 m had fe concentrations as high as 1 7 mm al concentrations up to 122 m and h2s up to 10 mm at a ph of only 1 2 at brothers the deepest sampling site down to 1600 m we identified two different fluid types 1 a magmatically influenced type at the upper and lower cone with highest temperatures of 115 c up to 95 6 mm mg the highest mg concentration measured in fluids from intraoceanic arc systems so far elevated so42 76 9 mm high h2s 5 0 mm but fe concentrations of only 15 m and 2 a fluid with low mg 5 4 mm low h2s 1 1 mm temperatures reaching 311 c and high fe contents 12 4 mm at the upper caldera and nw caldera wall typical of a black smoker fluid chloride concentrations in all fluids were similar or highly enriched when compared to seawater e g up to 787 mm brine fluids with also one low chlorinity vapor phase fluid sample recovered indicating that phase separation is occurring at brothers unusual highly elevated mg concentrations in fluids from the brothers lower cone 95 6 mm compared to 53 2 mm in ambient seawater combined with highly elevated concentrations of so42 76 9 mm compared to 29 0 mm in ambient seawater indicate dissolution of mg and so42 bearing minerals in the subsurface such as caminite our data show how highly diverse and variable island arc systems can be with respect to their fluid chemistry both spatially and temporally it adds to the still limited data set of arc systems compared to mid ocean ridges and supplies an important contribution towards a better understanding of geochemical processes along arc volcanoes the higher range in fluid chemistry together with shallower water depth implies that the fluids from intraoceanic arcs may contribute a significant fraction of dissolved metals not only to the global oceanic biogeochemical cycle but also into the photic zone the area of highest bioproductivity

dissolution of primary basaltic minerals in natural waters saturation state and kinetics abstract the state of saturation of olivine orthopyroxene and plagioclase of variable composition has been assessed in various types of natural waters in iceland including river waters groundwater and geothermal waters with temperatures up to 250 c the stability of olivine and orthopyroxene decreases with increasing mg content similarly the stability of plagioclase decreases with increasing anorthite content the river waters which are representative of the weathering environment are always undersaturated with both olivine and orthopyroxene the degree of undersaturation being dominated by the water ph all river waters tend to dissolve olivine of the composition encountered in basalts according to the linear rate law and orthopyroxene when the ph is 200 c are undersaturated with olivine orthopyroxene and plagioclase the first two particularly when fe rich and sufficient to cause olivine to dissolve according to the linear rate law at intermediate temperatures 50 150 c the geothermal waters are close to equilibrium with these minerals except for mg rich olivine it seems likely that dissolution of glass from basalt which is very reactive will favor stability of the igneous minerals

mobilization of ree during crustal aging in the troodos ophiolite cyprus ree data for secondary minerals from low and high temperature alteration environments in the troodos ophiolite have been determined using a combined mass spectrometry neutron activation technique smectite and analcime ree mimic fresh rock profiles and have concentrations ranging from 1 5 times chondritic values celadonite is depleted in lree and total ree relative to the rocks groundmass replacing chlorite and epidote are similar to or enriched in ree relative to fresh rocks in contrast fault related chlorite and void filling epidote are lree enriched with large positive eu anomalies and yield comparable ree profiles to those of hydrothermal fluids venting at mid ocean ridges the zeolites clinoptilolite and laumontite are also lree enriched with ree contents significantly lower than rock values carbonate is enriched in hree relative to lree and concentrations vary from 0 2 to 18 times chondritic values ree data for these minerals indicate that seawater ree contents are modified by seawater rock interaction in volcanic sequences and sheeted dykes in oceanic crust during axial hydrothermal alternation and subsequent crustal aging the absolute and relative abundances of ree in seawater derived solutions evolve in response to the precipitation of secondary minerals and the prevailing water rock ratios rocks altered at low temperatures will show no change or a decrease in ree content the lree hree ratio will reflect the proportion of smectite celadonite and carbonate in the groundmass assemblage in contrast rocks altered at high temperatures will show no change or an increase in ree the lree hree ratio will reflect the proportion of void filling and groundmass replacing chlorite and epidote in the rock

