a carbon isotope reference curve for ca 1700 1575 ma mcarthur and mount isa basins northern australia abstract shallow marine paleo and mesoproterozoic sedimentary successions are widely distributed in several major basins across northern australia the successions are only gently deformed and their stratigraphy is relatively continuous thus offering an ideal opportunity to document secular variations in carbon isotopes marine carbonate intervals from two of these major basins the mcarthur and mount isa basins have been sampled to document secular variation in 13ccarb from approximately 1700 to 1575 ma in all cases the samples have been tied to a well established sequence stratigraphy which along with u pb shrimp zircon dates provides a time resolution of the order of 1 m y the data presented here thus provide the most comprehensive and best dated 13ccarb stratigraphy yet obtained from such ancient rocks diagenesis occurred early in the carbonate rocks from both basins with the result that fluid movements were restricted and primary carbon isotopic signatures were retained the 13ccarb values from both basins vary within a very narrow range around a mean of 0 6 with extreme values seldom lying further than 1 from the mean that is the curves are essentially flat the results of this study combined with earlier studies on younger rocks imply that the global ocean reached a state of equilibrium in the mid paleoproterozoic and remained stable for much of the following billion years current models of the ocean suggest that to maintain the carbon mass balance relatively low levels of tectonic activity would be required which in turn suggests that the availability of nutrients such as phosphorus was stable and low prolonged nutrient stability may therefore have exerted a major influence upon the evolution of the biosphere over this time interval

a comment on tectonics and the future of life on terrestrial planets it is argued that the tight interconnection between biological climatological and geophysical factors in the history of the terrestrial biosphere can teach us something of wider importance regarding the general astrobiological evolution of planets in the galactic habitable zone of the milky way motivated by a recent debate on the future of earth s biosphere we suggest an additional reason why the impact of plate tectonics on the biological evolution is significant on the global galactic level

the martian hemispheric dichotomy may be due to a giant impact mars is divided into two fundamentally different geological provinces of approximately hemispherical extent1 3 the more southerly province is heavily cratered contains relatively old geological units and superficially resembles the lunar and mercurian highlands the northern province is relatively lightly cratered and contains younger geological units including extensive plains volcanic edifices and volcanic calderas except for the tharsis and elysium regions and other large volcanoes most of the younger northern province consists of lowlands which lie an average of 3 km below the highlands lowlands occupy about one third of mars they are separated from the highlands by a distinct scarp or by a sloping transitional zone as much as 700km wide in which highland materials have been disrupted and partly replaced by lowland deposits fig 1 the transition is characterized by a variety of landforms unknown on other planets the highlands and lowlands are in isostatic equilibrium across the transitional zone4 no generally accepted explanation for the cause of the highland lowland dichotomy has been proposed although thinning of the lithosph re in the northern hemisphere by internal processes has been suggested5 large impacts which were a feature of early solar system history have also been suggested as an important cause of such early planetary surface heterogeneities3 6 7 subcircular lowlands such as argyre chryse hellas and isidis planitia and the plains south of tharsis occupy previously recognized impact basins8 10 we propose here that the largest expanse of lowlands also results from formation of a large impact basin early in mars history that has profoundly shaped the planet s surface

the ediacaran sedimentary architecture and carbonate productivity in the atar cliffs adrar mauritania palaeoenvironments chemostratigraphy and diagenesis abstract the neoproterozoic strata of the taoudeni basin west african craton display a single glaciogenic deposit late cryogenian in age and included within a stratigraphic marker triad of tillite carbonate and bedded chert this work is focused on the analysis of the sedimentary architecture and episodic carbonate productivity related to its transgressive deglaciation recorded in the atar cliffs of adrar mauritania it offers a joint chemo event and sequence stratigraphic analysis that allows us to control problems of stratigraphic completeness and time resolution necessary for regional and worldwide stratigraphic correlation in the atar cliffs the cap carbonate sequence is underlain by a composite unconformity that comprises the pan african i discordance and an inherited palaeorelief associated with the glaciation the transgressive sequence began with accumulation of a sheet like apron onlapped by a toe of slope to basin transition with cap carbonates bedded cherts and distal turbidites tichilit el beida shales the carbonate strata of the atar cap carbonate sequence have recorded both dolomitization and dedolomitization processes destroying the original cement textures carbon isotope values from the sheet like apron range from 0 to 0 6 were directly controlled by the reworking of the underlying atar strata and do not reflect primary variations in seawater composition the general pattern of 13 c fluctuations within the overlying incomplete cap carbonate sequence is consistent with other post late cryogenian strata except in the initial shift from slightly to moderately negative values recognized elsewhere that is not preserved in the study area carbon isotope values in the preserved upper part of the cap carbonate record a pronounced rise in 13 c from 6 2 to highly enriched values 3 7 followed by the final demise of carbonate productivity the cap carbonate sequence is topped by an erosive unconformity succeeded by the recovery of carbonate accumulation represented by an onlapping dolostone deposited in coastal to foreshore environments there the carbon isotope values reflect the return to moderately negative values ranging from 0 9 to 2 0 the palaeogeographic development of a palaeorelief associated with the end of glacial conditions and deposition of the onlapping atar cap carbonate is related to the presence of interbedded felsic bentonites and phenocrysts and reflects the intermittent influence of a neighbouring explosive volcanism

