controls on the siting and style of volcanogenic massive sulphide deposits abstract volcanogenic massive sulphide vms deposits form in subaqueous environments from circulating hydrothermal fluids heated by volcanic activity these deposits form as sulphide mounds stratiform exhalative and or replacive bodies and commonly have stockwork vein mineralization in their immediate footwall these various styles are essentially facies of mineralization each one being the product of a particular set of conditions that control the ore forming processes and the consequent geometry and architecture style of the deposits these controls include the physical and or chemical nature of the host rocks the temperature and composition of the hydrothermal fluids and the redox state of the depositional environment the style of exhalative deposits is controlled by the salinity of the vented fluids and the redox state at the seafloor hydrothermal fluids with salinities less than twice that of seawater that vented into open oxic oceanic environments typically formed small mound and chimney complexes unless they were rapidly covered by sediments or volcanic rocks the massive sulphides were rapidly oxidized and partly dissolved by seawater in contrast stratiform sheet like deposits are typically formed in anoxic bottom waters anoxic marine conditions were periodically of global extent particularly prior to 2 4 ga or of a regional nature local anoxic conditions can also be self induced by the exhalation of saline and reducing hydrothermal fluids that ponded in bathymetric depressions such as second or third order basins to form a brine pool these exhalative systems may have been initiated as chimney vent complexes and subsequently overlain by stratiform sulphides formed under the self induced anoxic conditions deposits formed in anoxic environments can be significantly larger than those in oxic settings and this is attributed to several factors that include longer lived hydrothermal circulation more efficient sulphide precipitation and reduced or inhibited oxidation thereof replacement of volcanic and sedimentary strata by sulphide typically occurs within the feeder zones beneath the exhalative mineralization however successions with abundant porous permeable and or reactive rocks such as glassy and or pumiceous volcaniclastic rocks and in some cases limestone favoured the development of large replacive deposits that may have had little surficial expression on the sea floor vms deposits at spreading centres within oceanic crust formed almost exclusively as mounds most of them have not been preserved likely due to oxidation of the sulphides in the prevailing oxic environment and or destruction of oceanic crust during subsequent subduction intra continental rifts arc rifts and back arc rifts commonly have more complexity in their structure and facies architecture and environments and can host all styles of vms mineralization in these settings early extension favoured the formation of restricted basins with ideal conditions for the onset of hydrothermal activity and development of anoxic bottom waters whereas in mature rifts the conditions were less conducive for the formation of regionally extensive anoxic environments formation of replacive deposits was permissible in all settings with porous or reactive subsea floor strata replacive mineralization is the most likely to be preserved in the geological record due to the sulphides being physically shielded from oxidative weathering and mechanical erosion at the seafloor the various styles of vms mineralization can rarely be distinguished using a single criterion in most cases multiple criteria are required mound style mineralization is distinguished by a mound or lens shaped morphology b presence of chimney fragments c presence of abundant sedimented sulphide breccias d location on a stratigraphic boundary ore horizon and e association with a thin horizon or thicker stratigraphic interval of fine grained clastic rocks e g shale mudstone that accumulated at slow sedimentation rates stratiform exhalative mineralization is distinguished by a sheet like morphology prior to deformation b presence of fine grained clastic host rocks that accumulated at relatively slow rates e g mudstone c presence of local or extensive planar stratification replacive mineralization is characterized by a irregular geometry and distribution of sulphide bodies b gradation from massive sulphides to semi massive sulphides and disseminated mineralization with relict textures of the host rock and c originally pumiceous glassy or reactive host rocks emplaced at high depositional rates mass flow deposits lavas carbonate altered mass flow deposits or limestone one deposit or district may comprise two or more of these main styles of mineralization in many cases the main styles of vms mineralization present in a particular region can be predicted from examination of the facies architecture and depositional environments of the host succession recognition of the style s of mineralization that occur in a particular basin or mineral belt enables exploration models to be improved and should influence the strategy of exploration for vms deposits

a laboratory and theoretical study of the growth of black smoker chimneys abstract observational evidence suggests that black smoker chimneys are formed by the precipitation of anhydrite from seawater producing a solid framework which is replaced successively by iron zinc and copper sulfides we have demonstrated the feasibility of this process using a laboratory model in which kno3 is first crystallized from a warm nearly saturated solution round an inflowing plume of cold k2co3 the chimney grows in length at a nearly constant rate and at the same time it thickens as heat conduction causes further crystallization the dynamic replacement process has been modelled separately with cuso4 passed through a previously formed chimney of kno3 and flowing out through the porous walls when the flow rate and hence the pressure difference is increased the formation of chimneys at a line or slit source has also been investigated in the laboratory it has been shown that in this case the slit is quickly blocked off by crystallization over most of its length and that the growth is concentrated at just a few points to form a small number of nearly axisymmetric chimneys a theory has been developed which predicts both the diameter of the outlet vent and the sign of the pressure difference between the inside and the outside of an axisymmetric chimney of constant internal diameter for a specified flow rate and density difference it suggests that changes in flow rate or in the internal diameter of the chimney can cause fluid to flow in or out through the porous wall leading to changes in the position of mineral stability fields within the evolving chimney the theory has been extended to describe the pressure distribution in tapering interior conduits and it leads to the conclusion that the direction of flow through a porous chimney can reverse along its length

new mineral occurrences and mineralization processes wuda coal fire gas vents of inner mongolia five unique mineral assemblages that include the sulfates millosevichite alunogen anhydrite tschermigite coquimbite voltaite and godovikovite as well as the halide salammoniac and an unidentified phase according to x ray diffraction and eds data were found as encrustations on quartzofeldspathic sand and sandstone adjacent to coal fire gas vents associated with underground coal fires in the wuda coalfield of inner mongolia the mineral assemblage of alunogen coquimbite voltaite and the unidentified phase collected from the same gas vent is documented for the first time coquimbite also occurs as rosettes secondarily nucleated on a cryptocrystalline mass of alunogen coquimbite voltaite and the unidentified phase during storage in a sealed container at room temperature field observations analyses of vent gases sem images and mineral compositions suggest that the sulfates millosevichite alunogen coquimbite voltaite godovikovite and the unidentified phase crystallized in response to a complex sequence of processes that include condensation hydrothermal alteration crystallization from solution fluctuating vent temperatures boiling and dehydration reactions whereas the halide salammoniac crystallized during the sublimation of coal fire gas tschermigite and anhydrite formed by the reaction of coal fire gas with quartzofeldspathic rock or by hydrothermal alteration of this rock and crystallization from an acid rich aqueous solution variations in the mineral assemblages found at five gas vents are possibly due to differences in coal bed chemistry exchange reactions involving coal fire gas and the composition of sediment rock and aqueous solutions prior to the exhalation of gas at the surface as well as the temperature and cooling rate at a vent few studies have addressed the interaction of coal fire gas with sediment rock and aqueous solutions and the subsequent mineralization processes coal fires present opportunities for discovering rare and new mineral occurrences these minerals have potentially important environmental significance and may be vectors for the transmission of toxins coal fires also provide insight for the recognition in the geologic record of preserved mineral assemblages that are diagnostic of ancient fires

