Develpment of a Laser-Excited System for 16 O, 17 O, and 18 O Analysis of Molecular Oxygen from Small Samples of Silicate and Oxide Minerals

9708023佩里这笔赠款提供65,895美元，作为购买必要组件的一半支持，以开发基于激光的氧气提取系统，用于对从氧化物和硅酸盐矿物中释放出来的分子氧进行直接质谱分析。直接分析分子氧具有以下优势：减少氧在转化为CO而不是传统激光氟化中的二氧化碳时发生的同位素分馏；将能够分析包括17O在内的所有三种稳定的氧同位素，而由于等压干扰，传统的二氧化碳质谱分析无法确定17O；并且将能够分析亚毫克大小的样品，从而提高硅酸盐和氧化物矿物氧同位素研究中可实现的空间分辨率。这一系统的能力应当能够研究一些地球科学的基本问题，这些问题本来可能很难解决，例如阐明记录在非常小的、可确定的未改变的海洋硅质岩和碳酸盐样品中的海水氧同位素历史和微化石测试，以及根据对橄榄石斑晶的氧同位素分析确定俯冲成分(即沉积物、蚀变洋壳、流体、熔体)对弧形火山的相对贡献。***

9708023 Perry This grant provides $65,895 as one-half support of the costs of acquiring necessary components to develop a laser-based oxygen extraction system for direct mass spectrometric analyses of molecular oxygen liberated from oxide and silicate minerals. Direct analysis of molecular oxygen has the advantages of; reducing isotopic fractionation that occurs when oxygen is converted to CO instead of CO2 as in conventional laser fluorination; will allow analysis of all three stable isotopes of oxygen including 17O, which cannot be determined by conventional CO2 mass spectrometric analysis due to isobaric interference; and, will allow analysis of sub-milligram size samples, thereby increasing the spatial resolution achievable in oxygen isotope studies of silicate and oxide minerals. The capabilities of this system should allow study of a number of fundamental Earth science problems that might otherwise be difficult to address such as, elucidation of the oxygen isotope history of seawater as recorded in very small, indentifiably unaltered samples of precipitated marine cherts and carbonates and microfossil tests, and the determination of relative contributions of subducted components (i.e. sediment, altered oceanic crust, fluids, melt) to arc volcanics based on oxygen isotopic analyses of olivine phenocrysts. ***