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Meteorite research based on microanalysis of oxygen isotopes using SIMS

基于 SIMS 氧同位素微量分析的陨石研究

基本信息

批准号：
09440183
负责人：
HIYAGON Hajime
金额：
$ 1.54万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09440183/
关键词：
SIMS carbonaceous chondrites refractory inclusions isotopic anomaly oxygen isotopes magnesium isotopes potassium isotopes

项目摘要

I have improved the technique of microanalysis of oxygen isotopes using SIMS (secondary ion mass spectrometry). Precision of the analysis for the oxygen 17/16 and 18/16 ratios for a 10 μm spot is about ±2‰, which is excellent when compared with other laboratories in the world. Using this technique, micro-distribution of oxygen isotopes were intensively studied for inclusions and chondrules in different types of chondrites. It has been well known that refractory inclusions, or CAIs, have 4-5% excess in 0-16, and an important aim of this study was to understand their origin. During the course of the study, I and Dr. Hashimoto discovered olivine-rich inclusions which also have large O-isotopic anomalies similar to those found in CAIs, and the results were published in Science The results are very important in considering the origin of the O-isotopic anomalies, because olivine is a mineral less refractory than CAI-minerals and much abundant in chondrites. We also found that various types of inclusions in different carbonaceous chondrite groups have very similar O-isotopic anomalies. This suggests a common source or a common process for the formation of these inclusions. The results of this study suggests a possibility that some kind of chemical processes in the early solar system may be responsible for the observed O-isotopic anomalies. Also some important results were obtained for Mg and K isotopic compositions in some selected inclusions. Most of the results obtained in the present study were presented at international conferences as well as domestic ones.

我改进了使用 SIMS（二次离子质谱）进行氧同位素微量分析的技术。 10μm点的氧17/16和18/16比率的分析精度约为±2‰，与世界其他实验室相比是非常优秀的。利用这项技术，对不同类型球粒陨石中的包裹体和球粒的氧同位素微观分布进行了深入研究。众所周知，难熔夹杂物 (CAI) 在 0-16 范围内过量 4-5%，本研究的一个重要目的是了解其来源。在研究过程中，我和桥本博士发现了富含橄榄石的包裹体，其中也有与 CAI 中发现的类似的大型 O 同位素异常，结果发表在《科学》杂志上。这些结果对于考虑 O 同位素异常的起源非常重要，因为橄榄石是一种比 CAI 矿物难熔的矿物，但在球粒陨石中含量丰富。我们还发现不同碳质球粒陨石群中的各种类型的包裹体具有非常相似的O同位素异常。这表明这些内含物的形成有共同的来源或共同的过程。这项研究的结果表明，早期太阳系中的某种化学过程可能是造成观测到的 O 同位素异常的原因。对于一些选定的包裹体中的镁和钾同位素组成也获得了一些重要的结果。本研究获得的大部分成果已在国际会议和国内会议上发表。