linking basement carbonate vein compositions to porewater geochemistry across the eastern flank of the juan de fuca ridge odp leg 168 leg 168 of the ocean drilling program odp investigated the heat flow fluid chemistry and crustal alteration associated with ridge flank hydrothermal systems ten sites were drilled on the eastern flank of the juan de fuca ridge along an 80 km transect between 20 and 100 km east of the spreading centre recovered cores consisted of 100 500 m of sediment with shallow penetration 1 7 48 1 m into the underlying igneous basement 0 8 3 6 ma here we use the composition of calcium carbonate minerals from veins within the upper basement to reconstruct the evolving chemistry of hydrothermal fluids with increasing crustal age and sediment cover thickness we show for the first time a clear link between the alteration of the basement rocks as recorded by secondary minerals and the near basement sedimentary pore fluids which are often assumed to be representative of the basement fluids responsible for low temperature alteration of the upper crust carbonates precipitated from basement fluids that ranged in strontium isotopic composition from near modern seawater 87sr 86sr ap 0 70918 to the near basement pore fluid values at any one site 87sr 86sr ratios are independent of mineralogy with both aragonite and calcite precipitating from variably evolved fluids with the range in carbonate 87sr 86sr increasing with crustal age a parallel geochemical evolution of basement fluids and sediment porewaters is shown since 87sr 86sr ratios of near basement pore fluids decrease from 0 709013 to 0 707108 away from the ridge axis a correlation exists between 87sr 86sr ratios and delta 18o calculated fluid temperatures with more geochemically evolved carbonates having precipitated from warmer fluids basement fluid compositions calculated from carbonate sr mg fe and mn concentrations combined with suitable partition coefficients are also temperature dependent given an observed increase in basement temperature with age from 16 deg c to 64 deg c along the transect a progressive chemical development of basement fluid is demonstrated carbonate veins in volcanic basement from odp holes 504b and 896a on the costa rica rift record the same temperature compositional evolution of basement fluid as those from the juan de fuca ridge flank although these locations have different thermal histories and therefore must have experienced different temporal geochemical evolution of basement fluid basement temperature appears to be the dominant control on basement fluid composition

sulfur isotope evidence for microbial sulfate reduction in altered oceanic basalts at odp site 801 the subsurface biosphere in the basaltic ocean crust is potentially of major importance in affecting chemical exchange between the ocean and lithosphere alteration of the oceanic crust commonly yields secondary pyrite that is depleted in 34s relative to igneous sulfides although these 34s depleted sulfur isotope ratios may point to signatures of biological fractionation previous interpretations of sulfur isotope fractionation in altered volcanic rocks have relied on abiotic fractionation processes between intermediate sulfur species formed during basalt alteration here we report results for multiple s isotope 32s 33s 34s compositions of altered basalts at odp site 801 in the western pacific and provide evidence for microbial sulfate reduction within the volcanic oceanic crust in situ ion microprobe analyses of secondary pyrite in basement rocks show a large range of 34s values between 45 and 1 whereas bulk rock 34s analyses yield a more restricted range of 15 8 to 0 9 these low and variable 34s values together with bulk rock s concentrations ranging from 0 02 up to 1 28 are consistent with loss of magmatic primary mono sulfide and addition of secondary sulfide via microbial sulfate reduction high precision multiple sulfur isotope 32s 33s 34s analyses suggest that secondary sulfides exhibit mass dependent equilibrium fractionation relative to seawater sulfate in both 33s and 34s values these relationships are explained by bacterial sulfate reduction proceeding at very low metabolic rates the determination of the s isotope composition of bulk altered oceanic crust demonstrates that s based metabolic activity of subsurface life in oceanic basalt is widespread and can affect the global s budget at the crust seawater interface

hydrothermal fluid fluxes calculated from the isotopic mass balance of thallium in the ocean crust abstract hydrothermal fluids expelled from the seafloor at high and low temperatures play pivotal roles in controlling seawater chemistry however the magnitude of the high temperature water flux of mid ocean ridge axes remains widely disputed and the volume of low temperature vent fluids at ridge flanks is virtually unconstrained here we determine both high and low temperature hydrothermal fluid fluxes using the chemical and isotopic mass balance of the element thallium tl in the ocean crust thallium is a unique tracer of ocean floor hydrothermal exchange because of its contrasting behavior during seafloor alteration at low and high temperatures and the distinctive isotopic signatures of fresh and altered morb and seawater the calculated high temperature hydrothermal water flux is 0 17 2 93 1013 kg yr with a best estimate of 0 72 1013 kg yr this result suggests that only about 5 to 80 of the heat available at mid ocean ridge axes from the crystallization and cooling of the freshly formed ocean crust is released by high temperature black smoker fluids the residual thermal energy is most likely lost via conduction and or through the circulation of intermediate temperature hydrothermal fluids that do not alter the chemical budgets of tl in the ocean crust the tl based calculations indicate that the low temperature hydrothermal water flux at ridge flanks is 0 2 5 4 1017 kg yr this implies that the fluids have an average temperature anomaly of only about 0 1 to 3 6 c relative to ambient seawater if these low temperatures are correct then both sr and mg are expected to be relatively unreactive in ridge flank hydrothermal systems and this may explain why the extent of basalt alteration that is observed for altered ocean crust appears insufficient to balance the oceanic budgets of 87sr 86sr and mg

trends cycles and nonstationarities in isotope signals of phanerozoic seawater abstract the new set of 87 sr 86 sr 18 o and 13 c experimental data for phanerozoic seawater the bochum ottawa isotope dataset has been tested by wavelet discontinuity and sliding window correlation dimension analyses for cyclicities and nonstationarities in the isotope signal the tests indicate discontinuities in the strontium isotope signal at 500 340 288 210 65 and 28 ma while for the oxygen and carbon isotopes they are at 500 385 290 210 and 65 ma these discontinuities often coincident with major stage boundaries reflect mostly single likely tectonic events that do not affect the structure of the underlying system the two most pronounced nonstationarities in all isotope systematics are at 65 and 210 ma respectively that is at the k t and norian rhaetian transitions wavelet analysis for all three isotope systems yields a long term quasi periodicity at 94 125 ma best developed during the paleozoic with superimposed intermittent 48 57 and 29 35 ma oscillations all likely a reflection of plate reorganizations within the caledonian hercynian and alpine tectonic cycles

