The various modes of spallative LiBeB production are summarized, and
classified according to their dependence or independence on the abundance of
medium heavy elements (CNO) illustrated by that of oxygen in the interstellar
medium.
The predictions of the models are confronted to the available observational
correlations (Be, B vs O). Clearly, a primary mechanism should lead to a slope
one in the lg(Be/H) vs [O/H] plot and a secondary mechanism to a slope two. Due
to the ambiguity of the O data, another criterion, based on energetics, can
help us to select an adequate model. A purely secondary origin in the very
early Galaxy is much more energy demanding than a primary one. Indeed,
magnesium seems to be a possible surrogate of oxygen and iron since i) it is
spectroscopically more easy to cope with and ii) its nucleosynthetic yield is
independent of the mass cut and does not depend on metallicity.Comment: 10 pages, no figure, to be published in "Tle light Elements and their
Evolution", IAU Symp. 198 (Natal Conf.), ASP Conf. Series, 200
