[S-CG44] Rheology, fracture and friction in Earth and planetary sciences

[SCG44-P07] Synthesis of highly dense fine-grained upper mantle composites from sedimentary mud in the peridotite quarry

*Sanae Koizumi¹, Takehiko Hiraga¹ (1.Earthquake Research Institute,The University of Tokyo)

Keywords:Olivine, Horoman, wet jet milling, Spark plasma sintering, chemical composition

Recent deformation experiments on synthetic olivine polycrystals have shown that the addition of Ca and Al, which distribute (segregate) to grain boundaries, to olivine aggregates promotes grain boundary diffusion and weakens the aggregates (Yabe and Hiraga 2020 JGR). This result indicates that "impurities" in natural rocks dominate the strength of the upper mantle. Although it would be ideal to conduct high-temperature deformation experiments using mantle rocks to analyze their mechanical properties, this is experimentally difficult due to the nature of the samples, such as mineral distribution, grain size, and porosity.
We have developed a method to synthesize highly dense, fine-grained synthetic olivine aggregates suitable for laboratory experiments to investigate the effect of impurities in the measurement of upper mantle properties. We used sedimentary mud in the peridotite quarry as raw material. The chemical composition of the mud was found to represent the composition of various types of olivine exposed in an area of 80 km2. Jet milling of the mud in aqueous solution was used to obtain submicron powders while avoiding contamination. Pressure-assisted spark plasma sintering was applied to synthesize fine-grained (~1µm) and dense (porosity <1%) upper mantle composites. The microstructure and chemical composition of the samples will be reported in this presentation.