Rb–Sr whole rock analyses of rocks from the Hanson Lake area; Saskatchewan, combined with geological evidence suggest that there were three thermal events in that region during Precambrian time. During Archean time, a period of volcanism about 2520 m.y. ago was followed by a period of granite intrusion about 2445 m.y. ago. During Aphebian time, the rocks of the area were intruded by pegmatites about 1800 m.y. ago. If the analytical data alone are considered, the two earlier events should be considered as one that took place about 2425 m.y. ago.