Geodynamic implications of the 2012 Albany–Fraser … · Russell Korsch, C Spaggiari, S Occhipinti, M Doublier, D Clark, M Dentith, M Doyle, B Kennett, K Gessner, N Neumann,

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



A-F survey


Region mostly under cover

Albany-Fraser seismic survey


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


12GA-AF2

0

1s

2km Data quality

Albany-Fraser seismic survey – crustal architecture


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


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


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 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


Yilgarn (Youanmi)

Northern Foreland Inc. Munglinup

Biranup Nornalup


Major crustal boundaries – 12GA-AF1 Nornalup Zone

Biranup


Major crustal boundaries – 12GA-AF3

Biranup Yilgarn (Kurnalpi)

Nornalup NF Madura Fraser


Major crustal boundaries – 12GA-T1 Biranup Zone Tropicana Zone

Yilgarn (Yamarna)

Crustal deformation


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


Cenozoic structures

Base: SRTM DEM

Regional setting – new geochronology



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


Madura

Coompana

MSD3 MSD4 Hf model ages suggest

different protolith for the two samples ?Significance of Mundrabilla Shear Zone

Regional setting – new geochronology



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)


?

Significance of Tropicana Zone


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


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


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


? Links with surrounding provinces

Questions about geodynamics in Southeast WA


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


Transect across southern Western Australia


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


VE x ~3.5

Cross section showing present day relationships between the crustal provinces

SC1 YU1 YU2 EGF1 NY1 AF3

VE x ~1


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


To be continued ! new Eucla-Gawler seismic line

13GA-EG1 ~835 line km

To Tarcoola


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 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

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Documents

Geodynamic implications of the 2012 Albany–Fraser … · Russell Korsch, C Spaggiari, S Occhipinti, M Doublier, D Clark, M Dentith, M Doyle, B Kennett, K Gessner, N Neumann,