detailed tephrochronology and composition of major holocene eruptions from avachinsky kozelsky and koryaksky volcanoes in kamchatka abstract avachinsky kozelsky and koryaksky volcanoes form one of the most volcanically active clusters in the kamchatka volcanic arc and are located in close proximity of the cities of petropavlovsk kamchatsky and elizovo the most populated area in kamchatka in this paper we report a compilation of new and revised previously published data on the eruptive history of these volcanoes during the past 13 5 kyrs we identify 217 explosive eruptions of these volcanoes determine their ages using 207 radiocarbon dates and bayesian statistical modeling and characterize their tephra geochemically using major and trace element compositions of bulk samples 40 samples and volcanic glass 75 samples avachinsky has been the most active during the holocene time and had 150 explosive eruptions koryaksky produced 60 eruptions and kozelsky had only two eruptions in the early holocene our new data confirm the onset of the avachinsky postglacial activity at 11 3 cal ka bp and previously distinguished two major stages of avachinsky holocene eruptive history stage i 8 3 8 cal ka bp and stage ii 3 8 cal ka bp present during stage i eruptions were relatively rare but they included at least six large pumice eruptions with tephra volumes exceeding 0 5 km3 stage i tephras had low k andesitic bulk compositions and low k rhyolitic matrix glasses the andesites likely sampled volatile rich crystal mush from a long lived magma chamber under avachinsky volcano the stage ii started at 3 8 cal ka bp with a powerful eruption and was related to the construction of the young cone inside the avachinsky somma the subsequent late holocene eruptions were frequent but most of them did not exceed the volume of 0 3 km3 the stage ii tephras are mostly cindery basaltic andesites containing well crystallized groundmasses of andesitic composition these tephras originate from smaller perhaps more shallow magmatic reservoirs and their matrix glasses are likely products of in situ crystallization of relatively mafic magmas on their ascent to the surface koryaksky volcano was mostly active in the early holocene when avachinsky was quiet koryaksky tephras had a relatively constant bulk medium k andesitic composition during the holocene thanks to characteristic compositions high frequency and well constrained ages tephras of avachinsky and koryaksky volcanoes can be used for high resolution dating of local sediments some eruptions of avachinsky volcano reached volcanic explosivity index vei 5 and produced widely dispersed tephras these eruptions could have had global environmental effects and their tephras can be used for the correlation of disparate sedimentary archives some avachinsky and koryaksky eruptions were closely spaced in time however their tephras are easily distinguished by respective low k and medium k compositions and by different trace element patterns which imply compositionally different sources in the mantle wedge we interpret these differences to reflect the increasing slab surface temperature and transition of slab component from a relatively low temperature fluid like phase under avachinsky to more high temperature and solute rich supercritical fluid or melt under koryaksky the transition appears to be very sharp in kamchatka causing a large compositional shift in magmas just behind the volcanic front

petrological differentiation patterns and geomorphic distribution of ferricretes in central africa geomorphic distribution and petrological differentiation patterns of ferricretes widespread on landsurfaces were studied in the dembia zemio area southeastern central african republic four types of ferricretes are distributed on high plateaux hillslopes and low plateaux the main contrast corresponds to the differentiation between ferricretes of high plateaux rich in poorly hydrated minerals hematite and kaolinite and those covering hillslopes and low plateaux richer in hydrated minerals goethite and gibbsite a principal component analysis of geochemical and mineralogical data was used to characterize the main differentiation patterns of ferricretes in relation with their petrographic facies and the geomorphic features of the landscape the distribution of secondary minerals and their relationships to trace elements within and between the ferricrete types reflects differences in weathering and erosion processes our results document that the petrological patterns and the distribution of ferricretes are related to geomorphic features depending on hydroclimatic variations that govern the landscape evolution of many tropical shields

hydrographic structure of brine filled deeps in the red sea new results from the shaban kebrit atlantis ii and discovery deep abstract hydrographic profiles with ctd and water samples from four brine filled deeps in the red sea shaban kebrit atlantis ii and discovery deep were taken during the meteor 31 2 expedition in february march 1995 in the shaban deep area two smaller basins containing high saline brine were found in addition to the already known southern basins corresponding salinities 150 7 cl in the upper brine section and near equal brine levels around 1325 m water depth suggest subbottom connections below the sills separating the northern and southern basins an insignificant decrease in temperature to about 24 1 c has occurred in the upper brine since detection of the shaban deep in 1981 and no changes were found for the brine seawater level no significant changes have been observed in the kebrit deep over the last 23 years in temperature 24 3 c chlorinity 154 0 0 3 cl and brine level 1466 1 m the transition from high saline brine to normal seawater salinity probably extends over a depth of only a few decimetres or less strong changes however were registered for the atlantis ii deep the temperature increase known from numerous earlier investigations continued the gradient of increase was the steepest during the last 2 5 years and a temperature of 71 7 c was reached in the lower brine of the sw basin the structure of the lower transition zone between about 1990 m water depth and high saline brine has also changed significantly now containing two convective layers with nearly constant temperatures 61 and 55 c respectively the neighbouring discovery deep also shows evidence of increased hydrothermal activities while the temperature was nearly constant near 44 7 c until 1977 it has since increased to almost 50 c and the brine level has risen by about 17 m

heat and salt fluxes in the atlantis ii deep red sea abstract the atlantis ii deep is located on the red sea axial rift it is a topographic depression enclosing a volume of about 17 km3 between 1 900 m and 2 200 m depth that contains layered brines of temperatures up to 66 c and salinities up to 270 previous geochemical investigations showed that the hot brines result from discharge of hydrothermal solutions that have exchanged heat and chemical components with the basaltic substratum the last investigation of the deep in 1992 showed that the brines occurred in four well mixed layers with the shallowest at a depth of 2 000 m the temperature and salinity profiles describe a transition zone from 2 000 m to 1 900 m above which red sea water occurs the distribution of temperature and salt in this transition zone appears to be controlled by the topography of the deep the hydrographic structure of the brine column has been documented in the literature for seven time intervals between 1966 and 1992 examination of these data shows that the system changed with time the evolution of the entire package of brines that fill the deep shows the following changes 1 the temperature of the brines increased 2 the salinity of the solutions increased 3 the two brine layers described in 1966 still existed in 1992 but new layers appeared above them 4 for 26 years almost all additional heat and salt supplied in the deep were confined to the depression and were not dispersed into the overlying seawater the fourth point indicates that a heat and salt balance for the deep can be calculated the calculation of the heat that entered into the system was divided into two components the temperature increase of the brines and the heat loss at the wall rock the latter component was negligible the rate of heat input to the deep was constant during the period considered and amounted to 0 54 109 w the salt input was also constant and equalled 250 350 kg s during the period 1966 1992 heat and salt were most probably supplied by a hydrothermal solution with an average range of flow rate temperature and salinity of 670 1000 kg s 195 310 c and 270 370 respectively

gas and water geochemistry of geothermal systems in dominica lesser antilles island arc abstract four of the nine potentially active volcanoes on the island of dominica in the lesser antilles volcanic island arc have associated active volcanic hydrothermal systems between 2000 and 2006 the gas and thermal waters from these systems were investigated to geochemically characterise the fluids gain insight into the temperature and equilibrium state of the underlying reservoirs and evaluate the feasibility of monitoring geothermal features as a volcano surveillance tool in dominica the geothermal gases are typical of those found in arc type settings with n2 excess and low amounts of he and ar the dry gas is dominated by co2 ranging from 492 to 993 mmol mol and has a hydrothermal signature with hydrogen sulphide as the main sulphurous gas the waters are predominantly acid sulphate so4 100 4200 mg l ph 4 and likely formed as a result of dilution of acidic gases in near surface oxygenated groundwater enrichment in both 18o and d with respect to the global meteoric water line gmwl confirms that the waters are of primarily meteoric origin but have been affected by evaporation processes quartz geothermometers gave equilibrium temperatures of 83 c 203 c these temperatures contrast with the higher equilibrium temperature ranges 170 c 350 c obtained for the gases using the h2 ar ch4 co2 gas ratios plot suggesting that the quartz geothermometers are affected by non attainment of equilibrium this may be a result of precipitation of the dissolved silica and or dilution by relatively cold shallow aquifers of the thermal fluids generally no significant variations in fluid gas chemistry of the hydrothermal systems were observed during the study period and we propose that there were no changes in the state of volcanic activity in this period one exception to this occurred in a feature known as the boiling lake which underwent a month long period of significant compositional temperature and water level fluctuations ascribed to a drastic decrease of hydrothermal input related to a perturbation in the lake probably seismically induced this geochemical study is part of an ongoing monitoring programme of dominica geothermal systems aimed at establishing long term geochemical observations for the purpose of volcano monitoring

chemical and isotopic characteristics of geothermal fluids from sulphur springs saint lucia abstract sulphur springs is a vigorous geothermal field associated with the active soufriere volcanic centre in southern saint lucia lesser antilles island arc the sulphur springs park is an important tourist attraction touted as the world s only drive through volcano with some of the hot pools being developed into recreational pools some 200 000 people visit the park each year since 2001 the hydrothermal fluids of sulphur springs have been sampled as part of an integrated volcanic monitoring programme for the island gas and water samples were analysed to characterise the geochemistry of the hydrothermal system and to assess the equilibrium state and subsurface temperatures of the reservoir this has also enabled us for the first time to establish baseline data for future geochemical monitoring the gases are of typical arc type composition with n2 excess and low he and ar content the dry gas composition is dominated by co2 ranging from 601 993 mmol mol with deeper magmatic sourced h2s rich vapour undergoing boiling and redox changes in the geothermal reservoir to emerge with a hydrothermal signature in the fumarolic gases fluid contributions from magmatic degassing are also evident mainly from the moderate to high contents of hcl and deeply sourced h2s gas respectively sulphur springs hydrothermal waters have acid sulphate type compositions so4 78 4008 mg l ph 3 7 and are of primarily meteoric origin which have been affected by evaporation processes based on the enrichment in both 18o and d 18o 1 to 15 and d 9 to 14 respectively in relation to the global meteoric water line gmwl these waters are steam heated water typically formed by absorption of h2s rich gases in the near surface oxygenated groundwaters reservoir temperatures calculated from the evaluation of gas equilibria in the co2 ch4 h2 system reveal higher temperatures 190 to 300 c than those derived from quartz geothermometry 95 to 169 c which appeared to be affected by dilution with meteoric waters generally no significant variations in fluid geochemistry of the hydrothermal system were observed between 2001 and 2006 and we propose that there were no changes in the state of volcanic activity during this period

contrasting hydrothermal activity at sierra negra and alcedo volcanoes galapagos archipelago ecuador and approximately 85 so2 of the total sulfur gas relative amounts of he ar and n2 show a distinct hot spot signature the 13c co2 is approximately 3 6 and 34st is approximately 3 3 the d 18o of fumarole h2o indicates steam separation from local meteoric waters whose estimated minimum mean residence time from 3h analyses is 40 years fumarolic activity at alcedo is controlled by a caldera margin fault containing at least seven hydrothermal explosion craters and by an intracaldera rhyolite vent two explosion craters which formed in 1993 1994 produce approximately 15 m3 s of steam yet discharge temperatures are 97 c water content of the total gas is 95 97 mol noncondensible gas is 92 98 mol co2 and sulfur gas is dominated by h2s relative amounts of he ar and n2 show extensive mixing between hot spot and air or air saturated meteoric water components but the average the 13c co2 is approximately 3 5 and 34st is approximately 0 8 the d 18o of fumarole steam indicates separation from a homogeneous reservoir that is enriched 3 5 in 18o compared with local meteoric water 3h indicates that this reservoir water has a maximum mean residence time of approximately 400 years and empirical gas geothermometry indicates a reservoir temperature of 260 320 c the intracaldera hydrothermal reservoir in alcedo is probably capable of producing up to 150 mw however environmental concerns as well as lack of infrastructure and power users will limit the development of this resource

temporal variations of gas compositions of fumaroles in the tatun volcano group northern taiwan article i nfo he 4 he geochemical monitoring hydrothermal activity is common in the tatun volcano group of northern taiwan helium isotopic compositions of fumarolic samples show that mantle component occupies more than 60 in the previous study along with recent seismic results a magma reservoir is inferred to have existed beneath the area of da you keng where fumarolic venting is the most active in tatun volcano group progressive increases of hcl concentrations and so2 h2s ratio in fumaroles from da you keng have been observed since august 2004 the hcl concentration changed from almost the detection limit to thousands of ppm even up to 30 000 ppm so2 h2s ratios varied from almost 0 to 3 hence so2 became the dominated s species in this area these variations were accompanied by rising temperature of fumaroles in the tatun volcano group especially in the area of da you keng from boiling point to 131 c meanwhile 3

