prompt penetration electric fields ppefs and their ionospheric effects during the great magnetic storm of 30 31 october 2003 1 we explore the ionospheric effects of prompt penetration electric fields ppefs for a variety of interplanetary magnetic field directions we use the great magnetic storm of 30 31 october as an example of ppef effects for intense southward interplanetary magnetic fields imfs inward plasma sheet convection occurs with the result of magnetospheric ring current formation and an intense magnetic storm concurrent with the above positive phase ionospheric storms occur in the dayside and negative phase ionospheric storms occur on the nightside the topics of this paper the dayside ionospheric storms due to ppefs are characterized by transport of near equatorial plasma to higher altitudes and latitudes forming a giant plasma fountain these features are part of what is called the dayside ionospheric superfountain dis for these southward imfs dusk and dawn plasma are predicted to be transported toward the dayside for northward imfs negative phase ionospheric storms are expected on the dayside if the ppefs indeed reach that region of space imf by components are expected to have weak or neglible ionospheric effects on the basis of ppef arguments intervals of imf by should not be related to geomagnetic storms they are not imf by intervals should however cause a shearing of the magnetotail a feature that has been previously reported in the literature

mud plumbing system of an isolated phreatic eruption at akita yakeyama volcano northern honshu japan abstract a small phreatic eruption occurred on 16 august 1997 at the flank of a dacite lava dome of akita yakeyama northern honshu japan air falls and viscous mudflows were discharged from two craters mudflow effusion preceded discrete explosions followed by a fine ash discharge the air fall deposit consists of an upper fine ash deposit and a lower ballistic dominated poorly sorted tephra in which ranges in grain size from fine ash to blocks of ca 50 cm both air fall and mudflow deposits were composed of fine mud and coarse lithic fragments which contained abundant liquid water lithic fragments comprise fresh dacite of the host lava dome and hydrothermally altered stratocone andesite intensely altered andesite fragments contain quartz cristobalite andalusite pyrophyllite 7 a kaolin and anhydrite some mineral assemblages indicate hydrothermal temperatures greater than 300 c rare sandstone fragments are likely to be lacustrine from ca 1000 m depth the surface morphology of the mudflow deposits indicates that the mud contained ca 30 vol water the cube root similarity rules on crater size and the cloud shape of buried explosions provided energy of 3 5 10 9 j at depths of 6 10 m based on the observed crater size 20 m and fountain like cloud shape the depth estimate is consistent with the abundance of coarse dacite fragments derived from shallow lava in the explosion deposit thermodynamic energy release of ca 1 10 11 j was calculated based on the following estimated parameters product volume of 1 10 3 m 3 hydrothermal temperatures of 300 350 c and pressures of 11 24 mpa corresponding to the estimated source depth the thermodynamic estimation represents the total energy released during the eruption whereas the similarity rule yields an energy value as created by discrete explosions mud ascended from a hot aquifer at 1000 m depth first effused as a mudflow and was then expelled explosively from another crater explosivity depends on the shallow geologic structures reduction of pressure within the shallow permeable breccia resulted in effusive mudflow whereas overpressure confined by rigid dacite lava yielded explosive eruptions the mud plumbing system which includes deep aquifer mud and shallow explosions seems to be typical of phreatic eruptions

gas hydrate occurrence on the continental slope of the northern south china sea high resolution multi channel seismic data and geological samples were collected during two research cruises of the r v fendou 4 in 1999 and 2000 studies on these data and samples together with results from sites 1143 1145 and 1148 of odp leg 184 suggest that the geological structure on the continental slope of the northern south china sea is favorable for the formation of gas hydrates bottom simulating reflectors bsrs and geochemical anomalies which indicate the existence of gas hydrates have been recognized in sediments of the xisha trough the dongsha rise and the accretionary wedge of the manila subduction zone these gas hydrates are generated by two different mechanisms depending on the tectonic regime and the seismic and geochemical characteristics the first applies to the passive continental margin of the nor them south china sea on the dongsha rise and in the xisha trough the gas hydrates are associated with diapiric structures active faults slumps and gravity flows as well as high late cenozoic sedimentation rates their seismic expression includes bsrs seismic blanking zones and velocity anomalies the second mechanism is operative on the active continental margin along the manila subduction zone especially in the accretionary wedge here gas hydrate occurrence is marked by widespread bsrs and acoustic pull down possibly related to the existence of free gas in the sediments beneath the bsr the thickness of the seismic blanking zones averages 250 m suggesting that the stable gas hydrate zone has about the same thickness c 2005 elsevier ltd all rights reserved

triggering and dynamic evolution of the lusi mud volcano indonesia abstract mud volcanoes are geologically important manifestations of vertical fluid flow and mud eruption in sedimentary basins worldwide their formation is predominantly ascribed to release of overpressure from clay and organic rich sediments leading to impressive build up of mud mountains in submarine and subaerial settings here we report on a newly born mud volcano appearing close to an active magmatic complex in a backarc sedimentary basin in indonesia the location of the mud volcano close to magmatic volcanoes results in a high background temperature gradient that triggers mineralogical transformations and geochemical reactions at shallow depth the eruption of 100 c mud and gas that started the 29th of may 2006 flooded a large area within the sidoarjo village in northeast java thousands of people have so far been evacuated due to the mud flood hazards from the eruption since the initial eruption the flow rate escalated from 5000 to 120 000 m 3 d during the first eleven weeks then the erupted volume started to pulsate between almost zero and 120 000 m 3 d in the period august 14 to september 10 whereas it increased dramatically following swarms of earthquakes in september before reaching almost 180 000 m 3 d in december 2006 sampling and observations were completed during two fieldwork campaigns on the site the eruption of boiling water is accompanied by mud aqueous vapour co 2 and ch 4 based on geochemical and field results we propose a mechanism where the eruptions started following the 27th of may earthquake due to fracturing and accompanied depressurization of 100 c pore fluids from 1700 m depth this resulted in the formation of a quasi hydrothermal system with a geyser like surface expression and with an activity influenced by the regional seismicity

