organic geochemical studies of a recent inner great barrier reef sediment i assessment of input sources the concentration of solvent extractable se and bound hydrocarbons ketones alcohols sterols monocarboxylic acids hydroxyacids and dicarboxylic acids of a surface sample 0 2 5 cm from a recent carbonate tropical sediment taken at 60ft 18m depth north west of the low isles north queensland are reported in detail n alkanes are a minor constituent in the se and bound hydrocarbon fractions with the major component being unresolved complex hydrocarbon material which is not an anthropogenic input 6 10 14 trimethylpentadecan 2 one derived from chlorophyll as well as phytol were identified as major components of the ketone and alcohol constituents no chlorophyll pigments or pigmented degradation products were present implying degradation before incorporation into the sediment this conclusion is consistent with evidence for higher plant input in which all sensitive lipids have been degraded before incorporation se and bound fractions have been studied in detail and show considerable differences probably arising from the importance of viable biomass in the se fraction inputs to the sediment are determined as higher plants algae bacteria fungi and meiofauna in descending order of importance

intra oceanic subduction related hydrothermal venting kermadec volcanic arc new zealand intra oceanic volcanic arcs mark the boundaries between converging lithospheric plates where subduction produces volcanic and tectonic activity that ensures a steady supply of magmatic heat and hydrothermal fluids to the seafloor here we report on the first broad and systematic survey of hydrothermal emissions generated along a submarine arc front more than half seven of 13 of the volcanoes surveyed along 260 km of the southern kermadec arc ne of new zealand are hydrothermally active our results indicate that volcanic arcs represent a previously unheeded but potentially extensive source of shallow 2 km water depth vent fields expelling fluids of a unique and heterogeneous composition into the oceans

the upper end of the uk 37 temperature calibration revisited 1 being able to decipher paleo sea surface temperatures for warm oceanic waters is of the utmost importance to further evaluate the role of the tropics in global climate change the uk 37 index is one of such paleothermometers although the warm range of temperatures often poses serious analytical challenges this paper discusses and reviews several important aspects of the uk 37 index calibration for waters warmer than 26 27 c amongst them insights into the possible existence of a limit above which the uk 37 index is not able to accurately record temperature variations are presented some warnings are also given on the misleading practice and expected consequences of reporting uk 37 index values of unity in the cases when abundances of the minor triunsaturated alkenone below detection limit are encountered future directions toward an improved knowledge of the behaviour of the uk 37 calibration for warm waters are suggested

geochemistry of shallow tropical marine sediments from the arafura sea australia abstract tropical shelves have not been the focus of many biogeochemical studies this study presents new data from sediments collected in the arafura sea including headspace gas and lipid contents this allows assessment of modern depositional environments and reconstruction of environmental changes that have affected this tropical carbonate shelf during the last glacial transgression biomarker compositions from surface sediment and core samples from the upper 2 5 m revealed that marine algal input dominated the recently deposited organic matter over the survey area in a region closest to the shore high taraxerol abundance indicated a strong input of mangrove material to samples below 2 5 m indicating strong mangrove development associated with rising sea level during the transgression following the last glacial maximum when sea level stabilized around 6000 bp biomarker data indicate that the terrigenous contribution decreased and that palaeo channels formed during erosion of the continental shelf were infilled with marine dominated material sediments within these palaeo channels contained elevated concentration of dissolved ch4 at the base of the cores the source of the gas was determined to be microbial in origin based on depleted 13c isotopic composition 96 and very low concentration of wet gas components

formation of mid chain alkane keto ols by post depositional oxidation of mid chain diols in mediterranean sapropels abstract a high resolution 1 3 cm sediment intervals organic geochemical study was carried out on the upper 50 60 cm of three box cores including the s1 sapropel from eastern mediterranean sea sediments the corg ba al and mn al depth profiles were used to define the oxidised and unoxidised part of the s1 sapropel post depositional oxidation affected ca 50 of the original sapropel in all three cores resulting in a significant drop in corg c30 long chain 1 15 diol and keto ols in the extracts of these sediments were quantified by gc ms the vertical variation of these biomarkers in the three cores showed a common depth profile the c30 long chain 1 15 diol occurs almost exclusively in the unoxidised sapropel the corresponding c30 long chain keto ol follows this depth profile although the keto ol concentrations in the unoxidised sapropel are much lower than the diol concentrations however the keto ol keto ol diol ratio shows a significant increase at the base of the oxidised sapropel this suggests that the long chain diol was transformed upon post depositional oxidation into the chemically related long chain keto ol and that this keto ol was subsequently further oxidised these findings indicate that long chain keto ols which have no reported biological source but occur ubiquitously in marine sediments may be formed by oxidation of long chain diols both in the water column and in the sediment

bikpela a large siliceous chimney from the pacmanus hydrothermal field manus basin papua new guinea the 2 7 m bikpela chimney differs from sulfide rich chimneys at pacmanus eastern manus basin by virtue of high silica content a stromatolite like layered structure and the presence of a large internal collapse cavity its interior is dominated by 5 to 10 mm thick primary laminae of opal a dominated fronds clouded by submicroscopic sphalerite inclusions set between thin subhorizontal growth borders larger sphalerites with sulfosalt galena intergrowths at frond ends project into discoid cavities under the growth borders a steeper second order lamination reflects arrested expansion of the 50 cm high internal collapse cavity underlying the cavity floor an axial breccia pipe contains distorted fragments of laminated interior modified by dissolution and then redeposition of opal and further growth of pyrite and sphalerite beneath a thin mn oxide crust a hard outer sphalerite barite carapace 5 cm thick and devoid of opal is banded parallel to the chimney exterior at least three stages of chimney growth are evident beginning with repetitive deposition of opaline frond layers probably developed from microbial mat precursors by overgrowth of hydrothermal opal and fine sphalerite next with rising fluid temperatures hydrothermal fe poor sphalerite with pb sulfosalts and galena deposited at frond ends and under growth borders and via lateral diffusion and mixing with seawater formed abundantly in the outer carapace of the chimney passage of hot more acid fluids into the chimney axial zone then caused dissolution of primary opal and consequent formation of the collapse cavity and underlying breccia pipe together with deposition of fe rich sphalerite and pyrite in second order fractures and cavities related to the collapse finally conductive cooling during or after this latter stage produced films and spherules of clear opal coating pores and grain margins throughout the structure apart from in the carapace bikpela contains significant gold and silver avg 8 7 ppm au 250 ppm ag n 9 but it is low overall in cu up to 0 5 wt in the pipe and pb up to 0 7 wt in the carapace its carapace is relatively rich in zn up to 54 wt ag as and sb with one sample containing 0 12 wt silver

trace element systematics and ore forming processes in mafic vms deposits evidence from the troodos ophiolite cyprus abstract the volcanogenic massive sulfide vms deposits in the troodos ophiolite cyprus are ancient analogues for modern day seafloor massive sulfide mineralisation formed in a supra subduction zone environment in this study we present the first detailed in situ study of trace elements in sulfides from twenty vms deposits hosted in the troodos ophiolite to better understand factors that influence the distribution enrichment and incorporation of trace elements in different sulfide minerals on a mineral scale trace elements exhibit systematic variations between pyrite chalcopyrite and sphalerite pyrite preferentially incorporates as sb au and te whilst chalcopyrite is enriched in co and se sphalerite is trace element poor with the exception of ag and cd selenium averages 278 ppm n 150 in chalcopyrite but only 42 ppm n 1322 in pyrite bismuth and te in pyrite show a weak positive correlation r2 0 35 in some vms deposits possibly linked with the occurrence of bi telluride inclusions trace element concentrations also vary between colloform and euhedral pyrite with an enrichment of au as sb cu and zn in colloform compared to euhedral pyrite time resolved laser ablation profiles reveal that the trace element distribution on a mineral scale is not uniform and varies with crystallographic effects fluctuating physicochemical fluid conditions such as temperature ph fs2 fo2 and ligand availability during sulfide precipitation incorporation mechanisms in sulfides differ between elements in pyrite ag as se and pb are hosted in solid solution or as nanoscale inclusions whilst au sb and te may form micro scale inclusions on a regional scale 20 km the distribution of trace elements exhibits systematic variations between three major structural domains namely the solea mitsero and larnaca grabens the vms deposits of the magmatic tectonic solea graben are enriched in se co te au and cu relative to mitsero which is a purely extensional feature therefore we hypothesise that a variable magmatic volatile influx related to a magma volume b migration of the magmatic hydrothermal crack front and associated brine liberation or c a variation in protolith metal concentration are responsible for regional scale variations in vms geochemistry this is suggested to be intrinsically linked to the spreading architecture of troodos

