[S-MP42] 鉱物の物理化学

[SMP42-04] 高圧下におけるFeS-NiS二成分系メルトの密度測定

*浦川 啓¹、寺崎 英紀³、岸本 俊八¹、井上 尚紀²、田窪 勇作³、下山 裕太³、黒川 冬華⁴、町田 晃彦⁵ (1.岡山大学大学院自然科学研究科、2.岡山大学理学部、3.大阪大学大学院理学研究科、4.大阪大学理学部、5.日本原子力研究開発機構)

キーワード：硫化物メルト、密度、部分モル体積、惑星核

Planetary cores consist mainly of iron, nickle and some light elements. Sulfur is thought to be a primary lightening element in the metallic core of the small planets, satellites and planetesimals. Planetary magnetism arises from a dynamo driven by convection in the liquid core. Physical properties of sulfur-bearing Fe liquids are, therefore, fundamental to understand the dynamics of liquid core in the planetary interior. Here we report the results of density measurements of FeS-NiS binary sulfide melts at high pressure by means of X-ray absorption technique. Experiments were conducted at BL22XU of SPring-8, at which the cubic-type multi-anvil press is equipped and highly brilliant monochromatic X-ray is available. We determined the densities and the expansivities of NiS, (Fe_0.3Ni_0.7)S, (Fe_0.5Ni_0.5)S and (Fe_0.7Ni_0.3)S composition liquids at about 2GPa and 1273-1673 K. Density of (Fe,Ni)S liquid increases with Ni content. Compositional dependence of density allow us to evaluate the partial molar volumes of liquids FeS and NiS. The partial molar volumes of liquids FeS and NiS are consistent with those at 1 atmospheric pressure (Kress, 2008). On the other hand, the extrapolated densities of liquid FeS is 8-10% lower than the EoS determined by Nishida et al (2011). Our new data would contribute to understand compressional behavior as well as thermochemical properties of Fe-Ni-S liquid alloys under pressure.
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References
Kress,V (2008) Contrib Mineral Petrol, 156, 785-797.
Nishida, K et al (2011) Am Mineral, 96, 864-868.