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

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

zinc copper and lead in mid ocean ridge basalts and the source rock control on zn pb in ocean ridge hydrothermal deposits the contents of zn cu and pb in mid ocean ridge basalts morb and the morb source rock control on zn pb in ocean ridge hydrothermal deposits are examined the values of zn cu and pb for submarine mid ocean ridge basalts morb are respectively in ppm average morb 75 75 and 0 7 west valley juan de fuca ridge jfr 87 64 and 0 5 southern jfr 120 and 0 5 and 21 n east pacific rise epr 73 78 and 0 5 values of zn pb range from about 100 240 and cu pb from 100 156 in this study zn is found to correlate positively with tio2 feo mean square of weighted deviates mswd of 1 6 for jfr basalt and inversely with mg number mswd of 3 5 therefore contrary to statements in the literature that zn should be compatible in morb zn is a mildly incompatible element and must be enriched in the glass phase relative to olivine as zn does not fit into the other major phenocryst phase plagioclase in the source of morb zn likely is most enriched in oxides spinel magnetite and titanomagnetite copper generally does not correlate well with other elements in most morb data examined when differentiation is dominated by olivine cu has a tendency to behave incompatibly e g at mg numbers 70 but overall cu shows some tendency towards being a compatible element particularly along the mid atlantic ridge a behavior presumably due to separation of sulfides in which cu but not zn is markedly enriched copper thus may be in dispersed sulfides in the source of morb ocean ridges provide important data on source rock controls for sulfide deposits because in sediment starved ridges much is known about the possible source rocks and mineralization is presently occurring in contrast to zn pb 5 in continental hot cl rich brines zn pb in the hottest sediment starved ridge black smoker hydrothermal fluids at 21 n epr is about 110 similar to local morb 145 but cu pb is closer to 30 possibly due to subsurface deposition of cu at the jfr the best value of zn pb in the hydrothermal fluids is about 175 again similar to local morb 240 but cu is very low in the fluids that are at temperatures less than 300 c the large morb like zn pb in the hottest black smoker fluids suggests a source rock control for the metals that prohibits significant galena in the black smoker deposits of sediment starved ridges in contrast exhalative deposits on sediment swamped ridges have significant galena its presence is suggestive of pb derivation from sediments an origin supported by pb isotope studies of lehuray and colleagues in 1988

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

platinum group element distribution in base metal sulfides of the merensky reef from the eastern and western bushveld complex south africa base metal sulfides in magmatic ni cu pge deposits are important carriers of platinum group elements pge the distribution and concentrations of pge in pentlandite pyrrhotite chalcopyrite and pyrite were determined in samples from the mineralized portion of four merensky reef intersections from the eastern and western bushveld complex electron microprobe analysis was used for major elements and in situ laser ablation inductively coupled plasma mass spectrometry la icp ms for trace elements pge ag and au whole rock trace element analyses were performed on representative samples to obtain mineralogical balances in merensky reef samples from the western bushveld both pt and pd are mainly concentrated in the upper chromitite stringer and its immediate vicinity samples from the eastern bushveld reveal more complex distribution patterns in situ la icp ms analyses of pge in sulfides reveal that pentlandite carries distinctly elevated pge contents whereas pyrrhotite and chalcopyrite only contain very low pge concentrations pentlandite is the principal host of pd and rh in the ores palladium and rh concentrations in pentlandite reach up to 700 and 130 ppm respectively in the samples from the eastern bushveld and up to 1 750 ppm pd and up to 1 000 ppm rh in samples from the western bushveld only traces of pt are present in the base metal sulfides bms pyrrhotite contains significant though generally low amounts of ru os and ir but hardly any pd or rh chalcopyrite contains most of the ag but carries only extremely low pge concentrations mass balance calculations performed on the merensky reef samples reveal that in general pentlandite in the feldspathic pyroxenite and the pegmatoidal feldspathic pyroxenite hosts up to 100 of the pd and rh and smaller amounts 10 40 of the os ir and ru chalcopyrite and pyrrhotite usually contain less than 10 of the whole rock pge the remaining pge concentrations and especially most of the pt up to 100 are present in the form of discrete platinum group minerals such as cooperite braggite sperrylite moncheite and isoferroplatinum distribution patterns of whole rock cu ni and s versus whole rock pd and pt show commonly distinct offsets the general sequence of offset patterns of pge and bms maxima in the order from bottom to top is pd in pentlandite pd in whole rock cu ni and s the relationship is not that straightforward in general some of the reef sequences studied only partially show similar trends or are more complex in general however the highest pd concentrations in pentlandite appear to be related to the earliest volumetrically rather small sulfide liquids at the base of the merensky reef sequence a possible explanation for the offset patterns may be rayleigh fractionation

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

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

seafloor hydrothermal clay alteration at jade in the back arc okinawa trough mineralogy geochemistry and isotope characteristics seafloor hydrothermal activity at jade has resulted in extensive alteration of the host epiclastic sediments and pumiceous tuffs forming mica kaolins kaolinite and halloysite mg rich chlorite talc montmorillonite and a mixed layer mineral of dioctahedral chlorite and montmorillonite chl mont clay mineral assemblages show a vertical variation which reflects variable amounts of cold seawater incorporated into hot hydrothermal fluids in subsurface sediments and tuff however mixing alone cannot explain the occurrence of abundant kaolin minerals at jade the formation of kaolin minerals requires much more acidic fluid than expected from simple mixing of hydrothermal fluids and cold seawater low ph values are likely attained by oxidation of h2s either dissolved in the hydrothermal fluid or released from the fluid during decompression the fluid reaching the seafloor is discharged into cold seawater which caused precipitation of sulfides close to vents and native sulfur and barite at the margins of the vent areas halloysite barite and anhydrite show sr isotope compositions similar to marine sr indicating the derivation of marine sr directly from seawater or by the dissolution of calcareous nannoplanktons the isotopic compositions of kaolinite 18o 7 4 d 23 chl mont 18o 7 0 d 32 and mica 18o 5 4 to 9 9 d 30 to 26 suggest fluids of a heated seawater origin the o isotopic data yielded formation temperatures of 170 c for kaolinite 61 to 110 c for halloysite and 145 to 238 c for mica barite 34s values 21 0 to 22 5 are very similar to the marine sulfate value confirming that the barite formation took place due to mixing of ba bearing hydrothermal fluids and sulfate rich seawater native sulfur shows a large variation in 34s in one hand specimen probably because of rapid disequilibrium precipitation of s during fluid exhalation on the seafloor sulfur in hydrothermal fluids is usually consumed to form metal sulfides therefore abundant native sulfur at jade suggests high h2s metals ratios of the hydrothermal fluids the alteration assemblages and isotopic data of hydrothermal minerals from jade are very similar to those of kuroko type barite deposits of middle miocene age which formed from fluids of high s metals ratios at less than 200 c at jade there is only one black smoker actively discharging high temperature 320 c fluid but there are many fossil sulfide chimneys and mounds in the area the mineralogy and high au and cu in these precipitates suggest highly metalliferous hydrothermal activity in the past these activities likely resulted in discharge of hydrothermal plumes and fall outs of sulfides and sulfates on the seafloor these fall outs were incorporated in sediments far from the vent areas they are now recorded as high metal contents in sediments with no petrographic and mineralogical evidence of in situ hydrothermal activity some are high as 8 100 ppm for cu 12 500 ppm for zn 1 000 ppm for as 100 ppm for ag and 21 000 ppm for pb detrital grains of montmorillonite in such sediments are coated with fe oxyhydroxides during the suspension in seawater before settling on the seafloor the depths of such metal anomalies in sediments suggest high levels of metalliferous hydrothermal activities from 1 800 to 300 ybp

