natural tracers for identifying the origin of the thermal fluids emerging along the aegean volcanic arc greece evidence of arc type magmatic water atmw participation abstract the aegean volcanic arc is the result of a lithosphere subduction process during the quaternary time starting from the soussaki area from west to east the arc proceeds through the islands of egina methana milos santorini the columbus bank kos and nisyros volcano tectonic activities are still pronounced at santorini and nisyros in form of seismic activity craters of hydrothermal explosions hot fumaroles and thermal springs a significant number of cold water springs emerge in the vicinity of hot waters on these islands chemical and isotopic analyses were applied on water and fumaroles samples collected in different areas of the volcanic arc in order to attempt the assessment of these fluids stable isotopes of water and carbon have been used to evaluate the origin of cold and thermal water and co 2 chemical solute concentrations and isotopic contents of waters show that the fluids emerging in egina soussaki methana and kos areas represent geothermal systems in their waning stage while the fluids from milos santorini and nisyros proceed from active geothermal systems the 2 h 18 o cl relationships suggest that the parent hydrothermal liquids of nisyros and milos are produced through mixing of seawater and arc type magmatic water atmw with negligible to nil contribution of local ground waters and with very high participation of the magmatic component which is close to 70 in both sites a very high magmatic contribution to the deep geothermal system could occur at santorini as well perhaps with a percentage similar to nisyros and milos but it cannot be calculated because of steam condensation heavily affecting the fumarolic fluids of nea kameni before the surface discharge the parent hydrothermal liquid at methana originates through mixing of local groundwaters seawater and atmw with a magmatic participation close to 19 all in all the contribution of atmw is higher in the central eastern part of the aegean volcanic arc than in the western sector this difference which is spotted in the variable isotopic composition of the sampled fluids from west to east along the arc is probably due to several causes including the tectonic regime the depth of the deep reservoir below sea level the age of volcanic activity and in general the geomorphologic state of each island

the ordovician chondrite from brunflo central sweden ii secondary minerals abstract brunflo is an altered h4 h5 stony meteorite that fell in calcareous mud on the continental shelf of the iapetus ocean about 460 470 ma b p except for relicts of chromite all the original minerals are replaced by calcite barite an illite type mineral and some minor to rare phases carbonate fluorapatite quartz titanium dioxide chalcopyrite three different members of the cobaltite gersdorffite series including a phase with a composition close to coni ass 2 rammelsbergite safflorite nickeline maucherite orcelite native nickel anomalous bornite galena pyrite sphalerite and two cu phases cu1 66s and cu4fes4 the secondary mineralogy varies rapidly at a mm scale indicating non equilibrium conditions during the alteration by the time the mud was cemented to limestone most of the original minerals might have been transformed to secondary phases during subsequent stages of diagenesis the temperature remained within the 0 50 c range for millions of years probably explaining the formation of the phases of unusual compositions a temperature rise to 200 300 c chiefly due to regional heating during the caledonian orogeny in silurian devonian time might have modified the secondary mineralogy

methana the westernmost active volcanic system of the south aegean arc greece insight from fluids geochemistry abstract an extensive geochemical survey of the fluids released by the volcanic geothermal system of methana was undertaken gases were characterized based on the chemical and isotopic helium he and carbon c analysis of 27 samples carbon dioxide soil gas concentration and fluxes were measured at 179 sampling sites throughout the peninsula forty samples of thermal and cold groundwaters were also sampled and analysed to characterize the geochemistry of the aquifers gases of hydrothermal origin gave a preliminary geothermometric estimate of about 210 c the he isotope composition indicated mantle contributions of up to 40 and the c isotope composition of co 2 indicated that it predominantly 90 originated from limestone decomposition the groundwater composition was suggestive of mixing between meteoric and hydrothermally modified sea water endmembers and water rock interaction processes limited to simple rock dissolution driven by an increased endogenous co 2 content all of the thermal manifestations and anomalous degassing areas although of limited extent were spatially correlated with the main active tectonic system of the area the total co 2 output of the volcanic system has been preliminary estimated to be less than 0 05 kg s 1 although this value is very low compared to those of other volcanic systems anomalous co 2 degassing at methana which is currently restricted to limited areas and at present is the only volcanic risk of the peninsula is a potential gas hazard that warrants further assessment in future studies

application of stochastic simulation to co2 flux from soil mapping and quantification of gas release 1 conditional sequential gaussian simulations sgs have been applied for the first time to the study of soil diffuse degassing from different volcanic and nonvolcanic systems the application regards five data sets of soil co2 fluxes measured with the accumulation chamber methodology at the volcanic areas of solfatara of pozzuoli italy vesuvio cone italy nisyros greece and horseshoe lake california and at the nonvolcanic degassing area of poggio dell olivo italy the sgs algorithm was used to generate 100 realizations of co2 flux for each area probabilistic summaries of these simulations together with the information given by probability plots were used 1 to draw maps of the probability that co2 fluxes exceed thresholds specific for a background flux i e to define the probable extension of the degassing structures 2 to calculate the total co2 output and 3 to quantify the uncertainty of the estimation the results show that the sgs is a suitable tool to model soil diffuse degassing producing realistic images of the distribution of the co2 fluxes that honor the histogram and variogram of the original data moreover the relation between the sample design and the uncertainty of estimation was investigated leading to an empirical relation between uncertainty and the sampling density that can be useful for the planning of future co2 flux surveys

volcanology and petrology of volcanic products from the island of milos and neighbouring islets abstract new geochronological and volcanological data from volcanics of the island group of milos south aegean active volcanic arc allow four main cycles of volcanic activity to be distinguished ranging in age between 3 5 and 0 1 m y b p the oldest volcanic activity consists almost totally of pyroclastics and submarine products followed by subaerial ones the eruptive centers migrated in time and concentrated during the most recent volcanic phase in the central part of milos and on the island of antimilos the oldest products are dominated by andesites and dacites while the most recent ones mainly consist of rhyolites the volcanic evolution and the geochemical characters of the erupted products suggest that the feeding system of the oldest volcanism was located in the deep continental crust where contamination and fractional crystallization jointly occurred the younger cycle of volcanic activity was fed from small and relatively shallow magma chambers where contamination processes played a minor role these magma bodies are considered to responsible for the shallow thermal anomaly giving rise to the high enthalpy field on milos

