难以捉摸的Hadean丰富的水库,由Isua Archaean岩石中的142Nd赤字揭示出来
Hanika Rizo1, Maud Boyet, Janne Blichert-Toft
1Clermont Université, Université Blaise Pascal, Laboratoire Magmas et Volcans, CNRS UMR 6524, IRD R 163, BP 10448, 63000 Clermont-Ferrand, France. h.rizo@opgc.univ-bpclermont.fr
Nature
|November 7, 2012
概括
早期地球地幔的分化是由格陵兰西南部34亿年前的岩石中新-142 (142Nd) 缺陷证明的. 这一发现揭示了一种在哈迪时代形成的互补丰富成分,以前未被发现.
科学领域:
- 地质化学 地质化学
- 早期地球的差异化分化.
- 同位素计时仪的时间计.
背景情况:
- 已灭绝的萨马-146 (146Sm) 新-142 (142Nd) 系统提供了早期酸盐地球分化的证据.
- 在37亿年前的伊沙岩石中发现的142 (142Nd) 过剩表明它来自一个哈迪时代被耗尽的地幔.
- 质量平衡规定,早期的分化还必须创造一个互补的丰富成分,这一直是难以捉摸的.
研究的目的:
- 为了识别哈迪时代丰富地组成部分的特征,以补充伊沙岩石中发现的枯竭水库.
- 研究地球地幔中早期形成的异质的存在和性质.
主要方法:
- 在格陵兰西南部34亿年前的地形堤中分析同位素比率 ((142Nd/144Nd)).
- 将测量的142Nd值与地面标准进行比较,以检测缺陷.
主要成果:
- 在七个地形堤中,有七个的地形堤相对于陆地标准有142Nd的缺陷.
- 三个样本显示出可解决的重大赤字,降至-10.6百万分之一.
- 这些缺陷表明,地幔中存在哈第安丰富的成分.
结论:
- 鉴定到的142Nd赤字证实了哈地亚中存在一种富含成分的存在.
- 这种丰富的组成部分可能代表一个差异化的岩海洋储备或一个岩原地.
- 结果表明,格陵兰西南部地幔保留了早期形成的异质性,直到至少34亿年前.
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