Passive-margin prolonged volcanism, East Australian Plate : outbursts, progressions, plate controls and suggested causes

• Published in: Australian Journal of Earth Sciences
• Main Authors: Sutherland, Frederick L. (R13165), Graham, Ian T., Meffre, Sebastien, Zwingmann, Horst, Pogson, Ross E.
• Other Authors: School of Science and Health (Host institution)
• Format: Article in Journal/Newspaper
• Language: English
• Published: U.K., T. & F. Informa 2012
• Subjects: 040303 - Geochronology; 970104 - Expanding Knowledge in the Earth Sciences; Argon-argon dating; basalt; central volcano; Australian plate; mantle plumes; K-Ar dating; Queensland; Antarctic; Australian-Antarctic Discordance; Indian; Pacific; Antarc*
• Online Access: http://handle.uws.edu.au:8081/1959.7/515681; https://doi.org/10.1080/08120099.2012.688293

Prolonged intraplate volcanism along the 4000 km-long East Australian margin for ca 100 Ma raises many genetic questions. Studies of the age-progressive pulses embedded in general basaltic activity have spawned a host of models. Zircon U-Pb dating of inland Queensland central volcanoes gives a stronger database to consider the structure and origin of Australian age-progressive volcanic chains. This assists appraisal of this volcanism in relation to plate motion and plate margin tectonic models. Inland Queensland central volcanoes progressed south-southeast from 34 to 31 Ma (~5.4 cm/yr) until a surge in activity led to irregular southerly progression 31 to 28 Ma. A new inland southeastern Queensland central volcano line (25 to 22 Ma), from Bunya Mountains to North Main Range, followed 3 Ma behind the adjacent coastal progression. The Australian and Tasman Sea age-progressive chains are compared against recent plate motion modelling (Indian Ocean hotspots). The chain lines differ from general vector traces owing to west-facing swells and cessations in activity. Tectonic processes on the eastern plate margin may regulate these irregularities. These include subduction, rapid roll-back and progressive detachment of the Loyalty slab (43 to 15 Ma). West-flowing Pacific-type asthenosphere, related to perturbed mantle convection, may explain the west-facing volcanic surges. Such westward Pacific flow for over 28 Ma is known at the Australian-Antarctic Discordance, southeast of the present Australian plume sites under Bass Strait-West Tasman Sea. Most basaltic activity along eastern Australia marks asthenospheric melt injections into Tasman rift zone mantle and not lithospheric plate speed. The young (post-10 Ma) fields (Queensland, Victoria-South Australia) reflect new plate couplings, which altered mantle convection and stress regimes. These areas receive asthenospheric inputs from deep thermal zones off northeast Queensland and under Bass Strait.