dynamics of carbon dioxide emission at mammoth mountain california mammoth mountain a dormant volcano in the eastern sierra nevada california has been passively degassing large quantities of cold magmatic co2 since 1990 following a 6 month long earthquake swarm associated with a shallow magmatic intrusion in 1989 a search for any link between gas discharge and volcanic hazard at this popular recreation area led us to initiate a detailed study of the degassing process in 1997 our continuous monitoring results elucidate some of the physical controls that influence dynamics in flank co2 degassing at this volcano high coherence between variations in co2 efflux and variations in atmospheric pressure and wind speed imply that meteorological parameters account for much if not all of the variability in co2 efflux rates our results help explain differences among previously published estimates of co2 efflux at mammoth mountain and indicate that the long term annual co2 degassing rate has in fact remained constant since 1997 discounting the possibility of large meteorologically driven temporal variations in gas efflux at other volcanoes may result in spurious interpretations of transients that do not reflect actual geologic processes

continuous monitoring of fumarole temperatures at mount etna italy abstract in this paper we present the first data of temperature continuously recorded in two fumarole fields designated vor and hor located in the summit area of mount etna volcano italy the time series embraces two distinct periods 1 october 2007 to november 2009 during which an effusive eruption occurred from may 2008 to july 2009 and 2 november 2011 to june 2012 characterized by the occurrence of strong paroxysms fire fountains and lava flow the analysis of the temperature signal in both the time and frequency domains and its comparison with meteorological observations allowed us to separate the exogenous influences from the effects of variations in the activity state of the volcano the acquired data were weakly affected by seasonal cycles of the air temperature and strongly affected by the rainfall optimization of site conditions i e sensor depth and soil permeability markedly reduced meteorological disturbances the distance from the main degassing and or eruptive fractures was crucial to maximizing the probability of the technical survival of the monitoring apparatus which was seriously affected by the emission of acidic gases tephra fallout and lava flows apart from the exogenous influences the most appreciable variation was observed at vor where a huge increase in fumarole temperature was detected immediately after the onset of the 2008 2009 eruption such an anomalous increase was attributed to the rapid ascent of magma feeding the eruptive fracture another abrupt increase in temperature was recorded at hor in march and april 2012 during this period the frequency of paroxysm occurrence increased markedly and this led us to hypothesize that the thermal anomaly was due to the intrusion of a new batch of magma in the conduits of the southeast crater medium to long term monitoring weeks to months of fumarole temperatures revealed variations that were attributed to pressurization depressurization phases of the shallow volcanic system which varied between the various monitored sectors of the volcano our observations suggest that continuous monitoring of fumarole temperature can give useful information about the activity of mount etna moreover due to the complexity of its shallow plumbing system we conclude that the monitoring systems should be extended to cover the entire fumarole network of the summit area

niobium uranium evidence for early formation of the continental crust niobium uranium ratios in greenstone belt basalts and gabbros indicate that parts of the late archean mantle beneath western australia underwent a level of melt extraction resulting in formation of the continental crust comparable to that seen in the present mantle the implication is either that i the amount of continental crust that formed before 2 7 x 10 9 years ago was much greater than generally thought or ii crustal growth occurred by severe depletion of small volumes of the mantle rather than by moderate depletion of a large volume of mantle

explosion quakes at stromboli italy abstract this paper reports the results of two seismic experiments aimed at determining the wave field of explosion quakes at stromboli island mediterranean sea southern italy the typical strombolian activity mostly consists of explosive phenomena causing pyroclastic materials to be emitted together with jets of volcanic gases from one or more craters stromboli is an active volcano characterized by persistent seismic activity consisting of explosion quakes that are seismic events associated with the explosive volcanic phenomena explosion quakes are short lived seismic events occurring intermittently whose amplitude tends to decrease with distance from the vent a distinctive feature of explosion quakes is the presence on seismograms of two often clearly distinct seismic phases the first low frequency seismic phase 3 4 hz after one second or more the first seismic phase of explosion quakes has been shown to be characterized by a nearly radial linear polarization and by an apparent propagation velocity estimated at 600 800 m s the second phase is characterized by a more chaotic motion and a lower apparent propagation velocity of 150 450 m s the wavefield associated with the first low frequency seismic phase appears to be generated by a resonating p wave seismic source accompanying gas explosion and emission of pyroclastic materials the wavefield associated with the second high frequency seismic phase of explosion quakes appears to be mainly composed of scattered and converted waves due to the critical topography of the volcano

total co2 output from vulcano island aeolian islands italy 1 total co2 output from fumaroles soil gas bubbling gas discharges and water dissolved gases discharged from the island was estimated for vulcano island italy the co2 emission from fumaroles from the la fossa summit crater was estimated from the so2 crater output while co2 discharged through diffuse soil emission was quantified on the basis of 730 measurements of co2 fluxes from the soil of the island performed by using the accumulation chamber method the results indicate an overall output of 500 t day 1 of co2 from the island the main contribution to the total co2 output comes from the summit area of the la fossa cone 453 t day 1 with 362 t day 1 from crater fumaroles and 91 t day 1 from crater soil degassing the release of co2 from peripheral areas is 20 t day 1 by soil degassing palizzi and istmo areas mainly an amount comparable to both the contribution of water dissolved co2 6 t day 1 as well as to seawater bubbling co2 4 t day 1 measured in the istmo area presented data september 2007 refer to a period of moderate solphataric activity when the fumaroles temperature were 450 c and gas water molar ratio of fumaroles was up to 0 16 the calculated total co2emission allows the estimation of the mass release and related thermal energy from the volcanic hydrothermal system

how to remove the seasonal atmospheric effect an application on a surface volcanic temperature at nisyros active volcano hellenic volcanic arc abstract surface temperature at a volcanic system is the result of a mixture of two heat sources originating one from above and another from below the ground surface the atmosphere significantly affects the surface s temperature of the volcano and removal of the atmospheric effect is required for meaningful interpretations prior to any characterization of anomalous volcanic activity time series of meteorological data were acquired from the closest weather station to nisyros volcano and surface volcanic temperature from the southern part of nisyros caldera were analyzed time series analysis took place at different time scales through a decomposition method the decomposition of the time series into long seasonal and short term components was performed by the application of the kolmogorov zurbenko kz filter to separate the noise that appears on the obtained data the time series regression tsr model was applied in all time scales the long and the short term components of the surface volcanic temperature show no significant correlation with the atmospheric variables while the seasonal term indicates a very strong association with an r2 equal with 99 after the removal of the atmospheric effect our model indicates that there is a normal activity of the seasonal heat emission in nisyros with no anomalous signals in the temperature residuals during our survey this methodology may facilitate the process of filtering a seasonal atmospheric effect and better comprehend the heat emission of a volcano hydrothermal system from temperature surface readings

volcaniclastic dykes tell on fracturing explosive eruption and lateral collapse at stromboli volcano italy abstract in the upper part of the stromboli volcano in the le croci and bastimento areas two dyke like bodies of volcanic breccia up to two metre thick crosscut and intrude the products of vancori and neostromboli volcanoes we describe the lithofacies association of these unusual volcaniclastic dykes interpret the setting of dyke forming fractures and the emplacement mechanism of internal deposits and discuss their probable relationships with the explosive eruption and major lateral collapse events that occurred at the end of the neostromboli period the dyke volcaniclastic deposits contain juvenile magmatic fragments pyroclasts suggesting a primary volcanic origin their petrographic characteristics are coincident with the neostromboli products the architecture of the infilling deposits comprises symmetrically nested volcaniclastic units separated by sub vertical boundaries which are parallel to the dyke margins the volcanic units are composed of distinctive lithofacies the more external facies is composed of fine and coarse ash showing sub vertical laminations parallel to the contact wall the central facies comprises stratified lithic rich breccia and lapilli tuff whose stratification is sub horizontal and convolute discordant to the dyke margins only at le croci dyke the final unit shows a massive tuff breccia facies the volcaniclastic dykes experienced a polyphasic geological evolution comprising three stages the first phase consisted in fracturing explosive intrusion related to magma rising and upward injection of magmatic fluids and pyroclasts the second phase recorded the dilation of fractures and their role as pyroclastic conduits in an explosive eruption possibly coeval with the lateral collapse of the neostromboli lava cone finally in the third phase the immediately post eruption mass flow remobilization of pyroclastic deposits took place on the volcano slopes

active slide in tertiary bentonitic claystones upper hat creek british columbia potential exploitation of the 500 m thick coal deposit at upper hat creek british columbia required detailed investigation of the sequence of tertiary tuffaceous rocks surrounding the coal and the overlying surficial materials studies have shown that extensive bentonitic slide deposits partially cover the coal body on the west side of hat creek valley part of this area is currently active a translational debris slide of approximately 17 106 m3 volume and 2 km length is moving across the northwest boundary of the proposed pit into the valley bottom detailed field investigations complemented by laboratory testing have defined the basal plane of sliding and permitted a back analysis to be made from measured piezometric pressures the mobilized shear strength on the failure plane is calculated to be cr 0 which is largely in accord with laboratory test results slope stability in thick montmorillonite rich claystones siltstones is known to present difficulties as evidenced by the panama canal exc

