intra oceanic subduction related hydrothermal venting kermadec volcanic arc new zealand intra oceanic volcanic arcs mark the boundaries between converging lithospheric plates where subduction produces volcanic and tectonic activity that ensures a steady supply of magmatic heat and hydrothermal fluids to the seafloor here we report on the first broad and systematic survey of hydrothermal emissions generated along a submarine arc front more than half seven of 13 of the volcanoes surveyed along 260 km of the southern kermadec arc ne of new zealand are hydrothermally active our results indicate that volcanic arcs represent a previously unheeded but potentially extensive source of shallow 2 km water depth vent fields expelling fluids of a unique and heterogeneous composition into the oceans

continuous sampling of hydrothermal fluids from loihi seamount after the 1996 event for at least 9 years prior to july 1996 hydrothermal fluids flowed from pele s vents on loihi seamount hawaii in july august 1996 a tectonic volcanic event occurred that destroyed pele s vents creating a pit crater pele s pit and several sites with hydrothermal venting in october 1996 we deployed two new continuous water samplers osmosamplers at two of these hydrothermal sites and collected fluids using traditional sampling techniques to monitor the evolution of crustal and hydrothermal conditions after the event the samplers were recovered in september 1997 and additional discrete vent fluid samples were collected the osmosampler located along the south rift at naha vents captured a change in composition from a low chlorinity high k fluid relative to bottom seawater to a high chlorinity low k fluid these changes are consistent with the fluid cooling during ascent and being derived from several different sources which include high 330 c and low 330 c into which magmatic volatiles were added during the deployment thermal and fluid fluxes decreased at naha the transport of heat and chemicals was decoupled the chemical and thermal evolution of hydrothermal fluids after the event on loihi is consistent with previous models based on events that have occurred along mid ocean ridges the event at loihi clearly had an effect on the local hydrography however the integrated effect of chemical fluxes to global budgets from similar events is uncertain chemical fluxes from similar events may have a global impact if ratios of chemical e g co2 fe mn mg sulfate and k to thermal anomalies greatly exceed or are in the opposite direction to fluxes from mid ocean ridge hydrothermal systems

feasibility of reconstructing paleoatmospheric records of selected alkanes methyl halides and sulfur gases from greenland ice cores seven short lived atmospheric trace gases were measured in 25 ice core samples from summit greenland samples were selected from contemporaneous sections of fluid and dry drilled ice cores to examine what effects using n butyl acetate as the drill fluid would have on the measurements the gases include three light alkanes c2h6 c3h6 and n c4h10 two methyl halides ch3cl and ch3br and two sulfur compounds ocs and cs2 with gas ages from 125 to 325 years before present alkane levels are comparable to measurements in modern arctic air although c2h6 exhibits greater variability than expected compared with c3h6 and n c4h10 these results are not consistent with the idea that the alkanes are primarily of anthropogenic origin suggesting that the ice cores may not truly record a paleoatmospheric signal with respect to these gases the ch3br results are consistent with previous observations of excess ch3br in greenland firn air in situ production processes appear to overwhelm the paleoatmospheric signal of this gas ch3cl exhibits the same effect to a lesser extent ocs levels are similar to those in antarctic ice cores and appear to reflect paleoatmospheric levels cs2 results are similar to the limited database of modern atmospheric measurements only c3h8 and n c4h10 exhibit clear evidence of contamination because of the presence of the drill fluid the results indicate that it is possible to analyze many trace gases in fluid and dry drilled ice samples however it appears that in situ production may significantly alter the levels of some trace gases in greenland ice cores

long term fluvial archives in hungary response of the danube and tisza rivers to tectonic movements and climatic changes during the quaternary a review and new synthesis abstract the paper discusses the quaternary evolution of the danube and tisza rivers and their main tributaries in the context of evolution of the entire pannonian basin which is europe s largest intramontane basin within the alp carpathian orogen the palaeo drainage reconstruction of the pannonian basin for the pre quaternary period is outlined in connection with the gradual regression of lake pannon since the late miocene deltas of rivers that entered the basin from the northwest and northeast were gradually transformed into extended alluvial plains thus the earliest possible ancestor of the danube coming southeastwards from the alps could be as old as late miocene by the pliocene the whole lake pannon was infilled the former extensional basin formation was replaced by a compresional stress field which resulted in an uplift of the marginal flanks and late stage subsidence anomalies the increasing relief led to the formation of the quaternary drainage pattern the actively subsiding young basins were filled by fluvial sediments transported by the danube and tisza river systems from the uplifting mountains between the subsiding regions of the little and great plains the danube has formed an antecedent valley with terrace staircases between the uplifting sections of the transdanubian range and the north midmountains the formation of the terraces is attributed to periodic climate changes during the pleistocene combined with differences in the uplift rate the paper gives a complex overview of the classical chronology of the six terraces based on various data sources mostly dating of loess paleosol sequences travertines aeolian sand and tephra strata overlying the fluvial sediments complemented by scattered vertebrate faunal data and archaeological evidence directly from the terrace sediments the quaternary drainage pattern evolution of the great plain with a strong tectonic control is discussed in detail rivers originating from the uplifting marginal areas were drawn towards the subsiding depressions which served as local base level changes in subsidence rates in space and time throughout the quaternary resulted in the evolution of a complex drainage pattern a special emphasis is placed on the late pleistocene holocene development of the middle tisza region and the koros basin where the berettyo koros rivers form an eastern tributary system of the tisza river a comparative evaluation of these two areas is especially relevant as they provide insights into large scale late pleistocene avulsion of the tisza river osl dating complemented with inferred transport directions determined from heavy mineral analysis of fluvial sediments in the koros basin has revealed an ancient large meandering river system that can be identified with the palaeo tisza which was flowing along a tectonically controlled depression during the late pleniglacial successions in the middle tisza region have allowed differentiation between the older channels of the palaeo bodrog river and the sajo hernad alluvial fan and the younger meander belts of the new course of the tisza in the tisza system changes in river style braided to various scales of meandering show correspondence to millennial scale climate changes of the last 25 ka while in the koros basin the effects of tectonics are overprinted onto the regional climatic signals

analysis of fluid inclusions in seafloor hydrothermal precipitates testing and application of an integrated gc ic technique the principal research objective was to test an integrated gas gc and ion chromatographic ic technique for analysis of trapped fluids in seafloor hydrothermal precipitates and to compare the results with independently analyzed vent fluids twenty three samples of chalcopyrite pyrite sphalerite barite and anhydrite from hydrothermal chimneys from four seafloor sites axial seamount juan de fuca ridge the vai lili vent field lau basin the tag hydrothermal field mid atlantic ridge and the 21 n vent field east pacific rise as well as of pyrite marcasite and quartz from the tag mound were analyzed a new type of blank for sulphides and sulphates was also developed water contents obtained by gc analysis are in agreement with known compositions of seafloor hydrothermal solutions also the volatiles occur in the same order of abundance as in vent fluids co2 n2 co ar o2 ch4 cos c2 c3 hydrocarbons for all analyzed hydrothermal fluids the mean cl concentrations are similar to those for the respective measured vent fluid compositions furthermore the gc ic results are directly comparable to salinity data determined by microthermometric methods nh4 can be enriched and is most probably formed by decomposition of organic matter volatile concentrations in fluid inclusions and data from vent fluids differ significantly for some of the investigated sites furthermore the gc data indicate systematic variations regarding the volatile contents of trapped fluids from different active seafloor hydrothermal systems fluid inclusion volatile data of samples from the ashes vent field at axial seamount define an inclined array consistent with phase separation