no water no granites no oceans no continents water is essential for the formation of granite and granite in turn is essential for the formation of continents earth the only inner planet with abundant water is the only planet with granite and continents the moon and the other inner planets have little or no water and no granites or continents

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

a case study of the interaction of a mesoscale gravity wave with a mesoscale convective system abstractthis study documents the high amplitude mesoscale gravity wave mgw event of 7 march 2008 in which two mgws strongly impacted the sensible weather over a large portion of the southeast united states these mgws exhibited starkly contrasting character despite propagating within similar environments the primary i e long lived mgw was manifest by a solitary wave of depression associated with rapid sinking motion and adiabatic warming while the secondary short lived mgw was manifest by a solitary wave of elevation mgwel dominated by rising motion and moist adiabatic cooling genesis of the primary mgw occurred as a strong cold front arrived at the foot of mexico s high terrain and perturbed the appreciable overriding flow the resulting gravity wave became ducted in the presence of a low level frontal stable layer and caused surface pressure falls up to 4 hpa the mgw later amplified as it became coupled with a stratiform precipitation system which led to its evolution into an intense

mesoscale gravity waves and their environment in the central united states during storm fest abstract in an effort to better understand mesoscale gravity waves in winter storms in the central united states their frequency of occurrence wave characteristics the general conditions under which they occur and their effects upon the weather mesoscale surface and rawinsonde data as well as radar and satellite imagery collected during the storm scale operational and research meteorology fronts and experimental system test are analyzed in addition factors affecting the ability of objective surface map analysis to properly represent the waves are investigated thirteen coherent pressure pulse events with amplitudes of 0 2 4 0 mb and periods of 1 6 h were identified in the surface pressure data during the 6 weeks of the project involving 34 of the total hours investigated a variety of wave types occurred including wavelets wave trains and singular waves the three largest amplitude events were analyzed in detail using autospectral analysis and a barnes time to space conversion objective analysis

radioactive isotopes and trace elements in gaseous emissions from white island new zealand abstract measurements of the radioactivity of gases released by white island volcano show variations in 210 po concentrations with temperature in fumarolic gases and this is interpreted to be due to dilution of magmatic gases with vapours derived from an envelope of acid brines surrounding the vent system the degassing model derived for mount etna emissions is tested on white island magmatic gases the results are a short degassing time 2 days small degassing magma volume 5 10 6 m 3 and the following estimations of emanation coefficients pb 1 bi 2 7 cd 0 05 and cu 0 07 the initial content of s in the magma is estimated to be within the range 300 600 mg kg fluxes of trace metals kg day emitted by the volcano are estimated to be pb 125 bi 6 cu 300 and cd 9

cenozoic changes in atmospheric lead recorded in central pacific ferromanganese crusts the possible sources of pre anthropogenic pb contributed to the world s oceans have been the focus of considerable study the role of eolian dust versus riverine inputs has been of particular interest with better calibration of isotopic records from central pacific ferromanganese crusts using os isotope stratigraphy it now appears that deep water pb isotopic compositions were effectively homogeneous over a distance of 5000 km for the past 80 myr the composition shifted slightly from high 206pb 204pb ratios in the range of 18 87 0 02 before 65 ma to lower values of 18 62 0 02 by 45 ma and then gradually increased again very slightly to the present day ratio of 18 67 0 02 the regional homogeneity provides evidence of a dominant well mixed atmospheric source the most likely candidate for which is volcanic aerosols contributed either directly or as soluble condensates on eolian dust the slight shift in pb isotope composition of deep waters in the central pacific between 65 and 45 ma may be the result of a regional or perhaps global scale change in the sources of volcanic exhalations and volcanic activity caused by an increase in the importance of melting and assimilation of older continental crustal components over the cenozoic

