Study of the dynamics and the multisphere interaction of the Early earth

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Following topics were studied during this Co-operative research (A) project. Numerical simulation was conducted to clarify the process of formation of the terrestrial magma ocean during the accretion and formation of the primitive crust in the magma ocean stage. The high pressure experiments showed that a density crossover between olivine and the FeO rich peridotite magma of the Martian mantle composition occurs at around 7 GPa, which corresponds to the depth of about 600 km of the Martian interior. The similar density crossover is expected to occur at about 12 GPa which corresponds to the depth of 350 km in the terrestrial mantle. Petrogenesis of magmas observed in the early stage of the terrestial evolution, such as komatiite and kimberlite was also studied by using the multianvil high pressure apparatus. Tectonics of the early stage of the earth was also studied on the basis of the field work on geology of the Archean terrains, and showed that the tectonic style of the early Archean to 3.9 Ga ago was essentially similar to the modern plate tectonics. The high pressure research was conducted to study the phase transformation of the descending slab and the thermodynamic properties of the lower mantle minerals were also studied to discuss the secular change of the chemistry of the deep mantle. The symposium of this co-operative reserch was held during the 1993 joint meeting of the societies of the Earth and Planetary Sciences.