Rapid oxygen diffusion in melilite and its relevance to meteorites
Rapid oxygen diffusion in melilite and its relevance to meteorites
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黄长石中氧的快速扩散及其与陨石的相关性
DOI：
10.1016/0016-7037(86)90107-9
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发表时间：
1986
影响因子：
5
通讯作者：
K. Muehlenbachs
中科院分区：
文献类型：
--
作者：
Takakazu Hayashi;K. Muehlenbachs
用气/固同位素交换技术测量了黄长石中的氧扩散系数。在70 0~130 0°C温度范围内研究了两种组分的组成，对Aker5 0 GeH5 0晶体的数据符合方程：D=8.6×10−6exp[(−3 3.5±0.1)×10 3cal/RT]。Aker75GeH25：D=7.2×10−6exp[(−31.9±0.1)×103cal/RT]。氧在黄长石晶体中的扩散比在其他硅酸盐中快得多，特别是在较低的温度下。在黄长石熔体中，扩散速率与其他硅酸盐相当，但活化能相对较低。黄长石中氧的快速交换和扩散表明，碳质球粒陨石富钙铝包裹体中该矿物的同位素组成记录了它们接触到的最后一次星云气体的同位素组成。对这些包裹体早期历史的制约可能是从交换性较差的矿物的同位素组成推断出来的。
Oxygen diffusion coefficients were measured in melilite by a gas/solid isotope exchange technique. Two compositions were investigated over the temperature range of 700 to 1300° C. For Aker 50 Geh 50 crystals, the data fit well the equation: D= 8.6× 10− 6 exp [(− 33.5±0.1)× 10 3 cal/RT]. and for Aker 75 Geh 25: D= 7.2× 10− 6 exp [(− 31.9±0.1)× 10 3 cal/RT]. Oxygen diffuses much faster in melilite crystals than in other silicates, especially at lower temperatures. In melilite melts, the diffusion rate is comparable to other silicates but with a relatively low activation energy. The rapid exchange and diffusion of oxygen in melilite suggests that the isotopic composition of that mineral in the Ca-Al rich inclusions of carbonaceous chondrites records the isotopic composition of the last nebular gas to which they were exposed. Constraints on the earlier history of these inclusions may be deduced from the isotopic composition of the less exchangeable minerals.