a simple magma driven thermal balance model for the formation of volcanogenic massive sulphides abstract a simple model is used to examine the balance of heat water flow and temperature in a long lived single pass hydrothermal system heated by magmatic heat the geometry of the system is based on mid ocean ridge observations cold water percolates downward to the top of a shallow magma chamber is heated by conduction through a thin boundary layer and discharges through a permeable fault zone modelled as a bundle of narrow rough pipes as heat input is increased the model shows a catastrophic temperature transition at an exit water temperature of between 340 and 410 c depending on seafloor pressure which in nature would probably be represented by surging flow and sudden changes in the specific volume of the circulating fluids to generate a 3 million tonne sulphide deposit with 70 efficiency of deposition from water at 350 c within 4000 years would require a heat flux of 110 w m 2 from the magma chamber for a mass flow rate of 140 kg s 1 if the plan area of the reacting part of the system is 2 km 2 the total heat input would be 3 10 19 j under these conditions the thickness of the solid boundary layer between liquid magma and circulating water will be about 10 m and the integrated reactive water rock ratio over the lifetime of the system will be about 30 decreasing the water temperature to 250 c would require a heat flux of only 60 w m 2 but the time to form a 3 million tonne deposit is increased to 33 000 years and the overall heat requirement is more than quadrupled

large scale patterns associated with tropical cyclogenesis in the western pacific abstract five characteristic low level large scale dynamical patterns associated with tropical cyclogenesis in the western north pacific basin are examined along with their capacity to generate the type of mesoscale convective systems that precede genesis an 8 yr analysis set for the region is used to identify and create composites for the five characteristic patterns of monsoon shear line monsoon confluence region monsoon gyre easterly waves and rossby energy dispersion this brings out the common processes that contribute to tropical cyclogenesis within that pattern which are described in detail a 3 yr set of satellite data is then used to analyze the mesoscale convective system activity for all cases of genesis in that period and to stratify based on the above large scale patterns it is found that mesoscale convective systems develop in all cases of genesis except one seventy percent of cases developed mesoscale convective systems at more than one time during the genesis period and 44 of

evolution of a brine saturated layer at the base of a ridge crest hydrothermal system vent fluids with chlorinities significantly greater than seawater are indicative of mixing between hydrothermal seawater and brines that have formed as a result of supercritical phase separation we relate the evolution of a brine saturated layer to magmatic and tectonic processes at the base of a ridge crest hydrothermal system a conductive heat balance indicates that under steady state conditions such a brine saturated layer is typically 1 10 m thick and contains 107 to 108 kg of brine with 6 10 times the chlorinity of seawater simple mixing and fractionation models indicate that the depletion and replenishment of brine saturated layers may occur on a timescale of years to centuries a timescale of years is consistent with temporal changes in chlorinity of fluids at vents in areas of recent known dike injection in these systems brines may be undergoing depletion by mixing with liquid phase seawater vents stably emitting high chlorinity fluids on timescales of decades may represent older systems in which brines are being depleted by diffusion into an overlying liquid phase hydrothermal system

aerobic and anaerobic methane oxidation in terrestrial mud volcanoes in the northern apennines abstract methane oxidizing prokaryotes are ubiquitous in oxic and anoxic habitats wherever c1 compounds are present thus methane saturated mud volcano fluids should be a preferred habitat of methane consuming prokaryotes using the readily available electron donors in order to understand the relevance of methane as a carbon and energy source in mud volcano communities we investigate the diversity of prokaryotic organisms involved in oxidation of methane in fluid samples from the salse di nirano mud volcano field situated in the northern apennines cell counts were at approximately 0 7 106 microbial cells ml a fraction of the microbial biomass was identified as anme an aerobic me thanotroph archaea by fluorescence in situ hybridization fish analysis they are associated in densely colonized flakes of some tens of m in diameter embedded in a hyaline matrix diversity analysis based on the 16s rdna genes retrieved from amplified and cloned environmental dna revealed a high proportion of archaea involved in anaerobic oxidation of methane aom aerobic methane oxidizing proteobacteria could be highly enriched from mud volcano fluids indicating the presence of aerobic methanotrophic bacteria which may contribute to methane oxidation whenever oxygen is readily available the results imply that biofilms dominated by anme archaea colonize parts of the mud volcano venting system

extratropical impacts on atlantic tropical cyclone activity abstractwith warm sea surface temperature sst anomalies in the tropical atlantic and cold sst anomalies in the east pacific the unusually quiet hurricane season in 2013 was a surprise to the hurricane community the authors analyses suggest that the substantially suppressed atlantic tropical cyclone tc activity in august 2013 can be attributed to frequent breaking of midlatitude rossby waves which led to the equatorward intrusion of cold and dry extratropical air the resultant mid to upper tropospheric dryness and strong vertical wind shear hindered tc development using the empirical orthogonal function analysis the active rossby wave breaking in august 2013 was found to be associated with a recurrent mode of the midlatitude jet stream over the north atlantic which represents the variability of the intensity and zonal extent of the jet this mode is significantly correlated with atlantic hurricane frequency the correlation coefficient is comparable to the correlation of atlantic hurricane fre

the effect of vertical shear orientation on tropical cyclogenesis the effect of the relative orientation of the vertical wind shear to the surface wind on tropical cyclogenesis is explored in environments of radiative convective equilibrium rce through numerical simulation this study serves as a companion paper to an earlier study on the thermodynamics of genesis in rce it is found when the mean surface wind and shear are aligned a negative surface wind anomaly arises from the superposition of the mean and vortex surface flows left of the shear vector the resulting weak surface enthalpy fluxes and up shear quasi balanced subsidence leads to dry air being located cyclonically down wind of the down shear convective anomaly thus convection is inhibited from propagating cyclonically around the core leading to a large down shear vortex tilt conversely in a counter aligned orientation the negative surface wind anomaly and driest air is found right of the shear vector hence the driest air rotates into the down shear flank where it moistened by shear organized convection furthermore the boundary layer is relatively moist left of shear due to the positive surface wind anomaly therefore promoting the cyclonic propagation from down shear and constraining the magnitude of the vortex tilt genesis is intimately tied to the magnitude of the tilt and is found to occur once the mid level vortex has precessed into the up shear flank for smaller values of maximum tilt vortex precession is comparatively rapid aided by showerhead moistening provided by the up shear advection of frozen condensate aloft with the up shear flank pre moistened rapid precession of the mid level vortex at smaller radii leads to near saturation on the mesoscale and the onset of rapid intensification when the magnitude of the tilt is quite large precession is much slower and the showerhead effect is significantly reduced until just prior to the emergence of the mid level vortex in the up shear flank copyright 2011 royal meteorological society

concretionary methane seep carbonates and associated microbial communities in black sea sediments abstract gas seeps in the euxinic northwestern black sea provide an excellent opportunity to study anaerobic methane based ecosystems with minimum interference from oxygen dependent processes an integrated approach using fluorescence and electron microscopy fluorescence in situ hybridization lipid biomarkers stable isotopes 13c and petrography revealed insight into the anatomy of concretionary methane derived carbonates currently forming within the sediment around seeps some of the carbonate concretions have been found to be surrounded by microbial mats the mats harbour colonies of sulphate reducing bacteria dss group and archaea anme 1 putative players in the anaerobic oxidation of methane isotopically depleted lipid biomarkers indicate an uptake of methane carbon into the biomass of the mat biota microbial metabolism sustains the precipitation of concretionary carbonates significantly depleted in 13c the concretions consist of rectangularly orientated rod to dumbbell shaped crystal aggregates made of fibrous high mg calcite the sulphate reducing bacteria exhibit intracellular storage inclusions and magnetosomes with greigite fe3s4 indicating that iron cycling is involved in the metabolism of the microbial population transfer of fe3 into the cells is apparently mediated by abundant extracellular vesicles resembling known bacterial siderophore vesicles marinobactine in size 20 to 100 nm and structure

the nature and hydrogeologic significance of mud diapirs and diatremes for accretionary systems in accretionary wedges often morphologically similar sedimentary intrusions when observed by remote geophysical means may have one of two quite different driving mechanisms and a highly variable significance for the regional hydrogeologic picture for example mud diapirs are driven by buoyancy forces that arise from bulk density contrasts in them mud and pore fluid upwell en masse and fluid migration is a related sometimes important but generally subsidiary process in contrast diatremes contain sediments fluidized during rapid fluid advection and are forcibly and directly driven by the hydrogeologic system the nature of fluid input from local and exotic source regions can therefore strongly affect sedimentary intrusive processes and vice versa this complicates the process of defining the main features of the hydrogeological systems operating in accretionary wedges focused vertical advection through steep sided piercement mud diapirs requires conduit systems otherwise flow will be diffuse and directed more horizontally out of the low permeability mud mass however where the permeability of the overburden is less than that of the diapir the whole diapir may act as a conduit apart from this special case conduits will be associated with highly anisotropic scaly fabrics that can sometimes develop in the marginal shear zone of diapirs scaly fabrics form during deformation and compaction of a mud matrix under conditions of constant or increasing effective stress however the effective stress path can be complex as it is both controlled by the relative rates of upward intrusion and burial by sedimentation and or structural thickening and the hydrogeologic system due to this it appears likely that even in a geographically related group of diapirs effective stress histories will vary widely between intrusions so that some can form advective pathways for fluids and some cannot mixed systems of behavior may also be present with local diatremes developing within diapirs above the terminations of conduit systems and rapidly expanding methane gas pockets the potentially heterogeneous near surface behavior may be why the surface manifestations of sedimentary intrusions are so variable when observed in the field diatremes can also form separately as large primary features above any structural or stratigraphic conduit that rapidly expels water or gas into the base of an unlithified sediment column when active large diatremes require enormous quantities of fluid water or gas to drive them particularly if they are long lived features and hence are a direct indication of at least an episodically vigorous hydrogeologic system

accumulations of melt at the base of young oceanic crust as hot solid rock ascends through the mantle the pressure around it decreases while its temperature decreases approximately adiabatically during the ascent the melting temperature decreases faster than the adiabat temperature and if the initial temperature of the rock is high enough the rock will begin to melt at the depth where the adiabat crosses the melting temperature curve models of upwelling beneath mid ocean ridges predict significant melt production over a zone several tens of kilometres wider than the ridge axis region suggesting that some of the ascending melt must arrive away from the ridge axis here i report ocean bottom seismograph observations of an uncommon and previously unreported marine seismic phase which provide strong evidence that melt accumulates in sills at the base of young oceanic crust the phase results from the conversion of compressional p waves to shear s waves on interaction with the crust mantle boundary the moho this phase is rare and very difficult to model but when visible it is strikingly prominent and usually appears at unexpectedly great source to receiver ranges the observations imply the presence of bodies of extremely low rigidity presumably melt sills at the moho close to the receiver melt may be fairly mobile at the base of the crust allowing ridges to accumulate melt through a lateral plumbing system at the locally uplifted boundary between the crust and the underlying thermally expanded mantle escape of this melt to the sea floor may be responsible for the formation of off axis seamounts