s sr and pb isotopic systematics of hydrothermal chimney precipitates from the eastern manus basin western pacific evaluation of magmatic contribution to hydrothermal system 1 sulfur strontium and lead isotopic analyses were performed on chimneys from the hydrothermal vent fields the pacmanus and susu knolls in the eastern manus back arc basin lead isotope composition varies in a narrow range 206pb 204pb 18 75 18 78 207pb 204pb 15 51 15 54 and 208pb 204pb 38 31 38 40 strontium isotopic ratios 87sr 86sr of sulfate minerals vary from 0 7051 to 0 7077 falling between those of seawater 0 7090 and the hydrothermal fluid end member 0 7050 the 34s values of the chimneys are 8 0 to 3 9 for the susu knolls sulfide 1 0 to 4 3 for the pacmanus sulfides and 7 4 to 20 6 for sulfate the susu knolls sulfides have the lowest values so far reported for volcanic hosted massive sulfides from modern seafloor the low 34s values of sulfates and sulfides cannot be explained by a simple seawater circulation model without an additional source of light sulfur this is also supported by the presence of sulfate in hydrothermal end member fluid indicated by sulfur and strontium isotopic ratios in chimney sulfates biogenic sulfur and or oxidation of h2s after boiling are excluded from the possible sources of light sulfur because of the lack of sediment cover and nonequilibrium in isotopic fractionation by boiling at seafloor disproportionation of magmatic so2 introduced into hydrothermal system through preeruptive degassing is the most plausible mechanism for the observed low 34s values the lighter 34s values and more radiogenic lead isotope compositions of the susu knolls samples indicate that magmatic degassing was more vigorous at the susu knolls than pacmanus

hydrothermal activity in the northern tanganyika rift east africa abstract hydrothermal fluids from sub lacustrine and sub aerial sites were sampled in the north tanganyika rift during the 1991 tanganydro expedition two types of hydrothermal end member fluids a na hco 3 type and a na cl type have been identified within the sample set the na hco 3 hydrothermal fluids are emitted at the level of the sub lacustrine pemba and sub aerial kabezi and mashuzi sites which are located in the northernmost bujumbura sub basin the na cl hydrothermal fluid vents at the level of the sub lacustrine cape banza field on the southeastern edge of the ubwari ridge the two types of hydrothermal fluids display isotopic and chemical evidence of interaction with magmatic volatiles the magmatic effects are strongest in the fluid discharging on the pemba hydrothermal field where abundant co 2 bubbling accompanies fluid emission the 13 c values of the co 2 gas sampled at pemba and at cape banza indicate a magmatic origin the pemba fluid shows the highest alkalinity and boron content and the lowest ph of the hydrothermal end member fluids and it has equilibrated at depth at the highest temperature 214 7 c in addition the sulfide mineralizations associated with the pemba hydrothermal vents are enriched in as and tl which similarly to b can be transported as volatiles in magmatic fluids the northern tanganyika na hco 3 fluids are similar to the na hco 3 fluid of the geothermal system of lake bogoria in the eastern branch of the east african rift and they can be compared with the na hco 3 hydrothermal water that is inferred to flow into lake kivu the cape banza na cl fluids may derive from the mixing between meteoric water and a deep seated basement brine similar to the ones found in old continental shields such as the canadian shield the high equilibrium temperatures and the geochemistry of the north tanganyika rift hydrothermal fluids suggest that degassing magmatic bodies are present at depth in the area these magmatic bodies may be either the southern expression of the south kivu magmatism or a more recent activity not yet expressed as surface volcanism the hydrothermal sites are located along major active rift bounding faults which can be associated with deep and strong seismicity as in the case of the pemba field such deep fractures may have favoured the uprise of the magmatic bodies that are the source of heat and volatiles to the hydrothermal systems the circulation of hydrothermal fluids within the tanganyika lacustrine sedimentary pile could play an important role in the maturation of the organic matter enclosed in the lake sediments and the subsequent oil generation and migration

ice core record of methyl chloride over the last glacial holocene climate change 1 methyl chloride ch3cl concentration was measured in air trapped in a deep ice core from dome fuji antarctica covering the last glacial present interglacial holocene change the record shows that the ch3cl concentration was relatively constant being similar to the present levels during the pre industrial holocene in contrast the ch3cl concentration was significantly high and variable in the last glacial period possibly due to impurity related production of ch3cl in ice sheet under the assumption that the production was the sole cause of the excess ch3cl the atmospheric ch3cl concentration during the last glacial was estimated using simultaneously measured calcium data for the ice core to have been enhanced by 30 compared with the pre industrial holocene concentration because the major sink of ch3cl was stronger during the last glacial than during the holocene the enhancement of ch3cl during the last glacial was likely due to the glacial period source being enhanced

a far field hydrothermal plume from loihi seamount an extensive helium plume in the north central pacific emanates from loihi seamount on the flanks of hawaii the maximum helium signal is found at a depth of about 1100 meters the same depth as the near field plume directly above loihi seamount although this helium plume is strongest near hawaii where the 3he 4he ratio at a depth of about 1100 meters reaches values 28 percent above the atmospheric ratio it can be detected quite clearly at latitude 24 n over 400 kilometers to the north excess 3he is also present on the same isopycnal between 15 n and 20 n at 135 w some 2000 kilometers east of the hawaiian islands

gas rich submarine exhalations during the 1989 eruption of macdonald seamount in january 1989 we observed submarine eruptions on the summit of macdonald volcano during a french german diving programme with the ifremer submersible cyana gas streaming of large amounts of ch4 co2 and so2 from summit vents inferred from water column anomalies and observed by submersible was accompanied on the sea surface by steam bursts turbulence red glowing gases and black bubbles comprising volcanic ash sulphur and sulphides chloride depletion of water sampled on the floor of an actively degassing summit crater suggests either boiling and phase separation or additions of magmatic water vapour submersible observations in situ sampling and shipboard geophysical and hydrographic measurements show that the hydrothermal system of this hotspot volcano is distinguished by the influence of magmatic gases released from its shallow summit

cyclic eruptions and sector collapses at monowai submarine volcano kermadec arc 1998 2007 1 repeated multibeam bathymetric surveys at monowai cone a shallow submarine basaltic volcano and part of the monowai volcanic center in the northern kermadec arc were conducted in 1998 2004 and 2007 these surveys document dramatic depth changes at the volcano including negative changes up to 176 m from two sector collapses and positive changes up to 138 m from volcanic reconstruction near the summit and debris avalanche deposits downslope of the slide scars one sector collapse occurred on the se slope between 1998 and 2004 with a volume of 0 09 km3 and another occurred on the sw slope between 2004 and 2007 with a volume of 0 04 km3 the volume of positive depth change due to addition of volcanic material by eruption is of the same order 0 05 km3 between 1998 and 2004 and 0 06 km3 between 2004 and 2007 during these time intervals monitoring by the polynesian seismic network detected frequent t wave swarms at monowai indicative of explosive eruptive activity every few months an unusual t wave swarm on 24 may 2002 was previously interpreted as the collapse event between the 1998 and 2004 surveys but no similarly anomalous t waves were detected between 2004 and 2007 probably because the polynesian seismic network stations were acoustically shadowed from the second slide event we interpret that the sector collapses on monowai are caused by the unstable loading of fragmental erupted material on the summit and steep upper slopes of the volcano 20 moreover there appears to be a cyclic pattern in which recurrent eruptions oversteepen the cone and periodically lead to collapse events that transport volcaniclastic material downslope to the lower apron of the volcano volumetric rate calculations suggest that these two processes may be more or less in equilibrium the repeated collapses at monowai are relatively modest in volume involving only 0 1 0 5 of the edifice volume have occurred much more frequently than is estimated for larger debris avalanches at subaerial volcanoes and may be characteristic of how persistently active shallow submarine arc volcanoes grow

