microbial sulfate reduction in deep sea sediments at the guaymas basin hydrothermal vent area influence of temperature and substrates abstract microbial sulfate reduction was studied by a 35 s tracer technique in sediments from the hydrothermal vent site in guaymas basin gulf of california mexico in situ temperatures ranged from 2 7 c in the overlying seawater to 120 c at 30 cm depth in the hydrothermal sediment sulfate reduction was measured in intact cores of hydrothermal sediment at 3 20 35 50 70 and 90 c the maximum rates of sulfate reduction were found in the upper 0 2 cm of the sediment and ranged from 32 nmol cm 3 d 1 at 90 c to 1563 nmol cm 3 d 1 at 70 c the rates of sulfate reduction rapidly decreased with depth in the upper 0 10 cm of the sediment and the maximal depth integrated rate 0 10 cm was 70 3 mmol so 4 2 m 2 d 1 at 70 c in comparison the sulfate reduction rate in nonhydrothermal sediment from the vent area was 0 85 mmol m 2 d 1 at the in situ temperature of about 3 c the high subsurface rates of sulfate reduction in the hydrothermal vent area was attributed to an enhanced local substrate availability in slurries of hydrothermal sediment incubated at 10 120 c microbial sulfate reduction extended to 102 c and different temperature groups of microbial sulfate reducers had optimum temperatures at around 34 70 and 80 88 c the overall temperature response of thermophilic sulfate reduction was similar in hydrothermal sediment sampled at different sites addition of short chain fatty acids and yeast extract to the sediment slurries stimulated sulfate reduction rates at all incubation temperatures no sulfate reduction was detected in the temperature range from 102 120 c microbial rather than thermochemical sulfate reduction could be a possible source of h 2 s in sulfide deposits with formation temperatures at about 100 c

low temperature hydrothermal maturation of organic matter in sediments from the atlantis ii deep red sea abstract hydrocarbons and bulk organic matter of two sediment cores no 84 and 126 chain 61 cruise located within the atlantis ii deep have been analyzed although the brines overlying the coring areas were reported to be sterile microbial inputs and minor terrestrial sources represent the major sedimentary organic material this input is derived from the upper water column above the brines both steroid and triterpenoid hydrocarbons show that extensive acid catalyzed reactions are occurring in the sediments in comparison with other hydrothermal guaymas basin or intrusive systems cape verde rise the atlantis ii deep exhibits a lower degree of thermal maturation this is easily deduced from the elemental composition of the kerogens and the absence of polynuclear aromatic hydrocarbons of a pyrolytic origin in the bitumen the lack of carbon number preference among the n alkanes suggests especially in the case of the long chain homologs that the organic matter of atlantis ii deep sediments has undergone some degree of catagenesis however the yields of hydrocarbons are much lower than those observed in other hydrothermal areas the effect of lower temperature and poor source rock characteristics appear to be responsible for the differences

a molecular organic carbon isotope record of miocene climate changes the difference in carbon 13 13c contents of hopane and sterane biomarkers in the monterey formation naples beach california parallels the miocene inorganic record of the change in 18o 18o reflecting the miocene evolution from a well mixed to a highly stratified photic zone upper 100 meters in the pacific steranes 13c 25 4 0 7 per mil versus the pee dee belemnite standard from shallow photic zone organisms do not change isotopically throughout the miocene in contrast sulfur bound c35 hopanes likely derived from bacterial plankton living at the base of the photic zone have systematically decreasing 13c concentrations in middle and late miocene samples 13c 29 5 to 31 5 per mil consistent with the middle miocene formation of a carbon dioxide rich cold water mass at the base of the photic zone

carbon isotope systematics of individual hydrocarbons in hydrothermal petroleum from middle valley northeastern pacific ocean abstract individual aliphatic hydrocarbons in samples of bulk hydrothermal petroleum from middle valley odp site 858 were submitted to compound specific isotope analysis to trace their origins the c isotope compositions of the n alkanes and isoprenoid hydrocarbons means n alkanes 30 1 1 01 858a 28 3 1 7 858c and 24 8 1 4 858d isoprenoids 26 0 2 7 858c and 27 9 0 4 858d respectively reflect mixed marine and terrestrial organic matter sources biphytane from thermophiles has a 13 c value of 21 0

sedimentary geochemistry of hydrothermal vents in guaymas basin gulf of california mexico abstract surface sediments from 4 contrasting environmental settings in the southern trough of guaymas basin were analysed to determine their texture total organic matter tom p tp and n tn content as well as the spatial variation in their c n p atomic ratios in hydrothermally altered sediments particle size analysis revealed a marked spatial heterogeneity among sites cores taken at beggiatoa bacterial mats and at clam fields contained significant silt and clay content while those obtained near venting sites had sand and gravel as the main components because no fine sedimentary materials are deposited at these sites fine grain sediments were common farther away from vents high levels of organic c 3 4 to 12 4 were recorded in the upper 8 cm but no clear trends of decreasing toc with depth were noted the presence of hydrothermally generated petroleum in some cores increased the organic c content between 8 and 12 cm tn was generally high 456 3 4356 g g and sustained a significant correlation with tom r 0 834 p beggiatoa or vesicomyd clams are predominant

comparison of 14c ages of hydrothermal petroleums abstract in order to set limits on the time frame of formation of hydrothermal petroleum we have obtained 14 c ages on samples from three diverse regions gulf of california guaymas basin northeast pacific ocean escanaba trough and middle valley and the east african rift tanganyika trough the results date the source of carbon and therefore provide maximum ages for the formation and emplacement of the hydrothermal petroleums the youngest petroleum occurs iin the souther trough of guaymas basin 3200 6600 yr mean 4692 yr in the northern trough the petroleum is slightly older 7400 yr significantly older hydrothermal petroleum occurs in escanaba trough 17 000 yr and middle valley 29 000 yr a continental example from the east african rift has an age of 25 000 yr comparable to the ages observed in the oceanic samples from the northeast pacific ocean these ages affirm that hydrothermal petroleum formation is a very rapid process and took place some time between the latest pleistocene and the present in these active hydrothermal systems

glacial and nonglacial sediment contributions to wisconsin episode loess in the central united states the relative contributions of various glacial and nonglacial sediments to wisconsin episode loess units along the lower illinois and central mississippi valleys are estimated on the basis of a comparison of magnetic susceptibility and silt and clay mineralogy a mathematical method of source area calculation using four compositional parameters was guided by current knowledge of the regional glacial history on the basis of this technique the roxana silt along the illinois and mississippi river valleys is composed of significant superior lobe sediment 35 40 as well as wadena or des moines lobe sediment about 35 this can account for its high magnetic susceptibility feldspar content kaolinite content and pink hue lower peoria silt contains about 25 35 lake michigan lobe sediment with reduced contributions of the other sources after the mississippi river s diversion 20 4 ka the supply of superior des moines and wadena lobe sediment was cut off from the illinois valley in favor of lake michigan lobe sediment 75 80 contribution this major source area shift accounts for higher dolomite and illite contents and a more yellow hue in approximately the upper two thirds of peoria silt in the study area in loess south of st louis less pronounced compositional shifts occur because superior lobe sediment was not cut off and because des moines lobe wadena lobe and missouri river sediments having more intermediate composition compose 40 50 of the loess thereby diluting other source area changes nonglacial sediment from fluvial and periglacial sources is estimated to compose 10 40 of loess in both regions

high molecular weight polycyclic aromatic hydrocarbons in hydrothermal petroleums from the gulf of california and northeast pacific ocean hydrothermal petroleums and heavy tars have been analyzed for polycyclic aromatic hydrocarbons pah with molecular weights greater than that of coronene 300 da samples from the hydrothermal systems in the guaymas basin gulf of california and in the escanaba trough and middle valley northeastern pacific were analyzed by gas chromatography mass spectrometry and high pressure liquid chromatography with diode array absorbance detection mass spectra and fluorescence spectra were used to characterize the compounds several large pahs with six and more rings were identified among the heavy pah production routes via one ring build up and scholl condensation are proposed to explain the observed structures the variations in pah concentrations and distributions between samples from different locales are a consequence of the hydrothermal conditions of generation migration and post depositional alteration

trace element degassing and enrichment in the eruptive plume of the 2000 eruption of hekla volcano iceland during its last eruption in february 2000 hekla volcano iceland emitted a sub plinian plume that was condensed and scavenged down to the ground by heavy snowstorms offering the unique opportunity to study the chemistry of the gaseous plume released during highly explosive eruptions in this paper we present results on trace element and minor volatile species sulfates chlorides and fluorides concentrations in snow samples collected shortly after the beginning of the eruption the goal of this study is to better constrain the degassing and mobility of trace elements in gaseous emissions trace element volatility at hekla is quantified by means of enrichment factors ef relative to be well known volatile trace elements e g transition metals heavy metals and metalloids are considerably enriched in the volcanic plume of hekla their abundances are governed by the primary magmatic degassing of sulfate and or halide compounds which are gaseous at magmatic temperature their volatility is however slightly lower than in basaltic systems most likely because of the lower magma temperature and higher magma viscosity at hekla more surprisingly refractory elements e g ree th ba and y are also significantly enriched in the eruptive plume of hekla where their apparent volatility is two orders of magnitude higher than in mafic systems in addition ree patterns normalized to the hekla 2000 lava composition show a significant enrichment of hree over lree suggesting the presence of ree fluorides in the volcanic plume such enrichments in the most refractory elements and ree fractionation are difficult to reconcile with primary degassing processes since ree fluorides are not gaseous at magma temperature ree enrichments at hekla could be attributed to incongruent dissolution of tephra grains at low temperature by f rich volcanic gases and aerosols within the eruptive plume this view is supported by both leaching experiments performed on hekla tephra and thermodynamic considerations on ree mobility in hydrothermal fluids and modeling of glass dissolution in f rich aqueous solutions tephra dissolution may also explain the observed enrichments in other refractory elements e g th y and ba and could contribute to the degassing mass balance of some volatile trace elements provided they are mobile in f rich fluids it thus appears that both primary magmatic degassing and secondary tephra dissolution processes govern the chemistry of eruptive plumes released during explosive eruptions

atmospheric chemistry of a 33 34 hour old volcanic cloud from hekla volcano iceland insights from direct sampling and the application of chemical box modeling 1 on 28 february 2000 a volcanic cloud from hekla volcano iceland was serendipitously sampled by a dc 8 research aircraft during the sage iii ozone loss and validation experiment solve i it was encountered at night at 10 4 km above sea level in the lower stratosphere and 33 34 hours after emission the cloud is readily identified by abundant so2 1 ppmv hcl 70 ppbv hf 60 ppbv and particles which may have included fine silicate ash we compare observed and modeled cloud compositions to understand its chemical evolution abundances of sulfur and halogen species indicate some oxidation of sulfur gases but limited scavenging and removal of halides chemical modeling suggests that cloud concentrations of water vapor and nitric acid promoted polar stratospheric cloud psc formation at 201 203 k yielding ice nitric acid trihydrate nat sulfuric acid tetrahydrate sat and liquid ternary solution h2so4 h2o hno3 sts particles we show that these volcanically induced pscs especially the ice and nat particles activated volcanogenic halogens in the cloud producing 2 ppbv clox this would have destroyed ozone during an earlier period of daylight consistent with the very low levels of ozone observed this combination of volcanogenic pscs and chlorine destroyed ozone at much faster rates than other pscs that arctic winter elevated levels of hno3 and noy in the cloud can be explained by atmospheric nitrogen fixation in the eruption column due to high temperatures and or volcanic lightning however observed elevated levels of hox remain unexplained given that the cloud was sampled at night

