volatile transport of metals and the cu budget of the active white island magmatic hydrothermal system new zealand abstract evidence of metal transport by volcanic gases is found amongst others in volcanic plumes and sublimates growing around fumaroles the transport mechanisms i e volatile metal compounds are however not well constrained here we present results on the volatile transport of metals at the scale of a magmatic hydrothermal system white island volcano we studied metal emissions from the main vent through the crater lake covering the conduit volcanic gases injected in the lake are responsible for the waters and sediments enrichment in various metals while elemental sulfur forming at the bottom appears as the main sink for chalcophile metals metal chloride complexes are the dominant species in the hot and acidic crater lake waters nearby low temperature fumarolic gases are lower in metals than higher temperature gases reported in the 1970s emphasizing precipitation at depth and sequestration by condensing elemental sulfur efficient gaseous transport of metals by hcl and hbr is revealed by thermodynamic modeling whereas the role of sulfur is restrained to controlling redox conditions a copper budget for white island magmatic hydrothermal system is assessed taking into consideration all the potentials sinks about 3900 tons of copper are estimated to be retained in the subsurface environment every year over the 10 000 years lifetime of the magmatic hydrothermal system this adds up to 40 megatons depicting white island as a potential cu porphyry forming deposit

variability of passive gas emissions seismicity and deformation during crater lake growth at white island volcano new zealand 2002 2006 1 we report on 4 years of airborne measurements of co2 so2 and h2s emission rates during a quiescent period at white island volcano new zealand beginning in 2003 during this time a significant crater lake emerged allowing scrubbing processes to be investigated co2 emissions varied from a baseline of 250 to 2000 t d 1 and demonstrated clear annual cycling that was consistent with numbers of earthquake detections and annual changes in sea level the annual variability was found to be most likely related to increases in the strain on the volcano during sea level highs temporarily causing fractures to reduce in size in the upper conduit so2 emissions varied from 0 to 400 t d 1 and were clearly affected by scrubbing processes within the first year of lake development scrubbing caused increases of so42 and cl in lake waters and the ratio of carbon to total sulphur suggested that elemental sulphur deposition was also significant in the lake during the first year careful measurements of the lake level and chemistry allowed estimates of the rate of h2o g and hcl g input into the lake and suggested that the molar abundances of major gas species h2o co2 so2 and hcl during this quiescent phase were similar to fumarolic ratios observed between earlier eruptive periods the volume of magma estimated from co2 emissions 0 015 0 04 km3 was validated by cl increases in the lake suggesting that the gas and magma are transported from deep to shallow depths as a closed system and likely become open in the upper conduit region the absence of surface deformation further leads to a necessity of magma convection to supply and remove magma from the degassing depths two models of convection configurations are discussed

snapshot of a magmatic hydrothermal system from electrical resistivity tomography and fumarolic composition whakaari white island new zealand abstract combined interpretation of electrical resistivity tomography ert data with plume and fumarolic gas emissions provides a snapshot of the whakaari white island hydrothermal system 11 months prior to an eruption on december 9 2019 two and three dimensional inversion of the ert data images the f0 fumarole as a low resistivity 2 5 m feature reflecting the two phase zone surrounding the single phase vapour conduit crucially interpretation of the inversion images is well constrained by a large existing dataset of rock electrical properties including surface conductivity porosity and intrinsic formation factor alongside new measurements of liquid phase electrical conductivity taken from a range of hot springs on the island pore filling liquids are an order of magnitude more conductive than sea water with their low to very low ph 3 4 to 0 3 contributing to their extremely conductive nature an extensive low resistivity feature 0 2 m at 125 m depth is therefore interpreted as a liquid saturated layer exposed to hydrothermal alteration by acid fluids the intersection of the f0 fumarole trace with this layer is coincident with a previously determined source of deformation suggesting that heat transport inside the fumarole conduit pressurises surrounding liquid and vapour filled pore space generating the deformation signal the timeseries of fumarolic and plume emissions in the year prior to the ert survey show that the gases transported by the fumarole are a mixture of high temperature magmatic vapour and lower temperature gas equilibrated within the hydrothermal environment interpretation of the gas data suggests that the snapshot captured by the ert image shows the single phase vapour and two phase vapour liquid regions adjacent to the conduit were likely at close to their smallest extent consisting of mostly hydrothermal derived gases

dynamics of outgassing and plume transport revealed by proximal unmanned aerial system uas measurements at volcan villarrica chile volcanic gas emissions are intimately linked to the dynamics of magma ascent and outgassing and on geological timescales constitute an important source of volatiles to the earth s atmosphere measurements of gas composition and flux are therefore critical to both volcano monitoring and to determining the contribution of volcanoes to global geochemical cycles however significant gaps remain in our global inventories of volcanic emissions particularly for co2 which requires proximal sampling of a concentrated plume for those volcanoes where the near vent region is hazardous or inaccessible unmanned aerial systems uas provide a robust and effective solution to proximal sampling of dense volcanic plumes in extreme volcanic environments here we present gas compositional data acquired using a gas sensor payload aboard a uas flown at volcan villarrica chile we compare uas derived gas timeseries to simultaneous crater rim multi gas data and uv camera imagery to investigate early plume evolution so2 concentrations measured in the young proximal plume exhibit periodic variations that are well correlated with the concentrations of other species by combining molar gas ratios co2 so2 1 48 1 68 h2o so2 67 75 and h2o co2 45 51 with the so2 flux 142 17 t day from uv camera images we derive co2 and h2o fluxes of 150 t day and 2850 t day respectively we observe good agreement between time averaged molar gas ratios obtained from simultaneous uas and ground based multi gas acquisitions however the uas measurements made in the young less diluted plume reveal additional short term periodic structure that reflects active degassing through discrete audible gas exhalations