eruption fed particle plumes and volcaniclastic deposits at a submarine volcano nw rota 1 mariana arc 1 nw rota 1 is an active submarine volcano in the mariana arc with a summit depth of 517 m and an explosively erupting volcanic vent southwest of the summit at a depth of 530 560 m during a period of ongoing explosive eruptions particle plumes surrounded the volcano and at least 3 3 107 m3 of volcaniclastic material was deposited on the southern flank particle plumes over the summit were magmatic hydrothermal in origin characterized by 3he enrichment hydrothermal precipitates and low ph values plumes at multiple depths below the summit surrounded the volcano and were composed overwhelmingly of fresh glassy shards of basalt rare anhydrite particles were present but there was a complete absence of other hydrothermal components in the deep plume samples these short lived anhydrite particles indicate the source of the deep plumes is from within or very near the eruptive vent and the mechanism for transport down the flanks of the volcano must be far faster than settling of individual particles the deep plumes most likely originated from sediment gravity flows generated by explosive eruptions or slope failure and landslides of unstable materials that had accumulated near the eruptive vent suspended sediments detach from the volcano slopes at multiple depths and are transported laterally up to tens of kilometers where they contribute to fall out deposits in distal sediments these observations link mechanisms for the transport of volcanic ash in the submarine environment to the types of deposits common in volcaniclastic aprons and fine ash layers in distal sediments

a remarkable late saalian mis 6 loess dust accumulation in the lower danube at harletz bulgaria abstract while numerous high resolution studies concerning last glacial aeolian sequences are available for europe the approach of the penultimate glacial in this geographical area is still poorly developed in order to bridge this gap this study focuses on the bulgarian sequence of harletz along the danube river where extremely high sedimentation rates allow the depiction of high resolution signals during mis 6 at harletz in nw bulgaria on the western bank of the ogosta river tributary of the danube a 20 m thick loess palaeosols section was cleaned and sampled for a multi disciplinary study and detailed pedostratigraphic approach high resolution continuous bulk sampling 5 cm was carried out to characterise sedimentary grain size magnetic properties including magnetic susceptibility and its frequency dependence colour reflectance 1 cm and organic carbon geochronological control is based on 16 samples collected for osl and met pirir dating using a cyclo stratigraphic approach of the sequence combined with dating constraints provided by both met pirir dates and the age of a tephra layer occurring at a depth of 12 m within the main loess unit we can demonstrate that the harletz section exhibits a 10 m thick late saalian marine isotope stage 6 mis 6 loess accumulation unique in europe the lower part of the main loess unit is 4 m thick and overlies a basal brown soil complex allocated to mis 7 which includes an exceptionally thick 4 m and detailed succession of loess and four incipient soil horizons never described in european loess until now the closest and best dated high resolution palaeoenvironmental archive suitable for comparison comes from lake ohrid located about 400 km to the sw of harletz the ohrid palynological record shows a progressive step by step evolution in climate and in environmental change during the transition between mis 7 and mis 6 from which a parallel with the harletz pedosedimentary succession can be proposed during the younger part of mis 6 160 129ka steppe vegetation with abundant herbs artemisia is dominant in the lake ohrid record in good accordance with a global enhancement of aeolian dynamics especially well recorded in sections located close to the danube river from serbia to bulgaria and romania l2 loess according to interpretations stemming from this study the silts and fine sands building the harletz loess section would have been transported from the danube braided river system located at that time at about 4 5 km to the nw based on our data the main loess units are characterised by a very low to a total absence of coarse sand particles by contrast during the eemian interglacial mis 5e and to a lesser extent throughout mis 5 and during mis 3 interstadials the long distance transport of silt and fine sand particles is stopped and a weak aeolian sedimentation is likely driven by north easterly winds transporting coarse sand grains from the proximal ogosta river sandy banks finally the weak development of last glacial loess 4 m max likely results from a rapid infilling of the sedimentary trap during the saalian then followed by a strong anthropogenic erosion of the topsoil and of the upper part of the loess profile since the early holocene neolithic

the 1996 subaqueous eruption at academii nauk volcano kamchatka and its effects on karymsky lake a subaqueous eruption in karymsky lake in the academii nauk caldera dramatically changed its water column structure water chemistry and biological system in less than 24 h sending major floodwaves down the discharging river and eruption plumes with ash and gases high into the atmosphere prior to the eruption the lake had a ph of about 7 was dominated by bicarbonate and well stocked with fish but turned in early 1996 into a stratified initially steaming waterbody dominated by sulfate with high na and k levels and devoid of fish blockage of the outlet led to rising waterlevels followed by dam breakage and catastrophic water discharge the total energy input during the eruption is estimated at about 1016 j the stable isotope composition of the lake water remained dominated by the meteoric meltwaters after the eruption

chloride depletions and enrichments in seafloor hydrothermal fluids constraints from experimental basalt alteration studies na k ca cl fluid was reacted with diabase at 400 and 425 c 400 bars and fluidrock mass ratio of 0 5 to assess the relative mobility of dissolved cl fluids from the present experiments reveal relatively large time and temperature dependent decreases in cl temperature increase enhances cl removal whereas reaction progress has the opposite effect these changes are not due to boiling and or phase separation at 400 and 425 c 400 bars cl removal from solution is accompanied by ca and na fixation respectively both experiments produced mixed layer chlorite smectite clinozoisite and albite olivine was not detected by x ray diffraction or petrographic analysis of run products from either experiment however we propose that the time dependent changes in dissolved cl result from olivine replacement by an fe hydroxy chloride phase followed by hydration effects quenched and washed alteration products however did not reveal anomalous cl which suggests that the cl bearing phase is characterized by retrograde solubility this is consistent with the relative magnitude of cl fixation observed for experiments at both temperatures and from results of an isobaric cooling experiment the experiments provide evidence for the non conservative behavior of cl during hydrothermal alteration of basalt the data are particularly important in light of the cl depleted nature of some ridge crest hot spring fluids and suggest temperatures of formation for these fluids of approximately 410 c assuming sub seafloor pressure of 400 bars in addition the retrograde solubility of the cl bearing phase responsible for cl fixation during high temperature basalt alteration may help to explain cl enrichment in hot spring fluids which have conductively cooled below 350 c