non volatile hydrocarbon chemistry studies around a production platform on australia s northwest shelf abstract in september 1994 and 1995 scientists from the australian institute of marine science aims and the australian geological survey organization agso conducted surveys aboard the rv lady basten to determine the dispersion fates and effects of produced formation water pfw discharged from the harriet a oil production platform near the montebello islands this report is one of four related papers and describes the non volatile hydrocarbon chemistry studies the dispersion of the pfw into dissolved and particulate fractions of seawater were measured using moored high volume water samplers surface screen samplers and moored and drifting sediment traps bio accumulation was studied using transplanted oysters and dispersion measured into sediment with benthic grabs results showed enrichment in non volatile hydrocarbons in surface microlayer samples to a distance of 1 8 km in the direction of tidal flow concentrations in surface microlayers near the platform varied by an order of magnitude and corresponded to when a surface slick was visible or not visible concentrations of oil in seawater ranged from 2 0 to 8 5 g l 1 at near stations to 1 3 g l 1 at 1 8 km water column samples showed the processes of desorption from particles for soluble components occur within the range of 1 8 km most particulate hydrocarbons drop out of suspension within c 1 to 2 km from the platform fluxes of particulate hydrocarbons through the water column at c 1 km as estimated by moored sediment traps in 1995 were 138 to 148 ng cm 2 day 1 a decrease in sediment concentrations within c 1 km of the platform was measured as 2 45 1 29 g g 1 dry wt n 15 in 1994 to 0 86 0 54 g g 1 dry wt n 21 in 1995 after the platform installed a centrifugal separator in the discharge treatment process thus the residence time of this relatively low molecular weight oil was estimated in the coarse aerobic sands surrounding the platform to be less than one year oysters suspended near the platform bio accumulated hydrocarbons and other lipophilic organics in their tissues uptake rates and bio concentration factors of hydrocarbons indicated potential toxicity at the near field stations within c 1 km radius a mass balance was constructed to show the partitioning of the input of hydrocarbons from the pfw into the surrounding marine ecosystem the rates of dissipation processes were estimated as follows dilution from tidal currents degradation in the water column sedimentation evaporation the calculations based on maximum concentrations measured in the environmental samples accounted for 85 of the daily input suspended within a 1 km radius it is estimated that the potential zone of toxic influence in the water column extends to a distance of approximately 1 km concentrations of oil in sediments were too low to indicate potential toxicity by the collaborative application of oceanographic and geochemical techniques to marine environmental problems we endeavour to provide effective feedback to the oil industry to gauge the effectiveness of their operational strategies in minimizing impact in these pristine regions

systematic variations of trace element and sulfur isotope compositions in pyrite with stratigraphic depth in the skouriotissa volcanic hosted massive sulfide deposit troodos ophiolite cyprus the troodos ophiolite represents one of the best preserved fossil analogs of modern oceanic crust and includes numerous volcanic hosted massive sulfide deposits the skouriotissa deposit can be separated into a stockwork ore zone and an overlying massive sulfide lens that is covered by metalliferous sediments representing the former sulfide seawater interface pyrite is the dominant sulfide mineral within these ores the trace element composition of pyrite varies systematically with stratigraphic depth down to 150 mbsf probably reflecting fluid temperature variations and effects of phase separation co ni se te bi and cu metal remobilization due to hydrothermal zone refining zn sb and pb and fluid seawater mixing at the seafloor mo represent further important processes controlling the pyrite chemistry massive sulfide hosted sphalerite and euhedral pyrite probably formed from hot fluids 400 c while the occurrence of colloform pyrite indicates lower precipitation temperatures 400 c similar 18o quartz fluid equilibration temperatures 400 c in the stockwork zone suggest that the skouriotissa fluids did not cool significantly during the final 150 m of fluid ascent to the seafloor the 34s composition of deep stockwork pyrite 1 4 suggests that an isotopically light magmatic volatile phase 0 was added to the hydrothermal system of skouriotissa during further fluid ascent about 38 of cretaceous seawater 34s 18 19 was added leading to the precipitation of stockwork pyrite with positive 34s values 6 1 in addition the chemical and textural similarities between skouriotissa and modern seafloor vent systems and massive sulfide deposits suggest that the skouriotissa hydrothermal system has a modern analog

life on the edge microbial biomineralization in an arsenic and lead rich deep sea hydrothermal vent abstract unravelling complex microbial activity in modern hydrothermal vents can provide crucial insights into the evolution of ancient life on earth it is well established that microorganisms in hydrothermal vents have a significant impact on the cycling of metals and mineral formation however the detailed roles played by microorganisms in driving sulfide deposition and cycling of toxic metals like arsenic as and lead pb in high temperature deep sea hydrothermal vents remain unknown the understanding of these mechanisms in extreme environments is of particular importance as as has been postulated as a driver of microbial activities on the early earth here we present the first geologic evidence of pb as rich microbial filamentous clusters observed in a modern high temperature black smoker from the manus back arc basin papua new guinea the clusters occur as net like structures on the surface of barite and sulfides and are composed of multiple filaments and fine grained pb as sulfosalt each of the filaments includes an as pb rich sulfosalt core and organic rich shell structure with elevated carbon nitrogen and phosphorus further synchrotron x ray absorption near edge structure analysis shows that the clusters contain a mixture of as ii and as iii additionally those filaments show a close association with realgar as4s4 by penetrating and dissolving this as sulfide mineral we interpret the filaments to be a result of as related microbial activity in as and pb enriched hydrothermal environments the findings show possible processes through which extremophiles live in pb and as rich environments during chimney growth in addition as hydrothermal vents are regarded as modern analogs of ancient volcanogenic massive sulfide deposits the observed biominerals present the potential to be used as proxies to trace the signatures of early life in ancient geological systems

biogeochemistry of lipids in surface sediments of the peru upwelling area at 15 s abstract organic carbon lycopane a monoene of 2 6 10 trimethyl 7 3 methyl butyl dodecane c37 alkenones and 20 5 and 22 6 polyunsaturated fatty acid concentrations in two box cores from the peru continental margin area at 15 s in 90 and 268 m water depth have depth profiles that are synchronous and appear to indicate an historical record of fluctuating higher productivity lower productivity enso periods the u37k ratio calculated using c37 2 and c37 3 alkenones in the 268 m water depth core in the center of the upwelling zone varies with depth in the core in a manner consistent with the u37k functioning as an historical recorder of euphotic zone temperature concentrations and cpi for n alkanes c25 c31 are reported for both cores a c27 anthrasteroid has been identified and quantified in the 268 m water depth core

