  Earlier we obtained quasi-classical equations of motion of spin 1/2 massless
particle in a curved spacetime on base of simple Lagrangian model \cite{al2}.
Now we suggest an approach to derive the equations in framework of field
theory. Noether theorem formulated in terms of Cartan' formalism of orthonormal
frames gives equations for current of spin of the field and tensor of
stress-energy. It is shown that under eikonal approximation the above mentioned
equations can be reduced to equations for worldline of the particle and
equation of spin of the particle along the worldline. This way conformity
between corpuscular considerations of spin 1/2 massless particle and approach
in framework of spinor field theory in curved spacetime is demonstrated.
