地上の炭素と窒素の同位体比は,クレタセアス時代と第三期の境界ナノダイアモンドから得られた
Science (New York, N.Y.)
|December 4, 1992
まとめ
クレタセウス-第3期 (K-T) の境界にあるナノメートルのサイズのダイヤモンドは,星間型ではありません. 同位体分析により,それらは衝突によって生成され,既知の隕石のダイヤモンドとは異なることが明らかになった.
科学分野:
- 地質化学 地質化学
- 宇宙化学 (コスモケミストリー)
- 惑星科学 惑星科学
背景:
- ナノメートルのサイズのダイヤモンドは,白亜紀-三次紀 (K-T) の境界で発見されています.
- ある仮説によると,これらのダイヤモンドは小惑星の衝突による星間粒子の残骸である.
研究 の 目的:
- K-T境界におけるナノメートルのサイズのダイヤモンドの起源を調査する.
- これらのダイヤモンドが恒星間または衝突起源であるかどうかを判断するために.
主な方法:
- 北米とイタリアのK-T境界ダイヤモンドにおける炭素 (13C/12C) と窒素 (15N/14N) の同位体比の分析.
- 同位体シグネチャーを,既知の隕石や地上のダイヤモンドの源と比較した.
主要な成果:
- 北米の遺跡から採掘されたダイヤモンドは,炭素と窒素の同位体組成と窒素の豊富さを有する2つの成分混合物を示している.
- イタリアの遺跡から採取したダイヤモンドには,これらの構成要素の証拠はない.
- K-Tダイヤモンドの同位体シグネチャーは,星間ダイヤモンドを含む,既知の隕石ダイヤモンドとは異なる.
結論:
- K-T境界のナノダイアモンドは,星間起源ではない.
- 同位体データは,ダイヤモンドが小惑星の衝突イベントまたはそれに関連する火球の間に形成されたことを強く示唆しています.
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