a volcanologist s review of atmospheric hazards of volcanic activity fuego and mount st helens abstract the large amount of scientific data collected on the mount st helens eruption has resulted in significant changes in thinking about the atmospheric hazards caused by explosive volcanic activity the hazard posed by fine silicate ash with long residence time in the atmosphere is probably much less serious than previously thought the mount st helens eruption released much fine ash in the upper atmosphere these silicates were removed very rapidly due to a process of particle aggregation sorem 1982 carey and sigurdsson 1982 rose and hoffman 1982 there is some evidence to suggest that particle aggregation is particularly successful in removing glass shards with high surface areas mass ratios the primary atmospheric hazard of explosive eruptions is volcanic sulfur which is converted to sulfuric acid and sulfate crystals although the mount st helens dacite magma had a very low sulfur content before eruption the eruptions did make a significant contribution to the stratospheric sulfate layer newell 1982 evidence based on measurements of s and cl in erupted rocks glass inclusions gas samples and atmospheric samples collected for both mount st helens and fuego volcanoes suggests that both volcanoes released substantial contributions of s from intrusive non eruptive magma the amount of sulfur contributed to the atmosphere by an explosive eruption thus depends not only on the volume of magma erupted and its sulfur content but also on the degree of near surface non eruptive magma the data collected to assess atmospheric hazard and to evaluate the processes and mechanisms of explosive volcanic eruptions have helped illuminate our understanding of 1 the dispersion and atmospheric fractionation of volcanic ash and 2 the determination of the size and degassing energetics of shallow magma bodies beneath volcanoes

gas and aerosol emissions from lascar volcano northern chile insights into the origin of gases and their links with the volcanic activity abstract this study focuses on the chemical compositions of volcanic gases and aerosols emitted by lascar volcano northern chile the sustained volcanic plume was sampled in april 2009 april 2011 and november 2012 through filter packs and analyzed for major gaseous species so 2 hcl and hf and trace elements during fieldwork so 2 flux measurements were also performed by uv spectrometry doas the lascar volcano is a significant and sustained emitter of so 2 between 150 and 940 t d hcl between 170 t d and 210 t d and hf up to 100 t d combining the so 2 normalized trace element concentrations and the so 2 emission rates we evaluate that the quiescent degassing of lascar is an important local source of trace metals to the atmosphere with contributions to global volcanic fluxes generally less than 2 our data were used to infer the origin of the gas emitted at lascar two major degassing sources were identified a deep magmatic reservoir and a shallow hydrothermal system the variable interaction between these two sources is the most likely scenario for explaining the compositional ranges in acid gases but also in a volatile and fluid mobile trace element such as b these variations are related to changes in volcanic activity an extensive interaction between the hot ascending magmatic gases and the shallow aquifer occurred in 2009 possibly due to a long period of quiescence before magmatic activity renewed in 2011 and 2012 our study highlights therefore that filter pack measurements may be used to study changes in subsurface processes that probably play a key role in triggering volcanic eruptions

magmatic evolution of a volcano studied by 230th 238u disequilibrium and trace elements systematics the etna case age determinations of several lava flows from etna through 230th 238u disequilibrium internal isochrons yield a precise chronology of the volcano s history for the last 200 000 years and emphasize the main episodes in the formation of this huge complex strato volcano study of 230th232th 0 initial ratios of lavas together with their trace element compositions yields a consistent model of magmatic evolution implying the existence for 200 000 years of a deep reservoir of alkalic magma periodically mixed with magmas of tholeiitic affinity these short periods of mixing appear to be related to the formation of the large calderas of etna in addition to these processes affecting the deep reservoir fractional crystallization also occurred in more superficial levels of the volcanic edifice thereby yielding several series of differentiation of relatively short duration as for its geochemistry etna s volcanism is of oceanic type but with its own characteristics and in a peculiar geodynamic context at the edge of the african plate

sulphur dioxide particle and elemental emissions from mount etna italy during july 1987 sulphur dioxide emission rates were measured at mount etna italy during july 1987 while the volcano was undergoing relatively quiet activity the so2 flux averaged 930 587 1 mg d excluding 19 july when the flux was 3200 1730 1 mg d rising magma and or an influx of less degassed magma could explain the increased so2 flux the high so2 flux did not correlate with changes in observed volcanic activity this suggests that so2 monitoring may be useful as an indicator of shallow magmatic activity but not as a predictor of future eruptions of mount etna

geochemistry of fluids associated with the 1995 1996 eruption of mt ruapehu new zealand signatures and processes in the magmatic hydrothermal system abstract the 1995 1996 eruption of mt ruapehu has provided a number of insights into the geochemical processes operating within the magmatic hydrothermal system of this volcano both pre eruption degassing of the rising magma and its eventual intrusion into the convective zone of the hydrothermal system beneath the lake were clearly reflected in lake water compositions the eruptions of september october 1995 expelled the lake and provided the first ever opportunity to characterise gas discharges from this volcano the fumarolic discharges revealed compositions typical of andesite volcanoes and strong interaction with the enclosing meteoric and hydrothermal system fluids some 1 1 mt of so 2 gas was released from the volcano between september 1995 and december 1996 whereas ca twice this amount 2 2 mt equivalent so 2 was erupted as soluble i e leachable oxyanions of sulphur significantly more sulphur was released from the volcano over this period than can be accounted for from the magma volume actually erupted the evidence suggests that a sizable component of the evolved sulphur was remobilised from the long lived hydrothermal system within the volcano during the 1995 1996 activity

