Submitted AbstractsDCO Summer School 2014

Yemerith Alpizar Segura, National Seismological Network, UCR“Monitoring of Costa Rican active volcanoes using infrared technology: quickly detection of important changes at volcanoes and short term prediction of phreatic eruptions”Co-authors: Carlos José Ramírez Umaña, Gino González Ilama, Raúl Mora Amador

Volcano monitoring has been a hard task for the volcanologists, and many cases a big risk for their lives. Nowadays this is changing, thanks to remote sensing methods. Each volcano has a particular behavior, after some time is evidence when something is going on. Since a decade ago at Costa Rica there are two kinds of these cases, the first, it’s the Turrialba volcano, that was awake after 144 years with the reactivation of magmatic-hidrothermal system in 2005. The second is Poás volcano, this one have a hyperacidic hot lake, which has phreato-magmatic activity between 1820´s and 1950´s decades, and then was presented phreatic activity until today. For both cases, is not so practical and also dangerous to make “in situ” measurements, now is when the use or the remote sensing is useful. At Turrialba volcano, before the opening of new vents, some changes was detected, like temperature elevation of the fumaroles and a hot sulfur flows coming out from these same places. This signs, told us that we had to leave the volcano and the eruption happen three hours after. Other case at Poás volcano, the principal changes that was detected is on the acidic lake, when the phreatic eruptions are close to happen, because the hot lake normally present convective cells, that become hottest where the eruptions are coming. A prediction of small phreatic eruption with minutes of time, might don’t seem very important, but for the volcanologists can to mean the difference between life and death.

Kimberly Aviado, University of New Hampshire - Department of Earth Sciences“Melt generation beneath the West Antarctic Rift System: the volatile legacy of Gondwana Subduction?”

The West Antarctic Rift System (WARS) is one of the largest extensional alkali volcanic provinces on Earth, yet the mechanisms responsible for driving rift-related magmatism remain controversial. The failure of both passive and active models of decompression melting to adequately explain unusually voluminous volcanism has prompted debate about the relative roles of thermal plume-related melting and ancient subduction-related flux melting. The latter is supported by ~500 Ma of subduction along the paleo-Pacific margin of Gondwana, a processes capable of producing the broad seismic anomaly imaged beneath most of the Southern Ocean. Analysis of olivine-hosted melt inclusions (MIs) from mafic lavas provides a means to evaluate the volatile budget of the mantle responsible for active rifting. MIs are largely alkali-rich and silica-poor in composition, and exhibit water and CO2 contents ranging up to 2.94 wt % and 4657 ppm, respectively. Positive correlations observed between Cl and H2O may indicate enrich-ment by subduction-related fluids produced during slab dehydration, whereas the observed coupling between H2O and F, which is more highly retained in subducting slabs, may be related to partial melting of slab remnants. Major oxide data for MIs and primitive lavas support a volatilized lithology, and implicate pyroxenite as a potential source. These data suggest that voluminous Cenozoic magmatism is the product of partial melting of subduction-modified lithosphere.

Patrick Beaudry, CUNY Queens College“The origin of volatile-rich magmas in the Canary Islands”Co-author: Marc-Antoine Longpré

Intraplate volcanism in the Canary Islands is characterized by much compositional heterogeneity, both across and within individual islands, with extrusive products being largely alkaline. Alkaline magmas have been shown to have a stong positive effect on the solubility of CO2 in magmas, and Canary Island volcanics indeed contain widespread CO2 fluid inclusions, recording entrapment pressures as high as 1 GPa (e.g. Hansteen et al. 1998). This demonstrates that mafic magma may become saturated with a CO2-rich fluid at depths of 35 km. Recent data on crystal-hosted melt inclusions from the 2011-2012 submarine eruption at El Hierro, the first to be observed at this island, indicate high sulfur and carbon dioxide contents in the magma reaching 0.5 and 1.2 wt%, respectively, and exceeding the known global range for ocean island basalts (Longpré et al. 2013). These findings have important implications for deep S and C fluxes through hotspot volcanism. This work will use SIMS measurements of sulfur isotopes in sulfide and melt inclusions to determine the source of the abundant volatiles, and whether melting of recycled crust or contamination by oceanic sediments may be involved. Olivine phenocrysts from the 2011-2012 eruption are enriched in Ni and depleted in Ca relative to other islands, suggesting a more pronounced involvement of pyroxenite in El Hierro's mantle source, an indication of the presence of recycled oceanic crust.

Venkata Srinu Bhadram, JNCASR“Effect of external pressure on the octahedral distortions in multiferroic RCrO3” (R= rare-earth)Co-authors: R. Dhanya, D. Swain, A. Sundaresan, C. Narayana

Rare earth chromites RCrO3 (R= Rare-earth) are interesting class of perovskite oxides with an intriguing multiferroic property which is rooted from 4f-3d magnetic interactions which can be altered either by doping (chemical pressure) or by external pressure. We have aimed at studying the structural aspects of these materials as a function of pressure in order to have room temperature multiferroic RCrO3. We have studied the effect of external pressure on the octahedral distortions in rare-earth chromites (RCrO3; R= Lu, Tb, Gd, Eu, Sm) using Raman scattering and synchrotron x-ray powder diffraction up to 20 GPa. Our studies reveal that the octahedral distortions in RCrO3 increase with pressure at a rate which decreases with increase in R-ion size from Lu to Sm. The root cause for this effect is found to be the reduction in the compression of RO12 polyhedra with a corresponding increase in the R-ion radii. From the Raman studies we predict critical R-ion radii above which we expect the octahedral distortions in RCrO3 reduce with increase in pressure leading to the symmetry lowering phase transition as seen in LaCrO3. These results were further supported by the pressure dependent structural studies on RCrO3(R=Gd, Eu, Sm). Also, our results suggest that the pressure dependence of Néel temperature of Chromium in RCrO3 is mostly affected by the compression of Cr-O bonds rather than the alteration of octahedral tilts.

