biostratigraphic significance of stromatolites in upward shallowing sequences of the early proterozoic duck creek dolomite western australia abstract the branching columnar stromatolite pilbaria perplexa walter 1972 and the microdigitate asperia ashburtonia grey 1985 occur together in upward shallowing sedimentary sequences in the 2 ga duck creek dolomite the distribution of stromatolite taxa is controlled principally by sedimentary environment p perplexa grew in shallow lagoons with the larger p cf perplexa extending into the low intertidal zone a ashburtonia occupied a high intertidal or supratidal setting probably in laterally restricted pools throughout the world pilbariform and asperiform stromatolites occur in stratigraphic units of different ages within each group the taxa are not identical although morphologies are broadly similar the taxonomic variations may be due to evolutionary development rather than environmental factors

a heating process of kuchi erabu jima volcano japan as inferred from geomagnetic field variations and electrical structure since august 2000 we have recorded the total intensity of the geomagnetic field at the summit area of kuchi erabu jima volcano where phreatic eruptions have repeatedly occurred a time series analysis has shown that the variations in the geomagnetic field since 2001 have a strong relationship to an increase in volcanic activity these variations indicate thermal demagnetization of the subsurface around the presently active crater the demagnetization source for the early variations until summer 2002 was estimated at about 200 m below sea level for the variations since 2003 the source was modeled on the basis of the expansion of a uniformly magnetized ellipsoid the modeling result showed that the source is located at 300 m above sea level beneath the crater we carried out an audio frequency magnetotelluric survey with the aim of obtaining a relation between the demagnetization source and the shallow structure of the volcano a two dimensional inversion applied to the data detected two good conductors a shallow thin one which is restricted to a region around the summit area while the other extends over the edifice at depths between 200 and 800 m these conductors are regarded as clay rich layers with low permeability which were assumed to be generated through hydrothermal alteration the demagnetization source for the early variations was possibly located at the lower part of the deep conductor and the source after 2003 lies between the two conductors where groundwater is considered to be abundant based on these results as well as on seismological geodetic and geochemical information we propose a heating process of the kuchierabu jima volcano in the initial stage high temperature volcanic gases supplied from the deep seated magma remained temporarily at the level around the lower part of the less permeable deep conductor since the ascent path had not yet been established then when the pathway developed as a result of repeated earthquakes it became possible for a massive flux of volcanic gases to ascend through the conductor the high temperature gases reached the aquifer located above the conductor and the heat was efficiently transported to the surrounding rocks through the groundwater as a consequence an abrupt increase of the gas flux and di ffusion of the heat through the aquifer occurred and the high temperature zone expanded since the high temperature zone is located beneath another conductor which acts as caprock we assume that the energy of the phreatic explosion is accumulated there

preseismic hydrogen gas anomalies caused by stress corrosion process preceding earthquakes simultaneous monitoring of he h2 ar n2 ch4 and rn in gas bubbles of groundwater from the 1 500 m deep nagashima well in the active yoro fault zone central japan reveals that three microearthquakes with m 1 6 2 6 in the fault zone are accompanied and preceded by increases of h2 as is a moderately large event with m 5 4 in the same fault zone all the focal distances of the earthquakes are within 25 km no comparable anomalies were seen in the gas species other than h2 we suggest that the selective and preseimic increases of h2 in groundwater gas bubbles are geochemical signals of the earthquake nucleation process of stress corrosion mechanism aseismic slips preceding earthquakes in the active fault zone are likely to have enhanced h2 production by mechanochemical reaction of fractured rock surface with water in pre existing fault planes as groundwater conduits

itrf2014 a new release of the international terrestrial reference frame modeling nonlinear station motions for the first time in the international terrestrial reference frame itrf history the itrf2014 is generated with an enhanced modeling of nonlinear station motions including seasonal annual and semiannual signals of station positions and postseismic deformation for sites that were subject to major earthquakes using the full observation history of the four space geodetic techniques very long baseline interferometry vlbi satellite laser ranging slr global navigation satellite systems gnss and doppler orbitography and radiopositioning integrated by satellite doris the corresponding international services provided reprocessed time series weekly from slr and doris daily from gnss and 24 h session wise from vlbi of station positions and daily earth orientation parameters itrf2014 is demonstrated to be superior to past itrf releases as it precisely models the actual station trajectories leading to a more robust secular frame and site velocities the itrf2014 long term origin coincides with the earth system center of mass as sensed by slr observations collected on the two lageos satellites over the time span between 1993 0 and 2015 0 the estimated accuracy of the itrf2014 origin as reflected by the level of agreement with the itrf2008 both origins are defined by slr is at the level of less than 3 mm at epoch 2010 0 and less than 0 2 mm yr in time evolution the itrf2014 scale is defined by the arithmetic average of the implicit scales of slr and vlbi solutions as obtained by the stacking of their respective time series the resulting scale and scale rate differences between the two solutions are 1 37 0 10 ppb at epoch 2010 0 and 0 02 0 02 ppb yr while the postseismic deformation models were estimated using gnss gps data the resulting parametric models at earthquake colocation sites were applied to the station position time series of the three other techniques showing a very high level of consistency which enforces more the link between techniques within the itrf2014 frame the users should be aware that the postseismic deformation models are part of the itrf2014 products unlike the annual and semiannual signals which were estimated internally with the only purpose of enhancing the velocity field estimation of the secular frame

deflection of dykes into sills at discontinuities and magma chamber formation abstract many rift zones contain composite volcanoes central volcanoes most of which are supplied with magma from shallow crustal magma chambers volcanotectonic studies of eroded rift zones such as in iceland as well as geophysical studies indicate that many shallow magma chambers evolve from sills here i provide field description of sills and extinct magma chambers in the quaternary and tertiary palaeorift zones of iceland focusing on the felsic pluton of slaufrudalur southeast iceland as a fine example of a magma chamber developed through the injection of sills in this paper i review analyse and develop further two related mechanisms for the deflection of dykes into sills and thus the potential initiation of a magma chamber namely a cook gordon debounding delamination and b stress barriers and propose a third mechanism c favourable material toughness ratios due to elastic mismatch difference in young s moduli or stiffnesses of layers in contact in the cook gordon mechanism a weak contact opens up as a result of dyke induced tensile stress this mechanism is likely to operate primarily at shallow depths as is supported by field observations and numerical models a stress barrier is a layer where the local stress is unfavourable to a particular type of rock fracture here a dyke field observations and numerical models show that on meeting a stress barrier a dyke either changes into a sill or becomes arrested the material toughness mechanism indicates that when the upper layer at a contact has the same or less stiffness than the lower layer hosting the dyke there is little tendency for the dyke to become deflected into the contact however when the upper layer is stiffer such as when a stiff basaltic lava flow is on the top of a soft pyroclastic layer the dyke tends to become deflected into the contact to form a sill field results suggest that all these mechanisms may cause dyke deflection into sills and may operate together particularly where the rock consists of alternating soft and stiff layers since the quaternary lava pile in iceland has many more soft hyaloclastite layers than the tertiary lava pile these mechanisms were probably very efficient in generating sills and by implication shallow magma chambers during the quaternary this may be one reason why in comparison with the tertiary lava pile the quaternary lava pile contains so many sills and extinct plutons and active shallow magma chambers

unrest signals after 46 years of quiescence at cumbre vieja la palma canary islands abstract monogenetic eruptions are the most common volcanic activity in the world however unrest monitoring data are scarce due to the long intervening quiescence periods this study analyzes unrest signals recorded in one of the largest monogenetic fields in the canary islands cumbre vieja la palma two seismic swarms were registered in october 2017 and february 2018 with b values of 1 6 0 1 and 2 3 0 2 respectively suggesting an intense magmatic fluids contribution gas and or magma both swarms were linked to changes in gas emissions increases in hydrogen concentration and r ra c up to 7 52 0 05 were recorded before the first swarm at the sampling point closest to where seismicity was located indicating a deep gas input after the second swarm increases in r ra c and thoron soil concentration were recorded at two locations this dataset is compatible with a stalled magmatic intrusion at ca 25 km depth with an estimated volume between 5 5 10 4 km3 and 3 10 2 km3

the microfossils from the proterozoic urquhart shale mount isa queensland and their significance in relation to the depositional environment diagenesis and mineralisation the urquhart shale from mount isa queensland hosts major lead zinc and copper orebodies re examination of organic matter from the lead zinc ore bodies has shown that abundant microfossils characteristic of lacustrine environments are present and substantiates earlier results of love and zimmerman 1961 the framboid residues described by these authors are not microfossils but nevertheless the occurrence of framboidal pyrite has important implications for the timing of lead zinc mineralisation a diagenetic model is proposed for the lead zinc ore bodies and a later transgressive event accounts for the mode of occurrence of the copper ore bodies

years to weeks of seismic unrest and magmatic intrusions precede monogenetic eruptions seismic deformation and gas activity unrest typically precedes volcanic eruptions tracking the changes of this activity with monitoring data makes it increasingly possible to successfully forecast eruptions from stratovolcanoes however this is not the case for monogenetic volcanoes eruptions from these volcanoes tend to be small but are particularly difficult to anticipate since they occur at unexpected locations and there is very limited instrumental monitoring data many monogenetic volcanic fields occur in high density populated areas and or tourist destinations and thus even a small eruption can have a major economic and societal impact we have gathered the available instrumental data for unrest and combined it with new historical accounts of seismicity our occurrences are mainly from high magmatic flux oceanic islands canary islands iceland papua new guinea mexico and japan we find that seismic activity may start one or two years before eruption but it intensifies at approximately two or three months and one or two weeks the petrological and geochemical characteristics of the deposits show that multiple magma batches interacted in a subvolcanic reservoir and multiple intrusions occurred on a similar time scales to the seismicity we propose a general model for these eruptions where early dike intrusions in the crust do not erupt e g stalled intrusions and make small plumbing systems but they probably are key in creating a thermal and rheological pathway for later dikes to be able to reach the surface these observations provide a conceptual framework for better anticipating monogenetic eruptions in similar settings and magmatic fluxes and should lead to improved strategies for mitigation of their associated hazards and risks

depositional ages of the stratiform base metal deposits at mount isa and mcarthur river australia based on u pb zircon dating of concordant tuff horizons potassium rich tuff beds occur interbedded with major stratiform pb zn mineralization in shales and dolomitic shales of the mount isa group northwest queensland and the mcarthur group northern territory these deposits are some 600 km apart yet they exhibit many similarities which together with regional correlations suggest that the deposits formed by similar processes and that the successions developed more or less contemporaneously zircon is sparsely distributed as tiny crystal fragments or phenocrysts in the tuffs and its morphology and u pb systematics affirm that it is primarily of igneous origin u pb zircon data from a tuff in the mineralized h y c pyritic shale member of the mcarthur group give an age of the tuff of 1 690 super 29 sub 25 m y and from a tuff in the mineralized urquhart shale of the mount isa group an age of 1 670 super 20 sub 17 m y these results are consistent with all other geologic controls and are regarded as the best estimates of the depositional ages of the groups the ages of the mount isa and mcarthur groups are thus the same to within the present experimental uncertainties essentially confirming geologic synchrony of these important sedimentary successions pooled whole rock data from several of the mount isa tuff marker beds give an updated rb sr age of about 1 480 m y interpreted as indicating that isotopic exchange and regional metamorphism had essentially ceased by this time

