resolving volatile sources along the western sunda arc indonesia we present the chemical and isotope hecn characterization of active fumaroles and hydrothermal gases and waters from the summits and flanks of 19 volcanic centers along the western sunda arc indonesia samples were collected over two field expeditions 1991 and 2010 and cover 13 volcanic centers in sumatra 5 in java and one in bali in addition we present data from three geothermal sites in sumatra associated with active fault systems in between volcanic centers ibvc the overall aim is to resolve volatiles associated with the sub arc mantle subducting slab and mantle wedge from inputs derived from the over riding arc crust the western sunda arc is a prime locality to assess controls on volatile provenance at subduction zones due to changes in composition and thickness of over riding crust and variations in sediment input rates along the strike of the arc the dry gas chemistry of the majority of volcanic samples is dominated by co2 with inert gas variations hearn2 typical of subduction zone gases however there is a strong crustal control on the heco2 isotope and relative abundance systematics on a number of volcanic centers this effect is most clearly observed at flank localities and in water phase samples filtering the entire database for modifications due to air contamination degassing induced fractionation c isotopes and co2 3he ratios and crustal contamination associated with volatile transport within shallow level hydrothermal systems allows recognition of the magmatic volatile signature of individual volcanoes along the arc helium isotopes at all but two volcanic centers talang and dempo on sumatra range from 5 3 ra to 8 1 ra ra air 3he 4he pointing to the mantle wedge as the principal source of he but with a small input of crustal radiogenic he at some localities samples from java and bali span an even more limited range 6 6 to 7 9 ra implying a relatively smaller input of crustal he carbon isotope and co2 3he ratios vary from 1 4 to 6 4 and 4 38 to 150 109 respectively with higher and more variable values to the north of sumatra this latitudinal effect is not apparent in air corrected n isotope values 15nc 3 91 to 5 92 or various elemental ratios such as n2 ar and n2 he the three ibvc sites all located in sumatra have significantly lower 3he 4he ratios 3 6 ra with co2 3he values both higher and lower than volcanic centers their 13c 15nc and gas ratios overlap with the volcanic centers the elemental and isotopic characteristics of carbon and helium have been modified at ibvc sites due to crustal processes however based upon relationships between ch4 and 3he as well as co variations between hecn isotopes the over riding crust and associated sediments add minimal volatiles to volcanic centers throughout the western sunda arc in turn subducted sediment particularly the nicobar fan which supplies himalayan derived sediment to the slab off sumatra exerts a strong control on the magmatic co2 characteristics although it is less influential for n2 in spite of large sections of incoming sedimentary material being off scraped during subduction our data suggest that a significant fraction must enter the trench enhancing fluid melt production in the mantle wedge we propose that subduction related source contamination plays the dominant role over thick old crustal basement in supplying the major volatile output budget of the western sunda arc

the lamongan volcanic field east java indonesia physical volcanology historic activity and hazards abstract the lamongan volcanic field lvf in east java indonesia consists of up to 61 basaltic cinder or spatter cones a minimum of 29 prehistoric maars and a central compound complex comprising three main vents including the historically active lamongan volcano the field lies on the sunda volcanic arc and abuts onto the currently active tengger caldera semeru complex to the west between 1799 and 1898 lamongan was persistently active and discharged up to 15 lava flows of basaltic to basaltic andesite composition which is probably more than what was erupted by any other indonesian volcano in that period several seismic crises have been recorded in the lvf since lamongan s last eruption there are no existing records of cinder cone or maar forming eruptions in the area despite the possible hazards posed by future activity in the lvf the history and structure of the field have been subject to little scrutiny this contribution presents the results of a detailed morphometric and volumetric investigation of prehistoric vents and historic lava flows in the lvf using field data historic records satellite imagery and modelling of erupted volumes a typical lvf maar is characterised as a crater with a diameter of 450 m generated by an eruption with a model ejecta volume of 0 016 km 3 dense rock equivalent dre and a model juvenile component volume of 0 0096 km 3 dre diameter depth ratios of some maars display a morphological freshness comparable to recently formed phreatomagmatic eruption craters elsewhere the median lvf cinder spatter cone has a basal diameter of 600 m a height of 75 m a volume of 0 009 km 3 and a model total erupted volume of 0 014 km 3 variation in cone basal diameter to height ratios indicates that the age of some prehistoric cones may not exceed a few centuries and morphological classification identifies the youngest prehistoric vents on the northern flanks of the central edifice historic activity from vents on the western flanks of lamongan produced at least 0 05 km 3 of basaltic to basaltic andesite lava resurfacing rates at lamongan in the 19th century imply an age of 900 2100 years for the surface of the volcano the steady state eruptive rate from 1843 1898 is evaluated as 0 025 m 3 s 1 which is low in comparison to estimates from many presently active systems using eruptive rate and volume data the age of the lvf is estimated as between 13 and 40 ka placing it among the youngest dated indonesian volcanoes complex regional tectonics in conjunction with magmatic pressure have probably been the major influences on the distribution of volcanism in the lvf the occurrence of maar forming eruptions may have been controlled by a porous substrate possibly a deposit from the holocene iyang argapura complex to the east volcanic hazards from future eruptions in the lvf include base surges ash flows ashfall and ejected blocks associated with phreatomagmatic activity and ashfall and ejecta from magmatic eruptions

more than ten years of lusi a review of facts coincidences and past and future studies abstract the lusi mud eruption in east java indonesia has continued unabated for more than ten years with no end in sight this review summarizes what has been learned about this intriguing system from its inception to the current 2017 well established metastable geysering system that continuously erupts mud breccia gas steam and water we discuss the initiation of lusi highlighting discrepancies and evidence through the published data to build a comprehensive database that emphasizes how the results converge towards a natural scenario of this system we argue that attempts to understand constrain or predict the behaviour of this system that rely on a drilling trigger can not explain subsequent observations on the other hand we show that a well constrained conceptual model recognizing lusi as a volcanically linked hydrothermal system has provided important insights for the documented observations over the last eleven years the response of lusi to the yogykarta earthquake falls directly within the range of earthquake triggering phenomena globally of similar hydrothermal geothermal systems suggesting a natural trigger as the more likely culprit for the lusi phenomenon we also offer some future directions of additional scrutiny for understanding this newborn tectonic scale volcanic hydrothermal complex

the lusi mud volcano triggering controversy was it caused by drilling abstract following the yogyakarta earthquake on may 27th 2006 the subsequent eruption of a mud volcano has been closely observed and analyzed by the geological community the mud volcano known as lusi began erupting near the banjarpanji 1 exploration well in sidoarjo east java indonesia lusi offers a unique opportunity to study the genesis and development of a mud volcano for the first time this paper presents all raw and interpreted drilling data so any interested party can perform their own assessment our study suggests that lusi mud volcano was a naturally occurring mud volcano in an area prone for its mud volcanism pressure analysis done on the banjarpanji well shows that the pressure exerted at the well is lower than the fracture pressure at the last casing shoe and suggests that the well was intact and did not suffer an underground blowout this is further supported by evidence and observation made during drilling such as circulation was done on an open bop and subsequent relief wells sonan and temperature log runs this study offers a different alternative to earlier hypothesis that events at the banjarpanji well were the trigger for the lusi mud volcano more work is needed by the scientific community to study the sequence of events in order to explain and clarify the real trigger of lusi

estimating eddy stresses by fitting dynamics to observations using a residual mean ocean circulation model and its adjoint a global ocean circulation model is formulated in terms of the residual mean and used to study eddy mean flow interaction adjoint techniques are used to compute the three dimensional eddy stress field that minimizes the departure of the coarse resolution model from climatological observations of temperature the resulting 3d maps of eddy stress and residual mean circulation yield a wealth of information about the role of eddies in large scale ocean circulation in eddy rich regions such as the southern ocean the kuroshio and the gulf stream eddy stresses have an amplitude comparable to the wind stress of order 0 2 n m 2 and carry momentum from the surface down to the bottom where they are balanced

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

eulerian and eddy induced meridional overturning circulations in the tropics abstract inspired by recent measurements of the eddy induced meridional overturning circulation in the tropical north pacific ocean by roemmich and gilson the authors analyze an oceanic general circulation model for its eulerian and eddy induced meridional overturning circulations throughout the tropics the model representation for the mesoscale eddy induced circulation is the parameterization by gent and mcwilliams and there are also rectified contributions to the time mean overturning circulation due to seasonal and interannual fluctuations the eddy induced circulation is similar in all tropical basins it has a strength of about 10 of the eulerian mainly ekman circulation and its contribution to the meridional heat flux is a similar fraction the pattern of the meridional streamfunction is one of double cells in the vertical and antisymmetry about the equator near the equator there is downwelling above the undercurrent and upwelling below with the return circulations closed within the upper 2

sediment hosted geothermal systems review and first global mapping abstract sediment hosted geothermal systems shgss are hybrid geological systems where volcanic and sedimentary domains interact leading to mixtures of inorganic and organic gases typically characterized by geothermal thermometamorphic or mantle derived co2 and biotic microbial or thermogenic ch4 shgss occur in sedimentary basins crossed by magmatic intrusions or involved in volcanic plumbing systems these systems can be of considerable interest for petroleum exploration and natural greenhouse gas emission studies but systematic studies for their characterization and worldwide distribution are missing here we provide a review of shgss identified so far and propose methodological criteria for their definition and identification based on integrated geological and gas geochemical parameters we find that shgss are typically characterized by a fluids dominated by mantle or decarbonation methamorphic co2 50 vol b considerable amounts of ch4 and heavier hydrocarbons at least 1 5 vol generally up to 30 40 vol produced by microbial or thermogenic degradation of organic matter hosted in sedimentary rocks c tectonically active sedimentary basins back arc rift zones and foredeep generally hosting petroleum fields and within 300 km from recent or ancient volcanic centers this analysis resulted in a global map including a first set of 33 shgss located in north america central and eastern europe far east eastern oceania and northern new zealand and a second set of potential shgs prone areas occurring also in south america north africa middle east and kamchatka the present shgs map can evolve on the basis of more detailed geological analysis and new gas geochemical data

