  We have obtained high S/N Spitzer IRS spectra of 17 Virgo early-type galaxies
that lie on the colour-magnitude relation of passively evolving galaxies in the
cluster. To flux calibrate these extended sources we have devised a new
procedure that allows us to obtain the intrinsic spectral energy distribution
and to disentangle resolved and unresolved emission within the same object.
Thirteen objects of the sample (76%) show a pronounced broad silicate feature
(above 10micron) which is spatially extended and likely of stellar origin, in
agreement with model predictions. The other 4 objects (24%) are characterized
by different levels of activity. In NGC 4486 (M87) the line emission and the
broad silicate emission are evidently unresolved and, given also the typical
shape of the continuum, they likely originate in the nuclear torus. NGC 4636
show emission lines superimposed to extended silicate emission (i.e. likely of
stellar origin, pushing the percentage of galaxies with silicate emission to
82%). Finally NGC 4550 and NGC 4435 are characterized by PAH and line emission,
arising from a central unresolved region.
