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LABORATOIRE G-TIME

GEOCHIMIE: TRAÇAGE ISOTOPIQUE, MINERAL, ET ÉLEMENTAIRE

GEOCHEMISTRY: ISOTOPIC, MINERAL AND ELEMENT TRACING



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NEWS

4-8 July, 2016: 32nd annual SEGH conference at ULB

We would like to wish you a warm welcome and invite you to join us at the Université Libre de Bruxelles on the 4th-8th July, 2016 for the 32nd annual SEGH conference.

This annual conference of the Society for Environmental Geochemistry and Health provides a forum for international scientists, consultants, regulatory authorities and other practitioners (public health/environmental health) with an interest in the links between environment and health and working in the broad area of environmental geochemistry.

For the 32nd SEGH we are keen to receive contributions on three core themes (Dust and aerosols; Isotopes and speciation; Geochemistry and health) and three special sessions (SpatioTemporal trends of metal contaminants in the atmosphere; Nanoparticles in the environment: Fate and effects; Geochemistry and biomedical issues).

Young scientist contributions are especially encouraged and special awards will be given out by the SEGH for the best poster and talk. We look forward to welcoming you to Brussels in 2016!

More information here: http://segh-brussels.sciencesconf.org/


9 May, 2016: FNRS geochemistry contact group meeting

This year's FNRS geochemistry contact group meeting will be held at ULB. We have three invited speakers:

- Dr. Helen Williams (Cambridge University, Cambridge, UK): "Fe and Zn stable isotopic constraints on slab dehydration and devolatilization processes"

- Dr. David Neave (Leibniz University, Hanover, Germany): "Phenocrysts, xenocrysts, antecrysts and macrocrysts: mush disaggregation in basaltic systems"

- Dr. Olivier Namur (Leibniz University, Hanover, Germany): "Experimental data on Mercury"

...in addition to several speakers from the ULB and VUB. You are welcome at 10:00 in building K at ULB.


May 2016: New publication by group member Ashlea Wainwright available online

Highly Siderophile Element (HSE: Os, Ir, Pt, Pd, Re) concentrations coupled with Rhenium-Osmium (Re-Os) dating of mantle rocks can provide us with a lot of information. Traditionally, these methods have been used for investigating the mantle beneath cratons (the >2.5 billion year old nuclei of some continents). This is because, unlike in other radiometric dating methods, the parent (Re) behaves differently from the daughter (Os). When a melt forms in the mantle, the entire mantle rock is not melted, only the parts that are more ‘incompatible’, this means that some elements are more likely to go into the melt (they are incompatible elements) and others are happy to stay behind (they are compatible). In this system, Re is incompatible and Os is compatible. The other HSE elements also have varying degrees of compatibility, with Os and Ir behaving very compatibly whilst Pd and to alesser extent Pt are incompatible. Ultimately, this allows us to look at a mantle rock and assess if it has been highly depleted by extensive melting but also to date when this happens. As it only requires 15% of the entire rock to melt for all of the Re to be extracted, this locks in the Os composition, which we can compare to chondritic meteorites and derive a model age. By obtaining dates on a number of different samples we can begin to gain an idea about when the mantle melted beneath these cratons and hopefully begin to get an understanding of how and when the cratons formed.

Unfortunately, in reality this system isn't that simple. This is because the HSE are trace elements in a mantle rock, they are generally only found in the parts per billion! That means that they are strongly dependent on mineralogy, and unfortunately for us, the minerals that control them – sulphides and platinum group minerals – can be added to the mantle rock after melting, by other melts! This new paper investigates this mineralogy, with the first ever results of HSE and Os isotopic composition on Pt-Fe- alloys from a cratonic peridotite. These Pt-Fe- alloys are tiny, the biggest is about 0.00008cm across and the smallest 0.0000075cm (a human hair is 0.0017-0.0181cm!). The Pt-Fe- alloys investigated were found as an inclusion within a sulphide, interestingly the main result of the paper shows that despite being an inclusion the alloys have a very different 187 Os/ 188 Os compared to their host sulphide. The only way this can happen is if they have different Re/Os for a long period of time, allowing the parent 187 Re to decay to 187 Os. But as they are inclusions in the sulphide surely they should have the same Re/Os! And this is where the mineralogy becomes important, just as elements are compatible and incompatible in melts and rocks, they are also compatible and incompatible in different minerals. Both Re and Os are compatible in both sulphides and alloys, but they may (and do) prefer the alloy. The paper also details a small experiment the authors performed to check that this was the case. They show that the alloy will have a Re/Os 10 times higher than the sulphide! This is a very important discovery, as a lot of the dating of cratonic mantle rocks has been done by lasering sulphides, but if these sulphides contain alloys, the date obtained will be meaningless, as the alloy will have taken a lot of the Re and not allowed it to affect the sulphide 187 Os/ 188 Os composition. And as these alloys are so small and heterogeneously distributed, they may not be properly (or fully) analysed by the laser. This paper throws in to doubt all of the previously published data for the dating of cratonic mantle, and means that future workers will need to be extra careful about the mineralogy of the sulphides they date, as if any nano-sized alloys are hiding inside the sulphides they will completely change the sulphides age.

