dalamerian lachlan transition
Post on 11-Feb-2022
10 Views
Preview:
TRANSCRIPT
Transition between the Delamerian and Lachlan Orogens
A ramble through the Koonenberry Belt, Stawell Zone, Dimboola Arc, Thomson Orogen, and the Macquarie Arc
Bob MusgraveWith much assistance from
John Greenfield and Phil Gilmore
Let’s look at where we are…
“Tasman line”
Koonenberry Belt
TMIGeoscience Australia
Tilt-filter on TMIGeological Survey of NSW
Koonenberry Belt: Geological outline
250 km
Elements of the Mt Wright (Koonenberry) Arc
• Arc• Back-arc• Fore-arc/accretionary prism• Continental backstop (including
Neoproterozoic rift volcanics)
Mt Wright Volcanics+ Bancannia Trough
Tilt-filter + TMI, with gravity
“worms”
Potential field modelling
Bouguer gravityTotal Magnetic Intensity
Deep structure: reflection seismics and potential field modelling
TMI
1VD
Bouguer grav
Low-pass grav
TMI
1VD of TMI
Modelling 3D structure
Koonenberry 3D model
Mt Wright Arc
Mt Arrowsmith – deep bodies
• Linear structure of Koonenberry Belt looks simple enough – but note:
• Broad magnetic anomalies in Bancannia Trough – Mt Wright Volcanic Arc under Devonian basin
• Re-entrant bend at Grasmere Knee Zone – and nearby deep magnetic sources
• Bend at the Cobham Kink Zone – and “mystery” deep reversed remanence source
• And note how the gravity “ignores” both bends in the linear belt
– Suggests the bend is restricted to shallower structure
Structures from potential fields
Curnamona
Koonenberry Belt
Bancannia Trough
Grasmere Knee Zone
Cobham Kink Zone Mystery
source
Restoring the Bancannia rift20°
New Zealand CVZ and Bancannia
Parson & Wright, 1996
2.3 A/m
S. Soengkono, Journal of Volcanology and Geothermal Research 68 (1995) 193-207
Thanks to Supri Soengkono and Glass Earth (NZ) Inc
Grasmere Knee Zone: subducted seamount in accretionary margin?
0 20
km
Seamount subduction
Dominguez et al., 1998, 2000
Kodaira et al., 2000
Thomson accretionary margin: Benambran overprint on Delamerian wedge
Seamount deformation in the Thomson Orogen?
Thomson Orogen arc-arc collision?
Stawell
Bendigo
StavelyGlenelg
Hay- Booligal
Bootheragandra
Fault
Thomson
Delamerian accretionary margin - connection to the Stawell Zone
Scheibner & Basden, 1998
Delamerian and Benambran
Ponto GroupMarine- pelagic mudstone—siltstoneFelsic tuff (Mt Wright Arc equivalent)Mte-Qtz exhalativebasalt lava, tuff (tholeiite, MORB)
~511 Ma
(Evans 1993)
Grasmere (Ponto Gp) – Besshi-style VMSLate
qtz-carb-chalveins in FW
HWNon-mag
Massive sulphide ore
Brecciated & MS ore
FWMag
Orogenic Au - Warratta Inlier
Victorian Goldfields(Ramsay, 1998)
Australian Earth Sciences Convention, Perth, July 2008Warratta Inlier (Greenfield, 2008)
Mt Wright – Menidee – Dimboola Arc?
Dimboola Arc:Cambrian calc-alkaline volcs, supra- subduction zone ophiolite (oceanic arc)
Volcanic basement of Stawell Zone: Cambrian tholeiites, Besshi-style VMS, Benambran gold
Mt Wright (Koonenberry) Arc:Cambrian calc-alk volcs in rifted arc setting on continental margin.
Ponto Group: Cambrian tholeiites, Besshi-style VMS
Warrata inlier: Benambran orogenic gold
Bendigo Zone: Benambran orogenic gold
top related