Five topical research groups are organized among the various specialties in ISEI. These study groups will cooperate to advance an integrated, interdisciplinary program of advanced study with a strong international focus. Each research group invites public participation for international joint studies designed to acquire fundamental knowledge about the origin and evolution of planet Earth. To conduct this program at a high international standard, we organized an international advisory/evaluation commitee for selection and evaluation of the joint studies.
In the past ISEI, which was part of the first-generation COE program, participated in many joint research projects, mostly involving scientists from within Japan. There was little support available at that time to promote international collaborations. Under the new COE-21 program, we are able to develop much more extensive international collaboration by providing financial and language support to visiting international scientists.
|Phase Equilibria at Ultra High Pressure Group|
In a last few decades of 20th century, high-pressure Earth science revealed the constitution of the mantle to depths beneath the 660 km discontinuity (to ca. 26 GPa). Interpretation of deep mantle seismic tomography in terms of high-pressure mineral physics has led to firm views that the driving forces of both plate tectonics and mantle plumes, typical outcomes of a cooling dynamic Earth, originate in the lower mantle. From this perspective, high-pressure research in the next decade should be focused on acquisition of experimental information essential for elucidating the dynamic structure of the lower mantle, which includes phase equilibria, element partitioning, equation of state, and physical properties such as thermal conductivity, of the constituent materials. In addition, melting experiments on mantle materials and model primordial Earth materials are necessary for clarifying the early stages of Earth differentiation. These subjects will be explored experimentally up to pressures ca. 100 GPa using innovative new techniques in Kawai-type high-pressure apparatus equipped with sintered diamond anvils and to higher than 100 GPa with the diamond anvil cell. By synthesizing the high-pressure data with the results of the physical property and analytical chemistry groups, we will tackle the following important topics; the fate of descending plate in the lower mantle, the origin and material constituion of the deep geochemical reservoir, energy source of the mantle plume, core formation and mantle fractionation processes in the early Earth.
|Mineral Physics Group|
Our research aims at understanding the processes that control the evolution, dynamic behavior, and structure of the Earth's interior. Toward this end, we experimentally determine the various physical properties of important mantle minerals as follows. 1) Measurement of the elastic properties and their temperature derivatives by means of resonance techniques, which enables us to estimate the lateral temperature variation in the mantle by combining with results from seismic tomography; 2) Determination of thermal expansion coefficients as a function of temperature and pressure, which allows us to estimate the temperature distribution in the mantle; 3) Characterization of the local structures of mantle minerals by means of NMR, FT-IR and Raman spectroscopic techniques, which will assist evaluation of their physical and thermodynamic properties and phase relations; 4) Measurement of the electrical properties of lower mantle minerals as a function of Fe/Mg ratio, temperature, pressure, and redox state.
|Physicochemical Properties of Magmas Group|
Physicochemical information about Earth and planetary interiors are brought to the surface by magmas and locked in volcanic rocks. Therefore, there study provides a unique opportunity to reveal the origin and the evolution of the Earth and planets. In order to read the information, we need to understand the basic physicochemical properties of magmas under the conditions corresponding to the surface to the deep interior of the Earth. To achieve this goal, we focus on following subjects: 1) Development of in-situ observation techniques including Raman, FT-IR, XAFS and XRF at high pressures and temperatures using externally heated diamond anvil cell; 2) Refinement of high pressure X-ray radiography technique for physical properties measurements of magmas, and development of techniques to measure interdiffusion and thermal conductivity of magmas under pressure; 3) Studies of solubility mechanism(s) of volatile components, especially H2O, in the magmas by means of NMR,Raman, FT-IR and XAFS, and their effects to physical properties of the magmas; 4) Establishment of the physical basis for elemental partitioning between magmas and crystals by means of nano-area chemical analysis by the Chemical Analysis group and local structural study of transition-metal and rare earth elements, and determinations of effective partition coefficients by in-situ high temperature observation studies; 5) First-principles molecular dynamics studies of magmas that complement the above experimental studies.
|Group for Geochemical and Cosmochemical Analytical sciences|
The best way to understand the origin and evolution processes of the Earth and the solar system is to analyse comprehensively the elemental abundances and isotopic compositions of bulk samples and constituent minerals. The smaller the area analyzed, the more detailed the information obtained. For this purpose: 1) We refine the established quantitative analytical methods for 55 elements (REE, HFSE, B, S, etc.) in bulk samples using isotope dilution TIMS and ICP-MS to achieve higher accuracy and precision with smaller sample amounts; 2) We develop new analytical methods for elements which we could not determine previously (Be, Ga, Se, etc.); 3) We make reliable standard samples and develop new spot analysis techniques of HR-SIMS for Li, B, O and S isotopes, which are powerful tracers to understand mantle-crust recycling through subduction zones; 4) we apply these techniques to glass inclusions in olivines from OIBs to examine the "mantle-crust recycling" hypothesis; 5) We discuss the elemental transfer at subduction zones and the evolution processes of the mantle and crust by these techniques in combination with radiogenic tracers such as Sr, Ce, Nd, Os, Hf and Pb isotopes; and 6) We undertake the initial analysis of asteroidal samples which will be fetched by the spacecraft of ISAS (the MUSES-C project) to decipher the origin of the planets and meteorites.
For understanding the evolutionary processes governed by the solid Earth, it is essential to comprehend its internal chemical and physical structure as a function of time. Absolute age dating of natural materials using radioactive nuclides is particularly important, as such data provide direct information regarding timing of processes affecting the Earth's evolution at various scales. This group utilizes a comprehensive age dating system, covering the full time frame of the evolution of the solar system, and the dating system is applied to constrain possible models for the origin and evolution of the Earth, in collaboration with other research groups in this program. In the comprehensive age dating system, we have successfully developed the following age dating methods: the K-Ar method using rare gas mass spectrometer, in addition to the Rb-Sr, La-Ce, Sm-Nd, Re-Os, and U-Th-Pb methods using thermal ionization mass spectrometry (TIMS), as well as U-Pb zircon age dating utilizing a high mass resolution secondary ion mass spectrometer (HR-SIMS). In this COE-21program, we will further extend our chronological methodologies to U-series radioactive disequilibria determined with TIMS and ICP-MS, by which we can address time scales of 300,000 to several years in magmatic processes.