survey of hydrothermally generated petroleums from the guaymas basin spreading center abstract the guaymas basin spreading center and hydrothermal system are generating an assortment of petroleum like bitumens by pyrolysis of organic matter in the overlying uncosolidated sediments samples collected by d s v alvin from hydrothermal fields in the southern trough exhibit large variations in the quantities and character of the solvent soluble organic materials various pyrolytic regimes combined with fluctuating thermal gradients and migration velocities may impart a compositional fractionation possibly by differential gaseous solubilization and hydrodynamic alteration of the multi component fluids the data suggest that differential condensation solidification biodegradation and water washing cause selective removal of components at the seabed many hydrothermal oils are unlike normal reservoir petroleums because they contain significant concentrations of polar material due to their rapid genesis and transport and probable solubilization or advection of polar immature components the biomarker distributions confirm high temperature pyrolysis at depth with variable entrainment of less thermally mature bitumens during transport data for shallow core samples from the northern trough indicate that those locations experienced variable influx predominantly volatiles of a low temperature pyrolysate

hydrothermal petroleum genesis migration and deposition in guaymas basin gulf of california hydrothermal activity and seabed mounds have been explored in guaymas basin by the deep sea drilling project dsdp piston coring dredging and diving with the deep submersible research vessel dsrv alvin sedimentary organic matter derived primarily from immature degraded microbial detritus is easily converted to petroleum under the hydrothermal regime these petroleums are mature and migrate in the fluids and by diffusion to the seabed the fluid migration is aided by near critical aqueous solution and supercritical carbon dioxide and hydrocarbons petroleum compositions vary from condensates to naphthenic to waxy all with significant amounts of asphaltenes and hydrothermal products such as olefins and toxic polynuclear aromatic hydrocarbons pah the heavy ends condense at the seabed depositing mainly as a cement with the sulfides and other minerals and to a lesser extent as entrapped oil and crystalline wax in vugs and conduits of the mounds the pah are high temperature resynthesis aromatiza

crustal processes at spreading centers recent discoveries and research on mid ocean ridges mor s in the last four years have greatly increased our knowledge of this fundamental type of plate boundary the last iugg review of mor research was in 1975 aumento et al 1975 and its omission as a topic in 1978 may have reflected a feeling that spreading centers were reasonably well understood since that time however there has been a surfeit of important new observations and exciting research and there is now a turmoil of innovative ideas about the processes which create and leave their imprint on two thirds of the earth s crust new seismic measurements have been made and interpreted as evidence for the existence of shallow axial magma chambers amc beneath intermediate total opening rate 5 9 cm yr and fast 9 18 cm yr spreading centers fig 1 yet there is controversy as to whether they are steady state whether they persist beneath slow ridges as well in the steady state what the dimensions and shape of the chamber are its relation to oceanic crustal stratigraphy and its relation to observations in ophiolites black smoker hydrothermal vents have been discovered in the pacific spewing forth 350 c fluids blackened by polymetallic sulfide precipitates this discovery is embroiled in debate as to how long the vents last whether they occur at slow spreading rates as well whether the enormous heat flux of the vents freeze the magma chamber even at fast spreading rates their influence on geochemical balances in the ocean and the value of the sulfide deposits commercially it has been found that our initial view of mor s as two dimensional linear structures has served us well as an initial working model but must be significantly modified to account for variations in tectonic volcanic and hydrothermal activity along strike as well as for episodicity of these processes deep sea drilling project dsdp samples have raised fundamental questions about formation of the magnetic source layer hydrothermal circulation and fault mechanisms along the mor spreading centers which penetrate existing lithosphere along strike as propagating rifts have modified our views of how plate boundaries reorient themselves and how v shaped magnetic and topographic trends are formed we have also found that transform faults may modify spreading center processes for some distance away from their intersections with mor s and that rigid plate transform faults may fail to develop at fast spreading centers under certain conditions resulting in en echelon overlapping of spreading centers this review will focus on these developments and several others only example references to these topics will be given in the text and many important topics will not be discussed directly e g petrology and geochemistry mantle convection research on lithosphere older than 1 m y however i have tried to compile and have included an extensive bibliography for u s research on a broader range of mor topics for mid 1978 to mid 1982 which is the main purpose of this report pre 1978 references are occasionally included where appropriate abstracts are not included

petroleum generation an easy and widespread process in hydrothermal systems an overview abstract the conversion of organic matter to petroleum products by hydrothermal activity is an easy process occurring in nature in many types of environments geologically immature organic matter of marine sediments has been shown to be altered to petroleum products by this process in the guaymas basin escanaba trough bransfield strait and atlantis ii deep and this process probably occurs elsewhere in active sedimented rift systems contemporary organic detritus and or viable microorganisms are also converted in part to petroleum like products when they become entrained by turbulent mixing into hydrothermal vent waters resulting in their instantaneous hydrous pyrolysis this latter case occurs in hydrothermal vent fields without a sedimentary cover emanating directly from oceanic ridges as for example on the east pacific rise at 13 n and 21 n and on the mid atlantic ridge at 26 n this process is probably also ubiquitous for all actively venting sediment starved oceanic ridges the hydrocarbon products generated in these areas have been compared in terms of composition organic matter sources and analogy to reservoir petroleum they represent a major carbon source for chemosynthetic assimilation by vent biota and are compositionally similar to normal petroleum

hydrogen in the gas plume of an open vent volcano mount etna italy 1 we report here on the first hydrogen determinations in the volcanic gas plume of mount etna in italy which we obtained during periodic field surveys on the volcano s summit area with an upgraded multigas using a specific ezt3hyt electrochemical sensor we resolved h2 concentrations in the plume of 1 3 ppm above ambient background atmosphere and derived h2 so2 and h2 h2o plume molar ratios of 0 002 0 044 mean 0 013 and 0 0001 0 0042 mean 0 0018 respectively taking the above h2 so2 ratios in combination with a time averaged so2 flux of 1600 gg yr 1 we evaluate that etna contributes a time averaged h2 flux of 0 65 gg yr 1 suggesting that the volcanogenic contribution to the global atmospheric h2 budget 70 000 100 000 gg yr 1 is marginal we also use our observed h2 h2o ratios to propose that etna s passive plume composition is at least partially representative of a quenched temperatures between 750 c and 950 c equilibrium in the gas magma system at redox conditions close to the nickel nickel oxide nno mineral buffer the positive dependence between h2 so2 h2 h2o and co2 so2 ratios suggests that h2 is likely supplied at least in part by deeply rising co2 rich gas bubbles fluxing through a co2 depleted shallow conduit magma

petroleum characteristics of the oil in a guaymas basin hydrothermal chimney abstract extensive petroleum shows have been sampled from the seabed of guaymas basin these petroleums were generated at depth by hydrothermal activity from immature sedimentary organic matter and migrated to the sea floor there the heavy ends solodify due to the temperature drop and the volatiles are emitted as plumes thus it is of interest to determine the petroleum characteristics of such oils for comparison with normal reservoir petroleums an oil saturated sample of a chimney alvin dive 1630 emitting water at 200 c was studied in contained 21 7 solvent extractable oil and 19 2 s moisture the oil has an api gravity of 27 6 a specific gravity at 20 c of 0 8891 and contains 0 99 s the astm distillation yields vol are gasoline 3 0 ibp 149 c ibp 300 f intermediates 149 315 c 300 660 f 61 0 gas oil 315 538 c 660 1000 f 21 0 and residue 538 c 1000 f 15 0 gas chromatography and ft infrared spectrometry indicate that this oil is similar to typical reservoir petroleum but with the low ends and aromatics depleted due to water washing mild thermal conditions are indicated by the absence of cracking products

carbon isotope composition of hydrothermal petroleums from guaymas basin gulf of california abstract petroleum hydrocarbons are a major emanation from the active hydrothermal vent fields of guaymas basin the samples we describe here occur in hydrothermal mound crusts which have been collected in situ with a submersible the relative concentrations of the compound classes in the hydrothermal petroleum are highly variable with the following ranges saturate hydrocarbons 1 60 aromatic hydrocarbons 18 38 nso compounds 10 27 and asphaltenes 0 2 25 the sulfur concentrations range between 1 2 and 3 4 the s rich hydrothermal petroleums tend to be low in saturated hydrocarbons and high in nso and asphaltenes components and vice versa stable c isotope concentrations in whole hydrothermal petroleum vary little 13c 21 2to 22 2 0 vs pdb carbon isotope patterns for the compound classes are similar to typical crude oils with the saturated hydrocarbons being depleted in 13c 22 9 to 21 7 0 and asphaltenes being relatively enriched 20 5 to 20 8 0 the variability decreases from saturates to aromatics nso and asphaltenes this indicates that the hydrothermal petroleums oirginate from one source the higher variability in the non asphaltic compound classes is attributed to distillation and or biodegradation effects organic matter in recent unaltered sediments in the immediate vicinity of the hydrothermal vents has an average 13c of approximately 20 5 0 in a range consistent with their being the source for the oils this simlarity supports the contention that the hydrothermal petroleums are pyrolysis products of the immature sediments which are permeated by the hydrothermal fluids

acid alteration in the fumarolic environment of usu volcano hokkaido japan abstract the last eruptive activity of usu volcano in 1977 78 involved the development of high temperature 550 710 c fumaroles the gases emitted were h2o rich 95 99 mol with cl s 0 05 0 9 f cl 0 3 0 2 and with rh 2 5 close to the rock buffer feo feo1 5 cooling and oxidation of the high temperature gases resulted in the formation of acidic condensates ph 1 6 that interacted with the wall rock complete leaching of the cations ca na mg al and fe from the primary minerals and matrix glass occurred leaving in place only silica these mobilized cations precipitated as secondary minerals from acidic fluids that circulated in microcracks sem study shows mineral associations reflecting increasing fluid oxidation a al fluorides such as ralstonite namgalf6 h2o pyrite and anhydrite gypsum b an al hydroxide hematite gypsum and amorphous silica or cristobalite c al sulfates such as hydronium alunite h3o al3 so4 2 oh 6 alunite kal3 so4 2 oh 6 amorphous silica cristobalite hematite and anhydrite gypsum d al sulfates al fluorides amorphous silica cristobalite pyrite and anhydrite gypsum a ti oxide a fe mg sulfate and barite are present in minor amounts clay minerals are absent from the observed assemblages primary phenocrysts and matrix glass undergo a complete transformation to silica enriched in fluorine 1 7 wt this fluorine enrichment in the silicified parts of silicates and in silica incrustations suggests that f may play a role in silica mobilization modeling of the cooling of the high temperature gases was performed with the program gasworks the calculations suggest that 66 of the total sulfur from the gases may be lost by deposition as native sulfur at temperatures below 160 c thermochemical modeling of condensate rock interaction using chiller indicates that the cooling of gases was the source of the altering solutions oxidation by atmospheric o2 of the sulfur reduced species in the volcanic gas condensates resulted in their extreme acidification condensate rock interactions produce supersaturation with respect to the following mineral assemblages at 95 c 1 pyrite native sulfur cristobalite barite anhydrite diaspore log m h 2 s aq 2 32 2 cristobalite anhydrite hematite alunite diaspore log m h 2 s aq gypsum replaces anhydrite at t 25 c the calculated mineral assemblages are in agreement with those observed in the field

deep water hydrocarbon seeps in guaymas basin gulf of california abstract acoustically discovered hydrocarbon seeps along a transform fault zone on the sonoran margin of guaymas basin and in the southern trough of guaymas basin were examined and sampled during dives of dsv alvin seepage of methane and heavier hydrocarbons occurs through shallow pockmarks along the eroding crest of a steep anticline 1600 m below sea level extensive ledges of aragonite crop out around the rims of the pockmarks isotopic analysis indicates that carbonate precipitation is a result of methane oxidation seepage zones within the pockmarks support dense communities of calyptogena half buried in the mud tubeworms lamellibracheae sp have colonized many of the aragonite outcrops though the margin site is only a few kilometers from a high temperature sulfide precipitating and petroleum discharging vent system at a nearby center its structural setting is more akin to pockmarks described from continental shelves and its chemosynthetic fauna is more like that around low temperature seeps on other continental slopes and margins e g oregon u s a and japan the seep in the southern trough is a condensate type petroleum c 1 c 40 and rises as a plume from a young vent mound system about 2000 m below sea level