hydrography and geochemistry of sea surface hydrothermal plumes resulting from hawaiian coastal volcanism the entry of lava into the ocean at kilauea volcano hawaii has produced extensive sea surface hydrothermal plumes studies at this site over 1989 1991 showed that particle rich chemically altered thermal plumes of 1 3 m thickness can be mapped for distances up to 2 km from the entries using an array of physical and chemical tracers particle concentrations in the plumes were as high as 65 mg l 1 and produced light attenuation anomalies exceeding 11 m 1 the maximum observed seawater temperature was 69 c the following extremes in plume chemical markers were measured h2 2 1 m dissolved mn 320 nm dissolved si 55 m co2 1 6 mm alkalinity 1 5 meq l 1 and ph 7 1 dissolved h2 linearly increased and co2 ph and total alkalinity decreased with increasing seawater temperature dissolved mn and si also increased with increasing temperature but were better correlated with each other indicating that heat is not conserved in the surface plumes heat and mass inputs to the ocean are comparable to those from mid ocean ridge crest vent fields

emission of methane and heavier alkanes from the la brea tar pits seepage area los angeles natural hydrocarbon oil and gas seeps are widespread in los angeles california due to gas migration along faults from numerous subsurface petroleum fields these seeps may represent important natural contributors of methane ch4 and heavier alkanes c2 c4 to the atmosphere in addition to anthropogenic fossil fuel and biogenic sources we measured the ch4 flux by closed chamber method from the la brea tar pits park 0 1 km2 one of the largest seepage sites in los angeles the gas seepage occurs throughout the park not only from visible oil asphalt seeps but also diffusely from the soil affecting grass physiology about 500 kg ch4 d 1 is emitted from the park especially along a belt of enhanced degassing that corresponds to the 6th street fault additional emissions are from bubble plumes in the lake within the park order of 102 103 kg d 1 and at the intersection of wilshire boulevard and curson avenue 130 kg d 1 along the same fault the investigated area has the highest natural gas flux measured thus far for any onshore seepage zone in the usa gas migration oil biodegradation and secondary methanogenesis altered the molecular composition of the original gas accumulated in the salt lake oil field 300 m deep leading to high c1 c2 and i butane n butane ratios these molecular alterations can be important tracers of natural seepage and should be considered in the atmospheric modeling of the relative contribution of fossil fuel anthropogenic fugitive emission and natural geologic sources versus biogenic sources of methane on local and global scales

observations and sampling of an ongoing subsurface eruption of kavachi volcano solomon islands may 2000 a serendipitous encounter with an erupting shallow submarine volcano in the solomon islands provided a rare opportunity to map and sample the dispersal of volcanogenic emissions into the surrounding water column kavachi episodically active since at least 1939 is a forearc volcano located on the pacific plate only 30 km northeast of its convergent boundary with the downgoing indo australian plate during 14 may 2000 we observed explosive phreatomagmatic eruptions at several minute intervals creating a complex distribution of plumes of volcanic glass shards throughout the water column at a distance of 1 5 km from the summit at distances of 4 5 km shallow water 3 he fe and mn one sample only but not in co 2 we infer that the volcano flanks were essentially impermeable to fluid emissions and that the observed particle halo was created by magma shattering and resuspension most magmatic and hydrothermal fluids were thus discharged directly from the summit into the atmosphere

pleistocene evolution of the danube in the carpathian basin the present day drainage system of the carpathian basin originates from the gradual regression of the last marine transgression brackish pannonian sea the flow directions of the rivers including the danube are determined by the varying rates and locations of subsidence within the region the danube which forms the main axis of the drainage network first filled the depression of the little plain lake and then further southward the slavonian lake from the end of the pliocene the crustal movements which caused the uplift of the transdanubian mountains forced the danube to flow in an easterly direction towards the antecedent visegrid gorge and into the subsiding basins of the great plain climatic changes during the pleistocene had the effect of forming up to seven fluvial terraces the uplift of the mountains is demonstrated by the deformation of the terraces while the subsidence of the plains is proven by an accumulation of several hundred metres of sediment the river only occupied its present position south of budapest in the latest pleistocene

geochemistry of hydrothermal fluids from the pacmanus northeast pual and vienna woods hydrothermal fields manus basin papua new guinea abstract processes controlling the composition of seafloor hydrothermal fluids in silicic back arc or near arc crustal settings remain poorly constrained despite growing evidence for extensive magmatic hydrothermal activity in such environments we conducted a survey of vent fluid compositions from two contrasting sites in the manus back arc basin papua new guinea to examine the influence of variations in host rock composition and magmatic inputs both a function of arc proximity on hydrothermal fluid chemistry fluid samples were collected from felsic hosted hydrothermal vent fields located on pual ridge pacmanus and northeast ne pual near the active new britain arc and a basalt hosted vent field vienna woods located farther from the arc on the manus spreading center vienna woods fluids were characterized by relatively uniform endmember temperatures 273 285 c and major element compositions low dissolved co 2 concentrations 4 4 mmol kg and high measured ph 4 2 4 9 at 25 c temperatures and compositions were highly variable at pacmanus ne pual and a large newly discovered vent area fenway was observed to be vigorously venting boiling 358 c fluid all pacmanus fluids are characterized by negative d h 2 o values in contrast to positive values at vienna woods suggesting substantial magmatic water input to circulating fluids at pual ridge low measured ph 25 c values 2 6 2 7 high endmember co 2 up to 274 mmol kg and negative 34 s h 2 s values down to 2 7 in some vent fluids are also consistent with degassing of acid volatile species from evolved magma dissolved co 2 at pacmanus is more enriched in 13 c 4 1 to 2 3 than vienna woods 5 2 to 5 7 suggesting a contribution of slab derived carbon the mobile elements e g li k rb cs and b are also greatly enriched in pacmanus fluids reflecting increased abundances in the crust there relative to the manus spreading center variations in alkali and dissolved gas abundances with cl at pacmanus and ne pual suggest that phase separation has affected fluid chemistry despite the low temperatures of many vents in further contrast to vienna woods substantial modification of pacmanus ne pual fluids has taken place as a result of seawater ingress into the upflow zone consistently high measured mg concentrations as well as trends of increasingly non conservative so 4 behavior decreasing endmember ca cl and sr cl ratios with increased mg indicate extensive subsurface anhydrite deposition is occurring as a result of subsurface seawater entrainment decreased ph and endmember fe mn ratios in higher mg fluids indicate that the associated mixing cooling gives rise to sulfide deposition and secondary acidity production several low temperature 80 c fluids at pacmanus ne pual also show evidence for anhydrite dissolution and water rock interaction fixation of b subsequent to seawater entrainment hence the evolution of fluid compositions at pual ridge reflects the cumulative effects of water rock interaction admixing and reaction of fluids exsolved from silicic magma phase separation segregation and seawater ingress into upflow zones

a model for predicting the volumes of vesicles in submarine basalts the total volume percentage of vesicles in submarine pillow basalt rinds can be modelled by the exsolution of h o and co vapor using available solubility determinations for these components in basalt in accordance with observations on natural samples co is predicted to be the major vapor component in vesicles at eruption depths 1 2 km only small initial contents of co 0 1 0 2 wt are consistent with the vesicle volumes observed in most deep sea pillow lavas h o is important only at shallow depths crystallization of pillow interiors can lead to more extensive vesiculation inside of pillow lavas than in the vesicle poor outer rinds

