trace element distributions in the chalcopyrite wall of a black smoker chimney insights from laser ablation inductively coupled plasma mass spectrometry la icp ms abstract the thin walls of young black smoker chimneys experience steep physico chemical gradients during active venting of hydrothermal fluid and these gradients control trace element precipitation within those walls here we utilise a combination of high sensitivity icpms and uv laser ablation resolution of better than 30 m to demonstrate the existence of non random v ag in te ba au pb and u distributions within the chalcopyrite wall of an immature black smoker chimney the data are the first of their kind to be produced for black smoker chimney walls distributions of in and te are attributed to preferential incorporation into lattices at elevated temperature enrichments of u and v derived from seawater are the product of redox immobilisation on sulphide surfaces the distributions of au ag pb and ba may be related to interactions at the hydrothermal fluid seawater mixing front however comparison of distribution data with reaction transport models of chimney walls suggest a possible ph control on precipitation these data illustrate the power of the la icp ms method and such spatially resolved data have the potential to constrain models of element precipitation both in chimneys and in associated mounds

submarine hydrothermal activity along the mid kermadec arc new zealand large scale effects on venting 1 the 2 500 km kermadec tonga arc is the longest submarine arc on the planet here we report on the second of a series of cruises designed to investigate large scale controls on active hydrothermal venting on this arc the 2002 nzaplume ii cruise surveyed 12 submarine volcanic centers along 580 km of the middle kermadec arc mka extending a 1999 cruise that surveyed 260 km of the southern kermadec arc ska average spacing between volcanic centers increases northward from 30 km on backarc crust along the ska to 45 km on backarc crust along the southern mka to 58 km where the mka joins the kermadec ridge volcanic cones dominate in the backarc and calderas dominate the kermadec ridge the incidence of venting is higher along the mka 83 10 of 12 volcanic centers than the ska 67 8 of 12 but the relative intensity of venting as given by plume thickness areal extent and concentration of dissolved gases and ionic species is generally weaker in the mka this pattern may reflect subduction of the 17 km thick oceanic hikurangi plateau beneath the ska subduction of this basaltic mass should greatly increase fluid loss from the downgoing slab initiating extensive melting in the upper mantle wedge and invigorating the hydrothermal systems of the ska conversely volcanic centers in the southern mka are starved of magma replenishment and so their hydrothermal systems are waning farther north where the mka centers merge with the kermadec ridge fewer but larger magma bodies accumulate in the thicker older crust ensuring more widely separated caldera dominated volcanic centers

theoretical analysis of the acoustic response of suspended sediment for hebble abstract the vertical profile of the concentration and size distribution of sediment particles near the ocean bottom at the hebble site is correlated to the velocity field these two parameters of the sediment distribution can be inferred from an acoustic backscattering experiment using transducers in the megahertz frequency range in this paper the acoustic backscattering cross section and reflectivity of spherical and spheroidal particles is calculated numerically at 5 mhz and 500 khz using the size distribution and number density provided elsewhere in this volume the concentration even during a storm event although expected to be two orders of magnitude greater than in the quiescent state is low enough to permit a single scattering approximation

the abundance of seafloor massive sulfide deposits the possibility of mining seafl oor massive sulfide deposits has stirred debate about the sustainable use of this new resource and whether commercial development is worth the risk among the outstanding questions is how many deposits might be accessible to deep sea mining more than 300 sites of high temperature hydrothermal venting have been identifi ed since the discovery of black smokers but signifi cant massive sulfide accumulation has been found at only 165 of these sites estimates of the total number of vent fields and associated mineral deposits based on plume studies and deposit occurrence models range from 500 to 5000 we have used new deposit occurrence data from 10 000 km of ridge arc and backarc spreading centers to estimate the amount of massive sulfide in the easily accessible neovolcanic zones of the global oceans the total accumulation in these areas is estimated to be on the order of 6 108 tonnes containing 3 107 tonnes of copper and zinc this is similar to the total discovered copper and zinc in cenozoic massive sulfi de deposits mined on land but is insuffi cient to satisfy a growing global demand for these metals

trace element systematics of pyrite from submarine hydrothermal vents abstract submarine hydrothermal sulfide ores occur at mid ocean ridges intra oceanic arcs and in back arc basins associated with host rocks of highly variable composition pyrite is the dominant sulfide mineral in most samples presented within this study and thus the trace element composition of pyrite may reflect the different metal sources and precipitation processes here we report on a systematic study of minor and trace element contents in pyrite from active and inactive submarine hydrothermal vent fields at different plate tectonic settings including the indian and mid atlantic ridges the tonga kermadec intra oceanic arc the lau back arc and the central okinawa trough our results show that the trace element contents of pyrite from different locations vary significantly but for most elements without any systematic correlation to the concentration in the magmatic host rocks only as appears to be depleted in pyrite from ultramafic hosted vent systems that are affected by serpentinization these as depleted pyrites preferentially host au 0 micro or nano particles bismuth is enriched in pyrite from hydrothermal systems that contain a sedimentary component and micro inclusions of sphalerite are either due to fluid sediment interaction or phase separated fluid venting pyrites from individual locations have highly variable concentrations of elements like au co cu se mo ag and sb that are most likely related to fluid evolution and changes in fluid composition sub seafloor hydrothermal fluid seawater mixing influences the distribution of au co cu se and mo in pyrite elements like au ag sb and pb often have a characteristic affinity to as while cd correlates closely with zn a magmatic volatile contribution to the hine hina hydrothermal system may result in the precipitation of cu enriched pyrite our results show that the concentrations of most trace metals in pyrite are a function of the physicochemical parameters of the fluid phase rather than a reflection of the magmatic host rock composition

shedding light on ore deposits a review of synchrotron x ray radiation use in ore geology research abstract geology researchers commonly confront critical research questions that require microscopic and sub microscopic level observations e g distribution of chemical elements of economic interest nature of mineralising fluid in order to explain the macroscale phenomena related to the characterisation of and controls on ore mineralisation the emergence and technological evolution of fourth generation synchrotron radiation light sources render these facilities as important but still largely under utilised tools for advancing the frontiers of ore related research to this end the present contribution seeks to critically review and highlight the power and affordances of synchrotron x ray techniques specifically to the fields of fundamental and applied ore geology the review introduces a range of commonly applied synchrotron x ray techniques before comprehensively highlighting past applications of synchrotron x rays to a range of commodities and ore deposits types a synthesis of this information highlights the historical importance of synchrotron x ray techniques towards 1 understanding ore textures and chemical relationships at high m spatial resolutions 2 understanding coordination chemistry of metals in aqueous fluids at geologically relevant p t conditions 3 in situ evaluation of the chemistry and speciation of fluid inclusions 4 evaluating the coordination environment of deleterious and economic trace metal substitutions in major mineral structures and 5 understanding the biogeochemical behaviour and transformations of metals in the low temperature supergene mineralising environment these applications as well as recommendations for future work are described in the hope that a greater diversity of ore geology researchers will incorporate synchrotron x ray tools into their existing suite of analytical and experimental techniques