thermohaline circulation hysteresis a model intercomparison we present results from an intercomparison of 11 different climate models of intermediate complexity in which the north atlantic ocean was subjected to slowly varying changes in freshwater input all models show a characteristic hysteresis response of the thermohaline circulation to the freshwater forcing which can be explained by stommel s salt advection feedback the width of the hysteresis curves varies between 0 2 and 0 5 sv in the models major differences are found in the location of present day climate on the hysteresis diagram in seven of the models present day climate for standard parameter choices is found in the bi stable regime in four models this climate is in the mono stable regime the proximity of the present day climate to the stommel bifurcation point beyond which north atlantic deep water formation cannot be sustained varies from less than 0 1 sv to over 0 5 sv

magmatic helium in subduction zone natural gases abstract he isotope ratios provide important constraints on the input of magmatic gases into crustal systems natural gas associated with active continental margins from taiwan r o c new zealand the philippines indonesia thailand and alaska u s a contain a magmatic he component based on measured 3 he 4 he ratios r ranging from 0 5 to 3 8 times the atmospheric value ra the methane helium results can be interpreted as the result of a mixture between a low 3 he 4 he 0 01r a high ch 4 3 he crustal end member and a high 3 he 4 he 0 6 3 9r a low ch 4 3 he 6 magmatic component the presence of mantle he does not require significant amounts of mantle methane a better fit to the data is obtained using a zero methane magmatic end member the worldwide association of 3he and magmatic activity suggests that volcanism plays a role in methane generation by supplying the heat needed to convert organic matter to methane thermogenically only gases from the accretionary prism of barbados west indies appear totally devoid of magmatic he 3 he 4 he ratio 0 02ra the he is completely of crustal origin there is no evidence that faults within the accretionary prism of this fore arc act as conduits for the migration of mantle he many of the gases studied contain significant quantities of co2 which appear to result from two processes 3 he 4 he high co 2 3 he gases 0 01ra 1011 possibly result from decarbonation reactions in the crust while the high 3 he 4 he low co 2 3 he gases 2 4ra

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

genesis and evolution of the watukosek fault system in the lusi area east java abstract detailed analysis of two dimensional seismic lines acquired in the ne java basin has been performed to unravel the subsurface geology of the region around the lusi mud eruption this work revealed the existence of a system consisting of a complex set of faults here called the watukosek fault system forming triangular deformation zones converging at the top of the early miocene carbonates this system continues downwards with vertical individual fault segments often bordering the steep margins of the carbonate platforms the analysis of data includes the interpretation of seismic lines regional structural data inferred from basement gravity maps and present day main direction of stress results suggest that a possible rotation of stress direction from n40e s40w to n s occurred during the post miocene history of the java back arc tectonic evolution the watukosek fault system was first generated as a tensional lineament during the e w sinistral transpressive strain which involved the basement in this phase synthetic and antithetic riedel faults formed the former controlling the nw se orientation of the structural highs represented by oligo miocene carbonate platforms as a consequence of the rotation of the main principal stress direction to a n s direction the watukosek fault and similar parallel lineaments became sinistral riedel shears developing intense triangular deformation zones based on the stratigraphic position of gentle anticlinal deformations with axis corresponding to the n40e s40w oriented triangular deformation zones the transpressive strain linked to the n s main stress compression occurred likely in the late pliocene early pleistocene the detailed examination of a stratigraphy at the wells bjp 1 and porong 1 as well as b the seismo stratigraphic architecture of the entire succession in the study area allowed a new subsurface interpretation and revision of the stratigraphic units below lusi the thick early miocene tuban formation is found sandwiched between the coheval upper kalibeng formation and the early miocene carbonate of the kujung formation which in turn overlain the older ngimbang formation

diagnostic model of the three dimensional circulation in the upper equatorial pacific ocean abstract to investigate the processes that maintain the large scale annual average thermal structure of the equatorial pacific the three dimensional ocean circulation for a large area is determined from a diagnostic model applied to repeated meridional hydrographic sections along 150 w and 11o w from 5 n to 5 s geostrophic balances are used to determine velocity profiles from 0 to 500 db across the boundaries of the region zonal velocities across 150 w and 110 w at approximately 1 lattitude intervals from 5 n to 5 s and meridional velocities across 5 n and 5 s averaged over the zonal distance between 150 w and 110 w poleward wind driven flows across 5 n and 5 s based on climatological zonal wind stress are added to the geostrophic velocities in the mixed layers to achieve overall mass conservation the reference dynamic height field at 500 db is adjusted at four of the 21 stations by about 1 dyn cm horizontal nondivergence is used to determine meridional velocities between 0 75 and 5 latitudes

modeling study of growth and potential geohazard for lusi mud volcano east java indonesia abstract the mud volcano known as lusi first erupted in may 2006 in east java indonesia the eruption has continued for over two years and potentially will continue for many years to come impacting an ever larger area an obvious and significant question is how extensive the impacted area will become in the coming years the answer is important for planning scenarios for the relocation of people and infrastructure and for managing the environment and economy to make such a prediction an understanding of the geological processes controlling the mud volcanic evolution is needed a three dimensional simulation model was built to predict the area affected by the mudflow over a ten year period with a special focus on the period from december 2007 until june 2010 the primary model inputs are the mud debit rate the rate of subsidence and the topography the model prediction was validated at the december 2007 time step by comparing the results with satellite images from the same period the simulation was found to provide a good approximation for the mud overflow and growth the results indicate that the mudflow tends to spread to the west and particularly to the east and north from the currently inundated area the model predicts that in june 2010 the peak of the mud volcano will have risen 26 m above the original ground level and the maximum subsidence will have been 63 m below the original ground level the dynamic subsurface condition in the area creates geohazard risks and these are also discussed in this paper

hydrocarbons from near surface sediments of the barents sea north of svalbard indication of subsurface hydrocarbon generation abstract the barents sea is considered as an important target for oil and gas exploration but the petroleum potential of its shelf and slope regions is unknown here we present results of a research cruise to the northern hinlopen margin at the transition to the southern nansen basin and the eastern yermak plateau multichannel reflection seismic data acquisition heat flow measurements and geochemical analyses of near surface sediments obtained by gravity coring were conducted to study the northern barents sea shelf and the early opening of the nansen basin and decipher their petroleum potential seismic data indicate high thicknesses of up to 2000 m of cenozoic sediments heat flow density values in the study area range between 67 and 108 mw m 2 the sediment samples were analysed for bulk geochemistry and sorbed hydrocarbon gases and for two sites for extractable hydrocarbons data from extractable n alkanes n c 25 and bulk hi and oi from rock eval organic matter demonstrate predominantly terrigenous organic material most likely derived from ice transported allochthonous sediments none of the sediments revealed substantial amounts of methane in pore waters arguing against active hydrocarbon seepage in the studied areas however thermogenic gases sorbed to the sediment matrix clay minerals organic matter and or carbonates were found in concentrations of up to 600 ppb on sediment wet wt basis for the samples from the northern hinlopen margin and particularly from the adjacent nansen basin a paleo fluid flow of thermogenic gas is indicated and accompanied by higher n alkanes with a modal petroleum like distribution 13 c values of methane ethane and propane and gas compositions point at a mainly marine source rock origin of all studied gases with early oil window maturities of the associated rocks 0 6 0 9 vr from this data an admixture of type iii derived thermogenic gases is indicated for some of the yermak plateau sediments for which also the lowest abundances of sorbed gases 50 100 ppb were observed gas geochemical characteristics in the samples with low gas abundances can partially be explained by an input of gases through ice transport of allochthonous hydrocarbons which were bound to mature organic matter for a site on the northern hinlopen margin ne of svalbard right at the southern termination of the nansen basin a different situation is indicated in this area the highest concentrations of sorbed gases most likely derived from sediments with an early oil window maturity and a marine kerogen type ii typical isotopic distribution at this location a pseudo well was constructed from 2d seismic data for reconstruction of thermal and maturity evolution the simulation results indicate that an early to middle eocene source rock would be in the early oil window since the early miocene a possible source rock here and in the circum arctic region could have been formed by azolla algae and other flourishing primary producers

constraints on density changes in the funnel shaped caldera inferred from gravity monitoring of the lusi mud eruption abstract from its inception may 29 2006 the lusi mud eruption has continuously erupted fluids boiling mud and clasts through large active vents approximately 100 m in diameter in 2016 we conducted a dynamic gravity survey dg using a network built over four locations and two continuous gravity monitoring cg experiments to monitor the eruption activity the cg was done for 8 days from june 2nd to june 10th and for 9 days from august 20th to august 29th 2016 atmospheric pressure and atmospheric temperature variations were recorded during each experiment to constrain potential environmental effects and earth and oceanic tide effects were removed from gravity signals cg and dg atmospheric pressure effects were removed from cg gravity signals at the station closest to the hydrothermal pond the dg survey results show a gravity increase of 0 009 mgal month 1 which we interpret as the growth of the mud edifice in the central area cg monitoring shows that gravity variations occur at a period of 12 13 h with amplitudes reaching up to 0 020 mgal we interpret this as relating to density variation of the rising mud mixture fluids coarse mud clasts the observed 12 13 h period variations appear to indicate that tides may have some control on the density change of rising mud mixture by triggering the release of gas trapped at depth our 3d gravity results around the lusi vents show that density variations range from 100 kg m 3 to 775 kg m 3 similarly vent diameters better constrain density contrasts occurring within the caldera zone which is more likely to range between 400 and 450 kg m 3 and is equivalent respectively to 27 and 31 of gas ratio change over time