drilling shallow water massive sulfides at the palinuro volcanic complex aeolian island arc italy a subseafloor replacement style barite and sulfide occurrence was drilled in shallow waters at the palinuro volcanic complex the northernmost aeolian arc volcano in the tyrrhenian sea italy using a lander type drilling device 11 successful drill holes yielded a total of 13 5 m of core from a sediment filled depression located at a water depth of 630 to 650 m the longest continuous drill core recovered consists of 4 84 m of massive to semimassive barite and sulfides with abundant late native sulfur overprint seafloor observations suggest that the hydrothermal system associated with the formation of the subseafloor barite and sulfide ore zone is still active although black smoker activity does not occur on the seafloor the recovered drill core shows that the subseafloor deposit is zoned with depth the top of the mineralized zone is comprised of a variably silicified vuggy barite sulfide facies that shows notable polymetallic metal enrichment while the deeper portion of the mineralized zone is dominated by massive pyrite having distinctly lower base and precious metal grades metal zonation of the barite and sulfide deposit is related to the evolution of the hydrothermal fluids in space and time the barite cap and the massive pyrite present in the deeper portion of the mineralized zone appear to have formed early in the paragenesis during the main stage of the mineralization the barite cap was brecciated and cemented by a polymetallic assemblage of barite and pyrite with minor chalcopyrite and tetrahedrite trace famatinite and rare cinnabar lower temperature precipitates formed during the main stage of mineralization include sphalerite galena pyrite opal a and barite which are associated with traces of pb sb as sulfosalts such as bournonite seligmannite or semseyite a distinct mineral assemblage of fine grained anhedral enargite hypogene covellite chalcopyrite and galena is commonly associated with colloform sphalerite galena and pyrite as a late phase of this main stage colloform pyrite and marcasite are the last sulfides formed in the paragenetic sequence the deposit is interpreted to have formed from fluids having an intermediate sulfidation state although excursions to high and very high sulfidation states are indicated by the presence of abundant enargite and hypogene covellite laser ablation and conventional sulfur isotope analyses show that pyrite formed close to the seafloor within the zone of polymetallic metal enrichment has a variable sulfur isotope composition 34s 39 to 3 whereas a more narrow range is observed in the massive pyrite at depth 34s 10 to 0 similar variations were also documented for the late native sulfur overprint overall the negative sulfur isotope ratios at depth the intermediate to very high sulfidation conditions during mineralization and the abundance of native sulfur suggest contributions of magmatic volatiles to the mineralizing fluids from a degassing magma chamber at depth biological processes are interpreted to have played a major role during late stages of ore formation the combination of a subseafloor replacement deposit with a massive to semimassive barite cap rock overlying massive pyrite the intermediate to high sulfidation characteristics and the strong biological influence on the late stages of mineralization are distinct from other modern seafloor massive sulfide deposits and represents a style of submarine mineralization not previously recognized in a modern volcanic arc environment the barite and sulfide occurrence at palinuro shares many characteristics with porphyry related base metal veins and intermediate sulfidation epithermal deposits suggesting that metallogenic processes associated with arc related magmatic hydrothermal systems are not restricted to the subaerial environment

impacts of rapid sea level rise on mangrove deposit erosion application of taraxerol and rhizophora records we investigated a well dated marine sediment core from the tropical se atlantic covering the last 25 kyr applying taraxerol and rhizophora pollen as organic geochemical and palynological proxies for mangrove respectively taraxerol records are positively correlated with rhizophora pollen records showing an enhanced supply of mangrove materials into deep sea environments during the last deglaciation termination i sedimentation rates peaked during meltwater pulses 1a and 1b which were associated with the maxima of taraxerol and rhizophora pollen this study supports the view that mangrove input was dominantly controlled by erosion of mangrove rich shelf sediments during the transgressions whether reworked materials were penecontemporaneous or from much older deposits formed during previous sea level cycles is discussed copyright 2005 john wiley sons ltd

submarine magmatic hydrothermal systems at the monowai volcanic center kermadec arc the monowai volcanic center is located at the midpoint along the 2 530 km long tonga kermadec arc system the monowai volcanic center is comprised of a large elongate caldera monowai caldera area 35 km2 depth to caldera floor 1 590 m which has formed within an older caldera some 84 km2 in area to the south of this nested caldera system is a large composite volcano monowai cone which rises to within 100 m of the sea surface and which has been volcanically active for the past several decades mafic volcanic rocks dominate the monowai volcanic center basalts are the most common rock type recovered from the cone whereas basaltic andesites are common within the caldera hydrothermal plume mapping has shown at least three major hydrothermal systems associated with the caldera and cone 1 the summit of the cone 2 low temperature venting 60 c mussel ridge on the southwestern wall of the caldera and 3 a deeper caldera source with higher temperature venting that has yet to be observed the cone summit plume shows large anomalies in ph a shift of 2 00 ph units and 3he 358 and noticeable h2s up to 32 m and ch4 up to 900 nm the summit plume is also metal rich with elevated total dissolvable fe tdfe up to 4 200 nm tdmn up to 412 nm and tdfe tdmn up to 20 4 particulate samples have elevated fe si al and ti consistent with addition to the hydrothermal fluid from acidic water rock reaction plumes extending from 1 000 to 1 400 m depth provide evidence for a major hydrothermal vent system in the caldera the caldera plume has lower values for tdfe and tdmn although some samples show higher tdmn concentrations than the cone summit plume caldera plume samples are also relatively gas poor i e no h2s detected ph shift of 0 06 ph units ch4 concentrations up to 26 nm the composition of the hydrothermal plumes in the caldera have higher metal contents than the sampled vent fluids along mussel ridge requiring that the source of the caldera plumes is at greater depth and likely of higher temperature minor plumes detected as light scattering anomalies but with no 3he anomalies down the northern flank of the monowai caldera most likely represent remobilization of volcanic debris from the volcano flanks we believe the monowai volcanic center is host to a robust magmatic hydrothermal system with significant differences in the style and composition of venting at the cone and caldera sites at the cone the large shifts in ph very high 3he values elevated tdfe and tdfe tdmn and the h2s and ch4 rich nature of the plume fluids together with elevated ti p v s and al in hydrothermal particulates indicates significant magmatic volatile metal contributions in the hydrothermal system coupled with aggressive acidic water rock interaction by contrast the caldera has low tdfe tdmn in hydrothermal plumes however elevated al and ti contents in caldera particulate samples combined with the presence of alunite pyrophyllite sulfide minerals and native sulfur in samples from mussel ridge suggest past and perhaps recent acid volatile rich venting and active fe sulfide formation in the subsurface

sulfur isotope evidence for magmatic contributions to submarine and subaerial gold mineralization conical seamount and the ladolam gold deposit papua new guinea conical seamount is a submarine alkali basalt volcano situated 10 km south of lihir island in the tabar feni island chain papua new guinea polymetallic zn pb ag au as sb veins pyritic stockwork and hydrothermally altered rocks discovered on the summit of conical seamount represent a unique example of submarine gold mineralization with mineralogical chemical and textural characteristics common to some subaerial epithermal systems the giant ladolam epithermal gold deposit 42 moz au is situated in the crater of an alkali stratovolcano on lihir island portions of the epithermal mineralization and alteration assemblages at ladolam are similar to those observed on conical seamount conical seamount has the lightest hydrothermal i e nondiagenetic sulfide d34s values 17 5 to 6 1 measured to date from modern sea floor hydrothermal systems a previous model for the conical seamount hydrothermal system suggested a contribution of magmatic volatiles in the earliest stages of mineralization stage 1 followed by a combination of sulfur leached from the underlying volcanic rocks and reduced seawater sulfate during the main base and precious metal precipitating event stage 2 new sulfur isotope data allow a reinterpretation of this model that suggests a greater input of magmatic volatiles plus boiling throughout both stage 1 and 2 mineralization sulfides from the ladolam gold deposit have a range of sulfur isotope values 12 9 to 3 6 similar to that of conical seamount these sulfur isotope data have previously been interpreted as the result of magmatic volatiles escaping from a crystallizing magma and mixing with dilute meteoric ground water anhydrite associated with the gold mineralization has two populations of d34s values 8 14 and 20 22 which indicate the interaction of magmatic volatiles with seawater that has previously been discounted the range of sulfide and sulfate d34s values at ladolam is reinterpreted to be due to a complex interaction of magmatic hydrothermal fluids meteoric ground water and seawater native sulfur in thermal areas in luise caldera and pyrite in offshore hydrothermal vents in luise harbor have similar d34s values to the ladolam epithermal mineralization indicating that fluids similar to the young ladolam ore forming event are still reaching the floor of luise caldera sulfur isotope data from conical seamount and the ladolam deposit suggest that magmatic volatiles have contributed a significant amount of sulfur to both these gold rich hydrothermal systems

acidic and sulfate rich hydrothermal fluids from the manus back arc basin papua new guinea hot 88 120 c and acidic ph 2 1 hydrothermal fluids rich in sulfate were discovered venting in the desmos caldera depth 1926 m eastern manus back arc basin bismarck sea surrounded by papua new guinea the abundant sulfate 32 8 m m higher than the seawater value of 28 m m with elemental sulfur deposition around the vents and remarkably low d h 2 o and 34 s h 2 s values 8 1 and 5 6 respectively are suggestive of the incorporation of a magmatic fluid and the disproportionation of the exsolved so 2 from a magma body the desmos fluid may be similar in origin to the acidic sulfate chloride hot springs associated with subaerial volcanic activity in contrast to the typical hydrothermal end member mg concentration of 0 the desmos fluids are rich in mg 46 52 m m probably because of mg dissolution by acid attack upon magnesium silicate minerals