a genetic model of hydrocarbon derived carbonate chimneys in shelfal fine grained sediments the enza river field northern apennines italy abstract methane derived authigenic carbonate mdac concretions have been recently exposed in the pleistocene argille azzurre fm outcropping along the enza riverbanks northern apennines foothills italy the relations between the sediment deposition the coeval tectonic deformation and the mdac concretions have been investigated to unravel the mechanism of methane migration through the sediments and the processes leading to mdac occurrence the biogenic methane responsible for the formation of mdac chimneys and slabs has been generated in the organic rich pliocene sediments located in the po plain subsurface the gas migrated up dip towards the northern apennines foothills the mdac cements are mainly composed of dolomite whose precipitation requires thousand years and the absence of so 4 in the pore fluids according with the sedimentation rates of the mdac hosting pleistocene succession the sulphate methane transition zone migrated upwards faster than time required for dolomite precipitation therefore the connate water migrating together with the methane could have acted as second dic source allowing the mdac formation also in the methane rich zone

distributions of shallow to very deep precipitation convection in rapidly intensifying tropical cyclones abstractshear relative distributions of four types of precipitation convection in tropical cyclones tcs are statistically analyzed using 14 years of tropical rainfall measuring mission trmm precipitation radar pr data the dataset of 1139 trmm pr overpasses of tropical storms through category 2 hurricanes over global tc prone basins is divided by future 24 h intensity change it is found that increased and widespread shallow precipitation defined as where the 20 dbz radar echo height 6 km around the storm center is a first sign of rapid intensification ri and could be used as a predictor of the onset of ri the contribution to total volumetric rain and latent heating from shallow and moderate precipitation 20 dbz echo height between 6 and 10 km in the inner core is greater in ri storms than in non ri storms while the opposite is true for moderately deep 20 dbz echo height between 10 and 14 km and very deep precipitation 20 dbz echo height 14 km the authors argue that ri is more likely

structural boron as factor controlling illite crystallinity in a mud volcano environment northern apennine italy abstract mud extrusion is a well known phenomenon whereby fluid rich fine grained sediments ascend within a lithological succession due to their buoyancy in this study of the terrestrial mud volcanism associated to an active thrusted area in the northern apennines we investigated the effect of boron incorporation in illite crystalline lattice a significant variation was recorded on the investigated mud samples with respect to both the amount of fixed boron 118 529 g g and the full width at half maximum height value fwhm of illite 0 29 0 62 2 we attribute these variations to the interaction between boron rich formation waters and the silty clayey lithologies of the local sedimentary succession the lack of any geographical correlation between the selected geochemical and mineralogical parameters is likely due to intensive thrust and fold deformation of the study area comparison of fwhm values with those from dellisanti et al 2008 santerno succession northern apennine lead us to suggest that application of fwhm as a depth indicator could be misleading within b rich hydro geological environments

seismic evidence for a hydrothermal layer above the solid roof of the axial magma chamber at the southern east pacific rise a full waveform inversion of two ship wide aperture seismic reflection data from a ridge crest seismic line at the southern east pacific rise indicates that the axial magma chamber here is about 50 m thick is embedded within a solid roof and has a solid floor the 50 60 m thick roof is overlain by a 150 200 m thick low velocity zone that may correspond to a fracture zone that hosts the hydrothermal circulation and the roof itself may be the transition zone separating the magma chamber from circulating fluids furthermore enhanced hydrothermal activity at the sea floor seems to be associated with a fresh supply of magma in the crust from the mantle the presence of the solid floor indicates that at least the upper gabbros of the oceanic lower crust are formed by cooling and crystallization of melt in magma chambers

fluid migration and origin of a mud volcano in the northern apennines italy the role of deeply rooted normal faults introductionsurface seeps of gas oil and salinewaters areconsideredtobeindicatorsof deep seated hydrocarbon accumu lationandhavebeenused forover60years as a guide to hydrocarbonprospectivity a wide spectrum ofseepages belongs to di erent geologi cal settings e g camerlenghi etal 1992 1995 thrasher etal 1996 schulz etal 1997 kopf etal 1998 graue 2000 spectacular seepagescan be found in basins with highsedimentation rates that generateoverpressureandmuddiapirism gu liev and feyzullayev 1996 up dipcarrier beds and active tectonic fea tures act as channels for subsurface uidandlocalizesurfaceemissionsuptotens orevenahundred kilometresfrom the reservoir thrasher etal 1996 during migration the domi nant mechanism that changeshydrocarbon composition is phasepartitioning migration of hydrocar bons is then largely the result ofbuoyancy of the free phase formedduringthisprocess matthews 1996 eventually thegeologyofthebasinisthe key to interpreting complicated uidmigrationpathways manystud ies simply focus on the oil and gascomponents of the migrating uidrather than on the characteristics ofthewaterandmudthatareassociatedwithhydrocarbonmigrationandalsoextruded by spontaneous seeps eventhough water is invoked as beingresponsibleforatleastlighthydrocar bon removal klusman and saaed 1996 watersofdi erentprovenancecontributetotheascending uidsandtheir geochemical characteristics canhelp in understanding their evolutionduring diagenesis and migration e g white 1965 hanor 1987 holyshandto th 1996 thispaperpresentssomeanalytical data from a spontaneoussurface seep bearing saline water mud gas and oil at the foothills ofthe northern apennines the aimsare i to provide some insight intothedepthandoriginofthe uidsandthe nature of the seepage pathway and ii tode nethelossofsubsurface uids accumulation related to thegeologicalpattern geological setting and structuralcontrol of the regnano mudvolcanoin the external portion of the nor thern apennines spontaneous uidemissions are distributed along twobelts borgia etal 1986 nanni andvivalda 1999 minissaleetal 2000 the rst belt stretches along the poplainfoothills whilethesecondoneisinternal and runs nearly parallel tothe main apenninic divide fig 1 theregnanomudvolcanoconsistsofmud breccias and mud ows spread ing over an area of 0 5km

simulation of the downshear reformation of a tropical cyclone abstractthe downshear reformation of tropical storm gabrielle 2001 was simulated at 1 km horizontal resolution using the weather research and forecasting wrf model the environmental shear tilted the initial parent vortex downshear left and forced azimuthal wavenumber 1 kinematic thermodynamic and convective asymmetries the combination of surface enthalpy fluxes and a lack of penetrative downdrafts right of shear allowed boundary layer moist entropy to increase to a maximum downshear right this contributed to convective instability that fueled the downshear convection within this convection an intense mesovortex rapidly developed with maximum boundary layer relative vorticity reaching 2 2 10 2 s 1 extreme vortex stretching played a key role in the boundary layer spinup of the mesovortex cyclonic vorticity remained maximized in the boundary layer and intensified upward with the growth of the convective plume the circulation associated with the mesovortex and adjacent localized cyclonic vorti

assessing the influence of upper tropospheric troughs on tropical cyclone intensification rates after genesis abstractthe role of upper tropospheric troughs on the intensification rate of newly formed tropical cyclones tcs is analyzed this study focuses on tcs forming in the presence of upper tropospheric troughs in the north atlantic basin between 1980 and 2014 tcs were binned into three groups based upon the 24 h intensification rate starting at the time of genesis rapid tc genesis rtcg slow tc genesis stcg and neutral tc genesis ntcg composite analysis shows rtcg events are characterized by amplified upper tropospheric flow with the largest upshear displacement between the tc and trough of the three groups rtcg events are associated with greater quasigeostrophic qg ascent in upshear quadrants of the tc forced by differential vorticity advection by the thermal wind especially around the time of genesis this pattern of qg ascent closely matches the rtcg composite of infrared brightness temperatures conversely ntcg events are associated with an upper tropospheric trough that is closest to the

the role of vortical hot towers in the formation of tropical cyclone diana 1984 abstract a high resolution 3 km horizontal grid spacing near cloud resolving numerical simulation of the formation of hurricane diana 1984 is used to examine the contribution of deep convective processes to tropical cyclone formation this study is focused on the 3 km horizontal grid spacing simulation because this simulation was previously found to furnish an accurate forecast of the later stages of the observed storm life cycle the numerical simulation reveals the presence of vortical hot towers or cores of deep cumulonimbus convection possessing strong vertical vorticity that arise from buoyancy induced stretching of local absolute vertical vorticity in a vorticity rich prehurricane environment at near cloud resolving scales these vortical hot towers are the preferred mode of convection they are demonstrated to be the most important influence to the formation of the tropical storm via a two stage evolutionary process i preconditioning of the local environment via diabatic production of mul

lipid biomarkers and their specific carbon isotopic compositions of cold seep carbonates from the south china sea abstract cold seep carbonates were studied from two locations dongsha and chiasian in the northern south china sea and on taiwan island lipid biomarkers and their stable carbon isotopic compositions extracted from these seep carbonate samples were analyzed in this study and the results pointed at the anaerobic oxidation of methane aom as responsible for carbonate formation distinct aom communities were indicated by isotopically highly depleted archaeal biomarkers with 13c values as low as 140 8 vpdb and bacterial biomarkers with 13c values as low as 128 6 vpdb which confirmed that biogenic methane was the dominant carbon source lipid biomarker distributions indicated that anme 2 archaea were prevalent in sample tvg3 c2g from dongsha and sample jx8 from chiasian in addition differences of the aom communities between the carbonates appeared to be caused by the respective biogeochemical environments anme 1 archaea tended to be abundant in high mg calcite carbonates and their formation might be linked to low methane fluxes in contrast anme 2 consortia were prevalent in aragonite carbonates and appeared to have prospered at sites with high methane supply our data imply that the mineralogy of the seep carbonates precipitated in the northern south china sea appears to be influenced by the distinct anme consortia which are induced by methane flux

chlorine stable isotope composition of the oceanic crust implications for earth s distribution of chlorine abstract this first investigation of the cl stable isotope composition of seafloor rocks reveals systematic variations in 37 cl 35 cl of the oceanic crust and its mantle source s relative to seawater chlorine isotopic measurements expressed as 37 cl relative to the seawater 37 cl 35 cl ratio of fresh morb glass hydrothermally produced amphibole containing whole rocks and smectite veins are presented all the samples analyzed are isotopically enriched 0 2 7 5 relative to seawater 0 uptake of cl into amphibole during axial hydrothermal alteration fractionates cl relative to seawater the isotopic compositions of morb glasses are between 0 2 and 7 2 this range appears to be partially due to the assimilation of cl from hydrothermally altered wallrock into morb magmas samples which are unaffected by assimilation have 37 cl between 3 and 7 2 overall the data imply that cl is isotopically fractionated between the surface and mantle reservoirs of earth calculations based on the degree of fractionation suggest that approximately 40 of the cl originally in the degassed mantle now resides on earth s surface

