On the Timescale of Magma Ocean Solidification and Its Chemical Consequences: 2. Compositional Differentiation Under Crystal Accumulation and Matrix Compaction
On the Timescale of Magma Ocean Solidification and Its Chemical Consequences: 2. Compositional Differentiation Under Crystal Accumulation and Matrix Compaction
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DOI：
10.1029/2018jb016928
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发表时间：
2019-04-01
影响因子：
3.9
通讯作者：
Korenaga, Jun
中科院分区：
文献类型：
--
作者：
Miyazaki, Yoshinori;Korenaga, Jun
一个假定的岩浆海洋的凝固为随后的亚固相线地幔对流奠定了基础。虽然它可能导致了一个成分分层的地幔，有关过程的效率，导致化学分化，如晶体积累和基质压实，仍然不确定。本研究的目的是提出的热化学结构的端员的情况下，潜在的分化机制正在发挥充分的作用。我们采用了自洽的热力学模型，使我们的模型一致的热和化学方面。岩浆海底部的晶体堆积可以使上地幔富集铁，但这种全球尺度的成分分层可能很快被重力不稳定性消除，只留下小尺度的不均匀性。另一方面，深部地幔中固体基质的压实作用在核幔边界之上形成了一个持久的熔融层。我们的研究结果表明，压实效率是关键因素，在凝固过程中产生的成分分层。
The solidification of a putative magma ocean sets the stage for subsequent subsolidus mantle convection. Whereas it may have resulted in a compositionally stratified mantle, the efficiency of relevant processes to cause chemical differentiation, such as crystal accumulation and matrix compaction, remains uncertain. The purpose of this study is to present the thermochemical structure of end-member cases where potential differentiation mechanisms are taking full effect. We employ a self-consistent thermodynamic model to make our model consistent in both thermal and chemical aspects. The accumulation of crystals at the base of magma ocean can enrich the upper mantle with iron, but such a global-scale compositional stratification is likely to be quickly eliminated by gravitational instability, leaving small-scale heterogeneities only. On the other hand, the compaction of solid matrix in the deep mantle creates a long-lasting molten layer above the core-mantle boundary. Our results suggest that the efficiency of compaction is the key factor to generate compositional stratification during solidification.