resolving miss conceptions and misconceptions a geological approach to sedimentary surface textures generated by microbial and abiotic processes the rock record contains a rich variety of sedimentary surface textures on siliciclastic sandstone siltstone and mudstone bedding planes in recent years an increasing number of these textures have been attributed to surficial microbial mats at the time of deposition resulting in their classification as microbially induced sedimentary structures or miss research into miss has developed at a rapid rate resulting in a number of misconceptions in the literature here we attempt to rectify these miss misunderstandings the first part of this paper surveys the stratigraphic and environmental range of reported miss revealing that contrary to popular belief there are more reported miss bearing rock units of phanerozoic than precambrian age furthermore miss exhibit a pan environmental and almost continuous record since the archean claims for the stratigraphic restriction of miss to intervals prior to the evolution of grazing organisms or after mass extinction events as well as claims for the environmental restriction of miss appear to result from sampling bias in the second part of the paper we suggest that raised awareness of miss has come at the cost of a decreasing appreciation of abiotic processes that may create morphologically similar features by introducing the umbrella term sedimentary surface textures of which miss are one subset we suggest a practical methodology for classifying such structures in the geological record we illustrate how elucidating the formative mechanisms of ancient sedimentary surface textures usually requires consideration of a suite of sedimentological evidence from surrounding strata resultant interpretations microbial or non microbial should be couched within a reasonable degree of uncertainty this approach recognizes that morphological similarity alone does not constitute scientific proof of a common origin and reinstates a passive descriptive terminology for sedimentary surface textures that cannot be achieved with the current miss lexicon it is hoped that this new terminology will reduce the number of overly sensational and misleading claims of miss occurrence and permit the means to practically separate initial observation from interpretation furthermore this methodology offers a scientific approach that appreciates the low likelihood of conclusively identifying microbial structures from visual appearance alone informing the search for true miss in earth s geological record and potentially on other planetary bodies such as mars

growth history of hydrothermal black smoker chimneys hollow mineral spires known as black smoker chimneys precipitate around 350 c jets of hydrothermal fluid spouting from the sea floor on the east pacific rise epr at 21 n refs 1 2 i describe and discuss here the formation of mineral zoning across the walls of these structures throughout two major growth phases a sulphate dominated stage and a sulphide replacement stage during the sulphide replacement stage at least four distinct sulphide mineral zonation sequences develop across chimney walls from interior to exterior the apparently successive formation of these sulphide zonation sequences is attributed to evolution of radial thermal and chemical gradients accompanying the gradual thickening and sealing of black smoker chimney walls

quantified multi scale x ray fluorescence element mapping using the maia detector array application to mineral deposit studies the maia large solid angle detector array and imaging system is capable of collecting high resolution images of up to 100 m pixels in size with dwell times of less than 0 2 ms per pixel and thus it is possible to document variation in textures associated with trace element chemistry by collecting quantified elemental maps of geological samples on the scale of entire thin sections in a short time frame 6 8 hr the analysis is nondestructive and allows variation to be recognised on a centimetre scale while also recognising zonations at the micron scale

reduced and oxidized au cu bi iron oxide deposits of the tennant creek inlier australia an integrated geologic and chemical model iron oxide associated au cu bi deposits of the tennant creek gold field range from magnetite pyrrhotite pyrite reduced cu rich deposits through sulfide poor magnetite rich high grade au bi intermediate f o2 deposits to hematite rich high grade au oxidized deposits discordant magnetite hematite chlorite quartz ironstone bodies that host the ore formed hydrothermally during the 1840 to 1860 ma barramundi orogeny at temperatures up to 350 to 400 c and 2 5 to 5 kbars deposition of ironstone minerals was localized by dilatency that was generated during d1 reverse shearing and folding a separate au cu bi hydrothermal stage overprinted selected ironstones during d2 at or before 1825 to 1830 ma where favorable d1 structures and fluid pathways were reactivated the extremes of the reduced to oxidized deposit spectrum represent divergent chemical conditions that cannot be reconciled by the action of a single fluid we have identified both reducing and oxidizing fluids that helped to form the au cu bi deposits at the west peko deposit which represents the reduced end member subtype constraints from oxide silicate sulfide mineral stabilities fluid inclusions and chlorite thermochemistry indicate that au cu bi ore was introduced into ironstone at 300 to 340 c by a reducing pyrrhotite stable weakly acidic sulfur rich and n2 ch4 rich aqueous fluid containing 3 to 10 wt percent nacl equiv an ore fluid source outside the relatively oxidized metasedimentary host sequence warramunga formation is implied we suggest similar ore fluids for other reduced cu and sulfide rich deposits in the district chemical mass transfer modeling of reactions between reducing fluid and ironstone incorporating estimated thermodynamic properties for aqueous bismuth complexes indicates that highly efficient gold and native bi deposition was predominantly in response to desulfidation and oxidation of the fluid chalcopyrite precipitated mainly in response to increased ph gold bismuth ore in the eldorado deposit an oxidized and hematitic end member is interpreted to have involved mixing of an oxidizing hematite stable ca na cl brine with an intermediate f o2 low to moderate salinity ore fluid as well as reaction of both fluids with ironstone furthermore the mass transfer modeling suggests that mixing of reducing and oxidizing fluids in the absence of ironstones could have resulted in high grade au deposits lacking fe oxides a subtype that has received comparatively little exploration attention in the tennant creek district

identifying storm impacts on an embayed high energy coastline examples from western ireland abstract large sections of the western irish coast are characterised by a highly compartmentalised series of headland embayment cells in which sand and gravel beaches are backed by large vegetated dune systems exposure to modally high energy swell renders most of these beaches dissipative in character a mesotidal range c 3 5 4 5 m exists along much of the coast analysis of instrumental wind records from three locations permitted the identification of a variety of storm types and the construction of storm catalogues few individual storms were recorded at all three stations indicating a lack of regional consistency in storm record of the total storms recorded only a small percentage are potentially damaging onshore directed and even fewer span a high tide and thus potentially induce a measurable morphological response at the coast through a combination of historical records meteorological records field observations and wave modelling we attempt to assess the impact of storms quantifiable records of coastal morphology maps air photos and beach profiles are few in number and do not generally record responses that may be definitely attributed to specific storms numerical wave simulations and observations at a variety of sites on the west irish coast however provide insights into instantaneous and medium term decadal storm responses in such systems we argue that beaches and dunes that are attuned to modally high energy regimes require extreme storms to cause significant morphological impact the varying orientation of beaches a spatially nonuniform storm catalogue and the need for a storm to occur at high water to produce measurable change impart site specific storm susceptibility to these embayments furthermore we argue that long period wave energy attenuation across dissipative shorefaces and beaches reduces coastal response to distant storms whereas short period locally generated wind waves are more likely to cause major dune and beach erosion as they arrive at the shoreline unrefracted this apparently variable response of beach and dune systems to storm forcing at a decadal scale over a coastline length of 200 km urges caution in generalising regarding regional scale coastal responses to climatic change

