Radiogenic Osmium in the Earth's Mantle

本提案旨在检验在夏威夷洋岛玄武岩（OIB）和诺里尔斯克的西伯利亚溢流玄武岩中测得的放射成因Os同位素组成（186 Os/ 188 Os和187 Os/ 188 Os）是否是外核和下地幔之间相互作用的表现。我们建议测试这一假设，通过测量铂族元素（PGE）丰度和Os同位素组成（186 Os/ 188 Os和187 Os/ 188 Os）在各种地幔岩性，包括几代辉石，在~470我的老Trinity橄榄岩的北方加州。为了了解放射成因186 Os/ 188 Os特征在地幔源物质中出现的频率和地理范围，我们将测量来自世界不同地区超镁铁质岩和辉石岩样品的砂矿源富Os PGE合金的Os同位素组成。来自阿曼塞梅尔蛇绿岩的横断面。 这项工作的智力价值在于可能提供一个新的工具，量化的贡献，从辉石丰富的岩性生产的大洋玄武岩。所产生的数据集将增加我们的理解的特征长度尺度同位素和亲铁微量元素的不均匀性在上地幔，阐明交代过程中的作用PGE分馏，提高我们的理解熔体迁移和熔体/围岩反应，并帮助完善PGE预算上地幔地球的形成有益的宇宙化学模型。 拟议研究的更广泛影响将是为科学家在其职业生涯的早期阶段提供发展机会。 该项目还包含丹麦和美国科学家之间合作的重要组成部分，这将有助于加强国际科学合作，并支持两国的学术基础设施。

EAR-0309414 This proposal seeks to test if the proposed radiogenic Os isotopic compositions(186 Os/ 188 Os and 187 Os/ 188 Os) measured in the Hawaiian oceanic island basalts (OIB) and in the Siberian Flood Basalts at Norilsk are manifestations of interaction between the outer core and the lower mantle. We propose to test this hypothesis by measuring platinum-group element (PGE) abundances and Os isotopic compositions (186 Os/ 188 Os and 187 Os/ 188 Os) in a variety of mantle lithologies, including pyroxenites of several generations, in the ~470 My old Trinity Peridotite of northern California. In order to understand the frequency and geographical extent with which radiogenic 186 Os/ 188 Os signatures occur in mantle derived materials, we will measure the Os isotopic composition of placer-derived Os-rich PGE alloys from ultramafic rocks in different localities world wide and in samples of pyroxenite from a transect of the Semail Ophiolite, Oman available to us. The intellectual merit of this work lies in potentially providing a new tool for quantifying the contribution from pyroxene-rich lithologies to the production of oceanic basalts. The generated data set will increase our understanding of the characteristic length scales for isotopic and siderophile trace element heterogeneity in the upper mantle, elucidate the role of metasomatic processes in fractionation of PGEs, improve our understanding of melt migration and melt/wall-rock reactions, and help refine the PGE budget of the upper mantle benefiting cosmochemical models for Earth's formation. The broader impacts of the proposed research will be to provide an opportunity for the development of a scientist in the early stages of his career. This project also contains a strong component of collaboration between Danish and American scientists, which will serve to bolster international scientific collaboration, and support for academic infrastructure in both countries.