Noble gas retentivity of carbon allotropes and kerogen; Feasibility of kerogen as phase Q

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

To verify that kerogen is a carrier phase of Q-noble gases, X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) using synchrotron radiation were carried out for type II and III kerogens and carbon allotropes which had been bombarded by 3 keV Ar, Kr, and Xe ions, and noble gas retentivities of the materials were compared. Ar concentrations was estimated from XPS and XAS. Kr and Xe concentrations were estimated by the peak areas of Kr3p3/2 and Xe3d5/2 in XPS. The concentrations were used as indexes of the relative retentivity of noble gases. Our investigation shows that the surface concentrations of carbon allotropes (0.40-0.79 atom%) are much higher than those of kerogens (0.04-0.08 atom%). This unexpected result clearly shows that the terrestrial kerogens are inferior to other carbon materials in noble gas retentivity, and thus, phase Q might not be similar to terrestrial kerogen, especially coals tested in this work.