9405620 Kunk One of the most widely used techniques for measuring radiometric ages of rocks and minerals is the so-called 40Ar/39Ar or argon-argon method, a variation of the potassium-argon or K/Ar method. Both methods make use of the known decay rate of natural 40K to 40Ar and the retention of the daughter product argon inside the mineral grain. The argon-argon method is further dependent on irradiation of the unknown sample in a nuclear reactor in order to convert some 39K to 39Ar by an n, p nuclear reaction. A calibration standard of known age is irradiated at the same time as the sample. The precision of all ages reported by this method are determined by the precision with which the standard is known. This award will provide partial funding to allow personnel of the National Institute of Standards and Technology (NIST) and the U.S. Geological Survey to bring state-of-the-art methods to bear on producing the most reliable mineral standard possible for interlaboratory calibrations of argon-argon dating. The standard will be made available to the geochronology research community through distribution by the Standard Reference Materials Program of NIST. *** 9406684 Johnson This award provides partial funding for the support of a technician assigned to the Radiogenic Isotope Laboratory in the Department of Geology and Geophysics at the University of Wisconsin, Madison. The technician will assist in the operation and maintenance of the laboratory's equipment that includes a multicollector thermal ionization mass spectrometer and associated instrumentation for sample preparation and data analysis. The laboratory is a resource for mass spectrometric analysis needed in research and teaching projects in the earth sciences by a large number of researchers on-campus and off-campus. Research applications include work on Arctic Ocean sediments, mantle geochemistry, volcanism, geochronology of carbonates in the Michigan Basin and Wisconsin Arch provinces, and Archean and Proterozoic granites. The technician will also participate in the technical developmental work of the laboratory, including the development of new methods for the quantitative measurement of the isotopes of hafnium. ***