geochemistry of rainfall at stromboli volcano aeolian islands isotopic composition and plume rain interaction the chemical and isotopic compositions of the precipitation at stromboli island italy were investigated between october 2003 and october 2005 we employed a rain gauge network designed to cover the range in exposures and elevations of the volcanic edifice the hydrogen and oxygen isotopic ratios vary greatly on a seasonal basis and correlate with air temperature deuterium excess values show a positive correlation with altitude no direct contribution of volcanogenic h or o is evident in the isotopic composition of the rainwater the chemical composition of the rainwater is principally controlled by the sea aerosol contribution at the coastal sites whereas it is significantly influenced by volcanic activity near the summit vents interaction with volcanic acid gases is indicated by the ph which is usually 1 2 units lower near the craters than at the coastal sites the s cl cl f and s f molar ratios in rainwater 1 5 km from the craters are consistent with those measured in the volcanic plume using other methods diffusive tubes and fourier transform infrared spectroscopy rising of undegassed magmas changes these molar ratios because of the differential degassing of sulphur chlorine and fluorine from the magma we therefore propose that the chemical composition of precipitation within 1 5 km of the craters provides additional information that is useful for monitoring volcanic activity at stromboli island moreover this paper presents estimates of the fluxes of f cl s na k ca and mg to the soil that could be useful for geochemical studies on groundwater

gas emission from diffuse degassing structures dds of the cameroon volcanic line cvl implications for the prevention of co2 related hazards abstract in the mid 1980s lakes nyos and monoun violently released massive gas mainly magmatic co 2 killing about 1800 people subsequent geochemical surveys and social studies indicate that lakes nyos and monoun event is cyclic in nature and may occur anywhere in the about 37 other volcanic lakes located in the corridor of the cameroon volcanic line cvl this potential threat motivated us to check if alike nyos and monoun the internal dynamic of the other lakes is also controlled by inputs of deep seated derived co 2 and attempt to measure and provide comprehensive insights on the passive gas emission along the cvl this knowledge shall contribute to the prevention of volcanic lake related hazards in cameroon and the refinement of the global carbon cycle we used in situ fixation and dry gas phase sampling methods to determine co 2 origin and the concentration and the accumulation chamber technique to measure diffuse co 2 emission from nine lakes and on soil at nyos valley and mount manenguba caldera the results suggest that although in minor concentrations compared to nyos and monoun ranging from 0 56 mmol kg 1 to 8 75 mmol kg 1 the bottom waters of some lakes also contain measurable magmatic co 2 with 13 c varies from 4 42 to 9 16 vs pdb that finding implies that under certain circumstances e g increase to volcanic and or tectonic activities along the cvl the concerned lakes could develop a nyos type behavioural scheme the diffuse gas emission results indicate that the nine surveyed lakes release approximately 3 69 0 37 kt km 2 yr 1 of co 2 to the atmosphere extrapolation to the approximately 39 volcanic lakes located on the cvl yields an approximate co 2 output of 27 37 0 5 kt km 2 yr 1 representing 0 023 of the global co 2 output from volcanic lakes in addition to the precedent value the gas removal operation in lakes nyos and monoun released approximately 2 52 0 46 10 8 mol km 2 yr 1 co 2 to the atmosphere from january 2001 to march 2013 more than double the per area co 2 released by the yellowstone volcanic system the co 2 emission from soil was estimated to be 4 57 1 30 kt km 2 yr 1 the soil gas geochemistry of the mount manenguba caldera also indicates a dominant magma derived co 2 mean 13 c 8 6 vs vpdb

a review of the superior province of the canadian shield a product of archean accretion abstract the superior province consists of northern and southern high grade gneiss subprovinces and a central region of alternating granite greenstone and metasedimentary belts subprovinces are commonly fault bounded and display contrasting lithological assemblages metamorphic and structural styles geophysical characteristics and ages they are comparable to phanerozoic suspect terranes the middle and late archean rocks of the superior province are of mantle and juvenile crustal origin with little evidence of inheritance of components older than ca 3 1 ga high grade gneiss subprovinces are mainly deeper level equivalents of the supracrustal rich belts but one minnesota river valley is part of an older ca 3 6 ga terrane that was juxtaposed late in the tectonic history granite greenstone terranes are characterized by low grade volcano sedimentary sequences tholeiitic komatiitic submarine lava plain tholeiitic calc alkalic submarine to subaerial central complexes early platform type quartz arenite stromatolitic carbonate late timiskaming type shoshonitic alkalic volcanic fluvial sediment that range in age from ca 3 0 ga to 2 7 ga the volcanics represent oceanic island arc and continental arc volcanism the quartz arenite carbonate sequences deposition on relatively stable early formed ca 3 0 ga crust and the timiskaming type sequences deposition in pull apart basins developed along strike slip faults late archean ca 2 75 2 70 ga greenstone sequences occur throughout the superior province middle archean ca 3 0 2 8 ga sequences are common in northern and central superior province rare or absent in the south volcanism was accompanied by mafic to trondhjemitic plutonism the metasedimentary belts consist of variably metamorphosed volcanogenic turbidites with detrital zircons ranging in age from ca 3 0 ga to 2 7 ga the metasediments were deposited after major volcanism and probably represent accretionary prisms late archean orogenesis accompanied and followed by calc alkalic plutonism youngs southward from about 2 73 2 72 ga to 2 70 2 68 ga it involved large scale north south compression and dextral transpression and displays thin to thick skinned transitions the contemporaneity of events along the lengths of the belts and their southward younging coupled with the evidence of major compression are consistent with subduction driven oblique accretion of oceanic and continental volcanic arcs accretionary sedimentary wedges older microcontinental fragments etc in a convergent margin setting analogous to parts of the pacific rim differences eg abundance of komatiites and tonalitic plutonic suites are attributable to a hotter archean mantle

long time variation of soil co2 fluxes at the summit crater of vulcano italy here we report the first continuous data of geochemical parameters acquired directly from the active summit crater of vulcano this approach provides a means to better investigate deep geochemical processes associated with the degassing system of vulcano island in particular we report on soil co2 fluxes from the upper part of vulcano a closed conduit volcano from september 2007 to october 2010 large variations in the soil co2 and plume so2 fluxes order of magnitude coinciding with other discontinuous geochemical parameters co2 concentrations in fumarole gas and physical parameters increase of shallow seismic activity and fumarole temperatures have been recorded the results from this work suggest new prospects for strengthening geochemical monitoring of volcanic activity and for improving the constraints in the construction of a geochemical model this being a necessary condition to better understand the functioning of volcanic systems

monitoring volcanic hazard using eddy covariance at solfatara volcano naples italy an eddy covariance ec station was deployed at solfatara crater italy june 8 25 2001 to assess if ec could reliably monitor co2 fluxes continuously at this site deployment at six different locations within the crater allowed areas of focused gas venting to be variably included in the measured flux turbulent ec fluxes calculated in 30 min averages varied between 950 and 4460 g co2 m 2 d 1 the highest measurements were made downwind of degassing pools comparing turbulent fluxes with chamber measurements of surface fluxes using footprint models in diffuse degassing regions yielded an average difference of 0 4 indicating that ec measurements are representative of surface fluxes at this volcanic site similar comparisons made downwind of degassing pools yielded emission rates from 12 to 27 t co2 d 1 for these features reliable ec measurements i e measurements with sufficient and stationary turbulence were obtained primarily during daytime hours 08 00 and 20 00 local time when the wind speed exceeded 2 m s 1 daily average ec fluxes varied by 50 and variations were likely correlated to changes in atmospheric pressure variations in co2 emissions due to volcanic processes at depth would have to be on the same order of magnitude as the measured diurnal variability in order to be useful in predicting volcanic hazard first order models of magma emplacement suggest that emissions could exceed this rate for reasonable assumptions of magma movement ec therefore provides a useful method of monitoring volcanic hazard at solfatara further ec can monitor significantly larger areas than can be monitored by previous methods

new perspectives on volcano monitoring in a tropical environment continuous measurements of soil co2 flux at piton de la fournaise la reunion island france detecting renewal of volcanic activity is a challenging task and even more difficult in tropical settings continuous measurements of soil co2 flux were carried out at the piton de la fournaise volcano during 2013 2016 since this site is in the tropics periods of heavy rainfall are in the norm measurements covered volcanic unrest after a hiatus of 3 5 years we find that while temperature has the strongest effect extreme rainfall causes short term noise when corrected and filtered from the environmental influence soil co2 time series permit to detect a major deep magmatic event during march april 2014 three months before the first eruption of the new activity phase correlation with geophysical datasets allow timing of further stages of upward fluid ascent our study validates soil co2 flux monitoring in tropical environments as a valuable tool to monitor magma transfer and to enhance understanding of volcano unrest down to the lithospheric mantle

volatiles and energy released by purace volcano total co2 output of purace volcano colombia was estimated on the basis of fluids discharged by fumaroles soil gases and dissolved carbon species in the aquifer the soil co2 emission was computed from a field survey of 512 points of co2 soil flux measurements at the main degassing areas of purace volcano the co2 flux from purace s plume was estimated using an indirect method that used the so2 plume flux and co2 so2 ratio of the main high temperature fumarole the total output of co2 was estimated at 1500 t day the main contribution of co2 comes from the plume summit degassing and from soil degassing that emit 673 and 812 t day respectively the contributions of summit and soil degassing areas are comparable indicating an intermediate degassing style partitioned between closed and open conduit systems the estimated water vapor discharge as derived from the chemical composition of the fumaroles the h2o co2 ratio and the so2 plume flux allowed calculation of the total thermal energy fumarolic soil degassing and aquifer released from the purace volcanic system this was 360 mw