Christine Boucher, CNRS/ CRPG- RP2E doctoral school“High-precision Isotopic study of atmospheric helium: the applications in volcanic and environmental studies”Co-authors: Tefang Lan; Jennifer Mabry, Bernard Marty and Pete Burnard

Considered constant on a global scale [3], the 3He/4He atmospheric ratio, (1.39 ± 0.01) × 10-

6, is used as a standard in most laboratories. This convention is questioned since [5] observed a ratio of (1.343 ± 0.013) × 10-6 at Ueno Park, Japan. Several studies were therefore conducted to verify if this variation is caused by natural phenomena, influenced by time and/or location, or by experimental problems [1 to 5]. First results from [4] are consistent with no change in the helium composition over time. In volcanic areas, [2] detected average helium isotopic ratios from Hawaii and Ethiopia of 2.1 to 2.7 per mil higher than that in Nancy, France. The latter study indicates large variations within Etna’s plume column. An air sampling campaign is initiated, covering southern latitudes (Australia, South Africa and South of Chili), middle latitudes (USA, Italy, Japan), and high latitudes (France, USA). We shall particularly deepen research from volcanic areas, where appear to have great potential to elucidate volatile flux/budget by observing atmospheric helium isotopes. We will present the analysis and sampling methods, together with the previous results and the anticipated future directions. [1] Brennwald et al. (2013), EPSL 366, 27-37. [2] Lan et al. (2013), Goldschmidt2013 Conference Abstract, 1551. [3] Lupton (1983), AREPS 11, 371-414. [4] Mabry et al. (2013), Goldschmidt2013 Conference Abstract, 1662. [5] Sano et al. (1988), Geochemical Journal, 22, 177-181.’

Laura Clor, University of New Mexico“A new comprehensive database of global volcanic gas analyses”Co-authors: Tobias P. Fischer, Kerstin A. Lehnert, Brendan T. McCormick, Elizabeth Cottrell, Erik H. Hauri

Volcanic volatiles provide the driving force behind eruptions, are powerful indicators of magma provenance and tectonic regime, present localized hazards, and have broad implications for climate. Studies of volcanic emissions are necessary for understanding volatile cycling from the mantle to the atmosphere. Gas compositions vary with changes in volcanic activity, making it important to track this chemical variability over time. Further, as studies become increasingly interdisciplinary, it is critical to have a mechanism to integrate decades of gas studies across disciplines. Despite the value of this research to a variety of fields, there is currently no integrated network to house all volcanic and hydrothermal gas data, making spatial, temporal, and interdisciplinary comparison studies very time-consuming. To remedy this gap, we are working to establish a comprehensive database of volcanic gas emissions worldwide, as part of the DCO’s DECADE (Deep Carbon Degassing) initiative. This database will be useful in a variety of applications, for example: 1) correlating volcanic gas composition to volcanic activity; 2) establishing a characteristic gas composition or total volatile budget for a volcano in studies of global chemical cycles; or 3) better quantifying the flux and source of volcanic carbon to the atmosphere.

Laura Creon Bocquet, IFP Energies nouvelles“Modeling and quantification of mantle C fluxes to the crust – A multi-scale approach”Co-authors: ROUCHON Virgile, IFP Energies nouvelles (Rueil-Malmaison, France), DELPECH Guillaume, IDES (Orsay, France), GUYOT François, IMPMC (Paris, France), SZABO Csaba, Eotvos University of Budapest (Hungary)

Large quantities of CO2 are commonly observed in many petroleum Basins and are generally linked with a mantle origin. Carbon dioxide increases the overall oil and gas production costs. In order to make progresses in the assessment of such a CO2-risk, we are working on the characterization of the source of mantle-CO2 and its fluxes towards a basin in the case of the Pannonian basin. A petrographic study of fluid inclusion rich peridotitic and granulitic xenoliths sampled in Hungary was undertaken in order to quantify the potential amounts of CO2 released by the mantle. Microthermometric measurements and Raman analysis show that inclusions are purely CO2, with densities clustering between 0.6 and 0.9 g/cm3. Highresolution microtomography by Synchrotron is underway to quantify the fluid inclusion distribution, volumes and densities and thus the mass of CO2 present in the Pannonian mantle. Crushing experiments are planned in order to have a well-defined mantle end member He and C isotopic compositions to compare with basin fluids. Finally, a thermomechanical modelling will be performed in order to estimate the volumes of CO2 produced by melting in response to the P, T path, thanks to thermodynamic modelling. A direct comparison of the modelled fluxes and those estimated by fluid geochemistry will help us to give a critical analysis of the approach considered, together with novel insights on the buffering of mantle fluxes by the crust and the basin.

Joel Davis, University College London“Reconstructing the carbonate compensation depth from 0 to 100 Ma using geochemical modelling and bathymetry models”Co-author: Carolina Lithgow-Bertelloni

The oceans play an important part in regulating the carbon cycle and climate system, acting as a buffer between the carbon in the atmosphere and the deep earth. Of all dissolved inorganic carbon (DIC) in the ocean, only carbonate can exist in a solid state (mostly as calcite). In the near-surface ocean, calcite precipitates. Deeper in the ocean, more calcite dissolves and all is entirely dissolved at the carbonate compensation depth (CCD). The CCD today is around 4.5 km depth, though previous work that looked at the composition of sediments on the ocean floor has suggested that CCD was different in the past. These studies mostly show the CCD decreasing to shallower depths through the Cenozoic and the Mesozoic. The deepening of the CCD through time is consistent with the decrease in atmospheric CO2 over time shown in the GEOCARB models. We look at the evolution of the CCD since 100 Ma by focusing on changes in the volume of the ocean basins using geochemical modelling and ocean bathymetry. In one of the reconstructions, the CCD gradually deepens with time, consistent with other independent studies. Changes in CO2 concentrations likely influenced this, which would have affected the amount of silicate weathering from continents. We will show maps of the extent of the global carbonate cover for the last 100 my, which suggest that the amount of sedimentary carbon being subducted has increased with time, despite an overall decrease in volcanic activity since the Mesozoic.

