40 Ar‐ 39 Ar thermochronology of the southern Gawler Craton, Australia: Implications for Mesoproterozoic and Neoproterozoic tectonics of East Gondwana and Rodinia

40 Ar‐ 39 Ar thermochronology of the southern Gawler Craton, Australia, reveals a protracted history of slow cooling, with local crustal heating, rapid cooling, and fault reactivation, between ∼1700 and ∼700 Ma. Hornblendes from most of the southern part of the Craton, including the Kalinjala Mylonite Zone, yield ages ∼1580–1610 Ma, with younger more discordant samples showing evidence of retrogression. These results indicate that the region cooled below ∼500°C ∼100 m.y. after the Kimban Orogeny and coincident with the Gawler Range‐Hiltaba Suite magmatism, to the north, perhaps associated with postorogenic extension. Biotite and K‐feldspar data indicate that regional cooling after this time was more gradual, with a few exceptions. Locally, in the southeastern Eyre Peninsula, rapid cooling at ∼1425 Ma is indicated by nearly concordant hornblende and biotite ages and may record a phase of regional extension. Other exceptions include areas of lower grade Archean rocks that cooled to