intermediate sulfur oxidation state compounds in the euxinic surface sediments of the dvurechenskii mud volcano black sea abstract the deep black sea is known to be depleted in electron acceptors for sulfide oxidation this study on depth distributions of sulfur species s ii s 0 s n 2 s 2 o 3 2 so 3 2 so 4 2 in the dvurechenskii mud volcano a cold seep situated in the permanently anoxic eastern black sea basin sorokin trough 2060 m water depth showed remarkable concentrations of sulfide oxidation products sulfite concentrations of up to 11 mol l 1 thiosulfate concentrations of up to 22 mol l 1 zero valent sulfur concentrations of up to 150 mol l 1 and up to five polysulfide species were measured in the upper 20 cm of the sediment electron acceptors found to be available in the dvurechenskii mud volcano dmv for the oxidation of hydrogen sulfide to sulfide oxidation intermediates are iron minerals and probably also reactive manganese phases up to 60 mol g 1 of reactive iron minerals and up to 170 mol l 1 dissolved iron was present in the central summit with the highest fluid upflow and fresh mud outflow thus the source for the oxidative power in the dmv are reactive iron phases extruded with the mud from an ancient source in the deeply buried sediments leading to the formation of various sulfur intermediates in comparably high concentrations another possible source of sulfide oxidation intermediates in dmv sediments could be the formation of zero valent sulfur by sulfate dependent anaerobic microbial oxidation of methane followed by disproportionation of zero valent sulfur sulfide oxidation intermediates which are produced by these processes do not reach thermodynamic equilibrium with rhombic sulfur especially close to the active center of the dmv due to a short equilibration time thus mud volcano sediments such as in the dmv can provide oxidizing niches even in a highly reduced environment like the abyssal part of the black sea

lateral injection of oxygen with the bosporus plume fingers of oxidizing potential in the black sea saline and warm mediterranean water flowing through the bosporus strait maintains a permanent pycnocline with vertical separation of oxic o 2 suboxic absence of o2 and h2s and anoxic h2s zones in the black sea the stable suboxic zone implies restricted vertical mixing of the upper oxic and lower anoxic layers and limited vertical flux of oxygen that cannot balance the upward flux of sulfide we report data that directly confirm massive lateral injections 200 km from the bosporus of oxygen enriched waters of the bosporus plume created by the mixing of shallow cold intermediate layer black sea water with mediterranean water these plume waters are laterally injected into the oxic layer and more importantly into the suboxic and anoxic layers over several small vertical scales fingers of 5 m at water densities st from 15 0 to 16 4 o2 injection oxidizes mn ii to mn iii iv which then oxidizes h2s the onset of h2s detection occurs in deeper waters in the southwest 170 m st 16 4 relative to the west central black sea 110 m st 16 2 and coincides with increased mno2 and s8 formation in the southwest

focal mechanisms of three earthquakes in finland and their relation to surface faults abstract focal mechanisms for three recent earthquakes in finland are determined using p wave polarities together with sv p and sh p phase amplitude ratios the events occurred on may 11 2000 in toivakka central finland ml 2 4 on september 15 2000 in kuusamo northeastern finland ml 3 5 and on may 2 2001 in kolari western finnish lapland ml 2 9 in order to obtain reliable estimates of the source parameters one dimensional crust and upper mantle velocity models are derived for the epicenter areas from deep seismic sounding results the starting models are modified by one dimensional ray tracing using the earthquake observations the events are relocated by employing p and s phase arrival times from the nearest seismic stations and the final velocity models synthetic waveforms calculated with the reflectivity method are used to further constrain and verify the source and structural parameters the toivakka earthquake indicates thrust or reverse faulting mechanism at a depth of 5 km after comparison with aeromagnetic and topographic data we suggest the eastward dipping nodal plane 358 42 was the fault plane the best fitting fault plane solution of the kolari earthquake suggests pure thrust faulting at a depth of 5 km the nodal plane striking 035 30 correlates well with surface observations of the postglacial possibly listric fault systems in the source area the kuusamo earthquake focal depth 14 km has a normal faulting mechanism with the nodal planes trending 133 47 or 284 47 preference is given to the sw dipping nodal plane as it seems to coincide with topographic and magnetic lineament directions that have been active after the last ice age the three earthquakes have occurred in old precambrian faults and shear zones which have been reactivated the reactivated faults are favourably oriented in the local stress field