mineralization of an intra oceanic arc in an accretionary orogen insights from the early silurian honghai volcanogenic massive sulfide cu zn deposit and associated adakites of the eastern tianshan nw china the honghai volcanogenic massive sulfide vms deposit occurs in the kalatage inlier of the dananhu haerlik arc eastern tianshan in the southern altaids the deformed deposit hosted in a suite of early paleozoic basic to intermediate volcanic volcaniclastic and sedimentary rocks consists of lenticular massive to semimassive and sulfide silicate stockwork orebodies the orebodies are characterized by zoning of metallogenic elements and sulfide minerals outward from a central stockwork zone as follows fe cu fe cu zn au ag cu zn fe zn cu au ag zn cu and fe cu zn a typical vms hydrothermal alteration zone that formed around the foot of the massive orebodies is several times larger than the lenticular massive orebody the hydrothermally altered rocks contain sericite chlorite and epidote zones from the core outward re os and argon dating of pyrite and sericite shows that the honghai vms deposit formed in the early silurian 436 2 ma and was deformed in the early devonian 410 4 ma this is the first documented early paleozoic vms deposit in the eastern tianshan our multidisciplinary data indicate that the honghai cu zn deposit formed in an immature nascent island arc where early tholeiitic lavas evolved into transitional basic andesitic volcanic rocks and calc alkaline intrusions with relatively high epsilon nd t values 6 2 8 4 and low sr 87 sr 86 i ratios 0 70412 0 70541 the sr nd pb s isotopic and geochemical data suggest that the ore forming melts started in mantle derived volcanic rocks and deep subvolcanic intrusions and some alteration was influenced by seawater the deposit formed in a high level subvolcanic intrusion driven by sub seafloor co2 rich nacl cacl2 h2o hydrothermal fluids temperatures 99 377 degrees c salinities 6 18 nacl equivalent circulating in active extensional faults in a submarine caldera extension of the immature nascent intra oceanic arc was one of the important factors that controlled the development and preservation of the vms deposit future work will benefit from this improved understanding of the vms deposits formed in immature nascent intra oceanic arcs especially in early paleozoic island arcs in the eastern tianshan in the southern altaids

tidal correction of topex poseidon altimetry for seasonal sea surface elevation and current determination off the pacific coast of canada altimetry from the topex poseidon satellite is analyzed for the waters off british columbia canada tides are removed using harmonic constants from two coastal and two global models and the accuracy of this detiding is assessed by using these same models and one digital filter to remove the tide from the time series of three representative coastal tide gauges it is demonstrated that inaccurate m2 s2 and k1 tide removal from topex poseidon altimetry can introduce systematic biases to the calculation of seasonally averaged fields average summer and winter sea surface heights are calculated from the detided altimetry and estimates of their accuracy nearshore are computed using concurrent time series from 11 tide gauges finally these seasonal elevations are blended with those from the 11 tide gauges and the associated surface currents are calculated using a diagnostic finite element model these currents are compared with those calculated from historical conductivity and temperature versus depth measurements and those measured by historical near surface current meters

polymetallic sulfide exploration on the deep sea floor the feasibility of the mini moses experiment the recent discoveries of polymetallic sulfide deposits on the deep sea floor have created an interest in geophysical techniques for mapping them a magnetometric resistivity method mini moses has been developed for detecting the distribution of sub sea floor electrical resistivity a vertical long wire bipole feeds electric current into the ocean some of the current enters the sea floor and its magnetic field is measured at various distances by a low frequency induction coil magnetometer the method is sensitive to conductive and resistive zones at depth and information about three dimensional resistivity structures can be obtained the small load resistance of an electric transmitter grounded in the ocean allows high current to be driven by a battery powered instrument the induction coil receiver is more sensitive and less noisy than conventional flux gate magnetometers over the selected frequency band this receiver is therefore well adapted to the almost noise free deep sea floor environment b

eddy shedding from a boundary current around a cape over a sloping bottom abstract the authors discuss laboratory experiments that elucidate the mechanism of formation and westward drift of anticyclonic baroclinic vortices from a buoyant surface current flowing along a lateral boundary and around a cape experiments were carried out with a sloping bottom in order to simulate the topographic effect they showed how a vortex can be generated from the current where it separates and reattaches to the cape and that under some conditions the eddy is able to detach from the cape and drift westward following isobaths two important timescales regulate the flow the time tf that the current takes to generate a vortex and the time td that the vortex takes to drift westward for a distance equal to its radius when these two timescales are either of the same order of magnitude or tf td the vortex was able to form at the cape but it did not detach and drift westward the influence of the depth of the lower layer h0 on the flo

simulation of barotropic and baroclinic tides off northern british columbia abstract the tidal response of northern british columbia coastal waters is studied through simulations with a three dimensional prognostic primitive equation model the model is forced at the boundaries with the leading semidiurnal and diurnal constituents and experiments with stratified and homogeneous fluid are compared the barotropic response shows good agreement with previously published studies of tides in the region a comparison with tide gauge measurements indicates that average relative rms differences between observations and the model surface elevation field are less than 5 for the largest constituents an internal tide is generated in cases where the model is initialized with a vertical stratification diagnostic calculations of the baroclinic energy flux are used to identify regions of generation and propagation of internal tidal energy with a representative summer stratification the integrated offshore flux is about 0 5 gigawatts higher than previously estimated from theoretical model

seasonal and interannual variability in along slope oceanic properties off the us west coast inferences from a high resolution regional model a 6 year 2009 2014 simulation using a 2 km horizontal resolution ocean circulation model of the northeast pacific coast is analyzed with focus on seasonal and interannual variability in along slope subsurface oceanic properties specifically the fields are sampled on the isopycnal surface 26 5 kg m 3 that is found between depths of 150 and 300 m below the ocean surface over the continental slope the fields analyzed include the depth z26 5 temperature t26 5 along slope currents 26 5 and the average potential vorticity pv between 26 5 and 26 25 kg m 3 each field is averaged in the cross shore direction over the continental slope and presented as a function of the alongshore coordinate and time the seasonal cycle in z26 5 shows a coherent upwelling downwelling pattern from mexico to canada propagating to the north with a speed of 0 5 m s 1 the anomalously deep 20 m z26 5 displacement in spring summer 2014 is forced by the southern boundary condition at 24 n as a manifestation of an emerging strong el nino the seasonal cycle in t26 5 is most pronounced between 36 53 n indicating that subarctic waters are replaced by warmer californian waters in summer with the speed close 0 15 m s 1 which is consistent with earlier estimates of the undercurrent speed and also present 26 5 analyses the seasonal patterns and anomalies in z26 5 and t26 5 find confirmation in available long term glider and ship borne observations the pv seasonality over the slope is qualitatively different to the south and north of the southern edge of heceta bank 43 9 n