shear velocity structure in the aegean area obtained by inversion of rayleigh waves summary the purpose of this work is to derive a 3 d tomographic image of the shear wave velocity structure of the crust uppermost mantle in the aegean area using the group velocities of rayleigh wave fundamental mode the database consists of 185 regional earthquakes recorded at broad band stations that were installed for a period of 6 month in the aegean area within the framework of a large scale experiment in a previous work karagianni et al 2002 an averaged group velocity has been determined using the method of frequency time analysis ftan for each epicentre station ray path and the data were used in order to determine the local group velocities for different periods over the area covered by the seismic ray paths taking into account additional resolution results obtained for the local group velocities a grid of 0 5 was adopted for the aegean area and a local dispersion curve was defined for each gridpoint more than 80 local dispersion curves were finally inverted using a non linear inversion approach deriving the corresponding 1 d shear velocity models the interpolation of these models resulted in a 3 d s wave tomographic image of the crust and uppermost mantle in the broader aegean area as expected as a result of the complex tectonic setting of the aegean area strong lateral variations of the s wave velocities of the crust and uppermost mantle of the studied area are found in the southern aegean sea as well as in a large part of the central aegean sea a thin crust of approximately 20 22 km is observed whereas the remaining aegean sea area exhibits a crustal thickness less than 28 30 km on the contrary a crustal thickness of 40 46 km is observed in western greece along the hellenides mountain range whereas in the eastern continental greece the crust has a typical thickness of approximately 30 34 km for shallow depths 10 km low s wave velocities are observed under the sedimentary basins of the north aegean sea the gulf of thermaikos axios basin and western greece at depths ranging from 10 to 20 km low s wave velocities are mainly found in western greece under peloponnesus as well as in rhodes this low velocity zone seems to extend along the hellenic arc and can be correlated to the hellenides mountain range and the alpine orogenesis in agreement with previous p wave tomographic results in the southern aegean sea very low s wave velocities 3 6 4 0 km s 1 are observed at depths of approximately 30 40 km just below the moho discontinuity while in the rest of the inner aegean sea and continental greece the uppermost mantle is characterized by velocities around 4 3 4 4 km s 1 this low velocity zone in the southern aegean sea can be associated with the high temperatures and the presence of significant percentage partial melt in the mantle wedge of the southern aegean subduction zone in agreement with previous studies

co2 degassing along the san andreas fault parkfield california the fluxes concentrations and carbon isotopic compositions of soil co2 were measured along the parkfield segment of the san andreas fault saf single or double peak co2 flux anomalies 18 g m 2 d 1 were observed along 12 of 16 fault crossing transects at five sites flux anomalies did not coincide with concentration anomalies flux anomalies paralleled the fault trace suggesting zones of high diffusivity permeability one flux anomaly may have been accentuated by a 0 3 mm creep event however values of 13c 23 7 to 21 6 and 14c 110 5 to 111 9 pmc for soil gas co2 are characteristic of co2 of biogenic origin the co2 flux anomalies are therefore consistent with fault related biogenic gas flow and do not yield evidence for degassing of deeply derived co2

total co2 output from vulcano island aeolian islands italy 1 total co2 output from fumaroles soil gas bubbling gas discharges and water dissolved gases discharged from the island was estimated for vulcano island italy the co2 emission from fumaroles from the la fossa summit crater was estimated from the so2 crater output while co2 discharged through diffuse soil emission was quantified on the basis of 730 measurements of co2 fluxes from the soil of the island performed by using the accumulation chamber method the results indicate an overall output of 500 t day 1 of co2 from the island the main contribution to the total co2 output comes from the summit area of the la fossa cone 453 t day 1 with 362 t day 1 from crater fumaroles and 91 t day 1 from crater soil degassing the release of co2 from peripheral areas is 20 t day 1 by soil degassing palizzi and istmo areas mainly an amount comparable to both the contribution of water dissolved co2 6 t day 1 as well as to seawater bubbling co2 4 t day 1 measured in the istmo area presented data september 2007 refer to a period of moderate solphataric activity when the fumaroles temperature were 450 c and gas water molar ratio of fumaroles was up to 0 16 the calculated total co2emission allows the estimation of the mass release and related thermal energy from the volcanic hydrothermal system

recent activity of nisyros volcano greece inferred from structural geochemical and seismological data this study summarizes the results of structural geochemical and seismological surveys carried out at nisyros volcano aegean sea greece during 1999 2001 field mapping and mesostructural measurements at the summit caldera lakki plain indicate that faults follow two main strikes ne sw and n s the n s striking fault depicts extensional features accommodating the left lateral component of motion of the ne sw striking main faults the ne sw preferred strike of the lakki faults and of the mineral filled veins as well as the distribution and ne sw elongation of the hydrothermal craters indicate that tectonics plays a major role in controlling the fluid pathway in the nisyros caldera the same ne sw trend is depicted by co2 anomalies revealed through detailed soil co2 flux surveys thus indicating a structural control on the pattern of the hydrothermal degassing degassing processes account for a thermal energy release of about 43 mw most of which occurs at lofos dome an area that was affected by hydrothermal eruptions in historical times the seismic study was conducted in june 2001 using a deployment specifically aimed at detecting signals of magmatic hydrothermal origin our instruments recorded local and regional earthquakes a few local long period events lp and bursts of monochromatic tremor local earthquake activity is concentrated beneath the caldera at depths generally shallower than 6 km plane wave decomposition of tremor signal indicates a shallow 200 m source located in the eastern part of the caldera conversely lp events depict a source located beneath the central part of the caldera in the area of lofos dome at depths in the 1 2 km range in agreement with geochemical and structural measurements these data suggest that both the deeper and shallower part of the hydrothermal system are subjected to instability in the fluid flow regimes probably consequent to transient pressurization of the reservoir these instabilities may be related to input of hot fluids from the deeper magmatic system as suggested by the variations in geochemical parameters observed after the 1997 1999 unrest episode the significance of seismological and geochemical indicators as precursors of hydrothermal explosive activity at nisyros is discussed