evidence from fluid seeps atop serpentine seamounts in the mariana forearc clues for emplacement of the seamounts and their relationship to forearc tectonics abstract the mariana forearc is a non accretionary forearc with numerous seamounts dredge hauls from these seamounts are composed primarily of serpentinite indicating a non volcanic origin in addition dredged carbonate samples reveal 1 the presence of aragonite in water depths greater than the aragonite compensation depth 2 unusual porosity and cement types 3 light carbon and heavy oxygen isotopic compositions and 4 an unusual trace element geochemistry of aragonite and calcite these mineralogic petrologic and geochemical characteristics formed the basis of a prediction that methane bearing fluids are venting from these seamounts subsequent to this prediction submersible dives on a mariana forearc seamount found and sampled chimneys seeping cool water that contains dissolved methane the serpentine substrate beneath the chimneys appears to form from cold gravitational flows of serpentine material fluid inclusion contents of chimney samples also show an earlier history of methane as well as longer chain hydrocarbons aromatics and acetate ions drilling into the flank and the summit of this seamount by the ocean drilling program during leg 125 confirmed the presence of methane other light alkanes and organic acids in the present day interstitial pore fluid of the cores the presence of aromatic compounds and organic acids if derived from the maturation of organic compounds indicates a thermogenic origin for these volatiles strontium isotopic ratios of the aragonitic chimney samples and of the present day interstitial waters range from present day seawater values to significantly lower values the strontium isotopic ratios of the pore waters within the seamount trend toward a relatively less radiogenic composition with increasing depth below the seafloor this strontium isotopic signature is probably not the consequence of near surface processes but more likely a contribution from an igneous source deeper in the lithosphere the lack of a large accretionary prism in the mariana forearc removes the complication of fluid contribution from dewatering of the prism by compression during convergence as in the oregon washington or barbados margins the organic compounds in the fluid inclusions and interstitial pore fluids as well as the isotopic and the geochemical composition of the carbonates and the dissolved constituents suggest that fluids are derived from dewatering compression and dehydration of subducted sediments and the subducting plate furthermore the composition of the fluid is influenced by thermal maturation of organics in subducted sediments as well as by a contribution from a deep igneous source

infrared satellite observations of hydrogen sulfide in the volcanic plume of the august 2008 kasatochi eruption 1 hydrogen sulphide h2s is one of the main trace gases released from volcanoes with yearly global emissions estimated between 1 and 37 tg with sulfur dioxide so2 15 21 tg year it dominates the volcanic sulfur budget and the emission ratio h2s so2 is an important geochemical probe for studying source conditions sulfur chemistry and magma water interactions contrary to so2 measurements of h2s are sparse and difficult here we report the first measurements of a large h2s plume from space observations were made with the infrared sounder iasi of the volcanic plume released after the 7 8 august 2008 eruption of kasatochi volcano the eruption was characterized by 5 consecutive explosive events the first events were phreatomagmatic producing a plume rich in water vapor and poor in ash and so2 we show that the observed h2s plume calculated at 29 10 kt with integrated columns exceeding 140 25 dobson units du is likely associated with these first explosions h2s so2 ratios with maximum values of 12 2 are found representative of redox conditions in the hydrothermal envelop with a detection threshold of 25 du future space observations of h2s plumes are certain these will be important for improving the atmospheric sulfur budget and characterizing the h2s so2 fingerprint of different eruptions

volcanic controls on ash iron solubility new insights from high temperature gas ash interaction modeling abstract recent studies strongly suggest that volcanic ash can fertilize the surface ocean by releasing soluble iron however the volcanic and atmospheric processes that solubilize ash iron during its transport from the volcano to the ocean are poorly understood using thermodynamic equilibrium calculations we investigate the influence of gas ash interaction within the hot core t 600 c of the volcanic plume and the consequences of this for ash iron solubility simulations are performed by considering the plume hot core as a box model in which 1000 c magmatic gas ash and 25 c ambient air are mixed together we show that mixing and the resulting cooling of the gas ash air mixture affect the mineralogy and oxidation state of iron in the ash surface rim iron mineralogy in the ash surface layer after high temperature plume processing is primarily governed by the ratio of the h2 and h2s content of the magmatic gas to the amount of entrained o2 into the hot plume xmix the model results indicate that most of the iron in the ash surface layer is oxidized to ferric iron fe iii when log xmix drops below 3 5 in the hot core such conditions may be encountered at convergent plate volcanoes which release h2o rich magmatic gases in contrast high temperature gas ash interaction at divergent plate and hot spot volcanoes which tend to be associated with co2 rich and so2 rich magmatic gases respectively may produce ash surfaces where iron mostly occurs as ferrous fe ii these volcanoes seem to be more favorable for iron fertilization because log xmix does not fall below 3 5 and 80 of the iron in the ash surface remains ferrous fe ii which is more soluble in water than fe iii

real time simultaneous detection of volcanic hg and so2 at la fossa crater vulcano aeolian islands sicily 1 measuring hg so2 ratios in volcanic emissions is essential for better apportioning the volcanic contribution to the global hg atmospheric cycle here we report the first real time simultaneous measurement of hg and so2 in a volcanic plume based on lumex and multigas techniques respectively we demonstrate that the use of these novel techniques allows the measurements of hg so2 ratios with a far better time resolution than possible with more conventional methods the hg so2 ratio in the plume of f0 fumarole on la fossa crater vulcano island spanned an order of magnitude over a 30 minute monitoring period but was on average in qualitative agreement with the hg so2 ratio directly measured in the fumarole mean plume and fumarole ratios being 1 09 10 6 and 2 9 10 6 respectively the factor 2 difference between plume and fumarole compositions provides evidence for fast hg chemical processing the plume

inferring paleotemperature from the d h ratio of lacustrine organic matter abstract linking the d h d records of the kerogen from bulk organic matter in lake sediments to known temperature d of precipitation relationships may offer new possibilities in paleoclimate studies here we examine the hydrogen isotope ratio obtained from a radiocarbon dated lake core from wisconsin situated in the midwestern part of the united states to infer paleo surface temperatures paleotemperatures were estimated by converting the d values of the organic fraction to the d values of the lake water and by implication to that of local precipitation the temperature estimates show that the middle holocene from 7000 to 5000 years before present bp was warmer by about 3 c in general agreement with speleothem data from the midwestern united states our study shows the usefulness of the d h rations of kerogen from bulk sediment as a climate proxy that can compliment compound specific hydrogen isotope studies

hydrothermal petroleum in mineralized mounds at the seabed of guaymas basin petroleum has been dredged from an active hydrothermal mound area in the southern rift of guaymas basin gulf of california this organic matter is composed of gasoline range aliphatic and aromatic hydrocarbons and predominantly residual polar asphaltic material the aliphatic hydrocarbons of two bitumen samples have very different boiling range and composition both samples contain polynuclear aromatic hydrocarbons and olefins which indicate formation at pyrolytic temperatures the overall compositional data indicate an origin from biological detritus by thermal alteration and rapid quenching by hydrothermal removal followed by condensation at the seabed

late woodfordian and greatlakean history of the green bay lobe wisconsin advances of the green bay lobe deposited at least three till sheets that are late woodfordian age and younger in the western part of the lowland the tills are distinguished on the basis of stratigraphic position texture color and depth of leaching in the central part of the lowland tills are covered by lacustrine sediment on the east side however a similar sequence of tills is present here till units are distinguished on the basis of stratigraphic position magnetic susceptibility and depth of leaching the chilton till which is overlain by two creekan wood at one locality is correlative with the valders till of the lake michigan lowland as is the age equivalent kirby lake till one greatlakean till correlative with the two rivers till of the lake michigan lowland overlies forest beds at several localities

phenols in hydrothermal petroleums and sediment bitumen from guaymas basin gulf of california the aliphatic aromatic and polar nso fractions of seabed petroleums and sediment bitumen extracts from the guaymas basin hydrothermal system have been analyzed by gas chromatography and gas chromatography mass spectrometry free and silylated the oils were collected from the interiors and exteriors of high temperature hydrothermal vents and represent hydrothermal pyrolyzates that have migrated to the seafloor by hydrothermal fluid circulation the downcore sediments are representative of both thermally unaltered and thermally altered sediments the survey has revealed the presence of oxygenated compounds in samples with a high degree of thermal maturity phenols are one class of oxygenated compounds found in these samples a group of methyl dimethyl and trimethyl isoprenoidyl phenols c27 c29 is present in all of the seabed nso fractions with the methyl and dimethyl isoprenoidyl phenols occurring as major components and a trimethyl isoprenoidyl phenol as a minor component a homologous series of n alkylphenols c13 c33 has also been found in the seabed petroleums these phenols are most likely derived from the hydrothermal alteration of sedimentary organic matter the n alkylphenols are probably synthesized under hydrothermal conditions but the isoprenoidyl phenols are probably hydrothermal alteration products of natural product precursors the suites of phenols do not appear to be useful tracers of high temperature hydrothermal processes

bacterial incorporation of relict carbon in the hydrothermal environment of guaymas basin abstract radiocarbon analyses of bulk carbon and individual organic compounds are presented for the hydrothermal environment of the rebecca s roost vent in the southern trough of the guaymas basin hydrothermal field the 14 c values of co 2 and ch 4 in the hottest hydrothermal fluids 317 c are nearly radiocarbon dead 944 and 923 respectively in contrast the 14 c values of sediments and individual fatty acids 418 to 227 obtained from a bacterial mat located south of the vent site are similar to values previously reported for hydrothermal petroleum in this environment and are more depleted in 14 c than overlying waters hydrothermal fluids moving through the sediments appear to supply 14 c of intermediate age to the bacteria this carbon may take the form of or may be supplied by processes similar to the generation of hydrothermal petroleum although the bacterial mat visibly was dominated by beggiatoa spp such mats are known to include numerous other species individual compound data show that preaged carbon is being consumed by the integrated bacterial assemblage values of 13 c and 14 c indicate that petroleum derived carbon is incorporated directly into fresh bacterial biomass subsequently some of this newly synthesized material also is consumed by heterotrophs as eukaryotic sterols from the same sample also have 14 c depleted values 14 c 136 to 110 therefore the entire system may operate as a complex consortium to transform relict carbon back into biomass bacterial consumption of relict carbon occurs despite the ample supply of fresh carbon delivered from the productive overlying water column

influence of a turbidite deposit on the extent of pyritization of iron manganese and trace metals in sediments from the guaymas basin gulf of california mexico abstract a core collected in the guaymas basin contained an organic poor mn oxide rich and relatively fe oxide rich turbidite layer that affected the distribution of fe mn c s and trace metals results indicate that sediments not influenced by the turbidite layer achieved a 100 degree of pyritization and by extension that pyrite production is fe limited in these sediments in contrast the mud slide layer apparently supplied enough reactive fe to transfer essentially 98 of the total s present at the base of the turbidite 17 19 cm to the pyrite reservoir c s ratios showed rapid decreases with depth from a high of 38 close to the sediment water interface to minimum values of 2 8 at the lower limit of the turbidite layer a ratio equal to the average c s value of normal marine modern sediments where concentrations of organic c and pyrite supposedly have attained quasi steady values a significant part of the reactive mn was associated with carbonates 41 12 and to a much lower degree with pyrite 2 7 1 2 the turbidite layer is currently showing a depletion of mn relative to the host sediment it is possible that mn a major metal constituent in these sediments was initially present in high concentrations in the mud slide but was eventually mobilized and transferred either to the water column or to the sediments immediately below the turbidite layer metals associated with this element probably followed the same path affecting their incorporation into pyrite the turbidite layer apparently affected the distribution of most of the trace metals associated with pyrite except maybe cd pb and to a certain extent cr however cu cr zn ni and co were all found to be highly pyritized 80 in the sediments of the guaymas basin