rare earth element uptake during olivine water hydrothermal interaction abstract ultramafic hosted hydrothermal vent systems link the hydrosphere with the peridotitic mantle via serpentinization here the fractionation and mobility of selected trace nd sm gd dy yb sr and ba and major cations si ca mg fe ni during seawater peridotite interaction was investigated through a series of experiments where natural olivine grains were reacted with an artificial seawater solution at a range of temperatures 15 90 c and grain size distributions no evidence for any significant olivine dissolution or precipitation of carbonate and fe oxy hydroxide phases was observed in these experiments experimental data show a strong decoupling of ree nd sm gd dy and yb from sr and ba under all experimental conditions with sr and ba remaining quantitatively in solution the ree were removed from the solution and were adsorbed onto olivine surface with kinetic rate constants i e uptake over time that increase with increasing temperature and increasing surface area i e decreasing particle size dysprosium and yb heavy ree hree were removed from solution with a faster rate than nd and sm light ree lree gadolinium is decoupled from this trend with a slower kinetic rate constant than sm the activation energies ea of ree adsorption on olivine were higher for nd and sm than dy and yb this suggests that the adsorbance of lree is generally more dependent on temperature than the hree the ea correlates well with the summed 1st 2nd and 3rd ionization energies of ree suggesting a link between kinetic rates of element adsorption and electron configuration of the 4f orbitals gadolinium has higher ea than the other analyzed ree consistent with the electron configuration of gd3 where all 4f orbitals are filled with one electron each these experimental data suggest that ree are adsorbed on the surface of olivine via inner sphere complexes under low temperature hydrothermal conditions when alteration processes are limited or extremely slow scavenging and fractionation of ree may occur within the recharge zone of peridotite hosted hydrothermal systems at relatively low temperatures

carbonate veins trace seawater circulation during exhumation and uplift of mantle rock results from odp leg 209 carbonate veins hosted in ultramafic basement drilled at two sites in the mid atlantic ridge 15 n area record two different stages of fluid basement interaction a first generation of carbonate veins consists of calcite and dolomite that formed syn to postkinematically in tremolite chlorite schists and serpentine schists that represent gently dipping large offset faults these veins formed at temperatures between 90 and 170 c oxygen isotope thermometry and from fluids that show intense exchange of sr and li with the basement 87sr 86sr 0 70387 to 0 70641 7lil svec 3 3 to 8 6 carbon isotopic compositions range to high 13cpdb values 8 7 indicating that methanogenesis took place at depth the sr li c isotopic composition suggests temperatures of fluid rock interaction that are much higher t 350 400 c than the temperatures of vein mineral precipitation inferred from oxygen isotopes a possible explanation for this discrepancy is that fluids cooled conductively during upflow within the presumed detachment fault aragonite veins were formed during the last 130 kyrs at low temperatures within the uplifted serpentinized peridotites chemical and isotopic data suggest that the aragonites precipitated from cold seawater which underwent overall little exchange with the basement oxygen isotope compositions indicate an increase in formation temperature of the veins by 8 12 c within the uppermost 80 m of the subseafloor this increase corresponds to a high regional geothermal gradient of 100 150 c km characteristic of young lithosphere undergoing rapid uplift