intense ch4 plumes generated by serpentinization of ultramafic rocks at the intersection of the 15 20 n fracture zone and the mid atlantic ridge abstract as part of the fara french us program designed to study the mid atlantic ridge mar between 15 n and the azores twenty three dives with the submersible nautile were conducted during the french us faranaut 15n cruise on the eastern and western parts of the 15 20 n fracture zone ridge axis intersection south of the eastern ridge transform fault intersection nine nautile dives were made within the rift valley and along the western rift valley wall ch4 concentrations in the bottom waters reach 53 2 nmol kg along faulted zones on top and on the east flank of the ultramafic inner corner high 15 05 n 44 59 w where serpentinized rocks outcrop no 3he anomaly is associated with methane ruling out any primary mantle component fourteen dives were also made in the rift valley to the north close to the western intersection of the 15 20 n transform high ch4 anomalies up to 22 nmol kg are also present in the bottom waters of the rift valley northern segment on both the western and eastern valley walls and on the inner high adjacent to the eastern wall where ultramafic rocks outcrop seven vertical hydrocasts carried out in the axial valley 4500 m deep show an intense ch4 anomaly with a maximum 35 8 nmol kg at 3200 m depth this ch4 concentration is among the highest found along the mid atlantic ridge charlou and donval 1993 charlou et al 1997 ch4 concentrations of 9 9 14 9 nmol kg are also present on the western wall along the 3200 m isobath the high ch4 concentrations correspond to only weak 3he anomalies this ch4 rich plume is also associated with active fault zones that expose peridotite rocks ch4 output from ultramafic outcrops on the western and eastern intersections of the 15 20 n fracture zone with the mar is believed to reflect ongoing serpentinization these results associated with many other ch4 anomalies measured in the water column above ultramafic outcrops found between 12 n and the azores most likely reflect serpentinization processes extending along the whole slow spreading mid atlantic ridge

paleoceanographic record of the last glacial interglacial cycle in the red sea and gulf of aden abstract hydrographic conditions in the red sea are strongly controlled by regional climatic conditions and the restricted water exchange with the gulf of aden indian ocean in turn intermediate and deep water masses in the gulf of aden reflect the nature of red sea outflow planktonic and benthic foraminiferal faunas and the lithology and mineralogy of red sea and gulf of aden sediments were studied in order to evaluate changes in water mass conditions in the two basins during the last 18 000 years the results indicate that changes in the local climate and circulation regime during this period resulted in significant hydrographic changes in surface and bottom waters in the red sea and intermediate waters in the gulf of aden during the last glacial maximum high aridity and glacio eustatic sea level lowering resulted in surface and bottom water salinities in the red sea which were considerably higher than at present in the gulf of aden glacial surface salinities and temperatures remained similar to holocene values while surface water productivity may have been lower surface salinities in the red sea decreased after 18 000 years b p as the connection between the red sea and gulf of aden was reestablished however bottom water salinities remained high until at least 11 000 years b p pluvial conditions during deglaciation enhanced the density difference between surface and bottom waters in the red sea and resulted in a decrease in the oxygen content of the bottom waters hydrographic conditions in the western gulf of aden reflect a change in the properties of outflowing red sea water during deglaciation

sem image analysis for characterization of sand grains in thai paddy soils abstract this study presents a detailed characterization of sand grains in 34 samples of thai paddy soils mostly alfisols and ultisols that have formed from diverse parent materials computer analysis of sem images of thin sections provided a novel and reliable method to analyse the size and shape of quartz grains using the software imagej 1 34s sand grain size expressed as the feret value showed a log normal distribution for 16 samples whereas for the other samples the distribution was positively skewed a logit transformation of grain circularity values generated a normal distribution for 26 samples and eight samples had bimodal distributions these granulometric data indicate the diversity of the soil parent materials and the observed soil layers represent discrete sedimentary events with materials of different origins or different depositional energies pedogenesis including pedoturbation has not disrupted these sedimentary layers some sand grains consist of gold brass copper ilmenite zircon magnetite barite or monazite the diversity of these grains reflects the complex geology of the catchments providing the sediments and some anthropogenic materials may have been incorporated into the soils

helium 3 emission in and around teide volcano tenerife canary islands spain air corrected he 4he ratios of fluid samples collected in and around teide volcano tenerife canary islands ranged from 5 97 to 8 06 ra helium 3 emission spatial distribution has a quite different pattern from other stratovolcanoes which show commonly a decreased trend for the he 4he ratio with respect to distance from the summit crater this finding might be related to the volcano tectonic setting differences between subduction type and oceanic island type statrovolcanoes radiogenic helium production is a significant process for the dilution of uprising derived mantle fluids in and around subduction type stratovolcanoes while it can be almost negligible for polygenetic volcanoes at oceanic islands

fumarolic activity of avachinsky and koryaksky volcanoes kamchatka from 1993 to 1994 volcanic gas and condensate samples were collected in 1993 1994 from fumaroles of koryaksky and avachinsky basaltic andesite volcanoes on the kamchatka peninsula near petropavlovsk kamchatsky the highest temperature fumarolic discharges 220 c at koryaksky and 473 c at avachinsky are water rich 940 985 mmol mol of h2o and have chemical and isotopic characteristics typical of kamchatka kurile high and medium temperature volcanic gases the temperature and chemical and water isotopic compositions of the koryaksky gases have not changed during the past 11 years they represent an approximate 2 1 mixture of magmatic and meteoric end members low temperature near boiling point discharges of avachinsky volcano are water poor 880 mmol mol their compositions have not changed since the 1991 eruption and are suggested to be derived from partially condensed magmatic gases at shallow depth based on a simple model involving mixing and single step steam separation low water and high co2 contents as well as the observed cl concentration and water isotopic composition in low temperature discharges are the result of near surface boiling of a brine composed of the almost pure condensed magmatic gas high methane content in low temperature avachinsky gases and the 220 c koryaksky fumarole low c isotopic ratio in co2 at koryaksky 11 8 and water isotope data suggest that the meteoric end member contains considerable amounts of the regional methane rich thermal water discovered in the vicinity of both volcanoes

rainwater and ash leachate analysis as proxies for plume chemistry at soufriere hills volcano montserrat chloride and sulphate concentrations in rainwater and water soluble leachates from volcanic ash samples track the compositions of gas emissions at the soufriere hills volcano montserrat from 1996 to 2001 there are both systematic spatial and temporal variations in the chloride sulphate ratio expressed as the equivalent hcl so2 mass ratio in rainwater and ash leachates temporal variations reflect changes in eruption rate and eruptive style mass ratios of hcl so2 in ash leachates correspond closely with those obtained by open path fourier transform infrared op ftir spectroscopy and reflect changes in volatile emissions throughout the eruption both leachate and op ftir spectroscopic analyses show mass ratios of hcl so2 1 during dome growth and hcl so2 1 during non eruptive periods the hcl so2 mass ratios in rainwater samples from 1996 and 1997 show temporal variations that correlate with changes in extrusion rate the hcl so2 ratios in plume affected rainwater and ash leachates from june and july 2001 correlate positively with increasing rockfall energy and with increasing eruption rate prior to a dome collapse event the hcl so2 mass ratios in water soluble ash leachates and rainwater samples collected at the same time and from the same sites are linearly correlated with rainwater hcl so2 ratios systematically two to three times higher than ash leachate ratios spatial patterns of rainwater ph and hcl so2 in rainwater and ash leachates are principally influenced by the proximity of the sampling sites to the active dome and to the typical pattern of dispersion of the plume by tropospheric winds these results demonstrate that rainwater chemistry and ash leachate analysis provides a useful indicator of volcanic activity and represents a valuable supplement to volcano surveillance efforts

petrogenesis of alkaline basalts from socorro island mexico trace element evidence for contamination of ocean island basalt in the shallow ocean crust postcaldera mafic volcanism on socorro island mexico an island located in the eastern pacific ocean on a segment of a mid ocean ridge spreading center abandoned at 3 5 ma dominantly comprises alkalic basalt hawaiite and mugearite with subordinate mildly alkalic transitional basalt most major element data are consistent with differentiation of alkalic basalt to hawaiite and mugearite by up to 50 fractionation of plagioclase clinopyroxene olivine fe ti oxides high field strength element abundances are consistent with this interpretation and the narrow range in zr nb suggests that parental magmas formed by similar degrees of partial melting of a relatively homogeneous mantle source sr and nd isotopic ratios exhibit relatively narrow ranges 0 7031 0 7032 0 5128 0 5130 respectively despite this a subset of the alkalic basalts has negative ce anomalies and abundances of p2o5 ba y and some rare earth elements in excess of those predicted by fractional crystallization models these chemical features require open system processes the observed heterogeneities are perhaps best explained by assimilation of ocean crustal components by basalt in a shallow magma reservoir regional mantle heterogeneity is evident from elemental and isotopic data for mildly alkalic transitional basalt from socorro island mugearite from san benedicto island and submarine basalts from near socorro island evidence presented here indicates that compositional variations in ocean island basalts can be introduced by ocean crustal contamination and underscores the importance of considering this source of chemical heterogeneity in basalts before characterizing associated mantle

difference in n2 ar ratio of magmatic gases from northeast and southwest japan new evidence for different states of plate subduction two different plates are subductiog beneath the japanese island arcs the pacific plate in the north and the philippine sea plate in the south geophysical evidence indicates that the philippine sea plate subducts without extending beneath many of the volcanoes in the southwest japan arc the n 2 ar ratio 424 of a common magmatic gas from geothermal and volcanic areas in southwestern japan is an order of magnitude lower than the value 4250 in northeastern japan because the high n 2 ar values reflect input from subducted sediments the large difference in the n 2 ar ratios of magmatic gases indicates that the contribution of subducted sediment to the source of magma in southwestern japan is much lower than that in northeastern japan the n 2 ar ratios off magmatic gases from island arcs elsewhere may also yield information regarding the degree of contribution of subducted sediments to arc magma sources and differences in the states of plate subduction

stratigraphic control and chronology of peat bog deposition in the serra do espinhaco meridional brazil abstract peat bogs consist of a heterogeneous substrate whose physical characteristics vary in accordance with botanical composition inorganic sediment content and the degree of organic matter om decomposition although rare in the tropical zone of south america they can form in places where temperature and drainage favor the accumulation of om due to the anoxic character of the environment om remains preserved providing a valuable record of the climate during its genesis in the serra do espinhaco bogs can be found buried under sand deposits and given the difficulty of mapping such deposits by conventional methods ground penetrating radar gpr was used in their location and the study of the relationship between peat bog genesis and bedrock setting gpr data revealed blocks of quartzite located perpendicular to the drainage pattern which are assumed to partially restrict the water flow and maintain wet conditions upstream favoring the development of hygrophilous vegetation and the accumulation of om radiocarbon dating showed that buried bogs are contemporary to the deeper parts of non buried peats and that there is a strong correlation between their stratigraphy and climatic conditions between 30 250 and 12 400 years before present bp the conditions were favorable for the accumulation of om between 12 400 and 7900 years bp erosive processes caused sand deposition in the depression favorable conditions for deposition of om resumed around 7900 years bp and lasted until about 3300 years bp over the past 2600 years the climate has been similar to the present with three brief periods favorable to om deposition

origin of the fumarolic fluids of vulcano island italy and implications for volcanic surveillance variations in d and 18o values with h2o contents and outlet temperatures indicate that the fumaroles of la fossa crater have discharged mixtures of magmatic water and marine hydrothermal water since 1979 the contribution of meteoric water was low in the period 1979 1982 and very low afterwards the 18o values of the marine hydrothermal component of 5 to 7 2 are due to isotopic exchange with the 18o rich silicates of the rocks under high temperature and low permeability conditions the 18o value of the magmatic end member is generally 3 5 to 4 3 although values as high as 5 5 to 6 5 were reached in the summer of 1988 when magma degassing appears to have extended into the core of the magma body the d values of the end member were close to 20 typical of andesitic waters both the isotopic values and chemical data strongly support a dry model consisting of a central magmatic gas column and a surrounding hydrothermal envelope in which marine hydrothermal brines move along limited fracture zones to undergo total evaporation on approaching the conduits of magmatic fluids the vents at the eastern and western boundaries of the fumarolic field are fed by fluids whose pressure is governed by the coexistence of vapor liquid and halite giving rise to a high risk of phreato magmatic explosions should magma penetrate into these wet environments most la fossa eruptions were triggered by an initial hydrothermal blast and continued with a series of phreatomagmatic explosions the fluids discharged by the forgia vecchia fumaroles are mixed with meteoric water which is largely evaporated although subordinate loss of condensed steam may be responsible for scrubbing most of the acidic gas species the temperatures and pressures and the risk of a sudden pressure increase are low a boiling hydrothermal aquifer at 230 c is present underneath the baia di levante beach this area has a minor risk of hydrothermal explosions

the magmatic and hydrothermal dominated fumarolic system at the active crater of lascar volcano northern chile low to high temperature fumaroles discharging from the active crater of lascar volcano northern chile have been collected in november 2002 may 2005 and october 2006 for chemical and isotopic analysis to provide the first geochemical survey on the magmatic hydrothermal system of this active volcano chemical and isotopic gas composition shows direct addition of high temperature fluids from magmatic degassing mainly testified by the very high contents of so2 hcl and hf up to 87 800 29 500 and 2 900 mol mol and the high r ra values up to 7 29 contributions from a hydrothermal source mainly in gas discharges of the active crater rim has also been detected significant variations in fluid chemistry mainly consisting of a general decrease of magmatic related compounds i e so2 have affected the fumarolic system during the period of observation indicating an increase of the influence of the hydrothermal system surrounding the ascending deep fluids the chemical composition of active crater fumaroles has been used to build up a geochemical model describing the main processes that regulate the fluid circulation system of lascar volcano to be utilized in volcanic surveillance

