Multiple sources for volcanic rocks dredged from the Western Australian rifted margin

•New volcanic samples were collected from the offshore southwestern Australian margin.•Volcanic rocks come from a variety of tectonic settings.•Cretaceous volcanic rocks erupted in a continental extensional setting.•Younger volcanic rocks reflect a transition to a mature passive continental margin.•Volcanic cones with ocean island basalt chemistry formed in the final stage.

Igneous rock samples recovered during the 2008–09 Australian Southwest Margin Marine Reconnaissance Survey (GA-2476), off the Western Australian coast from Perth to the Wallaby Plateau, come from a variety of tectonic settings reflecting a complex magmatic history of this margin. Cretaceous rhyolite and basaltic andesite samples most likely erupted in a continental extensional setting, while younger volcanic samples reflect a transition to a mature passive continental margin with the generation of mid-ocean ridge basalt. During the last phase of volcanism, a series of volcanic cones and mounds with ocean island basalt geochemical signatures formed along the margin. The pre-rift sedimentary rocks sampled on the Wallaby Plateau support the viewpoint that it is an extended block of continental crust, overlain by syn-rift and post-rift volcanic rocks.