Marco Donnini, CNR-IRPI“A study on the gechemical processes that control the production and the consumption of atmospheric CO2 in Alpine region”Co-authors: Francesco Frondini, Jean-Luc Probst, Anne Probst, Carlo Cardellini, Stefano Caliro, Giovanni Chiodini, Ivan Marchesini, Fausto Guzzetti

On geological time-scales the CO2 fluxes from the solid Earth to the atmosphere mainly result from volcanism and metamorphic-decarbonation processes, while the CO2 fluxes from atmosphere to solid Earth mainly depend on silicate and carbonate weathering, biogenic precipitation and removal of CaCO3 and volcanic gases – seawater interactions. We show a balance for Alpine region between CO2 fixed by weathering and CO2 emitted by springs. The dissolved load of streams originates from rain, pollution, evaporite dissolution, silicate and carbonate weathering. We quantified each contributions for 33 sampled rivers. Depending on time-scales we used different equations to quantificate the CO2 fixed by weathering. The CO2 production was estimated from a database with composition of more than 1000 springs (both data from litterature and new data). For each point through an isotopic and mass balance approach we estimated: Ccarb (carbon from carbonate dissolution), Cinf (atmospheric and biogenic CO2) and Cdeep (CO2 from deep degassing). For each spring the flux of deep CO2 is given by Cdeep X Q/A, (Q: flow rate, A: recharge area), or by Cdeep X IE, (IE: effective infltration, IE=Q/A). IE have been estimated using a water balance model. The results shows: deep-CO2 rich springs are located along the more important Alpine tectonic structures and in the basins external to the Alps, Alpine chain at the present seems to be a sink for atmospheric CO2 but it is probably a source on long term.

Hannah Edwards, University College London“Feasibility Study into Monitoring of Geosequestration Sites”

Assessment of different methods used to monitor the concentration of CO2 stored through geosequestration. This is quantifiable to four key domains: atmosphere, surface, near-surface and subsurface. Geosequestration is increasingly being used by governments and organisations to reduce the concentration of atmospheric CO2 due to concerns that it contributes to global warming. It is therefore essential that we develop our understanding of the processes involved in geosequestration for environmental, economic and legal benefits. For the purpose of this investigation, the monitoring methods have been divided into two broad categories: remote and in-situ. Remote methods include satellite measurement (InSAR and DInSAR), ground based GPS, surface tiltmeters, gravimetry and bathymetry. In-situ methods include geochemical sampling, seismic monitoring (geophones), heat probes and pressure gauges. The conclusions of this project can help further our understanding of the behaviour of carbon in the subsurface environment to improve geosequestration techniques and more effective monitoring.

Pavel Enkovich, Institute for High Pressure Physics Russian Academy of Sciences“Isotope effects in diamond 13C and 12C at high pressures and at low temperatures”Co-authors: S. G. Lyapin, S. M. Stishov

The pressure dependence of first-order Raman scattering in natural diamond has been studied in a number of experimental and theoretical works. Much attention has been paid to studying physical properties of isotopically pure diamonds. One of the most interesting

findings of the studies was the discovery of a slight but distinct quantum effect on various properties of diamond, including the lattice and elastic constants, Raman scattering, indirect gap, optical absorption, etc. It was found that the ratio 12 /13 , where is the ν ν νfrequency of the first-order Raman line, decreases with pressure. This kind of behavior means that the quantum contribution to the physical properties of diamond increases with density. The question arises whether the quantum effects in diamond become more or less pronounced on compression at low temperatures. In the present study, first-order Raman scattering in natural and 13C-enriched diamond was measured at high pressures up to 12 GPa in a diamond anvil cell at 80K.

Sebastien Facq, University of Cambridge“Fluid speciation and solubility of aragonite in H20 and NaCl aqueous solutions at subduction zones conditions”Co-authors: Isabelle Daniel and Dimitri A. Sverjensky

During subduction, CaCO3 minerals may survive dehydration and partial melting of the subducting slab [1-3] and transfer C into the deep mantle. The investigation of the solubility of CaCO3 minerals and aqueous speciation of C under the PT range relevant to subduction zones remains largely unexplored experimentally and theoretically [4].Here, we report a combined experimental and theoretical study of the equilibrium of CaCO3

minerals with H2O and NaCl aqueous solutions in a larger PT range. The aqueous carbonate speciation was first studied by in-situ Raman spectroscopy in a DAC. Experimental solubilities of aragonite and relative amounts of the dissolved C-species were obtained and used to constrain a theoretical thermodynamic model of fluid speciation and solubility in equilibrium with aragonite. In H2O at 300–400°C, our results indicate that the proportion of dissolved CO2 strongly decreases in fluids at P > 10 kbar. CO2 is replaced by HCO3- and CaHCO3+ which predominate until P > 40 kbar, where CO32- and CaCO30 become the dominant C species. At higher T, the theoretical model indicates that CO‒ 2 again becomes a major species in fluids in equilibrium with aragonite depending on the P. The presence of NaCl in the fluid expands the P domain where the speciation of carbonate is highly variable.

[1] Yaxley & Green, (1994) EPSL. 128, 313. [2] Molina & Poli, (2000) EPSL. 176, 295. [3] Kerrick & Connolly, (2001) EPSL. 189, 19. [4] Martinez et al, (1994) Chem.Geol. 207, 47.

Mark Fox-Powell, University of Edinburgh“Microbial life in extreme, non-halite brines: controls on the distribution of subsurface life”Co-authors: John E. Hallsworth, Nicholas J. Tosca, Charles S. Cockell

Despite the critical dependence of life on the occurrence of liquid water, many other factors can define the habitability of aqueous fluids. Crucially, the composition and concentration of ionic solutes determine biologically-relevant stress parameters such as water activity, pH and chaotropicity, which act alongside temperature and pressure to restrict the functional biosphere. On the Earth’s surface, NaCl-enriched brines are common, and impose characteristic stresses that shape microbial ecology and evolution. In the deep subsurface, density dependent transport, low water:rock ratios and the dissolution of ancient evaporite deposits drive the diagenesis of compositionally diverse brines. Little is known of how salt-induced stresses might constrain the habitability of non-halite brines, thus impacting the distribution and productivity of microbial life in the deep biosphere. Here we have quantified habitability for eight non-halite brines, using a complex salt-

tolerant microbial community. Stress parameters were quantified and differed significantly from typical halite brines. Conspicuously, five brines did not permit the growth of any organism. Community structure in the three inhabited brines differed markedly from that encountered in NaCl-rich environments. These data suggest that for concentrated, non-halite brines, habitability is constrained to a smaller window than in NaCl, challenging the current paradigm that the availability of liquid water defines habitability.