comparative soil co2 flux measurements and geostatistical estimation methods on masaya volcano nicaragua we present a comparative study of soil co2 flux f rm co 2 measured by five groups groups 1 5 at the iavcei ccvg eighth workshop on volcanic gases on masaya volcano nicaragua groups 1 5 measured f rm co 2 using the accumulation chamber method at 5 m spacing within a 900 m2 grid during a morning am period these measurements were repeated by groups 1 3 during an afternoon pm period measured f rm co 2 ranged from 218 to 14 719 g m 2 day 1 the variability of the five measurements made at each grid point ranged from 5 to 167 however the arithmetic means of fluxes measured over the entire grid and associated total co2 emission rate estimates varied between groups by only 22 all three groups that made pm measurements reported an 8 19 increase in total emissions over the am results based on a comparison of measurements made during am and pm times we argue that this change is due in large part to natural temporal variability of gas flow rather than to measurement error in order to estimate the mean and associated co2 emission rate of one data set and to map the spatial f rm co 2 distribution we compared six geostatistical methods arithmetic and minimum variance unbiased estimator means of uninterpolated data and arithmetic means of data interpolated by the multiquadric radial basis function ordinary kriging multi gaussian kriging and sequential gaussian simulation methods while the total co2 emission rates estimated using the different techniques only varied by 4 4 the f rm co 2 maps showed important differences we suggest that the sequential gaussian simulation method yields the most realistic representation of the spatial distribution of f rm co 2 but a variety of geostatistical methods are appropriate to estimate the total co2 emission rate from a study area which is a primary goal in volcano monitoring research

the effect of changing regional tectonics on an arc volcano methana greece abstract the peninsula of methana has the longest recorded volcanic history of any volcanic centre in the south aegean arc regional fault patterns in the arc changed during the pliocene quaternary with e w striking listric faulting increasingly important through the quaternary as recorded in well dated sedimentary basins this study investigates how the geochemistry and eruptive style of volcanic products is influenced by regional tectonics the volcanic stratigraphy of methana was refined using radiometric dating lithogeochemistry and field observations that included recording deformational structures and enclave abundance small n s striking pliocene domes and a central volcano of uncertain type phase a were eroded to produce a widespread volcaniclastic apron phase b in the early quaternary an explosive central volcano with flank eruptions of andesite developed phase c dacite domes and small andesitic stratovolcanoes formed throughout the mid and late quaternary phases d h basaltic andesite and andesite of phase c are the least evolved rocks characterised by high tio 2 rocks that have experienced important assimilation and fractional crystallisation in the crust have a high abundance of enclaves th u and alkalies na k ni and cr are abundant in phase a andesites due to crystallisation and entrainment of olivine and pyroxene whereas phase h andesites have the highest relative abundance of ba rb and sr from crystallisation and entrainment of hornblende and biotite pliocene domes of phase a were emplaced on n s striking listric faults during regional e w extension onset of ne sw faulting arguably crustal scale and strike slip in character led to the eruption of the least evolved rocks of phase c thereafter e w striking faults controlled the location of volcanism volcanism in phases f and g was particularly voluminous and was synchronous with the onset of steep normal faulting in the gulf of corinth 150 km west of methana these steep faults cross cut older lower angle listric faults it is times of changes in regional fault patterns as in phases c f and g that have the greatest influence on the eruptive style and abundance of volcanic products

is there a link between faulting and magmatism in the south central aegean sea a distinct spatial relationship between surface faulting magmatic intrusions and volcanic activity exists in the aegean continental crust in this paper we provide detailed structural observations from key onshore areas as well as compilations of lineament maps and earthquake locations with focal plane solutions from offshore areas to support such a relationship although pluton emplacement was associated with low angle extensional detachments the nne to ne trending strike slip faults also played an important role in localizing the middle miocene plutonism providing ready pathways to deeper magma batches and controlling the late stage emplacement and deformation of granites in the upper crust additionally the linear arrangements of volcanic centres from the quaternary volcanoes along the active south aegean volcanic arc are controlled primarily by ne trending faults and secondarily by nw trending faults these volcanic features are located at several extensional settings which are associated with the main ne trending faults such as i in the extensional steps or relay zones between strike slip and oblique normal fault segments ii at the overlap zones between oblique normal faults associated with an extensional strike slip duplex and iii at the tip zone of a ne trending divergent dextral strike slip zone the ne trend of volcano tectonic features such as volcanic cone alignments concentration of eruptive centres hydrothermal activity and fractures indicates the significant role of tectonics in controlling fluid and magma pathways in the aegean upper crust furthermore microseismicity and focal mechanisms of earthquakes in the area confirm the activity and present kinematics of these ne trending faults

origin of methane and light hydrocarbons in natural fluid emissions a key study from greece abstract greece a country characterised by intense seismic and volcanic activity has a complex geodynamic and geological setting that favours the occurrence of many gas manifestations in this study we address the origin of ch 4 and light hydrocarbons in cold and thermal emissions discharging along the hellenic territory also we investigate their possible relationship with the main geochemical composition of the gases and the different geological settings of the sampling sites for this purpose we collected 101 new samples that were analysed for their chemical o 2 n 2 ch 4 co 2 he ne ar h 2 h 2 s and c 2 c 6 hydrocarbons and isotopic r r a 13 c co 2 13 c ch 4 and 2 h ch 4 composition results show that ch 4 presents a wide range of concentrations from 13 c ch 4 from 79 8 to 45 0 vs v pdb 2 h ch 4 from 311 to 301 vs v smow greece was subdivided in four geologic units external eh and internal ih hellenides hellenic hinterland hh and active volcanic arc va and a decreasing ch 4 concentration from eh to hh was recognized whereas ch 4 showed intermediate concentrations in va the ch 4 c 2 h 6 c 3 h 8 ratios from 1 5 to 93 200 coupled with ch 4 isotopic features suggest that the light alkanes derive from different primary sources and are affected by secondary processes an almost exclusive biotic mainly microbial origin of ch 4 can be attributed to eh gases cold gases at ih have mainly a thermogenic origin although some gases connected to continental serpentinization may have an abiogenic origin methane in gases bubbling in thermal waters of ih hh and va and fumarolic gases of the va seem to have an abiogenic origin although their chemical and isotopic characteristics may have been produced by secondary oxidation of thermogenic ch 4 a process that in some of the sampled gases causes extremely positive isotopic values 13 c ch 4 up to 45 0 vs v pdb and 2 h ch 4 up to 301 vs v smow

