Melting experiments of mantle materials under lower mantle conditions with implications for magma ocean differentiation
Melting experiments of mantle materials under lower mantle conditions with implications for magma ocean differentiation
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DOI：
10.1016/j.pepi.2003.09.016
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发表时间：
2004-06-15
影响因子：
2.3
通讯作者：
Walter, MJ
中科院分区：
文献类型：
--
作者：
Ito, E;Kubo, A;Walter, MJ
肥沃橄榄岩和 Cl 球粒状地幔材料的液相线相关系和主要元素分配已分别确定为 33 和 35 GPa。在橄榄岩中，在 31 GPa 下，第一液相由方镁石转变为镁钙钛矿，而在 33 GPa 时，镁钙钛矿的液相线在较小的温度范围内依次由方镁石和钙钛矿降低温度。在 CI 球粒陨石地幔中，镁钙钛矿是液相线，在压力高于 28 GPa 时，钙钛矿会降低温度。液相线处不存在铁镁石酶。已经针对 Cl 球粒陨石和两种橄榄岩块状硅酸盐地球模型检查了深层岩浆海洋中镁钙钛矿、铁方镁石和钙钙钛矿的晶体分异分化。质量平衡表明，从 CI 球粒状块状硅酸盐地球中减去约 40% 镁钙钛矿和 2% 钙钙钛矿，会产生具有模型肥沃上地幔成分的一些特征的残余熔体。由镁钙钛矿和钙钛矿组成的晶体层将堆积到约 100 微米的深度。 1400公里，由于钙钛矿具有容纳大阳离子（例如La和碱性元素）的高能力，因此可以被描述为富集且可能产热的储层。观察到的压力对元素分配的影响表明，对于较高压力的液相组合物可以获得更好的质量平衡解决方案。对于橄榄岩块状硅酸盐地球模型，分馏将非常有限，除了痕量的 Ca-Pv 之外，最多 10 wt.% 的 Mg-钙钛矿。 (C) 2004 Elsevier B.V. 保留所有权利。
Liquidus phase relations and major element partitioning have been determined for fertile peridotite and Cl chondritic mantle material to 33 and 35 GPa, respectively. In peridotite, the first liquidus phase changes from ferropericlase to Mg-perovskite at 31 GPa, and at 33 GPa liquidus Mg-perovskite is successively followed down temperature by ferropericlase and Ca-perovskite within a small temperature range. In CI chondritic mantle, Mg-perovskite is the liquidus phase followed down temperature by Ca-perovskite at pressures higher than 28 GPa. Ferropericlase is absent at the liquidus. Differentiation by crystal fractionation of Mg-perovskite, ferropericlase, and Ca-perovskite in a deep magma ocean has been examined for a Cl chondritic and two peridotitic bulk silicate earth models. Mass balance indicates that subtraction of about 40% Mg-perovskite and 2% Ca-perovskite from a CI chondritic bulk silicate earth yields a residual melt with some characteristics of model fertile upper mantle composition. A crystal layer composed of Mg- and Ca-perovskites would pile up to a depth ca. 1400 km, and may be characterized as an enriched and possibly heat-producing reservoir by the high capability of Ca-perovskite to accommodate large cations such as La and alkaline elements. The observed effect of pressure on element partitioning indicates that better mass balance solutions may be obtained for higher pressure liquidus phase compositions. For peridotitic bulk silicate earth models, fractionation would be quite limited, up to 10 wt.% of Mg-perovskite in addition to trace amount of Ca-Pv. (C) 2004 Elsevier B.V. All rights reserved.