hydrothermal vents as a kinetically stable source of iron sulphide bearing nanoparticles to the ocean hydrothermal vents emit metals such as iron to the ocean a chemical analysis of hydrothermal fluids suggests that up to 10 of the iron is present as stable iron bearing nanoparticles

seasonal dynamics of elemental sulfur in two coastal sediments a spectrophotometric method for elemental sulfur s0 analysis without interference from other reduced sulfur compounds was adapted for the use in reducing sediments the s0 distribution in two coastal sediments was studied regularly from summer to winter and compared to factors regulating the s0 accumulation such as redox potentials the rate of bacterial sulfide production and the general sulfur chemistry dense coatings of sulfur bacteria developed on the sediment surface of a sulfuretum which had an s0 concentration of up to 41 mol s cm 3 the 2 5 mm thick bacterial coating contained 40 of all s0 in the sediment a more typical marine sediment with a few cm thick oxidized surface layer had an s0 maximum of 1 3 mol s cm 3 at 2 4 cm depth the s0 maximum in both sediments increased from summer to winter as the sediments gradually became more oxidized the deeper layers maintained a low s0 concentration most of the s0 in the upper few mm of a laboratory sulfuretum was present inside sulfur bacteria and actively migrated up and down with the bacteria depending upon the changing light and oxygen conditions

combining double difference relocation with regional depth phase modelling to improve hypocentre accuracy summary precise and accurate earthquake hypocentres are critical for various fields such as the study of tectonic process and seismic hazard assessment double difference relocation methods are widely used and can dramatically improve the precision of event relative locations in areas of sparse seismic network coverage however a significant trade off exists between focal depth epicentral location and the origin time regional depth phase modelling rdpm is suitable for sparse networks and can provide focal depth information that is relatively insensitive to uncertainties in epicentral location and independent of errors in the origin time here we propose a hybrid method in which focal depth is determined using rdpm and then treated as a fixed parameter in subsequent double difference calculations thus reducing the size of the system of equations and increasing the precision of the hypocentral solutions based on examples using small earthquakes from eastern canada and southwestern usa we show that the application of this technique yields solutions that appear to be more robust and accurate than those obtained by standard double difference relocation method alone

the hyper enrichment of v and zn in black shales of the late devonian early mississippian bakken formation usa abstract black shales of the late devonian to early mississippian bakken formation are characterized by high concentrations of organic carbon and the hyper enrichment 500 to 1000s of mg kg of v and zn deposition of black shales resulted from shallow seafloor depths that promoted rapid development of euxinic conditions vanadium hyper enrichments which are unknown in modern environments are likely the result of very high levels of dissolved h2s 10 mm in bottom waters or sediments because modern hyper enrichments of zn are documented only in framvaren fjord norway it is likely that the biogeochemical trigger responsible for zn hyper enrichment in framvaren fjord was also present in the bakken basin with framvaren fjord as an analogue we propose a causal link between the activity of phototrophic sulfide oxidizing bacteria related to the development of photic zone euxinia and the hyper enrichment of zn in black shales of the bakken formation

