identification of sulfur sources and isotopic equilibria in submarine hot springs using multiple sulfur isotopes abstract multiple sulfur isotopes were measured in metal sulfide deposits elemental sulfur and aqueous hydrogen sulfide to constrain sulfur sources and the isotopic systematics of precipitation in seafloor hydrothermal vents areas studied include the eastern manus basin and lau basin back arc spreading centers and the unsedimented basalt hosted southern east pacific rise sepr and sediment hosted guaymas basin mid ocean ridge spreading centers chalcopyrite and dissolved hydrogen sulfide h 2 s 34 s values range from 5 5 to 5 6 in manus basin samples 2 4 to 6 1 in lau basin samples and 3 7 to 5 7 in sepr samples values of 34 s for cubic cubanite and h 2 s range from 1 4 to 4 7 in guaymas basin samples multiple sulfur isotope systematics in fluid mineral pairs from the sepr and lau basin show that crustal host rock and thermochemical reduction of seawater derived dissolved sulfate so 4 are the primary sources of sulfur in mid ocean ridge and some back arc systems at pacmanus and susu knolls hydrothermal systems in the eastern manus basin a significant contribution of sulfur is derived from disproportionation of magmatic sulfur dioxide so 2 while the remaining sulfur is derived from crustal host rocks and so 4 reduction at the sedimented guaymas basin hydrothermal system sulfur sources include crustal host rock reduced seawater so 4 and biogenic sulfide vent fluid flow through fresher less mature sediment supplies an increased quantity of reactant organic compounds that may reduce 34 s enriched so 4 while fluid interaction with more highly altered sediments results in h 2 s characterized by a small but isotopically significant input of 34 s depleted biogenic sulfides near zero 33 s values in all samples implicate the abiotic processes of so 4 reduction and leaching of host rock as the major contributors to sulfur content at a high temperature unsedimented mid ocean ridge and at a back arc system 33 s values indicate that so 2 disproportionation is an additional process that contributes sulfur to a different back arc system and to acid spring type hydrothermal fluid circulation at the sedimented guaymus basin near zero 33 s values are also observed despite negative 34 s values that indicate inputs of biogenic pyrite for some samples in contrast with previous studies reporting isotope disequilibrium between h 2 s and chalcopyrite the 34 s values of chalcopyrite sampled from the inner 1 2 mm of a chimney wall are within 1 of 34 s values for h 2 s in the paired vent fluid suggesting equilibrium fluid mineral sulfur isotope exchange at 300 400 c isotopic equilibrium between hydrothermal fluid h 2 s and precipitating chalcopyrite implies that sulfur isotopes in the chalcopyrite lining across a chimney wall may accurately record past hydrothermal activity

geochemical constraints on chemolithoautotrophic metabolism by microorganisms in seafloor hydrothermal systems mixing of hydrothermal fluids and seawater at the ocean floor combined with slow reaction kinetics for oxidation reduction reactions provides a source of metabolic energy for chemolithotrophic microorganisms which are the primary biomass producers for an extensive submarine ecosystem that is essentially independent of photosynthesis thermodynamic models are used to explore geochemical constraints on the amount of metabolic energy potentially available from chemosynthetic reactions involving s c fe and mn compounds during mixing of hydrothermal fluids with seawater for the vent fluid used in the calculations epr 21 n obs the model indicates that mixing environments are favorable for oxidation of h2s ch4 fe2 and mn2 only below 38 c with methanogenesis and reduction of sulfate or s favored at higher temperatures suggesting that environments dominated by mixing provide habitats for mesophilic but not thermophilic aerobes and thermophilic but not mesophilic anaerobes a maximum of 760 cal per kilogram vent fluid is available from sulfide oxidation while between 8 and 35 cal kg vent fluid is available from methanotrophy methanogenesis oxidation of fe or mn or sulfate reduction the total potential for chemosynthetic primary production at deep sea hydrothermal vents globally is estimated to be about 1013 g biomass per year which represents 0 02 of the global primary production by photosynthesis in the oceans thermophilic methanogens and sulfate and s reducers are likely to be the predominant organisms in the walls of vent chimneys and in the diffuse mixing zones beneath warm vents where biological processes may contribute to the high methane concentrations of vent fluids and heavy 34s32s s ratios of vent sulfide minerals the metabolic processes taking place in these systems may be analogs of the first living systems to evolve on the earth

temperatures of entering magma formation and dimensions of magma chambers of volcanoes a mechanism of formation of magma chambers that feed volcanoes is discussed heat conditions and dimensions of magma chambers which have existed for more than several thousand years may become stable the approximate equations of heat balance of these chambers are derived by calculating the temperaturet1 of the magma entering chambers and the radiia of chambers calculations show that the radius of the shallow peripheral chambers of the avachinsky volcano is less than 3 3 5 km possible maximum radii of peripheral magma chambers were estimated for the kamchatkan volcanoes of medial size the temperature difference in their chambers may reach 100 200 c this method can be applied to the calculations of roots of central type volcanoes

environmental controls on biomineralization and fe mound formation in a low temperature hydrothermal system at the jan mayen vent fields abstract diffuse low temperature hydrothermal vents on the seafloor host neutrophilic microaerophilic fe oxidizing bacteria that utilize the fe ii supplied by hydrothermal fluids and produce intricate twisted and branching extracellular stalks the growth behavior of fe oxidizing bacteria in strongly opposing gradients of fe ii and o2 have been thoroughly investigated in laboratory settings to assess whether extracellular stalks and aligned biomineralized fabrics may serve as biosignatures of fe oxidizing bacteria and indications of palaeo redox conditions in the rock record however the processes controlling the growth of biogenic fe oxyhydroxide deposits in natural modern hydrothermal systems are still not well constrained in this study we aimed to establish how variations in the texture of stratified hydrothermal fe oxyhydroxide deposits are linked to the physicochemical conditions of the hydrothermal environment we conducted 16s rrna gene analyses microscopy and geochemical analyses of laminated siliceous fe mounds from the jan mayen vent fields at the arctic mid ocean ridge chemical analyses of low and high temperature hydrothermal fluids were performed to characterize the hydrothermal system in which the fe deposits form our results reveal synchronous inter laminar variations in texture and major and trace element geochemistry the fe deposits are composed of alternating porous laminae of mineralized twisted stalks and branching tubes mn rich horizons with abundant detrital sediment domal internal cavities and thin p and ree enriched lamina characterized by networks of 1 m wide fibers zetaproteobacteria constitute one third of the microbial community in the surface layer of actively forming mounds indicating that microbial fe oxidation is contributing to mound accretion we suggest that mn oxide precipitation and detrital sediment accumulation take place during periodically low hydrothermal fluid discharge conditions the elevated concentrations of p and ree in distinct laminae suggest fe cycling and accumulation of diagenetic species at depth in the deposits during hydrothermal quiescence and co precipitation of these species with fe oxyhydroxides at the mound surface with reinitiated hydrothermal discharge the origin of the low temperature hydrothermal source fluid and the fe deposits are evident by low lree hree ratios and negative eu anomalies which clearly differ from the lree and eu enrichment of nearby high temperature white smoker venting fluids our study demonstrates that hydrothermal fluctuations exert the primary control on the formation of laminae and the activity of fe oxidizing bacteria in marine hydrothermal fe deposits and indicates that ree patterns may be used to distinguish high temperature plume fallout and biomineralized low temperature fe deposits in the rock record

