uniter phd day 26 february 2016 abstract book · cerebrosphaera populations from the...

UNITER PhD DAY 26 FEBRUARY 2016

ABSTRACT BOOK

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INVITED TALK

Lithium deposits and its global resources

Beate Orberger

ERAMET RESEARCH, France and Université Paris Saclay

The world market for hybrid vehicles may reach more than 11 million vehicles until 2020. Performances of new Li air batteries that should deliver similar high energy densities as gasoline may will extend the market for electric vehicles and consequently increase the demand of Lithium. Sedimentary rocks host about 87 % of total Lithium resources, from which 70% correspond to salar deposits in intramontane basins, where Lithium occurs in aqueous solutions (brines). Intensive exploration is performed on modern salars (Bolivia-Chile, Argentina Lithium Triangle; SW part of USA, Tibet Plateau, China), but also on fossil salar deposits (e.g., Jadar, Serbia hosting approximately 200 Mt of Lithium resources based on Rio Tinto exploration campaigns). Exploration, extraction, and metallurgical processing of Li-brine deposits is challenged by the understanding of Li-origin, geochemical evolution, and enrichment processes in the aquifers. The lecture gives an overview on the global Lithium resources in magmatic, sedimentary and aqueous environments. Lithium deposits in intramontane basins from the famous South American Lithium Triangle will be presented illustrating major processes of lithium concentration related to the geological context, exploration strategies and methods, accurate resource and reserve estimates, technologies allowing selective efficient extraction of Li from the other metals (K, B, Mg, SO4), and obtention of marketable Li-products for industries.

Reference: Orberger, B., Rojas, W., Millot, R., Flehoc, C. (2015). Stable Isotopes (Li, O, H) combined with brine chemistry: powerful tracers for Li-origins in Salar deposits form the Puna region, Argentina. Procedia EPSL, 13, 307-311.

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UNITER PhD Day26 February 2016Royal Academy – Brussels

abstract #24

Cartographie, petrographie et sedimentologie hauteresolution de l’unite SCIC du groupe du schisto-calcaire(Neoproterozoique) dans le bassin du Niari: secteur deMadingou (Republique du Congo).ACKOUALA MFERE Anna Perla

Université Libre de Bruxelles

En Afrique Centrale, la fragmentation de Rodinia débute vers 1000-825 Ma par un riftinginitié le long de la marge ouest du Craton du Congo et par l’ouverture de l’Océan Adamas-tor suivie par une sédimentation de type marge passive avec mise en place du SupergroupeOuest-Congolien. Les formations néoprotérozoïques du Supergroupe Ouest-Congolien af-fleurent au sud du Congo, en République Démocratique du Congo, en Angola, au Gabon eten Guinée équatoriale . Au Congo, le Supergoupe de l’Ouest-Congolien qui repose en discor-dance cartographique et/ou de ravinement sur les formations du Supergroupe du Mayombese décompose en trois groupes: de la base au sommet, le Groupe des Diamictites et GrésInférieurs, le Groupe du Schisto-Calcaire et le Groupe du Schiste-Gréseux. Le Groupe duSchisto-Calcaire, situé sur la bordure orientale de la chaîne du Mayombe se compose de qua-tre formations (SCI à SCIV), la formation SCI se subdivisant en 3 membres (SCIa, SCIb etSCIc). L’unité SCIc, objet de la thèse, représente un ensemble carbonaté sub-évaporitiqueassocié au développement d’un complexe stromatolithique de grande extension latérale etd’un niveau oolithique repère d’épaisseur variable jusqu’à quelques dizaines de mètres dansun système de rampe carbonatée. La problématique liée à ce travail de recherche est decaractériser d’un point de vue sédimentologique, diagénétique et structural la mise en placede l’unité SCIc à l’échelle régionale à travers le basin du Niari/Comba en République duCongo, par l’utilisation de méthodes variées telles que l’analyse pétrographique; les isotopesdu C, de l’O et du Sr; les éléments en traces et terres rares; la diffraction des rayons X. Lespremiers résultats montrent qu’une reconstitution paléogéopraphique du SCIc est possibleavec des faciès distaux (rampe externe) à grands stromatolithes en ‘cigares ou cônes’ déman-telés par des tempêtes (HCS) et dépôts d’argile entre les événements de forte énergie, relayésen position intermédiaire (rampe médiane) par des barres oolitihiques à intraclastes et on-coïdes, passant vers le paléorivage (rampe interne) à des faciès lagunaires semi-évaporitiques.L’évolution de la série est régressive liée à la progradation des corps sédimentaires. La pétro-graphie et la géochimie montrent que la série est affectée d’une diagenèse météorique. Lesanalyses chimiques des faciès oolithiques montrent que ceux-ci sont très purs et conviennentparfaitement pour la fabrication du ciment. La barre oolithique majeure se suit sur une cen-taine de kilomètres parallèlement au paléorivage, constitué du socle archéen faisant partiedu Craton du Congo.