gas emissions from failed and actual eruptions from cook inlet volcanoes alaska 1989 2006 cook inlet volcanoes that experienced an eruption between 1989 and 2006 had mean gas emission rates that were roughly an order of magnitude higher than at volcanoes where unrest stalled for the six events studied mean emission rates for eruptions were 13 000 t d co2 and 5200 t d so2 but only 1200 t d co2 and 500 t d so2 for non eruptive events failed eruptions statistical analysis suggests degassing thresholds for eruption on the order of 1500 and 1000 t d for co2 and so2 respectively emission rates greater than 4000 and 2000 t d for co2 and so2 respectively almost exclusively resulted during eruptive events the only exception being two measurements at fourpeaked while this analysis could suggest that unerupted magmas have lower pre eruptive volatile contents we favor the explanations that either the amount of magma feeding actual eruptions is larger than that driving failed eruptions or that magmas from failed eruptions experience less decompression such that the majority of h2o remains dissolved and thus insufficient permeability is produced to release the trapped volatile phase or both in the majority of unrest and eruption sequences increases in co2 emission relative to so2 emission were observed early in the sequence with time all events converged to a common molar value of c s between 0 5 and 2 these geochemical trends argue for roughly similar decompression histories until shallow levels are reached beneath the edifice i e from 20 35 to 4 6 km and perhaps roughly similar initial volatile contents in all cases early elevated co2 levels that we find at these high latitude andesitic arc volcanoes have also been observed at mid latitude relatively snow free basaltic volcanoes such as stromboli and etna typically such patterns are attributed to injection and decompression of deep co2 rich magma into a shallower chamber and open system degassing prior to eruption here we argue that the c s trends probably represent tapping of vapor saturated regions with high c s and then gradual degassing of remaining dissolved volatiles as the magma progresses toward the surface at these volcanoes however c s is often accentuated due to early preferential scrubbing of sulfur gases the range of equilibrium degassing is consistent with the bulk degassing of a magma with initial co2 and s of 0 6 and 0 2 wt respectively similar to what has been suggested for primitive redoubt magmas

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

eruptive activity at mount st helens washington usa 1984 1988 a gas geochemistry perspective the results from two different types of gas measurement telemetered in situ monitoring of reducing gases on the dome and airborne measurements of sulfur dioxide emission rates in the plume by correlation spectrometry suggest that the combination of these two methods is particularly effective in detecting periods of enhanced degassing that intermittently punctuate the normal background leakage of gaseous effluent from mount st helens to the atmosphere gas events were recorded before lava extrusion for each of the four dome building episodes at mount st helens since mid 1984 for two of the episodes precursory reducing gas peaks were detected whereas during three of the episodes cospec measurements recorded precursory degassing of sulfur dioxide during one episode october 1986 both reducing gas monitoring and so2 emission rate measurements simultaneously detected a large gas release several hours before lava extrusion had both types of gas measurements been operational during each of the dome building episodes it is thought that both would have recorded precursory signals for all four episodes evidence from the data presented herein suggests that increased degassing at mount st helens becomes detectable when fresh upward moving magma is between 2 km and a few hundred meters below the base of the dome and between about 60 and 12 hours before the surface extrusion of lava

airborne measurements of volcanic gas composition during unrest at kuchinoerabujima volcano japan airborne measurements of volcanic gas composition using an unmanned aerial vehicle uav and cessna aircraft were conducted at kuchinoerabujima volcano japan between 2014 and 2016 because eruptions occurred in august 2014 may 2015 and june 2015 access to the summit crater was limited because of the risk of sudden eruption such that airborne measurements were the only viable method to measure the volcanic gas composition multi gas and alkali filter pack measurements were made on the leeward side of the crater and around the crater using the cessna and uav respectively observations using the uav could measure the dense plume and quantify the gas species of h2o co2 so2 h2s h2 hcl and hf while the observations using the cessna could measure only the diluted plume and quantify co2 so2 h2s and h2 the seven airborne observations enabled us to monitor variations in the volcanic gas composition over the observation period the so2 h2s ratio decreased from 10 to 1 9 the h2o so2 ratio h2 so2 ratio and apparent equilibrium temperatures aet estimated using the volcanic gas composition increased after the 2014 eruption the decrease in the so2 h2s ratio might be attributed to changes in the pressure of degassing magma and interactions with the hydrothermal system the airborne methods presented here highlight the utility of using light aircrafts to safely conduct volcanic gas measurements during periods of volcanic unrest when traditional ground based methods are not possible

variability of volcanic gas emissions during a crater lake heating cycle at ruapehu volcano new zealand abstract we present the first routine measurements of emissions co 2 so 2 and h 2 s from ruapehu volcano new zealand during a crater lake heating cycle emissions were generally at a low level consistent with quiescent degassing of the volcano and the presence of a crater lake maximum concentrations 3 4 km downwind during the highest measurement in may 2004 were 14 ppm 0 37 ppm and 7 ppb for co 2 so 2 and h 2 s respectively co 2 emissions varied between not detectable to 900 t d 1 over periods of months so 2 was not detectable until february but gradually increased to 35 t d 1 emissions of h 2 s were detected in april and may although were 1 the co 2 so 2 ratio in the plume was 37 by weight for each measurement during the peak of the cycle suggesting that significant scrubbing of so 2 occurs through the crater lake and that a common source exists for both gases magma volumes estimated from co 2 emissions 0 001 0 004 km 3 are consistent with eruptive volumes given repose periods of 20 30 years delays between peaks in crater lake heating and degassing suggests that volcanic emissions do not primarily reside in the shallow hydrothermal system directly beneath the crater further data is needed to adequately model the system but first indications of the travel time associated with the degassing cycle suggests that the gas resides at minimally 300 m depth beneath the crater lake depths greater than 300 m are consistent with the top of the single phase steam zone in heat pipe models 200 700 m depth or perhaps even below the plastic brittle transition zone above the cooling magmas 1 km deep

