retrograde phases of former bridgmanite inclusions in superdeep diamonds abstract mg fe sio3 bridgmanite is the dominant phase in the lower mantle however no naturally occurring samples had ever been found in terrestrial samples as it undergoes retrograde transformation to a pyroxene type structure to identify retrograde phases of former bridgmanite single phase and composite inclusions of mg fe sio3 in a series of superdeep diamonds have been examined with electron microscopy electron microprobe raman spectroscopy and x ray diffraction techniques our study revealed that mg fe sio3 inclusions are represented by orthopyroxene orthopyroxenes in single phase and composite inclusions inherit initial chemical composition of bridgmanites including a high al and low ni contents in composite inclusions they coexist with jeffbenite ex tapp and olivine the bulk compositions of these composite inclusions are rich in al ti and fe which are similar but not fully resembling al rich bridgmanite produced in experiments on the morb composition the retrograde origin of composite inclusions due to decomposition of al rich bridgmanite may be doubtful because each of observed minerals may represent coexisting hp phases i e bridgmanite or ringwoodite

inclusions of nanocrystalline hydrous aluminium silicate phase egg in superdeep diamonds from juina mato grosso state brazil abstract inclusions in alluvial diamond from juina mato grosso brazil have been investigated by tem methods electron diffraction hrtem aem haadf eels and raman spectroscopy the inclusion paragenesis of juina diamonds is dominated by ultrahigh pressure superdeep phases one of these diamonds sample 1 1 4 contains several micrometer sized approximately 200 m by 50 70 m inclusions which have been studied tem foils prepared applying focused ion beam fib technique revealed that these inclusions consist of a porous nanocrystalline groundmass which is composed of nanometre sized crystals of a hydrous aluminium silicate phase with al si approximately 1 1 and chemical composition of phase egg alsio 3 oh a minor volume fraction of nanocrystalline stishovite and pore space which was originally filled with a fluid or gas the nanocrystalline hydrous aluminium silicate phase is idiomorphic randomly oriented approximately 20 30 nm in size predominantly with tetragonal crystal structure a 0 0 743 nm c 0 0 706 nm the monoclinic structure of synthetic phase egg determined at ambient conditions m w schmidt l w finger r j ross r e dinnebier synthesis crystal structure and phase relations of alsio 3 oh a high pressure hydrous phase american mineralogist 83 1998 881 888 is only occasionally observed the fluid filling in the porosity has been released into the vacuum of the fib during tem specimen preparation quench products of the fluid containing minor concentrations of f p s cl k ca and ba were detected at the walls of the pores in addition phase egg is identified by raman spectroscopy within a second sample rs 43a from the same location the presence of phase egg in the inclusions in diamond may suggest that crustal material has been subducted to a depth of the lower transition zone although metastable growth of nanocrystalline high pressure phases or extension of their respective stability fields to lower pressure can not ruled out completely

chemical and isotopical characterisation of fluid manifestations of ischia island italy abstract between 1994 and 1995 gas samples from fumaroles and thermal waters were collected on ischia island the chemical composition of the shallow and deep natural hydrothermal fluids discharged is related to the main hydrological and lithological characteristics of the rock formations present in the reservoir a biphase reservoir liquid gas is identified where the dominant liquid has a temperature of about 280 c on the basis of 13ctdc values it was possible to hypothesize a deep source characterised by carbon isotopic values varying from 0 to 3 these values are noticeably more positive with respect to those attributed to magmatic co2 13 c co 2 ranging from 5 to 8 thus suggesting a magmatic source modified by crustal contamination this hypothesis is supported by the carbon isotopic composition of co2 in sampled gases which varied from 0 to 5 the inferred isotopic value of carbon of magmatic co2 would then be about 2 the observed differences in c isotopic composition between fumarolic and magmatic gases would be caused by kinetic and or equilibrium fractionation processes these processes would cause a fractionation of 13c of deep co2 towards more negative values down to 5 actually co2 removal or addition processes caused by the interaction between deep gases and shallow hydrothermal waters are likely to be responsible for the different chemical and isotopic compositions of gaseous emissions for these reasons and on the basis of the homogeneity of geothermometric values the existence of a single large reservoir that feeds all of the fluids discharged at ischia island can be hypothesised based on acquired data a new geochemical model of the geothermal system of ischia island is proposed

genesis of fumarolic emissions as inferred by isotope mass balances co2 and water at vulcano island italy we have developed a quantitative model of co2 and h2o isotopic mixing between magmatic and hydrothermal gases for the fumarolic emissions of the la fossa crater vulcano island italy on the basis of isotope balance equations the model takes into account the isotope equilibrium between h2o and co2 and extends the recent model of chemical and energy two end member mixing by nuccio et al 1999 as a result the h2o and co2 content and the d 18o and 13c isotope compositions for both magmatic and hydrothermal end members have been assessed low contributions of meteoric steam added at a shallow depth have been also recognized and quantified in the fumaroles throughout the period from 1988 to 1998 nonequilibrium oxygen isotope exchange also seems to be occurring between ascending gases and wall rocks along some fumarolic conduits the 13cco2 of the magmatic gases varies around 3 to 1 vs peedee belemnite pdb following a perfect synchronism with the variations of the co2 concentration in the magmatic gases this suggests a process of isotope fractionation because of vapor exsolution caused by magma depressurization the hydrogen isotopes in the magmatic gases 1 to vs standard mean ocean water smow as well as the above 13cco2 value are coherent with a convergent tectonic setting of magma generation where the local mantle is widely contaminated by fluids released from the subducted slab magma contamination in the crust probably amplifies this effect the computed isotope composition of carbon and hydrogen in the hydrothermal vapors has been used to calculate the d and 13c of the entire hydrothermal system including mixed h2o co2 vapor liquid water and dissolved carbon we have computed values of about 10 vs smow for water and 2 to 6 5 vs pdb for co2 on these grounds we think that mediterranean marine water dh2o 10 feeds the hydrothermal system it infiltrates at depth throughout the local rocks reaching oxygen isotope equilibrium at high temperatures interaction processes between magmatic gases and the evolving seawater also seem to occur causing the dissolution of isotopically fractionated aqueous co2 and providing the source for hydrothermal carbon these results have important implications concerning fluid circulation beneath vulcano and address the more convenient routine of geochemical surveillance

chemical and isotopic composition of waters and dissolved gases in some thermal springs of sicily and adjacent volcanic islands italy hydrochemical major and some minor constituents stable isotope open image in new window and open image in new window 13ctdic total dissolved inorganic carbon and dissolved gas composition have been determined on 33 thermal discharges located throughout sicily italy and its adjacent islands on the basis of major ion contents four main water types have been distinguished 1 a na cl type 2 a ca mg na so4 cl type 3 a ca mg hco3 type and 4 a na hco3 type water most waters are meteoric in origin or resulting from mixing between meteoric water and heavy isotope end members in some samples 18o values reflect the effects of equilibrium processes between thermal waters and rocks positive 18o shift or thermal waters and co2 negative 18o shift dissolved gas composition indicates the occurrence of gas water interaction processes in thermal aquifers n2 o2 ratios higher than air saturated water asw suggest the presence of geochemical processes responsible for dissolved oxygen consumption high co2 contents more than 3000 cc litre stp dissolved in the thermal waters indicate the presence of an external source of carbon dioxide rich gas tdic content and 13ctdic show very large ranges from 4 6 to 145 3 mmol kg and from 10 0 and 2 8 respectively calculated values indicate the significant contribution from a deep source of carbon dioxide inorganic in origin interaction with mediterranean magmatic co2 characterized by heavier carbon isotope ratios open image in new window value from 3 to 0 vs v pdb capasso et al 1997 giammanco et al 1998 inguaggiato et al 2000 with respect to morb value and or input of co2 derived from thermal decomposition of marine carbonates have been inferred