2nd year of PhD (Supervisor: Preat Alain ) preference for oral

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abstract #28

Detecting terrestrial exoplanets with the SPECULOOSprojectBURDANOV Artem

University of Liege

SPECULOOS (Search for Planets EClipsing ULtra-cOOl Stars) is a project led by the Uni-versity of Liege that aims at detecting extrasolar planets orbiting the nearest coolest dwarfstars. Earth-sized exoplanets eclipsing these stars should provide a unique opportunity toget the first constraints on the atmospheres of terrestrial exoplanets with current astro-nomical facilities, while their detailed atmospheric characterisation, including the possibledetection of biosignatures, should be at reach of the next-generation telescopes such asthe European Extremely Large Telescope (E-ELT) and the James Webb Space Telescope(JWST). In this poster we present the main concepts of the SPECULOOS as well as someresults of the project’s prototype in operation on the TRAPPIST (TRAnsiting Planets andPlanetesImals Small Telescope) telescope in Chile since 2011.

1st year of PhD (Supervisor: Gillon Michael ) preference for poster

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abstract #22

Microanalyzes of remarkable microfossils of the LateMesoproterozoic–Early NeoproterozoicCORNET Yohan

Université de Liège

The Late Mesoproterozoic–Early Neoproterozoic is an important period to investigate thediversification of early eukaryotes [1]. Following the first appearance of red algae in the LateMesoproterozoic, other (morphological or molecular) fossils of crown groups are recordedduring the Early Neoproterozoic, including green algae, sponges, amoebozoa and possiblyfungi. Other microfossils also includes unambiguous eukaryotes, including several distinctiveforms for that time period, such as the acritarchs Cerebrosphaera buickii ( 820–720 Ma),Trachyhystrichosphaera aimika and T. botula (1100-720 Ma), and the multicellular eukary-otic problematicum taxon Jacutianema solubila (1100–?720 Ma). To further characterizethe taxonomy of these microfossils and to test hypotheses about their possible relationshipsto crown groups, we combine analyzes of their morphology, wall ultrastructure and micro-chemistry, using optical microscopy, Scanning and Transmission Electron microscopy (SEMand TEM), as well as Raman and FTIR microspectroscopy respectively.Cerebrosphaera populations from the Svanbergfjellet formation, Spitsbergen, and from theKanpa Formation, Officer Basin, Australia, include organic vesicles with dark and robustwalls ornamented by cerebroid folds [2]. Our study shows the occurrence of complex tri- orbi-layered wall ultrastructures and a highly aromatic composition [3].The genus Trachyhystrichosphaera includes various species characterized by the presence ofa variable number of hollow heteromorphic processes [2]. Preliminary infrared microspec-troscopy analyzes performed on two species, T. aimika and T. botula, from the 1.1 GaTaoudeni Basin, Mauritania, and from the 1.1 - 0.8 Ga Mbuji-Mayi Supergroup, RDC,indicate a strong aliphatic and carbonyl composition of the wall biopolymer, with some dif-ferences linked to thermal maturity between the two locations. TEM is also performed tocharacterize the wall ultrastructure of these two species.Various morphotypes of the species Jacutianema solubila from the Svanbergfjellet Formation,Spitsbergen and from the Taoudeni Basin, Mauritania, are also characterized with infraredand Raman microspectroscopy as well as with TEM, permitting to test a previous hypothesisproposing that Jacutianema represents part of the life cycle of a Vaucherian alga [4].Deciphering the identity of these distinctive microfossils will improve our understandingof the timing and pattern of eukaryote stem and crown group diversification in the mid-Proterozoic, prior to large “snowball Earth” glaciations and during time of changing oceanchemistry.[1] Knoll et al. (2006) Philos. Trans. R. Soc. B 361 1023-1038 [2] Butterfield et al. (1994)Fossils and Strata 34 82p [3] Cornet et al. (in preparation) [4] Butterfield (2004) Paleobiology30 (2), 231-25

2nd year of PhD (Supervisor: Javaux, Emmanuelle ) preference for oral

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abstract #25

Metallogenesis of supergene manganese deposits -Implications for the understanding of geodynamic inEuropeDEKONINCK Augustin

Université de Namur

Metallogeny aims to reconstruct the genesis and distribution of ore deposits, focusing ontheir relationships in space and time. For decades, Europe is highly dependent on importsof mineral resources. Characterizing and quantifying the petrological, mineralogical andchemical contents of the ores outside and inside Europe enable to recognize their economicpotential. Manganese is a little-known element occurring in natural environments in the formof silicate (e.g. braunite: Mn2+Mn3+6SiO12), carbonate (e.g. rhodocrosite: Mn2+CO3)or oxide (e.g. pyrolusite: Mn4+O2) minerals. It is the 12th abundant element in the earthcrust and one of the “Big Six” elements with a production of about 18 million tonnes peryear (Sverdrup and Ragnarsdottir 2014). It holds a major role in the world market dueto its use as alloys in steelmaking processes (90% of the Mn uses). Supergene weatheringencompasses inorganic and biologically mediated chemical and mechanical processes, leadingto an in situ modification of host-rock properties at surface temperatures in the continentalenvironment. These processes lead to the migration and oxidation of chemical elements, toform new supergene minerals. Because of its three valence states (Mn2+, Mn3+, Mn4+),manganese is highly sensitive regarding the redox potential of such environment, and then(re)concentrates in oxide and/or hydroxide minerals. The formation of weathering profilesis directly linked to large uplift periods that occurred during geological times, providing anatural gradient for meteoric water to percolate and modify ancient rocks or even mineraldeposits. Recording the vertical movements and geodynamic of the earth crust throughtimes in Europe is of great interest to understand the genesis of weathered manganese (andother) deposits. This framework allows us to characterize different manganese depositsrelated to the geodynamic of Europe and North Africa. Hence, we focus our studies onthe mineralogy, petrology, geochemistry and geochronology of deposits located in Morocco,Tunisia, France and Belgium in order to understand: 1) the effect of weathering, 2) theirgenesis, and 3) their link to geodynamic. References. [2014] Sverdrup H, Ragnarsdottir KV.Natural Resources in a Planetary Perspective, geochemical perspectives, v.3 2:228p.