the effects of weathering on rare earth element y and ba abundances in tertiary basalts from southeastern australia tholeiitic basalts showing anomalously high ba y and rare earth element ree concentrations occur within the tertiary newer volcanic province of victoria and these geochemical characteristics are related to incipient alteration accompanying weathering ree and y released during weathering of basalts are retained either in secondary phosphate or clay minerals and in rocks showing very high ba concentrations the ba is present as baso4 leaching experiments suggest that glassy or fine grained rocks are more likely to release ree y and ba while more extensively altered rocks are likely to hold these elements probably because they substitute in or are adsorbed on clay minerals or because secondary baso4 and ree phosphates are resistant to acid leaching samples taken sequentially across a weathering profile in a tholeiitic basalt flow from fresh to intensively altered rock illustrate that in the very earliest stages of alteration extreme variations in the abundances of ba y and ree can occur this is reflected in the broad patterns of trace element behaviour manifested by an extensive analysed sample suite from the victorian newer volcanic province where there is no correlation between anomalous enrichments in ba y or ree and the level of incipient alteration ba anomalies are not necessarily accompanied by abnormal y and ree behaviour and this is probably because the mobility of each trace element is a function of a the ionic radius and charge of the ionic species it forms in solution b local groundwater parameters such as eh ph groundwater flux and concentrations in the groundwater of species such as so42 and c the secondary mineral assemblages developed in a particular situation sr isotopic compositions are not strongly affected by incipient weathering and do not show significant changes until alteration has progressed to the point where plagioclase begins to break down the study illustrates that relatively slight alteration at the earliest stages of weathering can produce drastic changes in the concentrations of ree y and ba and petrographic assessment of the freshness of samples is not precise enough to eliminate prior to analysis cases where these effects may be manifested where weathering has caused changes in abundance patterns these may be recognised by careful comparisons of appropriate elemental ratios e g ba rb throughout a particular analysed sample suite

rare earth element mobility in the oceanic lower sheeted dyke complex evidence from geochemical data and leaching experiments hydrothermally altered rocks from the base metal depleted reaction zone in the lower sheeted dyke complex odp hole 504b show significant losses of rare earth elements ree in extensively altered domains alteration patches while very similar in major element composition and alteration mineralogy the alteration patches have up to 50 lower ree concentrations than the surrounding weakly altered diabases in order to test if there is a dependence of ree mobility on the alteration history we carried out leaching experiments on a weakly altered diabase and an adjacent alteration patch the leaching experiments are used as a probe to identify the hosting phases of major and trace elements before and after alteration they are not designed to simulate natural alteration processes major element compositions of the leaching solutions show that small amounts 9 to 14 of the rocks and similar proportions of plagioclase amphibole and chlorite were dissolved from both rock types in contrast to the major elements up to 100 of the ree could be leached from the strongly recrystallised alteration patch after 20 h all leaching solutions were light ree enriched and had negative eu anomalies compared to the host rock geochemical modelling suggests that mainly interstitial material formerly late stage magmatic liquids and probably some apatite are the main ree sources in the rocks affected during experimental leaching dissolution of plagioclase amphibole clinopyroxene and chlorite cannot explain the ree compositions of the leachates the higher ree leachability of the heavily altered rock suggests that the extensive hydrothermal alteration resulted in a complete redistribution of the ree from lattices of the magmatic minerals to the grain boundaries of secondary minerals this can explain the marked increase in ree accessibility during ongoing alteration which finally led to ree depletions in the highly altered rock we propose that late stage interstitial material provides the most important ree source of rocks in the oceanic crust this interpretation is in contrast to a model by klinkhammer et al klinkhammer g p elderfield h edmond j m mitra a 1994 geochemical implications of rare earth element patterns in hydrothermal fluids from mid ocean ridges geochim cosmochim acta vol 58 pp 5105 5113 who suggested that the similarity in the ree patterns of plagioclase and that of hydrothermal vent fluids is a result of chemical exchange between plagioclase and hot fluids in the ocean crust our leaching results indicate that although dramatic dissolution of plagioclase occurred it did not control the ree patterns of the leachates moreover ree patterns inferred for fluids that mobilised ree from the highly altered rock are different from those of vent fluids we therefore propose that the characteristic ree pattern of vent fluids may result from differences in aqueous chloride complex stabilities sorption controlled ree fractionation during fluid migration and mineral precipitation in the discharge zone

determination of easily accessible metal fractions in rocks by batch leaching with acid cation exchange resin the easily accessible fraction of metals in rocks is derived from leaching experiments aliquots of rock powders are mixed with ion exchange resin and distilled water the ph self adjusts to a value of 3 after batch leaching times of 2 48 hr at 70 c the resin is quantitatively separated from the rock powder and eluted with 4 n hno3 the metal contents of the leachates are determined and related to the respective contents of the whole rock the leaching kinetics of each element is related to that of a reference element aluminium is most commonly chosen as a reference element because it is considered to represent the dissolution behaviour of the main rock forming minerals the easily accessible trace element fraction eat is given as the percentage of leached element at 1 al dissolution these eat values are reproducible and independent from grain size and sample resin ratio the procedure is tested on basaltic glass and variably altered gneisses the glass shows congruent release of all metals a slightly crystalline glass of the same chemical composition displays heterogeneous leaching behaviour the leaching kinetics of variably altered gneisses provide insight into the mineralogical siting of elements and their accessibility to fluids consequences for rb sr dating of rocks are discussed

