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| Titel |
Thermal structure of the Newer Volcanic Province, Western Victoria, Australia from a long period Magnetotelluric (MT) array |
| VerfasserIn |
S. Aivazpourporgou, S. Thiel, P. Hayman, L. Moresi, G. Heinson |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250058497
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| Zusammenfassung |
| In 2010 and 2011, long-period MT data were collected in a rectangular grid with nominal 300
km x 150 km dimensions in western Victoria, Australia, across the southern end of mid
Paleozoic Lachlan and early Paleozoic Delamerian orogeny and Quaternary Newer Volcanic
Province (NVP). The aim of this survey is to map electrical resistivity variations in the crust
and upper mantle to understand the lithospheric structure and thermal regime of the
area.
The observed heat flow values in western and central Victoria (~85 μWK3) are well above
the world average for Paleozoic rocks. The Quaternary Newer Volcanic Province in western
Victoria, the youngest and the most extensive volcanoes (15000 km2 of basalts) in the
intraplate volcanism of eastern Australia, are evidence of a large recent volcanic event.
However, the nature and the mechanism(s) of magma production are still debated. Previous
teleseismic tomography studies of the region show a reduction of seismic wave speed (~ 3-4
per cent) at lithospheric depths of ~50-150 km beneath Central Highlands sub-province of
the NVP, providing supporting evidence for high elevated temperatures at the upper
mantle beneath the NVP and the possible existence of a mantle plume. However,
there is no clear age progression of volcanoes consistent with formation from a
mantle plume. Our MT data was collected at approximately the same survey sites as
existing teleseismic array to constraint the geological structures of the lithosphere of
western Victoria and to provide insight into questions related to magma genesis of the
NVP.
Preliminary results show that strike analysis using phase tensors are reflecting the
strike of the main geological feature of the Moyston fault, the structural boundary
between Delamerian and Lachlan orogeny. The induction arrows indicate there is
a large conductor beneath the Central Highlands sub-province of NVP relating
to periods between 50 s and 1000s, correlating to depths lower than 10 km. This
large conductor is correlated with interpreted elevated temperatures at upper mantle
depths beneath the NVP observed by teleseismic data. Preliminary two dimensional
modelling shows there is a large conductor beneath Central Highlands sub-province of
the NVP extended between ~20 km and 120 km. However, the ocean effect and
existence of Moyston fault and of a potential plume requires further three-dimensional
modelling. |
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