chemical and isotopic equilibrium between co2 and ch4 in fumarolic gas discharges generation of ch4 in arc magmatic hydrothermal systems the chemical and isotopic composition of fumarolic gases emitted from nisyros volcano greece and of a single gas sample from vesuvio italy was investigated in order to determine the origin of methane ch4 within two subduction related magmatic hydrothermal environments apparent temperatures derived from carbon isotope partitioning between ch4 and co2 of around 340 c for nisyros and 470 c for vesuvio correlate well with aquifer temperatures as measured directly and or inferred from compositional data using the h2o h2 co2 co ch4 geothermometer thermodynamic modeling reveals chemical equilibrium between ch4 co2 and h2o implying that carbon isotope partitioning between co2 and ch4 in both systems is controlled by aquifer temperature n2 3he and ch4 3he ratios of nisyros fumarolic gases are unusually low for subduction zone gases and correspond to those of midoceanic ridge environments accordingly ch4 may have been primarily generated through the reduction of co2 by h2 in the absence of any organic matter following a fischer tropsch type reaction however primary occurrence of minor amounts of thermogenic ch4 and subsequent re equilibration with co existing co2 cannot be ruled out entirely co2 3he ratios and 13cco2 values imply that the evolved co2 either derives from a metasomatized mantle or is a mixture between two components one outgassing from an unaltered mantle and the other released by thermal breakdown of marine carbonates the latter may contain traces of organic matter possibly decomposing to ch4 during thermometamorphism

geochemistry of reduced gas related to serpentinization of the zambales ophiolite philippines abstract methane hydrogen gas seeps with mantle like c and noble gas isotopic characteristics issue from partially serpentinized ultramafic rocks in the zambales ophiolite philippines new measurements of noble gas and 14c isotope abundances rock mixed volatile equilibrium calculations and previous chemical and isotopic data suggest that these reduced gases are products of periodotite hydration the gas seeps are produced in rock dominated zones of serpentinization and similar gases may be ubiquitous in ultramafic terranes undergoing serpentinization

noble gas geochemistry in thermal springs abstract the composition of noble gases in both gas and water samples collected from horseshoe spring yellowstone national park was found to be depth dependent the deeper the sample collection within the spring the greater the enrichment in kr xe radiogenic 4he and 40ar and the greater the depletion in ne relative to 36ar the compositional variations are consistent with multi component mixing the dominant component consists of dissolved atmospheric gases acquired by the pool at the surface in contact with air this component is mixed in varying degree with two other components one each for gas and water entering the bottom of the pool the two bottom components are not in equilibrium in horseshoe spring the bubbles entering at the bottom strip the atmospheric derived pool gases from the surrounding water while en route to the surface if the original bottom bubbles are noble gas poor as in the case of horseshoe the acquired pool gases can then quickly obliterate the original bubble composition these results are used to demonstrate that yellowstone spring surface gas samples and perhaps similarly sampled thermal springs from other hydrothermal systems have gas abundances that depend more on spring morphology than processes occurring deeper in the hydrothermal system

continuous mixing of crystal mush and replenished magma in the ongoing unzen eruption zoning profiles of magnetite phenocrysts in the successively effused dacite of the ongoing unzen eruption from 1991 wereanalyzed to estimate the time scale of magma mixing the dacite was formed by mixing of relatively high and low temperature t end member magmas the magnetite phenocrysts derived from the low t magma are reversely zoned by the mixing with high t magma a diffusion calculation for reequilibration of the reverse zonings gives the time interval from magma mixing to quenching for the mixed dacite erupted from may 1991 to may 1993 the typical diffusion time was estimated to be a few months regardless of the effused sequence for 2 yr this indicates that the mixing was continuous during the effusion the invariability of the other mixing signatures such as the thickness of reaction rims around biotite phenocrysts also supports the continuous mixing model low t end member magma is estimated by mass balance calculation to be a crystal rich mush of dacitic composition these observations lead to a model wherein the highly crystallized remnant magma of the preceding activity has been mixed with the newly injected hot magma of similar bulk composition just prior to the effusion the proposed mechanism implies that this type of magma mixing is an inevitable process in periodically erupting polygenetic volcanoes

quantitative provenance analysis of sediments review and outlook provenance analysis of sediments is aimed at reconstructing the parent rock assemblages of sediments and the climaticphysiographic conditions under which sediments formed inferring sediment provenance from the final product a basin fill is anything but straightforward because the detrital spectrum evolves as the sediment is transported along the pathway from source to basin successful provenance analysis requires that the nature and extent of compositional and textural modifications to the detrital spectrum be recognised if not quantified the history of quantification in sediment provenance studies is summarised and illustrated by tracking two fundamental ideas the concept of the sediment petrological province or petrofacies and the relation between sandstone composition and plate tectonic environment progress in sedimentary provenance analysis has been closely linked with advancements in measurement technology a brief survey of modern data acquisition tools illustrates the possibilities and limitations of modern provenance research an operational definition of quantitative provenance analysis qpa is presented in which the central role of mass balance is acknowledged extension of this definition to include quantitative predictions obtained by forward modelling computer simulation of sediment production as well as methodological improvements in data acquisition and processing is needed to cover likely future developments in qpa the contributions to the special issue quantitative provenance analysis of sediments illustrate the intrinsic multidisciplinarity and rapid expansion of qpa d 2004 elsevier b v all rights reserved

a geochemical model for fumaroles of the mutnovsky volcano kamchatka ussr abstract on the basis of the chemical isotopic and thermodynamic characteristics of fluids sampled between 1964 and 1989 a genetic model description is given for fumaroles of the mutnovsky volcano there are three individual groups of fumaroles in the mutnovsky crater which show stable activity for a long period of time the active funnel temperatures exceed 600 c the upper field up to 320 c and the bottom field from 100 to 150 c the three principal zones of emission have different gas composition water isotopic composition radioactivity and 3he 4he ratios the abundance of magmatic components in the high temperature fumaroles of the active funnel is much higher than those in gases from the other groups emission rate of so2 from the active funnel is about 200 t d which requires complete degassing as a minimum of 1 km3 of magma every 20 years fluids of the upper field contain up to 80 of steam from the mutnovsky geothermal system temperature variations of the bottom field fumaroles from 97 c before 1982 to 151 c in 1989 result from changes in hydrological conditions in the crater evaporation of high saline acid brine which is formed in the interior of the volcano is responsible for the composition of the bottom field gas steam discharges

effect of shallow level contamination on the helium isotope systematics of ocean island lavas the bimodal distribution of helium isotope ratios in ocean island lavas has provided powerful constraints on the composition and evolution of the earth s mantle1 3 high 3he hotspot ratios 3he 4he greater than in mid ocean ridge basalt morb found on hawaii4 and iceland5 are thought to trace pristine plumes from the deep er mantle whereas low 3he hotspot values 3he 3he morb value at tristan da cunha6 and st helena7 are considered to characterize plumes composed in part of recycled oceanic or continental crust here we report the observation of both high 3he and 6low 3he characteristics8 in lavas from a single ocean island heard island in the indian ocean whereas the high 3he lavas provide unambiguous evidence for the involvement of a deep seated plume in their genesis we argue that the low 3he 4he ratios in other lavas result from shallow level contamination by radiogenic helium before eruption these observations call into question the presumed association between low 3he ratios at heard island and elsewhere and ancient crustal material recycled back into the mantle

the high pco2 caprese reservoir northern apennines italy relationships between present and paleo fluid geochemistry and structural setting abstract the chemical and isotopic compositions of i co2 rich fluids exploited from the 5 000 m deep pieve santo stefano 1 pss1 borehole located in the upper tiber basin northern apennines italy and ii natural gas seeps located in its surroundings mainly in the mt fungaia ophiolitic bearing complex ligurian unit are presented and discussed deep seismic profiles have allowed to identify a thrust related antiform caprese antiform a regional geological structure trapping the pressurized deep fluids fluids from the caprese reservoir cr consist of a co2 n2 rich gas phase sourced by both mantle degassing and thermal degradation of carbonate rocks and organic rich sediments of the umbro tuscan sedimentary series and a na cl saline up to 82 g l of tds brine gases naturally discharging in the study area are related to those present in the cr these gases during their uprising toward the surface mix with shallow aquifers addition of i h2 and h2s derived by the interaction with ophiolite bearing ligurian units and ii thermogenic hydrocarbons originated from the degradation of organic matter contained in the turbiditic sandstone rich formations cervarola falterona unit was also evidenced fluid inclusions trapped in calcite and quartz crystals from the pss1 drill core at the depth of 3864 to 3867 m contain co2 n2 and h2o nacl phases the different paleo co2 n2 contents and densities found with respect to the fluids currently exploited from the cr have been related to the evolution of the reservoir throughout the time compositional data of fluids exploited from pss1 borehole provide a unique opportunity to better characterize chemical physical processes and source regions of past and present deep fluids circulating in northern apennines

tide influenced acidic hydrothermal system offshore ne taiwan elemental sulfur and hydrogen sulfide emitted offshore of northeastern taiwan known to local fishermen for generations but never studied until recently are found to have originated from a cluster of shallow 92 with small amounts of h2s helium isotopic ratios 7 5 times that of air indicate that these gases originate from the mantle high temperature hydrothermal fluids have measured temperatures of 78 116 degrees c and ph 25 degrees c values as low as 1 52 likely the lowest to be found in world records low temperature vents 30 65 degrees c have higher ph values continuous temperature records from one vent show a close correlation with diumal tides suggesting rapid circulation of the hydrothermal fluids c 2005 elsevier b v all rights reserved

structure and evolution of the northern red sea combined analyses of new geophysical data in the northern red sea with data from the gulf of suez and the gulf of aqaba dead sea rift strongly suggest that the development of the red sea took place in three stages 1 a gulf of suez stage in the oligocene accompanied by thinning of the continental lithosphere and the formation of an early red sea gulf of suez graben 2 an early dead sea stage with slow seafloor spreading from 25 to 15 myr accompanied by 62km of shear along the aqaba dead sea transform and 3 a recent dead sea stage with slow seafloor spreading from 4 5 to 0 myr accompanied by 45km of shear along the aqaba dead sea transform

soil co2 flux in hydrothermal areas of the tatun volcano group northern taiwan abstract we measured soil co2 flux in the representative hydrothermal areas of the tatun volcano group tvg to better understand the volcano s dynamic nature and to estimate its soil co2 degassing output results show that the average soil co2 fluxes obtained at da you keng dyk geng tze ping gtp she haung ping shp and tatun natural park tnp were 128 g m 2 d 1 518 g m 2 d 1 420 g m 2 d 1 and 25 g m 2 d 1 respectively the range is comparable to other active volcanic hydrothermal areas in the world along with liu huang ku lhk where the soil co2 flux is known the total soil co2 output from measured areas is evaluated at 82 t d 1 furthermore a first total soil co2 output from the whole hydrothermal areas of the tvg is roughly estimated at 113 t d 1 which includes 15 t d 1 mantle contribution considering the mantle derived co2 flux and h2o co2 ratio of fumarolic gas thermal energy associated with the diffuse degassing at the tvg hydrothermal area is estimated at 8 2 mw carbon 13c and helium 3he 4he isotopic ratios of soil samples of the studied areas ranged from 4 4 to 6 7 and 2 45 to 6 98 ra respectively the extent of air involvement in the soil degassing system as constrained by the helium and carbon isotopic compositions provides essential information for depicting regional degassing features of the hydrothermal areas

isotopic variation of the hydrothermal system on vulcano island italy the isotopic and chemical composition of thermal waters and the isotopic composition of high temperature fumarolic steam at vulcano island indicate an evolution of the hydrothermal system from its magmatic origin through interaction with rocks and mixing with meteoric water seawater is not a component in this system the isotopic values of the fumaroles indicate a local magmatic composition of 7 to 8 18o and 5 to 15 d the high d values of this vapor may reflect contamination of the magma by connate water the isotopic and chemical composition of water from well w2 indicates the existence of geothermal fluid formed by mixing of hcl and so2 bearing condensates of volcanic origin with groundwater with subsequent evolution via water rock interaction the estimated isotopic composition of the geothermal water is 18o 1 and d 5 local shallow seismic events result in a temporary increase in fracture permeability enabling the mixing of magmatic vapor with groundwater or geothermal water tectonic activity associated with deep structures appears to increase the contribution of magmatic vapor to the fumaroles

