Apatite: The Effect of Volatiles on its Structure, Stability and Thermodynamic Properties

磷灰石：挥发物对其结构、稳定性和热力学性质的影响

• 批准号: 0809283
• 负责人: Hanna Nekvasil
• 金额: $ 26.31万
• 依托单位: SUNY at Stony Brook
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-07-01 至 2013-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0809283&HistoricalAwards=false
• 关键词: Apatite; Effect; Volatiles; its; Structure

A series of experiments, analytical studies, and modeling efforts have been designed to further our understanding of the structure, stability, and thermodynamic properties of apatite as a function of its OH, F, and Cl contents. The proposed work will focus specifically on (1) compositional and structural characterization of synthesized endmember, binary, and ternary apatites; (2) crystallization experiments to assess the presence or absence of a solvus within the low OH portion of the system at magmatic temperatures; and (3) exchange experiments between OH-poor apatite and molten salt to investigate thermodynamic mixing properties along the fluorapatite-chlorapatite join and to develop binary and ternary mixing models for fluorapatite (FAp) - chlorapatite (ClAp) - hydroxylapatite (OHAp) solid solutions. These results will be applicable to a variety of fields of terrestrial and planetary geoscience, materials science, and technology development.Intellectual merit. Apatite is an almost ubiquitous mineral in geological systems on Earth and is found in a variety of planetary materials. Its ability to sequester trace elements makes it important to petrogenetic and geochronological studies of igneous, metamorphic, and sedimentary rocks. However, its stability remains poorly constrained due to the fact that its stability depends on an anionic solid solution with F, Cl, and OH. Modeling of this solid solution has been hindered by difficulties in analyzing these anionic constituents, lack of stability information in the OH-poor part of the system, and lack of systematic structural data within the ternary system. In this project, laboratory synthesis experiments, detailed X-ray and NMR characterization, and intensive compositional analysis, and crystallographic models will be linked to fill this gap. Finally, anion exchange experiments using KCl- KF molten salts will provide quantitative information on the excess energies of mixing needed for development of a thermodynamic model for ternary solid solutions in the system.Broader impacts. This project will support a graduate student at Stony Brook. The thermodynamic solution model for apatite is likely to have wide applicability in many fields of research as this mineral is the basis for diverse economic, engineering, and medical applications.

一系列的实验，分析研究和建模工作已经设计，以进一步了解磷灰石的结构，稳定性和热力学性质作为其OH，F和Cl含量的函数。建议的工作将特别集中在（1）合成端元、二元和三元磷灰石的组成和结构表征;（2）结晶实验，以评估在岩浆温度下系统的低OH部分内是否存在固溶线;（3）贫OH磷灰石与熔盐的交换实验，研究氟磷灰石-氯磷灰石加入，并建立氟磷灰石（FAp）-氯磷灰石（ClAp）-羟基磷灰石（OHAp）固溶体的二元和三元混合模型。这些成果将适用于地球和行星地球科学、材料科学和技术发展的各个领域。磷灰石是地球地质系统中几乎无处不在的矿物，存在于各种行星材料中。它对微量元素的螯合作用使其在火成岩、变质岩和沉积岩的岩石成因和年代学研究中具有重要意义。然而，由于其稳定性取决于具有F、Cl和OH的阴离子固溶体的事实，其稳定性仍然受到很差的限制。这种固溶体的建模一直阻碍了这些阴离子成分分析的困难，缺乏稳定性信息的OH-穷人的系统的一部分，并缺乏系统的结构数据内的三元体系。在这个项目中，实验室合成实验，详细的X射线和核磁共振表征，密集的成分分析，和晶体学模型将被链接到填补这一空白。最后，使用KCl-KF熔盐的阴离子交换实验将提供关于混合所需的过量能量的定量信息，用于开发系统中三元固溶体的热力学模型。这个项目将支持斯托尼布鲁克的一名研究生。磷灰石的热力学溶液模型可能在许多研究领域具有广泛的适用性，因为这种矿物是各种经济，工程和医学应用的基础。