nature and tectonic setting of the southern kermadec submarine arc volcanoes an overview abstract the 1000 km long kermadec subduction system northern new zealand and adjacent havre trough back arc basin associated with the pacific australian plate boundary is an archetypal example of an active island arc convergent margin although the position and tectonic setting of the frontal arc is critical to understanding tectonism and magmatism within an arc back arc system this has not been unequivocally established for the kermadec subduction system swath surveys from the 35 37 s segment of the kermadec system reveal that the frontal arc comprises seven large arc stratovolcanoes rumble ii iii iv silent ii rumble v tangaroa and clark the frontal arc continues south with the whakatane volcano sited at the northern extremity of the taupo volcanic zone of these eight volcanoes the latter four are newly identified and all have constructional volumes varying between 50 and 260 km 3 all of these arc edifices are sited 15 25 km west of the kermadec frontal ridge bathymetric data similarly indicate that other kermadec arc volcanoes between 32 and 35 s also lie west of the ridge axis within the back arc region while north of 32 s the arc volcanoes lie along the frontal ridge this apparent variation in the tectonic position of the frontal arc coincides with other changes in the morphology of the subduction system north and south of 32 s and as suggested by pelletier and dupont 1990 may reflect differences in the length of the underlying subducted slab the 35 37 s frontal arc segment is sited within 35 45 km of the present day back arc rift axis and may control the initial loci of rift graben evolution sidescan imagery and seafloor photography of the southern kermadec arc volcanoes reveal a complex volcanic stratigraphy with intertwined pillow lavas proximal pillow breccias highly vesicular scoriaceous lapilli and pervasively mass wasted volcaniclastic and epiclastic detritus all volcanic deposits interdigitate with pelagic sediments a single k ar dated andesite from whakatane volcano suggests that the history of the present frontal arc may extend back to at least 0 77 ma while rumble iii and v volcanoes are the major although not exclusive sites of geologically recent edifice construction the historical acoustic record of southern kermadec submarine eruptions since 1958 is now regarded as equivocal with the july 1986 eruption of rumble iii the only unambiguous volcanic activity recorded in modern times

crustal magnetization of brothers volcano new zealand measured by autonomous underwater vehicles geophysical expression of a submarine hydrothermal system near bottom magnetic anomaly data have been acquired using autonomous underwater vehicles at brothers volcano southern kermadec arc new zealand crustal magnetization for the study area was obtained by inverting the magnetic data and shows a strong correlation between areas of low magnetization and four hydrothermal fields one of which was unknown prior to our surveys the magnetization pattern is consistent with a model of discrete individual zones of fluid upflow focused along caldera ring faults that provide preferred pathways for the ascent of the hydrothermal fluids differences in the amplitude of the magnetization over the vent fields appear to correlate with age and temperature variations of the hydrothermal fields

detailed morphology and structure of an active submarine arc caldera brothers volcano kermadec arc a survey of the brothers caldera volcano kermadec arc with the autonomous underwater vehicle abe has revealed new details of the morphology and structure of this submarine frontal arc caldera and the geologic setting of its hydrothermal activity brothers volcano has formed between major sw netrending faults within the extensional field of the havre trough brothers may be unique among known submarine calderas in that it has four active hydrothermal systems two high temperature sulfide depositing sites associated with faulting on the northwestern and western walls i e the nw caldera and w caldera hydrothermal sites respectively and gas rich sites on the summits of the constructional cones that fill most of the southern part of the caldera i e the upper and lower cone sites the 3 0 3 4 km caldera is well defined by a topographic rim encompassing 320 of its circumference and which lies between the bounds of two outer half grabenshaped faults in the northwest and southeast sectors there is not a morphologically well defined continuous ring fault at the map resolution although near vertical scarps are present discontinuously at the base of sections of the wall the width of the wall varies from 200 m at its southwest portion to 750 m on its northern section the widest part of the wall is its northwest sector which also has the largest documented area of hydrothermal alteration and where sea floor magnetization is lowest in addition to primary northwest southeast elongation and southwest northeast structures caused by faulting within the regional back arc strain field there are also less well developed west southwestnorth northeast regional structures intersecting the volcano that is appar ent on the abe bathymetry and at outcrop scale from submersible observations asymmetrical trap doorstyle caldera collapse is considered a possible mechanism for the formation of the brothers caldera

high resolution hydrothermal mapping of brothers caldera kermadec arc submarine edifices with caldera summits are common along volcanic arcs and much more likely than simple cones to host hydrothermal venting compared with cones however locating all vent field locations on a caldera s complex bathymetry is a daunting logistical challenge here we describe the first use of an autonomous underwater vehicle abe to fully map the distribution of near bottom hydrothermal tracers over the caldera walls and cone complex of brothers volcano the most active hydrothermal source on the southern kermadec arc sensors on abe simultaneously measured hydrothermal plume anomalies in temperature light backscattering particle concentration and oxidation reduction potential dissolved reduced species every 2 to 3 m along track local maxima in these tracers confirmed known sites on the northwestern wall and the cone summits and more precisely mapped their extents we discovered evidence for new sites throughout the entire northwestern half of the caldera wall at the base of the southeastern wall and on the flanks of both cones systematic variations in the backscattering temperature ratio identified different types of fluid discharge plumes from high temperature metal rich sources dominated the caldera wall while on top of the caldera wall and on the cones we found only plumes from low temperature diffuse flow including occasional s rich plumes source distribution on the walls appears fault controlled but we detected no sources along the deepest fault defining the rim of the downdropped caldera floor advanced deep sea survey techniques using autonomous vehicles is an indispensible and cost effective tool for acquiring a comprehensive understanding of the relationship between hydrothermal discharge and geology on individual volcanoes

geochemical controls on hydrothermal fluids from the kairei and edmond vent fields 23 25 s central indian ridge prior to 2000 no mid ocean ridge hydrothermal systems were identified and sampled in the indian ocean the kairei field central indian ridge was discovered and sampled in 2000 gamo et al 2001 hashimoto et al 2001 this paper reports the chemical composition of hydrothermal fluids collected in 2001 from both the kairei and newly discovered edmond hydrothermal systems data are used to infer subsurface processes and conditions at the two sites as well as to place them within the global context of known hydrothermal sites on the mid ocean ridge system while both sites are located on the intermediate spreading central indian ridge their hydrologic systems have affinities with those observed on slow spreading ridges although the compositions of fluids from the four individual vents sampled at edmond and the three individual vents sampled at kairei vary respectively our interpretation is that a single source fluid at each site is subsequently modified by processes including phase separation subsurface mixing with seawater and deposition and or remobilization of metal sulfide deposits to generate the observed range of compositions both fields are located 6 km from the neovolcanic zone on steps on the east wall of the axial valley with the edmond field 160 km north of kairei and almost 1000 m deeper 3300 versus 2450 m the edmond fluids are extremely hot with maximum measured temperatures of 382 c compared to 365 c for kairei all of the fluids sampled have chlorinities greater than local ambient seawater due to phase separation of seawater at supercritical conditions visual observations suggest both sites have been active for a substantial period of time again similar to observations of slow spreading ridges our chemical data suggest that the substrate underlying kairei is highly altered while that at edmond is not significant albitization appears to be occurring below the edmond field but not at kairei the edmond fluids are by far the hottest brines yet observed venting from a mid ocean ridge hydrothermal site resulting in unusually high concentrations of several transition metals