40ar 39ar geochronological constraints on the evolution of lateritic iron deposits in the quadrilatero ferrifero minas gerais brazil weathering profiles overlying the sapecado pico and andaime iron ore deposits quadrilatero ferrifero qf minas gerais brazil reach depths of 150 400 m and host world class supergene iron orebodies in addition to hosting supergene ore bodies of global economic significance weathered banded iron formations at the quadrilatero ferrifero and elsewhere e g carajas hamersley are postulated to underlie some of the most ancient continuously exposed weathering profiles on earth laser incremental heating 40ar 39ar results for 69 grains of hollandite group manganese oxides extracted from 23 samples collected at depths ranging from 5 to 150 m at the sapecado pico and andaime deposits reveal ages ranging from ca 62 to 14 ma older mn oxides occur near the surface while younger mn oxides occur at depth however many samples collected at the weathering bedrock interface yield ages in the 51 41 ma range suggesting that the weathering profiles in the quadrilatero ferrifero had already reached their present depth in the paleogene the antiquity of the weathering profiles in the quadrilatero ferrifero is comparable to the antiquity of dated weathering profiles on banded iron formations in the carajas region brazil and the hamersley province western australia the age versus depth distributions obtained in this study but not available for other regions containing similar supergene iron deposits suggest that little further advance of the weathering front has occurred in the quadrilatero ferrifero lateritic profiles during the neogene the results suggest that weathering in some of these ancient landscapes is not controlled by the steady state advance of weathering fronts through time but may reflect climatic and geomorphological conditions prevailing in a remote past the geochronological results also confirm that the ancient landsurfaces in the quadrilatero ferrifero probably remained immune to erosion for tens of millions of years deep weathering mostly in the paleogene combined with low erosion rates account for the abundance and widespread distribution of supergene iron manganese and aluminum orebodies in this region

h2o and halogen f cl br behaviour during shallow magma degassing processes abstract degassing paths of silicic h2o rich magmas during explosive plinian and dome forming eruptions may be represented in simple evolution diagrams relating the residual volatile content of the melt to the volume ratio of gas over melt vg vl these parameters are measurable in erupted magma fragments they are used for interpreting the h2o and halogen contents determined in a series of variously degassed volcanic clasts from the 650 y b p eruption at mt pelee martinique fwi which is characterized by the succession of a dome extrusion and a plinian activity h2o degassing of plinian pumice clasts are modeled by an equilibrium closed system evolution which allows to calculate the partition coefficients of halogen between the aqueous fluid and the rhyolitic melt d v l i 1 for f 10 1 5 for cl and 3 7 1 for br at around 900 c the strong increase of the dv li values of cl and br during dome extrusion is explained by an open system degassing model with a simultaneous crystallization of the melt some significant br enrichments relative to cl in dome fragments are attributed to interactions with an hydrothermal fluid close to seawater in composition the models allow calculation of cl and br contents of aqueous fluids generated by the different degassing paths cl contents are 0 5 mol l for closed system evolution and vary between 0 2 and 1 mol l during open system evolutions these fluids are able to extract significant amounts of chloride complexed metals and silica from the magma during dome forming eruptions they also may generate mineralization of the wall rocks or the rising dome itself e g silica precipitation which may seal the volcanic system and be responsible for the dome explosivity and the transition from dome forming to plinian eruptive style the cl br ratio of initial melts of p1 eruption 250 is much lower than the basaltic and exospheric ratios 400 suggesting that strong cl br fractionation may occur during the production or the differentiation of subduction related magmas

hydrothermal processes governing the geochemistry of the crater fumaroles at mount etna volcano italy article i nfo we investigated the geochemistry of the fumaroles at the summit area of mt etna including sulfur speciation and the content of acidic gases the carbon isotope composition of the etnean plume was also measured in order to compare it to that of fumaroles two types of fumaroles were identified i low temperature fumaroles which are dominated by co2 with minor amounts of so2 and h2s and negligible chlorine contents and ii high temperature fumaroles which are strongly air contaminated and characterized by appreciable amounts of volcanogenic carbon sulfur and chlorine as recognized by martelli et al 2008 both groups of fumaroles are fed by the degassing of an underlying magma nevertheless compositional data clearly show that secondary processes affect the composition of the fluids once they leave the magma body here a model of cooling and condensation of fluids is proposed to explore such postmagmatic processes the model which uses etnean plume geochemistry as starting composition of fluids exsolved from magma shows that so2 and h2s control the redox conditions of the gas mixture during the cooling until the reactions involving co co2 and h2 h2o ratios are fully quenched at temperatures around 350 450 c the dissolution of gases in water subsequent to condensation must occur at thermobaric conditions over 50 bar and 260 c which allows a total removal of hcl b partial removal of sulfur species while preserving the so2 h2s ratio and c the c s ratio to increase by almost 10 fold relative to that in the plume the observed ch4 co2 ratios are higher than those calculated for the etnean magmatic gas and hence they provide evidence of modest contributions from peripheral hydrothermal fluids during the migration of magmatic gases toward the surface in both low and high temperature fumaroles due to the peculiar thermodynamic conditions the model predicts that carbon isotopes do not experience any postmagmatic fractionation and hence the isotopic composition of the fumaroles is representative of magmatic carbon measurements of the carbon isotope composition of the plume corroborate these findings

prolonged history of silicic peralkaline volcanism in the eastern pacific ocean socorro island mexico is an alkaline and peralkaline volcanic island located in the eastern pacific ocean on a mid ocean ridge spreading center that was abandoned at 3 5 ma silicic peralkaline rocks comprise up to 80 of the surface of the island rendering socorro virtually unique in the pacific ocean precise replicate 40ar 39ar ages of 21 peralkaline trachytes and rhyolites reveal a history of episodic volcanic activity from 540 to 370 ka that may have culminated with caldera formation repose periods between these episodes may have had maximum duration of 30 kyr after up to 200 kyr of quiescence 40ar 39ar ages indicate that postcaldera silicic peralkaline activity commenced by 180 ka forming the cerro evermann formation postcaldera mafic alkaline lavas of the lomas coloradas formation erupted dominantly between 70 and 150 ka based upon relative age relations the dominant lithology of precaldera and syncaldera silicic peralkaline deposits on socorro is nonfragmental and nonvesicular and lacks lithic fragments and fiamme despite this numerous lines of evidence including welding zonation presence of a proximal ignimbrite or co ignimbrite deposit association with a caldera and compositional heterogeneity within eruptive units suggest that they are dominantly ash flow tuffs a change in eruptive style from predominantly explosive to predominantly effusive followed caldera formation and suggests that a change in the efficacy of magma degassing may be linked to caldera formation on the basis of the presence of a caldera the magma chamber associated with socorro island is shallow and probably resides within the upper oceanic crust or the edifice this together with a prolonged history of silicic magmatism indicates that intrusion of mafic magma maintained thermal viability of the magmatic plumbing system the minimum calculated growth rate for the entire volcanic edifice 7 10 4 km3 yr exceeds those of nonhotspot off axis volcanoes in the pacific by almost an order of magnitude eruption rates for subaerial phases on socorro may be several orders of magnitude smaller than this growth rate and are comparable to subaerial eruption rates of isolated ocean islands related to mantle plumes

abundances distribution and sizes of volcanoes in the pacific ocean and implications for the origin of non hotspot volcanoes abstract in this paper i present data on the abundances sizes and crustal age for all volcanoes volcanic islands and seamounts which appear on published bathymetric charts of the pacific ocean these new data shed light on the origin of non hotspot volcanoes and are important in combination with data on the chemical compositions of seamounts and volcanic islands for estimates of the bulk composition of ocean crust these data also provide firm constraints on off ridge oceanic volcanism models results of this study show that the size frequency distribution of pacific volcanoes is poisson like and that the smallest volcanoes are much more abundant than large ones this study shows clearly that the most abundant volcanoes on the earth are the submerged oceanic volcanoes which comprise 5 25 of the oceanic volcanic layer on pacific crust of eocene age and younger the abundance of volcanoes number of volcanoes per unit area increases monotonically with increasing age assuming steady state the production rate of new off ridge volcanoes number of volcanoes per unit area per unit time is inversely proportional to the square root of the lithosphere age 1 on crust older than eocene the number of volcanoes per unit area of crust decreases monotonically with increasing age however the total volume of lava represented by these edifices increases with increasing age size frequency distributions of volcanoes on swaths of successively older crust indicate that these abundance patterns are partly due to the effect of sediment burial of small edifices on old pacific crust as well as the effect of increased lithosphere thickness on seamount size these general patterns are not appreciably changed by omitting from consideration known hotspot volcanoes 2 and volcanoes built at fossil constructional plate margins 3

reduced fluids in porphyry copper gold systems reflect the occurrence of the wall rock thermogenic process an example from the no 1 deposit in the xiongcun district tibet china abstract high fo2 conditions characterize the majority of global porphyry copper deposits and contain highly oxidized minerals such as magnetite and anhydrite in contrast the no 1 porphyry cu au deposit in the xiongcun district tibet china has abundant pyrrhotite reduced fluids ch4 co2 and a relative lack of highly oxidized minerals which are indicative of low fo2 conditions scanning electron microscopy fluid inclusion c h o he ar isotopes and whole rock organic carbon contents and isotope analysis were used to constrain the evolution of ore forming fluid the origin of ch4 and metal deposition mechanisms for the no 1 deposit the he ar isotopic compositions 3he 4he 0 11 0 96 ra 40ar 36ar 418 7 2920 2 suggest that the ore forming fluids predominantly derived from crust source with minor mantle input the h o isotopic analysis results 18oh2o 1 8 to 5 2 d 106 to 89 9 indicate that the ore forming fluids were derived from a magmatic source that mixed with some meteoric waters the element compositions of zircons and fluid melt inclusions from the mineralized middle jurassic quartz diorite porphyry reveal that the primary magma was characterized by high log fo2 nno conditions the quartz diorite porphyry intruded into the carbon bearing wall rocks produced abundant ch4 by thermal decomposition of organic matter 13cch4 26 3 to 28 5 which changed the redox state of the porphyry copper system from oxidized to reduced condition ore elements were deposited via fluid boiling as a consequence of the rapid decrease in temperature and pressure

modern shallow to deep water bivalve death assemblages in the red sea ecology and biogeography abstract this study provides quantitative comparisons of modern bivalve death assemblages between shallow marine deep shelf and bathyal settings cluster and discriminant analyses of the bivalve fauna distinguish four sample groups which are primarily separated by water depth shallow marine vs deeper shelf vs bathyal and sedimentological features fine grained shallow marine vs coarse grained shallow marine the four groups consist of taxonomically and or ecologically distinct faunal associations association 1 from fine grained shallow marine environments 6 40 m is characterized by the infaunal chemoautotrophic lucinoidea and suspension feeding corbulidae and veneroidea association 2 from coarse grained shallow marine environments 1 19 m is dominated by the infaunal suspension feeding cardioidea glycymerididae and deposit feeding tellinoidea but the importance of epifaunal cemented and byssate suspension feeding ostreoidea chamoidea arcoidea spondylidae and mytiloidea increases association 3 from deeper shelf mainly 50 100 m is strongly characterized by suspension feeding epifauna diverse pteriomorpha mainly limopsidae spondylidae and mytiloidea and association 4 from bathyal settings mainly 300 1900 m consists mainly of infaunal carnivorous cuspidariidae suspension feeding limopsidae and deposit feeding nuculanidae the two shallow water associations and the association from the deep shelf show considerable overlaps in taxonomic composition they also show a south to north alteration in their faunal composition which probably reflects their common post pleistocene immigration from refuge areas in the gulf of aden or gulf of oman the bathyal fauna in contrast is very distinct and homogeneous in all investigated respects throughout the red sea basin the dominance of endemic faunas the presence of bivalves with clearly tethyan origin and significant differences to deep sea faunas from the mediterranean basin and the gulf of aden indicate that in some deep water parts of the red sea pliocene faunas have survived during the pleistocene

extreme alteration in an acid sulphate geothermal field sulphur springs saint lucia abstract sulphur springs is a vigorous geothermal field associated with the soufriere volcanic centre in southern saint lucia intensely altered rocks occur over an area of at least 200 400 m together with bubbling hot pools and fumaroles the pools are sodium calcium sulphate type with phs of 3 7 and temperatures of 41 97 c fumaroles have temperatures up to and at times above 100 c gases collected from both fumaroles and bubbling pools have high contents of co2 601 993 mmol mol and commonly high h2s 3 190 mmol mol least altered host rocks surrounding sulphur springs comprise calc alkaline feldspar quartz porphyritic dacites of near uniform chemical composition these rocks which form massive domes and volcaniclastic units were emplaced 13 30 ka ago lindsay et al 2013 within the geothermal field the dacites have been moderately to highly altered to acid sulphate assemblages of kaolinite illite smectite alunite natroalunite cristobalite opaline silica native sulphur jarosite and amorphous compounds muddy sediments from grey to blackish thermal pools additionally contain iron sulphides despite intense alteration of the volcanic rocks and derived volcaniclastic sediments zr and ti have remained essentially immobile which allows identification of the precursors dacites and calculation of mass changes many of the altered rocks and sediments show major depletions of fe mg ca na extremely altered samples additionally show notable losses of al p k ree and y implying leaching by highly acidic waters a few of the highly altered rocks however have gained al together with p presumably due to neutralization or evaporation of acidic thermal waters also present within the geothermal field are metre scale zones with very high contents of silica and native sulphur and surface thermal waters define a linear trend in a plot of 18o vs d and reach high levels of isotopic enrichment the enrichment trend is ascribed to progressive evaporation in the thermal pools the low slope of the isotopic trend 1 4 is interpreted as being due to surficial mixing between meteoric waters and steam condensates derived at about 230 c from the deep brine that underlies the geothermal field the whole rock o h isotopic composition of four highly altered samples kaolinite smectite opal sulphates can be accounted for if the alteration fluid was a 50 50 mixture of steam and meteoric water and alteration occurred at 50 125 c whole rock 34s values of samples containing variable amounts of sulphates sulphides and native s are all notably negative 5 to 16 consistent with derivation of sulphur from volcanic gases such as so2 and h2s altered rocks and thermal pool sediments in the geothermal field are commonly enriched in hg and se up to 50 mg kg at sulphur springs primary dacitic rocks have been chemically and mineralogically transformed by reaction with acidic waters that formed when uprising volcanic gases condensed into neutral meteoric waters in many cases this has led to substantial mass losses or gains in al p and rees regardless of the degree of alteration however the precursor rocks can still be identified using ti zr relations

