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Integrated geophysical appraisal of crustal architecture in the eastern Lachlan Orogen


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Direen, NG, Lyons, P, Korsch, RJ and Glen, RA 2001 , 'Integrated geophysical appraisal of crustal architecture in the eastern Lachlan Orogen' , Exploration Geophysics, vol. 32, no. 4 , pp. 252-262 , doi: 10.1071/EG01252 .

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Forward modelling of potential field data, combined with new
geological mapping and deep seismic reflection transects acquired
by the Australian Geodynamics Cooperative Research Centre
(AGCRC) and New South Wales Department of Mineral
Resources, has led to iterative testing of models of crustal
architecture of the eastern Lachlan Orogen in New South Wales.
This integrated analysis has led to new conclusions about the
subsurface that are unlikely to be deduced solely from any of the
individual data sets used.
Conclusions supported by the consideration of these data
• Presence of lower crust in the eastern Lachlan Orogen,
characterised by higher than average crustal density, high P- wave
velocities, and repeated, stacked bands of strong reflectivity.
This crust is interpreted to be a stacked pile of metaturbidites
and modified oceanic crust (greenstones).
• Presence of large volumes of Ordovician volcanic rocks
underlying many areas of Silurian-Devonian basin rocks.
• Evidence for extensive, deep-cutting blind thrust faults and
detachments throughout the crustal section. Major movements
on these faults during the early Silurian appear to have
significantly thickened the whole crust.
• Evidence for many high-level upper crustal slivers, mostly
formed during the Carboniferous.
• Differences between the western Ordovician Junee-Narromine
Volcanic Belt and the eastern Ordovician Molong Volcanic Belt.
The former is quite dense, and is inferred to have a large volume
of lavas and intrusive rocks. Its structural style is predominantly
that of an imbricate stack around a deeper-rooted core. The latter
has lower bulk density, and a higher volume of volcaniclastic
material. It is now entirely composed of thin, imbricate slices.
These differences suggest that the eastern belt may be the rifted
off forearc or apron of the western belt which may be the
original magmatic centre.
• Evidence for different styles of granite intrusion, reflected in
different intrusive geometry of Silurian, Devonian and
Carboniferous granites.

Item Type: Article
Authors/Creators:Direen, NG and Lyons, P and Korsch, RJ and Glen, RA
Keywords: gravity, magnetics, forward modelling, seismic reflection, Macquarie Arc, tectonics
Journal or Publication Title: Exploration Geophysics
ISSN: 0812-3985
DOI / ID Number: 10.1071/EG01252
Additional Information:

© ASEG 2001

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