elemental fractionation in lavas during post eruptive degassing evidence from trachytic lavas rishiri volcano japan abstract trachytic lavas of rishiri volcano northern japan show a peculiar geochemical variation across lava flow units samples collected systematically in a vertical cross section from a lava flow unit with a thickness of about 20 m are nearly homogeneous in major element compositions however some trace elements including li b and cs are considerably depleted in samples collected from the main part of the flow unit compared to those obtained from the surface of the lava flow clinker layer in particular cs content of the main flow unit is as low as 30 of the clinker layer 11b 10b ratios of samples from the main flow unit are also slightly lower than those of the clinker samples and the isotope compositions positively correlate with boron concentrations these geochemical variations cannot be explained by magmatic processes in magma chambers post eruptive weathering or alteration process rather we infer these systematics resulted from escape of these elements from the lava flow unit during post eruptive degassing vapor phases in which li b and cs dissolved are suggested to have been transported through veins formed in the main flow unit as fractures due to slight shearing along the flow planes after lava emplacement in the tanetomi lava only rocks of the clinker layer preserve original composition of magmas although they are porous and brownish due to extensive oxidization on the other hand rocks of the main flow unit do not retain original magma compositions although they are dense and grayish and seem to be much fresher compared to the clinkers a similar geochemical modification of lavas can occur in other volcanic systems especially for lavas consisting of relatively thick flow units

evidence for zn isotopic fractionation at merapi volcano abstract fumarolic gases rocks and condensate samples from merapi volcano indonesia have been analyzed by multiple collector inductively coupled plasma mass spectrometry mc icp ms for their zn isotopic compositions the variation observed expressed as 66 zn 66 zn 66 zn 64 zn sample 66 zn 64 zn jmc 3 049l 1 10 3 ranges from 0 05 to 1 68 the overall reproducibility was found to be better than 0 10 2sd the 66 zn of andesitic rock samples are homogeneous with a mean value of 0 24 which is comparable to previously reported basalt data 66 zn in the woro fumerolic field are ranging from 0 05 to 0 85 and 1 48 to 1 68 in fumarolic gases and condensates respectively upon cooling from 590 to 297 c gaseous zn concentrations decrease and become increasingly enriched in the lighter zn isotopes while the condensates become increasingly enriched in the heavier isotopes gas and condensate isotopic compositions can be explained with a rayleigh condensation model with temperature dependent isotope fractionation factor solid vapor over the 574 c to 297 c range of observations 1000 ln solid vapour c 1 c 2 t c 3 t 2 with c 1 0 c 2 0 88 10 3 c 3 1 00 10 6 and t in degrees kelvin which corresponds to solid vapor of 1 00033 to 1 00153 respectively at the indicated temperatures

multi proxy record of the chicxulub impact at the cretaceous paleogene boundary from gorgonilla island colombia a 40 m stratigraphic section at gorgonilla island colombia provides a unique deepmarine low latitude southern hemisphere record of events related to the end cretaceous chicxulub impact and the

etude geochimique des elements condenses au cours du refroidissement de la phase gazeuse volcanique etna 1976 des sublimes ont ete recoltes a l etna en 1976 le long d un tube en silice la mesure de la temperature du depot et l analyse elementaire par activation neutronique permettent de mieux comprendre des mecanismes magmatologiques metallogeniques et volcanologiques

investigation of the effect of cl on the transport and sublimation of volatile trace metals in volcanic gases using benchtop fumarole experiments abstract volatile trace metals emitted from volcanoes are frequently complexed with ligands and sublime from gases as halides sulfides sulfates and oxides we investigate the effect of cl as a ligand on the sublimation process by degassing broadly phonolitic composition melts with added trace metals v cu zn as y mo cd sn yb pb and bi and cl in a benchtop fumarole apparatus at 100 kpa sublimates forming from the gas phase at 25 900 c along a silica glass tube suspended above degassed melts are characterized by electron microscopy raman spectroscopy and solution nebulization inductively coupled plasma mass spectrometry sn icp ms silica polymorphs are ubiquitous at all temperatures and halite forms below 600 c szenicsite cu3 moo4 oh 4 and molybdofornacite cupb2 moo4 aso4 oh occur at 500 c the latter phases may have formed from post experiment hydration of original anhydrous molybates or arsenates or alternatively are their cl bearing analogues arsenate and vanadate minerals such as bradaczekite nacu4 aso4 3 and leningradite pbcu3 vo4 2cl2 known in natural fumaroles also occur in the experiments chloride sublimates can host substantial pb tl as cu bi and zn the addition of cl to the melt in the experiments increases the concentration of li rb cs ag cr cu mo and w in the sublimates compared to cl free experiments in cl bearing volcanic gases molybdates and chlorides are the most likely hosts of volatile trace metals and when adhered to ash particles are potential sources of trace metals to the atmosphere and oceans