flankflux an experiment to study the nature of hydrothermal circulation in young oceanic crust the sediment buried eastern flank of the juan de fuca ridge provides a unique environment for studying the thermal nature and geochemical consequences of hydrothermal circulation in young ocean crust just 18 km east of the spreading axis where the sea floor age is 0 62 ma sediments lap onto the ridge flank and create a sharp boundary between sediment free and sediment covered igneous crust farther east beneath the nearly continuous turbidite sediment cover of cascadia basin the buried basement topography is extremely smooth in some areas and rough in others at a few isolated locations small volcanic edifices penetrate the sediment surface an initial cruise in 1978 and two subsequent cruises in 1988 and 1990 on this sedimented ridge flank have produced extensive single channel seismic coverage detailed heat flow surveys co located with seismic lines and pore fluid geochemical profiles of piston and gravity cores taken over heat flow anomalies complementary multichannel seismic reflection data w

tidally controlled stick slip discharge of a west antarctic ice a major west antarctic ice stream discharges by sudden and brief periods of very rapid motion paced by oceanic tidal oscillations of about 1 meter acceleration to speeds greater than 1 meter per hour and deceleration back to a stationary state occur in minutes or less slip propagates at approximately 88 meters per second suggestive of a shear wave traveling within the subglacial till a model of an episodically slipping friction locked fault reproduces the observed quasi periodic event timing demonstrating an ice stream s ability to change speed rapidly and its extreme sensitivity to subglacial conditions and variations in sea level

provenance stratigraphic architecture and hydrogeologic influence of turbidites on the mid ocean ridge flank of northwestern cascadia basin pacific ocean abstract the northwestern edge of cascadia basin north pacific ocean is unusual because late pliocene to holocene turbidites lap onto juvenile oceanic crust of the juan de fuca ridge subsidence of the ridge flank combines with irregular westward progradation of the turbidite facies to create a stratigraphic section that coarsens and thickens upward the sand provenance is mixed individual turbidity currents have funneled into the area through several shelf slope and abyssal floor conduits including vancouver valley juan de fuca channel barkley canyon and nitinat canyon local bathymetric blockage deflection and reflection of flow paths by basement relief remobilization by intrabasinal submarine slides and debris flows episodic channel switching and sporadic overbank flooding have combined to produce erratic recurrence intervals for the turbidity currents only the tallest basement highs have remained isolated from turbidite deposition during the last 500 000 years spatial and temporal differences in sediment accumulation are important because they modulate the three dimensional responses of compaction and consolidation those changes in physical properties govern where and when hydraulic communication with the underlying basement shuts down the basal hemipelagic layer of cascadia basin transforms to an effective hydrologic seal seepage rates 1 mm yr once the sediment basalt interface is buried by 100 150 m of strata rapid accumulation of turbidites therefore accelerates the hydrogeologic conversion of igneous basement from open to sealed

sulfur 33 constraints on the origin of secondary pyrite in altered oceanic basement abstract low temperature alteration of oceanic basement rocks is characterized by net gain of sulfur which commonly yields low 34s values suggesting involvement of microbial sulfate reduction in order to test whether secondary sulfide minerals are consistent with a biogenic source we apply high precision multiple sulfur isotope analysis to bulk rock sulfide and pyrite isolates from two contrasting types of altered oceanic basement rocks namely serpentinized peridotites and altered basalts samples from two peridotite sites iberian margin and hess deep and from a basalt site on the eastern flank of the juan de fuca ridge yield overlapping 34s values ranging from 0 to 44 in contrast sulfides in the basalt site are characterized by relatively low 33s values ranging from 0 06 to 0 04 compared to those from peridotite sites 0 00 to 0 16 the observed 33s signal is significant considering the analytical precision of 0 014 2 we present a batch reaction model that uses observed 34s and 33s relationships to quantify the effect of closed system processes and constrain the isotope enrichment factor intrinsic to sulfate reduction the estimated enrichment factors as large as 61 and 53 for peridotite and basalt sites respectively suggest the involvement of microbial sulfate reduction the relatively high 33s values in the peridotite sites are due to sulfate reduction in a closed system environment whereas negative 33s values in the basalt site reflect open system sulfate reduction a larger extent of sulfate reduction during alteration of peridotite to serpentinite is consistent with its higher h2 production capacity compared to basalt alteration and further supports in situ microbial sulfate reduction coupled with h2 production during serpentinization reactions

thallium isotope evidence for a permanent increase in marine organic carbon export in the early eocene article the first high resolution thallium tl isotope records in two ferromanganese crusts fe mn crusts cd29 and d11 from the pacific ocean are presented the crusts record pronounced but systematic changes in 205 tl 203 tl that are unlikely to reflect diagenetic overprinting or changes in isotope fractionation between seawater and fe mn crusts it appears more likely that the fe mn crusts track the tl isotope composition of seawater over time the present day oceanic residence time of tl is estimated to be about 20 000 yr such that the isotopic composition should reflect ocean wide events new and published os isotope data are used to construct age models for these crusts that are consistent with each other and significantly different from previous age models application of these age models reveals that the tl isotope composition of seawater changed systematically between 55 ma and 45 ma using a simple box model it is shown that the present day tl isotope composition of seawater depends almost exclusively on the ratio between the two principal output fluxes of marine tl these fluxes are the rate of removal of tl from seawater via scavenging by authigenic fe mn oxyhydroxide precipitation and the uptake rate of tl during low temperature alteration of oceanic crust it is highly unlikely that the latter has changed greatly therefore assuming that the marine tl budget has also not changed significantly during the cenozoic the low 205 tl

the potential hazard from tsunami and seiche waves generated by large earthquakes within lake tahoe california nevada we investigate the potential of local earthquakes to generate tsunamis and seiches within lake tahoe we calculated the long wavelength oscillations generated by 3 hypothetical m w 7 earthquake scenarios for faults with normal slip directly under and outside the lake basin the scenarios involving fault slip under the lake are the north tahoe incline village and west tahoe dollar point scenarios the genoa scenario involves a fault that crops out 10 km east of the lake faulting beneath the lake generates a tsunami followed by a seiche that continues for hours with waves as large as 3 to 10 m the seiche potentially threatens low lying lakeside communities and lifelines we also compare the spectral characteristics of synthetic tide gauge records with wind swell observations the fundamental mode calculated for a seiche is consistent with the wind swell observations