carbon isotopes and the rise of atmospheric oxygen new data for the isotopic composition of carbon in carbonate sediments deposited between 2 6 and 1 6 ga indicate that the value of 13c in these sediments underwent a very large positive excursion between 2 22 and 2 06 ga a reassessment of the earlier 13c data for carbonate sediments shows that this excursion was probably worldwide and that it was preceded and followed by several hundred million years during which the 13c of carbonate sediments differed little from that of modern carbonates the large 13c excursion between 2 22 and 2 06 ga was probably related to an abnormally high rate of organic carbon deposition which generated an abnormally high rate of o2 production we estimate that the total excess o2 produced during the excursion was between 12 and 22 times the present atmospheric o2 inventory the 13c data therefore suggest that the o2 content of the atmosphere increased very significantly between 2 22 and 2 06 ga this inference is supported strongly by several other lines of evidence

influences of gravity waves on convectively induced turbulence cit a review thunderstorms are known to produce turbulence such turbulence is commonly referred to as convectively induced turbulence or cit and can be hazardous to aviation although this turbulence can occur both within and outside the convection out of cloud cit is particularly hazardous since it occurs in clear air and cannot be seen by eye or onboard radar furthermore due to its small scale and its ties to the underlying convection it is very difficult to forecast guidelines for out of cloud cit avoidance are available but they are oversimplified and can be misleading in the search for more appropriate and physically based avoidance guidelines considerable research has been conducted in recent years on the nature of the phenomenon and in particular its connection to gravity waves generated by the convection this paper reviews the advances in our understanding of out of cloud cit and its relation to convective gravity waves and provides several detailed examples of observed cases to elucidate some of the underlying dynamics

evidence of very large amplitude solitary waves in the atmosphere atmospheric solitary waves are gravity waves that retain their integrity over long periods because of a near balance between nonlinearity and dispersion they have been observed on various scales in many regions of the world1 3 but we present here detailed measurements of solitary waves with amplitudes comparable to the scale height of the lower troposphere two such waves were generated downstream of intense mid tropospheric pressure troughs over the central united states they propagated over 1 000km several times their wavelength with no appreciable change in structure within a waveguide formed by surface inversion and a middle tropospheric critical level fluctuations in surface pressure associated with the two waves exceeded 6 mbar and 10 mbar the waves caused banded patterns of precipitation and significantly influenced other meteorological phenomena the restoration of balance between pressure driven air flow and the coriolis force geostrophic adjustment seems to have a prominent role in the formation of these solitary waves

sulfide breakdown controls metal signature in volcanic gas at kawah ijen volcano indonesia abstract immiscible sulfide liquid is thought to be an important intermediary in volcanic degassing of sulfur and chalcophile elements by concentrating and transferring metals from magma to hydrous fluid here we track the interaction of sulfide liquid with a fluid exsolving from basalt at kawah ijen volcano in indonesia as in many other volcanic systems neither sulfide nor fluid is preserved instead the reaction is recorded in changes in metal and sulfur concentrations in the melt during magma ascent and shows a two stage evolution deep seated progressive breakdown of sulfide during which metal concentrations in the melt are largely controlled by the sulfide followed by fluid melt partitioning controlling metal concentrations at shallow depth once this sulfide has been exhausted present day fumarole gases have similar zn cu pb cu and mo cu ratios to the reconstructed sulfide but are enriched in tl as and sb these enrichments are also observed in melt inclusions in the most recent dacitic deposits at kawah ijen this suggests that the fumarole gases are sourced from a deep degassing sulfide saturated basalt preserved in zn cu pb cu and mo cu ratios which subsequently interact with a shallow dacitic melt that enhances tl as and sb emissions

origin of the martian global dichotomy by crustal thinning in the late noachian or early hesperian the marked dichotomy in topography surface age and crustal thickness between the northern lowland and southern upland of mars has been explained as due to an initially inhomogeneous crust a single mega impact event several overlapping large basin impacts and first order convective overturn of the martian mantle all of the published hypotheses propose that the dichotomy was formed early in martian history before the end of the primordial heavy bombardment a primordial origin is inherent in the initial crustal inhomogeneity hypothesis and required for both impact hypotheses endogenic hypotheses are not so constrained geological data indicate episodes of fracturing and faulting in the late noachian and the early hesperian this fracturing and faulting occurred primarily within the northern lowland and along the boundary between lowland and highland igneous activity also peaked in the late noachian and early hesperian these data suggest a tectonic event near the noachian hesperian boundary characterized by enhanced heat loss and extensive fracturing including formation of the faults that define much of the highland lowland boundary we argue that the major result of this tectonic event was formation of the dichotomy by thinning of the crust above a large convection cell or plume

