Studies on the Primordial Noble Gases and the Carrier Phases in Carbonaceous Chondrites Using the Laser Microprobe.

由于原始稀有气体组分给我们提供了太阳系形成的信息，所以对原始陨石的稀有气体研究对于了解太阳系初始阶段的历史是非常重要的。已知原始稀有气体在碳质球粒陨石中分布不均匀。我们尝试用激光微探针对陨石中的斑点区域提取惰性气体，来研究陨石中惰性气体的载流相及其位置。改进了稀有气体质谱仪和稀有气体分析软件，使之能够准确、快速地测定极少量的稀有气体。分析了40多个点的Allende和Murchison碳质球粒陨石。到目前为止获得的一些有趣的结果如下：1)在阿连德的CaI中异常高的^4He、^&lt；40和^&lt；Ar和^&lt；129&gt；Xe意味着挥发性元素K和I的高浓度以及CaI中的高U含量。2)Allende球粒陨石和Murchison球粒陨石中捕获的Ne的同位素比值不同，这可能表明这些球粒陨石形成的环境不同。

Since the primordial noble gas component gives us informations about the formation of solar system, noble gas studies on primitive meteorites are very important to know the history of an initial stage of solar system. It is known that the primordial noble gases are distributed inhomogeniously in carbonaceous chondrites. We attempted to investigate the noble gas carrier phases and their position in meteorite using the laser microprobe for noble gas extraction from spot area in the meteorite. Noble gas mass spectrometer and software for noble gas analysis have been improved to be able to measure extremely small amount of noble gases accurately and quickly.More than 40 points of Allende and Murchison carbonaceous chondrites have been analyzed. Some of the interesting results obtained until now are followings ;1) Anomarously high concentrations of ^4He, ^<40>Ar and ^<129>Xe in CAIs of Allende imply high concentrations of volatile elements K and I as well as high U content in CAIs. As CAIs are thought to be high temperature condensates, the high concentrations of volatiles are difficult to be explained.2) Isotopic ratios of trapped Ne in chondrules are different between Allende and Murchison, which may suggest different circumstances for chondrule formation of these chondrites.