shock wave radon surface signals associated with the upsurge of t p solitons in volcanic systems abstract the present paper introduces a theoretical model in order to describe ground surface anomalies of radon emissions as a volcano is perturbed from its quiescent steady state based upon modern thermo poro elasticity theory which has been found to successfully explain rock deformation fracturing these anomalies are considered as being due to the build up of a buried thermo mechanical source which in turn gives rise to the upsurge of a thermo mechanical or t p soliton this sort of fluid solitary wave travelling upwards through induced deformed fractured horizons locally perturbes a pre existing stationary radon concentration profile as the wave approaches the ground surface in order to model radon anomalies a diffusive convective transport equation of radon is adopted with darcy s velocity change controlled by the upsurge of the t p soliton as a result a new flow mechanism of radon emission is found which we call shock wave radon propagation some cases of volcanic eruptions which have been preceded and accompanied by anomalies in radon emissions are examined in the light of the model a reasonably good agreement in the pattern between the observed radon concentration changes and the theoretical curves is found a theoretical tool for volcanic surveillance is thus proposed corresponding to both an effort to shed more light on the correlations that may exist between geophysics and geochemistry of fluid emissions and the recognition through ground surface radon anomalies of subsurface thermo mechanical instabilities possibly preceding volcanic eruptions

ground based insar reveals conduit pressurization pulses at stromboli volcano at stromboli volcano southern italy only few minor precursors gas output have been identified for major strombolian explosions we use ground based interferometric synthetic aperture radar gbinsar technology to monitor the displacement rate of the summit area of stromboli we analysed the 2009 2011 period the analysis of the displacement rate has been performed by dividing the summit zone monitored by the gbinsar into three regions corresponding to the edge of the crater area 1 and 2 and to the slope of the ne crater 3 pulses of rapid expansion of sector 3 of variable duration and amplitude appear in coincidence with periods of intense activity that include lava flows and major explosions we associate this expansion with the pressurization of the magma column that is recharged by deep derived gas promoting the onset of major explosion dominated activity

the influence of alteration on the trace element and nd isotopic compositions of komatiites abstract to investigate the effects of hydrothermal alteration and metamorphism on the chemical and isotopic compositions of komatiites we studied samples from the alexo and texmont regions in the 2 7 ga abitibi belt of canada and from the weltevreden mendon and komati formations of the 3 2 3 5 ga barberton belt of south africa particular emphasis was placed on multiple samples from individual layered spinifex olivine cumulate flows the argument being that if these flows showed variations in the ratios of elements incompatible with olivine then these variations were most likely due to chemical mobility during alteration data for rare earth ree and high field strength elements hfse reveal anomalies non chondritic hfse ree ratios particularly in the most altered samples after taking into account the limits of analytical precision these anomalies are attributed to element mobility not to fractionation of high pressure minerals as suggested by other authors for abitibi komatiites in barberton komatiites three separate processes produced hfse anomalies element mobility during alteration crust assimilation in some samples and majorite fractionation the effects of the latter process were recognized from systematic relationships between hfse ree and al ti that coincided with calculated majorite fractionation trends initial nd isotopic compositions of the komatiites were determined by analysis of magmatic pyroxenes the initial nd of pyroxene from the 2 7 ga alexo komatiite is 3 8 slightly higher than in whole rocks 0 6 to 3 5 average 2 5 in the carbonatized texmont samples the range in initial nd is far greater 6 2 to 8 8 the variable initial nd values in the rocks are attributed to isotopic exchange of nd with surrounding rocks during early alteration and fractionation of sm nd during later events pyroxene from 3 3 ga barberton komatiitic basalt had initial nd of 2 3

experimental monitoring of carbon dioxide by low power ir sensors soil degassing in the furnas volcanic centre azores abstract in october 1993 two experimental carbon dioxide sensors were installed at the furnas volcanic centre sao miguel the monitoring sites are tilt meter stations in furnas village and at castelo branco on the sw caldera rim the selection of these observation sites is meant to record changes in carbon dioxide outgassing close to an active fumarole ground furnas village 3 m deep well and at an outer caldera wall castelo branco 6 m deep well where geothermal processes are definitely absent recording of carbon dioxide was made for one year by hourly readings from october 1993 to october 1994 the experiment revealed carbon dioxide pulses characterised by short rise times hours and fading on the time scale of days interpretation of the data in relation to meteorological conditions is preliminary and suggestive an overall covariation of carbon dioxide outgassing and changes in atmospheric pressure and or precipitation is observed at the calderas fumarole grounds of the furnas village a favoured degassing mechanism is based on increased out diffusion of carbon dioxide from the soil layer at the onset of low pressure intervals due to increased boiling and carbon dioxide release from the shallow local hydrothermal aquifers increased soil degassing after heavy rain is attributed to closure of the porous surface layer resulting in an increased partial pressure of carbon dioxide at the base of the instrument well at the castelo branco station which is located on a narrow ridge some 20 m above the surroundings the opposite effect of barometric pressure is observed on the very low carbon dioxide flux this still unexplained covariation may be related to chemical conditions within the soil during high pressure dry soil and low pressure wet soil periods after every impulsive increase in carbon dioxide flux the normal baseline is slowly reached a periodic effect on soil degassing to a first approximation of tidal origin cannot be excluded at castelo branco it is concluded that the experimental sensors are adequate for detailed long standing evaluation of monitoring sites which needed prior to permanent monitoring of soil degassing

geochemical evidence of the renewal of volcanic activity inferred from co2 soil and so2 plume fluxes the 2007 stromboli eruption italy on 27 february 2007 a new eruption occurred on stromboli which lasted until 2 april it was characterized by effusive activity on the sciara del fuoco and by a paroxysmal event 15 march this crisis represented an opportunity for us to refine the model that had been developed previously 2002 2003 eruption and to improve our understanding of the relationship between the magmatic dynamics of the volcano and the geochemical variations in the fluids in particular the evaluation of the dynamic equilibrium between the volatiles co2 and so2 released from the magma and the corresponding fluids discharged from the summit area allowed us to evaluate the level of criticality of the volcanic activity one of the major accomplishments of this study is a 4 year database of summit soil co2 flux on the basis of which we define the thresholds low medium high for this parameter that are empirically based on the natural volcanological evolution of stromboli the so2 fluxes of the degassing plume and the co2 fluxes emitted from the soil at pizzo sopra la fossa are also presented it is noteworthy that geochemical signals of volcanic unrest have been clearly identified before during and after the effusive activity these signals were found almost simultaneously in the degassing plume so2 flux and in soil degassing co2 flux at the summit although the two degassing processes are shown to be clearly different the interpretation of the results will be useful for future volcanic surveillance at stromboli

mantle convection and early crustal evolution abstract the existence of peridotitic komatiites in the archaean suggests that the archaean mantle was significantly hotter than the modern mantle this evidence is contradicted by estimates of archaean continental geothermal gradients based on the pressure and temperature recorded in metamorphic rocks which suggest that there is no marked difference between archaean and modern continental geothermal gradients numerical modelling shows that small changes in the mantle temperature can have an important influence on convection if the average temperature of the upper mantle is increased by 200 c convection within the mantle becomes chaotic and an upper mantle partial melt zone encircles the globe the crust formed during this period will be komatiitic in composition but will be unstable and will be mixed back into the mantle by subduction later when the mantle temperature falls to 100 c above its present level the upper mantle partial melt zone contracts away from subduction areas it is suggested that the first primitive felsic magmas were generated at subduction zones the appearance of these magmas at 3 8 ga permitted the formation of buoyant continents and eventually led to crustal thickening as a consequence of this thickening the proto continents consisting of a bimodal suite of basalts and sodic granodiorites contained two types of latent energy 1 radioactive energy held in elements such as th k and u and 2 potential energy resulting from the elevation of the continents above sea level the potential energy of the continents led to sedimentation the increase in the rate of sedimentation during the archaean resulted from increased crustal buoyancy at the same time heat released by radioactive elements in the deep crust built up under the insulating blanket of the upper crust this caused a major metamorphic metasomatic and crustal melting event which produced the potassic granites of the late archaean once the radioactive elements had been removed from the lower crust that region of the continent become tectonically stable the proterozoic shelf sediments were deposited at the margins of these stable cratons convection models of the archaean mantle show hot diapirs rising from the boundary layer above the core mantle interface we suggest that these diapirs began to melt at a depth of 450 km giving rise to komatiitic magmas this model requires the average temperature of the archaean upper mantle to be 100 c above that of the modern mantle the similarity between archaean and modern continental geothermal gradients can be explained if archaean continents formed above subduction zones raising the temperature of the archaean mantle by 100 c 1 halves the thickness of the oceanic lithosphere 2 increases the oceanic geothermal gradient at the mid point of a convection cell 3 decreases the viscosity of the mantle by at least an order of magnitude the combination of these effects produces a marked decrease in the strength of the archaean lithosphere and mantle thus the form of archaean tectonics can be expected to have been very different from modern tectonics