degassing of stratified magma by compositional convection abstract a new model is proposed for passive degassing from sub volcanic magma chambers the water content in stably stratified shallow magma chamber will be equated to its solubility at the upper boundary by convection water from a lower layer high in water content can enrich the contact zone of the upper layer and lead to further convective overturn of this boundary layer a complete set of equations describing convection with bubble formation and dissolution is reduced to a simplified form by assuming a small bubble content the development and pattern of flow driven by vesiculation is modeled numerically in a 2d magma chamber for relatively low raleigh numbers 5 105 bubbles rising from the magma will collect near the roof in a layer of 8 10 vol and then escape upward to fumaroles the stokes flux of bubbles escaping from an andesitic magma with viscosity 104 p and a top surface of about 500 500 m corresponds with observed total magmatic water fluxes of 35 kg s pressure within the chamber is buffered by elastic and local visco elastic deformations in the solid rocks bounding the chamber to the range between ambient and close to lithostatic values in a chamber closed to fresh magma inputs the decrease in volume due to such gentle volatile escape lowers the reference pressure bubbles flux from the lower layer induced by variation of the saturation level around stratification boundary may be efficient mechanism for the water transport between layers

ground deformation patterns at white island volcano new zealand between 1967 and 2008 deduced from levelling data article i nfo since 1967 levelling measurements have been conducted in the main crater of white island volcano interpretation of these data using numerical modelling reveals that shallow pressure sources 200 600 m deep extending up to the subsurface dominated the long term deformation pattern consisting of inflation deflation cycles the time sequence of height changes magnetic changes and fumarole temperature and chemistry reveal that surface changes were caused by increasing temperature below the main crater reflecting the presence of magma at shallow depth the uplift and subsidence are interpreted in terms of increase or decrease in fluid pore pressure in response to changes of the heat and gas flux the subsidence during and following eruptions could be also linked with removal of material at depth to feed the eruptions

passive infrared remote sensing evidence for large intermittent co2 emissions at popocatepetl volcano mexico abstract passive infrared ftir and correlation spectrometer cospec measurements were conducted at popocatepetl volcano during february 10 to 26 1998 from sites 4 to 17 km distant from the summit volcano behavior was relatively quiet and so 2 flux averaged 1670 1420 t day 51 measurements relatively small for popocatepetl concurrent hcl so 2 and hf so 2 ratios were 0 17 0 01 and 0 031 0 003 respectively about the same as ratios measured from 1994 to 1997 the amount of co 2 in the volcanic plume was quantified using fascode in which atmospheric co 2 is numerically subtracted from the total infrared spectrum to obtain the residual magmatic co 2 surprisingly co 2 so 2 mass ratios rose dramatically to values as high as 140 about 30 times higher than typical values of 2 to 8 measured from 1994 to 1996 these excursions in high co 2 so 2 ratios were short lived lasting no longer than about 0 5 to 3 0 h but co 2 flux occasionally exceeded 100 000 t day we estimate that the average co 2 so 2 ratio for the period was about 23 yielding an average co 2 flux of roughly 38 000 t day chemical and petrographic analyses of lava and pumice erupted during explosions on june 30 1997 and january 1 1998 show conclusively that popocatepetl produces mixed products formed by injection of mafic magma into a more silicic chamber at temperatures and pressures of roughly 1040 c and 5 kbar in addition popocatepetl eruptive products include xenoliths of metamorphosed carbonate rocks containing wollastonite and other calc silicate minerals indicating reaction of magma with cretaceous limestone underlying the volcano using a normal co 2 so 2 ratio of 4 for reference we calculate an average excess co 2 production of 32 000 t day for 17 days this would require assimilation of only 5 10 4 km 3 of limestone an amount easily accessible in the 3 km thick cretaceous section beneath the volcano we also examine two scenarios in which excess co 2 is produced by degassing of subjacent basalt magma but these explanations seem less plausible to us because many other volcanoes are underlain by carbonate sequences short duration bursts of co 2 flux and increased co 2 so 2 ratio might be observed at other sites if simultaneous real time measurements of major gas species are made

heat flux from magmatic hydrothermal systems related to availability of fluid recharge abstract magmatic hydrothermal systems are of increasing interest as a renewable energy source surface heat flux indicates system resource potential and can be inferred from soil co 2 flux measurements and fumarole gas chemistry here we compile and reanalyze results from previous co 2 flux surveys worldwide to compare heat flux from a variety of magma hydrothermal areas we infer that availability of water to recharge magmatic hydrothermal systems is correlated with heat flux recharge availability is in turn governed by permeability structure lithology rainfall topography and perhaps unsurprisingly proximity to a large supply of water such as the ocean the relationship between recharge and heat flux interpreted by this study is consistent with recent numerical modeling that relates hydrothermal system heat output to rainfall catchment area this result highlights the importance of recharge as a consideration when evaluating hydrothermal systems for electricity generation and the utility of co 2 flux as a resource evaluation tool