controls on thallium uptake during hydrothermal alteration of the upper ocean crust abstract hydrothermal circulation is a fundamental component of global biogeochemical cycles however the magnitude of the high temperature axial hydrothermal fluid flux remains disputed and the lower temperature ridge flank fluid flux is difficult to quantify thallium tl isotopes behave differently in axial compared to ridge flank systems with tl near quantitatively stripped from the intrusive crust by high temperature hydrothermal reactions but added to the lavas during low temperature reaction with seawater this contrasting behavior provides a unique approach to determine the fluid fluxes associated with axial and ridge flank environments unfortunately our understanding of the tl isotopic mass balance is hindered by poor knowledge of the mineralogical physical and chemical controls on tl uptake by the ocean crust here we use analyses of basaltic volcanic upper crust from integrated ocean drilling program hole u1301b on the juan de fuca ridge flank combined with published analyses of dredged seafloor basalts and upper crustal basalts from holes 504b and 896a to investigate the controls on tl uptake by mid ocean ridge basalts and evaluate when in the evolution of the ridge flank hydrothermal system tl uptake occurs seafloor basalts indicate an association between basaltic uptake of tl from cold seawater and uptake of cs and rb which are known to partition into k rich phases although there is no clear relationship between tl and k contents of seafloor basalts the data do not rule out the incorporation of at least some tl into the same minerals as the alkali elements in contrast we find no relationship between the tl content and either the abundance of secondary phyllosilicate minerals or the k cs or rb contents in upper crustal basalts we conclude that the uptake of tl and alkali elements during hydrothermal alteration of the upper crust involves different processes and or mineral phases compared to those that govern seafloor weathering furthermore a correlation between the tl and s concentrations of upper crustal basalts from holes u1301b 504b and 896a indicates that tl is primarily incorporated into secondary sulfides given that some of these secondary sulfides formed as a result of microbial sulfate reduction microbial action is at least indirectly responsible for tl uptake thallium enrichment of ridge flank basalts requires a tl bearing fluid and physical chemical and microbial conditions that favor secondary sulfide formation uptake of tl occurs in reducing environments in the background rocks away from fluid flow pathways during early open circulation of oxidizing seawater but more pervasively throughout the system during later restricted circulation of reducing fluids the tl isotope system is therefore a useful tracer of the fluid flux through both the open and restricted ridge flank hydrothermal regimes

subseafloor seawater basalt microbe reactions continuous sampling of borehole fluids in a ridge flank environment 1 integrated ocean drilling program iodp hole 1301a was drilled cased and instrumented with a long term subseafloor observatory cork on the eastern flank of the juan de fuca ridge in summer 2004 this borehole is located 1 km south of odp hole 1026b and 5 km north of baby bare outcrop hole 1301a penetrates 262 m of sediment and 108 m of the uppermost 3 5 ma basaltic basement in an area of warm 64 c hydrothermal circulation the borehole was instrumented and those instruments were recovered 4 years later here we report chemical data from two continuous fluid samplers osmosamplers and temperature recording tools that monitored changes in the state of borehole formation fluids these changes document the effects of drilling fluid overpressure and flow seawater basalt interactions and microbial metababolic activity initially bottom seawater flowed into the borehole through a leak between concentric cork casing strings eventually the direction of flow reversed and warm altered formation fluid flowed into the borehole and discharged at the seafloor this reversal occurred during 1 week in september 2007 3 years after drilling operations ceased the composition of the formation fluid around hole 1301a generally lies within bounds defined by springs on baby bare outcrop to the south and fluids that discharged from hole 1026b to the north deviations likely result from reactions with drilling products simple conservative mixing of two end member fluids reveals reactions occurring within the crust including nitrate reduction presumably by denitrifying microbes the observed changes in borehole fluid composition provide the foundation for a conceptual model of chemical and microbial change during recharge of a warm ridge flank hydrothermal system this model can be tested through future scientific ocean drilling experiments

numerical modeling of the june 17 2017 landslide and tsunami events in karrat fjord west greenland on june 17 2017 the western coast of greenland was the site of a tsunami which flooded several villages killing 4 people and destroying 11 houses in the village of nuugaatsiaq this tsunami was triggered by a subaerial landslide which occurred in a fjord 32 km ene of nuugaatsiaq this paper presents the numerical modeling of this landslide of sim 50 million hbox m 3 and of the tsunami propagation from its source to nuugaatsiaq the landslide is considered as a granular flow under gravity forces and the water waves generated are related to the displacement of the sea bottom the results obtained are similar in amplitude to our inferences from videos i e three water waves between 1 and 1 5 m arriving at nuugaatsiaq with a period of roughly 3 min and are also in general agreement with the amplitude 1 m resulting from deconvolution of oscillations recorded on a horizontal seismogram operating at nuugaatsiaq nuug according to the field survey performed by fritz et al egu general assembly conference abstracts vol 20 of egu general assembly conference abstracts p 18345 2018a on july 2017 a second mass next to the landslide is threatening karrat fjord a sensitivity study is realized on its volume with 2 7 14 and 38 million hbox m 3 reaching the sea the shape of the water waves is found to be independent of volume and linearity is observed between the volume and the water wave heights finally the orientation of the slide does not seem to influence either the period or the shape of the generated water waves

observing calving generated ocean waves with coastal broadband seismometers jakobshavn isbrae greenland we use time lapse photography modis satellite imagery ocean wave measurements and regional broadband seismic data to demonstrate that icebergs that calve from jakobshavn isbrae greenland can generate ocean waves that are detectable over 150 km from their source the waves which are recorded seismically have distinct spectral peaks are not dispersive and persist for several hours on the basis of these observations we suggest that calving events at jakobshavn isbrae can stimulate seiches or basin eigenmodes in both ilulissat icefjord and disko bay our observations furthermore indicate that coastal land based seismometers located near calving termini e g as part of the new greenland ice sheet monitoring network glisn can aid investigations into the largely unexplored oceanographic consequences of iceberg calving

