MEASUREMENTS OF CL-36 IN ANTARCTIC METEORITES AND ANTARCTIC ICE USING A VANDEGRAAFF ACCELERATOR

Cosmic-ray produced 36Cl (t 1 2 = 3.0 × 105 years) has been measured in four Antarctic meteorites and one sample of Antarctic ice using a tandem Van de Graaff accelerator as an ultrasensitive mass spectrometer with the extremely low background level of 36Cl/Cl < 2 × 10-16. Results from this ion counting technique (applied here to extraterrestrial materals for the first time) are used to support a two-stage irradiation model for the Yamato-7301 and Allan Hills-76008 meteorites and to show a long terrestrial age (0.7 ± 0.1 m.y.) for Allan Hills-77002. Yamato-7304 has a terrestrial age of less than 0.1 m.y. The 36Cl content of the Antarctic ice sample from the Yamato Mountain area implies that the age of the ice cap at this site is less than one 36Cl half-life. © 1979.