experimental determination of the stability constants of naso4 and nab oh 40 in hydrothermal solutions using a new high temperature sodium selective glass electrode implications for boron isotopic fractionation abstract a new sodium selective glass electrode was used to measure the association constants of the sodium sulfate naso 4 and sodium borate nab oh 4 0 ion pairs at temperatures from 50 to 200 c these data were used to generate within the framework of the revised hkf model naso 4 and nab oh 4 0 equation of state parameters calculation of nab oh 4 0 association constants at temperatures up to 500 c and pressures up to 5 kbar demonstrates that this ion pair dominates boron speciation in sodium rich hydrothermal fluids at ph 8 because it has been shown that boron isotopic fractionation in natural processes is strongly affected by its aqueous speciation the formation of nab oh 4 0 complexes cannot be neglected when using boron isotopes to estimate water rock interactions occurring in the continental and oceanic crust at moderate and high temperatures

conduction model for the thermal influence of lithic clasts in mixtures of hot gases and ejecta the thermal influence of lithic clasts in mixtures of hot gases and ejecta produced during explosive eruptions is an important aspect of the dynamics of eruption columns and pyroclastic flows in order to study this aspect we present a heat conduction model which considers both the temperature distributions of the lithic clasts and the exchange of thermal energy between the lithic clasts and other constituents gases and juvenile pyroclasts the model quantifies the thermal energy of the system by means of a characteristic energy function that describes the energy absorbed by each lithic clast using this energy function and considering some hypothetical arrangements of lithic clasts it is possible to calculate by means of heat balance the temperature variations in mixtures of hot gases and ejecta as a function of time volume fraction of particles to gas and thermal diffusivity initial temperature diameter and volume fraction of lithic clasts theoretical results show that in an eruption a volume fraction of 12 of cool lithic clasts 20 100 c whose size is less than 5 cm will cause the mixture of hot gases and ejecta to cool by 300 c we suggest therefore that the thermal effects of lithic clasts should be considered in numerical models of eruption columns and pyroclastic flows

convection of geothermal fluids in the timanfaya volcanic area lanzarote canary islands a mathematical model has been derived to study the superficial thermal anomalies to be found in lanzarote 605 c at 13 m depth in association with the convection of geothermal fluids the model is valid for a wide range of conditions in particular for those found beneath the timanfaya volcano active between 1730 and 1736 geological and geophysical data suggest that the heat source is related to a cylindrical magma body with a radius of 200 100 m and a top temperature of 850 100 c at a depth of 4 1 km

magma rates in feeding conduits of different volcanic centres abstract a quasi stationary magma flow rate in asthenospheric and crustal conduits of central type volcanoes and volcanic centres was studied analytically under the following conditions magma rises through cylindrical channels in which the magma temperature does not change with time but the wall rocks are gradually heated the magma rates were calculated for basaltic andesitic and dacitic volcanoes using the continental and oceanic geotherms it follows from these calculations that the magma supply rate may determine the kind of activity of a volcanic centre being constant for large and very active volcanoes intermittent for usual volcanic centres of island arcs or sporadic for volcamic fields clusters of cinder cones and areal volcanism theoretical conclusions are consistent with observational data

fluid mixing and thermal regimes beneath the pacmanus hydrothermal field papua new guinea helium and oxygen isotope data abstract fluid mixing processes and thermal regimes within the snowcap and roman ruins vent sites of the pacmanus hydrothermal system papua new guinea were investigated using 3he 4he ratios from fluid inclusions within pyrite and anhydrite and the 18o signature of anhydrite depressed 3he 4he ratios of 0 2 6 91ra appear to be caused by significant atmospheric diffusive exchange whilst he ne diffusive fractionation precludes correction using 20ne 40ar 36ar ratios of 295 310 are elevated above seawater indicating the majority of argon is seawater derived but with a magmatic component 18o anhydrite ratios are 6 5 to 11 for snowcap and 6 4 to 11 9 for roman ruins using oxygen isotope fractionation factors for the anhydrite water system the temperatures calculated assuming isotopic equilibrium at depth are up to 100 c cooler than fluid inclusion trapping temperatures it is likely that anhydrite is precipitated rapidly preventing 18o equilibration by comparing new 18o values for anhydrite with corresponding published 87sr 86sr ratios seawater is inferred to penetrate deep into the snowcap system with little conductive heating a simple fluid mixing model has been constructed whereby the differing venting styles can be explained by a plumbing system at depth which favors delivery of end member hydrothermal fluid to the high temperature sites

submarine venting of magmatic volatiles in the eastern manus basin papua new guinea abstract the susu knolls and desmos hydrothermal fields are located in the back arc extensional transform zone of the eastern manus basin in 2006 highly acidic and so4 rich vent fluids were collected at both sites and analyzed for the chemical and isotopic composition of major and trace species fluids exiting the seafloor have measured temperatures from 48 to 215 c and are milky white in appearance due to precipitation of elemental s0 vent fluid concentrations of na k and mg are depleted by as much as 30 relative to seawater but have the same relative abundance in contrast the fluids are highly enriched in dissolved co2 cl sio2 aq fe and al relative to seawater measured ph 25 c ranged from 0 95 to 1 87 and aqueous so4 ranged from 35 to 135 mmol kg the chemical and isotopic composition points to formation via subsurface mixing of seawater with a na k mg and ca free volatile rich magmatic fluid exsolved from subsurface magma bodies during a process analogous to subaerial fumarole discharge estimates of the magmatic end member composition indicate a fluid phase where h2o so2 co2 cl f the hydrogen and oxygen isotopic composition of h2o and carbon isotopic composition of co2 in the vent fluids strongly suggest a contribution of slab derived h2o and co2 to melts generated in the mantle beneath the eastern manus volcanic zone abundant magmatically derived so2 undergoes disproportionation during cooling in upflow zones and contributes abundant acidity so42 and s0 to the venting fluids interaction of these highly acidic fluids with highly altered mineral assemblages in the upflow zone are responsible for extensive aqueous mobilization of sio2 aq fe and al temporal variability in the speciation and abundance of aqueous s species between 1995 and 2006 at the desmos vent field suggests an increase in the relative abundance of so2 in the magmatic end member that has mixed with seawater in the subsurface results of this study constrain processes responsible for the formation of hot spring fluids in magmatically active back arc environments and the resulting chemical exchange between the lithosphere and water column

