Complete wetting of olivine grain boundaries by a hydrous melt near the mantle transition zone
Complete wetting of olivine grain boundaries by a hydrous melt near the mantle transition zone
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DOI：
10.1016/j.epsl.2007.02.002
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发表时间：
2007-04
影响因子：
5.3
通讯作者：
T. Yoshino;Yu Nishihara;S. Karato
中科院分区：
文献类型：
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作者：
T. Yoshino;Yu Nishihara;S. Karato
地球深部含液体岩石的许多物理性质都受到其润湿行为的强烈控制。本文报道了在1200 °C和1 ~ 13 GPa压力范围内，镁橄榄石-水体系中二面角和微观结构变化的实验结果。系统的二面角随压力系统地减小，在地幔过渡区（深度约400 km）以上，二面角变为约0°，对应于完全润湿的晶界。达到这种条件可能是因为由于硅酸盐在液体中的溶解度急剧增加，固-液界面能随压力降低。这些结果表明，部分熔融的存在将有剧烈的影响，上地幔周围的过渡带的物理性质，即使熔体分数很低。地幔过渡带上方的低速区可能是由于含水熔体的存在。
Many physical properties of liquid-bearing rocks in the deep Earth's interior are strongly controlled by its wetting behavior. We report experimental results on the variation of dihedral angle and microstructures in the forsterite–H2O system at 1200 °C and pressures ranging from 1 to 13 GPa. The dihedral angle of the system decreases systematically with pressure and above the mantle transition zone (∼ 400 km depth) it becomes approximately 0°, corresponding to completely wetted grain boundaries. This condition is probably reached because of a decrease in the solid–liquid interfacial energy with pressure due to the dramatically increased solubility of silicates in the liquid. These results suggest that the presence of partial melt would have drastic influences on physical properties of upper mantle around the transition zone even if the melt fraction is very low. Low velocity regions just above the mantle transition zone may result from the presence of hydrous melt.