helium isotope compositions in sedimentary basins in china abstract the abundance and isotopic composition of he have been determined for a variety of natural gases oil field gases in sedimentary basins in the continent of china the 3 he 4 he and 4 he 20 ne ratios range from 0 004 to 4 99 ra where ra denotes atmospheric 3 he 4 he ratio 1 4 10 6 and from 100 39 000 respectively helium in the gas sample is composed of mantle derived he and crustal radiogenic he the high 3 he 4 he ratios were observed in the sedimentary basins which underwent cenozoic extension in the eastern domain such as the songliao liaohe north china subei sanshui and south china sea basins the basins where mantle derived he is recognized are characterized by the presence of surface and subsurface volcanic rocks high terrestrial heat flow deep faults and thinned crust on the other hand regions which underwent pre tertiary extension such as the jungar tarim tuba caidam and yumen basins in the nw and tectonic loading such as the ordos and sichuan basins in the central domain are marked by almost pure radiogenic 4 he of crustal origin and thus by an apparent absence of mantle derived he which coincides with complete lack of cenozoic volcanics low terrestrial heat flow and thickened crust such a 3 he 4 he distribution pattern clearly indicates that tectonic environment control the distribution of he isotopes in the continent of china

eddy mean flow decomposition and eddy diffusivity estimates in the tropical pacific ocean 1 methodology 1 eddy diffusivity of the surface velocity field in the tropical pacific ocean was estimated using satellite tracked drifting buoys 1979 through mid 1996 the tropical pacific surface current system is characterized by nonstationarity strong meridional shear and an energetic mesoscale velocity field eddy diffusivity may be defined as the integral of the autocovariance of lagrangian eddy velocities requiring both stationary and homogeneous statistics of the eddy field eddy velocities were obtained by removing a splined mean field to eliminate mean shear from observations binned 1 spatially to group data that have similar dispersion characteristics and 2 temporally to create stationary eddy statistics zonal diffusivity estimates are up to 7 times larger than meridional diffusivity estimates in the high eddy energy regions this anisotropy is associated with the meridional mesoscale wave motion i e by equatorial and tropical instability waves that increases eddy variance but does not lead to a proportional increase in water parcel diffusion because of the coherent character of the trajectory motion at least for initial time lags simple autoregressive models of first and second order are used to describe and classify the resulting eddy statistics an independent confirmation of the diffusivity estimate in the central eastern pacific was obtained by comparing tracer flux divergence computed from a parameterization using diffusivity estimates of our analysis with that from direct eddy reynolds stress flux divergence our results show that diffusivity can be estimated for regions not considered previously either because of sparse data or the complexities of the velocity field

shelf open ocean exchange forced by wind jets abstractthe general problem of exchange from a shallow shelf across sharp topography to the deep ocean forced by narrow cross shelf wind jets is studied using quasigeostrophic theory and an idealized primitive equation numerical model interest is motivated by katabatic winds that emanate from narrow fjords in southeast greenland although similar topographically constrained wind jets are found throughout the world s oceans because there is no net vorticity input by the wind the circulation is largely confined to the region near the forcing circulation over the shelf is limited by bottom friction for weakly stratified flows but stratification allows for much stronger upper layer flows that are regulated by weak coupling to the lower layer over the sloping topography the topographic beta effect limits the deep flow while for sufficient stratification the upper layer flow can cross the topography to connect the shelf to the open ocean this can be an effective transport mechanism even for short s

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

strong downslope wind events in ammassalik southeast greenland abstractammassalik in southeast greenland is known for strong wind events that can reach hurricane intensity and cause severe destruction in the local town yet these winds and their impact on the nearby fjord and shelf region have not been studied in detail here data from two meteorological stations and the european centre for medium range weather forecasts interim re analysis era interim are used to identify and characterize these strong downslope wind events which are especially pronounced at a major east greenland fjord sermilik fjord within ammassalik their local and regional characteristics their dynamics and their impacts on the regional sea ice cover and air sea fluxes are described based on a composite of the events it is concluded that wind events last for approximately a day and seven to eight events occur each winter downslope wind events are associated with a deep synoptic scale cyclone between iceland and greenland during the events cold dry air is advected down the ice sheet

the arjuno welirang volcanic complex and the connected lusi system geochemical evidences abstract for the first time we present the geochemical characterization of fluids emitted from the arjuno welirang volcanic complex and compare the results with those obtained sampling the neighboring spectacular lusi eruption site java island indonesia the isotopic composition of the hydrothermal and cold waters from the welirang volcanic complex indicate a meteoric origin for these springs with values ranging from 65 to 50 and 6 to 1 vs v smow respectively for d and 18 o the water erupted from the lusi site showed clustered higher d and 18 o isotopic values ranging around 6 and 10 vs v smow respectively we ascribe these results to mixing between hydrothermal fluids meteoric water saline formation fluids and water released during clay mineral illitization ultimately altered by additional evaporation processes the chemical and isotopic composition of fluids emitted from fumaroles and hydrothermal springs of the welirang volcano showed a clear magmatic signature where a co 2 dominated gas reveals 13 c co2 ranging between 5 9 and 2 4 and helium isotope with r ra 7 3 these values are very close to those measured at lusi site r ra 7 that also have high co 2 ch 4 ratio 1 7 2 2 supporting the high contribution of magmatic gases moreover a great contribution of andesitic water has been recognized in the water vapour emitted from the summit fumaroles converging geochemical data indicate that the plumbing system of the lusi eruption site is connected at depth with the arjuno welirang volcanic complex these data support a scenario where hydrothermal fluids from the volcanic system migrated in the sedimentary basin triggering metamorphic reactions in the organic rich sediments that ultimately resulted in a venting system at the surface after eleven years of incessant activity this venting system remains constantly fed by the fluids from the volcanic complex and became world known as lusi the largest ongoing clastic geysering system on earth

genesis of mud volcanoes in sedimentary basins a solitary wave based mechanism 1 mud volcanoes represent the ground surface morphological expression of highly focused fluid flow inside sedimentary basins sedimentary basins show usually the presence of overpressured compartments encapsulated by low permeability bounds seals which can have different origins capillary barriers with high entry capillary pressure diagenetically sealed formations a mud volcano can be formed in response to the hydrofracturation of such a permeability barrier when introducing the pressure dependence of permeability in poroelasticity the theory predicts the upsurge of fluid pressure fronts after the hydrofracturation of the seal initial shock these fronts take the form of hydro mechanical non linear shock waves which are solutions of a burgers type equation these solitary waves are associated with an upsurge of pore water which depends on the pore fluid pressure gradient carried up with the waves the arrival of these waves at the ground surface can generate mud volcanoes type features with spots of highly focused flow

do tropical cells ventilate the indo pacific equatorial thermocline source waters of the indo pacific equatorial thermocline are studied with a high resolution ocean model in the annual mean fields tropical and subtropical overturning cells are found that upwell at the equator and downwell at 5 degrees and 20 degrees poleward of the equator respectively tropical cells are common in ocean models but their role in ventilating the equatorial thermocline is obscure because the downwelled water is too warm to match the subsurface equatorial waters the tropical cells are much weaker when the overturning is considered in density coordinates when high frequency mass fluxes are included tropical cells are compensated by an eddy induced overturning seasonal variations and tropical instability waves are responsible for the compensation it follows that only subtropical cells transfer surface water to the equatorial thermocline strong tropical cells are shown to be an artefact

lusi hydrothermal structure inferred through ambient vibration measurements abstract the spectacular lusi mud eruption started in northeast java indonesia the 29th of may 2006 following a m6 3 strike slip seismic event after the earthquake several mud pools aligned along a ne sw direction appeared in the sidoarjo district the most prominent eruption site was named lusi lusi is located 10 km to the ne of the northernmost cone of the arjuno welirang volcanic complex with which it is connected by the watukosek fault system in this study we applied the hvsr method which is a common tool used for site effect investigations as well as to infer buried structures and reconstruct sub surface geology the method is based on the ratio of the horizontal to vertical components of ground motion and it generally exhibits a peak corresponding to the fundamental frequency of the site spectral ratio results highlight a fundamental frequency band between 0 4 and 1 0 hz in the lusi neighborhood we interpret these peaks as related to the velocity lithological contrast at depth between alluvial deposits and bluish grey clay our analysis also highlights the presence of a depocenter characterized by fundamental frequency up to 0 3 hz which is interpreted as the subsidence caused by withdrawal of mud and fluids from depth as also shown by the comparison of the hvsr results with gravimetry data moreover in the area of the lusi vent a broad band frequency range is related to the lusi conduit in this paper we show that detailed microtremor surveys could be used as a preliminary and fast approach to locate mud conduits with sufficient precision

winter eddy genesis in the eastern south china sea due to orographic wind jets abstract generation of mesoscale eddies in the eastern south china sea scs in winters during august 1999 to july 2002 is studied with a reduced gravity model it is found that the orographic wind jets associated with the northeast winter monsoon and the gaps in the mountainous island chain along the eastern boundary of the scs can spin up cyclonic and anticyclonic eddies over the scs results suggest that direct wind forcing could be an important generation mechanism for the rich eddy activity in the scs and that to simulate this mechanism the resolution of the wind forcing has to be high enough to resolve the local wind jets induced by orographic effects