constraints on the interpretation of s to p receiver functions summary we present results from forward modelling to study the feasibility of using s to p converted phases to image the seismic discontinuity structure of the crust and upper mantle we show that a significant level of p wave energy arriving before the direct s wave arrival can interfere with the s to p converted phases of interest and may result in sp receiver function phases that do not represent true earth structure the source of this p wave energy is attributable to a number of phases including those that have undergone multiple reflections off the earth s surface for deep focus earthquakes 300 600 km deep a significant amount of p wave energy is observed from pppp ppppp and spppp phases and arrives within the same time window as predicted for s to p converted phases from the direct s phase arrival furthermore for earthquakes at all depths interfering p wave energy arrives within the same time window as predicted for s to p converted phases from the sks phase arrival limiting the usefulness of sksp receiver functions for upper mantle imaging to isolate true sp receiver function phases from contamination due to other p wave phases we find it necessary to stack receiver functions from a range of epicentral distances and depths in order to aid the suppression of noise and other unwanted phases we provide constraints on the noise levels to be expected as a function of epicentral distance and earthquake depth we find that the lowest noise levels are achievable by restricting epicentral distance to less than 75 degrees and the depth of earthquakes used to less than 300 km

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

a multiple sulfur isotope study through the volcanic section of the troodos ophiolite abstract multiple s isotope systematics 34s and 33s and high resolution in situ s isotope measurements offer new perspectives on the study of biological and abiotic cycling of sulfur in hydrothermal systems we applied these techniques to the tethyian troodos ophiolite 91 ma from cyprus one of the best preserved remnants of oceanic crust in the world using materials from deep drill cores and surface sampling we focused on the volcanic section of the ophiolite including the hydrothermal massive sulfide deposit at agrokipia which represents a fossil zone of high temperature fluid upwelling and the akaki river section which displays a range of lower temperature alteration types the 34s and 33s values of bulk and sims secondary ion mass spectrometry analyses from the agrokipia sulfide deposits show that the sulfide minerals are largely derived from thermochemical reduction of entrained seawater sulfate and leached h2s from the root zone of hydrothermal upwelling the contributions of these two sources can vary substantially within individual sulfide grains indicating a very dynamic mixing between these sulfur sources microbial reworking of the sulfide mound is recorded in a sample with very elevated 33s values 0 22 the akaki and agrokipia volcanics experienced low temperature sulfur loss and removal of heavier sulfur isotopes due to partial oxidation by microbes while some intervals gained sulfur and have 34s and 33s values indicative of microbial sulfate reduction ree data of vein quartz containing pyrite with 34s 21 implies local ephemeral hydrothermal upwelling in the lower akaki volcanics possibly associated with the late stage boninitic magmatic activity in the troodos ophiolite suggesting that microbial sulfate reduction in oceanic crust may continue for 10 15 ma in crustal sections with prolonged igneous activity such as troodos

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

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

acidic and sulfate rich hydrothermal fluids from the manus back arc basin papua new guinea hot 88 120 c and acidic ph 2 1 hydrothermal fluids rich in sulfate were discovered venting in the desmos caldera depth 1926 m eastern manus back arc basin bismarck sea surrounded by papua new guinea the abundant sulfate 32 8 m m higher than the seawater value of 28 m m with elemental sulfur deposition around the vents and remarkably low d h 2 o and 34 s h 2 s values 8 1 and 5 6 respectively are suggestive of the incorporation of a magmatic fluid and the disproportionation of the exsolved so 2 from a magma body the desmos fluid may be similar in origin to the acidic sulfate chloride hot springs associated with subaerial volcanic activity in contrast to the typical hydrothermal end member mg concentration of 0 the desmos fluids are rich in mg 46 52 m m probably because of mg dissolution by acid attack upon magnesium silicate minerals

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

inorganic and biogenic as sulfide precipitation at seafloor hydrothermal fields highlights as sulfides are minor minerals at volcanic arc and back arc hydrothermal settings there are two modes of as sulfide precipitation inorganic and biogenic the most stable as sulfide at low t seafloor hydrothermal conditions is orpiment biogenic type of orpiment represents completely mineralized fungal hyphae fungal orpiment precipitation is a mechanism of bio sequestration of hydrothermal as we investigated as sulfides orpiment as2s3 and realgar as4s4 from four seafloor hydrothermal fields three from back arc and one from mid ocean ridge settings our studies suggest two different modes of as sulfide precipitation at the seafloor hydrothermal sites inorganic and biogenic the eh ph modeling shows that the most stable as sulfide at low temperature t 100 c seafloor hydrothermal conditions is orpiment whereas realgar appears as a stable as sulfide phase at t 25 c and under a narrow range of eh ph values inorganically precipitated realgar forms euhedral crystals whereas the orpiment is mostly colloform the biogenic type of orpiment no realgar of this type was found represents completely mineralized fungal hyphae the proposed scenario of biogenic orpiment formation assumes that crack dwelling fungal filaments in the sub seafloor were killed by an as rich hydrothermal fluid moving along the same crack network the fungal organic matter served as a geochemical trap for hydrothermal as which reacted with s leached from the basement or reduced from seawater sulfate and mineralized the fungal hyphae as as2s3 this process of fungal orpiment precipitation is a mechanism of bio sequestration of hydrothermal as and another mode of soft tissue fossilization not described so far

rare earth element abundances in hydrothermal fluids from the manus basin papua new guinea indicators of sub seafloor hydrothermal processes in back arc basins abstract rare earth element ree concentrations are reported for a large suite of seafloor vent fluids from four hydrothermal systems in the manus back arc basin vienna woods pacmanus desmos and susu knolls vent areas sampled vent fluids show a wide range of absolute ree concentrations and chondrite normalized reen distribution patterns lan smn 0 6 11 lan ybn 0 6 71 eu n eu n 1 55 reen distribution patterns in different vent fluids range from light ree enriched to mid and heavy ree enriched to flat and have a range of positive eu anomalies this heterogeneity contrasts markedly with relatively uniform reen distribution patterns of mid ocean ridge hydrothermal fluids in manus basin fluids aqueous ree compositions do not inherit directly or show a clear relationship with the ree compositions of primary crustal rocks with which hydrothermal fluids interact these results suggest that the rees are less sensitive indicators of primary crustal rock composition despite crustal rocks being the dominant source of rees in submarine hydrothermal fluids in contrast differences in aqueous ree compositions are consistently correlated with differences in fluid ph and ligand chloride fluoride and sulfate concentrations our results suggest that the rees can be used as an indicator of the type of magmatic acid volatile i e presence of hf so2 degassing in submarine hydrothermal systems additional fluid data suggest that near seafloor mixing between high temperature hydrothermal fluid and locally entrained seawater at many vent areas in the manus basin causes anhydrite precipitation anhydrite effectively incorporates ree and likely affects measured fluid ree concentrations but does not affect their relative distributions

