atmospheric sulfur dioxide measurements during the 2005 and 2007 eruptions of the piton de la fournaise volcano implications for human health and environmental changes abstract piton de la fournaise is an active volcano located in the south eastern part of reunion island a tiny island found in the south western indian ocean 21 s 55 5 e this volcano erupts regularly at least once a year with notable amount of degassing concerning the volcanic eruptions the regulation of the french ministry of environment on the air quality is mainly focussed on the standards applicable for the sulfur dioxide so 2 in terms of public health and environmental changes air samples have been collected continuously every 10 days on passive diffusion tubes of so 2 an atmospheric tracer of volcanic plumes by ora observatoire reunionnais de l air at 10 sites which have been located around the volcano since september 2005 the mean so 2 concentrations measured over a 10 day period in the absence of any volcanic eruption range between very low values 1 15 g m 3 for all 10 sites however during the december 2005 eruption notable so 2 concentrations factor 5 25 have been measured at the locations situated on the north west flanks of the volcano the so 2 degassing reached concentrations of 65 379 g m 3 which is mainly caused by the volcanic activity when coupled with the local to regional atmospheric circulations land sea breezes easterlies etc a wide range of atmospheric measurements was performed in the vicinity of piton de la fournaise in order to characterize the gaseous and particle emissions during the april may 2007 eruption so 2 concentrations were also measured continuously by sf 2000 analyser at several coastal locations in the vicinity of the volcano during and off eruption activities in the absence of any volcanic eruption the so 2 concentrations showed day to day variations with hourly mean concentrations varying between 1 and 20 g m 3 these values correspond to the background concentrations for this coastal rural location and might as well come in part from non volcanic origin the so 2 concentrations however were increased by a factor 10 30 with a maximum hourly mean concentration of 2486 g m 3 during the april may 2007 eruption hereby several statutory thresholds were exceeded particularly at the tremblet location indeed the information and recommendation threshold 350 g m 3 h as well as the alert threshold 500 g m 3 on 3 h consecutively were exceeded 32 and 5 times respectively at this site these measurements point out that during the times of eruptions with significant amounts of degassing the threshold values for protecting the ecosystems and the air quality for human health were exceeded at several inhabited locations with implications for human health and environmental changes on local to regional scale

numerical models of lithospheric deformation forming the southern alps of new zealand compression of the entire continental lithosphere is considered using two dimensional numerical models in order to study the influence of the lithospheric mantle on the geometry of continental collision in its initial stages the models are based on the central section of new zealand southern alps where continental collision has occurred along the alpine fault since about 7 ma they incorporate brittle elastic ductile rheology heat transfer surface processes and fault localisation the models are compared to the surface relief the gps convergence velocity the measured electrical conductivity and the geometry of the crustal root imaged from seismic velocity measurements the crustal deformation is characterized by localized uplift at the plate boundary alpine fault and by two secondary zones of faulting one is located about 60 to 80 km east of the alpine fault at the start of upper crust bending or tilting and the other is located about 100 to 130 km east of the alpine fault as a result from shear strain propagating to the surface through the ductile lower crust the observed asymmetric shape of the crustal root is best reproduced for a mantle lithosphere strength of the order of 200 mpa and an intermediate rate of strain softening a lower strength of the mantle lithosphere can produce symmetric thickening but provides an amplitude of the crustal root too small when compared to observations the observed 20 km offset between the maximum in surface relief and the crustal root was not satisfactorily reproduced this offset is most likely due to the three dimensionality of oblique collision in new zealand southern alps

hydrothermal source of radiogenic sr to himalayan rivers 1 k 1 and cl 2 all of which are high in the hydrothermal waters cation concentrations decrease along the lesser himalayan reach of the river hot spring dissolved co2 has a d 13 c value to 15 9 indicating that metamorphic decarbonation reactions contribute co2 to the fluids hydrothermal co2 is partially neutralized in high temperature weathering reactions which generate alkalinity and yield abundant radiogenic sr radiogenic hydrothermal carbonate can form from these solutions and later weather releasing silicate sr but imparting carbonate characteristics to the overall water chemistry

strontium hydrothermal systems and steady state chemical weathering in active mountain belts abstract hydrothermal systems are a common feature of active collisional orogens these systems can have a profound effect on the sr fluxes and sr isotopic composition of riverine waters through the direct input of sr from hot springs and groundwaters and the chemical weathering of hydrothermal calcite in an effort to quantify the role of calcite weathering we present an analytical model that examines the relationship between rock uplift and steady state chemical weathering of granites and greywackes that contain trace amounts we compare model results with sr fluxes and isotopic composition of riverine waters from the southern alps of new zealand an area that is frequently used as an example of a steady state collisional orogen as our model predicts roughly 50 of sr flux is from the weathering of calcite in the areas of highest uplift along the west flank of the southern alps this proportion decreases substantially

have volcanoes already passed their zenith influencing the ozone layer earth s ozone layer is only a very small part of the atmosphere but its intact abundance is most important to the vitality of human beings observations have shown that especially after the plinian eruption of pinatubo volcano in 1991 the ozone layer showed a dramatic depletion could a similar hypothetic eruption in the future cause an equal effective destruction of ozone while considering the increasing reduction of man made halogens in the stratosphere after the montreal protocol in 1987

fluid generation and pathways beneath an active compressional orogen the new zealand southern alps inferred from magnetotelluric data 1 forty one wideband magnetotelluric mt soundings were collected in a 150 km long transect across the southern alps of the central south island of new zealand an active compressional orogen decomposed mt impedance tensors vertical magnetic field relations and reconnaissance soundings at two locations off line imply an approximately two dimensional geometry here with average regional geoelectric strike of n40 e similar to surface geologic trends two independent two dimensional inversion algorithms were applied to the mt data and both imply a concave upward u shaped middle to lower crustal conductive zone beneath the west central portion of the island the average conductivity of this zone in the strike direction appears to be much higher than that required across strike and may represent anisotropy or along strike conductive strands narrower than the transverse magnetic cross strike mode mt data can resolve the deep crustal conductor under the southern alps is interpreted to represent mainly a volume of fluids arising from prograde metamorphism within a thickening crust fluid interconnection and electrical conduction are promoted by shear deformation the conductor rises northwestward toward the trace of the alpine fault but attains a near vertical configuration at a depth of 10 km and reaches close to the surface 5 10 km inland of the fault trace itself the transition to vertical orientation at this depth is interpreted to occur as fluids ascend across the brittle ductile transition in uplifting schist and approach the surface through induced hydrofractures the high grade schist becomes resistive after depletion of fluids and continues to extrude toward the alpine fault shallow extensions of the deep high conductivity are coincident with modern hydrothermal veining and gold mineralization interpreted to be of deep crustal provenance to the southeast high conductivity also reaches the surface coincident with a major back thrust fault zone of the doubly vergent southern alps orogen which also exhibits evidence for expulsion of high temperature fluids the higher conductivity inferred along strike possible anisotropy could reflect more efficient fluid interconnection in this higher strain direction as well as possible contributions by sheared fluid deposited graphite conductivity of the uppermost mantle of the south island is low consistent with advection of cold mantle lithosphere into the underlying asthenosphere as suggested by p wave delay studies

deformation monitoring of the ostler fault zone south island new zealand abstract the ostler fault zone is a zone of quaternary reverse faulting along the western margin of the mackenzie basin south island new zealand during investigations for and construction of the ohau a power project a number of survey patterns were designed and installed to monitor ground deformation in the area of the fault zone a triangulation network two long and two short levelling routes and six tilt levelling patterns have been installed at various times since 1964 analysis of the levelling data shows that vertical deformation has occurred within the ault zone at a near constant rate for the last 20 years deformation consists of buckling about fault traces at a maximum rate of uplift of approximately 1 mm yr the vertical deformation preserved over 16 000 25 000 yrs has a similar rate although it is dominated by displacement across the fault zone as a whole analysis of triangulation data spanning up to 100 years indicates that significant horizontal strain is occurring with the axis of relative contraction approximately perpendicular to the trend of the fault

combined effect of carbonate and biotite dissolution in landslides biases silicate weathering proxies abstract long term estimates of the dissolution of silicate rock are generally derived from a range of isotopic proxies such as the radiogenic strontium isotope ratio 87 sr 86 sr which are preserved in sediment archives for these systems to fairly represent silicate weathering the changes in isotopic ratios in terrestrial surface waters should correspond to changes in the overall silicate dissolution this assumes that the silicate mineral phases that act as sources of a given isotope dissolve at a rate that is proportional to the overall silicate weathering bedrock landsliding exhumes large quantities of fresh rock for weathering in transient storage and rapid weathering in these deposits is controlled primarily by dissolution of the most reactive phases in this study we test the hypothesis that preferential weathering of these labile minerals can decouple the dissolution of strontium sources from the actual silicate weathering rates in the rapidly eroding western southern alps wsa of new zealand we find that rapid dissolution of relatively radiogenic calcite and biotite in landslides leads to high local fluxes in strontium with isotopic ratios that offer no clear discrimination between sources these higher fluxes of radiogenic strontium are in contrast to silicate weathering rates in landslides that are not systematically elevated on a mountain belt scale radiogenic strontium fluxes are not coupled to volumes of recent landslides in large 100 km 2 catchments but silicate weathering fluxes are such decoupling is likely due first to the broad variability in the strontium content of carbonate minerals and second to the combination of radiogenic strontium released from both biotite and carbonate in recent landslides this study supports previous work suggesting the limited utility of strontium isotopes as a system to study silicate weathering in the wsa crucially however in settings where bedrock landsliding is a dominant erosive process there is potential for both random and systematic bias in isotope proxies if the most reactive phases exposed for dissolution by landslides disproportionately contribute to the proxy of choice this clearly suggests that the isotopic composition of marine sr is a proxy for periods of rapid mountain uplift and erosion rather than for the associated enhanced silicate weathering

