Acquisition of a State-of-the-Art Thermal Ionization Mass Spectrometer

EAR-0549300Walker将通过这笔资金购买新一代热电离质谱计，马里兰大学的科学家们将能够测量某些同位素比好于+5ppm，与我们目前限制在+25ppm左右的测量设备相比，这是一个实质性的改进。改进的测量能力将使我们能够进行一系列需要超高精度分析的新的地球科学项目。需要解决的具体分析任务包括超高精度地分析夏威夷、加那利群岛和亚速尔群岛等可能的热柱来源的地幔岩石的186Os/188Os比值。我们以前的工作表明，在一些推定的烟柱来源中的186O的浓缩可能反映了先前并入的外核物质。我们将继续利用新仪器的卓越测量能力来追求这一理念。我们还将使用新仪器通过检查钨的同位素来检验这一假说。宇宙化学观察和物质平衡论证表明，与地球的硅酸盐部分相比，地球的核心在182W时是枯竭的。羽流形成的岩浆中这种同位素的非常轻微的耗尽可能意味着岩芯物质的并入。预测的影响是如此之小，以至于只有使用新仪器可能实现的最高精度的测量才能提供该项目所需的足够分辨率。明确地识别羽流形成的岩石中的核心成分可能会解决地球动力学中的主要问题。

EAR-0549300WalkerThe new generation of thermal ionization mass spectrometer to be purchased via funding from this grant will allow scientists at the University of Maryland to measure certain isotopic ratios to better than +5 ppm, a substantial improvement relative to measurements with our current equipment that are limited to approximately +25 ppm. The improved measurement capability will allow us to pursue a host of new Earth science projects that require ultra-high precision analysis. Specific analytical tasks to be tackled include the ultra-high precision analysis of 186Os/188Os ratios of mantle-derived rocks from putative plume sources, such as Hawaii, the Canary Islands and the Azores. Our previous work has suggested that enrichments in 186Os in some putative plume sources may reflect prior incorporation of outer core materials. We will continue to pursue this concept utilizing the superior measurement capabilities of the new instrument. We will also use the new instrument to test this hypothesis via examination of isotopes of tungsten. Cosmochemical observations coupled with mass balance arguments imply that Earth's core is depleted in 182W compared to the silicate portion of the Earth. Very slight depletions in this isotope in plume derived magmas would potentially implicate incorporation of core material. The predicted effects are so small that only the highest precision measurements, made possible with the new instrument, provide sufficient resolution necessary for this project. Unequivocal identification of a core component in a plume-derived rock could potentially settle major questions in geodynamics.***