ERC FUNDED PROJECTS

Plate tectonics characterises the complex and dynamic evolution of the outer shell of the Earth in terms of rigid plates. These tectonic plates overlie and interact with the Earth's mantle, which is slowly convecting owing to energy released by the decay of radioactive nuclides in the Earth's interior. Even though links between mantle convection and plate tectonics are becoming more evident, notably through subsurface tomographic images, advances in mineral physics and improved absolute plate motion reference frames, there is still no generally accepted mechanism that consistently explains plate tectonics and mantle convection in one framework. We will integrate plate tectonics into mantle dynamics and develop a theory that explains plate motions quantitatively and dynamically. This requires consistent and detailed reconstructions of plate motions through time (Objective 1). A new model of plate kinematics will be linked to the mantle with the aid of a new global reference frame based on moving hotspots and on palaeomagnetic data. The global reference frame will be corrected for true polar wander in order to develop a global plate motion reference frame with respect to the mantle back to Pangea (ca. 320 million years) and possibly Gondwana assembly (ca. 550 million years). The resulting plate reconstructions will constitute the input to subduction models that are meant to test the consistency between the reference frame and subduction histories. The final outcome will be a novel global subduction reference frame, to be used to unravel links between the surface and deep Earth (Objective 2).

2 499 010 €

Start date: 2011-05-01, End date: 2016-04-30

The Earth's climate system contains a highly complex interplay of numerous components, such as atmospheric greenhouse gases, ice sheets, and ocean circulation. Due to nonlinearities and feedbacks, changes to the system can result in rapid transitions to radically different climate states. In light of rising greenhouse gas levels there is an urgent need to better understand climate at such tipping points. Reconstructions of profound climate changes in the past provide crucial insight into our climate system and help to predict future changes. However, all proxies we use to reconstruct past climate depend on assumptions that are in addition increasingly uncertain back in time. A new kind of temperature proxy, the carbonate ‘clumped isotope’ thermometer, has great potential to overcome these obstacles. The proxy relies on thermodynamic principles, taking advantage of the temperature-dependence of the binding strength between different isotopes of carbon and oxygen, which makes it independent of other variables. Yet, widespread application of this technique in paleoceanography is currently prevented by the required large sample amounts, which are difficult to obtain from ocean sediments. If applied to the minute carbonate shells preserved in the sediments, this proxy would allow robust reconstructions of past temperatures in the surface and deep ocean, as well as global ice volume, far back in time. Here I propose to considerably decrease sample amount requirements of clumped isotope thermometry, building on recent successful modifications of the method and ideas for further analytical improvements. This will enable my group and me to thoroughly ground-truth the proxy for application in paleoceanography and for the first time apply it to aspects of past climate change across major climate transitions in the past, where clumped isotope thermometry can immediately contribute to solving long-standing first-order questions and allow for major progress in the field.

1 877 209 €

Start date: 2015-08-01, End date: 2020-07-31

"The eruption of volcanoes appears one of the most unpredictable phenomena on Earth. Yet the situation is rapidly changing. Quantification of the eruptive record constrains what is possible in a given volcanic system. Timing is the hardest part to quantify. The main process triggering an eruption is the refilling of a sub-volcanic magma chamber by a new magma coming from depth. This process results in magma mixing and provokes a time-dependent diffusion of chemical elements. Understanding the time elapsed from mixing to eruption is fundamental to discerning pre-eruptive behaviour of volcanoes to mitigate the huge impact of volcanic eruptions on society and the environment. The CHRONOS project proposes a new method that will cut the Gordian knot of the presently intractable problem of volcanic eruption timing using a surgical approach integrating textural, geochemical and experimental data on magma mixing. I will use the compositional heterogeneity frozen in time in the rocks the same way a broken clock at a crime scene is used to determine the time of the incident. CHRONOS will aim to: 1) be the first study to reproduce magma mixing, by performing unique experiments constrained by natural data and using natural melts, under controlled rheological and fluid-dynamics conditions; 2) obtain unprecedented high-quality data on the time dependence of chemical exchanges during magma mixing; 3) derive empirical relationships linking the extent of chemical exchanges and the mixing timescales; 4) determine timescales of volcanic eruptions combining natural and experimental data. CHRONOS will open a new window on the physico-chemical processes occurring in the days preceding volcanic eruptions providing unprecedented information to build the first inventory of eruption timescales for planet Earth. If these timescales can be linked with geophysical signals occurring prior to eruptions, this inventory will have an immense value, enabling precise prediction of volcanic eruptions."

1 993 813 €

Start date: 2014-05-01, End date: 2019-04-30

Most changes in mineralogy, density, and rheology of the Earth’s lithosphere take place by metamorphism, whereby rocks evolve through interactions between minerals and fluids. These changes are coupled with a large range of geodynamic processes and they have first order effects on the global geochemical cycles of a large number of elements. In the presence of fluids, metamorphic reactions are fast compared to tectonically induced changes in pressure and temperature. Hence, during fluid-producing metamorphism, rocks evolve through near-equilibrium states. However, much of the Earth’s lower and middle crust, and a significant fraction of the upper mantle do not contain free fluids. These parts of the lithosphere exist in a metastable state and are mechanically strong. When subject to changing temperature and pressure conditions at plate boundaries or elsewhere, these rocks do not react until exposed to externally derived fluids. Metamorphism of such rocks consumes fluids, and takes place far from equilibrium through a complex coupling between fluid migration, chemical reactions, and deformation processes. This disequilibrium metamorphism is characterized by fast reaction rates, release of large amounts of energy in the form of heat and work, and a strong coupling to far-field tectonic stress. Our overarching goal is to provide the first quantitative physics-based model of disequilibrium metamorphism that properly connects fluid-rock interactions at the micro and nano-meter scale to lithosphere scale stresses. This model will include quantification of the forces required to squeeze fluids out of grain-grain contacts for geologically relevant materials (Objective 1), a new experimentally based model describing how the progress of volatilization reactions depends on tectonic stress (Objective 2), and testing of this model by analyzing the kinetics of a natural serpentinization process through the Oman Ophiolite Drilling Project (Objective 3).

2 900 000 €

Start date: 2015-09-01, End date: 2021-08-31