strontium alteration in the troodos ophiolite implications for fluid fluxes and geochemical transport in mid ocean ridge hydrothermal systems new and published strontium isotope analyses from the troodos ophiolite constrain fluid solid exchange processes and the magnitude and circulation paths of the hydrothermal fluids the87sr 86sr profile reflects alteration in the recharge zone of an evolving hydrothermal system fluid rock strontium isotope exchange in the upper 1 5 km of extrusive lavas was kinetically limited and seawater derived fluids emitted from the base of this zone were buffered to87sr 86sr ratios between 0 7047 and 0 7059 in contrast over the next 1 km depth interval of sheeted dykes and the uppermost plutonics 87sr 86sr values cluster about0 7054 7 2 and fluid flow is inferred to have been pervasive with near equilibrium fluid rock exchange quartz chlorite and epidosite zones the probable pathways of the concentrated high temperature upwelling fluids have identical87sr 86sr ratios to adjacent diabase dykes on troodos a time integrated fluid flux in excess of2 9 107 kg m 2 is required to transport the strontium isotope composition of 0 7054 set in the kinetically controlled exchange zone through the 1 km of sheeted dykes and into the zones of concentrated upwelling the uniformity of the87sr 86sr ratios in the diabase sheeted dykes and high temperature epidosite and quartz chlorite rocks indicate that the strontium isotopic alteration took place during the high temperature phase of hydrothermal circulation the inferred minimum time integrated fluid flux of2 9 107 kg m 2 substantially exceeds that of 5 106 kg m 2 inferred from thermal models of high temperature circulation but is comparable with estimates of the hydrothermal flux from oceanic budgets of3he mg and87sr the high flux estimate for troodos is consistent with the ophiolite venting fluids with87sr 86sr elevated significantly above rock values which contrasts with the near morb87sr 86sr ratios of fluids from active high temperature vents at mid ocean ridges and the87sr 86sr profile in dsdp hole 504b this requires that either the modern systems are immature and there is a protracted phase of lower temperature circulation or that circulation in the troodos ophiolite differed from that in normal mid ocean ridges and oceanic strontium budgets are balanced by another source the lack of very elevated87sr 86sr values in the vent fluids precludes significant channelling in the recharge zones of the active systems

lava lake sloshing modes during the 2018 kīlauea volcano eruption probe magma reservoir storativity abstract basaltic volcanoes like k lauea hawai i pose hazards through lava flows and other eruptive activity quantifying hazard requires constraining the volume of magma stored in shallow reservoirs as well as the capacity of those reservoirs to accumulate and discharge magma in response to pressure changes i e storativity shallow reservoirs are often connected through magmatic conduits to lava lakes which are frequently perturbed by rockfalls convection and outgassing here we present a novel method to quantify reservoir storativity at kilauea that exploits the seismically observable oscillatory response of the lake conduit reservoir system to perturbations during the may 2018 eruption seismic events recorded by the summit broadband seismometer network during the eruption feature multiple oscillatory modes in the very long period vlp band the longest period mode 30 40 s here termed the conduit reservoir mode persisted during drainage of the lava lake indicating its primary association with the underlying conduit reservoir system additional modes with periods of 10 20 s vanished during lake drainage and are attributed to lava lake sloshing the surface displacements of the two longest period sloshing modes are explained as the superimposed response to a near surface horizontal force along the axes of the crater from the pressure imbalance during sloshing on the crater walls and a volume change in a reservoir located at the conduit reservoir mode source centroid both sloshing modes are in the deep water surface gravity wave limit where disturbances are largest near the lake surface though pressure changes on the top of the conduit at the lake bottom provide the observed excitation of the underlying conduit reservoir system combining magma sloshing dynamics in the crater and a conduit reservoir oscillation model we bound the storativity of the reservoir to be greater than 0 4 m3 pa this implies a storage volume of a few km3 for an approximately equidimensional e g spherical reservoir a smaller volume is possible but requires the presence of other shapes of magma bodies such as sills or dikes and or significant finite source effect our work demonstrates the signature of lava lake sloshing modes in the seismic data and the potential of these modes in constraining the structure of the shallow magmatic system

seawater recharge into oceanic crust iodp exp 327 site u1363 grizzly bare outcrop 1 systematic differences in sediment thermal and pore water chemical profiles from integrated ocean drilling program site u1363 document mixing and reaction within the basaltic crust adjacent to grizzly bare outcrop a site of hydrothermal recharge into 3 6 my old basaltic crust a transect of seven holes was drilled 50 m to 750 m away from the base of the outcrop temperatures at the sediment basement interface increase from 6 c to 30 c with increasing distance from the outcrop and heat flow is suppressed within several hundred meters from the outcrop calculated fluid compositions at the sediment basement interface are generally explained by mixing between bottom seawater and altered crustal basement fluids with a composition similar but not identical to fluids from seeps at baby bare outcrop located 45 km to the northeast reactions within upper basement and overlying sediment affect a variety of ions mn fe mo si po43 v and u and 13dic indicating a diagenetic influence and diffusive exchange with overlying sediment pore waters the apparent 14c age of basal pore fluids is much older than bottom seawater collectively these results are consistent with seawater recharge at grizzly bare outcrop however there are strong gradients in fluid composition within 50 m of the outcrop providing evidence for complex flow paths and vigorous mixing of young recently recharged seawater with much older more reacted basement fluid the proximity of these altered fluids to the edge of the outcrop raises the possibility for fluid seepage from the outcrop in addition to seawater recharge

surface seiches in lakes of complex geometry in lakes of small to medium size the characteristic frequencies of free oscillations of the water surface seiches depend only on the basin geometry in irregularly shaped basins such as dendritic reservoirs and multibasin lakes these characteristic frequencies are not easily determined with simple formulas clear lake a multibasin lake in northern california is presented here as a case in point the signature of the seiches in clear lake were only revealed after solving the eigenvalue problem governing the structure and frequency of seiches derived from the linear and frictionless depth averaged shallow water equations in a nonrotating frame

twenty five years of progress in the science of geological tsunamis following the 1992 nicaragua and flores events we review a set of 47 tsunamis of geological origin triggered by earthquakes landslides or volcanoes which have occurred over the past 25 years and provided significant new insight into theoretical experimental field or societal aspects of tsunami science among the principal developments in our command of various aspects of tsunamis we earmark the development of the w phase inversion for the low frequency moment tensor of the parent earthquake the abandonment of the concept of a maximum earthquake magnitude for a given subduction zone controlled by simple plate properties the development and implementation of computer codes simulating the interaction of tsunamis with initially dry land at beaches thus introducing a quantitative component to realistic tsunami warning procedures and the recent in situ investigation of current velocities in addition to the field of surface displacements during the interaction of tsunamis with harbors continued research remains warranted notably in the field of the real time identification of tsunami earthquakes whose tsunamis are larger than expected from their seismic magnitudes especially conventional ones the recent tragedy during the 2018 krakatau flank collapse along a scenario which had been quantitatively forecast also emphasizes the need for a continued effort in the education of the populations at risk