fluid flow patterns in fast spreading east pacific rise crust exposed at hess deep tectonic exposures of a volcanic sequence and sheeted dike complex over a 4 km wide region at hess deep equatorial pacific reveal significant spatial heterogeneity 10 103 m in the extent and nature of hydrothermal alteration in young fast spreading east pacific rise crust the volcanic sequence is fairly uniformly altered with only minor oxidation and alteration to clay minerals sheeted dikes in the eastern part of the field area are highly fractured with narrow intervals of intact dikes that dip up to 60 their alteration characteristics show a simple depth trend such that with increasing depth the dominant secondary mafic mineral changes from chlorite to amphibole clinopyroxene replacement increases 40 whole rock 18o values decreases 4 4 5 5 to 3 5 4 5 and calculated peak metamorphic temperatures increase 250 c to 450 700 c within the deepest dikes localized zones up to 400 m wide are chlorite rich and have low 18o 2 9 4 1 and low peak metamorphic temperatures 345 c these alteration patterns likely formed within broad recharge zones whereby the low 18o zones developed in the regions with the highest fluid flux in the west massive slightly rotated sheeted dikes near the volcanic sheeted dike transition are 18o and cu depleted and display higher peak temperatures 345 c than elsewhere in the shallow dikes these characteristics are consistent with formation within a high temperature hydrothermal discharge zone we propose that the spreading history of a fast spreading ridge segment can create significant spatial heterogeneity in fluid flow and alteration patterns within sheeted dike complexes similar to those preserved in many ophiolites

fluid geochemical transect in the northern apennines central northern italy fluid genesis and migration and tectonic implications chemical and isotopic characteristics of natural gas and thermal water discharges from the western back arc tyrrhenian sea across the apennine thrust belt to the po valley and adriatic coast foredeep basins in the northern apennines central northern italy reveal a large scale fluid motion in the upper crust both vertically and horizontally on the basis of gas compositions two different domains of rising fluids have been distinguished 1 co2 rich he poor 3he 4he high domain in the western peri tyrrhenian extensional sector 2 ch4 rich he rich 3he 4he low domain in the eastern adriatic compressional sector such gases rising from various depths are crossed by a huge lateral n2 rich water flow in the peri tyrrhenian sector of ca so4 hco3 meteoric derived waters that move in a regional wide aquifer hosted in a quite thick mesozoic carbonate series morphologically the co2 vents consist of mud basins with high gas rate emission where the rising fluids move upwards through diatremes on the other hand ch4 emissions seep out from typical mud volcanoes with a reduced gas flow rate where the fluid motion is likely related to saline diapir extrusions and the methane is mostly carried to the surface by the associated mud the two rising mechanisms described locate southwest and northeast of the apennine watershed respectively from a seismic point of view the ch4 domain in the thrust belt and foredeep areas is characterized by a large number of earthquakes indirectly pointing to a different rheological behavior of the terrains with respect to the more internal peri tyrrhenian area owing to the quite high thermal gradient of the latter the boundary of the brittle ductile crust in the peri tyrrhenian sector can be located at a 10 km shallow depth although the presence of several post orogenic basins would suggest widespread extensional tectonics in all areas west of the apennine watershed those located in the easternmost part display gas vents with typical crustal 3he 4he ratios as this ratio is very sensitive to deep fluids rising from the mantle we hypothesize that such basins at the foot of the apennines are not due to tensive stress as suggested by their morphological shape they are piggy back thrust top basins developed and evolved in a still acting compressive tectonic regime

seismic images of active magma systems beneath the east pacific rise between 17 05 and 17 35 s seismic reflection data from the east pacific rise between 17 059 and 17 359s image a magma lens that varies regularly in depth and width as ridge morphology changes confirming the notion that axial morphology can be used to infer ridge magmatic state however at 17 269s where the ridge is locally shallow and broad the magma lens is markedly shallower and wider than predicted from regional trends in this area submersible dives reveal recent volcanic eruptions these observations indicate that it is where the width and depth of the magma chamber differ from regional trends indicating an enhanced magmatic budget that is diagnostic of current magmatism

depletion of a brine layer at the base of ridge crest hydrothermal systems the variable salinity of fluid venting from mid ocean ridges is indicative of mixing between hydrothermal seawater and fluids that have undergone supercritical phase separation in order to study the stability of a brine saturated layer that may form in the lowermost part of the hydrothermal system we have performed numerical simulations of a system that has returned into the subcritical regime for typical geological parameters it is shown that the interface between the brine layer and the overlying fluids is not very stable but vanishes by one of two dynamical mechanisms convective breakdown or vertical migration this contradicts the conventional picture of a steady layered convective system in which the brine is depleted only by dispersion and diffusion across the interface the depletion mechanism depends on the fluid dynamical stability of the brine layer convection within the brine layer results either in the convective breakdown for low excess salinity of the brine as compared to seawater or the upward migration of the interface for higher excess salinities consequently the depletion times are much shorter than for models with pure dispersion diffusion across the interface if the brine layer is static high chlorinity liquid is entrained slowly by the convecting overlying fluids leading to downward migration of the interface this gradual depletion of the brine layer results in almost constant vent salinities in agreement with measured salinities of chronic high chlorinity vents fl 2000 elsevier science b v all rights reserved

airborne doppler observations of the inner core structural differences between intensifying and steady state tropical cyclones abstractdifferences in the inner core structure of intensifying in intensity increase of at least 20 kt 24 h 1 where 1 kt 0 51 m s 1 and steady state ss intensity remaining between 10 kt 24 h 1 tropical cyclones tcs are examined using composites of airborne doppler observations collected from noaa p 3 aircraft missions the in dataset contains 40 eyewall passes from 14 separate missions while the ss dataset contains 53 eyewall passes from 14 separate missions intensifying tcs have a ringlike vorticity structure inside the radius of maximum wind rmw lower vorticity in the outer core a deeper stronger inflow layer and stronger axisymmetric eyewall upward motion compared with steady state tcs there is little difference in the vortex tilt between 2 and 7 km and both in and ss tcs show an eyewall precipitation and updraft asymmetry whose maxima are located in the downshear and downshear left region the azimuthal coverage of eyewall and outer core precipitation is greater for in tcs

dynamical and physical processes leading to tropical cyclone intensification under upper level trough forcing abstractthe rapid intensification of tropical cyclone tc dora 2007 southwest indian ocean under upper level trough forcing is investigated tc trough interaction is simulated using a limited area operational numerical weather prediction model the interaction between the storm and the trough involves a coupled evolution of vertical wind shear and binary vortex interaction in the horizontal and vertical dimensions the three dimensional potential vorticity structure associated with the trough undergoes strong deformation as it approaches the storm potential vorticity pv is advected toward the tropical cyclone core over a thick layer from 200 to 500 hpa while the tc upper level flow turns cyclonic from the continuous import of angular momentum it is found that vortex intensification first occurs inside the eyewall and results from pv superposition in the thick aforementioned layer the main pathway to further storm intensification is associated with secondary eyewall formation triggered by external

two paradigms of baroclinic wave life cycle behaviour two idealized baroclinic wave 6 life cycles examined here suggest a framework of opposite extremes a in which to view the behaviour of real synoptic scale disturbances in middle latitudes and b in which to interrelate the synoptic and wave theoretic viewpoints using the saturation propagation saturation sps picture of wave 6 life cycle behaviour the two life cycles dented by lc1 and lc2 are higher resolution versions of the simmons hoskins basic and anomalous cases showing strong and weak late decay of eddy kinetic energy eke they illustrate in varying degrees two extreme types of behaviour here disignated anticyclonic and cyclonic and epitomized by strongly contrasting upper air trough behaviour anticyclonic behaviour dominates the late stages of lc1 and is characterized by backward tilted thinning troughs being advected anticyclonically and equatorward as in the commoner cases of planetary scale mid stratospheric rossby wave breaking cyclonic behaviour dominates lc2 and is characterized by forward tilted broadening troughs wrapping themselves up cyclonically and poleward producing major cut off cyclones in high latitudes these morphologies are visualized by upper air maps of potential temperature on the nominal tropopause defined as a constant potential vorticity surface some atmospheric mid latitude disturbances examined here using the same visualization applied to operational analyses show the same two extreme types of trough behaviour together with intermediate cases the sps picture is re examined using eliassen palm and refractive index cross sections it is shown in particular by reference to a wave activity theorem of haynes that the late stages of lc2 can be looked upon as a remarkably clear and morphologically novel large amplitude counterpart of the nonlinear reflection scenario of rossby wave critical layer theory the late stages of lc1 by constrast look more akin to an nonlinear critical layer absorption scenario lc2 exhibits region of largely undular pv contours adjacent to a nonlinear of irreversiby deformen pv contous in the latter region pv rearrangement and hence absorption of rossby wave activity has largely ceased this accounts for the more persistent ekee in the lc2 case

in situ fluxes and zonation of microbial activity in surface sediments of the hakon mosby mud volcano from the hakon mosby mud volcano hmmv on the southwest barents sea shelf gas and fluids are expelled by active mud volcanism we studied the mass transfer phenomena and microbial conversions in the surface layers using in situ microsensor measurements and on retrieved cores the hmmv consists of three concentric habitats a central area with gray mud a surrounding area covered by white mats of big sulfide oxidizing filamentous bacteria beggiatoa and a peripheral area colonized by symbiontic tube worms pogonophora a fourth habitat comprised gray microbial mats near gas seeps the differences between these four methane fueled habitats are best explained by different transport rates of sulfate into the sediments and pore water upflow rates the upflow velocities were estimated by two independent methods at 3 6 m yr21 in the central area and 0 3 1 m yr21 in beggiatoa mats in the central area no sulfide was found indicating that the rapidly rising sulfate free fluids caused sulfate limitation that inhibited anaerobic oxidation of methane aom under beggiatoa mats a steep sulfide peak was found at 2 to 3 cm below the seafloor bsf most likely due to aom all sulfide was oxidized anaerobically possibly through nitrate reduction by beggiatoa the beggiatoa mats were dominated by a single filamentous morphotype with a diameter of 10 mm and abundant sulfur inclusions a high diversity of sulfide oxidizer morphotypes was observed in a grayish microbial mat near gas vents where aerobic sulfide oxidation was important the sediments colonized by pogonophora were influenced by bioventilation allowing sulfate penetration and aom to 70 cm bsf the hmmv is a unique and diverse ecosystem the structure and functioning of which is mainly controlled by pore water flow