did global tectonics drive early biosphere evolution carbon isotope record from 2 6 to 1 9 ga carbonates of western australian basins the 13 ccarb record of well preserved carbonates in outcrop and core is here examined from the 2 6 to 1 9 ga old basins of western australia these data which are constrained by a well defined stratigraphic and tectonic framework and by u pb zircon ages provide an insight into the variables coincident with the evolution of an oxidative atmosphere and the evolution of the early biosphere in the latest archaean ca 2 6 ga the secular 13 ccarb curve is flat much like that seen in the later palaeoproterozoic basins of northern australia 1 8 ga this implies that photosynthesis was a major component of the biosphere at that time and that the carbon mass balance was stable in the early palaeoproterozoic beginning after 2 5 ga and continuing until at least 1 9 ga the 13 ccarb the curve is much more dynamic with significant positive and negative excursions including a major positive excursion 9 pdb close to 2 2 ga these excursions can be correlated with the lomagundi event identified in africa europe and north america previously published studies of the overlying meso to palaeoproterozoic bangemall basin and of 1 8 1 5 ga old basins in northern australia suggest that the 13 ccarb curve became relatively monotonic again after ca 1 8 ga and remained so for most of the following mesoproterozoic comparisons with data from other ancient cratons especially africa suggest that the secular carbon curve may be even more complex than presently understood and probably comparable to the major excursions seen in the neoproterozoic when the western australian data are placed in their stratigraphic and tectonic framework we find that the monotonic latest archaean curve coincides with a tectonically quiescent period in which carbonates formed in an basinal setting on a craton surrounded by passive margins the data are consistent with an earth in which the carbon mass balance was in equilibrium the 13 ccarb curve began to oscillate following the onset of glaciation as the pilbara and yilgarn cratons began to converge during the capricorn orogeny suggesting periods of rapid carbon burial during continental dispersal however the major positive excursion is preserved in carbonates from back arc basins formed as the ocean closed and subduction began since similar tectonic processes can be recognised not only in northern australia but also on other early cratons it can be argued that the carbon excursions relate to supercontinent cycles and to major periods of mantle overturn and superplume development we explain this coincidence of carbon isotopic excursions

a billion years of environmental stability and the emergence of eukaryotes new data from northern australia carbon isotopes through 6km of fully cored drill holes in 1 7 to 1 5 ga carbonates of the mount isa and mcarthur basins australia which host the earliest known eukaryote biomarkers provide the most comprehensive and best dated delta 13c stratigraphy yet obtained from such ancient rocks both basins reveal remarkably stable temporal delta 13c trends mean of 0 6 2 pdb peedee belemnite and confirm the impression of delta 13c stasis between 2 0 and 1 0 ga which together with other evidence suggest a prolonged period of stability in crustal dynamics redox state of surface environments and planetary climate this delta 13c stasis is consistent with great stability in the carbon cycle controlled we suggest by p limitation of primary productivity recent evidence shows that p depletion is a major factor in obligate associations between photosymbionts and host cells we argue that a billion years of stability in the carbon and nutrient cycles may have been the driving force that propelled prokaryotes toward photosymbiosis and the emergence of the autotrophic eukaryote cell

a comment on tectonics and the future of terrestrial life theory and accumulating evidence suggest that mantle convection and plate tectonics facilitated the rise of molecular oxygen in earth s atmosphere through the burial of organic carbon mcculloch 1993 des marais 1994 and lindsay and brasier 2002

review of wave turbulence interactions in the stable atmospheric boundary layer flow in a stably stratified environment is characterized by anisotropic and intermittent turbulence and wavelike motions of varying amplitudes and periods understanding turbulence intermittency and wave turbulence interactions in a stably stratified flow remains a challenging issue in geosciences including planetary atmospheres and oceans the stable atmospheric boundary layer sabl commonly occurs when the ground surface is cooled by longwave radiation emission such as at night over land surfaces or even daytime over snow and ice surfaces and when warm air is advected over cold surfaces intermittent turbulence intensification in the sabl impacts human activities and weather variability yet it cannot be generated in state of the art numerical forecast models this failure is mainly due to a lack of understanding of the physical mechanisms for seemingly random turbulence generation in a stably stratified flow in which wave turbulence interaction is a potential mechanism for turbulence intermittency a workshop on wave turbulence interactions in the sabl addressed the current understanding and challenges of wave turbulence interactions and the role of wavelike motions in contributing to anisotropic and intermittent turbulence from the perspectives of theory observations and numerical parameterization there have been a number of reviews on waves and a few on turbulence in stably stratified flows but not much on wave turbulence interactions this review focuses on the nocturnal sabl however the discussions here on intermittent turbulence and wave turbulence interactions in stably stratified flows underscore important issues in stably stratified geophysical dynamics in general