intraplate seismicity of a recently deglaciated shield terrane a case study from northern ontario canada the economy of northern ontario canada is heavily dependent on mining so accurate knowledge of seismicity is important for the safe design and op eration of mines and other critical facilities including a proposed underground repos itory for nuclear waste in this study we analyzed 537 cataloged earthquakes that occurred from 1980 to 2006 seismicity is mainly concentrated in topographically elevated archean terranes northwest of lake superior and in the james bay and ka puskasing regions we analyzed waveforms to determine the focal depth for 331 re corded events using the regional depth phase modeling rdpm method coupled with surface wave relative amplitude analysis the majority of events are shallow 350 m although in the east ern part this pattern breaks down and some deeper earthquakes 12 km are ob served based on a moving window event counting technique we show that distinct spatial clusters of seismicity can be delineated that are statistically significant relative to background seismicity levels a particularly active cluster is located within james bay where focal depths range from a few kilometers to more than 20 km another cluster near kapuskasing contains deep focus events and may occur along a hot spot track that runs through western quebec near dryden a shallow 1 km earthquake swarm concentrated in a 1 1 km region commenced in may 2002 faded and then started up again in february 2003 shallow mining induced events are also common around sudbury a major world center for nickel mining the overall pattern of seis micity appears to correlate with upper mantle p wave velocity anomalies suggesting that lateral variations in mantle rheology may play a significant role in controlling intraplate seismicity of shield areas it is also likely that crustal stresses caused by glacial isostatic adjustment are an important factor although the correlation of seis micity with uplift rate is not as clear online material focal depth solutions for earthquakes in northern ontario canada

geochemistry of hydrothermal fluids from the ultramafic hosted logatchev hydrothermal field 15 n on the mid atlantic ridge temporal and spatial investigation abstract mantle derived ultramafic rocks commonly occur on the seafloor at slow spreading axes and are tectonically emplaced along shear zones since the early 1990s a growing number of hydrothermal systems have been detected in ultramafic settings but chemical data for fluid compositions in active systems are still limited besides the logatchev field at 15 n on the mid atlantic ridge mar the only other active high temperature 300 c hydrothermal field known to be strongly influenced by ultramafics is the rainbow field at 36 n on the mar the field at logatchev consists of six active vent sites at about 3000 m water depth situated along a nw se trending line with distances of 50 200 m between the individual sites the vent sites were mapped in detail and re sampled during two cruises in 2004 and 2005 using a rov the geochemical composition of the hydrothermal fluids is characterized by very high concentrations of dissolved methane and hydrogen up to 3 5 mm and 19 mm respectively related to serpentinization processes in the reaction zone together with moderate si concentrations of 9 mm a depletion in b compared to seawater and li concentrations lower than in basaltic systems this fluid composition has been identified as characteristic signature of high temperature hydrothermal fluids reacting with ultramafic rocks however additional alteration of gabbroic intrusions is likely the fluid composition is very similar at all vent sites indicating a common source in the reaction zone and little variation during upflow spatial differences in fluid composition were observed between smoking craters and the complex chimney system irina ii but are restricted to elements with strong temperature controlled solubility as cu and co these differences can be related to different exit temperatures up to 350 c and as it is known that more ultramafic hosted hydrothermal systems exist along slow spreading ridges this type of hydrothermal systems might have a significant influence on the elemental budget of the oceans detailed information about the fluid geochemistry and its spatial and temporal variations is an important prerequisite for an estimation of elemental fluxes in ultramafic hosted systems and their relative importance compared to basaltic hosted systems

distribution and size fractionation of elemental sulfur in aqueous environments the chesapeake bay and mid atlantic ridge elemental sulfur is an important intermediate of sulfide oxidation and may be produced via abiotic and biotic pathways in this study the concentration and size fractionation of elemental sulfur were measured in two different sulfidic marine environments the chesapeake bay and buoyant hydrothermal vent plumes along the mid atlantic ridge nanoparticulate sulfur 0 2 m was found to comprise up to 90 of the total elemental sulfur in anoxic deep waters of the chesapeake bay these data were compared with previous studies of elemental sulfur and represent one of the few reports of nanoparticulate elemental sulfur in the environment additionally a strain of phototrophic sulfide oxidizing bacteria isolated from the chesapeake bay was shown to produce elemental sulfur as a product of sulfide oxidation elemental sulfur concentrations are also presented from buoyant hydrothermal vent plumes located along the mid atlantic ridge in the mid atlantic ridge plume s0 concentrations up to 33 m were measured in the first meter of rising plumes at three different vent sites and nanoparticulate s0 was up to 44 of total elemental sulfur present