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

iridium bearing sublimates at a hot spot volcano piton de la fournaise indian ocean sublimates and incrustations derived upon the cooling of volcanic gases have been collected on various sites piton de la fournaise poas momotombo etna ardoukoba and erta ale they have been analysed for ir and other volatile elements se as cu au ag pb tl by means of instrumental neutron activation analysis inaa and proton induced x ray emission pixe among the investigated volcanoes only piton de la fournaise is found to release detectable amounts of iridium ir in piton de la fournaise sublimates is associated with f minerals this confirms its gaseous transport as a volatile fluoride compound iridium seems to be preferentialy released by hot spot type volcanoes and its detection in piton de la fournaise sublimates provides a positive argument in favour of a volcanic hypothesis to explain the ktb events

a new collector for sampling volcanic aerosols abstract a new apparatus venturi effect system ves designed for sampling volcanic plumes is described and tested at vulcano italy this device together with purified basic nh 4 oh solutions supplies optimal conditions to obtain reliable s total cl f ratios and enrichment factors for metallic trace elements mte good concordance for acid gas ratios and metal enrichment factors in both the gas phase and the related plume allows the procedure to be validated the ves appears in vulcano conditions as a simple robust and easily portable apparatus that allows reliable collection of both acid gases and mte within a single sample and the analysis with current chemical methods high pressure liquid chromatography inductively coupled plasma mass spectrometry this apparatus may be suitable for more difficult volcanoes where only the plume can be sampled

lithium isotope fractionation during magma degassing constraints from silicic differentiates and natural gas condensates from piton de la fournaise volcano reunion island abstract recent volcanic products from the piton de la fournaise volcano reunion show pronounced depletion or enrichment in lithium and significant isotopic fractionation related to degassing 1 trachytic pumices from the april 2007 eruption show extreme li depletion 90 and isotopic fractionation 7 li of 21 the depletion of water and volatiles cl f b cs in these samples suggests that li loss occurred in response to degassing which most likely occurred as the small isolated volume of magma underwent extensive differentiation near the surface because the pre degassing composition is relatively well known the composition of the degassed pumice constrains the partition coefficient to 60 v m v m to 1 010 at magmatic temperatures unlike d v m v m does not depend on whether crystallization and degassing occurred successively or concomitantly 2 basaltic samples from the interior wall of the long lived 1998 piton kapor were extensively altered by acidic gas they also show extreme li depletion but barely significant isotopic fractionation 7 li 4 5 suggesting that high temperature leaching of li by volcanic gas does not significantly fractionate li isotopes 3 high temperature 400 325 c gas condensates formed during degassing of the thick lava flow of april 2007 display high li contents 50 100 ppm which are consistent with li being as volatile as zn and sn their isotopically light li signature average of 1 7 is consistent with their derivation from isotopically heavy vapor 13 5 if the factor of isotopic fractionation between condensate and vapor is less than 0 985 a degassing crystallization model accounts for the evolution of trace species which like lithium are volatile but also moderately incompatible

geomagnetic conjugate observations of equatorial airglow depletions 1 we report for the first time large scale equatorial f region airglow depletions extending to low midlatitudes in both hemispheres the observational sites were located at low midlatitude geomagnetic conjugate points clear depletions of 630 0 nm airglow intensity due to equatorial plasma bubbles were simultaneously observed with two all sky imagers at sata japan magnetic latitude 24 n and its geomagnetic conjugate point darwin australia magnetic latitude 22 s on the night of november 12 2001 airglow depletion regions with east west scale sizes of 40 100 km extend poleward the maximum apex altitude of the plasma bubbles is about 1 700 km over the geomagnetic equator the depletions move eastward at about 100 m s without changing their structures the darwin depletion structures mapped onto the northern hemisphere along the geomagnetic field coincide closely with structures in the sata images even for the 40 km structure these observations indicate that plasma depletions in the equatorial ionosphere elongate along the geomagnetic field lines