composition resolved size distributions of volcanic aerosols in the mt etna plumes 1 particle size distributions for soluble and insoluble species in mt etna s summit plumes were measured across an extended size range 10 nm d 100 m using a combination of techniques automated scanning electron microscopy qemscan was used to chemically analyze many thousands of insoluble particles collected on pumped filters allowing the relationships between particle size shape and composition to be investigated the size distribution of fine silicate particles d 10 m was found to be lognormal consistent with formation by bursting of gas bubbles at the surface of the magma the compositions of fine silicate particles were found to vary between magmatic and nearly pure silica this is consistent with depletion of metal ions by reactions in the acidic environment of the gas plume and vent measurements of the size shape and composition of fine silicate particles may potentially offer insights into preemission synemission and postemission processes the mass flux of fine silicate particles from mt etna released during noneruptive volcanic degassing in 2004 and 2005 was estimated to be 7000 kg d 1 analysis of particles in the range 0 1 d m 100 by ion chromatography shows that there are persistent differences in the size distributions of sulfate aerosols between the two main summit plumes analysis of particles in the range 0 01 m d 0 1 m by scanning transmission electron microscopy stem shows that there are significant levels of nanoparticles in the mt etna plumes although their compositions remain uncertain

magnetotelluric measurements across the sorgenfrei tornquist zone in southern sweden and denmark the results of a magnetotelluric experiment across the sorgenfrei tornquist zone stz in the southwestern part of the baltic shield are presented the stz marks the border between the proterozoic

distribution of metals between particulate and gaseous forms in a volcanic plume in order to gain information on the distribution of metals between particles and gaseous forms in the plume of kilauea volcano a filter designed to collect metals associated with particles was followed in series by two other collectors intended to trap metals present in gaseous atomic molecular or complexed form first an acid bubbler bath and then a cold trap of the six metals measured all of the in tl and bi and almost all of the cd pb and cu were found on the filter none of any of the metals was detected in the acid bubbler bath masses equivalent to 0 3 of the amount of cd on the filter 0 4 of the amount of pb and 9 3 of the cu were measured in the cold trap the results indicate that all or nearly all of the six metals were partitioned to the particulate portion of the physical mixture of gases and particles that constitutes a volcanic plume but that there may be systematic differences between chalcophile metals in the ways they are partitioned between particulate and gaseous phases in a cooled plume and possibly differences in the acidity or other chemical properties of the molecular phases

phlogopite clinopyroxenite nodules from high k magmas roccamonfina volcano italy evidence for a low pressure metasomatic origin dense nodules containing phlogopite mg number 80 clinopyroxene and vesicular glass with subordinate olivine and cr spinel are found at roccamonfina volcano in pyroclastic deposits of widely varying ages and compositions significantly phlogopite has never been observed as a phenocryst in any volcanic rock at roccamonfina in the nodules phlogopite shows a variety of reaction textures in relation to both clinopyroxene and olivine each of the major minerals and glass is compositionally homogeneous within a single nodule and the suite as a whole shows systematic correlations of mg number among these phases clinopyroxene en40 47 and olivine fo81 87 compositions closely match phenocryst compositions from basic lavas at roccamonfina but cr spinel compositions strongly diverge from those in roccamonfina volcanic rocks sr and nd isotopic compositions of whole rock nodules and constituent minerals fall within the field for high k series hks volcanic rocks although minor isotopic disequilibrium is noted among minerals of individual nodules euhedral crystals are enclosed by interstitial glass indicating that the glasses represent residual melts and are not products of in situ partial melting of analyzed glasses from five nodules three are ne normative and compositionally similar to hks tephrite magma compositions one is hy normative and similar to low k series lks trachyandesites and the other has larnite in the norm and is unlike any known volcanic rock in addition to other more basic host rock types phlogopite pyroxenites are found within voluminous pyroclastics ranging from leucite tephrites to highly evolved phonolites and trachytes these rocks have strong depletions in sr ba and eu consistent with extensive fractionation in low pressure magma chambers consequently the phlogopite pyroxenites are also constrained to have formed at low pressures this interpretation conflicts with several previous hypotheses for the origin of similar phlogopite pyroxenites at other potassic volcanic centers including metasomatism of mantle protoliths and origins as high pressure plutonic assemblages textures in the roccamonfina nodules indicate that both clinopyroxene and olivine were consumed by reactions producing phlogopite we envision formation of these nodules in sub volcanic magma chambers through open system reaction of hks clinopyroxene olivine cumulates with a rising potassic hks melt or vapor phase

metal transport in volcanic plumes a case study at white island and yasur volcanoes abstract we report new data on trace metal emissions at white island volcano 2015 2016 the first estimates from yasur volcano 2016 and a brief review of global volcanic metal fluxes bi cd tl se sb te and au are the most enriched metals and metalloids in the particulate phase of volcanic plumes observations of the particulate phase from the volcanic plumes of white island yasur and etna reveal abundant silicates and sulfates sulfuric acid and more interestingly zn oxide containing variable amounts of cu thermodynamic speciation calculations show chloride species to be very important in terms of gaseous metal transport complexation with sulfur in contrast appears significant only in s rich and cl poor gases at high 700 c temperature bromine despite being a minor component of volcanic gases is very efficient at complexing with metals and especially with cu pb bi zn and cr metal emission rates in the study period at white island are one to two orders of magnitude lower than reported previously with 6 10 kg d of cu as se and zn and