coastal countercurrent and mesoscale eddy formation by tidal rectification near an oceanic cape abstract cape st james is an extensive triangular shaped promontory located in a tidally energetic region at the southern tip of the queen charlotte islands approximately 150 km off the mainland coast or british columbia several years of oceanographic data collected in vicinity of the cape reveal a regional circulation characterized by a strong 0 50 m s 1 coastal current along the western continental margin and respective clockwise and counterclockwise rotating mesoscale baroclinic eddies to the west and south of the cape the coastal current flows counter to the prevailing winds while the anticyclonic eddy to the west of the cape is a particularly intense feature that appears consistently in avhrr imagery of the region the structure of the mean flow combined with the marked o 0 1 0 m s 1 low frequency current variability at fortnightly and monthly tidal periods plus significant coherence at fortnightly periods between low frequency currents and demodulated tidal flow suggests that rectification o

active and relict sea floor hydrothermal mineralization at the tag hydrothermal field mid atlantic ridge the tag hydrothermal field is a site of major active and inactive volcanic hosted hydrothermal mineralization in the rift valley of the slow spreading mid atlantic ridge at 26 degree n the axial high is the principal locus of present magmatic intrusions the tag field contains three main areas of present and past hydrothermal activity 1 an actively venting high temperature sulfide mound 2 two former high temperature vent areas 3 a zone of low temperature venting and precipitation of fe and mn oxide deposits the volcanic centers occur at the intersections between ridge axis parallel normal faults and projected axis transverse transfer faults the intersections of these active fault systems may act as conduits both for magmatic intrusions from sources beneath the axial high that build the volcanic centers and for hydrothermal upwelling that taps the heat sources radiometric dating of sulfide samples and manganese crusts in the hydrothermal zones and dating of sediments intercalated with pillow lava flows in the volcanic center adjacent to the active sulfide mound indicate multiple episodes of hydrothermal activity throughout the field driven by heat supplied by episodic intrusions over a period of at least 140 times 10 sup 3 yr the sulfide deposits are built by juxtaposition and superposition during relatively long residence times near episodic axial heat sources counterbalanced by mass wasting in the tectonically active rift valley of the slow spreading oceanic ridge hydrothermal reworking of a relict hydrothermal zone by high temperature hydrothermal episodes has recrystallized sulfides and concentrated the first visible primary gold reported in a deposit at an oceanic ridge

anomalous eddy heat and freshwater transport in the gulf of alaska characteristics of eddies in the gulf of alaska are assessed from january 2003 through april 2012 ensemble statistics for eddy subsurface water properties on isopycnals are computed using temperature and salinity profiles from argo profiling floats located within eddies which are identified in sea surface height using objective techniques ninety cyclonic and 154 anticyclonic eddies are identified during this period the anticyclonic eddies are strongly nonlinear and exhibit significant warm subsurface temperature anomalies and associated salty anomalies on isopycnals while no clear distinguishing subsurface anomalies on isopycnals are detected in association with the cyclonic eddies heat and freshwater fluxes for the eddies are estimated from integrations in depth coordinates the anticyclonic eddies transport heat both westward off the continental shelf into the subarctic gyre and westward within the alaskan stream however they transport salt into the subarctic gyre and freshwater within the alaskan stream in both pathways eddy heat and freshwater transport show possible year to year fluctuations varying from 0 to 50 4 1018 j a 1 and 16 8 to 7 4 km3 a 1 respectively the anticyclonic eddies are capped by relatively fresh water year round

impact of haida eddies on chlorophyll distribution in the eastern gulf of alaska mesoscale haida eddies influence the distribution of surface phytoplankton in the eastern gulf of alaska through two processes enhanced productivity in central eddy water and seaward advection of highly productive coastal waters in the outer rings of eddies these two processes were observed in a sequence of monthly images over five years for which images of seawifs derived chlorophyll distributions were overlaid by contours of mesoscale sea surface height anomaly derived from topex and ers 2 satellite observations satellite measurements were supplemented with ship based chlorophyll observations through one of the eddies haida eddies are deep anticyclonic mesoscale vortices that normally form in winter and early spring near the southwest coast of the queen charlotte islands high levels of chlorophyll observed in eddy centres indicated that they supported phytoplankton blooms in spring of their natal years with timing of these blooms varying from year to year and exceeding in magnitude the chlorophyll concentrations of surrounding water elevated chlorophyll levels also were observed in eddy centres in late summer and early autumn of their natal year enhanced chlorophyll biomass is attributed to higher levels of macro nutrients and higher levels of iron enclosed within eddies than in surface deep ocean water by late spring and summer when coastal water supported higher chlorophyll biomass than did oceanic offshore regions eddies that straddled the continental margin entrained high chlorophyll coastal water into their outer rings and carried it several hundred kilometres into the gulf of alaska along their southern sides on some occasions a deep ocean eddy would entrain chlorophyll from an adjacent eddy located closer to the coast forming a conveyor belt transport process to inject coastal biota into the deep sea region of the gulf this process extended the coastal region of high chlorophyll surface water and therefore phytoplankton rich water several hundred kilometres seaward and dominated the shelf to deep ocean exchange of chlorophyll from late winter to the following autumn

laboratory models of growing flanges and a comparison with other growth mechanisms of black smoker chimneys the first measurements of the structure of black smoker chimneys suggested that they form initially by the precipitation of anhydrite from seawater because of the reverse solubility effect due to the heating of its surroundings by the effluent rather than directly from the less dense hot plume this initial growth is followed by replacement of the solid anhydrite framework successively by iron zinc and copper sulfides more recent observations of very large chimneys have shown that later precipitation directly from the plume can occur through the growth of flanges or large horizontal protrusions at the side of the chimneys light sulfide rich fluid leaking out of holes in the chimney wall ponds under these flanges which grow as the hot fluid percolates through the porous top or flows over their nearly horizontal edges and precipitates as it cools both of these processes have been demonstrated in laboratory models using the crystallization of solutes such as kno3 and na2co3 which have a strong dependence of solubility on temperature crystallization from the surroundings can be produced using an inflowing plume of cold k2co3 into a warm nearly saturated kno3 solution and in this case an axisymmetric chimney grows in length at a nearly constant rate and at the same time thickens as further crystallization takes place further experiments in which the inflowing k2co3 was constrained to spread horizontally near the source produced a cluster of chimney structures the first experiments demonstrating the second mechanism the process of crystallization directly from the incoming fluid were reported in the context of replenished magma chambers when dense saturated kno3 is injected slowly into cold surroundings some of the incoming fluid is quenched while the rest is forced upwards to form columns with a flat top these grow upwards as the gravitationally constrained fluid flows over the lip cooling and crystallizing as it does so in the new laboratory experiments reported here the same physical effects are observed in a more appropriate flange geometry if a small deflector plate is provided to produce an initial horizontal flow of the nearly saturated kno3 solution growing flanges have also been produced on the outer face of an existing crystal column in a geometry which is directly applicable to black smoker chimneys

