Abstract by Samuel Martin
Trace element, melt inclusion, and oxygen isotope characterization of sapphires from Bingham Canyon, Utah and Yogo Gulch, Montana
Trace amounts of sapphire occur in several intrusions and volcanic units near the major porphyry Cu deposit at Bingham Canyon, Utah. Bingham sapphires are small (<500 μm), but similar in color and morphology to well-known sapphires from Yogo Gulch, Montana. We used LA-ICP-MS and SIMS analysis to examine trace elements and oxygen isotope ratios of sapphires from the two deposits in order to investigate the conditions under which they crystallized. Both Bingham and Yogo sapphires are distinctively high in Mg, Fe, and Ti, along with exceptionally high Cr and V in Bingham sapphires. δ18O values for Yogo sapphires are low and fairly uniform, suggesting a purely magmatic origin, while the highly variable δ18O values of Bingham sapphires may indicate some incorporation of metasedimentary material into the Bingham magmas. Sapphire host rocks at both locations are associated with Eocene mafic alkaline magmatism, and we expect our ongoing trace element and inclusion analyses to provide additional detail on the evolution of the Bingham and Yogo magma systems.