geochemistry of dissolved gases from the eastern carpathians transylvanian basin boundary abstract we show the results of a study on the volatiles dissolved in mineral waters discharged over a 200 km long transect along the rodna b rg u area and c limani gurghiu harghita volcanic chain eastern carpathians romania all of the collected mineral water samples carry dissolved gas with carbon dioxide content up to 1 99 cm 3 stp gh 2 o and helium content up to 2 3 10 5 cm 3 stp gh 2 o carbon 13 c tdic total dissolved inorganic carbon ranging from 15 6 to 5 32 vs vpdb he systematics he isotopes in the range of 0 38 0 99 ra ra air normalized 3 he 4 he ratio and co 2 3 he ratio spanning over four orders of magnitude from morb like values of 2 92 10 9 to crustal type values of 3 02 10 13 coherently indicate the presence of fluids from different crustal sources e g sediments hydrocarbon reservoirs besides minor but detectable contributions of mantle magmatic derived fluids up to 16 45 our investigations show that the wide range of chemical and isotopic composition can be explained in terms of mixings among different gas sources feeding the groundwater and the contemporary occurrence of gas water interactions like degassing and deposition of carbonates affecting the circulating waters after their infiltration

origin of carbon in fumarolic gas from island arcs abstract we have measured 3 he 4 he ratios 13c values and co 2 3 he ratios of fumaroles and hot spring gases in three volcanic areas in japan the 3 he 4 he ratios 13c values and co 2 3 he ratios vary from 02 05 ratm 9 7 to 2 7 and from 7 74 109 to 1 18 1011 respectively based on these data and those in the literature we present the first quantitative estimates of the upper mantle sediment and limestone including slab components in co2 of volcanic and hydrothermal fluids from subduction zones taking compiled c isotopic data of limestone and organic sediment assuming that the co 2 3 he ratio and 13c value of mid ocean ridge basalt morb are representative of the upper mantle component and that later isotopic and elemental fractionations are minimal it is possible to deconvole each fraction of c on the basis of simple mixing equations up to 20 of the carbon in high temperature volcanic gases in subduction zones is derived from a morb type source while the major fraction of the gases is attributable to co2 produced by decarbonation of subducted marine limestone and slab carbonate

fluid geochemistry and geothermometry in the western sector of the sabatini volcanic district and the tolfa mountains central italy abstract a geochemical survey of 197 fluid discharges cold and thermal waters and bubbling pools and 15 gas emissions from the western sector of the sabatini volcanic district and the tolfa mountains latium central italy was carried out in 2007 2008 the chemical and isotopic compositions of the fluid discharges indicate the occurrence of two main sources 1 relatively shallow aquifers with ca na k hco 3 and ca mg hco 3 compositions when trapped in volcanic and sedimentary formations respectively and 2 a deep reservoir which is hosted in the mesozoic carbonate sequence rich in co 2 and having a ca so 4 hco 3 composition dissolution of a co 2 rich gas phase into the shallow aquifers produces high tds and high pco 2 cold waters while oxidation of deep derived h 2 s to so 4 2 generates low ph the 13 c co 2 values for gas emissions from 2 8 to 2 7 vs vpdb suggest that the origin of co 2 associated with the deep fluids is mainly related to thermo metamorphic reactions within the carbonate reservoir although significant mantle contribution may also occur however r r a values 0 37 0 62 indicate that he is mainly produced by a crustal source with a minor component from a crust contaminated mantle on the basis of the 13 c ch 4 and d ch 4 values from 25 7 to 19 5 vs vpdb and from 152 to 93 4 vs vsmow respectively ch 4 production is associated with thermogenic processes possibly related to abiogenic co 2 reduction within the carbonate reservoir the 34 s h 2 s values from 9 3 to 10 4 vs vcdt are consistent with the hypothesis of a sedimentary source of sulfur from thermogenic reduction of triassic sulfates geothermometric evaluations based on chemical equilibria co 2 ch 4 and separately h 2 s suggest that the reservoir equilibrium temperature is up to 300 c the d and 18 o data indicate that water recharging both the shallow and deep aquifers has a meteoric origin fluid geochemistry coupled with gravimetric data and tectonic lineaments supports the idea that significant contributions from a deep seated geothermal brine are present in the stigliano thermal fluid discharges exploration surveys investigated this area during 70 s 90 s for geothermal purposes nevertheless presently the area is still under exploited the presence of thermal waters and anomalous heat flow together with the demographic growth of the last years makes this site a suitable location for direct applications of the geothermal resource

dynamic fluid recycling at laguna caliente poas costa rica before and during the 2006 ongoing phreatic eruption cycle 2005 10

origin of hydrogen nitrogen gas seeps oman six gas samples were collected from five thermal springs in the semail nappe ophiolite and the calcareous calcite and dolomite hajar formation northern oman the3he 4he 4he 20ne 40ar 36ar and38ar 36ar ratios chemical compositions h2 n2 co2 ch4 o2 ar and he and stable isotope compositions dh2 dh2o 13cco2 13cch4 and 15nn2 are reported samples from the ophiolite region are significantly anoxic with major constituents of h2 ch4 and n2 while those from calcite and dolomite regions are ordinary gas seeps consisting of n2 co2 and or o2 the former h2 rich gas is characterized by relatively high3he 4he ratio 0 4 0 8 ratm with low he content 300 ppm slight radiogenic40ar 36ar ratio high n2 ar ratio 77 97 and low 15nn2 value 0 observed dh2 value of 536 in h2 rich gas is distinguished from the literature value of 699 in the ophiolite region giving discrepant isotope formation temperatures

glacio eustatic sea level control on red sea salinity previous studies of the red sea demonstrated that glacial surface and bottom water salinities in the basin were significantly higher than at present the very low abundance of planktonic foraminifera the so called aplanktonic zone during the last glacial indicates that surface water conditions approached or exceeded the tolerance limits of this plankton group1 2 glacial sediments are also characterized by high concentrations of magnesian calcite3 4 dolomite3 inorganically precipitated aragonite4 5 and benthic foraminifera typical of hypersaline environments3 6 additional evidence from oxygen isotope records of planktonic2 7 and benthic foraminifera8 9 as well as pteropods2 demonstrate that glacial interglacial contrasts in the red sea have an amplitude much larger than typically observed in open ocean records here we use both oxygen isotope data and a fractional overmixing model to estimate the impact of the most recent 18 000 yr bp pleistocene glacio eustatic sea level lowering on red sea salinity we estimate that during the last glacial maximum surface salinities in the central red sea were more than 10 0 higher than at present deep water salinities were also higher during the last glaciation and remained unusually high through deglaciation the combination of very high bottom salinities and the onset of pluvial conditions during deglaciation in the red sea region prevented ventilation of red sea bottom waters and resulted in the accumulation of organic rich sediments

geogenic and atmospheric sources for volatile organic compounds in fumarolic emissions from mt etna and vulcano island sicily italy 1 in this paper fluid source s and processes controlling the chemical composition of volatile organic compounds vocs in gas discharges from mt etna and vulcano island sicily italy were investigated the main composition of the etnean and volcano gas emissions is produced by mixing to various degrees of magmatic and hydrothermal components vocs are dominated by alkanes alkenes and aromatics with minor though significant concentrations of o s and cl f substituted compounds the main mechanism for the production of alkanes is likely related to pyrolysis of organic matter bearing sediments that interact with the ascending magmatic fluids alkanes are then converted to alkene and aromatic compounds via catalytic reactions dehydrogenation and dehydroaromatization respectively nevertheless an abiogenic origin for the light hydrocarbons cannot be ruled out oxidative processes of hydrocarbons at relatively high temperatures and oxidizing conditions typical of these volcanic hydrothermal fluids may explain the production of alcohols esters aldehydes as well as o and s bearing heterocycles by comparing the concentrations of hydrochlorofluorocarbons hcfcs in the fumarolic discharges with respect to those of background air it is possible to highlight that they have a geogenic origin likely due to halogenation of both methane and alkenes finally chlorofluorocarbon cfc abundances appear to be consistent with background air although the strong air contamination that affects the mt etna fumaroles may mask a possible geogenic contribution for these compounds on the other hand no cfcs were detected in the vulcano gases which are characterized by low air contribution nevertheless a geogenic source for these compounds cannot be excluded on the basis of the present data

brazilian laterite dynamics using in situ produced 10be abstract concentrations of in situ produced cosmogenic 10 be t 1 2 1 5 myr were measured using accelerator mass spectrometry ams in quartz samples from three brazilian lateritic systems in order to characterize and quantify processes involved in their development results from a bedrock embedded quartz vein outcropping at gentio do ouro lead to a calculated mean erosion rate of 2 5 m myr 1 for a muon participation to the total 10 be production set at 1 5 at itaberaba the 10 be content of the surficial sample yields a mean erosion rate of 9 0 0 5 m myr 1 in addition the systematic increase in 10 be concentrations of stone line quartz with distance from the quartz vein strongly suggests an autochthonous development the data constrain a model of stone line emplacement and imply a rate of lateral displacement on the order of 70 m myr 1 by contrast the constant 10 be concentration measured within the rounded quartz cobbles all along the cuiaba stone line suggests that it most likely results from almost contemporaneous rapid events that occurred at least 500 kyr ago the proposed scenario involves sheet washing at the surface of the lateritic paleolandscape leading to surficial dispersion of allochthonous quartz cobbles immediately followed by colluvial deposition of weathered lateritic material

time averaging taphonomy and their impact on paleocommunity reconstruction death assemblages in texas bays the death assemblages in upper copano bay and upper laguna madre texas were compared with the living communities as sampled over a two year period in order to determine how taphonomy and time averaging affect paleocommunity reconstruction the living and death assemblages were compared using taxonomic composition numerical abundance diversity biomass and trophic and habitat proportions taxonomic composition particularly adult taxonomic composition and the biomass of the death assemblage more accurately reflect the characteristics of the living community than do numerical abundance and other community attributes based upon numerical abundance such as diversity taxonomic composition and biomass are less modified by taphonomy and time averaging because they are temporally more persistent characteristics of the community community and paleocommunity attributes are not equivalent because the paleocommunity is described using time averaged data ecological theory must be supplanted by paleoecological theory that takes into account this temporal component

potential volcanological applications of the doris system a geodetic study of the socorro island mexico coordinate time series summary we analysed doris data from socorro island mexico providing weekly coordinates in itrf2000 from 1900 to 2006 careful analysis of this time series shows horizontal and vertical movements related to recent activity of the mt evermannn volcano a deflation of the volcano between 1993 and 1996 94 mm yr 1 in the n23 w direction directly pointing in the direction of the crater summit is observed we identify also a clear horizontal discontinuity of 81 mm and a significant change in velocity on 2002 october 3 we use a mogi formalism to provide constraints from our geodetic results on the successive locations and size of the depletion and inflation sources our model is consistent with a deflation source for the period 1993 1996 located beneath mt evermannn at a depth of about 6 2 km below sea level however our data constrain only the azimuth and dip angles of the source which could be located elsewhere along the azimuth of the summit depth and volume varying linearly with the distance

fluid geochemistry at vulcano island a change in the volcanic regime or continuous fluctuations in the mixing of different systems increasing fumarolic activity and the rise of outlet fumarole temperatures has occurred at vulcano island southern italy since september 1987 regular sampling and analysis have been conducted on the well known f5 fumarolic and later on f5ht and fa f umaroles on the fossa crater plus other gas emanations from different sites on the island significant chemical and isotopical oscillations have been recorded over the period 1987 1991 variations of water vapor in the fumarolic fluid follow a seasonal pattern and can be related to both external seasonal and magmatic influences but they suggest a control by a source other than magmatic significant variations of h2o and of some species in the anhydrous gas phase h2 co2 so2 n2 and he have been related in the past to chemical or dynamic changes in the feeding system at depth oscillations of the isotopic composition of helium and carbon suggest possible mixing with a nonsurficial source possibly crustal in origin argon and neon isotopic data support this hypothesis several mechanisms are considered for explaining the chemical and isotopic data in relation to the recent increase in activity not all of the chemical and isotopic variations recorded are related to geophysical parameters such as seismicity and deformation the low co content of the f5 fumarolic and the apparent constancy of the 3he 4he ratio do not suggest an increase in the input of deep magmatic fluids the high co content of the high temperature 650 c fa fumarole located at the interior of the crater along with helium and carbon isotopic ratios similar to other fumarolics is probably due to an easier ascent of these fluids to the surface apparent equilibrium temperatures close to the fumarolic outlet temperature indicate isothermal expansion of the gas from a shallow equilibration zone for both high and lower temperature gases in particular the chemical and isotopic features of fluids belonging to both crater and beach fumarole fields are consistent with the existence of two intermediate system independently feeding the two fields high 3he 4he ratios for the beach fluids similar to those of the crater fluids suggest a large magmatic reservoir at depth feeding both the crater and the beach intermediate reservoirs