two billion years of evolution enclosed in hydrothermal rutile recycling of the sao francisco craton crust and constraints on gold remobilisation processes abstract the quadrilatero ferrifero in the sao francisco craton brazil is known for its world class gold deposits hosted by the rio das velhas greenstone belt rdv as in other greenstone belts gold is also concentrated in late archean early paleoproterozoic supracrustal units in this case within the moeda formation this unit has been compared to the witwatersrand basin where there has been a long term debate over the nature of the gold and whether it is detrital placer hydrothermal or hybrid modified placer presently links between gold in the moeda formation and rdv are tenuous to enlighten this area of ambiguity a new approach using chemical isotopic and mineral inclusion data from detrital rutile found in the gold bearing horizons of the moeda formation is presented grain textures and mineral inclusions have contributed to establishing a primary hydrothermal origin for the rutile related to as fe cu sb pb w rich mineralising fluids fe nb and v indicate that the likely source of the gold related rutiles is the archean banded iron formations within the rdv where most of the lode gold occurs average nb ta values of these rutiles are lower than average continental crust ratios which suggests fractionation driven by fluid precipitation and or competing mineral phases u pb data yield primary crystallization ages older than deposition ages 2 58 ga supporting the detrital nature of these rutiles rutiles record either resetting or new growth at 2 1 ga and at ca 500 ma during which gold was remobilised hence this study supports a modified placer model for the gold bearing horizons of the moeda formation these fluid assisted gold remobilisation events can be found in other correlated paleoproterozoic gold bearing horizon units that represent intracratonic basins related to the rifting of the kenorland supercontinent this study reinforces the suitability of rutile and mineral inclusions as a powerful tool to elucidate processes and provenance

local variations of carbon isotope composition in diamonds from sao luis brazil evidence for heterogenous carbon reservoir in sublithospheric mantle abstract taking advantage of the common occurrence of superdeep mineral inclusion assemblages we examined core to rim primary zonation in 69 diamonds from the alluvial deposits of the sao luis river juina brazil syngenetic inclusions were represented by phases of superdeep paragenesis the dominant inclusions are majoritic garnets ferropericlases and casi and casiti perovskites rare inclusions of mgsi perovskites olivines clinopyroxenes tapp phases of sio2 kyanites alsi phases kfsp k hollandite cf nal grossular merwinite native iron fe sulphides magnesite and caco3 camgsi2o6 composite inclusions were also found the diamonds from sao luis display wide variations in carbon isotopic compositions 13c from 2 7 to 25 3 the diamonds with inclusions of ferropericlase have a very narrow range of 13c values from 2 1 to 7 7 which are close to the normal mantle values in many cases diamonds with inclusions of calcic majoritic garnet and casi and casiti perovskites display marked differences from this range low 13c values 10 to 25 were observed exclusively in a series of diamonds with majorite garnets ca silicates aluminous silicates and sio2 the 13c values from the cores to rims in certain individual crystals varied substantially indicating multiple stages of growth the highly negative 13c values in the cores 20 to 25 potentially represent organic matter in metasediments of altered oceanic crust and the lower 13c values may represent mixing trends towards normal mantle compositions in this study we also found a set of diamonds that display an opposite trend of change of the carbon source from primordial mantle to subducted crust either biotic or abiotic carbon

role of localized mixing around the kuril straits in the pacific thermohaline circulation 1 we investigate the pacific thermohaline circulation induced by the locally enhanced vertical mixing around the kuril straits by using a general circulation model when the strong vertical mixing reaches the sea surface localized upwelling is induced from the depth to the surface on the contrary in the cases where the strong vertical mixing does not reach the sea surface downwelling of surface water is induced in the shallow layer while upwelling of deep water is induced below the structure of the meridional overturning circulation in the pacific ocean significantly differs depending on whether the surface buoyancy flux is large enough to sustain upwelling of deep water or not the mixing induced downwelling of shallow water is not associated with the sea surface cooling and the source of dense water is in the deep ocean among the non surface reaching mixing cases the depth that separates the downwelling and upwelling is found to be relatively insensitive to the depth where the vertical diffusivity sharply changes

isotopic composition of co2 and dissolved carbon species in basalt glass the isotopic composition of coexisting fluid and dissolved carbon species in morb glass have been studied using a combination of replicate stepped heating experiments vacuum crushing and grain size analysis stepped heating carbon release profiles demonstrate the presence of isotopically light carbon released by combustion below 600 degree c ltc and isotopically heavier carbon released above 600 degree c htc up to 95 of the ltc component which mostly resides on the surface of the glass can be removed by extraction in dichloromethane combustion at 400 and 600 degree c ensures its complete removal prior to extraction of htc species above 600 degree c assuming that htc consists of fluid i e co sub 2 trapped within vesicles and dissolved i e carbonate ion complexes species limits on the net difference between the isotopic composition of coexisting fluid and dissolved carbon have been estimated from stepped heating data the apparent magnitude of carbon isotopic fractionation between co sub 2 vapor and basaltic melt is greater than 1 per thousand but significantly less than 4 5 per thousand and localized fractionation processes associated with magma degassing are associated with delta sub co sub 2 sub basalt melt values of approx 2 per thousand

carbon concentrations and isotopic ratios in fluid inclusion bearing upper mantle xenoliths along the northwestern margin of north america abstract at least three and perhaps four carbon components have been identified by step heating extraction of upper mantle xenoliths from nunivak island and prindle volcano alaska fort selkirk and alligator lake yukon jacques lake and castle rock british columbia one component released mostly between 200 and 600 c comprises 30 95 of the total carbon extracted and has 13c values between 28 and 23 this carbon corresponds mostly to complex carbon compounds condensed on surface minerals and cracks and will be referred to as isotopically light carbon ilc co2 released between 600 and 800 c is derived from interstitial carbonates it has variable 13c and concentrations that generally do not exeed 24 ppm c the carbon extracted from 1000 to 1450 c is a mixture of co2 from fluid inclusions and the ilc fraction the amount of ilc released in this temperature interval never exceeds 10 ppm because part of this ilc may have been introduced from the host lava the 13c variations of this carbon extracted above 800 c is not only characteristic for the original carbon present in fluid inclusion poor xenoliths however xenoliths enriched in co2 fluid inclusions show c isotopic variations at the highest temperature steps that fall in a relatively narrow range between 10 and 4 depending upon the fluid inclusion abundance the concentration of high temperature c derived from fluid inclusions varies from 0 1 to 66 ppm anhydrous spinel lherzolites and harzburgites generally contain

