Chemical composition of Fe-Ni metal and phosphate minerals in Yamato-82094 carbonaceous chondrite

概要

論文の詳細を見る
The mineralogy of Fe-Ni metal and associated minerals in the Yamato (Y)-82094 carbonaceous chondrite (CO) have been studied by optical, scanning electron microscope and electron microprobe techniques. There are some characteristic features for the Fe-Ni metal in the Y-82094 : (1) Ni contents in taenite grains are divided into two groups consisting of low-and high-Ni taenite. (2) Partition of Co between coexisting kamacite and taenite shows relatively higher temperatures (approximately 800℃), and their temperature ranges are wide. (3) polycrystalline taenite exists. (4) Fe-Ni metal and troilite form micron-sized intergrowths. (5) The Ni-Co trend of kamacite in chondrule is positive. The high-Ni taenite could have formed through thermal metamorphism on the parent body, while low-Ni taenite might have formed due to reheating caused by shock metamorphism on the parent body or during the colling process of chondrule formation. The positive Ni-Co trend of kamacite in Y-82094 is similar to that of the metal in CR chondrites. This trend may suggest that kamacite in Y-82094 preserves the primitive chemical composition indicating nebula condensation origin. The Fe-Ni metal grains have many phosphate mineral inclusions (whitlockite, brianite and panethite). The mode of occurrence of brianite and panethite indicates that they might have formed simultaneously with the Fe-Ni metal in the nebula.
国立極地研究所の論文