NOBLE GASES IN SILICATE INCLUSIONS OF KODAIKANAL

Analyses of the noble gases from silicate inclusion of Kodaikanal show extensive loss of the lighter cosmogenic gases. A comparison of the cosmogenic gases in the silicates with reported concentrations of cosmogenic noble gases in the metal phase indicates an exposure age between 7.5 and 40 million years if a chondritic composition is assumed for the silicates. An upper limit of 6 × 10-13 cm3 STP radiogenic 129Xe per gram is almost three orders of magnitude less than the radiogenic 129Xe in Toluca silicates. This agrees with the different K-Ar and Rb-Sr ages reported for the inclusions in these two meteorites. © 1968.