co 2 co fluid inclusions in a composite peridotite xenolith implications for upper mantle oxygen fugacity fluid inclusions occur in a composite xenolith from the lunar crater volcanic field nevada u s a the xenolith is an amphibole bearing wehrlite that is cut by an andesine amphibole vein the compositions of individual fluid inclusions in both portions of the xenolith have been determined using microthermometry and micro laser raman spectroscopy fluids in the host wehrlite are nearly pure co2 99 mol whereas those in the vein contain from 8 5 to 12 0 mol co in co2 chemical modelling shows that the composition of the vein fluids at t room is representative of the composition at the high p t conditions of trapping graphite has not been observed by optical microscopy in any of the fluid inclusions graphite is probably absent although stable at t 800 c most probably because of the kinetically unfavorable co decomposition reaction and rapid quenching by combining the measured fluid compositions with fluid p v t data and the chemical equilibrium co2 co 1 2 o2 we have calculated the oxygen fugacity of the fluid inclusions at 1200 c log f o 2 8 6 vein and 6 host if the f o 2 of the fluid in the vein represents that in equilibrium with the magma that crystallized to produce the vein then the f o 2 of the basalt magma is near qfm at 1200 c and 10 3 kbar this is similar to values reported for extrusive basaltic lavas if the much lower intrinsic oxygen fugacity values for divines and spinels from alkali basalt nodules are representative of upper mantle conditions then oxidation of basaltic magmas must occur in the upper mantle prior to ascent to the surface implications for the origin of co2 rich fluids and carbon isotope geochemistry are also discussed

mineral inclusions in diamonds associations and chemical distinctions around the 670 km discontinuity three new mineral associations have been discovered within diamonds from the juina district of brazil these include a previously unrecorded na al mg fe sio3 phase associated with ferropericlase and the tetragonal almandine pyrope phase tapp also reported are an association of corundum with aluminous pyroxene and an olivine composition phase associated with ferropericlase the minerals in each association often occurred within the same diamonds in addition to being recovered from individual diamonds in different combinations high pressure experimental data indicate that these associations formed at different depths within a region ca 60 km on either side of the upper mantle lower mantle boundary mineral compositions show that for the regions sampled the deep transition zone and lower mantle are chemically distinct and inhomogeneous importantly in the shallow lower mantle al is not solely accommodated within perovskite structured mg fe sio3 as some recent experimental studies have suggested

deep current measurements at 38 n east of japan 1 deep currents east of japan were investigated using direct current measurements and hydrographic observations current data recorded for 9 months along 38 n showed a pair of currents one southward and the other northward flowing along local isobaths above the western and eastern flanks respectively of the japan trench geostrophic velocities calculated from conductivity temperature depth ctd data showed a similar velocity pattern to the current measurements the transports referring to the mean current velocities were estimated below 2000 m the deep transports above the trench were southward 5 5 sv and northward 13 5 sv and the boundary was at the deepest point of the trench the mean current measured above the abyssal plain to the east of the trench was westward at 38 n since the bottom water properties above the eastern flank of the trench were colder and more saline than those on the abyssal plain the westward current does not enter the trench but rather is expected to turn northward just east of the trench its northward transport was estimated to be 6 2 sv and the total northward transport was estimated to be 19 7 sv at 38 n a pair of oppositely flowing deep currents is confirmed in the japan trench while the transports were similar to those of the izu ogasawara and kuril kamchatka trenches whose ends connect with the japan trench the current structure resembles that at the izu ogasawara trench rather than that at the kuril kamchatka trench

new insights into magma dynamics during last two eruptions of mount etna as inferred by geochemical monitoring from 2002 to 2005 two distinct eruptive events characterize the volcanic activity at mount etna during the 2002 to 2005 period we identified signals of magma ascent preceding these eruptions by geochemical monitoring of both chemical composition and he isotope ratio of gas emissions from five locations in the peripheral area of the volcano the geochemical signals are interpreted using the models proposed by caracausi et al 2003a 2003b and allow identification of episodes of magma ascent and estimation of the pressures of degassing magma as observed for the 2001 eruption caracausi et al 2003b magma ascent probably triggered the onset of the 2002 2003 eruption and minor events of magma ascent were observed between may and december 2003 in contrast to the previous two eruptions the 2004 2005 eruption was not preceded by significant geochemical signals of volcanic unrest suggesting that this eruption was mainly triggered by the failure of the upper portion of the volcanic edifice under the magmatic hydrostatic pressure in the conduits high 3he 4he ratio revealed new volatile rich magma accumulation the 2002 2003 eruption was preceded by a much shorter period of new magma accumulation from deep levels of the feeding system few minor signals of magma migration were detected at some of the sites during the months preceding the 2004 2005 eruption suggesting that the degassed 3he depleted magma resident in the volcanic conduits was not replaced by new volatile rich magma this is in agreement with the lack of explosive activity during the 2004 2005 eruption and with petrologic observations that the parent magma probably erupted in 2000 and 2001 new geochemical signals of magma ascent from the deep reservoir have been identified since june 2005 indicating that the volcanic activity of mount etna is evolving toward new pre eruptive conditions

corundum inclusions in diamonds discriminatory criteria and a corundum compositional dataset abstract mineral inclusions of corundum are reported from diamonds from alluvial deposits of tributaries of the rio aripuana juina brazil we present the first recorded occurrence of sapphire as an inclusion in diamond and expand on the database of ruby and white corundum inclusions ruby inclusions are found to occur both as isolated and touching grains with aluminous pyroxene and associated with ferropericlase mineral chemistry and phase relations place the origin of such ruby bearing diamonds within the lower mantle at 770 km mineral associations indaving other corundum inclusions were not observed hence their depth of origin is less certain compositions of corundum samples were characterised by electron and ion microprobe given the scarcity of literature data corundum samples from a variety of other geological settings were also analysed samples comprised corundums associated with granitic emplacement metasomatism amphibolite facies and granulite facies rocks gem and industrial synthetic origins and carmine coloured corundums recovered from kimberlite drill cores in addition to variable amounts of cr fe ti mg and si measurable quantities of other transition elements and high field strength elements were also detected corundums from similar geological settings show very similar compositions and are easily distinguishable from other settings irrespective of locality rubies from norwegian tanzanian and kenyan amphibolite facies rocks are compositionally indistinguishable additionally corundums from metasomatised zones associated with contact metamorphism from arizona and japan were very similar particularly characterised by unusually high abundance of mobile zr and nb tens of ppm all juina inclusions are particularly distinguishable from other corundums by high concentrations of ni 18 171 ppm weight typically at least an order of magnitude enriched over the same corundum varietal types from elsewhere furthermore the sapphire inclusion exhibited much larger ratios of ga and ge to hfse elements compared to otherwise similar samples and ruby inclusions are distinguished by high mg fe ratios 0 27 1 56 by weight compositional differences between inclusions in diamonds and corundums from other settings in addition to corundum s physical and chemical durability suggest that with the employment of rapid identification tools such as energy dispersive spectrometry eds and laser icpms corundum has promise as an indicator of diamond prospectivity

