Mass balance and phase density constraints on early differentiation of chondritic mantle
Mass balance and phase density constraints on early differentiation of chondritic mantle
复制标题
球粒状地幔早期分化的质量平衡和相密度约束
DOI：
10.1016/0012-821x(88)90097-0
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发表时间：
1988
影响因子：
5.3
通讯作者：
D. Walker
中科院分区：
文献类型：
--
作者：
C. Agee;D. Walker
一个非常简单和精确的主元素质量平衡与从部分熔融球粒质地球中通过减去钙钛矿和添加橄榄石推导出平均上地幔橄榄岩相一致。除非某些尚未确定的组成部分发挥作用，否则多数人的参与被排除在外。在原始熔融事件中，钙钛矿的减法是通过深层的晶体分选来实现的，而橄榄石的添加是通过浮力机制的组合来完成的：晶体从熔体的深层被其自身的可压缩性埋藏到固化的上地幔的底部，随后这种浮力镁橄榄石向上的固态对流。这些过程与已知的高压下晶体和液体的密度关系是一致的。物质平衡预测向上浮选供给橄榄石后的深部残余岩浆体可能为马马岩质。原始分异后约100 μ m的原C1慢性块状地球物质的分布为固体橄榄岩上地幔、钙钛矿下地幔和科马提岩液体夹层层。
A surprisingly simple and precise major element mass balance is consistent with derivation of average upper mantle peridotite from a partially molten chondritic Earth by subtraction of perovskite and addition of olivine. Majorite involvement is precluded unless some as yet unidentified components play a role. Perovskite subtraction during a primordial melting event is expected to occur by crystal fractionation at depth, while olivine addition is accomplished by a combination of buoyancy mechanisms: crystal flotation from a deep layer of melt buried by its own compressibility to the base of the solidifying upper mantle and subsequent solid state convection of this buoyant magnesian olivine upward. These processes are consistent with known density relations of crystals and liquid at very high pressure. Mass balance predicts that the residual magma body at depth after supplying olivine by flotation upward can be komatiitic. Distribution of originally C1 chrondritic bulk Earth material a few 100 m.y. after primordial differentiation is solid peridotite upper mantle, perovskite lower mantle, and a komatiitic liquid sandwich horizon.