katabatic wind driven exchange in fjords the general issue of katabatic wind driven exchange in fjords is considered using an idealized numerical model theory and observations two regimes are identified for fjords narrower than a viscous boundary layer width the exchange is limited by a balance between wind and friction in lateral boundary layers for the nonlinear viscous parameterization used here this boundary layer thickness depends on the properties of the fjord such as stratification and length as well as on the wind stress and numerical parameters such as grid spacing and an empirical constant for wider fjords typical of east greenland the balance is primarily between wind the along fjord pressure gradient and acceleration in general agreement with previous two layer nonrotating theories it is expected that o 10 of the surface layer will be flushed out of the fjord by a single wind event application of the idealized model to a typical katabatic wind event produces outflowing velocities that are in general agreement with observations in sermilik fjord the presence of a sill has only a minor influence on the exchange until the sill penetrates over most of the lower layer thickness in which cases the exchange is reduced it is concluded that the multiple katabatic wind events per winter that are experienced by the fjords along east greenland represent an important mechanism of exchange between the fjord and shelf with implications for the renewal of warm salty waters at depth and for the export of glacial freshwater in the upper layer

relationship of topex poseidon altimetric height to steric height and circulation in the north pacific topex poseidon altimetric height is compared with 20 transpacific eddy resolving realizations of steric height the latter are calculated from temperature expendable bathythermograph xbt and salinity expendable conductivity and temperature profiler xctd profiles along a precisely repeating ship track over a period of 5 years the overall difference between steric height and altimetric height is 5 2 cm rms on long wavelengths 500 km containing 17 of the steric height variance the 3 0 cm rms difference and lowered coherence are due to the sparse distribution of altimeter ground tracks along the xbt section the 2 4 cm rms difference in the basin wide spatial mean appears to be due to fluctuations in bottom pressure differences between steric height and altimetric height increase near the western boundary but data variance increases even more and so the signal to noise ratio is highest in the western quarter of the transect basin wide integrals of surface geostrophic transport from steric height and altimetric height are in reasonable agreement the 1 9 104 m2 s 1 rms difference is mainly because the interpolated altimetric height lacks spatial resolution across the narrow western boundary current a linear regression is used to demonstrate the estimation of subsurface temperature from altimetric data errors diminish from 0 8 c at 200 m to 0 3 c at 400 m geostrophic volume transport 0 800 m shows agreement that is similar to surface transport with 4 8 sverdrup sv 106 m3 s 1 rms difference the combination of altimetric height with subsurface temperature and salinity profiling is a powerful tool for observing variability in circulation and transport of the upper ocean the continuing need for appropriate subsurface data for verification and for statistical estimation is emphasized this includes salinity measurements which significantly reduce errors in specific volume and steric height

composition and flux of explosive gas release at lusi mud volcano east java indonesia the lusi mud volcano has been erupting since may 2006 in the densely populated sidoarjo regency east java indonesia forcing the evacuation of 40 000 people and destroying industry farmland and over 10 000 homes mud extrusion rates of 180 000 m 3 d 1 were measured in the first few months of the eruption decreasing to a loosely documented 4000 m for methane and approximately 600 m for carbon dioxide however the mass fractions of these gases are insufficient to explain the observed dynamics rather the primary driver of the cyclic bubble bursting activity is decompressional boiling of water which initiates a few tens of meters below the surface setting up slug flow in the upper conduit our measured gas flux and conceptual model lead to a corresponding upper bound estimate for the mud water mass flux of 10 5 m 3 d 1

numerical modeling of the lusi hydrothermal system initial results and future challenges abstract the lusi mud eruption in east java indonesia is an active clastic dominated geyser and a sedimentary hosted hydrothermal system that has generated wide interest across many disciplines this moderate to high enthalpy system is driven by multiphase and multicomponent processes fluid and rock mechanics and heat transport processes all which present challenges in developing realistic numerical models of the underlying physics we develop a hydrogeological conceptual model for this deep and complex hydrothermal system and construct an appropriate 3d geological model using the available data this geological model then serves as the basis for numerically simulations that include some of the dominant processes driving lusi we adopt a flexible continuum approach with an efficient numerical simulator based on the 3d geological model representing the deep structures of this hydrothermal system and geothermal reservoir by incorporating borehole information and seismic data obtained in the framework of the lusi lab project the geological model is transformed into a computational grid using binary space partitioning bsp of the input geometry and octree refinement on the grid to perform multi physics simulations thermodynamic calculations using the equation of state for a co 2 bearing aqueous nacl solution suggest that lusi is a two phase flow system water co 2 finally we present initial results from a simple hydro mechanical multiphase numerical model that simulates processes that likely contributed to the initiation of lusi

the lusi drone a multidisciplinary tool to access extreme environments abstract extreme and inaccessible environments are a new frontier that unmanned and remotely operated vehicles can today safely access and monitor the lusi mud eruption ne java island indonesia represents one of these harsh environments that are totally unreachable with traditional techniques here boiling mud is constantly spewed tens of meters in height and tall gas clouds surround the 100 m wide active crater the crater is surrounded by a 600 m diameter circular zone of hot mud that prevents any approach to investigate and sample the eruption site in order to access this active crater we designed and assembled a multipurpose drone the lusi drone is equipped with numerous airborne devices suitable for use on board of other multicopters during the missions three cameras can complete 1 video survey 2 high resolution photogrammetry of desired and preselected polygons and 3 thermal photogrammetry surveys with infra red camera to locate hot fluids seepage areas or faulted zones crater sampling and monitoring operations can be pre planned with a flight software and the pilot is required only for take off and landing a winch allows the deployment of gas mud and water samplers and contact thermometers to be operated with no risk for the aircraft during the winch operations that can be performed automatically the aircraft hovers at a safety height until the tasks controlled by the winch embedded processor are completed the drone is also equipped with gps connected co2 and ch4 sensors gridded surveys using these devices allowed obtaining 2d maps of the concentration and distribution of various gasses over the area covered by the flight path the device is solid stable even with significant wind affordable and easy to transport the lusi drone successfully operated during several expeditions at the ongoing active lusi eruption site and proved to be an excellent tool to study other harsh or unreachable sites where operations with more conventional methods are too expensive dangerous or simply impossible

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

origin and age of carbonate clasts from the lusi eruption java indonesia abstract deep stratigraphic constrains below the indonesian lusi mud eruption are currently lacking due to the absence of deep wells and good quality seismic data a collection of carbonate clasts has been sampled from the lusi site active since its birth in 2006 these specimens are part of a large variety of lithotypes erupted from the main crater the carbonates analysed comprise scleractinian coral and bivalve shell fragments probably shallow water in origin and clasts consisting of planktonic foraminifera bearing mudstone from pelagic deposits selected rocks were analysed using planktonic foraminifera and 87sr 86sr dating with the aim to constrain their age and to improve the understanding of the so far unknown sequence of limestone deposits inferred at this site based on biostratigraphy using planktonic foraminifera one group of samples reveal to belong to the planktonic foraminifera zone m5b with an age comprised between 16 29 and 15 10 ma miocene latest burdighalian to langhian the sr isotope based ages of clasts analysed for 87sr 86sr cover a larger time window spanning from pliocene zanclean and piacenzian miocene messinian down to eocene priabonian the pliocene and messinian ages are unreasonably young from what is known of the local geology and one sample provided an 87sr 86sr age that is 8 my younger compared to that obtained from the planktonic foraminifera assemblage occurring in that sample the discrepancy suggests that this and the other unduly young samples have possibly been contaminated by geological materials with radiogenic sr isotope composition the minimum age of 37 18 ma obtained by 87sr 86sr from a well preserved oyster shell indicates that some of the clasts can be attributed to the deep seated ngimbang formation the dating has been combined with the interpretation of seismic profiles to investigate the stratigraphy of inferred carbonates below lusi and the prg 1 well located some kilometres to the north east prg 1 borehole data are also integrated and discussed in this study the obtained results reveal multiple implications a the tuban and kujung formations are overlapping at lusi site b the lusi feeder conduit brecciated and mobilized to the surface carbonate lithologies buried as deep as possibly 3 8 km as well as even older and deeper seated lithotypes from the ngimbang formation c since the deeper carbonate samples erupted in 2006 belong to the typically not overpressured kujung formation an additional overpressure generated from deeper units ngimbang formation would be required to force these fragments to surface

a new hydrothermal scenario for the 2006 lusi eruption indonesia insights from gas geochemistry abstract the 29th of may 2006 gas and mud eruptions suddenly appeared along the watukosek fault in the north east of java indonesia within a few weeks several villages were submerged by boiling mud the most prominent eruption site was named lusi to date november 2011 lusi is still active and a 7 km2 area is covered by the burst mud breccia the mechanisms responsible for this devastating eruption remain elusive while there is consensus about the origin of the erupted mud the source of water is uncertain the origin of the gas is unknown and the trigger of the eruption is still debated in order to shed light on these unknowns we acquired a wide set of data of molecular and isotopic composition of gas sampled in several lusi vents in the surrounding mud volcanoes in the closest natural gas field wunut and in the hydrothermal vents at the neighbouring volcanic complex in the period 2006 2011 the boiling fluids erupted in the crater zone are apparently co2 dominated while colder ch4 dominated and c2 c3 bearing fluids are identified at several sites around the crater zone gas genetic diagrams maturity plots and gas generation modelling suggest that the hydrocarbons are thermogenic 13c1 up to 35 13c2 up to 20 deriving from marine kerogen with maturity of at least 1 5 ro for instance in the 4400 m deep ngimbang source rocks co2 released from the crater and surrounding seeps is also thermogenic 13c from 15 to 24 related to kerogen decarboxylation or thermal ch4 oxidation in deep rocks although three vents just outside the crater showed an apparent inorganic signature 7 5 4000 m magmatic intrusions and hydrothermal fluids responsible for the enhanced heat that altered source rocks and or gas reservoirs the neighbouring magmatic arjuno complex and its fluid pressure system combined with high seismic activity could have played a key role in the lusi genesis and evolution within this new model framework lusi is better understood as a sediment hosted hydrothermal system rather than a mud volcano