soil and fumarole gases of mount etna geochemistry and relations with volcanic activity abstract between 1993 and 1996 gas samples were collected on mt etna volcano from both high and low temperature fumaroles and from soils in areas of anomalous degassing located on the flanks of the volcanic edifice the chemical composition of all the emitted gases is consistent with their magmatic origin during their transport to the surface they would undergo shallow mixing processes mostly with air locally as in the case of a point in the lower southwestern flank of the volcano p39 very high contents of he and ch4 indicate that deep gases mainly interact with ground waters and also with a hydrocarbon reservoir the isotopic composition of carbon in co2 from these gases also suggests its primary magmatic origin with inferred 13 c values of magmatic co2 in the range 2 to 1 vs pdb such values significantly more positive than those measured in morbs are in the typical range measured at the other mediterranean volcanoes 5 to 0 more negative values can be explained by shallow interactions between magmatic and organic co2 and or between the former and cold t 120 c ground waters both chemical and isotopic gas geothermometers agree in indicating calculated temperatures ranging from 180 to 270 c for the soil gases collected from low temperature fumaroles near the summit and temperatures around 150 c for the cold gases from p39 thus confirming the presence of a hydrothermal aquifer beneath this point a chemical geothermometer applied on the gases collected from the high temperature fumaroles near the summit craters shows equilibrium temperatures ranging from 385 to 690 c lastly many of the studied parameters showed anomalous variations in time during the studied period the most important of these concerned the flux of co2 through the soil and the concentration of soil h2 which were closely correlated with strong increases in the volcanic activity of etna

diffusive fractionation of noble gases and helium isotopes during mantle melting abstract the large differences in he and ar diffusivities in silicate minerals could result in fractionation of the he ar ratio during melting of the mantle producing he ar ratios in the primary mantle melts that are higher than those of the bulk mantle modeling noble gas diffusion out of the bulk mantle into fast diffusion pathways such as fractures or melt channels suggests that significant order of magnitude he ar fractionation will occur if the fast diffusion channels are spaced several meters apart and the noble gas residence in these diffusion channels is of the order days to weeks in addition the 15 difference in 3he and 4he diffusivities could also produce isotopic fractionation between the melt and its solid source modeling the behavior of he and ar during melting shows that small increases few in 3he 4he should be correlated with larger variations factor of 5 in 4he 40ar however in order to test this hypothesis the effects of subsequent he ar fractionation that occur during degassing have to be corrected i describe a scheme that can separate he ar variations in the primary melt from overprinted fractionation during magmatic degassing using the degassing corrected data there is a correlation between the primary melt s 4he 40ar and 3he 4he in mid ocean ridge basalts morbs the slope of the correlation is consistent with the models of preferential diffusion of 3he relative to 4he and of 4he relative to 40ar from the solid mantle into the melt diffusive fractionation of noble gases during melting of the mantle can also account for low 4he 40ar ratios commonly found in residual mantle xenoliths preferential diffusion of he relative to ar will produce some regions of the mantle with low 4he 40ar the complement of the high 4he 40ar ratios in basalts diffusive fractionation cannot however account for differences between the he and ne isotopic compositions of morbs compared with ocean island basalts oibs not only are the extremely high 3he 4he ratios of oibs up to 50 ra difficult to produce at reasonable mantle time and lengthscales but also the ne isotopic compositions of morbs and oibs do not lie on a single mass fractionation line therefore cannot result from diffusive fractionation of a single mantle ne source if preferential diffusion of he from the solid mantle into primary melts is a significant process during generation of morbs then it is difficult to constrain the he concentration of the mantle he concentrations in basalts and the he flux to the ocean essentially result from extraction of he from a larger and unknown volume of mantle than that that produced the basalts themselves the he concentration of the mantle cannot be constrained until more accurate estimates of the diffusion contribution are available

a 3 800 million year isotopic record of life from carbon in sedimentary rocks an increased ratio of 12c to 13c an indicator of the principal carbon fixing reaction of photosynthesis is found in sedimentary organic matter dating back to almost four thousand million years ago a sign of prolific microbial life not long after the earth s formation partial biological control of the terrestrial carbon cycle must have been established very early and was in full operation when the oldest sediments were formed

geochemical evidence for mixing between fluids exsolved at different depths in the magmatic system of mt etna italy abstract a 4 year geochemical survey of some fumaroles at the voragine summit crater of mt etna was performed in combination with synchronous monitoring of peripheral gas emissions at the base of the volcano this was the first geochemical study at mt etna to have included the abundances of ar he and c isotopes once the effects of postmagmatic shallow processes were identified and quantitatively removed the he ar co 2 systematics of the voragine crater fumaroles and peripheral gas emissions described the same degassing path combining the carbon isotope composition with information about noble gases provided evidence that the crater fumaroles are fed from a two endmember mixture composed of a deep member coming from pressures between 200 and 400 mpa depending on time and a shallower one exsolved at 130 mpa similar mixing processes probably also occur in gases from peripheral vents the simultaneous assessment of 13 c co2 and he ar values of crater fumaroles over time has identified simple changes in the mixing proportion between the two endmembers and moreover periods during which the exsolution pressure of the deep fluid increased these periods seem to be linked to pre eruptive phases of the volcano the identified open system degassing processes are indicative of efficient bubble melt decoupling at depth whereas the mixing process requires a convective transfer of the deeply exsolved fluids toward shallower levels of magma where further vapor is exsolved in agreement with the most recent geophysical and petrological data from mt etna these observations allow inferences about a deep portion of the plumbing system 5 to 12 km b s l comprising sill like reservoirs connected by small vertical structures and a main reservoir at 2 3 km b s l that is probably fluxed by magmatic volatiles

carbon isotopes in xenoliths from the hualalai volcano hawaii and the generation of isotopic variability abstract the isotopic composition of carbon has been determined in a suite of xenoliths from lava of the 1800 1801 kaupulehu eruption of hualalai volcano hawaii several lithologies are represented in the suite including websterite dunite wehrlite pyroxenite and gabbro in addition there are composite xenoliths in which contacts between lithologies are preserved most of the xenoliths represent deformed cumulates the contact relations in the composite samples indicate that the lithologies originated from the same source region which based on pressures determined from fluid inclusions is estimated to be at a depth of 20 km or near the crust mantle boundary samples were heated in steps from 200 to 1475 c to obtain separation of the different carbonaceous phases and the isotopic composition of carbon released at each step was determined grossular glass was found to be a suitable flux to fuse refractory samples upon heating carbon exhibits the typical bimodal evolution behavior observed in other studies of xenoliths and basalts carbon extracted from all samples at temperatures below 900 c is characterized by a 13 c of about 25 vs pdb and is thought to be composed dominantly of graphitic and organic material which is known to be present on virtually all cracks the 13 c of the carbon fraction extracted at 1200 c and above from wehrlite and dunite is in the range 1 5 to 5 2 whereas that extracted from websterite ranges from 22 to 26 similarly in one composite sample the compositions of dunite and websterite were found to be 2 4 and 7 0 respectively the large difference can be associated with specific petrographic features unique to each lithology in wehrlite and dunite carbon exists mostly as co 2 rich inclusions in arrays representing partially annealed microcracks the websterite xenoliths contain megascopic zones of large irregularly shaped inclusions the zones traverse entire thinsections and are interpreted to represent fractures annealed at depth most of the carbon is believed to exist in the inclusion rich zones and to consist of carbonaceous material precipitated from fluid the observations and isotopic results demonstrate that isotopic variability can be generated by multistage fractionation processes such as degassing of co 2 from magma and precipitation of co 2 rich fluids to form graphitic compounds such processes operated over regions the scales of which were determined by style and intensity of deformation and by lithology

