  In this paper, we present a model of the formation and chemical enrichment of
elliptical galaxies that differs from the conventional picture in two ways:
1)Ellipticals do not form in a single monolithic collapse and burst of star
formation at high redshift. Instead, most of their stars form at modest rates
in disk galaxies, which then merge to form the ellipticals. 2)Galaxies do not
undergo closed-box chemical evolution. Instead, metals can be transferred
between the stars, cold gas and the hot gas halos of the galaxies. It is
assumed that metals are ejected out of disk galaxies during supernova
explosions and these metals enter the hot gas component. The fact that metals
are more easily ejected from small galaxies leads to the establishment of a
mass-metallicity relation for the disk systems. Big ellipticals are more metal
rich because they are formed from the mergers of bigger disks. We use
semi-analytic techniques to follow the formation, evolution, and chemical
enrichment of cluster ellipticals in a merging hierarchy of dark matter halos.
The inclusion of the new metallicity-dependent spectral synthesis models of
Bruzual & Charlot allow us to compute the colours, line indices and mass-to-
light ratios of these galaxies. If feedback is assumed to be efficient, we are
able to reproduce the slope and scatter of the colour-magnitude and the
Mg2-sigma relations. We also study the evolution of these relations to high
redshift. We show that the luminosity-metallicity relation remains fixed, but
the mean stellar ages of the galaxies scale with the age of the Universe.
Finally, we study the enrichment history of the intracluster gas. We find that
80% of the metals were ejected by low-mass galaxies at redshifts greater than
1. The metallicity of the ICM thus evolves very little out to z > 1.
