Direct Viscosity Measurement of Peridotite Melt to Lower-Mantle Conditions: A Further Support for a Fractional Magma-Ocean Solidification at the Top of the Lower Mantle
Direct Viscosity Measurement of Peridotite Melt to Lower-Mantle Conditions: A Further Support for a Fractional Magma-Ocean Solidification at the Top of the Lower Mantle
复制标题
橄榄岩熔体到下地幔条件的直接粘度测量：对下地幔顶部岩浆-海洋分式凝固的进一步支持
DOI：
10.1029/2021gl094507
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Y.
中科院分区：
文献类型：
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作者：
Xie;L.;Yoneda;A.;Katsura;T.;Andrault;D.;Tange;Y.;Higo;Y.
根据同位素地球化学的证据，原始储集层的持续存在表明，地球下地幔可能是不均匀的。这种不均质性可能是岩浆-海洋(MO)凝固的遗留问题。金属氧化物的粘度是制约金属氧化物凝固类型的关键参数。本文利用原位落球法，直接测量了深部地幔压力-温度条件下橄榄岩(类似于MO组分)熔体的粘度。S认为，橄榄岩熔体沿液相线的粘度在7~25 Gpa的压力范围内为38~17 Mpa，是根据端元组成粘度估算的0.9~0.4倍。低粘度有利于早期地幔的分步凝固和化学分层，至少到顶下地幔，这可能是现今地幔不均质性的一个来源。
As evidenced by isotope geochemistry, the persistence of primitive reservoirs indicates that the earth's lower mantle is likely to be heterogeneous. Such heterogeneity could be a legacy from magma‐ocean (MO) solidification. The viscosity of MO is a key parameter to constrain the solidification type of MO. Here we directly measure the viscosity of peridotite (an analog of MO composition) melt at the pressure‐temperature conditions of the deep mantle, using the in situ falling sphere method. The viscosity of peridotite melt along liquidus is in the range of 38–17 mPa s at pressures from 7 to 25 GPa, which is 0.9–0.4 times of the estimation based on the viscosity of endmember compositions. Low viscosity favors fractional solidification and chemically layering of the early mantle at least to the top lower mantle, which could be a source of heterogeneity for the present mantle.