experimental constraints on phreatic eruption processes at whakaari white island volcano vigorous hydrothermal activity interspersed by sequences of phreatic and phreatomagmatic eruptions occur at whakaari white island volcano new zealand here we investigate the influence of sample type hydrothermally altered cemented ash tuffs and unconsolidated ash lapilli and fragmentation mechanism steam flashing versus gas expansion on fragmentation and ejection velocities as well as on particle size and shape our rapid decompression experiments show that fragmentation and ejection speeds of two ash tuffs cemented by alunite and amorphous opal increase with increasing porosity and that both are significantly enhanced in the presence of steam flashing ejection speeds of unconsolidated samples are higher than ejection speeds of cemented tuffs as less energy is consumed by fragmentation fragmentation dominated by steam flashing results in increased fragmentation energy and a higher proportion of fine particles particle shape analyses before and after fragmentation reveal that both steam flashing and pure gas expansion produce platy or bladed particles from fracturing parallel to the decompression front neither fragmentation mechanisms nor sample type show a significant influence on the shape our results emphasize that under identical pressure and temperature conditions eruptions accompanied by the process of liquid water flashing to steam are significantly more violent than those driven simply by gas expansion therefore phase changes during decompression and cementation are both important considerations for hazard assessment and modeling of eruptions in hydrothermally active environments

vapor phase cristobalite as a durable indicator of magmatic pore structure and halogen degassing an example from white island volcano new zealand vesicles in volcanic rocks are physical records of magmatic degassing however the interpretation of their textures is complicated by resorption coalescence and collapse we discuss the textural significance of vesicle hosted vapor phase cristobalite high t low p sio2 polymorph and its utility as a complement to textural assessments of magmatic degassing using a representative dacite bomb erupted from white island volcano new zealand in 1999 imaging in 2d sem and 3d ct shows the bomb to have 56 bulk porosity almost all of which is connected 99 and devoid of sio2 phases the remaining 1 of porosity is in isolated sub spherical vesicles that have corroded walls and contain small 30 m across prismatic vapor phase cristobalite crystals 98 4 0 4 wt sio2 with diagnostic laser raman spectra halogen degassing models show vapor phase cristobalite to be indicative of closed system chlorine and fluorine partitioning into h2o rich fluid in isolated pores at white island this occurred during shallow 100s of meters ascent and extensive 50 groundmass crystallization associated with slow cooling in a volcanic plug pristine textures in this white island bomb demonstrate the link between pore isolation and vapor phase cristobalite deposition we suggest that because these crystals have higher preservation potential than the bubbles in which they form they can serve as durable qualitative textural indicators of halogen degassing and pre quench bubble morphologies in slowly cooled volcanic rocks e g lava flows and domes even where emplacement mechanisms have overprinted original bubble textures

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

soil co2 emissions as a proxy for heat and mass flow assessment taupō volcanic zone new zealand the quantification of heat and mass flow between deep reservoirs and the surface is important for understanding magmatic and hydrothermal systems here we use high resolution measurement of carbon dioxide flux co2 and heat flow at the surface to characterize the mass co2 and steam and heat released to the atmosphere from two magma hydrothermal systems our soil gas and heat flow surveys at rotokawa and white island in the taup volcanic zone new zealand include over 3000 direct measurements of co2 and soil temperature and 60 carbon isotopic values on soil gases carbon dioxide flux was separated into background and magmatic hydrothermal populations based on the measured values and isotopic characterization total co2 emission rates co2 of 441 84 t d 1 and 124 18 t d 1 were calculated for rotokawa 2 9 km2 and for the crater floor at white island 0 3 km2 respectively the total co2 emissions differ from previously published values by 386 t d 1 at rotokawa and 25 t d 1 at white island demonstrating that earlier research underestimated emissions by 700 rotokawa and 25 white island these differences suggest that soil co2 emissions facilitate more robust estimates of the thermal energy and mass flux in geothermal systems than traditional approaches combining the magmatic hydrothermal sourced co2 emission constrained using stable isotopes with reservoir h2o co2 mass ratios and the enthalpy of evaporation the surface expression of thermal energy release for the rotokawa hydrothermal system 226 mwt is 10 times greater than the white island crater floor 22 5 mwt

analogue modeling of instabilities in crater lake hydrothermal systems 1 we carried out analogue experiments on two phase boiling systems using a porous vertical cylinder saturated with water the base of the cylinder was heated and the top was cooled as in a natural hydrothermal system previous work had shown that once the two phase zone reached a certain level thermal instabilities would develop we made measurements of the acoustic energy related to boiling and we found that high levels of acoustic noise were associated with the part of the cycle in which there was upward water movement we repeated our experiments with a cooling water tank at the top of the system representing a crater lake this showed that periodic thermal instabilities still developed in this situation we then compared our analogue measurements to two natural systems known to exhibit periodic behavior there is good agreement between the thermal and acoustic cycling seen in our model and the observations made at inferno crater lake in the waimangu geothermal area new zealand whose level cycles by nearly 10 m with a typical period of 38 days particularly notable is how in both systems high levels of acoustic noise are associated with rising water level the much larger ruapehu crater lake also in new zealand cycled with a period of several months to a year for over a decade prior to the 1995 eruption strong acoustic and seismic energy usually occurred just before the lake temperature started to rise this suggests a slightly different model in which the increasing two phase flow zone triggers more general convection once it reaches the base of the lake