late metamorphic veins record deep ingression of meteoric water a la icpms fluid inclusion study from the fold and thrust belt of the rhenish massif germany abstract the fluid evolution of late metamorphic quartz vein systems in the fold and thrust belt of the rhenish massif has been studied by microthermometry and la icpms microanalysis the quartz veins are hosted by very low grade organic matter rich metasiltstones and metapelites of the hunsruck nappe complex the veins record two major stages of textural evolution a massive vein filling assemblage with elongate blocky quartz chlorite albite and apatite and a later open space filling assemblage with euhedral crystals of quartz ankerite dolomite and minor calcite and sulfides the euhedral quartz crystals host well preserved fluid inclusion assemblages which made it possible to reconstruct the chemical evolution of the fluid system with time the fluid inclusions are all aqueous two phase with low salinity and three successive fluid generations record a systematic decrease in salinity from 4 7 5 3 to 3 1 3 9 and then to 1 4 1 7 wt eqv nacl the salinity decrease is paralleled by a decrease in homogenization temperatures from 210 225 c to 148 164 c and 124 139 c using la icpms microanalysis of individual fluid inclusions reproducible elemental concentrations of li na k rb cs mg ca ba sr b al as sb s cl and br could be determined the concentrations of the alkali metals and of boron arsenic and antimony are correlated with the fluid salinity element concentrations are highest in the early fluid generation and decrease systematically in the latter two generations the systematic changes in fluid composition salinity homogenization temperature and elemental concentrations are best explained by fluid mixing between a hot metamorphic fluid of moderate salinity that carried elevated concentrations of b as and sb and a cooler dilute fluid that was of meteoric origin the fluid evolution therefore signals deep ingression of meteoric water during late metamorphic exhumation and uplift the molar cl br ratios of the fluid inclusions lie on a linear array that extends from close to seawater to values that are substantially below seawater because evaporitic sources are conspicuously absent in the shallow water marine sequence of the rhenish massif the elevated br concentrations and cl br ratios below seawater are best explained by fluid rock interaction and liberation of br from the organic matter in the metasediments

recent advances in modeling swash zone dynamics influence of surf swash interaction on nearshore hydrodynamics and morphodynamics the role of the swash zone in influencing the whole nearshore dynamics is reviewed with a focus on the interaction between surf and swash zone processes local and global hydromorphodynamic phenomena are discussed in detail and a description of the overall swash zone operation is given the effects of swash zone boundary conditions are highlighted together with the importance of surf zone boundary conditions major emphasis is placed on illustrating the interactions of various hydrodynamic modes which in turn control the swash and surf zone morphology finally methods to account for swash zone processes in coastal models with different temporal and spatial resolutions are proposed

characteristics and origin of the major authigenic minerals and their impacts on reservoir quality in the permian wutonggou formation of fukang sag junggar basin western china abstract this research is focused on the characteristics and origin of major authigenic minerals and the influences on the reservoir quality of the permian wutonggou formation sandstones in the eastern slope of fukang sag junggar basin western china authigenic cements were observed and described from thin sections scanning electron microscopy fluorescence and cathodoluminescence the elemental concentrations of the authigenic minerals were measured by electron probe microanalysis additional characterizations were obtained from o and c stable isotope ratios and from the homogenization temperature of aqueous fluid inclusions the results show that the sandstones in the wutonggou formation are dominated by volcanic lithic fragments carbonates and laumontites are the major authigenic minerals in the study area authigenic quartz and kaolinite can also be observed two types of carbonate cements are identified the first type is calcite with yellow fluorescent hydrocarbon inclusions the carbon and oxygen isotopes in the calcites are highly c depleted and o depleted the homogenization temperatures of the aqueous fluid inclusions in the calcite cements are higher than the highest paleogeotemperatures during the burial history combined with the presence of authigenic fibrous illites and the illitization of kaolinites it is determined that the precipitation of the calcites is related to the upwelling of deep fluids and was impacted by the co 2 from the thermal decarboxylation of organic matters during the middle late jurassic the second type is ferroan calcite with blue fluorescent hydrocarbon inclusions and higher contents of fe mn cr and mg than in the calcites the ferroan calcites in the beisantai uplift are rich in 13 c 13 c v pdb values are 22 10 and 22 16 the precipitation of these ferroan calcites was impacted by the co 2 from crude oil biodegradation after the late jurassic two types of laumontites are identified the first type is partially dissolved and is characterized by a high ca na ratio and low fe contents the second type is hardly dissolved has hydrocarbon inclusions with yellow and blue fluorescence and is characterized by a low ca na ratio and high fe contents the first type of laumontite was precipitated prior to hydrocarbon charging and the second type was formed after hydrocarbon charging and meteoric water leaching the hydration of the volcanic debris provided the source materials for both types of laumontite the authigenic quartz and kaolinite were formed by the alteration of feldspars laumontites and volcanic materials the evolution of the reservoir properties was impacted by various degrees of cementation and dissolution as a result the reservoir quality in the beisantai uplift was better than in the shaqiu area

the influence of swash based reflection on surf zone hydrodynamics a wave by wave approach abstract a detailed understanding of the behaviour of waves in the nearshore is essential for coastal engineers as these waves cause beach erosion coastal flooding and damage to coastal structures significantly the influence of reflected waves is often neglected in surf zone studies although they are known to influence wave properties and circulation in the nearshore in this paper a phase resolving model is rigorously applied to model conditions from the prototype scale bardexii experiment in order to examine and assess the influence of swash based reflection on surf zone hydrodynamics at both the individual wave and time averaged timescales surface elevation is separated into incoming and outgoing signals using the radon transform and a crest tracking algorithm is used to extract incident and reflected wave properties it is found that on steep beaches tan 1 9 the swash based reflection the reflection generated in the swash during the backwash contributes significantly to the intrawave variability of individual wave properties such as the wave height to water depth ratio through the generation of quasi nodes antinodes system for expressed with individual wave heights variations up to 25 and 40 are obtained for the modelled regular and irregular wave tests whereas it reaches 15 when it is based on the significant wave height the outgoing wave field induced hydrodynamics is also found to affect time averaged parameters undertow and horizontal velocity skewness the undertow is mainly strengthened particularly in the shoaling region where the outgoing component dominates over the contribution from the incoming wave field offshore of the bar an onshore directed flow streaming close to the bed is also generated under the outgoing wave field and is suspected to help in stabilising the bar position this along with the influence of the outgoing wave field on the horizontal velocity skewness and the presence of quasi standing waves suggests a complex contribution of the hydrodynamics induced by swash based reflection into sediment transport rates and nearshore bar generation migration

observations and predictions of fluid velocities in the surf and swash zones 1 surfzone and swashzone water level fluctuations and cross shore fluid velocities observed at seven cross shore locations for 139 51 min periods on a low sloped fine grained sandy beach are shown to be modeled well by the depth averaged nonlinear shallow water equations the model initialized with observations about 150 m from the shoreline in 300 cm water depth accurately predicts the observed decrease in sea swell wave heights and orbital velocities with decreasing water depth across the surf zone and the observed maxima in infragravity orbital velocities and offshore directed mean flows near the outer edge of the swash zone in the surf zone both the observed and predicted velocity fluctuations are dominated by sawtoothed shaped pitched forward asymmetrical sea swell waves in the swash zone infragravity waves contribute substantially to the total velocity variance and asymmetry shoreward of the outer swash zone observed and predicted total and infragravity velocity asymmetry decrease onshore changing sign from positive to negative in the upper swash

wave setup and runup an integrated approach abstract by extending and sharpening the usual definitions of water depth and mean water level throughout the swash zone it is shown that the elevation of the shore line on an impermeable beach is logically at the runup limit not at the average water line level thus the runup limit becomes a point on the setup profile and this leads to a significant expansion of the experimental information on setup which can be extracted from the existing literature from the experimental data base thus extended a first approximation to a universal description of setup profiles is derived i e the most appropriate vertical and horizontal scaling parameters are suggested for the shape of the mean water surface in the inner surf zone existing setup data show that traditional simplistic setup models are inadequate for modelling the shape of the most landward part of the mean water surface and hence for predicting the shoreline setup instead it is suggested to base estimates of the shoreline setup on the relation between this quantity and the maximum runup height together with well proven runup formulae the validity of this approach needs to be established quantitatively however through simultaneous measurements of runup and mean water surface on in natural beaches

incursion of meteoric waters into the ductile regime in an active orogen rapid tectonic uplift on the alpine fault new zealand elevates topography regional geothermal gradients and the depth to the brittle ductile transition and drives fluid flow that influences deformation and mineralisation within the orogen oxygen and hydrogen stable isotopes fluid inclusion and fourier transform infrared ft ir analyses of quartz from veins which formed at a wide range of depths temperatures and deformation regimes identify fluid sources and the depth of penetration of meteoric waters most veins formed under brittle conditions and with isotope signatures 18oh2o 9 0 to 8 7 vsmow and d 73 to 45 vsmow indicative of progressively rock equilibrated meteoric waters two generations of quartz veins that post date mylonitic foliation but endured further ductile deformation and hence formation below the brittle to ductile transition zone 6 8 km depth preserve included hydrothermal fluids with d values between 84 and 52 indicating formation from meteoric waters ft ir analyses of these veins show no evidence of structural hydrogen release precluding this as a source of low d values in contrast the oxygen isotopic signal of these fluids has almost completely equilibrated with host rocks 18oh2o 2 3 to 8 7 these data show that meteoric waters dominate the fluid phase in the rocks and there is no stable isotopic requirement for the presence of metamorphic fluids during the precipitation of ductilely deformed quartz veins this requires the penetration during orogenesis of meteoric waters into and possibly below the brittle to ductile transition zone

divergent behavior of the swash zone in response to different foreshore slopes and nearshore states abstract ultrasonic distance sensors were used to measure changes in bed elevation to a resolution of 0 1 mm following individual swash excursions in the high tide swash zone of an intermediate foreshore changes in bed elevation are related to depth averaged eularian swash velocities estimated by assuming mass balance of the swash discharge also measured using the ultrasonic distance sensors early in the study may 21 25 2008 the alongshore uniform foreshore had a cross shore slope of 0 18 and was fronted by a nearshore bar that forced wave breaking at low tide towards the end of the study june 5 9 2008 the foreshore had a slope of 0 12 and was fronted by a nearshore terrace that developed as the innermost bar migrated landward despite similar inshore wave heights and periods during these times the steeper foreshore eroded by 0 69 m 3 m 1 while the more gently sloped foreshore accreted by 0 21 m 3 m 1 the divergent behavior of the swash zone is attributed to the welding of the innermost bar to the foreshore creating a shallow nearshore terrace that saturated the inshore wave field this in turn led to a faster uprush velocity that promoted the landward advection of sediment picked up over the shallow terrace it is argued that accretion in the upper swash zone was the result of a larger supply of sediment at the base of the foreshore and a transformation of the wave field by the shallower depths of the welded feature in this respect swash hydrodynamics and morphological change can only be made if the swash zone is considered within the context of the broader nearshore state