3rd year of PhD (Supervisor: Yans, Johan ) preference for poster

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abstract #11

Nitrous oxide dynamics in sea iceKOTOVITCH Marie


Fluctuations in greenhouse gases (GHGs) concentration alter the energetic budget of theclimate system. There is high confidence that natural systems related to snow, ice andfrozen ground (including permafrost) are affected. Nitrous oxide (N2O) is one of the potentGHG naturally present in the atmosphere, but witch has seen his concentration growingsince industrial era. N2O has a lifetime in the atmosphere of 114 years and a global warmingpotential (GWP) of 298 to be compared to carbon dioxide that has a GWP of 1. N2O is alsodescribe as the dominant ozone-depleting substance emitted in the 21st Century. Yet, thereare still large uncertainties and gaps in the understanding of the cycle of this compoundthrough the ocean and particularly in sea ice. Sources and sinks of N2O are therefore stillpoorly quantified. The main processes (with the exception of transport processes) involvedin the N2O cycle within the aquatic environment are nitrification and denitrification. Todate, only one study by Randall et al. present N2O measurements in sea ice. Randall et al.pointed out that sea ice formation and melt has the potential to generate sea-air or air-seafluxes of N2O, respectively. Study on ammonium oxidation and anaerobic bacterial culturesshows that N2O production can potentially occur in sea ice. Denitrification can act as asink or a source of N2O. In strictly anaerobic conditions, N2O is removed by denitrification.However, denitrification can also occur in presence of O2 at trace level concentrations (<0.2mg L-1), and in these conditions there is a large N2O production. Recent observationsof significant nitrification in Antarctic sea ice shed a new light on nitrogen cycle withinsea ice. It has been suggested that nitrification supplies up to 70% of nitrate assimilatedwithin Antarctic spring sea ice. Corollary, production of N2O, a by-product of nitrification,can potentially be significant. This was recently confirmed in Antarctic land fast ice inMcMurdo Sound, where N2O release to the atmosphere was estimated to 4 µmol.m-2.yr-1.This assessment is probably an underestimate since it only accounts for dissolved N2O whilea significant amount of N2O is likely to occur in the gaseous form like N2, O2 and Ar. Finally,nitrification produces little N2O in oxygenated waters but the N2O production yield fromnitrification strongly increases as O2 levels decrease. Hence, it is not possible to distinguishthe sources of N2O solely based on bulk N2O concentrations or environmental conditions,while deepened knowledge of processes is needed to well understand N2O emissions.

1st year of PhD (Supervisor: Delille, Bruno ) preference for poster

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abstract #9

Iron biogeochemistry under a changing climate: Impacton phytoplankton growth and diazotrophic nitrogenfixationLI Xuefeng


Iron (Fe) plays an essential role in controlling the marine primary productivity and theefficiency of biological carbon pump. Although controversial, Fe is considered as an impor-tant trace element which has a strong link to climate change, the sequestration of atmo-spheric carbon dioxide (CO2) and the global carbon and nitrogen cycles. Oceanic systemsare undergoing continuous modifications at varying rates and magnitudes as a result ofchanging climate. The objective of our research is to evaluate how global climate changeprocesses (dust deposition, sea-surface warming and ocean acidification) affect Fe speciationand bioavailability. Will also be assessed the impact of the latter on the role of Fe in con-trolling biological N2 fixation. Laboratory culture experiments using Chaetoceros socialiswere examined at two temperatures (13◦C and 18◦C) and two CO2 conditions (400 µatmand 800 µatm). The present study demonstrates clearly the influence of ocean acidificationon the release of Fe upon dust deposition. It also shows that dust particles could provide areadily utilizable source of Fe and other macronutrients (dissolved phosphate and silicate)for phytoplankton growth. Elevated pCO2 may have an adverse impact on diatom growth;seawater warming may cause poleward shifts in the biogeographic distribution of diatoms.The impact of Fe on the natural N2 fixation was tested via field incubation experimentsusing natural phytoplankton assemblages in the Bay of Biscay and along the Iberian Mar-gin. N2 fixation rates in oligotrophic waters were greatly stimulated through the additionof dissolved Fe compared to the control, demonstrating the limitation of N2 fixation by Fe.Numerous factors can affect the extent of N2 fixation, but a better understanding of themajor controlling factors is highly required.