a study of a mesoscale solitary wave in the atmosphere originating near a region of deep convection abstract an analysis of a mesoscale wave which occurred over the eastern united states on 6 march 1969 is presented its origin is attributed to the perturbation of a midtropospheric inversion by a squall line after the wave formed it propagated in the direction of the mid and upper level tropospheric flow and expanded as an arc with the center located near the region of convective activity the wave travelled from western tennessee and kentucky over a distance of more than 1000 kilometers to nova scotia with a mean speed of 55 m s 1 the event was quite obvious on surface barographs throughout this region pressure traces showed an obvious v shaped pressure drop of 3 to 6 mb over much of the wave path the wave persisted for about 9 hours with little change in character the synoptic situation is analysed and compared with similar atmospheric conditions in other studies the generation mechanism of an internal gravity wave of depression is investigated by a simple model it is found that wave of depre

martian plate tectonics the northern lowlands of mars may have been produced by plate tectonics preexisting old thick highland crust was subducted while seafloor spreading produced thin lowland crust during late noachian and early hesperian time in the preferred reconstruction a breakup margin extended north of cimmeria terra between daedalia planum and isidis planitia where the highland lowland transition is relatively simple south dipping subduction occurred beneath arabia terra and east dipping subduction beneath thatsis montes and tempe terra lineations associated with gordii dotsum are attributed to ridge parallel structures while phelegra montes and scandia colles are interpreted as transform parallel structures or ridge fault fault triple junction tracks other than for these few features there is little topographic roughness in the lowlands seafloor spreading if it occurred must have been relatively rapid quantitative estimates of spreading rate are obtained by considering the physics of seafloor spreading in the lower c 0 4 g gravity of mars the absence of vertical scarps from age differences across fracture zones and the smooth axial topography to the first order the height of vertical scarps across fracture zones does not involve gravity crustal thickness at a given potential temperature in the mantle source region scales inversely with gravity thus the velocity of the rough smooth transition for axial topography also scales inversely with gravity plate reorganizations where young crust becomes difficult to subduct are another constraint on spreading age possible plate reorganizations for example the end of spreading through alba patera occur when the ridge axis is far from the trench that is rapid plate motions are inferred to have placed young oceanic crust far from the ridge axis the preferred full spreading rate 900 from the plate pole is 80 mm yr 1 plate tectonics if it occurred dominated the thermal and stress history of the planet a geochemical implication is that the lower gravity of mars allows deeper hydrothermal circulation through cracks and hence more hydration of oceanic crust so that more water is easily subducted than on the earth age and structural relationships from photogeology as well as median wavelength gravity anomalies across the now dead breakup and subduction margins are the data most likely to test and modify hypotheses about mars plate tectonics

source strength assessment of volcanic trace elements emitted from the indonesian arc abstract we have for the first time estimated volcanic emission of volatile metals for a large regional volcanic source showing permanent activity namely the indonesian arc we have done this by normalizing concentrations of metals ratios in volcanic plumes to so 2 emission rates metal so 2 ratios measured in magmatic gases are used to estimate emissions from eruptive activity whereas those measured in fumarolic gases are used to estimate emissions from non eruptive activity the so 2 emission rate obtained is 3 5 10 6 tons per year which represents about 20 of the annual worldwide volcanic flux of so 2 the obtained trace metal 210 po pb bi cd zn and cu fluxes account for only about 5 to 30 of their global volcanic flux these relatively low values for trace metal emissions relative to the volcanic activity and the number of active volcanoes of the region appear to reflect the andesitic magma composition of the volcanoes of the arc

volatile heavy metal mobility in silicate liquids implications for volcanic degassing and eruption prediction abstract the volatilization of cd re tl pb sb and te from melts in the system cao mgo al 2 o 3 sio 2 cmas and na 2 o mgo al 2 o 3 sio 2 nmas has been investigated at 0 1 mpa and 1200 1350 c experiments were conducted in air using metal doped melts in pt crucibles analysis of quenched glasses by laser ablation inductively coupled plasma mass spectrometry la icp ms normal to the melt gas interface produced concentration profiles for cd re tl pb sb and te to which a semi infinite one dimensional diffusion model could be applied to extract diffusion coefficients d the melt was also doped with cu zn in mo sn and w but concentration profiles for these metals did not develop in the cmas composition at 1300 c the fastest diffusing element was cd having a log d cd 6 5 0 2 the slowest element was re with log d re 7 5 0 3 diffusivities of sb te pb and tl have intermediate values where log d sb 7 1 0 1 log d te 7 2 0 3 log d pb 7 1 0 2 log d tl 7 0 0 2 cm 2 s in the nmas composition log d re 6 5 0 2 log d sb 6 0 0 2 log d pb 6 1 0 1 log d tl 5 8 0 2 cm 2 s values for cd and te were not determined differences in diffusivity of volatile heavy metal ions to a melt gas interface lead to significant fractionation between these metals in magmas during degassing given the observed differences in cd and re diffusivities in the cmas composition we predict an increase in the normalized cd re ratio in the gas phase with increasing bubble growth rate monitoring of the cd re ratios in aerosols from degassing volcanoes may provide a tool for predicting volcanic eruption

