This award will provide two year's of salary support for a postdoctoral associate at Lamont-Doherty Geological Observatory of Columbia University. The research associate will be employed full-time in the development of analytical techniques utilizing a new type of mass spectrometry system that combines a magnetic mass analyzer section, high-resolution, high-abundance sensitivity, and high-transmission characteristics with laser resonance ionization and sputtered source capabilities and with a multiple adjustable ion-counting multiplier assembly. The attributes of the instrument (new to the U.S.) will enable U.S. earth scientists to undertake types of isotopic analyses which are geochemically important but which have not been tackled to date because of analytical limitations. These include the measurements of osmium and thorium isotope ratios in rocks and minerals from the oceanic and continental crust.