水熱プロセスとボストーク湖の水交換の制限は,ヘリウム同位体から発生する
P Jean-Baptiste1, J R Petit, V Y Lipenkov
1Laboratoire des Sciences du Climat et de l'Environnement, CEA/CNRS, Centre d'études de Saclay, 91191 Gif sur Yvette, France. pjb@lsce.saclay.cea.fr
Nature
|May 25, 2001
まとめ
南極のヴォストーク湖のヘリウム同位体分析
科学分野:
- 地質化学 地質化学
- 氷河学 氷河学とは
- イソトープ分析とは
背景:
- ヴォストーク湖は,南極大陸最大の氷河下の湖で,氷の3,750×4,100mの下に埋まっている.
- 凍った湖水から形成された氷は,亜氷河環境の洞察力を提供します.
- 氷の中のヘリウムイソトープは,亜氷河湖の過程のユニークなトレーサーを提供します.
研究 の 目的:
- ヴォストーク湖の積んだ氷の中でのヘリウムの起源を調査するために.
- 湖内の水熱またはマントル駆動のエネルギー源の可能性を評価する.
- 湖の水の再生時間を推定するために.
主な方法:
- ウォストーク駅の掘削穴から採取した氷核サンプルにおけるヘリウムイソトープ (3He/4He比) の分析.
- 氷河の氷と蓄積した湖の氷の間の境界を表す氷のセクションの試験.
- 湖の再生時間を決定するためのヘリウム流と予算のモデリング.
主要な成果:
- アクレートされた氷は,大陸の地殻に特徴的な放射性同位体シグネチャーを持つヘリウム濃縮を示している.
- 測定された3He/4He比率は,高エンタピーマントルまたは水熱プロセスからの有意な投入と矛盾しています.
- 推定ヘリウム予算は,湖水再生時間が約5,000年であることを示唆しています.
結論:
- ヴォストーク湖のヘリウム源は,周囲の古代大陸の地殻から発生しています.
- 大量の水熱またはマントル駆動の熱源が湖に影響を与える可能性は低い.
- ヴォストーク湖は,数千年の間,比較的長い水再生の時間スケールを持っています.
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