alteration and mineralization of an oceanic forearc and the ophiolite ocean crust analogy mineralogical chemical and isotopic o c s and sr analyses were performed on minerals and bulk rocks from a forearc basement section to understand alteration processes and compare with mid ocean ridges mor and ophiolites ocean drilling program hole 786b in the izu bonin forearc penetrates 103 m of sediment and 725 m into volcanic flows breccias and basal dikes the rocks comprise boninites and andesites to rhyolites most of the section was affected by low temperature 100 c seawater alteration with temperatures increasing downward the rocks are partly 5 25 altered to smectite fe oxyhydroxide calcite and phillipsite and exhibit gains of k rb and p loss of ca variable changes in si na mg fe sr and y and elevated 18o and 87sr 86sr higher temperatures 150 c in the basal dikes below 750 m led to more intense alteration and formation of chlorite smectite corrensite albite k feldspar and quartz chlorite a 5 m thick hydrothermally altered and pyritized zone at 815 m in the basal dikes reacted with mixtures of seawater and hydrothermal fluids to mg chlorite albite and pyrite and gained mg and s and lost si and ca focused flow of hydrothermal fluids produced serialization halos na k sericite quartz pyrophyllite k feldspar and pyrite along quartz veins at temperatures of 200 250 c high 87sr 86sr ratios of chloritized 0 7055 and sericitized 0 7065 rocks indicate involvement of seawater via mixing with hydrothermal fluids low 34s of sulfide 2 to 5 5 and sulfate 12 5 are consistent with input of magmatic so2 into hydrothermal fluids and disproportionation to sulfide and sulfate alteration processes were generally similar to those at mors but the arc section is more intensively altered in part because of the presence of abundant glassy rocks and mafic phases the increase in alteration grade below 750 m and the mineralization in the basal dikes are analogous to changes that occur near the base of the volcanic section in mor and the troodos ophiolite

systematics of and postulated controls on submarine hydrothermal solution chemistry the chemical compositions of seafloor hydrothermal solutions from the galapagos spreading center 21 n and 13 n on the east pacific rise the southern juan de fuca ridge and the guaymas basin gulf of california are examined for systematic variations several elemental ratios elemental products and empirical geothermometers show much consistency among the various areas in spite of large absolute differences in elemental concentrations the results suggest that most of the major cations in these solutions are solubility controlled with respect to a similar phase assemblage at all of the sites examination of the solution chemistry in conjunction with experimental results and seafloor rock alteration data permits identification of phases which may be important in controlling the solution chemistry as potassium appears to be solubility controlled its use to calculate water rock ratios is inappropriate lithium appears to be a better element to use in these calculations a model to explain the observed solution chemistries as a result of three component mixing is discussed all of the solutions are postulated to be either the result of mixing between a seawater hydrothermal solution which has not undergone a phase separation and is hence gas containing a gas rich vapor phase and a gas poor brine phase or any one of these individual components alone the vapor and brine phases are the result of phase separation which may have occurred at some time in the past essentially all of the reported data fall within the field defined by these three components the solutions apparently have had sufficient time after the mixing event s to reequilibrate with the rock this is true for quartz as well as other chemical components the best test of this model is chloride together with gas and isotropic data as the model predicts that solutions with elevated chlorinities will be depleted in gases and enriched in 18 o and low chlorinity solutions will have elevated gas contents and lower 18 o

geologic methane seeps along boundaries of arctic permafrost thaw and melting glaciers in the arctic permafrost and glaciers form a cryosphere cap that traps methane leaking from hydrocarbon reservoirs restricting flow to the atmosphere aerial surveys and ground based measurements reveal the release of radiocarbon depleted methane along boundaries of permafrost thaw and retreating glaciers in alaska and greenland

osl ages and origin of late quaternary sediments in the north transdanubian hills hungary timing of neotectonic activity abstract the transdanubian hills south of lake balaton is a gently elevated area with well developed dissected morphology a new highway constructed through the area provided an excellent opportunity to make field observations and date the neotectonic movements deformed and undeformed fluvial and eolian sequences were dated using optically stimulated luminescence on quartz complemented by radiocarbon age data the distribution of the equivalent doses measured on small aliquots indicates that the sediments were poorly bleached before deposition and therefore the osl ages calculated by the mean equivalent doses represent the maximum depositional ages of the sediments to determine the source area of the sediments microscopic study was applied the oldest dated samples are 49 39 ka fluvial sands at maximum on the top of the sand a forest steppe type paleosol formed which interfingers with the coeval fluvial channel sand body these sediments are younger than about 30 ka loess like sediments were deposited later than 25 and 10 8 ka and fluvial sand was deposited a maximum of 22 and 9 ka the fluvial sediments except the youngest were transported from nnw of the transdanubian central range indicating that lake balaton did not exist during the late pleistocene and the drainage network was quite different from the recent situation field structural observations and osl dating showed that a deformation period started later than 49 ka in the study area while folding started after 22 ka gentle late stage uplift at maximum 9 ka ago was identified which might have been active sub recently

uranium series dating of travertine from suttő implications for reconstruction of environmental change in hungary abstract terrestrial carbonate formations such as travertines speleothems and lake sediments are important archives of terrestrial climate forcing at the sutt section in hungary a complex succession of travertine is covered by a loess palaeosol sequence both are high resolution terrestrial archives of climate and environment change uranium series 230th u dating was carried out to set up a more reliable chronological frame for the travertine as the growth of travertine is very complex pore cements may cause serious problems for precise dating the state of alteration of primary spar and micrite was characterised by microscopic cathodoluminescence and microprobe analyses the travertine from sutt showed homogeneous phases of primary calcite minor micropores and rare pore cements the carbon isotopic composition indicates that the source of carbon was a mixture of atmospheric and soil derived co2 calculated water temperatures based on oxygen isotope data range from 22 c to 31 c an attempt to provide an independent relative dating approach by palaeomagnetic techniques failed 230th u ages were determined applying an isochron approach using the leachate leachate method as the travertine deposits have a dense structure the bulk sampling method was successfully applied in determining uranium series ages with much higher precision than former studies with alpha spectrometry travertines from sutt yielded mid pleistocene ages ranging from the antepenultimate glacial to the penultimate interglacial 310 240 ka these results are in agreement with those from optically stimulated luminescence osl dating and amino acid racemisation aar dating of the overlying sediment indicating at least an mis 7 age for the travertine

submarine venting of phase separated hydrothermal fluids at axial volcano juan de fuca ridge since the discovery of high temperature venting on the east pacific rise in 19791 it has been expected2 3 because of the physical properties of sea water at pressures and temperatures encountered during submarine hydrothermal circulation4 5 that phase separated fluids would discharge from ridgecrest vents although this notion is supported by the reported large deviations in vent fluid chlorinity relative to that of sea water 40 200 6 7 by observations of venting at p t conditions clearly within the two phase region 220 bar and 420 c 8 and by fluid inclusion data9 10 unequivocal identification11 of phase separated venting fluids has remained elusive here we report observations of chloride and metal depleted gas enriched fluids from a shallow vent field on the juan de fuca ridge which confirm the expectation that phase separated effluents are delivered to the deep ocean from some sea floor venting systems