evidence from rare gases for magma chamber degassing of highly evolved mid ocean ridge basalt highly evolved lavas have been recovered from moderate to fast spreading centres along the mid ocean ridge system most commonly near propagating rifts and overlapping spreading centres1 7 their origin and occurrence are generally explained by extensive modification of a primary basalt magma by fractional crystallization at shallow levels in the oceanic crust model i 1 4 6 9 other crustal processes have also been invoked including periodic magma mixing of a highly fractionated liquid with multiple primary liquids model 2 10 11 and seawater interaction with the mantle derived magma model 3 12 14 here we report the first 4he and argon isotope data for several highly evolved mid ocean ridge basalts morbs and andesites the samples were recovered with the submersible alvin from a very limited section 8 km2 of the axial valley of the eastern galapagos rift between 85 52 and 85 50 w although they range in composition from moderately evolved normal n morb to ferrobasalts fe ti basalts and high silica andesites geochemical studies indicate that the suite is cogenetic facilitating interpretation of the data15 we find distinct differences in the rare gas data between the evolved and n morbs indicating that the evolved magmas have undergone pre eruption degassing in a process not common to the source magmas for normal morbs our data fit well with model 1 but provide no evidence for models 2 and 3

mud volcanoes the most important pathway for degassing deeply buried sediments abstract this paper discusses the nature of the phenomenon of mud volcanism with respect to degassing of deeply buried sediments mud volcanoes are defined as geological structures and their main elements are described based on the nature of activity mud volcanoes are grouped in to three main types and the relationship between each type and corresponding morphological expression is discussed the presented up to date data of the world geographical distribution of mud volcanoes show that they approximate to 1800 individuals a detail overview of geological environments in which they occur helps to deduce some necessary conditions for mud volcano formation the basic mechanisms of mud volcano formation are discussed specifically the fluid pressure hypothesis and some triggering events are identified the most common investigation approach and some criteria for recognizing of a submarine mud volcano on side scan sonar records and seismic sections are given mud volcanism in the mediterranean ridge an accretionary complex and black sea abyssal plane a back ark basin with tectonic regime of extension are described as case studies to show variety in morphology and common factors in development of mud volcanoes the manifestation of continuous gas migration through mud volcanoes is clarified and the attempt made to quantify the gas release shows that mud volcanoes are one of the significant natural sources of atmospheric methane emitting a total amount of about 10 3 to 12 6 tg annually

the relationship between storm motion vertical wind shear and convective asymmetries in tropical cyclones abstract the influence of the direction of storm motion on the azimuthal distribution of electrified convection in 35 atlantic basin tropical cyclones from 1985 to 1999 was examined using data from the national lightning detection network in the inner 100 km flashes most often occurred in the front half of storms with a preference for the right front quadrant in the outer rainbands r 100 300 km flashes occurred predominantly to the right of motion although the maximum remained in the right front quadrant the results are shown to be consistent with previous studies of asymmetries in rainfall radar reflectivity and vertical motion with respect to tropical cyclone motion the motion effect has been attributed to the influence of asymmetric friction in the tropical cyclone boundary layer the authors previously found a strong signature in the azimuthal distribution of lightning with respect to vertical wind shear because both effects show clearly vertical wind shear and storm motion must themse

salinity variations in submarine hydrothermal systems by layered double diffusive convection various mechanisms have been proposed to explain the salinity variations in vent fluids of seafloor geothermal systems new experiments reacting diabase and evolved seawater were carried out to reproduce earlier published observations of cl depletions attributed to formation of an ephemeral cl bearing mineral the absence of any cl depletions in the present study suggests that the formation of cl bearing minerals is not sufficiently widespread to account for the observed salinity variations in the vent fluids a re evaluation of both field and laboratory evidence has led to a new model for subseafloor circulation that accounts for salinity variations as well as other chemical and mineralogic observations in place of a simple single pass convection system we propose that the seafloor systems consist of two vertically nested convection cells in which a brine layer at depth heats and drives an overlying seawater cell such layering of salinities a process known in fluid mechanics as double diffusive conve

rapid development of the tropical cyclone warm core this paper presents a simple theoretical argument to isolate the conditions under which a tropical cyclone can rapidly develop a warm core thermal structure and subsequently approach a steady state the theoretical argument is based on the balanced vortex model and in particular on the associated transverse circulation equation and the geopotential tendency equation these second order partial differential equations contain the diabatic forcing and three spatially varying coefficients the static stability a the baroclinity b and the inertial stability c thus the transverse circulation and the temperature tendency in a tropical vortex depend not only on the diabatic forcing but also on the spatial distributions of a b and c experience shows that the large radial variations of c are typically the most important effect under certain simplifying assumptions as to the vertical structure of the diabatic forcing and the spatial variability of a b and c the transverse circulation equation and the geopotential tendency equation can be solved via separation of variables the resultingradialstructureequationsretainthedynamicallyimportantradialvariationofcandcanbe solvedin terms of green s functions these analytical solutions show that the vortex response to a delta function in the diabatic heating depends critically on whether the heating occurs in the low inertial stability region outside the radius of maximum wind or in the high inertial stability region inside the radius of maximum wind this resultsuggeststhatrapidintensification isfavoredforstormsthathaveat leastsome oftheeyewallconvection inside the radius of maximum wind the development of an eye partially removes diabatic heating from the high inertial stability region of the storm center however rapid intensification may continue if the eyewall heating continues to become more efficient as the warm core matures and static stability increases over the inner core conditions there become less favorable for deep upright convection and the storm tends to approach a steady state

central anomaly magnetization high constraints on the volcanic construction and architecture of seismic layer 2a at a fast spreading mid ocean ridge the epr at 9 30 50 n abstract the central anomaly magnetization high camh is a zone of high crustal magnetization centered on the axis of the east pacific rise epr and many other segments of the global mid ocean ridge mor the camh is thought to reflect the presence of recently emplaced and highly magnetic lavas forward models show that the complicated character of the near bottom camh can be successfully reproduced by the convolution of a lava deposition distribution with a lava magnetization function that describes the variation in lava magnetization intensity with age this lava magnetization function is the product of geomagnetic paleofield intensity which has increased by a factor of 2 over the last 40 kyr and low temperature alteration which decreases the remanence of lava with exposure to seawater the success of the forward modeling justifies the inverse approach deconvolution of the magnetic data for lava distribution and integration of that distribution for magnetic layer thickness this approach is tested on two near bottom magnetic profiles al2767 and al2771 collected using alvin across the epr axis at 9 31 n and 9 50 n our analysis of these data produces an estimate of the relative thickness of the magnetic lava layer which is remarkably consistent with existing multichannel estimates of layer 2a thickness from lines cdp31 and cdp27 the similarity between magnetic layer and seismic layer 2a at the 9 10 n segment of the epr crest provides independent support to the notion that seismic layer 2a in young oceanic crust represents the highly magnetic lava layer and that the velocity gradient at the base of layer 2a is related to the increasing number of higher velocity dikes with depth in the lava dike transition zone the near bottom magnetic anomaly character of the camh is a powerful indicator of the emplacement history of upper crust at mors which allows prediction of the relative thickness and architecture of the extrusive lavas independent of other constraints

a composite study of the interactions between tropical cyclones and upper tropospheric troughs abstract the objective of this study is to understand how interactions with upper tropospheric troughs affect the intensity of tropical cyclones the study includes all named atlantic tropical cyclones between 1985 and 1996 to minimize other factors affecting intensity change times when storms are over subcritical sea surface temperatures 26 c or near landfall are removed from the sample a trough interaction is defined to occur when the eddy momentum flux convergence calculated over a 300 600 km radial range is greater than 10 m s 1 day 1 the trough interaction cases are separated into four composites i favorable superposition tropical cyclone intensifies with an upper tropospheric potential vorticity pv maximum within 400 km of the tropical cyclone center ii unfavorable superposition iii favorable distant interaction upper pv maximum between 400 and 1000 km from the tropical cyclone center and iv unfavorable distant interaction for comparison two additional composites are cre

influence of magma supply and spreading rate on crustal magma bodies and emplacement of the extrusive layer insights from the east pacific rise at lat 16 n seismic reflection data from the east pacific rise at lat 16 n which is spreading at the high end of intermediate rates suggest that the depths at which axial magma chambers reside do not vary smoothly as a function of spreading rate rather magma chamber depths form two distinct populations each associated with a distinct axial morphology and with an abrupt transition occurring within the intermediate spreading rate range our data 1 show that the melt lens at high intermediate spreading ridges lies at a shallow level similar to lens depths at faster spreading ridges and 2 provide further support for the spreading rate invariance of ridges with axial highs noted in other ridge properties the axial morphology of the two ridge segments within the study area differs markedly and a large contrast in magma supply is inferred the ridge segment with greater magma supply is associated with a broader and more continuous melt lens a wider region over which the extrusive crust accumulates and a thicker extrusive layer off axis where supply to the ridge segment appears to be centered however on axis the extrusive layer is thinnest where magma supply is robust and a shallower melt lens is observed consistent with a model in which magma pressure controls the thickness of the extrusive layer accumulated above the magma lens

quadrant distribution of tropical cyclone inner core kinematics in relation to environmental shear abstractairborne doppler radar data collected in tropical cyclones by national oceanic and atmospheric administration wp 3d aircraft over an 8 yr period 2003 10 are used to statistically analyze the vertical structure of tropical cyclone eyewalls with reference to the deep layer shear convective evolution within the inner core conforms to patterns shown by previous studies convection initiates downshear right intensifies downshear left and weakens upshear analysis of the vertical distribution of radar reflectivity and vertical air motion indicates the development of upper level downdrafts in conjunction with strong convection downshear left and a maximum in frequency upshear left intense updrafts and downdrafts both conform to the shear asymmetry pattern while strong updrafts occur in the eyewall intense downdrafts show far more radial variability particularly in the upshear left quadrant though they concentrate along the eyewall edges strong updrafts are collocated with low level inflow and

tropical storm formation in a baroclinic environment abstract an analysis is presented of the large scale conditions associated with the initial development of tropical storm diana september 1984 in a baroclinic environment ordinary extratropical wave cyclogenesis began along an old frontal boundary east of florida after 0000 utc 7 september and culminated in tropical cyclogenesis 48 h later water vapor satellite imagery showed that the initial cyclogenesis and incipient tropical storm formation was nearly indistinguishable from a classical midlatitude development cyclogenesis occurred in three stages a large scale cold trough and associated frontal system crossed the atlantic coast while a small potential vorticity maximum aloft fractured off the main trough and stalled over central florida in the first stage as the main trough sheared off eastward cyclogenesis began along the southwestern end of the stalled frontal zone east of florida anticyclogenesis to the north in the wake of the shearing trough allowed a surge of cooler and drier air to flo