Full citation: A.N. Wainwright, A. Luguet, A. Schreiber, R.O.C. Fonseca, G.M. Nowell, J.-P. Lorand, R. Wirth and P.E. Janney (2016) Nanoscale variations in 187 Os isotopic compositions and HSE systematics in a Bultfontein peridotite, Earth and Planetary Science Letters 447, 60-71.


February 26, 2016: Goldschmidt abstracts are due!

G-Time postdoctoral scholar Ashlea Wainwright explains G-Time's current top priority:

"G-Time is going to Japan! The biggest event on the geochemistry calendar, Goldschmidt, is hosted in Yokohama, Japan, in July this year. The deadline is fast approaching and with the majority of the lab going, abstracts have been flying through the air thick and fast. We're going to be covering a wide range of topics and are looking forward to sharing them with the world. Starting with modern volcanics, Ph.D. student Katharine will present her most recent data on gas emissions from Taal volcano in the Philippines; going back in time to 3 billion years ago I will be discussing my first data on the West African Craton and its implications for global processes in the Archean; heading up into space, Ros will show high-precision data on some Martian samples and speculate on the geodynamic history of our red neighbour; and even further afield, Ph.D. student Maria will delve into the complicated and elusive history of ureilites. We are all eagerly looking forward to it!


December 14, 2015: PhD student Maria Valdes is awarded the F.R.S.-FNRS FRIA fellowship!

Maria Valdes is one of four doctoral students to win the FRIA fellowship from the FNRS (Fonds de la Recherche Scientifique, the national fund for scientific research of French-speaking Belgium). She has been awarded funding for three years to support her lunar research.

The F.R.S.-FNRS trains and provides funding to high-achieving graduates who wish to prepare a doctoral thesis in a university of the Wallonia-Brussels Federation.

Congratualations, Maria!


November 11-13, 2015: Paneth Kolloquium in Nördlingen, Germany

G-Time postdoctoral scholar Ashlea Wainwright chronicles the colloquium:

"Nördlingen, a stunning medieval town in Bavaria, Germany, also happens to be situated in the middle of the Ries Impact Crater, which makes it a perfect place for a planetary science meeting. In the years when the Meteoritical Society meeting is outside Europe, the German Mineral Society (DMG) has a small meeting: The Paneth Kolloquium. It is mainly visited by scientists from German universities, but is open to everyone. At the 2016 meeting there were a number of people from France, as well as my colleague Ros and I representing Belgium.

The colloquium was run over three days, with two days of talks and a poster session. Whilst neither Ros nor I presented, we sure learnt a lot! Topics ranged widely, including modelling the formation of proto-planets, the formation of Earth's core, the effects of p-processes, petrology of chondrules and exotic meteorites to name a few! The great thing about small meetings like this is the ability to chat with everybody after the talks and really get to know your fellow scientists. It is also not limited to ust geochemistry, which gives us geochemists a brief (and detailed!) look into how other planetary scientists think and how they view the evolution of the solar system.

Unfortunately, as it was the middle of November, a field trip to explore the Ries Crater wasn't planned as they had been expecting freezing temperatures. But as the weather is wont to do, it turned out to be picture perfect so Ros, myself and my former colleague Maxwell Thiemens (Univerity of Köln) took off to explore. After getting a map and some wonderful advice from the Ries Museum we made our way to some of the more spectacular locations to look for Suevite (an impact rock). Check out the photos we managed to snap before we lost the light.

All in all it was a great little conference with much learnt, whilst making new friends and catching up with old."


November 10, 2015: NASA's CAPTEM grants Maria Valdes' lunar sample request

Hurrah! We're excited to get started on lunar studies!


November 14, 2014: Symposium on Antarctic meteorites and their curation in Belgium: From dinosaurs to meteorites

The Belgian Federal Science Policy Office and the Royal Belgian Institute of Natural Sciences invite you to the Symposium on Antarctic meteorites and their curation in Belgium. Scientific talks will be given throughout the day and in the evening, the permanent accessioning and inauguration of the 18 kg Antarctic meteorite collected by the Belgian Antartic team in 2013 will take place.

Royal Belgian Institute of Natural Sciences: Rue Vautier 29, 1000 Brussels

9:30 AM - 5:00 PM: Scientific talks

5:00 PM - 7:00 PM: Antarctic meteotite inauguration and cocktail reception


October 6, 2014: New PhD student, Maria Valdes, arrives in Brussels!

Having recently completed her Master's degree at Washington University in St. Louis (USA), Maria Valdes will now continue her PhD studies at ULB.

Maria is interested in meteorites and the early evolution of the solar system. At ULB, she will study the early differentiation of the Moon using stable calcium isotopes.

Welcome, Maria!


DATE HERE: Arrival of the TIMS Triton Plus!

Thanks to an ERC starting grant awarded to Vinciane Debaille, we welcome the Triton Plus, which will be dedicated to understanding the evolution of the solar system.

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Welcome, Triton!


