We study a quenched disordered d =3 tJ Hamiltonian with static vacancies as a model of nonmagnetic impurities in high-T c materials. Using a renormalization-group approach, we calculate the evolution of the finite-temperature phase diagram with impurity concentration p and find several features with close experimental parallels: Away from half filling, we see the rapid destruction of a spin-singlet phase ͑analogous to the superconducting phase in cuprates͒ which is eliminated for p տ 0.05; in the same region for these dilute impurity concentrations, we observe an enhancement of antiferromagnetism. The antiferromagnetic phase near half filling is robust against impurity addition and disappears only for p տ 0.40.The electronic properties and phase diagram of high-T c materials are particularly sensitive to impurities--substitution of 3d transition elements ͑Zn, Ni, Co, and Fe͒ or other metals ͑Al and Ga͒, for the Cu atoms of the CuO 2 planes. 1 The interplay between disorder, strong antiferromagnetic correlations in the parent compound and doped charge carriers offers a window onto the nature of both the superconducting phase and the normal state above T c . Doping by nonmagnetic ͑S =0͒ Zn ions provides one representative example: the most pronounced effect is the rapid destruction of the superconducting phase. 1,2 In yttrium barium copper oxide ͑YBCO͒, the transition temperature is reduced at a rate of ϳ15 K / at % of impurities so that it takes Zn concentrations of only about 6% to entirely eliminate superconductivity. 2 This is in contrast to the antiferromagnetic phase at half filling, which requires a far larger Zn concentration ͓about 40% in lanthanum strontium copper oxide ͑LSCO͒ ͑Ref. 3͔͒ to completely suppress. The effects in the metallic region above T c are equally surprising: nuclear-magnetic-resonance experiments have found that Zn atoms induce local magnetic moments at nearest-neighbor Cu sites 4 and enhance antiferromagnetic correlations for several lattice spacings around the impurity. 5,6 In lightly hole-doped LSCO, there have been observations of an initial increase in the Néel temperature with Zn addition and even impurity-induced reappearance of long-range antiferromagnetic order. 7,8 In this work we model the effects of nonmagnetic impurities in high-T c materials through a d =3 tJ Hamiltonian with quenched disorder in the form of static vacancies. Through a renormalization-group ͑RG͒ approach, we obtain the evolution of the global temperature vs chemical-potential phase diagram with disorder. Our results capture, in a single microscopic model, some of the major qualitative features of impurity doping in real materials: the rapid suppression of a spin-singlet phase, analogous to the superconducting phase in cuprates, the gradual reduction of the antiferromagnetic phase near half filling, and the enhancement of antiferromagnetism away from half filling for small impurity concentrations.We consider the quenched disordered tJ model on aThe static impurities at each site i occur with probability ...