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有力工具，并将帮助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存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水平的过程与观察到的化学反应联系起来来开发这种新工具。这项研究将改善古代海洋的温度估计和与石油储集层有关的岩石的温度历史。该项目将培训研究生和本科生，并将增加一个新的顶点本科课程部分，将高年级学生介绍到该领域。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用碳酸钙矿物（如方解石）中的两种稀有同位素（“块状同位素”）测量分子的相对丰度，并应用该技术揭示古代海洋的温度或现在暴露在地表的沉积物的埋藏温度。然而，团块同位素古温学的一个主要复杂问题是在100℃高温下（以百万年为时间尺度）特征的再平衡（重新排序）。虽然使古气候研究复杂化，但这种重新排序为测量地质构造的埋藏、隆起和挖掘速率提供了巨大的潜力，但前提是重新排序的速率（动力学）得到很好的理解。目前，只对矿物方解石（CaCO3）的重排序动力学进行了详细的研究。为了解决这一知识差距，将进行实验，对不同的矿物进行加热，并测量它们重新排序的速度。团块同位素重排序的机制将在原子水平上进行研究，使用一系列复杂的化学技术，如可编程加热阶段同步x射线衍射、全散射、拉曼光谱和扫描透射x射线显微镜，并结合先进的原子键合模型。将原子特征与动力学参数和矿物学特征相关联，可以确定各种碳酸盐矿物中控制重排序速率的详细方程。该项目将培训研究生和本科生，并将增加一个新的顶点本科课程部分，将高年级学生介绍到该领域。该项目还将招收来自少数族裔的化学研究生和本科生。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

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.