Rubidium‐strontium total‐rock geochronology of granulite‐facies gneisses in the western Musgrave Block, Central Australia records distinct metamorphic and earlier events. The Tomkinson Ranges are subdivided into two regions with similar relative geological sequences of events, but different primary ages and lithologies; the boundary between the regions is the latitudinally‐trending Hinckley Fault. A 90‐km traverse along regional strike in the northern region produces consistent 1550 m.y. ages. Sampling at several structural levels over a slight range of metamorphic grade in the southern region reveals a single regional isochron with a 1330 m.y. age. Both ages are interpreted as the time of supracrustal genesis of the rocks. Subsequently, granulite‐facies metamorphism occurred throughout the area at 1200 m.y.: attribution of this age to the metamorphism is based upon evidence for outcrop scale isotopic homogenization, and the dating of a granitoid intrusion contemporaneous with the metamorphism.