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

methane derived authigenic carbonates formed by subduction induced pore water expulsion along the oregon washington margin authigenic magnesian calcite dolomite and aragonite are precipitated in the uppermost terrigenous sediments of the washington oregon accretionary prism by subduction induced dewatering these distinctive carbonates are methane derived and occur at sites of concentrated pore water expulsion unique biologic communities that subsist at least indirectly on methane suess et al 1985 are also found at some of these sites the methane which is dominantly biogenic is carried to the uppermost sediments of the prism by fluids and is oxidized by sulfate reducers before being incorporated into a carbonate cement carbonate precipitation occurs below the oxic layer probably no deeper than several centimetres to a few metres below the seabed cementation may be induced by three factors 1 increased carbonate alkalinity resulting from microbial sulfate reduction 2 decreased co 2 solubility resulting from a pressure decrease when the pore water escapes the prism and or 3 the addition of ca 2 and mg 2 ions from sea water near the sediment water interface the convergent margin setting engenders precipitation of authigenic carbonates in several ways compressive stresses induce anomalously rapid compaction and dewatering rates and they may cause overpressuring in migrating pore water thereby delaying precipitation of carbonates until pressure is released near the sediment water interface structural deformation of the accretionary prism creates pathways such as fault zones secondary fracture porosity and dipping permeable layers often exposed by mass movement for efficient advection and expulsion of methane enriched pore water these characteristic conditions which lead to the precipitation of methane derived carbonates may be found at other convergent margins

theoretical effects of geomagnetic activity on low latitude ionospheric electric fields 1 the influence of geomagnetic activity on middle and low latitude thermospheric winds and ionospheric electric fields is investigated using model results from the national center for atmospheric research thermosphere ionosphere electrodynamics general circulation model model runs are made for different levels of geomagnetic activity model results show that the equatorward ionospheric currents produced by disturbance winds develop positive charge accumulation at low latitudes that maximizes in the premidnight sector the local time of maximum electric potential perturbation depends significantly on universal time so that the local time of reversal of the equatorial zonal perturbation electric field varies with longitude by 2 to 3 hours depending on the intensity of geomagnetic activity the westward perturbation electric field in the postsunset period indicates that stronger geomagnetic activity will produce a lower driven height of the evening f region after geomagnetic activity ceases model results show that the zonal disturbance winds can last for many days in the postrecovery period while the meridional disturbance winds decay more rapidly the long lasting zonal winds through the pedersen currents they drive help maintain meridional disturbance potential drops that decay much more slowly than the zonal disturbance potential drops after the activity ceases

the origin and migration of mud volcano fluids in taiwan evidence from hydrogen oxygen and strontium isotopic compositions abstract mud volcanoes are important gateways for deep fluids to migrate upward and provide windows for studying fluid sediment interaction at depth fluids emitted from 40 terrestrial mud volcanoes were collected in southern and eastern taiwan to study their chemical compositions including h o and sr isotopes 87sr 86sr and 88 86sr relative to seawater the mud volcano fluids are depleted in cl mg so42 and d and are elevated in b ba li and 18o possibly due to water rock interaction and clay dehydration mainly smectite to illite transformation in the source region the distribution of sr in mud volcano fluids shows patterns associated with their localities and geological settings most fluids have higher 87sr 86s than seawater indicating water rock interaction at depth the low na 87sr 86s and high ca fluids emitted from eastern taiwan imply intense interaction with igneous basement most fluids have higher sr cl and lower 88sr than seawater except mud volcanoes in the northern chu kou fault which emit low sr cl and extremely high 88sr up to 0 82 fluids we performed laboratory carbonate precipitation experiments that indicate that these high sr isotope ratios are caused by co precipitation of carbonates from high alkalinity fluids mud volcano fluids in taiwan originate at depth and their chemical compositions are controlled by the host rock degrees of water rock interaction and clay dehydration but also are masked by retrograde progresses such as carbonate precipitation during migration our results show that an approach combining water isotopes d and 18o and strontium isotopes 87sr 86sr and 88 86sr provides a robust tool for tracing fluid sources and migration pathways in accretionary prisms

marine pore water sulfate profiles indicate in situ methane flux from underlying gas hydrate marine pore water sulfate profiles measured in piston cores are used to estimate methane flux toward the sea floor and to detect anomalous methane gradients within sediments overlying a major gas hydrate deposit at the carolina rise and blake ridge u s atlantic continental margin here sulfate gradients are linear implying that sulfate depletion is driven by methane flux from below rather than by the flux of sedimentary organic matter from above thus these linear sulfate gradients can be used to quantify and assess in situ methane flux which is a function of the methane inventory below

structural controls on mud volcano vent distributions examples from azerbaijan and lusi east java structural mapping nearest neighbour and two point azimuth statistical analysis of mud volcano vent distributions from nine examples in azerbaijan and the lusi mud volcano in east java are described distributions are non random forming alignments subparallel to faults within anticlines ring faults conjugate faults and detachment faults this finding confirms a spatial relationship and supports a model for subsurface flow along these features as well as showing fractionation at depth as fracture and fault orientations are related to structures such as anticlines and the in situ stress state they are therefore predictable we use vent distributions in azerbaijan where the structural geology is well constrained to propose what controls the distribution of 169 vents at the lusi mud volcano this mud volcano system shows evidence for initial eruptions along a ne sw trend parallel to the watukosek fault changing to eruptions that follow east west trends subparallel to regional fold axes our analysis indicates that regions east and west of the lusi mud volcano are more likely to be affected by new vents than those to the north and south owing to probable onset of elongate caldera collapse within a 10 km diameter of the central vent

ionospheric and magnetic signatures of a space weather event on 25 29 august 2018 cme and hssws we present a study concerning a space weather event on 25 29 august 2018 accounting for its ionospheric and magnetic signatures at low latitudes and midlatitudes the effects of a storm in several longitudinal sectors asia africa america and the pacific have been analyzed using various parameters such as total electron content tec geomagnetic field and column o n2 ratio positive ionospheric storms are found in all the longitudinal sectors having its maximum effects in the asian sector whereas the negative ionospheric storms have been observed in the summer hemisphere northern hemisphere a large decrease in o n2 ratio in the northern hemisphere is a possible cause of the observed negative storm effects ionospheric f2 region maximum electron density nmf2 and tec have shown a positive correlation during this storm the study suggests that storm time generated wind does not have a uniform planetary extension and mainly affects dayside america and pacific and duskside africa sectors during the space weather event we observe an asymmetric variation of the magnetic field as a function of the longitude on the other hand the magnetic variations at midlatitudes are found to be symmetric in both hemispheres a signature of the disturbance dynamo anti sq circulation has been observed mainly at low latitudes we emphasize that the partial ring current prc estimated by the asym h magnetic index must also be taken into account along with the sym h index for a better approximation of ionospheric currents the study further suggests existence of several electric current cells in the ionosphere which is consistent with the blanc richmond model

