Passive-margin prolonged volcanism, East Australian Plate: Outbursts, progressions, plate controls and suggested causes
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Sutherland, FL and Graham, IT and Meffre, S and Zwingmann, H and Pogson, RE, Passive-margin prolonged volcanism, East Australian Plate: Outbursts, progressions, plate controls and suggested causes, Australian Journal of Earth Sciences, 59, (7) pp. 983-1005. ISSN 0812-0099 (2012) [Refereed Article]
Copyright 2012 Geological Society of Australia
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. © 2012 Copyright Taylor and Francis Group, LLC.
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