Melting experiments on peridotite to lowermost mantle conditions
Melting experiments on peridotite to lowermost mantle conditions
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DOI：
10.1002/2013jb010616
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发表时间：
2014-06
期刊：
影响因子：
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通讯作者：
Shigehiko Tateno;K. Hirose;Y. Ohishi
中科院分区：
文献类型：
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作者：
Shigehiko Tateno;K. Hirose;Y. Ohishi
基于激光加热金刚石砧室 (DAC) 技术，在 34 至 179 GPa 的压力范围内对热解地幔材料进行了熔化实验。使用场发射型电子微探针（FE-EPMA）对淬火样品进行了结构和化学表征。本研究中由 46 至 77 wt.% 部分熔化形成的熔体在成分上属于超基性，并且随着压力的增加，SiO2 含量变得更加贫乏，FeO 含量更加丰富。熔融织构表明，液相线相从方镁石铁矿转变为富含 MgSiO3 的钙钛矿，至少高于 34 GPa，并进一步转变为后钙钛矿。在 68 至 82 GPa 之间，熔化（消失）的第一相从 CaSiO3 钙钛矿转变为 (Mg,Fe)O 方镁石。方镁石在固相线温度以上的稳定性随着压力的增加而降低（最后熔化低于 34 GPa，最初熔化低于 82 GPa），导致较高压力下部分熔体中的 (MgO + FeO)/SiO2 比率较高。此外，随着压力的增加，钙钛矿/后钙钛矿和熔体之间的Fe-Mg分配系数（KD）显着下降，导致部分熔体中Fe强烈富集。它支持下地幔深处的致密部分熔体，这些熔体向下迁移到核心地幔边界（CMB）。
Melting experiments on a pyrolitic mantle material were performed in a pressure range from 34 to 179 GPa based on laser‐heated diamond‐anvil cell (DAC) techniques. The textural and chemical characterizations of quenched samples were made by using field‐emission‐type electron microprobe (FE‐EPMA). Melts formed by 46 to 77 wt.% partial melting in this study were ultrabasic in composition and became more depleted in SiO2 and more enriched in FeO with increasing pressure. Melting textures indicate that the liquidus phase changed from ferropericlase to MgSiO3‐rich perovskite at least above 34 GPa and further to post‐perovskite. The first phase to melt (disappear) changed from CaSiO3 perovskite to (Mg,Fe)O ferropericlase between 68 and 82 GPa. The stability of ferropericlase above solidus temperature shrinks with increasing pressure (melting last below 34 GPa and first 82 GPa), resulting in higher (MgO + FeO)/SiO2 ratio in partial melt at higher pressure. Additionally, the Fe‐Mg distribution coefficients (KD) between perovskite/post‐perovskite and melt decreased considerably with increasing pressure, leading to strong Fe‐enrichment in partial melts. It supports dense partial melts in a deep lower mantle, which migrate downward to the core mantle boundary (CMB).