trace elements in the gas emissions from the erta ale volcano afar ethiopia high temperature 1084 c fumarolic emissions from a spatter cone at the erta ale north pit crater granted a rare opportunity to collect giggenbach bottles condensates and sublimates from the fumarolic gases of a rift plume volcano in the immediate proximity of degassing lava these results represent the highest temperature gases sampled directly for trace elements and the first high t fumarolic samples for a rift plume volcano sixty seven metals and metalloids were measured quantitatively by icp aes and icp ms in liquid gas condensates and solid sublimates the total amount of trace elements in the gas without si exceeded 170 ppm the ten most abundant elements transported in nonsilicate modes were na 61 ppm fe 41 ppm k 32 ppm br 12 4 ppm cd 3 0 ppm se 2 3 ppm cu 2 0 ppm zn 2 0 ppm te 1 7 ppm and as 1 2 ppm the gases contained 27 ppb re 1 5 ppb au 0 5 ppb pt and 0 27 ppb os rh and pd containing phases were observed in solid sublimates the only metal not detected by all analytical methods was ruthenium chalcophile elements cd cu zn se te as were transported primarily in the gaseous form alkali metals were emitted at least partially as liquid micron size sulfate droplets whereas alkali earths aluminum and ree had a high affinity to silicate aerosol in the form of basaltic microspheres the silicate aerosol content was evaluated at 59 ppm on average but varied within a 7 5 fold range during sampling because of the extremely high temperature refractory elements ca ba ta u and lree showed evidence of transport in the form of gaseous species the so2 flux in january 2011 was evaluated at 91 24 t d for the entire volcano including 31 t d from the north crater and 60 t d from the lava lake the daily output of trace elements from both erta ale craters without si was estimated at 53 kg d including 20 kg of na 13 5 kg of fe 10 5 kg of k 4 5 kg of chalcophile elements 9 g of re 0 5 g of au and 0 17 g of pt the trace element pattern of erta ale fumarolic gases do not possess any distinct geochemical specialization and resemble te patterns from fumarolic emissions of studied arc and plume volcanoes

halogens in volcanic systems the transport degassing and atmospheric release of halogens from active volcanism on earth have been the focus of increasing interest over the last few decades and have recently been the subject of the 1st workshop on halogens in volcanic systems and their environmental impacts that was held in december of 2007 at yosemite lodge in yosemite national park california as an introduction to this chemical geology special issue collecting contributions from many of the participants at the workshop we review here recent advances in this field including experimental and theoretical investigations of halogen behaviour in volcanic and related magmatic systems we discuss previous research on several aspects of halogen geochemistry including halogen abundances in the mantle and magmas on earth the effects of halogens on phase equilibria and melt viscosities their partitioning between melt and fluid phase s upon decompression cooling and crystallisation of magmas in the earth s crust and their final atmospheric release as volcanic gases the role of halogens in the genesis of hydrothermal systems and in the transport of ore forming metals is also reviewed and we discuss our current understanding of atmospheric processing of volcanic halogens in both the troposphere and stratosphere and their consequent impacts in spite of these recent advancements our current understanding of halogen geochemistry at active volcanoes is still far too fragmentary and the key questions that require answers from future research are summarised in our conclusions

