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

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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.