In Situ Mineral Analysis of Earth's Early Crust and Impact Rocks by LA-(MC)-ICPMS

地球的前半段历史我们知之甚少，但在第一个大陆的形成、富氧大气层和生命的初步发展以及大量小行星和彗星撞击地球表面方面，这是一个关键时期。 在所有这些领域取得进展的关键是建立一个全面、自洽的模型，说明大陆如何以及何时从地幔中分离出来，地球表面的条件变得适合生命存在，这与年轻太阳系中大量岩石和冰体撞击的原因和影响有关。 我的研究创造了关于大陆形成的关键领域以及构建这样一个全面模型所需的撞击坑过程的作用的知识。 我使用的方法耦合自动扫描电子显微镜成像的新发展与激光烧蚀ICP质谱原位分析，以确定特定的矿物颗粒或颗粒域，保存在地壳变质或冲击冲击期间从岩浆结晶或重结晶的记录。今后五年将实施三个项目。一种是利用古代岩石中矿物的放射性同位素组成来确定地球地幔在大约40亿至25亿年前形成大陆的元素中耗尽的程度。 它还可以确定地球上保存有年龄超过40亿年的岩石和矿物的地方，这是非常罕见的。 第二个检查的影响，冲击变质作用的放射性同位素组成的矿物形成在一个小的，最近的，但在北方拉布拉多大部分未经勘探的陨石坑，文件同位素标准，可用于确定矿物在古代地质记录中的影响，在小陨石坑事件。 第三个测量月球陨石中矿物的放射性同位素组成，以确定它们如何受到非常大的撞击事件的影响。我的研究项目的副产品是原位矿物分析的分析方法，这些方法被应用于寻找矿物和碳氢化合物资源，以及其他学科，如环境中的污染物追踪和监测气候变化。

The first half of Earth's history is very poorly understood but was a critical time in terms of creation of the first continents, initial development of an oxygen-rich atmosphere and life, and bombardment of large numbers of asteroids and comets on its surface. The key to progress in all of these areas is a comprehensive, self-consistent model of how and when the continents were extracted from the mantle and conditions at Earth's surface became suitable for life, linked to the causes and effects of large numbers of impacts with rocky and icy bodies in the young solar system. My research creates knowledge on critical areas of continent formation and the role of impact cratering processes that is needed to construct such a comprehensive model. The approach I use couples new developments in automated scanning electron microscopic imaging with in situ analysis by laser ablation ICP mass spectrometry to identify specific mineral grains or grain domains that preserve a record of crystallization from a magma or recrystallization during crustal metamorphism or impact shock. Three projects will be carried out over the next five years. One uses the radiogenic isotope compositions of minerals in ancient rocks to determine the extent to which Earth's mantle was depleted in elements that formed the continents between about 4.0 and 2.5 billion years ago. It may also identify places on Earth that preserve rocks and minerals older than 4 billion years in age, which are exceedingly rare. The second examines the effect of impact shock metamorphism on the radiogenic isotope compositions of minerals formed in a small, recent, but largely unexplored crater in northern Labrador, to document isotopic criteria that may be used to identify minerals in the ancient geological record that were affected by impact in small cratering events. The third measures the radiogenic isotope compositions of minerals in lunar meteorites to determine how they were affected by very large impact events. Spin-offs of my research program are analytical methods for in situ mineral analysis that are being applied to the search for mineral and hydrocarbon resources, and other disciplines such as contaminant tracing in the environment and monitoring climate change.