Probing the Structure and Energetics of Reactive Sites at the Mineral-Water Interface: Implications for Element Partitioning and Geochronology

探测矿泉水界面反应位点的结构和能量：对元素划分和地质年代学的影响

• 批准号: 9814691
• 负责人: John Rakovan
• 金额: $ 7.08万
• 依托单位: Miami University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-01-01 至 2003-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9814691&HistoricalAwards=false
• 关键词: Probing; Structure; Energetics; Reactive; Sites

9814691RakovanReactions that take place at the mineral-water interface (e.g., sorption and desorption, growth and dissolution, catalysis, etc.) affect many fundamental processes that occur on the Earth's surface. One of thehallmarks of mineral surface reactivity is its heterogeneous nature. Fundamental to understanding such heterogeneities is knowledge of the structure of protosites and the energetics of protosite reactions such assorption and incorporation. This project has two parallel goals. First, to determine the structure and energetics of different reactive surface sites that lead to heterogeneous reactivity of minerals; specifically heterogeneous adsorption and incorporation of trace metals into fluorite. This will be accomplished by using the differential incorporation REEs into fluorite as a probe of the structural differences between nonequivalent surface sites and to quantify energy differences associated with adsorption and incorporation of these elements. The resulting data will be the foundation for surface site selectivity models, which will be derived by first principle methods, based on molecular orbital theory. The second goal of this study will utilize the product of heterogeneous incorporation of REEs and the results from Part I to further develop a technique of intracrystalline isochron dating. In this method the Sm-Nd isotope systematics of coeval portions of compositionally different sectors of a single crystal are used to calculate an isochron age for the formation of that crystal, obviating several crucial assumptions required in normal isochron dating. This procedure thus represents a potentially powerful new method of dating that can complement more traditional techniques.

9814691在矿物质-水界面发生的Rakovan反应（例如，吸附和解吸、生长和溶解、催化等）影响着地球表面发生的许多基本过程。矿物表面活性的一个特点是其非均匀性。理解这种异质性的基础是了解原核位点的结构和原核位点反应的能量学，如吸附和掺入。 这个项目有两个平行的目标。 首先，确定导致矿物非均相反应性的不同反应性表面位点的结构和能量;特别是痕量金属在萤石中的非均相吸附和结合。这将是通过使用微分掺入稀土到萤石作为探针的非等效表面网站之间的结构差异，并量化与这些元素的吸附和结合的能量差异。由此产生的数据将是表面位点选择性模型的基础，该模型将基于分子轨道理论通过第一原理方法导出。本研究的第二个目标是利用稀土元素非均相掺入的产物和第一部分的结果，进一步发展晶内等时线定年技术。在这种方法中，Sm-Nd同位素系统的组成不同部门的单晶的同时代部分被用来计算等时线年龄的形成，避免了正常的等时线定年所需的几个关键的假设。因此，这一程序代表了一种潜在的强大的新的测年方法，可以补充更传统的技术。