3rd year of PhD (Supervisor: LEI CHOU ) preference for oral

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abstract #8

The Split-Band Interferometry as a new Approach tosolve the Phase Unwrapping Offset Problem: Tests onthe Kivu Region using TerraSARLIBERT Ludivine


For many years, Synthetic Aperture Radar (SAR) Interferometry (InSAR) has been widelyused to map topography with a large spatial coverage by exploiting the phase differencebetween two SAR images. Even though this technique is attractive and offers several ad-vantages, the fact that the phase is wrapped on the (-π,π] interval for each pixel of theinterferogram can be a major obstacle to map the true topography. Since the phase ismeasured modulo 2π, the entire number of cycles in the true phase is unknown. Phaseunwrapping consist in recovering this missing integer number of cycles in each point to re-build a continuous and realistic phase surface. However, phase unwrapping methods usuallyattempt to retrieve the phase value of a pixel relative to the others, rather than the absolutephase. This kind of approach induces a 2πn-offset (n integer) in the phase values, whichcan be different for two regions separately unwrapped. The absolute phase must be knownat one point at least to connect such regions and to be able to compare their phase values.Besides, recent sensors like TerraSAR-X, Cosmo-Skymed or Sentinel-1 use wide band signals(100-150 MHz) to reach metric range resolution. Split-Band Interferometry (SBInSAR) ex-ploits such a large bandwidth to split it into sub-bands and generate several lower-resolutionimages from a single SAR acquisition, each being centered on a slightly different frequency.This technique takes advantage of the decomposition into sub-bands of two images con-stituting an InSAR pair to compute a stack of interferograms, each interferogram havinga different central carrier frequency. Scatterers keeping a coherent behaviour in each sub-band interferogram show a phase that varies linearly with the carrier frequency, the slopebeing proportional to the absolute optical path difference. It is then possible to computethe absolute phase on a point-wise basis by using the linear regression parameters. In orderto determine the 2πn-offsets in an interferogram made up of several regions separately un-wrapped, we combined the classical InSAR processing with the Split-Band Interferometryand we performed a statistical analysis of the phase shift distribution. The results wereimproved based on quality estimators (spectral coherence, phase standard deviation, slopestandard deviation) thresholds.

2nd year of PhD (Supervisor: Christian Barbier ) preference for oral

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abstract #2

The effects of the storm events in 2015 on the radiationbelts observed by EPT/PROBA-VLOPEZ ROSSON Graciela

UCL, BISA

With the Energetic Particle Telescope (EPT) on board the ESA satellite PROBA-V, weanalyze the high-resolution measurements of electrons at LEO (820 km). On 17 March2015, a big geomagnetic storm event injected unusual fluxes up to low radial distances inthe radiation belts. EPT electron measurements show a deep dropout at L>4 starting duringthe main phase of the storm, associated to the penetration of high energy fluxes at L valuelower than 2 filling completely the slot region. After10 days, the formation of a new slotaround L=2.8 separates the outer belt from the inner belt extending at other longitudes thanthe South Atlantic Anomaly. This is believed to be a result of enhanced precipitation lossesof energetic electrons due to their interactions with VLF waves in the magnetosphere. Twoother similar events occurred in January and June 2015, again with injection of electrons inthe inner belt, contrary to what was observed in 2013 and 2014. These events and the EPTmeasurements help us to better understand the formation of three belts structures.

2nd year of PhD (Supervisor: Pierrard, Viviane ) preference for poster

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abstract #20

Carbon dioxide dynamics in Taal Main Crater Lake, Taalvolcano, PhilippinesMAUSSEN Katharine

ULB

Taal Volcano is a complex volcano 60km south of Manila, capital of the Philippines. Thevolcano has developed at the centre of a large caldera, filled with Lake Taal. It contains a1.5x1km lake in its largest crater, called the Main Crater Lake (MCL). The MCL is warm (T= 30◦C) and acidic (pH = 3). The chemical composition of the MCL is relatively stable intime, showing variations of less than 10% for most major elements since the early nineties.Its large volume makes the MCL rather inert to changes in fluid input compared to smallercrater lakes. Carbon dioxide flux has been measured regularly since 2008 on MCL and widevariations have been seen ranging from 482 to 4670 Tonnes/day (Arpa et al., 2013). Wetherefore surveyed the MCL with a single-beam sonar to produce images of sublacustrinefumarolic activity, which were analysed for their volumetric concentration in gas bubbleson the lake floor. Individual profiles were interpolated over the entire lake using kriging toevaluate the spatial distribution of fumaroles. Areas with very low fumarole density canclearly be distinguished from more active zones but there is only little variation betweenthe different surveys, which suggests the direct input of gaseous carbon dioxide is only aminor contributor to the total CO2 flux. The dissolved carbon dioxide (pCO2) in the lakewaters was measured in situ by an infrared gas analyser protected by a PTFE membrane.The membrane allows for CO2 exchange while keeping water out. Point measurements ondifferent occasions have indicated the pCO2 is very homogeneous over the entire lake, exceptfor one area in the northeast sector of the lake, close to an hydrothermal alteration zone,which is characterised by significantly higher pCO2 and temperature. Several spots can beseen in this zone where warm CO2-rich waters rise to the surface, and it can therefore beassumed that this is the major source of carbon dioxide to the MCL. A permanent monitor-ing station was installed in MCL starting in 2013, continuously measuring dissolved carbondioxide (pCO2), lake temperature, lake level and various meteorological sensors. pCO2 andtotal CO2 flux are highly correlated. This confirms the hypothesis that most of the carbondioxide is transported to the lake in dissolved state, and allows us to calculate CO2 fluxdirectly, dramatically increasing the temporal resolution of carbon dioxide flux, an impor-tant monitoring parameter. Furthermore, it allows us to see the impact of environmentalparameters like solar radiation and rainfall on carbon dioxide dynamics. References: Arpa,M. C., Hernández, P. A., Padrón, E., Reniva, P., Padilla, G. D., Bariso, E., . . . Solidum, R.U. (2013). Geochemical evidence of magma intrusion inferred from diffuse CO2 emissionsand fumarole plume chemistry: the 2010–2011 volcanic unrest at Taal Volcano, Philippines.Bulletin of Volcanology, 75(10), 747