changing depths of magma fractionation and stagnation during the evolution of an oceanic island volcano la palma canary islands la palma canary islands represents an oceanic island volcano with an active rift zone inferred to have formed during the last 800 ka following southward growth of the former radial symmetrical stratovolcano taburiente we carried out clinopyroxene melt thermobarometry and microthermometry of fluid inclusions to reconstruct the evolution of the magma plumbing systems over time and to understand the genetic relationship between taburiente and the presently active cumbre vieja rift zone clinopyroxene melt equilibria of phenocryst rims and glassy groundmass indicate pressures of 0 60 1 04 gpa 19 34 km depth for taburiente 0 47 1 17 gpa 16 40 km for the former cumbre nueva rift arm of taburiente and 0 50 0 78 gpa 16 26 km for bejenado volcano that formed after collapse of the cumbre nueva rift these pressures are interpreted to reflect depths of magma storage and major crystal fractionation co2 dominated fluid inclusions hosted by clinopyroxenes and olivines indicate pressures of formation or re equilibration within an overall range of 0 25 0 61 gpa 8 19 km depth respective frequency maxima are at 0 41 0 50 gpa for taburiente dunite xenoliths 0 26 0 43 gpa for cumbre nueva ankaramites and 0 26 0 32 gpa for bejenado cumulate xenoliths these pressures are interpreted to reflect levels of temporary magma stagnation during ascent our data show that the magma pathways during all volcanic phases including the presently active cumbre vieja rift klugel a hansteen t h galipp k 2005 magma storage and underplating beneath cumbre vieja volcano la palma canary islands earth and planetary science letters 236 211 226 are characterized by two distinct storage levels a system of prolonged storage within the upper mantle and a system of short term stagnation within the lower crust or near to the moho both the mantle and crustal storage systems show a migration to shallower levels from 1 0 ma to present probably as a result of changing thermomechanical properties of the mantle and crust and possibly stoping our combined barometric data and field observations suggest that the extinct taburiente cumbre nueva and the active cumbre vieja represent two distinct volcanoes with separate magma plumbing systems in this case the present rift configuration does not reflect continuous growth of the taburiente shield volcano during the last 800 ka none of the la palma volcanoes shows any indicators of a long lived shallow magma reservoir where magmas fractionate and from which rift zones emanate which is an important difference to hawaiian shield volcanoes characterized by shallow subcaldera magma chambers

hotspot volcanism close to a passive continental margin the canary islands the canarian archipelago is a group of volcanic islands on a slow moving oceanic plate close to a continental margin the origins of the archipelago are controversial a hotspot or mantle plume a zone of lithospheric deformation a region of compressional block faulting or a rupture propagating westwards from the active atlas mountains fold belt have been proposed by different authors however comparison of the canarian archipelago with the prototypical hotspot related island group the hawaiian archipelago reveals that the differences between the two are not as great as had previously been supposed on the basis of older data quaternary igneous activity in the canaries is concentrated at the western end of the archipelago close to the present day location of the inferred hotspot this is the same relationship as seen in the hawaiian and cape verde islands the latter archipelago associated with a well defined but slow moving mantle plume shows anomalies in a plot of island age against distance which are comparable to those seen in the canary islands these anomalies cannot therefore be used to argue against a hotspot origin for the canaries individual islands in both archipelagoes are characterized by initial rapid growth the shield building stages of activity followed by a period of quiescence and deep erosion erosion gap which in turn is followed by a post erosional stage of activity the absence of post shield stage subsidence in the canaries is in marked contrast with the major subsidence experienced by the hawaiian islands but is comparable with the lack of subsidence evident in other island groups at slow moving hotspots such as the cape verdes comparison of the structure and structural evolution of the canary islands with other oceanic islands such as hawaii and reunion reveals many similarities these include the development of triple mercedes star rift zones and the occurrence of giant lateral collapses on the flanks of these rift zones the apparent absence of these features in the post erosional islands may in part be a result of their greater age and deeper erosion which has removed much of the evidence for their early volcanic architecture we conclude that the many similarities between the canary islands and island groups whose hotspot origins are undisputed show that the canaries have been produced in the same way

forecasting etna eruptions by real time observation of volcanic gas composition it is generally accepted but not experimentally proven that a quantitative prediction of volcanic eruptions is possible from the evaluation of volcanic gas data by discussing the results of two years of real time observation of h2o co2 and so2 in volcanic gases from mount etna volcano we unambiguously demonstrate that increasing co2 so2 ratios can allow detection of the pre eruptive degassing of rising magmas quantitative modeling by the use of a saturation model allows us to relate the pre eruptive increases of the co2 so2 ratio to the refilling of etna s shallow conduits with co2 rich deep reservoir magmas leading to pressurization and triggering of eruption the advent of real time observations of h2o co2 and so2 combined with well constrained models of degassing represents a step forward in eruption forecasting

comment on the paper a test of the reliability of the rbsr dates for selected glauconite morphologies of the upper cretaceous navesink formation of new jersey by r l montag and d e seidemann the reliability of rb sr data on glauconite is a question which has not been very much investigated and every contribution to this subject will certainly be appreciated by all geochronologists interested in dating sediments however we have the strong feeling that by drawing a conclusion which seems very unlikely montag and seidemann 1 have not helped much in clarifying a situation which is already obscure enough due to lack of data the assumption which we consider improbable is the following that rb sr model age of glauconite could be drastically affected by preferential rb loss upon weathering we find the arguments presented unconvincing and think that other possibilities must be taken into account such as reworking a possibility considered by montag and seidemann themselves or the immatur i ty of glauconite a possibility not considered by them or the presence of non glauconitic detrital material in the samples analysed a possibility also not considered by them in our opinion alteration by weathering tends to cause a lowering of rb sr ages by preferential removal of a7sr d three points tend to support this contention 1 unpublished data obtained by one of us p p on glauconites from new jersey show a systematic tendency for weathered glauconite to yield rb sr ages which are too low while no case of the opposite was observed in cases of pervasive weathering as illustrated by the navesink formation the k ar ages may also be lowered 2 aside from these unpublished data unknown to the authors of the paper under discussion a lowering of rb sr ages also appears probable simply on the basis of the evident lowering of the k ar ages for the navesink formation indeed the conclusion of montag and seidemann according to which a 60 2 41 5 ma value corresponds to the true age of this late upper campanian lower maestrichtian formation see discussion in owens and sohl 2 is at variance with data given in references 3 4 5 6 7 8 9 and 10 in addition the well defined isochron as it is called by montag and seidemann in fig 1 of their paper and which corresponds to an age of 60 2 1 5 ma is defined by dark green lobate glauconites yielding almost exactly the same rb content 231 34 237 58 ppm this line is most probably a dark green lobate glauconitecarbonate mixing line and is the graphical representation of conventional apparent ages calculated with an initial sr isotope ratio of 0 7076 0 0009 of course it is by no means evident that if arra d is lost srra d should also be lost by the same agency although a priori this would also appear possible but that the agency i e chemical weathering should cause preferential ar versus k loss and rb versus sr loss is not at all probable why should rubidium behave like radiogenic argon and radiogenic strontium like potassium 2 it has been demonstrated in other cases that weathering causes a lowering of rb sr ages of

rbsb age determinations on precambrian carbonate rocks of the carpentarian mcarthur basin northern territories australia abstract the applicability and the uncertainty range of rb sr age determinations on carbonate rocks are discussed briefly a study of clay minerals isolated from carbonate rocks of the mcminn formation provides an isochron age of 1429 31 ma and thus the age for cessation of the proterozoic mcarthur basin sedimentation the eukaryots recently described in this area are therefore the oldest occurrences found in earth history a second sequence of measurements on a homogeneous dolomite siltstone ca 23 km southeast of the mcarthur river h y c pb zn deposits yields an rb sr age of 1537 52 ma for the upper barney creek formation in broad agreement with recent age determinations on feldspar beds of this horizon these data are compared with previous isotopic results from data presently available it can be concluded that the sediments in the mcarthur basin the type locality of the carpentarian were deposited between 1800 1400 ma

radon surveys and real time monitoring at stromboli volcano influence of soil temperature atmospheric pressure and tidal forces on 222rn degassing abstract we used a network of stations to perform systematic radon surveys at stromboli volcano the time series of periodic measurements show that monthly average 222rn emissions reflect changes in volcanic activity and exhibit increasing trends prior and during the last major eruptive cycles maps of radon emissions indicate that diffuse degassing is operative at stromboli volcano concentrated degassing essentially occurs in the summit area and within a sector proximal to the two major ne trending faults these sites were chosen for deploying the two real time stations that are currently operating at stromboli in these devices the 222rn electronic dosimeters are connected to a radiomodem for wireless data transfer to a receiving station at the volcano observatory radon activity soil temperature and atmospheric pressure data are sampled and instantaneously transferred via web so that they can be checked remotely collected time series reveal an overall inverse correlation between radon emissions and seasonal temperature variations radon emissions in sectors of diffuse degassing are modulated by tidal forces as well radon activities recorded at the summit station located along the fracture zone where the gas flux is concentrated are positively correlated with changes in atmospheric pressure and confirm the occurrence of the atmospheric stack effect we finally emphasize that real time radon monitoring is an innovative technique that may be systematically applied in volcano surveillance

timing of superposed volcanism in the proterozoic mount isa inlier australia metamorphosed proterozoic successions in the mount isa inlier contain a variety of volcanic suites interspersed at several intervals throughout the 30 km thick stratigraphic pile the u pb isotopic systematics of zircons crystallised in superposed felsic volcanic units allow detailed definition of the chronology of this volcanism and therefore of the major depositional cycles this supracrustal development spanned a 270 ma interval in the early to mid proterozoic new u pb zircon data from the earliest recognised volcanic cycle leichhardt metamorphics yield a pooled age for this event at 1867 5 ma a far northern segment of the same basement succession contains a geochemically similar felsic sequence 1852 7 ma old these results confirm the coevality between this felsic volcanism and nearby intrusive bodies of the same age the second major cycle of volcanism is 60 80 ma younger than the first this interval representing the maximum duration of the intervening regional unconformity dacitic and mafic volcanic rocks bottletree formation which unconformably overlie the western flank of the 1870 ma basement are dated in two areas at 1790 810 and 1808 1722 rhyodacites argylla formation on the eastern side of the basement have a similar age 1783 5 ma so for purposes of correlation and crustal evolution these two sequences flanking either side of the basement can be considered to comprise a single volcanic cycle subsequent cycles of felsic volcanism are recognised in stratigraphically younger sequences which include rhyolites with well resolved u pb zircon discordance patterns indicating ages of 1720 7 ma doherty formation and 1678 3 ma carters bore rhyolite the youngest volcanic cycle 1603 6 ma is evidenced by rhyolitic lavas in a part of the sequence previously considered to be much older at least 1740 ma recognition of such a young volcanic episode has an important economic bearing for it implies that rocks equivalent in age to the prospective pb zn rich mount isa group in the west ca 1670 ma could well exist in the eastern succession of the inlier

scaling laws of the size distribution of monogenetic volcanoes within the michoacan guanajuato volcanic field mexico abstract the michoacan guanajuato volcanic field displays about 1040 monogenetic volcanoes mainly composed of basaltic cinder cones this monogenetic volcanic field is the consequence of a dextral transtensive tectonic regime within the transmexican volcanic belt tmvb the largest intra continental volcanic arc around the world related to the subduction of the rivera and cocos plates underneath the north american plate we performed a statistical analysis for the size distribution of the basal diameter wco for cinder cones dataset used here was compiled by hasenaka and carmichael 1985 monogenetic volcanoes obey a power law very similar to the gutenberg richter law for earthquakes with respect to their size distribution log 10 n wco log 10 wco with 5 01 and 2 98 therefore the monogenetic volcanoes exhibit a wco size distribution empirical power law suggesting a self organized criticality phenomenon

dynamics of diffuse carbon dioxide emissions from cumbre vieja volcano la palma canary islands we report herein the results of 13 soil co2 efflux surveys at cumbre vieja volcano la palma island the most active basaltic volcano in the canary islands the co2 efflux measurements were undertaken using the accumulation chamber method between 2001 and 2013 to constrain the total co2 output from the studied area and to evaluate occasional co2 efflux surveys as a volcanic surveillance tool for cumbre vieja soil co2 efflux values ranged from non detectable up to 2442 g m 2 days 1 with the highest values observed in the south where the last volcanic eruption took place teneguia 1971 isotopic analyses of soil gas carbon dioxide suggest an organic origin as the main contribution to the co2 efflux with a very small magmatic gas component observed at the southern part of the volcano total biogenic and magmatic combined co2 emission rates showed a high temporal variability ranging between 320 and 1544 t days 1 and averaging 1147 t days 1 over the 220 km2 region two significant increases in the co2 emission observed in 2011 and 2013 were likely caused by an enhanced magmatic endogenous contribution revealed by significant changes in the 3he 4he ratio in a co2 rich cold spring the relatively stable emission rate presented in this work defines the background co2 emission range for cumbre vieja during a volcanic quiescence period

the history of the origin evolution and dispersal of the late pleistocene mammuthus coelodonta faunal complex in eurasia large mammals

