Jurassic quartz-normative tholeiite dikes from Anticosti Island in the Gulf of St. Lawrence are generally similar to the low-TiO₂, quartz-normative tholeiites (Weigand and Ragland, 1970) of the eastern North American province, but have TiO₂ contents intermediate between low- and high-TiO₂ types. The Anticosti dikes contain olivine microphenocryst pseudomorphs, sparse plagioclase phenocrysts, groundmass plagioclase laths, ophitic pigeonite and augite, ± interstitial Fe-Ti oxides, ± hornblende, ± biotite, and variable proportions (0%–20%) of interstitial devitrified glass. High K, light rare earth element, and Ba contents suggest some crustal contamination, but the low Zr/Y ratio of plausible model contaminants into normal mid-ocean ridge basalt implies that the assimilate was poor in Zr.