High intensity ultrashort pulse driven ion acceleration is an important area of research due to its richness in underlying physics and potential technological applications. A strong impediment towards employing such sources, in practice, lies in the inherent challenge of producing mono-energetic ions with fine energy control. We demonstrate consistent, highly reproducible, charge-independent mono-energetic acceleration of heavy gold ions to sub-MeV energies with a reasonably high flux of 9 × 1010 ions per shot from the gold-carbon nano-composite target irradiated at moderate laser intensities of 1018-1019 W/cm2. The experimental results establish that the thermal pressure of the expanding hot plasma, instead of the "hot" electrons, is responsible for the acceleration of the mono-energetic heavy Au ions. Our results pave the way for a simple and new way of producing mono-energetic heavy ions. This may find potential applications in advanced particle accelerators, isochoric heating of matter, surface science, swift heavy ion sources, and basic plasma physics. © 2018 Author(s).