  I demonstrate by means of high resolution cosmological simulations, which
include modelling of a two-phase interstellar medium, that the dominant
mechanism for transporting heavy elements from the proto-galaxies into the IGM
is the merger mechanism as discovered by Gnedin & Ostriker. Direct ejection of
the interstellar gas by supernovae plays only a minor role in transporting
metals into the IGM: for a realistic cosmological scenario only a small
fraction of all metals in the IGM is delivered by the supernova-driven winds,
while most of all metals in the IGM are transported by the merger mechanism. As
the result, the metallicity distribution in the IGM is highly inhomogeneous, in
agreement with studies of the QSO metal absorption systems, and the predicted
metallicity distribution of Lyman-alpha absorbers as a function of their column
density is in excellent agreement with the observational data.
