  We show that generic, slow dynamics can occur in the contact process on
complex networks with a tree-like structure and a superimposed weight pattern,
in the absence of additional (non-topological) sources of quenched disorder.
The slow dynamics is induced by rare-region effects occurring on correlated
subspaces of vertices connected by large weight edges, and manifests in the
form of a smeared phase transition. We conjecture that more sophisticated
network motifs could be able to induce Griffiths phases, as a consequence of
purely topological disorder.
