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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 >Osmium and lead isotopes of rare OsIrRu minerals: derivation from the core-mantle boundary region?
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Osmium and lead isotopes of rare OsIrRu minerals: derivation from the core-mantle boundary region?

机译：稀有OsIrRu矿物的s和铅同位素：是源自岩心幔边界区域？

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摘要

We report exceptionally high ~(186)Os/~(188)Os for rare crystals of OsIrRu found in unconsolidated sediment near Port Orford, SW Oregon (USA), that are held to be derived from peridotite in the nearby Klamath Mountains. These OsIrRu samples differ in composition from OsIr alloys thought to have formed in the upper mantle. They have resided in equilibrium with an evolved and highly supra-chondritic Pt/Os reservoir. We explore these data in the content of the core-mantle mixing model relevant to some deep-seated plume systems, and find the investigated alloys to exhibit an apparent coupled ~(186)Os/~(188)Os and ~(187)Os/~(188)Os (#gamma#Os(t = 1.4Ga) = +6 to 10) enrichment relative to the chondritic mantle at approx 1.4 Ga. Our interpretation is that these samples crystallized at approx 1.4 Ga in a long-term Pt/Os and Re/Os enriched region, similar to that expected for Earth's outer core or the core-mantle transition zone (D" layer). Subsequently, these OsIrRu samples were transported from the core-mantle boundary region to the lithosphere as xenoliths in a mantle plume/convection system. Lead isotopes positively exclude a crustal origin of these OsIrRu crystals and support our estimated time of crystallization.
机译：我们报道俄勒冈州西南部奥福德港附近的未固结沉积物中发现的OsIrRu稀有晶体异常高〜（186）Os ~~（188）Os，这些晶体被认为是源自附近克拉马斯山的橄榄岩。这些OsIrRu样品的成分与认为在上地幔中形成的OsIr合金不同。它们一直处于平衡状态，且处于演化的高度超软骨状的Pt / Os储层中。我们在与某些深层羽流系统有关的芯幔混合模型的内容中探索了这些数据，并发现所研究的合金表现出明显的〜（186）Os /〜（188）Os和〜（187）Os耦合/〜（188）Os（＃gamma＃Os（t = 1.4Ga）= +6至10）在约1.4 Ga时相对于软骨膜地幔富集。我们的解释是，这些样品长期在约1.4 Ga下结晶Pt / Os和Re / Os富集区域，类似于地球外核或核幔转换区（D”层）的预期区域。随后，这些OsIrRu样品作为异岩被从核幔边界区域运至岩石圈。在地幔柱/对流系统中，铅同位素确实排除了这些OsIrRu晶体的地壳起源，并支持了我们估计的结晶时间。

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