enhanced hydrothermal processes at the new born lusi eruptive system indonesia abstract little is known about the processes taking place in new born hydrothermal systems we investigate the eruptive activity of lusi a sediment hosted hydrothermal system active since 2006 in east java indonesia we show that superimposed on the regular geysering activity lusi features periods of enhanced hydrothermal processes during which boiling mud breccia is violently discharged from the eruptive vents this results in sudden flooding lasting from several minutes to several hours and featuring almost instantaneous temperature peaks i e from 35 c to more than 65 c in less than 2 min such activity here named hydrothermal waves is marked by high frequency seismic radiations and is distinguished by sharp peaks of ch4 and co2 concentrations in the erupted fluids this suggests fluids upwelling from at least tents of meters below the near surface the injection into the shallow plumbing system of ch4 and co2 rich batches of fluids may promote instabilities in the mud breccia column leading to the hydrothermal waves our findings provide key insights into the deep charging dynamics of a new born hydrothermal system and highlight the effects imposed by subtle variations in fluid chemistry changes at depth

subsidence associated with the lusi mud eruption east java investigated by sar interferometry abstract a mud volcano lusi initiated its eruption on 29 may 2006 adjacent to a hydrocarbon exploration well in east java ground subsidence in the vicinity of the lusi eruptive vent was well recorded by a synthetic aperture radar sar palsar onboard the japanese alos satellite we apply an interferometric sar insar technique on ten palsar data scenes acquired between 19 may 2006 and 21 may 2007 in order to obtain continuous maps of ground displacements around lusi although the displacements in the area closest to the eruptive vent spatial extension of about 1 5 km are not detectable because of the erupted mud all the processed interferograms indicate subsidence in an ellipsoidal area of approximately 4 km north south 3 km east west centered at the main eruptive vent in particular interferograms spanning the first four months until 4 oct 2006 and the subsequent 46 days between 4 oct 2006 and 19 nov 2006 show at least about 70 cm and 80 cm of displacements away from the satellite respectively possible causes of the subsidence i e 1 loading effect of the erupted mud 2 creation of a cylindrical mud conduit and 3 pressure decrease and depletion of materials at depth are investigated the effects of the first two causes are found to be insufficient to explain the total amount of subsidence observed in the first six months the third possibility is quantitatively examined using a boundary element approach by modeling the source of deformation as a deflating oblate spheroid the spheroid is estimated to lie at depths of a few hundred to a thousand meters the estimated depths are significantly shallower than determined from analyses of erupted mud samples the difference is explained by presence of significant amount of inelastic deformation including compaction and downward transfer of material

evidence of subsurface anaerobic biodegradation of hydrocarbons and potential secondary methanogenesis in terrestrial mud volcanoes abstract the assessment of gas origin in mud volcanoes and related petroleum systems must consider post genetic processes which may alter the original molecular and isotopic composition of reservoir gas beyond eventual molecular and isotopic fractionation due to gas migration and microbial oxidation investigated in previous studies we now demonstrate that mud volcanoes can show signals of anaerobic biodegradation of natural gas and oil in the subsurface a large set of gas geochemical data from more than 150 terrestrial mud volcanoes worldwide has been examined due to the very low amount of c 2 in mud volcanoes isotopic ratios of ethane propane and butane generally the best tracers of anaerobic biodegradation are only available in a few cases however it is observed that 13 c enriched propane is always associated with positive 13 c co2 values which are known indicators of secondary methanogenesis following anaerobic biodegradation of petroleum data from carbon isotopic ratio of co 2 are available for 134 onshore mud volcanoes from 9 countries azerbaijan georgia ukraine russia turkmenistan trinidad italy japan and taiwan exactly 50 of mud volcanoes all releasing thermogenic or mixed methane show at least one sample with 13 c co2 5 pdb thermogenic ch 4 associated with positive carbon isotopic ratio of co 2 generally maintains its 13 c enriched signature which is therefore not perturbed by the lighter secondary microbial gas there is however high variability in the 13 c co2 values within the same mud volcanoes so that positive 13 c co2 values can be found in some vents and not in others or not continuously in the same vent this can be due to high sensitivity of 13 c co2 to gas water rock interactions or to the presence of differently biodegraded seepage systems in the same mud volcano however finding a positive 13 c co2 value should be considered highly indicative of anaerobic biodegradation and further analyses should be made especially if mud volcanoes are to be used as pathfinders of the conditions indicative of subsurface hydrocarbon accumulations in unexplored areas

the geochemistry and origin of the hydrothermal water erupted at lusi indonesia abstract the spectacular lusi mud eruption started in northeast java the 29th of may 2006 despite extensive research the origin of the erupted water remains elusive and poorly constrained here we present a comprehensive study of the geochemistry of lusi waters compared with those collected from surrounding areas all collected between 2006 and 2013 including data from mud volcanoes and volcano hosted hydrothermal springs within this broad context the geochemical characteristics of the fluids expelled in the lusi region suggest that we can classify the waters in three groups 1 meteoric waters expelled in cold springs and artesian wells 2 hydrothermal waters typically mixed with meteoric waters and 3 formation water from marine sediments altered by diagenetic processes such as clay mineral dehydration samples collected from the lusi crater are cl and na dominated up to 527 mm and 471 7 mm respectively similar to seawater indicating that altered sedimentary formation waters are predominant in this system in addition they are enriched in sr up to 808 4 m and other elements commonly associated with hydrothermal systems such as li up to 877 6 m compared to 26 m in seawater some of these elements are up to ten times enriched compared to seawater values high temperature fluid mineral interactions in the subsurface appear to have facilitated the transfer of li and other mobile elements into the fluids high temperature fluid mineral interaction reactions are also supported by si concentrations significantly higher compared to other sampled mud volcanoes in the island crater samples also show the highest 18o values 5 after correction for evaporation compared to 1 at the mv localities 87sr 86sr ratios vary between of 0 7077 and 0 7083 and seem to reflect a general mixture of fluids from clay mineral dehydration carbonate recrystallization alteration of volcanic rocks and hydrothermal imprint eight years of geochemical monitoring indicate that the composition of the deep sourced lusi fluids remain fairly constant through time thus our findings show that the lusi crater waters represent a regional geochemical anomaly and we suggest that a combination of high temperatures in the source region and fluid rock interactions with silicates and possibly carbonate rich lithologies can explain the data this is consistent with a model where the emitted gases migrate from a deep seated 4 km source region likely associated with the presence of hot igneous intrusions and or high t reactions related to the presence of neighbouring active volcanoes

mantle co2 degassing at mt vulture volcano italy relationship between co2 outgassing of volcanoes and the time of their last eruption abstract mantle volatiles are mainly lost from the earth to the atmosphere through subaerial and submarine volcanism recent studies have shown that degassing of mantle volatiles also occurs from inactive volcanic areas and in tectonically active areas a new challenge in earth science is to quantify the mantle derived flux of volatiles e g co2 which is important for understanding such diverse issues as the evolution of the atmosphere the relationships between magma degassing and volcanic activity gas pressure and seismogenic processes and the hazards posed by volcanic lakes here we present a detailed study of mantle derived co2 budget from mt vulture volcano in the apennines italy whose latest eruption occurred 141 11 kyr ago the relationship between 13cco2 and total dissolved carbon at mt vulture volcano indicates that the emitted co2 is a mixture of a biogenic end member with an average 13cco2 of about 17 and a mantle derived co2 end member with 13cco2 values from 3 to 2 these values of mantle derived 13cco2 are in the range of those for gas emitted from active volcanoes in the mediterranean we calculated the contribution of individual components co2 in groundwater in lakes and from main pools to the total co2 budget in the area we used new measurements of water flow combined with literature data to calculate the co2 flux associated with groundwater and measured the gas flux from the main pools on the volcanic edifice finally we calculated the co2 flow in the lakes based on the gradient concentration and eddy diffusivity the total mantle derived co2 budget in the area is 4 85 10 8 mol yr 1 which is more than double previous estimates this is higher than those observed in younger volcanic systems elsewhere thereby supporting the existence of actively degassing mantle melts below mt vulture volcano a structural map highlights the tectonic control on co2 flow across the mt vulture volcanic edifice indeed the tectonic discontinuities that controlled the magma upwelling during the most recent volcanic activity are still the main active degassing structures the new estimate of co2 budget in the mt vulture area together with literature data on co2 budget from historically active and inactive italian volcanoes suggests a power law functional relationship between the age of the most recent volcanic eruption and both total discharged co2 r 2 0 73 and volcano size normalized co2 flux r 2 0 66 this relation is also valid by using data from worldwide volcanoes highlighting that deep degassing can occur over very long time too in turn the highlighted relation provides also an important tool to better evaluate the state of activity of a volcano whose last activity occurred far in time finally our study highlights that in the southern apennines an active degassing of mantle derived volatiles i e he co2 occurs indiscriminately from west to east this is in contrast to the central northern apennine which is characterized by a crustal radiogenic volatile contribution which increases eastward coupled to a decrease in deep co2 flux this difference between the two regions is probably due to lithospheric tears which control the upwelling of mantle melts their degassing and the transport of volatiles through the crust

