Study of thermal history of the constituent components in chondrites and the parent body process

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The scientific results of 2004-2006 are summarized as follows ;1. Study of thermal metamorphism : I studied petrological and mineralogical features of Fe-Ni metal and spinel group minerals from various kinds of chondrites, in comparison with the characteristic features of silicates in these chondrites. I found these minerals are the best indicator for the thermal metamorphism of the most primitive chondrites. Especially, the characteristic features of Fe-Ni metal, such as texture and chemical composition, well reflect the thermal process under low-temperature conditions. I proposed a quantitative indicator to show the metamorphic degree from Fe-Ni metal, which is well consistent with another metamorphic indicator proposed recently. Spinel group minerals also reflects the low-grade thermal metamorphism. In addition, I found some spinel group minerals are relic phase which did not melt in chondrules. This indicates that some spinel group minerals preserve the information in the precursor stage of chondrules.2. Study of shocked CB chondrite : I studied a CB chondrite, Gujba, in comparison with heavily shocked ordinary chondrites. I found some high-pressure polymorphs from this chondrites. Especially, I found coesite which is the first discovery from any kinds of meteorites. I proposed that some kinds of carbonaceous chondrites experienced heavy impact process, like ordinary chondrites.I reported all these results in the annual meeting of the Meteoritical society, the international mineralogical association, and the meteorite symposium in National Institute of Polar Research.