Kristen Fristad, NADA Ames“Hydrogen Production and Habitability in Non-ultramafic Geologic Systems”Co-authors: Sanjoy Som and Tori Hoehler

Dihydrogen (H2) is a nearly ubiquitous product of water-rock interaction and is potentially an important reductant and source of energy for the rock-hosted deep biosphere. Previous studies on deep-sea hydrothermal vent systems suggest that H2 produced by water-rock interaction feeds microbial ecosystems. However, such studies represent a small corner of physicochemical space where conditions are highly favorable for H2 production. Dihydrogen (H2) can be lithogenically produced by the hydrolytic oxidation of the ferrous iron component in Fe-bearing minerals as well as by radiolytic cleavage of water by , , orα β

radiation produced during the decay of radioactive isotopes. Initial work on lithogenic Hγ 2 production has focused on ultramafic serpentinization, however, lithogenic H2 production mechanisms can operate across a range of rock types thus increasing the diversity of potential habitats in the Earth's crust. A field sampling campaign was undertaken in 2013 to assess the variation in lithogenic H2 abundance across a range spring waters hosted in non-ultramafic rocks. Aqueous hydrogen concentration from this survey reveals that dissolved hydrogen concentration can vary across several orders of magnitude irrespective of host rock type, and absolute values overlap those found in serpentinizing ultramafic sytems. Thus, this initial survey suggests the possibility for supporting H2-based metabolisms in a range of geologic environments beyond ultramafic systems.

Donato Giovannelli, Rutgers University – IMCS“Insight into the evolution of carbon fixation revealed by comparative genomic of the anaerobic chemosynthetic bacterium Thermovibrio ammonificans HB-1”Co-authors: Hugler M, Sievert S, Vetriani C

The biosphere is globally autotrophic and carbon fixation is a key step in the global carbon cycle. The deep biosphere (i.e. subsurface environements, oceanic crust and hydrothermally influenced areas) represents the largest ecosystem on earth. Dark carbon fixation, the fixation of carbon dioxide in the absence of light and oxygen, is an important source of organic carbon in the deep biosphere. In deep-sea hydrothermal vents chemolithoautotrophic anaerobes provide an important source of organic carbon entering the food chain. We reconstructed the full genome and central metabolism of Thermovibrio ammonificans strain HB-1, a hyperthemophilic member of the early branching bacterial phylum Aquificae. T. ammonificans is able to grow chemolithoauthotrophically using hydrogen as sole energy source coupled to sulfur or nitrate respiration. Comparative genomic analyses showed a high degree of genetic mosaicism with the simultaneous presence of ancestral and horizontally acquired genes. We present evidence for a potentially active reductive acetyl-CoA cycle in addition to the previously described rTCA cycle. We hypothesize that T. ammonificans is able to use switch carbon fixation pathway in response to energy and oxygen stress and argue that this type of redundancy could confer

the organism an ecological advantage. The simultaneous presence of both pathways sheds light into the evolution of carbon fixation, and may represent the ancestral carbon fixation phenotype.

Brendan Hanger, Australian National University“Do garnet peridotite xenoliths preserve a signature of carbonated silicate melts?”Co-authors: Greg Yaxley, Andrew berry, Mike Jollands, Joerg Hermann

The redox state of the cratonic mantle can be determined using the Fe3+/ΣFe ratio of garnet sourced from kimberlite-bourne peridotite xenoliths. Knowledge of the redox state provides information about the potential stability of carbon-bearing species, including diamond, graphite, carbonates and carbonated silicate melts. We have studied garnet peridotite xenoliths from two kimberlite pipes, Wesselton and Kimberley, in South Africa using EPMA and LA-ICP-MS. The xenoliths are a combination of harzburgites and lherzolites, sampling a pressure range of 3.7 to 4.7 GPa with temperatures of 900 to 1120 °C. Backscattered electron imaging revealed that multiple garnets from one xenolith were zoned in major and trace elements. Fe K-edge X-ray near edge structure (XANES) spectroscopy, an in-situ, high resolution synchrotron technique, was used to determine Fe3+/ΣFe in garnet. Most samples had an oxygen fugacity of between 1 and 2.5 log units below the fayalite-magnetite-quartz (FMQ) buffer, whilst two samples, including the zoned garnets had values up to that of the FMQ buffer, indicating a more oxidised origin. The bulk of the samples reveal a strong trend of decreasing oxygen fugacity with depth which corresponds with a silicate melt containing between 1 and 10 wt.% carbonate, whilst the more oxidised samples indicate that they may have been sourced from a region where carbonate may be stable. Thus garnet peridotite xenoliths may preserve a signature of carbonated silicate melts.

Adrienne Hoarfrost, University of North Carolina“Investigating Microbial Activities Driving Organic Carbon Transformations in the Deep Subsurface”Co-author: Carol Arnosti

Organic carbon degradation is central to microbial life in the deep subsurface, and heterotrophic microbes in turn influence the fate of organic carbon in these deep reservoirs. Despite the importance of heterotrophy in this environment, key questions remain about the factors controlling microbial heterotrophic activity in subsurface sediments. This study directly measures extracellular enzyme activity, the initial step of heterotrophic carbon cycling by microbial communities, in deep subsurface sediments from high- and low-carbon strata in single cores. Metagenomic and metatranscriptomic analyses are being done for bulk sediment communities, while culturable microbes are being isolated to investigate the underlying physiology driving extracellular enzymatic hydrolysis of organic matter in the deep biosphere. High hydrolytic activity by subsurface microbes has been observed in this medium, and novel insights into the physiological processes underlying heterotrophic carbon cycling in the deep subsurface are expected through comparison of activity and metatranscriptomic data with future culture studies.