a discussion of flow pathways in the central and eastern equatorial pacific abstract an eddy permitting global ocean model is used to interpret kinematics within the central and eastern equatorial pacific ocean from 160 e to the coast of america because of high levels of variability in this region observational studies of meridional flow are contradictory in particular as to whether the net flow is northward or southward unlike most oceanographic datasets model output can be analyzed at high temporal and spatial resolution providing clues as to real ocean behavior in the model a net southward flow occurs across the equator east of 160 w at most density layers throughout the year in the central pacific from 160 e to 160 w the net flow is northward but varies with season and occurs primarily in the mixed layer this is a key region for the flow of equatorial undercurrent water into the northern hemisphere the three dimensional flow is very complex and seasonally dependent it is vital that these flows are analyzed in an isopycnal framework or else the pathways are ve

an estimate of the eddy induced circulation in the labrador sea regions of oceanic deep convection such as the labrador sea are prone to baroclinic instability the resulting geostrophic eddies play a crucial role in the post convection adjustment process which involves both rearrangement of mass so as to release available potential energy and exchange of heat and salt with the boundaries in this study it is proposed that the slumping of isopycnals associated with baroclinic instability drives an eddy induced overturning circulation consisting of a surface intensified flow transporting low salinity water from the boundary currents into the interior sinking motion in the interior and an outflow at depth transporting newly ventilated labrador sea water towards the boundaries typical eddy induced velocities estimated from hydrographic data are roughly 0 5 cm s for the surface inflow 1 m day for the vertical motion and 0 1 cm s for the deeper outflow in close agreement with those calculated in a numerical model

isopycnal mixing in ocean circulation models abstract a subgrid scale form for mesoscale eddy mixing on isopycnal surfaces is proposed for use in non eddy resolving ocean circulation models the mixing is applied in isopycnal coordinates to isopycnal layer thickness or inverse density gradient as well as to passive scalars temperature and salinity the transformation of these mixing forms to physical coordinates is also presented

the deep subsurface structure beneath lusi and the adjacent volcanic chain inferred from local travel time tomography abstract since 2006 the lusi mud eruption is ongoing in the northeast of java island indonesia we perform a 3d seismic tomography of the area surrounding lusi and the adjacent arjuno welirang volcanic complex using p wave arrivals of 797 local earthquakes recorded on 31 seismic stations for two years between 2015 and 2016 resolution tests show that we can reasonably well constrain the subsurface velocity structure beneath lusi down to a depth of 20 km the results of our tomography reveal that lusi has a shallow plumbing system that is interconnected with the neighboring penanggungan volcano their joint system reaches down to a depth of 20 km the arjuno welirang volcanic complex has its own deep rooted plumbing system that might be connected to penanggungan volcano and lusi along the watukosek fault zone the connection of lusi with this large reservoir volume elucidates the longevity of the lusi eruption

insights on the structure of lusi mud edifice from land gravity data abstract since may 2006 the active lusi mud eruption has continuously erupted boiling mud during the early stages of the eruption in 2006 previous gravity studies showed that the piling up of the mud constructed a large edifice that subsides within the unconsolidated sediment especially around a large area over the active crater after ten years of continuous eruption the size of the edifice has grown significantly over a surface framed by 10 m tall containment embankments in 2015 and 2016 several land gravity surveys were carried out to investigate the structure of the mud edifice and the effect of local geological active features the new residual bouguer anomaly map calculated for a reference density of 2670 kg m 3 shows significant changes in the local gravity field in comparison to the previous 2006 gravity map survey the new data set shows that the gravity decrease is generally restricted along the faulted and fractured zones around erupting vents and in the southern part of the mud edifice maximum gravity variations reach 1 4 mgal in some areas of the mud edifice in the region outside the embankment the gravity reductions are 0 6 mgal e w and 1 0 mgal n s a second vertical derivative analysis of gravity data indicates that the mud edifice continues to pile up and subside mostly in the western and southern part of the edifice results of a 3d forward model of a vertical cylinder shape allowed characterising the extent of compacted material along the watukosek fault system that originates from the neighbouring volcanic arc and crosses the mud edifice our results support the hypothesis of local pinched volume of mud ongoing between the subsided and uplifted masses of mud the density of compacted mud breccia material increases between 16 and 27 gravity data also shows that the lusi mud edifice is built over an extended nw se gravity increase interpreted as a sediment density variation within the basin and which is parallel to the trend of the basin

10 years of lusi eruption lessons learned from multidisciplinary studies lusi lab abstract the spectacular lusi eruption started in northeast java indonesia on may 29th 2006 continuously erupting mud water gas oil and clasts ever since lusi provides an unprecedented opportunity to study the birth and the evolution of a large scale and hot mud eruption lusi is interpreted as a hybrid between a traditional hydrocarbon driven piercement structure mud volcano and a hydrothermal system fuelled by magmatic heat lusi is therefore an exciting natural laboratory for understanding analogue modern and palaeo piercement systems such as mud volcanoes sediment hosted hydrothermal systems and hydrothermal vent complexes this special issue collects recent multidisciplinary work completed in the framework of the erc funded lusi lab project these studies were conducted at and near lusi contributions span across disciplines such as engineering geochemistry geophysics geology and numerical modelling including fieldwork laboratory and theoretical approaches the acquired results contribute to characterise the dynamics of complex interactions between volcanism and an ongoing erupting clastic system lusi still saves many mysteries that will be unravelled by future scientific investigations

modelling of gas generation following emplacement of an igneous sill below lusi east java indonesia highlights we have tested a hypothesis where a sill intrusion is present at depth near lusi we have calculated the co2 generation following the emplacing a 150 m sill in an organic rich sequence at 4 5 km this scenario may provide the co2 currently emitted from lusi and are consistent with geological information abstract the lusi mud eruption started in 2006 and is located near the arjuno welirang volcanic complex in northeastern java lusi is characterized by the eruption of aqueous vapor co2 and ch4 in addition to mud breccia and boiling water however the ultimate driving force for the eruption remains unclear here we investigate if lusi could have been driven by the heat released from a deep seated igneous sill originating from the neighboring volcanic arc we have used a 1d thermal model to calculate the production of co2 from thermally matured organic matter in the contact aureole of a hypothetical 150 m thick sill the sill is tentatively emplaced at 1100 c at 4 5 km depth within the organic rich eocene ngimbang formation the carbon gas produced from the thermal perturbation reaches a peak of 1357 kg m2 y co2 equivalents shortly after sill emplacement stressing the efficiency of organic matter transformation in contact aureoles our simulations show that during the first 1000 years after emplacement 53 5 ton co2 m2 is produced in the contact aureole when scaled to a sill size of 150 m 25 km2 i e a sill volume of 3 75 km3 the aureole has the potential to generate a total of 1350 mt co2 during the first 1000 years with a peak generation of about 34 mt co2 y we conclude that contact metamorphism in our hypothetical geological scenario generates co2 in the gigaton range and represents a plausible source for the lusi gas

secular variations of helium and carbon isotopes at galeras volcano colombia copyright c 1997 elsevier science b v all rights reserved we have measured 3 he 4 he 4 he 20 ne and co 2 4 he ratios and d 13 c values of co 2 in eighteen samples from crater fumaroles of galeras volcano colombia and seven samples of bubbling gases of the pandiaco mineral spring located about 8 km east of the volcano from april 1988 to july 1995 the 3 he 4 he ratios of crater fumaroles corrected for atmospheric contamination increased significantly from 5 47 r atm in december 1989 to 7 93 r atm in august 1990 and reached a maximum of 8 84 r atm in may 1992 the ratio then decreased gradually until july 1995 overall variation of helium isotopes appears to be related to the current activity of the volcano the 3 he 4 he ratios of pandiaco mineral spring were constant between april 1988 and november 1991 and increased in april 1993 although experimental error is large the d 13 c values of co 2 of crater fumaroles show negative correlation to the helium isotopes while those of pandiaco are relatively constant based on the d 13 c values and co 2 3 he ratios it is possible to estimate fractions of upper mantle carbon in these samples calculated mantle fractions are 3 10 in crater fumaroles while those in pandiaco spring are negligibly small

evidence of deep magma degassing and ascent by geochemistry of peripheral gas emissions at mount etna italy assessment of the magmatic reservoir pressure 1 five gas discharges in the area of mount etna volcano italy and in the near hyblean plateau have been monitored since 1996 all the emissions displayed low contributions from crustal fluids whereas magmatic gases were the main component selective dissolution of these gases into hydrothermal aquifers has been recognized and modeled allowing us to calculate the original composition of the magma released gases the inferred composition of the magmatic gases exhibits synchronous variations of he ne and he co2 ratios which are coherent with the magma degassing process on the basis of numerical simulations of volatile degassing from etnean basalts we have computed the initial and final pressures of the magma batches feeding the emissions we thus can define the levels of the etna plumbing system where magmas are stored pressure values were around 360 and 160 mpa for initial and final stages respectively meaning related depths of about 10 and 3 km below sea level matching those obtained by geophysical investigations for the deep and shallow magma reservoirs in addition we have been able to recognize episodes of magma migration from the deeper reservoir toward the shallow one an important magma injection into the shallow storage volume was detected during the onset of the 2001 eruption 17 july no further injection had taken place during this period until september 2001 providing a possible reason for the quick exhaustion of the eruption in view of this we suggest that the sampled emissions are a powerful geochemical tool to investigate the etna s plumbing system and its magma dynamics as well as the development of eruptive events

