Melt has much higher element diffusivity and is much more mobile. Melts should play vital roles in geochemical processes in the Earth's interior. Melt properties are, however, difficult to investigate by high P-T experiments due to the following reasons.

1. Melting points of mantle materials such as peridotite and basalt are incredibly high.
2. Mantle melts cannot be recovered to ambient conditions. Although many high-pressure minerals can be recovered to ambient conditions, melts structures should be changed during recovery. In many cases, the melt cannot be quenched even to glasses, especially at high pressures.
3. Melts migrate in sample chambers due to the steep temperature gradients produced by tiny furnaces in high-pressure cells.

In order to overcome these problems, we have developed the following technologies.

1. Temperatures up to 3000 K can be routinely generated using newly developed CVD-synthesized boron-doped diamond heaters [Xie et al., 2020; Nishida et al., 2020].
2. Conditions of melt quenching have been expanded by increasing cooling rates [Bondar et al., 2020].
3. Uniform temperature fields are produced by a new furnace geometry [Zarei et al., 2018].

We investigate melting relations, element partitioning, and melt (quenched glass) structures using these technologies.

Experimental techniques

• Bondar, D., Fei, H., Withers, A. C., Katsura, T., A rapid-quench technique for multi-anvil high-pressure-temperature experiments, Review of Scientific Instruments, 91, 065105, 2020.
• Nishida, K., Xie, L., Kim, E.J., Katsura, T., A strip-type  boron-doped diamond heater synthesized by chemical vapor deposition for large volume presses, Review of Scientific Instruments, in press. doi.org/10.1063/5.0011742
• Xie, L., Yoneda, A., Liu, Z., Nishida, K., Katsura, T., Boron-doped diamond synthesized by chemical vapor deposition as a heating element in a multi-anvil apparatus, High Pressure Research 40, 369-378, 2020.
• Zarei, A., Li, Y., Fei, H.-Z. and Katsura, T., A nearly zero temperature gradient furnace system for high pressure multi-anvil experiments.