failed eruptions revealed by pattern classification analysis of gas emission and volcanic tremor data at mt etna italy during the spring of 2007 paroxysmal activity occurred at the southeast crater of mt etna always associated with sharp rises in the amplitude of the volcanic tremor activity ranged from strong strombolian explosions to lava fountains coupled with copious emission of lava flows and tephra during inter eruptive periods recurrent seismic unrest episodes were observed in the form of temporary enhancements of the volcanic tremor amplitude but they did not culminate in eruptive activity here we present the results of an analysis of these inter eruptive periods by integrating seismic volcanic tremor in soil radon plume so2 flux and thermal data so2 flux and thermal radiation are envisaged as the smoking gun and certifying that changes in seismic or radon data can be considered as volcanogenic short term changes were investigated by pattern classification based on kohonen maps and fuzzy clustering on volcanic tremor radon and ambient parameters pressure and temperature our results unveil failed eruptions between february and april 2007 that are explained as ascending magma batches which triggered repeated episodes of gas pulses and rock fracturing but that failed to reach the surface

the k ar and 40ar 39ar methods revisited for dating fine grained k bearing clay minerals abstract the strengths and weaknesses of the two ar isotopic methods k ar and 40ar 39ar were evaluated on the basis of respective recent applications mainly on low temperature k bearing illite type clay minerals this review includes a presentation of basic analytical and technical aspects for both methods as well as a discussion of varied claims on the two methods and of requests about sample preparation and characterization whenever possible the advantages and weaknesses of each method were compared on coeval results obtained by both methods on the same mineral separates the comparative review examines stratigraphic dating of glauconites indirect dating of low temperature ore deposits dating of burial related illitization and dating of polyphased tectono thermal activity more specifically of fault gouges some pending questions such as the necessary encapsulation due to 39ar recoil and its restoration into step heating patterns are also raised together with the new potential of ar dating of nanometric illite crystals weakness of the k ar method is in its pioneering status that makes many believe that it is no longer accurate because of its traditional analytical aspects and of the k determinations leading to somewhat large uncertainties however precise evaluation of varied applications points to a k ar method having probably larger applicability in sedimentary to diagenetic environments than the 40ar 39ar method the drawbacks become less important if the method is applied to nanometer sized clay minerals in diagenetic to low grade metamorphic environments in this instance the extracted size fractions are generally homogeneous and the relative uncertainty given by the age calculations if mathematically justified can be reduced by duplicate analyses weakness of the 40ar 39ar method is in its basics such as the 39ar recoil the necessary encapsulation the reintegration of the 39ar into the step heating patterns and the meaning of the step heating patterns that are more suggestive of variable 39ar reservoirs created among the clay particles by irradiation than of meaningful geologic ages if the k ar method is the preferred method for dating diagenetic clay processes such as glauconitization illite crystal nucleation and growth or low temperature hydrothermal activities then the 40ar 39ar method has more potential in dating low temperature tectono thermal activities and in detailing mixtures of multi generation illite

contrasting radon background levels in volcanic settings clues from 220rn activity concentrations measured during long term deformation experiments to better understand the mechanisms leading to different radon background levels in volcanic settings we have performed two long term deformation experiments of 16 days using a real time setup that enables us to monitor any variation of radon activity concentration during rock compression our measurements demonstrate that in the case of highly porous volcanic rocks the emanating power of the substrate changes as a function of the volcanic stress conditions constant magmatic pressures such as those observed during dike intrusions and hydrothermal fluid injections can result in pervasive pore collapse that is mirrored by a significant radon decrease until a constant emanation is achieved conversely repeated cycles of stress due to for example volcano inflation deflation cycles cause a progressive radon increase a few days but even weeks and months before rupture after rock failure however the formation of new emanation surfaces leads to a substantial increase of the radon signal our results suggest that surface deformation in tectonic and volcanic settings such as inflation deflation or constant magmatic pressures have important repercussions on the emanating power of volcanic substrates

age and origin of albian glauconites and associated clay minerals inferred from a detailed geochemical analysis abstract glauconitic grains are abundant in sandstones and siltstones from albian and cenomanian transition between lower and upper cretaceous formations of southeastern france morphological and crystal chemical data show that the green grains can be considered as glauconite s s with minute amounts of pyrite dolomite calcite and other clay minerals as grain coatings or crack fillings glauconite grains formed early during sedimentation generally from detrital chlorite biotite or clay particles and were found scattered together with other detrital mineral phases muscovite quartz in the silt in which porosity was considerably reduced afterwards by four stages of carbonate calcite dolomite cementation geochemical data especially the fe u and ce contents of the glauconitic grains strongly suggest increasing oxidizing conditions with time in the sedimentation environment the detailed geochemical analyses also allow the pristine glauconite grains to be distinguished from the other clay minerals occurring in the sequence this enabled k ar and rb sr dating of the glauconitic material which yields identical results of 97 9 0 4 and 97 9 3 5 ma respectively these dates point to a synsedimentary origin for the glauconites during the late albian about 97 98 ma the k ar data also indicate that the albian cenomanian boundary should be placed at 96 0 1 9 ma the similarity between the k ar and rb sr ages precludes any further significant pervasive recrystallization of these minerals during burial of the sequence either by heat flux or fluid flow the k ar study of the clay matrix from the same siltstones suggests synsedimentary precipitation of additional clay minerals probably together with the glauconite grains such as mixed layer illite smectite identified in the clay size fraction of the sedimentary succession

deep intrusions lateral magma transport and related uplift at ocean island volcanoes abstract oceanic intraplate volcanoes grow by accumulation of erupted material as well as by coeval or discrete magmatic intrusions dykes and other intrusive bodies within volcanic edifices are comparatively well studied but intrusive processes deep beneath the volcanoes remain elusive although there is geological evidence for deep magmatic intrusions contributing to volcano growth through uplift this has rarely been demonstrated by real time monitoring here we use geophysical and petrological data from el hierro canary islands to show that intrusions from the mantle and subhorizontal transport of magma within the oceanic crust result in rapid endogenous island growth seismicity and ground deformation associated with a submarine eruption in 2011 2012 reveal deep subhorizontal intrusive sheets sills which have caused island scale uplift of tens of centimetres the pre eruptive intrusions migrated 15 20 km laterally within the lower oceanic crust opening pathways that were subsequently used by the erupted magmas to ascend from the mantle to the surface during six post eruptive episodes between 2012 and 2014 further sill intrusions into the lower crust and upper mantle have caused magma to migrate up to 20 km laterally resulting in magma accumulation exceeding that of the pre eruptive phase a comparison of geobarometric data for the 2011 2012 el hierro eruption with data for other atlantic intraplate volcanoes shows similar bimodal pressure distributions suggesting that eruptive phases are commonly accompanied by deep intrusions of sills and lateral magma transport these processes add significant material to the oceanic crust cause uplift and are thus fundamentally important for the growth and evolution of volcanic islands we suggest that the development of such a magma accumulation zone in the lower oceanic crust begins early during volcano evolution and is a consequence of increasing size and complexity of the mantle reservoir system and potentially the lithospheric stresses imposed by increasing edifice load

geochemical evidence for mixing between fluids exsolved at different depths in the magmatic system of mt etna italy abstract a 4 year geochemical survey of some fumaroles at the voragine summit crater of mt etna was performed in combination with synchronous monitoring of peripheral gas emissions at the base of the volcano this was the first geochemical study at mt etna to have included the abundances of ar he and c isotopes once the effects of postmagmatic shallow processes were identified and quantitatively removed the he ar co 2 systematics of the voragine crater fumaroles and peripheral gas emissions described the same degassing path combining the carbon isotope composition with information about noble gases provided evidence that the crater fumaroles are fed from a two endmember mixture composed of a deep member coming from pressures between 200 and 400 mpa depending on time and a shallower one exsolved at 130 mpa similar mixing processes probably also occur in gases from peripheral vents the simultaneous assessment of 13 c co2 and he ar values of crater fumaroles over time has identified simple changes in the mixing proportion between the two endmembers and moreover periods during which the exsolution pressure of the deep fluid increased these periods seem to be linked to pre eruptive phases of the volcano the identified open system degassing processes are indicative of efficient bubble melt decoupling at depth whereas the mixing process requires a convective transfer of the deeply exsolved fluids toward shallower levels of magma where further vapor is exsolved in agreement with the most recent geophysical and petrological data from mt etna these observations allow inferences about a deep portion of the plumbing system 5 to 12 km b s l comprising sill like reservoirs connected by small vertical structures and a main reservoir at 2 3 km b s l that is probably fluxed by magmatic volatiles

driving magma to the surface the 2011 2012 el hierro volcanic eruption we reanalyzed the seismic and deformation data corresponding to the pre eruptive unrest on el hierro canary islands in 2011 we considered new information about the internal structure of the island we updated the seismic catalogue to estimate the full evolution of the released seismic energy and demonstrate the importance of non located earthquakes using seismic data and gps displacements we characterized the shear tensile type of the predominant fracturing and modelled the strain and stress fields for different time periods this enabled us to identify a prolonged first phase characterized by hydraulic tensile fracturing which we interpret as being related to the emplacement of new magma below the volcanic edifice on el hierro this was followed by post injection unidirectional migration probably controlled by the stress field and the distribution of the structural discontinuities we identified the effects of energetic magmatic pulses occurring a few days before the eruption that induced shear seismicity on pre existing faults within the volcano and raised the coulomb stress over the whole crust we suggest that these magmatic pulses reflect the crossing of the moho discontinuity as well as changes in the path geometry of the dyke migration towards the surface the final phase involved magma ascent through a pre fractured crust

geographical distribution of 3he 4he ratios in japan implications for arc tectonics and incipient magmatism the 3he 4he and 4he 20ne ratios of 115 natural gas samples including various types of gases from volcanoes hot springs mineral springs water wells petroleum fields and natural gas fields were measured using a mass spectrometer the observed 3he 4he and 4he 20ne ratios range from 7 47 10 8 to 9 65 10 6 and from 0 26 to 1100 respectively the 3he 4he ratios reflect well the geotectonic structure of the japanese islands in northeastern ne japan there is a clear geographical difference in the 3he 4he ratios between the frontal arc forearc and volcanic arc back arc regions lower ratios were found in the trench side region and higher ratios in the back arc side this result suggests that the mantle derived helium in the volcanic arc region is associated with the diapiric uprise of a magma lower 3he 4he ratios in the frontal arc region may be due to radiogenic he produced by radioactive decay of u and th in the crustal and sedimentary rocks in southwestern sw japan there is no clear geographical contrast in the 3he 4he ratios some samples in the frontal arc region show quite high 3he 4he ratios the tendency of the 3he 4he ratios agrees with the distribution of terrestrial heat flow data and reflects geotectonic structures different from ne japan the high 3he 4he ratios observed in the frontal arc region in sw japan may be indicative of renewed or incipient magmatism due to a descending young and warm slab

helium emission at cumbre vieja volcano la palma canary islands abstract we report herein the results of three soil helium surveys undertaken at cumbre vieja volcano la palma island canary islands helium content analyses at the surface environment of the volcano were carried out in the summers of 2002 2003 and 2004 to estimate the diffusion contribution of helium emission soil porosity was estimated indirectly from the granulometry data measured on a previous soil survey carried out in 1997 helium enrichments in the soil layer with respect to the air concentration measured on cumbre vieja indicate a strong structural control in the degassing processes of the volcano and the excess helium seems to be emitted mainly along both n s and n w rifts of the volcano 4 he flux values calculated following a pure diffusive model ranged between non detectable values and 1 0 mg m 2 d 1 in 2002 2003 and 2004 surveys total 4 he emission rate at cumbre vieja was estimated in the range of 18 38 kg d 1 isotopic composition of helium measured in soil gases along the n s volcanic rift of cumbre vieja showed small contributions of morb type helium increasing towards the southern part of the volcano a 3 he 4 he ratio of 9 95 0 12 r a was measured at a cold spring geothermal sample showing a 7 2 contribution of plume type helium 3 he emission results in the range of 0 6 0 7 mol yr support the hypothesis of contemporary degassing at cumbre vieja coming from magmas stored at different depths under la palma island