5th year of PhD (Supervisor: Bernard, Alain ) preference for poster

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abstract #1

Etude dynamique de populations synthétiques de débrisspatiauxPETIT Alexis


The evolution of space debris populations is a hot topic for the whole community of spaceapplica-tions. Since the beginning of the space era, the number of space debris has drasticallyin-creased. This last decade, several fragmentations and collisions, in the LEO region, led toan augmentation of more than 40% of the total number of space debris. Thus, the stabilityof clouds of space debris, the risk of mutual collisions, and the reentry rates are major issuesof the field.

The University of Namur is involved in the study of space debris dynamics, developingtools to propagate orbits, to detect collisions, or to study chaotic behavior. Thanks tothis expertise, we propose now to build huge synthetic populations of hundred thousandsof space debris in order to estimate the safety of the future orbital environment. Indeed,only the largest objects are detectable by optical and radar telescopes and represent a weakpercentage of the total population. We count 13.000 objects with a size upper than 10 cm(catalogued and tracked) but we estimate at 500.000 the objects between 1 and 10 cm andat 30 millions the objects smaller than 1 cm.

Several major obstacles appear. First, the computation time to propagate a huge populationof space debris; thus we develop efficient methods like a symplectic integrator which presentsa re-markable property to (almost) conserve the energy of the system but also allows in-tegrations with large time steps. Second, the collision events require to check N2 pairs,with N the number of objects, increasing the calculation time. An innovative algorithm,developed at the University of Namur, using a method of filters, reduces the number of testsrequired and solves the problem. Third, another challenge is the correct computation of thelow Earth orbits (i.e. under 2.000 of alti-tude) where debris undergo the atmospheric drag,before falling. This force depends on space weather, acting on the atmospheric density, andthe debris ballistic properties are difficult to fore-cast or to evaluate. Four, our knowledgeabout the real population of space debris is incomplete, the creation of a final syntheticpopulation with the same global properties as the real one is a great challenging option.The main way consists in using different models of fragmentation based on power laws tocreate cloud of space debris calibrated on several kinds of observations. The largest debris,identified and tracked, punctual surveys of the smallest objects, and measures in-situ of thespace debris flux should help us in this calibration task.

2nd year of PhD (Supervisor: Lemaitre, Alexis ) preference for oral

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abstract #7

Concentrations of nitric acid and ozone in thestratosphere through satellite observationsRONSMANS Gaétane


The main objective of the thesis is to understand the behaviour of nitric acid (HNO3) andozone (O3) in the stratosphere. Both these species are key components of the stratosphereand we aim at identifying and quantifying the processes influencing their spatial and tem-poral variability. The measurements are made through satellite observations and the dataare retrieved thanks to a software developed at ULB (FORLI, Fast Optimal Retrievals onLayers for IASI). The work so far has focused on HNO3, which is one of the main speciesinvolved in the stratospheric ozone cycles. Until recently, the distribution of HNO3 in thestratosphere was available only from limb-sounding instruments, such as MLS, MIPAS orACE-FTS. The IASI nadir looking thermal infrared instrument is now providing HNO3concentration distributions with unprecedented spatial and temporal sampling since 2007.In this presentation we will briefly review the IASI observational capabilities for HNO3 (interms of vertical sensitivity and errors) and compare the IASI retrieved profiles and columnsto those obtained from correlative measurements from ground-based FTIR instruments atseveral sites (validation study). We will discuss the global distributions of HNO3 seen fromIASI with emphasis on the temporal (seasonal and inter-annual) variability at tropical, midand polar latitudes. The possibility to infer distributions with IASI both day and night,and to investigate chemical processes thanks to the simultaneous measurements of HNO3with other species (O3; sulphate aerosols) will be highlighted. Preliminary results from asimple multivariable regression model, including amongst other parameters solar flux andQBO variability, applied to several years of IASI data will also be shown.

2nd year of PhD (Supervisor: Coheur, Pierre-François ) preference for oral

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abstract #13

Quantifying the uncertainty of CO2 exchange at theair-water interface related to the formulation of the gasexchange velocity in the open oceanROOBAERT Alizée


In the land-ocean aquatic continuum (i.e. lakes, rivers, estuaries and ocean), the quantifi-cation of air-water CO2 exchange (FCO2) is still characterized by large uncertainties partlydue to the lack of agreement over the parameterization of the gas exchange velocity (k).Although the ocean is generally regarded as the best constrained system of the continuumbecause k is mostly controled by the wind speed and the gradient of partial pressure in CO2(pCO2) at the air-water interface, numerous formulations are still currently used, leading topotentially large differences in FCO2. Here, we compare several polynomial forms of k-windspeed relationships and use Monte Carlo simulations over the entire range of observed windspeed to better identify which formulations diverge the most from the others and for whichwind conditions. Theses simulations use the Rayleigh distribution for the wind speed and adistribution taken from a 30 years pCO2 climatology for the open ocean (Landschützer et al.,2015). Those pCO2 are continous 1 degre resolution maps producted by a 2 steps artificialneural network from measured pCO2 from the SOCAT database (Baker et al.,2014). Ourfirst results indicate that high wind speeds (>14 m s-1), which cumulated frequencies ac-count for less than 6% of all observed wind speed, contribute to roughly a forth of the globaloceanic FCO2 and, for this range of wind speeds, the uncertainty induced by the choice offormulation for k is maximum ( 50%). Additionnally, our approach can be generalized toother compartments of the land-ocean aquatic continuum by taking into account the systemspecific environemental drivers contributing to the forumation of the gas exchange.

