  Assuming a minimal seesaw model with two heavy neutrinos (N), we examine
effects of leptonic CP violation induced by approximate mu-tau symmetric
interactions. As long as N is subject to the mu-tau symmetry, we can choose CP
phases of Dirac mass terms without loss of generality in such a way that these
phases arise from mu-tau symmetry breaking interactions. In the case that no
phase is present in heavy neutrino mass terms, leptonic CP phases are
controlled by two phases alpha and beta. The similar consideration is extended
to N blind to the mu-tau symmetry. It is argued that N subject (blind) to the
mu-tau symmetry necessarily describes the normal (inverted) mass hierarchy. We
restrict ourselves to mu-tau symmetric textures giving the tri-bimaximal mixing
and calculate flavor neutrino masses to estimate CP-violating Dirac and
Majorana phases as well as neutrino mixing angles as functions of alpha and
beta. Since alpha and beta are generated by mu-tau symmetry breaking
interactions, CP-violating Majorana phase tends to be suppressed and is found
to be at most O(0.1) radian. On the other hand, CP-violating Dirac phase tends
to show a proportionality to alpha or to beta.