parent material influence on soil distribution and genesis in a paleudult and kandiudult complex southeastern usa parent materials greatly influence soil development and the distribution of soils on the southeastern us coastal plain we examined the physical chemical and mineralogical properties of 11 pedons in a 1 ha plot on the upper coastal plain of georgia usa uniformity of parent materials was assessed by sand grain size characteristics the soils have sandy epipedons of variable thickness and argillic horizons of variable texture six of the pedons also have kandic horizons they are classified us soil taxonomy in psammentic grossarenic arenic and typic subgroups of paleudults and kandiudults loamy pedons possess argillic horizons with two distinct increases in clay and greater differences between eluvial and illuvial horizons than sandy pedons the upper boundary of the argillic horizon is approximately parallel to the present geomorphic surface suggesting that it is associated with the contemporary surface discontinuities identified by changes in sand grain size ratios and plots of the third skewness and fourth kurtosis moments of sand grain distribution roughly correspond to the bottom of the solum our data suggest that there are both eolian and fluvial components in the solum whereas subjacent horizons are completely derived from fluvial deposits sandier pedons have greater gibbsite kaolinite ratios possibly because greater permeability has enhanced leaching and si loss our data suggest parent materials largely control soil distribution over this plot

the application of quartz grain morphology measurements to studying iron rich duricrusts abstract iron rich duricrust profiles are commonly located on old flat surfaces they promote landscape stability by the protective action of ferricrete providing important records of multiple soil and geomorphic processes as well as paleoclimatic events in the southern serra do espinhaco sse in brazil iron rich duricrust profiles occur on flat to slightly convex hills of quartzite at elevations of mostly 1200 1400 m a s l some of these profiles may be remnants of old paleosurfaces here we describe an image analysis technique to measure morphological attributes of quartz grains in thin sections of iron rich duricrusts we present a way to investigate the genesis of these materials size and shape variations of quartz grains were measured for iron rich duricrust profiles from four different locations gs2 pf1 pf2 and pf3 thin sections of 5 7 5 cm from surface horizons and iron rich duricrusts were studied distinct morphological regions iron concretion and matrix of iron rich duricrusts were separately analyzed to identify variations in regolith morphology a tescan vega3 scanning electron microscope sem was used to produce backscattered electron bse images for regions of sufficient area to enable the use of image analysis software imagej 1 50i bse images provide a clear contrast between quartz grains and iron rich duricrust matrix allowing resolution of quartz grains for specific investigation the size circularity and roundness of many quartz grains were easily determined this procedure enables the quantitative analysis of soil materials allowing comparisons of soils and the testing of hypotheses for soil genesis quartz grains within iron concretions of pf3 had different morphological properties from quartz in the surrounding ferricrete indicating that different processes had occurred during the genesis of the two materials in contrast pf1 which showed no evidence of parent material diversity contained quartz grains that are indicative of a polycyclic character we observed fragments of iron concretions with pores previously occupied by quartz grains indicating that extensive quartz dissolution had occurred during duricrust evolution

size shape and orientation of grains in sands and sandstones image analysis applied to rock thin sections abstract a computer based image analysis system is used to determine the grain size distribution grain shape and grain orientation from rock thin sections a monte carlo simulation allows correction of the grain size distribution for the corpuscle effect grains cut marginally in the thin section plane have smaller apparent diameters thin section derived grain size distributions of modern and ancient samples have been compared with distributions obtained from sieving of the same samples different grain shape parameters have been compared with the wadell formula the grain orientation can be easily and reliably measured in thin sections from different cuts of a sample grain orientation data can help to determine paleocurrent directions

u th he geochronology of goethite and the origin and evolution of cangas abstract u th he geochronology of 147 grains of goethite cements extracted from ferruginous duricrusts cangas developed on banded iron formations from the quadrilatero ferrifero region minas gerais brazil records a history of protracted mineral dissolution reprecipitation that started at ca 48 1 4 8 ma and continues intermittently until the present a large majority of the samples more than 30 are younger than 2 ma revealing active mineral dissolution reprecipitation in the recent past within cangas goethite cements are younger near the surface and become progressively older towards the bottom of the weathering profile indicating that iron is more effectively cycled in the parts of the weathering profile more strongly affected by biogenic activity u th he geochronology of 14 goethite grains from saprolites in the same profiles yield results ranging from 55 3 5 5 to 25 7 2 6 ma for a single weathering profile goethite cements from cangas are invariably younger than goethite grains from the underlying saprolite indicating that the duricrust and the saprolite behave as independent and separate systems responding to different environmental controls thorium shows conservative behaviour during goethite dissolution reprecipitation and it is enriched towards the surface of the weathering profile uranium on the other hand is preferentially leached from the surface into the saprolite or out of the weathering profile recurrent goethite dissolution reprecipitation lends great textural complexities to cangas but it is also responsible for its capacity to reheal when physically disrupted this self healing property accounts for canga s role in armoring banded iron formation landscapes

reduction of co2 during serpentinization of olivine at 300 c and 500 bar co 2 reduction processes occurring during experimental serpentinization of olivine at 300 c and 500 bar confirm that ultramafic rocks can play an important role in the generation of abiogenic hydrocarbon gas data reveal that conversion of fe ii in olivine to fe iii in magnetite during serpentinization leads to production of h 2 and conversion of dissolved co 2 to reduced c species including methane ethane propane and an amorphous carbonaceous phase hydrocarbon gases generated in the process fit a schulz flory distribution consistent with catalysis by mineral reactants or products magnetite is inferred to be the catalyst for methanization during serpentinization because it has been previously shown to accelerate fischer tropsch synthesis of methane in industrial applications involving mixtures of h 2 and co 2 the carbonaceous phase was predominantly aliphatic but had a significant aromatic component although this phase should ultimately be converted to hydrocarbon gases and graphite if full thermodynamic equilibrium were established its formation in these experiments indicates that the pathway for reduction of co 2 during serpentinization processes is complex and involves a series of metastable intermediates

shallow crustal velocities and volcanism suggested from ambient noise studies using a dense broadband seismic network in the tatun volcano group of taiwan abstract the tatun volcano group tvg is situated adjacent to the taipei metropolis and was active predominantly around 0 8 0 2 ma pleistocene various recent lines of evidence suggest that the tvg is a potentially active volcano and that future volcanic eruptions cannot be ruled out geothermal activities are largely constrained to faults but the relationship between volcanism and detailed velocity structures is not well understood we analyzed ambient seismic noise of daily vertical components from 2014 using a dense seismic network of 40 broadband stations we selected a 0 02 grid spacing to construct 2d and 3d shallow crustal phase velocity maps in the 0 5 3 s period band two s wave velocity profiles transect chishingshan mt cs in the shallow 3 km crust are further derived the footwall of the shanchiao fault is dominated by low velocity which may relate to tertiary bedrock buried under andesitic lava flows dozens to hundreds of meters thick the hanging wall of the shanchiao fault is the location of recent major volcanic activities low velocity zones in the southeast of dayoukeng dyk may be interpreted as hydrothermal reservoirs or water saturated tertiary bedrock related to cenozoic structures in the shallow crust high velocities conspicuously dominate the east of the tvg where the earliest stages of volcanism in the tvg are located but where surface hydro geothermal activities were absent in recent times between the shanchiao fault and kanchiao fault high velocities were detected which converge below mt cs and may be related to early stages of magma conduits that gradually consolidated these two faults may play a significant role with the tvg the submarine volcanism adjacent to the keelung coastline also requires further attention

evolution of volcanic gas composition during repeated culmination of volcanic activity at kuchinoerabujima volcano japan abstract chemical and isotopic compositions of low to medium temperature fumarolic gasses were measured at various fumaroles of kuchinoerabujima volcano from 1993 to 2009 by the combination of fumarolic gas sampling and multi gas measurement of volcanic plumes repeated culmination of the volcanic activity was observed as contemporaneous occurrence of seismic swarms summit inflation and demagnetization almost every two years after 1999 fumarolic activity also increased parallel with these activities new fumarolic fields of low temperature fumaroles at boiling point formed at the southern and western rims of the summit crater in 2003 and intense degassing activity started at medium temperature fumaroles inside the summit crater in 2008 the low temperature fumarolic gasses have peculiar composition with high h2 h2o co co2 and so2 h2s ratios typical features of high temperature volcanic gasses but also with low hcl and total s contents typical features of low temperature gasses these features indicate that the gasses are formed by low temperature differentiation of high temperature gasses variation of h and o isotopic ratios of the low temperature gasses indicates that the gasses are formed by isoenthalpic processes of vapor liquid separation at 100 c of a high temperature gas and meteoric water mixture implying that the high temperature gas was injected into a shallow aquifer without cooling temperatures of the high temperature gasses were estimated as 550 700 c based on the equilibrium temperature calculation with considering the low temperature differentiation the medium temperature fumarolic gasses from the summit crater have typical compositions of high temperature volcanic gasses and are estimated as the source gas of the boiling point fumaroles the h2 h2o and co2 st ratios of the low temperature fumaroles increased from 2004 to 2009 which is interpreted to be caused by the evolution of thermal structure of a shallow gas storage region of a few hundred meters deep increase of magmatic gas supply caused enlargement of a high temperature zone of the gas storage region widening the surrounding temperature transit zone with smaller temperature gradient the enlargement of the high temperature zone also reduces the overlying low temperature aquifer which caused the decrease of co2 st ratio by reduction of sulfur removal reaction the enlargement of the high temperature zone resulted in the leakage of the high temperature gasses directly to the surface as the medium temperature gasses from the summit crater

long term monitoring on a closed conduit volcano a 25 year long time series of temperatures recorded at la fossa cone vulcano island italy ranging from 250 c to 520 c abstract the longest record of temperature data from an active volcano in southern italy is presented the dataset comes from continuous monitoring of fumarole temperatures from the la fossa cone of vulcano aeolian islands running from 1991 to 2016 the discussion includes an empirical approach based on a large number of direct measurements at vulcano island geochemical monitoring of the uprising fluids allows detection of the surface effects of perturbation in the state variables of the buried hydrothermal and magmatic systems the presented datasets show that fumaroles changing temperatures which are related to surface heat flow are useful indicators over the past 25 years the combined effects of runoff and chemo physical alterations were negligible on the output temperature of the earliest monitored fumaroles the maximum recorded variation was 298 c measured in the ground very close to the steaming vents at a depth of 0 5 m repetition of output temperature values occurred after 19 years in the same position the time variations suggest a cyclic characteristic although more years are needed to register the complete cyclic modulation a combination of minor cyclical variations has also been registered in the fumarole output the minor cycles appeared in this long series of data after 1995 and they can be interpreted as one of the surface effects of temporary departures from a stationary state assumed for the system feeding the la fossa area in this sector of the mediterranean area the steady state pressure field as well as the steady state temperature gradients can be perturbed either by magmatism or by seismo tectonic processes related to regional dynamics this long term monitoring allowed comparisons of many temperature subsets with other validated geochemical and geophysical data series and highlighted common source mechanisms accounting for endogenous processes changes in the magma source and or seismo tectonic activity have been the primary causes of the time variations the collected data show the effectiveness of the geochemical approach for following the heat flow changes that originated from a deep source in real time even though an estimation of magmatic and or hydrothermal energy release cannot be retrieved by surface temperature monitoring alone

origin of fumarolic fluids from tupungatito volcano central chile interplay between magmatic hydrothermal and shallow meteoric sources tupungatito is a poorly known volcano located about 100 km eastward of santiago chile in the northernmost sector of the south volcanic zone this 5 682 m high volcano shows intense fumarolic activity it hosts three crater lakes within the northwestern portion of the summit area chemical compositions of fumarolic gases and isotopic signatures of noble gases 3he 4he and 40ar 36ar are up to 6 09 ra and 461 respectively and steam 18o and d suggest that they are produced by mixing of fluids from a magmatic source rich in acidic gas compounds so2 hcl and hf and meteoric water the magmatic hydrothermal fluids are affected by steam condensation that controls the outlet fumarolic temperatures 200 c and redox conditions are consistent with those inferred by the presence of the so2 h2s redox pair typical of fluids that have attained equilibrium in magmatic environment a comprehensive conceptual geochemical model describing the circulation pattern of the tupungatito hydrothermal magmatic fluids is proposed it includes fluid source regions and re equilibration processes affecting the different gas species due to changing chemical physical conditions as the magmatic hydrothermal fluids rise up toward the surface

