Pre-exposure to cosmic rays of chondrules and Ca-, Al-rich inclusions

在确定太阳系原始物质的年代时，最不直接的可能是确定第一个组成单元形成和它们压实之间的时间。在原始陨石（陨石）的情况下，这些组成单位是基质，球粒和（特别是在碳质陨石的情况下）富含Ca-Al的包裹体。如果在太阳系早期，这些陨石暴露在宇宙辐射中，它们应该显示出相对于其暴露年龄（从陨石母体到地球旅行期间的“最近”辐射）产生的丰度的宇宙成因同位素过剩，这应该是可检测的。文献数据在少数情况下提供了一些线索，说明球粒中宇宙成因惰性气体同位素相对于大块物质过量，因此被解释为太阳星云中球粒的预辐照。我们计划通过分析大量球粒和相应的具有明确化学成分的大块/基质样品，特别是顽火辉石和铬榴石，扩大和改进数据库;在文献中提供化学成分不同样品的新生产率也将使解释结果比过去更可靠。在稍后的阶段，我们计划将这些调查扩展到富钙铝夹杂物。

In dating primitive Solar System materials, probably least straightforward is the determination of the time between formation of the first compositional units and their compaction. In case of the primitive meteorites (the chondrites) these compositional units are matrix, chondrules and (in the particular in case of the carbonaceous chondrites) Ca-Al-rich inclusions. If in the Early Solar System these were exposed to the cosmic radiation, they should show excesses of cosmogenic isotopes relative to the abundances produced during their exposure age (the “recent” irradiation during travel from meteorite parent body to Earth) that should be detectable. Literature data provide hints in a few cases for excesses of cosmogenic noble gas isotopes in chondrules relative to bulk material that accordingly have been interpreted as pre-irradiation of chondrules in the solar nebula. We plan to enlarge and improve the database by analysis of a large number of chondrules and corresponding bulk / matrix samples with well determined chemical composition, in particular from enstatite and CR chondrites; the availability in the literature of new production rates for chemically diverse samples will also make it possible to interpret the results more reliably than in the past. At a later stage we plan to extend these investigations to Ca-Alrich inclusions.