multiple sources of selenium in ancient seafloor hydrothermal systems compositional and se s and pb isotopic evidence from volcanic hosted and volcanic sediment hosted massive sulfide deposits of the finlayson lake district yukon canada volcanic hosted massive sulfide vhms and volcanic sediment hosted massive sulfide vshms i e hosted by both volcanic and sedimentary rocks deposits in the finlayson lake district yukon canada provide a unique opportunity to study the influence of seafloor and sub seafloor hydrothermal processes on the formation of se poor gp4f vhms deposit 7 ppm se average intermediate kudz ze kayah kzk vhms deposit 200 ppm se average and se enriched wolverine vshms deposit 1100 ppm se average mineralization all three deposits are hosted by mid paleozoic 360 346 ma felsic volcanic rocks but only the wolverine deposit has voluminous coeval carbonaceous argillites black shales in the host rock package here we report the first application of se isotope analyses to ancient seafloor mineralization and use these data in conjunction with pb and s isotope analyses to better understand the source s and depositional process es of se within vhms and vshms systems the wide range of 82se 10 2 to 1 3 relative to nist 3149 34s 2 0 to 12 8 cdt and elevated se contents up to 5865 ppm within the wolverine deposit contrast with the narrower range of 82se 3 8 to 0 5 34s 9 8 to 13 0 and lower se contents 200 ppm average of the kzk deposit the wolverine and kzk deposits have similar sulfide depositional histories i e deposition at the seafloor with concomitant zone refining the se in the kzk deposit is magmatic leaching or degassing in origin whereas the wolverine deposit requires an additional large isotopically negative se source i e 15 82se the negative 82se values for the wolverine deposit are at the extreme light end for measured terrestrial samples and the lightest observed for hypogene sulfide minerals but are within calculated equilibrium values of 82se relative to nist 3149 30 at 25 c between seo4 and se2 we propose that the most negative se isotope values at the wolverine deposit record the 82se of the se source and that the wide range in 82se values results from the combined effects of thermal and chemical degradation and se loss from the carbonaceous argillite source to a hydrothermal fluid including magmatic se i e leached and or magmatic hydrothermal with deposition at or near the paleoseafloor pristine unaltered black shales show little variation in 82se relative to bulk earth se accumulation and fractionation to more negative isotopic values is interpreted to have been produced by post sediment deposition but pre ore stage reduction of seawater se within the black shales

trace elements in the gas emissions from the erta ale volcano afar ethiopia high temperature 1084 c fumarolic emissions from a spatter cone at the erta ale north pit crater granted a rare opportunity to collect giggenbach bottles condensates and sublimates from the fumarolic gases of a rift plume volcano in the immediate proximity of degassing lava these results represent the highest temperature gases sampled directly for trace elements and the first high t fumarolic samples for a rift plume volcano sixty seven metals and metalloids were measured quantitatively by icp aes and icp ms in liquid gas condensates and solid sublimates the total amount of trace elements in the gas without si exceeded 170 ppm the ten most abundant elements transported in nonsilicate modes were na 61 ppm fe 41 ppm k 32 ppm br 12 4 ppm cd 3 0 ppm se 2 3 ppm cu 2 0 ppm zn 2 0 ppm te 1 7 ppm and as 1 2 ppm the gases contained 27 ppb re 1 5 ppb au 0 5 ppb pt and 0 27 ppb os rh and pd containing phases were observed in solid sublimates the only metal not detected by all analytical methods was ruthenium chalcophile elements cd cu zn se te as were transported primarily in the gaseous form alkali metals were emitted at least partially as liquid micron size sulfate droplets whereas alkali earths aluminum and ree had a high affinity to silicate aerosol in the form of basaltic microspheres the silicate aerosol content was evaluated at 59 ppm on average but varied within a 7 5 fold range during sampling because of the extremely high temperature refractory elements ca ba ta u and lree showed evidence of transport in the form of gaseous species the so2 flux in january 2011 was evaluated at 91 24 t d for the entire volcano including 31 t d from the north crater and 60 t d from the lava lake the daily output of trace elements from both erta ale craters without si was estimated at 53 kg d including 20 kg of na 13 5 kg of fe 10 5 kg of k 4 5 kg of chalcophile elements 9 g of re 0 5 g of au and 0 17 g of pt the trace element pattern of erta ale fumarolic gases do not possess any distinct geochemical specialization and resemble te patterns from fumarolic emissions of studied arc and plume volcanoes

high so2 flux sulfur accumulation and gas fractionation at an erupting submarine volcano strombolian style volcanic activity has persisted for six years at the nw rota 1 submarine volcano in the southern mariana arc allowing direct observation and sampling of gas rich fluids produced by actively degassing lavas and permitting study of the magma hydrothermal transition zone fluids sampled centimeters above erupting lava and percolating through volcaniclastic sediments around an active vent have dissolved sulfite 100 mmol kg total dissolved sulfide 1 mmol kg if nw rota is representative of submarine arc eruptions then volcanic vent fluids from seawater lava interaction on submarine arcs have a significant impact on the global hydrothermal flux of sulfur and al to the oceans but a minimal impact on mg removal gas ratios so 2 co 2 h 2 and he are variable on small spatial and temporal scales indicative of solubility fractionation and gas scrubbing elemental sulfur s e is abundant in solid and molten form produced primarily by disproportionation of magmatic so 2 injected into seawater s e accumulates within the porous rock surrounding the lava conduit connecting the magma source to the seafloor accumulated s e can be heated melted and pushed upward by rising magma to produce molten s e flows and lavas saturated with s e molten s e near the top of the lava conduit may be ejected up into the water column by escaping gases or boiling water this mechanism of s e accumulation and refluxing may underlie the relatively widespread occurrence of s e deposits of many sizes found on submarine arc volcanoes

modeling of gold scavenging by bismuth melts coexisting with hydrothermal fluids the effect of gold scavenging by bismuth melts is investigated using equilibrium thermodynamic modeling of an aqueous solution mineral melt system the calculations for the au bi na cl s h o system performed at temperatures between 300 and 450 c demonstrate that au concentrations in the melt are several orders of magnitude higher than in the coexisting fluid indicating the possible formation of economic gold deposits from undersaturated aqueous fluids in which mineralization would not be expected in the absence of a bismuth melt the model applies to any deposit where a bi melt is stable and coexists with a hydrothermal fluid examples of such deposits are known from skarn intrusion related orogenic and volcanogenic massive sulfide vms gold systems in sulfur poor systems the partitioning curves presented here can be used directly to correlate the gold concentration in the fluid and the au grade in the ore e g escanaba trough vms deposit these results also illustrate important principles generally applicable to understanding magmatic hydrothermal and metamorphic deposits that may have contained significant volumes of more complex polymetallic melts

