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DCO - Deep Carbon Observatory
Focus on the properties of carbon under extreme conditions and the physical and chemical processes that govern its behavior in Earth.
Deep Carbon is an essential part of long-term global geochemical cycles and has likely played an essential role in the origin of life, in the evolution of our atmosphere, and in the origin and distribution of some of our most widely used energy and mineral resources.
One of the challenges in understanding the physics and chemistry of deep carbon is that the relevant range of pressure and temperature is vast. The production of diamonds in the mantle reveals that significant amounts of carbon exist at least up to pressures of 5 GPa (150 km depth) and about 1500 K. Subduction likely carries carbon-bearing phases to much greater depth, and carbon has been proposed as a major constituent of Earth's core (136 GPa, 2890 km depth, 4000 K). A key point is that carbon throughout this wide regime may be important to the global geochemical cycles that produced our surface environment. One reason so little is known of the deep carbon cycle is our ignorance of the basic physics and chemistry of carbon at the pressure and temperature conditions of the interior. In order to fill this gap of knowledge, "Physics & Chemistry" (DCC) DCO directorate coordinates a campaign of experimental, theoretical, and modeling focused on the thermodynamics of deep carbon including phase stability and physical properties in systems containing C-H-O fluids and their interactions with silicate melts, and carbonate, silicate, oxide, and metallic minerals, the dynamics and transport properties of C-bearing geo-fluids including C-H-O fluids, and C-bearing silicate melts, the role of surfaces in controlling the rates of reaction between C-rich material and minerals and in stabilizing novel forms of carbon in the deep Earth.
The activity of the DCC directorate will be focused on mineral-fluid interactions under extreme conditions and on surface and interface science. Understanding and controlling interfacial processes for carbonates and other C-bearing minerals and colloids, particularly at the high pressure typical of Earth's interior, is crucial to many DCO objectives. C-bearing minerals such as calcite, graphite, and magnesite interact with H2O-CO2-hydrocarbon fluids during extraction of fossil fuels from deep oil reservoirs or from high-pressure clathrate deposits during geothermal energy production, at subsurface nuclear waste sites (deep boreholes), and most importantly during the geologic sequestration of CO2. In addition, interfacial interactions involving C species in the crust and mantle are relevant for processes such as the conductivity of the lower crust, the wetting behavior and extraction of carbonatite magmas in the upper mantle, deep biomineralization, and possibly for core-lower mantle interactions. The groups participating to the project plan to combine experiments and ab-initio calculations to characterize interfacial processes and pursue the following, specific objectives:
- Determine speciation, nature of bonding, the nature and role of the electric double layer, and complexation of C-species and of other cations and anions at solid C-based and silicate interfaces, and in interfacial fluids.
- Understand how properties at confined interfaces (buried interfaces) differ from those of free fluid/solid interfaces.
- Determine (and ultimately control) surface free energies of C-phase/fluid interactions in the crust and mantle as a function of P-T-X and stress state.
- Determine how the physical and transport properties of C-phase colloids vary as a function of P-T-X.
- Understand how the presence of a silicate rock surface impacts pathways and product distribution of chemical reactions between C-fluid components.
- Determine the role of surface energies in stabilizing novel forms of carbon, including nanodiamond.
Within the project framework the activity of the LENS group will regard the experimental characterization of the formation and decomposition dynamics and of the reactivity of clathrate hydrates at high pressure. These systems are indeed extensively studied at ambient pressure and up to the MPa pressure range, whereas knowledge of their high pressure properties (GPa range) is limited. Taking advantage of the Diamond Anvil Cell technology the high pressure properties of methane hydrate and of other hydrocarbons hydrates will be performed by using different spectroscopic tools including time-resolved pump-probe techniques utilizing ultrashort laser pulses.
Only publications with LENS-affiliated authors are listed and for now there is no one.
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Elenco Siti Tematici