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

fluid fluid interactions in the earth s lithosphere fluids rich in water carbon and sulfur species and a variety of dissolved salts are a ubiquitous transport medium for heat and matter in the earth s interior fluid transport through the upper mantle and crust controls the origin of magmatism above subduction zones and results in natural risks of explosive volcanism fluids passing through rocks affect the chemical and heat budget of the global oceans and can be utilized as a source of geothermal energy on land fluid transport is a key to the formation and the practical utilization of natural resources from the origin of hydrothermal mineral deposits through the exploitation of gaseous and liquid hydrocarbons as sources of energy and essential raw materials to the subsurface storage of waste materials such as co2 different sources of fluids and variable paths of recycling volatile components from the hydrosphere and atmosphere through the solid interior of the earth lead to a broad range of fluid compositions from aqueous liquids and gases through water rich silicate or salt melts to carbon rich endmember compositions different rock regimes in the crust and mantle generate characteristic ranges of fluid composition which depending on pressure temperature and composition are miscible to greatly variable degrees for example aqueous liquids and vapors are increasingly miscible at elevated pressure and temperature the degree of this miscibility is however greatly influenced by the presence of additional carbonic or salt components a wide range of fluid fluid interactions results from this partial miscibility of crustal fluids vastly different chemical and physical properties of variably miscible fluids combined with fluid flow from one pressure temperature regime to another therefore have major consequences for the chemical and physical evolution of the crust and mantle several recent textbooks e g walther and wood 1986 carrol and holloway 1994 shmulovich et al 1995

upper crustal velocity structure in slovenia from rayleigh wave dispersion the inversion of surface wave dispersion curves can provide information on the average elastic properties of the upper crustal layers that are usually poorly sampled by body waves the broad band digital records of earthquakes which recently occurred in slovenia and neighbouring regions are used to extract the group velocity of the fundamental mode of rayleigh waves using frequency time analysis ftan the obtained dispersion curves permit a good resolution for the velocity and the thickness of the upper crust the thickness of the uppermost sedimentary layer varies between 4 and 6 km and its shear wave velocity is less than 3 km s the lower sedimentary layer is 7 to 9 km thick and its shear wave velocity ranges from about 3 05 km s in eastern slovenia to about 3 25 km s in western slovenia the shear wave velocity in the crystalline layer is around 3 5 3 7 km s in the eastern part while in the western part it reaches a rather high value of about 3 85 km s

continuation of the hydrothermal fluid chemistry time series at tag and the effects of odp drilling new data are presented for major dissolved species in vent fluids from the tag hydrothermal mound on the mid atlantic ridge sampled in 1993 1994 and 1995 the latter two cruises bracket the drilling of the mound by the ocean drilling program in september november 1994 changes in venting patterns have been observed over this time period both before and after drilling however the major ion chemistry of venting fluids appears to be stable indicating that the drilling did not penetrate the primary plumbing system of the mound

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

metabasalts from the mid atlantic ridge new insights into hydrothermal systems in slow spreading crust an extensive suite of hydrothermally altered rocks were recovered byalvin and dredging along the mark mid atlantic ridge south of the kane fracture zone 23 24 n where detachment faulting has provided a window into the crustal component of hydrothermal systems rocks of basaltic composition are altered to two assemblages with these characteristics i type i albitic plagioclase an02 10 mixed layer smectite chlorite or chlorite actinolite quartz sphene 20 of the clinopyroxene is altered and cu and zn are leached the geochemical signature of these alteration types reflects the relative proportion and composition of secondary minerals and the degree of alteration of primary phases and does not show simple predictive relationships element mobilities indicate that both alteration types formed at low water rock ratios the mark assemblages are typical of the greenschist and transition to the amphibolite facies and represent two distinct albeit overlapping temperature regimes type i 180 to 300 c and type ii 250 to 450 c by analogy with dsdp odp hole 504b and many ophiolites the mark metabasalts were altered within the downwelling limb of a hydrothermal cell and type i and ii samples formed in the upper and lower portions of the sheeted like complex respectively episodic magmatic and hydrothermal events at slow spreading ridges suggest that these observed mineral assemblages represent the cumulative effects of more than one hydrothermal event groundmass and vein assemblages in the mark metabasalts indicate either that alteration conditions did not change during successive hydrothermal events or that these assemblages record only the highest temperature event lack of retrograde reactions or overprinting of lower temperature assemblages e g zeolites suggests that there is a continuum in alteration conditions while crustal segments remain in the ridge axis environment the type ii samples may be representative of thereaction zone where compositions of hydrothermal fluids actively venting at the seafloor today become fixed this prediction necessitates interaction between hydrothermal fluids and intersertal glass and or mafic phases in addition to plagioclase in order to produce the observed range in vented fluid ph

the magnetite crisis in the evolution of arc related magmas and the initial concentration of au ag and cu the association of large au cu ag ore deposits with convergent margins is commonly attributed to the higher content of chalcophile elements in the parental magmas generated at subduction zones compared with mid ocean ridges we present new geochemical data for arc like relatively oxidized mantle derived basalt to rhyolite magmas from the pual ridge and vicinity eastern manus basin which show that the initial abundances of base and precious metals in the parental basalts are similar to those of mid ocean ridge basalt morb the contents of au cu and ag are built up in the evolving pual ridge liquids to levels considerably in excess of those in morb because unlike morb they are not saturated in a sulfide phase which is a consequence of their being more oxidized than morb the behaviour of s during the evolution of the pual ridge magmas is obscured by late stage so2 loss during eruption but we show that it may be inferred by using se as a proxy because this element follows s closely during magmatic evolution except it is not lost during low pressure near sea floor degassing the onset of magnetite fractionation at 60 wt sio2 and an mg number of 40 is accompanied by an abrupt decrease in the contents of au cu and ag previously attributed to separation of cu au rich fluid which is also shown by se implying that magnetite fractionation triggers sulfide saturation petrological modelling reveals that the amount of magnetite fractionation involved is sufficient to convert most of the s originally dissolved in the magma as sulfate so42 to sulfide s2 triggering saturation in a cu rich sulfide phase tentatively identified as bornite cu5fes4 this sulfide phase sequesters au and ag elements with the same valence as cu in sulfides but not other potentially chalcophile elements such as ni re and pt which suggests that the phase is crystalline rather than an immiscible sulfide melt the relatively high contents of cu and au characteristic of evolved convergent margin magmas requires no enrichment from subducted material instead the association of major cu au deposits with convergent margin magmatism results specifically from the process of magmatic evolution under oxidizing conditions this same property also leads to early magnetite fractionation triggering the abrupt saturation in the cu rich sulfide hence the easily recognizable trend of magmatic evolution under oxidizing conditions i e the sharp drop in chalcophile element concentrations may be an exploration guide to economic au ag cu provinces or a crucial pre enrichment step in the formation of such deposits the decrease in p2o5 and sr at the same stage in the fractionation sequence 60 wt sio2 indicates that saturation in apatite is concomitant with magnetite sulfide saturation in the eastern manus basin

delineation of the geometry of nodes in the alps dinarides hinge zone and recognition of seismogenic nodes m 6 we introduce a new method based on the analysis of the topographical alignments and used to delineate the structural boundaries of the nodes which permits the definition of relatively narrow earthquake prone areas by the pattern recognition approach the structurally bounded nodes capable of earthquakes with m 6 0 identified with pattern recognition in fact cover a significantly smaller area of the study region as compared with that defined by gorshkov et al 2004 who used conventional circles the proposed method thus improves the precision in the location of potential large earthquakes