References : 1. Landschützer, P. (2015). et al. The reinvigoration of the Southern Oceancarbon sink, Science, 349, 1221-1224. doi: 10.1126/science.aab2620 2. Bakker, D. C. E. etal. (2014) An update to the Surface Ocean CO2Atlas (SOCAT version 2), Earth SystemScience Data, 6, 69–90, doi:10.5194/essd-6-69-2014.

2nd year of PhD (Supervisor: Regnier, Pierre ) preference for poster

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abstract #23

Design and Modelization of a convex grating forhyperspectral imager: spectral optimization based onfree form profileSABUSHIMIKE Bernard

ULG

For hyperspectral imaging, diffraction gratings based spectrometers agree much more withtheir high spectral resolution and optical performance that can be achieved. Among thespectrometers used gratings, the Offner type spectrometers offer a lot of advantages. Forspectrometry, one successful approach to achieving excellent grating imaging spectrometerperformance in a compact optical system has been to employ convex grating in Offnerconfiguration. In this paper, we propose a design and modelization of a convex grating forhyperspectral imager using the multi-blaze method. This method is used if the spectral bandis too wide to use a diffraction grating with a single blaze to optimize a diffraction gratingin a fixed order. In this case, the grating is divided into different sections and each sectionhas its own blaze wavelength and consequently its own depth and blaze angle which givesthe character free form to grating lines. Another method we use alone or in combinationwith the previous one in the optimization of the diffraction gratings is the dual angle profile.This method consists in using a profile whose facet has two different slopes that is to say twoblaze angles. It is a method that can be used for example to optimize a diffraction gratingsimultaneously in two diffraction orders. Modeling tools we use are the scalar and rigoroustheories. The scalar theory is valid for a ratio of the grating period to the wavelength greaterthan or equal to 10. This condition is met over the entire spectral band that goes from 0.7microns to 5 microns as the grating period is 50 microns. We show in this paper using asingle blaze wavelength that PCGrate rigorous theory gives the same results as the scalartheory to a low incidence and that this spectral band cannot be covered with the desireddiffraction efficiency in the first order, hence the use of multi-blaze solution. We also knowthat there may be errors in grating manufacturing. Thus we built realistic profiles flattenedat the top and rounded bottom grooves for each blaze to show the impact of these errorson the diffraction efficiency. The calculation of the diffraction efficiency, by the rigoroustheory PCGrate, of grating designed with these profiles shows that the diffraction efficiencydecreases compared with that of the grating with ideal profiles. The major disadvantagewhen working with grating is their sensitivity to polarization. In reality the TE and TMdiffraction efficiencies are different. We have in this paper studied the degree of polarizationof both single blaze and multi-blaze grating each time using the realistic and ideal profiles.The scalar theory considering only one electromagnetic component, we used only the rigoroustheory for the study of sensitivity to polarization.

3rd year of PhD (Supervisor: Serge Habraken ) preference for oral

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abstract #21

Diagenetic imprints on saddle dolomites and calcitesinduced by hydrothermal fluids in Bekhme Formation,Upper Cretaceous, NE KurdistanSALIH ALKURDI Namam

ULB-Brussels

Partly dolomitized Upper Cretaceous Bekhme Formation is studied from three outcrops(Spelek, Sulauk A and B) integrating fieldwork, petrography, CL, SEM, geochemistry andfluid inclusion microthermometry. Petrological study indicates that early diagenetic dolomitesfrequently formed small-medium size, planar-s crystals. Saddle dolomites and blocky calciteswere related to an aggrading process associated with hydrothermal fluids, leading to geodicdolomites and calcites during mesogenesis. An ultimate telogenic process with calcretiza-tion of the rocks ended the diagenetic evolution of the Bekhme Formation in Spelek. Thissection is highlighted by strongly depleted δ18O (-6.3‰ to -17.5‰) and δ13C (2.3‰ to-9.7‰) values. The δ18O values in Sulauk A & B sections are less negative with a smallerrange, their δ18O and δ13C values range from (-6.7‰ to - 10.2‰ and 0.0‰ to 2.1‰, re-spectively). Microthermometry results point out that homogenization temperatures in thehydrothermal minerals vary from 85◦C to 190◦C in the Bekhme Formation. The three sec-tions record a considerable range of salinity (15.8 to 25% eq. wt%NaCl-zone I) suggestingthat calcite and dolomite precipitated from basinal brines. As these high salinity fluctuationsoccur within the same range of homogenisation temperatures in the hydrothermal minerals,a fault-derived hot fluid channeled through the Bekhme Formation after passing throughtwo oil source rocks is proposed. In contrast to the Sulauk sections, the Spelek section, inaddition to be fed by high salinity fluids, is characterized by a very low saline fluid (0.2 to2.6 eq.wt.% NaCl-zone II). This zone is associated with secondary single phase liquid oilor liquid aqueous inclusions, which is consistent with the late diagenetic calcrete products.Its δ18O and δ13C values are also depleted. These data are consistent with the presenceof meteoric water under low temperature (< 50◦C). Two upward and laterally hydrocarbonmigrations affected the Bekhme Formation. The first migration is inferred from 2-phase(liquid+vapour) and 3-phase (liquid oil+ aqueous liquid + vapour) inclusions trapped incarbonates coeval with the hydrothermal fluids. The second migration, only recorded inthe Spelek section, is related to single phase secondary oil inclusions, thus with low tem-perature inclusions. This study highlights two different diagenetic styles. The first startedwith early dolomitization of a former matrix (eogenesis) and ended with the opening offractures by saddle dolomititic and calcitic precipitation in a shallow deep diagenetic setting(mesogenesis). The second style, only present in the Spelek, suffered a telogenetic evolu-tion with pedogenic products. These results could have broader implications at a regionalscale in order to consider the Bekhme Formation as a potential oil reservoir despite diffusehydrocarbon seepage can also occur along the fault-controlled hydrothermal dolomitization.