formation of volcanogenic massive sulfide deposits the kuroko perspective abstract the main objective of this paper is to identify the geochemical hydrological igneous and tectonic processes that led to the variations in the physical size geometry and chemical mineralogy metal ratios and zoning characteristics of volcanogenic massive sulfide deposits with respect to space from a scale of mining district size area to a global scale and time from a all volcanogenic massive sulfide deposits vmsds appear to have formed in extensional tectonic settings such as at mid ocean spreading centers backarc spreading centers and intracontinental rifts and failed rifts all vmsds appear to have formed in submarine depressions by seawater that became ore forming fluids through interactions with the heated upper crustal rocks submarine depressions especially those created by submarine caldera formation and or by large scale tectonic activities e g rifting become most favorable sites for the formation of large vmsds because of hydrological physical and chemical reasons the fundamental processes leading to the formation of vmsds include the following six processes 1 1 intrusion of a heat source typically a 10 3 km size pluton into an oceanic crust or a submarine continental crust causes deep convective circulation of seawater around the pluton the radius of a circulation cell is typically 5 km the temperature of fluids that discharge on the seafloor increases with time from the ambient temperature to a typical maximum of 350 c and then decreases gradually to the ambient temperatures in a time scale of 100 to 10 000 years the majority of sulfide and sulfate mineralization occurs during the waxing stage of hydrothermal activity 2 2 reactions between low temperature t 2 4 as disseminated gypsum and anhydrite in the country rocks 3 3 reactions of the modified seawater with higher temperature rocks at depths during the waxing stage cause the transformation of the seawater to metal and h 2 s rich ore forming fluids the metals and sulfide sulfur are leached from the county rocks the previously formed gypsum and anhydrite are reduced by fe 2 bearing minerals and organic matter providing additional h 2 s the mass of high temperature rocks that provide the metals and reduced sulfur is typically 10 11 tons 40 km 3 in volume the roles of magmatic fluids or gases are minor in most massive sulfide systems except for so 2 to produce acid type alteration in some systems 4 4 reactions between the ore forming fluids and cooler rocks in the discharge zone cause alteration of rocks and precipitation of some ore minerals in the stockwork ores 5 5 mixing of the ore forming fluids with local seawater within unconsolidated sediments and or on the seafloor causes precipitation of primitive ores with the black ore mineralogy sphalerite galena pyrite barite anhydrite 6 6 reactions between the primitive ores with later and hotter hydrothermal fluids cause transformation of primitive ores to matured ores that are enriched in chalcopyrite and pyrite variations in the mineralogical and elemental characteristics the geometry and the size of submarine hydrothermal deposits are controlled by the following four parameters 1 a the chemical and physical characteristics of seawater composition temperature density which depend largely on the geographical settings e g equatorial evaporating basins 2 b the chemical and physical characteristics of the plumbing system lithology fractures 3 c the thermal structure of the plumbing system which is determined largely by the ambient geothermal gradient and the size and temperature of the intrusive and 4 d the physical characteristics of the seafloor depth basin topography for example the submarine hydrothermal deposits developed in basaltic plumbing systems are generally poor in pb and ba compared to those developed in felsic plumbing systems the lower temperature systems are generally poorer in sulfides but richer in iron oxides and sulfates the higher temperature and larger hydrothermal systems tend to produce chalcopyrite and pyrite rich ores contrasts in the metal ratios between the noranda type archean vmsds and the younger vmsds reflect the differences in the geothermal gradient of the plumbing systems the submarine hydrothermal deposits developed in the near equatorial regions tend to form large continuous bedded type ores because of the likeliness of creating large stratified basins the basic processes of submarine hydrothermal mineralization have remained essentially the same throughout the geologic history from at least 3 5 billion year ago to the present

zooplankton community composition along the inner portion of line p during the 1997 1998 el nino event the 1996 1999 zooplankton samples from oceanic waters off southern british columbia provide time series descrip tions of biomass and community composition before during and immediately after the 1997 1998 el nino event our most frequent sampling every month in 1998 and three to four times per year in other years was off southern van couver island and extended seaward from the shelf break to approximately 200 km offshore along and adjacent to the inner third of the long term line p station p section 48 30 49 n 126 130 40w el nino associated changes in the zooplankton community were most apparent over the shelf break and slope and weaker further offshore at the nearshore portion of this line p03 p06 the 1997 1998 differences from long term seasonal averages included both lower total biomass and shifts in community composition reduced abundance of endemic boreal temperate species increased abundance of mid california neritic and oceanic species toward the seaward end of the section p08 p12 changes of zooplankton species composition were much less apparent and the main signal associated with the 1997 1998 event was an early and narrow spring peak of neocalanus spp although most extreme in 1998 both the nearshore and offshore sets of anomalies were continuations of trends that had developed progressively off british columbia through the 1990s a few taxa normally endemic to southern parts of california current and previously absent or very rare off british columbia appeared in our samples in 1997 1998 and persisted through summer of 1998 and at some locations into 1999 the changes observed over the continental slope of vancouver island were very similar to the observations of 1970s versus late 1990s differences in the zooplankton of the central oregon coast continental shelf pices sci rep 10 1999 45 prog oceangr 2002 suggesting that there was alongshore continuity of both oceanic forcing and zooplankton response crown copyright 2002 published by elsevier science ltd all rights reserved

an atlantic hydrothermal plume trans atlantic geotraverse tag area mid atlantic ridge crest near 26 n the physical characteristics of an atlantic hydrothermal plume and its seafloor sources are described from the first data set of water column properties associated with a high temperature source area at a slow spreading oceanic ridge the observations comprise five near bottom tows of a camera color video and still temperature sensor array through the buoyant portion and 23 conductivity temperature depth ctd profiles through the neutrally buoyant portion of the plume made at the trans atlantic geotraverse hydrothermal field in the rift valley of the mid atlantic ridge at 26 08 n 44 49 w in july 1985 the source area is a mound up to 250 m wide and 50 m high constructed primarily of massive sulfides between depths of 3620 and 3670 m at the base of the east wall flow and discharge regimes systematically changed from the center to the edge of the mound high temperature black smokers vented at fast rates 1 m s from discrete sulfide chimneys and at slow rates from fractures and clear solutions vented at slow rates from diffuse sources in the inner zone of the mound intermediate temperature blue white and white smokers vented at slow rates from discrete sulfide sulfate chimneys and clear solutions vented from diffuse sources in the middle zone patchy diffuse discharge of clear solutions through sulfide talus occurred in the outer zone the diffuse discharge of clear solutions and the discrete discharge from the white smokers were observed to turbulently rise up to several meters above the seafloor where the discharge was laterally advected in prevailing laminar flow at several centimeters per second a convective heat flux of 8 8 106 w for only the black smokers that vented from fractures was estimated by applying a buoyant plume model to temperature anomalies measured with the towed array this value is intermediate between values estimated for entire vent fields at the fast spreading east pacific rise discharge from the black smokers rose to form the neutrally buoyant portion of the plume that was cold and fresh relative to surrounding seawater where it attained density equilibrium between 190 and 350 m above the mound in contrast hydrothermal plumes observed in the pacific were warm and salty relative to surrounding seawater the difference is attributed to the effect on plume density of entrainment during rise through opposite salinity profiles that decrease downward in the atlantic and increase downward in the pacific resulting in different temperature salinity compensations at neutral buoyancy the temperature difference between the neutrally buoyant portion of the plume and surrounding seawater negative for the atlantic positive for the pacific is not a unique function of convective heat flux from a source area as a consequence of both the effect of the entrainment of salinity on plume density and the separation of diffuse and discrete components of discharge the hydrothermal plume and the hydrothermal mound are inferred to have grown in size and complexity in response to the development of hydrothermal flow and discharge regimes for at least the past 104 years