composition and sedimentation of hydrothermal plume particles from north cleft segment juan de fuca ridge in 1990 and 1991 particles from buoyant and neutrally buoyant hydrothermal plumes above hydrothermal vents at the north cleft segment of the juan de fuca ridge were sampled to study their changing composition and fluxes away from the vent field in the rising buoyant plume 75 of the p v cr and as scavenging from seawater by hydrothermal precipitates occurs in the first 50 m above the vent cu and zn are most enriched in buoyant plume particles collected from the first few meters above the vent however the degree of enrichment decreases very rapidly with increased height above the vents due to sedimentation of the more dense cu and zn rich sulfide phases using the plume data coupled with the results of our analysis of sediment trap samples we estimated that more than 99 and 99 9 respectively of the total hydrothermal fe and mn produced at the vent field are transported beyond the vent field and dispersed in the open ocean

depth of faulting during the 1968 meckering australia earthquake sequence determined from waveform analysis of local seismograms waveforms for 11 foreshocks and 48 aftershocks of the ms 6 8 meckering earthquake recorded at the world wide standard seismograph network station mundaring are analyzed to determine the depth distribtion of faulting during this unusual intraplate earthquake sequence clear depth phases including sp and rg are seen in the local seismograms at distances of 60 95 km and are studied using synthetic seismograms computed using generalized ray theory and wave number integration techniques large rg s ratios seen on the vertical component short period data for many events imply source depths less than 2 km the short period p waveform contains the best depth estimator in the form of sp so that depth can be estimated to within an uncertainty of about 1 km for most events the foreshocks cluster at less than 2 km depth and most aftershocks occur within 1 km of the surface a few aftershocks occur as deep as 7 km these results are consistent with a previous teleseismic waveform study in which faulting was inferred to start near the surface at 1 5 km depth with rupture proceeding downward and not exceeding 6 km depth these results coupled with previous stress studies in the australian shield and models of crustal strength show that faulting in a cold shield area is a near surface phenomenon and implies that most of the crust is too strong to be fractured

thermal rheological and kinematic conditions for channelized lower crustal flow in a threshold example abstract lower crustal flow zones occur in large and hot orogens and rifts where they occur in association with large areas possessing high gravitational potential energy gpe and low lower crust viscosity lower crustal flow zones are also known from regions where neither the rheological nor gpe conditions are sufficiently well developed for widespread flow to occur for these examples the conditions required to form crustal flow zones are less well defined one such case occurs within the ca 600 530 ma petermann orogeny in central australia this work investigates the conditions under which this flow zone developed considering differences with the adjacent regions where flow is not observed a transect of crustal structure in the central petermann orogen is developed that takes into account geological and geophysical data including time constrained pressure and temperature estimates for the petermann orogeny the deformation of this region is reconstructed showing that lower crustal flow was driven by high amplitude crustal scale folding the folding extruded the lower crust towards the foreland causing crustal thickening and buoyant uplift of the orogenic core channelized lower crustal flow is not known from either the eastern or western parts of the orogen and a comparison with these regions suggests three main conditions are required firstly the lower crust must be sufficiently hot and volatile rich to allow melt weakening secondly crustal rheology must allow ductile deformation of the mid to lower crust without high strength layers finally a high degree of lateral confinement is required to form pressure gradients capable of driving flow these three conditions were met only in the central petermann orogen and not in the east or the west this example of a lower crustal flow zone illustrates the combined influence of thermal rheological and kinematic threshold conditions on the initiation and development of channelized lower crustal flow in orogens

