The solid Earth, consisting of the crust, mantle and core, has continuously evolved since its birth at 4.6 billion years ago. Geochemical Evolution Research Program seeks a comprehensive understanding of Earth evolution, based on the petrology and geochemistry of solid earth materials.
Within the solar system continental crust is only found on the Earth. It is thought to be created in subduction zones, but many questions regarding its genesis remain unanswered. For example, how are magmas generated in the mantle wedge of subduction zones and how do subduction zone magmas evolve into continental crust.These important questions are tackled using petrological and geochemical methods.
Schematic cross-section of the Izu-Bonin arc and the Honshu arc, showing accretion of middle crust at the collision zone (Tamura et al. 2010).
This team is investigating how the mantle has evolved over the Earth's 4.6 billion years history. The mantle extends from 15 to 2900 km into the Earth's interior, constituting approximately 84% of the Earth's volume. We are analyzing the abundances of various element and radiogenic isotopes contained in mantle rocks and magmas formed by mantle melting and erupted on the Earth's surface at mid-ocean ridges, ocean islands and island arcs. Our final goal is to elucidate the geochemical evolution of the mantle and material recycling in and out of the mantle.
IFREE is developing experiments that create the pressures and temperatures experienced towards the center of the Earth. These will decode the physical properties of the mantle and the core, leading to an understanding of the processes of Earth evolution.
High-P/T experiments by using Laser-Heating Diamond Anvil Cell (LHDAC) in collaboration with SPring-8 and TIT is successfully reproducing the physical state of the deep Earth and producing numerous leading results.
IFREE have proposed to the IODP four sites in the Izu-Bonin-Mariana arc (IBM) for drilling with the riser drilling vessel Chikyu and with non-riser vessels. These proposals are currently being reviewed by the Science Planning Committee (SPC) and Science Steering and Evaluation Panel (SSEP) of IODP's Science Advisory Structure (SAS). If successful the results from the drilling will be integrated with ongoing sampling and seismic surveys using JAMSTEC vessels, remotely-operated vehicles (ROVs) and submersibles in the IBM. Together these all aid in understanding crustal formation and mantle evolution from the initiation of subduction, through the evolution of the oceanic arc, to the genesis of continental crust.
Drilling through the oceanic crust to the Mohorovičić discontinuity and further into the uppermost mantle (the Mohole Project) is a long-standing goal of scientific ocean drilling and should provide answers to fundamental questions about the dynamics of the Earth and global elemental cycles. IFREE is taking the lead in the Mohole project in collaboration with international colleagues.
This team is investigating subduction zones, the active margins of the ocean basins. The subduction process transfers energies and materials from the subducted oceanic crust to the seismic and volcanic activities occurring at these active margins, known as island or continental arcs. Our research team investigates the seismic structures and the volcanic rocks in the Northeastern and the Southwestern Japan arcs. We study the origins of the seismic and volcanic processes by analyzing both the crustal structures and the conditions in the mantle and crust beneath the arcs. Comparative studies of the circum-Pacific subduction zones are also conducted through international collaborative projects in order to elucidate both the unique and general features of the areas studied.