Submitted Abstracts
DCO 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.