  We suggest a new approach to study the cosmis ray (CR) mass composition in
the energy region from 30 TeV/nucleus up to the "knee" region, i.e. up to a few
PeV/nucleus, using an array of imaging atmospheric Cherenkov telescopes (IACTs)
of a special architecture. This array consists of telescopes with a relatively
small mirror size (~10 square meters) separated from each other by large
distances (~500 meters) and equipped by multichannel cameras with a modest
pixel size (0.3-0.5 degree) and a sufficiently large viewing angle (6-7
degree).
  Compared to traditional IACT systems (like HEGRA, HESS or VERITAS) the IACT
array considered here could provide a very large detection area (several square
kilometers or more). At the same time, it allows an accurate measurement of the
energy of CR induced air showers (the energy resolution ranges within 25-35%)
and an effective separation of air showers created by different nuclei.
Particularly, it is possible to enrich air showers belonging to the nucleus
group assigned for selection up to ~90% purity at a detection efficiency of
15-20% of such showers.