mud volcanoes indicators of stress orientation and tectonic controls abstract this study examines the use of specific mud volcano features i e elongated calderas aligned vents and elongated volcanoes as potential indicators of tectonic stress orientation the stress indicator principles widely recognised for magmatic systems have been discussed and applied to mud volcano settings such as in the northern apennines and the azerbaijan greater caucasus as well as in other instances where the analysis was fully based on a remote sensing study the results of these applications are promising the obtained maximum horizontal stress sh directions generally showing a good correlation with those determined in the upper crust by classical methods i e earthquake focal mechanism solutions well bore breakouts therefore stress information from mud volcanoes could be used as a proxy for stress orientation 1 where stress data is lacking 2 where settings are inaccessible i e underwater or the surface of planets or simply 3 as supplementary stress indicators this study also pays special attention to structural elements that may control fluid expulsion at various length scales and pathways that should have spawned the mud volcanoes and controlled their paroxysmal events and eruptions different types of sub planar brittle elements have been found to focus fluid flow rising up through fold cores where the vertical zonation of stresses may take part in this process by creating distinctive feeder fracture fault sets on a regional scale mud volcanoes in active fold and thrust belts may occur over wider areas such as the prolific mud volcanism in azerbaijan or may cluster along discrete structures like the steep pede apennine thrust in the northern apennines where the generation of overpressures is expected to establish a positive feedback loop allowing for fault movement and mud volcanism

martian mud volcanism terrestrial analogs and implications for formational scenarios the geology of mars and the stratigraphic characteristics of its uppermost crust mega regolith suggest that some of the pervasively occurring pitted cones mounds and flows may have formed through processes akin to terrestrial mud volcanism a comparison of terrestrial mud volcanism suggests that equivalent martian processes likely required discrete sedimentary depocenters volatile enriched strata buried rheological instabilities and a mechanism of destabilization to initiate subsurface flow we outline five formational scenarios whereby martian mud volcanism might have occurred a rapid deposition of sediments b volcano induced destabilization c tectonic shortening d long term load induced subsidence and e seismic shaking we describe locations within and around the martian northern plains that broadly fit the geological context of these scenarios and which contain mud volcano like landforms we compare terrestrial and martian satellite images and examine the geological settings of mud volcano provinces on earth in order to describe potential target areas for piercement structures on mars our comparisons help to evaluate not only the role of water as a functional component of geological processes on mars but also how martian mud volcanoes could provide samples of otherwise inaccessible strata some of which could contain astrobiological evidence

when mud volcanoes sleep insight from seep geochemistry at the dashgil mud volcano azerbaijan the worlds 1500 mud volcanoes are normally in a dormant stage due to the short duration of eruptions their dormant stage activity is often characterized by vigorous seepage of water gas and petroleum however the source of the fluids and the fluid rock interactions within the mud volcano conduit remain poorly understood in order to investigate this type of activity we have combined satellite images with fieldwork and extensive sampling of water and gas at seeping gryphons pools and salsa lakes at the dashgil mud volcano in azerbaijan we find that caldera collapse faults and e w oriented faults determine the location of the seeps the seeping gas is dominated by methane 94 9 99 6 with a 13c v pdb in the 43 9 to 40 4 range consistent throughout the 12 analysed seeps ethane and carbon dioxide occur in minor amounts seventeen samples of seeping water show a wide range in solute content and isotopic composition pools and salsa lakes have the highest salinities up to 101 043 ppm cl and the lowest 18o v smow values 1 4 the mud rich gryphons have low salinities 18 000 ppm cl and are enriched in 18o 18o 4 6 the gas geochemistry suggests that the gases migrate to the surface from continuously leaking deep seated reservoirs underneath the mud volcano with minimal oxidation during migration however variations in gas wetness can be ascribed to molecular fractionation during the gas rise in contrast the water shows seasonal variations in isotopic composition and surface evaporation is proposed as a mechanism to explain high water salinities in salsa lakes by contrast gryphons have geochemical signals suggesting a deep seated water source these results demonstrate that the plumbing system of dormant mud volcanoes is continuously recharged from deeper sedimentary reservoirs and that a branched system of conduits exists in the shallow subsurface while the gas composition is consistently similar throughout the crater the large assortment of water present reflects the type of seep i e gryphons versus pools and salsa lakes and their location within the volcano our data highlight the importance of a carefully planned sampling strategy when the target is water geochemistry whereas the methane content and isotopic composition is relatively independent of the particular seep morphology

fluid sediment interactions at eastern mediterranean mud volcanoes a stable isotope study from odp leg 160 abstract pore fluids from two odp sites at eastern mediterranean mud volcanoes have been analyzed for their cl concentration and their 18o and d isotopic composition the cl data span a wide range of concentrations from extremely depleted with respect to seawater as low as 60 mm at the crest of milano dome site 970 to strongly enriched up to 5 4 m at napoli dome site 971 chloride enrichment is known to be due to dissolving messinian evaporites whereas the source of the low cl fluid is deduced from stable isotope data presented here the isotopic composition of the endmember fluid is found to be 10 for 18o and 32 for d for low as well as for high cl waters from this signature it can be concluded that neither gas hydrates nor meteoric water play a significant role in the freshening of the pore water several other processes altering the 18o d composition of pore waters are discussed and considered to be of only negligible influence the process characterizing the isotopic composition of the fluid is found to be clay mineral dehydration mainly smectite illite transformation corresponding to a depth range of 3 5 7 km and an elevated temperature of about 120 165 c a quantitative estimate shows that this reaction is capable of producing the observed extreme cl depletion