volatilization transport and sublimation of metallic and non metallic elements in high temperature gases at merapi volcano indonesia abstract condensates silica tube sublimates and incrustations were sampled from 500 800 c fumaroles and lava samples were collected at merapi volcano indonesia in jan feb 1984 with respect to the magma merapi gases are enriched by factors greater than 105 in se re bi and cd 104 105 in au br in pb and w 103 104 in mo cl cs s sn and ag 102 103 in as zn f and rb and 1 102 in cu k na sb ni ga v fe mn and li the fumaroles are transporting more than 106 grams day g d of s cl and f 104 106 g d of al br zn fe k and mg 103 104 g d of pb as mo mn v w and sr and less than 103 g d of ni cu cr ga sb bi cd li co and u with decreasing temperature 800 500 c there were five sublimate zones found in silica tubes 1 cristobalite and magnetite first deposition of si fe and al 2 k ca sulfate acmite halite sylvite and pyrite maximum deposition of cl na k si s fe mo br al rb cs mn w p ca re ag au and co 3 aphthitalite k na sulfate sphalerite galena and cs k sulfate maximum deposition of zn bi cd se and in higher deposition of pb and sn 4 pb k chloride and na k fe sulfate maximum deposition of pb sn and cu and 5 zn cu and k pb sulfates maximum deposition of pb sn ti as and sb the incrustations surrounding the fumaroles are also chemically zoned bi cd pb w mo zn cu k na v fe and mn are concentrated most in or very close to the vent as expected with cooling atmospheric contamination and dispersion the highly volatile elements br cl as and sb are transported primarily away from high temperature vents ba si p al ca and cr are derived from wall rock reactions incomplete degassing of shallow magma at 915 c is the origin of most of the elements in the merapi volcanic gas although it is partly contaminated by particles or wall rock reactions the metals are transported predominantly as chloride species as the gas cools in the fumarolic environment it becomes saturated with sublimate phases that fractionate from the gas in the order of their equilibrium saturation temperatures devolatilization of a cooling batholith could transport enough acids and metals to a hydrothermal system to play a significant role in forming an ore deposit however sublimation from a high temperature high velocity carrier gas is not efficient enough to form a large ore deposit re se cd and bi could be used as supporting evidence for magmatic fluid transport in an ore deposit

major and trace element distributions around active volcanic vents determined by analyses of grasses implications for element cycling and bio monitoring samples of grass were collected at masaya volcano nicaragua rhynchelytrum repens and andropogon angustatus and the piton de la fournaise around the april 2007 eruptive vent la reunion vetiveria zizanioides to investigate the controls on major and trace element concentrations in plants around active volcanic vents samples were analysed using inductively coupled plasma mass spectrometry for a wide range of elements and atomic absorption spectroscopy for hg at masaya as cu mo tl and k concentrations in both grass species showed a simple pattern of variability consistent with exposure to the volcanic plume similar variability was found in a angustatus for al co cs hg and mg at the piton de la fournaise the patterns of variability in v zizanioides were more complex and related to variable exposures to emissions from both the active vent and lava flow these results suggest that exposure to volcanic emissions is for many elements the main control on compositional variability in vegetation growing on active volcanoes thus vegetation may be an important environmental reservoir for elements emitted by volcanoes and should be considered as part of the global biogeochemical cycles

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

volatile transport on venus and implications for surface geochemistry and geology the high vapor pressure of volatile metal halides and chalcogenides e g of cu zn sn pb as sb bi at typical venus surface temperatures coupled with the altitude dependent temperature gradient of 8 5 k km 1 is calculated to transport volatile metal vapors to the highlands of venus where condensation and accumulation will occur the predicted geochemistry of volatile metals on venus is supported by observations of cu zn sn pb as sb and bi minerals around terrestrial volcanic vents spectroscopic observations of cucl in volcanic gases at kilauea and nyiragongo and large enrichments of these and other volatile elements in terrestrial volcanic aerosols a one dimensional finite difference vapor transport model shows the diffusive migration of a thickness of 0 01 to 10 m yr of moderately to highly volatile phases e g metal halides and chalcogenides from the hot lowlands 740 k to the cold highlands 660 k on venus the diffusive transport of volatile phases on venus may explain the observed low emissivity of the venusian highlands hazes at 6 km altitude observed by two pioneer venus entry probes and the pioneer venus entry probe anomalies at 12 5 km