zinc enrichment in the phreatic ashes of mt st helens april 1980 abstract micrometer size condensate particles consisting of zincite zno with possibly minor zinc silicate occur in the phreatic ashes of mt st helens that were deposited in early april 1980 zincite probably results from the reaction between steam air and magmatic zinc halide thermodynamic calculations indicate that oxidation of zinc halide proceeds under the prevailing conditions in the eruption cloud the zinc enrichment in the phreatic ashes adds evidence to the hypothesis that magmatic vapors were involved in the phreatic eruptions it appears as if zinc is released from the magma already in the earliest stages of volcanism monitoring of zinc in fumaroles and hot springs could possibly be helpful in the prediction of volcanic activity

sulfur dioxide and particles in quiescent volcanic plumes from poas arenal and colima volcanos costa rica and mexico measurements of so2 emission rates and concentrations and of particle distribution size shape and composition were made in quiescent volcanic plumes emitted into the troposphere from poas and arenal volcanos costa rica and colima volcano mexico so2 emission rates were 700 180 metric tons per day t d for poas 210 30 t d for arenal and 320 50 t d for colima the concentrations of so2 calculated from the cospec lidar data were 5 380 ppb concentrations of so2 measured directly by flame photometry were 10 250 ppb particles collected in the plumes with a quartz crystal microbalance impactor were mostly less than 3 m in diameter and consisted of droplets of dilute sulfur bearing solutions and minor amounts of larger silicate particles coated with a sulfur bearing film or crust total particle concentrations were 4 7 g m3 for poas and 18 8 g m3 for colima comparison of concentrations of so2 in the plumes with gas samples collected at fumaroles on the ground suggests that the plumes are diluted by the atmosphere by factors of up to 105

chemical characterisation of rainwater at stromboli island italy the effect of post depositional processes abstract volcanoes emit fluids and solid particles into the atmosphere that modify the chemical composition of natural precipitation we have investigated the geochemistry of stromboli s rainfall during the period from november 2014 to march 2016 using a network of a new type of sampler specifically designed for operations on volcanic islands we found that most of the chemical modifications are due to processes occurring after the storage of rainwater in the sampling bottles these processes include dissolution of volcanogenic soluble salts encrusting volcanic ash and a variable contribution of sea spray aerosol our data showed noticeably less scatter than has previously been achieved with a different sampling system that was more open to the atmosphere this demonstrates the improved efficacy of the new sampler design the data showed that post depositional chemical alteration of rain samples dominates over processes occurring during droplet formation ad precipitation this has important implications for the calculation of fluxes of chemicals from rainfall in volcanic regions

bismuth oxide nanoparticles in the stratosphere platey grains of cubic bi2o3 bi2o3 and bi2o2 75 nanograins were associated with chondritic porous interplanetary dust particles w7029c1 w7029e5 and 2011c2 that were collected in the stratosphere at 17 19 km altitude similar bi oxide nanograins were present in the upper stratosphere during may 1985 these grains are linked to the plumes of several major volcanic eruptions during the early 1980s that injected material into the stratosphere the mass of sulfur from these eruptions is a proxy for the mass of stratospheric bi from which we derive the particle number densities p m 3 for average bi2o3 nanograins due to this volcanic activity and those necessary to contaminate the extraterrestrial chondritic porous interplanetary dust particles via collisional sticking the match between both values supports the idea that bi2o3 nanograins of volcanic origin could contaminate interplanetary dust particles in the earth s stratosphere copyright 1997 by the american geophysical union

variations of cl f and s in mount etna s plume italy between 1992 and 1995 this study investigates data on the cl f and s concentrations of plume filter samples collected between 1992 and 1995 from mount etna the samples were collected during eruptive and noneruptive activity and show fairly constant cl f ratios but wide variation in the cl s ratios the determination of the cl f ratio between 5 and 14 allows an estimate of f degassing to be derived that ranges from 10 to 30 of the initial f content of the magma the variation in the cl s ratio fits an empirical two stage degassing model where gas with high cl s ratio is discharged during quiescient degassing and gas with low cl s ratios is discharged during eruptive degassing the typical permanent degassing occurs from a depth at which chlorine exsolution exceeds sulfur exsolution cl s 1 the opposite of this behavior is observed during eruptive periods when significant sulfur degassing occurs because magma degasses at near atmospheric pressure cl s 0 1 the cl s ratio in the plume characterizing the type of degassing has the potential to be a useful geochemical tool for monitoring the volcano

development and spatial distribution of soils on an active volcano mt etna sicily abstract as a large active volcano mt etna presents a complex soil forming environment with a spatial diversity of lava flow age tephra deposition local climate and agriculture following a review of previous published research on etna s soils this paper analyses physical and chemical data for 23 profiles between 120 m and 1030 m elevation on all flanks of the volcano with the aim of characterising the soils and determining the extent to which the chief controls on their nature and geography may be identified soils are sampled across a chronosequence of lava flows dating from 72 yr to between 28 ka and 42 ka bp which occur in conditions of diverse land use and local climate ages of flows 3000 yr are only broadly constrained the majority of soils comprise mostly tephra chief soil processes inferred have been identified in previous published research on mt etna accumulation of soil organic matter rapid loss of na and production of fine grained materials particularly those inferred to be of short range order other developments are soil structural formation and evidence of increasing soil mesofaunal activity despite the complexity of environmental diversity and spatial variation in tephra deposition a number of soil properties including material