mesoscale dynamics in the palm sunday tornado outbreak abstract radar and satellite imagery suggest that strong mesoscale forcing occurred in the palm sunday tornado outbreak on 27 march 1994 parallel lines of severe thunderstorms within each of three mesoscale convective systems developed just ahead of a cold front in mississippi and alabama on this date analyses of routine meteorological observations barograph data and forecasts from the eta and ngm models and a mesoscale research model mass are used to examine the relative roles of large scale dynamics and mesoscale processes in triggering and organizing the mesoscale convection quasigeostrophic forcing was absent in the outbreak region likewise a thermally direct circulation system transverse to the upper level jet that was present to the northwest of the outbreak region was decoupled from the strong low level ascent occurring in northern alabama and mississippi at the time of the outbreak strong ageostrophic frontogenesis in the presence of conditional symmetric instability csi was the chief

plate tectonics on mars last month it was reported that magnetometers on the mars global surveyor had identified lineated magnetic anomalies on mars the discovery of such anomalies on the earth s seafloor in the 1960s was explained by continental drift the suggestion that plate tectonics might be occurring on mars was entirely unexpected

a study of cyclone mesoscale structure with emphasis on a large amplitude inertia gravity wave abstract an analysis is presented of prominent mesoscale structure in a moderately intense cyclone with emphasis on a long lived large amplitude inertia gravity wave igw that moved through the northeastern united states on 4 january 1994 available national weather service wsr 88d doppler radar and wind profiler observations are employed to illustrate the rich time dependent three dimensional structure of the igw as the igw amplified peak crest to trough pressure falls exceeded 13 hpa 30 min 1 it also accelerated away from the cyclone reaching a peak forward speed of 35 40 m s 1 across eastern new england the igw was one of three prominent mesoscale features associated with the cyclone the others being a weak offshore precursor warm frontal wave and an onshore band of heavy snow snow bomb in which peak hourly snowfalls of 10 15 cm were observed none of these three prominent mesoscale features were well forecast by existing operational prediction models particularly with regard to preci

volatility of se and te during subduction related distillation and the geochemistry of epithermal ores of the western united states subduction partial melting of mantle and magma generation and ultimately magma degassing can lead to the preferential mobilization of volatile elements and compounds research indicates that devolatilization reactions in a subducted slab can cause the overlying mantle to be enriched in volatile ore forming constituents water co2 sulfur metal loid s this process of mantle enrichment plays an important role in subsequent magma generation and initiation of ore genesis furthermore the relative volatility of metal loid s appears to play a role in the ultimate geochemistry of shallow epithermal epizonal hydrothermal ores in the western united states for example there is a general west to east geographic zonation of tertiary ores from se rich to te rich it is proposed that this geographic geochemical zonation is the direct result of the higher geochemical volatility of se as compared to te previously au ag te se hg as sb and tl have been referred to as the epithermal suite of elements it is suggested here that their geochemical cycles are linked by their similar volatile behavior through subduction partial melting in the mantle and subsequent magma degassing processes essentially specific tectonomagmatic events that affected the western united states e g oligocene eocene magmatism in the great basin and southern rocky mountains mid miocene magmatism associated with the inception of the yellowstone hotspot in the pacific northwest were distillation events that drove devolatilization of fertile mantle after the laramide shallow slab event furthermore the metal loid volatility behavior likely occurs in other regions affected by subduction and may play a fundamental role in the metal endowment of these regions

fractionation of metals in volcanic emissions abstract the enrichment of some metals al mg na k cu zn cd in volcanic gases is measured by an emanation coefficient ex relating the amount of the element x in lavas and in aerosols ex is determined in the volcanic emissions of mount etna sicily with regard to that of210pb the accuracy of the results is limited by the geochemical behavior of common lead compared to that of210pb concerning the most volatile species it appears that practically all the volcanic aerosols are produced by evaporation followed by gas to particle conversion and the spattered fraction appears to be negligible