sulfur speciation in the upper black sea sediments abstract we report solid phase sulfur speciation of six cores from sediments underlying oxic suboxic and anoxic sulfidic waters of the black sea our dataset includes the five sulfur species pyrite sulfur acid volatile sulfides avs zerovalent sulfur s 0 organic polysulfides rsx humic sulfur together with reactive iron and manganese as quantified by dithionite extraction and total organic carbon pyrite sulfur was the major phase in all cores 200 400 mol g dry wt 1 except for the suboxic core however zerovalent sulfur and humic sulfur also reached very significant levels up to about 109 and 80 mol g dry wt 1 respectively humic sulfur enrichment was observed in the surface fluff layers of the eastern central basin sediments where unit 1 type depositional conditions prevail elemental sulfur accumulated as a result of porewater sulfide oxidation by reactive iron oxides in turbidities from the anoxic basin margin and western central basin sediments the accumulation of elemental sulfur to a level close to that of pyrite s in any part of central black sea sediments has never been reported before and our finding indicates deep basin turbidites prevent the build up of dissolved sulfide in the sediment this process also contributes to diagenetic pyrite formation whereas in the non turbiditic parts of the deep basin water column formed syngenetic pyrite dominates the sulfur inventory in slope sediments under suboxic waters organic sulfur humic sulfur organic polysulfides account for 33 42 of total solid phase s indicating that the suboxic conditions favor organosulfur formation our study shows that the interactions between depositional patterns unit 1 vs turbidite redox state of overlying waters oxic suboxic sulfidic and organic matter content determine sulfur speciation and enable the accumulation of elemental sulfur and organic sulfur species close to a level of pyrite s

focal depths for small to moderate earthquakes mn 2 8 in western quebec southern ontario and northern new york regional depth phase modeling is a useful technique to constrain earthquake focal depths for events within sparse networks we demonstrate how regional depth phases can be used to obtain focal depths for hundreds of earthquakes with m n 2 8 that occurred from 1980 to 2004 in southern ontario western quebec and northern new york state we discuss the development of regional depth phases with distance their use in focal depth determinations by matching waveforms to synthetics and possible sources of error in general focal depths can be determined to within about 3 km when there is at least one record at regional distances with clearly identifiable depth phases such as spmp or spg in southwestern ontario and northern new york focal depths range from 2 to 15 km in areas of western quebec and along the ottawa river valley in ontario focal depths range from 2 to 25 km more than half of the earthquakes in a cluster of activity near maniwaki in western quebec are deeper than 20 km all earthquakes deeper than 20 km occurred north of about 45 3 n there is an intriguing tendency for earthquake depths to cluster near 8 km 12 km 15 km and 22 km another interesting observation is that there are several earthquake pairs or small groups with very similar epicenters but quite different depths the most active regions in western quebec and along the ottawa river valley tend to exhibit a relatively wide range of focal depths along broad zones that trend roughly northwest suggesting that seismicity is occurring along diffuse northwest trending faults throughout the crust the wide range of focal depths may indicate the potential for a larger maximum scale of fault rupture and serve as a contemporary marker of locations where large events have occurred in the recent geologic past