volatilization transport and sublimation of metallic and non metallic elements in high temperature gases at merapi volcano indonesia abstract condensates silica tube sublimates and incrustations were sampled from 500 800 c fumaroles and lava samples were collected at merapi volcano indonesia in jan feb 1984 with respect to the magma merapi gases are enriched by factors greater than 105 in se re bi and cd 104 105 in au br in pb and w 103 104 in mo cl cs s sn and ag 102 103 in as zn f and rb and 1 102 in cu k na sb ni ga v fe mn and li the fumaroles are transporting more than 106 grams day g d of s cl and f 104 106 g d of al br zn fe k and mg 103 104 g d of pb as mo mn v w and sr and less than 103 g d of ni cu cr ga sb bi cd li co and u with decreasing temperature 800 500 c there were five sublimate zones found in silica tubes 1 cristobalite and magnetite first deposition of si fe and al 2 k ca sulfate acmite halite sylvite and pyrite maximum deposition of cl na k si s fe mo br al rb cs mn w p ca re ag au and co 3 aphthitalite k na sulfate sphalerite galena and cs k sulfate maximum deposition of zn bi cd se and in higher deposition of pb and sn 4 pb k chloride and na k fe sulfate maximum deposition of pb sn and cu and 5 zn cu and k pb sulfates maximum deposition of pb sn ti as and sb the incrustations surrounding the fumaroles are also chemically zoned bi cd pb w mo zn cu k na v fe and mn are concentrated most in or very close to the vent as expected with cooling atmospheric contamination and dispersion the highly volatile elements br cl as and sb are transported primarily away from high temperature vents ba si p al ca and cr are derived from wall rock reactions incomplete degassing of shallow magma at 915 c is the origin of most of the elements in the merapi volcanic gas although it is partly contaminated by particles or wall rock reactions the metals are transported predominantly as chloride species as the gas cools in the fumarolic environment it becomes saturated with sublimate phases that fractionate from the gas in the order of their equilibrium saturation temperatures devolatilization of a cooling batholith could transport enough acids and metals to a hydrothermal system to play a significant role in forming an ore deposit however sublimation from a high temperature high velocity carrier gas is not efficient enough to form a large ore deposit re se cd and bi could be used as supporting evidence for magmatic fluid transport in an ore deposit

spatial analysis of mount st helens tephra leachate compositions implications for future sampling strategies tephra particles in physically and chemically evolving volcanic plumes and clouds carry soluble sulphate and halide salts to the earth s surface ultimately depositing volcanogenic compounds into terrestrial or aquatic environments upon leaching of tephra in water these salts dissolve rapidly previous studies have investigated the spatial and temporal variability of tephra leachate compositions during an eruption in order to gain insight into the mechanisms of gas tephra interaction which emplace those salts however the leachate datasets analysed are typically small and may poorly represent the natural variability and complexity of tephra deposits here we have conducted a retrospective analysis of published leachate analyses from the 18 may 1980 eruption of mount st helens washington analysing the spatial structure of the concentrations and relative abundances of soluble ca cl na and s across the deposits we have identified two spatial features 1 concentrated tephra leachate compositions in blast deposits to the north of the volcano and 2 low s cl and na cl ratios around the washington idaho border by reference to the bulk chemistry and granulometry of the deposit and to current knowledge of gas tephra interactions we suggest that the proximal enrichments are the product of pre eruptive gas uptake during cryptodome emplacement we speculate that the low s cl and na cl ratios reflect a combination of compositional dependences on high temperature so2 uptake and preferential hcl uptake by hydrometeor tephra aggregates manifested in terrestrial deposits by tephra sedimentation and fallout patterns however despite our interrogation of the most exhaustive tephra leachate dataset available it has become clear in this effort that more detailed insights into gas tephra interaction mechanisms are prevented by the prevalent poor temporal and spatial representativeness of the collated data and the limited characterisation of the tephra deposits future leachate studies should aim to extensively sample across tephra deposit limits whilst simultaneously characterising deposit stratigraphy and tephra chemistry mineralogy and granulometry taking steps to ensure the quality and comparability of collected leachate datasets

oil source rock correlation of the lower paleozoic petroleum system in the baltic basin northern europe the correlation of lower paleozoic marine source rocks with reservoired oils by biomarkers is complex because of the uniform early phanerozoic biomass bacteria and algae and the lack of land plant and animal input accordingly the main source rocks for the most prolific oil province in the baltic basin are still a matter of debate the 10 source rocks and 15 oil samples from 5 northern european countries bordering the baltic sea basin were analyzed by gas chromatography gc with flame ionization detector gc mass spectrometry gcms and gcms ms to detect acyclic isoprenoids and aliphatic aromatic and nitrogen sulfur and oxygen biomarkers chemometric tools were applied to screen for meaningful source and age related biomarkers and to highlight genetics extended tricyclic terpane ratios c24 tetracyclic terpane c26 tricyclic terpane ratios and relative c29 sterane concentrations are considered the most promising biomarkers in differentiating llandovery shales from cambrian to ordovician alum shale and for correlation with expelled oil the uranium irradiation related c26 c28 triaromatic steroid concentrations provide possible distinguishing criteria for the source potential of the different alum shale units enhanced oil maturation by volcanic intrusion is highlighted by sterane biomarkers and polycyclic aromatic hydrocarbons the alum shale is here considered the main source rock for oil accumulations in lower paleozoic reservoirs of the baltic basin oil seepage occurring in ordovician limestone was mainly generated by the middle cambrian alum shale and middle cambrian sandstone reservoirs were mainly sourced by upper cambrian and lower ordovician alum shale with higher maturity considerations about the assessment of migration distance are based on carbazole concentrations and c29 sterane isomerization advanced studies to unravel detailed lower paleozoic oil source rock correlations are based on meaningful biomarkers offer approaches to significantly reduce the exploration risk in this area and could be applied to similar early paleozoic petroleum systems in other basins

geochemistry and mineralogy of late quaternary loess in the upper mississippi river valley usa provenance and correlation with laurentide ice sheet history abstract the midcontinent of north america contains some of the thickest and most extensive last glacial loess deposits in the world known as peoria loess peoria loess of the upper mississippi river valley region is thought to have had temporally varying glaciogenic sources resulting from inputs of sediment to the mississippi river from different lobes of the laurentide ice sheet here we explore a new method of determining loess provenance using k rb and k ba values in k feldspars and micas in loess from a number of different regions in north america results indicate that k rb and k ba values can distinguish loess originating from diverse geologic terrains in north america further different loess bodies that are known to have had the same source sediments using other criteria have similar k rb and k ba values we also studied three thick loess sections in the upper mississippi river valley region at each site the primary composition of the loess changed over the course of the last glacial period and k rb and k ba values parallel changes in carbonate mineral content and clay mineralogy we thus confirm conclusions of earlier investigators that loess composition changed as a result of the shifting dominance of different lobes of the laurentide ice sheet and the changing course of the mississippi river we conclude that k rb and k ba values are effective robust and rapid indicators of loess provenance that can be applied to many regions of the world

carbon isotopic compositions of 28 30 bisnorhopanes and other biological markers in a monterey crude oil abstract an immature tar like oil api 3 13 c 23 6 vs pdb from the miocene monterey formation offshore california was selected for a study of carbon isotopic signatures of individual biomarkers the three principal stereoisomers of 28 30 bisnorhopane c 28 have within analytical precision identical carbon isotopic compositions average 13 c 32 3 0 4 and are considerably depleted in 13 c compared to the whole oil these 28 30 bisnorhopanes bnh differ isotopically from c 29 and c 30 17 h hopanes 25 8 and 26 1 and c 31 c 35 extended hopanes 13 c 27 7 and suggest different precursors for the c 28 hopanes than for c 29 c 35 hopanes the relative depletion of bnh of almost 9 compared to the isotopic composition of the whole oil suggests that these hopanes derive from chemoautotrophic bacteria possibly not yet identified h 2 s oxidizers which utilize 13 c depleted substrates the c 29 and c 30 hopanes are within analytical precision isotopically identical 26 and similar to algal derived compounds e g c 27 steranes 25 9 which is consistent with a cyanobacterial source for these hopanes an archaebacterial biomarker 1 1 biphytane 13 c 25 5 likely derived from methanogens is also isotopically similar to c 27 sterane norpristane pristane and phytane liberated by desulfurization of the aromatic and polar maltene fractions show isotopic compositions similar to the same isoprenoids in the free lipids of the bitumen total range from 24 5 to 27 5 this isotopic similarity supports a common origin for the free and sulfur bound forms of these isoprenoids this origin could be algal and or archaebacterial lipids which both show isotopic compositions within the range of the c 18 c 20 isoprenoids like other marine derived organic matter this monterey oil does not show the strong 13 c depletion typical for methylotroph derived compounds characteristically found in organic matter of lacustrine origin this may indicate fundamental differences of methane recycling processes in marine sulfate dominated as compared to lacustrine environments

composition and spatial organization of a cold seep community on the south barbados accretionary prism tectonic geochemical and sedimentary context abstract deep faunal assemblages were observed on cold seeps between 1000 and 2000m depth along the southern termination of the barbados accretionary prism during the caracolante ii and diapicar cruises faunal composition and microdistribution of a cold seep community were analyzed at one site using deep sea photographs and seismic 3 5 kz profiles the community is dominated by large mussels up to 20cm long possibly related to the genus bathymodiolus tiny vesicomyid clams and vestimentiferan clusters in which animals are up to 2m long there is a high density of sponges three species bryozoans and gorgonians other taxa occasionally associated with this assemblage include galatheid crabs anemones holothurians and possibly pennatulaceans which are numerous at boundaries of the site a typical deep sea fauna of fish asteroids and ophiuroids is also scattered about the vicinity this seep community is distributed as a band of discontinuous colonies 40 50m in width and more than 10km in length living colonies alternate with accumulations shells and bare areas the substratum is hard mud covered by a ferrugineous crust and cemented by carbonates the early diagenetic character of the bottom and the occurrence of biological assemblages indicate that seepages of sulphur and or methane which have been revealed along the decollement zone of the barbados prism must diffuse through the sea floor these biological and geological features are located on the crests of ne sw anticlinal ridges and mud volcanoes which have been built by diaprism

igneous activity and organic maturation in the midland valley of scotland abstract the general relationship of erich stach s research work to the effects of igneous activity on organic maturation is briefly considered the geological history of the midland valley of scotland is then reviewed as a graben which developed in devonian old red sandstone times and continued to do so as lithospheric tensional stretching was maintained throughout the carboniferous a significant factor in relation to the development of organic maturation was the widespread igneous activity that persisted throughout much of upper palaeozoic times calc alkaline volcanic rocks are a major feature within the molasse type deposits of the old red sandstone after a period of quiescence in later old red sandstone times the continuing tensional stretching initiated or rejuvenated major crustal fractures extensive volcanic sill and dyke activity exercised an important influence on the predominantly shallow water deltaic deposits of the carboniferous alkaline olivine basalts were erupted in the early carboniferous while volcanic activity in the later carboniferous was essentially phreatic two major intrusive episodes occurred the first of alkaline sills in early to mid carboniferous times which were closely related to volcanic plugs and eruptive centres the second in post westphalian times when tholeiitic sills and dykes with no known relationships with any extrusive rocks were injected the effects of this igneous activity on organic maturation can be considered under four headings 1 1 although the general development of maturation of carboniferous organic matter which includes many coal seams and oil shales was controlled to some degree by burial history the regional pattern of igneous activity was also influential thus there is a gradual increase of coalification from east to west in the midland valley which corresponds with an increasing thickness of volcanic pile in the central and westerly parts of the graben suggesting that there may have been a greater regional heat sink in the west during the carboniferous the level of coalification is nowhere particularly high except where affected by intrusions and regional reflectance gradients generally vary between r oil vitrinite 0 2 km to 0 4 km without displaying any consistent pattern 2 2 the post westphalian tholeiitic quartz dolerite midland valley sill which underlies most of the central and eastern parts of the graben has produced extensive reflectance thermal aureoles in the organic matter above and below the intrusion the olivine dolerite and teschenite sills of namurian early westphalian times many of similar thickness to the quartz dolerite intrusions fail to produce significant reflectance thermal aureoles this major difference in organic matter response to the intrusions can only be explained in terms of the initial rank level of the organic matter differences in degree of compaction of the sediments and particularly in the amount of water the sediments contained at the time of intrusion 3 3 maturation of organic matter closely associated with extensive surtseyan type volcanic activity in the eastern part of the graben displays no relationship to the regionally developed coalification in associated sediments although some vitrinite clasts in the pyroclastic deposits have had their reflectances raised to meta anthracitic rank reflectance levels of clasts in tuffs and agglomerates are generally not much raised above the regional reflectance level suggesting incorporation of organic matter in ash streams in which water was an important cooling and protective component 4 4 the close relationship of organic matter of all kinds with volcanic and intrusive igneous rocks has led to a marked increase of parent polycyclic aromatic hydrocarbons pah in the aromatic fractions of organic extracts the source of these hydrocarbons is the combustion and or pyrolysis of organic matter caused by the high temperatures of the igneous materials whether volcanic or intrusive these pah may be directly generated or absorbed from the surrounding environment

