Magma ascent in Australian Intraplate basaltic volcanic provinces

Handley Heather1, Cas Ray2, England Tom1, Didonna Rosa1, Ezad Isra1

1Department of Earth and Environmental Sciences, Macquarie University, Sydney, Australia; 2School of Earth, Atmosphere and Environment, Monash University, Clayton, Australia

Basaltic intraplate volcanic fields, those located within tectonic plates, occur on every continent, often in close proximity to large population centres and yet they are amongst the least well-understood volcanic systems on Earth. In this study we use textural and chemical information stored within minerals from two of the youngest volcanic eruptions in northeast and southeast Australia to investigate magmatic plumbing systems and magma ascent in intra-plate volcanic fields. Volcanic rock samples from the three main eruptive phases at Mt Schank volcano in the Newer Volcanics Province, South Australia, reveal textural and mineralogical differences throughout the evolution of the eruption that correspond to variations in eruption style and the availability of external water. Crustal xenoliths (e.g., quartz and limestone) are abundant in the middle, maar-forming phase of the eruption. The lack of mantle-derived xenoliths and xenocrysts throughout the eruption, olivine compositions and sector and oscillatory zoned, euhedral clinopyroxene suggest a more stalled ascent pathway of magma compared to the mantle xenolith-bearing volcanoes in parts of the Victorian sector of the province. Skeletal olivine crystals and dendritic clinopyroxene microlites indicate moderate degrees of undercooling at Mt Schank during magma ascent. In northeast Queensland, interaction of magma with a mantle xenolith (pyroxenite) is used to determine magma ascent dynamics. Disequilibrium and quench textures and chemical zoning patterns in olivine, clinopyroxene, orthopyroxene and spinel on xenolith margins and within host glass reveal a detailed and complex history of magma ascent.


Heather Handley is an Associate Professor of Volcanology and Geochemistry Macquarie University and 2012-2018 Australian Research Council Future Fellow. Heather is a passionate science communicator and strong advocate for equity and inclusion. She is Co-Founder and President of the Women in Earth and Environmental Sciences Australasia Network (WOMEESA).

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