A coherent picture of water at extreme negative pressure.

International audienceLiquid water at atmospheric pressure can be supercooled to 41 C (ref. 1) and superheated to C302 C (ref. 2). Experiments involving fluid inclusions of water in quartz suggest that water is capable of sustaining pressures as low as 140 MPa before it breaks by cavitation3. Other techniques, for which cavitation occurs consistently at around 30MPa (ref. 4), produce results that cast doubt on this claim. Here we reproduce the fluid-inclusion experiment, performing repeated measurements on a single sample--a method used in meteorology5, bioprotection6 and protein crystallization7, but not yet in liquid water under large mechanical tension. The resulting cavitation statistics are characteristic of a thermally activated process, and both the free energy and the volume of the critical bubble are well described by classical nucleation theory when the surface tension is reduced by less than 10%, consistent with homogeneous cavitation. The line of density maxima of water at negative pressure is found to reach 922:8 kgm3 at around 300 K, which further constrains its contested phase diagram

Experimental study of water and aqueous solutions metastables : implications for the natural environment

L’eau tensile est de l’eau liquide métastable qui persiste dans le champ de stabilité de lavapeur à pression négative, sa durée de vie est finie. Des états de traction de l’eau jusqu’à -1400 baront été mesurés de façon spécifique dans des micro-inclusions intracristallines. La nucléation devapeur (Tn) marque le retour à l’équilibre. Les effets destructeurs liés à la rupture d’états transitoiresd’eau tensile sont observés dans le milieu naturel : explosions phréato-magmatiques, geysers.Modéliser la cinétique de l’eau métastable est fondamental pour gérer les risques qui lui sontassociés. Des inclusions fluides synthétiques (IF) de composition et de densité connues, piégées dansdu quartz, ont été placées dans le champ métastable par refroidissement isochore et leurs gammesde métastabilité ont été mesurées. On montre que la traction maximale de l’eau dans chaque IFdépend de son volume et de sa forme, de la méthode de synthèse de l’IF, de la chimie des solutionsoccluses. Des expériences de durée de vie ont été ensuite réalisées sur des IF placées de 0,5° à10°C au-dessus de leurs Tn. Les 8 IF choisies rende nt compte de la diversité des formes, desvolumes, des densités et gammes de traction observées. Les résultats montrent que la durée de viede l’eau tensile en IF est d’autant plus courte que la traction de l’eau est plus forte. Une loiempirique est proposée qui permet de calculer la durée de vie de la métastabilité pour chaque IF deTn et volume fixés. Par ailleurs, nos données peuvent être rendues compatibles avec la ThéorieClassique de la Nucléation. Nos résultats montrent que l’eau dans les réservoirs poreux naturels peutrester métastable pendant des durées géologiques et ainsi, contrôler les interactions fluides-rochesdans la croûte.Stretched (tensile) liquid water is a metastable liquid which persists at negative pressures inthe stability field of vapour. The lifetime of metastability is limited. Tensions down to - 1400 bar havebeen specifically measured in aqueous inclusions inside quartz monocrystals. Vapour nucleation (Tn)marks the end of metastability. The destructive effects related to vapour nucleation in transientlytensile fluids are observed in nature: phreato-magmatic explosions, geysers. Modelling the kinetics oftensile water is critical in order to control the risks associated to metastable liquids. Quartz-hostedsynthetic fluid inclusions (FI) with known densities and chemistries have been placed into themetastable tensile field by isochoric cooling and their Tn have been measured. We show that thetensile strength of water in individual FI depends on the FI volume and shape, the method used tosynthetize the FI and the fluid chemistry. Experiments on metastability lifetimes have been performedby placing FI at temperatures 0.5° to 10°C above th eir Tn. Eigth FI were chosen that encompass thediversity of FI volumes, shapes, densities, fluid chemistries and tensile strengths. Our results showthat tensile water lifetimes are all the shorter as the trapped water is more stretched. An empiricalkinetic law is proposed that allows the lifetimes of tensile water in FI to be calculated as a function ofthe FI volume and Tn. Our data can also be reconciled with the Classical Nucleation Theory. Our datafinally show that water in natural porous reservoirs can remain stretched for geologically-relevanttimescales. Tensile water can therefore control fluid-rock interactions in the continental crust

Fluid Inclusions, Solid-Solid Transitions in Salt, Ceramics and Minerals to Calibrate the Microthermometric Stage

International audienceThe Linkam THMS 600 microthermometric stage use the fluid inclusions to deliver quantitative paleo-temperatures of subsurface past environments that are critical not only for understanding past climate evolution but also to validate the outcome of predictive models of future climates. In this case, the calibration of the microthermometric stage is the primordial condition to have the most precise temperatures. Thus the calibration of the microthermometric stage is performed from −56 to +573 °C using reversible fusions or solid-solid transitions in standards as salts, ceramics, minerals or synthetic fluid inclusions. The nine transitions measured define a linear calibration curve with negative slope, showing a correction ranging from 1.6 to 16 °C between −60 and 600 °C. The vertical and lateral gradients (temperature bias) are estimated and discussed

Brillouin spectroscopy of fluid inclusions proposed as a paleothermometer for subsurface rocks

International audienceAs widespread, continuous instrumental Earth surface air temperature records are available only for the last hundred fifty years, indirect reconstructions of past temperatures are obtained by analyzing "proxies". Fluid inclusions (FIs) present in virtually all rock minerals including exogenous rocks are routinely used to constrain formation temperature of crystals. The method relies on the presence of a vapour bubble in the FI. However, measurements are sometimes biased by surface tension effects. They are even impossible when the bubble is absent (monophasic FI) for kinetic or thermodynamic reasons. These limitations are common for surface or subsurface rocks. Here we use FIs in hydrothermal or geodic quartz crystals to demonstrate the potential of Brillouin spectroscopy in determining the formation temperature of monophasic FIs without the need for a bubble. Hence, this novel method offers a promising way to overcome the above limitations

Exploring water and other liquids at negative pressure

International audienceWater is famous for its anomalies, most of which become dramatic in the supercooled region, where the liquid is metastable with respect to the solid. Another metastable region has been hitherto less studied: the region where the pressure is negative. Here we review the work on the liquid in the stretched state. Characterization of the properties of the metastable liquid before it breaks by nucleation of a vapour bubble (cavitation) is a challenging task. The recent measurement of the equation of state of the liquid at room temperature down to 26 MPa opens the way to more detailed information on water at low density. The threshold for cavitation in stretched water has also been studied by several methods. A puzzling discrepancy between experiments and theory remains unexplained. To evaluate how specific this behaviour is to water, we discuss the cavitation data on other liquids. We conclude with a description of the ongoing work in our groups