SHRIMP zircon U–Pb age and tectonic significance of the Palaeoproterozoic Boolaloo Granodiorite in the Ashburton Province, Western Australia

The age of the Ashburton Province, comprising an older divergent‐margin megasequence and a younger convergent‐margin megasequence, is poorly constrained. The Boolaloo Granodiorite, which intruded the divergent‐margin megasequence on the western margin of the Ashburton Province, has given a SHRIMP zircon U–Pb age of 1786 ± 5 Ma, and therefore post‐dates convergent‐margin, backarc basin sequences, with established conventional zircon U7sbnd;Pb ages of ca 1843–1828 Ma. However, it pre‐dated deformation of convergent‐margin, remnant‐ocean sequences. Similarly aged (ca 1797–1791 Ma) granitoids are present in the adjacent Gascoyne Province, thereby identifying a magmatic fold‐thrust belt that abutted a remnant ocean in the Ashburton Province.