Evaluating the Relationship Between Melt Inclusions and Host for high Anorthite Plagioclase: Prevalence and Significance of Trace element Diversity in MORB Plagioclase

摘要（Nielsen - 0453090）地球释放内部热量的主要方式之一是洋中脊玄武岩的喷发。本研究研究了这些海底熔岩中许多套具有的大型高富钙斜长石晶体的起源，以研究地幔和地壳之间的物质和热量交换。这些矿物质是不寻常的，因为它们从未被发现与它们所在的玻璃处于平衡状态。本研究将对斜长石晶体和其中的玻璃包裹体进行微量元素分析，以获得地幔和结晶过程以及岩浆与下地壳相互作用的信息。斜长石晶体和玻璃包裹体被认为是斜长石结晶的岩浆。由于分析化学梯度和微量元素在小距离上变化的困难，研究的初始阶段侧重于开发微分析技术，用于使用激光ICP质谱和电子显微探针测量玄武岩中化学和空间上的微小差异。第二阶段包括对高钙斜长石晶体及其玻璃包裹体及其主玻璃进行地球化学遍历。玻璃和矿物中需测定的微量元素有Ti、Zr、REE、Sr、Ba等。这些分析的结果将用于通过使用从实验室实验中获得的分配系数来评估晶体和主玻璃中的熔融夹杂物达到平衡的程度。最终的目标是将高钙斜长石放入地壳和岩浆演化的框架中，以便更好地理解海洋地壳的形成。

ABSTRACT (Nielsen - 0453090)One of the primary ways the Earth gives up its inner heat is by eruption of mid-ocean ridge basalts. This research studies the origin of the large high Ca-rich plagioclase crystals characteristic of many suites of these ocean floor lavas to examine the exchange of material and heat between the mantle and crust. These minerals are unusual because they have never been found to be in equilibrium with the glass in which they occur. In this study, plagioclase crystals and glass inclusions within them, which are thought to represent the magmas from which the plagioclase crystallized, will be analyzed for trace elements to obtain information on mantle and crystallization processes as well as with magma interaction with the lower crust. Because of difficulties analyzing chemical gradients and trace elements that vary over small distances, the initial stage of the research focuses on development of micro-analytical techniques for measuring small differences, chemically and spatially in basaltic rocks using laser ICP mass spectrometry and the electron microprobe. The second stage involves making geochemical traverses of high Ca-plagioclase crystals and their glass inclusions, as well as their host glasses. Trace elements to be measured and their gradients in the glasses and minerals include Ti, Zr, REE, Sr, Ba. Results of these analyses will be used to assess the degree to which melt inclusions in the crystals and the host glasses have achieved equilibrium through use of partition coefficients obtained from laboratory experiments. The final objective will be to put high Ca plagioclase into a framework of crustal and magmatic evolution that permits better understanding of formation of the ocean crust.