  We consider isotropic $XY$ spin chains whose magnetic potentials are
quasiperiodic and the effective one-particle Hamiltonians have absolutely
continuous spectra. For a wide class of such $XY$ spin chains, we obtain lower
bounds on their Lieb--Robinson velocities in terms of group velocities of their
effective Hamiltonians: $\mathfrak v\ge\mathrm{ess\,sup}_{[0,1]}
\frac{2}{\pi}\frac{dE}{dN},$ where $E$ is considered as a function of the
integrated density of states.