planetary magnetic signature of the storm wind disturbance dynamo currents ddyn 1 during magnetic storms joule heating and ion drag in auroral zones strongly influence the circulation of thermospheric neutral winds joule heating produces equatorward neutral winds at f region heights with return flow at e region altitudes around the equator the so called hadley cell the modified thermospheric circulation produces upwelling of molecule enriched air at high latitudes and global changes in the atmospheric composition the equatorward neutral winds extending from the auroral zone to mid and low latitudes through the coriolis force create westward storm wind which drives an equatorward dynamo current in this paper we detect for the first time in the three longitude sectors the planetary magnetic signature ddyn of ionospheric disturbance dynamo with its main features 1 the decrease of the equatorial electrojet due to a westward electric current flow opposite to the regular eastward current flow and 2 the equatorward ionospheric disturbance dynamo currents at midlatitudes

characteristics and possible origin of native aluminum in cold seep sediments from the northeastern south china sea abstract although native aluminum al has been reported to occur in various geological settings for more than 20 locations but its mechanism of formation still remains to be elucidated we report the occurrence and characterization of al particles recovered from the surface sediment cf4 and a short core sediment rov g 37 cm length obtained at cold seeps in the northeastern continental slope ncs of the south china sea scs x ray diffraction analysis shows that the collected particles are metallic aluminum with the unit cell edge a of 4 059 0 005 a cf4 2 and 4 029 0 004 a t26 28 2 rov g the al particles occur as spherules irregular plates and elongated forms with typical lamellar structures their chemical compositions are 95 07 99 84 al the average values is 98 42 with very small amounts of si fe ti s zn mg ca k na cu co and p and are similar to al particles from the east pacific rise and the central indian basin but differ markedly to those from other locations after ruling out several possibilities of al sources and mechanism of formation an alternative cold seep mechanism is proposed for the origin of al in the scs during the processes of anaerobic oxidation of methane aom and pyrite formation high h2s and h2 partial pressures result in strong reducing micro environments under which al oh 4 is reduced to its metallic state by the microbial bacterial processes

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

native aluminium spherules and particles in the central indian basin sediments implications on the occurrence of hydrothermal events abstract we have sampled particles of native aluminium al in two sediment cores from the central indian basin cib the cores are geographically separated but are located at the base of two seamounts the native al particles occurring as grains and spherules have an average al content of 95 and are associated with volcanogenic hydrothermal material morphologically and compositionally the specimens are similar to those reported from the east pacific rise after ruling out several processes for the presence of the native al we hypothesize that during progressive melting of magma a basaltic magma is produced which has high contents of reductants such as methane and hydrogen and a low oxygen fugacity during the upward migration of such magma reduction to metallic aluminium and the formation of native al particles takes place

the mud volcanoes of pakistan marine geologic investigations on the arabian sea by bundesanstalt fur geowissenschaften und rohstoffe bgr in 1995 and 1998 and land expeditions in 1998 and 1999 to the coastal regions of the makran desert pakistan have extended the knowledge of the aerial distribution of mud volcanoes these structures rise from under compacted formations within the regional accretionary prism which is built by the subduction of the oceanic crust of the arabian sea and its km thick sedimentary load the occurrence of mud volcanoes is limited to the abyssal plain near the accretionary front to the coastal region of the makran desert and to a region in the interior of the desert to the south to southeast of the so called hinglay synform the location of mud volcanoes in pakistan is clearly tied to fault systems mud volcanoes are conspicuously absent on the lower slope of the accretionary prism where thick gas hydrate layers have developed the presence of large gas plumes emerging from the seafloor landward of the gas hydrate stability zone at water depths of less than 800 m points to a redirection of fluids from depth which might explain the absence of mud volcanoes along the lower slope

native aluminium in metalliferous sediments from the east pacific rise axial zone 21 s abstract an endogenous model of the formation of small amounts of 100 m metallic aluminium particles from the metalliferous sediments of the east pacific rise 21 s is proposed on the basis of a detailed study of their morphology chemical composition x ray data spatial and temporal distribution according to this model native aluminium is formed as an accessory mineral during the process of the pre chamber evolution of basic and ultrabasic systems in the spreading zones under high p t and low o 2 conditions as well as during the later serpentinization of basites and ultrabasites from the second and third oceanic layer as a result of the active tectono magmatic processes in the rift zones the native aluminium particles are carried upwards into the seafloor water layer by the upwelling vent fluids of the hydrothermal circulation cells during periods of high hydrothermal activity the number of al particles carried upwards increases the spatial distribution of the particles depends on the energy of the hydrothermal system and the direction and energy of the seafloor currents the thin oxyhydroxide silicate and chloride crusts formed on the surface of the al particles as well as a monoatomic oxide film prevent further alteration of the particles

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

an investigation of ionospheric responses and disturbance thermospheric winds during magnetic storms over south american sector 1 this paper presents the results of a study of the ionospheric and thermospheric response to magnetic storm disturbances for four stations covering a wide range of latitude in the south american region the study is based on the f layer critical frequency fof2 and the peak height hmf2 from fortaleza fz which is equatorial cachoeira paulista cp which is low latitude concepcion con a midlatitude site and king george island kgi a middle to high latitude site equivalent neutral winds are extracted from the measured hmf2 by employing the field line interhemispheric plasma flip model the equatorial ionization anomaly eia can undergo enhancement due to magnetospheric disturbance electric field that penetrates to low latitudes during the growth phase of a storm substorm whereas eia inhibition occurs more often under disturbance dynamo dd electric field season dependent meridional transequatorial winds can significantly alter the eia response to disturbance electric fields large amplitudes of dd electric field is observed during evening and morning hours in equinoctial but not in winter months over the brazilian low latitude of large westward magnetic declination angle large equatorward meridional wind surges seem to be helped by the presence of disturbance zonal westward winds the low latitude disturbance can in some cases be traced to specific disturbance fronts originating promptly from auroral activity enhancements this study confirms earlier studies that show that the quiet time meridional wind increases with increase of latitude and that over midlatitude it shows decreases with increase of solar flux due to the effect of the ion drag force this study further shows that the disturbance meridional wind and the intensity of dd electric field increase with increasing intensity of high latitude energy input the negative ionospheric storm phase over middle latitude observed in equinox and not in winter is also intensified with the increasing intensity of high latitude energy input