significance of mud volcanism 1 mud volcanism and diapirism have puzzled geoscientists for 2 centuries they have been described onshore and offshore in many places on earth and although they occur in various tectonic settings the majority of the features known to date are located in compressional tectonic scenarios this paper summarizes the main thrusts in mud volcano research as well as the various regions in which mud volcanism has been described mud volcanoes show variable geometry up to tens of kilometers in diameter and several hundred meters in height and a great diversity regarding the origin of the fluid and solid phases gas predominantly methane water and mud may be mobilized at subbottom depth of only a few meters but in places can originate from several kilometers depth with minor crustal or mantle input the possible contribution of mud extrusion to global budgets both from quiescent fluid emission and from the extrusive processes themselves is important in regions where mud volcanoes are abundant such as the collision zones between africa and eurasia fluid flux through mud extrusion exceeds the compaction driven pore fluid expulsion of the accretionary wedge also quiescent degassing of mud volcanoes may contribute significantly to volatile budgets and hence to greenhouse climate

introduction to the special issue signatures of microbes and microbial mats and the sedimentary record abstract the present special issue originated from a session ssp4 5 at the egu general assembly 2010 vienna microbes and microbial mat signatures and the sedimentary record this special issue comprises a set of papers that focus on several aspects of microbial and microbial mat signatures grouped into four major fields 1 microbial biomineralisation 2 microbial communities and mat related structures 3 organo sedimentary accretion and microbial deposits and 4 processes and products in submarine cold seeps and terrestrial mud volcanoes

the role of synoptic scale flow during tropical cyclogenesis over the north atlantic ocean abstract the synoptic scale flow during tropical cyclogenesis and cyclolysis over the north atlantic ocean is investigated using compositing methods genesis and lysis are defined using the national hurricane center nhc now known as the tropical prediction center best track data genesis lysis occurs when nhc first last identifies and tracks a tropical depression in the final best track dataset storm centered composites are created with the analysis of the tropical oceanic lower level atoll 900 hpa and 200 hpa winds for june november produced by nhc for the years 1975 93 results show that significant regional differences exist in 200 hpa flow during genesis across the atlantic basin composites of genesis in the western part of the basin show a 200 hpa trough ridge located to the west east of the atoll disturbance in the eastern half of the basin composites of genesis show a sprawling 200 hpa ridge centered northeast of the atoll disturbance the major axis of this elliptically shaped 20

interrelations of mud volcanism fluid venting and thrust anticline folding examples from the external northern apennines emilia romagna italy 1 the present work aims to provide an example of connection between fluid seepage and fault fracture zones associated with compressional thrust folds surface fluid seepage along the pede apennine margin consists of mud volcanism and methane rich emissions showing an intimate link with thrust related folds dominant gaseous or ch4 bearing fluid emissions characterize thrust fold settings in which fluid escape from the main reservoir and source rock i e the marnoso arenacea flysch is not impeded by a seal layer conversely remarkable mud volcanism is closely linked to the presence of the impermeable ligurian units sealing the marnoso arenacea reservoir structural analyses focused on selected thrust folds exhibiting clear relations between surface seepage and brittle elements associated with the fold various scenarios potentially explaining mud volcanism and venting over the crestal region of the thrust related folds are discussed with respect to fluid pressure state and the development of second order fault and fracture sets that are observed to control surface fluid expulsion it is proposed that mud volcanism can be potentially triggered by first order fault failure cycles during which the overpressured fluid is released during faulting events past anomalous eruptions associated with strong earthquakes seem to support this hypothesis the relatively quiescent but continuous activity of the current pede apennine mud volcanoes could instead reflect a short lived leakage of overpressured fluids along permeable fractures faults expansion of methane contained in the rising mud may assist this process fundamentally

geochemical characterization of the nirano mud volcano italy abstract the nirano mud volcano is located in the western sector of the modena apennine margin italy it represents one of the most spectacular phenomena of sedimentary volcanism in the entire italian territory and is among the largest in europe here numerous aligned gryphon clusters and seeping pools constantly burst gas and mud inside a morphological depression besides the obvious surface expressions of these emission spots until now the type and amount of gas released in the rest of the large nirano caldera zone remained unknown an extensive geochemical soil gas survey o2 n2 co2 ch4 222rn he h2 and light hydrocarbons and exhalation fluxes co2 and ch4 was carried out inside the mud volcano field with the aim of identifying soil degassing distribution and to estimate the micro and macro seepage budget for both co2 and ch4 soil gas data highlight the presence of two zones characterized by high concentrations and flux values these enhanced seepage zones are located in the sw and ne sectors of the mud volcano suggesting that the enhanced gas emissions present in the peripheral zones are controlled by caldera collapse structures the most significant co2 flux up to 91 g m 2 d 1 and 222rn anomalies are located in the central part of the crater in correspondence of a morphological escarpment here we infer the presence of a buried tectonic system of collapsed terraces that facilitate fluids degassing in contrast ch4 fluxes show a scattered distribution and low values mean 221 mg m 2 d 1 overall the ch4 degassing budget is low 27 09 t km 2 y 1 when compared with other italian mud volcanoes this could be related to a relative low emission activity during the period of the geochemical survey and to a more homogeneous dilution of surface distribution of the emission point s chemical and isotopical composition of the gas discharged from the active gryphons is methane dominated and the thermogenic signature ranging from 41 to 47 suggests a deep reservoir source this conclusion is supported by noble gas measurements he ne ar kr xe conducted in the pore water phase of the emitted mud indicating a secondary gas exchange occurring at a depth of a few kilometers the geochemical anomalies found in this study successfully predicted the occurrence of new degassing phenomena towards the ne sector of the caldera indeed recently i e after the survey data acquisition new manifestations of mud and gas emissions appeared in the north eastern edge of the caldera

typhoon vamei an equatorial tropical cyclone formation 1 due to the diminishing coriolis effect the belt 300 km either side of the equator has been considered tropical cyclone free typhoon vamei which developed near singapore on 27 december 2001 was the first recorded tropical cyclone formation within 1 5 degrees of the equator the development was the result of two interacting systems a weak borneo vortex that drifted into the southern tip of the south china sea and remained there for four days and a strong and persistent cold surge that created the large background cyclonic vorticity at the equator the probability of a similar equatorial development is estimated to be once every 100 400 years

external influences on hurricane intensity part i outflow layer eddy angular momentum fluxes abstract outflow layer winds were objectively analyzed every 12 h for 6 days during the life cycle of hurricane elena 1985 a high correlation was found between angular momentum fluxes by azimuthal eddies at large radii and central pressure changes in the storm 27 33 h later momentum flux by eddies exceeded that by the azimuthal mean outside the 800 km radius while vortex spinup by the eddies reached instantaneous magnitudes as large as 25 m s 1 day outflow maxima and minima repeatedly appeared more than 1000 km from the hurricane center and tracked inward with time the results provide evidence of significant environmental control on the behavior of the storm after reaching hurricane strength elena experienced a major secondary intensification associated with a large inward cyclonic eddy momentum flux produced by the passage of a middle latitude trough north of the hurricane an outflow maximum appeared radially inside of the eddy momentum source consistent with balanced vortex theory and tracke

terrestrial mud volcanoes of the salse di nirano italy as a window into deeply buried organic rich shales of plio pleistocene age abstract the terrestrial mud volcanoes of the salse di nirano are situated in the northern apennines italy and were formed by the expulsion of mud water liquid hydrocarbons and gases predominantly methane ch 4 previous studies revealed that methane is consumed by microbial associations using the anaerobic oxidation of methane aom a process also occurring in marine settings this was supported by the presence of 13 c depleted biomarkers specific to sulfate reducing bacteria and archaea however the vast majority of biomarkers appeared to have other so far unexplained sources than microorganisms that in situ feed on hydrocarbon gases therefore lipid biomarker distributions of fluid samples from the salse di nirano mud volcanoes were revisited and compared to those extracted from organic rich shales from the underlying geological formations the organic chemical analyses of the mud volcano fluids revealed signals of various eukaryotic bacterial and archaeal organisms in addition to signals from higher plants specific bacterial dialkyl glycerol diethers dage in particular ai 15 ai 15 and 16 16 were found which putatively originate from sulfate reducing bacteria srb the presence of archaea is evidenced by archaeol and trace amounts of sn2 hydroxyarchaeol most biomarkers were not depleted in 13 c suggesting mainly non methane consuming source organisms organic chemical analyses of the plio pleistocene shales from the underlying geological formation revealed the same pattern for most of the bacterial and archaeal components the strong similarities between both samples suggest that the majority of the biomarkers in the emitted fluids in nirano originate from these marine organic rich deposits through which the fluids passed these biomarkers clearly obscure signals from microorganisms growing in situ in the mud volcanoes but the extent of this process is spatially and temporarily highly variable

rapid intensification of a sheared tropical storm abstract a weak tropical storm gabrielle in 2001 experienced a 22 hpa pressure fall in less than 3 h in the presence of 13 m s 1 ambient vertical wind shear a convective cell developed downshear left of the center and moved cyclonically and inward to the 17 km radius during the period of rapid intensification this cell had one of the most intense 85 ghz scattering signatures ever observed by the tropical rainfall measuring mission trmm the cell developed at the downwind end of a band in the storm core maximum vorticity in the cell exceeded 2 5 10 2 s 1 the cell structure broadly resembled that of a vortical hot tower rather than a supercell at the time of minimum central pressure the storm consisted of a strong vortex adjacent to the cell with a radius of maximum winds of about 10 km that exhibited almost no tilt in the vertical this was surrounded by a broader vortex that tilted approximately left of the ambient shear vector in a similar direction as the broad precipitation shield this st

volatiles in basaltic glasses from the east pacific rise at 21 n implications for morb sources and submarine lava flow morphology pillow rim glasses from a suite of moderately evolved lavas erupted along the axis of the east pacific rise epr at 21 n were analyzed by high temperature mass spectrometry for volatile content concentrations of h2o f and cl in the 21 n glasses are low and correlate inversely with mg yielding well defined trends these and other geochemical data indicate derivation of the 21 n glasses from similar parental magmas produced from a highly depleted nearly homogeneous source 1 total volatile h2o f and s contents are lower and co2 content is somewhat higher in these samples than in previously analyzed mid atlantic ridge mar glasses 21 n glasses are similar in volatile content to glasses from the galapagos spreading center gsc at 95 w except in cl lower and co2 higher unlike most mar and gsc glasses co2 is the dominant volatile in all of the 21 n glasses with mg 62 all of the epr and gsc glasses contain reduced carbon species co and ch4 unlike most previously analyzed mar samples these data indicate that sources for mid ocean ridge basalts are extremely volatile poor 0 10 wt and are probably dominantly reduced below quartz fayalite magnetite buffer sheet flow and pillow basalts contain identical volatile contents thus volatile abundance is not a factor controlling flow morphology extrusion rate and or surface topography are probably the most important factors influencing flow morphology in submarine basalts h2o release patterns are however related to flow morphology mass pyrograms for sheet flow and pillow basalt glasses both show bimodal h2o release behavior at the same temperatures 800 c and1000 c 50 c however the dominant h2o release peak for sheet flow glasses is at the lower temperature for pillow rim glasses it is at the higher temperature infrared spectroscopic studies indicate that h2o in these glasses is present only as hydroxyl groups thus the cause of differences in the bimodal h2o release and how it is related to flow morphology is unclear