metal bearing molten sulfur collected from a submarine volcano implications for vapor transport of metals in seafloor hydrothermal systems gray metal bearing molten sulfur was collected from the central volcanic cone of an active off axis caldera mtj 1 in the northeastern lau basin southwestern pacific ocean during an expedition for hydrothermal vents undertaken by the korea deep ocean study kodos program in 2006 the molten sulfur enveloped the frame and chain bag of the dredge at a depth of 1700 m microscopically the sulfur matrix contains numerous covellite cus inclusions of various sizes and irregular shapes indicating their formation via volcanic sublimation the molten sulfur is enriched in elements commonly associated with magmatic input including cu as au bi te and sb the low sulfur isotope composition of the sulfur 34 s 7 5 to 8 2 indicates an origin via the magmatic degassing of so 2 and disproportionation the present results represent field scale evidence for metal transport via sulfur rich volcanic degassing in submarine massive sulfide deposits the molten sulfur deposit plays an important role in enhancing the efficiency of the transfer of magmatic fluid to the hydrothermal system

trace element mapping of copper and zinc rich black smoker chimneys from brothers volcano kermadec arc using synchrotron radiation xfm and la icp ms

storm swash terraces a previously overlooked element of the cliff shore platform system storm swash terraces are a distinctive and previously unreported component of the cliff shore platform sedimentary system they consist of laminated marine sands and gravels with occasional large rounded clasts and fine muddy laminae the planar deposits dip gently seaward are up to 1 m thick at the seaward margin and thin landwards forming a wedge they are laterally continuous over tens of meters in a coast parallel dimension they occur in coastal re entrants at the rear of boulder beaches and shore platforms at elevations between 1 and 9 m above contemporary high tide level the terrace sediments represent deposition at the limit of wave run up during extreme storms during such events wave energy is largely dissipated by a shore platform and or boulder beach but sufficient energy remains to carry water and fine sediment to higher levels where it then accumulates the deposition and preservation of storm swash terraces depend on a coastal topography that combines partial wave energy dissipation on a shore platform or boulder beach with available depositional space to landwards these deposits contain a sedimentary record of past storminess on high energy coasts that has yet to be exploited

chemical microenvironments within sulfide structures from the mothra hydrothermal field evidence from high resolution zoning of trace elements abstract massive portions of a 300 c black smoker finn and a diffusely venting intermediate temperature 200 c chimney roane recovered from the mothra hydrothermal field on the juan de fuca ridge have been analyzed in detail for bulk chemistry the size of the recovered pieces of chimney enabled physical segregation and analysis of distinct chemical zonation within the structures in particular large variations in the concentrations of minor and trace elements in the different mineralogical zones provide new insight into the processes involved in chimney growth that are not evident from the bulk mineralogy systematic zonation of trace and minor elements is strongly influenced by redox conditions multiple host phases single or dual fluid source and the mixing cooling history of the fluids even within an individual mineralogical zone distinct chemical microenvironments within the chimneys are recognized that provide a basis for detailed reconstruction of the changing conditions in the interiors of the chimneys during their growth in finn 14 discrete chemical microenvironments are recognized in 80 of 90 samples based on high resolution zoning of major and trace elements four of the microenvironments are cu rich three are zn rich one is fe rich with low cu two are ca rich three are sio2 rich and one is ba and sio2 rich in roane 24 discrete chemical microenvironments are recognized six of the microenvironments are sio2 poor

surficial beach structures formed by wave generated foam in this article we report on the modification of an intertidal beach surface by processes connected with the generation and redistribution of foam during a coastal storm foam generated by breaking waves initially accumulated at the swash line but was reworked across the beach by onshore winds a distinctive suite of sedimentary structures capable of preservation in the geological record was produced that displayed a distinctive cross shore arrangement from the zone of foam generation to the zone of foam deposition and also varied according to tidal level and wind speed foam marks with wind transverse linear elements characterized the upper sections of the beach other distinctive features formed during this storm include foam swash lines wind parallel foam stripes mud drapes and sand drapes on the upper beach and supratidal zone these features formed a surface veneer on a high energy dissipative beach their formation began during a high tide and continued during the subsequent falling tide during the later stages of the falling tide still forming foam driven features were in places being modified by and themselves modifying surface features characteristic of late stage emergence runoff e g double crested ripples rill marks microdeltas

magnetic anomalies and tectonic fabric of marginal basins north of new zealand detailed airborne magnetic studies conducted over the region of the s w pacific marginal basins extending from the solomon islands to new zealand suggest that three major phases of basin formation and island arc development have occurred in this region development of the tasman sea took place during the late cretaceous paleocene development of the basins to the east of the tasman sea occurred predominantly during the oligocene as well as during the upper miocene to recent the south fiji basin consisting of the kupe and minerva abyssal plains is marked by the presence of possibly two rrr triple junction spreading centers that were active between the times of anomalies 13 to 7 36 25 5 m y the kupe abyssal plain shows the presence of residual magnetic anomalies 7 to 13 of the eastern limb of the proposed spreading center the western limb appears to have been subducted beneath the present site of the three kings rise this seafloor spreading phase calculated half spreading rate of 35 mm yr was coincident with the overthrusting phase of the new caledonia ultramafic rocks during that period active volcanism along the then continuous solomons new hebrides fiji lau island arc was taking place magnetic anomalies from 1 to 4 0 8 m y b p are seen to extend along a clearly defined lineation pattern over the north fiji basin analysis of the magnetic anomalies suggests that during the upper miocene at about the time of magnetic anomaly 4 8 m y the solomons lau island arc commenced breaking up through the development of an active spreading center calculated half spreading rate of 35 mm yr located between the new hebrides and fiji portions of the island arc portions of the northeastern sector of the minerva abyssal plain were subducted beneath the north fiji basin during this period between 0 8 m y b p at the time of about anomaly 3 to 2 4 5 3 5 m y the development of the north fiji basin extended into the lau basin and havre trough thus separating the tonga and lau ridges as a result a distinct series of active spreading centers developed southward along the axis of the havre trough lau basin the havre trough is marked by present seismic and submarine volcanic activity residual magnetic anomalies 1 2 0 1 8 m y b p form a symmetrical pattern around the axis of the trough extending south from the lau basin to the active taupo white island volcanic zone of new zealand phases of development of the marginal basins described in this paper may be correlated with phases of changes in the direction and rate of pacific plate motion

mineral precipitation in the walls of black smoker chimneys a quantitative model of transport and chemical reaction a quantitative model of transport and chemical reaction is developed to examine the interplay of physical and chemical processes controlling the evolution of black smoker chimneys diffusion and advection yield steady state profiles of temperature and concentration across a porous wall bound on one side by hydrothermal fluid and on the other by seawater the pressure gradient is estimated from the fluid dynamics of high velocity flow inside the chimney parametric studies reveal the importance of diffusion driven by gradients in activity coefficients resulting from the strong thermal gradient the model wall is a series of vertical layers each with specified physical properties chemical reaction calculated assuming chemical equilibria for the local temperature and concentration conditions significantly modifies the physical properties of the wall as it evolves model calculations demonstrate the sensitivity of mineral zonation to the physical environment and can be used to re create the aging of chimneys inferred from petrologic studies

