High-pressure experimental constraints of partitioning behavior of Si and S at the Mercury's inner core boundary
High-pressure experimental constraints of partitioning behavior of Si and S at the Mercury's inner core boundary
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DOI：
10.1016/j.epsl.2021.116849
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发表时间：
2021-05
影响因子：
5.3
通讯作者：
Renbiao Tao;Y. Fei
中科院分区：
文献类型：
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作者：
Renbiao Tao;Y. Fei
轻元素在内核边界（ICB）处的液体和固体之间的分配控制着外核和内核之间的成分差异和密度不足。 MESSENGER 任务对水星表面高 S 和低 Fe 浓度的观测表明，水星是在比其他类地行星更加还原的条件下形成的，这可能会导致含有 Si 和 S 的金属 Fe 核心。在本研究中，我们进行了高压实验，以研究与水星 ICB 条件相关的 15 和 21 GPa 下 Fe-Si-S 系统中 Si 和 S 在液体和固体之间的分配行为。实验结果表明，几乎所有的S都分配到液体中。 Si 在液体和固体之间的分配系数 (D Si) 与液体 (X S 液体) 中的 S 含量密切相关，如下所示： log 10(D Si)= 0.0445+ 5.9895⁎ log 10(1− X S 液体)。在我们的实验范围内，压力对 Si 和 S 在液体和固体之间的分配行为影响有限。对于具有 Fe-Si-S 核心的水星，内核和外核之间的成分差异很大程度上取决于核心的 S 含量。地核中的硫含量越低，液体外核和固体内核之间的成分差异和密度赤字就越小。对于含有 1.5 wt% 大量 S 的核心，模型 ICB 温度将与熔化曲线在~ 17 GPa 处相交，对应于半径为~ 1600 km 的内核。
The partitioning of light elements between liquid and solid at the inner core boundary (ICB) governs compositional difference and density deficit between the outer and inner core. Observations of high S and low Fe concentration on the surface of Mercury from MESSENGER mission indicate that Mercury is formed under much more reduced conditions than other terrestrial planets, which may result in a Si and S-bearing metallic Fe core. In this study, we conducted high-pressure experiments to investigate the partitioning behavior of Si and S between liquid and solid in the Fe-Si-S system at 15 and 21 GPa, relevant to Mercury's ICB conditions. Experimental results show that almost all S partitions into liquid. The partitioning coefficient of Si (D Si) between liquid and solid is strongly correlated with the S content in liquid (X S liquid) as: log 10(D Si)= 0.0445+ 5.9895⁎ log 10(1− X S liquid). Within our experimental range, pressure has limited effect on the partitioning behavior of Si and S between liquid and solid. For Mercury with an Fe-Si-S core, compositional difference between the inner and outer core is strongly dependent on the S content of the core. The lower S content is in the core, the smaller compositional difference and density deficit between the liquid outer core and solid inner core should be observed. For a core with 1.5 wt% bulk S, a model ICB temperature would intersect with the melting curve at∼ 17 GPa, corresponding to an inner core with a radius of∼ 1600 km.