Density of hydrous silicate melt at the conditions of Earth's deep upper mantle
Density of hydrous silicate melt at the conditions of Earth's deep upper mantle
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DOI：
10.1038/nature04241
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发表时间：
2005-11-24
期刊：
影响因子：
64.8
通讯作者：
Karato, S
中科院分区：
文献类型：
--
作者：
Matsukage, KN;Jing, ZC;Karato, S
地球和类地行星的化学演化在很大程度上受硅酸盐熔体密度的控制。如果熔体密度高于周围固体的密度，溶解在熔体中的不相容元素将被隔离在深部地幔(1，2)。以前对干燥(无水)熔体的研究表明，在深部地幔条件下(3-8)，硅酸盐熔体的密度可以高于周围固体的密度。然而，在深部地幔条件下形成的熔体也可能含有一些水，这将降低熔体的密度。在这里，我们提供了在类似于410公里深的条件下限制水合硅酸盐熔体密度的数据。我们发现，硅酸盐熔体中的水比其他组分更容易压缩，因此在高压条件下，水对降低熔体密度的作用明显减弱。我们的研究表明，存在一系列条件，在这些条件下，(含水的)熔体可能被困在410公里的边界上，因此不相容的元素可能被隔离在深部地幔中，尽管这些条件对熔体成分以及周围地幔的成分很敏感。
The chemical evolution of the Earth and the terrestrial planets is largely controlled by the density of silicate melts. If melt density is higher than that of the surrounding solid, incompatible elements dissolved in the melt will be sequestered in the deep mantle(1,2). Previous studies on dry (water-free) melts showed that the density of silicate melts can be higher than that of surrounding solids under deep mantle conditions(3-8). However, melts formed under deep mantle conditions are also likely to contain some water(2), which will reduce the melt density. Here we present data constraining the density of hydrous silicate melt at the conditions of similar to 410 km depth. We show that the water in the silicate melt is more compressible than the other components, and therefore the effect of water in reducing melt density is markedly diminished under high-pressure conditions. Our study indicates that there is a range of conditions under which a ( hydrous) melt could be trapped at the 410-km boundary and hence incompatible elements could be sequestered in the deep mantle, although these conditions are sensitive to melt composition as well as the composition of the surrounding mantle.