hydrothermal alteration of a 1 km section through the upper oceanic crust deep sea drilling project hole 504b mineralogy chemistry and evolution of seawater basalt interactions deep sea drilling project hole 504b penetrates 1076 m into oceanic layer 2 and is the first hole to pass through the transition from pillow basalts altered at low temperatures into hydrothermally metamorphosed sheeted dikes alteration of the crust at site 504 occurred in four stages related to the movement of the crust away from the spreading axis 1 dikes reacted with seawater 200 300 c in the upwelling zone of an axial convection cell at the spreading axis resulting in the formation of greenschist facies parageneses in veins and host rocks mixing of the upwelling hydrothermal fluids with seawater circulating in the overlying more permeable pillow section occurred in the upper part of the lithologic transition zone causing a steep temperature gradient at the base of the pillow section secondary minerals formed in the lower pillow section from the resultant reducing mixed fluids at temperatures of around 100 c at the same time the initial effects of seafloor weathering began in the upper 320 m of the pillow section at low temperatures 50 c and under conditions of open circulation of oxidizing seawater 2 following refracturing of the dikes a second stage of axial upwelling occurred hydrothermal fluids 200 380 c were probably similar to those presently sampled from spreading ridges on the seafloor mixing of these fluids with seawater in the lithologic transition zone caused deposition of quartz epidote and sulfides in veins and formation of a sulfide rich stockworklike zone within this transition zone alteration of the pillow section proceeded under the prior conditions with the effects of seafloor weathering extending progressively downward into the crust 3 seawater recharge penetrated to depths of at least 1075 5 m subbasement and deposited anhydrite locally in veins 4 off axis alteration of the dikes was characterized by formation of zeolites calcite and prehnite in veins and host rocks from more highly evolved and lower temperature 100 250 c fluids alteration in the upper pillow section evolved from seafloor weathering conditions to more reducing and rock dominated as cracks in the basalt were sealed with secondary minerals and the basement was covered with a layer of sediment zeolites and calcite were the last phases to form throughout the pillow section sealing of the crust to convective cooling also allowed conductive reheating of the crust from below calculations of seawater crustal chemical fluxes from whole rock data are complicated by the low recovery and heterogeneity of alteration effects but indicate that basalt seawater interactions are a sink for seawater mg and k and a source for si and ca

benthic foraminiferal mg ca paleothermometry a revised core top calibration core top samples from different ocean basins have been analyzed to refine our current understanding of the sensitivity of benthic foraminiferal calcite magnesium calcium mg ca to bottom water temperatures bwt benthic foraminifera collected from hawaii little bahama bank sea of okhotsk gulf of california ne atlantic ceara rise sierra leone rise the ontong java plateau and the southern ocean covering a temperature range of 0 8 to 18 c were used to revise the cibicidoides mg ca temperature calibration the mg ca bwt relationship of three common cibicidoides species is described by an exponential equation mg ca 0 867 0 049 exp 0 109 0 007 bwt stated errors are 95 ci the temperature sensitivity is very similar to a previously published calibration however the revised calibration has a significantly different preexponential constant resulting in different predicted absolute temperatures we attribute this difference in the preexponential constant to an analytical issue of accuracy some genera notably uvigerina show apparently lower temperature sensitivity than others suggesting that the use of constant offsets to account for vital effects in mg ca may not be appropriate downcore mg ca reproducibility as determined on replicate foraminiferal samples is typically better than 0 1 mmol mol 1 2 s e thus considering the errors associated with the cibicidoides calibration and the downcore reproducibility bwt may be estimated to within 1 c application of the revised core top mg ca bwt data to cenozoic foraminiferal mg ca suggests that seawater mg ca was not more than 35 lower than today in the ice free ocean at 50 ma

chemical composition of basement fluids within an oceanic ridge flank implications for along strike and across strike hydrothermal circulation compositions of basement fluids are presented for four sites along a 3 5 m y old partly buried basement ridge on the eastern flank of the juan de fuca ridge this ridge is roughly parallel to the active ridge axis of the endeavor segment 100 km to the west from south to north these sites are baby bare outcrop ocean drilling program odp site 1026 and the southern and northern sides of mama bare outcrop the composition of basement fluids is determined or estimated from analyses of pore water samples that were extracted from sediments at each of these sites spring waters from baby bare and basement fluids that vented from the open odp hole 1026b chemical trends in basement fluids along this transect show increasing alteration from south to north a similar trend was observed along an odp transect perpendicular to the ridge axis with increasing fluid alteration from west to east much of the increase in fluid alteration along the odp transect is explained by greater water rock exchange with increasing basement temperature to the east in contrast the trend along the 3 5 m y old ridge is best explained by diffusive exchange with the overlying sediment the rate of this exchange is used to constrain hydrologie properties within basaltic basement flow within the 3 5 m y old ridge is inferred to occur from south to north and lacks significant exchange with basement fluids from the active ridge crest to the west thus the two flow systems are hydrologically distinct and flow paths are likely influenced by the complex distribution of permeability in basement the pattern of seafloor morphology and the type and rate of sedimentation

