The São João do Sabugi Pluton (SJSP) (~579 Ma) is one of the most expressive occurrences of Ediacaran, syn-to post-collisional shoshonitic rocks in the Rio Piranhas-Seridó Domain, Borborema Province, NE Brazil. The petrography, whole rock and mineral composition of this pluton were investigated to characterize its open-system magmatic differentiation processes. The pluton is composed of three rock groups: gabbro-diorite, with clinopyroxene ± orthopyroxene ± amphibole ± biotite; monzodiorite, with amphibole and biotite (± pyroxenes); and granodiorite, with biotite as the main mafic mineral. Evidences of open-system processes, including partially resorbed metasediment xenoliths, are widespread. These rocks are metaluminous, alkali-calcic and magnesian, and have shoshonitic affinity. They show relative LILE and LREE enrichment and pronounced negative Nb-Ta anomalies. Major and trace element geochemical modeling favors magma differentiation by fractional crystallization (56-62%) after crustal assimilation of ~30% of local paragneisses and schists from the Seridó Group in a relatively stationary magma chamber at crustal depth, under pressures of 5-6 kbar, temperatures of ~800-1,000 o C and relatively oxidizing conditions. The less evolved gabbro-diorite was generated by ~18% modal dynamic partial melting of a metasomatized mantle source.