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

评估高钙长石斜长石熔体包裹体与宿主之间的关系：MORB 斜长石中微量元素多样性的普遍性和意义

• 批准号: 0453090
• 负责人: Roger Nielsen
• 金额: --
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-05-01 至 2009-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0453090&HistoricalAwards=false
• 关键词: Evaluating; Relationship; Between; Melt; Inclusions

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.

摘要(尼尔森-0453090)地球释放内部热量的主要方式之一是大洋中脊玄武岩的喷发。这项研究研究了这些海底熔岩中许多套所特有的大而大的高钙斜长石晶体的起源，以考察地幔和地壳之间的物质和热交换。这些矿物是不寻常的，因为它们从未被发现与它们所在的玻璃处于平衡状态。在这项研究中，斜长石晶体和其中的玻璃包裹体被认为代表了斜长石结晶的岩浆，将对其进行微量元素分析，以获得关于地幔和结晶过程以及与下地壳岩浆相互作用的信息。由于很难分析在很小距离上变化的化学梯度和微量元素，研究的初始阶段侧重于开发微观分析技术，利用激光电感耦合等离子体质谱仪和电子探针在化学和空间上测量玄武岩中的微小差异。第二阶段包括对高钙斜长石晶体及其玻璃包裹体以及它们的宿主玻璃进行地球化学穿越。玻璃和矿物中待测的微量元素及其梯度包括钛、锆、稀土、锶、钡。这些分析的结果将被用来通过使用从实验室实验获得的分配系数来评估晶体和宿主玻璃中的熔融包裹体达到平衡的程度。最终目标将是将高钙斜长石置于地壳和岩浆演化的框架内，以便更好地了解洋壳的形成。