dynamics of the december 2002 flank failure and tsunami at stromboli volcano inferred by volcanological and geophysical observations 1 the 2002 effusive flank eruption at stromboli volcano started on december 28 after several months of strong explosive activity at the summit craters on december 30 the seismic network recorded two large flank failures and associated tsunami waves this is the first time that a flank collapse and tsunami and their associated phenomena have been recorded by a multi disciplinary monitoring system volcanological and geophysical monitoring as well as thermal surveys performed immediately before and after the failure allowed us to define and interpret the sequence of events the still on going eruption has provided for the first time the opportunity to look into the dynamics of stromboli s effusive eruptions flank failure and landslide formation and their potential hazard

review of the evolution of geochemical monitoring networks and methodologies applied to the volcanoes of the aeolian arc italy abstract fluids discharged from volcanic systems are the direct surface manifestation of magma degassing at depth and provide primary insights for evaluating the state of volcanic activity we review the geochemical best practice in volcanic surveillance based to a huge amount of monitoring data collected at different active volcanoes using both continuous and discontinuous approaches the targeted volcanoes belong to the aeolian arc located in the tyrrhenian sea italy and they have exhibited different activity states during the monitoring activities reported here la fossa cone on vulcano island has been in an uninterrupted quiescent stage characterized by variable solfataric activity in contrast stromboli island has shown a persistent mild explosive activity episodically interrupted by effusive eruptions in 1985 2002 2007 and 2014 panarea island which is the summit of a seamount rising from the seafloor of the southern tyrrhenian sea showed only undersea fluid release the only observable clues of active volcanism at panarea island have been impulsive changes in the undersea fluid release with the last submarine gas burst event being observed in november 2002 the geochemical monitoring and observations at each of these volcanoes has directly involved the volcanic plume and or the fumarole vents thermal waters and diffuse soil degassing depending on the type of manifestations and the level of activity encountered through direct access to the magmatic samples when possible and the collection of as much observable data related to the fluid release as possible the aim has been i to verify the thermodynamic equilibrium condition ii to discern among the possible hydrothermal magmatic marine and meteoric sources in the fluid mixtures iii to develop models of the fluid circulation supported by data iv to follow the evolution of these natural systems by long term monitoring and v to support surveillance actions related to defining the volcanic risk and the evaluation and possible mitigation of related hazards the examples provided in this review article show the close relationships among data analysis interpretation and modeling we particularly focus on describing the fieldwork procedures since any theoretical approach must always be verified and supported by field data rather than just by experiments controlled in laboratory indeed the natural systems involve many variables producing effects that cannot be neglected the monitored volcanic systems have been regarded as natural laboratories and all of the activities have focused on both volcanological research and surveillance purposes in order to ensure that these two goals have overlapped an appendix is also included that explains the scientific approach to the systematic activities regarding geochemical monitoring of volcanic activity

the 1997 eruption of okmok volcano alaska a synthesis of remotely sensed imagery abstract okmok volcano in the eastern aleutian islands erupted in february and march of 1997 producing a 6 km long lava flow and low level ash plumes this caldera is one of the most active in the aleutian arc and is now the focus of international multidisciplinary studies a synthesis of remotely sensed data airsar derived dems landsat mss and etm data avhrr ers jers radarsat has given a sequence of events for the virtually unobserved 1997 eruption elevation data from the airsar sensor acquired in october 2000 over okmok were used to create a 5 m resolution dem mosaic of okmok volcano avhrr nighttime imagery has been analyzed between february 13 and april 11 1997 landsat imagery and sar data recorded prior to and after the eruption allowed us to accurately determine the extent of the new flow the flow was first observed on february 13 without precursory thermal anomalies at this time the flow was a large single lobe flowing north according to avhrr band 3 and 4 radiance data and ground observations the first lobe continued growing until mid to late march while a second smaller lobe began to form sometime between march 11 and 12 this is based on a jump in the thermal and volumetric flux determined from the imagery and the physical size of the thermal anomalies total radiance values waned after march 26 indicating lava effusion had ended and a cooling crust was growing the total area 8 9 km 2 thickness up to 50 m and volume 1 54 10 8 m 3 of the new lava flow were determined by combining observations from sar landsat etm and airsar dem data while the first lobe of the flow ponded in a pre eruption depression our data suggest the second lobe was volume limited remote sensing has become an integral part of the alaska volcano observatory s monitoring and hazard mitigation efforts studies like this allow access to remote volcanoes and provide methods to monitor potentially dangerous ones

constraints on early archean crustal extraction and tholeiitic komatiitic volcanism in greenstone belts of the northern superior province numerous small remnants of archean greenstone belts in the northern superior province ca 2875 2710 ma have chemical characteristics similar to those of the larger greenstone belts of the southern superior province and preserve direct evidence of crustal conditions prior to the major volcanic events of the late archean wawa abitibi subprovinces ca 2760 2700 ma three of the best preserved belts are engulfed in tonalite intrusions of the faribault thury complex ftc and exhibit common chemical characteristics which may imply a similar origin the dominant tholeiitic basalts typically have mgo contents 7 wt tio2 15 low cao al2o3 1 2 and chondritic gd yb ratios similar to 2 7 ga al undepleted komatiites the trace element ratios of komatiitic rocks are indistinguishable from those of the associated tholeiites suggesting either a derivation from similar mantle sources or a comagmatic relationship nb thpm 0 8 1 1 la cepm 0 9 1 3 nb ce 0 7 0 9 y hopm 1 and th lapm 0 7 1 1 numerical modelling of trace and major elements during low pressure crystal fractionation reproduces the spectrum of both inferred liquid and cumulate compositions and is consistent with a comagmatic origin between the komatiites and tholeiites the relatively low nb th ratios of these mid archean volcanic rocks relative to both modern day basalts and late archean basalts may indicate that they were derived from a mantle source that had not lost its crustal components nor seen significant recycled oceanic crust high nb th the extraction of continental crust from this archean mantle source might then postdate the ftc volcanism and may be associated with the generation of the voluminous tonalites that engulf the belts 445

co2 output discharged from stromboli island italy abstract total co 2 output from soil gas and plume discharged from the stromboli island was estimated the co 2 emission of the plume emitted from the active crater was estimated on the basis of the so 2 crater output and c s ratio while co 2 discharged through diffuse soil emission was quantified on the basis of 419 measurements of co 2 fluxes from the soil of the whole island performed by using the accumulation chamber method the results indicate an overall output of 416 t day 1 of co 2 from the island the main contribution to the total co 2 output comes from the summit area 396 t day 1 with 370 t day from the active crater and 26 t day 1 from the pizzo sopra la fossa soil degassing area the release of co 2 from peripheral areas is 20 t day 1 by soil degassing scari area mainly the result of the soil degassing survey confirms the persistence of the highest co 2 degassing areas located on the north east crater side and scari area

soil co2 flux in hydrothermal areas of the tatun volcano group northern taiwan abstract we measured soil co2 flux in the representative hydrothermal areas of the tatun volcano group tvg to better understand the volcano s dynamic nature and to estimate its soil co2 degassing output results show that the average soil co2 fluxes obtained at da you keng dyk geng tze ping gtp she haung ping shp and tatun natural park tnp were 128 g m 2 d 1 518 g m 2 d 1 420 g m 2 d 1 and 25 g m 2 d 1 respectively the range is comparable to other active volcanic hydrothermal areas in the world along with liu huang ku lhk where the soil co2 flux is known the total soil co2 output from measured areas is evaluated at 82 t d 1 furthermore a first total soil co2 output from the whole hydrothermal areas of the tvg is roughly estimated at 113 t d 1 which includes 15 t d 1 mantle contribution considering the mantle derived co2 flux and h2o co2 ratio of fumarolic gas thermal energy associated with the diffuse degassing at the tvg hydrothermal area is estimated at 8 2 mw carbon 13c and helium 3he 4he isotopic ratios of soil samples of the studied areas ranged from 4 4 to 6 7 and 2 45 to 6 98 ra respectively the extent of air involvement in the soil degassing system as constrained by the helium and carbon isotopic compositions provides essential information for depicting regional degassing features of the hydrothermal areas

