  We revisit the production of leptonic asymmetries in minimal extensions of
the Standard Model that can explain neutrino masses, involving extra singlets
with Majorana masses in the GeV scale. We study the quantum kinetic equations
both analytically, via a perturbative expansion up to third order in the mixing
angles, and numerically. The analytical solution allows us to identify the
relevant CP invariants, and simplifies the exploration of the parameter space.
We find that sizeable lepton asymmetries are compatible with non-degenerate
neutrino masses and measurable active-sterile mixings.
