Geodynamic implications of the 2012 Albany–Fraser … · Russell Korsch, C Spaggiari, S...
Transcript of Geodynamic implications of the 2012 Albany–Fraser … · Russell Korsch, C Spaggiari, S...
Geodynamic implications of the 2012 Albany–Fraser deep seismic reflection survey: a transect from the Yilgarn Craton across the Albany–Fraser Orogen to the Madura Province
Russell Korsch, C Spaggiari, S Occhipinti, M Doublier, D Clark, M Dentith, M Doyle, B Kennett, K Gessner, N Neumann, E Belousova, I Tyler, R Costelloe, T Fomin and J Holzschuh
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
Project Partners
Contributors RSES, Australian National University CET, University of Western Australia
GEMOC, Macquarie University
Albany-Fraser seismic survey
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
12GA-AF2 12GA-AF1
12GA-T1
12GA-AF3
Seismic sections displayed at V = H, (assuming average crustal velocity of 6000 ms-1) 1 s TWT is approximately 3 km depth All “dips” and “dip directions” are apparent dips
W E
W E
NW SE
0
20
TWT
0
20
TWT
0
20
TWT
Data quality
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
12GA-AF2
0
1s
2km Data quality
Albany-Fraser seismic survey – crustal architecture
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
12GA-AF2 12GA-AF1
12GA-T1
12GA-AF3
Reflectivity: usually good, but some nonreflective areas Moho Key provinces Major structures Geodynamic implications Transect across SE Western Australia
W E
W E
NW SE
0
20
TWT
0
20
TWT
0
20
TWT
Structure of the Moho – 12GA-AF1 and 12GA-AF2
W E 12GA-AF2 12GA-AF1
Moho Moho
Nonreflective lower crust
Moho strongly to weakly reflective Crust ~35-46 km thick Crust thicker beneath nonreflective region
0
20
TWT
0
20
TWT
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
Nonreflective upper mantle
Moho moderately reflective Moho possibly faulted on seismic line 12GA-T1 Crust 39-49 km thick
Structure of the Moho – 12GA-T1
Moho
NW SE NW SE 0
20
TWT
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
Structure of the Moho – 12GA-AF3 W E
Moho – faulted of downwarped?
Moho moderately to weakly reflective Moho faulted (A) or downwarped (B)? Crust 39-49 km thick
A
B
?
0
20
TWT
0
20
TWT
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
Albany-Fraser seismic survey – key crustal provinces
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
Albany-Fraser seismic survey – key crustal provinces
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
Albany-Fraser seismic survey – key crustal provinces
Yilgarn – Youanmi, Kurnalpi, Yamarna Albany-Fraser – Northern Foreland, Tropicana Albany-Fraser – Biranup, Fraser, Nornalup Madura Province Lower crustal SPs - Yarraquin, Udarra, Babool Gunnadorrah Seismic Province
Major crustal boundaries – 12GA-AF2
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
Yilgarn (Youanmi)
Northern Foreland Inc. Munglinup
Biranup Nornalup
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
Major crustal boundaries – 12GA-AF1 Nornalup Zone
Biranup
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
Major crustal boundaries – 12GA-AF3
Biranup Yilgarn (Kurnalpi)
Nornalup NF Madura Fraser
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
Major crustal boundaries – 12GA-T1 Biranup Zone Tropicana Zone
Yilgarn (Yamarna)
Crustal deformation
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
Seismic sections are images of present-day crustal architecture End result of numerous geological events Structures suggest west-directed shortening was dominant Structures formed during Albany-Fraser Orogeny Stages I & II Plus older structures reworked during AFO
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
MSD3
Drilling by WMC Resources Ltd Analyses by GEMOC, Macquarie University MSD4
MSD4 Madura Province Granitic gneiss
Magmatism 1500 ± 11 Ma
MSD3 Coompana Province
granite Magmatism 1280 ± 11 Ma
Metamorphism 1216 ± 12 Ma
Hf results from MSD3 and MSD4
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
Madura
Coompana
MSD3 MSD4 Hf model ages suggest
different protolith for the two samples ?Significance of Mundrabilla Shear Zone
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
0.04
0.06
0.08
0.10
0.12
2.5 3.5 4.5 5.5 6.5238U/206Pb
207 Pb
/206 Pb
data-point error ellipses are 2σ
Th/U
0
1.5
1000
1400
1800
GA 2152082, GSSA R1964851Unnamed granitoid
Kutjara-1All; n = 58
Age = 1591 ± 11 Man = 30 of 31
MSWD = 1.3; Prob. = 0.14
Age = 1167 ± 7 Man = 24 of 25
MSWD = 0.99; Prob. = 0.47
a)
0.04
0.06
0.08
0.10
0.12
1 3 5 7 9 11 13238U/206Pb
207 Pb
/206 Pb
data-point error ellipses are 2σ
Th/U
0
4
600
1000
1400
1800
GA 2152083, GSSA R1964856Unnamed adamellite
Mulyawara-1All; n = 41
Age = 1168 ± 6 Man = 22 of 22
MSWD = 0.62; Prob. = 0.91
b)
Sampling with permission from Rodinia Oil (Australia) Pty Ltd
Coompana Province
Kutjara 1 Magmatism 1591 ± 11 Ma
Metamorphism 1167 ± 7 Ma Mulyawara 1
Magmatism 1168 ± 6 Ma
Revised extent of Yilgarn Craton (including the subsurface)
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
?