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

partition coefficients of hf zr and ree between zircon apatite and liquid concentration ratios of hf zr and ree between zircon apatite and liquid were determined for three igneous compositions two andesites and a diorite the concentration ratios of these elements between zircon and corresponding liquid can approximate the partition coefficient although the concentration ratios between apatite and andesite groundmass can be considered as partition coefficients those for the apatite in the diorite may deviate from the partition coefficients the hree partition coefficients between zircon and liquid are very large 100 for er to 500 for lu and the hf partition coefficient is even larger the ree partition coefficients between apatite and liquid are convex upward and large d 10 100 whereas the hf and zr partition coefficients are less than 1 the large differences between partition coefficients of lu and hf for zircon liquid and for apatite liquid are confirmed these partition coefficients are useful for petrogenetic models involving zircon and apatite

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

rare earth element geochemistry of hydrothermal deposits from the active tag mound 26 n mid atlantic ridge the rare earth element ree geochemistry of various phases from the active tag hydrothermal mound has been examined and related to their mineralogy and fluid chemistry the mound deposits range from black and white smoker chimneys massive anhydrite sulphide mixtures oxides and ochres all phases except black smoker chimney anhydrite demonstrate a positive eu anomaly when normalised to chondrite ree values ree substitution into sulphide and sulphate phases appears to be strongly influenced by crystallographic control for all ree other than eu precipitation of anhydrite within the tag mound is the major mechanism for removal of ree during mound circulation and 0 15 0 35 g anhydrite is inferred to precipitate from every kg of fluid venting from the white smoker chimneys oxides from the mound fall into three different categories with distinct ree patterns oxide rims on sulphides atacamite bearing oxides and silica rich fe oxides and ochres the oxide rim phases contain sulphide and seawater derived rees whereas the atacamite bearing oxides and the ochreous material exhibit no seawater signature which suggests precipitation from or alteration by a modified hydrothermal fluid

ree controls in ultramafic hosted mor hydrothermal systems an experimental study at elevated temperature and pressure a hydrothermal experiment involving peridotite and a coexisting aqueous fluid was conducted to assess the role of dissolved cl and redox on ree mobility at 400 c 500 bars data show that the onset of reducing conditions enhances the stability of soluble eu 2 species moreover eu 2 forms strong aqueous complexes with dissolved cl at virtually all redox conditions thus high cl concentrations and reducing conditions can combine to reinforce eu mobility except for la trivalent ree are not greatly affected by fluid speciation under the chemical and physical condition considered suggesting control by secondary mineral fluid partitioning lree enrichment and positive eu anomalies observed in fluids from the experiment are remarkably similar to patterns of ree mobility in vent fluids issuing from basalt and peridotite hosted hydrothermal systems this suggests that the chondrite normalized ree patterns are influenced greatly by fluid speciation effects and secondary mineral formation processes accordingly caution must be exercised when using ree in hydrothermal vent fluids to infer ree sources in subseafloor reaction zones from which the fluids are derived although vent fluid patterns having lree enrichment and positive eu anomalies are typically interpreted to suggest plagioclase recrystallization reactions this need not always be the case