rare earth element abundances in hydrothermal fluids from the manus basin papua new guinea indicators of sub seafloor hydrothermal processes in back arc basins abstract rare earth element ree concentrations are reported for a large suite of seafloor vent fluids from four hydrothermal systems in the manus back arc basin vienna woods pacmanus desmos and susu knolls vent areas sampled vent fluids show a wide range of absolute ree concentrations and chondrite normalized reen distribution patterns lan smn 0 6 11 lan ybn 0 6 71 eu n eu n 1 55 reen distribution patterns in different vent fluids range from light ree enriched to mid and heavy ree enriched to flat and have a range of positive eu anomalies this heterogeneity contrasts markedly with relatively uniform reen distribution patterns of mid ocean ridge hydrothermal fluids in manus basin fluids aqueous ree compositions do not inherit directly or show a clear relationship with the ree compositions of primary crustal rocks with which hydrothermal fluids interact these results suggest that the rees are less sensitive indicators of primary crustal rock composition despite crustal rocks being the dominant source of rees in submarine hydrothermal fluids in contrast differences in aqueous ree compositions are consistently correlated with differences in fluid ph and ligand chloride fluoride and sulfate concentrations our results suggest that the rees can be used as an indicator of the type of magmatic acid volatile i e presence of hf so2 degassing in submarine hydrothermal systems additional fluid data suggest that near seafloor mixing between high temperature hydrothermal fluid and locally entrained seawater at many vent areas in the manus basin causes anhydrite precipitation anhydrite effectively incorporates ree and likely affects measured fluid ree concentrations but does not affect their relative distributions

geology hydrothermal activity and sea floor massive sulfide mineralization at the rumble ii west mafic caldera abstract sea floor imagery volcanic rock massive sulfide and hydrothermal plume samples 3 he ph dissolved fe and mn and particulate chemistry have been collected from the rumble ii west volcano southern kermadec arc new zealand rumble ii west is a caldera volcano with an 3 km diameter summit depression bounded by ring faults with a resurgent central cone rocks recovered to date are predominantly mafic in composition i e basalt to basaltic andesite with volumetrically lesser intermediate rocks i e andesite on the basis of its size geometry volcanic products and composition rumble ii west can be classified as a mafic caldera volcano rumble ii west has a weak hydrothermal plume signature characterized by a small but detectable 3 he anomaly 25 time series light scattering data though obtained from vertical casts and tow yos do show that hydrothermal activity has increased in intensity between 1999 and 2011 massive sulfides recovered from the eastern caldera wall and eastern flank of the central cone are primarily comprised of barite and chalcopyrite with lesser sphalerite pyrite and traces of galena the weak hydrothermal plume signal indicates that the volcano is in a volcanic hydrothermal quiescent stage compared to other volcanoes along the southern kermadec arc although the preponderance of barite with massive sulfide mineralization indicates higher temperature venting in the past of the volcanoes along the kermadec tonga arc known to host massive sulfides i e clark rumble ii west brothers monowai volcano 19 and volcano 1 the majority five out of six are dominantly mafic in composition and all but one of these mafic volcanoes form moderate size to large calderas to date mafic calderas have been largely ignored as hosts to sea floor massive sulfide deposits that 75 of the presently known massive sulfide bearing calderas along the arc are mafic in composition the dacitic brothers volcano is the exception has important implications for sea floor massive sulfide mineral exploration in the modern oceans and ancient rock record on land

genesis of acid sulfate alteration and au cu ag mineralization at summitville colorado the summitville au cu ag deposit occurs within a porphyritic quartz latite primarily in a zone of vuggy silica alteration characterized by leaching of all major elements except silica and iron vuggy silica is best developed between an elevation of 3 700 and 3 500 m where it occurs in irregular pipes and lenticular pods up to 70 m wide and is enclosed by up to 30 m of intense quartz alunite alteration the vuggy silica zones diminish in size with decreasing elevation and rarely exceed a width of 2 m below an elevation of 3 400 m these deep vuggy silica zones are enclosed by quartz kaolinite alteration with little or no alunite sulfide mineralization occurs primarily within the vuggy silica the sulfide assemblage changes with decreasing elevation from covellite luzonite or native gold to chalcopyrite tennantite sulfides occur lining voids or in microveinlets and are accompanied by minor kaolinitc but not by alunite gold also occurs in a near surface barite goethite jarosite assemblage that crosscuts the vuggy silica consideration of alunite kaolinitc and pyrite stability relations and of aluminum speciation at 250 degrees c indicates that a ph of 2 or below and a log f sub o 2 of 31 or 1 at 250 degrees c were necessary to produce vuggy silica alteration the chalcopyrite tennantite mineralization occurring at depth in the vuggy silica zone is indicative of less oxidizing and less acidic conditions the covellite luzonite or gold assemblage requires conditions intermediate between those necessary for vuggy silica alteration and for deep sulfide mineralization barite gold mineralization is interpreted as a near surface assemblage produced under highly acidic oxidizing conditions these textural and geochemical relationships indicate that sulfide and gold mineralization postdate the formation of vuggy silica alteration in the deposit and are not directly related to the highly acidic solutions necessary for this early acid leaching event the change from extreme acid leaching to copper sulfide and precious metal deposition may represent a transition from a magmatic vapor dominated to a liquid dominated system leading to more reducing and less acidic conditions during sulfide deposition

effects of magmatic volatile influx in mafic vms hydrothermal systems evidence from the troodos ophiolite cyprus abstract the troodos ophiolite cyprus is the principal on land analogue for mafic hosted volcanogenic massive sulfide vms deposits this study for the first time presents sulfur isotope 34s data on a regional scale from vms deposits and other mineralised zones across the troodos ophiolite in combination 34s se s ratios and trace element chemistry e g se cu and au of different hydrothermal sulfides are used to assess variations in magmatic volatile influx and the source of metals and sulfur in ancient hydrothermal systems sulfur isotope analyses n 180 across 19 mineral deposits indicate a variable source of sulfur in the troodos vms hydrothermal system this in turn allows a variable source of metals to be inferred pyrite 34s range from 5 5 to 13 2 with an average of 4 6 n 160 for all deposits investigated these 34s variations cannot only be explained by variable proportions of thermochemical seawater sulfate reduction 34s 18 to 19 and leaching of primary magmatic sulfur from igneous rocks 34s 0 1 consequently two processes are proposed explaining the trace metal and 34s variation across the troodos ore forming systems including i a variable source of metals in the sheeted dyke complex and ii the addition of a magmatic volatile rich phase to the vms hydrothermal systems two distinct lava units exist in the troodos stratigraphy namely the upper and lower pillow lavas upl and lpl the more primitive upl are enriched in au se and cu relative to as sb and zn that are concentrated in the lpl some vms deposits pre date the formation of the upl e g agrokipia a suggesting se cu and au depleted source rocks hence the stratigraphic position of vms deposits and the ratio of upl lpl affinity elements e g as zn sb vs cu se au imply a systematic relationship between trace element distribution and stratigraphic depth this relates to the relative proportion of upl and lpl affinity lavas within the metal source region 34s values 106 ratios 500 in pyrite suggest the contribution of a magmatic volatile component e g apliki and skouriotissa we demonstrate that the source of metals and sulfur in the troodos vms hydrothermal system is affected by regional scale processes related to i variable source lithologies and ii the contribution of a magmatic volatile phase to some troodos vms hydrothermal systems