vapor deposition of trace elements from degassed basaltic lava piton de la fournaise volcano reunion island abstract silica tube sublimates resulting from the cooling of high temperature volcanic gases from degassed lava in lava tunnels have been sampled at piton de la fournaise volcano mineral phases deposited in the tube are mainly halides na k and cu chlorides si and k fluorides the distribution of most of the chemical elements as a function of the temperature is mainly controlled by their volatility volatile elements such as rb cs se pb and tl are associated with low temperature deposits whereas refractory elements such as r e e alkaline earth sc ta hf th and zr are not detected the mineral assemblages are characterized by the lack of sulfides sulfates native sulfur and oxides in the same way numerous transition and semi metallic elements are lacking this is interpreted as the result of the magma transport in surface lava tunnels leading to extensive degassing upstream of the collection site

the sirung volcanic boiling spring an extreme chloride rich acid brine on pantar lesser sunda islands indonesia abstract the sirung volcano with a history of phreatomagmatic outbreaks has its present active center within a 1000 m wide subsidence crater the sirung crater lake scl has 15 g l 1 cl and 19 g l 1 so4 ph 0 75 temperature 40 c a highly saline brine sirung boiling spring sbs boils to the surface beside the lake it contains 116 g l 1 cl ph 1 4 chemical geothermometers indicate a reservoir temperature of 240 c the maximum depth of this reservoir is estimated to be 400 m the stable isotope composition is d 12 and 18o 5 0 to 6 0 tritium in the sbs is 0 0 tu in the scl 4 6 tu evidence against invading seawater as a source is the negative d value in addition to the six times higher cl concentration of the sbs evaporites are rejected as a source of the cl because of the geologic setting the average cl h 2 o ratio in sirung volcanic glasses as estimated by microprobe is very close to the cl h 2 o ratio of 0 047 for the sbs the zero tritium level in the sbs its high cl concentration and the acid character are other evidences for magmatic water as source for the sbs the acid sbs is poor in sulphur which may have been precipitated at depth as sulphides theories on porphyry cu formation in volcanic arc environments invoke highly saline brines as the transporting agent the acid saline brines from the sirung and white island new zealand craters and cl rich crater lakes associated with andesitic volcanism in subduction zones indicate that such fluids occur more frequently at the surface than has been possibly realized hitherto

the historic magmatic hydrothermal eruption of the breccia di commenda vulcano italy the historic breccia di commenda bc explosive eruption of vulcano aeolian islands italy opened with a phase that generated a gray fine ash layer dispersed to the northwest phase 1 the eruption continued with a dilute pyroclastic density current pdc that was dispersed to the east followed by the emplacement of radially distributed topographically controlled pdc deposits phase 2 the last phase of the eruption produced a sequence of accretionary lapilli and gray fine ash dispersed toward the southeast phase 3 the most impressive feature of the bc is its high lithic juvenile clast ratio and the yellow color of the deposits of phase 2 lithic fragments are mainly hydrothermally altered rocks in the silicic and advanced argillic facies juvenile fragments ranging from 20 to 40 by volume are mainly confined to the ash component of the deposits and comprise rhyolitic to trachyandesite poorly to non vesicular fragments the fine ash fraction of the deposits is richer in s cu zn pb and as than the bc juvenile lapilli and bombs and also the juvenile components of other la fossa units suggesting that the bc formed in the presence of an anomalously high amount of s and metals sulfur and metals may have been carried as aerosols by chloride and sulfate bearing micro crystals derived from the condensation of magmatic gas in the eruptive cloud the high content of hydrothermally altered lithic clasts in the deposits suggests that explosions involved the fluid saturated hydrothermally altered rocks residing in the conduit zone however the presence of a juvenile component in the deposits supports the idea that this explosion may have been triggered by the ascent of new magma we categorize this eruption as magmatic hydrothermal to emphasize that in this type of phreatomagmatic eruption the external water was an active hydrothermal system rock magnetic temperatures of non altered lava lithic fragments indicate a uniform deposit temperature for the pdc deposits of between 200 and 260 c with a maximum at 280 c these homogeneous relatively low temperatures are consistent with the idea that the phase 2 explosions involved the expansion of abundant steam from the flashing of the hydrothermal system in addition recent paleomagnetic dating of the bc provides an age of between 1000 and 1200 ad younger than that reported in the previously published data suggesting that previous interpretations and the recent history of la fossa and mt pilato require re evaluation

