由同位素记录的地球演变的地力学状态
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在PubMed上查看摘要
概括
此摘要是机器生成的。地球的地幔有层层的结构. 同位素揭示了大陆地的重要提取发生在35亿至27亿年前,有限的地幔混合保留了原始的下层地幔储备.
科学领域
- 地质化学
- 同位素地质学
- 星球科学
背景情况
- 地球的地幔分为上层和下层,由660公里深的地震断层分开.
- 地球历史上这些地幔层之间的物质交换程度尚不清楚.
- 大陆地形成导致 (Ti) 同位素分离,留下同位素较轻的残留物.
研究的目的
- 通过使用稳定的同位素, 调查地球地幔领域之间的质量转移.
- 重建地球上层地幔组成的演变及其与大陆地的联系.
- 评估地质时间上的上层和下层地幔水库之间的混合程度.
主要方法
- 超高精度测量49Ti/47Ti的比率,古代地幔衍生的岩 (3.82.0亿年前),和现代海洋岛基岩 (OIBs).
- 基于体价值的新批量土 (BSE) 同位素估计的计算.
- 同位素组成的比较,以追踪地幔演变和地循环.
主要成果
- 大量酸盐地球 (BSE) 的同位素成分估计比现代上层地幔 (正常的中海基岩,N-MORBs) 重0.052±0.006‰.
- 地球的上层地幔在35亿年前之前具有同位素的比率,并在大约35亿至27亿年前演变为类似N-MORB的组成.
- 观察到的同位素偏移意味着不到30%的地幔与回收的地物质保持平衡,这表明上下地幔交换有限.
结论
- 大陆地的重要提取发生在35亿至27亿年前的时期.
- 地幔层之间的有限质量交换在地球历史的大部分时间里都保留了原始的下层地幔储存库.
- 现代板块构造学,以实质上下地幔质量转移为特征,是地球进化中相对较新的现象.
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