Temporal correlation of magmatic-tectonic events in the lower and upper crust in north-east Australia

Abstract

Hf model ages yielded by rutiles in a garnet-rich lower-crustal granulite xenolith from the McBride Province and whole-rock Nd and Hf model ages for the plagioclase- and garnet-rich Chudleigh and McBride granulites overlap with the well-defined U–Pb ages for detrital zircons and zircons in granitoids (Murgulov et al. Chem Geol 245:198–218, 2007; Mineral Petrol 95:17–45, 2009), suggesting temporal correlation of magmatic-tectonic events in the lower and upper crust in the north-east Australian craton. Intrusion of basaltic magmas into and below the lower crust beneath the Chudleigh Province around 1.4, 1.7 and 2.3 Ga and beneath the McBride Province around 1.5, 1.7, 2.3 and 2.5 Ga provided heat for remelting and supplied magmas with juvenile mantle isotope signatures to the upper crust. Similar magmas provided enough heat to cause melting in the lower crust beneath the Chudleigh Province around 0.12 and 0.8–0.9 Ga and beneath the McBride Province around 0.42, 0.8–0.9 Ga, 1.1 and 1.3 Ga but were not sufficient to cause significant melting in the upper crust. A wide range in initial 176Hf/177Hf values and a ~1.55 Ga Hf model age yielded by rutiles in the McBride granulite provide a link to the genesis of ~420 Ma granitoids. The data for a plagioclase-rich granulite from the Atherton Province are similar to those for the Chudleigh and McBride granulites. However, additional samples are required to test whether the lower crust of the Tasman orogenic belt is lithologically and isotopically similar to the lower crust of the craton.