volcanic dust in the stratosphere between 34 and 36 km altitude during may 1985 abstract the morphology mineralogy chemistry and size distribution of nonspherical particles collected in the stratosphere between 34 and 36 km altitude during may 1985 were determined by analytical electron microscope analysis the single crystal grains are between a few nanometers in diameter and 14 m in length and occur as single particles and in mono and polymict clusters about 70 of all particles are tridymite cristobalite keatite and anorthite that delineate cotectic plagioclase mullite and tridymite mullite crystallisation in order of decreasing abundance the particles further include orthopyroxene olivine barite and metal oxides all particle properties including salt microcrystals and sulfuric acid droplets on their surface uniquely support a volcanic origin the abundance of ca al silicate and silica particles could indicate fractionation in ascending volcanic plumes or be an artifact of lacking data for ash fall deposits at comparable size fractions the observed upper size limit of nonspherical particles is accurately predicted by the wilson huang settling law when particle diameters are equal to or larger than the gas mean free path of the atmosphere the abundance of particles m in size at collection altitude suggests that nonspherical particles smaller than the gas mean free path behave as spherical particles with faster settling rates settling rate modelling the mineralogical and chemical properties of the nonspherical particles support that they could be from the top of the 1982 el chichon eruption plume that reached an altitude similar to the 1985 collection altitude

magmatic and phreatomagmatic volcanic activity at mt takahe west antarctica based on tephra layers in the byrd ice core and field observations at mt takahe abstract the morphology grain size characteristics and composition of ash particles in 30 ka to 150 ka tephra layers from the byrd ice core were examined to characterize the eruptions which produced them and to test the suggestion that they were erupted from mt takahe a shield volcano in marie byrd land west antarctica volcanic deposits at mt takahe were examined for evidence of recent activity which could correlate with the tephra layers in the ice core coarse and fine ash layers have been recognized in the byrd ice core the coarse ash layers have a higher mass concentration than the fine ash layers and are characterized by fresh glass shards 50 m diameter many containing elongate pipe vesicles the fine ash layers have a lower mass concentration and contain a greater variety of particles typically mt takahe is the favored source for the tephra because a chemical analyses of samples from the volcano are distinctive being peralkaline trachyte and similar in composition to the analyzed tephra b mt takahe is a young volcano a speculative eruptive history for mt takahe is established by combining observations from mt takahe and the byrd ice core tephra initial eruptions at mt takahe were subglacial and then graded into alternating subaerial and subglacial activity the tephra suggest alternating subaerial magmatic and hydrovolcanic eruptions from 30 to 20 ka b p followed by a sustained period of hydrovolcanic eruptions from 20 to 14 ka b p which peaked at 18 ka b p

trace elements in the particulate phase of the plume of masaya volcano nicaragua masaya volcano nicaragua has been passively degassing since 1993 this gas crisis provides a unique opportunity for investigating the degassing of magmatic volatiles here we studied the chemical composition of the volcanic particulate phase collected directly from the plume the objective was to gain new insights into the volatilities and emission rates of trace elements the results indicate enrichments in the aerosol phase of all analyzed trace elements including not only those known to be volatile such as cu and te but also elements considered as refractory such as rare earth elements rees and th rees were fractionated with a significant enrichment of light rare earth elements lrees over heavy rare earth elements hrees this pattern suggests degassing of lrees as chlorides in general the emission of most trace elements in volcanic plumes is governed by the primary degassing of chloride compounds however sem eds data and chemical analysis of aerosol filters allow us to state that trace elements can also be released as sulphate and chloro sulphate compounds the trace element emission rates at masaya are significant and place this volcano as a major gas emitter however for some elements like cu masaya s contribution to the global volcanic flux seems disproportionate probably pointing to the poor dataset available for other degassing volcanoes

rapid oxidation of mercury hg at volcanic vents insights from high temperature thermodynamic models of mt etna s emissions a major uncertainty regarding the environmental impacts of volcanic hg is the extent to which hg is deposited locally or transported globally an important control on dispersion and deposition is the oxidation state of hg compounds hg 0 is an inert insoluble gas while hg ii occurs as reactive gases or in particles which deposit rapidly and proximally near the volcanic vent using a new high temperature thermodynamic model we show that although hg in etna s magmatic gases is almost entirely hg 0 i e gaseous elemental mercury significant quantities of hg ii are likely formed at etna s vents as gaseous hgcl2 when magmatic gases are cooled and oxidised by atmospheric gases these results contrast with an earlier model study and allow us to explain recent measurements of hg speciation at the crater rim of etna without invoking rapid 1 min low temperature oxidation processes we further model hg speciation for a series of additional magmatic gas compositions compared to etna hg ii production i e hg ii hgtot is enhanced in more hcl rich magmatic gases but is independent of the hg hbr and hi content of the magmatic gases hg ii production is not strongly influenced by the initial oxidation state of magmatic gases above nno although production is hindered in more reduced magmatic gases the model and results are widely applicable to other open vent volcanoes and may be used to improve the accuracy of chemical kinetic models for low temperature hg speciation in volcanic plumes

global mercury flux from volcanic and geothermal sources abstract the global hg flux from natural sources is poorly known we present data on hg levels in volcanic fumaroles that in combination with sulfur analyses and published so 2 flux data lead to new global hg flux estimates the volcanogenic hg flux from passively degassing volcanoes is small 30 mg hg yr the flux from erupting volcanoes is much larger but less well constrained we estimate it at about 800 mg yr these data are interpreted as evidence for early hg degassing from magmas geothermal sources contribute roughly 60 mg yr hg to the atmosphere an estimate based on average hg contents of hot springs and global convective heat transport total natural hg emissions from land amount to 1290 mg yr including a revised soil vapor flux of 400 mg yr estimates of anthropogenic contributions to the atmospheric hg budget vary between 3000 and 11 500 mg yr and are substantial compared to our natural hg flux estimate