pb in the pacmanus sea floor hydrothermal system eastern manus basin numerical modeling of a magmatic versus leached origin mass balance calculations of metal leaching and deposition in the pacmanus submarine hydrothermal vent field in the eastern manus basin in the bismarck sea off the east coast of papua new guinea indicate that simple leaching of the underlying volcanic pile by hydrothermal fluids cannot account for the pb found in associated sulfide deposits and pb enriched altered volcanic rocks with 100 percent leaching transport and precipitation efficiencies 1 69 km3 of volcanic rock would need to be leached to account for pb applying realistic leaching efficiencies of 50 to 60 percent and transport precipitation efficiencies of 10 to 20 percent 14 to 34 km3 of volcanic rock would need to be leached assuming a static reaction zone the estimated available volume of leachable rock is 0 144 km3 much less than required applying a dynamic reaction zone model 98 to 235 volumes of fresh leachable rock 1 volume 0 144 km3 would need to be exposed to hydrothermal fluids this translates into a 588 to 1 410 m migration of the reaction zone a model incorporating such values would not be tenable previously published compositions of melt inclusions in volcanic rocks from pacmanus indicate an aver age of 199 ppm cu 68 ppm zn and 5 2 ppm pb in the melt and 1 3 to 1 7 wt percent of degassed h2o these data suggest that 37 7 million tonnes mt of magmatic fluid containing 7 2 wt percent cu and 2 3 wt percent zn could be released from a 1 km3 body of magma using the same metal transfer efficiency of 80 percent the degassed fluid would have a maximum concentration of 0 17 wt percent pb which translates to 58 000 t of pb from the melt for the highest known fluid discharge rate of 92 000 g s and over a 100 000 year period a concentration of only 12 ppm pb in the original magmatic component could account for all the pb in the pacmanus deposits assuming that 1 percent of the mixed end member fluid is of magmatic origin a wide range of durations of hydrothermal activity and discharge rates assuming a maximum 0 17 wt percent pb concentration in the degassed magmatic fluid can account for the total pb in the deposit

altimeter derived surface circulation in the large scale ne pacific gyres part 1 seasonal variability abstract the seasonal variability of sea surface height ssh and currents are defined by analysis of altimeter data in the ne pacific ocean over the region from central america to the alaska gyre the results help to clarify questions about the timing of seasonal maxima in the boundary currents as explained below the long term temporal mean of the ssh values must be removed at each spatial point to remove the temporally invariant and large signal caused by the marine geoid we refer to the resulting ssh values which contain all of the temporal variations as the residual ssh our main findings are 1 the maximum surface velocities around the boundaries of the cyclonic alaska gyre the alaska current and the alaska stream occur in winter at the same time that the equatorward california current is weakest or reversed forming the poleward davidson current the maximum surface velocities in the california current occur in summer these seasonal maxima are coincident with the large scale atmospheric wind forcing over each region 2 most of the seasonal variability occurs as strong residuals in alongshore surface currents around the boundaries of the ne pacific basin directly connecting the boundaries of the subpolar gyre the subtropical gyre and the equatorial current system 3 seasonal variability in the surface velocities of the eastward north pacific current west wind drift is weak in comparison to seasonal changes in the surface currents along the boundaries 4 there is an initial appearance next to the coast and offshore migration of seasonal highs and lows in ssh alongshore velocity and eddy kinetic energy eke in the alaska gyre similar to the previously described seasonal offshore migration in the california current 5 the seasonal development of high ssh and poleward current residuals next to the coast appear first off central america and mainland mexico in may june prior to their appearance in the southern part of the california current in july august and their eventual spread around the entire basin in november december similarly low ssh and equatorward transport residuals appear first off central america and mexico in january february before spreading farther north in spring and summer 6 the maximum values of eke occur when each of the boundary currents are maximum

hydrothermal fluid migration and brine pool formation in the red sea the atlantis ii deep numerical heat and fluid flow simulations of the atlantis ii deep in the red sea were conducted to investigate the development migration and discharge of hydrothermal fluids into a submarine depression and determine the conditions necessary to form a brine pool high salinity fluids are predicted to form by leaching miocene evaporates migrate and convect within young oceanic crust and discharge onto the seafloor predicted fluid discharge temperatures t max 301 c discharge fluid velocities v max 0 09 m s and salinities s max 21 wt increase over time and reach values comparable to modern seafloor observations established convection patterns and discharge behavior are robust and are not greatly affected by geometry of rock property changes modeling results were used to calculate the minimum conditions for hydrothermal fluids from a developing hydrothermal system to mix with seawater reverse buoyancy and begin to form a brine pool in a submarine depression under conditions encountered on the seafloor t 25 300 c s 5 25 wt fluid mixtures predicted to pond on the seafloor range from late in the mixing process 99 at low temperatures t 26 c to much earlier 36 mixing at higher temperatures t 94 c a model of brine pool evolution is proposed that describes the processes and conditions necessary to initiate brine pool formation and compares formation conditions with accumulated ore material in the atlantis ii deep and other locations

iron transport by mesoscale haida eddies in the gulf of alaska abstract a two year study of the iron distributions in anticyclonic mesoscale haida eddies of the eastern north pacific ocean has shown that such eddies are a major source of iron to the high nitrate low chlorophyll hnlc waters of the central gulf of alaska basin these eddies which are typically about 100 km in diameter form off the west coast of canada in winter and then track roughly westward into the open ocean therefore they carry large quantities of iron rich coastal waters into iron limited waters of the oligotrophic gyre when the eddies had first formed their dissolved iron concentrations were nearly two orders of magnitude higher than is typically observed at station papa 50 n 145 w 3 n m versus less than 0 05 n m and the total iron in the eddies surface waters 10 40 m was more than 13 n m higher than open ocean waters of the alaska gyre 14 n m versus 0 5 n m while the overall iron content of the eddies decreased rapidly during the first year after they formed the eddy we were able to track the longest still contained 1 5 2 times more iron than the surrounding waters 16 months after its formation therefore although iron concentrations in the surface mixed layers of the eddies drop to levels observed outside very rapidly within 4 months upward transport along isopycnals and upwelling due to eddy decay as well as vertical advective and diffusive transports typical of north pacific waters probably provide steady fluxes of iron into the euphotic zone from the still iron rich eddy core waters throughout the lifetime of the eddy