June 23 2014: Seminar - Jean-François Moyen of Université Jean Monnet, Saint-Étienne

Jean-François Moyen will present "Geochemistry of Archaean granites: What's the message?" (Room DB5.236; 2 PM).

The Atomia Prize aims to promote the position of women in scientific research and innovation in the Brussels-Capital Region and to increase the scientific vocation of young girls in Brussels.


March 12, 2014: Vinciane Debaille wins the 2014 Atomia Prize!

On the initiative of the Brussels Minister of scientific research, the Brussels-Capital Region has awarded the first annual Atomia prize in the junior category to Vinciane Debaille for her work on understanding the early Earth and planets.

The Atomia Prize aims to promote the position of women in scientific research and innovation in the Brussels-Capital Region and to increase the scientific vocation of young girls in Brussels.

Congratulations, Vinciane!


DATE HERE: Arrival of our new MC-ICP-MS Nu-Plasma II

Thanks to the "Grands Équipements" grant from the FRS-FNRS (PI: Nadine Mattielli), we are pleased to welcome our new high-resolution MC-ICP-MS Nu-PLasma II!

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We're looking forward to all the cool science we'll get to do!


July 2013: Research on early-Earth tectonics published in EPSL!

A new paper, "Stagnant-lid tectonics in early Earth revealed by 142Nd variations in late Archean rocks", is now available in Earth and Planetary Science Letters.

The research, led by scientists at G-Time, and with contribution from Macquarie University, University of Houston, University of California in Davis and the Lunar and Planetary Institute, reveals that the Earth may have been very different in the past compared to what we can see now.

In Earth sciences, it is common to use natural radioactivity, where a parent element decays to a daughter element, to date geological events. Parent elements with short half-lives of radioactive decay that were present when the solar system began to condense into planets, can date very ancient events near or at the time when Earth began to form and undergo differentiation from 4.55 to 4.2 billion years ago. After the parent element goes extinct geological materials can retain the fingerprint of the decay of these short lived radioactive elements. Different materials in the Earth´s mantle that have different abundances of the parent element would then have distinct daughter element abundances as well, and should remain that way unless the different materials mix and become homogenized. An efficient way to generate mixing within the Earth is by convection in the terrestrial mantle, with hot material rising and cold material sinking. This process should have been very efficient during the early times of Earth when our planet was hotter, and the mantle was thus convecting faster.

The team discovered that a small anomaly in 142Nd, resulting from the decay of 146Sm during the first 350 million years of Earth history, was still present in an ancient, 2.7 billion-year-old lava flow located in the Ontario Province, Canada. This is the youngest lava sample presenting this anomaly. This is paradoxical because the anomaly in 142Nd created by ancient geological process during the first 350 million years of the Earth should have been mixed and erased very rapidly by convection, while here, we can still observe this anomaly 1.8 billion years after the formation of the Earth.

By using numerical modeling, the team found out that the mixing process can be slow, even in a highly convective mantle, if tectonic plates are not moving at the surface of the Earth. This has major implications for our knowledge of ancient Earth because this means that the Archean Earth (older than 2.5 billion years) was very different of the present day situation. It was more like the planet Mars, with no plates moving at the surface. Sometimes, a short disruption of this unique plate may have occurred, but the continuous motion of tectonic plates as we observe now probably started after 2.7 billion years. A major change in the functioning of the Earth has already been postulated by other studies, but this is the first time that we are able to apprehend the plate tectonic regime of the Archean by using geochemistry. This finding has also implications for other planets such as Mars, for which the mantle is thus not well mixed and still preserves evidences of the geological processes that formed the planet. The fundamental change in Earth´s tectonics and its link to how the mantle convected also has ramifications to how the continents grew over time. There has been debate on whether the early Earth geologic record of continental growth is preserved or if significant portions are missing from erosion. The Nd isotope models in this study indicate that there is no more room to add additional major crustal growth events in the Archean, so we now have a strong constraint on when crustal growth occurred and can now move forward with the bigger picture of Earth´s evolution.


June 5, 2013: FNRS geochemistry contact group meeting

Invited speaker professor Reto Gieré (Univeristy of Freiburg) will discuss "Mineralogy of the atmosphere: assessing environmental and health impacts of airborne particulate matter" (Room DB5.236; 10:15 AM).

Many other speakers from the ULB, VUB (Vrije Universiteit Brussel), and ULG (Université de Liège) will participate in this day dedicated to the geochemistry of rocks, soil, atmopshere, and meteorites.


May 23, 2013: Welcome to new visitng scientist, Akira Yamaguchi!

Professor Akira Yamaguchi of the National Institute of Polar Research will visit and conduct research at ULB for one month thanks to a mobility grant awarded by ULB. Welcome!


April 26, 2013: Seminar - Liane Benning of Leeds University

Liane Benning will present "How to make a mineral or: the birth and life cycle of a nanoparticle" (Room DB5.236; 12 noon).


December 3, 2012: G-Time goes to Antarctica!

From December 3 to February 12, 6 scientitsts from VUB and ULB will be on the Nansen Ice Field, South of the Princess Elizabeth Station, Antarctica. Their goal? Collecting meteorites!