Collaborative Research: Developing a Practical and Quantitative Method for Measurement of Metamorphic Porphyroblast Crystallization Kinetics and Strain Rate

合作研究：开发一种实用且定量的方法来测量变质斑母细胞结晶动力学和应变率

• 批准号: 0911582
• 负责人: Ethan Baxter
• 金额: $ 10.5万
• 依托单位: Trustees of Boston University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2012-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0911582&HistoricalAwards=false
• 关键词: Collaborative; Research; Developing; Practical; Quantitative

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)." This project, which is a collaboration between researchers at Western Washington University, the University of Alabama at Tuscaloosa, and Boston University, is focused on improving our understanding of what happens when rocks are heated, pressurized, and deformed deep within the Earth's crust, a process (metamorphism) that is occurring every day under our feet. The researchers strive to understand the rates at which rocks are deformed and at which new crystals grow during metamorphism. These basic parameters of metamorphism are very poorly known. The researchers will develop and test a new method for determining these rates on rocks from Townshend Dam, VT, which were metamorphosed about 380 million years ago during a collision between North America and a micro-continent to the east. The study will estimate the rates of metamorphism and deformation during this collision (and by extension, other similar collision events), but more importantly, the project will develop a new method by which these and related aspects of metamorphism can be studied in other areas by other researchers in the future. The investigation will focus on garnet, a commonly formed metamorphic mineral that tends to record details of its environment as it grows. The research relies on recent advances in Sm-Nd radiometric dating of tiny volumes of garnet. The investigators will date well-characterized parts of garnet crystals in a rock to link the garnet chemistry to the time of garnet growth. The crux of the method is that it will allow numerous indirect dates to be easily obtained by reference to the arduously obtained time-chemistry link. The specific questions being studied are: What are metamorphic nucleation rates and how do they vary with time? What are growth rates for individual crystals and how do they vary over the course of a crystal's growth? How fast are rocks deformed during continental collisions, and is that deformation continuous or episodic? How fast are rocks heated and loaded during collisions? Finally, the study will provide the first data set of its kind, against which theoretical models of nucleation and growth can be tested.

“该奖项的资金来源是《2009 年美国复苏和再投资法案》（公法 111-5）。”该项目由西华盛顿大学、阿拉巴马大学塔斯卡卢萨分校和波士顿大学的研究人员合作，重点是提高我们对地壳深处岩石受热、加压和变形时发生的情况的理解，我们脚下每天都在发生的过程（变质）。研究人员努力了解变质过程中岩石变形的速度以及新晶体生长的速度。人们对这些变质作用的基本参数知之甚少。研究人员将开发并测试一种新方法，用于确定佛蒙特州汤森德大坝岩石的这些速率，该大坝在大约 3.8 亿年前北美与东部微大陆碰撞期间发生变质。该研究将估计这次碰撞（以及其他类似碰撞事件）期间的变质和变形速率，但更重要的是，该项目将开发一种新方法，通过该方法可以在其他领域研究变质作用和相关方面未来的其他研究人员。这项调查将集中在石榴石上，石榴石是一种常见的变质矿物，在生长过程中往往会记录其环境的细节。该研究依赖于对少量石榴石进行 Sm-Nd 放射性测年的最新进展。研究人员将对岩石中石榴石晶体的特征明确的部分进行年代测定，以将石榴石化学成分与石榴石生长时间联系起来。该方法的关键在于，通过参考艰难获得的时间-化学联系，可以轻松获得大量间接日期。正在研究的具体问题是：什么是变质成核率以及它们如何随时间变化？单个晶体的生长速率是多少？它们在晶体生长过程中如何变化？大陆碰撞期间岩石变形的速度有多快？这种变形是连续的还是间歇性的？碰撞过程中岩石加热和加载的速度有多快？最后，该研究将提供同类中的第一个数据集，可以测试成核和生长的理论模型。