the geochemistry of fluids from an active shallow submarine hydrothermal system milos island hellenic volcanic arc abstract geothermal activity in the aegean island of milos greece associated with island arc volcanism is abundant both on and off shore hydrothermal fluids venting from several sites mainly shallow submarine up to 10 m but also just above seawater level in one locality were sampled over four summer field seasons some of the discharging fluids are associated with the formation of hydrothermal edifices overall the main characteristics of the hydrothermal fluids are low ph and variable chlorinity the lowest recorded ph was 1 7 and chlorinity ranged from 0 1 to 2 5 times that of seawater the highest fluid temperatures recorded on site were 115 c two main types of fluids were identified low chlorinity fluids containing low concentrations of alkalis potassium lithium sodium and calcium and high concentrations of silica and sulphate and high chlorinity fluids containing high concentrations of alkalis and calcium and lower concentrations of silica and sulphate the type locality of the high chlorinity fluids is shallow submarine in palaeochori near the east end of the south coast of the island whereas the type locality of the low chlorinity fluids is a cave to the west of palaeochori the two fluid types are therefore often referred to as submarine and cave fluids respectively both fluid types had low magnesium and high metal concentrations but were otherwise consistently different from each other the low chlorinity fluids had the highest cobalt nickel aluminium iron and chromium up to 1 6 m 3 6 m 1586 m 936 m and 3 0 m respectively and the high chlorinity fluids had the highest zinc cadmium manganese and lead up to 4 1 m 1 0 m 230 m and 32 m respectively geochemical modelling suggests that metals in the former are likely to have been transported as sulphate species or free ions and in the latter as chloride species or free ions isotopic values for both water types range between d 12 to 33 and 18 o 1 2 to 4 6 the range of fluid compositions and isotopic contents indicates a complex history of evolution for the system both types of fluids appear to be derived from seawater and thus are likely to represent end members of a single fluid phase that underwent phase separation at depth

a geochemical traverse along the sperchios basin e evoikos gulf graben central greece origin and evolution of the emitted fluids the studied area is a 130 km long fast spreading graben in central greece its complex geodynamical setting includes both the presence of a subduction slab at depth responsible for the recent quaternary volcanic activity in the area and the western termination of a tectonic lineament of regional importance the north anatolian fault a high geothermal gradient is made evident by the presence of many thermal springs with temperatures from 19 to 82 c that discharge along the normal faults bordering the graben in the period 2004 2012 58 gas and 69 water samples were collected and their chemical and isotopic analysis revealed a wide range of compositions two main groups of thermal waters can be distinguished on the basis of their chemical composition the first represented by dilute waters e c 0 6 ms cm of the westernmost sites is characterised by the presence of ch4 rich and mixed n2 ch4 gases the second displays higher salinities e c from 12 to 56 ms cm due to mixing with a modified marine component reservoir temperatures of 150 160 c were estimated with cationic geothermometers at the easternmost sites along the graben from west to east the gas composition changes from ch4 to co2 dominated through mixed n2 ch4 and n2 co2 compositions while at the same time the he isotopic composition goes from typical crustal values 0 1 r ra up to 0 87 r ra showing in the easternmost sites a small 3 11 but significant mantle input the 13c values of the co2 rich samples suggest a mixed origin mantle and marine carbonates

middle ordovician chondrite in fossiliferous limestone from brunflo central sweden the few discoveries of fossil meteorites have been attributed1 to the ignorance about the appearance of meteorites among palaeontologists and other geologists who examine limestone quarries coal mines and other excavations in sedimentary rocks we now report the first find of a fossil stony meteorite in ordovician limestone the meteorite is a chondrite possibly an h chondrite and its terrestrial age is 463 myr the fine structural details of the chondrules are often extremely well preserved but the chemical composition and the mineralogy have changed dramatically chromite being the only primary mineral preserved the present major minerals are calcite barite a cr v phengite and a cobaltite group mineral

methanotrophy in geothermal soils an overlooked process the example of nisyros island greece abstract a multidisciplinary field campaign was carried out at nisyros island greece hydrothermal gases were sampled and analysed and ch4 and co2 fluxes from the soils were measured with the accumulation chamber method the sampling area lakki plain covers an area of about 0 08 km2 and includes the main fumarolic areas of kaminakia stefanos ramos lofos and phlegeton flux values measured at 130 sites range from 3 4 to 1420 mg m 2 d 1 for ch4 and from 0 1 to 383 g m 2 d 1 for co2 the fumarolic areas show very different ch4 degassing patterns kaminakia showing the highest ch4 output values about 0 8 t a 1 from an area of about 30 000 m2 and phlegeton the lowest about 0 01 t a 1 from an area of about 2500 m2 the total output from the entire geothermal system of nisyros should not exceed 2 t a 1 previous indirect estimates of the ch4 output at nisyros based on soil co2 output and ch4 co2 ratios in fumarolic gases were more than one order of magnitude higher the present work further underscores the utmost importance of direct ch4 flux data because indirect methods totally disregard methanotrophic activity within the soil ten soil samples were collected for ch4 consumption experiments and for metagenomic analysis seven of the soil samples showed small but significant ch4 consumption up to 39 7 ng g 1 h 1 and were positive for the methanotrophs specific gene pmoa confirming microbial ch4 oxidation in the soil notwithstanding the harsh environmental conditions high temperature and h2s concentrations and low ph