middle to late pleistocene uplift rate of the hungarian mountain range at the danube bend pannonian basin using in situ produced 3he topography of the terraced danube bend area indicates fast incision of the danube river which was followed by its tributaries dissecting deeply the former terrace levels these surfaces are vertically bended along the river course indicating antecedent incision of the danube into the sw ne trending hungarian mountain range hmr timing and rate of the incision of the danube into the hmr and consequently the rate of vertical motions have remained unresolved so far this study aims at quantifying the landscape evolution and neotectonic deformation of the central part of the hmr we used terrace levels along the antecedent section of the danube river to constrain its incision rate which is a measure for the uplift rate of the hmr here we use 3 he a terrestrial in situ produced cosmogenic nuclide tcn to date uplifted geomorphologic levels along in the danube bend gorge this method first applied in the carpathian pannonian system in the framework of present study proved to be suitable for the quantification of landscape evolution in this area our 3 he exposure age data suggest a maximum incision rate of 2 7f0 1 mm y for the last 170 ky considering likely effect of erosion a more conservative value of 1 6 mm y for the last 270 ky was obtained both rates are significantly higher than the incision rate of 0 41 mm y of the danube derived from previous geologic and geomorphic data for the last 360 ky the formation of the terrace levels in the danube bend probably occurred during the last two glacial cycles ois 1 8 according to the exposure age data there is no direct relationship between the terrace formation and climate in the danube bend incision of the danube appears to be connected to the uplift of the hmr obtained incision rate values can be taken as valid approximations of the uplift rate in the danube bend area d 2005 elsevier b v all rights reserved

quantification of quaternary vertical movements in the central pannonian basin a review of chronologic data along the danube river hungary abstract this study aims at a new quantification of neotectonic deformation of the central part of the pannonian basin we use terrace levels and associated travertine as well as speleothem data along the danube river to quantify its incision rate and thus estimate the amount and rate of uplift at the axis of the hungarian mountain range hmr several terrace levels and other geomorphic features along the danube river are indicative for quaternary uplift of the axial part of the emerging hungarian mountain range while the correlative terraces are at considerable height at the axis of the hmr the terraces are gradually dipping below the basin fill of the adjacent lowlands the correlation of the terrace segments is difficult because of their poor preservation small size and variable height the geomorphologic horizons indicate gradual incision of the river throughout the quaternary during simultaneous deformation however no reliable chronological data have been available so far to quantify landscape forming processes such as uplift incision or erosion rates a reconsideration of existing published data for three consecutive segments of the danube valley yields incision rates between 0 14 and 0 41 mm year for the last 360 ky with the highest value for the area of the danube bend accordingly the middle to late quaternary uplift rate of the axial zone of the hmr exceeded significantly that of the marginal areas these rates represent an approximation as some quantitative data are still controversial our results suggest that formation of the danube terraces is result of river incision triggered by the uplift of the hmr and modified by periodic climate changes

vailulu u undersea volcano the new samoa 1 vailulu u seamount is identified as an active volcano marking the current location of the samoan hotspot this seamount is located 45 km east of ta u island samoa at 169 03 5 w 14 12 9 s vailulu u defines the easternmost edge of the samoan swell rising from the 5000 m ocean floor to a summit depth of 590 m and marked by a 400 m deep and 2 km wide summit crater its broad western rift and stellate morphology brand it as a juvenile progeny of ta u seven dredges ranging from the summit to the se rift zone at 4200 m recovered only alkali basalts and picrites isotopically the volcano is strongly em2 in character and clearly of samoan pedigree 87sr 86sr 0 7052 0 7067 143nd 144nd 0 51267 0 51277 206pb 204pb 19 19 19 40 the 210po 210pb data on two summit basalts indicate ages younger than 50 years all of the recovered rocks are extremely fresh and veneered with glass an earthquake swarm in early 1995 may attest to a recent eruption cycle a detailed nephelometry survey of the water column shows clear evidence for hydrothermal plume activity in the summit crater the water inside the crater is very turbid nephelometric turbidity unit ntu values up to 1 4 and a halo of smog several hundred meters thick encircles and extends away from the summit for at least 7 km the turbid waters are highly enriched in manganese up to 7 3 nmol kg providing further evidence of hydrothermal activity vailulu u is similar to loihi hawaii in being an active volcanic construct at the eastern end of a hotspot chain it differs importantly from the hawaiian model in its total lack of tholeiitic basalt compositions

geotectonic setting of hydrothermal activity on the summit of lucky strike seamount 37 17 n mid atlantic ridge we have investigated the relations between volcanic tectonic and hydrothermal activity on lucky strike seamount 37 17 n mid atlantic ridge using a nested survey strategy involving collection of data from different deep sea mapping systems the highly tectonized seamount summit consists of three volcanic cones surrounding a relatively flat depression with a young lava lake in its center hydrothermal activity is focused mainly within the summit depression with most of the vents located proximal to the lava lake isolated active and inactive chimneys and mounds are widespread throughout the summit depression and occur on both volcanic pillow lava and hydrothermal sulfide rubble and hydrothermally cemented breccias substrates the large volume of sulfide rubble together with the nature of the sulfide structures indicates that hydrothermal activity has been episodic but ongoing for a long period of time hundreds to thousands of years on the basis of the distribution of hydrothermal deposits we propose a model of alternation between tectonic and volcanic control on hydrothermalism at lucky strike seamount midsegment melt focusing produces a spatially and temporally stable heat source that sustains focused high temperature hydrothermal activity over long time periods during periods of amagmatic extension active faulting within the summit depression provides multiple near surface fluid flow pathways for discharge of high temperature fluids and widespread deposition of massive sulfides during eruptive events rapid effusion of very hot lava creates a lava lake and hyaloclastite deposits the new sheet flows form a cap on the hydrothermal system and fluid upflow is reorganized discharge of high temperature fluids is restricted to isolated sites with relatively high permeability for example the edges of the lava lake much of the upwelling hydrothermal fluid pools in the subsurface conductively cools and mixes with entrained seawater before discharging as widespread low temperature diffuse flow hyaloclastites become cemented further augmenting the sealing of the system present day activity at lucky strike seamount represents this locally volcanically controlled phase of activity despite the segment as a whole being dominantly amagmatic

lithospheric memory state of stress and rheology neotectonic controls on europe s intraplate continental topography abstract to date research on neotectonics and related continental topography development has mostly focused on active plate boundaries characterized by generally high deformation rates the intraplate sedimentary basins and rifts of the northern alpine foreland are associated with a much higher level of neotectonic activity than hitherto assumed seismicity and stress indicator data combined with geodetic and geomorphologic observations demonstrate that europe s intraplate lithosphere is being actively deformed this has major implications for the assessment of its natural hazards and environmental degradation the lithosphere of the northern alpine foreland has undergone a polyphase evolution with an intense interplay between upper mantle thermal perturbations and stress induced intraplate deformation that points to the importance of lithospheric folding of the thermally weakened lithosphere in this paper we address relationships between deeper lithospheric processes neotectonics and surface processes in the northern alpine foreland with special emphasis on tectonically induced topography the objectives are to quantify the effects of ongoing alpine collision and atlantic ridge push on the intraplate deformation in europe and its impact on topography evolution and related natural hazards this paper reviews the four dimensional topographic evolution of the european lithosphere through a multi disciplinary approach linking geology geophysics and geotechnology until now research on neotectonics and related topography development of intraplate regions has received little attention our study examines a number of selected natural laboratories in continental europe from orogen through platform to continental margin these natural laboratories include the carpathians pannonian system the northwest european platform iberia and the atlantic continental margin we focus on lithosphere memory and neotectonics with special attention to the thermo mechanical structure of the lithosphere mechanisms of large scale intraplate deformation late neogene anomalies in subsidence and uplift and links with surface processes and topography evolution