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

isotope geochemistry of pantelleria volcanic fluids sicily channel rift a mantle volatile end member for volcanism in southern europe chemical and isotopic ratio he c h and o analysis of hydrothermal manifestations on pantelleria island the southernmost active volcano in italy provides us with the first data upon mantle degassing through the sicily channel rift zone south of the african european collision plate boundary we find that pantelleria fluids contain a co2 he rich gas component of mantle magmatic derivation which at shallow depth variably interacts with a main thermal 100 c aquifer of mixed marine meteoric water the measured 3he 4he ratios and 13c of both the free gases 4 5 7 3 ra and 5 8 to 4 2 respectively and dissolved helium and carbon in waters 1 0 6 3 ra and 7 1 to 0 9 together with their covariation with the he co2 ratio constrain a 3he 4he ratio of 7 3 0 1 ra and a 13c of ca 4 for the magmatic end member these latter are best preserved in fluids emanating inside the active caldera of pantelleria in agreement with a higher heat flow across this structure and other indications of an underlying crustal magma reservoir outside the caldera the magmatic component is more affected by air dilution and at a few sites by mixing with either organic carbon and or radiogenic 4he leached from the u th rich trachytic host rocks of the aquifer pantelleria magmatic end member is richer in 3he and has a lower closer to morb 13c than all fluids yet analyzed in volcanic regions of italy and southern europe including mt etna in sicily 6 9 0 2 ra 13c 3 1 this observation is consistent with a south to north increasing imprint of subducted crustal material in the products of italian volcanoes whose he and c but also o and sr isotopic ratios gradually evolve towards crustal values northward of the african eurasian plate collision boundary our results for pantelleria extend this regional isotopic pattern further south and suggest the presence of a slightly most pristine or less contaminated 3he richer mantle source beneath the sicily channel rift zone the lower than morb 3he 4he ratio but higher than morb co2 3he ratio of pantelleria volatile end member are compatible with petro geochemical evidence that this mantle source includes an upwelling himu em1 type asthenospheric plume component whose origin according to recent seismic data may be in the lower mantle

world ocean circulation diagnostically derived from hydrographic and wind stress fields 1 the velocity field using a robust diagnostic model the steady circulation in the world ocean is determined from climatological annual mean fields of hydrographic data and wind stress the upper circulation reflects the surface geopotential anomaly of the input hydrographic data in addition the warm water route is prominent the water passing through the indonesian seas flows westward across the indian ocean to return to the north atlantic in the deep atlantic ocean the north atlantic deep water is transported southward by the dominant deep western boundary current in the depth range from about 1500 m to the bottom whereas the weddell sea deep water does not extend northward from the argentine basin an important result is a westward current appearing near 25 n in the middepth atlantic ocean such a current has been inferred from tracer distributions but hardly detected with objective methods the velocity maximum at middepth suggests that the current is not a lower part of a wind gyre but is a baroclinic flow caused by a thermohaline effect in the indian ocean a swift middepth current appears along the western boundary but it may be questionable because the resulting heat transport does not agree with earlier estimates the deep water flowing into the southern basins from the antarctic circumpolar current does not flow further northward even in the madagascar basin the cause of these unsuccessful results is probably that the present model does not take into account large seasonal variations in the indian ocean

carbon dioxide solubility and carbon isotope fractionation in basaltic melt abstract carbon dioxide solubility and isotope fractionation data for a morb composition at 1200 1400 c and 5 20 kbar have been obtained using piston cylinder apparatus and stepped heating mass spectrometry carbon dioxide solubility in basalt melt at 5 10 and 20 kbar is 0 15 0 17 0 45 0 51 and 1 49 respectively values for co 2 vap co 2 3 basalt melt obtained from the difference between the isotopic compositions of coexisting vapour and melt vary from 1 8 to 2 2 a review of measured and estimated values for carbon isotope fractionation between co 2 vapour and carbon dissolved in basic melts shows variation from 1 8 to 4 6 results of this study and other considerations favour relatively small equilibrium co 2 vapour melt fractionation factors around 2

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

changes in fluid geochemistry and physico chemical conditions of geothermal systems caused by magmatic input the recent abrupt outgassing off the island of panarea aeolian islands italy abstract hydrothermal systems and related vents can exhibit dramatic changes in their physico chemical conditions over time as a response to varying activity in the feeding magmatic systems massive steam condensation and gas scrubbing processes of thermal fluids during their ascent and cooling cause further compositional changes that mask information regarding the conditions evolving at depth in the hydrothermal system here we propose a new stability diagram based on the co2 ch4 co h2 concentrations in vapor which aims at calculating the temperatures and pressures in hydrothermal reservoirs to filter gas scrubbing effects we have also developed a model for selective dissolution of co2 h2s n2 ch4 he ne mixtures in fresh and or air saturated seawater this methodology has been applied to the recent november 2002 crisis that affected the geothermal field off the island of panarea italy where the fluid composition and fluxes have been monitored for the past two decades the chemical and isotopic compositions of the gases suggest that the volatile elements originate from an active magma which feeds a boiling saline solution having temperatures of up to 350 c and containing 12 mol co2 in vapor the thermal fluids undergo cooling and re equilibration processes on account of gas water rock interactions during their ascent along fracture networks furthermore steam condensation and removal of acidic species partial dissolution in cold air saturated seawater and stripping of atmospheric components affect the composition of the geothermal gases at shallow levels the observed geochemical variations are consistent with a new input of magmatic fluids that perturbed the geothermal system and caused the unrest event the present state evolution shows that this dramatic input of fluids is probably over and that the system is now tending towards steady state conditions on a time scale of months

elastic moduli of jadeite enstatite majorite 1 the adiabatic bulk ks and shear g moduli of a polycrystalline majorite garnet solid solution with composition na0 92mg2 08 mg0 02al1 06si0 92 si3o12 were measured at ambient conditions by brillouin spectroscopy ks and g were found to be 171 6 3 5 gpa and 103 5 2 0 gpa respectively assuming a linear dependence of the elastic moduli on composition for the mg2si2o6 enstatite majorite en mj naalsi2o6 jadeite majorite jd mj join the calculated ks and g of the fictive jd mj end member are 178 and 125 gpa respectively at ambient conditions the shear velocity change associated with the pyroxene to majorite transition increases dramatically with increasing na content in the system in contrast there is virtually no shear velocity increase associated with the pyroxene to majorite transition in mgsio3 if this relationship holds at high pressures and temperatures it suggests that for mineral assemblages containing an abundance of large radius cations such as ca and na the pyroxene garnet reaction will produce higher shear velocity gradients than assemblages that are relatively deficient in these elements such chemical effects could play a significant role in explaining high seismic velocity gradients in the transition zone