fractionation of families of major minor and trace metals across the melt vapor interface in volcanic exhalations chemical families of metals fractionate systematically as they pass from a silicate melt across the interface with the vapor phase and on into a cooled volcanic plume we measured three groups of metals in a small suite of samples collected on filters from the plumes of kilauea hawaii usa etna sicily and merapi java volcanoes these were the major minor and trace metals of the alkali and alkaline earth families k rb cs ca sr ba a group of ordinarily rare metals cd cu in pb tl that are related by their chalcophile affinities and the radon daughter nuclides 210po 210bi and 210pb the measurements show the range and some details of systematic melt vapor fractionation within and between these groups of metals in the plumes of all three volcanoes the alkali metals are much more abundant than the alkaline earth metals in the kilauea plume the alkali metals are at least six times more abundant than the alkaline earth metals relative to abundances in the melt at etna the factor is at least 300 fractionations within each family are commonly also distinctive in the kilauea plume in addition to the whole alkaline earth family being depleted the heaviest metals of the family sr ba are progressively more depleted than the light metal ca in plumes of fumaroles at merapi k cs ratios were approximately three orders of magnitude smaller than found in other earth materials this may represent the largest observed enrichment of the light ion lithophile lil metals changes in metal ratios were seen through the time of eruption in the plumes of kilauea and etna this may reflect degree of degassing of volatiles with which metals complex from the magma bodies at kilauea the changes in fractionation were seen over about three years fractionation within the alkaline earth family increased and that between the two families decreased over that time all of the ordinarily rare chalcophile metals measured are extremely abundant in volcanic plumes and cd and tl are enriched relative to the others indium is much more abundant in the plume of the hotspot volcano kilauea than in the etna plume probably non hotspot in character it may be a useful indicator of the tapping of deep mantle zones or could aid in the interpretation of reports of pt group metals in exhalations from hot spot volcanoes indium in old glacial ice strata could help assess magnitude and variability of exhalations from hotspot volcanoes in past time strong melt vapor fractionation of the alkali and alkaline earth metals may only be observed in plumes during quiescent degassing of volcanoes when large amounts of ash or spatter undifferentiated lava enter the plume its alkali and alkaline earth metal composition may approach that of the melt ratios among the chalcophile metals may not be much changed by addition of ash because their concentrations in melt are so small and masses of them in any plume may remain dominated by transfer across the melt vapor interface radon daughter nuclides give information about state of volcanic activity at time of sampling the precisely known origins ultratrace detectability decay systematics and wide variations in volatility of these species provide information about residence times degassing and travel histories and identities of melt bodies in volcanic systems

zircon u pb and hf isotope constraints from the ailao shan red river shear zone on the tectonic and crustal evolution of southwestern china abstract the ailao shan red river asrr shear zone one of the most prominent geologic strike slip shear zones in southeast asia consists of high grade metamorphic complexes that provide a rare opportunity to sample the mid crustal rocks along the western margin of the yangtze block of south china here we report combined in situ analyses of zircon u pb and lu hf isotopes of eight gneisses from the diancang shan and ailao shan segments of the asrr shear zone our zircon u pb data indicate that the rocks contain abundant magmatic zircons ranging in age from 1785 to 25 ma with peak ages at ca 770 350 and 240 ma suggesting three major periods of protolith formation the 350 ma zircons observed only in an orthogneiss from the diancang shan show uniform initial hf isotopic ratios marked by high and positive e hf t values from 16 to 10 this is in contrast with the other two zircon populations that are more common occurring in both the diancang shan and ailao shan and overall delineate very heterogeneous hf isotopic compositions with e hf t values ranging from 15 to 16 many zircons reveal distinctive core rim age variations zircon rims formed between ca 34 and 26 ma show significant variations in th u ratios 5 0 01 and e hf t values 14 to 10 that suggest complicated magmatic and metamorphic zircon overgrowth during the oligocene the presence of both metamorphic and magmatic overgrowths on zircons suggests that the metamorphism reached upper amphibolite facies corresponding to mid crustal level p t conditions as also suggested by structural and petrologic data our data furthermore suggest that the asrr gneisses were not produced solely by shear heating during the tertiary strike slip faulting but are uplifted mid crustal basement rocks that formed essentially during two major stages of magmatism represented by the neoproterozoic kangding complex and late permian emeishan large igneous province as a result of the india asia collision these basement rocks underwent regional magmatic and metamorphic overprinting in the oligocene that based on our relevant work searle et al 2010 geosphere 6 1 23 predated the initial left lateral movement along the asrr shear zone the 350 ma protolith which requires a dominant depleted mantle input in the petrogenesis cannot be linked to any major magmatic events in south china but may be interpreted as part of the paleotethys remnants that were later incorporated into the asrr shear zone