on the dynamics of tropical cyclone and trough interactions abstractthe interaction between a tropical cyclone tc and an upper level trough is simulated in an idealized framework using coupled ocean atmosphere mesoscale prediction system coamps for trop

effects of vertical wind shear and storm motion on tropical cyclone rainfall asymmetries deduced from trmm abstract vertical wind shear and storm motion are two of the most important factors contributing to rainfall asymmetries in tropical cyclones tcs global tc rainfall structure in terms of azimuthal distribution and asymmetries relative to storm motion has been previously described using the tropical rainfall measuring mission microwave imager rainfall estimates the mean tc rainfall distribution and the wavenumber 1 asymmetry vary with storm intensity and geographical location among the six oceanic basins this study uses a similar approach to investigate the relationship between the structure of tc rainfall and the environmental flow by computing the rainfall asymmetry relative to the vertical wind shear the environmental vertical wind shear is defined as the difference between the mean wind vectors of the 200 and 850 hpa levels over an outer region extending from the radius of 200 800 km around the storm center the wavenumber 1 maximum rainfall asymmetry is downshear left right in the northern

melt to mush variations in crustal magma properties along the ridge crest at the southern east pacific rise the determination of along axis variations in melt properties within the crustal axial magma chamber beneath fast spreading axes is important for understanding melt delivery from the mantle eruption history along the ridge crest and the process of crustal accretion seismic reflection images1 2 3 4 have shown the molten sill to be continuous along the ridge crest for many tens of kilometres with varying widths 250 4 500 m but variations in its seismic properties and thickness have remained elusive despite several attempts to constrain these properties5 6 7 here we report that the melt sill along the southern east pacific rise which is about 50 m thick undergoes abrupt changes in its internal properties ranging from pure melt to mush the 60 km long ridge crest segment near 14 00 s is characterized by three 2 4 km sections containing pure melt embedded within a magma chamber rich in mush these small pure melt pockets may represent a fresh supply of magma from the mantle capable of erupting and forming the upper crust conversely the 80 90 of the magma chamber which is mushy is unlikely to erupt and may influence the lower crustal accretion

seismic imaging of oceanic layer 2a between 9 30 n and 10 n on the east pacific rise from two ship wide aperture profiles we analyze two ship multichannel seismic wide aperture profiles wap acquired on the east pacific rise epr between 9 30 c and 10 n in may and june 1985 for offsets between 2 and 5 km most of the wap common depth point cdp gathers exhibit a strong retrograde reflection like seismic arrival that corresponds to rays turned within a very strong velocity gradient zone underlying the uppermost crustal layer 2a stacking of this postcritical arrival for hundreds of cdp gathers along the wap lines yields remarkably clear and virtually continuous images of the bottom of layer 2a for several tens of kilometers along and across the epr an innovative combination of this image with others of the seafloor sf and of the axial magma chamber amc provides an unusually clear composite picture of young upper crust we combine these images with detailed seismic velocity information also obtained from the cdp gathers to achieve an accurate determination of the layer 2a thickness in the area along the epr axis between 9 30 n and 10 n layer 2a shows a relatively constant thickness between 100 and 150 m 80 120 ms two way travel time across the axis however a line near 9 30 n indicates that layer 2a thickness rapidly increases by approximately a factor of 2 within 2 4 km of the axis and remains nearly constant afterwards thus the final thickness of layer 2a is attained before the development of large scale tectonic faulting strongly suggesting that the thickening of layer 2a away from the axis is due to successive episodes of volcanic activity increasing the thickness of the uppermost crustal section from the top rather than tectonic fracturing lowering the uppermost crustal seismic velocities and pushing the bottom of layer 2a downwards as the crust moves away from the axis

roof assimilation at fast spreading ridges an investigation combining geophysical geochemical and field evidence 1 the role of assimilation at the roof of the axial magma chamber amc at fast spreading mid ocean ridges is investigated using field geophysical and geochemical data field observations from ophiolites indicate that roof assimilation is a common process but provide little constraint on the amount of material assimilated arguments based on geophysical data that include the subsidence of the layer 2a 2b boundary across the width of the amc and the depth of large axial summit troughs require at least 50 100 m of assimilation however significant variations in the depth of the amc on the east pacific rise epr over short along axis distances suggest up to 500 m fluctuations in the depth of the amc may be common on short timescales geochemical modeling of the over enrichment of chlorine in epr basalts suggests that 20 of the oceanic crust may go through a cycle of crystallization alteration then assimilation this is far more than can be accounted for by roof subsidence and suggests that fluctuations in the level of the roof must account for the majority of the assimilation assimilation most likely occurs on a number of different timescales ranging from decadal due to perturbations in the thermal regime related to diking to longer period fluctuations controlled by magma supply from the mantle large scale roof assimilation has implications for the accretion of the lower crust due to heat losses associated with assimilation and for the interpretation of the geochemistry of the oceanic crust

mud volcanism an updated review abstract mud volcanism or sedimentary volcanism represents one of the most intriguing phenomena of the earth s crust with important implications in energy resource exploration seismicity geo hazard and atmospheric budget of greenhouse gases since the first review papers were issued at the beginning of 2000s a large amount of new geological geophysical and geochemical data has been acquired which clarified ambiguous concepts and significantly improved our knowledge of mud volcanism here we offer an updated review of the knowledge and implications of mud volcanoes with emphasis on the terminology used to describe different processes and structures the physical chemical and morphological characteristics of the several fluid emission structures the chemical properties of the released fluids in particular the molecular and isotopic composition of the gas the mud volcano formation dynamics and the several implications for petroleum exploration geo hazards and global atmospheric methane budget this review integrates new fluids data collected in azerbaijan and is complemented with field observations from various mud volcano provinces worldwide although the total number of mud volcanoes on earth is still uncertain 600 main onshore structures with a large variety in shapes and sizes are documented in recent global data sets and several thousand are assumed to exist in the oceans it is clear that a mud volcanoes are broadly distributed throughout the globe in active margins compressional zones of accretionary complexes thrust and overthrust belts passive margins deep sedimentary basins related to active plate boundaries as well as delta regions b they are specifically located in hydrocarbon bearing basins along anticline axes strike slips and normal faults and fault related folds in petroleum systems c they represent a specific category of natural gas oil seepage manifestation often related to deep and pressurised reservoirs d the main engine driving mud volcanism is given by a combination of gravitative instability of shales and fluid overpressure build up followed by hydrofracturing e hydrocarbons are generally of thermogenic origin while microbial gas is released in only a few cases mud volcanism on other planets e g mars and titan and microbial activity associated with gas seepage represent emerging issues and opportunities for future research

relationship between spreading rate and the seismic structure of mid ocean ridges different parts of the global mid ocean ridge system create oceanic crust at rates that differ by more than a factor of ten the rates of supply of heat to these different systems must also vary substantially and it is this heat supply in the form of hot mantle material rising beneath the ridge axis that determines the nature of the magmatic tectonic and hydrothermal processes that control the production of new oceanic crust here we present evidence suggesting that a systematic relationship exists between the depth to zones of elevated temperature and partial melt beneath mid ocean ridges and their spreading rate recent seismic measurements provide robust determinations at six different locations of the depth to the top of the axial low seismic velocity zone which suggest that as full spreading rate decreases from 150 to 20 mm yr 1 the depth below the sea floor to the top of the lvz increases from 1 to 4 km although this relationship might arise in a number of ways our preferred explanation is that the major faults that extend to greater depths on slower spreading ridges1 allow a vigorous circulation of cooling sea water to reach greater depths blocking the upward migration of large melt bodies

the origin of oceanic plagiogranites from the karmoy ophiolite western norway both field relationships and geochemical characteristics indicate two suites of plagiogranitic and related rocks coexisting in the higher parts of the karmoy ophiolite of western norway the plutonic zone of this ophiolite can be subdivided into three complexes the east karmoy igneous complex the visnes high level complex and the veavagen igneous complex and plagiogranitic rocks are well developed in the first two of these within the east karmoy igneous complex plagiogranites are associated with high temperature pre basic dyke shear zones rare earth element modelling indicates that these plagiogranites were derived by anatexis of amphibolite hydrated diabase assuming a starting material consisting of 40 hornblende and 60 plagioclase and that batch melting occurred within the stability field of hornblende in comparison plagiogranite occurs in a number of bodies in the upper part of the visnes high level complex and forms a sandwich horizon together with biotite diorites and epidosites between a roof assemblage of dykes microgabbros and magnetite gabbros and a floor assemblage of layered and non layered gabbros the r e e modelling of the petrogenesis of this series of plagiogranites indicates that they were derived by filter pressing of a differentiated interstitial liquid to the vari textured gabbros although the distribution of highly hygromagmatophile elements such as k rb ba etc cannot be explained satisfactorily by this model alone depletion in these elements appears to be an autometasomatic effect

mid ocean ridge sulfide deposits evidence for heat extraction from magma chambers or cracking fronts numerous seafloor observations show that the sizes of high temperature hydrothermal sulfide edifices vary dramatically with spreading rate on fast spreading ridges venting occurs from spindly chimneys which reach heights of about 10 m while on slow spreading ridges vents are frequently located near the tops of large sulfide mounds whose volumes may reach 105 106 m3 we argue that such variations are the result of a profound difference in the nature of hydrothermal heat extraction between fast spreading ridges where spreading occurs predominantly by magmatism and slow spreading ridges where there is a significant component of tectonic extension along fast spreading ridges a steady state axial magma chamber can be insulated by a relatively thick conductive boundary layer because heat extraction is limited by low permeability in such systems episodes of vigorous venting are linked to diking events not only because these introduce a significant heat source into the upper crust but also because the intrusion of a dike is the primary source of increased permeability near the ridge axis over a time scale of the order of a decade mineral deposition tends to clog the reaction and upflow zones and there is a high probability that young sulfide structures will be buried by subsequent eruptions on slow spreading ridges tectonic extension maintains the fluid pathways necessary to support vigorous convection in the waning stages of magmatism hydrothermal circulation driven by a downward migrating cracking front can cool the entire crust leading to the formation of very large sulfide deposits as the depth of circulation increases overburden pressures reduce the permeability and the hydrothermal heat fluxes decrease progressively once hydrothermal fluids penetrate the moho serpentinization clogs the fluid pathways and high temperature venting ceases until it is reactivated by a fresh magmatic intrusion