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

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

the coupled geochemistry of au and as in pyrite from hydrothermal ore deposits the ubiquity of au bearing arsenian pyrite in hydrothermal ore deposits suggests that the coupled geochemical behaviour of au and as in this sulfide occurs under a wide range of physico chemical conditions despite significant advances in the last 20years fundamental factors controlling au and as ratios in pyrite from ore deposits remain poorly known here we explore these constraints using new and previously published empa la icp ms sims and pixe analyses of as and au in pyrite from carlin type au epithermal au porphyry cu cu au and orogenic au deposits volcanogenic massive sulfide vhms witwatersrand au iron oxide copper gold iocg and coal deposits pyrite included in the data compilation formed under temperatures from 30 to 600 c and in a wide variety of geological environments the pyrite au as data form a wedge shaped zone in compositional space and the fact that most data points plot below the solid solubility limit defined by reich et al 2005 indicate that au1 is the dominant form of au in arsenian pyrite and that au bearing ore fluids that deposit this sulfide are mostly undersaturated with respect to native au the analytical data also show that the solid solubility limit of au in arsenian pyrite defined by an au as ratio of 0 02 is independent of the geochemical environment of pyrite formation and rather depends on the crystal chemical properties of pyrite and post depositional alteration compilation of au as concentrations and formation temperatures for pyrite indicates that au and as solubility in pyrite is retrograde au and as contents decrease as a function of increasing temperature from 200 to 500 c based on these results two major au as trends for au bearing arsenian pyrite from ore deposits are defined one trend is formed by pyrites from carlin type and orogenic au deposits where compositions are largely controlled by fluid rock interactions and or can be highly perturbed by changes in temperature and alteration by hydrothermal fluids the second trend consists of pyrites from porphyry cu and epithermal au deposits which are characterised by compositions that preserve the au as signature of mineralizing magmatic hydrothermal fluids confirming the role of this sulfide in controlling metal ratios in ore systems

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

crustal and upper mantle structure of the mediterranean area derived from surface wave data abstract a summary of results based mainly on the inversion of available surface wave dispersion data is given for the mediterranean area both for crustal and upper mantle structure the results are presented on maps outlining the regionalization of the crust and the lithosphere asthenosphere system in the area it is possible to distinguish several types of crust with average s wave velocities in the range 2 8 3 8 km s 1 and thickness varying from a minimum of about 10 16 km in the western mediterranean to a maximum of about 50 km including a possible transitional layer beneath the ionian sea the average properties of the crust and of the lithospheric part of the mantle indicate a possible continuous structure extending from north africa through the ionian sea to the adriatic sea characterized by the presence of a transitional layer at the crust mantle boundary strong lateral variations are present in the lithosphere asthenosphere system both in thickness from 30 km in the western mediterranean to about 130 km under the alps and in s wave velocity from 4 1 4 2 km s 1 up to 4 7 km s 1 the relatively high position of low resistivity material that seems to characterize the mediterranean area agrees fairly well with the shallower average top of the asthenosphere found in this area from the study of the elastic properties the usefulness of combining seismological and electromagnetic studies is stressed

constraints on earth evolution from antimony in mantle derived rocks abstract we have analyzed sb in a variety of mantle derived volcanic rocks peridotites and in the ci chondrite orgueil by spark source mass spectrometry concentrations vary from 0 02 to 0 8 ppm in oceanic basalts mid ocean ridge basalts morb oceanic island basalts oib antimony is a moderately siderophile element which behaves like the incompatible lithophile element pr during igneous processes in the mantle both morb and oib samples have similar sb pr ratios of about 0 02 which are different from those in continental crustal rocks antimony resembles pb in that it behaves like a highly incompatible element during formation of continental crust whereas it behaves only moderately incompatible during formation of oceanic basalts morb or oib consequently sb pb ratios of oceanic basalts agree within error limits with those of the continental crust and with the ci chondritic value indicating that sb pb is not strongly fractionated during crust mantle core differentiation from the sb pb ratios we estimate a sb concentration of 11 5 ppb for the primitive mantle an alternative estimate for the primitive mantle abundance is obtained by assuming the sb pr ratio of the primitive mantle to be intermediate between the morb 01b value 0 02 and that of the continental crust 0 05 this approach yields sb 8 4 ppb for the primitive mantle antimony is depleted in the bulk silicate earth by a factor of 45 the volatility corrected depletion factor of 7 is similar to other moderately siderophile elements

evolution of magmatic vapor to gold rich epithermal liquid the porphyry to epithermal transition at nevados de famatina northwest argentina fluid inclusions in the subeconomic porphyry cu mo au system at nevados de famatina and closely associated high sulfidation epithermal cu au ag as sb te veins at la mejicana northwest argentina were studied to reconstruct the evolution of hydrothermal fluids from their deep magmatic source to the shallow epithermal environment field geology vein petrography fluid inclusion microthermometry and single inclusion microanalysis by laser ablation inductively coupled plasma mass spectrometry la icp ms were combined to determine the evolution of pressure temperature and ore metal concentrations in the fluids cathodoluminescence imaging complements transmitted light petrography to constrain the successive stages of quartz formation and the entrapment sequence of the fluid inclusion populations aqueous liquid inclusions of 5 wt percent nacl equiv salinity trapped in quartz sericite pyrite qsp veins between 360 and 325 c contain unusually high concentrations of cu 400 5 000 ppm as 200 ppm sb and te both up to 100 ppm and au several ppm along with other ore forming elements these veins are paragenetically transitional between subeconomic porphyry copper mineralization exposed in the valley floor and high sulfidation epithermal veins with high au grades which are preserved along a high ridge adjacent to the porphyry stock low density vapor and hypersaline liquid i e brine inclusions were trapped in early formed quartz of the porphyry stockwork veins between 450 and 600 c the brine contains lower cu and au concentrations than coexisting vapor inclusions and texturally even earlier inclusions of intermediate density that are trapped in phenocrysts and some stockwork veins the latter may be equivalent to a parental fluid the low and intermediate density fluids compositionally overlap in salinity with the aqueous liquids recorded by the later transitional quartz sericite pyrite veins fluid inclusions and geologic time relations indicate that the transitional quartz sericite pyrite veins were the channelways for metal rich aqueous liquids that generated the high sulfidation epithermal cu au deposit these mineralizing liquids are interpreted to have evolved by continuous density increase contraction from a low salinity s rich magmatic fluid of low to intermediate density this vaporlike fluid was produced by exsolution from a magma that existed at greater depth during the late stages of cooling of the magmatic hydrothermal complex and probably underwent minor brine separation prior to reaching the present level of exposure epithermal mineral precipitation occurred upon dilution of the low salinity magmatic fluid with meteoric water which entered the hydrothermal system as it was cooled and successively eroded during continued magmatic fluid ascent

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

mineralogical and geochemical features of sulfide chimneys from the meso zone central indian ridge hydrothermal activity is fairly well documented from most mid ocean ridges however despite various efforts there is only one hydrothermal field recognized so far in the indian ocean products of former hydrothermal activity were sampled in the fourth segment of the central indian ridge cir north of the rodriguez triple junction rtj near 23 s the mineralized area referred to as meso zone covers an area of about 0 6 km2 and is located at a water depth of 2850 m close to the height of a neovolcanic intrarift ridge hydrothermal mineralization is structurally controlled by fissures and cracks running both parallel and orthogonal to the general strike direction of the cir axis 152 n sulfides of the meso zone formed over a period of at least 30 000 years hydrothermal activity ceased 10 000 years ago detailed mineralogical and geochemical studies of sulfides establish the growth and decay of chimney structures which are mainly composed of pyrite marcasite and chalcopyrite chimneys show high concentrations of base metals particularly cu and fe more than 40 wt as well as high trace element contents like co up to 0 24 wt and as 1 wt in contrast sphalerite is rarely observed which is attributed to replacement and refining processes during the weathering and physical disintegration of the hydrothermal products the zn content is generally low 1 wt only selected samples show higher zn concentrations up to 7 9 wt remnants of chimney structures are characterized by the absence of sulfates but they contain minor amounts of amorphous silica