beach face and berm morphodynamics fronting a coastal lagoon this study documents two different modes of berm development i vertical growth at spring tides or following significant beach cut due to substantial swash overtopping and 2 horizontal progradation at neap tides through the formation of a proto berm located lower and further seaward of the principal berm concurrent high frequency measurements of bed elevation and the associated wave runup distribution reveal the details of each of these berm growth modes in mode i sediment is eroded from the inner surf and lower swash zone where swash interactions are prevalent the net transport of this sediment is landward only resulting in accretion onto the upper beach face and over the berm crest the final outcome is a steepening of the beach face gradient a change in the profile shape towards concave and rapid vertical and horizontal growth of the berm in mode 2 sediment is eroded from the lower two thirds of the active swash zone during the rising tide and is transported both landward and seaward on the falling tide sediment is eroded from the inner surf and transported landward to backfill the zone eroded on the rising tide the net result is relatively slow steepening of the beach face a change of the profile shape towards convex and horizontal progradation through the formation of a neap berm the primary factor determining which mode of berm growth occurs is the presence or absence of swash overtopping at the time of sediment accumulation on the beach face this depends on the current phase of the spring neap tide cycle the wave runup height and indirectly offshore wave conditions and the height of the pre existing berm a conceptual model for berm morphodynamics is presented based on sediment transport shape functions measured during the two modes of berm growth c 2006 elsevier b v all rights reserved

miocene 87sr 86sr ratios of ostracods in the northern qaidam basin ne tibetan plateau and links with regional provenance weathering and eolian input abstract late cenozoic changes in chemical weathering and the dust cycle in response to the regional aridification and global cooling in the tectonically active northern tibetan plateau is an intriguing issue although it remains poorly understood the change in the 87sr 86sr ratio of basin water is linked to variations in the overall input of various sr sources with different 87sr 86sr ratios and analyses of such changes can be a useful tool for revealing changes in regional lithology weathering regimes and the dust cycle linked to tectonics and climate in this study we collected fossil shells of ostracods and gastropods from the miocene dahonggou section to reconstruct the paleolake water 87sr 86sr ratio from 14 8 ma to 11 1 ma in the northern qaidam basin on the northeastern tibetan plateau the reconstructed paleolake water 87sr 86sr ratios based on fossil shells and bulk carbonates from sediments display a coincident and stable 87sr 86sr ratio of approximately 0 7115 which did not show any detectable change in response to the enhanced aridification since 13 ma as inferred by the ostracod assemblage and its stable carbon and oxygen isotopes the results indicate that the sr influx regime from various sources did not change significantly during the aridification processes 13 ma which may have been caused by a less detectable change in proportion of silicate versus carbonate weathering and or an overwhelming sr source e g extrabasinal eolian dust that occurred from 14 8 ma to 11 1 ma further the 87sr 86sr ratios of modern lake water and river sand carbonates in the study region are significantly higher approximately 0 001 than those of the miocene lake water this observation can be explained by two possible mechanisms that need to be tested in the future 1 given a miocene sr input regime that is similar to today a large contribution from some extrabasinal sr source e g eolian dust with a much lower 87sr 86sr ratio is expected to have prevailed from 14 8 ma to 11 1 ma but is absent in the modern setting or 2 given a miocene sr input regime that could yield an overall lower lake water 87sr 86sr ratio of approximately 0 7115 a significant increase in the 87sr 86sr ratio of catchment scale sr source may have occurred after 11 ma in response to the uplift of the qilian mountains which would have enhanced hydrothermal activity metamorphism glaciation and landslide processes thereby resulting in more radiogenic sr source our study suggests that reconstructions of river lake water 87sr 86sr ratios can place powerful constraints on the complex interactions among tectonics climate and landscape evolution in the northeastern tibetan plateau based on a new perspective

a reactive transport model for examining tectonic and climatic controls on chemical weathering and atmospheric co2 consumption in granitic regolith we developed a 1d reactive transport model for examining how tectonic and climatic parameters namely uplift rate water seepage velocity and temperature control chemical weathering and atmospheric co2 consumption rates during regolith development the model consists of mass conservation equations describing how mineral and solute concentrations change temporally and spatially vertically during weathering of granite containing 30 plagioclase an20 and up to 3 accessory calcite the equations are coupled by volumetric weathering rates which depend on mineral abundances intrinsic dissolution rate constants and surface areas as well as the departure of pore water from thermodynamic equilibrium we numerically solve a non steady state non dimensional version of the model by eliminating the need to prescribe regolith thickness non dimensionalization introduces two key scaling parameters that drive variations in the model results the rock residence time r the time for rock to travel upward through the model domain and the water residence time w the time for water to travel downward through the model domain we use the model to examine fundamental properties of chemical weathering especially reaction front propagation with the primary aim of characterizing weathering regimes and identifying factors that maximize the dissolution of plagioclase because only silicate weathering regulates atmospheric co2 levels over geological timescales weathering regimes are commonly classified as transport or supply limited versus weathering or kinetically limited but as outgrowths of geomorphology these terms primarily refer to the role of r in regulating regolith thickness our findings suggest that the paradigm should be expanded to include kinetic controls determined by w both regimes can experience far from and near equilibrium mineral dissolution however transport limited regimes generally have lower w r ratios compared to kinetically limited regimes under transport limitation thick to thin reaction fronts propagate downward indefinitely yielding extensive mineral depletion deeply weathered regolith and high ratios of silicate to carbonate weathering under kinetic limitation thin to non existent reaction fronts evolve to steady state yielding minimal mineral depletion no regolith development and low ratios of silicate to carbonate weathering kinetically limited regimes typifying tectonically active mountain ranges have low long term atmospheric co2 consumption rates transport limited regimes typifying tectonically stable cratons also have low long term atmospheric co2 consumption rates but because much of the earth s surface is transport limited we infer that such environments have the greatest impact on the global atmospheric co2 consumption flux the model output leads us to hypothesize that the maximum contribution should occur for extensive regions of silicate bedrock consolidated in warm wet climates because the combination of tectonic stability high temperatures and rapid seepage velocities accelerates reaction front propagation facilitates calcite depletion and sustains deep regolith development over long timescales our findings point to the importance of internal climate feedbacks for stabilizing long term atmospheric co2 levels

overview of hydrothermal activity associated with active orogenesis and metamorphism nanga parbat pakistan himalaya the nanga parbat massif is located in northwestern pakistan and occurs in the interior of the western syntaxis of the himalaya recent studies have shown that the massif exposes an active metamorphic anomaly developed in indian plate rocks exhumed from beneath and surrounded by rocks of the kohistan ladakh island arc geochemical and geophysical data from nanga parbat show that an active hydrothermal system exists within the massif in the upper 5 to 6 kilometers of the crust above a shallow brittle ductile transition constrained by microseismic data there is a shallow hydrothermal system with meteoric fluids channelized along active fault zones in contrast below the brittle ductile transition fluids are metamorphic in origin and restricted to unconnected packets along grain boundaries the shallow system is stratified with water rich fluid inclusions near the surface grading to vapor rich inclusions at the brittle ductile transition as evidenced from fluid inclusion studies these fluids are meteoric in origin and enter the massif along shear and fracture zones and exit the massif along the bordering fault zones evidence for these channelized meteoric fluids comes from stable isotopic values of minerals and rocks collected from fault zones that show that these rocks have interacted with meteoric fluids as well as magnetotelluric mt data that show that the fault zones are electrically conductive and embedded in very resistive rocks the deeper portions of the hydrothermal system consist of unconnected metamor phic fluids stable isotopic and fluid inclusion data show that fluids were present during the recent metamorphism but the rocks did not extensively interact with these fluids existence of an unconnected fluid system is supported by the mt studies showing that below the brittle ductile transition the rocks are relatively resistive values ranging from 1000 10 000 ohm m ruling out an interconnected fluid network seismic and mt data also show no evidence of a large magma body at depth we suggest that the type of hydrothermal system observed at nanga parbat can be an important feature of late stage orogenic evolution especially near the tectonically complex edges of orogens the tectonism in these areas exposes deep relatively dry rocks that have previously lost their volatile content during the earliest stages of tectonic thickening and metamorphism these relatively dry rocks are rapidly uplifted and exposed within the massifs where they interact with surface waters at high temperatures and shallow depths

the april 2007 eruption and the dolomieu crater collapse two major events at piton de la fournaise la reunion island indian ocean abstract after 10 years of high activity and 24 eruptions piton de la fournaise pdf produced on april 2 to may 1 2007 one of its most voluminous and intense eruption since at least one century the eruption focused at 590 m elevation in the grand brule on the south east flank of piton de la fournaise 7 km away from summit it was located close to the southern cliff of the grand brule volcano tectonic collapse the rempart du tremblet and to the nearby village called le tremblet and it highly rattled and incommoded the inhabitants there eleven hours after the beginning of the eruption the lava flows reached the sea and created 0 45 km 2 of new land until the end of eruption in the night of april 5 the rock column beneath dolomieu crater started to collapse with a piston like mechanism into the magma chamber forming within less than 24 h the most recent and well documented caldera we report in this paper the chronology of these two related major events in the recent activity of pdf seen by the scientific networks of the volcanological observatory ovpf ipgp and field observations which allowed to back up the scenario of the caldera formation and to quantify these two exceptional episodes

seismic monitoring and modeling of an active volcano for prediction we describe seismic monitoring and modeling of an active volcano for the purpose of predicting the magma transport process in real time we selected the piton de la fournaise which has been monitored by an observatory since the early 1980s and is active with 28 eruptions from 1980 until august 1992 it erupted on march 9 1998 after an unusually long quiet period the eruption lasted until september 21 1998 before the march eruption we completed the initial construction of a model of a magma system based primarily on long period lp events and coda localization we found that lp events are associated with the lateral movement of magma to the rift zone and not with the vertical movement to the summit we also found that the source of 2 hz lp events is located below that of 1 hz lp events the coda localization is a newly discovered phenomenon that helped to locate a magma body this model was used for interpreting the incoming information from the precursory seismic crisis and the eruption tremor during the 6 months of the eruption the simultaneous monitoring and modeling of an active volcano led us to a quantitative simulation of the eruption process computing excess pressure and flow rate in a system of reservoirs connected by channels

field observations of wave driven setdown and setup wave driven setdown and setup observed for 3 months on a cross shore transect between the shoreline and 5 m water depth on a barred beach are compared with a theoretical balance between cross shore gradients of the mean water level and the wave radiation stress the observed setdown the depression of the mean water level seaward of the surf zone is predicted well when radiation stress gradients are estimated from the observations using linear theory at each location along the transect the observed setdown also agrees with analytical predictions based on offshore wave observations and the assumption of linear dissipationless normally incident waves shoaling on alongshore homogeneous bathymetry the observed setup the superelevation of the mean water level owing to wave breaking is predicted accurately in the outer and middle surf zone but is increasingly underpredicted as the shoreline is approached similar to previous field studies setup at a fixed cross shore location increases with increasing offshore wave height and is sensitive to tidal fluctuations in the local water depth and to bathymetric changes numerical simulations and the observations suggest that setup near the shoreline depends on the bathymetry of the entire surf zone and increases with decreasing surf zone beach slope defined as the ratio of the surf zone averaged water depth to the surf zone width a new empirical formula for shoreline setup on nonplanar beaches incorporates this dependence

