This study proposes analysis, using ion microprobe and conventional mass spectrometric techniques, of three important constituents of the ore paragenesis of the Viburnum Trend: 1) The "Octahedral" and "Cubic" stages of galena, including the more complex textures which occur in addition to the simple forms. (Pb and S isotopes will both be determined by ion microprobe.) 2) Other major sulfide phases, including pyrite, marcasite and chalcopyrite. (Pb and S isotopes by ion microprobe; Pb supplemented by conventional MS.) 3) Hydrothermal dolomite. (Pb isotopes in distinct cathodoluminescent zones and intrazonal bands by conventional MS.) This work will include late-stage calcite. This study is designed to provide critical information about: 1) the source of the Pb and S which formed the Viburnum Trend ores and, as a consequence, 2) the number of identifiable fluid sources which contributed to the formation of the ores, and, 3) the mechanism(s) which precipitated the sulfide ores.