hydrothermal gases offshore milos island greece hydrothermal fluids emerge from the seafloor of paleohori bay on milos the gases in these fluids contain mostly co2 but ch4 concentrations up to 2 are present the stable carbon isotopic composition of the co2 near 0 indicates an inorganic carbon source dissociation of underlying marine carbonates the carbon and hydrogen isotopes of most ch4 samples are enriched in the heavy species delta 13c 9 4 to 17 8 per mille sign delta d 102 to 189 per mille sign which is believed to be characteristic for an abiogenic production of ch4 by co2 reduction fischer tropsch reactions depletions in the deuterium content of three ch4 samples to 377 are probably caused by unknown subsurface rock alteration processes secondary hydrogen isotope exchange processes between methane hydrogen and water are most likely responsible for calculated unrealistic methane formation temperatures we show that excess helium slightly enriched in 3he is present in the hydrothermal fluids emerging the seafloor of paleohori bay when the isotopic ratio of the excess component is calculated a 3he 4heexcess of 3 6 10 6 is obtained this indicates that the excess component consists of about one third of mantle helium and two thirds of radiogenic helium we infer that the mantle derived component has been strongly diluted by radiogenic helium during the ascent of the fluids to the surface

geographical distribution of 3he 4he ratios in japan implications for arc tectonics and incipient magmatism the 3he 4he and 4he 20ne ratios of 115 natural gas samples including various types of gases from volcanoes hot springs mineral springs water wells petroleum fields and natural gas fields were measured using a mass spectrometer the observed 3he 4he and 4he 20ne ratios range from 7 47 10 8 to 9 65 10 6 and from 0 26 to 1100 respectively the 3he 4he ratios reflect well the geotectonic structure of the japanese islands in northeastern ne japan there is a clear geographical difference in the 3he 4he ratios between the frontal arc forearc and volcanic arc back arc regions lower ratios were found in the trench side region and higher ratios in the back arc side this result suggests that the mantle derived helium in the volcanic arc region is associated with the diapiric uprise of a magma lower 3he 4he ratios in the frontal arc region may be due to radiogenic he produced by radioactive decay of u and th in the crustal and sedimentary rocks in southwestern sw japan there is no clear geographical contrast in the 3he 4he ratios some samples in the frontal arc region show quite high 3he 4he ratios the tendency of the 3he 4he ratios agrees with the distribution of terrestrial heat flow data and reflects geotectonic structures different from ne japan the high 3he 4he ratios observed in the frontal arc region in sw japan may be indicative of renewed or incipient magmatism due to a descending young and warm slab

stable isotope geochemistry of coals humic kerogens and related natural gases isotope systematics are well defined for conventional sapropelic type i ii kerogens and their associated bacterial and thermogenic natural gas products these geochemical tools are used to estimate source type maturity and depositional environment and as a correlation technique in many cases the natural gas signatures in near surface samples and drill cuttings can be used to classify or predict a deeper lying source rock or reservoir corresponding interpretative schemes for coals type iii kerogens and their associated hydrocarbons are progressing quickly the shift in attention to humic sources is driven primarily by depletion of conventional oil and gas resources and the economic and societal requirements of coal and coal bed methane carbon hydrogen and nitrogen stable isotope variations can be large between different coals and humic kerogens these differences can often be recognized in their bulk 13corg dorg and 15norg values isotope signatures of coals can be diagnostic of several factors including deposit age type geographic location maturity and generation history however these characteristic isotopic variations are substantially better defined by the c h and n isotope ratios of the separate maceral groups such as vitrinite exinite and inertinite this new application of stable isotopes at the maceral and compound levels have great potential to improve the interpretative precision over conventional whole coal or bulk techniques hydrocarbon gases including coal gases derived from coals and humic kerogens can be distinguished from type i ii sources based on their molecular rations i e c1 c2 c3 and by comparing their stable isotope compositions especially 13cch4 and dch4 the 13cc2h6 can also be valuable but ethane is generally present in small amount 1 vol and requires

carbonate compositions in cm and ci chondrites and implications for aqueous alteration abstract carbonate minerals in fourteen cm chondrites and two ci chondrites have been analyzed by electron microprobe to provide a better understanding of the aqueous processes that affected carbonaceous chondrite parent bodies calcites in cm chondrites and dolomites and magnesites in ci chondrites display the compositions expected of stable phases formed at low temperatures dolomites in cm chondrites identified here for the first time in five members of the group have small amounts of excess ca which may reflect metastable growth the distribution of fe between dolomite and coexisting serpentine differs in the two chondrite groups if the distributions reflect an approach to chemical equilibrium then the difference implies higher alteration temperatures for the ci group than the cm group in agreement with the results of previously published oxygen isotope thermometry and mineral solubility modeling of the alteration process dolomite fe contents are relatively uniform in the two chondrite groups dolomite mn contents by contrast vary widely the variations may reflect transport controlled coprecipitation of mn resulting from a heterogeneous distribution of the element in the anhydrous precursor material if this interpretation is correct then the altering fluids were essentially immobile while hydration reactions proceeded on the meteorite parent bodies the near closed system character of the alteration process long known from bulk chemical analyses of the meteorites is a direct consequence of the limited mobility of dissolved species

multiple origins of methane in the earth methane occurrences in the earth s crust are predominantly of biogenic origin i e their ultimate source is biologically formed organic matter methane can also form through inorganic reactions and is consequently termed abiogenic biogenic methanes can either form through bacterial or thermogenic processes bacterial processes follow a co2 reduction and or fermentation pathway the fermentation processes are quantitatively more important in recent fresh sediments and swamps methane formed by co2 reduction however is most common in older sediments and commercial gasfields temperature organic substrate and age may be the major factors controlling the relative importance of the two pathways stable isotope concentrations in thermogenic methanes seem to be controlled by the extent of conversion of organic matter the timing of gas expulsion and trapping the different character of methane in individual sedimentary basins may be a result of the geologic history geothermal methanes are most likely derived from pyrolysis of organic matter abiogenic methane occurs in hydrothermal vents and ophiolite complexes inorganic reactions either surficial or deep seated are the likely source of such methanes a uniform mantle origin of methane is not supported by the observed isotope variations in naturally occurring methanes