Carolin Hoefer, ETH Zurich“Experimental determination of carbon isotope fractionation between metal- and silicate melts”Co-author: Max Schmidt

The present day global cycle of carbon is governed by the interaction of surface reservoirs with the silicate mantle. Surface material is recycled into the mantle when oceanic crust is subducted and returns to the surface by mantle derived magmatism and its gaseous emissions. Fractionation of carbon isotopes takes place during interactions of these different modern carbon reservoirs but also occurred during Earth formation, when carbon was distributed between the metallic core, the silicate magma ocean, and a hot potentially dense atmosphere. The scope of this project is to experimentally determine carbon fractionation factors between metal- and silicate melts relevant for the early stage of the Earth. High pressure experiments will cover a range of oxygen fugacities thought to have prevailed during core formation (IW -5 to IW +0.5; IW = oxygen fugacity defined by the Iron-Wustite buffer, Fe-FeO), pressure (1-25 GPa), temperature (1400-2200°C) and silicate melt composition to investigate the variations in carbon fractionation. The experimental run products will be analysed by bulk and in-situ methods, whereas for bulk analyses the two melts need to get separated by centrifugation. The results of this study will help to refine models of core formation, enable us to estimate both the bulk composition of the Earth and how much carbon may have been lost into space during Earth formation, and enhance our understanding of the complete carbon cycle from 4.57 Ga to present.

William Hutchison, University of Oxford“Structural controls on degassing and surface volcanism at a young rift volcano”Co-authors: Tamsin A. Mather, David M. Pyle, Juliet Biggs and Gezahegn Yirgu

Coupling high-resolution imagery with mapping of hydrothermal alteration and degassing at Alutu (a young silicic volcano in the Main Ethiopian Rift) provides important insights into how volcanic fluids reach the surface in an extensional tectonic regime. New LiDAR DEMs support evidence from deep geothermal wells that show the Alutu volcanic complex is dissected by rift-related extensional faulting. Mapping reveals that lava flow vents and explosion craters are controlled by both rift-aligned faults and a ring fracture system beneath the volcano. Therefore both tectonic and inherited volcanic structures direct the flow of magma to the surface. Mapping of surface hydrothermal alteration with aerial photos constrains the location of geothermal fluid upwelling and their links to the faulting. Results of volcanic CO2 degassing surveys also confirm elevated fluxes along major faulting and volcanic structures. However, small-scale studies along the fault zones reveal that complex changes in near-surface lithology impart important local controls on volcanic degassing. These observations reveal that volcanic and tectonic structures, topography and near surface geology all govern the flow of volcanic fluids to the surface at Alutu. This study contributes to our understanding of how volcanic processes are controlled in extensional tectonic regimes and has clear implications for understanding the geothermal field and volcanic hazards on Alutu, and elsewhere.

Alicja Lacinska, British Geological Survey, Nott University“Carbon capture and storage by mineralisation using serpentinites and ultramafic rocks”Co-authors: MT Styles, J Naden, M Maroto-Valer, S Kemp and PD Brown

The anthropogenic release of CO2 into the atmosphere has substantially augmented the natural greenhouse effect. To mitigate the effects of man-made climate change, technologies for CO2 capture and storage are being developed and refined, particularly storage within deep geological formations. One of the proposed solutions is to react the CO2

with Mg-rich minerals to form carbonates. This process mimics the natural weathering of Mg-rich silicates and is commonly called carbon capture and storage by mineralization (CCSM). Our study aims at assessing the suitability of Mg-rich sheet silicates - the serpentine minerals as well as a variety of ultramafic rocks for the CCSM. We have devised a set of experiments that represent the PT conditions of a deep underground reservoir in ultramafic rock complimented with a scenario for accelerated CCSM in a laboratory environment. The data from our study provides insights into the reaction kinetics and factors that govern Mg-release from different minerals and rocks at various conditions. Improved understanding of the reaction controls will help to indicate the characteristics of the best potential material as well as a deep storage host for large scale carbon capture and storage by mineralization.

Xiaojing Lai, Peking University and University of Hawaii“Synchrotron Raditiation X-ray Fluorescence Analysis of Trace Elements in Diamond”Co-authors: Wei Xu, Dongliang Chen, Bin Chen, Xiang Wu, Shan Qin

Trace elements in synthetic diamonds and natural diamonds from various locations such as Hunan, Liaoning and Shandong, China have been investigated by means of synchrotron radiation X-ray fluorescence. The measurements demonstrate that the synthetic diamonds contain trace amount of fourth-period elements (except As, Ge, Kr and Br) and Pb, in which the concentrations of Fe, Co, Ni are relatively high likely due to the mixture of the catalyst during the high-temperature and high-pressure synthesis processes. In comparison, trace element species in natural diamonds are Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, W, Au and Pb, whose corresponding concentrations are lower than those of the synthetic diamonds. Natural diamonds of different origins vary in the species and concentrations of trace elements, reflecting difference in the pressure-temperature conditions and melts or liquids from the surrounding environment involved in the growth of diamond crystals.

Xiao-Ming Liu, Carnegie Institute of Science“Trace elements in carbonates as tracers of Earth’s O2 evolution?”Co-authors: Robert Hazen, Linda Kah, Dimitri Sverjensky

Different major and trace elements in sedimentary records (e.g. BIFs, black shales) have been developed as proxies to reconstruct paleoenvironmental information in deep time (e.g., Sahoo et al., 2012). However, many of the sedimentary records are underepresented during the “boring billion” (1.8 ~ 0.8 Ga). Carbonate rocks are pervasive through Earth’s history and can provide additional information on paleoenvironments, such as seawater chemistry and/or atmospheric O¬2, during the evolution of Earth. We analyzed the major and trace element concentrations in micro-drilled carbonate rocks from six different localities around the world during the period of Paleo- to Meso- proterozoic and Ordovician. We explored the use of elemental ratios (e.g. Ce/Ce*, Cr/Sr) as redox proxies to

trace redox-state of seawater evolution. In shale-normalized (PAAS) REE+Y diagrams, we observed similar patterns to modern seawater—relative depletion of the light REE over the heavy REE. A negative Ce anomaly (Ce/Ce* < 1) is present in most carbonates, suggesting these carbonates were deposited in oxic marine environements. In addition, we find that some redox-sensitive elements (normalized to Sr), such as Fe and Cr, are more depleted during times of more oxidized environments (e.g., Ordovician) compared to those in more anoxic environments (e.g., Proterozic) through Earth’s history.