recent volatile evolution in the magmatic system of hekla volcano iceland estimates of the volatile budgets for volcanic eruptions are often based on volatile concentrations measured in melt inclusions mis versus groundmass glass here we present new measurements and estimates of pre eruptive volatile concentrations in magma from the hekla volcano in iceland based on mis in recent basalts and basaltic icelandites from the 2000 eruption the last eruption at hekla occurred from 26 february to 8 march 2000 it began with a short sub plinian phase followed by lava effusion that produced 0 17 km 3 of basaltic icelandite volatile s cl f and h2o and major element concentrations were measured in mis trapped in olivine and plagioclase phenocrysts contained in the basaltic icelandite from the 2000 eruption and in basalt erupted in 1913 from a fissure adjacent to the hekla volcano same elements were measured in the groundmass glass from the 2000 tephra the observed compositional range of mis from the basalt mgo 7 73 to the basaltic icelandite mgo 2 51 is readily explained by fractional crystallisation allowing the prediction of the evolution of dissolved volatile concentrations within the magma plumbing system beneath hekla the incompatible behaviour of the volatile elements controls their concentrations in mis during the crystal fractionation and consequently the highest concentrations are found in the most evolved basaltic icelandite mis with the notable exception of sulphur volatile concentrations in the basaltic mis exhibit strong linear correlations with k2o and this relationship can be used to estimate the theoretical expected volatile contents in the basaltic icelandite melt just prior to eruption such an approach avoids underestimation of the pre eruptive volatile contents measured in mis and improves constraints on the volatile mass release into the atmosphere the difference of volatile contents between expected concentrations and those present in the groundmass scaled to the mass of erupted magma yields maximum atmospheric mass loading of 0 10 mt hcl 0 17 mt hf and 3 77 mt so2 during the 2000 hekla eruption whereas calculations using the measured values in the inclusions give a significant lower mass yields of 0 05 mt hcl 0 17 mt hf and 0 6 mt so2 these results are discussed and compared to the data derived from remote sensing and snow proxy of the gas phase measurements 2007 elsevier b v all rights reserved

generation of short chain acid anions in hydrothermally altered sediments of the guaymas basin gulf of california an initial investigation of the concentration distribution of short chain organic acid anions in hydrothermally altered sediments of the guaymas basin reveals the presence of high concentrations of acetate and propionate relative to normal marine sediments acetate and propionate concentrations appear to vary as a function of sediment temperature and reach concentrations 1100 and 200 m respectively at temperatures 100 c as in previously studied oil field formation waters these acid anions probably play a key role in the generation of co2 and hydrocarbons gases hydrogen ion ph buffering the complexing of aqueous ions and mineral dissolution and precipatation at temperatures 100 c these and other acid anions should be important substrates for heterotrophic bacterial processes including sulfate reduction

hydrothermal pyrolysis of organic matter in guaymas basin i comparison of hydrocarbon distributions in subsurface sediments and seabed petroleums abstract the bitumens of a selection of subsurface sediments from guaymas basin gulf of california have been analyzed in order to assess the hydrothermal effects on the organic matter and to better delineate the processes influencing the generation deposition and alteration of the hydrothermal petroleums at the seabed although the thermally generated subsurface bitumens are generally rich in polar asphaltic materials as are the seabed oils the hydrocarbon transformations parallel the extent of hydrothermal alteration as reflected in the downcore mineralogy at dsdp sites 477 and 478 at site 477 a progressive change from n alkane to aromatic hydrocarbon dominated patterns in the high resolution gas chromatography resolvable fractions of the bitumens accompanies decreases in organic carbon and bitumen yields with depth these transformations are indicative of sequential hydrothermal alteration of the sediments with depth due to increasing temperature and or progressive passage of hydrothermal fluid through the sedimentary column the polycyclic aromatic hydrocarbon pah distributions undergo extensive transformations e g dealkylation consistent with hydrothermal alterations are dominant at depth and have the broadest range as thermal maturation indices the aliphatic and aromatic components of the seabed oils can be transported to the seabed independently as a result of their generation under different temperature or depth regimes and sequentially over time during pyrolysis the concentrations of the parent pah in the thermally altered subsurface bitumens are comparable to those in the seabed oils the differential dissolution of the more soluble aromatics and selective solidification condensation of the higher molecular weight pah out of the high temperature fluids exiting at the seabed chimneys result in aromatic distributions of the oils significantly skewed towards the larger components e g benzo ghi perylene relative to the subsurface bitumens comparison of the downcore hydrocarbon distributions with those in the seabed petroleums support the contention that the hydrothermal oils are mixtures of pyrolysates from different depths or thermal regimes and are significantly altered by differential solubilization during transport and at the seabed

h2s fluxes from mt etna stromboli and vulcano italy and implications for the sulfur budget at volcanoes abstract we present here new measurements of sulfur dioxide and hydrogen sulfide emissions from vulcano etna and stromboli italy made by direct sampling at vents and by filter pack and ultraviolet spectroscopy in downwind plumes measurements at the f0 and fa fumaroles on vulcano yielded so 2 h 2 s molar ratios of 0 38 and 1 4 respectively from which we estimate an h 2 s flux of 6 to 9 t d 1 for the summit crater for mt etna and stromboli we found so 2 h 2 s molar ratios of 20 and 15 respectively which combined with so 2 flux measurements suggest h 2 s emission rates of 50 to 113 t d 1 and 4 to 8 t d 1 respectively we observe that source and plume so 2 h 2 s ratios at vulcano are similar suggesting that hydrogen sulfide is essentially inert on timescales of seconds to minutes this finding has important implications for estimates of volcanic total sulfur budget at volcanoes since most existing measurements do not account for h 2 s emission

palynological and radiocarbon evidence for deglaciation events in the green bay lobe wisconsin abstract a new and significant site of organic silty sand has been found beneath the valders till at valders quarry in northeastern wisconsin this is now the earliest known late glacial site associated with red till ice advances in the western great lakes area leaves of terrestrial plants washed into a small depression provide a date of 12 965 200 yr b p wis 2293 which is significantly older than the two creeks forest bed ca 11 800 yr b p percentage and concentration pollen diagrams suggest that the site was open and distant from a closed picea forest no wood or picea needles have been found this date is statistically indistinguishable from 12 550 233 yr b p the mean of three dates for the end of inorganic varve sedimentation at devils lake 160 km southwest at the terminus of the green bay lobe assuming that the green bay lobe vacated its outermost moraine in the interval from 13 000 to 12 500 yr b p only a short time was available for retreat of the ice margin over 350 km drainage of red sediment from lake superior into the lake michigan basin readvance of over 250 km retreat of at least 80 km and advance to this site the time for these events appears to have been too short to resolve by current radiocarbon technique this extremely rapid collapse of the green bay lobe has a calibrated age of about 15 000 cal yr b p about that of the dramatic warming seen in the greenland ice cores

hot fluids burial metamorphism and thermal histories in the underthrust sediments at iodp 370 site c0023 nankai accretionary complex abstract drilling during international ocean discovery program iodp expedition 370 at site c0023 encountered instances of hydrothermal mineralization from 775 to 1121 m below seafloor fluid inclusion homogenization temperatures measured on barite veins within this interval indicate precipitation from fluids with temperatures up to 220 c and salinities ten times higher than interstitial water 16 25 c f 2 8 3 6 wt nacl patches of stratabound mineralization rhodochrosite calcite barite and anhydride are largely confined to the vicinity of veins and have vertical thicknesses and extents that can be explained by precipitation within the thermal aureoles of veins thermal maturities measured on petroleum biomarkers in underthrust sediments record a rise from pre oil window to early oil window thermal maturities basin models show that increases in thermal maturity can be explained by burial metamorphism and kinetic based calculations suggest that hot fluids would only have had a minimal effect on hydrocarbon generation however the movement of hot fluids still has geochemical implications and creates a complex thermal history where both short duration localized heating within fracture zones at hot temperatures 200 c for less than 1 yr and heating during burial over long durations 80 110 c for 0 5 2 myrs need to be considered

ketones in hydrothermal petroleums and sediment extracts from guaymas basin gulf of california the polar compound nso fractions of seabed petroleums and sediment extracts from the guaymas basin hydrothermal system have been analyzed by gas chromatography and gas chromatography mass spectrometry the oils were collected from the interiors and exteriors of high temperature hydrothermal vents and represent hydrothermal pyrolysates that have migrated to the seafloor by hydrothermal fluid circulation the downcore samples are representative of both thermally unaltered and thermally altered sediments the survey has revealed the presence of oxygenated compounds correlated with samples exhibiting a high degree of thermal maturity several homologous series of related ketone isomers are enriched in the interiors of the hydrothermal vent samples or in hydrothermally altered sequences of the downcore sediments dsdp holes 477 and 481a the n alkanones range in carbon number from c11 to c33 with a cmax from 14 to 23 distributions that are similar to those of the n alkanes the alkan 2 ones are usually in highest concentrations with lower amounts of 3 4 5 6 7 and higher alkanones and they exhibit no carbon number preference there is an odd carbon number preference of alkanones observed for downcore samples the alkanones are enriched in the interiors of the hydrothermal vent spires or in downcore hydrothermally altered sediments indicating an origin at depth or in the hydrothermal fluids and not from an external biogenic deposition minor amounts of c13 and c18 isoprenoid ketones are also present simulation of the natural hydrothermal alternation process by laboratory hydrous pyrolysis techniques provided information regarding the mode of alkanone formation hydrous pyrolysis of n c32h66 at 350 c for 72 h with water only or water with inorganic additives has been studied using a stainless steel reaction vessel in each experiment oxygenated hydrocarbons including alkanones were formed from the n alkane the product distributions indicate a reaction pathway consisting of n alkanes and olefins as primary cracking products with internal olefins and alkanones as secondary reaction products hydrous pyrolyses of messel shale spiked with molecular probes have been performed under similar time and temperature constraints to produce alkanone distributions like those found in the hydrothermal vent petroleums

hydrothermal petroleum at the seafloor and organic matter alteration in sediments of middle valley northern juan de fuca ridge abstract sediments from high heat flow areas of middle valley northern juan de fuca ridge contain traces of bitumens with insignificant amounts of thermogenic components and mainly lipid material which has experienced accelerated diagenesis these sediments have been exposed to mild hydrothermal conditions 50 120 c based on their bitumen compositions the hydrothermal bitumen in a barite alteration products the aliphatic fraction represents the mildly transformed and immature matter and the major polynuclear aromatic hydrocarbons are the high temperature constituents 300 c the 14c age of this bitumen is about 29 000 abp reflecting rapid organic carbon cycling