the rare earth element geochemistry of acid sulphate and acid sulphate chloride geothermal systems from yellowstone national park wyoming usa rare earth element ree concentrations have been determined by inductively coupled plasma mass spectrometry icp ms in acid sulphate and acid sulphate chloride waters and the associated sinters and volcanic rocks from the yellowstone national park ynp wyoming usa geothermal system ree concentrations in the volcanic rocks range from 222 to 347 ppm their chondite normalised ree patterns are typical of upper continental crust with lree hree and negative eu anomalies total ree concentrations in the fluids range from 3 to 1133 nmol kg 1 162 ppm and ree concentrations in sinter are 181 ppm ree abundances and patterns in drill core material from ynp indicate some ree mobility normalisation of ree concentrations in altered lava creek tuff lct from y 12 drill core to ree concentrations in fresh lct indicate that the ree overall have been depleted with the exception of eu which has been decoupled from the ree series and concentrated in the altered rocks relative to the host rocks the ree patterns of the fluids are variably depleted in hrees and lrees and usually have a pronounced positive eu anomaly this decoupling of eu from the ree suite suggests that 1 eu has been preferentially removed either from the host rock glass or from the host rock minerals or 2 the waters are from a high temperature or reducing environment where eu2 is more soluble than the trivalent rees since the latter is inconsistent with production of acid sulphate springs in a low temperature oxidising near surface environment we suggest that the positive eu anomalies in the fluids result from preferential dissolution of a eu rich phase in the host rock spatial and temporal variations in major element chemistry and ph of the springs sampled from norris geyser basin and crater hills accompany variations in ree concentrations and patterns of individual geothermal springs these are possibly related to changes in subsurface plumbing which results in variations in mixing and dilution of the geothermal fluids and may have lead to changes in the extent and nature of ree complexing

a spectrophotometric study of erbium iii speciation in chloride solutions at elevated temperatures abstract the speciation of erbium in chloride bearing solutions was investigated spectrophotometrically at temperatures of 100 to 250 c and a pressure of 100 bars the hydrated ion er 3 is predominant at ambient temperature but chloride complexes are dominant at elevated temperature formation constants were calculated for the following reactions 1 er 3 cl ercl 2 2 er 3 2 cl ercl 2 the values obtained for the first formation constant 1 were 0 88 0 11 1 59 0 12 2 34 0 11 and 3 09 0 14 at 100 150 200 and 250 c respectively values of the second formation constant could only be determined at 200 and 250 c and were 2 95 0 34 and 4 12 0 12 respectively the values for the first formation constant 1 are identical within experimental error to the values predicted by haas et al haas j r shock e l and sassani d c 1995 rare earth elements in hydrothermal systems estimates of standard partial molal thermodynamic properties of aqueous complexes of the rare earth elements at high pressures and temperatures geochim cosmochim acta 59 4329 50 whereas the values for the second formation constant 2 agree relatively well with those predicted by haas et al 1995 and determined experimentally by gammons et al gammons c h wood s a and li y 2002 complexation of the rare earth elements with aqueous chloride at 200 c and 300 c and saturated water vapor pressure special publication the geochemical society water rock interactions ore deposits and environmental geochemistry 191 207

long term eruption rates and dimensions of magma reservoirs beneath quaternary polygenetic volcanoes in japan abstract long term eruption rates of 18 quaternary volcanoes in japanese islands are estimated to range from 5 to slightly greater than 0 05 km 3 10 3 y the long term rate correlates well with the variation of phenocryst assemblage which reflects the crystallization temperature the long term eruption rate and temperature of magma from the volcanoes in northeastern japan are higher than those in southwestern japan in northeastern japan the long term rate is higher at volcanoes located near the colcanic front than those on the back arc side applying the estimated long term eruption rates to the model calculation of continuous magma supply the appropriate radius of the magma chamber is estimated to be less than 3 5 km

geochemistry of hydrothermal fluids from the pacmanus northeast pual and vienna woods hydrothermal fields manus basin papua new guinea abstract processes controlling the composition of seafloor hydrothermal fluids in silicic back arc or near arc crustal settings remain poorly constrained despite growing evidence for extensive magmatic hydrothermal activity in such environments we conducted a survey of vent fluid compositions from two contrasting sites in the manus back arc basin papua new guinea to examine the influence of variations in host rock composition and magmatic inputs both a function of arc proximity on hydrothermal fluid chemistry fluid samples were collected from felsic hosted hydrothermal vent fields located on pual ridge pacmanus and northeast ne pual near the active new britain arc and a basalt hosted vent field vienna woods located farther from the arc on the manus spreading center vienna woods fluids were characterized by relatively uniform endmember temperatures 273 285 c and major element compositions low dissolved co 2 concentrations 4 4 mmol kg and high measured ph 4 2 4 9 at 25 c temperatures and compositions were highly variable at pacmanus ne pual and a large newly discovered vent area fenway was observed to be vigorously venting boiling 358 c fluid all pacmanus fluids are characterized by negative d h 2 o values in contrast to positive values at vienna woods suggesting substantial magmatic water input to circulating fluids at pual ridge low measured ph 25 c values 2 6 2 7 high endmember co 2 up to 274 mmol kg and negative 34 s h 2 s values down to 2 7 in some vent fluids are also consistent with degassing of acid volatile species from evolved magma dissolved co 2 at pacmanus is more enriched in 13 c 4 1 to 2 3 than vienna woods 5 2 to 5 7 suggesting a contribution of slab derived carbon the mobile elements e g li k rb cs and b are also greatly enriched in pacmanus fluids reflecting increased abundances in the crust there relative to the manus spreading center variations in alkali and dissolved gas abundances with cl at pacmanus and ne pual suggest that phase separation has affected fluid chemistry despite the low temperatures of many vents in further contrast to vienna woods substantial modification of pacmanus ne pual fluids has taken place as a result of seawater ingress into the upflow zone consistently high measured mg concentrations as well as trends of increasingly non conservative so 4 behavior decreasing endmember ca cl and sr cl ratios with increased mg indicate extensive subsurface anhydrite deposition is occurring as a result of subsurface seawater entrainment decreased ph and endmember fe mn ratios in higher mg fluids indicate that the associated mixing cooling gives rise to sulfide deposition and secondary acidity production several low temperature 80 c fluids at pacmanus ne pual also show evidence for anhydrite dissolution and water rock interaction fixation of b subsequent to seawater entrainment hence the evolution of fluid compositions at pual ridge reflects the cumulative effects of water rock interaction admixing and reaction of fluids exsolved from silicic magma phase separation segregation and seawater ingress into upflow zones