rbsr and kar ages of paleozoic glauconites from ohio indiana and missouri u s a abstract glauconite pellets from the lower silurian brassfield formation on both limbs of the cincinnati arch in ohio and indiana give a rb sr age of 370 11 ma which is substantially younger than the stratigraphic age of the formation the age is concordantcwith conventional k ar ages of 355 6 and 368 5 ma for two of the same glauconites concordant ages were also obtained from the viburnum trend in missouri where glauconite pellets from the davis formation in an ore zone collapse structure into the underlying bonneterre formation give a rb sr age of 387 21 ma and conventional k ar ages of 368 5 and 369 5 and 369 5 ma a third suite of glauconite from the bonneterre formation in the old lead belt 10 km from the nearest ore body has given a rb sr age of 423 7 ma and slightly older conventional k ar ages of 434 6 445 6 and 441 11 ma because these glauconite bearing rocks have been buried to depths of less than 1 km thermal resetting of the rb sr and k ar systematics appears unlikely the initial 87 sr 86 sr ratios of the rb sr isochrons are similar to the ratios for vein and vug filling dolomite and calcite this is consistent with resetting of the rb sr and k ar systems during diagenetic changes which included the isotopic equilibration perhaps by cation exchange of the sr in the glauconite with that in the diagenetic and mississippi valley type ore fluids this interpretation implies that the age of the mississippi valley type mineralization in the viburnum trend is devonian rather than carboniferous permian as has been inferred from paleomagnetic measurements cation exchange experiments with a dilute sr bearing solution and an artificial oilfield brine indicate that glauconite adsorbs large amounts of sr some of which is sufficiently strongly attached to the glauconite lattice as to resist leaching with ammonium acetate the introduction of this strongly attached sr may be the first step in the resetting of the rb sr systematics of glauconite by cation exchange

insights into mantle type volatiles contribution from dissolved gases in artesian waters of the great artesian basin australia abstract the geochemical features of the volatiles dissolved in artesian thermal waters discharged over three basins millungera galilee and cooper basin of the australian great artesian basin gab consistently indicate the presence of fluids from multiple gas sources located in the crust e g sediments oil reservoirs granites as well as minor but detectable contributions of mantle magma derived fluids the gases extracted from 19 water samples and analyzed for their chemical and isotopic composition exhibit amounts of co2 up to about 340 mlstp lh2o marked by a 13ctdc total dissolved carbon ranging from 16 9 to 0 18 vs pdb while ch4 concentrations vary from 4 4 10 5 to 4 9 mlstp lh2o helium contents were between 9 and 2800 times higher than equilibrium with air saturated water asw with a maximum value of 0 12 mlstp lh2o helium isotopic composition was in the 0 02 0 21 ra range ra air normalized 3he 4he ratio the three investigated basins differ from each other in terms of both chemical composition and isotopic signatures of the dissolved gases whose origin is attributed to both mantle and crustal volatiles mantle he is present in the west central and hottest part of the gab despite no evidence of recent volcanism we found that the partial pressure of helium significantly higher in crustal fluids than in mantle type volatiles enhances the crustal he signature in the dissolved gases thus masking the original mantle contribution neotectonic activity involving deep lithospheric structures and magma intrusions highlighted by recent geophysical investigations is considered to be the drivers of mantle magmatic volatiles towards the surface the results although pertaining to artesian waters from a vast area of 542 000 km2 provide new constraints on volatile injection and show that fluids geochemistry can provide additional and independent information on the geo tectonic settings of the great artesian basin and its geothermal potential

constructive and destructive episodes in the building of a young oceanic island la palma canary islands and genesis of the caldera de taburiente the results of new field observations 23 new k ar determinations and sixteen previously published determinations provide the basis for the reconstruction of the subaerial volcanic history of the island of la palma after the seamount activity represented by the materials of the basal complex an eruptive phase between 2 0 and 1 3 ma formed a large shield a period of volcanic quiescence followed until around 1 ma during which a large lateral collapse partly destroyed the former edifice between 1 05 and 0 7 ma activity was renewed in the shield and a n s ridge was built in the southern part of the island around 0 7 ma two new large lateral collapses affected the western part of both edifices and they were followed by eruptions between 0 71 and 0 65 ma which built a new edifice that partly filled the depressions thus created the caldera de taburiente constitutes the eroded remnants of the depression formed in the northern shield from 0 65 ma to present activity has been restricted to the n s ridge which has continued to grow southwards there was a general n s migration of volcanic activity with time but in the shield the trend was northwest to southeast eruptive rates seem to have been fairly constant during the different eruptive phases considered between 0 15 and 0 37 km3 ka a very similar succession of constructive and destructive episodes has been obtained for the neighboring island of hierro but in this case the activity started around 0 8 ma and eruptive rates were about 0 5 km3 ka

palaeomagnetism of australian hematite ore bodies i the middleback ranges of south australia summary the results of a palaeomagnetic study on high grade hematite ore bodies of south australia are reported the two major ore bodies iron monarch and iron prince gave consistent directions of magnetization with either steep to moderate negative and positive inclinations the positive and negative groups of iron monarch are not antiparallel because of the presumably long time interval represented by the sampling this is interpreted as being due to polar wandering with a superimposed reversal of the earth s field the remanent magnetization is carried by hematite and is extremely stable against alternating field and thermal demagnetization the intensity of the nrm is very weak compared to the trm which suggests it to be a crm in origin lack of a detailed polar wandering curve for the pre cambrian of australia prevents precise palaeomagnetic dating of the ores but the results clearly suggest a pre cambrian age the magnetic anisotropy of the ores is low and the distribution of the principal susceptibility axes reflects in part the structure of the host rock the iron duke orebody did not yield a reliable palaeomagnetic result

rb sr and k ar dating of precambrian clays and glauconies abstract isotopic dating of sedimentary material requires a different approach from the isotopic dating of plutonic volcanic and high grade metamorphic rocks the present contribution presents mineralogical criteria such as clay composition illite or glauconite crystallinity indices illite or glauconite polymorphic types sedimentological criteria such as mechanisms of genesis as well as chemical criteria such as the sr composition and content of the carbonates associated with the studied clays and glauconies these criteria help in the interpretation of the numerical results and should always be considered in attempts to obtain radiometric ages of sedimentary clays and or glauconies it is emphasized that a difference between measured and expected age seldom means that the chronometer used is inaccurate but it commonly means that a parameter was not recognized or even disregarded a critical review of the uncertainties typically related to sedimentary dating is also proposed they may be grouped into four types 1 genetic uncertainties dependent on the genetic mechanisms of the studied minerals 2 historic uncertainties dependent on the alteration events imprinted in the sediments since deposition weathering diagenesis and or tectono metamorphism 3 stratigraphic uncertainties dependent on the precision of the sample location in the sedimentary sequence and 4 analytic uncertainties dependent on the representativeness and the preparation of the samples as well as the accuracy of the measurements a reliability test of the rb sr and k ar methods as applied to dispersed precambrian clays and glauconies is discussed from an extensively studied sequence from west africa it shows that the k ar system of these minerals is much more sensitive to later modifications than the rb sr system therefore the two techniques may be complementary in geochronological studies of precambrian sediments

k ca ages of authigenic sediments examples from paleozoic glauconite and applications to low temperature thermochronometry k ca ages of cambrian glauconites from the llano uplift central texas were determined in order to re evaluate the ability of the k ca system to constrain the timing of deposition of sedimentary packages all of the k ca ages presented here were found to be younger than their stratigraphic ages in addition to being too young the k ca ages are also highly variable ranging in age from silurian to permian the oldest subset of glauconite ages are in agreement with previously published rb sr ages from the same outcrop and provide further evidence for there having been a post depositional thermal or recrystallization event that reset both the rb sr and k ca systems the range of younger glauconite k ca ages is similar to the distribution of available apatite fission track ages for the llano basement k ca ages are interpreted as thermochronologic data reflecting partial retention of ca in thermally fluctuating basin conditions estimates of the closure temperature of ca in glauconite are found to be 60 90 c for cooling rates of 0 5 1 c my the k ca system is potentially useful as a low temperature thermochronometer with closure temperatures 100 c for glauconite

shallow flank deformation at cumbre vieja volcano canary islands implications on the stability of steep sided volcano flanks at oceanic islands abstract volcano flank instability has been recognized at many volcanoes around the globe structural morphological geodetic and geophysical evidence supports the continuous deformation of their flanks while identification of instability has been recognized in well documented examples until recently the initial stages of such processes have been difficult to capture using a combination of geological geodetic and geophysical data analysis we study the stability of the cumbre vieja new descending radar interferometric data covering a volcanologically quiet period between 1992 and 2008 at cumbre vieja indicate movement away from the satellite on the western volcano flank using an inversion of stacked velocity maps we determine the geometry and slip for a near horizontal dislocation beneath the western flank of cumbre vieja our ground deformation modelling results position and depth are in agreement with a low density anomaly constrained by gravity data the previously undetected intereruptive ground deformation at cumbre vieja volcano flanks was explained as an indicator of a kinematic passive response model of the flank where the flanks were mobilized only during periods of magmatic activity shallow dike intrusions and remained stable and undeformed during intereruptive periods here we present new results indicating that active creeping stress release due to gravitational loading is also a dominant deformation mechanism for current intereruptive periods at cumbre vieja which would contribute positively to the stabilization of the edifice and reduce the associated hazard related to the volcano flank dynamics this study at cumbre vieja can be considered as a prototype for similar volcanoes around the macaronesian islands group e g fogo teide el hierro pico and elsewhere

radon and thoron emission from lithophysae rich tuff under increasing deformation an experimental study 1 radon and thoron emissions from lithophysae rich tuff under increasing deformation are measured to determine how mechanical damage affects gas emission levels in tuffs mechanical properties of rocks under stresses should be carefully considered to properly interpret data from geochemical field monitoring two samples are uniaxially loaded up to failure while two others are unloaded at the end of the elastic phase in order to achieve the highest compaction of existing pores changes in the porosity of deformed samples are evidenced by helium pycnometer and microscopy analyses radon and thoron exhalation rates are measured on groups of two samples by alpha spectrometer technique results show that tuff samples are characterised by a dual porosity consisting of a macroporosity given by isolated large pores with sizes from mm up to cm scale and a microporosity ranging between microns to hundreds of microns at the end of the elastic phase pervasive pore collapse is observed due to the closure of the cm scale macropores this is mirrored by a significant decrease of radon and thoron release after failure a further reduction of porosity in the rock adjacent to the fault planes is observed due to extensive closure of both macropores and micropores at this stage radon and thoron emissions increase the formation of new exhaling surfaces is the main carrier of the bulk increase of radon and thoron exhalations strongly prevailing over the densification carried out from the compaction mechanisms in terms of volcanic hazard negative anomalies in radon emissions should be considered as indicators of forthcoming ruptures key words radon and thoron exhalation tuff deformation seismic precursor

palaeoenvironmental research at rexidora cave new evidence of cold and dry conditions in nw iberia during mis 3 abstract the rexidora cave asturias nw spain discovered in 2012 provided a remarkable large mammal assemblage of mis 3 age the ongoing excavation works yielded 445 fossil remains including cold adapted elements as woolly rhinoceros coelodonta antiquitatis and reindeer rangifer tarandus two species of special interest since they are poorly represented in the iberian pleistocene the woolly rhinoceros assemblage comprises numerous unusually well preserved elements as one mandible one femur and one partially preserved skull the steppe bison bison priscus is the dominant species in the assemblage providing an outstanding collection of well preserved elements that comprises two skulls and numerous limb bones carnivores are represented by a partial skeleton including a complete skull of spotted hyena crocuta crocuta radiocarbon ams analyses of the fossil assemblage yielded two dates of 44 5 and 37 6 cal ka bp corresponding to mis 3 a phase of climatic instability characterized by fast climate changes from extreme cold to temperate conditions these dates are coeval with the maximum registered expansion of the mammoth fauna in the iberian peninsula and with the onset of glacier retreat in the cantabrian mountain range after the last local glacial maximum geomorphological and sedimentological evidence suggests that bone accumulation took place as the result of gravity processes in a collapse doline filled by a chaotic accumulation of calcareous boulders pebbles and bone fragments embedded in a silt clay matrix which points to a possible natural trap origin of this fossil assemblage the exceptional well preservation of the fossils as well as the lack of any evidence of human or carnivore activity supports this idea palynological analyses suggest an open landscape under variable climatic conditions responsible for the fluctuating presence absence of the arboreal taxa the predominance of steppe and to a lesser extent xeric herbaceous plants indicate very dry conditions whereas presence of mesophilous forest taxa implies the existence of a refuge area at distance this open and dry landscape developed in a karst area with a relative smooth relief is consistent with the occurrence of the large mammal species steppe bison woolly rhinoceros and reindeer faunal and pollen analyses hence provides a new evidence for the development of cold and dry steppe like environments in nw iberia during mis 3

