Matching funds are requested for the purchase of a thermal ionization, solid-source mass spectrometer. The instrument, to be located in the Department of Geological Sciences at the University of Rochester, will be used in research on the systematic distribution of Ru-Sr, Sm-Nd, Th-Pb, and Hf-Lu isotopes in geological systems. Knowledge accrued from the isotopic analyses will be integrated with other data to determine the age of rock formations and their associated ores and put into a larger interpretational framework of crust- mantle evolution through geologic time.