hydrothermal petroleum generation in red sea sediments from the kebrit and shaban deeps abstract petroleum impregnated sediments and massive sulfides have been found in two deeps of the northerns red sea biological marker distributions in extracts and polar fraction degradation products were analyzed in order to elucidate the source of the petroliferous material two organic phases could be distinguished according to their source and maturity the amounts of n alkanes show a marked decrease with depth whereas the concentrations of various branched and cyclic hydrocarbons increase resulting in a humpof unresolvable compounds in a depth as shallow as 300 cm changes in concentrations and distributions of hopanoids in the kebrit deep sediments indicate a rapid increase of maturity with depth the deepest core section 300 cm and the masive sulfide reveal comparable maturation indices typical for mature oils by chemical degradation of the polar fractions a series of c 40 isoprenoids was obtained which reveals a considerable contribution from methanogenic and thermophilic archapbacteria to the immature organic matter the data suggest that petroliferous material ofthermogenic origin migrates through the younger sequences superimposes the autochthonous organic substances in the sediments and furthermore forms asphaltic impregnations in the massive sulfides

unusual carbon isotope compositions of biomarker hydrocarbons in a permian tasmanite abstract the permian oil shale sample of this study is from a deposit in tasmania in which the only recognizable structures are large thick walled unicellular specimens of the green alga tasmanites the fossils are so densely packed that this shale is termed tasmanite the carbon isotopic composition of bulk kerogen carbon c 13 c org 16 6 vs pdb is unusually enriched in 13 c compared to marine permian organic carbon 25 to 30 this 13 c enrichment suggests specific environmental conditions co 2 draw down and or physiological specialties cell size and growth rate of tasmanites which in modern environments are known to cause 13 c enrichment in marine phytoplankton isotope signatures of extractable organic species unlike in normal immature oil shales are considerably enriched in 13 c compared to the kerogen the bitumen 10 9 is composed predominantly of extended saturated c 18 c 25 tricyclic terpane hydrocarbons 9 9 to 12 2 total range with an average of 10 8 these tricyclics are not only found as free lipids in the extract but also in pyrolysates with similar isotopic signatures and are therefore likely biosynthesis products of tasmanites the monoaromatic and diaromatic tricyclic terpane hydrocarbons c 17 c 19 have similar isotopic signatures 9 3 to 12 8 total range with an average of 10 6 two monoaromatic tetracyclic hydrocarbons c 23 and c 24 a quantitatively minor but biogenetically interesting group average at 10 2 in contrast pristane and phytane as well as n alkanes 18 to 22 are depleted in 13 c compared to kerogen carbon the isotopic similarity of all the cyclic terpanes in this sample together with their occurrence in the free lipids and kerogen suggests that they have a common origin and are biosynthesis products of the marine unicellular green algae tasmanites the tetracyclic terpanes therefore are not des a oleananes derived from land plants but are possibly monoaromatic des a gammaceranes or other des a triterpenoids derived from marine sources the unusual enrichment in 13 c in the cyclic hydrocarbons is hypothesized to result from the special growth conditions of the algae isoprenoids and n alkanes are also likely biosynthesis products of tasmanites possibly during the spore formation stage when physiological and environmental conditions were different than during planktonic biosynthesis

sulphur solubility in andesitic to basaltic melts implications for hekla volcano the solubility of sulphur in sulphide saturated h2o bearing basaltic andesitic and basaltic melts from hekla volcano iceland has been determined experimentally at 1 050 c 300 and 200 mpa and redox conditions with oxygen fugacity logfo2 between qfm 1 2 and qfm 1 1 qfm is a quartz fayalite magnetite oxygen buffer in the systems containing various amounts of s and h2o the s content of the h2o rich glasses saturated with pyrrhotite decreases from 2 500 ppm in basalt to 1 500 ppm in basaltic andesite at the investigated conditions furthermore the reduction of water content in the melt at pyrrhotite saturation and fixed t p and redox conditions leads to a decrease in s concentration from 2 500 to 1 400 ppm for basaltic experiments for h2o decrease from 7 8 to 1 4 wt and from 1 500 to 900 ppm for h2o decrease from 6 7 to 1 7 wt for basaltic andesitic experiments our experimental data combined with silicate melt inclusion investigations and the available models on sulphide saturation in mafic magmas indicate that the parental basaltic melts of hekla were not saturated with respect to sulphide during magmatic differentiation the s content in the residual melts increased and might have reached sulphide saturation with 2 500 ppm dissolved s with further magma crystallization the s concentration in the melt was controlled by the sulphide saturation of the magma decreasing from 2 500 to 900 ppm s

origin of petroliferous bitumen from the buyuk menderes gediz geothermal graben system denizli saraykoy western turkey abstract the kb 5 well is located at the intersection of the geothermally active menderes and gediz graben systems in western turkey significant volumes of petroleum like material plm with its associated thermal water 120 c erupted onto the surface during drilling from a depth of 120 132 m i e from the claystone and marl rich early to middle pliocene kolonkoya formation the purpose of this paper is 1 to characterize this plm 2 to assess the source characteristics from which the plm was likely generated and 3 to recognize the generation mechanism considering the geothermal gradual versus the hydrothermal rapid processes analytical organic geochemistry using thin layer chromatographic separation followed by gas chromatography mass spectrometry gc ms was carried out the plm is composed primarily of polar nso compounds asphaltenes 77 this feature is similar to hydrothermal petroleums e g calcite springs yellowstone national park wyoming the plm shows n alkanes ranging from n c 19 to n c 38 i e with a maximum at n c 30 but n alkanes are depleted in n c 19 an absence of acyclic isoprenoids pristane and phytane and considerably large ucm unresolved complex mixture indicate that the plm has been subjected to a moderate degree of alteration possibly by the accompanying hot geothermal waters the source specific biomarkers i e low c 29 nh c 30 h ratio presence of gammacerane and 18 h oleanane high c 35 c 34 homohopane ratio and c 29 sterane concentration n c 28 n c 27 n c 29 c 28 27 29 r steranes c 29 r c 27 r suggest that the plm is a petroleum and was most likely generated from a tertiary source rock with a carbonate clay rich lithology the source organic matter was predominantly terrestrial and bacterial detritus deposited in relatively saline anoxic environmental conditions maturity sensitive biomarker parameters i e t m t s c 29 sterane 20 s 20 s 20 r 0 35 c 32 hopane 22 s 22 s 22 r 0 57 low diasterane regular sterane ratio correspond to a maturity level of approximately 0 50 0 60 r o this level of maturation could not be reached by such a young upper miocene lower pliocene and shallow sedimentary column max 600 m in the absence of instantaneous hydrothermal activity pahs are not detectable but series of alkylbenzenes alkyltoluenes alk 1 enes and triaromatic steranes are present the lack of organic richness and maturity in the drilled section of the kb 5 well indicates that the petroleum was generated in the deeper sections of the formation the temperature profile of the well and composition of the hydrocarbons in the petroleum suggest that the temperature of the hydrothermal activity during hydrocarbon generation was

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

correlation of glacial deposits of the huron lake michigan and green bay lobes in michigan and wisconsin michigan and eastern wisconsin were glaciated several times during the pleistocene ice erosion overdeepened river valleys in the weaker units of the sequence of sedimentary rocks now exposed as a result of structural basining glacial erosion led to development of the three relatively deep bedrock basins now occupied by lakes huron michigan and superior as a result whenever an ice margin crossed the area it had a lobate form with ice tongues extending relatively far south in the bedrock basins while much of the area between the lobes was ice free lobe margins within the basins terminated in proglacial lakes the ice lobes of importance in the area are a the huron lobe and its saginaw sublobe b the lake michigan lobe and c the green bay lobe fig 1 the granulometry and mineralogy of the drift related to each lobe reflect the nature of both the bedrock and older surficial units upice in much of the area the glacially related deposits are over 30 m thick and in some places the thickness is more than 300 m the surface deposits nearly everywhere are late wisconsin in age and relatively little is known of the glacial history of the area prior to that time formal names have not been established for lithostratigraphic units in michigan and most units in wisconsin have only recently been formally defined mickelson et al 1984

an association between organic matter and localised prehnite pumpellyite alteration at builth wells wales u k metcalfe r banks d and bottrell s h 1992 an association between organic matter and localised prehnite pumpellyite alteration at builth wells wales u k chem geol 102 1 21 the builth volcanic group of the builth wells ordovician inlier wales is a sequence of basic intermediate lavas and volcaniclastics which shows a unique association between pyrobitumen and localised domainal calc silicate alteration the pyrobitumens occur in calcite veins and disseminated throughout alteration domains which form haloes to these veins the pyrobitumens were emplaced by ordovician hydrothermal fluids which were also responsible for the domainal alteration combined petrographic gas chromatography and stable isotopic studies show that light organic gases c2 c5 were liberated into the hydrothermal fluids by devolatilisation of liquid petroleum to form the pyrobitumens these light organic gases mixed with methane characterized by 13c 13 o which was already present in the fluids this methane was most likely mantle derived or produced from inorganic synthesis the organic content of the fluids exerted an important control on the inorganic secondary assemblages a similar control of inorganic assemblages by organic matter might possibly occur deep within modern petroleum bearing hydrothermal systems such as the guaymas basin and escanaba trough hydrothermal systems

the millennium eruption of hekla in february 2000 the 18th historic eruption of hekla started on 26 february 2000 it was a short lived but intense event emitting basaltic andesitic 55 5 wt sio2 pyroclastic fragments and lava during the course of the eruption monitoring was done by both instruments and direct observations together providing unique insight into the current activity of hekla during the 12 day eruption a total of 0 189 km3 dre of magma was emitted the eruptive fissure split into five segments the segments at the highest altitude were active during the first hours while the segments at lower altitude continued throughout the eruption the eruption started in a highly explosive manner giving rise to a subplinian eruptive column and consequent basaltic pyroclastic flows fed by column collapses after the explosive phase reached its maximum the eruption went through three more phases namely fire fountaining strombolian bursts and lava effusion in this paper we describe the course of events of the eruption of hekla and the origin of its magma and then show that the discharge rate can be linked to different style of eruptive activity which are controlled by fissure geometry we also show that the eruption phases observed at hekla can be linked with inferred magma chamber overpressure prior to the eruption

hydrocarbons in waters and particulate material from hydrothermal environments at the east pacific rise 13 n the fast spreading east pacific rise at 13 n consists of an active circulating hydrothermal system with associated massive sulfide deposits and large communities of animals clustered around hot smokers the main food source of these benthic organisms is supplied by symbiotic chemosynthetic activity of sulfur oxidizing bacteria biomarker lipids such as hydrocarbons were analyzed to describe their sources and composition and also the relationships among microorganisms biological communities and dissolved and particulate organic materials in this productive area the organic matter of vent waters is both quantitatively and qualitatively different from the non vent bottom water dissolved hydrocarbon concentrations in warm water t 15 c from fissures in basalts and hot clear water t 250 c from smokers are 100 and 400 times more concentrated respectively than the water outside active areas the biomarker compounds from hot clear water are characteristic of thermally mature organic matter as indicated by the 17 h 17 h hopane series and the dominance of 5 h 14 h 17 h steranes over the 5 h 14 h 17 h 20r steranes i e the biologically inherited configuration the dissolved hydrocarbons from the warm waters may be correlated with bacterial lipid residues as indicated by the presence of isoprenoid hydrocarbons pristane phytane and low molecular weight cyclic hydrocarbons the water column samples collected near hydrothermally active areas contain bicyclic alkanes with drimane and rearranged drimane skeletons and mature biomarkers 17 h hopanes and steranes these components probably derived from thermally altered microbial sources the dissolved lipid matter is found to be degraded more rapidly by microbial activity and thermal processes especially in the warm water effluent and in the water column around hydrothermal vents than the lipids of the particulate matter

