Solidus and liquidus profiles of chondritic mantle: Implication for melting of the Earth across its history
Solidus and liquidus profiles of chondritic mantle: Implication for melting of the Earth across its history
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DOI：
10.1016/j.epsl.2011.02.006
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发表时间：
2011-04-01
影响因子：
5.3
通讯作者：
Mezouar, Mohamed
中科院分区：
文献类型：
--
作者：
Andrault, Denis;Bolfan-Casanova, Nathalie;Mezouar, Mohamed
利用激光加热金刚石对顶砧装置，研究了核幔边界压力下人工合成地幔的熔融特性。熔化标准基本上是基于同步辐射提供的X射线的使用。我们报告的固相线熔化曲线低于以前确定的光学方法。液相线高于固相线300 - 600 K，覆盖整个下地幔。在CMB压力（135 GPa）下，地幔的固相线和液相线分别达到4150（150）K和4725（150）K。我们讨论了下地幔不可能在D”层熔融，除非地幔底部温度剖面的最高估计值（与一个非常热的核有关）得到证实。因此，我们认为，根据对超低速带的地震观测，最近提出的关于地幔最下部部分熔融的建议表明：（1）在CMB处有一个温度超过4150 K的外核，或者（2）我们观察到的高液相线温度以及固相线和液相线温度之间的大差距对我们的研究具有重要意义。岩浆海洋在增生过程中的性质。不仅下地幔的完全熔化需要过高的温度，而且，低于液相线温度的部分熔化应该发生在比以前认为的更大的深度间隔上。此外，岩浆热液表明，在岩浆海洋的情况下，将延伸到40 GPa以上，如亲铁金属硅酸盐分区数据所示，非常高的表面温度。如此高的表面温度，热覆盖是无效的，指出了岩浆海洋的瞬态特性，具有非常快的冷却速率。(C)2011 Elsevier B. V.保留所有权利。
We investigated the melting properties of a synthetic chondritic primitive mantle up to core-mantle boundary (CMB) pressures, using laser-heated diamond anvil cell. Melting criteria are essentially based on the use of X-rays provided by synchrotron radiation. We report a solidus melting curve lower than previously determined using optical methods. The liquidus curve is found between 300 and 600 K higher than the solidus over the entire lower mantle. At CMB pressures (135 GPa), the chondritic mantle solidus and liquidus reach 4150 (150) K and 4725 (150) K, respectively.We discuss that the lower mantle is unlikely to melt in the D"-layer, except if the highest estimate of the temperature profile at the base of the mantle, which is associated with a very hot core, is confirmed. Therefore, recent suggestions of partial melting in the lowermost mantle based on seismic observations of ultra-low velocity zones indicate either (1) a outer core exceeding 4150 K at the CMB or (2) the presence of chemical heterogeneities with high concentration of fusible elements.Our observations of a high liquidus temperature as well as a large gap between solidus and liquidus temperatures have important implications for the properties of the magma ocean during accretion. Not only complete melting of the lower mantle would require excessively high temperatures, but also, below liquidus temperatures partial melting should take place over a much larger depth interval than previously thought. In addition, magma adiabats suggest very high surface temperatures in case of a magma ocean that would extend to more than 40 GPa, as suggested by siderophile metal-silicate partitioning data. Such high surface temperature regime, where thermal blanketing is inefficient, points out to a transient character of the magma ocean, with a very fast cooling rate. (C) 2011 Elsevier B.V. All rights reserved.