tectonic and climatic control on terrace formation coupling in situ produced 10be depth profiles and luminescence approach danube river hungary central europe abstract the terrace sequence of the hungarian part of the danube valley preserves a record of varying tectonic uplift rates along the river course and throughout several climate stages to establish the chronology of formation of these terraces two different dating methods were used on alluvial terraces exposure age dating using in situ produced cosmogenic 10 be and luminescence dating using monte carlo approach to model the denudation rate corrected exposure ages in situ produced cosmogenic 10 be samples originated from vertical depth profiles enabled the determination of both the exposure time and the denudation rate post ir irsl measurements were carried out on k feldspar samples to obtain the ages of sedimentation the highest terrace horizon remnants of the study area provided a best estimate erosion corrected minimum 10 be exposure age of 700 ka we propose that the abandonment of the highest terrace of the hungarian danube valley was triggered by the combined effect of the beginning tectonic uplift and the onset of major continental glaciations of quaternary age around mis 22 for the lower terraces it was possible to reveal close correlation with mis stages using irsl ages the new chronology enabled the distinction of tiib 90 ka mis 5b c and tiiia 140 ka mis 6 in the study area surface denudation rates were well constrained by the cosmogenic 10 be depth profiles between 5 8 m ma and 10 0 m ma for all terraces the calculated maximum incision rates of the danube relevant for the above determined 700 ka time span were increasing from west

preindustrial atmospheric ethane levels inferred from polar ice cores a constraint on the geologic sources of atmospheric ethane and methane 2016 american geophysical union all rights reserved ethane levels were measured in air extracted from greenland and antarctic ice cores ranging in age from 994 to 1918 common era c e there is good temporal overlap between the two data sets from 1600 to 1750 c e with ethane levels stable at 397 28 parts per trillion ppt 2standard error s e over greenland and 103 9ppt over antarctica the observed north south interpolar ratio of ethane 3 9 0 1 1 implies considerably more ethane emissions in the northern hemisphere than in the southern hemisphere suggesting geologic ethane sources contribute significantly to the preindustrial ethane budget box model simulations based on these data constrain the global geologic emissions of ethane to 2 2 3 5tgyr 1 and biomass burning emissions to 1 2 2 5tgyr 1 during the preindustrial era the results suggest biomass burning emissions likely increased since the preindustrial period biomass burning and geologic outgassing are also sources of atmospheric methane the results place constraints on preindustrial methane emissions from these sources

submarine eruption near socorro island mexico geochemistry and scanning electron microscopy studies of floating scoria and reticulite abstract products of an underwater eruption near socorro island in the ne pacific were observed directly on january 29 1993 ten days after precursors were first recorded by sofar sound fixing and ranging hydrophones located in hawaii and tahiti eruptive activity was noticed from boats and ships as small steam plumes rising from the sea at an area centered at 18 48 n 111 05 w 2 4 km nw of punta tosca and 4 6 km ssw of cape henslow on socorro island the observed steam was produced by 1 3 m large blocks of hot dark grey highly vesiculated basalt rising buoyantly to the surface from two submarine shallow vents at 210 and 30 m depth tens of blocks accompanied by bubbles could be observed rising to the surface in irregular pulses these scoriaceous blocks remained floating at the surface until they would crack into smaller pieces by thermal contraction emitting hissing noises from vapourizing seawater in contact with the hot interior of the blocks steam jets several metres in height were produced and occasionally blocks were propelled laterally by the steam jet depending on vesicularity and permeability blocks remained floating and drifting with the surface current for 1 15 minutes before sinking back floating rocks covered an area of about 6000 m2 this intermittent activity has been observed ever since and has not stopped as of april 1994 buoyant scoria and reticulite are indicative of volatile mostly co2 supersaturation and exsolution in the magma prior to rapid quenching which inhibits loss of volatiles by bubble escape a high velocity ascent of low viscosity magma in a relatively narrow conduit is also required to prevent substantial gas escape and allow formation of reticulite the buoyant scoria is most probably ejected by intermittent lava fountaining at fixed vents as a result of changes in eruption velocities due to changes in the exsolved gas content of the lava between january and july 1993 floating blocks of scoria and reticulite were collected on several occasions from the surface of the sea for chemical and mineralogical analyses major and minor element analyses including ree as well as electron microprobe analyses of different phases revealed that the composition of the emitted lava has not changed through time blocks of basalt sio2 45 47 are highly vitric and vesicular with tabular anorthite phenocrysts up to 3 mm in length and minor grains of forsteritic olivine ree and trace element composition of these rocks suggest an anomalous mantle source for the erupted alkali basalt lava the ongoing eruption will either continue in a similar fashion as described and eventually cease or built up a mound that reaches the surface and forms an island with accompanying change in eruptive style

iron enrichments in hydrothermal plumes over the east pacific rise abstract manganese iron and helium isotopes have been measured in samples taken near the crest of the east pacific rise at 19 s samples were enriched in mn and in he isotopes as is typical for waters of this area samples were also enriched in fe fe enrichments covary with mn and 3 he enrichments the fe mn ratio at four sites ranged from about 2 to 9 spanning the average value found for metalliferous sediments 3 5

incision of a river curvature due to exhumed miocene volcanic landforms danube bend hungary a new model for the formation and relief evolution of the danube bend northern hungary is discussed on geomorphological and volcanological grounds we propose that the present day u shaped loop of the danube bend was partly inherited from the horseshoe caldera morphology of keser s hill volcano a mid miocene ca 15 ma lava dome complex with an eroded central depression open to the north according to combined palaeogeographical data and erosion rate calculations the drainage pattern in the danube bend region was formed when pleistocene tectonic movements resulted in river incision and sedimentary cover removal formation of the present curvature of the river was due to the exhumation of the horseshoe shaped caldera as well as the surrounding resistant volcaniclastic successions i e visegrad castle hill and a hilltop lava dome szent mihaly hill the process accelerated and the present narrow gorge of the danube bend was formed by very rapid as young as late quaternary differential tectonic uplift also enhancing the original volcanic morphology on the basis of comparative long term erosion rate calculations we estimated successive elevation changes of the volcanic edifice including partial burial in late miocene time in comparison with various order of magnitude changes the mid to late quaternary vertical movements show increased rates and or base level drop in the pannonian basin

luminescence and amino acid racemization chronology of the loess paleosol sequence at suttő hungary abstract the loess paleosol sequences in hungary provide an excellent upper pleistocene climate archive of the carpathian basin loess deposits up to 20 m thick cover the sutt travertine complex located in the very northern part of hungary next to the right bank of the danube river the loess is intercalated with two weakly developed greyish horizons two thinner brownish steppe like soils and a pedocomplex including a reddish brown clay enriched horizon covered by a chernozem like paleosol infrared optically stimulated luminescence irsl dating was applied on polymineral fine grain material to determine the depositional age of the loess the uppermost loess yields irsl age estimates ranging from 15 to 40 ka the loess on top of the pedocomplex yields irsl age estimates ranging from 48 to 60 ka the pedocomplex most likely correlates with the marine oxygen isotope stage mis 5 interglacial period the loess from below the pedocomplex was deposited during the penultimate glaciation as evidenced by amino acid racemization aar results further independent age control is provided by radiocarbon dating for the upper part of the profile and by uranium series 230th 234u ages correlating the travertine below the loess with mis 7 8 the magnetic susceptibility record through the sequence shows a strong correlation with the loess layers and soil horizons

