Annette Kleppe
Extreme Conditions
Annette Kleppe is a Postdoctoral Research Associate at the Extreme Conditions Beamline I15 and Visiting Senior Research Fellow in the Department of Earth Sciences at the University of Oxford. She studied Physics at the University of Essen, Germany, and obtained her D.Phil. from the University of Oxford. Her research interests cover the many fields of high-pressure high-temperature Earth and Planetary Science. Recently her work has focused on hydrogen in the Earth’s deep mantle and core.
Email: Annette Kleppe
Tel: +44 (0) 1235 778672
Beamline I15: Extreme Conditions
Key Research Areas
High-pressure physics and chemistry, Earth and planetary interiors, diamond-anvil cell, synchrotron X-ray diffraction, micro-Raman spectroscopy.
Current Research Interests
The majority of minerals in the Earth are hidden at great depths under high-pressures and high-temperatures. The behaviour of these minerals controls the large-scale processes of our planet, which are manifested at the surface by volcanism, earthquakes, and plate tectonics. I explore the physical properties and crystal structures of geological materials under extreme pressures and temperatures in order to understand the structure, composition and formation of the Earth’s mantle and core.
In the laboratory I create the conditions that prevail within the Earth’s deep interior in a diamond-anvil cell: Two brilliant-cut diamonds under a load of several tonnes compress a sample, a few micrometers in size, up to pressures of the Earth’s core (360 GPa = 3.6 million atm). Simultaneous high-temperatures (up to 4000 K) are achieved by focusing high-power infra-red laser beams through the diamond-windows on the sample. I study changes in structure and bonding, and phase transformations of materials in-situ under high-pressures and/or temperatures with synchrotron X-ray diffraction techniques and micro-Raman spectroscopy.
My research here at Diamond will concentrate on deep Earth and planetary materials such as silicates, metals and molecular solids. One of my research projects focuses on the Earth’s core: Iron, Fe, is the main constituent of the Earth’s core. The pressure of the core is known within a percent (329 GPa at the inner core boundary, 136 GPa at the core-mantle boundary) but its temperature is unknown within at least 2000 K at about 330 GPa. However, it is crucial to know the core’s temperature accurately because it is a key element in predictions of the internal heat budget of the Earth, the heat flow to the surface and models of the geo-dynamo. A first-order constraint on the temperature of the core is the melting temperature of iron, which defines the position of the boundary between the solid inner and liquid outer core. I am investigating the melting curve of e-Fe to pressures in the 100-200 GPa range and the structure of liquid iron using the advanced X-ray diffraction set-up at I15 and developing with the I15 team an integrated double-sided laser-heating system for the diamond-anvil cell.
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| Figure: Cross section through the Earth showing the major division between solid and liquid inner core and ceramic mantle. Inset bottom left: Two opposed diamond-anvils (0.8 mm tip) compressing a thin metal sheet to form the sample chamber. |
Selected Publications
- Raman spectroscopic studies of hydrous and nominally anhydrous deep mantle phases, A.K. Kleppe and A.P. Jephcoat, Geophysical Monograph Series 168: Earth’s Deep Water Cycle, 69-93 (2006).
- High-pressure Raman spectroscopic studies of hydrous wadsleyite II, A.K. Kleppe, A.P. Jephcoat, and J.R. Smyth, American Mineralogist, 91: 1102-1109 (2006).
- Crystal chemistry of wadsleyite II and water in the Earth’s interior, J.R. Smyth, C.M. Holl, F. Langenhorst, H.M.S. Laustsen, G.R. Rossman, A.K. Kleppe, C.A. McCammon, T. Kawamoto, and P.A. van Aken, Physics and Chemistry of Minerals, 31: 691-705 (2005).
- High-pressure Raman spectroscopic studies of FeS2 pyrite, A.K. Kleppe and A.P. Jephcoat, Mineralogical Magazine, 68: 433-441, (2004).
- Novel high-pressure behaviour in chlorite: A synchrotron XRD study of clinochlore to 27 GPa, M.D. Welch, A.K. Kleppe, and A.P. Jephcoat, American Mineralogist, 89: 1337-1340 (2004).