| 英文摘要: | Observational sciences, such as astronomy and geology, are directly limited by the clarity of the tools we use for observing, whether it be a telescope or a mass spectrometer. For every order of magnitude increase in how far we can see, how precisely we can see, or in how small a scale at which we can see, fundamental discoveries await. Our understanding of the Earth and its place in the solar system was revolutionized in the 1960s by the advent of the modern mass spectrometer, which now permits highly accurate measurement of isotope ratios of elements. These analyses permit us to date the age of the solar system and determine when a mountain range rose or when a sedimentary basin reached temperature conditions suitable for forming petroleum. Early such measurements were performed on bulk rock samples, but as methods emerged that permit analysis on tiny (about the width of one of the hairs on your head) spots, we discovered a rich world of information that had eluded us when we looked only at bulk samples. The ion microprobe emerged in the 1980s as the ultimate tool for in situ microscale isotopic analyses of geologic materials. However, these instruments are large, complex, and expensive - so expensive that even a nation as large and rich as ours can only afford to support a handful in the Earth sciences. Since 1993, when UCLA took delivery of the first ion microprobe in the northern hemisphere, we have operated a national facility that provides access of this specialized instrumentation to the broader community of Earth scientists. Over 300 external investigators, including numerous students and postdocs, have accessed the facility. At the same time, we bear a continuing responsibility to demonstrate scientific leadership within the community by pursuing a broad range of important questions. Data produced from the UCLA national ion microprobe facility, as documented in over 480 scientific articles, has led to an array of significant discoveries such as the isotopic composition of the Sun and the age of the oldest known evidence for water and life on Earth. Funds provided in this grant 1) ensure that the nation's geochemists, cosmochemists, and geochronologists continue to have access to our near-unique facilities, and 2) provide UCLA scientists the resources required to continue to develop and refine existing and new methods for research in geochemistry, geobiology, cosmochemistry, and geochronology. Research training is an important aspect of the facility work. Between 2010 and 2016, 81 theses (44 Ph.D., 34 M.S., and 3 B.S.) that relied on UCLA ion microprobe data were completed with another 13 theses ongoing. In context of this support grant, we conduct an annual workshop that bring students from across the country to UCLA for one week to learn about applications of the ion microprobe to the geosciences and to acquire exposure to the ion microprobe and related equipment and techniques. Over 150 students have participated in these workshops. Center scientists continue to be involved in synergistic activities both locally and nationally, including professional activities and K-12 education and outreach.
This proposal requests continued support of the UCLA ion microprobe laboratory as a national facility for research in the geosciences. In addition to enabling access to the facility by external investigators, funds are sought to further develop analytical methods that take advantage of the unique strengths of secondary ion mass spectrometry for in situ analyses of isotopic abundances relevant to problems in geochemistry and geochronology. With the commissioning of the new CAMECA ims1290 and its high brightness Hyperion-2 ion source, we propose to optimize each of our two instruments for the principal applications undertaken in our laboratory - the ims1270 to become a dedicated U-Pb multi-collection instrument and the ims1290 to focus on high precision stable isotope ratio measurements. Specifically, we propose to develop: 1) SIMS multi-collector Lu-Hf isotopic analysis, 2) cross-calibration of Ti-in-quartz, Ti-in-zircon, and Zr-in-rutile thermobarometers, 3) correlated stable isotope variations in otoliths as monitors of fish habitat and lifecycles, 4) sulfur isotopes as geochemical tracers on Earth and Mars, and 5) C and S in zircon as magma volatile monitors. |