on the sr isotope and ree compositions of anhydrites from the tag seafloor hydrothermal system abstract sr isotope analyses have been conducted on anhydrite samples from the tag trans atlantic geotraverse active hydrothermal mound 26 08 n mid atlantic ridge that have previously been shown to exhibit two distinct patterns of ree behavior when normalized to tag end member hydrothermal fluid despite differences in ree patterns the sr isotope data indicate that all the anhydrites precipitated from fluids with a similar range of hydrothermal fluid and seawater components and all but one were seawater dominated 52 75 speciation calculations using the eq3 6 software package for geochemical modeling of aqueous systems suggest that the ree complexation behavior in different fluid mixing scenarios can explain the variations in the ree patterns anhydrites that exhibit relatively flat ree patterns labs ybbs 0 8 2 0 subscript bs indicates normalization to end member black smoker hydrothermal fluid and a small or no eu anomaly eubs eu bs 0 8 2 0 are inferred to have precipitated from mixes of end member hydrothermal fluid and cold seawater ree complexes with hard ligands e g fluoride and chloride are less stable at low temperatures and trivalent eu has an ionic radius similar to that of ca2 and the other ree and so they behave coherently in contrast anhydrites that exhibit slight lree depletion labs ybbs 0 4 1 4 and a distinct negative anomaly eubs eu bs 0 2 0 8 are inferred to have precipitated from mixes of end member hydrothermal fluid and conductively heated seawater the lree depletion results from the presence of very stable lree chloro complexes that effectively limit the availability of the lree for partitioning into anhydrite above 250 c eu is present only in divalent form as chloride complexes and discrimination against eu2 is likely due to both the mismatch in ionic radii between eu2 and ca2 and the strong chloro complexation of divalent eu which promotes stability in the fluid and inhibits partitioning of eu2 into precipitating anhydrite these variations in ree behavior attest to rapid fluctuations in thermal regime fluid flow and mixing in the subsurface of the tag mound that give rise to heterogeneity in the formation conditions of individual anhydrite crystals

insights to magmatic hydrothermal processes in the manus back arc basin as recorded by anhydrite microchemical analyses of rare earth element ree concentrations and sr and s isotope ratios of anhydrite are used to identify sub seafloor processes governing the formation of hydrothermal fluids in the convergent margin manus basin papua new guinea samples comprise drill core vein anhydrite and seafloor massive anhydrite from the pacmanus roman ruins snowcap and fenway and susu knolls north su active hydrothermal fields chondrite normalized ree patterns in anhydrite show remarkable heterogeneity on the scale of individual grains different from the near uniform ree n patterns measured in anhydrite from mid ocean ridge deposits the ree n patterns in anhydrite are correlated with ree distributions measured in hydrothermal fluids venting at the seafloor at these vent fields and are interpreted to record episodes of hydrothermal fluid formation affected by magmatic volatile degassing 87 sr 86 sr ratios vary dramatically within individual grains between that of contemporary seawater and that of endmember hydrothermal fluid anhydrite was precipitated from a highly variable mixture of the two the intra grain heterogeneity implies that anhydrite preserves periods of contrasting hydrothermal versus seawater dominant near seafloor fluid circulation most sulfate 34 s values of anhydrite cluster around that of contemporary seawater consistent with anhydrite precipitating from hydrothermal fluid mixed with locally entrained seawater sulfate 34 s isotope ratios in some anhydrites are however lighter than that of seawater which are interpreted as recording a source of sulfate derived from magmatic so 2 degassed from underlying felsic magmas in the manus basin the range of elemental and isotopic signatures observed in anhydrite records a range of sub seafloor processes including high temperature hydrothermal fluid circulation varying extents of magmatic volatile degassing seawater entrainment and fluid mixing the chemical and isotopic heterogeneity recorded in anhydrite at the inter and intra grain scale captures the dynamics of hydrothermal fluid formation and sub seafloor circulation that is highly variable both spatially and temporally on timescales over which hydrothermal deposits are formed microchemical analysis of hydrothermal minerals can provide information about the temporal history of submarine hydrothermal systems that are variable over time and cannot necessarily be inferred only from the study of vent fluids

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

contrasting evolution of hydrothermal fluids in the pacmanus system manus basin the sr and s isotope evidence ocean drilling program odp leg 193 investigated two sites of hydrothermal activity along the crest of the pual ridge in the eastern manus basin a site of low temperature diffuse venting snowcap site 1188 and a high temperature black smoker site roman ruins site 1189 were drilled to depths of 386 and 206 m below seafloor mbsf respectively although the two sites are 1000 m apart the 87sr 86sr and 34s signatures of anhydrite recovered at both sites are very different the data suggest a complex interplay among hydrothermal fluid magmatic fluid and seawater during alteration and mineralization of the pacmanus papua new guinea australia canada manus system these new results significantly expand the subsurface data on seafloor hydrothermal systems and may begin to explain the earliest processes of multistage mineralization and alteration history that typify ancient massive sulfide systems

the effect of diagenesis and fluid migration on rare earth element distribution in pore fluids of the northern cascadia accretionary margin analytical challenges in obtaining high quality measurements of rare earth elements rees from small pore fluid volumes have limited the application of rees as deep fluid geochemical tracers using a recently developed analytical technique we analyzed rees from pore fluids collected from sites u1325 and u1329 drilled on the northern cascadia margin during the integrated ocean drilling program iodp expedition 311 to investigate the ree behavior during diagenesis and their utility as tracers of deep fluid migration these sites were selected because they represent contrasting settings on an accretionary margin a ponded basin at the toe of the margin and the landward tofino basin near the shelf s edge ree concentrations of pore fluid in the methanogenic zone at sites u1325 and u1329 correlate positively with concentrations of dissolved organic carbon doc and alkalinity fractionations across the ree series are driven by preferential complexation of the heavy rees simultaneous enrichment of diagenetic indicators doc and alkalinity and of rees in particular the heavy elements ho to lu suggests that the heavy rees are released during particulate organic carbon poc degradation and are subsequently chelated by doc ree concentrations are greater at site u1325 a site where shorter residence times of poc in sulfate bearing redox zones may enhance ree burial efficiency within sulfidic and methanogenic sediment zones where ree release ensues cross plots of la concentrations versus cl li and sr delineate a distinct field for the deep fluids z 75 mbsf at site u1329 and indicate the presence of a fluid not observed at the other sites drilled on the cascadia margin changes in ree patterns the presence of a positive eu anomaly and other available geochemical data for this site suggest a complex hydrology and possible interaction with the igneous crescent terrane located east of the drilled transect