subsidence and uplift of sidoarjo east java due to the eruption of the lusi mud volcano 2006 present global positioning system gps and satellite based insar interferometric synthetic aperture radar measurements of the subsidence and uplift of a populated area of sidoarjo east java are due to the eruption of the lusi mud volcano 2006 present these data are the first direct quantitative measurements of deformation due to the growth of a mud volcano edifice the gps data were recorded over periods of a few hours to several months and show that between june 2006 and september 2007 the earth s surface has been subsiding at rates of 0 1 4 cm day maximum rates of subsidence occurred in an area 300 400 m to the northwest of the main mud volcano vent horizontal displacements were 0 03 0 9 cm day and were also towards this area in general uplifts of up to 0 09 cm day were recorded in areas outside of the edifice changes in elevation measured using satellite imagery insar technique provide regional datasets of subsidence and uplift they confirm that during the first year a roughly circular area was undergoing sag like subsidence centered to the northwest of the main vent and that uplift was occurring 3 4 months after the initiation of the eruption due to the movement watukosek fault system subsidence occurred due to the weight of mud and man made dams and the collapse of the overburden due to removal of mud from the subsurface assuming constant rates of subsidence of 4 cm day then in the centre of the edifice there would be up to 44 m of subsidence in 3 years and up to 16 m in 10 years the mud volcano is now in a self organizing state with new fluid conduits forming as a result of the collapse

seismicity at lusi and the adjacent volcanic complex java indonesia abstract we study the local seismicity in east java around the arjuno welirang volcanic complex that is connected via the watukosek fault system to the spectacular lusi eruption site lusi is a sediment hosted hydrothermal system which has been erupting since 2006 it is fed by both mantellic and hydrothermal fluids rising and mixing with the thermogenic gases and other fluids from shallower sedimentary formations during a period of 24 months we observe 156 micro seismic earthquakes with local magnitudes ranging from m l 0 5 to m l 1 9 within our network the events predominantly nucleate at depths of 8 13 km below the arjuno welirang volcanic complex despite the geological evidence of active tectonic deformation and faulting observed at the surface practically no seismicity is observed in the sedimentary basin hosting lusi although we cannot entirely rule out artifacts due to an increased detection threshold in the sedimentary basin the deficit in significant seismicity suggests aseismic deformation beneath lusi due to the large amount of fluids that may lubricate the fault system an analysis of focal mechanisms of nine selected events around the arjuno welirang volcanic complex indicates predominantly strike slip faulting activity in the region sw of lusi this type of activity is consistent with observable features such as fault escarpment river deviation and railroad deformation suggesting that the watukosek fault system extends from the volcanic complex towards the ne of java our results point out that the tectonic deformation of the region is characterized by a segmented fault system being part of a broader damage zone rather than localized along a distinct fault plane

the plumbing system feeding the lusi eruption revealed by ambient noise tomography lusi is a sediment hosted hydrothermal system featuring clastic dominated geyser like eruption behavior in east java indonesia we use 10 months of ambient seismic noise cross correlations from 30 temporary seismic stations to obtain a 3 d model of shear wave velocity anomalies beneath lusi the neighboring arjuno welirang volcanic complex and the watukosek fault system connecting the two our work reveals a hydrothermal plume rooted at a minimum 6 km depth that reaches the surface at the lusi site furthermore the inversion shows that this vertical anomaly is connected to the adjacent volcanic complex through a narrow 3 km wide low velocity corridor slicing the survey area at a depth of 4 6 km the ne sw direction of this elongated zone matches the strike of the watukosek fault system distinct magmatic chambers are also inferred below the active volcanoes the large scale tomography features an exceptional example of a subsurface connection between a volcanic complex and a solitary erupting hydrothermal system hosted in a hydrocarbon rich back arc sedimentary basin these results are consistent with a scenario where deep seated fluids e g magmas and released hydrothermal fluids flow along a region of enhanced transmissivity i e the watukosek fault system damage zone from the volcanic arc toward the back arc basin where lusi resides the triggered metamorphic reactions occurring at depth in the organic rich sediments generated significant overpressure and fluid upwelling that is today released at the spectacular lusi eruption site

late winter generation of spiciness on subducted isopycnals the origins of density compensating anomalies of temperature and salinity spice are investigated using a model forced with the most realistic surface products available over the 40 years 1958 97 in this hindcast the largest interannual spiciness anomalies are found in the pacific ocean near the isopycnal s 0 5 25 5 where deviations as great as 1 28c and 0 6 psu are generated equatorward of winter outcropping in the eastern subtropics in both hemispheres these source regions are characterized by very unstable salinity gradients and low mean density stratification in winter two related signatures of winter mixing in the southeast pacific sep are density that is well mixed deeper than either temperature or salinity and subsurface density ratios that approach 1 all ocean basins in the model are shown to have regions with these characteristics and signatures however the resultant spiciness signals are focused on different isopycnals ranging from s 0 5 25 0 in the northeast pacific to s 0 5 26 5 in the south indian ocean a detailed examination of the sep finds that large positive anomalies are generated by diapycnal mixing across subducted isopycnals e g s 0 5 25 5 whereas negative anomalies are the result of a steady isopycnal advection moderated by vertical advection and heave there is considerable interannual variability in the strength of anomalies and in the density on which they occur historical observations are consistent with the model results but are insufficient to verify all aspects of the hindcast including the processes of anomaly generation in the sep it was not possible to relate isopycnal anomaly genesis to local surface forcing of any kind a complex scenario involving basinwide circulation of both the ocean and atmosphere especially of surface water through the subtropical evaporation zones is put forward to explain the decadal time scale evident in sep salinity anomalies on s 0 5 25 5 pacific anomalies generated on s 0 5 25 5 can be traced along mean geostrophic streamlines to the western boundary where decadal salinity variations at 78s are about 2 times as large order 60 1 psu as at 128n although there may be more variance on shallower isopycnals in the north at least portions of the s 0 5 25 5 signals appear to continue along the boundary to a convergence at the equator suggesting that the most robust sources of pacific spiciness variance coincide with equatorial exchange pathways

mantle helium in sacramento basin natural gas wells abstract helium isotope ratios in sacramento basin natural gas wells show a strong mantle signal the3he 4he ratios range from 0 11 times the atmospheric ratio 0 11 ra in the rio vista field to 2 75 ra in the moon bend field indicating that 1 to 34 of the helium is mantle derived 3he 4he versus ch4 4he ratios provide evidence of two component mixing between crustal and magmatic end members extrapolation of the linear regression line to ch4 4he 0 gives a hypothetical magmatic end member 3he 4he ratio of 3 84 ra half the typical mantle ratio this indicates that the magmatic end member may actually represent a mixture of mantle and crustal helium gases which deviate from the simple two component mixture can be explained by addition of pure methane radiogenic 4he or a high n2 he component with 3he 4he 0 6 ra to 1 0 ra the ch4 3he ratio of the magmatic end member remains poorly constrained 0 to 3 109 and one cannot rule out the possibility that a significant proportion of the methane in some fields may be of deep earth origin however fields with the highest 3he 4he ratios are associated with buried plio pleistocene intrusives which have up arched sediments to form hydrocarbon traps the methane in these fields may have been produced by rapid thermal alteration of the intruded sediment elsewhere the methane appears either to have migrated from deeply buried sediments in the western basin or to have been produced by local microbial activity

deep hydrothermal activity driving the lusi mud eruption abstract the lusi mud eruption in east java continues unabated after more than a decade of activity as a pulsating geyser system bursting mud clasts water and gas the origin of the fluids and their properties at depth are not well constrained thus hampering our understanding and modelling of the system previous geochemical and geophysical studies show that lusi is a sediment hosted hydrothermal system with two sources of mud at depths between 0 3 2 km and another between 3 5 4 75 km here we present results of mineral thermometry using raman spectroscopy and chlorite composition on clasts erupted at lusi the results show that some of these specimens originate from the two main fluid sources and at depths consistent with the geochemical and geophysical interpretation two main clast lithotypes erupt at lusi the first lithotype is a light grey shale returned to the surface from the upper kalibeng formation the primary mud source and equilibrated at temperatures below 200 c the second lithotype is a black shale whose source is the ngimbang formation at 3800 m depth two distinct temperature clusters are recorded in these black shales one at 179 17 c consistent with the temperature estimate at 3800 m depth with the pre eruption geothermal gradient while younger minerals in the same specimen recorded substantial anomalous heating at 250 c these high temperatures indicate interaction with a heat source associated with the eruption through mixing with hydrothermal fluids this temperature jump suggests rapid heating at 4000 m depth consistent with a scenario of a magmatic intrusion and hydrothermal fluids circulation this rapid and significant temperature increase would initiate devolatilisation reactions of hydrous minerals within the deep sedimentary package and generate substantial highly overpressured fluids at depths significantly below the main source of erupted mud we infer that reactive and thermal pressurisation led to a deep and metastable system susceptible to e g seismic activity ultimately opening fluid pathways towards the surface along the watukosek fault system the two temperatures clusters recorded in the clasts show that conductive heat flow was the dominant heat transport prior to the eruption while the system is now driven by large scale convection and advective heat transport the lusi eruption occurred in a highly populated area forcing the evacuation of several tens of thousands of people this system appears unstoppable and poses a real and present hazard for the settlements still surrounding the eruption site continuous research is necessary to understand this spectacular phenomenon both for its important scientific relevance and the societal impact of this natural disaster

