Helium isotopes point to new sources of geothermal energy By measuring helium isotope ratios in fluids at the surface, geochemists Mack Kennedy of the Department of Energy's Lawrence Berkeley National Laboratory and Matthijs van Soest of Arizona State University have discovered a new tool for identifying potential geothermal energy resources. The potential resources arise not from volcanism but from the flow of surface fluids through deep fractures that penetrate the earth's lower crust, in regions far from current or recent volcanic activity. in !Bookmarks Toolbar > #RSSwith fluidsgeochemistsheliumisotopemeasuringratiosrsssurface