A detailed 40Ar/39Ar age study of an Abitibi dike from the Canadian Superior Province

40Ar/39Ar step-heating analyses were performed on 11 felsic and mafic mineral separates from a 90m wide Precambrian Shield. Deuterically altered minerals from the dike interior define a primary age of 2150 +- 25 Ma. Updated ages, obtained from felsic separates within 30, and mafic within 1.5 m of the dike border, are evidence of a previously undetected Hudsonian (1.7-1.8 Ga) hydrothermal event in the area. It is possible to distinguish the deuteric from the later hydrothermal alteration by both dating and petrographic methods. The data from this study demonstrate the successful application of 40Ar/39Ar dating to early Proterozoic dikes which have suffered low grade metamorphism. The ages support a north to south sense of motion of the Track 5 apparent polar wander path (APWP). A monotonic decrease in apparent age of felsic spectra indicates reactor induced recoil effects which are correlated with the fine-grained saussurite in the feldspar. (auth)