In situ buoyancy test for the density measurement of basaltic liquid at high pressure and high temperature

In situ buoyancy test for the density measurement of basaltic liquid at high pressure and high temperature Akio Suzuki, Eiji Ohtani, Hidenori Terasaki, Tatsuya Sakamaki, Keisuke Nishida, Kenichi Funakoshi We have been carried out density measurement of silicate and metallic liquid at high pressure and high temperature by using the buoyancy test. In this method, the density of liquid was bounded by that of the sinking or floating buoyancy marker. The uncertainty of the determined density of liquid is caused by 1) the uncertainty of the equation of state of the buoyancy marker 2) the uncertainty of the pressure of experiment. In the pervious experiments, the pressures were estimated on the basis of the pressure calibration curve, which had been established from the separate experiments. Therefore, the uncertainty of pressure is about 10% and makes it difficult to obtain the precise equation of state of liquid. This serious problem can be solved if the pressure of the experimental condition is determined precisely. In the present study we carried out buoyancy test to determine the density of basaltic liquid at high pressure and high temperature. The starting material has a composition of lunar high-Ti basalt, which was synthesized by using a gas-mixing furnace. Experiments were performed at BL04B1 beamline at SPring-8, Japan. The sinking and flotation of the buoyancy markers were observed from the X-ray radiography and X-ray diffraction study. The pressure was determined by using an equation of state of MgO. Sinking of diamond was observed at 3.88+-0.03 GPa and 1800K, and 4.19+-0.05 GPa and 1780K. Flotation of diamonds was observed at 4.74+-0.08 GPa and 1810K, and 5.08+-0.07 GPa and 1870K. A compression curve determined in the present study is consistent with Circone and Agee (1996).