geochemistry of vent fluid particles formed during initial hydrothermal fluid seawater mixing along the mid atlantic ridge we present geochemical data of black smoker particulates filtered from hydrothermal fluids with seawater dilutions ranging from 0 99 results indicate the dominance of sulphide minerals fe cu and zn sulphides in all samples taken at different hydrothermal sites on the mid atlantic ridge pronounced differences in the geochemistry of the particles between logatchev i and 5 s hydrothermal fields could be attributed to differences in fluid chemistry lower metal sulphur ratios me h2s 1 compared to logatchev i result in a larger amount of particles precipitated per liter fluid and the occurrence of elemental sulphur at 5 s while at logatchev i fe oxides occur in larger amounts systematic trends with dilution degree of the fluid include the precipitation of large amounts of cu sulphides at a low dilution and a pronounced drop with increasing dilution moreover fe sulphides or oxides precipitation increases with dilution of the vent fluid by seawater geochemical reaction path modeling of hydrothermal fluid seawater mixing and conductive cooling indicates that cu sulphide formation at logatchev i and 5 s mainly occurs at high temperatures and low dilution of the hydrothermal fluid by seawater iron precipitation is enhanced at higher fluid dilution and the different amounts of minerals forming at 5 s and logatchev i are thermodynamically controlled larger total amounts of minerals and larger amounts of sulphide precipitate during the mixing path when compared to the cooling path differences between model and field observations do occur and are attributable to closed system modeling to kinetic influences and possibly to organic constituents of the hydrothermal fluids not accounted for by the model

volcanic eruption of the mid ocean ridge along the east pacific rise crest at 9 45 52 n direct submersible observations of seafloor phenomena associated with an eruption event in april 1991 in april 1991 we witnessed from the submersible alvin a suite of previously undocumented seafloor phenomena accompanying an in progress eruption of the mid ocean ridge on the east pacific rise crest at 9 45 n 52 n the volume of the eruption could not be precisely determined although comparison of pre and post eruption seabeam bathymetry indicate that any changes in ridge crest morphology resulting from the eruption were 10 m high effects of the eruption included 1 increased abundance and redistribution of hydrothermal vents disappearance of numerous vent communities and changes in characteristics of vent fauna and mineral deposits within the eruption area since december 1989 2 murkiness of bottom waters up to tens of meters above the seafloor due to high densities of suspended mineral and biogenic particulates 3 destruction of a vent community by lava flows mass wasting and possible hydrovolcanic explosion at a site known as tubeworm barbecue in the axial summit caldera asc at 9 50 6 n 4 near critical temperatures of hydrothermal vent fluids ranging up to 403 c 5 temporal variations over a 2 week interval in both temperatures and chemical isotopic compositions of hydrothermal fluids 6 unusual compositions of end member vent fluids with ph values ranging to a record low of 2 5 salinities ranging as low as 0 3 wt nacl one twelfth that of seawater and dissolved gases reaching high concentrations 65 mmol l for both co2 and h2s 7 venting at temperatures above 380 c of visually detectable white vapor that transformed to plumes of gray smoke a few centimeters above vent orifices 8 disorganized venting of both high temperature fluids black and gray smoke and large volumes of cooler diffuse hydrothermal fluids directly from the basaltic seafloor rather than from hydrothermal mineral constructions 9 rapid and extensive growth of flocculent white bacterial mats species unknown on and under the seafloor in areas experiencing widespread venting of diffuse hydrothermal fluid and 10 subseafloor downslope migration of magma normal to the ridge axis in a network of small scale 1 5 m diameter lava tubes and channels to distances at least 100 200 m outside the asc we suggest that in april 1991 intrusion of dikes in the eruption area to 200 m beneath the asc floor resulted in phase separation of fluids near the tops of the dikes and a large flux of vapor rich hydrothermal fluids through the overlying rubbly cavernous lavas low salinities and gas rich compositions of hydrothermal fluids sampled in the eruption area are appropriate for a vapor phase in a seawater system undergoing subcritical liquid vapor phase separation boiling and phase segregation hydrothermal fluids streamed directly from fissures and pits that may have been loci of lava drainback and or hydrovolcanic explosions these fissures and pits were lined with white mats of a unique fast growing bacteria that was the only life associated with the brand new vents the prolific bacteria which covered thousands of square meters on the ridge crest and were also abundant in subseafloor voids may thrive on high levels of gases in the vapor rich hydrothermal fluids initially escaping the hydrothermal system white bacterial particulates swept from the seafloor by hydrothermal vents swirled in an unprecedented biogenic blizzard up to 50 m above the bottom the bacterial proliferation of april 1991 is likely to be a transient bloom that will be checked quickly either by decline of dissolved gas concentrations in the fluids as rapid heat loss brings about cessation of boiling and or by grazing as other organisms are re established in the biologically devastated area

