James Saunders, professor in the Department of Geology and Geography, received a three-year National Science Foundation grant for his research project titled, "Transport and Deposition of Metallic Nanoparticles as a Hydrothermal Ore-forming Process." The grant is supported by the Petrology and Geochemistry program and will allow Saunders to expand his research in the realm of metallic nanoparticle transport, particularly those involved in the formation of shallow deposits of gold and silver, which were the type of precious-metal ores commonly mined in the western U.S. in the 1800s.
"These ores not only exhibit spectacular mineral textures formed as a result of aggregation of metallic nanoparticles, but preliminary isotopic (copper, lead and sulfur) investigations have suggested that the nanoparticles that formed the ore mineral textures appear to have come from much deeper down in the crust than the shallow setting where they were deposited," said Saunders.
Saunders will test the hypothesis that basaltic magmas, formed from partial melting in the underlying mantle, may release metals in a sulfur-rich, low density phase akin to a 'vapor,' which forms nanoparticles of metals, metalloids and sulfur upon some degree of cooling.
"The nanoparticles appear to lock in high temperature and primitive isotopic compositions, similar to the source magma chambers, and therefore must be transported upward a considerable distance to form the shallow ores," Saunders said. "If this can be substantiated by the planned new isotopic investigations of ores from Nevada and Idaho, this will be a new aspect of hydrothermal ore-forming processes that can guide how and where such valuable ores occur, both at a regional and district scale."
Saunders' research has implications for a better understanding of metal release and transport from magmas, and will perhaps shed light on the sources of magma composition that lead to formation of such ores.