pb o and c isotopes in silicified mooidraai dolomite transvaal supergroup south africa implications for the composition of paleoproterozoic seawater and dating the increase of oxygen in the precambrian atmosphere abstract the mooidraai dolomite formation is a unit of marine sedimentary carbonates in the upper transvaal supergroup which recorded significant changes in the composition of the earth s atmosphere and ocean previously available data had suggested that this dolomite was about 2 2 ga old and showed 13ccarb values around 0 8 pdb and hence was an exception to the positive excursion of 13ccarb values observed worldwide in marine carbonates deposited between 2 25 and 2 05 ga ago we studied the pb o c isotope systematics of drill core samples from a highly silicified and aluminosilicate free sub unit of the mooidraai dolomite formation that yields well preserved micritic dolomite grains selective leaching of the silicified dolomite revealed a significant pb isotopic contrast between the carbonate and the quartz fraction the former shows only a narrow range of 208pb 204pb 35 35 35 58 which does not correlate with 206pb 204pb indicating the absence of th derived detrital pb the carbonate bound pb defines an isochron that corresponds to an age of 2394 26 ma 2 mswd 1 8 n 22 which we interpret as the diagenetic age of the mooidraai dolomite the 13ccarb values range from 0 51 to 0 64 pdb and confirm the previous data the 18ocarb values range from 2 08 to 0 18 pdb and are amongst the heaviest reported yet from early precambrian marine sedimentary carbonates the quartz fraction is considerably lighter than the carbonate fraction and shows 18oqtz values between 9 22 and 6 73 pdb 21 40 and 23 97 smow together with evidence from fluid inclusion microthermometry suggesting that the quartz formed at minimum temperatures between 130 and 155 c this indicates that the intense silicification was post depositional comparison of 18ocarb values of silicified and non silicified mooidraai samples suggests that the post depositional silicification had sealed the system and thereby protected the primary isotopic compositions of the micritic dolomite the heavy 18ocarb values suggest that 2 4 ga ago the oxygen isotopic composition of seawater differed only little from that of today the new pb pb carbonate age for the mooidraai dolomite indicates that the upper transvaal supergroup is about 200 my older than previously thought this explains the normal carbon isotopic composition of the mooidraai dolomite and suggests that the pronounced increase of the oxygen content in the precambrian earth s atmosphere that is seen in strata underneath the mooidraai dolomite occurred before 2 4 ga ago on this background it appears unlikely that the positive excursion of the carbon isotopic ratios of 2 25 2 05 ga old marine sedimentary carbonates is related to this increase in atmospheric oxygen

eruption of basalt and andesite lava degasses 222rn and 210po activities of 222rn and 210po were measured in a september 1983 basic andesite lava from arenal and a november 1983 basalt from kilauea starting 3 and 1 days after eruption respectively in both cases in growth patterns show that all rn volatalized during eruption po degassing also was complete at kilauea but only 84 10 at arenal

origin evolution and finescale structure of the st valentine s day mesoscale gravity wave observed during storm fest part iii gravity wave genesis and the role of evaporation abstract on 14 february 1992 a long lived moderate amplitude mesoscale gravity wave formed in kansas during the storm scale operational and research meteorology fronts experiment systems test storm fest wave formation was evident in correlated surface pressure and wind fields the wave of depression accompanied by a weak rainband tracked across the state a wealth of data was collected on the mature wave as it passed over the storm fest dual doppler domain however the mechanism of genesis remained difficult to ascertain since wave formation occurred in a region of less comprehensive observations the genesis of the storm fest gravity wave is successfully simulated using the fifth generation pennsylvania state university national center for atmospheric research penn state ncar mesoscale model mm5 which was run at 6 km grid spacing in the innermost domain the lee cyclone movement dry airmass development and gravity wave formation over kansas were successfully captured by the model results

large impact basins and the mega impact origin for the crustal dichotomy on mars the origin of the fundamental crustal dichotomy on mars remains the outstanding unsolved problem in martian geologic evolution the hypothesis that this dichotomy is due to a single giant mega impact early in martian history is tested by comparing the observed number of large impact basins on mars with the number expected from a d 2 distribution this test is based on the assumption that the mega impact borealis basin is the largest member of such a distribution the difference between observed and expected basins is the number of missing basins that might have been obscured by subsequent geologic events if the borealis basin were the largest member of a d 2 impact population there would be a very large number of missing basins on mars 1 larger than 5000 km 10 larger than 2000 km and 40 50 larger than about 1000 km diameter the area occupied by these missing basins allowing for overlap is too large to be hidden by the younger surface units a large population of presently unrecognized large impact basins would have to be located in the well preserved cratered highlands by contrast if chryse is the largest member of a d 2 impact population the more modest number of missing basins could in principle be confined to areas of mars that have been resurfaced or reworked by subsequent geologic processes a possible alternative to the mega impact hypothesis is that the crustal dichotomy is due to the cumulative effects of multiple overlapping large but not giant impacts

