The mobilisation of Platinum-Group Elements in altered oceanic crust from ODP-borehole 1256D for tracing the noble metal flux in the crust

ODP 钻孔 1256D 改变的洋壳中铂族元素的动员，用于追踪地壳中的贵金属通量

• 批准号: 49066181
• 负责人: Professor Dr. Heinz-Günter Stosch
• 金额: --
• 依托单位: Abteilung Mineralogie und Petrologie
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2007
• 资助国家: 德国
• 起止时间: 2006-12-31 至 2010-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/49066181?language=en
• 关键词: mobilisation; Platinum; Group; Elements; altered

Mafic volcanic rocks of different tectonic settings display a wide range of Pt/Pd-ratios lower than that of the primitive mantle (PM) which cannot be accounted for by known partition coefficients of Pd and Pt between sulphide melt and silicate melt. Various processes have been invoked to explain this observation, including hydrothermal rock/water interactions or serpentinisation. However, so far no study has systematically investigated the effects of hydrothermal alteration on the PGE budget for example on a complete section of altered upper oceanic crust. Hence, little is known on Pt-Pd fractionation during alteration. We propose to fill this gap by studying a complete profile of altered upper oceanic crust and the uppermost gabbroic section, formed at the East Pacific Rise some 15 Ma ago and drilled at the multicruise ODP-borehole 1256D (Wilson et al., 2006). Combined measurements of platinum-group elements (PGE) and Cu-Sisotopes in key pool samples, shared with other shipboard party members, will help to evaluate PGE mobility during alteration and to study quantitatively the fractionation behaviour of Pt and Pd along the hydrothermal fluid path in the oceanic crust. These insights are highly relevant for understanding ore forming processes in the oceanic crust, since large PGE deposits are related to mafic volcanism (i.e. Norils’k).

不同构造环境的基性火山岩显示出比原始地幔 (PM) 低的大范围 Pt/Pd 比率，这不能用已知的 Pd 和 Pt 在硫化物熔体和硅酸盐熔体之间的分配系数来解释。人们利用各种过程来解释这一观察结果，包括热液岩石/水相互作用或蛇纹石化。然而，到目前为止，还没有研究系统地研究热液蚀变对 PGE 预算的影响，例如对蚀变上洋地壳的完整部分的影响。因此，人们对蚀变过程中 Pt-Pd 分馏知之甚少。我们建议通过研究蚀变上洋地壳和最上面的辉长岩部分的完整剖面来填补这一空白，这些剖面形成于大约 15 Ma 前的东太平洋隆起，并在多巡航 ODP 钻孔 1256D 中钻探（Wilson 等人，2006 年）。对关键池样品中铂族元素 (PGE) 和铜同位素的联合测量，并与其他船上成员共享，将有助于评估蚀变过程中 PGE 的迁移率，并定量研究 Pt 和 Pd 沿洋壳热液路径的分馏行为。这些见解对于了解洋壳中的成矿过程高度相关，因为大型 PGE 矿床与镁铁质火山活动（即 Norils’k）有关。