  The relation between the star formation rate and the stellar mass of
star-forming galaxies has been used to argue that major mergers cannot be the
main driver of star formation. Here, we re-examine these arguments using the
representative IMAGES-CDFS sample of star-forming galaxies at z=0.4-0.75,
taking advantage of their previously established classification into
pre-fusion, fusion, and relaxing galaxy mergers. Contrary to previous claims,
we show there is no tension between the main sequence scatter and the average
duration of the fusion star formation rate SFR peak. We confirm previous
estimates of the fraction of SFR due to morphologically-selected galaxies
(~23%) or the SFR enhancement due to major merger during the fusion phase
(~10%). However, galaxy mergers are not instantaneous processes, which implies
that the total fraction of the SFR associated to galaxies undergoing major
mergers must account for the three merger phases. When doing so, galaxies
involved in major mergers are found to represent 53-88% of the total SFR at
z~0.6. The fraction of LIRGs in the fusion phase is found to be in agreement
with the observed morphological fraction of LIRGs without disks and with the
observed and expected major merger rates at z<1.5.
