We performed numerical simulations of mergers between gas-rich disc galaxies, which result in the formation of late-type galaxies. Stars formed during the merger end up in a thick disc that is partially supported by velocity dispersion and has high [α/Fe] ratios at all metallicities. Stars formed later end up in a thin, rotationally supported disc which has lower [α/Fe] ratios. While the structural and kinematical properties of the merger remnants depend strongly upon the orbital parameters of the mergers, we find a clear chemical signature of gas-rich mergers.