elemental and isotope covariation of noble gases in mineral phases from etnean volcanics erupted during 2001 2005 and genetic relation with peripheral gas discharges abstract during 2001 2005 mount etna was characterized by intense eruptive activity involving the emission of petrologically different products from several vents which involved at least two types of magma with different degrees of evolution we investigated the ratios and abundances for noble gas isotopes in fluid inclusions trapped in olivines and pyroxenes in the erupted products we confirm that olivine has the most efficient crystalline structure for preserving the pristine composition of entrapped gases while pyroxene can suffer diffusive he loss both the minerals also experience noble gas air contamination after eruption helium isotopes of the products genetically linked to the two different magmas fall in the isotopic range typical of the etnean volcanism this result is compatible with the metasomatic process that the etnean mantle is undergoing by fluids from the ionian slab during the last ten kyr as previously inferred by isotope and trace element geochemistry significant differences were also observed among olivines of the same parental magma that erupted throughout 2001 2005 with 3he 4he ratios moving from about 7 0 ra in 2001 volcanites to 6 6 ra in 2004 2005 products changes in he abundances and isotope ratios were attributed to variations in protracted degassing of the same magma bodies from the 2001 to the 2004 2005 events with the latter lacking any contribution of undegassed magma the decrease in 3he 4he is similar to that found from measurements carried out every fifteen days during the same period in gases discharged at the periphery of the volcano to our knowledge this is the first time that such a comparison has been performed so in detail and provides strong evidence of the real time feeding of peripheral emissions by magmatic degassing

mount etna geochemical signals of magma ascent and unusually extensive plumbing system fiveyearsofgasmonitoringfromselectedsitessuggestthatmtetna splumbingsystemismuchmoreextensivethanpreviously reported it extends at least 40 km sw from thevolcano s boundary along the ne sw regional fault whereit discharges about 200 tons day of gas containing heliumwith mantle type isotopic composition synchronousvariations of

the carbon isotope signature of ultramafic xenoliths from the hyblean plateau southeast sicily italy evidence of mantle heterogeneity we investigated the carbon isotope composition of mantle source beneath the hyblean plateau southeast sicily italy by studying co2 in fluid inclusions from ultramafic xenoliths recovered in some miocene diatremes in order to constrain the processes influencing the isotopic marker of carbon we combined 13cco2 results with information about noble gases he and ar obtained in a previous investigation of the same products although ar co2 and he ar ratios provide evidence of rayleigh type fractional degassing the isotopic geochemistry of carbon is poorly influenced by this process mixing related to metasomatic processes where morb type pyroxenitic melts permeate a peridotite mantle probably contaminated by crustal fluids inherited from a fossil subduction can explain the measured 13c and co2 3he variations ranging from 4 to 2 and from 109 to 1010 respectively simple mass balance calculations highlighted that the hyblean peridotite source was mainly contaminated by the carbonate source being carbonate and organic matter present at a ratio that varied within the range from 7 1 to 4 1

helium 3 plume over the east pacific rise at 25 s 1 we have measured helium isotopic ratios of sixty eight water samples collected in the southeastern pacific at 25 s the maximum excess 3he of 47 5 is observed just above the east pacific rise which is comparable to that of 50 5 at 15 s in literature a negative correlation between helium isotopes and neon to helium ratios of seawater samples suggests that the source of excess helium 3 in the mid depth water is considered to be a morb type mantle contour of excess 3he shows symmetrical pattern that is plume of 30 excess can be traced up to 1000 km on both east and west of the east pacific rise this pattern is consistent with a northward flow along the rise at 25 s estimated by a physical model our observation also supports a flow pattern of deep ocean currents which has been suggested by contour of excess 3he obtained from previous studies

geochemical monitoring of the 2002 2003 eruption at stromboli volcano italy precursory changes in the carbon and helium isotopic composition of fumarole gases and thermal waters significant changes in the helium and carbon isotopic composition of shallow thermal waters vs gas and a crater fumarolic gas have been recorded at stromboli prior and during the 2002 2003 eruption the3he 4he ratios corrected for air contamination rc ra and 13c of fumarolic gases gradually increased from may to november 2002 before the eruption onset these variations imply early degassing of a gas rich magma at depth that likely fed both the intense strombolian activity and small lava overflows recorded during that period the lava effusion of late december 2002 was shortly preceded by a marked rc ra decrease both in water and fumarolic gases comparison of he co2 and ch4 co2 ratios in dissolved gas and with rm delta 13 rm c rm co 2 values rules out the rc ra decrease due to an increasing input of radiogenic4he the rc ra decrease is attributed to the he isotope fractionation during rapid magma ascent and degassing a new uprising of 3he rich magma probably occurred in january to february 2003 when rc ra ratios displayed the highest values in dissolved gases ever measured before 4 56 rc ra the increase in he co2 and ch4 co2 ratios and decrease in 13c of dissolved co2 was recorded after the 5 april 2003 explosive paroxysm likely caused by enhanced gas water interaction inducing co2 dissolution no anomalous rc ra values were recorded in the same period when usual strombolian activity gradually resumed

chemical heterogeneity of mt etna magmas in the last 15 ka inferences on their mantle sources abstract primitive basaltic magmas are crucial in the study of the geochemical heterogeneity documented in etna magmas and their inferred mantle sources we undertook a systematic sampling of the less evolved basalts mg 50 erupted over the last 15 ka a time period which corresponds to the activity of the youngest volcanic edifice of mt etna complex i e mongibello volcano we focused on lava flows and pyroclastites emplaced during deep dyke fed ddf eruptions which were driven by the rapid ascent of deeply rooted magma intrusions that bypassed the shallow plumbing system of the volcano all the samples were analyzed by the same laboratory to avoid analytical bias to build a comprehensive dataset on their major and trace element compositions and to propose a coherent framework for interpreting the geochemical fingerprints of present day etna basalts trace element modeling together with literature data for sr isotopes gave insight into long term magmatic processes related to different melting degrees of the heterogeneous mantle beneath mt etna ddf magma batches provide good snapshots of their mantle source heterogeneities that point to the variable involvement of clinopyroxenitic lithology rb 87 sr cl rich fluid component s possibly controlled by their source mineralogy and slab derived fluids selectively enriched in alkalis rb k the ongoing alkali rb k enrichment of the present day magmas well manifest since the 1970s is decoupled from that of sr and cl we propose that this process is linked to mantle source composition and is concomitant with changes in both volcanological and seismotectonic patterns of the volcano there is no time evolution of ddf magma chemistry

shock induced minerals in meteorite provide prospecting tools for mineral physics over the last 40 years a combination of seismic data from earth s interior and experimentation at high pressures on materials of composition similar to that in earth s mantle has led to an increasingly accurate picture of what succession of phases must be present at increasing depths during the same time period it has been discovered that many of these phases are present in minute amounts in meteorites that before their arrival on earth were shocked to high pressures and temperatures during collisions between the asteroids from which the meteorites were derived in a recent issue of pnas chen et al 1 reported a previously uncharacterized mineral from such a shocked meteorite and by using diamond anvil experiments and synchrotron x ray analysis derived the stability conditions of that mineral and another closely related one discovered earlier this year from the same meteorite both of these phases are high pressure polymorphs of the mineral chromite fecr2o4 which is a common although minor mineral in peridotites rocks of the upper mantle that are abundantly exposed at the surface and also found as inclusions xenoliths in volcanic rocks some of this volcanism e g kimberlite also carries diamonds and hence must be derived from a minimum depth of 120 km the authors suggest that the newly discovered polymorphs of chromite if found in natural rocks on earth could serve as anchor points for estimation of the depths of origin of rocks transported from great depth the two polymorphs place minimum pressures of 12 13 gpa cafe2o4 structure and 20 gpa cati2o4 structure these pressures are equivalent in earth to depths of 400 km and 680 km respectively however is there any reason to believe that any rocks presently at the surface have ever seen such pressures