geochemistry of early carbonate cements in the cardium formation central alberta abstract authigenic minerals and diagenetic textures in the marine conglomerates and sandstones of the cretaceous cardium formation in the northeast pembina area preserve a complex sequence of diagenetic events textural relationships observed in thin section and under the scanning electron microscope were used to determine the relative timing of diagenetic events in these marine sediments paragenetic sequences are similar for the conglomerate sandstone and siderite nodules in the enclosing shales extensive cementation by siderite and calcite occurred early in the diagenetic history before any significant compaction the geometry and distribution of lithofacies in the cardium may have influenced the diagenesis and internal stratigraphy of the conglomerate overlying shale matrix conglomerate may have trapped upward migrating fluids increased in buoyancy by dissolved co2 produced by decay of organic matter in the enclosing shales these fluids could have infiltrated the upper portion of open matrix conglomerate causing cementation petrographic evidence shows alternating precipitation of siderite and pyrite implying fluctuating activities of dissolved carbonate and hydrogen sulfide probably caused by bacterially mediated processes during early diagenesis early sequences of siderite and pyrite precipitation can be related to zones of iron reduction sulfate reduction and possibly decarboxylation during diagenesis carbon and oxygen isotopic data indicate a systematic change in the isotopic compositions of calcite and siderite from 25 to 3013c and 018o for cements early in the paragenetic sequence to 0 to 513c and 15 18o for cements which are interpreted to occur later in the paragenetic sequence this observation is consiste t with the influence of meteoric water on later stages of cement deposition in the cardium a unit considered to be marine and deposited well offshore on a shallow marine shelf the intrusion of meteoric water far offshore may be related to changes in sea level many variables must be accounted for but it is feasible using the estimated regional dip of the cardium at the time of deposition 0 005 for a 1 m drop in sea level to push the freshwater seawater interface seaward on the order of 100 km

magma transport and storage at piton de la fournaise la reunion between 1972 and 2007 a review of geophysical and geochemical data abstract since the middle of the 20th century improvement in volcano monitoring techniques has provided large data sets that can be used to evaluate the evolution of magma plumbing systems at piton de la fournaise volcano abundant eruptive activity and a dense monitoring network are especially conducive to such research analysis of the extensive set of geophysical and geochemical data associated with the last 35 years of activity provides new insights into magma transport and storage at piton de la fournaise two periods of frequent eruptions separated by 6 years of inactivity can be distinguished 1972 1992 and 1998 2007 considering these two periods we show evidence of major changes in the shallow plumbing system in 2000 during 1972 1992 and 1998 2000 lava compositions and weak long term eruptive precursors lasting few days to three weeks characterized by no significant summit inflation and about ten volcano tectonic earthquakes per day suggest that eruptions were fed by the progressive drainage of an occasionally recharged shallow magma reservoir geophysical evidence of shallow magma reservoir recharge was only recorded in 1986 and 1998 in contrast from 2000 to 2007 geophysical data highlight the appearance of long term precursors 1 to 5 months of summit inflation and strong seismicity up to one hundred events per day preceding cycles of successive eruptions each cycle of eruptions was characterized by a sequence 3 to 10 months in duration of summit and near summit proximal eruptions and ended with a distal low altitude oceanite olivine abundances 20 vol eruption on the eastern flank of the volcano within each of these eruptive cycles lavas became progressively more magnesian over time the preferential motion of the eastern flank caused by continuous recharging of the shallow reservoir since 2000 would favour the occurrence of distal eruptions towards this flank at the end of a cycle

large runup controls on a gently sloping dissipative beach observations on a mildly sloping beach suggest that the largest runup events are related to bore bore capture bbc a numerical model based on the reynolds averaged navier stokes equation is implemented to evaluate the effects that bbc have on runup from simulations with realistic sea states bbc is found to be a necessary but not sufficient condition for large runup generation the dominant dynamics leading to bbc are amplitude dispersion and interactions with infragravity waves in the outer and inner surf zone respectively when the effects of bbc are isolated it is found that the runup associated with the merging of two bores is at least 50 larger than that associated with the larger of the two waves in a monochromatic wave train the phase difference of the incident waves with the infragravity wave can generate up to 30 variability of the runup maxima the majority of the shoreward directed momentum flux prior to runup initiation is related to the interaction between the bores and the infragravity wave followed by that of the incident infragravity waves alone

shallow level metamorphic fluids in a high uplift rat metamorphic belt alpine schist new zealand fluids some of which are co2 rich up to 40 mol co2 and some of which are highly saline up to 18 wt nacl equivalent are trapped as fluid inclusions in quartz calcite metallic minerals veins which cross cut the pumpellyite actinolite to amphibolite facies rocks of the alpine schist fluids were commonly trapped as immiscible liquid vapour mixes in quartz and calcite showing open space growth textures fluid entrapment occurred at fluid pressures near 500 bars possibly as low as 150 bars at temperatures ranging from 260 to 330 c saline fluids may have formed by partitioning of dissolved salts into an aqueous phase on segregation of immiscible fluids from a low density co2 rich fluid calcite deposited by these fluids has 13c ranging from 8 4 to 11 5 and 18o from 4 to 13 isotopic data fluid compositions and mode of occurrence suggest that the fluids are derived from high grade metamorphic rocks fluid interaction with wall rock has caused biotite crystallization and or recrystallization in some rocks and retrogression of biotite to chlorite in other rocks fluid penetration through the rock is almost pervasive in many areas where permeability probably related to alpine fault activity has focussed fluids on a regional scale into fractured rocks the fluid flow process is made possible by high uplift rates in excess of 10 mm year bringing hot rocks near to the surface

syn tectonic hematite growth in paleoproterozoic stirling range red beds albany fraser orogen australia evidence for oxidation during late stage orogenic uplift abstract the timing of hematite growth in ancient red colored sedimentary rocks red beds is controversial while most of the hematite is considered to have formed at or near the land surface shortly after deposition paleomagnetic evidence suggests that some hematite in ancient red beds formed long after deposition during orogenic fluid flow metamorphosed red sandstones and shales in the stirling range formation western australia were deposited in a shallow marine environment between 2 0 and 1 8 billion years ago the sandstones which preserve an assemblage of discoidal and trace like fossils are stained red by abundant fine grained hematite crystals the hematite is aligned in a spaced cleavage defined by elongate laths of muscovite and chlorite and its occurrence as inclusions in 1 2 ga metamorphic monazite indicates that the oxide formed during the 1 2 1 15 ga albany fraser orogeny 600 million years after deposition thermometry of two distinct populations of chlorite an earlier fe chlorite chl1 and a later mg chlorite chl2 indicates a cooling trend from 370 c chl1 to 290 c chl2 consistent with evidence for rapid late stage uplift elsewhere in the orogen the results indicate that most of the hematite in the stirling red beds formed during syn to late orogenic oxidation of previously more reduced marine sediments the migration of oxidizing fluids during orogenesis possibly related to rapid uplift and gravity driven influx of surface water could explain the origin of other post orogenic red beds

fluid acceleration effects on suspended sediment transport in the swash zone 1 suspended sediment concentrations and fluid velocities measured in the swash zone of a high energy steep beach were used to investigate the importance of fluid accelerations to suspended sediment transport swash flow acceleration was nearly constant at about one half downslope gravitational acceleration with two important exceptions we observed strong short lived periods of accelerating uprush at the beginning of the swash cycle and decelerating backwash at the end of the swash cycle magnitudes of both approximately twice that of the expected downslope gravitational acceleration interestingly spikes in suspended load followed the anomalies in acceleration in a way that was not apparent from the nearly symmetric in magnitude ensemble averaged velocity time series suspended load values were largest during accelerating uprush associated with the shoreward propagating turbulent bore or swash front during backwash suspended loads were generally not as large correspondingly suspended sediment transport rates obtained from the sediment concentration and velocity measurements showed best comparisons with a modified sediment transport model that includes a physical mechanism for enhancing transport rates due to flow acceleration the modified sediment transport model reduced the overall root mean square prediction error by up to 35 and shifted the predicted peak in uprush sediment transport rate earlier in the swash cycle resulting in a better fit to the observations these findings suggest that the inclusion of the acceleration term may account for physical mechanisms that include bore turbulence and horizontal pressure gradients typically associated with the accelerating portion of uprush

airborne measurements of particle and gas emissions from the december 1994 january 1995 eruption of popocatepetl volcano mexico abstract airborne and ground based correlation spectrometer cascade impactor and photoelectric counter together with intake filter probes measurements are described for the volcanic emissions from popocatepetl volcano mexico from december 23 1994 to january 28 1995 measurements of so 2 restarted 48 h after the eruption onset of december 21 1994 maximum sulfur dioxide 4560 t d 1 plus 3 8 10 4 t d 1 of particulate matter were ejected on december 24 1994 the maximum rate of ejection occurred coincidentally with the maximum amplitude of harmonic tremor and the maximum number of seismic type b events sulfur dioxide emission rates ranged from 1790 to 2070 t d 1 december 23 24 1994 afterwards sulfur dioxide emission rates clearly indicated a consistent decline however frequent gas and ash emission puffs exhibited so 2 fluxes reaching values as high as 3060 t d 1 the emission so 2 baseline for the period of study february 1994 january 1995 was about 1000 t d 1 ejection velocity of particulate matter was approximately 270 m s 1 reaching a height of about 2 5 km over the summit the immediate aerosol dispersion area was estimated at 6 0 10 4 km 2 maximum the microscopic structure of particles aerosol and tephra showed a fragile material probably coming from weathered crustal layers x ray fluorescence and neutron activation analysis from the impactor samples found the following elements si al ca s p cl k ni fe ti sc cu zn mn sr cr co y br se ga rb hg and pb morphological analysis shows that ash samples might be from pulverized basaltic rock indicating that the popocatepetl eruption of december 21 1994 was at low temperature the microscopic structure of puff material showed substance aggregates consisted of fragile rock water and adsorbed so 2 these aggregates were observed within water droplets of approximately 1 mm and even larger sulfur transformations in the droplets occurred intensively volcanic ash contained 5 6 of sulfur during the first expulsion hours elemental relative concentrations with respect to al show that both si and s have relative concentrations 1 i e 13 73 and 2 17 respectively in agreement with the photoelectric counter and cospec measurements

