Phase relations of a carbonaceous chondrite at lower mantle conditions
Phase relations of a carbonaceous chondrite at lower mantle conditions
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DOI：
10.1016/j.pepi.2003.10.011
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发表时间：
2004-06-15
影响因子：
2.3
通讯作者：
Kondo, T
中科院分区：
文献类型：
--
作者：
Asahara, Y;Kubo, T;Kondo, T
阿连德陨石属于CV碳质球粒陨石，在22-25GPa和1600-2300℃下研究了其相关系。随着压力的增加，液相相在约 24.5 GPa 时从石榴石转变为镁钙钛矿。在整个研究的压力范围内，镁方铁矿作为第二相结晶，并且固相线与低于 23 GPa 的尖角铁矿、23-24 GPa 的镁钙钛矿和高于 24 GPa 的钙钙钛矿的出现一致。不混溶的硅酸盐和金属液相存在于整个熔化范围内，并且在至少 1600 摄氏度以下的固相线以下仍存在单一金属液体。 Kd(Fe/Mg)（晶体/硅酸盐）远低于镁方铁矿 (0.7-0.8)、石榴石 (0.35-0.39) 和镁钙钛矿 (0.34) 的统一值。 Ni和S强烈分配到金属液体中，并且金属液体和共存矿物之间的Ni和Fe分配系数随着压力或温度的变化而相对恒定。控制Fe和Ni的D-金属/晶体的一个重要因素是氧逸度。我们的结果为早期地球分化和核心形成的模型提供了进一步的限制。 (C) 2004 Elsevier B.V. 保留所有权利。
The phase relations of Allende meteorite, which belongs to the CV carbonaceous chondrites, were investigated at 22-25 GPa and 1600-2300 degreesC. With increasing pressure, the liquidus phase changes from garnet to Mg-perovskite at about 24.5 GPa. Magnesiowustite crystallizes as the second phase throughout the investigated pressure range, and the solidus curve coincides with the appearance of ringwoodite below 23 GPa, Mg-perovskite at 23-24 GPa and Ca-perovskite above 24 GPa. Immiscible silicate and metallic liquid phases are present in the entire melting range, and a single metallic liquid persists below the solidus down to at least 1600 degreesC. The Kd(Fe/Mg)(crystal/silicateliq.) is well below unity for magnesiowustite (0.7-0.8), garnet (0.35-0.39) and Mg-perovskite (0.34). Ni and S are strongly partitioned into the metallic liquid, and the Ni and Fe partition coefficients between metallic liquid and coexisting minerals are relatively constant with variations in pressure or temperature. An important factor controlling D-metalliq./crystal of Fe and Ni is the oxygen fugacity. Our results provide further constraints on models for early Earth differentiation and core formation. (C) 2004 Elsevier B.V. All rights reserved.