hydrothermal buffering of the so2 h2s ratio in volcanic gases evidence from la fossa crater fumarolic field vulcano island 1 sulfur speciation in volcanic gases is a potentially valuable tracer of degassing processes at volcanoes hitherto observations of sulfur speciation in volcanic gas plumes have however been limited both in number and quality here we report on periodic measurements of so2 to h2s proportions in the volcanic gases from la fossa volcano vulcano island performed during 2004 2006 a period which encompasses two heating events of the fumarolic field in january april 2005 and december 2005 results indicate a systematic relative increase by a factor of 2 6 of so2 to h2s proportions in the fumaroles during the heating events which we ascribe to a temperature increase in the mixing zone between magmatic and hydrothermal fluids we also demonstrate that sulphur speciation in la fossa fumaroles reflects re equilibration within a poly baric hydrothermal system and that this hydrothermal re equilibration erases the pristine so2 h2s ratios of any magma derived sulphur present

carbon isotope systematics of individual hydrocarbons in hydrothermal petroleums from the guaymas basin gulf of california abstract individual aliphatic and aromatic hydrocarbons in hydrothermal petroleums from the guaymas basin were subjected to compound specific isotope analysis to trace their origins the carbon isotope compositions of the alkanes and polycyclic aromatic hydrocarbons means 23 1 and 21 2 respectively all reflect their marine source and confirm their generation from the sedimentary kerogen

the permian kupferschiefer of southwest poland a geochemical trap for migrating metal bearing solutions abstract the ore grade cu mineralization in southwest poland is associated with the presence of the rote faule zone that overlies the contact of saxothuringian and rhenohercynian zones in these areas the soluble organic matter in the kupferschiefer is altered strongly saturated hydrocarbons and alkylated aromatic compounds are depleted significantly in comparison to non altered shale samples of a similar maturation instead unsubstituted di and tricyclic aromatic hydrocarbons are the dominant components of the extractable bitumen the observed alteration points to late diagenetic oxiadtion reactions caused by upward migrated metalliferous solutions moreover polycyclic aromatic hydrocarbons pah associated with polycyclic aromatic sulphur hydrocarbons pash are abundant in some samples these compounds are considered to originate from the underlying carboniferous strata and were carried upward to the kupferschiefer zone which acted as a geochemical trap

mount st augustine volcano fumarole wall rock alteration mineralogy zoning composition and numerical models of its formation process abstract intensely altered wall rock was collected from high temperature 640 c and low temperature 375 c vents at augustine volcano in july 1989 the high temperature altered rock exhibits distinct mineral zoning differentiated by color bands in order of decreasing temperature the color bands and their mineral assemblages are a white to grey tridymite anhydrite b pink to red tridymite hematite fe hydroxide molysite fecl 3 with minor amounts of anhydrite and halite and c dark green to green anhydrite halite sylvite tridymite with minor amounts of molysite soda and potash alum and other sodium and potassium sulfates the alteration products around the low temperature vents are dominantly cristobalite and amorphous silica with minor potash and soda alum aphthitalite alunogen and anhydrite compared to fresh 1986 augustine lava the altered rocks exhibit enrichments in silica base metals halogens and sulfur and show very strong depletions in al in all alteration zones and in iron alkali and alkaline earth elements in some of the alteration zones to help understand the origins of the mineral assemblages in altered augustine rocks we applied the thermochemical modeling program gasworks in calculations of a reaction of the 1987 and 1989 gases with wall rock at 640 and 375 c b cooling of the 1987 gas from 870 to 100 c with and without mineral fractionation c cooling of the 1989 gas from 757 to 100 c with and without mineral fractionation and d mixing of the 1987 and 1989 gases with air the 640 c gas rock reaction produces an assemblage consisting of silicates tridymite albite diopside sanidine and andalusite oxides magnetite and hercynite and sulfides bornite chalcocite molybdenite and sphalerite the 375 c gas rock reaction produces dominantly silicates quartz albite andalusite microcline cordierite anorthite and tremolite and subordinate amounts of sulfides pyrite chalcocite and wurtzite oxides magnetite sulfates anhydrite and halides halite the cooling calculations produce a anhydrite halite sylvite b cu mo fe and zn sulfides c mg fluoride at high temperature 370 c d chlorides fluorides and sulfates of mn fe zn cu and al at intermediate temperature 170 370 c and e hydrated sulfates liquid sulfur crystalline sulfur hydrated sulfuric acid and water at low temperature

organic matter sources and early diagenetic alterations in arctic surface sediments lena river delta and laptev sea eastern siberia ii molecular and isotopic studies of hydrocarbons abstract the hydrocarbons extracted from three surface sediment samples from the delta of the lena river and adjacent areas of the laptev sea were examined to derive information on their source s natural vs anthropogenic terrestrial vs marine the abundance nature distribution and individual stable carbon isotope ratios of these hydrocarbons were determined it thus appeared that the laptev samples are characterized by i a negligible level of oil pollution due to anthropogenic and or natural petrogenic inputs ii an almost exclusive occurrence of long chain predominantly odd carbon numbered n alkanes and iii some differences in the level of bacterial alteration with a relatively higher degradation of the n alkanes in the seaward sediment a non terrestrial origin is proposed for these n alkanes based on the present results and on previous observations on carboxylic acid moieties and the pyrolysis products of the three surface sediments such hydrocarbons are probably not derived from the epicuticular waxes of higher plants but chiefly correspond to autochthonous products likely of algal origin these observations added to recent results on samples from other types of marine environments stress that an abundance of long chain predominantly odd n alkanes in extracts should not be systematically considered alone as evidence for a major contribution of higher plant waxes the relatively low contribution of terrestrial n alkanes in the laptev sediments should result from the combination of i a major dilution of the terrestrial input due to high primary productivity in summer promoted both by a large influx of nutrients provided by the lena river and by the specific conditions in such an arctic environment and ii the high level of degradation of the organic material transported by the lena river thus the latter probably provided a low input of lipids from terrestrial sources to the laptev samples

numerical simulations of volcanic jets importance of vent overpressure journal of geophysical research vol 113 b02204 doi 10 1029 2007jb005133 2008 numerical simulations of volcanic jets importance of vent overpressure darcy e ogden 1 kenneth h wohletz 2 gary a glatzmaier 1 and emily e brodsky 1 received 24 april 2007 revised 5 october 2007 accepted 5 november 2007 published 29 february 2008 1 explosive volcanic eruption columns are generally subdivided into a gas thrust region and a convection dominated plume where vents have greater than atmospheric pressure the gas thrust region is overpressured and develops a jet like structure of standing shock waves using a pseudogas approximation for a mixture of tephra and gas we numerically simulate the effects of shock waves on the gas thrust region these simulations are of free jet decompression of a steady state high pressure vent in the absence of gravity or a crater our results show that the strength and position of standing shock waves are strongly dependent on the vent pressure and vent radius these factors control the gas thrust region s dimensions and the character of vertical heat flux into the convective plume with increased overpressure the gas thrust region becomes wider and develops an outer sheath in which the erupted mixture moves at higher speeds than it does near the column center the radius of this sheath is linearly dependent on the vent radius and the square root of the overpressure the sheath structure results in an annular vertical heat flux profile at the base of the convective plume which is in stark contrast to the generally applied gaussian or top hat profile we show that the magnitude of expansion is larger than that predicted from previous 1d analyses resulting in much slower average vertical velocities after expansion these new relationships between vent pressure and plume expansion may be used with observations of plume diameter to constrain the pressure at the vent citation ogden d e k h wohletz g a glatzmaier and e e brodsky 2008 numerical simulations of volcanic jets importance of vent overpressure j geophys res 113 b02204 doi 10 1029 2007jb005133 1 introduction 2 in large explosive volcanic eruptions the eruptive fluid issues from the vent as a high speed compressible gas with entrained solid particulates it is important to quantify the behavior of this gas thrust region because it provides a connection between the fluid dynamics in the conduit and that of the buoyant column if the eruptive fluid velocity is at or greater than sonic and vent pressure is higher than atmospheric pressure the dynamics will be complicated by the presence of standing shock waves that can drastically alter the distribution of the vertical heat flux necessary for eruption column stability the fluid dynamics and structure of a compressible jet issuing from a sonic nozzle into an ambient atmosphere of lower pressure are well known from experimental analytical and computational studies e g crist et al 1966 young 1975 norman et al 1982 figure 1 although application of compressible jet dynamics to explosive volcanic eruptions was first sug gested over 25 years ago by kieffer 1981 the concept has earth planetary sciences department university of california at santa cruz santa cruz california usa los alamos national laboratory los alamos new mexico usa copyright 2008 by the american geophysical union 0148 0227 08 2007jb005133 09 00 yet to be widely applied in modeling and analysis of explosive eruption columns 3 in this paper we present computational results that quantify the important effects of vent pressure on the fluid dynamics of volcanic jets and show that overpressured jets produce vertical heat flux profiles that are drastically different than those of pressure balanced jets note to avoid confusion here we use the physics convention and consider heat flux the thermal energy transfer per area per unit time j m 2 s 1 and heat flow the thermal energy transfer integrated over an entire area per time j s 1 in volcanology literature the term heat flux is often used to mean either of these things e g woods 1988 mastin 2007 the simulations shown here are time dependent though they assume a steady vent condition through these simulations we quantify the effects of vent pressure and radius on plume radius and heat flux distribution after expansion of the jet this may allow the prediction of major features of the eruptive structure we do not consider the effects of variations in conduit dynamics buoyancy or the presence of a crater in order to focus only on the effects of vent pressure and radius alone this study is not a complete picture of the complicated flow dynamics of a volcanic eruption rather the results presented here could be consid ered the simplest case to which one could compare the dynamics resulting from more complicated simulations and observations of high pressure volcanic jets b02204 1 of 18

high temperature mixtures of magmatic and atmospheric gases recent measurements of bro nox and near source sulfate in volcanic plumes suggest that volcanic vents might not simply act as point sources of emissions into the troposphere but may also act as high temperature reaction sites where mixtures of magmatic and ambient atmospheric gases may combine giving new and previously unexpected reaction products the detection of such species demands that a more complex model be developed for the interaction of volcanoes and atmospheres we show that general thermodynamic models can be applied successfully to volcanic gas equilibria by comparing the results from hsc chemistry with those from two volcanic gas equilibrium models solvgas and gasmix using a thermodynamic model optimized for volcanic gas chemistry c o s h f cl br i n ar speciation we show that the volume ratio of atmospheric gas to magmatic gas in a high temperature mixture is an important parameter of the volcanic plume chemistry and our results suggest that even small amounts of air a few for an h2o rich magmatic gas in the high temperature mixture are sufficient to yield elevated levels of reactive nitrogen halogen cl br and i and sulfur species within the volcanic plume further modifications of the plume chemistry may also occur due to low temperature reactions and chemical schemes for the modification of halogen cl br i nitrogen and sulfur chemistry are suggested within the constraints imposed by recent measurements

solid bitumens an assessment of their characteristics genesis and role in geological processes familiar since antiquity and subject in contemporary times to various characterization schemes the exact nature of solid bitumen is not yet fully known bitumens have random polymer like molecular structures are mobile as highly viscous fluids or were once fluids but have since turned into solids solid bitumens consist mainly of large moieties of polyclyclic aromatic hydrocarbons occasionally with finely admixed fine grained cryptocrystalline graphite solid bitumens are distinguished from kerogen which is the syngenetic and generally finely dispersed particulate organic matter in sedimentary rock that virtually does not migrate following its deposition occurrences of solid bitumens are relevant to petroleum exploration as well as the search for and evaluation of a variety of metallic mineral deposits genesis of bitumen is in many cases linked to the thermal and hydrothermal history of organic matter in sedimentary rock apparently bitumen or more specifically organic acids generated along with bitumen during diagenesis may alter porosity of reservoir rocks or otherwise prepare the ground for ore deposition bitumen is also relatively sensitive to alteration processes some of which such as oxidative weathering water leaching biodegradation contact metamorphism and ionizing radiation may likewise affect its nature elemental composition of bitumen commonly reflects the nature of mineral deposits is is possible that in petroleum exploration trace metal abundances of bitumen may eventually allow prediction of crude oil types and volumes anticipated from a given source rock beside transition elements notably ni and v highly anomalous concentrations of u pt and au occur in some solid bitumens during the generation of petroleum from kerogen the trend in 13c is toward lighter values the opposite seems to occur when liquid petroleum is subjected to thermal cracking and or related processes yielding solid bitumen enriched in 13c and isotopically light methane in fact except for deasphalting and possibly some irradiation processes the result of thermal cracking oxidation water leaching inspissation drying and bacterial degradation of crude oil is that lower molecular weight hydrocarbons are removed leaving bitumen residues enriched in aromatic hydrocarbons heteroatomic compounds nso and 13c such phenomena are relevant to bitumen paragenesis in petroleum reservoir rocks to certain phanerozoic occurrences of multiple generations of bitumens and to bitumens in mineral deposits