Guang-Sin Lu, University of Southern California“Microbial Fe-S-As cycling in a shallow-sea hydrothermal system”Co-author: Jan Amend

Soufriere Spring of Dominica, Lesser Antilles island arc is ideal investigating site to study the microbial influence of arenic (As) on a marine ecosystem, which is characterized by moderate temperatures spring (55oC). As(III) dominated in sediment core are 0.09-1.8 M,μ there are two As peaks (5-11cm and <11cm) with depth are regulated by Fe dissolution. Sediment and biofilm samples were used as inocula in enrichments targeting on heterotrophic arsenite oxidation and arsenate reduction. From these enrichments, multiple pure strains were isolated at 30, 50 and 70 oC. In the 50oC sediment enrichments on oxic, heterotrophic media inoculated, there are some unknown thermophilic sulfate reducers produce high concentration of sulfide and transform ferrihydrite to an amorphous As-metal-sulfide. Molecular biological surveys of microbial community diversity indicates that Bacteria (chloroflexi, deltaproteobacteria and gammaproteobacteria) is dominated microbes in all sample. However, Archaea (thermoprotei dominated) only occurs in venting fluid and button sediment, rather top sediment and biofilms. Site comparisons revealed that anaerobic, thermophilic, salt-tolerated microorganisms were prevalent in venting fluid and button sediment. In venting fluid, thermodesulfovibrio spp. might be the major rule to regulate the S cycle in situ. The current results implicate biological redox of Fe, S and As as primary biogeochmical processes in SOU Shallow-sea hydrothermal vent system.

Xiaogang Ma, Rensselaer Polytechnic Institute“Deep Carbon Virtual Observatory: A Platform for Linked Science of the Deep Carbon Observatory Community”Co-authors: Yu Chen, Han Wang, Patrick West, John Erickson, Peter Fox

Deep Carbon Observatory-Data Science is assembling a Deep Earth Computer for the Deep Carbon Observatory (DCO). The efforts will create a fundamental change in the conduct of Carbon-related research, resting upon a 21st century data science platform, and a series of aggregate data holdings that have never existed before. Data science combines aspects of informatics, data management, library science, computer science and physical science using cyberinfrastructure and information technology. Deep Earth Computer is to arise in several years’ time and be an embodiment of knowledge. What we have now is a Deep Carbon Virtual Observatory. It provides these functions at minimum: a concept-type repository, an ability to identify and manage all key entities, agents and activities in the platform, a repository for archiving datasets and associated metadata, collaboration tools, and an integrated portal to manage diverse content and applications, with varied access levels and privacy options. The Deep Carbon Virtual Observatory sets up a platform for the Linked Science of the Deep Carbon Community, that is, not only scientific assets like data and methods behind scientific settings are opened and inter-connected, but also the people,

organizations, groups, samples, instruments, activities, grants, meetings, etc. are recorded and inter-connected.

Izumi Mashino, Tohoku University

Hannah Miller, University of Colorado at Boulder“Low-temperature hydration, oxidation and hydrogen production from Oman peridotite”Co-authors: Lisa Mayhew, Alexis Templeton

Peridotite in the shallow subsurface undergoes hydration and oxidation during reactions with percolating fluids, generating H2 gas and releasing Mg2+, Fe2+, and Ca2+ into solution. The Samail Ophiolite in Oman contains large quantities of ultramafic rocks that are currently undergoing serpentinization and carbonation at low temperatures (30°C).However, the mechanisms of H2 generation and CO2 consumption in low-temperature systems are poorly characterized, particularly in the presence of chemolithoautotrophic microorganisms. Thus, we conducted 100°C water-rock reactions with Oman peridotite, measured H2 and characterized the speciation of Fe-bearing minerals before and after water-rock interaction using micro-X-ray Absorption Near Edge Structure ( XANES) μspectra. The water-rock reactions produce significant amounts of H2, peaking at 400nmol/gram of reacted peridotite before net H2 and CO2 concentrations decreased. The products include serpentine minerals, altered olivines and Fe(III) minerals, and we are currently investigating the mechanism of H2 generation and fate of dissolved carbon pecies. X-ray fluorescence ( XRF) maps reveal alteration of chromites, suggesting chromiteμ dissolution and oxidation as a possible H2 production pathway. In addition, these results suggest Oman may be a potential subsurface habitat for H2-utilizing microorganisms that can affect carbon availability.

Quin Miller, University of Wyoming“Organic complexes in carbon dioxide-rich fluids: Implications for metal transport and mineral transformations in the crust”Co-authors: J.P. Kaszuba, H.T. Schaef, M.E. Bowden

Supercritical CO2 (scCO2) is an effective solvent that can mobilize organic compounds naturally present in a reservoir. Consequently, it is possible that organics and metals could be scavenged, transported, and concentrated by migrating scCO2 fluids. We have undertaken an experimental and theoretical study to better understand the potential for organic-rich scCO2 migration and its impacts to subsurface geochemistry. The first series of experiments was conducted to examine impacts of organic ligands on silicate stability and mineral carbonation in water-saturated scCO2. Forsterite was exposed to scCO2, and the reaction progress was monitored by high pressure X-ray diffraction (XRD) at 35-90 °C and 90-100 bar. In some of the experiments, aqueous solutions (0.1 m) of salts of acetate, malonate, oxalate, and and citrate were in equilibrium with scCO2 but not in direct contact with the forsterite. Changes in both forsterite dissolution and magnesium carbonate formation were observed when organic ligands were present compared to the simpler H2O-scCO2 system. These results appear to indicate that scCO2 dissolved the organics and transported them where they could interact with the silicate surface. Additionally, we

performed atomistic simulations to characterize the interactions and partitioning behavior of acetate complexes and scCO2 in low water environments.