the influence of coastal origin eddies on oceanic plankton distributions in the eastern gulf of alaska abstract mesoscale anticyclonic eddies that form along the eastern continental margin of the gulf of alaska in winter transport large quantities of coastal water to the open ocean the continuous plankton recorder cpr sampled repeated transects that passed close to or through these eddies in 2000 and 2001 shelf species of diatoms and calanoid copepods were recorded in cpr samples within or in close proximity to eddies and they persisted through the sampling period several oceanic taxa also showed higher concentrations within the eddies significantly reduced occurrences of shelf taxa in oceanic samples were seen in 2001 coinciding with a weaker eddy than observed in 2000 images of ocean temperature and chlorophyll a prepared from satellite observations reveal changes in offshore transport mechanisms by eddies between winter and spring and between southern and northern eddies in this region these effects may also explain some of the seasonal and geographical variability in the cpr samples between april and june of 2000 the haida eddy straddled the low chlorophyll a waters of the gulf and the high chlorophyll a waters of the continental margin and entrained each water type into the neighbouring region the resulting swirling patterns were clearly observed in seawifs imagery sitka eddies failed to penetrate into low chlorophyll a waters during these months and were less effective in stirring high and low chlorophyll a concentrations surface currents in surrounding waters simulated by the ocean surface current simulations oscurs model were used to provide some insights into the likely fate of planktonic organisms once they leave the eddies we show that these eddies may play a significant role in distributing plankton species

formation of the haida 1998 oceanic eddy 1 two large mesoscale anticyclonic eddies formed along the west coast of the queen charlotte islands of western canada in early 1998 altimetry measurements from topex poseidon and ers 2 satellites suggest that these eddies first appeared near cape st james at the southern tip of the islands the eddies merged in june to form haida 1998 the highest eddy ever observed in the region currents near cape st james in winter follow complicated patterns attributed to tidal rectification and pressure driven outflow from hecate strait the adjustment of these flows to the bathymetric features likely contributes to the formation of haida eddies eddies that first appear farther north along the west coast of the queen charlotte islands are set up by other processes such as baroclinic instability

compositions growth mechanisms and temporal relations of hydrothermal sulfide sulfate silica chimneys at the northern cleft segment juan de fuca ridge three active hydrothermal vents forming sulfide mounds and chimneys monolith fountain and pipe organ and more widely distributed inactive chimneys are spatially related to a system of discontinuous fissures and young sheet flow lavas at the northern cleft segment juan de fuca ridge the formation of zoned tubular curich chimneys type i on the monolith sulfide mound is related to focused flow of high temperature to 328 c fluid bulbous chimneys type ii or beehives at the monolith and fountain vents are products of diffuse high temperature to 315 c discharge a broader zone of vigorous mixing between the hydrothermal fluid and seawater results in quench crystallization of anhydrite rich shells columnar zn sulfide rich chimneys with narrow channelways type iii are constructed where focused and relatively low temperature 261 c fluid vents directly from the basalt substrate the bulk chemistry low cu high pb ag and sio2 contents mineralogy pyrite marcasite wurtzite amorphous silica anglesite colloform and filamentous textures and oxygen isotope characteristics of inactive type iv chimneys indicate a low temperature 250 c origin involving diffuse and sluggish flow patterns and conductive cooling seafloor observations and 210pb data indicate that 1 type iv chimneys are products of an earlier period of hydrothermal activity that ended no more than 60 years ago but prior to the sheet flow eruption 2 the high temperature monolith and fountain vents are manifestations of the same heating event shallow emplacement of magma that led to the sheet flow eruption and recent megaplumes and 3 the pipe organ vent is in a very youthful stage of development and chimney deposition postdates the sheet flow eruption

a chemical model for the concentration of gold in volcanogenic massive sulphide deposits abstract study and review of the gold distribution in selected volcanogenic massive sulphide deposits rosebery and hellyer in tasmania mt chalmers in queensland and millenbach in quebec indicates that gold has two distinct occurrences in these deposits 1 a gold zinc lead silver association which is commonly found in the upper part of zinc rich massive sulphide lenses e g rosebery and hellyer and 2 a gold copper association which is commonly present in the stringers and lower portions of copper rich deposits e g mt chalmers and millenbach in each deposit one of these occurrence dominates almost to the exclusion of the other thermodynamic modelling of the volcanogenic fluid which is based on previous work by large 1977 eldridge et al 1983 and pisutha arnond and ohmoto 1983 indicates that gold in the upper part of the zinc rich massive sulphide lenses was transported as au hs 2 while gold in the stringers and bases of copper rich massive sulphide deposits was transported as aucl 2 the ph and o 2 of the ore forming fluid have an important control on gold deposition and therefore gold grades high gold grades in zinc rich massive sulphide are promoted by near neutral oxidised and low temperature 150 c to 275 c fluids as indicated by the presence of barite carbonate feldspar gangue high gold grades in the copper rich stringers and base of the massive sulphide are promoted by higher temperatures 275 c to 350 c relatively oxidised fluids as indicated by bornite or by barite or hematite gangue and relatively acid fluids as indicated by kaolinite gangue in o 2 t space significant gold transport by au hs 2 occurs only in the pyrite stability field at relatively low temperatures 2 is not restricted by iron mineral equilibria but is greatest in the hematite magnetite and pyrite fields at high temperatures 300 c and high o 2 10 30 under conditions of au hs 2 transport bonanza type gold deposition may be found in areas where the hydrothermal fluids passed from the field of pyrite stability to that of hematite stability oxidation of hydrothermal fluids by seawater mixing and the rapid precipitation of sulphide minerals at the top of the massive sulphide lens may cause the precipitation of gold via the mechanisms of either h 2 s oxidation or sulphide gold coprecipitation other types of gold deposits may be classified into either the gold zinc or gold copper association the gold copper bismuth association is developed in higher temperature systems of moderate to high salinity where aucl 2 is the dominant complex e g porphyry cu au deposits and au rich skarns whereas the gold zinc lead silver association is developed in systems of low salinity and high h 2 s where au hs 2 is the dominant complex e g epithermal au ag and archean greenstone hosted au quartz

