Noble Gases in Terrestrial Diamonds: Preliminary Results (original) (raw)

Abstract

Motivated by exciting, but puzzling, noble gas results in terrestrial diamonds (e.g. high 3 He/ 4 He ratios close to the solar value from industrial class diamonds [Ozima et al., 1983] and low 40 ArP 6 Ar [ = 189] from an Arkansas, U.S.A., diamond [Melton and Giardini, 1980]), we undertook the study of noble gases in diamonds from different locations. Although this is ongoing research, we can report preliminary results, some of which require confirmation. We have measured 15 diamond samples: Premier type I; Finsch type II; De Beers pool type I and II; Zaire; Arkansas; Australian (two samples); Brazilian (three); and industrial class diamonds, probably of South African origin (four). One industrial class diamond was successively heated for 30 minutes at 1200, 1700, 2000 and 2050°C. The fractional releases of 4 He were 0.007, 0.027, 0.964, and 0.002, respectively. All the He was confirmed to be released along with the 2000°C graphitization of the sample. All other samples were graphitized at 2000°C for noble gas analysis. The 3 HefHe ratios are characterized by a large spread (10 4), ranging from values below atmospheric to values in excess of the planetary (but not the solar) ratio. The highest

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