source processes of the thermal waters from the phlegraean fields naples italy by means of the study of selected minor and trace elements distribution abstract the geochemical characteristics of hydrothermal waters from the phlegraean fields p f naples italy were analysed for minor and trace elements selectively mobilised in hydrothermal systems such as b f hg as pb and tl the water samples collected from a shallow aquifer likely to be fed by deeper fluids showed various geochemical features resulting from the mixing of three components 1 surface waters of meteoric origin 2 hot deep waters deriving from water rock interaction and including deep waters of marine origin 3 magmatic fluids rising from the local magma chamber lying a few kilometres below the town of pozzuoli this setting although very complex provides a reliable means of studying the distribution of the investigated trace elements in particular within the phlegraean area high contents of b 0 1 48 mg l f 0 5 8 mg l as 16 6050 g l and hg 0 7 232 g l were observed the levels of thallium in the springs close to solfatara about 7 g l were in line with those normally recorded in hydrothermal areas whereas high levels of this element up to 23 3 g l were identified in other wells of the study area lead 1 3 to 29 1 g l appears to be anomalous with respect to its normal content in groundwater about 1 g l owing to the presence of high density brines at depth which enhance the solubility of pb in volcanic rocks under hydrothermal conditions the distribution of the investigated trace elements in the phlegraean fields thermal area is probably related to the different ascent pathways of the fluids clearly apart from the influence exerted by anomalous thermal conditions each element shows a different behaviour depending on its geochemical affinity with mineral phases and as a consequence of the different enthalpy values which determine ion partitioning in gaseous phases based on geochemical evidences and on the distribution of minor and trace elements the source processes of the investigated hydrothermal waters were defined five main groups were identified 1 acid sulphate waters resulting from mixing of meteoric water with magmatic gases mainly h 2 s 2 high sulphate chloride waters from a deep reservoir located in the major upflow zone 3 waters associated with significant degassing of magmatic co 2 4 waters from a deep geothermal neutral chloride reservoir resulting from heating of marine water modified by water rock interaction processes 5 cold waters from the inner area influenced by low temperature water rock interaction processes

simultaneous observations at darwin of equatorial bubbles by ionosonde based range time displays and airglow imaging 1 airglow observations of ionospheric electron density depletions made at darwin australia have demonstrated that the tree like structure of bubbles developed at the magnetic equator are mapped along magnetic field lines with considerable accuracy to the base of the ionosphere at higher latitudes ionosonde range time displays made at darwin and other equatorial sites in the australian region show characteristic approaching and receding echoes which converge on a typical spread f event these off angle echoes have often been referred to in the literature as satellite traces and associated with spread f with little recognition of their true significance all four optical depletions previously reported in the literature as being seen at darwin are found in this paper to be accompanied by such typical off angle spread f events the zonal drift velocity of the moving reflectors can be measured from the speed at which such echoes approach and recede since digital ionosondes in equatorial sites have existed for many years existing ionogram data when suitably processed into range time displays may allow the occurrence of such events over several sunspot cycles to be found a question remains as to whether all or only some of such equatorial range time events correspond to electron density depletions

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

high resolution size distributions and emission fluxes of trace elements from masaya volcano nicaragua active volcanoes are significant natural sources of trace elements to the atmosphere yet the processes of emission and the impacts of deposition into terrestrial and aquatic environments remain poorly understood the varying contributions of volatile degassing and magma ejection i e spattering spraying extrusion and fragmentation to the emission of trace elements from masaya volcano nicaragua are investigated through measurement of high resolution trace element size distributions using cascade impactors in 2009 and 2010 the volatile elements e g as cd tl cu pb zn are strongly correlated across the size distribution and exist in the plume primarily as fine sulfate 0 6 m diameter with lesser amounts transported as coarse sulfates 3 5 m diameter and coarse chlorides 11 m diameter these results suggest that trace elements released from the magma as chlorides react rapidly with h2so4 in the plume to form sulfates in contrast the non volatile elements e g alkali earth and rare earth exist primarily as particles in the 1 10 m range and show no correlation with sulfate chloride or the volatile elements suggesting that they are emitted primarily by magma ejection trace element emission fluxes from masaya in 2010 were estimated using filter pack measurements with emissions of cu zn as tl rb and cd each in excess of 10 kg d 1 these emission fluxes are similar to those measured in 2000 2001 suggesting notable decadal stability in the emission of trace elements from masaya

magnitude of lead flux to the atmosphere from volcanoes pb s tl s and bi s ratios were measured in eruptive and fumarolic volcanic gases and indexed to the global flux of volcanic s to characterize approximate global volcanic emissions of these three metals to the atmosphere which are about 1200 tons pb yr 600 tons tl yr and 4000 tons bi yr this volcanic pb input is similar to the magnitude of natural soil dust pb input which is about 1400 tons pb yr during the holocene interglacial both are negligible compared to annual industrial inputs of 300 000 tons pb yr which maintain the present tropospheric reservoir of pb however polar ice records indicate that thousands of years ago the atmospheric pb reservoir was only 1 of its present size which means that volcanic pb was the source of about half the pb in the atmosphere during preindustrial holocene times

