地球地-地幔系统的早期历史是从的同位素在chondrites推断的
Martin Bizzarro1, Joel A Baker, Henning Haack
1Geological Museum, Oster Voldgade 5-7, 1350 Copenhagen K, Denmark. mbi@dlc.ku.dk
Nature
|February 28, 2003
概括
-176到 hafnium-176 (Lu-Hf) 的衰变系统揭示了早期的地球.
科学领域:
- 地质化学 地质化学
- 太空化学 太空化学
- 同位素地质学的同位素.
背景情况:
- 卢-Hf同位素系统对于理解地球早期地和地幔演变至关重要.
- 精确的-176 (lambda176Lu) 放射性衰变常数和大量地球参数对于解释Lu-Hf同位素数据至关重要.
- 以前的解释表明,早期的大陆地是从丰富的地幔中提取的.
研究的目的:
- 通过使用外星样本来精制-176 (lambda176Lu) 的放射性衰变常数.
- 重新评估地球早期地幔演化的模型.
- 为了研究早期太阳系材料的同位素组成.
主要方法:
- 测量Lu-Hf同位素的测量是在地铁和岩地铁上进行的.
- 一个Lu-Hf的同位素被定义使用石数据.
- 兰巴达176Lu值的计算是基于混凝土的同位素和混凝土形成的年龄.
主要成果:
- 合金矿产生了一个精确的lambda176Lu值为1.983 +/- 0.033 x 10^-11 yr^-1.
- 这种衰变常数表明,地球上最古老的矿物质起源于一个枯竭的地幔源.
- 地幔枯竭事件发生在行星积聚后的3200万年内.
结论:
- 新的lambda176Lu值挑战了对同位素丰富的早期地球地幔的先前模型.
- 有证据表明,在地球历史上很早就存在着一个枯竭的地幔水库.
- 这些发现与从灭绝的放射性核素中推断出的时间一致,支持早期分化.
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