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

magma storage ascent and recharge history prior to the 1991 eruption at avachinsky volcano kamchatka russia inferences on the plumbing system geometry article i nfo textural and compositional features of plagioclase phenocrysts of the 1991 eruption lavas at avachinsky volcano kamchatka russia were used to investigate the feeding system processes volcanics are porphyritic basaltic andesites and andesites with low k affinity a fractionation modeling for both major and trace elements was per formed to justify the development of these evolved compositions the occurrence of other magma chamber pro cesses was verified through high contrast bse images and core to rim compositional profiles an and feo wt on plagioclase crystals textural types include small and large scale oscillation patterns disequilibrium textures at the crystal core patchy zoning coarse sieve textures dissolved cores disequilibrium textures at the crystal rim sieve textures melt inclusion alignments at the rim disequilibrium textures at the cores may testify episodes of destabilization at various decompression rates under water undersaturated conditions which suggests different pathways of magma ascent at depth at shallower water saturated conditions plagioclase crystallization continues in a system not affected by important chemical physical perturbations oscillatory zoning develops strongly sieve textured rims along with an increase at rather constant feo are evidence of mixing before the 1991 eruption between a residing magma and a hotter and volatile richer one the textural evidence implies that crystals underwent common histories at shallow levels supporting the existence of a large magma reservoir whose top is at 5 5 km of depth distinct textures at the outer rims in a hand size sample are evidence that crys

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

application of b mg li and sr isotopes in acid sulfate vent fluids and volcanic rocks as tracers for fluid rock interaction in back arc hydrothermal systems

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

from the subtropics to the central equatorial pacific ocean neodymium isotopic composition and rare earth element concentration variations 1 neodymium isotopic compositions end and rare earth element ree concentrations were measured for filtered surface to deep waters 112 samples in the southern tropical pacific the relatively detailed picture of these tracer distributions allowed us to refine the areas where oceanic end variations occur end values increase for most of the water masses flowing from samoa to the solomon sea and in the papua new guinea png area as already observed furthermore water masses arriving from the eastern equatorial pacific 200 550 m depth also revealed radiogenic values possibly acquired in the vicinity of the south american coasts and galapagos islands these end variations affect the whole water column the most likely process causing such variations is boundary exchange between the numerous radiogenic slopes margins located in this area and seawater flowing past dissolution of atmospheric deposition and or diffuse streaming of volcanic ash are also suggested to explain the radiogenic end observed at the surface in the png area interestingly a positive europium eu anomaly characterizes the normalized ree patterns of most of the studied water masses this anomaly is consistent with the ree patterns of sediment and rock samples that are potential sources for the local waters such consistency reinforces the hypothesis that lithogenic sources play a major role in the oceanic ree budget thanks to boundary exchange the data set presented here is a good basis for further sampling that will be realized in the framework of the ongoing geotraces program www geotraces org

metalliferous sediments associated with presently forming volcanogenic massive sulfides the susu knolls hydrothermal field eastern manus basin papua new guinea short sediment cores were examined from the active susu knolls hydrothermal field in the eastern manus back arc basin papua new guinea in order to explain the origin of the currently accumulating metalliferous sediments the mineralogy and geochemistry of the sediments were studied by x ray diffraction scanning electron microscopy energy dispersive x ray fluorescence and instrumental neutron activation analysis sediments of the suzette site originated from the deposition of volcaniclastic material with the addition of a hydrothermal component from the mass wasting of old oxidized chimneys a strong mass wasting event was recognized at the base of the studied sedimentary succession from the occurrence of chalcopyrite pyrite and barite aggregates similar to those found in chimneys as well as the presence of atacamite the metalliferous component is characterized by high concentrations of cu up to 2 3 and au up to 3 5 ppm elevated concentrations of as ba zn and fe as well as a positive eu anomaly the material derived from eroded chimneys was deposited together with abundant glass fragments eroded from the volcanic edifice the mass wasting was succeeded by deposition of volcaniclastic sediment containing dacite fragments ca plagioclase pyroxene glass shards cristobalite si rich amorphous material alunite pyrite barite and magnetite the volcaniclastic sediment may have originated from hydrothermal eruptions at north su and south su the present day plume at suzette is a likely source of rare barite aggregates amorphous cu containing aggregates and cu fe sulfides creating geochemical anomalies of ba and cu in the uppermost sediments at suzette interbedded volcaniclastic and hemipelagic sediments were retrieved east and west of susu knolls the enrichment of mn in these sediments is considered to be a result of settling of mn oxides from a hydrothermal plume

yttrium and rare earth elements in fluids from various deep sea hydrothermal systems rare earth element ree and yttrium y concentrations were measured in fluids collected from deep sea hydrothermal systems including the mid atlantic ridge mar i e menez gwen lucky strike tag and snakepit the east pacific rise epr i e 13 n and 17 19 s and the lau vai lili and manus vienna woods pacmanus desmos back arc basins bab in the south west pacific in most fluids y is trivalent and behaves like ho chondrite normalized y ree y reen concentrations of fluids from mar epr and two bab sites i e vai lili and vienna woods showed common patterns with lree enrichment and positive eu anomalies ree analysis of plagioclase collected at lucky strike strengthens the idea that fluid ree contents are controlled by plagioclase phenocrysts other processes however such as ree complexation by ligands cl f so42 secondary phase precipitation and phase separation modify ree distributions in deep sea hydrothermal fluids ree speciation calculations suggest that aqueous ree are mainly complexed by cl ions in hot acidic fluids from deep sea hydrothermal systems ree concentrations in the fluid phases are therefore influenced by temperature ph and duration of rock fluid interaction unusual y reen patterns found in the pacmanus fluids are characterized by depleted lree and a positive eu anomaly the demos fluid sample shows a flat y reen pattern which increases regularly from lree to hree with no eu anomaly these manus basin fluids also have an unusual major element chemistry with relatively high mg so4 h2s and f contents which may be due to the incorporation of magmatic fluids into heated seawater during hydrothermal circulation ree distribution in pacmanus fluids may stem from a subseafloor barite precipitation and the ree in demos fluids are likely influenced by the presence of sulfate ions

time series studies of vent fluids from the tag and mark sites 1986 1990 mid atlantic ridge a new solution chemistry model and a mechanism for cu zn zonation in massive sulphide orebodies

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 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

flux of volatiles and ore forming metals from the magmatic hydrothermal system of satsuma iwojima volcano the satsuma iwojima volcano southwest japan degasses 5 x 10 6 t yr h 2 o 9 x 10 4 t yr s and 6 x 10 4 t yr cl from high temperature 880 c fumaroles atop a now altered rhyolite dome that erupted 1200 yr ago acidic hot springs ph 1 1 1 8 discharge 20 x 10 6 t yr h 2 o to the sea this water is composed of 1 part magmatic vapor absorbed by 6 parts meteoric ground water the cl and so 4 in solution originate from the vapor whereas cation components are derived largely by dissolution of the rhyolite the flux of pb zn cu and mo in the vapor and acidic springs ranges from 0 1 to 10 t yr each whereas the au flux is 10 5 and 10 3 t yr respectively the low concentrations of nacl and metals in the vapor are due to the condensation of a hypersaline liquid from the vapor during ascent and depressurization meaning that the atmospheric pressure vapor does not reflect the composition of the fluid exsolving from the magma neither this low pressure vapor nor the acidic waters can account for high sulfidation cu au ore deposits deduced to have formed in this environment such mineralization requires the subsequent ascent of a metal rich fluid