structure of uppermost fast spread oceanic crust exposed at the hess deep rift implications for subaxial processes at the east pacific rise the uppermost 2 km of the oceanic crust created at the fast spreading 135 mm yr 1 full rate equatorial east pacific rise epr is exposed for tens of kilometers along escarpments bounding the hess deep rift mosaics of large scale digital images from the remotely operated vehicle rov argo ii and direct observations from the submersible alvin document a degree of geological complexity and variability that is not evident from most studies of ophiolites or prevailing models of seafloor spreading dramatic variations in the thickness and internal structure are documented in both the basaltic volcanic and sheeted dike rock units these rock units are characterized by extensive faulting fine scale fracturing and rotations of coherent crustal blocks meters to tens of meters across the uppermost basaltic lavas are essentially undeformed and have overall gently inclined flow surfaces through most of the basaltic lava unit however lava flow contacts dip 20 70 w toward the epr and generally increase in dip downward in the section dikes cutting the lavas and in the underlying sheeted dike unit generally dip 90 40 e away from the epr deeper level gabbroic rocks show little evidence of the intense fracturing typical of the overlying units we interpret this upper crustal structure as the result of subaxial subsidence within 1 2 km of the epr that accommodated the thickening of the basaltic lava unit to 500 m variations in the thickness of lava and dike units and spatially related structures along the rift escarpments suggest temporal fluctuations in magma supply these results indicate that substantial brittle deformation accompanied waxing and waning volcanism during the accretion of the crustal section exposed at the hess deep rift if this type of structure is typical of uppermost oceanic crust generated at the epr these processes may be common along fast spreading mid ocean ridges

a new model of the petroleum system in the northern apennines italy a geochemical study on fluids from selected spontaneous seepages and drilled wells was carried out together with geologic investigation and deep cross sections reconstruction to examine the petroleum system in the western northern apennines foothills the hydrocarbons occurring in the miocene foredeep units that form the reservoirs are commonly interpreted as generated in a source reservoir system however the low total organic carbon its elevated dilution in the sediment pile and the limited amount of successions that entered in the oil window indicate a low potential for the hydrocarbons generation the structures deformation in the northern apennines foothills is mainly late miocene to pliocene in age and involves successions that are progressively younger towards southeast the earlier structure forms the salsomaggiore anticline in the western sector the comparison of the fluids from the wells and the mud volcanoes shows high geochemical and thermal history similarities saline waters originate from the connate pore water entrapped in the miocene reservoir rocks during their deposition the gaseous hydrocarbons are a mixture of secondary biogenic methane and primary and secondary thermogenic gases the associated oils show both early and late maturities these evidences account for different generation and migration steps depending on burial conditions and deformation time the various reservoirs appear confined by the thrust detachment at different depths and by the occurrence of reactivated lateral ramps these results suggest the occurrence of a common source rock deeper than the tertiary reservoir units which progressively entered in the oil window this source rock could have wide lateral extension at least comparable with the width of the studied area and represent a prime exploration target to evaluate the undiscovered oil and gas resources

the effects of vertical wind shear on the distribution of convection in tropical cyclones abstract the influence of vertical wind shear on the azimuthal distribution of cloud to ground lightning in tropical cyclones was examined using flash locations from the national lightning detection network the study covers 35 atlantic basin tropical cyclones from 1985 99 while they were over land and within 400 km of the coast over water a strong correlation was found between the azimuthal distribution of flashes and the direction of the vertical wind shear in the environment when the magnitude of the vertical shear exceeded 5 m s 1 more than 90 of flashes occurred downshear in both the storm core defined as the inner 100 km and the outer band region r 100 300 km a slight preference for downshear left occurred in the storm core and a strong preference for downshear right in the outer rainbands the results were valid both over land and water and for depression storm and hurricane stages it is argued that in convectively active tropical cyclones deep divergent circulations oppose the ver

baroclinically induced tropical cyclogenesis abstract the authors investigate the transition of numerous subtropical cyclones into late season tropical storms and hurricanes during the 2000 and 2001 atlantic tropical cyclone seasons in all transitioning cases 10 the 900 200 hpa wind shear was initially near or in excess of the upper limit of vertical shear deemed suitable for tropical cyclogenesis in many of these cases the vertical shear decreased markedly near or prior to the time of tropical cyclone formation in cases that did not become named tropical cyclones either the tropospheric vertical shear remained in excess of 15 20 m s 1 or the underlying sea surface temperature sst dropped below about 26 c prior to or during the weakening of the shear cases in which the shear remained large featured multiple short wave upper tropospheric troughs interacting with the developing lower tropospheric disturbance such that classical occlusion did not occur through detailed analysis and simulation of the development of hurricane michael in 2000

development of north atlantic tropical disturbances near upper level potential vorticity streamers abstracttropical cyclone tc development near upper level potential vorticity pv streamers in the north atlantic is studied from synoptic climatology composite and case study perspectives midlatitude anticyclonic wave breaking is instrumental in driving pv streamers into subtropical and tropical latitudes in particular near the time mean midocean trough identified previously as the tropical upper tropospheric trough twelve tcs developed within one rossby radius of pv streamers in the north atlantic from june through november 2004 08 this study uses composite analysis in the disturbance relative framework to compare the structural and thermodynamic evolution for developing and nondeveloping cases the results show that incipient tropical disturbances are embedded in an environment characterized by 850 200 hpa westerly vertical wind shear and mid and upper level quasigeostrophic ascent associated with the pv streamer with minor differences between developing and nondeveloping cases the key differ

identification and era 15 climatology of potential vorticity streamers and cutoffs near the extratropical tropopause abstract a novel approach is introduced to identify potential vorticity pv streamers and cutoffs as indicators of rossby wave breaking near the extratropical tropopause and to compile climatologies of these features on different isentropic surfaces the method is based on a contour searching algorithm that identifies the dynamical tropopause 2 potential vorticity units pvu pvu 1 10 6 k kg 1 m2 s 1 isoline on isentropic surfaces the contour is then analyzed to search for cutoffs and filament like streamers whereas the identification of cutoffs is unambiguous the one for streamers requires the specification of two parameters that determine the width and length of the contour feature to be classified as a streamer this technique has been applied to the pv distribution in the northern hemisphere on isentropes from 295 to 360 k during the time period from 1979 to 1993 using the 15 yr european centre for medium range weather forecasts ecmwf re analysis era 15 the climatology reveals a pronou

poisson s ratio structure of young oceanic crust we have applied full waveform inversion to wide aperture seismic reflection data from the southern east pacific rise near 14 s the data contain clear compressional wave and doubly converted shear wave arrivals that provide good constraints on the p and s wave velocities vp vs and hence poisson s ratio and seismic attenuation qp qs structure of seismic layer 2 layer 2a is highly attenuating qp 18 30 and qs 8 15 and layer 2b is moderately attenuating qp 30 50 and qs 20 25 our results show high at the seafloor and in layer 2a 0 48 across the top of the 2a b transition the rapid increase in vp is accompanied by a sharp drop in to 0 25 within just 200 m of the seafloor we perform simple calculations to gain an insight into the porosity and crack distribution with depth these calculations suggest that porosity is in excess of 30 in layer 2a but reduces to 6 7 at the top of the 2a b transition and to about 5 at a depth of 600 m below seafloor within layer 2b our results suggest that there is an increase in the average aspect ratio with depth across the 2a b transition the most likely explanation is that numerous thin cracks either mechanically close or are infilled at depth our results show there to be an abrupt change in the pore structure across the 2a b transition which is consistent with a lithologic transition from extrusives to dykes but is equally consistent with a transition mechanical or hydrothermal within the extrusive pile

formation of crystal magma chambers in iceland formation of crustal magma chambers in iceland may be facilitated by the occurrence of stress barriers that lead to formation of thick sills such sills absorb the magma of all dikes that enter them and may evolve into magma chambers ideal sites for stress barriers and hence for magma chambers are rock formations where individual layers have different elastic properties the rocks formed during the pleistocene have notably different elastic properties and when buried in the volcanic zones they form more promising sites for magma chambers than the tertiary rocks this may explain why the number of magma chambers indicated by the number of corresponding central volcanoes during the late pleistocene i e during the past 0 7 m y appears to be proportionally greater than the number of chambers i e central volcanoes active during tertiary time

dinosterane and other steroidal hydrocarbons of dinoflagellate origin in sediments and petroleum abstract the steroidal alkanes of a selection of sediments and oils have been examined by gc ms with multiple metastable reaction monitoring specific 4 methyl sterane isomers have been identified by comparison with isomers synthesized from sterols isolated from dinoflagellates an immature marine oil shale and two mature marine oils of triassic to early cretaceous age contained high concentrations of c30 steranes comprising desmethyl 24 ethyl 4 methylcholestane and 4 23 24 trimethylcholestane dinosterane isomers an immature non marine oil shale and two non marine oils of cretaceous to eocene age contained stereoisomers of 24 ethyl 4 methylcholestane as the dominant c30 steranes reaction monitoring analyses in gc ms are particularly suited to unravelling complex distributions of homologous and stereoisomeric steroids encountered in oils and their source rocks

molecular stratigraphy a new tool for climatic assessment variations in sea surface temperatures over the past 500 000 years are inferred from the relative abundance behaviour of two organic compounds c37 alkenones over the upper 8 metres of a sediment core from the eastern equatorial atlantic this molecular record ascribed to contributions from prymnesiophyte algae correlates well with the variations in the 18 signal for the calcareous skeletons of certain planktonic foraminifera thus providing the first demonstration of a new stratigraphical technique which may be especially valuable where methods based on carbonate 18 fail

numerical simulations of the genesis of hurricane diana 1984 part i control simulation abstract the complete transformation of a weak baroclinic disturbance into hurricane diana is reproduced by numerical simulations using the fifth generation pennsylvania state university national center for atmospheric research mesoscale model three distinct phases of the evolution are evident first baroclinic and barotropic development strongly modified by the effects of latent heating occurs during the latter part of this phase the low level circulation is strengthened through the axisymmetrization of remote potential vorticity anomalies that are generated by condensational heating and then advected toward the incipient storm the axisymmetrization process evinces properties of both nonlinear discrete vortex merger and vortex rossby wave dynamics the transformation from cold core to warm core vortex occurs in this development stage in the second phase lasting 10 12 h little deepening occurs spiral bands of convection begin to form and the core of the storm moistens eventually reaching 95

