Room 101, Kogi-to Bldg, Faculty of Science
Abstract
Understanding the composition of the Earth's core is integral to answering many questions in the Earth Sciences, including the mechanisms, timing, and conditions of core formation, and also has important implications for the composition of the Earth's mantle. Because of the remote nature of the core, seismic profiles of the Earth's interior must be relied upon to determine the velocity and density structure of the deep Earth, and these profiles must then be compared with experimental data on candidate core phases at extreme conditions. I will present results of recent experimental studies of the physical properties of several iron/light-element alloy (ILEA) compounds at high pressures and temperatures in order to quantify their behavior under extreme conditions using both synchrotron-based static compression experiments in Diamond Anvil Cells (DAC) and combined ultrasonic interferometry and synchrotron X-radiation in a Multi-Anvil Cell (MAC). The results of these two different types of experiments were remarkably similar, showing much better agreement than has ever before been seen between MAC and DAC experiments on these types of materials. A density-velocity-compositional model was then constructed for the solid inner core by accommodating for the recent evidence from these ultrasonic experiments that iron minerals may not follow a linear "Birch's Law" density-velocity relationship. In addition, this model was then compared to existing cosmochemical and experimental data, as well as element partitioning studies, to form a more comprehensive model of the Earth's inner and outer cores. The results of this experimental model are also in excellent agreement with geochemical constraints on light-element content of the core, and can begin to reconcile the density deficits observed in the liquid outer core. This is the first model to have good agreement with all the parameters of PREM in the inner core, including r, VP, VBulk, VS, KS, and G, and it also resolves most of the density deficit in the liquid outer core. In this seminar, I will present the results of these experiments and how they led to the development of this model, and discuss the current work and future directions of this exciting research project.
For inquiry：Taku Tsuchiya TEL:（089）927-8198
E-mail takut@sci.ehime-u.ac.jp
