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- ISSN: 2202-0586
- E-ISSN:
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oa Geophysical and volcanological insights into the subsurface morphology and eruptive histories of complex maar volcanoes within the Newer Volcanics Province, Western Victoria
- Australian Society of Exploration Geophysicists
- Source: ASEG Extended Abstracts, Volume 2013, Issue ASEG2013 - 23rd Geophysical Conference, Dec 2013, p. 1 - 3
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- 01 Dec 2013
Abstract
To better characterise the eruptive histories and subsurface structures of several maar volcanoes from the Newer Volcanics Province, forward and inverse geophysical modelling is combined with a study on the geology of the volcanic centres. The maar volcanoes under investigation include the Red Rock Volcanic Complex (RRVC), Ecklin maar, the Mount Leura Volcanic Complex (MLVC).
High resolution gravity and magnetic data were acquired across each of the maars and the data was modelled in two and three dimensions to understand the subsurface morphology of the volcanoes vents.
Varied geophysical responses are observed across each of the maars surveyed, indicating the complex and variable nature of the subsurface volcanic vent, even when they present similar surface morphology. Where corresponding gravity and magnetic lows are detected across a maar crater, it is suggested that all the available magma was erupted and the maar diatreme (subsurface collapse structure) was not intruded by any dykes. The gravity low arises because of lower density lake sediments and pyroclastic debris infilling the crater. The lack of any intrusive dykes or remnant vents within the diatreme suggest that groundwater was available for phreatomagmatic explosions.
Maars with corresponding gravity and magnetic highs indicate a large volume of subsurface basalt, resulting from the ponding of magma at the surface of the vent. This results from a lack of groundwater for magma to interact with during the eruption, which facilitates magma rising upwards through the diatreme where it is fragmented at shallower levels.
© 2013 ASEG