volcanic emission of radionuclides and magma dynamics 210pb 210bi and210po the last decay products of the238u series are highly enriched in volcanic plumes relative to the magma composition moreover this enrichment varies over time and from volcano to volcano a model is proposed to describe 8 years of measurements of mt etna gaseous emissions the lead and bismuth coefficients of partition between gaseous and condensed phases in the magma are determined by comparing their concentrations in lava flows and condensated volatiles in the case of volatile radionuclides an escaping time is calculated which appears to be related to the volcanic activity finally it is shown that that magma which is degassing can already be partly degassed it should be considered as a mixture of a few to 50 of deep non degassed magma with a well degassed superficial magma cell

variability of alkali and heavy metal fluxes released by mt etna volcano sicily between 1991 and 1995 abstract we regularly collected volcanic gases and aerosols at mt etna volcano over a long period 1991 1995 and measured their chemical composition by icp ms based on these data we present new evidence on the high volatility of both alkali and some heavy metals in contrast both lanthanides and actinides are not produced as significant gaseous compounds at magmatic temperatures and can be used as tracers of spattered materials all metals of each chemical family maintained systematic trends during the study period at both summit craters and effusive vents located in the valle del bove during the 1991 1993 eruption during the eruption we observed high metal enrichments at effusive vents these enrichments seem to be characteristic of the secondary degassing of a magma previously degassed under the summit area lower metal enrichments are recorded in aerosols sampled in summit crater plumes according to the primary degassing type occurring at these vents while a primary degassing type still occurs at both bocca nuova and voragine during the post eruptive period sud est crater exhibits a transition from primary to secondary type according to the variations of the volcanic activity level we confirm that the alkali metals fractionate systematically within their family as they cross the melt vapour interface the heavier members being always more enriched than the lighter ones in aerosols we also show that this fractionation is not related to the volcanic activity and the degassing type but seems to be a significant feature of the alkali family itself estimation of new emanation coefficients for rubidium caesium tin and thallium 0 07 0 15 0 50 and 21 respectively yields annual outputs around 1000 t yr 60 t yr 240 t yr and 1600 t yr respectively mount etna is a very important source of metals injected into the atmosphere contributing to the global volcanic budget about 16 for heavy metals and 19 for alkali metals in eruptive periods and only 2 and 4 respectively in quiet periods

degassing of metals and metalloids from erupting seamount and mid ocean ridge volcanoes observations and predictions recently it has been reported that the element polonium degasses from mid ocean ridge and seamount volcanoes during eruptions published and new observations on other volatile metal and metalloid elements can also be interpreted as indicating significant degassing of magmatic vapors during submarine eruptions this process potentially plays an important role in the net transfer of chemical elements from erupting volcanoes to seawater in addition to that arising from sea floor hydrothermal systems in this paper a framework is constructed for predicting and assessing semiquantitatively the potential magnitude and chemical fingerprints in the water column of metal and metalloid degassing using 1 predictions from a summary of element volatilities during mafic subaerial volcanism worldwide and 2 limited data from submarine volcanic effusives the latter include analyses of polonium and trace metals in near volcano water masses sampled following a submarine eruption at loihi seamount hawaii 1000 m bsl in 1996 the element volatility predictions and observations show good agreement considering the limited dataset some of the highest volatility main group and transition element enrichments in seawater over loihi are predicted by the degassing mass transfer model i present when expanded to cover all submarine volcanic activity it is predicted that exit fluxes of these elements are up to 102 103 greater by degassing than by normal mor hydrothermalism in contrast mor exit fluxes of low volatility alkali and alkaline earth elements are likely 102 106 greater from hydrothermal inputs degassing inputs to the ocean are probably highly episodic occurring almost entirely during eruptions these are times of enhanced and abnormal hydrothermalism as well although major hydrothermal and degassing events may not be chemically recognizable in real water masses as wholly distinct entities it is nevertheless possible to predict to what extent each process flavors the effluents of the other degassing at mid ocean ridges may explain a variety of observations previously ascribed to complexities occurring during hydrothermal venting and or fluid ascent in the buoyant hydrothermal plumes above ridges

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