14c ages of hydrothermal petroleum and carbonate in guaymas basin gulf of california implications for oil generation expulsion and migration sup 14 c dates have been obtained by accelerator mass spectrometry and by conventional techniques from hydrothermally derived petroleum calcite and vent water from the southern trough of guaymas basin gulf of california the ages for petroleum range from 4240 to 5705 b p whereas those for calcite range from 7340 to 33 168 b p the co sub 2 in a sample of hydrothermal vent fluid 24 end member yielded an apparent age of 14 820 b p which is within the calcite age range these are not true ages but rather they reflect the age of carbon within these materials the data indicate that the conversion of sedimentary organic matter to petroleum occurs very rapidly and that the petroleum is mobilized from sedimentary organic matter in the upper 30 m of the sediment column le 500 m thick underlying the sea floor deposits the large difference in ages between the petroleum and most of the calcites indicates that the carbon source in the calcites is more complex the inorganic carbon pool probably originates from the dissolution of older detrital carbonates and autochthonous biogenic carbonates in the shallow sediments and or the decarboxylation of organic matter at greater depth with a magmatic component of dead carbon

how does the hot core of a volcanic plume control the sulfur speciation in volcanic emission 1 volcanic eruptions inject sulfur into the atmosphere mainly in form of so2 and h2s the ratio of these species h2s so2 which is usually used as the mirror of the oxidation state of the source magma varies significantly according to the type of activity tectonic setting etc this study aims to investigate the role of the hot core of plinian and sub plinian volcanic plumes t 600 c in sulfur speciation based on the thermodynamic equilibrium in this temperature range we consider the hot core as a box model in which 1000 c magmatic gas and 25 c ambient air are mixed and show that it functions as a hot oxidizing reactor for s species processes inside the hot core usually decrease the h2s content of the system but can either increase or decrease so2 depending on initial oxidation state thus the so2 injected into the atmosphere is not essentially generated directly from the magma but it can be produced in the hot core as the result of h2s oxidation besides volcanic cloud compositions do not mirror the source conditions considering three types of tectonic settings convergent plate divergent plate and hot spot we propose that h2s emission is more likely under reduced conditions in divergent plate and hot spot volcanic settings

hydrothermal discharge and alteration in near surface sediments from the guaymas basin gulf of california abstract in the guaymas basin gulf of california hydrothermal fluids discharge onto the seafloor via both direct emanation through hydrothermal spires and diffusely through the sediments the latter mode is the focus of this study short 20 cm sediment cores were taken in zones of diffuse hydrothermal flow for chemical investigation of interstitial fluids and bulk solids the hydrothermal component of the pore fluids was quite variable indicating the heterogenous nature of the near surface flow regimes the bulk solids chemistry indicates that the suite of cores has encountered different amounts of cumulative hydrothermal exposure dissolution of biogenic silica and deposition of large amorphous silica clasts in the sediment are related to the extent of hydrothermal exposure surface enrichments in ba are formed as barite precipitates when ba rich hydrothermal fluids mix with sulfate rich seawater at the seafloor formation of pyrite and removal of mg from the solid phases are also observed effects of hydrothermal flow through these sediments

volcanic sources of tropospheric ozone depleting trace gases 1 recent investigations report mixing ratios of bro gas reaching 1 ppb in plume 4 7 km downwind of the summit of soufriere hills volcano montserrat the detection of bro in volcanic plumes is potentially important evidence of halogen catalyzed tropospheric ozone destruction and suggests that volcanoes either directly emit bro or emit bromine species that are rapidly converted to reactive bromine in volcanic plumes species distribution models constrained by volcanic gas and condensate analytical data for arc rift and hot spot volcanoes demonstrate that shallow magma degassing generates volcanic gases with ppb to ppm levels of reactive radicals br cl h and ho but no significant bro or clo the conversion of volcanic br and cl by reaction with ozone in gas phase catalytic reaction cycles during plume transport can lead to secondary bro and clo at mixing ratios of a ppt and higher possibly approaching a ppb for especially halogen rich volcanic gases several kilometers downwind of degassing sources in general however ppb bro and clo levels in volcanic plumes several kilometers downwind probably require near vent high temperature reaction of magmatic gases with air and or in plume heterogeneous chemical processes involving aerosols during plume transport these processes oxidize bromine and chlorine in hbr and hcl giving rise to increased levels of reactive br cl and ho in addition to nox they can also produce significant amounts of the photochemically active precursors br2 brcl and cl2 which are photolyzable to reactive br and cl the precursors may build up in nighttime volcanic plumes and accelerate ozone destruction and bro and clo production after sunrise downwind conversion of reactive br cl h and ho from volcanic gas sources by catalytic reaction chains to hobr and hocl may trigger heterogeneous chemical processes which are probably essential for sustaining ozone destruction in volcanic plumes gas phase reactions of hbr and hcl with ho in volcanic plumes might also boost bro and clo downwind thus in plume processes that generate reactive halogens may contribute significantly to ozone destruction in volcanic plumes enhanced levels of hox and nox in volcanic emissions may trigger nonhalogen catalytic cycles depleting ozone in tropospheric volcanic plumes

in situ aircraft observations of the 2000 mt hekla volcanic cloud composition and chemical evolution in the arctic lower stratosphere abstract an instrumented nasa aircraft made comprehensive in situ measurements of trace gas concentrations and aerosol properties while flying through the eruptive cloud from mt hekla in february and march 2000 the data reveal novel aspects of the properties and evolution of the volcanic cloud in the lower arctic stratosphere thirty five hours after the initial sub plinian explosion on february 26 2000 the aircraft intersected the cloud at an altitude of 11 3 km so2 concentrations in the cloud exceeded 1 ppmv but no h2s was observed large hf concentrations of 50 ppbv were nearly equal to the hcl concentration the same ratio of halogen species adsorbed on fallen ash although reactive nitrogen species are rarely detected in volcanic clouds significant hno3 concentrations of 3 ppbv above background were measured a bimodal aerosol size distribution with total number densities exceeding 8000 particles cm3 and total aerosol volume of 65 m3 cm3 was observed approximately 1 3 of the fine aerosol particles were non volatile volcanic ash and the remaining 2 3 were volatile sulfate aerosol and ice the volcanic cloud was highly structured with clearly delineated boundaries in the 18 day period following the initial eruption increases in so2 sulfate aerosol hcl and hf volume mixing ratios were again detected analysis of the partitioning of sulfur between the gas and aerosol phases in these later cloud encounters shows that the rate of so2 oxidation to sulfuric acid was broadly consistent with changing oh concentrations at the time of the vernal equinox

characterization of hydrothermally generated oil from the uzon caldera kamchatka abstract this paper reports the analyses of unusual oils that accumulate in the uzon caldera situated in the central volcanic region of kamchatka russia gas chromatography mass spectrometry gc ms was used to determine the primary constituents and the 13 c and 14 c compositions provided information about the potential source and age of the oils the 14 c ages determined are 1030 40 a bp measured or 940 40 a bp conventional the 13 c value is 30 6 versus the pdb standard a value consistent with a biological origin the nearly contemporary age of the c content indicates a geologically recent origin from biogenic detritus and not by synthesis from mantle c the biogenic origin is supported by the presence of sterane and hopane biomarkers and the 13 c value of the bulk oil the overall compositions of the oils indicate that they are derived from rapid hydrothermal alteration of algal bacterial mat detritus buried by volcanic ashfall deposits of the uzon caldera the oils represent the youngest hydrothermal petroleum reported to date

controls on iron mobilisation from volcanic ash at low ph insights from dissolution experiments and mossbauer spectroscopy the deposition of volcanic ash from explosive eruptions to the surface ocean is a source of iron fe for marine phytoplankton however the factors that determine the soluble and thus potentially bioavailable fraction of fe in ash from magma source to ocean sink remain poorly understood we investigate for the first time the release of both fe ii and fe iii from six natural ash samples in ph 1 h2so4 representative of exposure to aqueous low ph conditions during airborne transport mossbauer spectroscopy analysis of the ash suggests that the overall 168 h trends in fetot and fe ii fetot release by individual samples are governed by dissolution of fe bearing aluminosilicates or oxides of the ash bulk in contrast the initial 6 h trends in fe release may reflect chemical properties of the ash surface imparted by the ash s eruptive history supported in part by x ray photoelectron spectroscopy analysis preferential release of fe iii relative to fe ii immediately on ash input to acid is attributed to oxidation of ash surfaces within the eruption plume additionally prior exposure of ash to a hf or hcl rich plume may enhance fe release by respectively reducing aluminosilicate resistance to acid dissolution or lowering the ph of the liquid film on airborne ash altogether our findings highlight that differing fe speciation in the ash bulk and surface reflecting its magmatic and eruptive history exerts a strong influence on the fe release behaviour of ash even from the same volcano the relative importance of bulk versus surface controls on fe mobilisation from ash during atmospheric transport will ultimately depend on the duration of contact with acids before deposition to the ocean

carbon isotope systematics of individual hydrocarbons in hydrothermal petroleum from escanaba trough northeastern pacific ocean abstract we submitted individual aliphatic and polycyclic aromatic hydrocarbons in samples of hydrothermal petroleum from escanaba trough to compound specific isotope analysis to trace their origins the carbon isotope compositions of the alkanes and polycyclic aromatic hydrocarbons means 27 5 and 24 7 respectively reflect a primarily terrestrial organic matter source

hydrocarbons in surface sediments from a guaymas basin hydrothermal vent site petroleum like materials found at the guaymas basin hydothermal vent site gulf of california are derived from pyrolysis of organic matter two characteristics surface sediment cores differing in temperature profiles and other parameters were collected by dsv alvin sectioned and analyzed for hydrocarbons the quantitative and qualitative composition of alkanes steranes diasteranes and triterpanes differed between these cores as well as within sections of the same core these differences apparent for scales of tens of centimeters are related to interactive physical chemical and microbial processes as well as the influence of multiple sources for the petroleum

two creeks interstade dated through dendrochronology and ams abstract dendrochronological analysis of fossil wood from two creeks wisconsin reveals that the two creekan intetstade lasted at least 252 yr the sites crossdated by tree rings cover an area of about 970 km 2 ams determinations from the beginning and end of the chronology open a 14 c time window for the episode from 12 050 to 11 750 yr b p the interval is contemporaneous with the older dryas in northern europe the development of a forest covering at least 970 km 2 on the western shore of lake michigan indicates a water level about as low as in modern times glacier retreat must have opened drainage channels either through the straits of mackinac or via the indian river plateau into the eastern lakes the beginning of the tree ring chronology coincides with the peak of meltwater pulse 1a at 12 000 yr b p increased amounts of meltwater seem to have disturbed the heat exchange between the waters and the atmosphere in the north atlantic off the gulf of st lawrence or affected the 18 o ratio of the evaporation causing the climatic or isotopic reversal of the older dryas in greenland and northern europe