  An Electron-Ion Collider (EIC) with center-of-mass energies sqrt(s_{eN}) ~
20-100 GeV and luminosity L ~ 10^{34} cm^{-2} s^{-1} would offer new
opportunities to study heavy quark production in high-energy electron or photon
scattering on protons and nuclei. We report about an R&D project exploring the
feasibility of direct measurements of nuclear gluon densities at large x
(gluonic EMC effect, antishadowing) using open charm production at EIC. We
describe the charm production rates and angle-momentum distributions at large x
and discuss methods of charm reconstruction using next-generation detector
capabilities (pi/K identification, vertex reconstruction). The results can be
used also for other physics applications of heavy quark production at EIC
(fragmentation functions, jets, heavy quark propagation in nuclei).