a new view of the he ar co2 degassing at mid ocean ridges homogeneous composition of magmas from the upper mantle abstract deep sea exploration is rapidly improving our understanding of volatiles geochemistry in mid ocean ridge igneous products it is also placing greater constraints on degassing processes of the earth s mantle with the result that degassing models based on vapour melt equilibrium are no longer able to explain the increasing number of data in fact such models force to postulate an upper mantle strongly heterogeneous at any scale and cannot account for the widespread carbon supersaturation of the recovered igneous products here we review the global he ar co 2 dataset of fluid inclusions in mid ocean ridge glasses using the framework of advanced modelling of multicomponent bubble growth in magmas we display that non equilibrium fractionations among he ar and co 2 driven by their different diffusivities in silicate melts are common in most of the natural conditions of magma decompression and their signature strongly depends on pressure of degassing due to the comparable ar and co 2 diffusivity magma degassing at low pressure fractionates both the he ar and he co 2 ratio by a similar extent while the slower co 2 diffusion at high pressure causes early kinetic effects on ar co 2 ratio and dramatically changes the degassing path on this ground the very different geochemical signatures among suites of data coming from different ridge segments mainly depend on the depth of the magma chamber where the melt was stored besides the variations inside a single suite highlight variable ascent speed and cooling rate of the emplaced lava the large variations in both the he co 2 and ar co 2 ratios at almost constant he ar displayed in glasses coming from the mid atlantic ridge 24 30 n segment and the rodriguez triple junction are therefore interpreted as a high pressure signature in contrast the simultaneous increase in both he co 2 and he ar of the east pacific rise pito seamount and south east indian ridge data sets suggests the dominance of low pressure fractionation implying that the shallow magma chambers are at a lower depth than those of the mid atlantic ridge 24 30 n and rodriguez triple junction our conclusions support the presence of a relationship between spreading rate and depth of high temperature zones below ridges and are consistent with the depth of magma chambers as suggested from seismic studies non equilibrium degassing explains the volatile systematics of mid ocean ridge basalts by starting from a single mantle derived magma dispensing with the supposed need for heterogeneities in abundance ratios of volatiles in the mantle below oceanic ridges

nanocrystalline diamond from the earth s mantle underneath hawaii abstract melt inclusions in a mantle derived garnet pyroxenite xenolith from salt lake crater hawaiian island of oahu have been analysed by means of transmission electron microscopy including energy dispersive x ray analysis electron energy loss spectroscopy and electron diffraction the melt inclusions represent trapped low degree melt that metasomatised the hawaiian mantle lithosphere before the eruption of the host magma the inclusions consist of a c cl s rich glass of basaltic composition an exsolved gas fluid phase mainly co2 with minor amounts of co h2o and some unidentified c h and h s species and or carbonate diamond is the major phase in the glass ranging in size between a few and several hundred nanometres two varieties of nanocrystalline diamonds are identified polycrystalline aggregates of nanometre size diamonds are tentatively explained as pseudomorphs after carbonate while single crystals are suggested to have crystallised from the melt other nanocrystalline phases include native fe and cu fes fes2 zns ags and several ti nb zr ir in pd rich phases of unknown composition overall the observed mineral assemblage suggests that the melt was highly reduced and strongly enriched in volatiles and trace elements of contrasting geochemical affinity our findings are the first evidence for a metasomatic impregnation of the hawaiian mantle by low degree melts here we report the first occurrence of diamond in the modern oceanic mantle

in situ observation of the decomposition of kyanite at high pressures and high temperatures in situ observations of the decomposition of kyanite al 2 sio 5 were carried out in a multi anvil high pressure apparatus using synchrotron radiation where the phase change from kyanite to stishovite corundum was observed at high pressures and high temperatures the phase boundary of this decomposition at t 1200 1900 k and p 5 15 gpa was determined to be p gpa 10 2 0 0016 t k previous studies using the quench method showed a discrepancy in the transition pressure of the decomposition our results using in situ observations resolve this dispute

origin of co2 and carbonate veins in mantle derived xenoliths in the pannonian basin the origin and evolution of co2 inclusions and calcite veins in peridotite xenoliths of the pannonian basin hungary were investigated by means of petrographic investigation and stable isotope analyses the fluid inclusions recovered in paragenetic olivine and clinopyroxene belong to distinct populations type a texturally early inclusions with regular shapes often with negative crystal forms forming intragranular trails type b texturally late inclusions defining randomly oriented trails that reach grain boundaries type b inclusions are often associated with silicate melt type c inclusions stable carbon isotope compositions in inclusion hosted co2 were obtained by vacuum crushing followed by conventional dual inlet as well as continuous flow mass spectrometry in order to eliminate possible lab artifacts olivines clino and orthopyroxenes of the host peridotite have oxygen isotope compositions from 5 3 to 6 0 relative to v smow without any relationship with xenolith texture some of the xenoliths contained calcite in various forms veins and infillings in silicate globules in veins secondary carbonate veins filling cracks and metasomatic veins with diffuse margins the former two carbonate types have 13c values around 13 relative to v pdb and low sr contents 0 5 wt whereas the third type veins with high temperature metasomatic features have a 13c value of 5 0 and high sr contents up to 3 4 wt in spite of the mantle like 13c value and the unusually high sr content typical for mantle derived carbonate trace element compositions have proven a crustal origin this observation supports the conclusions of earlier studies that the carbonate melt droplets found on peridotite xenoliths in the alkaline basalts represent mobilized sedimentary carbonate the large 13c range and the 12c enrichment in the carbonates can be attributed to devolatilization of the migrating carbonate or infiltration of surficial fluids containing 12c rich dissolved carbon carbon isotope compositions of inclusion hosted co2 range from 17 8 to 4 8 relative to v pdb with no relation to the amount of co2 released by vacuum crushing low 13c values measured by stepwise heating under vacuum suggest that the carbon component is pristine and not related to surficial contamination and that primary mantle fluids with 13c values around 5 were at least partly preserved in the xenoliths tectonic reworking and heating by the basaltic magma resulted in partial co2 release and local 13c depletion

mantle crustal and atmospheric noble gases in ailaoshan gold deposits yunnan province china abstract helium and argon isotopic and elemental compositions of fluids released by crushing pyrite grains are reported from the ailaoshan gold province china the province is a series of gold deposits hosted on a 200 km segment of a major normal fault formed during eocene extension the deposits have been well characterised using conventional geochemical and microthermometric techniques the results of which are consistent with a predominantly high temperature magmatic fluid present in the ore minerals in contrast analyses of noble gases from three gold deposits demonstrate the palaeofluids were a mixture between a mantle derived magmatic fluid and two different low temperature fluids similar to modern groundwaters the specific isotopic and abundance characteristics of helium and argon allow unequivocal identification of both a mantle derived component and a surface derived component to these fluids the magmatic fluid dominates deposits from the northern end of the fault the second groundwater is present only in deposits in the south of the province by assuming fluid inclusion homogenisation temperatures in coexisting quartz are representative of fluid temperature 3he heat ratios can be estimated the 3he heat ratios vary systematically along the fault from 30 10 12 cm3 stp j 1 in the northern deposits to