mineralogy of meteorite groups approximately 275 mineral species have been identified in meteorites reflecting diverse redox environments and in some cases unusual nebular formation conditions anhydrous ordinary carbonaceous and r chondrites contain major olivine pyroxene and plagioclase major opaque phases include metallic fe ni troilite and chromite primitive achondrites are mineralogically similar the highly reduced enstatite chondrites and achondrites contain major enstatite plagioclase free silica and kamacite as well as nitrides a silicide and ca mg mn na cr k and ti rich sulfides aqueously altered carbonaceous chondrites contain major amounts of hydrous phyllosilicates complex organic compounds magnetite various sulfates and sulfides and carbonates in addition to kamacite and taenite iron meteorites contain carbides elemental c nitrides phosphates phosphides chromite and sulfides silicate inclusions in iab iiicd and iie iron meteorites consist of mafic silicates plagioclase and various sulfides oxides and phosphates eucrites howardites and diogenites have basaltic to orthopyroxenitic compositions and consist of major pyroxene and calcic plagioclase and several accessory oxides ureilites are made up mainly of calcic chromian olivine and low ca clinopyroxene embedded in a carbonaceous matrix accessory phases include the c polymorphs graphite diamond lonsdaleite and chaoite as well as metallic fe ni troilite and halides angrites are achondrites rich in fassaitic pyroxene i e al ti diopside minor olivine with included magnesian kirschsteinite is also present martian meteorites comprise basalts lherzolites a dunite and an orthopyroxenite major phases include various pyroxenes and olivine minor to accessory phases include various sulfides magnetite chromite and ca phosphates lunar meteorites comprise mare basalts with major augite and calcic plagioclase and anorthositic breccias with major calcic plagioclase several meteoritic phases were formed by shock metamorphism martensite 2 fe ni has a distorted body centered cubic structure and formed by a shear transformation from taenite during shock reheating and rapid cooling the c polymorphs diamond lonsdaleite and chaoite formed by shock from graphite suessite formed in the north haig ureilite by reduction of fe and si possibly from olivine via reaction with carbonaceous matrix material ringwoodite the spinel form of mg fe 2sio4 and majorite a polymorph of mg fe sio3 with the garnet structure formed inside shock veins in highly shocked ordinary chondrites secondary minerals in meteorite finds that formed during terrestrial weathering include oxides and hydroxides formed directly from metallic fe ni by oxidation phosphates formed by the alteration of schreibersite and sulfates formed by alteration of troilite

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

convective hydrothermal c02 emission from high heat flow regions abstract in addition to volatiles released from volcanoes the flux of co2 to the atmosphere from other sources e g metamorphism and subsurface magmatism represents an important aspect of the global carbon cycle we have obtained a direct estimate of the present day atmospheric co2 flux from convective hydrothermal systems within subaerial seismically active high heat flow regions geothermal systems of the salton trough california u s a and the taupo volcanic zone new zealand provide benchmarks for quantifying convective hydrothermal co2 fluxes from such regions co2 fluxes from the salton trough 109 mol yr 1 and the taupo volcanic zone 8 109 mol yr 1 were computed using data on convective heat flow and the temperatures and co2 concentrations of reservoir fluids the similarity in specific co2 flux 106 mol km 2 yr 1 from these two disparate geologic tectonic settings implies that this flux may be used as a baseline to compute convective hydrothermal co2 emission from other areas of high heat flow if this specific flux is integrated over high heat flow areas of the circum pacific and tethyan belts the total global co2 flux could equal or exceed 1012 mol yr 1 adding this flux to a present day volcanic co2 flux of 4 1012 mol yr 1 the total present day earth degassing flux could balance the amount of co2 consumed by chemical weathering 7 1012 mol yr 1

geochemical characteristics of soil radon and carbon dioxide within the dead sea fault and karasu fault in the amik basin hatay turkey abstract the study area is close to the boundary of three tectonic plates anatolian arabian and african plates and is characterized by important tectonic lineaments which consist mainly of the dead sea fault dsf the karasu fault and the east anatolian fault eaf systems to understand the origin of soil gas emanation and its relationships with the tectonics of the amik basin hatay a detailed soil gas sampling was systematically performed together with co2 flux measurements 220 soil gas samples were analyzed for rn and co2 concentrations the distribution of soil rn kbq m3 co2 concentration ppm and co2 flux g m2 day in the area appears as a point source spot and or diffuses halo anomalies along the buried faults fractures due to crustal leaks the results revealed that rn and co2 concentrations in the soil gas show anomalous values at the specific positions in the amik basin the trace of these anomalous values is coincident with the n s trending dsf co2 is believed to act as a carrier for rn gas based on the rn and co2 concentrations of soil gases at least three gas components are required to explain the observed variations in addition to the atmospheric component two other gas sources can be recognized one is the deep crust component which exhibits high rn and co2 concentrations and is considered the best indicator for the surface location of fault fracture zones in the region the other component is a shallower gas source with high rn concentration and low co2 concentration moreover he isotopic compositions of representative samples vary from 0 94 to 0 99 ra illustrating that most samples have a soil air component and may have mixed with some crustal component without significant input of the mantle component based on the repeated measurements at a few sites soil gas concentrations at the same site were observed to be higher in 2014 than in 2013 which may be associated with the activity of the dsf in 2013 2014 this suggests that soil gas variations at fault zone are closely related to the local crustal stress and hence are suitable for monitoring fault activities

