* Astronomy

Mineralogy and petrology of the Kirin meteorite and its formation and evolution.
Research Group of the Composition of the Kirin Meteorite Shower, Kweiyang Institute of Geochemistry, Academia Sinica

Optical identification and X-ray powder study, coupled with monomineral microchemical and electron microprobe analyses have revealed 39 species of mineral in the Kirin Meteorite. On the basis of mineral assemblages characteristic of the meteorite, thermometric data on fluid inclusion and theoretical analysis, seven formation stages have been proposed for the minerals present in the Kirin Meteorite. The calculations of normative minerals and chemical parameters have been conducted in terms of the chemical analyses, and the chemical-petrological characteristics of the Kirin Meteorite specifies it to Type H_5. The present paper deals with the texture-structure of the Kirin Meteorite, and the meteoritic chondrules are divided into 17 categories of texture-structure, and three possible mechanisms regarding their origin are discussed. It is evident that the Kirin parent body once experienced marked thermal metamorphism and moderate-shock metamorphism and the major features concerned are herein described and analysed. On the grounds of the above studies, four stages, including 12 processes, have been suggested with respect to the formation and evolution, of the Kirin Meteorite: (i) fractionation and condensation of the solar nebula, (ii) accretion of the parent body and its thermal metamorphism, (iii) shock-metamorphism and breaking-up of the parent body, and (iv) falling process. Additionally, a preliminary theoretical analysis and discussion are made on the physico-chemical environments for each of the evolutional stages.

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