comparative mineralogy and geochemistry of gold bearing sulfide deposits on the mid ocean ridges a comparative study of the mineralogy and geochemistry of sulfide deposits on mid ocean ridges in the northeast pacific and the mid atlantic reveals common characteristics associated with primary gold enrichment average gold contents of 0 8 to 5 ppm au occur in sulfides from southern explorer ridge and axial seamount northeast pacific and from the tag hydrothermal field and snakepit vent field mid atlantic ridge the enrichment of gold in these deposits is consistently related to a phase of late stage low temperature 1 ppm au occur exclusively in pyritic assemblages and commonly with abundant fe poor sphalerite and a suite of complex pb sb as sulfosalts amorphous silica and locally barite or carbonate are important constituents of the gold rich precipitates but do not contain gold themselves high temperature 350 c black smoker assemblages consisting dominantly of pyrite chalcopyrite pyrrhotite isocubanite and abundant anhydrite are uniformly gold poor 0 2 ppm au to the extent that individual sulfides can be mechanically separated chemical analyses by neutron activation indicate that gold is most abundant in sphalerite up to 5 7 ppm au but also occurs in pyrite and marcasite samples of sphalerite with abundant inclusions of fine grained sulfosalts locally contain up to 18 ppm au suggesting that sulfosalts may be repositories for gold no free gold has been observed at 4000 magnification of polished specimens indicating that the gold is present only as submicroscopic inclusions or as a chemical constituent within the sulfides samples from gold rich deposits in the northeast pacific and mid atlantic are compared with similar but relatively gold poor sulfides from the galapagos rift and 13 n on the east pacific rise epr and with barren sulfides from 11 n epr 21 n epr the endeavour ridge and the southern juan de fuca ridge trace element analyses of more than 170 samples show that gold enrichment in almost all of the deposits is associated with high concentrations of ag as sb pb and zn and locally with high cd hg tl and ga in contrast gold is typically depleted in samples with high co se and mo the close association of au with ag as sb and pb may reflect the common behavior of these metals as aqueous sulfur complexes e g au hs 2 at low temperatures similar mineralogical and geochemical associations are observed in sulfide deposits from modern back arc settings and in the ancient geologic record

seismic zonation in albania using a deterministic approach abstract the modal summation method to compute synthetic seismograms is applied to carry out a study of seismic zonation in albania from a seismotectonic synthesis and the available earthquake data eight seismogenic zones are defined and for each of them a characteristic focal mechanism is selected a new seismic velocity model is used in the computations and is constructed on the basis of previous studies correlation relations between the maximum intensity values observed and the ground motion parameters obtained from this procedure are derived the distribution of the calculated values of displacement velocity and acceleration will contribute to the quality of anti seismic design practice in albania and to the mitigation of earthquake consequences

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

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

inferring time varying recharge from inverse analysis of long term water levels 1 water levels in aquifers typically vary in response to time varying rates of recharge suggesting the possibility of inferring time varying recharge rates on the basis of long term water level records presumably in the southwestern united states arizona nevada new mexico southern california and southern utah rates of mountain front recharge to alluvial aquifers depend on variations in precipitation rates due to known climate cycles such as the el nino southern oscillation index and the pacific decadal oscillation this investigation examined the inverse application of a one dimensional analytical model for periodic flow described by lloyd r townley in 1995 to estimate periodic recharge variations on the basis of variations in long term water level records using southwest aquifers as the case study time varying water level records at various locations along the flow line were obtained by simulation of forward models of synthetic basins with applied sinusoidal recharge of either a single period or composite of multiple periods of length similar to known climate cycles periodic water level components reconstructed using singular spectrum analysis ssa were used to calibrate the analytical model to estimate each recharge component the results demonstrated that periodic recharge estimates were most accurate in basins with nearly uniform transmissivity and the accuracy of the recharge estimates depends on monitoring well location a case study of the san pedro basin arizona is presented as an example of calibrating the analytical model to real data

effects of temperature sulfur and oxygen fugacity on the composition of sphalerite from submarine hydrothermal vents experimental studies have shown that temperature pressure sulfur fugacity fs2 and oxygen fugacity fo2 influence the fe content of sphalerite we present compositional in situ data on sphalerite from submarine volcanic hosted massive sulfide vhms ores of hydrothermal vents from different plate tectonic settings and with variable host rock compositions sphalerite from sediment hosted vents has systematically higher s contents and fe zn ratios than those of the sediment starved vents reflecting an influence of fs2 and fo2 on fe partitioning between fluid and sphalerite the fe zn ratios of sphalerite from sediment starved vent systems apparently increase systematically with the fluid temperatures of the corresponding vents we conclude that the composition of sphalerite can be used to 1 distinguish between sediment hosted and sediment starved hydrothermal processes and 2 estimate minimum fluid temperatures of sphalerite precipitation from inactive sediment starved hydrothermal vent sites and fossil vhms deposits

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

chemical and mineralogical influences on concentrations of trace metals in hydrothermal fluids abstract concentrations of trace metals in hydrothermal solutions from the southern juan de fuca ridge sjfr and the tag hydrothermal field on the mid atlantic ridge are influenced by the combined effects of source rock composition brine seawater mixing and complex interplay among various metals and minerals deposited and remineralized in vent mounds and chimneys copper mo and co show predicted sharp decreases in concentration for vent fluids as temperatures decrease below 350 c however concentrations of cu in 363 c fluids at the tag site are well above values determined from seawater basalt interactions due to subseafloor refining processes and remineralization of chalcopyrite concentrations of zn cd pb as and ga do not show any temperature dependence between 214 to 363 c however zn values do correlate well with cl on an area by area basis due to subseafloor mixing of brine with altered seawater zinc levels also correlate well with concentrations of cd pb and as for all vent fluid samples as well as with basalt and zn rich sulfides implying some continuity in behavior from source rock to vent fluid to sulfide minerals gallium values correlate with zn and cl levels for the sjfr but are high relative to zn at the tag site due to subseafloor refining processes concentrations of tl follow cl k and rb consistent with the behavior predicted for tl overall the cl and zn rich fluids from the sjfr are characteristic of a brine dominated system formed during recent volcanism in contrast high temperature fluids from the tag area are representative of a system that has evolved over the past 100 000 yr with high concentrations of cu co and ga that result from higher temperatures and complex refining processes within a large vent mound

hydrothermal activity and magma genesis along a propagating back arc basin valu fa ridge southern lau basin valu fa ridge is an intraoceanic back arc spreading center located at the southern prolongation of the lau basin bathymetric observations as well as detailed sampling have been carried out along the spreading axis in order to trace hydrothermal and volcanic activity and to study magma generation processes the survey shows that widespread lava flows from recent volcanic eruptions covered most of the vai lili hydrothermal vent field only diffuse low temperature discharge and the formation of thin layers of siliceous precipitates have been observed evidence of present day hydrothermal activity at the hine hina site is indicated by a thermal anomaly in the overlying water column our studies did not reveal any signs of hydrothermal activity either above the seismically imaged magma chamber at 22 25 s or across the southern rift fault zone 22 51 s lavas recovered along the valu fa ridge range from basaltic andesites to rhyolites with sio2 contents higher than reported from any other intraoceanic back arc basin on the basis of the highly variable degrees of crystal fractionation along axis the development of small disconnected magma bodies is suggested in addition the geochemical character of the volcanic rocks shows that the transition zone from oceanic spreading to propagating rifting is located south of the hine hina vent field in the vicinity of 22 35 s

hydrothermal venting at pressure temperature conditions above the critical point of seawater 5 s on the mid atlantic ridge hydrothermal circulation within oceanic crust depends on pressure p and temperature t the critical point cp of seawater at 298 bar and 407 c represents the threshold between subcritical and supercritical conditions here we present data from the first hydrothermal system in which the sampled fluids fall on and above the cp the vent system discovered at 5 s on the mid atlantic ridge is characterized by multiple fluid emanations at variable temperatures in water depths of 3000 m vigorous vapor phase bubbling stable emanation of superhot fluid at 407 c and decreased salinity indicate phase separation at conditions above the cp at one site at another site the measured maximum t of 464 c during a 20 s interval is by far the hottest fluid ever measured at the seafloor and falls into the vapor phase supercritical region of seawater besides these two separate fields with ongoing phase separation and extremely hot fluids a third vent field emanates non phase separated fluids at 349 c and is used as a reference site fluid chemistry shows that supercritical fluids evolve differently than subcritical fluids making this vent system a unique natural laboratory to investigate processes at high p t conditions the stability of the high temperature and fluid geochemistry measured in 2005 and 2006 after the assumed seismic trigger event in 2002 supports this as an exceptional site along the mid atlantic ridge