giant granulite terranes of northeastern superior province the ashuanipi complex and minto block the ashuanipi complex and minto block of the superior province are large regions that have been classified as high grade gneiss terranes on the basis of the presence of orthopyroxene bearing units like the granite greenstone and metasedimentary subprovinces of the southern superior province the two terranes consist predominantly of intrusive rocks but are distinguished by their primary magmatic orthopyroxene both high grade and gneiss are misnomers because granulite facies gneisses are only sparingly present and the regions consist dominantly of massive unmetamorphosed plutonic rock the ashuanipi complex consists of a deformed metamorphosed package of metasedimentary rocks and primitive early tonalite cut by widespread orthopyroxene garnet granodiorite diatexite as well as plutons of tonalite granite and syenite based on its lithological and chronological similarity and on strike position the complex appears to be the continuation of metasedimentary subprovinces such as the quetico its evolution involved deposition of immature greywacke in an accretionary prism early arc tonalitic magmatism and deformation followed by widespread intracrustal magmatism in the period 2700 2670 ma both metamorphic and igneous rocks record equilibration under granulite facies conditions 700 835 c 0 35 0 65 gpa a 0 3 and indicate exposure levels of 20 km the minto block at the latitude of leaf river consists of several north northwest trending domains of similar scale and diversity to the east trending subprovinces of the southern superior province the central goudalie domain is dominantly amphibolite facies tonalitic rocks including some with ages 3 ga with small belts of volcanic and sedimentary origin lake minto domain contains poorly preserved supracrustal remnants in a plutonic complex comprising hornblende granodiorite clinopyroxene orthopyroxene granodiorite orthopyroxene biotite diatexite and granite the hornblende granodiorite suite constitutes most of the utsalik and tikkerutuk domains and is thought to represent continental arc magmatism on the basis of their distinct aeromagnetic and lithological character two additional domains are evident north of the leaf river area the inukjuak domain in the west and the douglas harbour domain in the east the northerly grain of the minto block appears to have been established in situ with respect to the easterly belts of the southern superior province i e no large scale block rotation during the same interval of time 3 0 2 7 ga modification of the tectonic framework for the superior province is required to explain minto arc magmatism in the interval 2730 2690 ma ago a continental magmatic arc built the berens river and bienville subprovinces and minto block on the southern and eastern edges respectively of a northern protocratonic foundation in the same period primitive volcanic arcs and accretionary prisms developed outboard on oceanic crust and were accreted to form a southern tectonic regime

archean magmatism and deformation were not products of plate tectonics abstract the granite and greenstone terrains that dominate upper crust formed from about 3 6 to about 2 6 ga and record magmatic and tectonic processes very different from those of a younger time they indicate heat loss by the archean earth primarily by voluminous magmatism from a mantle much hotter than that of the present plate tectonic processes were not then operating the distinctive array of petrologic structural and stratigraphic features that characterize phanerozoic convergent plate systems ophiolites magmatic arcs accretionary wedges fore arc basins etc have no viable analogues in archean terrains purported archean plate tectonic indicators consist merely of rock types that even superficially resemble actual phanerozoic indicators only when considered in isolation from their association and structure archean ultramafic and mafic volcanic rocks neither resemble ophiolitic rocks in petrology nor occur in ophiolite type successions they often depositionally overlie felsic basement rocks and often overlie and are intercalated with sedimentary and felsic volcanic rocks and they require a mantle about 200 c hotter than now archean graywackes are coherent strata derived from nearby volcanic rocks late in the histories of their regions and they lack the setting and disruption that characterize modern accretionary wedges the lithologic structural and stratigraphic assemblages that typify proterozoic and phanerozoic rifted and reassembled margins also lack archean analogues and no evidence has been found for archean rifting rotation and reassembly of continental plates conversely characteristic archean assemblages lack modern equivalents in any tectonic setting ultramafic lavas erupted at liquidus temperatures are voluminous granite and greenstone terrains have no modern analogues greenstone belts are typically anastomosing networks of upright synforms formed by crowding aside by and sinking between large rising diapiric elliptical composite batholiths the batholiths include both the products of new crustal melts and variably remobilized mid crustal gneisses the greenstone belts are defined by late deformation of regionally semiconcordant volcanic and sedimentary successions and are not relics of successively formed volcanic chains little deformation generally preceded the diapirism and metamorphism was primarily of contact type the regionally uniform areal density and accordant crustal level of the diapiric batholiths their contacts primarily against the oldest strata of the synforms their general age 10 20 million years younger than most of the flanking stratiform rocks and considerations of high archean radiogenic heat productivity all fit the explanation that the batholiths were mobilized by partial melting of hydrous lower crust by radiogenic heating diapirism was accompanied by modest regional orthogonal shortening and extension of the hot upper crust producing the orientations of the batholiths rise of the batholiths greatly increased the petrologic fractionation of the crust and the concentration of radionuclides high in it resulting in cooling of the deeper crust and subjacent mantle and thus cratonization the upper crust containing the granite and greenstone aggregates was decoupled from the gneissic middle crust which underwent flattening and extension subparallel to the elongation of the shallow batholiths this deep deformation may have been driven by flow of dense restites toward delamination loci from which they sank into the mantle the early earth was probably wholly molten the surface of the earth like that of the moon must have been wholly recycled by impacts before 3 9 ga and heavily modified by them until 3 8 ga zircons as old as 4 2 ga have been found as clastic grains in much younger archean quartzites and polycyclic migmatites last partly melted and reconstituted under hydrous conditions only after 3 6 ga contain relict zircons as old as 4 0 ga the lithologies of the early earth protoliths in which these zircons formed have not been established but impact melts and breccias must be represented and magma ocean fractionates may be the nature of the transition in tectonic style into the granite and greenstone mode is unknown plate tectonic rifting and convergence were operating by about 2 0 ga and were in an essentially modern mode by about 0 8 ga the nature of the transition from the granite and greenstone mode at about 2 6 ga to plate mode by about 2 0 ga has yet to be defined the change may have been facilitated by the increasing content of water and carbon dioxide in the mantle as dense but hydrated delaminated archean crust sank into it

the 15 march 2007 explosive crisis at stromboli volcano italy assessing physical parameters through a multidisciplinary approach basaltic volcanoes are dominated by lava emission and mild explosive activity nevertheless many basaltic systems exhibit from time to time poorly documented and little understood violent explosions a short lived multiblast explosive crisis paroxysmal explosion occurred on 15 march 2007 during an effusive eruptive crisis at stromboli italy the explosive crisis which started at 20 38 14 ut had a total duration of 5 min the combined use of multiparametric data collected by the permanent instrumental networks seismic acoustic and thermal records and a field survey carried out immediately after the event enabled us to constrain the eruptive dynamics and quantify physical parameters the eruption consisted of three major pulses in the first lithic blocks and ash were ejected at speeds of 100 155 m s and 130 210 m s respectively the high solid load of the eruptive jet resulted in the partial collapse of the column with the formation of a small volume pyroclastic density current the second 12 s long pulse emitted 2 2 2 7 107 kg of tephra mass discharge rate 1 9 2 3 106 kg s forming a 3 km high convective plume dispersing tephra up to the west coast and a dilute density current with limited dispersal downslope of the craters a final 30 s long phase formed a scoria flow with a volume of 1 5 1 7 104 m3 mass discharge rate 5 9 6 7 105 kg s a total runout of 200 m and a velocity of 45 m s the total gas volume involved in the explosion was 1 3 1 9 104 m3 with an initial overpressure of 7 9 0 4 mpa we compared the 15 march 2007 event with historical paroxysms in particular with that of 5 april 2003 which was remarkably similar

oceanic plateau model for continental crustal growth in the archaean a case study from the kostomuksha greenstone belt nw baltic shield abstract field studies combined with chemical and isotope data indicate that the kostomuksha greenstone belt in the nw baltic shield consists of two lithotectonic terranes one mafic igneous and the other sedimentary separated by a major shear zone the former contains submarine komatiite basalt lavas and volcaniclastic lithologies and the latter is composed of shelf type rocks and bif komatiitic and basaltic samples yield sm nd and pb pb isochron ages of 2843 39 and 2813 78 ma respectively their trace element compositions resemble those of recent pacific oceanic flood basalts with primitive mantle normalized nb th of 1 5 2 1 and nb la of 1 0 1 5 this is in sharp contrast with island arc and most continental magmas which are characterized by nb th la n 1 calculated initial nd isotope compositions nd t 2 8 to 3 4 plot close to an evolution line previously inferred for major orogens momo which is also consistent with the compositions of recent oceanic plateaux the high liquidus temperatures of the komatiite magmas 1550 c and their al depleted nature require an unusually hot 1770 c mantle source for the lavas 200 c hotter than the ambient mantle at 2 8 ga and are consistent with their formation in a deep mantle plume in equilibrium with residual garnet this plume had the thermal potential to produce oceanic crust with an average thickness of 30 km underlain by a permanently buoyant refractory lithospheric mantle keel nb u ratios in the komatiites and basalts calculated on the basis of th u pb relationships range from 35 to 47 and are thus similar to those observed in modern morb and oib this implies that some magma source regions of the kostomuksha lavas have undergone a degree of continental material extraction comparable with those found in the modern mantle the mafic terrane is interpreted as a remnant of the upper crustal part of an archaean oceanic plateau when the newly formed plateau reached the active continental margin its upper part collided with the sedimentary terrane but was too buoyant to subduct as a result the volcanic section of the plateau was imbricated and obducted thus becoming a new segment of continental crust the deeper zones were delaminated and tectonically underplated or subducted

the 2002 2003 eruption of stromboli italy evaluation of the volcanic activity by means of continuous monitoring of soil temperature co2 flux and meteorological parameters 1 from december 2002 to july 2003 stromboli volcano was characterized by a new effusive stage of eruption after a period of extraordinary strombolian activity signals recorded in two continuous monitoring stations during the eruption which have already been presented in very recent papers evidenced anomalies in the co2 flux just before the onset of the eruption a more detailed analysis carried out on the data subset acquired during the eruption integrated by daily field observations of the scientific personnel working at the volcanological observatory in stromboli showed that co2 flux and soil temperature are strictly related to volcanic events furthermore the relative minima and maxima of the two parameters showed a strong correlation with wind speed and direction this fact was especially true at the summit station whereas at the coastal sites seasonal and meteorological effects masked the volcanic signal the analysis of the wind data particularly the relationships between wind speed and direction air and soil temperature and local circulation of atmospheric air masses revealed that during the eruption in the summit area of stromboli air movements were not only related to atmospheric circulation but were also significantly affected and in certain cases caused by volcanic activity this conclusion was reached by observing several anomalies such as the discrepancies in the wind direction between the two stations higher air temperatures at the summit site and inversion of direction for wind before and after the reopening of the conduit in a major explosion on 5 april 2003 the relationships found between volcanic activity soil temperatures co2 fluxes and wind speed and direction indicate that soil temperature measurements in an open conduit volcano such as in this case could be used to monitor the level of volcanic activity along with co2 flux furthermore the possible volcanic origin of a peculiar type of air circulation identified in the summit area of stromboli suggests that the separation between volcanic and atmospheric signals might not be obvious requiring monitoring over a wide area rather than a single location