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

eulerian flow velocities in the swash zone field data and model predictions measurements of eulerian flow velocity obtained within the swash zone on a relatively steep beach face gradient 1 23 are compared with an extended ballistic swash model the model only requires a friction factor beach slope and terminal bore velocity as input the following model predictions matched well with observations 1 the maximum eulerian flow velocity is the shoreline velocity when it arrives at the fixed point of interest on the beach face 2 at any location the time of flow reversal occurs prior to the shoreline reaching its maximum landward excursion 3 the maximum flow velocity in the backwash is the velocity recorded as the shoreline recedes past the fixed point of interest and this is less than the maximum uprush velocity and 4 the duration of the uprush flow is shorter than the duration of the backwash flow previous studies have already confirmed that the ballistic swash model including friction can accurately predict shoreline motion and maximum run up on steep beaches this study shows that it is similarly successful in predicting eulerian flow velocities during individual swash events the model does not presently account for interacting swash however and so may be less appropriate on gently sloping beaches

the gold conveyor belt large scale gold mobility in an active orogen the southern alps of new zealand are part of an active collisional orogen where metamorphism hydrothermal fluid flow and the formation of orogenic gold deposits are ongoing the southern alps are forming due to transpressional collision between continental crust fragments on the pacific and australian tectonic plates the plate tectonic rates and geometries the sources of fluid and broad scale fluid pathways in the hydrogeological system and the geochemical compositions of the torlesse terrane rock that is being advected through the orogen are well defined so that a mass balance of metal mobility during active orogenic processing in the southern alps of new zealand can be calculated advection of a 10 km wide x 5 km deep section of torlesse rock through the orogen at tectonic rates 0 01 m yr that is then metamorphosed up to amphibolite facies causes mobilisation of over 1127 t au 10 1mt as 47000 t hg 560000 t sb and 14000 mt h2o in 1 myrs the masses of elements mobilised at the same rate along the length of the southern alps 200 km for 5 myrs would be more than 100 times greater the metals were mobilised by the metamorphic fluid produced during the orogenic processing of the torlesse terrane rocks and the concentrations of au as hg and sb in this fluid are calculated to be 0 08 711 3 and 40 mg kg respectively the mobilised metals form the orogenic gold deposits that occur in the southern alps different styles of gold deposits form contemporaneously during the active orogenesis of the southern alps including those with a fluid temperature rock temperature that may appear have formed after the peak of metamorphism but are instead just the product hydrothermal fluid mineralising rocks on their retrograde metamorphic path the mass balance shows that there has been orders of magnitude more metal mobilised in the orogen than resides in the currently known deposits there is clear potential for large gold deposits occurring in the yet to be uplifted parts of the southern alps if there have been efficient enough fluid focussing and metal precipitation mechanisms occurring under the southern alps

hydrothermal arsenic enrichment in an active mountain belt southern alps new zealand abstract torlesse terrane greywackes and hydrothermal calcite associated with active fault systems in the main divide fault zone of new zealand s south island exhibit anomalous as concentrations relative to background values of similar rock types mass balance analysis of greywacke compositional data from the upper wilberforce valley of the main divide region demonstrate an average mass gain of as on the order of a factor of 6 above typical torlesse greywackes wilberforce mean 35 3 ppm 31 3 ppm n 44 torlesse mean 5 6 ppm 4 4 n 31 in addition hydride generated icp ms analyses of the weak acid soluble fraction of individual calcite rich veins and fault gouges in the main divide fault zone exhibit as concentrations mean 81 2 ppm 113 ppm n 17 in excess of a factor of 100 over hydrothermal calcite from other fault systems mean 1 7 ppm 4 0 n 29 stable isotopic analyses of these calcite veins show a wide range for both oxygen 18o 9 9 to 25 6 and carbon 13c 12 to 1 1 this observation suggests that the hydrothermal fluid source of these veins was of a mixed meteoric and highly exchanged fluid over a wide range of temperatures we suggest that the presence of high as concentrations in young hydrothermal calcite veins in the main divide region results from active transport of as rich deep crustal fluids upward along the fault zone this interpretation is consistent with both fluid flow tectonic models and geophysical observations which suggest that expansion in the main divide fault zone provides a conduit for the escape of deep exchanged fluids into the upper crust

geological controls on palaeo environmental change in a tectonic rain shadow southern new zealand abstract this study is a multidisciplinary synthesis that quantifies the geological processes that control surface palaeo environmental change and the associated biota in an evolving pliocene quaternary orographic rain shadow south island of new zealand the processes are relevant to evolution of older and more complex rain shadows of the andes western north america and the himalaya local rain shadow aridification can be distinguished from global climate change using asymmetry of stable isotope signatures across a steep orographic mountain rainfall gradient with 18 o and d values as low as 13 and 95 respectively salination in the rain shadow results from evaporative concentration of marine aerosols on impermeable rocks with only minor water rock interaction and a distinct flora has developed on these sites natural coal fires burning in excess of 1000 c contributed to maintenance of savannah environments uplift of fold mountains especially in the quaternary has maintained salination sites and their flora as well as lignites for coal fires with these environments progressively migrating laterally at 1 10 m thousand years numerous river capture events accompanied quaternary mountain uplift in the driest part of the rain shadow because of low erosion rates and these have facilitated radiation of freshwater galaxiid fish into nine sister species whereas an adjacent region with less complex tectonics and topography has only one species from that lineage the combination of tectonic uplift and rain shadow aridification has two main effects on the surface environment a topographic evolution and biological evolution are occurring at similar rates and growth of mountains has facilitated fish speciation b mountain uplift causes local environmental rejuvenation so that salination and local coal fires and the biological effects of these phenomena are maintained over long time scales by lateral migration

chemical and physical weathering in new zealand s southern alps monitored by bedload sediment major element composition abstract the haast and clutha rivers drain opposing flanks of new zealand s southern alps major element analyses of grain size fractions 2 1 mm 1 mm 355 m 355 63 m and 2 o 5 concentrations in all river sediment suggests that most cao is bound in a combination of phosphate bearing minerals such as apatite along with other heavy mineral phases with similar hydrodynamic properties e g epidote chemical index of alteration cia values for grain size fractions from both rivers are similar haast 54 63 clutha 49 61 and do not systematically vary with grain size or sample location al 2 o 3 cao na 2 o k 2 o a cn k relationships suggest that cia values are controlled by albite muscovite mixing rather than feldspar weathering both a cn k relationships and modal mineralogical calculations from clutha river samples indicate progressive downstream attrition of muscovite from coarser to finer grain size fractions in contrast haast river sediments display less variable normative muscovite concentrations and no downstream enrichment depletion trends the haast and clutha watersheds have drastically different sediment yields but the similarity of sediments from both rivers indicates that there is minimal climatic control on the weathering intensity of fluvial sediments rather bedload geochemistry is controlled primarily by mechanical breakdown of lithic fragments and subsequent preferential attrition of muscovite albite quartz the geochemical signature of mechanical attrition and hydrodynamic winnowing is more developed in clutha river samples because of longer sediment residence time within its fluvial system these findings suggest that high standing island hsi fluvial sedimentary evolution is characterized by the dominance of physical weathering processes and the absence of silicate chemical weathering signatures

three dimensional critical wedges tectonics and topography in oblique collisional orogens in orogens deforming in oblique compression both the long wavelength mean topography of averaged slopes and the higher frequency topography first harmonic of valleys and ridges are related to the mechanics of deformation in three dimensions and cannot be adequately modeled in two dimensions a method of analysis of the principal stresses failure planes and topography is presented for three dimensional critical wedges in a critical coulomb orogen which is at failure throughout the components of the stress tensor are interrelated through the failure condition defined in terms of the principal stresses variation of any of the cartesian components must be accommodated by adjustment of one or more of the other components so that the orogen remains at failure this coupling of cartesian components to maintain the wedge at failure permits exploration of the behavior of a three dimensional critical orogen in which shear stresses arise outside of the plane of convergence internal adjustment of shear stresses to externally imposed stress conditions results in the formation of characteristic orogen shapes for an oblique collision zone such as the southern alps of new zealand the resultant mountain belt is one of an obliquely deforming outboard fold thrust belt with subdued relief rising abruptly into a steep backslope to the main divide which falls steeply to the indentor forming the inboard slope the outboard topographic slope is reduced in relation to that of the two dimensional orogen the rigid indentor has a fixed strike and therefore imposes a failure orientation adjacent to the indentor that differs from that of the ideal three dimensional critical wedge solution this produces several different slip orientations and minor partitioning of strain near the indentor first harmonic topography of valleys and ridges arises due to nonlinear heterogeneous behavior of both erosional and mechanical processes and is characterized by uplift controlled ridges in the outboard and incision controlled valleys in the inboard

stable isotope geochemistry and formation mechanisms of quartz veins extreme paleoaltitudes of the central alps in the neogene quartzveins ranging in size from less than 50 cm length and 5 cm width to greater than 10 m in length and 5 m in width are found throughout the central swiss alps in some cases the veins are completely filled with milky quartz while in others sometimes spectacular void filling quartz crystals are found the style of vein filling and size is controlled by host rock composition and deformation history temperatures of vein formation estimated using stable isotope thermometry and mineral equilibria cover a range of 450 c down to 150 c vein formation started at 18 to 20 ma and continued for over 10 my the oxygen isotope values of quartz veins range from 10 to 20 permil and in almost all cases are equal to those of the hosting lithology the strongly rock buffered veins imply a low fluid rock ratio and minimal fluid flow in order to explain massive nearly monomineralic quartz formation without exceptionally large fluid fluxes a mechanism of differential pressure and silica diffusion combined with pressure solution is proposed for early vein formation fluid inclusions and hydrous minerals in late formed veins have extremely low d values consistent with meteoric water infiltration the change from rock buffered static fluid to infiltration from above can be explained in terms of changes in the large scale deformation style occurring between 20 and 15 ma the rapid cooling of the central alps identified in previous studies may be explained in part by infiltration of cold meteoric waters along fracture systems down to depths of 10 km or more an average water flux of 0 15 cm3 cm 2yr 1 entering the rock and reemerging heated by 40 c is sufficient to cool rock at 10 km depth by 100 c in 5 million years the very negative d values of