boiling vapour type fluids from the nifonea vent field new hebrides back arc vanuatu sw pacific geochemistry of an early stage post eruptive hydrothermal system in 2013 high temperature vent fluids were sampled in the nifonea vent field this field is located within the caldera of a large shield type volcano of the vate trough a young extensional rift in the new hebrides back arc hydrothermal venting occurs as clear and black smoker fluids with temperatures up to 368 c the hottest temperatures measured so far in the western pacific the physico chemical conditions place the fluids within the two phase field of nacl h2o and venting is dominated by vapour phase fluids with cl concentrations as low as 25 mm the fluid composition which differs between the individual vent sites is interpreted to reflect the specific geochemical fluid signature of a hydrothermal system in its initial post eruptive stage the strong cl depletion is accompanied by low alkali cl ratios compared to more evolved hydrothermal systems and very high fe cl ratios the concentrations of rey 180 nm and as 21 m in the most cl depleted fluid are among the highest reported so far for submarine hydrothermal fluids whereas the inter element rey fractionation is only minor the fluid signature which has been described here for the first time in a back arc setting is controlled by fast fluid passage through basaltic volcanic rocks with extremely high water rock ratios and only limited water rock exchange phase separation and segregation and at least two component fluid mixing metals and metalloids are unexpectedly mobile in the vapour phase fluids and the strong enrichments of fe rey and as highlight the metal transport capacity of low salinity low density vapours at the specific physico chemical conditions at nifonea one possible scenario is that the fluids boiled before the separated vapour phase continued to react with fresh glassy lavas the mobilization of metals is likely to occur by leaching from fresh glass and grain boundaries and is supported by the high water rock ratios the enrichment of b and as is further controlled by their high volatility whereas the strong enrichment of rey is also a consequence of the elevated concentrations in the host rocks however a direct contribution of metals such as as from magmatic degassing cannot be ruled out the different fluid end member composition of individual vent sites could be explained by mixing of vapour phase fluids with another fluid phase of different water rock interaction history

intra sill magmatic evolution in the cummings complex abitibi greenstone belt tholeiitic to calc alkaline magmatism recorded in an archaean subvolcanic conduit system abstract the stratigraphy of the abitibi greenstone belt in the chibougamau area southern superior province quebec is dominated by 2 cycles of mafic felsic metavolcanic and metasedimentary rocks constituting the roy group which is riddled by metagabbroic sills 25 the dore lake complex dlc 2728 ma is emplaced into the lower roy group the cummings complex sills 2717 ma were injected between the bruneau member and blondeau formations of the 2nd roy group cycle the sills of the cummings complex roberge ventures and bourbeau sills contain metaperidotite metapyroxenite metagabbro and metagranophyric facies the trace element contents of melts in equilibrium with these metacumulate rocks were calculated and are compared to roy group lavas to clarify the regional magmatic history many dlc model melts have fractionated trace element profiles with lile lree enrichment hree depletion and negative nb ta anomalies suggesting that the dlc formed largely from calc alkaline melts extracted from garnet bearing residues the dlc is coeval with and shows geochemical resemblances to waconichi formation tuffs the felsic cap of the 1st roy group cycle suggesting it could represent the waconichi s shallow magma chamber meta anorthosite rafts from the para autochtonous zone of the grenville province yield model melts closely resembling those of the dlc and are correlated on this basis most roy group sills yield model melts with trace element patterns typical of archaean tholeiites suggesting they fed the regionally dominant tholeiitic volcanic plain lavas of the roy group models for the cummings complex imply that it contained two types of magma model melts from the roberge sill have strongly fractionated calc alkaline like trace element patterns while those of the ventures and bourbeau sills are mostly flat n morb normalized tholeiitic like patterns that cannot be derived from the roberge sill melts by fractional crystallization the roberge sill must have a separate magmatic stem and represents the feeder system for a calc alkaline volcano possibly represented in part by blondeau formation rhyolites andesites and basalts if this is correct the roberge may be older than the ventures and bourbeau sills which would have fed the tholeiitic base of a third magmatic cycle since eroded

alteration effects of volcanic ash in seawater anomalous y ho ratios in coastal waters of the central mediterranean sea this paper presents the results of a study based on data collected during the oceanographic cruise ansic 2001 carried out in the ionian sea during the explosive activity of mount etna in the summer of 2001 anomalous low values of y ho ratios in seawater suggest extensive scavenging processes on the surfaces of smectitic alteration products with y and ho fractionation controlled by the differences in their electronic configurations and behaviour during solution surface complexation equilibria these processes can also be traced through the presence of significant tetrad effects recorded in the chondrite normalised rare earth elements and yttrium yrees patterns of suspended particulate matter this suggests that the preferential y scavenging from seawater is due to the formation of inner sphere complexes with oh groups on montmorillonite crystal surfaces the preliminary results of kinetic experiments of yree released from volcanic ash to coexisting seawater and the related effects on y ho ratios and ce anomalies are consistent with the fractionation of light rare earth elements lrees with respect to heavy rare earth elements hrees observed in dissolved phase they suggest a behaviour of y similar to that reported for lrees particularly for ce and pr