trace element transport rates in subduction zones evidence from th sr and pb isotope data for tonga kermadec arc lavas abstract trace element and th sr and pb isotope data for young lavas from the tonga kermadec arc in the southwest pacific suggest that geochemical variations in the lavas along the arc are linked to differences in the material being subducted beneath the arc lavas from the southern kermadec segment of the arc have relatively radiogenic pb isotope compositions which reflects a contribution from subducted sediment in contrast much of the pb in tonga lavas is derived from the altered oceanic crust in the subducting pacific plate and lavas from the northernmost tonga islands of tafahi and niuatoputapu contain pb and sr derived from the subducted part of the louisville seamount chain the origin of the pb in the lavas from these two islands can thus be traced to a point on the subducting slab and this observation is used to estimate the rate at which trace elements are transported beneath the arc our calculations suggest that fluid soluble elements such as u sr and pb are transported from the subducted slab across the mantle wedge and back to the surface in lavas over a period of approximately 2 3 ma and that magmas are erupted at the surface less than 350 ka after the melts are generated in the mantle wedge

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

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

chemical characteristics of newly discovered black smoker fluids and associated hydrothermal plumes at the rodriguez triple junction central indian ridge abstract the chemical characteristics of hydrothermal fluids in the indian ocean have been revealed for the first time a hydrothermal field called the kairei field including active black smoker chimneys was discovered by rov kaiko dives at 25 19 17 s 70 02 40 e 2450 m depth on the southwestern flank of an off axis knoll located 15 miles north of the rodriguez triple junction central indian ridge after detailed tow yo surveys of the hydrothermal plume distribution the temperature of the fluid expelled from the most active chimney was almost stable 359 360 c throughout three successive days of fluid sampling the endmember fluid has a chemical composition similar to the hydrothermal fluids sampled from sediment starved mid ocean ridges in the pacific and the atlantic oceans suggesting typical interactions between hot fluid and mid ocean ridge basalts in the subseafloor reaction zone

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

a deterministic seismic hazard map of india and adjacent areas a seismic hazard map of the territory of india and adjacent areas has been prepared using a deterministic approach based on the computation of synthetic seismograms complete with all main phases the input data set consists of structural models seismogenic zones focal mechanisms and earthquake catalogues there are few probabilistic hazard maps available for the indian subcontinent however this is the first study aimed at producing a deterministic seismic hazard map for the indian region using realistic strong ground motion modelling with the knowledge of the physical process of earthquake generation the level of seismicity and wave propagation in anelastic media synthetic seismograms at a frequency of 1 hz have been generated at a regular grid of 0 2 x 0 2 by the modal summation technique the seismic hazard expressed in terms of maximum displacement d m a x maximum velocity v m a x and design ground acceleration dga has been extracted from the synthetic signals and mapped on a regular grid over the studied territory the estimated values of the peak ground acceleration are compared with the observed data available for the himalayan region and are found to be in agreement many parts of the himalayan region have dga values exceeding 0 6 g the epicentral areas of the great assam earthquakes of 1897 and 1950 in northeast india represent the maximum hazard with dga values reaching 1 2 1 3 g the peak velocity and displacement in the same region is estimated as 120 177 cm s 1 and 60 90 cm respectively

serpentinized troctolites exposed near the kairei hydrothermal field central indian ridge insights into the origin of the kairei hydrothermal fluid supporting a unique microbial ecosystem the vent fluids of the kairei hydrothermal field khf on the central indian ridge near the rodriguez triple junction are atypical they have a very high h2 concentration a relatively high si concentration and a remarkably low ch4 h2 ratio recently particular attention has been paid to the khf because the hydrothermal fluids are suggested to support a hydrogen based hyperthermophilic subsurface lithoautotrophic microbial ecosystem hyperslime which is considered to be a likely modern analogue for the early earth ecosystems prior to photosynthesis despite the increasing interest in the fluid chemistry and associated biota the origin of the unusual chemistry of the hydrothermal fluids is still uncertain here we suggest interaction of seawater with troctolite recently discovered from small hills near the khf provide a possible explanation for the composition of the khf fluids dives with the manned submersible shinkai 6500 recovered plagioclase dunite troctolites and olivine gabbros which generally constitute the lower oceanic crust microscopic observations revealed that olivine crystals in the samples were partly to completely replaced by serpentine and magnetite indicating the generation of h2 by serpentinization reactions between olivine and hydrothermal fluids theoretical model calculations predict that the high h2 and high si concentrations of the hydrothermal fluids can be attributed to serpentinization of the troctolites and subsequent hydrothermal reactions with basaltic wall rocks under the khf the unique geological setting of the kairei hydrothermal system where deep crustal rocks are emplaced in the shallower part of oceanic crust is considered to be responsible for the unusual chemistry of the kairei hydrothermal fluids driving the occurrence of the hyperslime

the role of granites in volcanic hosted massive sulphide ore forming systems an assessment of magmatic hydrothermal contributions assessment of geological geochemical and isotopic data indicates that a significant subgroup of volcanic hosted massive sulphide vhms deposits has a major or dominant magmatic hydrothermal source of ore fluids and metals this group which is typically characterised by high cu and au grades includes deposits such as those in the neoarchean doyon bousquet laronde and cambrian mount lyell districts these deposits are distinguished by aluminous advanced argillic alteration assemblages or metamorphosed equivalents intimately associated with ore zones in many of these deposits 34ssulphide is low with a major population below 3 34ssulphate differs from coexisting seawater and 34ssulphate sulphide 20 30 these characteristics are interpreted as the consequence of disproportionation of magmatic so2 as magmatic hydrothermal fluids ascended and cooled and as a definitive evidence for a significant magmatic hydrothermal contribution other characteristics that we consider diagnostic of significant magmatic hydrothermal input into vhms ore fluids include uniformly high 3 times modern seawater values salinities or very 18o enriched 18o 5 ore fluids we do not consider other criteria e g variable salinity moderately high 18ofluid 2 5 34ssulphide near 0 metal assemblages or a spatial association with porphyry cu or other clearly magmatic hydrothermal deposits that have been used previously to advocate significant magmatic hydrothermal contributions to be diagnostic as they can be produced by non magmatic processes known to occur in vhms mineral systems however in general a small magmatic hydrothermal contribution cannot be excluded in most vhms systems considered conclusive data that imply minimal magmatic hydrothermal contributions are only available in the paleoarchean panorama district where coeval seawater dominated and magmatic hydrothermal systems appear to have been physically separated this district which is characterised by chloritic and sericitic alteration assemblages and lacks aluminous advanced argillic alteration assemblages is typical of many vhms deposits around the world suggesting that for garden variety vhms deposits a significant magmatic hydrothermal contribution is not required other than deposits associated with advanced argillic alteration assemblages the only deposit for which we ascribe a major magmatic hydrothermal contribution is the devonian neves corvo deposit this deposit differs from other deposits in the iberian pyrite belt and around the world in being extremely sn rich with the sn closely associated with cu and in having formed from high 18o rich fluids 18ofluid 8 5 we consider these characteristics particularly the last as diagnostic of a significant magmatic hydrothermal contribution our analysis indicates that two subgroups of vhms deposits have a major magmatic hydrothermal contribution cu au rich deposits with aluminous alteration assemblages and reduced very sn rich deposits in which sn was introduced in a high temperature ore assemblage comparison with normal vhms deposits suggests that these subgroups of vhms deposits may form in specialised tectonic environments the cu au rich deposits appear to form adjacent to magmatic arcs an environment conducive to the generation of hydrous oxidised melts by melting metasomatised mantle in the wedge above the subducting slab this contrasts with the back arc setting of normal vhms deposits in which relatively dry granites in this contribution we use the term granite sensu latto formed by decompression melting drive seawater dominated hydrothermal circulation the tectonic setting of highly sn rich vhms deposits such as neves corvo is less clear however thick continental crust below the ore hosting basin may be critical as it is in other sn deposits