rates of sulfur dioxide and particle emissions from white island volcano new zealand and an estimate of the total flux of major gaseous species airborne correlation spectrometry cospec was used to measure the rate of so2 emission at white island on three dates i e november 1983 1230 300 t d november 1984 320 120 t d and january 1985 350 150 t d t metric tons the lower emission rates are likely to reflect the long term emission rates whereas the november 1983 rate probably reflects conditions prior to the eruption of december 1983 the particle flux in the white island plume as determined with a quartz crystal microbalance cascade in november 1983 was 1 3 t d unusually low for volcanic plumes the observed plume particles as shown from scanning electron microscopy include halite native sulfur and silicates and are broadly similar to other volcanic plumes

magma origin and evolution of white island whakaari volcano bay of plenty new zealand white island is an active composite stratovolcano in the bay of of the north island the pacific plate is being subducted plenty new zealand that comprises many small volume westwards under the australian plate at a rate of 50 mm yr to form the taupo hikurangi arc trench with phenocryst contents of 15 44 minor high mg basaltic system volcanic activity is now concentrated in the andesite explosive eruptions such as those of 1976 1992 may taupo volcanic zone tvz the youngest expression have occurred at intervals throughout the history of white island of 22 ma cenozoic continental margin arc volcanism in but are rarely preserved these alternate with major episodes of the north island of new zealand cole 1990 tvz andesite dacite lava extrusion the high mg magmas form by fig 1 inset is at the southern end of the 2800 km hydrous melting of mantle metasomatized by fluids from the tonga kermadec taupo volcanic arc system and the dehydrating slab at the slab mantle wedge interface that rise lau basin havre trough ngatoro basin back arc basin rapidly to shallow magma chambers 2 7 km where limited system southern havre trough and tvz are offset mixing and contamination occurs before eruption some of this sinistrally by 40 50 km and wright 1992 believes the magma remains in the magma chamber where it interacts with the offset to be accommodated by a series of dextrally oblique crystal mush from which it inherits phenocrysts to form so called and en echelon bookshelf faults the southwestern limit dirty lavas total phenocryst content of these lavas is correspondingly of this fault system is placed 20 km north of white higher as more magma is intruded into the chamber the heat flux island and has nw se orientation fig 1 inset will increase and melt fraction will eventually rise to the surface to tvz extends offshore into the bay of plenty as a form high silica andesite dacite magma clean lavas with fewer graben structure of 45 km width fig 1 bounded by the inherited phenocrysts similar multi magma chamber plumbing tauranga fault zone to the west and the white island systems with complex evolution involving fractionation and confault zone to the east wright 1992 the eastern side tamination probably occur in most andesite dacite arc volcanoes of tvz coincides with the current active volcanic front and a broadly linear alignment of andesitic volcanoes extends from ruapehu in the southwest to whakatane

rates of carbon dioxide plume degassing from mount etna volcano 1 we report here on the real time measurement of co2 and so2 concentrations in the near vent volcanic gas plume of mount etna acquired by the use of a field portable gas analyzer during a series of periodic field surveys on the volcano s summit during the investigated period september 2004 to september 2005 the plume co2 so2 ratio ranged from 1 9 to 10 8 with contrasting composition for northeast and voragine crater plumes scaling the above co2 so2 ratios by uv spectroscopy determined so2 emission rates we estimate co2 emission rates from the volcano in the range 0 9 67 5 kt d 1 average 9 kt d 1 about 2 kt of co2 were emitted daily on average during quiescent passive degassing whereas co2 emission rates from etna s summit were 10 40 times larger during the 2004 2005 effusive event with a cumulative co2 release of 3800 kt during the 6 months of the eruption such a syneruptive increase ascribed to the replenishment of the shallow 6 km volcanic plumbing system by co2 rich 0 25 wt more primitive magmas supports the potential of co2 output rates as key parameters for volcanic hazard assessment

long term changes in quiescent degassing at mount baker volcano washington usa evidence for a stalled intrusion in 1975 and connection to a deep magma source abstract long term changes have occurred in the chemistry isotopic ratios and emission rates of gas at mount baker volcano following a major thermal perturbation in 1975 in mid 1975 a large pulse in sulfur and carbon dioxide output was observed both in emission rates and in fumarole samples emission rates of co 2 and h 2 s were 950 and 112 t d respectively in 1975 these decreased to 150 and 2 ch 4 ratio since 1975 suggest a long steady trend back toward a more hydrothermal gas signature the helium isotope ratio is very high 7 r c r a but has declined slightly since the mid 1970s and 13 c co 2 has decreased by 1 over time both trends are expected from a gradually crystallizing magma while other scenarios are investigated we conclude that magma intruded the mid to shallow crust beneath mount baker during the thermal awakening of 1975 since that time evidence for fresh magma has waned but the continued emission of co 2 and the presence of a long term hydrothermal system leads us to suspect some continuing connection between the surface and deep convecting magma