controls of fluid chemistry and complexation on rare earth element contents of anhydrite from the pacmanus subseafloor hydrothermal system manus basin papua new guinea ocean drilling program odp leg 193 successfully drilled four deep holes 126 to 386 m into basement underlying the active dacite hosted pacmanus hydrothermal field in the eastern manus basin anhydrite is abundant in the drill core material filling veins and vesicles cementing breccias and occasionally replacing igneous material we report rare earth element ree contents of anhydrite from a site of diffuse venting site 1188 which show extreme variability in terms of both absolute concentrations e g 0 08 28 3 ppm nd and pattern shape lan smn 0 08 3 78 smn ybn 0 48 23 1 eu eu 0 59 6 1 the range of ree patterns in anhydrite includes enrichments in the middle and heavy rees and variable eu anomalies the patterns differ markedly from those of anhydrite recovered during odp leg 158 from the tag hydrothermal system at the mid atlantic ridge which display uniform lree enriched patterns with positive eu anomalies very similar to tag vent fluid patterns as the system is active the host rock composition is uniform and the anhydrite veins appear to relate to the same hydrothermal stage we can rule out predominant host rock and transport control instead we propose that the variation in ree content reflects waxing and waning input of magmatic volatiles hf so2 and variable complexation of rees in the fluids ree speciation calculations suggest that increased fluoride and possibly sulfate concentrations at pacmanus may affect ree complexation in fluids whereas at tag only chloride and hydroxide complexes play a significant role the majority of the anhydrites do not show positive eu anomalies suggesting that the fluids were more oxidizing than in typical mid ocean ridge hydrothermal systems we use other hydrothermal fluids from the manus basin vienna woods and desmos which bracket the pacmanus fluids in terms of acidity and ligand concentrations to examine the dependence of ree complexation on fluid composition geochemical modeling reveals that under the prevailing conditions at pacmanus ph 3 5 t 250 300 c eu oxidation state and the relative importance of fluoride versus chloride complexing are very sensitive to small variations in oxygen fugacity temperature and ph patterns with extreme mid ree enrichment may reflect speciation effects free ion abundance coupled with crystal chemical control we conclude that the great variability in ree concentrations and pattern shape is likely due to variable fluid composition and ree complexation in the fluids

rare earth element abundances and distribution patterns in hydrothermally altered basalts experimental results oceanic tholeiites that have been experimentally reacted with seawater at 500 600 c 800 1000 bars have rare earth element ree abundances and distribution patterns that are essentially identical to those of the unaltered basalts although the data indicate the possibility of some ree leaching and redistribution the net effects are small and the ree patterns of basalts affected by submarine hydrothermal processes may still be valid petrogenetic indicators

major element ree and other trace element behavior in amphibolite weathering under semiarid conditions in southern india abstract a body of komatiitic amphibolite an enclave within the archean high grade orthogneisses in southern india shows mild chemical weathering under semiarid conditions along fractures chemical weathering has advanced chemical index of alteration documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10 9 7 6 begin document landscape mathrm cia 53 end document cia of fresh documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage

