  We present Sloan g and i imaging from the GMOS instrument on the Gemini North
telescope for the globular cluster (GC) system around the Virgo galaxy NGC 4649
(M60). Our three pointings, taken in good seeing conditions, cover an area of
about 90 sq. arcmins. We detect 2,151 unresolved sources. Applying colour and
magnitude selection criteria to this source list gives 995 candidate GCs that
is greater than 90% complete to a magnitude of i = 23.6, with little
contamination from background galaxies. We find fewer than half a dozen
potential Ultra Compact Dwarf galaxies around NGC 4649. Foreground extinction
from the nearby spiral NGC 4647 is limited to be A_V < 0.1. We confirm the
bimodality in the GC colour distribution found by earlier work using HST/WFPC2
imaging. As is commonly seen in other galaxies, the red GCs are concentrated
towards the centre of the galaxy, having a steeper number density profile than
the blue GC subpopulation. The varying ratio of red-to-blue GCs with radius can
largely explain the overall GC system colour gradient. The underlying galaxy
starlight has a similar density profile slope and colour to the red GCs. This
suggests a direct connection between the galaxy field stars and the red GC
subpopulation. We estimate a total GC population of 3700 +/- 900, with the
uncertainty dominated by the extrapolation to larger radii than observed. This
total number corresponds to a specific frequency S_N = 4.1 +/- 1.0. Future work
will present properties derived from GMOS spectra of the NGC 4649 GCs.
