天然ダイヤモンドの包有物から探るダイヤモンド生成環境

概要

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Recent progresses on mineralogy and geochemistry of diamond and its inclusions are reviewed. There are two categories of materials contained in natural diamonds. One is chemical impurities such as nitrogen, boron, hydrogen, nickel, cobalt, etc. that are all structurally bound to the diamond lattice. The latter two transition metals are typical impurities in synthetic diamonds grown in metal solvent at high pressure and high temperature. Nitrogen atoms in natural diamonds are aggregated at elevated temperatures and for geological time. The aggregation state of nitrogen can be investigated with infrared spectroscopy and provide us with chronological information on the history of diamonds. The other category is mineral and fluid inclusions. Diamond is chemically stable and the hardest material, and inclusions in diamonds can bring versatile information of mantle. In particular, residual pressures recorded in the inclusions can provide us with depth information where their inclusions were entrained in host minerals. Furthermore, mineralogical and geochemical features of diamonds from the lower mantle recently found are reviewed.
日本鉱物科学会の論文
2004-05-30