garnet and scheelite as indicators of multi stage tungsten mineralization in the huangshaping deposit southern hunan province china abstract the huangshaping w mo pb zn deposit in southern hunan province south china contains multiple generations of garnet and scheelite in skarn and sulfide carbonate altered rocks optical characteristics and chondrite normalized rare earth element reen patterns obtained by in situ laser ablation inductively coupled plasma mass spectrometry analysis were used to distinguish different generations of garnet and scheelite these data show a clear correspondence of garnet reen patterns to major element zonation with hrees e g gd lu being depleted overall coarse grained garnets in the huangshaping deposit have extreme hree depletions and significant lree e g la eu enrichment particularly for ce pr and nd this indicates that rees in these garnets are the result of coupled substitutions ca2 viii 1 ree3 viii 1 and fe2 iv 1 al3 iv 1 medium grained garnets have reen patterns showing significant lree enrichment and depleted hrees with high sn contents this suggests that substitution of rees in these garnets occurs as ca2 viii 1 ree3 viii 1 sn4 iv 1 al3 iv 1 the fact that medium grained garnets have high sn contents indicates mineralizing fluids were oxidizing which is consistent with significant positive eu anomalies however hump shaped reen patterns for garnet rims suggest substitution by ca2 viii 2 na viii 1 ree3 viii 1 where nd tb are preferentially incorporated into the garnet lattice over other rees group 1a scheelite has black cores in cathodoluminescence images and reen patterns showing extreme lree enrichment and hree depletion group 1b scheelite has cores with fine oscillatory zoning and enriched lrees with depleted hrees similar to the reen patterns of group 2a scheelite that occur as rims with bright cl surrounding both group 1a and 1b scheelite the substitution mechanism for rees in these three types of scheelite is ca2 viii 3 viii 1 ree3 viii 2 with being a ca site vacancy the influence of ree speciation in the hydrothermal fluid dominates the reen patterns of these types of scheelite however for group 2b bright rims of scheelite rees are incorporated as ca2 viii 2 na viii 1 ree3 viii 1 similar to the garnet rims finally scheelite mo contents and eu values that decrease from group 1a to 2b support a temporal decrease in oxygen fugacity of the mineralizing fluids ratios of y ho and mo contents that decrease from group 1a and 1b to group 2a and 2b scheelites are similar to those in porphyry related skarn w mo and quartz vein au w deposits respectively our studies also suggest that all these scheelites in this deposit formed from magmatic fluids at the huangshaping deposit medium grained garnets associated with group 1a scheelite precipitated from evolved magmatic fluids during prograde metamorphism as indicated by their complementary y ho ratios paragentically younger scheelite particularly group 2b may have formed from dilute magmatic fluids that underwent large scale hydrothermal circulation the characteristics of group 1b and 2a scheelite likely reflect a transitional environment and fluid mixing during tungsten mineralization in the polymetallic huangshaping deposit

shallow open system evolution of basaltic magma beneath a subduction zone volcano the masaya caldera complex nicaragua abstract lavas and pyroclastic material from the masaya caldera complex have a number of distinctive geochemical features relative compositional homogeneity low al2o3 and high feo contents a tholeitic differentiation trend and elevated large ion lithophile lil element concentrations e g ba 800 ppm on cmas projections their compositions always fall on or near low pressure cotectics in addition the basalts of masaya have unusually high 87sr 86sr and 10be masaya has exhibited medium term compositional cycles best exhibited by the sawtoothed changes in tio2 and feo mgo there are also a number of longer term compositional changes which are abrupt and generally coincide with caldera formation many of the geochemical characteristics of masaya coupled with a number of volcanological observations indicate masaya is underlain by a large shallow open system magma chamber perhaps on the order of 10 km3 in size although fractional crystallization is a significant magmatic process in masaya s open system chamber magma mixing contamination is equally important magma mixing is necessary to explain the discontinuous stratigraphic changes in magma composition observed at masaya and crustal contamination is necessary to explain their generally elevated 87sr 86sr and lil element concentrations two components therefore have been admixed into the magma chamber of masaya a lil poor basaltic component such has been erupted from the nearby nejapa and granada cinder cones and a lil rich acidic component such has been erupted from the nearby calderas of apoyo and apoyeque admixtures of the former have dominated admixtures of the latter ended with caldera formation ironically open system behavior has exerted fundamental control on the maintenance of relative compositional homogeneity

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

ni cu co rich hydrothermal manganese mineralization in the wallis and futuna back arc environment sw pacific abstract the wallis and futuna back arc system is a complex area composed of at least two active oceanic spreading centers the futuna and alofi spreading centers and young volcanic zones characterized by diffuse magmatism locally affected by the samoan hotspot this geological setting is favorable to the establishment of hydrothermal systems in the form of either high temperature ht hydrothermal venting or low temperature lt diffuse flow during the 2010 futuna cruise aboard the r v l atalante three remarkable inactive lt fe si mn deposits were discovered utu uli anakele and utu sega some of the mn rich precipitates discovered exhibit the highest base metals concentrations so far recorded in ferromanganese rocks including in the well documented hydrogenetic crusts and polymetallic nodules the deposits lie on top of volcanoes and formed in close association with the volcanic facies the manganese mineralization occurs in the form of massive layered crusts and mn rich cements within strongly altered basaltic pyroclastic rocks brecciated lavas and more rarely in sediments field observations and mineralogical and chemical studies support a hydrothermal origin for the mineralization and show that nickel cobalt and copper enrichments are controlled by the precipitation of 7 a and 10 a manganates the conventional geochemical classifications e g bonatti et al 1972 used to decipher the origin of mn mineralization cannot be used for this new type of deposit and new robust discrimination diagrams need to be established we suggest that the unusual enrichment of metals recorded in our samples is due to i a lack of precipitation of high temperature massive sulfides at depths that would have retained metals e g cu ni co ii isolation of the hydrothermal system thereby avoiding ni co and cu losses in the water column and iii the ability of birnessite and buserite todorokite to scavenge co ni and cu from aqueous fluids the utu uli and anakele deposits share certain characteristics with the active hydrothermal system at loihi seamount e g the depth of mineralization relationships with pyroclastic volcanoes and the influence of a mantle plume source and thus might represent late stage products of this specific type of hydrothermal activity elsewhere the co rich mineralization of the calatrava volcanic field cvf in spain may be a potential analog of the utu sega deposit the mn co deposits of the cvf formed in close proximity to pliocene volcanic rocks metals were transported by epithermal hydrothermal solutions with high fo 2 and cobalt was scavenged by mn oxides together with the well documented stratabound mn deposits gonzalez et al 2016 hein et al 2008 hein et al 1996 the mn deposits discovered in the wallis and futuna back arc provide crucial insights into lt hydrothermal activity in the deep ocean the metal rich character of this lt hydrothermal activity may be of major importance for future research on the net flux of hydrothermally derived metals e g ni co cu to the open ocean

