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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Re-Os systematics and platinum-group element distribution in metalliferous sediments from the Troodos ophiolite
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Re-Os systematics and platinum-group element distribution in metalliferous sediments from the Troodos ophiolite

机译：Troodos蛇绿岩中含金属沉积物中的Re-Os系统学和铂族元素分布

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Umbers from 8 of 11 localities studied yield ~(187)Os/~(188)Os ratios that range from 0.51 to 0.57. We interpret this range as reflecting the Os isotopic composition of mid-Cretaceous seawater. ~(187)Os/~(188)Os measured in samples from the remaining three localities fall above and below this range and are believed to result from post-depositional redistribution of Os. Extremely large ~(187)Os/~(188)Os ratios occur in hydrothermal sulfides (> 200) and in their oxidation products, ochres (3.6-13.2). Measured Re/Os ratios in these samples require open system behavior. Model age calculations indicate that ochre formation occurred a 1-5 million year interval after sulfide precipitation. In most samples > 99% Re loss occurred during sulfide oxidation. Comparison of element ratios in Cyprus umbers to those of modern seawater suggest the following sequence of scavenging efficiency by hydrothermal Fe-oxides: Ir > Pt > Os > Re. Cyprus sulfides exhibit the opposite pattern of element enrichment. These patterns of aqueous platinum-group element (PGE) fractionation are potentially relevant to study of recycled Os in mantle-derived rocks because they give rise to the following phenomena: (1) ephemeral Re enrichment within the basal sediments of the oceanic crust, (2) PGE concentrations in metalliferous sediments (Os up to 1 ppb and Pt up to 22 ppb) that are comparable to those in the mantle, and (3) Pt/Re ratios in Cyprus umbers that exceed those required to explain the coupled ~(186)Os-~(187)Os variations in Hawaiian basalts.
机译：来自11个地区中的8个的翁伯研究了〜（187）Os /〜（188）Os的比率，范围为0.51至0.57。我们将该范围解释为反映了白垩纪中期海水的Os同位素组成。从其余三个位置的样品中测得的〜（187）Os /〜（188）Os高于和低于此范围，并且被认为是由Os的沉积后重新分布引起的。在热液硫化物（> 200）及其氧化产物石（3.6-13.2）中，存在极高的〜（187）Os /〜（188）Os比。这些样本中测得的Re / Os比率要求系统开放。模型年龄计算表明，o石形成发生在硫化物沉淀后的1-5百万年。在大多数样品中，> 99％的Re损失在硫化物氧化过程中发生。塞浦路斯石楠与现代海水中元素比的比较表明，水热铁氧化物清除效率的顺序如下：Ir> Pt> Os> Re。塞浦路斯硫化物显示出相反的元素富集模式。铂族元素水溶液（PGE）的这些分馏模式可能与研究地幔衍生岩石中​​的回收Os有关，因为它们会引起以下现象：（1）大洋地壳基础沉积物中的短暂Re富集，（ 2）含金属沉积物中的PGE浓度（Os高达1 ppb，Pt高达22 ppb）与地幔中的PGE浓度相当;（3）塞浦路斯矿中的Pt / Re比值超过了解释耦合〜（ 186）Os-〜（187）Os在夏威夷玄武岩中的变化。

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