ABSTRACT

The isotopic composition of xenon has been determined in samples of the Navajo C-1 well gas, Wildcat Field, New Mexico. Our results indicate that xenon in the Navajo well gas contains radiogenic ¹²⁹Xe and fissiogenic ^131-136Xe. The fission yields across heavy xenon isotopes, ^131-136Xe, match those reported for the spontaneous fission of ²³⁸U; the spontaneous fission of extinct ²⁴⁴Pu accounts for no more than 6% of the excess ¹³⁶Xe in this well gas. Based on the high value of the ratio of radiogenic ¹²⁹Xe to CO₂ in this gas, we suggest that most this decay product of extinct ¹²⁹I may have been introduced in a carrier gas of primordial, abiogenic hydrocarbons. It is shown that values of the ratio of radiogenic ¹²⁹Xe to ²⁴⁴Pu-derived ¹³⁶Xe in this well gas, in air, and in other terrestrial samples are consistent with a very simple and straight-forward chronology of events in the early solar system that is also compatible with the I-Xe and Pu-Xe record of meteorites.