This grant will provide continued support of research on rare gasses, and isotopes of other rare gasses, from volcanic centers over hot spots, and along convergent plate margins and continental rifts. Primary emphasis has been on 3He as a "primordial" tracer for mantle volatiles, and its association with methane and the isotopic composition of carbon in CH4 and CO2. The cosmogenic nature of 3He in volcanic lavas has been recognized and its usefulness as a tracer in erosion studies has been demonstrated. High 3He/4He ratios, relative to Mid-Ocean Ridge Basalts, have been identified in eight Pacific hotspot terrains, clear evidence of transport of gases from the less depleted mantle by rising plumes. These and similar types of research using rare gasses to solve problems of mantle chemistry and dynamics will continue under the PIs supervision. This award will provide for the analysis of many samples already collected, and will support the operation of the PI's lab for another year
