ABSTRACT

Samples of travertine and siliceous sinter from hot-spring deposits in Yellowstone National Park of northwestern Wyoming have been analyzed for light stable (carbon and oxygen) and radiogenic (lead and strontium) isotopes. The Hillside Springs travertine contains significantly lighter δ¹³C than the previously studied Mammoth travertine. Although this relation could indicate a component of magmatic carbon, more likely it reflects a higher temperature of precipitation for Hillside Spring travertine. Our data on Mammoth travertine shows it to have been precipitated substantially below the orifice temperature. The oxygen isotope data on the newly analyzed deposits confirm the previous studies that found the hot-spring waters to be dominated by meteoric water. The lead isotope data show that there is a sedimentary component of lead in all the hot-spring deposits analyzed, including those inside the caldera limits. Either long lateral migration of waters are involved in the recharge of the springs or there must be sediments buried at some unknown depth beneath the volcanic rocks inside the caldera because no sediments are known at the surface. The high rainfall inside the limits of the caldera would favor sediments buried at depth.