  We consider a strongly correlated "t,t'-J" spin model with a positive
uniaxial anisotropy. We show that in 2+1 dimensions, this model is equivalent
to spin-charge excitations coupled to Z_2 Ising gauge fields and not to a U(1)
gauge fields (as in the "t-J" model). As a result a phase of frozen Z_2 gauge
fluctuations is possible, giving rise to a spin-charge-separated liquid.
