グラニートの低温結晶化と地殻のマグマティズムへの影響
Michael R Ackerson1,2, B O Mysen3, N D Tailby4
1Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC, USA. ackerm4@rpi.edu.
Nature
|June 29, 2018
まとめ
グレナイトの結晶化温度は,以前考えられていたよりもはるかに低く,より冷たいマグマ体を示唆し,地球の地殻と鉱石堆積物の形成モデルに影響を与えています.
科学分野:
- 地質学
- ペトロロジー
- 地化学
背景:
- グレナイトは,シリコン火山,大陸の形成,そして地殻の特性についての洞察を提供します.
- 現在のモデルは,花岩が650~700°C以上で結晶化することを示唆している.
- グラニートの結晶温度は,様々な地質現象を理解するために重要です.
研究 の 目的:
- グラニット岩の結晶化温度を調査する.
- グラニットの高結晶化温度という 支配的なパラダイムに挑戦するためです
- グラニットの結晶化温度を改定した意味を探求する.
主な方法:
- カリフォルニアのトゥーラムネ・イントラウシブ・スイートからのクォーツ結晶の分析
- チタンインクォーツ温度計の適用
- クォーツのチタン濃度の拡散モデリングを使用します.
主要な成果:
- トゥールームンのサンプルに含まれるクォーツ結晶は,結晶化温度474~561°Cを示している.
- グラニット鉱物組成物の重要な部分は,受け入れられた固体より100〜200°C以下で結晶化します.
- 試料中のクォーツの80%以上は,これまで考えられていたより低い温度で結晶化した.
結論:
- 岩石は火山岩に相当する 侵襲性の岩石で 伝統的に認められているよりも 極めて低い温度で結晶化します
- 改訂された花岩結晶温度は,より冷たいマグマ貯蔵の観測を支持する.
- 低温は,ポルフィール鉱石の堆積物形成と地殻の熱構造の理解に影響を与えます.
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