early diagenesis of iron and sulfur in bornholm basin sediments the role of near surface pyrite formation abstract pyrite formation in marine sedimentary environments plays a key role in the global biogeochemical cycles of carbon sulfur and iron regulating earth s surface redox balance over geological time scales the sulfur isotopic composition of pyrite is one of the major geochemical tools for investigating early diagenetic processes in modern marine sediments and substantive changes to the earth s surface environment in ancient sedimentary rocks we studied sulfur iron diagenesis and the sulfur isotopic evolution in sediments of the bornholm basin southwestern baltic sea to track the formation of pyrite in the near surface sediments pyrite accumulation is observed with depth over the uppermost 100 cm before the extent of pyritization of the highly reactive iron pool fepy fehr stays constant at ca 0 9 suggesting that the use of a single iron speciation parameter as a proxy for anoxic and sulfidic conditions needs to be supported by other independent indicators in sedimentary records stable sulfur isotopic analysis demonstrates that the bulk pools of elemental sulfur and iron monosulfide do not exchange isotopes completely with aqueous sulfide we suggest that the reactions with polysulfide and aqueous sulfide are probably restricted to the surface of the solid phase sulfur and iron sulfur aggregates although pyrite is growing throughout the uppermost sediment column the pyrite at depth has a sulfur isotopic composition similar to that of pyrite formed near the sediment surface to understand the isotopic discrepancy between pyrite and aqueous sulfide in the deeper sediments we developed a simple diagenetic model which reproduces the observed sulfur isotopic composition of pyrite well our results suggest that much of the pyrite is rapidly formed near the sediment water interface and its 34s is not as influenced by the 34s enriched pool of aqueous sulfide in the deeper part of the sediment allowing 32s enriched pyrite to be preserved in deeper sediments this near surface diagenesis and the associated isotopic pattern are possibly of relevance for many marine sediments with high organic matter content and high aqueous sulfide but low reactive iron availability moreover our sulfur isotopic data demonstrate that extremely slow pyritization is ongoing in the deep lacustrine clay sediments these results have implications for the interpretation of sulfur iron geochemical data in both modern and ancient settings as well as for improving reconstructions of ancient depositional environments and a better understanding of the marine sulfur cycle throughout earth s history

nanoparticulate pyrite and other nanoparticles are a widespread component of hydrothermal vent black smoker emissions abstract the presence of nanoparticulate pyrite is reported in hydrothermal emissions from rainbow tag and snakepit on the mid atlantic ridge mar when coupled with previously collected data from east pacific rise 9 n epr and lau basin these data demonstrate that pyrite nanoparticles are a widespread component of black smoker emissions from hydrothermal vents and are found in significant concentrations at a fast spreading mid ocean ridge epr a back arc basin lau basin and a slow spreading mid ocean ridge mar the maximum percentage of filtered iron emitted as nanoparticulate pyrite was found to be as high as 25 10 and 5 respectively as a widespread component of hydrothermal vent emissions these nanoparticles may be an important source of iron to the world s oceans metals such as cu and zn are detected in pyrite containing aggregates at all sites and chalcopyrite was a component of nanoparticle aggregates at mar iron containing silicate nanoparticles are also identified and indicate that nanoparticles other than sulfides should also be considered when determining transport implications of hydrothermal vent emissions the varied morphologies and the presence of different minerals within these nanoparticles provide insight into their formation and stability