Significance of Tropicana Zone
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
Different architecture and history to Yilgarn Craton and rest of Albany-Fraser Orogen
Hard-linked system of listric faults sole onto Plumridge (basal) Detachment
~2520-2515 Ma Tropicana Event not recognised elsewhere - thrust sheet derived from deeper level in SE
Yilgarn Craton extended prior to emplacement of Tropicana thrust sheet
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
From Kirkland et al. (2011),Spaggiari et al. (2014)
Proterozoic extension and contraction
Extensional (rift) basins Intracontinental or distal backarc setting Any subduction was well to east
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
From Spaggiari et al. (2014)
Proterozoic extension and contraction
Extensional displacements on shear zones are rarely observed in the seismic
Hangingwall (ramp) anticlines common – thrusts
Probable reactivation/inversion of extensional faults as thrusts during later contractional deformations
Questions about geodynamics in Southeast WA
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
? Links with surrounding provinces
Questions about geodynamics in Southeast WA
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
Mu
W
A-F
Y
R
C
G
Musgrave Province – keystone block in central Australia between WAC, NAC and SAC
Albany-Fraser Orogen, Madura Province and Coompana Province link the WAC and SAC
Ma
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
Composite section from Pinjarra Orogen to Madura Province
Y Z
11GA-SC1 10GA-YU1 10GA-YU2
BMR91-EGF01 01AGS-NY1 12GA-AF3
X Y
Y
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
VE x ~3.5
Cross section showing present day relationships between the crustal provinces
SC1 YU1 YU2 EGF1 NY1 AF3
VE x ~1
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
VE x ~3.5 Youanmi Terrane + Yarraquin Seismic Province form a central nucleus, or protocraton of Yilgarn Craton Narryer Terrane sutured to protocraton in northwest Terranes of Eastern Goldfields Superterrane in east accreted to protocraton, to form entire Yilgarn Craton Glenburgh Terrane sutured in NW to form part of West Australian Craton (WAC) Madura Province and Pinjarra Orogen sutured to WAC → present architecture
Transect across Western Australia 2 billion years in the making
~1080 Ma
~1965 Ma ~2750 Ma
?2800 Ma ~2655 Ma
~1330 Ma
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
To be continued ! new Eucla-Gawler seismic line
13GA-EG1 ~835 line km
To Tarcoola
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
Albany-Fraser Survey - Summary 1 Crustal architecture of SE Yilgarn Craton to Madura
Province
• First holistic view of the crustal architecture of this poorly-exposed region (672 line km of new seismic data) • Crosses several crustal-scale provinces
• Including cross section across Albany-Fraser Orogen • Tropicana Zone imaged
• Yilgarn Craton extends well to the east beneath the Albany-Fraser Zone
Albany-Fraser Seismic & MT Workshop, Perth, 9 April 2014
Albany-Fraser Survey - Summary 2 Assembly of southern Western Australia
• Several probable sutures recognised previously • Progressive accretion of continental slivers onto protocraton (Youanmi Terrane and Yarraquin Seismic Province) • Archean, Paleoproterozoic and Mesoproterozoic accretion events, including Madura Province
Phone: +61 2 6249 9495 Web: www.ga.gov.au Email: [email protected] Address: Cnr Jerrabomberra Avenue and Hindmarsh Drive, Symonston ACT 2609 Postal Address: GPO Box 378, Canberra ACT 2601
THANK YOU