electrodynamic coupling of high and low latitudes observations on may 27 1993 the penetration of disturbance electric fields from the polar region to the magnetic equator on the dayside of the earth is examined with geomagnetic data on may 27 1993 first we examine a dayside equatorial disturbance that followed the rapid recovery of magnetic activity from a storm and that has the characteristics of overshielding caused by persistent region 2 field aligned currents it lasted 0 3 hours second we analyze a series of fluctuations with periods of 25 75 min to determine the variations of amplitude and phase with magnetic latitude and magnetic local time the fluctuations were highly coherent at all latitudes between the magnetic equator and the auroral zone but the coherency decreasedin the polar cap a northward fluctuation at the equator during midday hours accompanied auroral zone fluctuations that were southward before noon eastward around noon and northward after noon the amplitudes decreased away from the auroral zone toward midlatitudes but were amplified under the equatorial electrojet no detectablep hased ifferencesa re found indicating that any temporal lags which might be inducedb y persistencein the region 2f ield alignedc urrentsa re less than i min for fluctuations having periods like those examined here a synoptic inversion analysis of the high latitude magnetic data to estimate the time varying high latitude electric potential patterns shows that fluctuations of the high latitude east west potential gradient tended to be concentrated around midday where they were in phase with fluctuations in the midday east west potential gradient at the magnetic equator

low latitude ionospheric thermospheric response to storm time electrodynamical coupling between high and low latitudes 1 using multi instrumental and multistation data we present low latitude ionospheric thermospheric behavior during the geomagnetic storm of 15 may 2005 the diurnal pattern of total electron content tec at a chain of equatorial to low latitude stations shows strong positive ionospheric storm on 15 may latitudinal variation of tec shows development of strong equatorial ionization anomaly eia on the same day evidence in terms of equatorial electrojet eej and magnetogram signatures is presented for the prompt penetration of interplanetary electric field ief as the cause of the positive ionospheric storm consequent to the storm time circulation resulting from the extra energy deposition via joule heating over high latitudes compositional changes occur in the global thermosphere tec enhancements on 16 may are attributed to enhancement of atomic oxygen at equatorial and low latitudes and the negative ionospheric storm on 17 may observed beyond certain low latitudes is explained in terms of enhancement of molecular species because of the storm time neutral composition changes strong esf plume structures on range time intensity rti map and l band scintillation and tec depletions in gps measurements are observed in the longitude sectors where the local time of sudden storm commencement ssc falls after the post sunset hours the ionospheric zonal electric fields are altered by the combined effects of eastward disturbance dynamo electric fields and direct prompt penetration of eastward electric fields associated with the northward turning of interplanetary magnetic field imf bz leading to subsequent development of esf after midnight

jiulong methane reef microbial mediation of seep carbonates in the south china sea chemoherm carbonates as well as numerous other types of methane seep carbonates were discovered in 2004 along the passive margin of the northern south china sea lithologically the carbonates are micritic containing peloids clasts and clam fragments some are highly brecciated with aragonite layers of varying thicknesses lining fractures and voids dissolution and replacement is common mineralogically the carbonates are dominated by high magnesium calcites hmc and aragonite some hmcs with mgco3 contents of between 30 38 mol extreme hmc occur in association with minor amounts of dolomite all of the carbonates are strongly depleted in 13c with a range from 35 7 to 57 5 pdb and enriched in 18o 4 0 to 5 3 pdb abundant microbial rods and filaments were recognized within the carbonate matrix as well as aragonite cements likely fossils of chemosynthetic microbes involved in carbonate formation the microbial structures are intimately associated with mineral grains some carbonate mineral grains resemble microbes the isotope characteristics the fabrics the microbial structure and the mineralogies are diagnostic of carbonates derived from anaerobic oxidation of methane mediated by microbes from the succession of hmcs extreme hmc and dolomite in layered tubular carbonates combined with the presence of microbial structure and diagenetic fabric we suggest that extreme hmc may eventually transform into dolomites our results add to the worldwide record of seep carbonates and establish for the first time the exact locations and seafloor morphology where such carbonates formed in the south china sea characteristics of the complex fabric demonstrate how seep carbonates may be used as archives recording multiple fluid regimes dissolution and early transformation events

a physical mechanism of positive ionospheric storms at low latitudes and midlatitudes 1 a physical mechanism of the positive ionospheric storms at low latitudes and midlatitudes is presented through multi instrument observations theoretical modeling and basic principles according to the mechanism an equatorward neutral wind is required to produce positive ionospheric storms the mechanical effects of the wind 1 reduce or stop the downward diffusion of plasma along the geomagnetic field lines 2 raise the ionosphere to high altitudes of reduced chemical loss and hence 3 accumulate the plasma at altitudes near and above the ionospheric peak centered at around 30 magnetic latitudes daytime eastward prompt penetration electric field ppef if it occurs also shifts the equatorial ionization anomaly crests to higher than normal latitudes up to approximately 30 latitudes the positive ionospheric storms are most likely in the longitudes where the onset of the geomagnetic storms falls in the ionization production dominated morning noon local time sector when the plasma accumulation due to the mechanical effects of the wind largely exceeds the plasma loss due to the chemical effect of the wind the mechanism agrees with the multi instrument observations made during the supergeomagnetic storm of 7 8 november 2004 with 18 h long initial phase ip and 10 h long main phase mp the observations which are mainly in the japanese australian longitudes where the mp onset was in the morning 0600 lt 2100 ut show 1 strong positive ionospheric storms in ne nmax hmax global positioning system total electron content gps tec and 630 nm airglow intensity in both northern and southern hemispheres started at the morning 0600 lt mp onset and lasted for a day 2 repeated occurrence of strong eastward ppef events penetrated after the mp onset and superposed with westward electric field started before the mp onset and 3 storm time equatorward neutral winds inferred from 1 and 2 repeated occurrence of an unusually strong f3 layer with large density depletions around the equator was also observed during the morning noon mp

