Argon retentivity of carbonaceous materials; Feasibility of kerogen as a carrier phase of Q-noble gases in primitive meteorites

Osawa, Takahito  ; Hirao, Norie; Takeda, Nobuyori*; Baba, Yuji  

To verify that kerogen is a carrier phase of Q-noble gases, XAS and XPS using synchrotron radiation were carried on for kerogens (coals) and carbon allotropes that had been bombarded by 3-keV Ar ions, and the Ar retentivities of the two materials were compared. This comparison of the estimated Ar concentrations in the target materials revealed that carbon allotropes (graphite, fullerene, carbon nanotube, and diamond) have a much higher Ar retentivity than kerogens. This unexpected result clearly shows that the terrestrial kerogens tested in our study are not suitable as a carrier phase of Ar and, consequently, that phase Q may not be similar to the terrestrial kerogen tested. If heavy noble gases are really concentrated in carbonaceous components of primitive meteorites, phase Q may have a more ordered structure than terrestrial kerogen based on the fact that the greatest difference between terrestrial kerogen and carbon allotropes is the degree of order of the molecular structure.