Download Abundances and isotopic compositions of rare gases in granites

Geochemical Journal, Vol. 11, pp. 75 to 90, 1977
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Abundances and isotopic compositions of rare gases in granites
P. K. KURODA1, R. D. SHERRILL1*and K. C. JACKSON2
Department of Chemistry1, and Department of Geology2,
University of Arkansas, Fayetteville, Arkansas 72701 U.S.A.
(Received December 20, 1976)
The contents and the isotopic compositions have been measured mass
-spectrometrically for neon,
argon, krypton and xenon released from four specimens of granites in stepwise-heating experiments.
These rocks contained appreciable amounts of 40Ar from the decay of 40K and 131-136Xe from the
238U spontaneous fission. The contents of neon, argon (excluding 40Ar), krypton and xenon in these
granites were considerably lower than the estimated rare gas contents of rocks reported by BROWN
(1949), except for the Red Rock granite, which contained an abnormally large amount of xenon. The
Ne/Xe, Ar/Xe and Kr/Xe ratios in the Red Rock granite were abnormal in that they resembled the
relative abundances in meteorites. Moreover, a large fraction of the total xenon released from the Red
Rock granite appeared to be a mixture of AVCC xenon and the atmospheric xenon. The Red Rock
granite is from the Sudbury structure, Ontario, Canada, which is believed to have been formed by the
impact of an asteroid in an event that formed a crater 30 miles in diameter 1,720 million years ago.