Clumped Isotope Reordering Kinetics in Carbonate Minerals: The key to accurate ocean paleotemperatures and basin thermal histories

地球化学中最令人兴奋的新想法之一是测量碳酸钙中的两种稀有同位素，而不仅仅是一种，并将它们“聚集”在一起。 这为研究古代海洋和沉积物的温度提供了一个新的强大工具，并将有助于科学家研究气候变化，板块构造和石油勘探。这项研究将有助于确定最有可能保持古代温度的碳酸钙矿物。 它还将提供同时使用两种矿物所需的化学信息，以更好地估计岩石的温度历史。该项目将通过将原子级过程与观察到的化学反应联系起来来开发这种新工具。这项研究将改进对古代海洋温度的估计和与石油储层有关的岩石的温度历史。 该项目将培训研究生和本科生，并将增加一个新的部分顶点本科课程，将介绍老年人到该领域。该项目还将吸引来自代表性不足的少数群体的化学研究生和本科生。21世纪地球化学最令人兴奋的发展之一是能够测量碳酸钙矿物中具有两种稀有同位素（“聚集同位素”）的分子的相对丰度（例如，方解石），并应用这种技术来揭示古代海洋的温度或现在暴露在表面的沉积物的埋藏温度。 然而，聚集同位素古温度测量的一个主要复杂性是在百万年时间尺度上高温（100 ℃）下的特征重新平衡（重新排序）。虽然复杂的古气候研究，这种重新排序提供了巨大的潜力，测量埋葬，隆起和折返的地质构造的速率，但只有当重新排序的速率（动力学）是很好地理解。目前，只有矿物方解石（碳酸钙）的重排动力学进行了详细研究。为了解决这一知识差距，将进行实验，其中不同的矿物被加热，并测量它们重新排序的速率。聚集同位素重排的机制将检查在原子水平上使用一系列复杂的化学技术，如可编程加热阶段同步加速器X射线衍射，总散射，拉曼光谱，扫描透射X射线显微镜，结合先进的模型原子键合。将原子特征与动力学参数和矿物学表征相关联，将允许确定控制各种碳酸盐矿物中重排速率的详细方程。 该项目将培训研究生和本科生，并将增加一个新的部分顶点本科课程，将介绍老年人到该领域。该项目还将吸引来自代表性不足的少数群体的化学研究生和本科生。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

One of the most exciting new ideas in geochemistry is to measure two rare isotopes in calcium carbonate instead of just one and "clump" them together. This provides a new and powerful tool to study the temperature of ancient oceans and sediments and will help scientists looking at climate change, plate tectonics, and petroleum exploration. This study will help identify the calcium carbonate minerals most likely to preserve ancient temperatures. It will also provide the chemical information needed to use two minerals at the same time to better estimate the temperature history of the rocks. This project will develop this new tool by connecting atom-level processes with observed chemical reactions. The study will improve temperature estimates of ancient oceans and the temperature history of rocks related to petroleum reservoirs. The project will train graduate and undergraduate students and will add a new section of a capstone undergraduate course that will introduce seniors to the field. The project will also engage chemistry graduate and undergraduate students from underrepresented minority groupsOne of the most exciting developments in geochemistry in the 21st century is the ability to measure the relative abundance of molecules with two rare isotopes ("clumped isotopes") in calcium carbonate minerals (e.g., calcite) and apply this technique to reveal the temperatures of ancient oceans or the burial temperatures of sediments now exposed at the surface. A major complication in clumped isotope paleothermometry however is reequilibration (reordering) of the signatures at elevated temperatures (100oC) on million-year timescales. While complicating paleoclimate studies, this reordering provides great potential for measuring rates of burial, uplift, and exhumation of geologic formations, but only if the rates (kinetics) of reordering are well understood. Currently, only the reordering kinetics of the mineral calcite (CaCO3) has been studied in detail. To address this knowledge gap, experiments will be conducted in which different minerals are heated and the rate at which they reorder is measured. The mechanisms of clumped isotope reordering will be examined at an atomistic level using a range of sophisticated chemical techniques such as programmable heated-stage synchrotron X-ray diffraction, total scattering, Raman spectroscopy, and scanning transmission X-ray microscopy, in conjunction with advanced models for atomic bonding. Correlating atomic characteristics with kinetic parameters and mineralogical characterization will allow determination of detailed equations governing the rates of reordering in a variety of carbonate minerals. The project will train graduate and undergraduate students and will add a new section of a capstone undergraduate course that will introduce seniors to the field. The project will also engage chemistry graduate and undergraduate students from underrepresented minority groupsThis award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.