volcano hydrothermal activity detected by precise levelling surveys at the tatun volcano group in northern taiwan during 2006 2013 abstract precise levelling surveys were conducted from 2006 to 2013 on three levelling routes in the tatun volcano group tvg located approximately 15 km northeast of taipei to detect deformation in relation to the volcano hydrothermal activities of the tvg uplift was detected around the most active fumarole tayoukeng fumarole throughout the period 2007 to 2011 the uplift rate throughout the period from march 2009 to march 2011 was reduced in comparison to the rate between 2007 and 2009 following this a dormant state or a small amount of subsidence was detected in the period march 2011 to march 2013 and throughout the period from june 2006 to march 2013 subsidence was centred on an area 0 5 km east of the summit of mt cising the highest peak in the tvg a model of two spherical sources was therefore estimated from the deformation recorded from august 2007 to march 2011 using a genetic algorithm a deflation source was obtained about 0 5 km northeast of mt cising at a depth of 2 km and an inflation source was situated approximately 1 km south of the tayoukeng fumarole at a depth of 0 7 km based on previous seismic and amt studies the estimated sources are interpreted as being hydrothermal reservoirs because almost all the benchmarks around mt cising show subsidence at a constant speed we conclude that the deeper hydrothermal reservoir at a depth of 2 km may have been releasing hydrothermal fluid at a constant rate throughout the period from 2006 to 2013 however it was suggested that in 2011 the shallower hydrothermal reservoir at a depth of 0 7 km changed from an inflation state to a dormant state or small deflation based on temporal vertical changes around tayoukeng fumarole a possible model for the volcano hydrothermal system is therefore proposed it is considered that the hydrothermal fluid may be supplied intermittently from the magma chamber to the deeper hydrothermal reservoir at a depth of 2 km although this type of fluid input event may not have occurred during our research period and that the hydrothermal fluid upwelling between mt cising and tayoukeng fumarole flows transversally into a highly cracked and fluid saturated area that continues to tayoukeng fumarole the existence of a shallower hydrothermal reservoir at a depth of 0 7 km in the highly cracked and fluid saturated area is therefore plausible

partitioning of f between h2o and co2 fluids and topaz rhyolite melt implications for mineralizing magmatic hydrothermal fluids in f rich granitic systems fluid melt distribution coefficients for f have been determined in experiments conducted with peraluminous topaz rhyolite melts and fluids consisting of h2o and h2o co2 at pressures of 0 5 to 5 kbar temperatures of 775 1000 c and concentrations of f in the melt ranging from 0 5 to 6 9 wt the major element f and cl concentrations of the starting material and run product glasses were determined by electron microprobe and the concentration of f in the fluid was calculated by mass balance the h2o concentrations of some run product glasses were determined by ion microprobe sims the solubility of melt in the fluid phase increases with increasing f in the system the solubility of h2o in the melt is independent of the f concentration of the system with up to 6 3 wt f in the melt no evidence of immiscible silica and fluoriderich liquids was detected in the hydrous but water undersaturated starting material glasses 8 5 wt f in melt or in the water saturated run product glasses f concentrates in topaz rhyolite melts relative to coexisting fluids at most conditions studied however df wt f in fluid wt f in melt increases strongly with increasing f in the system maximum values of df in this study are significantly larger than those previously reported in the literature linear extrapolation of the data suggests that df is greater than one for water saturated peraluminous granitic melts containing 8 wt f at 800 c and 2 kbar df increases as temperature and as h2o h2o co2 of the fluid increase for topaz rhyolite melts containing 1 wt f and with h2o rich fluids df is independent of changes in pressure from 2 to 5 kbar at 800 c for melts containing 1 wt f and in equilibrium with co2 bearing fluids the concentrations of f in fluid increases with increasing pressure f and lithophile element enriched granites may evolve to compositions containing extreme concentrations of f during the final stages of crystallization if f in the melt exceeds 8 wt df is greater than one and the associated magmatic hydrothermal fluid contains 4 molal f such f enriched fluids may be important in the mass transport of ore constituents i e f mo w sn li be rb cs u th nb ta and b from the magma

he ar n and c isotope compositions in tatun volcanic group tvg taiwan evidence for an important contribution of pelagic carbonates in the magmatic source abstract the tatun volcanic group tvg northeastern taiwan is considered to be the extension of the ryukyu arc and belongs to the post collisional collapse okinawa trough strong hydrothermal activity is concentrated along the chinshan fault and da you keng dyk represents the main fumarolic area where the most primitive isotopic and chemical composition is observed in this study we present chemical and he ar c and n isotopic compositions of fumaroles bubbling gas and water from hot springs sampled in 2012 and 2013 high 3 he 4 he ratios from dyk fumaroles 6 5 ra show a typical arc like setting whereas other sampling areas show a strong dependence of 3 he 4 he and ch 4 3 he ratios with the distance from the main active hydrothermal area dyk this could mean strong crustal contamination and thermal decomposition of organic matter from local sediments carbon isotope compositions of dyk range from 6 67 to 5 85 and indicate that carbon contribution comes mainly from pelagic carbonates from the slab limestone mantle and sediment contributions are 63 19 and 18 respectively this is consistent with the negative 15 n values 1 4 0 5 observed for dyk implying a strong nitrogen mantle contribution and an absence of contribution from nitrogen pelagic carbonates these results have important consequences related to the ryukyu subducted slab in fact the ryukyu margin presents little in off scraping the sedimentary cover to the subducting plate that does not permit any nitrogen contribution in magma from tvg

origin of nitrogen rich natural gases in the california great valley evidence from helium carbon and nitrogen isotope ratios abstract dry natural gases produced from the sacramento and northern san joaquin basins contain up to 87 nitrogen 15n measurements for gases with n2 8 vary from 0 9 to 3 5 methane 13c values vary from 61 to 15 3 he 4 he ratios indicate the presence of mantle derived helium in addition to radiogenic crustal helium and suggest that the gases may originate from mixing between three principal components a hydrocarbon rich gas with 3 he 4 he 0 1r a derived from the microbial and thermogenic alteration of sedimentary organic matter a hydrocarbonrich gas with 3 he 4 he 2 75r a derived from the localized pyrolysis of sediments by magmatic volatiles and a nitrogenrich gas with 3 he 4 he 1r a the nitrogen rich component is characterized by methane 13c less negative than 25 and n 2 ar ratios as high as 22 000 nitrogen concentrations tend to increase towards the basement along the shallow eastern margin of the valley suggesting that the nitrogen rich component is derived from metasedimentary rocks deep within the crust the coast ranges fraciscan complex which was thrust well beneath the great valley during late mesozoic and early cenozoic subduction appears to be the most likely source

geochemistry of hydrothermal fluids from an intraplate ocean island everman volcano socorro island mexico abstract socorro island mexico still volcanically active is an alkaline and peralkaline volcanic island in the eastern pacific ocean located on a mid ocean ridge spreading center that was abandoned at 3 5 ma gas and water samples collected on the island in 1999 from the dome fumaroles and hot springs of everman volcano have been analyzed for major components h o c s he and ar isotopic composition and noble gas abundances the boiling point temperature steam vents and low salinity thermal springs discharge cl free meteoric water and are typical surface manifestations of a high temperature hydrothermal system high h 2 and ch 4 contents up to 14 and 3 5 vol in dry gas respectively and an enrichment of ch 4 in 13 c 13 c ch 4 18 may suggest that these reduced gases were at least partially produced by the interaction of ultramafic rocks with water inside volcanic edifice due to serpentinization of olivine the 3 he 4 he ratios 6 0 6 6 r a which are lower than the morb values and the high he ne ratios 4000 and he ar ratios up to 4 indicate a contribution of radiogenic he from the oceanic crust or shallow magma chamber like at a low 3 he hot spot the maximum of the 40 ar 36 ar values 311 is close to the maximum value found in the socorro volcanic rocks noble gas abundances are close to values for the partially degassed air saturated water however with some excess ne concentrations an enrichment in 132 xe or depletion in 84 kr of the least air contaminated gas sample he ne 4000 relative to air saturated water can be related to the contribution of noble gases from a non atmospheric source probably oceanic crustal component assimilated in a shallow magma reservoir

an image analysis technique to measure grain size variation in thin sections of soft clastic sediments this paper presents a simple and fast image analysis technique to measure grain size variation in thin sections of soft elastic sediments optical and backscattered electron microscope photographs are digitised from thin sections cut by freeze drying to avoid disturbing the sediments processing of the 256 grey scale images produces binary black and white images where white pixels represent the clay rich sedimentary matrix and black pixels represent elastic grains data measured include grain surface grain perimeter and centre of gravity two indices are defined to quantify grain size d 0 equivalent disk diameter and p phase percentages the technique is applied to silt and clay laminations attributed to the d division of a distal turbidite from lake baikal the data obtained using image analysis are similar to the conventional descriptions of such deposits indices calculated on very small samples e g on a single lamina allow for greater precision in interpretation of sedimentary processes compared to photomicrographs backscattered electron microscope images have better qualities and allow to quantify variations in the grain size along a sediment core the technique produces objective and quantified grain size observations in less time than conventional petrographic methods c 1998 elsevier science b v all rights reserved

submarine eruption near socorro island mexico geochemistry and scanning electron microscopy studies of floating scoria and reticulite abstract products of an underwater eruption near socorro island in the ne pacific were observed directly on january 29 1993 ten days after precursors were first recorded by sofar sound fixing and ranging hydrophones located in hawaii and tahiti eruptive activity was noticed from boats and ships as small steam plumes rising from the sea at an area centered at 18 48 n 111 05 w 2 4 km nw of punta tosca and 4 6 km ssw of cape henslow on socorro island the observed steam was produced by 1 3 m large blocks of hot dark grey highly vesiculated basalt rising buoyantly to the surface from two submarine shallow vents at 210 and 30 m depth tens of blocks accompanied by bubbles could be observed rising to the surface in irregular pulses these scoriaceous blocks remained floating at the surface until they would crack into smaller pieces by thermal contraction emitting hissing noises from vapourizing seawater in contact with the hot interior of the blocks steam jets several metres in height were produced and occasionally blocks were propelled laterally by the steam jet depending on vesicularity and permeability blocks remained floating and drifting with the surface current for 1 15 minutes before sinking back floating rocks covered an area of about 6000 m2 this intermittent activity has been observed ever since and has not stopped as of april 1994 buoyant scoria and reticulite are indicative of volatile mostly co2 supersaturation and exsolution in the magma prior to rapid quenching which inhibits loss of volatiles by bubble escape a high velocity ascent of low viscosity magma in a relatively narrow conduit is also required to prevent substantial gas escape and allow formation of reticulite the buoyant scoria is most probably ejected by intermittent lava fountaining at fixed vents as a result of changes in eruption velocities due to changes in the exsolved gas content of the lava between january and july 1993 floating blocks of scoria and reticulite were collected on several occasions from the surface of the sea for chemical and mineralogical analyses major and minor element analyses including ree as well as electron microprobe analyses of different phases revealed that the composition of the emitted lava has not changed through time blocks of basalt sio2 45 47 are highly vitric and vesicular with tabular anorthite phenocrysts up to 3 mm in length and minor grains of forsteritic olivine ree and trace element composition of these rocks suggest an anomalous mantle source for the erupted alkali basalt lava the ongoing eruption will either continue in a similar fashion as described and eventually cease or built up a mound that reaches the surface and forms an island with accompanying change in eruptive style

quantitative bathymetric models for late quaternary transgressive regressive cycles of the po plain italy abstractin marine settings quantitative bathymetric models can be developed using various water depth proxies including epibiont distribution sedimentologic features and the distribution of benthic taxa in time and space here the late quaternary bathymetric history of the po coastal plain italy has been reconstructed using mollusk samples from a network of 16 cores multiple analytical approaches have been applied in a comparative fashion a direct ordination approach was used to estimate sample bathymetry using weighted averaging of genera with known preferred depth weighted averaging carries an advantage of analytical simplicity and produces direct ordination models expressed in environmentally meaningful units indirect ordination methods based on depth estimates developed using posteriori calibrated ordination strategies correspondence and detrended correspondence analysis calibrated against present day bathymetric data yielded results consistent with weighted averaging regardless of the

magma degassing process during the eruption of mt unzen japan in 1991 to 1995 modeling with the chemical composition of volcanic gas abstract during the dome forming eruption in 1991 to 1995 at mt unzen japan high temperature volcanic gases were sampled from fumaroles located at the western basement of the dacitic lava dome comparing the composition of volcanic gas the volatile in the pre eruptive melt of magma and the groundmass of lava we propose that the volatile in magma was liberated through three different gas separation steps the first gas separation happened at depth deeper than 3 9 km the liberated gas traveled along the conduit then discharged as the observed fumarolic gas the second gas separation took place beneath the lava dome the liberated gas was discharged on the top of lava dome the third gas separation occurred near surface in a so called open system degassing process the large variation in the co2 h2o ratio of fumarolic gas could be explained by the variation of the bubble fraction in the pre eruptive melt of magma chamber before the gas separations the estimated bubble fraction in the melt was less than 1 7 vol such a low fraction of bubbles in the magma chamber of mt unzen would be one of the reasons why the eruption was non explosive the fumarolic gas in the later stage of eruption was enriched in hcl and hf due to the effect of open system degassing of magma although the gas contained co2 and h2s with high concentrations the co2 and h2s would be derived from a vapor phase of hydrothermal system developed around the conduit