a model dependent method for inverting vertical profiles of scattering to obtain particle size spectra in boundary layers abstract a method for obtaining particle size spectra from vertical profiles of scattering strength in planetary boundary layers is presented it is assumed that the boundary layer is horizontally homogeneous and that the vertical turbulent diffusion of particles can be modeled from a knowledge of the surface friction velocity equilibrium boundary layer profiles for each class of suspended particles are assumed to be established resulting from the balance between vertical turbulent diffusion and gravitational settling the forward problem thus models the depth dependent scattering as the sum across size classes weighted by number density and scattering cross section in accordance with established scattering theory constrained inverses produce the size spectra results of inversions from synthetic ocean data are presented for optical transmissometry and acoustic backscattering inversions of acoustic field data from the hebble experiment are also presented finally the applications of the work presented for the design of ocean boundary layer experiments its application in other fields and the directions for future research are discussed

submarine volcanic morphology of the western galapagos based on em300 bathymetry and mr1 side scan sonar 1 a compilation of high resolution em300 multibeam bathymetric and existing mr1 side scan sonar data was used to investigate the volcanic morphology of the flanks of the western galapagos islands the data portray an assortment of constructional volcanic features on the shallow to deep submarine flanks of fernandina isabela and santiago islands including rift zones and groups of cones that are considered to be the primary elements in constructing the archipelagic apron ten submarine rift zones were mapped ranging in length from 5 to 20 km comparable in length to western canary island rift zones but significantly shorter than hawaiian submarine rift zones a detailed analysis of the northwestern fernandina submarine rift including calculated magnetization from a surface towed magnetic study suggests that the most recent volcanism has focused at the shallow end of the rift small submarine volcanic cones with various morphologies e g pointed cratered and occasionally breached are common in the submarine western galapagos both on rift zones and on the island flanks where no rifts are present at depths greater than 3000 m large lava flow fields in regions of low bathymetric relief have been previously identified as a common seafloor feature in the western galapagos by geist et al 2006 however their source s remained enigmatic the new em300 data show that a number of the deep lava flows originate from small cones along the mid lower portion of the nw submarine rift of fernandina suggesting that the deep flows owe their origin at least in part to submarine rift zone volcanism

gold and trace element zonation in pyrite using a laser imaging technique implications for the timing of gold in orogenic and carlin style sediment hosted deposits laser ablation icp ms imaging of gold and other trace elements in pyrite from four different sedimenthosted gold arsenic deposits has revealed two distinct episodes of gold enrichment in each deposit an early synsedimentary stage where invisible gold is concentrated in arsenian diagenetic pyrite along with other trace elements in particular as ni pb zn ag mo te v and se and a later hydrothermal stage where gold forms as either free gold grains in cracks in overgrowth metamorphic and or hydrothermal pyrite or as narrow goldarsenic rims on the outermost parts of the overgrowth hydrothermal pyrite compared to the diagenetic pyrites the hydrothermal pyrites are commonly depleted in ni v zn pb and ag with cyclic zones of co ni and as concentration the outermost hydrothermal pyrite rims are either as au rich as in moderate to highgrade deposits such as carlin and bendigo or co ni rich and as au poor as in moderate to low grade deposits such as sukhoi log and spanish mountain the early enrichment of gold in arsenic bearing syngenetic to diagenetic pyrite within black shale facies of sedimentary basins is proposed as a critical requirement for the later development of carlin style and orogenic gold deposits in sedimentary environments the best grade sediment hosted deposits appear to have the gold climax event toward the final stages of deformation related hydrothermal pyrite growth and fluid flow

sediment concentration profiling in hebble using a 1 mhz acoustic backscatter system abstract as part of the high energy benthic boundary layer experiment hebble a 1 mhz acoustic backscatter system abss was deployed in 4800 m of water on the nova scotian continental rise the purpose of the instrument was to measure non intrusively a time series of the vertical concentration profile over the course of one year from september 1985 to september 1986 in this paper we discuss the details of the abss instrument the results of the time series data analysis and the implications of the results on sediment transport modeling in hebble the systematic variation in the abss and light transmissometry calibration with changes of particle size distribution caused by environmental variability is discussed a comparison of the abss estimates of particle concentration with those obtained from light transmissometers seems to indicate that the suspended particle size distribution changed surprisingly little throughout the experiment

enargite luzonite hydrothermal vents in manus back arc basin submarine analogues of high sulfidation epithermal mineralization abstract active and inactive hydrothermal chimneys composed almost entirely of enargite and luzonite rare minerals in seafloor hydrothermal deposits were found at the summits of two submarine volcanoes north su and kaia natai in the manus back arc basin detailed mineralogical and geochemical studies revealed that most probably these deposits precipitated at t 200 330 c and high fs2 the negative 34s values 8 58 to 3 70 of the enargite luzonite are best explained by disproportionation reactions of magmatic so2 and suggest that the high fs2 is likely provided by direct magmatic input of so2 into the hydrothermal system fractionation of cu stable isotopes during the precipitation of enargite luzonite 65cu ranges from 0 20 to 0 35 is inferred to be associated with either rayleigh type fractionation or redox processes cu oxidation to cu2 and the mass balance of dissolved cu and cu2 species in the hydrothermal fluid the trace element composition of enargite and luzonite indicates a temporal fluctuation of the chemistry of the ore forming fluid with an increase of fe ga tl au hg pb and ag and decrease of sb sn te ge and v concentrations with time and points out that this type of deposits is the richest in au average 11 9 ppm and te average 169 ppm among all other types of seafloor metal deposits in addition to the widespread inorganic precipitation of enargite and luzonite in this setting there is evidence that this mineralization may be biogenically mediated on the external surfaces of the active vents fungi like filaments mineralized by luzonite imply that the fungi dikarya subkingdom may be implicated in a mechanism of bio sequestration of as s and cu and provide the initial substrate for luzonite precipitation the studied enargite luzonite deposits have characteristics similar to those of subaerial high sulfidation epithermal mineralization back arc basin setting acid sulfate and boiling ore forming fluids altered advanced argillic stage dacitic host rocks major enargite luzonite and minor pyrite barite and s0 34s au mineralization at depth