time dependent fisher information measure of volcanic tremor before the 5 april 2003 paroxysm at stromboli volcano italy the investigation of the time dynamics of volcanic tremor recorded at stromboli volcano before the paroxysm occurred on april 5 2003 was performed on the base of a new approach the fisher information measure fim which allows to detect changes in the dynamical behavior of a complex system the particular observed pattern suggests that the signal varies between sets of disordered states small fim and sets of ordered states large fim significant precursory changes in the temporal variation of the fim were revealed at least 42 h before the paroxysm and lasting about 17 h the timescales highlighted are compatible to those found by other authors and could qualify the fim as a good detector of regime changes and possible precursors of anomalous volcanic activity

multiple sector collapses at stromboli volcano italy how they work this paper demonstrates that four large sector collapses have affected the nw flank of the stromboli volcano in the past 13 ka alternating with growth phases in order to contribute to the evaluation of the critical conditions which trigger lateral collapses a reconstruction of the geometry of each collapse of the volcano edifice in the four stages that preceded the relative collapse events is also presented and a computation of the landslide volume this reconstruction is based on new field data plotted in three dimensions prior to the initial 13 ka collapse the volcano was 1125 100 m high above sea level the collapse had a volume of 2 23 0 87 km3 whereas the pre collapse volcano volume was 218 8 7 7 km3 the next edifice that failed was 900 70 m high a s l the collapse volume was 1 0 54 km3 with a precollapse volcano volume of 201 4 5 4 km3 the edifice then grew to 1000 60 m a s l the third collapse had a volume of 1 08 0 39 km3 and occurred within a volcano with a volume of 209 1 4 6 km3 this was followed by a new growth phase followed by the last collapse with a volume of 0 73 0 22 km3 the volcano volume was about the same as the present one the present active crater zone is at 780 m a s l in the first three collapses sliding surfaces cut the main magma conduit in the last collapse the upper scarp coincided with the conduit location dyking along a main ne trending weakness zone across the volcano summit exerted a lateral force for collapse inception the decrease of the landslide volumes with the age and the concentric scarps of the four collapses suggest that the younger sliding planes tended to become more superficial and to decrease the areal extent this is interpreted as due to a successively weaker eruptive products from dominantly lavas to dominantly pyroclastics and b the feedback effects between collapses and dykes that injected along the lateral segments of the first collapse slide plane

anomalous diffuse co2 emission prior to the january 2002 short term unrest at san miguel volcano el salvador central america on january 16 2002 short term unrest occurred at san miguel volcano a gas and steamash plume rose a few hundred meters above the summit crater an anomalous microseismicity pattern about 75 events between 7 30 and 10 30 hours was also observed continuous monitoring of co2 efflux on the volcano started on november 24 2001 in the attempt to provide a multidisciplinary approach for its volcanic surveillance the background mean of the diffuse co2 emission is about 16 g m 2 d 1 but a 17 fold increase up to 270 g m 2 d 1 was detected on january 7 nine days before the january 2002 short term unrest at san miguel volcano these observed anomalous changes on diffuse co2 degassing could be related to either a sharp increase of co2 pressure within the volcanic hydrothermal system or degassing from an uprising fresh gas rich magma within the shallow plumbing system of the volcano since meteorological fluctuations cannot explain this observed increase of diffuse co2 emission

crustal growth through successive arc magmatism reconnaissance u pb shrimp data from the northeastern superior province canada abstract north of the la grande subprovince in northern quebec the superior province is dominated by plutonic rocks of the bienville subprovince and minto block which have been further subdivided into domains on the basis of reconnaissance geological mapping and geochronology and projected along strike using aeromagnetic anomalies to test the validity of the extrapolations u pb ages were obtained through shrimp analyses of zircon from 18 small archival samples selected from a suite of 2000 specimens collected during a helicopter reconnaissance survey conducted in the 1960s the results reveal a history of successive arc magmatism between 3 07 and 2 70 ga followed by metamorphism emplacement of crustally derived granites 2 702 2 685 ga and late hydrothermal events ca 2 65 ga in the northeastern minto block the douglas harbour domain previously extrapolated from dated localities to the northeast is substantiated through an age of 2 87 ga the older tonalitic crust is punctured by 2 734 2 725 ga granodioritic plutons of the leaf river suite that locally carry 3 01 ga inherited zircon the northern utsalik domain is made up of pyroxene and hornblende bearing leaf river plutons with consistent 2 725 2 723 ga ages and local inheritance of 2 82 and 2 77 ga however the southern extension of utsalik domain contains pyroxene bearing granodiorites both older 2 762 ga and younger 2 692 ga than the leaf river suite a tonalitic rock from the southern goudalie domain with an age of 2 833 ga supports a linkage to 2 84 2 83 ga units of the qalluviartuuq domain along strike to the north tikkerutuk domain represents a north trending 50 km wide calc alkaline magmatic arc with ages between 2 71 and 2 70 ga that extends southward into the bienville subprovince on the basis of aeromagnetic anomalies and geochronology zircon inheritance ages indicate that the tikkerutuk arc was built upon antecedent arcs of 2 84 2 77 and 2 725 ga the inukjuak domain in the west consists mainly of granite dated in one locality at 2 72 ga

early evolution of continents how did the continents form and how long ago these questions have been the subject of debate for 30 years as hofmann discusses in his perspective results reported by sylvester et al p 521 reveal that measurements of niobium and uranium isotopes indicate that ancient rocks from western australia are indistinguishable from modern mantle rock this finding suggests that the mass and extent of continents today is comparable to that 2 7 billion years ago

anomalous diffuse co2 emissions at the masaya volcano nicaragua related to seismic volcanic unrest anomalous changes in the diffuse emission of carbon dioxide within the masaya caldera have been observed before two seismic events that occurred at 10 and 30 km from the observation site their epicenters are located respectively south of managua in las colinas 4 3 magnitude and the xiloa caldera 3 6 magnitude in 2002 and 2003 recorded by the geochemical station located at el comalito masaya volcano nicaragua anomalous increases were observed which occurred around 50 and 8 days before the main seismic event that took place in las colinas and 4 days before the seismic swarm at the xiloa caldera with a maximum co2 efflux of 9 3 and 10 7 kg m 2 day 1 respectively the anomalous co2 efflux increases remained after filtering with multiple regression analysis was applied to the co2 efflux time series which indicated that atmospheric variables during the first 4 months explained 23 co2 variability whereas during the rest of the time series co2 efflux values are poorly controlled with only 6 the observed anomalies of the diffuse co2 emission rate might be related to pressure changes within the volcanic hydrothermal system and or to geostructural changes in the crust due to stress strain changes caused before and during the earthquakes formation and seem not to be related to the activity of the main crater of masaya volcano

archean metavolcanics from the rouyn noranda district abitibi greenstone belt quebec 2 mobility of trace elements and petrogenetic constraints qualitative evaluation of altered mafic pillows from the rouyn noranda district of the abitibi metavolcanic belt reveals that for low grade metamorphism the high field strength elements hfs zr y ti and the rare earth elements ree are immobile however where alteration is extreme the ree elements are leached and redeposited by carbonate rich and k rich metasomatic fluids whilst zr y and zr ti remain unchanged rubidium ba and to a lesser extent sr are mobile at all levels of alteration however provided certain filters are applied the original geochemical values of the lavas for the alkaline elements the hfs elements and the ree can be defined the geochemical variations thus identified for the volcanic series of the rouyn noranda district are ascribed to a combination of contamination and fractional crystallization of a primitive tholeiitic magma

co2 and he degassing at el chichon volcano chiapas mexico gas flux origin and relationship with local and regional tectonics during 2007 2008 three co2 flux surveys were performed on el chichon volcanic lake chiapas mexico with an additional survey in april 2008 covering the entire crater floor including the lake the mean co2 flux calculated by sequential gaussian simulation from the lake was 1 190 march 2007 730 december 2007 and 1 134 g m 2 day 1 april 2008 with total emission rates of 164 9 5 march 2007 59 2 5 december 2007 and 109 6 6 t day 1 april 2008 the mean co2 flux estimated from the entire crater floor area was 1 102 g m 2 day 1 for april 2008 with a total emission rate of 144 5 9 t day 1 significant change in co2 flux was not detected during the period of survey and the mapping of the co2 flux highlighted lineaments reflecting the main local and regional tectonic patterns the 3he 4he ratio as high as 8 1 ra for gases in the el chichon crater is generally higher than those observed at the neighbouring transmexican volcanic belt and the central american volcanic arc the co2 3he ratios for the high 3he 4he gases tend to have the morb like values 1 41 109 and the co2 3he ratios for the lower 3he 4he gases fall within the range for the arc type gases the high 3he 4he ratios the morb like co2 3he ratios for the high 3he 4he gases and high proportion of morb co2 m 25 15 at el chichon indicate a greater depth for the generation of magma when compared to typical arc volcanoes

