陆地地幔的非混凝土性硫同位素组成
J Labidi1, P Cartigny, M Moreira
1Laboratoire de Géochimie des Isotopes Stables, Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, UMR 7154 CNRS, 1 rue Jussieu, 75005 Paris, France. labidi@ipgp.fr
Nature
|September 6, 2013
概括
地球的地幔显示了不同的硫同位素比率,挑战了同质组成的想法. 这种异质性表明,与核心-地幔分化和浮沉沉积物有联系,而不仅仅是晚期的添加.
科学领域:
- 地质化学 地质化学
- 行星科学 行星科学
- 同位素地球化学 同位素地球化学
背景情况:
- 核心-地幔分化是一个主要的行星事件,通过吸收硫等 siderophile 元素来影响地幔组成.
- 地球的地幔被认为具有同质的和同质的硫同位素比率 ((34) S/ ((32) S).
- 这种假设支持了地幔硫预算模型,其中占主导地位的是晚期积聚的材料.
研究的目的:
- 为了研究地球地幔的硫同位素组成 ((34) S / ((32) S).
- 为了确定地幔硫比是否均或异质.
- 为了将硫同位素与其它地幔同位素标记物相关联,并了解它们的起源.
主要方法:
- 在南大西洋山脊的中洋山脊玄武岩中分析硫同位素比例 ((34) S/(32) S).
- 在同一样本中测量 ((87) Sr / ((86) Sr) 和 (143) Nd / ((144) Nd) 同位素.
- 对同位素混合的建模,以解释观察到的异质性的起源.
主要成果:
- 地幔中硫同位素的比率 ((34) S/ ((32) S) 是异质的,不像以前认为的那样是同质的.
- 这些变化直接与 (87) Sr / (86) Sr) 和新 (143) Nd / (144) Nd) 同位素比率相关.
- 一个被耗尽的地幔末端显示出显著负的 δ(34) S 值,即使在表面添加了硫,也与体值不一致.
结论:
- 在硫同位素中观察到的地幔异质性表明一个回收组件,可能是沉积物.
- 数据表明核心-地幔分化记录,其中核心的 (34) S / (32) S比率略高于地质.
- 地幔的硫预算保留了早期核心-地幔分化的印记,尽管后来添加了元素.
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