southern dispersal and palaeoecological implications of woolly rhinoceros coelodonta antiquitatis review of the iberian occurrences abstract cold adapted large mammal populations spread southward during the coldest and driest phases of the late pleistocene reaching the iberian peninsula presence of woolly rhinoceros coelodonta antiquitatis can be identified from 23 iberian sites which is compiled and analyzed herein and the fossil specimens from seven of these sites are described here for first time morphological and biometrical analyses demonstrate that the iberian woolly rhinoceros did not significantly differ from individuals of other european populations but represent the westernmost part of a continuous eurasian belt of distribution the first presence of woolly rhino in the iberian peninsula has been identified during the late middle pleistocene and early late pleistocene however the highest abundance of this species is recorded during mis 3 and 2 the latest iberian occurrences can be dated around 20 ka bp the presence of woolly rhinoceros in the iberian peninsula correlates with periods of extreme dry and cold climatic conditions documented in iberian terrestrial and marine sediment sequences from a palaeobiogeographic point of view the maximum southern spread of c antiquitatis on the iberian peninsula was registered during the late middle pleistocene or early late pleistocene reaching the latitude of madrid about 40 n subsequently during mis 3 and 2 all iberian finds were restricted to the northern regions of iberia cantabrian area and catalonia the southern expansion of c antiquitatis during the late pleistocene in the iberian peninsula reached similar latitudes to other eurasian regions the ecological composition of fossil assemblages with presence of woolly rhinoceros was statistically analyzed results show that temperate ungulate species are predominant at iberian assemblages resulting in a particular mixture of temperate and cold elements different of the typical eurasian cold adapted faunal associations this particular situation suggests two possible explanations a eventual migrations during the coldest time spans resulting in a mixing of cold and temperate faunas instead a faunal replacing b persistence of woolly rhinoceros populations in the iberian peninsula during interglacial episodes confined at cryptic southern refugia

a test of the reliability of rb sr dates for selected glauconite morphologies of the upper cretaceous navesink formation of new jersey abstract glauconite samples from the navesink formation of new jersey were separated into different morphological groups each morphological type was dated using the rb sr method in an attempt to test the hypothesis that the mamillary and the lobate glauconite morphologies are more suitable than other morphologies for radiometric dating isochron dates of unaltered dark green lobate glauconites were found to be reliable indicators of the true age of the sedimentary rock weathering processes may drastically affect the87rb 87sr ratios of glauconite pellets by removal of rb from the glauconite this results in anomalously high apparent ages light green glauconites were shown to have suffered extensive rb loss and are hence inappropriate for dating a slightly altered dark green lobate glauconite appears to have suffered some rb loss x ray diffraction criteria were not always sufficient in indicating whether glauconite samples have remained closed systems with respect to87rb and87sr

the chemically zoned 1949 eruption on la palma canary islands petrologic evolution and magma supply dynamics of a rift zone eruption the 1949 rift zone eruption along the cumbre vieja ridge on la palma involved three eruptive centers 3 km spaced apart and was chemically and mineralogically zoned duraznero crater erupted tephrite for 14 days and shut down upon the opening of llano del banco a fissure that issued first tephrite and after 3 days basanite hoyo negro crater opened 4 days later and erupted basanite tephrite and phonotephrite while llano del banco continued to issue basanite the eruption ended with duraznero erupting basanite with abundant crustal and mantle xenoliths the tephrites and basanites from duraznero and llano del banco show narrow compositional ranges and define a bimodal suite each batch ascended and evolved separately without significant intermixing as did the hoyo negro basanite which formed at lower degrees of melting the magmas fractionated clinopyroxene olivine kaersutite ti magnetite at 600 800 mpa and possibly 800 1100 mpa abundant reversely zoned phenocrysts reflect mixing with evolved melts at mantle depths probably as early as 1936 hoyo negro basanite entered the deep rift system at 200 350 mpa some shallower pockets of this basanite evolved to phonotephrite through differentiation and assimilation of wall rock a few months prior to eruption a mixing event in the mantle may have triggered the final ascent of the magmas most of the erupted tephrite and basanite ascended from mantle depths within hours to days without prolonged storage in crustal reservoirs the cumbre vieja rift zone differs from the rift zones of kilauea volcano hawaii in lacking a summit caldera or a summit reservoir feeding the rift system and in being smaller and less active with most of the rift magma solidifying between eruptions

the use of rbsr and kar dating methods as a stratigraphic tool applied to sedimentary rocks and minerals abstract rb sr and k ar methods can be used for direct numerical chronostratigraphy of sediments using the clay silicates they contain the interpretation of the ages calculated depends on the satisfaction of the following requirements 1 1 the series studied must include diagenetic clay sediments coarsely detrital or alightly metamorphic formations must be excluded studies in progress concerning decarbonatation may lead to the application of direct dating of sediments being extended to carbonate sediments 2 2 careful mineralogical study of the clay minerals must prove early diagenetic recrystallization or new formation this part of the study must precede any isotopic work 3 3 the isotopic study must involve the use of both rb sr and k ar methods the extreme sensibility of the k ar isotopic system to late diagenesis helps to choose between early or late diagenesis a younger k ar age may generally be regarded as that of the late diagenesis whereas the rb sr age may be that of the early diagenesis 4 4 the initial 87sr 86sr isotopic ratio is not always a reliable criterion owing to the effects of the dilution of the radiogenic 87sr by the great amounts of primary sr contained in carbonates 5 5 the regularly decreasing succession of isotopic ages must follow the stratigraphic succession when this condition is satisfied there is a high probability that the calculated ages are indeed those of the deposition dates

the pliocene seamount series of la palma canary islands a pliocene submarine series of alkali basaltic pillow lavas hyaloclastites and breccias a a sheeted dike swarm b and a basal suite of gabbro and ultramafic rocks c from la palma canary islands is interpreted as a cross section through an uplifted seamount this series has been tilted to its present orientation of 50 230 plunge and azimuth probably by upwarping due to intrusions in the central portion of the island the basal plutonic complex c also includes intrusives coeval with up to 2000 m of younger subaerial alkali basaltic lavas unconformably overlying the submarine series the plutonic suite c is overlain abruptly by more than 1800 m of sills b 0 4 1 m thick on average with minor screens of lavas and breccias extrusives a form a 1750 m thick sequence of pillow lavas breccias and hyaloclastites the clastic rocks increase in abundance upward and are of four main types 1 breccias consisting of partly broken pillows formed nearly in situ 2 heterolithologic pillow fragment breccias 3 hyaloclastites composed dominantly of highly vesicular lapilli and ash sized shards the latter thought to have formed by near surface explosive eruptions and been subsequently transported downslope by mass flows 2 and 3 being interpreted to have been resedimented and 4 pillow scoria breccias from the upper 700 m of the extrusive section consisting of amoeboidal highly vesicular pillows and lava stringers and local bombs probably formed by cracking and bleeding of gas rich expanding pillow lava and some shallow submarine subaerial lava fountaining the extrusive series is chemically and mineralogically crudely zoned with the most differentiated rocks metatrachytes and mugearites at the base and most picritic lavas occurring near the top of the series subsequent to emplacement the entire extrusive and intrusive series has been hydrothermally altered the lower part to greenschist and the upper part to smectite zeolite facies mineral assemblages the la palma succession combined with evidence from surface studies of seamounts suggests that seamounts are formed by intrusive and extrusive processes in approximately equal portions the nature of eruptive clastic and depositional mechanisms changes drastically during growth of a seamount if the critical depth for major magmatic degassing is surpassed and especially if magmatic explosive processes can occur at very shallow water depth the critical depth depending on magma and thus volatile composition changes in slopes of a seamount influence depositional processes based on these factors at least three major depositional sites develop as a seamount grows summit flank and apron facies nonexplosive extrusive processes prevail in the deep water stage dominantly producing pillow lavas 75 these consist of individual pillow volcanoes up to 200 m high with large pillows near the base and decreasing pillow size toward the top of a volcano pillow breccias and pillow fragment breccias comprise approximately 20 of this facies the deep water flank and apron facies are characterized by debris flow deposits with possibjy rather dense matrix material the shallow water shoaling stage is reached when the seamount top reaches the critical depth for drastic increase in exsolution of magmatic volatiles about 800 m for the alkali basaltic seamount of la palma resulting in formation of mainly clastic rocks 70 in situ pillow rind breccias and scoriaceous amoeboidal breccias and pillows are formed in the summit regions of the seamount by repeated expansion and leaking of frothy pillow lava possibly by lava fountaining resedimented heterolithologic pillow fragment breccias lapilli breccias and hyaloclastites are deposited on the flanks and aprons of the seamount pillow lavas comprise 30 of these deposits

conditions for the arrest of a vertical propagating dyke magma ascent towards the earth s surface occurs through dyke propagation in the vast majority of cases we investigate two purely mechanical effects unrelated to cooling or solidification that lead to the arrest of propagation so that no eruption occurs the first is that the input of magma from the source is not maintained continuously such that a fixed volume of magma is released laboratory experiments show that in this case the dyke stops at a finite distance from the source this behaviour is specific to the fracturing process in 3 d we derive a relationship for the minimum magma volume required for an eruption as a function of magma buoyancy and source depth when large magma volumes are available eruption may also be prevented by a thick low density layer in the upper crust numerical studies of dyke propagation show that the dyke continues to rise even though it is negatively buoyant magma accumulates in a swollen nose region at the interface between the low density layer and the dense basement magma overpressure is largest at this interface and increases with increasing penetration into the upper layer it may become large enough to induce horizontal fractures in the dyke walls and lateral intrusion of a sill which prevents eruption this requires that the thickness of the low density layer exceeds a threshold value that depends on the density contrast between magma and host rock if the magma volume is smaller than a threshold value neither sill intrusion nor eruption are possible and magma gets stored in a horizontal blade shaped dyke straddling the interface scaling laws for variations of ascent rate and for the minimum magma volume allow diagnosis of a failed eruption

geochemical monitoring of the 2002 2003 eruption at stromboli volcano italy precursory changes in the carbon and helium isotopic composition of fumarole gases and thermal waters significant changes in the helium and carbon isotopic composition of shallow thermal waters vs gas and a crater fumarolic gas have been recorded at stromboli prior and during the 2002 2003 eruption the3he 4he ratios corrected for air contamination rc ra and 13c of fumarolic gases gradually increased from may to november 2002 before the eruption onset these variations imply early degassing of a gas rich magma at depth that likely fed both the intense strombolian activity and small lava overflows recorded during that period the lava effusion of late december 2002 was shortly preceded by a marked rc ra decrease both in water and fumarolic gases comparison of he co2 and ch4 co2 ratios in dissolved gas and with rm delta 13 rm c rm co 2 values rules out the rc ra decrease due to an increasing input of radiogenic4he the rc ra decrease is attributed to the he isotope fractionation during rapid magma ascent and degassing a new uprising of 3he rich magma probably occurred in january to february 2003 when rc ra ratios displayed the highest values in dissolved gases ever measured before 4 56 rc ra the increase in he co2 and ch4 co2 ratios and decrease in 13c of dissolved co2 was recorded after the 5 april 2003 explosive paroxysm likely caused by enhanced gas water interaction inducing co2 dissolution no anomalous rc ra values were recorded in the same period when usual strombolian activity gradually resumed

ungulate dietary traits and plasticity in zones of ecological transition inferred from late pleistocene assemblages at jou puerta and rexidora in the cantabrian region of northern spain abstract the diet and habitats of late pleistocene ungulate taxa were analyzed in the caves of jou puerta and rexidora marine isotope stage mis 3 in the cantabrian region of northern spain a zone of ecological transition between mainland europe and central southern iberia the two ungulate assemblages which are composed mainly by cold adapted species were analyzed through tooth mesowear and microwear the jou puerta community is dominated by the leaf browsers while at rexidora the dominant taxa are grazers that suggest an open landscape with availability of grass but also with significant presence of trees and or forbs our results suggest an open landscape with presence of arboreal plant taxa during the coldest events of the mis3 concerning dietary plasticity the diets for the cold adapted woolly rhino and the reindeer in populations that lived in the southwestern boundary of their eurasian distribution fit within the plasticity observed for other populations during the pleistocene it is proposed here that diet was not a limiting factor for the populations that inhabited the limit of their known range of distribution in the cantabrian region

