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

这笔拨款提供了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，用于直接质谱分析从氧化物和硅酸盐矿物中释放的分子氧。直接分析分子氧具有以下优点：减少同位素分馏，这种分馏是在将氧转化为CO而不是传统激光氟化过程中的CO2时发生的；将允许分析氧的所有三种稳定同位素，包括17O，由于等压干扰，传统的二氧化碳质谱分析无法确定；并且，将允许分析亚毫克大小的样品，从而增加在硅酸盐和氧化物矿物的氧同位素研究中可以实现的空间分辨率。这一系统的能力应允许研究一些否则可能难以解决的基本地球科学问题，例如，阐明在非常小的、无法辨认的未改变的海洋燧石和碳酸盐沉淀样品中记录的海水氧同位素历史，以及微化石测试，并确定俯冲成分(即沉积物、改变的海洋地壳、流体、基于橄榄石斑晶氧同位素分析的熔融-弧火山。＊＊＊

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. ***