西オーストラリア州ジャックヒルズのジルコンのハデアンダイヤモンド
Martina Menneken1, Alexander A Nemchin, Thorsten Geisler
1Institut für Mineralogie, Westfälische Wilhelms-Universität, Corrensstr. 24, 48149 Münster, Germany. m_menn03@uni-muenster.de
Nature
|August 24, 2007
まとめ
4.25億年前のジャック・ヒルズ・ジルコンの内で見つかった地上の最も古いマイクロダイアモンドは,初期の地球には厚い大陸の地殻があり,地殻とマントルの相互作用を経験したことを示唆しています. この発見は,初期の地球進化とダイヤモンドの形成に関する私たちの理解を形づくっています.
科学分野:
- 地質科学は地質科学である.
- ミネラロジーは,鉱物学です.
- 初期の地球の歴史 初期の地球の歴史
背景:
- ジャック・ヒルズのジルコンは,最も古い地殻の断片であり,初期の地球についての洞察を提供します.
- 以前の研究では,大陸の早期の地殻のリサイクルと花岩の溶融の生産が示唆されていた.
研究 の 目的:
- 古代のジャック・ヒルズ・ジルコンの内部にあるマイクロダイアモンドの含有物を調査するために.
- これらのマイクロダイアモンドの年齢と特徴を決定するために.
- ダイヤモンドの発見に基づいて,初期の地球進化の条件を推論する.
主な方法:
- デトリタルジルコンの内部のインクルージョンの顕微鏡検査.
- ジルコンの含有物の放射線年代測定.
- ダイヤモンドインクルージョンのラーマン光譜.
- ミネラル・アソシエーション (グラファイト) の分析.
主要な成果:
- ジャック・ヒルズのジルコンの微小ダイヤモンド含有物発見,年齢は3,058~4,252百万年.
- これらは,地上の岩石で発見された最も古いダイヤモンドです.
- ダイヤモンドの鉱物学は,超高圧変形過程で形成されたものによく似ています.
結論:
- この発見は,比較的厚い大陸の石層が少なくとも425億年前に存在していたことを示唆している.
- 重要な地殻-マントルの相互作用が,ハデウムやエオルケウム時代に起こったことを示唆しています.
- 年代差は,ダイヤモンドの形成条件が繰り返されているか,または古代のダイヤモンドのリサイクルが繰り返されていることを示しています.
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