boiling and dilution in the shallow portion of the waiotapu geothermal system new zealand abstract the waiotapu geothermal system is the largest in terms of surface extent and heat flow 17 km2 and 600 mw respectively of the 20 major geothermal systems in the taupo volcanic zone new zealand two extinct dacite cones and a rhyolite dome rise about 500 m above the waiotapu valley the majority of thermal features occurs in the valley over a relief of only 100 m and lies within coincident apparent resistivity and 30 m depth thermal anomalies thermal features comprise near neutral ph chloride springs often boiling acid sulfate springs and mud pools and mixed waters the latter including both bicarbonate chloride and acid sulfate chloride springs the majority of the sulfate discharges to the surface in the northern higher altitude area while most chloride that reaches the surface does so in the southern portion of the system comparison of measured and calculated surface chloride flux the latter from measured heat flow and reservoir chloride concentrations indicates that at least half of the deep chloride does not discharge at the surface but flows laterally to the south at shallow depths mixing with groundwater the composition of well discharges indicates a shallow 400 m reservoir of chloride fluid about 1350 mg cl kg at 230 c is diluted by a co2 rich steam heated water nil chloride at about 160 c the latter located on the margins of the system this same dilution trend is apparent from the compositional variation and k na and k mg geothermometry of hot spring waters however there is chemical and stable isotope evidence from hot springs that cold groundwater also acts as a diluent at shallow levels and very near the surface steam heated acid sulfate waters mix with the upflow boiling of the deep chloride fluids prior to dilution results in the stabilization of k feldspar in contrast dilution at shallower depths by the steam heated waters both co2 rich and acid sulfate leads to the water compositions initially shifting to k mica and interstratified clay stability and to kaolinite stability with further dilution and temperature decrease the composition and distribution of these fluids are consistent with alteration mineralogy and zonation observed in drill core although boiling occurs at deeper levels and up to the surface in the upflow zone at waiotapu mixing is also common and is the dominant process on the margin and in the near surface portion of the system boiling of deep chloride fluid is very common in the upper 1 2 km of the upflow zone of most geothermal systems though it may be quenched by mixing with marginal waters either cold groundwater in high relief terrane or steam heated waters in areas of lower relief co2 rich steam heated waters are common on the margins of systems and will generally underlie the near surface acid sulfate steam heated waters interaction with co2 rich waters will form k mica and interstratified clays while acid sulfate waters cause kaolinite and even alunite to form the former assemblage is commonly associated with typical low sulfidation epithermal gold mineralization as wallrock alteration where gold bearing veins comprise adularia and illite in contrast kaolinite is rare and alunite absent from a direct spatial and genetic association with gold mineralization in this environment this implies that mixing of the deep neutral ph chloride fluid with surficial acid sulfate waters does not commonly lead to ore grade gold deposition mixing with and cooling by co2 rich steam heated waters leads to clay stability accounting for the large halos of clay alteration and low grade metal anomalies which often surround veins of high gold grade in contrast mixing with surficial acid sulfate waters is unlikely to cause precious metal mineralization because the chloride fluids have already lost the majority of their gold through deeper boiling and dilution

magnetic signature of the ionospheric disturbance dynamo at equatorial latitudes ddyn 1 during magnetic storms wind disturbances produced by auroral phenomena can affect the whole thermospheric circulation and associated ionospheric dynamo currents for many hours after the end of the storms in this paper we define criteria to select a new simple type of ionospheric disturbance dynamo events that allow a simple interpretation over all longitude sectors these events exhibit a weak auroral activity during at least 24 ut hours on the day after the storm we analyze the magnetic disturbances ddyn observed at equatorial latitudes in the three longitude sectors of such selected events it is found for all the cases that the amplitude of the h component of the earth s magnetic field is reduced on the day after storm at equatorial latitudes in agreement with the ionospheric disturbance dynamo model blanc and richmond 1980 the observation of h component decrease on the day after storm is longitudinally asymmetric the observed signature of the ionospheric disturbance dynamo process in a specific longitude sector is strongly dependent on the magnitude the start time and the duration of the storm

seep carbonates and preserved methane oxidizing archaea and sulfate reducing bacteria fossils suggest recent gas venting on the seafloor in the northeastern south china sea seep carbonates formed by the synergistic metabolism of methane oxidizing archaea moa and sulfate reducing bacteria srb have been found in many places worldwide but have not been found to date in the south china sea mud volcanoes and shale diapirs have been reported in the south china sea however and microscope and geochernical analysis of carbonates dredged where bottom simulating reflectors bsr suggest the presence of gas hydrate on the northeastern continental slope of the south china sea suggest that the carbonates are hydrocarbon seep related carbonates the carbonates we dredged are chimney like and preserve moa srb fossils their very light carbon isotopic compositions 51 25 to 51 76 parts per thousand suggest that their carbon was derived from microbial methane oxidization these seep carbonates and their preserved moa srb fossils imply gas venting has occurred recently on the seafloor in the northeastern continental slopes in the south china sea c 2005 elsevier ltd all rights reserved

latitudinal profile of the magnetospheric convection electric field at ionospheric altitudes from a chain of magnetic and radar data in this paper a combination of magnetic records with coherent and incoherent radar data at auroral and middle latitudes stare and saint santin allows a quantitative analysis of the latitudinal profile of the convection electric field this latitudinal profile is compared with the predictions of the semi analytical convection model of senior and blanc the auroral conductivities used in this model are deduced from comparison of the stare electric field and the magnetic disturbance once this normalization is performed a good agreement is found between the experimental and theoretical electric field profiles

the goshogake mud volcano field tohoku northern japan an acidic high temperature system related to magmatic volcanism abstract the high temperature 33 98 c highly acidic ph 2 44 2 94 goshogake mud volcano field in akita prefecture northern japan is a mud volcano system associated with the quaternary andesitic composite volcano akita yakeyama the mud volcano features observed in goshogake include salsa ponds gryphons and mud pots this is a rare example of mud volcano systems linked with magmatic volcanism with the full range of landforms observed primarily in low temperature mud volcanism in sedimentary settings the goshogake mud volcano field is probably not a simple hydrothermal system related to a magmatic volcano instead it appears to be a hybrid system sedimentary volcanism linked with deep mud sources and strongly influenced by its surrounding magmatic volcanism the identified mineral species in the sampled mud include quartz group hydrous silica muscovite kaolinite pyrite and sulfur the presence of high temperature silica polymorphs tridymite and cristobalite and or microcrystalline opals opal c opal ct and an amorphous form of silica opal a in the mineralogy indicates that the mud volcano system likely involves conditions and processes such as high temperature hydrothermal circulation dehydration reaction at certain depths underneath the goshogake mud volcano field although the source of the mud is not clearly determined possible options include 1 hydrothermal alteration products of host rocks and sediments 2 fine grained sedimentary layer s at depth or 3 a combination of 1 and 2 in situ measurement of emitted gases from vents detected methane which is possibly linked with the organic rich sedimentary layer s aside from being a product of thermodynamic equilibrium with co2 under the subsurface pressure temperature conditions the increases in d and 18o of water in goshogake mud volcanoes with respect to the values of current meteoric water indicates that the water was derived not only from meteoric water and deviation of the values may be explained by processes such as evaporation and mixing of other waters from deeper sources regarding the driving mechanisms at the goshogake mud volcanoes buoyancy of muddy sediment high fluid pressure under overpressured or under compacted conditions due to rapid sedimentation together with the presence of a gas phase in the sediment could be key factors although the goshogake mud volcano field currently maintains a low level activity resulting in only minor morphological changes of the mud volcano landforms enhanced activities have been documented in the last half century the historical records are inconclusive about the relationship between earthquakes and activity in the goshogake mud volcano field

