GOLDSCHMIDTCONFERENCE TOULOUSE 1998 Mantle input into the mineralising fluids of the Colorado Mineral Belt: the noble gas story

The use of noble gas isotopes as inert tracers of palaeo-hydrothermal fluids is a relatively new technique. However, in recent studies they are proving to be extremely useful in determining the origins of such fluids (Simmons et al., 1987; Stuart et al., 1995; Bumard et al., 1998). This work reports such a study for selected ore deposits of the Colorado Mineral Belt. The noble gas budget of inclusion trapped fluids can come from three primary sources: the atmosphere, by way of air saturated ground waters (ASW); the crust and the mantle. These sources contain very distinct noble gas isotopic compositions, especially with respect to Helium and Argon. The noble gas composition of the atmosphere an