  We use a recently proposed perturbative numerical renormalization group
algorithm to investigate ground-state properties of a frustrated three
dimensional Heisenberg model on an anisotropic lattice. We analyze the ground
state energy, the finite size spin gap and the static magnetic structure
factor. We find in two dimensions a frustration-induced gapless spin liquid
state which separates two magnetically ordered phases. In the spin liquid
state, the magnetic structure factor shows evidence that this state is made of
nearly disconnected chains. This spin liquid state is unstable against
unfrustrated interplane couplings.