gas geochemistry and co2 output estimation at the island of milos greece abstract twenty gas samples have been collected from the natural gas manifestations of milos island the majority of which is found underwater along its coast furthermore three anomalous degassing fumarolic areas kalamos paleochori and adamas have been recognized on land almost all the gases are co2 dominated with co2 ranging from 88 to 99 vol for the samples taken underwater while the on land manifestations show a wider range 15 98 due to air contamination methane reaches up to 1 0 vol h2 up to 3 2 vol and h2s up to 3 5 vol indicating a hydrothermal origin of the gases the isotope composition of he points out to mantle contributions up to 45 while the c isotope composition of co2 from 1 9 to 1 3 vs v pdb with most of the values around 0 5 suggests a prevailing limestone origin isotope composition of ch4 ranging from 18 4 to 5 0 vs v pdb for c and from 295 to 7 vs v smow for h points to a geothermal origin with sometimes evident secondary oxidation processes additionally co2 flux measurements showed high values in the three fumarolic areas up to 1100 1500 and 8000 g m2 d at kalamos paleochori and adamas respectively with the highest co2 flux values up to about 23 000 g m2 d being measured in the sea at kanavas with a floating chamber the south western part of the island was covered with a lower density prospection revealing only few anomalous co2 flux values up to 650 g m2 d the total output of the island 30 5 t d is typical of quiescent closed conduit volcanoes and comparable to the other volcanic geothermal systems of the south aegean active volcanic arc nisyros kos nea kameni methana and sousaki

facies architecture and late pliocene pleistocene evolution of a felsic volcanic island milos greece the volcanic island of milos greece comprises an upper pliocene pleistocene thick up to 700 m compositionally and texturally diverse succession of calc alkaline volcanic and sedimentary rocks that record a transition from a relatively shallow but dominantly below wave base submarine setting to a subaerial one the volcanic activity began at 2 66 0 07 ma and has been more or less continuous since then subaerial emergence probably occurred at 1 44 0 08 ma in response to a combination of volcanic constructional processes and fault controlled volcano tectonic uplift the architecture of the dominantly felsic intermediate volcanic succession reflects contrasts in eruption style proximity to source depositional environment and emplacement processes the juxtaposition of submarine and subaerial facies indicates that for part of the volcanic history below wave base to above wave base and shoaling to subaerial depositional environments coexisted in most areas the volcanic facies architecture comprises interfingering proximal near vent medial and distal facies associations related to five main volcano types 1 submarine felsic cryptodome pumice cone volcanoes 2 submarine dacitic and andesitic lava domes 3 submarine to subaerial scoria cones 4 submarine to subaerial dacitic and andesitic lava domes and 5 subaerial lava pumice cone volcanoes the volcanic facies are interbedded with a sedimentary facies association comprising sandstone and or fossiliferous mudstone mainly derived from erosion of pre existing volcanic deposits the main facies associations are interpreted to have conformable disconformable and interfingering contacts and there are no mappable angular unconformities or disconformities within the volcanic succession

arctic ocean heat impact on regional ice decay a suggested positive feedback abstractbroad long living ice free areas in midwinter northeast of svalbard between 2011 and 2014 are investigated the formation of these persistent and reemerging anomalies is linked hypothetically with the increased seasonality of arctic sea ice cover enabling an enhanced influence of oceanic heat on sea ice and in particular heat transported by atlantic water the memory of ice depleted conditions in summer is transferred to the fall season through excess heat content in the upper mixed layer which in turn transfers to midwinter via thinner and younger ice this thinner ice is more fragile and mobile thus facilitating the formation of polynyas and leads when openings in ice cover form along the atlantic water pathway weak density stratification at the mixed layer base supports the development of thermohaline convection which further entrains warm and salty water from deeper layers convection induced upward heat flux from the atlantic layer retards ice formation either keeping ice thick

co2 release to the atmosphere from thermal springs of sperchios basin and northern euboea greece the contribution of hidden degassing abstract greece is a region characterised by intense geodynamic activity that favours the circulation of hydrothermal fluids in the crust transporting volatiles from either the deep crust or the mantle to the surface elevated heat flow values are detectable at sperchios basin and north euboea central greece two areas defined by a system of deeply rooted extensional faults and quaternary volcanic activity this setting contributed to the formation of numerous hydrothermal systems which are mostly expressed as co2 rich thermal springs with intense bubbling the co2 output from six bubbling pools has been determined by flux measurements with the use of the floating chamber method the highest bubbling co2 output has been found at thermopyles and psoroneria 0 6 and 0 84 t d respectively where the outgoing channels have an elevated flow 250 l s of gas charged water 15 mmol l of co2 although no bubbling is noticed along the stream the co2 content decreases by an order of magnitude after few hundreds of metres indicating an intense degassing from the water taking into account the water flow and the amount of co2 lost to the atmosphere the co2 output of the outgoing channels is quantified in 12 5 t d for thermopyles and 9 23 t d for psoroneria output estimation has also been made for the other springs of the area the diffuse co2 release from the outgoing channels has always been higher respect to that of the visible bubbling suggesting that most of the degassing is hidden furthermore the loss of co2 from the water has determined a shift in dissolved carbonate species as demonstrated by the ph increase along the channel that led eventually to an oversaturation in carbonate minerals and therefore travertine deposition the total co2 output to the atmosphere of the study area is estimated at 27 t d with the major contribution deriving from the degassing along the outflow channels of the thermal springs such output is comparable to that of the single active volcanic systems along the south aegean active volcanic arc and highlights the importance of hidden degassing along co2 oversaturated streams

impact melt products of chondritic material a large variety of objects in chondritic meteorites formed as a result of impact melting shock veins metal troilite mixtures metal and sulfide nodules melt pockets vugs agglutinates glassy and crystalline spherules and numerous types of melt rock clasts the type of object produced in an impact event is related to the interaction of the shock waves with the particular target rock impact melting has also affected large portions of several chondrite breccias many of these contain vugs and patches of silicate glass some workers have suggested that various iron meteorites including groups iab iiicd and iie as well as several ungrouped irons were formed from individual impact melt pools in chondritic regoliths the eagle station trio pallasites and several ungrouped meteorites bencubbin weatherford enon acapulco and allan hills a77081 may have formed from impact melted chondritic material it is also possible that the parent magmas of ureilites were derived from impact melted metal rich carbonaceous chondrite material