escape of unradiogenic osmium during sub aerial lava degassing evidence from fumarolic deposits piton de la fournaise reunion island abstract this study presents new re os isotope and elemental data in gas condensates and corresponding lavas in order to examine the geochemical behavior of these two elements during magma degassing at piton de la fournaise reunion island gas sublimates formed between 2007 and 2011 at temperature ranging from 400 to ca 100 c include na k sulfate aphthitalite na sulfate thenardite ca cu sulfate e g gypsum ca mg al fe fluoride e g ralstonite and native sulfur the high temperature deposits show trace element typical of volcanic gas with high enrichment in re 24 to 79 ppb almost two order of magnitude higher than the corresponding lavas but with os abundances similar to those of the lavas 14 132 ppt in contrast the os contents of the low temperature fluoride deposits 13 77 ppb are higher than any of the other condensates the fluorides are also enriched in re albeit to lesser extent than os 2 9 15 3 ppb based on high temperature samples the fluid melt partition coefficients estimated for re and os are 100 80 and 1 2 respectively considering 1 of fluid loss these partition coefficients translate into emanation coefficients of 0 50 0 17 0 65 for re and 0 01 0 0 03 for os these results indicate that re unlike os is highly volatile at piton de la fournaise osmium isotopic compositions of samples collected at medium and low temperature 187 os 188 os between 0 130 0 135 and plot within the range of the april 2007 lava flow and the historical lavas of piton de la fournaise i e 0 130 0 137 however the highest temperature condensates na k sulfates with t of 384 400 c yield lower 187 os 188 os ratios i e 0 124 0 129 within the field of mantle signal such unradiogenic compositions are best explained if old mantle sulfides occur in lavas and contribute to volcanic gases within the general frame of osmium mantle geochemistry loss of unradiogenic os during magmas degassing could help to explain osmium isotope disequilibrium between lavas and melting residues

evidence from geoid data of a hotspot origin for the southern mascarene plateau and mascarene islands indian ocean a high resolution geoid map of the madagascar and mascarene basins is constructed from geos 3 and seasat satellite altimetric data with an accuracy of 0 7 m large positive anomalies are due to topographic highs and their regional compensation the deflection of the lithosphere under volcanic loads and its effect on the geoid are modeled for the southern mascarene plateau mauritius reunion and rodriguez islands assuming a purely elastic lithospheric model the effective flexural rigidity is estimated for the four zones rigidity varies from 1 10 21 to 2 10 23 n m increasing from north to south the highest rigidity occurs under reunion island and suggests a recent origin for the volcanism 3 5 ma the southern mascarene plateau shows the lowest rigidity suggesting a near ridge origin rodriguez island shows the same trend but in another tectonic framework the topographic and geoid swell is studied as an effect of a thermal mantle plume using a conductive model of lithospheric heating we confirm the assumption of hotspot migration for the origin of the southern mascarene plateau and the mascarene islands

eruption at le piton de la fournaise volcano on 3 february 1981 piton de la fournaise in the island of la reunion indian ocean is a young 0 35 myr old basaltic shield volcano built on the flank of the extinct piton des neiges volcano it is one of the most active volcanoes in the world magma output rate of 0 32 m3 s 1 1 2 and has been under continuous surveillance by the volcanological observatory of the institut de physique du globe de paris since august 1980 the first detailed observations on the volcano reveal a remarkably low level of background seismicity the 3 february 1981 eruption was preceded by a deep event of volcanic origin at depths of 10 15 km on 2 january 20 days of quiescence followed this event until the onset of shallow seismicity close to the eruptive centres on 22 january the eruption began after 13 days of sustained shallow seismicity and occurred in three phases over 92 days and produced about 10 106 m3 of lava