extreme efficiency of mud volcanism in dewatering accretionary prisms drilling results from two mud volcanoes on the mediterranean ridge accretionary complex as well as bottom sampling and the wealth of geophysical data acquired recently have provided fundamental knowledge of the 3d geometry of mud extrusions mud volcanism is generally related to buoyancy density inversion and is triggered by the collision of the african and eurasian blocks forcing undercompacted clayey sediments to extrude along faults in the central and hinterlandward parts of the prism volumetric estimates of extruded mud in several well studied areas were based on pre stack depth migrated seismic profiles across the entire up to 150 km wide prism the resulting volumes of mud were combined with ages from mud dome drilling so that rates of mud extrusion were obtained subtracting the solid rock mass from the bulk mud volume using physical property data fluid flux as a function of mud volcanism alone has been quantified for the first time the volume of fluid extruding with the mud is found to be variable but reaches up to 15 km3 fluid per km trench length and ma along cross sections with abundant mud volcanoes such large fluid quantities in a region some 50 150 km behind the deformation front exceed estimates from those elsewhere where undoubtedly the majority of the interstitial fluid is lost due to compaction such fluids near the backstop are likely to result predominantly from mineral dehydration and diagenetic reactions at depth and consequently provide a window to understand deeper processes along the deep decollement more importantly the enormous rates with which such fluids and liquified mud escape along the out of sequence faults alter fluid budget calculations in subduction zones drastically

salinity of oceanic hydrothermal fluids a fluid inclusion study abstract an extensive microthermometric study of quartz epidote plagioclase anhydrite and sphalerite hosted fluid inclusions from ophiolitic semail oman and trinity california ophiolites and oceanic east pacific rise hydrothermal vents gorringe bank odp leg 111 hole 504b crust has been carried out in order to constrain a model accounting for wide salinity variations measured in the oceanic hydrothermal fluids recorded salinities in fluid inclusions vary between 0 3 and 52 wt nacl eq however more than 60 of the mean standard deviation salinities of the samples are within the range 3 2 0 3wt nacl eq microthermometric error and the mean salinity of all fluid inclusions without the brines is 4 0 wt nacl eq with a standard deviation of 1 6 wt nacl eq whereas most samples display slightly higher salinities than seawater several samples exhibit very high salinities more than two times that of seawater these high salinities are restricted to the plagiogranites semail and trinity ophiolites which mark the top of the fossil magma chamber in the transition zone between the plutonic sequence and the sheeted dyke complex the fluid inclusion population studied in the plagiogranites is characterized by the occurrence of four major fluid inclusion families 1 low to medium salinity liquid vapor fluid inclusions which homogenize into the liquid phase 2 low salinity liquid vapor fluid inclusions with pseudocritical homogenization 3 low to medium salinity liquid vapor fluid inclusions which homogenize into the vapor phase and 4 high salinity liquid vapor halite fluid inclusions which homogenize into the liquid phase by halite dissolution and exhibit salinities as high as 52 wt nacl eq these fluid inclusion families are interpreted as resulting from phase separation occurring in hydrothermal or magmatic fluids within the transition zone between the hydrothermal system and the magma chamber at temperatures higher than 500 c very low salinities less than half that of seawater have been found only in one dioritic sample from the gorringe bank mineralogical and petrological data from the semail ophiolite shows the absence of cl rich minerals furthermore hydration of the crust although very important cannot account for the large salinity variations thus the large salinity variations measured are interpreted as resulting from phase separation and generation of brine rich fluids at the top of the magma chamber this phase separation and subsequent phase segregation and brine accumulation may result in a double diffusive convection of the fluids in the hydrothermal system

a numerical study on rapid intensification of typhoon vicente 2012 in the south china sea part ii roles of inner core processes abstractin part i of this study the role of environmental monsoon flow in the onset of rapid intensification ri of typhoon vicente 2012 was discussed in this part ii key inner core processes that effectively resist environmental vertical wind shear during ri onset are investigated the convective precipitation shield cps embedded in the downshear convergence zone plays a vital role in preconditioning the tropical cyclone tc vortex before ri the cps induces a mesoscale positive vorticity band pvb characterized by vortical hot tower structures upstream and shallower structures 4 km downstream multiple mesovortices form successively along the pvb and are detached from the pvb at its downstream end rotating cyclonically around the tc center the sufficient amount of vorticity anomalies in the pvb facilitates the upscale growth of a mesovortex into a reformed inner vortex which eventually replaces the parent tc vortex i e downshear reformation leading to ri onset the timing of downshe

mesoscale aspects of the downshear reformation of a tropical cyclone the downshear reformation of tropical storm gabrielle 2001 was investigated using radar reflectivity and lightning data that were nearly continuous in time as well as frequent aircraft reconnaissance flights initially the storm was a marginal tropical storm in an environment with strong 850 200 hpa vertical wind shear of 12 13 m s 1 and an approaching upper tropospheric trough both the observed outflow and an adiabatic balance model calculation showed that the radial vertical circulation increased with time as the trough approached convection was highly asymmetric with almost all radar return located in one quadrant left of downshear in the storm reconnaissance data show that an intense mesovortex formed downshear of the original center this vortex was located just south of rather than within a strong downshear left lightning outbreak consistent with tilting of the horizontal vorticity associated with the vertical wind shear the downshear mesovortex contained a 972 hpa minimum central pressure 20 hpa lower than minimum pressure in the original vortex just 3 h earlier the mesovortex became the new center of the storm but weakened somewhat prior to landfall it is argued that dry air carried around the storm from the region of upshear subsidence as well as the direct effects of the shear prevented the reformed vortex from continuing to intensify despite the subsequent weakening of the reformed center it reached land with greater intensity than the original center it is argued that this intensification process was set into motion by the vertical wind shear in the presence of an environment with upward motion forced by the upper tropospheric trough in addition the new center formed much closer to the coast and made landfall much earlier than predicted such vertical shear induced intensity and track fluctuations are important to understand especially in storms approaching the coast

elliptical mud volcano caldera as stress indicator in an active compressional setting nirano pede apennine margin northern italy the relations between mud volcanism and active tectonic strain were investigated at the nirano mud volcano field nmvf near the active pede apennine thrust front of the northern apennines thrust and fold belt italy active fluid release occurs through numerous vents within an elliptical depression developed over the crest of a thrust related anticline this depression is interpreted as a caldera collapse like structure that may have developed in response to the deflation of a shallow mud chamber triggered by eruption and sediment fluid evacuation events like many volcanic calderas the nmvf caldera is elongated nearly parallel to the direction of least horizontal compressive stress s h and is thus deduced to reflect the regional tectonic stress axes it is concluded that mud volcano calderas exhibit mechanical similarities to the igneous analogs and that the methods used in this first test could be applied to other calderas imaged by seismic data and in the field

a climatology of rossby wave breaking along the subtropical tropopause ten years 1986 95 of global analyses from the european centre for medium range weather forecasts are used to investigate the temporal and spatial distributions of rossby wave breaking rwb at 350 k along the tropopause herein defined by the 61 5 potential vorticity pv unit 10 26 km 2 s21 kg21 contours though many studies acknowledge rwb as an important contributor to the complex of mixing processes in the atmosphere there exists no prior climatological study of its distribution near the tropopause as in previous studies rwb is identified in the global analyses by southward directed pv gradients at 350 k rwb along the tropopause occurs preferentially during summer over the midoceans in relative proximity to the planetary scale high pressure systems in the subtropics isentropic trajectories at 350 k show that outflow from the tops of these subtropical highs directly participates in rwb over the adjacent downstream oceanic regions two regions are highlighted in this study the north pacific during boreal summer and the south atlantic during austral summer synoptic maps of breaking rossby waves in these regions are provided to reveal the acute tropopause folding in the meridional plane which characteristically accompanies rwb the rich interaction between the tropical flow and the extratropical westerly current exhibited by these cases suggests that the subtropical highs serve as important agents in the coupling between the tropical troposphere and the extratropical stratosphere as expected from theoretical considerations the locations where rwb occurs most frequently known as surf zones are shown to coexist with regionally weak time mean wind speeds and horizontal gradients of pv at 350 k

processes of brine generation and circulation in the oceanic crust fluid inclusion evidence from the troodos ophiolite cyprus detailed temporal thermal and compositional data on aqueous fluid inclusions from a suite of plutonic and diabase samples from the troodos ophiolite cyprus provide the first documentation that generation of high temperature brines may be common at depth in the oceanic crust anastomosing arrays of fluid inclusions in rocks of the upper intrusive sequence record episodic fracturing events the earliest fracturing event at temperatures 450 600 c resulted in entrapment of brine rich aqueous fluids with salinities of 36 61 wt nacl equivalent homogenization of the brine inclusions by haute dissolution the virtual absence of vaporrich fluid inclusions throughout the upper level plutonic sequence and the restriction of brine inclusions to the most evolved plutonic rocks suggests that exsolution of brines off of the late stage gabbro and plagiogranite melts played a significant role in generating the quartz hosted high salinity inclusions cooling of the fluids during pulses of fluid migration associated with episodic fracturing events resulted in entrapment of the brines in the deep seated high temperature portion of the hydrothermal system in localized areas the high temperature brines nacl kcl cacl2 caused extreme alteration of the plagiogranite bodies and in the formation of podiform epidosites arrays of low temperature low salinity fluid inclusions which in some samples crosscut fractures dominated by brine inclusions indicate downward propagation of a cracking front subsequent to collapse of the high temperature magmatic system resulting in penetration of seawaterlike fluids into the plutonic sequence at temperatures 200 400 c hydration reactions under greenschist facies conditions or limited mixing with brine rich fluids may have resulted in salinity variations from 70 below to 200 above seawater concentrations temperatures and compositions of the low salinity inclusions are similar to those found in stockwork systems beneath troodos ore deposits and to those of fluids exiting active submarine hydrothermal vents at mid ocean ridge spreading centers the low temperature fracture networks may represent an extensive deep seated feeder system which coalesced to form zones of concentrated hydrothermal upflow

potential vorticity analysis of tropical cyclone intensification the interaction of marginal tropical storm danny 1985 with an upper tropospheric positive potential vorticity anomaly was examined the intensification mechanism proposed earlier for mature hurricane elena appears to be valid for danny as well despite significant differences in the synoptic scale environment and in the stage of the tropical cyclone prior to the interaction both storms experienced rapid pressure falls as a relatively smallscale positive upper potential vorticity anomaly began to superpose with the low level tropical cyclone center the interaction is described in terms of a complex interplay between vertical wind shear diabatic heating and mutual advection among vortices at and below the level of the outflow anticyclone despite this complexity the superposition principle appears to be conceptually useful to describe the intensification of tropical cyclones during such interactions