atmospheric sources and sinks of volcanogenic elements in a basaltic volcano etna italy abstract this study reports on the first quantitative assessment of the geochemical cycling of volcanogenic elements from their atmospheric release to their deposition back to the ground etna s emissions and atmospheric depositions were characterised for more than 2 years providing data on major and trace element abundance in both volcanic aerosols and bulk depositions volcanic aerosols were collected from 2004 to 2007 at the summit vents by conventional filtration techniques precipitation was collected from 2006 to 2007 in five rain gauges at various altitudes around the summit craters analytical results for volcanic aerosols showed that the dominant anions were s cl and f and that the most abundant metals were k ca mg al fe and ti 1 5 50 g m 3 minor and trace element concentrations ranged from about 0 001 to 1 g m 3 from such analysis we derived an aerosol mass flux ranging from 3000 to 8000 t a 1 most analysed elements had higher concentrations close to the emission vent confirming the prevailing volcanic contribution to bulk deposition calculated deposition rates were integrated over the whole etna area to provide a first estimate of the total deposition fluxes for several major and trace elements these calculated deposition fluxes ranged from 20 to 80 t a 1 al fe si to 0 01 0 1 t a 1 bi cs sc th tl and u comparison between volcanic emissions and atmospheric deposition showed that the amount of trace elements scavenged from the plume in the surrounding of the volcano ranged from 0 1 to 1 for volatile elements such as as bi cd cs cu tl and from 1 to 5 for refractory elements such as al ba co fe ti th u and v consequently more than 90 of volcanogenic trace elements were dispersed further away and may cause a regional scale impact such a large difference between deposition and emission fluxes at mt etna pointed to relatively high stability and long residence time of aerosols in the plume

mount st augustine volcano fumarole wall rock alteration mineralogy zoning composition and numerical models of its formation process abstract intensely altered wall rock was collected from high temperature 640 c and low temperature 375 c vents at augustine volcano in july 1989 the high temperature altered rock exhibits distinct mineral zoning differentiated by color bands in order of decreasing temperature the color bands and their mineral assemblages are a white to grey tridymite anhydrite b pink to red tridymite hematite fe hydroxide molysite fecl 3 with minor amounts of anhydrite and halite and c dark green to green anhydrite halite sylvite tridymite with minor amounts of molysite soda and potash alum and other sodium and potassium sulfates the alteration products around the low temperature vents are dominantly cristobalite and amorphous silica with minor potash and soda alum aphthitalite alunogen and anhydrite compared to fresh 1986 augustine lava the altered rocks exhibit enrichments in silica base metals halogens and sulfur and show very strong depletions in al in all alteration zones and in iron alkali and alkaline earth elements in some of the alteration zones to help understand the origins of the mineral assemblages in altered augustine rocks we applied the thermochemical modeling program gasworks in calculations of a reaction of the 1987 and 1989 gases with wall rock at 640 and 375 c b cooling of the 1987 gas from 870 to 100 c with and without mineral fractionation c cooling of the 1989 gas from 757 to 100 c with and without mineral fractionation and d mixing of the 1987 and 1989 gases with air the 640 c gas rock reaction produces an assemblage consisting of silicates tridymite albite diopside sanidine and andalusite oxides magnetite and hercynite and sulfides bornite chalcocite molybdenite and sphalerite the 375 c gas rock reaction produces dominantly silicates quartz albite andalusite microcline cordierite anorthite and tremolite and subordinate amounts of sulfides pyrite chalcocite and wurtzite oxides magnetite sulfates anhydrite and halides halite the cooling calculations produce a anhydrite halite sylvite b cu mo fe and zn sulfides c mg fluoride at high temperature 370 c d chlorides fluorides and sulfates of mn fe zn cu and al at intermediate temperature 170 370 c and e hydrated sulfates liquid sulfur crystalline sulfur hydrated sulfuric acid and water at low temperature

high temperature mixtures of magmatic and atmospheric gases recent measurements of bro nox and near source sulfate in volcanic plumes suggest that volcanic vents might not simply act as point sources of emissions into the troposphere but may also act as high temperature reaction sites where mixtures of magmatic and ambient atmospheric gases may combine giving new and previously unexpected reaction products the detection of such species demands that a more complex model be developed for the interaction of volcanoes and atmospheres we show that general thermodynamic models can be applied successfully to volcanic gas equilibria by comparing the results from hsc chemistry with those from two volcanic gas equilibrium models solvgas and gasmix using a thermodynamic model optimized for volcanic gas chemistry c o s h f cl br i n ar speciation we show that the volume ratio of atmospheric gas to magmatic gas in a high temperature mixture is an important parameter of the volcanic plume chemistry and our results suggest that even small amounts of air a few for an h2o rich magmatic gas in the high temperature mixture are sufficient to yield elevated levels of reactive nitrogen halogen cl br and i and sulfur species within the volcanic plume further modifications of the plume chemistry may also occur due to low temperature reactions and chemical schemes for the modification of halogen cl br i nitrogen and sulfur chemistry are suggested within the constraints imposed by recent measurements

volcanic particle aggregation in explosive eruption columns part i parameterization of the microphysics of hydrometeors and ash abstract the aggregation of volcanic ash particles within the eruption column of explosive eruptions has been observed at many volcanoes it influences the residence time of ash in the atmosphere and the radiative properties of the umbrella cloud however the information on the processes leading to aggregate formation are still either lacking or very incomplete we examine the fate of ash particles through numerical experiments with the plume model atham active tracer high resolution atmospheric model in order to determine the conditions that promote ash particle aggregation in this paper we describe the microphysics and parameterization of ash and hydrometeors in a companion paper this issue we use this information in a series of numerical experiments the parameterization includes the condensation of water vapor in the rising eruption column the formation of liquid and solid hydrometeors and the effect of latent heat release on the eruption column dynamics are considered the interactions of hydrometeors and volcanic ash within the eruption column that lead to aggregate formation are simulated for the first time within a rising eruption column the microphysical parameterization follows a modal approach the hydrometeors are described by two size classes each of which is divided into a liquid and a frozen category by analogy with the hydrometeor classification we specify four categories of volcanic ash particles we imply that volcanic particles are active as condensation nuclei for water and ice formation ash can be contained in all categories of hydrometeors thus forming mixed particles of any composition reaching from mud rain to accretionary lapilli collisions are caused by gravitational capture of particles with different fall velocity coalescence of hydrometeor ash aggregates is assumed to be a function of the hydrometeor mass fraction within the mixed particles the parameterization also includes simplified descriptions of electrostatics and salinity effects

