Japan Geoscience Union Meeting 2022

Presentation information

[E] Poster

S (Solid Earth Sciences ) » S-IT Science of the Earth's Interior & Techtonophysics

[S-IT17] Property and role of liquids inside terrestrial planets

Mon. May 30, 2022 11:00 AM - 1:00 PM Online Poster Zoom Room (21) (Ch.21)

convener:Tatsuya Sakamaki(Department of Earth Science, Tohoku University), convener:Yoichi Nakajima(Kumamoto University, Priority Organization for Innovation and Excellence), Chairperson:Tatsuya Sakamaki(Department of Earth Science, Tohoku University), Yoichi Nakajima(Kumamoto University, Priority Organization for Innovation and Excellence)

11:00 AM - 1:00 PM

[SIT17-P02] The partial molar volume of Fe2O3 in magma under high pressure

Rintaro Ban1, *Akio Suzuki1, Tatsuya Sakamaki1 (1.Department of Earth Science, Graduate School of Science, Tohoku University)

Keywords:Magma, Fe2O3, Density, Partial molar volume, Mantle

Density of magma is one of the most important properties to understand the magma behavior in the interior of the Earth. Considering the composition of Earth’s magma, iron is the heaviest component and has a strong influence on the melt density. Therefore, we need to investigate the behavior of iron and iron oxides in magmas under high pressure in order to discuss the magma density in the Earth’s mantle. Since the high concentration of Fe2O3 in the lower mantle has been proposed (e.g., McCammon, 2005), the generation of Fe2O3-bearing magma at the top of lower mantle has been implied (Nakajima et al., 2019). Although the partial molar volume of Fe2O3 in magma is essential to calculate the density of magma in the deep mantle, there is no data of the partial molar volume of Fe2O3 at high pressure and temperature. Here, we obtained the partial molar volume of Fe2O3 in silicate melts under high pressure based on high-pressure density measurement of the melts. Several Fe3+-rich starting material were prepared. For high-pressure generation, we used a Kawai-type multi-anvil apparatus installed at Tohoku University. We succeeded in measuring the density of Fe2O3-bearing magma based on sink-float method (Agee and Walker, 1988; Suzuki et al., 1995). Combining the obtained melt densities and partial molar volumes of other oxides calculated from Wakabayashi and Funamori (2013), the partial molar volumes of Fe2O3 at 8, 10 and 12 GPa were determined. Assuming that the thermal expansibility of Fe2O3 is constant regardless of pressure, the compression curve of Fe2O3 in magmas was derived. Although the compressibility of Fe2O3 is larger than FeO, it was not observed that the volume crossover between Fe2O3 and “2FeO+1/2O2”. It was indicated that the Fe2O3-bearing magma is about 0.1g/cm3 lighter than the FeO-bearing magma at the top of the lower mantle.