geochemistry of metallic trace elements in fumarolic condensates from nicaraguan and costa rican volcanoes metallic trace element composition of volcanic gas from cerro negro momotombo san cristobal telica and masaya volcanoes in nicaragua and poas volcano in costa rica is indicated by analyses of fumarolic condensates for alkalis alkaline earths transition elements precious metals halogens and sulphate the temperatures of the fumaroles varied from 85 to 852 c element concentrations range from 104 to 10 3 ppm statistical tests indicate that the trace element constituents of the condensates are log normally distributed although there are variations in element concentrations in individual condensates the general order of decreasing elemental abundances in nicaraguan and costa rican fumarolic gas is cl so4 certain igneous rock forming elements si al fe ti f and alkalis li na k alkaline earths mg ca ba br and transition elements cr mn co ni cu zn other ore forming elements mo cd sn pb semi metals as sb sc hg and precious metals au ag li mn cr and pb were found to be near or below detection limits in many of the condensates analyzed so4 ti al k na zn sn cr and br all tend to decrease in abundance as mean fumarolic temperature between volcanoes decreases the remaining elements remain constant in abundance or behave erratically the metallic trace element composition of the nicaraguan and costa rican fumarolic condensates is very similar to condensates from subduction zone volcanoes around the pacific margin and the mediterranean metals in volcanic gas are postulated to have been transported as halogen sulphate and oxide compounds chloride and fluoride compounds are considered to be the primary transporters of metals in volcanic gas correlations between metal and halogen content vary considerably between volcanoes statistically significant correlations between metal content and both chlorine and bromine are found in the cerro negro and between metal content and bromine and fluorine in the momotombo condensates metal bearing compounds in volcanic gas are postulated from correlation matrices bromine though seldom reported in condensates is a minor but important constituent of volcanic gas with concentrations similar to those of fluorine metal bromide compounds have higher volatilities than fluoride compounds and volatilities similar to chloride compounds significant correlations between bromine content and metal concentration suggests that bromide compounds play a role in the transportation of metals in volcanic gas

lead isotope composition of the sublimates from the fumaroles of vulcano aeolian islands italy inferences on the deep fluid circulation the fumarolic fluids of vulcano aeolian islands italy consist of a mixture of both deep and shallow components the final products the fumarolic gases and the sublimates associated with them provide information on the complex interactions that occur at depth as radiogenic isotopes do not undergo fractionation after they are incorporated in a fumarolic gas they can be used directly to characterize the components that mixed lead isotopes are particularly suitable because seawater which plays an important part in the formation of the fumarolic fluids of vulcano contains only negligible amounts of it 10 12 g g therefore the lead present in the fumarolic gases and sublimates is derived from the magmatic component and a water rock interaction process the lead isotope compositions of the lead sulfosalt sublimates collected from the fossa crater of vulcano in 1924 and between 1989 and 1993 are given the lead isotope ratios of most of the samples are the same within the range of analytical error regardless of their collection date the only samples that display slight variations are those collected in 1993 on the whole the compositional trend of the lead isotopes of the sublimates coincides with that of the latitic rhyolitic activity of fossa and differs substantially from that of the pre fossa trachy basaltic activity the lead composition of the sublimates is very different from that of the calabrian basement rocks the data presented here show that the magma presently degassing at vulcano has the same lead isotopic composition as the products of the recent activity of fossa whereas the fumarolic fluid circulation of vulcano has not involved basement rocks similar to the calabrian metasediments

cumulate clasts in the bellecombe ash member piton de la fournaise reunion island and their bearing on cumulative processes in the petrogenesis of the reunion lavas abstract among the ejecta from a phreatomagmatic eruption on piton de la fournaise volcano are wehrlitic and gabbroic cumulate clasts these fresh samples comprise olivine fo85 0 to fo69 0 augite en47 1wo44 6wo44 6 to en41 1fs15 4wo43 5 and plagioclase an82 8ab16 8or0 4 to an53 8ab44 8or1 4 with spinel ti rich ferrichromites to ti magnetite and some ilmenite a few percent of highly vesicular interstitial glass is commonly present textures indicate that the cumulates were not wholly crystalline at the time of eruption and that the glass represents a residual intercumulus melt that varies from basaltic to mugearitic sulphide globules typically spherical and up to 40 m diameter represent immiscible melts within the glasses the sulphides contain relatively high contents of cu and ni and appear to be high temperature homogeneous pyrrhotite rich compositions rank order of element abundance in the sulphides is fe s cu ni co and zn wt s although in one sample ni is more abundant than cu lack of correlation between the sulphide globule compositions and their host glasses is probably due to complex partitioning between the silicate melts silicate and oxide crystals sulphide melt and separating volatile phase whereas the cu cu ni at values of the sulphides are similar to those of the sulphide ore bodies from major gabbroic complexes the ni ni fe values are notably high with regard to the low mgo content of their host glasses oxide pairs regarded as reflecting equilibria prior to eruption indicate temperatures of 1017 897 c and log fo2 values of 9 6 12 7 compaction of analogous cumulate mushes with extraction of relatively low density basaltic to mugearitic and ultimately trachytic residual melts is inferred to have yielded the differentiated series lavas and ash flows of the older volcano on reunion piton des neiges the sequence of crystallisation with augite as the second silicate phase rather than plagioclase as is normal in the lava sequences suggests crystallisation at depths 5 km the bellecombe ash cumulate clasts show more evolved assemblages than most other xenolith suites on the volcano in which dunites predominate and are probably products of stagnated magma batches possibly arrested in sill like intrusions in the deeper crust the cumulates are recent components in what is probably a large ca 70 km across layered complex beneath the volcanic edifices accreted during the build up of reunion