volcano tectonic earthquakes a new tool for estimating intrusive volumes and forecasting eruptions abstract we present data on 136 high frequency earthquakes and swarms termed volcano tectonic vt seismicity which preceded 111 eruptions at 83 volcanoes plus data on vt swarms that preceded intrusions at 21 other volcanoes we find that vt seismicity is usually the earliest reported seismic precursor for eruptions at volcanoes that have been dormant for decades or more and precedes eruptions of all magma types from basaltic to rhyolitic and all explosivities from vei 0 to ultraplinian vei 6 at such previously long dormant volcanoes because large eruptions occur most commonly during resumption of activity at long dormant volcanoes vt seismicity is an important precursor for the earth s most dangerous eruptions vt seismicity precedes all explosive eruptions of vei 5 and most if not all vei 4 eruptions in our data set surprisingly we find that the vt seismicity originates at distal locations on tectonic fault structures at distances of one or two to tens of kilometers laterally from the site of the eventual eruption and rarely if ever starts beneath the eruption site itself the distal vt swarms generally occur at depths almost equal to the horizontal distance of the swarm from the summit out to about 15 km distance beyond which hypocenter depths level out we summarize several important characteristics of this distal vt seismicity including swarm like nature onset days to years prior to the beginning of magmatic eruptions peaking of activity at the time of the initial eruption whether phreatic or magmatic and large non double couple component to focal mechanisms most importantly we show that the intruded magma volume can be simply estimated from the cumulative seismic moment of the vt seismicity from log10 v 0 77 log moment 5 32 with volume v in cubic meters and seismic moment in newton meters because the cumulative seismic moment can be approximated from the size of just the few largest events and is quite insensitive to precise locations the intruded magma volume can be quickly and easily estimated with few short period seismic stations notable cases in which distal vt events preceded eruptions at long dormant volcanoes include nevado del ruiz 1984 1985 pinatubo 1991 unzen 1989 1995 soufriere hills 1995 shishaldin 1989 1999 tacana 1985 1986 pacaya 1980 1984 rabaul 1994 and cotopaxi 2001 additional cases are recognized at frequently active volcanoes including popocateptl 2001 2003 and mauna loa 1984 we present four case studies pinatubo soufriere hills unzen and tacana in which we demonstrate the above mentioned vt characteristics prior to eruptions using regional data recorded by neic we recognized in near real time that a huge distal vt swarm was occurring deduced that a proportionately huge magmatic intrusion was taking place beneath the long dormant sulu range new britain island papua new guinea that it was likely to lead to eruptive activity and warned rabaul volcano observatory days before a phreatic eruption occurred this confirms the value of this technique for eruption forecasting we also present a counter example where we deduced that a vt swarm at volcan cosiguina nicaragua indicated a small intrusion insufficient to reach the surface and erupt finally we discuss limitations of the method and propose a mechanism by which this distal vt seismicity is triggered by magmatic intrusion

some fundamental considerations in the dating of glauconies a comment on a test of the reliability of rbsr dates for selected glauconite morphologies of the upper cretaceous navesink formation of new jersey by r l montag and d e seidemann in an attempt to understand the geochemical behaviour of rb and sr in glauconies see below used for dating purpose montag and seidemann 1 stated several hypotheses in contradiction with some facts generally known to the specialists in these difficult problems in their introduction these authors define the word glauconite as a mineral but unfortunately also use it to describe the green sedimentary pellets in which glauconitic minerals occur the term has unfortunately come to be used loosely to cover two concepts on the one hand a concept of facies something green usually in pelletal form lying in a marine sediment on the other hand a mineralogic concept which designates a mica 2 the two concepts cover diverse possibilities this duality of significance leads us amongst others 3 to propose to solve this confusion by using glaucony or pelletal glauconite for the facies and glauconitic minerals for the authigenic components of the green pellets 4 these glauconies may be more or less evolved and fundamentally contain two kinds of components 1 t h e inherited ones which originate from the initial substrate of glauconitization quartz mica clay calcareous debris 5 there is no glauconitization without this preliminary substrate 2 the authigenic ones which are the glauconitic minerals ranging from a smectitic end member component to a micaceous endmember only the latter should actually be named glauconite the suffix ite characterizes a mineral this is a convention other conventions are possible and we do not intend to impose a solution but it is certain that the confusion of the two concepts and withirl each concept the non recognition of their diversity can only lead to complete confusion in the application to geochronology ages of glauconies are not generally 10 20 younger than the age of sedimentation this old assumption was based on the study of deeply buried samples from north america which had been rejuvenated or on a biased time scale 6 numerous recent studies have shown that the main problems with the dating of giauconies are in chronological order 1 the zero time problem see tisserant and odin 7 and fig 1 2 possible influences from tectonic and deep burial 8 and 3 possible changes due to weathering 9 whatever the colour or the form the green pellets may lack reliability for geochronology due to the three main causes listed above if the light green pellets give apparent ages which are often different from the age of sedimentation it is well recognized today that this is not related to their colour but to the fact that either they are little evolved or that

rates of magma ascent and depths of magma reservoirs beneath la palma canary islands peridotitic mantle xenoliths from historic and prehistoric eruptions on la palma show many similarities prolonged reactions of the xenoliths with their host magmas have been used to place constraints on the magma transport system beneath the island all xenoliths show crystalline selvages and 0 9 2 6 mm wide diffusion zones in olivine along most of their surface diffusion kinetics in olivine combined with fluid inclusion barometry document that selvages and diffusion zones formed at crustal levels within 8 to about 100 years some xenolith fractures lack selvages and were in contact with the host magma for less than 4 days a multistage magma ascent is proposed i peridotite wall rock was fragmented and became incorporated into the ascending magma years to decades prior to the eruption ii the xenoliths were rapidly transported to and deposited in crustal magma reservoirs forming selvages and diffusion zones at the xenolith rims iii renewed fragmentation of the xenoliths occurred days to hours prior to eruption possibly by decompressive strain fracturing during rapid ascent

magma storage and migration associated with the 2011 2012 el hierro eruption implications for crustal magmatic systems at oceanic island volcanoes 1 starting in july 2011 anomalous seismicity was observed at el hierro island a young oceanic island volcano on 12 october 2011 the process led to the beginning of a submarine nw se fissural eruption at 15 km from the initial earthquake loci indicative of significant lateral magma migration here we conduct a multifrequency multisensor interferometric analysis of spaceborne radar images acquired using three different satellite systems radarsat 2 envisat and cosmo skymed constellation of small satellites for mediterranean basin observation the data fully captures both the pre eruptive and coeruptive phases elastic modeling of the ground deformation is employed to constrain the dynamics associated with the magmatic activity this study represents the first geodetically constrained active magmatic plumbing system model for any of the canary islands volcanoes and one of the few examples of submarine volcanic activity to date geodetic results reveal two spatially distinct shallow crustal magma reservoirs a deeper central source 9 5 4 0 km and a shallower magma reservoir at the flank of the southern rift 4 5 2 0 km the deeper source was recharged explaining the relatively long basaltic eruption contributing to the observed island wide uplift processes and validating proposed active magma underplating the shallowest source may be an incipient reservoir that facilitates fractional crystallization as observed at other canary islands data from this eruption supports a relationship between the depth of the shallow crustal magmatic systems and the long term magma supply rate and oceanic lithospheric age such a relationship implies that a factor controlling the existence depth of shallow crustal magmatic systems in oceanic island volcanoes is the lithosphere thermomechanical behavior

measurements of 220rn and 222rn and co2 emissions in soil and fumarole gases on mt etna volcano italy implications for gas transport and shallow ground fracture this work was funded by the istituto nazionale di geofisica e vulcanologia s g m n and by the dipartimento per la protezione civile italy projects v3 6 28 etna m n and v5 08 diffuse degassing in italy s g and nsf ear 063824101 k w w s

upper proterozoic 1800 570 ma stratigraphy a survey of lithostratigraphic paleontological radiochronological and magnetic correlations classical stratigraphy which was conceived in relation to the phanerozoic can be extended into the precambrian particularly the upper part stromatolite biostratigraphy provides natural subdivisions of the upper proterozoic as indicated by studies on the riphean of the u s s r the correlation techniques are identical to those used in the phanerozoic imperfections in the biostratigraphic record however have encouraged the development of lithostratigraphic radiochronological and paleomagnetic techniques rocks of volcanic or volcano sedimentary origin and rocks that indicate extreme climatic conditions glaciogenic rocks red beds evaporites are widespread and easily identified they are accordingly useful for lithostratigraphic correlation tillites have for a long time been considered as useful in stratigraphic correlation but recent work has shown that many such glacial deposits are in fact slightly diachronous this is especially true of the widespread glaciogenic deposits of the uppermost proterozoic stromatolites are probably the most useful biostratigraphic tools progress has been made in separating the influence of the environment and that of the communities of algae and bacteria on the development of the stromatolitic structure biostratigraphic subdivisions based on biologically controlled structures such as the nature of microlamination have been found to be useful in large scale correlations in some cases such correlations have been verified by geochronology while such correlations are still somewhat crude 100 350 ma subdivisions they are probably more reliable than those based on microbiotas extracted from siliceous layers and or shales for the greater part of upper proterozoic time the possibility of dating argillaceous sedimentary rocks largely depends on the care taken in selection of the samples the samples should have the necessary mineralogy and should not contain inherited 40ar or 37sr good results have been obtained on glauconites rick in k2o and particularly on illite and smectite using the rb sr method the age of a magnetized rock from which the ancient pole position has been deduced can be obtained from the apparent polar wandering curve but there are still many problems with regard to the meaningful application of these techniques on the other hand magnetostratigraphy involving documentation of the earth s polarity inversions is a field of study which holds much promise for the subdivision and correlation of precambrian rock successions geochronology is the most precise of the four methods of correlation considered it also provides a framework on which to hang the results of lithostratigraphy and magnetostratigraphy

monitoring the volcanic unrest of el hierro canary islands before the onset of the 2011 2012 submarine eruption 1 on 10 october 2011 a submarine volcanic eruption started 2 km south from el hierro island spain since july 2011 a dense multiparametric monitoring network was deployed all over the island by instituto geografico nacional ign by the time the eruption started almost 10000 earthquakes had been located and the deformation analyses showed a maximum deformation of more than 5 cm earthquake migration from the north to the south of the island and acceleration of seismicity are in good correlation with changes in the deformation pattern as well as with some anomalies in geochemical and geomagnetic parameters an earthquake of local magnitude 4 3 at 12 km depth 8 october 2011 and shallower seismicity a day after preceded the onset of the eruption this is the first time that a volcanic eruption is fully monitored in the canary islands data recorded during this unrest episode at el hierro will contribute to understand reawakening of volcanic activity in this region and others of similar characteristics

a magmatic source for fumaroles and diffuse degassing from the summit crater of teide volcano tenerife canary islands a geochemical evidence for the 2004 2005 seismic volcanic crisis the present work reports the results of 15 studies of diffuse co2 degassing performed at teide volcano crater canary island spain and the chemical and isotopic compositions of fluids discharged from a fumarolic field located at the top of the volcano as measured between 1991 and 2010 a higher contribution of magmatic gases accompanied by enhanced total diffuse co2 emissions were observed in relation with a seismic crisis that occurred in tenerife island between 2001 and 2005 with the main peak of seismic activity between april and june 2004 a significant pulse in total diffuse co2 emission was observed at the crater of teide up to 26 3 t day 1 in 2001 in december 2003 the chemical composition of the teide fumarole changed significantly including the appearance of so2 an increase in the hcl and co concentrations and in the c2h6 c2h4 and c3h8 c3h6 ratios and a decrease in the h2s ch4 and c6h6 concentrations and in the gas steam ratio a few months after a drastic decrease in seismic activity the so2 hcl and co concentrations and the c2h6 c2h4 and c3h8 c3h6 ratios strongly decreased whereas the ch4 and c6h6 concentrations and the gas steam ratios increased according to the trends shown by both the geochemical parameters and the seismic signals late in the observation period the risk of a rejuvenation of volcanic activity at teide is considered to be low the associated temporal changes in seismic activity and magmatic degassing indicate that geophysical and fluid geochemistry signals in this system are related future monitoring programs aimed at mitigating volcanic hazard on tenerife island should involve coupled geophysical and geochemical studies