insights to magmatic hydrothermal processes in the manus back arc basin as recorded by anhydrite microchemical analyses of rare earth element ree concentrations and sr and s isotope ratios of anhydrite are used to identify sub seafloor processes governing the formation of hydrothermal fluids in the convergent margin manus basin papua new guinea samples comprise drill core vein anhydrite and seafloor massive anhydrite from the pacmanus roman ruins snowcap and fenway and susu knolls north su active hydrothermal fields chondrite normalized ree patterns in anhydrite show remarkable heterogeneity on the scale of individual grains different from the near uniform ree n patterns measured in anhydrite from mid ocean ridge deposits the ree n patterns in anhydrite are correlated with ree distributions measured in hydrothermal fluids venting at the seafloor at these vent fields and are interpreted to record episodes of hydrothermal fluid formation affected by magmatic volatile degassing 87 sr 86 sr ratios vary dramatically within individual grains between that of contemporary seawater and that of endmember hydrothermal fluid anhydrite was precipitated from a highly variable mixture of the two the intra grain heterogeneity implies that anhydrite preserves periods of contrasting hydrothermal versus seawater dominant near seafloor fluid circulation most sulfate 34 s values of anhydrite cluster around that of contemporary seawater consistent with anhydrite precipitating from hydrothermal fluid mixed with locally entrained seawater sulfate 34 s isotope ratios in some anhydrites are however lighter than that of seawater which are interpreted as recording a source of sulfate derived from magmatic so 2 degassed from underlying felsic magmas in the manus basin the range of elemental and isotopic signatures observed in anhydrite records a range of sub seafloor processes including high temperature hydrothermal fluid circulation varying extents of magmatic volatile degassing seawater entrainment and fluid mixing the chemical and isotopic heterogeneity recorded in anhydrite at the inter and intra grain scale captures the dynamics of hydrothermal fluid formation and sub seafloor circulation that is highly variable both spatially and temporally on timescales over which hydrothermal deposits are formed microchemical analysis of hydrothermal minerals can provide information about the temporal history of submarine hydrothermal systems that are variable over time and cannot necessarily be inferred only from the study of vent fluids

venting of acid sulfate fluids in a high sulfidation setting at nw rota 1 submarine volcano on the mariana arc a comprehensive survey of hydrothermal plumes and their geochemistry revealed 16 hydrothermally active volcanoes along 1 200 km of the mariana arc from 13 5 n to 22 5 n of these 16 one volcano nw rota 1 is discharging sulfuric acid rich fluids producing some of the largest chemical anomalies ever observed in non buoyant hydrothermal plumes two types of venting were observed one of focused flow rich in al s si co2 fe mn and 3he and a second of diffuse flow rich in fe mn co2 and 3he but without al s and si the plume waters from the acid rich focused flow showed decreases in ph up to 0 73 ph units compared to ambient seawater and an estimated 80 percent of this change was brought about by volcanic and or hydrothermal so2 and possibly hcl with the remaining 20 percent by co2 conservative estimates suggest that the ph of the venting fluids was 1 0 the chemistry of this plume was also greatly different from that observed in any other hydrothermal setting an acid sulfate or high sulfidation fluid source was indicated from plume water samples rich in sulfuric acid native s al sulfate phosphate minerals and weathered silicate and amorphous silica phases the alunite group minerals and acidic fluids indicate that the most important hydrothermal reactions taking place within the hydrothermal system were resulting in advanced argillic alteration of the host volcanic rocks gas chemistry of the fluids revealed an he isotope signature with r ra 8 35 and 3he co2 3 25 109 these values are similar to those found along the global midocean ridge mor suggesting that the source of the 3he and co2 found here is predominantly from the upper mantle consistent with the position of nw rota 1 closest to the back arc in a chain of cross arc volcanoes the chemical signatures of the plumes arising from the diffuse flow remain greatly enriched in fe mn 3he and co2 but compared to the focused flow are low in mineral acidity h al and s the source of this diffuse flow is likely a fluid similar to that producing the acid rich plume but with a lower water to rock ratio and a longer reaction time resulting in the consumption of the mineral acidity this results in an increase in ph and the deposition of the alunite phosphate sulfate and other minerals close to the seafloor by comparison it is likely that the low ph focused flow ejects the vast majority of its mineral load into the water column which is not conducive to the formation of a mineral deposit at the sea floor and potentially would produce a barren prospect

kinetics of sulfide mineral oxidation in seawater implications for acid generation during in situ mining of seafloor hydrothermal vent deposits abstract growth in global metal demand has fostered a new age of unconventional mining on the seafloor in situ pulverization and extraction of seafloor massive sulfide sms deposits is economically attractive due to minimal overburden and high ore grades however important environmental questions remain on the significance of localized acid generation via irreversible sulfide mineral oxidation data on the reaction kinetics are necessary to estimate anthropogenic acid production during seafloor mining laboratory experiments were performed to evaluate the effects of ph temperature dissolved oxygen and surface area on the oxidation rate of pyrrhotite and chalcopyrite in seawater these minerals were chosen to constrain the range of reaction rates because pyrrhotite oxidizes relatively quickly while chalcopyrite is kinetically slow the rate laws for the abiotic oxidation of pyrrhotite and chalcopyrite in seawater at 22 c are given in the form r sp k m o 2 a m h b where rsp is the specific rate moles m 2 sec 1 k is the rate constant oxygen and proton concentrations are expressed in molalities m and their reaction orders as a and b respectively the specific rate laws obtained for each sulfide studied are r sp pyrrhotite 10 7 27 m o 2 aq 0 51 0 08 m h 0 08 0 03 r sp chalcopyrite 10 9 38 m o 2 aq 1 16 0 03 m h 0 36 0 09 when used to quantitatively predict maximum acid generation rates these rate laws indicate that acid production from in situ sms mining is insufficient to exceed the buffering capacity of advecting seawater we also calculated the residence times of crushed sulfides in seawater with low po2 0 10 atm ph of 8 23 c and find that depending on grain size mining waste may persist near the seafloor for years the implications are positive in terms of slow acid production but potentially problematic considering the potential ecological effects of an unnatural influx of particulates

strontium and neodymium isotopic characteristics of a heterolithic breccia in the basement of the sudbury impact structure canada abstract rb sr and sm nd measurements were undertaken on footwall breccia samples originating from levack township in the north range of the sudbury structure the granitic to quartzdioritic matrix of this heterolithic breccia which contains shocked rock and mineral fragments yields a rb sr isochron age of 1 825 0 021 ga isr 0 70356 0 00005 2 errors based on the analysis of 3 6 mm thick adjacent whole rock slabs from a large hand specimen this age is interpreted as a cooling age after the thermal metamorphism of the footwall breccia by the 1 85 ga old sudbury igneous complex which had caused temperatures in excess of 1000 c in the matrix near the contact mafic rock fragments in this breccia were excluded from the sr isotope exchange at that time the sm nd system of the identical small whole rock samples was only partly disturbed by the sudbury igneous complex the data points scatter around a 2 05 0 49 ga regression line without age significance plagioclase k feldspar and mafic mineral phases of the breccia matrix combined with the corresponding whole rocks display a range in rb sr ages from 1 67 0 08 ga to 1 430 0 015 ga obviously associated with metasomatic processes in the footwall breccia during the declining penokean metamorphism strontium and neodymium model parameters of the footwall breccia matrix near levack show little variation esrt 16 33 to 18 07 endt 10 69 to 11 79 t 1 86 ga and mean tnddm 2 74 0 04 ga based on these results bedrocks exposed in the south range and rocks now forming the sedimentary filling of the sudbury basin can be excluded as major components in the matrix of the analyzed footwall breccia the convergence of neodymium model ages with u pb ages on zircons from the levack gneiss which forms the crystalline basement adjacent to the footwall breccia in the levack area support an exclusively local origin for matrix and fragments of this breccia it is proposed that the footwall breccia is part of the uplifted floor of the sudbury crater

