The Strathgordon area of low metamorphic grade (450±50°C, 4±1 Kb) and the eclogitebearing Lyell Highway-Collingwood River area, which is of higher grade (670±20°C, 11±1 Kb), have been studied by the Rb-Sr technique.Three deformational events, D1 to D3 correlate in time with two important P,T events, here termed D2−2 and D3, D1−2 reflects the continuous prograde P,T environment up to the ... [Show full abstract] metamorphic maximum of the two areas (D2), while D2 is a superimposed deformational event occuring at lower P,T conditions. According to stratigraphical constraints D3 must have occured before or about 550 m.y. ago.It is possible from rather complex Rb-Sr data to indicate ages for the D1–2 and D3 events. Two-point total rock+phengite (mica) ages together with total rock isochrons using closely spaced samples show that the main metamorphic event D1–22 occurrred at about 800 m.y. in both areas. Similar data suggest that the superimposed event D3 occurred between 550 and 630 m.y. ago, probably near the lower age limit. This deformation (crenulation cleavage) was responsible for the local resetting of total rock and mineral systems.Consistent with later Palaeozoic events, the Cambrian-early Ordovician Jukesian Movement and the Devonian Tabberabberan Orogeny, which affected some Rb-Sr mineral systems (phengite, amphibole and chlorite), have ages of 500±20 m.y. and 385-350 m.y. respectively.Due to dispersion of the eclogite total rock data points along secondary isochrons it is difficult to estimate an original age. The age of the original minerals must however have been set by the 800 m.y. D1–2 event, as the P,T history of the eclogite is the same as that of the surrounding schists.