co2 discharge from the bottom of volcanic lake rotomahana new zealand 1 from april 2010 to february 2011 co2 flux surveys were performed on lake rotomahana new zealand the area has been hydrothermally active with fumaroles and sublacustrine hydrothermal activity before and since the eruption of mt tarawera in 1886 the total co2 emission from the lake calculated by sequential gaussian simulation is 549 72 t d 1 two different mechanisms of degassing diffusion through the water air interface and bubbling are distinguished using a graphical statistical approach the carbon dioxide budget calculated for the lake confirms that the main source of co2 to the atmosphere is by diffusion covering 94 5 of the lake area mean co2 flux 25 g m 2 d 1 and to a lesser extent bubbling mean co2 flux 1297 g m 2 d 1 mapping of the co2 flux over the entire lake including over lake floor vents detected during the survey correlates with eruption craters formed during the 1886 eruption these surveys also follow regional tectonic patterns present in the southeastern sector of lake rotomahana suggesting a deep magmatic source 10 km for co2 and different pathways for the gas to escape to the surface the values of 13cco2 2 88 and 2 39 confirm the magmatic origin of co2

mechanical behaviour and failure modes in the whakaari white island volcano hydrothermal system new zealand abstract volcanic hydrothermal systems host a prodigious variety of physico chemical conditions the physico chemical state and mechanical behaviour of rocks within is correspondingly complex and often characterised by vast heterogeneity here we present uniaxial and triaxial compression experiments designed to investigate the breadth of mechanical behaviour and failure modes dilatant or compactant for hydrothermally altered lava and ash tuff deposits from whakaari white island volcano in new zealand a volcano with a well documented and very active hydrothermal system our deformation experiments show that the failure mode of low porosity lava remains dilatant over a range of depths up to pressures corresponding to depths of about 2 km upon failure shear fractures the result of the coalescence of dilatational microcracks are universally present the high porosity ash tuffs switch however from a dilatant to a compactant failure mode driven by progressive distributed pore collapse at relatively low pressure corresponding to a depth of about 250 m we capture the salient features of the dynamic conditions e g differential stress effective pressure in a schematic cross section for the whakaari hydrothermal system and map for the different lithologies areas susceptible to either dilatant vs compactive modes of failure the failure mode will impact for example the evolution of rock physical properties e g porosity permeability and elastic wave velocity and the nature of the seismicity accompanying periods of unrest we outline accordingly the potential implications for the interpretation of seismic signals outgassing ground deformation and the volcanic structural stability for whakaari and similar hydrothermally active volcanoes worldwide

globally significant co2 emissions from katla a subglacial volcano in iceland volcanoes are a key natural source of co2 but global estimates of volcanic co2 flux are predominantly based on measurements from a fraction of world s actively degassing volcanoes we combine high precision airborne measurements from 2016 and 2017 with atmospheric dispersion modeling to quantify co2 emissions from katla a major subglacial volcanic caldera in iceland that last erupted 100 years ago but has been undergoing significant unrest in recent decades katla s sustained co2 flux 12 24 kt d is up to an order of magnitude greater than previous estimates of total co2 release from iceland s natural sources katla is one of the largest volcanic sources of co2 on the planet contributing up to 4 of global emissions from nonerupting volcanoes further measurements on subglacial volcanoes worldwide are urgently required to establish if katla is exceptional or if there is a significant previously unrecognized contribution to global co2 emissions from natural sources we combine high precision airborne measurements from 2016 and 2017 with atmospheric dispersion modelling to quantify co2 emissions from katla a major subglacial volcanic caldera in iceland that last erupted 100 years ago but has been undergoing significant unrest in recent decades katla s sustained co2 flux 12 24 kt d is up to an order of magnitude greater than previous estimates of total co2 release from iceland s natural sources katla is one of the largest volcanic sources of co2 on the planet contributing up to 4 of global emissions from non erupting volcanoes further measurements on subglacial volcanoes world wide are urgently required to establish if katla is exceptional or if there is a significant previously unrecognized contribution to global co2 emissions from natural sources

short period volcanic gas precursors to phreatic eruptions insights from poas volcano costa rica abstract volcanic eruptions involving interaction with water are amongst the most violent and unpredictable geologic phenomena on earth phreatic eruptions are exceptionally difficult to forecast by traditional geophysical techniques here we report on short term precursory variations in gas emissions related to phreatic blasts at poas volcano costa rica as measured with an in situ multiple gas analyzer that was deployed at the edge of the erupting lake gas emitted from this hyper acid crater lake approaches magmatic values of so2 co2 1 6 days prior to eruption the so2 flux derived from magmatic degassing through the lake is measureable by differential optical absorption spectrometry sporadic campaign measurements which allows us to constrain lake gas output and input for the major gas species during eruptive and non eruptive periods we can further calculate power supply to the hydrothermal system using volatile mass balance and thermodynamics which indicates that the magmatic heat flux into the shallow hydrothermal system increases from 27 mw during quiescence to 59 mw during periods of phreatic events these transient pulses of gas and heat from the deeper magmatic system generate both phreatic eruptions and the observed short term changes in gas composition because at high gas flux scrubbing of sulfur by the hydrothermal system is both kinetically and thermodynamically inhibited whereas co2 gas is always essentially inert in hyperacid conditions thus the so2 co2 of lake emissions approaches magmatic values as gas and power supply to the sub limnic hydrothermal system increase vaporizing fluids and priming the hydrothermal system for eruption our results suggest that high frequency real time gas monitoring could provide useful short term eruptive precursors at volcanoes prone to phreatic explosions