volcanic signatures in time gravity variations during the volcanic unrest on el hierro canary islands gravity changes occurring during the initial stage of the 2011 2012 el hierro submarine eruption are interpreted in terms of the preeruptive signatures during the episode of unrest continuous gravity measurements were made at two sites on the island using the relative spring gravimeter lacoste and romberg gphone 054 on 15 september 2011 an observed gravity decrease of 45 mu gal associated with the southward migration of seismic epicenters is consistent with a lateral magma migration that occurred beneath the volcanic edifice an apparently clear precursor of the eruption that took place 25 days later on 10 october 2011 high frequency gravity signals also appeared on 6 11 october 2011 pointing to an occurring interaction between a magmatic intrusion and the ocean floor these important gravity changes with amplitudes varying from 10 to 90 mu gal during the first 3 days following the onset of the eruption are consistent with the northward migration of the eruptive focus along an active eruptive fissure an apparent correlation of gravity variations with body tide vertical strain was also noted which could indicate that concurrent tidal triggering occurred during the initial stage of the eruption

time lag between deformation and seismicity along monogenetic volcanic unrest periods the case of el hierro island canary islands between 2011 and 2014 there were at least seven episodes of magmatic intrusion in el hierro island but only the first one led to a submarine eruption in 2011 2012 in order to study the relationship between gps deformation and seismicity during these episodes we compare the temporal evolution of the deformation with the cumulative seismic energy released in some of the episodes both deformation and seismicity evolve in a very similar way but in others a time lag appears between them in which the deformation precedes the seismicity furthermore a linear correlation between decimal logarithm of intruded magma volume and decimal logarithm of total seismic energy released along the different episodes has been observed therefore if a future magmatic intrusion in el hierro island follows this behavior with a proper time lag we could have an a priori estimate of the order of magnitude the seismic energy released would reach

was grass more prevalent in the pronghorn past an assessment of the dietary adaptations of miocene to recent antilocapridae mammalia artiodactyla abstract molar teeth of both tertiary and quaternary representatives of the family antilocapridae were examined using mesowear and light stereomicroscopy microwear taxa from the central and southern great plains and the northern and southern great basin were included in the analyses and results compared to those obtained on the modern pronghorn antilocapra americana species included spanned from the early miocene late hemingfordian to the late pleistocene rancholabrean results are concordant with well known trends toward increasing aridity and shifts in vegetational structure in the late miocene early pliocene of north america both mesowear and microwear results indicate a shift toward more abrasive diets beginning in the hemphillian late miocene pliocene and then a return to a less abrasive dietary regime for the duration of the pleistocene and into the recent the more derived antilocaprines more hypsodont relatively longer limbs apparently depended more on grass than the less advanced merycodontines but even the earliest of the latter seem to have relied more on grass as a dietary staple than the modern pronghorn seasonal grit encroachment on food items encountered by fossil antilocaprids coupled with a heavier reliance on grasses may provide a possible explanation for the extreme hypsodonty present in the modern pronghorn despite its mainly browsing dietary behavior

aspects of proterozoic stromatolite biostratigraphy in western australia abstract stromatolites are abundant at many horizons in the proterozoic of western australia recent advances in knowledge of proterozoic stratigraphy of the state have provided a more detailed framework for interpreting the stromatolite data than has been available previously in the 1 7 ga earaheedy group of the nabberu basin a characteristic stromatolite assemblage occurs and within the basin a biostratigraphic succession can be recognized the assemblage contains several new forms which belong to new groups the need to erect new groups for these early proterozoic stromatolites is in agreement with recent studies in canada northern europe and south africa and suggests that the problem of younger or late proterozoic stromatolite groups in early proterozoic rocks mentioned by previous workers is a result of a lack of rigour in defining taxa examination of type material is necessary to determine how closely the earaheedy forms resemble those described from these other regions in western australia some stromatolite forms have a restricted vertical range and similar taxa occur in beds of approximately the same age in widely separated areas e g kimberley group and earaheedy group scorpion group and limbunya birrindudu mcarthur mt rigg and mt albert groups and bungle bungle dolomite tolmer and bullita groups moora and bangemall groups kai ki beds louisa downs mount house and albert edward groups stromatolite diversity shows a decline in the number of taxa at about 1 1 ga in the bangemall group more data are required to determine whether this decline is universal or specific to the bangemall group this study indicates that a stromatolite biostratigraphy for western australia is feasible and is consistent with data from other parts of australia thus emphasis on correlation should be placed on the stromatolite form rather than the group and intercontinental correlations should be attempted only when local biostratigraphic schemes have been firmly established

transient deformation associated with explosive eruption measured at masaya volcano nicaragua using interferometric synthetic aperture radar abstract deformation caused by processes within a volcanic conduit are localised transient and therefore challenging to measure however observations of such deformation are important because they provide insight into conditions preceding explosive activity and are important for hazard assessment here we present measurements of low magnitude transient deformation covering an area of 4 km 2 at masaya volcano spanning a period of explosive eruptions 30th april 17th may 2012 radial uplift of duration 24 days and peak displacements of a few millimeters occurred in the month before the eruption but switched to subsidence 27 days before the onset of the explosive eruption on 30th of april uplift resumed during and continued for 16 days after the end of the explosive eruption period we use a finite element modelling approach to investigate a range of possible source geometries for this deformation and find that the changes in pressurisation of a conduit 450 m below the surface vent radius 160 m and length 700 m surrounded by a halo of brecciated material with a young s modulus of 15 gpa gave a good fit to the insar displacements we propose that the pre eruptive deformation sequence at masaya is likely to have been caused by the movement of magma through a constriction within the shallow conduit system although measuring displacements associated with conduit processes remains challenging new high resolution insar datasets will increasingly allow the measurement of transient and lower magnitude deformation signals improving the method s applicability for observing transitions between volcanic activity characterised by an open and a closed conduit system

ungulates from teixoneres cave moia barcelona spain presence of cold adapted elements in ne iberia during the mis 3 abstract the site of teixoneres cave barcelona ne spain provided two ungulate associations of mis 3 age one of which from unit iii include two cold adapted species coelodonta antiquitatis blumenbach 1799 and mammuthus primigenius blumenbach 1799 which are infrequent in the iberian fossil record the collection includes the first iberian find of a m primigenius dp 2 a rare dental element this assemblage is relevant from chronological biogeographical and palaeoecological aspects age of this faunal association 44 210 to 33 060 cal ka bp is slightly older than most of the other late pleistocene iberian occurrences of m primigenius and c antiquitatis providing interesting information on the spatiotemporal distribution of these species the presence of these two cold adapted species in ne iberia is of special biogeographical relevance since they are infrequent and poorly known in this region the faunal association of unit iii was compared with other iberian and western european fossil assemblages that included c antiquitatis and or m primigenius by means of multivariate statistical analysis the teixoneres unit iii assemblage reflects a faunal mixture in which temperate ungulate species are predominant and cold adapted taxa are very scarce this pattern is the same that can be observed in most of the iberian analyzed assemblages and does not reflect the typical faunal composition of the eurasian mammoth steppe suggesting that that cold adapted taxa only reached the peninsula occasionally during the coldest episodes of the pleistocene cohabiting with the local faunas instead of replacing them

an investigation of seismicity clustered near the cordel field west central alberta and its relation to a nearby disposal well historically seismicity documented in the western canada sedimentary basin has been relatively quiescent and earthquakes are usually restricted to the foreland belt of the rocky mountains however exceptional clusters of events which have remained active for decades are recognized in alberta in this study we investigate the seismicity in this region using data obtained from recently established regional arrays emphasizing the relationship between a disposal well in the cordel field and a nearby cluster of previously reported earthquakes we explore temporal correlations of wastewater pumping rates and local seismic activity dating back to 1960 we find that the first statistically significant increase in seismicity lags the onset of wastewater injection october 1991 by 3 33 years in particular the waveform similarity of 32 events are analyzed from continuous data recorded at nor a nearby 30 km station operated by the university of alberta starting in september of 2006 results from this analysis suggest that many events are well correlated in the characteristics of the waveforms and thus are likely to share a similar origin and source mechanism the most prolific of these multiplets repeats more than 10 times sporadically throughout the entire duration of recorded data from october 2006 to march 2012 despite the limited availability of nearby stations which adversely affects the resolution of our analysis hypocenter depths could be relatively accurately determined from waveform synthesis and double difference methods the results of our analysis provide first order evidence that the seismicity is consistent with fluid injection induced events

magma storage and underplating beneath cumbre vieja volcano la palma canary islands we have conducted a barometric study of basaltic lavas and mafic to ultramafic xenoliths from cumbre vieja volcano la palma in order to reconstruct magma storage plumbing and related intrusive island growth the samples were collected both along the volcano s rift zone and from its subaerial and submarine flanks up to 30 km off the rift axis clinopyroxene melt barometry of lavas yields a well defined pressure range of 410 770 mpa average 600 mpa and shows no systematic variation with sample locality this pressure range reflects a major fractionation level at ca 15 26 km depth within the uppermost mantle where phenocrysts and melt last equilibrated in contrast microthermometry of co2 dominated fluid inclusions in phenocrysts and xenoliths gives pressure estimates of 240 to 470 mpa average 330 mpa within the lower oceanic crust these pressures are interpreted to reflect an underplating zone at 7 14 km depth where ascending magmas become ponded prior to eruption and where passing magmas temporarily stagnate during eruption the underplating zone is inferred to extend to a radius of ca 30 km at least and its depth appears to increase slightly with distance to the rift axis our data thus show a remarkable pressure bimodality for long term and short term storage of magma that appears to be characteristic for cumbre vieja by using a simple model based on the cumulative volume of material added to the crust we have estimated uplift rates of 0 5 m ka due to underplating that occurs on the island scale on a time scale of some 10 ka these uplift rates are of similar magnitude as global changes in sea level a second more local mode of uplift and related faulting is caused by shallow intrusions into the volcanic edifice as is indicated by the highly irregular morphology of the cumbre vieja we stress that intrusion related uplift should be qualitatively considered when reconstructing the evolution of oceanic island volcanoes since most of the underplated material is inferred to consist of cumulate rocks being intimately mixed and juxtaposed with the lower oceanic crust and having similar densities it is probably impossible to detect such an underplating zone seismically

spatial variation of seismic b values beneath makushin volcano unalaska island alaska abstract the frequency magnitude distribution was spatially mapped beneath makushin volcano unalaska island alaska using an earthquake catalog of 491 events that occurred between july 2001 and april 2005 an area of high seismic b values 2 0 is found 4 km east of makushin s main vent at a depth between 4 and 7 km the anomaly is statistically significant based on utsu s p test t utsu on seismicity in report of the joint research institute for statistical mathematics tokyo 1992 139 157 and is not data processing method or parameter dependent interestingly a recent insar interferometric study z lu j a power v s mcconnell c wicks jr d dzurism preeruptive inflation and surface interferometric coherence characteristics by satellite radar interferometry at makushin volcano alaska 1993 2000 j geophys res 107 2002 2266 doi 10 1029 2001jb000970 inferred a surface uplift of about 7 cm during the two year period prior to october 1995 centered approximately in the area with the observed anomalous b values the uplift was caused by the volume increase of an inferred magma chamber at a depth of about 7 km the close correspondence of the seismic and insar observations suggests that the heterogeneous area associated with the observed high b values is most likely the result of increased crack density associated with the magma chamber this study demonstrates the effectiveness of combining insar and seismological observations in locating magma chambers and areas of high heterogeneity in the crust

diffusive helium emissions as a precursory sign of volcanic unrest significant increases in helium emissions from the soil and 3 he 4 he ratios in groundwater on el hierro island canary islands spain were observed prior to the 2011 2012 submarine eruption off the coast of the island the changes of diffusive helium emissions rate were observed one month prior to the submarine eruption onset 12 october 2011 and the major increase preceded increases in seismic energy release during the volcanic unrest measured 3 he 4 he ratios in groundwaters from a well in el hierro island increased from 2 3 r a to 7 2 r a r a 3 he 4 he ratio in air 1 month prior to the eruption onset and reached a peak of 8 2 r a indicating a dominant magmatic contribution to the dissolved gases in ground waters 3 he 4 he values and diffusive helium emission studies have been extremely important for forecasting the onset of the volcanic unrest and subsequent volcanic eruption an aseismic exsolution of magmatic gases from magma bodies beneath el hierro island through fractures and vertical permeability structures increased the diffusive helium emission rate prior to episodes of seismic energy release associated with the volcanic unrest