submarine hydrothermal activity and gold rich mineralization at brothers volcano kermadec arc new zealand brothers volcano of the kermadec intraoceanic arc is host to a hydrothermal system unique among seafloor hydrothermal systems known anywhere in the world it has two distinct vent fields known as the nw caldera and cone sites whose geology permeability vent fluid compositions mineralogy and ore forming conditions are in stark contrast to each other the nw caldera site strikes for 600 m in a sw ne direction with chimneys occurring over a 145 m depth interval between 1 690 and 1 545 m at least 100 dead and active sulfide chimney spires occur in this field and are typically 2 3 m in height with some reaching 6 7 m their ages at time of sampling fall broadly into three groups 4 23 and 35 years old the chimneys typically occur near the base of individual fault controlled benches on the caldera wall striking in lines orthogonal to the slopes rarer are massive sulfide crusts 2 3 m thick two main types of chimney predominate cu rich up to 28 5 wt cu and more commonly zn rich up to 43 8 wt zn geochemical results show that mo bi co se sn and au up to 91 ppm are correlated with the cu mineralization whereas cd hg sb ag and as are associated with the dominant zn rich mineralization the cone site comprises the upper cone site atop the summit of the recent main dacite cone and the lower cone site that straddles the summit of an older smaller more degraded dacite cone on the ne flank of the main cone huge volumes of diffuse venting are seen at the lower cone site in contrast to venting at both the upper cone and nw caldera sites individual vents are marked by low relief 0 5 m mounds comprising predominately native sulfur with bacterial mats vent fluids of the nw caldera field are focused hot 300 c acidic ph 2 8 metal rich and gas poor calculated end member fluids from nw caldera vents indicate that phase separation has occurred with cl values ranging from 93 to 137 of seawater values by contrast vent fluids at the cone site are diffuse noticeably cooler 122 c more acidic ph 1 9 metal poor and gas rich higher than seawater values of so4 and mg in the cone vent fluids show that these ions are being added to the hydrothermal fluid and are not being depleted via normal water rock interactions iron oxide crusts 3 years in age cover the main cone summit and appear to have formed from fe rich brines evidence for magmatic contributions to the hydrothermal system at brothers includes high concentrations of dissolved co2 e g 206 mm kg at the cone site high co2 3he negative d and 18oh2o for vent fluids negative 34s for sulfides to 4 6 sulfur to 10 2 and 15n2 to 3 5 vent fluid ph values to 1 9 and mineral assemblages common to high sulfidation systems changing physicochemical conditions at the brothers hydrothermal system and especially the cone site occur over periods of months to hundreds of years as shown by interlayered cu au and zn rich zones in chimneys variable fluid and isotopic compositions similar shifts in 3he 4he values for both cone and nw caldera sites and overprinting of magmatic mineral assemblages by water rock dominated assemblages metals especially cu and possibly au may be entering the hydrothermal system via the dissolution of metal rich glasses they are then transported rapidly up into the system via magmatic volatiles utilizing vertical 2 5 km long narrow 300 m diameter pipes consistent with evidence of vent fluids forming at relatively shallow depths the nw caldera and cone sites are considered to represent stages along a continuum between water rock and magmatic hydrothermal dominated end members

long term geochemical surveillance of fumaroles at showa shinzan dome usu volcano japan this study investigates 31 years of fumarole gas and condensate trace elements data from showa shinzan a dacitic dome cryptodome complex that formed during the 1943 1945 eruption of usu volcano forty two gas samples were collected from the highest temperature fumarole named a 1 from 1954 800 c to 1985 336 c and from lower temperature vents condensates were collected contemporaneously with the gas samples and we reanalyzed ten of these samples mostly from the a 1 vent for 32 cations and three anions modeling using the thermochemical equilibrium program solvgas shows that the gas samples are mild disequilibrium mixtures because they a contain unequilibrated sedimentary ch4 and nh3 b have unequilibrated meteoric water or c lost co either by air oxidation or by absorption by the sodium hydroxide sampling solution solvgas also enabled us to restore the samples by removing these disequilibrium effects and to estimate their equilibrium oxygen fugacities and amounts of s2 and ch4 the restored compositions contain 98 h2o with minor to trace amounts of co2 h2 hcl so2 hf h2s co s2 and ch4 we used the restored gas and condensate data to test the hypotheses that these time series compositional data from the dome s fumaroles provide 1 sufficient major gas data to analyze long term degassing trends of the dome s magma hydrothermal system without the influence of sampling or contamination effects 2 independent oxygen fugacity versus temperature estimates of the showa shinzan dacite 3 the order of release of trace elements especially metals from magma and 4 useful information for assessing volcanic hazards the 1954 1985 restored a 1 gas compositions confirm the first hypothesis because they are sufficient to reveal three long term degassing trends 1 they became increasingly h2o rich with time due to the progressive influx of meteoric water into the dome 2 their csandscl ratios decreased dramatically while their clf ratios stayed roughly constant indicating the progressive outgassing of less soluble components f cl s c from the magma reservoir and 3 their h2oh2 co2coandh2sso2 ratios increased significantly in concert with equilibrium changes expected for the 500 c temperature drop when plotted against reciprocal temperature the restored gas log oxygen fugacities follow a tight linear trend from 800 c to nno 2 5 at 400 c this trend largely disproves the second hypothesis because the oxygen fugacities for the 800 c restored gases can only be explained by mixing of hot magmatic gases with 350 c steam from superheated meteoric water but above 800 c this trend intersects the opposing linear trend for other usu eruptive products implying a log oxygen fugacity of 11 45 at 902 c for the showa shinzan magma the time series trace element data also disprove the third hypothesis because rock and incrustation particle contaminants in the condensates account for most of the trace element variation nonetheless highly volatile elements like b and as are relatively unaffected by this particle contamination and they show similar time series trends as cl and f finally except for infrequent sampling around the 1977 usu eruption the results generally confirm the fourth hypothesis since the time series trends for the major gases and selected trace elements indicate that with time the system cooled degassed and was infiltrated by meteoric water all of which are positive signs that volcanic activity declined over the 31 year history this study also suggests that second boiling of shallow magma within and possibly beneath the cryptodome sustained magmatic degassing for at least 20 years after emplacement

characteristics of cu isotopes from chalcopyrite rich black smoker chimneys at brothers volcano kermadec arc and niuatahi volcano lau basin we analysed primary chalcopyrite from modern seafloor black smoker chimneys to investigate high temperature hydrothermal cu isotope fractionation unaffected by metamorphism samples came from nine chimneys collected from brothers volcano kermadec arc and niuatahi volcano lau backarc basin this is the first known study of cu isotopes from submarine intraoceanic arc backarc volcanoes with both volcanoes discharging significant amounts of magmatic volatiles our results n 22 range from 65cu 0 03 to 1 44 0 18 2 sd with the majority of samples between 0 00 and 0 50 we interpret this cluster n 17 of lower 65cu values as representing a mantle source for the chimney cu in agreement with 65cu values for mantle rocks the few higher 65cu values 0 90 occur 1 within the same chimneys as lower values 2 randomly distributed within the chimneys i e near the top and bottom interior and exterior and 3 within chalcopyrite of approximately the same age 1 year this suggests the higher 65cu values are not related to oxidation by mixing with ambient seawater but to isotopic variation within the vent fluids over a relatively short time theoretical studies demonstrate significant isotopic fractionation can occur between aqueous and vapourous complexing species when combined with evidence for periodic release of magmatic volatiles at brothers we believe vapour transport of cu is responsible for the observed isotopic fractionation when compared to global 65cu data for primary chalcopyrite volcanic arc chimneys are most similar to porphyry copper deposits that also form from magmatic hydrothermal processes in convergent tectonic settings