geochemical modeling of the madison aquifer in parts of montana wyoming and south dakota stable isotope data for dissolved carbonate sulfate and sulfide are combined with water compo sition data to construct geochemical reaction models along eight flow paths in the madison aquifer in parts of wyoming montana and south dakota the sulfur isotope data are treated as an isotope dilution problem whereas the carbon isotope data are treated as rayleigh distillations all reaction models reproduce the observed chemical and carbon and sulfur isotopic composition of the final waters and are partially validated by predicting the observed carbon and sulfur isotopic compositions of dolomite and anhydrite from the madison limestone the geochemical reaction models indicate that the dominant groundwater reaction in the madison aquifer is dedolomitization calcite precipita tion and dolomite dissolution driven by anhydrite dissolution sulfate reduction ca mg2 ina cation exchange and halite dissolution are locally important particularly in central montana the groundwater system is treated as closed to c02 gas from external sources such as the soil zone or cross formational leakage but open to c02 from oxidation of organic matter coupled with sulfate reduction and other redox processes occurring within the aquifer the computed mineral mass transfers and modeled sulfur isotopic composition of madison anhydrites are mapped throughout the study area carbon 14 groundwater ages adjusted for the modeled carbon mass transfer range from modem to about 23 000 years b p and indicate flow velocities of 7 7 ftlyr 2 1 26 5 rnlyr most horizontal hydraulic conductivities calculated from darcy s law using the average 14 c flow velocities are within a factor of 5 of those based on digital simulation the calculated mineral mass transfer and adjusted 14 c groundwater ages permit determination of apparent rates of reaction in the aquifer the apparent rate of organic matter oxidation is typically 0 12 jlidol uyr sulfate and to a lesser extent ferric iron are the predominant electron acceptors the kinetic biochemical fractionation of 34 s between sulfate and hydrogen sulfide is approximately 44 o at 25 c with a temperature variation of

high frequency earthquakes at white island volcano new zealand insights into the shallow structure of a volcano hydrothermal system abstract volcano tectonic earthquakes at white island are concentrated in a single seismically active zone southeast of the active vents and at depths of less than 1 km a few deeper earthquakes also occur beneath the active vents a composite focal mechanism indicates that the stress regime in the shallow seismic zone is n s extensional shallow seismicity occurs within the main volume of the volcano hydrothermal system that underlies the main crater floor and we interpret this as a region where the rocks have been weakened by past magmatic intrusions elevated pore fluid pressure and physico chemical effects of acid volcanic fluids thereby allowing preferential seismic failure brittle seismic failure within this region requires a temperature less than about 400 c and implies high horizontal temperature gradients close to the active craters and fumaroles spasmodic bursts events are also a result of brittle failure but occur close to zones of significant permeability in response to changes in local fluid pressure

cyclic processes and factors leading to phreatic eruption events insights from the 25 september 2007 eruption through ruapehu crater lake new zealand abstract a dangerous block ash eruption occurred without warning from ruapehu crater lake on 25 september 2007 ending a 6 month period of temperature decline in the lake the northerly directed blast sent ballistics of up to 2 m diameter more than 2 km from the source the ejecta comprised a variety of volcano lacustrine lithologies many showing evidence of intense hydrothermal alteration petrographic studies of the ballistics reveal numerous examples of pores vesicles being filled with assemblages of elemental sulphur anhydrite pyrite and natroalunite and many ballistics exuded liquid sulphur from their pores during cooling at atmospheric pressure up to 5 of the ash was comprised of fine grained juvenile glass material confirming the presence of magma in the shallow vent environment a long recognised characteristic of this volcano is the thermal cycling behaviour of the crater lake behaviour which has remained effectively unchanged through two magmatic eruption events in 1945 and in 1995 96 airborne measurements of co2 and so2 flux from the volcano since 2003 show a strong positive correspondence with temperature cycling in the lake pointing to a definitive link between heat and mass discharge through the system low so2 emission rates and c s mole ratios 30 were typical of the period 2003 to early 2007 and appear to reflect vigorous scrubbing of s gases in the hydrothermal system during this time to better understand the chemical and physical processes operating in this very dynamic volcanic hydrothermal system and its propensity to develop potentially dangerous hydrothermal seals we have developed an integrated finite difference tough2 heat mass transport simulation of the hydrothermal environment the model which is constrained by observed heat and mass flux characteristics of the volcano demonstrates the transient nature of the heating cycles on the vent lake system of particular interest is the role of co2 as a relatively inert pressure transmitting medium in the hydrothermal environment seal formation was simulated using the reactive transport code x1t which showed that condensation of magmatic vapour into a highly porous medium of andesitic composition leads to rapid formation of an elemental sulphur anhydrite natroalunite mineral assemblage and a drastic reduction in permeability we suggest that since the 1995 96 vent clearing eruptions a shroud of elemental sulphur and other alteration phases formed along the margins of the 2 phase liquid vapour region enclosing the conduit this effectively seals the upper portion of the vent from the adjacent hydrostatically controlled environment and allows for development of pressurised vapour static gas columns beneath the northern and central vents

seismicity at white island volcano new zealand a revised classification and inferences about source mechanism the classification of earthquakes at white island volcano new zealand has been revised to address problems in existing classification schemes to better reflect new data and to try to focus more on source processes seismicity generated by the direct involvement of magmatic or hydrothermal fluids are referred to as volcanic and that generated by fault movement in response to stresses caused by those fluids regional stresses thermal effects and so on are referred to as volcano tectonic spasmodic bursts form a separate category as we have insufficient information to classify them as volcanic or volcano tectonic volcanic seismicity is divided into short duration long period volcanic earthquakes long duration volcanic earthquakes and harmonic and non harmonic volcanic tremor while volcano tectonic seismicity is divided into shallow and deep volcano tectonic earthquakes harmonic volcanic tremor is related to sub surface intrusive processes while non harmonic volcanic tremor originates close to active craters at shallow depth and usually occurs during eruptive activity short duration long period volcanic earthquakes come from a single source close to the active craters but originate deeper than non harmonic volcanic tremor and are not related to eruptive activity long duration volcanic earthquakes often accompany larger discrete eruptions the waveform of these events consists of an initial low frequency part from a deep source and a later cigar shaped part of mixed frequencies from a shallow crater source