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

instability of partially saturated soil slopes due to alteration of rainfall pattern abstract the influence of climate change on rainfall patterns has the potential to alter stability of partially saturated soil slopes changes in rainfall patterns have a strong influence on stability of partially saturated soil slopes which recently have resulted in shallow landslides in this paper slope stability is assessed using a monolithically coupled finite element model for a deformable partially saturated soil subjected to surface infiltration of water numerical analysis solves for the matric suction distribution over a two dimensional cross section of a soil slope while varying permeability and considering a surface layer of soil with different permeability the formulation of hydraulic conductivity for a coupled analysis includes dependence on porosity and degree of saturation to illustrate the effects of water infiltration and deformation behavior in partially saturated soils numerical examples demonstrate that change in rainfall patterns may trigger slope instability earlier in the rainfall event than for rainfall events of the past assessment of these simulations can provide an indication of the potential influence of climate change on shallow landslides in many mountainous areas in south korea

subaqueous cryptodome eruption hydrothermal activity and related seafloor morphologies on the andesitic north su volcano abstract north su is a double peaked active andesite submarine volcano located in the eastern manus basin of the bismarck sea that reaches a depth of 1154 m it hosts a vigorous and varied hydrothermal system with black and white smoker vents along with several areas of diffuse venting and deposits of native sulfur geologic mapping based on rov observations from 2006 and 2011 combined with morphologic features identified from repeated bathymetric surveys in 2002 and 2011 documents the emplacement of a volcanic cryptodome between 2006 and 2011 we use our observations and rock analyses to interpret an eruption scenario where highly viscous crystal rich andesitic magma erupted slowly into the water saturated gravel dominated slope of north su an intense fragmentation process produced abundant blocky clasts of a heterogeneous magma olivine crystals within a rhyolitic groundmass that only rarely breached through the clastic cover onto the seafloor phreatic and phreatomagmatic explosions beneath the seafloor cause mixing of juvenile and pre existing lithic clasts and produce a volcaniclastic deposit this volcaniclastic deposit consists of blocky non altered clasts next variably 1 100 altered clasts hydrothermal precipitates and crystal fragments the usually applied parameters to identify juvenile subaqueous lava fragments i e fluidal shape or chilled margin were not applicable to distinguish between pre existing non altered clasts and juvenile clasts this deposit is updomed during further injection of magma and mechanical disruption gas propelled turbulent clast recycling causes clasts to develop variably rounded shapes an abundance of blocky clasts and the lack of clasts typical for the contact of liquid lava with water is interpreted to be the result of a cooled high viscosity crystal rich magma that failed as a brittle solid upon stress the high viscosity allows the lava to form blocky and short lobes the pervasive volcaniclastic cover on north su is partly cemented by hydrothermal precipitates these hydrothermally cemented breccias crusts and single pillars show that hydrothermal circulation through a thick layer of volcaniclastic deposits can temporarily increase slope stability through precipitation and cementation

active submarine eruption of boninite in the northeastern lau basin subduction of oceanic crust and the formation of volcanic arcs above the subduction zone are important components in earth s geological and geochemical cycles subduction consumes and recycles material from the oceanic plates releasing fluids and gases that enhance magmatic activity feed hydrothermal systems generate ore deposits and nurture chemosynthetic biological communities among the first lavas to erupt at the surface from a nascent subduction zone are a type classified as boninites these lavas contain information about the early stages of subduction yet because most subduction systems on earth are old and well established boninite lavas have previously only been observed in the ancient geological record here we observe and sample an active boninite eruption occurring at 1 200 m depth at the west mata submarine volcano in the northeast lau basin southwest pacific ocean we find that large volumes of h2o co2 and sulphur are emitted which we suggest are derived from the subducting slab these volatiles drive explosive eruptions that fragment rocks and generate abundant incandescent magma skinned bubbles and pillow lavas the eruption has been ongoing for at least 2 5 years and we conclude that this boninite eruption is a multi year low mass transfer rate eruption thus the lau basin may provide an important site for the long term study of submarine volcanic eruptions related to the early stages of subduction boninite lavas are erupted during the early stages of subduction however they have previously been found only in the ancient geological record discovery of an active boninite eruption shows that abundant volatile gases derived from the subducting slab drive this violent eruptive activity even in the deep sea

the influence of oxic degradation on the sedimentary biomarker record i evidence from madeira abyssal plain turbidites free and ester bound lipid biomarkers were analysed in oxidised and unoxidised parts of four distinct turbidites from the madeira abyssal plain map which contained 1 to 2 organic carbon homogeneously distributed throughout the turbidites at the time they were deposited these turbidites are well suited to study the effects of oxic degradation on lipid biomarkers without the complicating influence of varying organic matter sources sedimentation rates or bioturbation one sample from the oxidised turbidite was compared with two samples from the unoxidised part of each turbidite postdepositional oxic degradation decreased concentrations of biomarkers by several orders of magnitude the ester bound lipids were degraded to a far lesser extent than their free counterparts were the extent of degradation of different compounds differed substantially within a specific class of biomarkers degradation also took place to a different extent altering their distributions this study shows that oxic degradation of the organic matter may have a profound effect on the biomarker fingerprint and may result in a severe bias in for example the interpretation of organic matter sources and the estimation of the palaeoproductivity of specific groups of phytoplankton

native gold and gold rich sulfide deposits in a submarine basaltic caldera higashi aogashima hydrothermal field izu ogasawara frontal arc japan sulfide deposits with extremely high au concentrations up to 275 ppm avg 102 ppm n 15 high au ag ratios 0 24 n 15 and low cu cu zn ratios 0 03 n 15 were discovered in 2015 in active hydrothermal fields at a water depth of 760 m in a basalt dominated submarine caldera in the izu ogasawara frontal arc japan native gold grains occur in massive sulfide fragments concretions and metalliferous sediments from a sulfide mound 40 m across and 20 m high with up to 30 m high black smoker chimneys tiny native gold grains up to 14 m in diameter are mainly present in sulfide fallouts from chimney orifices and plumes larger native gold grains up to 150 m long occur mostly as discrete particles and or with amorphous silica and sulfides the larger gold grains are interpreted to represent direct precipitation from au bearing hydrothermal fluids circulating in and or beneath the unconsolidated sulfide mound deposits sulfur isotope compositions from a limited number of sulfide separates n 4 range from 4 3 to 5 8 34s similar to the quaternary volcanic rocks of the arc barite separates have values of 22 2 and 23 1 close to modern seawater values and indicate probable seawater sulfate origin the cu zn and pb concentrations in bulk samples of sulfide rich rocks are similar to those of volcanogenic massive sulfides formed in continental crustal environments the gold is interpreted to have formed by low temperature hydrothermal activity perhaps genetically different from systems with documented magmatic contributions or from seafloor hydrothermal systems in other island arc settings its presence suggests that basalt dominated submarine calderas situated on relatively thick continental crust in an intraoceanic arc setting such as the higashi aogashima knoll caldera may be perspective for gold mineralization

2 7 ga plume associated vhms mineralization in the eastern goldfields superterrane yilgarn craton insights from the low temperature and shallow water ag zn au nimbus deposit economic volcanic hosted massive sulfide vhms deposits of the archaean yilgarn craton of western australia are restricted to zones of juvenile crust as revealed through regional nd pb and hf isotopic variations and the geochemistry of felsic volcanic rocks interpreted as archaean paleo rift zones one of these runs n s through the eastern goldfields superterrane broadly coincident with the kurnalpi terrane and is associated with the high grade ca 2690 ma teutonic bore jaguar and bentley deposits plus sub economic vhms mineralization further south to date only small historic cu occurrences e g anaconda and barren pyritic lenses have been recognized in the older 2 7 ga plume dominated lower stratigraphy of the eastern goldfields superterrane the nimbus ag zn au deposit 12 1 mt at 52 g t ag 0 9 zn and 0 2 g t au is located approximately 10 km east of kalgoorlie near the margin of the kurnalpi terrane its origin has been contentious for a number of years with previous models favouring seafloor sub seafloor vhms mineralization or a high sulfidation fault hosted system we present a detailed account of the deposit its host stratigraphy and associated hydrothermal alteration plus two new shrimp u pb zircon ages pb isotope galena and o isotope zircon constraints compared to other vhms occurrences in the yilgarn craton the nimbus deposit is unusual in terms of its tectono stratigraphic position the geochemistry of its host sequence i e fi affinity felsic volcanic rocks ocean plateau like low th basalts mineralogy e g abundance of ag sb pb as bearing sulfosalts high hg low cu and quartz carbonate sericite dominated alteration assemblages classification of nimbus as a shallow water and low temperature vhms deposit with epithermal characteristics i e a hybrid bimodal felsic deposit is consistent with its position near the margin of the kurnalpi paleo rift zone and radiogenic 238u 204pb values the recognition that the nimbus deposit is associated with c 2705 ma plume magmatism opens new areas for vhms exploration in the eastern goldfields superterrane over a strike length exceeding 500 km