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

the influence of hydrothermal fluid composition and advection rates on black smoker chimney mineralogy insights from modeling transport and reaction abstract a detailed study of black smoker chimneys was carried out by drawing together mineralogical observations and measured fluid compositions the modeling technique which establishes a link between vent fluid chemistry and vent deposit mineralogy is used to examine the influence of the physical environment on transport across short length scales centimeters which are subject to steep thermal 350 c and chemical gradients and to predict saturation states of minerals as functions of position within chimney walls owing to short length scales steep gradients and constancy of bounding fluid compositions concentration profiles are controlled by transport the effect of reaction rates on profiles is assumed to be negligible precipitation at points within the chimney wall is thus kinetically controlled local equilibrium does not apply and precipitation must be suppressed when calculating distributions of species and saturation states of minerals model calculations are performed in a series of four steps the first is speciation of measured fluid compositions at in situ temperature and pressure conditions results of calculations are plotted on stability diagrams of log fo2 log f s2 and log fo2 log a fe 2 a cu 2 to examine how closely the predicted saturation states fit with observations of minerals coexisting with the hydrothermal fluid at the vent sites the second step is calculation of heat and mass transport across the chimney wall the third is speciation of the pore fluid compositions calculated to exist in the wall subsequent to transport and the fourth is comparison of calculated mineral saturation states to observations of naturally occurring chimney samples application of the modeling technique to five vent sites which exhibit distinct fluid compositions allows reproduction of observed mineralogy model results demonstrate the sensitivity of geochemical processes to the physical environment porosity tortuosity permeability mineral composition to rates of advection of seawater inward or hydrothermal fluid outward across chimney walls and to endmember fluid composition

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

climate variability and vadose zone controls on damping of transient recharge abstract increasing demand on groundwater resources motivates understanding of the controls on recharge dynamics so model predictions under current and future climate may improve here we address questions about the nonlinear behavior of flux variability in the vadose zone that may explain previously reported teleconnections between global scale climate variability and fluctuations in groundwater levels we use hundreds of hydrus 1d simulations in a sensitivity analysis approach to evaluate the damping depth of transient recharge over a range of periodic boundary conditions and vadose zone geometries and hydraulic parameters that are representative of aquifer systems of the conterminous united states u s although the models were parameterized based on u s aquifers findings from this study are applicable elsewhere that have mean recharge rates between 3 65 and 730 mm yr 1 we find that mean infiltration flux period of time varying infiltration and hydraulic conductivity are statistically significant predictors of damping depth the resulting framework explains why some periodic infiltration fluxes associated with climate variability dampen with depth in the vadose zone resulting in steady state recharge while other periodic surface fluxes do not dampen with depth resulting in transient recharge we find that transient recharge in response to the climate variability patterns could be detected at the depths of water levels in most u s aquifers our findings indicate that the damping behavior of transient infiltration fluxes is linear across soil layers for a range of texture combinations the implications are that relatively simple homogeneous models of the vadose zone may provide reasonable estimates of the damping depth of climate varying transient recharge in some complex layered vadose zone profiles

submarine volcanoes and high temperature hydrothermal venting on the tonga arc southwest pacific submarine hydrothermal vents and associated seafloor mineralization on the tonga arc have been found for the first time in the summit calderas of two shallow water volcanoes greatly extending the known areas and diversity of seafloor hydrothermal activity in the western pacific region the highest temperature vents 245 265 c occur at water depths of 385 540 m near the summit of one volcano at 24 s the vents are spatially related to basaltic dike swarms exposed at a summit cone and in the caldera walls clusters of large to 10 m high barite anhydrite and sulfide chimneys on the summit cone are vigorously discharging clear hydrothermal fluids with temperatures on the seawater boiling curve there is abundant evidence of phase separation which can be seen as flame like jets of steam h2o vapor at the chimney orifices pyrite marcasite sphalerite and chalcopyrite line the interiors of the highest temperature vents similar to black smoker chimneys on the mid ocean ridges

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

gold and native copper in supergene sulphides from the mid atlantic ridge in 1985 black smokers and massive sulphide deposits were discovered in the tag hydrothermal field in the rift valley of the mid atlantic ridge near latitude 26 08 n ref 1 sulphide samples from chimneys and mounds were recovered by dredging at depths between 3 620 and 3 670 m mineralogical and chemical analyses of the samples reveal 1 primary unaltered zn fe cu sulphides containing 0 8 4 0 p p m au 0 02 0 12 oz per ton and 2 secondary cu rich sulphides with native copper formed by supergene alteration of primary cu fe sulphides containing up to 16 4 p p m au 0 48 oz per ton as free native gold this is the first reported occurrence of secondary enrichment of gold and copper in recent submarine sulphides the high gold grades and native copper associated with secondary cu sulphides resemble occurrences in some supergene gossans overlying ancient massive sulphide deposits on land2

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

the seismotectonic characteristics of slovenia slovenia with its neighbouring areas lies at the junction of the alps the dinarides and the pannonian basin these belong to the three plates europe adria and tisza on the slovenian territory itself converge the external dinarides nw se oriented right lateral strike slip faults the transdanubian range ne sw oriented left lateral strike slip faults and the southern alps e w oriented thrusts the direction of the principal stress 1 azimuth 6 dip 8 is determined under the assumption of uniform stress throughout the region dip of the least principal stress 3 of 5 is consistent with the regional strike slip regime listed structures form a pure shear structural mechanism on a regional scale

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

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

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

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

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

decoupled geochemical behavior of as and cu in hydrothermal systems cu rich and as rich growth zones in pyrite provide new insights into the composition of late stage magmatic fluids and their host hydrothermal ore deposits the pyrite is from the pueblo viejo dominican republic and yanacocha peru high sulfidation gold silver deposits which are thought to form from hydrothermal systems that interacted with magmatic vapor plumes electron microprobe analysis secondary ion mass spectrometry and elemental maps show that pyrite the most common sulfide mineral in both deposits contains three different types of growth zones 1 as rich zones that are enriched in au ag sb te and pb 2 cu rich zones with significantly lower concentrations of these elements and 3 barren pyrite zones with no other elements these zones are interpreted to result from mixing between the pyrite forming fluid and vapors that invaded the main hydrothermal system episodically comparison to experimental studies of elemental partitioning and analyses of fumaroles and fluid inclusions from magmatic hydrothermal systems suggests that the as rich vapor formed at high and possibly magmatic temperatures whereas the cu rich vapor formed at lower temperatures possibly during migration of the original magmatic vapor the presence of finely spaced multiple growth zones in pyrite suggests that the composition of at least high sulfidation hydrothermal systems can be affected intermittently and repetitively by vapors probably from underlying magmas

classification seasonality and persistence of low frequency atmospheric circulation patterns abstract orthogonally rotated principle component analysis rpca of northern hemisphere 1 month mean 700 mb heights is used to identify and describe the seasonality and persistence of the major modes of interannual variability the analysis is detailed and comprehensive in that 1 a high resolution approximately equal area 358 point grid is used for the virtually maximum possible 35 year period of record 2 a positive bias in the nmc data base in the early 1950s in the subtropics is largely eliminated for the first time and 3 homogeneous separate analyses of each month of the year are carried out detailing the mouth to month changes in the dominant circulation patterns winter results are similar to those of other recent rpca and teleconnection studies except that some less obvious patterns are identified and further detail of the better known patterns is provided two north south dipole patterns are found over the pacific ocean west pacific oscillation and east pacific pattern and over the atla

