Passive-margin prolonged volcanism,East Australian Plate: outbursts,progressions, plate controls and suggested causes |
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| Authors: | F L Sutherland I T Graham S Meffre H Zwingmann R E Pogson |
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| Institution: | 1. School of Science, BCRI Campus, University of Western Sydney , Locked Bag 1797, Penrith , NSW , 2751 , Australia;2. Geoscience, Australian Museum , 6 College Street, Sydney , NSW , 2010 , Australia lin.sutherland@austmus.gov.au;4. School of Biological, Earth and Environmental Sciences, University of New South Wales , NSW , 2052 , Australia;5. Geoscience, Australian Museum , 6 College Street, Sydney , NSW , 2010 , Australia;6. Earth Sciences, University of Tasmania , Private Bag 79, Hobart , Tas , 7001 , Australia;7. Earth Science and Resource Engineering, CSIRO , PO Box 1130, Bentley , WA , 6102 , Australia;8. School of Earth and Environment, The University of Western Australia , Crawley , WA , 6009 , Australia;9. Department of Applied Geology , Curtin University , Perth , WA , 6102 , Australia;10. Geoscience, Australian Museum , 6 College Street, Sydney , NSW , 2010 , Australia |
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| Abstract: | 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. |
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| Keywords: | intraplate volcanism passive-margin central volcano basalt zircon U–Pb dating Ar–Ar dating K–Ar dating mantle plumes Australian Plate |
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