thallium isotope variations in seawater and hydrogenetic diagenetic and hydrothermal ferromanganese deposits results are presented for the first in depth investigation of tl isotope variations in marine materials the tl isotopic measurements were conducted by multiple collector inductively coupled plasma mass spectrometry for a comprehensive suite of hydrogenetic ferromanganese crusts diagenetic fe mn nodules hydrothermal manganese deposits and seawater samples the natural variability of tl isotope compositions in these samples exceeds the analytical reproducibility 0 05 by more than a factor of 40 hydrogenetic fe mn crusts have 205tl of 10 to 14 whereas seawater is characterized by values as low as 8 205tl represents the deviation of the 205tl 203tl ratio of a sample from the nist srm 997 tl isotope standard in parts per 104 this 2 difference in isotope composition is thought to result from the isotope fractionation that accompanies the adsorption of tl onto ferromanganese particles an equilibrium fractionation factor of 1 0021 is calculated for this process ferromanganese nodules and hydrothermal manganese deposits have variable tl isotope compositions that range between the values obtained for seawater and hydrogenetic fe mn crusts the variability in 205tl in diagenetic nodules appears to be caused by the adsorption of tl from pore fluids which act as a closed system reservoir with a tl isotope composition that is inferred to be similar to seawater nodules with 205tl values similar to seawater are found if the scavenging of tl is nearly quantitative hydrothermal manganese deposits display a positive correlation between 205tl and mn fe this trend is thought to be due to the derivation of tl from distinct hydrothermal sources deposits with low mn fe ratios and low 205tl are produced by the adsorption of tl from fluids that are sampled close to hydrothermal sources such fluids have low mn fe ratios and relatively high temperatures such that only minor isotope fractionation occurs during adsorption hydrothermal manganese deposits with high mn fe and high 205tl are generated by scavenging of tl from colder more distal hydrothermal fluids under such conditions adsorption is associated with significant isotope fractionation and this produces deposits with higher 205tl values coupled with high mn fe

trace element and ree composition of a low temperature ridge flank hydrothermal spring abstract warm 25 c hydrothermal springs have been sampled on baby bare a basaltic outcrop on 3 5 ma old crust 100 km east of the endeavor segment of the juan de fuca ridge the source for these springs is a 62 to 64 c formation water that has cooled conductively as it ascends to feed the springs this water originated as bottom seawater that probably descended into basement 52 km to the southwest at another much larger outcrop called grizzly bare as this seawater flows towards baby bare it is heated and altered by reactions within basaltic basement and by diffusive fluxes to and from the overlying sediment concentrations of mn co ni zn cd and mo in the spring waters are greater than in bottom seawater indicating that the oceanic crust is a source for these elements to the oceans at least a portion of this increase probably results from the redox cycling of mn in sedimentary sources near the basement interface that produces a diffusive flux to basement formation waters additional removal of mo and inputs of the other five elements to two of the three springs are observed locally near sites of venting where density gradients can form shallow circulation cells within the sediment and diffusive exchange occurs concentrations of cu u v y and the rare earth elements rees excluding ce in these samples are less than in bottom seawater indicating that the oceanic crust is a net sink for these elements in this environment copper is probably removed into newly formed carbonate and or sulfide phases removal of the oxyanions u and v is consistent with a net removal of phosphate demonstrated previously for ridge flank hydrothermal systems similarly removal of y and the rees is associated with carbonate phosphate rich and oxide phases calculated maximum global chemical fluxes from warm ridge flank hydrothermal systems such as baby bare are insignificant relative to riverine fluxes for these elements except possibly for mn and mo the impact on global geochemical budgets for these elements from lower temperature

calving event detection by observation of seiche effects on the greenland fjords with mass loss from the greenland ice sheet accelerating and spreading to higher latitudes the quantification of mass discharge in the form of icebergs has recently received much scientific attention here we make use of very low frequency 0 001 0 01 hz seismic data from three permanent broadband stations installed in the summers of 2009 10 in northwest greenland in order to monitor local calving activity at these frequencies calving seismograms are dominated by a tilt signal produced by local ground flexure in response to fjord seiching generated by major iceberg calving events a simple triggering algorithm is proposed to detect calving events from large calving fronts with potentially no user interaction our calving catalogue identifies spatial and temporal differences in calving activity between jakobshavn isbrae and glaciers in the uummannaq district similar to 200 km to the north the uummannaq glaciers show clear seasonal fluctuations in seiche based calving detections as well as seiche amplitudes in contrast the detections at jakobshavn isbrae show little seasonal variation which may be evidence for an ongoing transition to winter calving activity the results offer further evidence that seismometers can provide efficient and inexpensive monitoring of calving fronts

seismic records of the 2004 sumatra and other tsunamis a quantitative study following the recent reports by yuan et al 2005 of recordings of the 2004 sumatra tsunami on the horizontal components of coastal seismometers in the indian ocean basin we build a much enhanced dataset extending into the atlantic and pacific oceans as far away as bermuda and hawaii and also expanded to five additional events in the years 1995 2006 in order to interpret these records quantitatively we propose that the instruments are responding to the combination of horizontal displacement tilt and perturbation in gravity described by gilbert 1980 and induced by the passage of the progressive tsunami wave over the ocean basin in this crude approximation we simply ignore the island or continent structure and assume that the seismometer functions de facto as an ocean bottom instrument the records can then be interpreted in the framework of tsunami normal mode theory and lead to acceptable estimates of the seismic moment of the parent earthquakes we further demonstrate the feasibility of deconvolving the response of the ocean floor in order to reconstruct the time series of the tsunami wave height at the surface of the ocean suggesting that island or coastal continental seismometers could complement the function of tsunameters

thallium isotope variations in an ore bearing continental igneous setting collahuasi formation northern chile abstract thallium is a highly incompatible element and a large fraction of the bulk silicate earth tl budget is therefore expected to reside in the continental crust nonetheless the tl isotope systematics of continental rocks are essentially unexplored at present here we present new tl isotope composition and concentration data for a suite of 36 intrusive and extrusive igneous rocks from the vicinity of porphyry cu deposits in the collahuasi formation of the central andes in northern chile the igneous lithologies of the rocks are variably affected by the hydrothermal alteration that accompanied the formation of the cu deposits the samples display tl concentrations that vary by more than an order of magnitude from 0 1 to 3 2 g g whilst e 205 tl ranges between 5 1 and 0 1 e 205 tl is the deviation of the 205 tl 203 tl isotope ratio of a sample from a standard in parts per 10 4 these variations are primarily thought to be a consequence of hydrothermal alteration processes including metasomatic transport of tl and formation breakdown of tl bearing minerals which are associated with small but significant tl isotope effects the tl abundances show excellent correlations with both k and rb concentrations but no co variation with cu this demonstrates that tl displays only limited chalcophile affinity in the continental crust of the collahuasi formation but behaves as a lithophile element with a distribution that is primarily governed by partitioning of tl into k bearing phases collahuasi samples with propylitic alteration features which are derived from the marginal parts of the hydrothermal systems have on average slightly lighter tl isotope compositions than rocks from the more central sericitic and argillic alteration zones this small but statistically significant difference most likely reflects preferential retention of isotopically heavy tl in alteration phases such as white micas and clays which formed during sericitic and argillic alteration

