布什维尔德岩石和同期钻石的大陆地幔签名
Stephen H Richardson1, Steven B Shirey
1Department of Geological Sciences, University of Cape Town, Rondebosch 7701, South Africa. steve.richardson@uct.ac.za
Nature
|June 13, 2008
概括
布什维尔德 (Bushveld) 综合体是一个复杂的地区.
科学领域:
- 地质化学 地质化学
- 经济地质学 地质学
- 石化学 石化学是一门学科.
背景情况:
- 布什维尔德 (Bushveld) 综合体是地球上最大的层次侵入,是白金组元素 (PGEs) 的主要存储库.
- 现有的模型将布什维尔德PGE矿化归因于岩的地污染,但由于入侵的规模和均性,这一点受到挑战.
- 地震数据表明,地幔相互作用早于布什维尔德岩,暗示了其组成部分的更深层起源.
研究的目的:
- 调查布什维尔德复杂矿物化的起源及其相关的PGEs.
- 通过检查地幔贡献来测试当前地污染模型.
- 为了利用钻石包装作为古代大陆地幔的探测器.
主要方法:
- 分析来自威尼斯和Premier kimberlites的钻石中的硫化物含量.
- 在硫化物含量中确定 (Os) 同位素比率.
- 在硫化物和酸盐样本中测量Re-Os,Sm-Nd和Rb-Sr同位素组成.
主要成果:
- 钻石中的硫化物含量表现出比布什维尔德矿石更多的放射性同位素签名.
- 同位素数据表明来自大陆地幔 (哈兹堡石,生态石) 和对流地幔岩的贡献.
- 这些地幔组成部分很可能参与了钻石和布什维尔德综合体的起源.
结论:
- 布什维尔特PGEs的主要来源是地幔,而不是大陆地.
- 由钻石取样的大陆地幔在布什维尔德复杂的形成中起到了至关重要的作用.
- 这一发现挑战了既定模型,并突出了地幔过程在PGE大规模矿化中的重要性.
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