microorganisms in deep sea hydrothermal plumes the study of hydrothermal vents at oceanic spreading centres has led to a re evaluation of some basic tenets concerning energy flux through oceanic ecosystems and the sources and sinks for dissolved ions in sea water hydrothermal vents vary considerably from relatively low temperature 25 c fluid discharges to the spectacular high temperature 350 c black smokers1 3 the high temperature vents give rise to buoyant plumes which can be detected hundreds of kilometres away from ridge crests4 5 in the immediate vicinity of hydrothermal vents chemoautotrophic bacteria are present in vent fluids6 8 attached to rock surfaces9 10 and as endosymbionts in certain macro fauna11 deep sea hydrothermal plumes have not as yet been examined for the presence of bacteria we now report the presence of elevated bacterial biomass in a hydrothermal plume originating from the juan de fuca ridge and discuss the potential geochemical significance of these microorganisms

trace metal concentration and partitioning in the first 1 5 m of hydrothermal vent plumes along the mid atlantic ridge tag snakepit and rainbow abstract to determine the significance of metal fluxes from hydrothermal vents understanding the speciation reactivity and possible transformations of metals and metal sulfides within the hydrothermal plume is critical in this study we measure the concentration and partitioning of trace metals fe mn cu cd co pb ni and sulfide phases within the first 1 5 m of the rising plume at three vent fields tag snakepit and rainbow along the mid atlantic ridge a hcl hno3 leaching method was used to differentiate metals present in metal mono sulfides from those in pyrite and chalcopyrite at all three vent sites mn and fe are primarily in the

the rainbow vent fluids 36 14 n mar the influence of ultramafic rocks and phase separation on trace metal content in mid atlantic ridge hydrothermal fluids fluids were collected from the rainbow vent field 36 14 n on the mid atlantic ridge mar during the 1997 diving flores cruise this vent field in ultramafic rocks at a depth of 2300 m is composed of 10 black smokers emitting acidic ph 2 8 fluids at 365 c the low ph of the hot temperature rainbow fluids likely results from seawater ultramafic rock interaction that releases h ions into reducing hydrothermal fluids fluid chemistry is strongly influenced by phase separation generating cl rich brines clem 750 mm strongly enriched with mn fe co ni cu zn ag cd cs pb y and rare earth elements ree ree and transition metal abundance particularly fe and mn in the rainbow fluids is dramatically higher than in other mar fluids the abundance of trace element and ree enrichment is due to the greater solubility of these elements that is strongly favored by cl complexation at low ph and high temperature conditions chondrite normalized ree patterns show strong lree enrichment with evidence of the typical eu anomaly this ree partitioning suggests that either 1 ultramafic rocks represent only a part of rocks leached during hydrothermal alteration and or 2 that the unique rainbow fluid temperature ph and redox state issued from the ultramafic character of leached substratum can produce unique ree partitioning

comparison of pyrite fes2 synthesis mechanisms to reproduce natural fes2 nanoparticles found at hydrothermal vents abstract here we report the synthesis of pyrite in micrometer and nanometer sizes and with varied morphology the purpose of these syntheses was to mimic natural pyrite nanoparticles recently found at hydrothermal vents and to better understand the formation processes of these nano and micrometer sized particles the duration of synthesis surfactant used and chemical mechanism of pyrite formation were all found to have an effect on resultant size and morphology yields of pyrite were sometimes low as our goal was to stop growth quickly after nucleation in order to mimic hot vent fluids 350 c emanating to cold ocean bottom waters 2 c natural nanoparticles forming under these conditions have currently been identified at diverse hydrothermal vents including lau basin the mid atlantic ridge mar and the east pacific rise epr these natural nanoparticles were variable in size and morphology with aggregates of 50 350 nm diameter being the most prevalent syntheses occurring via the h2s pathway mimicked natural nanoparticles more closely than syntheses via the polysulfide pathway one synthesis reported is suggestive of a pyrite pyrrhotite equilibrium indicating that we have succeeded in mimicking redox conditions similar to those that occur at certain hydrothermal vents