iron and sulfide oxidation within the basaltic ocean crust implications for chemolithoautotrophic microbial biomass production microbial processes within the ocean crust are of potential importance in controlling rates of chemical reactions and thereby affecting chemical exchange between the oceans and lithosphere we here assess the oxidation state of altered ocean crust and estimate the magnitude of microbial biomass production that might be supported by oxidative and nonoxidative alteration compilations of fe2o3 feo and s concentrations from dsdp odp drill core samples representing upper basaltic ocean crust suggest that fe3 fe increases from 0 15 0 05 to 0 45 0 15 within the first 10 20 myr of crustal evolution within the same time frame 70 25 of primary sulfides in basalt are oxidized with an annual production of 4 0 1 8 1015 g of upper 500 200 m crust and average initial concentrations of 8 0 1 3 wt fe and 0 125 0 020 wt s we estimate annual oxidation rates of 1 7 1 2 1012 mol fe and 1 1 0 7 1011 mol s we estimate that 50 of fe oxidation may be attributed to hydrolysis producing 4 5 3 0 1011 mol h2 yr thermodynamic and bioenergetic calculations were used to estimate the potential chemolithoautotrophic microbial biomass production within ridge flanks combined aerobic and anaerobic fe and s oxidation may support production of up to 48 21 1010 g cellular carbon c hydrogen consuming reactions may support production of a similar or larger microbial biomass if iron reduction nitrate reduction or hydrogen oxidation by o2 aq are the prevailing metabolic reactions if autotrophic sulfate reduction or methanogenesis prevail the potential biomass production is 9 7 1010 g c yr and 3 2 1010 g c yr respectively combined primary biomass production of up to 1 1012 g c yr may be similar to that fueled by anaerobic oxidation of organic matter in deep seated heterotrophic systems these estimates suggest that water rock reactions may support significant microbial life within ridge flank hydrothermal systems these estimates suggest that water rock reactions may support significant microbial life within ridge flank hydrothermal systems

hydrothermal recharge and discharge across 50 km guided by seamounts on a young ridge flank hydrothermal circulation within the sea floor through lithosphere older than one million years myr is responsible for 30 of the energy released from plate cooling and for 70 of the global heat flow anomaly the difference between observed thermal output and that predicted by conductive cooling models 1 2 hydrothermal fluids remove significant amounts of heat from the oceanic lithosphere for plates typically up to about 65 myr old3 4 but in view of the relatively impermeable sediments that cover most ridge flanks5 it has been difficult to explain how these fluids transport heat from the crust to the ocean here we present results of swath mapping heat flow geochemistry and seismic surveys from the young eastern flank of the juan de fuca ridge which show that isolated basement outcrops penetrating through thick sediments guide hydrothermal discharge and recharge between sites separated by more than 50 km our analyses reveal distinct thermal patterns at the sea floor adjacent to recharging and discharging outcrops we find that such a circulation through basement outcrops can be sustained in a setting of pressure differences and crustal properties as reported in independent observations and modelling studies

seismically observed seiching in the panama canal 1 a large portion of the seismic noise spectrum is dominated by water wave energy coupled into the solid earth distinct mechanisms of water wave induced ground motions are distinguished by their spectral content for example cultural noise is generally 1 s period microseisms dominate the seismic spectrum from periods of 2 to 20 s and the earth s hum is in the range of 50 to 600 s we show that in a large lake in the panama canal there is an additional source of long period noise generated by standing water waves seiches induced by disturbances such as passing ships and wind pressure we compare seismic waveforms to water level records and relate these observations to changes in local tilt and gravity due to an oscillating seiche the methods and observations discussed in this paper provide a first step toward quantifying the impact of water inundation as recorded by seismometers this type of quantified understanding of water inundation will help in future estimates of similar phenomena such as the seismic observations of tsunami impact

seismic monitoring of the indian ocean tsunami the 26 december 2004 sumatra andaman earthquake of mw 9 3 triggered a massive tsunami in the indian ocean we here report on observations of the indian ocean tsunami at broadband seismic stations located on islands in the area the tsunami induces long period 1000 s signals on the horizontal components of the sensor frequency time analysis shows that the long period signals cannot be due to seismic surface waves but that it arrives at the expected time of the tsunami the waveforms are well correlated to tide gauge observations at a location where both observations are available to explain the signals we favour tilt due to coastal loading but we cannot at the present stage exclude gravitational effects the density of broadband stations is expected to increase rapidly in the effort of building an earthquake monitoring system they may unexpectedly become useful tsunami detectors as well

investigation of thallium fluxes from subaerial volcanism implications for the present and past mass balance of thallium in the oceans abstract a suite of 34 volcanic gas condensates and particulates from kilauea hawaii mt etna and vulcano italy mt merapi indonesia white island and mt nguaruhoe new zealand were analysed for both tl isotope compositions and tl pb ratios when considered together with published tl pb abundance data the measurements provide globally representative best estimates of tl pb 0 46 0 25 and e 205 tl 1 7 2 0 for the emissions of subaerial volcanism to the atmosphere and oceans e 205 tl is the deviation of the 205 tl 203 tl isotope ratio from nist srm 997 isotope standard in parts per 10 000 compared to igneous rocks of the crust and mantle volcanic gases were found to have i tl pb ratios that are typically about an order of magnitude higher and ii significantly more variable tl isotope compositions but a mean e 205 tl value that is indistinguishable from estimates for the earth s mantle and continental crust the first observation can be explained by the more volatile nature of tl compared to pb during the production of volcanic gases whilst the second reflects the contrasting and approximately balanced isotope fractionation effects that are generated by partial evaporation of tl during magma degassing and partial tl condensation as a result of the cooling and differentiation of volcanic gases mass balance calculations based on results from this and other recent tl isotope studies were carried out to investigate whether temporal changes in the volcanic tl fluxes could be responsible for the dramatic shift in the e 205 tl value of the oceans at 55 ma which has been inferred from tl isotope time series data for ferromanganese crusts the calculations demonstrate that even large changes in the marine tl input fluxes from volcanism and other sources are unable to significantly alter the tl isotope composition of the oceans based on modelling it is shown that the large inferred change in the e 205 tl value of seawater is best explained if the oceans of the early cenozoic featured significantly larger tl output fluxes to oxic pelagic sediments whilst the sink fluxes to altered ocean crust remained approximately constant