Elena Mukhina, Gubkin Russian State University of Oil and Gas"Experimental Investigation of Natural Gas’s Synthesis at Mantle Conditions: Lower Thermobaric Limit"Co-authors: A. Yu. Kolesnokov, V. G. Kutcherov

Experiments on the modeling of the deep abiogenic synthesis of hydrocarbons at the Earth's upper mantle conditions are the base of the whole stadying about hydrocarbons' (oil and gas) origin on our planet. It has repeatedly been confirmed that natural gas can be generated at the wide range of thermobaric parameters. Experiments presented here revealed lower thermobaric limit for hydrocarbons' generation from solid donor of carbon and water as donor of hydrogen. The limit was found not only for the expectable Earth's conditions, but also for the extended PT-spectrum. Experiments of different authors are included to compare and corroborate the results. Each experiment was conducted on the previously calibrated large reactive volume (LRV) press and analyzed by gas chromatography. Initial substances proved to exist in the upper mantle - CaCO3, H2O and FeO. These data are useful for detection of genuine depths into the Earth's interior where hydrocarbons (at least natural gas) are usually generated. Also, the PT limit out of the Earth's geotherms can be used to estimate possibilities of hydrocarbons' synthesis on other planets.

Philippe Robidoux, Universita degli studi di Palermo“First volcanic CO2 budget estimate for three actively degassing volcanoes in the Central American Volcanic Arc”Co-authors: Philippe Robidoux, Alessandro Aiuppa, Vladimir Conde, Bo Galle, Gaetano Giudice, Geoffroy Avard, and Angélica Muñoz

The objective of the project is to contribute for refining the current estimates of the total CO2 output from the Central American Volcanic Arc. We used a combination of remote sensing techniques and in-situ measurements of volcanic gas plumes to provide a first estimate of the CO2 output from three degassing volcanoes in Central America: Turrialba, in Costa Rica, and Telica and San Cristobal, in Nicaragua. During a field campaign in March-April 2013, we obtained (for the three volcanoes) a simultaneous record of SO2 fluxes (from the NOVAC network) and CO2 vs. SO2 concentrations in the near-vent plumes (obtained via a temporary installed fully-automated Multi-GAS instrument). The Multi-GAS time-series allowed to calculate the plume CO2/SO2 ratios for different intervals of time, showing relatively stable gas compositions. Distinct CO2 - SO2 - H2O proportions were observed at the three volcanoes, but still within the range of volcanic arc gas. The CO2/SO2 ratios were then multiplied by the SO2 flux in order to derive the CO2 output. At Turrialba, CO2/SO2 ratios fluctuated, between March 12 and 19, between 1.1 and 5.7, and the CO2 flux was evaluated at ~1000-1350 t/d. At Telica, between March 23 and April 8, a somewhat higher CO2/SO2 ratio was observed (3.3 ± 1.0), although the CO2 flux was evaluated at only ~100-500 t/d. At San Cristobal, where observations were taken between April 11 and 15, the CO2/SO2 ratio ranged between 1.8 and 7.4, with a mean CO2 flux of 753 t/d.

Cody Sheik, University of Michigan, Department of Earth and Environmental Sciences

“Unraveling the function of enigmatic microbes from Mid-Cayman Rise hydrothermal plumes”Co-author: Dick, G.J.

By leveraging de novo assembly of shotgun sequenced metagenomes followed by nucleotide composition based genomic binning, we characterized the functional potential of novel, ubiquitous, deep-ocean microorganisms from two contrasting hydrothermal vent fields. Geochemistry of Von Damm (~2290 m) and Piccard (~5000 m) plumes were markedly different, however, both are punctuated by high concentrations of hydrogen and methane. Microbial communities of these two vents were significantly different from one another and were more similar to background samples taken from similar depths, suggesting stratification of water masses limits microbial dispersion. Epsilonproteobacteria dominated Von Damm plume 16S rRNA libraries and genomes recovered suggests usage of both sulfur and hydrogen. MG1 Archaea and Alphaproteobacteria dominated Piccard and deep background waters. C1 metabolism was dominant at both sites, yet classic methanotrophy using either particulate or soluble methane oxygenases were not identified. Metagenomic and metatranscriptomic analysis coincides with thermodynamic modeling and suggests that hydrogen usage predominates methane. Together, this work shows many of these dark biosphere microorganisms are highly responsive to the plume environment and that hydrogen consumption is an important driver of productivity in the deep ocean.

Amy Smith, Oregon State University“Subseafloor mineral metagenomes”Co-authors: OU Mason, FS Colwell, MR Fisk

The igneous oceanic crustal aquifer contains a vast ecosystem where microbial life directly interacts with mineral surfaces. The most common minerals in oceanic crust are olivine, pyroxene, plagioclase, and glass. Previously we found that mineralogy and mineral chemistry influenced the composition of the microbial communities attaching to these minerals. Here we sequenced the metagenomes the common mineral classes to determine if mineralogy was also a factor in determining the ecological function of subseafloor communities. We found differences in functional distributions between mineral classes, including genes involved in methanogenesis and phosphorous metabolism. The importance of these pathways appears to be related to mineral chemistry.

Biao Tao, Peking University“Subduction zone: a potential factory for inexhaustible abiotic hydrocarbons”Co-authors: Lifei Zhang, Yingwei Fei, Meng Tian, Jinzhong Liu

We report the discovery of graphite-bearing fluid inclusions coexisting with ankerite and magnetite in carbonated eclogite from the low-temperature and ultrahigh-pressure oceanic subduction zone of Southwestern Tianshan, China. However, mechanisms and conditions permitting graphite precipitation from C-bearing fluids within subduction zone are still controversial. Therefore, we performed experiments at high pressure and temperature at the aim to better understand possible mechanisms that might be invoked to explain our finding. Abiotic hydrocarbons and graphite were observed after quenched experiments using piston cylinder and large volume press at pressures corresponding to upper mantle conditions along subduction zone. Gas chromatograph technique was employed to analyze the composition of coexisting fluids. Based on the experimental and geological observation,

we derive the following generalized reaction for graphite and hydrocarbons formation: Ankerite (high Fe) + water = ankerite (low Fe) + magnetite + graphite + carbon dioxide +hydrocarbons This study would confirm the possibility of abiotic hydrocarbons forming in subduction zones as a result of dissolution-disproportionation reaction of Fe-bearing carbonate. On the other hand, dissolution-disproportionate reaction of Fe-bearing carbonate is an important mechanism to explain the existence of graphite or diamond in subduction zones and Earth’s upper mantle.