on the use of the radon transform in studying nearshore wave dynamics in the nearshore describing the complex individual wave dynamics remains a key challenge in this paper we test the ability of the radon transform to produce estimates of individual wave celerities and to separate incoming and outgoing waves conserving the temporal characteristics the radon transform is a projection of a two dimensional field into polar space oblique features such as propagating crests in a spatio temporal space are identified with density peaks in the polar space in this paper the radon transform is applied to synthetic test cases including a wide range of beach slopes and wave conditions the radon transform shows good skills at estimating individual celerity and separating incoming and outgoing components with a relative rms error lower than 10 even a standing wave node the accuracy is fairly insensitive to wave characteristics whereas the main limitations rise from the sampling scheme and are the number and density of wave gauges the distance between gauges should be less than one third of the shortest wavelength while the set of gauges should cover more than one third of the longest wavelength

tales of volcanoes and el nino southern oscillations with the oxygen isotope anomaly of sulfate aerosol the ability of sulfate aerosols to reflect solar radiation and simultaneously act as cloud condensation nuclei renders them central players in the global climate system the oxidation of s iv compounds and their transport as stable s vi in the earth s system are intricately linked to planetary scale processes and precise characterization of the overall process requires a detailed understanding of the linkage between climate dynamics and the chemistry leading to the product sulfate this paper reports a high resolution 22 y 1980 2002 record of the oxygen triple isotopic composition of sulfate so4 aerosols retrieved from a snow pit at the south pole observed variation in the o isotopic anomaly of so4 aerosol is linked to the ozone variation in the tropical upper troposphere lower stratosphere via the ozone el nino southern oscillations enso index oei higher 17o values 3 3 4 5 and 4 2 were observed during the three largest enso events of the past 2 decades volcanic events inject significant quantities of so4 aerosol into the stratosphere which are known to affect enso strength by modulating stratospheric ozone levels oei 6 and 17o 3 3 oei 11 and 17o 4 5 and normal oxidative pathways our high resolution data indicated that 17o of sulfate aerosols can record extreme phases of naturally occurring climate cycles such as ensos which couple variations in the ozone levels in the atmosphere and the hydrosphere via temperature driven changes in relative humidity levels a longer term higher resolution oxygen triple isotope analysis of sulfate aerosols from ice cores encompassing more enso periods is required to reconstruct paleo enso events and paleotropical ozone variations

early evolution of a stratospheric volcanic eruption cloud as observed with toms and avhrr this paper is a detailed study of remote sensing data from the total ozone mapping spectrometer toms and the advanced very high resolution radiometer avhrr satellite detectors of the 1982 eruption of el chichon mexico the volcanic cloud atmosphere interactions in the first four days of this eruption were investigated by combining ultraviolet retrievals to estimate the mass of sulfur dioxide in the volcanic cloud krueger et al 1995 with thermal infrared retrievals of the size optical depth and mass of fine grained 1 10 m radius volcanic ash wen and rose 1994 our study provides the first direct evidence of gravitational separation of ash from a stratospheric gas rich plinian eruption column and documents the marked differences in residence times of volcanic ash and sulfur dioxide in volcanic clouds the eruption column reached as high as 32 km carey and sigurdsson 1986 and was injected into an atmosphere with a strong wind shear which allowed for an observation of the separation of sulfur dioxide and volcanic ash the upper more sulfur dioxide rich part of the cloud was transported to the west in the stratosphere while the fine grained ash traveled to the south in the troposphere the mass of sulfur dioxide released was estimated at 7 1 109 kg with the mass decreasing by approximately 4 1 day after the peak the mass of fine grained volcanic ash detected was estimated at 6 5 109 kg amounting to about 0 7 of the estimated mass of the ash which fell out in the mapped ash blanket close to the volcano over the following days 98 of this remaining fine ash was removed from the volcanic cloud and the effective radius of ash in the volcanic cloud decreased from about 8 m to about 4 m

nearshore wave height variation in unsaturated surf the nearshore evolution of wave height is presented from field observations during unsaturated surf conditions from 10 different beaches characterized by microtidal conditions and predominantly swell dominated wave climates wave evolution is presented in terms of wave height to water depth ratio gamma for comparison with previous data from saturated surf both conventional time averaged gamma rms and a new wave by wave analysis gamma w are performed values of gamma increase with increasing offshore wave height indicating unsaturated surf the observations show a variation in gamma values from near constant values in the mid surf zone to rapidly and asymptotically increasing gamma values in the inner surf zone in contrast to previous data from saturated surf gamma shows no dependence on either the absolute beach slope or the relative beach slope beta k h over bar the skewness of the distributions of gamma w is consistent with waves that are not depth limited the inner surf zone wave heights are approximately equally dependent on the water depth and offshore wave height the previous observations of gamma from saturated surf are shown to be consistent with a terminal bore height at the shoreline which is in excellent agreement with a previously derived value for the miche parameter in contrast for the present unsaturated surf conditions the terminal bore height at the shoreline can be approximated by h b approximate to 0 12h o which is consistent with recent laboratory data sets

tectonically driven fluid flow and gold mineralisation in active collisional orogenic belts comparison between new zealand and western himalaya abstract hydrothermal activity and mesothermal styled gold mineralisation occurs near the main topographic divide of most active or young collisional mountain belts the southern alps of new zealand is used in this study as a model for the mineralising processes the collisional tectonics results in a two sided wedge shaped orogen into which rock is transported horizontally upper crustal rocks pass through the orogen and leave the orogen by erosion whereas lower crustal rocks are deformed into the mountain roots high relief drives meteoric water flow to near the brittle ductile transition lower to upper greenschist facies metamorphic reactions driven by deformation at the crustal decollement and in the root release water rich fluids that rise through the orogen intimate chemical interaction between fluid and rock results in dissolution and later precipitation of gold arsenic and sulphur fluid flow and mineralisation in the topographic divide region is facilitated by a network of steeply dipping faults and associated rock damage zones where oblique strike slip faults intersect the thrust faults that strike subparallel to the main mountain range the nanga parbat massif of the western himalaya is an example of an active collisional zone which hosts hydrothermal activity but no gold mineralisation the lack of gold mineralisation is due to the following factors co 2 dominated rising metamorphic fluid in dehydrated amphibolite granulite facies metamorphic rocks does not dissolve gold and arsenic hot up to 400 c meteoric water confined to fractures in the gneiss limits dissolution of gold and arsenic low density of hot water dry steam and low reduced sulphur content of fluid restrict solubility of gold and arsenic absence of fracture networks in the core of the massif and the small volumes of circulating fluid limit metal concentration and lack of reactive rock compositions limits chemically mediated metal deposition

evolution of fluid driving forces and composition within collisional orogens subaerial collisional mountain belts have a predictable asymmetric two sided wedge geometry the major driving forces for crustal fluid flow in this framework arc thermal and topographic gradients it is possible to predict both a time averaged fluid state and the evolution of the fluid regime during orogenesis with three distinct fluid flow regimes the outboard toe where material is incorporated into the orogen a transitional zone of concentrated deformation and a zone of rapid exhumation along the inboard slope adjacent to the indentor as rocks move into the outboard wedge relatively low temperature compaction and head driven fluid flow dominates mid crustal material undergoes disequilibrium dehydration as rock fluid packets move into the transition zone producing a dominantly aqueous metamorphic fluid in the inboard region rapid uplift produces geothermal gradients in excess of 80 c km which encourage vigorous free convection advecting fluids evolve through immiscibility towards increasing co2 content during uplift of the rock fluid packets mixing of thermally driven and head driven fluids occurs at depths of 5 10 km the southern alps of new zealand the european alps and the himalaya represent variants of this orogenic hydrothermal system

gold mineralization as a consequence of continental collision an example from the southern alps new zealand abstract formation of gold quartz veins within the alpine schist near the alpine fault was synchronous with uplift the temperature of vein formation was greater than 320 c at a depth of 4 5 km vein precipitation was due to dilution and cooling of metamorphic metal bearing fluids by cooler less saline meteoric fluids numerical modeling of the topographic and thermal processes associated with continental collision has identified the time and space scales necessary for the generation of the geochemical conditions which resulted in vein genesis a predictable topographic pattern of 1500 m high ridges normal to the plate boundary leading to the main divide is established within the first 500 ka of uplift producing the head driven flow patterns of meteoric circulation the high thermal inertia of a rapidly uplifted region provides the thermal driving force leading to buoyancy driven convection of metamorphic fluids when the geothermal gradient is in excess of 50 c km using boundary conditions derived from the southern alps elevation of temperatures to 300 c at 5 km occurs after 1 8 ma of uplift at which time gold formation may occur if the intersection of head and buoyancy driven fluids lies within greenschist facies rocks further uplift causes erosion of the greenschist facies rocks together with the gold deposits adjacent to the fault and migration of the loci of mineralization further into the uplifting block the results of the examination of the southern alps gold regions are extended to other phanerozoic and archean deposits which are spatially related to major fault zones the characteristic topographic and thermal behavior of major collisional zones provides the driving forces necessary for gold mineralization to occur in the absence of any igneous heat source

diagenesis of fossiliferous concretions from the upper cretaceous fox hills formation north dakota abstract three fossiliferous concretions of the fox hills formation upper cretaceous of north dakota display similar diagenetic histories petrographic and geochemical data from each concretion have yielded the following diagenetic sequence 1 bioturbation by marine benthos 2 partial phosphatization of glauconite fecal pellets and shell material 3 sulfate reduction and pyrite formation 4 siderite precipitation 5 radial fibrous calcite precipitation and 6 equant calcite precipitation although the occurrence of open marine faunas and glauconite indicates that concretion sediments were deposited under marine conditions geochemical data suggest that marine pore fluids were replaced by brackish and meteoric water as the fox hills formation is part of a regressive marginal marine equence it is likely that the transition from marine to freshwater is recorded in concretion paragenesis early diagenetic minerals indicate oxidation of organic matter at shallow burial depths under normal marine conditions locally reducing conditions produced initially by degradation of molluscan soft parts and later by degradation of organic material in crustacean and annelid fecal pellets occurred at shallow burial depths alteration of iron silicates glauconite produced pore fluids enriched in fe2 due to the abundance of reactive organic matter subsequent reduction of marine sulfate yielded a small amount of disseminated pyrite following the removal of h2s elevated fe2 ph and bicarbonate concentrations soon exceeded siderite saturation and siderite was precipitated elevated ca and mg compositions and marine 18o values of siderite cements indicate that pore fluids were essentially reduced marine fluids depleted 13c values suggest that siderite precipitated in an environment dominated by the oxidation of organic matter isotopic compositions from the earliest and latest carbonate phases constrain intermediate phases and allow comparison of environments of precipitation carbon and oxygen isotopic data from skeletal aragonite provide an estimate of the isotopic composition of marine carbonate the latest phase of equant calcite cement is characterized by invariant 18o coupled with highly variable and light 13c this characteristic isotopic signature and occurrence in overlying fluvial sediments suggests a meteoricphreatic origin for equant spars isotopic values of radial fibrous calcite lie between those of marine aragonite siderite and freshwater equant calcite ph ses and represent a complex mixing of marine and meteoric pore fluids the paragenetic sequence of carbonate cements records a gradual decrease in ambient fluid mg fe and mn content during shallow burial such decreases are consistent with the influx of oxidizing meteoric fluids