equilibrium structure and dynamics of the california current system this paper addresses the structure and dynamical mechanisms of regional and mesoscale physical variability in the subtropical northeast pacific ocean using the regional oceanic modeling system roms the model is configured with a u s west coast domain that spans the california current system ccs with a mesoscale horizontal resolution up to as fine as 3 5 km its mean seasonal forcing is by momentum heat and water fluxes at the surface and adaptive nudging to gyre scale fields at the open water boundaries its equilibrium solutions show realistic mean and seasonal states and vigorous mesoscale eddies fronts and filaments the level of eddy kinetic energy eke in the model is comparable to drifter and altimeter estimates in the solutions with sufficiently fine resolution because the model lacks nonseasonal transient forcing the authors conclude that the dominant mesoscale variability in the ccs is intrinsic rather than transiently forced the primary eddy generation mechanism is the baroclinic instability of upwelling alongshore currents there is progressive movement of meanseasonal currents and eddy energy offshore and downward into the oceanic interior in an annually recurrent cycle the associated offshore eddy heat fluxes provide the principal balance against nearshore cooling by mean ekman transport and upwelling the currents are highly nonuniform along the coast with important influences by capes and ridges in both maintaining mean standing eddies and launching transient filaments and fronts

modelling the generation of haida eddies abstract a numerical model forced with average annual cycles of climatological winds surface heat flux and temperature and salinity along the open boundaries is used to demonstrate that haida eddies are typically generated each winter off cape st james at the southern tip of the queen charlotte islands of western canada annual cycles of sea surface elevation measured at coastal tide gauges and topex poseidon crossover locations are reproduced with reasonable accuracy model sensitivity studies show that haida eddies are baroclinic in nature and are generated by the merging of several smaller eddies that have been formed to the west of cape st james the generation mechanism does not require the existence of instability processes and is associated with the mean advection of warmer and fresher water masses around the cape from hecate strait and from the southeast these advected water masses generate plumes of buoyant flow which intensify and sustain small patches of anticyclonic circulation immediately to the northwest of the cape when the flow is stronger several of these smaller eddies can merge to generate a larger eddy the haida eddy similar to observations a typical generation shedding cycle for larger haida eddies in the model is 3 4 months consistent with previous in situ water property measurements these experiments show that the eddies are generally comprised of mixed layer water from hecate strait queen charlotte sound and the continental shelves off northern vancouver island their vertical extent during the mature stage is roughly 1000 m

acoustic imaging of hydrothermal plumes east pacific rise 21 n 109 w we report the first observations based on acoustic imaging of large scale structure and time variability of buoyant plumes emanating from black smoker type seafloor hot springs three dimensional plume reconstructions were made from a digital data set of acoustic backscattering information recorded on a prototype submersible mounted sonar system the acoustic images of two adjacent black smokers depict volume and show zones of flow organization meters to tens of meters in the lower 40 m of the buoyant plumes the two plumes coalesce bend in the prevailing current exhibit short term minutes variation in cross section and rapid seconds turbulent eddy variations at small scales 1 m the plume imaging system is being developed for determination of plume dynamics flux determinations when combined with chemical and thermal measurements and long term monitoring of the activity of seafloor hydrothermal fields

a forced baroclinic vortex around a hydrothermal plume a steady frictional flow around a hydrothermal plume is described which is forced by the entrainment of water into the buoyant part of the plume as it rises above its source the circulation is anticyclonic clockwise in the northern hemisphere near the equilibrium density level or spreading level of the plume and cyclonic below this level the strength of this flow is adequate to trap anomalous properties from the hydrothermal fluid near the source in the presence of weak background flow some observational support for such a flow is presented

oceanic ridge crest processes oceanic ridge crest processes constitute a vigorous frontier of multidisciplinary research with global ramifications in the earth atmospheric and biologic sciences this deep ocean frontier is gradually opening in response to investigations which are elucidating the role of these processes in the lithosphere hydrosphere atmosphere and biosphere and the application of advanced instrumental and interpretive techniques which are increasing the quality and quantity of data these techniques include crustal drilling with borehole logging deep sea drilling project reports high resolution bathymetry sea beam etc side scan sonar seamarc i and ii gloria etc imagery with video and photography multichannel seismics determination of water column properties ctd with rosette sampler etc and submersible applications

seasonal dynamics of the surface circulation in the southern california current system abstract the seasonal dynamics of the southern california current scc is investigated using a primitive equation ocean model with real coastlines and topography the model is tested with different wind forcing and the resulting flow fields are compared to the mean and seasonal circulation inferred from long term in situ observations california cooperative oceanic fisheries investigation calcofi the model integration forced with the output winds of a regional atmospheric model rsm best captures the statistics of the observed circulation with a 0 9 correlation coefficient for the streamlines and 0 5 for the velocity fields the model integrations reveal a pronounced linear response of the flow field to changes in winds on the shelf region a dynamical feature inferred from calcofi hydrography also suggested in topex ers maps is an annually recurrent westward propagation of ssh anomalies originated in the southern california bight scb during the upwelling season the rsm integration is the only one to capture the correct timing and spatial evolution of this process we therefore use this model integration for guidance in constructing a dynamical framework to interpret the observed circulation and its variability during the upwelling season in spring there is an upward tilt of the isopycnals along the coast directly forced by the winds in the bight as the spring transitions to the summer the upwelling winds relax in the bight but are still strong in the region offshore approximately in correspondence of the continental slope positive wind stress curl condition anomalous denser waters in the location of the southern california eddy are maintained and reinforced by the combined interaction of the coastal islands geometry and the wind stress curl through ekman dynamics the adjustment process to the denser water initiates a westward propagation of ocean density anomaly through rossby waves and reinforces the cyclonic gyre like circulation of the sce increasing positive vorticity surface poleward flow maintained by the positive wind stress curl is also reinforced in proximity of point conception as a consequence of the adjustment during the summer the cyclonic gyre becomes increasingly unstable as the core of the ocean anomalies crosses the continental slope instability processes within the cyclonic region characterized by a sharp increase in eke shed eddies that leave the region either drifting to the west or interacting with existing eddies in the region offshore the eke reaches a seasonal maximum at the end the summer in the cyclonic region and in late fall further offshore where the eddies are fully developed the shedding of eddies cannot be directly seen in the calcofi observations because of the sampling aliasing for this point we rely on the strong suggestion of the model which we assume is able to capture the leading order dynamics additional integrations with a linearized version of the model are also presented to reinforce our interpretation of the westward propagation of the isopycnal anomalous displacement associated with rossby wave dynamics

the anticyclonic baroclinic eddy off sitka alaska in the northeast pacific ocean abstract among the many mesoscale eddies found in the northeast pacific ocean is a well developed anticyclonic baroclinic eddy situated within a few hundred kilometers of sitka alaska 57 n 138 w it has definitely been observed during spring and summer 1958 summer 1960 and summer 1961 observations made at other times show some evidence of its occurrence also the trajectories of three norpax drifting buoys for april may 1977 also indicated the probable presence of an eddy there the eddy whose diameter ranges from 200 to 300 km and whose depth extends to 100 m and probably to as much as 2000 m recurs at the same location the center of the eddy is characterized by the following features the surface water is less saline and only somewhat warmer than at its periphery at depths within and below the halocline it is warmer less saline and contains more dissolved oxygen than at the periphery and a warm core is situated within the halocline the halocline is usually depressed by less than 100 m but

