A perovskitic lower mantle inferred from high-pressure, high-temperature sound velocity data
A perovskitic lower mantle inferred from high-pressure, high-temperature sound velocity data
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DOI：
10.1038/nature11004
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发表时间：
2012-05-03
期刊：
影响因子：
64.8
通讯作者：
Hirose, Kei
中科院分区：
文献类型：
--
作者：
Murakami, Motohiko;Ohishi, Yasuo;Hirose, Kei
确定地球下地幔的化学成分是地球科学中一个长期存在的挑战。准确了解下地幔矿物在相关高压、高温条件下的声速对于使用地震观测来限制矿物学和化学成分是必不可少的（1），但以前的声学测量仅限于低压和低温范围。在这里，我们使用布里渊散射光谱法（2）在下地幔深部的压力和温度条件下确定硅酸盐钙钛矿和铁方镁石的剪切波速度。与全球地震速度剖面最吻合的矿物学模型（1）表明，钙钛矿占下地幔体积的93%以上，这比传统橄榄岩地幔模型预测的比例高得多。这表明下地幔相对于上地幔是富硅的，这与南极地球模型是一致的。这种化学分层意味着上地幔和下地幔之间有限的物质输送的层状地幔对流。
The determination of the chemical composition of Earth's lower mantle is a long-standing challenge in earth science. Accurate knowledge of sound velocities in the lower-mantle minerals under relevant high-pressure, high-temperature conditions is essential in constraining the mineralogy and chemical composition using seismological observations(1), but previous acoustic measurements were limited to a range of low pressures and temperatures. Here we determine the shear-wave velocities for silicate perovskite and ferropericlase under the pressure and temperature conditions of the deep lower mantle using Brillouin scattering spectroscopy(2). The mineralogical model that provides the best fit to a global seismic velocity profile(1) indicates that perovskite constitutes more than 93 per cent by volume of the lower mantle, which is a much higher proportion than that predicted by the conventional peridotitic mantle model. It suggests that the lower mantle is enriched in silicon relative to the upper mantle, which is consistent with the chondritic Earth model. Such chemical stratification implies layered-mantle convection with limited mass transport between the upper and the lower mantle.