Dehydration Melting Below the Undersaturated Transition Zone
Dehydration Melting Below the Undersaturated Transition Zone
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DOI：
10.1029/2019gc008712
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发表时间：
2020-02
期刊：
影响因子：
3.7
通讯作者：
W. R. Panero;Christine Thomas;R. Myhill;Jeffrey S. Pigott;C. Raepsaet;H. Bureau
中科院分区：
文献类型：
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作者：
W. R. Panero;Christine Thomas;R. Myhill;Jeffrey S. Pigott;C. Raepsaet;H. Bureau
在接收函数和底面地震反射中观察到西藏下方过渡带底部以下70-130 km处的反射体，其深度与石榴石向硼镁石的过渡一致。地球过渡带和下地幔矿物储水能力的对比表明下地幔顶部存在脱水熔融的可能性。第一性原理计算结合实验室合成实验限制了地幔水容量穿过过渡带底部并进入下地幔顶部。我们解释所观察到的地震信号一致的3-4体积%的含水熔体产生的脱水熔融的石榴石到bridgmanite过渡。如果下降流区的地震信号明显来自全球上地幔水的代表性水含量，这将限制地幔中名义上无水矿物中储存的水小于表面海洋质量的30%。
A reflector 70–130 km below the base of the transition zone beneath Tibet is observed in receiver functions and underside seismic reflections, at depths consistent with the transition of garnet to bridgmanite. Contrast in water storage capacity between the minerals of the Earth's transition zone and lower mantle suggests the possibility for dehydration melting at the top of the lower mantle. First‐principles calculations combined with laboratory synthesis experiments constrain the mantle water capacity across the base of the transition zone and into the top of the lower mantle. We interpret the observed seismic signal as consistent with 3–4 vol % hydrous melt resulting from dehydration melting in the garnet to bridgmanite transition. Should seismic signals evident in downwelling region result from water contents representative of upper mantle water globally, this constrains the water stored in nominally anhydrous minerals in the mantle to <30% the mass of the surface oceans.