replenishment rates of crustal magma and their bearing on potential sources of thermal energy abstract a general model of magma intrusion into the crust is developed which is based on a viscous dissipation forced convection flow process driven by gravitational buoyancy forces although some of the points in this general model have been studied before it is possible with the present model to go further and calculate magma volumetric intrusion rates from fundamental properties and parameters equations for forced convection in a conduit with viscous dissipation are combined with results for the temperature dependence of magma viscosity the volumetric intrusion rate is shown to be not a function of viscosity as might be expected but rather a function primarily of the rate of change of viscosity with temperature the model predictions for intrusion rate correlate well with field results for several sites where data exist for both intrusion or extrusion rate and for the temperature dependent behavior of magma viscosity the model predicts magma chamber replenishment rates equivalent to thermal energy rates on the order 10 gw gigawatts for a single active magma site assuming active magma sites on a 50 km spacing along volcanic lineaments leads to an estimate of a renewable magma intrusion rate into the crust of the western u s on the order of 2 tw terawatts

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

mineralogical geochemical and isotopic characteristics of hydrothermal alteration processes in the active submarine felsic hosted pacmanus field manus basin papua new guinea during odp leg 193 4 sites were drilled in the active pacmanus hydrothermal field on the crest of the felsic pual ridge to examine the vertical and lateral variations in mineralization and alteration patterns we present new data on clay mineral assemblages clay and whole rock chemistry and clay mineral strontium and oxygen isotopic compositions of altered rocks from a site of diffuse low temperature venting snowcap site 1188 and a site of high temperature venting roman ruins site 1189 in order to investigate the water rock reactions and associated elemental exchanges the volcanic succession at snowcap has been hydrothermally altered producing five alteration zones 1 chlorite illite cristobalite plagioclase alteration apparently overprinted locally by pyrophyllite bleaching at temperatures of 260 310degreesc 2 chlorite mixed layer clay alteration at temperatures of 230degreesc 3 chlorite and illite alteration 4 illite and chlorite illite mixed layer alteration at temperatures of 250 260degreesc and 5 illite chlorite alteration at 290 300degreesc felsic rocks recovered from two holes 1189a and 1189b at roman ruins although very close together show differing alteration features hole 1189a is characterized by a uniform chlorite illite alteration formed at similar to250degreesc overprinted by quartz veining at 350degreesc in contrast four alteration zones occur in hole 1189b 1 illite chlorite alteration formed at similar to300degreesc 2 chlorite illite alteration at 235degreesc 3 chlorite illite and mixed layer clay alteration and 4 chlorite illite alteration at 220degreesc mass balance calculations indicate that the chloritization illitization and bleaching silica pyrophyllite assemblages alteration stages are accompanied by different chemical changes relative to a calculated pristine precursor lava the element cr appears to have a general enrichment in the altered samples from pacmanus the clay concentrate data show that cr and cu are predominantly present in the pyrophyllites illite shows a significant enrichment for cs and cu relative to the bulk altered samples considerations of mineral stability allow us to place some constraints on fluid chemistry hydrothermal fluid ph for the chloritization and illitization was neutral to slightly acidic and relatively acidic for the pyrophyllite alteration in general the fluids especially from roman ruins and at intermediate depths below snowcap show only a small proportion of seawater mixing 10 fluids in shallow and deep parts of the snowcap holes in contrast show stronger seawater influence copyright c 2004 elsevier ltd

phyllosilicate alteration mineral assemblages in the active subsea floor pacmanus hydrothermal system papua new guinea odp leg 193 pacmanus is an active submarine hydrothermal system in the manus back arc basin papua new guinea located at 1 600 to 1 700 m below sea level on the crest of a dacitic volcano it is inferred to represent a modern analogue of ancient mineralizing sea floor hydrothermal systems that produced volcanogenic polymetallic massive sulfide deposits ocean drilling program odp leg 193 drilled the subsea floor hydrothermal alteration zone of pacmanus in a high temperature discharge area roman ruins and a low temperature discharge area snowcap reaching a maximum depth of 380 m below the sea floor evidence from short wavelength infrared swir spectroscopy x ray diffraction xrd analyses calculated normative mineral abundances and electron microprobe data show that there are substantial variations in the hydrothermal phyllosilicate assemblages within the pacmanus hydrothermal system the altered dacite at roman ruins contains 10 to 25 wt percent normative chlorite smectite and up to 15 wt percent normative illite in contrast altered dacite below snowcap contains up to 50 wt percent combined normative illite paragonite chlorite smectite pyrophyllite swir data show that pyrophyllite is particularly abundant between 50 and 120 and between 220 and 270 m below sea floor indicating localized interaction of dacite with acidic hydrothermal fluids variations in the na k ratio of dioctahedral phyllosilicate determined by electron microprobe and spectral analyses confirm the presence of a paragonitic component at snowcap a model is suggested to explain the differences in the distribution of hydrothermal phyllosilicate assemblages in the two areas in terms of variations in fluid composition and changes to the subsea floor hydrology in a dynamically evolving volcanic hydrothermal environment

effect of tensile stress concentration around magma chambers on intrusion and extrusion frequencies what controls the intrusion and extrusion frequencies associated with volcanoes is still poorly understood i propose that for volcanoes at divergent plate boundaries these frequencies may be largely determined by the tensile stress concentration around the magma chambers that feed them this stress concentration is mainly a function of the applied tensile stress associated with spreading and the aspect height width ratios of the chambers high spreading rates and or aspect ratios lead to high rates of tensile stress concentration around the chambers and to an increase in their intrusion frequencies it is found that for chambers at the same depth in a volcanic zone the one of the highest aspect ratio will normally intrude magma most frequently also if the chambers are of equal aspect ratios the one at the greatest depth will intrude magma most frequently because the extrusion frequency of a volcano is a fraction of its intrusion frequency the extrusion frequency may also be largely determined by the rate of tensile stress concentration around the magma chamber that feeds the volcano these results are applied to the divergent plate boundary in iceland where many of the volcanoes appear to be fed by double chambers that is shallow chambers fed by deep seated chambers it is found that except when the aspect ratio of the deep seated chamber is much less than that of the shallow chamber the intrusion frequency of the shallow chamber is normally largely controlled by that of the deep seated chamber it is concluded that whereas the short term i e 103 yrs extrusion frequencies of volcanoes at the plate boundary in iceland may be similar to the dike intrusion frequencies of the source chambers the long term i e 104 yrs extrusion frequencies may be about ten times lower than the intrusion frequencies

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

rare earth element evolution and migration in plagiogranites a record preserved in epidote and allanite of the troodos ophiolite this study was funded by isf research grant 1044 09 to yaron katzir niels jons and wolfgang bach acknowledge support from the dfg research centre excellence cluster the ocean in the earth system