resistivity structure and geochemistry of the jigokudani valley hydrothermal system mt tateyama japan abstract this study clarifies the hydrothermal system of jigokudani valley near mt tateyama volcano in japan by using a combination of audio frequency magnetotelluric amt survey and hot spring water analysis in order to assess the potential of future phreatic eruptions in the area repeated phreatic eruptions in the area about 40 000 years ago produced the current valley morphology which is now an active solfatara field dotted with hot springs and fumaroles indicative of a well developed hydrothermal system the three dimensional 3d resistivity structure of the hydrothermal system was modeled by using the results of an amt survey conducted at 25 locations across the valley in 2013 2014 the model suggests the presence of a near surface highly conductive layer of 2 o isotopic ratios all hot spring waters had low ph and could be categorized into three types on the basis of the cl so 4 2 concentration ratio with all falling largely on a mixing line between magmatic fluids and local meteoric water lmw the geochemical analysis suggests that the hydrothermal system includes a two phase zone of vapor liquid a comparison of the resistivity structure and the geochemically inferred structure suggests that a hydrothermal reservoir is present at a depth of approximately 500 m from which hot spring water differentiates into the three observed types the two phase zone appears to be located immediately beneath the cap rock structure these findings suggest that the hydrothermal system of jigokudani valley exhibits a number of factors that could trigger a future phreatic eruption

geochemistry of the volcano hydrothermal system of el chichon volcano chiapas mexico the 1982 eruption of el chichon volcano ejected more than 1 km3 of anhydrite bearing trachyandesite pyroclastic material to form a new 1 km wide and 300 m deep crater and uncovered the upper 500 m of an active volcano hydrothermal system instead of the weak boiling point temperature fumaroles of the former lava dome a vigorously boiling crater spring now discharges 20 kg s of cl rich 15 000 mg kg and sulphur poor 200 mg kg of so4 almost neutral ph up to 6 7 water with an isotopic composition close to that of subduction type magmatic water d 15 18o 6 5 this spring as well as numerous cl free boiling springs discharging a mixture of meteoric water with fumarolic condensates feed the crater lake which compared with values in 1983 is now much more diluted 3000 mg kg of cl vs 24 030 mg kg less acidic ph 2 6 vs 0 56 and contains much lower amounts of s 200 mg kg of so4 vs 3550 mg kg with 34s 0 5 4 2 17 in 1983 agua caliente thermal waters on the southeast slope of the volcano have an outflow rate of approximately 100 kg s of 71 c na ca cl water and are five times more concentrated than before the eruption b r molina unpublished data relative n2 ar and he gas concentrations suggest extensional tectonics for the el chichon volcanic centre the 3he 4he and 4he 20ne ratios in gases from the crater fumaroles 7 3ra 2560 and agua caliente hot springs 5 3ra 44 indicate a strong magmatic contribution however relative concentrations of reactive species are typical of equilibrium in a two phase boiling aquifer sulphur and c isotopic data indicate highly reducing conditions within the system probably associated with the presence of buried vegetation resulting from the 1982 eruption all cl rich waters at el chichon have a common source this water has the appearence of a partially matured magmatic fluid condensed magmatic vapour neutralized by interaction with fresh volcaniclastic deposits and depleted in s due to anhydrite precipitation shallow ground waters emerging around the volcano from the thick cover of fresh pumice deposits red waters are ca so4 rich and have a negative oxygen isotopic shift probably due to ongoing formation of clay at low temperatures

fluid immiscibility in volcanic environments volatile components enter the atmosphere oceans and other surface waters through pre syn and post eruptive volcanic processes that involve a variety of fluids aluminosilicate poor fluids include aqueous or carbonic to sulfide sulfate chloride fluoride carbonate and phosphate rich compositions in volcanic environments but other more complex combinations of these constituents may be involved giggenbach 1977 roedder 1984 1992 lowenstern 1995 other rare gases and dissolved constituents e g h2 n2 he ar h3bo3 hg ch4 and other hydrocarbon compounds metals and metalloids are also present but in general they are not sufficiently concentrated to form their own phases or control bulk fluid composition and volcanic processes as a result of their diverse compositions volcanic fluids ranging from vapor to liquid exhibit widely different densities and show strong distinctions in heat capacity dielectric behavior viscosity and other chemical and physical characteristics geiger et al 2006a the density of a saline liquid in the system nacl h2o at 50 mpa and 800 c for example is more than 7 times that of the coexisting aqueous vapor e g 0 2 gm cm3 henley and mcnabb 1978 multiple fluids move mix and or unmix in magma chambers and volcanic conduits in the root zone of fumaroles and in the convective hydrothermal systems that are ubiquitous to volcanic environments hydrothermal systems are typically centered on magmatic intrusions and may include crater lakes at the top of eruptive conduits hydrothermal processes involving two or more fluid phases operate through a variety of geologically relevant shallow crustal pressure temperature composition conditions volcanic fluids occur at supersolidus to subsolidus conditions meaning that the dense aluminosilicate melt that is common to volcanism may or may not be present this chapter addresses the evidence for and occurrence of two or more low density aluminosilicate poor fluids

seismicity characteristics of a potentially active quaternary volcano the tatun volcano group northern taiwan the tatun volcano group tvg is located at the northern tip of taiwan near the capital taipei and close to two nuclear power plants because of lack of any activity in historical times it has been classified as an extinct volcano even though more recent studies suggestthattvgmighthavebeenactiveduringthelast20ka inmay2003aseismicmonitoringprojectatthetvgareawasinitiated by deploying eight three component seismic stations some of them equipped with both short period and broadband sensors during the 18 months observation period local seismicity mainly consisted of high frequency earthquakes either occurring as isolated events or as a continuous sequence in the form of spasmodic bursts mixed and low frequency events were also present during the same period eventhoughtheyoccurredonlyrarely arrivaltimesfromeventswithclearp s wavephaseswereinvertedinordertoobtaina minimum 1dvelocity modelwithstation corrections probabilistic nonlinear earthquakelocationswere calculated for allthese events using the newly derived velocity model most high frequency seismicity appeared to be concentrated near the areas of hydrothermal activity forming tight clusters at depths shallower than 4 km relative locations calculated using the double difference method and utilising catalogue and cross correlation differential traveltimes showed insignificant differences when compared to the nonlinear probabilistic locations in general seismicity in the tvg area seems to be primarily driven by circulation of hydrothermal fluids as indicated by the occurrence of spasmodic bursts mixed low frequency events and a b value 1 17 0 1 higher than in any other part of taiwan these observations that are similar to those reported in other dormant quaternary volcanoes indicate that a magma chamber may still exist beneath tvg and that a future eruption or period of unrest should not be considered unlikely

magmatic fluids of tatun volcanic group taiwan abstract two distinctive magmatic fluids were recognized in the tatun volcanic group tvg taiwan one is a relatively reduced fluid represented by the fumarolic gases at hsiao you ken hyk geothermal field another is an oxidized fluid containing high concentrations of hcl represented by the fumarolic gases at da you ken dyk an intermediate gas was recognized at gung tze ping gtp and she hung ping shp the fumarolic gases at hyk and gtp possess the features of so called primary steam generated on mixing of magmatic gas and meteoric groundwater the fumarolic gases at dyk are a simple mixture between magmatic gas and water vapor of meteoric origin the co 2 h 2 o molar ratio of the magmatic component in the fumarolic gases at dyk was estimated to be 0 018 meanwhile it was estimated to be 0 027 for the fumarolic gases at hyk and gtp suggesting the magma beneath dyk is depleted in volatiles relative to the magma beneath hyk and gtp the estimated co 2 h 2 o ratio for the magmatic component is comparable to that of some active volcanoes in japan suggesting the enrichment of volatiles in the magmas beneath tvg

fluid geochemistry of hydrothermal systems in the arica parinacota tarapaca and antofagasta regions northern chile we investigate the chemical and isotopic composition of water and gas thermal discharges from six hydrothermal systems in the tarapaca and antofagasta regions northern chile surire puchuldiza tuja pampa lirima pampa apacheta el tatio and torta de tocorpuri to determine the chemical physical conditions at the fluid source the chemical facies of the thermal discharges vary from na cl el tatio puchuldiza tuja and part of surire where so42 rich waters also occur to na ca2 cl so42 pampa lirima ca2 so42 hco3 torta de tocorpuri and ca2 so42 pampa apacheta the gas seeps are characterized by the dominance of co2 h2s and ch4 with n2 ar ratios that occasionally are up to 450 significant amounts of so2 and hcl are present at pampa apacheta water and gas geothermometry suggests that el tatio and puchuldiza tuja fluid reservoirs have relatively high reservoir equilibrium temperature up to 270 c gases from pampa apacheta apparently equilibrated at unusually high temperature for hydrothermal fluids up to 350 c being likely related to an active magmatic system as testified by the presence of highly acidic gas compounds such as so2 and hcl on the contrary low equilibrium temperatures were calculated for the surire fluids 200 c suggesting interactions of deep originated fluids with meteoric water at shallow depth shallow low temperature aquifers mask any signal of deep fluids in the pampa lirima and torta de tocorcupi thermal discharges despite the variations in temperatures he isotopic compositions and redox conditions of the fluid reservoirs consistently indicate a significant contribution from magmatic degassing although geophysical studies are necessary to better constrain the geothermal potential of northern chile the geothermometric estimations carried out in the present study indicate that el tatio pampa apacheta surire and puchuldiza tuja can be regarded as the most promising areas and deserve more detailed geological investigations

the mathematician paleoplate the pacific seafloor is littered with small fragments of lithosphere captured from adjacent plates by past plate boundary reorganizations one of the clearest examples of such a reorganization is documented in the mathematician seamounts region where a distinctive geomorphology and well developed magnetic anomalies are present this reorganization involved a short lived microplate between the failing mathematician ridge and a new propagating spreading center the east pacific rise it produced a transfer of a fragment of lithosphere from the farallon to the pacific plate and also created a number of landforms and magnetic patterns within and on the margins of the captured fragment these make up the mathematician paleoplate in many cases two sides of a microplate are active spreading ridges a microplate evolves into a paleoplate when dual spreading ceases and full spreading resumes at the prevailing spreading ridge we define a paleoplate as the area of the seafloor from the axis of a failed rift to the boundary of resumed full spreading it includes a fragment of captured lithosphere and the lithosphere slowly accreted to it during the period of dual spreading prior to complete abandonment of the failed rift the mathematician paleoplate has the following boundaries and components from west to east the axis of the mathematician failed rift the fragment of captured farallon plate a complex rift initiation site at the moctezuma trough a zone of slow spreading and an as yet ill defined eastern boundary where dual spreading stopped and full spreading resumed the northern boundary of the paleoplate is the rivera fracture zone its southeastern boundary a now inactive transform fault the west o gorman fracture zone in this case as well as in other more poorly documented ones relict landforms and magnetic patterns are carried on the aging lithosphere away from the spreading ridge recording a former geometry

origins of methane discharging from volcanic hydrothermal geothermal and cold emissions in italy abstract we have addressed the origins of methane in fumarolic thermal and cold emissions discharging from a diversity of geological settings spread all over the italian peninsula and at panarea and pantelleria islands fluid discharges from the main geothermal systems of the peri tyrrhenian area including mt amiata larderello latera and manziana show 13c ch4 and d ch4 values 28 v pdb and 160 v smow respectively and c1 c2 concentration ratios 1000 these patterns suggest that ch4 discharged from these systems is primarily generated by abiogenic reduction of co2 and or co methane seems to have at least partially a different origin than the higher hydrocarbons that might be entirely related to the thermal decomposition of organic matter or alternatively to methane polymerization fumaroles from the volcanic systems of solfatara vesuvio panarea and pantelleria have c1 c2 concentration ratios in a wide range from 17 to 4300 but 13c ch4 and d ch4 values 21 v pdb and 120 v smow respectively such isotopic values are very similar to those reported for ch4 discharging from ultramafic hydrothermal systems in agreement with recent evidence provided for solfatara and pantelleria we therefore infer that the ch4 in the volcanic fumaroles is mainly abiogenic too the 13c ch4 from 21 6 to 36 9 v pdb and d ch4 from 113 to 164 v smow values as well as the c1 c2 concentration ratios from 19 to 2240 in the co2 rich fluid discharges located between the geothermal volcanic systems and the apennine sedimentary chain tend to decrease eastwards as the temperatures of the fluid reservoirs progressively diminish suggesting that the ch4 production is mainly related to thermogenic processes according to this general trend the ch4 dominated fluids from mud volcanoes located eastwards of the co2 rich emissions are fed by an almost pure thermogenic source the easternmost fluid discharges from the po valley and the adriatic coast where organic matter evolves at relatively shallow depths in the presence of a low geothermal gradient record the lowest 13c ch4 and d ch4 values i e as low as 69 v pdb and