the heat source of ruapehu crater lake deductions from the energy and mass balances abstract regular observations of temperature outflow rates and water chemistry of crater lake mt ruapehu new zealand have been made for the last 25 years these data have been used to derive a model of the dynamics of the lake and determine the input of energy mass and chloride from the volcano to the crater lake the recent relatively quiescent state of the volcano when virtually no heat has been input to the lake has also enabled an assessment to be made of the surface heat loss characteristics which play an important role in the model of the lake the modelling suggests that since about 1982 the ratio of the volcanic heat to mass added to the base of the lake is about 6 mj kg which is not compatible with heating of the lake by magmatic steam alone thus only about 50 of the heating has been by magmatic steam it is suggested that heat could be transferred from a magmatic source to the region below the lake by a heat pipe mechanism commonly associated with geothermal systems the simultaneous upward movement of vapour phase and downward movement of liquid phase from condensed vapour allows efficient heat transfer without overall mass transfer the permeability necessary to supply the required heat is of the order of 10 darcy and is consistent with a rubble filled vent for at least the last five years there has been a characteristic pattern in the crater lake temperature record with alternate heating and cooling phases the heating phase generally lasts for one or two months while the cooling phase lasts for six months to a year a possible explanation for this cyclic behaviour is the presence of a layer of liquid sulphur under crater lake acting as a partial barrier between the heat pipe and the lake the unusual variations of the viscosity of liquid sulphur with temperature will mean that at temperatures greater than 160 c the layer of sulphur becomes highly viscous and would block any upwards steam flow and hence stop the heat input to crater lake so producing a cooling phase this blockage would last until the heating from below raised the temperature of the sulphur beyond the high viscosity region so gases could again pass through the sulphur

numerical simulation of convection and mixing in magma chambers replenished with co2 rich magma 1 magma convection and mixing and periodic refilling commonly occur in magma chambers we show here that the presence of co2 in the refilling magma is a very efficient mean of inducing buoyant driven plume rise and large scale convection numerical simulations performed with an appositely developed code for the transient 2d dynamics of multicomponent compressible to incompressible fluids reveal several features of the processes of plume rise convection and mixing in magma chambers associated with chamber refilling a parametric study on co2 abundance in the refilling magma shows that progressively larger amounts of this volatile produce a shift from simple plume rise and spreading near the chamber top to complex patterns of flow circulation and large scale vorticity and mixing lower chamber depth and lower magma viscosity largely enhance the efficiency of mixing and convection favoring the formation of multiple vortexes migrating with time

using volcanic tremor for eruption forecasting at white island volcano whakaari new zealand abstract eruption forecasting is a challenging task because of the inherent complexity of volcanic systems despite remarkable efforts to develop complex models in order to explain volcanic processes prior to eruptions the material failure forecast method ffm is one of the very few techniques that can provide a forecast time for an eruption however the method requires testing and automation before being used as a real time eruption forecasting tool at a volcano we developed an automatic algorithm to issue forecasts from volcanic tremor increase episodes recorded by real time seismic amplitude measurement rsam at one station and optimised this algorithm for the period august 2011 january 2014 which comprises the recent unrest period at white island volcano whakaari new zealand a detailed residual analysis was paramount to select the most appropriate model explaining the rsam time evolutions in a hindsight simulation four out of the five small eruptions reported during this period occurred within a failure window forecast by our optimised algorithm and the probability of an eruption on a day within a failure window was 0 21 which is 37 times higher than the probability of having an eruption on any day during the same period 0 0057 moreover the forecasts were issued prior to the eruptions by a few hours which is important from an emergency management point of view whereas the rsam time evolutions preceding these four eruptions have a similar goodness of fit with the ffm their spectral characteristics are different the duration amplitude distributions of the precursory tremor episodes support the hypothesis that several processes were likely occurring prior to these eruptions we propose that slow rock failure and fluid flow processes are plausible candidates for the tremor source of these episodes this hindsight exercise can be useful for future real time implementation of the ffm at white island a similar methodology could also be tested at other volcanoes even if only a limited network is available

eruptions of pavlof volcano and their possible modulation by ocean load and tectonic stresses all nine magmatic eruptions at pavlof volcano in six of the years from 1973 to 1984 have occurred between september 9 and november 20 volumes of erupted material range from 0 1 to 15 9 106 m3 dense rock equivalent at an average rate of 3 106 m3 yr 1 the volumes are estimated from eyewitness reports for two eruptions the others are estimated from a relationship that we derive between eruption volume and harmonic tremor duration and amplitude the volume of lava erupted is approximately time predictable a significant correlation exists between the eruptions and yearly nontidal variations in sea level and may result from ocean loading calculated volume changes beneath the volcano due to ocean loading are from 0 02 to 2 times eruption volumes and we postulate that the volcano acts as a long period several month volume strain meter with lava being preferentially erupted when strain beneath the volcano is compressive the volcano did not erupt during the period 1978 1980 when tilt seismic data and sea level data indicate that deep aseismic slip may have occurred models of this event predict a volume increase beneath the volcano that might have compensated strain from magma injection these observations indicate that pavlof volcano may be responsive to small slow changes in ambient stresses or strains and that these changes may modify or trigger eruptions