eddy transport of heat and thermocline waters in the north pacific a key to interannual decadal climate variability abstract high resolution xbt transects in the north pacific ocean at an average latitude of 22 n are analyzed together with topex poseidon altimetric data to determine the structure and transport characteristics of the mesoscale eddy field based on anomalies in dynamic height 410 eddies are identified in 30 transects from 1991 to 1999 including eddies seen in multiple transects over a year or longer their wavelength is typically 500 km with peak to trough temperature difference of 2 2 c in the center of the thermocline the features slant westward with decreasing depth by 0 8 of longitude on average from 400 m up to the sea surface this tilt produces a depth varying velocity temperature correlation and hence a vertical meridional overturning circulation in the mean 3 9 sv sv 106 m3 s 1 of thermocline waters are carried southward by the eddy field over the width of the basin balanced mainly by northward flow in the surface layer corresponding northward heat transport is 0 086 0 012 pw

strike slip faulting as a trigger mechanism for overpressure release through piercement structures implications for the lusi mud volcano indonesia piercement structures such as hydrothermal vent complexes pockmarks and mud volcanoes are found in various geological settings but are often associated with faults or other fluid focussing features this article aims to investigate and understand the mechanisms responsible for the formation of piercement structures in sedimentary basins and the role of strike slip faulting as a triggering mechanism for fluidization for this purpose four different approaches were combined fieldwork analogue experiments and math

hydrogen and carbon isotopic composition of methane as evidence for biogenic origin of natural gases from the green tuff basin japan abstract hydrogen and carbon isotopic analyses of methane were carried out to investigate the origin of natural gases commercially produced from volcanic rocks in the green tuff basin of northeast japan whose high 3he 4he ratios have been interpreted as an indication of their abiogenic origin methane isotopic signatures 13c 32 to 67 d 163 to 202 respectively suggest that these are thermogenic gases or mixtures of thermogenic gases with bacterial gases the correlations of methane d vs 13c for the gases from specific fields are consistent with a mixing model between bacterial and thermogenic end members which was previously proposed on the basis of 13c contents of c1 to c4 hydrocarbons sakata 1991 berner and faber 1996 the green tuff basin gases are isotopically distinct from well known abiogenic methanes e g geothermal methane from the east pacific rise a significant contribution of abiogenic methane would therefore be unlikely for these gases

helium and carbon gas geochemistry of pore fluids from the sediment rich hydrothermal system in escanaba trough abstract ocean drilling program odp leg 169 which was conducted in 1996 provided an opportunity to study the gas geochemistry in the deeper part of the sediment rich hydrothermal system in escanaba trough gas void samples obtained from the core liner were analyzed and their results were compared with analytical data of vent fluid samples collected by a submersible dive program in 1988 the gas geochemistry of the pore fluids consisted mostly of a hydrothermal component and was basically the same as that of the vent fluids the he isotope ratios r ra 5 6 6 6 indicated a significant mantle he contribution and the c isotopic compositions of the hydrocarbons 13c ch4 43 13c c2h6 20 were characterized as a thermogenic origin caused by hydrothermal activity on the other hand the pore fluids in sedimentary layers away from the hydrothermal fields showed profiles which reflected lateral migration of the hydrothermal hydrocarbons and abundant biogenic ch4 helium and c isotope systematics were shown to represent a hydrothermal component and useful as indicators for their distribution beneath the seafloor similarities in he and hydrocarbon signatures to that of the escanaba trough hydrothermal system were found in some terrestrial natural gases which suggested that seafloor hydrothermal activity in sediment rich environments would be one of the possible petroleum hydrocarbon generation scenarios in unconventional geological settings

p and s velocity structure of the crust and the upper mantle beneath central java from local tomography inversion here we present the results of local source tomographic inversion beneath central java the data set was collected by a temporary seismic network more than 100 stations were operated for almost half a year about 13 000 p and s arrival times from 292 events were used to obtain three dimensional 3 d vp vs and vp vs models of the crust and the mantle wedge beneath central java source location and determination of the 3 d velocity models were performed simultaneously based on a new iterative tomographic algorithm lotos 06 final event locations clearly image the shape of the subduction zone beneath central java the dipping angle of the slab increases gradually from almost horizontal to about 70 a double seismic zone is observed in the slab between 80 and 150 km depth the most striking feature of the resulting p and s models is a pronounced low velocity anomaly in the crust just north of the volcanic arc merapi lawu anomaly mla an algorithm for estimation of the amplitude value which is presented in the paper shows that the difference between the fore arc and mla velocities at a depth of 10 km reaches 30 and 36 in p and s models respectively the value of the vp vs ratio inside the mla is more than 1 9 this shows a probable high content of fluids and partial melts within the crust in the upper mantle we observe an inclined low velocity anomaly which links the cluster of seismicity at 100 km depth with mla this anomaly might reflect ascending paths of fluids released from the slab the reliability of all these patterns was tested thoroughly

on the pathways of the equatorial subsurface currents in the eastern equatorial pacific and their contributions to the peru chile undercurrent 1 theconnections between theequatorial currentsystem andtheperu currentsystem in the eastern tropical pacific etp are examined with a primitive equations eddy resolving regional model the quasi equilibrium solutions reproduce three eastward equatorial subsurface currents of interest the equatorial undercurrent euc located between 1 n and 1 s the primary southern subsurface countercurrent psscc between 3 and 4 s and farther south the secondary southern subsurface countercurrent ssscc between 7 and 8 s using a lagrangian tracking procedure the fate of these currents in the etp and their contribution to the peru chile undercurrent pcuc are studied lagrangian diagnostics show that for the most part the euc water contributes to westward flows including the south equatorial current and deeper flows below it and strikingly only a very little fraction feeds the pcuc while a significant part of both ssccs contribute substantially mesoscale eddies are shown to exert an effect on these connections in addition about 30 of the pcuc is fed by the three subsurface equatorial flows euc psscc ssscc the remaining part of the pcuc comes from an alongshore recirculation associated with flows below it and from the southern part of the domain south of 9 s

release of methane from a volcanic basin as a mechanism for initial eocene global warming a 200 000 yr interval of extreme global warming marked the start of the eocene epoch about 55 million years ago negative carbon and oxygen isotope excursions in marine and terrestrial sediments show that this event was linked to a massive and rapid approximately 10 000 yr input of isotopically depleted carbon it has been suggested previously that extensive melting of gas hydrates buried in marine sediments may represent the carbon source and has caused the global climate change large scale hydrate melting however requires a hitherto unknown triggering mechanism here we present evidence for the presence of thousands of hydrothermal vent complexes identified on seismic reflection profiles from the voring and more basins in the norwegian sea we propose that intrusion of voluminous mantle derived melts in carbon rich sedimentary strata in the northeast atlantic may have caused an explosive release of methane transported to the ocean or atmosphere through the vent complexes close to the palaeocene eocene boundary similar volcanic and metamorphic processes may explain climate events associated with other large igneous provinces such as the siberian traps approximately 250 million years ago and the karoo igneous province approximately 183 million years ago

methanogenic biodegradation of petroleum in the west siberian basin russia significance for formation of giant cenomanian gas pools approximately 1700 tcf 48 trillion m3 of dry gas 99 methane reserves and resources occur in western siberia mostly in shallow 1500 m 4921 ft cenomanian pools in the northern part of the basin this dry gas constitutes about 11 of the world s conventional gas endowment and about 17 of the annual gas production the origin of the dry gas has been debated extensively over the last 45 yr but remains controversial widely discussed hypotheses on the origin include early mature thermogenic gas from coal primary microbial gas from dispersed organic matter or coal and thermogenic gas from deep source rocks however all these hypotheses are in some ways inconsistent with the molecular or isotopic composition of the gases or the results of basin and petroleum systems modeling here i present geochemical and geological evidence that a significant although yet not quantified part of the shallow dry gas in the northern west siberian basin originated from methanogenic biodegradation of petroleum circumstantial evidence includes the occurrence of heavily biodegraded oil legs and residual oil in many cenomanian gas pools as well as geochemical evidence of heavy to slight biodegradation in jurassic albian reservoirs commonly underlying the cenomanian pools direct evidence includes most importantly 13c enriched co2 in pools with biodegraded oil although data are limited which indicates 40 70 wt conversion of oil derived co2 to secondary microbial methane distinctive hydrocarbon molecular and isotopic compositions of most gases in cenomanian pools average dryness c1 sum c1 c5 is 0 9976 average 13c of methane is 51 8 suggest that they represent mixtures of biodegraded thermogenic gases from deep mainly jurassic source rocks and secondary microbial methane with an occasional small addition of primary microbial methane contribution of early mature coal derived gas is possible in areas with the most significant thermal stress of hauterivian aptian sediments but remains speculative review of petroleum habitats of five representative oil gas condensate fields in western siberia including the world s second largest gas field urengoyskoe suggests that methanogenic biodegradation may best explain the observed distribution and properties of fluids in the shallow reservoirs of those fields recognition of secondary microbial gas in western siberia helps explain the observed dominance of gas in the shallow cool northern part of the basin where conditions were more favorable for prolonged petroleum biodegradation than in the central and southern parts of the basin secondary microbial gas has been recognized worldwide and may 1 represent a volumetrically significant exploration target in shallow reservoirs perhaps more significant than primary microbial gas and 2 indicate effective thermogenic petroleum systems in the deeper sections large volumes up to 66 500 tcf 1884 trillion m3 of secondary microbial methane could have been generated from biodegraded petroleum accumulations worldwide although a part of that gas accumulated as oil dissolved free and hydrate bound gas most gas apparently escaped into the overburden atmosphere and ocean and could have affected global climate in the geologic past