Abstract:
In order to characterize the planetary noble gas carrier Q, we separated a Q-rich floating fraction from the Allende meteorite into ten fractions by a combination of colloidal and density separations. All five noble gases in the separated fractions were analyzed by pyrolysis in 600 and 1600°C temperature steps. Half of Q in the floating fraction is concentrated in the fraction C1-8D with the density of 1.65 +/- 0.04 g/cm3. All the separated fractions show similar isotopic ratios except for 40Ar/36Ar ratios. C1-8D has the lowest 38Ar/36Ar and 40Ar/36Ar ratios (0.18784 +/- 0.00020 and 4.36 +/- 0.15, respectively) in the 1600°C fraction, confirming that the fraction is enriched in Q. Most grains in C1-8D are carbonaceous with small amounts of F and O. These results imply either that the density of Q is 1.65 +/- 0.04 g/cm3 or that Q preferentially sticks to matter of that density. All the separates have similar Q to diamond ratios, indicating that Q and diamond are closely associated.