seismic precursors of a basaltic paroxysmal explosion track deep gas accumulation and slug upraise 1 basaltic volcanoes though fed with low viscosity magma occasionally produce sudden paroxysmal explosions that are unforecasted and whose triggering mechanism remains poorly elucidated here we report on the first detection of seismic signals precursory to such an explosion on 5 april 2003 at stromboli volcano italy this strongest event in the past 73 years was preceded by 25 h of seismic tremor variation broadly coincident with strong geochemical anomalies in crater plume emissions followed by 15 h of tilt related long period inflation pulses of increasing amplitude these precursory signals are best explained by accelerating growth and leakage of a bubble melt foam layer formed at 10 km depth whose collapse triggered the fast ascent of co2 rich gas slugs and then the explosion our results open new perspectives for the forecasting of such paroxysmal explosions and associated hazards

the 2014 effusive eruption at stromboli volcano italy inferences from soil co2 flux and 3he 4he ratio in thermal waters a new eruption started at stromboli on 6 august 2014 which had been preceded by 2 months of increased strombolian activity and several lava overflows from the craters the eruption was characterized by a lava effusion in sciara del fuoco from a fracture at 650 m above sea level that lasted until 13 17 november here we present the first geochemical observations of this eruption based on the soil co2 flux in the summit area and on 3he 4he ratios in the thermal waters near stromboli village we infer that this eruption was triggered by the gradual replenishment of the feeding system by a co2 and 3he rich magma at the end of 2013 and after june 2014 suggested by the increase in 3he 4he ratio before eruption which reached its highest value since 2007 we thus infer that this eruption was unusual and we finally speculate on the evolutionary scenario of posteruption

the 2007 eruption of stromboli volcano insights from real time measurement of the volcanic gas plume co2 so2 ratio abstract the recent eruption of stromboli in february april 2007 offered a unique chance to test our current understanding of processes driving the transition from ordinary persistent strombolian to effusive activity and the ability of instrumental geophysical and geochemical networks to interpret and predict these events here we report on the results of two years of in situ sensing of the co 2 so 2 ratio in stromboli s volcanic gas plume in the attempt to put constraints on the trigger mechanisms and dynamics of the eruption we show that large variations of the plume co 2 so 2 ratio range 0 9 26 preceded the onset of the eruption since december 2007 interrupting a period of relatively steady and low ratios time averaged ratio 4 3 lasting from at least may to november 2006 by contrasting our observations with numerical simulations of volcanic degassing at stromboli derived by use of an equilibrium saturation model we suggest that the pre eruptive increase of the ratio reflected an enhanced supply of deeply derived co 2 rich gas bubbles to the shallow plumbing system this larger than normal ascent of gas bubbles was likely sourced by a 1 3 km deep gas melt separation region probably a magma storage zone and caused faster convective overturning of magmas in the shallow conduit an increase in the explosive rate and in seismic tremor and finally the collapse of the la sciara del fuoco sector triggering the effusive phase the high co 2 so 2 ratios up to 21 observed during the effusive phase and particularly in the days and hours before a paroxysmal explosion on march 15 2007 indicate the persistence of the same gas source and suggest that de pressurization of the same 1 3 km deep magma storage zone could have been the trigger mechanism for the paroxysm itself

holocene history of earthflow mass movements in south central british columbia the influence of hydroclimatic changes large earthflows in south central british columbia have exhibited regionally consistent fluctuations in their movement during the holocene over the past 60 years air photographs show that many earthflows were reactivated during the relatively wet period 1950 1985 over the past 300 years a fairly coherent relationship is established between periods of wetter climate defined by the tree ring record and phases of slope movement defined by the record of compression wood development in conifers located near earthflow headscarps on a time scale of several thousand years stratigraphic evidence shows that many large earthflows in the region underwent significant reactivation of movement in the post mazama period during the relatively wet cool neoglacial interval of the holocene these lines of evidence indicate that holocene hydroclimatic changes have exerted an important influence on the regimen of large earthflows earthflows present a wealth of paleogeomorphic information hitherto largely neglected

flux measurements of nonvolcanic co2 emission from some vents in central italy in central italy nonvolcanic co2 is discharged from many areas of focused degassing vents and associated strong diffuse emission and from high pco2 groundwater we estimate that there are at least 100 co2 vents in central italy many of which have a history of lethality to animals and humans the gas vents are extremely efficient pathways for transporting large amounts of deeply derived co2 from gas reservoirs to the surface as co2 fluxes from these vents were heretofore unmeasured several complementary methods were developed to measure the co2 flux from seven of these vents which cumulatively discharge 3 1 109 mol yr 1 co2 472 t d 1 considering all of the vents in central italy the total co2 flux from vents alone may be similar to the co2 emission from the taupo volcanic zone in new zealand 1010 mol yr 1 1200 t d 1 and other areas of high heat flow summing the co2 discharged from vents areas of diffuse co2 degassing and degassing of high pco2 groundwater we provisionally estimate that the total nonvolcanic co2 flux to the atmosphere in central italy may be 1011 mol yr 1 12 000 t d 1

allochthonous 2 78 ga oceanic plateau slivers in a 2 72 ga continental arc sequence vizien greenstone belt northeastern superior province canada embedded within the vast granitoid terrane of the minto block of northeastern superior province are late archean greenstone belts of the goudalie domain that preserve a long lived record of continent ocean interaction the vizien greenstone belt is one such belt and it contains four fault bounded structural panels the 2786 ma mafic ultramafic sequence is an allochthonous package of pillowed basaltic andesite komatiite and volcaniclastic rocks cut by peridotite and gabbro sills the mafic rocks are lree depleted tholeiites which have primitive mantle prim normalized abundances of th la nb and a range of nd values from 0 1 to 1 7 the 2722 ma lac serindac bimodal subaerial tholeiitic volcanic sequence contains andesite locally with tonalite xenoliths basalt gabbro sills lenses of quartz rich sedimentary rocks and a thick upper rhyolite sequence the lac serindac tholeiites are lree enriched have prim normalized th la nb high zr to 300 ppm and ti contents and low nd values from 0 8 in basalt to 1 4 in rhyolite the 2718 ma basement cover sequence comprises 2 94 ga tonalitic gneiss unconformably overlain by clastic sediments and a thin upper sequence of 2700 ma gabbro siliceous high mg basalt shmb and andesite the shmb are characterised by lree depletion and nd values of 2 6 whereas the andesite is lree enriched and has nd values of 0 3 the 2786 ma mafic ultramafic sequence is interpreted as a sliver of plume related oceanic plateau crust the 2724 lac lintelle sequence represents a continental arc formed on the eastern protocraton the 2722 ma lac serindac volcanic sequence represents late continental rift deposits the various 2 8 2 7 ga supracrustal sequences were accreted deformed and metamorphosed to mid amphibolite facies during late stage assembly of the minto block between 2 718 and 2 693 ga

geochemical precursors of the activity of an open conduit volcano the stromboli 2002 2003 eruptive events 1 marked increases of co2 h2 and he dissolved in thermal waters and changes in the dissolved carbon isotopic composition were observed at stromboli before the 28 december 2002 eruption and before a violent explosive paroxysm occurred on 5 april 2003 high anomalous co2 flux values were recorded at the crater rim since a week before the eruption onset the first anomalies in the thermal waters dissolved co2 amount appeared some months before the eruption when magma column rose at a very high level in the conduit high peaks of dissolved h2 and he were recorded a few days before the paroxysm carbon isotopic composition indicates a magmatic origin of the dissolved co2 whose increase together with those of h2 and he is attributed to an increasing output of deep gases likely produced by depressurization of a rising batch of a deep gas rich magma whose fragments have been emitted during the explosion

the contribution of fluid geochemistry to the volcano monitoring of stromboli abstract the persistent open vent mild explosive activity of stromboli volcano is episodically interrupted by more violent and dangerous explosive events major explosions and paroxysms according to the nature of erupted products paroxysms can be related either to the explosion of overpressured gas pockets located in the proximity of the magma column or to the sudden uprise of hot gas rich magma from a deep part of the plumbing system in both cases these more energetic explosive events should be preceded by an escape or a preferential uprise of the highly mobile volatiles which in turn should produce gas leakage anomalies at the surface in sites of high vertical permeability such as deep reaching faults in order to identify such gas leaking sites a systematic co2 soil flux survey has been carried out on the island using an accumulation chamber four hundred sixty one points have been measured with a high density in the summit crater area where high flux values have been found 10 3 10 2 cm s anomalous points are concentrated along the main ne sw axial feeding system of the volcano co2 soil flux decreases from the crater zone to the base of the volcanic cone where however an interesting gas leakage anomaly occurs pizzillo mofette in the pizzillo area thermal water wells also occur whose chemistry indicates an origin by sea water heated by hot gas soil gases have been sampled in the sites with the highest co2 flux in the crater area and at the base of the cone chemical and isotopic analyses indicate the presence of a deep gas component especially in the crater zone samples high co2 appreciable contents of he and h2 3he 4he values up to 3 55 13c of co2 2 the sc5 low flux fumarole on the crater rim has shown during six years a remarkable persistence of temperature 93 95 c with only minor fluctuations of chemistry appearance of anomalous peaks of h2 in correspondence with strombolian explosions was observed during a 2 h 30 min experiment of continuous recording of hydrogen content of the fumarole together with previous data on h2o co2 and he this experiment confirms that strombolian blasts produce rapid fluctuations in the fumarolic gas composition in the light of this study sc5 fumarole and pizzillo mofette look promising sites for the testing of a continuous geochemical monitoring system of stromboli volcano