particle geochemistry of volcanic plumes of etna and mount st helens particles in volcanic plumes include vapor condensates and reaction products of ash with vapors or condensed liquids in addition to abundant silicate particles in the 1980 mount st helens plume we detected abundant na k cl crystals as well as ca sulfates the latter commonly as overgrowths on ash or anthropogenic particles many of the chloride particles contained zinc and cadmium high temperature fumarolic incrustations showed strong enrichments of arsenic zinc alkalis and iron at etna we did not detect chloride crystals but found abundant al fe and ca sulfates sulfuric acid droplets were ubiquitous in both plumes bulk analyses of fumarole incrustations at etna showed an enrichment in the rare earth elements ree the chemical and textural data of the plume particles indicate that chloride particles form relatively early and react later with sulfuric acid droplets to form sulfates at etna aluminum as well as some ree are probably transported as volatile fluorine compounds the differences in plume chemistry between etna and mount st helens are most likely related to differences in f cl ratios of the vapors based on the abundance of particulate chlorine in plumes we suggest that only a small fraction of the total chlorine released during an eruption might reach the stratosphere in the vapor phase

airborne aerosol measurements in the quiescent plume of mount st helens september 1980 atmospheric particulate matter and condensed volatile species were collected in the quiescent plume of mount st helens volcano in sept 1980 using air filter systems mounted aboard a nasa turbo prop p 3 aircraft concentrations of 27 elements were determined by instrumental neutron activation analysis and ion chromotagraphy the volatile elements cl br f zn w in s cd se sb hg as and au were enriched relative to bulk ash emitted during the earlier eruptions by factors of 50 to 20 000 particulate s concentrations were approx 3 mu g m sup 3 and accounted for 6 of the total plume sulfur gas phase hg concentrations were 2 5 to 16 ng m sup 3 fluxes of elements were estimated by normalizing elemental concentrations to the concurrently measured total sulfur flux emission rates vary from 3500 kg day for particulate cl to 3 kg day for au with substantial quantities of the enriched elements zn as hg sb se and cd also being released estimated global fluxes of these elements from volcanoes to the atmosphere are in reasonable agreement with other literature estimates

small particles in plumes of mount st helens particles in the size range of 0 1 25 micrometers were sampled by aircraft carrying a quartz crystal microcascade in the mount st helens plume on three dates in august and september 1980 two of the sampling dates represented typical emissions of the volcano between plinian eruptions one sampling flight was made 1 4 hours before the small plinian eruption of august 7 1980 when the plume had become discontinuous and visibly darker size distributions were determined and individual particles were studied by using scanning electron microscopy the plume sampled on august 7 before the eruption contained mainly approximately 2 micrometer diameter silicic glass particles fragments of the mount st helens magma the typical plumes sampled on september 22 and august 6 had much smaller concentrations of particles trimodal size distributions with peaks at 10 0 4 and 0 1 micrometers the particles were largely nonsilicate and apparently represented cu zn oxide 10 micrometer peak al sulfate chloride and oxide and sulfuric acid smallest size peak the characterization of small particles in the plume may give information about approaching activity and possibly about changing conditions in the subsurface magma body

fluid immiscibility in volcanic environments volatile components enter the atmosphere oceans and other surface waters through pre syn and post eruptive volcanic processes that involve a variety of fluids aluminosilicate poor fluids include aqueous or carbonic to sulfide sulfate chloride fluoride carbonate and phosphate rich compositions in volcanic environments but other more complex combinations of these constituents may be involved giggenbach 1977 roedder 1984 1992 lowenstern 1995 other rare gases and dissolved constituents e g h2 n2 he ar h3bo3 hg ch4 and other hydrocarbon compounds metals and metalloids are also present but in general they are not sufficiently concentrated to form their own phases or control bulk fluid composition and volcanic processes as a result of their diverse compositions volcanic fluids ranging from vapor to liquid exhibit widely different densities and show strong distinctions in heat capacity dielectric behavior viscosity and other chemical and physical characteristics geiger et al 2006a the density of a saline liquid in the system nacl h2o at 50 mpa and 800 c for example is more than 7 times that of the coexisting aqueous vapor e g 0 2 gm cm3 henley and mcnabb 1978 multiple fluids move mix and or unmix in magma chambers and volcanic conduits in the root zone of fumaroles and in the convective hydrothermal systems that are ubiquitous to volcanic environments hydrothermal systems are typically centered on magmatic intrusions and may include crater lakes at the top of eruptive conduits hydrothermal processes involving two or more fluid phases operate through a variety of geologically relevant shallow crustal pressure temperature composition conditions volcanic fluids occur at supersolidus to subsolidus conditions meaning that the dense aluminosilicate melt that is common to volcanism may or may not be present this chapter addresses the evidence for and occurrence of two or more low density aluminosilicate poor fluids