hydrothermal alumina rich clays and boehmite on the gorda ridge abstract hydrothermal alteration of basalt on the northern gorda ridge produced an alteration crust up to 1mm thick that can be divided into two layers based on mineralogy an inner layer next to the basalt surface is an al rich interlayered smectite chlorite similar to high temperature al rich clays recovered from the east pacific rise 21 n with minor quartz zeolite phillipsite and relict plagioclase an exterior layer of boehmite alo oh and minor anatase results from severe leaching of the underlying clays the alteration crust is progressively enriched in al ti v and cr from interior to exterior by residual weathering the presence of boehmite and absence of a silica rich phase in the exterior of the crust indicates the hydrothermal fluids were silica undersaturated or silica was maintained in solution by extremely acidic fluids this constitutes the first reporting of boehmite as a major alteration mineral in a mid ocean ridge hydrothermal environment

sulfur isotope variability in biogenic pyrite reflections of heterogeneous bacterial colonization the top 20 cm of sediments at active cold seeps in monterey bay coastal california contain framboidal pyrite that occurs as infillings and pseudomorphs of the chambers of the tests of foraminifera and rarely as irregularly shaped grains sulfur isotope compositions obtained with the ion microprobe show depletions in 34 s d 34 s 52 41 to 25 cdt and large variations both within and among these pyrite grains intergranular differences in d 34 s values in the same sediment are as large as 35 and intragranular zoning reaches 15 zoning is regular in some grains with systematic isotope changes from core to rim or from one foraminiferal chamber to another but irregular in others the regular zoning is consistent with an increase in 34 s through time backscattered electron imaging reveals three types of pyrite isolated framboids in a porous aggregation pf pyrite agglomerated framboids with cementing interstitial pyrite f 1i pyrite and recrystallized pyrite with isolated relicts of framboids rf pyrite in individual grains rf pyrite cores grade into f1i pyrite toward grain rims and f1i pyrite grades into pf pyrite at the grain edges these textures are consistent with a paragenetic sequence whereby framboids first agglomerate pf pyrite then cement f1i pyrite and finally recrystallize rf pyrite the d 34 s values of rf pyrite are generally lower than that of f1i pyrite if the paragenetic sequence is correct then this trend parallels the regular core rim isotopic zoning observed in some grains the implied increase in d 34 s with time is consistent with rayleigh fractionation of sulfur in a closed system bacteria are intimately involved in the production of pyrite from our samples and heterogeneous colonization by bacteria provides a simple explanation for the sulfur isotope heterogeneity among and within grains the foraminifera provide open space for colonization and local nutrients for bacterial growth whereas the cell walls of the bacteria may provide a local nucleation site for sulfides if so then initial colonization is reflected in lower d 34 s values whereas later bacterial emigration to other foraminifera chambers is indicated by higher d 34 s values

small edifice features in chryse planitia mars assessment of a mud volcano hypothesis abstract small edifice features that are less than a few kilometers in diameter and up to a few hundred meters in height are widely distributed in chryse planitia on mars they exhibit a broad range of morphological properties that are here classified as type 1 steep sided cones typically with a summit crater type 2 nearly flat features with single or multiple central summit craters or cones and type 3 nearly circular features in plan view characterized by steep sides and a broadly flat summit area their origins have not been determined with certainty but our study utilizing the high resolution imaging science experiment hirise images supports the interpretation of mud volcanism based on the observed morphological characteristics of these small edifices and comparisons with terrestrial analogs additionally hydrated minerals detected on these edifice features in data from the compact reconnaissance imaging spectrometer for mars crism further support the mud volcano hypothesis injection features such as clastic mega pipes and sand blow features may coexist with the mud volcanoes alternative mechanisms such as magmatic volcanism are not excluded but they have less support from our remote sensing observations further confirmation or rejection of the mud volcano hypothesis will require in situ investigation by landers or rovers

penetration of magnetospheric electric fields to the equator during a geomagnetic storm 1 penetration of the magnetospheric electric field to the equatorial ionosphere was examined for the geomagnetic storm on 6 november 2001 by analyzing the difference in magnitude of the geomagnetic storm recorded at the dayside geomagnetic equator yap 0 3 gml and low latitude okinawa 14 47 gml the penetrated electric field caused the dp2 currents at the equator i e eastward currents during the main phase of the storm while the overshielding currents i e westward currents dominated during the recovery phase it is shown that the ring current started to develop simultaneously with the onset of the equatorial dp2 within the temporal resolution of a few minutes these results imply prompt transmission of the dawn to dusk convection electric field to the inner magnetosphere as well as to the equatorial ionosphere it is found that the equatorial dp2 started to decrease one hour after the onset of the ring current development indicating shielding effects becoming effective at the equator during the latter half of the storm main phase the dp2 was then overwhelmed by the overshielding which resulted in the counter electrojet cej in the beginning of the storm recovery phase the image magnetometer chain data indicate that the westward auroral electrojet aej in the dawn sector was driven over midlatitude centered at 57 corrected geomagnetic latitude cgml during the main phase while the aej shifted rapidly poleward to the auroral latitude centered at 67 cgml in the beginning of the recovery phase the overshielding must be caused by the abrupt poleward shift of the rl facs as inferred from the poleward shift of the aej in addition to the decrease in their magnitude due to the decrease in magnitude of the southward imf the geomagnetic storm at the dayside geomagnetic equator was enhanced in amplitude with the ratio of 2 7 as compared with the geomagnetic storm at low latitude this amplification is a result of both effects of the dp2 currents and the cej associated with the main and recovery phases respectively it is suggested that the electric field associated with the dp2 currents contributed to the development of the ring current during the main phase while the overshielding electric field may contribute to cease developing the ring current during the recovery phase