a deterministic seismic hazard analysis for shallow earthquakes in greece abstract the maximum expected ground motion in greece is estimated for shallow earthquakes using a deterministic seismic hazard analysis dsha in order to accomplish this analysis the input data include an homogeneous catalogue of earthquakes for the period 426 bc 2003 a seismogenic source model with representative focal mechanisms and a set of velocity models because of the discrete character of the earthquake catalogue and of errors in location of single seismic events a smoothing algorithm is applied to the catalogue of the main shocks to get a spatially smoothed distribution of magnitude based on the selected input parameters synthetic seismograms for an upper frequency content of 1 hz are computed on a grid of 0 2 0 2 the resultant horizontal components for displacement velocity acceleration and dga design ground acceleration are mapped the maps which depict these results cannot be compared with previously published maps based on probabilistic methodologies as the latter were compiled for a mean return period of 476 years therefore in order to validate our deterministic analysis the final results are compared with pga estimated from the maximum observed macroseismic intensity in greece during the period 426 bc 2003 since the results are obtained for point sources with the frequency content scaled with moment magnitude some sensitivity tests are performed to assess the influence of the finite extent of fault related to large events sensitivity tests are also performed to investigate the changes in the peak ground motion quantities when varying the crustal velocity models in some seismogenic areas the ratios and the relative differences between the results obtained using different models are mapped and their mean value computed the results highlight the importance in the deterministic approach of using good and reliable velocity models

linking north atlantic ocean atmosphere teleconnection patterns and hydrogeological responses in temperate groundwater systems climate signals exhibit periodicity over a range of frequencies e g diurnal seasonal annual and longer term climate phenomena that are modified as they propagate through the terrestrial water cycle much of both our present understanding and modelling of temperate hydrological and hydrogeological systems relies on the preservation of high frequency signals e g diurnal and seasonal cycles holman et al 2009 alley et al 2002 however there is evidence to suggest that low frequency oscillations in rainfall temperature and evapotranspiration are linked to the el ni no southern oscillation jones and banner 2003 pacific decadal oscillation gurdak et al 2007 north atlantic oscillation nao schroder and rosbjerg 2004 qian and saunders 2003 and other ocean climate cycles

overview of the spirit mars exploration rover mission to gusev crater landing site to backstay rock in the columbia hills spirit landed on the floor of gusev crater and conducted initial operations on soil covered rock strewn cratered plains underlain by olivine bearing basalts plains surface rocks are covered by wind blown dust and show evidence for surface enrichment of soluble species as vein and void filling materials and coatings the surface enrichment is the result of a minor amount of transport and deposition by aqueous processes layered granular deposits were discovered in the columbia hills with outcrops that tend to dip conformably with the topography the granular rocks are interpreted to be volcanic ash and or impact ejecta deposits that have been modified by aqueous fluids during and or after emplacement soils consist of basaltic deposits that are weakly cohesive relatively poorly sorted and covered by a veneer of wind blown dust the soils have been homogenized by wind transport over at least the several kilometer length scale traversed by the rover mobilization of soluble species has occurred within at least two soil deposits examined the presence of monolayers of coarse sand on wind blown bedforms together with even spacing of granule sized surface clasts suggests that some of the soil surfaces encountered by spirit have not been modified by wind for some time on the other hand dust deposits on the surface and rover deck have changed during the course of the mission detection of dust devils monitoring of the dust opacity and lower boundary layer and coordinated experiments with orbiters provided new insights into atmosphere surface dynamics

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

neo deterministic seismic hazard and pattern recognition techniques time dependent scenarios for north eastern italy an integrated neo deterministic approach to seismic hazard assessment has been developed that combines different pattern recognition techniques designed for the space time identification of impending strong earthquakes with algorithms for the realistic modeling of seismic ground motion the integrated approach allows for a time dependent definition of the seismic input through the routine updating of earthquake predictions the scenarios of expected ground motion associated with the alarmed areas are defined by means of full waveform modeling a set of neo deterministic scenarios of ground motion is defined at regional and local scales thus providing a prioritization tool for timely preparedness and mitigation actions constraints about the space and time of occurrence of the impending strong earthquakes are provided by three formally defined and globally tested algorithms which have been developed according to a pattern recognition scheme two algorithms namely cn and m8 are routinely used for intermediate term middle range earthquake predictions while a third algorithm allows for the identification of the areas prone to large events these independent procedures have been combined to better constrain the alarmed area the pattern recognition of earthquake prone areas does not belong to the family of earthquake prediction algorithms since it does not provide any information about the time of occurrence of the expected earthquakes nevertheless it can be considered as the termless zero approximation which restrains the alerted areas e g defined by cn or m8 to the more precise potential location of large events italy is the only region of moderate seismic activity where the two different prediction algorithms cn and m8s i e a spatially stabilized variant of m8 are applied simultaneously and a real time test of predictions for earthquakes with magnitude larger than a given threshold namely 5 4 and 5 6 for cn algorithm and 5 5 for m8s algorithm has been ongoing since 2003 the application of the cn to the adriatic region which is relevant for seismic hazard assessment in the northeastern part of the italian territory is also discussed examples of neo deterministic scenarios are provided at regional and local scale and for the cities of trieste and nimis friuli venezia giulia region where the knowledge of the local geological conditions permitted a detailed evaluation of the expected ground motion

geochemical constraints on the origin of bimodal magmatism at the okinawa trough an incipient back arc basin abstract the magmatism at the axial zone of the middle okinawa trough a young continental back arc basin comprises a bimodal basaltic rhyolitic suite accompanied by minor intermediate rocks we report major and trace element and sr nd isotopie data for the intermediate to silicic suites to provide constraints on their petrogenesis the rhyolites recovered as lava and pumice fall into three geochemical groups type 1 2 and 3 rhyolites type 1 rhyolites have 87sr 86sr 0 7040 0 7042 and 143nd 144nd 0 5128 0 5129 identical to those of associated basalts and are characterized by highly fractionated ree patterns petrogenesis of type 1 rhyolites is explicable in terms of fractional crystallization of the associated basalt in contrast type 2 rhyolites and andesite have slightly higher 87sr 86sr 0 7044 0 7047 but similar 143nd 144nd 0 5128 compared to those of the basalts the compositions of type 2 rhyolite and andesite can be explained by assimilation and fractional crystallization afc processes of the basalt magma quantitative analysis suggests assimilation fractional crystallization ma mc ratios of 0 05 hybrid andesite generated by mixing of evolved basalt and type 1 rhyolite is also present we emphasize that mechanical extension in this part of the okinawa trough involves gabbro ic lower crust that resulted from fractionation of mantle derived basaltic magmas type 3 rhyolite occurs only as pumice which makes its derivation questionable this rhyolite has major and trace element compositions and sr nd isotopie ratios which suggests that it may be derived from volcanic activity on the southern ryukyu volcanic front and arrived in the okinawa trough by drifting on the kuroshio current

neo deterministic seismic hazard assessment and earthquake occurrence rate abstract the aim of this study is to associate the expected ground motions from neo deterministic seismic hazard assessment ndsha to robust estimates of their long term average occurrence rates ndsha means scenario based methods for seismic hazard analysis where realistic and duly validated synthetic time series accounting for source propagation and site effects are used to construct ground motion scenarios ndsha in its standard form defines the hazard as the envelope ground shaking at the site namely the maximum estimate computed from a large set of possible scenario earthquakes thus the standard ndsha maps provide rather robust and conservative hazard estimates which do not require any assumption about the probabilistic model of earthquakes occurrence some specific applications however may benefit from temporal information about the computed ground shaking including a gross estimate of its average recurrence time for this purpose the definition of the frequency magnitude fm relation for earthquakes in the italian region is performed according to the multi scale seismicity model and an occurrence rate estimate is associated to each of the modeled sources the introduction of occurrence rate estimates in ndsha also allows for the generation of ground shaking maps for specified time intervals often improperly referred as return periods that permit a straightforward comparison between the ndsha and the psha maps