altimeter derived surface circulation in the large scale ne pacific gyres part 2 1997 1998 el nino anomalies abstract changes in the sea surface heights ssh and geostrophic transports in the ne pacific are examined during the 1997 1998 el nino using altimeter data sea level pressure slp fields proxy winds and satellite sea surface temperature sst most of the signal occurs along the boundaries of the basin from panama to the alaska peninsula changes in the ssh and alongshore transports along the boundaries are caused both by propagation of signals from the south stronger between the equator and the gulf of california and by local and basin scale winds stronger between the pacific northwest and the alaska peninsula two periods of high ssh occur at the equator may july 1997 and october 1997 january 1998 the first coastal ssh signal moved quickly polewards to approximately 24 n in early june then stalled and moved farther north during transient events in july september large scale wind forcing combined with the equatorial signals during the second period of high equatorial ssh fall 1997 to move the high ssh and poleward transports quickly around the alaska gyre a connection between the boundary currents and the interior north pacific developed as part of the large scale response to the basin scale winds after changes in the boundaries decreases in anomalies of ssh and poleward transports began in january 1998 south of 40 n and in february 1998 farther north

flow near submarine canyons driven by constant winds circulation over coastal submarine canyons driven by constant upwelling or downwelling wind stress is simulated and analyzed with a primitive equation ocean model astoria canyon on the west coast of north america is the focus of this study and model results are consistent with most major features of mean canyon circulation observed in astoria canyon near surface flow crosses over the canyon while a closed cyclone occurs within the canyon upwelling prevails within the canyon and is larger than wind driven upwelling along the adjacent shelf break water rises from depths reaching 300 m to the canyon rim and subsequently onto the adjacent shelf onshore flow within the canyon is driven by the onshore pressure gradient force due to the free surface slope created by the upwelling wind and is enhanced by the limitation to alongshore flow by the canyon topography density gradients largely compensate the surface slope with realistic stratification but continual upwelling persists near the edges of the canyon within the upper canyon 50 150 m below the canyon rim a cyclone is created by flow turning into the canyon mouth separating from the upstream edge and advecting toward the downstream rim below this layer the cyclone is created by vortex stretching due to the upwelling downwelling winds create nearly the opposite flow in which compression and momentum advection create a strong anticyclone within the canyon momentum advection is found to be important both in creating strong circulation within the canyon and in allowing the surface flow to cross the canyon undisturbed model results indicate that astoria like submarine canyons produce across shore transport of sufficient volume to flush a continental shelf in a few 2 5 years

measurements of plume flow from a hydrothermal vent field simultaneous velocity temperature and conductivity data were taken in the convective flow emanating from a hydrothermal vent field located at 10 56 n 103 41 w on the east pacific rise the horizontal profiles obtained indicate that the flow field approaches an ideal plume in the temperature and velocity distribution such parameters as total heat flow and maximum plume height can be estimated using either the velocity or the temperature information the results of these independent calculations are in close agreement yielding a total heat flow from this vent site of 3 7 0 8 mw and a maximum height of 150 10 m the nonlinear effects of large temperature variations on heat capacity and volume changes slightly alter the calculations applied to obtain these values

multiple sulfur isotope analyses support a magmatic model for the volcanogenic massive sulfide deposits of the teutonic bore volcanic complex yilgarn craton western australia we report sensitive high mass resolution ion microprobe stable isotopes shrimp si multiple sulfur isotope analyses 32s 33s 34s to constrain the sources of sulfur in three archean vms deposits teutonic bore bentley and jaguar from the teutonic bore volcanic complex of the yilgarn craton western australia together with sedimentary pyrites from associated black shales and interpillow pyrites the pyrites from vms mineralization are dominated by mantle sulfur but include a small amount of slightly negative mass independent fractionation mif anomalies whereas sulfur from the pyrites in the sedimentary rocks has pronounced positive mif with 33s values that lie between 0 19 and 6 20 with one outlier at 1 62 the wall rocks to the mineralization include sedimentary rocks that have contributed no detectable positive mif sulfur to the vms deposits which is difficult to reconcile with the leaching model for the formation of these deposits the sulfur isotope data are best explained by mixing between sulfur derived from a magmatic hydrothermal fluid and seawater sulfur as represented by the interpillow pyrites the massive sulfide lens pyrites have a weighted mean 33s value of 0 27 0 05 mswd 1 6 nearly identical with 0 31 0 08 mswd 2 4 for pyrites from the stringer zone which requires mixing to have occurred below the sea floor we employed a two component mixing model to estimate the contribution of seawater sulfur to the total sulfur budget of the two teutonic bore volcanic complex vms deposits the results are 15 to 18 for both teutonic bore and bentley much higher than the 3 obtained by jamieson et al 2013 for the giant kidd creek deposit similar calculations carried out for other neoarchean vms deposits give value between 2 and 30 which are similar to modern hydrothermal vms deposits we suggest that multiple sulfur isotope analyses may be used to predict the size of archean vms deposits and to provide a vector to ore deposit but further studies are needed to test these suggestions

a basin scale oceanic instability event in the gulf of alaska a composite noaa 14 satellite advanced very high resolution radiometer image of the gulf of alaska for early march 1995 reveals a sequence of six anticyclonic oceanic eddies spanning more than 1500 km of the continental margin of north america from central british columbia to central alaska although isolated mesoscale eddies have previously been documented for this eastern boundary region the composite image provides the first evidence that trains of such eddies can develop simultaneously along the entire coast the 80 km radius and 250 km spacing of these warm core eddies are consistent with a baroclinic instability event in the poleward coastal current that prevails along the northwest continental margin of north america in winter roughly october through march wind data from offshore meteorological buoys combined with partial cloud free thermal images for january and february suggest that the event was triggered in mid january by an abrupt coast wide reversal in the prevailing poleward wind the instability event disrupted the alongshore transport of relatively warm high salinity water and presumably resulted in a greatly enhanced cross shore flux of brackish nutrient rich coastal water into the open ocean on the basis of its basin scale extent and more than 2 month duration it is feasible that the event had a major impact on the early spring recruitment and survival of zooplankton and pelagic fish within the highly productive fishery zones of coastal british columbia and alaska less extensive eddy sequences found in several earlier satellite images for the region suggest that these instability events are fairly common if so this indicates that the poleward current that forms over the eastern pacific continental slope in late fall herein the northeast pacific coastal current is marginally stable and likely to deform into a series of mesoscale eddies following abrupt basin scale reversals in the seasonally dominant wind provided these wind events occur early enough in the season the coastal current could reform with the onset of poleward winter winds