the contribution of fluid geochemistry to the volcano monitoring of stromboli abstract the persistent open vent mild explosive activity of stromboli volcano is episodically interrupted by more violent and dangerous explosive events major explosions and paroxysms according to the nature of erupted products paroxysms can be related either to the explosion of overpressured gas pockets located in the proximity of the magma column or to the sudden uprise of hot gas rich magma from a deep part of the plumbing system in both cases these more energetic explosive events should be preceded by an escape or a preferential uprise of the highly mobile volatiles which in turn should produce gas leakage anomalies at the surface in sites of high vertical permeability such as deep reaching faults in order to identify such gas leaking sites a systematic co2 soil flux survey has been carried out on the island using an accumulation chamber four hundred sixty one points have been measured with a high density in the summit crater area where high flux values have been found 10 3 10 2 cm s anomalous points are concentrated along the main ne sw axial feeding system of the volcano co2 soil flux decreases from the crater zone to the base of the volcanic cone where however an interesting gas leakage anomaly occurs pizzillo mofette in the pizzillo area thermal water wells also occur whose chemistry indicates an origin by sea water heated by hot gas soil gases have been sampled in the sites with the highest co2 flux in the crater area and at the base of the cone chemical and isotopic analyses indicate the presence of a deep gas component especially in the crater zone samples high co2 appreciable contents of he and h2 3he 4he values up to 3 55 13c of co2 2 the sc5 low flux fumarole on the crater rim has shown during six years a remarkable persistence of temperature 93 95 c with only minor fluctuations of chemistry appearance of anomalous peaks of h2 in correspondence with strombolian explosions was observed during a 2 h 30 min experiment of continuous recording of hydrogen content of the fumarole together with previous data on h2o co2 and he this experiment confirms that strombolian blasts produce rapid fluctuations in the fumarolic gas composition in the light of this study sc5 fumarole and pizzillo mofette look promising sites for the testing of a continuous geochemical monitoring system of stromboli volcano

geochemical evaluation of observed changes in volcanic activity during the 2007 eruption at stromboli italy abstract on february 27 2007 a new eruption started at stromboli that lasted until april 2 and included a paroxysmal explosion on march 15 geochemical monitoring carried out over several years revealed some appreciable variations that preceded both the eruption onset and the explosion the carbon dioxide co 2 flux from the soil at pizzo sopra la fossa markedly increased a few days before the eruption onset and continued during lava effusion to reach its maximum value at 90 000 g m 2 d 1 a few days before the paroxysm almost contemporarily the 13 c co 2 of the sc5 fumarole located in the summit area increased markedly peaking just before the explosion 13 c co 2 1 8 following the paroxysm helium he isotopes measured in the gases dissolved in the basal thermal aquifer sharply increased almost contemporarily the automatic station of co 2 flux recorded an anomalous degassing rate also temperatures and the vertical thermal gradient which had been measured since november 2006 in the soil at pizzo sopra la fossa showed appreciable variabilities that lasted until the end of the eruption the geochemical variations indicated the degassing of a new batch of volatile rich magma that preceded and probably fed the paroxysm the anomalous 3 he 4 he ratio suggested that the ascent of a second batch of volatile rich magma toward the surface was probably responsible of the resumption of the ordinary activity a comparison with the geochemical variations observed during the 2002 2003 eruption indicated that the 2007 eruption was less energetic

helium isotopes in peridotite mineral phases from hyblean plateau xenoliths south eastern sicily italy abstract fourteen he isotope and abundance analyses have been performed on olivine orthopyroxene and clinopyroxene grains from selected spinel facies peridotite xenoliths collected from the hyblean plateau southeastern sicily these peridotites consist of protogranular textured spinel facies lherzolites and lherzolitic harzburgites microthermometric data on olivine and pyroxenes reveal that the fluid inclusions fis are nearly pure co 2 with densities ranging from 0 76 to 1 15 g cm 3 the densest inclusion trail occurs in an orthopyroxene grain and indicates a trapping pressure of 0 98 1 14 gpa estimated equilibration temperature of 1000 c for pure co 2 system corresponding to a depth of 36 41 km for an average estimated density of the lithospheric column of 2 85 g cm 3 these are minimum estimates the near unimodal distribution of co 2 densities indicates that these xenoliths have been stored at the pressure interval of 0 75 0 95 gpa corresponding to a depth of 27 35 km crust mantle boundary or just below en route to the surface they have not had any significant interaction with shallower volatile reservoirs he trapped in co 2 rich fluid inclusions ranges in abundance from 1 8 to 86 6 10 9 cm 3 stp g with clinopyroxenes usually showing higher he contents than coexisting olivines and orthopyroxenes the inter mineral differences are due to physical properties of minerals in contrast he isotope ratios cover a narrow range 7 3 0 3 r a where r a air 3 he 4 he indicating isotopic equilibration between the mineral phases he composition indicates a morb type source for the metasomatic agent s influenced by relatively minor radiogenic production in the source therefore in closed system conditions the calculated helium residence time is 790 myr geophysical and geochemical studies suggest the existence of a common fluid reservoir in the mantle beneath the central mediterranean area the most pristine he signature for the mantle endmember is found on pantelleria island sicily channel this he ratio is similar to that found in hyblean peridotite minerals testifying to a common source history we conclude therefore that hyblean xenoliths can be used as a powerful tool in defining the geochemical features of this portion of the upper mantle

baroclinic instability of density current along a sloping bottom and the associated transport process numerical experiments with a three dimensional nonhydrostatic ocean model have been carried out to investigate the dynamic processes of downslope density current and associated transport of dense water focusing on the effects of bottom slope for the range of slope inclination s from 0 to 0 04 bottom slope has two effects on baroclinic instability of the flow one is the stabilizing effect due to the topographic effect and to offshoreward increase in water depth the other is the destabilizing effect due to steepened inclination of isopycnal surface which increases available potential energy since the destabilizing effect over the upper slope overcomes the stabilizing one in the early stage unstable waves develop more rapidly with increasing s nonlinear energy conversion due to reynolds stresses also affects the flow stability and then the growth rate of instability increases linearly with s in this stage after the unstable waves have finite amplitudes in the mature stage the stabilizing effect of bottom slope becomes dominant especially over the lower slope thus vigorous unstable eddies are confined to the upper slope region in steep slope cases while they cover the whole slope region in gentle slope cases and this difference in the eddy field causes a drastic change in downslope transport of dense water in gentle slope cases efficiency of the transport becomes higher with increasing s since the destabilizing effect overcomes the stabilizing one as a whole on the contrary the efficiency becomes lower with increasing s in steep slope cases since the stabilizing effect surpasses the destabilizing one as a result the most effective transport is realized in the case with s 0 005 although the transport due to eddies in steep slope cases becomes weak over the lower slope it is still larger than that due to the bottom ekman current since the eddy transport occurs in the bottom layer with a thickness of 100 200 m which is 4 8 times the ekman layer thickness