On the Q-phase of carbonaceous chondrites

One of the unresolved puzzles of meteoritics is the nature of the carrier o f the so-called heavy planetary gases. apparently, these gases reside mainl y in a minor fraction, which has been dubbed Q by Lewis et al. [R.S. Lewis, B. Srinivasan, E. Anders, Science 190 (1975) 1251] in analogy of the namin g by Papanastasiou et al. [D.A. Papanastassiou, G.J. Wasserburg, Earth Plan et. Sci. Lett. 11 (1971) 37] of a minor glassy phase in lunar rocks highly enriched in trace elements such as Pb and U. Q stands for the archaic term quintessence, the fifth or last and highest substance in ancient and mediev al philosophy above fire, air, water and earth. In this contribution, an at tempt is made to provide evidence that Q is carbonaceous, with carbon in th e form of closed structures such as carbon nanotubes which serve as micro b ottles for the heavy noble gases. To this end, Q was characterised with mic ro-PIXE and NRA, whereas HREM was used to search for nanotubes. Q itself wa s obtained as residue after chemical destruction of samples of Allende, Leo ville and Vigarano. (C) 1999 Elsevier Science B.V. All rights reserved.