  Wide-field $u'g'r'i'z'$ Dark Energy Camera observations centred on the giant
elliptical galaxy NGC5128 covering $\sim21deg^2$ are used to compile a new
catalogue of $\sim3200$ globular clusters (GCs). We report 2404 new candidates,
including the vast majority within $\sim140$kpc of NGC5128. We find evidence
for a transition at a galactocentric radius of $R_{\rm gc}\approx55$kpc from
GCs intrinsic to NGC5128 to those likely to have been accreted from dwarf
galaxies or that may transition to the intra-group medium of the Centaurus A
galaxy group. We fit power-law surface number density profiles of the form
$\Sigma_{N, R_{\rm gc}}\propto R_{\rm gc}^\Gamma$ and find that inside the
transition radius, the red GCs are more centrally concentrated than the blue,
with $\Gamma_{\rm inner,red}\approx-1.78$ and $\Gamma_{\rm
inner,blue}\approx-1.40$. Outside this region both profiles flatten, more
dramatically for the red GCs ($\Gamma_{\rm outer,red}\approx-0.33$) compared to
the blue ($\Gamma_{\rm outer,blue}\approx-0.61$), although the former is more
likely to suffer contamination by background sources. The median
$(g'\!-\!z')_0\!=\!1.27$mag colour of the inner red population is consistent
with arising from the amalgamation of two giant galaxies each less luminous
than present-day NGC5128. Both in- and out-ward of the transition radius, we
find the fraction of blue GCs to dominate over the red GCs, indicating a lively
history of minor-mergers. Assuming the blue GCs to originate primarily in dwarf
galaxies, we model the population required to explain them, while remaining
consistent with NGC5128's present-day spheroid luminosity. We find that several
dozen dwarfs of luminosities $L_{dw,V}\simeq10^{6-9.3}L_{V,\odot}$, following a
Schechter luminosity function with a faint-end slope of
$-1.50\leq\alpha\leq-1.25$ is favoured, many of which may have already been
disrupted in NGC5128's tidal field.