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

methane derived carbonates and authigenic pyrite from the northwestern black sea abstract methane seeps in the northwestern black sea are accompanied by carbonate and pyrite precipitates sediments were sampled at locations on the romanian 120 m depth and ukrainian 180 200 m depth shelf and slope layered carbonate crusts are formed of i carbonate cemented siliciclastic sediment containing dreissenoid bivalves ii microcrystalline high mg calcite or aragonite and iii aragonitic cement the dreissena sediment is subrecent and was deposited during the freshwater phase of the black sea it has been affected by seepage of methane rich fluids which induced intergranular precipitation of authigenic carbonates the microcrystalline carbonates exhibit an intense autofluorescence high mg calcite contains 11 14 mol mgco3 the aragonitic cement 8300 9500 ppm sr forms either isopachous layers or botryoids microbial filaments about 10 20 m in diameter and up to 900 m in length are preserved within and on carbonate crusts the carbonates are depleted in 13c microcrystalline carbonate ranges from 27 to 41 pdb and botryoidal aragonite ranges from 26 to 38 pdb the 13c depletion indicates that the carbonates predominantly derive from the microbial oxidation of methane carbonate deposits do not project up into the oxic water column they are restricted to the anoxic water column and to anoxic sediments revealing the crucial role of anaerobic methane oxidation for carbonate precipitation 14c contents give apparent radiocarbon ages of 20 640 180 a bp for a sample of botryoidal aragonite and 19 110 180 a bp for a sample of microcrystalline carbonate compatible with minimum ages of carbon derived from a fossil hydrocarbon source the 18o values of methane derived carbonates show a narrow range from 1 2 to 0 2 pdb 87sr 86sr ratios of microcrystalline carbonate mean 0 70927 and aragonitic cement mean 0 70918 are indistinguishable from ambient seawater mean 0 70917 and thus indicate a shallow sr source higher 87sr 86sr ratios of the dreissena sediment mean 0 71005 are probably caused by sr derived from detrital mica carbonates are accompanied by blocks and crusts composed of pyrite the framboidal sulphide exhibits a palisade like fabric with framboids arranged to parallel pillars sulphur isotopic ratios 34s ranging from 16 8 to 19 7 cdt indicate that the sulphur derives not from the 34s depleted h2s of the water column or the uppermost sediment layers most likely pyrite formed in the lacustrine sediments after the first incursion of mediterranean seawater

composition and origin of holotype al cu zn minerals in relation to quasicrystals in the khatyrka meteorite we investigated the khatyrkite cupalite holotype sample 1 2 0 5 mm across it consists of khatyrkite cu zn al2 cupalite cu zn al and interstitial material with approximate composition zn cu al3 all mineral phases of the holotype sample contain zn and lack fe that distinguishes them from khatyrkite and cupalite in the khatyrka meteorite particles bindi et al 2009 2011 2012 2015 macpherson et al 2013 hollister et al 2014 neither highly fractionated natural systems nor geo or cosmochemical processes capable of forming the holotype sample are known so far the bulk chemistry and thermal history of khatyrkite cupalite assemblage in the holotype sample hint for its possible industrial origin likewise the aluminides in the khatyrka meteorite particles may also be derived from industrial materials and mixed with extraterrestrial matter during gold prospecting in the listvenitovy stream valley

two dimensional fluid flow models at two gas hydrate sites offshore southwestern taiwan abstract fluid migration patterns are important for understanding gas hydrate and hydrocarbon systems however conducting experiments on or below the seafloor is difficult because crustal fluid flow rates are usually very slow so long term observations are needed temperature can be used as a good tracer for studying fluid flows temperatures derived from bottom simulating reflectors bsrs might help to understand fluid migration patterns in shallow marine sediments in this study we studied 2d fluid flow patterns in two potential gas hydrate provinces offshore southwestern taiwan the yung an ridge in the active margin and formosa ridge in the passive margin we used 2d bathymetry average seafloor temperatures and regional geothermal gradients measured by thermal probes as constraints to construct 2d theoretical conductive temperature fields using finite element methods we then compared the bsr based temperature with the theoretical conductive temperature field the results show a temperature discrepancy attributed to advective heat transfer due to fluid migration for the yung an ridge the bsr based temperatures are about 2 c higher than the model especially in 1 near a fault zone 2 under the eastern flank where there are strong seismic reflectors in a pseudo 3d seismic dataset and 3 near a fissure zone for the formosa ridge our results showed a distinct decrease in temperatures around the southern peak of the ridge where an active gas plume was found bsr based temperatures predict on average 2 c lower than the model at these two sites the shallow temperature fields are strongly affected by 2d bathymetry however new insights regarding fluid flow patterns can be obtained using this model approach

the influence of nonmigrating tides on the longitudinal variation of the equatorial electrojet 1 the climatological model of the equatorial electrojet eejm 1 derived from orsted champ and sac c satellite measurements provides the opportunity to investigate the longitudinal variation of the current strength in detail special emphasis is put in this study on the effect of nonmigrating tides we have found that the influence of the diurnal eastward propagating mode with wavenumber 3 de3 is particularly strong in polar orbiting satellite observations the de3 tidal signal appears as a four peaked longitudinal structure we have put special emphasis in our analysis to isolate the de3 contribution from other sources contributing to the wavenumber 4 structure in satellite data the amplitude of the de3 signature in the eej not only peaks during equinox seasons but is also strong around the june solstice when looking at the modulation of the eej intensity the de3 accounts for about 25 during the months of april through september it is thus the dominant cause for longitudinal variations during december solstice months the influence of de3 is negligible a secondary three peaked longitudinal pattern emerges during solstice seasons when the de3 influence is removed from the data available it is however not clear whether this pattern is related to any tidal drivers