multi stage magma ascent beneath the canary islands evidence from fluid inclusions gabbroic and ultramafic xenoliths and olivine and clinopyroxene phenocrysts in basaltic rocks from gran canaria la palma el hierro lanzarote and la gomera canary islands contain abundant co2 dominated fluid inclusions inclusion densities are strikingly similar on a regional scale histogram maxima correspond to one or more of the following pressures 1 minimum 0 55 to 1 0 gpa within the upper mantle 2 between 0 2 and 0 4 gpa the moho or the lower crust 3 at about 0 1 gpa upper crust fluid inclusions in several rocks show a bimodal density distribution the lower density maximum comprising both texturally early and late inclusions this is taken as evidence for an incomplete resetting of inclusion densities and simultaneous formation of young inclusions at well defined magma stagnation levels for gran canaria pressure estimates for early inclusions in harzburgite and dunite xenoliths and olivine phenocrysts in the host basanites overlap at 0 9 to 1 0 gpa indicating that such magma reservoir depths coincide with levels of xenolith entrainment into the magmas magma chamber pressures within the mantle inferred to represent levels of mantle xenolith entrainment are 0 65 0 95 gpa for el hierro 0 60 0 68 gpa for la palma and 0 55 0 75 gpa for lanzarote the highest density fluid inclusions in many canary island mantle xenoliths have probably survived in situ near isobaric heating at the depth of xenolith entrainment inclusion data from all islands indicate ponding of basaltic magmas at moho or lower crustal depths and possibly at an additional higher level strongly suggestive of two main crustal accumulation levels beneath each island we emphasize that repeated magmatic underplating of primitive magmas and therefore intrusive accretion are important growth mechanisms for the canary islands and by analogy for other ocean islands comparable fluid inclusion data from primitive rocks in other tectonic settings including iceland etna and continental rift systems hungary south norway indicate that magma accumulation close to moho depths shortly before eruption is not however restricted to oceanic intraplate volcanoes lower crustal ponding and crystallization prior to eruption may be the rule rather than the exception independent of the tectonic setting

the jou puerta cave asturias nw spain a mis 3 large mammal assemblage with mixture of cold and temperate elements abstract the cave of jou puerta asturias nw spain provided an interesting large mammal assemblage including cold adapted elements like coelodonta antiquitatis and mammuthus primigenius which are not frequent in iberian sites the chronology of the fossils ranges from 36 6 to 30 2 cal ka bp corresponding to mis 3 an episode characterized by fast climate changes from extreme cold to temperate conditions the origin of the bone accumulation is related to a natural trap so most of the fossils were unusually well preserved the woolly rhinoceros remains yielded one of the most numerous and well preserved populations of this species from the iberian peninsula which allowed carrying out a detailed comparative anatomical study the faunal composition of jou puerta was statistically analyzed in comparison with other iberian and western european fossil assemblages where c antiquitatis and or m primigenius occurred the results showed that temperate ungulate species are predominant at most of the iberian assemblages including jou puerta resulting in a particular mixture of temperate and cold elements which does not reflect the typical faunal composition of the eurasian mammoth steppe this particular situation supports the idea that these cold taxa only reached the peninsula occasionally during the coldest episodes of the pleistocene resulting in a mixing of cold and temperate faunas instead of a faunal replacing

a test of the reliability of rbsr dates for selected glauconite morphologies of the upper cretaceous navesink formation of new jersey reply to the comment by g s odin and n h gale

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

subdivision and correlation of late precambrian sequences in australia abstract the diversity of the australian precambrian record is used to empirically assess the application of all available techniques of correlation of late precambrian rocks lithofacies isotopic ages palaeontology and palaeomagnetism within the framework of latest lithostratigraphic geochronologic correlation charts lithostratigraphy is the main tool for intrabasinal correlation and mapping but isotopic ages will continue for some time yet to provide the main criteria for interregional correlation lithostratigraphic correlation is demonstrated over hundreds of kilometres but is generally constrained by tectonic controls to individual major crustal blocks climatic markers such as tillites may be correlated interregionally over thousands of kilometres the most exciting recent development in platform geochronology is the application of u pb zircon dating to fine grained tuffs illite may provide reliable minimum estimates but can be shown to be up to 150 ma too young glauconite and rb sr total rock shale ages have provided useful broad age estimates of sequences for which better methods are unavailable but only when based on cautious assessment and multiple sampling their ages may be either minimum or maximum stromatolites continue to demonstrate their potential for broad correlation when based on rigorous taxonomic study but the framework of time ranges of known taxa must be expanded for stromatolites to achieve their full potential especially for rocks older than 1000 ma acritarchs in black shales provide diverse and complex assemblages with excellent correlation potential but once again the australian taxonomic framework is still inadequate black cherts contain an evolutionarily conservative biota with only limited correlation potential recent palaeomagnetic studies based on both apwp and magnetostratigraphy demonstrate excellent potential for detailed correlations down to at least 1700 ma old however the present chronologically calibrated data base is sparse and must be supplemented by many more detailed studies through thick continuous rock sequences spanning substantial intervals of time the value of multidisciplinary correlation is elegantly demonstrated by very detailed and unambiguous correlation of combined palaeomagnetic isotopic age and stromatolite data across the 1700 ma mcarthur basin previous regional lithostratigraphic correlations have been conclusively and significantly revised with major implications to regional palaeogeography

resistivity variations related to the large march 9 1998 eruption at la fournaise volcano inferred by continuous mt monitoring abstract the 2645 m high la fournaise volcano located in the southwest of reunion island indian ocean is a shield basaltic volcano where effusive eruptions generally occur along long fissures starting from the summit alongside major fractures that characterize the eruptions dynamism and effusivity between 1992 and 1998 the volcano underwent a quiet period during which few earthquakes were recorded minor seismic activity returned after 1997 and picked up in march 1998 during the 35 h preceding the march 9 eruption from 1996 two autonomous stations csv and bav were installed on the volcano csv was located inside the enclos fouque caldera while bav was positioned 8 2 km nw of the volcano summit horizontal components of the electric and magnetic fields were sampled every 20 s continuous time series were available from 1996 to 1999 at csv and from 1997 to march 1998 at bav data have been processed using both single station and remote reference processing both results show apparent resistivity variations synchronous to the eruption time lapse impedance estimates are computed on overlapping time windows of about two days at both stations the only major decrease of the observed impedance coincides with the march 1998 eruption at csv the resistivity started to drop about five days before the eruption reached several local minima until april and then slowly increased as the volcanic crisis reduced in activity after the end of the crisis in september 1998 the apparent resistivity recovered its pre crisis value the time lapse results also show variability in directionality sharp and elongated phase tensor ellipse residuals appear during the eruption with a n105 orientation suggesting the emergence of an almost ns striking dyke a 1d background model built from mt soundings performed during the quiet period 1996 to february 1998 on which a 3d ns striking dyke was added shows a good agreement with phase tensor residuals and spatial distribution of the resistivity variations observed during the eruption

what happens to in soil radon activity during a long lasting eruption insights from etna by multidisciplinary data analysis we analyze short to long term changes from days to months in radon rn activity measured nearby 2 km the eruptive fractures that fed a lava effusion at mt etna italy between 13 may 2008 and 6 july 2009 the n120 140 e eruptive fractures opened between 3050 and 2620 m above sea level before a dike forming intrusion fed the 14 month long lava emission our high rate data streams include rn ambient parameters barometric pressure and soil temperature and seismic data earthquakes and volcanic tremor recorded from january 2008 to july 2009 the analysis highlights repeated episodes of rock fracturing related to seismic swarms and vigorous gas pulses and peak values in rn emissions maximum 4 1x105 bq m3 on 16 november 2008 which we interpreted in a conceptual model as the response to inputs from the magmatic system during the eruption this multidisciplinary study i provides evidence of a close relationship between rn emission at a fumarole near the summit active craters and local earthquakes and ii enables exploring the important role of the volcanic source on the temporal development of the rn flux which may account for the much higher 94 m day ascent speed of the rn carrier vapor than diffusion the close location of rn probes to the active conduits along with the application of our multidisciplinary approach may shed new light on the internal dynamics of other active volcanoes worldwide

insights into the 2011 2012 submarine eruption off the coast of el hierro canary islands spain from statistical analyses of earthquake activity summary the purpose of this work is to gain insights into the 2011 2012 eruption of el hierro canary islands by mapping the evolution of the seismic b value the el hierro seismic sequence offers a rather unique opportunity to investigate the process of reawakening of an oceanic intraplate volcano after a long period of repose the 2011 2012 eruption is a submarine volcanic event that took place about 2 km off of the southern coast of el hierro the eruption was accompanied by an intense seismic swarm and surface manifestations of activity the earthquake catalogue during the period of unrest includes over 12 000 events the largest with magnitude 4 6 the seismic sequence can be grouped into three distinct phases which correspond to well separated spatial clusters and distinct earthquake regimes the estimated b value is of 1 18 0 03 and a magnitude of completeness of 1 3 for the entire catalogue b is very close to 1 0 which indicates completeness of the earthquake catalogue with only minor departures from the linearity of gutenberg richter frequency magnitude distribution the most straightforward interpretation of this result is that the seismic swarm reached its final stages and no additional large magnitude events should be anticipated similarly to what one would expect for non volcanic earthquake sequences the results dividing the activity in different phases illustrate remarkable differences in the estimate of b value during the early and late stages of the eruption the early pre eruptive activity was characterized by a b value of 2 25 in contrast the b value was 1 25 during the eruptive phase based on our analyses and the results of other studies we propose a scenario that may account for the observations reported in this work we infer that the earthquakes that occurred in the first phase reflect magma migration from the upper mantle to crustal depths the area where magma initially intruded into the crust because of its transitional nature is characterized by high fracturing thus favours anomalously high b values the larger magnitude earthquakes recorded in the second phase may reflect relaxation around the magma reservoir that had fed the eruption and thus lower b values

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

constraints on magma transfers and structures involved in the 2003 activity at piton de la fournaise from displacement data piton de la fournaise reunion island had shown 8 months of high activity during 2003 including four eruptions and one intrusion the monitoring networks provided by the volcanological observatory of piton de la fournaise show two different kinds of behavior strong and rapid deformations linked with the magma injections and a slight continuous intereruptive inflation of the summit area inversed modeling based on the deformation data using a three dimensional elastostatic boundary element code combined with seismicity provides new insights into the volcanic feeding system involved in the 2003 activity 1 the 2003 eruptions are fed from a pressurized magma chamber located beneath the summit at 300 m above sea level 2 a vertical path was activated between the magma chamber and the surface during the december 2002 collapse allowing the magma to rise into it and leading to the initial summit eruption in may 2003 3 the august and september 2003 lateral eruptions had been fed by dikes intruding along the same vertical pathway at an estimated velocity of 1 1 to 1 3 m s before intruding the flank into the rift zones at a velocity of 0 2 to 0 8 m s this last point suggests a strong structural control on the dike pathway

dissolved helium isotope ratios in ground waters a new technique based on gas water re equilibration and its application to stromboli volcanic system here a new technique for the determination of dissolved he isotope ratios in ground waters is presented this method is based on the extraction and subsequent equilibrium of dissolved gases in an added host gas phase ultra pure n2 is placed in glass flasks 250 cc containing water samples that were hermetically sealed after their collection after shaking in an ultrasonic bath for 10 min an aliquot of the separated gas phase was removed from the flask for ms analysis 3he 4he ratios are measured by using a modified double collector mass spectrometer vg 5400 tft helium and ne concentrations are calculated by comparing the partial pressures of masses 4 and 20 of the samples with those of the air standard measured by a quadrupole mass spectrometer qms vg quartz using he and ne equilibrium partitioning coefficients it is possible to calculate the amount of gas originally dissolved in the water the technique was tested on both air saturated waters asw and thermal waters from stromboli aeolian islands south italy the results of which confirmed good reproducibility 5 and accuracy 3 of the data the method was then applied to three thermal water samples collected from the same volcanic area and the results compared with those of a fumarolic and a soil gas the isotope ratios for dissolved he gave values of 4 06 4 23 ra which are significantly higher than those previously reported in the literature 3 0 3 5 and 2 9 ra and that measured at the fumarole 3 09 ra suggesting a newer and higher isotopic signature for the volcanic system the proposed method appears to be a useful tool in the determination of 3he 4he ratios in ground water systems especially when free gases are not available or are dangerous to collect