gold enrichment and the bi au association in pyrrhotite rich massive sulfide deposits escanaba trough southern gorda ridge high gold contents to 10 1 ppm avg 1 4 ppm n 34 occur in pyrrhotite rich massive sulfide samples from the sediment covered floor of the escanaba trough the slow spreading southernmost segment of gorda ridge these concentrations reflect the presence of primary gold formed during high temperature hydrothermal activity in mounds and chimneys and secondary gold deposited during sea floor weathering of massive sulfide primary gold occurs as fine grained 2 m secondary gold grains have a porous flaky morphology and occur in samples in which pyrrhotite is oxidized and replaced by fe oxyhydroxides fe sulfate and sulfur mounds and chimneys dominated by pyrrhotite and containing lesser amounts of isocubanite chalcopyrite and fe rich sphalerite were formed by high temperature estimated range 325 275 c reduced low sulfur vent fluids the mineral and fluid compositions during this main stage of hydrothermal venting reflect subsurface interaction between circulating hydrothermal fluids and turbiditic sediment containing as much as 1 1 percent organic carbon as the deposition of pyrrhotite cu fe sulfides and sphalerite waned a volumetrically minor suite of sulfarsenide arsenide bi and au minerals was deposited from highly reduced late main stage fluids diffusing through mounds and chimneys the low solubility of au as a bisulfide complex and the absence of fluid mixing during this stage of hydrothermal activity apparently inhibited the precipitation of gold directly from solution instead gold precipitation is thought to be linked to elevated concentrations of bi in the late main stage fluids the textural relationships of au and bi minerals in pyrrhotite rich samples low melting point of native bismuth 271 4 c and recent experimental results on au and bi in hydrothermal fluids contribute to the hypothesis that gold was effectively scavenged from the escanaba trough vent fluids by coexisting droplets of liquid bismuth additional phase relationships of alloys in the au bi system indicate that deposition of native bismuth and maldonite occurred at temperatures as low as 241 c bismuth droplets trapped in void space between main stage mineral grains scavenged gold from ambient hydrothermal fluid to a greater extent than bismuth enclosed by late forming pyrrhotite the limited solid solution of au in bi can explain the apparent exsolution texture in which gold blebs are hosted by native bismuth the electrum native bismuth with gold inclusions and galena represent the last traces of gold mineralization from late main stage fluids during sea floor weathering and the oxidation of pyrrhotite in the mounds and chimneys secondary gold formed as aggregates of colloidal particles along ph gradients between acidic pore waters and ambient seawater gold was mobilized from earlier formed primary gold minerals and transported as aqueous chloride complexes the reduction of au iii by residual fe2 in partly altered pyrrhotite and adsorption of colloids by fe oxyhydroxides may have influenced the location of secondary gold grains within the alteration front solubility differences between gold and silver chloride complexes at low temperature account for the low ag content of secondary gold grains the high concentrations of bi and thus the association of au and bi minerals in pyrrhotite rich massive sulfide can be ascribed to the extensive interaction of hydrothermal fluids with sediment in the escanaba trough in contrast the absence of the au bi association in massive sulfides at other ridges including other sediment covered sites at middle valley and the guaymas basin reflects the predominantly basaltic source rocks

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

emissions of trace elements during the 2012 2013 effusive eruption of tolbachik volcano kamchatka enrichment factors partition coefficients and aerosol contribution abstract gases and aerosols from the 2012 13 effusive eruption of tolbachik basaltic volcano kamchatka were sampled in february and may 2013 from a lava tube window located 300 m from the eruptive crater temperature at the sampling point was 1060 1070 c the chemical and isotopic compositions of the sampled gases 92 4 h 2 o 3 5 co 2 2 3 so 2 on average d from 25 0 to 38 6 correspond to a typical volcanic arc gas without dilution by meteoric or hydrothermal water halogen contents in the gases 1 37 hcl 0 5 hf were higher than average arc values the total amount of analyzed metallic and metalloid trace elements in the gas exceeded 665 ppm six most abundant trace elements k 250 ppm na 220 ppm si 74 ppm br 48 ppm cu 21 ppm and fe 12 ppm accounted for 95 of the total content of trace elements in the gas the gases contained 24 ppb re 12 ppb ag 4 9 ppb au and 0 45 ppb pt refractory rock forming elements mg al ca and some other elements such as ba and th were transported mainly in the form of silicate microspheres and altered rock particles the concentrations of metals in the eruptive tolbachik gases are higher than the corresponding concentrations in high temperature fumaroles worldwide although the mutual ratios of the elements are approximately the same the gas magma partition coefficients of eleven elements exceed unity including the non metals f s cl br as se and te and the rare metals cd re tl and bi despite the relatively low concentrations of trace elements in the volcanic gases at the highest temperatures superficial magma degassing provides information on the sources and sinks of metals

evaluation of gases condensates and so2 emissions from augustine volcano alaska the degassing of a cl rich volcanic system after the march april 1986 explosive eruption a comprehensive gas study at augustine was undertaken in the summers of 1986 and 1987 airborne cospec measurements indicate that passive so2 emission rates declined exponentially during this period from 380 45 metric tons day t d on 7 24 86 to 27 6 t d on 8 24 87 these data are consistent with the hypothesis that the augustine magma reservoir has become more degassed as volcanic activity decreased after the spring 1986 eruption gas samples collected in 1987 from an 870 c fumarole on the andesitic lava dome show various degrees of disequilibrium due to oxidation of reduced gas species and condensation and loss of h2o in the intake tube of the sampling apparatus thermochemical restoration of the data permits removal of these effects to infer an equilibrium composition of the gases although not conclusive this restoration is consistent with the idea that the gases were in equilibrium at 870 c with an oxygen fugacity near the ni nio buffer these restored gas compositions show that relative to other convergent plate volcanoes the augustine gases are very hcl rich 5 3 6 0 mol hcl s rich 7 1 mol total s and h2o poor 83 9 84 8 mol h2o values of d and 18o suggest that the h2o in the dome gases is a mixture of primary magmatic water pmw and local seawater part of the cl in the augustine volcanic gases probably comes from this shallow seawater source additional cl may come from subducted oceanic crust because data by johnston 1978 show that cl rich glass inclusions in olivine crystals contain hornblende which is evidence for a deep source 25km for part of the cl gas samples collected in 1986 from 390 642 c fumaroles on a ramp surrounding the inner summit crater have been oxidized so severely that restoration to an equilibrium composition is not possible h and o isotope data suggest that these gases are variable mixtures of seawater fmw and meteoric steam these samples are much more h2o rich 92 97 h2o than the dome gases possibly due to a larger meteoric steam component the 1986 samples also have higher cl s s c and f cl ratios which imply that the magmatic component in these gases is from the more degassed 1976 magma thus the 1987 samples from the lava dome are better indicators than the 1986 samples of degassing within the augustine magma reservoir even though they were collected a year later and contain a significant seawater component future gas studies at augustine should emphasize fumaroles on active lava domes condensates collected from the same lava dome fumarole have enrichments ot 107 102 in cl br f b cd as s bi pb sb mo zn cu k li na si and ni lower temperature 200 650 c fumaroles around the volcano are generally less enriched in highly volatile elements however these lower termperature fumaroles have higher concentration of rock forming elements probably derived from the wall rock