time variability of low temperature fumaroles at stromboli island italy and its application to volcano monitoring the constant and mild activity of stromboli volcano italy is occasionally interrupted by effusive events and or more energetic explosions referred to as major explosions and paroxysms which are potentially dangerous for the human community although several premonitory signals for effusive phases have been identified precursors of major explosions and paroxysms still remain poorly understood with the aim of contributing to the identification of possible precursors of energetic events this work discusses soil temperature data acquired in low temperature fumaroles at stromboli in the period 2006 2010 data analysis revealed that short term anomalies recorded in the thermal signal are potentially useful in predicting state changes of the volcano in particular sudden changes in fumarole temperatures and their hourly gradients were observed from several days to a few hours prior to fracturing and paroxysmal events heralded by peculiar waveforms of the recorded signals the qualitative interpretation is supported by a quantitative theoretical treatment that uses circuit theory to explain the time dependence of the short period temperature variations showing a good agreement between theoretical and observational data

the role of the aquifer in soil co 2 degassing in volcanic peripheral areas a case study of stromboli island italy abstract the peripheral area of stromboli island italy named scari was continuously studied between january 2009 and december 2010 data on soil co 2 flux and the partial pressure of co 2 pco 2 in equilibrium with the thermal aquifer linked to the magmatic system are presented soil co 2 fluxes range from 20 to 370 g m 2 d 1 and have been strongly affected by soil temperature variations soil co 2 flux data were filtered with respect to the soil temperature and the calculated values called residuals were considered to detect changes induced by the magmatic system the pco 2 values change in a wide range from 0 03 to 0 6 atm showing rapid variations the results of this study show that in the volcanic peripheral area the degassing process of soil co 2 is determined not only by the co 2 released directly from the magma but also by gas water interactions in the aquifer the aquifer is able to dissolve the high amount of co 2 discharged by the magmatic system moreover the residuals of co 2 flux diffused from the soil show a delay on the order of 1 month with respect to the pco 2 in equilibrium with the aquifer the soil co 2 flux is therefore not directly linked to the uprising of magmatic co 2 but instead depends on the co 2 discharged from the aquifer which buffers and modulates the volatile changes released by the magmatic system

geochemical evaluation of observed changes in volcanic activity during the 2007 eruption at stromboli italy abstract on february 27 2007 a new eruption started at stromboli that lasted until april 2 and included a paroxysmal explosion on march 15 geochemical monitoring carried out over several years revealed some appreciable variations that preceded both the eruption onset and the explosion the carbon dioxide co 2 flux from the soil at pizzo sopra la fossa markedly increased a few days before the eruption onset and continued during lava effusion to reach its maximum value at 90 000 g m 2 d 1 a few days before the paroxysm almost contemporarily the 13 c co 2 of the sc5 fumarole located in the summit area increased markedly peaking just before the explosion 13 c co 2 1 8 following the paroxysm helium he isotopes measured in the gases dissolved in the basal thermal aquifer sharply increased almost contemporarily the automatic station of co 2 flux recorded an anomalous degassing rate also temperatures and the vertical thermal gradient which had been measured since november 2006 in the soil at pizzo sopra la fossa showed appreciable variabilities that lasted until the end of the eruption the geochemical variations indicated the degassing of a new batch of volatile rich magma that preceded and probably fed the paroxysm the anomalous 3 he 4 he ratio suggested that the ascent of a second batch of volatile rich magma toward the surface was probably responsible of the resumption of the ordinary activity a comparison with the geochemical variations observed during the 2002 2003 eruption indicated that the 2007 eruption was less energetic

the effects of environmental parameters on diffuse degassing at stromboli volcano insights from joint monitoring of soil co2 flux and radon activity abstract soil co 2 flux and 222 rn activity measurements may positively contribute to the geochemical monitoring of active volcanoes the influence of several environmental parameters on the gas signals has been substantially demonstrated therefore the implementation of tools capable of removing or minimising the contribution of the atmospheric effects from the acquired time series is a challenge in volcano surveillance here we present 4 years long continuous monitoring from april 2007 to september 2011 of radon activity and soil co 2 flux collected on the ne flank of stromboli volcano both gases record higher emissions during fall winter up to 2700 bq m 3 for radon and 750 g m 2 day 1 for co 2 than during spring summer seasons short time variations on 222 rn activity are modulated by changes in soil humidity rainfall and changes in soil co 2 flux that may be ascribed to variations in wind speed and direction the spectral analyses reveal diurnal and semi diurnal cycles on both gases outlining that atmospheric variations are capable to modify the gas release rate from the soil the long term soil co 2 flux shows a slow decreasing trend not visible in 222 rn activity suggesting a possible difference in the source depth of the of the gases co 2 being deeper and likely related to degassing at depth of the magma batch involved in the february april 2007 effusive eruption to minimise the effect of the environmental parameters on the 222 rn concentrations and soil co 2 fluxes two different statistical treatments were applied the multiple linear regression mlr and the principal component regression pcr these approaches allow to quantify the weight of each environmental factor on the two gas species and show a strong influence of some parameters on the gas transfer processes through soils the residual values of radon and co 2 flux i e the values obtained after correction for the environmental influence were then compared with the eruptive episodes that occurred at stromboli during the analysed time span 2007 2011 but no clear correlations emerge between soil gas release and volcanic activity this is probably due to i the distal location of the monitoring stations with respect to the active craters and to ii the fact that during the investigated period no major eruptive phenomena paroxysmal explosion flank eruption occurred comparison of mlr and pcr methods in time series analysis indicates that mlr can be more easily applied to real time data processing in monitoring of open conduit active volcanoes like stromboli where the transition to an eruptive phase may occur in relatively short times

contemporary total dissolved gas pressure and soil temperature anomalies recorded at stromboli volcano italy 1 soil temperature and total dissolved gas pressure tdgp data were recorded by two continuous monitoring stations on the volcano of stromboli italy between march and october 2006 during this period several tdgp and soil temperature anomalies unrelated to external causes and characterized by a similar shape and occurrence time were recorded these anomalies were interpreted as transients due to changes in the degassing regime of the volcano which was in turn related to changes in the partition ratio of the volcanic fluids between the conduit and the soil in the same period stromboli experienced an anomalous phase of volcanic and tectonic activity the close correlation found between volcano tectonic activity and variations in anomalous monitored parameters suggests that their continuous monitoring may be a useful tool for the surveillance of volcanic activity on the island

sedimentology and clast fabric of subaerial debris flow facies in a glacially influenced alluvial fan abstract a large alluvial fan 2 km2 constructed between 11 000 and 7000 years b p at the mouth of cinquefoil creek in interior british columbia canada is identified as glacially influenced debris flow dominated the fan was rapidly constructed during and immediately after deglaciation when large volumes of glacial debris were resedimented downslope fans of this type are widespread in the glaciated portion of the north american cordillera diamict facies deposited as debris flows account for 48 of the fan volume sheetflodd gravels 37 and other facies 15 diamicts show three facies types crudely bedded facies containing rafts of soft sediment that are attributed to downslope collapse and mixing of heterogeneous glacial deposits these occur within the core of the fan massive and weakly graded inverse to normal diamict facies derived from the downslope flow of weathered volcanic bedrock occur within a well defined bed that can be traced across the entire fan the occurrence of weakly graded facies as lateral equivalents to massive facies within the same bed implies the partial development of turbulent high velocity streams within a viscous debris flow moving over a slope of 6 clast fabrics in these facies show weakly clustered a axes dipping up and downslope comparable to other debris flows and lahars the cinquefoil fan its internal structure and facies provides a good modern analogue for ancient diamictite sequences deposited in areas of active uplift rifting and glaciation

sedimentology of quartz pebble conglomerates and quartzites of the archean bababudan group dharwar craton south india evidence for early crustal stability the 3200 to 3000 ma bababudan group locally as thick as 1800 m consists of a variety of rocks indicating deposition on a stable platform u and au bearing pyritiferous quartz pebble conglomerate a few meters thick overlies a regolith at the basal unconformity with a gneissic basement the bulk of the column consists of mafic volcanics including subaerial flows lahars and sills ultramafic and felsic rocks iron formation and pelites are minor lithologies in most of the sequence but iron formation forms a major unit at the top of the group quartzite units intercalated with the volcanics are generally less than 40 m thick and make up 25 to 50 of the column they are mineralogically mature and texturally submature recrystallization generally obscures original textures but units that were originally clayey quartz arenites have survived total recrystallization rounded zircons dominate the nonopaque detrital heavy mineral suite verifying a history of extensive abrasion paleocurrent patterns bas