characteristics of hydrothermal plumes from two vent fields on the juan de fuca ridge northeast pacific ocean deep ctd transmissometer tows and water bottle sampling were used during 1985 to map the regional distribution of the neutrally buoyant plumes emanating from each of two major vent fields on the southern symmetrical segment sss and endeavour segment es of the juan de fuca ridge at both vent fields emissions from point and diffuse hydrothermal sources coalesced into a single 200 m thick plume elongated in the direction of current flow and with characteristic temperature anomalies of 0 02 0 05 c and light attenuation anomalies of 0 01 0 08 m 1 10 80 g l above background temperature anomalies in the core of each plume were uniform as far downcurrent as the plumes were mapped 10 15 km downcurrent light attenuation trends were non uniform and differed between plumes apparently because different vent fluid chemistries at each field cause significant differences in the settling characteristics of the hydrothermal precipitates vent fluids from the sss are metal dominated and mostly precipitate very fine grained hydrous fe oxides that remain suspended in the plume vent fluids from the es are sulfur dominated and precipitate a high proportion of coarser grained fe sulfides that rapidly settle from the plume the integrated flux of each vent field was estimated from measurements of the advective transport of each plume heat flux was 1700 1100 mw from the es and 580 351 mw from the sss particle flux varied from 546 312 g s to 204 116 g s at the es depending on distance from the vent field and was 92 48 g s from the sss

submarine magma degassing and explosive magmatism at macdonald tamarii seamount macdonald seamount is an active volcanic centre located at 29 98 s 140 25 w in the south central pacific since its discovery1 in 1968 a number of expeditions have surveyed and dredged rocks from the seamount during a scripps institution of oceanography expedition in october 1987 the first direct observation of volcanic activity at macdonald was made when a small eruption occurred spewing forth scoriaceous basaltic rocks which briefly floated to the sea surface the rocks were accompanied by huge bubbles of volcanic gas that created large sea surface slicks h craig personal communication similar activity at macdonald was observed by a joint french german team in january 1989 using the submersible cyana2 here we look at the radio geochemical features of the lone rock recovered from the october 1987 eruption we present analyses of u series nuclides from the first observed eruption of macdonald also known as tamarii seamount with interpretations focusing on the timescales of mag matic events and the implications of uranium series data for magma degassing this highly gas charged magma lost all of its volatile 210po upon eruption based on this estimates of the fluxes of other volatile elements to sea water which may contribute significantly to their oceanic budget are calculated high 230th 232th and 87sr 86sr ratios common signatures of altered crust suggest that the explosive nature of the macdonald volcan ism results partly from the sealing of magma conduits by seawater circulation

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

styles of eruptive activity on intraplate volcanoes in the society and austral hot spot regions bathymetry petrology and submersible observations submersible observations carried out in the society and austral hot spot regions south pacific during the teahitia ii cruise 1988 1989 enable us to propose a model relating the style of volcanism to the depth of eruption on large intraplate seamounts 1 the bases of volcanic edifices are characterized by broad flat flows formed during a high rate of discharge of a very fluid magma on the sea floor 2 the edifices flanks deeper than 500 m are mainly made up of bulbous tubular pillows and large drained lava tunnels occurring on slopes steeper than 60 70 these lava flows occur on lateral volcanic vents about 200 300 m high along linear rift zones which are formed on the flank of the major edifices 3 volcanic ejecta due to hydromagmatic eruptions occur at shallow depths 500 m in height are individual conical features built at a high rate of volcanic discharge localized along radial linear eruptive fissures called rift zones the slopes located between the rift zones are covered by talus material are limited and unimportant mass wasting sector collapse features were observed on the edifices the conical shaped features are the primary morphology of the intraplate volcanoes formed during edifice growth which is closely linked to the hydrostatic pressure of the magmatic column the mean values of the slopes 11 17 of intraplate seamounts are the same as those of subaerial intraplate shield volcanoes when the seawater hydrostatic pressure is taken into account

a major helium 3 source at 15 s on the east pacific rise an extensive plume of water enriched with helium 3 has been discovered in the deep pacific ocean at latitude 15 s on the east pacific rise in the core of the plume at a depth of 2500 meters over the ridge crest the helium 3 helium 4 ratio is 50 percent higher than the ratio in atmospheric helium indicating a strong injection of mantle or primordial helium at the spreading center axis through local hydrothermal systems the helium 3 plume is completely absent east of the rise but it can be traced over 2000 kilometers to the west above a newly observed physical feature a density discontinuity here caled the ridge crest front the injected plume provides a unique deep sea tracer with an asymmetric distribution which shows that the deep circulation across the rise is from east to west the striking intensity and lateral extent of this helium 3 anomaly compared to observations at known oceanic hydrohrmal sites suggest that the largest hydrothermal fields in the ocean are yet to be discovered and that they will be found near 15 s on the east pacific rise

methane anomalies in seawater above the loihi submarine summit area hawaii hydrothermal activity above loihi submarine volcano was characterized by water column distributions of methane ph and helium 3 it was found that the southern loihi summit is almost covered with hydrothermal plumes which have anomalously high concentrations of methane maximum 569 10 6cm3kg 1 accompanied by high concentrations of helium 3 and low ph values minimum 7 18 the plumes consist of two layers a shallow plume about 200 m above the summit and a deep plume about 100 m above the summit probably derived from different hydrothermal vents the shallow and deep plumes showed different ch43he and ch4ph ratios with the same 3heph ratio which implies that methane concentrations differ between the hydrothermal end members for the two plumes the variation of methane between the end members is suggested to result from inter vent inhomogeneity of bacterial activities that consume or produce methane within the vents comparison of the ch43he ratios of the two plumes with the previous data for loihi and other submarine hydrothermal areas confirms that the loihi hotspot has one to two orders of magnitude smaller ch43he value than those of the east pacific rise and the galapagos spreading centers

loihi seamount hawaii a mid plate volcano with a distinctive hydrothermal system the initial discovery of deep sea hydrothermal vents at the galapagos rift1 2 has resulted in a decade of exploration and experimentation subsequent discoveries in the pacific3 8 and atlantic9 ocean basins have established the importance of these features as sources of mantle derived gases and solutes10 2 and as loci for heat dissipation13 14 polymetallic sulphide mineral deposition15 16 and geochemical exchange17 19 the presence of dense communities of bacteria and specialized macrofauna20 22 has called into question the absolute role of sunlight as the principal energy source for marine organisms until recently these deep sea vents were known only at or near plate boundaries but recent dredging23 24 near bottom water sampling25 27 and sea floor camera survey28 programmes have indicated that hydrothermal vents are present at the summit of loihi seamount a mid plate hotspot submarine volcano at the southern end of the hawaiian island chain29 here we report results obtained from sampling two active vent fields the fluid chemistry especially high co2 and fe presence of alkalic lavas and iron depositing bacteria and absence of macrofauna suggest that mid plate vents may differ from the hydrothermal vents found at mid ocean ridges