The closest train station is:
Bugeat (in map between Viam and Jassonneix).
You can buy train tickets in: 
Flight option has not much sense: is very-very expensive. Anyway, the closest airport is in east: Clermont-Ferrand-Auvergne (2 hours by car to Tarnac)
if you want to arrive by the Bordeaux airport and share the travel to Limoges with people from there.
to have a pick up from train station to Tarnac
_Subscribe the list: 
_send a message to this tread to have a pick up from the train station to Tarnac 
not forget to write the time of your arrive!