Olga Taran Iourova“Metal oxides and sulfides form galvanic cells capable of providing energy for prebiotic reactions”Co-author: George M. Whitesides

Metal sulfides are common components both living and non-living systems that likely were present on Early Earth and have been widely used in prebiotic experiments. We have observed that some common metal sulfides and oxides are good electrical conductors. Combinations of these minerals and saline solutions compose simple voltaic cells. The minerals, working as cathodes or anodes, can form local oxidizing or reducing environments in overall neutral surroundings, with associated pH gradients. Surfaces of the minerals can also work as electrodes for electrochemical oxidations and reductions of organic molecules. We prepared electrodes from several metal sulfides and oxides to perform oxidation and reduction of model organic substances, such as hydroquinones. We achieved formation of galvanic cells with 0.3 to 1V of potential difference between cathode and anode, enough to perform most of the reactions of biological interest. We also observed formation of pH gradients near the surfaces of metal sulfides when low electrical potentials were applied. Variable redox and pH states, created around conductive minerals, are interesting environments that could provide conditions ultimately responsible for the selection of chemicals and reactions that we associate with life.

Dana Thomas, Stanford University “CO2 uptake and trace element mobilization in Icelandic geothermal areas”Co-authors: Dennis K. Bird, Stefan Arnorsson, Gordon E. Brown, Jr., Kate Maher

Hydrothermal systems serve as natural laboratories to investigate the fluid-rock interactions that modify magmatic CO2 fluxes to the atmosphere and affect groundwater quality. Here we present interpretations on CO2-rich low-temperature (≤180 °C) waters in basaltic geothermal areas in Iceland and the metasomatic processes that sequester CO2 through carbonate mineralization and mobilize trace elements to the fluid phase. Geothermal waters and gases contain up to ~80 mmol/kg CO2(aq) and 7 bar PCO2, whichΣ is up to 2 orders of magnitude greater than Icelandic geothermal systems of similar temperature. Based on D and 18O the fluids are of meteoric origin, and gas phase 13C δ δ δvalues are consistent with a magmatic source for CO2. Dissolved cation concentrations indicate that the fluids enhance silicate mineral dissolution, and that carbonate-forming cations are potentially removed by carbonate precipitation. The aqueous concentrations of elements of environmental concern (e.g. As, Ni) are above the World Health Organization guideline for safe drinking water in several samples. A potential sink for the trace metal(loids) is the incorporation within or adsorption to Fe-rich calcite/aragonite travertine deposits or Fe-(oxy)hydroxides that precipitate at spring discharge sites. Petrographic study of drill cuttings from wells in CO2-rich areas indicates that the sites

have undergone initial high-temperature and subsequent low-temperature alteration, including calcite precipitation.

Fatima Viveiros, CVARG – University of the Azores “Measuring hydrothermal CO2 fluxes in the Azores archipelago”Co-authors: Carlo Cardellini, Stefano Caliro, Teresa Ferreira, Catarina Silva, Giovanni Chiodini

Azores archipelago is formed by nine volcanic islands where present-day activity is characterized by manifestations of volcanism as fumarolic fields, thermal and cold CO2-rich springs as well as soil (CO2 and 222Rn) diffuse degassing areas. A permanent network to measure soil CO2 fluxes, based on the accumulation chamber method, started to be implemented in the islands in 2001 with the installation of the first automatic station in S. Miguel Island. Nowadays seven stations are running and CO2 fluxes recorded in the various monitoring sites vary from almost absence of degassing to values higher than 10000 g/m2/d1. Spatial variations of the soil CO2 emission have also been evaluated in some of the Azorean main degassing areas and the natural CO2 has been quantified in order to refine the global C-budget. At Furnas volcano (S. Miguel Island) about 1100 t/d of CO2 are emitted from an area with 6.2 km2, which are in the same order of magnitude of the CO2 released in other volcanic-hydrothermal areas of the world (e.g. summit area of Miyakejima Volcano, Japan; Mount Amiata, Italy; Yellowstone Volcano, USA). In order to distinguish the origin of the CO2, carbon isotopic composition of the CO2 efflux was determined and values varied between -12.28 ‰ and -3.11 ‰ vs. PDB. Based on these values, a value of 25 g/m2/d1 was proposed as a reliable limit for the CO2 biogenic emission and, from the total CO2 emitted by Furnas Volcano, about 86% has deep origin (954 t/d).

Zhihai Zhang, Dalhousie University“Diamond dissolution in the diamond hosting environments: constraints from experimental and natural diamond morphologies”Co-authors: Yana Fedortchouk; Jacob Hanley

C-H-O fluid plays role in diamond dissolution during mantle metasomatism, significantly shortening carbon residence in the mantle by transforming immobile carbon into mobile gas species, and it also helps to accelerate fast ascent rates of kimberlite magma. However, the composition of C-H-O in both processes is not well constrained. Diamonds crystallized in the mantle subsequently suffer dissolution caused by oxidizing metasomatism and host magmas during emplacement. Resultant diamond morphologies fingerprint dissolution events, and can be used to constrain the composition of the latest destructive fluid as they are experimentally documented to be sensitive to effective free fluids. However, lack of experimental data about pressure and fluid compositions on diamond resorption morphology has inhibited further development of such an idea. Here, we investigate the effect of pressure (1-3 GPa), silica content of aqueous fluid, and H2O:CO2 ratio in CHO fluid on diamond dissolution in order to decipher fluid composition in diamond destructive events. Our experimental data show that pressure exponentially suppress dissolution rates but shows no effects on morphologies and all etching pits form in a two-stage model (defect- and environment-controlled), and CO2/(CO2+H2O) molar ratio of diamond destructive fluids in kimberlitic fluid and destructive metasomatism under the central Slave craton fluid is < 50 mol. %, and > 50 mol. %, respectively.