swash zone boundary conditions derived from optical remote sensing of swash zone flow patterns 1 optical remote sensing is used to measure flow patterns in the swash zone timestack images are analyzed to measure the asymmetry and the relative duration of the inflow into the swash zone this varies significantly between individual swashes contrary to the classical analytical swash model for runup induced by bores which predicts a similar flow pattern for all events for swash forced by breaking bores the gradient of the x t locus of flow reversal varies over a wide range and flow reversal can occur simultaneously across the whole swash zone this variation of the gradient of the locus of flow reversal in x t space can be parameterized in terms of a single free variable in recent solutions to the nonlinear shallow water equations which fully defines the swash boundary inflow condition consistent with the theory the horizontal runup the swash period and the swash similarity parameter were observed to be independent of the swash inflow conditions but the flow asymmetry is not only a weak correlation was observed between the swash boundary condition and the iribarren number and beach slope conversely the analysis suggests that the degree of swash swash interaction does influence the swash boundary condition and the resulting internal flow kinematics the variation in inflow conditions is expected to influence the magnitudes of the velocity moments within the swash zone and therefore sediment transport rates

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

a citizen science approach for monitoring volcanic emissions and promoting volcanic hazard awareness at sulphur springs saint lucia in the lesser antilles arc abstract sulphur springs park ssp saint lucia in the lesser antilles is a popular geothermal area with a vigorous passively degassing hydrothermal field visitors staff and management of the park have raised concerns about the volcanic emissions and their possible effects on their health as part of the responsibility of the university of the west indies seismic research centre uwi src to provide volcanic surveillance through its geothermal monitoring programme a monitoring network was established for quantifying the ambient so2 concentrations at the park to assess the potential risk of unsafe exposure this required the development of a participatory citizen science effort with researchers training local personnel in field sampling and basic analytical techniques to measure so2 concentrations the operation of a citizen science network required engagement and collaboration with local stakeholders in saint lucia to ensure that the research addressed the needs of all partners this participatory approach was an effective option for scientists to engage local stakeholders and the wider community as partners in geoscience hazards education ambient so2 concentrations obtained with handmade active air samplers titrimetric hydrogen peroxide traps showed that when the atmospheric concentrations of so2 was lower the data from the diffusion tubes and the handmade samplers followed a similar pattern the ambient concentrations measured using the handmade samplers cannot be used as absolute values due to uncertainties related to the input parameters needed for the calculation of so2 concentrations however the data may be useful in identifying areas exposed to elevated so2 concentrations of potential concern to public health the samplers proved useful as a tool to promote volcanic hazard awareness and education among the local stakeholders and citizen scientists important lessons learned by the research team from participant surveys were that time constraints and personal motivation of volunteers are key factors in the success of the operations of this monitoring network

stable isotopic evidence for mixing between metamorphic fluids and surface derived waters during recent uplift of the southern alps new zealand recent studies have shown that the southern alps of new zealand have active hydrothermal systems driven by tectonic uplift these studies have concentrated on the rapidly exhumed rocks immediately adjacent to the alpine fault we present new stable isotopic evidence that shows that fluid flow and fluid mixing processes thought to be restricted to rocks near the alpine fault also occurred in the low uplift rate region of the southern alps orogen during the kaikouran orogeny 10 ma to present low 18ocalcite values of post metamorphic veins in the eastern southern alps indicate that meteoric waters have penetrated to hot midcrustal levels 350 300 c 5 km depth and mixed with metamorphic fluids in areas far removed from the alpine fault in addition the isotopic values of calcites precipitated in active faults in the mackenzie basin define a trend of increasing 18o decreasing 13c and decreasing temperature and form an isotopic mixing line between fault and vein calcites crosscutting metamorphic rocks and authigenic calcites precipitated in mackenzie basin sediments the isotope data indicate a second phase of mixing between a modified metamorphic fluid and a surficial diagenetic fluid at shallow depths we suggest that mixed metamorphic meteoric hydrothermal systems have developed in the east side of the southern alps during uplift and that active faults have played a critical role in transporting metamorphic fluids outward from the mountain front and into the adjacent intermontane basins

uplifted marine terraces along the alpine fault new zealand three types of evidence indicate that marine terraces are widespread in the southern alps of new zealand i remnants of shore platforms occur as distinct levels of notched ridge crests and flat summits degraded sea cliffs are common ii scattered quartz beach pebbles occur on 16 of 18 levels of exhumed shore platforms in the fox franz josef type area to altitudes as high as 1700 meters iii altitudinal spacings of new zealand terrace flights allow correlation with 18 dated global marine terraces at new guinea which were formed during glacio eustatic highstands of sea level within the last 336 x 10 3 years inferred uplift rates at fox franz josef increased from 3 2 to 7 8 meters per 10 3 years since about 135 x 10 3 to 140 x 10 3 years ago presumably because of increased convergence between the pacific and australian plates

in situ measurements of gas discharges across fissures associated with lava flows at reunion island abstract analysis of gases accumulating at a shallow depth below the ground surface can indicate the presence of fractures and other gas migration routes a technique for sampling and analysis of a range of gases is described which is fast and mobile and can be applied to gases emitted by an active volcano as it is particularly suitable for field conditions where little or no laboratory backup is available when used in conjunction with other geophysical techniques such as seismic and gravity measurements the methods described aid prediction of the point of emergence of an imminent eruption leading to improvements in early warning and public safety further development could make the technique applicable to different types of active volcanoes and would be particularly useful in areas where a population centre is close to an intermittently active volcano a trial analysing carbon dioxide carbon monoxide oxygen methane hydrogen sulphide and helium was conducted on piton de la fournaise reunion island during an eruptive phase results show that a major lava tube was detected and gradual degassing was measured with increasing distance of the lava from the point of emission

satellite based evidence for a large hydrothermal system at piton de la fournaise volcano reunion island 1 hydrothermal systems are active structures present at many volcanoes their characterization is essential as they reveal the evolution of the magmatic source and may play a role in the eruptive style many studies have already suggested the existence of a shallow hydrothermal system beneath the summit craters at piton de la fournaise volcano la reunion although there is still no clear evidence here we present new arguments on the basis of satellite based data acquired during april 2007 eruption suggesting the existence of a large hydrothermal system beneath the dolomieu crater at piton de la fournaise so2 released during the collapse phase of the dolomieu crater april 6 13 has been estimated at 935 244 kilotons whereas erupted so2 calculated from lava effusion rates was found to be clearly insufficient 179 89 kilotons we suggest that the excess of so2 originated from a large hydrothermal system suddenly opened by the collapse

a novel method for tracking individual waves in the surf zone a new method to obtain information on individual waves as they travel shoreward is described the wave tracking method involves analysis of synchronous water level records obtained from a shore normal transect of pressure transducers pts the method is illustrated here using data from field deployments inside the surf zone although the method could equally be applied outside the surf zone as a wave travels shoreward along the instrument transect it appears in the pt records at a progressively later time serial cross correlation techniques are used to shift each record in time so that each wave in the first record aligns approximately with the corresponding wave if it exists in subsequent records from along the transect a local minima analysis power et al 2010 is used to delimit individual waves in each record and then parameters of interest can be determined for each wave at each pt location the wave tracking method provides the evolution of these parameters for a single wave as it travels to shore and they can be analysed as a function of distance or local water depth the utility of the method is illustrated with case studies including the evolution of wave height and the evolution of the ratio of wave height to water depth for surf zone waves

role of fluids in the metamorphism of the alpine fault zone new zealand models of fluid rock interaction in and adjacent to the alpine fault in the hokitika area south island new zealand were investigated using hydrogen and other stable isotope studies together with field and petrographic observations all analysed samples from the study area have similar whole rock d values dwr 56 to 30 average 45 n 20 irrespective of rock type degree of chloritization location along the fault or across strike distance from the fault in the garnet zone the green chlorite rich fault rocks which probably formed from australian plate precursors record nearly isothermal fluid rock interaction with a schist derived metamorphic fluid at high temperatures near 450 500 c d of water in equilibrium with the green fault rocks dh2o green 18 d of water in equilibrium with the greyschists and greyschist derived mylonites dh2o grey 19 at 500 c dh2o green 17 dh2o grey 14 at 450 c there is no indication of an influx of a meteoric or mantle derived fluid in the alpine fault zone in the study area the alpine fault zone at the surface shows little evidence of late stage retrogression or veining which might be attributed to down temperature fluid flow it is probable that prograde metamorphism in the root zone of the southern alps releases metamorphic fluids that at some region rise vertically rather than following the trace of the alpine fault up to the surface owing to the combined effects of the fault the disturbed isotherms under the southern alps and the brittle ductile transition such fluids could mix with meteoric fluids to deposit quartz rich possibly gold bearing veins in the region c 5 10 km back from the fault trace these results and interpretations are consistent with interpretations of magnetotelluric data obtained in the south island geophysical transects sight programme

silicate versus carbonate weathering in iceland new insights from ca isotopes to trace sources of ca in icelandic rivers we report elemental and ca isotope data for rivers high and low temperature groundwater basalt hydrothermal calcite including iceland spar and stilbite and heulandite which are two types of zeolites commonly formed during low grade metamorphism of basalt in agreement with previous research we find that rivers have higher 44 40ca values than basalt with a maximum difference of 0 40 this difference may reflect isotope fractionation in the weathering zone i e preferential uptake of 40ca during clay mineral formation adsorption and other geochemical processes that cycle ca however calcite 44 40ca values are also up to 0 40 higher than bedrock values and on a diagram of 44 40ca versus sr ca nearly all waters plot within a plausible mixing domain bounded by the measured compositions of basalt and calcite with glacial rivers plotting closer to calcite than non glacial rivers calcite and heulandite form during hydrothermal alteration of basalt in the deep lava pile and often occur together in metabasalts now exposed at the surface because heulandite 44 40ca values are 1 2 lower than basalt we suggest that 40ca uptake by heudlandite explains the relatively high 44 40ca values of calcite and that calcite weathering in turn elevates riverine 44 40ca values high mechanical erosion rates are known to facilitate the exposure and weathering of calcite which explains the isotopic contrast between glacial and non glacial watersheds using a mixing model we find that calcite weathering provides 0 65 of the ca in non glacial rivers and 25 90 of the ca in glacial rivers with silicate weathering providing the remainder icelandic hydrothermal calcite contains mantle carbon noting that zeolite facies metamorphism and hydrothermal fluid circulation are ubiquitous characteristics of basaltic eruptions and assuming that hydrothermal calcite in other basaltic settings also contains mantle carbon we suggest that the contribution of basalt weathering to long term co2 drawdown and climate regulation may be less significant than previously realized

