Isotopic analyses of krypton and xenon in fourteen stone meteorites
Isotopic analyses of krypton and xenon in fourteen stone meteorites
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十四块石陨石中氪和氙的同位素分析
DOI：
10.1029/jb074i015p03874
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发表时间：
1969
影响因子：
--
通讯作者：
J. Geiss
中科院分区：
文献类型：
--
作者：
O. Eugster;P. Eberhardt;J. Geiss
本文测定了12块辉长岩和2块无球粒陨石的Kr和Kr同位素组成。除捕获组分外，还发现了由溅射和（n，γβ）反应以及裂变和放射成因的Kr和Kr，由于普通陨石的化学均匀性，在这些陨石中发现的溅射产生的Kr和Kr的浓度与溅射产生的轻稀有气体的浓度相关。结果表明，Kr谱的变化是由能谱的硬度差异引起的，而能谱的硬度差异又是造成普通方解石中Ne_（21）/He_（3）谱比变化的原因。过剩的Kr 80，Kr 82，和Xe 128产生的二次中子捕获Br和I，分别是屏蔽和大气层前陨石大小的敏感指标。在此基础上计算了一些被研究的中子慢化密度和最小大气层前半径和质量。获得了三种无球粒陨石和无球粒陨石的Kr 81辐射年龄。对于钙长石和钙贫无球粒陨石的Kr 81年龄同意从He 3浓度计算的年龄。然而，富钙的无球粒陨石显示Kr 81年龄高达一个数量级以上，表明氦3扩散损失。Br和捕获的Ar，Kr，和H2 O2的浓度之间的显着相关性已被发现。被捕获的组分的同位素组成的Kr-和Xe丰富的普通H2 O2被发现同意那些已知的碳质H2 O2;然而，霍尔Temiki无球粒陨石似乎在这方面有所不同。对于Mezo马达拉斯球粒陨石样品的不平衡的主机材料和样品的包含平衡的材料已被分析的所有五种稀有气体元素。这两个样品的spectrometric组件是在极好的协议，而被困的Ne，Ar，Kr，和氘的浓度是约20倍，在未平衡的样品。
The concentrations and isotopic compositions of Kr and Xe in twelve chondrites and two achondrites have been determined. In addition to the trapped component, Kr and Xe produced by spallation and (n, γβ) reactions as well as fission and radiogenic Xe have been found. Because of the chemical uniformity of the ordinary chondrites the concentrations of spallation-produced Kr and Xe found in these meteorites correlate with the concentrations of the spallation-produced light rare gases. It is shown that variations in the Kr spallation spectrum are caused by differences in the hardness of the energy spectrum, which are also responsible for the variations in the spallation ratio Ne21/He3 in ordinary chondrites. Excesses of Kr80, Kr82, and Xe128 produced by capture of secondary neutrons in Br and I, respectively, are sensitive indicators for shielding and preatmospheric meteorite sizes. Neutron slowing down densities and minimal preatmospheric radii and masses are calculated on this basis for some of the investigated chondrites. Kr81 radiation ages are obtained for three chondrites and for the achondrites. For the chondrites and for a Ca-poor achondrite the Kr81 ages agree with the ages calculated from the He3 concentrations. However, the Ca-rich achondrites show Kr81 ages up to one order of magnitude higher, indicating He3 diffusion losses. A remarkable correlation between the concentrations of Br and trapped Ar, Kr, and Xe in chondrites has been found. The isotopic compositions of the trapped components in Kr- and Xe-rich ordinary chondrites are found to agree with those known for carbonaceous chondrites; however, the Khor Temiki achondrite seems to differ in this respect. For the Mezo Madaras chondrite a sample of unequilibrated host material and a sample of an inclusion of equilibrated material have been analyzed for all five rare gas elements. The spallation components of both samples are in excellent agreement, whereas the concentrations of trapped Ne, Ar, Kr, and Xe are about twenty times higher in the unequilibrated sample.