Development and applications of high precision U-Pb geochronology for Earth and planetary sciences

资助1名博士后和1名研究生开展U-Pb年代学改进技术及其在了解地壳和早期太阳系发展中的应用研究。研究将集中在几个领域。首先是利用多捕收剂电感耦合质谱法在溶液模式下对锆石和其他含铀矿物进行高精度（0.01%年龄分辨率）测年，并利用202Pb-205Pb峰值分析热萃取Pb。在100 Ka水平上分辨古代岩石年龄的能力将为岩浆过程和火山作用与全球变化之间的关系提供新的见解。激光烧蚀电感耦合等离子体质谱（LA-ICPMS）在复杂生长历史矿物U-Pb定年中的新应用也将通过脉冲烧蚀采样的年龄深度谱分析进行探索。另一个研究目标是低温热液和含氢矿物的U-Pb定年。热液矿物的年龄将经济成矿作用置于其他地质作用的背景下，有助于找矿。识别这些矿物，确定它们在共生序列中的位置，并对它们进行地质年代学采样是主要的挑战。像方解石脉充填这样的含氢（地下水沉积）矿物已经成功地确定了年代，迄今为止开展的工作揭示了一个复杂的生长事件历史，似乎与遥远的构造过程有关。这可能是研究大陆地壳长期稳定性的一个有用的新工具。早期的太阳系研究将集中在对陨石物质进行Pb-Pb定年的新方法上，如热提取和捕获Pb，以及使用x射线断层扫描对球粒进行形状分析，以限制早期行星物质形成的过程。

This proposal is for funding one post-doctoral fellow (PDF) and one graduate student to carry out research on improved techniques of U-Pb geochronology and its applications to understanding the development of terrestrial crust and the early solar system. Research will focus on several areas. The first is applications of highly precise (0.01% age resolution) dating of zircon and other uraniferous minerals using multi-collector inductively coupled mass spectrometry in both solution mode and by analyzing thermally extracted Pb with 202Pb-205Pb spike. The ability to resolve ages at the 100 Ka level on ancient rocks will provide new insights into magmatic processes and the relationships between volcanism and global change. New applications of laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) to U-Pb dating of minerals with complex growth histories will also be explored through the use of age-depth profiling by pulsed ablation sampling. Another research objective is U-Pb dating of lower temperature hydrothermal and hydrogenic minerals. Ages of hydrothermal minerals put economic mineralization in the context of other geologic processes, which can help in exploration for ore deposits. Identifying such minerals, establishing their position in the paragenetic sequence, and sampling them for geochronology are the major challenges. Hydrogenic (groundwater deposited) minerals like calcite vein filling have been successfully dated and work carried out thus far reveals a complex history of growth events that appear to be related to distant tectonic processes. This may prove to be a useful new tool for studying the long-term stability of continental crust. Early solar system research will focus on novel approaches for Pb-Pb dating of meteoritic material such as thermal extraction and capture of Pb, as well as shape analysis of chondrules using X-ray tomography in order to constrain the processes by which early planetary material formed.