hydrothermal circulation through mid ocean ridge flanks fluxes of heat and magnesium thermally driven convection of seawater occurs through oceanic crust of all ages at the seafloor spreading axis on mid ocean ridge flanks and in the ocean basins at the ridge axis and on the flanks circulating seawater produces a major chemical exchange between the oceans and the crust based on heat budget constraints and the composition of hot springs between 10 and 40 of the river flux of mg can be taken up during high temperature alteration of the basaltic crust along the ridge axis most of the hydrothermal heat loss however occurs on the mid ocean ridge flanks where the temperatures are lower and the seawater flux correspondingly larger the estimated heat loss on the flanks is so large that upwelling must occur over a large fraction 5 30 of the seafloor less than 65 ma in age if temperatures are 20 c and seepage velocities are on the order of 10 to 100 cm y the circulating seawater needs to lose on average less than 1 2 of its mg content in order to solve the mg mass balance for the oceans chemical fluxes through mid ocean ridge flanks are poorly known because of the wide range of crustal conditions that prevail there and the paucity of study to date the most critical parameter for characterizing crustal conditions is temperature in basement which is a function of crustal age basement topography and sediment thickness and permeability basement temperature which can usually be inferred from heat flow and seismic reflection surveys largely determines the change in the composition of seawater circulating through basement this change can be inferred in turn from profiles of sediment porewater chemistry all sites studied to date with temperatures at the sediment basement interface 25 c have a large component of advective heat loss and show only a small 80 mg loss both types of sites may be important for chemical fluxes whether the cooler sites are important depends on how much the seawater changes in composition as it circulates through the crust only small changes are needed whether the warmer sites are important depends on how much heat is lost by advection in this type of setting the warmer sites could produce significant chemical fluxes even if they are scarce they could account for the entire river input of mg to the oceans even if they represent only 8 20 of the total advective heat loss on ridge flanks

low temperature fluid rock interaction an isotopic and mineralogical perspective of upper crustal evolution eastern flank of the juan de fuca ridge jdfr odp leg 168 abstract during odp leg 168 10 sites were drilled across the eastern flank of the juan de fuca ridge jdfr to examine the conditions of fluid rock interaction in three distinct hydrothermal regimes referred to as the hydrothermal transition ht buried basement bb and rough basement rb transects extending over a 120 km linear transect perpendicular to the spreading ridge this was carried out in an attempt to constrain the conditions and processes that control the location style and magnitude of low temperature 87 sr 86 sr and 18 o analyses of basalts from across the eastern flank of the jdfr reinforce petrological observations with 87 sr 86 sr and 18 o values slightly elevated above accepted pristine morb values for this region these results are consistent with an increase in the amount of fluid rock interaction with time across the flank enrichment in the 87 sr 86 sr and 18 o relative to morb is influenced by a number of factors including local and regional variations in the crustal lithology and structure the age of the crust the extent of bulk rock alteration and theoretically the relative abundance of different isotopically enriched secondary mineral phases in the crust

oxidative scavenging of thallium by birnessite explanation for thallium enrichment and stable isotope fractionation in marine ferromanganese precipitates tl stable isotopes recorded in marine ferromanganese crusts show great promise as a tracer of past marine and climatic conditions key to interpreting recent tl stable isotope time series data is a detailed molecular level understanding of tl scavenging by ferromanganese crust minerals and tl stable isotope fractionation occurring during uptake to this end we determine the mechanism of tl sorption to the primary ferromanganese minerals in crusts namely hexagonal birnessite todorokite and ferrihydrite using xas we compliment our data with micro focus xas of a tl enriched hydrogenetic ferromanganese crust we show that tl i is oxidised to tl iii during sorption to hexagonal birnessite but not during sorption to todorokite triclinic birnessite and ferrihydrite tl iii forms an inner sphere complex at the hexagonal birnessite surface located at vacant octahedral sites in the phyllomanganate sheets we show that oxidation of tl i to tl iii during reductive dissolution of birnessite is thermodynamically unfavourable and propose that oxidation of tl i is driven by the formation of the tl iii surface complex recent theoretical calculations predict a large equilibrium stable isotope fractionation between tl i and tl iii leading to tl iii species that are enriched in the heavy 205tl isotope in light of this work we propose a molecular sorption oxidation fractionation mechanism that provides a unifying explanation for the recently observed geochemical behaviour of tl in marine ferromanganese rich sediments in this mechanism the proportion of hexagonal birnessite dictates the extent of tl oxidation which controls the extent of tl enrichment and isotope fractionation this work is among the first to provide a molecular explanation for reported trends in trace element enrichments and stable isotope compositions in geologic deposits our molecular sorption oxidation fractionation mechanism will ultimately help interpret tl signals in marine sedimentary archives to provide new constraints on past oceanic and climatic change in addition our mechanism should also help explain compositional relationships of other redox sensitive elements in ferromanganese rich marine sediments that might also be used as paleoceanographic and paleoclimate proxies

field observations of waves generated by passing ships a note this short contribution reports the results of a field study on the nearshore characteristics of waves generated by both conventional and high speed passenger ferries the field observations took place in the late summer of 2005 at a beach close to the port of mytilene island of lesbos greece and involved the visual observation of ship waves using digital video recordings and image processing techniques the results showed that passage of the fast ferry was associated with a longer more complex and energetic nearshore event this event not only did include higher nearshore waves up to 0 74 m and was organised in different wave packets but it was also an order of magnitude longer 680 s than the conventional ferry event regarding the effects on beach sediment dynamics the fast ferry waves were estimated to be very efficient in mobilising the nearshore sediments in contrast to those of the conventional ferry the fast ferry service appears to generate daily prolonged nearshore events which contain waves with higher energy than those expected from the normal summer wind wave regime of the area these events also include some high and very steep waves which can be particularly erosive therefore fast ferry wakes may have considerable impacts on the seasonal beach sediment dynamics morphodynamics and the nearshore benthic ecology as well as they may pose significant risks to bathers affecting the recreational use of the beaches exposed to fast ferry traffic finally the study has shown that satisfactory field observations of the nearshore characteristics of ship generated and wind waves can be obtained using inshore deployments of calibrated poles digital video cameras and appropriate image processing algorithms