doppler radar sounding of volcanic eruption dynamics at mount etna besides their common use in atmospheric studies doppler radars are promising tools for the active remote sensing of volcanic eruptions but were little applied to this field we present the observations made with a mid power uhf doppler radar voldorad during a 7 h strombolian eruption at the se crater of mount etna on 11 12 october 1998 main characteristics of radar echoes are retrieved from analysis of doppler spectra recorded in the two range gates on either side of the jet axis from the geometry of the sounding the contribution of uprising and falling ejecta to each doppler spectrum can be discriminated the temporal evolution of total power backscattered by uprising targets is quite similar to the temporal evolution of the volcanic tremor and closely reproduces the overall evolution of the eruption before during and after its paroxysm moreover during the sharp decrease of eruptive activity following the paroxysm detailed analysis of video from camera recording radar and seismic measurements reveals that radar and video signals start to decrease simultaneously approximately 2 5 min after the tremor decline this delay is interpreted as the ascent time through a magma conduit of large gas slugs from a shallow source roughly estimated at about 500 m beneath the se crater detailed analysis of eruptive processes has been also made with voldorad operating in a high sampling rate mode signature of individual outburst is clearly identified on the half part of doppler spectra corresponding to rising ejecta temporal variations of the backscattered power exhibit quasi periodic undulations whereas the maximum velocity measured on each spectrum displays a sharp peak at the onset of each outburst followed by a slow decay with time periodicity of power variations between 3 8 and 5 5 s is in agreement with the occurrence of explosions visually observed at the se vent maximum vertical velocities of over 160 m s 1 were measured during the paraoxysmal stage and the renewed activity finally by using a simplified model simulating the radar echoes characteristics we show that when voldorad is operating in high sampling rate mode the power and maximum velocity variations are directly related to the difference in size and velocity of particles crossing the antenna beam

southern alps cu au hydrothermal system westland new zealand the southern alps of new zealand is an actively rising mountain belt which displays a thermal anomaly adjacent to the alpine fault the australian pacific plate boundary extensive fluid movement occurs in this uplift zone resulting in metallic vein mineralization gold mineralization is confined to greenschist facies rocks while younger veins in amphibolite facies rocks near the alpine fault are enriched in copper transport and deposition of metals in this complex hydrothermal system is governed by interaction between rising metamorphic fluids and downward percolating meteoric fluid metamorphic fluids have equilibrated with graphitic schist country rock and are relatively reduced infiltration and mixing of meteoric water increases oxygen activity and decreases sulphur activity in the fluid oxidised meteoric water heats up and dissolves cu during downward percolation this cu is deposited as the fluid becomes more reduced hence there is a progressive increase in copper content in the middle portions of the hydrothermal system especially in the more permeable highly fractured rocks near the alpine fault

a novel machine learning algorithm for tracking remotely sensed waves in the surf zone abstract this paper describes a novel image processing technique that detects wave breaking and tracks waves in the surf zone using machine learning procedures using time space images timestacks the algorithm detects white pixel intensity peaks generated by breaking waves confirms these peaks as true wave breaking events by learning from the data s true colour representation clusters individual waves and obtains optimal wave paths the method was developed and tested using data from four sandy australian beaches under different incident wave and light conditions results are a representation of the position of the wave front through time i e space time data which when shown overlaid on the original timestack shows the high degree of accuracy of the method developed here the utility of the method is demonstrated in two ways 1 through a comparison between the instantaneous wave speed calculated from the wave paths with the theoretical shallow water wave speed and 2 by obtaining optical intensities that could be translated into wave roller lengths the algorithm developed here has the potential to improve understanding numerous nearshore process such as bore propagation and capture in the surf zone surf zone energy dissipation surf beat and infragravity waves and as a direct speed input for depth inversion methods

fluid chemistry of veining associated with an ancient microearthquake swarm benmore dam new zealand steeply dipping strata in the vicinity of benmore dam otago new zealand are complexly deformed metasedimentary rocks of the torlesse supergroup middle triassic age over an exposed area 100 m wide 25 m high these strata are disrupted by a fault fracture mesh comprising conjugate coulomb shears interlinked by extensional and extensional shear fractures all formed in a common stress field and hosting quartz prehnite epidote calcite veining the combined effect of these structures is shortening perpendicular to beddings and subvertical extension so that in their present attitude they correspond to a set of conjugate thrust faults with associated extension fractures on the evidence of incremental vein textures the development of this distributed fault fracture mesh is interpreted as resulting from a fluid driven microearthquake swarm which postdated regional low grade metamorphism mechanical considerations suggest that the migrating hydrothermal fluids were significantly overpressured possibly to approximately lithostatic values if the mesh structure developed in its present attitude fluid inclusion microthermometric studies show that benmore vein quartz contains two phase aqueous inclusions with salinities between 1 4 and 2 9 wt nacl equivalent and homogenization temperatures t h between 189 and 217 c the assemblage quartz prehnite epidote suggests trapping temperatures t t of 280 c requiring the addition of an 70 c correction to t h values late calcite contains inclusions with noticeably lower salinity 0 0 0 9 wt nacl and t h values 129 175 c studies on quartz pumpellyite calcite veins from nearby lake aviemore show similar fluid inclusion salinity and t h values fluid inclusion gas analyses show all the vein samples to be dominated by h 2 o 99 3 99 9 mol with few other gases apparent including ch 4 0 5 n 2 0 1 co 2 0 1 and c 2 c 4 hydrocarbons cation and anion analyses when combined with the gas data show that nacl dominates the fluid inclusion salinities oxygen isotope results when combined with calculated t t values indicate that the water responsible for the deposition of benmore and aviemore quartz had 18 o compositions of 9 4 and 4 8 respectively calcite 13 c values between 25 3 and 38 0 are indicative of oxidation of ch 4 to co 2 as a result of hydrothermal fluids interacting with organic rich sediments fluid inclusion delta d h 2 o values for benmore range between 73 and 89 compared to 109 for the one aviemore sample this research has demonstrated that 1 water of meteoric origin probably from subantarctic latitudes penetrated to 6 km depth and underwent an oxygen isotope shift before depositing the benmore aviemore veins 2 the migrating hydrothermal fluids were likely overpressured well above hydrostatic to near lithostatic values if the mesh structure was active in its present orientation and 3 fluid migration was coupled to distributed brittle failure in the prevailing stress field self generating a permeable fault fracture mesh

variability of depth limited waves in coral reef surf zones wave breaking and transformation on coral reef flats is an important process protecting tropical coastlines and regulating the energy regimes of coral reefs however the high hydraulic roughness shallow water and steep bathymetries of coral reefs may confound common surf zone assumptions such as a depth limited and saturated surf zone with a constant wave height to water depth ratio here we examine wave transformation across a coral reef flat during three separate swell events on both a time averaged and a wave by wave basis we use the relationship between significant wave height and water depth to examine the change in surf saturation across the reef flat and compare the measured wave height decay to results of modelled wave energy dissipation in the surf zone our results show that was not cross reef constant and varied according to location on the reef flat and local water depth on average was greatest at the outer reef flat near the reef crest and progressively reduced towards the inner reef flat near the reef lagoon this was most pronounced in shallow water with large values 0 85 at the outer reef flat and small values 0 1 at the inner reef flat this indicates that there is an increase in wave energy dissipation in shallow water most likely due to increased breaker and bed frictional dissipation the measured wave energy dissipation across the entire reef flat could on average be modelled accurately however this required location specific calibration of the free parameters the wave friction factor f and and further suggests that there is no value for either parameter that is universally applicable to coral reef flats despite model calibration inaccuracies were still observed primarily at the outer reef flat these inaccuracies reflected the observed cross reef variation of on the reef flat and potentially the limitations of random wave breaker dissipation models in complex surf zones our results have implications for the use of wave energy dissipation models in predicting breaker dissipation and subsequent benthic community change on coral reef flats and suggest that careful consideration of the free parameters in such models such as f and is required

climatic and tectonic controls on chemical weathering in the new zealand southern alps abstract climatic and tectonic controls on the relative abundance of solutes in streams draining the new zealand southern alps were investigated by analyzing the elemental and sr isotope geochemistry of stream waters bedload sediment and hydrothermal calcite veins the average relative molar abundance of major cations and si in all stream waters follows the order ca2 50 si 22 na 17 mg2 6 k 5 for major anions the relative molar abundance is hco3 89 so42 7 cl 4 weathering reactions involving plagioclase and volumetrically small amounts of hydrothermal calcite define the ionic chemistry of stream waters but nearly all streams have a carbonate dominated ca2 and hco3 mass balance stream water ca sr and 87sr 86sr ratios vary from 0 173 to 0 439 mol nmol and from 0 7078 to 0 7114 respectively consistent with the ionic budget these ratios lie solely within the range of values measured for bedload carbonate ca sr 0 178 to 0 886 mol nmol 87sr 86sr 0 7081 to 0 7118 and hydrothermal calcite veins ca sr 0 491 to 3 33 mol nmol 87sr 86sr 0 7076 to 0 7097 streams draining regions in the southern alps with high rates of physical erosion induced by rapid tectonic uplift and an extremely wet climate contain 10 more ca2 and 30 more sr2 from carbonate weathering compared to streams draining regions in drier more stable landscapes similarly streams draining glaciated watersheds contain 25 more sr2 from carbonate weathering compared to streams draining non glaciated watersheds the highest abundance of carbonate derived solutes in the most physically active regions of the southern alps is attributed to the tectonic exhumation and mechanical denudation of metamorphic bedrock which contains trace amounts of calcite estimated to weather 350 times faster than plagioclase in this environment in contrast regions in the southern alps experiencing lower rates of uplift and erosion have a greater abundance of silicate versus carbonate derived cations these findings highlight a strong coupling between physical controls on landscape development and sources of solutes to stream waters using the southern alps as a model for assessing the role of active tectonics in geochemical cycles this study suggests that rapid mountain uplift results in an enhanced influence of carbonate weathering on the dissolved ion composition delivered to seawater