3rd year of PhD (Supervisor: Preat Alain ) preference for oral

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abstract #3

Formation of giant planetary systemsSOTIRIADIS Sotiris

naXys, University of Namur

Observational evidence shows that the orbits of extrasolar systems are more various than thecircular and coplanar ones of the Solar system. The generally accepted formation scenario ofthe Solar system is unfit to explain these diversified parameters, and a study of the formationof giant planetary systems is therefore essential. The interactions between the planets andtheir natal protoplanetary disc play an important role in sculpting a planetary system. Wefollow the orbital evolution of three giant planets in the late stage of the gas disc, emphasizingthe combined action of the gas disc and planet-planet scattering during the disc phase. Inparticular, we investigate the influence of the eccentricity and inclination damping due toplanet-disc interactions, on the final configurations of the systems. We present the resultsof 10000 numerical experiments, exploring different initial configurations, planetary massratios and disc masses. The population of planetary systems of our simulations matchesthe observed semi-major axis and eccentricity distributions. Most of the systems are foundwith small inclinations at the dispersal of the disc. Nevertheless, a significant fraction( 10%) of non-coplanar systems are formed, despite the strong inclination damping exertedby the disc. In future observations, this percentage could help to discriminate between theformation scenarios.

3rd year of PhD (Supervisor: Libert, Anne-Sophie ) preference for oral

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abstract #32

Mineral control on calcium isotopic fractionation inplanetary mantle reservoirsVALDES Maria

Université libre de Bruxelles

Calcium (Ca) isotopes are ideal tracers of the evolution of the interiors of rocky planetsand can help us explore the role of fractional crystallization and crystal segregation in theestablishment of mantle reservoirs (e.g. terrestrial, lunar). Not only does Ca, a refractorylithophile element, allow us to circumvent any issues related to impact-induced volatiliza-tion (which fractionates more volatile isotopes (e.g. Zn [1]), Ca is also a major element andhighly abundant in some samples, even those that are particularly depleted in trace elementscommonly used to investigate planet interiors. Notably, Ca, along with many other elements(e.g. Mg, Fe; [2-3]) has recently been shown to exhibit mass-dependent isotopic fraction-ation among co-existing minerals within terrestrial mantle xenoliths. Chen et al. (2014)showed that δ44Ca values for bulk mantle xenolith samples vary from 0.81 to 1.25 ± 0.10 ‰(2sd) and that olivine and orthopyroxene in xenoliths are isotopically much heavier than co-existing clinopyroxene [4]. Given these recent observations, we aim to investigate the mineralcontrol on mass-dependent fractionation of Ca isotopes among mantle reservoirs in order totrace reservoir development and evolution. For this, we are investigating the Archean Guelbel Azib ultramafic-mafic-anorthosite (UMA) layered complex in the West African cratonof Mauritania. This complex is composed of ultramafic cumulates, chromitites, gabbros,leucogabbros and highly calcic anorthosites metamorphosed under amphibolite and gran-ulite grades. The previous petrological observations [5] will be coupled with a geochemicalapproach based on Ca isotopic analyses of mineral separate and whole-rock samples from thecomplex. Such analyses will provide a more detailed picture of how crystallization affectedthe isotopic evolution of this particular layered complex, which in turn will lend us a deeperunderstanding of general planetary interior evolution.

[1] Paniello, R.C. et al. (2012). Nature Geoscience 490: 376-379. [2] Liu, S.A. et al. (2011).EPSL 308: 131–140. [3] Macris et al. (2015). GCA 154: 168-185. [4] Chen et al. (2014).Goldschmidt 2014 Meeting, #3940: [5] Berger et al. (2013). Precambrian Research 224:612-628.

