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).

不同构造环境的镁铁质火山岩显示出比原始地幔（PM）低的PT/PD-RATIOS，这些PT/PD（PM）无法通过硫化物融化和有机硅熔体之间的PD和PT的已知分区系数来解释。已经调用了各种过程来解释这一观察结果，包括水热岩/水相互作用或蛇形化。但是，到目前为止，还没有系统地研究了水热改变对PGE预算的影响，例如，上海皮的整个部分。因此，在改变过程中PT-PD分馏知之甚少。我们建议通过研究改变的上海皮和最上面的gabbroic部分的完整曲线，该部分在大约15 MA前的东太平洋上升，并在多元文化的ODP钻孔1256d钻探（Wilson等，2006）。与其他船只党成员共享的铂类元素（PGE）和CU-Sisotopes的合并测量将有助于评估PGE在变化过程中的PGE迁移率，并定量研究PT和PD在大洋壳中沿水热路径的分级行为。这些见解与在海洋地壳中理解矿石形成过程高度相关，因为大型PGE沉积物与镁铁质火山含量有关（即Norils’k）。