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

metalliferous sediments associated with presently forming volcanogenic massive sulfides the susu knolls hydrothermal field eastern manus basin papua new guinea short sediment cores were examined from the active susu knolls hydrothermal field in the eastern manus back arc basin papua new guinea in order to explain the origin of the currently accumulating metalliferous sediments the mineralogy and geochemistry of the sediments were studied by x ray diffraction scanning electron microscopy energy dispersive x ray fluorescence and instrumental neutron activation analysis sediments of the suzette site originated from the deposition of volcaniclastic material with the addition of a hydrothermal component from the mass wasting of old oxidized chimneys a strong mass wasting event was recognized at the base of the studied sedimentary succession from the occurrence of chalcopyrite pyrite and barite aggregates similar to those found in chimneys as well as the presence of atacamite the metalliferous component is characterized by high concentrations of cu up to 2 3 and au up to 3 5 ppm elevated concentrations of as ba zn and fe as well as a positive eu anomaly the material derived from eroded chimneys was deposited together with abundant glass fragments eroded from the volcanic edifice the mass wasting was succeeded by deposition of volcaniclastic sediment containing dacite fragments ca plagioclase pyroxene glass shards cristobalite si rich amorphous material alunite pyrite barite and magnetite the volcaniclastic sediment may have originated from hydrothermal eruptions at north su and south su the present day plume at suzette is a likely source of rare barite aggregates amorphous cu containing aggregates and cu fe sulfides creating geochemical anomalies of ba and cu in the uppermost sediments at suzette interbedded volcaniclastic and hemipelagic sediments were retrieved east and west of susu knolls the enrichment of mn in these sediments is considered to be a result of settling of mn oxides from a hydrothermal plume

episodic subseafloor hydrothermal activity within the eastern manus back arc basin determined by uranium series disequilibrium in barite the geochronology of seafloor hydrothermal activity from several mineralized active and inactive vent fields at suzette and pual ridge eastern manus back arc basin bismarck sea papua new guinea has been established using the 228th 228ra 228ra 226ra and 226ra ba uranium series disequilibrium methods for barite rich samples these hydrothermal systems underwent episodes of hydrothermal fluid circulation that produced barite over the last 6 000 years precipitation of hydrothermal barite disseminated within the host rock and lining fractures vugs and conduits was controlled by decreasing temperatures and mixing of hydrothermal fluids with oxidized seawater repeated fluctuations in hydrothermal fluid temperature and chemistry resulted in complex sequences of barite and sulfide minerals lining vugs and conduits whereas rapid cooling following fracture events led to precipitation of only barite and some fe oxide coatings on barite crystals a wide range in ages of barite within drill cores i e 380 5 990 yrs before present bp reflect repeated pulses of hydrothermal fluids through the altered volcanic and mineralized rocks that make up the hydrothermal mound structures with the younger ages i e 34 220 yrs bp representing more recent barite precipitating fluid circulation accessing fractures veins and vugs barite from chimney samples is mostly young i e 23 1 680 yrs bp with the majority precipitated between 23 to 41 yrs bp reflecting the structural stability standing life of the chimneys and possible influences from varying hydrothermal fluid chemistry or reactivation of vent fields three generalized age groupings representing major episodes of barite precipitating hydrothermal fluid circulation are resolved from the suzette area 19 45 810 1 900 and 3 740 4 710 yrs bp including 1 errors with the most recent ages recorded from both the suzette and pual ridge areas fast spreading rates within the manus basin an abundance of faults and variable magmatic inputs are major factors controlling the frequency and longevity of these episodes of hydrothermal activity mineral resource models and comparisons indicate that the cu zn ag au rich suzette deposit is small however the measured age range is comparable to ages given for modeled typical seafloor massive sulfide deposits from back arc and arc environments we suggest that the scale of the suzette deposit may have been limited during formation by a low hydrothermal fluid flux and or inappropriate physical and chemical conditions for sufficient metal precipitation from hydrothermal fluids

mineralogy and geochemistry of an archean tuffaceous exhalite the main contact tuff millenbach mine area noranda quebec the main contact tuff in the vicinity of millenbach mine noranda quebec is an extensive although discontinuous ore related volcanic exhalative metalliferous sediment or tuffaceous exhalite of archean age it was formed by the variable contribution of two constituents 1 exhalite chemical composed mainly of pyrite quartz sphalerite pyrrhotite and chalcopyrite and 2 tuff clastic composed of quartz chlorite and sericite tuffaceous exhalites such as the main contact tuff and the similar tetsusekiei of the japanese kuroko deposits miocene age indicate a fossil hydrothermal system that may or may not have produced economic concentrations of metallic sulfides the main contact tuff displays cryptic variations which provide exploration guides at different scales 1 the fe fe mg ratios of chlorite decrease from 0 63 to 0 32 over a distance of 0 3 km approaching ore from the north and from 0 72 to 0 32 over 1 5 km from the south 2 the feo feo mgo sulfide free ratios of who

palaeoclimatic signals recognized by chemometric treatment of molecular stratigraphic data abstract the high resolution stratigraphy of various marker compounds has been studied using gc hplc and gc ms in a 13 m gravity core recovered from the kane gap region eastern equatorial atlantic which provides a record of the glacial interglacial episodes over the last million years downhole variations in many presumed source specific components are observed e g in n alkanes from terrigenous land plants and dinosterol from dinoflagellates which may be due to perturbations or cyclicities resulting from climatic change fluctuations in the unsaturation of alkenones attributable to variations in water temperatures show correlations with the glacial interglacial cycles recorded in the 18 o values for planktonic foraminifera thereby providing a potential organic geochemical measure of past climates these molecular abundance data can be linked to the palaeotemperature record following computer treatments using principal component and spectral analyses molecular stratigraphy shows promise as a new chemostratigraphical tool where other means of stratigraphy fail for example through calcium carbonate dissolution

the susu knolls hydrothermal field eastern manus basin papua new guinea an active submarine high sulfidation copper gold system susu knolls comprises three steep sided conical volcanic peaks standing on a n nw trending ridge in the eastern manus basin a complex zone of convergence between the major indo australian and pacific plates the knolls consist of three porphyritic andesite to dacite domes each 1 0 to 1 5 km in diameter with crests ranging from 1 150 to 1 520 m below sea level an intense hydrothermal plume with peak transmission anomalies in excess of 40 originates from susu knolls and associated hydrothermal venting with fluid temperatures exceeding 300 c and sulfide mineralization has been detected on the crests of all three edifices the most important of these is the 2 47 million metric ton mt solwara 1 copper gold deposit on suzette knoll slated for mining by nautilus minerals the porphyritic dacite is commonly strongly altered by reaction with acidic fluids fragments of sulfide mineralization collected as part of the seafloor talus surrounding the crest of north su and south su are characterized by an assemblage of pyrite fukuchilite enargite covellite chalcopyrite by contrast there are actively venting chimneys on the crest of suzette that are typically zoned with chalcopyrite pyrite tennantite inner zones and barite dominated outer zones the knolls are covered by black sulfidic sediments that contain up to 2 4 wt cu and 3 2 ppm au primary feldspars have been obliterated by the hydrothermal activity that ranges from incipient to intense and which is characterized by natroalunite alunite north su only cristobalite tridymite and rare quartz and kaolinite most volcanic rocks exhibit a patchy surficial coating of native sulfur which may also fill vesicles no altered rocks were dredged from suzette because of the thick sulfidic sediment cover mass balance calculations for altered and unaltered rock from north and south su show that major and trace lithophile elements are depleted in the altered rocks except for ti al si and zr all near immobile in concert with the destruction of the primary minerals and removal of primary components by acidic fluids sulfur and chalcophile trace elements i e as au ba cd cu mo pb and se typically associated with magmatic cu au mineralization are enriched by orders of magnitude in both leached and mineralized rock sulfide and native sulfur 34s values from all three domes range from 7 4 to 0 4 indicating a magmatic component for the sulfur a small group of ore elements i e ag bi in sb and zn are strongly enriched in mineralized breccias and depleted in the altered dacites suggesting redistribution during alteration the presence of advanced argillic alteration the paragenesis of the fe cu as sulfide assemblage and presence of native sulfur together with the sulfur isotope evidence for magmatic input into the hydrothermal fluid at susu knolls are consistent with a submarine high sulfidation magmatic cu au hydrothermal system furthermore the sulfide assemblage pyrite enargite covellite chalcopyrite observed at north and south su and orders of magnitude enrichment of chalcophile elements in both altered and mineralized volcanic rocks relative to unaltered volcanic rock are also characteristic of subaerial high sulfidation epithermal mineralization the susu knolls hydrothermal field is a good example of a modern high sulfidation cu au submarine hydrothermal system