multiple origins of methane at the lost city hydrothermal field abstract the high concentrations of methane in the vent fluids of the lost city hydrothermal field represent the sum of abiotic and biological sources and sinks stable isotopes of carbon are of limited value in discriminating between the various sources of methane because the isotope effects associated with the multiple processes forming and consuming methane are each poorly constrained and the products of these processes are pooled furthermore reservoir effects complicate interpretation the near quantitative reduction of inorganic carbon to methane under highly reducing conditions limits the isotope effects associated with methanogenesis however the carbon isotope compositions of lipids derived from anaerobic methanotrophs suggest that more than one isotopically distinct pool of methane exists at lost city in this analysis we integrate multiple lines of evidence to constrain the relative contribution of various processes at lost city the processes that we consider here include i fischer tropsch type ftt abiotic synthesis of methane and other hydrocarbons ii the sabatier process for the abiotic synthesis of methane alone iii biological methane production by methanosarcinales and iv biological methane consumption by anaerobic and aerobic methanotrophs this analysis suggests that abiotic processes particularly the sabatier reaction are likely to be the dominant source of methane at lost city biological methane is present in the vent fluids but does not compose a high fraction of the total methane pool these observations imply that ultramafic systems could have supplied abundant reduced carbon to the early earth even without biological catalysis

global positioning system constraints on plate kinematics and dynamics in the eastern mediterranean and caucasus we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1997 at 189 sites extending east west from the caucasus mountains to the adriatic sea and north south from the southern edge of the eurasian plate to the northern edge of the african plate sites on the northern arabian platform move 18 2 mm yr at n25 5 w relative to eurasia less than the nuvel 1a circuit closure rate 25 1 mm yr at n21 7 w preliminary motion estimates 1994 1997 for stations located in egypt on the northeastern part of africa show northward motion at 5 6 2 mm yr also slower than nuvel ia estimates 10 1 mm yr at n2 4 e eastern turkey is characterized by distributed deformation while central turkey is characterized by coherent plate motion internal deformation of 2 mm yr involving westward displacement and counterclockwise rotation of the anatolian plate the anatolian plate is de coupled from eurasia along the right lateral strike slip north anatolian fault naf we derive a best fitting euler vector for anatolia eurasia motion of 30 7 0 8 n 32 6 0 4 e 1 2 0 1 myr the euler vector gives an upper bound for naf slip rate of 24 1 mm yr we determine a preliminary gps arabia anatolia euler vector of 32 9 1 2 n 40 3 1 1 e 0 8 0 2 myr and an upper bound on left lateral slip on the east anatolian fault eaf of 9 1 mm yr the central and southern aegean is characterized by coherent motion internal deformation of 2 mm yr toward the sw at 30 1 mm yr relative to eurasia stations in the se aegean deviate significantly from the overall motion of the southern aegean showing increasing velocities toward the trench and reaching 10 1 mm yr relative to the southern aegean as a whole

variation in noble gas isotopic composition of gas samples from the aegean arc greece abstract in contrast to most other arcs with oceanic plate subduction the aegean arc is characterized by continent continent subduction noble gas abundances and isotopic compositions of 45 gas samples have been determined from 6 volcanoes along the arc 2 islands in the back arc region and 7 sites in the surrounding areas the 3he 4he ratios of the samples ranged from 0 027ra to 6 2ra ra denotes the atmospheric 3he 4he ratio of 1 4 10 6 demonstrating that even the maximum 3he 4he ratio in the region is significantly lower than the maximum ratios of most oceanic subduction systems which are equal to the morb value of 8 1 ra regional variations in the 3he 4he ratio were observed both along and across the arc the maximum 3he 4he ratio was obtained from nisyros volcano located in the eastern end of the arc and the ratio decreased westward possibly reflecting the difference in potential degree of crustal assimilation or the present magmatic activity in each volcano across the volcanic arc the 3he 4he ratio decreased with an increasing distance from the arc front reaching a low ratio of 0 063ra in macedonia which suggested a major contribution of radiogenic helium derived from the continental crust at nisyros a temporal increase in 3he 4he ratio due to ascending subsurface magma was observed after the seismic crisis of 1995 1998 and mantle neon was possibly detected the maximum 3he 4he ratio 6 2ra in the aegean region which is significantly lower than the morb value is not probably due to crustal assimilation at shallow depth or addition of slab derived helium to morb like mantle wedge but inherent characteristics of the subcontinental lithospheric mantle sclm beneath the aegean arc

estimation of the co2 flux from furnas volcanic lake sao miguel azores abstract a study on diffuse co 2 degassing was undertaken at furnas lake sao miguel island azores in order to estimate the total diffuse co 2 output and identify anomalous degassing areas over the lake furnas lake is located in furnas volcano the easternmost of the three active central volcanoes of the sao miguel island the lake has an area of 1 87 km 2 and a maximum length and width equal to 2025 and 1600 m respectively the maximum depth of the water column is 15 m and the estimated water storage is 14 10 6 m 3 lake water temperature is cold with temperature values between 13 c and 15 c in the winter period and 18 9 c to 19 3 c in early autumn and the variation along the water column suggests a monomictic character the major ion relative composition is in decreasing order na k ca 2 mg 2 for cations and hco 3 cl so 4 2 for anions and conductivity and ph measurements respectively in the range of 152 to 165 s cm 1 and 5 3 to 8 7 suggests that furnas has neutral diluted waters and can be classified as a non active lake diffuse co 2 flux measurements were made using the accumulation chamber method with a total of 1537 and 2577 measurements performed in two different sampling campaigns the total amount of diffuse co 2 emitted to the atmosphere was estimated between 28 and 321 t km 2 d 1 respectively in the second and first sampling campaigns corresponding to 52 and 600 t d 1 the main anomalous degassing area identified over the furnas lake during both surveys is probably associated to a wnw ese trending tectonic structure other secondary areas are also suggested to be tectonically influenced identified anomalous areas showed similarities to the ones observed during previous soil co 2 degassing studies

soil co2 emissions at furnas volcano sao miguel island azores archipelago volcano monitoring perspectives geomorphologic studies and land use planning application accepted for publication in journal of geophysical research copyright 2010 american geophysical union