investigation of thallium fluxes from subaerial volcanism implications for the present and past mass balance of thallium in the oceans abstract a suite of 34 volcanic gas condensates and particulates from kilauea hawaii mt etna and vulcano italy mt merapi indonesia white island and mt nguaruhoe new zealand were analysed for both tl isotope compositions and tl pb ratios when considered together with published tl pb abundance data the measurements provide globally representative best estimates of tl pb 0 46 0 25 and e 205 tl 1 7 2 0 for the emissions of subaerial volcanism to the atmosphere and oceans e 205 tl is the deviation of the 205 tl 203 tl isotope ratio from nist srm 997 isotope standard in parts per 10 000 compared to igneous rocks of the crust and mantle volcanic gases were found to have i tl pb ratios that are typically about an order of magnitude higher and ii significantly more variable tl isotope compositions but a mean e 205 tl value that is indistinguishable from estimates for the earth s mantle and continental crust the first observation can be explained by the more volatile nature of tl compared to pb during the production of volcanic gases whilst the second reflects the contrasting and approximately balanced isotope fractionation effects that are generated by partial evaporation of tl during magma degassing and partial tl condensation as a result of the cooling and differentiation of volcanic gases mass balance calculations based on results from this and other recent tl isotope studies were carried out to investigate whether temporal changes in the volcanic tl fluxes could be responsible for the dramatic shift in the e 205 tl value of the oceans at 55 ma which has been inferred from tl isotope time series data for ferromanganese crusts the calculations demonstrate that even large changes in the marine tl input fluxes from volcanism and other sources are unable to significantly alter the tl isotope composition of the oceans based on modelling it is shown that the large inferred change in the e 205 tl value of seawater is best explained if the oceans of the early cenozoic featured significantly larger tl output fluxes to oxic pelagic sediments whilst the sink fluxes to altered ocean crust remained approximately constant

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

lead isotopes behavior in the fumarolic environment of the piton de la fournaise volcano reunion island abstract the recent activity of the piton de la fournaise volcano offers a rare opportunity to address the issue of pb isotope behavior in volcanic fumaroles as the composition of the degassing source is accurately and precisely known gas sublimates formed between 2007 and 2011 at temperature ranging from 400 to ca 100 c include na k sulfate aphthitalite ca cu sulfate e g gypsum na sulfate thenardite ca mg al fe fluoride e g ralstonite and native sulfur the high temperature deposits show trace element patterns typical of volcanic gas with pb concentration up to 836 ppm while the low temperature deposits are depleted in most volatile elements pb only for low temperature fluoride samples do pb isotope compositions plot significantly outside the field of lavas the isotopic shift is ascribed to leaching ubiquitous unradiogenic phases e g sulfides by acidic gas condensates the similarity in pb isotope signature between lavas and sublimate samples more representative of the gas phase sulfates indicates that the net fractionation of pb isotopes resulting from volatilization and condensation processes is smaller than the precision of pb isotope measurements better than 60 ppm a m u the absence of net fractionation could result from negligible isotope fractionation during pb volatilization followed by extensive condensation of gaseous pb with possibly significant isotopic fractionation at this stage although this scenario has to be refined by more direct measurement of the gas phase and its general applicability tested it suggests that a small fraction resolving very small isotopic differences between magmas and their gaseous products remains an analytical challenge high precision pb isotope measurements rest not only on instrumental performance but also on high yield chemistry as pb isotopes drastically fractionate 800 ppm a m u upon elution on anionic resin for 50 pb recovery the estimated isotopic bias is plus or minus 60 80 ppm a m u depending on which of the early isotopically light or late isotopically heavy pb fraction is lost