2nd year of PhD (Supervisor: Debaille Vinciane ) preference for oral

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abstract #10

Annual dynamics of CO2 partial pressure within bulk seaice and related CO2 fluxes at Cape Evans (Antarctica)VAN DER LINDEN Fanny


Sea ice is a biome actively participating in the regional cycling of CO2 as both a source anda sink at different times of the year. In the frame of the YROSIAE project (Year-RoundOcean-Sea-Ice-Atmosphere Exchanges), annual dynamics of sea ice pCO2 was comparedwith CO2 fluxes measured by automated accumulation chambers at Cape Evans (Ross Is-land, Antarctica). Results confirmed a general trend of brine pCO2 supersaturation withrespect to the atmosphere during the late winter (concentration of dissolved inorganic car-bon - DIC - in brine and brine expulsion in the brine skim) leading to CO2 degassing, andundersaturation during the spring (carbon-uptake by autotrophs and brine dilution) leadingto atmospheric CO2 uptake. Despite high primary production at the bottom of the ice inspring, DIC profiles suggest that sea ice as a whole appears to be net heterotrophic. Still,sea ice absorbs CO2 from the atmosphere, as a result of physical processes. Some variabilityin the CO2 fluxes (both in magnitude and sign) could not be explained by variability insea ice pCO2 but rather seemed driven by variability in atmospheric conditions and seaice surface properties. For instance, in late spring, CO2 fluxes showed a diurnal variability(from CO2 degassing to uptake) related to atmospheric temperature variations. Large andepisodic CO2 fluxes were systematically positively correlated with strong wind events, andlarge CO2 degassing was observed over thin, wet and salty snow cover.

1st year of PhD (Supervisor: Delille Bruno ) preference for poster

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abstract #26

Characterization and genesis of Cu-Pb-Zn-V supergeneore deposits in the Oriental High Atlas (ou Arfa,Morocco)VERHAERT Michèle


Renewed interest has been shown to supergene ore deposits over the last years, due to theirhigh metal contents, their easier extraction process, their softened host rocks, and theirlocation close to the surface.The deposits of Jbel Klakh (Cu) and Jbel Haouanit (Pb-Zn) are located at the northern edgeof the Oriental High Atlas (Morocco). This intracontinental mountain belt is the result oftwo major events: the Triassic-Liassic rifting and opening of the Atlantic and Tethys Oceans,and the Cenozoic uplift caused by the convergence of the African and Iberian plates. Themineralized veins are hosted in dolostones of Jurassic age.The Jbel Klakh deposit is characterized by the succession, from the bottom to the top, offour zones defined by mineral assemblages: the primary sulfides in the protolite, the sec-ondary sulfides in the cementation zone, the oxidized minerals in the saprolite, and the iron(hydr-)oxides in the laterite. Three phases of weathering and of supergene mineralizationhave been identified. The hypogene sulfides (mostly chalcopyrite) are first replaced by sec-ondary sulfides (bornite, digenite, chalcocite, covellite), when reduced and acidic conditionsare prevalent. Later, as the environment became more oxidizing and neutral, thanks to thedissolution (buffering) of the carbonate host rocks, malachite, azurite and other oxidizedminerals formed by recombination of metallic cations and ligands originating from the dis-solved host rocks and oxidized sulfides. Finally, late calcite and dolomite precipitated underneutral conditions. Iron (hydr-)oxides (goethite, hematite) have been precipitating alongthe whole sequence.Typical calamine minerals are observed at Jbel Haouanit; three steps of weathering arealso considered. The hypogene galena is firstly replaced by anglesite in locally acidic en-vironments. Cerussite precipitates later, at the same time as sphalerite is weathered insmithsonite, under oxidizing conditions. Smithsonite is often rapidly replaced by hydroz-incite. Again, late calcite and dolomite are the last minerals to precipitate, and iron (hydr-)oxides are found in the whole sequence. Occurrences of Cu minerals and of a Cu-Pb-Znvanadate (mottramite) have also been observed close to the Pb-Zn mineralization.A relation may be established between these weathering phases and the tectonic and climaticevolution of the High Atlas. The precipitation of the hypogene sulfides is most probablyrelated to the Triassic rifting. The hypogene ores and their host rocks were exposed to theoxidizing atmospheric conditions and precipitations during the Cenozoic uplift(s), leadingto their weathering. During this period, the alternation of long arid and short wet periodsmay have provided the optimal conditions for the concentration of metals in solution andthe precipitation of massive supergene ores.

1st year of PhD (Supervisor: Yans, Johan ; Bernard, Alain ) preference for poster

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abstract #5

Contribution of vegetation fires to atmospheric ammoniaemissions: time series and global distributions from theIASI sounder.WHITBURN Simon


Vegetation fires emit large amounts of ammonia (NH3) in the atmosphere. Excess NH3 canaffect the environment in many ways: eutrophication of the ecosystem, soil acidification andloss of plant diversity. Despite the numerous studies achieved in the past decades to betterquantify NH3 emissions from biomass burning, the uncertainties remain still large. NH3satellite measurements are now available for a few years and offer the possibility to betterassess the NH3 atmospheric budget, its spatial distribution and long-term trends. Globalbi-daily NH3 total columns can in particular be derived from the IASI infrared sounderonboard MetOp satellites using a retrieval method developed at the Université Libre deBruxelles (ULB). We first show global distributions of NH3 (molec.cm-2) and we discussabout some major hotspots related to agriculture and vegetation fires. We next focus ourattention on the intense fires which were devastating Indonesia in fall 2015. The region ofIndonesia is characterized by peat soils, whose burning is thought to emit large amountsof NH3. We analyze time series of daily mean NH3 total columns (molec cm-2) over theregion and derive total emissions using a simplified box model. In support to our analysis,we perform a similar estimation of the emissions for carbon monoxide (CO), also measuredby IASI.

3rd year of PhD (Supervisor: Coheur, Pierre-François ) preference for oral

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uniter phd day 26 february 2016 abstract book · cerebrosphaera populations from the...

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