下マントラフェーズ (Mg,Fe) 1-xOOの高温電気伝導メカニズム

Dobson¹, Richmond, Brodholt

¹Department of Geological Sciences, University College London, London WC1E 6BT, UK.

Science (New York, N.Y.)

|March 21, 1997

まとめ

下層マントルマグネシウスの電気伝導性は,温度によって変化します. 高温での小さなポラロンから大きなポラロン伝導への移行は,地球の深い内部のモデルに影響を与えます.

科学分野:

地質物理学と鉱物物理学
高圧・高温の実験研究

背景:

マグネシウスは,地球の下層マントルの重要な段階です.
前回の大気圧での研究では,Fe2+-Fe3+ホッピング (小さなポラロン) が導電性を支配することを示唆していました.

研究の目的:

下層マントル条件 (高圧,高温) のマグネシウムウステルの電気伝導性を調査する.
マントルの適切な温度で支配的な負荷輸送機構を決定する.
Fe3+ 含有量の変動が導電性に与える影響を評価する.

主な方法:

マグネシウムウステルで電気伝導性を実験的に測定した.
圧力,温度,Fe3+含有量の変動.
実験データに基づくチャージ輸送メカニズムの分析.

主要な成果:

電気伝導性の測定は,温度に依存する電荷輸送機構を明らかにしています.
低温では,結果は小さなポラロン伝導と一致する.
より高い温度 (マントル関連) では,大きなポラロンメカニズムが示されています.

結論:

マグネシウスの電荷輸送機構は,温度が上昇すると,小さなポラロンから大きなポラロンへと移行する.
この移行は,地質学的データを解釈し,下層マントルの電気的性質をモデル化するために重要な意味を持つ.
マントルの条件への正確なエクストラポレーションには,このメカニズムシフトとその組成的依存性を考慮する必要があります.

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