rare earth elements as indicators of hydrothermal processes within the east scotia subduction zone system the east scotia subduction zone located in the atlantic sector of the southern ocean hosts a number of hydrothermal sites in both back arc and island arc settings high temperature 348 c black smoker vents have been sampled at three locations along segments e2 and e9 of the east scotia back arc spreading ridge as well as white smoker 212 c and diffuse 28 c hydrothermal fluids from within the caldera of the kemp submarine volcano the composition of the endmember fluids mg 0 mmol kg is markedly different with ph ranging from 1 to 3 4 cl from 90 to 536 mm h2s from 6 7 to 200 mm and f from 35 to 1000 m all of the vent sites are basalt to basaltic andesite hosted providing an ideal opportunity for investigating the geochemical controls on rare earth element ree behaviour endmember hydrothermal fluids from e2 and e9 have total ree concentrations ranging from 7 3 to 123 nmol kg and chondrite normalised distribution patterns are either light ree enriched lacn ybcn 12 8 30 0 with a positive europium anomaly eucn eu cn 3 45 59 5 or mid ree enriched lacn ndcn 0 61 with a negative eu anomaly eucn eu cn 0 59 by contrast fluids from the kemp caldera have almost flat ree patterns lacn ybcn 2 1 2 2 eucn eu cn 1 2 2 2 we demonstrate that the ree geochemistry of fluids from the east scotia back arc spreading ridge is variably influenced by ion exchange with host minerals phase separation competitive complexation with ligands and anhydrite deposition whereas fluids from the kemp submarine volcano are also affected by the injection of magmatic volatiles which enhances the solubility of all the rees we also show that the ree patterns of anhydrite deposits from kemp differ from those of the present day fluids potentially providing critical information about the nature of hydrothermal activity in the past where access to hydrothermal fluids is precluded

element mobility in paragneisses and metabasites of the continental deep drilling project ktb germany leaching experiments ph 3 t 70 c have been performed on paragneisses and metabasites from the ktb drill cores the experiments yielded the fraction of total element content that is easily available to acidic aqueous fluids the intensity of mineralogic alteration in the studied samples is expressed in terms of easily leachable fractions of k or ba its reliability is shown by correlation with a petrographically determined alteration index for the paragneisses the easily available fractions of fe mg mn ca na k ba co cr ni sr v and y together with the variables whole rock content and depth of samples were subjected to a factor analysis the results of which are presented as a five factor model correlation plots of easily leachable element fraction and whole rock content vs an alteration index percentage of leachable k reveal the changes in leachability as a function of intensity of alteration in a cataclastic boundary between paragneisses and metabasites at 1610 m depth the changes in whole rock content and leachability of elements are studied in detail and compared with the general trends in alteration the results point to considerable intercrystalline element redistribution during retrograde metamorphism with only insignificant element transport on a meter scale although considerable fractions of many elements were easily available to acidic fluids 3 ph 4 in the experiments the whole rock element content was maintained during retrogression suggesting that water rock ratio and fluid flow were low during alteration k ba fe co ni cr and v are immobilized in situ whereas sr ca and y become more leachable across the studied strongly altered lithologic contact element transport up to 7 m normal to foliation can be traced here ca sr mg co ni and cr are slightly enriched whereas k ba fe and mn are slightly depleted

lithium isotopic composition of submarine basalts implications for the lithium cycle in the oceans abstract we have measured the li isotope composition of young pristine basalts from active ocean ridge crests of progressively older basalts along a dredging transect and a limited number of hydrothermally altered basalts the data significantly extend our limited knowledge of the isotopic abundance ratio of li in geological material fresh mid ocean ridge basalts have 6li values of between 3 4 and 4 7 relative to isotope standard l svec during low temperature weathering on the seafloor the isotopic composition of the rock becomes increasingly heavier due to addition of seawater li 6li 32 3 the oldest 46 m y and most altered rock studied has an isotopic composition of 14 a linear relationship exists between 6li and the inverse of li concentration suggesting that li in weathered basalts can be regarded as a two component mixture of basaltic li and seawater derived li that has been incorporated in alteration minerals most likely secondary clays such as smectite and phillipsite the inferred li isotopic composition of the alteration endmember indicates an apparent isotopic fractionation factor of 1 019 relative to the seawater source thus li uptake by secondary minerals from the low temperature weathering process and by analogy incorporation in similar authigenic minerals in marine sediments provides a mechanism for preferential removal of the lighter li isotope from ocean water however isotopic fractionation due to authigenic clay formation alone cannot account for the isotopic difference between seawater and its principal sources unless the hydrothermal flux is comparable to the river flux alternatively more important sinks of6li must exist if the steady state isotopic composition of li in ocean water is to be maintained

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

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