seismic zoning of slovenia based on deterministic hazard computations seismic hazard of the territory of slovenia is estimated using a deterministic approach based on the computation of complete synthetic seismograms the input data are the catalogues of earthquakes and fault plane solutions for slovenia and surrounding regions structural models are defined based on available seismological and geophysical information but are mainly constrained by surface wave dispersion and 3 d tomographic modelling of the upper crust seismogenic zones are delineated considering geotectonic characteristics fault plane solutions and distribution of earthquake hypocentres outside slovenia seismogenic zones are extended up to distances from which they can considerably influence seismic hazard estimates synthetic seismograms are computed using the receiver structure along the entire path by normal mode summation up to 1 hz for receiver sites on a 0 2 0 2 degrees grid and scaled to the magnitude of the earthquake allowing for spectral falloff at each site the maximum value of horizontal velocity horizontal displacement and design ground acceleration are considered as hazard parameter the highest values are obtained for western slovenia where the hazard is controlled by the strongest earthquake in the catalogue the idrija event of march 26 1511

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

constraints on the location and mechanism of the 1511 western slovenia earthquake from active tectonics and modeling of macroseismic data abstract the 1511 western slovenia earthquake m 6 9 is the largest event occurred so far in the region of the alps dinarides junction though it strongly influences the regional seismic hazard assessment the epicenter and mechanism are still under debate the complexity of the active tectonics of the alps dinarides junction is reflected by the presence of both compressional and transpressional deformations this complexity is witnessed by the recent occurrence of three main earthquake sequences the 1976 friuli thrust faulting events the 1998 bovec krn mountain and the 2004 kobarid strike slip events the epicenters of the 1998 and 2004 strike slip earthquakes ms 5 7 and ms 4 9 respectively lie only 50 km far from the 1976 thrust earthquake ms 6 5 we use the available macroseismic data and recent active tectonics studies to assess a possible epicenter and mechanism for the 1511 earthquake and causative fault according with previous works reported in the literature we analyze both a two and a single event case defining several input fault models we compute synthetic seismograms up to 1 hz in an extended source approximation testing different rupture propagations and applying a uniform seismic moment distribution on the fault segments we extract the maximum horizontal velocities from the synthetics and we convert them into intensities by means of an empirical relation a rounded to integer misfit between observed and computed intensities is performed considering both a minimized and a maximized databases built to avoid the use of half degree macroseismic intensity data points our results are consistent with a 6 9 magnitude single event rupturing 50 km of the idrija right lateral strike slip fault with bilateral rupture propagation

hydrogeologic and climatic influences on spatial and interannual variation of recharge to a tropical karst island aquifer 1 the hydrology and geochemistry of groundwater in tropical island aquifers such as on barbados are significantly influenced by tropical climatic conditions recharge to these aquifers is the product of regional and local climate patterns that control rainfall oxygen isotopes can be used to estimate the amount and timing of recharge on these islands because seasonal fluctuations of rainwater oxygen isotopic compositions are related to the amount of rainfall this study shows that estimates of average annual recharge to the limestone aquifer on barbados vary widely displaying a more direct relationship to the distribution of rainfall throughout each year than to total annual rainfall recharge estimates are higher during years when rainfall is concentrated in the peak wet season months than during years when rainfall is more evenly distributed throughout the year the el nino southern oscillation appears to be partially responsible for these rainfall and recharge fluctuations knowledge of interannual variation of recharge and processes responsible is important because recharge variation must be considered when setting groundwater management policies related to groundwater availability

toward a better understanding of palaeoclimatic regimes that recharged the fossil aquifers in north africa inferences from stable isotope and remote sensing data abstract the isotopic composition of modern precipitation collected monthly from the international atomic energy agency iaea stations over north africa is enriched average d morocco 25 8 algeria 21 3 tunisia 20 6 libya 17 7 egypt 11 7 compared to fossil groundwater across north africa which shows progressive west to east depletion this indicates that precipitation from paleowind regimes was different from those prevailing in the present day late holocene however a few monthly records march 1982 december 1987 december 1991 march 2002 and april 2002 collected from iaea stations sidi barrani cairo rafah and el arish showed isotopic depletions d 56 to 43 7 approaching those of the fossil groundwater in egypt for each of the five events we investigated the direction of cloud propagation in relation to the isotopic composition of precipitation as it travels over the african continent and surroundings cloud propagation directions and air parcel flow paths were extracted from temporal every 30 min meteosat image products 1 infra red eumetsat 2 cloud motion winds cmw and 3 back trajectory models btm the inferred wind regimes for each of these events were then compared to those for the remaining egyptian records 160 that produced precipitation with enriched to intermediate isotopic compositions d 39 7 to 34 6 the extracted cloud propagation directions and the observed spatial variation in the isotopic compositions of the precipitating rain support a model that attributes previous wet climatic periods over north africa to the intensification of palaeowesterlies during glacial periods

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

pyrite as a record of hydrothermal fluid evolution in a porphyry copper system a sims empa trace element study porphyry copper deposits are currently the world s largest source of copper and molybdenum and are also among the largest reservoirs of gold in the upper crust despite the fact that pyrite is a ubiquitous mineral phase in these deposits and secondary cu enrichment processes are commonly controlled by the abundance of this sulfide the major and trace element chemistry of pyrite from porphyry systems remains unconstrained in this study we report the first comprehensive trace element database of pyrite from the dexing deposit china s largest porphyry cu deposit by combining high spatial resolution and x ray mapping capabilities of electron microprobe analysis empa with low detection limits and depth profiling capabilities of secondary ion mass spectrometry sims in a suite of samples from the dexing deposit we show that the concentrations of precious metals e g au ag metalloids e g as sb se te and heavy metals e g cu co ni zn hg in pyrite from porphyry systems are more significant than previously thought among the elements analyzed cu as au and ni are the most abundant with concentrations that vary from sub ppm levels to a few wt i e 6 wt cu 3 wt as 0 25 wt au and 0 2 wt ni detailed wavelength dispersive spectrometry wds x ray maps and sims depth vs isotope concentration profiles reveal that pyrite from the dexing deposit is characterized by complex chemical zoning where the studied elements occur in different mineralogical forms while as occurs as a structurally bound element in pyrite cu and au can occur as both solid solution and micro to nano sized particles of chalcopyrite and native au or au tellurides respectively indicating that pyrite can control metal speciation and partitioning during porphyry cu mineralization the well developed oscillatory zoning detected in pyrite where cu rich as depleted growth zones alternate with cu depleted as rich layers indicates that cu is geochemically decoupled from as suggesting that this selective partitioning of metals into pyrite is most likely the result of changes in hydrothermal fluid composition

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

the 1998 bovec krn mountain slovenia earthquake sequence we study the 1998 bovec krn mountain slovenia earthquake sequence by combining hypocenters relocation strong motion inversion digital elevation modelling and field geology the main shock ms 5 7 a 12 km right lateral strike slip event on the dinaric fault system occurred on a sub vertical fault plane the rupture confined between 3 and 9 km depth with no evidence of surface faulting propagated bilaterally within two structural barriers the northwestern barrier is at the junction between dinaric and alpine structures where there is a sharp change in the geometry of faulting the southeastern barrier is within the dinaric system and its surface expression corresponds to the tolminka spring perched basin a 1 km restraining step over at this site the bovec krn earthquake fault overlaps with a 30 km strike slip fault segment that is free of aftershocks and could be undergoing an increase of stress this fault system represents the northern branch of the idrija right lateral fault

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