subsurface deposition of cu rich massive sulphide underneath a palaeoproterozoic seafloor hydrothermal system the red bore prospect western australia the proterozoic bryah and yerrida basins of western australia contain important base and precious metal deposits here we present microtextural data trace element and s isotope analyses of massive sulphide mineralisation hosted in palaeoproterozoic subvolcanic rocks dolerite recently discovered at red bore the small scale high grade mineralisation which extends from the sub surface to at least 95 m down hole is dominated by massive chalcopyrite and contains minor pyrite and bi te se phases massive sulphide mineralisation is surrounded by discontinuous brecciated massive magnetite and a narrow 2 m alteration halo which suggests very focussed fluid flow laser ablation icp ms analyses indicate that chalcopyrite contains up to 10 ppm au and in excess of 100 ppm ag sulphur isotope analyses of pyrite and chalcopyrite indicate a narrow range of 34svcd 0 2 to 4 6 and no significant mass independent fractionation 0 1 33s 0 05 re os isotope analyses yield scattered values which suggests secondary remobilisation despite the geographical proximity and the common cu au ag association the mineralisation at red bore has significant differences with massive sulphide mineralisation at neighbouring degrussa as well as other massive sulphide deposits around the world these differences include the geometry sub volcanic host rocks extreme cu enrichment and narrow 34s ranges although a possible explanation for some of these characteristics is leaching of s and metals from the surrounding volcanic rocks we favour formation as a result of the release of a magmatic fluid phase along very focussed pathways and we propose that mixing of this fluid with circulating sea water contributed to sea floor mineralisation similar to neighbouring vhms deposits our data are permissive of a genetic association of red bore mineralisation with vhms deposits nearby thus suggesting a direct connection between magmatism and mineralising fluids responsible for vhms deposition at surface therefore the red bore mineralisation may represent the magmatic roots of a vhms system

influences of the tonga subduction zone on seafloor massive sulfide deposits along the eastern lau spreading center and valu fa ridge abstract this study investigates the morphology mineralogy and geochemistry of seafloor massive sulfide sms deposits from six back arc hydrothermal vent fields along the eastern lau spreading center elsc and valu fa ridge vfr in the context of endmember vent fluid chemistry and proximity to the tonga subduction zone to complement deposit geochemistry vent fluid analyses of cu zn ba pb and h 2 aq were completed to supplement existing data and enable thermodynamic calculations of mineral saturation states at in situ conditions results document southward increases in the abundance of mantle incompatible elements in hydrothermal fluids ba and pb and sms deposits ba pb as and sb which is also expressed in the abundance of barite baso 4 and galena pbs in sms deposits these increases correspond to a decrease in distance between the elsc vfr and the tonga subduction zone that correlates with a change in crustal lithology from back arc basin basalt in the north to mixed andesite rhyolite and dacite in the south barite influences deposit morphology contributing to the formation of horizontal flanges and squat terraces results are also consistent with a regional scale lowering of hydrothermal reaction zone temperatures from north to south except at the southernmost mariner vent field that leads to lower temperature higher ph vent fluids relative to mid ocean ridges of similar spreading rates mottl et al 2011 these fluids are cu and zn poor and the deposits formed from these fluids are cu poor but zn rich in contrast at the mariner vent field higher temperature and lower ph vent fluids are hypothesized to result from higher reaction zone temperatures and the localized addition of acidic magmatic volatiles mottl et al 2011 the mariner fluids are cu and zn rich and vent from sms deposits that are rich in cu but poor in zn with moderate amounts of pb thermodynamic calculations indicate that the contrasting metal contents of vent fluids and sms deposits can be accounted for by vent fluid ph wurtzite sphalerite zn fe s and galena pbs are saturated at higher temperatures in higher ph zn cu and pb poor elsc vfr vent fluids but are undersaturated at similar temperatures in low ph zn cu and pb rich vent fluids from the mariner vent field indicators of ph in the elsc and vfr sms deposits include the presence of co precipitated wurtzite and chalcopyrite along conduit linings in deposits formed from higher ph fluids and different correlations between concentrations of zn and ag in bulk geochemical analyses significant positive bulk geochemical zn ag correlations occur for deposits at vent fields where hydrothermal fluids have a minimum ph at 25 c 3 6 data show that the compositions of the mineral linings of open conduit chimneys minerals present mol fes in zn fe s that precipitate directly from hydrothermal fluids closely reflect the temperature and sulfur fugacity of sampled hydrothermal fluids these mineral lining compositions thus can be used as indicators of hydrothermal fluid temperature and composition ph metal content sulfur fugacity

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

aliphatic hydrocarbons in great barrier reef organisms and environment abstract this investigation was undertaken to assess the chemical nature occurrence and possible origin of petroleum hydrocarbons in the great barrier reef ecosystem aliphatic hydrocarbons in surface sediments water and a suite of seven species from widely separated coral reefs in the great barrier reef area were analysed by gas chromatography and by gas chromatography coupled with mass spectrometry the hydrocarbons found were substantially of biogenic origin the major components were n pentadecane n heptadecane pristane and mono alkenes based on heptadecane and were believed to originate from benthic algae and phytoplankton there was no evidence to suggest that lipid content had any influence on hydrocarbon content hydrocarbons from the organisms and sediments have characteristic composition patterns which would be altered by the presence of petroleum hydrocarbons an unresolved complex mixture usually considered indicative of petroleum contamination was found in greater than trace amounts only in holothuria sea cucumber and acropora coral from the capricorn group and in some sediment samples from the capricorn group and lizard island area

the ree content of some hydrothermal fluids ree concentrations were determined in solutions from submarine hydrothermal vents on the east pacific rise and for the first time from continental geothermal fields in tibet and bulgaria they indicate that in hydrothermal systems ree are immobile at temperatures below 350 c and for water rock ratios of 105 nd values of submarine solutions and anhydrites 4 7 to 6 2 suggests recharge on the sedimentcovered flanks of the ridge carbonate anions as measured by alkalinity appear to increase the solubility of heavy ree somewhat but not to the extent that substantial amounts of ree could be driven out from rocks by hydrothermal activity

geochemistry of hot springs at the susu knolls hydrothermal field eastern manus basin advanced argillic alteration and vent fluid acidity abstract susu knolls is an area of ongoing magmatic activity and recent volcanism located in the back arc spreading environment of the manus basin in the bismarck sea papua new guinea in 2006 hydrothermal fluids were collected from three areas of submarine hot spring venting and analyzed for the chemical and isotopic composition of major and trace species fluids were characterized by temperatures that varied from 226 325 c and formed grey to black smoke as they mixed with bottom seawater the compositions of seawater derived vent fluids are regulated by the relative contributions of fluid rock and fluid sediment interaction phase separation and the addition of volatiles from magmatic degassing in addition to phase separation leaching of cl from felsic rocks that compose the lithosphere in back arc environments may produce cl concentrations in excess of seawater values the measured ph25 c of susu knolls smoker fluids varied from 1 5 3 7 a range that includes values substantially more acidic than typically observed in fluids at mid ocean ridge spreading centers late stage addition of magmatic volatiles in the shallow seafloor is directly responsible for the most acidic fluids ph25 c values below 2 in contrast the acidity of vent fluids characterized by ph25 c values between 2 and 3 is not the direct result of the direct addition of magmatically derived acidic species instead the ph of these fluids likely reflects reaction with rocks that were previously altered by highly acidic magmatic fluids to an advanced argillic alteration assemblage containing quartz illite pyrophyllite anhydrite alunite in hydrothermal upflow zones fluids that do not react with advanced argillic alteration assemblages during upflow have measured ph25 c values between 3 and 4